阅读说明：本技术 绝缘覆膜形成用处理液的制造方法和带有绝缘覆膜的钢板的制造方法以及绝缘覆膜形成用处理液的制造装置 (Method for producing treatment liquid for forming insulating coating, method for producing steel sheet with insulating coating, and apparatus for producing treatment liquid for forming insulating coat) 是由 寺岛敬 国府花梨 渡边诚 高宫俊人 于 2019-06-27 设计创作，主要内容包括：本发明的目的在于提供能够稳定地应用提高耐吸湿性、赋予张力的技术的绝缘覆膜形成用处理液的制造方法以及使用绝缘覆膜形成用处理液的带有绝缘覆膜的电磁钢板的制造方法,该绝缘覆膜形成用处理液是含有磷酸根离子和金属化合物的形成磷酸盐覆膜的处理液。其特征在于,将液体A与液体B混合,所述液体A含有以PO-4～(3-)换算计为0.20mol/L以上且10mol/L以下的磷酸和/或磷酸盐、并且含有以金属换算计小于0.50mol/L的粒状的金属化合物,所述液体B含有以金属换算计为0.50mol/L以上且20.0mol/L以下的粒状的金属化合物、并且含有以PO-4～(3-)换算计小于0.20mol/L的磷酸和/或磷酸盐,在液体A与液体B的混合开始后60秒以内利用涡轮定子型高速搅拌机以涡轮外周部的圆周速度为10m/s以上的方式进行搅拌。(The purpose of the present invention is to provide a treatment for forming an insulating coating film, which can stably apply a technique for improving moisture absorption resistance and imparting tensionA method for producing a liquid and a method for producing an electromagnetic steel sheet with an insulating coating using a treatment liquid for forming an insulating coating, the treatment liquid for forming an insulating coating being a treatment liquid for forming a phosphate coating containing a phosphate ion and a metal compound. Characterized in that a liquid A and a liquid B are mixed, the liquid A contains PO 4 3‑ 0.20mol/L to 10mol/L phosphoric acid and/or phosphate in terms of metal, and less than 0.50mol/L granular metal compound, and the liquid B contains 0.50mol/L to 20.0mol/L granular metal compound in terms of metal, and PO 4 3‑ Phosphoric acid and/or phosphate in an amount of less than 0.20mol/L is stirred by a turbine stator type high-speed stirrer within 60 seconds after the start of mixing of the liquid A and the liquid B so that the peripheral speed of the outer periphery of the turbine is 10m/s or more.)

1. A process for producing a treatment liquid for forming an insulating coating film, the treatment liquid containing phosphoric acid and/or a phosphate and a particulate metal compound,

mixing liquid A with liquid B, the liquid A containing PO₄ ^3-0.20mol/L to 10mol/L phosphoric acid and/or phosphate in terms of metal, and less than 0.50mol/L granular metal compound, and the liquid B contains 0.50mol/L to 20.0mol/L granular metal compound in terms of metal, and PO₄ ^3-Less than 0.20mol/L in terms of phosphoric acid and/or phosphate,

stirring is performed by a turbine stator type high-speed stirrer within 60 seconds after the start of mixing of the liquid A and the liquid B so that the peripheral speed of the outer periphery of the turbine is 10m/s or more.

2. The method for producing a treatment liquid for forming an insulating coating according to claim 1, wherein after the stirring by the high-speed stirrer, a dispersion treatment is further performed by a high-pressure disperser at a pressure of 20MPa or more.

3. The method for producing the treatment liquid for forming an insulating film according to claim 1 or 2, wherein the treatment liquid for forming an insulating film further contains colloidal silica.

4. The method for producing the treating liquid for forming an insulating coating according to any one of claims 1 to 3, wherein the granular metal compound contains one or two or more elements selected from Mg, Al, Ti, Zn, Y, Zr, and Hf.

5. The method for producing a treating liquid for forming an insulating coating according to any one of claims 1 to 4, wherein the particulate metal compound contains at least one oxide.

6. The method for producing the treatment liquid for forming an insulating coating according to any one of claims 1 to 4, wherein the particulate metal compound contains at least one nitride.

7. The method for producing the treatment liquid for forming an insulating coating according to any one of claims 1 to 6, wherein the particle diameter of the particulate metal compound is 3.0nm or more and 2.0 μm or less.

8. A method for producing a steel sheet with an insulating coating, comprising applying the treating liquid for forming an insulating coating obtained by the production method according to any one of claims 1 to 7 to a surface of a steel sheet, and then carrying out a sintering treatment.

9. The method for producing a steel sheet with an insulating coating according to claim 8, wherein the steel sheet is a grain-oriented electrical steel sheet.

10. A device for producing a treatment liquid for forming an insulating coating film, comprising a mixing tank for mixing a liquid A containing PO and a liquid B containing PO, and a turbine stator type high-speed stirrer₄ ^3-0.20mol/L to 10mol/L phosphoric acid and/or phosphate in terms of metal, and less than 0.50mol/L granular metal compound, and the liquid B contains 0.50mol/L to 20.0mol/L granular metal compound in terms of metal, and PO₄ ^3-Less than 0.20mol/L in terms of phosphoric acid and/or phosphate,

stirring is performed by a turbine stator type high-speed stirrer within 60 seconds after the start of mixing of the liquid A and the liquid B so that the peripheral speed of the outer periphery of the turbine is 10m/s or more.

11. The apparatus for producing a treatment liquid for forming an insulating coating according to claim 10, further comprising a circulation path for circulating the liquid stirred by the high-speed stirrer to the mixing tank.

12. The apparatus for producing a treatment liquid for forming an insulating coating according to claim 10 or 11, further comprising a particle size distribution measuring device for measuring a particle size distribution of the liquid stirred by the high-speed stirrer.

