Method for manufacturing grain-oriented electrical steel sheet

Abstract

This invention provides a method for manufacturing oriented electromagnetic steel sheets that can stably obtain good coating properties over the entire length and width of the steel sheet coil. The manufacturing method of oriented electromagnetic steel sheet includes the following steps: hot rolling of steel billet containing one or two of the following by mass: Si: 2.0% to 5.0%, Mn: 0.01% to 0.50%, totaling 0.001% to 0.100% S and Se; cold rolling once or more, or cold rolling with intermediate annealing; decarburization annealing; further coating with an annealing separating agent mainly composed of MgO; final annealing; and planarization annealing. The final annealing is carried out in an atmosphere with a gas flow rate of 0.2 L / min or more per ton of steel sheet and a dew point of 10°C or less. The planarization annealing is accompanied by a coating treatment including the application of a coating solution. Before applying the coating solution, pickling is performed for 1 to 60 seconds at a temperature of 15°C or higher using an acid with a concentration of 1% to 20%.

Description

Technical Field

[0001] This invention relates to a method for manufacturing oriented electromagnetic steel sheets suitable for transformer core materials. Background Technology

[0002] Electromagnetic steel sheets are widely used as core materials for transformers, motors, and other components. Electromagnetic steel sheets are broadly classified into oriented and non-oriented types. Oriented electromagnetic steel sheets are characterized by a highly integrated microstructure in which the <001> orientation, belonging to the iron's easy magnetization axis, is highly integrated along the rolling direction of the steel sheet. This microstructure is formed through secondary recrystallization during final annealing. This secondary recrystallization refers to the use of grain boundary energy to induce the {110} orientation, known as the Gaussian orientation. <001> The phenomenon where grains of a particular orientation preferentially grow into giant grains.

[0003] As a representative technique for inducing the aforementioned secondary recrystallization, there are techniques utilizing precipitates known as inhibitors. For example, Patent Document 1 discloses a method using AlN and MnS, and Patent Document 2 discloses a method using MnS and MnSe, both of which have been industrially applied. These methods using inhibitors are useful for stably promoting the growth of secondary recrystallized grains, but in order to achieve fine dispersion of the inhibitor in the steel, it is necessary to heat the slab at a high temperature of over 1300°C to dissolve the inhibitor components in a single step.

[0004] On the other hand, Patent Document 3 discloses a technique for growing Gaussian-oriented grains through secondary recrystallization in a billet without inhibitor components. This technique manifests the grain boundary orientation difference angle dependence of the grain boundary energy during primary recrystallization by minimizing impurities such as inhibitor components, thereby enabling secondary recrystallization of grains with the Goss orientation even without the use of inhibitors. This effect is called texture suppression effect. This method eliminates the need for fine dispersion of inhibitors in the steel, thus avoiding the previously necessary high-temperature slab heating, offering advantages in manufacturing compared to methods using inhibitors.

[0005] Furthermore, for oriented electromagnetic steel sheets, coating adhesion is an important indicator alongside magnetic properties. This is because when used in transformer cores, bending is performed at the corners, so close contact between the coating and the steel sheet at these locations is also crucial for ensuring insulation. Regarding this, Patent Document 4 discloses a technique to improve coating adhesion by performing pickling before coating application during planarization annealing.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Publication No. 40-15644

[0009] Patent Document 2: Japanese Patent Publication No. 51-13469

[0010] Patent Document 3: Japanese Patent Application Publication No. 2000-129356

[0011] Patent Document 4: Japanese Patent Application Publication No. 2-30778 Summary of the Invention

[0012] However, although the coating adhesion can be improved by specifying the type, concentration, temperature, and processing time of acid in the pickling process, as described in Patent Document 4, the coating adhesion sometimes becomes uneven or defective areas appear in parts of the steel coil, thus requiring further improvement. In particular, it is desirable to improve the coating characteristics of the central portion in both the long and width directions of the steel coil.

