Study On 420J1 Stainless Steel Transverse Magnetic Field-Assisted Millisecond Laser Percussion Drilling And Hole-Trepanning

Laser drilling is widely used in modern industrial processing due to its fast speed,high efficiency,good economic benefits and a large range of machinable materials.Compared with other types of laser drilling,millisecond laser drilling has higher processing efficiency,but millisecond laser drilling still has some quality defects such as poor roundness,large taper,and poor surface quality.In this paper,starting from the causes of defects in laser drilling,a method of using a magnetic field to assist millisecond laser drilling is proposed.On the basis of studying the mechanism of magnetic field-assisted millisecond pulsed laser drilling,related experimental researches have been carried out.This article first introduces the related historical background of lasers and the current applications of lasers in industry.The types and methods of laser drilling are classified,and then the auxiliary processes commonly used in laser drilling are explained.Then began to introduce the current research progress and status quo of laser drilling and magnetic field assisted laser processing at home and abroad.The characteristics of the laser and the principle of laser drilling materials and laser action are introduced.In addition,the plasma and the principle of interaction with the magnetic field are also explained.In addition,the pre-processing and post-processing methods of the experimental materials,the related equipment used in the experiment and the construction of the platform are also explained accordingly.Based on the APDL language,the life and death unit method was used to simulate the temperature field of millisecond laser percussion drilling and the structure of the microhole.After comparing the experimental results and the simulation results,it is found that the simulation results have a better fit with the experimental results except for the difference in the pore size.The difference in aperture comparison results is mainly related to the idealization of material removal in the simulation,Taken together,the simulation and experiment are in good agreement.An experimental study of millisecond laser hole-trepanning was carried out by using the built-up magnetic field-assisted millisecond hole-making platform.In the presence or absence of a magnetic field,the effects of the trepanning speed and the number of trepanning turns on the splash,the hole diameter and taper of the inlet and outlet,the roughness of the hole wall,the recast layer and the elements in the hole were studied.Through the analysis of the experimental results,it is found that the increase of the trepanning speed will lead to the decrease of the roundness and taper of the hole,and the magnetic field assistance is more effective when the trepanning speed is high.The increase in the number of trepanning turns is not conducive to the roundness of the entrance.The maximum taper occurs when the number of trepanning turns is 2 turns.The magnetic field can effectively reduce the recast layer on the inner wall of the hole but has no effect on the content of the elements in the hole wall,that is,the magnetic field cannot change the oxidation phenomenon in the hole.Finally,the magnetic field assisted millisecond laser percussion drilling hole experiment was carried out,the effects of pulse energy,pulse width,and number of pulses on entrance splash,entrance and exit aperture and taper,hole wall roughness and elements around the aperture are mainly studied.With the increase of pulse energy,the better the quality of hole forming,the magnetic field can effectively improve the efficiency of hole making at low laser energy.The increase in pulse width leads to an increase in the upper pore size,but it is not conducive to the forming effect of the microhole.The increase in the number of pulses has little effect on the hole diameter,the magnetic field assist can effectively reduce the splash around the hole entrance and has certain benefits to the shaping effect of the inner wall of the impact hole and the contour of the hole wall.Similarly,the magnetic field can effectively improve the thickness and roughness of the recast layer at different positions in the hole and increase the depth of the hole,but it cannot suppress the occurrence of oxidation around the orifice.