JP2017128759A - Non-oriented magnetic steel sheet and production method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-oriented magnetic steel sheet capable of providing low iron loss even when it is relatively thin and a production method therefor.SOLUTION: The non-oriented magnetic steel sheet has a single phase steel structure consisting of ferritic particles with an average crystal particle diameter of 120 μm or more. The number density of a precipitate with an average particle diameter of 5 nm or more and less than 100 nm is 1×10/mmor less. Hysteresis loss Wrepresented by "W=5×{W×(60/50)-W×(50/60)}" is 0.70 W/kg or less, eddy current loss W/trepresented by "W/t=250×(W/60-W/50)/t" is 1.5 W/kg mm. Wis iron loss [W/kg] at magnetic flux density of 1.0 T and frequency of 50 Hz, Wis iron loss [W/kg] at magnetic flux density of 1.0 T and frequency of 60 Hz and t is sheet thickness of the non-oriented magnetic steel sheet [mm].SELECTED DRAWING: Figure 1

Description

  The present invention relates to a non-oriented electrical steel sheet having a small iron loss. The non-oriented electrical steel sheet obtained by the present invention is suitable for a large rotating machine or an iron core of a generator.

  In accordance with demands for improving the efficiency of various electrical equipment, non-oriented electrical steel sheets used for iron cores are required to have an even lower iron loss. There is a strong demand for relatively thick plate thickness and low iron loss, especially for large rotating machines and generators.

  In order to reduce iron loss, it is common to reduce the hysteresis loss by increasing the crystal grain size or reducing the amount of impurities in the steel. For example, in Patent Document 1, the impurities S, O, and N in steel are reduced, and the average crystal grain size is set within a predetermined range, thereby improving the hysteresis loss and realizing a very small iron loss. Further, Patent Documents 2 to 4 disclose a method of obtaining a large particle size, reducing hysteresis loss, and easily obtaining small iron loss by controlling inclusions and improving grain growth. .

  However, in the conventional non-oriented electrical steel sheet, it is difficult to achieve both a relatively thick plate thickness and a low iron loss. In addition, it is difficult to stably manufacture with an actual machine of, for example, several tens of tons.

JP 59-74258 JP 2001-271147 A JP-A-8-333658 JP 2005-336503 A

L. J. Dijkstra and C. Wert "Effect of inclusions on coercive force of iron," Phys. Rev., vol. 79, pp. 979-985, Sep. 1950. Near angle "physics of ferromagnetic materials" Daejeon "Basics of Magnetic Engineering" R.A.McCurrie, “Ferromagnetic Materials” Fumio Kurosawa, Isamu Taguchi, Ryutaro Matsumoto: Journal of the Japan Institute of Metals, 43 (1979), p. 1068

  An object of this invention is to provide the non-oriented electrical steel plate which can obtain a low iron loss even when it is comparatively thick, and its manufacturing method.

  The present invention is a non-oriented electrical steel sheet with reduced hysteresis loss and eddy current loss, and a method for producing the same. In order to reduce hysteresis loss, the chemical composition, the average crystal grain size of ferrite, and the number density of fine precipitates are appropriately controlled. Further, in order to reduce eddy current loss, it is important to reduce strain remaining in the non-oriented electrical steel sheet.

  The outline of the present invention is as follows.

(1) In mass%,
C: 0.005% or less,
Si: 2.0% to 3.5%,
Mn: 0.1% to 1.5%,
Al: 0.3% to 1.5%
S: 0.004% or less,
N: 0.004% or less,
Ti: 0.004% or less,
P: 0.0% to 0.2%,
Sn: 0.00% to 0.15%,
Sb: 0.00% to 0.15%,
REM: 0.00% to 0.03%,
Ca: 0.00% to 0.01%, and the balance: Fe and impurities,
Having a chemical composition represented by
It has a single-phase steel structure consisting of ferrite grains having an average crystal grain size of 120 μm or more,
The number density of precipitates having an average particle size of 5 nm or more and less than 100 nm is 1 × 10 ¹⁰ pieces / mm ³ or less,
Hysteresis loss W _h represented by Formula 1: 0.70 W / kg or less, and Eddy current loss W _e / t ² represented by Formula ² : 1.5 W / kg · mm ² or less,
A non-oriented electrical steel sheet characterized by having a magnetic property represented by:
W _h = 5 × {W _10/50 × (60/50) −W _10/60 × (50/60)} Equation 1
W _e / t ² = 250 × (W _10/60 / 60−W _10/50 / 50) / t ² Formula 2
(W _10/50 is the iron loss [W / kg] when the magnetic flux density is 1.0 T and the frequency is 50 Hz, and W _10/60 is the iron loss when the magnetic flux density is 1.0 T and the frequency is 60 Hz [ W / kg], and t is the thickness [mm] of the non-oriented electrical steel sheet.)

(2) In the chemical component,
P: 0.01% to 0.2%
Sn: 0.01% to 0.15%,
Sb: 0.01% to 0.15%,
REM: 0.001% to 0.03%, or Ca: 0.0003% to 0.01%,
Or any combination of these is satisfy | filled, The non-oriented electrical steel sheet as described in (1) characterized by the above-mentioned.

