Non-oriented electrical steel sheet and method for manufacturing non-oriented electrical steel sheet

Patent metadata

Field	Value
Publication number	US-11114227-B2
Application number	US-201616065352-A
Country	US
Kind code	B2
Filing date	Dec 14, 2016
Priority date	Dec 28, 2015
Publication date	Sep 7, 2021
Grant date	Sep 7, 2021

Abstract

A non-oriented electrical steel sheet has low iron loss even under inverter excitation and can be suitably used as the iron core of a motor. The non-oriented electrical steel sheet has a specific chemical composition and an average grain size r of 40 μm to 120 μm. An area ratio R of a total area of grains having a grain size of ⅙ or less of the thickness of the steel sheet to a cross-sectional area of the steel sheet is 2% or greater, and the average grain size r (μm) and the area ratio R (%) satisfy a condition represented by Expression (1), R>−2.4×r+200 (1).

First claim

The invention claimed is:

1. A non-oriented electrical steel sheet comprising:
a chemical composition containing, in mass %,
C: 0.005% or less,
Si: 4.5% or less,
Mn: 0.02% to 2.0%,
Sol.Al: 2.0% or less,
P: 0.2% or less,
Ti: 0.007% or less,
S: 0.005% or less,
one or both of As and Pb: total of 0.0005% to 0.005%, and
the balance consisting of Fe and inevitable impurities;

wherein an average grain size r, measured in a cross-sectional area of the steel sheet, is 40 μm to 120 μm,
wherein an area ratio R, in percentage, of a total area of grains having a grain size of ⅙ or less of a thickness of the steel sheet in the cross-sectional area of the steel sheet is 2% or greater,
wherein the average grain size r μm and the area ratio R % satisfy a condition represented by Expression (1),
R>− 2.4× r+ 200  (1),

wherein the cross-sectional area of the steel sheet is an area of a cross-section yielded by cutting the non-oriented electrical steel sheet in a thickness direction, parallel to a rolling direction, at a center in a sheet transverse direction, and
wherein the thickness of the steel sheet is 0.35 mm or less.

2. The non-oriented electrical steel sheet of claim 1 , wherein the chemical composition further contains, in mass %, one or both of Sn: 0.01% to 0.2% and Sb: 0.01% to 0.2%.

3. The non-oriented electrical steel sheet of claim 2 , wherein a rate of increase in iron loss W inc % calculated as 100(W inv −W sin )/W sin is 100% or less, where using a ring test piece having a magnetic path cross-sectional area of 70 mm 2 and having wound thereon a wiring with a primary winding number of 120 turns and a secondary winding number of 100 turns, iron loss W inv is measured when performing excitation by pulse width modulation control using an inverter at a maximum magnetic flux density of 1.5 T, a fundamental frequency of 50 Hz, a carrier frequency of 1 kHz, and a modulation factor of 0.4, and iron loss W sin is measured when performing excitation at a maximum magnetic flux density of 1.5 T and with sinusoidal alternating current at a frequency of 50 Hz.

4. The non-oriented electrical steel sheet of claim 2 , wherein the chemical composition further contains, in mass %, one or more of
REM: 0.0005% to 0.005%,
Mg: 0.0005% to 0.005%, and
Ca: 0.0005% to 0.005%.

5. The non-oriented electrical steel sheet of claim 4 , wherein a rate of increase in iron loss W inc % calculated as 100(W inv −W sin )/W sin is 100% or less, where using a ring test piece having a magnetic path cross-sectional area of 70 mm 2 and having wound thereon a wiring with a primary winding number of 120 turns and a secondary winding number of 100 turns, iron loss W inv is measured when performing excitation by pulse width modulation control using an inverter at a maximum magnetic flux density of 1.5 T, a fundamental frequency of 50 Hz, a carrier frequency of 1 kHz, and a modulation factor of 0.4, and iron loss W sin is measured when performing excitation at a maximum magnetic flux density of 1.5 T and with sinusoidal alternating current at a frequency of 50 Hz.

