Numerical investigation of heat, flow and particle trajectory in A-TIG welding pool of 304L-SS
- PDF / 2,151,113 Bytes
- 13 Pages / 595.276 x 790.866 pts Page_size
- 97 Downloads / 219 Views
RESEARCH PAPER
Numerical investigation of heat, flow and particle trajectory in A-TIG welding pool of 304L-SS Sara Pourmand 1 & Amin Ramiani Jafari 1
&
Alireza Ebrahimi 1
Received: 29 February 2020 / Accepted: 8 September 2020 # International Institute of Welding 2020
Abstract A three-dimensional CFD-model was developed to investigate Active-TIG welding of 304L-SS, involving heat transfer, fluid flow, solidification, plasma arc effect, Marangoni convections, magnetohydrodynamics and oxide particle trajectory. The aim was to understand how flux-induced particles are distributed in the weld line. The results, validated with available experimental data, showed that A-TIG forms a pool with an increased maximum temperature (2800 K) and depth-to-width ratio (0.7). The flow pattern, dominated by two vortices due to Marangoni convection, collects particles from the surface, submerges them into the pool and leads to entrapment of the most in the weld cross section. The motion path of 70% of particles ended at the deeper half of the cross section. Detailed numerical picture of A-TIG weld pool was presented and discussed in this study to be a step in understanding of the nature of Active-TIG welding and to assist in improving the process. Keywords A-TIG welding . CFD . Solidification . Marangoni flow . Particle trajectory . Magnetohydrodynamics
1 Introduction Tungsten inert gas (TIG) is a common fabrication process for stainless steel products for its good-quality welds. The process is mainly concerned with a weld pool of molten metal, formed by heat source of the plasma arc, which itself is associated with multi-physics of melt flow, heat and mass transport, melting/ solidification, metallurgical structure evolutions, oxidation/reduction, thermo-capillary effects and magnetohydrodynamic interactions. Therefore, the weld pool essentially determines the performance of welding and the characteristics of the final joint. Though from experiments, it was seen that the weld pool goes undersized in depth when it comes to joint thick sections. Paton welding institute proposed to apply a covering of oxideflux on the surface of thick-sectioned pieceworks and made a significant improvement in the depth of welding, named Active-TIG [1]. Modenesi et al. [2] approved that all kinds of Recommended for publication by Study Group 212 - The Physics of Welding * Amin Ramiani Jafari [email protected] 1
Department of Materials and Metallurgical Engineering, Amirkabir University of Technology (Tehran Polytechnic), No.424 Hafez St, Tehran 15916-34311, Iran
fluxes change the weld pool and increase the penetration depth. Heiple and Roper [3] gave two hypotheses for that effect, arc contraction and inversion of Marangoni flow due to chemical change in top layers of melt. Marangoni flow is driven by unbalanced surface tension at points on top of the weld pool because of high gradient in temperature distribution. Using mathematical simulations, Zhao et al. [4] have demonstrated internal vortexes in the pool formed by surface tension effects. Bes
Data Loading...
