JP6488652B2 - Electric furnace operation method - Google Patents

Description

  The present invention relates to a method for operating an electric furnace, and more particularly to a method for operating an electric furnace provided with a rotating device that rotates a furnace body relative to an electrode.

Conventionally, as a melting furnace for melting metal materials such as scrap metal, a three-phase alternating current that generates an arc between the three electrodes inserted in the furnace body and the metal material in the furnace body and melts the metal material by arc heat A type arc furnace is widely used.
In the melting operation of the metal material using such an electric furnace, there has conventionally been a problem that the melting of the metal material becomes non-uniform.

In this three-phase AC type electric furnace, the three electrodes inserted downward into the furnace body form a triangle in plan view around the central axis of the furnace body, that is, each of the three electrodes has a triangular shape. It arrange | positions so that it may be located in a top part.
As a result, a so-called hot spot at a position where the distance from the electrode is short (that is, close to the electrode) and a so-called cold spot at a position where the distance from the electrode is long (that is, far from the electrode) are generated.
In the hot spot, the metal material is easy to melt because the electrode is heated strongly. On the other hand, in the cold spot, the heat from the electrode is relatively weak. However, the non-uniformity of melting, such as the metal material remaining undissolved, occurred.
In addition to the problem of poor melting efficiency and high power cost for melting due to such non-uniform melting, the hot spot is not suitable for the cold spot even after all the metal material is completely melted. While the metal material is continuously melted, it continues to receive strong heat, resulting in excessive power input and accelerated melting of the refractory material on the furnace wall. There was a problem that repair work had to be done.

As countermeasures against such problems, there have been proposed an electric furnace in which the furnace body is rotated with respect to the fixed electrode and an electric furnace in which the electrode is rotated with respect to the fixed furnace body. Yes.
For example, Patent Literature 1 and Patent Literature 2 below disclose the former electric furnace, and Patent Literature 3 discloses the latter electric furnace.

In the electric furnace equipped with the rotating device as described above, the furnace body is rotated relative to the electrode during melting, and the metal material originally located at the cold spot becomes the hot spot and the metal located at the hot spot. By moving the material to the cold spot, the problem of non-uniform dissolution can be improved.
In this case, by rotating the furnace body about 60 ° in the circumferential direction relative to the electrode, the electrode originally located in the circumferential center of the hot spot is placed in the circumferential center of the adjacent cold spot. It is effective to be positioned.

By the way, the present inventors, for the purpose of confirming the state in the furnace during the operation of the electric furnace, interrupted the operation, cooled the furnace and examined the inside, metal material around the outlet and the outlet of the furnace body It was found that there was a residual melt of.
The cause of the unmelted residue around the tap differs depending on the furnace type.
FIG. 12 is a view for explaining the unmelted metal material in an eccentric furnace bottom steel type electric furnace (EBT furnace).
80 is an EBT furnace, and the furnace bottom portion 84 of the furnace body 82 partially protrudes from the inner surface of the circular peripheral wall portion 85 of the furnace body 82 to the outside in the radial direction from the outer surface of the peripheral wall portion 85. The protruding portion 86 forms a shelf-like portion with a small inclination, and an opening penetrating therethrough, that is, a hot water outlet 88 is formed therein. The hot water outlet 88 is closed by a lid (not shown) outside the lower portion of the protrusion 86.
In the EBT furnace 80 having such a configuration, when a metal material is charged into the inside from the charging port 95 at the upper end of the furnace body 82, a part of the metal material may be placed on the shelf-like protrusion 86 around the outlet 88. is there. It is considered that a part of the metal material placed on the protruding portion 86 is far away from the electrode 83 and the heating is weak, so that the metal material of the part remains undissolved until the hot water is discharged. In addition, 87 in FIG. 12 (B) has shown the unmelted residue which arose around the pouring gate 88. FIG.

In the EBT furnace 80, there may be a case where metal remains unmelted even around the tap outlet 91 that is at a position opposite to the tap outlet 88 in the radial direction.
The EBT furnace 80 has a tap hole 91 that penetrates the peripheral wall 85 of the furnace body in the inner and outer directions, and a tap hole bottom portion 92 that extends radially outward from the tap port 91. The spout 91 may be blocked by a door or the like, but during melting operation, external air can enter the furnace from the spout 91 (the gap even when there is a door). As indicated by the arrow 12 (B), a cold air flow is generated in the furnace from the tap 91 to the dust collection port 94 attached to the furnace lid 93. For this reason, it is considered that the metal material in the furnace is cooled around the end portion of the tap outlet 91 on the dust collection port 94 side, resulting in an unmelted residue 96.

