Method for manufacturing grain-oriented electromagnetic steel sheet and rolling apparatus for manufacturing grain-oriented electromagnetic steel sheet

Abstract

The present invention provides a method for manufacturing an oriented electromagnetic steel sheet with low iron loss and small deviation in iron loss, which can be stably manufactured using a continuous rolling mill. A method for manufacturing an oriented electromagnetic steel sheet includes hot rolling a steel blank to produce a hot-rolled steel sheet, cold rolling the hot-rolled steel sheet one or more times with intermediate annealing to produce a cold-rolled sheet having a final sheet thickness, then decarburizing the cold-rolled sheet and performing secondary recrystallization annealing; and final cold rolling using a continuous rolling mill, heating the steel sheet to a temperature range of 70°C to 200°C, and then introducing the steel sheet into a first pass of the continuous rolling mill, wherein, in the first pass, the bite temperature T (°C) and the strain rate e (s －1 ) satisfy the following equation (1). 0.0378e 2 + 0.367e + 37.2 > T...(1).

Description

Technical Field

[0001] This invention relates to a method for manufacturing oriented electromagnetic steel sheets and rolling equipment for manufacturing oriented electromagnetic steel sheets used in this method. 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 towards Gaussian orientation, Patent Document 1 discloses a method for heat-treating and aging cold-rolled sheets at low temperatures. Patent Document 2 discloses a technique where the cooling rate during annealing of hot-rolled sheets or intermediate annealing before final cold rolling is 30°C / s or more, and further, during final cold rolling, inter-pass aging is performed at a temperature of 150–300°C for at least two passes of at least two minutes. Furthermore, Patent Document 3 discloses a technique utilizing dynamic strain aging, which involves warm rolling by increasing the temperature of the steel sheet during rolling, immediately fixing dislocations introduced during rolling with C and N.

[0004] The techniques described in these patent documents 1-3 all involve maintaining the steel plate temperature at an appropriate level before, during, or between rolling passes, thereby 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, further induces shear deformation, and improves the rolling texture. 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 of Gaussian orientation after the second recrystallization.

[0005] Furthermore, as a technique to further improve the aforementioned strain aging effect, Patent Document 4 discloses the following technique: In the annealing process prior to the final cold rolling in the cold rolling process, fine carbides are precipitated in the steel. The final rolling is divided into a first half and a second half. In the first half, the temperature is lower than 140°C with a reduction rate of 30-75%. In the second half, at least two reduction passes are performed at a high temperature of 150-300°C. Rolling is then carried out at a total reduction rate of 80-95% for both the first and second halves, thereby stably obtaining a highly integrated material with Gaussian orientation. Additionally, Patent Document 5 discloses the following technique: Before continuous cold rolling, a strain aging process is performed with a 0.5 kg / mm² annealing agent. 2 Under the above tension, heat treatment is carried out at 50-150°C for 30 seconds to 30 minutes, thereby precipitating fine carbides in the steel.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 50-016610

[0009] Patent Document 2: Japanese Patent Application Publication No. 08-253816

[0010] Patent Document 3: Japanese Patent Application Publication No. 01-215925

[0011] Patent Document 4: Japanese Patent Application Publication No. 09-157745

[0012] Patent Document 5: Japanese Patent Application Publication No. 04-120216 Summary of the Invention

[0013] In recent years, due to societal demands for energy conservation, the demand for low-iron-loss oriented electromagnetic steel sheets has been continuously increasing, necessitating the development of technologies for the stable mass production of low-iron-loss oriented electromagnetic steel sheets.

[0014] Here, continuous rolling mills, compared to reversible mills like Sendzimir, have a higher hourly throughput, which is beneficial for the mass production of oriented electromagnetic steel sheets. In the techniques disclosed in Patent Documents 1 and 2 that implement inter-pass aging during rolling, the desired effects cannot be achieved when the distance between passes is short and the linear speed is high, as in continuous rolling. Furthermore, in the method of rolling with heating at the entrance side of the continuous rolling mill disclosed in Patent Document 3, the improvement in iron loss is insufficient. The reasons are explained below. It is believed that primary recrystallized Gaussian oriented grains nucleate from shear bands introduced into the {111}<112> matrix structure, which is one of the stable orientations in rolling. It is believed that since the {111}<112> matrix structure develops through cold rolling at low temperatures, the method of rolling with heating at the entrance side of the continuous rolling mill cannot sufficiently form the {111}<112> matrix structure, resulting in an insufficient amount of primary recrystallized Gaussian oriented grains.

