JP4609149B2 - Jig for final finish annealing of grain-oriented electrical steel sheet - Google Patents

Description

  The present invention relates to a jig for final finishing annealing of grain-oriented electrical steel sheets, and more particularly to a technique effective for eliminating the problems that occur in the final finishing annealing process.

  Oriented electrical steel sheets are mainly used for iron core materials such as transformers, etc., but are required to have good magnetic properties. When used as an iron core, it is particularly important that its energy loss, that is, iron loss is low. Means for reducing this iron loss include (1) highly accumulating the crystal orientation of the steel plate in the {110} <001> orientation, and (2) eddy current loss by containing Si and increasing the electrical resistance of the steel plate. There are methods such as (3) reducing impurities that hinder domain wall movement, and (4) reducing the plate thickness of the steel sheet. Here, in order to highly accumulate the crystal orientation as described above, in the manufacture of the grain-oriented electrical steel sheet, final finish annealing is performed at a high temperature of about 900 to 1200 ° C. after the final finish rolling.

  This final finish annealing is generally a so-called “box annealing furnace” in which the steel sheet (steel strip) after finish rolling is wound in a coil shape and the winding shaft is in a vertical direction (also referred to as an up-end) ( (Also called a box-type annealing furnace). Recently, there has been a demand to reduce the thickness of the grain-oriented electrical steel sheet. To answer that, especially when the sheet thickness is reduced to less than 0.25 mm, one end of the steel strip wound in a coil shape is the inner winding of the coil. Since it is open in the central space formed on the side, the steel plate is distorted or, as shown in FIG. 3, in the central space 7 of the coil 4 during annealing, the steel strip ends to the inside. The problem that the fall 5 and the waist break 6 (buckling) as shown in FIG. 4 occur will occur.

  Regarding these problems, conventionally, a steel sleeve is inserted into the central space 7 of the coil 4 and subjected to final finish annealing (see, for example, Patent Document 1). A method of winding a plate over a thickness of 50 mm or more (for example, see Patent Document 2), a method of winding an unrolled portion that occurs during the final cold rolling (for example, see Patent Document 3), and reducing the winding tension of an internally wound steel plate Measures such as a method (for example, see Patent Document 4) are disclosed.

However, as in Patent Document 1, when a sleeve is used, insertion and extraction of the sleeve into and from the central space of the coil and transportation of the coil itself become complicated, and at high temperature annealing, the sleeve deforms and cannot be extracted from the coil. In some cases, the inner-rolled steel plate may be deformed at the time of extraction. In addition, in the method described in Patent Document 2, it is necessary to prepare a different type of steel material in advance when winding in a coil shape using a tension reel after finishing rolling, which hinders continuous steel strip production on the production line. It becomes. Furthermore, when the unrolled part is left as in Patent Document 3, there is a problem that it is difficult to pass through the production line during decarburization annealing performed after cold rolling and before finish annealing. It was. In addition, when a different kind of material is entrained as the inner winding as in the methods described in Patent Documents 2 and 3, the product weight is reduced by that amount, and thus the productivity is lowered. In addition, if the tension applied to the inner-rolled steel sheet is reduced as in the method described in Patent Document 4, buckling can surely be prevented, but the inner-rolled steel sheet tends to fall into the central space, and deformation due to it tends to occur. There was a case.
JP-A-60-141828 JP 61-124528 A JP 61-124529 A JP-A-4-131325

  In view of such circumstances, the present invention has a directionality that can suppress the occurrence of folding and buckling of the coil to the central part space side of the inner steel plate of the coil that occurs when the directional electromagnetic steel plate coil having a thin plate thickness is finally annealed. The object is to provide a jig for final annealing of electrical steel sheets.

  The inventor has intensively studied to achieve the above object, and the results have been embodied in the present invention.

That is, the present invention is a jig used when the material for grain-oriented electrical steel sheet is a coil, the coil is placed vertically on a table in a box annealing furnace, and used for final finish annealing, A strip-shaped metal ring inserted into the central space of the coil on which the coil shaft is vertically mounted, and a suspension member that suspends the metal ring on the upper end side of the coil, and the metal ring outer diameter and the metal ring The difference from the space diameter of the central portion of the coil is 3 to 8 mm, and the coefficient of thermal expansion of the metal ring material is larger than the coefficient of thermal expansion of the grain-oriented electrical steel sheet material forming the coil, and the metal ring This is a final finishing annealing jig for grain-oriented electrical steel sheets, characterized in that the insertion depth is 1/5 or less of the axial length of the coil . In this case, it is preferable that the suspension member is an annular flange connected to the metal ring, a semi-annular collar, or a lifting tool separate from the metal ring .

  According to the present invention, the metal ring expands during annealing and comes into contact with the inner coil of the coil so as to hold down that portion. The occurrence of falling and buckling of the coil-wound steel plate that occurs when annealing is performed toward the center space side of the coil is suppressed. As a result, the production yield of grain-oriented electrical steel sheets has been improved as compared with the prior art.

