Research On Welding Process Technology Based On The Integrated Loading Of Cold And Heat Sources Controlling Buckling Deformation

Welding residual stress and deformation are always accompanied by the welding process.It is not only an important factor in forming various welding defects,but also the root cause of embrittlement of the welding heat strain.It directly affects the manufacturing quality and service performance of the welded structure,and in severe cases can lead to the failure of welding components,even scrapped.Therefore,it is of great significance to improve the manufacturing quality and service performance of welded structures by ascertaining the formation mechanism,role and influence of welding stress and deformation,and mastering the methods of controlling and adjusting welding stress and deformation.Firstly,ANSYS finite element analysis software was used to calculate the temperature field and residual stress of the butt-welding of flat plates.Studies have shown that: the use of the heat rate of the body heat generation and the "life and death" treatment of the weld unit can simulate the docking of the sheet more accurately.For thin plates,the transverse and longitudinal residual stresses are the main driving forces causing the instability of the welding deformation.In this study,AH36 high-strength steel sheet was used as the research object.Based on the thermal elastic-plastic finite element theory,the numerical simulation method was used to study the mechanism and contrastive analysis of the two kinds of welding situations in which ordinary welding and heat and cold sources were integrated to control the welding deformation.To improve the optimization of the current welding process and provide a theoretical basis for the high-quality and highly efficient shipbuilding to achieve lightweight manufacturing precision.The main research content is as follows:(1)Based on the thermal elastic-plastic finite element method,numerical simulation study was conducted on butt welding of AH36 high-strength steel plate,and the variation law of the temperature field and residual stress and strain field of the plate butt joint specimen was obtained.The research shows that the heat source of the body heat rate and the treatment of the “life and death” unit of the weld can accurately calculate the butt welding of the thin plate.It is also known that the transverse and longitudinal residual stresses are the main driving forces that cause the instability deformation of the thin plate welding.(2)The effect of the width of the cold source on the welding deformation and residual stress was simulated.The numerical simulation study was conducted and compared with the conventional welding.Applying a cold source following the welding gun following the welding torch,the extreme cold shrinkage of the metal in the action site produces a strong tensile action,which results in a decrease in the longitudinal compressive plastic strain generated during the temperature increase of the weld and the near weld zone.The longitudinal tensile plastic strain generated in the system increases,the inconsistent strain in the weld zone and the near weld zone decreases,and the longitudinal residual stress decreases.The study shows that,due to the effect of cold source,the lateral stress,longitudinal stress and equivalent stress show a decreasing trend in the high stress region width and stress peak.Especially when the width of the cold source is greater than the width of the weld,the longitudinal residual stress at the center of the plate is reduced from 381 MPa for normal welding to 350 MPa,and the lateral residual stress is reduced from 330 MPa for ordinary welding to 15 MPa,and the total deformation is the smallest,the value was 2.1mm.It can be seen that the study of the relationship between the width of the cold source in the width direction and the width of the weld seam will also provide theoretical guidance for the design of the dry ice outlet nozzle shape.(3)Under the condition that the cold source intensity is constant and the optimum cold source width is optimized in the above study,the influence of the distance L between the cold and heat source,which is moved synchronously with the welding torch,on the welding deformation and the residual stress is numerically performed.Simulation study and comparative analysis.Studies have shown that the control of welding residual stress and deformation is closely related to the distance L between the cold and heat sources.When L is small,the welding deformation control ability is strong.When L is large,the welding deformation control ability is weak or even has no effect.It can be seen that the distance between cold and heat sources is a decisive process parameter for low stress non-deformation welding and plays a crucial role in controlling the instability of welding instability.