JPH0783566A - Water cooling ceiling for arc type electric furnace - Google Patents

Abstract

PURPOSE:To provide a water cooling ceiling, for use in arc type electric furnace, capable of achieving the improvement of production ability and the reduction of manufacturing coat by contriving the extension of lifetime of the furnace ceiling including the small ceiling part of a refractory structure. CONSTITUTION:An arc type electric furnace body is composed of a furnace with an open top and a furnace ceiling 5 consisting of a large ceiling part 9 and a small ceiling part 8. The small ceiling part 8 is integrally provided in the interior of the large ceiling part 9 of a water cooling structure and is formed of refractory around the periphery of an electrode hole 12 provided on a pitch circle coaxial of the furnace body. This small ceiling part 8 has the thickness of the refractory 15 around the periphery of the electrode on the pitch circle made larger than that of the other part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arc type structure which includes a bottomed furnace body which is opened upward and into which raw materials are charged, and a furnace ceiling which covers the bottomed furnace body so that it can be mounted from above. Regarding water-cooled furnace ceilings in electric furnaces, more specifically, it relates to water-cooled furnace ceilings that have excellent heat resistance, wear resistance, and impact resistance even when used under extremely high temperatures and severe conditions. is there.

[0002]

2. Description of the Related Art In recent years, the production amount of crude steel by an arc type electric furnace has been increasing, and with the increase of metal scrap as a main raw material, in order to improve the melting capacity, the furnace volume is increased and the electric power is increased. However, if the power is increased to a large extent, the refractory material in the electric furnace body will be greatly worn and damaged, which makes cooling the water in the furnace body indispensable. It is necessary to make it a structure.

FIG. 10 is a sectional view showing a typical prior art of a conventional arc type electric furnace. In general, as shown in this figure, the water cooling structure of the furnace wall 3 and the furnace ceiling 5 of the bottomed furnace body 2 that is water-cooled in the main body of the electric furnace 1 includes a heat transfer tube 1 for water cooling.
1 are provided concentrically at equal distances to the central axis of the furnace 1 main body (that is, the central axis of the furnace body 2 and also the central axis of the furnace ceiling 5), and the inner surface of the furnace 1 is Not arranged in a planar structure.

When the main body of the furnace 1 is water-cooled in this way, the amount of refractory used is greatly reduced and the durability is increased. Therefore, for example, the repair time required for replacement work of the furnace ceiling 5 can be greatly reduced. Therefore, it is possible to improve the economical efficiency and the productivity.

However, in this furnace ceiling 5,
Although it is desired to water-cool the entire furnace ceiling 5, water cooling is not performed in the furnace ceiling 5 portion around the electrodes 7 in which a plurality of electrodes 7 are charged, and electrical insulation is not performed for the reason described below. The small ceiling portion 8 made of refractory is unavoidably arranged.

A. When such a heat transfer tube 11 is arranged on the furnace ceiling 5 part around the electrodes 7, that is, on the small ceiling part 8 to form a water-cooled structure, the secondary voltage charged from the transformer to the plurality of electrodes 7 is in the furnace body 2. It is not possible to construct such a water-cooling structure because the metal scrap as the main raw material charged in the tank is not loaded, and a short-circuit occurs in the water-cooling structure in which the heat transfer tubes 11 that are present in a short distance are arranged and sparks are generated. point.

B. The heat load due to the arc of the electrode 7 is the largest, and the plurality of electrodes 7 inserts (descends) or ascends the electrode holes 12 in each electrode hole 12 by an elevating device (not shown), so that friction, collision, shock and vibration occur. The water cooling structure in which 11 is arranged is easily worn or damaged and cannot be used for a long time. c. Therefore, the furnace ceiling 5 that opens upward and blocks the bottomed furnace body 2 into which the raw material is charged so as to be freely mounted from above cannot cool the entire furnace ceiling 5 with water, and therefore the large ceiling portion 9 and the small ceiling portion 8 From the above, the entire furnace ceiling 5 is constituted, and the small ceiling portion 8 is integrated inside the large ceiling portion 9 corresponding to the peripheral portion, and the large ceiling portion 9 is made into a water cooling structure in which the heat transfer tubes 11 are arranged. The small ceiling portion 8 is formed of a refractory which is an electrical insulator, and a plurality of electrode holes 12 in which the electrodes 7 are formed on a pitch circle coaxial with the main body of the furnace 1 of the small ceiling portion 8 are provided. Inevitable point.

