JP2016196701A - Method for manufacturing iron core having interlayer of laminated electromagnetic steel sheet insulated by granular iron oxide (iii) particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an iron core, first without generating a problem on the processing of the iron core, second, having many properties required for an insulation layer, third, capable of continuously manufacturing a large number of iron cores at low cost using an inexpensive raw material.SOLUTION: The method for manufacturing an iron core comprises: applying a mixed solution of an alcohol dispersion of iron naphthenate with one of organic compounds consisting of carboxylate esters, glycols or glycol ethers on an electromagnetic steel sheet; laminating the electromagnetic steel sheet; punching the laminated sheet in the shape of the iron core by the application of a compressive load to form the iron core; manufacturing the iron core having an insulation layer consisting of an aggregate of granular fine maghemite particles and formed in an interlayer after applying a compressive load to the iron core to perform heat treatment and thermally decompose the iron naphthenate; and manufacturing the iron core having an insulation layer consisting of an aggregate of granular fine hematite particles after applying a compressive load to stress relief anneal the iron core. An inexpensive iron core can be manufactured since these iron cores does not have a problem of a conventional iron core.SELECTED DRAWING: Figure 1

Description

  The present invention relates to the manufacture of iron cores used in electric devices such as electric motors and transformers, and manufactures iron cores in which the layers of laminated electromagnetic steel sheets are insulated by a collection of granular particulates of iron (III) oxide.

Iron cores used in electrical equipment such as electric motors and transformers are coated with an insulating coating to reduce eddy currents, and then punched or sheared into the shape of the iron core. The iron core is manufactured by fixing by welding, caulking or adhesive. If the iron loss of the iron core manufactured in this way is negligible, the iron core is incorporated into an electric device for use.
On the other hand, when the end surfaces of the laminated electrical steel sheets are fixed by welding, the edge portion of the iron core is short-circuited to reduce insulation, and the iron loss of the electrical steel sheets increases due to the occurrence of thermal strain. Moreover, when the electromagnetic steel plates laminated by caulking are fixed, the iron loss of the electromagnetic steel plates increases due to the occurrence of processing distortion, and when the electromagnetic steel plates are thin, sufficient caulking strength cannot be obtained. Furthermore, when fixing a magnetic steel sheet processed with an adhesive, the workability of applying the adhesive to the processed magnetic steel sheet and laminating the magnetic steel sheets one by one is poor, or sufficient adhesive strength is obtained. Absent. As described above, various problems occur in the course of processing the iron core. It is difficult to fundamentally solve these problems unless the processing method is changed, that is, unless the iron core is manufactured by a new manufacturing method.

  Further, processing strain is generated when the electromagnetic steel sheet is processed by punching or shearing, thermal strain is generated when welding, and plastic deformation strain is generated at the crimped portion when caulking. Since the iron loss of the electrical steel sheet increases due to such various strains, the iron core may be incorporated into an electric device after performing strain relief annealing to reduce the iron loss. On the other hand, since the strain relief annealing is performed at a temperature of 750 ° C. to 820 ° C. in an atmosphere in which iron is not oxidized, a chromium compound having high heat resistance has been used for the insulating film between layers. However, the use of heavy metals, which are environmentally hazardous substances, is restricted by the RoHS Directive (Hazardous Substances Restriction Directive) for electrical products for Europe and the domestic Green Purchasing Law (Act on the Promotion of Procurement of Environmental Goods by the State) There is a need for an insulating coating that does not contain chromium compounds.

On the other hand, the insulating layer is required to have various properties described below for manufacturing not only the insulation resistance but also the iron core and for using the electric device incorporating the iron core for a long period of time.
First, there is continuous punchability. That is, when the electromagnetic steel sheet on which the insulating coating is formed is continuously punched out with a press machine, the wear of the cutter blade advances. For this reason, an insulating layer that does not attack the cutter blade is desirable. Second, there is weldability. In other words, when welding the end face of the iron core, it is easy to weld, and further, the material vaporized from the insulating layer during the welding or the scattered material does not attack the insulating layer and form a pinhole. I need it. Third, when processing or laminating electromagnetic steel sheets, adhesion strength is required to prevent the insulating layer from peeling off. Fourth, heat resistance that can withstand strain relief annealing is required. Fifth, it is necessary that the thermal distortion corresponding to the difference between the thermal expansion coefficient of the insulating layer and the thermal expansion coefficient of the electrical steel sheet does not occur in the electrical steel sheet during the strain relief annealing. Sixth, it is necessary not to cause seizure of magnetic steel sheets called sticking during the strain relief annealing. Seventh, it is necessary to have thermal shock resistance so that the insulating layer does not peel off even with a sudden temperature change. Eighth, corrosion resistance that can withstand water vapor and salt water is required. Ninth, it is necessary that the adhesion strength and the insulation resistance do not change even when immersed in high-temperature insulating oil for a long time. On the other hand, if the adhesion strength between the insulating layer and the electrical steel sheet is high, the third and ninth properties are satisfied. On the other hand, thermal stress is generated in the fifth electrical steel sheet and the seventh thermal shock resistance is achieved. become weak.
Since the properties required for the insulating layer described above have different functions required for the insulating layer for each property, it is difficult to realize an insulating layer that satisfies all the properties. In addition, in the insulating layer made of a conventional material, required properties may not be compatible. Therefore, all required properties cannot be realized unless the insulating layer is formed of a material completely different from the conventional one.

Various proposals have been made to solve various problems and problems related to the manufacture of such iron cores.
For example, in Patent Document 1, a surface treatment agent containing a silane compound, a silane coupling agent, and silica particles is used, and an insulating film is formed on the surface having a skewness Rsk of 1 or less by using the surface treatment agent. A technique has been proposed in which a chromium-free insulating film having excellent properties, tension pad resistance and punchability is formed. Here, the skewness Rsk represents the symmetry between the peak and the valley when the average line between the peak and the valley of the surface roughness is the center, and if Rsk is positive, Since it means that the surface roughness curve is biased to the side, the volume of the valley portion is larger than the peak portion in the surface roughness. Further, the tension pad resistance refers to the difficulty of peeling off the insulating coating when the felt-like tension pad rubs the surface of the electrical steel sheet with the insulating coating.
However, the thermal expansion coefficient of the insulating coating is almost an order of magnitude smaller than that of the electrical steel sheet. For this reason, the insulating layer peels from the magnetic steel sheet due to a rapid temperature change, and the peeled coating does not have corrosion resistance and oil resistance. Further, thermal distortion occurs in the electromagnetic steel sheet during the strain relief annealing, and the effect of the strain relief annealing cannot be obtained.

Patent Document 2 discloses that an insulating layer made of a phosphoric acid compound is formed using nitric acid and metal nitrate that are strongly acidic and highly etchable, and metal phosphate and a chelating agent. There has been proposed a technique for forming a chromium-free insulating film in which the whitening at the time and the deterioration of the adhesion after the blueing treatment are suppressed. Here, whitening means that when an electromagnetic steel sheet is etched with an acidic etching solution, iron of the electromagnetic steel sheet is eluted and reacts with a phosphate in a treatment solution for forming an insulating film to form iron phosphate. Or, when the electromagnetic steel sheet is stored in a high temperature and humidity environment for a long time, it means that hydroxide is formed on the surface of the electromagnetic steel sheet due to condensation, and the electromagnetic steel sheet is discolored by these. In addition, when processing a cut or punched electromagnetic steel sheet into a motor or transformer, the steel sheet is oxidized to the extent that the surface exhibits an interference color in order to suppress end face short circuit and improve rust prevention of the cut or punched end face (this (Also referred to as blueing treatment). When such a bluing process is performed, the adhesiveness of the insulating coating is deteriorated.
However, the properties required for the electrical steel sheet on which the insulating coating is formed are not limited to whitening prevention and the adhesion of the insulating film. For example, it has punchability. There is a description that an aqueous synthetic resin is added because sufficient punchability cannot be obtained only by this technology. However, the water-based synthetic resin does not have heat resistance in strain relief annealing. For this reason, it is impossible to achieve both punchability and strain relief annealing. Further, the insulating film has insulating properties. There is a description that colloidal silica is added because sufficient insulation resistance cannot be obtained by this technology alone. However, since the thermal expansion coefficient of colloidal silica is almost an order of magnitude smaller than that of the electrical steel sheet, the insulating coating peels off due to a rapid temperature change, and thermal distortion occurs in the electrical steel sheet during stress relief annealing. This causes a new problem that the effect of strain relief annealing cannot be obtained. Furthermore, since a strongly acidic etching solution is used, sufficient cleaning is required after the formation of the insulating coating, and a lot of cost is required for waste solution treatment from an environmental point of view. Therefore, the manufacturing cost increases.

