KR20010061455A - Method for manufacturing a grain oriented electrical steel sheet having a low magnetostriction and manufacturing apparaturs used therein - Google Patents

Abstract

PURPOSE: An apparatus and method for manufacturing oriented electronic steel sheets having low magnetostriction is provided to decrease magnetostriction usually deteriorated after grain micronization performed for the purpose of lowering iron loss. CONSTITUTION: The method for manufacturing oriented electronic steel sheet comprises the processes of carrying out magnetic domain refinement an oriented electronic steel sheet comprising Si 0.4-4.8wt.%, C 0.02-0.07wt.%, Mn 0.05-0.2wt.%, S 0.02-0.03wt.%, Cu 0.05-0.3wt.%, Ce 0.006-0.9wt.%, a balance of Fe, and other inevitable impurities; magnetizing the oriented electronic steel sheet in the temperature range of 200 to 600deg.C. The apparatus for manufacturing oriented electronic steel sheet comprises a grain-micronizing part (10); a heating means (20) installed at the rear part of the grain-micronizing part; a magnetic field supplying part (30) of which front end is located inside the heating furnace and rear end is located outside the heating furnace; a coating means installed between the heating means and the grain-micronizing part for coating the micronized oriented electronic steel sheet.

Description

AuthorWhy why manufacturing a grain-oriented electrical steel sheet and a manufacturing apparatus used therein {Method for manufacturing a grain oriented electrical steel sheet having a low magnetostriction and manufacturing apparaturs used therein}

The present invention relates to a method for producing a grain-oriented electrical steel sheet which can further improve the iron loss characteristics while improving the magnetostriction which is degraded after the magnetization microstructure treatment for reducing the iron loss of the grain-oriented electrical steel sheet used as the iron core of the electric machine. In addition, the present invention relates to a magnetic field heat treatment apparatus for performing magnetic domain micronization processing applied to such a manufacturing method online, and is an improved invention of Korean Patent Application Laid-Open Publication Nos. 99-12920 and 99-49605.

A grain-oriented electrical steel sheet has an aggregate structure of (110) [001] orientation in the rolling direction, and since many methods have been developed by many researchers since its manufacturing method was first proposed by NP Goss in US Patent 1,965,559. Invention and property improvement have been made.

A method for producing conventional grain oriented sliicon steel, which is currently mainly used industrially, is disclosed in Japanese Patent Publication No. 30-5651 by M. F. Littmann. According to this method, the secondary recrystallized structure is obtained by using MnS as two cold rolling, de-carbon annealing, MgO coating and inhibitor including silicon steel hot rolling, pre-annealing, pickling, intermediate annealing. As described above, various types of working conditions have been changed to improve characteristics of oriented electrical steel sheets manufactured by a series of processes, but the main ones are used without change.

The manufacturing technology of oriented electrical steel sheet is various, and in order to further improve the iron loss of the tension-coated oriented electrical steel sheet finally subjected to any treatment process, the magnetic domain micro-treatment is applied. The micronized microstructure treatment is intended to improve iron loss by reducing the width of magnetic domains. That is, the arrangement of the magnetic domains in the grain-oriented electrical steel sheet in which the final heat treatment is completed has a 180 ° magnetic domain, which is almost identical to the rolling direction. Iron loss of oriented electrical steel sheet is closely related to the width of the 180 ° domain. Since the distance of the magnetic wall reciprocating within a predetermined time (in the case of iron core operating at 60 Hz is 1/60 seconds), the moving speed of the magnetic wall increases, resulting in a large iron loss. Therefore, in order to reduce the iron loss, the width of the 180 ° magnetic domain should be reduced, and the width of the magnetic domain is known to be reduced by the micronized microstructure treatment which imparts residual stress or residual defect in the base metal of the steel sheet.

Therefore, a method of digging a groove using a sharp wedge or acid in a base metal of a steel sheet or a micronized microtreatment method of imparting residual stress or residual defect using a laser, plasma, electron beam, or light energy is proposed. Briefly summarized as follows (1) to (5).

(1) A method for improving iron loss by making a scratch using a sharp tool on the surface of a grain-oriented electrical steel sheet is disclosed in US Patent No. 647575.

(2) U.S. Patent No. 4203784 also discloses a method of introducing a linear strain to a steel sheet surface using a roller.

