S355J2W+N耐候钢板根部大熔深MAG对接焊工艺及接头的组织和性能

Study on deep penetration root welding proce-dure,microstructure and mechanical properties of S355J2W+N weather-resistant steel MAG butt welded joint

采用高频脉冲焊和常规脉冲MAG焊对S355J2W+N耐候钢12 mm厚板进行了对接焊工艺试验,研究了对接打底焊的大熔深工艺及接头的显微组织和力学性能。结果表明:与常规脉冲MAG焊相比,焊接间隙为“0”时,高频脉冲MAG焊具有较强的根部熔深能力,较小的焊接热输入(6.06 kJ/cm),使其可打底焊缝宽度由2.7 mm增加到3.2 mm,增加约18.5%;高频脉冲MAG焊接头呈较为理想的组织特征,焊缝中针状铁素体组织含量较多,焊缝、熔合区不含侧板条铁素体组织,过热区的晶粒粗化程度较小;接头抗拉强度均大于母材强度下限值,断裂位置均位于母材;接头弯曲试验中弯曲角度为180°时,受拉面无裂纹,接头塑性良好;相比常规脉冲MAG焊,高频脉冲MAG焊接头的低温(-40℃)冲击韧性较好,焊缝区冲击功高出约9.6%,热影响区冲击功高出约12.3%。

Butt welding tests were carried out on S355J2W+N weather-resistant steel by high-frequency pulse welding and ordinary pulse MAG welding respectively.By comparative analysis of the welded joint,the deep penetration root welding procedure,microstructure and mechanical properties of the joint were studied.The results show that,compared with ordinary pulse MAG welding,when the welding gap is"0",the high-frequency pulse MAG weld has a strong ability of root pene-tration,root weld width is increased by about 18.5%,in the case of smaller welding heat input(6.06 kJ/cm).Compared with ordinary pulse MAG welding,the microstructure characteristics of high-frequency pulse MAG welded joint are ideal,the more content of acicular ferrite(AF)at weld metal,none ferrite side plate(FSP)at weld metal and fusion zone,and the grain coarseness of the grain coarsened zone(CGZ)is less.The tensile strength of the butt-weled joint is greater than the lower limit of the base material strength,and the fracture position is located at the base material;when the bending angle of the bending sample reaches 180°,there is no crack on the tensile sample surface.Compared with the ordinary pulse MAG welding,the low temperature(-40℃)impact toughness of high frequency pulsed MAG welding joint is better,the impact energy of weld zone is about 9.6%higher than that of conventional pulsed MAG welding,and the impact energy of heat affected zone is about 12.3%higher.