KR940005461B1 - Heating element and manufacturing method thereof - Google Patents

Abstract

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Description

Heating element and its manufacturing method

1 is a cross-sectional view of a heating element of an embodiment of the present invention.

2 is a cross-sectional view showing the state of the preceding process for obtaining a copper heating element.

3 is a characteristic diagram showing the relationship between the nickel content and the corrosion resistance of the copper heating element.

4 is a cross-sectional view of an essential part showing an example when the copper heating element is used in a cooker.

5 is a planar heating element according to an embodiment of the present invention, obtained in a zigzag shape.

6 is a cross-sectional view of a heating element in one embodiment of the present invention.

7 is a cross-sectional view showing the state of the preceding step of the manufacturing method of the copper heating element.

* Explanation of symbols for the main parts of the drawings

(1): heating element (2): nickel or nickel-containing alloy

(3): aluminum oxide layer (4): nickel aluminum alloy

(5): aluminum layer (6): high frequency cooker

(7): Planar heating element (8): High frequency shield

(9): holding material (10): cooking chamber

(11): heating element (12): metal heating element

(13): nickel-containing body (14): aluminum oxide layer

(15): nickel layer (16): aluminum layer

(A): width direction of strip-shaped heating element

The present invention relates to a heating element to be used in the vicinity of 800 ℃ where the maximum amount of the radiation amount in the water absorbing means, such as cookers and heaters, and a method of manufacturing the same.

The heating elements used in conventional cookers and heaters are mainly quartz tube heaters. In addition, as a cooker, the so-called mic heater which wound the sheet heater and the heater wire to the mic was used.

However, in the prior art, the following problems exist.

In other words, in the case of a quartz tube heater, a heater wire wound in a toroidal shape is inserted into a quartz tube, or when a salt or the like is scattered during cooking and attached to the quartz tube, the quartz tube becomes opaque, which is necessary for cooking. It is difficult to obtain far infrared rays, or the quartz tube is easily broken. Therefore, about 700 degreeC was a limit as heat source temperature. In addition, it was difficult to develop a planar heater in a planar manner due to the structure of the quartz tube heater. In the case of the sheath heater, the heater wire is coated with stainless steel of heat resistance corrosion resistance, and when used for cooking, it takes time for the first operation of the temperature in order to use secondary radiation from the stainless steel. If the radiation temperature is 800 ° C, the temperature of the heater wire itself becomes higher and the service life becomes shorter. As in the case of a quartz tube heater, it was difficult to obtain a planar heating element having a uniform structure. In addition, it is easy to make a miter heater into a planar smoke body, but since it is mounted on the outside of the wall of a cooker via an insulator, heat transfer is bad, and the first operation | movement of the temperature of the wall surface of a cooker, ie, a radiation surface, is slow, and 800 degreeC It was difficult to bring about high temperature.

In order to solve the above problems, the first operating time of the temperature is fast, 800 ° C. suitable for cooking or heating is easily obtained, and as a heating element that is easy to develop on a plane, it is possible to use iron-chromium-aluminum, nickel-chromium or iron. -It is conceivable to use a nickel-chromium-based metal heating element as it is. Thereby, the said subject can be solved. However, the metal heating element has high heat resistance and is not damaged even when exposed to high temperature air. However, when used in a cooker, heat generated from food or a heated object adheres to the heating element. In this state, for example, when used at a high temperature such as 800 ° C., a new problem arises that the metal is easily corroded and broken. On the contrary, since such corrosion occurs, the heater structure of the said base material was considered.

An object of the present invention is to provide a heating element that is excellent in high temperature corrosion resistance and has a high temperature radiation of about 800 ° C. when the first operation of the temperature is fast, and which is easy to develop into a planar heating element.

In order to achieve the above object, the present invention uses a heating element comprising a metal heating element and an aluminum oxide layer obtained by oxidizing an aluminum layer on the metal heating element. In the case where particularly strong corrosion resistance is required, a metal body coated with nickel or a nickel-containing metal as a base metal, and after the coating is oxidized to form an aluminum oxide layer on the surface, is used as a heating element or nickel on the heating element. Alternatively, a metal body having a nickel-containing metal coated thereon and an aluminum layer formed thereon by coating and then oxidizing the aluminum layer to form an aluminum oxide layer on its surface may be used as a heating element.

