JPH11219781A - Cooling structure for furnace-bottom electrode of direct current arc furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling structure for a furnace-bottom electrode, which can prevent a deformation and a crack in a bonded part of an upper rod electrode and a lower rod electrode and can extend a life time of the furnace- bottom electrode. SOLUTION: This device is provided with a furnace-bottom electrode 19 which penetrates through a furnace-bottom plate 14 and a furnace wall 15 of refractories 12, 13 lined on the furnace-bottom plate 14 and is formed by bonding an upper rod electrode 17 of the same kind of metal as the one to refine and a lower rod electrode 17 of metal with excellent conductivity and thermal conductivity, and a space between the furnace-bottom electrode 19 and the furnace-bottom plate 14 is electrically insulated by insulating material 21. In this case, a side surface cooling member 20 is positioned up to a height level of a bonded surface 16 of the furnace-bottom electrode 19 and the bonded surface 16 is cooled from the surroundings.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the dissolution of metallic materials,
The present invention relates to a cooling structure for a bottom electrode of a DC arc furnace used for refining molten metal.

[0002]

2. Description of the Related Art Conventionally, as a refining arc furnace, a current is passed between an upper electrode disposed above a scrap or molten metal charged in the furnace and an electrode mounted on a furnace wall such as a furnace bottom or a side wall. There is known a DC arc furnace for flowing molten metal and refining molten metal. The bottom electrode in this type of DC arc furnace is
The furnace is exposed to an extremely severe use atmosphere due to heat received from a high-temperature molten metal in the furnace, Joule heat generated when a supply current passes, and the like. Also, this kind of hearth electrode,
An insulator is provided between the furnace bottom plate (or furnace shell) and is electrically insulated. If lead is present in the molten metal, when the metal is melted, the lead penetrates into the joints and cracks of the refractory from the upper surface of the refractory at the furnace bottom, and if the lead is contained in the insulator, , The electrical insulation between the bottom electrode and the bottom plate is destroyed, causing a spark accident. This dielectric breakdown is one of the controlling factors of the life of the furnace bottom electrode.

[0003] Therefore, in the furnace bottom electrode described in Japanese Patent Application Laid-Open No. 3-27981, a furnace bottom structure in which an insulator is electrically insulated between a furnace bottom plate provided with a rod-shaped electrode and a furnace bottom electrode. It is disclosed that a cooling member for solidifying lead penetrating from the upper surface of the refractory toward the insulator is provided in the refractory lined on the upper surface of the furnace bottom plate. However, in this furnace bottom electrode, even though the insulator can be cooled to prevent dielectric breakdown, since the furnace bottom electrode is made of one kind of metal conductor, that is, a steel rod, Joule heat generated is generated. However, there is a problem that the furnace bottom electrode itself is not sufficiently cooled, and the life due to melting of the furnace bottom electrode is short. In the furnace bottom electrode described in Japanese Patent Application Laid-Open No. 60-4787, the lower part of the furnace bottom electrode is made of a metal having high conductivity and high thermal conductivity (eg, copper), and the upper part is made of the same kind of metal as the metal to be refined. Metal (for example, SS
It is disclosed that the cooling of the entire bottom electrode is strengthened by joining the upper rod-shaped electrode and the lower rod-shaped electrode by a joining method that does not generate a gap.

[0004]

However, in the furnace bottom electrode described in Japanese Patent Application Laid-Open No. 60-4787, the molten surface of the furnace bottom electrode (see FIG.
(Indicated by reference numeral 17b in the drawing) is lowered, and when the joint surface between the upper rod-shaped electrode and the lower rod-shaped electrode is approached, the temperature of the joint including the joint surface becomes high, and as a result, the strength is reduced. There is a problem that a large thermal stress is generated due to a difference in thermal conductivity of the lower rod-shaped electrode, and as a result, a deformation or a crack is generated at a joint. In addition, when the operation is completed and natural cooling is performed, the joint may be deformed or cracked due to the large stress generated by the shrinkage due to solidification and the shrinkage due to the cooling, and furthermore, the separation between the upper and lower rod-shaped electrodes may occur. For this reason, it is difficult to reuse the furnace bottom electrode, resulting in an increase in the cost of the furnace bottom electrode.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and a DC arc furnace which can prevent deformation and cracking at a joint between an upper rod electrode and a lower rod electrode and can prolong the life of a furnace bottom electrode. An object of the present invention is to provide a cooling structure for a furnace bottom electrode.

