JP2010059513A - Insulated film agent for electromagnetic steel sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve moisture absorption resistance and film formability when an insulated film is formed on a grain oriented silicon steel sheet using a chromium-free phosphate treatment liquid. <P>SOLUTION: An insulated film agent comprising hydrotalcites and/or the basic salt of a trivalent metal by 0.1 to 50 pts.wt. to 100 pts.wt. of at least one kind selected from the primary phosphates of Al, Mg, Ca or the like expressed in terms of solid contents and 35 to 70 pts.wt. of colloidal silica is used. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an insulating film forming agent for grain-oriented electrical steel sheets. More specifically, the present invention relates to an insulating film forming agent capable of replacing toxic hexavalent chromium with a nontoxic compound.

  The grain-oriented electrical steel sheet is obtained by subjecting a silicon steel sheet slag containing 2 to 4% Si to Fe to hot and cold rolling to obtain a final thickness, followed by decarburization annealing and applying an annealing separator mainly composed of MgO. Then, finish annealing is performed to form a glass film. Next, an insulating coating agent is applied, and baking and heat flattening are performed to obtain a final product. Electrical steel sheets are used for iron core materials such as transformers and electrical equipment, and require high magnetic flux density and low iron loss.

  In the manufacture of the transformer core, the grain-oriented electrical steel sheet is cut into a predetermined length and width, and then stacked and stacked, or wound into a wound core. In the case of a wound iron core, it is further subjected to compression molding and strain relief annealing, and then the winding work is performed to form a transformer.

  The insulation coating is deeply related to the workability of transformer production and the performance of the transformer. If the adhesion of the insulating coating is weak, part of the coating will peel off and dust will be generated, deteriorating the working environment and reducing the electrical characteristics.If the insulating coating is partially missing, the electrical characteristics will be reduced. Make it worse. Furthermore, when the low melting point impurities are present in the insulating coating, the plates are fused to each other and are difficult to peel off during strain relief annealing after compression molding (film seizure).

  To provide a good insulating film without causing the above problems, use a mixture of primary phosphates such as Al and Mg and colloidal silica with a hexavalent chromium compound (chromic acid or chromate). Has been done.

  Hexavalent chromium compound to prevent formation of uniform insulation film without missing parts, hygroscopicity due to excessive free phosphoric acid phosphate (electrical insulation degradation) and film seizure during strain relief annealing Is essential. However, hexavalent chromium is highly toxic and is therefore banned.

Therefore, several techniques for replacing hexavalent chromium have been proposed to solve this problem. They use sulfates of Mg, Al, Fe, Co, Ni and Zn instead of chromium compounds [Japanese Examined Patent Publication No. 57-9963].
An inorganic compound of Fe, Ni, Co, Cu, Sr, and Mo, particularly preferably a hydroxide [Japanese Patent Laid-Open No. 2005-200705] is used.

  Since the metal sulfates described above are neutral to weakly acidic compounds, the reactivity with free phosphoric acid is weak. Metal organic acid salt has better reactivity with free phosphoric acid than sulfate, but there is a problem of gelation of primary phosphate and colloidal silica. Adversely affects. Metal hydroxides are free from gelation problems and have improved reactivity with free phosphoric acid over sulfates, but still do not reach the performance of chromium compounds.

  In addition to the above technique, as a non-primary phosphate-based new coating agent, the following formula (4)

の一般式で表わされる平均１μｍ の固溶型の複合金属水酸化物を用いる提案が出されている。［特開平７−１８００６４］
しかし、この新被膜剤は、従来の第一リン酸塩、コロイダイルシリカおよびクロム化合物から成る被膜剤に比べ被膜形成性がかなり劣る。

A proposal has been made to use an average 1 μm solid solution type composite metal hydroxide represented by the general formula: [JP-A-7-180064]
However, this new coating agent is considerably inferior in film forming properties as compared with a conventional coating agent comprising primary phosphate, colloidal silica and a chromium compound.

