淬火及回火温度对新型中碳合金钢42CrMo4M组织性能的影响

Effect of quenching and tempering temperature on microstructure and mechanical properties of a new medium carbon alloy steel 42CrMo4M

借助光学显微镜、扫描电镜、透射电镜、拉伸试验机、冲击试验机等研究了热处理工艺对新型中碳合金钢42CrMo4M组织性能的影响。结果表明,经800~900℃淬火油冷后,42CrMo4M钢的淬火态组织主要为板条马氏体,且随着淬火温度的升高,晶粒尺寸逐渐增大,马氏体板条粗化,在860℃淬火时,晶粒度均匀且硬度最高。经860℃淬火后,在580~700℃回火温度范围内,随着回火温度的升高,42CrMo4M钢中的碳化物由长条状向球形转化,并由马氏体边界处不均匀分布演变为基体中弥散分布;当回火温度达到700℃时,42CrMo4M钢中碳化物明显粗化;随着回火温度的升高,42CrMo4M钢的强度先升高后降低,-20℃低温冲击吸收能量先增大后减小。680℃回火时,42CrMo4M钢的冲击吸收能量达到峰值,为99 J。在试验条件下,42CrMo4M钢经860℃淬火及660~680℃回火后具有良好的综合力学性能。

Effect of heat treatment process on microstructure and mechanical properties of a new medium carbon alloy steel 42 CrMo4 M was studied by means of optical microscope, scanning electron microscopy, transmission electron microscopy, tensile testing machine and impact testing machine. The results show that after quenching at 800-900 ℃ and oil cooling, the quenched microstructure of the 42 CrMo4 M steel is mainly lath martensite, and with the increase of quenching temperature, the grain size gradually increases and the martensite lath coarsens. When quenched at 860 ℃, the grain size is uniform and the hardness is the highest. After quenching at 860 ℃, in the tempering temperature range of 580-700 ℃, with the increase of tempering temperature, the carbides in the 42 CrMo4 M steel change from long strip to spherical, and from uneven distribution at the boundary of martensite to dispersed distribution in the matrix. When the tempering temperature reaches 700 ℃, the carbides in the 42 CrMo4 M steel are obviously coarsened. With the increase of tempering temperature, the strength and the low-temperature impact absorbed energy at-20 ℃ of the 42 CrMo4 M steel first increase and then decrease. When tempered at 680 ℃, the impact absorbed energy of the 42 CrMo4 M steel reaches the peak value, which is 99 J. Under the test conditions, the 42 CrMo4 M steel has good comprehensive mechanical properties after quenching at 860 ℃ and tempering at 660-680 ℃.