JPH0710236Y2 - Bottom structure of DC electric furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention relates to a bottom structure 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. 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 furnaces" published by Japan Industrial Reactor Association, Industrial Heating Furnace, vol.25 (1988), No.2, P24-33 As stated in the text, small-diameter multi-electrode system (GHH system) in which a large number of small-diameter electrodes are embedded upright in a refractory lining the furnace bottom.
Also, there is known a large-diameter electrode system (CLEC system) in which one to three large-diameter electrode rods are arranged upright.

FIG. 7 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 upright in a refractory lined in the furnace bottom 16 such as a large number of steel rods of 50 to 200, 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. 7, as shown in FIG. 6, for example, a large-diameter steel round bar is placed on the same circumference equidistant from the center of the furnace bottom 16. A large-diameter electrode system in which, for example, three electrodes are arranged at equal pitches 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 the small-diameter multi-electrode type DC electric furnace, for example, the procedure shown in (a) to (h) of FIG. 6 has been performed.

First, as shown in FIG. 5 (a), while blowing air into the furnace body 10 by an air blower 40, a worker entered the furnace to remove the slag / metal 42 adhered to the furnace wall and buried the furnace bottom electrode. Cut the surrounding metal 44. Then, after setting the jack 46 on the bottom 8 as shown in (b) and jacking up the bottom 8 as shown in (c) to separate it from the furnace bottom,
As shown in (d), the bottom 8 is lifted by the wire 50 and carried out of the furnace.

Continue to take the working pan 52 into the furnace with the wire 50 (e)
As shown in (4), the bottom 8 is set in the void, and the refractory around it is broken and collected in the working pan 52. After collecting the surrounding refractories, stack the frame bricks 54 as shown in (f), set a new bottom 8 with the furnace bottom electrode embedded as shown in (g), and finally show in (h). When the stamp material is filled from the container 56 around the bottom 8 in this manner, 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. 6, the furnace wall 12 and the bottom 16 have a connection structure that can be detached vertically as shown by arrows. 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 part 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 the structure of the bottom of a direct current electric furnace is capable of efficiently and quickly exchanging the bottom electrode without a worker entering the furnace with a relatively small device. It is intended to provide.

<Means for Solving the Problems> The present invention for achieving the above-mentioned object is provided in the bottom opening of a DC electric furnace in which a bottom including a bottom electrode is attached to the bottom opening. The bottom edge of the bottom plate is brought into contact with the reinforcing flange from below and the bottom is attached to the bottom of the furnace by the fastening means, and the bottom of the bottom opening is provided between the seat provided on the bottom iron shell and the periphery of the bottom plate. A furnace bottom structure of a DC electric furnace, characterized in that a separating jack for separating the bottom can be arranged.

A bottom, a spring-loaded bolt, or a latching device can be used as the fastening means.

<Embodiment> Hereinafter, the configuration and operation of the present invention will be described in detail based on an embodiment.

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. The bottom 8 is composed of a furnace bottom electrode 30, a molded refractory 28, a water cooling box 2 and a bottom plate 11 supporting these. A seat 13a is provided on the iron skin 16a of the furnace bottom 16.
A separation jack 6 is arranged on the seat 13b of the bottom plate 11 corresponding to 13a. The jack 6 is preferably a small, portable type and is easy to handle.

Further, the reinforcing flange 4 is provided in the furnace bottom opening 15 provided in the iron shell 16a of the furnace bottom 16 to prevent the strength from being reduced, and the reinforcing flange 4, the bottom plate 11 and the bolt 17 are fastened together. Although the bottom 8 is supported by the bottom plate 11, it is preferable to reinforce by attaching a flange 19 and ribs 20 and 20 'as shown in FIGS. Further, it is preferable to tighten the bolt 17 via the spring 21 because a stable tightening force can be secured even if the bolt 17 is deformed to some extent due to thermal deformation or the like.

The operation of replacing the bottom of the above-described structure of the bottom of the DC electric furnace will be described with reference to FIG. In FIG. 1, a case where a steel receiving pan for receiving molten steel from a DC electric furnace is used for exchanging the bottom including the bottom electrode will be described below. Good.

