JP2008127600A - Non-oriented electromagnetic steel sheet for divided core - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-oriented electromagnetic steel sheet having optimal magnetic properties as a divided core of a motor and a transformer. <P>SOLUTION: A hot-rolled plate of the non-oriented electromagnetic steel sheet has a composition comprising, by mass%, 0.005% or less C, 2 to 4% Si, 1% or less Mn, more than 1 to 2% Al, 0.003 to 0.2% Sn and the balance Fe with unavoidable impurities. The non-oriented electromagnetic steel sheet with a thickness of 0.15 to 0.3 mm is manufactured by the steps of: annealing the hot-rolled plate; cold-rolling the hot-rolled plate once; and subsequently recrystallization-annealing the sheet. Then, the non-oriented electromagnetic steel sheet for the divided core has (i) a recrystallized structure in which a mean crystal grain size is 40 to 200 μm and (ii) the magnetic properties in which magnetic flux density B<SB>50</SB>(C) in a direction of 90 degrees (C direction) with respect to a rolling direction (L direction) and magnetic flux density B<SB>50</SB>(X) in a direction of 45 degrees (X direction) with respect to the rolling direction (L direction) satisfy the following expression (1): B<SB>50</SB>(C)/B<SB>50</SB>(X)≥-0.5333×t<SP>2</SP>+0.3907×t+0.945, wherein (t) represents a sheet thickness (mm). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a non-oriented electrical steel sheet used as a core (iron core) material for a motor or a transformer.

  In recent years, interest in electric vehicles has increased from the viewpoints of environmental protection and energy saving, and drive motors are required to be capable of being driven at a frequency of 400 to several kHz along with high-speed rotation and miniaturization.

  For this reason, in the non-oriented electrical steel sheet that is the core material of the motor, in order to reduce eddy current loss, the sheet thickness is reduced, the specific resistance is increased, and further the steel sheet strength (increasing the rotor rigidity) is improved. Therefore, it is necessary to increase the amount of Si and the amount of Al. Furthermore, non-oriented electrical steel sheets are also required to have a high magnetic flux density in order to improve the initial torque of the motor.

  Motor cores are manufactured by stamping non-oriented electrical steel sheets. Recently, motor cores are individually manufactured in the teeth part from the viewpoint of improving punching yield and reducing winding loss by improving winding efficiency. Tend to consist of split cores. And since a magnetic field is applied to the teeth part of a division | segmentation core in a length direction and a width direction, it is requested | required that magnetic flux density is high.

  Usually, when one motor core is punched from a non-oriented electrical steel sheet, the magnetic properties of the non-oriented electrical steel sheet include the rolling direction of the steel sheet (coil longitudinal direction, hereinafter referred to as “L direction”), L. There is a difference (anisotropy) in the direction perpendicular to the direction (coil width direction, hereinafter referred to as “C direction”), and in the L direction and 45 ° direction (hereinafter also referred to as “X direction”). It is desired to be small (see Patent Documents 1 to 5).

  However, when punching the split core, it is only necessary to punch through the teeth portion along the direction of excellent magnetic properties. Therefore, when using a non-oriented electrical steel sheet exclusively for the split core, the L direction, the C direction, and the X direction The anisotropy of the magnetic characteristics in is not necessarily small. In other words, the larger the magnetic property anisotropy, that is, the improvement of the magnetic properties in the L direction and the C direction at the expense of the magnetic properties in the X direction is required in the tooth portion of the divided core in the design of the divided core. It is preferable in that the magnetic characteristics can be secured.

JP 2001-164343 A JP 2006-45613 A JP 2006-45641 A JP 2006-144036 A JP 2006-199999 A

  The present inventor has a phenomenon that, in a non-oriented electrical steel sheet, in order to enhance magnetic properties, when the thickness of the steel sheet is reduced and the Si content and / or Al content is increased, the magnetic flux density anisotropy is reduced. I noticed. That is, the magnetic flux density in a specific direction, for example, the L direction or the C direction is reduced, and a desired magnetic flux density cannot be obtained. As a result, a non-oriented electrical steel sheet having such magnetic characteristics is suitable for a split core. Encountered the problem of not.

