DIEVAR
UDDEHOLM DIEVAR
DIEVAR
REFERENCE STANDARD
ASSAB DF-2
ARNE
ASSAB DF-3
AISI
WNr.
JIS
O1
(1.2510)
(SKS 3)
O1
(1.2510)
(SKS 3)
ASSAB XW-5
SVERKER 3
D6 (D3)
(1.2436)
(SKD 2)
ASSAB XW-10
RIGOR
A2
1.2363
SKD 12
ASSAB XW-41
SVERKER 21
D2
1.2379
SKD 11
D2
1.2379
SKD 11
ASSAB XW-42 CARMO
CARMO
1.2358
CALMAX
CALMAX
1.2358
CALDIE
CALDIE
ASSAB 88
SLEIPNER
ASSAB PM 23 SUPERCLEAN
VANADIS 23 SUPERCLEAN
(M3:2)
1.3395
SKH 53
ASSAB PM 30 SUPERCLEAN
VANADIS 30 SUPERCLEAN
(M3:2 + Co)
1.3294
SKH 40
ASSAB PM 60 SUPERCLEAN
VANADIS 60 SUPERCLEAN
VANADIS 4 EXTRA SUPERCLEAN
VANADIS 4 EXTRA SUPERCLEAN
VANADIS 6 SUPERCLEAN
VANADIS 6 SUPERCLEAN
VANADIS 10 SUPERCLEAN
VANADIS 10 SUPERCLEAN
VANCRON 40 SUPERCLEAN
VANCRON 40 SUPERCLEAN
ELMAX SUPERCLEAN
ELMAX SUPERCLEAN
(1.3292)
ASSAB 518
P20
1.2311
ASSAB 618
P20 Mod.
1.2738
ASSAB 618 HH
P20 Mod.
1.2738
ASSAB 618 T
P20 Mod.
1.2738 Mod.
ASSAB 718 SUPREME
IMPAX SUPREME
P20 Mod.
1.2738
ASSAB 718 HH
IMPAX HH
P20 Mod.
1.2738
NIMAX
NIMAX
MIRRAX 40
MIRRAX 40
VIDAR 1 ESR
VIDAR 1 ESR
UNIMAX
UNIMAX
CORRAX
CORRAX
ASSAB 2083
420 Mod. H11
1.2343
SKD 6
420
1.2083
SUS 420J2
STAVAX ESR
STAVAX ESR
420 Mod.
1.2083 ESR
SUS 420J2
MIRRAX ESR
MIRRAX ESR
420 Mod.
POLMAX
POLMAX
RAMAX HH
RAMAX HH
ROYALLOY
ROYALLOY
420 F Mod.
PRODAX ASSAB MM40 ALVAR 14
ALVAR 14
ASSAB 2714 ASSAB 8407 2M
ORVAR 2M
ASSAB 8407 SUPREME
ORVAR SUPREME
DIEVAR
DIEVAR
HOTVAR
HOTVAR
QRO 90 SUPREME
QRO 90 SUPREME
1.2714
SKT 4
1.2714
SKT 4
H13
1.2344
SKD 61
H13 Premium
1.2344 ESR
SKD 61
4340
1.6582
SNCM8
ASSAB 709
4140
1.7225
SCM4
ASSAB 760
1050
1.1730
S50C
ASSAB 705
ASSAB is a trademark of ASSAB Pacific Pte Ltd. The information contained herein is based on our present state of knowledge and is intended to provide general notes on our products and their uses. It should not therefore be construed as a warranty of specific properties of the products described or a warranty for fitness for a particular purpose. Each user of ASSAB products is responsible for making its own determination as to the suitability of ASSAB products and services. Edition D140715
2
DIEVAR
DIEVAR Dievar is a hot work die steel specially developed by Uddeholm Tooling, our steel mill in Sweden, to provide the best possible performance. The chemical composition and the very latest in production technique make the property profile outstanding. Dievar possesses a combination of excellent toughness and very good hot strength, resulting in a superior hot work die steel that have excellent resistance to heat checking and gross cracking. Dievar is suitable for high demand hot work applications like die casting, extrusion and forging. The property profile also makes it a suitable choice in other applications such as plastic moulding (e.g., to solve chipping/ cracking) and High Performance Steel. Dievar offers the potential for significant improvements in die life, thereby improving the tooling economy.
