JP5978009B2 - INSULATION COATING FORMING LIQUID AND METHOD FOR PRODUCING ELECTRIC STEEL STEEL WITH INSULATING COATING - Google Patents

Description

  The present invention relates to a treatment liquid for forming an insulating film on the surface of an electromagnetic steel sheet, and an electromagnetic steel sheet having an insulating film formed using the treatment liquid. The treatment liquid for forming an insulating film of the present invention does not contain harmful compounds such as hexavalent chromium.

  Insulating coatings for non-oriented electrical steel sheets that are generally used at present are roughly classified into the following three types: (1) Inorganic coatings that emphasize heat resistance and are capable of strain relief annealing, (2) Punchability and welding An organic / organic mixed organic semi-organic film that can be strain-relieved and (3) Organic film that emphasizes punchability and cannot be strain-annealed.

  Of these, insulating films containing inorganic components (1) and (2) that can be subjected to strain relief annealing are widely used. In particular, the semi-organic film (2) has become mainstream because it has much better punchability than inorganic films.

  Hitherto, dichromate has been widely used as a material for forming the inorganic component in the insulating films of the above (1) and (2). An insulating film using dichromate is heated after applying a treatment liquid obtained by mixing an organic reducing agent such as ethylene glycol or glycerin to an aqueous solution containing hexavalent chromium and a polyvalent metal salt on an electrical steel sheet. The coating film is baked, and hexavalent chromium is reduced to trivalent chromium to form a film. Baking is completed in a short time within 1 minute at a temperature of 200 ° C. to 330 ° C. However, due to recent social demands for reducing environmental impact, a non-chromium type insulating film that does not use chromium at all has been demanded.

  As an inorganic component that can be used to form an insulating film as with dichromate, there is a polyvalent metal phosphate that forms a film by a condensation reaction. Since the polyvalent metal phosphate aqueous solution is a system capable of forming a few films as an inorganic component and is obtained at a relatively low cost, it has been conventionally studied as an inorganic component for inorganic and semi-organic insulating films (for example, (See Patent Document 1 below).

  Patent Document 2 listed below proposes an aluminum phosphate-based non-oriented electrical steel sheet-containing surface treatment agent that does not contain chromium. The surface treatment agent described as having excellent coating properties contains an emulsion resin and a small amount of an OH group-containing organic compound in addition to primary aluminum phosphate in water.

  Further, in Patent Documents 3 to 6, the film can be formed at a baking temperature as low as that of the dichromate system, and even in that case, it is necessary for an insulating film for electrical steel sheets such as excellent water resistance, adhesion, and insulation. A phosphate-based treatment liquid having various performances is disclosed.

Japanese Patent Publication No.53-28375 JP-A-11-152579 JP 2001-107261 A JP 2002-47576 A JP 2002-249881 A JP 2008-303411 A

Although many electrical steel sheets having a polyvalent metal phosphate-based non-chrome insulating coating have been put into practical use, the following problems may be pointed out depending on the use environment.
(1) Whitening immediately after production The appearance may become whitish immediately after product production. This is because the treatment liquid for forming the insulating film is acidic, Fe on the steel sheet surface is eluted by the application of the treatment liquid, and binds to phosphate ions in the applied treatment liquid to form iron phosphate. This is probably because of this.

(2) Whitening during storage During coating and storage of the coil, the coating surface may be whitened. Since this is likely to occur when the environment is hot and humid, dew condensation or the like occurs inside the coil, which is considered to be a discoloration caused by this.

(3) Adhesion deterioration after bluing treatment When processing cut or punched electrical steel sheets into products such as motors and transformers, the surface interferes to suppress end face short circuit and improve the rust prevention of the cut / punched end face. The steel sheet may be oxidized (also referred to as blueing) to the extent that it exhibits color. When such bluing treatment is performed, the adhesiveness of the insulating film may be deteriorated.

  An object of the present invention is to provide a treatment liquid for forming an insulating film capable of forming an insulating film not using chromium on the surface of the electromagnetic steel sheet, and the electromagnetic steel sheet provided with such an insulating film, in which the above-described problems are improved. That is.