[0013] The present invention addresses the issue of coating adhesion within the aforementioned steel sheet coil, and aims to provide a method for manufacturing an orientation-oriented electromagnetic steel sheet capable of consistently achieving good coating properties throughout the entire length and width of the steel sheet coil.

[0014] The following describes the experiments that enabled the success of this invention.

[0015] <Experiment 1>

[0016] Oriented electromagnetic steel sheet, containing 0.025% C, 3.14% Si, 0.15% Mn, and 0.021% Se by mass, was hot-rolled to 1400°C to produce a 2.7mm thick hot-rolled sheet. This was followed by a 15-second hot-rolled annealing at 1000°C, pickling to remove oxide scale, and then cold rolling to a 0.55mm thickness. Next, an intermediate annealing at 1080°C for 100 seconds was performed, followed by a second cold rolling to a 0.23mm thickness. Then, a decarburization annealing was performed at 850°C for 90 seconds, with 50% H₂ + 50% N₂ and a dew point of 62°C. Finally, an annealing agent primarily composed of MgO was applied to the steel surface and dried, followed by a final annealing at 1200°C for 15 hours. After the annealing separator was applied and dried, only the annealing separator on the steel plate was collected, and the loss on ignition was determined by the method described in JIS K0067:1992, with a result of 3.2% by mass.

[0017] The atmosphere for the final annealing is N2 during heating up to 1000°C, H2 during cooling from 1000°C to 1000°C after holding at 1200°C, and Ar during subsequent cooling. Various changes are made to the atmosphere dew point and the flow rate of the atmosphere gas (N2 or H2). Next, unreacted annealing separating agent remaining on the steel plate surface is removed by water washing, followed by a 5% phosphoric acid pickling treatment at 60°C for 5 seconds. Then, a phosphate-based coating solution is applied, and a planarization annealing process is performed at 850°C for 50 seconds, serving as both a coating sintering process and a planarization of the steel plate.

[0018] The coating adhesion of the obtained steel sheets was evaluated. For coating adhesion, the steel sheets were wound into cylinders of various diameters, and the minimum diameter at which the coating did not peel off was used for evaluation. The smaller this minimum diameter, the better the coating adhesion. Furthermore, the samples evaluated were collected from each of the two ends and the central portion of the long side of the steel coil, as well as two locations at each end and one location at the center of the width direction of the steel coil, totaling nine locations per coil. For samples collected from these nine locations with dimensions of 280 mm in the rolling direction and 30 mm in the width direction, the minimum diameter at which the coating did not peel off was measured, and the maximum value at these nine locations was taken as the representative value for each steel coil.

[0019] The above evaluation results are summarized into the relationship between the atmospheric dew point and atmospheric gas flow rate during final annealing and the film adhesion, as shown below. Figure 1 .Depend on Figure 1 The results show that, in the final annealing atmosphere, good film adhesion can be achieved by making the flow rate of the atmosphere gas above 0.2 L / min per ton of steel and the dew point below 10°C.

[0020] It should be noted that in this experiment, the parts that show the representative value of the steel coil, that is, the parts with the worst film adhesion, are mostly the central parts of the long side and the width direction of the steel coil.

[0021] <Experiment 2>

[0022] Oriented electromagnetic steel sheet slabs containing C: 0.075%, Si: 2.88%, Mn: 0.05%, Se: 0.015%, Sb: 0.08%, Al: 0.021%, and N: 0.008% by mass were reheated to 1380°C and hot-rolled to produce 2.4 mm thick hot-rolled sheets. These sheets were then hot-rolled and annealed at 900°C for 30 seconds. Oxide scale was removed from the steel surface by pickling, followed by cold rolling to a thickness of 1.6 mm. Next, an intermediate annealing at 1125°C for 120 seconds was performed, followed by a second cold rolling to a thickness of 0.23 mm. Finally, a decarburization annealing was performed at 850°C for 90 seconds, with 50% H₂ + 50% N₂ and a dew point of 64°C. Next, an annealing release agent based on MgO was coated onto the steel plate surface and dried, followed by final annealing at 1200°C for 20 hours. After the coating and drying of the annealing release agent, only the annealing release agent on the steel plate was collected, and the loss on ignition was determined using the method described in JIS K0067:1992, with a result of 1.4% by mass.