  The present invention is a conventional insulating coating agent in which a primary phosphate compound is essential, and colloidal silica and a chromium compound are added thereto. Only a toxic chromium compound is nontoxic, and the chromium compound has The present invention provides a novel film forming agent capable of sufficiently replacing excellent free phosphate capturing property and dense film forming property.

The present invention provides the following formula (1)

（但し、式中、Ｍ^２＋はＦｅ，Ｎｉ，Ｃｏ，Ｍｎの少なくとも１種の２価金属、好ましくはＦｅおよび／またはＮｉを示し、Ｍ^３＋はＦｅ，Ｃｏ，Ｍｎの少なくとも１種の３価金属、好ましくはＦｅを示し、Ａ^ｎ−はｎ価のアニオン、好ましくはＯＨ⁻および／またはＣＯ_３ ^２−を示し、ｘとｍはそれぞれ次の範囲、０＜ｘ＜０．５、好ましくは０．２＜ｘ＜０．４，０≦ｍ＜４）で表わされるＭ^２＋（ＯＨ）_２のＭ^２＋の一部をＭ^３＋置換した固溶体であるハイドロタルサイト類、および／または、下記式（２）

(Wherein M ²⁺ represents at least one divalent metal of Fe, Ni, Co, and Mn, preferably Fe and / or Ni, and M ³⁺ represents at least one trivalent of Fe, Co, and Mn. metal, preferably an ^{Fe, a n-n-valent} anion, preferably OH ^- and / or _CO ^{3 2-} are shown, x and m each following range, 0 <x <0.5, preferably Hydrotalcite that is a solid solution obtained by substituting a part of M ²⁺ of M ²⁺ (OH) ₂ represented by 0.2 <x <0.4, 0 ≦ m <4) with M ³⁺ and / or the following formula (2)

（但し、式中、Ｍ^３＋は式（２）と同じ３価金属を示し、Ａ^ｎ−は１価または２価の陰イオンを示し、Ｍ^３＋およびＡ^ｎ−の最も好ましいのはそれぞれＦｅ^３＋，ＣＯ_３ ^２−であり、ｚは次の範囲、０＜ｚ＜２にある）で表わされる３価金属の塩基性塩をクロム化合物の代わりにリン酸塩とコロイダルシリカの系に添加する電磁鋼板用低毒性絶縁被膜剤である。更に詳しくは、本発明は［１］第一リン酸塩１００重量部に対し、コロイダルシリカをＳｉＯ_２換算で３５〜１００重量部及び式（１）および／または式（２）のハイドロタルサイト類および／または３価金属の塩基性塩を固形物換算で０．１〜５０重量部含有する、有毒なクロムを含有しない電磁鋼板用絶縁被膜剤である。ここで、固形物とは乾燥（１１０℃で３時間）して水分を除いた残りのものをいう。

^{(Wherein, M 3+} represents a same trivalent metal and Equation ^{(2), A n-} represents a monovalent or divalent ^{anion, M 3+} and ^{A n-} most preferably each ^{Fe 3+} of the , CO ₃ ^2- , z is in the following range, 0 <z <2), and a basic salt of a trivalent metal is added to a phosphate and colloidal silica system instead of a chromium compound. It is a low toxicity insulating coating agent for steel sheets. More specifically, the present invention is [1] 35 to 100 parts by weight of colloidal silica in terms of SiO ₂ and hydrotalcites of formula (1) and / or formula (2) with respect to 100 parts by weight of the primary phosphate. And / or an insulating coating agent for electrical steel sheets that contains 0.1 to 50 parts by weight of a basic salt of a trivalent metal in terms of solid matter and does not contain toxic chromium. Here, the solid matter means the remaining product after drying (at 110 ° C. for 3 hours) to remove moisture.

  According to the present invention, the problems of corrosion resistance and film imperfection caused by a phosphate-based insulating film not containing chromium can be solved, and the problem of toxicity (environmental contamination) due to the chromium-added system can be solved.

