Method for producing grain-oriented electrical steel sheet and method for evaluating insulating film treatment solution
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Filing Date
- 2025-09-03
- Publication Date
- 2026-06-16
Abstract
Description
Manufacturing method for grain-oriented electrical steel sheet and evaluation method for insulating coating treatment solution
[0001] The present invention relates to a method for producing grain-oriented electrical steel sheet and a method for evaluating an insulating coating treatment solution.
[0002] Grain-oriented electrical steel sheets are soft magnetic materials used as iron cores for transformers, generators, etc. They have a crystal texture in which the <001> orientation, which is the easy axis of magnetization of iron, is highly aligned in the rolling direction of the steel sheet. This texture is formed during the manufacturing process of grain-oriented electrical steel sheets through a finishing annealing (secondary recrystallization annealing) process, which preferentially grows grains with the {110} <001> orientation, also known as the Goss orientation.
[0003] Such grain-oriented electrical steel sheets generally comprise a steel sheet and insulating coatings disposed on both sides of the steel sheet. The insulating coatings not only apply tension to the steel sheet to reduce the iron loss of the grain-oriented electrical steel sheet, but also provide the grain-oriented electrical steel sheet with properties such as insulation, workability, and rust resistance. For example, chromium-free insulating coatings have been proposed as such insulating coatings from the perspective of environmental conservation (Patent Documents 1 to 4).
[0004] JP 2000-169972 A JP 2017-137540 A JP 2008-266743 A JP 2017-511840 A
[0005] The insulating coating is formed by applying an insulating coating treatment solution containing, for example, phosphate, colloidal silica, etc., to the surface of a steel sheet (e.g., a secondary recrystallized sheet) using, for example, a roll coater, followed by baking. In this process, the insulating coating treatment solution may be applied while the steel sheet is being transported, but if the transport speed is too high, the resulting grain-oriented electrical steel sheet may have poor appearance.
[0006] The present invention has been made in view of the above points, and has an object to produce a grain-oriented electrical steel sheet with excellent appearance.
[0007] As a result of extensive research, the inventors have found that the above object can be achieved by adopting the following configuration, and have completed the present invention. That is, the present invention provides the following [1] to [6]. [1] A method for manufacturing a grain-oriented electrical steel sheet comprising a steel sheet and an insulating coating disposed on a surface of the steel sheet, the method comprising: applying an insulating coating treatment liquid used to form the insulating coating on the surface of the steel sheet within X minutes from the completion of preparation of the insulating coating treatment liquid; baking the applied insulating coating liquid; and determining a yield value Y after X minutes from the completion of preparation of the insulating coating treatment liquid. Ｘ and the yield value Y 5 minutes after the completion of preparation of the insulating coating treatment solution. ５ Relative to Y Ｘ / Y ５ [2] The insulating coating treatment solution contains a phosphate containing at least one element selected from the group consisting of Mg, Ca, Ba, Sr, Zn, Al, and Mn, colloidal silica, and a metal compound containing a metal element, and the content of the colloidal silica is SiO 2 / SiO 3 / SiO 4 / SiO 5 / SiO 6 / SiO 7 / SiO 8 / SiO 9 / SiO 10 / SiO 11 / SiO 12 / SiO 13 / SiO 14 / SiO 15 / SiO 16 / SiO 17 / SiO 18 / SiO 19 / SiO 20 / SiO 21 / SiO 22 / SiO 23 / SiO 24 / SiO 25 / SiO 26 / SiO 27 / SiO 28 / SiO 29 / SiO 30 / SiO 25 / SiO 26 / SiO 27 / SiO 28 / SiO 29 / SiO 29 / SiO 26 / SiO 27 / SiO 28 / SiO 29 / SiO 29 / SiO 29 / SiO 24 / SiO 25 / SiO 26 / SiO 27 / SiO 28 / SiO 29 ... ２ [3] The method for producing a grain-oriented electrical steel sheet according to the above [1], wherein the yield value Y is 50 to 120 parts by mass in terms of solid content, and the content of the metal compound is 5 to 60 parts by mass in terms of metal element per 100 parts by mass of the solid content of the phosphate. ５ is 1.50 x 10 －５ N / cm ２[4] The method for producing a grain-oriented electrical steel sheet according to any one of [1] to [3] above, wherein the consistency index 5 minutes after completion of preparation of the insulating coating treatment solution is 10.0 mPa s or less and the flow index 5 minutes after completion of preparation of the insulating coating treatment solution is 0.80 or more and 1.20 or less. [5] The method for producing a grain-oriented electrical steel sheet according to any one of [1] to [4] above, wherein the metal compound contains at least one metal element selected from the group consisting of Zn, Ba, Sr, Mn, Ca, V, Ti, Mg, Hf, Zr, and Nb. [6] A method for evaluating an insulating coating solution used to form an insulating coating on a grain-oriented electrical steel sheet, the method comprising: applying the insulating coating solution to the surface of a steel sheet and baking the solution to form the insulating coating; and measuring the yield value Y 180 minutes after the completion of preparation of the insulating coating solution. １８０ and the yield value Y 5 minutes after the completion of preparation of the insulating coating treatment solution. ５ Relative to Y １８０ / Y ５ the appearance of the resulting grain-oriented electrical steel sheet is judged to be good if the value of the surface roughness satisfies the above condition of 8.00 or less.
