D2 die steel - heat treatment process

1. Stress relief annealing

2. After rough machining, the workpiece is heated to 600 ~ 650 ℃ for 2 h, cooled to 500 ℃ with furnace and air cooled.

3. The quenched workpiece is slowly heated to 600 ℃ and kept for 20min for the first preheating. After the average temperature is raised to 850 ℃, the second preheating is conducted after holding for 30min. Finally, the temperature is raised to 1020 ~ 1040 ℃, and the heat preservation is 25 ~ 40min, and the furnace is air cooled.

4. Tempering: tempering shall be carried out immediately after quenching, and tempering shall be carried out at least twice, with each holding time not less than 2H

5. Attention: after quenching, tempering should be carried out in time to prevent cracking and surface decarburization. Gauges and high-precision dies should be cryogenic (- 70 ℃), and high-temperature tempering should be used to reduce workpiece deformation. The high-temperature tempering temperature is 500-560 ℃, and the hardness is greater than 58hrc

6. Hardness: annealed, ≤ 255hb, indentation diameter ≥ 3.8mm; quenched, ≥ 59HRC