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| Teach you how to understand stainless steel easy to rust |
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Stainless steel is not easy to rusty stainless steel, in fact, a part of stainless steel, both stainless steel, and have acid (corrosion resistance). Stainless steel stainless steel and corrosion resistance is on the surface of chromium rich oxide film (film) formation. This stainless and corrosion resistance is relative. Experiments show that the steel in the air, water and the weak medium and nitric acid oxidation medium, the corrosion resistance with the steel chromium containing content increase and improve, when the chromium content reaches a certain percentage, mutations in the corrosion resistance of steel, namely from easy to rust to is not easy to rust, never corrosion resistance to corrosion. Stainless steel classification method a lot of:
According to the classification of microstructure: austenite, martensite, ferrite, double phase precipitation hardening stainless steel;
According to the main chemical composition classification, can be divided into chromium stainless steel and chromium nickel stainless steel two system:
CR series: ferrite series, martensite Series II.
CR-NI series: Austenitic series, abnormal series, precipitation hardening series.
According to the use of specific resistance of stainless steel, stainless steel, nitric acid sulfuric acid resistant seawater resistant stainless steel;
According to the corrosion type can be divided into pitting corrosion stainless steel, corrosion-resistant stainless steel, intergranular corrosion stainless steel;
According to the feature classification can be divided into non magnetic stainless steel, easy cutting stainless steel, low temperature stainless steel, high strength stainless steel, etc..
Austenitic stainless steel
The austenite structure of the steel contains about 18%, 8%~10% Ni, C about 0.1%, and has a stable austenite structure.. Austenitic chromium nickel stainless steel includes the famous 18Cr-8Ni steel and Cr, Ni content and Mo, Cu, Ti, Si, Nb and other elements developed Cr-Ni series steel. The austenitic stainless steel is not magnetic and has high toughness and plasticity, but the strength is lower, and it can not be strengthened by the phase transformation, and can be strengthened by cold work.. Such as S, Ca, Se, Te and other elements, it has a good machinability. In addition to the corrosion of such steel medium corrosion, if it contains Cu, Mo and other elements can also be resistant to sulfuric acid, phosphoric acid and formic acid, acetic acid, urea and other corrosion. The carbon content of this kind of steel can be significantly improved with the intergranular corrosion resistance if it is lower than 0.03% or Ti and Ni.. High silicon austenitic stainless steel concentrated nitric acid is willing to have good corrosion resistance. As the austenitic stainless steel has comprehensive and good comprehensive performance, it has been widely used in all walks of life..
Ferritic stainless steel
In the use of ferrite ferrite stainless steel. The chromium content in 11%~30%, with a body centered cubic crystal structure. This kind of steel in general does not contain nickel, sometimes also contains a small amount of Mo, Ti, Nb until the elements, this kind of steel with high heat conductivity, expansion coefficient is small, good oxidation resistance, resistance should be excellent characteristics of stress corrosion, used for the manufacture of air resistance, water vapor, water and oxidation corrosive acid components. This kind of steel has the disadvantages of plastic difference, plasticity and corrosion resistance, so it has limited its application.. The application of AOD or VOD can make the gap element such as carbon and nitrogen greatly reduce, so it is widely used for this kind of steel..
Austenite ferrite duplex stainless steel
Is the austenitic and ferrite microstructure of about half of the stainless steel. In the case of low Cr, the content of C in 18%~28%, Ni content in 3%~10%. Some steels also contain Cu, Si, Mo, Nb, Ti, N and other alloying elements. The steel both austenite and ferrite pigment of the stainless steel body characteristics, compared with ferrite, plasticity, toughness, brittleness at room temperature, resistance to intergranular corrosion resistance and welding performance were significantly increased, while maintaining ferrite stainless steel body 475 DEG C brittleness and thermal conductivity of high, with superplastic characteristics. Compared with the austenitic stainless steel, the high strength and intergranular corrosion and the resistance to chloride stress corrosion are obviously improved. The duplex stainless steel has good pitting corrosion resistance and also a nickel stainless steel.
Martensitic stainless steel
The mechanical properties of stainless steel can be adjusted by heat treatment, which is popularly said that it is a kind of hardening stainless steel. Typical grades are Cr13, such as 2Cr13, 3Cr13, 4Cr13, etc.. After the fire in pure high hardness and different tempering temperatures with different combination of strength and ductility, mainly used for steam turbine blades, cutlery, surgical instruments. According to the differences in chemical composition, martensitic stainless steel can be divided into martensite and martensite chromium chromium nickel steel two. According to the difference of microstructure and strengthening mechanism, martensite stainless steel, martensite and semi austenite (or semi martensite) precipitation hardening stainless steel and martensite stainless steel etc are also classified..
Not all stainless steel are not magnetic, only pure austenitic stainless steel is not magnetic, had made of austenitic stainless steel standard weight with magnetic, the effective elimination of the magnetic method is the solution heat. Martensitic stainless steel is magnetic, often used in the production of medical appliances, knives, cutlery.
Column, stainless steel ladders general test methods only through professional inspection syrup (containing Ni test drops, containing eight Ni above test drops), or by the inspection department by chemical analysis and metallographic examination to determine. American Standard does not absorb magnetic products for stainless steel processing, grinding a variety of reasons may be magnetic, so the general use of whether the magnetic absorption, if rust test material quality is not scientific; (304 stainless steel approximate China’s steel 0Cr18Ni9, containing Cr 13 percent (Cr13) more than can be said for stainless steel, with low Cr can be attracted by magnet (itself without magnetic), 304 stainless steel for the United States Code, will not be magnet adsorption, can be used for chemical plant acid corrosion resistance.Catalog printing
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