Annealed microstructure of Crl3 stainless steel

Generally speaking, the as cast alloy steel is mostly ferrite + carbide phase, and so is 2Crl3, which needs further annealing treatment. 2Crl3 is a medium and low carbon alloy steel. Relevant data show that it is generally maintained at 750-800 ° C for 2-6h and air cooled, Under this process, it is easy to make the internal and external of the structure uneven and produce different properties. Because the isothermal transformation of austenite is maintained on the pearlite area, a slow cooling and a small undercooling degree are required. The internal and external cooling speed of the material is inconsistent. The slower the cooling near the center, the higher the transformation temperature, the internal and external will be different. Isothermal annealing has accurate temperature and time control to obtain better metallographic structure and mechanical properties. The process is 1000 ° C for 4h, air cooling to 660 ° C for 8h and air cooling. As shown in the metallographic diagram of 2Crl3 isothermal annealed microstructure, the microstructure is relatively uniform and close to steady state.

However, in the annealed state, the structure is not suitable to be used as the processing object. First, the annealed steel forms carbon chromium compound, so the content of Cr element is reduced, which weakens the corrosion resistance of the material; Second, due to the large amount of chromium carbide formed in the matrix, the grain boundary is poor in chromium, and the carbide and chromium poor area form a “battery” electrode in a certain area, which accelerates the oxidation and corrosion of the material.