# Influence of Welding Parameters on the Weld Pool Dimensions and Shape in a TIG Configuration
## 4 Discussion
### Effect of the Welding Current  
To study the effect of the current intensity, cases n\({}^{\circ}\)1 (I = 100 A) and n\({}^{\circ}\)2 (I = 150 A) are compared. Figure 3a displays the weld pool width evolution from 1 to 20 s of interaction, involving Arcal.37, an arc length L = 5 mm and a tip angle \(\theta\) = 60\({}^{\circ}\). Figure 3: _Cont._ \begin{table}
\begin{tabular}{c c c c c c c c} \hline \multicolumn{6}{c}{**Arcal.37, Current 100 A, Arc Length 3 mm, Tip Angle: \(\alpha\)**} \\ \hline  & \multicolumn{3}{c}{**Case n\({}^{\circ}\):\(\alpha\) = 60\({}^{\circ}\)**} & \multicolumn{3}{c}{**Case n\({}^{\circ}\):\(\alpha\) = 30\({}^{\circ}\)**} \\ \hline  & **t = 1 s** & **t = 4 s** & **t = 8 s** & **t = 12 s** & **t = 16 s** & **t = 20 s** & **t = 20 s** \\ \hline \(E_{fusion}\) **(k)** & 0.111 & 0.297 & 0.362 & 0.427 & 0.577 & 0.614 & 0.850 \\ \(E_{applied}\) **(k)** & 1.14 & 5.68 & 10.32 & 15.96 & 21.88 & 27.82 & 28.94 \\ \(\gamma\) & 9.73\% & 5.22\% & 3.50\% & 2.67\% & 2.63\% & 3.44\% & 2.93\% \\ \hline \multicolumn{6}{c}{**Helium, Current 100 A, Arc Length 3 mm, Tip Angle: \(\alpha\)**} \\ \hline  & \multicolumn{3}{c}{**Case n\({}^{\circ}\):\(\alpha\) = 60\({}^{\circ}\)**} & \multicolumn{3}{c}{**Case n\({}^{\circ}\):\(\alpha\) = 30\({}^{\circ}\)**} \\ \hline  & **t = 1 s** & **t = 4 s** & **t = 8 s** & **t = 12 s** & **t = 16 s** & **t = 20 s** & **t = 20 s** \\ \hline \(E_{fusion}\) **(k)** & 0.187 & 0.478 & 0.652 & 1.029 & 0.972 & 1.230 & 1.145 \\ \(E_{applied}\) **(k)** & 1.43 & 5.87 & 13.65 & 19.57 & 27.44 & 35.15 & 37.42 \\ Y & 13.00\% & 8.14\% & 4.77\% & 5.26\% & 3.54\% & 3.50\% & 3.06\% \\ \hline \end{tabular}
\end{table} 
Table 3: _Cont._Values estimated by the three methods are consistent in both cases. Diameters evaluated in case n\({}^{\circ}\)2 are notably wider whatever the time of interaction. The expansion of the weld pool has a similar behaviour for the two current intensity values. A rapid increase of the weld pool dimensions during the two first seconds is observed followed by a slow expansion. This variation can be explained by two mechanisms: during the first instants, the weld pool width is a result of to the electrical flux components, then of the heat flux diffusion in the material. In case of a higher current intensity value, the current density distribution is enlarged and the welds pool width larger. This conclusion needs to be balanced depending on the distance between the cathode and the workpiece. The main difference obtained during the two first seconds is then conserved for up to 20 s. The comparison of the weld pool shapes for the two cases (n\({}^{\circ}\)1 and n\({}^{\circ}\)2) from 1 to 20 s is presented Figure 3b. The weld pool gets deeper with time for the higher welding current due to the higher flux transferred to the material. A stagnation of the weld pool depth is observed from time t = 12 s with a current of 100 A (case n\({}^{\circ}\)1), whereas the depth keeps increasing with an intensity of 150 A (case n\({}^{\circ}\)2). Maximal width reaches 10.5 \(\pm\) 0.02 mm (respectively 8.00 \(\pm\) 0.02 mm) and maximal depth reaches 5.92 \(\pm\) 0.02 mm (respectively 3.95 \(\pm\) 0.02 mm) in case n\({}^{\circ}\)2 (respectively case n\({}^{\circ}\)1) at time t = 20 s. We have performed the same experiments, changing the workpiece dimensions, in order to verify that the stagnation of the isotherms propagation was not due to natural anode cooling. If we observe the widths for the first measure (t = 1 s) we note 4 mm and 6 mm respectively for 100 A and 150 A. The stagnation is then observed at 8 mm and 10.4 mm for respectively 100 A and 150 A. In case n\({}^{\circ}\)2 from t = 1 s to 20 s the width is 2 mm greater than in case n\({}^{\circ}\)1. This behaviour must be due to the curve of diffusivity [1] which presents a minimum for temperatures higher than 1000 K. Figure 3c describes the evolution of depth-to-width ratio. A stabilization of this ratio is observed in case n\({}^{\circ}\)1 around 0.50, while it increases in case n\({}^{\circ}\)2.