对一台使用超过15 a(年)的门式起重机进行安全评估, 发现其制动轮表面存在较多裂纹。为分析裂纹的产生原因, 对其进行了宏观观察、化学成分分析、硬度测试和金相检验。结果表明: 制动轮在铸造过程中存在夹杂物、裂纹等缺陷, 在使用过程中, 由于摩擦生热, 外表面组织发生转变。在多重外力的作用下, 裂纹萌生于制动轮表面薄弱处, 并呈喇叭状向内扩展。

During the safety assessment of the gantry crane used for more than 15 years, lots of surface cracks were found on the brake wheel. The brake wheel was inspected to analyze the causes of cracks by means of macroscopic examination, chemical composition analysis, hardness test and metallographic examination. The results show that the inclusions, cracks and other defects were formed in the brake wheel during the casting process. The structure of the outer surface changed due to the friction heat during the use process. Under the multiple external forces, cracks generated at the weakness area of the surface, and extended with the horn shape.