JPS6366794B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a basic refractory composition using natural raw materials such as limestone and dolomite. [Prior Art] Examples of basic refractories include bricks and monolithic refractories such as magnesia, magnesia, and magnesia carbon, which are used in various steelmaking furnaces. However, recently, as the quality of steel has increased, the cleanliness of steel has come to be required, and it has become impossible to obtain sufficient cleanliness of steel with conventional basic refractories. For this reason, in molten steel ladles and tundishes,
Lime refractories that easily absorb inclusions are being considered. For example, "Refractories" 1984 issue
Volume 36, No. 3 describes the application of lime bricks containing CaCl ₂ to molten steel ladle. This ladle for molten steel using lime bricks removes Al ₂ O ₃ , SiO ₂ , and S in the steel.
It has been reported that it can be absorbed as 12CaO・7Al ₂ O ₃ , 3CaO・SiO ₂ and CaS. In addition, "Tetsu to Hagane" published by the Japan Iron and Steel Institute, 1983
Volume 69, No. 12 includes an example titled ``Development of technology for applying CaO refractories to tundish linings,'' and application to actual tundish linings is being considered. The CaO refractories used here contain CaCl ₂ as mentioned above;
It is reported that inclusions such as Al ₂ O ₃ can be reduced similarly to CaCl ₂ -containing lime bricks. [Problems to be solved by the invention] However, as mentioned above, in refractories that use CaCl ₂ as a binder, CaCl ₂ has a very high boiling point of 1600°C, so CaCl 2 is used as a basic refractory composition. CaCl ₂ becomes a liquid phase in the temperature range, resulting in poor hot strength and problems such as being easily deformed when subjected to wear or load from molten steel. On the contrary, as mentioned above, lime refractories have excellent properties in their ability to absorb inclusions. However, it has the disadvantage that it is very easily hydrated, so it has hardly been used industrially. Although various studies have been made to prevent this hydration of lime, the current situation is that it has not been possible to prevent hydration. Up until now, various additives have been added to lime clinker to retard the hydration of lime, or it has been calcined at high temperatures. However, in this operation, the inherent activity of lime is sacrificed, and the good reactivity of lime is lost. In order to solve the above-mentioned problems, the present inventors have developed a lime-based refractory that does not use lime clinker.
Patent Application No. 1982-122055 (Special Publication No. 58-34423)
(No. 2003), when one or more of silicates and phosphates (e.g., alkali metal silicate, alkali metal phosphate, etc.) are added to limestone, there is almost no shrinkage even when fired, resulting in an active CaO refractory. There is a disclosure that there is no need to worry about hydration as it remains in the form of limestone until it is used. [Means for solving the problem] In the above-mentioned Japanese Patent Publication No. 58-34423, the mechanism of heating volume stabilization by adding one or more of silicates and phosphates to limestone is described. CaO formed by heating from limestone reacts with silicate or phosphate to form β-2CaO・SiO ₂ , 3CaO・SiO ₂ ,
It was thought that a high melting bond involving _{SiO 2 or} P 2 O ₅ was formed as a 3CaO.P ₂ O ₅ or 24CaO.0.6Na _{2 O.P 2 O 5} system. but,
As described in Table 1 of this specification as a reference example, when compounds that do not contain alkali metals, such as silica sol, Portland cement, dibasic calcium phosphate, and dibasic magnesium phosphate, are added to limestone, it becomes desirable as a basic refractory. characteristics cannot be obtained. Therefore, the present inventors conducted various studies on inorganic compounds, inorganic salts, and organic salts other than silicates and phosphates, and found that alkali metal inorganic compounds, inorganic salts, and organic salts other than silicates and phosphates discovered that salts are useful as binding agents;
The present invention was completed based on the knowledge that when these are added to limestone, doloid lime, or both, a basic refractory composition with good properties can be obtained. The object of the present invention is to provide a lime-based refractory that does not use lime clinker, using an inorganic compound or an inorganic salt of an alkali metal other than an alkali metal silicate or an alkali metal phosphate as a binder for limestone or dolomite or both. The object of the present invention is to provide a basic refractory composition that exhibits little shrinkage upon firing by adding one or more salts. The present invention is limestone or dolostone or both.
0.1 to 100 parts by weight of one or more inorganic compounds, inorganic salts, or organic salts of alkali metals other than alkali metal silicates and alkali metal phosphates.
The basic refractory composition is characterized in that up to 20 parts by weight of the basic refractory composition is added. More specifically, the basic fireproof composition of the present invention contains 100 parts by weight of limestone, dolomite, or both, and an alkali metal compound other than an alkali metal silicate or an alkali metal phosphate, such as a chloride or an aluminate. , inorganic compounds and inorganic salts such as borates, sulfates, carbonates, hydroxides, nitrates, and organic salts of alkali metals.
~20 parts by weight is added. Examples of alkali metal compounds that can be used in the present invention include sodium chloride, potassium chloride, lithium chloride, sodium aluminate, potassium aluminate, lithium aluminate, sodium borate, potassium borate, lithium borate, sodium sulfate, and potassium sulfate. , lithium sulfate, soda carbonate, potassium carbonate, lithium carbonate, caustic soda, caustic potassium, lithium hydroxide, sodium nitrate, sodium formate, sodium citrate, and the like. [Action] When limestone and dolomite are simply fired, the temperature is 300 to 900℃.
Since decarboxylation occurs between the layers and causes linear shrinkage of about 20% at 1500°C, it cannot be used as is as a fireproof structure. However, when the above-mentioned binder is added to limestone or dolomite, it hardly shrinks even when fired at 1500°C, and can be used as a basic refractory composition. However, even when the above-mentioned binder is added to magnesite ore, which is an alkaline earth metal carbonate similar to limestone and dolomite, the firing shrinkage rate is as high as 20% or more, and CaO is required to prevent firing shrinkage. plays an important role. In addition, the shrinkage rate of limestone to which alkali metal-free compounds such as boric acid, alumina cement, Portland cement, silica sol, sulfuric acid, magnesium, ethylene glycol, and paraffin are added has a very high firing shrinkage rate. Therefore, CaO and the alkali metal-containing compound interact with each other, inhibiting sintering, and suppressing firing shrinkage.Thereby, the stability of the hot volume at high temperatures is obtained, and the refractory structure is It can be used as Although there is a concern that the use of alkali metal sulfates and alkali metal nitrates may contaminate steel, SO ₃ and NO ₂ will evaporate by preheating the basic refractory composition of the present invention at 1300°C or higher. Therefore, there is no problem in using it. The amount of the binder used in the basic fireproof composition of the present invention is 0.1 to 20 parts by weight, but if it is less than 0.1 part by weight, the binding force is weak and the fireproof structure cannot be formed, which is a problem. Moreover, if it exceeds 20 parts by weight, corrosion resistance will be significantly lowered, which is not preferable. The limestone and dolomite used in the basic refractory composition of the present invention are commonly produced and are not particularly limited. Corrosion resistance can also be improved by adding lime clinker, dolomite clinker, or magnesia clinker to the above-mentioned limestone and dolomite, but the more the above-mentioned clinker is added, the more active CaO content. The cleanliness of the molten steel decreases. However, basic refractory compositions also have different corrosion resistance depending on the steel type, and are inferior to aluminium-killed steel, high manganese steel, and silica steel.
Corrosion resistance can be improved by adding less than 100 parts by weight of lime clinker, dolomite clinker, or magnesia clinker to 100 parts by weight. The basic composition of the present invention can be used to obtain a refractory structure as a monolithic refractory such as unfired bricks, spraying, coating, or pouring. It is also possible to add commonly used plasticizers or hardeners to improve the workability of brick manufacturing or monolithic refractories. [Example] The present invention will be further explained below with reference to Examples. The particle size of limestone was adjusted to 70 parts by weight of 2 to 0.3 mm and 30 parts by weight of less than 0.3 mm, 5 parts by weight of various binders were added to this, and the sample was molded into a size of 50 mmφ x 50 mm (height) and fired at 1500℃. The subsequent results are shown in Table 1 below.

