JPS61146760A - Heater of silicon carbide - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a silicon carbide heating element that can be used both as a regular resistance heating element and as a heating element for high frequency heating.

Conventionally, silicon carbide heating elements have been used as resistance heating elements, usually at 1400°C. The production of silicon carbide heating elements is
It is made by silicifying silicon carbide powder, silica, carbon, etc. at temperatures reaching 2,400°C, and its porosity is over 20%, and its specific resistance at room temperature is about 0.5ΩC.

However, since the porosity is about 20%, it is easily oxidized and deteriorated in high-temperature air.

In other words, the bonding force between particles is weak, and grain boundary areas are easily oxidized.
Electrically insulating silicon dioxide is produced. At high temperatures,
Since silicon dioxide reacts with silicon carbide and volatizes, the performance of the heating element is significantly reduced.

In addition, the conventional silicon carbide heating element has a specific resistance of 1000°C.
, it is 0.1ΩC1, and it is impossible to change this specific resistance to any value.

Furthermore, as shown in FIG. 3, for example, when a conventional silicon carbide heating element 1 is used to fire an object to be fired, such as a pipe 2 with a circular cross section, through a furnace core tube 3, a rod-shaped heating element 1 is used. Unless the vibrator 1 is assembled and the intervals between the heating elements 1 are adjusted, the vibrator 2 cannot be fired at a uniform temperature, making the firing process very troublesome.

■The invention of the m1 mouth is chemically stable, has high strength, can be made thin and lightweight, has excellent heat resistance and is suitable for high-temperature parts, and can be carbonized to make firing work easier by generating heat with high frequency or direct energization. The purpose is to provide a silicon heating element. .

11” [To achieve this objective, the present invention utilizes silicon carbide 60
The gist of the invention is a silicon carbide heating element characterized by having a composition of ~94% by weight, 1-20% by weight of aluminum nitride, and 2-20% by weight of carbon.

° Considering the composition of silicon carbide, aluminum nitride, and carbon, the silicon carbide heating element of this invention can be made chemically stable by making silicon carbide the main component, and can be made chemically stable by adding aluminum nitride and carbon. As a result, it has high strength and excellent heat resistance, and can be generated by high frequency or direct energization.

11 Aluminum nitride (liN) is an electrically insulating substance. By adding this aluminum nitride to silicon carbide (SiC), a silicon carbide heating element is made, and by sintering silicon carbide, a heating element is made. It can be made into a material that can be used as

In Examples 1 to 4 shown in Table 1, the amount of carbon added was 5% by weight.
This figure shows the influence of changes in the amount of aluminum nitride added on various properties of the silicon carbide heating element when the temperature is set to .

As is clear from Table 1, if the amount of aluminum nitride added is 1% by weight or less, the densification of the silicon carbide heating element is inhibited, the density is small, and the strong bonding force that is the objective of the present invention cannot be obtained. The silicon carbide heating element deteriorates significantly due to repeated use.

In addition, the amount of aluminum nitride added was 20rii, m%
If this is the case, not only will the specific resistance of the silicon carbide heating element be large enough to prevent heat generation, but also the sintering of the silicon carbide will not proceed.

Therefore, the range of the amount of aluminum nitride added is 1 to 2
0% by weight is appropriate, and within this range, the silicon carbide heating element can have a high density and a low specific resistance.

Regarding (2), carbon is a conductive substance, exists as graphite after sintering, and can lower the specific resistance of the silicon carbide heating element.

Examples 5 to 9 shown in Table 2 show the effects of changes in the amount of carbon added on various properties of silicon carbide heating elements when the amount of aluminum nitride added was set at 5% by weight. In addition, Comparative Example 10 is described.

As shown in Table 2, when the amount of carbon added is 1% by weight or less, a dense self-sintering silicon carbide structure is formed, but the specific resistance is 1%.
The value is as high as 0.03 Ωcm or more, making it unsuitable as a heating element.

If the amount of carbon added exceeds 20% by weight, the resistivity will decrease, but the density will be low and the bonding strength will be weak, inhibiting the sintering of silicon carbide, and there will be a large amount of free graphite, which will reduce the oxidation resistance and generate heat. Physically unsuitable.

