摘要:
G20Cr2Ni4A钢属于CrNi系优质合金渗碳钢, Cr、Ni含量较高, 淬透性较好, 渗碳处理后表面有相当高的硬度、耐磨性和接触疲劳强度, 同时心部还保留良好的韧性, 具有优良的综合力学性能。由于G20Cr2Ni4A钢临界点Ac1和Ac3(Ac1为钢加热时开始形成奥氏体的温度, Ac3为所有铁素体均转变为奥氏体的温度)之间温度范围较窄, Ac3为785 ℃, 故可选择较低的淬火温度, 既可保证表面和心部硬度, 同时齿轮畸变也会减小。G20Cr2Ni4A经加热淬火+回火, 能提高材料的冲击韧性, 改善构件心部的综合力学性能。20Cr2Ni4A钢淬火试样经不同温度回火后的冲击韧性研究发现, 当回火温度为200 ℃左右时, 冲击韧性最高。选取回火温度为200 ℃, 通过两因素三水平的正交试验对G20Cr2Ni4A钢进行热处理, 观察淬火温度和回火时间对其金相组织、残余奥氏体含量、硬度和冲击性能的影响。正交试验采用800, 850, 900 ℃的淬火温度和1, 3, 5 h的回火时间对G20Cr2Ni4A钢进行热处理, 然后分别测出其硬度、冲击功和残余奥氏体含量, 通过正交试验分析, 并与原始样品对比, 得出: 淬火加热温度与回火时间对G20Cr2Ni4A钢的力学性能有显著影响。随淬火加热温度升高, 硬度、冲击功、残余奥氏体量均先增大后缓慢减小; 随回火时间延长, 硬度、冲击功、残余奥氏体量均先减小后增大。硬度随残余奥氏体含量的增加而增加, 冲击韧性与残余奥氏体量成近似直线关系。G20Cr2Ni4A钢经850 ℃淬火+200 ℃回火1 h后, 残余奥氏体含量为2.97%, 试验钢具有最佳的综合力学性能, 其硬度为45.1, 冲击功为25.0 J。
Abstract:
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 Ac1 and Ac3 of G20Cr2Ni4A steel is narrow and Ac3 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.