Hot-rolled steel sheet for electrical steel sheet production and method of producing same

Patent metadata

Field	Value
Publication number	US-11577291-B2
Application number	US-201716342015-A
Country	US
Kind code	B2
Filing date	Oct 18, 2017
Priority date	Oct 18, 2016
Publication date	Feb 14, 2023
Grant date	Feb 14, 2023

Abstract

With a hot-rolled steel sheet for electrical steel sheet production having a scale layer on the surface, where the surface of the steel sheet has a lightness L* as defined in JIS Z 8781-4: 2013 satisfying 30≤L*≤50, and chromaticities a* and b* as defined in JIS Z 8781-4: 2013 satisfying −1≤a*≤2 and −5≤b*≤3 respectively, and with one end portion in the longitudinal direction of a coil as a reference, a color difference ΔEab* as defined in JIS Z 8781-4: 2013 at the central portion and at the opposite end portion satisfies ΔEab*≤8, it is possible to obtain a grain-oriented electrical steel sheet where the variation of properties in a product coil is small.

First claim

The invention claimed is:

1. A hot-rolled steel sheet for electrical steel sheet production, comprising
a chemical composition containing, in mass %, C: 0.02% to 0.08%, Si: 2.5% to 5.0%, Mn: 0.02% to 1.0%, acid-soluble Al: 0.01% or less, and S: 0.0015% to 0.01%, wherein N is suppressed to less than 0.006%, and the balance is Fe and inevitable impurities, and
a scale layer on a surface, where the surface of the scale layer of the steel sheet has a lightness L* as defined in JIS Z 8781-4: 2013 satisfying 30≤L*≤50, and chromaticities a* and b* as defined in JIS Z 8781-4: 2013 within ranges of −1≤a*≤2 and −5≤b*≤3 respectively, wherein
with one end portion in the longitudinal direction of a hot-rolled coil as a reference, a color difference ΔE ab * as defined in JIS Z 8781-4: 2013 at a central portion and at the opposite end portion of the coil satisfies ΔE ab *≤8 respectively, and
a thickness of the scale layer is in a range of 30 μm to 50 μm.

2. The hot-rolled steel sheet for electrical steel sheet production according to claim 1 , further comprising, in mass %, at least one selected from Ni: 1.5% or less, Cu: 1.0% or less, Cr: 0.5% or less, P: 0.5% or less, Sb: 0.5% or less, Sn: 0.5% or less, Bi: 0.5% or less, Mo: 1.0% or less, Ti: 0.05% or less, Nb: 0.1% or less, V: 0.1% or less, B: 0.0025% or less, Te: 0.01% or less, or Ta: 0.01% or less.

3. A method of producing the hot-rolled steel sheet for electrical steel sheet production according to claim 1 , comprising
heating a slab to a temperature of 1180° C. or higher and 1300° C. or lower, and
subjecting the slab to hot rolling to obtain a steel sheet, the hot rolling comprising first-stage rolling and subsequent second-stage rolling, wherein
the first-stage rolling is performed until a thickness of the steel sheet of 100 mm or less is obtained,
a delivery temperature of the first-stage rolling, which is a temperature of the steel sheet delivered from the first-stage rolling, is 950° C. or higher,
the second-stage rolling is performed until a thickness of the steel sheet of 3.0 mm or less is obtained,
after the first-stage rolling and prior to the second-stage rolling, descaling with high-pressure water is performed, and
for scales on a surface of the steel sheet after the second-stage rolling, with one end portion in the longitudinal direction of a hot-rolled coil as a reference, a difference in thickness between a surface scale at the reference and a surface scale at a central portion of the coil is suppressed to less than 25 μm, and a difference in thickness between the surface scale at the reference and a surface scale at an opposite end portion of the coil is suppressed to less than 25 μm.

4. The method of producing a hot-rolled steel sheet for electrical steel sheet production according to claim 3 , wherein after the heating and prior to the first-stage rolling, primary scales are destroyed by a scale breaker.

5. A method of producing the hot-rolled steel sheet for electrical steel sheet production according to claim 2 , comprising
heating a slab to a temperature of 1180° C. or higher and 1300° C. or lower, and
subjecting the slab to hot rolling to obtain a steel sheet, the hot rolling comprising first-stage rolling and subsequent second-stage rolling, wherein
the first-stage rolling is performed until a thickness of the steel sheet of 100 μm or less is obtained,
a delivery temperature of the first-stage rolling, which is a temperature of the steel sheet delivered from the first-stage rolling, is 950° C. or higher,
the second-stage rolling is performed until a thickness of the steel sheet of 3.0 mm or less is obtained,
after the first-stage rolling and prior to the second-stage rolling, descaling with high-pressure water is performed, and
for scales on a surface of the steel sheet after the second-stage rolling, with one end portion in the longitudinal direction of a hot-rolled coil as a reference, a difference in thickness between a surface scale at the reference and a surface scale at a central portion of the coil is suppressed to less than 25 μm, and a difference in thickness between the surface scale at the reference and a surface scale at an opposite end portion of the coil is suppressed to less than 25 μm.

6. The method of producing a hot-rolled steel sheet for electrical steel sheet production according to claim 5 , wherein after the heating and prior to the first-stage rolling, primary scales are destroyed by a scale breaker.

Assignees

• Jfe Steel Corp

Inventors

• EHASHI Yuiko
• Takenaka Masanori
• Imamura Takeshi
• Takashima Minoru

Classifications

• C21D8/00

  Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment (hardening articles or materials formed by forging or rolling with no further heating beyond that required for the formation C21D1/02) · CPC title

• C21D8/1222

  Hot rolling · CPC title

• C22C38/60

  containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur · CPC title

• C21D6/004 Primary

  containing Cr and Ni · CPC title

• C21D9/46

  for sheet metals · CPC title