JP2013256702A - Method for annealing metal strip coil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for annealing a plurality of coils while stacking the coils in the axial direction thereof, in which the temperature of the coils is elevated uniformly between the mutual coils and between the inside and outside of the coils without delay.SOLUTION: A plurality of metal strip coils each formed by winding a metal strip are placed in an annealing furnace while the center axes of the metal strip coils are aligned in the vertical direction, the metal strip coils are covered with an inner case, and the metal strip coils are annealed by radiation heat from the inner case. The annealing is carried out in a state where a plurality of the metal strip coils are stacked in the axial direction while the metal strip coils are spaced from each other.

Description

  The present invention relates to a method for annealing a metal strip coil.

In a metal material manufacturer, when performing heat treatment (annealing) for a relatively long time, it is common to perform the batch process with the metal strip in a coil state.
Unlike continuous annealing in which a thin plate is heat-treated, this method anneals a thick metal strip coil (hereinafter also simply referred to as a coil), so that it takes time to penetrate heat into the interior. Therefore, it takes several tens of hours to several hundred hours for a single annealing. Therefore, shortening the time required for this process leads to a reduction in fuel costs in addition to an improvement in productivity.

  For example, annealing a plurality of coils at a time is extremely effective for shortening the process time. A method often used in this case is a method in which a plurality of coils are stacked in the axial direction (height direction) and annealed, and in the case of a large number of coils, four coils are stacked in the axial direction and annealed. . In this method, since the upper and / or lower end faces of the coil are always in contact with the stacked coils, heat input from the coil end faces is very small.

In addition, since most of the burners for the annealing furnace are installed on the outer peripheral side of the coil, the combustion gas hardly reaches the inner peripheral surface of the coil, and heat input from the inner peripheral surface side is small. Therefore, it is mainly the coil outer peripheral surface that receives heat transfer from the atmosphere around the coil and radiant heat from the case. Since heat input increases as the heat transfer area increases, stacking in the axial (height) direction is very inefficient in heating. Furthermore, since the thermal conductivity in the coil radial direction is smaller than that in the width direction and the circumferential direction, the speed at which the heat received by the coil outer circumferential surface penetrates into the inside is slow.
In addition, as the furnace height increases, a temperature distribution tends to occur in the axial direction of the coil, and uniform annealing becomes difficult. That is, there arises a problem that the coil closest to the burner is overheated, or the coil stacked on top is underheated.

  As a technique for achieving uniform heating between stacked coils, Patent Document 1 discloses a method of adjusting a burner output in the height direction of a furnace in an annealing furnace in which spacers are sandwiched and coils are mounted in four stages. Proposed.

JP-A-6-88138

  Conventional coil stacking annealing is a method in which the upper coil is directly placed on the upper surface of the coil positioned below, or a spacer is sandwiched and the coil is placed on the upper coil. Since the upper surface and the lower surface of the upper coil cannot receive heat transfer or radiant heat due to the gas in the furnace, it has not yet been solved that the temperature increase rate of the entire coil decreases.

  Furthermore, another problem is that the coil ear is distorted by the weight of the coil. That is, since the lower coil supports all the weight of the upper coil, ear distortion in which the coil edge portion is deformed in a wave shape is likely to occur on the upper surface of the lower coil to which the load directly acts. In particular, since the temperature of the coil outer winding is high, the temperature of the coil is increased, so that when thermally expanded, only the outer winding portion supports the weight of the coil mounted thereon, and defects frequently occur. If the temperature can be prevented from becoming extremely high only by the outer winding of the coil, the above problem does not occur, but the above-described conventional technique has not been solved.

  In addition, there is a method of arranging coils in the coil radial direction without stacking them in the axial direction, but there is no problem such as reduction of the heat transfer area that the coil axial stacking has, and the floor area required for heat treatment The factory building becomes huge and is not practical.

  Therefore, the present invention aims to provide a way to raise the temperature of the coils uniformly and without delay between the coils and inside and outside the coils when annealing a plurality of coils stacked in the coil axial direction. And

The inventors have intensively studied to solve the above problems, and obtained the knowledge that it is effective to secure heating from the end face of the stacked coil, and have completed the present invention. .
That is, the gist configuration of the present invention is as follows.
(1) A metal band coil wound with a metal band is placed in an annealing furnace with the center axis of the metal band coil aligned in the vertical direction, the metal band coil is covered with an inner case, and radiant heat from the inner case In annealing the metal strip coil at
A method of annealing a metal band coil, wherein a plurality of the metal band coils are stacked in the axial direction, and a space is provided between the metal band coils to perform annealing.

