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通过化学成分、低倍组织、断口、金相组织、机械性能测试等项目分析了42CrMo钢气缸细长活塞杆(长径比约为30)在矫直过程中发生断裂的原因。结果表明:活塞杆的力学性能、化学成分符合标准要求。断裂主要原因是材料表面淬火层分布不均,造成变形较大,在矫直过程中活塞杆的中部,受到的力矩最大,此处刚好是感应淬火与未感应淬火的过渡区,存在组织应力,因此在矫直过程中发生脆性断裂。
The causes of the fracture occurred in the straightening process of 42CrMo steel cylinder slender piston rod (aspect ratio of about 30) were analyzed by chemical composition, low magnification, fracture, microstructure and mechanical properties test. The results show that the mechanical properties and chemical composition of the piston rod meet the standard requirements. The main reason for the fracture is the uneven distribution of the surface quenched layer on the material, resulting in large deformation. During the straightening process, the middle part of the piston rod receives the maximum torque. Here, it is just the transition zone between induction hardening and non-induction hardening, Therefore brittle fracture occurs during straightening.