JPH0711390B2 - Bottom electrode exchange device for DC electric furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a bottom electrode exchange device of a DC electric furnace for melting and refining metal by a DC arc.

<Prior Art> There are an AC electric furnace and a DC electric furnace in the electric furnace, and the AC electric furnace is one in which three graphite electrodes are inserted from above the furnace to generate an arc with molten steel as a center point. The DC electric furnace is one in which one to three graphite electrodes are not necessarily inserted, but one to three electrodes are inserted, and a DC arc is generated with the furnace bottom portion as the other electrode.

Since the AC electrode has three electrodes, the upper structure of the furnace is complicated and the three-phase arc is bent outward by mutual electromagnetic force, resulting in a large amount of radiated heat and poor thermal efficiency. Also, the arc bending causes the furnace wall to be locally damaged. . Further, there is a problem that not only the amount of electrode consumption is large, but also noise is large and flicker is severe. On the other hand, the DC electric furnace has a small number of electrodes, so the area around the electrode above the furnace is simpler, and compared to the AC electric furnace, it has the advantage of being expected to reduce the basic unit of graphite electrode, the basic unit of electric power, and the flicker. However, there is a problem in the life of the bottom electrode.

For the bottom electrode of a DC electric furnace, for example, a report entitled "Current State and Future of DC Arc Furnace" published by Japan Industrial Reactor Association, Industrial Heating Furnace, vol.25 (1988), No.2, P24-33 As stated in the text, a small-diameter multi-electrode system in which a large number of small-diameter electrodes are embedded vertically in a refractory lined in the furnace bottom, and one to three large-diameter electrode rods are arranged upright. A large-diameter electrode system to be installed is known.

FIG. 5 is a schematic sectional view of the DC electric furnace, and the furnace body 10 is a furnace lid.
12, a furnace wall 14, and a furnace bottom 16, graphite electrodes 18 are inserted through the furnace lid 12, and a plurality of furnace bottom electrodes 30 made of steel rods are embedded in the furnace bottom 16 and the furnace The body 10 can be tilted left and right by a tilting device (not shown) such as a hydraulic cylinder.

The furnace bottom electrode 30 is embedded with a refractory lined in the furnace bottom 16 such as a large number of steel round bars of 50 to 200, and is embedded upright, and these furnace bottom electrodes 30 form the anode of the electrode circuit, A graphite electrode 18 protruding from the furnace lid 12 faces this anode as a cathode. In the case of this method, the maximum diameter of the bottom electrode 30 is 50 mmφ.

A stamp material is placed around the furnace bottom electrode 30, and the upper end surface of the furnace bottom electrode 30 is exposed on the upper surface of the stamp material,
Further, the lower end reaches a cooling plate 32 which is provided outside the furnace so as to be separated from the furnace bottom 16, and the furnace bottom electrode 30 is cooled by supplying cooling air from an air cooling pipe 34 connected to the cooling plate 32. It is supposed to do.

As the furnace bottom electrode 30, in addition to the small-diameter multi-electrode system shown in FIG. 5, for example, a large-diameter steel round bar 30 is provided on the same circumference equidistant from the center of the furnace bottom 16 as shown in FIG. A large-diameter electrode system in which, for example, three electrodes are arranged at a pitch equal to 1 is also adopted. The furnace bottom electrode 30 is exposed on the upper surface of the molded refractory, and the lower end is projected from the furnace bottom 16 to the outside of the furnace, which is the same as the small-diameter multi-electrode system, but the furnace projected outside the furnace. A water cooling box 2 surrounding the bottom electrode 30 is provided, and cooling water is supplied from a water cooling pipe to cool the water. In the case of this method, the maximum diameter of the furnace bottom electrode 30 is 250 mmφ.

As mentioned above, in the small-diameter multi-electrode method, many bottom electrodes embedded in the refractory are air-cooled outside the furnace, and in the large-diameter electrode method, the bottom electrodes embedded in the refractory are cooled outside the furnace. Although cooled, the part of the refractory where the bottom electrode contacts the molten steel melts.

However, as long as there is a refractory, the melted portion of the bottom electrode is filled with molten steel and solidified, so that it does not wear out, but when the refractory decreases, the bottom electrode also wears. Therefore, a thermocouple is inserted in the bottom electrode, and it is necessary to replace the bottom electrode when a certain set temperature is reached.

By the way, conventionally, in order to replace the bottom electrode in a small-diameter multi-electrode type DC electric furnace, for example, the procedure shown in (a) to (h) of FIG. 3 has been performed.