(3) The sheet thickness is 0.49 mm or more, the maximum magnetic flux density is 1.0 T, the excitation loss is 50 Hz, and the iron loss W _10/50 is 1.00 W / kg or less (1) or ( The non-oriented electrical steel sheet according to 2).

(4) A step of obtaining a slab by casting steel;
Cooling the slab to a temperature of 150 ° C. to 400 ° C .;
Inserting the slab into a heating furnace and heating to a temperature of 1030 ° C. to 1130 ° C .;
Subjecting the slab to hot rolling to obtain a hot rolled steel sheet;
Annealing the hot-rolled steel sheet to obtain a hot-rolled annealed steel sheet,
Cold-rolling the hot-rolled annealed steel sheet to obtain a cold-rolled steel sheet;
Applying a final annealing to the cold-rolled steel sheet;
Have
The steel is in mass%
C: 0.005% or less,
Si: 2.0% to 3.5%,
Mn: 0.1% to 1.5%,
Al: 0.3% to 1.5%
S: 0.004% or less,
N: 0.004% or less,
Ti: 0.004% or less,
P: 0.0% to 0.2%,
Sn: 0.00% to 0.15%,
Sb: 0.00% to 0.15%,
REM: 0.00% to 0.03%,
Ca: 0.00% to 0.01%, and the balance: Fe and impurities,
Having a chemical composition represented by
The said cold-rolled steel plate satisfies Formula 3, The manufacturing method of the non-oriented electrical steel plate characterized by the above-mentioned.
0.005 mm ≦ t _c − (t _w1 + t _w2 ) /2≦0.015 mm (formula 3)
(T _c is the average sheet thickness [mm] in the center of the cold rolled steel sheet in the sheet width direction, and t _w1 is the average sheet thickness [mm at a position 15 mm from one end in the sheet width direction of the cold rolled steel sheet. And t _w2 is an average plate thickness [mm] at a position of 15 mm from the other end in the plate width direction of the cold-rolled steel plate.)

(5) A step of obtaining a slab by casting steel;
Cooling the slab to a temperature of 150 ° C. to 400 ° C .;
Inserting the slab into a heating furnace and heating to a temperature of 1030 ° C. to 1250 ° C .;
Subjecting the slab to hot rolling to obtain a hot rolled steel sheet;
Annealing the hot-rolled steel sheet to obtain a hot-rolled annealed steel sheet,
Cold-rolling the hot-rolled annealed steel sheet to obtain a cold-rolled steel sheet;
Applying a final annealing to the cold-rolled steel sheet;
Have
The steel is in mass%
C: 0.005% or less,
Si: 2.0% to 3.5%,
Mn: 0.1% to 1.5%,
Al: 0.3% to 1.5%
S: 0.004% or less,
N: 0.004% or less,
Ti: 0.004% or less,
P: 0.0% to 0.2%,
Sn: 0.00% to 0.15%,
Sb: 0.00% to 0.15%,
REM: 0.00% to 0.03%,
Ca: 0.00% to 0.01%, and the balance: Fe and impurities,
Having a chemical composition represented by
In the chemical component,
REM: 0.001% to 0.03%, or Ca: 0.0003% to 0.01%,
Or any combination of these is satisfied,
The said cold-rolled steel plate satisfies Formula 3, The manufacturing method of the non-oriented electrical steel plate characterized by the above-mentioned.
0.005 mm ≦ t _c − (t _w1 + t _w2 ) /2≦0.015 mm (formula 3)
(T _c is the average sheet thickness [mm] in the center of the cold rolled steel sheet in the sheet width direction, and t _w1 is the average sheet thickness [mm at a position 15 mm from one end in the sheet width direction of the cold rolled steel sheet. And t _w2 is an average plate thickness [mm] at a position of 15 mm from the other end in the plate width direction of the cold-rolled steel plate.)

  According to the present invention, since the chemical composition, the steel structure, the number density of precipitates of a predetermined size, and the like are appropriate, a low iron loss can be obtained even when the deposit is relatively thick.

Hysteresis loss W _h, eddy current loss W _e / t ^2, is a diagram showing the relationship between iron loss W _10/50. Is a graph showing the relationship between the average crystal grain size and the hysteresis loss W _h ferrite. Is a diagram showing the relationship between the number density N and the hysteresis loss W _h has been reached. Is a graph showing changes in the hysteresis loss W _h before and after annealing. Is a graph showing changes in eddy current loss W _e / t ² before and after annealing. It is a diagram showing the relationship between the thickness reduction amount and the eddy current loss W _e / t ² of the cold-rolled steel plate.

First, the magnetic properties of the non-oriented electrical steel sheet according to the embodiment of the present invention will be described based on experiments conducted by the present inventors. Non-oriented electrical steel sheet according to the present embodiment, hysteresis loss W _h formula 1: 0.70 W / kg or less, and the eddy currents represented by the formula 2 loss W _e / t ^2: 1.5W / It has a magnetic characteristic represented by kg · mm ² or less.
W _h = 5 × {W _10/50 × (60/50) −W _10/60 × (50/60)} Equation 1
W _e / t ² = 250 × (W _10/60 / 60−W _10/50 / 50) / t ² Formula 2
(W _10/50 is the iron loss [W / kg] when the magnetic flux density is 1.0T and the frequency is 50 Hz, and W _10/60 is the magnetic flux density when the magnetic flux density is 1.0T and the frequency is 60 Hz. Iron loss [W / kg], t is the thickness [mm] of the non-oriented electrical steel sheet.)

