JP2002038279A - Grain-oriented magnetic steel sheet superior in bend adhesion to long transverse direction and suitable for direct ignition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grain-oriented magnetic steel sheet having an insulating layer most suitable for a core and a shield of a direct ignition and greatly superior in its bend adhesion to a long transverse direction. SOLUTION: The grain-oriented magnetic steel sheet having an insulating layer superior in the bend adhesion to the long transverse direction, comprises forming a layer of acrylic, epoxy, urethane, and/or phenolic resin with a glass transition point of 25-150 deg.C, on a surface of the grain-oriented magnetic steel sheet on which an insulating layer of forsterite or phosphate base is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grain-oriented electrical steel sheet suitable for a core and a shield constituting a direct ignition.

[0002]

2. Description of the Related Art In recent years, there has been a demand for improving the efficiency of various electric appliances from the viewpoint of energy saving. In particular, various measures have been taken for automotive electrical components due to the demand for carbon dioxide reduction. As one of them, there is a so-called direct ignition in which a high-voltage current generator of an ignition device of an internal combustion engine is installed near a plug. Conventionally, ignition used a generator installed along with the engine shaft, boosted the current with a high-voltage current generator, and then supplied high-voltage current to each plug.However, with direct ignition, the high-voltage current generator By installing the plug immediately before the plug, the energizing distance of the high-voltage current is shortened to save energy.

Therefore, the high-voltage current generator is required to be extremely small as compared with the conventional one, while the voltage conversion, that is, the magnetic characteristics as a transformer, are required to have the same function as the conventional one. As the iron core material, a grain-oriented electrical steel sheet having excellent magnetic properties is optimal. Also, the high-voltage current generator generates strong magnetic lines of force in response to the instantaneously generated high voltage, so a magnetic shield is required,
As for the magnetic shield, a grain-oriented electrical steel sheet having high magnetic permeability is optimal.

[0004] Therefore, grain-oriented electrical steel sheets are often used in direct ignition cores, but they need to be processed into various shapes from the viewpoint of space efficiency inside the engine. For example, in a so-called pencil type of an open magnetic circuit type, a directional magnetic steel sheet is used for a magnetic shield, but a special processing such as processing into a cylindrical shape in a direction perpendicular to the rolling direction is performed.

[0005] Usually, a forsterite layer called a primary coating and a mixed layer mainly composed of phosphate, chromate and silica called a secondary coating are formed on the surface of a grain-oriented electrical steel sheet. These coating layers are required to have insulation properties to prevent leakage current and improve the magnetic properties of the iron core when steel sheets are laminated, but in addition to insulation properties, they also have corrosion resistance, sliding properties, and adhesion. For example, various film properties are required.
The forsterite layer is formed at the time of finish annealing by rolling a grain-oriented electrical steel sheet to a predetermined thickness, performing decarburizing annealing, and then applying an annealing separator mainly containing MgO to the surface. This coating layer functions as an insulating coating and is effective as a base layer for the secondary coating.

[0006] When more excellent film properties such as insulation and corrosion resistance are required, a secondary film layer is formed. Tokunosho 5
Japanese Patent Application Laid-Open No. 3-28375 discloses that a phosphate-chromate-colloidal silica-based insulating coating having a specific composition is applied on a forsterite coating formed on a steel sheet surface after finish annealing, and dried. There is disclosed a method for improving the magnetic properties of a grain-oriented electrical steel sheet by imparting tension to the magnetic steel sheet.

[0007]

However, in transformers in which grain-oriented electrical steel sheets are usually used, bending is generally performed in the rolling direction like a wound iron core, and bending is performed in a direction perpendicular to the rolling direction. This has not been done conventionally, and there has been a problem that adhesion is deteriorated and peeling occurs. When the film is peeled off, problems such as a decrease in insulation properties and adhesion to a working press occur, which causes a decrease in productivity.

[0008] As a technique for improving the adhesion of the insulating coating of the grain-oriented electrical steel sheet, for example, Japanese Patent Application Laid-Open No. 01-198429 is disclosed.
Japanese Patent Application Laid-Open Publication No. H11-163,086 discloses a technique for forming a linear or broken fine flaw on the surface of a steel sheet before or after decarburizing annealing.
JP-A-62-133021 discloses a technique in which fine irregularities are formed on the surface of a steel sheet before decarburizing annealing, and an oxide is formed by decarburizing annealing or finish annealing.

As a technique for improving the adhesion of the secondary coating, Japanese Patent Application Laid-Open No. Hei 5-279864 discloses a first application of phosphoric acid or phosphate and chromic anhydride or chromate and colloid. A solution containing silica,
A method of baking and drying at 300 to 600 ° C. for 30 seconds or more, and further baking and drying the solution at 700 to 950 ° C. for 30 seconds or more after the second time to maintain good adhesion and increase the coating amount. Is disclosed. According to the method disclosed in JP-A-5-279864,
Conventionally, the amount of insulating coating, which was limited to 5 g / m ² at most,
Coating with a thickness as large as 6 to 8 g / m ² is possible, and a significant effect of increasing the tension is obtained without deteriorating the adhesion.