First, as shown in (a) of FIG. 3, while blowing air into the furnace body 10 with an air blower 40, a worker entered the furnace to remove the noro / bare metal 42 adhering to the furnace wall and buried the furnace bottom electrode. Cut the surrounding metal 44. Then, as shown in (b), set the jack 46 on the bottom 48 and jack up the bottom 48 as shown in (c) to separate it from the furnace bottom, and then attach the bottom 48 to the wire 50 as shown in (d). And lift it out of the furnace.

Subsequently, the working pan 52 is taken into the furnace with the wire 50 and set in the void portion where the bottom 48 is removed as shown in (e), and the surrounding refractory material is broken and collected in the working pan 52. After collecting the surrounding refractories, stack the frame bricks 54 as shown in (f), and then insert a new bottom 4 with the furnace bottom electrode embedded as shown in (g).
8 is set, and finally, as shown in (h), if a stamp material is filled around the bottom 48 from the container 56, a series of replacement work of the furnace bottom electrodes is completed.

On the other hand, in order to replace the bottom electrode in a large-diameter electrode type direct current electric furnace, for example, as shown in FIG. 4, the furnace wall 12 and the bottom 16 have a connection structure that can be detached vertically as shown by the arrow, The furnace bottom 16 is separated from the furnace wall 12, only the furnace bottom 16 is moved offline, and the furnace bottom 16 (with a new electrode embedded) prepared in advance as an alternative is taken in and combined with the existing furnace wall 12. The method of updating is adopted.

<Problems to be Solved by the Invention> Among the above-mentioned conventional techniques, the former method of jacking up the bottom portion into the furnace is the one in which a worker enters the furnace to cut metal, dismantle bricks, stack bricks, and remove old electrodes. It is necessary to perform work such as removing and taking in a new electrode. It takes about 4 to 5 hours to cool the inside of the furnace and put it in the furnace by the workers, so that it takes a long time to replace the furnace bottom electrode as a whole. Also, even though the furnace is cooled, the work must be done in a high-temperature atmosphere, and the work must be done for about 10 minutes at most. Therefore, 3 to 4 teams must be formed in turns and a large number of workers are required. There was a problem to do.

In addition, the latter method of removing the bottom of the furnace not only increases the equipment cost because it is necessary to prepare the bottom of the furnace in advance, but also requires an extra large repair shop and temporary storage area, and also requires a large-scale transfer for handling. Equipment is required. In a 100-ton DC electric furnace, the bottom electrode part is about 2 to 3 tons at the most, but it reaches 150 tons and the whole heavy bottom is to be replaced. There was a problem that it took a long time of about the time.

The present invention has been made in view of the above-mentioned circumstances, and a furnace bottom electrode of a DC electric furnace capable of efficiently and promptly exchanging the furnace bottom electrode without a worker entering the furnace by a relatively small device. The purpose is to provide a switching device.

<Means for Solving the Problems> The present invention for achieving the above-described object is to provide a dolly having a vertically movable pedestal on an upper end portion of a short cylindrical member having a size surrounding a furnace bottom electrode portion. An electrode puller equipped with connecting fittings and a plurality of hydraulic jacks mounted on a flange projecting on the outer circumference of the lower end is installed, and a stopper that fixes the connecting fittings provided on the upper end of the short cylindrical member to the bottom electrode of the furnace A bottom electrode of a DC electric furnace, characterized in that the bottom electrode is connected to a metal fitting, and the plurality of hydraulic jacks are brought into contact with and pressed against the bottom surface of the bottom of the furnace to pull the bottom electrode out of the furnace. It is an exchange device.

<Example> Hereinafter, an example of the present invention will be described with reference to the drawings. In FIG. 1, the case of using a steel receiving cart on which a steel receiving pot is placed and which receives molten steel from the DC electric furnace for replacement of the bottom electrode, will be described, but a dedicated cart may be used.

In FIG. 1, reference numeral 10 denotes a furnace body in which three large-diameter furnace bottom electrodes 30 are embedded in a furnace bottom 16, and a molded refractory 28 formed in a tapered shape around the bottom 30 of the furnace bottom electrode 30. The refractory bricks 29 are piled up around the molded refractory 28. In addition,
Reference numeral 16a denotes an iron shell of the bottom 16 of the furnace, and 11 denotes a metal stopper provided on the bottom surface of the electrode bottom 13 including the bottom electrode 30, the molded refractory 28, the water cooling box 2 and the like.

