JPH0393674A - Basic casting execution refractory - Google Patents

Abstract

PURPOSE:To provide basic casting execution refractory having excellent spalling resistance and slag permeation resistance by blending a refractory aggregate comprising zircon and magnesia in a specific weight ratio with a proper amount of a binder. CONSTITUTION:A refractory aggregate comprising 3-40wt.% zircon and the rest of magnesia is prepared. 100 pts.wt. refractory aggregate is blended with a proper amount of a binder (e.g. alumina cement or phosphate) and preferably further <=7 pts.wt. metallic fiber (e.g. stainless steel fiber) to produce basic casting execution refractory. When finely granulated zircon having <=0.5mm particle diameter is used as the zircon, hydration reaction of magnesia is prevented and corrosion resistance is further effectively improved. The addition of the metallic fiber effectively prevents residual contraction which is formed because liquid phase is produced by dissociation of zircon.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a basic refractory for pouring construction that has excellent spalling resistance. (Prior art) Basic pouring refractories (hereinafter referred to as basic pouring materials) based on magnesia are known as lining materials for tin plates, tundishes, vacuum degassing furnaces, pig iron mixers, etc. There is. Basic pouring materials have the advantage of exhibiting excellent corrosion resistance against highly basic slag, and are preferable for producing clean steel because they do not contaminate molten steel. However, on the other hand, thermal spalling and structural spalling due to slag penetration are significant, and the above-mentioned effects of basic properties are not fully demonstrated. Therefore, various proposals have been made to solve this spalling problem. For example, adding carbon to a basic pouring material mainly composed of magnesia (Japanese Unexamined Patent Publication No. 57-92581), adding alumina (Japanese Unexamined Patent Publication No. 60-60986), S
In, blending 80% by weight or more of silica (Japanese Unexamined Patent Publication No. 53-26734), blending chromite (
JP-A No. 52-140429). (Problem to be solved by the invention) However, none of the above conventional techniques can be said to be a sufficient solution. In other words, the corrosion resistance of carbon-containing products decreases due to carbon oxidation. Addition of alumina damages spinel due to its reaction with magnesia, and the accompanying expansion causes cracking or flaking. When silica is added, it reacts with magnesia to produce MgO-Sin, a low melting point substance, which reduces corrosion resistance. Chromite has insufficient effect in preventing slag penetration and causes large structural spalling. The present invention solves the problem of spalling in basic casting materials without impairing the high corrosion resistance inherent to basic properties. (Means for Solving the Problems) The present invention provides a refractory for basic pouring construction, which is composed of 100 parts by weight of a refractory aggregate mainly consisting of 3 to 40% by weight of zircon and the balance being magnesia, and an appropriate amount of a binder. It is. The graph in Figure 1 shows the relationship between the slag erosion ratio and the slag penetration ratio with respect to the zircon content in basic casting materials containing zircon. Zircon is
Particles with a particle size of 5 to 1 mm and 0.5 nu or less were used. The results in this graph confirm that slag penetration is reduced by the inclusion of zircon. Furthermore, since slag erosion increases in proportion to the proportion, it is clear that the proportion of zircon must be kept within a certain range.