[0008] According to the present invention, a grain-oriented electrical steel sheet having excellent appearance can be produced.
[0009] [Findings Obtained by the Inventors] The inventors have made the following findings.
[0010] The insulating coating solution is generally applied to the surface of the steel sheet using a roll coater, and then baked to form an insulating coating on the surface of the steel sheet.
[0011] When the insulating coating solution is applied to the surface of a steel sheet, if the viscosity of the insulating coating solution (viscosity at high shear rates) is high, the liquid surface (liquid surface of the insulating coating solution) between the steel sheet and the roll of the roll coater becomes unstable, and uneven coating such as ribbing defects (streaky defects) is likely to occur. If baking is performed with uneven coating, the resulting grain-oriented electrical steel sheet may have a poor appearance.
[0012] However, even if uneven coating such as ribbing defects occurs, poor appearance can be suppressed if the viscosity (viscosity at low shear rates) of the insulating coating solution applied to the surface of the steel sheet is low and the solution is sufficiently leveled and uniformed before baking. In other words, in order to obtain a good appearance, it is effective not only to improve uneven coating but also to improve the leveling properties of the insulating coating solution.
[0013] Incidentally, an insulating coating treatment solution is prepared by mixing raw materials (e.g., phosphate, colloidal silica) in a preparation container. After preparation is complete, the insulating coating treatment solution is stored in a stationary state in the preparation container (or in a stirred state in a temporary storage container). The stored insulating coating treatment solution is then transferred by a pump or the like to a roll coater and applied to the surface of the steel sheet. In many cases, the insulating coating treatment solution that overflows from the surface of the steel sheet and is not applied is recovered and transferred (circulated) back to the roll coater. Thus, it has been found that a certain amount of time may pass between preparation completion and application of the insulating coating treatment solution, during which time the viscosity characteristics of the insulating coating treatment solution may change.
[0014] That is, even if the viscosity of the insulating coating solution in the low shear rate range is low immediately after preparation, it may increase over time from preparation to application. In this case, the applied insulating coating solution is not sufficiently leveled before baking, and poor appearance cannot be prevented. On the other hand, if the viscosity change is small, the applied insulating coating solution is leveled before baking, resulting in a good appearance.
[0015] The present invention has been made based on the above findings and further investigations. Next, preferred embodiments of the present invention will be described.
[0016] [Method for manufacturing grain-oriented electrical steel sheet] The method for manufacturing grain-oriented electrical steel sheet of this embodiment is a method for manufacturing a grain-oriented electrical steel sheet comprising a steel sheet and an insulating coating disposed on the surface of the steel sheet, and generally comprises applying an insulating coating treatment solution to the surface of the steel sheet and baking the applied solution to form the insulating coating. The following description also serves as a description of a method for evaluating the insulating coating treatment solution.
[0017] <Steel Sheet> The steel sheet used in this embodiment is, for example, a secondary recrystallized sheet (finish annealed sheet) having a forsterite coating formed on the surface. The secondary recrystallized sheet is produced, for example, as follows.
[0018] First, a steel slab having the above-described chemical composition (steel composition) is obtained from molten steel produced using a conventionally known refining process using a continuous casting method or an ingot casting-blooming rolling method. The steel slab is then hot-rolled to obtain a hot-rolled sheet. The hot-rolled sheet is then annealed as needed, and then cold-rolled once or twice or more times with intermediate annealing in between to obtain a cold-rolled sheet of the final thickness. Next, the cold-rolled sheet is subjected to primary recrystallization annealing and decarburization annealing, and then an annealing separator containing MgO as the main component is applied, followed by finish annealing (secondary recrystallization annealing) to form a forsterite coating. In this way, a secondary recrystallized sheet having a forsterite coating on its surface is obtained.
