JPH02225379A - Castable refractory for lining molten steel ladles - Google Patents

Abstract

PURPOSE:To improve hot strength and releasability by adding short-cut organic fibers to the main material containing alumina, MgO-Al2O3 spinel and alumina cement. CONSTITUTION:100wt.% of the formulation mainly containing 40 to 90wt.% of alumina, 2 to 50wt.% of MgO.AL2O3 spinel and 2 to 25wt.% of alumina cement are combined with short-cut organic fibers of 0.5 to 200mm in an amount of 0.01 to 0.5wt.% based on the main materials to give the subject castable refractory. Alumina plays a role of resisting corrosion and stabilizing the volume. The alumina is preferably SiO2 component causing low-temperature melt formation. The particle size of MgO-Al2O3 spinel is preferably less than 1mm diameter. Less than 1mm spinel particle size more increases slag-permeation resistance of the castable refractory, while the shrinkage is also increased, and the shrinkage can be prevented by adding the above-stated short-cut organic fibers.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a castable refractory for lining a molten steel ladle.

(Prior Art) The lining of molten steel ladles is being transitioned from conventional brick masonry to monolithic refractories for the purpose of labor saving and mechanization of construction. The monolithic refractory used here is, for example, disclosed in Japanese Patent Application Laid-Open No. 60-60985, which comprises at least 60 parts by weight of spinel clinker, 10 to 35 parts by weight of alumina clinker, and 3 to 10 parts by weight of alumina cement. Spinel-alumina trade castable refractories, JP-A No. 60-60986, discloses that the weight ratio of magnesia clinker:alumina clinker is 7:3 to 8:2.
A magnesia-alumina-spinel castable large-sized material has been proposed, which has an aggregate consisting of 60 to 80 parts by weight of a mixture consisting of the following: and 20 to 40 parts by weight of spinel clinker.

(Problems to be Solved by the Invention) The above-mentioned materials have superior corrosion resistance compared to conventional monolithic refractories such as axite and zirconite. but,
In view of the recent harshness of furnace operations and the tendency to reduce the unit consumption of refractories, this cannot be said to be sufficient, and there is a strong desire to provide castable refractories with even greater durability.

(Means for Solving the Problems) The present inventors have made repeated efforts to develop a material that is more suitable for lining a molten steel ladle while taking advantage of the corrosion resistance of the alumina-spinel caster pull refractory. As a result, it was found that adding an appropriate amount of organic short fibers to a mixture of alumina and Mgo・A[,,0, spinel (hereinafter referred to as spinel) in a specific ratio is effective in improving hot strength and preventing peeling. This led to the completion of the present invention.

That is, in the present invention, the weight ratio is 40 to 90% alumina, M
gO・A 0. O, 100% of the mixture mainly composed of 2 to 50% spinel and 2 to 25% alumina cement,
Externally wrap organic short fibers with a length of 0.5 to 20+ ms to 0.0
A castable refractory for lining a molten steel ladle containing 1 to 0.5%.

Further, in the above refractory, the particle size of the MgO.A Q , O, spinel is 1+mm or less.

Next, the present invention will be explained.

Alumina-spinel has a high coefficient of thermal expansion, but since the lining of a molten steel ladle is constrained by an iron shell on the outer periphery and a holding fitting above, the expansion is absorbed by the refractory itself, weakening the refractory structure. do. On the other hand, when organic short fibers are added, when heated during use, the short fibers are burnt out, creating fine voids, and these voids absorb the expansion of the refractory and are thought to prevent the weakening of the structure. It will be done.

FIG. 1 shows the relationship between the amount of organic short fibers added and the maximum thermal expansion stress of a castable refractory in an alumina-spinel refractory. It can be seen that when organic short fibers are added, the maximum thermal expansion stress of the castable refractory becomes smaller. The blending composition of the castable refractories used in this experiment was the same as in Example 7 described below, with only the added amount of organic short fibers being changed.

