JP2004251530A - Arc melting furnace of cold iron source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the circumferential air from being sucked into a duct from a connecting part of a movable exhaust duct and a fixed exhaust duct, and stably sucking only the exhaust gas from as preheating shaft without sucking the air even during the tilting motion of a furnace. <P>SOLUTION: This arc melting furnace comprises a melting chamber, a preheating shaft directly connected to an upper part at one side of the melting chamber, the movable exhaust duct mounted on the preheating shaft, an arc electrode, a tapping part mounted in the melting chamber in a projected state and having a tapping port, and a tilting means for tilting the melting chamber to a tapping part side. The movable exhaust duct is connected to the fixed exhaust duct, and the tapping part is mounted in the direction different from the cold iron source supplying direction. The connecting part of the fixed exhaust duct and the movable exhaust duct coincides with a tilting rotation center axis of the melting chamber, and the movable exhaust duct is airtightly rotatable on the tilting rotation center axis, with respect to the fixed exhaust duct by an airtight joint. As the increase of the amount of exhaust gas caused by the air sucked from the connecting part of both ducts can not be found, the exhaust gas processing equipment can be miniaturized. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cold iron source arc melting furnace, and more particularly to a cold iron source arc melting furnace capable of sucking exhaust gas from a preheating shaft even when the melting chamber is tilted.
[0002]
[Prior art]
In recent years, due to resource and environmental problems, a process for melting a large amount of steel scrap using an arc furnace is increasing. In such an arc furnace, a large amount of electric power is consumed for melting the scrap, so the melting of the scrap is preheated with the exhaust gas generated from the furnace during melting, and the required electric power is reduced as much as possible. A furnace has been proposed.
[0003]
One of them is the arc melting furnace of Japanese Patent No. 3114713 (Patent Document 1). Hereinafter, the conventional arc melting furnace will be described with reference to the drawings.
[0004]
6 is a schematic perspective view showing a conventional arc melting furnace, FIG. 7 is a sectional view taken along line AA in FIG. 6, FIG. 8 is a sectional view taken along line BB in FIG. 6 before tilting, and FIG. FIG. 7 is a sectional view taken along line BB in FIG. 6 later.
[0005]
This conventional arc melting furnace is provided in a melting chamber 1, a melting furnace 1 for arc melting a cold iron source, a preheating shaft 2 directly connected to the upper part of one side 1a, and extending upward. And a hot spring section 3.
[0006]
A movable exhaust duct 4 connected to an exhaust gas suction system is provided at the upper end of the preheating shaft 2. The exhaust gas in the movable exhaust duct 4 is sent to the exhaust gas treatment facility through a fixed exhaust duct (not shown) connected to the exhaust gas treatment facility (not shown) side. The melting furnace 1 and the preheating shaft 2 are charged with iron scrap S as a cold iron source.
[0007]
A scrap charging bucket 5 is provided above the preheating shaft 2, and iron scrap S is charged into the preheating shaft 2 from the bucket 5. Moreover, in order to prevent shelf hanging, you may insert a carbon source, for example, coke, into the preheating shaft 2. FIG. In this case, the charging of the scrap S from the basket 5 is performed continuously to the preheating shaft 2 so that the scrap S is continuously present in the melting chamber 1 and the preheating shaft 2 during operation. Or supply intermittently. The charging of the scrap S at this time may be performed based on a preset recipe based on the operation results, or a sensor capable of detecting the amount of the scrap S in the preheating shaft 2 is provided. Based on the signal, the input of the scrap S by the bucket 5 may be controlled by appropriate control means.
[0008]
An openable / closable furnace lid 6 is provided at the top of the melting furnace 1, and an arc electrode 7 is inserted vertically from above the melting furnace 1 through the furnace lid 6. A furnace bottom electrode 9 is provided at a position facing the arc electrode 7 on the furnace bottom 8 of the melting furnace 1. Then, the scrap S is melted by the arc 10 formed by the arc electrode 7 to become the molten steel 11. A slag 12 is formed on the molten steel 11, and the arc 10 is formed in the slag 12. The arc electrode 7 is supported by a support member (not shown) and can be tilted by the tilt mechanism 13.
