What effect does refractory aggregate have on castable?

Refractory aggregate has great influence on the properties of castable.

Golden Triangle Refractory Among unshaped refractories, the content of refractory aggregate is generally between 60% and 73%, which plays a skeleton role and can significantly affect its performance. Refractory aggregate is generally divided into coarse aggregate and fine aggregate. Generally, the particle size greater than 5mm is called coarse aggregate; 5mm and below 5mm to 0.09mm is called fine aggregate. The critical particle size of aggregate depends on the thickness of the liner. At present, the critical particle size of refractory aggregate tends to increase. It should be pointed out that when preparing unshaped refractory, the particle gradation of refractory aggregate should meet the technical requirements.

Modern amorphous refractories use corundum, synthetic mullite, spinel, alumina and other advanced materials as refractory aggregate and powder, in which the volume density of refractory castable made of brown corundum, white corundum and special alum decreases once; With the increase of heating temperature, the bulk density of castable decreases, as long as the bulk density of castable made of special alum and brown corundum after firing at 1600℃ is greater than that after drying.

The flexural strength of castable keeps increasing, white corundum increases less, special alum increases more, and brown corundum is in the middle. With the increase of sintering temperature, the linear expansion of white corundum aggregate castable increases after firing, and it increases sharply between1100 ~1400℃, because it consists of more mineral deposits such as spinel. Between 1400~ 1600℃, the material contains less impurities, and the linear expansion continues to increase steadily after firing, and there is still about 2% linear expansion at 1600℃; The change law of brown corundum and special aluminum aggregate castable is basically similar, and the linear expansion is the largest after firing at 1400℃.

After firing at 1600℃, the content of SiO2 _ 2 and R2O in alum is the highest, and more liquid phase is produced, which offsets the volume expansion of MA and CA6. Therefore, the firing line of this material is shortened, which is not conducive to the use of ladle refractory castable. This is also the reason why more magnesium materials need to be added when special alum or alum is selected as refractory castable for ladle. The linear expansion of brown corundum aggregate castable is 0.62% after firing at 1600℃. Refractory aggregate is the main material in the arrangement structure of refractory castable, and its dosage is about 70~90. Its skeleton effect also affects its physical mechanics and high-temperature use function, especially for ladle refractory castable. Therefore, the variety, critical particle size and particle gradation of refractory aggregate should be reasonably selected according to the actual situation and process formula requirements, so as to obtain high-performance refractory castable for ladle.