Study On Cleaning Technology And Surface Quality Of Q345C Steel Rust Layer By Nanosecond Laser

With the increasing application of laser cleaning technology in the development of green ocean,the related theoretical and technological research has gradually become a major engineering demand.In this paper,the problem of efficient removal of rust layer on Q345 C steel pipe pile surface was regarded as the main target.First,the structural characteristics of the rust layer was studied.Then,the finite element model of the process of mobile nanosecond pulse laser cleaning was established,based on the interaction between the pulse laser and the rust layer material.After that,the step-by-step laser cleaning was carried out and the material removal mechanism of the step-by-step cleaning was summarized.Finally,the response surface optimization was used to divide step laser cleaning parameters for process control.The main work of this paper was as follows:(1)Based on the theory of metal corrosion,the composition and delamination characteristics of the rusty layer on Q345 C steel surface were analyzed.The absorption response of the rusty layer material to the nanosecond pulse laser beam was discussed.The temperature rise rule and thermal stress distribution of the rusty layer surface under the action of moving nanosecond pulse Gaussian heat source were analyzed.In view of the laser ablation theory,the mechanism of hole blaster,selective shallow layer gasification and recoil splashing in the process of laser cleaning the rusty layer were discussed.(2)The finite element model of rust layer on the Q345 C steel surface cleaned by nanosecond pulse laser was established on the COMSOL Multiphysics platform.The influence of different laser power and laser scanning speed on the temperature field distribution,cleaning threshold and cleaning surface contour(cleaning width,cleaning depth,ablation removal volume)of the rust layer were studied,providing the guidance for the following laser cleaning experiments.(3)The experiment of laser cleaning was carried out by using nanosecond pulse laser cleaning equipment.The effects of different laser power and laser scanning speed on the macro、micro morphology and surface roughness of rust layer and substrate surface after laser cleaning were studied.The mechanism of different material removal was revealed.The evaluation index of surface quality of laser cleaning was put forward,providing experimental basis for actual laser cleaning of Q345 C steel piles.(4)On account of the response surface optimization method,the second step of laser cleaning parameters was controlled,establishing the mathematical relationship between the step-by-step laser cleaning parameters and the removal rate of cleaning surface,the content of oxygen element and the surface roughness.The interactive influence trend of laser cleaning parameters on cleaning surface quality was analyzed,and the optimized combination of laser cleaning parameters was obtained,providing the technical guidance for actual laser cleaning of Q345 C steel pipe piles.