Microstructures and Mechanical Properties of Welded Joint of P22 Steel Pipes

The P22 steel pipe is butt welded by the shielded metal arc welding(SMAW)and the microstructure, tensile strength, bending property, hardness and Charpy V impact property of the welded joint are tested and analyzed.The results show that the welding quality of the welded joint is good with no cracks in the side bending samples;the tensile strength of the joint is 515 MPa;the average Charpy impact energy of the weld zone, heat affected zone and fusion line at 20℃ is 150 J, 317 J or 305 J respectively;the hardness of the weld zone and heat affected zone is 213~223 HV10 or 185~223 HV10 respectively;the chemical composition meets the specification BS EN ISO 15614-1:2004+A2:2012;the microstructure of the weld zone and heat affected zone is granular bainite and ferrite+granular bainite respectively; the heat affected zone is composed of overheated recrystallization zone, recrystallization fine grain size zone and incomplete recrystallization zone and the microstructure and hardness distribution of the joint is equivalent in different zones.