[0023] The final annealing atmosphere is N2 during heating up to 850°C, H2 during the holding period from 850°C to 1200°C, and Ar during subsequent cooling. At this point, the atmosphere dew point is -50°C, and the gas flow rate is 1.0 L / min per ton of steel. Next, unreacted annealing separating agent remaining on the steel plate surface is removed by water washing. Then, the plate is pickled for various durations using hydrochloric acid with varying concentrations and temperatures. Following this, a phosphate-based coating solution is applied, and a planarization annealing process is performed at 870°C for 20 seconds, serving as both a coating sintering process (coating treatment) and a planarization step for the steel plate.

[0024] The coating adhesion of the obtained steel sheets was evaluated. For coating adhesion, the steel sheets were wound into cylinders of various diameters, and the minimum diameter at which the coating did not peel off was used for evaluation. Furthermore, the samples evaluated were collected from each of the two ends and the central portion of the long side of the steel coil, as well as two locations at each end and one location at the center of the width direction of the steel coil, totaling nine locations per coil. For samples collected from these nine locations with dimensions of 280 mm in the rolling direction and 30 mm in the width direction, the minimum diameter at which the coating did not peel off was measured, and the maximum value at these nine locations was taken as the representative value for each steel coil.

[0025] Regarding the above evaluation results, the relationship between acid concentration, acid temperature, and pickling time involved in the pickling treatment before coating and the adhesion of the film is shown in the figure. Figures 2-4 Experiments were also conducted on conditions where no acid washing was performed before applying the coating solution, and the evaluation results of the film adhesion were as follows: Figure 4 The pickling time is 0 seconds, which represents the pickling time-dependent pickling process. Figures 2-4The results show that good film adhesion can be achieved by using an acid with a concentration of 1.0% to 20.0% by mass and performing an acid pickling treatment at a temperature above 15°C for 1 to 60 seconds before applying the coating solution in planarization annealing.

[0026] It should be noted that in this experiment, the parts that show the representative value of the steel coil, that is, the parts with the worst film adhesion, are mostly the central parts of the long side and the width direction of the steel coil.

[0027] The results of the above experiments show that by specifying the pickling conditions before applying the coating solution and the atmosphere conditions introduced during the final annealing, good coating properties can be obtained across the entire length and width of the steel coil. Furthermore, it was clarified that the areas with poor coating adhesion are the central portions of both the long side and the width direction of the steel coil. The reasons for these findings are not yet clear, but the inventors believe the following.

[0028] As indicated in Patent Document 4 above, it is speculated that the deterioration of the coating adhesion is due to the enrichment of S and Se near the base iron coating interface. These S and Se form precipitates such as MnS and MnSe in the steel before final annealing. During prolonged final annealing, these precipitates decompose, and S and Se become free and diffuse to the surface, reacting with H to form H₂S and H₂Se, which are released into the gas phase. However, some remain near the base iron coating interface, inducing the deterioration of coating adhesion as described above. The technique described in Patent Document 4 aims to remove these S and Se through pickling. However, the experimental results show that there is a distance between the center of the long side and the width of the steel coil and the end of the steel plate. During final annealing in the form of a steel coil, the atmosphere is sometimes difficult to reach, making it difficult for S and Se to be released into the gas phase. The enrichment of S and Se near the base iron-coating interface becomes extremely high, and pickling alone may not be sufficient to suppress the deterioration of coating adhesion. By ensuring that the flow rate of the atmosphere gas during the final annealing is above a certain level, it is possible to promote the flow of atmosphere gas in the central part of the long side and width directions of the steel coil, thereby promoting the gas phase release of H2S and H2Se and reducing the enrichment near the base iron-coating interface.

