JPH0961065A - Dc arc furnace with scrap preheating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To melt scrap within a short period of time and make a uniform steel melting temperature and uniform substances. SOLUTION: In a DC arc furnace in which a furnace bottom electrode and one electrode rod 6 inserted into a furnace body through a furnace lid are connected to a DC power supply device 10 through an electrical conductor, the furnace lid is provided with a scrap feeding port 14 at a position opposite to the DC power supply device 10 while the electrode rod 6 being held therebetween. Then, a shaft type scrap preheating device 20 is installed above the scrap feeding port 14, and then DC electromagnets 31, 41 having electrodes at positions where both sides of the electrode rod 6 as viewed from above are held are arranged at a lower part of the furnace body under a state in which the magnetic poles are placed at a lower part and/or a bottom part of a side wall of the furnace body, and magnetic pole center lines 35, 45 of each of the DC electromagnets connecting both opposite magnetic poles are crossed at a right angle as viewed from above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC arc furnace equipped with a scrap preheating device for obtaining molten metal from scrap as a main melting raw material, and more particularly to a DC arc furnace equipped with a shaft type scrap preheating device.

[0002]

2. Description of the Related Art An arc furnace equipped with a shaft type preheating device that preheats scrap in a shaft into a furnace body by utilizing high temperature exhaust gas from the arc furnace is disclosed in Japanese Patent Laid-Open Publication No. 3-505625. There is an arc furnace (AC arc furnace).

However, in this furnace, the shaft type preheating device avoids interference with the electrode rod penetrating the furnace lid.
Scrap provided at a position apart from the electrode rod and charged into the furnace from the preheating device is deposited at a position largely offset from the electrode rod to one side wall side of the furnace body. For this reason, the melting of scrap in the furnace does not proceed uniformly, and unmelted residue occurs, so it takes a long time to melt, and in some cases a troublesome oxygen cutting operation is required, and the furnace wall on the side where scrap is not accumulated locally It is easily damaged. In addition, since molten steel is not affected by the reflux effect and the degree of reflux is low, it takes time to melt scrap, and when alloy is added, it takes time to homogenize its components, resulting in poor productivity. It was These phenomena and problems similarly occur when the above-mentioned shaft type preheating device is combined with a DC arc furnace having one electrode rod penetrating the furnace lid.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art. The scrap can be melted in a short time in a state where there is no unmelted residue, and the temperature and composition of each part of the molten steel can be made uniform. The present invention aims to provide a DC arc furnace with a scrap preheater that has high productivity.

[0005]

A DC arc furnace with a scrap preheating device according to the present invention penetrates a furnace bottom electrode provided at the bottom of the furnace body and a furnace lid covered by the furnace body into the furnace body. In a DC arc furnace in which the inserted one electrode rod is connected to a DC power supply device via a conductor, the furnace lid is
A scrap charging port is provided at a position opposite to the DC power supply device across the electrode rod, and a shaft type scrap preheating device connected to an exhaust device with a scrap charging port at the upper part is provided above the scrap charging port. At the bottom of the furnace body, two DC electromagnets having magnetic poles at positions sandwiching the electrode rod from both sides when viewed from above are provided, and the magnetic poles are made to face the lower side wall and / or the bottom portion of the side wall of the furnace body. Arranged so that the center lines of the magnetic poles of the DC electromagnets that connect the opposing magnetic poles are crossed when viewed from above, and these DC electromagnets are connected to the DC power supply device for electromagnets whose polarity and current amount are variable. Is characterized by.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIGS. In the figure, 1 is a furnace body, 2 is a tapping hole projecting to the lower side of the furnace body 1, 3 is a slag discharge port, and the furnace body 1 is a horizontal axis line and a tapping port 2 moves up and down. It is tilt-driven by a tilting device (not shown).
Reference numeral 4 denotes a furnace lid that covers the furnace body 1 and that can be opened and closed. Reference numeral 5 is a furnace bottom electrode provided at the bottom of the furnace body 1, and 6 is an electrode rod which penetrates through the furnace lid 4 and is inserted into the furnace body 1 at a lower portion thereof almost directly above the furnace bottom electrode 5. It is gripped by a gripper 7 driven by a lifting / lowering device.

Reference numeral 10 is a DC power supply device provided in a transformer chamber 11 arranged on the side of the furnace body 1, and includes a furnace transformer and a rectifier (not shown). 12 is this DC power supply device 10
Is a lower conductor that connects the furnace bottom electrode 5 and 13 is an upper conductor that similarly connects the DC power supply device 10 and the electrode rod 6 (specifically, the gripper 7). Then, in the furnace lid 4, at a position opposite to the DC power supply device across the electrode rod 6, that is, at a position opposite to the upper conductor 13 and the lower conductor 12 reaching the DC power supply device 10, a scrap charging port is provided. 14 is provided as close as possible to the electrode rod 6.

