Mechanism And Experimental Research On Laser Cleaning Of Rust Layer On Oil Pipe Thread Surface

Modern laser cleaning technology is more and more widely used in the field of industrial surface repair,and related theories and processes occupy an important position in major projects.The technology uses a laser as a processing tool to act on the surface of the pollution layer to improve the surface quality of the substrate while removing the pollution layer.It has the characteristics of high efficiency,environmental protection and simple operation.This paper studies the laser cleaning and process parameter optimization of the rust layer on the surface of the NC50 oil pipe thread.Through microscopic inspection,it is concluded that the structure of the rust layer is composed of an external easy peeling layer and an inner dense oxide layer;based on the interaction between the rust layer and the laser,a temperature rise model of the rust layer on the surface of the oil pipe thread is established,and the mechanism of laser removal of the rust layer is studied.Finite element thermodynamic simulation and laser cleaning experiment based on the temperature rise model deduced by the mechanism;through the orthogonal experiment,the three factors of laser power,scanning speed and defocus amount on the significant order of cleaning effect;obtained through single factor experiment variation trends of micro-topography,surface roughness and oxygen content under different parameters;in order to improve the quality of laser cleaning,the combination of response surface method and particle swarm optimization algorithm with optimized inertia weight was used to obtain the optimal combination of laser process parameters and the predicted value of surface roughness.The feasibility of the optimization method is proved by testing experiments,and the cleaning effect is relatively good.The main research contents of this paper are as follows:(1)Based on the principle of steel corrosion,the element composition,phase and structural characteristics of the rust layer on the surface of the NC50 oil pipe thread were obtained;based on the surface adsorption force of the rust layer,the theoretical model of laser cleaning of the rust layer particles was studied;the mathematical model of the surface temperature rise of the rust layer was established and the common mechanism of Gaussian laser acting on the surface of the rust layer was analyzed;based on three laser rust removal mechanisms,the changes of the surface morphology of the substrate during the rust removal process were studied.(2)The thermodynamic simulation of the laser cleaning of the rust layer on the surface of the oil pipe thread was carried out.The Gaussian pulsed laser finite element model and the3 D model of the NC50 oil pipe thread were established.Based on the finite element heat conduction theory,the temperature variation law of the surface of the corrosion layer and the substrate under different laser parameters was studied.The temperature field analysis showed that the surface of the corrosion layer reached gasification under the cleaning threshold.The temperature can remove a certain thickness of the rust layer;through the thermal-mechanical coupling analysis,it is concluded that the laser rust removal process is a combination of various mechanisms.The finite element simulation data can provide a theoretical basis for subsequent laser cleaning experiments.(3)The cleaning experiment of the rust layer on the surface of the oil pipe thread was carried out by using a pulsed laser.Taking the surface roughness as the judging standard,the significance ranking of laser power,scanning speed and defocus amount on the surface cleaning effect of oil pipe thread samples was studied through orthogonal experiments of three factors and five levels,and different parameters were studied through 15 sets of single factor experiments.The variation law of the microscopic morphology,oxygen element content and surface roughness of the lower sample provides theoretical guidance for the laser rust removal of NC50 oil pipe threads in the industry.(4)Optimization of process parameters for laser cleaning of rust layer on oil pipe thread surface.The surface roughness is set as the optimization target,and the mathematical model between the optimization target and the three factors is obtained by the response surface method;the inertia weight in the particle swarm optimization algorithm is dynamically optimized.Combining the mathematical model with the optimized particle swarm optimization algorithm,the optimized process parameter combination is obtained.The microscopic detection experiment proves that the cleaning quality is good.The optimization process can provide technological guidance for the laser cleaning of the corrosion layer on the thread surface of the NC50 oil pipe in the industry.