Method for manufacturing grain-oriented electrical steel sheet

Abstract

Provided is a method for manufacturing an oriented electromagnetic steel sheet that can stably produce an oriented electromagnetic steel sheet having excellent magnetic properties and little variation in iron loss in the length direction of the steel sheet. The present invention is a method for manufacturing an oriented electromagnetic steel sheet, comprising the following steps: hot-rolling a steel blank, performing annealing as necessary, and then producing a cold-rolled sheet having a final sheet thickness by one cold-rolling or two or more cold-rolling with intermediate annealing interposed, and then performing decarburization annealing on the cold-rolled sheet having the final sheet thickness, and then performing secondary recrystallization annealing; and heating the steel sheet to a heating temperature of 100°C to 350°C at a temperature increase rate of 100°C / s or more before the final cold-rolling, and the time from reaching the heating temperature to the first pass of the final cold-rolling is 5 seconds or less.

Description

Technical Field

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

[0002] Oriented electromagnetic steel sheets are soft magnetic materials used as core materials for transformers and generators. They are steel sheets with excellent magnetic properties, characterized by a highly consistent crystalline structure with the iron's easy magnetization axis, i.e., {110}<001> orientation (Gaussian orientation), in the rolling direction of the steel sheet.

[0003] As a method to improve integration toward Gaussian orientation, for example, Patent Document 1 discloses a method for heat-treating and aging a cold-rolled sheet at a low temperature.

[0004] Patent document 2 discloses the following technology: the cooling rate during the annealing of hot-rolled plate or the intermediate annealing before the final cold rolling is 30°C / s or more, and the plate is further subjected to aging for more than 2 minutes at a temperature of 150 to 300°C twice during the final cold rolling.

[0005] Patent document 3 discloses a technology that utilizes dynamic strain aging, which involves warm rolling by increasing the temperature of the steel plate during rolling, so that dislocations introduced during rolling are immediately fixed with C and N.

[0006] The techniques in Patent Documents 1-3 maintain the steel plate temperature at an appropriate level before, during, or between rolling passes, allowing carbon (C) and nitrogen (N) as solid solution elements to diffuse at low temperatures. This fixes dislocations introduced during cold rolling, suppresses dislocation movement during subsequent rolling, induces shear deformation, and improves the rolled aggregate structure. Through the application of these techniques, a large number of Gaussian-oriented seed crystals are formed during the first recrystallization. These Gaussian-oriented seed crystals grow during the second recrystallization, thereby improving the integration towards the Gaussian orientation after the second recrystallization.

[0007] As a technique to further improve the effect of the above-mentioned strain aging, Patent Document 4 discloses the following technique: heat treatment is performed before the final cold rolling of the cold rolling process to precipitate fine carbides in the steel, the final cold rolling is divided into a first half and a second half, the first half is rolled at a low temperature of 140°C with a reduction rate of 30 to 75%, and the second half is rolled at a high temperature of 150 to 300°C with at least two reduction passes, and the total reduction rate of the first half and the second half is rolled in the range of 80 to 95%, thereby obtaining a stable material that is highly integrated in Gaussian orientation.

[0008] Patent document 5 discloses the following technique: applying 0.5 kg / mm² before cold rolling in a tandem rolling mill. 2The technique involves heat treatment at 50–150°C for 30 seconds to 30 minutes under the above tension, thereby precipitating fine carbides in the steel, and performing aging treatment during cold rolling.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: Japanese Patent Application Publication No. 50-016610

[0012] Patent Document 2: Japanese Patent Application Publication No. 08-253816

[0013] Patent Document 3: Japanese Patent Application Publication No. 01-215925

[0014] Patent Document 4: Japanese Patent Application Publication No. 09-157745

[0015] Patent Document 5: Japanese Patent Application Publication No. 04-120216 Summary of the Invention

[0016] However, in recent years, the requirements for energy conservation have become increasingly stringent, necessitating the development of further low-iron-loss technologies.