【table】

[Table] Classification indicates Example, Comparative Example, and Reference Example.
[Effect of the invention] As is clear from Table 1 above, the firing line change rate of the basic refractory composition to which a compound containing an alkali metal salt other than an alkali metal silicate or an alkali metal phosphate is added as a binder is It becomes a fireproof structure with extremely low apparent porosity and excellent heat insulation properties. Silicates, phosphates, without alkali metal salts,
Inorganic salts and organic salts such as alumina compounds and borates all exhibit large firing line change rates of 10% or more. This shows that when used as a refractory material, volumetric stability under hot conditions cannot be obtained, making it unsuitable for use as a refractory structure. Furthermore, since the basic refractory composition of the present invention contains very active CaO, it is more effective at absorbing inclusions such as Al ₂ O ₃ , P, and S in molten steel than lime bricks made with sintered lime clinker. It was excellent. The basic fireproof composition of the present invention has the following effects. (1) It is a lime-based basic fire-resistant composition that does not have to worry about hydration during storage and construction. (2) Active CaO adsorbs inclusions in molten iron and molten steel. (3) A heat insulating structure is obtained due to the porous structure after decarboxylation.

Claims (1)

[Claims] 1 Adding 0.1 to 20 parts by weight of one or more inorganic compounds or inorganic salts or organic salts of alkali metals other than alkali metal silicates and alkali metal phosphates to 100 parts by weight of limestone, dolomite, or both. A basic refractory composition characterized by: