JPH0534797B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a far-infrared heater that is widely applied to heating, drying, cooking, etc. Conventional technology Conventional far-infrared heaters include: infrared lamps, ceramics with a heating element embedded and fired, sheathed heaters with a far-infrared radiation layer formed on the surface, ceramic tubes with heating wires and electrical insulating powder inside. However, from the viewpoint of radiation characteristics, mechanical strength, lifespan, etc., those with a far-infrared radiation layer formed on the surface of the sheathed heater are often used. In this type of far-infrared heater, the far-infrared radiation layer is mainly formed by a thermal spraying method. In addition, far-infrared emitting materials include SrO ₂ ,
Mixtures of several types of transition metal oxides such as ZrO ₂ ·SiO ₂ , TiO ₂ , Al ₂ O ₃ and composite oxides are mainly used. However, the method of forming a far-infrared emitting layer by thermal spraying involves high manufacturing costs such as running costs. A method of manufacturing far-infrared heaters by enameling has been proposed. For example, there is a method of enameling a mixture of ZrO ₂ /SiO ₂ and glass frit to form a far-infrared radiation layer (Japanese Patent Application Laid-Open No. 1983-1983), and a method of enameling a mixture of ZrO 2 /SiO 2 and glass frit to form a far-infrared emitting layer (Japanese Patent Application Laid-open No. 1983-1908), and a method of enameling a mixture whose main components are ceramic and glass. A method has been proposed in which a radiation layer is formed by enameling the shape (Japanese Patent Publication No. 58-36821). Problems to be Solved by the Invention However, although the far-infrared heater manufactured by the above method has relatively excellent emissivity in the far-infrared region, it cannot be used at high temperatures of 600°C or higher, or When exposed to water in a temperature range, the far-infrared emitting layer easily cracks or peels off.
In reality, there were problems such as the overall white or black color and poor aesthetic sense. Therefore, the present invention solves the above-mentioned two problems and provides a far-infrared emitting layer that does not crack or peel even when used at high temperatures of 600°C or higher, or even when water is heated in such a temperature range. Furthermore, we aim to provide a far-infrared heater that is blue and beautiful. Means for Solving the Problems In order to solve the above problems, the present invention provides heat-resistant enamel containing 5 to 30% by weight of CoO on the surface of a metal pipe, the main components of which are BaO and _SiO2 . A far-infrared emitting layer made of a mixture of the following ingredients is provided. Function In the present invention, as a far-infrared radiation layer,
It uses heat-resistant enamel whose main ingredients are BaO and SiO ₂ , and this heat-resistant enamel has excellent thermal shock resistance even when used at high temperatures of 600℃ or higher.
Therefore, even if exposed to water, cracks or peeling will not occur easily. In addition, CoC, which is contained 5 to 30% by weight in heat-resistant enamel whose main components are BaO and SiO ₂ , has a high far-infrared emissivity and has the effect of coloring the far-infrared emitting layer a beautiful blue color. There is. For these reasons, it is possible to obtain a far-infrared heater that exhibits a beautiful blue color and can be used at high temperatures of 600°C or higher. Embodiment Hereinafter, an embodiment of the present invention will be described based on the accompanying drawings. NCF800 was used as the metal pipe 1. on the other hand,
A heating wire 3 made of a coiled nichrome wire (wire diameter 0.55 mm) with terminal rods 2 at both ends is prepared, inserted into the center of the metal pipe 1, and filled with electrical insulating powder 4 made of fused magnesia powder. , rolled and reduced in diameter. After this, the surface of the metal pipe 1 was heated to 1100°C in order to form an oxide scale mainly composed of Cr ₂ O ₃ .
It was heat treated for 10 minutes at a temperature of . Note that the atmosphere at this time was a reducing gas containing CO and H ₂ as main components. Subsequently, CoO was added to a glass frit mainly composed of BaO and SiO ₂ shown in Table 1, and viscosity, sodium nitrite, and water were added to each to prepare a slip.