[0006]

According to the present invention, there is provided a semiconductor device comprising:
The cooling structure of the bottom electrode of the direct current arc furnace described above, penetrates a furnace bottom plate and a furnace wall made of a refractory lined on the furnace bottom plate, and an upper rod-shaped electrode made of the same kind of metal as the metal to be refined. A furnace bottom electrode formed by joining a lower rod-shaped electrode made of a metal having good conductivity and thermal conductivity is provided, and the furnace bottom electrode and the furnace bottom plate are electrically insulated by an insulator. In the cooling structure of the bottom electrode of the DC arc furnace, the side cooling member is positioned up to the height of the bonding surface of the bottom electrode, and the bonding surface is cooled from the surroundings. The cooling structure of the bottom electrode of the DC arc furnace according to the second aspect is the cooling structure of the bottom electrode of the DC arc furnace according to the first aspect, wherein the side surface cooling member is provided close to the insulator.

According to a third aspect of the present invention, there is provided a cooling structure for a bottom electrode of a DC arc furnace, wherein the side surface cooling member comprises an outer peripheral surface of the bottom electrode. A cooling jacket that comes in contact with the cooling jacket. Claim 4
The cooling structure of the bottom electrode of the DC arc furnace according to claim 3 is a third embodiment.
In the cooling structure of the bottom electrode of the DC arc furnace described above, the cooling jacket has a structure in which a flow path of the refrigerant is narrowed on a tip side to increase a flow velocity of the refrigerant. Claim 5
The cooling structure of the bottom electrode of the DC arc furnace according to claim 1 is characterized in that:
In the cooling structure for a bottom electrode of a DC arc furnace described above, a coolant is circulated in the lower rod-shaped electrode to cool the vicinity of the joint surface.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. Here, FIG. 1 is an explanatory view of a cooling structure of a bottom electrode of a DC arc furnace according to one embodiment of the present invention. As shown in FIG. 1, a cooling structure 10 for a bottom electrode of a DC arc furnace according to an embodiment of the present invention has a furnace bottom 11 of a DC arc furnace which is not located inside a perm brick 12 (upper side in FIG. 1). A fixed refractory 13 is lined, and the outer side (the lower side in FIG. 1) of the perm brick 12 is supported by a furnace bottom plate (or iron shell) 14. The upper side of the upper surface 14a of the furnace bottom plate 14 is referred to as the inside of the furnace, and the perm bricks 12 and the irregular refractory 13 are referred to as refractories. A furnace bottom electrode 19 having a joint surface 16 penetrating a furnace wall 15 composed of a furnace bottom plate 14, a permanent brick 12, and an amorphous refractory 13 and having an upper bar-shaped electrode 17 and a lower bar-shaped electrode 18 joined together is provided. Mounted on the bottom 11.

A cooling jacket 20, which is an example of a side cooling member, is provided in the vicinity of the joint surface 16 and around the lower rod-shaped electrode 18, with an inner peripheral surface 25 being in contact with an outer peripheral surface 26 of the furnace bottom electrode 19. The insulator 21 is arranged between the cooling jacket 20 and the furnace bottom plate 14, and the cooling jacket 20 and the furnace bottom plate 14 are electrically insulated by the insulator 21. The low-temperature water 23, which is an example of the refrigerant sent from the refrigerant supply pipe 22 to the cooling jacket 20, is passed through the cooling jacket 20 from the vicinity of the joining surface 16 and around the lower rod-shaped electrode 18, and further from the insulator 21. The heat is removed from the surroundings, and is discharged as warm water 23 from the refrigerant discharge pipe 24. Hereinafter, these will be described in detail.