Japanese Patent Laying-Open No. 2015-10242 JP 2013-249486 A

As explained in the second paragraph, various problems occur in the manufacturing of conventional iron cores depending on the processing method, and these problems can be solved fundamentally unless the processing method is changed, that is, unless the core is manufactured with a new processing method. Difficult to do. Furthermore, as described in the fourth paragraph, the various properties required for the insulating layer have different functions required for the insulating layer for each property, and it is difficult to realize an insulating layer satisfying all the properties. For this reason, unless an iron core is manufactured by a processing method different from the conventional one and an insulating layer is formed of a material different from the conventional one, an insulating layer satisfying all properties cannot be realized. Furthermore, since iron cores are used in general-purpose electrical equipment such as electric motors and transformers, it is necessary to be able to manufacture a large number of iron cores continuously at low cost using inexpensive raw materials.
The problem to be solved by the present invention is that the problem of processing of the iron core described in the second paragraph does not occur, an insulating layer having the required properties described in the fourth paragraph can be realized, and an inexpensive raw material is used. The purpose is to realize a manufacturing technique of an iron core that can be manufactured at an inexpensive cost.

  The first characteristic means related to the production of the iron core in the present invention relates to the formation of a coating on the electromagnetic steel sheet, and the formation of the coating on the electromagnetic steel sheet is performed by alcoholizing a metal compound that precipitates an insulating metal oxide by pyrolysis. A first property of dissolving or mixing in the alcohol, a second property having a higher viscosity than the alcohol, and a third property having a boiling point lower than the thermal decomposition temperature of the metal compound. The organic compound having these three properties is mixed with the alcohol dispersion to prepare a mixed solution, and the mixed solution is applied to the electrical steel sheet, whereby the mixed liquid is applied to the electrical steel sheet. The film which consists of is in the point formed.

That is, according to this feature means, a coating film composed of a mixed liquid of an alcohol dispersion of a metal compound and an organic compound is continuously formed on the electrical steel sheet. On the other hand, the raw material of the coating consists of a metal compound that precipitates an insulating metal oxide by thermal decomposition, an alcohol, and an organic compound, both of which are general-purpose industrial chemicals. Further, the formation of the coating is a process of simply applying the mixed solution to the electromagnetic steel sheet. Furthermore, there is no restriction | limiting of the magnitude | size of the electromagnetic steel plate which forms a film. For this reason, a film can be continuously formed on the magnetic steel sheet at a low cost using an inexpensive raw material.
That is, an organic compound that is dissolved or mixed in an alcohol and has a higher viscosity than the alcohol is mixed with the alcohol dispersion of the metal compound at an arbitrary ratio. Therefore, the viscosity of the liquid mixture increases according to the mixing ratio of the organic compound, and the thickness of the coating film according to the viscosity of the liquid mixture is formed on the electrical steel sheet. Therefore, the thickness of the coating can be freely changed according to the thickness of the electromagnetic steel sheet.
Furthermore, the metal compound and the organic compound are uniformly mixed in a molecular state. That is, when a metal compound is dispersed in alcohol, the metal compound is uniformly dispersed in the alcohol in a molecular state. Furthermore, when an organic compound that is dissolved or mixed in alcohol is mixed with an alcohol dispersion, the metal compound and the organic compound are uniformly mixed in a molecular state. As a result, a coating film in which the metal compound is uniformly dispersed, which is completely different from the conventional coating film, is formed on the surface of the electrical steel sheet.
As described above, according to this feature means, a coating in which the metal compound is uniformly dispersed in a molecular state can be continuously formed on the surface of the electrical steel sheet at a low cost using an inexpensive raw material. .
In addition, the formation of the coating on the electromagnetic steel sheet includes a roll coating method, a bar coating method, a dipping method, a spray coating method, and the like, and an optimum method is appropriately selected depending on the shape and size of the electromagnetic steel sheet. Moreover, since the coating film made of the mixed solution has no adhesive force, even when the electromagnetic steel sheet with the coating film is wound in a coil shape, blocking where the electromagnetic steel sheet adheres through the coating film does not occur. Moreover, even if the magnetic steel sheet wound in the coil shape is returned to the flat plate shape again, the coating is not peeled off from the magnetic steel sheet. Therefore, the magnetic steel sheet on which the film is formed can be wound in a coil shape and stored.

  The second characteristic means related to the production of the iron core in the present invention relates to the production of the iron core in which a film is formed between the layers of the laminated electromagnetic steel sheets, and the production of the iron core has the film in the first characteristic means described above. Laminating electromagnetic steel sheets, applying a compressive load to the laminated electromagnetic steel sheets and punching or shearing into the shape of the iron core, thereby producing an iron core in which the coating film is formed between the layers of the laminated electromagnetic steel sheets .

That is, according to this feature means, an iron core having a coating formed between layers of laminated electromagnetic steel sheets can be manufactured continuously. Further, the present characteristic means is more than the conventional divided method of manufacturing the iron core by punching or shearing the coated steel sheet into the shape of the iron core and then laminating the processed magnetic steel sheets to produce the iron core. Since it consists of a continuous process from the formation of the coating to the production of the iron core, the production cost of the iron core is reduced. Furthermore, in the conventional iron core manufacturing method, there is a risk of damage to the coating film when the electromagnetic steel sheet is cut and when the processed electromagnetic steel sheets are laminated, but this feature means does not damage the coating film. For this reason, according to this feature means, an insulating layer having no defect is reliably formed between the layers of the laminated electrical steel sheets.
Furthermore, according to this characteristic means, the coating film formed on the electromagnetic steel sheet is a liquid and does not attack the cutter blade of the press machine. For this reason, even if the electromagnetic steel sheet with the coating formed is continuously punched or sheared, the cutter blade is not damaged. Further, since the laminated electrical steel sheets are punched or sheared in a state where a compressive load is applied, the coating does not scatter, and a coating having an equivalent thickness is reliably formed between the layers, so that the coating has a uniform thickness. As a result, a film in which the metal compound is uniformly dispersed in a molecular state is formed with a uniform thickness and a uniform thickness between all the layers.
As described above, according to this feature means, the iron core made of laminated electromagnetic steel sheets has a uniform thickness with a uniform thickness in which a metal compound is uniformly dispersed in a molecular state between all layers. These cores can be manufactured continuously and inexpensively.

  The third characteristic means related to the production of the iron core in the present invention relates to forming an insulating layer between the layers of the laminated electromagnetic steel sheets, and the formation of the insulating layer is performed between the layers of the laminated electromagnetic steel sheets in the second characteristic means described above. The iron core on which the film is formed is heat-treated by applying a compressive load, whereby the metal compound constituting the film is thermally decomposed to deposit insulating metal oxide fine particles, and the metal oxide fine particles In this point, an insulating layer is formed by the gathering.

