- The term Stainless steel is used to cover a wide variety of grades – at least 45 different types are listed in technical manuals. They can be classified into three basic groups. Austenitic AISI 300 Series. All grades in this series contain chromium and nickel. They are non-magnetic and non-hardenable by heat treatment. Common grades include –
- Type 301 – Contains nominally 17% chromium, 7% nickel – useful where extra strength is required and often supplied in a hard temper-rolled condition.
- Type 302 and 304 Sometimes referred to as 18/8(contains nominally 18% chromium, 8% nickel) widely used for kitchen sinks, tubs, piping and vessels for food and chemical processing, urinals and architectural work, both indoor and outdoor.
- Type 316 – In addition to chromium and nickel also contains Molybdenum to increase corrosion resistance. Commonly used outdoors at the seaside and in the more severely corrosive food and chemical processing applications.
- Ferritic (AISI 400)series - This group is magnetic and non-hardenable by heat treatment. Most common grade is –
- Type 430 – contains 16/18% Chromium –suitable only for mildly corrosive conditions and moderate temperature heat resisting applications. Widely used for motor vehicle trim and parts. Interior decoration, stove and commercial refrigeration facing kitchen utensils etc.
- Martensitic (AISI 400)Series – Also magnetic but can be hardened by heat treatments. Most common grade is-
- Type 420C – Contains 11/13% Chromium, used for cutlery, surgical instruments and special Engineering applications.
Standard Type & Chemical Composition
|AISI Type||Chemical Composition%|
|No.||C||Mn max||Si Max||P Max||S Max||Cr||Ni||Other element|
c x 10