JP2007131880A - Method of manufacturing grain oriented silicon steel without forsterite film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a grain oriented silicon steel without forsterite film by which side distortions of lower and upper ends of a coil caused in the finish annealing can be reduced. <P>SOLUTION: An Si-containing steel slab is hot-rolled to form a hot-rolled plate, which is formed into a cold-rolled plate by performing one time of cold rolling or two or more times of cold rolling including an intermediate annealing. The cold-rolled plate is subjected to the primary re-crystallization annealing, and thereafter, the annealing separating agent is coated on the surface of the steel plate, and the finish annealing is performed. In the method for manufacturing a grain oriented silicon steel without any forsterite film having small side distortions by a series of steps, the forsterite film is formed only one side end or on both ends of the width direction of the steel plate during the finish annealing. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a grain-oriented electrical steel sheet without a forsterite coating, and particularly in a direction without a forsterite coating that can reduce the side distortion generated at the edge of the coil when finish annealing is performed in a coil state. The present invention relates to a method for producing a heat-resistant electrical steel sheet.

  The grain-oriented electrical steel sheet is obtained by reheating a silicon-containing (Si) steel slab adjusted to a predetermined component composition to a predetermined temperature and then hot-rolling it into a hot-rolled sheet, and if necessary, performing hot-rolled sheet annealing. And cold-rolled sheet by cold rolling at least once with intermediate or intermediate annealing, followed by primary recrystallization annealing that also serves as decarburization annealing, coating and drying the steel sheet surface with an annealing separator. It is manufactured by winding in a coil shape under application of a take-up tension and performing a final annealing that combines secondary recrystallization annealing and purification annealing in a predetermined atmosphere gas.

  The coil annealed in the above-mentioned finish annealing is placed in the so-called up-end state in which the winding shaft is in the vertical direction, placed on the top surface of the coil cradle, and inserted into the annealing furnace for high-temperature and long-time heat treatment. Applied. Therefore, distortion called “side distortion” may occur at the edge (side) on the lower end side of the coil in contact with the coil cradle. This side strain is likely to occur particularly in a thin material having a plate thickness of 0.30 mm or less.

  On the other hand, the side distortion of the form different from the lower end side of a coil may arise also in the edge part of the upper end side of a coil. This distortion occurs when the upper end portion of the coil is deformed so as to fall in the outer circumferential direction of the coil by annealing at a high temperature for a long time.

  The side strain generated at both edge portions of the coil is a major obstacle in terms of magnetic properties and workability in the grain-oriented electrical steel sheets used by being laminated. Therefore, it is necessary to reduce the side distortion generated at both edge portions as much as possible.

  Several techniques have been proposed for reducing the side distortion of the coil edge portion that occurs in finish annealing. For example, Patent Document 1 discloses that the edge deformation during annealing is reduced by setting the amount of the separating agent applied per unit area in the coil edge portion to 30 to 80% of the amount of the separating agent applied per unit area in the coil central portion. Techniques to do this are disclosed. However, when the amount of the annealing separator at the coil edge portion is small, the magnetic properties of the edge portion are liable to be deteriorated. Moreover, when there is much quantity of an annealing separation agent, there also exists a problem that a film defect becomes easy to generate | occur | produce in a product.

  Further, in Patent Document 2, in the annealing of a thin plate coil by a batch type annealing furnace, an underlay plate of a ceramic fiber is raised on a coil pedestal, and an overlay plate made of the same material as the thin plate coil to be annealed is formed on the underlay plate. , And a steel plate coil is placed thereon and annealed to prevent distortion at the lower end of the thin plate coil. However, in this method, when the material to be annealed is a Si-containing steel, it is necessary that the material of the floor plate is also Si steel. Since ferritic steels such as Si steel have low high-temperature strength, the coil end face tends to bite into the top plate during finish annealing at high temperatures. As a result, the movement of the coil end face is constrained by the overlay, and there is a problem that side distortion is likely to occur.

  In addition, in Patent Document 3, a hoop coil wound tighter than the coil is placed between the coil to be annealed and the coil pedestal for high-temperature finish annealing to absorb the difference in thermal expansion between the coil and the coil pedestal. Thus, a technique for reducing the occurrence of side distortion is disclosed. However, this method has a problem that the hoop coil is buckled and deformed by only a few annealings, and on the contrary, a large strain is generated in the annealed coil, so that it is necessary to frequently replace the hoop coil and the cost is significantly increased. .