The upper bar-like electrode 17 constituting the upper part of the furnace bottom electrode 19 is made of the same kind of metal as the metal to be refined, that is, SS material or the like, as in the prior art. The rod-shaped electrode 18 is also made of copper, which is an example of a metal having good conductivity and thermal conductivity, as in the related art.
The upper bar-shaped electrode 17 and the lower bar-shaped electrode 18 are connected to each other by a method that does not generate a gap, and a furnace bottom electrode 19 having a strong joint surface 16 is provided.
Formed. During operation, the upper bar-shaped electrode 17 is melted to the position shown in the figure and becomes a molten metal portion 17a.
After the operation is completed, the upper electrode 17 is formed again by solidification. Reference numeral 17b in the figure represents the molten surface of the molten metal.

As shown in FIG.
The inner peripheral surface 25 is formed in a hollow cup shape made of copper so as to contact the lower end of the upper bar-shaped electrode 17 and the outer peripheral surface 26 of the entire lower bar-shaped electrode 18. Cooling jacket 20
The upper end surface 27 is arranged so as to be at the same level as the boundary surface between the permanent brick 12 and the refractory 13, and an annular flange portion 29 is provided so as to protrude from an outer peripheral surface 28 of the intermediate portion. The insulator 29, the insulator 21, and the furnace bottom plate 14 are fastened by a plurality of bolts (not shown) in consideration of insulation. The inner peripheral surface of the perm brick 12 is in contact with the outer peripheral surface 28 at the upper end of the cooling jacket 20. Therefore, the furnace bottom plate 14 and the perm brick 12 around the insulator 21 including the insulator 21 can be effectively cooled by the fin effect of the copper flange portion 29, so that the lead in the molten metal can reduce the lead in the perm brick 12 and the furnace. Insulator 21 through bottom plate 14
It can be reliably prevented from penetrating into.

Further, in the hollow portion 32 formed by the outer wall 30 and the inner wall 31 of the cooling jacket 20, in order to efficiently cool with the water 23, the partition piece 34 is formed so as to secure a passage 33 for the water 23. Are provided spirally, and water 2 is provided so as to enhance the cooling effect on the tip side of the cooling jacket 20, that is, near the lower end of the upper bar-shaped electrode 17.
The partitioning pieces 34 are arranged so that the cross-sectional area of the passage 33 becomes smaller so that the flow velocity of the passage 3 gradually increases. And
Refrigerant supply pipe 2 connected to the lower part of cooling jacket 20
The water 23 which has been sent from the cooling jacket 20 and whose speed has increased while turning upward in the passage 33 gradually narrowed in the cooling jacket 20.
When it reaches the upper end of the cooling jacket 20, it gradually descends while gradually decreasing its speed and is discharged from the refrigerant discharge pipe 24. For example, as a structure for forming such a passage 33, a structure similar to the shape of a double thread is formed, and a water inlet side and a water outlet side passage are formed.
The pitch of the screw may be gradually changed. Thus, the bonding surface 1 of the furnace bottom electrode 19
By effectively cooling 6, the molten surface 17b can be raised, and deformation of the joint including the joint surface 16,
Cracks can be effectively suppressed.

A refining operation using an arc furnace having a cooling structure 10 for a bottom electrode of a DC arc furnace according to an embodiment of the present invention having such a configuration will be described with reference to FIG. A scrap, which is a raw material for melting, is loaded on the furnace bottom 11 of the arc furnace, and power is supplied between an upper electrode (not shown) and a furnace bottom electrode 19, as is well known, so that the scrap is melted and the molten metal is melted. At the same time, the upper bar-shaped electrode 17 of the furnace bottom electrode 19 is also melted as shown in the figure, and a molten metal portion 17a is formed.