A feature of the present invention is to form aluminum oxide excellent in corrosion resistance on the surface of the heating element, and to form a nickel aluminum alloy layer especially when stronger corrosion resistance is required. Hereinafter, the structure of a heating element and the method of obtaining an aluminum oxide layer and a nickel aluminum alloy layer are demonstrated.

Example 1

In FIG. 1, the heating element 1 is produced between the nickel or nickel-containing alloy 2 and the aluminum oxide layer 3 and the nickel or nickel-containing alloy 2 and the aluminum oxide layer 3. It is made of one nickel aluminum alloy (4).

This heating element 1 is obtained as described later. That is, the aluminum layer 5 is formed on the surface of the nickel or nickel containing alloy 1. As a means for forming this aluminum layer 5, there exist various means, such as thermal spraying, plating, vapor deposition, and spatter coating. Among these means, the thermal spraying and coating can be easily obtained with a thick film layer. In particular, the means by coating is a method of bringing the aluminum foil into close contact with the heating element by rolling, so that the aluminum layer 5 without pinholes can be formed. There are various means for oxidizing the aluminum layer 5, but a means for heating to high temperature in the air is most practical. In particular, in the case of oxidizing by heating, the nickel aluminum alloy 4 excellent in corrosion resistance can be easily obtained between the nickel or nickel-containing alloy 2 and the aluminum oxide layer 3 as described above, so that the corrosion resistance is improved. .

Corrosion resistance was performed as described later as an evaluation method. Nickel-containing alloys having different nickel and nickel content (chromium content 21 ± 2%) were used as the base metal, and the aluminum foil 5 was coated on the surface thereof, and then cut into the required dimensions. Then, it heated at 900 degreeC in air | atmosphere for 5 hours, and obtained the aluminum oxide layer (3) on the surface. The heating body 1 having a width of 6 mm and a thickness of 50 µm obtained by the above method was energized, and the surface temperature was 800 ° C. In this state, 5% saline solution was dripped every 0.5 cc and every 2 minutes, and the corrosion resistance was evaluated by the number of times the saline solution was dripped until the heating element 1 broke. The result of examination with ten samples is shown in FIG. In FIG. 3, the arrow time indicates the upper limit and the lower limit of the measurement, and the display indicates the average value. In the figure, the X marks indicate the case where the base metal was tested without coating. If the nickel content exceeds 50%, the corrosion resistance rapidly increases. This is because the corrosion resistant nickel aluminum alloy 4 grows between the base metal and the aluminum oxide layer together with the aluminum oxide layer 3. This analysis of this heating element by X-ray diffraction method confirmed that NiAl and Ni ₃ Al were detected.

The heating element in which this aluminum layer was formed by coating aluminum foil did not form the aluminum layer 5 on the side surface (that is, the thick direction) before heating, but after the heat treatment, the nickel aluminum alloy layer 4 layer was also formed on the side surface. Was present. This is considered to be because the burrs of aluminum generated at this time moved to the side and diffused, since the base metal was coated with the aluminum foil as described above and then cut into the dimensions required for the heating element. In addition, the fracture by the corrosion resistance evaluation test is mostly caused by the hole corrosion of the width | variety part, and the cut surface (side surface) did not say that it was inferior in particular to corrosion resistance.

In the case where the cutting step is not included, the nickel aluminum alloy layer can be easily obtained on the same side as described above by coating the aluminum foil slightly wider than the width of the base metal.

