A Study on Surface Expulsion Phenomena and its Suppression in Series Spot Welding

概要

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Surface expulsion phenomena in series spot welding and its suppression technique have been investigated with a cold rolled steel sheet of 0.8mm thickness in order to guarantee a current density enough to produce large size nuggets as much as in direct spot one without the surface expulsion. Firstly, it is found that the current density is usually pretty lower than that in direct spot one even under a critical current condition of surface expulsion, and that the surface expulsion is caused by the process that a molten metal in the nugget part flows out through an overheated zone induced by shunting current through the upper side (transformer side) piece. Secondly, it is revealed that use of large contact diameter type tips for upper side and small one for lower side is effective to increase the critical expulsion current. Finally, the effectiveness of the above described different-shape-tips-couple-system is examined with flat or large radius type tips for upper side and truncated corn or truncated radius type for lower side. And then, it is demonstrated how not only nugget size but also nugget shape is greatly improved by this technique.
社団法人溶接学会の論文
1980-10-01