(3) US Patent Publication Nos. 4293350, 403714 and EPO100638A2 and Japanese Patent Laid-Open No. 60-46325 disclose a method of lowering iron loss by irradiating a surface of a steel sheet with a laser beam. Specifically, the method using the Nd-YAG laser in Q-mode is proposed in 4293350. In this case, the coating layer on the surface is damaged, so the laser must be recoated to prevent rust on the irradiated portion. On the other hand, in 403714 and EP 0100638A2, the magnetic micronization technique by Nd-YAG laser in CW-mode is proposed. In this case, since the coating layer does not go bad, there is no need for recoating.

(4) Also, Japanese Patent Laid-Open No. 61-73886 discloses a method of introducing molding strain into the surface of a steel sheet using a vibrating body.

(5) Japanese Patent Application Laid-Open No. 61-117285 proposes a method of lowering iron loss by irradiating light energy using Xe-lamp with a power density satisfying the relationship of log W ≤ 0.7t + 0.25 with respect to the film thickness t of the steel sheet. do.

All of these micronized micro-treatment techniques impart strain or stress to be substantially perpendicular to the rolling direction at intervals of 3 to 10 mm along the rolling direction of the steel sheet. However, the micronized micronized techniques have a positive effect of reducing iron loss, but all It is accompanied by a problem of increasing magnetostriction due to the formation of 90 ° or auxiliary domains at the micro-strain or stress-producing microsite.

The greater the magnetostriction, the greater the noise generated by the transformer. The accompanying magnetostriction problem in the magnetic domain micronization method is mentioned in part in U.S. Patent Publication 4293350. The content of the magnetic domain becomes very large when the magnetic domain of the grain-oriented electrical steel sheet is made fine according to the method proposed in U.S. Patent Publication No. 3647575. Point out. That is, when the micronized microstructure treatment is performed in a method of creating residual stress or residual defect in the base metal of the grain-oriented electrical steel sheet, the goth aggregate structure ((110) <001>) originally possessed by the electrical steel sheet is destroyed in the region of the minute portion and is 90 °. Magnetic domains or other auxiliary domains must be created. Other magnetic domains other than 90 ° or 180 ° domains act to induce or increase magnetostriction. . Therefore, the iron loss can be reduced through the magnetization method, but it is unavoidable that the magnetostriction that causes noise in the transformer increases.

More specifically, the magnetostriction is described as follows. A grain-oriented electrical steel sheet is placed inside a transformer or current transformer with iron cores stacked from tens to hundreds of sheets to convert voltage and current into the desired amount or phase. The coil is wrapped around the core, and when the iron core is operated by applying current to the coil, the length of the core is caused by the change of magnetic flux direction inside the core. This phenomenon is called magnetostriction, and the change in length occurs as a multiple of the frequency of the supplied voltage or current. This change in length causes the ends of the iron core to hit the air, which is audible to the human ear.

In general, the magnetostrictive size of the steel sheet is expressed as "length variation ÷ original specimen length", and in the case of a general general oriented electrical steel sheet, about 1.0x10 ^-6 at 1.7 Tesla. This amount is the magnetostrictive size without any stress applied to the specimen. If the specimen is subjected to compressive stress in the longitudinal direction of the steel sheet, this value will vary greatly. In other words, when the actual electrical steel sheet is used as the iron core of the transformer, compressing stress is applied to the steel sheet to increase the magnetostrictive size because the bolt is tightened or welded in order to laminate the steel sheet and eliminate the gap between the steel sheets. In addition, the value for the magnetostriction size is slightly different depending on the shape of the measuring instrument and the specimen. This is because the magnetostrictive value is sensitive to the microscopic stress, and the amount is so small that the friction between the specimen and the magnetostrictive measuring device is different for each measuring device. For this reason, the magnetostrictive size differs between the measurements of the reported literature. For regular grain-oriented electrical steel, and 1.0x10 ^-6 magnetostrictive size is approximately as described above, the stress-free and 1.7Tesla, under a compressive stress of 3MPa is about 5x10 ^-6.

