Abstract: In order to make the ultra-narrow gap welding have a well constricted arc and a stable and reliable welding process, based on the numerous advantages of narrow gap submerged arc welding and the thought of constricting the arc in the narrow gap so as to prevent it from climbing up, the method of constricted arc by ultra-fine granular flux applied to ultra-narrow gap welding is brought forward, special welding torch and the technology of underlaying ultra-fine granular flux with V type of metal mesh are developed. The results indicate that the molten slag wall formed by the molten ultra-fine granular flux can effectively constrict the arc, thus realizing stable and reliable ultra-narrow gap welding. With the decrease of particle sizes of ultra-fine granular flux, the tendency of forming convex weld is enhanced due to the increase of the bulk density of welding flux. The technology of underlaying ultra-fine granular flux with V type of metal mesh can obviously improve the heating effect of arc on the roots of sidewalls, and obtain enough penetration at the roots of sidewalls, which can ensure the fusion quality of ultra-narrow gap weld.

Key words: Constricted arc, Ultra-fine granular flux, Ultra-narrow gap welding