On the other hand, even in a hot water type electric furnace having a hot water outlet that penetrates the peripheral wall portion of the furnace body in the radial direction and a tub that extends outward in the radial direction from the hot water outlet, Since the tap is kept open, external air enters the furnace from there. For this reason, it is considered that the metal material in the furnace is cooled in the vicinity of the hot water outlet and is left undissolved in the vicinity of the hot water outlet due to the same cause as in the case of the tap hole 91 of the EBT furnace.
Further, the unmelted metal material is generated around the tap outlet in the hot water type electric furnace as well as around the tap outlet 91 of the EBT furnace.

The outlets and taps as described above are usually not located at the center of the cold spot or the center of the hot spot in the operation of the electric furnace. Therefore, the hot spot and the cold are simply caused by the relative rotation between the furnace body and the electrode. It is difficult to sufficiently dissolve the metal material remaining at the tap and the tap at the operation that only switches the spot.
Further, in an electric furnace operation in which the process of switching between a hot spot and a cold spot is not performed by rotation by a rotating device, it is naturally more difficult to sufficiently dissolve the metal material remaining in the tap and the tap.

Japanese Patent Laid-Open No. 60-122886 JP 2014-40965 A JP-A-7-190624

  The present invention is based on the above circumstances, and in an electric furnace operation that melts a metal material, it is possible to effectively prevent unmelted residue around the outlet and the outlet and to improve melting efficiency. It was made for the purpose of providing a method of operation.

Thus, according to the first aspect of the present invention, there is provided (a) a furnace body having a cylindrical peripheral wall portion and a furnace bottom portion, (b) a plurality of electrodes provided downward on the furnace lid side, and (c) the A rotating device that rotates the furnace body relative to the electrode about an axis in the vertical direction, and is generated between the electrode and the metal material charged in the furnace body in two or more times A method of operating an electric furnace in which the metal material is melted by the heat of the generated arc, wherein the electric furnace is an EBT furnace, and the furnace bottom part partially protrudes radially outward from the outer surface of the peripheral wall part additionally have the protrusions, are formed outflow by opening through the projecting portion up and down, are loaded into a dissolution of the metallic material, said furnace body to said metallic material from the charging hole during or immediately after the instrumentation step, a rotation step of relatively rotating the furnace body to said electrode, said that rotated relative The body, one of the plurality of the electrodes to melt the metallic material around the pouring opening or tapping port of the furnace body, the holding position set in proximity to the output hot water outlet, i.e. of the projecting portion When the angle between the line connecting one end in the circumferential direction and the rotation center and the line connecting the other end in the circumferential direction and the rotation center is α, the rotation center of the furnace body and any of the electrodes Is a position passing through a region within a range of ± α / 4 centered on a line passing through the center of the angle α, or a holding position set close to the spout, that is , the rotation center of the furnace body When the extension line of the line connecting the electrode and any one of the electrodes reaches a position passing through a range of less than 60 ° from the end of the opening at the tap outlet to the side of the dust collection port. rotation is stopped, and performing dissolution operations by running a holding step of holding in the holding position.

According to a second aspect of the present invention, (a) a furnace body provided with a cylindrical peripheral wall portion and a furnace bottom portion, (b) a plurality of electrodes provided downward on the furnace lid side, and (c) the furnace body A rotating device that rotates relative to the electrode about an axis in the vertical direction, and an arc generated between the electrode and the metal material charged in the furnace in two or more times An electric furnace operating method for melting the metal material by heat of the electric furnace, wherein the electric furnace is a brewing hot water type electric furnace, and a hot water outlet is formed at an opening penetrating the peripheral wall portion in and out. , And a bowl is provided in a form extending outward from the tap.
During the melting of the metal material, during or immediately after the loading process of charging the metal material into the furnace body from the loading port, the furnace body is rotated relative to the electrode, and the relative rotation is performed. and the furnace body, a holding position where one is set in proximity to said output sprue or tapping port to melt the metal material around the pouring opening or tapping port of the furnace body of the plurality of the electrodes That is, the extension line of the line connecting the rotation center of the furnace body and any one of the electrodes is a range of less than 60 ° from the end of the dust outlet to the side of the dust collector at the tap or tap outlet. rotation is stopped at that reached the position, through, and performing dissolution operations by running a holding step of holding in the holding position.

