PURPOSE: To obtain flux which improves welding efficiency and saves a welding material, by specifying the relation between Al2O3 and TiO2, increasing softening temperature and improving slag peeling properties, and reducing SiO2 and MnO while adding CaO and CaF2 and thus securing the toughness of welding metal.

CONSTITUTION: This flux contains 10.0W20.0wt% SiO2, 15.0W30.0wt%, 20.0W 40.0wt% Al2O3, 11.0W18.0wt% CaF2, 9.5W18.0wt% CaO, 4.0W10.0wt% MnO, 3.0W10.0wt% MgO, and 2.0W7.0wt% ZrO2 and also satisfies formulasIand II. In this case, TiO2 improves peeling properties, but when its amount exceeds an upper limit, a bead swells. Then, Al2O3 increases softening temperature and improves peeling properties, but when its amount exceeds an upper limit, an excellent bead is not obtained. Every component in the formulaIincreases the softening temperature and the formulaIshould be satisfied to secure the softening temperature. When the formula II is not satisfied, peeling properties deteriorate extremely.