According to the present invention, the above problem is solved by the following treatment liquid for forming an insulating film:
(1) A treatment liquid for forming an insulating film of an electrical steel sheet having good adhesion after bluing treatment and suppressing whitening of the film, and mainly containing Al and / or Mg in an aqueous medium. An electrical steel sheet comprising a polyvalent metal primary phosphate, a nitric acid compound selected from nitric acid and a polyvalent metal nitrate, and a chelating agent selected from a phosphonic acid compound and pyrophosphoric acid. Treatment liquid for insulating film formation.

  (2) The above-mentioned (1) containing the nitric acid compound in an amount of 5 to 50 parts by mass and the chelating agent in an amount of 5 to 100 parts by mass with respect to 100 parts by mass of the phosphate in terms of solid content. ) A treatment liquid for forming an insulating film on an electrical steel sheet.

  (3) The treatment liquid for forming an insulating film for an electrical steel sheet according to (1) or (2), wherein the polyvalent metal nitrate is a nitrate of at least one metal selected from Zn, Ca, Ba and Sr.

(4) The treatment liquid for insulating film formation of the electrical steel sheet according to (3), wherein the polyvalent metal nitrate is zinc nitrate.
(5) The treatment liquid for forming an insulating film on an electrical steel sheet according to any one of the above (1) to (4), further containing a polyvalent metal hydroxide.

(6) The treatment liquid for forming an insulating film on an electrical steel sheet according to (6), wherein the polyvalent metal hydroxide is strontium hydroxide.
(7) The treatment liquid for insulating film formation of the electrical steel sheet according to (6), wherein the amount of the strontium hydroxide is 5 to 50 parts by mass in terms of solid content with respect to 100 parts by mass of the phosphate.

(8) The treatment liquid for forming an insulating film for an electrical steel sheet according to any one of (1) to (7), further comprising an aqueous resin.
(9) The treatment liquid for insulating film formation of the electrical steel sheet according to (9), wherein the amount of the aqueous resin is 3 to 100 parts by mass in terms of solid content with respect to 100 parts by mass of the phosphate.

In another aspect, the present invention provides an electrical steel sheet with an insulating coating, wherein an insulating film is formed on the surface of the electrical steel sheet using the treatment liquid according to any one of (1) to (9) above . It is a manufacturing method .

  According to the present invention, there is provided an electrical steel sheet provided with a non-chrome type insulating film, in which the above-mentioned problems, namely, whitening immediately after production, whitening during storage, and adhesion deterioration after blueing treatment are suppressed or eliminated. It becomes possible to provide.

  The kind of the electrical steel sheet on which the insulating film is formed on the surface by the treatment liquid of the present invention is not particularly limited. The electromagnetic steel sheet may be non-directional or directional, and may be either a hot-rolled steel sheet or a cold-rolled steel sheet. A general electromagnetic steel sheet is a low carbon steel sheet containing about 0.1 to 5% by mass of Si, but a normal steel sheet containing almost no Si can also be used as the electromagnetic steel sheet.

  In accordance with the present invention, the treatment liquid used to form the insulating film on the magnetic steel sheet contains, in an aqueous medium, a polyvalent metal phosphate containing Al and / or Mg as a main component, nitric acid as an inorganic compound, and a polyvalent metal. It contains a nitric acid compound selected from valent metal nitrates and a phosphonic acid compound and / or pyrophosphoric acid as a chelating agent. This treatment liquid preferably contains no boric acid or borate.

  The aqueous medium that is a solvent may be composed only of water, but a mixed solvent of water and a water-miscible organic solvent (eg, alcohol, ketone, etc.) can also be used. It is preferable to adjust the solid content concentration of the treatment liquid so that a coating-applicable consistency can be obtained, an insulating film having a required film thickness can be formed by one application, and the stability of the application liquid can be maintained.

  By adding a polyvalent metal nitrate to an aqueous solution of a polyvalent metal phosphate containing Al and / or Mg as a main component, the film-forming property of the treatment liquid and the adhesion of the insulating film can be obtained, and as a chelating agent By containing a phosphonic acid compound and / or pyrophosphoric acid, whitening during coating is suppressed.

