Jfe Steel Corporation

Tomoyuki Okubo

Yoshihiko Oda

Yoshiaki Zaizen

Hiroaki Nakajima

Masanori Uesaka

Tadashi Nakanishi

Takaaki Tanaka

Yukino Miyamoto

Makoto Watanabe

Yukihiro Shingaki

Toshito Takamiya

Tatsuhiko Hiratani

Takashi Terashima

Kunihiro Senda

Hirotaka Inoue

Shinji Koseki

Shigehiro Takajo

Hiroaki Toda

Kohei Kurihara

Seiji Nabeshima

Akitoshi Matsui

Akifumi Harada

A non-oriented electrical steel sheet having a high magnetic flux density and a low iron loss at a high frequency is produced by subjecting a slab containing, in mass %, C: not more than 0.0050%, Si: 2.8 to 6.5%, Mn: 0.05 to 2.0%, P: not more than 0.10%, S: not more than 0.0050%, Al: 0.3 to 2.0%, N: not more than 0.0050% and Zn: 0.0005 to 0.0050% to a hot rolling, a hot-band annealing, a cold rolling and a finish annealing, a dew point in the hot-band annealing is set to 0 to 70° C. and an atmosphere of the finish annealing has a nitrogen content of not more than 30 vol % and a dew point of not higher than −20° C., and a ratio of the amount of nitrogen present as AlN in an entire sheet thickness to the amount of nitrogen present as AlN in a layer from one-side surface of steel sheet to a depth of 1/20 of sheet thickness is made to not less than 5.0.

Non-oriented electrical steel sheet and method for producing same

Provides is a non-oriented electrical steel sheet suitable for use in a rotor of an IPM motor that has excellent magnetic flux density Band high-frequency iron loss properties, high tensile strength and fatigue strength, and little variation in tensile strength. The non-oriented electrical steel sheet has a predetermined steel sheet chemical composition and a microstructure in which a ratio of non-recrystallized microstructure is 5% or more and 70% or less and the number of inclusion having a diameter of 5 μm or more is not more than 5 counts/mm.

Non-oriented electrical steel sheet and method for manufacturing the same

Provided are a motor core having excellent fatigue resistance and a method of manufacturing the motor core at a low cost. The motor core that is an electrical-steel-sheet-stacked body has an outer peripheral surface in which an appearance ratio of recrystallized grains with a grain size of 15 μm or less is 70% or more of a sheet thickness of the motor core.

Motor core and method of manufacturing the same

In a production of a non-oriented electrical steel sheet comprising subjecting a slab containing a particular composition to a hot rolling, a hot-band annealing, a cold rolling to form a cold-rolled sheet and a finish annealing, a rolling reduction of a final finish rolling pass in the hot rolling is not less than 10%, and a coiling temperature is not higher than 620° C., and a soaking temperature in the finish annealing is 600 to 800° C. to achieve such properties that a recrystallization ratio is less than 100% as an area ratio, a strength C is not less than 2.0 and a strength difference C−D is not more than 2.0, where C is a strength at Φ=0° and φ=0° and D is a strength at Φ=20° and φ=0° in a section of φ=45° of ODF obtained in a central layer of a sheet thickness.

Provided is a non-oriented electrical steel sheet having such a low Al concentration so that it is excellent in terms of the recycling efficiency of scrap iron and having a high magnetic flux density and low iron loss. The non-oriented electrical steel sheet according to the present invention has a chemical composition containing C; 0.0050 mass % or less, Si; 1.5 mass % to 5.0 mass %, Mn; 0.2 mass % to 3.0 mass %, sol.Al; 0.0030 mass % or less, P; 0.2 mass % or less, S; 0.0050 mass % or less, N; 0.0040 mass % or less, T.Ca; 0.0010 mass % to 0.0080 mass %, T.O; 0.0100 mass % or less, REM; 0.0001 mass % to 0.0050 mass %, and a balance of Fe and inevitable impurities, in which a value of a mass-related fractional expression ((T.Ca+REM)/(T.O+S)), which is a relational expression for the masses of the four constituents described above, that is, T.Ca, REM, T.O, and S, is 0.4 or more.

