球墨铸铁左转向节断裂原因分析

Breaking Reason Analysis of Nodular Iron Left Turning Knuckle

介绍了QT450-10左转向节的生产工艺,对铸件产生裂纹的原因进行了多项分析:(1)宏观检查发现,断裂显示为弯曲脆性疲劳断口特征,在近邻上表层区域可见自上而下的放射状撕裂棱,伴有疲劳弧带,在接近底部区域发生瞬间断裂,断口附近无缩颈现象,边缘无剪切唇;(2)SEM观察显示,表层及次表层存在不规则条带团絮状物质,且在不规则条带团絮状物质附近有微裂纹,其断裂机理属沿晶+准解理微观脆性断裂;(3)采用EDS对断口面进行分析,断口面处团絮状物质主要为氧化物类夹杂物。

The production process of QT450-10 nodular iron left turning knuckle was introduced. Multiple items analysises were conducted with the reasons causing casting cracking as following： （1）Macroscopic examination found that the breaking showed bending brittlement fracture,and the radiating type from top to bottom tear edge could be seen,combinated with fatigue arc zone,then instant fracture occurred at area near to the bottom. No shrinkage neck phenomenon existed in the neighbnuring area of the fracture,no seissorring lip found. （2）SEM observation indicated that there irregular tape-wadding type matter existing, and there tiny cracks existing near to the irregular tape-wadding type matter, their tearing mechanism belonged Io the inter-granular rapture＋quasi-cleavage tiny brittlement fracture. （3）The fracture face was analyzed by using EDS and it was found that the wadding type matter was mainly oxide type inclusions.