BACKGROUND OF THE INVENTION
1. Field of the Invention:
[0001] The present invention relates to a heating element used for a cooking apparatus and
a heating apparatus at temperatures of around 800°C, and a method for manufacturing
the same.
2. Description of the Prior Art:
[0002] As a heating element for a cooking apparatus and a heating apparatus, a silica tube
heater has been conventionally used. A sheath heater and a "mica heater" where a heating
wire is wound around a mica strip have also been used for a cooking apparatus.
[0003] However, the above conventional heating elements have problems as follows.
[0004] In the case of the silica tube heater where a heating wire wound in a toroidal shape
is inserted into a silica tube, when the heater is used for cooking, for example,
substances such as salt spattered from an object to be cooked may attach to the surface
of the silica tube. As a result, the silica tube is likely to be devitrified, failing
to provide a sufficient amount of extreme infrared radiation required for cooking,
or the silica tube may even become broken. Thus, only a temperature of 700°C at highest
is obtained from this heater. Further, it is difficult to form the silica tube heater
into a sheet due to the structure thereof.
[0005] In the case of the sheath heater where a heating wire is covered with a thermal resistant
and corrosive resistant stainless steel plate, when used for cooking, the heater utilizes
secondary radiation from the stainless steel sheath. This structure requires a longer
time until a predetermined temperature is attained. Further, in order to obtain the
radiation of 800°C, the temperature of the heating wire itself must be more than 800°C,
which will shorten the life of the heating wire. Moreover, as in the case of the silica
tube heater, it is difficult to form the sheath heater into a sheet due to the structure
thereof.
[0006] The mica heater can easily be formed into a sheet. However, since the heater is installed
through an insulation on the outer surface of the wall of a cooking apparatus, heat
conduction is not effective. Therefore, a longer time is required until a predetermined
temperature is attained on the inner surface of wall of the cooking apparatus from
which heat is radiated for cooking, and also it is difficult to obtain the radiation
of a high temperature of about 800°C.
[0007] To overcome the above-described problems, a bare metal heating element made of iron-chrome-aluminium,
nickel-chrome or iron-nickel-chrome can be used to serve as a heating element which
can be formed into a sheet and which can be rapidly and easily heated to provide radiation
of 800°C suitable for a cooking apparatus and a heating apparatus.
[0008] The bare metal heating element is highly thermal resistant and will not be damaged
when exposed in an atmosphere of high temperature. However, when used for a cooking
apparatus, corrosive substances such as salt spattered from an object to be cooked
may attach to the metal heating element. If such a contaminated metal heating element
is used under the condition of a temperature as high as 800 C, it will easily be corroded
and damaged. The structures of the afore-mentioned heating elements had originally
been developed to prevent such corrosion.
[0009] To obtain a heating unit with stable organisation and bigger oxidation resistance
in high temperature air JP-A-52-108 532 discloses a process for manufacturing an electric
heating material in which after reducing an area of a compound material, the core
material of which is a Fe-Cr-plate, both sides of it are covered by thin Al-plates
by rolling process. The Al-plate of the area reduction process material is heated
to diffuse into the core material. This electric heating material can also be obtained
by applying a blanking process.
[0010] Furthermore, it is already known a process for the production of a foil thermocouple
having an elongate shape which is bent in the plane of the thermocouple. This process
as known from GB-A-1 222 504 comprises forming by deposition on a metal foil a layer
of a different metal, the junction between the two metals constituting the thermo-junction
of the thermocouple, and the metal foil being provided with the elongate shape either
before or after the deposition. This thermocouple may be made from any standard thermocouple
materials which allow the deposition of one material on the other. Thus, for example,
the thermocouple may be made by depositing nickel-chrome on nickel-aluminium foil.
[0011] The objective of the present invention is to provide a heating element which is not
only highly corrosive resistant at high temperature, but also can be formed into a
sheet, and can be rapidly and easily heated to provide heat radiation of about 800°C.
SUMMARY OF THE INVENTION
[0012] The heating element of this invention, which overcomes the above-discussed and numerous
other disadvantages and deficiencies of the prior art, comprises a metal base having
nickel-aluminium alloy layers formed on the top and bottom surfaces thereof.
[0013] A further invention is a method for covering the nickel or nickel base alloy with
aluminium oxide layers.
[0014] In another preferred embodiment, the metal base is nickel or a nickel-base alloy.
