## 1 Introduction  
Submerged Arc Welding (SAW) is applied in heavy engineering industries to join thick steel plates at high productivity rates, for example in the building of large seafaring ships, the construction of large offshore structures, and the construction of pressure vessels [1]. The SAW process is an electrical arc-based process in which chemical and electrical parameters are combined in the arc cavity to form an arc between the weld wire tip and the steel base plate. The arc cavity is formed by a layer of raw unmelted flux covering a layer of molten flux (slag), which in turn covers the arc to form the arc cavity. The arc cavity encapsulates the arc plasma, weld wire tip, and gasses emanating from the arc. Weld wire and flux are continuously fed through the welding head arrangement as it moves along the weld. As the weld wire is melted, the molten weld wire metal droplets are transferred from the weld wire into the weld pool. In addition to melting of the weld wire and arc formation, complex physical and chemical interactions of heat and mass transfer occur in the arc cavity [1]. Chemical reactions proceed in the trailing molten weld pool of molten steel and its covering slag, until the steel is solidified as weld metal [2, 3]. Flux applied in the SAW process is made from a combination of oxides and fluorides, with the fluoride usually added as CaF\({}_{2}\). It is generally accepted from empirically determined measurements that the flux composition basicity index, the BI as expressed in Equation (1), should be larger than 1.5 in value to limit the weld metal hydrogen and weld metal total oxygen content (ppm O) to acceptable levels [4, 5]. \[\text{BI}\ =\ \frac{\%\text{CaF}_{2}+\%\text{CaO}+\%\text{MgO}+\%\text{BaO}+\% \text{SrO}+\%\text{Na}_{2}\text{O}+\%\text{K}_{2}\text{O}+\%\text{Li}_{2} \text{O}+0.5(\%\text{MnO}+\%\text{FeO})}{\%\text{SiO}_{2}+0.5(\%\text{Al}_{2} \text{O}_{3}+\%\text{TiO}_{2}+\%\text{ZrO}_{2})} \tag{1}\]  
It has been confirmed experimentally that the stability of oxides in the arc plasma is not exactly the same as the expected thermodynamic stability of oxides. Welding tests were made under an argon gas atmosphere for different binary oxide-CaF\({}_{2}\) flux mixtures to show that the arc plasma stability sequence of oxides ranges from most stable to least stable as follows: CaO, K\({}_{2}\)O, Na\({}_{2}\)O and TiO\({}_{2}\), Al\({}_{2}\)O\({}_{3}\), MgO, SiO\({}_{2}\), and MnO [6]. Thus, by increasing the flux CaF\({}_{2}\) content, the proportion of low stability oxides in the flux, and thus also in the molten flux (slag), is effectively diluted to ensure lower ppm O in the weld metal. The importance of total weld metal oxygen content in setting the carbon steel weld metal materials properties was illustrated from weld metal impact toughness test weld metal samples of different ppm O. It was shown that high weld metal impact toughness is maintained if the total oxygen content is maintained within the band of 200 ppm O to 500 ppm [7]. Therefore, it is important to control the carbon steel weld metal total oxygen content within this ppm O range. In addition to the formulation of fluxes for oxygen and hydrogen control, the flux chemistry is formulated to achieve targeted element transfer levels from the slag to the weld metal [3; 8; 9; 10; 11]. Because nickel has a low affinity for oxygen, it is typically added to the weld pool from the alloyed weld wire. Nickel is often alloyed in the weld wire with chromium as stainless steel weld wires, and the weld wire chemistry is usually over matched to the base plate composition. Therefore, the fluxes used in SAW of chromium and/or nickel containing steel are neutral or non-alloyed [12]. If any metallic powders of chromium, nickel, molybdenum, or niobium are added into the flux formulation, this is only done to compensate for element loss across the arc [13]. Manufacturing of weld wires of specific compositions is expensive and time consuming and cannot closely match all desired alloy compositions.