| With the development of computer technology and laser technology,laser cladding technology has been applied to more and more industries.Laser cladding technology is an advanced technology that forms a cladding layer on the surface of a substrate that is fused with the substrate and has completely different compositions and properties.The key of laser cladding technology is to ensure that the powder can be uniformly,stably and controllably transported to the cladding area to ensure the microstructure and properties of the molten pool and its heat affected zone.The key component to realize this key technology is the coaxial powder feeding nozzle for laser cladding.Therefore,it is particularly important to study the structural parameters of laser cladding nozzle and the technological parameters of powder feeding to improve the quality of laser cladding.In this paper,an improved laser cladding coaxial powder feeding nozzle with external shielding gas structure is optimally designed aiming at the problems of large powder gathering diameter,low powder utilization rate,easy blockage of the nozzle,poor cooling water system effect and unsTable powder feeding effect of the existing nozzle.(1)The motion model of a single particle in the pipeline is established,and the best airflow speed required for conveying powder particles is 1.81 m/s.The geometric model of nozzle structure is established,and the influence law of nozzle structure parameters on powder feeding effect without considering other factors is analyzed.(2)Using the newly designed nozzle model,the finite element model of the powder feeding process of the nozzle is established,and the powder feeding process of the contact nozzle is numerically simulated,which verifies the rationality of the powder cavity structure with internal and external inclination angles.The influence rules of the powder cavity radius,the powder cavity inclination angle and the powder cavity gap on the powder convergence effect are explored,and the optimized interval of nozzle structure parameters is determined.(3)BP neural network optimized by corresponding curved surface method and genetic algorithm is used to optimize the combination of nozzle structural parameters.The optimized nozzle structural parameters are:powder cavity inclination angle 18.94 mm,powder cavity radius 6.27mm and powder cavity clearance 0.6 mm.The powder convergence diameter is 2.752 and the powder convergence focal length is 10.86 mm.After determining the structural parameter combination of the nozzle,the range of the structural parameter of the outer protective gas is determined according to the structural parameter combination of the nozzle.The structural parameters of the external protective gas are optimized by orthogonal test design.The optimized structural parameters of the external protective gas are:the inclination angle of the external protective gas is 35 degrees,the radius of the external protective gas is 8mm,and the flow rate of the external protective gas is 1.5 m/s.Its powder convergence diameter is 2.631mm,and its powder convergence focal length is 10.59 mm.(4)Unsupported laser cladding coaxial powder feeding nozzle is made of photosensitive resin material,and its powder feeding effect is verified.The powder convergence focus,diameter,utilization rate and stability of the optimized nozzle were measured.The authenticity of the simulation results is verified.The optimized powder convergence diameter is 2.75mm,the powder utilization rate is about 57%,and the powder convergence focal length is 10 mm.It is proved that the powder feeding effect of the optimized nozzle is greatly improved compared with the original nozzle. |
PDF Full Text Request