  Among polyvalent metal primary phosphates, primary aluminum phosphate and primary magnesium phosphate are easy to obtain a high-concentration treatment solution and are industrially inexpensive. Two kinds are used as main components of the polyvalent metal monophosphate. The main component means that 50% by mass or more of the polyvalent metal primary phosphate is occupied. Therefore, 50 mass% or more of the polyvalent metal primary phosphate is the primary phosphate of Al and / or Mg.

  The treatment liquid of the present invention may contain a polyvalent metal primary phosphate other than those described above. In that case, the amount of the primary phosphate of the other polyvalent metal is less than 50% by mass in total, preferably less than 30% by mass, more preferably less than 20% by mass. Examples of other polyvalent metal primary phosphates that can be used include one or more selected from the primary phosphates of Ca, Sr, Ba, and Zn.

Needless to say, the primary phosphate is a metal dihydrogen phosphate, for example, the primary magnesium phosphate is Mg (H ₂ PO ₃ ) ₂ , and the primary aluminum phosphate is Al ( H ₂ PO ₃ ) ₃ However, since the primary phosphate is industrially produced by reacting phosphoric acid (orthophosphoric acid) with an appropriate amount of metal hydroxide, the amount of metal hydroxide can be changed by varying the amount of metal hydroxide. Phosphates with varying atomic ratios can be produced. In the present invention, a divalent metal primary phosphate (eg, primary Mg phosphate) means a metal / P atomic ratio of 0.7 / 2 to 1.2 / 2. A metal primary phosphate (eg, primary Al phosphate) means a metal / P atomic ratio of 0.7 / 3 to 1.2 / 3.

  By adding the polyvalent metal nitrate according to the present invention, the adhesion of the insulating coating is improved, and in particular, the adhesion after the bluing treatment is improved. Preferable nitrates include nitrates of at least one metal selected from Zn, Ca, Ba and Sr. Nitric acid itself can be used instead of or in addition to the polyvalent metal nitrate. A particularly preferred nitrate is zinc nitrate. Accordingly, the polyvalent metal nitrate preferably uses zinc nitrate as at least the main component and optionally contains other polyvalent metal nitrate or nitric acid in an amount of less than 50% by mass. More preferably, the polyvalent metal nitrate is zinc nitrate alone. However, nitric acid or a metal nitrate other than zinc nitrate can be used alone as the nitric acid compound.

  When the insulating film formed by applying the treatment liquid of the present invention to the surface of the magnetic steel sheet and drying it is analyzed, even if the treatment liquid does not contain an Fe component, the presence of Fe is present in the formed insulating film. It is confirmed. The amount of Fe is approximately 0.1 or more in terms of the molar ratio of Fe to P in the film (converted from strength), although it varies depending on the production opportunity, as measured by GDS from the surface. Of course, this Fe is derived from a steel plate. That is, the treatment liquid of the present invention containing a nitric acid compound selected from polyvalent metal nitrate and nitric acid strongly etches the surface of the steel sheet, which is considered to contribute to the improvement of adhesion.

  The content of the nitric acid compound in the treatment liquid of the present invention is preferably in the range of 5 to 50 parts by mass, more preferably in terms of solid content, with respect to 100 parts by mass of the polyvalent metal primary phosphate. 10 to 30 parts by mass. When this content is less than 5 parts by mass, the adhesion of the insulating coating may not be sufficiently improved, and when it exceeds 50 parts by mass, whitening after coating may easily occur.

  It is considered that the chelating agent captures Fe ions eluted in the treating liquid when the treating liquid contains at least one chelating agent selected from a phosphonic acid compound and pyrophosphoric acid. Therefore, even if the steel sheet surface is strongly etched by the treatment liquid containing a nitric acid compound as described above, whitening immediately after production is suppressed. On the other hand, for example, other chelating agents such as ethylenediamine do not have an acid group, and thus react with the primary phosphate ion in the treatment liquid to lose the chelate forming ability or the metal capturing ability.

