Grain-oriented electromagnetic steel sheet

Abstract

Provided is an oriented electromagnetic steel sheet having both low iron loss and low magnetostriction, which is excellent in transformer characteristics. The oriented electromagnetic steel sheet has a heat-strained region extending linearly in a direction transverse to a rolling direction, and in a strain distribution in the rolling direction of the heat-strained region, the strain at both ends of the heat-strained region is a tensile strain that is greater than the strain at the center of the heat-strained region.

Description

Technical Field

[0001] This invention relates to oriented electromagnetic steel sheets suitable as core materials for transformers and the like. Background Technology

[0002] Oriented magnetic steel sheets are used, for example, as materials for transformer cores. In such transformers, it is necessary to suppress energy loss and noise. The energy loss is affected by the iron loss of the oriented magnetic steel sheet, and the noise is affected by the magnetostrictive properties of the oriented magnetic steel sheet.

[0003] In recent years, in particular, from the perspective of energy conservation and environmental constraints, there has been a strong demand to reduce energy losses and noise in transformers. Therefore, the development of orientation-oriented electromagnetic steel sheets with good iron loss and magnetostrictive properties has become extremely important.

[0004] Here, the iron loss of the oriented electromagnetic steel sheet mainly consists of hysteresis loss and eddy current loss. Methods to improve hysteresis loss include developing methods to highly orient the (110)

[001] orientation, known as GOSS orientation, in the rolling direction of the steel sheet, and methods to reduce impurities in the steel sheet. Furthermore, methods to improve eddy current loss include increasing the resistance of the steel sheet by adding Si and applying film tension in the rolling direction of the steel sheet.

[0005] However, these methods have limitations in manufacturing when pursuing further reductions in iron loss of oriented electromagnetic steel sheets.

[0006] Therefore, as a method to further reduce iron loss in oriented electromagnetic steel sheets, magnetic domain refinement technology has been developed. Magnetic domain refinement technology refers to the process of introducing non-uniformity in magnetic flux by physical methods such as forming grooves or introducing localized strain into the steel sheet after final annealing or sintering of the insulating film. This refines the width of the 180° magnetic domains (main domains) formed along the rolling direction, thereby reducing iron loss, especially eddy current loss, in oriented electromagnetic steel sheets.

[0007] For example, Patent Document 1 discloses the following technology: by introducing linear grooves with a width of less than 300 μm and a depth of less than 100 μm into the surface of a steel plate, the iron loss of more than 0.80 W / kg is improved to less than 0.70 W / kg.

[0008] Furthermore, Patent Document 2 discloses the following method: by irradiating the surface of a steel plate with a plasma flame in the width direction after secondary recrystallization and locally introducing thermal strain, when the magnetic flux density (B8) of the steel plate is 1.935T when excitation is performed with a magnetization force of 800 A / m, the iron loss (W) when excitation is performed at a maximum magnetic flux density of 1.7T and a frequency of 50Hz is... 17 / 50 The efficiency was improved to 0.680 W / kg.

[0009] It should be noted that the method for introducing linear grooves disclosed in Patent Document 1 does not lose its domain refinement effect even after stress-relief annealing following core forming, and is therefore referred to as heat-resistant domain refinement. On the other hand, the method for introducing thermal strain disclosed in Patent Document 2 cannot achieve the effect of introducing thermal strain due to stress-relief annealing, and is therefore referred to as non-heat-resistant domain refinement.

[0010] Here, in heat-resistant domain refinement, linear grooves are applied to the steel plate, but it is known that this treatment degrades the permeability of the steel plate. On the other hand, in non-heat-resistant domain refinement, local strain is introduced into the steel plate, and the permeability degradation seen in heat-resistant domain refinement does not occur. Therefore, in transformers using laminated cores that do not require annealing during the manufacturing process, steel blanks subjected to non-heat-resistant domain refinement are typically used.

[0011] Furthermore, non-heat-resistant magnetic domain refinement can significantly reduce eddy current losses by introducing localized strain into the steel plate. On the other hand, it is known that non-heat-resistant magnetic domain refinement leads to deterioration of hysteresis losses and magnetostriction due to the introduction of this strain.

[0012] Therefore, in order to develop oriented electromagnetic steel sheets with better iron loss and magnetostriction characteristics than those of the past, and further in order to develop transformers with better energy loss and noise characteristics than those of the past, it is necessary to optimize the strain introduction during the refinement of non-heat-resistant magnetic domains.

