Narrow gap space contributes to chemical metallurgy of self-shielded arc welding

The slag-free self-shielded flux-cored wire was fabricated to apply for the narrow gap welding. The results showed that narrow gap welding shows lower welding spatter compared with hardfacing except under voltage of 30 V and current of 260 A. The deposition efficiency keeps over 90 % for both 12 mm and 8 mm narrow gap welding. For 12 mm narrow gap welding, when the voltage is 28 V and the current is 264 A (or 286 A), no pores are found in the narrow gap weld. In the continuous welding process, manganese vapor, aluminum vapor and CO continuously generate to form gasbag and occupy the narrow gap space, thus protecting the droplet and molten pool from the invasion of air.