KR20030095757A - Lower electrode of dc electric furnace with improved cooling-ability and transmitting-ability - Google Patents

Abstract

PURPOSE: A lower electrode of DC electric furnace having improved cooling ability and transmitting ability is provided to extend service life of the lower electrode by changing design of billet and installation conditions of the billet, thereby improving transmitting ability and cooling ability of a billet type lower electrode. CONSTITUTION: In a lower electrode of DC electric furnace formed of billets which penetrate hearth refractory in such a way that the billets are protected by protection brick, and the lower part thereof is protected in the solid state by side and lower cooling molds, the lower electrode of DC electric furnace comprises a billet protecting brick(4a) which is connected to groove(15) on the hearth refractory(5a) so that the outer circumferential surface of the billet protecting brick(4a) is protected by stamp material(8a); a pair of billets for lower electrode which penetrates the billet protecting brick(4a) so that a ratio of diameter to length is 3:13, an upper part thereof is formed of steel as billet liquid phase parts(1a,2a), and a lower part thereof is formed of copper as billet solid part; a side cooling mold(6a) completely sunk into lower metal case(9a) and lower plate(12a) of the electric furnace to cool and protect billet solid part(3a) of the billets for lower electrode; a lower cooling mold(7a) installed at a lower part of the billets for lower electrode to cool and protect a lower part of the billet solid part(3a); and an insulator(11a) inserted between the side cooling mold(6a) and the lower metal case(9a) and between the side cooling mold(6a) and the lower plate(12a).

Description

LOWER ELECTRODE OF DC ELECTRIC FURNACE WITH IMPROVED COOLING-ABILITY AND TRANSMITTING-ABILITY}

The present invention relates to a lower electrode of a direct current furnace in which electrical current and cooling ability are formed, and more particularly, by designing and changing a billet, which is a lower electrode rod capable of passing electricity to the bottom of a direct current furnace using molten iron as a part of a raw material to be used. The present invention relates to a lower electrode of a direct current furnace, which prevents leakage of molten steel and has an extended lifetime and cooling ability.

In general, as shown in FIG. 1, the lower electrode of the direct current furnace is a lower plate 12 located at the center bottom of the furnace body in which the hearth refractory 6, the billets 1 and 2, and the billet protection lead 4 are combined. Is installed on the bottom electrode, and the billets (1, 2) in the center of the lower electrode allow electricity to flow into the scrap metal and molten steel introduced into the electric furnace through the secondary electrode lead. Connected.

That is, the lower part 3 of the billet is made of copper (Cu) and is connected to the secondary electrode lead, and the upper part (1,2) of the billet is made of steel and is in contact with the molten steel in the electric furnace so that no electricity flows. However, it is present in a molten state of 1500 ℃ or higher during energization.

Therefore, in order to maintain the shape of the billets 1 and 2 even in the molten state, the billet is surrounded by a cylindrical billet protection lead 4, and the lower part 3 of the billet is cooled by the lower cooling mold 7 to cool. do.

Generally, the lower electrode is composed of two or more billets (1, 2), and the lower electrode, which is made once and installed on the floor of the electric furnace, may be discontinued for various reasons, but in general, the facilities around the lower electrode deteriorate. Or, because of this, the melt or the melt in the billet is leaked to the outside, or when the likelihood of the melt is leaked out of the use is stopped bar in the prior art is usually discarded more than 1000 times.

However, because the lower electrode is arcing during use and is immersed in the hot molten metal, and the molten metal is strongly stirred by the force of electromagnetic, the molten metal erodes the refractory around the lower electrode and penetrates into the refractory. There have been cases where leakage accidents occurred or billets made of steel deepened the melt depth during energization, causing the melt to flow out.

Known techniques include the Korean Patent Publication No. 95-33390, “Cooling Bottom Electrode for DC Furnace,” which is a method of improving cooling efficiency when connecting the upper liquid portion and the lower solid portion of a steel rod inserted into the bottom of an electric furnace refractory. It is a technology to provide, even if the contact between the upper and lower billets, the problem that the molten steel penetrates between the lower electrode protection lead and the surrounding stamp lead and outflow remains.

