KR20190046240A - Converter bottom refractories - Google Patents

Abstract

The present invention provides a fire resistant brick for a converter bottom which can stably operate a converter. The fire resistant brick comprises a composition including 81-88 wt% of a magnesia fire-resistant material and 12-19 wt% of graphite as a main material, and is formed by adding 5 parts by weight or lower of one or more additives selected among Al, Al/Mg, Si, SiC, B4C, CaB6, MgB2, and BN to 100 parts by weight of the main material. The size ratio of the fire resistant brick defined by relation 1 satisfies 1.1-1.37 if the weight of the fire resistant brick is 50 Kg or lower. The size ratio defined by relation 1 satisfies 1.1-1.33 if the weight of the fire resistant brick is 110 Kg or lower. The size ratio defined by relation 1 satisfies 1.1-1.24 if the weight of the fire resistant brick is 300 Kg or lower. The size ratio defined by relation 1 satisfies 1.1-1.17 if the weight of the fire resistant brick is 700 Kg or lower.

Description

Converter bottom refractories

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manufacturing method of a converter floor brick for stably using a refractory inside a converter, and more particularly, to a method for manufacturing a converter floor brick which is capable of increasing a size of a refractory brick for shortening a building time and improving a building quality, Which is capable of suppressing an increase in the resulting thermal expansion stress.

During the steelmaking operation, the converter equipment injects strong pressure oxygen to the pig iron produced in the blast furnace to change slag oxide form of the crushed components (C, Si, P, S) It is a typical refining facility to remove.

As shown in FIG. 1, such a converter is designed such that refractories are built therein to protect molten steel and slag from the use temperatures of the molten steel and the converter structure during the refining process.

The converter 100 includes a bottom center portion 111 on which a refractory is installed, a bottom portion 110 including the bottom center portion 111, a straight portion 120 formed in a cylindrical shape by being stacked on the bottom portion 110, A conical portion 130 formed at the upper portion of the straight portion, and a guide portion 140, and the like.

As shown in FIG. 2, the bottom 110 includes an eccentric brick 210, which is a central axis at which the converter refractory starts to be formed, and a bottom brick 220, which is formed around the eccentric brick 220.

Also, the bottom of the converter is designed to build refractory bricks in a hemispherical converter furnace in order to stably store high-temperature molten steel without leaking. In order to distribute the stress reliably, the refractory bricks are stacked in the shape of a cylinder, and the central axis thereof is a frustum-shaped eccentric brick 210, which is a center point of the converter.

These refractories are designed in the form of tapered bricks with different top and bottom lengths, and are used continuously and continuously along the ridge. These tapers are important not only for continuous construction, but also for keeping the refractory bricks in an arch-like structure, preventing bricks from falling out due to tilting movements, and evenly distributing the stresses generated between the refractories.

On the other hand, the converter is used at a high temperature between 1400 ° C and 1800 ° C according to the treatment process, and a refractory which can withstand the above temperature is used to contain high temperature molten steel and slag.

These refractories are damaged at a constant rate by physical chemical reaction between high temperature molten steel and slag during the conversion process, and refractories are repaired according to the situation, or the refractory is periodically stopped to be disassembled and rebuilt.

However, since the converter does not operate during the replacement of the refractory, it is necessary to improve the efficiency of the converter by shortening the time required to replace the refractory.

In the process of replacing the refractory, a large amount of time is spent to dismantle the refractory and reconstruct the refractory. The refractory of high weight (usually 60 ~ 120Kg / piece) Enhancement is limited.

For example, in Patent Document 1, a manipulator capable of quickly moving a brick with a high weight to the center of a bottom portion is fixed to a turntable, and a hoist is used to descend to the inside of the converter, Has been reduced by 52%, and the installation and demolition time of the device has been reduced by 55%, shortening the overall maintenance time by 53%

Patent Document 2 describes a mechanical device that enables free movement in all directions in a state of compensating the weight of refractory by adsorbing and moving the refractory using a robot arm having a pneumatic adsorbing portion. It is described that the robot arm is precisely controlled to reduce the work fatigue due to the overload of the worker and the precision can be improved by the cooperative operation of the robot arm in the time-consuming positioning work.

However, in the above-described shaft method, additional facility investment occurs, and there is a limit in shortening the shaft time depending entirely on the operation and construction speed of the operator and there is a problem that the number of the refractory bricks to be built can not be overcome. Also, when the bottom brick is attached to the periphery of the eccentric brick which is the central axis, the eccentric brick may deviate from the center due to the impact of the adjusting position adjustment process.