However, when the transformer is made of a general oriented electrical steel sheet having a magnetostriction size of this level, the noise problem due to the magnetostriction is seriously raised. Therefore, in order to reduce noise by reducing magnetostriction as much as possible, the magnetic flux density is used as low as possible. In consideration of this, the design magnetic flux density of a conventional transformer is 1.70-1.75 Tesla. However, this method has a problem of decreasing the efficiency of the transformer, so if a method can be used to reduce the magnetostriction of the oriented electrical steel sheet more than now, the transformer can be used at a higher magnetic flux density, and then the transformer in proportion In order to increase the efficiency or to reduce the size, the need for directional electrical steel sheet having a small magnetostrictive size is increasing.

The present inventors have applied for a magnetic field heat treatment (or 'magnetic flux heat treatment') method and a magnetic field heat treatment apparatus used therein which can reduce the magnetostrictive size, and the Korean Patent Application No. 97-36499, 97-68576. The above-mentioned patent publication No. 99-12920 discloses a technique for performing magnetic field heat treatment by applying a direct current magnetic field and a solenoid installed outside the heating furnace to facilitate the amount of magnetic flux inside the material. An adjustable magnetic field heat treatment apparatus is disclosed. Further, Japanese Patent Application Laid-Open No. 99-49605 discloses a technique for performing magnetic field heat treatment by simultaneously applying a direct current magnetic field and a pulsed magnetic field, and an apparatus used therein.

However, the magnetic field heat treatment device is not suitable for mass production because the magnetic field heat treatment by cutting the grain-oriented electrical steel sheet to a certain size. In addition, since the magnetic field is not processed on-line in the actual production line, the industrial utility value is low. In particular, the magnetic field heat treatment method suggests magnetic field heat treatment conditions suitable for grain-oriented electrical steel sheets, that is, final annealed steel sheets or tension coated steel sheets. This is due to the stereotype that does not combine magnetic domain microtreatment and magnetic field heat treatment in the technical field of the present invention, and there is no research on how the change of iron loss and magnetic distortion are related when magnetic domain microtreatment and magnetic field heat treatment are performed at the same time. It comes from inaccessibility.

The present invention has been devised in a series of studies to overcome the limitations of the prior art in which magnetostriction increases when magnetizing grain-oriented electrical steel sheet. It is also an object of the present invention to provide a method for manufacturing a grain-oriented electrical steel sheet which can further increase iron loss and magnetic flux density while basically reducing magnetic distortion.

Furthermore, the present invention which can be used in the method for manufacturing the grain-oriented electrical steel sheet of the present invention provides a manufacturing apparatus capable of continuously performing magnetic field heat treatment and magnetic domain micro-treatment in an on-line state in the actual production line of the grain-oriented electrical steel sheet. have.

1 is a schematic view of the manufacturing apparatus of the present invention.

* Description of the symbols for the main parts of the drawings *

1 ..... oriented electrical steel sheet

10 ..... Micronized microprocessor 20 ..... Heating means

30 ..... Magnetic feeding part 40 ..... Coating means

Method for producing a grain-oriented electrical steel sheet of the present invention for achieving the above object, after the final annealing or tension-coated grain-oriented electrical steel sheet micronized, and then heating the steel sheet to a magnetic field treatment at a temperature of 200 ~ 600 ℃ It is configured to include.

In addition, the manufacturing apparatus of the present invention, the magnetic domain micronized processing unit for miniaturizing the magnetic domain of the transfer steel sheet;

Heating means for heating the steel sheet which is installed at the rear of the magnetic domain micronized portion (seeing in the conveying direction of the steel sheet) and is introduced;

The front end is located in the furnace and the rear end is installed in the rear of the outside of the furnace magnetic field supply unit for exciting the steel sheet conveyed; is configured to include.

Hereinafter, the present invention will be described in detail.

[Method of manufacturing oriented electrical steel sheet]

The manufacturing method of the grain-oriented electrical steel sheet of the present invention reduces the 90 ° domain and other auxiliary domains inevitably generated after magnetic domain micronization, restoring magnetostriction to the level of magnetic domain micronization, as well as reducing iron loss and magnetic flux density. To further improve, there are features.