[0019] The steel sheet has a chemical composition (steel composition) containing, for example, 0.001 to 0.10% C, 1.0 to 5.0% (preferably 2.0 to 5.0%) Si, 0.003 to 0.050% sol. Al, 0.001 to 0.020% N, 0.001 to 0.05% of at least one element selected from the group consisting of S and Se, with the balance being Fe and unavoidable impurities. Note that "%" in the chemical composition means "mass %" unless otherwise specified.
[0020] The chemical composition of the steel sheet may further contain at least one selected from the group consisting of Cu: 0.01 to 0.2%, Ni: 0.01 to 0.5%, Cr: 0.01 to 0.5%, Sb: 0.01 to 0.1%, Sn: 0.01 to 0.5%, Mo: 0.01 to 0.5%, and Bi: 0.001 to 0.1%.
[0021] The chemical composition of the steel sheet may further contain at least one selected from the group consisting of B: 0.001 to 0.01%, Ge: 0.001 to 0.1%, As: 0.005 to 0.1%, P: 0.005 to 0.1%, Te: 0.005 to 0.1%, Nb: 0.005 to 0.1%, Ti: 0.005 to 0.1%, and V: 0.005 to 0.1%.
[0022] <Insulating Coating Treatment Solution> The insulating coating treatment solution used in this embodiment contains a phosphate and colloidal silica, and preferably further contains a metal compound containing a metal element.
[0023] <<Phosphate>> The phosphate preferably contains at least one element selected from the group consisting of Mg, Ca, Ba, Sr, Zn, Al, and Mn. Examples of the phosphate include magnesium phosphate, calcium phosphate, barium phosphate, strontium phosphate, zinc phosphate, aluminum phosphate, and manganese phosphate. Hereinafter, for example, magnesium phosphate will also be referred to as "Mg phosphate" (the same applies to other phosphates). As the phosphate, monophosphate (biphosphate) is easily available and is preferred.
[0024] <<Colloidal Silica>> The content of colloidal silica is SiO 2 per 100 parts by mass of the solid content of the phosphate. ２ The amount of colloidal silica is, for example, 30 parts by mass or more in terms of solid content, and is preferably 50 parts by mass or more, more preferably 60 parts by mass or more, because the resulting insulating coating has excellent moisture absorption resistance. ２ The amount is, for example, 150 parts by mass or less in terms of solid content, and is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, because the resulting insulating coating has excellent moisture absorption resistance.
[0025] <<Metal Compound>> When forming a chromium-free insulating coating, it is preferable to include a metal compound in the insulating coating treatment solution from the viewpoints of ensuring good moisture absorption resistance and corrosion resistance and increasing the tension (applied tension) that the insulating coating imparts to the steel sheet. The metal element contained in the metal compound is an element other than Cr, and from the viewpoint of moisture absorption resistance, it is preferable that the metal element be at least one selected from the group consisting of Zn, Ba, Sr, Mn, Ca, V, Ti, Mg, Hf, Zr, and Nb. The metal compound is, for example, a metal oxide, a metal nitride, or a metal nitrate. Specific examples of the metal compound include TiO ２ , ZrO ２ , HfO ２ , MgO, ZnO, Nb ２ O ５ , V ２ O ５ , TiN, ZrN, BaO, Ba(NO ３ ) ２ , Sr(NO ３ ) ２ , MnO, CaO, etc.
[0026] The content of the metal compound is, for example, 2 parts by mass or more in terms of metal element relative to 100 parts by mass of the solid content of the phosphate, and is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, because the resulting insulating coating has excellent moisture absorption resistance and a high applied tension. The content of the metal compound is, for example, 80 parts by mass or less in terms of metal element relative to 100 parts by mass of the solid content of the phosphate, and is preferably 60 parts by mass or less, more preferably 40 parts by mass or less, because an increase in viscosity of the insulating coating treatment solution is easily suppressed.
[0027] The metal compound may be in the form of particles (powder), for example. The particle size of the metal compound will be described later.
[0028] <<Dispersant>> The insulating coating treatment solution may further contain a dispersant, which will be described later.
[0029] <Chromium Compounds> The insulating coating treatment solution is preferably chromium-free, i.e., does not contain chromium compounds such as chromic anhydride (chromium trioxide), chromates, dichromates, etc. Specifically, the content of the chromium compounds is preferably 1.0 part by mass or less, more preferably 0.10 part by mass or less, and even more preferably 0.01 part by mass or less, calculated as elemental chromium (Cr) per 100 parts by mass of the solid content of the phosphate.