6. The non-oriented electrical steel sheet of claim 1 , wherein the chemical composition further contains, in mass %, one or more of
REM: 0.0005% to 0.005%,
Mg: 0.0005% to 0.005%, and
Ca: 0.0005% to 0.005%.

7. The non-oriented electrical steel sheet of claim 6 , wherein a rate of increase in iron loss W inc % calculated as 100(W inv −W sin )/W sin is 100% or less, where using a ring test piece having a magnetic path cross-sectional area of 70 mm 2 and having wound thereon a wiring with a primary winding number of 120 turns and a secondary winding number of 100 turns, iron loss W inv is measured when performing excitation by pulse width modulation control using an inverter at a maximum magnetic flux density of 1.5 T, a fundamental frequency of 50 Hz, a carrier frequency of 1 kHz, and a modulation factor of 0.4, and iron loss W sin is measured when performing excitation at a maximum magnetic flux density of 1.5 T and with sinusoidal alternating current at a frequency of 50 Hz.

8. The non-oriented electrical steel sheet of claim 1 , wherein a rate of increase in iron loss W inc % calculated as 100(W inv −W sin )/W sin is 100% or less, where using a ring test piece having a magnetic path cross-sectional area of 70 mm 2 and having wound thereon a wiring with a primary winding number of 120 turns and a secondary winding number of 100 turns, iron loss W inv is measured when performing excitation by pulse width modulation control using an inverter at a maximum magnetic flux density of 1.5 T, a fundamental frequency of 50 Hz, a carrier frequency of 1 kHz, and a modulation factor of 0.4, and iron loss W sin is measured when performing excitation at a maximum magnetic flux density of 1.5 T and with sinusoidal alternating current at a frequency of 50 Hz.

9. A method for manufacturing the non-oriented electrical steel sheet of claim 1 , the method comprising:
preparing a steel slab comprising a chemical composition containing, in mass %,
C: 0.005% or less,
Si: 4.5% or less,
Mn: 0.02% to 2.0%,
Sol.Al: 2.0% or less,
P: 0.2% or less,
Ti: 0.007% or less,
S: 0.005% or less,
one or both of As and Pb: total of 0.0005% to 0.005%, and
the balance consisting of Fe and inevitable impurities;

hot rolling the steel slab into a hot rolled sheet;
subjecting the hot rolled sheet to hot band annealing comprising a first soaking treatment performed with a soaking temperature of 800° C. to 1100° C. and a soaking time of 5 s or more and 5 min or less and a second soaking treatment performed with a soaking temperature of 1150° C. to 1200° C. and a soaking time of 1 s or more and 5 s or less;
subjecting the hot rolled sheet after the hot band annealing to cold rolling once or cold rolling twice or more with intermediate annealing in between to obtain a steel sheet with a final sheet thickness of 0.35 mm or less; and
subjecting the steel sheet after the cold rolling to final annealing;
wherein a heating rate from 400° C. to 740° C. during the final annealing is 30° C./s to 300° C./s.

10. The method of claim 9 , wherein the chemical composition further contains, in mass %, one or more of
REM: 0.0005% to 0.005%,
Mg: 0.0005% to 0.005%, and
Ca: 0.0005% to 0.005%.

11. The method of claim 9 , wherein the chemical composition further contains, in mass %, one or both of Sn: 0.01% to 0.2% and Sb: 0.01% to 0.2%.

12. The method of claim 11 , wherein the chemical composition further contains, in mass %, one or more of
REM: 0.0005% to 0.005%,
Mg: 0.0005% to 0.005%, and
Ca: 0.0005% to 0.005%.

Assignees

• Jfe Steel Corp

Inventors

• Uesaka Masanori
• Senda Kunihiro
• Omura Takeshi

Classifications

• H01F1/16 Primary

  in the form of sheets (H01F1/147 takes precedence) · CPC title

• H01F1/147

  Alloys characterised by their composition {(treatment thereof for enhancing their electromagnetic properties C21D8/12)} · CPC title

• C22C38/14

  containing titanium or zirconium · CPC title

• C21D8/12

  during manufacturing of articles with special electromagnetic properties · CPC title

• C22C38/60 Primary

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