In other words, according to this feature means, an insulating layer made up of a collection of metal oxide fine particles is formed between all the layers so as to have a uniform thickness and a uniform thickness simply by applying a compressive load to the iron core and heat-treating it. The In addition, the electromagnetic steel sheet is thermocompression bonded through the insulating layer. Furthermore, by applying a compressive load to a large number of iron cores and continuously heat-treating them, a large number of cores with insulating layers can be produced continuously, and at a very low cost compared to conventional iron core manufacturing methods. And an iron core can be manufactured.
That is, since a compressive load is applied between the layers, when the alcohol and the organic compound are vaporized, the gap between the layers is narrowed, and fine crystals of the metal compound remain uniformly between the layers. When the temperature is further increased, the metal compound is decomposed into a metal oxide and an organic substance, and when the organic substance is vaporized by taking heat of vaporization, the gap between the layers is further narrowed. When the temperature is further increased, the vaporization of the organic substance is completed, and a collection of metal oxide particulates having a size of 40 nm to 60 nm forms a uniform thickness with an equivalent thickness, and is deposited between the layers to complete the thermal decomposition. Since the metal oxide is a stable substance, the precipitated particulates are not joined together. Therefore, the granular fine particles receive a compressive load applied between the layers, and the granular fine particles move so as to fill the gaps between the layers, thereby filling the layers. In addition, since the size of the fine particles is one digit or more smaller than the surface roughness of the electrical steel sheet, the fine particles enter the unevenness on the surface of the electrical steel sheet and fill the unevenness. As a result, the particulate fine particles of the metal oxide fill up the interlayer which is a minute sealed space. Therefore, the metal oxide fine particles do not fall off from the interlayer. Further, no gap is formed between the layers, and sticking does not occur. Further, the interlayer is filled with granular fine particles of metal oxide at high density, and has an insulating property close to the insulation resistance of metal oxide. On the other hand, since the end face of the iron core is open to the outside, when welding the end face, the fine particles on the end face fall off and do not hinder the welding. Further, the fine particles that fall off are extremely fine and have almost no weight, so that they do not attack the insulating coating. Furthermore, since the particulate fine particles are stable metal oxides, they have heat resistance, corrosion resistance, and oil resistance. Further, a corrosive liquid or insulating oil cannot enter between layers filled with a collection of fine particles due to surface tension. Furthermore, since the fine particles do not join each other, the insulating layer has a thermal shock resistance only by a very small amount of expansion or contraction with respect to a rapid temperature change. Further, when the iron core is heat-treated, the electromagnetic steel sheet is thermally expanded, but since the fine particles are not joined, the insulating layer does not restrain the thermal expansion of the electromagnetic steel sheet. For this reason, thermal strain does not occur in the electromagnetic steel sheet. Furthermore, if the compression load is released and the iron core is gradually cooled after the metal compound is thermally decomposed, the distortion of the electrical steel sheet due to the compression load is eliminated and the iron loss is reduced. Therefore, if the size of the iron loss does not become a problem, the iron core manufactured by this feature means can be incorporated into an electric device and used without performing strain relief annealing.
As described above, according to this feature means, the iron core is manufactured by a manufacturing method completely different from the conventional one, and the insulating layer is formed by a collection of metal oxide fine particles completely different from the conventional one. Among the required properties described in the paragraph, it has all the properties except the heat resistance of strain annealing.
Furthermore, according to this feature means, heat treatment is performed with a compressive load applied to the iron core from the production of the iron core to the formation of the insulating layer. For this reason, the laminated electrical steel sheets are pressure-bonded via metal oxide fine particles. Therefore, it is not necessary to fix the end faces of the laminated electrical steel sheets by welding or by caulking. Furthermore, there is no troublesome process of applying an adhesive to the processed electrical steel sheet and further laminating it. As described above, since the processing method related to the manufacture of the iron core is completely different from the conventional one, the conventional iron core processing problems described in the second paragraph are not caused.

  In the fourth feature means related to the manufacture of the iron core in the present invention, the insulating layer made up of a collection of metal oxide fine particles in the third feature means described above is formed, and the insulation layer made up of a collection of iron (II) particulate fine particles. In connection with the formation of the insulating layer, the organic core on which iron (II) oxide is deposited by pyrolysis is applied to the iron core in which the coating is formed between the layers of the laminated electrical steel sheets in the third characteristic means. An alcohol dispersion in which an iron compound is dispersed in an alcohol; a first property that dissolves or mixes in the alcohol; a second property that has a higher viscosity than the alcohol; and a boiling point that is lower than the thermal decomposition temperature of the organic iron compound. Iron composed of a mixed solution of organic compounds having these three properties and having the three properties, and a film made of the mixed solution formed between the laminated electrical steel sheets Is subjected to a heat treatment by applying a compressive load in accordance with the third characteristic means described above, whereby the organic iron compound is thermally decomposed to precipitate the fine particles of the iron (II) oxide, and the iron (II) oxide. The collection of the particulate fine particles forms an insulating layer.

In other words, according to this feature means, an organic iron compound that precipitates insulating iron oxide (II) FeO by pyrolysis is used as the metal compound that constitutes the coating film in the third feature means, and the third feature described above. When the iron core is manufactured in accordance with the characteristic means, the organic iron compound is thermally decomposed to precipitate particulate particles of iron (II) FeO, and an insulating layer is formed by a collection of particulate particles of iron (II) FeO.
That is, an organic iron compound in which iron (II) FeO is precipitated by thermal decomposition is dispersed in alcohol, dissolved or mixed in alcohol, and has a higher viscosity than alcohol and a boiling point lower than the thermal decomposition temperature of the organic iron compound. An organic compound having properties is mixed with the alcohol dispersion to prepare a mixed solution. This mixed solution is applied to the electrical steel sheet. Furthermore, this electromagnetic steel sheet is laminated | stacked, a compressive load is applied, it punches or shears in the shape of an iron core, and the iron core in which the film which consists of the said liquid mixture was formed between the layers of the laminated | stacked electromagnetic steel sheet is created. A compression load is applied to the iron core and heat treatment is performed in an air atmosphere. When the alcohol and the organic compound are vaporized, and the organic iron compound is further decomposed into iron (II) oxide FeO and an organic acid, and the vaporization of the organic acid is completed, the iron (II) oxide having a size of 40 to 60 nm is completed. FeO granular fine particles are deposited and thermal decomposition of the organic iron compound is completed.
As described above, according to this feature means, an insulating layer made of a collection of granular fine particles of iron (II) FeO is formed between layers of laminated magnetic steel sheets.

  The fifth characteristic means relating to the production of the iron core in the present invention is that the organic iron compound in the fourth characteristic means is iron naphthenate.

That is, the iron naphthenate in this characteristic means finishes thermal decomposition at 340 ° C. in the air atmosphere and precipitates iron (II) oxide particulates. For this reason, iron naphthenate becomes a raw material of granular fine particles of iron oxide (II) FeO. Naphthenic acid is a mixture of saturated fatty acids having a 5-membered ring, represented by a general formula consisting of C _n H _2n-1 COOH, and the main component consists of C ₉ H ₁₇ COOH having a boiling point of 268 ° C. and a molecular weight of 170.
That is, iron naphthenate is a complex in which the oxygen ion O ⁻ constituting the carboxyl group of naphthenic acid becomes a ligand and coordinates with the iron ion Fe ²⁺ . That is, since the oxygen ion O ⁻ approaches the iron ion Fe ²⁺ , which is the largest ion, and is coordinated, the distance between the two becomes short. As a result, the distance between the oxygen ion O ⁻ coordinated to the iron ion Fe ²⁺ and the ion covalently bonded on the opposite side of the iron ion is the longest. When the iron naphthenate having such molecular structure features exceeds the boiling point of the main component of naphthenic acid, the oxygen ion O ⁻ constituting the carboxyl group is bonded to the ion covalently bonded to the opposite side of the iron ion Fe ^2+. Are first divided and decomposed into iron oxide (II) FeO, which is a compound of iron ions Fe ²⁺ and oxygen ions O ⁻ , and naphthenic acid. When the temperature is further increased, naphthenic acid takes the heat of vaporization and vaporizes, and when vaporization of naphthenic acid is completed, granular particles of iron (II) FeO are precipitated and thermal decomposition is completed.
Furthermore, iron naphthenate is an inexpensive industrial chemical that can be easily synthesized. That is, when naphthenic acid, which is a general-purpose organic acid, is reacted with a strong alkali, an alkali metal naphthenate is produced, and when an alkali metal naphthenate is reacted with an inorganic iron compound, iron naphthenate is synthesized. Therefore, it is the cheapest among organic acid iron compounds. In addition, since naphthenic acid as a raw material has a relatively low boiling point among organic acids, iron (II) oxide is precipitated by heat treatment at about 340 ° C. in an air atmosphere. Iron naphthenate with these properties is widely used in paint / printing ink dryers, rubber / tire adhesives, lubricant extreme pressure agents, polyester curing agents, combustion aids and polymerization catalysts. ing.
As described above, according to this feature means, an insulating layer composed of a collection of iron (II) FeO granular fine particles can be formed at low cost using iron naphthenate, which is an inexpensive industrial chemical.

