JP7375728B2 - Manufacturing method and manufacturing equipment for core members for stacked core transformers - Google Patents

Description

The present invention relates to a method for manufacturing a core member used in a core of a stacked core transformer, and a manufacturing device used in the method.

A transformer is an essential power device in daily life that changes the voltage of a power supply through the conversion of electrical energy and magnetic energy. During the operation of this transformer, energy losses such as iron loss and copper loss occur, but iron loss is decreasing year by year due to improvements in the magnetic properties of the soft magnetic materials used in the transformer core. be.

For example, when using grain-oriented electrical steel sheets, core loss has been reduced by techniques such as controlling crystal orientation, increasing resistivity, refining magnetic domains, and reducing plate thickness. Specifically, with crystal orientation control technology, we have achieved high magnetic flux density and low iron loss by optimizing the steel components and manufacturing process and highly aligning the crystal orientation to the Goss {110}<001> orientation. . Furthermore, in techniques for increasing specific resistance, eddy current loss, which is a part of iron loss, has been reduced by containing more Si or Al in steel to increase the electrical resistance of steel. However, if Si is excessively contained in steel, there is a problem in that it becomes difficult to manufacture by rolling. In addition, technology for reducing iron loss through magnetic domain control involves not only applying tensile stress to steel sheets using insulating coatings, but also forming grooves on the surface of steel sheets by etching, etc., and applying laser beams, electron beams, etc. to steel sheets. Techniques have been developed and put into practical use for refining magnetic domains by surface processing such as irradiating the surface to form linear or dotted strain regions. In addition, the plate thickness reduction technique is based on the theory that eddy current loss decreases as the plate thickness decreases. However, excessive reduction in plate thickness not only destabilizes the occurrence of secondary recrystallization, but also causes problems such as a decrease in the productivity of the steel plate itself and an increase in the number of man-hours for stacking the transformer core.

By the way, the iron loss characteristics of a stacked core transformer largely depend on the magnetic properties of the soft magnetic material that is the core material. was relying on improvements. As the above-mentioned soft magnetic material, grain-oriented electrical steel sheets are mainly used. The method for manufacturing grain-oriented electrical steel sheets includes melting steel having a predetermined composition, forming a steel material (slab) by continuous casting, etc., and then hot rolling the steel material into a hot-rolled sheet. After hot-rolled sheet annealing as necessary, cold-rolling is carried out once or two or more times with intermediate annealing to obtain a cold-rolled sheet of final thickness, and the cold-rolled sheet is subjected to primary recrystallization. After performing primary recrystallization annealing that also serves as annealing or decarburization annealing, and applying an annealing separator to the surface of the steel sheet, final annealing is performed, and an insulating coating is further applied. A manufacturing process consisting of a series of steps in which magnetic domain refining treatment is performed in the step or final step has been established, and the optimum conditions for each manufacturing step have also been found. Therefore, within the framework of the above manufacturing process, it has become quite difficult to reduce iron loss in stacked core transformers. On the other hand, it has been proposed to achieve even greater reductions in iron loss through the development of new technologies, but this has not been put into practical use due to many issues in terms of manufacturability and manufacturing costs.

Therefore, as an iron core loss reduction technology that is not limited by the above-mentioned conventional technology, Patent Document 1 discloses that by cutting out a CI type or EI type core member of a transformer, subjecting it to stress relief annealing, and irradiating it with a pulse laser, Methods have been proposed to improve the core loss of transformers.

Japanese Unexamined Patent Publication No. 56-083012

However, the technique of Patent Document 1 uses a pulsed laser, which is not preferable from the viewpoint of high production efficiency and prevention of coating damage, and also does not disclose strain relief annealing conditions, which are important conditions for reducing iron loss. Not yet. Furthermore, the method is aimed at relatively small CI or EI type transformers, and there is a problem in that it is difficult to directly apply it to large transformers.

Therefore, an object of the present invention is to propose a method for manufacturing a core member that can further reduce iron loss in a stacked core transformer, without being limited by the conventional manufacturing technology of grain-oriented electrical steel sheets, and to An object of the present invention is to provide a manufacturing apparatus for use in the method.

In view of the above-mentioned problems faced by the prior art, the inventors have proposed to improve the above-mentioned already established production process of grain-oriented electrical steel sheets, that is, to improve the iron loss characteristics of grain-oriented electrical steel sheets, thereby improving the stacked core type transformation. We focused on reducing iron loss in stacked core transformers by reviewing the method of manufacturing transformer core members from grain-oriented electrical steel sheets.

