40CrNiMo钢剪切闸板刃口断裂的原因

摘要

In an oil field,the edge of 40CrNiMo steel shear ram of blow-out preventer cracked.In order to find the fracture reasons of the ram edge,fracture morphology observation,microstructure analysis,chemical composition analysis,mechanical properties testing were used to analyze the fracture.The results indicate that,for 40CrNiMo steel ram edge,brittle fracture occurred under the role of greater impact force;The occurrence and propagation of cracks were caused by lack of ductility and inclusions particles at the grain boundaries of 40CrNiMo steel.The main reasons of edge fracture were lower tempering temperature or shorter holding time during the process of quenching and tempering heat treatment.%某油田用闸板防喷器的40CrNiMo钢剪切闸板在使用过程中发生了刃口断裂事故，为找到刃口断裂的原因，对其进行了断口形貌观察、显微组织分析、化学成分分析、力学性能测试等。结果表明：40CrNiMo钢剪切闸板刃口在较大冲击力作用下发生了脆性断裂；断裂是因钢的韧性不足、晶界间的夹杂物颗粒等导致裂纹萌生和扩展；刃口断裂的主要原因是40CrNiMo钢在调质热处理过程中的回火温度偏低或保温时间过短。