JPS6138155B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a carbon-magnesia casting refractory. In recent years, there has been a strong demand for labor and energy conservation in the steel industry, and the amount of monolithic refractories used has gradually increased in place of refractory bricks. Among monolithic refractories, especially casting refractories,
Compared to other materials, construction is easier and does not require skill. A uniform construction body can be obtained. It is widely used for a variety of purposes due to its characteristics such as: However, conventional refractories for casting use raw materials such as alumina, high alumina, high silicic acid, zircon, silicon carbide, and spinel as refractory materials, and alumina cement as a binding material. has been used a lot. However, the use of alumina cement in cast refractories has the drawback of poor fire resistance and hot properties, making it difficult to obtain sufficient durability.In addition, in recent years, phosphates have been used as a binder instead of alumina cement. Phosphate bonded refractories for casting have begun to be used, but compared to alumina cement-based refractories for casting, the curing speed varies, they are particularly susceptible to the temperature of the construction site, and they are quite expensive. It has the disadvantage of being. As the refractory material for casting refractories, basic materials, particularly magnesia, are preferred in terms of resistance to basic slag and fireproof properties. However, when magnesia comes into contact with water or acid, it hardens into hydrates or magnesium salts, and when this hardened product is heated, it cracks or explodes, resulting in significant structural deterioration. As a result of intensive research to improve these defects in cast refractories, the present inventors have developed a cast refractory that can withstand long-term use by forming a dense structure with low moisture content. I found out. In other words, by using magnesia as the main material for cast refractories and adding carbon and a water reducing agent to it, it is possible to form a dense structure by preventing cracks and explosions during heating. It was discovered that by using a bond-forming material, carbon bonds can be formed at high temperatures to form a strong structure, and as a result, it is possible to fully utilize the characteristics of carbon-magnesia to create a long-life refractory layer. This led to the present invention. That is, the gist of the present invention is that the carbon-magnesia casting refractory contains 72 to 96.9% by weight of magnesia, 2 to 20% by weight of carbon material, and 0.1 to 2.0% by weight of magnesia.
The first characteristic is that it consists of a water-reducing agent of 1% to 6% by weight and a carbon bond forming agent of 1 to 6% by weight, and also consists of a mixture of these with the addition of 95% by weight or more and 5% by weight or less of clay. It is the second characteristic of an object. Raw materials for magnesia, which is the main material used in the present invention, include seawater magnesia clinker, calcined magnesite, and fused magnesia.
72 to 96.9% by weight, preferably 80 to 96.8% by weight. If this amount is less than 72% by weight, the resistance to basic slag and fire resistance will be impaired, and if it is more than 96.9% by weight, cracks and explosions will easily occur, making it unsuitable. Next, carbon materials include natural graphite, artificial graphite, petroleum coke, foundry coke, carbon black,
Graphite clay or the like is used in an amount of 2 to 20% by weight, preferably 2 to 15% by weight. This is because if the amount of carbon material is less than 2% by weight, explosions are likely to occur and the characteristics of carbon will not be exhibited, and if it is more than 20% by weight, strength and oxidation resistance will decrease, and fluidity will be lost. It is for the sake of becoming popular. Water reducing agents are useful for reducing the water content of cast refractories to form dense structures, and generally commercially available compounds with a water reducing effect may be used, but lignin is a preferred water reducing agent. Sulfonate, β-
Sulfonic acid compounds such as naphthalene sulfonic acid formalin condensate and higher polyhydric alcohol sulfone compounds are used. And the amount of water reducing agent used is
The amount is 0.1 to 2.0% by weight, preferably 0.2 to 1.0% by weight, and if it is less than 0.1% by weight, the addition has no effect and a dense structure cannot be obtained. Further, even if the amount is used in an amount exceeding 2% by weight, the effect is not particularly improved, so it is not preferable from an economic point of view. Further, the carbon bond forming material as used in the present invention is a fine particulate material that can be melted by heating and then carbonized to form carbon bonds. As such materials, pitch, carbon resin, synthetic resin (for example, thermosetting phenolic resin, furan resin), resinous pitch, etc. can be used, and among them, those having a hardening point of 100° C. or higher are particularly preferred. A carbon bond-forming material that softens and melts at a temperature lower than the boiling point of water is undesirable because it tends to cause cracks and explosions when water evaporates. The amount of the carbon bond forming agent is 1 to 6% by weight, preferably 1 to 4% by weight. If this amount is less than 1% by weight, the addition has no effect and strong carbon bonds are not formed. Also 6
If it exceeds % by weight, the density decreases and cracks and explosions are more likely to occur, which is not preferable. Furthermore, in the present invention, the addition of clay has the effect of preventing water floating, improving the affinity between carbon and magnesia, and imparting fluidity. The amount added is 5% by weight or less, preferably 1 to 3% by weight. If it is more than 5% by weight, it is not preferable because it increases porosity, causes explosions, etc., and also deteriorates fire resistance and slag resistance. Useful examples of such clay include kaolin, kibushi clay, elutriated clay, and bentonite. The thus obtained carbon-magnesia casting refractory of the present invention has the above-mentioned structure, and thus has properties such as high corrosion resistance, spalling resistance, and prevention of slag penetration, which are characteristics of carbon-magnesia refractories. and can withstand long-term use. In addition, the use of a water reducing agent and carbon material makes the structure dense and prevents explosions, etc., and the use of clay improves the affinity between the carbon material and magnesia, giving it fluidity. Improve workability. Furthermore, by using a carbon bond forming material, a strong carbon bond is formed under high temperatures.
This allows the characteristics of magnesia refractories to be fully utilized. The refractory for casting of the present invention can be produced using the flow casting method (pouring), the vibration casting method (vibration molding)
The fluid casting method involves adding moisture to the sample and kneading the clay, pouring it into a mold, curing it, and drying it to obtain the construction object.The vibration casting method In this method, kneaded clay with added moisture is put into a formwork, vibrated by a vibrating device, and then dried to obtain a construction body. The carbon-magnesia casting refractory of the present invention is used as a lining material for furnace walls, gutters, etc. that come into contact with hot metal, molten steel, slag, etc. For example, it is suitable for the lining of ladles, tundishes, pig iron mixers, etc., as well as for blast furnace troughs, tapping troughs, etc. The present invention will be explained in detail below with reference to Examples. Examples 1 to 5 After mixing using a wet pan according to the formulation shown in Table 1, the kneaded clay with water added thereto was cast into a wooden frame, removed from the mold, and dried at 110°C for 5 hours to prepare a casting material. In addition, casting materials of Comparative Examples 1 and 2 were also produced in the same manner.