(Experiment 1)
The inventors of the present invention produced a non-oriented electrical steel sheet by using a cold rolled steel sheet having a chemical composition shown in Table 1 and a thickness of 0.5 mm as a raw material, followed by finish annealing. The balance of the chemical composition shown in Table 1 is Fe and impurities. Finish annealing is performed in a continuous furnace, the soaking temperature is changed in the range of 1050 ° C. to 1075 ° C., the soaking time is kept constant for 30 seconds, and the tension applied to the cold rolled steel sheet in the furnace is 2.0 N. / Mm ^{2 to} 4.0 N / mm ² . The cross-sectional structure of the non-oriented electrical steel sheet was a ferrite single phase, and the average crystal grain size of ferrite was in the range of 100 μm to 200 μm. A sample for magnetic measurement was cut out from the obtained non-oriented electrical steel sheet and subjected to magnetic measurement. The iron loss W _10/50, the iron loss W _10/60 were measured to determine the eddy current loss W _e / t ² normalized by the formulas 1 and 2 in the hysteresis loss W _h and steel plate thickness.

FIG. 1 shows the relationship between hysteresis loss W _h , eddy current loss W _e / t ² , and iron loss W _10/50 . As shown in FIG. 1, both the hysteresis loss W _h and the eddy current loss W _e / t ² were changed by changing the finish annealing conditions. Even if the chemical composition, that is, the specific resistance was constant and the plate thickness was constant, the eddy current loss W _e / t ² changed.

From FIG. 1, if the eddy current loss W _e / t ² is the same, the iron loss W _10/50 decreases rapidly when the hysteresis loss W _h becomes 0.70 W / kg or less, and the eddy current loss W _e It can be seen that the iron loss W _10/50 is effectively reduced when / t ² is 1.5 W / kg · mm ² or less. Therefore, in the embodiment of the present invention, in order to obtain a low iron loss W _10/50 , the hysteresis loss W _h is 0.70 W / kg or less, and the eddy current loss W _e / t ² is 1.5 W / kg · mm. ² or less.

<Reduced hysteresis loss>
Next, conditions for realizing a hysteresis loss W _h of 0.70 W / kg or less will be described.

(Experiment 2)
The inventors melted steel having the chemical composition shown in Table 2 in a laboratory vacuum melting furnace, cast this into a slab, and performed hot rolling of the slab under the conditions shown in Table 3. A plurality of hot-rolled steel sheets were obtained. The balance of the chemical composition shown in Table 2 is Fe and impurities. And the number density N of the precipitate whose average particle diameter in each hot-rolled steel plate is 5 nm or more and less than 100 nm was determined by the method described later. The results are also shown in Table 3.

Also, hot-rolled steel sheets are pickled and cold-rolled to form 0.5 mm-thick cold-rolled steel sheets, and finish annealing is performed at a soaking temperature of 950 ° C, 1000 ° C or 1050 ° C, and a soaking time of 30 seconds. And the non-oriented electrical steel sheet was manufactured. The obtained non-oriented electrical steel sheet was subjected to magnetic measurement, and the hysteresis loss W _h was calculated by the method described above. Further, the average crystal grain size of ferrite was determined by measuring the average number of crystal grains per unit area from the cross-sectional metal structure based on JIS G0551.

FIG. 2 shows the ferrite when the number density N is 0.65 × 10 ¹⁰ pieces / mm ³ of hot-rolled steel plate C1 and 1.2 × 10 ¹⁰ pieces / mm ³ of hot-rolled steel plate C3. The relationship between the average crystal grain size and the hysteresis loss W _h is shown. In both hot-rolled steel plates C1 and C3, the average crystal grain size of ferrite increased, and the hysteresis loss W _h decreased, approaching a substantially constant value with a size of 120 μm or more. The hysteresis loss W _h reached by the hot-rolled steel sheet C1 having a lower number density N was smaller.

Regarding the hot-rolled steel sheets C2 and C4, the relationship between the average crystal grain size of ferrite and the hysteresis loss W _h was investigated, and the average crystal grain size of ferrite at which the hysteresis loss W _h was substantially constant was determined. Similar to the rolled steel plates C1 and C3, the size of 120 μm or more approached a substantially constant value. Therefore, if the average crystal grain size of ferrite is 180 μm, it is presumed that the hysteresis loss W _h has reached a certain value, and the number loss N when the average crystal grain size is 180 μm and the hysteresis loss W reached. The relationship with _h was investigated. The result is shown in FIG. From FIG. 3, it can be seen that when the number density N is 1.0 × 10 ¹⁰ pieces / mm ³ or less, the hysteresis loss W _h is significantly reduced.

  From the above results, in the embodiment of the present invention, the average crystal grain size of ferrite and the number density N of precipitates having an average grain size of 5 nm or more and less than 100 nm are limited as follows.