The grain-oriented electrical steel sheet which is the object of the present invention does not particularly limit its component system and its manufacturing history, and may be a grain-oriented grain-oriented electrical steel sheet. Of course, the most preferred component system is Si: 0.4 to 4.8%, C: 0.02-0.07%, Mn: 0.05 to 0.2%, S: 0.02 to 0.03 %, Cu: 0.05 to 0.3% and the remaining Fe and other inevitable impurities. When 0.006 to 0.9% of Ce is contained therein, as found in 99-12920, the low distortion property is further improved. The component system of the above-described grain-oriented electrical steel sheet is hot-rolled by reheating the steel slab at a temperature of 1250 to 1400 ° C, performing two cold rolling, annealing in the middle of hot-rolled sheet annealing, pickling, and applying an annealing separator. By the final annealing process

In the present invention, after the tension coating treatment to the final annealed oriented electrical steel sheet or the final annealed oriented electrical steel sheet is subjected to magnetic domain micronization treatment. In the case of microfinishing of the final annealed grain-oriented electrical steel sheet, after the subsequent magnetic field heat treatment, tension coating is performed. In the present invention, the magnetic domain micronizing treatment can be applied to any method including the above-mentioned (1) to (5) to impart residual stress or residual defect to the grain-oriented electrical steel sheet. The important thing is to give stress or strain at intervals of 3 to 10 mm along the rolling direction of the steel sheet when micronized.

For example, there are two major methods for micronized laser treatment. The first method is to use pulse or Q-mode. In this case, local evaporation or melting is applied to the surface of the steel sheet, so that the base metal is exposed and rust is generated. In this case, therefore, the coating must be applied and cured. The curing temperature at this time is more than 600 ℃ because the micronized effect is released, it is preferable to harden below 450 ℃ in consideration of safety. Secondly, the CW-mode method is used. In this case, there is no damage to the coating layer on the surface of the plate, so there is no need to recoat it. In the case of using a laser (Nd-YG laser), the diameter of the beam and the energy per pulse are adjusted to irradiate the beam vertically, and thus the micronized process is performed.

As another method, when the surface of the steel sheet is pressed into the surface of the steel sheet using the gear roll, the stress relief heat treatment may be performed at about 800 ° C.

As described above, when the magnetic domain micronization treatment such as a laser is applied to the surface of the steel sheet, a large number of auxiliary magnetic domains are formed on the portion to which the laser is irradiated, and the auxiliary magnetic domain directly provides the cause of the magnetostriction.

Therefore, in the present invention, the magnetic field heat treatment to remove the 90 ° or auxiliary magnetic domain while maintaining the 180 ° magnetic domain as it is, the important thing is the magnetic field heat treatment to improve the magnetic properties (iron loss, magnetic flux density) while reducing the 90 ° or auxiliary magnetic domain It is to set the method (means).

First, in the present invention, the temperature of the magnetic field heat treatment is adjusted. The magnetic field heat treatment rearranges the magnetic domains inside the steel sheet in a direction less magnetostrictive. In order to rearrange the domain, it is advantageous to lower the magnetic anisotropy energy in the crystal. The magnetic anisotropy energy of the electrical steel sheet is rapidly lowered as the temperature increases, so the magnetic field heat treatment is performed at a high temperature. However, as the temperature approaches the magnetic transformation point (about 720 ° C.) of the electrical steel sheet, the permeability of the electrical steel sheet decreases. In addition, there is a risk of losing the micronized effect at 600 ℃ or higher. The magnetic field heat treatment effect is insignificant because the magnetic anisotropy energy of the grain-oriented electrical steel sheet is high when the magnetic field heat treatment temperature is 200 ° C or less. In consideration of this, in the present invention, the magnetic field heat treatment is performed at 550 to 200 ° C., which is preferably carried out during the cooling process after the micronized treatment and heating.

On the other hand, when coating the magnetic domain microtreatment before the magnetic field heat treatment with a laser, it is preferable to perform the hardening treatment using the heating furnace as a curing furnace and then perform the magnetic field heat treatment at a predetermined temperature as it is in the furnace. In addition, when the stress is released to 800 ° C. using the gear roll, the heating may be performed in this furnace and then magnetically heat treated at a predetermined temperature during the cooling process.

Next, the magnetic field during magnetic field heat treatment acts to align the magnetic moment in the steel sheet in one direction by applying a magnetic field to the grain-oriented electrical steel sheet at a heating temperature in which magnetic anisotropy energy is minimized. The magnetic field at this time can be given either alone or as a combination of a direct current magnetic field and a pulsed magnetic field, and preferably a compound. This is because a large amount of energy is required to change the direction of the magnetic domain in any one direction.

