Study On Mechanism And Process Optimization Of Laser Finishing Of Metal Parts Edge

In the manufacturing process of metal parts,redundant materials such as burrs,fins and slag often exist on the edges of them.The phenomena leads to lower processing quality of edges,so finishing prcoessing is needed.Nowadays,it is difficult for traditional technology to meet the requirement of finishing under the condition of high precision manufacturing.Laser processing technology is expected to improve the processing quality of metal parts edge due to its unique advantages such as non-contact processing,easy flexibility and high material removal speed.Therefore,laser finishing technology of metal parts edge is proposed to improve quality of edge,which utilizes the microfabrication ability of laser to quickly scan and remove redundant materials.Considering the problems and solutions above,the interaction of laser on metals is first simulated.Then experimental study of laser micro groove is carried out.The edge finishing experiments and optimized experiments of bearing steel GCr15 and titanium alloy TC11 are carried out by nanosecond laser and picosecond laser.Finally,the structure and hardness of metal after laser irradiation are analyzed.The main contents and conclusions are as follows:(1)Based on the interaction mechanism between laser and metal,the interaction models of nanosecond laser and picosecond laser of titanium alloy TC11 are established by software COMSOL Multiphysics.The ablation depth of single nanosecond laser pulse is 2.9 ?m and the removal accuracy is micron.The ablation depth of single picosecond laser pulse is 0.7 ?m and the removal accuracy is submicron.Convex profile is formed around the nanosecond laser action zone,which is consistent with the experimental morphology.The effects of laser power,scanning speed and repetition times on the ablation depth of micro groove are studied in detail about picosecond laser.The simulated value is slightly larger than the experimental value and the accuracy of simulation is high.The electro-acoustic relaxation time of 10 ps pulse width picosecond laser is 58 ps,which shows that the ablation is non-equilibrium.(2)The effect of pump current,scanning speed and repetition times on the titanium alloy TC11 surface micro groove morphology machined by nanosecond laser processing system is studied.Finishing experiments of bearing steel GCr15 and titanium alloy TC11 edges arecarried out according to micro groove process.The finishing effect is evaluated by defining removal amount,unit removal,relative removal and secondary burr size and the effects of different process parameters are investigated.It is found that nanosecond laser can finish sub-millimeter scale finishing.However,there are still secondary burrs and convex slag reducing the finishing quality.(3)In order to improve the quality of nanosecond laser processing,a method of laser processing assisted by liquid coatings is proposed.The morphology of pits processed in air,water,oil,water glass and water mixed water glass is investigated.It is found that the morphology is smoother under the condition of liquid coatings.Water can inhibit slag accumulation and water glass can improve ability of laser removal.The combination of the two can play a synergistic role.(4)The effect of pump current,scanning speed and repetition times on the titanium alloy TC11 surface micro groove morphology machined by picosecond laser processing system is studied.According to picosecond laser finishing experiments of bearing steel GCr15 and titanium alloy TC11 edges,it is found that picosecond laser can accomplish sub-millimeter scale finishing with high quality.The influence of power,scanning speed and repetition times on removal amount and unit removal is also obtained.(5)Orthogonal experiment is designed to optimize the parameters of picosecond laser finishing.The order of factors influencing the unit removal of bearing steel GCr15 is power,scanning speed,repetition times,and the optimum parameters are 30 W,200 mm/s and 10 times.The order of factors influencing the unit removal of titanium alloy TC11 is scanning speed,power,repetition times,and the optimum parameters are 300 mm/s,20 W and 5 times.(6)The metallographic structure and microhardness of nanosecond and picosecond laser irradiated zone are analyzed separately.It is found that thermal effect of nanosecond laser can refine the structure and greatly improve the hardness of melting zone and heat affected zone.Meanwhile,the metallographic structure and hardness of the material remained unchanged after picosecond laser irradiation.