[0015] In still another preferred embodiment, the nickel content in the nickel-base alloy
is at least 50 %.
[0016] Alternatively, the heating element of this invention comprises a metal base having
nickel layers and aluminium oxide layers formed in this order on the top and bottom
surfaces thereof.
[0017] In a preferred embodiment, the aluminium layers or the aluminium alloy layers are
formed by cladding.
[0018] According to another aspect of the present invention, the method for manufacturing
a heating element comprises the steps of forming aluminium layers on the top and bottom
surfaces of a nickel or nickel-base alloy base, and oxidising the aluminium layers
into aluminium oxide layers.
[0019] In a preferred embodiment, the aluminium layers are formed by cladding the nickel
or nickel-base alloy base with aluminium foils on both surfaces thereof.
[0020] In another preferred embodiment, the method further comprises the step of cutting
the nickel or nickel-base alloy base clad with the aluminium foils to a predetermined
shape between the step of forming the aluminium layers and the step of oxidising the
aluminium layers.
[0021] In still another preferred embodiment, the aluminium foils are wider than the nickel
or nickel-base alloy base.
[0022] In still another preferred embodiment, the nickel content in the nickel-base alloy
base is at least 50%.
[0023] Alternatively, the method of this invention comprises the steps of forming nickel
layers on the top and bottom surfaces of a metal base, forming aluminium layers on
the nickel layers, and oxidizing the aluminium layers into aluminium oxide layers.
[0024] In a preferred embodiment, the nickel layers and the aluminium layers are formed
by cladding.
[0025] In another preferred embodiment, the method further comprises the step of cutting
the metal base clad with the nickel layers and the aluminium layers to a predetermined
shape between the step of forming the aluminium layers and the step of oxidizing the
aluminium layers.
[0026] The heating element of the present invention with high corrosion resistance at high
temperature can be used in a bare form without the necessity of providing a sheath,
as required in the conventional heating elements, to protect against, for example,
attachment of corrosive substances spattered from an object to be cooked. Further,
the heating element without a sheath can easily be formed into a sheet heating element
by stamping it into a desired pattern or the like. Also, since the specific heat of
the heating element of the present invention can be small without an extra thickness
for a sheath, the heating element can rapidly be heated to a high temperature of,
for example, 800°C, and thereby radiation of high temperature is easily obtained.
[0027] Thus, the present invention makes possible the objective of providing a heating element
which can be formed into a sheet and which can be rapidly heated so as to provide
radiation of high temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] This invention may be better understood and its numerous objects and advantages will
become apparent to those skilled in the art by reference to the accompanying drawings
as follows:
Figure 1 is a sectional view of a heating element of the present invention;
Figure 2 is a sectional view showing a pretreated state of the heating element of
Figure 1;
Figure 3 is a chart showing the relationship between the nickel content and the corrosion
resistance of the heating element of Figure 1;
Figure 4 is a schematic sectional view of a cooking apparatus using the heating element
of Figure 1;
Figure 5 is a sheet heating element of the present invention stamped into a meander
shape;
Figure 6 is a sectional view of another heating element of the present invention;
and
Figure 7 is a sectional view showing a pretreated state of the heating element of
Figure 6.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Example 1
[0029] Referring to Figure 1, a heating element 1 comprises a metal base 2 made of nickel
or a nickel-base alloy having aluminium oxide layers 3 and nickel-aluminium alloy
layers 4 formed in this order on the top and bottom surfaces thereof.
[0030] The heating element 1 of the above structure is formed by the following procedure.
[0031] As shown in Figure 2, aluminium layers 5 are formed on both surfaces of the metal
base 2 by spraying, plating, evaporation, spattering, cladding or any other appropriate
method. When spraying or cladding is employed, a thicker layer is comparatively easily
obtained. Especially, by cladding where an aluminium foil is rolled on and tightly
attached to a heating element, an aluminium layer which is free from pinholes can
be formed. Then, the aluminium layers 5 are oxidized into the aluminium oxide layers
3 with high corrosion resistance. The aluminium layers 5 can be oxidized by various
methods such as anodic oxidation. Most practically, it is heated at high temperature
in the atmosphere. When this method is employed, the nickel-aluminium alloy layers
4 which are also highly corrosive resistant can easily be formed between the metal
base 2 and the aluminium oxide layers 3, thereby providing the resultant heating element
with the property of high corrosion resistance.
