AAM – Applications – 1 Power train Contents 1

Power train........................................................................................................................ 3 What to see in this section............................................................................................ 3 1.1 Engine ...................................................................................................................... 4 Aluminium engines ....................................................................................................... 4 1.1.1 Piston ................................................................................................................... 6 Pistons for gasoline and Diesel engines ...................................................................... 6 Operating conditions..................................................................................................... 7 Piston materials ............................................................................................................ 9 Design considerations for automotive pistons............................................................ 12 1.1.2 Cylinder block .................................................................................................... 14 Introduction ................................................................................................................. 14 Requirements for aluminium cylinder blocks.............................................................. 15 Competition between aluminium and grey iron .......................................................... 16 Design features .......................................................................................................... 17 Block design variants.................................................................................................. 18 Bolting concepts ......................................................................................................... 20 Open- and Closed-Deck concepts ............................................................................. 21 Pre-cast features and add-on parts............................................................................ 22 Cast-in inserts............................................................................................................. 24 Criteria for alloy selection ........................................................................................... 25 Alloys: Composition and heat treatment..................................................................... 26 Applicable casting processes ..................................................................................... 27 Example: Ford Zetec SE – CPS® Process ................................................................ 28 Example: PSA 2.0L HPI (HPDC)................................................................................ 29 Example: Lupo Block 1.2L.......................................................................................... 30 1.1.3 Cylinder linings................................................................................................... 31 Introduction ................................................................................................................. 31 Requirements ............................................................................................................. 33 Technologies – Overview ........................................................................................... 34 Comparison of liner technologies ............................................................................... 35 Liner solution: Heterogeneous concept Grey iron cast-in .......................................... 36 Liner solution: Monolithic concept (ALUSIL®)............................................................. 38 Liner solution: Quasi-Monolithic concept LOKASIL® .................................................. 39 Liner solution: Heterogeneous concept SILITEC® ..................................................... 41 Liner solution: Heterogeneous concept HYBRID, GOEDEL® ................................... 43 Liner solution: Quasi-Monolithic Concept TRIBOSIL®............................................... 44 Other liner solutions.................................................................................................... 46 Cylinder surface treatment – Honing of hypereutectic AlSi surfaces ......................... 48 1.1.4 Cylinder head..................................................................................................... 49 Introduction ................................................................................................................. 49 Requirements – Thermal conductivity vs. strength .................................................... 50 Requirements for aluminium cylinder heads – High- and low-cycle fatigue............... 51 Design features .......................................................................................................... 52 Criteria for alloy selection ........................................................................................... 54 Alloy composition and heat treatment ........................................................................ 55 Applicable casting processes ..................................................................................... 56 Example: PSA 2.0L HDI – Gravity Die Casting .......................................................... 57 Example: BMW 2.0L DI – Gravity Die Casting ........................................................... 58 Example: BMW 2,0l 4-Cylinder – Rotacast®.............................................................. 59 Example: Isuzu Diesel – Rotacast® ........................................................................... 60 1.2 Fuel system ............................................................................................................ 61 Aluminium helps to meet targets of HC-emission laws .............................................. 61 Future fuel systems need new materials technologies .............................................. 62 1.2.1 Fuel filler pipe..................................................................................................... 63 Product description..................................................................................................... 63 Example: Volvo V70/S80/S60/XC90 Fuel Filler Pipe ................................................. 64 Example: Porsche 911/Boxster Fuel Filler Pipe ......................................................... 65 1

1.2.2 Fuel tank ............................................................................................................ 66 Technical requirements .............................................................................................. 66 Technical feasibility .................................................................................................... 68 Prototype production .................................................................................................. 70 1.3 Liquid lines ............................................................................................................. 71 Aluminium tubing and connections............................................................................. 71 1.3.1 Applications........................................................................................................ 72 Application requirements ............................................................................................ 72 Tube materials for liquid lines..................................................................................... 73 1.3.2 Connections ....................................................................................................... 74 Screw Connections – Fittings ..................................................................................... 74 Hose-to-tube connection ............................................................................................ 76 Special connections – Magnetic pulse forming .......................................................... 77 Quick connectors........................................................................................................ 78 Connections by flame brazing .................................................................................... 79 Connections by flame brazing – Materials ................................................................. 80 1.3.3 Burst pressure.................................................................................................... 81 Burst pressure of liquid lines ...................................................................................... 81 1.3.4 Bending.............................................................................................................. 82 Bending of liquid lines................................................................................................. 82 1.3.5 Corrosion ........................................................................................................... 83 Corrosion Resistance – Long Life Materials............................................................... 83 1.4 Heat shields............................................................................................................ 84 Use of Aluminium Heat Shields .................................................................................. 84 Application Areas........................................................................................................ 86 Choice of Aluminium – Thermal Properties................................................................ 87 Choice of Aluminium – Material Specification ............................................................ 88 1.4.1 Requirements..................................................................................................... 89 Requirements / Specifications .................................................................................... 89 1.4.2 Design of heat shields........................................................................................ 90 Three basic types of heat shields ............................................................................... 90 Design for heat management: Exhaust system.......................................................... 92 1.4.3 Assembly techniques ......................................................................................... 93 Assembly techniques.................................................................................................. 93 1.5 Drive shaft .............................................................................................................. 94 Aluminium drive shafts ............................................................................................... 94 1.6 Heat exchangers .................................................................................................... 95 General aspects ......................................................................................................... 95 1.6.1 Radiators............................................................................................................ 97 Engine cooling system................................................................................................ 97 Engine cooling system – Material requirements and functions .................................. 98 Engine cooling system – Air-side corrosion ............................................................... 99 Engine cooling system – Water-side corrosion ........................................................ 100 1.6.2 Oil coolers ........................................................................................................ 101 Oil cooler applications .............................................................................................. 101 1.6.3 Air conditioning ................................................................................................ 107 General requirements............................................................................................... 107 Refrigerants .............................................................................................................. 108 Heater core – Design considerations ....................................................................... 109 Heater core – Production aspects ............................................................................ 110 Evaporator – Design aspects ................................................................................... 111 Evaporator – Production and environmental aspects .............................................. 112 Condenser – Design considerations ........................................................................ 113 Condenser – Productions aspects ........................................................................... 114 1.6.4 Charge air coolers............................................................................................ 115 Design and production aspects ................................................................................ 115 Different placements within the car .......................................................................... 116 Air-to-Air solutions .................................................................................................... 117 Air-to-Coolant Cooler................................................................................................ 119 Air-to-Air solutions – Manufacturing aspects............................................................ 120 1.6.5 Others .............................................................................................................. 121 Mechanically assembled radiator ............................................................................. 121 2

1 Power train What to see in this section The power train includes all assemblies from the energy generating engine through to the power transmitting road wheels. All power train components are subjected to alternating stresses, particularly the engine, which also has to withstand thermal stress. Aluminium, combined with intelligent design and optimum alloy selection, can meet the specific demands in this area. More detailed descriptions of aluminium applications in power train components are presented in the following subchapter: •

Engine

•

Fuel system

•

Liquid lines

•

Heat shields and

•

Heat exchangers.

Power train of a Daimler-Chrysler

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1.1

Engine

Aluminium engines The development of modern engines is marked by great dynamic. Current petrol engines already fulfil the strict emission regulations (CO2 emissions) but they still have to be optimised with regard to fuel consumption. Manufacturers are devising lightweighting concepts for medium-sized cars and are developing high-performance engines to meet customer demands. Modern diesel engines combine high output with low fuel consumption. The main challenges here are to optimise their acoustic behaviour and meet even lower emission limits.

Source: MTZ

Source: MTZ

Source: MTZ

Source: MTZ

Source: MTZ

Source: MTZ

(click to enlarge illustrations) Examples of current engines with aluminium crankcases: Petrol 1 Ford: 2 BMW: 3 Audi:

4-cyl., 1.4l, 66kW 4-cyl. 1.8l, 85kW W12, 6.0l, 309kW

Diesel 4 Volkswagen: 3-cyl., 1.2l, 45kW 5 Volvo: 5-cyl., 2.4l, 120kW 6 DaimlerChrysler: V8, 4.0l, 184kW Modern engines must have reduced emissions and lower fuel consumption. We therefore need: • Lightweight design • Lightweight materials • Reduced friction in moving parts • Increased specific performance The most important parts to fulfil these goals are: • Cylinder Head • Engine Block • Piston 4

Source: Mahle / piston ; VAW ; MTZ

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1.1.1 Piston

Pistons for gasoline and Diesel engines Pistons convert the thermal energy into mechanical work. The functions of the pistons are •

to transmit the gas forces via the connecting rod to the crank shaft

•

in conjunction with the piston rings to seal gas from the combustion chamber to the crankcase and oil from the crankcase to the combustion chamber.

•

to transmit the absorbed combustion heat to the cylinder liner and to the cooling oil.

Various combustion engines with aluminium pistons Source : F. Rösch

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Operating conditions Literature: - Röhrle, M. D.: Pistons for Internal Combustion Engines, Verlag Moderne Industrie, 1995 - Junker, H.and Ißler, W.J.: Kolben für hochbelastete Dieselmotoren mit Direkteinspritzung, Technische Information Mahle GmbH Stuttgart Mechanical loads result from • pressures in the combustion chamber - up to 75 bar in gasoline engines - up to 110 bar in naturally aspirated Diesel engines - up to 180 bar (and more) for supercharged Diesel engines • inertia forces caused by extremely high acceleration during reciprocating motion of pistons at speeds - up to 17 m/sec in automotive gasoline engines and - up to 22 m/sec in racing engines Mechanical loads are superimposed by thermal stresses which are primarily generated by high temperature gradients on the piston top.

Important piston terms Source: M. Röhrle. Mahle, 1995 Thermal loads resulting from combustion are generated by peak gas temperatures in the combustion chamber 1800 - 2600°C depending on type of engine, fuel, gas exchange, compression, fuel/gas ratio. Exhaust gases have temperatures between 500 and 800 °C. Combustion heat is transferred to the chamber walls and piston top primarily by convection. The heat is dissipated by the water cooling of the chamber walls and by the oil cooling of the piston. A large share of the heat absorbed by the piston top is transferred by the piston ring belt area. The remainder is essentially removed by the oil lubricant impinging on the underside of the piston. Resulting temperature profiles of the piston, see figure.

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Operating temperatures in automotive engines under full load Source: M. Röhrle, Mahle GmbH, 1995

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Piston materials Links: - AAM – Products – 6 Cast alloys and products > Alloys > Typical application areas) Literature: - Aluminium Taschenbuch, 15. Auflage, Dezember 1997, Band 3, Aluminium Verlag Düsseldorf (ISBN 3-87017-243-6) - Röhrle, M. D.: Pistons for Internal Combustion Engines, Verlag Moderne Industrie, 1995 Today almost all automotive pistons are made out of special aluminium piston alloys, see tabled property data on the following pages. The standard piston alloy is an eutectic Al12%Si alloy containing in addition approx. 1% each of Cu, Ni and Mg. Hypereutectic alloys with 18 and 24% Si provide lower thermal expansion and wear, but have lower strength. The majority of pistons are produced by gravity die casting. Forged pistons from eutectic and hypereutectic alloys exhibit higher strength and are used in high performance engines. Pistons with Al2O3 fiber reinforced bottoms are produced by squeeze casting and used mainly in truck diesel engines.

Source: F. Rösch, Alcan

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Mechanical properties of piston alloys at various temperatures Source: F. Rösch

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Physical properties of piston alloys Source: F. Rösch

Microstructure of a eutectic piston alloy Source : M. Röhrle, Mahle GmbH, Stuttgart

Microstructure of a hypereutectic piston alloy Source : M. Röhrle, Mahle GmbH, Stuttgart Microstructures of piston alloys with eutectic (above) and hypereutectic (below) compositions. Magnification approx. 100 times

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Design considerations for automotive pistons Literature: - Röhrle, M. D.: Pistons for Internal Combustion Engines, Verlag Moderne Industrie, 1995 Monometal pistons without cast-in parts (steel control struts and/or ring carriers) are used today only in lowperformance engines with cast iron engine blocks due to the larger clearances needed on account of the difference in thermal expansion between cast iron and aluminium. In aluminium engine blocks this causes no problem, but either piston or cylinder surface need to be protected by a wear resistant coating (chromium plating or chemical nickel deposit or tin-plated iron layer).

