JP4461861B2 - Magnetic steel sheet with chrome-free insulation coating - Google Patents

Description

  The present invention relates to an electrical steel sheet with an insulating coating mainly composed of an inorganic material containing no chromium compound.

  Insulating coatings on electrical steel sheets used for motors, transformers, etc. 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, depending on the conditions, there was a problem of stickiness.

For example, Patent Document 3 describes a method of forming an insulating film using one or more of colloidal silica, alumina sol, and zirconia sol. However, even when this method is applied, the above problem may occur when the mixing ratio of the zirconia sol is about 50% by mass or more.
Further, in the case of the phosphate film described in Patent Document 4 having a composition containing no chromium, stickiness is generated, and the above-described problem tends to become apparent.
Japanese Patent Publication No. 60-36476 JP-A-10-130858 JP-A-10-46350 Japanese Patent No. 2944849

  The present invention has been made for the purpose of solving the above-mentioned problems, and is a chromium-free insulating film having good corrosion resistance, powder blowing resistance, and stickiness resistance of a product plate (an electromagnetic steel plate before strain relief annealing). It is an object of the present invention to provide a magnetic steel sheet with an attachment.

  As a result of diligent studies to solve the above-mentioned problems, the present inventor contains a specific amount of a Zr compound containing as a main component at least one inorganic substance selected from the group consisting of Si compounds, Al compounds, and P compounds. Thus, the inventors have found that a magnetic steel sheet with a chromium-free insulating coating having the above-mentioned coating properties can be obtained, and completed the present invention.

That is, the present invention provides the following (a) to (c).
(a) In an electrical steel sheet having an insulating coating composed mainly of at least one inorganic material selected from the group consisting of Si compounds, Al compounds, and P compounds,
The insulating coating is
Each of the inorganic substances is converted into SiO _2, converted into Al ₂ O ₃ , converted into PO _4, and the total amount is 100 parts by mass,
Containing 10 to 90 parts by mass of the Zr compound in terms of ZrO ₂ ;
An electromagnetic steel sheet with a chromium-free insulating coating that has excellent corrosion resistance, powder blowing resistance, and stickiness resistance.

  (b) The electromagnetic steel sheet with a chromium-free insulating coating according to (a), wherein the Zr compound is obtained by applying a composition containing a water-soluble Zr compound to a steel sheet and baking it.

(c) With respect to 100 parts by mass of the insulating film, each of the inorganic substances and the Zr compound is converted to SiO ₂ , Al ₂ O ₃ , PO ₄ , ZrO ₂
The electromagnetic steel sheet with a chromium-free insulating coating according to (a) or (b), further containing 50 parts by mass or less of a resin.

“Chromium-free” or “not containing chromium” means that no chromium is intentionally contained, and does not mean that no chromium is contained. In other words, mixing of chromium as an impurity from the raw material or the like means that each of the inorganic substances and the Zr compound is 100 parts by mass in terms of a total amount of SiO ₂ conversion, Al ₂ O ₃ conversion, PO ₄ conversion, and ZrO ₂ conversion. On the other hand, it is acceptable if the mixed Cr compound is 0.1 part by mass or less in terms of CrO ₃ .

  According to the present invention, it is possible to obtain a magnetic steel sheet with a chromium-free insulating coating that is excellent in corrosion resistance, powder blowing resistance, and stickiness resistance of a product plate.

Below, the electromagnetic steel plate with a chromium free insulating film which concerns on this invention is demonstrated concretely based on the example of a manufacturing process.
The present invention
In the electrical steel sheet having an insulating coating composed mainly of at least one inorganic material selected from the group consisting of Si compounds, Al compounds, and P compounds,
The insulating coating is
Each of the inorganic substances is converted into SiO _2, converted into Al ₂ O ₃ , converted into PO _4, and the total amount is 100 parts by mass,
Containing 10 to 90 parts by mass of the Zr compound in terms of ZrO ₂ ;
It is a magnetic steel sheet with a chromium-free insulating coating excellent in corrosion resistance, powder blowing resistance, and stickiness resistance.

  In the present invention, the electromagnetic steel plate (electric iron plate) may be a steel plate having any composition adjusted to obtain a desired magnetic characteristic by changing the specific resistance, and is not particularly 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.

  An insulating coating substantially free of chromium is provided on the surface of the electrical steel sheet using a treatment liquid containing at least one inorganic material selected from the group consisting of Si compounds, Al compounds, and P compounds, and a Zr compound. An electrical steel sheet is formed.

<Zr compound>
In the present invention, it is necessary to contain a specific amount of the Zr compound. As an appropriate amount, at least one inorganic substance selected from the group consisting of Si compound, Al compound, and P compound is converted into SiO ₂ , Al ₂ O ₃ , PO ₄ , respectively, It is 10-90 mass parts with respect to 100 mass parts, Preferably it is 15-80 mass parts, More preferably, it is 20-70 mass parts. Since the Zr compound has three or more, generally four bonds, a tough film can be formed without using a chromium compound by causing a crosslinking reaction. In particular, a Si compound, an Al compound, This is because a great effect can be obtained only when the main component is at least one inorganic substance selected from the group consisting of P compounds and the Zr compound is contained in the specific content.
When the Zr compound is a simple substance or a main component, there are many bonds, so the network is not formed well. On the contrary, it is considered that the film becomes brittle and the corrosion resistance is inferior. It is not demonstrated. That is, it is considered that the effect can be exhibited only when there is another specific inorganic substance.

As the form of bonding, it is considered that Al—O—Zr—O—Al, Si—O—Zr—O—Si, and P—O—Zr—OP are bonded via oxygen. In addition, it is considered that the organic resin has a bond such as CO—O—Zr—O—OC and C—O—Zr—O—C with respect to a carboxyl group, a hydroxyl group, and the like. It is considered that the same effect can be obtained for resins such as silicone.
That is, it is considered that a composite oxide film containing at least one element selected from the group consisting of Si, Al, and P and a Zr element is formed.

  Zr compounds of the present invention include zirconium acetate, zirconium propionate, zirconium oxychloride, zirconium nitrate, ammonium zirconium carbonate, potassium zirconium carbonate, zirconium hydroxychloride, zirconium sulfate, zirconium phosphate, sodium zirconium phosphate, zirconium hexafluoride. Examples thereof include potassium, tetranormal propoxyzirconium, tetranormalbutoxyzirconium, zirconium tetraacetylacetonate, zirconium tributoxyacetylacetonate, zirconium tributoxy systemate, and the like, which can be selected depending on compatibility with inorganic components. These can be used alone or in combination.

  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>
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>
As the 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.

<P compound>
As the P compound, phosphate can be applied, and examples thereof include aluminum phosphate, magnesium phosphate, calcium phosphate, iron phosphate, and zinc phosphate.

  Si compounds, Al compounds, and P compounds can be used alone or in combination as long as sufficient film properties are obtained. Specific examples include a composite system of silica sol and alumina sol, phosphate and silica sol, phosphate and alumina sol, silica sol, alumina sol and phosphate.

<About resin>
In the present invention, at least one inorganic substance selected from the group consisting of a Si compound, an Al compound, and a P compound in the treatment liquid for forming an insulating coating is converted into SiO ₂ , Al ₂ O ₃ , respectively. It is preferable to include the resin at 50 parts by mass or less with respect to 100 parts by mass in terms of the total amount of PO ₄ converted and Zr compound converted to ZrO ₂ . Even if it does not contain a resin, a practically sufficient film can be formed, but the corrosion resistance can be further improved by adding a small amount of the resin. This is presumably because cracks tend to occur due to shrinkage during film formation with the inorganic component alone, but the shrinkage stress is relieved by the addition of resin.

  When the resin is added, even when manufactured by low-temperature baking at 300 ° C. or lower, the corrosion resistance is excellent.

In order to obtain such an effect, at least one inorganic substance selected from the group consisting of Si compound, Al compound, and P compound is converted into SiO ₂ , Al ₂ O ₃ , PO ₄ , respectively, It is preferable to contain 10 parts by mass or more of the resin with respect to 100 parts by mass of the total amount of the Zr compound and the amount converted to ZrO ₂ . On the other hand, if it exceeds 50 parts by mass, the film after strain relief annealing becomes brittle and tends to peel off. The resin amount specified above is more preferably 10 to 40 parts by mass.