As described above, according to the means of the present invention, the corrosion resistance of the heating element is remarkably improved. Hereinafter, the case where this heating element 1 is used for a cooker is demonstrated concretely. 4 shows a microwave oven 6. This high frequency cooker (6) has a configuration in which a planar heating element (7) made of the heating element (1) of the present invention is provided on a holding member (9) provided on a high frequency shielding plate (control floating according to the present invention). It is omitted because there is no). The high frequency shielding plate 8 prevents the high frequency from being absorbed by the planar heating element 7 by cutting off the high frequency at the time of high frequency heating, and radiates the heating element directly to the workpiece when the heater is heated. The steel plate has a configuration in which a plurality of holes having a diameter of about 3 mm is formed, and the area of the hole is about 60% of the total area. As the heat generating element 1, a heat transfer nickel chromium strip (NCHRW 1) shaped body is used, and an aluminum foil is coated thereon to obtain a zigzag shape. It was set as. This planar heating element 7 has an output of 1.2 KW. When the static voltage 100V was applied, it reached 700 degreeC in about 1 minute, and high temperature of 800 degreeC was obtained after 3 minutes. When the fish (heated material) was put in the cooking chamber 10 and baked, the fish could be baked to have a pressed place in about 15 minutes by the 800 ° C. high temperature radiation. The conventional planar heating element, for example, a micro heater, requires about 25 minutes to burn completely, and like the sheath heater and the quartz tube heater, it is impossible to make a pressed seat.

As described above, according to the planar heating element 7 of the present application, the burned and pressed seat can be made to have high efficiency. This is because the heating element not only develops on the surface but also has a strong radiant strength for the heated object from the heating element. That is, radiation is radiated in a direction perpendicular to the plane of the heating element. Therefore, as shown in FIG. 5, the band-shaped heating element is theoretically radiated only in a direction perpendicular to the width Acm of the heating element (the thickness is small compared to the width, so the radiation in the thickness direction is ignored). Since there are irregularities on the surface of the heating element, it is radiated with some spread. Because of that, you can get all the seats you have pressed down. Either way, in the case of the band-shaped heating element, radiation in the width direction of the heating element is strong, and the heating element is efficiently heated while placing the heated object in this direction.

On the other hand, in the case of the sheath heater or the quartz tube heater, since the cross section of the heating element and the outer shell is circular, it is uniformly radiated with respect to the entire direction of the space. Therefore, if the output is the same as that of the strip-shaped heating element and the radiant temperature is the same, the amount of radiation to the surface of the heated object in the case of the sheath heater or the quartz tube heater is smaller than that in the case of the strip-shaped heating element. In other words, the heating efficiency is low.

Moreover, in the structure of the said high frequency cooker 6, the salt scattering from a food or a to-be-heated thing adheres to the surface of the heat generating body 1 during cooking. However, since the heat generating element 1 of the present invention is excellent in corrosion resistance, there is no problem in practical use. In other words, the high-frequency heating with 5% saline to be heated and the heater heating with fish to be heated were alternately performed. The heating element 1 of the present invention was hardly damaged even after 500 cycles. . On the other hand, when the nickel chromium band for heat transfer not subjected to the treatment of the present invention was taken out and used as a planar heating element, it was damaged in 60 cycles due to corrosion.

As described above, it can be seen that the heating element of the present invention is a heating element that is excellent in corrosion resistance and has little change with time.

Example 2

EMBODIMENT OF THE INVENTION Hereinafter, one Embodiment of this invention is described based on an accompanying drawing. In FIG. 6, the heat generating element 11 is comprised by the nickel containing layer 13 and the aluminum oxide layer 14 formed in the surface of the metal heat generating body 12. As shown in FIG. The metal heating element 12 is made of iron-chromium, iron-chromium-aluminum, and stainless steel sheets such as SUS 430, SUS 430A, and SUS 444. The nickel layer 15 is formed on the surface of the metal heating element 12, and the aluminum layer 16 is formed on the upper surface thereof. As a method of forming these nickel layer 15 and the aluminum layer 18, there exist various methods, such as thermal spraying, plating, vapor deposition, spatter, coating. Among these methods, thermal spraying and coating are easy to obtain a thick film layer. In particular, the method by coating can form a layer free of pinholes. Thereafter, as the method of oxidizing the aluminum layer 16 to form the aluminum oxide layer 14 or the method of oxidizing the aluminum layer 16, there are various methods such as anodizing and hot air heating. Practically, high temperature heating in the air is recommended. In particular, when oxidizing by heating, the nickel aluminum alloy layer is formed as described above, and the corrosion resistance is further improved. In order to sufficiently grow the nickel aluminum alloy layer, a method of heating at 500 to 700 ° C. in an inert gas layer other than the high temperature heating method in the air to sufficiently generate the alloy layer, and then heating to a temperature of 800 ° C. or higher in the air You can use The nickel-containing layer 13 in the present invention is a layer in which all or part of the nickel layer is made of nickel aluminum alloy. The aluminum layer 6 may be completely oxidized. If the aluminum component remains, it is exposed to high temperatures during use as a heating element. Therefore, the conductivity of the aluminum component is oxidized and the insulation changes to aluminum oxide, so that the resistance of the heating element gradually increases during use.