  Furthermore, by incorporating a chelating agent composed of a phosphonic acid compound and / or pyrophosphoric acid into the condensed phosphoric acid film, a denser insulating film can be formed in combination with the effect of the trapped Fe (polyvalent metal). Presumed.

  Examples of phosphonic acid compounds that act as chelating agents include hydroxyethylidene mono- and di-phosphonic acids, aminotrimethylene phosphonic acids, and the like. The above is only an example, and other compounds can be used. Pyrophosphate is also suitable as a chelating agent.

  The content of these chelating agents is preferably in the range of 5 to 100 parts by mass, more preferably 10 to 70 parts by mass, based on 100 parts by mass of the polyvalent metal primary phosphate, in terms of solid content. is there. If this content is less than 5 parts by mass, the stability of the treatment liquid may not be maintained, and if it exceeds 100 parts by mass, whitening of the steel sheet surface tends to occur.

  The treatment liquid for forming the insulating coating of the present invention comprises the above-described polyvalent metal primary phosphate, polyvalent metal nitrate, phosphonic acid compound and / or pyrophosphoric acid mainly composed of Al and / or Mg. In addition to the chelating agent, it can further contain other components.

Other components that are preferably added to the treatment liquid of the present invention include polyvalent metal hydroxides and water-soluble resins.
When the treatment liquid further contains a polyvalent metal hydroxide, the ratio of the polyvalent metal to the phosphate ions can be increased, and the effect of improving the film formability at low temperature baking can be obtained. Can do. In order to efficiently obtain this effect, the polyvalent metal hydroxide is preferably strontium hydroxide. Strontium hydroxide is easily dissolved in an acid, can be easily made into a solution, and has a great effect of improving the film forming property by baking at a low temperature. In addition, a polyvalent metal hydroxide can also be mix | blended with a process liquid with the form of a metal oxide.

  When the treatment liquid contains strontium hydroxide, the content thereof is preferably in the range of 5 to 50 parts by mass, more preferably 10 in terms of solid content with respect to 100 parts by mass of the polyvalent metal primary phosphate. -30 mass parts. If the content is less than 5 parts by mass, the effect of improving the film formability at low temperature baking cannot be obtained sufficiently. On the other hand, if it exceeds 50 parts by mass, the stability of the treatment liquid may not be maintained.

  The treatment liquid of the present invention can further contain an aqueous synthetic resin. By adding a synthetic resin, a semi-organic film having good punchability can be formed. On the other hand, since the coating tends to deteriorate during the annealing at 700 ° C. to 800 ° C. by adding the synthetic resin, attention must be paid to the amount added. The addition amount of the synthetic resin is preferably in the range of 3 to 100 parts by mass in terms of solid content with respect to 100 parts by mass of the polyvalent metal primary phosphate. When the amount of the synthetic resin is less than 3 parts by mass, improvement in punchability is hardly obtained, and when it exceeds 100 parts by mass, the interlayer resistance after strain relief annealing may be lowered. The amount of the synthetic resin added is more preferably 5 to 70 parts by mass, and still more preferably 10 to 50 parts by mass.

  As the synthetic resin, an aqueous synthetic resin is used because the treatment liquid is aqueous. The aqueous synthetic resin may be any of an emulsion type, a water dispersible type, and a water soluble type. Specific examples of synthetic resins include acrylic resins, acrylic styrene resins, alkyd resins, polyester resins, silicone resins, fluororesins, polyolefin resins, styrene resins, vinyl acetate resins, epoxy resins, phenol resins, urethane resins, melamine resins, etc. It is done. One or more synthetic resins can be added.

  The treatment liquid of the present invention may also contain colloidal silica in order to improve interlayer resistance. The amount of colloidal silica added is preferably 50 parts by mass or less (ie, the Si / P mass ratio is 50 or less) in terms of Si per 100 parts by mass of P in the primary phosphate. If the amount of silica added is excessive, the stability of the treatment liquid may be lost or the surface properties may be impaired. This addition amount is more preferably 2 to 30 parts by mass.

