Martensitic stainless steel whose mechanical properties can be adjusted by heat treatment is, in a nutshell, a type of hardenable stainless steel. Typical grades are Cr13, such as 2Cr13, 3Cr13, 4Cr13, etc. After quenching, the hardness is higher, and different tempering temperatures have different combinations of toughness and are mainly used for steam turbine blades, tableware and surgical instruments.
According to the difference in chemical composition, martensitic stainless steel can be divided into martensitic chromium steel and martensitic chromium nickel steel. According to the organization and strengthening mechanism, it can be divided into martensitic stainless steel, martensite and semi-austenitic (or semi-martensitic) precipitation hardening stainless steel and maraging stainless steel.
Martensitic stainless steels are high-strength and corrosion-resistant and can be used to make machine parts such as steam turbine blades (1Cr13), steam-equipped shafts and tie rods (2Cr13), and parts that work in corrosive media such as valves, bolts, etc. (4Cr13). Steel grades with high carbon content (4Cr13, 9Cr18) are suitable for the manufacture of medical devices, table knives, measuring tools, springs, etc.
The corrosion resistance of martensitic stainless steel mainly depends on the chromium content, and the carbon in the steel indirectly affects the corrosion resistance of the steel due to the formation of stable chromium carbide with chromium. Therefore, in the 13% Cr steel, the lower the carbon content, the higher the corrosion resistance. In the four steels of 1Cr13, 2Cr13, 3Cr13 and 4Cr13, the order of corrosion resistance and strength is just the opposite.
When processing products, in order to increase the strength and hardness of the martensitic stainless steel product, the carbon content is increased, resulting in a decrease in the plasticity and corrosion resistance of the product. Therefore, the products processed by martensitic stainless steel usually have poor corrosion resistance.
Model 304 - universal model; ie 18/8 stainless steel. The GB grade is 0Cr18Ni9.
Model 316—After 304, the second most widely used steel grade is used primarily in the food industry and surgical equipment, adding molybdenum to give it a special structure that resists corrosion. It is also used as "ship steel" because it has better resistance to chloride corrosion than 304. SS316 is commonly used in nuclear fuel recovery units.