Source: M. Röhrle, Mahle GmbH Pistons with cast-in control elements When used in cast-iron engine blocks the thermal expansion of aluminium pistons is controlled by cast-in steel struts in the pin boss areas. During engine operation undesired thermal expansions are thereby avoided and the advantages of small clearances can be fully utilized.

Source: M. Röhrle, Mahle GmbH Pistons for automotive Diesel engines Automotive Diesel engines with pre-chamber, swirl chamber or direct injection operate under higher gas pressures and temperatures compared with gasoline engines. This increases the loads on the first ring groove, which is strengthened by a Niresist ring carrier in standard 12

designs. The even higher loads in supercharged Diesel engines are reduced by efficient cooling through a cast-in cooling gallery.

Source: M. Röhrle, Mahle GmbH

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1.1.2 Cylinder block

Introduction Literature: - Köhler, E.: Verbrennungsmotoren: Motormechanik, Berechnung und Auslegung des Hubkolbenmotors. Braunschweig, Wiesbaden: Vieweg, 1998. ATZ-MTZ-Fachbuch, ISBN 3528-03108-5 — Chapter 4.5 - Menne, R.J. and Rechs, M.: Optimierte Prozesse für die Großserie (Reduzierte Entwicklungszeiten bei Verbrennungsmotoren). Berlin: Springer, 1999 Using aluminium casting alloys for the production of cylinder blocks has several benefits such as weight savings and a better thermal conductivity compared to grey cast iron. Bearing in mind that most of the cylinder heads are also made from aluminium, compatibility problems between grey cast iron and Al can be overcome by the use of a similar material. However, designing aluminium castings for engine applications requires knowledge about the material and the manufacturing process, which will be described in this chapter. This chapter contains the following aspects, which have to be considered for the application of aluminium blocks. Requirements cylinder blocks Comparison Al/grey iron Design features Alloys and heat treatment Applicable casting processes Examples - Ford Zetec - PSA 2.0L HPI - Smart (HPDC)

P. 2 P. 3 PP. 4-9 PP. 10-11 P. 12 P. 13 P. 14 P. 15

2L HPI gasoline block, PSA

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Requirements for aluminium cylinder blocks - Thermal conductivity Modern aluminium engine blocks "see" temperatures of 150°C in crank-shaft bearings up to 200°C in the inter-bore region, where the high thermal conductivity of Al cast alloys leads to an efficient heat flow into the coolant. - Strength at elevated temperatures Static strength up to 150°C (oil temperature) is required mainly in the joint face due to the load of the head bolts and in bearing saddles to withstand the forces coming from the crankshaft rotation and the thermal expansion of the engine block. - Strength at room temperature and hardness Strength at RT is needed for assembly, whereas a minimum hardness of the Al alloy is necessary to ascertain good machinability, depending on machining parameters. - Fatigue strength During engine operation, parts are exposed to the oil temperature (150°C) as well as to cyclic tensile stress. Therefore, fatigue data are needed for these conditions.

Fatigue testing Samples from main bearing, R = 0.05; T = 150 °C; 50 Hz Source: VAW

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Competition between aluminium and grey iron Substitution process After an almost complete replacement of grey iron by aluminium as material for cylinder heads, this substitution takes now place for engine blocks as well. Driving force are achievable weight savings up to 50 % when using aluminium, even if the lower strength of Al compared to grey cast iron is considered. Concerning thermal expansion, the use of similar materials for head and block avoids high thermal stresses during the start-up and after the stop of the engine.

Grey cast iron and aluminium HPDC engine blocks

Production numbers of engine blocks in western Europe (grey iron and Al-cast alloys) Source: VAW AG, Marketing Systems

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Design features Links: - AAM – Applications – 1 Power train > Engine > Cylinder linings Literature: - Menne, R.J. and Rechs, M.: Optimierte Prozesse für die Großserie (Reduzierte Entwicklungszeiten bei Verbrennungsmotoren). Berlin: Springer, 1999 — Chapter 3.1.6 Design features to be considered (bolt expressions are explained in more detail in design considerations underneath) Basic Structure When looking at existing engine block solutions a broad variety of designs can be found. The principal concepts are described by the basic structure of the engine block such as deep-skirt, short-skirt, with and without bed-plate or ladder-frame. Another characteristic is the array of the cylinders. Bolting The connection between block and head can be done either conventionally or by the through-bolt technique. Joint Face Here, the open deck and the closed deck concepts of a cylinder block have to be considered because they are determining the applicable casting process. Add-on parts and pre-cast features Depending on casting process, additions such as water pump housings and flanges can be incorporated into the main casting. Furthermore, bolt bores and oil channels can be directly cast. Cast-in inserts In the case of very high loaded application of an engine block (i.e. direct injection diesel engines), critical areas of the casting can be reinforced by high-strength materials such as grey iron inserts. Running surfaces Due to the non-sufficient tribological properties of cast aluminium, the cylinder bores of an aluminium engine block have to consist of another wear resistant cast-in material or the cast alloy has to be coated, laser-treated or alloyed in order to achieve a wear resistant surface. This will be treated in more detail under "Cylinder linings".

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Block design variants Literature: - Menne, R.J. and Rechs, M.: Optimierte Prozesse für die Großserie (Reduzierte Entwicklungszeiten bei Verbrennungsmotoren). Berlin: Springer, 1999 — Page 59 - Metzner, F., u.a.: The New W Engines from Volkswagen with 8 and 12 Cylinders, MTZ 62, 2001, No.4, p.280-290 - Tielkes, U., u.a.: Die neue Ottomotoren-Generation Duratec HE von Ford, MTZ 61, 2000, No.10, p.646-654

Different possibilities of cylinder array Source: Metzner u.a., VW/MTZ Cylinder array For small engines in high volume production the inline array up to 6 cylinders is the most common concept. Due to space restrictions, the V - and now also the W concept - is used for compact engines with 4 or more cylinders.

Design variants bottom end Source: Menne, Rechs

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Ladder frame / bearing beam, High pressure die casting Source: Tielkes u.a. Ford/MTZ Design variants bottom-end The simple design consists of a short-skirt block with single crankshaft bearings and a steel sheet oil pan, which leads to low stiffness and bad acoustic behaviour. Higher stiffness can be achieved by using a short-skirt design with a bed plate or a deep-skirt design using a ladder frame. These parts have to be cast separately which leads to higher costs for production and assembly. Concerning assembly, tightness of the whole system against oil leakage is another important factor.

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Bolting concepts Literature: - Menne, R.J. and Rechs, M.: Optimierte Prozesse für die Großserie (Reduzierte Entwicklungszeiten bei Verbrennungsmotoren). Berlin: Springer, 1999 — Page 54

V6 gasoline engine block with grey iron bearing caps Conventional bolting In this case, head and grey iron bearings are bolted directly to the block resulting in high stresses in the vicinity of the thread and the bolt head. This concept reaches its limits when considering high loaded direct injection diesel engines.

Volkswagen Lupo Block, 1.2L, trhough-bolt concept Through-Bolt Concept In order to prevent high tensile stresses in the engine block, main bearings and cylinder head can be connected directly by long bolts which penetrate the whole block and head, thus setting them under compressive stress only. Drawback is the more complicated assembly because bearing caps and cylinder head are not any more independent of each other, i.e. the final assembly of bearings and heads has to be carried out at the same time. This problem can be solved by screwing in the through-bolts so that head and bearing caps can be mounted separately while maintaining the load-bearing benefit of the through-bolt.

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Open- and Closed-Deck concepts Links: - AAM – Manufacturing – 1 Casting methods The interface between block and head (joint face) not only has to seal the combustion chamber but also has to provide space for oil and water channels while maintaining stiffness against the combustion pressure and the forces coming from the head-block assembly. Open deck In the open deck concept the water jacket is completely open towards the joint face. This has the disadvantage of relatively low stiffness, but on the other hand, this is the only way to realize the water jacket in the high-pressure-die-casting process with a permanent and retractable steel-core. The weaker structure may lead to higher bore distortion and has to be compensated by increased wall thickness or an appropriate liner concept. Above a certain specific power the open deck concept is difficult to maintain. Closed deck In this concept, the water jackets of the block and the head are only connected by sufficiently big openings in the joint face leading to a much higher stiffness of the structure. In this case, of course, the casting has to be produced by using sand cores for the water jacket i.e. with the sand casting, gravity die-casting or lost foam process.

Audi-Block 1.6L, High pressure die casting, open deck concept Source: VAW

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Pre-cast features and add-on parts Links: - AAM – Manufacturing – 1 Casting methods > Core package casting

Oil gallery core for Ford Zetec 1.6L Block Source: VAW

Oil gallery Ford Zetec 1.6L Block Source: VAW Pre-cast features While pre-casting of bolt bores is a standard technique today, the casting of very tiny features such as oil channels is now possible with advanced casting processes e.g. CPS or lost foam.

Detail of the Ford Zetec Block Source: VAW

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Side view of a Ford Zetec Block with pre-cast water pump housing and oil filter flange Source: VAW Add-on parts By means of high-precision sand cores, a variety of parts and flanges can be incorporated into one single casting. Here, issues like dimensional stability and accuracy of positioning have to be addressed. Higher costs for using an advanced casting process are easily compensated by savings in the area of machining and assembly.

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Cast-in inserts Cast iron inserts for bearings Most aluminium cast alloys are not suitable for bearing application for two reasons: Firstly, the wear resistance is not sufficient to withstand the sliding wear of the crankshaft. Secondly, the higher thermal expansion compared to grey iron may lead to an untolerable increase of the gap between crankshaft and bearing which is strongly influencing the required oil pressure. Cast iron inserts are often placed into the part after machining, but they can also be directly cast in resulting in reduced costs for machining and handling.

Ladder frame with casting grey iron bearings, High pressure die casting Source: Porsche Cast iron liners Grey iron cylinder linings can also be considered as cast-in inserts. Again, wear resistance is the main driving force. Problems concerning the bonding between liner and matrix material are discussed in more detail in the chapter "cylinder linings"

Ford Zetec Block with grey iron linings Source: VAW

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Criteria for alloy selection Links: - AAM – Applications – 1 Power train > Engine > Cylinder linings - AAM – Materials – 3 Designation system > Cast alloys - AAM – Products – 6 Cast alloys and products Choosing a casting alloy for an engine block requires the consideration of various criteria. Please refer also to the chapter "Cast alloys & Products". The most common alloys are presented in the next screen. Strength In the development phase of an engine block the design is strongly coupled to the strength of the alloy with respect to wall thicknesses etc. High strength alloys may have drawbacks such as high price (e.g. AlSi7Mg), poor castability (e.g. AlCu4Ti) and insufficient high temperature performance. Price Due to cost aspects, almost all aluminium engine blocks are cast from secondary alloys (AlSi8Cu3, AlSi6Cu4). However, upcoming requirements for a certain ductility could give rise to the use of alloys with reduced impurity content close to primary cast alloys. Castability Castability is generally improved with increased Si content while Cu, which is needed for high temperature strength is negatively effecting the feeding behaviour. In high pressure die casting alloys certain iron content is necessary to prevent sticking to the die. On the other hand, iron additions reduce the mechanical properties. Other benefits In some cases other requirements may be more important than costs and castability. In order to avoid the use of weight-increasing cast iron liners or costly coating solutions for the cylinder surface, some V8 engines are produced completely from hypereutectic alloys (AlSi17Cu4) which directly provide a wear-resistant cylinder lining (see link). For racing engines other high strength alloys (e.g. AlCu4Ti) could come into consideration.

