X80厚壁管线钢不同焊接速度下焊缝韧性研究

Research on Weld Toughness of X80 Heavy Section Pipeline Steel at Different Welding Speeds

采用西气东输二线用X8018.4mm壁厚管线钢,匹配BG-H06H1焊丝和BGSJ101-H1焊剂,研究了不同焊接速度下焊缝的外观形貌和组织性能。结果表明,在不同焊速下,焊缝成型好,表面光滑,焊缝抗拉强度均在720MPa以上,硬度小于276HV10;在焊速为1.6～1.8m/min时,焊缝冲击功稳定,-20℃下平均值可达136～176J;在1.4～1.5m/min时,冲击功出现波动,最低45J。针对低速下焊缝韧性的波动,采用光镜、SEM等对焊缝微观组织变化、冲击断口形貌、成分偏析、板材及焊材纯净度等进行了分析。研究结果表明,焊缝原始奥氏体晶粒大小对韧性有显著影响;晶界AlN、硫化物析出是形成焊缝光滑脆性断口的主要原因;焊接线能量过大或过小,以及焊缝中高熔点氧化物夹杂均会引起冲击值下降。

The weld appearances, microstructure and mechanical properties were studied under different welding speeds using X80 pipeline steel （18.4mm）, BG-H06Hlwelding wire and BGSJ101-HI welding flux. The results show that the welds have good forming and smooth appearances, the tensile strength of the welds are all above 720 MPa, hardness is less than 276 HV10 at different welding speeds. The welds have stable impact energy, and the average value can be up to 136~ 176J at the speed of 1.6~ 1.8m/rain; the fluctuation of the impact energy occurs when the welding speed is 1.4~ 1.5 m/min, the lowest value is 45 J. According to the fact that the fluctuation of weld toughness at low welding speeds, the weld microstructure, appearances of impact fracture, composition segregation, purity of the plate and welding materials were analyzed by adopting light microscope and SEM, etc. Approved by the research consequence, the prior austenite grain size has significant effect on weld toughness; the grain boundaries AIN, sulfide precipitation are the main reasons of the formation of smooth brittle fracture on the welds; both excessive or less welding line energy and high melting oxidate inclusions in the welds can result in the decrease of impact value.