(2) The metal band coil annealing method according to (1), wherein the space between the metal band coils is 0.1D to 1.0D in the coil axial direction with respect to the coil outer diameter D.

(3) The method for annealing a metal strip coil according to (1) or (2), wherein the second and subsequent coils from below the stacked metal strip coils are supported by a coil base.

  In the present invention, when the coils are stacked and annealed, by providing a space between the coils, the coil end face can reliably receive convection heat from the ambient gas and radiation heat from the surroundings. Heat input from the coil end surface, which was not obtained by the stacking method using the stacking method or the stacking method using the spacer, is applied, and the temperature of the coil can be increased evenly and in a short time.

It is a figure which shows the annealing method by the stacked structure using the upper coil stand which connected two plates with the pillar. It is a figure which shows the annealing method by the stacked structure using the upper coil stand which has a leg. It is a figure which shows the annealing method by the stacked structure using the coil stand which has the leg which penetrates a coil center part. It is a figure which shows the annealing method by the stacked structure which fixed the upper coil stand to the furnace wall. It is a figure which shows the annealing method by the stacked structure in case there are two coils in each stage.

  According to the present invention, a uniform rise in coil temperature can be promoted by providing a space in which atmospheric gas and radiant heat in the furnace enter between the stacked coils during annealing. Specifically, in order to provide an appropriate space between the stacked coils, it is important to appropriately support the upper coil, and a support base for the upper coil that satisfies these conditions is required. Hereinafter, the present invention will be described in detail with reference to the drawings specifically showing a stacked structure of coils.

First, when stacking two coils 1 and 2 in the axial direction, the stacked structure shown in FIG. 1 is connected via a coil base 3 in which two plates 3a and 3b are connected by a column 3c in the center in the radial direction. An upper coil (also referred to as an upper coil) 1 is placed on a lower coil (also referred to as a lower coil) 2. In addition, the code | symbol 4 is a coil stand for mounting the coil 2 of the lower side.
According to this stacked structure, since the diameter of the column 3c is smaller than that of the plates 3a and 3b, a space S sufficient for atmospheric gas and radiant heat to enter between the coils can be provided. That is, although the lower end face of the coil 1 and the upper end face of the coil 2 are not directly subjected to radiant heat, the plates 3a and 3b exposed to the atmospheric gas and radiant heat through the space S receive heat and become high temperature. The coil end faces in contact with the plates 3a and 3b are heated. Then, heat transfer proceeds from both the end face and the outer peripheral portion of the coil, so that the coil can be heated uniformly. Furthermore, since distortion caused by only the temperature from the coil outer winding becoming extremely high is also alleviated, deformation of the coil edge portion can be particularly suppressed.
Moreover, since the heating condition between the stacked coils is equalized, non-uniform heating between the coils is also avoided.
In addition, since the strength of the pillars decreases when the atmosphere becomes high temperature, the number of the pillars 3c may be increased or a higher strength material may be added depending on the weight of the upper coil.

  Here, in the space S provided between the coils 1 and 2, the distance t in the coil axial direction is preferably 0.1D to 1.0D with respect to the outer diameter D of the coil. The space S is effective if it is secured, that is, if the distance t is not 0 mm. However, if the space S is too narrow, it is possible to avoid the case where the degree of heating with the open end face of the coil having a reduced heat input is different. In order to sufficiently receive the radiant heat from the inner case, it is preferable that the shape factor, that is, the ratio of the plate and the upper coil upper surface to receive the radiant heat from the inner case is preferably designed. On the other hand, if the gap is too wide, the effect is small for the furnace to be enlarged. From the above, when the outer diameter of the coil is D, the distance t is preferably in the range of 0.1D to 1.0D where the form factor increases, and more preferably in the range of 0.3D to 0.7D. Recommended. This space S is the same in the cases shown below.

  Moreover, the material of the coil base 3, particularly the plate 3 a, preferably has a high thermal conductivity from the viewpoint of efficiently transmitting the radiant heat from the space to the coil side and is strong from the viewpoint of coil weight support. That is, when a material having a low thermal conductivity is used, the heat input from the end faces between the coils is reduced, so that the effect of providing the space S is reduced. Therefore, not a highly heat-insulating material such as refractory bricks but a material having high thermal conductivity and heat resistance is suitable. In particular, the thermal conductivity is preferably 10 W / m · K or more. As specific materials, materials used as furnace materials for annealing furnaces such as SUS304, SUS310, and SS400 are suitable. The same applies to the material of this plate in the following cases.

  Next, in the stacked structure shown in FIG. 2, the plate 5 a on which the upper coil 1 is placed is supported by a plurality of legs 5 b to 5 e, and the legs 5 b to 5 e are arranged on the coil base 4 of the lower coil 2. Do it. In this case, the space S can be secured without loading the lower coil 2 with the weight of the upper coil 1.

