... used for welding steel structures,such as boilers,pressure vessels,bridges,oilcans,ships and so on.· ATTENTION : a.Before welding,the welding flux ... should be baked at the temperature from 300 to 350°C for 1-2 hours .b ... .Before welding,the weld metal must be cleared away impurities,such as rust,oil,moisture etc. SUBMERGED-ARC WELDING FLUX ...