JP5125072B2 - Electrical steel sheet with insulating coating - Google Patents

Description

  The present invention relates to an electrical steel sheet having an insulating coating that does not contain Cr.

Insulating coatings on electrical steel sheets used for motors, transformers and the like are required to have not only interlayer resistance but also various characteristics. For example, convenience during processing, storage, stability during use, and the like. Furthermore, since electromagnetic steel sheets are used for various applications, various insulating coatings have been developed according to the applications.
For example, when a magnetic steel sheet is subjected to punching, shearing, bending, etc., the magnetic properties are deteriorated due to residual strain. Therefore, in order to recover the deteriorated magnetic characteristics, strain relief tempering is often performed at about 750 to 850 ° C. In this case, the insulating coating must withstand strain relief annealing.

  Insulation coating (1) Emphasis on weldability and heat resistance, inorganic coating that can withstand strain relief annealing (in principle, does not include organic resin), (2) strain relief annealing with the aim of achieving both punchability and weldability Inorganic coating containing an organic resin that resists (3) Organic coating that cannot be subjected to strain relief annealing for special purposes. Among these, as a general-purpose product, it is a film containing the inorganic substances (1) and (2) that can withstand strain relief annealing, and both contain a chromium compound in the film. In particular, the chromate-based insulating coating containing the organic resin in the type (2) is widely used because punchability can be remarkably improved as compared with the inorganic insulating coating.

For example, Patent Document 1 discloses that a dichromate aqueous solution containing at least one divalent metal has a vinyl acetate / veova (TM) ratio of 90/10 with respect to 100 parts by weight of CrO ₃ in the aqueous solution. A resin emulsion having a ratio of ˜40 / 60 is blended in a proportion of 5 to 120 parts by weight in terms of resin solids and an organic reducing agent in a proportion of 10 to 60 parts by weight to form a coating liquid. There is described an electrical steel sheet having an electrical insulating coating that is applied to the surface of a steel sheet and formed through a conventional baking process.
However, in recent years, environmental awareness has increased, and in response to this demand, products having an insulating coating that does not contain Cr have been desired in the field of electrical steel sheets.

  In response to this situation, an electromagnetic steel sheet with an insulating coating that does not contain Cr has been proposed. Patent Document 2 describes a resin and a material containing alumina-containing silica as a colloidal silica as an insulating film that does not contain Cr and has good punchability.

  Patent Document 3 discloses an aqueous solution in which 15 to 400 parts by weight or more of a water-soluble or emulsion type resin is added to 100 parts by weight of an inorganic colloidal substance composed of one or more of colloidal silica, alumina sol, and zirconia sol. An insulating coating formed by applying and baking is described.

  In Patent Document 4, a coating made of an oxide-based polymer containing at least one of Al, Si, Ti, and Zr is coated with an oxide fine particle (particle diameter of 10 to 10) of at least one of Al, Si, Ti, and Zr. Insulating coatings containing 35 to 90% by weight of 100 nm) are disclosed.

  Patent Document 5 describes an insulating coating mainly composed of a phosphate containing no chromium and containing a resin and optionally colloidal silica.

Further, Patent Document 6 discloses that 100 parts by weight of an organic resin is 5 to 100 parts by weight of phosphoric acid, 20 to 200 parts by weight of a compound such as Mn, Mg, and Al, ZrO ₂ , Al ₂ O ₃ , SiO ₂ , SnO. ₂ , a composition for surface treatment of a chromium-free electrical steel sheet, in which one or more colloids (sols) of Sb ₂ O ₅ are blended in an amount of 5 to 150 parts by weight, is disclosed.
Japanese Patent Publication No. 60-36476 JP-A-10-130858 JP-A-10-46350 Japanese Patent No. 2861702 Japanese Patent No. 2944849 JP 9-316655 A

  However, the electrical steel sheet with an insulating coating that does not contain Cr does not have sufficient corrosion resistance as compared with the case of containing a chromium compound. Further, there is a problem that powder blowing is likely to occur with the tension pad when the coil is passed, and the film becomes weak after the strain relief annealing, so that scratches are easily generated. Note that the baking temperature should be as low as possible from the viewpoint of reducing energy consumption and manufacturing cost, but the above problem is particularly likely to occur when baking at a relatively low temperature of 300 ° C. or lower.

