JP2008019462A - Method for producing magnetic steel sheet excellent in magnetic characteristic in direction perpendicular to rolling direction - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for producing a magnetic steel sheet excellent in a magnetic characteristic in the direction perpendicular to a rolling direction by utilizing a secondary crystallization phenomenon. <P>SOLUTION: The method for producing the magnetic steel sheet excellent in the magnetic characteristic in the direction perpendicular to the rolling direction is produced so that a slab composed of ≤0.020% C, 2.5-4.0% Si, 0.022-0.035% acid soluble Al, 0.005%≤(S+0.405Se)≤0.014% N, 0.05-0.15% Mn and the valance Fe with inevitable impurities is heated within the temperature range of <1,200°C, is hot-rolled and successively is subjected to a hot-rolled plate annealing and a finish-cold rolling applying 25% to <60% rolling-reduction ratio to be made into a finish sheet thickness, thereafter is subjected to a primary-recrystallizing annealing under wet-hydrogen atmosphere, and is nitrogenized under running strip state, is coated with an annealing separating agent, and is subjected to a finish-annealing so that the secondary recrystallizative phenomenon is utilized. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method of manufacturing an electrical steel sheet having excellent magnetic properties in the direction perpendicular to the rolling direction, which is mainly used as an iron core of a joint of an actuator, a rotor or a transformer.

  According to the recent demands for energy saving, electrical equipment mounted on transportation / mobile devices such as automobiles and airplanes not only improves the energy efficiency of the electrical equipment itself, but also reduces the weight of the equipment to reduce energy consumption. This is inevitably required. However, at present, there is a limit to the reduction in weight due to the low magnetic flux density perpendicular to the rolling of materials used in equipment. Therefore, by improving the magnetic properties not only in the rolling direction but also in the direction perpendicular to the rolling direction, it is possible to reduce the weight even with the same output electrical equipment. ing.

  There are roughly two types of electrical steel sheets, one is a directional electrical steel sheet and the other is a non-oriented electrical steel sheet. These have different uses and different manufacturing methods (principles).

  The grain-oriented electrical steel sheet is mainly used as an iron core material for transformers and other electrical devices. The texture produced by utilizing the secondary recrystallization phenomenon is Goss texture ({110} <001>). ), And the hard axis (<111>) of iron is included in the rolling surface, so that the magnetic properties are excellent in the rolling direction, but the other directions are inferior, and magnetization is performed in a plurality of directions on the same surface. It is not suitable for the equipment to be used. For this reason, in order to meet the recent demand for energy saving, there has been a demand for the production of an electrical steel sheet having a texture that does not include the hard axis of magnetization in the rolling surface and also excellent in the direction perpendicular to the rolling direction. In particular, current automobiles, airplanes, and the like are equipped with a large number of rotating electrical devices, and the magnetic material contains almost iron, so that the weight increases. For this reason, it is not sufficient to reduce the energy consumption of the moving object simply by improving the energy efficiency of each electrical device, and there is a strong demand for reducing the weight of the device.

  On the other hand, a non-oriented electrical steel sheet is generally used as an electrical steel sheet for rotating equipment, but this steel sheet is produced by applying only the primary recrystallization phenomenon without using the secondary recrystallization phenomenon. Does not include a rotating cube system or a cube system, and includes a hard magnetization direction (<111>) on the plate surface, so the magnetic flux density in the direction perpendicular to the rolling direction is low. For this reason, there has been a limit to the reduction in size and improvement in efficiency of rotating equipment mounted on mobile / transport equipment using conventional electrical steel sheets.

  As a method of manufacturing an electrical steel sheet having a texture that does not include a hard axis in the rolling plane, a method using cross cold rolling as disclosed in Patent Document 1 and the like including a bidirectional magnetic steel sheet and the like In addition, an interface energy minimization method (columner grain growth) disclosed in Patent Document 2 is known. In cross cold rolling, since the second rolling direction is perpendicular to the first direction, it cannot be manufactured continuously by an industrial manufacturing method in the form of a coil, and a process of joining by shearing and some other method must be added. , Difficult to put into practical use. In addition, the interface energy minimization method increases costs such as ensuring an annealing atmosphere, and this is also difficult to put into practical use. For this reason, although the usefulness of the electrical steel sheet excellent in the direction perpendicular to the rolling has been widely recognized, it is actually not industrially produced.

