JPH05330930A - Castable refractory - Google Patents

Abstract

PURPOSE:To provide a castable refractory used for a lining material of a hot iron runner of a blast furnace. CONSTITUTION:In a castable refractory composed mainly of magnesia-alumina base spinel and the rest of alumina, silicon carbide, carbon and a binder, 5-20wt.% silicon carbide having >=30 particle size and 5-20wt.% hydrophilic carbon having <=2mm particle size are compounded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an unshaped refractory for casting used as a lining material for a blast furnace tap gutter, especially a gutter, and has improved corrosion resistance to metal (hot metal), particularly to FeO. It is a thing.

[0002]

2. Description of the Related Art Casting refractories are used as lining materials for blast furnace tappipe, but the size of the blast furnace is increased, the tapping interval is shortened, the tapping amount is increased, and the tapping temperature is increased. Etc., and especially in the gutter from the taphole to the skinmer damper, the refractory is becoming more and more severe. In order to respond to that, various materials have been developed,
Recently, alumina-carbon system, alumina-silicon carbide-
From carbon type amorphous refractory for pouring to magnesia
Mainly alumina-based spinel, alumina, silicon carbide,
A spinel-silicon carbide-carbon cast molding refractory material comprising carbon and a binder is disclosed in, for example, JP-A-53-53.
No. 82824, JP-A-55-37459, and JP-A-55-85478.

[0003]

In the blast furnace gutter, the hot metal and slag from the tap hole are separated into the lower part and the upper part by the difference in specific gravity, and the slag moves to the lower part of the gutter. To go.
At the separation boundary between the molten pig iron and the molten slag, the refractory is particularly erosive, and is usually deeply engraved in a narrow area near the interface, which is the interface between the molten pig iron and the molten slag. It is considered that this is a phenomenon that occurs when highly reactive FeO is generated and reacts with the refractory. This magnesia-alumina spinel, which is hard to be eroded by FeO, is used as a refractory material to prevent erosion.

However, when silicon carbide is contained in the refractory mixture, silicon carbide and FeO undergo a reaction of the formula SiC + 2FeO → SiO ₂ + 2Fe + C (1), which reduces the effect of using magnesia-alumina spinel. .. Silicon carbide is useful for ensuring the corrosion resistance to molten slag, the spalling resistance of refractory materials, and the like, and there is a problem that if these are removed, these properties deteriorate.

[0005]

The present invention has been made to solve the above-mentioned problems, and magnesia-alumina is obtained by limiting the grain size and the amount of silicon carbide used and by adding carbon. Spinel-Silicon Carbide-
This is an improved refractory carbon type castable amorphous material. The gist of this is that in cast amorphous refractories consisting mainly of magnesia-alumina spinel, the balance being alumina, silicon carbide, carbon, and a binder, 5 to 20% by weight of silicon carbide of 30 μm or more and hydrophilicity of 2 mm or less in particle size. The present invention relates to an amorphous refractory material for casting, which is characterized by containing 5 to 20% by weight of carbon treated with heat resistance.

[0006]

The present invention will be described in detail below. Magnesia-alumina spinel is a compound having a theoretical composition of MgO 28.3% by weight and Al ₂ O ₃ 71.7% by weight. Highly pure magnesia with theoretical chemical composition
Alumina spinel is very expensive and difficult to use in large quantities as a refractory material. Therefore, in the present invention, an economical commercially available spinel that is industrially mass-produced by the electrofusion method or firing method. To use. Such an industrially mass-produced alumina-magnesia spinel does not always match the theoretical chemical composition, but as the crystal composition, it is composed of the necessary magnesia-alumina spinel, and therefore There are no obstacles to the implementation.

[0007] Such magnesia-alumina spinel has been introduced into the lining refractory of a molten steel ladle in a steelmaking plant and the lining refractory of a blast furnace gutter, and has already been used. Magnesia contained
The erosion mechanism focusing on alumina spinel is not always clear.

From the researches by the present inventors, the inventors of the present invention have studied the local melting loss of a so-called metal zone part which is sharply scooped near the interface between the slag and hot pig iron of a large gutter. Although spinel has excellent corrosion resistance to molten pig iron (FeO resistance), it is eroded by the mixed slag and reacts with SiO ₂ derived from silicon carbide as shown in the above formula (1) to give Tight (enstate MgO / Si
It was found that low-melting components such as O ₂ ) are generated and further the erosion of magnesia-alumina spinel in the refractory proceeds.

In order to suppress this reaction, it is preferable to make the magnesia-alumina spinel particles coarser than 74 μm. Further, when the amount of magnesia-alumina spinel in the refractory according to the present invention is 40% by weight or less, there is no great effect as corrosion resistance, and when it is 70% by weight or more, corrosion resistance to molten pig iron is improved, but corrosion by molten slag And the spalling resistance is deteriorated.