The center off-axis causes an asymmetrical construction of the bottom bricks, which leads to ineffective processes of dismantling and rebuilding the built bricks as they cause the risk of molten steel leakage and refractory damage due to stress imbalance.

Korean Patent No. 10-0905121 Korean Patent No. 10-1359968

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in order to overcome the limitations of the prior art, and it is an object of the present invention to reduce the number of times of building and rebuilding by making the size of the converter eccentric brick large, shorten the converter shaft time, and reduce the thermal stress caused by the enlargement of the refractory brick The present invention provides a refractory brick for a converter that can operate the converter stably.

Further, the technical problems to be solved by the present invention are not limited to the technical problems mentioned above, and other technical problems which are not mentioned can be understood from the following description in order to clearly understand those skilled in the art to which the present invention belongs .

In the converter bottom refractory brick,

Al, Mg, Si, SiC, B4C, CaB6, and SiC are added to 100 parts by weight of the main raw material, and the refractory brick is composed mainly of a composition containing 81 to 88% of magnesia refractory material and 12 to 19% MgB2, and BN is added in an amount of 5 parts by weight or less,

Wherein the refractory brick has a dimensional ratio defined by the following relational expression 1 satisfying 1.1 to 1.37 when the weight of the refractory brick is 50 kg or less,

When the weight is 110 kg or less, the dimensional ratio defined by the following relational expression 1 satisfies 1.1 to 1.33,

When the weight is 300 kg or less, a dimensional ratio defined by the following relational expression 1 satisfies 1.1 to 1.24; And

And a dimensional ratio defined by the following relational expression 1 satisfies 1.1 to 1.17 when the weight is 700 kg or less.

[Relation 1]

Dimensional Ratio = B / A

Where A is the length of the upper surface of the brick in contact with the molten steel and the length of the lower surface of the brick not in contact with molten steel.

The present invention having the above-described structure can control the thermal stress of the refractory brick by controlling the weight of the refractory brick and the dimensional ratio of the upper surface and the lower surface, thereby increasing the size of the refractory brick, The eccentric brick having a high weight has a beneficial effect of preventing the eccentric brick from escaping from the central axis due to the solid bottom support and reducing the time taken to rebuild the eccentric brick.

Fig. 1 is a cross-sectional view of a conventional oxygen-cascaded furnace and a refractory.
2 is a schematic sectional view of the converter bottom.

Hereinafter, the present invention will be described.

In the method of designing converter refractories, there is no clear design standard, and the size and shape of the bricks have been determined by repetition of trial and error considering the easiness of construction. Particularly, the converter bottom has attempted to increase the size of the bricks to shorten the construction time or prevent the deviation of the center axis. However, due to problems such as cracks, leakage of molten steel has been a concern, and the mere brick length has been changed.

For example, in the conventional means capable of solving the increase in the thermal stress of the refractory brick, a bulb or styrofoam, which is burnt at a high temperature, is inserted into the brick at a constant thickness to create a space capable of expanding, However, the converter bottom portion is a portion supporting high-temperature molten steel, and due to the expansion, the molten steel may flow out into a gap between the bricks, so that the use of the expansion band is inappropriate.

In addition, there is a method of changing the material of the refractory to reduce the thermal expansion and the elastic modulus to eliminate the thermal stress. However, the modification of the material has a disadvantage that it can not be easily changed due to the complex erosion and thermal shock characteristics.

Therefore, the present inventor has repeatedly conducted various tests on the change of thermal stress by giving the dimensional ratio of the volume of the refractory brick, the upper surface and the lower surface dimension as important parameters of the large brick design. As a result, as the volume of the brick increases, And that the increase was proportional. Particularly, it is confirmed that such thermal stress can be solved by reducing the dimension ratio of the lower surface to the upper surface of the brick in contact with molten steel, and the present invention is presented.

The transformer bottom eccentric refractory brick according to the present invention comprises, as main components, a composition containing 81 to 88% of magnesia refractory material and 12 to 19% of graphite as a main raw material, and Al, Al / Mg, Si , At least one additive selected from SiC, B4C, CaB6, MgB2 and BN is added in an amount of 5 parts by weight or less,

The refractory brick satisfies a dimensional ratio defined by the relational expression 1 satisfying 1.1 to 1.33 when the weight of the refractory brick satisfies 1.1 to 1.37 and a weight of 110 kg or less when the weight of the refractory brick is 50 kg or less, , And when the weight is 300 kg or less, the dimensional ratio defined by the above-mentioned relational expression 1 satisfies 1.1 to 1.24; And when the weight is 700 kg or less, the dimensional ratio defined by the above-mentioned relational expression 1 satisfies 1.1 to 1.17.

