## 2 Experimental Procedure
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Parameter** & **MMA** & **MIG** & **MAG** \\ \hline \multirow{4}{*}{Consumables} & INOX B 18/8/6; & MIG 18/8/6 Si; & MIG 75; \\  & Shielded Electrode & Electrode Wire & Electrode Wire \\  & Diameter (\(\omega\)) 3.25 mm & Diameter (\(\omega\)) 1.2 mm & Diameter (\(\omega\)) 1.2 mm \\ \hline Welding current (I\({}_{\text{z}}\)) & I\({}_{\text{z1}}\approx\) 120 A & I\({}_{\text{z1}}\approx\) 110 A & I\({}_{\text{z1}}\), I\({}_{\text{z2}}\), I\({}_{\text{z3}}\approx\) 250 A \\  & U\({}_{\text{z1}}\approx\) 24 V & U\({}_{\text{z1}}\approx\) 24 V & U\({}_{\text{z1}}\), U\({}_{\text{z2}}\), U\({}_{\text{z3}}\approx\) 25V \\ Welding speed (v\({}_{\text{z2}}\)) & v\({}_{\text{z1}}\approx\) 0.2 cm/s & v\({}_{\text{z1}}\approx\) 0.35 cm/s & v\({}_{\text{z1}}\), V\({}_{\text{z2}}\), V\({}_{\text{z3}}\approx\) 0.35 cm/s \\  & Fatigue energy (q\({}_{\text{l}}\)) & q\({}_{\text{l1}}\approx\) 12 kJ/cm & q\({}_{\text{l1}}\approx\) 13 kJ/cm & q\({}_{\text{l1}}\), q\({}_{\text{l2}}\), q\({}_{\text{l3}}\approx\) 15 kJ/cm \\  & Welding depth (\(\delta\)) & \(\delta_{1}\approx\) 1.8 mm & \(\delta_{1}\approx\) 1.8 mm & \(\delta_{1}\), \(\delta_{2}\), \(\delta_{3}\approx\) 1.9 mm \\ Wire handling speed & - & - & - & 8 m/min \\  & Protective gas & - & 100\% Ar (M11) & Gas compound M21, \\  & Protective gas flow & - & 14 L/min & 14 L/min \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Welding parameters and related consumables. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Type** & \multicolumn{4}{c}{**Chemical Composition (\%)**} & \multicolumn{4}{c}{**Mechanical Characteristics**} \\ \hline  & **C** & **Si** & **Mn** & **Cr** & **Ni** & **Mo** & **R\({}_{\text{m}}\) (MPa)** & **R\({}_{\text{p0,2}}\)** & **Ag (\%)** & **KV (J)** \\ \hline INOX B18/8/6 & 0.12 & 0.8 & 7 & 19 & 9 & - & 590 to 690 & \(>\)350 & \(>\)40 & 60–100 (+20 \({}^{\circ}\)C) \\ MIG 75 & 0.08 & 0.6 & 1.7 & 0.25 & 1.5 & 0.5 & 770 to 940 & \(>\)690 & \(>\)17 & \(>\) 47 (-40 \({}^{\circ}\)C) \\ MIG 18/8/6 Si & 0.08 & 0.80 & 7 & 18.5 & 9 & - & 560 to 660 & \(>\)380 & \(>\)35 & \(>\) 40 (+20 \({}^{\circ}\)C) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Chemical composition and mechanical characteristics of thefiller materials used. Figure 2: Cross-sections of metallographic samples with directions and microhardness measuring spots: (**a**) the MMA/MAG weld; (**b**) the MIG/MAG weld. Directions of analysis and microhardness measuring spots were set in characteristic zones in metallographic sample cross-sections so that they ran through the parent metal, heat-affected zone and the weld metal: _I-I_ was on the face of the weld; _II-II_ was in the central zone with interfered impacts of the root and other passes and _III-III_ was on the side of the root pass. Microhardness testing was performed according to the standard SRPS EN ISO 9015-1: 2013, [26]. Microhardness was measured on a Vickers HPO 250 (Aquastyl, Povazska Bystrica, Slovakia) with diamond pyramid load F = 98.1 \(N\) (HV 10). The hardness of the standard (etalon) was 473 \(HV\), and it was used to calibrate the device. A microhardness tester type HPO-250 KR/AQ (Aquastyl, Povazska Bystrica, Slovakia) was used. The microstructure state was evaluated by the reflex optic micrograph method at magnifications of 200 and 500\(\times\). The next phase of experimental tests, which was conducted to evaluate the impact toughness of the executed welded joints and to analyze the mechanical behavior during the fracture, was done on aseries of three test samples, each with welded joints obtained by the MMA/MAG and MIG/MAG procedures. Specimens were notched at the characteristic zones from the face side and then on the root side of the welded joint. Shapes and dimensions of the test samples for the impact toughness testing of type ISO-\(V\) (\(55\times 10\times 10\)) are presented in Figure 3. The testing procedure, shape and dimensions of the test samples were in compliance with adequate standards [27].