Granted Patent B2

US 12,571,068 · App. 18/005,186 · Granted Mar 10, 2026

Inventors: Hidekazu Minami (Tokyo, JP); Kazuki Endoh (Tokyo, JP); Yuki Toji (Tokyo, JP)

Assignee: JFE STEEL CORPORATION

C21D9/562C21D1/04C21D1/26C21D3/06C21D6/005C21D6/008C21D9/46C21D9/561C22C38/001C22C38/002C22C38/02C22C38/04C22C38/06C22C38/12C22C38/14C23C2/26C23C2/28C23C2/29C23C2/40C21D2241/00C22C2202/04

Abstract

Claims (38)

1 . A steel sheet production method comprising, in the following order:

a step (A) of uncoiling a cold-rolled coil to feed a cold-rolled steel sheet by a payoff reel;

a step (B) of passing the cold-rolled steel sheet through an annealing furnace in which a heating zone, a soaking zone, and a cooling zone are arranged in said order in a sheet passing direction, to continuously anneal the cold-rolled steel sheet by a step (B-1) of annealing the cold-rolled steel sheet in a reducing atmosphere containing hydrogen in the heating zone and the soaking zone and a step (B-2) of cooling the cold-rolled steel sheet in the cooling zone;

a step (C) of continuously passing the cold-rolled steel sheet discharged from the annealing furnace, the step (C) including a step (C-1) of immersing the cold-rolled steel sheet in a hot-dip galvanizing bath located downstream of the annealing furnace in the sheet passing direction to apply a hot-dip galvanized coating onto the cold-rolled steel sheet; and

a step (D) of coiling the cold-rolled steel sheet by a tension reel to obtain a product coil,

wherein the steel sheet production method comprises

a sound wave irradiation step of irradiating the cold-rolled steel sheet being passed downstream of the hot-dip galvanizing bath after the step (C-1) and before the step (D) with sound waves so that a sound pressure level at a surface of the cold-rolled steel sheet will be 30 dB or more.

2 . The steel sheet production method according to claim 1 , wherein the step (C) includes, following the step (C-1), a step (C-2) of passing the cold-rolled steel sheet through an alloying furnace located downstream of the hot-dip galvanizing bath in the sheet passing direction to heat and alloy the hot-dip galvanized coating.

3 . The steel sheet production method according to claim 1 , wherein the sound waves have a frequency from 10 Hz to 100000 Hz.

4 . The steel sheet production method according to claim 1 , wherein in the sound wave irradiation step, a sound wave irradiation time for the cold-rolled steel sheet is 1 second or more.

5 . The steel sheet production method according to claim 1 , wherein the cold-rolled steel sheet is a high strength steel sheet having a tensile strength of 590 MPa or more.

6 . The steel sheet production method according to claim 1 , wherein the cold-rolled steel sheet has a chemical composition containing, in mass %,

C: 0.030% to 0.800%,

Si: 0.01% to 3.00%,

Mn: 0.01% to 10.00%,

P: 0.001% to 0.100%,

S: 0.0001% to 0.0200%,

N: 0.0005% to 0.0100%, and

Al: 0.001% to 2.000%,

with the balance being Fe and inevitable impurities.

7 . The steel sheet production method according to claim 6 , wherein the chemical composition further contains, in mass %, at least one element selected from the group consisting of

Ti: 0.200% or less,

Nb: 0.200% or less,

V: 0.500% or less,

W: 0.500% or less,

B: 0.0050% or less,

Ni: 1.000% or less,

Cr: 1.000% or less,

Mo: 1.000% or less,

Cu: 1.000% or less,

Sn: 0.200% or less,

Sb: 0.200% or less,

Ta: 0.100% or less,

Ca: 0.0050% or less,

Mg: 0.0050% or less,

Zr: 0.1000% or less, and

REM: 0.0050% or less.

8 . The steel sheet production method according to claim 1 , wherein the product coil has a diffusible hydrogen content of 0.50 mass ppm or less.

Assignments (1)

Priority Claims (2)

Continuity (1)

References Cited (28)