[0032] A heating element of the above structure was manufactured to assess the corrosion
resistance as follows.
[0033] A nickel or an alloy containing a varying content of nickel (chrome content: 21 ±
2%) was used as the metal base 2. Then, the metal base 2 was clad with aluminium foils
on both surfaces thereof. The resultant aluminium-clad base was cut into a size required,
and then heated at 900°C in the atmosphere for five hours so as to produce the aluminum
oxide layers 3 on both surfaces thereof. In this way, the heating element 1 having
a width of 6 mm and a thickness of 50 µ was obtained. Electricity was applied to the
heating element 1 to raise the temperature of the surfaces thereof to 800°C. Under
this condition, a 5% saline solution was dropped by 0.5 cc to the heating element
1 every two minutes, and the number of drops applied until the heating element 1 was
corroded and cut apart was used to determine the level of the corrosion resistance
of the heating element 1. This test was performed for ten samples, of which results
are shown in Figure 3.
[0034] In Figure 3, each two-direction arrow shows the range of the numbers of drops counted
for the samples of each nickel content, and each mark · shows the average thereof.
Each mark X shows a result obtained from a sample of the metal base without cladding
of an aluminium foil. As is apparent from this figure, the corrosion resistance sharply
increases when the nickel content exceeds 50%. This is because, with such a high nickel
content, the corrosive resistant nickel-aluminium alloy layers 4 were further formed
between the metal base 2 and the aluminium oxide layers 3. This formation was confirmed
by analyzing the heating element 1 by an X-ray diffraction method, where NiAl and
Ni₃Al were detected.
[0035] In the above heating element 1, the aluminium layers 5 were formed on the top and
the bottom surfaces of the metal base 2, but not on the side faces thereof (in the
direction of the thickness thereof). However, after the heat treatment, the formation
of the nickel-aluminium alloy layer 4 was also observed on the side faces. This is
probably because burrs of the aluminium foils produced at the aforementioned cutting
process after the cladding of the aluminium foils were spread onto the side faces
of the metal base 2. Further, in the corrosion resistance test, most of the sample
heating elements were finally cut apart by corrosion in the portions except the cut
side ends thereof, which shows that the cut side ends are not especially inferior
in corrosion resistance.
[0036] When the base metal clad with the aluminium foils is not cut to a size of the heating
element, but used as it is as a heating element, the aluminium foils can be slightly
wider than the metal base, so that the nickel-aluminium alloy layer can also be formed
on the side faces of the base metal as in the case described above.
[0037] From the result of the aforementioned test, it is proved that the method of the present
invention significantly improves the corrosion resistance of the resultant heating
element.
[0038] Next, an application of the above-described heating element 1 to a cooking apparatus
will be described as follows.
[0039] Figure 4 shows a microwave oven 6 which has a structure of a sheet heating element
7 comprising the heating element 1 of the invention being disposed on support members
9 placed on a microwave shielding plate 8. A control panel and other components of
the microwave oven 6 not directly relating to this invention are not shown in the
figure for simplicity.
[0040] The microwave shielding plate 8 is made of a corrosive resistant stainless steel
plate having a number of bores of a diameter of about 3 mm so that the total area
of the bores should occupy about 60% of the total area of the plate. The microwave
shielding plate 8 has two functions; shielding the sheet heating element 7 from receiving
microwave radiated during microwave cooking and passing radiation from the heating
element directly onto an object to be cooked during heat cooking.
[0041] A nickel-chrome strip (NCHRW1) for heating was used as the metal base 2, which was
clad with aluminium foils on both surfaces thereof. Then, the resultant strip was
stamped into a meander shape and heated at 900°C in the atmosphere for five hours
to produce the sheet heating element 7 having an output of 1.2 KW. When a rated voltage
of 100 V was applied to the heating element 7, the temperature of the heating element
reached 700°C in about one minute, and further rose to 800°C in three minutes,
[0042] An object to be cooked, for example, a fish, was put in an oven chamber 10 for heat
cooking. The fish was uniformly broiled under the radiation of 800°C for fifteen minutes.
When a conventional sheet heating element, for example the mica heater, was employed
to broil the fish, 25 minutes were required. Further, in any of the mica heater, the
sheath heater and the silica tube heater, uniform browning as attained in the heating
element of the invention was not possible.