  The hydrotalcite of the formula (2) of the present invention is a solid solution (0 <x <0.5) in which a trivalent metal is substituted for a divalent metal hydroxide, and has the same crystal structure as that of hydrotalcite. Show. Therefore, the above-mentioned JP-A-7-180064 mainly comprises a trivalent metal hydroxide (this can be explained by the fact that the range of x is 0.8 ≦ x ≦ 0.9 in the embodiment). The present invention is completely different from the present invention in that it is a solid solution and the solid solution itself is an insulating coating agent and does not use phosphate and colloidal silica in combination. The crystal structure of the present invention belongs to hydrotalcites (for example, properties and applications of hydrotalcites, Miyata, zeolite, vol. 8, No. 4, 1991), while JP-A-7-180064 is trivalent. They are metal hydroxides, both of which have completely different compositions and crystal structures.

The present invention is a technique realized by further improving the performance of a trivalent metal hydroxide. Compared with divalent metal phosphates, trivalent metal phosphates, when reacted, form excellent moisture resistance (insulating properties) and a dense film. However, trivalent metal hydroxides have poorer reactivity with free phosphoric acid than divalent metal hydroxides, no matter how fine. As a result of diligent research, it was considered that the performance of the target chromium compound could be sufficiently replaced if the reactivity of the trivalent metal, particularly Fe ³⁺ hydroxide, with free phosphoric acid could be improved. It came to complete.

It is the compound of the formula (1) or the formula (2), particularly preferably the compound of the formula (1) that has achieved the above object. Since the trivalent metal hydroxides ^{Fe 3+} such as divalent metal hydroxide hydrotalcite of formula (1) is ^{Ni 2+} Toka ^{Fe 2+} are dispersed (dissolved) into ^{atomic, M 2+} ( It was found to show reactivity with phosphoric acid close to OH) ₂ . In addition, the basic salt of M ³⁺ of formula (2), for example, basic carbonate; Fe ³⁺ (OH) _3-2z (CO ₃ ) _z · aH ₂ O, makes the reactivity with phosphoric acid water. It has also been found that there is a marked improvement over oxide.

  The compound of formula (1) and / or formula (2) used in the present invention is preferably finer in order to improve the reactivity with phosphoric acid and the reactivity with colloidal silica. The average secondary particle diameter is 1 μm or less, more preferably 0.5 μm or less, and particularly preferably 0.2 μm or less.

  The fine particles as described above can be carried out, for example, by wet pulverization using a bead mill. The bead diameter can be 0.05 to 0.5 mm, particularly preferably 0.05 to 0.2 mm. What is necessary is just to select processing time suitably, and it is 1 to 20 hours normally.

  Production of hydrotalcites of the formula (1) used in the present invention is known, and can be carried out, for example, by a method of coprecipitation by adding an alkali to a water-soluble salt solution of divalent and trivalent metals.

  The basic salt of the metal of the formula (2) can be produced by reacting an aqueous solution of a water-soluble salt of a trivalent metal, an alkali component and an anion component such as sodium carbonate containing both.

  The phosphate used in the present invention is preferably a primary phosphate of Al or Mg. When the amount of colloidal silica added is less than the above range with respect to 100 parts by weight of phosphate, the tension effect is reduced, and the corrosion resistance, insulation, adhesion, and seizure properties are reduced. On the other hand, if the amount is too large, cracks occur in the coating and the corrosion resistance deteriorates.

  When the amount of the compound of the formula (1) or formula (2) used in the present invention is less than the above range, the scavenging ability of free phosphoric acid is insufficient. Thus, the film tension may be reduced.

  The insulating coating agent of the present invention is prepared as a coating treatment solution having an appropriate concentration, and this is applied to a magnetic steel sheet (with an inorganic coating) by an appropriate application means such as a roll coater, and this is applied to an appropriate furnace such as a continuous furnace. Is baked at a temperature of 100 ° C. or higher, preferably 150 to 350 ° C.

Following the drying step of the coating solution, it is preferable to anneal at 750 to 900 ° C. for 2 to 120 seconds in a reducing atmosphere of N ₂ or N ₂ + H ₂ .

  The insulating coating agent of the present invention can be applied not only to a material in which a glass film mainly composed of forsterite is formed by final annealing but also to a material from which the glass film has been removed.