[0009]
Two lances 14a and 14b are inserted into the melting furnace 1 with their tips facing the molten steel surface, oxygen is supplied from the lance 14a, and coke as an auxiliary heat source is injected from the lance 14b. The
[0010]
The scrap S in the preheating shaft 2 is supplied in a direction from one side (preheating shaft 2 side) 1a of the melting furnace 1 to the other side (opposite side) 1b. It projects from the melting furnace 1 so as to face in a direction orthogonal to the direction. And the melting furnace 1 can be tilted by the tilting means (not shown) about the tilting axis (L) toward the hot water outlet 3 side. Further, the portion of the melting furnace 1 provided with the preheating shaft 2 and the portion provided with the tapping part 3 are separated by a distance a, and when the melting furnace 1 is tilted, scraping is caused by the wall portion of the part. S is prevented from flowing out to the hot water outlet 3 side.
[0011]
A hot water outlet 15 is formed at the bottom near the tip of the hot water outlet 3, and a vertically movable stopper 16 for opening and closing the hot water outlet 15 is provided. Furthermore, a slag door 17 that is opened when the slag 12 is discharged is provided on the side surface of the front end of the hot water outlet 3.
[0012]
In the conventional arc melting furnace configured as described above, when melting iron scrap, first, the iron scrap S is charged into the melting furnace 1 and the preheating shaft 2, and the iron scrap S is transferred to the melting furnace 1 and the preheating shaft 2. It is assumed that it exists continuously.
[0013]
In this state, the arc 10 is formed by the arc electrode 7 and the iron scrap S is melted. At this time, oxygen is supplied from the lance 14a to assist the melting of the scrap. When molten steel accumulates in the furnace, coke as an auxiliary heat source is injected from the lance 14b into the slag to shift to the slag forming operation, the tip of the electrode 7 is buried in the slag 12, and the arc 10 is slag 12 To be formed inside. The coke as the auxiliary heat source contributes to the dissolution of the scrap S.
[0014]
The exhaust gas generated by such scrap melting is discharged outside the furnace via the preheating shaft 2 and the movable exhaust duct 4, and the scrap S in the shaft 2 is preheated by the heat of the exhaust gas. As the scrap S melts in the melting furnace 1, the scraps of the preheating shaft 2 are sequentially supplied to the melting furnace 1, so that the upper end position of the scrap S in the preheating shaft 2 is lowered. In this case, the scrap S is continuously or intermittently supplied from the bucket 5 to the preheating shaft 2 so that the scrap S is continuously present in the melting chamber and the preheating shaft. As a result, a state where a certain amount or more of scrap is always present in the melting furnace 1 and the preheating shaft 2 is maintained. As described above, the charging of the scrap S at this time may be performed based on a recipe set in advance based on the operation results, or a sensor capable of detecting the amount of the scrap S in the preheating shaft 2 is provided. Based on the signal from the sensor, the input of the scrap S by the bucket 4 may be controlled.
[0015]
As the scrap S melts, the scrap S, which is a cold iron source, and the molten steel coexist in the melting furnace 1, and the temperature of the molten steel is low, for example, 1540 to 1550 ° C., the solidification temperature of the molten steel. There is only a little super heat with respect to 1530 ° C., and this causes problems such as clogging of the tap at the time of pouring. For this reason, as shown in FIG. 9, the melting furnace 1 is tilted to the side of the hot-water part 3 and the arc heating is continued before the hot water.
[0016]
In this case, the hot water discharge section 3 is protruded from the melting furnace 1 so as to face in a direction perpendicular to the inflow direction of the scrap S to the melting furnace 1, and the preheating shaft 2 of the melting furnace 1 is provided. The portion provided with the hot water discharge unit 3 is separated by a distance a, and the wall portion of the portion prevents the scrap S from flowing out to the hot water discharge unit 3 side. The contact area between the molten steel that has flowed in and the scrap S can be reduced. Therefore, the superheat of molten steel can be made high and the problem that the temperature of the molten steel discharged is low can be avoided.