As described above, the periphery of the plurality of electrodes 7, that is, the small ceiling portion 8 is formed of a refractory material. The refractory material is directly subjected to the heat load of the electrode arc, and in addition, friction, collision, impact, vibration are caused. Therefore, the amount of wear and damage is very large. Therefore, the life of the small ceiling portion 8 is limited by the amount of wear of the refractory material around the plurality of electrodes 7, and the fire resistance around the electrodes 7 is maintained even when the portions other than the electrodes 7 are hardly worn or damaged. Since the amount of wear of the object is much more severe, there is no choice but to replace the small ceiling portion 8, that is, the furnace ceiling 5 having the small ceiling portion 8. This replacement of the small ceiling part 8 in the furnace ceiling 5 not only leads to an increase in cost, but also takes a very long time, which causes a problem of reducing the production capacity, an increase in the number of preliminary storages of the furnace ceiling 5, and a small ceiling part. There is a problem such as an increase in the site area required for the 8 repair shops.

[0009]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is, in particular, for a small ceiling portion of a refractory structure in a furnace ceiling, in particular, for a peripheral portion of a pitch circle connecting a plurality of electrode centers in this small ceiling portion. Even if exposed to extremely harsh conditions such as the heat load of the electrode arc, by constructing a material and structure with excellent heat resistance, abrasion resistance, impact resistance, etc., this small ceiling It is an object of the present invention to provide a water-cooled furnace ceiling for an electric arc furnace, which is capable of extending the life of the furnace ceiling, improving the production capacity, and reducing the cost, which leads to this.

[0010]

According to the present invention, there is provided a bottomed furnace body which opens upward and into which raw materials are charged, and a bottomed furnace body which can be mounted so as to be mountable from above and which has a large ceiling portion and a small ceiling portion. A furnace main body is configured to include a furnace ceiling consisting of, and a small ceiling part that is integrated inside the large ceiling part of the water-cooling structure that corresponds to the peripheral part,
An arc-type electric furnace comprising a plurality of electrode holes into which electrodes are inserted on a pitch circle that is coaxial with the furnace body, and a small ceiling portion around the pitch circle of the electrode is formed of a refractory material. The small ceiling part is a water-cooled furnace ceiling for an electric arc furnace, characterized in that the thickness of the refractory material around the pitch circle of the electrode is formed thicker than the thickness of other parts.

According to the present invention, the refractory around the pitch circle of the electrode in the small ceiling has a wall thickness 1.2 to 2.0 times as thick as the wall thickness of other portions. In this area, the distance from the central axis of the furnace ceiling, which is coaxial with the furnace body, to the electrode pitch circle is r, and the distance to the inner peripheral surface of the water cooling jacket provided on the outer peripheral part of the small ceiling part is R. When
It is characterized by being in the range of 0.5 · r to (R-500) [mm].

Further, in the present invention, the refractory in the small ceiling portion is formed by using a high alumina amorphous refractory containing 75% by weight or more of each main component of Al ₂ O ₃ and SiO _2. It is characterized by being done.

Further, in the refractory in the small ceiling portion of the present invention, the refractory around the pitch circle of the electrode has a shape of a brick (mass brick) having electrode holes in a portion having a plurality of electrode holes into which the electrodes are inserted. , Cylindrical brick) or using a fixed brick laid around the electrode hole to form an electric hole, and the other part is molded using an irregular refractory material.