  Further, in Patent Document 4, when the silicon steel coil is placed on the coil pedestal and subjected to finish annealing, the average crystal grain size of one side edge portion in contact with the coil pedestal of the coil before finish annealing is set to 15 μm or more, A technique for reducing the side strain generated at the lower end of the coil by preventing high-temperature creep deformation due to grain boundary sliding has been disclosed. However, although this method can reduce the buckling strain at the lower end of the coil to some extent, it has often been found that the shape of the coil is deteriorated. There is also a problem that the magnetic characteristics of the coil end are deteriorated.

Furthermore, Patent Document 5 discloses that high-temperature finishing is performed with a steel material containing 0.2 mass% or more of C and having a transformation point interposed between the grain-oriented electrical steel sheet coil and the coil cradle as a floor plate. A technique for reducing the side distortion at the coil end portion on the side in contact with the coil cradle by annealing and causing the deformation accompanying the transformation of the coil cradle slowly is disclosed. However, this method also shows a moderate side strain reduction effect.For example, when applied to finish annealing that causes secondary recrystallization at a high temperature, such as a grain-oriented electrical steel sheet using AlN as an inhibitor, It was not necessarily effective in reducing side distortion.
As described above, all of the conventional techniques have left considerable problems in practical use.
Japanese Patent Laid-Open No. 55-110721 JP 58-61231 A JP-A-62-56526 Japanese Patent Laid-Open No. 2-97622 JP-A-5-179353

  By the way, in recent years, a grain-oriented electrical steel sheet having no forsterite film has been developed. This steel sheet is intended to facilitate the movement of the domain wall by eliminating the irregularities at the interface between the forsterite coating and the ground iron, thereby reducing the iron loss.

  As a method for producing a grain-oriented electrical steel sheet without a forsterite film, there is a method of removing the forsterite film by subjecting the grain-oriented electrical steel sheet produced in the conventional process to pickling or polishing. However, this method has a problem that the process is complicated and the manufacturing cost is high.

  Therefore, it has been proposed to adjust the main components and additives of the annealing separator used during finish annealing to prevent the formation of a forsterite film. For example, a method using an annealing separator mainly composed of alumina or the like that does not produce forsterite, or an annealing separator mainly composed of magnesia, even if a forsterite film is not formed or formed, it adheres to the steel plate surface. This is a technique of blending an additive that forms a forsterite film that can be easily removed without being formed.

  However, when such annealing separator is applied and finish annealing is performed, the side distortion of the coil tends to be extremely large. The reason is that the surface of the steel sheet on which the forstenite coating is not formed is smooth, so that the frictional force between the coil layers becomes small, and the steel sheet tends to shift downward or outside the diameter due to gravity during finish annealing. Conceivable. As a result, even if the above-described conventional technique is applied to the finish annealing of the grain-oriented electrical steel sheet without the forsterite film, a sufficient effect cannot be obtained for reducing the side strain.

  Accordingly, an object of the present invention is to propose an advantageous manufacturing method for reducing the side strain at the lower end and upper end of the coil that occurs during finish annealing when manufacturing a grain-oriented electrical steel sheet having no forsterite coating.

  In order to solve the above-described problems of the prior art, the inventors perform high-temperature finish annealing of grain-oriented electrical steel sheets using an annealing separator having various components and blending amounts, and are generated at the coil edge portion. The relationship between lateral strain and forsterite film formation was investigated. As a result, it has been found that by forming a forsterite film only at the widthwise end of the coil, buckling deformation at the lower end of the coil and deformation at the upper end of the coil can be prevented, and the present invention has been completed. .

  That is, in the present invention, a Si-containing steel slab is hot-rolled to form a hot-rolled sheet, which is cold-rolled by performing cold rolling twice or more times with one or more intermediate annealings. In the method of manufacturing a grain-oriented electrical steel sheet without a forsterite film by a series of processes in which a crystal annealing is performed and then an annealing separator is applied to the surface of the steel sheet and then a finish annealing is performed, the forsterite film is applied during the finish annealing. It is a method for producing a grain-oriented electrical steel sheet without a forsterite film having a small side strain, which is formed only at one end or both end parts in the width direction of the steel sheet.

  The production method of the present invention is characterized in that the forsterite film is formed within 100 mm from the widthwise end of the steel sheet.

Moreover, the said manufacturing method of this invention, when forming a forsterite film in the one side edge part of the width direction of a steel plate, it mounts and the finish annealing is carried out so that the formed side may become a lower side. .

