US 12,454,745 B2
Method for producing grain oriented electrical steel sheet
Shinsuke Takatani, Tokyo (JP); and Yoshiyuki Ushigami, Tokyo (JP)
Assigned to NIPPON STEEL CORPORATION, Tokyo (JP)
Appl. No. 17/422,390
Filed by NIPPON STEEL CORPORATION, Tokyo (JP)
PCT Filed Jan. 16, 2020, PCT No. PCT/JP2020/001198
§ 371(c)(1), (2) Date Jul. 12, 2021,
PCT Pub. No. WO2020/149351, PCT Pub. Date Jul. 23, 2020.
Claims priority of application No. 2019-005133 (JP), filed on Jan. 16, 2019.
Prior Publication US 2022/0081747 A1, Mar. 17, 2022
Int. Cl. C22C 38/54 (2006.01); C21D 8/02 (2006.01); C21D 9/46 (2006.01); C22C 38/00 (2006.01); C22C 38/02 (2006.01); C22C 38/04 (2006.01); C22C 38/06 (2006.01); C22C 38/42 (2006.01); C22C 38/44 (2006.01); C22C 38/46 (2006.01); C22C 38/48 (2006.01); C22C 38/50 (2006.01)
CPC C22C 38/54 (2013.01) [C21D 8/0205 (2013.01); C21D 8/0226 (2013.01); C21D 8/0236 (2013.01); C21D 9/46 (2013.01); C22C 38/001 (2013.01); C22C 38/002 (2013.01); C22C 38/008 (2013.01); C22C 38/02 (2013.01); C22C 38/04 (2013.01); C22C 38/06 (2013.01); C22C 38/42 (2013.01); C22C 38/44 (2013.01); C22C 38/46 (2013.01); C22C 38/48 (2013.01); C22C 38/50 (2013.01)] 10 Claims
OG exemplary drawing
 
1. A method for producing a grain oriented electrical steel sheet,
the method comprising:
a hot rolling process of hot-rolling a steel piece to obtain a hot rolled steel sheet, the steel piece consisting of, as a chemical composition, by mass %,
0.030 to 0.100% of C,
0.80 to 7.00% of Si,
0.01 to 1.00% of Mn,
0 to 0.060% in total of S and Se,
0.010 to 0.065% of acid soluble Al,
0.004 to 0.012% of N,
0 to 0.30% of Cr,
0 to 0.40% of Cu,
0 to 0.50% of P,
0 to 0.30% of Sn,
0 to 0.30% of Sb,
0 to 1.00% of Ni,
0 to 0.008% of B,
0 to 0.15% of V,
0 to 0.20% of Nb,
0 to 0.10% of Mo,
0 to 0.015% of Ti,
0 to 0.010% of Bi, and
a balance consisting of Fe and impurities;
a cold rolling process of cold-rolling the hot rolled steel sheet to obtain a cold rolled steel sheet;
a decarburization annealing process of decarburization-annealing the cold rolled steel sheet to obtain a decarburization annealed sheet;
an annealing separator applying process of applying and drying an annealing separator including MgO to the decarburization annealed sheet;
a final annealing process of final-annealing the decarburization annealed sheet after applying the annealing separator to obtain a final annealed sheet;
an annealing separator removing process of removing a redundant annealing separator from a surface of the final annealed sheet;
a smoothing process of smoothing the surface of the final annealed sheet after removing the redundant annealing separator; and
an insulation coating forming process of forming an insulation coating on the surface of the final annealed sheet after being smoothed,
wherein, in the decarburization annealing process,
PH2O/PH2 which is an oxidation degree of an atmosphere is 0.18 to 0.80, an annealing temperature is 750 to 900° C., and a holding is 10 to 600 seconds,
wherein, in the final annealing process,
the decarburization annealed sheet after applying the annealing separator is held at 1100 to 1200° C. for 10 hours or more in a mixed gas atmosphere including 50 volume % or more of a hydrogen,
wherein, in the annealing separator removing process,
the final annealed sheet is water-washed using a solution with an inhibitor which is at least one of a triethanolamine, a rosinamine, or a mercaptan in order to remove the redundant annealing separator from the surface thereof, and an amount of an iron hydroxide and an iron oxide on the surface thereof is controlled to 0.9 g/m2 or less per a side,
wherein, in the smoothing process,
the final annealed sheet after removing the redundant annealing separator is annealed at 1000° C. or more in a mixed gas atmosphere including 50 volume % or more of a hydrogen or a carbon monoxide, and
wherein, in the insulation coating forming process,
the insulation coating is formed on the surface of the final annealed sheet after being smoothed by applying an insulation coating forming solution which includes a phosphate or a colloidal silica, by baking at 350 to 600° C., and then by heat-treating at 800 to 1000° C. in an atmosphere where an oxidation degree (PH2O/PH2) is 0.01 to 1.5.