[0013] To address this requirement, recent oriented electromagnetic steel sheets have achieved a significant improvement in iron loss by combining the above methods, particularly by implementing high orientation and magnetic domain refinement on the steel sheets.

[0014] Existing technical documents

[0015] Patent documents

[0016] Patent Document 1: Japanese Patent Publication No. 6-22179

[0017] Patent Document 2: Japanese Patent Application Publication No. 7-192891 Summary of the Invention

[0018] However, when the oriented electromagnetic steel sheets manufactured in this way are processed into transformers, the iron loss increases due to the high orientation, resulting in an increased assembly factor (hereinafter also referred to as BF). This leads to the problem of not being able to fully utilize the low iron loss characteristics of the billet. It should be noted that BF refers to the ratio of the transformer's iron loss to the iron loss of the electromagnetic steel sheet billet. The closer this value is to 1, the better the transformer's iron loss.

[0019] One important factor contributing to increased flow factor (BF) is the rotating iron loss generated at the joints between electromagnetic steel sheets during transformer assembly. This rotating iron loss refers to the iron loss generated in the electromagnetic steel sheet blank when a rotating magnetic flux with a long axis is applied in the rolling direction.

[0020] Because the magnetization direction of oriented electromagnetic steel sheets is highly integrated in the rolling direction, as described above, when a rotating magnetic flux with a long axis is applied in the rolling direction, significant losses (rotating iron losses) are generated. In particular, such rotating magnetic flux is generated at the joints in transformer cores.

[0021] In contrast, the iron loss of electromagnetic steel slab blanks is the iron loss when an alternating magnetic field with magnetization components is applied only in the rolling direction. Therefore, when assembling into a transformer, if the rotational iron loss of the electromagnetic steel slab blanks is large, the iron loss of the transformer will increase relative to the iron loss of the electromagnetic steel slab blanks, i.e., the BF will increase.

[0022] Therefore, in order to improve the assembly factor of the transformer, it is necessary to reduce the rotating iron loss, that is, to promote the rotation of magnetization.

[0023] In non-heat-resistant magnetic domain refinement, for example, an energy beam is irradiated onto the surface of a steel sheet after final annealing or after sintering of the insulating film, thereby introducing local thermal strain. At this time, the location where the energy beam was irradiated in the direction intersecting the rolling direction retains compressive stress in the rolling direction. That is, in an orientation electromagnetic steel sheet with grains having a GOSS orientation (110)

[001] that becomes an easy magnetization axis, if compressive stress is generated in the rolling direction by introducing thermal strain, magnetic domains (closed magnetic domains) with magnetization directions are formed in the width direction (the direction orthogonal to the rolling direction) due to the magnetoelastic effect.

[0024] It should be noted that the magnetoelastic effect refers to the following effect: if a tensile stress is applied to an orientation-oriented electromagnetic steel sheet, the direction of the tensile stress is energy-stable; if a compressive stress is applied, the direction orthogonal to the compressive stress is energy-stable.

[0025] Since the closed magnetic domains formed in this way have magnetization components in the direction orthogonal to the rolling direction, they can improve the rotational iron loss and are beneficial to the improvement of the assembly coefficient.

[0026] However, it is known that if thermal strain is introduced in order to form closed magnetic domains, it will also lead to an increase in magnetostriction, that is, an increase in transformer noise.

[0027] Therefore, in order to achieve both improved assembly coefficient and reduced noise compared to the past, it is necessary to develop a new strain introduction mode that can effectively suppress the increase in magnetostriction and assembly coefficient.

[0028] The present invention was made in view of the above circumstances, and its purpose is to provide an orientation-oriented electromagnetic steel sheet that combines excellent transformer characteristics with low iron loss and low magnetostriction.

[0029] The inventors conducted repeated and in-depth research in order to achieve the above objectives.

[0030] First, methods to improve rotating iron loss, which leads to an increase in the assembly coefficient, were investigated.

[0031] The results showed that, in addition to forming closed magnetic domains as described above, rotating iron loss could also be improved by forming magnetic domains with magnetization components in a direction different from the rolling direction (hereinafter also referred to as auxiliary magnetic domains) when a rotating magnetic field was applied. Furthermore, it was found that such auxiliary magnetic domains tend to form starting from regions with high static magnetic energy, such as defects and strain.

[0032] Next, in steel slabs where non-heat-resistant magnetic domain refinement was performed, the optimal distribution of regions forming such auxiliary magnetic domains was investigated. Candidate locations for the formation of auxiliary magnetic domains considered during the study are shown below. Figure 1 .

