1. Develop appropriate firing system
In addition to the porosity, the dirt absorption capacity of cast steel bricks is closely related to the pore structure. During the firing process, with the increase of firing temperature, the number of small holes decreases, while the volume of large holes increases. If the firing temperature further increases, the green body will expand, and there will be large holes in the brick which can hold dirt, and the surface quality will become significantly worse. The anti fouling ability of steel pouring bricks is also affected by those large pores larger than 60 microns. Therefore, when formulating the firing system, the steel pouring bricks must have a small number of small sized isolated pores, and the appearance of large pores and connected pores must be strictly controlled. Generally speaking, this kind of structure can be obtained by sintering at a temperature slightly higher than the compact sintering temperature. In addition, properly prolonging the temperature range of 1051~1150 ℃ can promote the density of green body, reduce the closed porosity of green body, and avoid grain coarsening.
2. Control of blank fineness
In the ball milling process, the fineness of the blank shall be strictly controlled. Generally, the 250 mesh sieve is less than 1%, and the particle size of most quartz particles is less than 40 microns, so that during the sintering process, the stress Rongsheng refractory caused by the different expansion coefficients of quartz particles and glass phases during cooling is small, and there are fewer cracks in the brick blank. In addition, when formulating a reasonable cooling system, it is necessary to prevent microcracks of quartz particles due to large stress caused by crystal transformation at 573 ℃.
3. Pay attention to the formulation and crystal transformation of green body
Good sintering degree and low water absorption are the basic conditions for cast steel bricks to have good surface anti fouling ability. For example, in terms of the internal quality of the product, the anti fouling ability is also related to the composition of the formula and the calcination state. Sometimes, although the water absorption of the product is less than 0.2%, which only shows that the porosity of the microstructure is reduced to a small extent, the degree of crystal phase transformation still largely affects the anti fouling performance of the product. For example, from the perspective of anti fouling, the longer the calcination time is, the more thorough the crystal transformation is, and the stronger the anti fouling ability is, the larger the SiO2/Al2O3 ratio in the formula is, the more high-temperature glass phases will be, and the less the crystal phases of kaolin residues are, the better the anti fouling performance of the product will be.