Adhesion amount of the insulating coating is not particularly specified, preferably per both surfaces 1 to 15 g / ^{m 2} (after drying), particularly preferably from 5 to 10 g / ^{m 2.}

  In addition to the above components, the insulating coating agent of the present invention may contain a resin component as an improvement in corrosion resistance. Examples of the resin include resins such as acrylic, alkyd, olefin, styrene, vinyl acetate, epoxy, phenol, polyester, urethane, and melamine, and these are used as a suspension or an aqueous solution. The addition amount of these resin is 5-50 weight part with respect to 100 weight part of primary phosphates.

  Hereinafter, the present invention will be described in more detail based on examples.

[Production of chromium substitute] A mixed aqueous solution of nickel chloride and ferric sulfate (Ni ²⁺ = 1.0 M / L, Fe ³⁺ = 0.4 M / L) and an aqueous sodium hydroxide solution (NaOH = 4 M / L) Using a metering pump, feed the reaction tank with a capacity of 2 liters with overflow at a flow rate of 200 ml / min and 140 ml / min, respectively, with stirring, and adjust the pH to about 7.0 while adjusting the pH with the flow rate of the alkaline aqueous solution. The coprecipitation reaction was maintained at about 40 ° C. After the resulting yellow-green precipitate filtered under reduced pressure, at 0.5M / L aqueous sodium carbonate solution, the filtrate was washed until no white turbidity by adding BaCl ₂ aqueous solution. Thereafter, washing with water, after dispersion in water and mixed with ZrO ₂ beads phi = 0.1 mm, were wet-ground for 15 hours a ball mill. As a result of measuring the particle size distribution of the pulverized product by a laser diffraction method, the average secondary particle size with a cumulative 50% was 0.2 μm. A part of the pulverized product was filtered, dried, and subjected to X-ray diffraction. As a result, it was found that it was a crystal belonging to hydrotalcite having d ₀₀₃ = 7.7 kg. As a result of elemental analysis by ICP and measurement of water of crystallization by CO ₃ and AG-DTA by the AGK method, the chemical composition was as follows.
Ni _0.72 Fe ³⁺ _0.28 (OH) ₂ (CO ₃ ) _0.14 · 0.4H ₂ O

In Example 1, the mixed metal aqueous solution was changed to a mixed aqueous solution of ferrous sulfate and ferric chloride (Fe ²⁺ = 1.0 M / L, Fe ³⁺ = 0.4 M / L), and the reaction pH was set to 8.5. The procedure was the same except that it was used instead. The particle size distribution of the obtained product was 50% in cumulative average secondary particle size of 0.16 μm, identified as hydrotalcites by X-ray diffraction, and d ₀₀₃ was 7.9 mm. The chemical composition was as follows:
_{^{Fe 2+ 0.25 Fe 3+ 0.75 (OH}} ) 2 (CO 3) 0.38 · 0.45H 2 O

3.6 L (about 30 ° C.) of a 1.0 M / L sodium carbonate (Na ₂ CO ₃ ) aqueous solution was placed in a 10 liter reaction vessel, and a ferric sulfate aqueous solution (1.0 M / L) was stirred with a chemi stirrer. (L, about 30 ° C.) 1 liter was added and reacted. The obtained precipitate was filtered, washed with water, dispersed in water, and wet-ground as in Example 1. The 50% cumulative average secondary particle size of this product was 0.12 μm, the crystal structure was amorphous (amorphous) by X-ray diffraction, and the chemical composition was as follows.
Fe ³⁺ (CO ₃ ) _0.42 (SO ₄ ) _0.02 (OH) _2.12 · aH ₂ O [where a = 0.4 to 0.8]