[0017] In techniques that implement inter-pass aging during rolling, such as those described in Patent Documents 1-3, there are problems such as the fact that, as in the case of rolling using a tandem rolling mill, the short distance between each pass and the high linear speed of rolling cannot provide satisfactory results.

[0018] In technologies such as patent documents 4 and 5 that involve heat treatment before cold rolling, the following problem exists: due to the temperature difference inside the coil after winding, the precipitation morphology of carbides changes, resulting in a large deviation in iron loss along the length of the coil.

[0019] Therefore, the purpose of this invention is to solve the problems existing in the prior art and to provide a method for manufacturing oriented electromagnetic steel sheets that can stably produce oriented electromagnetic steel sheets with excellent magnetic properties and low deviation of iron loss in the length direction of the steel coil.

[0020] To solve the above problems, the inventors conducted repeated and in-depth research on methods for heat treatment before cold rolling. They discovered that in the manufacturing process of oriented electromagnetic steel sheets, heating the steel sheet to a heating temperature of 100°C to 350°C at a heating rate of 100°C / s or higher before the final cold rolling, so that the time from reaching the heating temperature to entering the first pass of the final cold rolling is less than 5 seconds, can improve the aggregate structure and stably manufacture oriented electromagnetic steel sheets with excellent magnetic properties and low iron loss deviation in the length direction of the steel coil, thus completing the present invention.

[0021] Final cold rolling refers to the cold rolling process where the thickness of the steel sheet after cold rolling becomes the final sheet thickness.

[0022] Before the final cold rolling refers to before the first pass of the final cold rolling process. In the case of a single cold rolling process, it refers to before the first pass of that cold rolling process. In the case of two or more cold rolling processes with intermediate annealing, it refers to before the first pass of the final cold rolling process.

[0023] The heating temperature of 100℃~350℃ refers to the highest temperature (maximum temperature) reached by the steel plate within this temperature range.

[0024] The method for manufacturing the oriented electromagnetic steel sheet of the present invention includes heating the steel sheet to a heating temperature of 100°C to 350°C at a heating rate of 100°C / s or higher before final cold rolling. This reduces deviations in magnetic properties. The reason for the reduction in magnetic property deviations is not yet clear, but it is speculated as follows.

[0025] By heating the steel sheet before the final cold rolling, the entry temperature of the first rolling pass is increased, resulting in a greater variety of slip systems active during the first rolling pass compared to the case without heating. In subsequent rolling passes, the entry temperature is lower than in the first pass due to the influence of the strip coolant. Therefore, some slip systems active in the first pass become inactive in subsequent passes due to the reduced processing temperature. Dislocations active in such slip systems cannot move in subsequent rolling passes, hindering the movement of dislocations generated in subsequent passes. This has an effect equivalent to fixing dislocations with fine carbides. Consequently, shear deformation during rolling is promoted, the microstructure is improved, and the magnetic properties of the final oriented electromagnetic steel sheet are enhanced. Furthermore, the movement-impeding effect generated by dislocations is stronger than the pinning effect of dislocations generated by fine carbides, resulting in a reduction in the influence of morphological changes of carbides in the steel sheet along the length of the coil.

[0026] The method for manufacturing the oriented electromagnetic steel sheet of the present invention includes ensuring that the time from reaching a predetermined heating temperature to entering the first pass of the final cold rolling is within 5 seconds before final cold rolling. This suppresses the deterioration of magnetic properties. The reason for suppressing the deterioration of magnetic properties is not yet clear, but it is speculated as follows.

[0027] If the time from reaching the specified heating temperature to entering the first pass of cold rolling becomes longer, the temperature of the steel plate will drop sharply after reaching the specified heating temperature. As a result, the entry temperature of the first pass of cold rolling will be lower, making it difficult to exhibit the movement-resisting effect of dislocations generated by each other in the second pass and beyond. However, by making this time less than 5 seconds, the movement-resisting effect can be fully exhibited.

