Flux cored wire for duplex stainless steel and method of manufacturing the same

1. A flux cored wire for duplex stainless steel comprising a sheath and a flux filled into the sheath,

wherein the flux cored wire comprises about 24.0-30.0 wt % Cr, about 7.0-10.5 wt % Ni, about 2.0-4.0 wt %) molybdenum, about 0.10-2.50 wt % Cu, about 0.40-1.00 wt % Si, about 1.5-3.0 wt % Mn, about 0.10-0.30 wt % N compound (converted value of N), and the remainder including iron Fe and inevitable impurities on the basis of a total weight of the wire;

the flux comprises about 6.50-12.00 wt % of TiO 2 +SiO 2 +ZrO 2 +Al 2 O 3 , about 0.10-0.50 wt % of Li 2 O+K 2 O+Na 2 O, about 0.10-2.00 wt % of other oxides, and about 0.10-0.50 wt % of metal fluoride (converted value of F) on the basis of the total weight of the wire; and

the flux is filled into the sheath at a ratio of about 26-35%.

2. The flux cored wire according to claim 1 ,

wherein the sheath comprises about 0.015 wt % or less of C, about 0.10% or less of P+S+Co+B+Bi, and the remainder including Fe and inevitable impurities on the basis of the total weight of the sheath.

3. The flux cored wire according to claim 2 ,

wherein a total amount Po (wt %) of oxygen supplied by TiO 2 +SiO 2 +ZrO 2 +Al 2 O 3 , Li 2 O+K 2 O+Na 2 O, and the other oxides within the flux filled into the sheath, which is expressed by the following equation, satisfies a range of about 3.00-5.20 wt % on the basis of the total weight of the wire:

Po

=

∑

i

=

1

n

⁢

⁢

(

Xi

×

δ

⁢

⁢

i

)

,

where Po represents the total amount (wt %) of oxygen supplied by oxides within the flux filled into the sheath on the basis of the total weight of the wire, i represents an oxide within the flux filled into the sheath, n represents the number of oxides within the flux filled into the sheath, Xi represents the weight (%) of an oxide within the flux filled into the sheath on the basis of the total weight of the wire, and δi represents a percentage of oxygen atoms included in an oxide i within the flux.

4. The flux cored wire according to claim 1 ,

wherein a total amount Po (wt %) of oxygen supplied by TiO 2 +SiO 2 +ZrO 2 +Al 2 O 3 , Li 2 O+K 2 O+Na 2 O, and the other oxides within the flux filled into the sheath, which is expressed by the following equation, satisfies a range of about 3.00-5.20 wt % on the basis of the total weight of the wire:

Po

=

∑

i

=

1

n

⁢

⁢

(

Xi

×

δ

⁢

⁢

i

)

,

where Po represents the total amount (wt %) of oxygen supplied by oxides within the flux filled into the sheath on the basis of the total weight of the wire, i represents an oxide within the flux filled into the sheath, n represents the number of oxides within the flux filled into the sheath, Xi represents the weight (%) of an oxide within the flux filled into the sheath on the basis of the total weight of the wire, and δi represents a percentage of oxygen atoms included in an oxide i within the flux.

5. The flux cored wire according to claim 1 ,

wherein an apparent density of the flux is about 3.50 g/L to about 4.50 g/L.

6. The flux cored wire according to claim 1 ,

wherein particles of the mixed flux can all pass through a 60-mesh standard sieve, and wherein a ratio (P 1 ) of the particles of the mixed flux which cannot pass through a 230-mesh standard sieve to the particles of the mixed flux with can pass through a 230-mesh standard sieve is from about 65% to about 85%.

7. A method of manufacturing a flux cored wire for duplex stainless steel including a sheath and a flux filled into the sheath, the method comprising filling a mixed flux into the sheath;

wherein the flux cored wire comprises about 24.0-30.0 wt % Cr, about 7.0-10.5 wt % Ni, about 2.0-4.0 wt % Mo), about 0.10-2.50 wt % Cu, about 0.40-1.00 wt % Si, about 1.5-3.0 wt % Mn, about 0.10-0.30 wt % N compound (converted value of N), and the remainder including iron (Fe) and inevitable impurities on the basis of a total weight of the wire;

the flux comprises about 6.50-12.00 wt % of TiO 2 +SiO 2 +ZrO 2 +Al 2 O 3 , about 0.10-0.50 wt % of Li 2 O+K 2 O+Na 2 O, about 0.10-2.00 wt % of other oxides, and about 0.10-0.50 wt % of metal fluoride (converted value of F) on the basis of the total weight of the wire; and

the flux is filled into the sheath at a ratio of about 26-35%.

8. The method according to claim 7 ,

wherein the sheath comprises about 0.015 wt % or less of C, about 0.10% or less of P+S+Co+B+Bi, and the remainder including Fe and inevitable impurities on the basis of the total weight of the sheath.