When applying DC magnetic field, it is desirable to use 10 (Oe) strength or more. In this case, if the magnetic flux of steel sheet is saturated, magnetic field moment is almost completely aligned in one direction, so it is preferable to heat-treat at DC saturation flux. Do. In addition, when imparting a pulsed magnetic field, it is preferable to set the intensity to 300 (Oe) or more. Pulsed magnetic field can flow more powerful magnetic field, so that even if the magnetic anisotropy energy in the crystal is very large, the magnetic domain can be rotated to facilitate rearrangement of the magnetic domain.

[Production apparatus of directional electrical steel sheet]

The magnetic domain microtreatment and the magnetic field heat treatment of the grain-oriented electrical steel sheet can be effectively carried out by reducing the size of the installation on-line. An example of the apparatus of the present invention is shown in FIG. The apparatus of the present invention is based on a magnetic domain micronized treatment unit, a heating unit, a magnetic field supply unit, and a coating unit 40 may be additionally installed therein.

First, the magnetic domain micro-processing unit 10 imparts residual stresses or residual defects in the base metal of the steel sheet being transferred. For example, a sharp tool or a roller, a laser, a plasma, an electron beam, or an optical energy may be adopted. 1 shows a laser as an example, and reference numeral 7 denotes a laser irradiation groove.

In addition, the heating means 20 is installed in the rear (viewed in the conveying direction of the steel sheet) of the magnetic domain micronized portion, a heating element (not shown) is provided to heat the steel sheet.

In addition, the magnetic field supply unit 30 excites a steel sheet whose front end is located in the heating furnace and the rear end is located at the rear of the outside of the heating furnace, and the DC magnetic field supply means 32 and the pulse magnetic field supply means 34 are provided. At least one of is provided. The magnetic field supply unit is configured to wind the steel plate with a solenoid, for example, to impart a magnetic field. The front end of the magnetic field supply part is provided near the cooling stand of the heating furnace so that it can be carried out in the heating furnace in the 200-550 ° C section.

Between the magnetic micronization processing unit 10 and the heating furnace 20 may be additionally provided with a coating means 40 for coating the surface of the steel sheet in accordance with the magnetic micronization treatment.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

Electricity consisting of C: 0.048%, Si: 3.15%, Mn: 0.065%, S: 0.024%, Cu: 0.17%, N: 0.0050%, Ce: 0.05% by weight and the remaining Fe and other unavoidable elements The steel sheet slab was heated to 1350 ° C. and then hot rolled to obtain a hot rolled sheet having a plate thickness of 2.0 mm. This hot rolled sheet was annealed at 950 ° C. for 2 minutes, and secondary cold rolling to a thickness of 0.3 mm was performed. The cold rolled plate was decarburized for 2 minutes with a mixed gas of 25% H ₂ + 75N _{2 having} a dew point of 51 ° C. in a furnace maintained at 850 ° C. Next, MgO, an annealing separator, was applied to the surface of the steel sheet to perform final high temperature annealing. The high temperature annealing was heated to 1200 ° C. at a temperature rising rate of 15 ° C./hr in 25% H ₂ + 75N ₂ atmosphere, and maintained at 100% H ₂ atmosphere for 10 hours after reaching 1200 ° C. As described above, a stable secondary recrystallized grain-oriented electrical steel sheet was obtained.

The tension coating material was applied to the surface of the grain-oriented electrical steel sheet after the secondary recrystallization and cured at 800 ° C. The magnetism was then measured. Subsequently, the sheet was irradiated perpendicularly to the longitudinal direction of the steel sheet by using a Nd-YGA laser with a beam diameter of 100 µm, a frequency of 6 KHz, and an energy per frequency of about 15 mJ. The interval of the irradiation line was 5 mm. After the laser irradiation, magnetic field heat treatment was performed. The conditions of the magnetic field heat treatment are as follows. The temperature was maintained at 450 ° C. for 2 minutes and cooled to 200 ° C. at a rate of 83 ° C. per minute. The magnetic field supplied DC waveform up to 450 ~ 200 ℃ and the magnetic field strength was 15 (Oe). Table 1 shows the magnetic properties before and after magnetic domain micronization using laser and after magnetic field heat treatment.

