JP4855221B2 - Non-oriented electrical steel sheet for split core - Google Patents

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. The difference (anisotropy) is small in the direction perpendicular to the direction (coil width direction, hereinafter referred to as “C direction”) and in the L direction and 45 degrees (hereinafter referred to as “X direction”). It is desired (see Patent Documents 1 to 6).

  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 sacrifice of the magnetic properties in the X direction, the teeth of the divided core in the design of the divided cores. This is preferable in that required magnetic characteristics can be secured.

  Patent Document 1 discloses that the second cold rolling (hereinafter sometimes referred to as “cold rolling”) is performed by skin pass rolling, which is performed after the skin pass rolling. A so-called full process is used, in which finish annealing is performed at a low cost, and there are problems such as cost and deterioration of iron loss characteristics due to punching distortion.

Japanese Patent Laid-Open No. 2001-49402 Japanese Patent Laid-Open No. 2001-164343 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 0.1 to 0.3 mm containing Si: 2 to 4% and Al: 0.3 to 2% by mass%. Add 003 to 0.2% to increase the Goss-oriented crystal grains and improve the magnetic properties (magnetic flux density) in the L and C directions, ensuring optimum magnetic properties for the split core We studied earnestly about the technique to do. As a result, the following knowledge was obtained.

(X) Differences in magnetic properties (anisotropy) in the L, C, and X directions are sheet thickness (product sheet thickness), reduction ratio in cold rolling, distribution of the reduction ratio, and crystals before and after skin pass rolling. Although it is closely related to the particle diameter, if these are finally controlled, it is possible to secure a required magnetic flux density B _{50 having} a large anisotropy (magnetic flux density [T] obtained with a magnetizing force of 5000 A / m). it can.

(Y) L direction and the C direction connecting the magnetic properties 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 it is necessary to maintain it within a predetermined difference range in relation to the magnetic properties in the L 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: 0.3-2%, Sn: 0.003-0.2% The thickness of the steel sheet manufactured by annealing the hot-rolled sheet consisting of Fe and unavoidable impurities, followed by cold rolling, followed by recrystallization annealing, followed by skin pass rolling and strain relief annealing: A 0.1 to 0.3 mm semi-processed non-oriented electrical steel sheet,
(I) having a recrystallized structure having an average crystal grain size after strain relief annealing of 80 to 300 μm, and
(Ii) The magnetic flux density B ₅₀ (L) in the rolling direction (L direction) and the magnetic flux density B ₅₀ (X) in the rolling direction (L direction) and 45 ° (X direction) A non-oriented electrical steel sheet for a split core, characterized by having magnetic properties to satisfy.
B ₅₀ (L) −B ₅₀ (X) ≧ 0.07T (1)

(2) The non-oriented electrical steel sheet for split core according to (1), wherein the iron loss W _10/800 is ₃₈ W / kg or less in the magnetic characteristics.

  (3) The non-oriented electrical steel sheet for split core according to (1) or (2), wherein the annealing temperature of the hot-rolled sheet is higher than 900 ° C.

  (4) The non-oriented electrical steel sheet for split core according to any one of (1) to (3), wherein an average crystal grain size before the skin pass rolling is 10 to 60 μm.

  (5) The non-oriented electrical steel sheet for split core according to any one of (1) to (4), wherein a rolling reduction in the skin pass rolling is 2 to 15%.

  (6) The non-oriented electrical steel sheet for split core according to any one of (1) to (5), wherein the strain relief annealing is performed at 770 to 850 ° 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: 0.3-2%, Sn: 0.003-0.2% Then, after the hot rolled sheet consisting of Fe and inevitable impurities is annealed, the sheet is cold rolled, then recrystallized annealed, and then subjected to skin pass rolling and strain relief annealing. 1 to 0.3 mm semi-process non-oriented electrical steel sheet,
(I) having a recrystallized structure having an average crystal grain size after strain relief annealing of 80 to 300 μm, and
(Ii) The magnetic flux density B ₅₀ (L) in the rolling direction (L direction) and the magnetic flux density B ₅₀ (X) in the rolling direction (L direction) and 45 ° (X direction) It is characterized by having magnetic properties that satisfy.
B ₅₀ (L) −B ₅₀ (X) ≧ 0.07T (1)

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

  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 0.3%. However, if the content exceeds 2%, the saturation magnetic flux density deteriorates, so the upper limit was made 2%.