  In view of the above circumstances, the present invention is an insulating coating mainly composed of an inorganic material not containing Cr, and particularly after being baked at 300 ° C. or less (before strain relief annealing), corrosion resistance, powder blowing resistance, and It is an object of the present invention to provide an electrical steel sheet having an insulating coating excellent in corrosion resistance and scratch resistance after strain relief annealing.

The inventors of the present invention have intensively studied to solve the above problems. As a result, the following knowledge was obtained.
1) By containing a specific amount of Zr compound in the film, Zr can be strongly bonded to an oxide, hydroxide, etc. on the Fe surface, and a tough film can be formed without using a chromium compound.
2) By making the amount of the alkali metal contained in the Zr compound within a predetermined range, a great improvement effect can be obtained in corrosion resistance and scratch resistance after strain relief annealing.

The present invention has been made based on the above findings, and the gist thereof is as follows.
[1] An electrical steel sheet having an insulating coating containing Zr, P and alkali metal M, wherein P is a molar ratio of P / Zr = 0.4 to 4.0 with respect to Zr, and the total amount of alkali metal M is An insulating coating characterized in that the molar ratio (total amount of M) / Zr is 0.2 to 2.5 with respect to Zr, and the alkali metal M is selected from one or two of Na and K. Having electrical steel sheet.
In [2] [1], wherein the insulation in the coating, further containing Si compound, SiO _2, ZrO ₂ and P ₂ O ₅ in terms of SiO by weight ₂ / (SiO ₂ + ZrO ₂ + P ₂ O ₅ ) Is 0.7 or less, an electrical steel sheet having an insulating coating.
[3] In the above [1], the insulating coating further contains a resin in a solid content weight conversion of resin solid content / (resin solid content + ZrO ₂ + P ₂ O ₅ ) of 0.5 or less. An electrical steel sheet having an insulating coating characterized by that.
[4] In the above [2], the resin is further contained in the insulating coating in a solid content weight conversion of resin solid content / (resin solid content + SiO ₂ + ZrO ₂ + P ₂ O ₅ ) of 0.5 or less. An electrical steel sheet having an insulating coating characterized by containing.
[5] In the above [3] or [4], the resin is a polyethylene resin, polypropylene resin, polyolefin resin, polyester resin, acrylic resin, alkyd resin, styrene resin, vinyl acetate resin, epoxy resin, phenol resin, urethane resin. An electrical steel sheet having an insulating coating, which is one or more of melamine resins.

  According to the present invention, an electrical steel sheet having an insulating coating excellent in corrosion resistance, powder blowing resistance, and corrosion resistance and scratch resistance after strain relief annealing after baking (before strain relief annealing) can be obtained. In particular, the present invention exhibits its effect at a baking temperature of 300 ° C. or less, and can be said to be an excellent invention from the viewpoint of reducing energy consumption and manufacturing cost.

The present invention is described in detail below.
The electrical steel sheet of the present invention is an electrical steel sheet having an insulating coating, and the insulating coating contains a Zr compound, a P compound and an alkali metal, and if necessary, a Si compound and a resin as main components. This is the most important requirement in the present invention. And by having such an insulating film, it is excellent in corrosion resistance and powder blowing resistance after baking at 300 ° C. or less (before strain relief annealing) and excellent in corrosion resistance and scratch resistance after strain relief annealing. become.

First, the electrical steel sheet used in the present invention will be described.
Any electromagnetic steel plate (also referred to as an electric iron plate) before forming an insulating coating that can be used in the present invention is a steel plate (iron plate) adjusted to obtain a desired magnetic property by changing the specific resistance. The steel plate may be of any composition and is not particularly limited.

An example of the composition is given below. Since it is effective to increase the specific resistance for improving the iron loss, at least one selected from Si, Al, Mn, Cr, P, Ni, Cu and the like, which are specific resistance improving components, is added as necessary. It is preferable to do. The content of these elements may be determined according to the desired magnetic properties, but Si: about 5% by mass or less (including no addition, the same applies hereinafter), Al: about 3% by mass or less, Mn: about 1. 0% by mass or less, Cr: about 5% by mass or less, P: about 0.5% by mass or less, Ni: about 5% by mass or less, and Cu: about 5% by mass or less are common. The composition of a typical electrical steel sheet is one in which Si is added in an amount of 0.1% by mass or more. However, in the case of lower grades, the addition of Si: 0.05% by mass or more is preferable for improving the magnetic properties.
In addition, in order to improve the magnetic properties, at least one selected from an inhibitor forming element or a segregating element such as Mn, Se, S, Al, N, Bi, B, Sb and Sn may be added as necessary. it can. When adding an inhibitor-forming element or the like, it is usually preferable to contain these elements in a total amount of 0.5% by mass or less.
The balance other than the above is iron and inevitable impurities. Examples of the impurity include C, N, O, and a small amount of S that is less effective as an inhibitor. Less impurities are better, but if it is not a high-grade product, it may contain about 0.02 to 0.05% by mass of C.