  Then, an object of this invention is to provide the non-oriented electrical steel sheet which has the optimal magnetic characteristic for the division | segmentation cores of a motor or a transformer.

  The inventor of the present invention is a non-oriented electrical steel sheet having a thickness of 0.15 to 0.3 mm containing Si: 2 to 4% and Al: more than 1 to 2% by mass%, and Sn is 0.003. Add 0.2% to increase the number of goth-oriented crystal grains and improve the magnetic properties (magnetic flux density) in the L and C directions, and ensure optimal magnetic properties for the split core. We have studied earnestly about the method. As a result, the following knowledge was obtained.

(X) The difference in magnetic properties (anisotropy) in the L, C, and X directions is closely related to the plate thickness (product plate thickness), the reduction ratio in cold rolling, and the crystal grain size after recrystallization annealing. Although related, finally, if these are controlled, a required magnetic flux density B _{50 having} a large anisotropy (magnetic flux density [T] obtained at a magnetizing force of 5000 A / m) can be secured.

(Y) connecting the magnetic properties of the L direction and the C direction and to reduce the magnetic flux density B ₅₀ in the X direction, because there is a tendency that the magnetic flux density B ₅₀ in the L direction and C direction are improved, the magnetic properties of the X-direction This is an important index for evaluating the magnetic properties of the non-oriented electrical steel sheet for the split core, and needs to be maintained within a predetermined range in relation to the magnetic properties in the C direction.

  This invention was made | formed based on the said knowledge, and the summary is as follows.

(1) By mass%, C: 0.005% or less, Si: 2-4%, Mn: 1% or less, Al: more than 1-2%, Sn: 0.003-0.2%, Thickness: 0.15 to 0.3 mm non-directional, which is manufactured by annealing a hot-rolled sheet consisting of Fe and unavoidable impurities, followed by cold rolling and then recrystallization annealing Electrical steel sheet,
(I) having a recrystallized structure having an average crystal grain size of 40 to 200 μm, and
(Ii) Magnetic flux density B ₅₀ (C) in the rolling direction (L direction) and 90 ° direction (C direction), and magnetic flux density B ₅₀ (X in the rolling direction (L direction) and 45 ° direction (X direction). ) Has a magnetic property satisfying the following formula (1).
B ₅₀ (C) / B ₅₀ (X) ≧ −0.5333 × t ² + 0.3907 × t + 0.945 (1)
Where t: plate thickness (mm)

(2) In the magnetic characteristics, the magnetic flux density B ₅₀ (L) in the rolling direction (L direction) satisfies the following formula (2): steel sheet.
B ₅₀ (L) /Bs≧0.82 (2)
Where Bs: saturation magnetic flux density

(3) The non-oriented electrical steel sheet for split core according to (1) or (2), wherein the iron loss W _10/800 is 40 W / kg or less in the magnetic characteristics.

  (4) The non-oriented electrical steel sheet for split core according to any one of (1) to (3), wherein the cold rolling is lever rolling.

  (5) The non-oriented electrical steel sheet for split core according to any one of (1) to (4), wherein a rolling reduction is 75 to 89% in the cold rolling.

  (6) The non-oriented electrical steel sheet for split core according to any one of (1) to (5), wherein a temperature increase rate is 100 to 5000 ° C./second in the recrystallization annealing.

  (7) The non-oriented electrical steel sheet for split core according to any one of (1) to (6), wherein an annealing temperature of the hot-rolled sheet is higher than 900 ° C.

  ADVANTAGE OF THE INVENTION According to this invention, the non-oriented electrical steel sheet which has the optimal magnetic characteristic as an object for the split cores of a motor or a transformer can be provided. Further, according to the present invention, since the split core can be designed and punched according to the shape of the split core and / or the magnetic characteristics required for the tooth portion of the split core, the utilization of the non-oriented electrical steel sheet Increase.