  Sn increases the number of Goss orientation grains in the recrystallized structure of non-oriented electrical steel sheets containing Si: 2 to 4% and Al: 0.3 to 2%. In order to improve (density), 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 surface defects increase due to hot brittleness, so the upper limit was made 0.2%.

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

  In addition, the range in which the desired anisotropy is not inhibited is Cu <0.2%, Ni <0.1%, Cr <0.1%, Ca <0.01%, REM <0. 0.01%, Nb <0.003%, and Ti <0.003%, so that these elements are preferably suppressed within the above ranges. Note that Sb should not be added because it reduces anisotropy. When Sb is inevitably contained, it is preferably less than 0.001%.

  After annealing the hot-rolled sheet having the above component composition, cold rolling is performed, then recrystallization annealing is performed, and then skin pass rolling is performed. Thereafter, after being punched into the split core at the customer or processing center, strain relief annealing is performed, and a recrystallized structure having an average crystal grain size of 80 to 300 μm is formed.

In the present invention, based on the knowledge (x) described above, the average crystal grain size after strain relief annealing is regulated to 80 to 300 μm. When the average crystal grain size is large, the iron loss characteristics are improved, but the magnetic flux density is deteriorated, and the magnetic flux density anisotropy (B ₅₀ (L) −B ₅₀ (X)) is slight. , Tend to be smaller.

If the average grain size after strain relief annealing is less than 80 μm, the iron loss characteristics are unsatisfactory, and if it exceeds 300 μm, the magnetic flux density B ₅₀ (L) is greatly deteriorated. The crystal grain size is limited to 80 to 300 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.

In the present invention, a semi-processed illegal back electrical steel sheet having a thickness of 0.1 to 0.3 mm having a recrystallized structure having an average crystal grain size of 80 to 300 μm after strain relief annealing satisfies the following formula (1): It has the characteristics.
B ₅₀ (L) −B ₅₀ (X) ≧ 0.07T (1)

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

“B ₅₀ (L) −B ₅₀ (X)” is the difference itself between B _{50 in} the L direction and the X direction. And, it is extremely important to determine this difference within a predetermined range in determining the appropriateness of the non-oriented electrical steel sheet for the split core for the following reasons. “B ₅₀ (L) −B ₅₀ (X)” was introduced as an index for evaluating the magnetic properties of the film.

  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.

That is, the present inventor should design the material so that the difference between the magnetic characteristics in the L direction and the magnetic characteristics in the X direction: B ₅₀ (L) −B ₅₀ (X) is greater than a predetermined value (0.07T). The idea was that the magnetic properties of the entire split core 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 (L) −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 an extremely important index for judging the accuracy of the non-oriented electrical steel sheet for the split core.

In the present invention, if “B ₅₀ (L) −B ₅₀ (X)” is less than 0.07T, the anisotropy is small, and the required magnetic properties in the L and C directions cannot be obtained. “B ₅₀ (L) −B ₅₀ (X)” is 0.007T or more.

Further, the plate thickness (product plate thickness) needs to be 0.3 mm or less in order to obtain a desired high-frequency characteristic, that is, W _10/800 ≦ ₃₈ W / kg. However, if it is less than 0.1 mm, it is too thin, and breakage and the like during recrystallization annealing increase, which is not industrial.

Since the present invention requires that the hot-rolled sheet is annealed, then cold- rolled, then recrystallized annealed, and then subjected to skin pass rolling and strain relief annealing. The preferable manufacturing requirements will be described. In addition, since the non-oriented electrical steel sheet manufactured by this manufacturing process is shipped from a steel mill after skin pass rolling, it is called a semi-processed non-oriented electrical steel sheet.