In addition to the above, other additives such as a rust inhibitor, an antifoaming agent, and a treatment liquid stabilizer can be appropriately blended in the treatment liquid as desired.
For example, by adding a rust inhibitor to the treatment liquid for forming an insulating film of the present invention, an electrical steel sheet with an insulating film having excellent rust prevention properties can be obtained during transportation, storage and the like. The rust inhibitor is selected from quaternary imidazolium compounds, polyamine compounds, quinoline compounds, thiocarbonyl compounds, thiazole compounds, mercapto compounds, sulfide compounds, thiocarbamates, pyridinium compounds, thiocyanates and isothiocyanates. 1 type or 2 types or more are mentioned. Of these, quaternary imidazolium compounds and polyamine compounds are preferred.

  On the other hand, it is preferable that the treatment liquid of the present invention does not contain boric acid (or a salt thereof) that has been widely used. This is because although boric acid is not as much as chromium, it can be a component subject to environmental regulations. In this invention, it has the effect regarding the adhesiveness of the membrane | film | coat which conventionally boric acid (salt) has borne by containing nitrate in a process liquid.

  When the treatment liquid of the present invention is used, this is applied to the surface of a magnetic steel sheet as a base material (usually double-sided but can also be applied to one side), heated and baked to form a coating film. As a result, a phosphate insulating film having excellent surface whitening resistance due to elution of the film components is formed.

  The coating method of the treatment liquid is not particularly limited, and various coating methods such as roll coater, curtain flow coater, spray coating, knife coater, and immersion, which are generally used industrially, can be applied.

  The film can be baked by a hot air type, infrared type, induction heating type or the like, which is usually performed, and the baking temperature is similar to that of the conventional dichromate, that is, within a temperature range of 200 to 350 ° C. within 1 minute. The film formation by short-time seizure produces an insulating film with excellent adhesion and surface whitening resistance due to elution of film components, and has a beautiful appearance and good insulation.

  The thickness of the insulating film of the electrical steel sheet is preferably in the range of 0.05 μm or more and 2 μm or less. When the film thickness is less than 0.05 μm, not only uniform coating becomes difficult, but also seizure resistance, corrosion resistance and interlayer resistance during annealing are insufficient. When the film thickness exceeds 2 μm, the improvement in interlayer resistance is saturated and the adhesion of the film is lowered. The upper limit of the film thickness is more preferably 1.5 μm or less. The insulating film is usually formed on both sides of the electrical steel sheet, but can be formed on only one side.

  When interlayer resistance, that is, insulation is mainly required, the film thickness is preferably 0.5 μm or more. On the other hand, for example, when improvement in weldability is required to improve productivity during production of iron cores and rotating machines, a thin film with a thickness of less than 0.5 μm, preferably 0.25 μm or less, is used. Required. Thus, the film thickness can be set according to the performance that is important in the application. The treatment liquid of the present invention can be coated with a thin film, and various performances can be obtained even with a thin film.

  Since the electrical steel sheet having an insulating film formed from the treatment liquid according to the present invention is excellent in punchability, it can be easily punched according to a conventional method. In addition, after forming the iron core by laminating and welding or mechanical integration after punching, it may be subjected to strain relief annealing or bluing treatment at 700 to 800 ° C. before being incorporated into an electrical device. However, after the strain relief annealing and after the bluing treatment, the high adhesion is maintained, the peeling of the insulating film in these treatments is prevented, and the iron core having the predetermined characteristics can be manufactured reliably.

  In order to improve the rust prevention of the punched end face, the bluing process is a process that blows water vapor when the final temperature of the annealing furnace (200 to 300 ° C) or the temperature of the batch type annealing furnace is lowered to generate an oxide film on the steel sheet surface. is there. In addition, strain relief annealing is a process performed to remove the stress generated during the shearing and punching of electrical steel sheets and to obtain the necessary magnetic properties, and incomplete nitrogen gas, argon gas, butane gas, etc. This is performed by soaking in a non-oxidizing atmosphere gas such as carbon monoxide generated by burning at 700 to 800 ° C. for about 2 hours and then gradually cooling.