  Moreover, the plate | board thickness of the electromagnetic steel plate of this invention is not specifically limited. It is preferably about 0.02 to 1.0 mm which is a normal thickness. Moreover, although it is a flat shape normally, the curved shape may be sufficient depending on the objective.

  In addition, the surface of the electrical steel sheet on which the insulating coating is formed may be subjected to any pretreatment such as degreasing treatment with alkali, pickling treatment with hydrochloric acid, sulfuric acid, phosphoric acid, etc., and finish annealing is performed. It may be an untreated surface as is.

  Furthermore, although it is not always necessary to form the third layer between the insulating coating and the surface of the ground iron, it may be formed as necessary. For example, in a normal manufacturing method, a metal oxide metal oxide film may be formed between the insulating film and the metal iron surface, but it may be possible to omit the trouble of removing this.

Next, the insulating coating of the present invention applied to the surface of the electromagnetic steel sheet will be described.
The insulating coating of the present invention is obtained by applying a coating material containing the following essential components (Zr compound, P compound and alkali metal), or further suitable components (Si compound and / or resin) to the surface of the electrical steel sheet, drying and / or Or it can obtain by performing a baking process. As the coating material to be applied, an aqueous paste or liquid can be used. From the viewpoint of not increasing the coating thickness (coating adhesion amount) more than necessary and from the viewpoint of effects, it is preferable to use a liquid (aqueous liquid). In the following description, when a treatment liquid is used, in principle, liquid and pasty raw materials are also included.

P Compound The insulating coating applied to the electrical steel sheet of the present invention contains a specific amount of P compound. The P compound is necessary to form a film by firmly bonding with the Zr compound. In the present invention, examples of the P compound that can be used as a raw material for the insulating coating include sodium phosphate, potassium phosphate, and phosphoric acid.
The P compound has a molar ratio of P / Zr = 0.4 to 4.0 with respect to the Zr compound. If P / Zr exceeds 4.0, the corrosion resistance will deteriorate, so the upper limit is made 4.0%. Preferably, it is P / Zr: 0.5-2.5. The molar ratio P / Zr can be calculated from the added weight at the time of preparation, or the abundance ratio can be obtained by fluorescent X-rays or the like.

Further, “converted to P ₂ O ₅ ” means that the content of P ₂ O ₅ is calculated on the assumption that all the contained P forms P ₂ O ₅ . Hereinafter, it is simply referred to as “P ₂ O ₅ conversion”. The same applies to the conversion of other compounds.

Zr compound and alkali metal The insulating coating applied to the magnetic steel sheet of the present invention contains a specific amount of Zr compound. Zr has a maximum of eight coordination numbers, and generally bonds strongly to other substances, particularly oxygen, by four bonds. For this reason, it is considered that a strong film can be formed without strongly using a chromium compound by binding firmly to an oxide, hydroxide, or the like on the Fe surface.
However, when only the Zr compound is used as the main component of the insulating coating, the corrosion resistance is slightly inferior, and the scratch resistance after strain relief annealing tends to be greatly deteriorated. This is presumably because the network is not formed well because there are many bonds of the Zr compound, and a fragile film is formed.
Thus, as a result of further research, the present inventors have found that a great improvement effect can be obtained when the amount of the alkali metal M contained in the Zr compound is limited to a predetermined range.

  An appropriate content of the P compound is as described above. Moreover, as suitable content of the alkali metal M, the molar ratio (total amount of M) / Zr of the alkali metal M and Zr is 0.2-2.5. More preferably, it is 2.3 or less. In such a range, it is considered that a good network can be formed by controlling the bonding hands of the Zr compound, and the film becomes strong. When the amount of alkali metal M is large and the molar ratio (total amount of M) / Zr exceeds 2.5, the number of bonds is too small to provide a sufficiently strong coating.

  The molar ratio (total amount of M) / Zr can be calculated from the added weight at the time of preparation. Alternatively, the abundance ratio may be taken with fluorescent X-rays.