3
DIEVAR
General Dievar is a high performance chromium-molybdenumvanadium alloyed hot work tool steel which offers a very good resistance to heat checking, gross cracking, hot wear and plastic deformation. Dievar is characterised by:
DIE CASTING
Excellent toughness and ductility in all directions Good temper resistance Good high-temperature strength Excellent hardenability Good dimensional stability throughout heat treatment and coating operations
Type
Cr-Mo-V alloyed hot work tool steel
Standard specification
None
Delivery condition
Soft annealed to approx. 160 HB
Colour code
Yellow / Grey
Part
Aluminium / Magnesium alloys
Dies
44-50 HRC
EXTRUSION
Dievar is a premium hot work tool steel developed by Uddeholm. It is manufactured utilising the very latest in production and refining techniques. The Dievar development has yielded a die steel with the ultimate resistance to heat checking, gross cracking, hot wear and plastic deformation. The unique properties profile of Dievar makes it the best choice for die casting, forging and extrusion.
Applications Heat checking is one of the most common failure mechanisms, e.g., in die casting and nowadays also in forging applications. Dievar’s superior ductility yields the highest possible level of heat checking resistance. With Dievar’s outstanding toughness and hardenability, its resistance to heat checking will be further improved. If gross cracking is not a factor, then a higher working hardness can be utilised (+2 HRC).
Part
Copper alloys
Aluminium / Magnesium alloys
Dies
-
46-52 HRC
46-52 HRC
44-52 HRC
Liners, dummy blocks, stems
HOT FORGING
Regardless of the dominant failure mechanism (e.g., heat checking, gross cracking, hot wear or plastic deformation), Dievar offers the potential for significant improvements in die life as well as tooling economy. Part
Dievar is the material of choice for the high demand die casting, forging and extrusion industries.
4
Inserts
Steel / Aluminium 44-52 HRC
DIEVAR
Properties The reported properties are representative of samples which have been taken from the centre of a 610 x 203 mm bar. Unless otherwise indicated, all specimens were hardened at 1025°C, quenched in oil and tempered 2 + 2 hours at 615°C to 45±1 HRC. PHYSICAL PROPERTIES
Charpy V-notch impact toughness at elevated temperatures Short transverse direction.
Hardened and tempered to 44 - 46 HRC. Temperature
At a hardness of approximately 45 HRC, the minimum average unnotched impact ductility is 300 J in the short transverse direction.
20°C
Impact energy, J
400°C
140
600°C
120 Density kg/m3 Modulus of elasticity MPa
7800
7700
7600
210 000
180 000
145 000
45 HRC 100 80 47 HRC 60
Coefficient of thermal expansion per °C from 20°C
-
13.3 x 10 -6
12.7 x 10 -6
40 20
Thermal conductivity W/m °C
-
31
50 HRC
32 50
100 150
200 250 300 350 400 450°C Testing temperature
MECHANICAL PROPERTIES Temper resistance
Approximate tensile properties at room temperature, tested in the short transverse direction. Hardness
The specimens have been hardened and tempered to 45 HRC, and then held at different temperatures from 1 to 100 hours.