  In the stacked structure shown in FIG. 3, a pillar 7 that supports the upper coil 1 is passed through the plate 6 through the hollow portion 2 a at the center of the lower coil 2 and fixed to the coil base 4. It is significant that the weight of the upper coil 1 is not applied to the lower coil 2 and that the column 7 does not block the radiant heat to the coil outer winding. Normally, as shown in FIG. 3B, a pipe 4 a that supplies atmospheric gas toward the central portion 2 a of the lower coil 2 passes through the coil base 4. In such a case, it is preferable to make the inside of the pillar 7 hollow and provide a hole 7a for supplying atmospheric gas on the side surface. Incidentally, when the inside of the pillar 7 is hollow and the strength is insufficient, reinforcement similar to that of the legs 5b to 5e shown in FIG. 2 may be added. This atmosphere gas supply pipe can also be implemented with the column 3c as a cavity in the coil base 3 shown in FIG.

  The stacked structure shown in FIG. 4 is to fix the support plate 8 for the upper coil 1 to the wall 9a of the inner case 9, but when this structure is installed the lower coil 2 and the inner case 9 Any structure may be used as long as the support plate 8 of the upper coil 2 fixed to 9a does not become an obstacle. For example, by using a plate that can be removed from the wall, a structure can be considered in which the plate is removed when the lower coil is installed, and the plate is attached immediately before the upper coil is installed.

  In addition, the stacking of the coils is not limited to the two stages described above, but can be three or more stages by repeating the same stacking structure. Alternatively, the number of coils in the first stage is not limited to one. As shown in FIG. 5, two coils 2 are arranged side by side, and a plurality of legs are formed in the same manner as the coil base shown in FIG. 2. It is also possible to install the plate 11 via 10a to 10d and place two coils 1 side by side on the plate 11. Of course, the number of coils in each stage may be three or more.

In order to investigate the effect of the present invention, an actual machine experiment was conducted. That is, the lower coil and the upper coil were used as the coils, and the various stacked structures described above were applied according to the place shown in Table 1, and the temperature rising times of the two coils were compared in each case. The results are shown in Table 2. The distance t of the space S between the lower coil and the upper coil was adjusted as shown in Table 1. SUS304 was used for the plate and legs that support the coil.
The coil material was iron (carbon steel). The coil has a weight of 10 tons obtained by winding a steel strip having a length of 3000 m to a diameter of 1.3 m. The temperature condition in the annealing treatment was that the furnace temperature during heating was raised to 800 ° C., then the coil temperature was kept uniform until 800 ° C., and then cooled to room temperature.

  As shown in Table 2, under condition 1, the upper coil having a slow temperature rise required a heating time of 80 hours. On the other hand, in condition 2 in which a space was provided between the coils, the heating time was 65 hours, which was greatly shortened. However, in condition 2, ear distortion was confirmed on the upper surface of the lower coil. Under condition 3 in which the weight of the upper coil was not applied to the lower coil, ear distortion on the upper surface of the lower coil was not observed. Under conditions 4 and 5, there is a difference of 3 hours in the heating time, which is considered to be due to the heat capacity of the plate. In condition 4, since the column of the coil base is present near the inner periphery of the coil, the column accumulates heat to a certain extent and functions to block radiant heat to the inner peripheral surface. Under the condition 5 where the best result was obtained, the time required for the temperature rise of the upper coil was shortened by 15 hours, and the same time for the lower coil could be shortened by 16 hours.

DESCRIPTION OF SYMBOLS 1 Coil 2 Coil 3a, 3b Plate 3c Pillar 3 Coil stand 4 Coil stand S Space 5a Plate 5b-5e Leg 6 Plate 7 Pillar 8 Support plate 9 Inner case 9a Wall
10a-10d legs
11 plates

Claims (3)

A metal band coil wound with a metal band is placed in an annealing furnace with the center axis of the metal band coil aligned in the vertical direction, the metal band coil is covered with an inner case, and the radiant heat from the inner case In annealing the metal strip coil,
A method of annealing a metal band coil, wherein a plurality of the metal band coils are stacked in the axial direction, and a space is provided between the metal band coils to perform annealing.   2. The method for annealing a metal band coil according to claim 1, wherein a distance between the metal band coils in a coil axial direction is 0.1 D to 1.0 D with respect to a coil outer diameter D. 3. The method of annealing a metal strip coil according to claim 1 or 2, wherein a coil stage on the second and subsequent stages from below the stacked metal strip coils is supported by a coil base.

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