Refractory castable for converter spray gun

Through the application of refractory castables of converter spray gun, the addition of pure calcium aluminate cement can make the castables have higher strength. If the amount of pure calcium aluminate cement added is too much, it will bring more CaO, thus reducing the pouring. The high temperature performance of the material; therefore, under the conditions of ensuring a certain normal temperature strength and construction performance, the amount of addition should be minimized to improve the high temperature performance of the castable; the addition amount is preferably 5%.

Adding a certain amount of silica fume to the castables contributes greatly to reducing the amount of water added, increasing the hydration bonding strength of the cement, reducing the porosity of the castable, and increasing the temperature of the castable material. Meanwhile, since the main component of the silica fume is SiO2 and impurities The content is high, and when the amount of addition is too high, the high temperature performance of the castable is easily lowered. The amount of silica ash added is preferably 3%. The α-Al2O3 micropowder has the effect of adjusting the volume stability of the refractory castable. On the one hand, due to its fine particle size, it can be filled into the gap between the larger particles of the castable, so that the porosity of the castable is lowered and the room temperature strength is increased. On the other hand, due to its high reactivity, it can promote the reaction with SiO2 to form mullite, which is beneficial to improve the strength and thermal shock resistance of the castable; as the amount of α-Al2O3 fine powder increases, The porosity of the castable is reduced, the medium temperature strength is increased, and the fluidity is improved. However, when the amount is too large, the fluidity of the castable is decreased, and the addition amount is preferably 6% to 8%. Because the wall of the spray gun is thin, the temperature fluctuates greatly during use, and the mechanical vibration of the gun body is severe. Therefore, the high temperature volume stability of the gun body is very important. In order to minimize the difference between the thermal expansion of the inner core of the steel pipe and the castable, the spray material must be poured in the spray gun. It has a certain expansion under high temperature conditions.

The kyanite powder can undergo a conversion reaction below 1350 ° C to produce a small volume expansion, and the precipitated SiO 2 can react with α-Al 2 O 3 in the material to form mullite, which also contributes to the bonding. If expansion occurs in the liquid phase, expansion can cause movement of the liquid, and many voids of the castable may be filled with liquid. Therefore, the formation of mullite can not only improve the structural strength of the castable, improve the change of the post-fire line, but also partially eliminate the shrinkage crack generated during the high temperature and cooling process of the castable, thereby improving the service life of the castable, so An appropriate amount of kyanite powder should be added to the fine powder. However, when the amount of addition is too large, the castable is peeled off, so the addition amount is preferably about 10%.

The addition of stainless steel fiber can effectively prevent the casting material from cracking. Even if cracks are generated, the flexibility of the fiber can prevent the crack from expanding and improve the thermal shock resistance of the castable. At the same time, the normal temperature and medium temperature strength of the refractory castable can be enhanced, but when the temperature exceeds 1100 ° C, the effect of the steel fiber is not obvious. When the steel fiber is added in an amount exceeding 3%, the strength of the castable is no longer enhanced or even decreased. Therefore, the amount of steel fiber added is preferably from 1% to 3%. To increase the strength of the castable, the amount of water added should be reduced. When a certain amount of water reducing agent is introduced into the castable, the water reducing agent can be adsorbed on the surface of the dispersed phase (solid microparticles or colloidal particles) after being dissolved in water to increase the particles in the solution. The zeta potential (electrokinetic potential) of the surface, or the formation of a space-limiting effect (steric hindrance), increases the repulsive force between the particles, and as a result, the free water encapsulated in the agglomerated structure composed of dispersed particles is released, thereby It acts as a lubricant and disperses particles.