| 摘要 |
PURPOSE:To join both steel pipes in a good shape and good quality without causing a zinc inclusion and spark by heating the steel pipe whose one part at least is zinc plated each other by electrifying within the range of a specific time with pressurizing in a specific pressure range and feeding in at proper speed. CONSTITUTION:The steel pipes 1, 2 for a heat exchanger, for instance, whose one part at least is zinc plated are fed in slowly in the range of 2-10mm/sec by heating them by passing the current of 1V1,000A for 0.2-1.2sec, for instance, with giving the pressurizing force of 10-40kgf by clamping with electrodes 6, 7 respectively. Owing to the heating and pressing being performed comparatively slowly the surface zinc is evaporated and not contaminated in the joining face without causing a spark, so the joining becomes well. The current is passed more on the outer surface of the steel pipe and a butt welding spread part 8a is formed at the outer side, scarcely caused on the inner face to make the joining part in good shape.
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