Flux-cored wire, welding method using flux-cored wire, method for manufacturing weld joint using flux-cored wire, and weld joint

1. A flux-cored wire comprising:

an outer steel sheath; and

a flux with which the outer steel sheath is filled, wherein:

one or more of a fluoride of CaF 2 , BaF 2 , SrF 2 , MgF 2 , and LiF are included in the flux, wherein a total amount thereof is defined as α, and α is 3.3 to 6.0% in terms of mass % with respect to a total mass of the flux-cored wire, and a ratio of an amount of the CaF 2 with respect to the α is 0.89 or more,

one or more of a metal oxide of a Ti oxide, a Si oxide, a Zr oxide, a Mg oxide, and an Al oxide are included in the flux and, a total amount thereof is defined as β, wherein β is 0.4 to 1.2% in terms of mass % with respect to the total mass of the flux-cored wire,

one or more of a metal carbonate of CaCO 3 , BaCO 3 , SrCO 3 , MgCO 3 , and Li 2 CO 3 are included in the flux and a total amount thereof is 0.1 to 0.5% in terms of mass % with respect to the total mass of the flux-cored wire,

an amount of an iron powder in the flux is less than 10% in terms of mass % with respect to the total mass of the flux-cored wire,

a chemical composition excluding the fluoride, the metal oxide, and the metal carbonate includes, in terms of mass % with respect to the total mass of the flux-cored wire,

C: 0.04 to 0.09%;

Si: 0.3 to 1.0%;

Mn: 1.0 to 2.5%;

Al: 0.001 to 0.050%;

Ni: 1.5 to 3.5%;

V: 0 to 0.04%;

P: 0.02% or less;

S: 0.02% or less;

Cu: 0 to 0.5%;

Cr: 0 to 0.5%;

Mo: 0.3 to 1.0%;

Ti: 0 to 0.30%;

Nb: 0 to 0.10%;

B: 0 to 0.0100%;

Ca: 0 to 0.50%;

REM: 0 to 0.0100%; and

a remainder including Fe and an impurity,

a Ceq defined by Expression A is 0.60 to 0.75 mass %,

a TE defined by Expression B is 2.9 to 4.4 mass %,

Ceq=“C”+“Si”/24+“Mn”/6+“Ni”/40+“Cr”/5+“Mo”/4+“V”/14:  Expression A,

TE=“Mn”/2+“Ni”+3דCr”:  Expression B, and

elements to which double quote is attached express amounts of the elements in terms of mass %, respectively.

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

an amount of CaO in the flux-cored wire is 0.15% or less in terms of mass % with respect to the total mass of the flux-cored wire.

3. The flux-cored wire according to claim 1 or 2 , wherein the ratio of an amount of the CaF 2 with respect to the α is 0.90 or more.

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

a ratio of the α with respect to the β is 3.1 to 15.0.

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

a tensile strength of a deposited metal is 780 to 940 MPa in a tensile test to the deposited metal regulated in Japanese Industrial Standards JIS Z 3111-2005 with respect to a gas-shielded arc welding using the flux-cored wire.

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

the outer steel sheath has a seamless shape.

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

a perfluoropolyether oil is applied on a surface of the flux-cored wire.

8. A welding method, comprising:

welding a steel with a flux-cored wire, and with a pure Ar gas, a pure carbon dioxide, or a mixed gas of Ar and 3 to 30 volume % of CO 2 as a shielding gas,

wherein the flux-cored wire comprises an outer steel sheath and a flux with which the outer steel sheath is filled,

wherein:

one or more of a fluoride of CaF 2 , BaF 2 , SrF 2 , MgF 2 , and LiF are included in the flux, wherein a total amount thereof is defined as α, and α is 3.3 to 6.0% in terms of mass % with respect to a total mass of the flux-cored wire, and a ratio of an amount of the CaF 2 with respect to the α is 0.89 or more,

one or more of a metal oxide of a Ti oxide, a Si oxide, a Zr oxide, a Mg oxide, and an Al oxide are included in the flux and a total amount thereof is defined as β, wherein β is 0.4 to 1.2% in terms of mass % with respect to the total mass of the flux-cored wire,

one or more of a metal carbonate of CaCO 3 , BaCO 3 , SrCO 3 , MgCO 3 , and Li 2 CO 3 are included in the flux and a total amount thereof is 0.1 to 0.5% in terms of mass % with respect to the total mass of the flux-cored wire,

an amount of an iron powder in the flux is less than 10% in terms of mass % with respect to the total mass of the flux-cored wire,

a chemical composition, excluding the fluoride, the metal oxide, and the metal carbonate, includes, in terms of mass % with respect to the total mass of the flux-cored wire,

C: 0.04 to 0.09%;

Si: 0.3 to 1.0%;

Mn: 1.0 to 2.5%;

Al: 0.001 to 0.050%;

Ni: 1.5 to 3.5%;

V: 0 to 0.04%;

P: 0.02% or less;

S: 0.02% or less;

Cu: 0 to 0.5%;

Cr: 0 to 0.5%;

Mo: 0.3 to 1.0%;

Ti: 0 to 0.30%;

Nb: 0 to 0.10%;

B: 0 to 0.0100%;

Ca: 0 to 0.50%;

REM: 0 to 0.0100%; and

a remainder including Fe and an impurity,

a Ceq defined by Expression A is 0.60 to 0.75 mass %,

a TE defined by Expression B is 2.9 to 4.4 mass %,

Ceq=“C”+“Si”/24+“Mn”/6+“Ni”/40+“Cr”/5+“Mo”/4+“V”/14:  Expression A,

TE=“Mn”/2+“Ni”+3דCr”:  Expression B, and

elements to which double quote is attached express amounts of the elements in terms of mass %, respectively.