The inventors first organized the steps from manufacturing a grain-oriented electrical steel sheet to assembling a transformer. For example, in the case of a stacked core type transformer, the core is made by slitting a grain-oriented electromagnetic steel sheet (material coil) wound into a coil to a desired width, and then from the slit coil, the legs and Generally, a core member such as a yoke is cut out by a shearing process such as bevel cutting, and the cut-out core members are stacked one by one to assemble the core and incorporate it into a transformer. However, this method using shear processing has a problem in that processing strain is introduced when cutting out the core member, increasing iron loss of the transformer.

On the other hand, in the case of a wound core type transformer, after the above-described slit coil is assembled into a coiled wound core, strain relief annealing is performed. This is because when assembling the wound core, the material (grain-oriented electrical steel sheet) is bent and a large strain is introduced, which significantly increases the iron loss of the material itself, so this strain is removed by strain relief annealing. . However, although strain relief annealing has the advantage of removing processing strain, it also has the disadvantage of eliminating the effects of non-heat-resistant magnetic domain refining treatment, such as laser beam irradiation, applied to grain-oriented electrical steel sheets. There is.

Therefore, the inventors reviewed the process of manufacturing the core of the transformer from a grain-oriented electrical steel sheet after finish annealing, removed the processing distortion when cutting out the core member in a stacked core transformer, and We investigated a technology that can further enhance the effect of reducing iron loss through magnetic domain refining processing.

First, the inventors studied the manufacturing flow of three stacked core transformers shown in Table 1 below.
Manufacturing flow 1 is a manufacturing flow for manufacturing a stacked core transformer using a conventional grain-oriented electrical steel sheet coated with an insulating film after final annealing. In this case, as described above, there is a problem in that the iron loss of the transformer worsens due to processing distortion when cutting out the core member.
In addition, in manufacturing flow 2, the insulation coating in manufacturing flow 1 is performed after the core member is cut out, and the processing strain at the time of cutting out the iron core member can be removed by heat treatment when the insulation coating is applied, but at this stage. There is a problem in that the productivity of forming the insulating film is lower than that in the conventional manufacturing flow 1 in which the insulating film is formed on a large coil.
On the other hand, manufacturing flow 3 is a manufacturing flow in which a strain relief annealing step is added between the core member cutting and core/transformer assembly in the conventional manufacturing flow 1. This manufacturing flow is preferable in that it is possible to enjoy the effect of removing processing strain, but the addition of strain relief annealing and further addition of magnetic domain refining treatment at the above stage is less convenient than conventional manufacturing in terms of productivity and manufacturing cost. This is more disadvantageous than flow 1.

However, as a result of further studies, the inventors found that strain relief annealing in manufacturing flow 3 can be carried out in a short time if an appropriate temperature range is selected, and an excessive increase in manufacturing costs can be suppressed. In addition, the stress relief annealing does not only remove processing strain, but also increases the tensile stress that the insulating coating imparts to the steel sheet. By performing the magnetic domain refining process by irradiating the laser beam at a high temperature until the end of the process, it is possible to not only efficiently perform the magnetic domain refining process, but also to perform the magnetic domain refining process without causing film damage even with high-power laser beam irradiation. The present inventors discovered that the treatment became possible and that a more excellent iron loss reduction effect could be obtained, leading to the development of the present invention.

Based on the above knowledge, the present invention provides a method for manufacturing an iron core member for a stacked core transformer by cutting out an iron core member from a soft magnetic material having a thickness of 0.30 mm or less. After strain relief annealing is performed by holding at a temperature of 1 to 1000 seconds at a temperature of 1 to 1000 seconds, when the core member is cooled, from 600 to 50 °C, in a direction transverse to the rolling direction of the core member. We propose a method for manufacturing a core member for a stacked core transformer, which is characterized in that magnetic domain refining treatment is performed by repeatedly irradiating laser beams at intervals of 1 to 30 mm in the rolling direction.

The method of manufacturing a core member for a stacked core transformer according to the present invention is characterized in that the core member is cut out by shearing.

Further, in the method for manufacturing a core member for a stacked core transformer of the present invention, the strain relief annealing is performed in an atmosphere of any one of nitrogen gas, hydrogen gas, and Ar gas, a mixed gas of one or more of the above gases, or DX. It is characterized in that it is carried out in any of the following atmospheres: a gas or RX gas atmosphere, a reduced pressure atmosphere in which the degree of vacuum of any of the above gases is 10 ⁴ Pa or less, and a reduced pressure atmospheric atmosphere in which the degree of vacuum is 10 ³ Pa or less. shall be.

In addition, in the method of manufacturing a core member for a stacked core transformer of the present invention, when performing magnetic domain refining treatment by irradiating the core member after strain relief annealing with a laser beam, the laser beam is The method is characterized in that at least one of the output of the laser beam, the scanning speed, the repetition interval in the rolling direction, and the angle formed between the rolling direction and the scanning direction of the laser beam is changed.