44 HRC
48 HRC
52 HRC
Tensile strength, Rm
1480 MPa
1640 MPa
1900 MPa
Yield strength, RP0.2
1210 MPa
1380 MPa
1560 MPa
Elongation, A 5
13 %
13 %
12.5 %
Reduction of area, Z
55 %
55 %
52 %
Hardness, HRC 50 500°C 45 550°C 40
35
Approximate tensile properties at elevated temperatures
600°C 30
Short transverse direction, 45±1 HRC. A5, Z % 100
Rm, Rp0.2 MPa 2000 Z
1800
90
25 0.1
650°C
1
10
100
Time, h
80
1600
70
1400 Rm
1200
60 50
1000 800
40
Rp0.2
30
600
20
400 200
10
A5 100
200 300 400 500 Testing temperature
600
700ºC
5
DIEVAR
Heat treatment SOFT ANNEALING
QUENCHING
Protect the steel and heat through to 850°C. Then cool in the furnace at 10°C per hour to 650°C, then freely in air.
As a general rule, quench rates should be as rapid as possible. Accelerated quench rates are required to optimise tool properties specifically with regards to toughness and resistance to gross cracking. However, risk of excessive distortion and cracking must be considered.
STRESS RELIEVING
The quenching media should be capable of creating a fully hardened microstructure. Different quench rates for Dievar are defined by the CCT graph as shown in page 7.
After rough machining, the tool should be heated through to 650°C, holding time 2 hours. Cool slowly to 500°C, then freely in air.
High speed gas/circulating atmosphere Vacuum (high speed gas with sufficient positive pressure). An interrupted quench at 320–450°C is recommended for distortion control, or when quench cracking is a concern. Martempering bath, salt bath or fluidised bed at 450–550°C Martempering bath, salt bath or fluidised bed at approx. 180–200°C Warm oil, approx. 80°C
HARDENING Preheating temperature: 600–900°C. Normally a minimum of two preheats, the first in the 600–650°C range, and the second in the 820–850°C range. When three preheats are used, the second is carried out at 820°C, and the third at 900°C. Austenitising temperature: 1000–1030°C
Temperature °C
Soaking time minutes
Hardness before tempering
1000
30
52±2 HRC
1025
30
55±2 HRC
Note: Temper the tool as soon as its temperature reaches 50–70°C.
TEMPERING Choose the tempering temperature according to the hardness required by reference to the tempering graph below. Temper at least three times for die casting dies, and two times for forging and extrusion tools. The tool should be cooled to room temperature between the tempers. The minimum holding time at tempering temperature is 2 hours.
Soaking time = time at hardening temperature after the tool is fully heated through.
Tempering in the range of 500–550°C is normally not recommended, and it will result in a lower toughness.
Protect the tool against decarburisation and oxidation during austenitising.
Tempering graph Hardness, HRC 60
Hardness, grain size and retained austenite as functions of austenitising temperature Grain size ASTM Hardness, HRC 10 60 8
58
6
56
1000°C
Retained austenite
1010
1020
1030
1040 1050°C
Austenitising temperture
6
Temper
45
54
50 990 1000
50
Grain size
Hardness
52
Austenitising temperature 1025°C
55 Retained austenite %
Retained austenite, %
40
6
4
35
4
2
30
0
25
Retained austenite
100
200
300
400
2
500
Tempering temperature (2 + 2h)
600
700°C
DIEVAR
Effect of tempering temperature on room temperature Charpy V-notch impact energy
DIMENSIONAL CHANGES DURING HARDENING AND TEMPERING
Short transverse direction.
During hardening and tempering, the tool is exposed to both thermal and transformation stresses. These stresses will result in distortion. Insufficient levels of machine stock may result in slower than recommended quench rates during heat treatment. To reduce the level of distortion, a stress relief is always recommended bewteen rough and semi-finish machining, prior to hardening.
Impact strength 60
Hardness HRC 60
50
50
40
40 Temper brittleness zone
30
30
20
20
10
10 200
300
400
500
600
For a stress relieved Dievar tool, a minimum machining allowance of 0.3% is recommended to correct for distortion during heat treatment with a rapid quench.
