Grain-oriented electrical steel sheet and manufacturing method thereof

Patent metadata

Field	Value
Publication number	US-10208372-B2
Application number	US-201213978925-A
Country	US
Kind code	B2
Filing date	Jan 12, 2012
Priority date	Jan 12, 2011
Publication date	Feb 19, 2019
Grant date	Feb 19, 2019

Abstract

A grain-oriented electrical steel sheet being a grain-oriented electrical steel sheet containing Si of 0.8 mass % to 7 mass %, Mn of 0.05 mass % to 1 mass %, B of 0.0005 mass % to 0.0080 mass %, each content of Al, C, N, S, and Se of 0.005 mass % or less, and a balance being composed of Fe and inevitable impurities and having a glass coating film made of composite oxide mainly composed of forsterite on the steel sheet surface, in which when glow discharge optical emission spectrometry (GDS) to the surface of a secondary coating film formed on the surface of the glass coating film under a predetermined condition is performed, a peak, of B, in emission intensity having a peak position in emission intensity different from a peak position, of Mg, in emission intensity is obtained and the peak position, of B, in emission intensity from the steel sheet surface is deeper than the peak position, of Mg, in emission intensity.

First claim

The invention claimed is:

1. A grain-oriented electrical steel sheet having a composition comprising 0.8 mass % to 7 mass % of Si, 0.05 mass % to 1 mass % of Mn, 0.0005 mass % to 0.0080 mass % of B, 0.005 mass % or less of each of Al, C, N, S and Se, and a balance comprising Fe and inevitable impurities, and having a glass coating film, comprising a composite oxide mainly comprising forsterite on a steel sheet surface, wherein:
a peak position of B in emission intensity from the steel sheet surface is different from and deeper than a peak position of Mg in emission intensity when glow discharge optical emission spectrometry (GDS) is performed, and
out of peaks of B in emission intensity observed by the glow discharge optical emission spectrometry (GDS), a peak occurrence time tB of a peak that is the farthest from the steel sheet surface is expressed by the following Expression (1):
tMg×1.6≤tB≤tMg×5  (1)

where tMg represents a peak occurrence time of Mg, and the peak position of B, Mg, the values tB and tMg are measured by the GDS on a surface of a secondary coating film containing 26 to 38 mass % of colloidal silica, 4 to 12 mass % of one type or two types selected from the group consisting of chromium anhydride and chromate, and a balance comprising aluminum biphosphate, and having a thickness of not less than 1 μm nor more than 2 μm.

2. A manufacturing method of the grain-oriented electrical steel sheet according to claim 1 , comprising:
at a predetermined temperature, heating an electrical steel sheet material containing Si of 0.8 mass % to 7 mass %, acid-soluble Al of 0.01 mass % to 0.065 mass %, N of 0.004 mass % to 0.012 mass %, Mn of 0.05 mass % to 1 mass %, B of 0.0005 mass % to 0.0080 mass %, at least one type selected from a group consisting of S and Se of 0.003 mass % to 0.015 mass % in total amount, a C content of 0.085 mass % or less, and a balance being composed of Fe and inevitable impurities;
performing hot rolling of the heated silicon steel material to obtain a hot-rolled steel strip;
performing annealing of the hot-rolled steel strip to obtain an annealed steel strip;
performing cold rolling of the annealed steel strip one time or more to obtain a cold-rolled steel strip;
performing decarburization annealing of the cold-rolled steel strip to obtain a decarburization-annealed steel strip in which primary recrystallization has been caused;
applying an annealing separating agent having MgO as its main component on the decarburization-annealed steel strip;
finish annealing the decarburization-annealed steel strip and thereby causing secondary recrystallization;
and further performing a nitriding treatment in which an N content in the decarburization-annealed steel strip is increased between start of the decarburization annealing and occurrence of the secondary recrystallization in the finish annealing, wherein
the predetermined temperature, when S and Se are contained in the silicon steel material, is a temperature T1 (° C.) expressed by Expression (2) below or lower, a temperature T2 (° C.) expressed by Expression (3) below or lower, and a temperature T3 (° C.) expressed by Expression (4) below or lower,
when no Se is contained in the silicon steel material, the predetermined temperature is the temperature T1 (° C.) expressed by Expression (2) below or lower and the temperature T3 (° C.) expressed by Expression (4) below or lower,
when no S is contained in the silicon steel material, the predetermined temperature is the temperature T2 (° C.) expressed by Expression (3) below or lower and the temperature T3 (° C.) expressed by Expression (4) below or lower, and a finishing temperature Tf of finish rolling in the hot rolling satisfies Expression (5) below,
amounts of BN, MnS, and MnSe in the hot-rolled steel strip satisfy Expressions (6), (7), and (8) below, and at the time of finish annealing, a temperature falls within a temperature range of 800° C. to 1100° C. and an atmosphere satisfies Expressions (9) and (10) below,
T1=14855/(6.82−log([Mn]×[S]))−273  (2)

