The 20MnCr5H steel for precision formed gears was subjected to subcritical spheroidizing annealing(710 ℃ × 8.5 h)and spheroidizing annealing in dual-phase region(750 ℃ × 1.5 h+680 ℃×7 h,750 ℃ ×4 h+710 ℃ ×4 h,770 ℃ ×4 h+720 ℃ ×4 h),and the spheroidizing effects under different processes were investigated.The results show that under the spheroidizing annealing in dual-phase region,higher austenite zone temperature will make it difficult for lamellar pearlite to spheroidize in a short time,while shorter austenite zone holding time will help to improve the spheroidization efficiency.Good spheroidization effect is achieved under 750 ℃ × 1.5 h+680 ℃ ×7 h process.Compared with the spheroidizing annealing in dual-phase region,the spheroidization effect of the 20MnCr5H steel is the best under 710 ℃ ×8.5 h subcritical spheroidizing annealing,and the spheroidization rate reaches 98％.This is due to the fact that after the process treatment,more dislocations and small-angle grain boundaries in the microstructure can promote the dissolution and spheroidization of flaky cementite more quickly.It is a reasonable spheroidizing annealing process for precision forming gears.
关键词
20MnCr5H钢/亚温球化退火/双相区球化退火/球化率
Key words
20MnCr5H steel/subcritical spheroidizing annealing/spheroidizing annealing in dual-phase region/spheroidizing rate
维普
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