Further, according to the present invention, a fixed brick having an electrode hole and a fixed brick laid around the electrode hole to form an electric hole contain SiO ₂ as a main component together with 80% by weight or more of Al ₂ O _3. It is characterized in that it is a high-alumina shaped brick or a maguro-shaped shaped brick containing MgO and Cr ₂ O ₃ as main components.

[0015]

According to the respective means of the present invention described above, in the small ceiling portion of the refractory structure in the furnace ceiling, the peripheral portion of each electrode hole (peripheral portion of the pitch circle of each electrode) through which a plurality of electrodes are inserted is formed. Refractory is exposed to various severe conditions including the heat load of a very high temperature electrode arc, and even if its wear and damage amount is very large, each of the present invention in terms of its shape structure and material Depending on the method, it takes time to reach the thinness of the service limit, and under the condition of the service limit, other parts other than the peripheral part of the electrode hole also wear, and the remaining thickness is about the same as the peripheral part of the electrode hole. It can be used until the state of. That is, the service life of the small ceiling portion is extended, the service life of the small ceiling portion, and thus the furnace ceiling, can be improved, the decrease in production capacity due to the replacement of the small ceiling portion can be eliminated, and the cost can be reduced.

[0016]

【Example】

(Embodiment 1) FIG. 1 is a vertical sectional view showing a state in which a furnace ceiling 5 of an arc type electric furnace 1 according to an embodiment of the present invention is opened. In this embodiment, the main body of the arc type electric furnace 1 is an AC three-phase type and has a bottomed furnace body 2 which is opened upward and into which metal scrap as a main raw material and other auxiliary raw materials are charged. The bottomed furnace body 2 is closed from above so that it can be mounted freely, and includes a furnace ceiling 5 composed of a large ceiling portion 9 and a small ceiling portion 8.

The bottomed furnace body 2 has a furnace bottom 3 and a furnace wall 4 having a substantially right cylindrical inner peripheral surface, and the furnace wall 4 is a water-cooled furnace wall 4 in which a group of heat transfer tubes 11 is arranged. Has been done. On the other hand, the furnace ceiling 5 according to the present invention is, for example, a large ceiling portion 9 of a water cooling structure corresponding to a peripheral portion of a hat type and having a group of heat transfer tubes 11 integrated therein. And a small ceiling portion 8 having a refractory structure, which is provided with electrode holes 12 into which a plurality of (three) electrodes 7 can be inserted respectively on a pitch circle coaxial with the main body of the furnace 1. Configured.
The furnace ceiling 5 is opened / closed by a device (not shown) that vertically moves (rotates) the entire furnace ceiling 5 up and down with respect to the opening above the furnace body 2 that is fixedly installed.

In this way, through the electrode holes 12 provided in the small ceiling portion 8 of the furnace ceiling 5 mounted on the upper opening of the furnace body 2 from above, a plurality of electrode elevating and lowering devices (not shown) are operated to operate a plurality of devices. The (three) electrodes 7 are respectively inserted. Then, in the internal space 6 of the furnace body 2, a hot metal or a molten metal obtained by melting and melting the main and auxiliary raw materials including the metal scraps, etc., which have been charged in advance by an arc generated by energizing each of the inserted electrodes 7. And the slag layer are stored. Due to the generation of such an electrode arc, the internal space 6 in the furnace body 2 has a high temperature of, for example, about 1000 ° C., and the hot spot near the electrode 7 directly under the heat load of the electrode arc has a temperature of 1500 to 2000 ° C. It becomes a high temperature region.