[0030] <Mixing and application of insulating coating treatment liquid> <Application within X minutes after completion of mixing and ratio Y Ｘ / Y ５ In this embodiment, the above-described insulating coating treatment solution is prepared and applied to the surface of the steel sheet within X minutes after the preparation is completed. At this time, the yield value Y Ｘ and the yield value Y 5 minutes after the completion of preparation of the insulating coating treatment solution. ５ Relative to Y Ｘ / Y ５ When the above conditions are satisfied, the viscosity (viscosity in the low shear rate range) of the insulating coating treatment solution applied to the surface of the steel sheet is low, and sufficient leveling occurs before baking, resulting in a good appearance. Ｘ / Y ５ is preferably 5.00 or less, more preferably 4.50 or less, and even more preferably 3.00 or less.
[0031] ratio Y Ｘ / Y ５ However, the lower limit of the ratio Y Ｘ / Y ５ If the ratio Y is too low, the viscosity of the applied insulating coating treatment solution may decrease excessively before baking, and the desired amount of insulating coating may not be obtained. Ｘ / Y ５ is preferably 0.10 or more, more preferably 0.50 or more, and even more preferably 1.00 or more.
[0032] For example, X minutes is 180 minutes. For example, the yield value Y １８０ and the yield value Y 5 minutes after the completion of preparation of the insulating coating treatment solution. ５Relative to Y １８０ / Y ５ If the value satisfies the above range (for example, 8.00 or less), it may be determined that a good appearance is obtained.
[0033] <<How to Determine the Yield Value>> The yield value of the insulating coating treatment solution is determined as follows: First, using a B-type viscometer, the shear rate γ is measured at 13.2 to 330.0 s －１ The shear stress τ of the insulating coating treatment liquid (liquid temperature: 20°C) was measured within the range of 100°C. Then, the Herschel-Bulkley equation "τ = τ ０ + kγ ｎ ” (τ ０ : Yield value, k: Consistency Index, n: Flow Index). In this way, the yield value (τ ０ ) is "Y ５ " and the yield value (τ ０ ) is "Y Ｘ " We demand.
[0034] <<Yield value Y 5 minutes after completion of compounding>> ５ The yield value of the insulating coating treatment solution is not particularly limited. However, the yield value Y ５ If the yield value Y is too high, it may be difficult to apply the insulating coating treatment solution. ５ is 3.00 x 10 －５ N / cm ２ The following is preferred: 2.50 x 10 －５ N / cm ２ More preferably, 2.00 x 10 －５ N / cm ２ More preferably, 1.50 x 10 －５ N / cm ２ The following is particularly preferred: On the other hand, the yield value Y 5 minutes after the completion of mixing ５ is, for example, 0.05 × 10 －５ N / cm ２ or more, 0.10 × 10 －５ N / cm ２ It may be more than that.
[0035] <<k 5 Minutes After Completion of Blending>> The consistency index (k) 5 minutes after completion of blending is, for example, 18.0 mPa s or less, preferably 16.0 mPa s or less, more preferably 14.0 mPa s or less, even more preferably 12.0 mPa s or less, and particularly preferably 10.0 mPa s or less. On the other hand, the consistency index (k) 5 minutes after completion of blending is, for example, 1.0 mPa s or more, and may be 1.5 mPa s or more.
[0036] <<n 5 Minutes After Completion of Blending>> The n (Flow Index) 5 minutes after completion of blending is, for example, 1.20 or less, preferably 1.10 or less, and more preferably 1.00 or less. On the other hand, the n 5 minutes after completion of blending is, for example, 0.60 or more, may be 0.70 or more, and preferably 0.80 or more.
[0037] <<Definition of Blending and Blend Completion>> Blending is generally performed by adding raw materials (phosphoric acid, colloidal silica, etc.) to a blending container and mixing them. Specifically, blending refers to the overall process of adding raw materials (including dispersants), mixing the raw materials, and improving the uniformity and dispersibility of the mixed liquid obtained by mixing the raw materials (for example, the dispersion process described below). Blend completion refers to the point at which such blending is completed.
[0038] After the blending is complete, other post-blending tasks are performed, such as transferring the insulating coating treatment liquid from the blending container to the temporary storage container; stirring the insulating coating treatment liquid in the temporary storage container; transferring the insulating coating treatment liquid from the blending container or the temporary storage container to a coater; circulating the insulating coating treatment liquid; and applying the insulating coating treatment liquid using a coater. However, these post-blending tasks are not included in the blending process.
[0039] In order to adjust the amount of the insulating coating to be formed, the insulating coating treatment solution may be diluted with water after preparation. In this case, a correction formula is prepared in advance, and the yield value (Y ５ , Y Ｘ ) is required.
[0040] <<Mixing temperature>> Ratio Y of insulating coating treatment liquid Ｘ / Y ５ The mixing temperature refers to the temperature of the raw materials and the temperature of the mixed solution (insulating coating solution) obtained by mixing the raw materials.
