Stainless Steels and Nickel 100 years of Working Together

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1 Gary Coates Consultant to the Nickel Institute Stainless Steels and Nickel Towards the Next 100 Years May 16, 2012 Beijing, China

2 Before stainless steels were developed, the main metals and alloys used by man included: Iron, steel and alloys Copper and copper alloys (incl. brass, bronze, nickel-silver) Pure nickel and nickel alloys - including 65%Ni 35% Cu alloy (patented 1906) Tin and tin-plated Zinc-plated Aluminum Lead and lead alloys Precious metals (e.g. gold, silver) 1909 Roof of Railroad Station in New York City - 120t Monel 2

3 Early Discoveries Many steps leading to the commercialization of stainless steel 1799 Vauquelin (France) discovered chromium metal 1821 Berthier (France) made chromium alloys, found that increasing chromium content increased corrosion resistance, but the high carbon content did not allow them to be stainless 1904 Guillet (France) studied ferritic and martensitic families, then in 1906 studied the nickel-containing austenitic stainless steels, but not their corrosion resistance 1908 Monnartz (Germany) - discovered passivity in Fe-Cr alloys as Cr content neared 12% - the property of stainlessness 3

4 Development of Austenitic Types Mauer and Strauss (Germany) - tested Cr-Ni-Fe alloys, initially for high temperature use, but then for corrosionresisting applications Patents issued in 1912 for 2 nickel-containing stainless steels The grade V2A (20% Cr and 7% Ni) found to have exceptional corrosion resistance compared to the Cr-Fe alloys, especially in nitric acid Today the 18-8 grade (304L) is still the most commonly used stainless steel for nitric acid, and is the alloy that is most widely used by far in the world 4

5 Development of Ferritic and Martensitic Types 1911 Portevin (France) ferritic 18%Cr-Fe (~AISI 430) 1911 Becket & Dantsizen (U.S.) ferritic types for lead-in wires of electric light bulbs; in 1914, a ferritic grade for steam turbine blades 1911 Haynes (U.S.) started working with martensitic types; applied for a patent in Brearley (G.B.) produced a 13%Cr with 0.24% carbon which could be hardened; initially called Firth`s Aeroplane Steel, as it was used in exhaust valves for aeroplane engines. (During World War I from 1914 to 1918, all the production of this grade was requisitioned for military purposes.) 5

6 First major commercial application Brearley produced first commercial melt of his steel, but it was difficult to forge so knife blade producers were reluctant to use it. 1914, the first knife blades are produced in Sheffield England. After the war ended in 1918, this alloy became very popular for table knives in the home 1920`s the nickel-containing alloy 18-8 becomes popular for spoons and forks while the hardenable martensitic alloy remains popular for knives 6

7 Early Use of Stainless Steel in Milk Processing Paper by Fink and Rohrman (1931) It has long been known that milk in contact with iron and copper will not only acquire a metallic taste, but corrode these metals readily. (Tin-coated metals were most often used at that time.) High chromium nickel (18-8) iron alloys are very resistant to corrosion by milk and are satisfactory for dairy equipment They reported that some materials that are otherwise suitable for milk itself do not stand up well to the action of cleaning compounds that are commonly used in dairies. But the 18-8 alloy was suitable for the cleaning compounds. Milk tanker truck 7

8 Modern Milk Packaging Plant Modern Barn Stainless everywhere for ease of sanitation 8

9 Early Use in Architectural Applications 1929 entrance canopy at Savoy Hotel in London, England 1930 Chrysler Building (New York City) 1931 Empire State Building (New York City) Iconic Buildings 9

10 Modern Use in Architectural Applications Petronas Twin Tower, Kuala Lumpur, Malaysia Trump Tower, Chicago, U.S.A. Jin Mao Tower, Shanghai, China Modern iconic buildings 10

