JPH06220548A - Method for annealing metallic foil - Google Patents

Abstract

PURPOSE:To enhance energy efficiency of vacuum annealing by executing the heat treatment of coiled metallic foil by superheating with the heat conducted from the end face sides of the coils. CONSTITUTION:The heat treatment of the metallic foil of soft ductile malleable metals such as aluminum and copper, noble metals such as gold and silver, or iron, etc., wound to a coil form, more preferably the rolled foil (planar material of metals thinner than about 2mm) of the soft ductile malleable metals such as aluminum and copper is executed by heating with the heat conducted from the end faces of the coils. The variations in the temp. between the coils and within the individual coils are decreased and the treatment temp. of the coils is arbitrarily controlled. As a result, the energy efficiency in vacuum annealing is enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an annealing method for the purpose of degreasing and annealing a rolled metal foil, and more particularly to an annealing method effective in vacuum annealing.

[0002]

2. Description of the Related Art Metal foil has metallic luster and conductivity,
It has excellent barrier properties against gas and moisture, light shielding properties, and is widely used in decorative materials, conductive materials, packaging materials, machine materials, etc., and soft, ductile metals such as aluminum, copper, gold, and silver are used as metal foils. Widely used. In particular, since aluminum is used in large quantities as the main component of metal foil, the following aluminum foil (aluminum in the present invention means both aluminum and aluminum alloy, and foil is thinner than about 2 mm even if it is 200 μm or more) If the material is a plate-shaped material, this is included.) Will be described as a representative, but the same can be applied to other metals.

Annealing of an aluminum foil is generally carried out by winding an aluminum foil immediately after rolling into a coil shape, placing the coil (aluminum foil wound in a coil shape) in a heating furnace (annealing furnace), and heating the entire furnace. Annealing and rolling oil are removed.

The heat transfer from the heating furnace to the coil at this time is due to convection and radiation from the heating means.
In particular, when performing vacuum annealing, there is no gas convection, so there is no choice but to rely only on radiation, and many problems arise.

For example, (1) In the case of heat-treating a plurality of coils at one time, if the positional relationship of each coil is not proper, a shadow portion will be generated from the heating means, and between the coils and within one coil. The temperature tends to be uneven. Heating rate, holding temperature,
It is impossible to make the holding time the same for all coils. (2) It is difficult to control the temperature of the coil because there is a large time lag from when the heating means of the heating furnace starts to raise the temperature to when the coil starts to raise the temperature. The temperature raising rate and the temperature lowering rate are also considerably limited. (3) When the coil is heated only by radiation or by convection and radiation, it is gradually heated from the outside of the coil, so that the outside of the aluminum foil expands due to thermal expansion and the coil winding loosens. The heat transfer due to the contact between the layers increases the heat transfer resistance due to the formation of a minute gap between the foil layers, and the temperature becomes nonuniform between the inner and outer layers of the coil. Especially in annealing in a vacuum furnace, since there is no air as a heating medium, the thermal resistance is greatly increased and a large temperature difference is generated. (4) In vacuum annealing, heat transfer depends only on radiation, but aluminum has remarkably high reflectivity and poor heat input efficiency. For this reason, the rate of temperature rise and temperature decrease cannot be increased, and the energy efficiency is poor. There was such a problem.

As a result, the removal of rolling oil becomes insufficient,
Since it causes troubles in subsequent printing and lamination, it is unavoidable to remove the rolling oil by carrying out a heat treatment for a long time as a countermeasure, and this heat treatment process has become a bottleneck in the aluminum foil manufacturing process. .

[0007]

DISCLOSURE OF THE INVENTION According to the present invention, in the step of heat-treating a metal foil wound in a coil shape, (1) variation in temperature between each coil and within each coil is reduced, and further, the processing temperature of each coil is reduced. Control arbitrarily. (2) Energy efficiency is improved, especially in vacuum annealing. The purpose of the invention is to develop a method of annealing a metal foil that can be used, and a means for making it possible.

[0008]

SUMMARY OF THE INVENTION The present invention has been developed by developing a method for annealing a metal foil, which is characterized in that, in heat treatment of a metal foil wound in a coil shape, heating is performed from the end face side of the coil by heat conduction. Achieved the purpose of.

In the present invention, examples of the metal foil include soft and malleable metals such as aluminum and copper, precious metals such as gold and silver, and metals such as iron. Among them, the soft and malleable metals such as aluminum and copper are preferable. Rolled foil (about 2
A metal plate material thinner than mm is suitable.