[0043] As described above, the sheet heating element 7 of the invention effects uniform
browning over the object to be cooked, because the heating element 7 is formed as
a sheet and the radiation from the sheet heating element 7 to the object is intensive.
That is, since the radiation is sent in the direction vertical to the surface of the
heating element 7, in the case of a strip heating element as shown in Figure 5, the
radiation is theoretically sent only to an area right below the width A of the heating
element 7. (The radiation in the horizontal direction along the heating element is
not counted in this case since the thickness of the heating element is negligibly
small compared with the width thereof.) Actually, however, the radiation is somewhat
diffused since the surface of the heating element is uneven, which as a result, enables
the uniform browning of the object to be cooked. Thus, in the case of a strip heating
element, radiation is more intensive in the direction vertical to the heating element,
and therefore effective heating can be accomplished by placing the object to be cooked
in this direction.
[0044] In the case of the sheath heater or the silica heater where a heating element with
a sheath is round in section, heat is radiated to every direction in the space. Therefore,
the amount of radiation reaching the object to be cooked is small, that is, the heating
efficiency is low when the sheath heater or the silica heater is used compared with
when the strip heating element is used, under the condition that both heating elements
have the same output and the same temperature of radiation.
[0045] In the above-described structure of the microwave oven 6, salt or other substances
spattered from an object to be cooked may attach to the surface of the heating element
7. However, this will not cause any practical problem for the heating element 7 of
the invention because it is highly corrosive resistant. The corrosion resistance of
the heating element 7 was tested by repeating a cycle of alternating the microwave
cooking of a 5% saline solution and the heat cooking of a fish. The result was that
the heating element 7 of the invention had been little damaged after 500 cycles, while
a sheet heating element made of the nickel-chrome strip stamped without the treatment
according to the invention had been corroded and damaged after 60 cycles.
[0046] From the above results, it was found that the heating element of this example had
high corrosion resistance and was little deteriorated after a long period of usage.
Example 2
[0047] Another example of the present invention will be described with reference to Figures
6 and 7 as follows.
[0048] Referring to Figure 6, a heating element 11 comprises a metal base 12 having nickel-base
layers 13 and aluminium oxide layers 14 formed in this order on the top and bottom
surfaces thereof. The metal base 12 is made of iron-chrome, iron-chrome-aluminium
or stainless steel such as SUS 430, SUS 430A or SUS 444.
[0049] The heating element 11 of the above structure is formed in the following procedure.
First nickel layers 15 and then aluminium layers 16 are formed on both surfaces of
the metal base 12 by spraying, plating, evaporation, spattering, cladding or any other
suitable method, as described in Example 1. Then, the aluminium layers 16 are oxidized
into the aluminium oxide layers 14 most practically by heating at high temperature
in the atmosphere. At the same time, layers of the nickel-aluminium alloy can be formed,
as described in Example 1. The nickel-aluminium alloy layers can be sufficiently formed
by heating at 500 to 700°C in an environment of an inactive gas, not in the atmosphere,
and then heating at a temperature of 800°C or higher in the atmosphere. The nickel-base
layers 13 of this example are the nickel layers 15 wholly or partly changed to the
nickel-aluminium alloy. The aluminium layers 16 should be completely oxidized because,
during the use of the heating element, any unoxidized aluminium which is conductive
remaining in the heating element is exposed to high temperature and oxidized into
aluminium oxide which is insulating, causing a gradual increase of resistance of the
heating element.
[0050] The heating element of the above structure was manufactured to assess the corrosion
resistance as follows.
[0051] First, the metal base 12 made of iron-chrome (FCHRW1) was clad with nickel foils
and then aluminium foils on both surfaces thereof. The total thickness of the clad
base was 50 µ with 42 µ for the metal base 12, 4 µ for the two nickel layers and 4
µ for the two aluminium layers, and the width thereof was 6 mm. The clad base was
then heated at 900°C in the atmosphere for five hours so as to produce the aluminum
oxide layers 14 on both surfaces. The formation of the nickel-aluminium alloy layers
between the metal base 12 and the aluminium oxide layers 14 was confirmed by an X-ray
diffraction method. Electricity was applied to the thus obtained heating element 11
to raise the surface temperature thereof to 800°C.