  In addition, the present invention hot-rolls a Si-containing steel slab to form a hot-rolled sheet, which is cold-rolled by performing cold rolling twice or more with one or more intermediate annealings between the first and second cold-rolled sheets. In a method for producing a grain-oriented electrical steel sheet without a forsterite film by a series of processes in which a crystal annealing is performed and then an annealing separator that does not form a forsterite film is applied to the steel sheet surface and then a finish annealing is performed, An annealing separator capable of forming a stellite film is applied only to one end or both ends in the width direction of the steel sheet. is there.

  The manufacturing method of the present invention is characterized in that an annealing separator capable of forming a forsterite film is applied within 100 mm from the widthwise end of the steel sheet.

  In addition, when the annealing separator for forming the forsterite film is applied to one end in the width direction of the steel sheet, the manufacturing method of the present invention is placed so that the applied side becomes the lower side during finish annealing. It is characterized by finish annealing.

  According to the present invention, it is possible to remarkably reduce the side distortion generated at both edges of the coil of the grain-oriented electrical steel sheet without the forsterite film, so that the product yield can be improved, and at the time of lamination when being incorporated in a transformer or the like. Can be reduced and the magnetic properties can be improved.

  The method for producing a grain-oriented electrical steel sheet of the present invention applies an annealing separator that forms a forsterite coating only on the lower end of the coil that contacts the coil cradle of the box-type annealing furnace and / or the upper end of the coil on the opposite side. The other part is characterized by applying an annealing separator that suppresses the formation of the forsterite film. Thereby, the side distortion can be effectively reduced while improving the iron loss.

Any Si-containing steel slab, which is a starting material for the grain-oriented electrical steel sheet targeted by the present invention, is suitable as long as it is adjusted to a conventionally known component composition as the grain-oriented electrical steel sheet. A preferable component composition will be described below.
C: 0.01-0.10 mass%
C is a useful component that contributes to uniform refinement of the structure after hot rolling and also contributes to the development of goth-oriented grains, and is preferably contained in an amount of at least 0.01 mass%. However, if the content exceeds 0.10 mass%, the Goth orientation is disturbed, and therefore the upper limit is preferably about 0.10 mass%.

Si: 2.0 to 5.5 mass%
Si increases the specific resistance of the steel sheet and contributes to the reduction of iron loss, but if it exceeds 5.5 mass%, the cold rolling property is impaired. On the other hand, if it is less than 2.0 mass%, not only the specific resistance is lowered, but also the α-γ transformation is caused during the high temperature finish annealing for secondary recrystallization and purification, thereby randomizing the crystal orientation. And a sufficient iron loss improvement effect cannot be obtained. Therefore, the Si content is preferably in the range of 2.0 to 5.5 mass%.

Mn: 0.02 to 2.5 mass%
In order to prevent hot embrittlement, Mn is preferably contained at least about 0.02 mass%. However, if Mn is excessively increased, the magnetic characteristics are deteriorated, so the upper limit is preferably limited to about 2.5 mass%. Moreover, if it is content of this range, it is enough to precipitate MnS and MnSe as an inhibitor.

Next, components that form inhibitors will be described. In order to highly accumulate crystal grains oriented in the Goss direction by secondary recrystallization, an inhibitor that precipitates uniformly and finely in steel is required prior to secondary recrystallization. The inhibitors are roughly classified into MnS, Cu ₂ -XS, MnSe, Cu _{2 -X} Se and AlN so-called precipitate types, and grain boundary segregation types such as Sn and Sb.

S, Se as an inhibitor for controlling secondary recrystallization of grain-oriented electrical steel sheet, precipitates form of _MnS, which is a useful component in the case of using the _{Cu 2-X S, MnSe,} Cu 2-X Se. In order to exhibit the effect as an inhibitor, it is preferable to add 0.005 mass% or more of one or two of S and Se. However, if it exceeds 0.06 mass%, the effect is impaired. Therefore, it is preferable to add S and Se in a range of 0.005 to 0.06 mass% in one or a total of two. In addition, when using Cu as an inhibitor component, the addition amount of Cu is desirable in the range of 0.005 to 0.50 mass%.

Moreover, when using a precipitate type AlN type | system | group as an inhibitor, it is preferable to set it as the range of Al: 0.005-0.10 mass% and N: 0.004-0.015 mass%. As in the case of MnS, Cu ₂ -XS, MnSe, and Cu _{2 -X} Se described above, if it falls below the above range, the effect as an inhibitor is not sufficiently exhibited. Conversely, if it is too high, the effect as an inhibitor is achieved. It is because it loses.
In addition, in order to stably manufacture a steel plate having excellent electromagnetic characteristics, the above-described inhibitors of MnS, Cu ₂ -XS, MnSe, Cu _{2 -X} Se and AlN are used in combination. preferable.