[0015] Furthermore, in the technology of performing carbide precipitation treatment in the annealing process before final cold rolling as described in Patent Documents 4 and 5, the carbides coarsen depending on the time elapsed from the precipitation treatment to the final cold rolling. As a result, the texture changes due to the time variation, leading to a problem of increased deviation in iron loss of the product coil.

[0016] 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 with low iron loss and small deviation in iron loss using a continuous rolling mill, and the rolling equipment used in the method.

[0017] To solve the above problems, the inventors conducted repeated and in-depth research on a method for heat treatment before cold rolling in a series of processes for oriented electromagnetic steel sheets. The experimental results achieving the present invention are described below.

[0018] A steel billet with the following composition was heated to 1210°C and then hot-rolled to produce a hot-rolled sheet with a thickness of 2.0 mm. The composition, by mass%, contained 0.037% C, 3.4% Si, and 0.05% Mn; by mass%, it contained 31 ppm each of S and Se, 50 ppm of N, and 85 ppm of sol.Al; the remainder being Fe and unavoidable impurities. The hot-rolled sheet was then subjected to hot-rolled annealing at 1000°C for 60 seconds, followed by cooling from 800°C to 350°C at a rate of 20°C / s, and then wound into coils. The resulting hot-rolled annealed sheet was then continuously rolled in one pass using a continuous rolling mill (300 mm roll diameter, 5 stands) to produce a cold-rolled sheet with a thickness of 0.20 mm.

[0019] At this point, the hot-rolled annealed sheet is heated to various temperatures ranging from 50°C to 250°C, as shown in Table 1, via a heating device installed between the uncoiler and the first pass of the rolling mill. After heating, the following two types of coils are produced: with a strain rate of 25 s in the first pass of the tandem rolling mill. －1 The method involves adjusting the roll speed and directly biting the coil into the first rolling stand at the original temperature, as well as biting the coil after cooling the steel plate to room temperature (25°C). In addition, coils that are bitten into the first pass without heating the steel plate have also been produced.

[0020] Then, the cold-rolled sheet is subjected to a primary recrystallization annealing at a homogenization temperature of 840°C for 100 seconds, which also serves as a decarburization annealing. An annealing separating agent with MgO as the main component is then applied to the surface of the steel sheet, followed by a final annealing for secondary recrystallization. After the final annealing, a coating solution containing phosphate-chromate-colloidal silica in a mass ratio of 3:1:2 is applied to the surface of the steel sheet, and a planarization annealing is performed at 800°C for 30 seconds to produce the finished coil.

[0021] The iron loss of 10 rolls manufactured under the same conditions was measured, and their average value and standard deviation were calculated. The iron loss was measured by cutting a sample from the center of the roll length with a total weight of 500g or more and performing an Epstein test. The results of the iron loss measurement, along with the heating temperature and the bite temperature of the first pass, are shown in Table 1.

[0022] [Table 1]

[0023] Table 1

[0024]

[0025] Table 1 shows that when the steel sheet is heated to a temperature range of 70°C to 200°C before the first pass during cold rolling (for heating at 200°C, the first pass bite temperature is 25°C), the deviation in iron loss decreases. Furthermore, it is found that when the steel sheet is heated to a temperature range of 70°C to 200°C and then the bite temperature for the first pass is set to a low level (25°C), the iron loss is even lower.

[0026] The mechanism by which iron loss was reduced and the deviation of iron loss was improved in the above experiment is still unclear, but the inventors believe the following.

[0027] The mechanism by which iron loss deviation is improved is believed to be as follows: During cold rolling, the steel sheet is heated from the uncoiler before the first pass, and the time from heating to the first pass is constant, which suppresses the time-dependent changes in fine carbides precipitated due to heating. Furthermore, the mechanism for low iron loss when the steel sheet temperature is kept low after heating and before the first pass is believed to be as follows: The primary recrystallized Gaussian-oriented grains are believed to nucleate from shear bands introduced into the {111}<112> matrix, which is one of the rolling-stabilized orientations.

[0028] Therefore, as in the above experiment, it is believed that by heating the steel plate to cause fine precipitation of carbides, and setting the biting temperature to a low temperature, the {111}<112> matrix structure is formed through low-temperature rolling. At the same time, the formation of shear bands is locally promoted by the fine carbides, thereby effectively increasing the Gaussian orientation grains.

