Another necessary condition to obtain a stable electroslag process is that the flux must have good conductivity. The electrical conductivity of the common ESR surfacing flux should reach 2 ~ 3 Ω - 1cm-1, which is 4 ~ 5 times of that of ordinary submerged arc welding flux. Most of the electroslag fluxes used at home and abroad are sintered. The electric conductivity of flux depends on the amount of fluoride (NaF, CaF2, na3aif6, etc.) in flux components. When the fluoride content is less than 40%, the surfacing process is an arc process, and in the range of 40% - 50%, it is roughly the combined process of arc and electroslag; when the fluoride is greater than 50%, the whole electroslag process can be formed. CaF2 is not only a good conductive material, but also a main slag forming agent, so CaF2 is usually the main component of electroslag surfacing flux. In addition to electrical conductivity, the flux also needs to have good surfacing processability (slag removal, forming, wettability), good metallurgical properties (small alloy element burning loss, less unfavorable element increment), and appropriate particle size (generally finer than submerged arc welding flux). To meet the above requirements, there are many kinds of flux used in production, such as FJ-1 (Japan), est122 (Germany), Sandvik 37s (USA), sj15, shd202, etc.