汽车转向节锻后直接淬火的组织和硬度

Microstructure and Hardness of Automotive Steering Knuckle Quenched Directly after Forging

对轴径为30mm、40mm和55mm的40Cr钢汽车转向节锻造后分别空冷至840℃、600℃、650℃和700℃,随后淬入水和5%聚乙烯醇水溶液。检测了经不同工艺热处理的转向节的表面和离表面不同距离处的显微组织和截面硬度分布。结果表明:轴径40mm的转向节锻后空冷至840℃淬聚乙烯醇水溶液可以淬透;而轴径55mm的转向节水淬的淬透性较好,但采用聚乙烯醇水溶液淬透性刚能达到要求。此外,锻后空冷至650℃以上温度淬火的转向节,其显微组织和硬度均能达到要求。

The 40Cr steel automotive steering knuckles 30 mm,40 mm and 55 mm in axle diameters were air cooled to 840℃,600℃,650℃ and 700℃ then quenched in water and 5%aqueous polyvinyl alcohol solution after forging,respectively.The steering knuckles heat treated by these different procedures were tested for microstructure at the surface and the different depths below the surface,and for cross-sectional hardness distribution.The results showed that the steering knuckle 40 mm in axle diameter forged and air cooled to 840℃ might be throughout hardened by quenching in aqueous polyvinyl alcohol solution,whereas the steering knuckle 55 mm in axle diameter had better hardenability when quenched in water,but exhibited hardenability which conformed scarcely with the requirement when quenched in aqueous polyvinyl alcohol.Also,the steering knuckle forged then air cooled to temperatures above 650℃and quenched had microstructure and hardness which met the requirements.