  The present invention is specifically illustrated by the following examples, but the present invention is not limited by these examples. Unless otherwise specified, “%” and “part” in the examples are “% by mass” and “part by mass” in terms of solid content.

A treatment liquid containing the following components in the proportions shown in Table 1 was prepared. The total solid concentration of the treatment liquid was in the range of 10 to 20%. The ingredients used are as follows:
Polyvalent metal monophosphate: primary aluminum phosphate (Al / P atomic ratio = 0.9 / 3) and primary magnesium phosphate (Mg / P atomic ratio = 0.85 / 2);
Nitrate components: zinc nitrate or nitric acid;
Chelating agent: 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) and / or pyrophosphoric acid;
Water-based resin: Water-soluble acrylic styrene resin (Nippon Gosei Kagaku 6655);
Polyvalent metal hydroxide: strontium hydroxide.

  A roll coater was applied so that the film thickness of the insulating film after baking the treatment liquid on one side of a non-oriented electrical steel sheet having a thickness of 0.5 mm containing 0.3% Si was 0.05 to 2.0 μm. After coating, the coating film was baked by heating in a hot air oven for 30 seconds so that the maximum plate temperature was 300 ° C., and immediately cooled with water and dried to form an insulating film.

  Table 2 shows the results of evaluating the various performances of the electrical steel sheet with an insulating film thus obtained by the following evaluation methods and criteria.

[Stability of processing solution]
After storing the treatment liquid at 50 ° C. for 1 month, the treatment liquid was visually observed and evaluated as follows according to the state of the treatment liquid (whether or not solid matter was generated):
○: Solid matter is not generated,
X: Solid matter is generated.

[Coating appearance (whitening after painting)]
The appearance of the test piece of the electrical steel sheet on which the insulating film was formed by painting was observed visually. Evaluation was made in the following three stages, and ○ was accepted:
○: Clear film (entirely transparent),
X: There is white unevenness partially or entirely.

[Insulating film adhesion]
The following three types of adhesion evaluation methods were implemented. In any adhesion test, ○ or more was considered acceptable.
(A) Initial adhesion A test piece of a magnetic steel sheet with an insulation film having a length of 50 mm and a width of 25 mm was wound around a steel bar having a diameter of 5 mm, and a tape peeling test was performed on the wound outer portion to determine the insulation film remaining on the steel sheet. The situation was investigated. The following four levels were evaluated, and ◎ and ○ were accepted:
A: No film peeling,
○: Film peeling occurred (area ratio is 5% or less),
Δ: Occurrence of film peeling (over 5% in area ratio, 30% or less),
X: Occurrence of film peeling (over 30% in area ratio).

(B) Adhesiveness after bluing treatment A test piece of a magnetic steel sheet with an insulating film having a length of 50 mm and a width of 25 mm was subjected to heat treatment simulating a bluing treatment (DX gas containing about 2 to 4% CO (propane and air The gas is burned in a combustion chamber at a certain ratio and is heated in an atmosphere at a temperature of 450 ° C. to 500 ° C. and a dew point of 35 ° C. to 40 ° C. for 2 hours. The steel strip was wound around an iron bar having a diameter of 10 mm, and a tape peeling test was performed on the wound outer portion to investigate the state of the insulating film remaining on the steel plate.

The following four levels were evaluated, and ◎ and ○ were accepted:
A: No film peeling,
○: Film peeling occurred (area ratio is 5% or less),
Δ: Occurrence of film peeling (over 5% in area ratio, 30% or less),
X: Occurrence of film peeling (over 30% in area ratio).

(C) Adhesiveness after strain relief annealing A test piece of an insulating steel sheet with an insulating film having a length of 50 mm and a width of 25 mm was subjected to heat treatment simulating strain relief annealing (heating in a nitrogen atmosphere at 750 ° C. for 2 hours, and then in a nitrogen atmosphere) The film was wound around an iron bar having a diameter of 10 mm with the film facing outward, and a tape peeling test was performed on the wound outer part to investigate the state of the insulating film remaining on the steel sheet. . The following four levels were evaluated, and ◎ and ○ were accepted:
A: No film peeling,
○: Film peeling occurred (area ratio is 5% or less),
Δ: Occurrence of film peeling (over 5% in area ratio, 30% or less),
X: Occurrence of film peeling (over 30% in area ratio).

