X80鋼級大直徑直縫埋弧焊管裂紋研究與工藝改進(jìn)

Research on Forming of Crack of Large-sized X80 SAWL Pipe and Improvement of Relevant Manufacturing Process

摘要: X80鋼級大直徑厚壁直縫埋弧焊管在擴(kuò)徑后存在焊縫趾部開裂現(xiàn)象。通過對該裂紋的斷口及其理化性能進(jìn)行檢測,認(rèn)為造成焊縫趾部開裂的原因是:焊接熱輸入量較高,熱影響區(qū)韌性惡化;鋼管擴(kuò)徑前焊縫附近母材存在應(yīng)力集中;鋼管熱影響區(qū)與擴(kuò)管模具發(fā)生擠壓。針對上述因素,進(jìn)行工藝改進(jìn),使得裂紋發(fā)生率從2.00%降低到0.12%。

Abstract: Cracking is found at the foot area of the welding seam of the large-sized X80 SAWL pipe as expanded. Relevant physical tests and chemical analysis are made to the fracture,and the results reveal the main elements which responsible for the cracking,including rather high welding heat input that makes the toughness of the metal of the HAZ greatly decreased,concentration of the stress in the base metal near the welding seam of the pipe that occurs before it is expanded,and extrusion that takes place between the HAZ of the tube and the expanding die. Based on the elements as identified,the welding process is improved,and thus the crack incidence rate is decreased from 2.00% to 0.12%.