JP2008057001A - Grain-oriented electromagnetic steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low core-loss grain-oriented electromagnetic steel sheet with which the core-loss is not deteriorated after strain-removal annealing and the low core-loss characteristic can be obtained, even after working as a transformer core. <P>SOLUTION: The grain-oriented electromagnetic steel sheet, has a plurality of grooves directed to almost at right angle to the rolling direction, and further, in the interval of respective grooves, the sheet thickness decreasing parts are formed as the studded-state and the sum total of the sheet thickness decreased amount in the sheet thickness decreasing parts is 0.01-0.05% in the weight decreasing ratio to the steel sheet before forming the above sheet thickness decreasing parts. For example, as the sheet thickness decreasing parts, the recessed parts having 45μmϕ diameter and 25μm depth, are introduced at the interval of the respective grooves at 0.03% of the weight decreasing ratio. A demagnetizing field is formed by arranging this sheet thickness decreasing parts between the respective grooves and in the case of carrying magnetic flux except the rolling direction, the raising of the core-loss can be restrained by forming the demagnetizing field. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a low iron loss direction-oriented electrical steel sheet used as an iron core of a transformer or other electric equipment, and particularly aims to prevent deterioration of iron loss characteristics due to stress relief annealing.

  Oriented electrical steel sheets are used as iron cores for transformers and other electrical equipment, and are required to have excellent magnetic properties, especially low iron loss. This iron loss can be roughly expressed by the sum of hysteresis loss and eddy current loss. Hysteresis loss is caused by precipitates (AlN, MnS, MnSe, etc.) called inhibitors when secondary recrystallization occurs. By strengthening the grain growth inhibiting power of the primary recrystallized grains, the pinning factor (precipitate) that prevents the domain wall movement when the crystal orientation is highly accumulated in the Goth orientation, that is, {110} <001> orientation, or when magnetized is generated. It has been greatly reduced by reducing the causative impurity elements.

On the other hand, for eddy current loss, increasing the Si content to increase the electrical resistance, reducing the thickness of the steel sheet, or forming a coating with a different thermal expansion coefficient on the steel sheet surface Reduction has been achieved by, for example, reducing the magnetic domain width by applying tension to the base iron or by refining crystal grains.
Further, as a method for reducing eddy current loss, Patent Document 1 proposes a method of irradiating laser light along a direction perpendicular to the rolling direction of a steel sheet, and Patent Document 2 proposes a method of irradiating a plasma flame or the like. Has been. These methods are intended to subdivide the magnetic domains by introducing minute thermal strains in the form of lines or dots on the surface of the steel sheet, thereby greatly reducing the iron loss. However, in the methods of Patent Documents 1 and 2, if annealing is performed at a high temperature after magnetic domain subdivision, the thermal strain is removed and the iron loss reduction effect disappears. Therefore, a wound iron core that requires strain relief annealing after irradiation treatment. It could not be used as a raw material.

  Accordingly, various methods for forming grooves in a steel sheet have been proposed as magnetic domain subdivision methods that can withstand strain relief annealing. For example, there is a method in which grooves are locally formed in the steel sheet after final finish annealing, that is, after secondary recrystallization, and the magnetic domains are subdivided by the demagnetizing field effect. Patent Document 3 describes a mechanical processing method as the groove forming means, and Patent Document 4 describes a method of performing electrolytic etching after locally removing the insulating film and the base film by laser light irradiation. Patent Document 5 discloses a method of subdividing magnetic domains by achieving groove formation and recrystallization by stamping and annealing after gear rolling, and Patent Document 6 discloses a steel plate before final finish annealing. A method of forming grooves in each of the above is disclosed.

Thus, in recent years, the combination of high crystal orientation as described above (B8 is 1.91 T or more in the product after groove formation) and magnetic domain refinement have improved the low iron loss characteristics of materials to an extremely high level. Has been. However, the iron loss after being processed into a transformer core has a problem that the building factor deteriorates due to the effect of high orientation, and the low iron loss characteristics of the material cannot always be fully utilized by design or the like.
Japanese Patent Publication No.57-2252 JP 62-96617 A Japanese Patent Publication No. 50-35679 JP-A 63-76819 Japanese Examined Patent Publication No.62-53579 JP 59-197520

  The present invention was made in order to advantageously solve the above problem, and the iron loss is not deteriorated after the stress relief annealing, and the low iron loss direction capable of obtaining the low iron loss characteristic even after being processed as a transformer core. An object of the present invention is to provide an electrical steel sheet.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive research focusing on making further improvements on the basis of providing a linear groove in a grain-oriented electrical steel sheet and performing a magnetic domain refinement treatment. As a result, a low iron loss directional electromagnetic wave that does not deteriorate even after strain relief annealing by introducing, for example, a recess or a through hole, that is, a reduced thickness portion, between each groove to form a demagnetizing field. It has been found that a steel sheet can be obtained.

