Method for producing grain-oriented electrical steel sheet

Patent metadata

Field	Value
Publication number	US-12338504-B2
Application number	US-202017421766-A
Country	US
Kind code	B2
Filing date	Jan 16, 2020
Priority date	Jan 16, 2019
Publication date	Jun 24, 2025
Grant date	Jun 24, 2025

Abstract

A method for producing a grain-oriented electrical steel sheet which has an intermediate layer containing silicon oxide as a main component on a surface of a base steel sheet in which a forsterite film is substantially absent and has an insulation coating on a surface of the intermediate layer includes: a decarburization annealing process of obtaining a decarburization-annealed steel sheet which has the oxygen content or 320 ppm or less and the carbon content of 25 ppm or less by subjecting a cold rolled steel sheet containing Si to decarburization annealing; a final annealing process of heating the decarburization-annealed steel sheet in a state in which a surface of the decarburization-annealed steel sheet is coated with an annealing separator to subject a steel sheet to secondary recrystallization; a removal process of obtaining a finally-annealed steel sheet by removing the annealing separator on the steel sheet which has been subjected to the final annealing process; an intermediate layer forming process of forming the intermediate layer by subjecting the finally-annealed steel sheet to thermal oxidation annealing; and an insulation coating forming process of forming the insulation coating on the finally-annealed steel sheet having the intermediate layer formed thereon.

First claim

The invention claimed is:

1. A method for producing a grain-oriented electrical steel sheet which has an intermediate layer containing silicon oxide as a main component on a surface of a base steel sheet in which a forsterite film is substantially absent and has an insulation coating on a surface of the intermediate layer, comprising:
a decarburization annealing process of obtaining a decarburization-annealed steel sheet which has an oxygen content of 320 ppm or less and a carbon content of 25 ppm or less by subjecting a cold-rolled steel sheet containing Si to decarburization annealing;
a final annealing process of heating the decarburization-annealed steel sheet in a state in which a surface of the decarburization-annealed steel sheet is coated with an annealing separator containing 10 to 50 mass % of MgO and 90 to 50 mass % of Al 2 O 3 to cause secondary recrystallization to occur in a steel sheet;
a removal process of obtaining a finally-annealed steel sheet by removing the annealing separator on the steel sheet which has been subjected to the final annealing process;
an intermediate layer forming process of forming the intermediate layer by subjecting the finally-annealed steel sheet to thermal oxidation annealing; and
an insulation coating forming process of forming the insulation coating on the finally-annealed steel sheet having the intermediate layer formed thereon,
wherein the cold-rolled steel sheet contains, as a chemical composition, in terms of mass %,
Si: 0.80 to 7.00%;
C: 0.085% or less;
acid-soluble Al: 0.015 to 0.065%;
N: 0.012% or less;
Mn: 1.00% or less;
a total amount of S and Se: 0.003 to 0.015%; and
the remainder: Fe and impurities.

2. The method for producing a grain-oriented electrical steel sheet according to claim 1 , wherein, in the decarburization annealing process, in a soaking area configured to subject the cold-rolled steel sheet to decarburization annealing, an atmosphere gas is introduced from two locations which are an initial part and a latter part of the soaking area.

3. The method for producing a grain-oriented electrical steel sheet according to claim 2 , wherein, in the decarburization annealing process, a dew point DP1 of the atmosphere gas introduced from the initial part of the soaking area is set to 40 to 70° C. and a dew point DP2 of the atmosphere gas introduced from the latter part of the soaking area satisfies DP2≤DP1 and 60−DP1≤DP2≤100−DP1.

4. A method for producing a grain-oriented electrical steel sheet which has an intermediate layer containing silicon oxide as a main component on a surface of a base steel sheet in which a forsterite film is substantially absent and has an insulation coating on a surface of the intermediate layer, comprising:
a decarburization annealing process of obtaining a decarburization-annealed steel sheet which has an oxygen content of 320 ppm or less and a carbon content of 25 ppm or less by subjecting a cold-rolled steel sheet containing Si to decarburization annealing;
a final annealing process of heating the decarburization-annealed steel sheet in a state in which a surface of the decarburization-annealed steel sheet is coated with an annealing separator to cause secondary recrystallization to occur in a steel sheet;
a removal process of obtaining a finally-annealed steel sheet by removing the annealing separator on the steel sheet which has been subjected to the final annealing process; and
an intermediate layer-insulation coating forming process of forming the intermediate layer and the insulation coating on the finally-annealed steel sheet in one process,
wherein the cold-rolled steel sheet contains, as a chemical composition, in terms of mass %,
Si: 0.80 to 7.00%;
C: 0.085% or less;
acid-soluble Al: 0.015 to 0.065%;
N: 0.012% or less;
Mn: 1.00% or less;
a total amount of S and Se: 0.003 to 0.015%; and
the remainder: Fe and impurities, and
in the intermediate layer-insulation coating forming process, a surface of the finally-annealed steel sheet is coated with a coating solution and annealed within a temperature range of higher than 650° C. to 950° C. or lower for 5 to 300 seconds in an atmosphere of a gas oxidation degree (P H2O /P H2 ) of 0.01 to 0.30.

5. The method for producing a grain-oriented electrical steel sheet according to claim 4 , wherein, in the decarburization annealing process, in a soaking area configured to subject the cold-rolled steel sheet to decarburization annealing, an atmosphere gas is introduced from two locations which are an initial part and a latter part of the soaking area.

Assignees

• Nippon Steel Corp

Inventors

• Imai Takeshi
• Okumura Shunsuke

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

• C21D8/1233

  Cold rolling · CPC title

• H01F1/18

  with insulating coating · CPC title

• C23C22/74

  for obtaining burned-in conversion coatings · CPC title

• C23C22/33

  containing also phosphates · CPC title