Martensitic Chromium-Nickel Steel
Martensitic chromium-nickel steel include martensitic precipitation hardening stainless steel, semi-austenitic precipitation hardening stainless steel, and maraging stainless steel. These are high strength or ultra high strength stainless steel. This type of steel has a low carbon content (less than 0.10%) and contains nickel. Some grades also contain higher elements such as molybdenum and copper. Therefore, the steel has high strength, and the combination of strength and toughness, corrosion resistance and weldability are superior to 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, and Cu. It is to increase the strength of the steel by precipitation hardening on the martensite matrix by precipitation hardening, such as Crl7Ni4Cu4. The semi-austenitic (or semi-martensitic) precipitation hardened stainless steel is still austenitic due to the quenched state. Therefore, the quenched state can still be cold-formed and then strengthened by processes such as intermediate treatment and aging treatment. In this way, the austenite in the martensitic precipitation hardening stainless steel can be directly converted into martensite after quenching, which leads to the disadvantage that subsequent processing is difficult. Commonly used steel grades are 0Crl7Ni7AI, 0Crl5Ni7M02A1, and the like. Such steels have high strength, generally ranging from 1200 to 1400 MPa, and are often used to make structural parts that require less high corrosion resistance but require high strength, such as aircraft skins.