[0017]
Further, when the melting furnace 1 is tilted, the arc electrode 7 becomes the position of the wavy line in FIG. 9 and the arc is not supplied effectively, but by tilting the arc electrode 7 from the tilting mechanism 13, the position of the solid line in FIG. The arc can be effectively supplied to the molten steel.
[0018]
When melting proceeds as described above and a predetermined amount of molten steel has accumulated in the furnace, the melting furnace 1 is tilted to reduce the contact area between the molten steel and scrap, and the molten steel is superheated by arc heating for a certain period of time. After that, the melting furnace 1 is further tilted, and the stopper 16 that has blocked the hot water outlet 15 of the hot water outlet 3 is raised while maintaining the state where the scrap S is continuously present in the melting furnace 1 and the melting shaft 2. Then, the tap 15 is opened, and the molten steel for one charge is poured from the tap 15 into a ladle.
[0019]
In the case of melting scrap in this way, the preheating shaft 2 is not equipped with equipment for scrap transport and supply such as pushers and fingers, so the amount of oxygen used is higher than that of the conventional melting equipment provided with these. The exhaust gas temperature can be increased. Therefore, it becomes possible to preheat the scrap to a higher temperature than the conventional melting equipment.
[0020]
Further, the scrap S is always supplied to the preheating shaft 2 so that the scrap S is continuously present in the melting furnace 1 and the preheating shaft 2, and molten steel of one charge or more is formed in the melting furnace 1. Also when the hot water is discharged, scrap continuously exists in the melting furnace 1 and the preheating shaft 2, so that the efficiency of preheating the scrap by the exhaust gas is high. In this case, preheating efficiency becomes extremely high by allowing scraps of 50% or more for one charge to be continuously present in the melting furnace 1 and the preheating shaft 2 during melting and at the time of tapping.
[0021]
As described above, since no equipment such as a pusher or fingers is required, the exhaust gas temperature can be increased, and the scrap S can always be kept continuously in the melting furnace 1 and the preheating shaft 2 so that the scrap can be kept. The dissolution efficiency of is extremely high. In addition, since the contact area between the scrap S, which is a cold iron source, and the molten steel produced by melting it can be reduced, the molten steel can be superheated and the temperature of the molten steel discharged is low. Conventional arc melting furnaces have various advantages, such as being able to eliminate the problem.
[0022]
[Patent Document 1]
Japanese Patent No. 3114713 [0023]
[Problems to be solved by the invention]
However, conventional arc melting furnaces have the following problems.
[0024]
Conventionally, the movable exhaust duct 4 provided on the preheating shaft 2 of the arc melting furnace and the fixed exhaust duct have not been directly connected. That is, the edge of the movable exhaust duct 4 and the fixed exhaust duct was cut. Accordingly, ambient air is sucked into the duct from the connection portion between the movable exhaust duct 4 and the fixed exhaust duct, and there is a fear that the amount of exhaust gas increases. For this reason, it is necessary to design the exhaust gas treatment facility according to the maximum amount of exhaust gas, and it has been unavoidable.
[0025]
Therefore, the object of the present invention is to prevent the surrounding air from being sucked into the duct from the connecting portion of the movable exhaust duct and the fixed exhaust duct, and stably without sucking air even when the furnace is tilted. An object of the present invention is to provide an arc melting furnace capable of sucking only exhaust gas from the preheating shaft.
[0026]
[Means for Solving the Problems]
The invention according to claim 1 is a melting chamber for melting a cold iron source, a preheating shaft that is directly connected to the upper part of one side and preheats the cold iron source, a movable exhaust duct provided on the preheating shaft, An arc electrode for melting a cold iron source in the melting chamber; a tapping part projecting from the melting chamber and having a tapping outlet; and tilting means for tilting the melting chamber toward the tapping part, the movable exhaust The duct is connected to a fixed exhaust duct, and the cold iron source in the preheating shaft is supplied from one side to the other side where the preheating shaft of the melting chamber is provided during melting, In the arc melting furnace of the cold iron source provided in a direction different from the supply direction of the cold iron source, the connecting portion between the fixed exhaust duct and the movable exhaust duct is aligned with the tilt rotation center axis of the melting chamber. The movable exhaust duct With respect to the fixed exhaust duct by joint, and it has the characteristics that it is rotatable hermetically about said tilt central axis of rotation.