Technical Field

The present invention relates to a method for producing an insulating coating treatment liquid containing phosphate ions and a metal compound, a method for producing a steel sheet with an insulating coating, and an apparatus for producing a treatment liquid for forming an insulating coating.

Background

Generally, as an insulating film having heat resistance, a phosphate film based on a phosphate of a polyvalent metal such as Al, Mg, and Ca is known. In order to impart insulation properties, workability, rust resistance, and the like, grain-oriented electrical steel sheets are generally provided with a base coating mainly composed of forsterite formed during final finish annealing and a phosphate-based surface coating formed thereon.

These coatings are formed at high temperatures and have low thermal expansion coefficients, and therefore, the difference in thermal expansion coefficient between the steel sheet and the coating when the steel sheet is lowered to room temperature gives tension to the steel sheet, which has the effect of reducing the iron loss. Therefore, it is desirable to impart as high a tension as possible to the steel sheet.

In order to meet such a demand, various coatings have been proposed. For example, patent document 1 proposes a coating mainly composed of magnesium phosphate and colloidal silica. Patent document 2 proposes a coating mainly composed of aluminum phosphate, colloidal silica, and one or more of chromic anhydride and chromate. In either of these documents, chromic acids such as chromic anhydride, chromate, dichromate, and the like are used to reduce the thermal expansion coefficient in order to avoid deterioration of moisture absorption resistance peculiar to phosphate coatings.

On the other hand, in recent years, attention to environmental protection has been increased, and there is an increasing demand for products that do not contain harmful substances such as chromium and lead, and development of chromium-free coatings has also been desired for grain-oriented electrical steel sheets. However, in the case of a chromium-free coating, there are problems that the moisture absorption resistance is remarkably reduced and the tension is not sufficiently applied, and therefore, the coating cannot be made chromium-free.

As a method for solving the problems of the decrease in the moisture absorption resistance and the insufficient tension application, patent document 3 discloses a method of adding an oxide colloidal substance to a phosphate or colloidal silica. Patent document 4 discloses a technique of including a colloidal compound containing a metal element such as Fe, Al, Ga, Ti, or Zr in a phosphate or colloidal silica. Patent document 5 discloses a method of adding Al to phosphate or silica₂O₃、TiO₂、ZrO₂Techniques for such particles. Patent document 6 discloses a technique of including fine particles of a zirconium phosphate compound in a phosphate or colloidal silica. Patent document 7 discloses a technique of containing a metal phosphate, colloidal silica nanoparticles, hollow nanoparticles, ceramic nanofibers, and mesoporous nanoparticles.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 50-79442

Patent document 2: japanese laid-open patent publication No. Sho 48-39338

Patent document 3: japanese patent laid-open publication No. 2000-1699972

Patent document 4: japanese patent laid-open publication No. 2007-23329

Patent document 5: japanese Kokai publication No. 2017-511840

Patent document 6: japanese patent laid-open publication No. 2017-137540

Patent document 7: japanese Kohyo publication No. 2018-504516

Disclosure of Invention

Problems to be solved by the invention

However, the techniques described in patent documents 3 to 7 have large variations in moisture absorption resistance and applied tension, and thus good characteristics cannot be stably obtained.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for producing a treatment liquid for forming an insulating coating, which is a treatment liquid for forming an insulating coating containing phosphoric acid and/or a phosphate and a particulate metal compound, capable of stably applying a technique for improving moisture absorption resistance and imparting tension, a method for producing a steel sheet with an insulating coating using the treatment liquid for forming an insulating coating, and an apparatus for producing the treatment liquid for forming an insulating coating.

Means for solving the problems

In order to solve the above problems, the present inventors have conducted extensive studies on a particulate metal compound (ZrO)₂: average particle diameter of 100nm) is added to a treating liquid for forming an insulating film based on phosphoric acid and/or a phosphate to form a film, thereby obtaining good characteristics (film tension of 8.0MPa or more, phosphorus elution amount of 150[ mu ] g/150 cm)²Below) and a steel sheet sample in which no good characteristics were obtained were compared, and the following findings were obtained.

The results of observing the surface of the steel sheet sample with good properties by SEM are shown in fig. 1, and the results of observing the surface with SEM are shown in fig. 2Results of the surface of the well-worked steel plate samples. On the surface of the steel sheet sample which did not obtain a good result, a plurality of convex portions and cracks accompanying the convex portions were found. Accordingly, the present inventors have found out the cause of the formation of the convex portion and found ZrO in the convex portion₂Large aggregates of (a). Further, the reason for the formation of the aggregate was examined and found to be due to the fact that a phosphate ion-containing aqueous solution such as an aluminum phosphate aqueous solution or a magnesium phosphate aqueous solution, which is a raw material of the treatment liquid for forming the insulating film, and ZrO is dispersed therein₂When the liquid of the particles is mixed, ZrO may be present due to pH fluctuation or the like₂The particles aggregate.

In order to avoid such aggregation, coating treatment of the particle surface of the granular metal compound or the like is considered depending on the properties of components in the treatment liquid to be prepared. However, excessive attempts are required, and even if development is possible, the manufacturing cost increases. Therefore, as an inexpensive method, a method of producing an insulating film treatment liquid capable of stably reducing the aggregate density of the surface of a steel sheet after coating and sintering to such an extent that the insulating film performance is not lowered has been considered, and the present invention has been completed. The aggregate density of the steel sheet surface after coating and sintering was 1.0 piece/10000 μm to such an extent that the insulating coating performance was not lowered²The following.

That is, the gist of the present invention is as follows.

