Research On The Key Technology Of Shot Blasting And Rust Removal For Ship Q235 Steel

Corrosion failure is the most important failure mode in Marine environment,so ship rust removal and coating become the key surface treatment technology.Shot blasting has the advantages of self-feed and high processing efficiency,which is suitable for the derusting treatment of ship deck,pretreatment steel plate and other large working surface.However,due to the large treatment area,although the existing surface treatment equipment can achieve the purpose of improving the treatment efficiency by speeding up the feed speed,but the effect of rust removal processing is difficult to guarantee,so the accurate grasp of rust-pellet,treatment process and parameters and other key technologies is an important premise for the rational design of surface treatment equipment.In this paper,the surface rust layer of Q235,a commonly used material on ship deck,is taken as the research object,with the purpose of improving the efficiency of rust removal and improving the surface quality after processing,a mechanical model of the projectile impact rust layer rupture is established,the process of rust removal is simulated by finite element method,and the shot blasting test is designed.Based on the simulation model and the processed sample,the removal mechanism of the surface rust layer of Q235 steel is revealed.The influence of processing parameters such as projectile material characteristics and feed speed on surface properties was analyzed.The main research contents include:(1)Establish a mechanical model for material rust layer fracture under projectile impact,obtain the limit value of the number of cracks that cause tensile fracture of the rust layer due to substrate deformation during projectile impact,and provide determined material parameters for finite element simulation;Based on the analysis of the energy consumption distribution of the shot blasting machine and the motion trajectory of the shot on the blade,a mapping relationship between the shot blasting amount,blade speed,and the power of the shot blasting machine was established.It was proved that the trajectory of the shot on the blade is a helix,and blade speed is the main factor affecting the shot blasting speed and incidence angle.(2)Based on the tensile fracture mechanics model,tensile tests were conducted to obtain the damage parameters of the brittle fracture of the rust layer.A finite element simulation model for shot blasting processing was established by combining the damage parameters.The influence of bullet impact on the indentation depth,residual stress,and rust removal area of Q235 steel under different working conditions was explored.The results showed that the impact angle of the bullet had the greatest impact on the residual stress and rust removal area,while the diameter of the bullet had the greatest impact on the indentation depth.(3)A deck shot blasting processing experiment was designed and completed to study the rust removal efficiency and effect under different matching combinations of rust layer,feed speed,and shot material.The pixel histogram method was used to quantitatively characterize and evaluate the degree of rust removal.The results showed that the rust removal effect of shot material was closely related to the material,with steel sand being the best,followed by steel shot and steel wire cutting shot,which had the lowest rust removal efficiency.It compensates for the current deficiency in classifying steel rust removal grades.(4)The surface performance of Q235 steel after surface rust removal treatment was studied,including indicators such as microstructure,surface roughness,residual stress,droplet contact angle,and paint adhesion.The mechanism of processing parameters,shot material on surface performance,and ship coating effect was elucidated.The maximum residual stress on the surface of steel shot after rust removal treatment was found,and the maximum gradient residual stress after multiple impacts was located on the surface,The stress value gradually decreases with the increase of depth;The surface roughness is inversely proportional to the feed rate,and the paint processed with steel shot has the best adhesion.The surface hydrophilicity is negatively correlated with the feed rate.