The selection principle of quenching heating temperature of hypoeutectoid steel and hypoeutectoid steel is described. Why can't quenching temperature of hyperprecipitation steel exceed Accm line?
Quenching temperature selection principle: to obtain uniform fine austenite grain as the principle, in order to obtain fine martensite structure. Hyposteel usually heated to above AC3 30-50 ℃, hypereutectoid steel heated to AC1 above 30-50 ℃. 1, hypereutectoid steel quenching heating temperature more than Accm line of carbide all dissolve in austenite, increase the carbon content of austenite, reduce the Ms and Mf point of steel after quenching residual austenite volume increase, will reduce the hardness and wear resistance of steel 2, hypereutectoid steel quenching temperature is too high, the austenitic grain coarsening, carbon content is high, easy to get a microcrack after quenching coarse acicular martensite, lower steel plastic toughness 3 large thermal stress, high temperature quenching when quenching, oxidation decarburization is serious, It also increases the tendency of deformation and cracking.