[0033] As candidates, the interior of a closed magnetic domain (I), the end of a closed magnetic domain (II), and the region between irradiation lines (III) were considered.

[0034] In such candidates, closed magnetic domains have already formed inside closed magnetic domains (I), so the formation of auxiliary magnetic domains contributes little to the improvement of rotating iron loss.

[0035] Furthermore, in the region between irradiation lines (III), although the rotational iron loss is improved, the increased strain may lead to a deterioration in magnetostriction and hysteresis losses. In addition, besides the process of irradiating the energy beam in a manner that crosses the rolling direction, a new process of energy beam irradiation is required, which is not preferred from a manufacturing point of view.

[0036] In contrast, since the closed domain end (II) can eliminate the concerns of the situation described in (III) above, and auxiliary domains are formed on the outside of the closed domain, an improvement in rotating iron loss can be expected.

[0037] Further research was conducted on the strain distribution at the core of the location where the end (II) of the closed magnetic domain becomes the formation of the auxiliary magnetic domain.

[0038] The experimental results for completing this invention will be described below.

[0039] A 0.23 mm thick oriented electromagnetic steel strip, manufactured using a known method, is irradiated with an electron beam having a ring-shaped or Gaussian-shaped beam profile using energy beams of different outputs to form a thermally strained region (magnetic domain refinement). In this case, an electron beam with a beam diameter of 300 μm is used. Here, a beam with a ring-shaped beam profile refers to a beam with two peaks when the beam profile is obtained by scanning in any direction in the two-dimensional plane of the scanning beam. A schematic diagram of such a beam profile is shown below. Figure 2 .

[0040] A portion of the steel strip from the oriented electromagnetic steel sheet irradiated with such an electron beam was cut out, and the magnetic flux density (B8) and iron loss (billet iron loss: W) as magnetic properties were measured using the single-piece magnetic measurement method described in JISC2556. 17 / 50 ).

[0041] Furthermore, a three-phase stacked transformer (core weight 500kg) was fabricated from the aforementioned steel strip. At a frequency of 50Hz, the iron loss (transformer iron loss: W) was measured when the magnetic flux density at the core legs was 1.7T. 17 / 50 (WM)). The iron loss W of the transformer at 1.7T and 50Hz. 17 / 50 (WM) is the no-load loss measured using a wattmeter. Based on this W... 17 / 50 The value of (WM) and the W measured by the above-mentioned single-piece magnetic measurement method 17 / 50 The assembly coefficient is calculated using the following formula (1).

[0042] Assembly coefficient = W 17 / 50 (WM) / W 17 / 50 ···(1)

[0043] Furthermore, as described above, a three-phase model transformer for use in a transformer was fabricated using an oriented electromagnetic steel sheet irradiated with an electron beam. This model transformer was then energized in a soundproof room under conditions of maximum magnetic flux density Bm = 1.7T and a frequency of 50Hz, and the noise level (dBA) was measured using a noise meter.

[0044] In addition, similarly as described above, a portion was cut from the steel strip, and the strain distribution along the rolling direction around the thermal strain zone introduced by electron beam irradiation was measured using high-brightness X-ray strain scanning. As an example of such a strain distribution, a schematic diagram of the strain curve is shown below. Figure 3 .

[0045] As mentioned above Figure 3The strain curve is shown, indicating a strain distribution with two peaks near the ends of the hot strain zone. Let A be the average strain at both ends of the hot strain zone (average strain), and B be the strain at the center of the hot strain zone. The difference between these strains, ΔAB (=A-B), is calculated. Additionally, the billet iron loss W relative to ΔAB is investigated. 17 / 50 The relationship between transformer noise level and transformer assembly coefficient.

[0046] It should be noted that when the d-value of the reference point (strain-free point) is set to d0 and the d-value of the measurement object point is set to d1, Figure 3 The strain shown can also be calculated using the following formula: tensile strain is positive and compressive strain is negative.

[0047] {(d1―d0) / d0}×100 (unit: %)

[0048] The difference in dependent variable ΔAB is compared with the billet iron loss W. 17 / 50 The relationship is shown in Figure 4 The relationship between the difference in dependent variable ΔAB and the transformer noise level is shown in the figure. Figure 5 The relationship between the difference in dependent variables ΔAB and the transformer assembly coefficient is shown in the figure. Figure 6 .

