Cold-rolled steel sheet for flux-cored wire and method for producing same

Patent metadata

Field	Value
Publication number	US-12590345-B2
Application number	US-202017783862-A
Country	US
Kind code	B2
Filing date	Dec 16, 2020
Priority date	Dec 20, 2019
Publication date	Mar 31, 2026
Grant date	Mar 31, 2026

Abstract

The present embodiments relate to a cold-rolled steel sheet for a flux-cored wire and a method for manufacturing the same. According to an exemplary embodiment, a cold-rolled steel sheet for a flux-cored wire, including: by wt %, 0.0005 to 0.01% of carbon (C), 0.05 to 0.25% of manganese (Mn), 0.03% or less (except for 0%) of silicon (Si), 0.0005 to 0.01% of phosphorus (P), 0.001 to 0.008% of sulfur (S), 0.0001 to 0.010% of aluminum (Al), 0.0005 to 0.003% of nitrogen (N), 0.5 to 1.7% of nickel (Ni), 0.0005 to 0.0030% of boron (B), and the balance Fe and inevitable impurities, can be provided.

First claim

The invention claimed is:

1 . A cold-rolled steel sheet for a flux-cored wire, comprising: by wt %, 0.0005 to 0.01% of carbon (C), 0.05 to 0.25% of manganese (Mn), 0.03% or less, except for 0%, of silicon (Si), 0.0005 to 0.01% of phosphorus (P), 0.001 to 0.008% of sulfur(S), 0.0001 to 0.010% of aluminum (Al), 0.0005 to 0.003% of nitrogen (N), 0.5 to 1.7% of nickel (Ni), 0.0005 to 0.0030% of boron (B), and the balance Fe and inevitable impurities.

2 . The cold-rolled steel sheet of claim 1 , wherein W, f defined by the following Equation 1 is 2.0 to 15.0;
W, f =(41×[C]+28×[Al]+3.4×[S])*(25×[Ni]×30×[B])/(25×[N])  [Equation 1]
in Equation 1, [C], [Al], [S], [Ni], [B] and [N] indicate the contents (wt %) of C, Al, S, Ni, B and N, respectively.

3 . The cold-rolled steel sheet of claim 1 , wherein
the cold-rolled steel sheet has an elongation of 40% or more.

4 . A method for manufacturing a cold-rolled steel sheet for a flux-cored wire of claim 1 , the method comprising: manufacturing a slab comprising: by wt %, 0.0005 to 0.01% of carbon (C), 0.05 to 0.25% of manganese (Mn), 0.03% or less except for 0% of silicon (Si), 0.0005 to 0.01% of phosphorus (P), 0.001 to 0.008% of sulfur(S), 0.0001 to 0.010% of aluminum (Al), 0.0005 to 0.003% of nitrogen (N), 0.5 to 1.7% of nickel (Ni), 0.0005 to 0.0030% of boron (B), and the balance Fe and inevitable impurities;
heating the slab;
obtaining a hot-rolled steel sheet by hot rolling the heated slab such that a finishing hot rolling temperature is 890 to 950° C.;
winding the hot-rolled steel sheet in a temperature range of 550 to 700° C.;
obtaining a cold-rolled steel plate by cold rolling the wound hot-rolled steel plate at a rolling reduction ratio of 50 to 85%; and
annealing the cold-rolled steel sheet in a temperature range of 700 to 850° C.

5 . The method of claim 4 , wherein
the slab has a W, f of 2.0 to 15.0, which is defined by the following Equation 1;
W, f =(41×[C]+28×[Al]+3.4×[S])*(25×[Ni]×30×[B])/(25×[N])  [Equation 1]

in Equation 1, [C], [Al], [S], [Ni], [B] and [N] indicate the contents (wt %) of C, Al, S, Ni, B and N, respectively.

6 . The method of claim 4 , wherein
in the obtaining of the cold-rolled steel sheet, the rolling reduction ratio is in a range of 65 to 80%.

7 . The method of claim 4 , wherein
the annealing of the cold-rolled steel sheet is performed in a range of 730 to 845° C.

8 . The method of claim 4 ,
further comprising, after the annealing of the cold-rolled steel sheet, temper-rolling the annealed cold-rolled steel sheet.

9 . A flux-cored wire comprising: an outer skin made of the cold-rolled steel sheet described in claim 1 ; and
a flux filled inside the outer skin.

10 . The flux-cored wire of claim 9 , wherein
the flux-cored wire has an impact energy of 50 J or more at −20° C.

11 . The flux-cored wire of claim 9 , wherein
the flux-cored wire has a welded portion segregation index of 0.15% or less.

12 . A welded member welded using the flux-cored wire of claim 9 and having a yield strength of 440 MPa or more.

13 . The cold-rolled steel sheet of claim 1 , comprising 1.03 to 1.7% of nickel (Ni).

14 . The cold-rolled steel sheet of claim 1 , comprising 1.37 to 1.7% of nickel (Ni).

Assignees

• Posco

Inventors

• Kim Jai-Ik
• Jeon Jea-Chun

Classifications

• C22C38/08

  containing nickel {(C22C38/105 takes precedence)} · CPC title

• C22C38/06

  containing aluminium · CPC title

• C22C38/04 Primary

  containing manganese · CPC title

• C22C38/02 Primary

  containing silicon · CPC title

• C22C38/004

  Very low carbon steels, i.e. having a carbon content of less than 0,01% · CPC title