Research On Low Power Laser-arc Hybrid Welding Technology

Thick plates/medium plates are widely used in offshore platforms,rail transit and other fields.Their welding methods are mainly arc welding methods such as traditional MIG welding and submerged arc welding,which require grooves and multi-layer and multi-pass welding.The welding efficiency is low,the welding energy consumption is large,and the input heat input is large,and the heat-affected zone is large,resulting in large post-weld deformation and decreased mechanical properties of the welded joint.Therefore,finding an efficient and energy-saving welding solution is of great significance to industrial production.This paper selects20 mm low-alloy high-strength steel Q345 E in the high-speed train bogie structure as the object,explores the low-power laser-arc hybrid welding process,and uses the method of combining numerical simulation and process test to study the influence of welding process parameters on the quality of weld formation It also tests and analyzes the microstructure of the weld and the mechanical properties of the joint.The research results are expected to provide theoretical guidance and technical support for the high-efficiency and low-energy-consumption welding of thick/medium-thick plate components.In this paper,a finite element model for laser-arc hybrid welding of20 mm low-alloy high-strength steel Q345 E is first established.Based on temperature field simulation,the bottom welding process parameters in laser-arc hybrid welding are determined.In the numerical simulation,the welding heat source is a combination of 3D Gauss heat source + double ellipsoid heat source.By comparing the simulated calculation results with the actual weld shape,the rationality of the heat source model is verified and the bottom welding process parameters are optimized.Second,explore the low-power laser-arc hybrid welding process.Before the bottom welding,select the plate with the same thickness as the blunt edge,design the groove size,and test the parameters such as laser power;after determining the laser power,optimize the distance between the two plates to achieve 4mm blunt edge bottom welding;follow-up In filler wire welding,by studying the influence of laser parameters and arc parameters on the weld formation in a given groove,and on this basis,20 mm Q345E welding is completed;in hybrid welding,it is found that adjusting the laser parameters and arc parameters can suppress the bottom welding When welding defects such as pores,undercuts,and underfills are formed;during fill welding,the laser mainly functions to compress and enhance the arc.If the laser power is too small,the effect of compression and enhancement of the arc is not obvious.Finally,the microstructure of the weld and the mechanical properties of the joint were tested and analyzed.It was found that the microstructure of the weld center was composed of ferrite and pearlite,and the heat-affected zone contained acicular ferrite,massive ferrite and pearlite.The maximum hardness of the weld joint appears in the coarse grain zone in the center of the weld,while the hardness value at the local location of the remelting zone is relatively low.The tensile test show that the mechanical properties of the joint are less affected,but meet the requirements of the weld.Strength requirements;observe the fracture morphology,the fracture type is plastic fracture,and the fracture mode is transcrystalline fracture;EDS analysis of the element distribution in the area between the weld and the base metal shows that the difference between the welded joint and the base metal is not obvious.