Study of Ultra-Narrow-Gap Gas Metal Arc Welding of 980 Steel

摘要

The ultra-narrow-gap gas metal arc welding (UNG-GMAW) technique was used to achieve the welding of 50-mm thick ultra-high strength 980 steel. A torch-inside-groove type UNG-GMAW technique with about 6 mm gap width has been successfully developed in this paper. The welding principle and system was introduced, and the selection of welding parameters was analyzed. The welded joints were evaluated using macrostructure and microstructure observation, microhardness distribution analysis, and mechanical properties test. The results show that an excellent joint without welding defects and with a narrow (≤ 2 mm) HAZ has been produced. Furthermore, there is no great coarsening of grain in the overheated zone, and no soften and conspicuous harden in HAZ. The mechanical properties of weld metal are near that of the base metal, and can attain the standard requirement. In conclusion, UNG-GMAW is an excellent welding technique for the joining of thicker plate 980 steel.