[1] A process for producing a treatment liquid for forming an insulating coating film, the treatment liquid containing phosphoric acid and/or a phosphate and a particulate metal compound,

mixing liquid A with liquid B, the liquid A containing PO₄ ^3-0.20mol/L to 10mol/L phosphoric acid and/or phosphate in terms of metal, and less than 0.50mol/L granular metal compound, and the liquid B contains 0.50mol/L to 20.0mol/L granular metal compound in terms of metal, and PO₄ ^3-Less than 0.20mol/L in terms of phosphoric acid and/or phosphate,

stirring is performed by a turbine stator type high-speed stirrer within 60 seconds after the start of mixing of the liquid A and the liquid B so that the peripheral speed of the outer periphery of the turbine is 10m/s or more.

[2] The method for producing the treating liquid for forming an insulating film according to [1], wherein the treating liquid is stirred by the high-speed stirrer and then subjected to a dispersion treatment by a high-pressure disperser at a pressure of 20MPa or more.

[3] The method for producing the treatment liquid for forming an insulating film according to [1] or [2], wherein the treatment liquid for forming an insulating film further contains colloidal silica.

[4] The method for producing the treating liquid for forming an insulating film according to any one of [1] to [3], wherein the granular metal compound contains one or two or more elements selected from Mg, Al, Ti, Zn, Y, Zr, and Hf.

[5] The method for producing a treating liquid for forming an insulating coating according to any one of [1] to [4], wherein the granular metal compound contains at least one oxide.

[6] The method for producing the treatment liquid for forming an insulating film according to any one of [1] to [4], wherein the granular metal compound contains at least one nitride.

[7] The method for producing the treatment liquid for forming an insulating film according to any one of [1] to [6], wherein the particle size of the particulate metal compound is 3.0nm or more and 2.0 μm or less.

[8] A method for producing a steel sheet with an insulating film, wherein a treatment liquid for forming an insulating film obtained by the production method according to any one of [1] to [7] is applied to the surface of the steel sheet, and then a sintering treatment is performed.

[9] The method for producing a steel sheet with an insulating coating according to [8], wherein the steel sheet is a grain-oriented electrical steel sheet.

[10]A device for producing a treatment liquid for forming an insulating coating film, comprising a mixing tank for mixing a liquid A containing PO and a liquid B containing PO, and a turbine stator type high-speed stirrer₄ ^3-0.20mol/L to 10mol/L phosphoric acid in terms ofAnd/or a phosphate, and contains a particulate metal compound of less than 0.50mol/L in terms of metal, and the liquid B contains a particulate metal compound of 0.50mol/L to 20.0mol/L in terms of metal, and contains PO₄ ^3-Less than 0.20mol/L in terms of phosphoric acid and/or phosphate,

stirring is performed by a turbine stator type high-speed stirrer within 60 seconds after the start of mixing of the liquid A and the liquid B so that the peripheral speed of the outer periphery of the turbine is 10m/s or more.

[11] The apparatus for producing a treatment liquid for forming an insulating coating according to [10], further comprising a circulation path for circulating the liquid stirred by the high-speed stirrer to the mixing tank.

[12] The apparatus for producing a treatment liquid for forming an insulating coating according to [10] or [11], further comprising a particle size distribution measuring device for measuring a particle size distribution of the liquid stirred by the high-speed stirrer.

Effects of the invention

According to the present invention, it is possible to produce a treatment liquid for forming an insulating film that does not generate aggregates that degrade film performance on the surface after coating and sintering, and to stably obtain an insulating film that is resistant to moisture absorption and has high tensile strength at low cost.

Drawings

Fig. 1 is a result of observing the surface of a steel sheet sample with good characteristics by SEM.

Fig. 2 is a result of observing the surface of a steel sheet sample in which no good characteristics were obtained by SEM.

Fig. 3 is a schematic view showing a manufacturing apparatus of the treatment liquid for forming an insulating coating film of the present invention.

Detailed Description

The following describes experimental results that form the basis of the present invention.

As a material for applying and sintering the treatment liquid for forming an insulating film, a grain-oriented electrical steel sheet having a forsterite film after finish annealing and having a sheet thickness of 0.23mm, which is manufactured by a known method, was used. Insulating coating film formationThe treatment liquid was produced by the following method. First, as the liquid A, 30g of magnesium dihydrogen phosphate aqueous solution in terms of solid content and 20g of colloidal silica in terms of solid content were mixed in 250ml of pure water. At this time, the phosphate ion content in the liquid A was 1.10mol/L, and no granular metal compound was added. Further, as the liquid B, a granular metal compound was prepared as a solid component (ZrO)₂) ZrO converted to 15 mass%₂150ml of sol. At this time, the particulate metal compound in the liquid B was 1.36mol/L in terms of metal (Zr), and no phosphate ion was added. Then, the liquid a and the liquid B were mixed by two stirring methods described in table 1, thereby producing a treatment liquid for forming an insulating film.

As the propeller mixer, a mixer having a propeller type mixing blade of phi 100mm attached to a Tornado type mixer manufactured by AS ONE was used at 3000 rpm. In addition, as a turbine stator type agitator, a laboratory mixer L5MA manufactured by SILVERSON was used at 5000 rpm. Further, the rotating bodies of these mixers are different in size, and the number of revolutions is set for each mixer so that the peripheral speed of the tip end of the rotating body is 15.7 m/s.

The total weight of the two surfaces of the prepared treatment solution was dried to give a weight per unit area of 10g/m²Coating is performed in the manner of (1). Next, the film was dried at 300 ℃ for 1 minute in a drying furnace, and then subjected to heat treatment (800 ℃ for 2 minutes, N) which was used as both planarization annealing and sintering of the insulating film₂100%). Then, test pieces for test described later were cut by shearing. Further, the test piece for the tensile test was subjected to stress relief annealing (800 ℃ C., 2 hours, N)₂100% atmosphere).

