US 5,885,371 AGranted

Method of producing grain-oriented magnetic steel sheet

AssigneeKawasaki Steel Corporation

InventorsMichiro Komatsubara, Toshito Takamiya, Kunihiro Senda, Mineo Muraki, Chizuko Goto, Mitsumasa Kurosawa, Kazuaki Tamura

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Abstract

A method of producing a grain-oriented magnetic steel sheet exhibiting a very low core loss and high magnetic flux density uses a slab of silicon steel containing Al, B, N, and S and/or Se. The method employs hot rolling conducted such that the rolling reduction falls within the range of from about 85 to 99%, and the hot-rolling finish temperature falls within the range of from 950.degree. to 1150.degree. C. and is based on the contents of Si, Al and B. The hot-rolled steel sheet is rapidly cooled at a cooling rate of about 20.degree. C./s and is coiled at a temperature of about 670.degree. C. or lower. Hot-rolled sheet annealing or intermediate annealing is executed by heating the hot-rolled steel sheet up to about 800.degree. C. at a heating rate of from 5.degree. to 25.degree. C./s and holding at a temperature of from about 800.degree. to 1125.degree. C. for a period not longer than about 150 seconds. Final cold rolling is executed at a rolling reduction of from 80 to 95%, followed by final finish annealing conducted with specific control of annealing atmosphere.

Claims24

Dependent claims

A method of producing a grain-oriented magnetic steel sheet exhibiting a very low core loss and high magnetic flux density, which method includes preparing a silicon steel slab having a composition comprising C:

from about 0.025 to 0.095 wt %, Si:
from about 1.5 to 7.0 wt %, Mn:
from about 0.03 to 2.5 wt %, S and/or Se:
from about 0.003 to 0.0400 wt %, a nitride inhibitor component comprising Al:
from about 0.010 to 0.030 wt % and/or B:
from about 0.0008 to 0.0085 wt %, and N:
from about 0.0030 to 0.0100 wt %;
heating said slab to a temperature not lower than about 1300.degree. C.;
hot-rolling said slab, hot-rolled sheet annealing said slab, rapidly cooling the resulting steel sheet after said hot rolling, at a cooling rate that is not less than about 20.degree. C./s and coiling the resulting sheet at a temperature not higher than about 670.degree. C. followed by cold rolling into a final cold-rolled sheet thickness, conducting primary recrystallizing annealing, application of an annealing separator and final finish annealing;
wherein said cold rolling being single-stage cold rolling down to final cold-rolled thickness in a single step at a rolling reduction of from about 80 to 95%;
wherein said hot rolling is executed such that the cumulative rolling reduction at said finish hot rolling ranges from about 85 to 99% and such that the finish temperature of said finish hot rolling ranges from about 950.degree. to 1150.degree. C. and substantially meets the condition of the following equation (1):
610+35X+max(Y, 3Z).ltoreq.T.ltoreq.900+40X+max(Y, 3Z) (1)
where T represents the finish temperature of the finish hot rolling (.degree.C.), X represents the Si content (wt %), Y represents the Al content (wt ppm), Z represents the B content (wt ppm) and max(Y, 3Z) represents the maximum value of either the Al content or three times the B content;
wherein said hot-rolled sheet annealing being conducted under such conditions that said steel sheet is heated to about 800.degree. C. at an average heating rate of from about 5.degree. to 25.degree. C./s and held for a period not longer than about 150 seconds at a temperature ranging from about 800.degree. to 1125.degree. C.;
and wherein said final finish annealing being executed in an H.sub.2 -containing atmosphere at least after said steel sheet temperature has reached about 900.degree. C. in the course of heating of said steel sheet.