700°C
Tempering temperature (2h + 2h)
CCT graph Austenitising temperature 1025°C. Holding time 30 minutes. °C 1100
Austenitising temperature 1025ºC Holding time 30 minutes
1000
AC1 = 890ºC
900
f
AC1 = 820ºC
Carbides
800
s
Pearlite
700 600 500
Cooling Hardness Curve No. HV 10
400 300
1 2 3 4 5 6 7 8 9
Bainite
MS
200
Mf
Martensite
100 1
1
3
2
10
100 1
4
1000 10
1.5
6
10 000
10
8
7
100 000
100
1000
1 0.2
5
1.5 15 280 1248 3205 5200 10400 20800 41600
Seconds Minutes
10 90
9
681 627 620 592 566 488 468 464 405
T800-500 (sec)
600
100 Hours Air cooling of bars, Ømm
7
DIEVAR
Machining recommendations The cutting data below are to be considered as guiding values and as starting points for developing your own best practice.
MILLING Face and square shoulder milling
Condition: Soft annealed condition ~160 HB TURNING
Cutting data parameters
Rough turning
Fine turning
Fine turning
150 - 200
Feed (f) mm/r
0.2 - 0.4
0.05 - 0.2
0.05 - 0.3
2-4
0.5 - 2
0.5 - 2
P20 - P30 Coated carbide
P10 Coated carbide or cermet
-
Carbide designation ISO †
Turning with HSS†
Turning with cabide
Cutting speed (vc) m/min
Depth of cut (ap) mm
Milling with carbide
Cutting data parameters
200 - 250
Rough milling
Fine milling
Cutting speed (vc) m/min
130 - 180
180 - 220
Feed (f z) mm/tooth
0.2 - 0.4
0.1 - 0.2
2-4
≤2
P20 - P40 Coated carbide
P10 Coated carbide or cermet
15 - 20 Depth of cut (ap) mm Carbide designation ISO
End milling
High speed steel
Type of milling Cutting data parameters
Solid carbide
Carbide indexable insert
High speed steel
130 - 170
120 - 160
25 - 301
Feed (f) mm/tooth
0.03 - 0.202
0.08 - 0.202
0.05 - 0.352
Carbide designation ISO
-
P20 - P30
-
DRILLING High speed steel twist drill Drill diameter mm
Cutting speed (vc) m/min
Feed (f) mm/r
≤5
15 - 20 *
0.05 - 0.15
5 - 10
15 - 20 *
0.15 - 0.20
10 - 15
15 - 20 *
0.20 - 0.25
15 - 20
15 - 20 *
0.25 - 0.35
Cutting speed (vc) m/min
1
For coated HSS end mill, vc~ 45–50 m/min
* For coated HSS drill, vc~ 35–40 m/min
GRINDING Wheel recommendation
Carbide drill
Type of grinding
Type of drill Cutting data parameters
Cutting speed (vc) m/min Feed (f) mm/r 1 2
Indexable insert
Solid carbide
180 - 220
120 - 150
60 - 90
0.05 - 0.252
0.10 - 0.252
0.15 - 0.252
Drill with replaceable or brazed carbide tip Depending on drill diameter
8
Brazed carbide1
Grinding wheel designation
Face grinding straight wheel
A 46 HV
Face grinding segments
A 24 GV
Cylindrical grinding
A 46 LV
Internal grinding
A 46 JV
Profile grinding
A 100 LV
DIEVAR
Machining recommendations The cutting data below are to be considered as guiding values and as starting points for developing your own best practice.