[0052] The same corrosion resistance test as that in Example 1 was performed. As a result,
the number of drops applied to the above heating element 11 until it was corroded
and cut apart was 80. The same test was also performed on the following three comparative
samples; a heating element made of iron-chrome and heated at 900°C in the atmosphere
for five hours, a heating element made of SUS 430 and SUS 444 on which the same steps
of cladding of nickel and aluminium and of thermally oxidizing the aluminium as in
Example 2 were performed, and a heating element made of the same material as the above
on which the step of cladding of nickel and aluminium was not performed but the step
of heating was performed. The results were 10, 80, and 10, respectively. These results
indicate that the corrosion resistance at high temperature shown in the heating element
of this invention is irrespective of the type of the base metal.
[0053] Next, an application of the above-described heating element 11 to the microwave oven
6 shown in Figure 4 will be described as follows.
[0054] An iron-chrome strip (FCHRW1) for heating was used as the metal base 12, which was
clad with nickel foils and aluminium foils on both surfaces thereof. Then, the resultant
strip was stamped into a meander shape and heated at 900°C in the atmosphere for five
hours to produce a sheet heating element 7′ having an output of 1.2 KW. When a rated
voltage of 100 V was applied to the heating element 7′, the temperature of the heating
element reached 700°C in about one minute, and further rose to 800°C in three minutes.
An object to be cooked, for example, a fish, was put in the oven chamber 10 for heat
cooking. The fish was broiled with uniform browning under the radiation of 800°C for
fifteen minutes.
[0055] The same corrosion resistance test as in Example 1 was performed on the microwave
oven comprising the sheet heating element 7′ of this example, and the same favorable
results as in Example 1 were obtained.
[0056] From the above results, it was found that the heating element of this example had
high corrosion resistance and was little deteriorated after a long period of usage.
[0057] In the aforementioned examples, the strip-shaped metal base was used. However, the
metal base applicable to the present invention is not limited to the strip shape,
but a linear metal base can also be used to obtain the same high corrosion resistance
when the structure and the method of the present invention is applied thereto.
Example 3
[0058] In this example, a metal base made of iron-chrome, iron-chrome-aluminium or stainless
steel such as SUS 430, SUS 430A or SUS 444 was used. On the top and bottom surfaces
of the metal base were formed aluminium layers in the same manner as shown in Example
1. The aluminium layers were then oxidized into aluminium oxide layers in the same
manner as shown in Example 1. The same test as in Example 1, that is, dropping a 5%
saline solution was performed on the resultant heating element, and the result was
20 drops until the heating element was corroded and cut apart, indicating that the
corrosion resistance of the heating element of this example was about twice as high
as that of a heating element lacking an aluminium oxide layer.
[0059] It was also found that when the aluminium layers were formed by cladding of aluminium
foils on the metal base as in Examples 1 and 2, the resultant heating element showed
stable results in the corrosion resistance test.
[0060] The heating element obtained in this example was formed into a sheet heating element
in the same manner as in Example 1 for the application to a microwave oven, and the
same test as in Example 1 was performed. After 500 cycles, some small corrosion was
observed on the surface of the heating element, but such corrosion did not cause inferiority
in the cooking ability nor any other practical problems.
[0061] In the above examples, the aluminium layer was formed and oxidized in order to obtain
the aluminium oxide layer. It should be appreciated that an aluminium-base alloy can
also be used instead of aluminium to attain the above objective.
1. A heating element comprising a metal base (2, 12) having nickel-aluminium alloy layers
(4) formed on the top and bottom surface thereof.
2. A heating element according to claim 1, wherein the nickel-aluminium alloy layers
(4) are covered with aluminium oxide layers (3, 14).
3. A heating element according to claim 1 or 2, wherein the metal base (2, 12) is nickel
or a nickel-base alloy.
4. A heating element according to claim 3, wherein the nickel content in the nickel-base
alloy is at least 50%.
5. A method for manufacturing a heating element (1, 7, 7′, 11) comprising the steps of:
- forming aluminium layers (5, 16) on the top and bottom surfaces of a nickel or nickel-base
alloy base (2, 12), and
- oxidizing the aluminium layers (5, 16) into aluminium oxide layers (3, 14).
6. A method for manufacturing a heating element (1, 7, 7′, 11) according to claim 5,
wherein the aluminium layers (5, 16) are formed by cladding the nickel or nickel-base
alloy base with aluminium foils.
7. A method for manufacturing a heating element (1, 7, 7′, 11) according to claim 6,
further comprising the step of cutting the nickel or nickel-base alloy base clad with
the aluminium foils to a predetermined shape between the step of forming the aluminium
layers (5, 16) and the step of oxidizing the aluminium layers (5, 16).