This type of castable refractory uses alumina cement as a binder. Alumina cement is AQ20.
The main components are and CaO. CaQ from this alumina cement reacts with MgO from spinel and A0.03 from alumina etc. at high temperatures during use.
A Q 20. - MgO-CaO-based low melting material (melting point 1
370°C). This tendency becomes more pronounced as the particle size of spinel becomes smaller. Conventional alumina-spinel castable refractories shrink due to the formation of this low-melting material, resulting in the generation of oxidation and then metal insertion, resulting in peeling.

In contrast, in the castable refractory of the present invention, fine voids are created in the refractory structure due to the addition of organic short fibers, and as a result, contact between each component, which causes the formation of low-melting-point substances, is reduced. It is thought that this reduces the generation of and prevents peeling.

FIG. 2 shows the high-temperature expansion curves of a castable refractory having the same composition as Example 8, which will be described later, in which short organic fibers were added, and a castable refractory of Comparative Example 2, in which short organic fibers were not added. It can be seen that the shrinkage in the case where organic short fibers were added was smaller than in the case without addition.

Next, one compound used in the present invention will be explained in detail. Note that all percentages shown below are based on weight ratios.

Alumina has roles such as corrosion resistance and volumetric stability, and its types include artificial products such as sintered alumina and fused alumina, and natural products such as clay shale, bauxite, and sillimanite. One or more selected from can be used. Among them, those with a small amount of SiO□ component, which causes low-melting material formation, are preferable.The particle size is not particularly different from the conventional one, but the maximum particle size is set to 10 to 25 cm, for example, so that the monolithic refractory is densely packed during construction. Coarse grain.

It is divided into medium grains and fine grains as appropriate.

The proportion of alumina is 40-90%, preferably 50-80%
%. If it is less than 40%, corrosion resistance and durable lag permeability will be poor. Moreover, if it exceeds 90%, the proportion of spinel decreases accordingly, resulting in poor slag penetration resistance.

Spinel can be either electromagnetic or fired crystal.

A combination of these may also be used. MgO that makes up spinel
' The ratio of each component of A Q 203 is MgO・
Ag2O.

is 0.7 to 1.3: A range of 1.3 to 0.7 can be used, and the grain size of the desk spinel is preferably 1 m or less. 6 Figure 3 shows:
1 is a graph showing the relationship between spinel particle size and slag permeability of castable refractories in alumina-spinel castable refractories.

The method for measuring slab permeability was the same as in the examples described below.

In addition, the composition of each raw material in this case is sintered alumina 55%
, 30% sintered spinel, 15% alumina cement, and 5111 m long vinylon short fibers were applied to the outside to make 0.1%.

From the figure, it can be seen that the slag penetration resistance of the castable refractory is further improved when the particle size of the spinel is one size or less. The reason for this is that since the spinel is fine, it is uniformly filled into the matrix without gaps, and the spinel thoroughly dissolves components such as FeO and MnO in the slag, thereby increasing the effect of preventing penetration into the slab.

In an alumina-spinel castable refractory, if the particle size of the spinel is set to 1 m+a or less, although the above effects can be obtained, the shrinkage becomes even more significant, but in the present invention, this shrinkage can be prevented by adding organic short fibers. The proportion of spinel is 2 to 50%, more preferably 5 to 45%. 2
If it is less than 50%, it will not be effective in preventing slag penetration, and if it exceeds 50%, the expansion stress will become too large.

The alumina cement may be similar to those used conventionally in boating as a binder for refractories.

The particle size shall be a fine powder of 180 mesh or less. The ratio is 2
-25%, preferably 5-20%.

If it is less than 2%, it has no effect of imparting strength as a binder;
If it exceeds 5%, corrosion resistance will be reduced.

As the organic short fibers, materials such as polyester, polyamide, acrylic, cellulose, vinylon, polypropylene, nylon, polyvinyl, and polyethylene can be used. The size is 0.5 to 20 m in length. 0.5
If it is less than 20 na, it will not be effective as a fiber, and if it exceeds 20 na, the slag penetration resistance in castable refractories will be poor. Additive 100 is a compound based on fire-resistant aggregate and binder.
%, the external multiplication is 0.01 to 0.5%. 0.
If it is less than 0.01%, there is no effect, and if it exceeds 0.5%, corrosion resistance will decrease.

