The synthesizing control scheme is put forward based on the requilement of narrow-gap all-position welding technology in terms of the moving track of tungsten electrode.

Side weld penetration technique of all position narrow gap and thick walled pipe welding is developed.

A tungsten electrode oscillating controller for all position narrow gap and thick walled pipe welding is developed about tungsten electrode oscillating control,tungsten electrode oscillating orbit analysis and welding arc length adjusment.

The possibility of engineering application of technical methods of flux cored arc welding to the field of narrow gap welding is studied.

Realization of ultra-narrow gap welding with flux strips constraining arc;

Method of gaseous protection of ultra-narrow gap welding with arc-constricting flux strips;

Heating characteristic of constricting arc with flux strips in ultra-narrow gap welding;

Based on the experiment of twin-wire narrow gap welding in single pool mode by employing alternative pulsed arcs, the influences of welding parameters on the appearance of weld and welding process stability were investigated.

Lateral oscillation arc welding, high-speed-rotating arc welding, twin-wire welding, and ultra NGW(narrow gap welding) can all assure the fusion of side wall and improve the oppearance of weld in relatively small welding variables.

The hollow-axis motor drives the offset nozzle and rotates the arc on the tip of wire at high speed,so as to ensure enough penetration into the sidewalls in narrow gap welding.