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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SA335P91钢焊缝根部裂纹的影响,分析了裂纹的性质、类型和产生机理。结果表明,SA335P91钢焊缝根部裂纹属于结晶裂纹,其产生与焊接工艺密切相关,结晶裂纹产生与否不是取决于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将焊接电弧在左右焊道闭合小孔处停留时间控制在5 s以内,可有效预防结晶裂纹的产生。
Different welding process parameters were used to simulate the full-position welding of large diameter SA335P91 steel pipe. The influence of welding parameters on the root crack of SA335P91 steel was studied by metallographic observation, electron microscope and micro-area energy spectrum analysis. The nature, type and mechanism of production. The results show that the root crack of SA335P91 steel weld belongs to the crystal crack and its occurrence is closely related to the welding process. The occurrence of the crystal crack is not determined by the absolute content of S, but mainly depends on the distribution of S low melting point eutectic compound in the grain boundary Morphology; select the appropriate welding parameters and the welding arc in the left and right beads closed hole residence time control within 5 s, which can effectively prevent the generation of crystal cracks.