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

1. 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 CaF 2 , MgF 2 , Na 3 AlF 6 , LiF, NaF, K 2 ZrF 6 , BaF 2 , and K 2 SiF 6 , 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 MgCO 3 , Na 2 CO 3 , LiCO 3 , CaCO 3 , K 2 CO 3 , BaCO 3 , FeCO 3 and MnCO 3 , 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 CaF 2 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 MgCO 3 , the Na 2 CO 3 , and the LiCO 3 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]+[MgF 2 ]+[Na 3 AlF 6 ]+1.50×([K 2 SiF 6 ]±[K 2 ZrF 6 ]+[LiF]+[BaF 2 ])+3.50×([CaF 2 ]),

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.

2. The flux-cored wire according to claim 1 ,

wherein the 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,

Mg: 0.07% or less.

3. The flux-cored wire according to claim 1 ,

wherein the chemical composition excluding the fluorides, the oxides, the CaO, the carbonates, and the iron powder satisfies:

([Mg]+10×[Al])≤0.45

wherein element symbols with square brackets each indicate, 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.

4. The flux-cored wire according to claim 1 ,

wherein the total amount of the carbonates ranges from more than 0.30% to 3.50%, and

wherein the total amount of one or at least two of the MgCO 3 , the Na 2 CO 3 , and the LiCO 3 ranges from more than 0.30% to 3.00%.

5. The flux-cored wire according to claim 1 ,

wherein the total amount of the fluorides is 0.50% or more in terms of the F-equivalent value.

6. The flux-cored wire according to claim 1 ,

wherein the value of Y is 4.0% or less.

7. The flux-cored wire according to claim 1 ,

wherein the amount of the Ti oxides ranges from 0.10% to 1.80% by mass % with respect to the total mass of the flux-cored wire.

8. The flux-cored wire according to claim 1 ,

wherein the amount of the CaF 2 is 0.20% or less by mass % with respect to the total mass of the flux-cored wire.

9. The flux-cored wire according to claim 1 ,

wherein the ratio of the α to the β ranges from 0.50 to 2.50.

10. The flux-cored wire according to claim 1 ,

wherein the total amount of Na 3 AlF 6 and NaF by unit mass % with respect to the total mass of the flux-cored wire is 50% or more of the total amount of the fluorides by unit mass % with respect to the total mass of the flux-cored wire.

11. The flux-cored wire according to claim 1 ,

wherein the steel sheath has a seamless shape.

12. The flux-cored wire according to claim 1 ,

wherein the steel sheath has a slit-shaped gap.

13. The flux-cored wire according to claim 1 , further comprising:

perfluoropolyether oil that coats a surface of the flux-cored wire.

14. A manufacturing method of a welded joint, comprising:

performing gas shield arc welding of a steel material by using the flux-cored wire according to claim 1 .

15. The manufacturing method of a welded joint according to claim 14 ,

wherein the steel material is a steel sheet of which a sheet thickness ranges from 12 to 100 mm, of which a C content ranges from 0,20% to 0.55% by unit mass %, and of which a value of CEN ranges from 020% to 0.70%; or a steel sheet of which the sheet thickness ranges from 12 to 20 mm, of which the C content ranges from 0.20% to 0.55% by unit mass %, and of which the CEN ranges from more than 0.70% to 0.85%, wherein the CEN is defined as:

CEN=[C]+(0.75+0.25×TAN H(20×([C]-0.12)))×([Si]/24+[Mn]/6+[Cu]/15+[Ni]/20+([Cr]+[Mo]+[Nb]+[V])/5+5×[B]),

wherein element symbols with square brackets each express, by unit mass %, an amount of each element corresponding to each of the element symbols included in the steel material, and

wherein in a case where a temperature of the steel material is lower than 10° C. when the steel material is subjected to the gas shield arc welding, the gas shield arc welding is performed after the steel material is preheated such that the temperature thereof becomes 10° C. or higher; or in a case where the temperature of the steel material is 10° C. or higher when the steel material is subjected to the gas shield arc welding, the gas shield arc welding is performed without preheating the steel material.

16. The manufacturing method of a welded joint according to claim 14 ,

wherein the steel material is a steel sheet of which a sheet thickness ranges from more than 20 mm to 50 mm, of which a C content ranges from 0.20% to 0.55% by unit mass %, and of which a value CEN ranges from more than 0.70% to 0.8%, wherein CEN is defined as:

CEN=[C]+(0.75+0.25×TAN H(20×([C]-0.12)))×([Si]/24+[Mn]/6+[Cu]/15+[Ni]/20+([Cr]+[Mo]+[Nb]+[V])/5+5×[B]),

wherein element symbols with square brackets each express, by unit mass %, an amount of each element corresponding to each of the element symbols included in the steel material, and

wherein the method further comprises preheating the steel material before the gas shield arc welding such that a temperature of the steel material becomes 100° C. or higher.

17. A welded joint which is obtained by the manufacturing method of a welded joint according to claim 14 .

18. A flux-cored wire comprising:

a steel sheath; and

a flux that fills an inside of the steel sheath,

wherein an amount of diffusion hydrogen of a weld metal, which is obtained by performing direct current gas shield arc welding using the flux-cored wire under a condition regulated by JIS Z 3118, is 1.0 ml/100 g or smaller, and

wherein a weight per welding time of a spatter, which has a diameter of 1.0 mm or greater and is generated when direct current gas shield arc welding is performed by using the flux-cored wire under conditions that wire polarity is positive, a current value is 270 A, a voltage value ranges from 29 to 32 V, a welding rate is 30 cm/min; a type of a shielding gas is 100% CO 2 gas, and a flow rate of the shielding gas is 25 L/min, is 5.0 g/min or smaller.

19. A flux-cored wire comprising:

a steel sheath; and

a flux that fills an inside of the steel sheath,

wherein the flux-cored wire has an amount of Ti oxides ranging from 0.10% to 2,50% by mass % with respect to a total mass of the flux-cored wire and includes Ni: 0% to 0.5%,

wherein an amount of diffusion hydrogen of a weld metal, which is obtained by performing direct current gas shield arc welding using the flux-cored wire under a condition regulated by JIS Z 3118, is 1.0 ml/100 g or smaller, and

wherein a weight per welding time of a spatter, which has a diameter of 1.0 mm or greater and is generated when direct current gas shield arc welding is performed by using the flux-cored wire under conditions that wire polarity is positive, a current value is 270 A, a voltage value ranges from 29 to 32 V, a welding rate is 30 cm/min, a type of a shielding gas is 100% CO 2 gas, and a flow rate of the shielding gas is 2.5 L/min, is 5.0 g/min or smaller.

20. The flux-cored wire according to claim 2 ,

wherein the chemical composition excluding the fluorides, the oxides, the CaO, the carbonates, and the iron powder satisfies:

([Mg]+10×[Al])≤0.45

wherein element symbols with square brackets each indicate, 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.