What are the reasons for the black heart of refractory bricks?
Black heart is a phenomenon that easily occurs in the production of refractory bricks. The characteristics of this kind of brick are: the surface color of the brick gradually changes, from yellow-green on the surface to gray-black inside. If this kind of black core brick is re-calcined in an oxidizing atmosphere, the black core part can be re-fired to white.
The main impurity oxides in bricks are iron oxide and titanium oxide. It can be inferred from the fact that the black core brick becomes white after re-fired in an oxidizing atmosphere, it can be inferred that the firing atmosphere and the impurity oxides of iron and titanium are the conditions for the generation of black cores. However, when iron and titanium oxides coexist or exist alone, they have different effects on the coloring of refractory bricks. When titanium ion exists alone, the coloring is not significant, and the brick body is slightly blue, while when iron ion exists alone, the brick body is orange-brown.
The above is the reason why the refractory bricks produce black cores. In addition, even in an oxidizing atmosphere, the coloring and sintering of alumina can also increase the black cores. During production, it is necessary to control the preparation of raw materials, the control of heat and temperature, to reduce the probability of black heart problems.