8. A method for manufacturing a heating element (1, 7, 7′, 11) according to claim 6,
wherein the aluminium foils are wider than the nickel or nickel-base alloy base.
9. A method for manufacturing a heating element (1, 7, 7′, 11) according to any of claims
5 to 8, wherein the nikkel content in the nickel-base alloy base is at least 50%.
10. A heating element comprising a metal base (2, 12) having nickel layers (15) and aluminium
oxide layers (3, 14) formed in this order on the top and bottom surfaces thereof.
11. A method for manufacturing a heating element (1, 7, 7′, 11) comprising the steps of:
- forming nickel layers (15) on the top and bottom surfaces of a metal base (2, 12),
- forming aluminium layers (5, 16) on the nickel layers (15), and
- oxidizing the aluminium layers (5, 16) into aluminium oxide layers (3, 14).
12. A method for manufacturing a heating element (1, 7, 7′, 11) according to claim 11,
wherein the nickel layers (15) and the aluminium layers (5, 16) are formed by cladding.
13. A method for manufacturing a heating element (1, 7, 7′, 11) according to claim 12,
further comprising the step of cutting the metal base (3, 12) clad with the nickel
layers (15) and the aluminium layers (5, 16) to a predetermined shape between the
step of forming the aluminium layers (5, 16) and the step of oxidizing the aluminium
layers (5, 16).
1. Heizelement mit einer Metallbasis (2, 12) mit Schichten aus einer Nickel-Aluminium-Legierung
(4), die an ihren oberen und unteren Oberflächen ausgebildet sind.
2. Heizelement nach Anspruch 1, dadurch gekennzeichnet, daß die Schichten aus der Nickel-Aluminium-Legierung
(4) mit Aluminiumoxid-Schichten (3, 14) bedeckt sind.
3. Heizelement nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Metallbasis (2,
12) Nickel oder eine Nickelbasis-Legierung ist.
4. Heizelement nach Anspruch 3, dadurch gekennzeichnet, daß der Nickelanteil in der Nickelbasis-Legierung
mindestens 50 % ist.
5. Verfahren zur Herstellung eines Heizelements (1, 7, 7′, 11) mit den folgenden Schritten:
- Bildung von Aluminium-Schichten (5, 16) an den oberen und unteren Oberflächen einer
Nickel- oder Nickelbasis-Legierung-Basis (2, 12), und
- Oxidierung der Aluminiumschichten (5, 16) zu Aluminiumoxidschichten (3, 14).
6. Verfahren zur Herstellung eines Heizelements (1, 7, 7′ 11) nach Anspruch 5, dadurch
gekennzeichnet, daß die Aluminiumschichten (5, 16) durch Umhüllung der Nickel- oder
Nickelbasis-Legierung-Basis mit Aluminiumfolien gebildet werden.
7. Verfahren zur Herstellung eines Heizelements (1, 7, 7′ 11) nach Anspruch 6, mit dem
weiteren Schritt des Zuschneidens der mit den Aluminiumfolien umhüllten Nickel- oder
Nickelbasis-Legierung-Basis auf eine vorgegebene Form, zwischen dem Schritt der Bildung
der Aluminiumschichten (5, 16) und dem Schritt der Oxidierung der Aluminiumschichten
(5, 16).
8. Verfahren zur Herstellung eines Heizelements (1, 7, 7′ 11) nach Anspruch 6, dadurch
gekennzeichnet, daß die Aluminiumfolien breiter als die Nickel- oder Nickelbasis-Legierung-Basis
sind.
9. Verfahren zur Herstellung eines Heizelements (1, 7, 7′ 11) nach einem der Ansprüche
5 bis 8, dadurch gekennzeichnet, daß der Nickelanteil in der Nickelbasis-Legierung-Basis
mindestens 50 % ist.
10. Heizelement mit einer Metallbasis (2, 12) mit Nickelschichten (15) und Aluminiumoxidschichten
(3, 14), die in dieser Reihenfolge auf ihren oberen und unteren Oberflächen ausgebildet
sind.
11. Verfahren zur Herstellung eines Heizelements (1, 7, 7′ 11) mit den folgenden Schritten:
- Bildung von Nickelschichten (15) auf den oberen und unteren Oberflächen einer Metallbasis
(2, 12),
- Bildung von Aluminiumschichten (5, 16) auf den Nickelschichten (15), und
- Oxidierung der Aluminiumschichten (5, 16) zu Aluminiumoxidschichten (3, 14).
