History of the 200 series and current developments
The 200 series of stainless steels was developed in the early 1930s. Although the first chemical analyses were of the 205 kind ( Nicontent close to 1% and stabilization of the austenitic phase by simultaneous high manganese and nitrogen additions-see Figures 1 and 2), the first grades to receive the AISI label in the mid-1950s were the 201 and 202 grades (nickel content around 4-6% and nitrogen additions below 0.25%). These became more popular during the korean War, due to the need to conserve nickel. At that time, the use of nickel was mainly restricted to military applications. Grade 214, with less than 1% Ni and about 0.35% N was produced at the end of the 1950s. Austenitic CrMn grades containing Mo to improve corrosion resistance appeared in the mid-1960s, both in the U.S. and Europe.
Simultaneously, Mn and Cu containing grades were developed which made it possible to produce 4-6% Ni austenitic grades ( grades 211 and 203) with relatively low nitrogen content ( <0.06% N). Drawing properties equivalent to those of 304 could be
Achieved. Due to a new Ni shortage, these grades began to be popular in the early 1970s. The new AOD technology made adding nitrogen to the 200 series easier and more cost-effective( Table 1). Once again the nickel shortage ended and, with high availability, Ni prices went down again. For more than 30 years, grade 304 was the standard of the stainless steel family, at an average yearly growth of 5-6%.