Martensitic

This group contains a minimum of 12% chrome and usually a maximum of 14% with carbon in the range of 0.08% - 2.00%. Due to the high carbon content of the steel, it responds well to heat treatment to give various mechanical strengths, such as hardness. The carbon, however, is detrimental when welding and care should be taken during this operation. In the heat-treated condition this group of steels show a useful combination of corrosion resistance and mechanical properties that qualify them for a wide range of applications. The numbers listed below represent grades within British Standard 970. The figures in brackets after each number are the Euronorms currently being introduced to supersede British Standards.

Type 410 (BS EN 10088 1.4006)

A 13% chrome, 0.5% carbon stainless alloy possessing good ductility and corrosion resistance. It can be easily forged and machined and exhibits good cold working properties.

Type 416 (BS EN 10088 1.4005)

Similar to type 410 but has added sulphur to improve usability, usually in bar form.

Type 431 (BS EN 10088 1.4057)

A 17% chrome, 2.5% nickel, 0.15% (max) carbon stainless alloy which has superior corrosion resistance to 410 or 416 due to the addition of nickel. It can be heat treated to ensure good tensile strength, in the range of 55/56 tonnes tensile. Due to its good machining properties combined with strength it has numerous applications, particularly in machined components where the above mechanical property is required. The material is usually supplied in bar form.