  Further, in Patent Document 3, a method using nitriding has been proposed, but in this case, the final cold rolling rate is 60% or more, and there is a problem in the atmosphere adjustment during primary recrystallization annealing, Excellent magnetic properties in the direction perpendicular to rolling cannot be obtained stably.

  The excitation characteristics are expressed by magnetic flux density (B8 value: T) at a magnetic field strength of 800 A / m. The iron loss characteristic is represented by energy loss W17 / 50 (W / kg) per kg of iron core when the iron core is magnetized to 1.7 Tesla at a frequency of 50 Hz. The magnetic flux density of the electrical steel sheet is the largest controlling factor of the iron loss characteristic. Generally, the higher the magnetic flux density, the better the iron loss characteristic.

Japanese Patent Laid-Open No. 01-139722 Japanese Patent Laid-Open No. 01-108345 JP 2004-10986 A Proceeding of the Twelfth International Conference on Texture of Materials (ICOTOM-12,1999), 1009-1014. ISIJ, Vol. 42 (2002), 440-449 Materials Science Forum, Vol .204-206 (1996), 143-154 (Journal of magnetism and magnetic materials 160 (1996) 123-124)

  The present invention is premised on low-temperature slab heating of 1200 ° C. or less, the components (particularly C and Si), the reduction ratio of the final cold rolling is less than 60%, the primary recrystallization annealing atmosphere is defined, and the primary recrystallization is further performed. Secondary recrystallization texture with excellent magnetic properties in the direction perpendicular to the rolling by nitriding between primary recrystallization and secondary recrystallization by modifying the primary recrystallization texture after decarburization annealing by controlling the grain size An object of the present invention is to provide a method capable of stably producing the product.

  The present invention is characterized in that the primary recrystallized texture is improved by controlling the primary recrystallized grain size to be large, and an electrical steel sheet having excellent magnetic properties in the direction perpendicular to the rolling can be produced in a low final cold rolling rate region. There is.

  In addition, the electrical steel sheet according to the present invention generates secondary recrystallization in the final finish annealing step, and has a {100} plane on the steel sheet surface, a <001> axis in the rolling direction, and a <010> axis in the perpendicular direction. It has a so-called rotating Cube structure ({HK0} <001>).

The gist of the present invention is as follows.
(1) By mass%, C ≦ 0.020%, Si: 2.5-4.0%, acid-soluble Al: 0.022-0.035%, N: 0.0050-0.010%, 0 0.005% ≦ (S + 0.405Se) ≦ 0.012%, Mn: 0.05 to 0.15%, the slab composed of the remaining Fe and inevitable impurities is heated to a temperature range of less than 1200 ° C., Hot-rolled to obtain a hot-rolled steel strip, and this hot-rolled steel strip is not annealed or annealed. Or, after performing the heat treatment at least once before the final cold rolling, and making the final sheet thickness by final cold rolling applying a rolling reduction of 25% or more and less than 60%, at a temperature of 800 ° C. or more and 890 ° C. or less, wet hydrogen atmosphere PH ₂ O / PH _2: 0.02~0.33 subjected to primary recrystallization annealing, travels scan It is characterized in that the product thickness is 0.50 mm or less and the average primary recrystallized grain size is 20.0 μm or more and 31.0 μm or less by nitriding in a lip state, applying an annealing separator, and then performing finish annealing. A method for producing an electrical steel sheet having excellent magnetic properties in the direction perpendicular to the rolling.
(2) The hot rolling finishing start temperature is more than 900 ° C. and less than 1150 ° C., and the additional rolling reduction in the final stand of finish rolling and the stand immediately before is 55% or more (1) The manufacturing method of the electrical steel sheet excellent in the magnetic characteristic of the rolling perpendicular direction of description.

  The present invention makes it possible to manufacture an electromagnetic steel sheet having excellent magnetic properties in the direction perpendicular to the rolling, which could only be manufactured only by techniques such as cross cold rolling, by a method similar to that for manufacturing a unidirectional electrical steel sheet.

  Hereinafter, the present invention will be described in detail.