First, the main ingredient composition of the refractory brick of the present invention will be described.

The refractory brick of the present invention is composed of 81 to 88% of magnesia refractory material and 12 to 19% of graphite as a main material in weight percent.

The above-mentioned magnesia refractory material has a high melting point and is chemically stable to the slag, thus enduring the erosion of molten steel and slag in the converter. If the content is less than 81%, the corrosion resistance is insufficient. If the content is more than 88%, the content of graphite is insufficient. Therefore, cracking or peeling may occur due to deterioration of thermal shock resistance.

In addition, the graphite plays a role of reducing the temperature gradient between the molten steel contact surface and the non-contact surface due to its excellent heat conduction characteristics, thereby improving the thermal shock resistance of the refractory brick. If the content is less than 12%, the thermal shock property is deteriorated. If the content is more than 12%, the content of magnesia is insufficient and sufficient corrosion resistance may not be exhibited.

The refractory brick of the present invention further contains at least 5 parts by weight of at least one additive selected from Al, Al / Mg, Si, SiC, B4C, CaB6, MgB2 and BN per 100 parts by weight of the main raw material. These additives prevent the oxidation of graphite at high temperatures and react with the main raw materials of refractory bricks to form compounds to improve physical properties. If the content of the additive exceeds 5 parts by weight, the corrosion resistance tends to deteriorate. Therefore, in the present invention, it is preferable to limit the addition amount of the additive to 5 parts by weight or less.

In addition, the refractory brick of the present invention may include a binder and the like.

In the present invention, when the weight of the refractory brick is 50 kg or less, a dimensional ratio defined by the following relational expression 1 is 1.1-1.33 , And when the weight is 300 kg or less, a dimensional ratio defined by the following relational expression 1 satisfies 1.1 to 1.24; And when the weight is 700 kg or less, the dimensional ratio defined by the following relational expression 1 satisfies 1.1-1.17.

[Relation 1]

Dimensional Ratio = B / A

Where A is the length of the upper surface of the brick in contact with the molten steel and the length of the lower surface of the brick not in contact with molten steel.

In order to enlarge the size of the bricks, it is essential to use the dimensional ratio that does not change even if the taper angle is changed.

First, the thermal stresses generated in the refractories were analyzed by computer simulation test (FEM). As a result, compressive stress due to thermal expansion occurred in the lower surface of the refractory surrounded by all directions and suppressed in expansion, but the stress value generated in the low temperature region was not large enough to damage the refractory. On the other hand, in a situation where the static pressure of the molten steel above the refractory is dissolved by the molten steel tapping in contact with the molten steel at high temperature, the refractory material is combined with the stress for expanding upwardly and the stress for suppressing by tapering of the peripheral bricks, Tensile stress is generated. This stress increases the displacement due to thermal expansion as the size of the brick becomes larger, and the thermal stress increases by the amount of the increased displacement, thereby acting as an obstacle to the enlargement.

Particularly, tensile stresses generated on the bricks exposed without being constrained by the peripheral portion of the lower portion where a stress increase is small and compression stress favorable to the refractory occurs are caused to cause fatal cracks and dropouts in the refractory bricks.

These tensile stresses reduce the dimensional ratio of the upper and lower surfaces of the refractory material, thereby relieving the interference of the peripheral bricks for suppressing the stress to expand to the upper side. Thus, a large tensile stress can be reduced, and even if the refractory bricks are enlarged, And it is based on the design criteria.

On the other hand, the taper shape of the refractory brick can be changed to relieve the stress. However, the feature of the use of refractory bricks is that the movable surface is high temperature and the back surface is low temperature. Unlike the original design, the dimension ratio converges to 1.0 due to the expansion of the movable surface The brick is dropped and the arch structure is collapsed with respect to the tilting motion, so that there is a fatal problem that the molten steel leaks out.

Therefore, it is desirable to design the above-mentioned dimensional ratio to be 1.1 or more, and it is necessary to design the upper limit to suppress the excessive increase of the thermal stress, in order to secure the stability in use.

From this viewpoint, when the weight of the refractory brick of the present invention is 50 kg or less, the dimensional ratio defined by the relational expression 1 is controlled to 1.1 to 1.37, and when the weight is 110 kg or less, the dimensional ratio Is controlled to 1.1 to 1.33, and when the weight is 300 kg or less, the dimensional ratio defined by the above-mentioned relational expression 1 is controlled to 1.1 to 1.24; And when the weight is 700 kg or less, the dimensional ratio defined by the above-mentioned relational expression 1 is controlled to 1.1-1.17.

Hereinafter, the present invention will be described in detail by way of examples.