Further, the soft magnetic material used in the method of manufacturing a core member for a stacked core transformer of the present invention is characterized in that it is a grain-oriented electrical steel sheet subjected to heat-resistant magnetic domain refining treatment.

The present invention also provides processing equipment for cutting out members that will become the core of a stacked core transformer from a soft magnetic material with a thickness of 0.30 mm or less, and a conveyor that aligns and conveys the cut out core members. , a tunnel-type annealing furnace that performs strain relief annealing held at a temperature of 700° C. or more and 1000° C. or less for 1 second or more and 1000 seconds or less, and if necessary, cooling equipment that forcibly cools the iron core member after the heat treatment; A stacked core type equipped with a laser beam irradiation device that repeatedly irradiates a laser beam in a direction transverse to the rolling direction of each core member at intervals of 1 to 30 mm in the rolling direction in synchronization with the conveyance speed of the conveyor. This is a manufacturing device for transformer core members.

According to the present invention, it is possible to reduce the iron loss of a stacked core transformer more than before, improve the energy usage efficiency of the transformer, and expand the usage environment, which has industrial effects. is large.

It is a figure explaining an example of the core member for stacked core type transformers of a three-phase tripod. It is a figure explaining the example of a change of the process pattern of magnetic domain refinement performed on an iron core member. It is a figure explaining the method of measuring the amount of warpage of a steel plate.

First, the experiment that led to the development of the present invention will be explained.
<Experiment 1>
A grain-oriented electrical steel sheet (Material A) with a thickness of 0.23 mm, which has been subjected to non-heat-resistant magnetic domain refining treatment using plasma flame and has a phosphate-based tension-imparting insulation coating on its surface, and magnetic domain refining. A grain-oriented electrical steel sheet (Material B) having a thickness of 0.23 mm and having a phosphate-based tension-imparting insulating coating formed on its surface was prepared without being subjected to chemical treatment. The above materials A and B have the same manufacturing conditions except for the magnetic domain refining treatment, and the magnetic flux density B ₈ (magnetic flux density at magnetic field strength: 800 A/m) in the rolling direction is 1. 939T, which is almost the same value as 1.941T for the material without magnetic domain refining treatment. From both materials, 5 sets of 30 pieces per set were cut out by shearing into SST specimens measuring 300 mm in length x 100 mm in width with the rolling direction as the length direction, and then subjected to the treatments shown in Table 2. Thereafter, the iron loss W _17/50 of each test piece was measured by an SST test, and the average value of the 30 pieces was determined. Note that all the end surfaces of the sheared test pieces were left as they were. Moreover, the strain relief annealing in the table was carried out under conditions of soaking and holding at a temperature of 800° C. for 2 hours in an Ar atmosphere. Further, the magnetic domain refining treatment after strain relief annealing was carried out using the method and conditions applied to the above-mentioned material A using a plasma flame.

Table 2 also shows the measured values of the iron loss W _17/50 . From the above table, No. 1 was subjected to shearing, strain relief annealing, and then magnetic domain refining treatment. It can be seen that under condition No. 5, a significantly low iron loss value was obtained. Also, No. 2 (as-sheared condition) and No. Comparing 3 (conditions in which strain relief annealing was performed after shearing), there is no noticeable change in the magnetic flux density after shearing, so the reduction in iron loss is due to the increase in magnetic flux density due to simple removal of processing strain. It is thought that this is not due to

Therefore, in order to investigate the above cause, No. 2 and no. Regarding the steel plate under condition 3, the radius of curvature of the steel plate when the tension-applying insulation coating was removed with alkali was measured, and the tension imparted to the steel plate by the insulation coating was estimated using Stoney's formula below.
σ=Ed/3(1-ν)R
Here, E: Young's modulus in the rolling direction, d: plate thickness (mm), ν: Poisson's ratio, R: radius of curvature (mm) when the coating on one side is removed, and in the above calculation, E: 125GPa, ν=0.38.
In addition, the radius of curvature R of the steel plate used in the above calculation is calculated using a test piece of width: 30 mm x length: 320 mm, with the width direction perpendicular to the horizontal plane, as shown in Figure 3, when the rolling direction is the length direction. (vertical), the free length L and the amount of warpage δ of the steel plate were measured, and these values were determined using the following formula.
R≒L ² /2δ

As a result of the above measurement, No. The coating tension σ of the steel plate under condition No. 2 was 13 MPa, whereas the coating tension σ of the steel sheet under condition No. 2 was 13 MPa. The coating tension of the steel plate under condition 3 was 15 MPa. From this result, it was inferred that strain relief annealing has the effect of increasing the coating tension imparted by the insulating coating through some mechanism, although the cause is not yet fully clear.

