JP4552642B2 - Electrical steel sheet with insulation coating - Google Patents

Description

  The present invention relates to an electrical steel sheet with an insulating coating that does not contain a chromium compound and is excellent in corrosion resistance and powder blowing resistance of a product plate (before strain relief annealing) and appearance and scratch resistance of the strain relief annealed plate.

  Insulating coatings on electrical steel sheets used for motors, transformers, and the like are required not only for interlayer resistance but also for various characteristics such as convenience during processing and storage, and stability during use. Since electrical steel sheets are used for various applications, various insulating coatings have been developed according to the applications. When the magnetic steel sheet is punched, sheared, bent, etc., the magnetic properties are deteriorated due to residual strain. However, in order to recover the deteriorated magnetic properties, strain relief tempering is often performed at about 750 to 850 ° C. In this case, the insulating coating must withstand strain relief annealing.

The insulating coating is (1) an inorganic coating that emphasizes weldability and heat resistance and resists strain relief annealing, (2) a resin-containing inorganic coating that resists strain relief annealing to achieve both punchability and weldability, (3 ) Organic coatings that can not be strain-relieved and annealed for special applications, but are generally classified as (1) and (2) inorganic coatings that are resistant to strain-relieving annealing. It contained a compound. In particular, the chromate-based insulating coating containing the organic resin of the type (2) can be widely used because the punching property can be remarkably improved as compared with the inorganic insulating coating in the manufacture of one coat and one bake. Has been. For example, Patent Document 1 discloses that a dichromate aqueous solution containing at least one divalent metal has a vinyl acetate / veova ratio of 90/10 to 10 as an organic resin with respect to 100 parts by weight of CrO ₃ in the aqueous solution. A treatment liquid in which a resin emulsion having a ratio of 40/60 is blended in a ratio of 5 to 120 parts by weight of resin solids and 10 to 60 parts by weight of an organic reducing agent is applied to the surface of the base iron plate and baked by a conventional method. An electrical steel sheet having an electrical insulating film characterized by being obtained through a process is described.

  However, recently, environmental awareness has increased, and in the field of electrical steel sheets, products having an insulating coating that does not contain a chromium compound have been desired by customers and the like.

  Accordingly, an electromagnetic steel sheet with an insulating coating that does not contain a chromium compound has been developed. For example, Patent Document 2 discloses an insulating coating that does not contain chromium and has good punchability, and is composed of resin and colloidal silica (alumina-containing silica). Are listed. Further, an insulating coating comprising one or more of colloidal silica, alumina sol, and zirconia sol and containing a water-soluble or emulsion resin is described in Patent Document 3, and is mainly composed of a phosphate containing no chromium. Patent Document 4 discloses an insulating coating containing bismuth.

  However, the electrical steel sheet with an insulating coating that does not contain these chromium compounds has a problem that the corrosion resistance deteriorates because the bonding between the inorganic substances is relatively weak as compared with the case of containing the chromium compounds. Further, when the back tension is applied by rubbing the surface of the steel sheet with felt in slit processing (use of a tension pad), there is a problem of powder blowing. Furthermore, there is a problem that the film becomes weak after the strain relief annealing, and scratches are easily generated.

For example, even if one or more of colloidal silica, alumina sol, and zirconia sol are simply used by the method described in Patent Document 3, the above problem cannot be solved. Even when mixed, it has not been sufficiently studied. Further, in the case of a phosphate coating composition as described in Patent Document 4 that does not contain chromium, stickiness occurs, and the above problem tends to become apparent. These problems were likely to occur when baking at a relatively low temperature of 300 ° C. or lower.
Japanese Patent Publication No. 60-36476 JP-A-10-130858 Japanese Patent Laid-Open No. 10-46350 Japanese Patent No. 2944849

  The present invention has been made for the purpose of solving the above-mentioned problems, and is an insulating film mainly composed of an inorganic substance not containing chromium, and is a product plate even when manufactured by coating and baking at 300 ° C. or lower. It is an object of the present invention to provide an electrical steel sheet with an insulating coating that is excellent in corrosion resistance (before strain relief annealing) and powder blowing resistance, as well as appearance and scratch resistance of the strain relief annealed plate.

  In order to solve the above problems, the present invention provides the following electrical steel sheet with an insulating coating.