[0041] Generally, raw materials such as phosphate and colloidal silica are liquids with different pH values. Therefore, when the raw materials are mixed, the pH of the mixed liquid passes near the isoelectric point of each raw material, causing aggregation, formation of precipitates, and gelation, which may increase the yield value of the mixed liquid.
[0042] By maintaining a low mixing temperature, the formation of precipitates and gelation can be suppressed, and the ratio Y Ｘ / Y ５ can be controlled within the above-mentioned range. Specifically, the blending temperature is preferably 13° C. or lower, more preferably 10° C. or lower, and even more preferably 7° C. or lower. There is no particular lower limit to the blending temperature, but the blending temperature may be, for example, 0° C. or higher, or 3° C. or higher.
[0043] <Dispersion Processing> Yield value Y 5 minutes after completion of compounding ５ In order to control the dispersion density within a suitable range, it is preferable to carry out a dispersion treatment on the raw materials (mixed liquid) placed in a blending vessel. The dispersion treatment is preferably carried out using a homogenizer such as an ultrasonic homogenizer. Examples of commercially available homogenizers include the Sonicmix manufactured by Mitsui Electric Seiki Co., Ltd.; the Ultrasonic Processor atomizer manufactured by F.T. Associates; and an industrial high-efficiency ultrasonic generator (UIP1000, etc.) manufactured by Hielscher.
[0044] The intensity of the dispersion treatment (treatment intensity) is expressed as a value calculated by the following formula: treatment output (unit: W) x treatment time (unit: h) ÷ treatment liquid volume (unit: L). Specifically, when performing dispersion treatment, the treatment intensity is preferably 2 Wh / L or more, and more preferably 4 Wh / L or more. On the other hand, the treatment intensity is preferably 12 Wh / L or less, and more preferably 8 Wh / L or less.
[0045] Addition of Dispersant: From the viewpoint of adjusting the consistency index k (5 minutes after the completion of blending) to a suitable range, it is preferable to add a dispersant as a raw material. The dispersant reduces the viscosity of the insulating coating treatment solution and inhibits re-aggregation of colloidal silica and the like, thereby reducing the ratio Y Ｘ / Y ５ can be controlled within the above range.
[0046] Examples of dispersants include cationic surfactants, anionic surfactants, and nonionic surfactants, with cationic surfactants being preferred because the surfaces of the metal compound particles described above are negatively charged in the insulating coating treatment solution, and it is believed that cationic surfactants are likely to be adsorbed onto these surfaces.
[0047] As the cationic surfactant, a quaternary ammonium salt type is preferred because of its low foaming property. Examples of commercially available quaternary ammonium salt type cationic surfactants include SN Dispersant 4215 manufactured by San Nopco and Adekamin 4DAC-85 manufactured by ADEKA.
[0048] The content of the dispersant in the insulating coating treatment solution is, for example, 0.3 parts by mass or more, preferably 0.7 parts by mass or more, more preferably 1.0 parts by mass or more, even more preferably 1.5 parts by mass or more, and particularly preferably 2.0 parts by mass or more, per 100 parts by mass of the solid content of the phosphate.
[0049] On the other hand, if there is too much dispersant, the ratio Y Ｘ / Y ５ Therefore, the content of the dispersant in the insulation coating treatment solution is, for example, 5.0 parts by mass or less, preferably 4.0 parts by mass or less, more preferably 3.5 parts by mass or less, and even more preferably 3.0 parts by mass or less.
[0050] In addition, when the dispersant is diluted with a solvent, the content of the dispersant means the amount excluding the solvent.
[0051] <<Particle size of metal compound>> From the viewpoint of adjusting the flow index (n) 5 minutes after the completion of blending to a suitable range, it is preferable to control the particle size of the metal compound. When the particle size of the metal compound is appropriately small, the non-Newtonian fluidity of the insulating coating treatment solution becomes prominent, and the flow index (n) becomes smaller or larger than 1. On the other hand, when the particle size of the metal compound is too large, the reactivity between the insulating coating treatment solution and the steel sheet during baking becomes insufficient, and the moisture absorption resistance and applied tension of the insulating coating tend to become insufficient.
[0052] Therefore, the particle size of the metal compound is, for example, 1.50 μm or less, preferably 1.20 μm or less, more preferably 1.00 μm or less, and even more preferably 0.80 μm or less. On the other hand, the particle size of the metal compound is, for example, 0.01 μm or more, preferably 0.03 μm or more, and more preferably 0.05 μm or more.
[0053] The particle size is the 50% particle size (median size) on a volume basis, determined by a laser diffraction / scattering method.
