Abstract: 6 kW fiber laser-MAG hybrid welding is used for 6 mm-thick 30CrNiMo high-strength steel plate. The microstructure and mechanical properties of the steel plate which were welded with ER50-6 and ER308 wires in the same welding process are studied. The result shows that the ER50-6 weld seam is an acicular martensite, and the ER308 weld seam is a coarse columnar austenite. The welded joints of diverse welding wires have significantly different hardness distributions. The low hardness distribution along the fusion line appears in the ER50-6 weld seam, and the low hardness of ER308 weld seam is concentrated in the lower part of the weld seam center. The corresponding tensile fracture positions are found in the fusion line and the weld seam center, respectively. The energy spectrum shows that the high content of Cr in ER308 weld seam is concentrated in the upper part of the weld seam center, which leads to the increase of hardenability and hardness, and sharp decline in toughness on this part, and finally leads to the weakness of the mechanical properties of the weld seam. The hybrid welding method and ER50-6 wire can be used to weld 6 mm-thick 30CrNiMo steel plate without distortion, and the weld strength is up to 1 197 MPa. Key

Key words: manufaturingtechnologyandequipment, fiberlaser, high-strengthsteel, laser-archybridwelding, weldedjoint, hardnessdistribution