X70抗大变形管线钢焊接接头的组织与力学性能

Microstructure and Mechanical Properties of X70 Pipeline Steel with High Deformability

采用三种不同的焊接工艺对X70抗大变形管线钢进行焊接试验,通过组织观察、拉伸及冲击试验分析了焊接接头的显微组织和力学性能。结果表明:采用GMAW焊接的试样,其焊缝金属主要由针状铁素体和少量准多边形铁素体组成,热影响区组织为粗大的粒状贝氏体和少量准多边形铁素体,具有较高的强度和韧性,但塑性变形能力较差;采用GMAW+FCAW焊接的试样,其焊缝主要由针状铁素体和少量准多边形铁素体组成,热影响区为粗大的粒状贝氏体和板条贝氏体,具有很高的屈强比;采用SMAW+FCAW焊接的试样,其焊缝主要为粗大的多边形铁素体,热影响区为准多边形状铁素体和贝氏体,焊缝硬度低于热影响区和母材的,其焊接接头具有优良的强度和韧塑性,同时具有较高的抗变形能力。

Three kinds of welding processes were adopted in the welding test for X70 pipeline steels with high deformability,and the microstructure and mechanical properties of the welded joints were analyzed by microstructure observation,tensile test and impact test.The results show that the weld metal of the welded joints by GMAW was composed of acicular ferrites and little quasi-polygonal ferrites,while the HAZ consisted of coarse granular bainites and quasi-polygonal ferrites.And the welded joints had good strength and toughness but low ductility.The weld metal of welded joints by GMAW+FCAW was mainly comprised of acicular ferrites and little quasi-polygonal ferrites,the HAZ was composed of coarse granular bainites and lath bainites,and the welded joint had a very high yield ratio.Coarse polygonal ferrites and little bainites composed the weld metal of the welded joints by SMAW+FCAW,and quasi-polygonal ferrites and bainites composed the HAZ,which led to the hardness of weld metal lower than those of the HAZ and the base metal.Furthermore,the welded joint by SMAW+FCAW had good strength,toughness and ductility and high resistance to deformation ability.