  On the other hand, when a grain boundary segregation type inhibitor is used, it is preferable to add Sn in the range of 0.01 to 0.25 mass% and Sb in the range of 0.005 to 0.15 mass%. If the amount is less than the above range, the effect as an inhibitor is not sufficient. On the other hand, if the amount exceeds the above range, the saturation magnetic flux density decreases, and good magnetic properties cannot be obtained. These inhibitor components may be added alone or in combination.

  Furthermore, conventionally known inhibitor components such as Cr, Te, Ge, As, Bi, and P can be added for the purpose of improving magnetic characteristics. These preferable addition amounts are in the range of 0.01 to 0.15 mass% for Cr, 0.005 to 0.1 mass% for Te, As, Ge and Bi, and 0.01 to 0.2 mass% for P. These inhibitor components may be added alone or in combination.

Next, the manufacturing method of the grain-oriented electrical steel sheet of this invention is described.
The Si-containing steel slab having the above preferred component composition, which is a raw material for grain-oriented electrical steel sheets, is either produced by a continuous casting method or produced by split rolling an ingot obtained by ingot casting. It may be used. Moreover, you may use the pre-rolled slab after continuous casting.

  Prior to hot rolling, the Si-containing steel slab needs to be reheated to form a solution of the inhibitor component. In the present invention, heating conditions for solution treatment are not particularly specified, but a gas furnace, an induction electric furnace, or a combination of the above, is heated for 5 minutes or more at a temperature that is equal to or higher than the solubility product of each inhibitor component. It is desirable to do. Note that the slab structure after heating may be refined by performing light rolling under 20% or less during or before heating the slab.

  The slab after heating is subjected to hot finish rolling after being formed into a sheet bar by normal hot rough rolling to obtain a hot rolled sheet. Next, hot-rolled sheet annealing is performed as necessary, followed by pickling and cold rolling to obtain a cold-rolled sheet having a target thickness. In this case, the cold rolling may be performed by a single cold rolling method with a target sheet thickness by one strong rolling, or by a double cold rolling method in which cold rolling is performed twice with intermediate annealing interposed therebetween. However, when the latter is performed, it is preferable to set the reduction ratio of the first cold rolling to about 5 to 50%. The final cold rolling preferably employs warm rolling or aging treatment between passes in order to improve the primary recrystallization texture. Further, after the final cold rolling, it is possible to perform a magnetic domain refinement process in which a linear groove is provided on the surface of the steel plate as is well known.

  The cold-rolled sheet obtained as described above is subjected to primary recrystallization annealing that also serves as decarburization annealing by a known method. Then, an annealing separator having a component composition capable of forming a forsterite film is applied to one side or both sides of the width direction edge (end), and the forsterite film is applied to the remaining central portion in the width direction. An annealing separator whose component composition has been adjusted so as not to form a film is applied, and a final finish annealing is performed.

  As an annealing separator that does not form a forsterite film, the main component is alumina, silica, calcia, etc., and a composition containing about 30 mass% or less of magnesia, or a magnesia as a main component, chloride, bromide, Pb alloy or its compound, Bi alloy or its compound, etc. blended as additives can be preferably applied.

  In addition, as the annealing separator for forming the forsterite film, conventionally known ones mainly composed of magnesia can be used, and further, the adhesion of forsterite is improved or the amount of forsterite formed is increased. A compound having a function to act (for example, Li, K, Na, Mg, Ca, Sr, Ba, Ti, V, Cr, Mn, Sn, Sb, B and Al oxides, hydroxides, halides, sulfates) , Nitrates, carbonates, etc.) may be added.

  The width of both ends of the coil to which the annealing separator for forming the forsterite film is applied is 10 mm or more (one side) from the end in order to prevent slipping between the coil layers and to suppress the side distortion. Is preferred. However, if the application width is too large, the product yield decreases, so the application width is preferably 100 mm or less (one side). More preferably, it is the range of 10-50 mm.

  As a method of forming a forsterite film on the edge of the steel sheet, in addition to the method of separately applying an annealing separator having a different film forming ability as described above, before applying an annealing separator that does not form a forsterite film to the entire width of the steel sheet. And / or later, compounds that promote the formation of forsterite coatings only at the coil ends (eg, Li, K, Na, Mg, Ca, Sr, Ba, Ti, V, Cr, Mn, Sn, Sb, B, A method of forming a forsterite film by applying an Al oxide, hydroxide, halide, sulfate, nitrate, carbonate, etc.) and changing the composition of the annealing separator may be used.