Therefore, the appropriate range of the amount of carbon added is 2 to 20% by weight, and within this range, the silicon carbide heating element can have a high density and low specific resistance.

As is clear from (1) and (2) above, by controlling the amounts of aluminum nitride and carbon added to silicon carbide, the structure of the sintered body can be adjusted and silicon carbide 60-9
4! Aluminum nitride is 1 to 20% by weight relative to 1% by weight.
A silicon carbide heating element having properties suitable as a heating element is obtained having a composition of 2 to 20% by weight of carbon, and the specific resistance at room temperature can be arbitrarily set in the range of 0.01 to 10 Ωcm.

The theoretical density of silicon carbide is 3.21 g/C13. Therefore, a suitable silicon carbide heating element can have its actual density set at 70-95% of the theoretical density, and aluminum nitride has aluminum oxynitride (AQ
-〇-N).

Furthermore, as a result of strength experiments, the bending strength was 300 to 550.
It has been found that it extends to spas.

Table 3 shows Examples 11 to 13 and Comparative Example 14 that were used in the induction heating test using high frequency.

The results of the high frequency heat generation test are shown in FIG. 1, which shows power consumption versus temperature. As is clear from this, Examples 12.13 of the silicon carbide heating element of the present invention
It can be seen that it is suitable as a high frequency heating element and can be used in a high temperature range.

By the way, FIG. 2 shows an example in which a silicon carbide heating element is used as a high frequency heating element. Reference numeral 21 denotes a high frequency coil wound around the outer periphery of a quartz furnace core tube 22, and a cylindrical silicon carbide heating element 23 of the present invention is inserted into the quartz furnace core tube 22. This silicon carbide heating element 23 preferably has a cylindrical shape because it can be heated by high frequency. A vibrator 2, which is an object to be fired, is inserted into the silicon carbide heating element 23.

In such a configuration, when a current is passed through the high-frequency coil 21, the silicon carbide heating element 23 continuously generates heat, unlike the conventional method, so that the pipe 2 can be fired at a uniform temperature, and there is no uneven firing of the pipe 2.

Furthermore, even if the vibrator 2 is long, the pipe 2 can be completely fired by moving the vibrator 2 because the silicon carbide heating element 23 is pipe-shaped.

In this way, compared to the conventional heating elements that were assembled and fired, by using the silicon carbide heating element of the present invention, the shape of the heating element can be made into a continuous, integrated piece, making the work easier and more uniform. It can be fired completely at a temperature of

By the way, it goes without saying that the silicon carbide heating element of the present invention can also be used as a normal resistance heating element by direct energization.

L As explained above, according to this invention, since carbon is the main component, it can be made chemically stable, and by adding appropriate amounts of aluminum nitride and carbon, the bonding force is strong (high strength, and it can be used in actual use). In this case, the wall becomes thinner and the weight is removed,
It also has excellent heat resistance, making it suitable for high-temperature components, and has the excellent effect of making firing work easier than before by generating heat through high frequency or direct energization.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the power consumption versus temperature of the silicon carbide heating element of the present invention, Fig. 2 is a perspective view showing the case of firing using the silicon carbide heating element of the invention, and Fig. 3 is a diagram showing the power consumption of the silicon carbide heating element of the present invention. FIG. 3 is a perspective view showing a case where a firing operation is performed using a silicon heating element. 21...High frequency coil 23...Silicon carbide heating element 2...Pipe as an object to be fired Figure 1 Sea (°C Figure 2 Figure 3 procedural amendment (voluntary) April 1985 22nd of the month

Claims (4)

[Claims] (1) A silicon carbide heating element characterized by having a composition of 60 to 94% by weight of silicon carbide, 1 to 20% by weight of aluminum nitride, and 2 to 20% by weight of carbon. (2) The silicon carbide heating element according to claim 1, wherein the actual density is 70 to 95% of the theoretical density. (3) The silicon carbide heating element according to claim 1, which has a specific resistance at room temperature of 0.01 to 10 Ωcm. (4) The silicon carbide heating element according to claim 1, wherein the aluminum nitride includes aluminum oxynitride.