JPH05195086A - Coil loading table for heat treatment of metallic strip coil - Google Patents

Abstract

PURPOSE:To suppress generation of the defects in quality of the bottom surface of a coil by providing cutout parts from the bottom surface of a coil loading table to a top surface in a point-symmetrical manner, thereby reducing the upward warp of the coil loading table during the annealing operation. CONSTITUTION:A plurality of cutout parts are provided in a point-symmetrical manner to the bottom surface through the top surface of a coil loading table where a metallic strip coil is loaded, and the upward warp of the coil loading table during the annealing operation is reduced. The holes of the cutout parts should preferably be penetrated in the vertical direction. These cutout parts and the holes allow the heat-receiving quantity of the top surface part of the coil loading table to be increased, and the temperature rise of the top part to be promoted. Heat is supplemented to the bottom surface of the center part in the thickness direction where the temperature rise within the coil is delayed, leading to a uniform effect of heat treatment within the coil.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coil holder used for annealing a metal strip coil.

[0002]

2. Description of the Related Art FIG. 12 shows coil annealing of a general metal strip. The coil 3 is placed on the coil holder 1 and the inner case 5 is covered to anneal. For heating, the electric heater 4 on the hearth and the heating from the outside of the inner case 5 are used together.
When the temperature of the annealing is increased, the lower surface of the table which is directly heated is heated faster than the upper surface on which the coil is placed. For this reason, the amount of thermal expansion of the upper surface becomes smaller than the amount of thermal expansion of the lower surface, and the table is warped. As a result, the lower surface of the coil comes into uneven contact with the stand, causing a quality defect called ear distortion.

Conventionally, as a method for preventing the quality deterioration of the ear portion of the coil due to the warp of the coil cradle, Japanese Patent Laid-Open No. 58-6 has been proposed.
As shown in Japanese Patent No. 1231, a method of dividing the coil pedestal, and as shown in Japanese Patent Laid-Open No. 60-131928, a method of lowering the outer circumference of the coil pedestal than the inner circumference,
Further, as disclosed in Japanese Patent Laid-Open No. 1-110255, a method of making the coil pedestal made of ceramic is introduced.
Further, a method of heating the upper part of the stand has been proposed.

However, the method of dividing the pedestal has a problem that it is difficult to maintain the flatness of the pedestal. Further, in the method of lowering the outer circumference of the coil pedestal from the inner circumference, the difference in thickness between the inner and outer circumferences cannot be increased in consideration of the influence on the lower part of the coil, and the effect cannot be expected when the pedestal is largely warped. Furthermore, the method of using a ceramic pedestal is not feasible in terms of material toughness and cost. In addition, in the method of heating the upper part of the stand, it is necessary to provide an electric heater and a temperature measuring device, and also an arithmetic circuit and the like, which leads to complication of the device.

[0005]

According to the present invention, the pedestal is not particularly divided, the material can be an ordinary metal system, and the warp does not warp so as to cause quality defects during annealing. It is an object of the present invention to provide a coil holder that does not require a special arithmetic unit, a heater, or a temperature measuring device.

[0006]

That is, according to the present invention, a metal strip coil is placed on a disk-shaped coil stand in a heat treatment furnace, an inner case is covered, and the heat treatment furnace hearth is placed under a predetermined atmosphere. In a heat treatment furnace of a metal strip that heats by using both an electric heater provided and the heat from the outside of the inner case, a cutout is provided in a point symmetrical manner from the bottom surface to the top surface of the coil holder, and the warp of the coil holder is warped. Is a coil stand for heat treatment of a metal strip coil, and the cutout portion can be vertically penetrated.

The shape and arrangement of the notch may be selected according to the size of the table and the weight of the coil. In order to maintain the flatness of the upper surface of the table, point symmetry is essential, the larger the number of cutouts, the better, and the intervals (pitch) should be even.

[0008]

[Operation] It is self-evident that ear distortion does not occur if warp is eliminated, and warp does not occur if the temperature difference between the upper and lower surfaces of the coil holder is eliminated. Further, it has been confirmed from an experiment that the lower surface of the coil pedestal becomes hotter than the upper surface during the annealing temperature rise, but according to the present invention, the coil holder is provided by the notch or the through hole provided in the holder. The amount of heat received by the upper surface of the table is increased, and the temperature rise of the upper section can be promoted. As a result, the temperature difference between the upper and lower surfaces of the coil receiving table can be reduced, so that the upward warp can be reduced.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is one of the embodiments of the present invention and is a cross-sectional view in the case where eight circular notch portions are provided in point symmetry. Figure 2
Is one of the other embodiments and shows an example in which a hole is penetrated. Figure 3
FIG. 3 is a view on arrow AA in FIG. 2. Direct radiation from the hearth heater 4 is obtained outside the outer diameter of the foot 2 of the coil cradle,
Optimally, the centers of the holes to be provided are arranged at equal intervals on the circumference intermediate between the outer diameter of the foot 2 and the outer diameter of the pedestal 1.