  In addition, when the annealing separator for forming the forsterite film is applied only to one side of the coil edge portion, the applied side may be either the upper side or the lower side during finish annealing, but the lower side The effect of suppressing the occurrence of side strain is greater when the sample is placed and finished annealed.

  After finishing annealing, after removing the unreacted annealing separator, the coil surface is coated with an insulating film to make a product, but if necessary, the surface of the steel sheet is mirror-finished before coating the insulating film. Alternatively, a tension coating may be used as the insulating coating. Moreover, you may perform the application | coating baking process of an insulating film and a planarization process. Furthermore, in order to further enhance the iron loss reduction effect, the steel sheet after the secondary recrystallization is subjected to a known magnetic domain refinement process, for example, a plasma jet or laser irradiation in a linear manner, or a linear dent region by a projecting roll. Or a process of providing

  C: 0.07 mass%, Si: 3.2 mass%, Mn: 0.07 mass%, S: 0.0020 mass%, Al: 0.023 mass% and N: 0.0090 mass%, the balance being Fe and inevitable The Si-containing steel slab composed of mechanical impurities is hot-rolled and then cold-rolled with a thickness of 0.23 mm and a width of 1200 mm by two cold rollings with intermediate annealing, and then 860 in a continuous decarburization annealing furnace. Decarburization annealing was performed at a temperature of 140 ° C. for 140 seconds. Thereafter, an annealing separator having a composition for forming a forsterite film is applied to one end or both ends in the width direction of the coil under the conditions shown in Table 1, and magnesia is applied to the remaining central portion of the plate width. An annealing separator that does not form a forsterite coating containing 1% of magnesium chloride was applied, wound into a coil, placed on the coil cradle, and finished annealing. . After removing the unreacted annealing separation agent from this coil by washing with water and phosphoric acid, it was measured how much side distortion occurred at both edges of the coil from the end to the inside. The extent of side distortion was evaluated by the total amount of edge generation width.

  The results of the above measurements are shown together in Table 1. From Table 1, it is confirmed that even in the finish annealing of grain-oriented electrical steel sheets that do not have a forsterite coating, side strain can be effectively reduced by applying an annealing separator that forms a forsterite coating to the coil edge portion. It was.

Claims (6)

A Si-containing steel slab is hot-rolled to form a hot-rolled sheet, which is cold-rolled by subjecting it to cold rolling at least once with one or more intermediate annealings, and subjected to primary recrystallization annealing, In the method of manufacturing a grain-oriented electrical steel sheet without a forsterite film by a series of processes in which the annealing separator is applied to the surface of the steel sheet and then finish annealing, the forsterite film is applied to one side in the width direction of the steel sheet during the finish annealing. A method for producing a grain-oriented electrical steel sheet without a forsterite film having a small side strain, wherein the grain-shaped electrical steel sheet is formed only at an end portion or both end portions. The method for producing a grain-oriented electrical steel sheet according to claim 1, wherein the forsterite film is formed within 100 mm from an end in the width direction of the steel sheet. 3. The directionality according to claim 1 or 2, wherein when the forsterite film is formed at one end portion in the width direction of the steel sheet, the forsterite film is placed and finished annealing so that the formed side is the lower side. A method for producing electrical steel sheets. A Si-containing steel slab is hot-rolled to form a hot-rolled sheet, which is cold-rolled by subjecting it to cold rolling at least once with one or more intermediate annealings, and subjected to primary recrystallization annealing, In a method for producing a grain-oriented electrical steel sheet without a forsterite film by a series of processes in which an annealing separator that does not form a forsterite film is applied to the steel sheet surface and then finish annealing, the forsterite film is formed on the steel sheet surface. A method for producing a grain-oriented electrical steel sheet without a forsterite film having a small side strain, wherein an annealing separator that can be applied is applied only to one end or both ends in the width direction of the steel sheet. The method for producing a grain-oriented electrical steel sheet according to claim 4, wherein an annealing separator capable of forming a forsterite film is applied within 100 mm from an end in the width direction of the steel sheet. The annealing separator for forming the forsterite film is applied to one side end in the width direction of the steel sheet, and the applied side is placed so as to be the lower side during finish annealing, and finish annealing is performed. A method for producing a grain-oriented electrical steel sheet according to 4 or 5.