激光焊接650MPa相变诱发塑性钢的组织与性能

采用固体Nd:YAG激光器焊接拉伸强度级别为650MPa、厚度为1.2mm的相变诱发塑性钢(TRIP)薄板,利用光学显微镜和电子显微镜研究了其不同焊接速度下对接焊缝的形貌和组织特点。测试了接头的硬度和抗拉强度,借助杯凸试验对比研究了激光焊接接头和母材的成形能力,并分析了焊接速度对接头组织、性能的影响。研究表明:TRIP钢的相组成主要是大量铁素体、贝氏体和少量的残余奥氏体;激光焊缝金属则主要由马氏体构成。焊缝金属或焊接热影响区的近缝区具有最高的硬度。焊缝金属的屈服强度和抗拉强度在垂直于焊缝方向与母材基本相同,但在平行于焊缝方向明显高于母材。与母材相比,激光焊接TRIP钢薄板的冲压成型能力明显下降。

Microstructure and property of laser welded 650 MPa transformation induced plasticity steel sheet

Microstructures and mechanical properties of Nd: YAG laser welded transformation induced plasticity(TRIP) steel with tensile strength 650 MPa and 1.2 mm thickness were studied.The hardness and tensile strength of butt welding joint were investigated by optical and electronic microscopies under different welding speeds.The formability of raw material and welding joint were tested with Erichsen experiment.The study showed that the welded metal mainly consists of martensite which is different from the original TRIP or parent metal,which is composed of ferrite matrix plus bainite and a little residual austenite.Therefore,the welded metal or the heat affected zone has the maximum hardness for the whole welded joint.The yield strength(YS) and tensile strength(TS) of the welded specimens tested perpendicular to the weld line were almost equal to those of the parent metal.But the YS and TS of the welded specimens tested parallel with the weld line were obviously higher than those of the parent metal.The stamping formability of laser welded TRIP steel sheet was obviously decreased compared with that of the parent metal.