Orthoronal Experimental Study on the Effect of Heat Treatment on the Properties of G20Cr2Ni4A Steel

G20Cr2Ni4A steel belongs to CrNi system high quality alloy carburized carbon steel and Cr and Ni content is high. The hardenability of G20Cr2Ni4A is good and its carburized surface has quite high hardness, wear resistance and contact fatigue strength, while its core also retains good toughness, which has excellent comprehensive mechanical properties.Because of the temperature range between critical point A_c1 and A_c3 of G20Cr2Ni4A steel is narrow and A_c3 is 785 ℃, a lower quenching temperature can be selected to ensure surface and core hardness and reduce gear distortion.G20Cr2Ni4A can improve the impact toughness of the material and the comprehensive mechanical properties of the core of the component by heating quenching and tempering.The impact toughness of G20Cr2Ni4A steel after tempering at different temperatures was studied. It was found that the impact toughness was the highest when the tempering temperature was about 200 ℃.The 200 ℃ tempering temperature was selected. G20Cr2Ni4A steel was conducted heat treatment, through the orthogonal test of two factors and three levels, and the effects of quenching temperature and tempering time on the metallographic structure, residual austenite content, hardness and impact properties were observed.Orthogonal test adopted quenching temperature of 800, 850, 900 ℃ and tempering time of 1, 3, 5 h to heat G20Cr2Ni4A, and then measureed its hardness, impact energy and residual austenite content respectively. Through orthogonal test analysis and comparison with the original sample, the corresponding experimental conclusions was drawn: quenching heating temperature and tempering time had significant effects on mechanical properties of G20Cr2Ni4A steel.With the quenching heating temperature increased, the hardness, impact energy and residual austenite volume increased first and then decreaseed slowly; with the extension of tempering time, hardness, impact energy and residual austenite volume all decreased first and then increased.The hardness increased with the increase of residual austenite content, and the impact toughness had an approximate linear relationship with the residual austenite volume.After quenching at 850 ℃ and tempering at 200 ℃ for 1 h, the residual austenite content of G20Cr2Ni4A steel was 2.97%. The experimental steel had the best comprehensive mechanical properties with 45.1 hardness and 25.0 J impact energy.