The thus obtained sample was examined for the imparting tension and moisture absorption resistance. The applied tension is set to be a tension in the rolling direction. One surface of a test piece having a rolling direction length of 280mm × a rolling perpendicular direction length of 30mm was masked with an adhesive tape so as not to remove the insulating coating, and then one surface of the insulating coating was peeled off and removed with an aqueous sodium hydroxide solution, and then one end of the test piece was fixed at 30mm, and a portion of the test piece of 250mm was used as a measurement length, and the amount of warpage was measured, and the applied tension was calculated using the following formula (I).

Tension applied to steel sheet [ MPa ]]Young's modulus [ GPa ] of steel plate]X sheet thickness of [ mm]X amount of warping (mm)]Div (length of measurement [ mm ]])²×10³… formula (I)

The Young's modulus of the steel sheet was 132 GPa. The applied tension was evaluated as good (excellent film tension) at 8.0MPa or more.

The moisture absorption resistance was evaluated by a phosphorus elution test. In this test, three test pieces 50mm X50 mm were boiled in distilled water at 100 ℃ for 5 minutes to measure the amount of phosphorus released [ μ g/150cm ]²]The ease of dissolution of the insulating film in water was evaluated. The amount of P (phosphorus) eluted was 150[ mu.g/150 cm²]The following is good (excellent in moisture absorption resistance). The method for measuring the amount of P eluted is not particularly limited, and the amount of P eluted can be measured by quantitative analysis based on ICP emission spectroscopy, for example.

The measurement results of the applied tension and the amount of phosphorus released are shown in Table 1.

[ Table 1]

As is clear from the results in table 1, by preparing the treatment liquid for forming an insulating film using a turbine stator type stirrer, an insulating film having excellent tensile strength and moisture absorption resistance can be obtained.

Next, the reason for limiting each constituent element of the present invention will be described.

First, a method for producing the treatment liquid for forming an insulating film of the present invention will be described. The treatment liquid for forming an insulating film needs to contain phosphate ions (phosphoric acid and/or phosphate) and a particulate metal compound. Phosphate ions (phosphoric acid and/or phosphate) are an essential component for forming a skeleton of the insulating coating film by polymerization through a dehydration condensation reaction during the drying and sintering process. The phosphoric acid formed by polymerization is easily hydrolyzed by reaction with moisture in the atmosphere and the like, and has poor resistance to moisture absorption, but the hydrolysis reaction can be suppressed by containing a particulate metal compound. Therefore, in the present invention, a granular metal compound is an essential component.

Phosphate ions are easily physically and chemically adsorbed on the surface of the particulate metal compound, and if the both are inadvertently mixed, the particulate metal compound is aggregated, and therefore, the content thereof needs to be limited in advance in the liquid before mixing (raw material liquid).

Since phosphate ions can take various forms in an aqueous solution, they include not only PO₄ ^3-And also includes HPO₄ ^2-、H₂PO₄ ^-Hydrogen phosphate ions, and the like.

Therefore, in the present invention, the liquid A containing PO as PO and the liquid B as liquids before mixing (raw material liquids)₄ ^3-0.20mol/L to 10mol/L phosphoric acid and/or phosphate in terms of metal, and less than 0.50mol/L granular metal compound, and the liquid B contains 0.50mol/L to 20.0mol/L granular metal compound in terms of metal, and PO₄ ^3-Less than 0.20mol/L phosphoric acid and/or phosphate in conversion.

In liquid A, phosphoric acid and/or phosphate is PO₄ ^3-When the amount is less than 0.20mol/L, the amount of phosphate ions in the liquid after the stirring, mixing and dispersing treatment described later is small, and a film having a sufficient thickness cannot be formed, and thus the insulation properties are deteriorated. In another aspect, the phosphoric acid and/or phosphate is PO₄ ^3-When the amount is more than 10.0mol/L, the phosphate ions are present in excess, and therefore it is difficult to disperse the metal compound in the form of particles even by the stirring treatment of the present application. Thus, in the liquid A, phosphoric acid and/or phosphate is/are converted into PO₄ ^3-Converted into 0.20mol/L to 10.0 mol/L. In addition, in the liquid A, it is necessary to make the particulate metal compound less than 0.50mol/L in terms of metal. When the metal compound is contained in a granular form in an amount of 0.50mol/L or more in terms of metal, an aggregate is formed. Preferably less than 0.30 mol/L.

Also, in the liquid B, it is necessary to use phosphoric acidAnd/or phosphates with PO₄ ^3-The conversion is less than 0.20 mol/L. If the amount of the particulate metal compound in the liquid B is less than 0.50mol/L, the amount of the liquid used for mixing the particulate metal compound in an amount sufficient for phosphate ions increases, and the concentration of phosphate ions in the mixed liquid becomes too low, so that a coating film having a sufficient thickness cannot be formed, and the insulation properties deteriorate. On the other hand, when the amount of the particulate metal compound exceeds 20.0mol/L, the distance between the particulate metal compounds in the treatment liquid becomes too close to each other, and aggregation is likely to occur. Therefore, in the liquid B, the particulate metal compound is set to 20.0mol/L or less, preferably 18.0mol/L or less.

In order to avoid the possibility of aggregation, it is desirable to prepare the phosphoric acid and/or the phosphate salt and the particulate metal compound separately as respective liquids without controlling the stirring. Phosphoric acid and/or phosphoric acid salt is PO₄ ^3-When the amount is less than 0.20mol/L in terms of metal or the amount of the particulate metal compound is less than 0.50mol/L in terms of metal, the metal compound can be mixed into the same liquid without aggregation regardless of the mixing or stirring method. Preferably, the particulate metal compound is less than 0.30mol/L in terms of metal.

