JP2719302B2 - Finish annealing equipment for oriented silicon steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a finish annealing apparatus for a directional silicon steel coil (hereinafter referred to as "coil"), and more particularly to a so-called moisture pattern and buckling distortion of an insulating film at a lower end portion of the coil generated during the finish annealing. And technology for simultaneously suppressing the above.

[0002]

2. Description of the Related Art FIG. 3 shows a finish annealing apparatus for a steel strip coil which is generally used at present. That is, the coil 1 is placed in an up-end manner on a support metal 2 on a hearth 6, a base plate 3 serving as a coil receiving stand, and a spacer metal 4 laid one on top of another, and the inner case 5 is covered and heated and cooled. Things. By the way, when the temperature of the coil 1 is raised by this apparatus, the lower surface of the base plate 3 to be directly heated is heated faster than the upper surface on which the coil 1 of the huge heat absorbing source is mounted, so that the thermal expansion of the upper surface of the base plate 3 is performed. The amount becomes smaller than the lower surface, and the base plate 3 warps (the upper surface is concave). Therefore, since the coil 1 supports its own weight only by the outer winding portion, the lower surface of the coil 1 contacts the base plate 3 unevenly, and that portion (circled in FIG. 3) is shown in FIG.
Buckling occurs as shown in FIG. 4A, which causes buckling distortion called so-called ear distortion (FIG. 4B). Since this buckling strain reduces the product yield of the coil, it is a major problem in manufacturing the steel strip coil.

Many measures have been taken to address this problem, and the applicant of the present invention has proposed a method of annealing by regulating the temperature difference between the upper and lower surfaces of the base plate 3 in Japanese Patent Application No. 4-3111099. As a method of absorbing the upward warpage of the base plate 3, there is a technique disclosed in Japanese Patent Publication No. Sho 62-15615, which discloses the use of an underlay plate made of ceramic fiber. In addition, the spacer 4 mounted on the base plate 3 has a special shape. There is also a technique described in Japanese Patent Application Laid-Open No. 4-272137.

As described above, the buckling distortion suppression at the lower end of the outer coil portion is not perfect, but there are techniques that can be expected to have a certain effect, and it is expected that research will be continued in the future. On the other hand, another aim of the present patent application is to suppress the occurrence of the moisture pattern of the insulating film generated at the lower end of the coil winding portion, which is a problem inherent to the grain-oriented silicon steel. It is not enough to give it. This is because the buckling distortion at the lower end of the outer winding portion of the coil and the mechanism of generating the moisture pattern at the lower end of the middle winding portion are completely different.

[0005] Here, a few words about the moisture pattern. Generally, oriented silicon steel sheets usually have 2 to 4
A steel sheet cold-rolled to a final product thickness is subjected to primary decarburization recrystallization treatment using a hot-rolled material containing wt% Si, and a slurry of an annealing separator made of MgO is applied to the surface of the steel sheet. Wind up the coil. Thereafter, a final secondary recrystallization and finish annealing are performed to obtain a product. The reason for applying the annealing separating material is to prevent mutual adhesion of the coiled layered steel sheets during the final secondary recrystallization and finish annealing, and to form SiO ₂ formed on the steel sheet surface after the decarburization primary recrystallization treatment. And forming a glass-like insulating film by the following reaction. This insulation coating
It is necessary to uniformly adhere to the grain-oriented silicon steel sheet, otherwise the magnetic properties of the steel sheet are adversely affected.

SiO ₂ + 2MgO → 2MgO · SiO ₂
(Forsterite) By the way, this insulating film is 900 to 110 according to the above equation.
It is formed in a temperature range of 0 ° C., but its reaction rate depends on the type of atmospheric gas. That is, the reaction proceeds rapidly in H ₂ gas, but slows in N ₂ gas. In the finish annealing of normal grain silicon steel, N ₂ gas is used up to around 900 ° C. to suppress the decomposition of MnS as an inhibitor and to smoothly complete the secondary recrystallization. Then, after the completion of the secondary recrystallization, the gas is switched to H ₂ gas. However, the replacement of N ₂ → H ₂ is delayed in a middle coil having poor gas permeability. Therefore, the lower end of the coil and its 30 to 100 m
A difference occurs in the partial pressure of H ₂ between the region inside m and the growth rate of the forsterite grains. As a result, the difference in the forsterite particle size is visually different from other portions, and appears as a so-called moisture pattern.

[0007] When the moisture pattern is generated, as described above, it is insufficient as an insulating film and has a bad influence on magnetic characteristics and the like, which is a serious problem for products. Therefore, much research has been conducted in the past, and it is known that it is necessary to increase the amount of contact between the atmosphere gas and the coil during annealing in order to suppress the moisture pattern. In other words, it is essential that the air permeability at the lower end of the coil middle winding is good.

As measures against the contact amount up of the atmospheric gas and the coil, Japanese Utility Model Publication No. Sho 62-14126, Japanese Unexamined Patent Publication No. Hei 3-20411, in which a breathable refractory sheet is wound between steel sheets in the inner winding portion of the coil, Japanese Patent Application Laid-Open No. 60-18016 discloses a technique in which the method of applying a separating material is improved. However, these techniques have problems in realization and are currently not used. In addition, the Japanese Patent Application
However, since there is a plate described in Japanese Patent Application Laid-Open No. 177262, which has a wide slit under the coil, the placement of the coil is unstable, and it can be used for a cold-rolled steel plate which is performed at a relatively low temperature. However, there is a problem that it cannot be applied to a directional silicon steel strip coil which is subjected to finish annealing at a high temperature of 1200 ° C.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and is intended to solve the above-mentioned problems. It is an object of the present invention to provide an annealing apparatus that does not generate a so-called moisture pattern and buckling distortion.

