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采用光学及扫描电镜观察分析了自行车多飞飞轮轮芯冷挤压凸模显微组织结构,探究了其断裂失效的原因。观察显微组织发现,失效模具的显微组织中明显存在不均匀带状分布的碳化物。断口形貌及裂纹附近EDS测试分析表明,碳化物集中区为断裂裂纹发生区。模具组织中存在不均匀带状分布的碳化物是产生断裂失效的内在原因,而模具在冷挤压成型过程中形成的应力积累是导致模具断裂失效的外在诱因。
The microstructure of the cold extrusion die for bicycle multi-flywheel wheel core was observed and analyzed by optical and scanning electron microscopes, and the reason of fracture failure was discussed. Observe the microstructure found that the microstructure of the failure mode is obviously uneven distribution of carbides. The EDS test and analysis of the fracture surface morphology and crack show that the carbide concentration zone is the fracture crack initiation area. The uneven distribution of carbides in the die structure is the intrinsic cause of fracture failure, and the stress accumulation in the die during cold extrusion process is the external cause of die failure.