9. A method for manufacturing a weld joint, comprising welding a steel with a flux-cored wire, and with a pure Ar gas, a pure carbon dioxide, or a mixed gas of Ar and 3 to 30 volume % of CO 2 as a shielding gas,

wherein the flux-cored wire comprises an outer steel sheath and a flux with which the outer steel sheath is filled,

wherein:

one or more of a fluoride of CaF 2 , BaF 2 , SrF 2 , MgF 2 , and LiF are included in the flux, wherein a total amount thereof is defined as α, and α is 3.3 to 6.0% in terms of mass % with respect to a total mass of the flux-cored wire, and a ratio of an amount of the CaF 2 with respect to the α is 0.89 or more,

one or more of a metal oxide of a Ti oxide, a Si oxide, a Zr oxide, a Mg oxide, and an Al oxide are included in the flux and a total amount thereof is defined as β, wherein β is 0.4 to 1.2% in terms of mass % with respect to the total mass of the flux-cored wire,

one or more of a metal carbonate of CaCO 3 , BaCO 3 , SrCO 3 , MgCO 3 , and Li 2 CO 3 are included in the flux and a total amount thereof is 0.1 to 0.5% in terms of mass % with respect to the total mass of the flux-cored wire,

an amount of an iron powder in the flux is less than 10% in terms of mass % with respect to the total mass of the flux-cored wire,

a chemical composition excluding the fluoride, the metal oxide, and the metal carbonate includes, in terms of mass % with respect to the total mass of the flux-cored wire,

C: 0.04 to 0.09%;

Si: 0.3 to 1.0%;

Mn: 1.0 to 2.5%;

Al: 0.001 to 0.050%;

Ni: 1.5 to 3.5%:

V: 0 to 0.04%;

P: 0.02% or less;

S: 0.02% or less;

Cu: 0 to 0.5%;

Cr: 0 to 0.5%;

Mo: 0.3 to 1.0%;

Ti: 0 to 0.30%;

Nb: 0 to 0.10%;

B: 0 to 0.0100%;

Ca: 0 to 0.50%;

REM: 0 to 0.0100%; and

a remainder including Fe and an impurity,

a Ceq defined by Expression A is 0.60 to 0.75 mass %,

a TE defined by Expression B is 2.9 to 4.4 mass %,

Ceq=“C”+“Si”/24+“Mn”/6+“Ni”/40+“Cr”/5+“Mo”/4+“V”/14:  Expression A,

TE=“Mn”/2+“Ni”+3דCr”:  Expression B, and

elements to which double quote is attached express amounts of the elements in terms of mass %, respectively;

wherein a thickness of the steel is 3 to 100 mm, and a tensile strength of the steel is 780 MPa or more.

10. A weld joint, comprising a steel plate and a weld metal, manufactured by the method for manufacturing a weld joint according to claim 9 .

11. The weld joint according to claim 10 , wherein

an amount of a diffusible hydrogen in the weld metal is less than 1.0 ml/100 g,

an amount of an oxygen in the weld metal is 300 to 400 ppm,

tensile strength of the weld metal is 780 to 940 MPa, and

a charpy absorbed energy at −40° C. of the weld metal is 86 J/cm 2 or more.

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

the chemical composition, excluding the fluoride, the metal oxide, and the metal carbonate, includes, in terms of mass % with respect to the total mass of the flux-cored wire,

V: 0 to 0.03%.

13. The welding method according to claim 8 , wherein

the chemical composition, excluding the fluoride, the metal oxide, and the metal carbonate, includes, in terms of mass % with respect to the total mass of the flux-cored wire,

V: 0 to 0.03%.

14. The method for manufacturing a weld joint according to claim 9 , wherein

the chemical composition, excluding the fluoride, the metal oxide, and the metal carbonate, includes, in terms of mass % with respect to the total mass of the flux-cored wire,

V: 0 to 0.03%.

15. The welding method according to claim 8 , wherein

an amount of CaO in the flux-cored wire is 0.15% or less in terms of mass % with respect to the total mass of the flux-cored wire.

16. The welding method according to claim 8 or 15 , wherein

the ratio of an amount of the CaF 2 with respect to the α is 0.90 or more.

17. The welding method according to claim 8 or 15 , wherein

a ratio of the α with respect to the β is 3.1 to 15.0.

18. The method for manufacturing a weld joint according to claim 9 , wherein

an amount of CaO in the flux-cored wire is 0.15% or less in terms of mass % with respect to the total mass of the flux-cored wire.

19. The method for manufacturing a weld joint according to claim 9 or 18 , wherein

the ratio of an amount of the CaF 2 with respect to the α is 0.90 or more.

20. The method for manufacturing a weld joint according to claim 9 or 18 , wherein

a ratio of the α with respect to the β is 3.1 to 15.0.