A bottom pedestal 23 is movably supported by an elevating cylinder 3 at the center of the steel receiving cart 1, and a work deck 5 is arranged around the bottom pedestal 23 which is movably supported. . The bottom pedestal 23 is provided with a support member 23a that supports the portion of the bottom plate 11 when the bottom 8 is separated. Reference numeral 22 denotes a wheel of the steel receiving cart 1.

Next, the operation of the device of the present invention will be described. A bottom pedestal 23 is mounted on the steel receiving cart 1 to prepare for removal of the bottom electrode 30 of the DC electric furnace together with the bottom 8. When the preparation is completed, the steel receiving cart 1 is stopped below the furnace bottom 16, and a cable is connected from the work deck 5 to the furnace bottom electrode 30 by a worker or a cooling pipe connected to the water cooling box 2. Removes the thermometer cable and arranges the portable jack 6 on the pedestal 13b of the bottom plate 11 corresponding to the plurality of seats 13a provided on the bottom iron shell 16. Needless to say, a hydraulic pipe (not shown) for supplying or discharging pressure oil is connected to each jack 6.

After the completion of these preliminary operations, first, the bolts 17 that fasten the reinforcing flange 4 provided on the furnace bottom iron skin 16a and the bottom plate 11 of the bottom 8 are removed. Thus, when the work of removing the bolt 17 is completed, the detaching jack 6 is operated so that the upper end of the jack 6 is attached to the iron shell of the furnace bottom 16.
When it abuts against the seat 13a provided on 16a and presses it, the shaped refractory 28 having a taper that spreads downward is separated from the refractory brick 30, and the electrode bottom 8 including the furnace bottom electrode 30 moves out of the furnace bottom opening 15 to outside the furnace. It is pulled out.

When the removal of the bottom 8 is completed, the peeled surface of the refractory 30 is repaired and repaired, and the bottom 8 with the new bottom electrode 30 embedded
Is carried in by the steel receiving trolley 1, and the worker fits the bottom 8 on the pedestal 23 on the workbench 5 into the furnace bottom opening 15 of the furnace bottom 16, and then the reinforcing flange 4 provided on the furnace bottom iron shell 16a. And bottom plate 11
The bolts 17 are fastened and fixed together, and subsequently, the joint surface of the molded refractory 28 and the refractory brick 29 is filled with mortar or the like to complete the replacement of the bottom 30.

FIG. 4 shows the structure of the bottom of another DC electric furnace according to the present invention, in which a reinforcing flange 4 is provided on the bottom iron shell 16a and a flange or rib is provided on the bottom plate 11 on the bottom side for reinforcement. The description is omitted because it is the same as the above-mentioned embodiment, but the fourth embodiment
In the embodiment shown in the drawing, instead of using bolts, the outer peripheral edge of the bottom plate 11 is fastened to the furnace bottom iron skin 16a at a plurality of locations using latching devices 24.

In FIG. 4, the same parts as those in the embodiment shown in FIG. A swing bracket 27 is supported by a pin 26 on a support bracket 25 provided on the bottom plate 11, and the swing bolt 27 has a spherical washer 31 and a nut.
35 is attached, and the bottom plate 11 is provided with a guide bracket 36 having an inclined surface.

On the other hand, a joint support bracket 7 is provided on the bottom iron shell 16a, and a joint 9 is attached to the joint support bracket 7 with its position adjustable by an adjusting screw 37 provided at one end. Further, a link 39 is swingably attached to the other end of the joint 9 via a link pin 38. The link 39 is provided with a loose hole 41 for allowing the swing bolt 27 to pass through loosely. A spherical seat 43 is formed at one end of the loose hole 41 and a roller 47 is attached.

Next, the operation of the latching device of the present invention will be described. Note that the related work with the steel receiving cart 1 that conveys the bottom 8 and the preparatory work are the same as those in the above-described embodiment, and therefore will be omitted.

When the bottom 8 is normally attached to the iron bottom 16a of the furnace bottom, the swing bolt 27 is passed through the loose hole 41 formed in the link 39 as shown by the solid line, and the spherical washer 43 is brought into contact with the spherical seat 43 of the link 39 and the nut is attached. The bottom plate 11 is attached to the furnace bottom iron skin 16a by tightening 5 and moving the roller 47 provided on the link 39 along the inclined surface of the guide bracket 36.