[0029] Furthermore, regarding the dew point, it is speculated that the MgO used as an annealing separator improves the flow of gas between the steel plates. The annealing separator is suspended in water and coated as a slurry, but the surface of the MgO particles is hydrated due to the water, becoming Mg(OH)₂. Therefore, it exhibits a certain degree of volume expansion. By setting the dew point of the atmosphere during final annealing below a certain level, the moisture evaporates and the volume shrinks, improving the flow of gas. Based on this mechanism, it is speculated that if MgO undergoes a certain degree of hydration and expansion before final annealing, it can be expected that the volume will shrink during final annealing, improving gas flow. The results of Experiment 2 suggest that a hydration content of 1% by mass or more is effective. Here, a hydration content of 1% by mass or more for MgO means that the loss on ignition after drying (according to JIS K0067:1992) of the annealing separator, which is mainly composed of MgO, is 1% by mass or more.

[0030] As described above, the inventors have discovered that by specifying the conditions of the pickling treatment prior to the application of the coating solution and the conditions of the atmosphere introduced during the final annealing, good coating properties can be stably obtained. This invention is based on the above insights.

[0031] That is, the essence of the present invention is as follows.

[0032] 1. A method for manufacturing an oriented electromagnetic steel sheet, comprising the following steps: hot rolling a steel billet containing, by mass percent, any one or two of S and Se, namely, Si: 2.0%–5.0%, Mn: 0.01%–0.50%, and a total of 0.001%–0.100%; followed by one cold rolling or two or more cold rolling processes with intermediate annealing; then decarburization annealing; further coating with an annealing separating agent mainly composed of MgO and drying; then final annealing; and finally planarization annealing; wherein,

[0033] The final annealing described above is carried out in an atmosphere with a gas flow rate of 0.2 L / min or higher per ton of steel plate and a dew point of 10°C or lower.

[0034] The above planarization annealing is accompanied by a coating process including the application of a coating solution.

[0035] Before applying the above coating solution, use an acid with a concentration of 1.0% to 20.0% by mass to perform an acid pickling treatment for 1 to 60 seconds at a temperature above 15°C.

[0036] 2. The method for manufacturing oriented electromagnetic steel sheet according to 1 above, wherein the acid is any one of phosphoric acid, hydrochloric acid, sulfuric acid or nitric acid.

[0037] 3. The method for manufacturing oriented electromagnetic steel sheet according to 1 or 2 above, wherein the loss on ignition of the annealing separating agent after drying is 1.0% to 7.0% by mass.

[0038] According to the present invention, by specifying the conditions of the pickling treatment before applying the coating solution and the conditions of the atmosphere introduced in the final annealing, good coating properties can be stably obtained over the entire length and width of the steel coil. Attached Figure Description

[0039] Figure 1 This is a graph showing the relationship between the atmospheric dew point and atmospheric gas flow rate during final annealing and the film adhesion.

[0040] Figure 2 This is a graph showing the relationship between acid concentration and film adhesion during the pickling process before coating.

[0041] Figure 3 This is a graph showing the relationship between acid temperature and film adhesion during the pickling process before coating.

[0042] Figure 4 This is a graph showing the relationship between pickling time and film adhesion during the pickling process before coating. Detailed Implementation

[0043] The present invention will now be described in detail.

[0044] <Steel billet>

[0045] First, regarding the composition of the billet (slab) for oriented electromagnetic steel sheets, the preferred composition range is described below. It should be noted that the "%" in the composition refers to "mass %" unless otherwise specified.

[0046] Si: 2.0%–5.0%

[0047] Si is an element needed to increase the resistivity of steel and improve iron loss, but if it is less than 2.0%, the effect is poor, and if it exceeds 5.0%, the workability of the steel deteriorates and it becomes difficult to roll. Therefore, the concentration is 2.0% to 5.0%. Si is preferably 3.0% or more. Si is preferably 3.6% or less.

[0048] Mn: 0.01%~0.50%

[0049] Mn is an element required for heat workability, but if it is less than 0.01%, the effect is poor, and if it exceeds 0.50%, the magnetic flux density of the product board decreases. Therefore, the optimal concentration is 0.01% to 0.50%. Mn is preferably 0.03% or more. Mn is preferably 0.15% or less.