A final finish annealing is performed, and a test piece is formed to a width of 150 mm and a length of 300 mm from a 0.23 mm thick high magnetic flux density directional electrical steel sheet coil on which a glass film mainly composed of forsterite is formed on the steel sheet surface. After cutting and washing with water, strain relief annealing was performed at 850 ° C. for 4 hours. Thereafter, _2% H ₂ SO ₄ aqueous solution, subjected to 15 Byosan'arai at 85 ° C., was prepared a test plate. On this steel sheet surface, 50% concentrated aluminum phosphate 50 ml (solid content 35 g) (free phosphoric acid 7%) and 20% colloidal silica 100 ml (solid content 23 g) 8% concentration of the additive of the present invention Was applied at a rate of 9 g / m ² (after drying) on both sides and baked at 850 ° C. for 30 seconds in a dry N ₂ atmosphere furnace. An insulating coating was formed. Table 1 shows the evaluation results of the obtained electrical steel sheet. Each performance evaluation method is as follows.
<Surface appearance> Evaluated by visual observation and touch.
<Corrosion resistance> It was kept for 3 days in an atmosphere of 50 ° C. and humidity of 98%, the surface rust generation area ratio was obtained visually, and the corrosion resistance was evaluated according to the following criteria.
<Criteria> A: Rust occurrence rate = 0 to 5%, O: Rust occurrence rate = 5-20%, Δ: Rust occurrence rate = 20-50%, X: Rust occurrence rate = 50% or more.
<Peeling resistance> The sample was wound around a cylinder having a diameter of 10 to 70 mm, and the minimum cylindrical diameter when peeling occurred was evaluated as the peeling diameter. ○: 50 mm or less, ×: more than 50 mm [Examples 5 and 6]

In Example 4, the primary phosphate was obtained in Example 1, using primary magnesium phosphate [Example 5] and a mixture of primary aluminum phosphate and primary magnesium phosphate [Example 6]. Table 1 shows the results obtained in the same manner as in Example 4 except for using hydoltalsites (HT).
[Comparative Examples 1 and 2]

In Example 4, the evaluation results in the case of using CrO ₃ chromate as an additive (Comparative Example 1) and in the case of using no additive (Comparative Example 2) are shown in Table 1. As is apparent from Table 1, it can be seen that the hydrotalcite-based or Fe ³⁺ basic salt of the present invention exhibits a performance equal to or higher than that obtained when a chromium compound is added.

The X-ray diffraction pattern of Ni-Fe-CO ₃ type hydrotalcite used for the present invention is shown.

Claims (5)

An insulating coating agent for electrical steel sheets that does not contain chromium, comprising all of the following three components.
[1] 100 parts by weight of a metal primary phosphate,
[2] 35 to 100 parts by weight of colloidal silica in terms of SiO _2,
[3] The following formula (1)

(Wherein M ²⁺ represents at least one divalent metal of Fe, Ni, Co, and Mn, preferably Fe and / or Ni, and M ³⁺ represents at least one trivalent of Fe, Co, and Mn. metal, preferably an ^{Fe, a n-n-valent} anion, preferably OH ^- and / or _CO ^{3 2-} are shown, x and m each following range, 0 <x <0.5, preferably Hydrotalcite that is a solid solution obtained by substituting a part of M ²⁺ of M ²⁺ (OH) ₂ represented by 0.2 <x <0.4, 0 ≦ m <4) with M ³⁺ and / or the following formula (2)

^{(Wherein, M 3+} represents a same trivalent metal and Equation ^{(2), A n-} represents a monovalent or divalent ^{anion, M 3+} and ^{A n-} most preferably each ^{Fe 3+} of the , CO ₃ ^2- , and z is in the following range, 0 <z <2) 0.1 to 50 parts by weight in terms of solid matter of a basic salt of a trivalent metal. The insulating coating agent according to claim 1, wherein the average secondary particle size of component [3] of claim 1 is 0.5 µm or less. The insulating coating agent according to claim 1, wherein M ³⁺ of component [3] of claim 1 is Fe. The insulating coating agent according to claim 1, wherein component [3] of claim 1 is a hydrotalcite represented by formula (1). The hydrotalcite of claim 4 is represented by the following formula (3)

(Wherein x and m are hydrotalcites having a specific composition represented by the following ranges, 0.2 <x <0.4 and 0 <m <4), respectively. Coating agent.

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