Process Simulation And Experimental Research On Shot Blasting Of Acidless Descaling For Strip Rolling

It is necessary to remove the oxide scale on the surface of the hot-rolled steel coil before cold rolling.However,the traditional scale removal process by pickling leads to acid pollution of the environment.Using the mechanical method to achieve the acidless-descaling is an important research direction in the field of steel research.Blast descaling technology utilizes high-speed projectile to hit the strip surface,in order to force the scale layer to break and fall off.This technology has broad application prospect in cold strip production line.At present,the theoretical research on acidless-descaling is scarce,and some important mechanisms have not been clarified yet,especially the critical stress/strain of rupture of scales under external load,and the effect of descaling on impact angle,particle size,speed and amount of pellets.The core issues such as the law of influence have not been well solved,which restricts the promotion and application of acidless descaling technology.In this paper,the failure criterion of scale layer was researched,and the finite element simulation model of the descaling process was established.Combined with the finite element numerical simulation operation and descaling experiment,the influence of main process parameters on descaling was analyzed.The paper has achieved the following innovative results:(1)Through theoretical analysis and tensile experiment,the crack criterion of scale layer was established and the finite element model of descaling process was established.The composition and microstructure of the scale layer were observed,and the stress state of the scale layer under the impact of the projectile was analyzed.The failure strength theory of fracture mechanics and material mechanics was expounded,and the cracking behavior of the scale layer under tension was studied by tensile experiment,and the critical strain of the scale layer fracture was obtained by combining with the analysis of the evolution law of the crack.Based on the scale fracture criterion and the life-or-death element method,a three-dimensional impact descaling finite element model was established,and the accuracy of the model was verified by experiments.(2)Through the finite element simulation and the interference theory analysis,the best impact angle of the projectile was obtained and verified by experiment.The descaling behavior of a single projectile at different impact angles was simulated by using the finite element model.The influencing factors of the mutual interference of the pellet flow were analyzed in theory.Based on the combined consideration of two aspects,the optimal value interval of impact angle was obtained.The best impact angle value was obtained by shock descaling test in this optimal value interval of impact angle.(3)The particle size and impact velocity of the projectile were optimized through finite element simulation and kinetic energy analysis.Firstly,the effect of particle size and impact velocity on descaling effect was analyzed by using finite element model.Then,by parsing blasting system with a single power relations between the kinetic energy of the projectile,blast descaling process energy consumption calculation model was established.Under the condition of limited energy consumption,the particle size and impact velocity parameters of the projectile with the best descaling effect were obtained by using finite element simulation and descaling experiment.