MILLING Face and square shoulder milling
Condition: Hardened and tempered to 45±1 HRC TURNING Cutting data parameters
Turning with carbide Rough turning
Fine turning
Cutting speed (vc) m/min
40 - 60
70 - 90
Feed (f) mm/r
0.2 - 0.4
0.05 - 0.2
1-2
0.5 - 1
Depth of cut (ap) mm Carbide designation ISO
Milling with carbide
Cutting data parameters
P20 - P30 Coated carbide
Rough milling
Fine milling
Cutting speed (vc) m/min
50 - 90
90 - 130
Feed (f z) mm/tooth
0.2 - 0.4
0.1 - 0.2
2-4
≤2
P20 - P40 Coated carbide
P10 Coated carbide or cermet
Depth of cut (ap) mm Carbide designation ISO
P10 Coated carbide or cermet
End milling Type of milling Cutting data parameters
DRILLING
Solid carbide
Carbide indexable insert
High speed steel TiCN coated
60 - 80
70 - 90
5 - 10
Feed (f) mm/tooth
0.03 - 0.201
0.08 - 0.201
0.05 - 0.351
Carbide designation ISO
-
P10 - P20
-
High speed steel twist drill (TiCN coated) Drill diameter mm
Cutting speed (vc) m/min
Feed (f) mm/r
≤5
4-6
0.05 - 0.10
5 - 10
4-6
0.10 - 0.15
10 - 15
4-6
0.15 - 0.20
15 - 20
4-6
0.20 - 0.30
Cutting speed (vc) m/min
1
Depending on radial depth of cut and cutter diameter
GRINDING Wheel recommendation
Carbide drill
Type of grinding
Type of drill Cutting data parameters
Cutting speed (vc) m/min Feed (f) mm/r 1 2
Indexable insert
Solid carbide
Brazed carbide1
60 - 80
60 - 80
40 - 50
0.05 - 0.252
0.10 - 0.252
0.15 - 0.252
Grinding wheel designation
Face grinding straight wheel
A 46 HV
Face grinding segments
A 36 GV
Cylindrical grinding
A 60 KV
Internal grinding
A 60 IV
Profile grinding
A 120 JV
Drill with replaceable or brazed carbide tip Depending on drill diameter
9
DIEVAR
Surface treatment NITRIDING AND NITROCARBURISING
Depth of nitriding
Nitriding and nitrocarburising result in a hard surface layer which has the potential to improve resistance to wear and soldering, as well as resistance to premature heat checking. Dievar can be nitrided using gas or plasma. It can also be nitrocarburised via gas or salt bath process. The nitriding and nitrocarburising temperature should be at least 25–50°C below the highest previous tempering temperature, depending upon the process time and temperature. Otherwise, a permanent loss of core hardness, strength, and/or dimensional tolerances may be experienced. During nitriding and nitrocarburising, a brittle compound layer, known as the white layer, may be generated. The white layer is very brittle and may result in cracking or spalling when exposed to heavy mechanical or thermal loads. As a general rule, the white layer formation must be avoided.
Process
Surface hardness
HV0.2
Depth* mm
Gas nitriding at 510°C
10 30
1100 1100
0.16 0.22
Plasma nitriding at 480°C
10
1100
0.15
2
1100
0.13
1
1100
0.08
Nitrocarburising – in gas at 580°C – in salt bath at 580°C *
Time h
Depth of case = distance from surface where hardness is 50 HV0.2 over base hardness
Electrical discharge machining Following the EDM process, the applicable die surfaces are covered with a resolidified layer (white layer) and a rehardened and untempered layer, both of which are very brittle and hence detrimental to die performance. If EDM is used, the white layer must be completely removed by grinding or stoning. After finish machining, the tool should be given an additional temper at approx. 25°C below the highest previous tempering temperature.
Nitriding in ammonia gas at 510°C, or plasma nitriding at 480°C, both result in a surface hardness of approx. 1100 HV0.2 . In general, plasma nitriding is the preferred method because of better control over nitrogen potential. However, careful gas nitriding can give perfectly acceptable results. The surface hardness after nitrocarburising in either gas or salt bath at 580°C is approx. 1100 HV0.2 .