  The sixth characteristic means relating to the production of the iron core in the present invention is that the organic compound in the above-mentioned fourth characteristic means is any organic compound consisting of carboxylic acid esters, glycols or glycol ethers.

That is, according to this feature means, in carboxylic acid esters, glycols or glycol ethers, firstly dissolved or mixed in alcohol, secondly higher in viscosity than alcohol, and thirdly iron naphthenate. There is an organic compound having these three properties, the boiling point of which is lower than the temperature at which pyrolysis occurs. Such organic compounds are all general industrial chemicals.
Therefore, when any one of the organic compounds in the feature means is mixed with the alcohol dispersion of iron naphthenate, a mixed solution in which the iron naphthenate and the organic compound are uniformly dispersed in a molecular state can be prepared. When this mixed solution is applied to the electrical steel sheet, a film is formed on the electrical steel sheet.
For this reason, the organic compound in this characteristic means becomes a raw material of the film formed on the magnetic steel sheet together with iron naphthenate. As a result, an insulating layer made of a collection of iron (II) FeO granular fine particles is formed between the layers of the laminated electrical steel sheets.

  The seventh characteristic means relating to the manufacture of the iron core in the present invention is related to forming an insulating layer with a collection of granular fine particles of maghemite, and the formation of the insulating layer is in accordance with the formation of the insulating layer of the fourth characteristic means described above. , Forming an insulating layer with a collection of granular particulates of iron (II), and further heating the iron core by applying a compressive load, whereby the iron (II) oxide is oxidized to iron (III), The insulating layer is formed of a collection of granular fine particles of maghemite.

That is, according to the present feature means, in accordance with the fourth feature means described above, an insulating layer is formed from a collection of granular fine particles of iron (II) oxide by heat treatment at 340 ° C., and further, an iron core to which a compressive load is applied. The temperature is raised to 390 ° C. while suppressing the heating rate. At this time, in iron oxide (II) FeO, the oxidation reaction in which the divalent iron ion Fe ²⁺ becomes the trivalent iron ion Fe ³⁺ gradually proceeds. In the initial stage of this oxidation reaction, a part of the divalent iron ions Fe ²⁺ constituting iron (II) FeO become trivalent iron ions Fe ³⁺ to become Fe ₂ O ₃ , and the composition formula is FeO. · becomes _Fe 2 _{O 3} of magnetite _Fe 3 _{O 4.} Furthermore, when the oxidation reaction proceeds, all of the iron (II) FeO becomes magnetite Fe ₃ O ₄ . Further, when the oxidation reaction proceeds, all of the divalent iron ions Fe ²⁺ constituting the magnetite FeO · Fe ₂ O ₃ become trivalent iron ions Fe ³⁺ and become iron oxide (III) Fe ₂ O _3. Finish the oxidation reaction. This iron (III) Fe ₂ O ₃ is maghemite γ-Fe ₂ O ₃ having a cubic crystal structure similar to that of magnetite Fe ₃ O ₄ . Note that the crystal structure of hematite α-Fe ₂ O ₃ , which is the α phase of iron (III) Fe ₂ O ₃ , is a trigonal system, and the crystal structure is different from that of magnetite. Moreover, if iron (II) is oxidized to iron (III) and then the compression load is released and the iron core is gradually cooled, the distortion of the electrical steel sheet due to the compression load is eliminated, and the iron loss is reduced. Therefore, if the size of the iron loss does not become a problem, the iron core manufactured by this characteristic means can be incorporated into an electric device and used without performing strain relief annealing.
As described above, an insulating layer is formed from a collection of granular fine particles of maghemite by an extremely simple means by simply heat-treating laminated magnetic steel sheets in the atmosphere. This maghemite has the following four properties and forms an insulating layer that brings about an epoch-making action and effect.
The first is an insulator having a specific resistance of 10 ⁶ Ωm. Therefore, the interlayer filled with maghemite fine particles has an insulation property similar to maghemite. Incidentally, the specific resistance of the electrical steel sheet is 10 ⁻⁷ Ωm, and the eddy current loss of the iron core is inversely proportional to the specific resistance, so the eddy current loss becomes extremely small.
Second, it has ferrimagnetic properties that are ferromagnetic. For this reason, the maghemite fine particles are strongly magnetically adsorbed to the magnetic steel sheet, and the maghemite fine particles are also magnetically adsorbed. Maghemite fine particles once magnetically adsorbed are fine particles having almost no weight, and it is difficult to cancel the magnetic adsorption. Accordingly, the maghemite fine particles filled between the layers do not fall off from the layers.
Third, the Mohs hardness is 6.5, which is a material that is significantly harder than the electrical steel sheet. For this reason, even if it receives a compressive load, the fine particle of maghemite is not destroyed, and it is not destroyed even by friction between maghemite fine particles. The maghemite fine particles in contact with the magnetic steel sheet bite into the surface of the magnetic steel sheet and are magnetically adsorbed, and other maghemite fine particles are magnetically adsorbed on these maghemite fine particles. For this reason, the collection of magnetically adsorbed maghemite fine particles does not fall off from the interlayer.
It is the fourth stable oxide and is known as a substance that forms a passive film of iron. Therefore, it has corrosion resistance and oil resistance. Although it has heat resistance, it undergoes phase transition to hematite at 530 ° C or higher.
That is, maghemite having a cubic crystal structure is a γ-phase iron oxide (III) _Fe 2 _{O 3,} when the temperature is raised to suppress the Atsushi Nobori rate, the iron oxide from around _{530 ℃ (III) Fe 2 O} 3 The phase transition gradually proceeds to hematite having a trigonal crystal structure, which is an α phase, and the phase transition is completed at around 670 ° C.
As described above, maghemite brings about an epoch-making action and effect as a material that insulates the layers of electrical steel sheets, and the insulating layer made up of a collection of granular particles of maghemite has the required properties described in the fourth paragraph. Among them, it has all the properties except the heat resistance of strain relief annealing.
Conventional maghemite γ-Fe ₂ O ₃ is produced as acicular fine particles. That is, ferrous sulfate or ferric sulfate is reacted in an alkaline aqueous solution while sending air to precipitate iron (III) α-FeOOH called acicular fine particles called goethite. This goethite is dehydrated once in an atmosphere of hydrogen gas to hematite α-Fe ₂ O _3, and further reduced to produce magnetite Fe ₃ O ₄ . Thereafter, when magnetite is slowly heated and oxidized in the atmosphere, acicular maghemite fine particles are generated. Since the acicular fine particles have a larger aspect ratio than the granular fine particles, that is, the ratio of the length to the width, the collection of magnetically adsorbed acicular fine particles forms a large number of gaps, and the insulation is reduced. Furthermore, the manufacturing process for generating the needle-shaped maghemite fine particles is more expensive than the above-described manufacturing process for generating the granular maghemite fine particles because it is composed of many divided manufacturing processes. As described above, in the case where the collection of fine particles is packed at a high density, the granular fine particles are much more effective than the acicular fine particles.