[0028] The main points of this invention are as follows.

[0029] [1] A method for manufacturing an oriented electromagnetic steel sheet includes the following steps: hot rolling a steel billet, annealing it as appropriate, and then producing a cold-rolled sheet with a final plate thickness by one cold rolling or two or more cold rollings with intermediate annealing, followed by decarburizing annealing of the cold-rolled sheet with the final plate thickness, and then performing secondary recrystallization annealing.

[0030] Before the final cold rolling, the steel plate is heated to a heating temperature of 100℃~350℃ at a heating rate of 100℃ / s or higher. The time from the steel plate reaching the heating temperature to entering the first pass of the final cold rolling is less than 5 seconds.

[0031] [2] According to the manufacturing method of the oriented electromagnetic steel sheet described in [1] above, the steel billet has the following composition: containing, by mass %:

[0032] C: 0.01%~0.10%

[0033] Si: 2.0%–4.5%

[0034] Mn: 0.01%~0.5%

[0035] Al: 0.0100%~0.0400%

[0036] The total of one or two selected from S and Se: 0.0100% to 0.0500%, and

[0037] N: greater than 0.0050% and less than 0.0120%,

[0038] The remainder consists of Fe and unavoidable impurities.

[0039] [3] According to the manufacturing method of the oriented electromagnetic steel sheet described in [1] above, the steel billet has the following composition: containing, by mass %:

[0040] C: 0.01%~0.10%

[0041] Si: 2.0%–4.5%

[0042] Mn: 0.01%~0.5%

[0043] Al: less than 0.0100%

[0044] S: below 0.0070%

[0045] Se: below 0.0070%, and

[0046] N: below 0.0050%,

[0047] The remainder consists of Fe and unavoidable impurities.

[0048] [4] The method for manufacturing oriented electromagnetic steel sheet according to [2] or [3] above, wherein the steel billet further contains, by mass percent, a material selected from:

[0049] Sb: 0.005%~0.50%

[0050] Cu: 0.01%–1.50%

[0051] P: 0.005%~0.50%

[0052] Cr: 0.01%~1.50%

[0053] Ni: 0.005%~1.50%

[0054] Sn: 0.01%~0.50%

[0055] Nb: 0.0005%~0.0100%

[0056] Mo: 0.01%–0.50%

[0057] B: 0.001%–0.007%, and

[0058] Bi: 0.0005% to 0.05% of one or more of the following.

[0059] According to the method for manufacturing oriented electromagnetic steel sheets of the present invention, it is possible to stably manufacture oriented electromagnetic steel sheets with excellent magnetic properties and low deviation of iron loss in the length direction of the steel coil. Attached Figure Description

[0060] Figure 1 This is a graph showing the relationship between heating temperature (maximum temperature) and iron loss in Example 1.

[0061] Figure 2 This is a graph showing the relationship between heating time and iron loss in Example 2.

[0062] Figure 3 This is a graph showing the relationship between the heating rate and iron loss in Example 3. Detailed Implementation

[0063] The present invention will be described in detail below.

[0064] <Steel billet>

[0065] The steel billet (steel material) used in the manufacturing method of the present invention can be manufactured by known manufacturing methods, such as steelmaking-continuous casting and agglomeration-segment rolling. In steelmaking, molten steel obtained from converters, electric furnaces, etc., can be refined to the desired composition through secondary refining such as vacuum degassing.

[0066] The composition of the steel billet can be that used in the manufacture of oriented electromagnetic steel sheets, and the composition used for oriented electromagnetic steel sheets can be well-known. From the viewpoint of obtaining oriented electromagnetic steel sheets with excellent magnetic properties, it is preferable to contain C, Si, and Mn. Examples of the contents of C, Si, and Mn are as follows. Here, unless otherwise stated, "%" in relation to composition means "mass %".