[0054] The above-mentioned dispersion treatment, addition of dispersant, and control of particle size of metal compound do not affect only the yield value, k (Consistency Index), and n (Flow Index) independently, but affect multiple factors. The above description has been given by listing factors that have a particularly large effect.
[0055] <<Application Method>> When applying the insulating coating treatment liquid to the surface of a steel sheet, it is preferable to apply the insulating coating treatment liquid to the surface of the steel sheet using a roll coater while transporting the steel sheet. In this case, the transport speed of the steel sheet is, for example, 100 mpm (m / min) or more, preferably 200 mpm or more, and may be 300 mpm or more.
[0056] Before applying the insulating coating treatment liquid, the surface of the steel sheet may be pickled with phosphoric acid or the like.
[0057] <Baking of Insulating Coating Solution> After applying the insulating coating solution to the surface of the steel sheet, the solution is dried as needed and then baked to form an insulating coating. Planarization annealing, which also serves as baking, may be performed. The baking temperature is preferably 600 to 1000°C, more preferably 700 to 930°C, and even more preferably 800 to 860°C. The baking atmosphere is preferably an inert gas atmosphere such as a nitrogen gas atmosphere. The baking time is preferably 1 to 300 seconds, preferably 5 to 200 seconds, and more preferably 10 to 100 seconds.
[0058] The amount of the insulating coating to be formed on both sides is, for example, 2.0 to 12.0 g / m ２ and 4.0 to 10.0 g / m ２ is preferred.
[0059] [Grain-oriented electrical steel sheet] The grain-oriented electrical steel sheet obtained by the manufacturing method of this embodiment has excellent appearance with reduced appearance defects. Furthermore, in the grain-oriented electrical steel sheet obtained, the tension (applied tension) applied to the steel sheet by the insulating coating is preferably 10.0 MPa or more, because the magnetic properties are excellent. １７／５０ In addition, the amount of phosphorus elution in the obtained grain-oriented electrical steel sheet is preferably 150 μg / 150 cm because the sheet has excellent moisture absorption resistance. ２ Preferably, 100 μg / 150 cm or less ２ The following is more preferable: The methods for measuring the applied tension, iron loss, and amount of eluted phosphorus will be described later (see Examples below).
[0060] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples described below.
[0061] [Test 1] <Production of Grain-Oriented Electrical Steel Sheet> A secondary recrystallized sheet (finish-annealed sheet) with a thickness of 0.23 mm was prepared as a steel sheet. The surface of the prepared steel sheet was pickled with phosphoric acid. Then, raw materials (phosphate, colloidal silica, and metal compound) were charged into a mixing vessel and mixed. In this way, an insulating coating treatment solution (solvent: pure water, specific gravity: 1.150) having the component composition shown in Table 1 below was prepared at the mixing temperature shown in Table 1 below.
[0062] Primary phosphate was used as the phosphate. Snowtex N (manufactured by Nissan Chemical Industries, Ltd.) was used as the colloidal silica. The particle size of the metal compound was in the range of 0.05 to 0.60 μm. No dispersion treatment or addition of a dispersant was performed.
[0063] In Table 1 below, the content of phosphate means the content of the solid content of phosphate (unit: parts by mass). The content of colloidal silica means the SiO content per 100 parts by mass of the solid content of phosphate. ２ The term "content" refers to the content (unit: parts by mass) converted into solid content. The term "content of metal compound" refers to the content (unit: parts by mass) converted into metal element per 100 parts by mass of the solid content of the phosphate. These are the same as in [Test 2] described later.
[0064] The prepared insulating coating treatment solution was measured for its yield value Y 5 minutes after preparation was completed according to the method described above. ５ and the yield value Y 180 minutes after the completion of mixing １８０ Furthermore, the yield value Y ５ Yield value Y １８０ The ratio Y １８０ / Y ５ The results are shown in Table 1 below.
[0065] The Brookfield LVDV3T digital viscometer was used as the Brookfield viscometer. The insulating coating treatment liquid at a liquid temperature of 20°C was placed in a small-volume sample adapter of the Brookfield viscometer, and the shear rate γ was measured at 13.2 to 330.0 s using an SC4-18 spindle. －１ The shear stress τ was measured at 18 points within the range of 1. During the measurement, the temperature of the insulating coating treatment solution was maintained at 20° C. using a water-cooling jacket.
[0066] The prepared insulating coating solution was applied to the surface of the steel sheet within 180 minutes (specifically, 180 minutes after the completion of preparation). More specifically, the insulating coating solution was applied using a roll coater while the steel sheet was conveyed at a conveying speed of 200 mpm. After that, baking (baking temperature: 850°C, baking time: 25 seconds, baking atmosphere: nitrogen atmosphere) was performed to form an insulating coating (adhesion amount on both sides: 8.0 g / m). ２) was formed. In this way, a grain-oriented electrical steel sheet was obtained.