FIG. 2 is a plan view of the furnace ceiling 5 shown in FIG. FIG. 3 also shows a vertical section of the furnace ceiling 5. Further, FIG. 4 shows an enlarged plan view of the small ceiling portion 8 of the furnace ceiling 5. The furnace ceiling 5 is formed in a substantially truncated cone shape, and has a cooling structure in which a small ceiling portion 8 through which each electrode 7 is inserted is provided in the central portion and a group of heat transfer tubes 11 for flowing cooling water is provided along the inner surface side. The small ceiling portion 8 is surrounded by the large ceiling portion 9 so as to be integrated. In the small ceiling portion 8, on the pitch circle 13 having a radius r [mm] from the center which is coaxial with the main body of the furnace 1 and the furnace body 2, a predetermined diameter is provided at each position that divides the circumference into three equal parts. Electrode hole 12
Are drilled, and the carbon electrodes 7 are inserted into the respective electrode holes 12. Moreover, the small ceiling portion 8 is provided with a water cooling jacket 10 formed in a ring shape on the outer peripheral portion thereof. Similarly, from the central axis O of the furnace body 1, the furnace body 2 and the furnace ceiling 5, the inner peripheral surface of the water cooling jacket 10 is provided. Is set to R [mm]. The heat transfer tubes 11 provided in the large ceiling portion 9 are arranged in a multi-row concentric pattern with respect to the center of the furnace ceiling 5, the arrangement pattern of which is schematically shown in FIG.

Referring to FIGS. 3 and 4, the small ceiling portion 8
Is a reinforcing material 14 made of, for example, ordinary steel and a refractory material 15.
It is molded into a disk shape by and. The reinforcing material 14 includes a round bar-shaped core material portion 14A serving as a central portion of the small ceiling portion 8, a ring-shaped edge material portion 14B serving as a peripheral portion inscribed in the water cooling jacket 10, and these core material portions 14A and It is composed of a Y-shaped rib portion 14C that connects the edge member portion 14B. Refractory 15
Is formed by filling the inner space of the reinforcing member 14,
As shown in the cross-section of FIG. 3, the wall thickness of the electrode 7 from the peripheral portion of the pitch circle 13 to the inner space portion is formed thicker than the wall thickness of other portions. In this embodiment, the refractory material 15 is formed such that the portion outside the pitch circle that is in contact with the edge member portion 14B is the thinnest and the wall thickness gradually increases toward the vicinity of the pitch circle 13. Since the thin portion is close to the water cooling jacket 10, the temperature does not rise to a high temperature and the wear is very small, so there is no problem even if it is thin. It also serves the purpose of reducing the weight of the furnace ceiling 5. In addition, in FIG. 3, black circles indicate
In particular, since it is a portion where the melting loss is great, it is also a preferable means to make it thickly project downward and be thickly molded.

The refractory 15 in the small ceiling portion 8 is molded into the shape and structure as described above. Based on various experimental results, the type of refractory and the material of the refractory to be molded into. The construction method will be described below.

Conventionally, as the refractory material 15, a method of manually laying and molding a predetermined relatively expensive fixed-sized brick was used, but labor saving, improvement in workability and working environment,
Since there are problems from the viewpoints of safety, work efficiency, and cost reduction above all, recently, a method of forming and molding with an irregular refractory material [indeterminate] has been adopted.

Therefore, as the refractory material 15 for the small ceiling portion 8 according to the present invention, a non-standard refractory material is used for molding, and various experimental results regarding the material thereof show that 75% by weight or more of Al ₂ O _{3 is used.}
It is preferable to use a high-alumina amorphous refractory material containing major components of SiO ₂ and SiO ₂ .

More preferably, 80% by weight or more of Al ₂
It is preferred to use a highly alumina amorphous refractory containing the major components of O ₃ and about 10 wt% SiO ₂ .

If the dimensional structure of the entire furnace ceiling 5 is constant and the shape and structure of the refractory material 15 itself in the small ceiling part 8 are first set to be suitable, then a suitable formwork should be set up as above. The amorphous refractory described in 1 above can be kneaded, poured, and dried to repeatedly and easily form the refractory 15.

Therefore, since the refractory material 15 in the small ceiling portion 8 according to the present invention is formed by using the irregular-shaped refractory material as described above in a suitable shape and structure, the heat resistance of the electrode arc is reduced. Even when exposed to extremely harsh conditions such as load, it has excellent heat resistance, abrasion resistance, impact resistance and durability.

