JP2001279458A - Silicon steel sheet having chromium-free insulating film excellent in corrosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a silicon steel sheet having a chromium-free insulating film having excellent corrosion resistance equal to that of a chromium series insulating film. SOLUTION: This silicon steel sheet has an insulating film on the surface, containing an inorganic colloid and resin in the insulating film, and one or more kinds of metal compounds, the metal selected from the group of Mo and W, 0.001 to 5 mass % of the insulating film as Mo+W, and further a content of Cl in the insulating film is <=0.1 mass %.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is excellent in performance required for an insulating film such as corrosion resistance, and can be used not only in a steel sheet coated with an insulating film itself but also in a processing solution for the insulating film. The present invention relates to an electromagnetic steel sheet having an environmentally friendly insulating coating that does not contain an environmentally harmful substance such as hexavalent chromium.

[0002]

2. Description of the Related Art Insulating coatings formed on magnetic steel sheets used for motors, transformers and the like are required to have various characteristics from the viewpoint of not only interlayer resistance but also convenience in working and storage. . In addition, 750 to 850 steel sheets with an insulating coating formed for the purpose of improving magnetic properties after punching
In many cases, the strain relief annealing is performed at about ° C. Therefore, the insulating coating may need to withstand the strain relief annealing. As described above, since the electromagnetic steel sheet is used for various uses, various insulating coatings are being developed according to the use.

[0003] The insulating coating of electrical steel sheets is (1) an inorganic coating that emphasizes weldability and heat resistance and resists strain relief annealing, and (2) a resin that resists strain relief annealing with the aim of achieving both punchability and weldability. Semi-organic coatings containing (3) Organic coatings that cannot be strain-annealed for special applications. Of these, the coatings containing inorganic substances described in (1) and (2) above are resistant to strain relief annealing as general-purpose products. Above all, chromate-based insulating coatings containing organic resins are coated in one coat and one bake. It is widely used because it can be manufactured and can significantly improve the punching properties as compared with inorganic insulating coatings.

[0004] For example, Japanese Patent Publication No. 60-36476 discloses a dichromate-based aqueous solution containing at least one divalent metal, and an organic resin containing vinyl acetate / 100 parts by weight of CrO ₃ in the aqueous solution. A resin emulsion having a peoba ratio of 90/10 to 40/60 in a resin solid content of 5 to 120 parts by weight,
Also disclosed is an electric iron plate having an insulating coating obtained by applying a treatment liquid containing an organic reducing agent in a ratio of 10 to 60 parts by weight to the surface of a dough iron plate and performing a baking step by a conventional method.

[0005] The chromate in such a chromate-based coating containing an organic resin is almost trivalent chromium at the stage of forming a steel sheet product, and thus has no problem of harm. However, it is necessary to use harmful hexavalent chromium at the stage of applying the raw material liquid for the coating. Therefore, in order to ensure a good working environment, it is disadvantageous from an environmental point of view because it is required not only to enhance the facilities but also to comply with strict handling standards.

As an insulating film mainly composed of an inorganic substance other than chromic acid, many semi-organic insulating films mainly composed of an inorganic colloid such as silica have been disclosed. When an insulating film is formed using these inorganic colloids, it is not necessary to handle a harmful hexavalent chromium solution, so that it can be applied in an environmentally advantageous manner.

[0007] The function of chromium in the chromate-based insulating film is to impart good corrosion resistance.
It is desired that the inorganic colloid-based semi-organic insulating coating having no chromium has corrosion resistance equal to or higher than that of the chromate-based insulating coating. Methods for improving the corrosion resistance of an inorganic colloid-based semi-organic insulating coating include, for example, a method disclosed in JP-A-10-34812.
There is a method in which the amounts of Cl and S in the resin / silica coating are reduced to specified amounts or less. Although this method greatly improved the corrosion resistance, particularly the corrosion resistance after strain relief annealing, there still remains a problem that the corrosion resistance of the product sheet is lower than that of the chromate-based insulating film.

[0008]

As described above, at present, there is no inorganic colloidal coating having as excellent corrosion resistance as a chromium-based insulating coating on a product plate. Accordingly, the present invention has been made to solve the above-described problems, and has as its object to propose an electromagnetic steel sheet having a chromium-free insulating film having excellent corrosion resistance equivalent to that of a chromium-based insulating film.

