# High-Speed Welding of Stainless Steel with Additional Compensatory Gas Jet Blow Molten Pool
## 4 Results and Discussion  
### Butt Welding Using Compensatory Gas Jet Impinging on Molten Pool  
The voltage and current are shown in Figure 4. As shown in Figures 5 and 6, the welding uses a segmental compensatory gas jet and the welding direction proceeds from right to left. In Figure 4, there is no significant difference in current waveform between sample 1# and sample 2#. However, both sample 1# and sample 2# demonstrate that the average voltage without compensation is obviously higher than with compensation. The results show that the compensation gas jet has a slight disturbance effect on the arc work of the front welding gun when impacting the molten pool, appearing as a slight drop in welding voltage. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Component** & C & Mn & Si & Cr & Ni & Mo & P & S & Cu & Ti & Nb \\ \hline
**Test Value** & 0.027 & 1.81 & 0.55 & 19.71 & 9.84 & 0.02 & 0.014 & 0.006 & 0.03 & – & – \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Chemical composition of ER-308 stainless steel solid welding wire (%). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Number** & **Welding Speed \(\upsilon\) (cm/min)** & **Compensatory Status** & **Average Current \(I\) (A)** \\ \hline
1\#S & 154 & without compensation & 268 \\
1\#B & 154 & with compensation & 268 \\
2\#S & 167 & without compensation & 268 \\
2\#B & 167 & with compensation & 268 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Main welding parameters of high-speed welding of stainless steel. Figure 5 shows the front and back of the butt weld. The welding method used is single-sided welding. The back is oxidized since no protective measures are provided, and such oxidation is  
Figure 4: Current and voltage waveforms during the butt welding of 304 stainless steel: (**a**) Sample 1#; (**b**) sample 2#. Figure 5: Weld bead shape of sample 1#: (**a**) Front view; (**b**) back view. conducive to judging the difference caused by the two welding methods. The purpose of this experiment is mainly to verify the effect of the compensation gas jet and the conventional welding method on the weld under the same welding parameters, especially the same heat input. As can be seen from Figure 5a, there is a difference in the width of the weld, and the uncompensated weld section is flat, but it is not fully penetrated due to the high excess weld metal. The weld of the compensation gas jet section is better formed than the uncompensated weld section and has been penetrated. The tensile test also shows that the mechanical properties of the compensating gas jet segment are significantly better compared with the uncompensated gas jet segment, showing the prominent role of the method proposed herein. Figure 6 shows the butt weld formed at a welding speed of 167 cm/min. The uniformity and straightness of the weld in the non-gas jet compensated segment are poor. As metal accumulates locally, humping bead formation is initially high. The humping bead is formed due to the high speed of welding and it is unrelated to the compensating gas jet. The method of impacting the molten pool by a compensating gas jet proposed in the thesis is to exert influence on the molten pool before solidification, so as to ensure the stacking hump of liquid metal flows to a lower position with insufficient liquid metal and to ensure the weld joint is flat, uniform and has a good appearance. However, the shape of the weld with the additional and compensatory gas jet segment is high quality and the molten width is increased. The back view of the weld shows further differences between the two segments. The molten droplet of the compensatory gas jet segment fully penetrates the workpiece, effectively connecting the two parts of the parent material. However, obvious gaps remain in the segment with no compensatory gas jet, and full penetration is not observed. The above four groups of tests can be divided into two categories, depending on the presence or absence of gas jet compensation.