11 Use in Sculpture News (1940) New York City, U.S.A. Charm of the Sea (1999) Dalian, China Genghis Khan - Mongolia 11

12 Families of Stainless Steels The alloys are categorized based on their microstructure (crystal structure) or the hardening mechanism Family Series Hardenable Nickel-containing? Ferritic Part of 400 series Martensitic Part of 400 series No Yes, by heating & quenching A few have a small content, up to 4% A few have a small content, up to 6% Austenitic 300 series Only by cold work Yes, 7-40% Austenitic 200 series Only by cold work Yes, less than 300 series, 1-5% Duplex - Only by cold work Yes, 1-9% PH 600 series Yes, by heating Yes, 3-27% All of the austenitic, duplex and PH grades contain nickel, only a few of the ferritic and martensitic grades contain nickel 12

13 Reasons for Nickel Alloying in Stainless Steels Family Ferritic Martensitic PH Duplex Austenitic Principal properties desired by Nickel alloying In %Cr grades, nickel permits grain size control which is very important for weldability. In high alloyed grades, it gives increased toughness and ductility, beneficial during hot rolling and in the end use. In higher Cr grades, nickel allows for martensite transformation. In all grades, improves corrosion resistance, weldability and other properties Nickel allows for martensite transformation. Improves corrosion resistance, ductility, weldability, etc. Stability of austenite, ductility, toughness, corrosion resistance Stability of austenite and the properties of the austenitic structure, corrosion resistance, and much more to be discussed 13

14 `000 of tonnes of stainless steel `000 of tonnes of new nickel Stainless Steels and Nickel Growth of Stainless Steels and Growth of Nickel Since 1950 In 2010, 64.8% of all nickel produced was used in making stainless steel (versus 34% in 1960); In 2011, 72% of all stainless steel contained nickel Worldwide Crude SS Production Worldwide Nickel Production

15 Increasing corrosion resistance Stainless Steels and Nickel Corrosion resistance of the Families Highest Corrosion Resistance Nickel alloys Lowest Corrosion Resistance 15

16 Usefulness of the Ferritic Stainless Steels Potential useful properties - low alloy, low cost stainless e.g. 409 for auto exhaust systems - ferro-magnetic - lower thermal expansion rate (than austenitic types) - higher thermal conductivity (than austenitic types) - good formability / good weldability in thin sections - specific corrosion properties e.g. to chloride stress corrosion cracking; can be useful when nickel contamination is detrimental 16

17 Usefulness of the Ferritic Stainless Steels Potential drawbacks - inability to produce heavier sections - inability to weld heavier sections - low temperature toughness - embrittlement at temperatures above 300C (except 12%Cr) - susceptible to hydrogen embrittlement - lower corrosion resistance in certain environments 17

18 Usefulness of the Martensitic and PH Stainless Steels Potential useful properties - very high strength and high hardness - good for knife blades, dies and tools - PH grades have less tendency to distort during hardening Potential drawbacks - most have corrosion resistance lower than a 304 level - poor formability and weldability Scalpel Water Turbines Pump Shafts 18

19 Usefulness of the Duplex Stainless Steel Types Duplex stainless steels have a microstructure that is about 50% austenitic and 50% ferritic Potential useful properties - higher strength (than either austenitic or ferritic grades) - good weldability (better than ferritic grades) - better corrosion resistance in certain environments (e.g. chloride stress corrosion cracking) Potential drawbacks - high strength makes forming more difficult - susceptibility to certain types of corrosion (e.g. hydrogen embrittlement) - brittle at low temperatures / become brittle with time at temperatures ~ 300 o C 19

20 Usefulness of the Duplex Stainless Steel Types Deck tanks Chemical tankers 1932 Brobec cooler for P&P Industry Modern P&P vessel Cargo tanks Gas and Oil systems on offshore platforms 20

21 Usefulness of the Austenitic Types About 60% of all stainless steels produced today fall into the 300 series family % of Total Production by Family (2011) 300 series 28.0% 200 series 400 series 13.8% 58.2% Source: ISSF 21