[0029] In addition, the inventors also studied the relationship between the bite temperature of the first pass in the final cold rolling and the strain rate of that first pass. The details of the experiment are described below.

[0030] That is, the hot-rolled sheet produced in the above experiment was subjected to hot-rolled annealing at 1000℃ for 60 seconds, followed by cooling from 800℃ to 350℃ at 20℃ / s, and then wound into a coil. The resulting hot-rolled annealed sheet was then rolled into a cold-rolled sheet with a thickness of 0.20mm using a continuous rolling mill (300mm roll diameter, 5 stands) in one continuous rolling pass. At this time, the steel sheet was heated to 100℃ by a heating device set between the uncoiler of the rolling mill and the first rolling stand. Then, the bite temperature was varied from 20℃ to 180℃ to induce bite, while the strain rate in the first tandem pass was maintained from 0 to 50s. －1 Changes. In addition, a roll material was also produced that bites into the first pass without heating the steel plate.

[0031] Then, the cold-rolled sheet is subjected to a primary recrystallization annealing at a homogenization temperature of 840°C for 100 seconds, which also serves as a decarburization annealing. An annealing separating agent with MgO as the main component is then applied to the surface of the steel sheet, followed by a final annealing for secondary recrystallization. After the final annealing, a coating solution containing phosphate-chromate-colloidal silica in a mass ratio of 3:1:2 is applied to the surface of the steel sheet, and a planarization annealing is performed at 800°C for 30 seconds to produce the finished coil.

[0032] The iron loss of 10 rolls of the product fabricated under identical conditions was measured, and their average value and standard deviation were calculated. The iron loss was determined by cutting a sample from the center of the roll length with a total weight of 500g or more and performing an Epstein test. The iron loss measurement results were compared with the aforementioned bite temperature T (°C) and strain rate e (s). －1 The results obtained by organizing the relationships are shown below. Figure 1 It should be noted that results with an average iron loss of 0.9 W / kg or less and a standard deviation of 0.05 W / kg or less are represented as “〇”, and results otherwise are represented as “×”.

[0033] Depend on Figure 1 It can be seen that at the strain rate e(s) －1 When the bite temperature T (°C) of the first pass and the first pass satisfy the following formula, the iron loss is low and the deviation of iron loss between rolls is small.

[0034] 0.0378e 2 +0.367e+37.2>T

[0035] Based on these insights, further research was conducted, leading to the completion of this invention.

[0036] That is, the main idea of ​​this invention is as follows.

[0037] [1] A method for manufacturing an oriented electromagnetic steel sheet, comprising hot rolling a steel billet to produce a hot-rolled steel sheet, subjecting the hot-rolled steel sheet to one or more cold rolling processes with intermediate annealing to produce a cold-rolled sheet with a final sheet thickness, then subjecting the cold-rolled sheet to decarburization annealing, and then subjecting it to secondary recrystallization annealing.

[0038] In the case of one or more cold rolling processes mentioned above, if the cold rolling is defined as the final cold rolling process in the case of one cold rolling process, and if the final cold rolling process is defined as the final cold rolling process in the case of two or more cold rolling processes, then...

[0039] The final cold rolling process uses a continuous rolling mill to heat the steel sheet to a temperature range of 70°C to 200°C, and then feeds it into the first pass of the continuous rolling mill. In this first pass, the bite temperature T (°C) and the strain rate e (s) are... －1 It satisfies the following equation (1).

[0040] 0.0378e 2 +0.367e+37.2>T····(1)

[0041] [2] In the method for manufacturing oriented electromagnetic steel sheet as described in [1] above, the decarburization annealing is performed at a heating rate of 200°C / s or higher between 400°C and 700°C.

[0042] [3] According to the manufacturing method of the oriented electromagnetic steel sheet described in [1] or [2] above, the steel billet has the following composition: C: 0.01 to 0.10%, Si: 2.0 to 4.5%, Mn: 0.01 to 0.50%, Al: 0.0100 to 0.0400%, the total of any one or two of S and Se: 0.01 to 0.05%, and N: 0.0050 to 0.0120%, with the remainder being Fe and unavoidable impurities.

[0043] [4] According to the manufacturing method of the oriented electromagnetic steel sheet described in [1] or [2] above, the steel billet has the following composition: C: 0.01 to 0.10%, Si: 2.0 to 4.5%, Mn: 0.01 to 0.50%, Al: less than 0.0100%, S: less than 0.0070%, Se: less than 0.0070%, and N: less than 0.0050% by mass, with the remainder being Fe and unavoidable impurities.

[0044] [5] The method for manufacturing the oriented electromagnetic steel sheet according to [3] or [4] above, wherein the steel billet further contains, by mass%, one or more of the following: Sb: 0.005-0.500%, Cu: 0.01-1.50%, P: 0.005-0.500%, Cr: 0.01-1.50%, Ni: 0.005-1.500%, Sn: 0.01-0.50%, Nb: 0.0005-0.0100%, Mo: 0.01-0.50%, B: 0.0010-0.0070%, and Bi: 0.0005-0.0500%.

[0045] [6] A rolling mill for manufacturing oriented electromagnetic steel sheet, comprising a continuous rolling mill arranged on a production line for oriented electromagnetic steel sheet, and a heating device and a cooling device arranged sequentially from the upstream side of the production line on the inlet side of the first stand of the continuous rolling mill.

[0046] [7] According to the rolling equipment for manufacturing oriented electromagnetic steel sheet described in [6] above, the heating device has the function of spraying high-temperature liquid onto the steel sheet on the production line, and the cooling device has the function of spraying low-temperature liquid onto the steel sheet on the production line.

[0047] According to the present invention, it is possible to stably manufacture oriented electromagnetic steel sheets with excellent magnetic properties and small iron loss deviation between coils using a continuous rolling mill. Attached Figure Description

[0048] Figure 1 This indicates that the measurement results of iron loss are expressed in conjunction with the bite temperature T (°C) and strain rate e (s). －1 The diagram is the result of organizing the relationships between the elements.

[0049] Figure 2 This indicates that the measurement results of iron loss are expressed in conjunction with the bite temperature T (°C) and strain rate e (s). －1 The diagram is the result of organizing the relationships between the elements. Detailed Implementation

[0050] The present invention will be described in detail below.

[0051] <Steel billet>

[0052] In addition to slabs, large blooms and small billets can also be used as the steel billet material in the manufacturing method of this invention. For example, billets manufactured by known manufacturing methods can be used. Examples of manufacturing methods for steel billets include steelmaking-continuous casting and billet-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.

[0053] The composition of the steel billet can be that used in the manufacture of oriented electromagnetic steel sheets, and such compositions are generally known. From the viewpoint of manufacturing oriented electromagnetic steel sheets with excellent magnetic properties, it is preferable to contain C, Si, and Mn. Preferred contents of C, Si, and Mn are as follows. Here, unless otherwise stated, "%" in relation to composition refers to "mass %".

[0054] C: 0.01~0.10%

[0055] Carbon (C) is an element that helps improve the texture of primary recrystallization by precipitating fine carbides. If it exceeds 0.10%, it may be difficult to reduce it to below 0.0050% to avoid magnetic aging due to decarburization annealing. On the other hand, if it is less than 0.01%, the amount of fine carbide precipitation may be insufficient, and the texture improvement effect may be inadequate. Therefore, the C content is preferably 0.01 to 0.10%, and more preferably 0.01 to 0.08%.

[0056] Si: 2.0–4.5%

[0057] Si is an effective element for increasing the electrical resistance of steel and improving iron loss. If the Si content exceeds 4.5%, the workability is significantly reduced, making rolling difficult. On the other hand, if it is less than 2.0%, it may be difficult to obtain a sufficient reduction in iron loss. Therefore, the Si content is preferably 2.0 to 4.5%, more preferably 2.5 to 4.5%.

[0058] Mn: 0.01~0.50%

[0059] Mn is an element required to improve hot workability. If the Mn content exceeds 0.50%, the primary recrystallization texture may deteriorate, making it difficult to obtain secondary recrystallized grains with a highly integrated Gaussian orientation. On the other hand, if it is less than 0.01%, sufficient hot rolling workability may be difficult to obtain. Therefore, the Mn content is preferably 0.01 to 0.50%, more preferably 0.03 to 0.50%.

[0060] In addition to C, Si, and Mn, the composition of the steel billet may also contain Al: 0.0100–0.0400% and N: 0.0050–0.0120% as inhibitors in secondary recrystallization. That is, if the Al and N contents are below the lower limits mentioned above, it may be difficult to achieve the desired inhibitory effect. On the other hand, if they exceed the upper limits mentioned above, the dispersion of the precipitates may become uneven, and it may still be difficult to achieve the desired inhibitory effect.

[0061] Furthermore, in addition to Al and N, the inhibitory component may also contain any one or a total of two of S and Se: 0.01% to 0.05%. The presence of these components allows the formation of sulfides (MnS, Cu₂S, etc.) and selenides (MnSe, Cu₂Se, etc.). Sulfides and selenides can also precipitate in combination. Here, if the S and Se content is below the aforementioned lower limit, it may be difficult to achieve a sufficient inhibitory effect. On the other hand, if it exceeds the aforementioned upper limit, the dispersion of the precipitate may become uneven, again making it difficult to achieve a sufficient inhibitory effect.

[0062] In addition, as a component composition, the Al content can be suppressed to less than 0.0100%, which is suitable for inhibitor-free systems. In this case, the composition can be N: less than 0.0050%, S: less than 0.0070%, and Se: less than 0.0070%.

[0063] In addition to the above-mentioned composition, to improve magnetic properties, the composition may also contain one or more elements selected from Sb: 0.005–0.500%, Cu: 0.01–1.50%, P: 0.005–0.500%, Cr: 0.01–1.50%, Ni: 0.005–1.500%, Sn: 0.01–0.50%, Nb: 0.0005–0.0100%, Mo: 0.01–0.50%, B: 0.0010–0.0070%, and Bi: 0.0005–0.0500%. 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, the elements contained herein are preferably within the above-mentioned ranges.

[0064] The remaining components of the steel billet, besides the components mentioned above, are Fe and unavoidable impurities.

[0065] <Manufacturing Process>

[0066] The manufacturing method of the present invention, for example, involves hot rolling a steel billet to produce a hot-rolled sheet. The steel billet can be supplied for hot rolling after heating. 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 slab; therefore, temperatures below 1450°C are preferred.

[0067] There are no special restrictions on hot rolling conditions other than those specified; well-known conditions can be applied.

[0068] It should be noted that, in cases where the above-mentioned cold rolling is performed more than twice, hot-rolled sheet annealing can be carried out as needed. In this case, the annealing conditions are not particularly limited, and well-known conditions can be applied. If necessary, descaling can also be performed by pickling or other methods after hot-rolled sheet annealing and before cold rolling.

[0069] In the cold rolling process, a cold-rolled sheet of the final thickness can be produced by a single cold rolling operation, or by performing two or more cold rolling operations with intermediate annealing. The total reduction rate of the cold rolling is not particularly limited and can be 70% to 95%. In this invention, the final cold rolling process needs to be controlled as described below. It should be noted that the reduction rate of the final cold rolling is not particularly limited and can be 60% to 95%. The final sheet thickness is not particularly limited and can be, for example, 0.1 mm to 1.0 mm.

[0070] Here, "final cold rolling" refers to the last cold rolling process in one or more cold rolling processes. For example, in the case of a single-process cold rolling method where only one cold rolling is performed, that single cold rolling is the final cold rolling. In the case of a two-process cold rolling method where two cold rolling processes are performed, the second cold rolling is the final cold rolling. Similarly, in the case of three or more cold rolling processes, the final cold rolling is the final cold rolling.

[0071] The final cold rolling is carried out using a continuous rolling mill. When the steel sheet is fed from the uncoiler and introduced into the first pass of the final cold rolling, it is heated to 70°C–200°C before being bitten into the first pass. In this first pass, the strain rate e(s) is crucial. －1 The bite temperature T (°C) and the bite temperature satisfy the following formula (1).

[0072] 0.0378e 2 +0.367e+37.2>T····(1)

[0073] First, the final heating temperature of the cold-rolled steel sheet is 70℃ to 200℃. That is, if the heating temperature is below 70℃, fine carbides will not be fully precipitated; on the other hand, if the temperature exceeds 200℃, the carbon diffusion rate becomes too high, and coarse carbides precipitate, thus negating the effect of improving texture through strain aging and causing magnetic degradation. The preferred heating temperature is 100℃ to 170℃.

[0074] Furthermore, in the first rolling pass, the strain rate e(s) is crucial. －1 The bite temperature T (°C) satisfies the above equation (1). That is, by satisfying the above equation (1) in the first pass of rolling, rolling at low temperature or high strain rate can be achieved, resulting in the formation of a {111}<112> matrix structure as a stable orientation for rolling. Under rolling conditions that do not satisfy the above equation (1), the {111}<112> matrix structure cannot be fully formed, and the texture improvement effect is lost.