[0067] C: 0.01%~0.10%

[0068] Carbon (C) is an element required to improve the microstructure of hot-rolled steel sheets. If it exceeds 0.10%, it is difficult to reduce it to below 0.0050% without causing magnetic aging by decarburization annealing. On the other hand, if it is less than 0.01%, the microstructure coarsens during billet heating, making recrystallization in subsequent processes difficult. Therefore, the C content is preferably 0.01% to 0.10%, more preferably 0.01% to 0.08%.

[0069] Si: 2.0%–4.5%

[0070] Si is an effective element for increasing the electrical resistance of steel and improving iron loss. If the content exceeds 4.5%, the workability is significantly reduced, making it difficult to roll and manufacture. On the other hand, if it is less than 2.0%, it is difficult to obtain a sufficient effect in reducing iron loss. Therefore, the Si content is preferably 2.0% to 4.5%.

[0071] Mn: 0.01%~0.5%

[0072] Mn is an element required to improve hot workability. If it exceeds 0.5%, the primary recrystallization aggregate structure deteriorates, making it difficult to obtain highly integrated secondary recrystallized grains with Gaussian orientation. On the other hand, if it is less than 0.01%, it is difficult to obtain sufficient hot rolling workability. Therefore, the Mn content is preferably 0.01% to 0.5%, more preferably 0.03% to 0.5%.

[0073] In addition to C, Si, and Mn, the composition may also contain Al: 0.0100% to 0.0400% and N: more than 0.0050% and less than 0.012% as inhibitory components in secondary recrystallization. If the Al and N contents are below the lower limits mentioned above, it is difficult to obtain the desired inhibitory effect. On the other hand, if they exceed the upper limits mentioned above, the dispersion of the precipitate becomes uneven, and it is still difficult to obtain the desired inhibitory effect.

[0074] Furthermore, in addition to Al and N, as inhibitory components, one or two of S and Se can be included in the mixture within a total range of 0.0100% to 0.0500%. The presence of any one or two of S and Se can form sulfides (MnS, Cu₂S, etc.) and selenides (MnSe, Cu₂Se, etc.). Sulfides and selenides can also precipitate in combination. If the total content of one or two of S and Se is less than the lower limit mentioned above, the inhibitory effect cannot be sufficiently obtained; if it exceeds the upper limit mentioned above, the dispersion of the precipitate becomes uneven, and the inhibitory effect still cannot be sufficiently obtained.

[0075] The composition can also suppress the Al content to less than 0.0100%, making it suitable for inhibitor-free systems. In this case, the N content can be less than 0.0050%, S less than 0.0070%, and Se less than 0.0070%.

[0076] To improve magnetic properties, in addition to the elements mentioned above, one or more elements selected from Sb: 0.005%–0.50%, Cu: 0.01%–1.5%, P: 0.005%–0.50%, Cr: 0.01%–1.50%, Ni: 0.005%–1.50%, Sn: 0.01%–0.50%, Nb: 0.0005%–0.0100%, Mo: 0.01%–0.50%, B: 0.001%–0.007%, and Bi: 0.0005%–0.05% may be included. Sb, Cu, P, Cr, Ni, Sn, Nb, Mo, B, and Bi are elements useful for improving magnetic properties. From the viewpoint of not hindering the development of secondary recrystallized grains and fully obtaining the effect of improving magnetic properties, when included, the above-mentioned ranges are preferred.

[0077] The remaining components of the steel billet are Fe and unavoidable impurities.

[0078] <Manufacturing Process>

[0079] The manufacturing method of the present invention involves hot rolling a steel billet to produce a hot-rolled sheet. The steel billet can be heated before hot rolling. From the viewpoint of ensuring hot rollability, the heating temperature is preferably around 1050°C or higher. There is no particular upper limit to the heating temperature, but temperatures exceeding 1450°C are close to the melting point of steel, making it difficult to maintain the shape of the billet; therefore, temperatures below 1450°C are preferred.

[0080] There are no special restrictions on hot rolling conditions other than those specified; well-known conditions can be applied.