  Although not specified as a resin component, one or more aqueous resins such as acrylic resin, alkyd resin, polyolefin resin, styrene resin, vinyl acetate resin, epoxy resin, phenol resin, polyester resin, urethane resin, melamine resin, etc. (Emulsion, dispersion, water-soluble) is preferable.

<Other additives>
In addition, in order to further improve the performance and uniformity of the coating, additives such as surfactants, rust inhibitors, boric acid, silane coupling agents, lubricants, antioxidants, etc. are blended as necessary. Also good. 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 weight of the solid film after drying.

<Insulating film formation method>
A coating film is formed by applying and baking a treatment liquid containing an Si compound, an Al compound, a P compound, a Zr compound, and, if necessary, a resin on the electromagnetic steel sheet. Various methods, such as a roll coater, a flow coater, a spray, and a knife coater, which are generally used industrially, can be applied to the insulating film forming method. As for the baking method, a normal method such as a hot air method, an infrared method, an induction heating method and the like which are usually performed can be applied. 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 electromagnetic steel sheet with a chromium-free insulating coating according to 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>
Although the adhesion amount of the insulating coating is not particularly specified, it is preferably 0.05 to 5 g / m ² per side. Tend adhesion amount is insufficient only one insulation corrosion is less than 0.05 g / m ^2, the adhesion amount is When it is 5 g / m ^2, greater than the adhesion decreases, blistering occurs during paint baking This is because the paintability tends to decrease. More preferably, it is 0.1-3.0 g / m < ² >.
The amount of adhesion, that is, the weight of the solid content of the film can be measured from the decrease in weight after removing the film by alkali peeling.
The insulating coating is preferably on both sides of the steel sheet, but it does not lie on only one side depending on the purpose.

  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 1-37 and Comparative Examples 1-17>
Each treatment solution was prepared by adding Si compound, Al compound, P compound, Zr compound, and resin to deionized water so as to have a mass part (converted amount) shown in Table 1. _Here, the sum of _{SiO 2, Al 2 O 3,} PO 4, ZrO 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.
Each performance evaluation method is 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 to 5%
○: Rust generation area ratio = 5 to 20%
Δ: Rust generation area ratio = 20 to 50%
×: Rust generation area ratio = 50% or more

<Product sheet dust resistance>
Test conditions: Felt contact surface width 20 × 10 mm, load: 2 kg / cm ² (0.2 MPa), and simple reciprocation 400 m 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

<Stickness>
Each test piece coated with each treatment solution is held in a constant temperature and humidity chamber with a relative humidity of 80% and 50 ° C. for 7 days. Evaluated according to.
(Criteria)
Existence: Absorbs moisture and the coating turns white, or touch is slimy No: No change from before test

  As is apparent from Table 1 and FIGS. 1 and 2, all of the examples of the present invention are excellent in corrosion resistance, powder blowing resistance, and stickiness resistance.

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 addition amount of the Zr compound on the powder blowing resistance.

Claims (3)

In the electrical steel sheet having an insulating coating composed mainly of at least one inorganic material selected from the group consisting of Si compounds, Al compounds, and P compounds,
The insulating coating is
Each of the inorganic substances is converted into SiO _2, converted into Al ₂ O ₃ , converted into PO _4, and the total amount is 100 parts by mass,
Containing 10 to 90 parts by mass of the Zr compound in terms of ZrO ₂ ;
An electromagnetic steel sheet with a chromium-free insulating coating that has excellent corrosion resistance, powder blowing resistance, and stickiness resistance.   The electrical steel sheet with a chromium-free insulating coating according to claim 1, wherein the Zr compound is obtained by applying a composition containing a water-soluble Zr compound to a steel sheet and baking the composition. With respect to 100 parts by mass of the insulating coating, each of the inorganic substances and the Zr compound in terms of SiO ₂ , Al ₂ O ₃ , PO ₄ , ZrO ₂
Furthermore, the electromagnetic steel plate with a chromium free insulating film of Claim 1 or 2 which contains 50 mass parts or less of resin.

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