As can be seen from FIG. 2, since the average crystal grain size of ferrite is 120 μm or more and the hysteresis loss W _h is a constant value, the steel structure is composed of a single phase of ferrite, and the average crystal grain size of ferrite is preferably 120 μm or more. Is 150 μm or more. An upper limit is not specified, but if the average crystal grain size is too large, eddy current loss increases, so 200 μm or less is preferable. It is also effective to adjust to the optimum size according to the drive frequency of the application destination. The average crystal grain size of ferrite is obtained by measuring the average number of crystal grains per unit area of the cross-sectional metal structure based on JIS G0551.

The number density N of precipitates having an average particle diameter of 5 nm or more and less than 100 nm is 1.0 × 10 ¹⁰ pieces / mm ³ or less. The hysteresis loss W _h is influenced by the precipitate because the domain wall movement is hindered by the precipitate. Non-Patent Document 1 states that the hysteresis loss W _h is maximized when the size of the precipitate is equal to the domain wall thickness. Since the domain wall thickness of Fe is 40 nm to 100 nm (Non-Patent Document 2, Non-Patent Document 3, and Non-Patent Document 4), the number density N of precipitates having an average particle diameter of 5 nm or more and less than 100 nm is the hysteresis loss W _It is thought that it had a big influence on _h . The number density N of the precipitates is measured by, for example, collecting a replica after etching the test material by the method described in Non-Patent Document 5, observing the precipitates using a transmission electron microscope, and measuring the precipitates. .

<Reduction of eddy current loss>
Next, conditions for realizing an eddy current loss W _e / t ² of 1.5 W / kg · mm ² or less will be described.

(Experiment 3)
The inventors cut out Epstein test pieces from the non-oriented electrical steel sheet having a thickness of 0.5 mm manufactured in Experiment 1 and bound them, using a box furnace, soaking temperatures of 750 ° C. and 850 ° C. Then, strain relief annealing was performed with a soaking time of 2 hours. The change in the hysteresis loss W _h before and after annealing are shown in FIG. 4 shows the change in the eddy current loss W _e / t ² normalized by the steel sheet thickness before and after annealing in FIG. Hysteresis loss W _h does not change significantly even when strain relief annealing is performed, but the maximum value of eddy current loss W _e / t ² normalized by the steel plate thickness decreases with strain relief annealing. The variation was reduced. When the tested non-oriented electrical steel sheet is manufactured, finish annealing is performed at 1050 ° C. or higher, and crystal grains do not grow in strain relief annealing at 850 ° C. or lower. In the strain relief annealing, there is no change in the steel structure and only the residual strain in the non-oriented electrical steel sheet disappears. Therefore, reducing the residual strain introduced into the non-oriented electrical steel sheet in the manufacturing process is effective in reducing the eddy current loss W _e / t ² . In order to reduce the residual strain in the manufacturing process, it is preferable to appropriately control the shape of the cold-rolled steel sheet used for finish annealing, the cooling rate, variations in the steel sheet, tension, catenary, and the like. Details of the manufacturing method will be described later.

  Next, the non-oriented electrical steel sheet according to the embodiment of the present invention and the chemical composition of the steel used for manufacturing the steel sheet will be described. Although details will be described later, the non-oriented electrical steel sheet according to the embodiment of the present invention is manufactured through steel casting, cooling, heating, hot rolling, annealing, cold rolling, finish annealing, and the like. Therefore, the chemical composition of the non-oriented electrical steel sheet and steel takes into account not only the properties of the non-oriented electrical steel sheet but also these treatments. In the following description, “%”, which is a unit of content of each element contained in a non-oriented electrical steel sheet or steel, means “mass%” unless otherwise specified. The non-oriented non-oriented electrical steel sheet according to the present embodiment or the steel used for manufacturing the non-oriented non-oriented electrical steel sheet is mass%, C: 0.005% or less, Si: 2.0% to 3.5%, Mn: 0.1%. -1.5%, Al: 0.3-1.5%, S: 0.004% or less, N: 0.004% or less, Ti: 0.004% or less, P: 0.0% -0 0.2%, Sn: 0.00% to 0.15%, Sb: 0.00% to 0.15%, rare earth metal (REM): 0.00% to 0.03%, Ca: It has a chemical composition represented by 0.00% to 0.01% and the balance: Fe and impurities. REM is a generic name for a total of 17 elements including 15 elements from La with atomic number 57 to Lu with 71 and Sc with atomic number 21 and Y with atomic number 39. Examples of the impurities include those contained in raw materials such as ore and scrap and those contained in the manufacturing process.

<C: 0.005% or less>
C deteriorates iron loss and also causes magnetic aging. Therefore, the lower the C content, the better. Such a phenomenon is remarkable when the C content exceeds 0.005%. Therefore, the C content is 0.005% or less, preferably 0.003% or less, and more preferably 0.002% or less.

<Si: 2.0 to 3.5%>
Si increases the specific resistance of steel and reduces iron loss. If the Si content is less than 2.0%, these effects cannot be obtained sufficiently. Accordingly, the Si content is set to 2.0% or more, preferably 2.5% or more, and more preferably 2.9% or more. On the other hand, if the Si content exceeds 3.5%, the steel becomes brittle and the rollability deteriorates. Therefore, the Si content is 3.5% or less, preferably 3.2% or less.