  The eighth characteristic means relating to the production of the iron core in the present invention relates to the formation of an insulating layer by a collection of granular fine particles of hematite, and the formation of the insulating layer is based on the granular fine particles of maghemite in the seventh characteristic means described above. The iron core on which the insulating layer is formed by gathering is further subjected to strain relief annealing, whereby the maghemite is phase-transformed into hematite, and the insulating layer is formed by a collection of particulate fine particles of the hematite.

That is, in this feature means, when performing strain relief annealing to reduce the iron loss of the iron core due to the residual strain on the electromagnetic steel sheet, the iron core manufactured by the seventh feature means is in a state where a compression load is applied, The temperature is raised to a temperature of 750 ° C. to 820 ° C. in an atmosphere in which iron is not easily oxidized, and after left at this temperature for a certain period of time, the compression load is released, and then the strain relief annealing is performed to gradually cool. In this case, the γ-phase maghemite of iron (III) oxide undergoes phase transition to the α-phase hematite of iron (III) during the temperature rising process, and an insulating layer is formed by a collection of particulate hematite particles. This hematite has the following properties, and is a substance that forms an insulating layer that provides a more innovative effect than maghemite.
Hematite α-Fe ₂ O ₃ has a specific resistance of 10 ⁷ Ωm, and the insulation between layers is further improved by an order of magnitude by the treatment of strain relief annealing, and the eddy current loss is further reduced. Hematite is a passive state that is not affected by a very stable oxide, that is, a strong acid or a strong alkali, and has heat resistance close to a melting point of 1566 ° C., corrosion resistance, and oil resistance. For this reason, hematite does not chemically change during strain relief annealing, and no chemical reaction such as a diffusion phenomenon occurs with the electromagnetic steel sheet. Moreover, it has weak ferromagnetism and has a magnetic Curie point of 950 ° C. Accordingly, even after the strain relief annealing, although the magnetic adsorption force is weak, hematite is magnetically adsorbed on the magnetic steel sheet, and the hematite fine particles are also magnetically adsorbed. Further, hematite is a material harder than a magnetic steel sheet having a Mohs hardness of 6, and the fine particles are not broken by a compressive load, and are not broken by friction between hematite fine particles. Further, as described in paragraph 22, since the maghemite fine particles enter the irregularities on the surface of the magnetic steel sheet to fill the irregularities and fill the layers, the hematite fine particles likewise fill the layers. Accordingly, hematite particles are surely present and no voids are present in any part of the gap between the stacked electrical steel sheets. This prevents sticking during strain relief annealing.
As described above, the insulating layer composed of a collection of fine particles of hematite brings about an epoch-making action effect as compared with maghemite, and has all the required properties described in the fourth paragraph.
In addition, the interlayer which is a minute sealed space was filled with magnetically adsorbed maghemite fine particles without gaps, and the laminated electrical steel sheets were pressure-bonded via a collection of maghemite fine particles. In such a temperature rising process in which a compressive load is applied to the iron core, maghemite undergoes a phase transition to hematite, so that even if the compressive load is released during the slow cooling process, the hematite fine particles do not fall out of the interlayer. Further, the laminated electrical steel sheets are pressure-bonded through a collection of hematite fine particles. On the other hand, the hematite particles present on the end face of the iron core easily fall off and do not hinder welding.
As described above, according to the present feature means, when the core is subjected to stress relief annealing, not only the iron loss of the iron core is reduced, but also insulation by the collection of granular particles of hematite, which is an extremely stable passive state. Since the layer is formed, the eddy current loss of the iron core is further reduced, and the iron core having both heat resistance, corrosion resistance, oil resistance and sticking resistance higher than the heat resistance of the strain relief annealing is manufactured.

  In the present invention, a method for producing an iron core in which layers are insulated by a collection of granular fine particles of maghemite includes a first step in which iron naphthenate is dispersed in alcohol to form a dispersion, and carboxylic acid esters, glycols, or A second step of mixing any organic compound consisting of glycol ethers with the alcohol dispersion prepared in the first step to prepare a mixed solution, and a third step of applying the mixed solution to the electrical steel sheet. The fourth step of laminating the magnetic steel sheets and punching or shearing the iron core in a state where a compressive load is applied, and the fifth step of heat-treating the iron core in a state where the compressive load is applied. Thus, the manufacturing method in which these five steps are continuously performed is a manufacturing method for manufacturing an iron core in which an interlayer is insulated by a collection of granular fine particles of maghemite.

In other words, according to this feature means, the five extremely simple processes are continuously performed, so that there is no problem in manufacturing the conventional iron core described in the second paragraph, and the stress relief annealing described in the fourth paragraph. An iron core on which an insulating layer satisfying all the properties excluding heat resistance is formed can be continuously produced at low cost. Therefore, if the magnitude of the iron loss of the iron core manufactured by this characteristic means does not become a problem, the iron core manufactured by this characteristic means can be incorporated into an electric device as it is and used as an iron core.
The first step is simply a step of dispersing inexpensive iron naphthenate in alcohol. The second step is simply a step of mixing an inexpensive organic compound into the alcohol dispersion. A 3rd process is a process only of apply | coating a liquid mixture to an electromagnetic steel plate. The fourth step is a step of manufacturing an iron core by punching or shearing in a state where magnetic steel sheets are laminated and a compressive load is applied. The fifth step is simply a heat treatment in a state where a compression load is applied to the iron core.

  According to the present invention, the method of manufacturing an iron core in which the interlayer is insulated by a collection of granular fine particles of hematite produces the iron core in which the interlayer is insulated by the collection of granular fine particles of maghemite, and further, the core is subjected to strain relief annealing. The manufacturing method is to manufacture an iron core whose layers are insulated with a collection of granular fine particles of hematite.

  In other words, according to this feature means, the maghemite is phase-transformed into hematite by simply carrying out strain relief annealing on an iron core whose layers are insulated by a collection of particulate maghemite particles, and the collection of particulate hematite particles. In this way, an iron core having an insulated layer is manufactured. As a result, the residual strain of the electromagnetic steel sheet is released and the iron loss of the iron core is reduced, the eddy current loss of the iron core is further reduced, and the heat resistance, corrosion resistance and oil resistance are higher than the heat resistance of strain relief annealing. Iron cores with both properties and sticking resistance are produced.

It is the figure which illustrated typically the state in which the aggregate of the granular fine particles of a maghemite forms an insulating layer in the gap | interval of two electromagnetic steel plates. It is the figure which illustrated typically the state in which the gathering of the hematite granular fine particles forms an insulating layer in the gap | interval of two electromagnetic steel plates.

Embodiment 1

  This embodiment has these three properties which are firstly dissolved or mixed in alcohol, secondly higher in viscosity than alcohol, and thirdly lower in boiling point than 340 ° C. where iron naphthenate is thermally decomposed. It is embodiment regarding an organic compound. Since the organic compound having these three properties is mixed with the alcohol dispersion of iron naphthenate at an arbitrary ratio, it becomes a raw material for the film formed on the magnetic steel sheet. Among organic compounds having these three properties, there are many organic compounds belonging to carboxylic acid esters, glycols, or glycol ethers.

