钢轨窄间隙全自动电弧焊电流稳定性分析及控制

Stability Analysis and Control of Welding Current for Automatic Rail Narrow-gap Arc Welding System

采用钢轨窄间隙全自动电弧焊系统,对无缝钢轨线路的钢轨进行原位焊接,焊接过程中发现焊接电流电压存在较大波动,对焊接质量造成不利影响。分析造成焊接电流电压不稳定的主要原因,认为与采用陶瓷衬垫打底的异形窄间隙钢轨焊缝、焊丝伸出角度、不规则的进枪路径和进枪速度等钢轨窄间隙电弧焊焊接工艺有关。试验发现,除过程可控的工艺参数焊接电流和电压外,焊接速度变化对实际焊接电流也有较大影响。针对钢轨窄间隙电弧焊系统的工艺特点,提出采用电流传感的焊接速度与焊枪高度联合控制方法,通过焊接过程实时反馈焊接电流值,采用分段PID控制,优化控制焊枪多个方向的运动速度和位移,达到减小焊接电流电压波动,稳定电弧的目的。试验结果表明,该方法可以有效地稳定焊接电流,降低飞溅,并能在打底焊过程中有效避免断弧、熄弧现象的发生。

An automatic rail narrow-gap arc welding system is developed for in-situ welding of seamless railroad.It is found in the welding process that the welding current and voltage are unstable,and which is adverse to welding quality.Considering the technological features of rail narrow-gap arc welding,the reason of the problem can be related with some aspects,including anomalous shape narrow-gap seam of rail with ceramic backing,protruding angle of welding wire,anomalistic welding track and welding speed and so on.Besides the controllable parameters,i.e.welding current and voltage,experiments show that the variation of welding speed is also a controllable parameter which has an effect on the actual welding current.By using welding current feedback to control the welding speed and torch altitude,the arc length control system is established.With real-time welding current feedback,segment PID control is adopted to drive the welding torch in different aspects with different speed.The welding experiments show that the realized system can smooth the fluctuation of welding current and voltage,and at the same time it stabilizes the arc burning and reduces metal spattering.And it works well especially in avoiding arc faults during the backing welding.