Studies On Narrow Gap Pulse Submerged Arc Welding Process For 27SiMn Hydraulic Oil Cylinder Girth

This paper proposed a new welding process, narrow gap pulse submerged arc welding, to weld 27SiMn hydraulic oil cylinder aiming at improving the welding quality and production efficiency of it, referring to application and development trend of narrow gap pulse submerged arc welding. The pulse current was developed by the pulse controller controlling the arc welding power source in the test.27SiMn steel was welded by SAW,narrow gap submerged arc welding and narrow gap pulse submerged arc welding,respectively. The influnce of narrow gap pulse submerged arc welding on the welding efficiency was discussed through comparing the time consumed for welding. The time that the narrow gap pulse submerged arc welding spent on one specimen was 18min less than SAW, and welding efficiency was increased by 36% which showed that welding efficiency can be improved largely by using narrow gap pulse submerged arc welding. The microstructure of the welded joints was observed and analyzed by using optical microscope.The reasons for different mechanical properties of welding joints were analyzed by the microstructure characteristics of weld and HAZ as well as tensile test, impact test and bending test comprehensively. Tensile strength of narrow gap submerged arc welding joints was considerably better than that of SAW joints. The compared plasticity of narrow gap submerged arc welding and narrow gap pulse submerged arc welding joints was better than that of SAW. The impact absorption power of SAW joints was larger than that of narrow gap pulse submerged arc welding joints. The impact absorption power of submerged arc welding HAZ was only 54J. The impact absorption power of narrow gap pulse submerged arc welding HAZ was increased by 222% comparing with SAW. We found that narrow gap pulse submerged arc welding had the best welding efficiency, and joints had the optimal comprehensive mechanical properties.This paper also studied the slag removal problem in narrow gap pulse submerged arc welding. The problem was discussed from the choice of the flux,groove design, bead arrangement and welding parameters. The parameters above were optimized to improve the slag removal with the theories and welding tests.