During operation, heat from the molten metal is transmitted to the furnace bottom 11, and the refractory 13, the permanent brick 12
And the temperature of the furnace bottom plate 14 rises. For this reason, when lead is mixed in the scrap, the lead melted by melting penetrates from the upper surface 35 and the inner peripheral surface 36 of the amorphous refractory 13 through the cracks in the amorphous refractory 13 and further through the joints and cracks of the permanent brick 12. However, the water 23 flows through the passage 33 in the cooling jacket 20, and the furnace bottom plate 14 and the perm brick 12 around the insulator 21, including the insulator 21.
Can be effectively cooled, so that the lead in the molten metal can be reliably prevented from penetrating into the insulator 21 through the perm brick 12 and the furnace bottom plate 14. At the same time, the vicinity of the joint surface 16 of the bottom electrode 19 and the lower end of the upper bar electrode 17 are cooled by the cooling jacket 20, so that the bottom electrode 19 is cooled.
Is effectively cooled, the molten surface 17b can be raised, and the temperature of the joint surface 16 can be kept low. Accordingly, since a decrease in the strength of the bonding portion including the bonding surface 16 can be suppressed, deformation, cracking, and separation between the lower bar-shaped electrodes 17 and 18 can be suppressed.

FIG. 2 is an explanatory view of a cooling structure 10a of a bottom electrode of a DC arc furnace according to another embodiment of the present invention.
Note that the same components are denoted by the same reference numerals,
Similar components are appended with subscripts and detailed description is omitted. The difference between the cooling structure 10a of the bottom electrode of the DC arc furnace according to another embodiment of the present invention and the cooling structure 10 of the bottom electrode of the DC arc furnace is that the lower rod-shaped electrode 18a is joined to the upper rod-shaped electrode 17. The inside of the lower rod-shaped electrode 18a is cooled in the vicinity of the joint surface 16 while circulating a coolant such as water through a coolant supply pipe and a coolant discharge pipe (not shown). I have. The cooling jacket 20a, which is an example of the side cooling member, has substantially the same arrangement and structure as the cooling jacket 20.
The outer peripheral surface 26a of 9a and the inner peripheral surface of the perm brick 12 are configured to be cooled. Here, reference numeral 34a denotes two equally-partitioned partition pieces, whereby a water inlet side and a water discharge side are alternately formed at an intermediate portion of each partition piece 34a. Also in the cooling structure 10a of the bottom electrode of the DC arc furnace, as shown in the figure, the vicinity of the joining surface 16 is cooled from the inside of the lower rod-shaped electrode 18a. 17b can be kept away from the joining surface 16.

In the embodiment shown in FIG. 1, when the position of the joint surface 16 between the upper bar-shaped electrode 17 and the lower bar-shaped electrode 18 is in the furnace (representing above the upper surface 14a of the furnace bottom plate 14), In order to strongly cool the vicinity of the joining surface 16, water is supplied to the cooling jacket 20 as a side cooling member, but the position of the joining surface 16 is outside the furnace (the furnace bottom plate 14).
If necessary, a simpler side cooling member (for example, a coolant having one end protruding outside the furnace body) may be used. Further, the cooling jacket 20 is used as a side cooling member.
Was used, but it is also possible to embed a pipe body through which the refrigerant can pass through in the furnace and circulate the refrigerant through the pipe body. In the embodiment shown in FIG. 2, a columnar coolant circulation space is provided inside the lower rod-shaped electrode 18 a for cooling the vicinity of the joint surface by the lower rod-shaped electrode 18 a, but the present invention is not limited to this structure. .

