JPH04268010A - Steel tapping hole in electric furnace - Google Patents

Abstract

PURPOSE:To reduce molten slag quantity flowing out together with a molten steel and to facilitate the construction and the repairing of a steel tapping hole by constituting a steel tapping hole in an electric furnace for steelmaking with C-MgO refractory and making the inclination the same angle as that of a steel tapping trough. CONSTITUTION:A cylindrical steel tapping hole brick 12 in the steel tapping hole in the electric furnace for steelmaking is made of C-MgO based refractory brick composed of 1-30wt.% C, >70wt.% MgO, and into a gap between a tuyere brick 14 and the steel tapping hole 12, MgO series castable refractory 13 is poured. Lower face of an inner hole in the steel tapping hole brick 12 is formed as the same level as furnace bottom composed of stamping material 3 of the castable refractory and further, at the time of tapping the molten steel, lower face level of the molten slag 1 is positioned at an upper part from the upper face of inner hole in the steel tapping hole brick 12 and flowing-out of the molten slag 1 together with the molten steel 2 at the time of tapping molten steel 2 by tilting the electric furnace is reduced as less as possible. Rephosphorization from the molten slag into the molten steel in a ladle due to flowing-out of the molten slag 1, is little, and dephosphorization and desulfurization are executed in the little quantity of slag making agent, and also the construction and repairing exchanging work of the steel tapping hole are facilitated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the structure of a refractory that forms the tapping port of an electric furnace used for steel manufacturing.

0002

2. Description of the Related Art FIG. 3 shows a cross-sectional structure of a tap hole and a gutter of a conventional electric furnace, and FIG. 4 shows the structure of the tap hole as seen from line B--B in FIG. 3.

[0003] As shown in the figure, the tapping port 8 is composed of a stamp material 3 constructed on a tapping brick 7 and a wear brick 9, and the opening communicates with a gutter 10 through a taper at the bottom of the hearth. ing. The levels of the slag 1 and molten steel 2 in the electric furnace having this structure and the level position of the upper end of the tapping port 8 have the relationship shown in the figure. Therefore, in order to prevent slag from flowing out when the furnace is tilted during tapping, the slag level in the furnace needs to be higher than the lower end surface of the tapping opening brick 7. However, as the tapping process progresses, the molten steel in the furnace decreases and the slag level in the furnace decreases, and the outflow of slag from the tapping port 8 occurs at a relatively early stage, causing slag to flow into the ladle. Runoff volume increases.

[0004] For this reason, the current situation is that the slag in the ladle that has flowed from the electric furnace must be scraped out manually or mechanically before proceeding to the next step of secondary refining such as LF.

[0005]Recently, when producing steel using an electric furnace, the target product has shifted from the conventional ordinary steel for steel bars and shapes to the melting of high-grade steel with high added value. Bottom-out steel method (CBT: Concen)
tric Bottom Tapping or EB
T: Eccentric Bottom Tapp
ing) was developed.

[0006] The advantages of this furnace bottom tapping method include the following.

[0007] The flow of electric furnace slag into the ladle, which is important in melting high-grade steel, can be reduced compared to the conventional gutter steel method. As a result, the amount of rephosphorus in the molten steel that occurs during secondary refining in LF etc. is reduced. Also, when dephosphorizing and desulfurizing molten steel, less slag forming agent is required.

[0008]■ It is possible to reduce the cost of slag forming agent by reducing the amount of slag forming agent used, to reduce the electricity bill due to the reduction in energy for dissolving the slag forming agent, and to improve the alloy yield by reducing the amount of slag in the ladle. It is.

[0009] ■ Furnace bottom tapping enables high-speed steel tapping with less slag outflow, and because of its structure, the temperature drop of molten steel is small and the refining temperature of the electric furnace can be lowered, so it extends the life of the ladle and improves productivity. Improvement is possible.

However, in order to adopt this furnace bottom tapping method, it is necessary to significantly modify the furnace bottom shell of the conventional electric furnace.

[0011] Therefore, various attempts have been made to improve the furnace bottom tapping system and the structure of the tapping port to reduce the amount of slag flowing into the ladle, even though the conventional tapping trough is used.

FIG. 5 shows a structure in which a part of the structure in FIG. 3 is improved, and FIG. 6 shows the structure as seen from line CC in FIG. In this structure, the tap hole brick 11 is installed without changing the positional relationship with the existing tap hole, and the tap hole inside the furnace is designed to minimize the amount of slag inside the electric furnace flowing into the ladle during tapping. It has a structure in which it is close to the bottom of the hearth.

In the figure, a tap hole brick 11 with a tap hole formed in the center of its cross section is divided into three parts in the length direction, and each divided part is bonded with alumina bond to prevent joint opening. It is glued with.

However, the tapping brick 1 of this structure
1 has a square outer shape with a circular inner hole, so the bricks tend to crack due to thermal stress in each part, the connections are weak, and the joints open and the tip bricks easily fall off. There are disadvantages such as the amount of machining required for the surrounding bricks to match the shape of the steel opening bricks.