[0009]

Means for Solving the Problems In order to solve the above problem advantageously, the present inventors actively add an additive for improving corrosion resistance in addition to purifying to remove factors that inhibit corrosion resistance. I thought it was necessary.

As a result of intensive studies based on such a policy, the inventors found that Cl in the coating was reduced to a certain amount or less in order to improve corrosion resistance.
Alternatively, it has been found that it is effective to add W. Regarding Mo and W to be added, any compound containing these elements is effective for improving corrosion resistance regardless of the compound, but in particular, a heteropolyacid or heteropoly containing Mo or W having an oxidizing performance. It has been found that acid salts can be applied advantageously.

The present invention based on the above findings is an electromagnetic steel sheet having an insulating coating on the surface, comprising an inorganic colloid and a resin in the insulating coating, and further comprising an insulating coating in the insulating coating.
One or more compounds selected from Mo and W are contained at a ratio of 0.001 mass% to 5 mass% of the insulating coating in terms of Mo + W, and the Cl ratio in the insulating coating is 0.1 mass% or less. This is an electrical steel sheet having a chromium-free insulating film having excellent corrosion resistance. More preferably, the total amount of the inorganic colloid in the present invention is 3 to 300 parts by weight in terms of the total amount of the oxide of the inorganic colloid with respect to 100 parts by weight of the resin. In addition, one or more compounds selected from Mo and W are preferably a heteropolyacid or a heteropolyacid salt. Further, it is preferable that the basis weight of the insulating coating is 0.05 to 7 g / m ² .

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail. The base material of the magnetic steel sheet may be adjusted in steel composition in order to obtain a desired magnetic property by changing the specific resistance. In the present invention, any component composition used as a magnetic steel sheet can be applied.

The insulating coating contains an inorganic colloid in order to ensure the performance after strain relief annealing. Any inorganic colloid can be applied, for example,
Silica, alumina, titania, antimony oxide, zirconia, tin oxide, tungsten oxide, molybdenum oxide,
An oxide sol such as iron oxide is applicable.

The amount of the inorganic colloid is preferably 3 to 300 parts by weight in terms of the total amount of the inorganic colloid as an oxide based on 100 parts by weight of the organic resin of the insulating film. When the amount of the inorganic colloid is less than 3 parts by weight, there is a problem that sticking occurs when performing strain relief annealing, and when the amount is more than 300 parts by weight, the punching property tends to be rapidly reduced. The oxide conversion means SiO ₂ , Al ₂ O ₃ , Ti
_{O 2, Sb 2 O 5,} ZrO 2, SnO 2, WO 3, MoO 3, may be converted to the amount as Fe ₂ O ₃ or the like. When importance is attached to the corrosion resistance after strain relief annealing, one or two kinds selected from silica and alumina are included, and alumina is 0 to 100 parts by weight in terms of SiO _{2 and} alumina is 0 to 100 parts by weight in terms of Al ₂ O _3. When it is 500 parts by weight, it can be used particularly suitably. Al ₂ O to 100 parts by weight of SiO _{2
If the} amount exceeds ₃ parts by weight, the corrosion resistance after strain relief annealing tends to decrease.

Further, a resin is added in order to secure film properties such as punching property and film forming property. The resin is not particularly limited, and various resins compatible with the inorganic colloid can be applied. Any form and type may be used as long as they are compatible with the inorganic colloid, such as water-soluble, emulsion, dispersion and powder. For example, acrylic resin, alkyd resin, polyolefin resin, styrene resin, vinyl acetate resin, epoxy resin, phenol resin, urethane resin,
Various resins such as a melamine resin, an amide resin, an imide resin, and a copolymer or a mixed resin of two or more of these resins can be suitably applied.

