LNG储罐用低温高锰钢埋弧焊材料组织和性能研究

Study on the microstructure and properties of low temperature high manganese steel submerged arc welding materials for LNG storage tanks

针对LNG储罐用低温高锰钢,设计了一种用于丝级埋弧横焊的焊丝、焊剂及焊接工艺。通过拉伸、冲击、侧弯试验评估焊缝金属力学性能,采用OM,SEM,EDS等设备分析组织形貌。试验结果表明:焊剂工艺性能优良,焊缝成形较好,脱渣良好,无气孔、裂纹等缺陷,抗拉强度大于660 MPa,-196℃夏比冲击吸收能量大于60 J;焊缝金属组织为全奥氏体组织,组织致密,晶间有细小的夹杂物析出,冲击试样断口形貌多为细小的韧窝;利用EDS对冲击断口中少量解理面处合金成分进行分析,发现焊缝高Si区会在受冲击下产生解理面成为断裂的启裂位置,降低了材料低温韧性。总结试验结果,确定性能最佳的焊材成分与焊接工艺参数。

For low temperature high manganese steel used on LNG storage tanks,a submerged arc welding wire,a wire electrode submerged arc transverse welding wire,flux and welding process were designed.The mechanical properties of the weld metal were evaluated by tensile,impact and side-bending tests.The microstructure morphology was analyzed by OM,SEM and EDS.The test results show that the welding flux has excellent welding process performance,good weld metal forming,excellent deslagging,no porosity,no cracks and other defects,the tensile strength is greater than 660 MPa,and the charpy impact absorption energy at-196℃is greater than 60 J.The weld metal is fully austenitic,with dense microstructure and small intergranular inclusions precipitated.The fracture morphology of the impact sample is mostly fine dimples.The alloy composition of the minor cleavage surface in the impact fracture was analyzed using EDS.It was found that the high Si zone of the weld would become the initiation site of fracture,where cleavage surface was generated by impact,reducing the low temperature toughness of the weld metal.The test results were summarized to determine the best welding material composition and welding process parameters.