At the upper part of the scrap charging port 14, the scrap discharging port 22 at the lower end of the tower body 21 is made to face the scrap charging port 14, and the shaft type scrap preheating device 2 is provided.
0 is set. A scrap inlet 24 having an openable / closable lid 23 is provided at the upper end of the tower body 21, and an exhaust port 25 provided on the side wall of the tower body 21 is connected to an exhaust device (not shown).

The tower body 21 is in the shape of a bent rectangular tube, and 26a
Is a scrap bearing portion 26b provided in a stepped shape below
Is a scrap lower bearing portion provided below the scrap. Scraps stored on the scrap bearing part 26 and preheated by the exhaust gas by the pushing devices 29a and 29b that reciprocally drive the extruded bodies 27a and 27b supported along the upper surface of each of the bearing parts by the cylinders 28a and 28b. S is intermittently supplied through the scrap discharge port 22 into the scrap input port 14.

On the other hand, two DC electromagnets 31, 41 are provided in the lower portion of the furnace body 1. The DC electromagnets 31 and 41 are
The coils 33 and 43 are wound around the magnetic cores 32 and 42, and the coils are connected to the electromagnet DC power supply devices 34 and 44.
This DC power supply device has a transformer (not shown), a rectifier, and a switch, and has a variable polarity (positive / negative) and a supply current amount. The DC electromagnet 31 has magnetic poles 32a and 32b formed at both ends of the magnetic core 32 at a position sandwiching the electrode rod 6 (and therefore the furnace bottom electrode 5) from both sides when viewed from above, that is, in a plan view. Magnetic pole 32a
The magnetic pole 32b faces the bottom of the furnace body 1 with a small gap.

Similarly, the DC electromagnet 41, when viewed from above,
That is, in the plan view, magnetic poles 42a and 42b formed at both ends of the magnetic core 42 are provided at positions sandwiching the electrode rod 6 (and hence the furnace bottom electrode 5) from both sides. The magnetic poles 42a and 42b are the DC electromagnet 31. At a position different from the above, a small amount of space is made to face the bottom of the furnace body 1. The magnetic pole center line 35 connecting the facing magnetic poles 32 a and 32 b of the DC electromagnet 31 and the facing magnetic poles 42 of the DC electromagnet 41.
The magnetic pole center line 45 connecting a and 42b is seen from above,
That is, in the plan view, there is a mutual relationship in which the central portion of the electrode rod 6 (and therefore the furnace bottom electrode 5) intersects at a predetermined angle α.

Next, the operation of the DC arc furnace 50 with a scrap preheating device having the above structure will be described. First, the scrap S preheated by the exhaust gas flow in the shaft type scrap preheating device 20 (scrap at room temperature at the start of melting operation) is
When the scrap S is supplied into the furnace body 1 through the scrap input port 14, the scrap S is intensively charged in the lower position of the scrap input port 14 and a large amount is accumulated in the lower position. 2 and 4, this scrap S
Is not shown.

Therefore, the DC power supply device 10 is used for the bottom electrode 5 of the furnace.
If a DC voltage is applied between the electrode and the electrode rod 6 to generate an arc 51, the DC power supply 10 causes the lower conductor 12 and the furnace bottom electrode 5 (in addition to this when molten steel 52 exists at the furnace bottom). A magnetic flux B ₀ is generated in the vicinity of the arc 51 in the furnace body 1 as shown in FIG. 2 due to a current flowing through the power supply circuit 53 that reaches the DC power supply device 10 via the molten steel 52), the electrode rod 6, and the upper conductor 13, and this magnetic flux B ₀ is generated. arc 51 flowing B in ₀ by the arc current and the magnetic flux B _0, deflected on the opposite side the scrap inlet 14 side of the DC power supply 10 as shown by receiving electromagnetic force F ₀ according to the Fleming's left-hand rule At the same time, the molten steel 52 through which the arc current flows also receives the electromagnetic force F ₀ and is driven in the direction of the electromagnetic force, and the reflux action of the molten steel is obtained. The deflected arc 51 heats and melts a large amount of the scrap deposit portion below the scrap input port 14 disposed on the deflecting side, and the undissolved scrap S in the deposit portion.
Is the arc wall 51 and the furnace wall 1 on the opening side of the scrap charging port 14.
It is interposed between a and a to prevent the furnace wall from overheating.