However, all of the techniques disclosed in the above publications assume the use of a normal grain-oriented electrical steel sheet such as a wound transformer, and are perpendicular to the rolling direction, such as a core or shield of direct ignition. In the case where adhesiveness is required, no solution is specified.

Further, as a technique for improving the punching property and corrosion resistance of an electromagnetic steel sheet, Japanese Patent Publication No. 53-44892 discloses a technique for improving the surface resistance of an electric steel sheet having an oxide film or a chemical conversion film.
A technique relating to an electric iron plate with an organic coating having excellent punching properties and corrosion resistance by forming a thin polyethylene film of 0 mg / dm ² is disclosed. Further, JP-A-58-
No. 103107 discloses that a phosphate-based treatment liquid is applied as an undercoat on the surface of an electromagnetic steel sheet to a dry film thickness of 0.3 to 1.0 μm.
And baking it to form an amorphous film, on which one or more water-soluble resins of polyester-based, epoxy-ester-based and acrylic-based resins are dried to a thickness of 3 to 3 mm. A technique is disclosed in which the coating is applied to a thickness of 12 μm and baked, thereby forming a coating having excellent punching properties, electrical insulation properties, and corrosion resistance, particularly water resistance, on the surface.

In Japanese Patent Application Laid-Open No. 62-14405, a coating mainly containing 100 to 500 mg / m ^{3 of} an acrylic organic resin is formed on the surface of a grain-oriented electrical steel sheet having a forsterite coating. Cutability with a two-layer coating,
100 to 500 mg / m ^{3 on} the surface of grain-oriented electrical steel sheet for wound iron cores with excellent slipperiness and strain relief annealing properties, and on the surface of grain-oriented electrical steel sheet with inorganic insulating coating on forsterite coating
2 formed a coating mainly composed of acrylic organic resin
There is disclosed a technology relating to a grain-oriented electrical steel sheet for wound iron cores having a layer coating and having excellent cutting properties, slip properties, and strain relief annealing properties.

However, the above publications do not suggest or disclose the coating adhesion in the direction perpendicular to the rolling direction as used for the core and shield of direct ignition, and are not disclosed in each publication. The problems of punching, electrical insulation, corrosion resistance, water resistance, cutability, slippage, strain relief annealing, and adhesion in the direction perpendicular to the rolling direction do not overlap at all.

The present inventors have proposed bending of a grain-oriented electrical steel sheet having a forsterite layer on the surface or a grain-oriented electrical steel sheet having a phosphate-based insulating film on the forsterite layer in a direction perpendicular to the rolling direction. As a result of intensive studies on the adhesion, the formation of a specific organic resin having a glass transition point within a specific range on the uppermost surface of the grain-oriented electrical steel sheet will significantly improve the bending adhesion in the direction perpendicular to the rolling direction. Was found to be possible. The present invention is based on such knowledge, and provides a grain-oriented electrical steel sheet suitable for a core and a shield of direct ignition.

[0015]

The gist of the present invention is as follows. (1) On the surface of a grain-oriented electrical steel sheet having a forsterite layer, there is provided a two-layer coating in which a coating mainly composed of an organic resin having a glass transition point of 25 to 150 ° C. is formed in a thickness of 0.5 to 10 μm. A grain-oriented electrical steel sheet with excellent bending adhesion in the direction perpendicular to the rolling direction and suitable for direct ignition. (2) The organic resin is one or a mixture of two or more of acrylic resin, epoxy resin, urethane, and phenol resin, or a compound, and is bent and adhered in a direction perpendicular to the rolling direction according to (1). Grain-oriented electrical steel sheet with excellent directivity and suitable for direct ignition. (3) A phosphate insulating coating is formed on the surface of a grain-oriented electrical steel sheet having a forsterite layer, and a coating mainly composed of an organic resin having a glass transition point of 25 to 150 ° C. is formed on the surface. A grain-oriented electrical steel sheet having a three-layer coating formed in a thickness of 5 to 10 µm and having excellent bending adhesion in a direction perpendicular to the rolling direction and suitable for direct ignition. (4) The bending adhesion in a direction perpendicular to the rolling direction according to (3), wherein the organic resin is one or a mixture or a compound of two or more of acrylic resin, epoxy resin, urethane, and phenol resin. Grain-oriented electrical steel sheet with excellent directivity and suitable for direct ignition.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
As the phosphate-based insulating film used in the present invention, a film structure disclosed in the above-mentioned JP-B-53-28375 is preferable, and aluminum phosphate, magnesium phosphate,
As a main component, a phosphate composed of one or more of calcium phosphates, and appropriately added colloidal silica and chromate can be used.