The present invention has been made based on the above findings, and the gist thereof is as follows.
[1] A grain-oriented electrical steel sheet having a plurality of grooves extending in the width direction of the steel sheet, wherein a thickness reduction portion is formed between the grooves, and a thickness reduction amount by the thickness reduction portion. Is a grain-oriented electrical steel sheet characterized by a weight reduction rate of 0.01 to 0.05% with respect to the steel sheet before the thickness reduction portion is formed.
[2] The grain-oriented electrical steel sheet according to [1], wherein the thickness reduction portion is formed of a recess and / or a through hole.

  According to the present invention, it is possible to obtain a low iron loss directional electrical steel sheet in which iron loss does not deteriorate even after strain relief annealing. And even when the grain-oriented electrical steel sheet of the present invention is processed and used as a transformer core, it is possible to obtain low iron loss characteristics. As a result, the transformer's low iron loss characteristics can be used to the maximum in transformers, reducing iron loss in transformers, leading to the efficient use of industrial and consumer electrical energy, and saving energy in society. Can contribute.

  As a result of earnest research focusing on combining various processes with magnetic domain subdivision processing by groove formation, the present invention has completed a steel plate that can advantageously improve the iron loss of a transformer. That is, the grain-oriented electrical steel sheet of the present invention has a plurality of grooves in a direction substantially orthogonal to the rolling direction, and is formed by interspersing the thickness reduction portions between the grooves. The total thickness reduction amount at is a weight reduction rate of 0.01 to 0.05% with respect to the steel plate before the plate thickness reduction portion is formed. This is the most important requirement in the present invention. In this way, a demagnetizing field is formed by each of the plate thickness reduction portions by interposing the plate thickness reduction portions between the grooves. And by forming a demagnetizing field, it becomes possible to suppress an increase in iron loss when magnetic flux flows in a direction other than the rolling direction, and the problem of the present invention is solved. In the present invention, the plate thickness reduction part is formed in a flat part between the grooves, for example, a minute recess having a diameter of 200 μm or less and a depth of about 40 μm or less, or a minute part having a diameter of about 100 μm or less. It is formed by a through hole. Moreover, the said weight reduction rate is a steel plate weight reduction rate at the time of introduce | transducing a plate thickness reduction part with respect to the steel plate weight when not introducing a thickness reduction part between linear grooves.

The present invention is described in detail below. First, an experiment that led to the present invention will be described.
Using a cold rolled steel sheet with a final thickness of 0.23 mm for grain oriented electrical steel sheets, an etching resist is formed such that grooves with a depth of 15 μm and a width of 70 μm are formed with a pitch of 3 mm, and electropolishing is performed to form the grooves. did. Further, after removing the etching resist, the electrolysis conditions were adjusted by the same electrolysis technique, and in order to introduce a plate thickness reduction portion into the flat portion between the grooves, concave portions having a diameter of 75 μm and a depth of 20 μm were scattered. At this time, by changing the amount of recessed portions to be scattered, a maximum weight reduction rate of 0.10% was introduced (Condition 1).
Further, as condition 2, through-holes with a diameter of 40 μm were introduced by laser processing for the same weight reduction rate as described above for the introduction of a reduced thickness portion. Further, in condition 3, a concave portion having a diameter of 75 μm and a depth of 20 μm and a through hole having a diameter of 40 μm were used in combination for the introduction of a reduced thickness portion. The weight reduction rate is the same as in conditions 1 and 2. Further, as a comparison, a sample was prepared in which only the groove formation was performed and no recess or through hole was provided (Condition 4). Each material subjected to the treatments of Condition 1, Condition 2, Condition 3, and Condition 4 was subjected to decarburization annealing and secondary recrystallization treatment, and then a final product was obtained by planarization annealing. As a result of measuring the magnetic properties of the obtained final products by the Epstein method described in JIS C2550, all the properties of the final products were 1.91 T or more in magnetic flux density B8.
Next, a three-phase transformer core (core weight 500 kg) was manufactured from the final product obtained above, and the iron loss characteristics were measured when the magnetic flux density of the core leg portion was 1.7 T at a frequency of 50 Hz. The iron loss characteristics at 1.7T and 50Hz were measured for no-load loss using a wattmeter. The obtained results are shown in FIG.
From Fig. 1, the iron loss of the transformer is reduced by introducing the recesses and through-holes in a weight reduction rate of 0.01% to 0.05% in addition to the groove processing, and the recesses and through-holes between the grooves are made of low iron. It has been found that it works favorably. Although these improvement mechanisms are not clear, the reason why the transformer iron loss is improved at 0.01% or more is that the magnetic flux flow in the transformer core is crystal oriented due to the formation of the demagnetizing field by the reduced thickness part. This is thought to be due to the suppression of iron loss increase when flowing in other directions. On the other hand, in the region exceeding 0.05%, the disturbance of the magnetic domain becomes remarkable, and conversely, the iron loss increasing component such as the in-plane eddy current loss is considered to have increased.

