31.1
The Nickel Advantage in Stainless Steels
Peter Cutler: Director Promotion, Nickel Institute 3rd International Stainless Steel Symposium, Stresa, October 2009
The Nickel Institute does not present forecasts or comments on nickel markets, prices or supply/demand. The Nickel Institute does promote the long term use of nickel to contribute to a sustainable future.
Nickel-containing stainless steels • • • • • •
Versatile Reliable Hygienic Long-lasting Recyclable Available
2 Stresa, 2009
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31.1
Chrysler Building, 1927
Stainless steel containing about 7% Ni, similar in composition to the V2A grade first developed in Germany and today’s widely-used Type 304 3 Stresa, 2009
Stainless Crude Steel by Categories (preliminary)
25,7 13,6
28,1 12,2 57,2 2008
28,4 11,5 57,5
60
2007
9,4 23,0
9,8 63,1 2005
24,8
9,4 23,0 65,5 2004
7,4 21,8 70,8 2003
70
5,7 22,1
80
72,2
90
2002
100
5,3 23,2
%
50
60,7
20
65,5
30
71,5
40
Provided by ISSF
Stresa, 2009 CrNi austenitic share remains on average around 60%
qu1 09p
.
2006
0
Cr CrMn CrNi
2001
10
4
2
31.1
Chromium is the essential element in stainless steel.
How does nickel add its advantages?
5 Stresa, 2009
Nickel, an austenite stabiliser
Nickel equivalent = Ni% + 30C% + 30N% + 0.5Mn% + 0.3Cu%
(by weight)
Metals with an austenitic, face-centred cubic structure like aluminium, copper, nickel and gold are very ductile, even at low temperatures. 6 Stresa, 2009
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Schaeffler diagram
Increasing nickel allows an increasing amount of chromium to be added, thus increasing the corrosion resistance whilst maintaining the austenitic structure. Other elements besides nickel also stabilise the austenitic structure but may not be so easy to add or may have other effects. 7 Stresa, 2009
Strength and ductility
The high work hardening rate and high ductility of the austenitic grades. Stresa, 2009
ISSF/ICDA
8
4
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Work hardening
High work hardening rate of the austenitic grades 9 Stresa, 2009
Energy absorption - bus frame roll-over test
Centro Inox
The combination of toughness, strength and work hardening leads to good energy absorption and crash worthiness
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Effedi 4cycle
Centro Inox
Effedi 4cycle
Centro Inox
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Railcar interior, Mumbai, India
Duplex stainless steels Wrought material
Alloy
%Cr
%Ni
%Mo
%N
S32101
21.5
1.5
0.4
0.22
S32205
22.5
5.5
3.2
0.17
S32750
25.0
7.0
4.0
0.28
Weld filler metal for above
Alloy
%Cr
%Ni
%Mo
%N
2101
23.0
7.0
0.2
0.14
ER2209
23.0
8.5
3.2
0.17
25-10-4L
25.0
9.5
4.0
0.25
Two phase steels with an austenite + ferrite structure. These also contain nickel, which stabilises the austenitic phase. They have an attractive combination of mechanical and corrosion resistant properties. Stresa, 2009 This application is in the pulp and paper industry.
2205 14
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Duplex stainless steel in desalination plant
Centro Inox
Nickel and toughness
Ferritic stainless steels show a ductile to brittle transition at low temperatures but austenitic grades can retain their toughness down to liquid helium temperature.
Large Hadron Collider, CERN 16
Stresa, 2009
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Other grades • Martensitic - some contain nickel • Precipitation hardening grades contain nickel
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Formability
Stala
Good formability of the common austenitic grades is demonstrated by this one-piece sink.
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Formability Deep drawing
Stretch forming The edges of the blank are clamped in stretch forming 19 Stresa, 2009
Formability
Ferritic grades perform a little better than 304 in deep drawing but are not so good in stretch forming. This is illustrated by the forming limit diagram below which shows the ability of the material to resist local thinning.
ISSF/ICDA
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Delayed cracking
Stresa, 2009
ISSF/ICDA 21
Weldability
Type 304 and similar nickel containing austenitic grades are readily welded in thick section. They are probably the most commonly welded stainless steels. 22 Stresa, 2009
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Hygienic
304 wine tanks, Italy 23 Stresa, 2009
High temperature properties
Austenitics have higher high temperature creep streng th than ferritics 24 Stresa, 2009
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Toughness after elevated temperature exposure Room Temp. Charpy Keyhole Impact Strength after 10,000 hr Stainless Unexposed Type (J)
480C (J)
565C (J)
650C (J)
304
123
107
84
64
316
108
118
66
28
321
145
119
98
84
410
45
53
4
28
430
62
1
4
5
300 series retain good room temperature ductility after exposure at elevated temperatures
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From stainless steels to nickel alloys
It is interesting to note that there is a continuum of composition from nickel containing 304 austenitic stainless steel right through to the nickel based superalloys used for the hot parts of jet engines. 26 Stresa, 2009
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Corrosion resistance
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Pitting Resistance Equivalent
PRE = Cr% + 3.3Mo% + 16N%
This expression shows the relative resistance to pit initiation. Nickel does not feature but it does have other influences on corrosion. 28 Stresa, 2009
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Nickel and corrosion propagation
Nickel reduces pitting corrosion propagation rate. Charles 29 Stresa, 2009
Nickel and Chloride Stress Corrosion Cracking
Stainless steels with around 8-10% Ni are prone to stress corrosion cracking if the right chloride level, tensile stress and temperature are present. This can be avoided by using grades with less or more nickel. Stresa, 2009
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Consider all operating conditions
Cleaning or operating excursions? When designing equipment and selecting grades it is important to consider operating condition excursions outside the normal. For example, a milk packaging plant (above) must not only be able to withstand the product but also incorrect application of cleaning fluids. This even more important for the safe operation of chemical plants.
