Low iron loss grain oriented electrical steel sheet and method for manufacturing the same

Patent metadata

Field	Value
Publication number	US-2017298467-A1
Application number	US-201515516935-A
Country	US
Kind code	A1
Filing date	Oct 5, 2015
Priority date	Oct 6, 2014
Publication date	Oct 19, 2017
Grant date	—

Abstract

A grain oriented electrical steel sheet is subjected to a temperature holding treatment at a temperature T of 250-600° C. for 1-10 seconds in the primary recrystallization annealing and heated from temperature T to 700° C. at not less than 80° C./s and from 700° C. to a soaking temperature at not more than 15° C./s, wherein an oxygen potential from 700° C. to the soaking temperature is 0.2-0.4 and an oxygen potential during the soaking is 0.3-0.5 and an area ratio of secondary recrystallized grains is not less than 90% when an angle α deviated from {110}<001> ideal orientation is less than 6.5° and an area ratio is not less than 75% when a deviation angle is less than 2.5° and an average length [L] in the rolling direction is not more than 20 mm and an average value [β] of the angle β is 15.63×[β]+[L]<44.06.

First claim

1 - 5 . (canceled)

6 . A grain oriented electrical steel sheet having a chemical composition comprising Si: 2.5-5.0 mass % and Mn: 0.01-0.8 mass % and the remainder being Fe and inevitable impurities, wherein continuous or discontinuous linear grooves or linear strain regions are formed on one surface or both surfaces of the steel sheet in a direction crossing a rolling direction at an interval d in the rolling direction of 1-10 mm and a forsterite film and a tension coating are formed on the both surfaces of the steel sheet, wherein an area ratio S α6.5 of secondary recrystallized grains occupied in the surface of the steel sheet is not less than 90% when an absolute value of an angle α deviated from {110 }<001> ideal orientation around a direction perpendicular to a rolling face is less than 6.5° and an area ratio S β2.5 of secondary recrystallized grains occupied in the surface of the steel sheet is not less than 75% when an absolute value of an angle β deviated from {110}<001> ideal orientation around a widthwise direction is less than 2.5°, and an average length [L] (mm) of the secondary recrystallized grains in the rolling direction and an average value [β] of the angle β (°) satisfy equations (1) and (2):
15.63×[β]+[ L]< 44.06  (1)

[L]≦20  (2).

7 . The grain oriented electrical steel sheet according to claim 6 , containing one or more selected from Cr: 0.01-0.50 mass %, Cu: 0.01-0.50 mass %, P: 0.005-0.50 mass %, Ni: 0.010-1.50 mass %, Sb: 0.005-0.50 mass %, Sn: 0.005-0.50 mass %, Bi: 0.005-0.50 mass %, Mo: 0.005-0.10 mass %, B: 0.0002-0.0025 mass %, Te: 0.0005-0.010 mass %, Nb: 0.0010-0.010 mass %, V: 0.001-0.010 mass % and Ta: 0.001-0.010 mass % in addition to the above chemical composition.

8 . A method of manufacturing a grain oriented electrical steel sheet as claimed in claim 6 , comprising: hot rolling a steel slab having a chemical composition comprising C: 0.002-0.10 mass %, Si: 2.5-5.0 mass %, Mn: 0.01-0.8 mass %, Al: 0.010-0.050 mass % and N: 0.003-0.020 mass % and the remainder being Fe and inevitable impurities to form a hot rolled sheet, subjecting the hot rolled sheet to one cold rolling or two or more cold rollings interposing an intermediate annealing therebetween after hot band annealing or without hot band annealing to form a cold rolled sheet having a final thickness, subjecting the cold rolled sheet to a primary recrystallization annealing, applying an annealing separator to the surface of the steel sheet, subjecting the sheet to a finish annealing and forming a tension coating, wherein the sheet is subjected to a temperature holding treatment at any temperature T of 250-600° C. for 1-10 seconds in a heating process of the primary recrystallization annealing and then heated from the temperature T to 700° C. at a heating rate of not less than 80° C./s, and a ratio (I max /I min ) of a maximum value I max in an emission intensity profile in a depth direction of Si to a minimum value I min found in a position deeper than the maximum value I max when the steel sheet surface after the primary recrystallization annealing is observed by a glow discharge optical emission spectrometry is not less than 1.5, and continuous or discontinuous linear grooves or linear strain regions are formed on one surface or both surfaces of the steel sheet in a direction crossing the rolling direction at an interval d in the rolling direction of 1-10 mm in any process after the cold rolling.

9 . The method according to claim 8 , wherein the steel slab contains one or two selected from Se: 0.003-0.030 mass % and 5: 0.002-0.030 mass % in addition to the above chemical composition.

10 . The method according to claim 8 , wherein the steel slab contains one or more selected from Cr: 0.01-0.50 mass %, Cu: 0.01-0.50 mass %, P: 0.005-0.50 mass %, Ni: 0.010-1.50 mass %, Sb: 0.005-0.50 mass %, Sn: 0.005-0.50 mass %, Bi: 0.005-0.50 mass %, Mo: 0.005-0.10 mass %, B: 0.0002-0.0025 mass %, Te: 0.0005-0.010 mass %, Nb: 0.0010-0.010 mass %, V: 0.001-0.010 mass % and Ta: 0.001-0.010 mass % in addition to the above chemical composition.

11 . The method according to claim 9 , wherein the steel slab contains one or more selected from Cr: 0.01-0.50 mass %, Cu: 0.01-0.50 mass %, P: 0.005-0.50 mass %, Ni: 0.010-1.50 mass %, Sb: 0.005-0.50 mass %, Sn: 0.005-0.50 mass %, Bi: 0.005-0.50 mass %, Mo: 0.005-0.10 mass %, B: 0.0002-0.0025 mass %, Te: 0.0005-0.010 mass %, Nb: 0.0010-0.010 mass %, V: 0.001-0.010 mass % and Ta: 0.001-0.010 mass % in addition to the above chemical composition.

Assignees

• Jfe Steel Corp

Inventors

• Suehiro Ryuichi
• Terashima Takashi
• Takamiya Toshito
• Watanabe Makoto
• Uesaka Masanori

Classifications

• C21D8/1244 Primary

  characterised by the heat treatment · CPC title

• C21D8/1294

  involving a localised treatment · CPC title

• C22C38/04

  containing manganese · CPC title

• C22C38/02

  containing silicon · CPC title

• C22C38/54

  with boron · CPC title