  From the above, in the present invention, plate thickness reduction portions corresponding to 0.01 to 0.05% in weight reduction rate are interspersed between the linear grooves.

Next, the composition of the grain-oriented electrical steel sheet suitably used in the present invention will be described. The material of the present invention is silicon-containing steel, and any conventionally known composition can be adapted. However, it is preferable to use the following composition from the viewpoint of improving magnetic properties.
C: 0.01 to 0.10% by mass (hereinafter simply referred to as%)
C is an element useful not only for uniform refinement of the structure during hot rolling and cold rolling but also for the development of Goss orientation, and is preferably added in an amount of 0.01% or more. On the other hand, if the content exceeds 0.10%, the Goth orientation may be disturbed, so the upper limit is preferably 0.10%.
Si: 2.0 to 4.5%
Si increases the specific resistance of the steel sheet and contributes effectively to the reduction of iron loss. However, if it exceeds 4.5%, the cold rolling property is impaired. On the other hand, if it is less than 2.0%, not only the specific resistance is lowered, but also the crystal orientation is randomized by α-γ transformation during the final high-temperature annealing performed for secondary recrystallization and purification, and sufficient iron loss is caused. The improvement effect may not be obtained. Therefore, the Si content is preferably 2.0% to 4.5%.
Mn: 0.02 to 0.12%
Mn needs to be at least about 0.02% to prevent hot embrittlement. On the other hand, if it is too much, the magnetic properties may be deteriorated. Therefore, 0.02% to 0.12% is preferable.
Inhibitors (precipitates) include so-called MnS, MnSe, and AlN. In the case of MnS and MnSe, it is preferable to contain at least one selected from Se and S in an amount of 0.005% to 0.06%. Se and S are both effective elements as inhibitors for controlling secondary recrystallization of grain-oriented silicon steel sheets. From the viewpoint of securing restraining power, at least 0.005% is required. On the other hand, if it exceeds 0.06%, the effect may be impaired. The lower and upper limits are preferably about 0.005% and 0.06%, respectively.
In the case of AlN, Al: 0.005% or more and 0.10% or less and N: 0.004% or more and 0.015% or less are preferable for the same reason as in the case of the MnS and MnSe systems described above. MnS, MnSe, and AlN can be used together.
In addition to the above-described S, Se, Al, Cu, Sn, Cr, Ge, Sb, Mo, Te, Bi, and P are also advantageously adapted as inhibitor components, so Cu, Sn, Cr, Ge, Sb , Mo, Te, Bi, and P can also be contained in small amounts. The preferred range of addition of each component when contained is 0.01% to 0.15% for Cu, Sn, Cr, 0.005% to 0.1% for Ge, Sb, Mo, Te, Bi, and 0.01% to 0.2% for P It is as follows. Each of these inhibitor components can be used alone or in combination. Among the above, C, Al, N, S, and Se are blunted and removed after fulfilling the intended purpose in the manufacturing process, and remain in the product plate to the extent of impurities.

Next, the manufacturing method of the grain-oriented electrical steel sheet of this invention is demonstrated.
The steel containing the above components is usually made into a slab by a continuous casting machine or ingot forming, and then finished to a thickness of 2 to 3 mm by hot rolling. Next, the hot-rolled steel sheet is subjected to hot-rolled sheet annealing as necessary, and then cold-rolled steel sheet having a final product thickness is obtained by one cold rolling or two cold rolling sandwiching intermediate annealing. This cold-rolled steel sheet is usually subjected to secondary recrystallization annealing and removal of impurities by high-temperature box annealing up to about 1200 ° C. after decarburization annealing. The coil that has been subjected to the box annealing corrects the winding of the plate and is flattened and annealed to apply and bake a glass coating, resulting in a product.