Non-oriented electrical steel sheet and method for manufacturing slab used as material for the same

In the production of a non-oriented electrical steel sheet by subjecting a steel slab having a certain component composition to a hot rolling, a hot-band annealing, a cold rolling and a finish annealing, the conditions of the finish annealing are controlled such that a yield stress of the steel sheet after the finish annealing is not less than 480 MPa. Also, when a motor core is produced by using the above steel sheet, there can be provided a non-oriented electrical steel sheet capable of producing a rotor core and a stator core as the same raw material where the stator core is subjected to a stress relief annealing at a soaking temperature of 780 to 950° C. in an atmosphere having a nitrogen content of not more than 30 vol % and a dew point of not higher than −20° C., while a motor core is produced with such a steel sheet.

Method for producing non-oriented electrical steel sheet, method for producing motor core, and motor core

Provided is a method of easily producing a non-oriented electrical steel sheet that contains substantially no Al and contains large amounts of Si and Mn and has low iron loss, comprising hot rolling a slab having a specified chemical composition to obtain a hot-rolled sheet; coiling the hot-rolled sheet; cold rolling the hot-rolled sheet once or twice with intermediate annealing being performed therebetween, to obtain a cold-rolled sheet; and subjecting the cold-rolled sheet to final annealing, wherein the hot-rolled sheet after the hot rolling is cooled at an average cooling rate from 800° C. to 650° C. of 30° C./s or more, and thereafter the coiling is performed at 650° C. or less.

Method of producing a non-oriented electrical steel sheet

A grain-oriented electrical steel sheet having an insulating film disposed on a surface thereon. The insulating film having a chemical composition comprising Si, P, O, and at least one selected from the group consisting of Mg, Ca, Ba, Sr, Zn, Al, Mn, and Co. The insulating film has a crystallinity in a range of 20% or more, and a minimum tension provided to the steel sheet by the insulating film at a temperature in a range of 100° C. to 200° C. is 10 MPa or more.

Grain-oriented electrical steel sheet, iron core of transformer, transformer, and method for reducing noise of transformer

Proposed is a non-oriented electrical steel sheet being low in iron loss and excellent in tensile strength and fatigue strength, which has a chemical composition comprising C: not more than 0.005 mass %, Si: 3 to 5 mass %, Mn: not more than 5 mass %, P: not more than 0.1 mass %, S: not more than 0.01 mass %, Al: not more than 3 mass %, N: not more than 0.005 mass %, Zn: 0.0005 mass % to 0.003 mass %, and the remainder being Fe and inevitable impurities, an average crystal grain size being not more than 40 &#x3bc;m, the number of the inclusions having a diameter of not less than 5 &#x3bc;m being not more than 5/mm, a tensile strength being not less than 600 MPa, and the fatigue strength being not less than 450 MPa.

Non-oriented electrical steel sheet

A non-oriented electrical steel sheet with an average magnetostriction &#x3bb;at 400 Hz and 1.0 T of not more than 4.5&#xd7;10, and area ratio of recrystallized grains at a section in rolling direction of steel sheet of 40 to 95% and an average grain size of 10 to 40 &#x3bc;m is obtained by subjecting a steel slab containing, in mass %, C: not more than 0.005%, Si: 2.8 to 6.5%, Mn: 0.05 to 2.0%, Al: not more than 3.0%, P: not more than 0.20%, S: not more than 0.005%, N: not more than 0.005%, Ti: not more than 0.003%, V: not more than 0.005% and Nb: not more than 0.005% and satisfying Si-2Al&#x2014;Mn&#x2265;0 to hot rolling, hot-band annealing, cold rolling and finish annealing under adequate cold rolling and finish annealing conditions, and a motor core is manufactured by such a steel sheet.

