厚板不锈钢激光填丝多道焊的接头组织分析

Investigation on Microstructure of Thick Plate Stainless Steel Joint Welded by Multi-Pass Laser Welding with Filler Wire

作为一种新颖的不锈钢厚板连接方法,窄间隙激光填丝多道焊接可以显著提高焊接效率,但目前关于该工艺的不锈钢焊缝组织特点缺乏详细的研究。用CO2激光填丝多道焊连接16mm厚的304钢板,通过光学显微镜、背散射电子衍射(EBSD)、能谱分析(EDS)研究接头组织特征。结果显示:以8kW功率激光、三道次焊接可以获得无裂纹和气孔的良好焊缝。接头组织特征主要为焊缝宏观形貌整体窄而高,上下的宽度基本一致。焊接热影响区极窄,熔合线一侧奥氏体晶粒形貌与母材相当;焊缝中存在长条骨架状和等轴状两种铁素体形貌。奥氏体形貌以柱状晶为主,晶粒尺寸粗大。多道焊的重复加热未造成靠近重熔区焊缝组织的明显变化。主要合金元素Cr,Ni在焊缝中均匀分布,无明显偏析。

As a novel way for the joint of thick plate stainless steel, multi-pass laser welding with narrow gap and filler wire can improve the welding efficiency, but seldom research has conducted to the microstructure of this method. In this article, 304 stainless steel plate with 16 mm thickness are welded by C02 laser welding with filler, the microstructure of joint are analyzed by optical microscope, electron backscatter diffraction （EBSD） and energy dispersive spectrometer （EDS）. The results show that, fine joint without crack and porosity can be obtained by 8 kW laser power and three pass of welding. The welding seam profile is narrow and high with homogenous width from bottom to top. The heat affected zone （HAZ） is very narrow and no coarse austenitic grains are seen beside fusion line. Two profiles of ferrite such as skeletal and equiaxial exist in welding seam. The characteristic of austenitic is mainly columnar grains and the size is very coarse. There is no obvious change in the area near re-melted region in spite of the re-heating of multi-pass laser welding. The main alloy elements Cr, Ni are distributed evenly in welding seam and no obvious segregation are seen.