  The inventors of the present invention have specified the C, Si content, which has not been attracting attention in the past, to be an α single phase, paying attention to the cold rolling rate, and the rolling reduction after the final two passes after the final hot rolling, Utilizing the phenomenon that occurs here, the manufacturing process by the final high-pressure cold rolling that applies cold reduction of 25% or more and less than 60% by applying cold rolling twice with annealing, assuming low-temperature slab heating In order to establish a method for stably producing a magnetic steel sheet manufactured with a magnetic thickness excellent in magnetic properties in the direction perpendicular to rolling and having a product thickness of 0.50 mm or less, the present invention has been completed. .

The electrical steel sheet having excellent magnetic properties in the direction perpendicular to the rolling direction, which is the subject of the present invention, is a continuous casting of molten steel obtained by a conventionally used steelmaking method to form a slab directly or injecting molten steel into a mold. , Solidified into a steel ingot, this is rolled into a slab, then hot rolled into a hot-rolled sheet, and then subjected to hot-rolled sheet annealing, with a reduction of less than 60% in the final cold rolling process The final plate thickness is 0.50 mm or less by two or more cold rollings with intermediate annealing applied, and after the primary recrystallization annealing, nitriding is performed, and MgO, Al ₂ O _{3 and the} like are the main components. It is manufactured by a process of applying an annealing separating agent and applying a finish annealing (secondary recrystallization annealing).

  The present inventors have studied extensively from various viewpoints, paying attention to the reduction ratio and final cold rolling ratio of the material after the final two passes of finish rolling in hot rolling (hereinafter simply referred to as finish rolling). As a result, a primary recrystallized texture suitable for an electrical steel sheet having a rotating cube texture ({HK0} <001>) as a secondary recrystallized texture is obtained. We have found that electrical steel sheets with excellent magnetic properties can be manufactured.

  The academic reason for the present invention will be described. Although the reason is not necessarily clear, the present inventors presume as follows.

  According to HARASE et al. (Non-Patent Document 1), secondary recrystallization in the case of an Fe—Si alloy containing about 3% of silicon requires the strength of the secondary recrystallization nuclei to grow and Σ9 in the corresponding orientation. , Σ7 is stated to be important.

  In addition, it is stated that Σ9 and Σ5 are important, according to Kumano et al.

  In the case of Cube system, according to Hara et al., It is said that Σ7. However, in the study by the present inventors, it has been found that Σ9 and Σ5 are important instead of Σ7 in the case of Cube. It is inferred that there is no necessity that the Goss secondary recrystallized texture is Σ9 and the Cube secondary recrystallized texture is Σ7 in electrical steel sheets of the same component system. Therefore, after earnestly examining this, in a conventionally known method for producing a unidirectional electrical steel sheet, when an appropriate amount of C and Si is contained to form an α single phase, the hot rolling rate and the cold rolling rate are optimized. It has been found that the strength of the Cube system and the strengths of Σ9 and Σ5 are increased. Further, when this material is processed by the same method as the production of grain-oriented electrical steel sheet utilizing an acquired inhibitor that nitrides the material (Non-Patent Document 3), the rotational Cube orientation ({HK0} <001>, where H and K are arbitrary numbers) Was found to undergo secondary recrystallization.

  In the present invention, it is important that the C content is small and the α single phase does not have the γ phase in all steps. When it becomes α single phase, a diagonal cube ({100} <011>), which is an approximation of a rotating Cube system, is formed on a hot-rolled sheet at a relatively high pressure ratio at a later stage in hot rolling, This is probably because many Σ9 orientations of the rotating Cube are formed in the primary recrystallization texture.

  Next, the primary recrystallization average particle diameter will be described. The basic metallurgical concept of the present invention is to control the primary recrystallization texture by optimizing the composition of the primary recrystallization texture, the rolling rate after the hot rolling, the cold rolling rate, and the primary recrystallization grain size. The corresponding secondary recrystallization is realized by an acquired inhibitor method. At this time, the texture becomes appropriate as the primary recrystallized grain size increases, but if it becomes too large, the secondary recrystallization becomes unstable, the limit is 31.0 μm, and the primary recrystallized grain size is small. The secondary recrystallization start temperature decreases, the time of secondary recrystallization progress to secure the preferential growth property is shortened, the primary recrystallization texture is not reflected in the secondary recrystallization texture, An electromagnetic steel sheet with excellent magnetic properties cannot be produced, and the minimum value is 20.0 μm. Outside this range, an electrical steel sheet having excellent magnetic properties in the direction perpendicular to the rolling direction (for example, B8, W17 / 50) cannot be obtained.