Non-oriented electrical steel sheet and method for producing same, and motor core and method for producing same

Provided is a non-oriented electrical steel sheet that contains substantially no Al and contains large amounts of Si and Mn and has low iron loss, comprising a chemical composition containing C: 0.0050% or less, Si: 2.0% or more and 6.0% or less, Mn: 1.0% or more and 3.0% or less, P: 0.20% or less, S: 0.0050% or less, N: 0.0050% or less, Al: 0.0050% or less, and one or more selected from B: 0.0001% or more and 0.0050% or less, Nb: 0.0001% or more and 0.0050% or less, and V: 0.0005% or more and 0.0500% or less, with a balance consisting of Fe and inevitable impurities, wherein a number density of Si&#x2014;Mn nitrides with an average diameter of 50 nm or more and 500 nm or less is 1 or less per &#x3bc;m.

Non-oriented electrical steel sheet and method of producing same

A non-oriented electrical steel sheet with an average magnetostriction &#x3bb;at 400 Hz and 1.0 T of not more than 4.5&#xd7;10, and area ratio of recrystallized grains at a section in rolling direction of steel sheet of 40 to 95% and an average grain size of 10 to 40 &#x3bc;m is obtained by subjecting a steel slab containing, in mass %, C: not more than 0.005%, Si: 2.8 to 6.5%, Mn: 0.05 to 2.0%, Al: not more than 3.0%, P: not more than 0.20%, S: not more than 0.005%, N: not more than 0.005%, Ti: not more than 0.003%, V: not more than 0.005% and Nb: not more than 0.005% and satisfying Si&#x2014;2Al&#x2014;Mn&#x2265;0 to hot rolling, hot-band annealing, cold rolling and finish annealing under adequate cold rolling and finish annealing conditions, and a motor core is manufactured by such a steel sheet.

A non-oriented electrical steel sheet produced by hot rolling a steel slab containing, by mass %, C: not more than 0.0050, Si: 3.2 to 4.5%, Mn: 0.1 to 2.0%, P: not more than 0.020%, As: not more than 0.0030%, Sn+Sb: 0.005 to 0.10%, and one or two elements selected from Mo and W by a content ranging from 0.0020 to 0.10% in total, subjecting the resultant steel sheet to one cold rolling or two or more cold rollings including an intermediate annealing therebetween to achieve a final sheet thickness, and then subjecting the cold rolled sheet to finish annealing, a Ncontent in an atmosphere in the finish annealing is set to not more than 20 vol %, and average strain rate in the first pass is set to not more than 4/sec, allowing the cold rolling property to improve with no degradation in magnetic property and no decrease in productivity.

According to the disclosure, it is possible to increase the magnetic flux density and reduce iron loss by setting a chemical composition containing, by mass %, C: 0.0050% or less, Si: 1.50% or more and 4.00% or less, Al: 0.500% or less, Mn: 0.10% or more and 5.00% or less, S: 0.0200% or less, P: 0.200% or less, N: 0.0050% or less, O: 0.0200% or less, and at least one of Sb: 0.0010% or more and 0.10% or less, and Sn: 0.0010% or more and 0.10% or less, with the balance being Fe and inevitable impurities, an Artransformation temperature of 700&#xb0; C. or higher, a grain size of 80 &#x3bc;m or more and 200 &#x3bc;m or less, and a Vickers hardness of 140 HV or more and 230 HV or less.

A method for producing a non-oriented electrical steel sheet by hot rolling a steel slab having a chemical composition including C: not more than 0.0050 mass %, Si: not more than 4.0 mass %, Mn: 0.03-3.0 mass %, P: not more than 0.1 mass %, Se: not more than 0.0010 mass %, Al: not more than 3.0 mass %, Ni: not more than 3.0 mass %, Cr: not more than 5.0 mass %, Ti: not more than 0.003 mass %, and Nb: not more than 0.003 mass % and subjecting the sheet to hot band annealing if necessary, a cold rolling, and further a finish annealing, wherein the heating in the finish annealing is conducted in two stages of performing induction heating and subsequently a radiation heating and a zone from 600&#xb0; C. to 740&#xb0; C. in the induction heating is heated at an average heating rate of not less than 50&#xb0; C./sec, whereby a high magnetic flux density can be obtained stably.

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Tokyo, Japan

Tomoyuki Okubo