In the present invention, examples of the Zr compound that can be used as the raw material for the insulating coating include Zr ammonium carbonate, Zr potassium carbonate, Zr sodium carbonate, Zr ammonium potassium, and Zr ammonium sodium carbonate. It is preferable to use 1 type or in mixture of 2 or more types. Zr ammonium carbonate is (NH ₄ ) ₂ [Zr (CO ₃ ) ₂ (OH) ₂ ], (NH ₄ ) ₂ ZrO (CO ₃ ) ₂ , and Zr potassium carbonate is K ₂ [Zr (CO ₃ ) ₂ ( OH) ₂ ], K ₂ ZrO (CO ₃ ) ₂ , and any of them can be suitably used.
The Zr compounds listed above contain a total of about 5% by mass or less of impurities such as Hf, Ti, or their oxides (HfO ₂ , TiO ₂ ), which are the same elements of Zr, and SiO ₂ , Fe ₂ O _3, etc. You may go out. The main impurity is Hf or HfO ₂ .

  Further, the alkali metal M contained in the insulating coating of the present invention may be in the compound state with Zr described above, or may be added in the form of other alkali metal compounds. In addition, the amount of alkali metal contained as an impurity in the Si compound or the like that can be contained in the insulating film may be adjusted and used. Of the alkali metals, Li may cause precipitation depending on the type of compound used, and therefore, the alkali metal M is preferably Na or K.

In the present invention, the Zr compound as a raw material for the insulating coating is preferably a water-soluble Zr compound rather than a paste-insoluble water. This is because the bond with other substances becomes strong and a denser film is formed. The water-soluble material herein refers to a material that dissolves in water or forms a colloid and is stably dispersed in water.
Since the treatment liquid of the present invention exhibits alkalinity, it is considered that Fe elution of the electrical steel sheet, which is likely to occur with an aqueous treatment liquid, is suppressed and the appearance is improved.

Si Compound The insulating coating of the present invention preferably contains a Si compound. The Si compound is a stable compound with high heat resistance, and reacts with Zr to form a complex such as zircon (Zr (SiO ₄ )), thereby contributing to the relaxation of shrinkage stress during film formation, and the characteristics of the film. May contribute to improvement. If contained, SiO ₂ / (SiO ₂ + ZrO ₂ + P ₂ O ₅ ) is 0.7 or less in terms of weight of SiO ₂ , ZrO ₂ and P ₂ O ₅ . If it exceeds 0.7, the coating becomes hard and brittle, and defects increase, resulting in deterioration of corrosion resistance and adhesion. Note that “converted to ZrO ₂ ” means that the content of ZrO ₂ is calculated on the assumption that all of the contained Zr forms ZrO ₂ . The same applies to the conversion of other compounds.
Colloidal silica is preferably applied as the Si compound contained in the treatment liquid.
Colloidal silica is an inorganic colloid mainly composed of SiO ₂ and is often amorphous. The particle diameter of colloidal silica is preferably 200 nm or less, more preferably 100 nm or less. Although the lower limit is not particularly limited, it is considered that when the content is ultrafine, even if the content is the same, the entire surface area becomes large, so that the interaction with other components increases and the strength of the coating increases. In addition, when the particle diameter is small, aggregation is likely to occur between the silica particles and other components, so the colloidal silica concentration should be adjusted to a low level. Conversely, the particle size may be set to a practically suitable particle size from a desired concentration. In addition, an average particle diameter can be measured by BET method (converted from the specific surface area by an adsorption method). It is also possible to substitute an average value (in terms of sphere diameter) actually measured from an electron micrograph.
It is desirable that the Si compound used in the present invention does not contain other metal elements at an impurity level or more. Other possible impurities are preferably Na ₂ O: 5% or less, Cl: 5% or less, and SO ₄ : 3% or less with respect to the SiO ₂ equivalent weight.