Alumina is industrially mass-produced by an electrofusion method or a firing method, and has a chemical composition with a purity of 98% or more, and its crystal is α type which is stable up to a high temperature. Unlike magnesia-alumina spinel, alumina is easily eroded by FeO in the hot metal component, but on the other hand, it is relatively hard to be eroded by the slag component. Therefore, it is preferable to use alumina for the aggregate portion in the refractory and for the fine grain portion of 74 μm or less where it is difficult to use the magnesia / alumina spinel particles. If the amount of alumina used is 3% by weight or less, the sinterability that progresses as a fine powder is reduced, and the strength of the refractory structure cannot be sufficiently exhibited. On the other hand, if the content is 15% by weight or more, the erosion by the hot metal is advanced, which is not preferable.

It is well known that silicon carbide has a high corrosion resistance against various molten metals and slag, and further has a high resistance to spalling fracture. However, FeO generated in the molten steel or the hot metal is decomposed by the reaction represented by the formula (1), and the melting loss of the refractory using magnesia-alumina spinel is promoted. In the present invention, the weakness of the magnesia-alumina spinel contained in the refractory,
That is, it is used to improve the erosion resistance to the molten slag and the spalling resistance.

Silicon carbide is also industrially mass-produced, and it can be said that the higher the purity, the better the corrosion resistance. However, the purity of about 85%, which is often used for refractories, is high.
Is the lower limit. Furthermore, the present invention delays the progress of the reaction of the above formula (1) and reduces the production amount of SiO ₂ which reacts with magnesia-alumina spinel and leads to melting loss of refractory, so that the particles of silicon carbide are 30 μm or more. Use a coarse particle size. If it is less than 30 μm, the reaction with the magnesia-alumina spinel is likely to proceed, and the melting loss of the refractory material proceeds. If the amount of silicon carbide used is less than 5% by weight, the corrosion resistance to molten slag and the spalling resistance as a structure are insufficient, and if it exceeds 20% by weight, the corrosion resistance and spalling resistance are improved, but FeO Corrosion resistance to hot metal containing Cu decreases significantly.

Carbon has the disadvantage that it is oxidized and consumed when heated to a high temperature in the atmosphere, but it is difficult to wet with various molten metals and molten slag, and, for example, has a corrosion resistance to molten steel, hot metal and FeO contained therein. It is excellent. Further, it is well known that it has the advantage that it has a large resistance to thermal spalling fracture due to its small expansion coefficient.
Examples of refractory materials incorporating such advantages of carbon include magnesia-carbon bricks that have been developed for converters and electric furnaces and have an excellent track record.

However, in the castable refractory for casting, in which water is added and kneaded to be fluidized and cured, the carbon is water-repellent. Therefore, if the amount of carbon added is increased, it is necessary to obtain a predetermined fluidity. The amount of water added will increase. As a result, the compactness of the structure after forming is lost, and molten pig iron and molten slag penetrate to accelerate the melting loss. Therefore, the present situation is to suppress the amount of carbon added to the refractory as much as possible.

In the present invention, the metal resistance (FeO resistance) of magnesia-alumina spinel is utilized to improve the corrosion resistance against molten slag, which is its disadvantage, so that the amount of silicon carbide used and the grain size are limited, and further, carbon is used. Is to increase the usage of. For this reason, it is necessary to treat the carbon to be used so that it can be easily wet with water and to make the surface of the carbon particles hydrophilic.

Examples of carbon used include pitch, mesophase carbon, carbon black, coke, graphite and the like. To produce hydrophilic carbon, for example, sodium linoleate, ammonium humate, sodium alginate, sodium lignin sulfonate, sodium alkylbenzene sulfonate, etc. are added to these carbons and kneaded, and then dried with a spray dryer.

The product thus produced can be used, or a commercially available product that has been treated to impart hydrophilicity can be used. That is, without increasing the amount of kneading addition water required as an amorphous refractory for casting,
It is important to use hydrophilically treated carbon that allows the amount of carbon to be increased. FIG. 1 shows the relationship between the amount of water added and the amount of added carbon required to obtain a certain fluidity between hydrophilically treated carbon and untreated carbon.

The formulation except for the hydrophilically treated carbon of Example 1 in Table 1 was kept constant and the amount of hydrophilically treated carbon was 2-14.
The amount of added water and the amount of untreated carbon when the flow value is 150 mm when changed to 2% by weight are 2 to 10% by weight.
The case where the flow value when changed to 50 mm was 150 mm was measured. As a result, compared with the case where the amount of carbon is 10% by weight, the hydrophilic treated carbon has 5.5%, whereas the untreated carbon has 8.0%, which requires a large amount of water. If such carbon has a thickness of 2 mm or more, the strength of the refractory structure decreases, or the carbon particles are oxidized to deteriorate the corrosion resistance of the refractory. Further, the smaller the particle size, the more the corrosion resistance is improved even if the amount of carbon added is small. If the amount used is less than 5% by weight, sufficient corrosion resistance will not be exhibited, and if it exceeds 20% by weight, the amount of added water will increase even with carbon imparting hydrophilicity, and the compactness of the refractory structure will be impaired. As a result, the corrosion resistance decreases.

