Abstract
In the wire arc additive manufacturing (WAAM) process, the flow behavior of the molten pool determines the formation accuracy and formation defects. Therefore, it is significant to understand the complex physical process of the molten pool behavior in the WAAM. A real-time X-ray direct observation method and volume of fluid method (VOF) were performed to study the flow in molten pool and liquid flow in the molten pool. X-ray was used to observe the liquid flow in the molten pool and the droplet transfer from the WAAM. A three-dimensional model of the molten pool and droplet was established based on the VOF method, and the temperature distribution and flow status of the molten pool were calculated. By controlling different wire feeding speeds, two different droplet transfer modes were observed by X-ray, which include globular transfer and bridging transfer. Compared with globular transfer, bridging transition has little effect on molten pool flow. The flow model during the deposition process is established; the x–z plane is divided into four regions according to the flow characteristics of different positions in the molten pool. The maximum velocity in the molten pool appears in the action area of plasma arc force, which is 0.277 m/s, which leads to the increase in melting depth and promotes the flow of molten metal.
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Abbreviations
- ρ :
-
Mass density
- t :
-
Time
- u :
-
X-velocity component
- v:
-
Y-velocity component
- w :
-
Z-velocity component
- \({m}_{s}\) :
-
Mass source term
- U s :
-
Thermal energy item
- p :
-
Pressure acting on fluid micro-element body
- p v :
-
External pressure acting on free surface
- P max :
-
Peak value of arc pressure
- \(\mu\) :
-
Viscosity
- F x :
-
X-component of volume force
- F y :
-
Y-component of volume force
- F z :
-
Z-component of volume force
- F drag :
-
Plasma flow force
- K :
-
Drag coefficient
- T :
-
Temperature
- \(\lambda\) :
-
Fluid thermal conductivity
- c :
-
Specific heat capacity of fluid
- η :
-
Heat efficiency
- η d :
-
Absorption rate of droplet
- rd :
-
Droplet radius
- rq :
-
Effective radius of arc
- T m :
-
Room temperature
- C p :
-
Specific heat capacity of droplet
- τ :
-
Droplet transfer frequency
- U:
-
Arc voltage
- \({\mu }_{m}\) :
-
Vacuum permeability
- H b :
-
Base metal thickness
- \({\sigma }_{j}\) :
-
Current density distribution parameters
- C ds :
-
Spherical drag coefficient
- \({\rho }_{g}\) :
-
Density of plasma gas
- \({D}_{d}\) :
-
Droplet diameter
- \({\nu }_{g}\) :
-
Velocity of plasma gas
- H W :
-
Arc length
- \({\mu }_{g}\) :
-
Plasma flow viscosity
- F s :
-
Local solid volume fraction
- F cr :
-
Critical solid volume fraction
- C0 :
-
Drag coefficient constant
- R:
-
Gas constant
- Q p :
-
Power output energy
- Q d :
-
Energy absorbed by droplets
- Q s :
-
Energy of welding wire separation
- Q w :
-
Energy entering molten pool
- Q dr :
-
Energy lost in droplets
- Q wr :
-
Energy lost in molten pool
- \(\varnothing\) :
-
Droplet transfer frequency
- I:
-
Arc current
- r :
-
Gaussian distribution radius
- σ :
-
Gauss heat distribution parameter
- \({\rho }_{p}\) :
-
Radius of Gaussian pressure
- \(\overrightarrow{n}\) :
-
Vector perpendicular to local free surface
- κ :
-
Free surface curvature
- γ :
-
The surface tension
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This work was financially supported by the National Natural Science Foundation of China (No. 5206050261).
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Jiankang Huang and Ding Fan proposed the research project, and conceived and designed the study and revised the manuscript; Zhuoxuan Li studied the welding process and wrote the manuscript; Shurong Yu improved the research by theory and revised the manuscript; Xiaoquan Yu corrected and modified the text and language.
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Huang, J., Li, Z., Yu, S. et al. Real-time observation and numerical simulation of the molten pool flow and mass transfer behavior during wire arc additive manufacturing. Weld World 66, 481–494 (2022). https://doi.org/10.1007/s40194-021-01214-z
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DOI: https://doi.org/10.1007/s40194-021-01214-z