The present invention relates to a magnetic steel sheet having an insulating coating containing a Zr compound, an Al compound and a Si compound as main components, and the Zr compound content relative to the total solid mass of the insulating coating is 45 to 90 in terms of ZrO _2. The electrical steel sheet with an insulating coating, wherein the ratio of the content of the Al compound and the Si compound is 20:80 to 80:20 in terms of Al ₂ O ₃ and SiO ₂ It is.

  In such an electrical steel sheet with an insulating coating, it is preferable that the surface of the insulating coating further has at least a second insulating coating.

  Furthermore, the second insulating coating preferably contains an Al compound, a Si compound, and a resin.

  According to the present invention, an insulating coating mainly composed of an inorganic material not containing chromium, and even when manufactured by coating and baking at 300 ° C. or less, the corrosion resistance and powder blowing resistance of the product plate (before strain relief annealing), and It is possible to provide an electrical steel sheet with an insulating coating that is excellent in appearance and scratch resistance of the strain relief annealed sheet.

The present invention is described in further detail below.
The present invention is an electrical steel sheet having an insulating coating containing a Zr compound, an Al compound, and an Si compound as main components.

<Electromagnetic steel sheet (electric iron plate)>
The electromagnetic steel plate (electric iron plate) before forming the insulating coating, which can be used in the present invention, may be a steel plate of any composition adjusted to obtain a desired magnetic property by changing the specific resistance. Not limited. Moreover, the surface of the electrical steel sheet on which the insulating coating is formed may be left untreated or pretreated. Pretreatment is optional, but degreasing treatment with alkali and pickling treatment with hydrochloric acid, sulfuric acid, phosphoric acid and the like are preferably applied.

<Zr compound>
The insulating coating of the present invention contains a specific amount of Zr compound. Appropriate content is 45% or more and 90% or less with respect to the total solid mass of the insulating coating. More preferably, it is 50% or more and 80% or less. In such a range, it is considered that a bonding network between the Zr compound and another substance is well formed, and the film is strengthened.
Here, the “total solid content mass” is an adhesion amount after drying of the coating formed on the surface of the magnetic steel sheet by a method described later, and can be measured from a weight reduction after removing the coating by alkali peeling.

Examples of the Zr compound that can be used in the present invention include zirconium acetate, zirconium propionate, zirconium oxychloride, zirconium nitrate, ammonium zirconium carbonate, zirconium carbonate potassium, zirconium zirconium chloride, zirconium sulfate, zirconium phosphate, and sodium phosphate. Zirconium, potassium hexafluorozirconium, tetranormal propoxyzirconium, tetranormalbutoxyzirconium, zirconium tetraacetylacetonate, zirconium tributoxyacetylacetonate, zirconium tributoxy systemate and the like can be mentioned, one or two of these. A mixture of the above can be used. These can be selected according to the compatibility with Al compounds and Si compounds which are essential components of the present invention, and other inorganic compounds, organic compounds and additives which are optional components described later. These may contain impurities such as Hf, HfO ₂ , TiO ₂ , SiO ₂ , and Fe ₂ O ₃ .

  The Zr compound of the present invention is preferably water-soluble rather than insoluble in pasty water. This is because the above bond becomes strong and a denser film is formed.

<Si compound>
The insulating coating of the present invention contains a Si compound. As the Si compound, colloidal silica is preferably applied.
Colloidal silica is an inorganic colloid mainly composed of SiO ₂ and is often amorphous. The particle diameter is preferably 20 nm or less, more preferably 10 nm or less, and the smaller the value, the better the film is formed, so the lower limit is not particularly limited. It is considered that the ultrafine particles have a large surface area, so that the interaction with other components is increased and the strength of the coating is increased. However, as the particle size becomes smaller, aggregation tends to occur between the silica particles and other components, so the concentration of colloidal silica must be lowered. Considering these points, the particle diameter can be set to be practical.
The average particle size can be measured by the BET method (converted from the specific surface area by the adsorption method). It is also possible to substitute an average value actually measured from an electron micrograph.

<Al compound>
The insulating coating of the present invention contains an Al compound. As this Al compound, an Al compound composed of a hydroxyl group and an organic acid and / or a dehydration reaction product thereof is preferably applied, and examples thereof include alumina sol. In order to apply and bake the steel sheet with a water-based paint, the Al compound is preferably one that can be dissolved in water or dispersed in a colloidal or suspended state. The shape may be any shape such as a feather shape or a spherical shape as long as there is no problem in characteristics.

