Two main cracks appear on the upper end of the inner hole of a hammer anvil after 130 hours’ impact. The fracture morphology, microstructure, metallographic microscopy results and nonmetallic inclusions of the cracked anvil are analyzed. The chemical composition and mechanical properties of the anvil are examined. In its material, carbon content is shown to be higher than the highest limit of 40CrMnMo specifications, with multiple sulfide inclusions, which affects the comprehensive mechanical properties to some extent. The cracks originate from mechanical fatigue, propagating from the stress concentration point near the upper end of the inner hole. Low material toughness and high local working stresses are the main contributors of fatigue cracking. The lines of optimizing the operating conditions and improving the anvil structure and material are put forward.

中文翻译：

---

液压锤砧的疲劳裂纹影响评估和运行条件优化

冲击130小时后，锤砧内孔的上端出现两个主要裂纹。分析了裂纹砧的断裂形态，显微组织，金相显微镜结果和非金属夹杂物。检查了砧的化学成分和机械性能。在其材料中，碳含量显示高于40CrMnMo规格的最高限值，其中包含多个硫化物夹杂物，这在一定程度上影响了综合机械性能。裂纹源于机械疲劳，从内孔上端附近的应力集中点传播。较低的材料韧性和较高的局部工作应力是造成疲劳开裂的主要原因。