[0050] Any one or both of S and Se: Total 0.001% to 0.100%

[0051] The problem addressed by this invention is primarily caused by S and Se in steel; therefore, these elements are included as a prerequisite in this invention. Specifically, if the total of any one or both of S and Se is less than 0.001%, the problem itself will not occur; on the other hand, if it exceeds 0.100%, secondary recrystallization becomes difficult, thus the content is limited to 0.001% to 0.100%. The aforementioned total is preferably 0.003% or more. The aforementioned total is preferably 0.030% or less.

[0052] The basic components of the present invention have been described above. However, in the present invention, the steel billet may also contain the elements described below appropriately.

[0053] That is, in order to suppress end cracking and surface defects during casting or hot rolling, it may contain 0.01% to 0.10% C. Preferably, the C content is 0.03% to 0.08%.

[0054] In addition, when using AlN as an inhibitor, it can contain Al: 0.01% to 0.04% and N: 0.003% to 0.010%.

[0055] Furthermore, to improve magnetic properties, the following components can be used: Ni: greater than 0% and less than 1.50%; Cr: greater than 0% and less than 0.50%; Cu: greater than 0% and less than 0.50%; P: greater than 0% and less than 0.50%; Sb: greater than 0% and less than 0.50%; Sn: greater than 0% and less than 0.50%; Bi: greater than 0% and less than 0.50%; Mo: greater than 0% and less than 0.50%; B: greater than 0 ppm and less than 25 ppm; Nb: greater than 0% and less than 0.020%. The following additives may be used individually or in combination: V: more than 0% and less than 0.010%; Zr: more than 0% and less than 0.10%; Co: more than 0% and less than 0.050%; Pb: more than 0% and less than 0.0100%; As: more than 0% and less than 0.0200%; Zn: more than 0% and less than 0.020%; W: more than 0% and less than 0.0100%; Ge: more than 0% and less than 0.0050%; and Ga: more than 0% and less than 0.0050%. If the amount of any of these additives exceeds the upper limit, there is a risk that the growth of secondary recrystallized grains will be suppressed, leading to a deterioration in magnetic properties.

[0056] <Manufacturing Process>

[0057] Steel billets with the above-mentioned composition can be manufactured into slabs using conventional ingot casting or continuous casting methods, or into thin castings with a thickness of less than 100 mm using direct casting methods. These slabs and thin castings, which are used as steel billets, are usually hot-rolled after reheating, but they can also be hot-rolled immediately after casting without reheating.

[0058] In hot rolling, especially the hot rolling after reheating, from the viewpoint of controlling the microstructure of the hot-rolled sheet, it is preferable to perform rough rolling at least once at 900°C to 1200°C, followed by finish rolling at least twice at 700°C to 1000°C. Furthermore, after hot rolling, the sheet can be wound into coils. In this case, from the viewpoints of controlling carbide morphology and preventing defects such as cracking, a winding temperature of 400°C to 750°C is preferred. A winding temperature of 500°C to 700°C is even more preferred.

[0059] After hot rolling, the hot-rolled sheet can be annealed as needed. Annealing the hot-rolled sheet helps to homogenize the microstructure and reduce deviations in magnetic properties. From the viewpoint of achieving this microstructure homogenization, the annealing temperature is preferably 800°C to 1250°C, and the holding time is preferably 5 seconds or more. More preferably, the annealing temperature is 900°C to 1150°C, and the holding time is 10 seconds to 180 seconds. After annealing, the hot-rolled sheet can be cooled. From the viewpoint of controlling the morphology of the second phase and precipitates, such cooling is preferably performed at a cooling rate of 5°C / s to 100°C / s in the temperature range of 800°C to 350°C. The cooling rate is further preferably 15°C / s or more to 45°C / s.