<Experiment 2>
Next, the inventors prepared the same materials A and B as above, and made all the core members constituting the core of the stacked core transformer shown in FIG. 1 so that the length direction of the core members was in the rolling direction. After cutting with an angle cutter and performing the treatments shown in Table 3, the core of the stacked core transformer shown in FIG. 1 was assembled, and the core loss W _17/50 of the transformer was measured. Note that all the end faces of the obliquely cut iron core member were left as sheared surfaces. In addition, the strain relief annealing was performed under conditions of soaking and holding at a temperature of 800° C. for 2 hours in an Ar atmosphere. Further, the magnetic domain refining treatment was performed using the method and conditions using plasma flame, which were applied to the material A in <Experiment 1> described above. The transformer core was made of steel plates with an outer diameter of 500 mm square and a width of 100 mm, and was made by laminating 70 steel plates so that the stacked thickness was about 15 mm and the core weight was about 20 kg. The lamination method at this time was 5-step step wrap stacking of two sheets.

The measurement results of the iron loss value of the above transformer are also listed in Table 3. As in the case of the veneer test in Table 2 above, after cutting at an angle, strain relief annealing was performed, and then magnetic domain refining treatment was performed. In the case where the iron was applied (No. 4), a significant reduction in iron loss was observed.

<Experiment 3>
Next, the inventors conducted an experiment to investigate appropriate stress relief annealing conditions.
A grain-oriented electrical steel sheet (B ₈ = 1.940T) with a thickness of 0.23 mm, which has not been subjected to magnetic domain refining treatment and whose surface is coated with a phosphate-based tension-imparting insulating coating, is processed by shearing. Several sets of 30 SST specimens each having a length of 300 mm in the rolling direction and 100 mm in the perpendicular direction to the rolling direction were cut out and heat treated to simulate strain relief annealing under various different conditions shown in Table 4. After that, a laser beam was irradiated to perform magnetic domain refining treatment, and then an iron loss W _17/50 was measured by an SST test. Note that all the end faces of the sheared SST specimens were left as they were. In addition, the laser beam irradiation was carried out with a beam diameter of 0.3 mm, an output of 100 W, and a repetition interval of 5 mm in the rolling direction.After the laser beam irradiation, visual observation of the irradiated area revealed that there was no coating damage on any of the test pieces. was not confirmed. Further, the heat treatment was performed using a tunnel furnace type continuous annealing furnace for soaking times up to 120 s, and using a batch annealing furnace for soaking times of 1200 s and 7200 s. Note that the above heat treatments were all performed under an Ar atmosphere. Further, the magnetic domain refining treatment after strain relief annealing was performed using the method and conditions using plasma flame applied to material A in <Experiment 1> described above.

Table 4 shows the average value of iron loss of the 30 SST test pieces along with the heat treatment conditions. From this result, regarding the heat treatment temperature, the iron loss improvement effect was not observed at 650°C, but was observed at temperatures of 700°C or higher. However, even if the heat treatment temperature is increased to 1000° C., the iron loss improvement effect is almost saturated. Therefore, in the present invention, the soaking temperature for strain relief annealing is in the range of 700°C or higher and 1000°C. Regarding the heat treatment time, at a temperature of 700° C. or higher, an iron loss improvement effect was observed when the soaking time was 1 s or longer. However, a heat treatment time of 1200 seconds or more is not suitable for continuous annealing and requires batch annealing, making it difficult to perform magnetic domain refining treatment immediately after annealing. Furthermore, compared to continuous annealing, it is not possible to obtain a significantly lower iron loss effect. Therefore, in the present invention, the soaking time for strain relief annealing is set in a range of 1 to 1000 seconds, which is suitable for continuous annealing.

<Experiment 4>
Next, the inventors conducted an experiment to investigate the influence of the atmosphere during strain relief annealing on iron loss.
The experiment was conducted under the same conditions as <Experiment 3> above, except that the atmosphere during strain relief annealing was changed variously as shown in Table 5. Table 5 shows the heat treatment conditions including the atmosphere and the measurement results of the iron loss W _17/50 after the magnetic domain refining treatment.

As can be seen from Table 5, strain relief annealing was performed in nitrogen gas, Ar gas, reduced pressure atmosphere (30 Pa), reduced pressure nitrogen (200 Pa), and hydrogen gas atmospheres, all of which showed a high iron loss reduction effect. . However, when compared in more detail, the nitrogen atmosphere is slightly less effective in reducing iron loss than other atmospheres. Therefore, in order to further enhance the iron loss reduction effect, it is preferable to use an atmosphere other than nitrogen, and it is particularly preferable to use an Ar atmosphere that can be stably supplied. Further, although not shown in the above table, a similar iron loss reduction effect was observed in a reduced pressure atmosphere using nitrogen gas, Ar gas, hydrogen gas, DX gas, or RX gas alone or in a mixture. Note that the above-mentioned "reduced pressure atmosphere" in the present invention refers to an atmosphere of 10 ⁴ Pa or less. However, in the case of a reduced pressure atmospheric atmosphere, the residual oxygen reacts with the insulating tension coating and reduces the tension imparting effect of the coating, so it is preferably 10 ³ Pa or less.

