Generally speaking, stainless steel is not easy to rust steel, in fact, some stainless steel, both stainless steel and acid resistance (corrosion resistance). The rust resistance and corrosion resistance of stainless steel are due to the formation of chromium rich oxide film (passive film) on the surface of stainless steel. This rust resistance and corrosion resistance are relative. The results show that the corrosion resistance of steel increases with the increase of chromium water content in the weak medium such as atmosphere, water and nitric acid. When the chromium content reaches a certain percentage, the corrosion resistance of steel changes suddenly, that is, from easy to rust to not easy to rust, from non corrosion to corrosion resistance.
There are many ways to classify stainless steel. According to the structure classification at room temperature, there are martensite, austenite, ferrite and duplex stainless steel; according to the main chemical composition, it can be divided into two systems: chromium stainless steel and chromium nickel stainless steel; It can be divided into pitting corrosion resistant stainless steel, stress corrosion resistant stainless steel, intergranular corrosion resistant stainless steel, etc. according to the functional characteristics, it can also be divided into non-magnetic stainless steel, free cutting stainless steel, low-temperature stainless steel, high-strength stainless steel, etc. Because of its excellent corrosion resistance, formability, compatibility and toughness in a wide temperature range, stainless steel has been widely used in heavy industry, light industry, daily necessities industry and building decoration industry.
Austenitic stainless steel: stainless steel with austenite structure at room temperature. When the content of Cr is about 18%, Ni is 8% ~ 10%, C is about 0.1%, the austenite structure is stable. Austenitic Cr Ni stainless steel includes famous 18Cr-8Ni steel and high Cr Ni series steel developed by adding CR and Ni contents and adding Mo, Cu, Si, Nb, Ti and other elements. Austenitic stainless steel is non-magnetic and has high toughness and plasticity, but its strength is low. It can not be strengthened by phase transformation, but can only be strengthened by cold working. If s, CA, Se, TE and other elements are added, it has good machinability. This kind of steel can resist the corrosion of sulfuric acid, phosphoric acid, formic acid, acetic acid, urea, etc. The intergranular corrosion resistance of this kind of steel can be significantly improved if the carbon content in the steel is less than 0.03% or contains Ti and Ni. High silicon austenitic stainless steel with concentrated nitric acid has good corrosion resistance. Because of its comprehensive and good comprehensive properties, austenitic stainless steel has been widely used in all walks of life.
This paper is provided by mechanical knowledge network, please pay attention to the content provided by mechanical knowledge network
Ferritic stainless steel: stainless steel with ferrite structure as the main structure in service state. The content of chromium is in the range of 11% ~ 30%, and it has a BCC crystal structure. This kind of steel generally does not contain nickel, and sometimes contains a small amount of Mo, Ti, Nb and other elements. This kind of steel has the characteristics of large thermal conductivity, small expansion coefficient, good oxidation resistance and excellent stress corrosion resistance. It is mainly used for manufacturing parts resistant to atmospheric, steam, water and oxidizing acid corrosion. This kind of steel has some disadvantages, such as poor plasticity, obvious reduction of plasticity and corrosion resistance after welding, which limits its application. The application of secondary refining technology (AOD or VOD) can greatly reduce the interstitial elements such as carbon and nitrogen, so this kind of steel is widely used.
Austenite ferrite duplex stainless steel: it is a stainless steel with austenite and ferrite structure accounting for about half. 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.
This paper is provided by mechanical knowledge network, please pay attention to the content provided by mechanical knowledge network
Martensitic stainless steel: stainless steel whose mechanical properties can be adjusted by heat treatment. Generally speaking, it is a kind of hardenable stainless steel. The typical brand is Cr13, such as 2Cr13, 3Cr13, 4Cr13, etc. It is mainly used for steam turbine blades, tableware and surgical instruments. According to the difference of chemical composition, martensitic stainless steel can be divided into martensitic chromium steel and martensitic chromium nickel steel. According to the different structure and strengthening mechanism, it can be divided into martensitic stainless steel, martensitic and semi austenitic (or semi martensitic) precipitation hardening stainless steel and maraging stainless steel.Two phases (austenite ferrite),
④ Stainless steel, precipitation hardening stainless steel and high alloy with iron content less than 50% are usually named by patent name or trademark.
4) . classification and classification of standards
4-1 classification:
① National standard GB
② Industry standard Yb
③ Local standards
④ Enterprise standard Q / CB
4-2 classification:
① Product standards
② Packaging standard
③ Method standard
This paper is provided by mechanical knowledge network, please pay attention to the content provided by mechanical knowledge network
④ Basic standards
4-3 standard level (divided into three levels)
Y level: international advanced level
Level I: international general level
Class H: domestic advanced level
4-4 national standards
GB1220-84 stainless steel bar (grade I)
Gb4241-84 stainless welded disc (grade H)
Gb4356-84 stainless welded disc (grade I)
GB 1270-80 stainless steel pipe (grade I)
GB 12771-91 stainless steel