[Surface whitening resistance during storage]
Apply a seal tape with a width of 5mm to the end face of the back surface and the front surface (film formation surface) on the test piece of insulating steel sheet with insulation film punched out to 55mm x 55mm (the film exposed area is a square of 50mm x 50mm) After immersion in ion-exchanged water at 50 ° C. and applying ultrasonic waves for 1 hour, the film was taken out and the appearance when the film was dried and the P amount after ultrasonic immersion / initial P amount (film remaining amount) were measured. Each was evaluated in the following four stages.

appearance:
○: Whitening, no color irregularity, beautiful appearance,
X: There is white unevenness partially or entirely.

Amount of remaining film:
A: 98% or more remaining,
○: 95% or more remaining
Δ: 90% or more and less than 95% remaining,
X: Remaining less than 90%.

  As can be seen from Table 2, when the insulating film was formed from the treatment liquid of the example according to the present invention, a test result that passed all the test items was obtained. On the other hand, when the insulating film was formed from the treatment liquid of the comparative example not containing one or both of the nitric acid compound and the chelating agent, at least one test item was unsatisfactory. Further, instead of the nitric acid component, it has been used conventionally, but compared to the treatment solutions of comparative examples No. 31 to 34 using boric acid, which is environmentally concerned, the treatment solutions of the examples are: In particular, the adhesion after bluing was excellent.

  According to the present invention, not only a chromium compound such as a dichromic acid compound but also a boric acid compound that is concerned about environmental problems is used. By using this, it becomes possible to form on the surface of the electrical steel sheet an insulating film exhibiting performance superior to that of using a boric acid compound.

Claims (10)

A treatment liquid for forming an insulating film of an electrical steel sheet having good adhesion after bluing treatment and suppressing whitening of the film, wherein the polyvalent metal is mainly composed of Al and / or Mg in an aqueous medium. An insulating film for an electrical steel sheet, comprising: a first phosphate, a nitric acid compound selected from nitric acid and polyvalent metal nitrate, and a chelating agent selected from phosphonic acid compounds and pyrophosphoric acid Forming treatment liquid (except when it contains a nonionic surfactant) .   It is content of solid content conversion, The said nitric acid compound is contained in the quantity of 5-50 mass parts and the said chelating agent in the quantity of 5-100 mass parts with respect to 100 mass parts of said phosphates. Treatment liquid for insulating film formation of electrical steel sheets.   The treatment liquid for forming an insulating film on an electrical steel sheet according to claim 1 or 2, wherein the polyvalent metal nitrate is a nitrate of at least one metal selected from Zn, Ca, Ba and Sr.   The treatment liquid for forming an insulating film on a magnetic steel sheet according to claim 3, wherein the polyvalent metal nitrate is zinc nitrate.   Furthermore, the processing liquid for insulation film formation of the magnetic steel sheet in any one of Claims 1-4 containing a polyvalent metal hydroxide.   The treatment liquid for forming an insulating film on an electrical steel sheet according to claim 5, wherein the polyvalent metal hydroxide is strontium hydroxide.   The treatment liquid for forming an insulating film on an electrical steel sheet according to claim 6, wherein the amount of the strontium hydroxide is 5 to 50 parts by mass in terms of solid content with respect to 100 parts by mass of the phosphate.   Furthermore, the processing liquid for insulating film formation of the electromagnetic steel sheet in any one of Claims 1-7 containing aqueous resin.   The processing liquid for insulating film formation of the electrical steel sheet according to claim 8, wherein the amount of the aqueous resin is 3 to 100 parts by mass in terms of solid content with respect to 100 parts by mass of the phosphate. An insulating coating film is formed on the surface of the electromagnetic steel sheet using the treatment liquid according to claim 1.