[Table] Physical properties such as bulk specific gravity and apparent porosity and the presence or absence of explosions and cracks were measured for the obtained cast material, and the results shown in Table 2 were obtained.

【table】

[Table] [For the explosion (crack) test, each sample was cast in a wooden frame of 30cm x 30cm x 19cm, left for 2 hours, removed from the mold, placed in a dryer preheated to 400℃, taken out after 2 hours, and tested for explosion. and the presence or absence of cracks was observed. In addition, slag tests such as the adhesion amount of base metal and slag were carried out by laminating the casting materials of Examples 1 to 5 and Comparative Examples 1 to 2 to a container with an inner side of 6 cm and a height of 20 cm, and placing iron inside the container. : Slag=9.5:0.5 (Slag composition: SiO ₂ ...23%, CaO...52%, Total-
FeO...11%, MnO...6%, MgO...5%) were put there and melted in an induction furnace, and after being held at 1650 to 1680°C for 2 hours, the molten steel and slag were discharged. ] From the table above, the carbon-magnesia cast refractory of the present invention shows no explosion or cracking compared to conventional refractories. It has a small amount of metal and slag attached, and has excellent corrosion resistance. This has been proven. Example 6 Casting materials were produced in the same manner as Examples 1 to 5 using the formulations shown in Table 3. Casting materials of Comparative Examples 3 and 4 were also produced in the same manner. Table 3 shows the results of measuring physical properties such as bulk specific gravity and apparent porosity, explosion strength, and firing strength at various reduction temperatures for the obtained cast material.

【table】

[Table] From the above table, the carbon-magnesia cast material of the present invention had a higher compressive strength, especially in the high temperature section, than that of the comparative example. As a result of the above, the carbon-magnesia casting refractory of the present invention exhibits long-life characteristics as a lining material for furnace walls and gutters that come into contact with hot metal, molten steel, slag, etc., and its value is extremely high. It is large.

Claims (1)

[Claims] 1 72-96.9% by weight magnesia, 2-20% by weight
of carbon material, 0.1 to 2.0% by weight of water reducing agent and 1 to 2.0% by weight of water reducing agent.
A carbon-magnesia casting refractory characterized by comprising 6% by weight of a carbon bond forming material. 2 72-96.9% by weight magnesia, 2-20% by weight
of carbon material, 0.1 to 2.0% by weight of water reducing agent and 1 to 2.0% by weight of water reducing agent.
A carbon-magnesia casting refractory characterized by comprising 95% by weight or more of a mixture of 6% by weight of a carbon bond forming material and 5% by weight or less of clay.