Study On Laser-Arc Hybrid Welding Technology And Properties Of Marine High Strength Steel

With the development of shipbuilding industry in the world,the ship structure has gradually adopted the higher strength grade steel instead of the traditional structural steel.EH36 is a high-strength steel,so far,traditional welding methods have been more widely used for welding.Although it can meet the requirements of the ship class society,it is easy to produce defects such as depression and edge bite on the weld surface,it is easy to produce welding beading on the back,large welding deformation and it has low welding efficiency.The laser-arc hybrid welding method can not only avoid the above defects,but also improve the welding efficiency.However,the research on welding technology and performance of ship plate is still at the primary stage,so it is of great significance to further study it.In this paper,the laser-arc hybrid heat source system is used to weld the 14 mm thick EH36.The influence of different welding process parameters on the weld formation is studied.The results show that laser power determines the penetration depth of weld,welding speed determines the upper and lower width of weld,wire feeding speed only affects the width of the upper surface of weld,the wire spacing and heat source sequence have little influence on the weld width,but have a greater impact on the weld formation quality.Under the optimum welding parameters,weld formation is good,no welding defects exist;The XRD diffraction analysis of the base metal and weld seam is carried out,the results show that the microstructure of weld metal and base metal is mainly composed of?-Fe solid solution;The microstructures of weld metal consist of a large amount of martensite,a small amount of bainite and a small amount of ferrite.The heated affected zone consists of a large number of strip martensite and a small amount of bainite,Compared with weld metal,the martensite in HAZ superheated zone is larger in size;the weld metal hardness is higher than that of the base metal,the hardness of weld metal in laser zone is higher than that in arc zone,the hardness of HAZ in laser zone is lower than HAZ hardness in arc zone;the average tensile strength of the joint at normal temperature is 569.4Mpa,the extension rate is about 21% and the section contraction rate is about 49%,the fracture position of the tensile specimen is in the base metal;The fracture surface of tensile specimens is covered with dimples,which belongs to plastic fracture morphology.There is no crack in the tensile surface after the transverse bending test.The average impact energy ofthe weld zone at room temperature is 92 J,which is about 95% of the base metal,and the average impact energy of the metal in the heat affected zone is 88 J,which is about 91% of the base metal;The cross section of weld impact specimens(middle part)conforms to the quasi-cleavage fracture morphology characteristics;Through static weightlessness test,and electrochemical corrosion test corrosion morphology observation,it is found that the corrosion resistance of welded joint is better than that of base metal,the performance index is superior to the requirements of the classification society.