Further, in order to improve the corrosion resistance, Mo, W
And at least 0.001 mass% to 5 mass% of the total coating weight in terms of Mo + W. Mo, W
If the compound containing at least one element selected from the group consisting of at least one is less than 0.001 mass% of the total coating weight in terms of Mo + W, the effect of addition cannot be obtained, while if it exceeds 5 mass%, there is no further improvement effect and the cost increases. Because it becomes. The compound containing Mo and W can be in any compound form other than chloride. In particular, when the compound containing at least one selected from Mo and W is a heteropolyacid or a heteropolyacid salt having an oxidizing agent function, it is advantageous because particularly excellent corrosion resistance can be obtained. Heteropoly acid is an acid having two or more metals, and examples thereof include phosphomolybdic acid, phosphotungstic acid, silicomolybdic acid, and silicotungstic acid. Also, these salts can be suitably applied.

In order to sufficiently exhibit the film performance of the above-mentioned film component composition, it is necessary that the Cl ratio in the film be 0.1 mass% or less. Cl is a component that lowers the corrosion resistance, and when the Cl ratio in the coating exceeds 0.1 mass%, the corrosion resistance is significantly adversely affected.

Although the weight per unit area of the insulating coating can be applied to any conventional range, it is more preferably 0.05 to 7 g / m ² per side. If it is less than 0.05 g / m ^2, a uniform coating is difficult, it is difficult to secure a stable punching property, because the coating adhesion as a 7 g / m ² than is seen a tendency to decrease is there. More preferably, it is 0.05 to 4 g / m ² .

The insulating film is formed by applying the above-mentioned chemicals containing the respective raw materials onto an electromagnetic steel sheet and baking it. Various methods, such as a roll coater method, a flow coater method, a spray coating method, a knife coater method, and a bar coater method, which are generally used industrially, can be applied to the method for forming an insulating film. The baking method is not particularly limited, such as a hot air method, an infrared method, an induction heating method, and the like, which are usually performed. In addition, various additives may be blended in order to further improve the performance of the film, but Cr is not contained in order to obtain a chromium-free coat.

[0020]

EXAMPLES Hereinafter, the effects of the present invention will be specifically described based on examples, but the present invention is not limited to these examples. (Example 1) As steel components, Si: 0.45 mass%, Mn: 0.25
A coating material liquid was applied and baked on a full-process electrical steel sheet containing 0.5% thickness and a thickness of 0.5 mm and containing Al and 0.48 mass% of Al to form an insulating coating. The insulating coating of the obtained magnetic steel sheet was obtained by converting 80 parts by weight of high-purity alumina-containing silica to 100 parts by weight of epoxy resin in terms of Al ₂ O ₃ + SiO ₂ (100 parts by weight of SiO ₂ : Al ₂ O ₃ : 20). Parts by weight), and contains phosphomolybdic acid in various amounts, and the Cl content in the coating is
It was in the range of 0.01 to 0.03 mass%. 0.5g / m ²
Met. FIG. 1 shows the result of investigation on the corrosion resistance of the magnetic steel sheet having the insulating coating.

FIG. 1 shows that the amount of Mo in the coating was 0.1% in the insulating coating.
When the content is 001 mass% or more, it is clear that the corrosion resistance is excellent.

(Example 2) As a steel component, Si: 0.45 mass
%, Mn: 0.25 mass%, Al: 0.48 mass%
Using a 5 mm-thick full-process electrical steel sheet which had been subjected to finish annealing, a film was formed with the insulating film components and the basis weight shown in Table 1. The coating performance of the magnetic steel sheet thus obtained is also shown in Table 1. In addition, the coating performance evaluation method is as shown below.

● Boiling water vapor exposure property The appearance after 30 minutes of boiling water vapor exposure and the amount of film component elution into water after the test were investigated. ◎: no change, elution 50 mg / m ² or less ○: little change None, elution amount 50~200mg / m ² △: slight discoloration (chalky, rust), elution amount 200 ~500mg / m ² ×: change size (chalky, rust), elution amount 500 mg / m ² greater

Solvent resistance Various solvents (hexane, xylene, methanol, ethanol) were impregnated into absorbent cotton, and the appearance change of the steel sheet after 5 reciprocations was investigated. ：: No change ○: Almost no change △: Slight discoloration ×: Large change

