THE STUDY OF ALL POSITION PROGRAMMED PULSED TIG-WELDING OF SMALL THICK-WALLED TUBES——ITS TECHNOLOGY AND EQUIPMENT

This work contributes to the study of the all position welding technology for small thick-walled tubes φ32~42×3~5mm and its equipment. By comparing the effect of four kinds of pulsed current wave forms (zig-zag, trapezoid, trapezoid with sharp front impulse and step form) on the formation of weld, we propose that step wave form has the best advantage for all position tube welding. By adopting step pulsed current wave form and its programmed welding parameters(magnitude of main pulsed current and wire feeding speed), it is possible to weld small thick-walled tudes in all position efficiently with a sound quality without any edge preparation, and it is also possible to have complete fusion in the first pass followed by a second covering pass with filler metal. The special features of successfully developed all position programmed pulsed TIG tube welding machine are briefly described:no "pig tail" welding head with "three steel balls" wire feeding mechanism, step wave form pulsed welding current source with low distortion and its overall control system. The technology and equipment developed by this research work has been applied already in industrial production and satisfactory results have been achieved.