FIG. 7 shows a structure in which the defects of the tap brick shown in FIG. 5 have been improved, and FIG. 8 shows the structure as seen from the line DD in FIG. 7. This structure is made by integrally molding the tapping brick 12 into a cylindrical shape. Further, in order to facilitate manufacturing, a cylindrical tap brick 12 is provided, and the outer periphery of the brick 12 is constructed with stamp material 3.

[0016] Although this method has improved the problem of cracking of the tapping bricks, this structure also has the disadvantage that when repairing the tapping opening, the stamp around the tapping opening and the upper brick must be reloaded, which requires time and effort. be.

[0017]

[Problems to be Solved by the Invention] The problems to be solved by the present invention are that a conventional tapping trough can be used without major modification of equipment, that forming and repairing is easy, and that it can be easily applied to a ladle. To provide a tapping port for an electric furnace which has a small amount of electric furnace slag flowing out and which can tap steel in a short time.

[0018]

[Means for Solving the Problems] In the electric furnace tapping port of the present invention, the inclination angle of the tapping hole of the tapping brick and the inclination angle of the tapping gutter are the same, and the bottom surface of the electric furnace is In a tap structure where the inner hole of the tap is below the slag level in the electric furnace, the tap brick is provided inside the tuyere brick, and a monolithic refractory is installed between the tap brick and the tuyere brick. It is characterized by forming layers.

[0019] Refractories used for tapping bricks include:
A refractory composition containing 1 to 30% by weight of C and 70% by weight or more of MgO is particularly preferred because it is stable against slag infiltration and spalling erosion.

[0020]

[Function] With this configuration, on-site assembly and construction is possible, and when replacing the tap hole, after crushing the monolithic refractory layer, the new tap hole bricks are inserted into the tuyere bricks. This can be easily done by simply setting the refractory on the inner surface of the refractory and providing a layer of amorphous refractory between them.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of an electric furnace tap structure according to the present invention in cross section taken along the tap. Figure 2 is A-
The structure seen from line A is shown.

In these figures, the tapping brick 12 is installed inside the tuyere brick 14, and the tuyere brick 14
The gap between the tap hole brick 12 and the MgO-based monolithic refractory 13
It is constructed by pouring. The lower surface of the inner hole of the tapping brick 12 is formed at the same level as the bottom surface of the electric furnace made of three stamp materials, and the slag 1 is
The lower surface level is located above the upper surface of the inner hole of the tapping brick 12, so that slag does not flow out during tapping by tilting the electric furnace.

[0023] With this configuration, the tap hole can be formed as a single piece, and moreover, it is possible to assemble and construct the tap on site. In addition, if the tap hole brick 12 needs to be replaced due to melting damage, the tap hole brick 1
After breaking the monolithic refractory 13 between 2 and the tuyere brick 14 with a breaker, insert the tap brick 12 into the tuyere brick 14 again, seal the gap, and perform monolithic construction. , repair and maintenance is possible with the minimum repair scope and effort. In this case, the monolithic refractory 13 may be formed using a general MgO-based spray material. Further, the tuyere brick 14 used does not have to be a single piece, and may be of a type divided in the length direction, width direction, and height direction.

[0024]

[Effects of the Invention] The present invention provides the following effects.

(1) It becomes possible to reduce the outflow of slag during tilting steel tapping in an electric furnace.

(2) This makes it possible to achieve the same molten steel component level as in conventional molten steel ladle slag without slag being discharged from the molten steel ladle.

(3) Construction, repair and replacement of the tap hole becomes easy.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an embodiment of the present invention taken in the longitudinal direction of the tap hole.

FIG. 2 is a diagram of FIG. 1 seen from line AA.

FIG. 3 is a sectional view showing a tapping port of a conventional electric furnace.

FIG. 4 is a diagram of FIG. 3 viewed from line BB.

FIG. 5 is a sectional view showing an improved example of a conventional electric furnace.

FIG. 6 is a diagram of FIG. 5 viewed from line CC.

FIG. 7 is a sectional view showing a second improved example of the conventional electric furnace.

FIG. 8 is a diagram of FIG. 7 viewed from line DD.

[Explanation of symbols]

1 Slag 2 Molten steel 3 Stamp material 7 Steel tapping brick 8 Steel tapping port 9 Ware brick 10 Gutter 11 Steel tapping brick 12 Cylindrical steel tap brick 13. Monolithic refractories 14 Tuyere brick

Claims (1)

[Claims] Claim 1: The inclination angle of the tapping hole of the tap hole brick and the inclination angle of the tapping gutter are the same angle, and the inner hole of the tap hole on the bottom surface of the electric furnace is below the slag level in the electric furnace. In the tapping structure in
Further, a tapping spout for an electric furnace is provided, in which a monolithic refractory layer is formed between the tap bricks and the tuyere bricks.