In the so-called batch annealing in which the metal foil, for example, an aluminum foil is heat-treated while being wound in a coil on a winding core, in the present invention, a heating means is provided on the end surface of the coil wound with the aluminum foil, whereby the coil end surface Is heated, and the heat is transferred to the aluminum foil to heat the coil as uniformly as possible.

As means for heating the end face of the coil,
It suffices if the coil end face can be heated, and there is no particular reason for limitation. For example, (1) heating means for bringing a planar heater into contact with the coil end face (2) heating means by infrared irradiation (3) heating means by induction heating (4) Heating means such as heating means by radiative heat transfer of adjacent heating means may be appropriately adopted depending on the processing conditions of the target metal foil, the site conditions and the like.

In heating from the end face of the coil, it is necessary to uniformly supply the heat to the foils of all layers on the end face of the coil, so that the end face of the coil and the contact face of the planar heater are in contact with each other over the entire surface. It is necessary. For that purpose, the flatness of the coil end surface and the contact surface of the heater is increased, or a heater having a flexible contact surface is used, and a heat transfer comparand, aluminum nitride powder, graphite powder, etc. are used for both contact surfaces. It is effective to

For example, a sheathed heater 1 as shown in FIG. 1 is brazed to a copper disk 2 and a sheet heater is brazed on a coil 5 of a metal foil 4 wound around a winding core 5 so as to be heated. . In this case, it is necessary for the sheet heater to cover the sheath heater side with the heat insulating material 3 or the like so as to reduce the heat loss, and to crimp the coil end face with a necessary load. Further, in order to prevent the heat radiation from the coil surface and the winding core surface and maintain the uniformity of the entire temperature, it is also an effective means to take measures such as heat retention and heating of these surfaces.

The end faces of the coil may be heated by irradiating them with electromagnetic rays such as infrared rays, defocused laser rays and electron rays. In this case, aluminum foil or the like may be directly irradiated, but if it does not hinder the process because it has strong reflectivity, it is coated with graphite powder, carbon black, or other powder with low reflectivity, and if it is irradiated, energy efficiency is improved. Get higher

Alternatively, heating may be performed by using an induction heating device capable of passing an induction current to the very surfaces of both ends of the coil.

Further, a nichrome wire is provided near the coil,
It is also possible to provide uniform heating by providing heating means such as a ceramic heater and radiating from a very close vicinity.
When this heating method is used, it is effective to coat with a material having low reflectivity as in the case of electromagnetic radiation irradiation.

Whichever method is adopted, it is essential to efficiently supply heat to the coil end faces, and this makes temperature control free. That is, the temperature rising rate of the coil can be easily calculated from the total heat capacity of the object to be heated, the input heat power, and the heat radiation amount, and thus the entire temperature control can be facilitated.

Further, in order to reduce the heat radiation amount of the heat treatment, reduce the heat loss, and facilitate the control of the temperature of the entire coil, heat treatment is performed in a conventional annealing furnace or a heat insulating chamber as an auxiliary means of heating, or A planar heating element may be adhered to the outer surface of the coil, or may be heated by a winding core or the like having a built-in heating means. Even when external heating is not performed, it is necessary to shield the coil surface from the outside air with a heat-resistant woven fabric such as glass fiber or rock wool except in vacuum annealing.

The conditions such as heat treatment temperature and heat treatment time vary depending on the material of the metal foil to be treated, the required degree of annealing, the size of the coil, etc. and are not constant, but for aluminum foil, they are shorter than those for batch annealing. ˜450 ° C., several hours to several tens hours.

[0020]

In heating from the outer peripheral surface of the coil or the winding core, it is necessary to transfer the heat to the inner layer or the outer layer through the contact portion of the rolled surface of the foil. Therefore, the heat transfer resistance in the contact portion of the foil is dominated, and the minute gaps between the foil layers caused by the unevenness of the foil, the winding distortion of the coil, the winding looseness due to the temperature increase, etc. increase the heat transfer resistance. Especially in vacuum annealing, since there is no gas (heat medium) in this gap, the heat transfer resistance is significantly increased.

In the present invention, since heating is performed by heat conduction of a continuous foil in principle, it is not necessary to consider the shadow of radiation even in a vacuum heating furnace in which there is no convection of air in the heating furnace and only relies on radiant heating. In addition, since the heating is performed by heat conduction, it has a high reflectivity, and there is a merit that it is not necessary to consider the reflection of radiation in metals such as aluminum, copper, and silver having good heat conductivity.