According to a third aspect of the present invention, in any one of the first and second aspects, after heating the metal material in a state where the electrode is held at the holding position, a portion that is the center of the cold spot is a hot spot. The furnace body is further rotated relative to the electrode until it reaches the center or substantially the center, and the metal material remaining undissolved in a state of being positioned at the cold spot is melted .

  As described above, the present invention rotates the furnace body relative to the electrode during melting of the metal material, and any one of the plurality of electrodes removes the metal material around the tap or the tap. In order to melt, the rotation is stopped when it reaches the holding position set close to the tap or the tap, and the metal material around the tap and the tap is melted by holding at the stop position. In the present invention, it is possible to efficiently perform heating from the electrode to the metal material located around the tap and the tap, and thus, metal that has conventionally been generated around the tap and the tap. The problem of undissolved material can be solved satisfactorily.

The present invention can be suitably applied to operations using any of the following types of electric furnaces. In this case, the holding position set close to the tap or the tap differs depending on the type of the electric furnace, that is, the type and structure of the tap and the tap.
Conventionally, as the electric furnace, the aforementioned EBT furnace and the hot water type electric furnace are mainly used.

In the case of the former (EBT furnace), the holding position set in the vicinity of the pouring gate is that the extension line of the line connecting the rotation center of the furnace body and any of the electrodes is the circumference of the protruding portion located around the pouring gate. It is desirable that the position pass between one end of the direction and the other end.
That is, when the angle formed between the line connecting one end in the circumferential direction of the protrusion and the rotation center and the line connecting the other end in the circumferential direction and the rotation center is α, It is desirable that the line connecting the electrodes pass through a region within an angle α (generally α = 100 °).
In the present invention, the angle α is set within a range of ± α / 4 with a line passing just through the center as the center . More desirable is within a range of ± α / 6.
In this way, the metal material remaining undissolved around the hot water outlet, that is, in the protruding portion, can be efficiently dissolved.

In addition, the holding position set close to the tap outlet is such that the range of the metal material that remains undissolved around the tap outlet ranges from the end on the dust collecting port side of the tap outlet to a range of less than 60 ° from the dust collecting port side. In many cases, the extension line of the line connecting the center of rotation of the furnace body and any one of the electrodes is in a range of less than 60 ° from the end of the opening at the tap outlet to the side of the dust collector. It shall be the position, such as to pass through the.

On the other hand, in the case of the latter (salted hot water type electric furnace), the situation is almost the same as the outlet of the above-mentioned EBT furnace in both the outlet and the outlet, and therefore close to the outlet or the outlet. The holding position set in this way is an extension of the line connecting the center of rotation of the furnace body and one of the electrodes, less than 60 ° from the end of the dust outlet to the side of the dust collector at the tap or tap outlet. It shall be the position, such as to pass through the range of.

  In the rotation process of the present invention, the furnace body is rotated relative to the electrode from the original position, and one of the electrodes is rotated to reach the holding position, and then the rotation is stopped and then held at the rotation stop position. Then, it can be held at the stop position until the final stage of melting, that is, until all the metal material is melted, or after being held at the stop position for a predetermined time, the portion that was the center of the cold spot is The furnace body may be further rotated relative to the electrode until it reaches the center or almost the center of the hot spot, and the metal material remaining undissolved in the state of being located at the cold spot may be melted to the end.

The rotation step in the present invention, Ru can be carried out after finishing the boring.
Also the charging process, Ru can be performed two or more times of a plurality of times.
Further, in the present invention, the electric furnace includes a tilting body that tilts the furnace body with itself while supporting the furnace body, and a rotating device that rotates the furnace body on the tilting body about the vertical axis, preferably around the central axis. It can be kept as provided.

  According to the present invention as described above, in an electric furnace operation for melting a metal material, it is possible to effectively prevent unmelted residue from being produced around a tapping outlet and a tapping outlet, thereby increasing melting efficiency.

