内焊余热和焊接热循环对螺旋埋弧预精焊管焊缝性能的影响

Effect of Inside Welding Residual Heat and Welding Thermal Cycle on Weld Microstructure of SAWH Pipe by Adopting Two-step Welding Process

采用Charpy冲击、显微硬度和金相试验研究了内焊余热和焊接热循环对螺旋埋弧预精焊管焊缝韧性、显微硬度分布及微观组织的影响。结果表明,内焊余热和焊接热循环对焊缝及焊接热影响区(HAZ)韧性、硬度分布及微观组织形貌有较大影响。在内焊余热和焊接热循环作用下,焊缝及HAZ夏比冲击功均有明显降低,韧性呈现衰减趋势,显微硬度峰值均出现在焊缝中心附近,而微观组织则有不同程度长大。焊缝中心处主要由针状铁素体(AF)+少量准多边形铁素体(QPF)组成,HAZ则主要由尺寸粗大且均匀性差的粒状贝氏体组成。

The effect of inside welding residual heat and welding thermal on weld impact toughness,microhardness distribution and microstructure of SAWH pipe was investigated by Charpy impact toughness test,micro-hardness test and metallographic test.The results indicated that inside welding residual heat and welding thermal cycle seriously affect toughness,microhardness distribution and microstructure of weld and heat-affected-zone（HAZ）.Under the behavior of inside welding residual heat and welding thermal cycle,the Charpy impact values of weld and HAZ decrease obviously,the toughness reduces and the peak of microhardness appears near the weld center,while the microstructure grow up at different extent.The microstructure of weld center consist of acicular ferrite（AF） ＋ a small fine quasi-polygonal ferrite（QPF）,while the microstructure of HAZ mainly compose of rough and poor uniformity granular bainite.