[0081] The obtained hot-rolled sheet can be subjected to hot-rolled sheet annealing. At this time, there are no particular restrictions on the annealing conditions, and well-known conditions can be applied.

[0082] Hot-rolled sheets are annealed and then cold-rolled to produce cold-rolled sheets, depending on the circumstances. Oxide scale can be removed by pickling or other methods before cold rolling.

[0083] Cold-rolled sheets of the final thickness can be produced by a single cold rolling process, or by performing two or more cold rolling processes with intermediate annealing. The total reduction rate of the cold rolling process is not particularly limited and can range from 70% to 95%. The final reduction rate of the cold rolling process is not particularly limited and can range from 60% to 95%. The final sheet thickness is not particularly limited and can range from 0.1 mm to 1.0 mm.

[0084] Before the final cold rolling, the steel plate is heated to a heating temperature of 100℃~350℃ at a heating rate of 100℃ / s or higher, and the time from reaching the heating temperature to entering the first pass of the final cold rolling is less than 5 seconds.

[0085] The heating rate is 100℃ / s or higher. At temperatures above 100℃, the diffusion rate of carbon in steel increases dramatically. Therefore, maintaining the steel plate at this temperature for an extended period causes a sharp increase in carbide coarsening, resulting in a significant reduction in the amount of dissolved carbon and fine carbides in the steel. Consequently, the pinning effect of dislocations generated by carbides is considered to outweigh the effect produced by the temperature rise, leading to a deterioration of the aggregate structure. Therefore, a heating rate of 100℃ / s or higher is required to reach the specified heating temperature in a short time. A heating rate of 150℃ / s or higher is preferred. Since a shorter heating time is better, there is no upper limit to the heating rate; for example, it can be below 300℃ / s.

[0086] The heating temperature (maximum temperature) is 100°C to 350°C. If it is below 100°C, the effect of the temperature rise from the first pass cannot be fully realized. Furthermore, if it exceeds 350°C, poor lubrication during rolling will lead to deterioration of the sheet shape. The heating temperature is preferably 120°C or higher, and more preferably 300°C or lower.

[0087] The time from reaching the specified heating temperature to entering the first pass of the final cold rolling process should be within 5 seconds. If it exceeds 5 seconds, the effect of the temperature rise during the first pass will not be fully realized due to the decrease in the steel plate temperature. It is preferable to maintain the specified heating temperature as much as possible after reaching it until entering the first pass.

[0088] There are no particular limitations on the heating method; examples include air bath, oil bath, sand bath, and induction heating. From the perspectives of not requiring large-scale equipment, having minimal impact on the appearance of the rolled steel sheet, and being able to heat the steel in a short time, induction heating is preferred. When using induction heating, the specified heating temperature can be the steel sheet temperature at the outlet side of the induction heating device.

[0089] There are no particular limitations on the rolling mill used in cold rolling; examples include reverse rolling mills and tandem rolling mills. Tandem rolling mills with induction heating devices on the inlet side are particularly preferred because they can perform rolling immediately after heating. Induction heating devices for heating and soaking the steel plate can also be installed on the inlet side of the tandem rolling mill.

[0090] Heat treatments such as aging or warm rolling can be inserted during cold rolling.

[0091] In the manufacturing method of the oriented electromagnetic steel sheet of the present invention, the cold-rolled sheet having a final sheet thickness can be decarburized and annealed, followed by a second recrystallization annealing to obtain the oriented electromagnetic steel sheet. An insulating film can be applied after the second recrystallization annealing.

[0092] There are no particular limitations on the conditions for decarburization annealing. Generally, decarburization annealing is often combined with a recrystallization annealing, and in the manufacturing method of the present invention, it can also be combined with a recrystallization annealing. In this case, there are no particular limitations on the conditions, and known conditions can be applied. For example, annealing conditions of 800°C for 2 minutes in a warm hydrogen atmosphere can be cited.