[0060] Next, it is preferable to remove the oxide scale generated on the surface of the steel sheet during hot rolling. Known methods such as using heated acid or mechanically removing the oxide scale can be employed. Then, a final sheet thickness is achieved by one cold rolling pass or two or more cold rolling passes with intermediate annealing, followed by decarburization annealing. During intermediate annealing, from the viewpoint of microstructure control, it is preferable to hold the sheet at a temperature range of 800°C to 1250°C for at least 5 seconds. During cooling after holding the intermediate annealing, from the viewpoint of controlling the morphology of the second phase and precipitates, it is preferable to set the cooling rate from 800°C to 350°C at 5°C / s to 100°C / s. The above cooling rate is further preferably 15°C / s to 45°C / s. It should be noted that before intermediate annealing, it is preferable to degrease the steel sheet to remove the rolling oil from the previous process. On the other hand, it is preferable to remove the oxide scale from the surface of the steel sheet after intermediate annealing. Known methods such as using heated acid or mechanically removing the oxide scale can be employed.

[0061] In cold rolling, lubricants such as rolling oil are preferred to reduce rolling load and improve rolling shape. Furthermore, to obtain a good recrystallized aggregate structure before secondary recrystallization, the total reduction rate of the final cold rolling is preferably 50% to 92%.

[0062] The cold-rolled steel sheet is then supplied for decarburization annealing, but preferably degreasing and pickling are performed beforehand to clean the steel sheet surface. Decarburization annealing is preferably performed at a temperature range of 750°C to 950°C for at least 10 seconds, in a humid atmosphere containing H2 and N2, with a dew point of 20°C to 80°C for part or all of the decarburization annealing process. A further preferred condition for the atmosphere is a dew point of 30°C to 70°C within a temperature range of 800°C to 900°C.

[0063] Then, an annealing separating agent mainly composed of MgO is applied to the steel plate and dried. The preferred application amount of the annealing separating agent is 2.5 g / m² on each side of the steel plate. 2 The above. Here, "MgO as the main component" means that the MgO content in the annealing separating agent, converted to solids, is 60% or more by mass. Preferably, the MgO content in the annealing separating agent, converted to solids, is 80% or more by mass. MgO is coated onto the steel plate in the form of a slurry solution suspended in water. At this time, in order to suppress the increase in viscosity, the slurry solution is preferably maintained at a constant temperature within the range of 5°C to 30°C.

[0064] Here, as described above, to ensure the flowability of the atmosphere gas during final annealing, it is preferable to hydrate MgO to 1.0% by mass or more. Furthermore, to increase the hydration amount, the mixing time needs to be extended; therefore, to reduce the required time, the hydration amount is preferably 7.0% by mass or less. That is, the loss on ignition of the annealing separating agent after drying is preferably 1.0% to 7.0% by mass. It should be noted that the above-mentioned loss on ignition was determined according to JIS K0067:1992.

[0065] Furthermore, to maintain a constant slurry concentration during coating, the slurry solution of the annealing separating agent is preferably divided into a mixing tank and a coating tank. The annealing separating agent is prepared into a slurry solution, coated, and dried, followed by final annealing. This allows for the growth of secondary recrystallized grains and the formation of a forsterite film. During final annealing, to achieve secondary recrystallization, the temperature is preferably raised to 800°C or higher; in the case of forming a forsterite film, the temperature is preferably raised to 1050°C or higher.

[0066] However, final annealing typically takes a long time, so the steel coils are loaded vertically into the final annealing furnace and prepared for annealing. Therefore, it is preferable to wind a strip or similar material around the steel coil before final annealing to prevent the outer coil of the upper part of the steel coil from unwinding.

[0067] In addition, during the final annealing, in order to purify inhibitor-forming elements such as S and Se from the steel and obtain good iron loss characteristics, it is preferable to hold the temperature at 1050°C to 1300°C for more than 3 hours and introduce part or all of the atmosphere containing H2 within the temperature range above 1050°C.