At this time, the contact position between the roller 47 provided on the link 39 and the guide bracket 36 can be adjusted by adjusting the screw position of the adjusting screw 37. At that time, even if the contact position changes, the spherical washer 31 links. Since the spherical seats 43 of 39 are in spherical contact with each other, the nut 35 can be tightened smoothly. As shown in FIG. 4, a jack 6 is arranged on the peripheral edge of the bottom plate 11 of the bottom 8 at a position offset from the latching device 24 in the circumferential direction.

When disconnecting the bottom 8 from the furnace bottom opening 15, first loosen the nut 35 and remove the nut 35 together with the spherical seat 43.
When the swing bolt 27 is removed from the loose hole 41 by rotating the link 39 using the link pin 38 as a fulcrum, the swing bolt 27 and the ring 39 are respectively pin 26 as shown by the chain line.
And it will be in the state of hanging through the ring pin 38,
The fastening state is released.

Subsequently, as shown in FIG. 4, the plurality of separating jacks 6 arranged on the peripheral portion of the bottom plate 11 are operated to separate the molded refractory 28 and the refractory brick 29 from the joint, and the bottom 8 is opened at the bottom of the furnace. It is taken out from the part 15. The new bottom 8 can be attached in the reverse order of the above case.

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

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an embodiment of the bottom structure of a DC electric furnace of the present invention, FIG. 2 is a vertical cross-sectional view showing an enlarged main part of FIG. 1, and FIG. 3 is FIG. FIG. 4 is a plan view showing an AA arrow of FIG. 4, FIG. 4 is a longitudinal sectional view showing a latching device fastening portion according to another embodiment of the furnace bottom structure of the present invention, and FIG. 5 is a conventional furnace bottom electrode replacement. FIG. 6 is an explanatory view showing an example of a procedure, FIG. 6 is an explanatory view showing a conventional large-diameter electrode type furnace bottom electrode replacement means, and FIG.
The figure is a schematic cross-sectional view showing a furnace bottom electrode structure of a small diameter multi-electrode system. 1 ... Steel receiving cart, 2 ... Water cooling box, 3 ... Lifting cylinder,
4 ... Reinforcing flange, 5 ... Deck, 6 ... Separation jack, 7 ... Latch support bracket, 8 ... Bottom, 9
...... Joint, 10 …… Furnace body, 11 …… Bottom plate,
12 …… furnace lid, 13 …… jack cradle, 14 …… furnace lid, 15 ……
Opening of the bottom of the furnace, 16 ...... Bottom of the furnace, 17 ...... Bolt, 18 ...... Graphite electrode, 19 ...... Flange, 20 ...... Rib, 21 ...... Spring, 22 ......
Wheels, 23 ... bottom cradle, 24 ... latching device,
25 …… Support bracket, 26 …… Pin, 27 …… Swing bolt, 28 …… Molded refractory, 29 …… Refractory brick, 30 …… Bottom electrode, 31 …… Spherical washer, 32 …… Cooling board, 34 ...... Air cooling tube, 35 ...... nut, 36 …… guide bracket, 37 …… adjustment screw, 38 …… link pin, 39 …… link, 41 …… loose hole, 43 …… spherical seat, 45 …… jack receiver Flange, 47 ...
…roller.

Claims (3)

[Scope of utility model registration request] 1. In a furnace bottom structure of a DC electric furnace in which a bottom including a furnace bottom electrode is attached to a furnace bottom opening, a peripheral edge of a bottom plate is contacted from below with a reinforcing flange provided in the furnace bottom opening. The bottom is attached to the furnace bottom by the fastening means, and a separating jack for separating the bottom from the furnace bottom opening is arranged between the seat provided on the furnace bottom iron shell and the peripheral edge of the bottom plate. A bottom structure of a DC electric furnace characterized by the above. 2. The furnace bottom structure of a DC electric furnace according to claim 1, wherein the fastening means is a bottom or a bolt with a spring. 3. The furnace bottom structure of a DC electric furnace according to claim 1, wherein the fastening means is a latching device.