The diameter and the number of holes are preferably obtained as follows. In FIG. 2, the vertical axis represents the compressive stress in the radial direction generated when the coil is placed on the stand, and the horizontal axis represents (hole diameter /
It is the graph which took the diameter of the circle which arranges the center of a hole. FIG. 3 is a graph in which the degree of heating of the side surface of the hole by radiation is plotted along the horizontal axis (diameter of the hole / diameter of a circle having the center of the hole). FIG. 4 is a graph in which the ordinate indicates the position on the side surface of the hole, and the abscissa indicates the intensity of radiation heating with the parameter (diameter of the hole / diameter of the circle having the center of the hole) as a parameter.

It can be seen from FIG. 4 that when the hole is large, it is heated to reduce the temperature difference between the upper and lower surfaces of the coil holder as compared to when the hole is small. Also, from FIG. 3 (b), it can be seen that the larger the diameter of the hole, the greater the degree of heating of the side surface of the hole, and that if the diameter exceeds a certain value, the heating rate becomes constant.
The size of the hole cannot be larger than the straight line shown in (c) in the figure. This is because the diameter of the hole becomes larger than the value obtained by subtracting the diameter D of the circle in which the center of the hole is arranged from the diameter of the stand. Proportion of heating most efficiently ((c) in the figure)
(Limited with), if you make the desired hole size up to 80%,
A desirable hole size is 0.18 to 0.26 x (diameter D of the circle that lays the center of the hole).

If the diameter of the hole is increased, the internal stress generated when the coil is placed increases. The line indicated by (a) in FIG. 2 indicates the allowable stress. The line shown in (b) shows 80% of the allowable stress. When the size of the holes is in the above range, the number of holes allowed in (b) is from 8
14 is suitable. Figure 1 (a) shows an example in which the holes are not penetrated. By leaving the upper part of the stand thin, a heated surface parallel to the hearth heater can be provided, and the heating of the upper part of the stand can be promoted by efficiently utilizing radiant heating. Also, it is slightly advantageous in terms of strength as compared with the case of forming a through hole.

FIG. 5 (b) shows an embodiment in which a cutout portion is provided on the outer periphery of the coil holder and the cutout portion is penetrated.
(c) is a view on arrow AA in (b). The centers of the cutouts to be provided are optimally arranged at equal intervals on the outer periphery of the pedestal 1 so that the cutout side surfaces can efficiently receive the radiation from the side surfaces of the inner case. The number and size of the cutouts were determined by the same idea as in the above-mentioned embodiment. FIG. 4 shows a graph in which the vertical axis represents the area of the cutout and the horizontal axis represents (diameter of the cutout / diameter of the coil holder). In the figure, (a) represents the limitation of the diameter of the cutout. If the notch diameter is made too large, quality defects will occur in the lower part of the coil, overlying the notch. The diameter of the cutout is limited so that the area of the portion of the cutout that overlaps the cutout (hatched portion in FIG. 7) is 70% or less. In the figure (b)
The curve indicated by indicates the limit due to the stress generated in the table. From Fig. 6, the number of cutouts is 6 to 12, and the diameter is 0.15 to 0.
23 × (stand diameter) is suitable.

FIG. 5 shows an example in which the cutout is not penetrated. By leaving the upper part of the stand thin, a heated surface parallel to the hearth heater can be provided, and the heating of the upper part of the stand can be promoted by efficiently utilizing radiant heating. In addition, it is slightly advantageous in terms of strength as compared with the case where the notch is formed therethrough. FIG. 8 (a) shows a sectional view of another embodiment. (b) is a view from the arrow AA of (a).
The number and size of the holes to be provided are determined by the same idea as in the above-mentioned embodiment. FIG. 7 shows a graph in which the vertical axis represents the total area of holes and the horizontal axis represents (hole diameter / table thickness). The straight line in (a) in the figure indicates the limit of the diameter of the hole. As for the size of the hole, it is at least necessary to leave 1/2 of the diameter above and below the hole for the thickness of the table, so the maximum thickness of the table is 1
/ 2. In the figure, (B) shows the limitation due to the stress generated in the stand. From Figure 9, the number of holes is 8 to 15, and the size of the holes is
0.2 to 0.4 × (stand thickness) is suitable.

