Abstract: Tested steel 18CrNiMo7-6 (/%: 0. 17C, 0. 59Mn, 0. 24Si, 1.56Ni, 1.71Cr, 0. 28Mo) is a case-hardening steel for gear, it is required that the structure of normalized steel is ferrite + pearlite and has lower HB hardness value. The higher hardness bainite structure is easily obtained in steel 18CrNiMo7-6 after continuous cooling. The tested results by high temperature chamber electric resistance furnace in laboratory show that with 870 〜900 °C 1 h-640 ~ 660°C 4 h furnace cooling to 300 °C air cooling the structure of steel is ferrite + pearlite + bainite with HB hardness value 340 ~ 350, while with 870 -900 X. 1 h, 30 Y/h cooling to 640 ~660 °C furnace cooling to 300 °C air cooling the structure of steel is ferrite + pearlite with HB hardness value 190 ~ 210. The commercial production test results show that with 900 °C 10 h, ≤30°C /h cooling to 650 °C 25 h, then 30 °C/h cooling to 500 °C air cooling for 30 t Φ180 mm finished forged products the structure of steel 18CrNiMo7-6 has ferrite + pearlite structure.

摘要： 18CrNiM07-6钢(/%:0.17C、0.59Mn、0.24Si、1.56Ni、1.71Cr、0.28Mo)为表面硬化齿轮钢要求正火后钢的组织为铁素体+珠光体和较低的HB硬度值。18CrNiM07-6钢连续冷却后易得到高硬度的贝氏体组织。通过实验室高温箱式电阻炉试验表明,870～900℃1 h-640～660℃4 h炉冷至300℃,空冷,该钢的组织为铁素体+珠光体+贝氏体组织,HB硬度值为340～350;而870～900℃1 h,30℃/h至640～660℃,炉冷至300℃,空冷,该钢的组织为铁素体+珠光体,HB硬度值为190～210:生产试验表明,30 t Φ 180 mm 18CrNiM07-6钢锻材经900℃10 h,≤30℃/h至650℃25 h,30℃/h至500℃空冷,可获得铁素体+珠光体组织。