9. The method according to claim 8 ,

wherein a total amount Po (wt %) of oxygen supplied by TiO 2 +SiO 2 +ZrO 2 +Al 2 O 3 , Li 2 O+K 2 O+Na 2 O, and the other oxides within the flux filled into the sheath, which is expressed by the following equation, satisfies a range of about 3.00-5.20 wt % on the basis of the total weight of the wire:

Po

=

∑

i

=

1

n

⁢

⁢

(

Xi

×

δ

⁢

⁢

i

)

,

where Po represents the total amount (wt %) of oxygen supplied by oxides within the flux filled into the sheath on the basis of the total weight of the wire, i represents an oxide within the flux filled into the sheath, n represents the number of oxides within the flux filled into the sheath, Xi represents the weight (%) of an oxide within the flux filled into the sheath on the basis of the total weight of the wire, and δi represents a percentage of oxygen atoms included in an oxide i within the flux.

10. The method according to claim 7 ,

wherein a total amount Po (wt %) of oxygen supplied by TiO 2 +SiO 2 +ZrO 2 +Al 2 O 3 , Li 2 O+K 2 O+Na 2 O, and the other oxides within the flux filled into the sheath, which is expressed by the following equation, satisfies a range of about 3.00-5.20 wt % on the basis of the total weight of the wire:

Po

=

∑

i

=

1

n

⁢

⁢

(

Xi

×

δ

⁢

⁢

i

)

,

where Po represents the total amount (wt %) of oxygen supplied by oxides within the flux filled into the sheath on the basis of the total weight of the wire, i represents an oxide within the flux filled into the sheath, n represents the number of oxides within the flux filled into the sheath, Xi represents the weight (%) of an oxide within the flux filled into the sheath on the basis of the total weight of the wire, and δi represents a percentage of oxygen atoms included in an oxide i within the flux.

11. The method according to claim 7 ,

wherein an apparent density of the flux is about 3.50 g/L to about 4.50 g/L.

12. The method according to claim 7 ,

wherein particles of the mixed flux can all pass through a 60-mesh standard sieve, and wherein a ratio (P 1 ) of the particles of the mixed flux which cannot pass through a 230-mesh standard sieve to the particles of the mixed flux with can pass through a 230-mesh standard sieve is from about 65% to about 85%.

13. A method of manufacturing a flux cored wire for duplex stainless steel including a sheath and a flux filled into the sheath, the method comprising filling a mixed flux into the sheath;

wherein an apparent density of the mixed flux is about 3.50 g/L to about 4.50 g/L; and wherein particles of the mixed flux can all pass through a 60-mesh standard sieve; and wherein a ratio of the particles of the mixed flux which cannot pass through a 230-mesh standard sieve to the particles of the mixed flux with can pass through a 230-mesh standard sieve is from about 65% to about 85%;

wherein the flux cored wire comprises about 24.0-30.0 wt % Cr, about 7.0-10.5 wt % Ni, about 2.0-4.0 wt % molybdenum), about 0.10-2.50 wt % Cu, about 0.40-1.00 wt % Si, about 1.5-3.0wt % Mn, about 0.10-0.30 wt % N compound (converted value of N), and the remainder including iron (Fe) and inevitable impurities on the basis of a total weight of the wire;

the mixed flux comprises about 6.50-12.00 wt % of TiO 2 +SiO 2 +ZrO 2 +Al 2 O 3 , about 0.10-0.50 wt % of Li 2 O+K 2 O+Na 2 O, about 0.10-2.00 wt % of other oxides, and about 0.10-0.50 wt % of metal fluoride (converted value of F) on the basis of the total weight of the wire; and

the mixed flux is filled into the sheath at a ratio of about 26-35%.

14. The method according to claim 13 ,

wherein the sheath comprises about 0.015 wt % or less of C, about 0.10% or less of P+S+Co+B+Bi, and the remainder including Fe and inevitable impurities on the basis of a total weight of the sheath.

15. The method according to claim 14 ,

wherein a total amount Po (wt %) of oxygen supplied by oxides within the mixed flux filled into the sheath, which is expressed by the following equation, satisfies a range of about 3.00-5.20 wt % on the basis of the total weight of the wire:

Po

=

∑

i

=

1

n

⁢

⁢

(

Xi

×

δ

⁢

⁢

i

)

,

where Po represents the total amount (wt %) of oxygen supplied by oxides within the flux filled into the sheath on the basis of the total weight of the wire, i represents an oxide within the flux filled into the sheath, n represents the number of oxides within the flux filled into the sheath, Xi represents the weight (%) of an oxide within the flux filled into the sheath on the basis of the total weight of the wire, and δi represents a percentage of oxygen atoms included in an oxide i within the flux.

16. The method according to claim 13 ,

wherein a total amount Po (wt %) of oxygen supplied by oxides within the flux filled into the sheath, which is expressed by the following equation, satisfies a range of about 3.00-5.20 wt % on the basis of a total weight of the wire:

Po

=

∑

i

=

1

n

⁢

⁢

(

Xi

×

δ

⁢

⁢

i

)

,

where Po represents the total amount (wt %) of oxygen supplied by oxides within the flux filled into the sheath on the basis of the total weight of the wire, i represents an oxide within the flux filled into the sheath, n represents the number of oxides within the flux filled into the sheath, Xi represents the weight (%) of an oxide within the flux filled into the sheath on the basis of the total weight of the wire, and δi represents a percentage of oxygen atoms included in an oxide i within the flux.