柴油机20钢机油冷却喷嘴断裂原因

Cracking Reason of 20 Steel Engine Oil Cooling Nozzle of Diesel Engine

某型号柴油机的机油冷却喷嘴在使用中,喷嘴管从铜钎焊焊缝位置发生断裂。通过微观形貌观察、化学成分分析、显微组织观察和硬度测试等方法分析了断裂的原因,并提出了质量控制措施。结果表明,在钎焊过程中,液态铜沿着奥氏体晶界渗透,并在晶界上形成了薄膜,弱化了晶界的结合强度,此类裂纹被称作铜的渗透裂纹。在外力作用下,从渗透裂纹开始起裂,导致喷嘴管断裂。

The nozzle tube of engine oil cooling nozzle of a diesel engine fractured at the copper brazing seam in the course of service.The fracture reason was analyzed by the methods such as microscopic morphology observation,chemical composition analysis,microstructure observation and hardness test,and the quality control measures were proposed.The results show that the molten copper penetrates the austenite grain boundaries in the brazing process and brittle film is formed,which weakens grain boundaries'cohesive force.This type of cracking is known as copper-contamination cracking.The crack propagates from copper-contamination cracking zone and leads to the fracture of nozzle tube when it is subjected to external force.