Research On The Detection And Control Of Laser Over-lap Welding Deformation Of Thin Q235 Steel Plates

Q235 low carbon steel is widely used in the manufacture of key components such as new energy vehicle battery case sheets due to its excellent characteristics.Laser welding is increasingly used in the manufacturing of low carbon steel sheets due to its high aspect ratio,high energy welding power and small heat affected zone.The battery box is mainly welded by a box plate and a rib sheet,and the box board and the rib sheet form a lap joint.The number of ribs in the battery box is generally large.Although the laser welding of each rib is not much deformed,the accumulation of welding deformation of multiple ribs will make the final deformation of the box more obvious and does not meet the production requirements of the box.Therefore,there is an urgent need to study a flexible laser welding process to meet the manufacturing needs of new energy vehicle battery box sheet welding.In this paper,1.5 mm thick Q235 low carbon steel was used as the research object.The effects of laser power,welding speed and defocusing amount on the laser lap welding deformation of low carbon steel were studied by laser lap welding.The deformation control method based on adaptive cooling of protective gas proposed in this paper effectively reduces the laser lap welding deformation of low carbon steel.The main research work is as follows:(1)A system for detecting laser lap welding deformation is built based on a laser ranging sensor.The direct-type laser ranging method is determined by the principle of triangulation.The mechanical device and working process of the detection system are elaborated.Through a series of experimental tests,the performance index of the system is obtained,and the microlevel precision detection is realized for the deformation.(2)The laser lap welding test of Q235 low carbon steel sheet was carried out,and the deformation mechanism and characteristics were analyzed.The influence of laser processing parameters on the laser lap welding deformation of low carbon steel was studied.The test results show that Q235 low carbon steel sheet out-of-plane combination deformation occurs mainly in the longitudinal bending deformation;the deformation amount gradually increases with the increase of the laser power,and gradually decreases with the increase of the welding speed.(3)A lap welding deformation control method based on adaptive cooling of shielding gas is proposed.The dynamic chilling treatment is used to realize the active control of laser lap welding deformation.The laser lap welding test of Q235 low carbon steel sheet was carried out by this method.The deformation of the test piece before and after dynamic chilling treatment was compared,and the influence of chilling parameters on the deformation control effect was further studied.The test results show that the longitudinal bending deformation of the specimen after dynamic chilling treatment is significantly reduced.When the angle between the protection air gun and the vertical direction is 40° and the flow rate of the shielding gas is 15 L/min,the longitudinal bending deformation ratio of the specimen is dynamic.It is reduced by about 80% before the chilling treatment,and a good control effect can be achieved.The deformation detection and control technology proposed in this paper realizes the dynamic detection and control of laser lap welding deformation,ensuring high efficiency and high precision.The optimized laser process parameters meet the welding deformation requirements of the battery box sheet and can effectively guide new energy.Welding manufacturing of automotive battery box sheet members.