It is the figure which showed the structure of the electric furnace used with the operating method of one Embodiment of this invention. It is the figure which showed the electric furnace of FIG. 1 in a different cross section. It is a whole perspective view of the rotating apparatus of FIG. It is a whole top view of the rotation device. It is VV sectional drawing of FIG. It is VI-VI sectional drawing of FIG. It is explanatory drawing which showed an example of the operation method for every process. It is a figure for demonstrating the holding position in an EBT furnace. It is explanatory drawing which showed the example of the operation method different from FIG. It is explanatory drawing which showed the example of the operation method different from FIG. 7, FIG. It is a figure for demonstrating the holding | maintenance position in a brewing hot water type electric furnace. It is a figure for demonstrating the unmelted remainder of the metal material in an EBT furnace.

Next, an embodiment when the present invention is applied to an electric furnace for melting a metal material (here, a steel material) will be described in detail with reference to the drawings.
FIG.1 and FIG.2 is the figure which showed the structure of the electric furnace used with the operating method of this embodiment.
In FIG. 1, reference numeral 10 denotes an electric furnace, which is a furnace body 16 having a cylindrical (cylindrical) peripheral wall portion 12 and a furnace bottom portion 14, and a furnace that closes an inlet 18 at the upper end of the furnace body 16 so as to be opened and closed. A lid 20 and three electrodes 22 inserted through the furnace lid 20 and inserted downward into the furnace body 16 are provided.

  The respective electrodes 22 are arranged near the center of the furnace lid 20 having a substantially circular shape in plan view, and are arranged at equal intervals (120 ° intervals) around the vertical axis of the furnace body 16, here the central axis. It is supported by an elevating device so as to be individually adjustable in height, and is configured to be able to adjust the vertical separation distance between the lower end of the electrode 22 and the metal material charged in the furnace body 16.

  The furnace lid 20 is configured to be movable up and down with respect to the furnace body 16 by a lifting device and a swirling device (not shown), and swings in the horizontal direction to open the inlet 18 of the furnace body 16 and open the furnace body. It is possible to insert a metal material into the inside 16.

The electric furnace 10 of the present embodiment is an EBT furnace, and as shown in FIG. 2, the furnace bottom portion 14 partially protrudes radially outward from the peripheral wall portion 12 of the furnace body 16, and the protruding shelf-like protrusion The part 26 is provided with a hot water outlet (a steel outlet) 27 penetrating it vertically.
The molten metal (molten steel) in the furnace body 16 is discharged from the outlet 27 toward the ladle 23 (FIG. 1) by tilting the entire furnace body 16.

In addition, a tap outlet 29 is provided at a position (symmetrical position) opposite to the tap outlet 27 in the radial direction. The outlet 29 is provided through the peripheral wall 12 of the furnace body in the inner and outer directions.
In this example, the entire furnace body 16 is tilted in the direction opposite to that at the time of pouring, so that the slag generated during the melting operation can be discharged to the outside from the tap outlet 29.

In the electric furnace 10 of this embodiment, the furnace body 16 can tilt and can rotate relative to the furnace lid 20 and the electrode 22.
In FIG. 1, 34 is a tilting body that tilts while supporting the furnace body 16 and tilts the furnace body 16, and is tiltably supported by a furnace stand 36 provided on the ground.
Engagement teeth are formed on the upper surface of the furnace table 36 that supports the tilting body 34 and the lower surface of the leg portion 37 that has a downwardly convex shape in contact with the tilting body 34, respectively. The displacement of the tilting body 34 with respect to the furnace table 36 is prevented by the engagement.
The tilting body 34 has a tilting floor 35 for supporting the furnace body 16, and the furnace body 16 is supported by the tilting floor 35 of the tilting body 34 via a rotating device 32 described later.

In the present invention, the rotating device can be configured as follows.
That is, the rotating device is a) a support means for rotatably supporting the furnace body on the tilting body, and b) a guide rail that is provided between the furnace body and the tilting body and guides the furnace body to rotate around its central axis. And c) a driven part for receiving rotational driving force provided on the furnace body side; and d) a drive provided on the tilting body side for engaging the driven part and transmitting the rotational driving force to the driven part. And a drive source for generating a driving force provided on the side of the tilting body and configured to tilt integrally with the tilting body.