The present invention contains, in mass%, C: 0.005% or less, Si: 2-4%, Mn: 1% or less, Al: 1 more than 2%, Sn: 0.003-0.2%. Then, after annealing the hot-rolled sheet consisting of Fe and inevitable impurities, the cold rolling is performed once, and then the recrystallization annealing is applied to the non-directional electromagnetic material having a thickness of 0.15 to 0.3 mm. A steel plate,
(I) having a recrystallized structure having an average crystal grain size of 40 to 200 μm, and
(Ii) and C direction (L direction and 90 °) the magnetic flux density B ₅₀ of (C), the magnetic flux density B ₅₀ in the X direction (L direction and 45 °) is (X), the magnetic properties satisfying the following formulas (1) It is characterized by having.
B ₅₀ (C) / B ₅₀ (X) ≧ −0.5333 × t ² + 0.3907 × t + 0.945 (1)
Where t: plate thickness (mm)

B ₅₀ (C) is a magnetic flux density (unit: T) in the C direction measured by being magnetized at 5000 A / m in the C direction on the steel plate surface. B ₅₀ (X) is the magnetic flux density in the X direction measured by magnetization at 5000 A / m in the X direction on the steel plate surface. B ₅₀ (L) is the magnetic flux density in the L direction measured by magnetizing at 5000 A / m in the L direction.

  First, the reason for limiting the component composition of the hot-rolled sheet will be described. Hereinafter, “%” means mass%.

  C is an element that reinforces the steel sheet. However, C is an element harmful in terms of magnetic properties and is preferably reduced as much as possible. Therefore, C is limited to 0.005% or less. Preferably, it is 0.003% or less.

Since Si is an element that increases the electrical resistance of the steel sheet and reduces iron loss, it contains 2% or more. When the content exceeds 4%, the steel sheet is embrittled, and since the required magnetic flux density B ₅₀ is not obtained, and 4% the upper limit of Si.

  Mn is an element that fixes S as MnS at the time of hot rolling and prevents steel plate ear cracks during hot rolling. The solute Mn increases the electrical resistance of the steel sheet and reduces the iron loss. However, if Mn is too much, crystal grain growth is inhibited, so the upper limit of Mn is set to 1%.

  Al, like Si, is an element that increases the electrical resistance of the steel sheet and reduces the iron loss, so it contains more than 1%. However, since the anisotropy of the magnetic flux density tends to decrease as the Al content increases, various measures adopted in the present invention are required. On the other hand, if the content exceeds 2%, there is a concern about the problem of addition cost and a decrease in saturation magnetic flux density, so the upper limit was made 2%.

  Sn increases the number of Goss orientation grains in the reconstituted structure of non-oriented electrical steel sheets containing Si: 2 to 4% and Al: more than 1 to 2%. In particular, the magnetic properties in L direction (magnetic flux density) In order to improve the above, it is necessary to contain 0.003% or more. On the other hand, even if the content exceeds 0.2%, the above improvement effect is saturated and wrinkles increase due to hot brittleness, so the upper limit was made 0.2%.

  In addition to the above elements, the present invention may contain S, P, N, O, Cu, Ni, Cr, Ca, etc. as inevitable impurities as long as the mechanical properties and magnetic properties of the present invention are not impaired. . However, as in the past, it is preferable that S, N, and O as impurities are small. Each of these components is preferably 0.001% or less, 0.0025% or less, and 0.003% or less.

  Further, the ranges where it is confirmed that the target anisotropy is not inhibited are Cu <0.2%, Ni <0.1%, Cr <0.1%, Ca <0.01%, Nb <0. Since 0.002% and Ti <0.003%, these elements are preferably suppressed within the above ranges. Note that Sb should not be added because it reduces anisotropy. When Sb is unavoidably contained, it is preferably less than 0.001%.

  After annealing the hot-rolled sheet having the above component composition, cold rolling is performed once, and then recrystallization annealing is performed to form a recrystallized structure having an average crystal grain size of 40 to 200 μm.

In the present invention, based on the above-described knowledge (x), the average crystal grain size of the recrystallized structure is limited to 40 to 200 μm. When the average grain size is large, the iron loss characteristics are improved, but the anisotropy of the magnetic flux density tends to be small. From this tendency, the average crystal grain is preferably small, but if it is less than 40 μm, the desired high-frequency iron loss W _10/800 cannot be obtained.