<Ratio of Si compound to Al compound>
The insulating coating of the present invention comprises the Al compound and the Si compound in an amount of 20:80 to 80:20 (mass ratio) in terms of Al ₂ O ₃ and SiO _{2 with} respect to the total solid mass of the insulating coating. ), Preferably 30:70 to 70:30 (mass ratio), more preferably 35:65 to 65:35 (mass ratio). If the Al compound and the Si compound are contained in the insulating film in such a mass ratio, there is an effect that both corrosion resistance and strain relief annealing plate scratch resistance can be achieved at a high level.

As described above, the present invention is an electrical steel sheet having an insulating coating containing the Zr compound, the Al compound, and the Si compound as main components.
Among these, the Zr compound has three or more, generally four bonds, and has a strong bonding force with other substances, particularly oxygen. 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 the Zr compound is used alone, the corrosion resistance is slightly inferior, and the scratch resistance on the strain relief annealed plate tends to be greatly deteriorated. This is thought to be because the network is not formed well because there are many bonds of the Zr compound, and on the contrary, it becomes a fragile film. As a result of the investigation, it was discovered that when the Zr compound was reduced to 90% by mass or less in terms of ZrO ₂ and mixed with the Al compound and the Si compound, a great improvement effect was obtained. On the other hand, when the amount of the Zr compound added is less than 45% by mass, the effect is naturally small, which is not preferable.

  In the insulating coating of the present invention, the Zr compound may be Zr—O—Fe, Zr—OH—Fe via oxygen with other substances, or Al—O—Zr—O— for Al compounds and Si compounds. It is considered that Al, Si—O—Zr—O—Si are in a bonded state.

As described above, the present invention is an electrical steel sheet having an insulating coating containing the Zr compound, the Al compound, and the Si compound as main components, but having an insulating coating consisting of only these three components. It is preferable that The reason is that the corrosion resistance or the like deteriorates depending on the case when other components are contained.
In addition to these three components, it is also preferable to contain the following additives.

<Additives>
In order to further improve the performance and uniformity of the coating, the insulating coating of the present invention is organic, such as a surfactant, a rust inhibitor, boric acid, a silane coupling agent, a lubricant, and an antioxidant, as necessary. It is also preferable to contain an inorganic additive. In this case, 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 content weight of the insulating film of the present invention.

<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 in addition to the Zr compound, the Al compound, and the Si compound. Examples of such other inorganic compounds and organic compounds include acrylic resins, epoxy resins, vinyl acetate resins, polyester resins, melamine resins, urethane resins, and silicone resins. These copolymers and composite additives are also preferable. Illustrated.
The content of such other inorganic compounds and organic compounds is preferably 50% by mass or less with respect to the total solid mass of the insulating coating of the present invention. The reason is that when it exceeds 50% by mass, the Zr compound, Al compound, and Si compound, which are the main components, are reduced, and the coating is likely to be brittle.

<Method for producing insulating coating>
A method for producing the insulating coating of the present invention on the surface of the electromagnetic steel sheet will be described.
As a starting material of the present invention, an electromagnetic steel plate (electric iron plate) is used.
The pretreatment of the steel plate in the present invention is not particularly defined. Untreated or alkaline degreasing treatment, pickling treatment with hydrochloric acid, sulfuric acid, phosphoric acid or the like is preferably applied.
Then, a treatment liquid containing the Zr compound, the Al compound, the Si compound, and, if necessary, the additive and the like is applied onto the electromagnetic steel sheet and baked to form an insulating film. Various methods such as a roll coater, a flow coater, a spray, and a knife coater that are generally used for industrial coating can be applied. In addition, a hot air method, an infrared method, an induction heating method, or the like, which is usually performed, is also possible for the baking method. The baking temperature should just be a normal level, and what is necessary is just about 150-350 degreeC by ultimate temperature.

