Laser Polishing Die Steel Assisted by Steady Magnetic Field

Abstract

To improve the surface roughness of SKD61 die steel and reduce the secondary overflow of the molten pool, a steady magnetic field-assisted laser polishing method is proposed to study the effect of steady magnetic field on the surface morphology and melt pool flow behavior of SKD61 die steel. Firstly, a low-energy pulsed laser is used for the removal of impurities from the material surface; then, the CW laser, assisted by steady magnetic field, is used to polish the rough surface of SKD61 die steel to reduce the material surface roughness. The results show that the steady magnetic field-assisted laser polishing can reduce the surface roughness of SKD61 die steel from 6.1 μm to 0.607 μm, which is a 90.05% reduction compared with the initial surface roughness. Furthermore, a multi-physical-field numerical transient model involving heat transfer, laminar flow and electromagnetic field is established to simulate the flow state of the molten pool on the surface of the SKD61 die steel. This revealed that the steady magnetic field is able to inhibit the secondary overflow of the molten pool to improve the surface roughness of SKD61 slightly by reducing the velocity of the molten pool. Compared with the molten pool depth obtained experimentally, the molten pool depth simulation was 65 μm, representing an error 15.0%, thus effectively demonstrating the accuracy of the simulation model.

Numerical and Experimental Analysis of Dual-Beam Laser Polishing Additive Manufacturing Ti6Al4V

“…The traditional computational fluid dynamics method was used to solve the problem in this simulation. The heat transfer equation for a material surface governed by Fourier’s law is described as follows [ 30 ]: where is the density, is the temperature, is the time, is the velocity of molten pool flow, is the thermal conductivity, is the laser heat source, and is the modified heat capacity, which is defined as [ 31 , 32 ]: where is the specific capacity of solid materials, is the latent heat of melting, and is the liquid fraction, which can be described as [ 32 ]: where (1877 K) and (1900 K) are the solid and liquid temperatures of Ti6Al4V, respectively.…”

“… where can be written in COMSOL weak form format, and a detailed implementation is covered in ref. [ 30 ]. Our integral is equal to zero.…”

“…The traditional computational fluid dynamics method was used to solve the problem in this simulation. The heat transfer equation for a material surface governed by Fourier's law is described as follows [30]:…”

Flame-Assisted Laser Polishing of Alumina Ceramic Surface Properties

“…In recent years, a large number of scholars at home and abroad have conducted experimental studies on the laser polishing of different materials, including metals and glass [ 5 , 6 , 7 , 8 , 9 ]. However, due to the high melting point and the low creep rate of the ceramic materials themselves, there are fewer reports on the use of laser polishing in ceramics.…”

A Study on the Dynamic Evolution Mechanism of the Steady Magnetic Field on the Internal Flow Behavior of a Laser Melting Pool

“…Furthermore, Wang et al established a mathematical model of the regulation of the electromagnetic complex field on the gradient of the particle distribution enhanced by laser melting and injection and analyzed the influence of the electromagnetic complex field parameters on the flow field, temperature field, and particle distribution inside the melt pool [23]. To improve the rough surface of SKD61 die steel, and reduce the secondary overflow of the molten pool, Zhou et al adopted a steady magnetic-field-assisted laserpolishing method to study the effect of a steady magnetic field on surface morphology and melt pool flow behavior [24]. The study revealed that the steady magnetic field can inhibit the secondary overflow of the molten pool to slightly improve SKD61 surface roughness by reducing the velocity of the molten pool.…”