In this embodiment, the rotating device is specifically configured as follows.
First, the tilting mechanism will be described.
As shown in FIG. 2, one end side of the drive cylinder 38 is rotatably connected to the right end of the tilting body 34 in the drawing. The other end of the drive cylinder 38 is rotatably connected to the ground side. By extending the drive cylinder 38, the tilting body 34 tilts together with the furnace body 16 so that the left side in the figure is downward and the right side is upward. . As a result, the molten steel in the furnace body 16 is discharged from the tap outlet 27 toward the ladle 23.

FIG. 3 is an overall perspective view of the rotating device 32 in the present embodiment, and FIG. 4 is a plan view thereof.
The rotating device 32 has a circular ring-shaped support frame 40 having a large number of standing walls, and the furnace body 16 is mounted and fixed on the upper surface of the support frame 40.
A ring-shaped gear body 42 is provided on the inner peripheral portion of the lower surface of the ring-shaped support frame 40, and a tooth profile is formed on the inner periphery thereof.

On the other hand, as shown in FIG. 5, the outer peripheral intermediate portion of the gear body 42 protrudes outward with a square cross section, and constitutes an inner ring portion 46 of the bearing member 44.
An outer ring portion 48 having a U-shaped cross section is disposed so as to wrap the inner ring portion 46, and a roller bearing 49 is interposed between the concave surface of the outer ring portion 48 and the convex surface of the inner ring portion 46, that is, the upper and lower surfaces and the outer peripheral end surface. ing.

  With such a structure, the support frame 40 is supported by the bearing member 44 and can rotate in a plane parallel to the tilting floor 35 around the center of the ring. As a result, the furnace body 16 supported by the rotating device 32 can be rotated relative to the electrode 22 with the central axis of the furnace body 16 as the center of rotation.

  A gear box 50 is provided on the tilting floor 35 in a radially symmetric position inside the ring of the support frame 40 (FIG. 4), and a gear body is disposed therein. In FIG. 5, a hydraulic motor 52 as a drive source is provided on the tilting floor 35 side, and a gear body 53 is attached to the output shaft thereof. The gear body 53 meshes with a gear body 55 rotatably supported by a shaft body 54 standing on the tilting floor 35 side, and the gear body 55 meshes with the tooth profile of the ring-shaped gear body 42. .

Thereby, when the hydraulic motor 52 is rotated forward and backward, the support frame 40 is rotated forward and backward via the gear bodies 53, 55, and 42.
In this embodiment, the support frame 40, the gear body 42, and the bearing member 44 constitute support means, and the inner ring portion 46 and the outer ring portion 48 of the bearing member 44 also serve as guide rails.
Further, the tooth profile of the gear body 42 constitutes a driven part, the gear bodies 55 and 53 constitute a driving part, and the hydraulic motor 52 constitutes a driving source.

  In the present embodiment, the support frame 40, that is, the furnace body 16 is rotated by the hydraulic motor 52 within a range of 60 ° counterclockwise from the original position shown in FIG. 4 where the outlet 27 of the furnace body 16 faces the hot water yard. be able to.

A stopper mechanism 56 is disposed at an intermediate position in the circumferential direction of the support frame 40 between the two gear boxes 50, 50. Details of the stopper mechanism 56 are shown in FIG. In FIG. 6, the support frame 40 is provided with a sheath member 57 facing inward. The sheath member 57 is a cylindrical body and has a tapered shape in which the inner periphery of the inner half gradually expands inward.
On the other hand, a plug member 60 that is linearly moved back and forth inward and outward by a drive cylinder 59 is provided on a base 58 on the tilting floor 35 side. The plug member 60 is a cylindrical body whose distal end located on the outer side gradually decreases in diameter toward the distal end, and the rear end of the plug member 60 is connected to the rod 61 of the drive cylinder 59.

  When the support frame 40 is in the original position, as shown in FIG. 6, the sheath member 57 faces the plug member 60, and when the plug member 60 is advanced by the drive cylinder 59, the plug member 60 is in the sheath member 57. The tapered tip of the plug member 60 is fitted into the tapered half of the sheath member 57. Thereby, the rotation of the support frame 40, that is, the furnace body 16, is reliably regulated, and in this state, the tapping or pouring tilting of the furnace body 16 can be performed.