[0027]
According to a second aspect of the present invention, the airtight joint includes a flexible joint member provided between the fixed exhaust duct and the movable exhaust duct, and a sliding portion between the fixed exhaust duct and the movable exhaust duct. And a sealing material provided in the above.
[0028]
The invention according to claim 3 is characterized in that the flexible joint member is made of heat-resistant bellows.
[0029]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of a cold iron source arc melting furnace of the present invention will be described with reference to the drawings.
[0030]
1 is a schematic perspective view showing an arc melting furnace of the present invention, FIG. 2 is a sectional view taken along line AA of FIG. 1, and FIG. 3 is a sectional view showing an airtight joint of the arc melting furnace of the present invention. FIG. 5 is a view in the A direction of FIG. 3, and FIG. 5 is a view in the B direction of FIG.
[0031]
1 and 2, the same numbers as those in FIGS. 6 and 7 denote the same items. That is, 1 is a melting furnace, 2 is a preheating shaft, 3 is a tapping part, 4 is a movable exhaust duct, 5 is a scrap charging bucket, 6 is a furnace lid, 7 is an arc electrode, 8 is Furnace bottom, 9 is a furnace bottom electrode, 10 is an arc, 11 is molten steel, 12 is a slag, 13 is a tilting mechanism, 14a and 14b are lances, 15 is a tap, 16 is a stopper, 17 Is a slag door and S is iron scrap.
[0032]
The feature of the present invention coincides with the tilting central axis (L) of the melting chamber 1 of the portion connected to the fixed exhaust duct 18 provided on the preheating shaft 2 in the arc melting furnace. That is, the movable exhaust duct 4 is curved downwardly in an L shape from the preheating shaft 2, and the central axis of the horizontal portion of the movable exhaust duct 4 </ b> A coincides with the tilting central axis (L) of the melting chamber 1. The movable exhaust duct 4A is airtightly rotatable about the tilting central axis (L) with respect to the fixed exhaust duct 18 by the airtight joint 19.
[0033]
Details of the airtight joint 19 will be described with reference to FIGS. 3 to 5.
[0034]
3 to 5, 20 is a movable exhaust duct side flange fixed to the end of the movable exhaust duct 4A, 21 is a fixed exhaust duct side flange fixed to the end surface of the fixed exhaust duct 18, and 22 is both It is a heat-resistant bellows as a flexible joint member that is airtightly connected between the flanges 20 and 21. The flexible joint member is not particularly limited to the bellows as long as it can expand and contract in the axial direction and the circumferential direction of the joint.
[0035]
A movable exhaust duct side water cooling duct 23 is provided in an annular shape over the entire circumference of the movable exhaust duct 4A in the bellows 22 portion, and is fixed to the lining refractory 25 of the movable exhaust duct 4A by an anchor 24. The cooling water in the movable exhaust duct side water cooling duct 23 is injected from the inlet 23A and drained from the outlet 23B.
[0036]
26 is a non-asbestos fireproof sealing material wound around the outer peripheral surface of the tip of the water-cooled duct 23 on the movable exhaust duct side. The sealing material 26 is pressed against the outer peripheral surface of the distal end of the movable exhaust duct side water cooling duct 23 by a sandwiching plate 27 fixed to the inner surface of the fixed exhaust duct side flange 21. When the melting chamber 1 is tilted, the sandwiching plate 27 slides on the outer peripheral surface of the sealing material 26. 28 is a refractory padding sandwiched between the end surfaces of the movable exhaust duct 4A and the fixed exhaust duct 18.
[0037]
Reference numeral 29 denotes a fixed exhaust duct side water-cooled duct provided in an annular shape over the entire circumference of the end of the fixed exhaust duct 18, and is fixed to the lining refractory 31 of the fixed exhaust duct 18 by an anchor 30. The cooling water in the fixed exhaust duct side water cooling duct 29 is injected from the inlet 29A and drained from the outlet 29B.