Therefore, as a result of various experiments and examinations conducted by the present inventor based on the details described above, the small ceiling portion 8 according to the present invention is compared with the conventional example and the comparative example. It has been confirmed to be excellent in terms of service life.

That is, Table 2 shows that the small ceiling part according to the present invention and the small ceiling parts of the conventional and comparative examples are installed in a large 90T electric furnace, and the steel type SUS3 with the main and auxiliary raw material combinations shown in Table 1 is installed.
The results obtained by melting and melting 04 series stainless steel are shown.

[0029]

[Table 1]

[0030]

[Table 2]

In Table 2, Comparative Example 1 is a conventional small ceiling portion, and Comparative Example 2 is an example when the thickness portion of the refractory material is less than 1.2 times that of the other portions. In Comparative Example 2, the thickness of the refractory material around the electrodes is not sufficient to eliminate the rate-determining of the amount of wear. Therefore, the refractory portion other than the electrodes also has a low service life limit in the state where the wear does not proceed, and The service life is almost the same as the small ceiling part of the structure.

However, when the wall thickness of the refractory is 1.2 times or more that of the other parts as in the present invention, the refractory around the pitch circle of the electrode is directly subjected to the heat load of the electrode arc, Even if the amount of wear is very large, it takes time to reach the thinness of the service limit.In the state of the service limit, wear of the refractory parts other than around the electrode also progresses, and the remaining thickness is Since the service life of the small ceiling portion can be extended to the same level, the service life of the small ceiling portion is extended, and the service life is twice as long as that of the small ceiling portion of the conventional structure of Comparative Example 1.

However, if the thickness of the refractory material is 2.0 times or more that of the other portions as in Comparative Example 3, conversely, the wear of the refractory material other than the periphery of the pitch circle of the electrode becomes rate-determining, The service life of the present invention is not extended and the refractory around the electrodes is molded to a thicker wall, leading to an increase in cost.

FIG. 5 shows the relationship between the distance from the center of the small ceiling to the water cooling jacket and the wear rate of the refractory. 1 / the distance r of the electrode pitch circle from the center of the electrode
Up to 2, since the distance from the electrode is large, the heat load of the electrode arc is small and the wear rate is smaller than the peripheral portion of the electrode pitch circle. Further, within a range of 500 mm or less from the inner peripheral surface of the water-cooling jacket in the small ceiling part, the heat removal from the water-cooling jacket is large and the refractory material is cooled, so that the wear rate of the refractory material becomes small. Comparative Example 4 in Table 2 shows the results when a small ceiling portion having a thick portion of the refractory material of less than 0.5r is used, and Comparative Example 5 shows a thick portion portion of the refractory material having a small ceiling portion. It is a result when a small ceiling part having a distance R-500 mm or more to the inner peripheral surface of the water cooling jacket is used. In Comparative Example 4, the amount of wear of the refractory material in the region distant from the electrode, that is, the region ½ of the distance r of the electrode pitch circle from the center of the furnace ceiling is small, and this region is thicker than the present invention. The thick molding leads to higher costs. Further, in Comparative Example 5, the amount of wear of the refractory material in the region of the distance R-500 mm or more is small, and as compared with the present invention, the region is molded thickly, which leads to an increase in cost.

(Embodiment 2) Since Embodiment 2 has many parts which are basically carried out in substantially the same manner as Embodiment 1 described in detail above, it will be described below while omitting the overlapping portions.

In the furnace ceiling 5 described in the first embodiment,
It has been described that when the refractory material 15 in the small ceiling portion 8 is molded into a suitable shape or structure, it is preferable to use an irregular-shaped refractory material for construction and molding.