[0049] observe Figure 4 It can be confirmed that in the region where the difference in the dependent variable ΔAB is positive (greater than 0.000%), W 17 / 50 The change is small. This is because such domain refinement is promoted by blocking the flow of magnetic poles, so in the region where ΔAB is positive (greater than 0.000%), the strain distribution in the thermal strain region does not have a significant adverse effect on the improvement of iron loss. On the other hand, in the region where ΔAB is negative, the deterioration of iron loss can be confirmed. This is thought to be because the total strain increases, and the hysteresis loss also increases.

[0050] observe Figure 5 It can be confirmed that transformer noise is suppressed in the region where the difference in strain ΔAB is positive (greater than 0.000%). This is believed to be because the thermal strain, which forms a distribution concentrated at both ends for magnetic domain refinement, is thus reduced in the total amount of strain within the thermal strain region.

[0051] observe Figure 6 It can be seen that the larger the difference in strain ΔAB, the lower the assembly coefficient tends to be. This is thought to be because the strain is concentrated in the region at the end (II) of the aforementioned closed magnetic domain, thus promoting the formation of the aforementioned auxiliary magnetic domain, improving rotating iron loss, and thereby reducing the iron loss of the transformer.

[0052] Based on the above experimental results, it was found that in the strain distribution of the above-mentioned hot strain zone in the rolling direction, the strain at both ends of the above-mentioned hot strain zone is a tensile strain greater than the strain at the center of the above-mentioned hot strain zone. That is, in the region where ΔAB is positive (greater than 0.000%), the transformer noise and assembly coefficient can be improved while maintaining the low iron loss effect brought about by magnetic domain refinement. Furthermore, when ΔAB is 0.040% to 0.200%, it has a higher effect of low noise and low assembly coefficient.

[0053] It was discovered that a linear thermal strain zone is preferably formed along the direction that crosses the rolling direction. Within this thermal strain zone, a larger tensile strain is formed at both ends of the rolling direction than at the center of the rolling direction. In particular, it was discovered that when the difference ΔAB (=A-B) between the average strain A at both ends of the thermal strain zone and the strain B at the center of the thermal strain zone is 0.040%~0.200%, it becomes an orientation-oriented electromagnetic steel sheet with higher transformer characteristics.

[0054] This invention was completed based on such insights and further repeated research, and the essential elements of this invention are as follows.

[0055] 1. A type of oriented electromagnetic steel sheet, characterized in that it is an oriented electromagnetic steel sheet having a thermal strain zone extending linearly along the transverse rolling direction.

[0056] In the strain distribution along the rolling direction of the aforementioned hot strain zone, the strain at both ends of the aforementioned hot strain zone is a tensile strain greater than the strain at the center of the aforementioned hot strain zone.

[0057] 2. According to the orientation-oriented electromagnetic steel sheet of 1, wherein, in the strain distribution in the rolling direction of the above-mentioned hot strain zone, the difference ΔAB (=A-B) between the average strain A at both ends of the above-mentioned hot strain zone and the strain B at the center of the above-mentioned hot strain zone is 0.040%~0.200%.

[0058] 3. The oriented electromagnetic steel sheet according to 2 above, wherein the ΔAB is 0.050% to 0.150%.

[0059] According to the present invention, an orientation-oriented electromagnetic steel sheet that reduces energy loss and noise in transformers can be provided. Attached Figure Description

[0060] Figure 1 This is a schematic diagram showing the candidate positions of magnetic domains with magnetization components formed in a steel slab with non-heat-resistant magnetic domain refinement used in the study of the present invention, in a direction different from the rolling direction.

[0061] Figure 2 This is a schematic diagram illustrating an example of a ring-shaped beam profile.

[0062] Figure 3 This is a schematic diagram illustrating an example of strain distribution in the thermal strain zone of the oriented electromagnetic steel sheet of the present invention.

[0063] Figure 4 It represents the difference in dependent variables ΔAB (=A-B) and the iron loss of billet W. 17 / 50 A diagram showing the relationships between them.

[0064] Figure 5 This is a graph showing the relationship between the difference in the dependent variable ΔAB (=A-B) and the transformer noise level.

[0065] Figure 6 This is a graph showing the relationship between the difference in dependent variables ΔAB (=A-B) and the transformer assembly coefficient. Detailed Implementation

[0066] (Oriented magnetic steel sheet)

[0067] The preferred embodiments of the present invention will now be described in detail.

[0068] <Composition of Oriented Electromagnetic Steel Sheets>

[0069] The composition of the oriented electromagnetic steel sheet or the slab used as its blank in this invention only needs to be a composition that produces secondary recrystallization. Furthermore, when using inhibitors, for example, if an AlN-based inhibitor is used, only appropriate amounts of Al and N are required; and if a MnS·MnSe-based inhibitor is used, only appropriate amounts of Mn, Se, and / or S are required. Of course, both AlN-based and MnS·MnSe-based inhibitors can be used simultaneously.

