Cause of Disqualification of Tensile Breaking Force of 20Mn2 Steel of Short Link for Lifting

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.