[0010]

In order to achieve the above object, the inventor made various trials and examinations, and by securing air permeability at the lower end of the coil and reducing the surface pressure, the above-mentioned two different generation mechanisms were used. I was convinced that I could solve one problem. The present invention
Based on the results of the study, in an annealing furnace in which coils of a directional silicon steel strip are placed on a base plate in an up-end shape and finish annealing is performed, the coils and the base plate are spaced apart from each other. A finishing annealing apparatus for directional silicon steel, comprising a plurality of small-piece blocks and a spacer having a large number of through holes superposed on the small-piece blocks. Furthermore, specifically, the finish annealing apparatus for directional silicon steel according to claim 1, wherein an opening ratio of the spacer through-hole is 50 to 80%.

In this case, the material of the small piece block is preferably a steel material, but it is not necessary to particularly define the material, and a square or rectangular shape is usually sufficient. However, the shape is not particularly limited since it may be a circle, an ellipse, or the like. However, as for the thickness, it is preferable that both the small piece block and the spacer are about 10 to 20 mm.

[0012]

According to the present invention, small blocks are placed at intervals on a base plate of an annealing apparatus, and a steel spacer having a large number of through-holes is laid thereon to mount a coil. Therefore, the air permeability at the lower end of the coil is improved, and the surface pressure that the coil receives from the spacer can be reduced. As a result, the occurrence of the moisture pattern and the buckling distortion generated at the lower end of the coil during annealing can be suppressed.

The contents of the present invention will be described below with reference to FIGS. FIG. 1 is a longitudinal sectional view showing one example of the present invention. There, a plurality of small piece blocks 8 are arranged on the base plate 3 in the inner case 5 at a certain interval from each other, a spacer 4 having a large number of through holes is placed thereon, and the coil 1 is further placed thereon. Is placed. With this arrangement, the atmosphere gas 9 is supplied to the base plate 3
After passing through the central space, there is a lot of free space on the surface of the base plate 3, and so-called air permeability can be sufficiently secured. In addition, the interval between the small piece blocks 8 is
Since it is not a wide slit as in 2-14126, it can withstand the weight of the coil 1 even at a high temperature, the opening area of the through hole of the spacer 4 is 50% or more of the plane area of the spacer 4, and 50% or more of the lower surface of the coil 1 is the spacer. 4 makes contact with the non-opening portion 4 to ensure stable support of the coil 1.

FIG. 2 is a plan view of a through hole formed in the spacer 4, and an embodiment described below is performed using these spacers 4. Implementation results will be described later.

[0015]

EXAMPLE A grain-oriented silicon steel containing 3.0% Si was 0.30%.
The steel sheet was cold-rolled to a thickness of 1 mm and then decarburized. The surface of the steel strip was coated with MgO in the form of a slurry as a so-called annealing separating material, and wound into a coil. Next, this was placed on the base plate 3 in an up-end shape, and was subjected to finish annealing at 1200 ° C.

At this time, of course, the present invention is applied and the spacer 4
A steel plate having a thickness of 20 mm and having a hole with a diameter of 10 mm opened so as to have an opening area of 80% was used (B in FIG. 2).
For the small piece block 8, 166 square steel materials having a thickness of 20 mm and a side of 50 mm were used. The method of placing the small block 8 on the base plate 3 was to form a mosaic shape with each other, and to provide an interval so that the distance between two squares became 50 mm.

On the other hand, for comparison, an experiment using a spacer 4 (A and C in FIG. 2 and no opening not shown) under the three conditions shown in Table 1 was also performed. At this time, the small piece block 8 is placed in the same state as described above. The results are also shown in Table 1, but in the annealing using the apparatus to which the present invention is applied,
There was no buckling distortion at the lower end of the coil 1 and no moisture pattern was generated. In contrast, in the three comparative examples,
In each case, the initial goal was not fully achieved.

[0018]

[Table 1]

[0019]

According to the present invention, in the finish annealing of directional silicon steel, the moisture pattern is suppressed by improving the air permeability at the lower end of the coil 1 and reducing the surface pressure, and the buckling distortion is not generated. As a result, the product yield was improved and the resources were effectively used. In addition, since a simple technique of forming a through hole in the spacer or laying a small piece of steel plate is adopted, it is economically feasible without a large equipment change.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one embodiment of the present invention.

FIG. 2 is an illustration of a spacer having a large number of through holes according to the present invention, wherein (A) is an aperture ratio of 95%, (B) is 80%,
(C) is a plan view in the case of 50%.

FIG. 3 is a longitudinal sectional view of a conventional finish annealing apparatus for a directional silicon steel coil.

FIG. 4 (A) shows a position where a buckling strain occurs in a coil;
(B) is an explanatory diagram showing an occurrence situation.

[Explanation of Signs] 1 Coil 2 Support metal 3 Base plate 4 Spacer (non-perforated or perforated) 5 Inner case 6 Hearth 7 Heating heater 8 Small block 9 Atmosphere gas (nitrogen or hydrogen)

Claims (2)

(57) [Claims] 1. An annealing furnace for finish-annealing a directional silicon steel strip coil placed on a base plate in an up-end manner, comprising: a plurality of small-piece blocks spaced apart from each other between the coil and the base plate. And a spacer having a large number of through-holes overlapping the small piece block. 2. An opening ratio of said spacer through-hole is 50-8.
The finish annealing apparatus for grain-oriented silicon steel according to claim 1, wherein the content is 0%.