Alumina cement, ultrafine silica (amorphous), and refractory clay are used as the binder. Alumina cement is used in an amount of 0.5 to 2% by weight. If it is 0.5% by weight or less, the shape retention of the structure after construction is not sufficient, and if it is 2% by weight or more, the corrosion resistance of the refractory is reduced due to the influence of CaO contained in the alumina cement, which has neither fire resistance nor corrosion resistance. descend.

About 1% by weight of refractory clay is added. If it is 1% by weight or more, the viscosity of the composition increases and the pouring property decreases. About 1% by weight of ultrafine silica powder is added. Mostly 1
It is a spherical amorphous material with a size of μm or less, and its high temperature strength increases when added. To improve the dispersibility of these compounded powders, approximately 0.1
% Peptizer is used.

[0021]

EXAMPLE An example of the composition containing 8 parts by weight of the ultrafine silicon carbide powder in Comparative Example 1 and an example of the composition containing 3 parts by weight of the ultrafine silicon carbide powder in Comparative Example 2 are shown in this comparative example. Was used as the standard. Comparative Example 3 shows an example of blending with a small amount of spinel aggregate. Metal Resistant (FeO Resistant) Examples 1 and 2 are examples of the present invention in which fine particles of silicon carbide having a size of 30 μm or more and hydrophilically treated carbon are used.
Metal (FeO) resistance erosion index is 84 and 81, respectively.
Then, good results were obtained. Flow Value Generally, it is said that if the amount of fine carbon powder is large, the fluidity is lowered. However, in both Examples 1 and 2, although the carbon amount was 10 parts by weight or more, the fluidity was lower than that in Comparative Example 3 parts by weight. There is no change. Hardening strength The strength after curing for 24 hours has the strength required for deframed, and is suitable for the amount of alumina cement in this example. 800 ° C. Hot Strength The strength at 800 ° C., which is said to decrease in strength when alumina cement was used, was measured and found to be sufficient. 1,450 ° C fired physical properties The linear change rate is within ± 0.1%, and the volume stability is excellent.

[0022]

[Table 1]

[Remarks] Alumina aggregate 8,000-44 μm Spinel aggregate (magnesia / alumina spinel) 8,000-74 μm Alumina fine powder 44 μm or less Silicon carbide fine powder 30-125 μm Silicon carbide ultrafine powder 10 μm or less Hydrophilic treated carbon 2 mm Below fire-resistant clay Sarutoki-bushi clay Silica ultrafine powder About 1 μm or less

[Test method] Flow value (mm) JIS
According to R2521. In the case of pouring construction 130-150
mm is suitable. 1k in a flow cone with an inner diameter of 100mm
The sample containing g of the sample was placed on the flow table of the flow tester, the flow cone was removed, and a lumpy sample remained on the table, and measurement was performed by a test method in which the flow table was hit. The sample sinked and expanded on the table by the impact of vertical movement of the flow table, and the longest and shortest parts of the material flowing over a wide area were measured, and the average value was used as the flow value. Corrosion resistance test For metal erosion resistance and slag erosion resistance, test samples are laminated to the lining in a high frequency melting test furnace, and blast furnace pig iron and blast furnace slag (basic C
aO / SiO ₂ = 1.3) was dissolved at a ratio of 1: 1 by weight and immersed in 1,550 ° C. × 6 Hrs, and the erosion depth was measured. The case of Comparative Example 2 was set to 100.

[0025]

As described above, the magnesia-alumina spinel is mainly used, and the balance is alumina, silicon carbide,
In a cast refractory for casting, which comprises carbon and a binder, by blending 5 to 20% by weight of silicon carbide having a particle size of 30 μm or more and 5 to 20% by weight of hydrophilic carbon having a particle size of 2 mm or less, a blast furnace It was possible to improve the corrosion resistance of hot metal as a lining material for tap gutters, especially large gutters.

[Brief description of drawings]

FIG. 1 shows the relationship between the amount of added carbon and the amount of water added in an amorphous refractory for casting.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Kojima 1 Kimitsu, Kimitsu-shi, Chiba Inside Nippon Steel Corporation (72) Inventor Noriyuki Inoue 4-3-3 Misato Toyota, Aichi (72) ) Inventor Hideaki Ohashi 1-24-2 Eiyo-cho, Toyota City, Aichi Prefecture

Claims (1)

[Claims] 1. An amorphous refractory for casting, which comprises magnesia / alumina spinel and the balance alumina, silicon carbide, carbon and a binder, and has a particle size of 5 to 20% by weight and a particle size of 30 μm or more. An amorphous refractory material for casting, comprising 5 to 20% by weight of hydrophilically treated carbon of 2 mm or less.