MISCONCEPTION: There are only two types of stainless steel, 304 and 316. 

FACT: There are hundreds of stainless steels from high strength duplex 2205 supporting bridges, to furnace ducts of ferritic 3/5Cr12 and the high temperature 310, but the most common types are the austenitic 300 series.

Stainless steels were invented a little over 100 years ago. The corrosion resistance, ease of cleanability, and bright appearance of stainless steels meant its compound growth since 1950 has been about 5% year-on-year. Because of the ease of forming and welding, about 70% of stainless steel use has been within the austenitic family. Within 30 years the accepted chromium level for good corrosion resistance settled at about 18% and “304” was born. Then stainless moved to the seaside and corroded, which led to the development of “316” by adding molybdenum. This in turn created the popular myth of two readily weldable and formable stainless steels despite the hundreds of austenitic grades recognised in standards.

About 25% of global use is seen in (mainly) thin sheet ferritics for cladding. The remaining 5% sees strong duplex, extra strong martensitic blades and wear resistance, and the precipitating hardening grades where strength/hardness is the priority.