By preparing the liquid a and the liquid B separately and mixing them by the following method, aggregation of the particulate metal compound by the phosphate ions can be prevented, and the dispersion can be achieved to such an extent that aggregates that degrade the coating performance do not occur on the surface after coating and sintering. Further, the liquid a and the liquid B may be mixed with each other in advance without fear of aggregation. For example, colloidal silica or the like may be previously mixed in the liquid a or the liquid B, and the stirring method in this case is not particularly limited, and a general-purpose mixing method such as a propeller stirrer or a magnetic stirrer or a stirring bar in a laboratory scale is sufficient.

When the liquid a and the liquid B are mixed, it is necessary to stir the mixture with a turbine stator type (also referred to as a rotor stator type) high-speed stirrer within 60 seconds after the start of the mixing. If the stirring is not performed for more than 60 seconds from the start of the mixing, the aggregation of the granular metal compound becomes strong, and the aggregated granular metal compound is difficult to disperse even if the stirring is performed by a turbine stator type high-speed stirrer. More preferably within 45 seconds. The liquid a and the liquid B may be stirred by a turbine stator type high-speed stirrer within 60 seconds after the start of mixing. Therefore, as shown in FIG. 3, a tank for liquid A (tank A) and a tank for liquid B (tank B) may be prepared, and the single substance or the substance mixed in the middle from the tank A and the tank B may be transferred to the high-speed mixer. The liquid mixture tank in which the liquid a and the liquid B are mixed may be connected to a turbine stator type high-speed stirrer via a pipe or the like, for example. In addition, when a connection portion such as a pipe is provided, the flow rate and the flow path may be appropriately designed so that the stirring is performed by the high-speed stirrer within 60 seconds or less after the start of the mixing of the liquid a and the liquid B.

Further, the system may further include a circulation path for introducing the liquid stirred by the high-speed stirrer from the mixing tank into the high-speed stirrer again to circulate the liquid. By circulating the stirred liquid, a sufficient dispersion state can be obtained even for a raw material which is difficult to disperse.

The dielectric dispersion machine such as a bead mill may be contaminated with impurities as an apparatus for dispersing a particulate metal compound for mixing, and is not suitable for producing an insulating coating treatment liquid by stirring liquid a and liquid B with a turbine stator type high-speed stirrer, and then leaving it to stand, stirring by a usual method, stirring with a turbine stator type high-speed stirrer, or the like until coating. In the case of a turbine stator type high-speed stirrer, the medium-free disperser is suitable for the present invention because only the liquid that has passed through the stator is collected, and the treated portion (liquid that has passed through the stator) and the untreated portion (liquid that has not passed through the stator) can be reliably separated. The faster the peripheral speed of the leading end portion of the stirring blade is, the more preferable. In the present invention, the peripheral speed of the turbine outer peripheral portion is set to 10m/s or more. Preferably, the peripheral speed of the turbine outer peripheral portion is 40m/s or more.

Examples of the turbine stator type High-speed stirrer include a High shear mixer manufactured by SILVERSON, a Cavitron manufactured by pacifier corporation (High performance emulsification and dispersion machine), and Quadro Ytron Z manufactured by POWREX corporation (emulsification and dispersion machine).

The start of mixing of the liquid a and the liquid B means that the liquid a and the liquid B start to contact each other.

Further, when it is desired to increase the degree of dispersion of the particulate metal compound, it is preferable to treat the metal compound with a high-pressure disperser after treating the metal compound with a turbine stator type high-speed stirrer. The high-pressure dispersing MACHINE is a device for dispersing solids by applying a high pressure to a liquid to be treated and then applying a shearing force or the like to the liquid at the time of releasing the pressure, and examples of commercially available devices include a Star Burst (wet micronizing device) manufactured by SUGINO MACHINE corporation, a NanoVater (Nano dispersing device) manufactured by yokokuwa shiji co, and a Nano Jet Pul (wet Jet mill) manufactured by kokuwa koku corporation. The higher the pressure at the time of treatment, the better, the more preferably 20MPa or more, and the more preferably 50MPa or more.

In the present invention, the particle size distribution measuring apparatus may further include a particle size distribution measuring device for measuring a particle size distribution of the liquid stirred by the high-speed stirrer. The particle size distribution measuring apparatus is not particularly limited, and when the particle size distribution is measured on line, for example, a particle size distribution measuring apparatus using ultrasonic waves is exemplified. When a high-pressure disperser is provided, a particle size distribution measuring device may be provided to measure the particle size distribution of the liquid treated by the high-speed disperser. In order to set the measured value of the particle size distribution within a predetermined range, it is more preferable to feed back the operating conditions of the high-speed stirrer and the high-pressure disperser (see fig. 3).

In the present invention, the treatment liquid for forming an insulating film may further contain colloidal silica in order to increase the applied tension. The colloidal silica may be contained in the liquid a and/or the liquid B, or may be contained when the liquid a and the liquid B are mixed. Alternatively, the liquid a and the liquid B may be contained after mixing (both before and after the dispersion treatment). In addition, the colloidal silica may be contained plural times. As colloidal silica content relative to PO₄ ^3-Phosphoric acid and/or phosphate in terms of 100 parts by mass, preferably SiO₂The content of the solid component is 60 to 200 parts by mass in terms of solid content.

As the phosphate ion source used in the liquid a and the liquid B, orthophosphoric acid (H) is preferably used₃PO₄) An aqueous solution, or one or more than two kinds of phosphates selected from Mg, Ca, Ba, Sr, Zn, Al and Mn. Phosphates of alkali metals (Li, Na, K, etc.) are not suitable because of their significantly poor resistance to moisture absorption. Generally, one kind of phosphate is used, but by using two or more kinds of phosphates in a mixture, the physical property values of the insulating film (coating) can be strictly controlled. As the kind of phosphate, biphosphate (biphosphate) is easily available, and is therefore preferable.