It evaluated by the method mentioned later as an evaluation method of corrosion resistance. The iron-chromium (FCHRW 1) metal heating element 12 was coated with nickel foil and aluminum foil as a base metal. The completed dimensions of the heating element after coating were 50 µm in total with the thickness of the metal heating element 12 having a thickness of 42 µ, 4 µ on both sides of the nickel layer, and 4 µ on both sides of the aluminum layer 16, and the width was 6 mm in width. The heating element after this coating was heated at 900 degreeC in air | atmosphere for 5 hours, and the aluminum oxide layer 14 was obtained on the surface. It was confirmed by X-ray diffraction that a nickel aluminum alloy layer was interposed between the metal heating element 2 and the aluminum oxide layer 14 by this heating. The heating element 11 (1) obtained by the above method was energized, and the surface temperature was 800 degreeC. In the same manner as in Example 1, 5% saline was added dropwise at 0.5cc for 2 minutes in this state, and the corrosion resistance was evaluated by dropping the number of drops until the heating element broke. As a result, the number of droppings until break was about 80 times. On the other hand, when the iron-chromium-metal heating element 2 was heated as it was in the same manner as the above dropwise test on the heating element 1 heated in 900 占 폚 for 5 hours, the number of times until fracture was about 10 times. In addition, the number of times of dropping until the rupture after heat oxidation treatment was formed about 80 times by forming a layer of nickel and aluminum by coating the SUS 430 and SUS 444 as described above. When the same test which does not perform the same heat treatment was performed, the number of times of dropping until failure was about 10 times similarly to the above. In this way, the high temperature corrosion resistance of the present invention can be considered to be attributable to products such as intermetallic compounds by treatment of the nickel layer and the aluminum layer irrespective of the base metal heating element.

Hereinafter, the case where the heat generating element 11 is used for the high frequency cooker 6 shown in FIG. 4 is demonstrated concretely. In other words, using a heat transfer iron-chromium (FCHRW 1) shaped body as the heating element 1, it is coated with nickel foil and aluminum foil to obtain a zigzag shape, and is heated for 5 hours at 900 ° C in the air. It was set as the planar heating element 7. This planar heating element 7 has an output of 1.2 KW. When a rated voltage of 100V is applied, 700 ° C is reached in about 1 minute, and a high temperature of 800 ° C can be obtained after 3 minutes. When the fish (heated material) was put in the cooking chamber 10 and baked, the fish could be baked to have a pressed place for about 15 minutes by the high-temperature radiation at 800 ° C. Moreover, in the structure of the said high frequency cooker 6, the salt scattering from a foodstuff or a to-be-heated thing adheres to the surface of the heat generating body 11 during cooking.

However, since the heat generating element 11 of the present invention is excellent in corrosion resistance, there is no problem in practical use. Moreover, the same corrosion resistance test as Example 1 was done and the favorable result was obtained similarly.

As described above, the band-forming metal heating element is described. However, the present invention is not limited to the band-shaped metal heating element, and a heating element excellent in corrosion resistance can be obtained similarly even when the structure and method of the present invention are used for the linear metal heating element.

As described above, it can be seen that the heating element of the present invention is a heating element having excellent corrosion resistance and less change with time.