The resin resin contributes to improving the properties of the coating by effectively relieving the shrinkage stress during film formation in the inorganic coating made of the Zr compound. For this reason, it is preferable to contain resin in an insulating film. In particular, those that are soft and those that exceed the glass transition point or melting point during coating baking are preferred. In containing, when solid content / (resin solid content + ZrO ₂ + P ₂ O ₅ ) is 0.5 or less and the Si compound is contained, the resin solid content / (resin solid content + SiO ₂₎ + ZrO ₂ + P ₂ O ₅ ) is preferably contained in an amount of 0.5 or less. If it exceeds 0.5, scratch resistance particularly after strain relief annealing deteriorates.
As the resin contained in the above, one or two of polyethylene resin, polypropylene resin, polyolefin resin, polyester resin, acrylic resin, alkyd resin, styrene resin, vinyl acetate resin, epoxy resin, phenol resin, urethane resin, melamine resin, etc. It is preferable that the resin is an aqueous resin (emulsion, dispersion, water-soluble) of more than seeds. These may be an oxidation treatment, a block copolymer, or a graft copolymer in order to improve emulsification and compatibility with other materials. In the case of a thermoplastic resin, the molecular weight is not particularly defined, but Mw of about 500 to 1,000,000 is particularly preferable.

  From the above, the present invention can obtain the desired characteristics with the electromagnetic steel sheet having an insulating coating made of Zr, P and alkali metal M, and preferably Si compound and / or resin. In addition, the following additives, other inorganic compounds, and organic compounds can be contained for the following purpose within a range not impairing the effects of the present invention.

Additives In order to further improve the performance and uniformity of the coating, the insulating coating of the present invention is optionally provided with a surfactant (nonionic, cationic, anionic surfactant; silicone surfactant; acetylenic diol). ), Rust preventives (amine-based, non-amine-based rust preventives, etc.), boric acid, silane coupling agents (aminosilane, epoxysilane, etc.), and organic and inorganic additives such as lubricants (wax, etc.) be able to. As these additives, known additives applicable to conventionally known chromate-based insulating coatings and non-chromate-based insulating coatings hitherto proposed can be used.
When these additives are used, in order to maintain sufficient film characteristics, it is preferable that the content is about 10% by mass or less based on the total solid mass of the insulating film of the present invention. In addition, "total solid content mass" here is the adhesion amount after drying of the film formed on the surface of the magnetic steel sheet by a method described later. The total solid mass can be measured from the weight reduction after removal of the film by alkali peeling.

Other inorganic compounds and organic compounds The insulating coating of the present invention may contain other inorganic compounds and / or organic compounds to the extent that the effects of the present invention are not impaired. For example, if the liquid stability can be ensured, another oxide sol can be added. Examples of the oxide sol include alumina sol, iron sol, titania sol, tin sol, cerium sol, antimony sol, tungsten sol, and molybdenum sol.
In addition, this invention aims at obtaining a favorable film characteristic, without adding a chromium compound. Therefore, it is preferable that the insulating coating of the present invention substantially does not contain Cr from the viewpoint of preventing environmental contamination from the manufacturing process and products. The amount of chromium allowed as an impurity is preferably 0.1% by mass or less in terms of CrO ₃ with respect to the total solid mass of the insulating coating.

Next, the manufacturing method of the electrical steel sheet which has an insulating film of this invention is demonstrated.
The pretreatment of the electrical steel sheet used as the starting material of the present invention is not particularly defined. After finish annealing, untreated or washed with water, degreasing treatment such as alkali, and pickling treatment such as hydrochloric acid, sulfuric acid and phosphoric acid are preferably applied.
And the process which contains the Zr compound mentioned above on this electromagnetic steel sheet, the P compound mentioned above, the alkali metal M mentioned above, the Si compound mentioned above as needed, resin, the additive mentioned above as needed further, etc. Apply liquid. Then, an insulating film is formed on the magnetic steel sheet by subjecting the magnetic steel sheet coated with the treatment liquid to a baking process as necessary.
As a method for applying the insulating coating, a method using various facilities such as a roll coater, a flow coater, a spray, and a knife coater, which are generally used in industry, can be applied. In addition, a hot air method, an infrared heating method, an induction heating method, or the like, which is usually performed, is also possible for the baking method.
The baking temperature may be a normal level, but is preferably 350 ° C. or lower. A more preferable range is 150 ° C. or higher and 300 ° C. or lower.

Distortion annealing The electrical steel sheet with an insulating coating of the present invention can be subjected to strain relief annealing to remove, for example, distortion caused by punching. As a preferable strain relief annealing atmosphere, an atmosphere in which iron is hardly oxidized such as an N ₂ atmosphere and a DX gas atmosphere is applied. However, there is an advantage in slight oxidation, and in the above atmosphere, the dew point is high, for example, Dp: set to about 5 to 60 ° C., and the corrosion resistance can be further improved by slightly oxidizing the surface and the cut end face.
A preferred strain relief annealing temperature is 600 ° C. or higher and 900 ° C. or lower. A more preferred lower limit is 650 ° C., more preferably 700 ° C. or more. Furthermore, it is more preferable to set the temperature around 750 ° C. or 750 ° C. or higher. On the other hand, a more preferable upper limit is 850 ° C. The holding time in strain relief annealing is preferably longer, and more preferably 2 hours or longer.