[0067] <Evaluation> The grain-oriented electrical steel sheets obtained were subjected to the tests described below to evaluate various properties. The results are shown in Table 1 below.
[0068] <<Appearance>> The surface condition of the obtained grain-oriented electrical steel sheet was visually observed, and if there were no ribbing defects, it was given an "A", and if there were ribbing defects, it was given a "B", as shown in Table 1. If it was given an "A", it was evaluated as having excellent appearance.
[0069] <<Applied Tension>> The tension in the rolling direction (applied tension) applied to the steel sheet by the insulating coating was determined for the obtained grain-oriented electrical steel sheet. A test specimen (30 mm length in the direction perpendicular to the rolling direction × 280 mm length in the rolling direction) was taken from the grain-oriented electrical steel sheet. One side of the taken test specimen was masked with adhesive tape, and the insulating coating on the other side was removed using acid and alkali. Next, one end of the test specimen, 30 mm, was fixed, and the remaining 250 mm was used as the "warpage measurement length" to measure the "warpage amount," and the "applied tension" was calculated using the following formula. The "Young's modulus of the steel sheet" was set to 132 GPa. Applied tension [MPa] = Young's modulus of steel sheet [GPa] × thickness of steel sheet [mm] × warpage amount [mm] ÷ (warpage measurement length [mm]) ２ x10 ３ The applied tension is preferably 10.0 MPa or more.
[0070] Iron loss W １７／５０ Test pieces (width 30 mm x length 280 mm) were taken from the obtained grain-oriented electrical steel sheets, and the iron loss W １７／５０ was calculated. Iron loss W １７／５０ The lower the value, the better the magnetic properties can be evaluated. １７／５０ is preferably 0.88 W / kg or less.
[0071] <<Amount of Phosphorus Elution>> Three test specimens (50 mm × 50 mm) were taken from the obtained grain-oriented electrical steel sheet. The three test specimens were immersed in distilled water at 100°C and boiled for 5 minutes to elute phosphorus from the surface of the insulating coating of each test specimen, and the amount of phosphorus eluted (unit: μg / 150 cm ２The smaller the amount of phosphorus elution, the better the moisture absorption resistance. The amount of phosphorus elution was 150 μg / 150 cm ２ Preferably, 100 μg / 150 cm or less ２ The following is more preferred:
[0072]
[0073] <Summary of evaluation results> As shown in Table 1 above, the ratio Y １８０ / Y ５ Nos. 1-3, 1-12 and 1-25, which had a porosity of more than 8.00, had insufficient appearance.
[0074] In contrast, the ratio Y １８０ / Y ５ Nos. 1-1, 1-2, 1-4 to 1-11, 1-13 to 1-24, and 1-26 to 1-33, which had a viscosity of 8.00 or less, had good appearances.
[0075] Comparing Nos. 1-4 to 1-6, No. 1-5, in which the colloidal silica content was 110 parts by mass, had a lower amount of phosphorus elution and better moisture absorption resistance than Nos. 1-4 and 1-6, in which the colloidal silica content was 40 parts by mass or 130 parts by mass.
[0076] Furthermore, when comparing Nos. 1-7 to 1-9, it was found that the magnetic properties and moisture absorption resistance tended to improve as the content of the metal compound increased. A similar tendency was also seen in the comparison between Nos. 1-10 and 1-13.
[0077] [Test 2] <Production of Grain-Oriented Electrical Steel Sheet> A secondary recrystallized sheet (finish-annealed sheet) with a thickness of 0.18 mm was prepared as the steel sheet. The surface of the prepared steel sheet was pickled with phosphoric acid. Then, raw materials (phosphate, colloidal silica, metal compound, and optional dispersant) were charged into a mixing vessel and mixed. In this way, an insulating coating treatment solution (solvent: pure water) having the component composition shown in Table 2 below was prepared at a mixing temperature of 5°C.
[0078] As the phosphate, primary phosphate was used, and as the colloidal silica, Snowtex N (manufactured by Nissan Chemical Industries, Ltd.) was used.
[0079] A quaternary ammonium salt type cationic surfactant was used as the dispersant. Specifically, SN Dispersant 4215 manufactured by San Nopco (referred to as "SN4215" in Table 2 below) or Adekamin 4DAC-85 manufactured by ADEKA (referred to as "4DAC" in Table 2 below) was used. When no dispersant was added, a "-" was entered in the corresponding column in Table 2 below.