[0093] After decarburization annealing, the cold-rolled sheet undergoes final annealing for secondary recrystallization. Before final annealing, an annealing separating agent can be applied to the surface of the steel sheet. There are no particular limitations on the annealing separating agent; any known annealing separating agent can be used. Examples include annealing separating agents with MgO as the main component and, if necessary, TiO2, etc., added; and annealing separating agents with SiO2 and Al2O3 as the main components.

[0094] After final annealing, it is preferable to coat the steel plate surface with an insulating film and sinter it. Planarization annealing is then performed as needed to adjust the shape of the steel plate. There is no particular limitation on the type of insulating film. When forming an insulating film that imparts tensile tension on the steel plate surface, it is preferable to use a coating solution containing phosphate-colloidal silica as described in Japanese Patent Application Publication Nos. 50-79442, 48-39338, and 56-75579, and sinter at around 800°C.

[0095] Example

[0096] <Example 1>

[0097] A steel billet consisting of the following components is heated to 1210°C and then hot-rolled to produce a hot-rolled plate with a thickness of 2.0 mm. The above components contain, by mass %: C: 0.037%, Si: 3.4%, and Mn: 0.05%, and by mass ppm: S and Se: 31 ppm, N: 50 ppm, and sol.Al: 85 ppm, with the remainder being Fe and unavoidable impurities.

[0098] The hot-rolled sheet was annealed at 1000°C for 60 seconds, then cooled from 800°C to 300°C at a rate of 20°C / s, and then wound onto a steel coil. The resulting annealed hot-rolled sheet was then rolled in a tandem rolling mill (300mm roll diameter, 5 stands) in one pass to produce a cold-rolled sheet with a thickness of 0.20mm. At this point, the steel sheet was heated to the specified heating temperature (maximum temperature) at a rate of 100°C / s using an induction heating device located before the first rolling stand. After reaching the heating temperature, the sheet entered the first rolling stand 3 seconds later. The heating temperature is the steel sheet temperature at the exit side of the induction heating device.

[0099] After performing a primary recrystallization annealing on the cold-rolled sheet, which also serves as a decarburization annealing, at a homogenization temperature of 840℃ and a homogenization time of 100 seconds, an annealing separating agent with MgO as the main component is coated on the surface of the steel sheet, followed by a final annealing for secondary recrystallization.

[0100] The steel plate after the above-mentioned secondary recrystallization annealing is coated with a coating solution containing phosphate-chromate-colloidal silica in a weight ratio of 3:1:2, and then subjected to planarization annealing at 800℃ for 30 seconds to produce the product steel coil.

[0101] For the product steel coil, the iron loss at three points along the length of the steel coil was measured, and the average value and standard deviation were calculated. In the example, the iron loss was measured by cutting samples from a steel coil with a total weight of 500g or more at positions 200m, 2500m, and 4800m from the end of the coil and conducting iron loss tests.

[0102] By varying the heating temperature (maximum temperature) within the range of 50℃ to 450℃, the relationship between the heating temperature (maximum temperature) and iron loss is shown in the figure. Figure 1 .

[0103] like Figure 1 As shown, the induction heating temperature (maximum temperature) ranges from 100℃ to 350℃, exhibiting good magnetic properties with minimal deviation. However, at heating temperatures above 375℃, defects and fractures were observed in the steel plates.

[0104] <Example 2>

[0105] The hot-rolled annealed sheet manufactured in Example 1 was heated to a maximum temperature of 100°C using the induction heating device and tandem rolling mill used in Example 1 at a heating rate of 100°C / s. The time from reaching the heating temperature to entering the first pass of the rolling mill (time elapsed after heating) was varied within the range of 1 to 10 seconds during cold rolling to produce a cold-rolled sheet with a thickness of 0.20 mm. Using the obtained cold-rolled sheet, product steel coils were manufactured in the same manner as in Example 1. For the product steel coils, iron loss was measured at three points along the length of the coil, as in Example 1, and the average value and standard deviation were calculated. The relationship between time elapsed after heating and iron loss is shown in... Figure 2 .

