Study On Mechanism And Process Of Cleaning Rust Layer With Nanosecond Pulse Laser

In the process of transportation and storage of steel,the water vapor and oxygen in the air will make the steel surface form a thick rust layer,which greatly affects the quality and efficiency of industrial processing.Using laser cleaning technology to remove rust layer on steel surface can greatly improve the cleaning quality and efficiency.This paper uses the combination of theoretical analysis,numerical simulation and experiment to carry out the theory of laser cleaning Q235B low carbon steel surface rust layer experiment simulation and on-line monitoring technology.The mechanism and process control scheme of cleaning rust layer by nanosecond pulse laser were investigated.Firstly,the model of moving nanosecond pulsed laser source is established,and the heat conduction model in laser cleaning process is established based on heat transfer theory.The temperature field and surface morphology of the corrosion layer on Q235B low carbon steel were simulated by COMSOL Multiphysics FEM software,and the simulation results show that the laser parameter combination with pulse width of 200 ns,average power of 100W and medium lap rate is more suitable for cleaning the corrosion layer on the surface of steel plate,which provides a reference for the experimental study of laser cleaning the corrosion layer.Secondly,the single spot ablation threshold values of Q235B low carbon steel substrate and corroded layer were measured by the area method under different pulse widths and laser average power.The ablation threshold values of 200 ns pulse width laser were lower than that of 60 ns pulse width laser.The effect of heat accumulation of spot lap on the ablation threshold was studied,and the ablation threshold of single row spot cleaning was calculated under different lap rates.With the increase of spot overlap rate,the ablation threshold showed a decreasing trend.Finally,the effects of average laser power,spot lap rate and cleaning times on cleaning quality and efficiency were studied.A laser cleaning online monitoring system was set up,and the cleaning degree of the cleaned metal surface was calculated by using image recognition technology.By analyzing the changing law of cleaning degree under different parameters,the appropriate process parameter combination was optimized.The cleaning process of small area was monitored by laser-induced plasma spectrum,and the cleaning times of different thickness of corroded layers were dynamically adjusted.The high quality automatic laser cleaning was achieved with the cleaning degree of 99.1%,the roughness of 1.45 μm and the oxygen content of the surface reaching the oxygen content of the substrate surface.Salt spray corrosion test results show that the corrosion resistance of steel plate samples after laser cleaning is significantly improved,which verifies the effectiveness of the laser cleaning on-line monitoring system.