1. The influence of reasonable particle grading on forming and blanking
First, when the particles in the mud are piled up during the forming and blanking of the shaped product, a certain amount of medium particles are usually added to the large particles to fill the gaps between the large particles. Finally, the fine powder fills the remaining gaps between the large and medium particles. The gaps between the deposits can be further reduced, thereby achieving the most compact accumulation of the mud. In the process of the most compact accumulation of mud, all kinds of raw materials, such as coarse, medium and fine, are generally indispensable. If all the raw materials are coarse particles, the gaps between the particles are large, the refractory bricks are not well bonded, the green body density is low, the porosity is high, the plasticity is low during molding, and it is difficult to make a green body. If all are fine particles, although the gaps between the particles are small and the bonding is firm, the porosity is low, and the bulk density of the raw material fine powder will be relatively low, which cannot reach the volume density required during the forming and blanking. In addition, due to the absence of coarse particles to play a skeleton support role, the strength of the formed green body is not high. If multi-component particle grading is considered, the porosity of the obtained clay will be smaller. However, in actual production, as the particle components increase, the diameter ratio of each particle continues to decrease, its effect is significantly weakened, and it brings difficulties to the production process, and increases the energy consumption of the equipment, thereby increasing the process cost. Therefore, in actual production, we use three-component particles to meet production.
So what is the ratio of coarse, medium and fine particles in the clay? According to theoretical calculations and experimental results, it can be concluded that the content percentage of the three component particles in the clay is 7:1:2. That is to say, in the process of the most dense stacking of raw materials, the percentage of coarse particles and fine particles is greater than the percentage of medium particles. In this way, the clay with the most reasonable particle grading has better plasticity and can achieve a semi-finished product with higher density, lower porosity and higher body strength. In actual production, if the raw material particles are too coarse, a certain amount of fine powder must be added to the clay or the amount of large particles must be reduced, otherwise there will be a rough surface, the appearance of the product is not very beautiful, and there will be many open pores, which will increase the apparent porosity and reduce the performance of the product. If the raw material particles are too fine, a certain amount of coarse particles must be added to the raw materials or the amount of fine powder added must be reduced, otherwise the plasticity of the mud will be reduced and cracks will easily occur during molding.
The influence of reasonable particle grading on the drying of finished products
When the mud can be most densely packed during molding, it is most beneficial to the molding of refractory bricks and can maximize the density of semi-finished products. However, this will make it difficult to discharge the moisture in the mud, and drying cracks will occur when the drying temperature is slightly higher; or a large amount of moisture cannot be discharged completely, resulting in explosions at the beginning of firing.
The influence of particle grading on the firing process of finished products
The coarseness of the mud particle grading also has a certain influence on the shrinkage during firing. The shrinkage of fine powder during firing is greater than that of particles. Therefore, in actual production, if the mud particles are too fine, it is easy to cause excessive shrinkage during firing, resulting in waste. If the mud is too coarse, the shrinkage is too small, which will cause uneven shrinkage.
2. How to ensure the rationality and stability of particle grading
The particle grading of clay materials often appears unreasonable, mainly because the vast majority of the raw material processing work is not in place, or the particle size of the raw material crushing does not meet the production requirements, or the fluidity of the crushed material in the silo causes particle segregation. Therefore, in actual production, the raw materials must first be crushed to the required particle size, and the cone crusher and vibrating screen must be stable to ensure the stability of the raw material particle grading. Secondly, the stability of the fluidity of the crushed material in the silo prevents particle segregation and affects the particle grading of the clay materials.
Reasonable clay particle grading is crucial to the production of alkaline shaped refractory brick products. Mixing clay materials with reasonable particle grading makes semi-finished products easy to shape, and can obtain green bodies with high density and good appearance quality, which can ensure the qualified rate of drying and the rationality of shrinkage during firing, thereby obtaining high-quality alkaline shaped refractory products.