The granular metal compound is preferably a granular metal compound of a metal element having a large valence or a small ionic radius from the viewpoint of the ability of replenishing the phosphate ion, and specifically preferably contains one or two or more elements selected from Mg, Al, Ti, Zn, Y, Zr, and Hf. The form of the particulate metal compound is preferably an oxide or a nitride, and among them, a metal compound which hardly reacts with water is more preferable. It is to be noted that boron (B), silicon (Si), germanium (Ge), arsenic (As), antimony (Sb), and tellurium (Te) are semimetals and are not included in the metal.

The particle size of the particulate metal compound is preferably smaller because the smaller the particle size, the larger the specific surface area, from the viewpoint of the ability of the particulate metal compound to replenish phosphate ions. On the other hand, from the viewpoint of surface energy, the larger the particle diameter, the more the dispersibility of the particulate metal compound in the treatment liquid for forming an insulating film is improved. Therefore, in the present invention, the particle diameter of the particulate metal compound is preferably set to 3.0nm or more and 2.0 μm or less. Here, the particle diameter is not a particle diameter when the metal compound is aggregated in the treatment liquid, but an average particle diameter when the particle diameter of one particle is observed and imaged by SEM or TEM and the area thereof is changed to an equivalent circle. The particles in which the primary particles are sintered to be integrated are regarded as one particle.

The thus obtained insulating coating film is used for formationThe treatment liquid is applied to the surface of the steel sheet and sintered to form an insulating film. The total weight per unit area after sintering of the insulating coating is preferably set to 4.0 to 30g/m². Less than 4.0g/m²When the amount of the polymer is too small, the interlayer resistance is lowered and exceeds 30g/m²When the pressure is higher than the set pressure, the pressure-superposition coefficient is reduced. More preferably 4.0 to 15g/m²。

The sintering of the insulating coating is also used as the flattening annealing, and is preferably set to a soaking time of 10 to 300 seconds in a temperature range of 800 to 1000 ℃. When the sintering temperature is too low or the soaking time is too short, the planarization is insufficient and the shape is defective, so that the yield is lowered. On the other hand, when the sintering temperature is too high or the soaking time is too long, the flattening annealing effect is too strong, creep deformation occurs, and the magnetic properties deteriorate.

The steel sheet to which the treatment liquid for forming an insulating coating of the present invention is applied, that is, the steel sheet to be subjected to the present invention may be any of carbon steel, high tensile steel sheet, stainless steel sheet, and the like, and grain-oriented electrical steel sheet is particularly preferable.

In addition, a preferred composition of the steel sheet coated with the treatment liquid for forming an insulating coating film in the present invention will be described by taking a method for producing a grain-oriented electrical steel sheet as an example.

The steel sheet preferably has the following composition ranges.

C: 0.001 to 0.10% by mass

C is a component useful for generating gaussian-oriented grains, and in order to effectively exhibit this effect, it is necessary to contain 0.001 mass% or more. When the C content exceeds 0.10 mass%, decarburization defects are caused even by decarburization annealing, and therefore, C is preferably in the range of 0.001 to 0.10 mass%.

Si: 1.0 to 5.0% by mass

Si is an essential component for reducing iron loss by increasing electrical resistance, stabilizing the BCC structure of iron, and enabling high-temperature heat treatment, and at least 1.0 mass% is required. When the Si content exceeds 5.0 mass%, cold rolling is difficult, and therefore Si is preferably 1.0 to 5.0 mass%.

Mn: 0.01 to 1.0% by mass

Mn not only contributes effectively to improvement of hot shortness of steel, but also forms precipitates such as MnS and MnSe when S, Se is present in a mixed state, and functions as an inhibitor. When the content of Mn is less than 0.01 mass%, the above effect is insufficient, while when it exceeds 1.0 mass%, the grain size of the precipitates such as MnSe coarsens and loses the effect as an inhibitor, so Mn is preferably in the range of 0.01 to 1.0 mass%.

Al: 0.003 to 0.050% by mass

Al is a useful component that forms AlN in steel and functions as a dispersion second phase inhibitor, but when the amount of Al added is less than 0.003 mass%, the amount of precipitation cannot be sufficiently secured. On the other hand, when the amount exceeds 0.050% by mass, AlN precipitates coarsely and loses the function as a suppressor, and therefore sol.al is preferably in the range of 0.003 to 0.050% by mass.

N: 0.001 to 0.020% by mass

N is an essential component for forming AlN, as with Al. When the amount is less than 0.001 mass%, precipitation of AlN becomes insufficient. On the other hand, if the amount exceeds 0.020% by mass, expansion or the like occurs during heating of the billet, so that N is preferably in the range of 0.001 to 0.020% by mass.

One or two selected from S and Se: 0.001 to 0.05 mass%

S or Se is combined with Mn and Cu to form MnSe, MnS and Cu₂-xSe、Cu₂xS and as a useful component of the dispersed second phase in the steel acting as inhibitor. When the total content of S, Se is less than 0.001 mass%, the effect of addition is poor. On the other hand, if the amount exceeds 0.05 mass%, not only the solid solution is not complete during heating of the billet, but also the defects on the product surface are caused, and therefore, the amount is preferably in the range of 0.001 to 0.05 mass% in either case of single addition or combined addition.

Is selected from Cu: 0.01 to 0.2 mass%, Ni: 0.01 to 0.5 mass%, Cr: 0.01 to 0.5 mass%, Sb: 0.01 to 0.1 mass%, Sn: 0.01 to 0.5 mass%, Mo: 0.01 to 0.5 mass%, Bi: 0.001 to 0.1 mass% of one or more

The magnetic properties can be further improved by adding an element having an action as an auxiliary inhibitor. Examples of such an element include those which are easily segregated in the crystal grain size and surface. When any of them is smaller than the above-mentioned amount, the effect cannot be obtained. When the amount of addition exceeds the above range, the appearance of the coating film tends to be poor, and secondary recrystallization tends to be poor.