Zircon dissociates into zirconia and silica glass at high temperatures. The above-mentioned prevention of slag penetration is thought to be caused by the highly viscous silica glass produced by this dissociation filling the matrix of the refractory structure.If the zircon particles are fine, the above-mentioned dissociation is likely to occur; Also, perhaps because dissociated silica glass exists in the matrix, as shown in the graph in Figure 1, a particle size of 0.5 rm or less is more effective than a particle size of 5-1. prevents oversintering due to the reaction between slag and magnesia, eliminating structural spalling.The graph in Figure 2 shows the basic casting materials for a product without zircon additives and a product containing 20% by weight of zircon. The results of this graph show that the inclusion of zircon reduces thermal expansion. Refractories with small thermal expansion are less likely to cause thermal spalling. This is a graph showing the relationship between the amount of zircon added and the spalling resistance of a basic cast material using a single-sided heating spall test.It can be seen that the addition of zircon improves the spalling resistance. However, it can be seen that fine zircon particles with a particle size of 0.5 m or less are more effective.In addition, in the above magnesia zircon system, the liquid phase grows due to the dissociation of zircon, resulting in residual shrinkage. The contraction is
It causes peeling. In the present invention, this residual shrinkage can be prevented by further adding metal fibers. Figure 4 shows zircon 2
This is a graph showing the relationship between the amount of metal fiber (stainless steel fiber is used as an example) and the rate of residual line change in a basic pourable material containing 0% by weight. The addition of metal fibers prevents residual shrinkage because
The presence of metal fibers between the liquid phases generated by the dissociation of zircon prevents contact between the liquid phases.
This seems to be because shrinkage due to liquid phase sintering is prevented. Since pouring materials are constructed by adding a large amount of moisture, basic pouring materials have the problem that some of the MgO in the magnesia raw material undergoes a hydration reaction, weakening the refractory structure. This is a phenomenon that cannot be observed in stamped materials, which require almost no water addition during construction, even though they are monolithic refractories.
In the present invention, when zircon is blended with a particle size of mainly fine particles, it is effective in preventing hydration reactions, and corrosion resistance can be further improved. The particle size of pouring materials is adjusted to coarse, medium, and fine particles in order to obtain a densely packed structure and to provide fluidity during construction, but when zircon is blended with a particle size that is mainly fine particles, the particle size structure increases. , the number of fine particles of magnesia can be reduced accordingly. Hydration reactions are more likely to occur in magnesia that has a large specific surface area, so reducing the number of fine magnesia particles can prevent hydration reactions. Figure 5 is a graph showing the relationship between the proportion of fine zircon particles with a diameter of 0.5 m or less and the hydration reaction in basic pouring materials. In this case, the proportion of fine particles of 0.5 or less in the total refractory aggregate is 4
It was standardized to 0% by weight, and fine magnesia was reduced as fine zircon increased. The specific methods of the tests shown in FIGS. 1 to 5 above were the same as those shown in the Examples section below.

Zircon used in the present invention is, for example, zircon sand,
Any of zircon grog, which is made by granulating zircon sand, zircon flour, which is made by pulverizing zircon sand, and ultrafine zircon powder, which is further finely pulverized. The proportion of zircon in the refractory aggregate is 3 to 40% by weight.
Suppose that If it is less than 3% by weight, the present invention will not be effective. If it exceeds 40% by weight, too much silica glass will be produced due to dissociation, which will reduce corrosion resistance. As shown in the results shown in Figure 5, when the particle size of zircon is mainly fine, it is effective in preventing the hydration reaction. To obtain this effect, use particles with a particle size of 0.5 m or less. Magnesia has excellent slag erosion resistance due to its high melting point. As long as the MgO purity is 80% by weight or more, it does not matter whether it is a natural product or a synthetic product. Also, either sintered or electrofused products are acceptable. As with conventional materials, the particle size is adjusted to coarse, medium, or fine, taking into consideration fluidity during pouring, filling properties after construction, etc. When combining fine grains of zircon, it is preferable to reduce the number of fine magnesia grains due to the particle size structure. The proportion of refractory aggregate other than zircon is mainly magnesia as mentioned above, but other refractory raw materials may be mixed as part of the refractory aggregate as long as it does not impede the effects of the present invention. You may do so. The specific type and addition ratio of the binder are not particularly different from conventional materials. For example, alumina cement, phosphate, silicate, etc., and the preferable ratio is 100% refractory aggregate.
It is 1 to 20 parts by weight. When adding metal fibers, the material is most preferably stainless steel from the viewpoint of heat resistance, but is not limited to this, for example, iron, carbon steel, Ni-Cr steel, Cr-No steel, C
r steel. Cr-V steel, Ai AQ alloy, Cu%Cu alloy, etc. may also be used. The shape can be straight, curved, chevron-shaped, wavy, etc. The dimensions are preferably 0.1 to 2 inches in diameter, and the length is about 5 to 50 times the diameter (for example, 5 to 40 cm). The proportion of metal fibers to be added is within the range of 7 parts by weight or less, and is determined as appropriate depending on the specific gravity of each fiber. Although the effect can be seen even with a very small proportion, since metal aivar is also a low melting point substance, if it exceeds 7 parts by weight, the corrosion resistance of the castable refractory will decrease. More preferably, 1 to
It is 5 parts by weight. As with conventional pouring materials, an appropriate amount of peptizer may be added. The proportion is 1.0 parts by weight or less, preferably 0.0 parts by weight.
The amount should be 1 to 0.5 parts by weight. Examples of peptizers include sodium tripolyphosphate, sodium hexametaphosphate,
Selected from inorganic salts such as ultra-sodium polyphosphate, acidic sodium hexametaphosphate, sodium borate, and sodium carbonate, and organic salts such as sodium citrate, sodium tartrate, sodium polyacrylate, and sodium sulfonate. One or more types. When a phosphate misilicate or the like is used as a binder, the binder itself has a peptizing effect, so there is no need to add a peptizer.

