Research On Multi-layer And Multi-pass Robot Horizontal Welding Process Of Thick Plate

With the rapid development of shipbuilding,higher requirements of the hull plate connection are put forward.There are some disadvantages such as low production efficiency and low production quality existing in the traditional hull connection processes,for example,semi-automatic welding.As a result,it’s urgently needed to improve the level of welding automation to make sure the efficient production in the connection of hull plates.The rapidly developing robot technology and CO₂ gas shielded welding system are combined together to set up the thick plate multi-layer and multi-pass horizontal position welding system in this paper.And the welding method is systematically researched to explore the effects of the related process parameters on welding results,and which will provide certain theoretical support for its better application in the practical production.Thick plate with different specifications are welded with the multi-layer and multi-pass horizontal position welding respectively in this subject.Through the analysis of the welding parameters given by robot system to explore the system’s automatic detection algorithm and filling strategy;Through the electrical signal acquisition system to test the welding process.What’s more,the microstructure observation,hardness test and tensile test are used to learn more about mechanical properties of welding joints.In addition,finite element analysis software ABAQUS is used to explore the stress distribution in welding joints.And the welding stress simulation results on the surface will be compared with the measured results.Research results show that the relative lengths between different welding layers are the same,and which is done by changing different welding heat input in different welding layers.Besides,the welding passes in one welding layer have the same width by making sure the heat input is constant.Through the microstructure observation and hardness test,it’s found that when the groove angle is the same,the microstructure grains in weld of thick plate are smaller than that in thin plate,and the hardness results also show that the wear resistance of thick plate is better.Moreover,when the thickness is constant,the influence of groove angle of microstructure is little.And because of the heat treatment effect of subsequent bead,the hardness values are also bigger in the filled layer.And the results are proved by analyzing the temperature field and thermal cycle curves in the subject.Tensile test results show that the tensile properties of weld joints are better than that of the parent metal.And to analyze residual stress distribution on plate surface and cross section by finite element simulation software.The results of surface residual stress show that the longitudinal residual stress in the weld area and the area close to weld area is tensile stress,and with the distance between the area and the weld becomes longer,the residual stress becomes compressive stress.Besides,transverse stress in the center of weld joint is compressive stress,while that in other areas of the plate is tensile stress.And the stress simulation results on the surface are almost the same with the measured results.Longitudinal residual stress in cross section in the entire weld joint is tensile stress,while transverse stress in the joint center is compressive stress,and transverse stress in the upper and lower joint are tensile stress.