50CrVA弹簧钢断裂失效分析

Fracture Failure Analysis of 50CrVA Spring Steel

某热处理厂生产的合金弹簧钢50CrVA在卷成盘放置一段时间后发生断裂。采用直读光谱仪、洛氏硬度计、金相光学显微镜、扫描电镜对50CrVA失效合金弹簧钢的化学成分、力学性能、显微组织、断口形貌进行了分析。结果表明:淬火过程中马氏体的转变是不完全的,留有残余的奥氏体,经过回火后残余的奥氏体会产生二次马氏体。断口特征呈冰糖状,属于沿晶脆性断裂,同时断口上存在许多球状颗粒的氧化物和碳化物。因此,回火后产生的二次马氏体和球状颗粒状的氧化物和碳化物是卷成盘型弹簧钢失效的主要原因。

Alloy spring steel 50 CrVA produced by a heat treatment plant breaks after the coil is placed for a period of time.The chemical composition,mechanical properties,microstructure and fracture morphology of 50 CrVA failure alloy spring steel were analyzed by direct reading spectrometer,Rockwell hardness tester,metallographic microscope,which has electron microscope.The results show that the transformation of martensite during quenching is incomplete and retained retained austenite.After tempering,the residual austenite produces secondary martensite.The fracture features are sugar-like and belong to brittle fracture along crystal.At the same time,there are many oxides and carbides of spherical particles on the fracture surface.Therefore,secondary martensite and spherical granular oxides and carbides produced after tempering are the main causes of failure of coiled spring steel.