[0070] When using the above-mentioned inhibitor, the preferred contents of Al, N, S, and Se in the oriented electromagnetic steel sheet or the slab used as its billet are respectively

[0071] Al: 0.010–0.065% by mass

[0072] N: 0.0050~0.0120% by mass

[0073] S: 0.005–0.030% by mass, and

[0074] Se: 0.005~0.030% by mass.

[0075] Furthermore, the present invention can also be applied to orientation-oriented electromagnetic steel sheets with limited Al, N, S, and Se content, without the use of inhibitors. In this case, the Al, N, S, and Se content in the orientation-oriented electromagnetic steel sheet or the slab used as its blank is preferably controlled to be as follows:

[0076] Al: less than 0.010% by mass

[0077] N: less than 0.0050% by mass

[0078] S: less than 0.0050% by mass, and

[0079] Se: less than 0.0050% by mass.

[0080] Next, the basic composition and any added components of the oriented electromagnetic steel sheet or the slab used as its blank material of the present invention will be described in further detail.

[0081] C: less than 0.08% by mass

[0082] Carbon (C) is one of the basic components added to improve the microstructure of hot-rolled steel sheets. However, if the C content exceeds 0.08% by mass, it becomes difficult to decarburize to below 50 ppm by mass during the manufacturing process, preventing magnetic aging. Therefore, the C content is preferably below 0.08% by mass. Furthermore, since secondary recrystallization can occur even in C-free steel billets, a lower limit for the C content does not need to be specifically set. Therefore, the C content can also be 0% by mass.

[0083] Si: 2.0–8.0% by mass

[0084] Si is a fundamental component and an effective element for increasing the electrical resistance of steel and improving iron loss. Therefore, its content is preferably 2.0% by mass or more. On the other hand, if the content is greater than 8.0% by mass, in addition to deteriorating workability and passability, the magnetic flux density will also decrease. Therefore, the Si content is preferably 8.0% by mass or less. Furthermore, the Si content is more preferably 2.5% by mass or more, and even more preferably 7.0% by mass or less.

[0085] Mn: 0.005~1.0% by mass

[0086] Mn is one of the basic components and is an element required to improve hot workability. Therefore, its content is preferably 0.005% by mass or more. On the other hand, if the content exceeds 1.0% by mass, the magnetic flux density will deteriorate, so the Mn content is preferably 1.0% by mass or less. Furthermore, the Mn content is more preferably 0.01% by mass or more, and even more preferably 0.9% by mass or less.

[0087] In this invention, in addition to the basic components described above, Ni, Sn, Sb, Cu, P, Mo, and Cr can be used as appropriate additives known to effectively improve magnetic properties.

[0088] That is, the slab used as a oriented electromagnetic steel sheet or as its billet may preferably contain ingredients selected from...

[0089] Ni: 0.03–1.50% by mass

[0090] Sn: 0.01–1.50% by mass

[0091] Sb: 0.005~1.50% by mass

[0092] Cu: 0.03–3.0% by mass

[0093] P: 0.03–0.50% by mass

[0094] Mo: 0.005–0.10% by mass, and

[0095] Cr: 0.03 to 1.50% by mass of one or more.

[0096] Of the aforementioned additives, Ni is an effective element for improving the magnetic properties by enhancing the microstructure of the hot-rolled sheet. When the Ni content is less than 0.03% by mass, its contribution to magnetic properties is small. On the other hand, if it exceeds 1.50% by mass, secondary recrystallization becomes unstable, and the magnetic properties may deteriorate. Therefore, the Ni content is preferably in the range of 0.03 to 1.50% by mass.

[0097] Furthermore, among the aforementioned added components, Sn, Sb, Cu, P, Mo, and Cr, like Ni, are elements that improve magnetic properties. In either case, if the content is below the aforementioned lower limit, the effect is insufficient; conversely, if it is above the aforementioned upper limit, the growth of secondary recrystallized grains is suppressed, and the magnetic properties deteriorate. Therefore, the contents of Sn, Sb, Cu, P, Mo, and Cr are preferably within the aforementioned ranges.

[0098] It should be noted that the remaining components, besides those mentioned above, consist of Fe and unavoidable impurities.