<Mn: 0.1% to 1.5%>
Mn has the effect of preventing the fine precipitation of sulfide during hot rolling by increasing the solution temperature of MnS as well as increasing the specific resistance of steel. If the Mn content is less than 0.1%, these effects cannot be obtained sufficiently. Therefore, the Mn content is 0.1% or more, preferably 0.2% or more, more preferably 0.3% or more, and still more preferably 0.4% or more. On the other hand, if the Mn content exceeds 1.5%, the cost increases. Therefore, the Mn content is 1.5% or less, preferably 1.4% or less, more preferably 1.2% or less, and still more preferably 1.0% or less.

<Al: 0.3 to 1.5%>
Al is effective as a deoxidizing material, and nitrogen can be fixed by forming coarse AlN. Furthermore, like Si and Mn, the specific resistance of steel is increased and the iron loss is reduced. If the Al content is less than 0.3%, these effects cannot be obtained sufficiently. Therefore, the Al content is 0.3% or more. On the other hand, if the Al content exceeds 1.5%, the steel becomes brittle and the rollability deteriorates. Therefore, the Al content is 1.5% or less, preferably 1.0% or less, and more preferably 0.7% or less.

<S: 0.004% or less>
S is not an essential element but is contained as an impurity in steel, for example. S forms fine precipitates together with Mn, Cu, Mg, etc., and adversely affects the magnetic properties. Therefore, the lower the S content, the better. Such an adverse effect on the magnetic properties is significant when the S content exceeds 0.004%. Therefore, the S content is 0.004% or less.

<N: 0.004% or less>
N is not an essential element but is contained as an impurity in steel, for example. N forms fine precipitates together with Al and Ti, and adversely affects the magnetic properties. Therefore, the lower the N content, the better. Such an adverse effect on the magnetic properties is significant when the N content exceeds 0.004%. Therefore, the N content is 0.004% or less.

<Ti: 0.004% or less>
Ti is not an essential element but is contained as an impurity in steel, for example. Ti forms nitrides and carbides and adversely affects magnetic properties. Therefore, the lower the Ti content, the better. Such an adverse effect on the magnetic properties is significant when the Ti content exceeds 0.004%. Therefore, the Ti content is 0.004% or less.

  P, Sn, Sb, REM, and Ca are not essential elements, but are arbitrary elements that may be appropriately contained in a non-oriented electrical steel sheet within a predetermined amount.

<P: 0.0% to 0.2%>
P has the effect of increasing the mechanical strength of the steel and improving the texture. Therefore, P may be contained. In order to sufficiently obtain this effect, the P content is preferably 0.01% or more. On the other hand, if the P content exceeds 0.2%, the steel becomes brittle. Therefore, the P content is 0.2% or less.

<Sn: 0.00% to 0.15%, Sb: 0.00% to 0.15%>
Sn and Sb improve the texture and increase the magnetic flux density. Therefore, Sn or Sb or both of them may be contained. In order to sufficiently obtain this action effect, preferably, the Sn content is 0.01% or more, the Sb content is 0.01% or more, and more preferably, the Sn content is 0.03% or more. Yes, the Sb content is 0.03% or more. On the other hand, if the Sn content exceeds 0.15%, the steel becomes brittle or the adhesiveness of the insulating coating deteriorates. Therefore, the Sn content is 0.15% or less. If the Sb content exceeds 0.15%, the adhesiveness of the insulating coating deteriorates. Therefore, the Sb content is 0.15% or less.

<REM: 0.00% to 0.03%, Ca: 0.00% to 0.01%>
REM and Ca fix coarse S by forming coarse sulfates and sulfides, and suppress the production of fine sulfides. As a result, the grain growth property is improved, and there is no obstacle to the domain wall movement, and the hysteresis loss is improved. Therefore, REM or Ca or both of these may be contained. In order to obtain this effect sufficiently, the REM content is preferably 0.001% or more, the Ca content is 0.0003% or more, and more preferably, the REM content is 0.003% or more. Yes, the Ca content is 0.001% or more. On the other hand, if the REM content exceeds 0.03%, the volume fraction of inclusions containing REM increases, resulting in deterioration of grain growth and increase in hysteresis loss. Therefore, the REM content is 0.03% or less, preferably 0.01% or less. If the Ca content exceeds 0.01%, the volume fraction of inclusions containing Ca increases, resulting in deterioration of grain growth and increase in hysteresis loss. Therefore, the Ca content is 0.01% or less, preferably 0.005% or less.

  Therefore, P: 0.01% to 0.2%, Sn: 0.01% to 0.15%, Sb: 0.01% to 0.15%, REM: 0.001% to 0.03%, Alternatively, it is preferable that Ca: 0.0003% to 0.01% or any combination thereof is satisfied.

According to the present embodiment, it is possible to stably obtain a low iron loss, satisfy the needs of consumers, and answer energy saving requirements. For example, it is possible to obtain characteristics in which the plate thickness is 0.49 mm or more, the maximum magnetic flux density is 1.0 T, the excitation frequency is 50 Hz, and the iron loss W _10/50 is 1.00 W / kg or less.