As a result of further experiments and investigations conducted by the inventor, the refractory material 15 in the small ceiling portion 8 constructed and molded using the irregular refractory material as described above.
Is exposed to the extremely harsh conditions described above,
As can be understood from the results shown and described in [Table 2],
Although it has a better service life than the conventional one and is satisfactory, in order to further extend the service life, a refractory 1 constructed and molded using such an irregular shaped refractory 1
It was found that 5 is not sufficient for thermal and mechanical spalling. Moreover, it can be understood from the contents already described in the above [Prior Art] and shown and described as the wear rate ratio of the refractory material 15 at each position corresponding to each distance from the central axis of the furnace ceiling 5 in FIG. As described above, the refractory material 15 in the small ceiling 8 is
The peripheral parts of the plurality (three) of electrodes 7 (around the electrode 7, peripheral parts of the pitch circle 13 of the electrode 7) are most worn, and the refractories 15 in the other parts are not worn but are sound,
It has been found that the service life of the small ceiling portion 8 and thus the furnace ceiling 5 is limited.

Therefore, the inventor has, as the refractory material 15 in the small ceiling portion 8, only the peripheral portions of the plurality (three) of the electrodes 7 that are most severely worn, as described in the first embodiment, of the electrodes 7. Use a fixed refractory (fixed brick) with more excellent thermal and mechanical spalling resistance instead of forming and molding up to the inner peripheral surface of the electrode hole 12 to be inserted using an irregular refractory Was conceived. Based on this idea. As a result of conducting various experiments and making further studies, a more preferable means was obtained, which will be described below with reference to FIGS. 6 to 9.

FIG. 6 shows the small ceiling portion 8 of the furnace ceiling 5 shown in FIG.
A fixed brick in which an electrode hole 12 through which the electrode 7 can be inserted is bored is laid, and the other portion is constructed by using the irregular refractory material 15 as described in the first embodiment and integrally molded. It is a longitudinal cross-sectional explanatory view showing each case. FIG. 7 shows the small ceiling portion 8 of the furnace ceiling 5 shown in FIG.
It is an enlarged plan view for explaining the longitudinal cross-sectional explanatory view of each case shown in FIG.

Referring to FIGS. 6 and 7, a case where a mass brick 15B having a shape different from that of a normal rectangular parallelepiped is laid as a fixed-shape brick at the portion A of the portion through which the electrode 7 is inserted and integrally molded is also shown in B. In the example, a cylindrical brick (sleeve brick) 15C is laid as a standard brick in the section and integrally molded.

On the other hand, FIG. 8 shows the furnace ceiling 5 shown in FIG.
In the small ceiling portion 8 in, a fixed brick is laid around the electrode hole 12 through which the electrode 7 is inserted to form the electrode hole 12 in the portion through which each electrode 7 is inserted, and the other portions are formed according to the first embodiment.
It is a longitudinal cross-sectional explanatory view showing a case in which the same irregular shaped refractory material 15 as in the case of (1) is used and integrally molded. Figure 9
FIG. 9 is an enlarged plan view for explaining a vertical cross-sectional explanatory view of the case shown in FIG. 8 in the small ceiling portion 8 of the furnace ceiling 5 similarly shown in FIG. 2.

Referring to FIGS. 8 and 9, as shown in a portion C, a mass brick 15A having a shape different from that of an ordinary rectangular parallelepiped is laid as a regular brick around the electrode hole 12 through which the electrode 7 is inserted. A case is shown in which the hole 12 is formed and the other portion is constructed by using an irregular shaped refractory material 15 and integrally formed.

From the examination results described above with reference to FIGS. 6 to 9, the refractory material 15 forming the small ceiling portion 8 in the furnace ceiling 5 is located in the peripheral portion of the electrode 7 (the pitch circle 13 of the electrode 7).
A plurality of electrode holes 1 into which electrodes 7 are inserted in the peripheral portion)
In a portion where 2 is present, a fired or non-fired regular brick having an electrode hole 12 formed therein, specifically, a mass brick 15B or a cylindrical brick (sleeve brick) 15C having an irregularly shaped electrode hole 12 formed therein A deformed mass brick 15 which is used or is laid around the electrode hole 12 to form the electrode hole 12.
The use of A and the other parts using the irregular-shaped refractory material 15 and the integral molding are combined with the fact that the thickness of the refractory material 15 is thick as described above. It is a preferable means for increasing durability.