[0038]
Since the movable exhaust duct 4A and the fixed exhaust duct 18 are connected by the airtight joint 19, the movable exhaust duct 4A rotates with the preheating shaft 2 as the melting chamber 1 tilts (the rotation angle is several tens of degrees). Then, since the bellows 22 are twisted, the bellows 22 are rich in elasticity, so that airtightness is maintained. In addition, high sealing performance is obtained by the sealing material 26 that slides in close contact with the sandwiching plate 27 and the filling 28 between the ducts 4A and 18.
[0039]
【The invention's effect】
As described above, according to the present invention, the movable exhaust duct of the portion connected to the fixed exhaust duct is made to coincide with the tilting central axis of the melting chamber, and the movable exhaust duct is connected to the fixed exhaust duct by the airtight joint. By enabling airtight rotation about the tilting center axis, ambient air can be prevented from being sucked into the duct from the connection between the movable exhaust duct and the fixed exhaust duct, and the air can be moved even while the furnace is tilting. Thus, only the exhaust gas can be stably sucked from the preheating shaft without being sucked. Therefore, since the amount of exhaust gas is not increased by the suction air from the connecting portion between the fixed exhaust duct and the movable exhaust duct as in the prior art, a useful effect that the exhaust gas treatment facility can be miniaturized is brought about. .
[Brief description of the drawings]
FIG. 1 is a schematic perspective view showing an arc melting furnace of the present invention.
FIG. 2 is a cross-sectional view taken along line AA in FIG.
FIG. 3 is a cross-sectional view showing an airtight joint of the arc melting furnace of the present invention.
4 is a view in the A direction of FIG.
FIG. 5 is a view in the B direction of FIG. 3;
FIG. 6 is a schematic perspective view showing a conventional arc melting furnace.
7 is a cross-sectional view taken along line AA in FIG.
8 is a cross-sectional view taken along line BB of FIG. 6 before tilting.
9 is a cross-sectional view taken along line BB in FIG. 6 after tilting.
[Explanation of symbols]
1: Melting furnace 2: Preheating shaft 3: Hot water outlet part 4: Movable exhaust duct 5: Scrap charging bucket 6: Furnace lid 7: Arc electrode 8: Furnace bottom 9: Furnace bottom electrode 10: Arc 11: Molten steel 12: Slag 13 : Tilt mechanism 14a, 15b: lance 15: tap 16: stopper 17: slug door 18: fixed exhaust duct 19: airtight joint 20: movable exhaust duct side flange 21: fixed exhaust duct side flange 22: bellows 23: movable exhaust duct side Water cooling duct 24: Anchor 25: Lined refractory 26: Sealing material 27: Clamping plate 28: Stuffing 29: Fixed exhaust duct side water cooling duct 30: Anchor 31: Lined refractory

Claims (3)

A melting chamber that melts the cold iron source, a preheating shaft that is directly connected to the upper part of the cold iron source, preheats the cold iron source, a movable exhaust duct provided on the preheating shaft, and the cold iron source is melted in the melting chamber. And a tilting means for tilting the melting chamber toward the outlet portion, the movable exhaust duct being connected to a fixed exhaust duct. The cold iron source in the preheating shaft is supplied from one side to the other side where the preheating shaft of the melting chamber is provided during melting, and the hot water source is the supply direction of the cold iron source. In an arc melting furnace with a cold iron source provided in different directions,
The connecting portion between the fixed exhaust duct and the movable exhaust duct coincides with the tilting rotation center axis of the melting chamber, and the movable exhaust duct has the tilting rotation center axis aligned with the fixed exhaust duct by an airtight joint. A cold iron source arc melting furnace characterized by being airtightly rotatable as a center. The airtight joint includes a flexible joint member provided between the fixed exhaust duct and the movable exhaust duct, and a seal member provided at a sliding portion between the fixed exhaust duct and the movable exhaust duct. The arc melting furnace of a cold iron source according to claim 1, characterized by comprising: The arc melting furnace of a cold iron source according to claim 2, wherein the flexible joint member is made of heat-resistant bellows.

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