Insulating coating amount The insulating coating amount is not particularly specified, but is preferably 0.01 g / m ² or more and 5 g / m ² or less in total per side. In addition, the amount of adhesion, that is, the measurement of the total solid mass of the insulating coating of the present invention can be measured from the decrease in weight after removing the coating by alkali peeling. Moreover, when there is little adhesion amount, you may measure using a fluorescent X ray. In this case, it is preferable to calculate the adhesion amount using a calibration curve created using the alkali peeling method.
If the adhesion amount is less than 0.01 g / m ² , corrosion resistance and insulation may be insufficient. On the other hand, when the adhesion amount exceeds 5 g / m ² , workability in coating may be deteriorated. More preferably, it is 0.1 g / m ² or more and 3.0 g / m ² or less. Even more preferably, it is 0.2 g / m ² or more and 2.5 g / m ² or less.
The insulating coating of the present invention is preferably on both sides of the electrical steel sheet, but depending on the purpose, only one side may be used. That is, depending on the purpose, only one surface may be applied, and the other surface may be another insulating coating, or the other surface may not be provided with an insulating coating.

Second insulation coating (upper coating)
The surface of the insulating coating of the present invention (hereinafter referred to as “undercoat”) can further have a second insulating coating (hereinafter referred to as “upper layer”) having a component different from that of the undercoat.
Here, at least one layer of the upper layer film may be formed on the surface of the base film, but two or more layers may be formed. Although it is not necessary to specifically limit each upper layer coating composition, it is preferable that Cr is not included substantially for the same reason as the base coating.
The upper layer film of the present invention can be produced by the same method as that for the undercoat film. That is, an upper layer film can be manufactured on the surface of the base film manufactured by the above method by a similar method. It should be noted that when the electromagnetic steel sheet on which the upper layer film of the present invention is formed is subjected to strain relief annealing, it may be the same as the annealing method when only the base film is formed.
Although the amount of coating applied when forming the upper layer coating is arbitrary, the amount of coating of the base coating is 0.001 to 1.0 g / m ² and the amount of coating of the upper layer coating is 0.04 to 4.0 g / m 2. ² is preferable. Within this range, the base coating becomes a thin insulating coating, and cracks that are considered to cause corrosion resistance deterioration are particularly difficult to enter. Adhesion amount of the underlying coating, more preferably to 0.005 g / m ² or more, and even more preferably to a 0.01 g / m ² or more. Moreover, it is more preferable to set it as 0.2 g / m < ² > or less.
On the other hand, the addition of the upper layer film is very useful for ensuring insulation, and it is preferable to apply a thicker, for example, 0.2 g / m ² or more in order to seal the scratches and defects of the base film.
In addition, the effect which improves an external appearance is seen by setting it as the thin base treatment. When the upper layer is applied after applying the base, it is considered that Fe elution of the magnetic steel sheet, which is likely to occur with the aqueous treatment liquid, is suppressed and the appearance is improved.

Hereinafter, although the effect of the present invention is concretely explained based on an example, the present invention is not limited to these examples.
P compound, Zr compound, alkali metal M, Si compound, resin are added to deionized water so as to have the insulating coating composition shown in Tables 1 and 2, and each for the first layer (single layer coating or base coating) The treatment liquid was adjusted. Here, the total of P ₂ O ₅ , ZrO ₂ , SiO ₂ equivalent amount, and resin solid content weight was adjusted so as to be a treatment liquid added with 50 g / l with respect to the coating liquid. Next, each of these treatment liquids was applied by a roll coater to the surface of a test piece cut into a size of 150 mm in width and 300 mm in length from a 0.5 mm thick electromagnetic steel sheet (Si: 0.25% by mass), After baking at an ultimate temperature of 200 ° C. by direct heating with propane gas, it was allowed to cool at room temperature to form an insulating coating. In addition, the particle diameter of colloidal silica was about 10-15 nm. With respect to the electrical steel sheet having the insulating coating obtained as described above, the following coating properties were measured and evaluated.