[Table] As shown in Table 2, the amount of CoO added at this time was adjusted to the respective amount contained in the far-infrared emitting layer after firing. The amount of CoO contained in the far-infrared radiation layer was varied in the range of 0% to 50% by weight, as shown in Table 2. Each of the slips prepared in the above manner is applied by a spray method to the metal pipe 1 on which oxide scale has been formed in advance, and baked at 1050°C for 5 minutes to form a long sleeve made of heat-resistant enamel, as shown in Figure 1. An infrared emitting layer 5 was formed. Finally, attach both ends of the metal pipe 1 to the low melting point glass 6
and sealed with heat-resistant resin 7, diameter 11 mm, length
Each far-infrared heater of 500 mm shown in FIG. 2 was completed and designated as sample numbers 1 to 8. Note that the heater of sample number 1 was not particularly subjected to heat-resistant enameling treatment and corresponded to a conventional sheathed heater. Metal pipe 1 of each far infrared heater above
The voltage was adjusted so that the surface temperature was 800° C., and after the surface temperature was saturated, it was placed in water, and the degree of peeling of the far-infrared emitting layer 5 was evaluated. The results are shown in Table 2. In Table 2, ◯ indicates that no peeling occurred, and × indicates that peeling occurred. Table 2 also shows the color of each far-infrared heater when it is not energized. Furthermore, 2.5 μm
The average emissivity in the wavelength range of ~30 μm was also measured and is also shown in Table 2.

[Table] As is clear from Table 2, when CoO is added to the far-infrared emitting layer 7, which is mainly composed of BaO and SiO ₂ , the color changes from black to blue, and when added to water from 800℃, It also becomes stronger against thermal shock, and has the effect of suppressing peeling of the far-infrared emitting layer 7. Furthermore, regarding the average emissivity from 2.5μm to 30μm, since CoO with excellent emissivity is added,
It increases as the CoO content increases. These trends show that the CoO content is between 5% and 30% by weight.
% by weight, that is, sample numbers 4, 5, 6, and 7 of the far infrared heater of the present invention were ideal. As described above, the far infrared heaters of sample numbers 1, 2, and 3, in which the content of CoO is 5% by weight or less, are black in color and have poor thermal shock resistance and average emissivity. On the other hand, in the far-infrared heater of sample number 8 in which the CoO content is 30% by weight or more, the temperature is insufficient under the firing condition of 1050°C, and it is impossible to form a uniform far-infrared radiation layer 5. Ta. In addition, in the embodiment of the present invention, the metal pipe 1
Although NCF800 was used as the material, the material is not particularly limited to this, and other heat-resistant steels such as SUS321 may be used. In addition, although the glass frits shown in Table 1 are used as glass frits whose main components are BaO and SiO ₂ , the glass frits shown in Table ₁ are not limited to these. Good to have. Effects of the Invention As is clear from the above description, according to the present invention, heat-resistant enamel containing BaO and SiO ₂ as main components and CoO in a weight ratio of 5 to 30 are applied to the surface of a metal pipe.
Since the heat-resistant enamel is equipped with a far-infrared emitting layer consisting of a mixture containing % CoO
This far-infrared heater has a beautiful blue color and does not crack or peel off the far-infrared radiation layer even when used at high temperatures of 600℃ or higher, or even when exposed to water in such temperature ranges. This is something that can be provided.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of essential parts of a far-infrared heater showing an embodiment of the present invention, and FIG. 2 is a sectional view of the same heater. 1...Metal pipe, 5...Far-infrared radiation layer.

Claims (1)

[Claims] 1. A far-infrared ray that is characterized by providing a far-infrared radiation layer on the surface of a metal pipe, which is made of a mixture of heat-resistant enamel containing BaO and SiO ₂ as main components and containing CoO at a weight ratio of 5 to 30%. heater.