大线能量焊接对原油储罐用钢焊接接头机械性能影响研究

Study on the Effect of High Heat Input Welding on the Mechanical Property of Welded Joint of the Steel Plate of Crude Oil Storage Tank

针对原油储罐钢板经大线能量焊后出现的焊接接头断裂等机械性能恶化问题,本文采用气电立焊的焊接工艺对大型原油储罐用钢12MnNiVR进行100kJ/cm大线能量焊接。通过焊接后接头的微观组织观察及冲击、拉伸等力学试验分析,探究焊接接头机械性能恶化的机理。研究表明,大线能量对焊接接头粗晶热影响区的强度和韧性影响较大。该区域显微组织表现为晶粒异常粗大、板条贝氏体大量存在,冲击断口微观形貌由大的解理面组成,河流状花样密度低,因此屈服强度值低、韧性差,导致出现断裂问题。

In view of the deterioration of the mechanical properties of the steel plate of crude oil storage tank,such as the fracture of the welded joint caused by high heat input welding,high heat input welding of 100kJ/cm of 12MnNiVR steel of large-scale crude oil storage tank is carried out by means of gas-electric vertical welding process,and the deterioration mechanism of mechanical properties of welded joint is investigated in the paper.The results show that the strength and toughness of the coarse-grained heat-affected zone of the welded joint are greatly affected by high heat input.The microstructure of the zone is characterized by unusually large grain size and large amount of lath bainite.The micro-morphology of impact fracture is composed of large cleavage surface and low density of Fluvial pattern,which results in low yield strength and poor toughness,leading to fracture.