关键词: 18CrNiMo7-6齿轮钢, Φ540 mm锻材, 铸锭高温扩散, 正火, 退火, 带状组织

Abstract: Process flowsheet of test heavy gear steel 18CrNiMo7-6 (/% ： 0.165C , 0.59Mn, 0.24Si, 0.006S, 0.008P, 1.56Ni, 1.71Cr, 0.28Mo, 0.034Al, 0.0129N) is 60 t UHP EAF-LF-VD-12.5 t ingot casting process. The effect of ingot heating process (1200-1220 °C , 7-8 〜13-15 h) , forged product complete annealing (900 °C 12 h, with ≤ 80 °C/h slow cooling to 650 °C 50 h, air cooling) , isothermal annealing (900 °C 12 h, air cooling to 650 °C 50 h, air cooling) and normalizing (900 °C 12 h, air cooling) process on banded structure of Φ540 mm forged bar has been tested and studied. Results show that as ingot heating at 1200-1220 °C for 7-8 h, the rating of banded-structure of forged bar by complete annealing, isothermal annealing or normalizing process is respectively 4.0, 3.5 and 3.0, while as ingot heating at 1200-1220 °C for 13-15 h, then normalized, the rating of banded-structure of forged bar is 2.5 , it is an optimum process.

Key words: Gear Steel 18CrNiMo7-6, Φ540 mm Forged Bar, Ingot High Temperature Diffusion Process, Normalizing, Annealing, Banded-Structure