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Whether stainless steel plate or heat-resistant steel plate, austenitic steel plate has the best comprehensive performance, with sufficient strength, excellent plasticity, and low hardness, which is also one of the reasons why they are widely used. Austenitic stainless steel is similar to most other metal materials in terms of tensile strength, yield strength, and hardness, which increase with the decrease of temperature; Plasticity decreases with decreasing temperature. Its tensile strength increases relatively uniformly within the temperature range of 15-80 degree C. More importantly, as the temperature decreases, its impact toughness decreases slowly and there is no brittle transition temperature. So stainless steel can maintain sufficient plasticity and toughness at low temperatures. The heat resistance of stainless steel refers to its ability to resist oxidation or gas medium corrosion at high temperatures, which is also known as thermal stability.
The etki of krom
Chromium is the most important alloying element in austenitic stainless steel, and the achievement of its rust resistance and corrosion resistance is mainly due to the effect of alloying, which promotes the passivation of steel and keeps it in a stable and passive state. ○ 1 Effect of chromium on microstructure: In austenitic stainless steel, chromium is an element that strongly forms and stabilizes ferrite, reducing the austenite zone. As the steel content increases, ferrite can appear in austenitic stainless steel（ δ） Research has shown that in chromium nickel austenitic stainless steel, when the carbon content is 0.1 percent and the chromium content is 18 percent , the nickel content required to obtain a stable single austenitic structure is the lowest, about 8 percent . In this regard, the commonly used 18Cr-8Ni type chromium nickel austenitic stainless steel is the most suitable one with chromium and nickel content ratio. In austenitic stainless steel, as the chromium content increases, some intermetallic phases (such as δ The formation tendency of phase increases, and when molybdenum is present in the steel, the chromium content will increase χ The formation of equality, as mentioned earlier, σ,χ The precipitation of phase not only significantly reduces the plasticity and toughness of steel, but also reduces the corrosion resistance of steel under some conditions. The increase of chromium content in austenitic stainless steel can reduce the hydrocarbon transfer temperature (Ms) of Martensite, thus improving the stability of austenitic matrix. Therefore, it is difficult to obtain Martensite structure for high chromium (such as more than 20 percent ) austenitic stainless steel even after cold working and low temperature treatment.
Chromium is a strong carbide forming element, and it is no exception in austenitic stainless steel. Common chromium carbides in austenitic stainless steel include Cr23C6; When steel contains molybdenum or chromium, carbides such as expired Cr6C can also be seen, and their formation can have a significant impact on the properties of the steel under certain conditions. ○ 2 Effect of chromium on performance: Generally speaking, as long as austenitic stainless steel maintains complete austenitic structure without δ The formation of ferrite and other elements does not significantly affect the mechanical properties by only increasing the chromium content in the steel. The greatest impact of chromium on the properties of austenitic stainless steel is corrosion resistance, mainly manifested as: chromium improves the oxidation resistance of the steel medium and the performance of acidic chloride medium; Under the combined action of nickel, molybdenum, and copper, chromium improves the resistance of steel to reducing media such as organic acids, urea, and alkaline media; Chromium also improves the resistance of steel to localized corrosion, such as intergranular corrosion. Pitting corrosion, Crevice corrosion and stress corrosion performance under certain conditions.