激光焊接热输入对26Cr-3.5Mo铁素体不锈钢组织性能的影响

Effect of Laser Welding Heat Input on Microstructure and Properties of 26Cr-3.5Mo Ferritic Stainless Steel

采用连续激光焊接工艺对26Cr-3．5Mo铁素体不锈钢进行焊接，研究了激光焊接热输入（HI）对焊接接头显微组织和力学性能的影响。采用光学显微镜（OM）、扫描电子显微镜（SEM）、透射电镜（TEM）和能谱分析仪（EDS）研究焊缝显微组织和析出相的析出规律，采用维氏显微硬度仪和拉伸试验机对焊接接头的机械性能进行测试。结果表明，焊缝中心产生细小的等轴晶，随着激光焊接热输入的增加，焊缝中心等轴晶区的宽度增加，其占整个焊缝截面的比例先增加再减小。热影响区（HAZ）宽度较窄，为0．1～0．2mm，且没有发生明显的晶粒粗化现象。焊接接头HAZ发生软化，其显微硬度值低于焊缝和母材。焊接接头抗拉强度与母材相当，但断后伸长率小于母材，且随激光焊接热输入的增加而减小。

Continuous laser welding is conducted to investigate the effect of heat input （HI） on the microstructure and mechanical properties of 26Cr-3.5Mo ferritic stainless steel. The optical microscope （OM）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and energy dispersive spectrometer （EDS） are used to observe the microstructure and the precipitates in the weld. And the mechanical properties are tested by the microhardness tester and the tensile tester. The result show that there are fine equiaxed grains at the center of the weld, and with the increase of the laser welding heat input, the width of equiaxed crystal zone increases, but the proportion of equiaxed crystal zone to the weld cross section increases firstly and then drops. The heat affected zone （HAZ） is narrow. Its width is 0.1-0.2 mm, and no obvious grain coarsening appeares in the HAZ. The HAZ is soften and its microhardness is lower than that of the weld and the base metal. The tensile strength of the welded joint is close to that of the base metal. But the percentage elongation of the welded joint after fracture is less than that of the base metal and decreases with the increase of the laser welding heat input.