Q345R中厚板焊接接头冲击不合格原因分析及控制措施

Cause Analysis and Control Measures of Substandard Impact Performance of 55mm Q345R Welded Joint

针对公司55mmQ345R焊接试板随炉进行淬火+回火热处理后,-40℃低温冲击不合格的问题,通过体视显微镜、电镜及光学显微镜对冲击残样的断口形貌及金相组织进行分析,指出淬火时水温高,导致淬火不完全而形成的贝氏体+马氏体混合组织是造成淬火+回火后低温冲击性能不合格的主要原因。通过进行水淬时不同入水水温的模拟试验,摸索出该规格产品的极限淬火水温,并通过焊接热输入控制、热处理工艺控制、淬火入水水温控制,改善了Q345R淬火+回火试板的低温冲击韧性,提高了产品合格率。

In view of the problem that the 55mm Q345R welding test plate is unqualified under-40°℃low temperature impact after quenching and tempering heat treatment in the furnace,the fracture morphology and the metallographic structure of the impact sample were analyzed by the stereo microscope,electron microscope and optical microscope,and it was pointed out that the high water temperature during quenching caused the mixed structure of bainite and martensite formed by incomplete quenching,which is the main reason for unqualified low temperature impact performance after quenching+tempering.By conducting simulation experiments with different inlet water temperatures during water quenching,the ultimate quenching water temperature of this specification of product was found.Through welding heat input control,heat treatment process control,and quenching inlet water temperature control,the low-temperature impact toughness of Q345R quenching and tempering test plate was improved,and the product qualification rate was increased.