Example 3

As the metal heating element, stainless steel sheets such as iron-chromium, iron-chromium-aluminum, SUS 430, SUS 430A, or SUS 444 are used. An aluminum layer is formed on the surface of this metal heating element. As the method for forming this aluminum layer, the method described in Example 1 may be used. The aluminum layer thus obtained was heated in the same manner as in Example 1 to obtain an aluminum oxide film. The saline dropping test as described above was about 20 times until breaking, and had a corrosion resistance twice that of the aluminum oxide layer.

As the method for forming the aluminum layer for obtaining the aluminum oxide layer, the aluminum foil was coated on the metal heating element as in the case of Examples 1 and 2, and the nonuniformity was most stable and stable by the corrosion resistance evaluation test.

In the same manner as in Example 1, the heating element obtained in Example 1 was used as a planar heating element and a high-frequency cooker, and the same test as in Example 1 was carried out. After 500 cycles, slight corrosion was observed on the surface of the heating element. However, there was no difference in cooking performance and it did not matter practically.

In addition, although the method of forming an aluminum layer and oxidizing it in order to obtain an aluminum oxide layer in Example 1 thru | or 3 was demonstrated, of course, if the said objective is achieved, you may use an aluminum alloy instead of aluminum.

As described above, according to the heat generating element of the present invention, the following effects can be obtained. That is, since the heating element of the present invention is very excellent in high temperature corrosion resistance, an outer skin for shielding is provided to the cooking by-products at the time of cooking, such as conventional sheath heaters, quartz tube heaters, and miker heaters. We can just use without doing. Therefore, the planar heating element can be easily produced by, for example, pitting. In addition, since there is no outer skin having an extra thickness other than the thin oxide film layer and the nickel aluminum alloy layer, the specific heat is small. Therefore, the first operation of the temperature is quick, and since the surface temperature of the heating element itself becomes the radiation temperature, it is possible to easily perform high temperature radiation heating.

As described above, when the heating element of the present invention is used, it is possible to obtain a heater that can easily be a planar heating element and at the same time obtain a high temperature radiation easily.

Claims (15)

A heating element comprising a metal heating element and at least a nickel aluminum alloy layer formed on the surface thereof. The heating element according to claim 1, wherein the surface of the nickel aluminum alloy layer has an aluminum oxide layer. The heating element according to claim 1 or 2, wherein the metal heating element is nickel or a nickel-containing alloy. The heating element according to claim 3, wherein a nickel-containing alloy having a nickel content of 50% or more is used. An aluminum layer is formed on nickel or a nickel-containing alloy, and the aluminum layer is oxidized to form an aluminum oxide layer. The method of manufacturing a heating element according to claim 5, wherein the aluminum layer is formed by coating aluminum foil. The method of manufacturing a heating element according to claim 5, wherein aluminum is coated on nickel or a nickel-containing alloy, thereafter cut into a predetermined shape, and the aluminum foil is oxidized to form an aluminum oxide layer. 8. A method for producing a heating element according to claim 7, wherein a nickel or a nickel-containing alloy is used as a base material to cover a wider aluminum foil than the base material, and then the aluminum foil is oxidized to form an aluminum oxide layer. The method for producing a heating element according to claim 5, wherein a nickel-containing alloy having a nickel content of 50% or less is used. A heating element, wherein a nickel layer is formed on the surface of the metal heating element, and an aluminum oxide layer is formed on the surface of the nickel layer. The method of manufacturing a heating element according to claim 10, wherein after forming a nickel layer on the surface of the metal heating element and forming an aluminum layer thereon, the aluminum layer is oxidized by heating. The method for producing a heating element according to claim 11, wherein a nickel layer or an aluminum layer is formed by coating. The method of manufacturing a heating element according to claim 12, wherein after coating the aluminum layer, the aluminum layer is cut into a predetermined shape and the aluminum layer is oxidized. An aluminum or aluminum alloy layer is formed on a surface of a metal heating element, and the aluminum or aluminum alloy layer is oxidized to an aluminum oxide layer. The heating element according to claim 14, wherein the aluminum or aluminum alloy layer is formed by coating.