  The steel component composition prescribed | regulated by this invention is demonstrated in detail below. In addition, all component composition is the mass%.

  C: When C exceeds 0.020% in the final product, it is in balance with the Si content, but since the γ phase is formed, the crystal grain size before cold rolling is reduced, and the primary recrystallization texture is Goss. Suitable for growth of unidirectional electrical steel sheet. For this reason, it is essential that C be 0.020% or less, which has no transformation in balance with Si. Also, the content should be as low as possible to reduce the load of decarburization annealing.

  Si: Si increases the specific resistance of the steel sheet and contributes to the reduction of iron loss. In addition, if the Si content is less than 2.0%, regardless of the content of C, transformation occurs and there is no effect of texture modification, and finish annealing at a high temperature is performed for purification and secondary recrystallization. However, randomization of crystal orientation due to α-γ transformation occurs, and sufficient magnetic properties cannot be obtained. On the other hand, if it exceeds 4.0% and the grain size before cold rolling becomes large, the cold rolling property is impaired and the production becomes difficult. Further, since the secondary recrystallization phenomenon is utilized, if the crystal grain size in the product is large and the amount of Si is large, the end face is likely to be chipped when the product is processed, and the workability is deteriorated. Therefore, the Si content is set to 2.5 to 4.0%. Preferably it is 2.8 to 3.5% of range.

  Mn: Mn is unavoidably present in the molten steel, but in the present invention, an inhibitor is formed by nitriding treatment, and thus is not essential as an inhibitor element. However, Mn is an element effective for preventing cracking during hot rolling due to hot brittleness, and the effect cannot be obtained at less than 0.05%. On the other hand, if added over 0.15%, the solid solution of MnS and MnSe becomes non-uniform during hot rolling, resulting in fluctuations in magnetic properties, resulting in unstable quality, and formation of MnO during primary recrystallization annealing. Thus, it is easy to form a thick graph film after secondary recrystallization, and the electrical steel sheet manufactured according to the present invention is not preferable because it is punched for rotation. Therefore, the Mn content is 0.05 to 0.15%. Preferably it is 0.08 to 0.15% of range.

  Al: Al is an element that forms AlN and acts as an inhibitor of secondary recrystallization. If the Al content is less than 0.022%, the suppressive force cannot be secured sufficiently, and preferential growth that is secondary recrystallization cannot be secured, and if it exceeds 0.035%, secondary recrystallization failure occurs. Therefore, it is set to 0.022 to 0.035%. A preferable range is 0.025 to 0.031%.

  N: N is an element that forms AlN and acts as an inhibitor. In the present invention, AlN is almost completely precipitated during hot rolling, so that it is limited by the balance with Al. When the N content is less than 0.005%, it is not sufficient to secure the suppressive force, resulting in poor secondary recrystallization. On the other hand, when the N content exceeds 0.01%, blistering defects (blowing) occur. A preferable range is 0.0060 to 0.0090%.

  S, Se: S and Se are effective elements that act as inhibitors by forming MnS and MnSe in the production of a unidirectional electrical steel sheet that is completely dissolved by high temperature hot rolling. However, in the present invention, since it is a relatively low temperature slab heating of 1200 ° C. or less which does not completely dissolve, it is better that the contents of both elements are not large. Since the precipitate distribution at the time of casting remains as it is, if the content is large, nonuniformity of the precipitation state due to temperature nonuniformity occurs during hot rolling heating, and magnetic fluctuation (so-called skid mark) occurs after secondary recrystallization annealing. Therefore, the upper limit is S + 0.405Se ≦ 0.014%. However, if the amount is too small, secondary recrystallization becomes unstable, so the content is made 0.005% or more.

  In the present invention, Sn, Sb, P, Cr, and Cu can be contained in addition to the above-mentioned elements in addition to the elements described above as elements for ensuring and reinforcing the inhibitor function. The preferred addition range of these components is 0.02 to 0.3%, respectively. Furthermore, addition of Ni, Mo, Cd, etc. is also effective in the present invention, and Ni is effective at 0.03 to 0.3%, and Mo and Cd are effective at 0.005 to 0.3%.

  Next, the slab (re) heating temperature will be described.

