Study On The Welding Property Of 22MnB5 Steel And Toughness Reinforcement Of The Joints

22MnB5 steel is widely used in automobile manufacturing and other industry,which is suitable for the high safety requirements of the vehicle,such as the vehicle’s collision avoidance beams,door frames and so on.Heat treatment process has a great influence on the strength of 22MnB5 steel.Quenching treatment can make the strength increase from 500 MPa to 1700 MPa.During the welding process of 22MnB5 steel,the hardness,tensile strength and fatigue strength of the heat affected zone decrease due to the influence of complex welding thermal cycle.Therefore,research the welding ability and the toughening mechanism of 22MnB5 steel has very important practical significance.Firstly,original and quenching condition 22MnB5 steel was heated to different peak temperature 600℃,750℃,900℃,1050℃ and 1200℃ respectively according to the welding heat cycle of the heat affected zone,which respectively corresponded to different part of the heat affected zone.Then the microstructure,tensile,micro,hardness,corrosion resistance and other performance were tested.The results showed that the microstructure of the original 22MnB5 steel is not affected by the welding thermal cycle,but the microstructure of the quenched 22MnB5 steel changes obviously,after different weld thermal cycle.The original 22MnB5 steel after weld thermal cycle in the peak temperature 750 ℃ has the lowest tensile strength.The tensile strength is 378 MPa.Quenched 22MnB5 steel after weld thermal cycle in the peak temperature 900 ℃ has the lowest tensile strength,the tensile strength is 664 MPa.The original 22MnB5 steel and quenched 22MnB5 have the lowest micro hardness after weld thermal cycle in the peak temperature of 750 ℃,150 HV and 214 HV respectively.The corrosion resistance of original 22MnB5 steel and quenched 22MnB5 steel was not affected by the welding thermal cycle.It can be found that the incomplete recrystallization region of the heat affected zone is the weakest region of the performance of joint for 22MnB5 steel.This paper studied the welding process.The 188J/mm is the best heat input.The paper also study the strengthening and toughening treatment of 22MnB5 steel.It is to use three kinds of strengthening and toughening treatment process which were controlled cooling with water in welding,liquid nitrogen copious cooling and mechanical spinning during welding process of original and quenched steel.Then the strength,microstructure,hardness and corrosion resistance were tested.The results showed that the controlled cooling with water in welding enhanced the strength of the both quenched steel and original steel.The weld tensile strength of quenched steel joint increased from 840 MP to 980 MPa.There was no obvious difference between the strength of original 22MnB5 steel joint with liquid nitrogen copious cooling in welding and without.The mechanical spinning improved the strength of 22MnB5 steel joint,too.It reaches 530 MPa for original 22 Mn B5 steel joint and 940 MPa for quenched steel joint.It is because the plastic deformation layer and pressure stress formed by mechanical spinning.There was no difference between the corrosion resistance of 22MnB5 steel joints with controlled cooling with water in welding,liquid nitrogen copious cooling and mechanical spinning.It can be found that the controlled cooling with water in welding and mechanical spinning can improve the strength and hardness effectively while mechanical spinning cannot.So one can see for the original and quenched22MnB5 steel weld joint,controlled cooling with water in welding and mechanical spinning during welding process can effectively improve the strength.But there is almost no influence using liquid nitrogen copious cooling.