A case in which the use of the billet-type lower electrode to the direct current electric current using molten iron becomes impossible will be described with reference to FIG. 2, which illustrates a path through which molten steel penetrates into the lower electrode.

First, as in the case of path A, when the temperature between the billets (1, 2) is high, the impact occurs when the stamp refractory (8) is sintered to charge raw materials, cracks are formed between the refractory materials, and molten steel penetrates into the molten steel. Will result.

Secondly, as in the case of the path B, the melt inside the billets 1 and 2 erodes the protective lead 4 and flows around to damage the insulator 11 or damage the installation.

Third, as the path C, if the liquid portion (1, 2) inside the billet is too low during energization, there is a problem that the molten steel flows out between the protective edge and the lower end and the cooling device (13) or to the weak portion.

In order to solve the above problems, the present invention is to minimize the penetration of molten steel into the lower electrode in the electric furnace using a molten iron of 1000 ℃ or more as a raw material, that is, a direct current electric furnace for supplying electricity to the molten iron through the billet-type lower electrode. By changing the design of the billet and changing the installation conditions so as to improve the electrical conductivity and cooling ability of the billet-type lower electrode to provide the lower electrode of the DC electric furnace with improved electrical conductivity and cooling ability to extend the life of the lower electrode. The purpose is.

Figure 1 is a schematic side cross-sectional view of the lower electrode showing a billet type of a general direct current electric furnace;

Figure 2 is a side cross-sectional view showing a path through which molten steel penetrates the lower electrode and the lower electrode with a conventional direct current electric current.

3 is a side view showing a lower electrode of a direct current electric furnace in which current conduction and cooling capacity are formed according to the present invention;

4 is a rear view of a lower electrode of a direct current electric furnace in which current conduction and cooling capacity are formed according to the present invention.

♣ Explanation of symbols for main part of drawing ♣

1a, 2a: billet solid part 3: billet solid part 4a: billet protective lead and 5a: hearth refractory

6a: Side cooling mold 7a: Lower cooling mold 8a: Stamp refractory

9: Furnace outer shell 10: Molten steel and molten iron 11a: Insulator 12a: Lower plate

In order to achieve the above object, the present invention provides a billet protection edge (4a) and the outer circumferential surface is protected by a stamp refractory (8a) by groove coupling (15) and the hearth refractory (5a); The billet liquid portion 1a, 2a having a diameter: length ratio of 3:13 while penetrating the billet protective lead 4a is made of steel, and the bottom of the billet solid portion 3a is made of copper. Lower electrode billets 1 and 2; A side cooling mold (6a) completely recessed in the lower shell (9a) and the lower plate (12a) of the electric furnace to protect the billet solid portion (3a) of the lower electrode billets (1,2); A lower cooling mold 7a installed at the lower end of the lower electrode billets 1 and 2 for cooling and protecting the lower end of the billet solid part 3a; It provides a lower electrode of the direct current electric furnace is characterized by consisting of an insulator (11a) inserted between the side cooling mold (6a) and the lower shell (9a).

In addition, the present invention provides a thickness ratio of the hearth refractory material 5a and the stamp refractory material 8a while satisfying the ratio of the hearth refractory material 5a: stamp refractory material 8a = 4: 9, and the billet protective lead 4a. The lower electrode of the direct current furnace having the current carrying capacity and the cooling capacity is characterized in that the ratio of the length of the stamp refractory 8a satisfies the ratio of the billet protective lead 4a: stamp refractory 8a = 7: 10.

On the other hand, the billet protection edge 4a constituting the present invention is characterized in that the billet protection edge 4a made integrally with the hearth refractory 5a when the length is less than 1000mm,

In addition, the insulator 11a constituting the present invention has a height equal to the thickness of the lower plate 12a and the lower shell 9a, and is installed to surround the side cooling mold 6a.

The installation interval of the pair of lower electrode billets (1,2) is to provide a lower electrode of the direct current electric furnace characterized by the conductivity and cooling capacity characterized in that the installation is wider than the length of the billet (1,2).