  As is well known, in the production of conventional unidirectional electrical steel sheets, the slab (re) heating temperature is as high as about 1400 ° C., because this dissolves and dissolves the inhibitor. At such a high temperature, grain growth occurs in the slab, which tends to cause secondary recrystallization failure. To prevent this, the γ rate is improved by increasing the amount of carbon added, or breakdown (reduction before reheating the slab is performed). ) Refinement is essential.

  On the other hand, this invention is based on the manufacturing method (nonpatent literature 3) of the electrical steel sheet using the secondary recrystallization phenomenon by the acquired inhibitor method of Takahashi et al. In the present invention, since the purpose is to reduce C and reform the primary recrystallization texture to a rotating Cube structure ({HK0} <001>), the slab (re) heating temperature is set to less than 1200 ° C. Further, if it is higher than this, an inhibitor substance such as MnS, MnSe, and AlN precipitates non-uniformly after hot rolling (so-called skid mark), and the magnetic properties are not uniform, which is not preferable. The lower limit is sufficient if it can be hot-rolled, but is practically 1050 ° C. or higher.

  Moreover, in order to obtain a hot-rolled steel strip, a normal continuous hot rolling mill may be used, a reversible Steckel rolling mill, or a combination of a thin slab continuous casting machine and a finishing hot rolling mill. In this case, it should be noted that precipitates in the hot-rolled steel strip are uniformly distributed. The heating method may be any of conventionally known gas heating, induction heating using electromagnetic action, energization heating using electric resistance of slab, and the like.

  The final cold rolling rate is 25% or more and less than 60%. Regarding the cold rolling rate, the final cold rolling rate in one cold rolling or two or more cold rollings sandwiching intermediate annealing is less than 60%. If it exceeds 60%, excellent magnetic properties in the direction perpendicular to the rolling direction cannot be stably obtained, and the unidirectional electrical steel sheet in which the rotational Goss orientation ({110} <UUW>, U and W are arbitrary) is the main orientation. If it is less than 60%, the rotational Cube texture ({HK0} <001>) orientation develops. In addition, when performing cold rolling twice or more, you may abbreviate | omit hot-rolled sheet annealing by performing intermediate annealing. Beyond this, it becomes difficult to control the texture, and if it is lower than the lower limit (25%), the productivity decreases and the magnetic properties in the direction perpendicular to the rolling deteriorate. The main reason for performing cold rolling twice is to make the product thickness 0.50 mm or less and to secure the final cold rolling rate to less than 60%.

  The hot rolling conditions have a great influence on the formation of the primary recrystallization texture together with the cold rolling rate. When the finishing start temperature is higher than 1150 ° C., recrystallization occurs during hot rolling, and the primary recrystallization texture is not appropriate. Further, although lower than 900 ° C. is satisfactory from the viewpoint of metallurgy, a steel sheet having 2.5% or more of Si is difficult to hot-roll.

  As the rolling reduction of the hot rolling finishing stand is as high as possible, the additional rolling reduction of the latter two stands is better in the magnetic properties in the direction perpendicular to the rolling. When the additional rolling reduction is less than 55%, the magnetic properties in the direction perpendicular to the rolling are not improved so much.

  If the primary recrystallization annealing temperature is less than 800 ° C., recrystallization is not sufficient. On the other hand, when the temperature exceeds 890 ° C., in the state where the inhibitor is not present, the average particle size exceeds 31 μm, and abnormal grain growth of undesired orientation grains occurs, resulting in poor secondary recrystallization.

In addition, the atmosphere at the time of primary recrystallization annealing is PH ₂ O / PH ₂ and is 0.02 to 0.33. If it is lower than this, nitriding in the running strip state after primary recrystallization annealing is extremely difficult. If the temperature is higher than this, the surface oxide layer becomes thick, and when MgO is used as an annealing separator, a forsterite film is easily formed during secondary recrystallization annealing. In addition, if the atmosphere is the above, the C content is as low as 0.020% or less compared to a normal grain-oriented electrical steel sheet, and therefore there is nothing regarding decarburization that should be 0.0030% or less to prevent magnetic aging. no problem.

  In addition, the nitriding method includes a method of mixing manganese nitride, chromium nitride, etc. as a nitrogen source into the annealing separator during the secondary recrystallization annealing after the primary recrystallization annealing, but this controls the amount of nitriding Since it is not possible and the quality is uneven, the method is limited to using a uniform nitriding method in a running strip state. The amount of nitriding must be 0.015% or more as the total amount of nitrogen in the steel after nitriding because it is necessary to suppress grain growth until secondary recrystallization. In the present invention, since there is no need to form a glass film mainly composed of forsterite, there is no upper limit on the total nitrogen amount because the presence of so-called nitrogen-induced surface defects can be ignored. However, if it exceeds 0.030%, the magnetic properties deteriorate and a long time is required for purification.