12. Verfahren zur Herstellung eines Heizelements (1, 7, 7′ 11) nach Anspruch 11, dadurch
gekennzeichnet, daß die Nickelschichten (15) und die Aluminiumschichten (5, 16) durch
Umhüllung gebildet werden.
13. Verfahren zur Herstellung eines Heizelements (1, 7, 7′ 11) nach Anspruch 12 mit dem
weiteren Schritt des Zuschneidens der mit den Nickelschichten (15) und den Aluminiumschichten
(5, 16) umhüllten Metallbasis (3, 12) auf eine vorgegebene Form zwischen dem Schritt
der Bildung der Aluminiumschichten (5, 16) und dem Schritt der Oxidierung der Aluminiumschichten
(5, 16).
1. Elément de chauffage comprenant une base métallique (2, 12) présentant des couches
d'alliage nickel-aluminium (4) formées sur ses surfaces supérieure et inférieure.
2. Elément de chauffage suivant la revendication 1, dans lequel les couches d'alliage
nickel-aluminium (4) sont recouvertes de couches d'oxyde d'aluminium (3, 14).
3. Elément de chauffage suivant la revendication 1 ou 2, dans lequel la base métallique
(2, 12) est du nickel ou un alliage à base de nickel.
4. Elément de chauffage suivant la revendication 3, dans lequel la teneur en nickel de
l'alliage à base de nickel est d'au moins 50%.
5. Procédé pour la fabrication d'un élément de chauffage (1, 7, 7′, 11) comprenant les
étapes consistant à:
- former des couches d'aluminium (5, 16) sur les surfaces supérieure et inférieure
d'une base en nickel ou en alliage à base de nickel (2, 12), et
- oxyder les couches d'aluminium (5, 16) en couches d'oxyde d'aluminium (3, 14).
6. Procédé pour la fabrication d'un élément de chauffage (1, 7, 7′, 11) suivant la revendication
5, dans lequel les couches d'aluminium (5, 16) sont formées par placage de la base
en nickel ou en alliage à base de nickel de films d'aluminium.
7. Procédé pour la fabrication d'un élément de chauffage (1, 7, 7′, 11) suivant la revendication
6, comprenant, en outre, l'étape consistant à découper la base en nickel ou en alliage
à base de nickel plaquée de films d'aluminium en une forme prédéterminée entre l'étape
de formation des couches d'aluminium (5, 16) et l'étape d'oxydation des couches d'aluminium
(5, 16).
8. Procédé pour la fabrication d'un élément de chauffage (1, 7, 7′, 11) suivant la revendication
6, dans lequel les films d'aluminium sont plus larges que la base en nickel ou en
alliage à base de nickel.
9. Procédé pour la fabrication d'un élément de chauffage (1, 7, 7′, 11) suivant l'une
quelconque des revendications 5 à 8, dans lequel la teneur en nickel de la base en
alliage à base de nickel est d'au moins 50%.
10. Elément de chauffage comprenant une base métallique (2, 12) présentant des couches
de nickel (15) et des couches d'oxyde d'aluminium (3, 14), formées dans cet ordre,
sur ses surfaces supérieure et inférieure.
11. Procédé pour la fabrication d'un élément de chauffage (1, 7, 7′, 11) comprenant les
étapes consistant à:
- former des couches de nickel (15) sur les surfaces supérieure et inférieure d'une
base métallique (2, 12),
- former des couches d'aluminium (5, 16) sur les couches de nickel (15), et
- oxyder les couches d'aluminium (5, 16) en couches d'oxyde d'aluminium (3, 14).
12. Procédé pour la fabrication d'un élément de chauffage (1, 7, 7′, 11) suivant la revendication
11, dans lequel les couches de nickel (15) et les couches d'aluminium (5, 16) sont
formées par placage.
13. Procédé pour la fabrication d'un élément de chauffage (1, 7, 7′, 11) suivant la revendication
12, comprenant, en outre, l'étape consistant à découper la base métallique (3, 12)
plaquée de films de nickel (15) et de films d'aluminium (5, 16) en une forme prédéterminée
entre l'étape de formation des couches d'aluminium (5, 16) et l'étape d'oxydation
des couches d'aluminium (5, 16).