First, carboxylic acid esters will be described. Carboxylic acid esters include three types of esters consisting of a first ester composed of a saturated carboxylic acid, a second ester composed of an unsaturated carboxylic acid, and a third ester composed of an aromatic carboxylic acid. Divided into classes.
Esters consisting of saturated carboxylic acids as the first esters are acetic acid esters, propionic acid esters, butyric acid esters, bivalic acid esters, caproic acid esters, caprylic acid esters, capric acid esters, lauric acid. It consists of acid esters, myristic acid esters, palmitic acid esters, stearic acid esters and the like.
Here, acetates having a small molecular weight will be described. Acetic acid esters include methyl acetate, ethyl acetate, butyl acetate, propyl acetate, isopropyl acetate, octyl acetate, heptyl acetate, benzyl acetate, phenyl acetate, vinyl acetate, and the like. Acetic esters other than methyl acetate have a higher boiling point than methanol and a lower boiling point than n-butanol. It is also soluble in methanol and has a higher viscosity than methanol. For this reason, if iron naphthenate is dispersed in methanol and any one of acetates excluding methyl acetate is mixed in this dispersion, it becomes a raw material for a film to be formed on the magnetic steel sheet. For example, vinyl acetate (monomer) is dissolved in methanol, has a higher viscosity than methanol, and has a boiling point of 72.7 ° C. higher than that of methanol. Therefore, when iron naphthenate is dispersed in methanol and vinyl acetate is mixed with this dispersion, the viscosity of the dispersion increases according to the amount of the mixed vinyl acetate.
In addition, lauric acid esters having a large molecular weight will be described. Octyl laurate dissolves in n-butanol, has a higher viscosity than n-butanol, and has a boiling point of 355 ° C., which is higher than the thermal decomposition temperature of iron naphthenate. Therefore, lauric acid esters having a molecular weight smaller than that of octyl laurate are used as a raw material for the coating formed on the magnetic steel sheet.
As described above, saturated fatty acid esters have been described with representatives of low molecular weight acetic acid esters and high molecular weight lauric acid esters. Many of the saturated fatty acid esters having a small molecular weight are soluble in methanol, have a higher viscosity than methanol, have a boiling point higher than that of methanol, and lower than a temperature at which iron naphthenate is thermally decomposed. In addition, saturated fatty acid esters having a large molecular weight have a property that the boiling point is lower than 340 ° C. at which iron naphthenate is thermally decomposed if the esters have a relatively small molecular weight.

Next, esters made of unsaturated carboxylic acid include acrylic acid esters, crotonic acid esters, methacrylic acid esters, oleic acid esters and the like.
Low molecular weight acrylic esters include methyl acrylate having a boiling point of 80 ° C., ethyl acrylate having a boiling point of 100 ° C., isobutyl acrylate having a boiling point of 132 ° C., butyl acrylate having a boiling point of 148 ° C., and a boiling point of 214 ° C. And 2-ethylhexyl acrylate. Since methyl acrylate and ethyl acrylate are dissolved in methanol and have a higher viscosity than methanol, iron naphthenate is dispersed in methanol, and this dispersion is mixed with methyl acrylate or ethyl acrylate to form a coating. It becomes a mixed liquid to be formed. Also, since the boiling point of butyl acrylate and isobutyl acrylate is higher than the boiling point of n-butanol and lower than the temperature at which iron naphthenate is thermally decomposed, iron naphthenate is dispersed in n-butanol, and acrylic acid is dispersed in this dispersion. When butyl acid or isobutyl acrylate is mixed, a mixed solution is formed to form a film.

Furthermore, esters composed of aromatic carboxylic acids include benzoates and phthalates.
Among benzoic acid esters, benzoic acid esters that are dissolved in methanol, have a higher viscosity than methanol, and have a boiling point lower than the thermal decomposition temperature of naphthenic acid are esters having a molecular weight of benzyl benzoate or lower. By the way, the boiling point of benzyl benzoate is 324 ° C. Therefore, these benzoic acid esters become raw materials for forming a film. Among phthalic acid esters, phthalates having a property of being dissolved or mixed in methanol, having a higher viscosity than methanol and a boiling point lower than 340 ° C. Acid esters are esters having a lower molecular weight than dibutyl phthalate. By the way, the boiling point of dibutyl phthalate is 340 ° C. Therefore, these phthalates are the raw materials for forming the film.

Next, glycols will be described. Examples of glycols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol.
Ethylene glycol is a liquid monomer that dissolves in methanol and n-butanol and has a boiling point of 197 ° C. Further, diethylene glycol is a liquid monomer having a boiling point of 244 ° C. dissolved in methanol and n-butanol. Further, propylene glycol is a liquid monomer that is miscible with methanol and n-butanol and has a boiling point of 188 ° C. Further, dipropylene glycol is a liquid monomer that is miscible with methanol and n-butanol and has a boiling point of 232 ° C. Tripropylene glycol is a liquid monomer that is miscible with methanol and n-butanol and has a boiling point of 265 ° C. Thus, the boiling point of glycols is lower than the thermal decomposition temperature of iron naphthenate. Therefore, it becomes the raw material of the film formed on the electromagnetic steel sheet.

Finally, glycol ethers will be described. Examples of glycol ethers include ethylene glycol ethers, propylene glycol ethers, and dialkyl glycol ethers in which hydrogen at the terminals of ethylene glycol, diethylene glycol, and triethylene glycol is substituted with an alkyl group.
Furthermore, ethylene glycol ethers are methyl glycol, methyl diglycol, methyl triglycol, methyl polyglycol, isopropyl glycol, isopropyl diglycol, butyl glycol, butyl diglycol, butyl triglycol, isobutyl glycol, isobutyl diglycol, hexyl glycol Hexyl diglycol, 2-ethylhexyl glycol, 2-ethylhexyl diglycol, allyl glycol, phenyl glycol, phenyl diglycol, benzyl glycol, benzyl diglycol and the like.
These ethylene glycol ethers are all dissolved in n-butanol, have a higher viscosity than n-butanol, are higher than the boiling point of n-butanol, and are lower than the temperature at which iron naphthenate is thermally decomposed. For this reason, it becomes the raw material of the film formed in an electromagnetic steel plate.

Propylene glycol ethers include methylpropylene glycol, methylpropylene diglycol, methylpropylene triglycol, propylpropylene glycol, propylpropylene diglycol, butylpropylene glycol, butylpropylene diglycol, butylpropylene triglycol, phenylpropylene glycol, methylpropylene For example, glycol acetate.
All of these propylene glycol ethers are soluble in n-butanol, have a higher viscosity than n-butanol, are higher than the boiling point of n-butanol, and lower than the temperature at which iron naphthenate is thermally decomposed. For this reason, it becomes the raw material of the film formed in an electromagnetic steel plate.

Dialkyl glycol ethers include dimethyl glycol, dimethyl diglycol, dimethyl triglycol, methyl ethyl diglycol, diethyl diglycol, dibutyl diglycol, dimethylpropylene diglycol and the like.
All of these dialkyl glycol ethers are soluble in n-butanol, have a higher viscosity than n-butanol, are higher than the boiling point of n-butanol, and lower than the temperature at which iron naphthenate is thermally decomposed. For this reason, it becomes the raw material of the film formed in an electromagnetic steel plate.