Magnetic properties are exhibited as compared to the magnetostrictive according to the external stress applied to the iron loss (W _17/50) and the specimen in the magnetic field flux density (B ₁₀₎ induced in the sample under the environment of 1000A / m and the magnetic field before and after heat treatment and 1.7Tesla . The magnetostriction is the peak to peak value and represents the width from the lowest value to the highest value. The size is about ^10-6 . Two types of magnetostrictions were measured at 1.5, 1.7 and 1.85 Tesla. One was measured with no stress on the material and the other with a compressive stress of 2 MPa on the material. This is because the compressive stress is applied to the steel sheet in the actual transformer manufacturing.

fair Magnetic flux density at 1000 A / m 1.7 Iron Loss at Tesla 1.5 Permeability at Tesla Magnetostrictive (peak to peak value) × 10 ^-6 1.5Tesla 1.7Tesla 1.85Tesla B ₁₀ (Tesla) W _17/50 μ _1.5 σ = 0 σ = -2 σ = 0 σ = -2 σ = 0 σ = -2 Before laser irradiation 1.9048 1.029 43300 0.5 0.5 0.7 0.7 0.6 0.7 Comparative material after laser irradiation 1.9030 0.977 31900 0.8 2.5 1.3 4.2 1.5 5.2 Comparative material After heat treatment 1.9045 0.970 39500 0.4 1.8 0.8 3.6 1.0 4.5 Invention

As shown in Table 1, the magnetic flux density (B ₁₀ : magnetic flux density at 1000 A / m) was lowered by 0.0018 Tesla after laser irradiation, but was improved by 0.0015 Tesla after magnetic flux heat treatment. Iron loss was reduced by about 5% after laser irradiation and lowered by 0.7% through flux heat treatment. The permeability after laser irradiation at 1.5Tesla was about 26%, but after magnetic field treatment, the results were much improved.

Also, in case of magnetostriction, 1.5Tesla and compressive stress At = 0, it was about 60% higher after laser irradiation and 20% lower than the original magnetostrictive value after magnetic field heat treatment. 1.5Tesla and compressive stress At 2 MPa, it was about 400% higher after laser irradiation, and after magnetic field heat treatment, it was found to be 26% lower than the magnetostrictive value after laser irradiation. Similar results are shown for 1.7 Tesla and 1.85 Tesla.

Looking at these, the iron loss is improved after the micronized microstructure treatment, but the magnetostriction worsens, and even worse in the state of applying the compressive stress. After the direct-current magnetic field heat treatment, it can be seen that a substantial recovery. All of these effects are due to the rearrangement of the microspheres irradiated with the laser in a direction that favors the required characteristics of the oriented electrical steel sheet. Among them, the improvement of the properties after the magnetic field heat treatment than the original state is because the 90 ^O and the assisting spheres existing in other parts besides the laser irradiation part were improved to some extent. The reason why the magnetostriction of the invention material does not recover to the original state above 1.7 Tesla is because the strength of the magnetic field imparted during the magnetic field heat treatment is not high, and thus it is not affected by the 90 ^O and the auxiliary domain that can be rotated in this region.

Example 2

Subsequently to the oriented electrical steel sheet coated with the tension coating material of Example 1 using a Nd-YAG laser to make the diameter of the beam 100㎛, frequency 6KHz and energy per frequency about 15mJ perpendicular to the longitudinal direction of the steel sheet It was investigated. The interval of the irradiation line was 5 mm. After the laser irradiation, magnetic field heat treatment was performed. The conditions of the magnetic field heat treatment are as follows. The temperature was maintained at 450 ° C. for 2 minutes and cooled to 200 ° C. at a rate of 83 ° C. per minute. The magnetic field supplied pulse waveforms up to 450 ~ 200 ℃ and compared the results. The pulse field strength was 350 (Oe). The pulse magnetic field was set at 1 Hz and the pulse applying time was 20 ms. Table 2 shows the magnetic properties before and after magnetic domain micronization using laser and after magnetic field heat treatment.

fair Magnetic flux density at 1000 A / m 1.7 Iron Loss at Tesla 1.5 Permeability at Tesla Magnetostrictive (peak to peak value) × 10 ^-6 1.5Tesla 1.7Tesla 1.85Tesla B ₁₀ (Tesla) W _17/50 μ _1.5 σ = 0 σ = -2 σ = 0 σ = -2 σ = 0 σ = -2 Before laser irradiation 1.9050 1.022 43400 0.6 0.6 0.8 0.9 0.7 0.75 Comparative material after laser irradiation 1.9030 0.971 32000 0.9 2.6 1.3 4.3 1.6 5.5 Comparative material After heat treatment 1.9045 0.960 42000 0.45 1.4 0.6 2.5 0.8 4 Invention

