The Main Classification Of Martensitic Stainless Steel

Martensitic stainless steel can be divided into two categories based on its chemical composition: martensitic chromium steel and martensitic chromium nickel steel; According to the different organization and strengthening mechanisms, it can be divided into martensitic and semi austenitic precipitation hardening stainless steels, as well as martensitic aging stainless steels.
(1) Martensitic chromium steel. In addition to chromium, steel also contains a certain amount of carbon. The chromium content determines the corrosion resistance of steel, and the higher the carbon content, the higher the strength, hardness, and wear resistance. The normal structure of this type of steel is martensite, and some also contain a small amount of austenite, ferrite, or pearlite. Mainly used for manufacturing parts, components, tools, cutting tools, etc. that require high strength and hardness but not high corrosion resistance. Typical steel grades include 2Crl3, 4Crl3, 9Crl8, etc.
(2) Martensitic chromium nickel steel. This includes martensitic precipitation hardening stainless steel, semi austenitic precipitation hardening stainless steel, and martensitic aging stainless steel, all of which are high-strength or ultra high-strength stainless steels. This type of steel has a lower carbon content (less than 0.10%) and contains nickel. Some grades also contain higher elements such as molybdenum and copper. Therefore, this type of steel not only has high strength, but also has a better combination of strength and toughness, as well as better corrosion resistance and weldability than martensitic chromium steel. Crl7Ni2 is the most commonly used low nickel martensitic stainless steel. Martensitic precipitation hardening stainless steel usually contains elements such as Al, Ti, Cu, etc. It precipitates dispersed strengthening phases such as Ni3A1 and Ni3Ti on the martensitic matrix through precipitation hardening, further improving the strength of the steel, such as Crl7Ni4Cu4 and other grades; However, for semi austenitic (or semi martensitic) precipitation hardened stainless steel, as the quenched state is still austenitic, it can still be cold worked and formed, and then strengthened through intermediate treatment, aging treatment and other processes. This can avoid the disadvantage of austenite in martensitic precipitation hardened stainless steel directly transforming into martensite after quenching, which leads to difficulties in subsequent processing and forming. Commonly used steel types include 0Crl7Ni7AI, 0Crl5Ni7M02A1, etc. This type of steel has high strength, generally reaching 1200-1400MPa, and is commonly used in the production of structural components that do not require high corrosion resistance but require high strength, such as aircraft skins.