<Experiment 5>
Next, in order to investigate the influence of member temperature when performing magnetic domain refining treatment by laser beam irradiation, the inventors varied the member temperature during laser beam irradiation to determine the presence or absence of coating damage and iron loss. The effect on W _17/50 was investigated and the results are shown in Table 6. Here, the laser beam diameter shown in Table 6 refers to 1/e ² width of the maximum intensity. In addition, the presence or absence of coating damage was evaluated by visual judgment, and when damage was observed, it was indicated by ×, and when no damage was observed, it was indicated by ○. Moreover, iron loss W _17/50 is an average value when 30 test pieces having a length in the rolling direction of 300 mm and a length in the direction perpendicular to the rolling direction of 100 mm are subjected to an SST test.

From the results in Table 6, it can be seen that if the laser beam output is small, the iron loss reduction effect cannot be sufficiently obtained.On the other hand, if the laser beam output is too large, the iron loss reduction effect increases, but it may cause coating damage. However, it can be seen that when the temperature of the iron core member to which the laser beam is irradiated is raised, there is a tendency for coating damage due to laser beam irradiation to not occur up to high laser output. Therefore, when performing magnetic domain refining treatment by laser beam irradiation, it is best to perform the treatment after the strain relief annealing process in the previous process is completed and until the temperature of the core member has completely decreased, without causing coating damage and at high output. It is possible to irradiate a laser beam, which in turn makes it possible to further enhance the effect of the magnetic domain refining process and reach a lower core loss level. Specifically, the laser beam irradiation is preferably performed when the member temperature is 50° C. or higher. However, if the member temperature is excessively high, strain will not be sufficiently introduced and no magnetic domain refining effect will be obtained, so laser beam irradiation must be performed when the member temperature is 600° C. or lower.
The present invention was developed based on the above novel findings.

Next, a method for manufacturing a core member for a stacked core transformer according to the present invention will be specifically described.
<Material of iron core member>: Soft magnetic material with a thickness of 0.30 mm or less The material used for the iron core of the stacked core transformer of the present invention may be any soft magnetic material that is generally used for the iron core of a transformer. For example, grain-oriented electrical steel sheets, non-oriented electrical steel sheets including pure iron-based soft magnetic materials, amorphous alloy ribbons, etc. can be used. The material may be in the form of a coil or may be pre-sheared into a sheet. However, the thickness should be 0.30 mm or less in order to achieve low iron loss. Preferably it is 0.27 mm or less.

In addition, when _the above-mentioned soft magnetic material is a grain-oriented electrical steel sheet, it is desirable to use a steel sheet with a high magnetic flux density in order to further enhance the iron loss improvement effect by magnetic domain refining treatment. It is preferable that there be. In addition, when placing particular importance on iron loss characteristics, it is preferable to use a steel plate that has been subjected to heat-resistant magnetic domain refining treatment in which grooves, base metal fusion parts, etc. are formed on the surface of the steel plate.

Furthermore, when using a material in the form of a coil, a pre-process such as slitting is required before shearing, which reduces the yield of the material as a whole process. Furthermore, in the slitting process in which a coil is taken out, slit, and then wound into a coil, defects in the shape of the material, such as ear waves, are undesirable because they promote meandering and plate breakage. Therefore, it is preferable that the shape of the raw coil is good, and in particular, it is preferable that the flatness of the width end portion of the coil is equal to or higher than that of the width center portion.

In addition, when cutting out the iron core member from the material discharged from the slit coil by diagonal cutting, which will be described later, even if the material coil before slitting has a shape defect such as an ear wave, it is assumed that there is no shape defect. It is possible to process them equally. However, if the bevel cutting is to be performed with higher precision, it is preferable to trim the ends of the coil before the bevel cutting.

Cutting out the core member: shearing process The method for cutting out the core member for a stacked core transformer from the grain-oriented electrical steel sheet, which is the above-mentioned material, is preferably shearing process. For shearing, there are bevel cutting (using a shear or in-line swing shear), which is the most common method at present, and press processing (punching) using a mold, which was adopted in the experiment mentioned above. etc. However, methods such as laser cutting using a laser beam and wire cut cutting may also be used. Further, in order to position each member when laminating the stacked core members, it is desirable to perform hole drilling inside the core member in this step before strain relief annealing. The apparatus for manufacturing a core member for a stacked core transformer according to the present invention is provided with processing equipment for performing these processes.

