JPH06290855A - Terminal metal fixture for silicon carbide heater - Google Patents

Abstract

PURPOSE:To obtain a terminal fixture for bar-like electric heater, which can preventing the lowering of the fastening force due to the heat, by bonding a first layer made of metal having a small coefficient of thermal expansion and a second layer made of metal having a large coefficient of thermal expansion with a terminal fixture. CONSTITUTION:A first layer 1 made of metal having a small coefficient of thermal expansion and a second layer 2 made of metal having a large coefficient of thermal expansion are bonded together by a terminal fixture 3. Since the coefficient of thermal expansion of the second layer 2 is larger than that of the first layer 1, the second layer 2 is expanded larger than the first layer 1 to generate the fastening force. As a result, lowering of the fastening force of the terminal fixture due to the heat is prevented. Coefficient of thermal expansion in a range from 10X10<-6>/ deg.C to 20X10<-6>/ deg.C (l00 deg.C) is appropriate. In the case where the alloy such as invar having a coefficient of thermal expansion at 10X10-<-6>/ deg.C (l00 deg.C) or less is used, the spring effect is hard to be obtained, and in the case where the metal having a coefficient of thermal expansion at 20X10<-6>/ deg.C or more is used, coefficient of thermal expansion is excessively large, and the fastening force is therefor lowered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a terminal fitting for a silicon carbide type heating element which is a heat source of an electric furnace used for firing and sintering ceramics and the like.

[0002]

2. Description of the Related Art Silicon carbide heating elements are widely used as a heat source for firing metals and ceramics, but since the material is made of ceramics, a terminal connection method different from that of metal heating elements is adopted. There is. That is, the silicon carbide heating element is generally in the shape of a rod. As shown in FIG. 4, a flexible metal terminal is wound around the end of the heating element and connected with a V-shaped terminal fitting as shown in FIG. The method of doing is adopted.

[0003]

The silicon carbide-based heating element utilizes its heat resistance, and is 1000 ° C. which is impossible with a metal heating element.
Although it is used at the above-mentioned high temperature, the temperature will rise near the edges due to heat conduction and convection. Therefore, for long-term use, V
The tightening effect of the mold terminal metal fittings deteriorates, which causes problems such as poor contact and melting of the terminals in a short time. These damaged the heating element and the brick wall of the furnace, and required a great deal of time and money for repair. Conventionally, against such a problem, contact failure could be prevented to some extent by using a bolt tightening type terminal fitting as shown in FIG. However, bolt-tightening type terminal fittings are not common because they are difficult to construct due to their structure, and there is a problem that the bolts are seized after use.

[0004]

SUMMARY OF THE INVENTION The present invention solves these problems and enables stable use of a silicon carbide heating element. That is, in a terminal fitting of a silicon carbide-based heating element used as a heat source of an electric furnace for firing or sintering ceramics or the like, a terminal fitting made of two kinds of metals having different thermal expansion coefficients is bonded to each other. The coefficient of thermal expansion of the metal is 10 × 10 ⁻⁶ / ° C. to 20 × 10 ⁻⁶ / ° C. (10
0 ° C.) and the difference in thermal expansion between the two metals is 3
× characterized in that at ^{10 -6} / ° C. or more is less than 7 × ^{10 -6} / ℃.

[0005]

The terminal fitting of the present invention will be described with reference to FIG.
The terminal fitting of the present invention has a V-shape that is easy to install, and in order to prevent the tightening force from decreasing due to heat, two kinds of metal are stuck together. The tightening force does not decrease due to the difference in expansion so that it does not loosen. In the terminal fitting of the present invention, the first layer 1 made of a metal having a small coefficient of thermal expansion and the second layer 2 having a large coefficient of thermal expansion are three layers.
Are joined by rivets. Since the coefficient of thermal expansion of the second layer 2 is larger than that of the first layer 1, heat causes the second layer 2 to extend beyond the first layer 1 to generate tightening stress. Due to this effect, it is possible to prevent the terminal fitting from being lowered in the tightening force due to heat. Here, the coefficient of thermal expansion is 10 ×
The range from 10 ⁻⁶ / ° C. to 20 × 10 ⁻⁶ / ° C. (100 ° C.) is defined as the metal of 10 × 10 ⁻⁶ / ° C. (100 ° C.) or less (for example, amper: 1.2 × 10 ⁻⁶ /). (° C), it is difficult to obtain a spring effect, and it is expensive and not suitable as a terminal fitting. In addition, if a metal having a coefficient of thermal expansion of 20 × 10 ⁻⁶ / ° C. or more is used, the coefficient of expansion is too large, which leads to a decrease in tightening. Furthermore, the difference in thermal expansion between the two metals is 7 × 10 ⁻⁶ / ° C. or more at 3 × 10 ⁻⁶ / ° C. or more.
If less than 3 × 10 ⁻⁶ / ° C., the ratio of extension in the tightening direction is smaller than the total thermal expansion, and effective tightening cannot be achieved. Also, when the difference in thermal expansion between the two kinds of metals is 7 × 10 ⁻⁶ / ° C. or more, the ^bonded portion is peeled off and it cannot be used.

[0006]

As is clear from Table 1, in Examples 2 and 3, the terminal metal fitting was loosened when the end temperature of the silicon carbide based heating element was 350 ° C., and when the end temperature reached 400 ° C. The test was stopped due to the occurrence of fusing. Example 4 has an end temperature of 3
The terminal fitting was deformed at 00 ° C and the terminal wire was melted at 350 ° C, making it unusable. Further, the conventional product of the comparative example was loosened at 300 ° C and could not be used at 350 ° C. On the other hand, in Example 1 of the product of the present invention, no change occurred up to the end temperature of 450 ° C., and the product could be stably used.

[0008]

As is apparent from the examples, it was found that the terminal fitting of the present invention can be stably used even at 300 ° C. or higher, which is difficult to use with the terminal fitting of the conventional silicon carbide heating element. When the product of the present invention is used, the original high temperature use of the silicon carbide heating element can be stably obtained, and the life of the heating element can be dramatically improved. This can be expected to significantly reduce the firing cost.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a terminal fitting of a silicon carbide based heating element of the present invention.

FIG. 2 is a cross-sectional view showing a terminal fitting of a conventional silicon carbide heating element.

FIG. 3 is a cross-sectional view showing another example of a conventional silicon carbide based heating element.

FIG. 4 is a view showing a state in which a conventional terminal fitting is connected to an end of a silicon carbide heating element.

[Explanation of symbols]

 1 Metal of 1st layer 2 Metal of 2nd layer 3 Rivet 4 Tightening bolt 5 Silicon carbide heating element 6 Terminal fitting 7 Power supply terminal

Claims (1)

[Claims] 1. A terminal fitting of a silicon carbide heating element used as a heat source of an electric furnace for firing or sintering ceramics or the like, wherein the terminal fitting is formed by laminating two kinds of metals having different thermal expansion coefficients, The coefficient of thermal expansion of two kinds of metal is
All are from 10 × 10 ⁻⁶ / ° C. to 20 × 10 ⁻⁶ / ° C.
(100 ° C.) range, and the difference in thermal expansion between the two metals is 3 × 10 ⁻⁶ / ° C. or more and less than 7 × 10 ⁻⁶ / ° C., the terminal of the silicon carbide heating element. Metal fittings.