JP2991472B2 - Refractory for ladle lining - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to an alumina-spinel-based ladle refractory with improved heat insulation.

[Related Art] As a refractory for ladle lining, it is easy to construct a large-sized ladle, and the cast refractory has good durability when performing refining or the like using a basic slag. Refractories are preferred. From However, it alumina mineral constituting the refractory (Al ₂ O _3), spinel (MgO · Al ₂ O _3, etc.) is a relatively good thermal conductivity, these refractories mainly heat When this kind of refractory is lined with a ladle, the heat loss from the ladle is large, so slag and metal are gradually attached to the inside of the ladle and the ladle There is a problem that the capacity gradually decreases. On the other hand, Japanese Patent Publication No. 59-32423 proposes a refractory for lining a ladle to which slag and metal do not adhere. That is, in this refractory for lining a spinel ladle, 1 to 20% by weight of graphite or a mixture of graphite and silicon carbide is added to the refractory, and graphite is less likely to wet the refractory with metal or slag. By doing so, the silicon carbide dissolves into the slag as SiO ₂ or the like and lowers the melting point of the slag, thereby preventing the slag and the ingot from adhering to the refractory. However, all of these additives are substances with good thermal conductivity, cannot reduce the heat loss from the ladle, and often increase the temperature of the molten steel contained before moving on to the next step. Had to be taken separately.

An object of the present invention is to provide a refractory for lining a ladle that can prevent slag and metal from adhering and reduce heat loss of molten steel contained in the ladle.

[Effects of the Invention] The present invention has been made to solve the above-mentioned problems, and the refractory for ladle lining of the present invention is an alumina-spinel cast refractory, and has a particle diameter in the refractory. 0.3-3
It is characterized by containing 2.5 to 12% by weight of hollow particles having a diameter of 2.5 mm, an apparent porosity of 20 to 32%, and non-spinelized magnesia in the refractory.

In a preferred embodiment of the refractory for ladle lining according to the present invention, the refractory contains 4 to 10% by weight of the hollow particles.

In another preferred embodiment of the refractory for ladle lining according to the present invention, the hollow particles are electroformed hollow particles, and more preferably the hollow particles are alumina-based.

In the refractory for ladle lining of the present invention, alumina clinker, spinel clinker and hollow particles are blended as main constituent materials, but magnesia clinker is added to further improve corrosion resistance. As the alumina clinker, natural minerals such as alumite shale, calcined bauxite, synthetic alumina clinker, electrofused alumina clinker, and the like are used. As the spinel clinker, synthetic spinel clinker, electrofused spinel clinker, and the like are used.

As hollow particles, an air stream is blown against the electro-fused molten metal to achieve 0.
It is preferable to use hollow particles of alumina or spinel as hollow particles having a thickness of about 1 mm. Magnesia (Mg
Regarding O), hollow particles cannot be obtained by the electrofusion method with the current technology, but hollow particles can be obtained by sintering powder. As the hollow particles, it is preferable to use those having a dense structure in order to ensure corrosion resistance,
The electrofused hollow particles have a dense structure, and have good corrosion resistance due to being composed of coarse crystal particles, and the cast refractories containing the electrofused hollow particles have excellent durability. ing.

If the particle diameter of the hollow particles is smaller than 0.3 mm, the porosity of the hollow particles is small, so the effect of imparting heat insulating properties is small, and the effect of improving the heat insulating properties of the poured refractory is also unpreferable because the particle diameter is larger than 3 mm. In this case, the internal pores are large, so that the corrosion resistance is reduced in spite of the effect of imparting heat insulation, which is not preferable. When the amount of the hollow particles is 2.5% or more, the effect of imparting heat insulation is recognized. When the amount exceeds 12%, the corrosion resistance of the cast refractory decreases, which is not preferable.

The pores in the refractory are closed pores introduced by hollow particles,
There are both open pores present between the particles of the raw material, and the insulation is provided by the presence of both. However,
If the number of open pores is large, the corrosion resistance is reduced, and if the number is small, the heat insulating property is reduced. Therefore, it is appropriate to set the apparent porosity of the refractory (showing the porosity of only open pores) to 20 to 32%. The content of the hollow particles is more preferably 4 to 10% by weight in consideration of the balance between the corrosion resistance and the heat insulation performance.

Since the refractory material of the present invention contains magnesia which is not spinelized, a high melting point compound is formed on the surface of the refractory material during use and shows good corrosion resistance.

