Effect Of Mechanical Vibration On Microstructure And Mechanical Properties Of High Strength Steel Welding Joints Under Longitudinal Magnetic Field

WQ960 high strength steel is widely used in engineering machinery、shipbuilding、mining and other industries because of its high strength and toughness. High strength steel can reduce overall quality of the structure, making the machinery large-scale、energy-saving, achieving the goal of energy conservation and emissions reduction. But as for the welding structure,under the conventional welding conditions, the high strength characteristic of high strength steel also makes some problems such as its hardening tendency to be larger、easy to crack after welding and the strength of the joint decline and so on. Therefore, this article introduces magnetic field and vibration into the process of welding WQ960 high strength steel, to study the combined effect on mechanical property and microstructure of the welded joint.In this paper, the WQ960 high strength steel is selected as the base metal, the JM-100 C is selected as the welding wire. The base metal is welded according to the vibration frequency、vibration amplitude、magnetic field current that designed by the orthogonal experiment. After welding, mechanics performance testing is made for determining the optimal parameters of the magnetic and vibration. Weld the base metal under the optimal parameters, keeping two of them unchanged, changing another one for welding the base metal. After welding mechanics performance testing and microstructure analysis experiment are made to study the combined effect on mechanical property and microstructure of the WQ960 high strength steel welding joints and to analyze the influence mechanism.The experimental results show that under the conventional welding condition, the mechanical performance index of the welding joints are: the tensile strength is 711.21 MPa, the impact absorbing energy is 78.33 J. The optimal parameters of the magnetic field and vibration are: vibration frequency is 50Hz、vibration amplitude is 0.05mm、magnetic field current is6.5A. The mechanical performance index of the welding joints under the optimal parameters are: the tensile strength is 877.87MPa、the impact absorbing energy is 89 J. Compared with the conventional welding, tensile strength increased by 23.43%, the impact absorbing energy increased by 13.6%. The microstructure of the welding joints contains plenty of the fine interlocking acicular ferrite and small amount of pro-eutectoid ferrite and ferrite sideplate. The tension and impact fracture are all typical dimple models, the dimple is deep and is homogeneous distributed. Found by the orthogonal experiment, the influence of vibration frequency on mechanical properties of welding joints is the most significant, the vibration amplitude is weaker, of the three parameters, the influence of magnetic field current on mechanical properties of the welding joints is minimal.