JP3172781B2 - DC electric furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC electric furnace used for melting metal materials, refining molten metal, and the like.

[0002]

2. Description of the Related Art As an electric furnace for refining, a current flows between an electrode disposed above a molten metal charged in a furnace and an electrode attached to a furnace wall such as a furnace bottom and a side wall, and a metal material is formed. DC electric furnace for melting and refining molten metal, and alternating current electricity for melting metal materials and refining molten metal by passing current between three electrodes placed above the molten metal charged in the furnace. Furnaces are known. In this type of electric furnace operation, a system that uses the exhaust gas places a preheating tank between the electric furnace and the dust collection equipment, loads the metal material into the preheating tank together with the bucket, and introduces the metal material using the introduced exhaust gas. Was generally preheated.

However, the exhaust gas duct between the electric furnace and the preheating tank is water-cooled because high-temperature gas generated from the electric furnace passes therethrough, and the temperature of the exhaust gas reaching the preheating tank is reduced by the amount of water-cooling. Therefore, the heat possessed by the exhaust gas was not efficiently used for preheating the metal material, resulting in a large loss in thermal efficiency. In addition, white smoke and odor generated when the preheated metal material is transported to the electric furnace together with the bucket has been a serious problem in the working environment.

Therefore, various methods have been proposed for efficiently utilizing the heat of the exhaust gas for preheating the metal material and charging the preheated metal material to the electric furnace without transporting the metal material from the preheating tank to the electric furnace. For example, in JP-A-3-505625, a metal material is preheated in a preheating tower provided on a furnace lid and in a pre-tropical zone formed by a part of the furnace body, and the preheated metal material stored in the preheating tower is removed. An electric furnace characterized by being naturally dropped and charged is disclosed. However, in this case, in the so-called refining period after the metal material stored in the preheating tower provided on the furnace lid naturally drops and melts, the metal material does not remain in the preheating tower and the heat of the exhaust gas heats the metal material. There was no preheating, and there was still a challenge in terms of thermal efficiency.

Therefore, as a technique for solving this problem, for example, in Japanese Patent Laid-Open No. 5-500263, two electric furnaces are arranged, and the metal material stored in the preheating tower of the electric furnace that is being energized naturally is used. After dropping and melting, a method has been proposed in which the other metal material is stored in a preheater and exhaust gas is introduced into an electric furnace on standby to preheat the metal material to improve thermal efficiency. In Japanese Patent Application Laid-Open No. 4-309789, a pre-tropical zone is formed only by a preheating tower, a door is provided in the preheating tower, and a metal material can be always stored in the preheating so that the heat of the exhaust gas during the refining period is effectively used. Possible ways have been proposed.

[0006]

Most of the energy for melting metal materials in an electric furnace is electric energy, and in a DC electric furnace, it is the heat of an arc generated from an upper carbon electrode. When considering the energy efficiency in melting metal materials, place an arc that is an energy source at the center of the furnace body as much as possible, that is, place an upper carbon electrode, and place the charging portion of the metal material to be melted in the furnace body. It is preferable that the center of the metal material is formed as much as possible, and an arc is ignited from the upper carbon electrode at the center of the metal material to dissolve the circumference uniformly. This is a great advantage of a DC electric furnace that requires only one upper carbon electrode, and the energy efficiency is superior to that of an AC electric furnace that requires three upper carbon electrodes. The same is naturally true even if the material is preheated.

However, JP-A-3-505625, JP-A-5-500263, JP-A-4-309
In the case of Japanese Patent No. 789, the preheating tower is installed on the side wall of the furnace body, so that the preheated metal material is charged only on the side wall of the furnace body, and the metal material is not charged. The opposite side wall is not always used to melt the metal material unnecessarily heated by the arc heat, causing a decrease in energy efficiency. Also, since the metal material is charged only in a portion distant from the upper carbon electrode In addition, there is a problem that the dissolution rate is lower than that of a method in which an upper carbon electrode is disposed in the center of a metal material to dissolve it, leading to a decrease in energy efficiency.

As a method of correcting this, a method of moving the furnace lid so that the preheating tower is located at the center of the furnace body and then charging the metal material can be considered. When the lid is moved, the upper part of the furnace body is released, and when the metal material of the preheating tower is charged into the furnace, a gas containing high-temperature dust is blown out from the upper part of the furnace body, thereby significantly impairing the working environment. Therefore, an object of the present invention is to provide a DC electric furnace that can increase the melting electric energy of a preheated metal material without increasing the working environment while increasing the preheating efficiency of the metal material by exhaust gas. I do.