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Alloys: Composition and heat treatment Links: - AAM – Manufacturing – 1 Casting methods > Gravity die casting - AAM – Manufacturing – 1 Casting methods > High pressure die casting - AAM – Manufacturing – 1 Casting methods > Low pressure die casting - AAM – Products – 6 Cast alloys and products > Alloys > Foundry alloys - AAM – Materials – 3 Designation system > Cast alloys - AAM – Applications – 1 Power train > Engine > Cylinder linings

The secondary alloys AlSi8Cu3 and AlSi6Cu4 are similar to the American standard alloys A380.2 and A319 respectively. They are mostly used for engine blocks produced in the gravity casting processes. The as-cast (F) condition and the T4 and T5 heat treatments are commonly used. Almost all high pressure die cast engine blocks are produced with the very common alloy AlSi9Cu3(Fe). Except moderate annealing for reduction of residual stresses usually no further heat treatment can be applied. Engine blocks cast from the alloys AlSi7Mg0,3 and AlSi7Mg achieve very high strength and elongation values at room temperature when a T6 heat treatment is applied. Attention has to be paid to residual stresses resulting from quenching during T6 treatment. Due to limited contents of impurity elements such as Fe, Mn, Cu, and Ni the price is significantly higher compared to the mentioned secondary alloys. Blocks from hypereutectic AlSi alloys (AlSi17Cu4) are usually produced with low pressure die casting and are subsequently T6 treated. The primary alloy is more expensive compared to the standard secondary alloys.

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Applicable casting processes Links: - AAM – Manufacturing – 1 Casting methods High pressure die casting (HPDC) For the majority of the currently produced aluminium engine blocks this process is applied. Issues to be considered are: • High productivity if the production volume is big enough to ensure pay-back of the high investment for the tooling. • The complexity of the block is limited due to the fact that no sand cores can be used. No undercuts are possible and hence, only the open-deck variant can be produced. • Due to very turbulent mould filling, a certain amount of casting defects is unavoidable resulting in relatively low mechanical properties and making a T5 and T6 treatments impossible Gravity die casting (GDC) Compared to the HPDC process, the complexity can be increased by the use of sand cores. The use of water cooling and feeders results in directional solidification and hence sound castings with a low amount of defects. Filling can be further improved using low pressure filling or the Rotacast®-Process. With these benefits together with the possibility of a T5 or T6 heat treatment the achievable mechanical properties are significantly higher than with the HPDC process. Sand casting processes The highest degree of complexity can be achieved with advanced sand casting processes (e.g. CPS). By this means, water pump housing, oil filter flanges and oil galleries can be integrated. Directional solidification and mech. properties can be enhanced by using cooling chills. Lost foam process (LFC) allows very complex geometries while cast-in liners, additional chilling and porosity problems are not yet solved issues. Porosity problems can however largely be solved by Pressurised LFC.

Schematic diagram showing the economic relationship between complexity, production volume and casting process Source: VAW 27

Example: Ford Zetec SE – CPS® Process Links: - AAM – Manufacturing – 1 Casting methods > Core package casting Literature: - Wölfle, M., Grünert, T., Kuske, A., Königs, M. und Warren G.: Die weiterentwickelten 16VZetec-E-Motoren, Sonderausgabe ATZ/MTZ: Ford Focus, Jahrgang 1999 - Wölfle, M., Tielkes, U., Grünert, T., Hohage, C., Warren, G.: Die neuen 1,4l- und 1,6l-ZetecSE Motoren mit Vierventiltechnik für den Ford Focus, Sonderausgabe ATZ/MTZ: Ford Focus Jahrgang 1999 - Smetan, H.: Kernpaketverfahren im Aluminiummotorenguss, MTZ 61, 2000, No.10, P.712715 Ford Zetec SE Displacement: 1.250-1.700 cm3 Power: 55 – 92 kW Weights: - Casting with feeders: 32 kg - Cast iron liners: 6.8 kg - Pre-machined (OP10): 20.2 kg Casting process: CPS with roll-over Alloy: EN-AC-AlSi8Cu3 Production volume: 400.000 p/a No. of cores: 23 Integrated features: oil gallery and oil channels for main bearings, water pump housing, oil filter flange Remarks This Zetec block, designed as closed-deck and deep-skirt block, is the first high volume engine block production using the CPS® (core package system), where the whole mould consists of cold-box cores. The casting is filled upside-down using the contact pouring process and later, after roll-over, fed via the joint face with no additional cooling applied. The max. capacity of one casting line is 160 parts/hour. The grey iron liners are assembled into the mould, then preheated and cast in, the positioning range being ± 0.3 mm. Decoring and T5 heat treatment take place simultaneously. Pre-machining is done to the "OP10"-level on site

Block Ford Zetec SE 1.25L, core package process, VAW alucast GmbH

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Example: PSA 2.0L HPI (HPDC) Links: - AAM – Manufacturing – 1 Casting methods > High pressure die castings PSA 2.0L HPI engine (16V) Type: gasoline, direct injection Displacement: 2.000 cm3 Power: 105 kW Design type: open deck, deep skirt Weights: - As-cast with grey iron liners: 21 kg - Machined with grey iron liners: 18 kg - Liners (machined): 2.5 kg Dimensions (LxWxH): 433mm x 230mm x 218mm Casting process: HPDC Production volume: > 200.000 parts/year Alloy: EN-AC-AlSi9Cu3(Fe) Heat treatment: None

2L HPI gasoline block, PSA

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Example: Lupo Block 1.2L Links: - AAM – Manufacturing – 1 Casting methods > Gravity die castings Literature: - Winterkorn, M.; Bohne, P.: Das Drei-Liter-Auto von Volkswagen - der Lupo 3L-TDI, Part 1: ATZ 101, 1999, No.6, P.390-401, Part 2: ATZ 101, 1999, No.7/8, P.562-570 - Ermisch, N., Scheliga, W.: Der Rekord- Lupo, 25 Jahre VW Dieselmotoren, Sonderausgabe der MTZ 5/ 2001 VW Lupo 1,2L Diesel (3l/100km) Displacement: Power: Weights: - Casting w. feeders: - Cast iron liners: - Ready to build-in: Casting process: Alloy: Production volume: No. of cores: Integrated features:

1.200 cm3 45 kW 33.4 kg 3.0 kg 15.95 kg Gravity die casting EN-AC-AlSi8Cu3 12 000 parts/year 10 water pump housing, oil filter flange

Remarks This cylinder block for the "3-Liter-Lupo", designed as closed-deck and deep-skirt block, has the through-bolt concept, i.e. there are no threads in the block or head but the two parts are held together with steel bolts going through both parts. This concept reduces cylinder deformations and gives an optimum force line through the cylinder head gasket into the cylinder head. The grey iron liners with rough outer surface are cast in directly. The four grey iron main bearing caps reduce the main bearing clearance at operating temperatures.

3-cyl. 1.2 L VW-Lupo block Source: ATZ, VW

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1.1.3 Cylinder linings

Hypereutectic AlSi-Liner (SILITEC®, PEAK)

Introduction The reduction of friction losses in automotive engines is one of the biggest potentials when looking for possibilities to cut down fuel consumption. In the tribological system "Cylinderpiston-piston ring" the material, the structure and the quality of the running surface in the cylinder bore of an engine block plays a crucial role. Grey iron as a more and more disappearing engine block material provides a good tribological behaviour itself. Switching to cast aluminium alloys which - except for the hypereutectic AlSi-alloys - are not sufficiently wear resistant, and require the development of new liner solutions and tribological systems. This chapter contains the following aspects, which have to be considered for the application of cylinder linings in aluminium engine blocks: • Requirements cylinder linings • Liner technologies • Examples and current developments - Grey iron, cast-in - Hypereutectic engine block - LOKASIL® - SILITEC®, cast-in (DC V6) - GOEDEL® and HYBRID-Liner - Laser alloying (TRIBOSIL®) - Others - Honing of hypereutectic AlSi

P. 2 P. 4 P. 6 P. 7 P. 8 P. 10 P. 11 P. 12 P. 13 P. 14

V6 engine (DaimlerChrysler) with cast-in SILITEC®-Liners (PEAK)

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Boxer engine block (Porsche) with LOKASIL®-Lining (Kolbenschmidt)

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Requirements Friction and wear The principal task of cylinder linings is to provide an appropriate tribological partner for the moving piston and piston rings in the engine block. Low friction and good wear resistance of the lining material towards the piston ring material are important, the latter being in general grey cast iron, steel, or a coated hybrid solution. Operation without lubrication Usually, an oil film supplied from the oil sump ensures lubrication for the tribological system. However, in case of lack of oil, the oil film has to be maintained to guarantee the engine operation for a certain time period. Thermal conductivity and contact Thermal conductivity and contact A good thermal conductivity is also needed in order to withdraw the combustion heat and to keep the surface temperature low. However, the heat extraction can only work properly, if an optimum contact between the liner and the surrounding casting material is achieved. If no metallic, but only a mechanical bonding can be realised, at least a stable and constant gap is required to avoid loosening of the liner. Wall thickness Regarding the trend towards steadily decreasing interbore spacings (< 5mm), the thickness of cast-in or pressed-in liners be-comes increasingly critical. Consequently, solutions where the bulk material is coated or alloyed come into consideration. Compatibility Another point to look at is the compatibility of the thermal expansion of the liner and the piston material which influences the gap between piston rings and liner and hence the blow-by and the oil consumption of the engine. Further targets in the development of cylinder linings are: • low weight, e.g. aluminium based liner solutions or coatings • environmentally friendly production process, especially if coatings are applied • good recycling capability which can be difficult with cast iron or fibre reinforced liners • low cost

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Technologies – Overview Before the substitution process by aluminium, engine blocks were mainly produced in (monolithic) grey iron which itself provides an excellent tribological behaviour. Transferred to aluminium, this concept only works with relatively costly hypereutectic AlSi alloys which, by means of primary silicon particles, provide a wear resistant surface. An obvious solution was then to use the well-known grey iron as liner material to be castin or pressed-in into an engine block produced from a low-cost casting alloy. In this heterogeneous concept draw-backs are high weight, low thermal conductivity and lacking of compatibility and bonding with the surrounding cast material. These problems are tried to be addressed by use of hypereutectic AlSi-liners or Al-coated grey iron liners. The most convenient solution would be a quasi-monolithic block with a running surface being locally created by coating or alloying. New developments like plasma coating and local enrichment of primary silicon are aiming into this direction. The different technologies will be explained in more detail in the following screens.

Cylinder lining technologies for aluminium engine blocks Source: Kolbenschmidt

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Comparison of liner technologies The shown table is an attempt to compare the different liner technologies which are currently in series production or under development. "Thermal behaviour" takes into account both, the problem of different thermal expansion coefficients and the differences in the contact quality between the tribological surface and the surrounding cast aluminium. "Costs" are highly dependant on the current process development and may therefore change rapidly. "Recycling/Environment" considers the environmental impact of the production process and eventual arising difficulties during recycling due to the combination of different materials

Comparison of different liner technologies Source: VAW

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Liner solution: Heterogeneous concept Grey iron cast-in Grey iron has excellent tribological properties due to its microstructure consisting of ferrite and lamellar graphite, the latter being a good dry lubricant. Grey iron liner can be pressed in after pre-machining of the engine block which is more expensive than the direct castingin of the liner using conventional gravity or high pressure die casting processes. Contact quality: By casting-in of grey iron liners no metallic bonding between the liner material and the surrounding Al cast alloy can be achieved, but only a mechanical contact. The quality of the mechanical contact depends on the casting parameters and the surface conditions (e.g. special rough outer as-cast or machined surfaces). Gap formation: The size of the always existing gap between the grey iron liner and the surrounding casting alloy may be altered by eventual heat treatments or by the operation at high temperatures leading to an uncontrolled local reduction of the heat transfer coefficients which is difficult to predict. In the design phase of an engine block, this has to be taken into account in the thermal and stress calculations.

