Heat treatment apparatus

Details Heat treatment apparatus Heat treatment apparatus

2000-08-24

2001-10-16

Walberg, Teresa (Department: 3742)

Electric heating

Heating devices

Combined with container, enclosure, or support for material...

C219S390000, C219S405000, C118S724000, C118S725000, C392S416000, C392S418000

Reexamination Certificate

active

06303908

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a heat treatment apparatus which performs a heat treatment in a magnetic field. Particularly, the invention relates to a heat treatment apparatus which applies a heat treatment in a high magnetic field to a magnetic material such as an MR film or a GMR film.
2. Description of the Related Art
A magnetic film such as a thin film of an Fe—Ni alloy or the like formed on a substrate, by sputtering or the like, which is a magnetic material used for a magnetic head or the like can exhibit its magnetic properties by subjecting it to a heat treatment in a high magnetic field.
For this purpose, there is conventionally proposed a heat treatment apparatus in which an electric furnace, an induction heating furnace or the like is disposed to apply a heat treatment in a magnetic field formed with electromagnets. A schematic configuration of a typical conventional heat treatment apparatus is illustrated in FIG.
7
.
As shown in
FIG. 7
, the heat treatment apparatus
1
A has a cylindrical vacuum vessel
2
, and magnetic field generating means
20
arranged outside the vacuum vessel
2
. In the vacuum vessel
2
, a holder supporting unit
4
is attached to an upper part thereof. A holder
3
holding an object to be heat-treated such as a magnetic material is charged into the interior by this supporting unit
4
and held. The magnetic field generating means
20
is provided with a pair of electromagnets
21
arranged oppositely outside the vacuum vessel
2
, and the electromagnet
21
has a magnetic core
22
and a coil
23
.
Heating means
100
is provided between the outer surface of the vacuum vessel
2
and the end face of the magnetic core
22
of the electromagnet
21
. Usually, the heating means
100
is spaced apart from the outer surface of the vacuum vessel
2
by a prescribed distance, and comprises electric heaters
101
arranged so as to surround the outer periphery of the vacuum vessel
2
. The electric heater
101
is formed, for example as shown in
FIG. 7
, by providing, for example spiral grooves
103
on the inner periphery of a heater support
102
made of bricks or ceramics arranged so as to surround the vacuum vessel
2
, the inner periphery facing the outer periphery of the vacuum vessel. A heating wire such as a nickel-chromium wire
104
is positioned in each of these grooves
103
. Heat insulators
105
such as alumina felt or bricks are arranged on the outer periphery of the heater support
102
so that heat of the heating means
100
is not transferred to the electromagnets
21
.
In the conventional heat treatment apparatus, however, since the heating means
100
with the structure as mentioned above is provided between the outer periphery of the vacuum vessel
2
and the magnetic core of each of the electromagnets
21
, the distance between the magnetic cores
22
and
22
of the pair of electromagnets
21
is inevitably large. The distance (L) between the inner surface of the vacuum vessel
2
and the magnetic core
22
is usually within a range of from 135 to 250 mm. If the vacuum vessel
2
is assumed to have an outside diameter (D
1
) of 240 mm, the distance (LO) between the magnetic cores
22
of the electromagnets
21
would therefore be within a range of from 520 to 700 mm.
In order to achieve a uniform magnetic field and a prescribed magnetic field strength, therefore, the electromagnet composing the magnetic field generating means
20
must necessarily be large in size, and the current fed to the electromagnet
21
must be increased. The increase in weight and current resulting from the use of larger electromagnets leads to the necessity to provide a larger equipment space and a larger power supplying facility.
Adoption of a larger electromagnet leads to a larger overall construction of the heat treatment apparatus, and considerably increases the equipment cost and the running cost.
Furthermore, with the aforementioned heating means, in which bricks or the like are used as heat insulators, dust is produced, and this causes problems when using in a clean room.
SUMMARY OF THE INVENTION
An object of the present invention is therefore to provide a heat treatment apparatus which can generate a uniform magnetic field with a desired strength by the use of relatively small-sized magnetic field generating means, permits rapid heating and cooling, and makes it possible to sufficiently improve properties of a magnetic material.
Another object of the invention is to provide a heat treatment apparatus which improves the degree of freedom for design, permits downsizing of the overall configuration of the apparatus, reduction of the equipment cost, inhibition of power consumption and considerable reduction of the equipment running cost, while avoiding heating of the magnetic field generating means by the increase in temperature of the electric furnace and thus without limiting the material selection.
Still another object of the invention is to provide a heat treatment apparatus which does not use an apparatus component parts which may produce waste, and is applicable in a clean room.
The aforementioned objects are achieved by the heat treatment apparatus of the present invention. In summary, the present invention provides a heat treatment apparatus comprising a vacuum vessel, magnetic field generating means arranged outside the vacuum vessel, and heating means arranged between the vacuum vessel and the magnetic field generating means; wherein the heating means comprises:
an electric heater arranged so as to surround the outer periphery of the vacuum vessel; and
a fluid cooling section arranged between the electric heater and the magnetic field generating means.
According to an embodiment of the invention, the heating means comprises an electrically insulating inner cylinder arranged so as to surround the outer periphery of the vacuum vessel, and said inner cylinder is arranged between the vacuum vessel and the electric heater. Preferably, the vacuum vessel and the inner cylinder are made of an optically transparent material.
According to another embodiment of the invention, the electric heater comprises a resistance-heating wire covered with an electrically insulating tube. Preferably, the resistance-heating wire is a nickel-chromium wire, or a non-magnetic metal heater made of a noble metal, and the electrically insulating tube is a tube made by knitting alumina fibers, or a tube made by connecting a plurality of quartz or alumina tubes.
According to still another embodiment of the invention, in the electric heater, the current flowing through the resistance-heating wire flows in a counter current to the current flowing through an adjacent resistance-heating wire to avoid inducing of occurrence of a magnetic field caused by the applied current.
According to further another embodiment of the invention, the fluid cooling section is a water-cooled jacket through which a fluid flows.
According to another embodiment, a sheet-shaped electric insulator may be arranged between the water-cooled jacket and the electric heater. Preferably, the water-cooled jacket is made of a metal.
According to another embodiment of the invention, the magnetic field generating means comprises electromagnets oppositely arranged outside the vacuum vessel, and the distance (L) between the end face of the magnetic core of the electromagnet and the inner surface of the vacuum vessel is within a range of from at least 0.05 times to up to 0.15 times as long as the distance (LO) between the magnetic cores of the magnetic field generating means, or more specifically, from at least 15 mm to up to 45 mm, or preferably, from at least 15 mm to up to 30 mm.


REFERENCES:
patent: 4487161 (1984-12-01), Hirata et al.
patent: 4487162 (1984-12-01), Cann
patent: 4798926 (1989-01-01), Sakai
patent: 5167717 (1992-12-01), Boitnott
patent: 5217560 (1993-06-01), Kurono et al.
patent: 5245171 (1993-09-01), Hayakawa et al.
patent: 5261962 (1993-11-01), Hamamoto et al.
patent: 5453125 (1995-09-01), Krogh
patent: 5472508 (1995-12-01), Saxe

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