On the other hand, when the average crystal grain size exceeds 200 μm, the anisotropy of the magnetic flux density decreases, and it becomes difficult to secure the desired B ₅₀ (C) / B ₅₀ (X) aimed by the present invention. In order to further improve the high-frequency iron loss, the average crystal grain size of the recrystallized structure is preferably 70 to 200 μm.

  The average crystal grain size was obtained by counting and averaging the number of crystal grain boundaries intersecting the line segment in the L direction in the structure obtained by observing the cross section of the steel sheet with an optical microscope.

The present invention is characterized in that a non-oriented electrical steel sheet having a thickness of 0.15 to 0.3 mm having a recrystallized structure having an average crystal grain size of 40 to 200 μm has magnetic properties satisfying the following formula (1). .
B ₅₀ (C) / B ₅₀ (X) ≧ −0.5333 × t ² + 0.3907 × t + 0.945 (1)
Where t: plate thickness (mm)

B ₅₀ (C), B ₅₀ (X), and B ₅₀ (L) are as described above.

B ₅₀ (X) in the X direction is a process in which B ₅₀ (L) in the L direction transitions to B ₅₀ (C) in the C direction (usually B ₅₀ (L)> B ₅₀ (C)). Magnetic flux density B ₅₀ to be connected. The inventor paid attention to B ₅₀ (X) in the X direction.

_{B 50 (C) / B 50} (X) is focused on the X-direction of the B ₅₀ (X), the difference between the B ₅₀ (C) and B ₅₀ (X), an indicator for evaluating in their ratio, Defining this ratio within a predetermined range means that the difference between B ₅₀ (C) and B ₅₀ (X) is suppressed within the predetermined range.

The present inventor has recognized that this is extremely important in determining the appropriateness of the non-oriented electrical steel sheet for the split core for the following reasons, and the non-direction for the split core. "B ₅₀ (C) / B ₅₀ (X)" was introduced as an index for evaluating the magnetic properties of the heat-resistant electrical steel sheet.

  1 (a) and 1 (b) show how the split core is punched. FIG. 1A shows an aspect in which the tooth portion of the split core is set in the C direction (90 degrees with respect to the L direction) and punching is performed with the highest priority on the punching yield (hereinafter sometimes referred to as “punching aspect A”). In FIG. 1B, the tooth portion of the split core is set in the L direction, and punching is performed with emphasis on the core characteristics (magnetic flux density of the tooth portion) as well as the punching yield (hereinafter referred to as “punching mode B”). .)

  Recently, in the field of electric motors, in addition to the conventional integrated core, the number of cases using a split core is increasing from the viewpoint of improving the punching yield and improving copper loss by increasing the efficiency of winding. In many cases, the split core is punched in the punching mode A or the punching mode B with respect to the rolling direction (L direction) of the magnetic steel sheet coil wound in a coil shape after rolling.

  In general, non-oriented electrical steel sheets manufactured industrially have inferior magnetic properties (magnetization characteristics, iron loss characteristics) in the C direction and X direction compared to magnetic characteristics (magnetization characteristics, iron loss characteristics) in the L direction. Yes, the magnetic characteristics in the C direction or the X direction influence the magnetic characteristics of the entire split core iron core.

  The flux flow of the split core iron core includes a transitional X direction in the middle of the magnetic flux rotating from the L direction to the C direction in both cases of the split core punched in the punching mode A and the punching mode B. Although there is a magnetic flux flow, in the split core, the transitional magnetic flux region in the X direction is small, and it is estimated that the degree of influence on the magnetic properties of the split core iron core is small.

In other words, the present inventor can control the magnetic properties of the entire split core iron core by designing the material so that the ratio of the magnetic properties in the C direction to the magnetic properties in the X direction: B ₅₀ (C) / B ₅₀ (X) is increased. I thought it could be improved.

