JPS6020079A - 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 bottom structure of a DC arc furnace for melting.

There are two types of arc furnaces: AC five-phase arc furnaces and DC arc furnaces. In AC three-phase arc furnaces, six electrodes are inserted from one L side of the furnace, and an arc is generated using molten steel as a neutral point. can be,
A DC arc furnace generates a DC hook by inserting one electrode and using the electrode provided at the bottom of the furnace as the other electrode.

When comparing the two, the AC three-phase arc furnace has six electrodes, so the upper structure of the furnace is complicated, and the six-phase arc is bent outward due to mutual electromagnetic force, resulting in a large amount of heat dissipated and poor thermal efficiency. In addition, there are other problems such as arc bending, which causes local damage to the furnace wall, large amount of electrode wear, loud noise, and severe flicker.On the other hand, DC arc furnaces do not have the above problems. There are problems with the lifespan and safety of the bottom electrode, and as mentioned above, even though DC arc furnaces are superior in various respects to AC three-phase arc furnaces, there are currently very few that have been put into practical use. It is.

Here, the bottom structure of a DC arc furnace provided with a conventional bottom electrode will be explained with reference to FIG.

In the figure, (1) is a hearth bottom plate, and the hearth bottom plate (1) is lined with refractory bricks (2), and a stamp (3) is rammed inside to form a hearth bottom (4).

A conventional furnace bottom electrode is constructed by driving or burying a large number of spike materials (5) into the furnace bottom (4) from the outside of the furnace so that their tips contact the molten metal. This spike material (5) is an electrically conductive metal with a melting point lower than that of molten metal such as molten steel, and has a cooling medium (7) between the outer plate (6) and the furnace bottom plate (1).
) is allowed to cool from one end of the spike material (5). However, the spike material (5) is directly molten metal (8
), so even if it is cooled, it will gradually melt away. If the spike material (5) is completely melted, it will cause a leak, so check the spike material (5) after each melting operation, and
5) Always monitor the state of melting damage, and when the melting damage reaches a predetermined amount, it must be repaired.

Since the conventional hearth electrode has an integral structure with the hearth bottom (4), it is difficult to inspect the hearth electrode, and the life of the hearth electrode becomes the same as the life of the hearth.

The lifespan of the furnace bottom with such a furnace bottom electrode is 100 to 200 times (heats), whereas the lifespan of the furnace bottom of an AC six-phase arc furnace is 20,000 to 30,000 times (heats, s).
) There is an overwhelming difference. This is largely the reason why DC arc furnaces are not popular, even though they have various advantages over AC arc furnaces.

The present invention significantly extends the life of the furnace bottom by providing a furnace bottom structure that allows easy inspection of the furnace bottom electrode and facilitates repair and replacement of the furnace bottom electrode, thereby promoting the practical use of DC arc furnaces. The purpose is to

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) includes a furnace lid part θ0), a furnace side part (11
), a furnace bottom (4), and a furnace lid (10).
An exhaust gas port (12) is provided at the bottom of the furnace (4), and a gage for tapping hot water is provided at the bottom of the furnace (4). This gate (13) also serves as a hearth bottom electrode, as will be described later. In the figure (23) is a slag.

An electrode rod 0 (a) is inserted into the furnace cover (10), and the electrode rod 04) is connected to a DC power source (not shown).

(13) is shown in detail in Figure 5,
A tap hole (1) is drilled in the furnace bottom (4), and the tap hole (19
Loosely fit the protrusion (17) of the gate body αG) into the gate body αG). The height of the protrusion (17) is lower than the thickness of the furnace bottom (4), and a conductive monolithic refractory (18) is placed around the protrusion (17).
bury it.

The gate body (I6) is made of a metal or non-metal conductive material, and the gate body (16) is pivoted to the tip of an arm θ9) that pivots on the outer surface of the furnace bottom (4). The connection terminal CI is located at the required position on the main body (1G)! 0) is attached, and by connecting a cable (21) from a power source (not shown) to the connection terminal (20), the electrode rod (1
・In the arc furnace mentioned above, scrap, sponge iron, etc. are charged into the furnace, and a direct current is applied between the electrode rod (14) and the gate body (lIij). When a current is applied, a DC arc (22) can be generated at the tip of the electrode rod 0 (1), and scrap, sponge iron, etc. can be melted.

To dispense hot water, cut off the electrical connection between the gate body (16) and the power supply, remove the arm (turn 1 turn and remove the gate body α6) from the hot water outlet (15), open the hot water outlet 05), and tap the hot water. do.

The bottom electrode must be inspected after each melting process, but with this device, the main part of the bottom electrode is exposed, so this work is extremely easy. Rotate the arm a9 again and move the gate body α6) to the outlet (
15), and bury monolithic refractories around it.

Also, if the gate body α6) is found to be so damaged that it is unsuitable for work during inspection, you can simply separate the arm (I) and the gate body (16) and replace it with a new gate body. , only the gate body (16) needs to be replaced, and the gate body (16) can be manufactured in advance at a factory, etc., so the work is easy and the construction period is short.In the above embodiment, the gate body (16) Although I did not specifically mention the cooling of the main body, it is recommended to provide a cooling channel inside the gate body and cool it appropriately by flowing water, air, etc.Furthermore, the gate main body can be mated and unmated by rotating the arm, but it is a sliding type. The gate body may be moved by a normal drive device such as a hydraulic cylinder or a pneumatic cylinder.Furthermore, the material of the monolithic refractory may be carbon, or zirconium oxide, which exhibits electrical conductivity at high temperatures. Any material with good conductivity, such as magnesia carbon or magnesia, may be used.As stated above, the present invention exhibits the following excellent effects.1) Electrode melting can be easily checked. Operational safety is high.

! It is easy to repair the 'flj pole.

11)) Simple structure and fewer repair parts 0-

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing a conventional furnace bottom structure, Fig. 2 is a cross-sectional schematic diagram of a DC arc furnace in which the present invention is implemented, and Fig. 4 is an explanatory diagram of another embodiment. At the bottom, (15) indicates the tap, αG) indicates the gate body, and α8) indicates the monolithic refractory. Patent applicant Ishikawajima Harima Heavy Industries Co., Ltd.

Claims (1)

[Claims] 1. A gate body made of a conductive material is removably fitted into a tap hole provided at the bottom of the furnace, and a conductive monolithic refractory is buried between the gate body and the tap hole, and the gate body is directly connected to the gate body. L
A bottom structure of a DC arc furnace characterized by a bottom electrode connected to a power source.