| As one kind of quality and efficient welding process, the laser-TIG arc hybrid welding has attracted growing interest at home and abroad with the advantages of high welding speed, high stability and small deformation. Relative to the high power laser-TIG arc hybrid welding, the low power pulsed laser-TIG arc hybrid welding can not only give full play to the advantages of the two traditional heat source, but also can further reduce the waste of laser energy due to the low electro-optical conversion efficiency, and reduce the equipment cost and welding production cost, which benefits the application promotion of the practical welding and has high practical value and broad application prospects.Combined with the photo and electrical parameters collection system, the low power pulsed laser-TIG arc hybrid welding has been studied by surfacing on 304 austenitic stainless steel, including the influencing factors and rules of the arc shape, conductive characteristics, the weld pool dynamic behavior and weld appearance, which provide theoretical basis and supporting date for the application promotion of this welding process.The results showed that a small amount of metal vapor could stabilize arc anode spots at the laser spots, leading to the compression of the arc root. The composite of laser plasma and arc plasma made the high temperature zone of arc center expand. The TIG arc voltage went up slightly when the pulsed laser to join. The results showed, although the high temperature zone of arc center expand, the effective conductive area was contracted, which is the reason of TIG voltage rise. The TIG arc voltage returned to normal after the pulsed laser disappeared.The length of the weld pool changed periodically due to the pulsed laser, but the width remained the same. When the heat source distance was-0.5 mm and 0 mm, an oval weld pool formed, but when the heat source distance ranged from 0.5mm to 1.5mm, irregular oval weld pool formed, with a wide rear and a narrow head, and a part of the laser working position located in the concave field in the front of the weld pool. When the heat source distance reached 2.5mm, the weld pool was separated into laser weld pool and TIG weld pool. During the hybrid welding process, obvious fish-scale patterns appeared on the weld surface with the pulsed laser, and the number of fish-scale patterns coincided with the laser frequency.The cross-sectional area of low pulsed laser-TIG hybrid welding was 1.5 times of the sum of laser and TIG welding cross-sectional area with either heat source acting alone, which achieved the composite effect of 1+1> 2. Part of welding parameters were optimized, and the best defocusing distance of 0 mm and the best heat source distance between 0mm and 1mm were obtained. The effect of hybrid mode on weld appearance was studied, and the results showed that good weld appearance and deep penetration could be achieved under YAG-TIG hybrid welding, but poor weld appearance and shallow penetration would be achieved under TIG-YAG hybrid welding.The low pulsed laser-TIG welding at high speed welding could improve weld appearance effectively. Relative to the pulsed laser welding, the discontinuous phenomenon of weld could be eliminated due to the reduction of the overlap rate for spot if proper TIG arc heat source to join. For the TIG welding, the humping defects caused by TIG high-speed welding could be eliminated. The temperature of weld pool was improved and the surface tension of the weld pool was reduced when the laser was joined. And the molten metal produced by laser could effectively increase the thickness of liquid metal in the front of weld pool, avoiding the hump defect. |
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