Annealing microstructure of Crl3 stainless steel

Generally speaking, as cast alloy steel is mostly ferritic + carbide phase, so is 2Crl3 stainless steel, which needs further annealing treatment. 2Crl3 stainless steel is a medium low carbon alloy steel. Relevant data show that under the traditional 750-800 ° C heat preservation for 2-6h and air cooling, it is easy to make the internal and external structure uneven and produce different properties, This is because the isothermal transformation of austenite is maintained in the pearlite region, which requires a slow cooling and a small undercooling degree. The internal and external cooling speed of the material is inconsistent. The slower the cooling near the center, the higher the transformation temperature, and the internal and external parts will be different. Isothermal annealing has precise temperature and time control, and better metallographic structure and mechanical properties are obtained. The adopted process is holding at 1000 ° C for 4h, air cooling to 660 ° C for 8h, and air cooling. As shown in the metallographic diagram of 2Crl3 stainless steel in isothermal annealing state, the microstructure is relatively uniform and close to stable state.

However, in the annealed state of stainless steel, the structure is not suitable for processing. First, the annealed steel forms carbon chromium compounds, so the content of Cr element decreases and the corrosion resistance of the material weakens; Secondly, due to the large amount of chromium carbide formed in the matrix, the grain boundary is poor in chromium, and the carbide and the chromium poor area form a “battery” electrode in a certain area, and at the same time, the oxidation corrosion of the material is accelerated.

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