[0099] Here, of the above components, C is decarburized in the first recrystallization annealing, and Al, N, S, and Se are purified in the second recrystallization annealing. Therefore, these components can be reduced to an unavoidable level of impurities in the steel sheet after the second recrystallization annealing (as the oriented electromagnetic steel sheet of the final product).

[0100] <Manufacturing of Oriented Electromagnetic Steel Sheets (before the formation of the thermal strain zone)>

[0101] The oriented electromagnetic steel sheet of the present invention can be manufactured in the following order before the thermal strain zone is formed.

[0102] That is, after hot rolling the steel billet (slab) of the orientation-oriented electromagnetic steel sheet composed of the above-mentioned composition, hot-rolled sheet annealing is performed as needed. Next, it is cold-rolled once or twice or more with intermediate annealing to process it into a steel strip of the final sheet thickness. Then, the steel strip is decarburized and annealed, coated with an annealing separating agent mainly composed of MgO, and then wound into a roll and subjected to a final annealing for the purpose of secondary recrystallization and formation of a magnesium olivine coating. As needed, the steel strip after such final annealing is subjected to planarization annealing to form an insulating coating (e.g., a magnesium phosphate-based tension coating). Thus, an orientation-oriented electromagnetic steel sheet before the formation of the hot strain zone can be obtained.

[0103] <Formation of thermal strain zone>

[0104] Next, a thermal strain region is formed in such an orientation-oriented electromagnetic steel sheet. The thermal strain region can be formed by non-heat-resistant magnetic domain refinement as one of the magnetization refinements. In this non-heat-resistant magnetic domain refinement, for example, thermal strain (forming a thermal strain region) can be locally introduced by irradiating the surface of the steel sheet after the final annealing or after the formation of the insulating film.

[0105] • Methods of irradiating with energy beams

[0106] When forming the thermal strain zone, the strain distribution of the present invention can be formed more effectively by using an energy beam with a circular (ring-shaped) intensity distribution, as seen in a ring-mode laser system.

[0107] As the beam source for the energy beam, lasers and electron beams can be used, and the desired strain distribution can be obtained by using either one. In the case of using a laser, a ring-mode laser system is sufficient; conversely, in the case of using an electron beam, a circular (ring-shaped) protrusion is formed on the cathode surface. Thus, the strain distribution of the present invention can be formed.

[0108] • Direction of energy beam

[0109] When manufacturing the oriented electromagnetic steel sheet of the present invention, thermal strain zones can be formed linearly on the steel sheet by irradiation with energy beams such as electron beams as described above.

[0110] Specifically, one or more electron guns are used to irradiate a beam of light intersecting the rolling direction while introducing linear thermal strain (forming a thermal strain zone). The scanning direction of the beam is preferably within the range of 60° to 120° relative to the rolling direction, and more preferably 90° relative to the rolling direction, i.e., scanning along the width direction of the sheet. This is because a larger deviation from the width direction increases the strain introduced into the steel sheet, leading to a deterioration in magnetostriction.

[0111] Furthermore, as long as the other requirements of this invention are met, the irradiation method of the energy beam can be either continuous irradiation along the scanning direction (continuous linear irradiation) or repeated irradiation with pauses and movements (point irradiation). Regardless of the irradiation method, the improved assembly coefficient and magnetostriction of this invention can be achieved.

[0112] It should be noted that the continuous linear and dotted patterns mentioned above are both forms of "linear".

[0113] The preferred conditions for irradiating the oriented electromagnetic steel sheet of the present invention will be described in further detail below.

[0114] Accelerating voltage: 60kV~300kV

[0115] A higher accelerating voltage increases the linearity of electrons and reduces the thermal impact on the outer side of the electron beam irradiation site, which is therefore preferable. For this reason, an accelerating voltage of 60 kV or higher is preferred. More preferably, it is 90 kV or higher, and even better if it is 120 kV or higher.

[0116] On the other hand, if the accelerating voltage is too high, shielding the X-rays generated by the electron beam irradiation becomes difficult. Therefore, from a practical point of view, the accelerating voltage is preferably 300 kV or less, and more preferably 200 kV or less.

[0117] • Spot diameter (electron beam diameter): less than 300 μm

[0118] A smaller spot diameter allows for more localized strain induction, which is therefore preferable. Thus, the spot diameter (beam diameter) of the electron beam is preferably 300 μm or less. Furthermore, the spot diameter (beam diameter) is more preferably 280 μm or less, and even more preferably 260 μm or less. It should be noted that the spot diameter refers to the full width at half maximum (WHM) of the beam profile obtained using a slit with a width of 30 μm and through the slit method.

