Basic refractory composition

#This invention relates to a basic refractory such as unburned bricks, gunning materials, trowelling materials, and castable materials for steel-making containers such as electric furnaces, converters, ladles, and tundishes.

#Various types of chemical binders are used in basic unburned bricks and various types of basic castable refractories. Namely, well-known chemical binders such as organic binders such as tar, pitch, and phenol resins, and magnesium sulfate, alkali phosphates, alkali earth metal phosphates, alkali silicates, alkali borates, alumina cement, and the like are used. These chemical binders play a very important roll, increasing the binding power of the refractory, making the refractory easy to apply, and the like.

#However, there are various problems with refractories employing the above-described chemical binders. Namely, when refractories employing organic chemical binders such as phenol resins, tar, pitch, and the like are used in an oxidizing atmosphere, combustion of carbon takes place, the texture deteriorates, and there is the drawback that adequate durability can not be obtained. Furthermore, with refractories using magnesium sulfate, various types of phosphates, and alkali borates, there is the fear of molten steel being contaminated by the phosphorus, sulfur, boron, and the like contained in the chemical binder. In addition, the hot strength of a basic refractory employing alumina cement or alkali silicate is low, the damage from wear by molten steel and the like is large, and the fire resistance is inadequate.

#FIG. 1 is an illustration of the laminar structure of acidic china clay.

#Hereinbelow, the present invention will be further explained by means of examples.

#The basic refractory compositions having the compositions shown in Table 2 were molded under a molding pressure of 1.5 tons per square centimeter, and unburned basic bricks (Products I and II of the present invention and Conventional Products I and II) were obtained. The hot bending strengths at 1400 degrees C. of the resulting unburned basic bricks are also shown in Table 2.

#TABLE 2 ______________________________________ Product of Conventional Invention Product I II I II ______________________________________ Composition (Parts by Weight) Seawater magnesia clinker 60 60 60 60 3-0.5 mm Seawater magnesia clinker 20 37 40 40 -0.5 mm Limestone 20 5 -0.5 mm Calcium hydroxide 2 -0.3 mm **MIZUKANEX-100 *4 *5 (liquid product) Sodium silicate No. 3 *10 *5 Levigated clay *2 Sodium hexametaphosphate *0.5 CaO/SiO.sub.2 in composition 6.7 2.2 0.3 0.3 Molding pressure (tons/cm.sup.2) 1.5 1.5 1.5 1.5 Hot bending strength at 1400.degree. C. 60 50 10 5 (kg/cm.sup.2) Linear change after heating -0.5 -0.4 -1.5 -2.0 (%) (1500.degree. C. 2 hours) ______________________________________ *indicates outer percentage **MIZUKANEX100 is a tradename for modified sodium silicate