Study On Transverse Welding Process With Pulsed Submerged Arc Welding Technology And Its Application In Oil Tank Manufacturing

In the common transverse submerged arc welding(SAW) of thick plates, high heat input usually makes Heat Affected Zone overheated, which causes weld grain bigger; meanwhile, high welding speed always makes undercut happen to the upper part of weld, the lower part of which turns to be intumescent as the liquid drops. Since the larger grain size and undercut have negative effect on the weld, a mechanism of undercut elimination with pulsed controller is proposed in the dissertation to decrease these pessimistic effects.The molten pool in transverse pulse SAW was simplified into a liquid metal on the surface of solid metal, which receives pulse load regularly. In this way, quantitative and qualitative analysis was carried out of the pulse current's effect on the surface tension and on the arc force loaded to the pool as well as on the impact force of droplet transfer. A stressed model of the transverse molten pool was thereafter built up, with which the arc force loaded to the pool was calculated out.With such simplification and calculation, the mechanism of undercut elimination with pulse current demonstrates that the arc force loaded to the pool, the impact force of droplet transfer and the resultant surface tension all follow the regular pulse current change. Such regular change of these forces helps to spread the liquid metal, which results in undercut elimination in filling and cosmetic welding.Meanwhile, special attention was paid in backing process of transverse double-wire pulse SAW to the dynamic movement of molten pool, which is under the load of pulse forces from two different sides. The forces follow the regular changes of pulse current, the peak value of which ensures a pleasant penetration to prevent incomplete penetration. The pulse current can also decrease the situation of burning through base metal, which is rather common for ordinary single wire transverse SAW. Consequently, the range of processing parameters in ordinary single wire transverse SAW can be increased with the technology of double-wire pulse SAW.