  The appropriate balance of magnetic characteristics in the L direction and the C direction is determined by the size and shape of the split core piece.

Since defining B ₅₀ (C) / B ₅₀ (X) within a predetermined range is to limit the anisotropy of the magnetic properties of the non-oriented electrical steel sheet to a predetermined range, a split core is designed. At this time, the shape of the split core and the punching mode can be designed in consideration of the improvement of the magnetic characteristics of the entire split core iron core.

Therefore, B ₅₀ (C) / B ₅₀ (X) is a very important index for judging the accuracy of the non-oriented electrical steel sheet for the split core.

However, since the anisotropy of the magnetic characteristics in the non-oriented electrical steel sheet is affected by the plate thickness and tends to decrease as the plate thickness decreases, in the present invention, B ₅₀ (C ) / B ₅₀ (X) is not simply numerically limited, but the following formula (1) is defined in relation to the thickness t (0.15 to 0.3 mm) of the non-oriented electrical steel sheet.
B ₅₀ (C) / B ₅₀ (X) ≧ −0.5333 × t ² + 0.3907 × t + 0.945 (1)

  As described above, the thickness of the non-oriented electrical steel sheet greatly affects the anisotropy of the magnetic characteristics of the non-oriented electrical steel sheet, and the anisotropy of the magnetic characteristics decreases as the thickness decreases.

Therefore, the inventor maintains the required magnetic flux density anisotropy in the L and C directions and the X direction, and sets the required magnetic flux density in the L and C directions, which are important for the magnetic properties of the split core. In order to ensure, the relationship between B ₅₀ (C) / B ₅₀ (X) and the plate thickness (t) was intensively analyzed using a regression analysis method.

  In the range of the plate thickness of 0.15 to 0.3 mm, the present inventors found that the anisotropy of the magnetic properties gradually increases as the plate thickness increases. Regression analysis was performed as an approximation with a quadratic function. As a result, it was found that the above formula (1) holds.

That is, if B ₅₀ (C) / B ₅₀ (X) is smaller than the value on the right side of the above formula (1) (= A value, hereinafter may be referred to as “A value”), the anisotropy of the magnetic properties. It becomes difficult to secure a required magnetic flux density in the L direction and the C direction, which are important in evaluating the magnetic properties of the non-oriented electrical steel sheet.

  In addition, said Formula (1) is a relational expression which is materialized when the plate | board thickness of a non-oriented electrical steel sheet is 0.15-0.3 mm. When the plate thickness exceeds the above range, the coefficient changes, and therefore it cannot be applied to a non-oriented electrical steel sheet having a plate thickness exceeding the above range.

For example, when the plate thickness t exceeds 0.3 mm, B ₅₀ (C) / B ₅₀ (X) increases rapidly, which is satisfactory as a magnetic property for a split core, but not as a high frequency core. Eligible.

According to the present invention, even if the plate thickness is thin (the thin the sheet, the magnetic property anisotropy becomes small), and B ₅₀ (C) / B ₅₀ (X) is large (ie, the magnetic property anisotropy). As a result, we have developed non-oriented electrical steel sheets for split cores.

That is, the present invention introduces an index “B ₅₀ (C) / B ₅₀ (X)” indicating the anisotropy of the magnetic properties in order to evaluate the magnetic properties of the non-oriented electrical steel sheet for the split core. The basic idea is to define the lower limit in relation to the index and the plate thickness that affects the magnetic characteristics.

  The correlation between the magnetic property anisotropy and the plate thickness according to the above equation (1) will be demonstrated in experimental results in the examples described later, but the details of the correlation are for further study. .

  The present inventor has found that the magnetic domain structure on the surface changes as the plate thickness decreases, and this change particularly affects the magnetization process in the X direction. As a result, the magnetic characteristics that can be analyzed by the above equation (1) differ. It is presumed that anisotropy appears.

When designing a split core, the magnetic flux density B ₅₀ (L) in the L direction that does not appear in the above equation (1) is also an important index. Since the value of B ₅₀ (L) naturally changes depending on the composition of the steel plate, the ratio with the saturation magnetic flux density Bs is adopted: B ₅₀ (L) / Bs (crystal orientation index). Therefore, it is preferable to evaluate the magnetic properties of the non-oriented electrical steel sheet.