[0017]

According to the cooling structure for a bottom electrode of a DC arc furnace according to the first to fifth aspects, the side cooling member is positioned up to the height of the bonding surface of the bottom electrode, and the bonding surface is cooled from the surroundings. Therefore, a decrease in the strength of the bonding surface is suppressed, and deformation and cracking at the bonding portion can be prevented, and the life of the furnace bottom electrode can be extended. In particular, in the cooling structure of the bottom electrode of the DC arc furnace according to the second aspect, since the side cooling member is provided close to the insulator, the side cooling member allows the insulator, the furnace bottom plate and the bottom plate to be placed on the bottom plate. The lined refractory can be effectively cooled to a temperature below the melting point of lead, so that even if the lead present in the molten metal penetrates into the joints and cracks of the refractory, it reaches the insulator. And a spark accident occurring between the bottom electrode and the bottom plate can be prevented.

In the cooling structure for a bottom electrode of a DC arc furnace according to the third aspect, the side cooling member is a cooling jacket that contacts the outer peripheral surface of the bottom electrode and the insulator.
The joint surface of the furnace bottom electrode and the insulator can be more effectively cooled. In the cooling structure for the bottom electrode of the DC arc furnace according to the fourth aspect, the cooling jacket has a structure in which the front end side of the cooling passage is narrowed to increase the flow velocity of the cooling medium, thereby improving the cooling efficiency. it can. In the cooling structure for the bottom electrode of the DC arc furnace according to the fifth aspect, since the coolant is circulated in the lower rod-shaped electrode to cool the vicinity of the joint surface, a decrease in the strength of the joint surface can be further suppressed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a cooling structure of a bottom electrode of a DC arc furnace according to one embodiment of the present invention.

FIG. 2 is an explanatory view of a cooling structure of a bottom electrode of a DC arc furnace according to another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Cooling structure of bottom electrode of DC arc furnace 10a Cooling structure of bottom electrode of DC arc furnace 11 Furnace bottom 12 Perm brick 13 Irregular refractory 14 Furnace bottom plate 14a Upper surface 15 Furnace wall 16 Joining surface 17 Upper bar electrode 17a Melting Metal part 17b Fused surface 18 Lower rod electrode 18a Lower rod electrode 19 Furnace bottom electrode 19a Furnace bottom electrode 20 Cooling jacket (side cooling member) 20a Cooling jacket (side cooling member) 21 Insulator 22 Refrigerant supply pipe 23 Water (coolant) ) 24 Refrigerant discharge pipe 25 Inner peripheral surface 26 Outer peripheral surface 26a Outer peripheral surface 27 Upper end surface 28 Outer peripheral surface 29 Flange part 30 Outer wall 31 Inner wall 32 Hollow part 32a Hollow part 33 Passage 34 Partition piece 34a Partition piece 35 Upper face 36 Inner peripheral face

Claims (5)

[Claims] 1. An upper rod-shaped electrode made of a metal of the same kind as a metal to be refined penetrating a furnace wall made of a furnace bottom plate and a refractory lined on the furnace bottom plate and having good conductivity and thermal conductivity. A bottom electrode formed by joining a lower rod-shaped electrode made of metal is provided, and a bottom electrode of a DC arc furnace in which the bottom electrode and the bottom plate are electrically insulated by an insulator. The cooling structure for a bottom electrode of a DC arc furnace, wherein a side cooling member is positioned up to a height of a joint surface of the bottom electrode, and the joint surface is cooled from the periphery. 2. The cooling structure for a bottom electrode of a DC arc furnace according to claim 1, wherein said side cooling member is provided close to said insulator. 3. The cooling structure for a bottom electrode of a DC arc furnace according to claim 1, wherein the side surface cooling member is a cooling jacket that contacts an outer peripheral surface of the bottom electrode. 4. The cooling structure for a bottom electrode of a DC arc furnace according to claim 3, wherein the cooling jacket has a structure in which a flow path of the refrigerant is narrowed at a tip end side to increase a flow velocity of the refrigerant. 5. A coolant is circulated in the lower rod-shaped electrode,
The cooling structure for a bottom electrode of a DC arc furnace according to claim 1, wherein the vicinity of the joint surface is cooled.