Grey iron liner with rough outer surface Source: Kolbenschmidt

Grey iron liner with machined surface Source: Kolbenschmidt

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Cut through cast-in grey iron liner for Diesel application Source: VAW

Engine block with cast-in grey iron liners Source : VAW

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Liner solution: Monolithic concept (ALUSIL®) Hypereutectic AlSi alloys (AlSi17Cu4Mg, e.g. ALUSIL®) can be used to produce monolithic engine blocks. During solidification, primary Si particles are precipitated which – after an appropriate machining and honing procedure – directly provide the tribological surface for engine operation. Advantages are: • Low mass (no grey iron liner) • Short component length (no liner, minimum interbore spacing: 4 mm) • Good thermal conductivity (no gap) • Low distortion • Small assembly tolerances for pistons (similar therm. exp. coefficient compared to piston material). A great share of the big V-engines (>=8 cylinders) was made from this hypereutectic alloy (currently a change has to be observed). However, according to the state-of-the-art, this alloy can only be cast using the LPDC process due to the following restrictions: • Ηigh pouring temperature • Great solidification interval • Segregation and inhomogeneous precipitation of primary silicon Besides their higher price, hypereutectic (primary) alloys are therefore only used in low and medium volume series and not in the mass market of straight 4 cyl. engines.

V8 gasoline engine (BMW M5) made from ALUSIL® (Kolbenschmidt)

W12 gasoline engine (VW) made from ALUSIL® (Kolbenschmidt)

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Liner solution: Quasi-Monolithic concept LOKASIL® In order to avoid the disadvantages arising from the use of hypereutectic alloys for the entire engine block (costs for material and LPDC process), the LOKASIL®-concept locally provides a hypereutectic microstructure where it is needed (quasi-monolithic concept). Porous preforms with 25 vol. % of Si particles (30 – 70 µm) are produced with the gelfreeze-casting process, sintered subsequently and then infiltrated with an inexpensive secondary casting alloy using the squeeze casting process which provides both, slow mould filling and high pressure for optimum infiltration.

LOKASIL® (I + II): preform and composite structure Source: KS Aluminium-Technologie The tribological bore surface is created similarly to the other hypereutectic solutions (ALUSIL®, SILITEC®) by machining, honing and mechanical recessing of the Al-matrix.

6 cyl. Boxer engine with LOKASIL® bore surface (Porsche, KS AluminiumTechnologie)

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6 cyl. Boxer engine with LOKASIL® bore surface (Porsche, KS AluminiumTechnologie)

6 cyl. Boxer engine with LOKASIL® bore surface (Porsche, KS AluminiumTechnologie) Attempts are currently made to achieve good infiltration with the high productive HPDC process as well.

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Liner solution: Heterogeneous concept SILITEC® Links: - AAM – Manufacturing – 1 Casting methods > High pressure die castings As an alternative to the relatively expensive monolithic engine block made from AlSi17Cu4, hypereutectic liners can be cast-in via the high pressure die casting process using lower cost secondary AlSiCu alloys. The hypereutectic liners are produced by spray compaction and subsequent extrusion (SILITEC®). This process is claimed to be more economic than the production (low pressure die casting) of a monolithic hypereutectic block. Furthermore, the achieved mean size of the primary silicon particles is much smaller compared to the structure of permanent mould castings leading to excellent tribological properties of the liner surface after a special honing process (s. page 13). Metallic bonding between liner and cast alloy is achieved at about 50% of the contact surface resulting in low distortion and dimensional stability. The application of this liner material using gravity casting processes is currently under development

Ultrasonic scan showing areas of good (blue) and bad (red) metallic contact (PEAK/DaimlerChrysler)

Micrograph showing as-cast microstructure of hypereutectic AlSi17Cu4

V6 gasoline engine block (DaimlerChrysler) with SILITEC®-Liners (PEAK)

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Micrograph showing interface between SILITEC®-Liner and casting (PEAK)

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Liner solution: Heterogeneous concept HYBRID, GOEDEL® The idea of this concept is to keep the well-known tribological properties of grey iron and – at the same time – to solve the problems of lack of contact and gap formation, which lead to problems with heat extraction and dimensional stability in current grey iron liner solutions. GOEDEL® (in development) In this concept, an iron layer is thermally sprayed on a cylindrical base geometry followed by a layer of an appropriate AlSi alloy, creating a well defined and gap-free transition from iron to aluminium. The micro-roughness of the outer surface leads to a real metallic bonding during casting-in of the liner, especially when the HPDC process is applied. Trials with conventional gravity casting processes are promising. The benefit of the metallic bonding is a better heat flow and a higher stiffness (+30%) of the liner-block compound resulting in a lower bore distortion and thus in lower blow-by, oil consumption and wear. The multi-layer can be tailored according to the needs of tribology and castability. HYBRID (in series production) Compared to GOEDEL, this concept uses a thin-walled grey iron tube instead of the sprayed iron layer which is cheaper in production. The HYBRID-Liner is in series production in a four cylinder gasoline engine produced with the HPDC process.

Four cylinder gasoline engine with HYBRID-Liner (BMW)

Micrograph of the transition zone between thermal sprayed multi-layer and casting alloy (GOEDEL®, Federal Mogul)

Outer surface structure (SEM image) of the Al alloy layer of the GOEDEL® or HYBRIDLiner (Federal Mogul)

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Liner solution: Quasi-Monolithic Concept TRIBOSIL® The ideal solution is a monolithic all-aluminium block made of easy-to-cast, cost-efficient aluminium alloys, whereby high stability and high heat dissipation are achieved in the interbore area. Liner surfaces must display the following properties: • High stability at high ignition pressures • Corrosion resistance • Good friction and wear behaviour This can be achieved with the TRIBOSIL®-concept where liner surfaces are created by means of laser alloying of gravity cast engine blocks made from conventional secondary casting alloys. Using this technique, the original aluminium cast matrix is locally enriched with silicon to create a hypereutectic surface structure. In this process, a moving laser beam locally melts the cylinder surface and silicon powder is injected simultaneously into the melt pool which describes a helical movement. Layers with a thickness of about 600 µm are achieved revealing an optimum structure and distribution of primary silicon particles resulting in high hardness and excellent tribological properties after appropriate honing. The TRIBOSIL® liner surfaces, not being in series production yet, have passed test programmes in prototype engines and are currently tested at different car manufacturers.

Laser alloying of a cylinder bore (schematic) (VAW)

Cut through the wall of a laser alloyed cylinder (VAW)

Hypereutectic layer with gap-free transition zone towards the matrix alloy (AlSi9Cu3) (VAW)

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Structure of the laser-alloyed surface after recessing of the matrix by means of honing (VAW)

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Other liner solutions Grey iron liner with rough outer surface This special kind of the conventional grey iron liner is used to achieve a better mechanical contact when the liner is cast in. No metallic bonding is achieved, but an improved mechanical contact due to the undercuts at the interface grey iron/ cast alloy.

Grey iron liner with rough outer surface (Mahle, picture: Kolbenschmidt)

Micrograph showing metall contact between cast alloy and grey iron liner with rough surface (VAW) NIKASIL®, GALNICAL® This galvanic coating process of a Ni-SiC-dispersion layer, which requires a very low porosity in the cast surface, is in series production. However, environmental issues due to the presence of nickel and problems with corrosion of the galvanic layer due to sulphur-containing fuels have reduced the application of this process significantly. Surface Layer • Nickel matrix • 10 % SiC particles • Size 1-3 µm • Hardn. 610 HV • Cast alloy AlSi9Cu3 Plasma coating (ROTAPLASMA®) The development of this process has proceeded so far that first gasoline engines are now in series production with plasma coated cylinder surfaces. Good results were achieved using Fe as a coating material. Furthermore, FeO and Fe3O4 can be dispersed in the layer acting as a solid lubricant such as graphite in grey iron

Micrograph showing Ni-SiC-dispersion layer (Kolbenschmidt)

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Micrograph showing plasma coating layer (Sulzer-Metco)

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Cylinder surface treatment – Honing of hypereutectic AlSi surfaces The hypereutectic AlSi (ALUSIL®, SILITEC®, TRIBOSIL®) technologies provide various microstructures regarding the hard primary Si particles which are the tribological partner for piston and piston rings. Requirements like low friction, stability and lubrication under dry sliding conditions can only be met with an appropriate surface structure. This structure is created by special honing which is different from conventional honing of grey iron. Honing of hypereutectic AlSi surfaces usually requires the following steps: The pre-honing step provides a correction of the cylinder shape and almost removes the damaged microstructure resulting from pre-machining. During the following base-honing step, the final surface shape of the primary silicon particles is created. Subsequently, a recessing of the Al-matrix and an exposure of the Si particles is carried out providing both hard particles to withstand the sliding wear of the piston and to provide oil reservoirs for good distribution of the lubricant. For this honing step special tools are used with the abrasive particles being smaller than the Si particles and embedded in a soft matrix. Compared to recessing by etching, this technique provides smooth particle edges which prevent break-outs.

Honing steps for hypereutectic AlSi cylinder surfaces (Nagel)

SEM-Micrograph showing the final surface after honing with recessed Al-Matrix and exposed Si particles (Gehring)

Image from white light interference microscope showing the topography of the final cylinder surface (VAW)

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1.1.4 Cylinder head

Opel cylinder head 4 valves, 3 cylinders, gravity die casting Source: VAW

Introduction In Europe, grey iron cylinder heads has been almost completely replaced by cast aluminium alloys during the past 20 years. In this application, the main advantage of aluminium, besides its lower density, is the excellent thermal conductivity, which allows the combustion heat to be extracted more rapidly compared to grey iron. Compatibility problems with the block become more and more obsolete as the market share of aluminium blocks is steadily growing. As a result of the permanent increase of combustion pressures and temperatures, the potential of the common cylinder head alloys is almost fully exploited, demanding for sophisticated casting processes and newly developed or optimised casting alloys. This chapter contains the following aspects, which have to be considered for the application of Al cylinder heads: Requirements cylinder heads P. 2 Design features P. 4 Used alloys (criteria) P. 6 Alloys and heat treatment P. 7 Applicable casting processes P. 8 Examples - PSA Diesel HDI (grav. die) P. 9 - BMW M47 Diesel (grav. die) P. 10 - BMW gasoline (rotacast®) P. 11 - Isuzu Diesel (rotacast®) P. 12

Opel cylinder head 4 valves, 3 cylinders, gravity die casting 49

Source: VAW

Requirements – Thermal conductivity vs. strength Literature: - Feikus, F.J.: Optimization of Al-Si Cast Alloys for Cylinder Head Applications; AFS Transactions 105, 1997, p.225-231 - Loeprecht, M.; Maassen, F.: Life Time Prediction (Low-Cycle-Fatigue) of a High Thermal and Mechanical Loaded Cast Aluminum Cylinder Head. SIA Congress: What challenges for the diesel engine of the year 2000 and beyond?, Paris, 11 May 2000 For thermodynamic reasons, high combustion temperatures require efficient cooling and therefore high thermal conductivity of the head material. On the other hand, high strength and sufficiently high hardness at room temperature are necessary for machining and assembly. Furthermore, high strength and creep resistance at elevated temperatures (up to 250°C) are crucial to ensure that the block-head assembly withstand the combustion forces and the forces resulting from thermal expansion and contraction during service cycles without loosing tightness of the cylinder head gasket. As a matter of fact, any addition of alloying elements to aluminium for the purpose of increasing strength or creep resistance results in a decrease of thermal conductivity. Hence, a compromise between the two counteracting targets has to be found. Surface smoothness For the combustion process, the flow conditions of the incoming gas are of major importance. Consequently, great demands on surface smoothness of the inlet and outlet channels are made. The roughness of the flame deck surface has to be considered as well, because it represents notches for the initiation of fatigue cracks (s. next page)

Temperature distribution on the flame deck of a cylinder head Source: Loeprecht, Maassen

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Requirements for aluminium cylinder heads – High- and lowcycle fatigue Cylinder heads are exposed to high-cycle fatigue (HCF) due to the combustion cycles (10 to 20 millions) and to low-cycle fatigue (LCF) resulting from thermal expansion and contraction during start-up and engine stop (1 to 10 times a day). Critical HCF areas are on the water jacket side of the flame-deck wall because of the prevailing cyclic tensile stresses, while LCF may cause cracks in the valve bridge areas which are thin-walled and, at the same time, exposed to the highest temperatures within the cylinder head. LCF strength is partly related to the static strength at high temperatures which in turn is strongly influenced by alloy composition. However, HCF strength can only be slightly influenced by the alloy composition, whereas microstructure, porosity and surface quality are the dominating parameters. Creep strength is required in particular for the head gasket area.