In order to obtain a split core having better magnetic properties, it is necessary to design the material so that B ₅₀ (L) / Bs satisfies the following formula (2).
B ₅₀ (L) /Bs≧0.82 (2)

When the crystal orientation index B ₅₀ (L) / Bs is less than 0.82, the magnetic properties as a split core are insufficient.

  Since the present invention requires that the hot-rolled sheet is annealed and then cold-rolled once and then recrystallized, the preferable manufacturing requirements will be described below.

  The annealing of the hot rolled sheet is preferably performed at a high temperature. When the crystal grain size of the hot-rolled sheet is increased by this annealing, Goss orientation grains are easily formed by recrystallization after cold rolling, and the anisotropy of magnetic flux density increases. Therefore, the annealing temperature should be as high as possible, preferably over 900 ° C.

The cold rolling after annealing is preferably lever rolling. According to this rolling, B ₅₀ (L) can be improved by about 0.02 T, compared with so-called tandem rolling of unidirectional rolling. Lever's rolling can be performed by ordinary Sendzimir mill rolling or the like.

The rolling reduction in cold rolling is important because it sensitively affects the indices B ₅₀ (C) / B ₅₀ (X) and B ₅₀ (L) / Bs. When the rolling reduction is smaller, both B ₅₀ (C) / B ₅₀ (X) and B ₅₀ (L) / Bs are improved, but if the rolling reduction is less than 75%, It is necessary to make the thickness a plate thickness in a thin region that is difficult to industrially, and this is virtually impossible. On the other hand, if the rolling reduction exceeds 89%, it becomes difficult to secure the required B ₅₀ (C) / B ₅₀ (X) and B ₅₀ (L) / Bs.

In the recrystallization annealing, it is preferable that the heating rate is 100 to 5000 ° C./second in the range of at least 600 to 700 ° C. and rapid heating is performed. By this rapid heating, Goss orientation grains can be increased in the recrystallized structure, and in particular, B ₅₀ (C) / B ₅₀ (X) can be improved. If the rate of temperature increase is less than 100 ° C./second, the above improvement effect is small, and if it is 5000 ° C./second or more, it is impossible in terms of industrial equipment cost.

Moreover, when evaluating the magnetic characteristics of a non-oriented electrical steel sheet, the iron loss characteristics are also important. In the present invention, the iron loss W _10/800 is preferably 40 W / kg or less. This is because it is applied to high-speed rotation specifications to make a compact motor core.

  Next, examples of the present invention will be described. The conditions of the examples are one example of conditions adopted for confirming the feasibility and effects of the present invention, and the present invention is limited to this one example of conditions. Is not to be done. 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 component composition was adjusted while melting steel in a vacuum melting furnace, and an ingot having the component composition shown in Table 1 was cast. This was heated to 1200 ° C. and hot-rolled to obtain a hot-rolled sheet having a thickness of 1.5 mm. Next, annealing was performed by heating at 920 ° C. for 90 seconds in an N ₂ atmosphere. After pickling, cold rolling was performed to obtain a cold-rolled sheet having a sheet thickness of 0.25 mm (a rolling reduction of 83.3%).

Thereafter, the cold-rolled plate was soaked at 1000 ° C. for 20 seconds in an H ₂ atmosphere, and the cold-rolled plate was subjected to recrystallization annealing. The heating rate during recrystallization annealing was 10 ° C./second. The average crystal grain size of the cold rolled sheet was in the range of 40 to 60 μm. The magnetic characteristics were measured for each angle with a 55 mm square SST. The obtained results are also shown in Table 1.

The magnetic flux density B ₅₀ is a magnetic flux density (unit T) at a magnetizing force of 5000 A / m.

The saturation magnetic flux density Bs was measured with a vibrating sample magnetometer. W _10/800 is an iron loss at a magnetic flux density of 1.0 T and a frequency of 800 Hz, and is an average of measured values in the L direction and the C direction.

