Research on Welding Parameters For High-frequency Welding Pipe

The cold-bending steel pipe was welded with different technology parameters in order to improve the quality of steel pipe. By means of metallographic examination,scanning electron microscope examination,hardness test,impact test,bend test,tensile test and so on,the microstructure and mechanical properties of steel pipe were investigated. The results show that some welding defects such as crack and blowholes are not found. The microstructure of the weld is widmanstatten microstructure;the microstructure of heat affected zone is widmanstatten microstructure,pearlite and proeutectoid ferrite,the base metal is pearlite and ferrite microstructure. The metal brinell hardness is the highest in the weld,the seconds is in the heat affected zone,the third is in the base metal. The microstructure of the weld metal is coarse,which results in that toughness of the weld is the lowest,but hardness of the weld is the highest in the weld zone. The bend angles of weld present mountainous shape with the change of surface energy. The mechanical properties of the weld is the best when the surface energy in the best value.