Further, since the product of the present invention is processed by punching, it is desirable that a glass film containing forsterite as a main substance is not formed on the surface as much as possible in order to ensure punchability. For this reason, Al ₂ O ₃ can be applied as an annealing separator during finish annealing. Moreover, when MgO is the main component, a method is adopted in which a glass film is not formed by addition of chloride (Non-patent Document 4).

  The product thickness is limited to 0.50 mm or less. This is to ensure good iron loss. Since the magnetic steel sheet produced by this technology has a high magnetic flux density in the direction perpendicular to the rolling direction, it can be reduced in weight even with the same output electrical equipment, and is therefore suitable for application to transportation equipment. For example, an automobile, a locomotive, an aircraft, and the like. For this reason, since not only magnetic flux density but a low iron loss is calculated | required, the upper limit of plate | board thickness is prescribed | regulated. In the present invention, since purification for denitrification is performed in the latter half of the secondary recrystallization annealing, if the product plate thickness is thick, it takes time for purification (mainly denitrification), resulting in insufficient purification and iron loss. Is inferior. Thus, the maximum product thickness is 0.50 mm or less to ensure the absolute value of iron loss and productivity. On the other hand, the minimum product thickness does not need to be particularly concerned. It is desirable that the thickness is 0.20 mm or more in order to reduce (in particular iron loss) and the number of laminating steps.

(Example 1)
The molten steel having the components shown in Table 1 was continuously cast by a normal method to obtain a slab. After reheating at 1150 ° C. and 1250 ° C., a 1.8 mm hot rolled steel strip was obtained with a continuous hot rolling mill. afterwards,
Case (1): 1120 ° C. × 30 seconds, then held at 930 ° C. for 120 seconds, cooled to 750 ° C. and then water-cooled, followed by two-stage hot rolling plate annealing, pickling and cold rolling rate of 75% In the final cold rolling, a 0.45 mm cold rolled sheet was obtained.
Case (2): A 1.8 mm hot-rolled steel strip is pickled, cold-rolled to 1.0 mm, subjected to the same heat treatment as Case (1), and then subjected to final cold-rolling to 0.45 mm. It was.

Thereafter, each cold-rolled sheet was subjected to primary recrystallization annealing at 810 ° C. to 880 ° C. for 180 seconds, H ₂ : 75%, N ₂ : 25%, dew point 45 ° C. (PH ₂ O / PH ₂ = 0.14). To change the primary recrystallized grain size. Thereafter, nitriding is performed in an ammonia atmosphere in a strip state where the total nitrogen content is 0.022 to 0.025 mass%, and an annealing separator having a ratio of 1: 2 is applied to Al ₂ O ₃ and MgO. Then, secondary recrystallization annealing was performed. The conditions were a temperature increase rate of 15 ° C./hour up to 1200 ° C., atmosphere H ₂ : 75%, and N ₂ : 25%. Thereafter, a purification treatment was performed at 1200 ° C. for 20 hours in an H ₂ : 100% atmosphere. After cooling, light pickling and shape correction treatment were performed, and a chromate semi-organic insulating coating was applied. The results are also shown in Table 1.

(Example 2)
The molten steel having the components shown in Table 2 was continuously cast by a normal method to obtain a slab. After reheating at 1150 ° C. and 1270 ° C., a 1.8 mm hot rolled steel strip was obtained by a continuous hot rolling mill. afterwards,
Case (1): 1120 ° C. × 30 seconds, then held at 930 ° C. for 120 seconds, cooled to 750 ° C. and then water-cooled, followed by two-stage hot rolling plate annealing, pickling and cold rolling rate of 81% In the final cold rolling, a 0.35 mm cold rolled sheet was obtained.
Case (2): After pickling a 1.8 mm hot-rolled steel strip and cold rolling to 0.58 mm, 0.64 mm, and 0.70 mm, the same heat treatment as in case (1) was performed, and then 0. The final cold rolling to 35 mm was performed.

