JPH0636472Y2 - Brick structure of hearth of steelmaking arc furnace - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to a brick-layer structure of a hearth portion of an arc furnace (also known as an Eru type electric arc furnace) used for manufacturing special steel, casting, forged steel, etc. In particular, MgO-C refractory is applied to improve its durability.

[Prior Art] Conventionally, as a hearth refractory for a steelmaking arc furnace, a magnesia stamp material is mainly used for the innermost layer on the molten steel side.
The magnesia brick was once used, but in addition to the large damage caused by spalling,
Since it has four sides as shown in the figure, there is a problem that it takes time to construct, so it is hardly done at present.

In a recent steelmaking arc furnace, as shown in FIG. 5, first chamotte brick 3 is squeezed, and then fired magnesia brick 4 is laid on it.
And the magnesia stamp material 5 is further applied on it.

[Problems to be solved by the invention]

Recently, in steelmaking arc furnaces, the tap-tap is shortened to reduce the cost, resulting in an increase in the heat load, which causes severe damage to the magnesia stamp material of the hearth and a large amount of refractory materials for repair is used. It has become so. Also, as the hearth capacity changes, the position of the slag layer above the hearth changes significantly, so the range of damage to the hearth refractory that contacts the slag layer expands, and the amount of refractory used for repair tends to increase. .

On the other hand, the MgO-C quality refractory that was developed around 1970 as a hot spot furnace material for UHP arc electric furnaces, due to its excellent properties, the furnace wall 6 except the hot spot, the tap hole 7, The range of use is expanding to the Idemitsu gutter 8. MgO-C
A high quality refractory has excellent refractory properties because both its main components, magnesia and carbon, are high melting point substances, and both have no eutectic relationship. Also, due to the high thermal conductivity, low thermal expansion, and low elastic modulus of carbon, it is resistant to thermal spalling, and because carbon is difficult to wet with slag, the generation of an altered layer is small and structural spalling is less likely to occur. is there.

It was eagerly desired to apply it to the hearth of a steelmaking arc furnace in order to make full use of such characteristics of the MgO-C refractory material, but there is no example that has been implemented due to the following problems.

(A) Since the MgO-C refractory has high fire resistance, seizure between bricks is poor, and there is a possibility that the refractory will rise due to impact force when the furnace tilts or buoyancy due to molten steel.

(B) Since the MgO-C refractory has a high thermal conductivity, the ingot easily enters the joint, and the ingot may raise the refractory.

(C) When the conventional four-sided brick 9 is used, it takes a long time for construction.

(D) Since the MgO-C refractory has low frictional resistance, expansion of the refractory may cause a squeeze-out phenomenon and float up.

Therefore, the present invention solves the above problems (1) to (2) and replaces MgO-
The purpose is to fully utilize the advantages of the C-type refractory material and improve the service life of the hearth of a steelmaking arc furnace.

[Means for solving problems]

The inventors of the present invention have completed the present invention as a result of repeated studies of the shape of the arc furnace hearth brick, the construction method, and the mortar in order to make full use of the above-mentioned properties of the MgO-C refractory material.

In other words, the present invention is characterized by stacking book-shaped MgO-C quality refractories in a direction perpendicular to the tap hole in order to achieve the object. In addition, when laying bricks, alumina-based joint mortar may be used on the lateral surface. In addition, the lower part and the periphery of the book-shaped MgO-C refractory to be connected and built shall be made of magnesia stamp material.

[Action]

In the present invention, the reason why the MgO-C quality refractory cannot be applied to the steelmaking arc furnace hearth in the past (a) to
The problem of (d) was solved as follows.

(B) The problem of poor seizure of MgO-C refractories was solved by using alumina mortar for joints. Mg
The MgO contained in the O—C refractory and Al ₂ O ₃ in the mortar act to generate spinel (MgO · Al ₂ O ₃ ),
Since the adhesive force is generated between the bricks, the adverse effect of defective printing is eliminated.

(B) The problem that the ingot easily penetrates into the joint was solved by changing the brick shape into a book shape as shown in FIG. 4 and making the joint portion 10 into a curve to substantially lengthen the joint. The use of alumina mortar on the lateral surface also helps prevent the intrusion of metal.

