Abstract: The subcritical spheroidization annealing, ordinary spheroidizing annealing, and isothermal spheroidizing annealing heat treatment process experiment on 20CrNiMo steel are carried out. By means of optical microscope and brinell hardness tester is carried out to observe respectively after the spheroidizing microstructure. The results show that the hardness value in 20CrNiMo steel can be controlled below 160HBW through ordinary spheroidizing annealing and isothermal spheroidizing annealing ； when the subcritical spheroidizing annealing at 710 °C , the spheroidization rate has increased with the extension of time, when the spheroidizing annealing time more than 25 h, the spheroidization rate may be more than 65% ； the normal spheroidizing annealing process, which is held at 750 °C for 6 h and slow cooling, can obtain 83% spheroidizing rate； by using isothermal spheroidizing annealing, when at 750 °C for 6 h, the in 30 min furnace cooling to 650 °C for 6 h, the spheroidizing rate is 93% and the hardness value is 145HBW.

摘要： 采用亚温球化退火、普通球化退火、等温球化退火对20CrNiMo钢进行热处理工艺试验,利用光学显微镜和布氏硬度计分别对球化后的显微组织进行观察和硬度检测。结果表明,20CrNiMo钢经过普通球化退火、等温球化退火、硬度值≤160HBW,且经过710℃亚温球化退火,随着时间的延长,球化率有所上升,当球化退火时间达25 h以上时,亚温球化退火能获得65%以上的珠光体球化率;采用750℃保温6 h后再以10℃/h的冷却速度缓慢冷却的普通球化退火工艺,能获得83%以上的珠光体球化率;采用750℃保温6 h,经30 min炉冷到650℃保温6 h的等温球化退火,能获得硬度值为145HBW和93%的球化率。