  First, the inventors conducted a survey on the actual condition of a plurality of coils in which deformation was observed in several layers on the inner winding side after the final finish annealing, and the deformation started from the upper part of the coil placed on the up-end. Ascertained what is happening. That is, in the case of a plurality of coils having different degrees of deformation, unlike the conventional case where only the buckling occurs when the winding tension of the internally wound steel plate is high, the coil is deformed from the top. It has become clear that is spreading.

Therefore, if only the upper part of the coil in the up-end state is constrained, it is considered that the deformation that falls into the inner side of the steel sheet starting from the upper part on the coil inner winding side can be suppressed, and FIG. As shown in FIG. 2, a metal ring 1 having an outer diameter substantially the same as the central space diameter of the coil 4 is made of steel, and this is attached to the central space 7 of the coil 4 as shown in FIG. An experiment was conducted in which a final finish annealing at 1200 ° C. was performed. In other words, a final finish annealing jig 3 for a grain-oriented electrical steel sheet provided with a band-shaped metal ring 1 and a suspension member 2 (in this case, an annular flange) that suspends the metal ring 1 on the upper end side of the coil 4. (Hereinafter simply referred to as a jig). Here, the insertion depth of the metal ring 1 is set to about 1/5 or less of the axial length (plate width) of the coil so that the coil is not deformed during attachment and detachment . Good Mashiku is, is good for a 1 0~200mm. If the thickness is less than 10 mm, the collapse of the inner-rolled steel sheet cannot be sufficiently prevented, and if it exceeds 200 mm, the contact portion is too large and the coil may be deformed.
The insertion depth means the vertical length of the metal ring 1.

  By using such a jig, it has become possible to prevent deformation due to falling. However, since the metal ring 1 is in close contact with the inner winding side of the coil 4 in the same manner as the above-described sleeve as the prior art, when the ring 1 is extracted from the coil 4 after the annealing is completed, there is not a little distortion. Sometimes it happened.

  Therefore, the inventors tried to further improve the jig 3. That is, based on the state when the metal ring 1 is attached to the coil 4 at room temperature before the final finish annealing, the difference between the central space diameter of the coil 4 and the outer diameter of the metal ring (the part in contact with the coil) 3-8 mm, and the coefficient of thermal expansion of the material of the metal ring 1 is made larger than the coefficient of thermal expansion of the coil material. The shape of the metal ring 1 was the same as that with the flange shown in FIG. As a result, it was found that in several layers from the coil inner winding side, deformation during finish annealing is prevented, and deformation during attachment / detachment of the metal ring 1 is also prevented.

  Here, the difference between the space diameter of the central portion of the coil and the outer diameter of the metal ring (the portion in contact with the coil) is set to 3 to 8 mm. If the difference is less than 3 mm, the ring is inserted into the central space 7 of the coil 4. The work cannot be performed smoothly and quickly, and if it exceeds 8 mm, the gap between the coil 4 and the ring is too large, and contact between the ring and the coil-wound steel sheet may not occur during annealing. This is to avoid this. Also, the reason why the coefficient of thermal expansion of the metal ring material is made larger than the coefficient of thermal expansion of the coil material is that the metal ring 1 is thermally expanded during annealing so as to come into contact with the inner steel plate of the coil 4. It is to make it.

  Further, as the suspension member 2 for suspending the metal ring 1 on the upper end of the coil 4, an annular flange is effective in the direction along the inner diameter of the coil as shown in FIG. As shown in FIG. 1 (a), if the shape has a flange on the entire circumference, the rigidity of the suspension member 2 can be increased, the thickness of the metal ring 1 can be reduced, and the jig 3 as a whole can be reduced in weight. This is advantageous for handling. Moreover, even if it is not perfect annular, as shown in FIG.1 (b), the thing (it is called a semi-annular flange) of the shape which a part of said annular flange chipped may be sufficient. Furthermore, when the shape of the jig 3 is a simple annular shape (that is, only a metal ring) along the coil-wound steel plate as shown in FIG. 1 (c), the metal ring 1 is suspended separately. It is preferable to use a tool (not shown, but, for example, a hanging tool that has been bent to a wire).

  In addition, the thickness of the metal ring 1 is preferably 1 mm or more in the case of a steel ring, but the rigidity is given so that the metal ring 1 can withstand falling down due to the weight of the coil inner coil at high temperature. It is sufficient to adjust the thickness appropriately according to the material.