There are no particular restrictions on the core of the stacked core transformer to which the technology of the present invention is applied, but in consideration of productivity during cutting, each member constituting the core must have a length of 100 mm or more. It is preferable that there be.

Strain relief annealing: 700° C. or higher and 1000° C. or lower x 1 s or more and 1000 s or less Next, the cut out iron core member is subjected to strain relief annealing to remove the processing strain introduced at the time of cutting. From the results of the above-mentioned <Experiment 3>, this strain relief annealing is preferably performed under conditions of soaking and holding at a temperature of 700° C. or more and 1000° C. or less for a period of 1 s or more and 1000 s or less. If the above temperature is less than 700°C or the holding time is less than 1 s, the iron loss reduction effect cannot be sufficiently obtained, whereas if it exceeds 1000°C or 1000 s, not only the above effect is saturated, but also productivity and energy costs are reduced. disadvantageous in terms of A preferable soaking temperature is in the range of 750° C. or more and 900° C. or less, and a preferable soaking time is in the range of 2 seconds or more and 120 seconds or less.

In addition, the atmosphere for strain relief annealing is an atmosphere of a single gas of nitrogen gas, hydrogen gas, or Ar gas, an atmosphere of a mixed gas of one or more of the above, an atmosphere of DX gas or RX gas, or a vacuum of any of the above gases. It is preferable to perform the treatment under either a reduced pressure atmosphere with a degree of vacuum of 10 ⁴ Pa or less, or a reduced pressure atmospheric atmosphere with a degree of vacuum of 10 ³ Pa or less. Note that the above-mentioned "reduced pressure atmosphere" in the present invention refers to an atmosphere of 10 ⁴ Pa or less. However, in the case of a reduced pressure atmospheric atmosphere, the residual oxygen reacts with the insulating tension coating and reduces the tension imparting effect of the coating, so it is preferably 10 ³ Pa or less.

Here, as the heat treatment furnace for performing the strain relief annealing, it is preferable to use a tunnel type furnace that can continuously perform heat treatment while transporting the cut out iron core member on a conveyor (conveyor belt). Further, in consideration of productivity and downsizing of equipment, an induction heating device may be installed in the heating zone of the heat treatment furnace.

Further, the cooling method after the heat treatment may be furnace cooling or air cooling, but from the viewpoint of preventing the equipment from becoming too long, forced cooling may be performed by installing gas cooling equipment, mist cooling equipment, or the like. At this time, it is important to prevent the temperature difference within the core member or between the core member and the conveyor belt from becoming large. This is because if there is a temperature difference, thermal strain will occur in the iron core member, causing an increase in iron loss. Incidentally, from the viewpoint of the above-mentioned temperature difference and maintainability, gas cooling is more preferable than mist cooling.

Magnetic domain refining treatment Next, the iron core member after the stress relief annealing is subjected to a non-heat resistant magnetic domain refining treatment by irradiating it with a laser beam. In addition to the laser beam irradiation method, known methods for non-heat-resistant magnetic domain refining processing include an electron beam irradiation method, a method using a plasma flame, a method using a micro-protrusion roll, etc. The most advantageous method is to use a laser beam, which has a large iron loss reduction effect and is easy to use in terms of equipment.

Here, when performing magnetic domain refining treatment by laser beam irradiation, it is necessary to align the iron core members on the conveyor. For example, when a core member discharged from a strain relief annealing furnace is irradiated with a laser beam on a conveyor, before or after strain relief annealing, a side guide or the like is used to ) and the transport direction of the conveyor, and then apply laser beam irradiation based on the positional information of the aligned iron core members.

In addition, when performing magnetic domain refining treatment by laser beam irradiation, it can be carried out until the core member has finished cooling, but as shown in the results of <Experiment 5> mentioned above, the temperature of the core member is high. The more damage to the coating caused by laser beam irradiation can be suppressed and the laser beam irradiation can be performed at high power, making it possible to obtain a sufficient iron loss reduction effect. Therefore, the magnetic domain refining process by laser beam irradiation is performed when the temperature of the iron core member is 50° C. or higher. However, if the member temperature is too high, the thermal strain caused by laser beam irradiation will disappear due to recovery etc., making it impossible to introduce sufficient strain, so the upper limit temperature is set at about 600°C. The irradiation temperature of the laser beam is preferably 60 °C or higher, and preferably 300°C or lower.