(C) Regarding the construction time, in terms of shape, it was eliminated by eliminating the four-way drop 9 that was conventionally used and adopting the book shape 1. Since the book-shaped brick has convex and concave surfaces of the same R at both ends, as shown in Fig. 7, even if the magnesia stamp material 5'underlying the MgO-C brick to be constructed is not flat. , The convex surface 11 depending on the undulation
By sliding the concave surface 12 and the concave surface 12, it is possible to easily build without expanding the joint thickness 10. Therefore, the construction time can be shortened.

(D) The problem of MgO-C refractory swelling due to expansion is M
The lower part 5'of gO-C refractory and the surrounding 5 "are made of magnesia stamp material and absorbed by the expansion of MgO-C refractory. Not only that, but also as shown in FIG.

〔Example〕

 Hereinafter, the present invention will be described in more detail by implementation.

As shown in FIGS. 1, 2, and 3, MgO-C of book shape 1
The refractory material was installed in the direction perpendicular to the tap hole 7. The dimensions of MgO-C refractory are thickness a = 230mm, length b = 230mm, width C
= 80 mm, radius of curvature r = 180 mm, and the materials are shown in Table 1. Al ₂ O ₃ on the lateral surfaces 2 and 2'of MgO-C refractory
Mortar with a content of 95.5% was used. For the lower part 5'and the periphery 5 "of the MgO-C quality refractory, the magnesia stamp material shown in Table 2 was used.

Next, the results of practical tests at companies A to C3 will be described. Table 3 shows the operating conditions of the steelmaking arc furnaces at companies A, B, and C3, the inner diameter of the furnace, and the construction range of MgO-C quality refractories.

Company A: Intermittent operation of 8 heats / day (the number of steel operations per day is 8). There is lime injection into the hearth. Life is 1200heats
And the amount of wear was 0.15 mm / heats at the maximum.

Company B: Continuous operation of 17 heats / day, currently 5000 heats (about 1
In use). No lime was added to the hearth.

Company C: Currently using 2000 heats (about 8 months) due to intermittent operation of 10 heats / day. Especially no damaged part is found. Injecting lime into the hearth Sometimes.

As a result of practical tests, by using the brickwork structure according to the present invention, damage to the bottom refractory material is reduced and the position of the slag line is stabilized. 20-30% floor repair material usage
It was found that the amount of spray material used decreased by 5-10% and the amount of brick used in the slag line decreased 5-10%.

[Effect of device]

As described above, in the present invention, by constructing a book-shaped MgO-C quality refractory material at right angles to the direction of the tap hole, or by additionally using aluminous mortar, A steelmaking arc furnace hearth that is structurally stable and has excellent corrosion resistance can be obtained. Therefore, the productivity of the steelmaking arc furnace can be improved as described below.

a. The amount of hearth repair material used will be reduced.

b. Stable operation is possible because there is little wear of the hearth.

c. The amount of spray material used decreases.

d. Since the position of the slag line is constant, the amount of bricks used in the slag line is reduced.

e. Electricity consumption is reduced.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a brickwork structure of a hearth of a steelmaking arc furnace according to the present invention, FIG. 2 is a cross-sectional plan view taken along the line I--I of FIG. 1, and FIG. 3 is FIG. II is a partial longitudinal sectional view, FIG. 4 is a perspective view of the book-shaped refractory material of the present invention, FIG.
Figure is a vertical cross-sectional view showing the brickwork structure of the conventional steelmaking arc furnace hearth, Figure 6 is a perspective view of a conventional four-sided brick, and Figure 7 shows the book-shaped refractory of the present invention with the bottom surface undulating. Accordingly, FIG. 8 is a vertical cross-sectional side view showing that construction can be performed without widening the joint thickness, and FIG. 8 is a diagram showing a construction direction in which the joint easily falls. In the figure, 1 ... Book-shaped refractory, 2, 2 '... Side surface, 3
…… Chamotte brick, 4 …… Magnesia brick, 5, 5 ',
5 ″ ... magnesia stamp material, 6 …… furnace wall, 7 …… de tap, 8 …… decod gutter, 9 …… four-sided brick, 10 …… joint,
11 …… Convex, 12 …… Concave.

Claims (2)

[Scope of utility model registration request] 1. A brick in the hearth of a steelmaking arc furnace, characterized in that book-shaped MgO-C refractory materials (1) are stacked in the hearth of the steelmaking arc furnace at right angles to the direction of the tapping port. Product structure. 2. A utility model registration claim characterized in that an alumina joint mortar is used on the lateral surfaces (2), (2) 'of the book-shaped MgO-C refractory material (1). Brick structure of the hearth of the steelmaking arc furnace described in paragraph.