  Annealing of a hot-rolled sheet has the advantage of increasing the magnetic flux density anisotropy. The annealing condition may be a normal temperature of 800 ° C. or higher, but more preferably 900 ° C. or higher. The annealing may be continuous annealing or box annealing. Cold rolling after annealing employs normal tandem rolling or lever rolling.

  In the subsequent recrystallization annealing, it is desirable to control the crystal grain size. If the crystal grain size is too small or too large, the anisotropy is small, so it is necessary to make the crystal grain size within an appropriate range. In order to obtain desired anisotropy, 10 to 60 μm is preferable. The annealing temperature for controlling the crystal grain size within this range is about 700 to 850 ° C.

  In the manufacture of high-grade non-oriented electrical steel sheets by the usual single cold rolling method, since recrystallization annealing is performed at a high temperature of about 1000 ° C., it is difficult to flatten the shape of a particularly thin steel sheet. It was. However, since the recrystallization annealing temperature in the process of the present invention is low, it is very advantageous industrially.

  If unrecrystallized is left in the crystal structure, the crystal grain size after strain relief annealing becomes unstable and is not preferable. Therefore, it is necessary to avoid leaving unrecrystallized in the crystal structure. It is industrial that the insulating film is baked at this stage (after recrystallization annealing).

In the present invention, the recrystallized structure after cold rolling is subjected to skin pass rolling, and the difference between the magnetic flux density B ₅₀ (L) in the L direction and the magnetic flux density B ₅₀ (X) in the X direction, that is, the magnetic property It is characterized by increasing the anisotropy.

  In a non-oriented electrical steel sheet with increased magnetic property anisotropy, a split core having a teeth portion with a high magnetic flux density can be obtained by setting the split core in the L direction.

By adjusting the reduction ratio of the skin pass rolling, the difference (anisotropy) between the magnetic flux density B _{50 in} the L direction and the X direction can be adjusted, so that depending on the required magnetic flux density of the split core, A non-oriented electrical steel sheet can be manufactured by designing magnetic characteristics.

  The rolling reduction in skin pass rolling is preferably 2 to 15%. If the rolling reduction is less than 2%, it is difficult to increase the magnetic property anisotropy to a desired level, and if it exceeds 15%, the magnetic property anisotropy becomes small. The rolling reduction that provides the greatest anisotropy is 4-7%.

  Metallurgy by skin pass rolling is generally a kind of abnormal grain growth mechanism called strain-induced grain growth, and grain growth occurs explosively by prolonged annealing (strain relief annealing) for several hours after skin pass. It is. The orientation-selective grain growth mechanism at this time is basically that orientation grains with little internal strain grow explosively. However, the orientation selection is known to change slightly depending on the inclusion, component system, grain size, reduction rate of skin pass rolling, etc., but the theory that unifies these complex phenomena has not yet been formed. Absent.

  The strain relief annealing is performed at a normal temperature of 700 to 850 [deg.] C. for 2 hours, but the annealing temperature is preferably on the high temperature side in order to obtain coarse grains aimed at the crystal structure. A preferable annealing temperature is 770 to 850 ° C. When the annealing temperature exceeds 850 ° C., the adhesion of the insulating film may be deteriorated.

The high-frequency iron loss W _10/800 is preferably ₃₈ W / kg or less. This is to meet the high-speed rotation specification for 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 1050 ° C. and hot-rolled to obtain a hot-rolled sheet having a thickness of 2.3 mm. Next, annealing was performed by soaking 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 0.315 mm (reduction rate of 86.3%).

Recrystallization annealing was performed in a H ₂ atmosphere at 750 ° C. for 30 seconds. The average grain size was in the range of 15-20 μm. Next, skin pass rolling was performed to obtain a plate thickness of 0.300 mm (5% reduction). After punching out to 55 mm square, annealing was performed at 750 ° C. for 2 hours in an H ₂ atmosphere, and the magnetic characteristics were measured for each angle by SST.

The average grain size was 130-150 μm. The obtained results are shown in Table 1. 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 (unit: T) = B ₅₀ (L) −B ₅₀ (X)

  In addition, Example 2 and the following also conform to these symbols.

The Sn amount was within the range of the present invention, and excellent B ₅₀ (L) and desired anisotropy could be obtained.