As shown in Table 2, the results of improved magnetization and magnetostriction were obtained after the pulse magnetic field heat treatment immediately after the micronization. In particular, the permeability at 1.5 Tesla has recovered substantially. The magnetostriction under pressure stress is also improved, which can be seen to be more improved than the heat treatment in the direct-current magnetic field of Table 1.

Example 3

Subsequently to the oriented electrical steel sheet coated with the tension coating material of Example 1, the diameter of the beam was 100 μm using Nd-YAG laser, the frequency was 6 HKz, and the energy per frequency was about 15 mJ. It was investigated. The interval of the irradiation line was 5 mm. After the laser irradiation, the magnetic field heat treatment was performed by simultaneously applying the DC magnetic field and the pulse magnetic field. The conditions of the magnetic field heat treatment are as follows. The temperature was maintained at 450 ° C. for 2 minutes and cooled to 200 ° C. at a rate of 83 ° C. per minute. The pulsed magnetic field was applied at the intensity of 15 (Oe) and the intensity of 350 (Oe) up to 450 ~ 200 ℃. The pulse magnetic field was set at 1 Hz and the pulse applying time was 20 ms. Table 3 shows the magnetic properties before and after magnetic domain micronization using laser and after magnetic field heat treatment.

fair Magnetic flux density at 1000 A / m 1.7 Iron Loss at Tesla 1.5 Permeability at Tesla Magnetostrictive (peak to peak value) × 10 ^-6 1.5Tesla 1.7Tesla 1.85Tesla B ₁₀ (Tesla) W _17/50 μ _1.5 σ = 0 σ = -2 σ = 0 σ = -2 σ = 0 σ = -2 Before laser irradiation 1.9049 1.019 43300 0.5 0.5 0.7 0.7 0.6 0.7 Comparative material after laser irradiation 1.9032 0.955 32100 0.8 2.5 1.4 4.2 1.6 6 Comparative material After heat treatment 1.9047 0.946 43400 0.4 1.2 0.45 1.9 0.7 3 Invention

As shown in Table 3, the magnetization and magnetostriction were significantly improved after the magnetic field heat treatment with the direct current and the pulsed magnetic field at the same time. In particular, we can see that the permeability at 1.5 Tesla has recovered. The magnetostriction in the compressive stress state is also improved, which can be seen to be more improved than the heat treatment in the DC magnetic field of Table 1 and the pulse magnetic field of Table 2.

As described above, the present invention has a useful effect of improving magnetic properties while reducing magnetic distortion by simultaneously performing magnetic domain micronization treatment and magnetic field heat treatment.

Claims (5)

A method of producing a grain-oriented electrical steel sheet, comprising subjecting a grain-oriented electrical steel sheet subjected to final annealing or tension coating treatment to a magnetic domain, and then heating the steel sheet to a magnetic field at a temperature of 200 to 600 ° C. The method of manufacturing a grain-oriented electrical steel sheet according to claim 1, wherein the magnetic field treatment simultaneously imparts a direct current magnetic field and a pulse magnetic field. The said grain-oriented electrical steel sheet is a Si: 0.4-4.8%, C: 0.02-0.07%, Mn: 0.05-0.2%, S: 0.02-0.03%, Cu: 0.05-0.3% , Ce is produced from a steel slab composed of 0.006 to 0.9% and the remaining Fe and other unavoidable impurity. Magnetic domain micronization processing unit 10 for miniaturizing the magnetic domain of the transfer steel sheet; Heating means (20) for heating the steel sheet which is installed at the rear of the magnetic domain micronized portion (seeing in the conveying direction of the steel sheet) and is introduced; The front end is located in the heating furnace and the rear end is installed in the rear of the outside of the furnace magnetic field supply unit for exciting the conveyed steel sheet; 30; 5. The apparatus according to claim 4, wherein a coating means (40) is further provided between the magnetic micronized processing section (10) and the heating furnace (20) to coat the surface of the magnetic micronized steel sheet.