Fatigue properties at 250 °C for different cylinder heads and alloys Source: VAW

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Design features Links: AAM – Applications – 1 Power train > Engine > Cylinder block > Block design variants Engine type Conventional engines with an „in-line" array of the cylinders have one cylinder head. Vengines generally need two cylinder heads, which may have identical or differing geometry. Provided that the angle between the two cylinder axis planes is not to big ( Overview of casting processes and their use in automotive applications Gravity die casting is worldwide the traditional casting process for cylinder heads. Depending on the position of the casting in the mould, the process allows a high cooling rate in the flame deck region resulting in a fine microstructure with low porosity, and hence in good mechanical properties. With the application of sand cores, very sophisticated and complex geometries of the water-jacket can be realised. Especially the latter requirements preclude the application of the high pressure die casting process. Rotacast® process, based on gravity die casting, provides even higher cooling rates in the flame deck area and at the same time a higher productivity due to a smaller volume of feeder and runner. Low pressure die casting provides similar benefits as the conventional gravity die casting process. Additionally there is nearly no return scrap (feeder etc.). However, due to the fact that the machinery is blocked during the entire solidification time, the total cycle time is relatively high, which in turn decreases productivity. Lost foam process. This emerging process is predestined for castings with very complicated and complex geometries which in fact is the case for water jackets in cylinder heads. Besides the need of perfect mastering of the process, the safe avoidance of porosity in important areas (flame deck) can be a problem, because the implementation of a local cooling is difficult.

BMW 4 cylinder head, gravity die casting Source: VAW

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Example: PSA 2.0L HDI – Gravity Die Casting PSA 2.0L HDI diesel cylinder head Type: Diesel, direct injection Displacement: 1.997 cm³ Power: 84 kW Weights: - machined with camshaft bearings: - without camshaft bearings: Dimensions (LxWxH): Casting process: Production volume: Alloy: Heat treatment:

11.6 kg 10.5 kg 455mmx165mmx164mm

Gravity die casting > 500.000 parts/year EN-AC-AlSi7Mg0.3 T6

PSA HDI diesel cylinder head Source: PSA

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Example: BMW 2.0L DI – Gravity Die Casting BMW 2.0L cylinder head Type: Diesel, direct injection Displacement: 2000 cm³ Power: 100, 110 kW Weights: - as cast: - machined: Dimensions (LxWxH):

--16,73 kg 490mmx320mmx135mm

Casting process: Production volume: Alloy: Heat treatment:

Gravity die casting 118.000 parts/year AlSi7MgCu0.5 T6

BMW DI diesel cylinder head Source: VAW

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Example: BMW 2,0l 4-Cylinder – Rotacast® BMW 4-cylinder head (Valvetronic) Type: gasoline, Valvetronic Displacement: 1600- 2000 cm³ Power: max. 105 kW Weights: - as cast: - machined: Dimensions (LxWxH):

20,50 kg 19,14 kg 520mmx300mmx155mm

Casting process: Production volume: Alloy: Heat treatment:

Rotacast® 170.000 parts/year EN-AC-AlSi8Cu3 F (as cast)

BMW 4-cylinder head (valvetronic) Source: VAW

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Example: Isuzu Diesel – Rotacast® Isuzu diesel cylinder head Type: Diesel, direct injection Displacement: 1700 cm³ Power: 55 kW Weights: as cast: machined: Dimensions (LxWxH):

10,52 kg 410mmx175mmx100mm

Casting process: Production volume: Alloy: Heat treatment:

Rotacast® 230.000 parts/year EN-AC-AlSi7Mg (LM25) T6

Isuzu Diesel 4-cylinder head Source: VAW

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1.2

Fuel system

Aluminium helps to meet targets of HC-emission laws New laws for carbon hydrate emission reduce the emission values of cars and their fuel systems. The time schedule for the introduction of the appropriate limits, LEV I and II (Low Emission Vehicle) and ZEV (Zero Emission Vehicle, only State of Califonia), in the US is shown in the graphic. Current plastic tank production technologies do not meet future fuel emission standards. As a metal, aluminium offers zero permeability for HC and excellent corrosion resistance against all relevant fuels. The high electrical conductivity, moreover, helps to avoid electrostatic sparking. Aluminium is, therefore, a choice material for components of the fuel system, e.g. fuel tank and fuel pipe, to meet the targets of the HC-emission laws.

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Future fuel systems need new materials technologies Links: - AAM – Manufacturing – 3 Forming > Semi-hot forming The graph (below) shows the average values for HC-emission for current cars and the contribution of the fuel system. Compared to the limiting values of LEV II and ZEV for the HC-emission of future cars it is clear that current materials technology for the fuel system needs to undergo significant changes. While the aluminium fuel filler pipe is already a standard component in several cars, the aluminium fuel tank is still in a state of development as described in subsequent chapters.

Current and future limits for HC-emissions of cars and their fuel system

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1.2.1 Fuel filler pipe

Fuel Filler Pipe Source: Krönert/Hydro

Product description Links: - AAM – Applications – 1 Power train > Liquid lines > Bending Product Description The aluminium fuel filler tube is an extrusion based tube bent and formed in order to increase the ability to flex and bend without leakage in case of car crash. The advantages of the aluminium tube beside low weight are the tightness for HC emissions as well as the high electrical conductivity, which is important to avoid static electricity and thus sparking. There is no significant cost difference compared to steel pipes. Alloy The alloy used is EN AW 6063, which is a highly extrudable alloy and can be extruded with thin wall. Typical Dimensions Diameter [D]: Wall thickness [WT]:

36…70 mm 1.5 mm

Minimum Bend Radius [BRmin] BRmin = 1.5 * D (if WT > = 1/30 D) to avoid wrinkling and sagging; Wall thickness should be above 1.3 mm; Calc. formula (s. link) can be used. Diameter Expansion Up to 100% expansion possible without significant thinning, when material is fed longitudinally. Diameter Reduction > 40% possible. Examples of Aluminium fuel filler pipe are described in the subsequent pages (other applications in European cars are Audi A8 and Mercedes A-class).

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Example: Volvo V70/S80/S60/XC90 Fuel Filler Pipe Specifications Fuel filler pipe with air pipe and pipe-integrated thread for filler cap. Length: 700…800 mm Diameter: 36…57 mm Wallthickness: 1.5 mm Alloy: EN AW-6063 Other SOP 1998 Annual Volume: ca. 300 000 Different versions for US and RoW, petrol and Diesel and LPG

Process • • • • • •

Extruded Main Pipe and Air Pipe, Rotary Draw Bending, Endforming, TIG welding of airventing pipe, Epoxy-powder coating, Leak Testing (use of positive pressure or vacuum), Restrictor mounting by electromagnetic forming

Fuel Filler Pipe, Volvo P2X Source: Krönert/Hydro

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Example: Porsche 911/Boxster Fuel Filler Pipe Specifications Fuel filler pipe with thread for filler cap integrated in plastic restrictor. Length: 650 mm Diameter: 36…70 mm 1.5 mm Wall thickness: Alloy: EN AW-6063 Other SOP 1997 Annual Volume: 50 000 (in four different types, versions for RoW and US, 2WD and 4WD)

Process • • • • • •

Extruded Main Pipe and Air Pipe, Rotary Draw Bending, Endforming, Forming of bellows, Mounting (Restrictor mechanically fixed), Leak Testing

Fuel Filler Pipe, Porsche 9X6 Source: Krönert/Hydro

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1.2.2 Fuel tank

Technical requirements As listed in the figure at right the tank shell has to meet several technical requirements beyond the fuel emission limits ("civil law rules"), which set constraints to the choice of materials. With respect to these requirements aluminium offers big potential as a lightweight future zero emission fuel tank material.

Source: VAW AG The specific characteristics of aluminium promise to meet all the requirements for application in passenger car fuel tanks. Development tasks to exploit the advantages of aluminium are: • Selection of an adequate alloy - Corrosion stability - Formability • Forming technology - Meeting constraints package • Joining technology - Tightness - Automation - Reliability The following screens show the results of recent development work outlining some promising approaches.

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Source: VAW AG

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Technical feasibility Corrosion behaviour: • Sheet metal alloy AlMg3 annealed (EN-AW 5754-0) • Corrosive media - Eurosuper + 3 % water - Biodiesel + 0,3 % water - E22 + 3 % water • Test condition liquid phase, half wetted and gas phase • Test temperatures: -5°C, -25°C, -50°C Fabrication concept: • Test results after 80 days - Layer degradation products of the fuel - No corrosion visible Two shell concept: Joining after forming • Application of conventional deep drawing or other sheet metal forming processes. • Possibility of mounting of system assemblies, slosh baffles, tubes and system assemblies before joining. • Possibility of 3-d shaped flange One shell concept: Forming after joining • Suitable for cold/warm hydroforming technologies • System assemblies have to be introduced through holes in the tank walls. • Mounting technique for pump, tubes, slosh baffles, etc. not evident.

Source: Allgaier, IFU, Stuttgart, VAW • Application of a prototype tool of a series production fuel tank in steel • Adapting of deep drawing parameters to aluminium by simulation • Prototyping of tank shells with AlMg3 (EN AW-5754-O), thickness 1,2 mm MIG – welding of flange • Joint configuration: Edge weld • One side of fusion flange bordered, other side of flange flat • Welding wire: AlMg4,5Mn 1,2 mm • Use of low cost shield gas Argon Properties: • Alloy AlMg3, thickness 1,2 mm • Welding speed up to 3 m/min • Bridging of 0,8 mm gaps without adapting • Stable welding process

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Source: C. Maier, VAW

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Prototype production

Pressure test with modified tank of a series production car Bursting pressure (water) 2,5 bar Prototype production of fuel tank: • Selection of corrosion resistant alloy: AlMg3, thickness 1,2 mm • Deep drawing of shells: - 3-d shaped flange possible - optionally different wall thickness for upper and lower shell • Mounting of slosh baffles, tubes and system assemblies • MIG-welding of fusion flange: - welding speed up to 3 m/min - simultaneous processing with several robots possible

Prototype of shell concept fuel tank

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1.3

Liquid lines

Aluminium tubing and connections Links: - AAM – Products – 3 Automotive tubes > Available forms and thicknesses > Drawn Aluminium Liquid Lines comprise hydraulic tubing materials and connections. Aluminium alloys as tubing materials for liquid lines meet the important requirement of high internal and external corrosion resistance. At the same time, hydraulic tubes have to resist high burst pressures and must be formable to small bend radii. Other requirements can e.g. include flame brazing for the attachment of connections. The selection of tube alloys for liquid lines has, therefore, to involve the following issues: • Tube connections, • Calculation of minimum burst pressure, • Bendability and • Corrosion resistance. For details on tube products refer to drawn and coated tubing (s. link above).

