Effect Of Intense Cooling Treatment For The TIG Remelted Layer Of Weld Toe On Residual Stress Distribution

This paper studied how to attain the distribution regulation of welding residual stress of butt joint of plate after weld toe was TIG remelted and intense cooled by finite element method. It includes residual stress distribution after welded and weld toe TIG remelting. The welding plate is 14mm in thickness, which is welded by V-shape groove butt weld form. The No. of the material is Q345C, which is low-alloy high-tensile structural steel but not heat-treatment.The subject establishes model of finite element based on the welding plate, and selects the element according to welding sequence by comparing the center coordinate of the elements which are in the weld area and weld remelting layer. In the subject the welding process, weld toe TIG remelting and intense cooling are simulated by means of the units living and dying technique, as well as the coupling function between heat and structure in the ANSYS software. The simulation results about the welded residual stress are almost identical with the measuring results by testing methods. The paper offers two dimensional distribution curves of residual stresses, which is at middle of joint and vertical to joint surface. The conclusions are as follows: the axial residual stress on weld toe surface is tension stress, and where the lateral residual stress is peak value. After weld toe remelting, the residual stress on weld toe surface is still tension stress. While weld toe TIG remelting and cooling naturally to a certain temperature, it was treated with intense cooling, thus the residual stress value of weld toe surface reduced obviously. There would be biaxial residual stress on weld toe surface ; when remelting layer was intense cooled more than 450℃.TIG remelting technique is a way to improve endurance strength of weld structure, while it came up with in the past few years, and applied broadly. However, the method mainly improves shape of weld toe and reduces stress collection. It is inadequate to adjust residual stress field to come into being impress stress field. To apply TIG remelting technique effectively and ensure security and reliability of structure, it is a very important subject to accurately estimate the mechanical behavior and residual stresses during TIG remelting. It affects endurance strength severely because of existence of weld residual stress. Especially tension stress may reduce endurance strength of structure strongly. Therefore, when researching on joint organize, weld joint and toe form dimension, it is more important to research on distribution of weld residual stress systematically and regularly.The test methods of measuring residual stress are often by cutting or boring which not only take more time and more work, but lead to a greater error owing to many factors. Those methods are not suitable for researching on problems which are systematical and complex process. The paper calculates residual stresses by finite element method, which overcomes shortage of test methods, and can testify measuring results of testing methods as well. So the research result is important to science research or engineering application.