[0080] In some cases, a dispersion treatment was carried out using a Hielscher industrial high-efficiency ultrasonic generator (UIP1000) while circulating 1,000 L of the mixed liquid obtained by mixing the raw materials, at a processing output of 10,000 W for various processing times (unit: h). The dispersion strength (unit: Wh / L) is shown in Table 2 below. When dispersion treatment was not carried out, a "-" is entered in the corresponding column in Table 2 below.
[0081] The prepared insulating coating treatment solution was subjected to the same test as in Test 1 to measure the yield value Y 5 minutes after the completion of preparation. ５ and the yield value Y 180 minutes after the completion of mixing １８０ Furthermore, the yield value Y ５ Yield value Y １８０ The ratio Y １８０ / Y ５ The results are shown in Table 2 below. The consistency index (k) and flow index (n) 5 minutes after the completion of blending are also shown in Table 2 below. In Table 2 below, the values are simply represented as "k" and "n".
[0082] The prepared insulating coating solution was then applied to the surface of the steel sheet within 180 minutes (specifically, 180 minutes after the completion of preparation). More specifically, the insulating coating solution was applied using a roll coater while the steel sheet was conveyed at a conveying speed of 300 mpm. After that, baking (baking temperature: 820°C, baking time: 30 seconds, baking atmosphere: nitrogen atmosphere) was performed to form an insulating coating (adhesion amount on both sides: 6.5 g / m). ２) was formed. In this way, a grain-oriented electrical steel sheet was obtained.
[0083] <Evaluation> Various properties of the obtained grain-oriented electrical steel sheets were evaluated in the same manner as in Test 1. The results are shown in Table 2 below.
[0084]
[0085] <Summary of evaluation results> As shown in Table 2 above, the ratio Y １８０ / Y ５ All of No. 2-1 to No. 2-25, which had a value of 8.00 or less, had good appearances. In addition, the magnetic properties and moisture absorption resistance were also good.
Claims
1. A method for manufacturing a grain-oriented electrical steel sheet comprising a steel sheet and an insulating coating disposed on the surface of the steel sheet, The insulating coating solution used to form the insulating coating is applied to the surface of the steel plate within X minutes of the completion of the preparation of the insulating coating solution, and then baked. Yield value Y after X minutes from the completion of preparation of the insulating coating solution. Ｘ The yield value Y 5 minutes after the completion of the preparation of the insulating coating solution. ５ Y Ｘ / Y ５ A method for manufacturing grain-oriented electrical steel sheets, wherein the value is 8.00 or less.
2. The insulating coating solution contains a phosphate containing at least one element selected from the group consisting of Mg, Ca, Ba, Sr, Zn, Al, and Mn, colloidal silica, and a metal compound containing a metal element. The content of the colloidal silica is such that, relative to 100 parts by mass of the solid content of the phosphate, SiO ２ This is 50 to 120 parts by mass in terms of solid content. The method for manufacturing grain-oriented electrical steel sheets according to claim 1, wherein the content of the metal compound is 5 to 60 parts by mass in terms of metal elements per 100 parts by mass of solid content of the phosphate.
3. The method for producing grain-oriented electrical steel sheets according to claim 2, wherein the metal compound contains at least one metal element selected from the group consisting of Zn, Ba, Sr, Mn, Ca, V, Ti, Mg, Hf, Zr, and Nb.
4. The yield value Y ５ 1.50 x 10 －５ N / cm ２ The method for manufacturing grain-oriented electrical steel sheets according to any one of claims 1 to 3, as follows:
5. The Consistency Index five minutes after the completion of preparation of the insulating coating solution is 10.0 mPa·s or less. A method for manufacturing grain-oriented electrical steel sheets according to any one of claims 1 to 3, wherein the Flow Index five minutes after the completion of preparation of the insulating coating treatment liquid is 0.80 or more and 1.20 or less.
6. The Consistency Index of the insulating coating solution five minutes after the completion of preparation is 10.0 mPa·s or less. The method for manufacturing grain-oriented electrical steel sheets according to claim 4, wherein the Flow Index five minutes after the completion of preparation of the insulating coating treatment liquid is 0.80 or more and 1.20 or less.
7. A method for evaluating an insulating coating treatment liquid used to form an insulating coating on a grain-oriented electrical steel sheet, The insulating coating solution is applied to the surface of the steel plate and baked to form the insulating coating. The yield value Y 180 minutes after the completion of the preparation of the insulating film treatment liquid １８０ and the yield value Y 5 minutes after the completion of the preparation of the insulating film treatment liquid ５ the ratio Y １８０ / Y ５ When it satisfies 8.00 or less, it is determined that the appearance of the obtained oriented electromagnetic steel sheet is good. An evaluation method for an insulating film treatment liquid