JPH0688137A - Method for box-annealing metallic coil - Google Patents

Abstract

PURPOSE:To prevent edge strain at the time of anneling by laying plural spacers of concentric disks between a metallic coil and a base plate. CONSTITUTION:At least two or more pieces of the spacers 2 of concentric disks divided as ring of the material having the same coefficient of thermal expansion as the metallic coil 1 are laid between the metallic coil 1 and the base plate 3. For example, at the time of executing the high temp. finish annealing to the coil of a grain-oriented silicon steel sheet having 3% coefficient of thermal expansion, ordinarily, 30mm of the edge part is cut off because of the strain at the lower part of the coil, but by using these concentric circular spacers 2, the coil is not need to cut off the edge part, or the cut-off width is made to be narrow and the expensive grain-oriented electrical steel sheet can effectively be used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a grain-oriented electrical steel sheet used for iron cores of transformers, turbine generators and the like.

[0002]

2. Description of the Related Art Conventional metal coil (hereinafter referred to as coil)
For example, high-temperature finish annealing of a grain-oriented electrical steel sheet in a box furnace is performed by placing the coil on the base plate in a direction perpendicular to the coil winding axis.
Since it takes a long time at a high temperature of 00 ° C., distortion called ear strain is generated in the lower portion of the coil in contact with the base plate, which must be cut off, which is a serious problem in yield.
As a solution, coil winding method, M as a separating agent
There are patents that devise the method of applying gO and the shape of the spacer between the coil and the pedestal. Especially for the spacer,
As in Japanese Patent Publication No. 53-38683, a method of using one floor plate divided into two or more in the radial direction, or by stacking layers, and in Japanese Patent Laid-Open No. 62-56526, a hoop coil wound tightly is used as a spacer. A method, and a method of forming a slit in a spacer is proposed in Japanese Utility Model Laid-Open No. 59-51051. Distortion is reduced by these methods, and some effects are mentioned, but there is still room for improvement in practical use.

[0003]

When box-annealed by winding in a coil shape, the lower side of the coil is distorted due to annealing at high temperature for a long time, and deformation remains even after the final heat flattening. For this reason, about 10 to 100 mm is slit and cut off in the refining process, so if the cut part is coiled from the beginning and laid and annealed, the main body coil will have no distortion. can get. This method is disclosed in JP-A-62-56256. However, this method can be used only once because it is crushed because it is placed under a heavy coil.
When the hoop having a width of about mm is rolled up to an outer diameter of 2000 mm for handling, there is a safety problem that the hoop tends to fall and fall apart. The present invention solves the above problem by using a concentric spacer divided into a ring shape.

[0004]

According to the present invention, in a method for box annealing a metal coil, a material having the same coefficient of thermal expansion as that of the metal coil is laid as a spacer in the lower part of the metal coil, and the spacer has a ring shape. It is a box annealing method of a metal coil, which is a concentric circular plate divided into at least two or more.

[0005]

FIG. 1 shows a state in which the metal coil 1 is placed on the base plate 3 above the pedestal 4 via the spacer 2. When laying concentric spacers, the spacers will be distorted on the bottom surface of the coil unless they are made of a material that expands and contracts the same as the coil being annealed. For example, in the case of a 3% silicon steel sheet, the coefficient of thermal expansion is about 10 × 10 ⁻⁶ / ° C., so a mild steel material may be used instead of the 3% silicon steel sheet as long as it is close to this.
However, the heat-resistant steel was large at 20 × 10 ⁻⁶ / ° C., which was not preferable. Next, the thickness of the concentric spacers may be 0.3 mm, for example, if they have the same expansion and contraction, but if they are too thin, they will be affected by the unevenness of the lower surface. On the other hand, when it is thick, it wastes an object to be heated, resulting in poor thermal efficiency. The concentric spacer is also deformed by heating and cooling several times, but for example, in the case of a 3% silicon steel sheet, it can be repeatedly used at 10 to 50 mm, and strain in the coil does not occur, so 10 to 50 mm is desirable. . This may be one or several, but from the handling point of view, 1
Sheets are desirable.

Since the strain generated on the lower side of the coil is limited to the outer winding portion, the strain is not uniform, and the strain is considered to be large because the temperature difference between the inside and the outside of the coil is large. Therefore, it is necessary that the rug is not a unitary piece but a concentric ring shape with some gaps between the rings. This concentric circle needs to behave especially in synchronization with the coil deformation of the outer coil, and the width of the outermost ring is narrowed so that the number of concentric circles is at least two, preferably three.
The distortion of the coil remained with one, and the distortion of the coil decreased with two. In addition, when divided into two concentric circles, an experiment was conducted by changing the width of the outer concentric circles from 5 mm. At 5 mm, the spacer deforms and can be used only once. Endured the use of.
If the width is 150 mm or more, the effect of reducing ear strain on the coil is reduced.

[0007]

EXAMPLE A 3% grain-oriented silicon steel sheet was cold-rolled to a final sheet thickness of 0.23 mm, followed by decarburization annealing and continuous annealing also serving as primary recrystallization, and a MgO separating agent was applied between the coils. Then, it was wound into a coil and subjected to high temperature finish annealing. At this time, annealing was performed under the following conditions A to E between the base plate supporting the coil and the coil. A: Place the coil directly on the base plate without spacers. B: One-piece spacer, thickness 10 mm. C: Spacer divided in two in the radial direction, thickness 10 mm, width W of the outer peripheral spacer is changed to 5, 20, 100, 300 mm D: Spacer divided in three in the radial direction (FIG. 2), thickness 10
mm, the width W ₁ of the outer peripheral spacer: the width of the intermediate spacer corresponds to 5,20,50,100mm W _2: 5,80,90,100mm to alter. E: Spacer divided into two in the radial direction, thickness is 5, 10,
It is changed to 50 and 100 mm. The width of the outer spacer is 5
0 mm. As shown in Table 1, although the strain did not completely become 0, the ratio of the strained length was 15% or less and the depth was 20 mm or less, and the deformation and twist of the spacer were small. C- is one that can be used more than three times.
It was 2, -3, D-2, -3, and E-2, -3.

[0008]

[Table 1]

[0009]

EFFECT OF THE INVENTION Conventionally, 30 mm has been cut off due to the distortion of the lower part of the coil after high temperature annealing. By using the concentric circle spacers as in the present invention, it is not necessary to cut off, or the width of the cutoff is reduced, and the expensive grain oriented electrical steel sheet can be effectively used.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a state in which a coil is placed on a cradle.

FIG. 2 is a plan view illustrating a spacer divided into three in the radial direction.

[Simple explanation of symbols]

 1 metal coil 2 spacer 3 base plate 4 cradle

Claims (1)

[Claims] 1. A method of box annealing a metal coil, wherein a material having the same coefficient of thermal expansion as the metal coil is laid as a spacer below the metal coil, and the spacer is divided into at least two pieces in a ring shape. A box annealing method for a metal coil, which is a concentric circular plate.