Further, as the type of laser used for the magnetic domain refining process, known lasers such as YAG, CO ₂ , fiber laser, etc. can be used. However, when using a grain-oriented electrical steel sheet as a soft magnetic material, if the beam diameter of the laser beam is large, the heat-affected zone becomes large and the iron loss reduction effect becomes small, so it is more advantageous to have a smaller beam diameter. Specifically, the beam diameter is preferably 0.3 mm or less, more preferably 0.2 mm or less. From this point of view, in the case of grain-oriented electrical steel sheet as the soft magnetic material, it is preferable to use a fiber laser whose diameter can be easily reduced. Here, in the present invention, the above-mentioned beam diameter refers to the diameter in the direction perpendicular to the scanning direction of the laser beam (in the rolling direction when the scanning direction is perpendicular to the rolling direction), and when the beam cross section is elliptical, The diameter in the direction parallel to the scanning direction of the laser beam (in the direction perpendicular to rolling when the scanning direction is perpendicular to rolling) may be larger than the above value.

In addition, in order to perform magnetic domain refining processing, a laser beam is repeatedly scanned and irradiated in a direction transverse to the conveying direction of the conveyor, thereby creating an interval (RD) of 1 to 30 mm in the length direction (rolling direction). It is necessary to form a thermally strained region with an interval (interval). If the distance between the thermally strained regions in the rolling direction is less than 1 mm, thermal strain due to laser beam irradiation is excessively introduced, which not only reduces the effect of reducing iron loss but also causes a decrease in productivity. On the other hand, if it exceeds 30 mm, a sufficient iron loss reduction effect cannot be obtained. Preferably it is in the range of 3 to 15 mm. The angle between the scanning direction of the laser beam and the conveying direction of the conveyor (which can range from 0 to 90 degrees) is preferably in the range of 45 to 90 degrees in order to obtain a sufficient magnetic domain refining effect.

Moreover, it is preferable that the laser beam irradiation scans the surface of the iron core member over the entire width without interruption. This is because if there is a part that is not irradiated with the laser beam, the magnetic domain refining effect cannot be obtained in that part.

The conventional method of performing magnetic domain refining on a product coil (raw material steel sheet) of grain-oriented electrical steel sheet is to divide the coil into multiple pieces with a width of about 1 m and perform magnetic domain refining using multiple laser beam irradiation devices. As a result, there were gaps in the beam irradiation in the width direction of the material, which was an unfavorable condition from the perspective of reducing iron loss. However, in the present invention, since the laser beam irradiation target is the cut-out iron core member, processing can be performed without causing intermittent beam irradiation.

Note that as a means for scanning the laser beam in a direction perpendicular to the conveyance direction of the conveyor, a known method such as a polygon mirror scanner or a galvano scanner can be used. Furthermore, in order to obtain a desired processing interval in the rolling direction, it is necessary to drive the scanner described above in synchronization with the transport speed of the core member. As for other irradiation conditions such as laser beam output, scanning speed, beam focus, etc., it is preferable to conduct experiments in advance to determine the optimum conditions so that the desired iron loss or surface condition can be obtained.

In addition, since the core members subjected to magnetic domain refining processing have different shapes and dimensions, the shape and dimensions of the core members are recognized (understood) in advance and the results are fed into the laser processing system. It is preferable to forward the laser beam irradiation and apply laser beam irradiation according to the shape and dimensions of the iron core member.

Furthermore, in the present invention, in order to further obtain the effect of reducing iron loss, it is preferable to utilize the above function and change the laser beam irradiation conditions depending on the location within one core member. For example, FIG. 2 shows an example in which the scanning interval of the laser beam in the rolling direction (conveyance direction) is not changed (FIG. 2(a)) and an example in which it is changed (FIG. 2(b)) depending on the location of the core member. It is something that In addition to the scanning interval in the rolling direction mentioned above, the irradiation conditions to be changed include at least one of the following: laser beam output, scanning speed, and the angle formed by the rolling direction and the beam scanning direction. I can do it. Such changes in processing conditions within one core member can only be realized in the present invention, in which the magnetic domain refining process is performed after cutting out the core member.

Assembling the core The core member subjected to the magnetic domain refining process may be assembled into the core of the transformer using a commonly known method. However, it is desirable that the core member subjected to the magnetic domain refining treatment is not subjected to processing strain due to shearing or the like until the core is assembled.