In addition to the above-mentioned formulations and additives, other substances may be added to the present invention as long as they do not inhibit the effects of the present invention.

For example, an appropriate amount of magnesia may be added, but since magnesia has an extremely large coefficient of thermal expansion, the proportion thereof is preferably 5% or less. In addition, suitable amounts of short metal fibers, metal powder, carbon powder, carbides, nitrides, etc. may be added to the lining of the molten steel ladle, depending on the area of use.

(Example) Table 1 shows examples of the present invention and comparative examples thereof.

In each test, the mixture shown in Table 1 was mixed with an appropriate amount of water and then vibration cast into a mold at 110°C x 24°C.
After drying for several hours, measurements were taken.

Bending strength: According to JIS-R2553.

Linear change rate: According to JIS-R2554.

Rotational erosion: Steel slab: molten steel ladle slag = 1:1 was soaked in a solvent, and the test was carried out at 1650°C for 4 hours, after which the Ia loss dimension and slag penetration dimension were measured.

All of the castable refractories of the examples of the present invention have small thermal expansion stress, small shrinkage due to heating (measured by linear change rate), and have the high corrosion resistance of alumina-spinel. In addition, those containing spinel with a particle size of 1 m or less have further improved durable lag permeability.

On the other hand, in Comparative Example 1, the strength (measured by bending strength) was low due to the small amount of alumina cement, and the corrosion resistance was also poor. Comparative Example 2, in which no organic short fibers were added, had a large thermal expansion stress and a large shrinkage.

Comparative Example 3 has poor corrosion resistance due to the large amount of alumina cement. Comparative Example 4 had a high proportion of organic short fibers and had poor corrosion resistance. In Comparative Example 5, the amount of spinel was too large and the slag penetration resistance was poor. Comparative Example 6 has poor slag penetration resistance because the length of the short organic fibers is too long. In Comparative Example 7, the shrinkage was small because the particle size of the spinel was large, but the thermal expansion stress was large because no organic short fibers were added.

As an actual machine test, some of the examples and comparative examples were tested.
No. 10 was used for lining a molten steel ladle and tested.

The embodiments of the present invention have - no peeling that was seen in conventional materials;
As shown in Table 1, excellent durability was obtained.

(Effects of the Invention) As described above, the present invention solves the problems of weakening of the structure due to thermal expansion stress and shrinkage due to the formation of low-melting substances, which were observed in conventional alumina-spinel castable refractories. As a result, the castable refractory of the present invention can fully exhibit the corrosion resistance of the alumina-spinel material, and its service life as a lining for a molten steel ladle is significantly improved.

Therefore, in view of the recent trend toward harsher molten steel ladle operation and reduction of refractory unit consumption, the present invention, which can provide castable refractories with excellent service life, has extremely high industrial value.

[Brief explanation of the drawing]

FIG. 1 shows the relationship between the amount of organic short fibers added and the maximum thermal expansion stress of castable refractories in alumina-spinel refractories. FIG. 2 shows high-temperature expansion curves of the castable refractory of Example 8 to which organic short fibers were added and the castable refractory of Comparative Example 2 to which no organic short fibers were added. FIG. 3 is a graph showing the relationship between spinel particle size and slag permeability of the castable refractory in alumina-spinel castable refractories. 0.1 θ・3 0.4 σ6 θ, 6.7 Save a Um table *ItlOi (7,) Figure 2 3 - &('C)

Claims (2)

[Claims] (1) Weight ratio: 40-90% alumina, MgO/Al
_2O_3 spinel 2 to 50% and alumina cement 2 to 25% as the main ingredients, 100% of the mixture has a length of 0.
5-20mm organic short fibers are wrapped around 0.01-0.5
Castable refractories for lining molten steel ladles. (2) The particle size of MgO・Al_2O_3 spinel is 1 m
The castable refractory according to claim 1, wherein the refractory is less than or equal to m.