10
DIEVAR
Welding
Further information
Welding of die components can be performed, with acceptable results, as long as proper precautions are taken during the preparation of the joint, the filler material selection, the preheating of the die, the controlled cooling of the die and the post weld heat treatment processes. The following guidelines summarise the most important welding process parameters. Welding method
TIG
MMA
Working temp.1
325 - 375ºC
325 - 375ºC
Filler material
QRO 90 TIG-WELD DIEVAR TIG-WELD
QRO 90 WELD
475°C
475°C
Maximum interpass temp.2 Cooling rate Hardness after welding
For further information, i.e., steel selection, heat treatment, application and availability, please contact our ASSAB office nearest to you.
20 - 40ºC/h for the first 2 to 3 hours and then freely in air
50 - 55 HRC
50 - 55 HRC
Heat treatment after welding
1 2
Hardened condition
Temper at 25°C below the original tempering temperature.
Soft annealed condition
Soft anneal the material at 850°C in protected atmosphere. Then cool in the furnace at 10°C per hour to 600°C, then freely in air.
Preheating temperature must be established throughout the die and must be maintained for the entire welding process, to prevent weld cracking The temperature of the tool in the weld area immediately before the second and subsequent pass of a multiple pass weld. When exceeded, there is a risk of distortion of the tool or soft zones around the weld.
11
DIEVAR
Relative comparison of ASSAB hot work die steels QUALITATIVE COMPARISON OF CRITICAL DIE STEEL PROPERTIES ASSAB grade
Temper resistance
Hot yield strength
Creep strength
Coefficient of thermal expansion
Heat conductivity
Ductility
ALVAR 14 ASSAB 8407 2M ASSAB 8407 SUPREME DIEVAR HOTVAR QRO 90 SUPREME
QUALITATIVE COMPARISON OF RESISTANCE TO DIFFERENT DIE FAILURES ASSAB grade ALVAR 14 ASSAB 8407 2M ASSAB 8407 SUPREME DIEVAR HOTVAR QRO 90 SUPREME
12
Heat checking
Gross cracking
Hot wear / Erosion
Plastic deformation
Corrosion (Al)
DIEVAR
13
DIEVAR
Case study RESISTANCE TO HEAT CHECKING Product : Automotive housing Work material : A380 Aluminium alloy Work temp. : 690°C Tooling size : 406 x 508 x 508 mm Die material : Premium H13 at 44-46 HRC vs DIEVAR 46-48 HRC Background : Severe heat checking begins on Premium H13 at approximately 20,000 shots. The customer wanted better die life.
Premium H13
DIEVAR
Comparison of Premium H13 and DIEVAR after 42,000 shots.
Premium H13
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DIEVAR
DIEVAR
Ningbo ASSAB Tooling Technology (Ningbo) Co., Ltd. Tel : +86 574 8680 7188 Fax: +86 574 8680 7166
[email protected]
Cikarang* PT. ASSAB Steels Indonesia Tel : +62 21 461 1314 Fax: +62 21 461 1306/ +62 21 461 1309
[email protected]
MALAYSIA Kuala Lumpur - Head Office ASSAB Steels (Malaysia) Sdn. Bhd. Tel : +60 3 6189 0022 Fax: +60 3 6189 0044/55
[email protected]
Tel : +62 21 5316 0720-1
Jiangxi* ASSAB Tooling (Dong Guan) Co, Ltd., Jiangxi Branch Tel : +86 769 2289 7888 Fax : +86 769 2289 9312
[email protected]
15
Choosing the right steel is of vital importance. ASSAB engineers and metallurgists are always ready to assist you in your choice of the optimum steel grade and the best treatment for each application. ASSAB not only supplies steel products with superior quality, we offer state-of-the-art machining, heat treatment and surface treatment services to enhance steel properties to meet your requirement in the shortest lead time. Using holistic approach as a one-stop solution provider, we are more than just another tool steel supplier. ASSAB and Uddeholm are present on every continent. This ensures you that high-quality tool steels and local support are available wherever you are. Together we secure our position as the world's leading supplier of tooling materials. For more information, please visit www.assab.com