As the hollow particles, it is preferable to use an electrofused hollow element having a dense and coarse crystal structure and good corrosion resistance. Particularly, the electrofused alumina element of alumina is easily available as a commercial product and has a high corrosion resistance. It is preferred as a component of the refractory of the present invention because it has a good thermal insulation property.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples.
The examples are merely examples of the present invention and do not limit the present invention in any way.

Nos. 1 to 5 in Table 1 are refractories for ladle pouring according to an embodiment of the present invention, and No. 6 is a comparative example thereof. As raw materials, 3 to 10 mm coarse particles of fused alumina clinker, 3 m
Fine particles of synthetic alumina clinker finer than 325 mesh, and fine particles finer than 325 mesh of fused spinel clinker, 1 mm of synthetic magnesia clinker
The following medium-sized, and hollow particles of fused alumina with a particle size of 0.
A mixture of 5 mm to 2.5 mm was prepared in the proportions shown in Table 1, and 3 parts by weight of an appropriate amount of alumina cement as a binder and a peptizer such as sodium pyrophosphate were added. Water was added, the mixture was kneaded with a universal mixer, and poured into a mold to prepare a 40 mm × 40 mm × 160 mm test piece.

The bulk specific gravity, apparent porosity, and thermal conductivity of the obtained test piece were measured, and the results are shown in Table 1.

The corrosion resistance test was performed using a rotary erosion test furnace. That is, the six test pieces were filled with a stamp material therebetween and assembled into a cylindrical shape to form a crucible with an edge. In this crucible arranged horizontally, 54.8 wt% of CaO and 28.5 wt% of Al ₂ O _{3 were} placed. , SiO ₂ 8.6wt
%, MgO7.1wt%, and Fe ₂ O ₃ were placed together 1.0 wt% of a basic slag 0.6Kg same weight billet SS41 consisting of a composition, This was dissolved by heating with a gas burner, at 1650 ° C. The crucible was held for 6 hours while rotating. The corrosion resistance index is determined by calculating the maximum erosion depth of the test piece eroded by the erosion component consisting of the slag and the molten steel from the difference between the thickness before the test and the thickness after the test, and does not include hollow particles. No.6
Calculated from the maximum corrosion depth C _n of the various refractory to the maximum corrosion depth C ₆ refractory in C ₆ / C _n × 100, showed corrosion resistance index of comparison also in conjunction with Table 1.

The temperature drop of the hot water when this refractory is constructed on a ladle is assuming a state in which 250 t of 1650 ° C molten steel is put in a 250 t capacity ladle at an ambient temperature of 20 ° C. 65mm alumina-silica permanent refractory (thermal conductivity 2.
05Kcal / mh ℃) and a waxy quasi-permanent refractory with a thickness of 65mm (thermal conductivity 2.0Kcal / mh ℃) combined with a 180mm-thick cast lining refractory. This is the result of calculating the temperature drop of the molten steel one hour after the occurrence of the molten steel by heat transfer calculation, and the calculation results are also shown in Table 1. To confirm that the calculation results were correct, No. 3 cast refractory was installed on a ladle of the same capacity, and the temperature drop after 1 hour was measured with 250t of 1650 ° C molten steel put in. And the temperature drop of 4.5 ° C is smaller than that of the data when using the conventional cast refractory. Also, it was recognized that the adhesion of slag and ingots was also very small due to the decrease in the temperature of the hot water being reduced.

[Effect of the Invention] The refractory for pouring a ladle of the present invention has an excellent effect of reducing a drop in the temperature of molten steel and preventing sticking of slag and ingot. In other words, the slag line (refers to the level of slag on the upper surface of molten steel) is stabilized by drastically reducing the slagging compared to when the conventional refractory is constructed, and there is almost no decrease in the capacity of the ladle, In addition to avoiding the risk of molten steel overflow,
By reducing the temperature drop of 4.5 ° C, there is no need to raise the temperature of the molten steel in the ladle containing 250t of molten steel again. A full 250t ladle saves about one million yen in energy costs. This saving effect is an effect that greatly exceeds the increase in the basic unit of the refractory due to the sacrificed corrosion resistance of the refractory, and the industrial use effect of the ladle pouring refractory of the present invention is great. .

Claims (1)

(57) [Claims] An alumina-spinel cast refractory, wherein hollow particles having a particle diameter of 0.3 to 3 mm are contained in the refractory in an amount of 2.5 to 12 watts.
A refractory for lining a ladle, characterized in that the refractory contains 20% to 32% by mass, an apparent porosity of the refractory is 20 to 32%, and magnesia which is not spineled is contained in the refractory.