[0075] Here, the bite temperature T (in °C) in equation (1) refers to the temperature of the steel plate before it bites into the rolling mill, which can be determined by measuring it with a contact thermometer or a radiation thermometer. Additionally, the strain rate e (in seconds) －1) refers to the time change of the nominal strain during rolling, which can be easily calculated using the following formula.

[0076]

[0077] Here, t0: plate thickness at the mill inlet (in mm), t1: plate thickness at the mill outlet (in mm), v: steel plate speed at the mill inlet (in mm / s), and R: work roll diameter (in mm).

[0078] These can be controlled by factors such as the volume and temperature of the coolant sprayed before the steel plate is bitten, or by factors such as the diameter of the work roll, the reduction rate, and the mill throughput speed.

[0079] There are no particular limitations on the heating method for the steel sheet before final cold rolling. Examples include air bath, oil bath, sand bath, induction heating, spraying heated lubricating oil onto the steel sheet, and hot water. However, since the heating is carried out on the inlet side of the continuous rolling mill, a method that can heat the steel sheet in a short time is preferred. It should be noted that the heating temperature refers to the temperature of the steel sheet on the outlet side of the heating device.

[0080] There are no particular limitations on the cooling method after heating before final cold rolling. Examples include coolant blowing, cooling rolls, and oil baths. However, since cooling is carried out on the inlet side of the continuous rolling mill, cooling needs to be carried out in a short time.

[0081] To implement the aforementioned cold rolling, the continuous rolling mill used in this invention needs to have a heating device at the entrance side of the first stand and a cooling device at the exit side of the heating device. The heating device is not particularly limited in its heating method, but spraying heated lubricating oil or hot water, which are high-temperature liquids, onto the steel sheet is preferred due to its ease of implementation. Similarly, the cooling device is not particularly limited in its cooling method, but blowing coolant, which is a low-temperature liquid, is preferred due to its ease of implementation.

[0082] Heat treatments such as aging or warm rolling can be incorporated into cold rolling, but the method described in Patent Document 4 above, which divides the final rolling into two parts—a first half and a second half—with the first half rolled at a low temperature and the second half rolled at a high temperature, is preferred. This is believed to be because the primary recrystallized Gaussian-oriented grains nucleate from shear bands introduced into the {111}<112> matrix, which is one of the rolling-stable orientations. Since the {111}<112> matrix develops through cold rolling at a low temperature, a large amount of {111}<112> matrix can be formed by rolling at a low temperature in the first half, followed by efficient formation of Gaussian-oriented recrystallization nuclei through rolling at a high temperature.

[0083] In the manufacturing method of the oriented electromagnetic steel sheet of the present invention, the oriented electromagnetic steel sheet (product sheet) can be obtained by decarburizing and annealing the cold-rolled sheet that has been finished to the final thickness as described above, followed by a second recrystallization annealing. An insulating film can be applied after the second recrystallization annealing.

[0084] The conditions for decarburization annealing described above are not particularly limited. Generally, decarburization annealing is often combined with a recrystallization annealing, and it can also be combined with a recrystallization annealing in the manufacturing method of the present invention. In this case, by heating at a heating rate of 200°C / s or more between 400°C and 700°C during the heating process, the Gaussian-oriented grains formed in the final cold rolling process are effectively recrystallized, thus further improving the texture improvement effect of the present invention. Other conditions are not particularly limited, and known conditions can be applied. For example, annealing conditions of 800°C for 2 minutes in a warm hydrogen atmosphere can be cited.

[0085] After decarburization annealing, cold-rolled steel sheets undergo final annealing for secondary recrystallization. Before final annealing, an annealing separating agent can be applied to the steel sheet surface. 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.

[0086] 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.

[0087] Example 1

[0088] A steel billet consisting of the following composition is 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: 0.037%, Si: 3.4%, and Mn: 0.05%, and further by mass ppm: S and Se: 31 ppm each, N: 50 ppm, sol.Al: 85 ppm, with the remainder being Fe and unavoidable impurities.