22 Role of nickel in the 300 series Austenitic Types First role of nickel is to change the microstructure from ferritic to austenitic For an alloy with 18% Cr, we need a minimum of about 7% nickel to form a stable austenite Other austenitising elements include: nitrogen manganese carbon copper 22

23 Usefulness of the 300 series Corrosion Resistance The corrosion resistance in any environment is a complex result of the interaction of all the alloying elements. Increasing nickel content increases corrosion resistance in certain environments, e.g. sodium hydroxide. Effect of Ni, Mo, and Cr on the Threshold Temperature at which the Corrosion Rate Exceeds 0.13 mm/a 23

24 Usefulness of the 300 series Corrosion Resistance Increasing nickel content increases corrosion resistance during active corrosion, such as during the propagation of pitting and crevice corrosion. Effect of nickel content on the crevice corrosion rate of a 17% Cr -2.5% Mo alloy 24

25 Usefulness of the 300 series Low Temperature Many austenitic alloys are extremely tough down to near 0 o K ( o C). Their strength increases as the temperature decreases. The ASME (U.S.) Pressure Vessel code says that the toughness of e.g. wrought 304, 304L and 316L are exempt from toughness testing down to -254 o C. Used for cryogenic gases incl. LNG piping and tanks, liquid oxygen liquid helium, etc. 25

26 Usefulness of the 300 series High Temperature - 1 Austenitic alloys have higher strength than other stainless families at elevated temperatures. 26

27 Usefulness of the 300 series High Temperature - 2 However the main limiting factor for materials is often the formation of brittle intermetallic phases with long term exposure. The ferritic and duplex stainless steels may embrittle by 2 different mechanisms, starting as low as 300 o C. The austenitic alloys do not embrittle at the lower temperatures, and take much longer to embrittle at the higher temperatures, depending on their alloying content. With increasing nickel content we have nickel alloys and nickel superalloys. Stainless Type Room Temp. Charpy Keyhole Impact Strength after 10,000 hr Unexposed (J) 480C (J) 565C (J) 650C (J)

28 Usefulness of the 300 series Welding The 304L and 316L alloys are quite easy to weld in all thicknesses, up to 250mm thick and greater Higher alloyed 300 series stainless steels are weldable with minimum precautions. 28

29 Usefulness of the 300 series Formability Many of the 300 series stainless steels have outstanding formability 29

30 Selection of the Proper Stainless Steel Stainless steels are chosen for applications varying from - chosen for appearance only - chosen for handling dangerous chemicals Important to look at the full set of material requirements - non-standard conditions and usage (including abuse) - effect of deterioration of the metal (safety issues) - long term experience - life cycle costing - environmental and sustainability considerations The proper grade of stainless steel for the particular application 30

31 Food and Beverage - Processing Meat packaging, Germany Milk Tanks, Thailand The American 3-A standard specifies 300-series or equivalent for proper corrosion resistance Brewery, China 31

32 Food and Beverage kitchens, domestic, serving Attractive, hygienic, durable 32

33 Medical / Dental Applications Easily disinfected, safe 33

34 Chemical / Petrochemical / Pharmaceutical Applications Corrosion resistant, weldable, formable, available 34

35 Water Applications Hygienic, easily installed, low maintenance, long lasting 35

36 Transportation Applications Attractive, low maintenance, long lasting 36

37 Energy Applications Corrosion resistant, weldable, durable, cost-efficient 37

38 Summary Many researchers contributed to the discovery and commercialization of stainless steels The use of nickel in stainless steels started 100 years ago with an alloy very similar to the most common alloy today The value of properties that nickel provides to stainless steels has been discovered, well documented and utilized over the last one hundred years to the benefit of industry and society in general The properties that nickel contributed during the first hundred years will continue to be utilized over the next 100 years, with some new alloys and many new applications 38

39 Looking Forward to the Next 100 Years 39