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通过材料化学成分、断口宏微观观察、金相组织检查、硬度测试和力学性能试验等方法找出了冲击砧子的开裂原因。结果表明,砧子材料碳含量稍高于40CrMnMo规范要求的上限,其金相组织为回火索氏体+少量铁素体,属于正常的调质组织,砧子基体材料的塑性较低;砧子裂纹属于机械疲劳裂纹,裂纹起源于内孔端面附近的应力集中位置,因此局部工作应力偏高是导致疲劳开裂的主要原因。
Through the chemical composition of the material, the macro-microscopic fracture observation, metallographic examination, hardness testing and mechanical properties of the test method to find out the cause of cracking anvil cracking. The results show that the carbon content of the anvil material is slightly higher than the upper limit of the 40CrMnMo specification. The microstructure of the anvil material is tempered sorbite + a small amount of ferrite and belongs to the normal tempering tissue. The plasticity of the anvil substrate material is low. The crack belongs to the mechanical fatigue crack, and the crack originates in the stress concentration position near the end face of the inner hole. Therefore, the local working stress is the main cause of fatigue cracking.