Modeling&Prediction Of Laser Welding Distortion For Ultra-thin SS316L Sheets

Proton Exchange Membrane Fuel Cell(PEMFC)is an ideal mobilepower supply and independent power supply device, having broadapplication prospects in vehicle, electronics, national defense military and soon. It can translate chemical energy of hydrogen into electrical energywithout burning process, and the only product is water. Besides the workingtemperature is low, starting speed is high and working life is long. Bi-polarplate is one of the kernel parts of the PEMFC, accounting for about29%ofthe total cost attributed to manufacturing. Recently Graphite bi-polar plate iswidely used in PEMFC, however, because of high manufacturing costs andmaterial brittleness, Graphite bipolar plate has been difficult to meet theneeds of low manufacturing cost and is gradually replaced by metal bi-polarplate.Bi-polar plate is attained by connecting two single plates together.Requirements like good sealing, strong corrosion resistance, long workinglife and small deformation are demanded for the connector. Optical fiberlaser welding technique, featured by its fast speed, high power density andsmall welding deformation, has been acknowledged as the main connection method for metal bi-polar plate. However, as its thickness is only0.1mm andthe welding line is terribly complicated, huge welding deformation stillappears in metal bi-polar plate, which does great damage to the battery’sperformance.According to the problems above, this paper studied the weldingdeformation mechanism of ultra-thin stainless steel, raised the weldingdeformation evaluation method. Local deformation prediction model isestablished, and it’s influence on overall deformation is expound byanalytical model, based on which overall welding deformation predictionmodel of ultra-thin stainless steel is developed, serving as a reference for thefurther welding deformation control.Main work in this paper is as follows:(1) Development of welding distortion evaluation method ofultra-thin stainless steelExperimental system was built. Influence of welding parameters, suchas welding power, welding speed and beam focus position, on weldingquality was studied, providing a basis for the development of the weldingparameters range. Analyzed metal bi-polar plate overall deformation’sinfluence on the assembly pressure distribution of battery, and raiseddeformation height range and concentration as the evaluation indicator ofultra-thin stainless steel overall welding deformation (2)Local welding distortion research for ultra-thin stainless steelInherent strain method was used to study the mechanism of localdeformation of ultra-thin stainless steel, based on which transverse shrinkagedeformation and longitudinal shrinkage deformation prediction model wasestablished. According to physical characteristic of welding formation, gotthe fitted curve of the border of laser beam penetration welding seam, andthus got its relationship model with angular deformation by experimentalangular deformation, from which angular deformation prediction model isdeveloped. Laser welding experiment with0.5mm and0.2mm thick316Lstainless steel was conducted, and showed that the local deformationprediction models were highly reliable.(3)Overall welding distortion research for ultra-thin stainless steelCombining with practical situation and theory, analyzed localtransverse deformation, longitudinal deformation and angular deformation’sinfluence on the overall distortion, and expounded it by analytical model.Welding process with only part of the local deformation existed wassimulated by ABAQUS software to verify the analytical model. Finallyoverall deformation separately caused by transverse deformation,longitudinal deformation and angular deformation was linearly added toestablish the overall deformation prediction model of ultra-thin stainlesssteel. Experiment showed that the prediction results were in good agreementwith experiment. This paper focused on laser welding deformation of ultra-thin stainlesssteel. Ultra-thin stainless steel laser welding deformation evaluation, localwelding deformation mechanism, local welding deformation’s influence onoverall welding deformation, simulation of laser welding process, andprediction of overall laser welding deformation of ultra-thin stainless steelwere presented in this work, providing reference for the further ultra-thinmetal laser welding deformation control.