When such a phosphate-based insulating film is formed on the surface of a grain-oriented electrical steel sheet, it is preferable to prepare a predetermined treatment liquid, apply it to the steel sheet using a roll coater or the like, and dry-bake it. The composition of the processing solution to be used is not particularly limited, but from the characteristics of the insulating film and the workability during application, phosphate: 3 to 24% by mass, chromate: 0.2 to 4. 5% by mass, colloidal silica: 4-1
An aqueous solution or slurry containing 6% by mass as a main component is preferable. Further, a surfactant, a vitrifying agent or the like may be added to the aqueous solution for improving the film properties.

The coating amount of the phosphate insulating film is as follows.
The range is preferably 0.5 to 5 g / m ² , more preferably 1 to 3 g / m ^2.
g / m ² is good. Even if the organic resin layer used in the present invention is formed directly on the forsterite layer without forming a phosphate insulating coating, there is no problem in bending adhesion in a direction perpendicular to the rolling direction, but phosphate insulating By forming the coating, the surface roughness can be controlled and the slipperiness of the steel sheet surface during processing can be controlled. Therefore, forming a phosphate-based insulating coating improves workability during processing.

As the organic resin used in the present invention, one or a mixture of two or more of acrylic resin, epoxy resin, urethane and phenol resin, or a compound is used. Specifically, the acrylic resin is a resin formed from an α, β monoethylenically unsaturated monomer and a polymerizable monomer. For example, acrylates (methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, isooctyl acrylate, 2-ethylbutyl acrylate, octyl acrylate,
Methoxyethyl acrylate, ethoxyethyl acrylate, 3-ethoxypropyl acrylate, etc.), methacrylates (methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, butyl methacrylate,
Isobutyl methacrylate, n-hexyl methacrylate, lauryl methacrylate, decyl octyl methacrylate, stearyl methacrylate, 2-methylhexyl methacrylate, 3-methoxybutyl methacrylate, etc.), acrylonitrile, methacrylonitrile, vinyl acetate, vinyl chloride, Vinyl ketone, vinyl toluene and styrene.

The monomers copolymerizable therewith include styrene, α-methylstyrene, vinyltoluene, t-butylstyrene, ethylene, toluene, propylene, acrylamide, hydroxypropyl acrylate, acrylic acid 2
Hydroxyethyl, 2-hydroxyethyl methacrylate,
Hydroxypropyl methacrylate, N-methylolacrylamide, as well as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid and the like can be used.

Next, the epoxy resin is a resin having two or more epoxy groups in a monomer, and specifically, bisphenol A type, bisphenol F type, bisphenol AD type, naphthalene type, phenol novolak type, and ortho resin. Cresol novolak type, glycidyl ester type, alicyclic type and the like are used.

The urethane used in the present invention only needs to have a urethane bond in the molecule, and is formed mainly by the reaction of an isocyanate compound with a polyol or polyether. Specifically, as the isocyanate compound, tolylene diisocyanate, diphenylmethane 4,4 ′ diisocyanate, hexamethylene diisocyanate, trimethyl propane 1-
Examples thereof include methyl 2-isocyano 4-carbamate, polymethylene polyphenyl isocyanate, and meta-xylylene diisocyanate. Examples of polyols and polyethers include polyethylene glycol, polypropylene glycol, and polyether triol.

Next, as the phenol resin, phenol alcohols, so-called phenol resols, are preferable. In the case of the phenol resin, a mixture of various methylol phenols is often used. Is not particularly limited.

Each of the above organic resins may be used alone, but in the case of a mixture, or in the case of a phenol or epoxy resin, it may be modified and used as a compound.
Further improvement in workability is expected.

In the present invention, it is necessary that the glass transition temperature of the organic resin is in the range of 25 to 150 ° C. If the glass transition point is less than 25 ° C., there is a risk that the organic resins will stick together or a so-called blocking phenomenon will occur when kept in a coiled state at room temperature. This is because dissociation from the surface of the salt-based insulating film occurs, and the improvement effect cannot be obtained.
More preferably, the glass transition point is in the range of 60 to 130 ° C.

The coating thickness of the organic resin used in the present invention is suitably between 0.5 and 10 μm. 0.5 μm
If it is less than 10 μm, it is difficult to control the uniform coating amount.
This is because if it is more than the above, the adhesion between the organic resin and the phosphate insulating film is reduced. More optimally it is between 1 and 6 μm.
Further, fine particles such as polyethylene wax may be added to the organic resin in order to enhance lubrication during bending.

Usually, in a bending test of a transformer or the like using a grain-oriented electrical steel sheet, the evaluation is made at 20 mmφ. However, in the case of direct ignition cores and shields, not only bend in the direction perpendicular to the rolling direction,
From the viewpoint of miniaturization, further strict evaluation at 15 mmφ is required. In the present invention, sufficient adhesion can be ensured even if such a severe bending test is performed.