The coil holder of the present invention may have a structure in which plates are welded as shown in the cross section of FIG. 10 (a). (b) is
It is an AA arrow line view of (a). By doing so, it is possible to prevent the warp of the coil holder, which causes a problem in quality. By the way, with the conventional stand, 900
The maximum value of the temperature difference between the upper and lower surfaces of the pedestal during the process of raising the temperature to ℃ was about 120 ℃. The amount of warpage (difference in height between the inner circumference and the outer circumference of the stand) at that time was about 5 mm. On the other hand, eight holes parallel to the axis shown in FIG. 11, which is an example of the present invention,
As a result of annealing under the same conditions using a stand placed on the circumference so as not to penetrate, the maximum temperature difference was about 70 ° C. The warp was about 3 mm. As a result, in the annealing using the stand according to the present invention, the rejection rate was reduced to about 1/3 as compared with the annealing using the conventional stand.

[0016]

As described above, according to the present invention, it is possible to prevent the warp of the coil holder during the coil annealing and to suppress the occurrence of quality defects on the lower surface of the coil, thereby improving the yield of the product. it can. Further, heat is replenished to the lower surface of the central portion of the thickness where the temperature rise is delayed most in the coil, so that the heat treatment effect in the coil becomes more uniform, and thus the uniformity of product quality can be improved.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a coil holder with an axial hole.

FIG. 2 is a graph showing the relationship between the stress generated in the stand and the diameter of the hole / the diameter of the circle in which the center of the hole is arranged.

FIG. 3 is a graph in which the degree to which the side surface of a hole is heated by radiation is plotted on the horizontal axis (diameter of hole / diameter of circle arranging center of hole).

[FIG. 4] The vertical axis indicates the position on the side surface of the hole, and the horizontal axis indicates (hole diameter /
It is the graph which took the diameter of the circle which arranges the center of a hole.

FIG. 5 is a diagram showing an embodiment of a coil holder provided with a cutout in the axial direction.

FIG. 6 is a graph showing a relationship between a total area of cutouts and a diameter of cutouts / a diameter of a coil holder.

FIG. 7 is a diagram showing a relationship between an area of a cutout and an area of a coil overlapping the cutout.

FIG. 8 is a view showing an embodiment of a coil holder with holes formed in the radial direction.

FIG. 9 is a graph showing the relationship between the total area of holes and (hole diameter / stand thickness).

FIG. 10 is a diagram showing an embodiment of a coil holder having a plate welding structure.

FIG. 11 is an explanatory diagram showing a specific implementation status of the present invention.

FIG. 12 is a side view showing general coil annealing.

[Explanation of symbols]

 1 Coil stand 2 Coil stand support legs 3 Coil 4 Hearth heater 5 Inner case

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yutaka Kosaka, 1-chome, Mizushima Kawasaki-dori, Kurashiki-shi, Okayama Prefecture (no address) Inside the Mizushima Steel Works, Kawasaki Steel Co., Ltd. (72) Kazushige Adachi, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Prefecture 1 chome (without street number) Kawasaki Steel Works Mizushima Works

Claims (3)

[Claims] 1. A metal strip coil is placed on a disk-shaped coil stand in a heat treatment furnace, an inner case is covered, and an electric heater provided on the hearth of the heat treatment furnace in a predetermined atmosphere and from the outside of the inner case. In a heat treatment furnace for metal strips that heats together with the above heat, the metal strip is characterized in that cutout portions are provided in point symmetry from the bottom surface to the top surface of the coil holder to reduce the warp of the coil holder. Coil stand for heat treatment of coils. 2. The coil holder for heat treatment of a metal strip coil according to claim 1, wherein the cutout portion penetrates vertically. 3. A metal strip coil is placed on a disk-shaped coil stand in a heat treatment furnace, an inner case is covered, and an electric heater provided on the hearth of the heat treatment furnace in a predetermined atmosphere and from the outside of the inner case. In a heat treatment furnace for metal strips that heats together with the above heat, a plurality of holes are provided point-symmetrically from the outer peripheral surface of the coil holder toward the center to reduce the warp of the coil holder. Coil stand for heat treatment of metal strip coil.