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采用自回火方法热处理的钢锹产品在施工现场出现了批量断裂的现象,应用扫描电子显微镜观察断口,金相显微镜分析显微组织,洛氏硬度计测量硬度值。结果表明:混凝土施工现场断裂钢锹的金相组织是马氏体与少量的回火马氏体,产品强度硬度高、塑性韧性低、易脆断,原因是应用自回火热处理工艺时,淬火的冷却时间长,产品温度下降多,余热未能使产品达到自回火温度;钢锹断口为沿晶断裂,能谱分析发现晶间存在夹杂物,夹杂物的聚集进一步削弱了材料晶间结合力,促进材料脆性化。河沙施工现场断裂钢锹的金相组织为铁素体与马氏体,该组织不适宜做工具产品,其断口微观形貌由准解理、韧窝、孔洞构成。
The self-tempering method of heat treatment of shovel products appeared in the construction site batch fracture phenomenon, the use of scanning electron microscopy fracture, metallographic microscope analysis of microstructure, Rockwell hardness measurement. The results show that the microstructure of steel shovels is a martensite and a small amount of tempered martensite at the site of concrete construction. The product has high strength and hardness, low ductility and brittle fracture. The reason is that when self-tempering heat treatment process is applied, The cooling time is long, the temperature of the product drops a lot, the residual heat can not make the product reach the self-tempering temperature; the fracture of the steel spade is the intergranular fracture; the energy spectrum analysis shows that the intergranular inclusions exist and the inclusion aggregation further weakens the intergranular bond Force to promote material brittleness. The fractured steel shovels on the river sand construction site are composed of ferrite and martensite, which are not suitable for tool products. The fracture surface morphology consists of quasi-cleavage, dimples and holes.