(Example 2)
Experiment No. 1 shown in Table 1. No. 4 cold-rolled sheet having a thickness of 0.315 mm was used, the soaking time under recrystallization annealing conditions was fixed at 15 seconds, and the annealing temperature was changed to change the crystal grain size. The annealing atmosphere was 10% H ₂ + 90% N ₂ . Next, skin pass rolling was performed to make the plate thickness 0.28 mm (11.1% reduction). After punching into a 55 mm square, annealing was performed at 780 ° C. for 2 hours in an N ₂ atmosphere, and magnetic properties were measured for each angle by SST, and the crystal grain size was also measured. The obtained results are shown in Table 2.

  Those whose average crystal grain size after recrystallization annealing is within the range of the present invention show magnetic characteristics having excellent anisotropy for a split core. Further, the average crystal grain size after recrystallization annealing is strongly related to the average crystal grain size after strain relief annealing, and it can be seen that if recrystallization annealing is a coarse grain, the grain size is also coarse after strain relief annealing.

(Example 3)
In terms of mass%, C: 0.001%, Si: 3.0%, Mn: 0.7%, Al: 0.3%, Sn: 0.01%, and other inevitable components, Cu: 0.00%. A slab containing 1%, Ni: 0.05%, Ni: 0.01%, Ti: 0.002%, Mo: 0.002%, P: 0.01% is heated to 1100 ° C and finish-rolled A hot-rolled sheet having a thickness of 2.8 mm was obtained at a temperature of 870 ° C.

After annealing in a N ₂ atmosphere at 1000 ° C. for 120 seconds, pickling and cold rolling were performed. Recrystallization annealing was performed at 770 ° C. for 10 seconds in an H ₂ atmosphere.

The crystal grain size was in the range of 13-15 μm. Next, skin pass rolling with a reduction rate shown in Table 3 was performed to obtain a plate thickness of 0.12 mm. After the Epstein sample was cut out, strain relief annealing was performed in an H ₂ atmosphere at 820 ° C. for 2 hours, and the magnetic characteristics and crystal grain size were measured for each angle. The obtained results are shown in Table 3.

  When the rolling reduction ratio of the skin pass rolling is within the range of the present invention, anisotropy suitable for the split core is developed, an appropriate crystal grain size can be obtained by strain relief annealing, and high frequency iron loss is also satisfied. was gotten.

  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 (6)

In mass%, C: 0.005% or less, Si: 2-4%, Mn: 1% or less, Al: 0.3-2%, Sn: 0.003-0.2%, the balance being Thickness of 0.1 mm produced by annealing a hot rolled sheet made of Fe and unavoidable impurities, followed by cold rolling, followed by recrystallization annealing, followed by skin pass rolling and strain relief annealing: 0.1 -0.3mm semi-processed non-oriented electrical steel sheet,
(I) having a recrystallized structure having an average crystal grain size after strain relief annealing of 80 to 300 μm, and
(Ii) The magnetic flux density B ₅₀ (L) in the rolling direction (L direction) and the magnetic flux density B ₅₀ (X) in the rolling direction (L direction) and 45 ° (X direction) A non-oriented electrical steel sheet for a split core, characterized by having magnetic properties to satisfy.
B ₅₀ (L) −B ₅₀ (X) ≧ 0.07T (1) 2. The non-oriented electrical steel sheet for split core according to claim 1, wherein an iron loss W _10/800 is ₃₈ W / kg or less in the magnetic characteristics.   The non-oriented electrical steel sheet for a split core according to claim 1 or 2, wherein an annealing temperature of the hot-rolled sheet is higher than 900 ° C.   The non-oriented electrical steel sheet for split core according to any one of claims 1 to 3, wherein an average crystal grain size before the skin pass rolling is 10 to 60 µm.   The non-oriented electrical steel sheet for split core according to any one of claims 1 to 4, wherein a rolling reduction in the skin pass rolling is 2 to 15%.   The non-oriented electrical steel sheet for split core according to any one of claims 1 to 5, wherein the strain relief annealing is performed at 770 to 850 ° C.

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