Next, an operation method of the electric furnace 10 for melting the metal material will be described with reference to FIG.
Usually, metal materials such as scrap are charged into the furnace in a plurality of times. In this example, the metal material is charged into the furnace in two steps.
First, the furnace lid 20 is prevented from turning, the loading port 18 of the furnace body 16 is opened, the scrap bucket holding the metal material is moved up to the loading port 18 by a crane, and the metal material in the scrap bucket is moved to the furnace. Insert inside.

When the material charging is completed, the furnace lid 20 and the electrode 22 are placed on the upper portion of the furnace body 16, an arc downward from the tip of the electrode 22 is generated, and the material located at the tip of the electrode 22 is preferentially melted. Digs through a metal material (this process is hereinafter referred to as a boring process). FIG. 7A shows a state where the boring is performed.
When the boring is completed and the electrode 22 reaches the vicinity of the furnace bottom portion 14, the material around the electrode 22 is dissolved (FIG. 7B).
Thus, when there is no undissolved metal around the electrode 22, the furnace body 16 can be rotated relative to the electrode 22. In the figure, the portion indicated by halftone dots in the furnace is the undissolved metal material, and the portion indicated by the white background is the molten metal material. At this stage, extreme dissolution non-uniformity has not yet occurred.

Next, after the melting progresses and the volume of the undissolved metal material in the furnace decreases, the remaining metal material is reattached. The furnace lid 20 is prevented from turning, and the furnace body 16 is rotated from the original position by 60 ° in the counterclockwise direction in the figure, and then a metal material is additionally mounted (FIG. 7C). After that, when the furnace lid 20 and the electrode 22 are placed on the furnace body 16 and the metal material is melted again by arc discharge including a boring process, three hot spots and cold spots are formed in the circumferential direction of the furnace body 16. As a result, the metal material is dissolved unevenly (FIG. 7D).
Therefore, the furnace body 16 is rotated 60 ° clockwise to the original position in the state where the furnace lid 20 is spaced upward, and the undissolved metal material is moved to the hot spot (FIG. 7E). In this state, the furnace lid 20 is closed and the discharge from the electrode 22 is started, so that the undissolved metal material can be effectively heated from the electrode 22. Then, as shown in FIG. 7F, the melting of the metal material charged in the furnace is completed.

However, in the operation in which the hot spot and the cold spot are simply switched by relatively rotating the furnace body and the electrode as in the above-described operation method, the electrode 22 is not in contact with the metal material positioned around the outlet 27. It is far away and it is difficult to dissolve it sufficiently.
Therefore, in this embodiment, as shown in FIGS. 8 and 9, a holding position is set at a position close to the hot water outlet 27, and when any electrode reaches the holding position, the furnace body 16 is stopped and the holding position is set. By performing heating by arc discharge from the electrode 22 in the held state, the metal material around the hot water outlet 27 can be dissolved.

FIG. 8A shows a holding position set with respect to the hot water outlet 27 when the electric furnace is an EBT furnace.
An extension line OP of a line connecting the rotation center O of the furnace body and any one of the plurality of electrodes 22 (the electrode closest to the hot water outlet 27 in the figure) is a protrusion (a hot water outlet) around the hot water outlet 27. It is desirable to set a position that passes between one end in the circumferential direction of the bottom portion 26 and the other end as the holding position. Usually, the angle range α is 100 °.
By setting it as such, the electrode 22 can be positioned close to the metal material around the pouring gate 27, and the metal material around the pouring gate 27 can be effectively heated.
More preferably, the angle formed by the extension line OP with respect to the line connecting the rotation center O of the furnace body and the center of the outlet 27 is less than α / 4 (less than 25 °), more preferably less than α / 6 ( Less than 17 °).
By doing in this way, it can heat effectively with respect to the metal material located in the immediate vicinity of the tap hole 27 which is located in the radial direction outward and is especially away from the electrode.

FIG. 9 shows an example of an operation method in which a holding position is set with respect to the hot water outlet 27 and heating from the electrode is performed at the holding position.
In this example, the steps of FIGS. 9A to 9D are the same as the steps of FIGS. 7A to 7D.
In this example, instead of rotating the furnace body 16 directly from the state of FIG. 9D to the original position, the furnace body 16 is moved from the state of FIG. 9D as shown in FIG. 9E. In the drawing, it is rotated 30 ° clockwise and stopped at a position rotated 30 ° counterclockwise from the original position.
The state shown in FIG. 9E is a state in which the electrode 22 at the closest position to the hot water outlet 27 reaches the holding position set for the hot water outlet 27 in this example. In this example, the extension line OP of the line connecting the rotation center of the furnace body 16 and the electrode 22 closest to the pouring gate 27 sets the position passing through the pouring gate 27 as the holding position.
By performing the arc discharge from the electrode 22 while the electrode 22 is held at the holding position, the metal material around the tap hole 27 can be efficiently heated (FIG. 9F).