Next, the manufacturing method of the non-oriented electrical steel sheet which concerns on embodiment of this invention is demonstrated. In the method for producing a non-oriented electrical steel sheet according to the present embodiment, steel is cast to obtain a slab, the slab is cooled to a temperature of 150 ° C. or higher and 400 ° C. or lower, and the slab is inserted into a heating furnace to be 1030 ° C. or higher. Heat to a temperature of 1130 ° C. Thereafter, the slab is hot-rolled to obtain a hot-rolled steel plate, the hot-rolled steel plate is annealed to obtain a hot-rolled annealed steel plate, and the hot-rolled annealed steel plate is cold-rolled to cold-rolled steel plate Get. Then, finish annealing is performed on the cold-rolled steel sheet. The cold-rolled steel sheet satisfies Equation 3.
0.005 mm ≦ t _c − (t _w1 + t _w2 ) /2≦0.015 mm (formula 3)
(T _c is the average sheet thickness [mm] in the center of the cold rolled steel sheet in the sheet width direction, and t _w1 is the average sheet thickness [mm at a position 15 mm from one end in the sheet width direction of the cold rolled steel sheet. And t _w2 is an average plate thickness [mm] at a position of 15 mm from the other end in the plate width direction of the cold-rolled steel plate.)

In the present embodiment, as described above, in order to reduce the hysteresis loss W _h , it is important to control the number density N of precipitates having an average particle diameter of 5 nm or more and less than 100 nm. Therefore, the slab is cooled to 400 ° C. or lower, preferably 300 ° C. or lower for the purpose of growing the precipitate in the slab after casting as coarse as possible. On the other hand, when it is cooled to 150 ° C. or lower, the slab is easily cracked. Therefore, the temperature which cools a slab shall be 150 degreeC or more. And the slab whose temperature is 150 to 400 degreeC is inserted in a heating furnace.

In the heating furnace, the slab is heated to a temperature of 1030 ° C to 1130 ° C. When the slab heating temperature is higher than 1130 ° C., impurities such as sulfides are re-dissolved, and the impurities are finely precipitated as the temperature lowers thereafter. This impairs grain growth and increases the hysteresis loss W _h . Therefore, the slab heating temperature is 1130 ° C. or lower, preferably 1120 ° C. or lower, more preferably 1100 ° C. or lower. On the other hand, when the slab heating temperature is lower than 1030 ° C., the hot rolling ability is reduced. Therefore, the slab heating temperature is set to 1030 ° C or higher, preferably 1050 ° C or higher, more preferably 1080 ° C or higher.

  When steel contains 0.001% to 0.03% REM, 0.0003% to 0.01% Ca, or both, the melting temperature of inclusions with impurities increases, and 1250 ° C. Even if heated up to, re-dissolving hardly occurs. Therefore, the slab heating temperature in this case is good also as 1030 degreeC-1250 degreeC.

  In addition, as explained earlier, eddy current loss changes even if the chemical composition and thickness of the non-oriented electrical steel sheet are constant, and in order to reduce eddy current loss, residual strain is reduced in the manufacturing process. It is important to let As a result of examining a method for reducing the residual strain in the manufacturing process of the non-oriented electrical steel sheet, the present inventors preferably perform the finish annealing after the cold rolling in a continuous annealing furnace, and perform the cold annealing used for the finish annealing. It has been found that it is effective to slightly reduce the thickness of both end portions in the width direction of the rolled steel sheet.

(Experiment 4)
The present inventors annealed a cold rolled steel sheet having a thickness of 0.5 mm, a width of 950 mm to 1150 mm, and a target component of 3% Si-0.15% Mn-1.15% Al using a continuous annealing furnace of an actual machine. in the case of, to investigate the relationship between the eddy current loss W _e / t ² normalized by the thickness reduction amount and the steel sheet thickness at both ends. The result is shown in FIG. Here, the thickness reduction at both ends is the average plate thickness t _c [mm] at the center in the plate width direction of the cold rolled steel plate, and the average plate thickness at a position 15 mm from one end in the plate width direction is t _w1. [Mm], where the average plate thickness at a position 15 mm from the other end is t _w2 [mm], and is expressed by t _c − (t _w1 + t _w2 ) / 2.

FIG. 6 shows that the eddy current loss W _e / t ² normalized by the steel plate thickness decreases as the thickness reduction at both ends increases, and the variation becomes smaller. This effect was observed when the amount of thickness reduction was 0.005 mm or more, and was found to be saturated when it exceeded 0.015 mm. On the other hand, when the thickness reduction amount is too large, the yield decreases. Therefore, the thickness reduction amount of the cold rolled steel sheet is 0.005 mm or more, preferably 0.010 mm or more. Moreover, the thickness reduction amount of a cold rolled steel plate shall be 0.015 mm or less.

  Thus, the non-oriented electrical steel sheet according to the present embodiment can be manufactured.

  The above-described embodiments are merely examples of implementation in carrying out the present invention, and the technical scope of the present invention should not be construed in a limited manner. That is, the present invention can be implemented in various forms without departing from the technical idea or the main features thereof.