<Annealing method>
The electrical steel sheet with an insulating coating of the present invention can be subjected to strain relief annealing to remove, for example, strain due to punching. As a preferable strain relief annealing atmosphere, an atmosphere in which iron is not easily oxidized, such as an N ₂ atmosphere or a DX gas atmosphere, is applied. Here, the dew point is set high, for example, about Dp 5 to 60 ° C., and the corrosion resistance can be further improved by slightly oxidizing the surface and the cut end face. Moreover, as preferable strain relief annealing temperature, it is 700-900 degreeC, More preferably, it is 750-850 degreeC. The holding time of the strain relief annealing temperature is preferably longer, but more preferably 2 hours or longer.

<Insulation coating amount>
The adhesion amount of the insulating coating is not particularly specified, but is preferably 0.05 to 5 g / m ² in total per one surface. The amount of adhesion, that is, the total solid weight of the insulating coating of the present invention can be measured from the decrease in weight after removal of the coating by alkali peeling. Moreover, when there is little adhesion amount, it can measure from the calibration curve of a fluorescent X ray and an alkali peeling method. Attached amount insufficient only one insulation corrosion is less than 0.05 g / m ^2, when the deposition amount is 5 g / m ^2, greater than the adhesion is lowered, such as blistering occurs during paint baking Sex is reduced. More preferably, it is 0.1-3.0 g / m < ² >. The insulating coating is preferably on both sides of the steel plate, but depending on the purpose, only one side may be used. Depending on the purpose, only one side may be applied, and the other side may have no other insulating coating or insulating coating.

<Second insulating film (upper layer film)>
In the present invention, on the surface of an insulating film containing the Zr compound, the Al compound, and the Si compound (hereinafter also referred to as “undercoat”), at least a second insulating film having a component different from that of the undercoat ( Hereinafter, it is also preferable to have an “upper layer coating”.
Here, at least one layer of the second insulating film may be formed on the surface of the base film, and two or more insulating films may be formed on the surface of the base film. Hereinafter, a case where only one layer of the second insulating film is formed on the surface of the base film will be described.
By applying an insulating coating containing an Al compound, a Si compound and a resin as the upper coating on the surface of the base coating of the present invention, it is preferable because further excellent corrosion resistance, scratch resistance and appearance can be obtained.

<Al compounds, Si compounds>
As the Al compound and the Si compound contained in the upper layer film of the present invention, the same compounds as the Al compound and the Si compound contained in the base film of the present invention can be used.

<Resin>
The resin component contained in the upper film of the present invention is not particularly specified, but includes acrylic resin, alkyd resin, polyolefin resin, styrene resin, vinyl acetate resin, epoxy resin, phenol resin, polyester resin, urethane resin, melamine resin, etc. One or two or more aqueous resins (emulsion, dispersion, water-soluble) are preferable.

  The upper layer film of the present invention can contain other components and additives similar to the above-mentioned undercoat film. The content is also the same as that contained in the base coating.

The content rate of the said Al compound contained in the upper film of this invention is 10-90 mass% with respect to the total solid content mass of an upper film, 15-85 mass% is preferable, and 20-80 mass% is preferable. Further preferred.
Moreover, the content rate of the said Si compound contained in the upper film of this invention is 10-90 mass% with respect to the total solid content mass of an upper film, 15-85 mass% is preferable, and 20-80 mass is preferable. % Is more preferable.
Moreover, the content rate of the said resin contained in the upper layer film of this invention is 0.1-50 mass% with respect to the total solid content mass of an upper layer film, 1-45 mass% is preferable, and 5-40 More preferred is mass%.
If the content ratio of the Al compound, the Si compound, and the resin contained in the upper layer film of the present invention is within the above ranges, corrosion resistance, powder blowing resistance, and scratch resistance after strain relief annealing can be achieved in a balanced manner. This is preferable.
Here, the “total solid content mass of the upper layer coating” is the same as in the case of the above-mentioned base coating, and is the amount of adhesion after drying of the coating produced on the surface of the electromagnetic steel sheet, and the weight reduction after removal of the coating by alkali peeling Can be measured from

<Method for producing upper layer 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.

<Annealing method>
Even when the magnetic steel sheet on which the upper layer film of the present invention is formed is annealed, it is the same as the annealing method in the case where only the base film is formed.

<Amount of upper layer coating>
In the case of forming the upper layer film, the adhesion amount of the base film is preferably 0.01 to 1.0 g / m ² , and the adhesion amount of the upper layer film is preferably 0.04 to 4.0 g / m ² . This is to make the base film a thin insulating film so that cracks that are considered to be a cause of corrosion resistance deterioration are difficult to enter, and an attempt is made to secure necessary insulation by adding an upper film. Moreover, 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 the Fe elution of the steel sheet, which is likely to occur with the aqueous processing 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.