The groove processing for magnetic domain subdivision and the introduction of the reduced thickness portion between the grooves, which are the characteristics of the present invention, may be performed after the final cold rolling or before the completion of the flattening annealing. Furthermore, it can also be implemented in the form of additional machining after planarization annealing. However, in this case, it is necessary to re-apply and bake a glass film having an insulating effect.
The introduction method is not particularly limited. As the groove processing, there are methods by electrolytic polishing, chemical polishing, and machining. The grooving is only required to have a plurality of lines in the direction (steel plate width direction) substantially orthogonal to the rolling direction, and the shape, size, etc. are not particularly limited. From the viewpoint of preventing deterioration of B8 (magnetic flux density at a magnetizing force of 800 A / m), which is a general index for evaluating magnetic flux density, the groove cross-section is preferably a shape close to a rectangle, with a width of 150 μm or less and a depth of 40 μm or less.
Examples of the introduction of the recesses between the grooves include electrolytic polishing, chemical polishing, and machining. On the other hand, the introduction of the through hole includes a method of irradiating a focused laser beam or plasma. In introducing the plate thickness reduction portion, for example, minute recesses and minute through holes are interspersed so that the weight reduction rate is 0.01 to 0.05% between the linear grooves. When the concave portions and the through holes are scattered, it is preferable to introduce the concave portions and the through holes so that the concave portions and the through holes are uniformly scattered between the linear grooves. The shape of the thickness reduction portion is not limited, but the slope of the portion (wall surface) that intrudes into the recess from the steel plate surface is preferably as steep as possible from the viewpoint of demagnetizing field formation, preferably in the thickness direction It is preferably 60 ° or less, more preferably 45 ° or less. Further, the size is preferably about 200 μm or less for the longest diameter (in the case of a substantially circular shape) in order to prevent the deterioration of B8 and maintain the strength of the steel sheet. The depth is preferably 5 μm or more in order to obtain an effect of reducing iron loss by forming a demagnetizing field.

  Using a cold rolled steel sheet for directional electrical steel sheets with a plate thickness of 0.27 mm, half the conventional groove forming treatment as a comparative example, the remaining half is a recess formed between the grooves Was formed by electrolytic polishing at the same timing as the groove formation. At this time, the grooves were linear grooves, all of the groove widths were average 65 μm, the depth was 19 μm on average, and the pitch was 3.5 mm. The size of the recesses between the grooves was 45 μmφ, the depth was 25 μm, and the weight reduction rate was 0.03%.

The material obtained as described above was subjected to normal decarburization annealing and box annealing for secondary recrystallization, and then an insulating film was applied and baked in flattening annealing. Next, when the magnetic flux density was measured, B8 of the comparative example was 1.916T, and B8 of the invention example was 1.912T. The measurement of the magnetic flux density is the same method as in FIG.
Next, the material after applying the insulating coating was processed into a three-phase transformer core having a core weight of 750 kg, and the iron loss characteristics were measured. The iron loss measurement is the same method as in FIG.
As a result, the iron loss at a magnetic flux density of 1.7 T and 50 Hz of the iron core leg of the comparative example is 690 W, whereas the iron loss at a magnetic flux density of 1.7 T and 50 Hz of the iron core leg of the present invention example is as follows. Was 660W. From this result, improvement of iron loss was recognized in the examples of the present invention.

  For example, when the grain-oriented electrical steel sheet of the present invention is used as an iron core of a transformer, low grain loss characteristics can be obtained. It is expected to be used in a wide range of applications, especially in applications that require low iron loss such as equipment.

It is the figure which showed the relationship between the weight reduction rate by a recessed part and a through-hole, and a transformer iron loss.

Claims (2)

A grain-oriented electrical steel sheet having a plurality of grooves extending in the steel sheet width direction,
A plate thickness reduction portion is formed between the grooves, and the total thickness reduction amount by the plate thickness reduction portion is a weight reduction rate with respect to the steel plate before the plate thickness reduction portion is formed. A grain-oriented electrical steel sheet characterized by being 0.01 to 0.05%.   2. The grain-oriented electrical steel sheet according to claim 1, wherein the thickness-reducing portion comprises a recess and / or a through hole.

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