Furthermore, the electrode hole 12 as described above is used.
Of a fixed-shaped brick [mass brick 15B in which an odd-shaped electrode hole 12 is drilled, cylindrical brick (sleeve brick) 1]
5C] and a fixed-shape brick (a different-shaped mass brick 15A) laid around the electrode hole 12 to form the electric hole 12,
About 10% by weight of Si together with Al ₂ O _{3 by} weight% or more
A high-alumina calcined shaped brick containing O ₂ as each main component, or MgO in the range of 55 to 65 wt% and 10
It is preferable to use a non-sintered fixed-type brick of magchromic material containing Cr ₂ O ₃ in the range of ˜30 wt% as each main component, together with the various preferable means described in detail above. Is.

In the second embodiment, the shape and structure of the fixed refractory (various fixed bricks) laid around the electrode hole 12 and the wall thickness thereof and the supporting method thereof can be freely changed. For example, a double-type fixed brick may be used by stacking another fixed brick on the outer circumference of a fixed brick made of a material that is more expensive but has a significantly higher durability.

Further, in the case of the second embodiment, the fixed refractories (various fixed bricks) laid around the electrode holes 12 in the peripheral portion of each electrode 7 that is most worn or damaged.
Local repairs can be performed in a short time by replacing old and new and stamping the surrounding area with an irregular refractory.

In any case, in the case of the second embodiment,
The small ceiling part 8 of the furnace ceiling 5 is hard and durable only around the electrode hole 12 exposed to the most severe conditions.
5A, 15B, 15C) and the irregular shaped refractory 15 having various advantages as described above are also integrally molded, so that it can be molded in the same manner as in the first embodiment, and is durable. The life is doubled.

[0048]

As described above in detail, in the water-cooled furnace ceiling for an electric arc furnace according to the present invention, since it is exposed to various severe conditions including the electrode arc, the amount of wear and damage is large, The circumference of the pitch circle of a plurality of electrodes in the small ceiling part of the refractory structure that is considered to affect the life of the water-cooled furnace ceiling is formed by a thicker refractory than other parts, and the shape structure and It is configured by each means preferable in terms of material.

Therefore, the durability of the portion of the small ceiling portion having the largest amount of wear is remarkably improved, and the water-cooled furnace is integrated with the small ceiling portion of the refractory structure and the large ceiling portion of the water cooling structure. The service life of the entire ceiling can be significantly extended. As a result, the service life is extended by 2 to 4 times as compared with the conventional water-cooled furnace ceiling having a small ceiling, and the replacement frequency that is performed every 2-3 months is greatly reduced, and the operation per operation is reduced. It is possible to significantly reduce the loss time, which required about 4 hours for the replacement work performed while stopped, and it is possible to greatly improve the efficiency (operation rate) and the productivity.

It is possible to save labor in such replacement work, improve workability and work environment, ensure safety, improve work efficiency, and reduce the total cost related to this work.

That is, the object of the present invention is achieved, the productivity is improved, and it is possible to establish stable production in an electric furnace with low cost and economical efficiency and energy saving. Great value is recognized.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an arc type electric furnace 1 according to an embodiment of the present invention.

FIG. 2 is a partially cutaway plan view of a furnace ceiling 5 in the electric furnace 1 shown in FIG.

FIG. 3 is a vertical cross-sectional view showing the furnace ceiling 5 shown in FIG.

FIG. 4 is an enlarged plan view of a small ceiling portion 8 in the furnace ceiling 5 shown in FIG.

FIG. 5 is a diagram showing a refractory wear rate ratio at each portion of a small ceiling portion.