(Example)

Converter floor refractories having the main ingredient composition and additive composition as shown in Table 1 below were prepared. At this time, the ratio of the length of the lower surface to the upper surface of the brick in contact with the molten steel of the manufactured refractories was set to satisfy the conditions of the present invention for each refractory weight (Kg) as shown in Table 1 below. For comparison, the ratio (length ratio) of the length of the lower surface to the upper surface of the brick in contact with the molten steel of the refractories manufactured was also set to the extent that the refractory weight (Kg) .

That is, the following Tables 1 and 2 show chemical compositions, general physical properties, dimensional ratios and weights of refractory bricks designed with the refractory materials, and stress indices by which the thermal stresses are calculated using the chemical ratios and general properties of the refractories used in the tests. Here, the stress index is expressed as a relative index with reference to a bending strength value as a reference value (100) by using a tensile stress value measured by performing a thermal stress analysis in a use condition of a bottom of a converter and a hot bending strength value of a used refractory, If the stress index is less than 100, it expresses that the thermal stress of the refractory is safe on use.

division
Honor One 2 3 4 5 6


Fireproof
brick




Composition Magnesia (% by weight) 81 81 81 81 88 88 Graphite (% by weight) 18 19 19 19 12 12 additive
(Extrapolation)


Al 3 3 3 3 One Al / Mg One One One One Si 3 B ₄ C 0.7 0.7 0.7 0.7 0.7 MgB ² 0.7 Product properties

Weight
(g / cm ³⁾ 2.88 2.88 2.88 2.88 2.92 2.93 Porosity (%) 2.1 2.1 2.1 2.1 2.3 2.7 Compressive strength
(Kg / cm2) 337 337 337 337 392 416 Design Method
Dimensional Ratio (B / A) 1.37 1.33 1.24 1.17 1.33 1.33 Weight (Kg) 50 110 300 700 110 110 Thermal stress characteristics Stress index 92 90 92 90 89 87

division
Comparative Example One 2 3 4 5 6


Fireproof
brick




Composition Magnesia (% by weight) 81 81 81 81 88 88 Graphite (% by weight) 19 19 19 19 12 12 additive
(Extrapolation)


Al 3 3 3 3 One Al / Mg One One One One Si 3 B ₄ C 0.7 0.7 0.7 0.7 0.7 MgB ² 0.7 Product properties

Weight
(g / cm ³⁾ 2.88 2.88 2.88 2.88 2.92 2.93 Porosity (%) 2.1 2.1 2.1 2.1 2.3 2.7 Compressive strength
(Kg / cm2) 337 337 337 337 392 416 Design Method
Dimensional Ratio (B / A) 1.47 1.43 1.34 1.27 1.43 1.43 Weight (Kg) 50 110 300 700 110 110 Thermal stress characteristics Stress index 113 109 114 110 108 106

As can be seen from Table 1-2, Inventive Examples 1-6 of Table 1, which satisfy not only the refractory brick composition of the present invention but also the dimensional ratio of each brick weight, satisfy the range of the present invention, And it is confirmed that it shows a stable thermal stress value.

On the other hand, it can be confirmed that the refractory brick composition components are within the scope of the present invention, but the stress index is 100 or more in all of Comparative Examples 1-6 in Table 2 in which the dimensional ratio of each brick weight is out of the range of the present invention. Therefore, the increase of the dimensional ratio increases the thermal stress, and serious damage of the refractory due to the enlargement of the shape at the bottom of the converter can be expected.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the scope of the present invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. And will be apparent to those skilled in the art.

Claims (1)

In the converter bottom refractory brick,
Al, Mg, Si, SiC, B4C, CaB6, and SiC are added to 100 parts by weight of the main raw material, and the refractory brick is composed mainly of a composition containing 81 to 88% of magnesia refractory material and 12 to 19% MgB2, and BN is added in an amount of 5 parts by weight or less,
Wherein the refractory brick has a dimensional ratio defined by the following relational expression 1 satisfying 1.1 to 1.37 when the weight of the refractory brick is 50 kg or less,
When the weight is 110 kg or less, the dimensional ratio defined by the following relational expression 1 satisfies 1.1 to 1.33,
When the weight is 300 kg or less, a dimensional ratio defined by the following relational expression 1 satisfies 1.1 to 1.24; And
And a dimension ratio defined by the following relational expression 1 satisfies 1.1 to 1.17 when the weight is 700 kg or less.
[Relation 1]
Dimensional Ratio = B / A
Where A is the length of the upper surface of the brick in contact with the molten steel and the length of the lower surface of the brick not in contact with molten steel.

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