Production method for grain-oriented electrical steel sheet and primary recrystallized steel sheet for production of grain-oriented electrical steel sheet

Patent metadata

Field	Value
Publication number	US-9905343-B2
Application number	US-201314650073-A
Country	US
Kind code	B2
Filing date	Dec 25, 2013
Priority date	Dec 28, 2012
Publication date	Feb 27, 2018
Grant date	Feb 27, 2018

Abstract

A method for producing a grain-oriented electrical steel sheets includes subjecting a steel slab to hot rolling to obtain a hot rolled sheet, the steel slab having a specific composition; then subjecting the hot rolled sheet to annealing and rolling to obtain a cold rolled sheet; then subjecting the cold rolled sheet to nitriding treatment with a nitrogen increase of 50 to 1000 ppm, during or after primary recrystallization annealing; then applying an annealing separator on the cold rolled sheet; and setting the staying time in a temperature range of 300 to 800° C. in the secondary recrystallization annealing to 5 to 150 hours.

First claim

The invention claimed is:

1. A production method for a grain-oriented electrical steel sheet, the method comprising:
subjecting a steel slab to hot rolling, without re-heating or after re-heating, to obtain a hot rolled sheet, the steel slab having a composition comprising, by mass % or mass ppm:
C: 0.08% or less,
Si: 2.0% to 4.5%,
Mn: 0.5% or less,
S: less than 50 ppm,
Se: less than 50 ppm,
O: less than 50 ppm,
sol.Al: less than 100 ppm,
N controlled within a range where the relationship sol.Al/(26.98/14.00) ppm≦N≦80 ppm is satisfied, and
the balance being Fe and incidental impurities;

then subjecting the hot rolled sheet to annealing and rolling to obtain a cold rolled sheet of final sheet thickness;
then subjecting the cold rolled sheet to nitriding treatment with a nitrogen increase in a range of 50 ppm or more and 1000 ppm or less, during or after primary recrystallization annealing;
then applying an annealing separator on the cold rolled sheet; and
setting the staying time in a temperature range of 300° C. to 800° C. in the heating stage of secondary recrystallization annealing to 5 hours or more to 150 hours or less to diffuse N into a steel substrate so as to selectively precipitate silicon nitride at a grain boundary with a precipitate size of 100 nm or more in order to provide a pinning force for normal grain growth,
wherein the nitriding treatment is performed at a temperature of 800° C. or lower, and
89% or more of the nitrogen introduced into the cold rolled steel sheet localizes in a surface region of 3 μm thick in the nitriding treatment.

2. The production method for a grain-oriented electrical steel sheet according to claim 1 , wherein the steel slab further comprises, by mass %, one or more of Ni: 0.005% to 1.50%, Sn: 0.01% to 0.50%, Sb: 0.005% to 0.50%, Cu: 0.01% to 0.50%, Cr: 0.01% 1.50%, P: 0.0050% to 0.50%, Mo: 0.01% to 0.50% and Nb: 0.0005% to 0.0100%.

Assignees

• Jfe Steel Corp

Inventors

• Shingaki Yukihiro
• Hayakawa Yasuyuki
• Yamaguchi Hiroi
• Matsuda Hiroshi
• WAKISAKA Yuiko

Classifications

• H01F41/02

  for manufacturing cores, coils, or magnets (H01F41/14 takes precedence; for dynamo-electric machines H02K15/00) · CPC title

• C23C8/02

  Pretreatment of the material to be coated (C23C8/04 takes precedence) · CPC title

• C22C38/02

  containing silicon · CPC title

• C23C8/80

  After-treatment · CPC title

• C21D2211/004

  Dispersions; Precipitations · CPC title