At the center of the steel receiving cart 1, there is a receiving stand 4 by means of a lifting cylinder 3.
Is supported so that it can be raised and lowered, and a work deck 5 is arranged around the pedestal 4 which is supported so that it can be raised and lowered. On the pedestal 4, as shown in detail in FIG. 2, a short cylindrical member 6 having a size surrounding the furnace bottom electrode 30 and a cylindrical member 6 are provided.
Flange-shaped connection fitting 7 provided on the outer periphery of the upper end of the cylindrical member 6, a flange 8 protruding on the outer periphery of the lower end of the cylindrical member 6, and a plurality of hydraulic jacks (4 in the drawing) arranged on the flange 8.
Table) and an electrode pulling machine 20 consisting of A hydraulic pipe (not shown) is connected to each hydraulic jack 9 so that pressurized oil can be supplied or discharged. Reference numeral 22 is a wheel of the steel receiving cart, and 15 is a bolt hole provided in the connection fitting 7.

Next, the operation of the device of the present invention will be described. The electrode pulling machine 20 is mounted on the steel receiving cart 1 to prepare for removing the bottom electrode 30 of the DC electric furnace. When the preparation is completed, the steel receiving cart 1 is placed on the bottom of the furnace.
It is stopped below 16 and the worker removes the cable connected to the bottom electrode 30 from the work deck 5, the cooling pipe connected to the water cooling box, and the thermometer cable.

When these preliminary operations are completed, the bolt 17 is screwed into the fastener 11 provided on the bottom surface of the electrode bottom 13 from the bolt hole 15 of the fastener 7 provided at the upper end of the short cylindrical member 6 to connect the fastener 7 and the fastener. Connecting. The connecting means is not limited to the bolt, and other means such as a cotter may be used. Thus, when the fixing of the electrode extractor 20 and the electrode bottom 13 is completed, the hydraulic jack 9 is actuated and the upper end of the hydraulic jack 9 is brought into contact with and pressed by the iron shell 16a on the bottom of the furnace. 28 is separated from the refractory brick 30 and the electrode bottom 13 including the furnace bottom electrode 30 is pulled out of the furnace.

When the removal of the electrode bottom 13 is completed, the peeled surface of the refractory 30 is repaired and repaired, the electrode bottom 13 with the new furnace bottom electrode 30 embedded therein is carried in by the steel receiving cart 1, and the work table 5 is operated. When the worker fixes the electrode bottom 13 on the pedestal 4 by the stationary fixing means fitted in the set portion of the furnace bottom 16, and finishes the periphery of the electrode bottom 13, the replacement of the furnace bottom electrode 30 is completed.

<Effects of the Invention> As described above, according to the present invention, the furnace bottom electrode can be replaced efficiently and quickly by a relatively simple device without entering the furnace. And the operating rate of the DC electric furnace is improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a furnace bottom electrode exchanging device of the present invention, FIG. 2 is a perspective view showing a part of an electrode extracting machine of the furnace bottom electrode device of the present invention, and FIG. 3 is a conventional furnace. FIG. 4 is an explanatory view showing an example of a bottom electrode exchange procedure, FIG. 4 is an explanatory view showing a conventional means for exchanging a large-diameter electrode type furnace bottom electrode, and FIG. FIG. 1 ... Steel receiving cart, 2 ... Water cooling box, 3 ... Lifting cylinder,
4 ... pedestal, 5 ... work deck, 6 ... short cylindrical member, 7 ... connection fitting, 8 ... flange, 9 ... hydraulic jack, 11 ... stop fitting, 13 ... electrode bottom, 15 …… Bolt hole, 16 …… Bottom of furnace, 18 …… Graphite electrode, 20 …… Electrode drawing machine.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kiyoshi Takahashi, Kiyoshi Takahashi, 1-chome, Mizushima Kawasaki-dori, Kurashiki-shi, Okayama (no address), inside the Mizushima Works, Kawasaki Steel Co., Ltd. (56) References )

Claims (1)

[Claims] 1. A trolley having a pedestal that can be raised and lowered is provided with a connecting metal fitting on the upper end of a short cylindrical member having a size surrounding the furnace bottom electrode part, and a plurality of flanges are provided on the outer periphery of the lower end. Is equipped with an electrode extractor equipped with a hydraulic jack, and the connecting metal fittings provided on the upper end of the short cylindrical member are connected to a metal fitting fixed to the furnace bottom electrode, and the plurality of hydraulic jacks are connected to the furnace bottom. A furnace bottom electrode exchanging device for a DC electric furnace, wherein the furnace bottom electrode is constructed so that the furnace bottom electrode is pulled out of the furnace by coming into contact with and pressing the bottom surface.