[0009]

In order to solve the above-mentioned problems, the present invention provides a preheating tower for storing and preheating a metal material on a furnace lid, and a heater which is located at the center of the furnace lid and which can be moved up and down. In a DC electric furnace in which a bon electrode is integrally disposed, the furnace lid is formed so as to be movable in the horizontal direction, and the furnace lid is formed so as to cover the upper part of the furnace body even when the furnace lid is moved. Features.

[0010]

According to the present invention, since the preheating tower having the door provided inside the furnace lid is arranged on the furnace lid, the metal material can be always stored in the preheating tower, and the preheated metal is improved while increasing the thermal efficiency by the exhaust gas. The material can be charged into the central part of the furnace body by moving the furnace lid so that the preheating tower arranged on the furnace lid is located at the central part of the furnace body. Since the furnace lid has a furnace lid shape that is not released, the furnace body can be maintained in a sealed state, and dust generation due to metal material charging from the preheating tower can be significantly suppressed. Become.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
FIG. 1 is an overall vertical sectional view of a DC electric furnace according to the present invention.
FIG. 2 is an overall vertical cross-sectional view when the metal material in the preheating tower of the DC electric furnace according to the present invention is charged into the furnace. FIG. 3 is FIG.
FIG. 3 is a plan view taken along plane AA.

A furnace bottom electrode 2 is arranged below the furnace body 1.
An upper carbon electrode 4 is arranged so as to penetrate through the furnace lid 3 from above. A preheating tower 5 is provided on the furnace lid 3, a door 7 for holding a metal material 6 is installed inside the preheating tower 5, and a metal material 6 is charged into the preheating tower 5 above. And an exhaust gas duct 9 for connecting exhaust gas to a dust collecting facility (not shown). Although the embodiment shows one example of the preheating tower 5 on the furnace lid 3, the present invention can be applied to a case where two preheating towers 5 are provided. High-temperature exhaust gas generated during melting and refining of the molten metal 10 inside the furnace body 1 passes through the preheating tower 5, and is sent to the dust collecting facility via the exhaust gas duct 9.

At this time, the metal material 6 in the preheating tower 5 is efficiently preheated by the high-temperature exhaust gas. When the heating of the molten metal 10 in the furnace body 1 is completed and the metal material 6 in the preheating tower 5 is charged, the upper carbon electrode 4 is pulled up by an electrode lifting device (not shown), and then the furnace lid 3 is moved to the furnace. The preheating tower metal material 6 to be charged is moved by the lid driving device so as to be located at the center of the furnace body 1.

FIG. 2 shows a state immediately after the metal material 6 in the preheating tower 5 is charged. The metal material 6 has a door 7 provided in the preheating tower 5.
Is released into the furnace body 1, the door 7 is closed after the charging, and the upper metal material 6 is received and stored. As shown in FIG. 3, when the furnace lid 3 is moved and the preheating tower metal material 6 is charged into the furnace body 1, the furnace cover 3 is shaped so as to completely cover the upper part of the furnace body 1. 6 is also suppressed from deteriorating the working environment due to dust generation from the inside of the furnace body 1 due to charging. In the embodiment, the movement of the furnace lid 3 is shown by a horizontal carriage system, but the present invention can be applied to other systems.

After charging the metal material 6 into the center of the furnace body 1,
The furnace lid is moved again, the upper carbon electrode 4 is lowered, and the arc 12 is ignited at the center of the metal material, thereby starting melting. As described above, according to the present invention, the arc can always be ignited at the center of the furnace body, and the arc 12 can be ignited at the center of the metal material 6. It is possible to operate with.

[0016]

As described above, in the DC electric furnace according to the present invention, while preheating the metal material effectively,
In addition, operations that increase the use efficiency of electrical energy for melting and refining metal materials can be performed without deteriorating the work environment at all, and greatly contribute to reducing energy costs, improving productivity, and improving the work environment. Things.

[Brief description of the drawings]

FIG. 1 is an overall vertical sectional view of a DC electric furnace according to an embodiment of the present invention.

FIG. 2 is an overall vertical cross-sectional view when a metal material in a preheating tower of a DC electric furnace according to an embodiment of the present invention is charged into the furnace.

FIG. 3 is a plan view taken along the plane AA of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Furnace body 2 Furnace bottom electrode 3 Furnace lid 4 Upper carbon electrode 5 Preheating tower 6 Metal material 7 Door 8 Loading port 9 Exhaust gas duct 10 Molten metal 11 Furnace lid driving device 12 Arc

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI F27D 13/00 F27D 13/00 DF

Claims (1)

(57) [Claims] 1. A direct current electric furnace in which a preheating tower for storing and preheating a metal material on a furnace lid and a carbon electrode which is located at the center of the furnace lid and which can be moved up and down are integrally provided. A DC electric furnace, wherein the furnace lid is formed so as to be movable in the horizontal direction, and the furnace lid is formed so as to cover the upper part of the furnace body even when the furnace lid is moved.