FIG. 6 is a regular brick in which a small ceiling portion 8 in the furnace ceiling 5 shown in FIG. 2 is provided with an electrode hole 12 through which an electrode 7 is inserted, an A portion is a mass brick 15B, and a B portion is a cylindrical (sleeve) brick. 15C is a longitudinal cross-sectional explanatory view showing each case in which 15C is laid and the other parts are constructed by using the irregular refractory material 15 and integrally molded.

7 is an enlarged plan view for explaining a vertical cross-sectional explanatory view of each case shown in FIG. 6 in the small ceiling portion 8 in the furnace ceiling 5 shown in FIG.

8 shows a small ceiling portion 8 of the furnace ceiling 8 shown in FIG. 2 in which a fixed brick 15A is laid around the electrode hole 12 through which the electrode 7 is inserted to form an electric hole 12,
It is a longitudinal cross-section explanatory drawing which shows the example which it constructed | assembled and integrated and was shape | molded using the amorphous refractory material 15 in the other part.

9 is an enlarged plan view for explaining a vertical cross-sectional explanatory view of the case shown in FIG. 8 in the small ceiling portion 8 in the furnace ceiling 5 shown in FIG.

FIG. 10 is a vertical cross-sectional view illustrating a typical prior art of a conventional electric arc furnace.

[Explanation of symbols]

 1 arc type electric furnace (main body of furnace) 2 furnace body 3 furnace bottom 4 furnace wall 5 furnace ceiling 6 internal space 7 electrodes 8 small ceiling 9 large ceiling 12 electrode holes 13 pitch circle 15 refractory (irregular refractory)

Claims (5)

[Claims] 1. A furnace including a bottomed furnace body which is opened upward and into which a raw material is charged, and a furnace ceiling composed of a large ceiling portion and a small ceiling portion which can be mounted so as to be freely mountable from above. The main body is configured and the small ceiling part that is integrated inside the large ceiling part of the water cooling structure corresponding to the peripheral part has a plurality of electrode holes into which electrodes are inserted on the pitch circle that is coaxial with the furnace body. In an arc type electric furnace comprising, and a small ceiling portion of the pitch circle peripheral portion of the electrode is formed by a refractory, the small ceiling portion, the thickness of the refractory material in the electrode pitch circle peripheral portion, other A water-cooled furnace ceiling for an electric arc furnace, which is characterized by being formed thicker than the wall thickness of the part. 2. The refractory around the pitch circle of the electrode in the small ceiling has a wall thickness of 1.2 to 2.0 times the wall thickness of other portions, The region is 0 when the distance from the central axis of the furnace ceiling, which is coaxial with the furnace body, to the pitch circle of the electrode is r, and the distance to the inner peripheral surface of the water cooling jacket provided on the outer peripheral portion of the small ceiling is R. .5r
The water-cooled furnace ceiling for an electric arc furnace according to claim 1, characterized in that it is in a range of (R-500) [mm]. 3. The refractory in the small ceiling portion is molded using a high alumina amorphous refractory containing 75% by weight or more of Al ₂ O ₃ and each of the main components of SiO _2. A water-cooled furnace ceiling for an electric arc furnace according to claim 1 or 2. 4. The refractory in the small ceiling portion is a fixed brick (mass brick, cylindrical brick) having electrode holes in a portion having a plurality of electrode holes into which electrodes are inserted in the refractory around the pitch circle of the electrodes. ) Is used or a fixed brick laid around the electrode hole to form an electric hole is used, and the other part is molded using an irregular shaped refractory material. The water-cooled furnace ceiling for an electric arc furnace according to item 1. 5. The fixed brick having an electrode hole and the fixed brick laid around the electrode hole to form an electric hole are 80% by weight.
A high-alumina shaped brick containing SiO ₂ as a main component together with the above Al ₂ O ₃ , or MgO, Cr ₂
The water-cooling structure for an electric arc furnace according to claim 4, wherein the water-cooling structure is a fixed-sized brick of magchromic containing O ₃ as each main component.