Copyright 2003, The AISE Steel Foundation, Pittsburgh, PA. All rights reserved.1Continuous casting (CC) of stainless (or corrosion- and heat-resisting) steels has played a front- running role in overall CC development112of flat products, which comprise about 75% of the total stainless steel output (85% strip, 15% plate). The CC ratio attained the 90% mark around 1980, when worlds total crude steel production still dwelled at 30% (compare Chapter 1). The driving force behind this fast growth was the very important yield gain for these highly alloyed steels, which assured satisfactory returns on investments even for a relatively small caster output. CC development was also helped by the comparably small heat sizes that are conveniently manage- able at moderate casting speeds of around 40 inches per minute.In flat products, the product mix for most casters comprises 90% or more in the austenitic Type 300 series; only some units also specialize in the casting of Type 400 series ferritic and marten- sitic grades. (Note: for standard chemistries, compare pertinent norms or supplier manuals; see Refs. 13 and 14.) For long products, very few dedicated plants exist (e.g., Ugine Savoie), but sev- eral plants have a combined flat and long products program exclusively in stainless steels (e.g., Acerinox, NSC Hikari and Yieh United). More commonly, bloom or billet casting of stainless steels is integrated within the diversified product mix of specialty steelmakers producing bar and wire as well as seamless tubing (e.g., Daido Chita, EWK Witten and Sandvik Steel). Due to the yield incentive, stainless steel long products feature the highest billet casting ratio of all specialty steel bar and wire productswith few steelmakers still relying on bloom casting and two-heat rolling.The history of stainless steel manufacturing coincides with the period of early precursor CC devel- opments (see Chapter 1). Although the high corrosion resistance of chromium-alloyed steels has been known since the first half of the nineteenth century,15,16industrial application started just before WWI. The austenitic Cr/Ni-alloyed types are due to the development work of Eduard Maurer and Benno Strauss at Krupp in Essen, with their patent application in 1912.15,17 The martensitic type 12% Cr-steel was invented in 1913 by Harry Brearley, head of research at Thomas Firth Holtzer in Unieux, France, in 1950; and Krasny Oktjabr (Red October, 1951) in Stalingrad, Russia. (Also compare Chapter 1.)The first operation commercially sustainable for a long period was at the Welland Works of Atlas Steels Ltd. in Ontario, Canada, starting in 1954 (honored by ASM as a “Historical Landmark” in 1977) and casting slabs of 5.5 x 21.5 inch as well as twin billets of 5.5 x 7.5 inchthe former cogged on a blooming mill down to 4 x 19 inch before being fed into a Sendzimir hot planetary mill.24Thereafter, further slab casting milestones essential to the widespread CC application are the following:25 The first wide slab caster (max. 1250 mm) for stainless steels of vertical type started operation on Dec. 22, 1960, at the Hikari Works of Yawata Iron and Steel (todays Nippon Steel Corp.)26,27and is still producing as the worlds longest-operating CC machine. The first curved mold slab caster (5 x 50 inch) for stainless steels began to operate early in 1965 at the Tracy Works of Atlas Steels in Quebec, Canada.28This unit was directly followed by a tunnel type reheat furnace and a Sendzimir hot planetary mill (the only one still working today). The start of stainless steel mass production on Japanese slab casters2,7was first of vertical type at Pacific Metal Hachinohe (1964), Nippon Yakin (1965 and 1971), Nippon Metal Sagamihara (1968) and Sumitomo Metal Wakayama (1969). This was followed by the curved mold casters at Nisshin Steel Shunan Works (1971), Kawasaki Steel Chiba (1971) and Nippon Metal Kinuura Works (1972).Later in the 1970s, large curved mold slab casters were built in the U.S., namely, Armco Butler (1970, after a first unit in 1966), Crucible Steel Midland (1972), Eastern Stainless Baltimore (1974) and Allegheny Ludlum Brackenridge (1978). Concurrently, the first activity in Europe before the 1980s yielded the curved mold casters at Ugine Isbergues (1972), ALZ in Genk, Bel- gium (1976),Acerinox Palmones Works (1977) and British Steel Stainless in Sheffield (1978); and the straight-mold/bending type caster at Outokumpu Tornio (1976). In Brazil, the start of the curved mold caster at Acesita in 1979 signalled the incipient participation of developing countries in stainless steelmaking. All these efforts contributed to the rapid growth in stainless steel manu- facture29(see Fig. 22.1), and a new record in world total output (flat and long products) of 16.3 Mt was reported for 1997.22.1 Constitution and CastabilityClose to 75% of total stainless steel production is of the austenitic 300 Series, of which, in turn, about 80% is the standard 18Cr-9Ni Type