In this way, first, the scrap inlet 14 is
By disposing the electrode rod 6 at a position opposite to the DC power supply device 10 by sandwiching it, the self-deflection of the arc 51 by the current flowing through the power feeding circuit 53 is effectively utilized, and the deflected arc 51 lowers the scrap inlet 14 below. Since the scrap deposition part of is melted by heating, no other energy for arc deflection is required when a good melting rate can be obtained only by the above deflection, and the arc deflection is also performed when the following additional deflection is performed. It requires less energy for.

On the other hand, the arc deflection direction due to the above arc current is limited to the center line 14a of the scrap inlet 14, and the deflection amount is determined by the arc current, which is determined by the melting condition of the scrap.
The amount of deflection cannot be adjusted arbitrarily. Therefore,
Larger arc 51 depending on the amount of scrap S deposited
Or deflect the arc 5 in the left-right direction in FIG.
In the case of deflecting 1, the DC electromagnet 31,
Additional deflection of the arc 51 is performed using 41 as follows.

That is, when a DC current is applied to the coil 33 of the DC electromagnet 31 by the electromagnet DC power supply 34, the magnetic pole 32a (N pole in FIG. 2) and the magnetic pole 32b (S in FIG. 2).
A magnetic flux B ₁ is generated between the magnetic pole 42a and the magnetic pole 42a. Similarly, when a direct current is applied to the DC electromagnet 41 by the electromagnet DC power supply device 44, the magnetic pole 42a (N pole in FIG. 2) and the magnetic pole 42b (S pole in FIG. 2)
And a magnetic flux B ₂ is generated between them and the magnetic flux B ₃ is generated near the arc 51. Thereby, the arc 51 receives the electromagnetic force F ₃ in accordance with the similar to Fleming's left hand rule by the synthetic magnetic flux B _3, deflected in the direction of the electric force F _3, the molten steel is also driven in the same direction.

During the arc discharge, the above-mentioned power supply circuit 53 is provided.
Since the electromagnetic force F ₀ is generated due to the conductor arrangement, the arc 51 eventually receives the combined electromagnetic force F of the electromagnetic forces F ₃ and F ₀ and is deflected in the combined electromagnetic force direction, and the molten steel 52 also moves in the same direction. Driven. The combined electromagnetic force F can also be referred to as an electromagnetic force generated by the total combined magnetic flux of the magnetic flux B ₀ and the combined magnetic flux B ₃ .

By adjusting the polarity and the amount of the DC current supplied to the DC electromagnets 31 and 41 in this manner, the direction and magnitude of the combined electromagnetic force F can be freely changed, and the arc 51 can be directed in a desired direction. Deflect the desired amount to
The scrap S can be efficiently melted in a short time in a state where there is no unmelted residue, and since the molten steel 52 is refluxed in the scrap direction, the melting of the scrap is promoted, the temperature of each portion of the molten steel is made uniform, and the alloy is added. In this case, the molten steel components are made uniform, and the refining reaction between the molten steel and the slag is promoted.

Next, during the temperature rising period when the melting of the scrap S is completed and the molten steel surface becomes flat, the electromagnetic force F ₀ determined by the conductor arrangement of the power feeding circuit 53 and the arc current value.
As a result, the arc 51 may be largely deflected toward the scrap charging port 14 side to locally damage the furnace wall 1a.
At that time, as shown in FIG. 4, the amount and polarity of the current supplied to the DC electromagnets 31 and 41 are adjusted to generate a composite magnetic flux B ₃ having substantially the same magnitude as the magnetic flux B ₀ but in the opposite direction. _If an electromagnetic force F ₃ having substantially the same magnitude as ₀ and in the opposite direction is generated, the arc 51 is formed substantially directly below (vertically) the electrode rod 6 without being deflected. Local damage can be prevented.

Further, when the molten slag on the molten steel 52 is discharged prior to the tapping after melting, by directing the synthetic electromagnetic force F ₃ toward the slag discharge port 3, a molten steel flow driven in that direction is used. The discharge of the molten slag can be promoted, and the slag discharge time can be shortened.

Next, FIG. 5 shows another embodiment of the present invention, which has the same structure as the above embodiment except that the type of the shaft type scrap preheating device 60 is different.
The same parts as those of the above are denoted by the same reference numerals, and detailed description thereof will be omitted. The tower body 61 of the shaft-type scrap preheating device 60 has a straight cylindrical shape, and has a gate 62 that is a blocking member that can be opened and closed at the bottom. The gate 62 is a rotating shaft 63 arranged along the side wall of the tower which extends in the horizontal direction and extends in the horizontal direction.
In addition, a pair of forks 65, 65 in which heat-resistant steel fingers 64 are fixed in parallel at a small interval are opened and closed by a fork drive device (not shown) that rotationally drives the rotary shaft 63. Have. Then, as shown by the solid line, with the fingers 64 protruding into the tower 61 so that they are substantially horizontal, the scrap S is retained and preheated by the exhaust gas flow, and tilted downward as shown by the chain line 66. As a result, a desired amount of preheated scrap S is charged into the furnace from the scrap charging port 14.

