Technical Research Of Pulsed Laser Cleaning Aluminum Alloy Surface Paint Coating

Spraying paint is a common method to protect and decorate the surface of equipment in the industrial field.When the paint is damaged or the equipment is overhauled,the original paint needs to be removed.The quality and effect of paint removal has a direct impact on the operation of the equipment.Laser cleaning is a new type of surface cleaning technology,compared to the traditional cleaning method with ecological,precise and controllable advantages.It is of great significance to apply laser cleaning technology to the field of paint coating cleaning.This paper conducted research on laser cleaning technology of 2024 aluminum alloy surface paint coating,this mainly content of three aspects:The effect of laser angle on laser paint removal;Optimization of laser paint removal process parameters by response surface method;An ultrasonic assisted laser two-step cleaning method to improve cleaning quality was proposed,and the relevant experimental study was carried out.The specific content of the research is as follows:In order to explore the influence of laser incidence angle on paint removal effect,by changing the angle between the laser beam and the sample,the laser paint removal test at different angles is realized.Under the same experimental conditions,the surface paint removal effect was tested and analyzed.The results showed that the amount of paint removal first gradually increased and then decreased as the laser incident angle decreased,and the inflection point appeared at 70°.When the laser energy density is 5 J/cm2,the paint removal depth at the inflection point will increase by 160.57 μm compared with 40°,and this difference will become more significant as the paint thickness increases.In addition,the incident angle of the laser will change the surface roughness of the sample.Similarly,the minimum surface roughness is obtained at the 70°,which is increased by 0.438 μm～0.812 μm compared to the initial surface roughness.At the same time,the laser incident angle can also reduce the length of the smoke plume in the laser transmission direction and the concentration of plume particles.The actual laser cleaning effect is not determined by a single parameter,but the result of the common role of multiple process parameters.In order to explore the best cleaning parameters of laser densities.The experimental scheme was designed by response surface method,and the laser process parameters were optimized by taking the surface roughness of substrate after laser paint removal as the response value.When 2024 aluminum alloy is the base,the paint thickness is 100 μm,the optimal parameters obtained by response surface analysis method are:laser power 45 W,laser frequency 400 kHz,laser scanning speed 600 mm/s,scanning times 6.Surface roughness of the substrate is Sa1.739 μm,the error rate between simulation and experiment is only 0.6%.The results show that the macroscopic morphology of the substrate surface is uneven and laser scan trace,and the surface roughness increases from Sa1.319 μm to Sa1.739 μm.It is found that there are passivation layer and bulge molten substance on the surface of the substrate,and the local area is smoother and even,and the chemical composition of the matrix has not changed.After laser paint removal microhardness of the substrate decreased from 141.59 HV to 130.37 HV,the corrosion rate decreased from 0.008852 mm/a to 0.0023404 mm/a,the microhardness of the substrate decreased and the corrosion resistance improved.For further reduce matrix damage and obtain higher cleaning quality,an ultrasonic auxiliary laser two-step cleaning method is proposed,and the related experimental studies were carried out.The first step in the two-step method is ultrasonic auxiliary laser cleaning;the second step is closed,and the remaining paint is removed by ultrasonic vibration.Two-step method cleaning avoids the laser directly to the surface of the substrate,reducing the degree of matrix damage.The experimental results show that the ultrasonic auxiliary laser cleaning method is removed from the laser dry cleaning method due to the liquid membrane,which removes the same thickness of the paint coating to consume more laser energy than the single laser dry cleaning method.Determine when the remaining paint depth is 20 μm～30 μm.At this currently,the effect is the best,the influence of laser energy on the substrate is the smallest,and the remaining paint can be completely removed through ultrasonic vibration.The morphology of the surface and the distribution of the elements of the cleaning area are analyzed.The ultrasonic assisted laser two-step cleaning method has the best cleaning effect than the laser dry cleaning method,has the least impact on the substrate,and will not leave obvious traces on the substrate surface.By analyzing the hardness and corrosion resistance of the substrate,it can be seen that the surface hardness of the substrate after removing paint by two-step method is close to the original surface hardness and corrosion resistance.