First, the definition of stainless steel
A high alloy steel that resists corrosion in air or in chemically aggressive media. Stainless steel is aesthetically pleasing the surface and corrosion resistance are good. It is not necessary to perform surface treatment such as plating, but to exert the inherent surface properties of stainless steel.A type of steel used in many ways, often called stainless steel. Representative performance of 13 chrome steel, 18-chrome nickel steel, etc.High alloy steel.From the perspective of metallographic analysis, because the stainless steel contains chromium and forms a thin chromium film on the surface, this film is separated from the steel.Internally invaded oxygen plays a role in corrosion resistance.In order to maintain the inherent corrosion resistance of stainless steel, steel must contain more than 12% chromium.
Second, stainless steel types:
Stainless steel can be roughly classified according to its use, chemical composition and metallographic structure.The austenite type steel consists of 18% chromium-8% nickel, and the amount of each element added varies.Made various types of steel.
Classification by chemical composition:
1. CR Series: Ferritic Series, Martensitic Series
2. CR-NI Series: Austenitic Series, Abnormal Series,Precipitation Hardening Series.
1. Austenitic stainless steel
2. Ferritic stainless steel
3. Martensitic stainless steel
4. Duplex stainless steel
5. Precipitation hardening stainless steel
Third, stainless steel professional terms
1. Austenitic stainless steel: Austenitic stainless steel at room temperature. Steel contains about 18% Cr, Ni 8%~10%,When C is about 0.1%, it has a stable austenite structure. Austenitic chromium-nickel stainless steel includes the famous 18Cr-8Ni steel and Based on this, a high
Cr-Ni series is developed by increasing the content of Cr and Ni and adding Mo, Cu, Si, Nb,Ti and other elements steel. Austenitic stainless steel is non-magnetic and has high toughness and plasticity, but its strength is low and it is impossible to make it through phase change.Strengthening can only be enhanced by cold working. Such as adding S, Ca, Se, Te and other elements, it has good ea Tearability. In addition to corrosion of oxidation-resistant acid media, such steels contain Mo, Cu, and other elements that are resistant to sulfuric acid and phosphoric acid.And formic acid, acetic acid, urea and other corrosion. If the carbon content in this type of steel is less than 0.03% or contains Ti, Ni,Improve its resistance to intergranular corrosion. High-silicon austenitic stainless steel concentrated nitric acid may have good corrosion resistance. Oxygen Body stainless steel has a comprehensive and good overall performance and has been widely used in various industries.
2. Ferritic stainless steel: Stainless steel with ferrite structure in use. Chrome content is 11%~30%, with a body-centered cubic crystal structure. This type of steel is generally nickel-free and sometimes contains small amounts of Mo, Ti, and Nb.This type of steel has many advantages such as high thermal conductivity, small expansion coefficient, good oxidation resistance, excellent resistance to stress corrosion, etc.In the manufacture of resistance to atmospheric, water vapor, water and oxidizing acid corrosion parts. This type of steel has poor plasticity and post-weld plasticity.The corrosion resistance is significantly reduced and other shortcomings, thus limiting its application. Application of outside refining technology (AOD or VOD).It can make carbon, nitrogen and other gap elements greatly reduced, so that this kind of steel is widely used.
3. Austenitic-ferritic duplex stainless steel: Austenitic and ferritic stainless steels are approximately one-half of each.In the case where the C content is low, the Cr content is 18% to 28%, and the Ni content is 3% to 10%. Some steels also contain Mo, Cu, Si, Nb, Ti, N and other alloying elements. This type of steel combines the characteristics of austenitic and ferritic stainless steels compared to ferrite., Plasticity, toughness, no room temperature brittleness, resistance to intergranular corrosion and welding performance are significantly improved, while maintaining Holds ferritic stainless steel 475 °C brittleness and high thermal conductivity, with features such as superplasticity. Austenite stainless .Compared with steel, high strength and resistance to intergranular corrosion and chloride stress corrosion resistance are significantly improved. Duplex stainless steel has excellent The resistance to pitting corrosion is also a kind of nickel-nickel stainless steel.
4. Martensitic stainless steel: Stainless steel that can adjust its mechanical properties through heat treatment, in layman’s terms, is a Hardenable stainless steel. Typical grades are Cr13 type, such as 2Cr13, 3Cr13, 4Cr13 and so on. After the fire hardnessHigh, different tempering temperatures with different toughness combinations, mainly for steam turbine blades, cutlery, surgical instruments Mechanical. According to the difference in chemical composition, martensitic stainless steel can be divided into martensitic chromium steel and martensitic chromium nickel steel. root According to different organization and strengthening mechanisms, it can be divided into martensitic stainless steel, martensite maraging stainless steel.