Although the detailed mechanism of the present invention is not clear, when a grain-oriented electrical steel sheet is bent in a direction perpendicular to the rolling direction, the steel sheet is easily buckled along the rolling grooves on the surface of the steel sheet. Buckling occurs and forsterite is easily broken. However, when a normal organic resin is applied to the surface of the forsterite layer or the surface of the phosphate insulating film, a large amount of adsorbed water exists on the surface of the forsterite layer or the outermost surface of the phosphate insulating film. However, it cannot exhibit sufficient adhesiveness to withstand bending in a microscopic manner. On the other hand, the organic resin used in the present invention has many functional groups such as hydroxyl groups on the resin surface, so it absorbs water and strongly adheres to the forsterite layer surface or the outermost layer of the phosphate insulating film. In addition, since the glass transition point is optimized for bending, it is presumed that the forsterite is prevented from breaking and peeling.

[0029]

[Example] After decarburizing annealing, the surface of a 0.23 mm grain-oriented electrical steel sheet coated with an annealing separator containing MgO as a main component and subjected to finish annealing was washed with water to remove excess MgO. A treatment solution shown in Table 1 was applied to some of the samples and baked. Further, an organic resin shown in Table 2 was applied thereon and dried under predetermined conditions. Table 3 shows the results.

Test contents of a) to d) in Table 3 are as follows. a): A bending adhesion test was performed as an adhesion test. First,
A test piece was sampled in the direction perpendicular to the rolling direction, bent 180 degrees while pressing the test piece against a 15 mm-diameter round bar, and observed the peeling state of the coating at the bent portion. ◎, ○, △, ×, ×
A five-point evaluation was given. ◎ indicates no peeling, は indicates slight peeling, 軽 indicates slight peeling, × indicates severe peeling, and XX indicates complete peeling.
b): Conforms to JIS C2550 c): Conforms to JIS Z2371 (test time: 5 hours) The sample after the test was visually evaluated and evaluated as a five-point scale of ◎, ○, Δ, ×, XX. ◎ indicates no rusting, ○ indicates slight rusting, △ indicates slight rusting, × indicates severe rusting, and XX indicates rusting. d): After 10 days pressurization at normal temperature (25 ° C.) and left for 7 days, the state of adhesion was evaluated.
Was evaluated on a three-point scale. As is clear from Table 3, according to the present example, the effect of greatly improving the bending adhesion in the direction perpendicular to the rolling direction is obtained.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

[0034]

According to the present invention, it is possible to greatly improve the bending adhesion in the direction perpendicular to the rolling direction, which is optimal for the outer cylinder core of direct ignition.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02P 15/00 303 F02P 15/00 303A 5E041 H01F 1/16 H01F 1/16 B 1/18 1/18 F Term (reference) 3G019 KC01 KC10 4D075 CA13 DA03 DB03 DC13 DC16 EB22 EB32 EB33 EB38 EB53 4F100 AB03A AD20B AK01C AK25C AK33C AK51C AK53C BA03 BA07 BA10A BA10C EJ68B GB41 CA05 BA08 BA06 BA06 4K044 AA02 AB02 BA12 BA17 BA21 BB03 BB04 BC05 BC14 CA16 CA53 CA62 5E041 AA11 BC01 BC05 BC08 CA02 CA06 HB14 NN05

Claims (4)

[Claims] 1. A grain-oriented electrical steel sheet having a forsterite layer has a two-layer coating formed by forming a coating mainly composed of an organic resin having a glass transition point of 25 to 150 ° C. on a surface of 0.5 to 10 μm. A grain-oriented electrical steel sheet with excellent bending adhesion in the direction perpendicular to the rolling direction and suitable for direct ignition. 2. The organic resin according to claim 1, wherein the organic resin is one or a mixture of two or more of acrylic resin, epoxy resin, urethane and phenol resin.
A grain-oriented electrical steel sheet with excellent bending adhesion in the direction perpendicular to the rolling direction described and suitable for direct ignition. 3. A phosphate-based insulating film is formed on the surface of a grain-oriented electrical steel sheet having a forsterite layer, and a film mainly composed of an organic resin having a glass transition point of 25 to 150 ° C. is formed on the surface. A grain-oriented electrical steel sheet having a three-layer coating formed in a thickness of 0.5 to 10 µm and having excellent bending adhesion in a direction perpendicular to the rolling direction and suitable for direct ignition. 4. The organic resin according to claim 3, wherein the organic resin is one or a mixture of two or more of acrylic resin, epoxy resin, urethane and phenol resin.
A grain-oriented electrical steel sheet with excellent bending adhesion in the direction perpendicular to the rolling direction described and suitable for direct ignition.