| In the shipbuilding industry,welding work volume in hull construction is about 70%,and the hull construction material is generally plate Q235 steel.At present,the medium-thick plate generally adopts the traditional manual arc welding,submerged arc welding,electroslag welding,FCB welding and other multi-layer multi-channel welding methods.However,these welding methods have their own disadvantages.For example,For example,manual arc welding is strongly dependent,welding performance is poor,labor intensity is high,and working conditions are poor.Submerged arc welding requires high welding position and welding process.It is not easy to observe the situation of molten pool,and it is easy to produce welding defects such as pores,cracks,and slag inclusions.Electroslag welding is prone to local non-fusion,intermittent leak-welding,leaking residue,leaking iron and other welding defects.FCB welding is prone to reverse surface forming,cracks,pores and other welding defects.The most important is that the welding efficiency of these welding methods is relatively low.The multi-arc hybrid welding can effectively solve the limitations of the above welding methods because of its advantages of low welding cost,high welding performance,beautiful appearance of welding seams,high welding speed,and high production efficiency,and the advantages of welding on medium and thick plates are obvious.In this paper,the multi-arc hybrid welding technology was used to conduct a forming experiment on 16 mm,20mm,25 mm and 30 mm thick plates.By changing the butt gap of the plate,the vertical distance of the welding torch and the horizontal distance of the welding torch,the carbon dioxide shielding gas is used to weld the plate,and the influence on the quality of the joint and the appearance of the weld seam is observed.Change welding parameters,use mixed gas to weld the plate,observe its joint quality and weld appearance.Compared with multi-arc hybrid welding protected by carbon dioxide and mixed gas,the mixed gas-protected multi-arc hybrid welding has better weld formation and joint quality,and the welding heat input is also relatively low,which can improve the mechanical properties of the joint well.After observing the macroscopic morphology and microstructure of the joints,it was found that the weld appearance of the multi-arc hybrid welding is generally a “goblet”shape.Due to the effect of the thermal cycle,from the third layer of welds to the first layer ofwelds,the grains in most areas of the weld joint are gradually refined.In the weld zone of the mixed gas-protected welded joints,pro-eutectoid ferrite increased significantly,pearlite decreased significantly,and there was no significant change in the microstructure of other areas.In addition,the grain of mixed gas-protected welded joint is smaller than the grain of carbon dioxide-protected welded joint.After testing the hardness of the joints,it was found that the hardness in the overheated zone> the hardness in the weld zone> the hardness in the completely recrystallized zone> the hardness in the incomplete recrystallization zone> the hardness in the base material zone.The hardness in the overheating zone and weld zone of the backing weld seam were significantly higher than the capping weld seam,and the hardness of mixed gas-protected joints was generally higher than the hardness of carbon dioxide-protected joints.After tensile tests on the joints,it was found that the tensile strength of the two multi-arc hybrid welded joints protected by the protective gas was in line with the standard.After the joints was bent at 180°,it was found that the side-bending performance of carbon dioxide-protected joints was unacceptable,while the side-bend performance of mixed gas-protected joints was in compliance with the requirements.After the joints were impacted at room temperature,it was found that the impact performance of carbon dioxide-protected joints could not reach the standard,while the impact energy of mixed gas-protected joints was in compliance with the requirements. |
PDF Full Text Request