Cr8钢冲模试模过程早期断裂失效分析

Cr8 steel failure analysis of early fracture in stamping die test

Cr8钢冲模在试模过程中产生断裂,采用金相显微镜、扫描电镜及能谱仪对断裂样品进行检测。对冲模崩裂断口进行检测,沉孔平台存在片层状挤压变形,表明该处材料强度低。沉孔平台表层氧化严重,样品经过加热及油淬过程,且加热过程未进行真空热处理。沉孔凹槽R角极小,该处应力集中很大,极易产生应力集中开裂。热处理后基体组织大部分已经形成回火索氏体,材料强度大幅度降低。对侧面断口进行检测,显示多条表面裂纹,并造成样品基体严重变形。该冲模断裂的主要原因,是由于热处理工艺不规范,材料强度显著降低,在外力作用下模具产生断裂。沉孔平台氧化剥层严重,沉孔凹槽R角极小,产生的应力集中很大,极易造成应力集中开裂,导致模具沉孔部位崩裂。

The fracture of the Cr8 steel stamping die occurred in the process of die testing.The fracture samples were examined by metallographic microscope,sem and eds.The collapse fracture of the stamping die was examined,and the sheet-like extrusion deformation was found on the sinking platform,which indicated that the strength of the material was low.The surface of the platform was heavily oxidized,the sample was heated and oil quenched,and the heating process was not vacuum heat treatment.The R angle of the groove is very small,and the stress concentration is very large,so the stress concentration cracking is easy to occur.The tempered sorbite has been formed in most of the Matrix after heat treatment,and the strength of the material is greatly reduced.Many surface cracks were observed on the side fracture surface,which resulted in severe deformation of the sample Matrix.The fracture of the stamping die is mainly caused by the abnormal heat treatment process,the obvious decrease of material strength and the fracture of the die under the external force.The oxidation delamination of the platform is serious,the R angle of the groove is very small,and the stress concentration is very large.