The formation process of martensitic stainless steel

The formation process of martensitic stainless steel

When there are requirements for formability, softness, etc. in manufacturing, steel with xxx carbon content of 0.12% is usually used in the soft state. As the carbon content increases, tensile strengths in the range of 600 to 900 MPa (87 to 131 ksi) can be obtained by quenching and tempering, along with reasonable toughness and ductility. In this case, these steels have many useful general applications where mild corrosion resistance is required. Additionally, in the hardened and lightly tempered condition, a tensile strength of approximately 1,600 MPa (230 ksi) may be achieved due to the higher carbon content, but with reduced ductility.

Martensitic stainless steel is a type of stainless steel whose properties can be adjusted through heat treatment (quenching, tempering). In layman's terms, it is a type of hardenable stainless steel. This characteristic determines that this type of steel must meet two basic conditions: First, there must be an austenite phase region in the equilibrium phase diagram, and heating is performed for a long time within the temperature range of this region to solid dissolve the carbides into the steel. After that, quenching is performed to form martensite, that is, the chemical composition must be controlled in the γ or γ+α phase region. Second, in order for the alloy to form a passive film that is resistant to corrosion and oxidation, the chromium content must be above 10.5%. According to the difference in alloy elements, it can be divided into martensitic chromium stainless steel and martensitic chromium-nickel stainless steel.