Even when the winding diameter of the coil becomes large or the temperature difference from the outside air temperature becomes large, external heating may be used together as long as the heating from the end surface of the coil is the main purpose. Even in such a case, when the heating means from the coil end surface is used, a plurality of coils can be heat-treated without variation even if they are collectively heat-treated in a vacuum heating furnace or the like, and conversely, each coil is independently heated under respective conditions. It is also possible to control it.

[0023]

Example An aluminum pipe having an outer diameter of 80 mmφ and a length of 500 mm was wound with an aluminum foil having a width of 500 mm and a thickness of 100 μm until the outer diameter became 300 mm to form a coil.

As the end face heating heater, two 10 mm thick copper disks brazed with a sheath heater (2.5 kw in total) as shown in FIG. 1 were prepared, and jigs were used on both end faces of the coil. I crimped strongly.

This was placed in a vacuum chamber, the chamber itself was not heated, and only the end face heater was used to raise the temperature 5
Heating was performed under the conditions of 0 ° C./hr and heat treatment temperature (holding) 400 ° C./2 hours.

Since the heating by the heater closely attached to the foil (heating by continuous heat conduction of the foil) causes little heat transfer, the target heating profile is used as it is as the heater heating program. As shown in FIG. 3, heating could be performed almost as desired. The temperature difference between the end surface portion and the central portion of the coil was 7 ° C. about 8 hours after the start of heating. The temperature difference between the coil core vicinity and the outer peripheral portion (temperature difference in the thickness direction) was less than 0.5 ° C.

(Comparative Example) An aluminum pipe having an outer diameter of 80 mmφ and a length of 500 mm was used as a winding core, and the outer diameter was 30.
The same aluminum foil coil as in Example 1 wound to 0 mm was prepared.

This coil was placed in the vacuum chamber used in Example 1 which can be heated by an electric heater from the outside, and the coil was evacuated and radiantly heated from the outside. In order to make the coil temperature have the target heating profile shown in FIG. 3, it was necessary to consider a time lag with the heater and to make a heater program such as the heater heating program of FIG. At this time, the temperature of the foil body was S-shaped with respect to the target profile, and the temperature was overheated by 50 ° C. from the target value. Further, a maximum temperature difference of 30 ° C. occurred between the center of the foil and the outer periphery.

Since the foil is heated from the outside, the foil wound on the outside is first heated to a high temperature and is loosened due to thermal expansion, so that a minute gap is formed at the overlapping interface of the foils or the contact degree is high. It is considered that the heat resistance increases due to weakening.

[0030]

EFFECTS OF THE INVENTION By providing heating means on the coil end faces of the metal foil coil and heating and annealing the metal foil by heat conduction from both end faces of the coil, (1) heat conduction in the continuous foil Good transmission, less time lag for temperature rise, and easy coil temperature control. (2) Since each coil is heated from the end face, all coils can be heated to the same condition even when a plurality of coils are annealed at the same time, and the temperature variations of individual coils can be eliminated. In addition, the temperature rising conditions of each coil can be controlled independently. (3) Since it is not necessary to heat the entire periphery such as an annealing furnace, the heat loss as a whole can be reduced and the required energy can be reduced. (4) In particular, in vacuum annealing that does not allow heat transfer by convection, there is no need to consider radiation because heating is due to heat conduction, there is no problem of coil positional relationship and shadow, and thermal efficiency is high. Can be maintained.

[Brief description of drawings]

FIG. 1 is a sectional view of a sheet heater.

FIG. 2 is a cross-sectional view of annealing with a sheet heater.

FIG. 3 is a temperature rising curve in vacuum annealing.

[Explanation of symbols]

 1 sheath heater 2 copper disc 3 planar heater heat insulating material 4 coiled metal foil 5 core

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takashi Tamura Inventor Takashi Tamura 6-224 Kaiyamacho, Sakai City, Osaka Prefecture Showa Aluminum Co., Ltd.

Claims (3)

[Claims] 1. A method for annealing a metal foil, characterized in that, in the heat treatment of the coil-shaped metal foil, the coil is heated by heat conduction from the end face side of the coil. 2. The heating means comprises: (1) heating means for bringing a planar heater into contact with the end surface of the coil; (2) heating means by infrared irradiation; (3) heating means by induction heating; and (4) radiative heat transfer from adjacent heating means. The method for annealing a metal foil according to claim 1, wherein any one of the heating means according to 1. is used. 3. The heating step includes (1) heating in a heated annealing furnace; (2) keeping the outer surface of the coil covered with a planar heating element and / or using a winding core having heating means; The method for annealing a metal foil according to claim 1 or 2, wherein heating is performed by (3) placing a coil in a heat insulating chamber and heating.