Numerical Simulation And Experiment Of Welding Residual Stress For EH47 Super-high Strength Steel

With high strength, low-temperature flexibility, EH47 super-high strength steel is developed by Japan after 7 years. At recently, it is mainly applied to building the hatch coaming of 10000 TEU container ship. Because of the nonuniform thermoplastic deformation and phase transformation by welding process, there are residual stresses in the joint which result in deformation, early cracking and brittle fracture. Therefore, order a study of residual stresses in the joint to EH47 steel is of importance to improve the reliability of the structure of hatch coaming of container ship.The main contents of this paper contain:(1) Material properties with temperature changes in the calculation process, which belongs to the material non-linear problems, this paper presents a study of the physical properties of EH47 steel based Jmatpro of heat.(2) The temperature field model and stress field model of the multi-layer multi-pass welding of EH47 steel is established by ANSYS software.(3) The welding experiment is in progress, X type groove of EH47 steel, and combine SAW with technology of multi-layer multi-pass welding to butt welding, the joint is obtained.(4) Measuring the residual stress of the plate after welding by using blind-hole method, and compared with the model data, to verify the accuracy of the model.(5) Compared with the stress of the different heat treatment after welding in the condition of the same welding method, to check out the effect of reducing the stress after the heat treatment.(6) Experiment the mechanical properties test of welding joint of EH47 steel to improve the welding process.The experimental results show that the EH47 steel of preheating before welding without heat treatment after welding, the longitudinal residual stress is symmetrical distribution along the seam center line. The edge of the stress value is almost 0, which decreases gradually with approaching to the center of seam. It will appear the maximum compressive stress in the joint and heat affected zone. The longitudinal residual stress will increase rapidly when it approach to the center of seam, the compressive stress becomes tensile stress. The maximum tensile stress value is about 214 MPa, when it is in the center of seam. The distribution of transverse residual stress is similar to the longitudinal stress, but the value is smaller obviously. The residual stress distribution of the EH47 steel of heat treatment is similar to the former. The maximum tensile stress value is about 176 MPa, which is about the 82% of the former. The stress value of other position is lower than former. The results indicate the effect of heat treatment to decrease the residual stress of welding is remarkable.Compare model value with experimental value, the results show that the distribution of model value is similar to experiment value, and the three maximum tensile stresses tested by experiment in the center of seam is very close to the curve model. The distribution of stress tested from model is similar to experimental value to verify the accuracy of welding numerical model.