In addition to the above components, further added to the steel is a steel selected from the group consisting of B: 0.001 to 0.01 mass%, Ge: 0.001 to 0.1 mass%, As: 0.005-0.1 mass%, P: 0.005-0.1 mass%, Te: 0.005 to 0.1 mass%, Nb: 0.005-0.1 mass%, Ti: 0.005-0.1 mass%, V: 0.005 to 0.1 mass%, whereby the suppression force is further enhanced and a higher magnetic flux density can be stably obtained.

The balance being Fe and unavoidable impurities.

The steel having the above-described preferred composition is smelted by a conventionally known refining process, and is made into a steel material (billet) by a continuous casting method or an ingot-cogging rolling method. The slab is hot-rolled to produce a hot-rolled sheet, and after annealing the hot-rolled sheet as necessary, the cold-rolled sheet is subjected to one cold rolling or two or more cold rollings with intermediate annealing interposed therebetween to produce a cold-rolled sheet having a final thickness. Next, recrystallization annealing and decarburization annealing are performed once, and then an annealing separator containing MgO as a main component is applied to perform finish annealing, thereby forming a coating layer mainly containing forsterite. The insulating film can be produced by a production method including a series of steps of applying the treatment liquid for forming an insulating film obtained by the production method of the present invention and performing planarization annealing which also serves as firing. The production conditions of the treatment liquid for forming an insulating film and the production conditions other than the sintering conditions of the treatment liquid for forming an insulating film may be conventionally known conditions, and are not particularly limited. Alternatively, Al may be applied after decarburization annealing₂O₃Etc. as a main separating agent, does not form forsterite after the final finish annealing, forms a film mainly containing crystals by a method such as CVD, PVD, sol-gel method, steel plate oxidation, etc., and then coats the filmThe treatment liquid for forming an insulating film obtained by the production method of the present invention is applied to form an insulating film.

Example 1

< investigation of treating liquid for Forming insulating coating >

Magnesium dihydrogen phosphate (Mg (H) shown in table 2 was used as a raw material of the treatment liquid for forming an insulating film₂PO₄)₂) And 85% phosphoric acid (H)₃PO₄) The aqueous solution was used as a phosphate ion source, and a zirconia sol (BIRAL Zr — C20 manufactured by polywood chemistry) was used as a particulate metal compound source (metal element: zr), liquid a described in table 2 was prepared. Similarly, a liquid B shown in table 2 was prepared using a zirconia sol and an 85% phosphoric acid aqueous solution. The liquid amount was adjusted using pure water.

200ml of each of the liquid a and the liquid B were mixed, and stirred for 1 minute by a turbine stator type disperser (L5 MA manufactured by SILVERSON) 20 seconds after the start of mixing, thereby preparing 400ml of a treatment liquid for forming an insulating film.

Next, a grain-oriented electrical steel sheet having a thickness of 0.23mm after completion of finish annealing was prepared. The grain-oriented electrical steel sheet was subjected to phosphoric acid pickling, and then each of the treatment liquids for forming an insulating coating described in Table 2 was applied so that the total of both surfaces thereof was dried to have a weight per unit area of 30g/m²Then, at 850 ℃ for 30 seconds, N₂Sintering treatment is carried out under the condition of 100% atmosphere. Then, test pieces for test described later were cut by shearing. For use in the tensile force imparting test, N was measured at 800 ℃ for 2 hours₂And performing stress relief annealing under the condition of 100% atmosphere.

The insulating film properties of the grain-oriented electrical steel sheet thus obtained were examined. The insulating film properties were evaluated as follows.

(1) Imparting tension

The tension applied to the steel sheet is set as the tension in the rolling direction, and the amount of warpage of the steel sheet after peeling off the single-sided coating with alkali, acid, or the like is calculated by using the following formula (1).

Tension applied to steel sheet [ MPa ]]Young's modulus [ GPa ] of steel plate]X sheet thickness of [ mm]X amount of warping (mm)]Div (warpage measuring length [ mm)])²×10³… type (1)

The Young's modulus of the steel sheet was 132 GPa.

The applied tension was judged to be satisfactory at 8.0 MPa.

(2) Moisture absorption resistance

The moisture absorption resistance was evaluated by a phosphorus elution test. In this test, three test pieces 50mm X50 mm were boiled in distilled water at 100 ℃ for 5 minutes to measure the amount of phosphorus released [ μ g/150cm ]²]The ease of dissolution of the tensile coating in water was evaluated. The amount of elution was 150[ mu.g/150 cm²]The following is good (excellent in moisture absorption resistance). The amount of P eluted was measured by quantitative analysis based on ICP emission spectrometry.

(3) Appearance of the coating film

The insulating film after stress relief annealing was visually evaluated for appearance uniformity and gloss. It is to be noted that the sample which was not glossy by visual observation was judged to have pockmarks.

(4) Lamination coefficient

The lamination coefficient was measured by a method prescribed in JIS C2550. The value of the lamination coefficient varies depending on the thickness of the steel sheet, and 96.0% or more is judged to be good for the steel sheet of 0.23mm thickness of the present example.

(5) Interlayer insulation

The interlayer insulation was determined to be good by measuring the total value of the current flowing through the contact as the interlayer resistance current according to method a in the measurement method of the interlayer resistance test described in JIS C2550, and determining that the value was 0.20A or less.

The results are shown in table 2.

As shown in table 2, it is understood that the present invention provides excellent insulating film properties.

