Stainless steels are usually divided into martensitic steel, 5261 ferritic steel, austenitic steel, austenitic steel, austenitic steel, austenitic 4102 ferrite (dual phase) stainless steel and precipitation hardening stainless steel. In addition, it can be divided into chromium stainless steel, chromium nickel stainless steel and chromium manganese nitrogen stainless steel. There are also special stainless steel "gb24511" for pressure vessels_ 2009_ Stainless steel plates and strips for pressure equipment.

1. Ferritic stainless steel

It contains 15% - 30% chromium. Its corrosion resistance, toughness and weldability increase with the increase of chromium content, and its chloride stress corrosion resistance is better than other kinds of stainless steel. Crl7, cr17mo2ti, Cr25, cr25mo3ti and Cr28 belong to this category. Because of its high chromium content, ferritic stainless steel has good corrosion resistance and oxidation resistance, but poor mechanical and technological properties, so it is mostly used in acid resistant structure with little stress and as anti-oxidation steel. This kind of steel can resist the corrosion of atmosphere, nitric acid and brine solution, and has the characteristics of good high temperature oxidation resistance and small thermal expansion coefficient. It can be used for nitric acid and food factory equipment, and can also be used for parts working at high temperature, such as gas turbine parts.

2. Austenitic stainless steel

It contains more than 18% chromium, about 8% nickel and a small amount of molybdenum, titanium, nitrogen and other elements. It has good comprehensive performance and can resist corrosion of various media. The common grades of austenitic stainless steel are 1Cr18Ni9, 0Cr19Ni9, etc. The WC of 0Cr19Ni9 steel is less than 0.08%, which is marked as "0" in the steel grade. This kind of steel contains a lot of Ni and Cr, which makes the steel austenite at room temperature. This kind of steel has good plasticity, toughness, weldability, corrosion resistance and no magnetism or weak magnetism. It has good corrosion resistance in oxidizing and reducing media. It can be used to make acid resistant equipment, such as corrosion resistant container and equipment lining, transportation pipeline, nitric acid resistant equipment parts, etc. in addition, it can also be used as the main material of stainless steel watch accessories. Austenite stainless steel is generally treated by solution treatment, that is, the steel is heated to 1050 ~ 1150 ℃, and then cooled by water or air to obtain single phase austenite structure.

3. Austenitic ferrite duplex stainless steel

It has the advantages of both austenitic and ferritic stainless steels and superplasticity. Stainless steel in which austenite and ferrite account for about half each. In the case of low C content, Cr content is 18% ~ 28%, Ni content is 3% ~ 10%. Some steels also contain Mo, Cu, Si, Nb, Ti, N and other alloy elements. This kind of steel has the characteristics of both austenitic and ferritic stainless steel. Compared with ferrite, this kind of steel has higher plasticity and toughness, no room temperature brittleness, significantly improved intergranular corrosion resistance and welding performance. At the same time, it also maintains the brittleness of ferritic stainless steel at 475 ℃, high thermal conductivity and superplasticity. Compared with austenitic stainless steel, it has higher strength, intergranular corrosion resistance and chloride stress corrosion resistance. Duplex stainless steel has excellent pitting corrosion resistance and is also a nickel saving stainless steel.

4. Precipitation hardening stainless steel

The matrix is austenite or martensite. The common grades of precipitation hardening stainless steel are 04cr13ni8mo2al, etc. Stainless steel that can be hardened (strengthened) by precipitation hardening (also known as age hardening).

5. Martensitic stainless steel

High strength, but poor plasticity and weldability. The common grades of martensitic stainless steel are 1Cr13, 3Cr13, etc. due to its high carbon content, it has high strength, hardness and wear resistance, but its corrosion resistance is slightly poor. It is used in some parts with high mechanical properties and general corrosion resistance requirements, such as springs, turbine blades, hydraulic compressor valves, etc. This kind of steel is used after quenching and tempering. Annealing is required after forging and stamping.

6. Stainless steel plate and strip for pressure equipment

Special stainless steel for pressure vessels has clear requirements on classification, code, size, shape and allowable deviation, technical requirements, test methods, inspection rules, packaging, marking and product quality certificate. The common brands are 06cr19ni10, 022cr17ni12mo2, and the digital codes are s30408, s31603, etc. Mainly used in food machinery, pharmaceutical machinery and other health equipment.