[0106] like Figure 2 As shown, when the heating time is less than 5 seconds, the magnetic properties show little deviation and good magnetism. However, if the time exceeds this time, the iron loss deteriorates and the deviation increases.

[0107] <Example 3>

[0108] Using the induction heating device and tandem rolling mill used in Example 1, the heating rate was varied within the range of 10–200 °C / s. The hot-rolled annealed sheet manufactured in Example 1 was heated to a heating temperature (maximum temperature) of 100 °C. After reaching the heating temperature, it was cold-rolled in the first pass of the rolling mill 3 seconds later to produce a cold-rolled sheet with a thickness of 0.20 mm. Using the obtained cold-rolled sheet, product steel coils were manufactured in the same manner as in Example 1. For the product steel coils, iron loss was measured at three points along the length of the coil, as in Example 1, and the average value and standard deviation were calculated. The relationship between heating rate and iron loss is shown in… Figure 3 .

[0109] like Figure 3 As shown, when the heating rate is above 100℃ / s, the iron loss is below 0.90W / kg, which is good.

[0110] <Example 4>

[0111] A steel billet consisting of the following composition is heated to 1400°C and then hot-rolled to produce a hot-rolled plate with a thickness of 2.0 mm. The above composition, by mass %, contains C: 0.06%, Si: 3.4%, and Mn: 0.06%, N: 90 ppm, 250 ppm of sol.Al, 0.02% of S and Se respectively, and the remainder is Fe and unavoidable impurities.

[0112] The hot-rolled sheet was annealed at 1000°C for 60 seconds, then cooled from 800°C to 300°C at a rate of 20°C / s, and then wound onto a steel coil. The resulting annealed hot-rolled sheet was first cold-rolled using a tandem rolling mill (300mm roll diameter, 5 stands), followed by intermediate annealing at 1100°C for 80 seconds in an atmosphere of 75 vol% N2 + 25 vol% H2 and a dew point of 46°C. Finally, a final cold rolling was performed using a tandem rolling mill (300mm roll diameter, 5 stands) to produce a cold-rolled sheet with a thickness of 0.20mm. During the final cold rolling, induction heating was performed using an induction heating device for heating and homogenizing the steel sheet, located before the first rolling stand. The heating temperature (maximum temperature), heating rate, and time from reaching the heating temperature to entering the first rolling stand (time elapsed after heating) in the induction heating were varied as shown in Table 1.

[0113] After performing a primary recrystallization annealing, which also serves as a decarburization annealing, on the cold-rolled sheet at a homogenization temperature of 840°C and a homogenization time of 100 seconds, an annealing separating agent with MgO as the main component is coated on the surface of the steel sheet, followed by a final annealing for secondary recrystallization.

[0114] The steel plate after the above-mentioned secondary recrystallization annealing is coated with a coating solution containing phosphate-chromate-colloidal silica in a weight ratio of 3:1:2, and then subjected to planarization annealing at 800℃ for 30 seconds to produce the product steel coil.

[0115] For the product steel coil, the iron loss at three points along the length of the coil was measured in the same manner as in Example 1, and the average value and standard deviation were calculated. The results are shown in Table 1.

[0116] Table 1

[0117]

[0118] As shown in Table 1, even when a large amount of steel billet with added inhibitors is used as in Example 4 and intermediate annealing is inserted in the cold rolling process, the magnetic properties are good and the deviation of the properties in the length direction of the steel coil is reduced when the specified heat treatment is performed in the final cold rolling.

