Study On Quantitative Evaluation Of Welding Cold Cracking In Y-type Node Of Jacket

At present,E36 high strength steel is used widely in jacket structure of marine engineering,and its cold cracking problem in welding construction is prominent,in which the disadvantage caused by lag of pipe node cold cracking is especially serious.Therefore,it has become a difficult problem faced by welding workers to how to quantitatively determine the cold cracking tendency of steel welded joints and to determine the welding cracking sensitivity of pipe node.In this paper,the rigid restraint welding cracking test of E36 high-strength steel was carried out by using rigid restraint welding cold cracking test device.The restrain stress of jacket Y-type node was calculated by numerical simulation using SYSWELD and research on quantitative evaluation of the welding cracking sensitivity of Y-type node is developed.The main results of the paper are as follows:First,this paper uses the large-scale rigid restraint welding cold cracking test device developed by Tianjin University to carry out the rigid restraint welding crack test of E36 high-strength steel with GFL-71Ni wire and DW-A55L wire,and obtains critical restraint distance,critical restraint degree and critical restraint stress of different wires under certain welding parameters.It is found that the critical restraint distance of GFL-71Ni wire joint is 1.70 m,the critical restraint degree is 6058.82N?mm^-2,the critical restraint stress is 666.7 MPa;and the critical restraint distance of DW-A55L wire joint is 1.60 m,the critical restraint degree is 6437.50 N?mm^-2,the critical restraint stress is 625.1 MPa.Secondly,through the analysis of diffusion hydrogen content,chemical composition and microstructure of two kinds of wire welded joints,and combining the critical restraint degree obtained from the test,and by calculation,the cold cracking sensitivity coefficient of GFL-71Ni wire joint is higher than that of the DW-A55L wire joint,and the values are 0.345 and 0.326 respectively,which indicates that the cold cracking sensitivity of DW-A55L wire is low and its anti-cracking performance is better than GFL-71Ni wire.Finally,the optimization scheme of preheating temperature during the welding of E36 high-strength steel is obtained:GFL-71Ni welding wire:T₀=105?,DW-A55L welding wire:T₀=78?.Finally,the finite element software of SYSWELD is used to simulate the welding stress of jacket Y-type node.The restraint stress of the dangerous point is compared with the critical restraint stress of the material,and the quantitative evaluation of the welding cold cracking sensitivity of jacket Y-type node is realized,which provides reference for the design of jacket structure.