Abstract：The narrow gap multi-pass laser welding with filler wire addition of 30-mm-thick S275 ferritic steel was investigated in this paper. The purpose of this paper is to understand the formation mechanism and influencing factors of laser welding defects, in order to optimize the welding process and avoid the formation of cracks, lack of fusion, porosity and other defects. The experimental results show that, properly increasing the heat input can reduce the cooling rate of molten pool and restrain the generation of welding cracks. When the heat input is 0.9 kJ/mm, the longitudinal surface crack is 2.3 mm deep. When the heat input increases to 1.05 kJ/mm, the depth of longitudinal surface crack decreases to 0.8 mm. When the heat input reaches 1.2 kJ/mm, no crack is found in the joint. Choosing a smaller distance between the laser and wire can ensure the contact between the molten metal and the weld pool, and avoid the lack of fusion on the side wall. When the distance between the smooth wires is 1mm, no fusion or splashing is found on the groove side wall. When the distance between the laser and wire is 3 mm, the side wall is not fused. When the distance between the laser and wire 5 mm, the deposited metal is found above the side wall of the welding groove. When a 15 mm diameter pipe is used to transport protective gas at the top of the groove, a large number of air holes can be avoided. The welding joint with better mechanical properties can be obtained by using 6 m/min wire feeding speed.
[1] 王智祥, 张瑶, 张吉祥. 2205DSS焊接接头腐蚀疲劳性能分析[J]. 焊接学报, 2014, 35(5): 67-70. WANG Zhixiang, ZHANG Yao, ZHANG Jixiang.Corrosion fatigue performance of 2205 DSS welded joints[J]. Transactions of the China Welding Institution, 2014, 35(5): 67-70. [2] ADEDIPE O, BRENNAN F, MEHMANPARAST A.Corrosion fatigue crack growth mechanism in off shore monopile steel weldments[J]. Fatigue & Fracture of Engineering Materials & Structures, 2017, 11(40): 1868-1881. [3] 朱政强, 陈立功, 徐济进, 等. 厚板窄间隙多道埋弧焊温度和残余应力分布[J]. 机械工程学报, 2007, 43(2): 225-229. ZHU Zhengqiang, CHEN Ligong, XU Jijin, et al.Temperature distribution and residual stress in multi-pass narrow gap submerged arc welding[J]. Chinese Journal of Mechanical Engineering, 2007, 43(2): 225-229. [4] 张富巨, 郭嘉琳, 张国栋. 三种窄间隙焊接技术的特性比较与应用选择[J]. 电焊机, 2017, 47(6): 23-27. ZHANG Fuju, GUO Jialin, ZHANG Guodong.Characteristic comparison and application of three narrow gap welding technologies[J]. Electric Welding Machine, 2017, 47(6): 23-27. [5] AYRES K R, HURRELL P R, GILL C M, et al.Development of reduced pressure electron beam welding process for thick section pressure vessel welds[M]. Washington: Pressure Vessels and Piping Conference, 2010: 107. [6] ASSUNCAO E, QUINTINO L, MIRANDA R.Comparative study of laser welding in tailor blanks for the automotive industry[J]. Int J Adv Manuf Technol, 2017, 49: 123-131. [7] JONES L P, AUBERT P, AVILOV V, et al.Towards advanced welding methods for the ITER vacuum vessel sectors[J]. Fusion Eng Des, 2003, 69(3): 215-220. [8] ZHANG X D, ASHIDA E, TARASAWA S, et al.Welding of thick stainless steel plates up to 50 mm with high brightness lasers[J]. J Laser Appl, 2011, 23(2): 1-8. [9] 黄彪, 唐正平, 陈鑫, 等. 6061-T6 铝合金激光焊接接头腐蚀疲劳裂纹扩展[J]. 精密成形工程, 2017, 9(2): 27-33. HUANG Biao, TANG Zhengping, CHEN Xin, et al.Corrosion fatigue crack growth in laser welded 6061-T6 aluminum alloy[J]. Journal of Netshape Forming Engineering, 2017, 9(2): 27-33. [10] SUN B, ZHANG Y, LI Z X.A multi-scale corrosion fatigue damage model of aluminum alloy considering multiple pits and cracks[J]. Acta Mechanica Solida Sinica, 2018, 31(6): 731-743. [11] KONG L J, FENG Z D, XU C, et al.PEG modified high transmittance TiO2 thin film and its super hydrophilic properties[J]. Journal of Xiamen University: Natural Science, 2015, 54(6): 774-779. [12] HUANG W, LEI M, HUANG H, et al.Effect of polyethyleneglycol on hydrophilic TiO2 films: Porosity-driven super-hydrophilicity[J]. Surface and Coating Technology, 2010, 204(24): 3954-3961. [13] CRISTIAN Iacovita, RARES Stiufiuc, TEODORA Radu, et al.Polyethylene glycol-mediated synthesis of cubic iron oxide nanoparticles with high heating power[J]. Nanoscale Research Letters, 2015, 10(1): 1-16.
2020, Vol. 25 