Embodiment 2

In this embodiment, an insulating layer composed of a collection of maghemite granular fine particles is formed between two electromagnetic steel sheets, the adhesion strength of the insulating layer, the insulation resistance, the corrosion resistance based on the salt spray test, and the heat resistance based on the thermal shock test. Examine the impact. A non-oriented electrical steel sheet (for example, product number 35JNE250 having a thickness of 0.35 mm, which is a product of JFE Steel Corporation) was used as the electrical steel sheet. Non-oriented electrical steel sheets are used as cores for transformers other than large transformers and distribution transformers and as cores for various rotating machines. Note that the direction of magnetization of the magnetic steel sheet and the magnitude of the iron loss are properties inherent to the magnetic steel sheet, and any electromagnetic steel sheet can be used in forming the insulating layer. Further, iron naphthenate (for example, a product of Toei Chemical Co., Ltd.) was used as a raw material for maghemite.
First, iron naphthenate was dispersed in n-butanol at a rate of 10% by weight. The dispersion was mixed so that ethylene glycol accounted for 20% by weight. In addition, ethylene glycol is mixed with n-butanol at an arbitrary ratio, has a boiling point 80 ° C. higher than that of n-butanol, and has a viscosity 5.4 times that of n-butanol. Next, two electromagnetic steel sheets obtained by cutting the above-described electromagnetic steel sheets into 50 mm × 30 mm were prepared. The above mixed solution was applied to the corner of one electromagnetic steel sheet with a width of 12.5 mm and a length of 30 mm and a thickness of 20 μm. This mixed liquid was applied so that the width of 12.5 mm at the corner of another magnetic steel sheet overlapped with the applied portion of the mixed liquid, and a load of 30 kg was applied to the overlapped portion (the applied pressure on the applied surface was 8 kg / equivalent to cm ² ). The two laminated electrical steel sheets were heat-treated in the atmosphere with a load applied. First, the temperature was raised to 120 ° C. to vaporize n-butanol, and then the temperature was raised to 200 ° C. to vaporize ethylene glycol. Further, the temperature was raised to 340 ° C. and left at 340 ° C. for 1 minute to thermally decompose iron naphthenate. Further, from 340 ° C. to 1 ° C./min. The temperature was raised to 390 ° C. at a rate of temperature rise of 390 ° C. and left at 390 ° C. for 30 minutes. Thereafter, the applied load was released and the mixture was gradually cooled to room temperature. In this way, 22 samples were prepared.
First, for one sample, a portion where two electromagnetic steel plates overlap, that is, a portion where an insulating layer was formed was cut, and a plurality of portions of the cut surface were observed with an electron microscope. The electron microscope used was an ultra-low acceleration voltage SEM from JFE Techno-Research Corporation. This apparatus is capable of observing the surface with an extremely low acceleration voltage from 100 V, and has a feature that the surface of the sample can be directly observed without forming a conductive film on the sample. First, a secondary electron beam between 900 V and 1 kV of the reflected electron beam was taken out, image processing was performed, and the surface of the cross section was observed. In any part, granular fine particles having a size of 40 nm to 60 nm were joined together, and the collection of granular fine particles formed an average thickness of about 2 μm to fill the gap. Next, the energy and intensity of characteristic X-rays were subjected to image processing, and the types of elements constituting the cross section and their distribution states were analyzed. Since both iron atoms and oxygen atoms are present uniformly and unevenly distributed portions are not observed, the particles are granular fine particles made of iron oxide. Furthermore, an EBSP analysis function was added to the function of the extremely low acceleration voltage SEM, and the crystal structure of the fine particles was analyzed. From this result, it was confirmed that the particulate fine particles forming the insulating layer were maghemite γ-Fe ₂ O ₃ which is a γ phase of iron oxide (III). The EBSP analysis function means that when a sample is irradiated with an electron beam, reflected electrons are diffracted by the atomic plane in the sample to form a band-like pattern, and the symmetry of this band corresponds to the crystal system. Since the band interval corresponds to the atomic plane interval, the pattern is analyzed to measure the crystal orientation and the crystal system. The result is schematically shown in FIG. 1 is a magnetic steel sheet, and 2 is granular fine particles of maghemite. Engaging in the irregularities on the surface of the two electromagnetic steel sheets 1, the collection of granular fine particles 2 of maghemy filled the layers.
Next, the adhesion strength of the insulating layer of the five samples was evaluated by a tensile test. The sample was 3 mm / min. The maximum tensile stress at the time when the insulating layer breaks was defined as the adhesion strength. The adhesion strength is 2.5 MPa to 3.0 MPa, and has sufficient adhesion strength as a processed iron core.
Furthermore, the resistance of the insulating layer broken in the tensile test was measured by the four-terminal method. The specific resistance of the five samples is 55 to 60 μΩm, and the insulating layer has high insulation properties that sufficiently reduce eddy current loss.
Next, a salt spray test using neutral 5% salt water was performed using the sample fractured in the tensile test. Since no discoloration was observed on the surface of the insulating layer, the insulating layer has excellent corrosion resistance.
Lastly, five samples were subjected to an air-bath thermal shock test that gave a temperature change of −30 ° C. to 120 ° C., and then the change in the adhesion strength of the insulating layer was examined by the tensile test described above. Since the adhesion strength after the thermal shock test was not different from the adhesion strength before the thermal shock test, the insulating layer has excellent thermal shock resistance.

Embodiment 3

In the present embodiment, assuming that 11 samples manufactured in Embodiment 2 are subjected to strain relief annealing, a 35 kg load is applied to the overlapped portion, and the temperature is raised to 800 ° C. in a nitrogen atmosphere. After standing for 2 hours, it was gradually cooled to room temperature. Also for this sample, the adhesion strength, insulation resistance, corrosion resistance, and thermal shock resistance of the insulating layer were examined as in the second embodiment.
First, as in Embodiment 2, for one sample, a portion where two electromagnetic steel plates overlap was cut, and a plurality of portions of the cut surface were observed with an electron microscope. First, a secondary electron beam between 900 V to 1 kV of the reflected electron beam was taken out, image processing was performed, and the surface of the cross section was observed. As in the second embodiment, the granular fine particles having a size of 40 nm to 60 nm are bonded to each other in the cross section, and the aggregate of the bonded granular fine particles forms an average thickness of about 2 μm to fill the gap. . Next, the energy and intensity of characteristic X-rays were subjected to image processing, and the types of elements constituting the cross section and their distribution states were analyzed. As in the second embodiment, since both iron atoms and oxygen atoms are present uniformly, and unevenly distributed portions are not seen, the fine particles are granular fine particles made of iron oxide. Furthermore, an EBSP analysis function was added to the function of the extremely low acceleration voltage SEM, and the crystal structure of the fine particles was analyzed. From this result, it was confirmed that the particulate fine particles forming the insulating layer were hematite α-Fe ₂ O ₃ which is an α phase of iron oxide (III). The result is schematically shown in FIG. The gathers of granular fine particles 4 of hematite filled the interlayers by entering the irregularities on the surfaces of the two electromagnetic steel sheets 3.
Next, as in Embodiment 2, the adhesion strength of the insulating layer was evaluated for the five samples by a tensile test. The adhesion strength is 1.5 MPa to 2.0 MPa, and the cause of the slight decrease in adhesion strength from the second embodiment is that maghemite has undergone phase transition to hematite, so that the magnetic adsorption force between the hematite fine particles and the magnetic steel sheet, and the hematite fine particles This is thought to be due to a reduction in the magnetic attractive force between each other. However, the insulating layer still has sufficient adhesion strength as a processed iron core. The reason for this is considered to be that when the maghemite fine particles were deposited, the heat treatment was performed by applying a compressive load, so that the magnetic steel sheets were already pressure-bonded via the maghemite fine particles.
Further, as in the second embodiment, the resistance of the insulating layer broken by the tensile test was measured by the four-terminal method. The specific resistance of the five samples was 500 to 600 μΩm, and the single-digit insulation resistance increased from that of the second embodiment.
Next, similarly to Embodiment 2, a salt spray test was performed using the sample fractured in the tensile test. Since no discoloration was observed on the surface of the insulating layer, the insulating layer has excellent corrosion resistance.
Finally, as in the second embodiment, the five samples were subjected to an air tank thermal shock test giving a temperature change of −30 ° C. to 120 ° C., and then the change in the adhesion strength of the insulating layer was determined by the tensile test described above. Examined. The adhesion strength after the thermal shock test is the same as before the thermal shock test, and the insulating layer has excellent thermal shock resistance.