Grain-oriented electrical steel sheet A (B ₈ : 1.902T) with a plate thickness of 0.23 mm and subjected to heat-resistant magnetic domain refining treatment, and grain-oriented electrical steel sheet B (B ₈ As shown in Table 7, a core member for a three-phase tripod stacked core transformer having the shape and dimensions shown in Fig. ) and wire cut cutting. Note that under some conditions, a hole with a diameter of 3 mm was punched in the center of the member having a shape C using a punching method using a mold.
Next, the cut out iron core members are aligned on a conveyor belt made of a metal mesh belt using side guides so that the members do not overlap each other and the rolling direction of the members coincides with the conveyance direction. It was transported into a heat treatment furnace and subjected to strain relief annealing. In the heating zone of the above heat treatment furnace, the temperature is heated to 700℃ using an induction heating device, and in the soaking zone, after soaking at the temperature and time shown in Table 7 in the atmosphere listed in Table 7, the temperature is raised to 600℃. The cooling up to 600° C. was carried out by furnace cooling under the same atmosphere as above, and the cooling in the temperature range below 600° C. was carried out by standing to cool under the atmosphere shown in Table 7. At this time, when the member temperature during cooling reached the temperature shown in Table 7, the surface of each core member was irradiated with a laser beam under the conditions shown in Table 7 to perform magnetic domain refining treatment. A fiber beam was used as the laser beam, and a galvano scanner was used to irradiate the entire width of the core member in the width direction (direction perpendicular to the rolling direction of the raw steel plate). At this time, the irradiation pattern of the laser beam was changed for some members depending on the member position. Note that as a result of visual observation of the surface of the member after the above magnetic domain refining treatment, no damage to the coating due to laser beam irradiation was observed under any conditions.
Next, an iron core for the three-phase tripod stacked core transformer shown in FIG. 1 described above was assembled using the iron core member subjected to the magnetic domain refining. This core was assembled by stacking 70 core members in a 5-step step-lap stack of two layers so that the stacked thickness was about 15 mm and the core weight was about 20 kg.
Next, the iron core of the transformer assembled above was excited with three phases with a phase shift of 120°, and the iron loss W _17/50 of the transformer at a magnetic flux density of 1.7T was measured, and the results are also listed in Table 7. did.

From the results in the table above, it can be seen that the transformer core assembled from core members that meet the conditions of the present invention has excellent core loss characteristics. In particular, it can be seen that a transformer core assembled from members in which the processing pattern of magnetic domain refining is changed depending on the position within the core member has better iron loss characteristics.

The technology of the present invention is applicable not only to core members for three-phase tripod stacked core transformers, but also to core members used in stacks, such as core members for single-phase stacked core transformers and stacked core members for reactors. Can be applied.

Claims (6)

In a method for manufacturing a core member of a stacked core transformer by cutting out a core member from a soft magnetic material having a thickness of 0.30 mm or less,
After applying strain relief annealing to the cut out iron core member by holding it at a temperature of 700°C or more and 1000°C or less for 1 second or more and 1000 seconds or less, the iron core member is cooled from 250 °C to 50°C, An iron core member for a stacked core transformer characterized in that a laser beam is repeatedly irradiated in a direction transverse to the rolling direction of the iron core member at intervals of 1 to 30 mm in the rolling direction to perform magnetic domain refining treatment. Production method. 2. The method of manufacturing a core member for a stacked core transformer according to claim 1, wherein the core member is cut out by shearing. The strain relief annealing is carried out in an atmosphere of a single gas such as nitrogen gas, hydrogen gas and Ar gas, a mixed gas of one or more of the above gases, or an atmosphere of DX gas or RX gas, and the degree of vacuum of any of the above gases is 10 The core member for a stacked core transformer according to claim 1 or 2, wherein the core member is applied in either a reduced pressure atmosphere having a degree of vacuum of ⁴ Pa or less, or a reduced pressure atmospheric atmosphere having a degree of vacuum of 10 ³ Pa or less. manufacturing method. When performing magnetic domain refining treatment by irradiating the iron core member after strain relief annealing with a laser beam, depending on the part of the iron core member, the output of the laser beam, the scanning speed, the repetition interval in the rolling direction, the rolling direction and the laser beam The method for manufacturing a core member for a stacked core transformer according to any one of claims 1 to 3, characterized in that at least one of the angles formed with the scanning direction is changed. The method for manufacturing a core member for a stacked core transformer according to any one of claims 1 to 4, wherein the soft magnetic material is a grain-oriented electrical steel sheet subjected to heat-resistant magnetic domain refining treatment. . Processing equipment for cutting out a member that will become the core of a stacked core transformer from a soft magnetic material with a thickness of 0.30 mm or less;
a conveyor that aligns and conveys the cut out iron core members;
A tunnel-type annealing furnace that performs strain relief annealing held at a temperature of 700°C or more and 1000°C or less for 1 second or more and 1000 seconds or less;
If necessary, cooling equipment for forcibly cooling the iron core member after the strain relief annealing ;
A stacked iron core comprising a laser beam irradiation device that repeatedly irradiates a laser beam in a direction transverse to the rolling direction of each core member at intervals of 1 to 30 mm in the rolling direction in synchronization with the conveyance speed of the conveyor. Manufacturing equipment for core parts for transformers.

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