Due to the characteristics of stainless steel and its material organization has a close relationship, so usually in classifications for each department. Such as daily commodities, by the system of austenite stainless steel SUS304 represent and SUS430 and ferritic stainless steel of high purity iron series system, and by the quench hardening SUS420J1 represent high system of martensite stainless steel, etc., and other special varieties and duplex stainless steel and precipitation strengthening is stainless steel, etc. If look from the main component, the system of austenite stainless steel, duplex stainless steel and precipitation hardening stainless steel can be called Ni - Cr or Ni stainless steel; Stainless steel and iron element system and the system of martensite stainless steel is referred to as the Cr stainless steel duplex stainless steel.