Effect of Chemical Composition on Flash Weldability

Effect of Si and Mn

Abstract

This report is conserned with the effect of chemical composition of base material, especially Si and Mn, on flash weldability. Si and Mn influence the fracture or crack of welded part in practical production line, for example, wheel-rim forming line in the automobile companies and pickling line or cold-rolling line in the steel industries. The reason why Si and Mn influence the fracture or crack is that fracture is caused by Si-Mn-Al oxide in the weld line which hasn't been removed out from weld line to outside at the upset stage. Though the fracture or crack ratio is proportional to the contents of Si and Mn, the influence of Si is more effective than that of Mn. In addition, even if the Mn content is high, fracture or crack can be decreased by the selection of optimum welding condition. But in the case of Si, that improvement is almost impossible. The reason why the influence of Si is different from that of Mn is as follows:
It's observed by plasma arc welding that amount of oxide and condition of oxide formation on molten pool in the high-Si steel are different from those in the high-Mn steel. Namely, the amount of oxide on molten layer during flash welding is much in the high-Si steel than that in the high-Mn steel. In addition, the fluidity of oxide in the high-Mn steel is better than that in the high-Si steel. Therefore, Si influences the fracture or crack more significantly than Mn.