In FIG. 9, after heating the metal material positioned around the outlet 27 by arc discharge while being held at the holding position, the furnace body 16 is rotated to the original position with the furnace lid 20 spaced apart upward. (FIG. 9G), the dissolution of the undissolved metal material remaining on the inner surface of the peripheral wall portion 12 is promoted. Then, as shown in FIG. 9H, the melting of the metal material charged in the furnace is completed.
That is, in the operation example shown in FIG. 9, it is possible to effectively prevent the unmelted portion around the tap outlet 27 from being added to the example of FIG. 7 by adding the steps of FIG. 9 (E) → (F). .

In the example shown in FIGS. 7 and 9, the furnace body 16 is rotated by 60 ° at the time of remounting, and then the furnace 22 is re-entered until the electrode 22 located near the pouring gate 27 reaches the holding position with respect to the pouring gate 27. Although the body 16 is rotated, as in the example shown in FIG. 10, the furnace body 16 is rotated from the beginning until reaching the holding position with respect to the hot water outlet 27 at the time of reattachment of FIG. After charging the material, the material can be heated at the holding position to melt the metal material located around the outlet port 27.
In this example, the furnace body 16 is then rotated to the original position (FIG. 10 (F)), the undissolved metal material remaining on the inner surface of the peripheral wall 12 is melted, and the interior of the furnace as shown in FIG. 10 (G). Complete the dissolution of the metal material charged in

  The above is the operation method for preventing the unmelted hot water outlet 27 from being melted. However, when the metal material located around the hot water outlet 29 is efficiently heated, the hot water outlet 27 is set. After heating at the holding position, the furnace body 16 is rotated to reach the holding position set with respect to the spout 29, and then stopped and then held at the stop position. It is also possible to efficiently heat the surrounding metal material.

FIG. 8B shows a holding position set with respect to the tap outlet 29 when the electric furnace is an EBT furnace.
In many cases, the unmelted residue generated around the tap outlet 29 occurs over a range of about 60 ° from the end of the tap outlet 29 on the dust collection port 94 side to the dust collection port 94 side. The holding position is such that the extension line OQ of the line connecting the rotation center O of the furnace body and any one of the plurality of electrodes 22 extends from the end on the dust collection port 94 side of the tap outlet 29 to the dust collection port 94. It is desirable that the angle be set to be within a range of less than 60 ° on the side.
However, the most undissolved amount is in the range of less than about 45 °, particularly less than about 30 ° from the end of the tap outlet 29 on the dust collection port 94 side to the dust collection port 94 side. The position is preferably set so that the angle β shown in the figure is less than 45 °, and more preferably the angle β is less than 30 °.
By doing in this way, the metal material which remained undissolved in the edge part of the spout 29 can be melt | dissolved efficiently.

FIG. 11 is a diagram showing a configuration of a brewing hot water type electric furnace.
In this type of electric furnace, a hot water outlet 65 is formed by an opening penetrating the peripheral wall portion 12 of the furnace body 16 in the radial direction, and a bowl 66 extends from the hot water outlet 65.
In the hot water type electric furnace, the hot water outlet 65 is kept open during the melting operation, so that external air enters the furnace and is attached to the furnace lid from the hot water outlet 65 in the furnace. A cold air flow is generated toward the dust collection port 94, and the metal material in the furnace is cooled around the end of the hot water outlet 65 on the dust collection port 94 side, causing unmelted residue. That is, the situation around the tap 65 is almost the same as the tap of the EBT furnace.
For this reason, in the case of a dredging hot water type electric furnace, the holding position set with respect to the hot water outlet 65 is the rotation center O of the furnace body 16 and the electrode closest to the hot water outlet 65 of the plurality of electrodes 22. It is desirable that the extended line OR of the lines connecting the two is set so that the angle from the end of the tap outlet 65 on the dust collection port 94 side to the dust collection port 94 side is less than 60 °.
More preferably, the angle γ is set in a range of less than 45 °, and more preferably, the angle γ is set in a range of less than 30 °.
By doing in this way, the metal material located around the end part of the hot water outlet 65 can be melt | dissolved efficiently.
Note that the structure of the tap outlet in the hot water type electric furnace is the same as that of the EBT furnace, and the holding position with respect to the tap outlet is preferably set in the same range as in the case of the EBT furnace.

