Austenitic stainless steel
Stainless steels may be classified by their crystalline structure into three main types: Austenitic, Ferritic and Martensitic. Austenitic steels have austenite as their primary phase (face centered cubic crystal). These are alloys containing chromium and nickel (sometimes manganese and nitrogen), structured around the Type 302 composition of iron, 18% chromium, and 8% nickel. Austenitic steels are not hardenable by heat treatment. The most familiar stainless steel is probably Type 304, sometimes called T304 or simply 304. Type 304 surgical stainless steel is an austenitic steel containing 18-20% chromium and 8-10% nickel.
Austenitic stainless steel can be tested by nondestructive testing using the dye penetrant inspection method but not the magnetic particle inspection method. Eddy-current testing may also be used. Primary stainless steel used in aviation construction. Chemical and steel industry-applicable grades are 308,308L,316,316L, 316LN Nitrogen bearing, 312, 309L, 310L L denotes carbon percentage less than .03% mostly used for corrosion heat resistance has work hardening properties welding primarily done by TIG and MMAW process however GMAW, FCW, SAW process are also used. Another grade 312 is used for dissimilar steel welding, also known as universal alloy steel as unknown composition steels can be welded. For high temperature application >600*C ss309,310 grades are preferred.