Provided is a wire containing flux for gas-sealed welding. Said wire can reduce the oxygen content of the welded metal, resulting in a high-toughness welded joint, and also allows DC reverse-polarity all-position welding. The wire contains, by mass: between 0.2% and 7.0% CaO; a total of at least 1.0% of at least one fluoride selected from among MgF2, CaF2, SrF2, and BaF2 (the sum of the amount of said fluoride(s) and the amount of CaO being between 3.0% and 12.0%); a total of between 0.2% and 2.0% of at least one element selected from among silicon, aluminum (less than 0.3%), titanium, magnesium, zirconium, calcium, cerium, and lanthanum; and a total of between 0.2% and 3.0% of at least one oxide selected from among oxides of silicon, manganese, aluminum, titanium, boron, and zirconium. Also, alpha = C + Si / 30 + Mn / 20 + Cu / 20 + Ni / 60 + Cr / 20 + Mo / 15 + V / 10 + Nb / 10 + 5B is between 0.15% and 0.40%, the sum of the phosphorus content and the sulfur content is at most 0.040%, and the remainder comprises iron, an arc stabilizer, and unavoidable impurities. The iron powder content of the flux is at most 5.0%.