<Examples 1-42 and Comparative Examples 1-16>
A Zr compound, an Al compound, and an Si compound were added to deionized water so as to have a mass part (converted amount) shown in Table 1 to prepare each treatment liquid for the first layer (undercoat). _Here, the sum of _{ZrO 2, Al 2 O 3,} SiO 2 in terms of weight against deionized water was adjusted to 50 g / l the added processing solution.
Each of these treatment liquids was applied to the surface of a test piece cut out from a magnetic steel sheet having a thickness of 0.5 mm into a width of 150 mm and a length of 300 mm with a roll coater, and baked at a final temperature of 230 ° C. by propane gas direct fire. Then, it was allowed to cool at room temperature to form an insulating film.

In some examples and comparative examples, an Al compound, an Si compound, and a resin are added to deionized water so as to have a mass part (converted amount) shown in Table 1, and a second layer (upper layer coating) Each treatment solution was prepared. _Here, the Al ₂ O 3, SiO ₂ equivalent amount, and the resin solid mass, against deionized water was adjusted to 50 g / l the added processing solution.
Each of these treatment liquids was used to form an upper surface of the first layer (undercoat film) formed by the above method.
As is apparent from Table 1, FIG. 1 and FIG. 2, the present invention is excellent in corrosion resistance and powder blowing resistance. Other performance evaluation methods are as follows.

<Corrosion resistance evaluation>
Each test piece coated with each treatment solution was held in a constant temperature and humidity chamber with a relative humidity of 98% and 50 ° C. for 2 days, the rust generation area ratio on the surface of the test piece was determined, and the corrosion resistance was evaluated according to the following criteria. In addition, a rust generation | occurrence | production area ratio is a percentage of the sum total of the rust generation | occurrence | production area with respect to the total area observed visually.
(Criteria)
◎: Rust generation area ratio = 0 or more and less than 5% ○: Rust generation area ratio = 5 or more and less than 20% △; Rust generation area ratio = 20 or more and less than 50% ×: Rust generation area ratio = 50% or more

<Product sheet dust resistance>
Test conditions: felt contact surface width 20 × 10 mm, load: 3.8 kg / cm ² (0.4 MPa), and 400 m simple reciprocation on the coating surface. The rubbing trace after the test was observed, and the peeling state and the powder blowing state of the film were evaluated.
(Criteria)
◎: Almost no rubbing traces are observed. ○: Some rubbing traces and slight powder blowing are observed. △; The peeling of the coating progresses and the rubbing traces and powder blowing are clearly seen. Dust is enormous

<Annealing plate scratch resistance>
Test conditions: The surface of a sample annealed by holding at 750 ° C. for 2 hours in an N 2 atmosphere was scratched with a steel plate shear edge, and the degree of scratching and powder blowing was determined.
(Criteria)
◎: Scratches and powder are hardly observed. ○: Some rubbing traces and some powder blowing are observed. Large

<Appearance>
The surface after coating was visually observed and judged.
(Criteria)
◎: Uniform appearance ○: Almost uniform with slight rainbow pattern △: Medium rainbow pattern is generated and non-uniform ×: Discoloration is large and uneven

FIG. 1 is a diagram showing the effect of the addition amount of a Zr compound on corrosion resistance. FIG. 2 is a diagram showing the influence of the added amount of the Zr compound on the scratch resistance of the strain relief annealed plate.

Claims (3)

In the electrical steel sheet having an insulating coating containing a Zr compound, an Al compound and a Si compound as main components,
The content of the Zr compound with respect to the total solid mass of the insulating coating is 45 to 90% by mass in terms of ZrO ₂ , and the ratio of the content of the Al compound and the Si compound is in terms of Al ₂ O ₃ and SiO ₂ An electrical steel sheet with an insulating coating, which is 20:80 to 80:20 in terms of ₂ .   The electrical steel sheet with an insulating coating according to claim 1, further comprising at least a second insulating coating on the surface of the insulating coating.   The electrical steel sheet with an insulating coating according to claim 2, wherein the second insulating coating contains an Al compound, a Si compound, and a resin.

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