Examples of aluminium liquid lines Source: Hydro Aluminium

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1.3.1 Applications

Application requirements General A main selection criteria applied for hydraulic tube products is the pressure level for the specific application. The typical hydraulic system has a feed line / pump side (high pressure, HP) and a return line (low pressure, LP) which may include a cooling loop. For these systems characteristic pressure levels are HP > 100 – 150 bar and LP < 50 bar. For example, the characteristic pressure levels for power steering systems are HP = 100 – 150 bar, LP = 30 bar incl. cooling loop. Aluminium High Pressure standard ( > 0.5 bar ) s. EN 12392 Functional requirements Depending on the specific application hydraulic tube products have to meet functional requirements which include : • Tolerances (s. EN 754-7, EN 754-8) • Burst pressure / Bending • Tube connections / fitting • Corrosion resistance Tube Connections / Fittings • Screw connections • Hose connections • Quick connections • Flame Brazed connections • Special connections; Magnetic Pulse Forming

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Tube materials for liquid lines Links: - AAM – Products – 3 Automotive tubes > Available forms and thicknesses > Drawn Tube material for general engineering applications: EN AW 3103 ( s. link ) Material with good formability, medium strength, good brazing properties and fair corrosion resistance. High strength tube material : Commercially available alloys are EN AW 5049, EN AW 6101, EN AW 6106 ( s. link ) Alloy standard : EN 573 – 3 Tube dimensions - Drawn tube OD : 4 – 25 mm Wall thickness : 0.8 – 2.0 mm

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1.3.2 Connections

Screw Connections – Fittings Tube to tube connections Screw connections: • Single Flared tube • Double Flared tube/ F-bead connection • Tube–O–connection/ Saginaw Connections Applications Typical high pressure applications as • Power steering lines • Potential brake line applications (not yet in production) References: SAE Handbooks - J533, J514 Note: Although the following information can be applied to general tube applications, all of the pictures are taken of coated aluminium tubes and steel screw nuts. Figure 1: A cross section of single flared and double flared tube / F-bead to allow for a screw connection

Figure 2: Example of flared tube fitting for screw connection

Figure 3:Two types of screw connections • top: F-bead connection • bottom: Tube - O – connection, a bead formed tube

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Figure 4: A flared tube screw connection

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Hose-to-tube connection Hose to Tube Connections Main solutions for hose to tube connections are • Hose crimp shell connection • Hose clamp connection Applications • Power steering lines • Clutch lines Hose Crimp Shell Connections Crimp shell connection is made out of two parts, tube end, fig. 1, and shell, fig. 2. The hose is inserted into the shell, pressed on to the tube end, and the shell is crimped around the tube/hose connection, see fig. 3. Hose Clamp Connection Hose is pressed onto the tube end form and fastened by metal clamps. In fig. 4, tube end form with two locking rings ensures a tight connection between hose and tube.

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Special connections – Magnetic pulse forming Magnetic Pulse Forming (MPF) Magnetic Pulse Forming makes it possible to connect polyamid coated aluminium tubes with steel fittings without damaging the coating and thereby affect the corrosion resistance. Advantages of MPF joining method: 1) Contact free process with a high capability 2) Environmentally friendly and economical - no pre- and post cleaning - no addition of soldering material - subsequent corrosion protection is not required 3) Low weight of the tube 4) No change in material properties due to thermal effects 5) A high degree of automation and a short cycle time. Figure 1 shows a cross section of a banjo connection for tube to plate, a hollow screw connection.

Figure 2 shows a coated tube with a banjo connection. Magnetic pulse forming has produced the tube/banjo connection.

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Quick connectors For low pressure connections (< 5 bars), quick connectors offer a flexible way of connecting lines that need to be disconnected during maintenance or repair. Figure 1: This picture shows a typical tube end form prepared for a quick connector.

Figure 2: A Legris quick connector mounted on a coated aluminium tube ready to be connected to a tube end as shown in Figure 1. The tube is released by a simple finger push button.

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Connections by flame brazing Flame brazing is frequently used for joining of simple configurations such as tube-to-tube, tube-to-fitting and for joints having large thermal mass differences. Since much faster heating rates are possible than in furnace brazing, flame brazing is versatile and allows use of alloys with higher Mg-content. Some relevant alloys are presented on the following screen for Nokolok Flame brazing (Solvay). Figure 1 shows a practical flame torch made for a soft propane flame for good temperature control.

Figure 2 shows a tube – screw fitting connected by flame brazing.

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Connections by flame brazing – Materials Aluminium alloys suitable for flame brazing.

Source: Hydro Aluminium AS

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1.3.3 Burst pressure

Burst pressure of liquid lines Burst Pressure The internal burst pressure depends on the tube dimension (OD and WT) as well as material and temper. According to the Boardman formula described in SAE J1065, the theoretical burst pressure can be calculated. P(burst) = 20 x S x WT/(OD- 0.8 x WT) P(burst) = Burst pressure (bar) S = Tensile strength Rm (MPa) WT = Wall thickness (mm) OD = Outer diameter (mm) Material properties for higher service temperatures, T > 100°C, would be different from room temperature properties.

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1.3.4 Bending

Bending of liquid lines Bending Bending is normally necessary for most liquid line applications. Bending operation is usually depending on • bending radius, • tube material, • tube temper, • external tube follower, • internal mandrel support, etc. For more basic material information see "Automotive Tubes". For more basic bending information, see "Bending of Tubes and Shapes". Bending Formula The following formula can be used for calculating the smallest bending radius for given alloy and temper. Major liquid line alloy is EN AW 3103. Usually apply H12-temper for bending. Higher or lower tempers increase or reduce smallest bending radius, BR, given by this formula

with BR = Bending radius (mm) OD = Outer diameter (mm) WT = Wall thickness (mm)

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1.3.5 Corrosion

Corrosion Resistance – Long Life Materials During recent years, a new line of long life alloys (LLA) have been developed which have substantially improved the life of aluminium tubes with respect to SWAAT exposure. Focus for life time improvement has been on variants of EN AW-3103 alloy for drawn tubes. For the test method SWAAT (= Salt Water Acetic Acid Test) see ASTM G85 Annex 3. The figure presents a comparison between EN AW-3103 and one Long Life Alloy, both tested according to SWAAT. However, each application needs to be evaluated carefully. Especially, tube and fin assemblies for a cooling loop need a corrosion design approach to avoid any galvanic corrosion effects. Features of LLA: • huge improvement in corrosion resistance (life), • mechanical properties comparable to EN AW-3103/3003, • improved formability and grain size.

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1.4

Heat shields

Ford Focus - Exhaust heat shield Source: Dahmen, Alcan

Use of Aluminium Heat Shields

DC 200 E - heat shield in the engine compartment Until the mid eighties heat shields were mainly used for heat management in the engine compartment, specifically to protect against "hot spots" like exhaust manifolds. They consisted of double aluminium shells with an intermediate rock wool layer.

Ford Focus Catalytic converters, more powerful engines and the closed engine compartment for reduced noise emissions has strongly contributed to promoting the use of heat shields.

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Audi A4 underbody In addition, car designers have placed the exhaust system closer to the underbody in order to reduce aero-dynamic drag. This has made heat management more difficult: not only are the hot surfaces closer to the underbody, the slipstream also has less cooling effect.

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Application Areas Heat sources The exhaust system from the engine exhaust manifold to the tailpipe is the biggest producer of heat and noise after the engine itself. The surfaces of the parts of it that actually carry the exhaust gases can reach 900°C. Number and volume of heat shields: Small, low-power vehicles may need only as many as two heat shields, whereas highpowered luxury cars may have up to thirty. About 30000 to 40000 metric tons p.a. of rolled aluminium semis and a substantial tonnage of foil are used today for making automotive heat shields.

Ford Focus

DaimlerChrysler E200 Heat shield in the motor room

DaimlerChrysler E200 Heat shield dashboard

Underbody: The centre and rear underbody have to be protected against heat from front and rear silencers and catalytic converter. Parts such as the lambda probe, petrol and hydraulic lines, electric wiring and the petrol tank itself have to be protected. Engine compartment: Engine compartment heat shields are used for the engine exhaust manifold and the turbocharger. Dashboard: Heat shields for the dashboard often have to dampen noise also. Fireshield: Off-road vehicles are equipped with "fireshields", which are fixed under the exhaust system. These heat shields help avoid igniting dry grass and scrub when driving in grassland or open woodland.

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Choice of Aluminium – Thermal Properties Why make heat shields of aluminium? The physical properties of aluminium - reflectivity and emissivity, thermal conductivity and specific heat - make it very suitable for the fabrication of heat shields and well match the service requirements of the product. The excellent reflectivity and low emissivity of the aluminium surface ensure that it both absorbs and retransmits little infrared radiation. As a rule of thumb, 70 % of the heat management task in the car can be handled by the aluminium surface alone. The remaining 30 % have to be mastered by the heat shield design. The thermal conductivity of aluminium – 4x that of steel – ensures that heat is quickly conducted away from potential hot spots in the heat shield. Aluminium has a high specific heat. This means that its temperature increase after absorbing a given amount of heat energy is less than for many other materials.

Source: Alcan - Sierre, G. Dahmen

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Choice of Aluminium – Material Specification The alloy EN AW-1050A, soft, is today the usual material for exhaust heat shields. Its properties - among others excellent corrosion resistance, good cold formability, adequate tensile strength, excellent energy absorption before rupture (stone impact, car crash) - make it the preferred material as regards both ease of fabrication and its behaviour in service. Besides EN AW-1050A, alloys such as EN AW-3003, EN AW-5052 and EN AW-5182 are used. Although they are stronger, their lower cold formability limits the range of heat shield shapes for which they can be used.

Embossed heat shield, BMW 7 Series, Produced by SEVEX AG Source: VAW

Embossed Heat Shield Audi Source: VAW

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1.4.1 Requirements

Embossed heat shield Source: VAW

Requirements / Specifications Heat Management Heat shields have to prevent overheating of the car body and sensitive parts and modules. Normal driving conditions: heat shields to protect parts from nearby heat sources with surface temperatures of up to 650°C. Misfire conditions: spark plug failure may cause overheating of catalytic converter. Downstream parts of the exhaust system will reach abnormally high temperatures. Crash conditions: in case of rear crash to protect plastic petrol tank against rupture from hot exhaust parts. Noise Management Heat shields can contribute to noise management in the car and to noise emission to the environment (currently max. 74 dB). Space limitation Typically, heat shields can be 15 - 25mm from the underbody, 10 - 15mm from the petrol tank and 25 - 50mm from the exhaust pipe. The form of the edges The form of the edges of aluminium heat shields has to be designed to minimise the risk of injury to people handling them. Anticorrosion requirements Contaminants such as salt water, liquid asphalt, street dirt and mud must not, during the car's lifetime, lead to unacceptable corrosion of the heat shield. The joining technique has to be such that the heat shield does not suffer unacceptable corrosion in service.

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1.4.2 Design of heat shields

Heat shields with and without noise absorption Audi A4

Three basic types of heat shields Single shell or double shell (not insulated) • One-layer or two-layer sheet metal, each 0.3 - 1.0 mm thick.

Single shell heat shield Sandwich (insulated) • Carrier: 0.3 - 1.0 mm thick aluminium • Insulation: 2 to 6 layers of 0.03 - 0.05 mm aluminium foils; or ceramic felt or glass fiber mat • Cover: 0.03 to 0.1 mm foil or 0.2 to 0.5 mm cover sheet

Sound absorbing heat shield with viscoelastic layer Sandwich (noise absorbing) • Carrier with partial perforation, backed up by a • Membrane foil, aluminium 0.03 - 0.05 mm thick, followed by • Insulation (see description above) or consisting of • two-layer sheet metal with viscoelastic core.

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Noise absorbing carrier shell with partial perforation

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Design for heat management: Exhaust system Underbody exhaust system • Single shell type: for relatively low temperatures and generous distances. Aluminium sheet, 0.3 - 1 mm thick. • Double shell type: for moderate temperatures and distances. These heat shields are made of two aluminium sheets. • Sandwich type: the highest temperatures and smallest distances require the use of a single sheet as carrier (e.g. 0.5 mm thick) and several embossed aluminium foil layers 0.03 - 0.05 mm thick, which are sandwiched together. Insulating mats of ceramics, glass fibre, cotton or wood fibre are also used. The cover sheet can be foil 0.03 - 0.1 mm thick, or sheet 0.2 - 0.5 mm. The sheets used may be flat or embossed.

Courtesy: Rieter Automotive

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1.4.3 Assembly techniques

Assembly techniques The assembly technique has to be chosen according to the requirements of • stiffness and strength, • serviceability and • life (corrosion resistance). Apart from using rivets and screws (electrolytically galvanised) the main method of attaching heat shields to the car is by nut and sacrificial washer: The heat shield is fastened with nuts on screw bolts, which are stud-welded to the underbody. A 2 mm thick sacrificial washer of aluminium is built into in the heat shield at the mounting points. This disk is pressed by a spring to the underbody and corrodes away over the car's service life, hence the term "sacrificial". This avoids corrosion of the heat shield where the mounting points contact the underbody (see Fig.). The spring and nut typically have a galvanised surface.