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Ferromagnetism • Austenitic grades are generally not ferromagnetic • Special applications • Impact on recycling Some applications such as magnetic resonance imaging requires non-magnetic grades. The non-magnetic nature of the austenitic grades is utilised in separating them during recycling. There is a tendency for the ferritic (magnetic) grades to end up with carbon steel scrap and so to be lost from the stainless steel recycling loop. 32 Stresa, 2009
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Lustre - an intangible quality Olympic hockey stadium, Turin
Although subtle, the appearance of stainless steel is influenced by both the grade and its finish. Nickel containing austenitic grades are widely used for architectural applications. [Cheung Kong Center, Hong Kong]
Centro Inox 33 Stresa, 2009
Environmental aspects
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Nickel, stainless steel and CO2 “content” kg CO2 equivalent*/kg material Primary nickel has a high CO2 equivalent output …
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Highly resource-intensive production of nickel demands credible response from industry to realize resource savings potential 15.2
13.1 5.5
Mg
Ni
Al
Cu
5.4
Plastics
3.4
2.2
Stain- Iron & less steel steel
Nickel has a high CO2 footprint but it is more appropriate to compare that of nickel containing stainless steel with competing materials. 35 Source: Leiden EU report 2005, Eurofer, EU Webpage, ISSF
Stresa, 2009
Nickel, stainless steel and CO2 “content” kg CO2 equivalent*/kg material Primary nickel has a high CO2 equivalent output …
31.1
Highly resource-intensive production of nickel demands credible response from industry to realize resource savings potential 15.2
Ni
Nickel in use lower than most non-stainless substitutes
15.2
13.1 5.5
Mg
… but in its major use its CO2 output is lower than that of aluminum, copper or plastics
Al
Cu
5.4
Plastics
13.6 3.4
3.4
2.2
Stain- Iron & less steel steel
Ni
Nickel has a high CO2 footprint but it is more appropriate to compare that of nickel containing stainless steel with competing materials.
Only 10% nickel needed
0.8
0.8
50% nickel coming from scrap
CO2 related to primary nickel
2.6 CO2 other than nickel
Total CO2
Stainless steel 36 Source: Leiden EU report 2005, Eurofer, EU Webpage, ISSF
Stresa, 2009
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Energy use and product life cycle
It is even more relevant to look at how energy is used throughout the whole life cycle of a product. Thus small differences in energy content in the manufacturing phase of a car are not relevant if they lead to much greater reduction of energy in use. 37 Stresa, 2009
Importance of recycling For a metal like stainless steel, which has a long service life, “recycled content” does not reflect the true extent of recycling. It makes much more sense to talk about the “recycling ratio”, that is the proportion of end-of-life scrap which is actually recycled. Stainless steel is then one of the World’s most recycled materials.
Because so much stainless steel is still in use and is not yet available for recycling
ISSF 38
Stresa, 2009
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Importance of recycling
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Waste water treatment - Life Cycle Cost ← Old
Huddersfield, UK Waste water treatment
New ↓
• 98% reduction in maintenance costs • 25% extra plant capacity When choosing a grade, it is essential to Stresa, 2009 consider the whole life cycle costs and benefits
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Consider all the factors when selecting a grade • • • • • • • • • • • • •
Corrosion resistance Operating temperature Strength - influences thickness & weight Other mechanical properties Fabrication and welding Physical properties Appearance Tooling costs Life cycle costs Availability: confidence in suppliers Familiarity Recyclability, environmental impacts and benefits Degree of comfort (risk, insurance)
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300 series is available in many forms This is one reason why they are so widely used
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The Nickel Advantage • Nickel-containing stainless steels have a continuing role because of their combination of characteristics • Appropriate grades for appropriate applications
↓ • • • • •
Performance Customer satisfaction Shareholder value Enhanced image Market growth The correct approach to grade selection is to consider all the factors on the earlier slide. That leads to the selection of appropriate grades for appropriate applications - and the subsequent benefits shown above. Stresa, 2009
43
Nickel - lasting value
www.nickelinstitute.org The Nickel Institute produces information on all aspects of the selection and use of nickel-containing materials
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