[0119] • Beam current: 0.5mA~40mA

[0120] From the viewpoint of beam diameter, a low beam current is preferable. This is because if the current increases, the beam diameter tends to expand due to Coulomb repulsion. Therefore, a beam current of 40 mA or less is preferred. On the other hand, if the beam current is too low, the energy used to generate strain is insufficient. Therefore, a beam current of 0.5 mA or more is preferred.

[0121] Electron beam output: 300W~4000W

[0122] The electron beam output is calculated as the product of the accelerating voltage and the beam current. From the viewpoint of incorporating strain, a small electron beam output is preferable. This is because if the electron beam output is large, the amount of strain introduced is excessive, and the degradation of hysteresis loss is more severe than the improvement of eddy current loss, leading to noise degradation. Therefore, under the condition that the accelerating voltage and beam current meet the above-mentioned preferred range, the electron beam output is preferably 4000W or less. On the other hand, if the electron beam output is too small, the energy used to form strain is insufficient. Therefore, the electron beam output is preferably 300W or more.

[0123] • Vacuum level of the environment irradiated by the beam

[0124] Electron beams are scattered by gas molecules, resulting in an increase in beam diameter and halo diameter, and a decrease in energy. Therefore, the higher the vacuum level of the electron beam irradiation environment, the better; the pressure is preferably below 3 Pa. There is no particular limit to the lower limit, but if it is reduced too much, the cost of vacuum systems such as vacuum pumps will increase. Therefore, in practical applications, a vacuum level of 10 Pa is preferably preferred for electron beam irradiation. -5 Pa or above.

[0125] Furthermore, the conditions for irradiating with a laser during the manufacture of the oriented electromagnetic steel sheet of the present invention will be described in more detail.

[0126] Laser output: 20W~500W

[0127] From the perspective of incorporating strain, a low laser output is preferable. This is because if the laser output is too high, the amount of strain introduced will be excessive, and the deterioration of hysteresis loss will be more severe than the improvement of eddy current loss, leading to noise degradation. Therefore, the laser output is preferably below 500W. On the other hand, if the laser output is too low, the energy used to form strain will be insufficient. Therefore, the laser output is preferably above 20W.

[0128] <Strain Characteristics of Oriented Electromagnetic Steel Sheets>

[0129] Strain distribution

[0130] The strain distribution along the rolling direction in the hot strain zone of a steel plate surface can be determined using the EBSD-Wilkinson method. In this EBSD-Wilkinson method, for example, an electron beam is irradiated onto the steel plate surface to obtain Kikuchi patterns at each measurement point. Using a strain-free point as a reference point, analysis software such as CrossCourt is used to calculate the strain based on the strain of the Kikuchi patterns at each point.

[0131] Here, the thermal strain zone in this invention refers to the same region as the linear closed magnetic domain region formed by an energy beam linearly irradiating the steel plate. Furthermore, the length of the closed magnetic domains formed on the steel plate surface in the rolling direction (which is the same as the length of the thermal strain zone) can be determined using a commercially available magnetic domain observation instrument to obtain the magnetic domain pattern on the steel plate surface.

[0132] • Average dependent variable A and dependent variable B

[0133] The strain distribution along the rolling direction of the hot strain zone on the surface of the steel plate was determined using the method described above. The average strain at both ends of the hot strain zone along the rolling direction was designated as A, and the strain at the center of the hot strain zone along the rolling direction was designated as B. It should be noted that the strain at both ends of the rolling direction can be the same or different.

[0134] At this point, if the difference ΔAB(A-B) between A and B is positive (greater than 0.000%), the effects of the present invention can be obtained. If it is 0.040% to 0.200%, an orientation-oriented electromagnetic steel sheet with higher properties can be obtained. Furthermore, ΔAB is more preferably in the range of 0.050% to 0.160%.

[0135] Example

[0136] Next, the present invention will be described based on embodiments. The following embodiments represent preferred examples of the present invention and are not limited to any of these embodiments. Furthermore, modifications can be made to implement the invention within the scope that remains consistent with the spirit of the invention, and such modifications are naturally included within the technical scope of the present invention.

[0137] In this embodiment, a slab containing the components shown in Table 1, with the remainder being Fe and unavoidable impurities, is used as the blank material for the oriented electromagnetic steel sheet. This slab is subjected to hot rolling, hot-rolled annealing, a single cold rolling, decarburization annealing, application of an annealing separating agent, and final annealing under specified conditions to obtain a steel strip of oriented electromagnetic steel sheet with a thickness of 0.23 mm.