In addition, the lower plate (12a) constituting the present invention is characterized in that the electricity supply and cooling ability is characterized in that the cooling water inlet 13 and the outlet 14 has its own cooling jacket 16 is formed to circulate the cooling water therein, respectively. It provides a lower electrode of the shaped direct current electric furnace.

Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

Figure 3 is a side view showing a lower electrode of the direct current electric furnace is characterized by the current conduction and cooling ability according to the present invention, Figure 4 is a rear view of the lower electrode of the direct current electric furnace is characterized by the current conduction and cooling ability.

As shown in Figures 3 to 4, the lower electrode of the DC electric furnace of the current-carrying and cooling ability according to the present invention, while the lower portion of the billet (1,2) is cooled by the lower cooling mold (7a) as before, The protective edge 4a is laterally cooled to a position of 200 mm or more above the bottom of the furnace bottom bar 9a and the lower plate 12a or to a depth of 800 mm or more from the molten iron 10 on the top of the hearth refractory 5. The mold 6a is provided to cool with water.

That is, a protective lead 4a is installed from the upper side of the side cooling mold 6a to the upper part of the billet. When the length of the billet protective lead 4a is less than 1000 mm, the protective lead wire 4a and the road refractory body are manufactured in one piece. There should be no seams between (5a),

When the length of the said billet protection lead 4a exceeds 1000 mm, it is preferable to divide into two pieces and to reduce the thermal stress in the hearth refractory 5a.

It is preferable to install the groove 15 between the billet protection lead 4a and the road refractory 5a so as to not be shaken between the road refractory 5a and the protection lead 4a even when tilting the electric furnace.

In addition, while maintaining the height from the lower plate 12a to the upper part of the hearth refractory 5a as high as possible, the thickness of the pure stamp refractory material 8a except for the hearth refractory 5a is 800 mm or more so that the thickness-free refractories are (5a): Stamp refractory (8a) = 4: 9 ratio is satisfied.

In addition, the diameter of the lower electrode billet (2) constituting the present invention is such that the current density is 60 ~ 80 Ampere / cm2, the lower plate 12a, as shown in Figure 4, the cooling water therein In order to circulate, the cooling water inlet 13 and the outlet 14 are provided with their own cooling jackets 16, respectively, by flowing the cooling water to improve the cooling capacity of the lower plate (12a).

In addition, in order to increase the cooling efficiency of the lower billet solid portion 3a of the lower electrode billets 1 and 2, the billet solid portion 3 is coupled to the lower plate 12a in a conventional protruding form. In the present invention, the side cooling mold (6a) for cooling the water is produced in the form completely inserted into the lower plate (12a) and the lower shell (9a), constituting the present invention shown in FIG. ) Was installed as follows.

An insulator is provided on the outer circumferential surface of the side cooling mold 6a constituting the present invention installed as described above to prevent current flowing through the billets 1 and 2, which are the lower electrodes, from passing through the lower plate 12a and the lower shell 9a. (11a) is installed, the height of the insulator (11a) to the same height as the thickness of the lower plate (12a) and the lower shell (9a) is installed so as to surround each billet (1, 2) independently and circularly To insulate.

In addition, the installation intervals of the pair of lower electrode billets (1,2) are installed at least as long as the length of the billet (1,2), but to be installed at a wide interval as possible as the structure of the lower plate (12a) Preferably, in the embodiment of the present invention, a pair of lower electrode billets 1 and 2 are installed at intervals of 1450 mm.

In addition, as described above, each device portion constituting the lower electrode of the direct current furnace having the current conduction and cooling ability according to the present invention can be used in combination when the lower electrode is installed, but the excellent effect may occur, but each configuration is independently As a constituent factor that can exert the effect can also be used separately installed for the purpose of reinforcing the weak part according to the characteristics of the lower electrode of the direct current furnace installed in each industry.