Sticking property Ten pieces of 50 mm square steel sheets are stacked and annealed at 750 ° C. for 2 hours under a nitrogen atmosphere while applying a load (200 g / cm ² ). Then, 500 g of a weight is dropped on the steel sheet and divided into five parts. The height of the fall was investigated. ◎: Drop height 10cm or less ○: Drop height 10-15cm △: Drop height 15-30cm ×: Drop height more than 30cm

The corrosion resistance of the product plate was evaluated by the area ratio of red rust after 5 hours of salt spray test (35 ° C.) specified by JIS. ◎: Red rust area ratio 0 to 25% ○: Red rust area ratio 25 to 50% △: Red rust area ratio 50 to 75% ×: Red rust area ratio 75 to 100%

● Corrosion resistance after strain relief annealing The magnetic steel sheet annealed in nitrogen at 750 ° C. for 2 hours was evaluated by a constant temperature and humidity test (50 ° C., relative humidity 80%) and a red rust area ratio after 14 days. ◎: Red rust area ratio 0 to 20% ○: Red rust area ratio 20 to 40% △: Red rust area ratio 40 to 60% ×: Red rust area ratio 60 to 100%

● Punching Efficiency The evaluation was made based on the number of punches until the burr height reached 50 μm in a 15 mmφ steel die. ◎: More than 500,000 times ○: 300,000 to 500,000 times △: 100,000 to 300,000 times × Less than 100,000 times

● Adhesiveness Each of the product sheet and the strain relief annealed sheet (annealed in nitrogen at 750 ° C. × 2 hours) was evaluated by the peeling rate of the film after the 180 ° bending-back test at 20 mmφ. ：: No peeling ○: ~ Peeling 20% △: Peeling 20% ~ Peeling 40% ×: Peeling 40% ~ Full peeling

[0030]

[Table 1]

[0031]

Since the present invention is configured as described above, various performances including corrosion resistance are excellent. In addition, since it does not contain chromium, it is environmentally friendly not only in the final product but also in the manufacturing process, and has excellent insulating film performance such as film adhesion and corrosion resistance, so it is widely used for motors and transformers. be able to.

[Brief description of the drawings]

FIG. 1 is a diagram showing the effect of the amount of Mo in a coating on the corrosion resistance of a product plate.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C23C 22/42 C23C 22/42 H01F 1/18 H01F 1/18 (72) Inventor Atsuto Honda Kurashiki, Okayama Prefecture 1-chome, Kawasaki-dori, Mizushima-shi, Ichigo (without address) Inside the Mizushima Works, Kawasaki Steel Co., Ltd. (72) Inventor Masaki Kozoku, 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Prefecture F-term (in reference) ) 4D075 CA13 CA23 CA33 CA44 DA03 DA06 DB03 DC18 EB13 EB14 EB19 EB22 EB32 EB33 EB36 EB38 EB39 EC01 EC54 4F100 AA02A AA17A AA19 AA33A AB03B AK01A AK53 BA02 EH46 EJ08 GB02 J03A02 J02A03 CA29 CA31 CA39 CA41 DA15 DA16 EB11 5E041 AA11 AA19 BC01 BC05 CA02 CA04 NN05

Claims (4)

[Claims] An electromagnetic steel sheet having an insulating coating on its surface, comprising an inorganic colloid and a resin in the insulating coating, and one or more compounds selected from Mo and W in the insulating coating. , 0.001 mass% to 5 ma of insulation film in Mo + W conversion
ss% ratio, and the Cl ratio in the insulation coating is 0.1 ma
An electrical steel sheet having a chromium-free insulating film with excellent corrosion resistance, characterized by being at most ss%. 2. The inorganic colloid has a total amount of resin.
2. The magnetic steel sheet having a chromium-free insulating film excellent in corrosion resistance according to claim 1, wherein the amount is 3 to 300 parts by weight in terms of the total amount of the inorganic colloid oxide per 100 parts by weight. 3. The magnetic steel sheet having a chromium-free insulating film having excellent corrosion resistance according to claim 1, wherein the at least one compound selected from the group consisting of Mo and W is a heteropolyacid or a heteropolyacid salt. . 4. The electrical steel sheet having a chromium-free insulating film having excellent corrosion resistance according to claim 1, wherein the basis weight of the insulating film is 0.05 to 7 g / m ² .