[0068] As described above, in the final annealing, it is important to ensure that the flow rate of the atmosphere gas per ton of steel is 0.2 L / min or more, and that the atmosphere dew point is 10°C or less. The atmosphere dew point is preferably 0°C or less. The flow rate of the atmosphere gas per ton of steel is preferably 0.5 L / min or more. On the other hand, there are no particular restrictions on the lower limit of the atmosphere dew point and the upper limit of the atmosphere gas flow rate, but from a cost perspective, the atmosphere dew point is preferably -60°C or more, and the atmosphere gas flow rate is preferably 5.0 L / min or less.

[0069] After final annealing, it is useful to wash with water, brush, and pickle in order to remove the attached annealing separator.

[0070] Then, planarization annealing is performed. This planarization annealing is accompanied by a coating process including the application of a coating solution. Furthermore, before applying the coating solution, an acid pickling treatment is performed at a temperature of 1.0% to 20.0% concentration at a temperature of 15°C or higher for 1 to 60 seconds. As mentioned above, such a pickling treatment is necessary. Furthermore, the concentration of the acid is preferably 2.0% to 10.0%. Furthermore, the temperature of the acid is preferably 40°C or higher, and preferably 90°C or lower. Furthermore, the pickling time is preferably 2 to 15 seconds. Here, the acid used in the pickling treatment is preferably any one of phosphoric acid, hydrochloric acid, sulfuric acid, or nitric acid.

[0071] Furthermore, electromagnetic steel sheets are mostly used in multiple layers of laminated steel sheets, so applying an insulating coating to the surface of the steel sheets is effective in ensuring insulation. This insulating coating is preferably one that can apply tension to the steel sheet to reduce iron loss.

[0072] Example

[0073] (Example 1)

[0074] Oriented electromagnetic steel sheets containing 2.99% Si, 0.09% Mn, and 0.014% Se (by mass%) were hot-rolled to 1400°C to produce 2.7mm thick hot-rolled sheets. The oxide scale on the steel surface was removed by pickling, followed by cold rolling to a thickness of 0.68mm. Next, an intermediate annealing was performed at 900°C for 100 seconds, followed by a second cold rolling to a thickness of 0.23mm. Then, a decarburization annealing was performed at 850°C for 120 seconds with 50% H₂ + 50% N₂ and a dew point of 62°C. Finally, an annealing separating agent based on MgO was applied to the steel surface and dried, followed by a final annealing at 1210°C for 10 hours. After the annealing separator was applied and dried, only the annealing separator on the steel plate was collected, and the loss on ignition was determined by the method described in JIS K0067:1992, with a result of 2.5%.

[0075] The final annealing atmosphere was N2 up to 1000°C during heating, H2 up to 1000°C after holding at 1210°C from above 1100°C, and Ar during subsequent cooling. The atmosphere dew point and gas flow rate were changed as described in Table 1. Next, unreacted annealing separating agent remaining on the steel plate surface was removed by water washing. Then, the plate was acid-washed with phosphoric acid at the acid concentration and temperature specified in Table 1 for the time specified in Table 1. Afterward, a phosphate-based coating solution was applied, and a planarization annealing process was performed at 820°C for 100 seconds, serving as both a coating sintering process (coating treatment) and a planarization of the steel plate.

[0076] The coating adhesion of the obtained steel sheet was evaluated. For coating adhesion, the steel sheet was wound into cylinders of various diameters, and the minimum diameter at which the coating did not peel off was used for evaluation. In addition, for the evaluation, samples were collected from each of the two ends and the central portion of the long side of the steel coil, and from two locations at each end and one location at the center in the width direction of the steel coil—a total of nine locations per steel coil—with dimensions of 280 mm in the rolling direction and 30 mm in the width direction. The maximum value at these nine locations was taken as the representative value for each steel coil. Furthermore, magnetic evaluation samples were collected from the locations showing the representative value of coating adhesion, and the iron loss W was measured using the method described in JIS C2550-1 (2011). 17 / 50 (Iron loss under excitation at a magnetic flux density of 1.7T and a frequency of 50Hz). The results are shown in Table 1. As can be seen from the table, by following the present invention, an orientation-oriented electromagnetic steel sheet with excellent coating adhesion and iron loss characteristics can be obtained.

