Cause analysis of girth weld cracking in automatic welding for X80M pipeline steel
LI Zengzhen1,2, YANG Die1,2, DAI Xiaobo3, LU Fenghua1,2, LI Yanlong*3, YAN Xinyu1,2
1. China Petroleum Pipeline Research Institute Co.,Ltd.,Langfang 065000,China; 2. National Engineering Research Center for Oil and Gas Pipeline Transportation Safety, Langfang 065000,China; 3. Caofeidian Xintian LNG Co.,Ltd.,Tangshan 063200,China
Abstract：The suspected cracking of girth weld cracking in automatic welding was found in site non-destructive testing for one pipeline engineering of high-grade X80M steel with pipe diameter of 1 422 mm.In order to analyze the causes for the girth weld cracking in automatic welding of X80M pipeline steel,a series of test methods were employed to find out the formation reason of cracking,including chemical composition analysis of steel pipe and welding material,non-destructive testing positioning of cracking,cutting of cracking defects,macro and micro morphology and structure observation of cracking,microhardness,analysis of cracking and nearby regions.The analysis results showed that the cracking was located on the filling layer of weld joint.Cu was enriched in the nearby matrix of cracking,which was mainly in isometric crystal.The surrounding microhardness was obviously higher than the weld which was far away from the cracking.Moreover,the cracking was extended along with the grain boundary.Cu was found inside of cracking and surrounding areas.Combined with welding information in site,the copper contact tube contacted with groove wall in the process of filler welding,leading to short circuit.The high temperature due to the short circuit caused the hot melting of contact position between copper contact tube and groove.The molten Cu entered the weld and diffused along the grain boundary,resulting in Cu enrichment area and cracking of the girth weld.
李曾珍, 杨叠, 代晓波, 鹿锋华, 李彦龙, 闫新宇. X80M钢级管道自动焊环焊缝裂纹成因分析[J]. 冶金分析, 2024, 44(1): 99-105.
LI Zengzhen, YANG Die, DAI Xiaobo, LU Fenghua, LI Yanlong, YAN Xinyu. Cause analysis of girth weld cracking in automatic welding for X80M pipeline steel. , 2024, 44(1): 99-105.
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