Silicon carbide castable matters need attention

Silicon carbide refractory castable is the development of SiC refractory products (bricks, plates, rods, tubes, and saggers, etc.). Usually, SiC-based refractory castables are formulated with low-cement and ultra-low-cement formulations, with SiC as the main raw material, and aluminum cement (CA-70C or CA-80C, etc.) and nf-SiO2 and Al2O3 fine powder are used as a combination agent. However, the following problems will be encountered when producing SiC-based unshaped refractory materials, especially SiC-based refractory castables:

(1) SiC is hydrophobic, which leads to poor fluidity of SiC refractory castables, poor construction performance, and low density of the castable.

(2) SiC is difficult to sinter, so it is not easy to obtain a high-strength sintered body.

In order to improve the fluidity of silicon carbide refractory castables, it is necessary to select SiC raw materials with little influence on fluidity as the SiC source for producing silicon carbide refractory castables. This can be achieved by changing the shape of SiC particles and adjusting the type and amount of dispersant (water reducer) (that is, to improve the fluidity and workability of SiC refractory castables).

By changing the shape of SiC particles and adjusting the type and amount of dispersant (water reducer), an ideal SiC refractory castable body can be obtained. The internal flow value is larger, and the green body is denser and stronger.

Since the SiCa particles are needle-like, segregation occurs during vibration molding, so it can be concluded that the sample needs to add more water to have better fluidity. The SiC material is spherical particles, which can make the SiC refractory castable body more compact, so sample c does not need to add too much water.

It can be seen that for the production of SiC refractory castables, spherical SiC particles have better performance than acicular SiC particles.

The research results show that the fluidity and construction properties of SiC refractory castables can also be improved by using uf-SiC to replace part of the angular SiC raw materials or sheets and adding more effective dispersants (water reducers), such as SM and sodium polyacrylate, etc.

The purpose of adding Si powder to the SiC refractory castable is to improve the oxidation resistance of the material. The particle-optimized SiC granular material used 75% AI2O3 pure aluminate cement as the binder and Uf-SiO2 (95% SiO2) as the auxiliary binder to make the refractory castable form a hydration coagulation system. The effect of adding different amounts of Si powder on the oxidation resistance of SiC refractory casting materials.

Silicon carbide refractory castables are combined with Uf-SiO2 in the system, mainly to improve the physical properties of the material. When the addition amount of Uf-SiO2 reaches a certain value, the refractory castable will have higher strength, especially after the medium temperature treatment, the strength will be nearly doubled, and the mixing water consumption of the material will be reduced by more than 0.9%.