JPS6014090A - Furnace bottom structure of direct current arc 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 furnace bottom structure of a direct current arc furnace in which metal is melted by an arc, particularly a direct current arc.

The arc furnace has an AC three-phase arc furnace and a DC arc furnace, and the AC three-phase arc furnace has three electrodes inserted from the top of the furnace.
An arc is generated using the molten steel as a neutral point. Normally, a DC arc furnace has one upper electrode inserted and the electrode provided at the bottom of the furnace polarized at i[J 4% to generate a DC arc. be.

When comparing the two, the AC 6-phase arc furnace has 6 electrodes, so the upper structure of the furnace is complicated, the 6-phase arc is bent outward due to mutual electromagnetic force, resulting in a large amount of heat dissipated, and thermal efficiency is poor. There are problems such as local damage to the furnace wall, high electrode wear, high noise, and severe flicker. On the other hand, DC arc furnaces have problems with the lifespan and reliability of the bottom electrode, and as mentioned above, DC arc furnaces are
Despite being superior in various respects to phase arc furnaces, there are currently only a few that have been put into practical use.

Here, we will explain the furnace bottom structure of a DC arc furnace equipped with a conventional furnace bottom electrode according to Figure 1. In Figure 0, (1) is the furnace bottom plate, and the furnace bottom plate (1) is made of refractory bricks (2). The furnace bottom (4) is formed by lining the furnace with a stamp material (3) and tamping it inside.

A conventional furnace bottom electrode is constructed by implanting or burying a large number of spike materials (5) on the outside of the furnace in the furnace bottom (4) so that their tips contact the molten metal. This spike material (5) is usually an electrically conductive metal, which has a lower melting point than molten metal such as molten steel, and is made by applying a cooling medium (force) between the outer plate (6) and the furnace bottom plate (1) to prevent the spike material from flowing. The material (5) is cooled from one end side.The spike material (5) is directly cooled from the molten metal (5).
8), so even if it is cooled, it will gradually melt and wear away. If the spike material (5) is completely melted, it will cause a leakage of hot water, so maintenance work is complicated, such as requiring inspection of the spike material after each melting operation, and the lifespan of this hearth bottom electrode is extremely short.

The lifespan of the hearth bottom with such a hearth electrode is 100 to 200 heats, whereas the lifespan of the hearth bottom of an AC three-phase arc furnace is 20,000 to 30,000 heats, which is an overwhelming difference. be. This is largely the reason why DC arc furnaces have not become popular, even though they have various advantages over AC arc furnaces.

An object of the present invention is to provide a furnace bottom structure that can significantly extend the life of the furnace bottom electrode, thereby promoting the practical use of DC arc furnaces.

The present invention will be described in detail below with reference to the drawings.

FIG. 2 is a schematic cross-sectional view of a DC arc furnace in which the present invention is implemented, and the melting furnace body (9) is comprised of a furnace lid (c), a furnace side (1υ
, a furnace bottom (20), and a furnace lid (25).
An exhaust gas port 03) and a furnace side part (10 have an outlet a→ and a slag outlet α5) are formed.

The inner surfaces of the furnace lid part (25) and the furnace side part Uυ are lined with commonly used refractories αG) and α7), and the furnace bottom (towards)
A refractory layer (I9) is formed on the inner surface of the tube by lining it with chamotte bricks and then compacting the stamp material.

A hollow electrode (22) is installed at a desired position on the furnace bottom (20), and the electrode (22) is connected to a DC power supply (24) via a cable (24).
(not shown) and allows inert gas (Ar, N2, etc.) to be supplied through this hollow part (23).

Further, an electrode rod (26) is inserted through the furnace cover (25), and the electrode rod (2υ) is connected to the DC power source.

In the arc furnace, an arc (27) is generated between the electrode (22) and the electrode rod 06), and an inert gas is supplied through the hollow part C3).

Molten metal (8) is generated by the arc (21), and the electrode (
The tips of the two electrodes come into contact with the molten metal (8), but since the inert gas cools down to the tips of the stain electrodes, melting loss is significantly reduced. In addition, the molten metal (8) is stirred by blowing inert gas, which promotes uniformity of temperature and components, making it possible to obtain a high-quality product.

The material of the fireproof layer α-wings may be magnesia (MgO), zirconium oxide (ZfQ), or magnesia carbon (
If a material such as MgC) whose electrical resistance decreases in a high temperature state is used, there is no need for the electrodes (2 and 3) to be in direct contact with the hot water.
It is also possible to cover the tip of the electrode CD with a refractory layer (19) as shown in the figure.

Further, in the above embodiment, only a hollow electrode is used, but this hollow portion may be filled with a porous material, such as a porous plug, or the outer periphery of the electrode may be surrounded with a porous material. It goes without saying that in a structure in which a porous material is arranged around the electrode, the electrode may be solid.

Incidentally, if sufficient capacity cannot be obtained with the electrode of the present invention alone, it is desirable to use an electrode of another type such as a spike material in combination.

As described above, according to the present invention, (1) the cooling surface of the electrode is wide and direct cooling is performed, so the cooling efficiency is high, and the life of the bottom electrode, that is, the life of the DC arc furnace, can be extended. (11) Since the molten metal can be forcibly stirred by the gas that cools the electrode, it exhibits various excellent effects such as uniformity of components and temperature, and (ii) simple furnace bottom structure.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a conventional furnace bottom structure, FIG. 2 is a schematic cross-sectional diagram of a DC arc furnace in which the present invention is implemented, and FIG. 3 is an explanatory diagram of another embodiment. a91 is the refractory layer, O) is the furnace bottom, (2 is the electrode, (2
3) indicates a porous material. Patent applicant Ishikawajima Harima Heavy Industries Co., Ltd.

Claims (1)

[Claims] 1) A furnace bottom structure of a DC arc furnace, in which an electrode is provided at a required position at the furnace bottom, and a polarization cooling gas can be fed into the furnace through the electrode.