Flux-cored wire, manufacturing method of welded joint, and welded joint

A flux-cored wire comprising:

• a steel sheath;
• and
• a flux that fills the steel sheath,
• wherein the flux contains:
• fluorides which include one or at least two selected from the group consisting of CaF2, MgF2, Na3AlF6, LiF, NaF, K2ZrF6, BaF2, and K2SiF6, wherein a value α, which is defined as a total value of F-equivalent values, is 0.21% or more with respect to a total mass of the flux-cored wire;
• oxides which include one or at least two selected from the group consisting of Fe oxides, Ba oxides, Na oxides, Ti oxides, Si oxides, Zr oxides, Mg oxides, Al oxides, Mn oxides, and K oxides, while excluding CaO, wherein a value β, which is defined as a total value of amounts of oxides, ranges from 0.30% to 3.50% by mass % with respect to the total mass of the flux-cored wire;
• and
• carbonates which include one or at least two selected from the group consisting of MgCO3, Na2CO3, LiCO3, CaCO3, K2CO3, BaCO3, FeCO3 and MnCO3, wherein a total value of amounts of carbonates ranges from 0% to 3.50% by mass % with respect to the total mass of the flux-cored wire,
• wherein an amount of CaO in the flux ranges from 0% to 0.20% by mass % with respect to the total mass of the flux-cored wire,
• wherein an amount of iron powder in the flux ranges from 0% to less than 10.0% by mass % with respect to the total mass of the flux-cored wire,
• wherein an amount of CaF2 is less than 0.50% by mass % with respect to the total mass of the flux-cored wire,
• wherein an amount of Ti oxides ranges from 0.10% to 2.50% by mass % with respect to the total mass of the flux-cored wire,
• wherein a ratio of the α to the β ranges from 0,10 to 4.00,
• wherein a total value of amounts of the MgCO3, the Na2CO3, and the LiCO3 ranges from 0% to 3.00% by mass % with respect to the total mass of the flux-cored wire,
• wherein a chemical composition excluding the fluorides, the oxides, the CaO, the carbonates, and the iron powder includes, by mass % with respect to the total mass of the flux-cored wire:
• C:
• 0.003% to 0.030%,
• Si:
• 0.10% to 1.50%,
• Mn:
• 0.50% to 3.50%,
• Mg:
• 0.10% or less,
• P:
• 0.020% or less,
• S:
• 0.020% or less,
• Al:
• 0.001% to 0.100%,
• Cu:
• 0% to 0.50%,
• Ni:
• 0% to 0.50%,
• Cr:
• 0% to 1.00%,
• Mo:
• 0% to 1.00%,
• Nb:
• 0% to 0,100%,
• V:
• 0% to 0.40%,
• Ti:
• 0% to 0.300%,
• B:
• 0% to 0,0100%,
• Bi:
• 0% to 0.0100%,
• Ca:
• 0% to 0.50%, and
• REM:
• 0% to 0.0100%,
• while having a remainder comprising iron and impurities,
• wherein a value of Y is 5.0% or less, and wherein Y is defined as:
• Y═[NaF]+[MgF2]+[Na3AlF6]+1.50×([K2SiF6]±[K2ZrF6]+[LiF]+[BaF2])+3.50×([CaF2]),
• wherein chemical formulas with square brackets each indicate, by unit mass % with respect to the total mass of the flux-cored wire, an amount of fluoride corresponding to each of the chemical formulas;
• and
• wherein a value of Ceq is from 0.10% to 0.44%, wherein said Ceq is defined as:
• Ceq=[C]+[Si]/24+[Mn]/6+[Ni]/40+[Cr]/5+[Mo]/4+[V]/14,
• wherein element symbols with square brackets each express, by unit mass % with respect to the total mass of the flux-cored wire, an amount of each element corresponding to each of the element symbols included in the chemical composition excluding the fluorides, the oxides, and the carbonates.