| 摘要 |
PURPOSE:To make possible the prevention of damaging of backing strips and the defect-free multi-layer welding of I-beam steel by specifying the mixing ratio of Ar and CO2 being shielding gas at the first and second and subsequent layer welding while automatically feeding a wire to the base metal groove applied with the backin strip made basically of copper. CONSTITUTION:A welding wire 2 from a welding torch 1 is positioned at the center of the groove spacing of the base metals 3 contacted with a backing strip 5 of copper or the alloy composed primarily of copper. In the first layer, the mixed gas of 65- 100% Ar and 0-35% CO2 is used as shielding gas and in the second and third layers, it is changed to the mixed gas of 0-50% Ar and 50-100% CO2, whereby the multi-layer welding of I-beam steel is done. As a result of this, arc 10 generates directly in the strip 5 in part but its potential gradient is small, resulting in smaller energy density. If the current value and welding speed are proper, the strip 5 does not melt. In the second and subsequent layers, CO2 which is inexpensive and gives deep penetration is much used. |
