关键词: 等离子弧焊接, 对接焊, 受控脉冲穿孔控制策略

Abstract: The controlled pulse key-holing plasma arc welding system is used to conduct butt-welding of stainless steel plates of medium thickness. Joint gap exists in weld seam during the butting welding process and influences the measuring result of efflux plasma voltage and the stability of the controlling process, thus causes the control system to make misjudgment and fine welding quality cannot be attained, so the system should be improved to achieve a good key-holing process. Through employing the strategy of controlled pulse key-holing and appropriate joint fit-up, the system avoids any misjudgment when the plasma jet passes through the gap. Butt-welding experiments are carried out on type 304 stainless steel plates with thicknesses of 6 mm and 8 mm to get the optimum process parameters. A group of varied plate-thickness tests are designed and made to examine the effectiveness of the control system during butt welding. The control system makes in-process adjustment of welding current peak level and its dropping slopes according to the measured plasma efflux voltage. As the plate thickness gets less, the system gives fast and timely response. The dynamic process of one keyhole per pulse is stable, the control effect is remarkable, and the weld formation quality is good.

Key words: Butt welding, Plasma arc welding, Strategy of controlled pulse keyholing