SA335P91钢焊缝结晶裂纹产生机理的研究

Study of Formation Mechanism on Weld Solidification Cracking of SA335P91 Steel

选用不同的焊接工艺参数进行大口径SA335P91钢管对接全位置焊接模拟试验,通过金相观察、电镜和微区能谱分析等方法研究了焊接工艺参数对其焊缝根部裂纹的影响,对裂纹的性质、类型和产生机理进行了分析。结果表明,SA335P91钢焊缝根部裂纹属于结晶裂纹,它的产生与焊接工艺有密切的关系,结晶裂纹产生与否不取决于S的绝对含量,而主要取决于S的低熔点共晶化合物在晶界的分布形态;选择合适的焊接工艺参数并控制焊接电弧在左右焊道闭合小孔处停留时间在5s以内可有效预防结晶裂纹的产生。

All position wlding simulation test on large diameter pipe of SA335P91 steel under different welding process parameters,The effects of different welding process parameters on the root crcaking of SA335P91 steel pipe were investigated by metallographic observation、SEM and micro-spectroscopy analysis and property、type and mechanism of crack were analyzed.The results show that the root cracking of SA335P91 steel is solidification cracking and has closely related to do with welding process,It is not dependent the absolute content of S and mainly depends on the distribution patterns in the grain boundary structure of the low-melting-point eulectic compounds of S.The solidification cracking can be effectively prevented by selecting the appropriate welding parameters and controling the residence time of the welding arc at the closed holes less than 5 seconds.