For example, in an electric furnace in which molten steel leakage frequently occurs due to the 'path A' shown in FIG. 2 or the possibility of molten steel leakage is high and the service life of the lower electrode is stopped, the cooling method of the lower plate 12a and the lower steel shell ( 9) That is, the thickness of the stamp refractory 8a from the lower plate 12a to the lower part of the hearth refractory 5a is maintained at 800 mm or more to sufficiently ensure the thickness of the sound stamp refractory 8a that is not sintered from the heat generated in the molten steel. At the same time, even if the molten steel 10 penetrates between the stamp refractory materials 8a, the molten steel 10 is solidified in the stamp refractory materials 8a due to the cooling action of the lower plate 12a. This eliminates the use of the billets (1, 2) as the lower electrode can be used for a long time.

By inserting scrap metal and molten iron in a DC electric furnace provided with a lower electrode according to the present invention and flowing electricity to the billet (1,2) of the electrode rod, the electricity in the state of melting the upper steel material of the billet (1,2) of the lower electrode In this case, due to the side cooling mold (6a) installed on the side of the lower solid portion (3a) of the billet where the liquid phase and the solid phase in the billet (hereinafter referred to as "liquid line") of the side cooling mold (6a) Since it is formed in the upper position it is difficult to flow the melt between the protective lead and the lower end and the cooling device as shown in the 'path C' of FIG.

Even if it flows out, since the stamped refractory material 8a is filled, there is no possibility that molten steel will leak out.

At this time, the side cooling mold (8a) installed on the side of the billet (1, 2) is preferably a height of 200mm or more from the bottom of the billet, and less than 200mm has a small effect of raising the position of the liquid line in the billet is sufficient stability Difficult to secure,

If the side cooling mold (8a) is installed close to within 800mm from the upper molten steel to the molten iron 10, the heat load is too large so that the side cooling mold (8a) may be damaged by the molten iron, so the empirically judged side cooling mold ( The height of 8a) is to be 200mm or more, but the upper part of the mold 8a is to be installed 800mm or more away from the molten iron 10.

The larger the diameter of the lower electrode billets (1, 2), the smaller the surface area per unit weight, the smaller the cooling efficiency, and if the diameter of the billet is too small, the current density passing through the billet through electricity is high. There is a problem that the resistance heat is too large.

Therefore, the diameter of the billet (1, 2) is set based on the amount of current flowing through the billet, but in general, since the shape of the billet cross section is cylindrical, the current density is 60 ~ 80 Ampere per square centimeter in the electric furnace for melting and refining the molten iron (10). If the current density is less than 60 Ampere / cm2, the billet diameter is too large, which reduces the cooling efficiency of the billet.When the current density exceeds 80 Ampere / cm2, the electric resistance heat in the billet is increased to protect the billet. It will damage the smoke.

In addition, since the insulator 11a provided around the billets 1 and 2 is intended to insulate between the lower plate 12a and the billet, the insulator 11a should be installed therebetween, but the upper part of the insulator 11a should not be higher than the lower plate 12a as much as possible. Install it,

The billet protective wire 4a is integrally manufactured and installed so as not to generate joints in the wire, but when the length of the wire exceeds 1000 mm, heat generated inside the wire when the wire receives heat from the molten iron 10. It is appropriate to install them in two pieces because the stresses are so great that cracks can occur.

This increases the cooling capacity of the billet lower solid part 3a so that the molten steel in the billets 1 and 2 does not damage the billet protective edge 4a as in the 'path B' of FIG. ) To minimize the weak edges of the protective lead and 4a, but in the event of damage to the billet protective lead 4a and to prevent the molten steel from contacting the heat insulator 11a even if it penetrates into the stamp refractory 8a. Due to the cooling effect acting from the lower plate 12a, it is possible to solidify inside the stamp refractories 8a to prevent the outflow of the molten steel 10.

