Abstract: The microstructure, impact performance and fracture morphology of 42CrMo steel after pre-heat treatment (annealing,quenching, tempering) and treatment of quenching from dual phase range + tempering at high temperature ( also referred to as quenching from critical range + tempering) were observed and analyzed by means of metallographic micro¬scope , hardness tester and scanning electron microscope. The results show that the residual ferrite is uneven in distribution between tempered sorbite when the preparatory heat treatment is tempering, whereas the residual ferrite is small and even when the preparatory heat treatment is quenching and hardening and tempering. The hardness difference of sub-heat treatment is very small when different preparation heat treatment is used. After sub-temperature treatment, the impact performance of 42CrMo steel is higher than that of conventional hardening and tempering. When pre-heat treatment is hardening and tempering, the impact energy after sub-temperature treatment is the largest, and it can be seen from the fracture morphology. The cracking area and crack fiber expansion area of hardening and tempering account for a larger proportion than annealing and quenching. Therefore, the hardening and tempering treatment is more suitable as a preparatory heat treatment for the 42CrMo steel.

Key words: Preparatory Heat Treatment, Sub-Heat Treatment, 42CrMo Steel, Impact Energy, Fracture Morphology

摘要： 利用金相显微镜、洛氏硬度计和扫描电镜,对经过预备热处理(退火、淬火、调质)+亚温淬火+高温回火处理(又称临界区淬火+回火)后的42CrMo钢的组织、冲击性能以及断口形貌进行了观察和分析。结果表明,预备热处理为退火处理时,亚温处理后残留的铁素体粗大不均;且在回火索氏体之间分布不均匀;预备热处理为淬火处理和调质处理时,残留的铁素体形态细小,且与回火索氏体均匀分布。采用不同预备热处理时,亚温处理后的硬度差别很小。亚温处理后42CrMo钢的冲击性能均高于常规调质处理后的冲击性能;预备热处理为调质处理时,亚温处理后的冲击功最大,从其断口形貌中可以看出,其起裂区和裂纹纤维扩展区所占比例较退火处理和淬火处理时要大。因此,调质处理更适合作为42CrMo钢的预备处理。