JPH08190982A - Oxidation preventive method of carbon type heating element - Google Patents

Abstract

PURPOSE: To extend the service life of a heating element by forming a coating membrane of a silicon carbide on the surface of a carbon type heating element, as an oxidation preventive method of the carbon type heating element, at a low cost in respect of the material equipment and the manufacturing process. CONSTITUTION: On the surface of a carbon type heating element, a powder which consists of silicon, or silicon and carbon, is contact coated, and the silicon is converted into a silicon carbide by the temperature rise in the power feeding heating time, so as to form a coating membrane of the silicon carbide. Since a silicon carbide is formed on the surface of the carbon type heating element, a hard coating membrane of the silicon carbide is formed, so as to exercise an oxidation preventive effect of long service life. And, a special equipment is unnecessary, the processing requires no time and labor, the anti-oxidation property is improved at a low cost, and the lining cost of the heating element can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbonaceous heating element used in vacuum degassing equipment such as RH and DH.

[0002]

2. Description of the Related Art In vacuum degassing equipment such as RH and DH used for adjusting the composition of steel and degassing in the field of steelmaking, a heat generating element used for preheating and heat retention is heat resistant. A carbonaceous heating element is used in terms of heat resistance and reactivity. In order to prevent the oxidation of carbon, it is generally used while flowing an inert gas such as argon or nitrogen. However, since some oxygen in the air enters the RH degassing device from the outside, the carbon of the carbonaceous heating element is oxidized and the service life of the heating element is shortened.

As a method for solving this drawback, SiO ₂ ,
Although the coating and impregnation of an antioxidant mainly composed of Al ₂ O ₃ are carried out, at the time of operation, the surface of the heating element becomes a heater and the temperature becomes around 2000 ° C.
The glass phase formed of a composition containing iO ₂ and Al ₂ O ₃ as its main components has a reduced viscosity and is washed off from the surface or volatilized, so that the antioxidant effect does not last long. Further, since the wettability of the carbon itself is poor, the coated antioxidant is likely to be peeled off, and that portion often becomes a defect and oxidation progresses in many cases.

Therefore, as means for solving this drawback, improvement of the oxidation resistance by changing the glass component of the antioxidant, coating of the heating element with silicon carbide by the vapor deposition method, and the like are being studied. However, very few glass components are stable up to 2000 ° C., and expensive components must be added. In addition, coating by the vapor deposition method requires a large cost.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
Heat generation by forming a coating film of silicon carbide on the surface of the carbonaceous heating element at a low cost in the raw material equipment and process as an oxidation prevention method for the carbonaceous heating element used in vacuum degassing equipment such as It extends the life of the body.

[0006]

The present invention is a method for preventing oxidation of a carbonaceous heating element by forming a coating film of silicon carbide on the surface of the carbonaceous heating element to prevent the oxidation of the heating element.

As a method for this, powder of silicon or silicon and carbon is dispersed in a thermosetting resin, and this is applied to the surface of the carbonaceous heating element and thermoset. The carbonaceous heating element after thermosetting is set in the RH vacuum degassing apparatus and heated by energization. During heating, silicon reacts with the resin, the added carbon, or the carbon component of the carbonaceous heating element to form a silicon carbide coating film having excellent oxidation resistance on the surface of the heating element. The heating element is heated to 1000 ° C. or higher in a few minutes by electric heating, and silicon carbide is converted into silicon carbide, so that the carbonaceous heating element is not oxidized at a low temperature. Further, since silicon reacts with the carbon component of the carbonaceous heating element, it also has a strong adhesive force as a coating film.

As a result, the carbonaceous heating element is protected from oxidation and its life is improved. Further, since silicon is adhered by the resin, there is no peeling during coating or transportation. The carbonaceous heating element according to the oxidation preventing method of forming the coating film of silicon carbide on the surface of the carbonaceous heating element according to the present invention is not only the heating element of the vacuum degassing device such as RH and DH but also the conventional carbonaceous heating element. It can also be widely used as a heating element for various atmosphere furnaces used.

Examples of the present invention and comparative examples will be described below. Table 1 shows the quality of the standard material of the carbonaceous heating element prepared by insert molding and firing using graphite as the carbon agent.

[0010]

Example 1 Silicon powder (# 350) and phenol resin were uniformly mixed at a weight ratio of 1: 1 to obtain 1 g / c.
At a rate of m ^2, the standard carbonaceous heating element material shown in Table 1 was coated on the surface of the sample, dried at 150 ° C. for 1 hour, and then set in an electric furnace under the oxidizing conditions shown in Table 2 to perform an oxidation test. It was

[0011]

[Example 2] Silicon powder (# 350), carbon as coke (# 200), and phenol resin in a weight ratio of 1:
A uniform mixture of 1: 2 was applied at a rate of 1 g / cm ^{2 on} the surface of a cut sample of the standard carbonaceous heating element material shown in Table 1, and dried at 150 ° C. for 1 hour. An oxidation test was conducted under the same conditions as in 1.

Comparative Example 1 Silica sol was applied to a cut sample of the same material as in Example 1 by vacuum decompression injection method in a weight ratio of 1
What was dried at 100 ° C. for 6 hours after impregnation with 0% was subjected to an oxidation test under the same conditions as in Example 1.

Comparative Example 2 A slurry-like antioxidant composed of Al ₂ O ₃ and SiO ₂ was applied on the surface of a cut sample made of the same material as in Example 1 at a rate of 1 g / cm ² , and the temperature was 100 ° C.
What was dried for 6 hours was subjected to an oxidation test under the same conditions as in Example 1. The results are summarized in Table 3 below.

[0014]

[Table 1]

[0015]

[Table 2]

[0016]

[Table 3]

As can be seen from these results, the oxidation preventing method of forming a silicon carbide coating film on the surface of the carbonaceous heating element of the present invention forms a strong coating film on the surface of the carbonaceous heating element, and suppresses deterioration due to oxidation. To be done. In Comparative Example 1, remarkable oxidation was observed, and in Comparative Example 2, the applied antioxidant flowed down at a high temperature, and the oxidation proceeded from the flowed-down portion.

[0018]

EFFECT OF THE INVENTION The method for preventing oxidation of a carbonaceous heating element according to the present invention comprises uniformly mixing powder of silicon or a mixture of silicon and carbon with a thermosetting resin and coating the surface of the carbonaceous heating element with an adhesive coating. Due to the temperature rise due to the heating of the carbonaceous heating element by the electric current, silicon carbide is formed on the surface of the carbonaceous heating element, so that a strong carbon-silicon coating film is formed, and the long-life antioxidant effect is exhibited. Furthermore, it does not require special equipment, does not require a great deal of work in the process, and can improve the oxidation resistance performance at a low cost and reduce the lining cost of the heating element.

Claims (1)

[Claims] The surface of the carbonaceous heating element is adhesively coated with silicon or a powder consisting of silicon and carbon, and due to the temperature rise of the heating element of carbon during electric heating, silicon is combined with carbon to change to silicon carbide. A method for preventing oxidation of a carbonaceous heating element, characterized in that a coating film of silicon carbide is formed on the surface.