  Next, examples of the present invention will be described. The conditions in the examples are one condition example adopted to confirm the feasibility and effects of the present invention, and the present invention is not limited to this one condition example. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

<Example 1>
The slab having the chemical composition shown in Table 4 is cooled after casting, inserted into a slab heating furnace in the range of 200 ° C to 280 ° C, the heating temperature is 1080 ° C to 1100 ° C, and the plate thickness after finish rolling is 2.0 mm. Hot rolling was performed. Then, hot-rolled sheet annealing was performed at 970 ° C. for 1 minute, and after pickling, cold-rolled steel sheets of 0.35 mm, 0.49 mm, 0.5 mm, and 0.55 mm were obtained by cold rolling. The amount of thickness reduction of the cold rolled steel sheet was set to 0.01 mm to 0.015 mm. Thereafter, it was subjected to finish annealing with a soaking temperature of 1000 ° C. and a soaking time of 30 seconds to obtain a non-oriented electrical steel sheet product. The balance of the chemical composition shown in Table 4 is Fe and impurities. The underline in Table 4 indicates that the numerical value is out of the scope of the present invention. In some samples, nozzle clogging occurred during continuous casting and steel could not be produced, and in some other samples, cracks occurred during cold rolling.

Then, the average crystal grain size of the ferrite of the product, the number density N of precipitates, the hysteresis loss W _h, eddy current loss is normalized by the steel sheet thickness W _e / t ^2, the iron loss W _10/50, iron loss W _{10 / 60} was measured. The results are shown in Table 5. The underline in Table 5 indicates that the numerical value is out of the scope of the present invention.

As shown in Table 5, in the samples D1 to D16 within the scope of the present invention, the hysteresis loss W _h is 0.70 W / kg or less, although the plate thickness is relatively thick as 0.49 mm or more, and the eddy current The loss W _e / t ² was 1.5 W / kg · mm ² or less, and the iron loss W _10/50 was an excellent characteristic of 1.0 W / kg or less. On the other hand, in the samples E1 to E12 outside the scope of the present invention, sufficient magnetic properties were not obtained or trouble occurred during the production.

From this result, according to the present invention, the hysteresis loss W _h is 0.70 W / kg or less and the eddy current normalized by the steel plate thickness even for the non-oriented electrical steel plate having a relatively thick plate thickness of 0.49 mm or more. It can be seen that a loss W _e / t ² of 1.5 W / kg · mm ² or less is obtained and an excellent characteristic that an iron loss W _10/50 of 1.0 W / kg or less is obtained.

<Example 2>
A slab having a chemical composition shown in Table 6 was cast, hot-rolled under the conditions shown in Table 7, subjected to hot-rolled sheet annealing at 970 ° C. for 1 minute, pickled, and then cold-rolled to 0.5 mm. A cold rolled steel sheet was obtained. Table 7 also shows the thickness reduction of the cold rolled steel sheet. Thereafter, it was subjected to finish annealing with a soaking temperature of 1000 ° C. and a soaking time of 30 seconds to obtain a non-oriented electrical steel sheet product. The balance of the chemical composition shown in Table 6 is Fe and impurities. The underline in Table 7 indicates that the numerical value is out of the scope of the present invention. In some samples, cracks occurred, and in some other samples, coil winding defects occurred.

Then, the average crystal grain size of the ferrite of the product, the number density N of precipitates, the hysteresis loss W _h, eddy current loss is normalized by the steel sheet thickness W _e / t ^2, the iron loss W _10/50, iron loss W _{10 / 60} was measured. The results are shown in Table 8. The underline in Table 8 indicates that the numerical value is out of the scope of the present invention.

As shown in Table 8, the samples F1~F7 are within the scope of the present invention, the hysteresis loss W _h is 0.70 W / kg or less, eddy current loss W _e / t ² is 1.5W / kg · mm ² or less The iron loss W _10/50 was as excellent as 1.0 W / kg or less. On the other hand, in samples G1 to G6 outside the scope of the present invention, sufficient magnetic properties could not be obtained, or trouble occurred during production.

From this result, it can be seen that according to the present invention, excellent characteristics with an iron loss W _10/50 of 1.0 W / kg or less can be obtained.

<Example 3>
A slab having a chemical composition shown in Table 9 was cast, hot-rolled under the conditions shown in Table 10, and the same evaluation as in Example 2 was performed. The results are shown in Table 11. Underlines in Tables 10 and 11 indicate that the numerical values are out of the scope of the present invention.

As shown in Table 11, in the samples H1 to H2 within the scope of the present invention, the hysteresis loss W _h is 0.70 W / kg or less, and the eddy current loss W _e / t ² is 1.5 W / kg · mm ² or less. The iron loss W _10/50 was as excellent as 1.0 W / kg or less. On the other hand, sample J1 outside the range of the present invention could not obtain sufficient magnetic properties.

From this result, it can be seen that according to the present invention, excellent characteristics with an iron loss W _10/50 of 1.0 W / kg or less can be obtained.