T2=10733/(4.08−log([Mn]×[Se]))−273  (3)

T3=16000/(5.92−log([B]×[N]))−273  (4)

Tf≤1000−10000×[B]  (5)

B asBN ≥0.0005  (6)

[B]−B asBN ≤0.001  (7)

S asMnS +0.5×Se asMnSe ≥0.002  (8)

0.75≥P N2 ≥0.2  (9)

−0.7>Log [P H20 /P H2 ]  (10)

here, [Mn] represents the Mn content (mass %) of the silicon steel material, [S] represents the S content (mass %) of the silicon steel material, [Se] represents the Se content (mass %) of the silicon steel material, [B] represents the B content (mass %) of the silicon steel material, [N] represents the N content (mass %) of the silicon steel material, B asBN represents an amount of B (mass %) that has precipitated as BN in the hot-rolled steel strip, S asMns represents an amount of S (mass %) that has precipitated as MnS in the hot-rolled steel strip, and Se asMnSe represents an amount of Se (mass %) that has precipitated as MnSe in the hot-rolled steel strip; further, P N2 represents a nitrogen partial pressure, and P H2O and P H2 represent a water vapor partial pressure and a hydrogen partial pressure respectively.

3. The manufacturing method of the grain-oriented electrical steel sheet according to claim 2 , wherein
at the time of finish annealing, the temperature falls within the temperature range of 800° C. to 1100° C. and the atmosphere satisfies Expression (11) below,
4 Log [P N2 ]=3 Log [P H2O /P H2 ]+A+3455/T  (11)

here, −3.72≥3 Log [P H2O /P H2 ]+A≥−5.32 and −0.7≥Log [P H2O /P H2 ] are satisfied and A represents a constant determined in such a manner that 3 Log [P H2O /P H2 ]+A falls within a predetermined range according to Log [P H2O /P H2 ], and T represents the absolute temperature.

4. The manufacturing method of the grain-oriented electrical steel sheet according to claim 2 , wherein
at the time of finish annealing, an atmosphere at 1100° C. or higher satisfies Expressions (12) and (13) below,
0.1≥P N2   (12)

−2≥Log [P H2O /P H2 ]  (13).

5. The manufacturing method of the grain-oriented electrical steel sheet according to claim 2 , wherein
the electrical steel sheet material further contains at least one type selected from a group consisting of Cr: 0.3 mass % or less, Cu: 0.4 mass % or less, Ni: 1 mass % or less, P: 0.5 mass % or less, Mo: 0.1 mass % or less, Sn: 0.3 mass % or less, Sb: 0.3 mass % or less, and Bi: 0.01 mass % or less.

Assignees

• Takahashi Fumiaki
• Ushigami Yoshiyuki
• Mizukami Kazumi
• Nakamura Shuichi
• Fujii Norikazu
• Yamamoto Norihiro
• Urago Masahide
• Nippon Steel & Sumitomo Metal Corp

Inventors

• Takahashi Fumiaki
• Ushigami Yoshiyuki
• Mizukami Kazumi
• Nakamura Shuichi
• Fujii Norikazu
• Yamamoto Norihiro
• Urago Masahide

Classifications

• C21D2201/05

  Grain orientation · CPC title

• C23C8/02 Primary

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

• C23C28/04

  only coatings of inorganic non-metallic material · CPC title

• C22C38/002

  containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60 · CPC title

• C22C38/08

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