A DC arc furnace 7 with a scrap preheater equipped with this shaft type scrap preheater 60
Even at 0, the same action as that of the above-described embodiment can be obtained as the deflection action of the arc 51 and the reflux action of the molten steel 52 with respect to the scrap S charged into the furnace.

The present invention is not limited to the above-described embodiments. For example, as a shaft type scrap preheating device, the scrap lower bearing portion 26b and the extruding device 29b in FIG. 1 are omitted, and the tilt type scrap preheating device in FIG. With a plurality of gates 62 vertically arranged, instead of the tilting type gate 62, a grate type shutter is used to open and close the door in a sliding door system, or the gate is omitted and the gate is omitted. Other types of devices other than the above may be used, such as a device in which the lower end of the column body is directly opened to the scrap charging port 14.

Depending on the size and shape of the furnace body, the magnetic poles of the DC electromagnet may be arranged so as to face the lower side wall of the furnace body or the lower side wall and the bottom of the furnace body.
Further, the tip end of the magnetic pole may be inserted or embedded in the wall body forming the side wall and the bottom of the furnace body 1 so as not to penetrate the wall body. Furthermore, the magnetic core of the DC electromagnet may be configured to pass through a position other than below the bottom of the furnace, such as outside the side wall of the furnace body.

[0025]

As described above, according to the present invention,
By adjusting the polarity and the amount of direct current supplied to the DC electromagnet, the arc can be deflected in the desired direction by the desired amount, and in large furnaces, scrap from the preheater accumulates extensively in the furnace. Even if you do, you can efficiently dissolve the scrap in a short time without leaving any residue,
Further, after the scrap is melted, the arc is formed in the direction directly below the electrode rod, whereby local damage on the furnace wall can be prevented. In addition, as the molten steel is circulated in the scrap direction by the electromagnetic force as the arc is deflected, the melting of the scrap is promoted, the temperature of each molten steel and the molten steel components when alloys are added are homogenized, and the refining between the molten steel and the slag is performed. The reaction is accelerated, and the productivity is improved in combination with the above rapid dissolution.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a DC arc furnace with a scrap preheating device showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG. 2;

FIG. 4 is a cross-sectional view taken along the line AA of FIG. 1 showing a state in which an arc is formed immediately below an electrode rod.

FIG. 5 is a view corresponding to FIG. 1 showing another embodiment of the present invention.

[Explanation of symbols]

1 ... Furnace body, 4 ... Furnace lid, 5 ... Furnace bottom electrode, 6 ... Electrode rod, 10
... DC power supply device, 12 ... lower conductor, 13 ... upper conductor, 1
4 ... scrap input port, 20 ... shaft type scrap preheating device, 21 ... tower body, 24 ... scrap charging port, 25 ...
Exhaust port, 31 ... DC electromagnet, 32 ... Magnetic core, 32a ... Magnetic pole, 32b ... Magnetic pole, 34 ... DC power supply device for electromagnet, 35
... magnetic pole center line, 41 ... DC electromagnet, 42 ... magnetic core, 42a
... magnetic pole, 42b ... magnetic pole, 44 ... DC power supply device for electromagnet,
45 ... Magnetic pole center line, 50 ... DC arc furnace with scrap preheating device, 60 ... Shaft type scrap preheating device, 61
… Tower, 62… Gate, 70… DC arc furnace with scrap preheater.

Claims (1)

[Claims] 1. A furnace bottom electrode provided at the bottom of a furnace body and a single electrode rod inserted into the furnace body through a furnace lid covered with the furnace body are connected to a direct current through a conductor. In a DC arc furnace connected to a power supply device, a scrap charging port is provided on the furnace lid at a position opposite to the DC power supply device with the electrode rod sandwiched between them, and a scrap charging port is provided on the upper part to connect to an exhaust device. The shaft type scrap preheating device described above is provided at the upper part of the scrap charging port, and two DC electromagnets having magnetic poles at positions sandwiching the electrode rod from both sides when viewed from above are provided at the lower part of the furnace body. The direct current electromagnets are arranged in such a manner that the magnetic poles are exposed to the lower part and / or the bottom part of the side wall of the furnace body and the center lines of the direct current electromagnets connecting the opposite magnetic poles are crossed when viewed from above, and these direct current electromagnets are provided, Polar and electric respectively A DC arc furnace with a scrap preheating device, characterized by being connected to a DC power supply device for a variable flow electromagnet.