The A value was defined by the following formula.
A value = −0.5333 × t ² + 0.3907 × t + 0.945 (t: plate thickness)

  In addition, Example 2 and the following also follow the above symbols and formulas.

Experiment No. 1-5 change Sn amount. Table 1 shows that excellent magnetic flux density anisotropy: B ₅₀ (L) / B ₅₀ (C) is obtained with an Sn content within the scope of the present invention, and that the Sn content increases. It can be seen that the magnetic flux density B ₅₀ (L) in the L direction is improved.

Experiment No. 6 to 10 are obtained by changing the amount of Al. As the Al content increases, the anisotropy of magnetic flux density: B ₅₀ (C) / B 50 (X) decreases. That is, it can be seen that the increase in the amount of Al tends to make it difficult to ensure the anisotropy of the magnetic flux density.

The present invention provides a non-oriented electrical steel sheet for a split core in a region where there is a large amount of Al, that is, it is difficult to ensure anisotropy of magnetic properties. It can also be seen that if the Al content is within the range of the present invention, an excellent high-frequency iron loss W _10/800 is obtained.

(Example 2)
In mass%, C: 0.003%, Si: 3%, Mn: 0.15%, Al: 1.5%, S: 0.0001%, N: 0.0010%, Sn: 0.05% The ingot containing was heated to 1050 ° C. to produce hot-rolled plates having various plate thicknesses shown in Table 2. Next, the hot-rolled sheet is soaked at 1150 ° C. for 60 seconds in an N ₂ atmosphere, the hot-rolled sheet is annealed, and then cold-rolled to produce cold-rolled sheets having the thicknesses shown in Table 2. did.

Next, recrystallization annealing was performed by soaking at 1100 ° C. for 10 seconds in an atmosphere of 20% H ₂ + 80% N ₂ . Heating was performed using a radiant tube at a heating rate of 20 ° C./second. The average grain size was 150 μm. The results obtained are shown in Table 2.

  Experiment No. In Nos. 1 to 6, the thickness of the hot-rolled sheet was adjusted, but the thickness of the cold-rolled sheet was fixed, and the influence of the cold rolling rate (rolling rate) on the magnetic properties was investigated. As shown in Table 2, if the cold rolling rate is within the range of the present invention, excellent magnetic flux density anisotropy is obtained.

Experiment No. 7-12 fix the plate | board thickness of a hot rolled sheet, and change the plate | board thickness of a cold rolled sheet. If the thickness of the cold-rolled sheet (that is, the product sheet thickness) is within the range of the present invention, an excellent high-frequency iron loss W _10/800 can be obtained, and the cold- _rolling rate is within the range of the present invention. If it exists, the anisotropy of the outstanding magnetic flux density is acquired. When the cold rolling rate exceeds the range of the present invention, B ₅₀ (L) is greatly deteriorated.

Further, the plate thickness of the cold-rolled plate may be regarded as the plate thickness of the product plate. However, when the plate thickness is reduced, the anisotropic B ₅₀ (C) / B ₅₀ (X) is decreased. It can be seen that this anisotropy decreases significantly from 32 mm to 0.30 mm.

In addition, about 0.35 mm thickness (experiment No. 7) and 0.32 mm thickness (experiment No. 8), it is outside the plate thickness range of the A value defined by the above formula (1), but forcibly, A value obtained by substituting the thickness is shown as an A value. When the A value on this quadratic curve is compared with the measured B ₅₀ (C) / B ₅₀ (X), the values for the thick plate thicknesses of 0.35 mm and 0.32 mm differ greatly. It can be seen that the value is large. That is, when the plate thickness exceeds 0.30 mm, it is easy to increase the anisotropy B ₅₀ (C) / B ₅₀ (X).

  However, according to the present invention, the anisotropy of the magnetic flux density is intentionally improved particularly in a thin plate thickness region of 0.30 mm or less where a sudden decrease in the anisotropy of the magnetic flux density is inevitable.

