Research On Pre-welding Laser Cleaning Of Aluminum Alloy And Evaluation

With the rapid development of transportation industry,the three major problems including energy wasting,safety risks and environmental degradation are becoming more and more serious.The lightweight development of the vehicle can help save energy,reduce emissions and improve the transportation's overcontrol.Aluminum alloy is widely used in welding components such as car and airplane body because of its high strength,corrosion resistance,easy to process and excellent mechanical properties.However,aluminum is easy to oxidize and absorb moisture from the air,which may severely affect the welding quality if its not cleaned before welding,thus will led to safety risks in transportations.Traditional cleaning methods with high pollution,severe material damage,incomplete cleaning and offline cleaning have great influence on welding quality and production efficiency.So how to clean aluminum alloy before welding with high quality and efficiency becomes an urgent.Aiming at the above problems,this paper presents a method of using pulse fiber laser to clean the surface of aluminum alloy.This paper mainly studied the equipment,process and mechanism of the laser cleaning of aluminum alloy and conducted the welding evaluation after cleaning.We started with a research of the composition of laser cleaning devices and built a laser cleaning operation platform,concluded that pulsed fiber laser is suitable for removal of aluminum alloy's oxide film.Then we studied the influence of scanning mode,point spacing,laser power and pulse width on surface morphology,roughness and oxygen content,with which we determined the evaluation standard and efficiency of laser cleaning.Combined with scanning electron microscopy(SEM),laser confocal and high-speed camera,we further studied the cleaning process and results,found that there are two mechanisms in cleaning process according to two different gradient of energy density: phase explosion at low energy density and ablation at higher situation.We also presented a three-layer model of ablation process concerning about the formation of the products and microtopography after cleaning.The approximate threshold of aluminum alloy ablation mechanism is obtained by theoretical analysis.By applying the optimized process in pretreatment of laser welding and MIG welding,the effect of laser cleaning on welding was comprehensively evaluated and the feasibility of laser cleaning for pre-welding is verified through the observation of weld forming,evaluation of the mechanical properties and residual stress test after welding.