Mounting of heat shield by nut and washer to welded stud bolt

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1.5

Drive shaft

Source: Otto-Fuchs Metallwerke

Aluminium drive shafts Links: - AAM – Products – 3 Automotive tubes > Available forms and thicknesses > HF-welded (incl. Clad) For rear wheel or 4-wheel drive cars the "prop shafts" or "drive shafts" are a possible application for aluminium products, i.e. both for the tubes as well as for the cardanic links. The reason for using light weight materials is the reduction of inertia forces as well as of vibratory excitations. The fact that all parts have rotational symmetry and that friction welding permits joints between aluminium and steel has resulted in drive shafts consisting of seam-welded aluminium tubes and forged steel or aluminium cardanic links. Details about these applications will be presented. The work is planned for the 2nd edition of this Automotive Manual.

Drive shaft BMW 5 series

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1.6

Heat exchangers

General aspects Links: - AAM – Joining – 4 Brazing > Flux and fluxless brazing Brief history • As early as 1950, aluminium heat exchangers made moderate inroad to the automobile industry. • With the introduction of the vacuum brazing techniques, large scale production of aluminium based heat exchangers began to flourish. • Significant growth in the use of aluminium heat exchangers resulted from advantages of the Nocolok™ brazing process introduced by ALCAN. • Introduction of long life alloys by the aluminium producers further aided to improve performance of the aluminium heat exchangers. • Large demands for Al heat exchangers resulted primarily from the extensive market growth of automobile air- conditioning. Applications of heat exchangers • Aluminium heat exchangers are used in one of the following three main application categories: - Engine and transmission cooling - Air-conditioning - Charge-air and fuel cooling • Oil coolers and radiators typically work towards cooling the engine. • Evaporator, condenser and heater core are components of an automobile air- conditioning system. Advantages of aluminium in the design of heat exchangers • Weight reduction potential • Higher thermal conductivity in the brazed condition • Good corrosion resistance • Good formability • Good resistance to temperature and pressure cycle • Environmentally friendly • Commercial availability of wide range of alloys to meet different design options Brazed heat exchanger design • Although a wide variety of designs exist, they invariably fall into one of the following categories: - Tube / fin - Plate-fin - Plate-bar - Extrusion / fin • Due to intensifying demands on compactness combined with light weight, heat exchangers are increasingly being produced as modules, e.g. radiator + oil cooler or condenser + oil cooler. Brazing process • The following brazing processes are used commercially to manufacture heat exchangers: - Controlled atmosphere brazing - Vacuum brazing - Salt bath brazing - Neitz process - Ni brazing • The major fraction of heat exchangers are produced by the Controlled Atmosphere and Vacuum Brazing processes. 95

• Aluminium producers / flux producers / furnace builders actively develop the brazing process for better economy and environmental friendliness. Future Prospective • Continually increasing demands for air conditioning of automobiles imply an increasing market for aluminium. • The need for more environmentally friendly refrigerant also favours the use of aluminium alloys as candidate materials for heat exchanger designs. • Although the use of aluminium alloys in automotive heat exchangers has been a success story, it also faces challenges from other materials such as copper/brass and stainless steel.

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1.6.1 Radiators

Engine cooling system Aluminium brazing sheet and finstock are now well established materials for the manufacture of automotive heat exchangers. They offer properties that can be utilised in various components of the radiator unit such as: • high strength • high thermal conductivity • low density • good formability • excellent corrosion resistance. The combination of these properties gives the manufacturer the potential for weight, size and cost reduction as well as improved heat transfer performance. These improvements can also be linked to environmental benefits. There are a number of joining methods for aluminium radiators: • adhesive bonding • mechanical assembly and • brazing. Brazing, whether in controlled atmosphere (CAB) or vacuum (VB), is now the dominant process worldwide. Radiator – Key Components (see figure below) • Header Tank - plastic as shown (1) • Header Plate (2) • Fins (3) • Tubes (4)

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Engine cooling system – Material requirements and functions Environmental considerations, i.e. • control of exhaust gases, • control of fuel consumption and • material recycling will continue to push both suppliers and manufacturers to improve materials, processes and the radiator design and performance. The amount of heat to be dissipated by the engine cooling system is increasing due the use of higher engine speeds, increasing engine power output and the use of turbo-charged diesel engines. In addition, items like power steering and other driven units will increase the amount of heat to be dissipated by the radiator. Basic construction of a radiator: The header tank allows for the appropriate coolant volume to be circulated through the tubes. Heat is then dissipated via the fins to air. Tube materials must have high strength and fatigue resistance together with good air-side and waterside corrosion resistance. As more complex tube designs are used, formability of the tube alloys becomes of greater importance. Fins require high thermal conductivity, strength and corrosion resistance. This latter property is important if thermal performance is to be maintained throughout the life of the radiator.

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Engine cooling system – Air-side corrosion As the materials used in automotive radiators have been down-gauged, it has been necessary to further improve the corrosion resistance of the tube and fin stock alloys. Historically, air-side corrosion resistance has been achieved by suitable pre-treatment and protection systems. However, with the introduction of extended and long-life alloys for tube stock products it has been possible to eliminate these costly and sometimes environmentally unfriendly treatments. If additional protection of the external surface of the tube is required it can be achieved by using fin stock alloys that behave sacrificially to the tube alloy, i.e. which are more electronegative. One option for achieving a fin that galvanically protects the tube is the addition of zinc, typically in the range of 1.0 to 2.5 wt%. However, in vacuum brazing (VB) the low vapour pressure of Zn means that a significant proportion is vaporised and therefore the level remaining in the fin becomes difficult to control. For VB products the use of elements with a high vapour pressure is preferred and for this reason, tin and indium have found favour with some manufactures. The low melting point Al-Si alloys used to clad the tube stock are, once brazed, slightly sacrificial to most Al-Mn based tube materials.

Schematic showing galvanic compatibility with AA3003 based alloys. For LL- alloys Zn and internal clad are optional.

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Engine cooling system – Water-side corrosion Together with other additives, engine coolants contain chemical anti-corrosion systems which only remain effective, if the recommended levels are maintained. Some manufactures favour water-side cladding alloys for corrosion protection. High purity EN AW-1050 or the Zn-containing alloy EN AW-7072 are typical examples of water-side cladding alloys. It has been shown that the optimum Zn level for internal clad alloys is about 1% depending on core alloy. However, the Al-Mn-Cu "LL"-alloys have also been shown to have adequate corrosion resistance without the need for an internal cladding alloy for some customer tests. There are a number of test methods and test solutions for evaluating the resistance of materials to water-side corrosion. The latter fall into two general categories: (1) simulated service test as described in ASTM D2570 and (2) continuous immersion tests at elevated temperature, typically 80 to 95°C. Examples of test solution used for (2) are shown below (all values are in ppm):

Figure (above): Relative corrosivity of the 3 test solutions. Ref. Ando et al., SAE 870180

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1.6.2 Oil coolers

Oil cooler applications Oil cooling raises the viscosity and hence the oil lubricating power. Herewith the oil change intervals are prolonged and the motor working time is increased. Besides classic engine oil coolers for Otto- and Diesel-engines there are oil coolers in the application fields of automatic and mechanical driving gears, steering gears, differential gears, hydraulic components of fan-drives and retarder brakes as well as absorbing systems for improving the driving comfort. Moreover there are fuel coolers for diesel engines. In principle one can distinguish between oil coolers working with air and those working with a water-based coolant or direct and indirect cooling, respectively. Oil coolers can be produced in a large variety of designs. Due to the liquid state of oil and the typical service conditions in terms of pressure and temperature they can not only be mechanically assembled but must be brazed. Five different examples of oil coolers are presented in the following pages.

Engine Oil Cooler Courtesy: Modine

Fuel to Air Cooler Courtesy: Modine

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Function: Cooling of car engines Coolant: Air Medium to be cooled: Engine oil Service Conditions: Pressure: max. 10 bar Oil side temperature: ~ 60°C Air side temperature: ~ 30°C Material Requirements: Pressure resistance / Strength / Corrosion resistance Formability Application: Audi, 4 cylinder engine Design Considerations: • Tube & fin design • Tubes with inner turbulators • Compact design • Cooler is lacquered Cooler is positioned in the cooling air flow in cars, equipped with an additional fan. Production Aspects: • Salt bath brazing • Water tank brazed to bottom sheet Tube and header stock is two sides clad with a braze liner; side plate stock is one side clad with a braze liner, fin stock is not clad.

Photo image of an engine oil cooler Courtesy: AKG

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Function: Cooling of car engines Coolant: Water based coolant Medium to be cooled: Engine oil Service Conditions: Pressure: 10-15 bar Temperature: -40°C to 150°C Material Requirements: Pressure resistance / Strength / Corrosion resistance Application: 6 and 8 cylinder V-engines for cars, DaimlerChrysler Design Considerations: • Stacked plate design • Extremely compact • Optics due to visibility with open motor bonnet Production Aspects: • Vacuum brazing • Plate stock is two sides clad with a braze liner • Oil filter housing is made by die casting and is screwed to the cooler • Extruded tubes are brazed to the cooler

Photo image of an engine oil cooler with screwed-on oil filter housing Courtesy: Behr – Photo: VAW

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Function: Cooling of car engines Coolant: Water based coolant Medium to be cooled: Engine oil Service Conditions: Pressure: max. 6 bar Oil side temperature: ~ 150°C Air side temperature: ~ 115°C Material Requirements: Pressure resistance / Strength / Corrosion resistance Application: Ferrari and Maserati, V8 cylinder engine Design Considerations: • Plate & bar design • Inner turbulators • Assembly between V8-cylinder-series Production Aspects: • Salt bath brazing • Plate stock is two side clad with a braze filler • Connections on oil side are welded • Sealing for coolant by motor housing and cast plate, welded to the cooler

Photo image of an engine oil cooler with welded oil circuit connection Courtesy: AKG

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Function: Cooling of driving gear Coolant: Air Medium to be cooled: Gear oil Service Conditions: Pressure: 10-15 bar Temperature: -40 °C to 150°C Material Requirements: Pressure resistance / Strength / Corrosion resistance Application: Audi, 2.5 L TDI and 2.7 L patrol, 6 cylinder engine Design Considerations: • Tube & fin design • Flat, compact and lightweight • Cooler is positioned in front of radiator in the cooling air flow Production Aspects: • Vacuum brazing • Tube stock is two side clad with a braze liner; side plate stock is one side clad with a braze liner • Header tanks are hydroformed tubes • Pressure valve with oil connections is brazed to the header tank

Photo image of a transmission oil cooler Courtesy: Behr – Photo: VAW

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Function: Cooling of transmission oil Coolant: Water based coolant Medium to be cooled: Gear oil Service Conditions: Pressure: max. 8 bar Oil side temperature: ~ 120°C Coolant side temperature: ~ 85°C Material Requirements: Pressure resistance / Strength / Corrosion resistance Application: Audi, 6 cylinder engine, automatic Design Considerations: • Drawn cup plate design • Inner turbulators • Fitting into the radiators water tank Production Aspects: • Salt bath brazing, Ni brazing • Plate stock is two side clad with a braze liner • Oil circuit connection is brazed to the cooler

Photo image of a transmission oil cooler and its assembly in radiator water tank Courtesy: AKG

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1.6.3 Air conditioning

General requirements • Automotive air conditioning is similar to stationary air conditioning in the sense that it also requires the cyclic flow of the refrigerant through an evaporator to absorb the heat and dissipating that in the condenser. • Automotive air conditioning face several variables - temperature parameters involved with the evaporator, condenser - variables related to air flow - variable compressor speed arising from - engine speed - air flow through the condenser which is related to the vehicle speed. The last two variables not only contrast the vehicle air conditioning from stationary types but are also very demanding. • Space limitations, demands on fuel efficiency and pollution control place stringent requirements on design. • A blower unit, heating unit and a cooling unit are the main components of automobile air conditioning system. • The blower unit is placed at the upstream end of air flow. The cooling unit is placed in the mid portion of the air flow and the heater unit is positioned at the downstream side of the air flow. • The cooling unit in turn consists of an evaporator, compressor, condenser and an expansion valve and the attached control systems. • The heating unit primarily consists of a heater core and the associated control mechanisms. • Generally, systems blend warm air to cold air or control the hot water supply to the heater core.

