3D Multiphysical Modelling of Fluid Dynamics and Mass Transfer in Laser Welding of Dissimilar Materials
Abstract
:1. Introduction
2. Experimental Procedure
3. Model Description
- (1)
- The effect of side shielding gas on the behavior of keyhole and molten pool is ignored.
- (2)
- The calculated fluid is Newtonian and incompressible and is in local thermal equilibrium; furthermore, this fluid satisfies the basic equations of fluid motion.
- (3)
- The temperature-dependent thermo-physical parameters are calculated, derived from the JMatPro software (Release Version 7.0.0, Sente Software Ltd., Guildford, UK).
- (4)
- In the simulation, only iron and titanium components are considered, and other alloy elements are ignored.
3.1. Laser Heat Source Model
3.2. Governing Equation
3.3. Boundary Conditions
3.4. Numerical Method
4. Results and Discussion
4.1. Keyhole Formation and Weld Pool Dynamics
4.2. Mass Transfer
4.3. Validation of Simulation Results
5. Conclusions
- (1)
- Recoil pressure is the driving force for keyhole formation. The laser beam heats the workpiece through the keyhole wall, and the flow of the molten pool has an important effect on energy transmission.
- (2)
- Fluid flow and diffusion are two important mechanisms of mass transport. As the laser line energy increases, the thickness of the intermetallic reaction layer and the diffusion of elements in the weld will increase. Accurate control of laser energy is the key to reduce the formation of intermetallic compounds.
- (3)
- In the premise of ensuring connection strength and avoiding the burning of alloying elements, the depth of the keyhole in the lower region should be controlled accurately, and the melted metal in the lower region should also be prevented from entering the upper region in large quantities.
Author Contributions
Acknowledgments
Conflicts of Interest
Symbol
Symbols | Meaning | Symbols | Meaning |
Maximum heat flux density of the laser beam | Recoil pressure components along the x-axis | ||
Radius | Volume fraction gradient along the x-axis | ||
Waist radius | Volume fraction of cells | ||
Heat flux density at radius | Mass source | ||
Beam quality factor | Mass source | ||
Longitudinal coordinate of the waist | Cell mass | ||
Rayleigh constant | Liquid volume fraction of cells | ||
Welding speed | A tiny number | ||
Welding time | Porous medium constant | ||
Density | Specific heat | ||
Velocity vector | Mass fraction of the species | ||
Mass source | Vector normal | ||
Pressure | Convection heat transfer coefficient | ||
Gravity constant | Ambient temperature | ||
Dynamic viscosity | Boltzmann constant | ||
Momentum source | Emissivity of radiation | ||
Enthalpy | Speed of evaporation | ||
Coefficient of thermal conductivity | Latent heat of evaporation | ||
Temperature | Surface tension | ||
Energy source | Surface curvature | ||
Mass fraction of species | Temperature-dependent surface tension coefficient | ||
Diffusion flux of species | Adjustment coefficient | ||
Mass diffusion coefficient for species | Evaporation constant | ||
Thermal diffusion coefficient | Temperature of the keyhole surface | ||
Recoil pressure | Constant related to the material |
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304L | |||||||
---|---|---|---|---|---|---|---|
C | Si | Mn | P | S | Ni | Cr | Fe |
≤0.03 | ≤1.00 | ≤2.00 | ≤0.035 | ≤0.03 | 8.00~11.00 | 18.00~20.00 | balance |
TA2 | |||||||
Fe | C | N | H | O | Si | Ti | |
≤0.30 | ≤0.10 | ≤0.05 | ≤0.015 | ≤0.25 | ≤0.015 | balance |
Power (W) | Welding Speed (m/min) | Beam Defocus (mm) | Gas Flux Rate (L/min) |
---|---|---|---|
500 | 3.2 | 0 | 15 |
500 | 3.6 | 0 | 15 |
520 | 3.6 | 0 | 15 |
Physical Properties | 304L | TA2 |
---|---|---|
Density (kg/m3) | 7000 | 4110 |
Specific heat (J/(kg·K)) | 712 | 594 |
Heat conductivity (W/(m·K)) | 29 | 40 |
Dynamic viscosity (N·s/m2) | 0.007 | 0.005 |
Boiling point (K) | 3100 | 3315 |
Surface tension (N/m) | 1.4 | 1.65 |
Surface tension temperature coefficient (N (m·K)) | −4.9 × 10−4 | −2.6 × 10−4 |
Coefficient of thermal expansion (/K) | 1.96 × 10−5 | 1.1 × 10−5 |
Melting latent (J/kg) | 2.47 × 105 | 3.89 × 105 |
Evaporation latent (J/kg) | 6.34 × 106 | 8.88 × 106 |
Nomenclature | Value |
---|---|
Laser beam radius at focus (mm) | 0.2 |
Planck constant (J·s) | 5.67 × 10−8 |
Stefan-Boltzmann constant (W/(m2·K4)) | 1.38 × 10−23 |
Ambient temperature (K) | 300 |
Density of plasma (kg/m3) | 0.06 |
Specific heat of plasma (J/(kg·K)) | 610 |
Heat conductivity of plasma (W/(m·K)) | 3.72 |
Convective heat transfer coefficient (W/(m2·K)) | 60 |
Radiation Emissivity | 0.4 |
Gas constant (J/(kg·mol)) | 8.3 × 103 |
Element | A | B | C | D | E |
---|---|---|---|---|---|
Fe | 44.45 | 45.39 | 62.50 | 37.73 | 0 |
Ti | 33.22 | 41.82 | 11.23 | 40.71 | 100 |
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Wu, J.; Zhang, H.; Feng, Y.; Luo, B. 3D Multiphysical Modelling of Fluid Dynamics and Mass Transfer in Laser Welding of Dissimilar Materials. Metals 2018, 8, 443. https://doi.org/10.3390/met8060443
Wu J, Zhang H, Feng Y, Luo B. 3D Multiphysical Modelling of Fluid Dynamics and Mass Transfer in Laser Welding of Dissimilar Materials. Metals. 2018; 8(6):443. https://doi.org/10.3390/met8060443
Chicago/Turabian StyleWu, Jiazhou, Hua Zhang, Yan Feng, and Bingbing Luo. 2018. "3D Multiphysical Modelling of Fluid Dynamics and Mass Transfer in Laser Welding of Dissimilar Materials" Metals 8, no. 6: 443. https://doi.org/10.3390/met8060443