The molten steel outflow by 'path A' of FIG. 2 indicates that the molten iron 10 on the top of the hearth refractory 5a passes through a weak portion of the hearth refractory 5a, or the melt in the billets 1 and 2 is stamp-refractory 8a. And the sintered refractory material 8a are penetrated between the sintered refractory material 5a and the sintered refractory material is cracked due to mechanical impact, and the molten iron 10 to the melt penetrate again between the cracks. In order to prevent penetration of the melt, the thickness of the stamp refractory material 8a should be as thick as possible to prevent penetration of the melt, but since the sintered thickness of the stamp refractory material 8a is about 500 mm at the melt temperature around 1600 ° C, it is stable. In order to secure a healthy stamp refractory layer 8a, the thickness of the stamp refractory layer 8a is set to 800 mm or more, and at the same time, the billet protection edge 4a has a length with the stamp refractory 8a. The billet protection kite (4a): is configured to satisfy a ratio of 10: Stamp refractory (8a) = 7.

In addition, when the wedge is formed in the upper part of the billet protection lead 4a and the road refractories 5a are dug and inserted into the lower part, the molten iron 10 penetrates under the road refractory 5a even if the furnace body is tilted during the use of an electric furnace. It can be minimized.

In general, the molten iron 10 penetrating the lower part of the hearth refractory 5a is penetrated in the middle portion of the billets 1 and 2, that is, the point where the temperature is highest in the lower part of the furnace, that is, in the middle of the lower plate 12a. If the side cooling mold 6a is manufactured and installed so that the cooling water flows to the site, molten steel that penetrates into the stamp refractory 8a is solidified in the stamp refractory 8a before penetrating downward, thereby preventing the leakage of molten steel. .

As described above, the lower electrode of the direct current furnace having the current conduction and cooling ability according to the present invention, although the life of the lower electrode was about 1000 times in the past, it was shown to exceed 2000 times after the present invention, which greatly increases the life of the electrode. At the same time, conventionally, molten steel leaks to the lower electrode portion or erosion materials are eroded. However, after applying the lower electrode according to the present invention, molten steel leakage and refractory erosion hardly occur, and thus stable electric work can be performed. There is an effect.

Claims (7)

In the lower electrode of the direct current electric furnace consisting of billets (1,2) which penetrates the hearth refractory (5) and is protected by a protective lead (4), and the lower part is protected in a solid state by side and lower cooling molds (6,7). , A billet protection edge 4a whose outer circumferential surface is protected by a stamp refractory 8a by groove coupling 15 with the hearth refractory 5a; The billet liquid portion 1a, 2a having a diameter: length ratio of 3:13 while penetrating the billet protective lead 4a is made of steel, and the bottom of the billet solid portion 3a is made of copper. Lower electrode billets 1 and 2; A side cooling mold (6a) completely recessed in the lower shell (9a) and the lower plate (12a) of the electric furnace to protect the billet solid portion (3a) of the lower electrode billets (1,2); A lower cooling mold 7a installed at the lower end of the lower electrode billets 1 and 2 for cooling and protecting the lower end of the billet solid part 3a; The lower electrode of the DC electric furnace, characterized in that it is composed of an insulator (11a) inserted between the side cooling mold (6a) and the lower shell (9a) and the lower plate (12a). The method of claim 1, The hearth refractory 5a and the stamped refractory 8a have a thickness ratio of the hearth refractory 5a: stamp refractory 8a = 4: 9. Bottom electrode. The method according to claim 1 or 2, The billet protective lead 4a has a length ratio between the stamped refractory 8a and the billet protective lead 4a: stamp refractory 8a = 7: 10. Bottom electrode of electric furnace. The method of claim 1, The billet protective lead 4a is a billet protective lead 4a formed integrally with the hearth refractory 5a when the length thereof is within 1000 mm. The method of claim 1, The insulator 11a has a height equal to the thickness of the lower plate 12a and the lower metal shell 9a, and is installed to surround the side cooling mold 6a. Bottom electrode of electric furnace. The method of claim 1, The installation intervals of the pair of lower electrode billets (1,2) is wider than the billet (1,2) the length of the lower electrode of the direct current electric furnace characterized by the conductivity and cooling capacity. The method of claim 1, The lower plate 12a is provided with its own cooling jacket 16 formed with a coolant inlet 13 and an outlet 14 so that the coolant can circulate therein. electrode.