Claims (5)

% By mass
C: 0.005% or less,
Si: 2.0% to 3.5%,
Mn: 0.1% to 1.5%,
Al: 0.3% to 1.5%
S: 0.004% or less,
N: 0.004% or less,
Ti: 0.004% or less,
P: 0.0% to 0.2%,
Sn: 0.00% to 0.15%,
Sb: 0.00% to 0.15%,
REM: 0.00% to 0.03%,
Ca: 0.00% to 0.01%, and the balance: Fe and impurities,
Having a chemical composition represented by
It has a single-phase steel structure consisting of ferrite grains having an average crystal grain size of 120 μm or more,
The number density of precipitates having an average particle size of 5 nm or more and less than 100 nm is 1 × 10 ¹⁰ pieces / mm ³ or less,
Hysteresis loss W _h represented by Formula 1: 0.70 W / kg or less, and Eddy current loss W _e / t ² represented by Formula ² : 1.5 W / kg · mm ² or less,
A non-oriented electrical steel sheet characterized by having a magnetic property represented by:
W _h = 5 × {W _10/50 × (60/50) −W _10/60 × (50/60)} Equation 1
W _e / t ² = 250 × (W _10/60 / 60−W _10/50 / 50) / t ² Formula 2
(W _10/50 is the iron loss [W / kg] when the magnetic flux density is 1.0 T and the frequency is 50 Hz, and W _10/60 is the iron loss when the magnetic flux density is 1.0 T and the frequency is 60 Hz [ W / kg], and t is the thickness [mm] of the non-oriented electrical steel sheet.) In the chemical component,
P: 0.01% to 0.2%
Sn: 0.01% to 0.15%,
Sb: 0.01% to 0.15%,
REM: 0.001% to 0.03%, or Ca: 0.0003% to 0.01%,
Or the arbitrary combination of these is satisfy | filled, The non-oriented electrical steel sheet of Claim 1 characterized by the above-mentioned. 3. The iron loss W _10/50 having a plate thickness of 0.49 mm or more, a maximum magnetic flux density of 1.0 T, and an excitation frequency of 50 Hz is 1.00 W / kg or less. Non-oriented electrical steel sheet. A process of casting steel to obtain a slab;
Cooling the slab to a temperature of 150 ° C. to 400 ° C .;
Inserting the slab into a heating furnace and heating to a temperature of 1030 ° C. to 1130 ° C .;
Subjecting the slab to hot rolling to obtain a hot rolled steel sheet;
Annealing the hot-rolled steel sheet to obtain a hot-rolled annealed steel sheet,
Cold-rolling the hot-rolled annealed steel sheet to obtain a cold-rolled steel sheet;
Applying a final annealing to the cold-rolled steel sheet;
Have
The steel is in mass%
C: 0.005% or less,
Si: 2.0% to 3.5%,
Mn: 0.1% to 1.5%,
Al: 0.3% to 1.5%
S: 0.004% or less,
N: 0.004% or less,
Ti: 0.004% or less,
P: 0.0% to 0.2%,
Sn: 0.00% to 0.15%,
Sb: 0.00% to 0.15%,
REM: 0.00% to 0.03%,
Ca: 0.00% to 0.01%, and the balance: Fe and impurities,
Having a chemical composition represented by
The said cold-rolled steel plate satisfies Formula 3, The manufacturing method of the non-oriented electrical steel plate characterized by the above-mentioned.
0.005 mm ≦ t _c − (t _w1 + t _w2 ) /2≦0.015 mm (formula 3)
(T _c is the average sheet thickness [mm] in the center of the cold rolled steel sheet in the sheet width direction, and t _w1 is the average sheet thickness [mm at a position 15 mm from one end in the sheet width direction of the cold rolled steel sheet. And t _w2 is an average plate thickness [mm] at a position of 15 mm from the other end in the plate width direction of the cold-rolled steel plate.) A process of casting steel to obtain a slab;
Cooling the slab to a temperature of 150 ° C. to 400 ° C .;
Inserting the slab into a heating furnace and heating to a temperature of 1030 ° C. to 1250 ° C .;
Subjecting the slab to hot rolling to obtain a hot rolled steel sheet;
Annealing the hot-rolled steel sheet to obtain a hot-rolled annealed steel sheet,
Cold-rolling the hot-rolled annealed steel sheet to obtain a cold-rolled steel sheet;
Applying a final annealing to the cold-rolled steel sheet;
Have
The steel is in mass%
C: 0.005% or less,
Si: 2.0% to 3.5%,
Mn: 0.1% to 1.5%,
Al: 0.3% to 1.5%
S: 0.004% or less,
N: 0.004% or less,
Ti: 0.004% or less,
P: 0.0% to 0.2%,
Sn: 0.00% to 0.15%,
Sb: 0.00% to 0.15%,
REM: 0.00% to 0.03%,
Ca: 0.00% to 0.01%, and the balance: Fe and impurities,
Having a chemical composition represented by
In the chemical component,
REM: 0.001% to 0.03%, or Ca: 0.0003% to 0.01%,
Or any combination of these is satisfied,
The said cold-rolled steel plate satisfies Formula 3, The manufacturing method of the non-oriented electrical steel plate characterized by the above-mentioned.
0.005 mm ≦ t _c − (t _w1 + t _w2 ) /2≦0.015 mm (formula 3)
(T _c is the average sheet thickness [mm] in the center of the cold rolled steel sheet in the sheet width direction, and t _w1 is the average sheet thickness [mm at a position 15 mm from one end in the sheet width direction of the cold rolled steel sheet. And t _w2 is an average plate thickness [mm] at a position of 15 mm from the other end in the plate width direction of the cold-rolled steel plate.)

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