[0089] The hot-rolled sheet was subjected to hot-rolled annealing at 1000°C for 60 seconds, followed by cooling from 800°C to 350°C at a rate of 20°C / s, and then wound into a coil. The resulting hot-rolled annealed sheet was then rolled into a cold-rolled sheet with a thickness of 0.20 mm using a continuous rolling mill (300 mm roll diameter, 5 stands) in one continuous rolling pass. At this time, the first pass was entered into the rolling stand at the heating temperature, strain rate, and first pass entry temperature shown in Table 2. It should be noted that the heating temperature, strain rate, and first pass entry temperature are all within the suitable range of this invention.

[0090] Then, the cold-rolled sheet was subjected to a primary recrystallization annealing, which also served as a decarburization annealing, at a homogenization temperature of 840°C and a homogenization time of 100 seconds. During the heating process of the primary recrystallization annealing, the heating rate within the temperature range of 400°C to 700°C was divided into two periods of 50°C / s and 300°C / s. Then, an annealing separating agent with MgO as the main component was coated on the surface of the steel sheet, followed by final annealing and secondary recrystallization.

[0091] 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 product coils.

[0092] For the product rolls, the iron loss of 10 rolls manufactured under the same conditions was measured, and the average value and standard deviation were calculated. The iron loss was measured by cutting a sample from the center of the length of the roll with a total weight of 500g or more and performing an Epstein test. The results of this iron loss measurement, along with the heating temperature, strain rate, and bite temperature of the first pass mentioned above, are shown in Table 2.

[0093] [Table 2]

[0094] Table 2

[0095]

[0096] As shown in Table 2, under the condition that the heating rate of decarburization annealing is 300℃ / s, it further becomes a low iron loss process.

[0097] Example 2

[0098] 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 contains, by mass %: C: 0.06%, Si: 3.4%, and Mn: 0.06%; by mass ppm: N: 90 ppm, sol.Al: 250 ppm; by mass %: S and Se: 0.02% each; and the remainder is Fe and unavoidable impurities.

[0099] The hot-rolled sheet was subjected to hot-rolled annealing at 1000°C for 60 seconds, followed by cooling from 800°C to 350°C at a rate of 10°C / s, and then wound into coils. The resulting annealed hot-rolled sheet was subjected to a first cold rolling on a continuous 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, and then cooled at a rate of 25°C / s during the cooling process from 800°C to 350°C. Finally, a final cold rolling was performed on a continuous rolling mill (300mm roll diameter, 5 stands) to produce a cold-rolled sheet with a thickness of 0.20mm. In the final cold rolling process, the steel sheet is heated to the temperatures shown in Table 3 using a steel sheet heating device located between the uncoiler and the first pass rolling stand. After heating, the steel sheet is bitten into the first pass rolling stand at the first pass bite temperature shown in Table 3 and rolled at the strain rate shown in Table 3. Additionally, a device for rolling at a heating temperature of 100°C was also manufactured. Figure 2 The steel plates bitten into the rolling mill stand at various strain rates and first-pass biting temperatures are shown.

[0100] Then, the cold-rolled sheet is subjected to a primary recrystallization annealing at a homogenization temperature of 840°C for 100 seconds, which also serves as a decarburization annealing. An annealing separating agent with MgO as the main component is then applied to the surface of the steel sheet. Following this, a final annealing is performed, followed by a secondary recrystallization. The surface of the steel sheet after the secondary recrystallization annealing is then coated with a coating solution containing phosphate-chromate-colloidal silica in a mass ratio of 3:1:2, and a planarization annealing is performed at 800°C for 30 seconds to produce the finished coil.

[0101] For the product rolls, the iron loss of 10 rolls manufactured under the same conditions was measured, and the average value and standard deviation were calculated. The iron loss was measured by cutting a sample from the center of the roll length with a total weight of 500g or more and performing an Epstein test. The results of this iron loss measurement, along with the heating temperature, strain rate, and first pass bite temperature mentioned above, are shown in Table 3. Furthermore, the results of this iron loss measurement are compared with the bite temperature T (°C) and strain rate e (s). －1 The results obtained by organizing the relationships are shown below. Figure 2 It should be noted that results with an average iron loss of 0.9 W / kg or less and a standard deviation of 0.05 W / kg or less are represented as “0” (Example of the Invention), and results other than these are represented as “×” (Comparative Example).

[0102]

[0103] As shown in Table 3, even when using billets with a large amount of added inhibitor system and inserting intermediate annealing in the cold rolling process, the iron loss is good and the deviation is small when rolled under specified conditions by final cold rolling. Furthermore, from Figure 2 It can be seen that by satisfying the above formula (1), the average value of iron loss is less than 0.9 W / kg and the standard deviation is less than 0.05 W / kg.