In this example, the liquid mixture produced in the second embodiment is applied to an electrical steel sheet, 20 sheets of this electrical steel sheet are laminated, processed into a shape of an iron core by applying a compressive load, and further applied by applying a compressive load to the iron core. Is an example in which an iron core is formed by heat-treating and forming an insulating layer with maghemite granular fine particles.
The mixed liquid produced in the second embodiment was applied to the magnetic steel sheet used in the second embodiment in a thickness of 20 μm, and 20 sheets of this magnetic steel sheet were stacked and a load of 280 kg was applied (the applied pressure was 7.9 kg / equivalent to cm ² ). Then, it was cut into a ring shape having an inner diameter of 3 inches (corresponding to 7.62 cm) and an outer diameter of 4 inches (corresponding to 10.16 cm). This laminated electrical steel sheet was heat-treated in air with a load applied. First, the temperature was raised to 120 ° C. to vaporize n-butanol, and then the temperature was raised to 200 ° C. to vaporize ethylene glycol. Further, the temperature was raised to 340 ° C. and left at 340 ° C. for 1 minute to thermally decompose iron naphthenate. Further, from 340 ° C. to 1 ° C./min. The temperature was raised to 390 ° C. at a temperature rising rate of 390 ° C. and left at 390 ° C. for 30 minutes. After that, the applied load was released and gradually cooled to room temperature to produce an iron core.
The iron loss of this iron core was measured using a magnetic property measuring device manufactured by Sumitomo Metal Technology Co., Ltd. When the frequency of the iron core is 50 Hz and the magnetic flux density is 1.5 Tesla, the iron loss is 2.9 W / kg, and the iron loss is close to 2.50 W / kg or less, which is the catalog value of the magnetic steel sheet manufacturer, and maghemite fine particles It was found that an excellent insulating layer was formed on the prepared iron core.

  In this example, the iron core manufactured in Example 1 was further heated to 800 ° C. in a nitrogen atmosphere by applying a load of 320 kg, allowed to stand for 2 hours, and then gradually cooled to room temperature. In the same manner as in Example 1, the iron loss of this iron core was measured. The iron loss was 2.7 W / kg, and it was found that a better insulating layer was formed by the collection of fine particles of hematite.

  As described above, both the aggregates of granular fine particles of maghemite and hematite form an excellent insulating layer having not only the value of insulation resistance but also various properties described in the fourth paragraph. Further, such an excellent insulating layer can be formed only by thermally decomposing inexpensive iron naphthenate. Furthermore, in the present invention, a large number of iron cores are manufactured simultaneously and continuously in a continuous process from the formation of a coating on an electromagnetic steel sheet to the formation of an insulating layer between layers. On the other hand, conventional iron core production is divided by punching or shearing a magnetic steel sheet with a coating formed into the shape of the iron core, and then laminating the processed magnetic steel sheets so that there is no misalignment to form the iron core. In addition, there is a troublesome process of laminating processed magnetic steel sheets. For this reason, according to the present invention, an iron core can be manufactured at a significantly lower cost than a conventional iron core. Furthermore, according to the present invention, various problems due to the conventional iron core processing method described in the second paragraph are not caused. Further, in the conventional iron core manufacturing method, there is a risk of damage to the coating film when processing and laminating the electromagnetic steel sheets. However, according to the iron core manufacturing method of the present invention, the coating film is not damaged. Absent. As a result, a defect-free insulating layer having excellent properties made of maghemite or hematite can be reliably formed between all the layers of the electromagnetic steel sheets. As described above, the present invention can produce a large number of iron cores at the same time at a significantly lower cost than the conventional manufacturing method, with the iron core having various excellent effects that cannot be considered in the past. This is a revolutionary iron core manufacturing technology.

  1 and 3 Electrical steel sheet 2 Granular fine particles of maghemite 4 Granular fine particles of hematite

Claims (10)

The formation of coatings on electrical steel sheets
A metal compound that precipitates an insulating metal oxide by thermal decomposition is dispersed in alcohol to create an alcohol dispersion, and the first property is dissolved or mixed in the alcohol, and the second property is higher in viscosity than the alcohol. An organic compound having these three properties, the boiling point of which is lower than the thermal decomposition temperature of the metal compound, is mixed with the alcohol dispersion to prepare a mixed solution. Coating on a magnetic steel sheet, whereby a film made of the mixed liquid is formed on the magnetic steel sheet.   The magnetic steel sheets on which the coating film is formed according to claim 1 are laminated, a compressive load is applied to the laminated electromagnetic steel sheets, and the laminated electromagnetic steel sheets are punched or sheared into the shape of an iron core, whereby the interlayer of the laminated electromagnetic steel sheets An iron core having a coating formed between layers of laminated electrical steel sheets, wherein the iron core having the coating formed thereon is manufactured.   The iron core having a film formed between the layers of the laminated electrical steel sheets according to claim 2 is heat-treated by applying a compressive load, whereby the metal compound constituting the film is thermally decomposed to form insulating metal oxide fine particles. The insulating layer is formed of a collection of metal oxide fine particles, wherein the metal oxide fine particles are collected to form an insulating layer between the laminated electrical steel sheets.   The insulating layer made of a collection of metal oxide fine particles according to claim 3 is an insulating layer made of a collection of iron (II) particulate fine particles, and the insulating layer is formed by stacking the electromagnetic steel sheets according to claim 3. A first property of dissolving or mixing in an alcohol dispersion liquid in which an organic iron compound in which iron (II) oxide is deposited by thermal decomposition is dispersed in an alcohol, and an iron core in which a film is formed between the layers. And a second property having a viscosity higher than that of the alcohol and a third property having a boiling point lower than the thermal decomposition temperature of the organic iron compound, and a mixed solution of the organic compound having these three properties. The iron core in which the coating film made of the mixed solution is formed between the layers of the laminated electrical steel sheets is subjected to heat treatment by applying a compressive load according to claim 3, whereby the organic iron compound is heated. The granular particles of iron (II) oxide are precipitated, and the collection of granular particles of iron (II) forms an insulating layer between the layers. Formation of an insulating layer consisting of a collection of   The organic iron compound according to claim 4, wherein the organic iron compound is iron naphthenate.   5. The organic compound according to claim 4, wherein the organic compound in claim 4 is any organic compound composed of carboxylic acid esters, glycols, or glycol ethers.   According to the formation of the insulating layer of claim 4, an insulating layer is formed by a collection of granular fine particles of iron (II) oxide, and the iron core is heated by applying a compressive load, whereby the iron oxide (II) ) Is oxidized to iron (III) oxide, and the insulating layer is formed of a collection of particulate maghemite particles. The formation of an insulating layer formed of a collection of particulate maghemite particles.   The iron core on which an insulating layer is formed with a collection of maghemite particulates according to claim 7 is subjected to strain relief annealing, whereby the maghemite undergoes a phase transition to hematite, and the collection of particulate hematite particles forms an insulation layer. Formation of an insulating layer formed of a collection of granular fine particles of hematite, characterized in that it is formed.   The manufacturing method of an iron core in which the layers of laminated electrical steel sheets are insulated by a collection of granular fine particles of maghemite includes a first step in which iron naphthenate is dispersed in alcohol to form a dispersion, and carboxylic acid esters or glycols. Or a second step of mixing any organic compound consisting of glycol ethers with the alcohol dispersion prepared in the first step to prepare a mixed solution, and a third step of applying the mixed solution to the electrical steel sheet. A fourth step of laminating the magnetic steel sheets coated with the mixed liquid, and punching or shearing the laminated magnetic steel sheets into a shape of an iron core by applying a compressive load, and the iron core; A manufacturing process in which these five processes are carried out continuously is a collection of granular fine particles of maghemite between the layers of the laminated electrical steel sheets. Production wherein the method is method of manufacturing a core of layers insulated with a collection of granular particles of maghemite laminated electromagnetic steel sheets to produce the insulated core with Ri.   The manufacturing method of the iron core in which the layers of the laminated electrical steel sheets are insulated by the collection of granular fine particles of hematite is manufactured according to claim 9, and the manufacturing method for carrying out the stress relief annealing on the iron core is Manufacturing of an iron core in which the layers of laminated magnetic steel sheets are insulated with a collection of granular particles of hematite, characterized in that it is a manufacturing method for manufacturing an iron core in which the layers of magnetic steel sheets are insulated with a collection of granular particles of hematite Method.

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