<Corrosion resistance after baking and after strain relief annealing>
Each test piece coated with each treatment solution and provided with an insulating film is held in a constant temperature and humidity chamber with a relative humidity of 98% and 50 ° C. for 2 days, and the rust generation area ratio on the surface of the test piece is obtained. Evaluation was made according to the criteria. The rust generation area ratio is a percentage of the total rust generation area with respect to the entire observation area, and was determined visually. Furthermore, the same test was performed on the surface of the sample which was annealed by holding at 750 ° C. for 2 hours in an N ₂ atmosphere, and the corrosion resistance was evaluated.
(Criteria)
A: Rust generation area ratio = 0% or more and less than 5% B; Rust generation area ratio = 5% or more and less than 20% C; Rust generation area ratio = 20% or more and less than 50% D; Rust generation area ratio = 50% or more < Dust resistance after baking>
The test piece was reciprocated in a state where the felt was pressed against one side of the test piece to which the insulating coating was applied, the rubbing trace after the test was observed, and the peeled state and the powder blowing state of the coating were evaluated according to the following criteria. The contact surface of the felt was 20 × 10 mm wide, the pressing load was 3.8 kg / cm ² (0.4 MPa), and the reciprocating motion was repeated in a simple reciprocating manner corresponding to 400 m.
(Criteria)
A: Almost no rubbing traces are observed B; Some rubbing traces and slight powder blowing are observed C; Detaching of the coating progresses and the rubbing traces and powder blowing are clearly seen D; Dust is enormous <Scratch resistance after strain relief annealing>
The sample surface which was kept at 750 ° C. for 2 hours and annealed in an N ₂ atmosphere was scratched with an edge portion made by shearing the same steel plate, and the degree of scratches and powder blowing was determined according to the following criteria.
(Criteria)
A: Scratch and powder generation are hardly observed B; Some rubbing marks and slight powder blowing are recognized C; Rub marks and powder blowing are clearly seen D; The results obtained from the above are shown in Tables 1 to 3 together with the experimental conditions, and in FIGS. In the table, the determination A is indicated as ◎, B as ○, C as Δ, and D as ×.

  As is clear from Tables 1 and 2 and FIGS. 1 and 2, the examples of the present invention are excellent in corrosion resistance, powder blowing resistance, and scratch resistance of the strain relief annealed plate. On the other hand, in the comparative example, the corrosion resistance is inferior.

  Although it is an insulating film mainly composed of an inorganic material that does not contain Cr, it has performance equivalent to or higher than that of a Cr-containing insulating film, such as corrosion resistance, and is expected to be used in various applications such as motors and transformers. .

It is a figure which shows the influence which it has on ratio: P / Zr (horizontal axis) and corrosion resistance (vertical axis) with respect to Zr content of phosphoric acid content. Example 1 It is a figure which shows the influence which it has on ratio: M / Zr (horizontal axis) and corrosion resistance (vertical axis) with respect to Zr content of alkali metal M content. Example 1

Claims (5)

An electrical steel sheet having an insulating coating containing Zr, P and alkali metal M,
P is a molar ratio of P / Zr = 0.4 to 4.0 with respect to Zr,
The total amount of alkali metal M in molar ratio to Zr (total amount of M) / Zr is 0.2 to 2.5,
Further, the electromagnetic steel sheet having an insulating coating, wherein the alkali metal M is selected from one or two of Na and K. Said during insulation coating further contains a Si _{compound, SiO 2 / (SiO 2 +} ZrO 2 + P 2 O 5) with SiO _2, ZrO ₂ and P ₂ O ₅ converted weight is 0.7 or less An electrical steel sheet having an insulating coating according to claim 1. 2. The resin according to claim 1, wherein the insulating coating further contains a resin in a solid content weight conversion of resin solid content / (resin solid content + ZrO ₂ + P ₂ O ₅ ) of 0.5 or less. Electrical steel sheet having an insulating coating. The insulating film further contains a resin in a solid content weight conversion of resin solid content / (resin solid content + SiO ₂ + ZrO ₂ + P ₂ O ₅ ) of 0.5 or less. 2. An electrical steel sheet having the insulating coating according to 2. The resin is one or more of polyethylene resin, polypropylene resin, polyolefin resin, polyester resin, acrylic resin, alkyd resin, styrene resin, vinyl acetate resin, epoxy resin, phenol resin, urethane resin, melamine resin. An electrical steel sheet having an insulating coating according to claim 3 or 4.

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