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Refrigerants Refrigerant flow / Overview • The refrigerant enters the evaporator in the sub-cooled liquid state, picks up the heat from the air and becomes vapour. • The vapour is compressed by the compressor and the compressed vapour enters into the condenser where the vapour to liquid phase transformation occurs. The outside air picks up the heat from the vapour in the condenser. • The liquid refrigerant passes through an expansion valve before it enters in the evaporator. Refrigerant • R12 and R134a are the two refrigerants which are used in automobile air conditioning. • R12 is a chlorofluorocarbon (CFC). Although it has several unique properties such as low toxicity, non-inflammability, non-corrosive etc, its instability in combination with its chlorine content is being linked to ozone layer depletion. • R134a does not contain chlorine and therefore has no ozone depletion potential and consequently is an environmentally acceptable alternative to R12. • New refrigerants for AC/HVAC system based on CO2 is under development. The use of this refrigerant calls for new designs with an operating pressure of ~320 bars and at a temperature of ~180°C

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Heater core – Design considerations Function: Supplies hot air to the passenger cabin Heating Medium: Hot water from the engine Medium to be heated: Air Service Conditions: Pressure: 1.0-1.5 bar Temperature: 100-120°C Material requirements: Strength / Corrosion resistance / Braze ability Design Considerations • A heater core consists of tanks for inlet, outlet, outlet and a core and the core consists of tubes and fins. • Heater cores are typically either of mechanically assembled or of brazed type although the latter is gaining more popularity. • Compared to mechanically assembled radiators, generally, the brazed heater cores have better thermal performance. • Design developments are typically aimed at achieving higher degree of uniformity in flow between the inlet and the outlet tanks.

Schematic of a typical heater core assembly

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Heater core – Production aspects • Practically all the heater cores are produced using the Nocolok brazing process. • The tubes produced from clad aluminium stock in a tube mill which in turn consists of a set of rolls to produce the shape and a high frequency welding station. • The tube stocks may have one side clad with a corrosion protection alloy and the other with a braze filler. • The tubes are then stacked in combination with interposed fins which are unclad aluminium alloys. • The header and side supports are mainly stamped from rolled clad aluminium alloy stocks. • Header materials are two side clad whereas the side supports are one side clad aluminium alloys. • The tanks are made both from plastic and aluminium. The tanks are crimped to the headers after the brazing operation.

Digital image of a Heater core Model : Ford Transit Photo Courtesy : Visteon, France

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Evaporator – Design aspects Function: • Cools the air supplied to cabin Coolant: • Refrigerant (e.g.: R134A) Medium to be cooled: • Air Service conditions: • Pressure: ~ 6 bar • Temperature: ~ -10°C to +30°C Material Requirements • Pressure resistance / Strength / Corrosion resistance / Formability / Brazeability Design Aspects : • Primarily evaporators for automobile air conditioning are of drawn-cup plate type. The use of Serpentine design has declined. An alternative design involves the use of extruded micro-channel tubes. • Primary advantage: More efficient than the serpentine type which is produced by brazing clad fins to an extruded tube which is bent in the form of a serpentine. • Originating from the design, the drawn cup plate type evaporators do not aid in smooth drainage of water condensed on the surfaces of plate tubes and interposed fins. • Design developments are typically aimed at making the evaporator more compact, even distribution of refrigerant and different arrangements of inlet and outlet connections.

Schematic of a drawn cup plate type evaporator

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Evaporator – Production and environmental aspects Production Aspects • Although a significant fraction of the evaporators are produced by vacuum brazing, Nocolok brazing is expected to gain more share. • Brazing of aligned pairs of stamped plates results in integral flow tubes and header pipe which constitute this type evaporator. • Since both internal (turbulators formed by opposing ribs) and external (header pipes) brazing requirements must be met, the material for core plates are clad both sides with braze liner. • In general, long life aluminium brazing alloys are used for producing the evaporator core plates. • Extruded tubes are used for the manifolds and are joined by induction/plasma brazing. • To allow the smooth drainage of condensed water collected on the surface of core plate tubes and fins, a hydrophilic coating is done. • To improve the corrosion resistance it is common to apply a chromate coating. Environmental Aspects: • Evaporators still receive chromate coating. Due to intensifying environ-mental requirements, the chromate coating will become obsolete

Digital image of a drawn cup plate evaporator Model : Ford Mondeo Photo Courtesy : Visteon, France

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Condenser – Design considerations Function: Condense the refrigerant Coolant: Air Medium to be cooled: Refrigerant : e.g.: R134A Service Conditions: Pressure : ~ 20 bars Temperature : ~ RT to +30°C Material Requirements: Pressure resistance / Sag resistance / Strength / Corrosion resistance Design Considerations: • Typically the condensers are of either parallel flow or of serpentine type and a very small fraction of condenser designs are based on mechanically assembled solutions. • Serpentine condenser has a refrigerant tube bent in the form of a "serpentine" and clad fins are brazed to this tube. This design is quite robust, but characterised by a high pressure drop. • In parallel flow design, a pair of parallel vertical header tanks distribute the refrigerant to horizontally aligned tubes which in turn are connected to fins. Parallel flow design is more efficient than the serpentine design. • Condenser design developments are typically aimed at providing an increased heat transfer area and to reduce the pressure drop on the refrigerant side.

Schematic of a Serpentine type condenser

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Condenser – Productions aspects Production Aspects • In the "serpentine" design, the refrigerant tube is normally an extruded tube bent in the form of a serpentine. • Most widely, extruded multi-port tubes are used in the parallel flow design as refrigerant tubes. • A wide variety of multi-port extrusion designs can be produced. • The headers, end caps, baffles, brackets and side supports are produced from rolled aluminium alloy stocks. • Depending on the design the header stock can be one or two sides clad with a braze liner. • Practically all the condensers are produced by Nocolok brazing method.

Photo image of a Parallel Flow Condenser Courtesy : Behr

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1.6.4 Charge air coolers

Design and production aspects Links: - AAM – Products – 3 Automotive tubes Charge Air Cooler (CAC) - Function An engine charge air cooler is a heat exchanger used to cool the charge air of an internal combustion engine after it has been compressed by an exhaust driven turbo charger, an engine driven turbo charger, or a mechanically or electrically driven blower. Coolant Typical cooling media include the engine's coolant, ambient air, or an external water or coolant source. Service conditions CAC air inlet temperature: 150-240°C CAC input pressure: 2 – 6 bar CAC output air temperature: < 70°C Material requirements Elevated temperature strength. For further details see link. Design aspects - general The specific design of a CAC is affected by factors such as package size, price, weight, location in the vehicle and the availability of cooling air. The most important technical aspect is the balance between high heat transfer performance and low charge air energy loss (charge air pressure loss). Type of charge air-cooling to be used - coolant cooled or air cooled - depends on the temperatures to be attained. Major methods of charge air cooling processes are • Direct charge-air-cooling with air. Chassis mounted systems in various locations. Dominant solution for present market. See page 2. • Indirect charge air-cooling with coolant, see page 3. Production aspects CACs use similar assembly technology to that of automotive heat exchangers. Production aspects see page 4.

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Different placements within the car Figure 1: A box type CAC fitted on the engine close to turbo charger to have low pressure drop. However, ambient air supply is insufficient, particularly at low vehicle speeds.

Figure 2: A box type CAC fitted in the wheel housing or beside the radiator. Ambient air supply is good, but inlet and outlet ducts are long, pressure drops are high.

Figure 3: A full face CAC is located in front of the radiator and takes full advantage of the dynamic and forced ventilation. Thermal efficiency is generally high, but duct to engine would be long. A common drawback for this location is the overcrowded front space occupied by radiator, CAC, condenser and electric fans.

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Air-to-Air solutions Links: - AAM – Products – 3 Automotive tubes Aluminium solutions Competitive aspects of aluminium in automotive heat exchangers are the combination of specific weight and thermal properties in comparison to copper or steel solutions. Efficient production systems for high volume and high performing products are established. A potential disadvantage with aluminium has been corrosion resistance and strength at elevated temperatures. These aspects are well addressed during the recent years in various R&D programs which have brought several new high performing alloys to the market. All-aluminium CAC for light weight design and optimised heat transfer. All-aluminium CAC represent a fully recyclable solution. Most critical location for failure are the tube to header joints. Critical for the CAC tube life is the response to a combination of axial compression and bending stresses due to cyclic temperatures. The phenomenon of lateral thermal expansion is called "thermal breathing". This term is a descriptive one in that it describes the tendency of the core to "belly up" in the centre with the tube ends pinned to the header, increasing with tube length and number of tubes. Design solutions must reduce stress build-up at the joints. Figure 1: Charge Air Cooler, air-to-air, a full face type configuration. Controlled Atmosphere brazed cores with plastic end-tanks and acrylic gaskets. CAC depth typically would be close to 30 mm for cars.

Figure 2: Charge air coolers, air-to-air, a box type configuration. Vacuum brazed core with plastic endtanks and acrylic gaskets. CAC depth is typically in the range of 40–85 mm.

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Air-to-Coolant Cooler Design aspects The charge air cooling can be done with a liquid coolant, circulating first through an auxiliary "low temperature" (LT) radiator and then through a water-to-air cooler. An adequate cooling of the liquid (below 45°C) can be obtained in the LT radiator by means of a sufficient low coolant flow rate. Air-to-water cooler may be chosen when there is a lack of space in front of the engine compartment or /and when it offers the possibility to cool other fluids as engine oil, power steering fluid etc. with the same loop. For this solution two heat exchangers are needed, one for the air-to-water cooling and one for the water-to-air cooling. The air-to-coolant cooling would be a small radiator, standard design concept, located either next to the main radiator or in front of the radiator. The coolant-to-air heat exchanger is based on conventional cores for water cooling enveloped by a housing for controlled air flow. This type of heat exchanger is often an integrated part of the engine air intake manifold, but could also be a remotely mounted unit. Some concepts are illustrated in Figures 1 and 2.

Figure 1: Air-to-coolant heat exchanger mounted in the air intake manifold. The core design is based on conventional tube-fin configurations applied in automotive heat exchangers.

Figure 2: Air-to-coolant heat exchanger mounted remotely. Conventional core design, water cooled tubes are passing through a fin pack for cooling the charged air, the core is enveloped by a housing. Coolant traverses may be single pass or a multi pass arrangement.

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Air-to-Air solutions – Manufacturing aspects Brazing assembly Service temperatures, 150 to 240°C, are well below brazing temperature of 580°C. Vacuum brazing uses Mg-containing alloys to break the oxide to prepare for a good brazed joint. Fluxless brazing permits cores with larger depth. Full-face CAC use CAB technology for brazing. Tube/Fin designs Figure 1: Common type of CAC in standard tube design with fins (0.15 mm).

Figure 2: as before, but extruded tube, width 28 - 34 mm, height 5 - 8 mm, enhancement optional, increased wall thickness optional (heavy duty). Extruded tube give flexibility in performance and strength.

Figure 3: Inserted fins into standard tube design is one way of improving cooler efficiency significantly.

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1.6.5 Others

Mechanically assembled radiator Function: To cool the engine coolant Coolant: Air Medium to be cooled: Engine coolant Service Conditions: Pressure: 1.0-1.5 bars Temperature : 100-120°C Material Requirements: Strength / Corrosion resistance Design Considerations • Typically, a mechanically assembled radiator consists of drawn aluminium alloy tubes and fins. • The tubes and fins are mechanically joined, which is usually carried out by expanding the tubes after the fin assembly has been made. • The primary advantage of mechanically assembled radiators is costs when compared to brazed radiators. However, brazed aluminium radiators have better specific thermal performance rating in comparison to mechanically assembled ones.

Digital image of a mechanically assembled radiator Photo Courtesy: Behr

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