The chemical composition of 16MnCrS5 steel for cold forged gear used in the test is shown in Table 1, and the sample size is selected as the diameter The height of ϕ35mm round steel is 150mm, which is used to measure the hardness value (average value of 3 ~ 5 points) under different spheroidizing annealing processes, as well as the microstructure analysis and spheroidizing rate evaluation after heat treatment.
| C | Si | Mn | Cr | P | S | Al |
| 0.155 | 0.17 | 1.1 | 1.03 | 0.013 | 0.02 | 0.03 |
The AC1 temperature of 16MnCrS5 steel for cold forged gear is 740 ℃ measured by thermal simulation tester. Heat the material to the temperature of 20 ℃ above AC1 for spheroidizing annealing, that is, 760 ℃ is used as the spheroidizing annealing temperature. In order to investigate the effect of heating temperature on the hardness after softening, 730 ℃ is taken as the comparison temperature. The specific process is shown in Table 2.
| Process number | Spheroidizing annealing process parameters |
| 1 | Heat preservation at 760 ℃ for 4h, cooling at 12 ℃ / h to 710 ℃, then heat preservation for 3h, cooling at 12 ℃ / h to 680 ℃, heat preservation for 2h, and discharge when the furnace is cooled to 500 ℃ |
| 2 | Heat preservation at 760 ℃ for 4h, cooling at 12 ℃ / h to 680 ℃, then heat preservation for 5h, cooling at 12 ℃ / h to 500 ℃ and discharging |
| 3 | Heat preservation at 730 ℃ for 4h, cooling at 12 ℃ / h to 660 ℃ for 5h, cooling at 12 ℃ / h to 500 ℃ and discharging |
| 4 | Heat preservation at 730 ℃ for 4h, cooling at 12 ℃ / h to 680 ℃ for 3h, cooling at 12 ℃ / h to 660 ℃ for 2h, and discharging at 500 ℃ |