JPS5837675B2 - Menhatsnetsutaino Seizouhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a surface heating element, particularly a surface heating element in which a metal heating element is integrated into ceramics.

Most conventional surface heating elements have a structure in which the heater is wrapped around an insulating material such as mica.

However, at the initial stage of energization, heat was absorbed by the base material, resulting in a slow rise in temperature.

Furthermore, although heating elements using carbon, tin oxide, etc. as heat sources have the advantage of being able to design their heat capacity values relatively arbitrarily, it is difficult to change the heat capacity distribution.
There was a problem in that the temperature of the central part of the heating element was higher than the temperature of other parts.

Moreover, many of them had poor manufacturing workability and productivity.

In addition to such a surface heating element, there is also a surface heating element having a structure in which a heater is embedded in the glass.

These have the problem that the usable temperature is about 300° C. or lower.

and. Products using these glass components had poor heat-resistant spalling characteristics, rapid deterioration of mechanical strength with repeated use, and poor life characteristics compared to other heating elements.

In addition, in a heating element using recrystallized heat-resistant glass, it is difficult to embed inexpensive nichrome wire or iron chloride wire, and the crystallized glass itself is expensive, making it difficult to obtain an inexpensive heating element. could not.

However, according to the method of the present invention, it is possible to obtain a surface heating element that does not have the drawbacks mentioned in -L, has excellent heat resistance, protects the heating element, and has good life characteristics.

Specifically, mixed compositions for each starting material are calcined to obtain a coefficient of thermal expansion of 50 x 10-7/°C (20 to 500
℃) A ceramic or glassy sintered body having the following characteristics is obtained, and the powder obtained by pulverizing this sintered body is used. When molding it, a metal heating element is embedded, and the molded body with the metal heating element embedded is sintered at high temperature to integrate the ceramic and the metal heating element,
This method of manufacturing a surface heating element is characterized in that a graphite layer is formed on a part or the entire surface of the element, and a metal layer is further formed thereon by a spraying method.

In general, the bonding properties between ceramics and metals are poor, and there are many problems with thermal shock resistance, heat resistance, workability, etc., especially when electricity is applied to metals to generate heat and use it as a heat source. .

However, in the present invention, by using a mixture having the above-mentioned characteristics as a starting material, the bondability between the ceramic and the metal heating element is significantly improved, and the surface heating element is prevented from cracking or bending. It has the feature that it eliminates the defects caused by metal wires and can integrate ceramics and metal wires.

Here, the reason why the thermal expansion coefficient value of the ceramic or glassy sintered body obtained by calcining the mixed composition as the starting material is limited as described above is that the thermal expansion coefficient value is 50. If it is thicker than X 1 0-7/°C, it will be difficult to integrate it with a metal heating element due to sintering, and furthermore, there will be drawbacks such as heat shock occurring during energization and destruction of the element.

Furthermore, the reason why a metal layer was formed on the surface of the surface heating element by a spraying method via a graphite layer was to improve the thermal conductivity of the element.

Further, by providing a metal layer, the strength of the element can be increased and stable characteristics against high temperatures can be obtained.

Note that when forming a metal layer, it is important to form a graphite layer on the surface of the element in advance because when forming the metal layer using the spraying method, some of the metal may penetrate into the graphite layer and form on the surface of the element. This is because the mechanical strength is improved compared to the case where the metal layer is directly formed by a spraying method.

Furthermore, this graphite component forms a film that adheres completely along the unevenness of the ceramic surface, so there is no air space between them compared to when a metal plate such as an aluminum plate is brought into contact with the ceramic surface. Thermal conductivity improves accordingly.

Note that if the thickness of the graphite layer is made thicker than necessary, the thermal conductivity will deteriorate, so it is preferable to make the thickness 2 m/m or less.

Here, the melting method is a method in which metal wire or metal powder is once melted using gas, electricity, etc., and then firmly attached to the surface of the element body.

This method allows the thickness of the metal layer to be freely controlled.

Next, the method of the present invention will be specifically explained based on an example.

In the sample preparation process, natural shirasu raw material powder CaCO3 and Si02. Li2cO3,A
Using 1203, first equimolar amounts of CaCO3 and S t 0
2 and further 1:1:4 Ll2CO3 and Al203
and Sl02 were prepared and pre-calcined by treating at a temperature of 1200 to 1350°C for 2 hours.

The resulting material was examined by X-ray diffraction and was found to be a single solid solution of CaSi.
It was confirmed that it was 03 and β sposhmen.

Then, the ingredients were mixed in such a manner that the raw material powder of whitebait was 20 weight φ, the CaSi03 powder was 30 weight φ, and the β-sposhmen was 50 weight φ, and wet-mixed using a rubber-lined pot mill.

Thereafter, water was evaporated, calcined for 1 hour at a temperature of iooo°C, and further ground to obtain a fine powder.

Next, 15 weights of polyvinyl alcohol solution having a concentration of 6φ was added, the particles were sized through a 32-mesh sieve, and molded using a conventional method.

At that time, as shown in the figure, the diameter is 0. 3 5 mm length 8
A 0 cm nichrome wire, iron chrome wire, or Kanthal wire was processed into a spiral shape and embedded within a size range of 120×80×5M1iL.

This molded body was heated in an electric furnace having a SiC heating element at a heating rate of 50 to 1500C/hour and a temperature of 1080 to 1260C.
The main firing was carried out between ℃.

In the obtained surface heating element, the coefficient of thermal expansion of the glass ceramic material was 15×10-7/°C.

In addition, a mixture of graphite powder and tar is applied to the surface of the surface heating element 2cm, and then hardened at a temperature of 1000°C in a neutral atmosphere using N2 gas, and then a copper layer is thickened by a hot-spraying method. It was formed into three palanquins.

When a voltage of 40 V was applied to the obtained surface heating element, the surface temperature reached 500° C. after 1 minute and 50 seconds.

In the figure, 1 is a glass ceramic, 2 is a metal heating element, and 3 is a metal heating element.
is a graphite layer, and 4 is a metal layer.

As described above, according to the method of the present invention, a surface heating element having a structure in which a metal heating element is embedded in ceramic can be easily manufactured.

Moreover, the raw materials used are harmless, and their handling becomes very easy.

Since the metal heating element is embedded in the molding powder, the heat capacity and heat distribution of the surface heating element can be arbitrarily set depending on the purpose of use.

Furthermore, the surface heating element obtained by this method is. Good adhesion with ceramic metal heating elements, approximately 50-600℃
Can be used in a temperature range of

In addition, there is no risk of damage even if the heating element is rapidly cooled in a heated state, and there is no risk of the heating element being damaged by the influence of outside air.

Therefore, its change over time is small and its life characteristics are good.

The surface heating element itself is nonflammable and has excellent chemical and moisture resistance.

In addition, as mentioned above, since the raw materials are harmless, surface heating elements can also be used in the field of food hygiene equipment, and are extremely suitable as surface heating elements for rice cookers, toasters, ovens, pots, etc. It is.

[Brief explanation of drawings]

The figure is a sectional view showing an example of a surface heating element obtained by the method of the present invention. 1...Ceramics, 2...Metal heating element. 3...graphite layer, 4...metal layer.

Claims (1)

[Claims] 1. Calcinate the starting material mixture to obtain a ceramic or vitreous sintered body having a coefficient of thermal expansion of 50 x 10-'/°C or less, and pulverize this sintered body. A metal heating element is embedded during molding, and the molded body is sintered to integrate the ceramic and the metal heating element, forming a graphite layer on the surface of the resulting element. and further forming a metal layer thereon by a spraying method.