某公司使用20Mn2钢盘条生产起重用短环链，成品链条出厂前进行拉伸破断试验时发现部分链条的拉伸破断力不符合标准要求，且环链发生了脆性断裂。为找到链条拉伸破断力不合格的原因，对20Mn2钢环链进行了宏观分析、微观分析、化学成分分析、金相检验、显微硬度测试等。结果表明：环链焊接时温度过高、时间过长，导致焊缝区发生高温氧化及严重脱碳，使得焊缝区产生了较多低强度的铁素体组织，降低了焊缝区的强度，导致链条拉伸破断试验时在环链焊缝区发生低负荷的脆性断裂。

The short link for lifting was produced by a company used 20Mn2 steel wire rod. It was found that the tensile breaking force of several links didn't meet the standard requirements and the links presented be brittle fracture during tensile breaking test before the finished links leave the factory. In order to find out the cause of disqualification of tensile breaking force of the links, the macro analysis, micro analysis, chemical composition analysis, metallographic examination, microhardness test were conducted on the 20Mn2 steel link. The results show that too high welding temperature and too long welding time lead to high temperature oxidation and serious decarburization in the weld zone, resulting in a lot of ferrite with low strength produced in the weld zone, reducing the strength of the weld zone, thereby low load brittle fracture presented in the weld zone of link during the tensile fracture test of the link.