Can silicon carbide composite bricks be used if they don't react well?
Silicon carbide composite bricks are refractory bricks produced by combining different silicon carbide contents with alumina, including silica molybdenum bricks, silica molybdenum red bricks, sintered silicon carbide bricks, etc. Because silicon carbide is suitable for sintering in a reducing atmosphere, there is no problem. If there is little reaction during sintering in an oxidizing atmosphere, the surface layer will not react.
So can silicon carbide bricks with poor reaction be used? It can still be used, but a key indicator is very important, that is strength. If the strength of silicon carbide bricks is lower than 80MPa, it can only be used downgraded. It cannot be used at high temperatures or in severely corroded areas.
Why does the surface layer of silicon carbide bricks not react? TOPOWER tells you:
If there is no oxidation reaction on the surface of silicon carbide composite bricks, or there is only a slight change in oxidation reaction, and the oxide layer is not too thick, it will not affect its use. However, if the oxidation is serious and the strength is low, it cannot be used. But it will not be scrapped and can be used at the service temperature of first-grade high alumina bricks.
So why does the surface layer of silicon carbide bricks not react? First, the sintering atmosphere is caused by an oxidizing atmosphere. Second, no metallic silicon powder is added during the production process. If a reasonable proportion of metallic silicon powder is added, the oxidation of silicon carbide can be prevented.
There are also some silicon carbide brick manufacturers who pre-adjust the placement order on the kiln car when the semi-finished products are being sintered, that is, the bricks are placed in a circle in the middle of the kiln car, and high alumina bricks are placed around them. This makes the sintering atmosphere a reducing atmosphere, and the sintered silicon carbide composite bricks will be uniform. The strength is also stable and high. The friction coefficient is high and the effect of resisting kiln lining crusting under high temperature is better.
All in all, the strength of silicon carbide composite bricks mainly determines the correct use of silicon carbide composite fire bricks. If the strength is lower than 80MPa, it can only be used downgraded. Never use high temperature or severely corroded parts.
