JPS5814487A - Heater for electric furnace - 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 The present invention relates to a heater for an electric furnace, and more particularly to a heater for an electric furnace that has excellent oxidation resistance and wear resistance at high temperatures, and therefore has a long life.

For example, molybdenum wire is used as a resistance heating element in a high-temperature vacuum furnace or a reducing zero HfAPR. Since this has a high single point (MP, approx.!4130C), a molybdenum wire rod with a circular cross section, which is usually obtained by powder metallurgy, is made into a sinusoidal shape, and 16 pieces of this rri are attached to the furnace wall, etc. It is attached closely and generates heat through electricity. -1 This molybdenum wire rod is produced by molding molybdenum powder into a columnar shape and sintering it using powder metallurgy. As a result, a wire rod having the desired shape is obtained.

However, because molybdenum has a high melting point, conventional molybdenum heaters are often used in high-temperature (~1800C) vacuum furnaces, reducing atmosphere furnaces, etc., but they are not practical. At such high temperatures, molybdenum is oxidized by the unavoidable partial pressure of oxygen, or molybdenum itself is consumed at high temperatures, causing deterioration of the heater's surface and even breaking, reducing its lifespan.
One object of the present invention is to provide a heater for electric furnaces that overcomes the above-mentioned disadvantages of conventional heaters for electric furnaces, has excellent oxidation resistance and wear resistance at high temperatures, and has a long lifespan. It's about doing.

That is, the electric furnace heater of the present invention includes a molybdenum wrapping body;
It is characterized by being made of a ceramic thin film that covers the entire surface layer of the compact.

Examples of the ceramic thin film mentioned above include carbides such as titanium carbide, he7nium carbide, tantalum carbide, zirconium carbide, niobium carbide, tungsten carbide, molybdenum carbide, chromium carbide, silicon carbide, tantalum nitride, zirconium nitride, titanium nitride, Nitrides such as niobium nitride, vanadium nitride, boron nitride, etc., borides such as zirconium boride, titanium boride, tantalum boride, vanadium boride, tantalum silicide, etc. , tungsten silicide, molybdenum silicide, niobium silicide, zirconium silicide, silicide oxide, etc. Examples include oxides 1 such as dunesium, zirconium oxide, beryllium oxide, and aluminum oxide.

Among these, carbides such as hafnium carbide, tantalum carbide, zirconium carbide, niobium carbide, titanium carbide, chromium carbide, and silicon carbide, nitrides such as zirconium nitride, titanium nitride, and boron nitride, boron, zirconium boride, Borides such as titanium boride, tantalum boride, vanadium boride, and chromium boride; Silicides such as tantalum silicide, tungsten silicide, molybdenum silicide, and chromium silicide; magnesium oxide, zirconium oxide, beryllium oxide, and aluminum oxide. Oxide books such as silicon carbide, boride, chromium boride, tungsten silicide, molybdenum silicide, a
It is preferable to use aluminum, magnesium oxide, zirconium oxide, beryllium oxide, etc. because they have excellent oxidation resistance and abrasion resistance at high temperatures.

The thickness of such a ceramic thin film is preferably 3 to 20 μm1, and preferably 5 to 10 sw*.

If the thickness is less than 3 μm, a sufficient coating effect cannot be obtained by the thin film, and if it exceeds 20 μm, the molybdenum wire and the ceramic thin film tend to peel off due to the difference in thermal expansion coefficient between the two.

Next, the electric furnace heater of the present invention will be described in more detail with reference to manufacturing examples described below.

First, a molybdenum wire is obtained based on the usual powder metallurgy method. The award of this molybdenum wire is not particularly specified.

Usually, the cross section of the line lit~7ms is circular.

Next, the entire surface layer of the molybdenum wire thus obtained is covered with a ceramic thin film.

As the apparatus method, any method used as a normal ceramic coating method, such as a vapor phase deposition method, a plasma spray method, an ion pretender method, etc., may be used. Among these, the vapor phase deposition method is preferred because a thin film with excellent adhesion to the molybdenum wire can be obtained and the film thickness can be easily controlled.

As the vapor deposition method, any commonly used method may be used, for example, T
i, Hf, Ta, Zr, Nb, W, Me,
Cr, 81, V.

B, M7. A single substance such as a molybdenum wire is also used to heat a mixed gas consisting of a vaporized product of the eyelids, hydrogen gas, and if necessary a vaporized product of hydrocarbon II'1, nitrogen gas or carbon dioxide gas, etc., to a molybdenum wire. A method is used in which a desired ceramic thin film is formed on a molybdenum wire body by arranging the molybdenum wire body and introducing it into a reaction furnace maintained at an appropriate deposition temperature.

According to the electric furnace heater of the present invention, even if the entire surface layer of the molybdenum heater is coated with a ceramic thin film, even if the heater is energized for a long period of time and heated to high temperature, the unavoidable oxygen partial pressure Molybdenum will not become depleted or molybdenum itself will be consumed. Therefore, it has a long life.

The electric furnace heater of the present invention is useful for high-temperature vacuum furnaces, reducing atmosphere furnaces, and the like.

EXAMPLE An electric furnace heater of the present invention having a circular cross section (6 diameters) was manufactured.

That is, based on the vapor phase deposition method, a molybdenum wire body obtained by ordinary powder metallurgy and metallurgy methods was arranged, and the deposition temperature was 1100 m.
A mixed gas consisting of a vaporized titanium cyclide, hydrogen gas, and nitrogen gas was introduced into the reactor maintained at a temperature of A heater for an electric furnace of the present invention was obtained by coating with a team TIN film.

As a comparative example, a heater for an electric furnace according to the same summary was obtained using the same materials and method as in the above example except that the TiN film was not coated.

The thus obtained electric furnace heater of the present invention and the comparative example were processed into a sine wave shape and attached to the furnace wall of a vacuum furnace, and the furnace temperature was about 1.
It was used by heating with electricity to a temperature of 300C.

As a result, the electric furnace heater of the present invention had no cracks or heater disconnections after 5 years, and the surface did not deteriorate due to nitrogen removal. On the other hand, the comparative example broke after one cycle and became unusable.

As is clear from the above results, the electric heater of the present invention has excellent uniformity at high temperatures and wear resistance, and has a longer lifespan than the conventional Mo9pden heater.

Claims (1)

[Scope of Claims] t. A heater for an electric furnace, comprising a molybdenum wire body and a ceramic thin film covering the entire surface layer of the wire body. 2. A heater for an electric furnace according to claim 1, wherein the ceramitus thin film is a thin film formed by a vapor phase deposition method.