[0119] <Example 5>

[0120] The steel with the following composition is melted, made into a billet, heated to 1210°C, and then hot-rolled to produce a hot-rolled plate with a thickness of 2.0 mm. The above composition contains, by mass %: C: 0.036%, Si: 3.4%, and Mn: 0.06%; by mass ppm: N: 50 ppm, sol.Al: 72 ppm, S: 31 ppm, and Se: 31 ppm respectively; and by the composition shown in Table 2: Sb, Cu, P, Cr, Ni, Sn, Nb, Mo, B, and Bi as other components, with the remainder being Fe and unavoidable impurities.

[0121] The hot-rolled sheet was annealed at 1000°C for 60 seconds, then cooled from 800°C to 300°C at a rate of 20°C / s, and then wound onto a steel coil. The resulting annealed hot-rolled sheet was then rolled in a tandem rolling mill (300mm roll diameter, 5 stands) to produce a cold-rolled sheet with a thickness of 0.20mm in one pass. At this point, the sheet was heated to 100°C at a rate of 100°C / s using an induction heating device located before the first pass of the rolling mill, and then entered the first pass 3 seconds after reaching 100°C.

[0122] After performing a primary recrystallization annealing on the cold-rolled sheet, which also serves as a decarburization annealing, at a homogenization temperature of 840°C and a homogenization time of 100 seconds, an annealing separating agent with MgO as the main component is applied to the surface of the steel sheet, followed by a final annealing for secondary recrystallization.

[0123] The steel sheet surface after the above-mentioned secondary recrystallization annealing was coated with a coating solution containing phosphate-chromate-colloidal silica in a weight ratio of 3:1:2, and then subjected to planarization annealing at 800°C for 30 seconds to produce product steel coils. For the product steel coils, the iron loss at three points along the length direction of the steel coil was measured in the same manner as in Example 1, and the average value and standard deviation were calculated. The results are shown in Table 2.

[0124]

[0125] As shown in Table 2, the iron loss of steel plates with any one or more of Sb, Cu, P, Cr, Ni, Sn, Nb, Mo, B, and Bi is below 0.80 W / kg, especially with reduced iron loss and small characteristic deviation in the length direction of the steel coil.

Claims

1. A method for manufacturing an oriented electromagnetic steel sheet, comprising the following steps: hot rolling a steel billet, annealing as appropriate, then producing a cold-rolled sheet with a final sheet thickness by one cold rolling or two or more cold rollings with intermediate annealing, then decarburizing the cold-rolled sheet with the final sheet thickness, and then performing secondary recrystallization annealing. Before the final cold rolling, the steel plate is heated to a heating temperature of 100°C to 350°C at a heating rate of 100°C / s or higher, and the time from the steel plate reaching the heating temperature to entering the first pass of the final cold rolling is less than 5 seconds.

2. The method for manufacturing the oriented electromagnetic steel sheet according to claim 1, wherein, The steel billet has the following composition: containing, by mass %: C：0.01％～0.10％、 Si: 2.0%–4.5% Mn: 0.01%~0.5% Al：0.0100％～0.0400％、 The total of one or two selected from S and Se: 0.0100% to 0.0500%, and N: greater than 0.0050% and less than 0.0120%, The remainder consists of Fe and unavoidable impurities.

3. The method for manufacturing the oriented electromagnetic steel sheet according to claim 1, wherein, The steel billet has the following composition: containing, by mass %: C：0.01％～0.10％、 Si: 2.0%–4.5% Mn: 0.01%~0.5% Al: less than 0.0100% S: below 0.0070% Se: below 0.0070%, and N: below 0.0050%, The remainder consists of Fe and unavoidable impurities.

4. The method for manufacturing an orientation-oriented electromagnetic steel sheet according to claim 2 or 3, wherein, The steel billet further contains, by mass percent, a selection from: Sb: 0.005%~0.50% Cu: 0.01%–1.50% P：0.005％～0.50％、 Cr：0.01％～1.50％、 Ni: 0.005%~1.50% Sn: 0.01%~0.50% Nb: 0.0005%~0.0100% Mo: 0.01%–0.50% B: 0.001%–0.007%, and Bi: 0.0005% to 0.05% of one or more of the following.

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