What is the reason for linear shrinkage of refractory castablePublished by：2021-10-4 Categories:News Viewed by: 7383 times Refractory castables are divided into hydraulic binder, pneumatic binder and thermal binder according to the way of hardening. With the continuous change of kiln ambient temperature, the requirements for its own physical properties are more stringent. The physical change of refractory castable in high temperature environment is the key factor to reflect the service life of refractory castable, and whether the linear change rate of castable shrinks at low temperature is also the most important, It is also an important index to measure that the refractory castable will not shrink and crack in use. The linear change of refractory castable refers to the ratio of the irreversible change of the length of refractory castable test block after heating for a certain time at the specified temperature to its length before drying, expressed in percentage. The calculation result is a negative value, which is expressed by "-", and the take-up shrinkage; on the contrary, it is called linear expansion, which is expressed by "+". If the linear change rate of refractory castable is too large, it will cause great damage to the poured lining, easy to peel off the lining and reduce its service life. Therefore, technical measures such as additives shall be adopted to minimize the linear shrinkage change of materials. The causes of low-temperature shrinkage of refractory castable usually occur in two cases: (1) after pouring, mold removal and maintenance, it is necessary to dry the furnace to dry and discharge the crystalline water and free water in the refractory castable. (2) The linear change caused by chemical reaction of refractory castable during high-temperature use. The above two conditions will cause the shrinkage of refractory castable. This phenomenon is caused by improper allocation of refractory castable materials. It is necessary to improve the material quality of raw materials selected for refractory castable and introduce other raw materials into the matrix to optimize the matrix composition of castable, which can reduce pouring The linear shrinkage of the castable improves the high temperature resistance of the product, so that the castable has excellent high temperature linear change rate resistance, thermal shock stability and high load softening temperature. Adding different admixtures to the refractory castable, such as metal silicon, andalusite powder and kyanite powder, can play a certain high-temperature shrinkage resistance. However, when adding admixtures, it is also necessary to comprehensively consider the cost of the refractory castable and select appropriate refractory raw materials to achieve better application effect.
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