汽车变速操纵杆ZG310-570钢与45钢焊接接头焊后发现产生冷裂纹。采用化学成分分析和金相检验的方法对冷裂纹的产生原因进行了分析。结果表明：焊接接头出现淬硬组织以及粗大的魏氏组织是导致冷裂纹产生的主要原因;另外焊条含有的水分、焊件表面的油污和铁锈以及接头的拘束应力也会影响到冷裂纹的产生。并提出相应的预防措施。

Cold crack was found in the welding joint of ZG310-570 and 45 steels of automobile variable speed control handle. The generation reason of cold crack was analysed by means of chemical composition analysis and metallographic examination. The results showed that the main reason was quench hardening microstructure and bulky widmanstatten structure emerged in the welding joint. Moisture of welding rod,oil and rust on weldment surface and constrained stress of welding joint could also effect the generation of cold crack. Preventive measures were proposed to decrease or eliminate cold crack.