Thereafter, each cold-rolled sheet was subjected to primary recrystallization annealing at 810 ° C. to 880 ° C. for 150 seconds, H ₂ : 75%, N ₂ : 25%, dew point 45 ° C. (PH ₂ O / PH ₂ = 0.14). To change the primary recrystallized grain size. Then, in a strip state running so that the total nitrogen content is 0.022 to 0.025 mass%, nitriding is performed in an ammonia atmosphere, and Al ₂ O ₃ and MgO are applied with an annealing separator in a ratio of 1: 1. Then, secondary recrystallization annealing was performed. The conditions were a temperature increase rate of 15 ° C./hour up to 1200 ° C., atmosphere H ₂ : 75%, and N ₂ : 25%. Thereafter, a purification treatment was performed at 1200 ° C. for 20 hours in an H ₂ : 100% atmosphere. After cooling, light pickling and shape correction treatment were performed, and a chromate semi-organic insulating coating was applied. The results are also shown in Table 2.

(Example 3)
C: 0.013%, Si: 3.29%, Al: 0.0278%, N: 0.0081%, Mn: 0.099%, S: 0.0072%, Sn: 0.05%, balance A slab is obtained from molten steel composed of Fe and unavoidable impurities by a normal continuous casting method, heated by slab at 1150 ° C., the finishing temperature of hot rolling is 1000 to 1050 ° C., and the reduction rate of the final two passes of the finishing stand is 40%. 40% to obtain a hot-rolled steel strip having a thickness of 1.8 mm, then pickled, cold-rolled to 1.0 mm and 0.67 mm, then annealed at 1120 ° C. for 3 minutes and pickled And final cold rolled to 0.50 mm and 0.40 mm.

Thereafter, primary recrystallization annealing was performed at 810 ° C. to 880 ° C. for 150 seconds, H ₂ : 75%, N ₂ : 25%, and dew point 45 ° C. (PH ₂ O / PH ₂ = 0.14). Changed. Then, in a strip state running so that the total nitrogen content is 0.022 to 0.025 mass%, nitriding is performed in an ammonia atmosphere, and Al ₂ O ₃ and MgO are applied with an annealing separator in a ratio of 1: 1. Then, secondary recrystallization annealing was performed. The conditions were a temperature increase rate of 15 ° C./hour up to 1200 ° C., atmosphere H ₂ : 75%, and N ₂ : 25%. Thereafter, purification treatment was performed at 1200 ° C. for 20 hours in an H ₂ : 100% atmosphere. After cooling, light pickling and shape correction treatment were performed, and a chromate semi-organic insulating coating was applied. The results are also shown in FIG. The magnetic flux density in the claims is excellent in both the rolling direction and the direction perpendicular to the rolling direction.

The figure which shows the relationship between a primary recrystallization grain size and magnetic flux density: B8 (T).

Claims (2)

% By mass, C ≦ 0.020%, Si: 2.5-4.0%, acid-soluble Al: 0.022-0.035%, N: 0.0050-0.010%, 0.005% ≦ (S + 0.405Se) ≦ 0.012%, Mn: 0.05 to 0.15%, slab composed of remaining Fe and inevitable impurities is heated to a temperature range of less than 1200 ° C., and hot-rolled Obtain a hot-rolled steel strip and either anneal or not anneal this hot-rolled steel strip, and then perform cold rolling twice or two times sandwiching the intermediate annealing to the final sheet thickness, or the final Before the cold rolling, heat treatment is performed once or more, and the final sheet thickness is obtained by final cold rolling applying a rolling reduction of 25% or more and less than 60%, and then a wet hydrogen atmosphere at a temperature of 800 ° C. or more and 890 ° C. or less. PH ₂ O / PH _2: subjected to primary recrystallization annealing at 0.02 to 0.33, running strip The product thickness is 0.50 mm or less and the primary recrystallized average grain size is 20.0 μm or more and 31.0 μm or less by nitriding in a state and applying an annealing separator, followed by finish annealing. A method for producing electrical steel sheets with excellent magnetic properties in the direction perpendicular to rolling.   2. The rolling according to claim 1, wherein the hot rolling finishing start temperature is more than 900 ° C. and less than 1150 ° C., and the additional reduction ratio in the final stand of the finish rolling and the stand immediately before is 55% or more. A method for manufacturing electrical steel sheets with excellent perpendicular magnetic properties.

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