What causes the shrinkage of refractory castables at low temperatures?

When the linear change rate of refractory castables at low temperatures is too large, it will cause significant damage to the castable body and lead to structural spalling, reducing the service life of the castable. The reasons for the low-temperature shrinkage of refractory castables usually occur in two situations:

After the formwork is removed and cured during the casting and molding process, the furnace needs to be baked. When the crystalline water and free water in the refractory castable are dried and discharged, if the temperature rises too quickly, volume changes will occur.

Second, excessive linear changes caused by chemical reactions during the high-temperature use of castable materials.

Both of the above situations can cause shrinkage of refractory castables. Such phenomena are caused by inappropriate material blending of refractory castables. It is necessary to improve the material quality. Introducing metallic silicon into the matrix to optimize the matrix composition of the castable can reduce shrinkage, enhance the high-temperature resistance of the product, and endow the castable with excellent high-temperature linear change rate resistance and thermal shock stability. The performance of load-softening temperature.

So, how can the shrinkage of refractory castables at low temperatures be improved? Technical measures such as admixtures should be adopted to reduce the linear shrinkage changes of materials. Different admixtures can be added to refractory castables, such as metallic silicon, red columnar powder, and kyanite powder, all of which can achieve certain high-temperature anti-shrinkage performance.

By adding metallic silicon powder, the refractory castable can completely solve the problem of high-temperature shrinkage at 1400℃, counteract its high-temperature linear shrinkage changes, and reduce the phenomenon of shrinkage cracks during high-temperature use. The effect of adding metallic silicon powder is better than that of kyanite powder and red columnar powder. However, due to the relatively high price of metallic silicon, it will increase certain material costs. Add admixtures selectively according to the usage conditions.