[0104] Example 3

[0105] 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 and Se: 31 ppm each; and as shown in Table 4: Sb, Cu, P, Cr, Ni, Sn, Nb, Mo, B, and Bi as other additives, with the remainder being Fe and unavoidable impurities.

[0106] The hot-rolled sheet was annealed at 1000℃ for 60 seconds, then cooled from 800℃ to 350℃ at a rate of 20℃ / s, and then wound into coils. The resulting annealed hot-rolled sheet was then rolled into a cold-rolled sheet with a thickness of 0.20mm using a continuous rolling mill (300mm roll diameter, 5 stands) in a single pass. During the final cold rolling, the steel sheet was heated to 100℃ using a steel sheet heating device located between the uncoiler and the first rolling stand of the rolling mill, then cooled to 25℃, with a strain rate of 25s. -1 It bites into the first rolling stand.

[0107] Then, after performing a first recrystallization annealing that also serves as a decarburization annealing on the above-mentioned 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 final annealing and secondary recrystallization.

[0108] The steel sheet surface after final annealing was coated with a coating solution containing phosphate-chromate-colloidal silica in a mass ratio of 3:1:2, and then subjected to planarization annealing at 800°C for 30 seconds to produce product coils. For each product coil, the iron loss of 10 coils produced under the same conditions was measured, and the average value and standard deviation were calculated. The iron loss was measured by cutting a sample from the center of the length of the coil with a total weight of 500g or more and performing an Epstein test. The results of this iron loss measurement, along with the composition of the above-mentioned additives, are shown in Table 4.

[0109]

[0110] As shown in Table 4, the iron loss of steel plates with one or more of Sb, Cu, P, Cr, Ni, Sn, Nb, Mo, B, and Bi is reduced to below 0.80 W / kg, and the characteristic deviation in the length direction of the coil is also small.

Claims

1. A method for manufacturing an oriented electromagnetic steel sheet, comprising hot rolling a steel billet to produce a hot-rolled steel sheet, subjecting the hot-rolled steel sheet to one or more cold rolling passes with intermediate annealing to produce a cold-rolled sheet with a final sheet thickness, then subjecting the cold-rolled sheet to decarburization annealing, and then subjecting it to secondary recrystallization annealing. In the case of one or more cold rolling processes, if the cold rolling is defined as the final cold rolling process in the case of one cold rolling process, and if the final cold rolling process is defined as the final cold rolling process in the case of two or more cold rolling processes, then... The final cold rolling uses a continuous rolling mill to heat the steel plate to a temperature range of 70℃ to 200℃, and then feeds it into the first pass of the continuous rolling mill. In this first pass, the bite temperature T and the strain rate e satisfy the following equation (1), where, The bite temperature T is measured in °C, and the strain rate e is measured in seconds. －1 , 。 2. The method for manufacturing the oriented electromagnetic steel sheet according to claim 1, wherein, The decarburization annealing is performed by heating at a rate of 200°C / s or higher between 400°C and 700°C.

3. The method for manufacturing the oriented electromagnetic steel sheet according to claim 1 or 2, wherein, The steel billet has the following composition by mass: C: 0.01-0.10%, Si: 2.0-4.5%, Mn: 0.01-0.50%, Al: 0.0100-0.0400%, the total of any one or two of S and Se: 0.01-0.05%, and N: 0.0050-0.0120%, with the remainder being Fe and unavoidable impurities.

4. The method for manufacturing an orientation-oriented electromagnetic steel sheet according to claim 1 or 2, wherein, The steel billet has the following composition: by mass % C: 0.01-0.10%, Si: 2.0-4.5%, Mn: 0.01-0.50%, Al: less than 0.0100%, S: less than 0.0070%, Se: less than 0.0070%, and N: less than 0.0050%, with the remainder being Fe and unavoidable impurities.

5. The method for manufacturing an orientation-oriented electromagnetic steel sheet according to claim 3 or 4, wherein, The steel billet further contains, by mass%, one or more of the following: Sb: 0.005–0.500%, Cu: 0.01–1.50%, P: 0.005–0.500%, Cr: 0.01–1.50%, Ni: 0.005–1.500%, Sn: 0.01–0.50%, Nb: 0.0005–0.0100%, Mo: 0.01–0.50%, B: 0.0010–0.0070%, and Bi: 0.0005–0.0500%.

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