12 more elements

from about 0.025 to 0.095 wt %, Si:
from about 1.5 to 7.0 wt %, Mn:
from about 0.03 to 2.5 wt %, S and/or Se:
from about 0.003 to 0.0400 wt %, a nitride inhibitor component comprising Al:
from about 0.010 to 0.030 wt % and/or B:
from about 0.0008 to 0.0085 wt %, and N:
from about 0.0030 to 0.0100 wt %;
heating said slab to a temperature not lower than about 1300.degree. C.;
hot-rolling said slab, hot-rolled sheet annealing said slab, rapidly cooling the resulting steel sheet after said hot rolling, at a cooling rate that is not less than about 20.degree. C./s and coiling the resulting sheet at a temperature not higher than about 670.degree. C., followed by cold rolling into a final cold-rolled sheet thickness, conducting primary recrystallizing annealing, application of an annealing separator and final finish annealing;
wherein said cold rolling being two-stage cold rolling with intermediate annealing, said two-stage cold rolling utilizing a first step comprising a rolling reduction of from about 15 to 60% and a second step after intermediate annealing comprising a rolling reduction of from about 80 to 95% into the final cold-rolled sheet thickness;
wherein hot rolling is executed such that the cumulative rolling reduction at said finish hot rolling ranges from about 85 to 99% and such that the finish temperature of said finish hot rolling ranges from about 950.degree. to 1150.degree. C. and substantially meets the condition of the following equation (1):
610+35X+max(Y, 3Z).ltoreq.T.ltoreq.900+40X+max(Y, 3Z) (1)
where T represents the finish temperature of the finish hot rolling (.degree.C.), X represents the Si content (wt %), Y represents the Al content (wt ppm), Z represents the B content (wt ppm) and max(Y, 3Z) represents the maximum value of either the Al content or three times the B content;
wherein both said hot-rolled sheet annealing and said intermediate sheet annealing being conducted under such conditions that said steel sheet is heated to about 800.degree. C. at an average heating rate of from about 5.degree. to 25.degree. C./s and held for a period not longer than about 150 seconds at a temperature ranging from about 800.degree. to 1125.degree. C.;
and wherein said final finish annealing being executed in an H.sub.2 -containing atmosphere at least after said steel sheet temperature has reached about 900.degree. C. in the course of heating of said steel sheet.

12 more elements

from about 0.025 to 0.095 wt %, Si:
from about 1.5 to 7.0 wt %, Mn:
from about 0.03 to 2.5 wt %, S and/or Se:
from about 0.003 to 0.0400 wt %, a nitride inhibitor component comprising Al:
from about 0.010 to 0.030 wt % and/or B:
from about 0.0008 to 0.0085 wt %, and N:
from about 0.0030 to 0.0100 wt %;
heating said slab to a temperature not lower than about 1300.degree. C.;
hot-rolling said slab, rapidly cooling the resulting steel sheet after said hot rolling, at a cooling rate that is not less than about 20.degree. C./s and coiling the resulting sheet at a temperature not higher than about 670.degree. C., followed by cold rolling into a final cold-rolled sheet thickness, conducting primary recrystallizing annealing, application of an annealing separator and final finish annealing;
wherein said cold rolling being two-stage cold rolling with intermediate annealing, said two-stage cold rolling utilizing a first step comprising a rolling reduction of from about 15 to 60% and a second step after intermediate annealing comprising a rolling reduction of from about 80 to 95% into the final cold-rolled sheet thickness;
wherein said hot rolling is executed such that the cumulative rolling reduction at said finish hot rolling ranges from about 85 to 99% and such that the finish temperature of said finish hot rolling ranges from about 950.degree. to 1150.degree. C. and substantially meets the condition of the following equation (1):
610+35X+max(Y, 3Z).ltoreq.T.ltoreq.900+40X+max(Y, 3Z) (1)
where T represents the finish temperature of the finish hot rolling (.degree.C.), X represents the Si content (wt %), Y represents the Al content (wt ppm), Z represents the B content (wt ppm), and max(Y, 3Z) represents the maximum value of either the Al content or three times the B content;
wherein said intermediate sheet annealing being conducted under such conditions that said steel sheet is heated to about 800.degree. C. at an average heating rate of from about 5.degree. to 25.degree. C./s and held for a period not longer than about 150 seconds at a temperature ranging from about 800.degree. to 1125.degree. C.;
and wherein said final finish annealing being executed in an H.sub.2 -containing atmosphere at least after said steel sheet temperature has reached about 900.degree. C. in the course of heating of said steel sheet.

12 more elements

Dependencies are inferred from the claim text.