Although the embodiment of the present invention has been described in detail above, this is merely an example. For example, in the present invention, the holding step can be performed separately from the method of switching between a hot spot and a cold spot.
Moreover, the case where an electrode rotates instead of rotating a furnace body may be sufficient, and the number of electrodes may be 2, 4 or other.
Furthermore, the present invention can be implemented in variously modified modes within a range not departing from the gist of the present invention, such as being applicable to an operating method of an electric furnace that melts a metal other than steel.

DESCRIPTION OF SYMBOLS 10 Electric furnace 12 Perimeter wall part 14 Furnace bottom part 16 Furnace body 18 Charge inlet 20 Furnace lid 22 Electrode 26, 86 Protrusion part 27,65,88 Hot water outlet 29,91 Outlet outlet 30,92 Discharge outlet bottom part 32 Rotating device 66

Claims (3)

(A) a furnace body including a cylindrical peripheral wall portion and a furnace bottom portion;
(B) a plurality of electrodes provided downward on the furnace lid side;
(C) a rotating device that rotates the furnace body relative to the electrode about the vertical axis;
And an electric furnace operating method for melting the metal material with the heat of an arc generated between the electrode and the metal material charged in the furnace body in two or more times. ,
The electric furnace is an EBT furnace, and the bottom of the furnace has a protrusion partly protruding radially outward from the outer surface of the peripheral wall part. Is formed,
A rotation step of rotating the furnace body relative to the electrode during or immediately after a loading step of charging the metal material into the furnace body from a loading port during melting of the metal material ;
Relative the rotated furnace body, a holding position where one is to melt the metallic material around the pouring opening or tapping port of the furnace body was set in close proximity to said output water outlet of the plurality of the electrodes That is, when the angle formed by a line connecting one end in the circumferential direction of the protrusion and the rotation center and a line connecting the other end in the circumferential direction and the rotation center is α, the rotation center of the furnace body and a line connecting the one of the electrodes, a position passing through the area within the range of ± alpha / 4 about a line passing through just the center of the angle alpha, or holding position set close to the tapping port, i.e. A position where an extension line of a line connecting the rotation center of the furnace body and any one of the electrodes passes through a range of less than 60 ° from the end of the opening at the tap outlet to the dust collection port side. a holding step led rotation is stopped at and held in the holding position, the
The operation method of the electric furnace characterized by performing melting operation by performing. (A) a furnace body including a cylindrical peripheral wall portion and a furnace bottom portion;
(B) a plurality of electrodes provided downward on the furnace lid side;
(C) a rotating device that rotates the furnace body relative to the electrode about the vertical axis;
And an electric furnace operating method for melting the metal material with the heat of an arc generated between the electrode and the metal material charged in the furnace body in two or more times. ,
The electric furnace is a pouring hot water type electric furnace, and a hot water outlet is formed at an opening penetrating the peripheral wall inward and outward, and a firewood is provided in a form extending outward from the hot water outlet. ,
A rotation step of rotating the furnace body relative to the electrode during or immediately after a loading step of charging the metal material into the furnace body from a loading port during melting of the metal material ;
Relative the rotated furnace body, set close to the output sprue or tapping port for any one to melt the metal material around the pouring opening or tapping port of the furnace body of the plurality of the electrodes The extended position of the holding position , that is, the line connecting the center of rotation of the furnace body and any one of the electrodes is 60 ° from the end of the dust outlet to the side of the dust outlet. less position through the range of the rotation is stopped at that led, a holding step of holding in the holding position,
The operation method of the electric furnace characterized by performing melting operation by performing. 3. The method according to claim 1, wherein after the metal material is heated in a state where the electrode is held at the holding position, a portion that is the center of the cold spot reaches the center or almost the center of the hot spot. And further rotating the furnace body relative to the electrode to melt the metal material remaining undissolved in a state of being positioned at the cold spot.

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