DP590镀锌双相钢CMT焊接接头显微组织及力学性能

针对汽车制造中薄板焊接质量问题及鉴于汽车行业对镀锌双相钢的大量需求，在弧长修正系数为0，送丝速度为3.0 m/min，焊接速度为400 mm/min的焊接工艺参数下，对1.0 mm厚的DP590镀锌双相钢进行了CMT搭接焊试验，并通过X射线衍射仪、扫描电子显微镜与维氏硬度计等设备研究了焊接接头的显微组织与力学性能。试验结果表明，CMT焊接DP590镀锌钢能够得到成形良好的焊接接头。焊缝组织主要为板条马氏体,粗晶区由板条马氏体和少量铁素体组成,细晶区组织多为马氏体及少量贝氏体,不完全相变区中的铁素体含量增加，马氏体含量减少；焊接接头拉伸试验断裂位置在不完全相变区，属于塑性断裂，最大载荷为10.48 kN，与母材接近。焊缝平均硬度值最高，约为260 HV，不完全相变区显微硬度值最低，约为170 HV。该研究为DP590镀锌双相钢薄板CMT焊接提供工艺参考，对汽车轻量化生产制造具有重要的工程意义。创新点： (1)针对汽车用钢薄板焊接的难点，提出具有低热输入焊接特点的CMT工艺。(2)研究DP590镀锌双相钢CMT焊接接头显微组织及力学性能，研究结果可为工厂实际生产提供理论依据与数据支持。

Microstructure and mechanical properties of DP590 galvanized dual-phase steel CMT welded joint

In view of welding quality problem of thin plate in automobile manufacturing and large demand of galvanized dual-phase steel in automobile industry, CMT lap welding experiment of DP590 galvanized dual phase steel with 1.0 mm thickness was carried out under welding parameters of arc length correction coefficient 0, wire feeding speed 3.0 m/min and welding speed 400 mm/min. Microstructure and mechanical properties of welded joint were studied by X-ray diffractometer, scanning electron microscope and Vickers hardness tester. The experimental results showed that welded joints with good formation were obtained by CMT welding of DP590 galvanized steel. Microstructure of weld was mainly lath martensite. Coarse grain zone was composed of lath martensite and a small amount of ferrite. There were more martensite and a small amount of bainite in fine grain zone. In the incomplete phase transformation zone, ferrite content increased, while martensite content decreased. Tensile test of welded joints showed that fracture locations were in incomplete phase transformation zone, which belonged to plastic fracture. And the maximum load was 10.48 kN, which was close to that of base metal. The average microhardness of weld was the highest, about 260 HV. The lowest microhardness appeared in incomplete phase transformation zone, about 170 HV. The study provided technical reference for CMT welding of DP590 galvanized dual-phase steel sheet, and had important engineering significance for automobile lightweight production and manufacturing.Highlights: (1) Aiming at difficulty in welding of automobile steel sheet, CMT process with characteristics of low heat input welding was proposed.(2) Microstructure and mechanical properties of CMT welded joints of DP590 galvanized dual-phase steel were studied. The results could provide theoretical basis and data support for actual production of factories.