Example 2

< investigation of stirring method >

As the raw materials of the treatment liquid for forming the insulating film, each phosphate and 85% phosphoric acid (H) shown in Table 3 were prepared₃PO₄) Liquid A which is an aqueous solution as a phosphate ion source and contains colloidal silica (ST-C manufactured by Nissan Chemicals). In addition, similarly, a titania sol (NTB-100 manufactured by Showa Denko K.K.) and magnesium oxide (MgO (500A) produced by vapor phase method by Uygur. RTM. material) were used as a granular metal compound source, and a liquid B shown in Table 3 was prepared. The liquid amount was adjusted to 1000L in total using pure water. The concentrations of the granular metal compound in liquid A and the phosphate ion in liquid B were both 0 mol/L.

200L of each of the liquid A and the liquid B were mixed, and stirred under the stirring conditions shown in Table 3 to prepare 400L of a treatment liquid. The stirring time was set to 2 minutes.

Next, a grain-oriented electrical steel sheet having a thickness of 0.20mm after completion of finish annealing was prepared. After the grain-oriented electrical steel sheet was acid-washed with phosphoric acid, each of the insulating film treatment liquids shown in Table 3 was applied so that the weight per unit area of the dried insulating film was 15g/m on both sides²Then at 900 deg.C for 30 seconds, N₂Sintering treatment is carried out under the condition of 100% atmosphere. Then, test pieces for test described later were cut by shearing. For use in the tensile force imparting test, N was measured at 800 ℃ for 2 hours₂And performing stress relief annealing under the condition of 100% atmosphere.

The insulating film properties of the grain-oriented electrical steel sheet thus obtained were examined. The properties of the insulating film were evaluated for the tensile strength, moisture absorption resistance, appearance, and lamination coefficient, and the evaluation method was performed in the same manner as in example 1. Since the value of the lamination coefficient varies depending on the thickness, 95.0% or more is judged to be good in the present example in which the thickness is 0.20 mm.

The results are shown in table 3.

As shown in table 3, it was found that the present invention provides excellent insulating film properties.

Example 3

< high pressure Dispersion treatment, etc. >

As raw materials of the treatment liquid for forming the insulating film, phosphate salts and 85% phosphoric acid (H) shown in table 3 were prepared₃PO₄) Liquid A which is an aqueous solution as a phosphate ion source and contains colloidal silica (ST-O manufactured by Nissan Chemicals). In addition, Al is added in the same manner₂O₃(BIRAL Al-C20 manufactured by polywood chemistry), ZnO (MZ-300 manufactured by TAYCA), Y₂O₃、HfO₂、ZrCa(PO₄)₂、Zr₂WO₄(PO₄)₂(all were prepared by pulverizing commercially available reagents and had a particle size of 0.5 μm) as a granular metal compound source, liquids B shown in Table 4 were prepared. The liquid amount was adjusted to 1000L in total using pure water.

The liquid A and the liquid B were mixed at 200L each, left to stand for 10 seconds after mixing, and stirred for about 5 minutes using a High shear mixer manufactured by SILVERSON. Then, in some examples, the dispersion treatment was further performed after the stirring treatment by using a high-pressure disperser shown in table 4.

Next, a grain-oriented electrical steel sheet having a thickness of 0.27mm after completion of finish annealing was prepared. After the grain-oriented electrical steel sheet was acid-washed with phosphoric acid, various insulating film treatment liquids shown in Table 4 were applied so that the weight per unit area of the insulating film after drying was 8.0g/m on both sides²Then at 820 ℃ for 30 seconds, N₂Sintering treatment is carried out under the condition of 100% atmosphere. Then, test pieces for test described later were cut by shearing. For use in the tensile force imparting test, N was measured at 800 ℃ for 2 hours₂And performing stress relief annealing under the condition of 100% atmosphere.

The insulating film properties of the grain-oriented electrical steel sheet thus obtained were examined. The properties of the insulating film were evaluated for the tensile strength, moisture absorption resistance, appearance, and lamination coefficient, and the evaluation method was performed in the same manner as in example 1. Since the value of the lamination coefficient differs depending on the thickness of the sheet, 97.0% or more was judged to be good in the present example in which the sheet thickness was 0.27 mm.

The results are shown in table 4.

As shown in table 4, the present invention all obtained good insulating film characteristics. Further, it was found that the properties of tension, phosphorus elution amount, and lamination coefficient were remarkably improved by the treatment with the high-pressure disperser.

In examples 2 and 3, by applying the method for producing the treatment liquid for forming an insulating film of the present invention, both of the examples of the present invention can be marketed as final products, leading to improvement in productivity.

Example 4

The particle size distribution was measured with respect to the treatment liquid for forming an insulating coating of No.11 shown in table 2. The particle size distribution was measured using an ultrasonic particle size distribution measuring apparatus (OPUS manufactured by JASCO Co., Ltd.). As a result, the particle diameter (D50, median diameter) was 0.087. mu.m. Further, the treatment solution was subjected to a complementary stirring treatment for 1 minute by a turbine stator type disperser (L5 MA manufactured by SILVERSON) in the same manner as in example 1. As a result, it was found that the average particle diameter (D50, median particle diameter) was 0.0083 μm, and the dispersibility was improved. Further, as a result of evaluating the characteristics of the insulating film in the same manner as in example 1, the applied tension was 12.6MPa, and the amount of phosphorus eluted was 11. mu.g/150 cm²It was confirmed that the resulting mixture showed better characteristics than those before the additional stirring treatment.

As is apparent from the above, according to the present invention, in the production of a treatment liquid for forming an insulating film containing a phosphate ion and a particulate metal compound, in order to effectively prevent a decrease in moisture absorption resistance due to elution of the phosphate ion and to increase the tensile tension applied to a steel sheet by the insulating film, dispersion of the particulate metal compound in the treatment liquid for forming an insulating film, which is a problem when a method using various particulate metal compounds is applied, can be stably dispersed at low cost as compared with a high-cost method of surface-treating a metal compound, and as a result, a treatment liquid capable of obtaining an insulating film having high moisture absorption resistance and high tension can be obtained.