核电钢制安全壳SA738 Gr.B搭接接头裂纹成因分析

Causes of cracks in SA738 Gr.B lap joints of a nuclear power plant steel containment

文中研究了在核电站钢制安全壳SA738 Gr.B模拟件焊接过程中,自动熔化极气体保护电弧焊(GMAW)与焊条电弧焊(SMAW)纵向搭接接头裂纹的产生原因,重点讨论了搭接接头的热影响区粗晶区的显微组织与力学性能。为了对裂纹发源位置进行定位,首先采用相控阵超声检测技术(PAUT)对裂纹进行测量,反演裂纹发源位置,然后对裂纹发源位置自动GMAW和SMAW焊缝热影响区粗晶区进行光学显微镜(OM)和电子背散射衍射(EBSD)显微组织观察,并进行显微硬度、室温拉伸和室温冲击等力学性能试验。试验结果表明,不同焊接方法导致搭接接头热影响区粗晶区的显微组织与力学性能存在差异,残余应力作用下的力学性能失配导致搭接接头裂纹产生。

Causes of cracks in SA738 Gr.B lap joints by auto gas metal arc welding(auto-GMAW)and shield metal arc welding(SMAW)was studied in the construction test of steel containment in a nuclear power station.The microstructure and mechanical properties of the coarse grain heat-affected zone were emphatically discussed.The phase array ultrasonic test(PAUT)was firstly used to measure the cracks to confirm the cracks initiation position,and then the optical micrograph(OM)and electron back-scatter diffraction(EBSD)were used to analyzed the microstructure and grain boundary characterize around the cracks.Furthermore,microhardness,room temperature tensile and impact tests were carried out to get the mechanical properties around the cracks in lap joints.The experimental results showed that microstructure and mechanical properties of coarse grain zone in heat-affected zone of lap joints were different in different welding methods,and the mechanical properties mismatch under residual stress caused the cracks of lap joints.