LNG储罐用9Ni低温钢横位置焊条电弧焊和埋弧焊接头微观组织与力学性能对比

Comparison of microstructure and mechanical properties of transverse shielded metal arc welding and submerged arc welding joints of 9Ni low temperature steel for LNG storage tank

文中针对LNG储罐用9Ni低温钢,分别采用焊条电弧焊和埋弧焊进行横位置焊接试验。通过力学性能测试和微观组织分析研究不同焊接方法对焊接接头性能的影响。试验结果表明:2种焊接接头力学性能都符合标准要求,热影响区冲击吸收功高于焊缝,埋弧焊接头比焊条电弧焊接头低温冲击韧性更好。焊条电弧焊和埋弧焊接头焊缝组织均为奥氏体与析出相,2种接头焊缝组织都呈现多种结晶形态,焊条电弧焊接头焊缝结晶形态主要为柱状树枝晶,埋弧焊接头焊缝结晶形态主要为胞状树枝晶。焊条电弧焊接头过热区组织为粗大板条马氏体,且发生晶界粗化现象,韧性较差。埋弧焊接头过热区组织为板条马氏体和粒状贝氏体,韧性较好。

The transverse welding test of 9Ni low temperature steel for LNG storage tank was carried out by covered electrode arc welding and submerged arc welding respectively,and the effects of different welding methods on the properties of welded joints were studied by mechanical property test and microstructure analysis.The test results show that the mechanical properties of the two kinds of welded joints meet the standard requirements,the impact absorption energy of heat affected zone is higher than that of weld,and the low-temperature impact toughness of submerged arc welded joints is better than that of covered electrode arc welded joints.The weld microstructure of covered electrode arc welding and submerged arc welding joints is austenite and precipitated phase,and the weld microstructure of both joints presents various crystal forms.The weld of covered electrode arc welding joint is mainly columnar dendrite,while that of submerged arc welding joint is mainly cellular dendrite.The microstructure of overheated zone of covered electrode arc welding joint is coarse lath martensite,and grain boundary coarsening occurs,which leads to poor toughness.The microstructure in the overheated zone of submerged arc welding joint is lath martensite and granular bainite with good toughness.