[0138] [Table 1]

[0139]

[0140] The steel strip of the aforementioned orientation-oriented electromagnetic steel sheet was used as the test material, and the test material was irradiated with an energy beam. As the beam source for this energy beam, either a laser or an electron beam (as shown in Table 2) was used, and irradiation was performed in either a continuous linear or point-like pattern (as shown in Table 2). This resulted in the formation of a thermal strain zone (magnetic domain refinement treatment) on the surface of the steel strip of the orientation-oriented electromagnetic steel sheet. Here, point-like irradiation refers to an irradiation pattern in which the energy beam is repeatedly stopped and moved in the scanning direction.

[0141] In the irradiation conditions of the energy beam, both the laser and electron beams are irradiated in a direction approximately 90° relative to the rolling direction. The beam output is 0.6–6 kW (accelerating voltage: 60–150 kV, beam current: 1–40 mA). Furthermore, in the case of the electron beam, the vacuum level of the irradiation environment is 0.3 Pa. The irradiated beam profile is annular, and a beam diameter of 200 μm is used. To change the values ​​of the average strain A, strain B, and ΔAB, in addition to the beam output, the energy difference between the energy maxima and the energy minima at the center of the annular profile, and the distance between the energy maxima, are adjusted during beam irradiation.

[0142] Thus, a portion is cut from the steel strip of the orientation-oriented electromagnetic steel sheet with the thermal strain zone formed, and the magnetic flux density (B8) and iron loss (billet iron loss: W) as magnetic properties are measured by the single-piece magnetic measurement method described in JIS C2556. 17 / 50 Furthermore, a three-phase stacked transformer (core mass 500kg) was fabricated from the aforementioned steel strip. The iron loss (transformer iron loss: W) was measured at a frequency of 50Hz when the magnetic flux density at the core legs was 1.7T. 17 / 50 (WM)). The iron loss W of the transformer at 1.7T and 50Hz. 17 / 50 (WM) is the no-load loss measured using a wattmeter. Based on this W... 17 / 50 The value of (WM) and the W measured by the above-mentioned single-piece magnetic measurement method 17 / 50 The assembly factor (BF) is calculated using the following formula (1). The results are shown in Table 2.

[0143] Assembly coefficient = W 17 / 50 (WM) / W 17 / 50 ···(1)

[0144] Furthermore, as described above, a three-phase model transformer for use was fabricated using oriented electromagnetic steel sheets that underwent magnetic domain refinement treatment. This model transformer was energized in a soundproof room under conditions of maximum magnetic flux density Bm = 1.7T and a frequency of 50Hz, and the noise level (dBA) was measured using a noise meter. The results are shown in Table 2.

[0145] In addition, a portion was cut from the steel strip as described above, and the strain distribution along the rolling direction around the hot strain zone was determined using the EBSD-Wilkinson method. Furthermore, the length of the closed magnetic domains formed on the steel plate surface along the rolling direction (the same length as the hot strain zone) was measured using a commercially available magnetic domain observer (SigmaHi-Chemical MV-95). Then, the average strain at both ends of the hot strain zone (average strain) was denoted as A, and the strain at the center of the hot strain zone was denoted as B. The difference in their strain, ΔAB (=A-B), was calculated. It should be noted that tensile strain is considered positive, and compressive strain is considered negative. These values ​​are shown in Table 2.

[0146] [Table 2]

[0147]

[0148] As shown in Table 2, compared to Nos. 37-40 where ΔAB is negative, Nos. 2-9, 11-18, 20-27, and 29-36 where ΔAB is positive (greater than 0.000%) consistently demonstrate low noise and low assembly coefficient effects regardless of the energy beam source or irradiation method. Particularly noticeable are the effects when ΔAB is between 0.040% and 0.200%. Furthermore, even higher effects are observed when ΔAB is between 0.050% and 0.150%.

Claims

1. A type of oriented electromagnetic steel sheet, characterized in that, It is an orientation-type electromagnetic steel sheet with a thermal strain zone extending linearly along the transverse rolling direction. In the strain distribution along the rolling direction of the hot strain zone, the strain at both ends of the hot strain zone is a tensile strain greater than the strain at the center of the hot strain zone. In the strain distribution along the rolling direction of the hot strain zone, the difference ΔAB between the average strain A at both ends of the hot strain zone and the strain B at the center of the hot strain zone, i.e., A-B, is 0.040%~0.200%.

2. The oriented electromagnetic steel sheet according to claim 1, wherein, The ΔAB is 0.050% to 0.150%.

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