科研之友
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摘要
To improve the welding process behavior and quality of short-circuit CO2 arc welding further, the effects of molten droplet shape just before short-circuit on the short-circuit of molten droplet with weld pool, the spread of molten droplet in weld pool and the formation of liquid bridge neck are analyzed through the images of molten droplet and its short-circuit transfer photographed by a high-speed CCD camera. By using a static force balance model of molten droplet, the relationships among molten droplet shape, electromagnetic force (arc current), surface tensile force and gravity are studied. The molten droplet shape is controlled effectively via precise adjusting of arc current. When the molten droplet shape just before short-circuit is columned, the short-circuit transfer process is stable and gentle. But the flat-shaped molten droplet makes the short-circuit transfer unfavorable, generates transient short-circuit even. The molten droplet shape during arc phase embodies the action of various forces on the molten droplet, in which the electromagnetic force (arc current) is the dominative factor to determine the molten droplet shape. To obtain appropriate molten droplet shape during different stages of arc phase, a control principle by adopting a large arc current in prophase and a small current in anaphase during the arc phase is proposed according to the influence regulation of arc current on the molten droplet shape. The experimental results show that a favorable molten droplet shape just before short-circuit is achieved with this control approach, which is adapted to short-circuit transfer. The short-circuit transfer is stable and gentle, the transient short-circuits and the metal spatter induced by them are eliminated, the short-circuit behavior of molten droplet is improved and the residual liquid metal quantity at the end of wire electrode after the completion of short-circuit transfer has good equality.
- 出版日期2006
- 单位清华大学