(Example 3)
By mass%, C: 0.002%, Si: 2.3%, Mn: 0.17%, Al: 1.8%, S: 0.0004%, N: 0.0019%, Sn: 0.00. A slab containing 17% was heated to 1150 ° C. to produce a 1.3 mm thick hot rolled coil. When other components (as inevitable impurities) were analyzed, Cu: 0.1%, Ni: 0.05%, Cr: 0.05%, Ca: 0.0003%, V: 0.001%, Ti: 0.001%, Nb: 0.001%, Mo: 0.002%, Sb: 0.0001%.

This hot rolled coil was soaked at 1100 ° C. for 100 seconds in an N ₂ atmosphere and annealed, and then a cold rolled sheet having a thickness of 0.15 mm was manufactured by lever rolling (reduction rate of 88.5%). Next, as shown in Table 3, the temperature was raised from room temperature to 1100 ° C. in an N ₂ atmosphere at various heating rates by an induction heating method, and then in a 50% H ₂ + 50% N ₂ atmosphere, 15 A second soaking was performed. The average particle size was 200 μm. The results are shown in Table 3.

From Table 3, it can be seen that the anisotropy of the magnetic flux density is greatly improved when the heating rate is increased. In particular, it can be seen that the unprecedented anisotropy: B ₅₀ (C) / B ₅₀ (X) is obtained at a temperature rising rate of 100 ° C./second or more. In addition, the temperature rising rate exceeding 5000 ° C./second is not industrial because of a cost problem such as a power source.

  As described above, according to the present invention, it is possible to provide a non-oriented electrical steel sheet that has optimum magnetic characteristics for a split core of a motor or a transformer and has high utilization. Therefore, the present invention has great applicability in the electrical equipment manufacturing industry using non-oriented electrical steel sheets as raw materials.

It is a figure which shows the punching aspect of a split core. (A) shows a mode in which the tooth portion of the split core is set in the C direction (90 ° C. in the L direction) and punched, and (b) shows a mode in which the tooth portion of the split core is set in the L direction and punched. Indicates.

Explanation of symbols

1 split core 2 teeth

Claims (7)

In mass%, C: 0.005% or less, Si: 2 to 4%, Mn: 1% or less, Al: more than 1 to 2%, Sn: 0.003 to 0.2%, the balance being Fe And a non-oriented electrical steel sheet having a thickness of 0.15 to 0.3 mm, which is manufactured by annealing a hot-rolled sheet made of inevitable impurities and then performing cold rolling once and then recrystallizing annealing. Because
(I) having a recrystallized structure having an average crystal grain size of 40 to 200 μm, and
(Ii) Magnetic flux density B ₅₀ (C) in the rolling direction (L direction) and 90 ° direction (C direction), and magnetic flux density B ₅₀ (X in the rolling direction (L direction) and 45 ° direction (X direction). ) Has a magnetic property satisfying the following formula (1): a non-oriented electrical steel sheet for split cores.
B ₅₀ (C) / B ₅₀ (X) ≧ −0.5333 × t ² + 0.3907 × t + 0.945 (1)
Where t: plate thickness (mm) 2. The non-oriented electrical steel sheet for split core according to claim 1, wherein a magnetic flux density B ₅₀ (L) in a rolling direction (L direction) satisfies the following formula (2) in the magnetic characteristics.
B ₅₀ (L) /Bs≧0.82 (2)
Where Bs: saturation magnetic flux density 3. The non-oriented electrical steel sheet for split core according to claim 1, wherein an iron loss W _10/800 is 40 W / kg or less in the magnetic characteristics.   The non-oriented electrical steel sheet for a split core according to any one of claims 1 to 3, wherein the cold rolling is lever rolling.   The non-oriented electrical steel sheet for split core according to any one of claims 1 to 4, wherein a rolling reduction is 75 to 89% in the cold rolling.   The non-oriented electrical steel sheet for split core according to any one of claims 1 to 5, wherein in the recrystallization annealing, a temperature rising rate is 100 to 5000 ° C / second.   The non-oriented electrical steel sheet for split core according to any one of claims 1 to 6, wherein an annealing temperature of the hot-rolled sheet is higher than 900 ° C.

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