## 2 Materials and Methods
### Welding Procedure  
In accordance with EN-ISO 17642-2 [46] the Tekken weldability test was chosen for the experiment. This test enables assessment of susceptibility to cold cracking in all joint areas. The Tekken test is one of the weldability tests, which is characterized by high thermal severity. This test was chosen because it allows us to study even a small impact of factors on weldability. For the experiment, six Tekken test were prepared. The upper surfaces of all specimens were placed 0.5 m below the water surface. The schematic view of the Tekken specimens is presented in Figure 1.  
In the first step of investigations, the Tekken butt welded joints were performed. The welding was carried out in the flat position in accordance to EN ISO 17642-2 standard [46]. In the next step five of the Tekken specimens were modified. On the surface of the prepared butt welded joints, the additional stitches were laid immediately after preparation of Tekken joints, to check the influence of the proposed technique on the HSLA steel weldability in wet-welding conditions. The in situ heat treatment was an effect of the heat impact generated by the process of welding of additional stitches. They were laid in the same direction as the Tekken test weld, within the maximum time of two minutes after completion of the previous welding process. The scientific hypothesis stated that this modification causes changes in microstructure in heat affected zone (HAZ), which decreases the hardness. The specimens were modified by applying one, two or three additional stitches to the face of the Tekken weld. The stitches were welded with different distance between axes of the stitches calculated as percentage overlapping. During the process, the welding arc was unstable, which produces difficulties in keeping the constant welding speed and planned overlapping of the stitches. One of the reasons was limited visibility of the welding area, which disturbed the process of welding. These factors are typical for underwater  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Material** & **C** & **Si** & **Mn** & **P** & **Cr** & **Mo** & **Ni** & **Cu** & **V** & **Ce\({}_{\text{HIV}}\)**1** \\ \hline S3552C+N in accordance to control analysis & 0.20 & 0.50 & 1.10 & 0.02 & 0.02 & 0.001 & 0.001 & 0.02 & 0.005 & 0.386 \\ E 38 0 R 11 electrodes & & & & & & & & & & \\ deposit in accordance to manufacturer data & 0.07 & 0.44 & 0.55 & 0.01 & 0.04 & - & - & 0.05 & - & - \\ \hline \hline \end{tabular}  
* \({}^{1}\) Ce\({}_{\text{HIV}}\)—carbon equivalent by International Institute of Welding.  
\end{table}
Table 1: Chemical composition of used materials wt. %.  
Figure 1: Schematic illustration of the Tekken test specimen.  
wet-welding processes [25; 27; 36]. The welding parameters are presented in Table 3. The additional stitches were welded with higher heat input values in accordance with the literature proceedings [25]. The schematic view of cross-sections of the tested area of each specimen is shown in Figure 2.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Specimen No.** & **Stitch No.** & **Overlapping (\%)** & **I (A)** & **U (V)** & **ql (k)/mm)** \\ \hline
1 & 1 & - & 180 & 26.3 & 0.60 \\ \hline
2 & 1 & - & 184 & 26.0 & 0.92 \\  & 2 & 100 & 200 & 28.0 & 0.91 \\ \hline
3 & 1 & - & 184 & 27.3 & 0.76 \\  & 2 & 90 & 200 & 27.0 & 0.86 \\ \hline
4 & 1 & - & 188 & 25.0 & 0.80 \\  & 2 & 80 & 196 & 30.0 & 0.95 \\ \hline  & 1 & - & 180 & 25.0 & 0.68 \\
5 & 2 & 100 & 200 & 29.0 & 0.65 \\  & 3 & 100 & 200 & 28.8 & 0.64 \\ \hline  & 1 & - & 180 & 27.3 & 0.59 \\  & 2 & 100 & 200 & 27.5 & 0.81 \\
6 & 3 & 100 & 200 & 27.8 & 0.97 \\  & 4 & 10 & 204 & 28.0 & 0.90 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Welding conditions for tested specimens.  
Figure 2: \(Cont\).