1997 Volume 15 Issue 3 Pages 484-493
In case of arc welding of hot-dip zinc-coated carbon steel sheets, the generation of spatters, blowholes and pitting causes some problems due to the vaporization of zinc while welding. To solve these problems, the method to positively vaporize zinc both in front of a molten pool and in joint gaps by taking full advantage of the property of zinc of easy vaporization has been examined in an ordinary single electrode process of high practical application. As the results, it has been found that for the reduction of generation of spatters, to do welding at high speed using comparatively high current and also to avoid the short-circuiting by refining the droplets from a wire using the pulse current wave shape of high peak current and a short time in a pulse arc are effective. Practically the effect of both current and welding speed on the generated amount of blowholes has hardly been seen. It is the basic guidelines for the reduction of generation of blowholes that the application of a pulse MAG welding process of high arc time ratio is more advantageous than a CO2 welding process accompanied by short-circuiting and to avoid the welding positions wherein molten metal is apt to cover zinc layers. As for pitting, even in the conditions wherein many blowholes are generated, it is little generated in either a flat or a horizontal welding position but significantly generated in a vertical downward welding position. It is advantageous for the reduction of generation of pitting in a vertical downward welding position, to decrease welding speed, to add oxygen to shielding gas and to tilt a welding torch in push angle.