In addition to this, the pouring material of the present invention can also include metal powder, glass powder,
One or more selected from clay, organic fibers, ceramic fibers, carbon powder, carbides, nitrides, borides, zirconia, subinel, etc. may be added within a range that does not impede the effects of the present invention.

In use, approximately 3 to 10% by weight of water is added to the entire pouring material, mixed, and then applied. (Example) Examples of the present invention and comparative examples thereof are shown below. Table 1 shows the combination strength and test results for each example.

In each example, 7.0% by weight of construction moisture was added on the outside, and the molding was performed by applying vibration. [Test method] Apparent specific gravity: After drying a certain shape at 110°C for 24 hours, it was measured according to JIS-R2205. Rotational erosion; Steel billet: Molten steel ladle slag = 1 = 1 was used as a solvent, and after 4 hours at 1650°C, the dimensions of erosion and slag penetration were measured. Bending strength: According to JIS-R2553. Line rate of change: According to JIS-R2554. Single-sided heated spall: heating at 1400°C for 3G → forced air cooling was repeated, and the number of repetitions until flaking occurred was measured. Hydration resistance: After heating and drying the molded article at 110°C for 24 hours, the weight increase rate due to permanent hydration was determined by subtracting the weight immediately after molding from the weight after heating and drying. In this case, the amount of added water was subtracted from the calculation. Durability in actual equipment test ■: The product was poured into the slag line of a 250-ton molten steel ladle to a thickness of 180 mm, and the presence or absence of flaking and the number of durable uses were investigated. ■: The lining of the lower tank of a 250-ton RH vacuum degassing furnace was poured to a thickness of 200 mm, and the number of durable uses was investigated. (Effects of the Invention) The basic pouring material obtained by the present invention has excellent slag penetration resistance and low thermal expansion, so it has high resistance to both structural spalling and thermal spalling. Poor spalling resistance is the biggest drawback of basic pouring materials. By eliminating this drawback, the present invention can fully demonstrate the excellent effects inherent to basic pouring materials, such as exhibiting high corrosion resistance against high basicity slag and being suitable for making clean steel. ．． The above basic pouring materials have small thermal expansion, but on the other hand,
Indicates residual contraction. In the present invention, residual shrinkage can be eliminated by further adding metal fibers. Further, in the present invention, when zircon is contained in fine particles of 0.5 - or less, the hydration reaction of magnesia is prevented and corrosion resistance is further effectively improved.

[Brief explanation of drawings]

The figure is a graph of the measurement results of various physical properties of basic pouring materials. Figure 1 shows the relationship between the amount of zircon added and slab erosion resistance and slag penetration resistance, and Figure 2 shows the thermal expansion curves for products with no zircon added and products containing 20% zircon. , Figure 3 shows the relationship between the amount of zircon added and spalling resistance, and Figure 4 shows the relationship between the amount of metal fiber added and the residual linear change rate for a product containing 20% zircon. Figure 5 shows the relationship between the amount of fine zircon added and hydration resistance. Fig. 1 0 10 20 30 40 50 60 70 Zircon containing location (Im:/:) Fig. 2 Temperature C℃) Fig. 3 Fig. 4

Claims (3)

[Claims] (1) A basic refractory for pouring construction consisting of 100 parts by weight of a refractory aggregate mainly consisting of 3 to 40% by weight of zircon and the balance being magnesia, and an appropriate amount of a binder. (2) A basic refractory for pouring construction consisting of 100 parts by weight of a refractory aggregate mainly composed of 3 to 40% by weight of zircon and the remainder magnesia, 7 parts by weight or less of metal fibers, and an appropriate amount of a binder. (3) Claim 1, wherein the particle size of the zircon is 0.5 mm or less.
or the basic refractory for pouring construction described in 2.