基于理化检测的某LPG储罐热影响区裂纹形成机理研究

Formation Mechanism of Cracks Existed in Weld Heat-affected Zone of LPG Tank Based on Physical and Chemical Detections

以某气站1#LPG储罐合拢焊缝B5热影响区裂纹a1O为对象,对其进行理化检测,分析裂纹形成机理。结果表明,裂纹a10尖端平直,断面光滑,呈穿晶形态发展,主体带有分支,末端尖细,走向近似与焊缝垂直,为典型脆性裂纹;裂纹附近异常区域(二次焊接作业施焊区域)在焊接完成后,未再次进行焊后热处理工作,在金属深部区域形成局部微小缺陷;受高焊接残余应力与罐体内压的共同作用,微小缺陷不断生长,在各施焊区域发展为不同长度的表面裂纹;a3、a5、a11裂纹的理化检测结果验证了a10裂纹的分析结果。

Based on physical and chemical detections,formation mechanism of crack alO existed in heat-affected zone of weld B5 in LPG tank 1#was analyzed.Results indicate that crack alO presents typical brittle and transcrystalline crack which has a flat,straight and smooth fracture surface.The body of the crack whose direction is nearly perpendicular to the weld has branches which the end is sharp.Micro defects existed inside the metal of abnormal areas(Districts resulted from the second welding operation)were caused of the absence of heat treatment after welding.With the action of the high welding residual stress and internal pressure of tank 1#,the defects grow gradually to surface cracks which have different length.Results of physical and chemical detections of cracks a3,a5 and all have verified the analysis result of crack alO.The analysis process of this paper provides a reference for the type of research.