Although it does not specifically limit in this invention as a material of such a metal ring 1, As mentioned above, it is important to use a thing higher than the thermal expansion coefficient (thermal expansion coefficient) of a coil raw material. For example, it is preferable to select appropriately from steel materials in terms of having both heat resistance and a high coefficient of thermal expansion. A grain-oriented electrical steel sheet, that is, a steel having a Si content of about 3% by mass has a thermal expansion coefficient of about 13 × 10 ⁻⁶ (K ⁻¹ ). For example, SUS304 (thermal expansion coefficient: 17.3 × 10 ⁻ Austenitic stainless steel such as ⁶ (K ⁻¹ )) can be preferably used because of its high coefficient of thermal expansion.

  In the production of grain-oriented electrical steel sheets, the process prior to final finish annealing is performed by hot rolling a slab having a known chemical composition, performing cold rolling, decarburization annealing, etc. by a known method, and then appropriately performing MgO. After applying an annealing separator such as a coil, the coiled coil is a directional electrical steel sheet coil that is the subject of the present invention. Therefore, the jig 3 according to the present invention is charged with the coil 4 in a batch-type annealing furnace and heated to about 900 to 1200 ° C. before performing final finish annealing for the purpose of secondary recrystallization. Mount on the coil 4. Then, after finishing the final finish annealing, the jig 3 is removed from the coil 4 at room temperature, and thereafter annealing for the purpose of flattening and coating and baking of an insulating coating are appropriately performed. When the metal ring 1 is removed at normal temperature, the thermal expansion has disappeared and the state before the mounting is restored, so that no trouble in operation occurs.

  After decarburizing and annealing the material for grain oriented electrical steel sheets of Si: 3% by mass, which had a final thickness of 0.23 mm through hot rolling and cold rolling, an annealing separator was applied and wound into a coil. At this time, the space diameter of the central portion of the coil was 500 mmφ. This coil was placed in an up-end state on the coil stage on the entry side of the final finishing annealing furnace. A jig 3 provided with a SUS304 (metal) ring 1 similar to the shape shown in FIG. 1A was mounted from the upper part of the central space of the coil as shown in FIG. The outer diameter of the ring 1 was 495 mmφ, the thickness of the ring 1 was 2 mm, the insertion depth into the coil 4 (ring band width) was 50 mm, and the outer diameter of the annular flange of the suspension member 2 was 600 mm.

  On the other hand, as a comparative example, the coil 4 not equipped with the metal ring 1 was also placed on the coil mount. A plurality of coils in both of these states were charged into a final finishing annealing furnace (box-type annealing furnace) and subjected to final finishing annealing at 1200 ° C. for 50 hours in a hydrogen atmosphere.

  As a result, in the coil 4 equipped with the jig 3 according to the present invention, the end of the steel strip into the central space 7 of the coil 4 did not collapse, and no buckling was observed. On the other hand, in the coil 4 to which the jig 3 was not attached, the coil corresponding to about 20% caused collapse of the end of the steel strip, and buckling was also observed in the coil corresponding to about 5%.

  From the above, it has been found that the application of the present invention can effectively prevent the collapse of the end of the inner steel plate into the central space of the coil and the defect due to buckling, which has been a problem in the final finish annealing.

It is a perspective view which shows what was equipped with the annular flange-shaped suspension member among the jigs for final finishing annealing of the grain-oriented electrical steel sheet which concerns on this invention. It is a perspective view which shows what was equipped with the semi-annular flange-shaped suspension member among the jigs for final finishing annealing of the grain-oriented electrical steel sheet which concerns on this invention. FIG. 3 is a perspective view showing a hanging tool with a separate metal ring, among the jig for final finishing annealing of the grain-oriented electrical steel sheet according to the present invention. It is a schematic diagram which shows an example which mounted | wore the coil for the final finishing annealing of the grain-oriented electrical steel sheet which concerns on this invention. It is a perspective view which shows collapse of the inner volume steel plate to the coil center part space. It is a perspective view which shows the waist fold (buckling) which arises in the internally wound steel plate of a coil.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal ring 2 Suspension member 3 Jig 4 Coil 5 Collapse of a steel plate 6 Waist folding (back ring) of a steel plate
7 Central space of coil

Claims (2)

The material for the grain-oriented electrical steel sheet is a coil, the coil is placed on a table in a box annealing furnace, the coil shaft is placed vertically, and used for final finishing annealing,
A belt-shaped metal ring inserted into the central space of the coil on which the coil shaft is vertically mounted, and a suspension member that suspends the metal ring on the upper end side of the coil ,
The difference between the outer diameter of the metal ring and the central space diameter of the coil is 3 to 8 mm,
The thermal expansion coefficient of the metal ring material is larger than the thermal expansion coefficient of the grain-oriented electrical steel sheet material forming the coil,
The final finishing annealing jig for grain-oriented electrical steel sheets, wherein the insertion depth of the metal ring is 1/5 or less of the axial length of the coil .   2. The grain-oriented electrical steel sheet according to claim 1, wherein the suspension member is an annular flange connected to the metal ring, a semi-annular collar, or a lifting tool separate from the metal ring. Jig for final finish annealing.

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