[0077]

[0078] (Example 2)

[0079] Oriented electromagnetic steel sheet, containing 0.075% C, 3.66% Si, 0.24% Mn, and 0.028% S by mass, was reheated to 1420°C and hot-rolled to produce a 2.2mm thick hot-rolled sheet. This was followed by a 30-second hot-rolled annealing at 980°C, pickling to remove oxide scale, and then cold rolling to a 1.20mm thickness. Next, an intermediate annealing was performed at 1100°C for 100 seconds, followed by a second cold rolling to a 0.23mm thickness. Then, a decarburization annealing was performed at 850°C for 120 seconds with 48% H₂ + 52% N₂ and a dew point of 63°C. Finally, an annealing separating agent based on MgO was applied to the steel surface and dried, followed by a final annealing at 1200°C for 10 hours. The temperature of the coating solution for blending the annealing separator was set to 10°C, and the blending time was varied to change the hydration amount of MgO as recorded in Table 2. For the hydration amount, after coating and drying of the annealing separator, only the annealing separator on the steel plate was collected, and the loss on ignition was determined using the method described in JIS K0067:1992, which was taken as its value.

[0080] The final annealing atmosphere was N2 up to 900°C during heating, H2 down to 900°C after holding at 1200°C, and Ar during subsequent cooling. The atmosphere dew point was -55°C, and the gas flow rate was 1.5 L / min per ton of steel. Next, unreacted annealing separating agent remaining on the steel plate surface was removed by water washing, followed by a 5-second pickling treatment at 60°C using the acid types and concentrations listed in Table 2. Then, a phosphate-based coating solution was applied, and a planarization annealing process was performed at 860°C for 35 seconds, serving as both a coating sintering (coating treatment) and a planarization of the steel plate.

[0081] The coating adhesion of the obtained steel sheet was evaluated. For coating adhesion, the steel sheet was wound into cylinders of various diameters, and the minimum diameter at which the coating did not peel off was used for evaluation. In addition, for the evaluation, samples were collected from each of the two ends and the central portion of the long side of the steel coil, and from two locations at each end and one location at the center in the width direction of the steel coil (a total of nine locations per steel coil), with dimensions of 280 mm in the rolling direction and 30 mm in the width direction. The maximum value at these nine locations was taken as the representative value for each steel coil. Furthermore, magnetic evaluation samples were collected from locations showing representative values ​​for coating adhesion, and the iron loss W was measured using the method described in JIS C2550-1 (2011). 17 / 50 (Iron loss under excitation at a magnetic flux density of 1.7T and a frequency of 50Hz). The results are shown in Table 2. As can be seen from the table, by following the present invention, an orientation-oriented electromagnetic steel sheet with excellent coating adhesion and iron loss characteristics can be obtained.

[0082] Table 2

[0083]

Claims

1. A method for manufacturing an oriented electromagnetic steel sheet, comprising the following steps: hot rolling a steel billet containing, by mass %, any one or two of S and Se, namely, Si: 2.0% to 5.0%, Mn: 0.01% to 0.50%, totaling 0.001% to 0.100%, followed by cold rolling once or more, or cold rolling with intermediate annealing, then decarburization annealing, then coating with an annealing separating agent mainly composed of MgO and drying, then final annealing, and finally planarization annealing; in, The final annealing is carried out in an atmosphere where the flow rate of the gas is 0.2 L / min or more relative to the ton of steel sheet and the dew point is below 10°C. The planarization annealing is accompanied by a coating process including the application of a coating solution. Before applying the coating solution, an acid pickling treatment is performed at a temperature of 55°C to 70°C for 1 to 60 seconds using an acid concentration of 1.0% to 20.0% by mass.

2. The method for manufacturing the oriented electromagnetic steel sheet according to claim 1, wherein, The acid is any one of phosphoric acid, hydrochloric acid, sulfuric acid, or nitric acid.

3. The method for manufacturing the oriented electromagnetic steel sheet according to claim 1 or 2, wherein, The loss on ignition of the annealing separator after drying is 1.0% to 7.0% by mass.

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