The causes of more waste products and low yields are mainly the following:
At the top of the list, the moisture content of the material during molding is too high, which will cause the compactness of the clay sticks to be molded, and the shortening of the green body after boring will be too large, resulting in the addition of boring shortening cracks, or the slight boring cracks will increase, forming a boring yield.
Second, when the material is made into a green body, there are many internal injuries in the green body. There are many invisible cracks in the mud strip. When the mud strip is cut into a brick, the invisible cracks are brought into the wet body. Only at this time The appearance is not shown, but it is fully displayed after boring, so that the cracks are fully exposed to people's sight;
Third, because the grading of the materials is unreasonable, and the principle of the most densely packed dispersion has not been reached, the content of the same kind of particles is too high, which results in a low strength of the formed green body structure, and the boring speed is too fast, which leads to boring cracks.
According to the various causes of low boring rate and the selection of certain coping methods, the problems in labor can be dealt with.
Reasonably add water in the original guess and control the moisture content of the molding material
Regardless of the use of coal gangue, shale, fly ash, or one or more of other industrial waste residues as the production material, if the material moisture content is not in a more reasonable state, regardless of the material molding moisture content is too high, it is still too low , Can not produce a good quality of wet billets, can not reduce the dull waste rate of the authentic dry room, or even make the production process normal.
In general, the molding moisture must be controlled according to the function of the extruder used in the molding. If a hard plastic vacuum extruder with high vacuum and high extrusion pressure is used in production, the moisture content of the material must be controlled at 13 during molding. % ~ 15%. When using semi-rigid plastic extruder, the molding moisture content is controlled between 15% and 17%. When using general extruder molding, the material molding moisture content is controlled at about 18%. Together, the molding moisture should be controlled according to the plastic unevenness of the material. When the plasticity of the material is high, the molding moisture content can be appropriately reduced; when the plasticity of the material is low, the molding sweat rate can be appropriately added.
From the point of view of the boring body, the lower the molding moisture content of the material, the more conducive to the boring process. After the boring body, the size of the body is shortened and the boring cracks are less likely to occur. In the production process, to adjust the unevenness of the moisture in the molding of the material, the amount of water added must also be determined according to the unevenness of the natural moisture content of the material. When the natural moisture content of the material is high, add less water, and when the natural moisture content of the material is low, add more water.
Strengthen material processing and improve material forming function
When the material forming function is uniform, the moisture content, compactness, and shortening function of the mud sticks after extrusion are consistent. Only in this way, the formed mud sticks will not have internal damage. After cutting into wet billets, each piece The green body has outstanding overall functions, and the boring functions on the surface, left, right, and up are uniform. When boring and dehydrating, the dehydration conditions and dehydration ability of each part are similar. The shortening of the blank in the boring process is basically appropriate. It does not show that one part is shortened greatly, and the other part is shortened slightly and unevenly, which causes the body to attack. Reduces the onset of crack conditions.
The sludge presents internal damage and the phenomenon of cracks after the body is boring. Most of the reasons are because the material processing work is not in place, or the particle size of the broken material does not meet the production requirements, or because of two or more materials. Uneven mixing, or uneven water content in the mud flow after adding water, some local water content is high, and some local water content is low, so that some particles in the original guess are coarse, while others are fine and some are The seed material content is high, and the other part of the B material content is high. The local material with high water content is more plastic, and the local material with low water content is poor. This makes the function of each part of the same mud bar relatively large. The dehydration speed is different when boring. The boring shortening is also greatly different. It is easy to make the green body crack when it is boring.
The method to deal with the above problems is to first crush the material to the required particle size in the production process. For coal gangue material, the particle size of the largest particle in the original guess must be less than 2mm. Secondly, for the production of two kinds of materials, or more than two kinds of materials, the mixing of the materials should be strengthened so that each of the materials can sufficiently penetrate into the other side so that each component can be evenly dispersed in the materials used. . Moreover, according to the natural moisture content of the material, the amount of water added to the original guess is determined. The higher the natural moisture content, the less water is added, the lower the natural moisture content, and the more water is added.
Adjust the material particle gradation and add the density of the green body
The size of the material particles is large and small, and whether the gradation of the material particles is reasonable is not only related to the inherent quality of the sludge during molding, but also to the boring quality and firing quality of the green body. Grain gradation of reasonable materials, the compactness of the green body is uniform throughout the molding, the shortening rate is basically the same, and the changes in various parts after the dullness are generally appropriate, and the dull cracks do not simply occur. How to achieve a reasonable gradation of material particles? First of all, you must have a good understanding of material molding. Whether it is hard plastic extrusion or semi-rigid plastic extrusion, it is still plastic molding. When molding, the original guess of particle accumulation is still the basis. The same principle is carried out. When stacked, large particles of material are first neatly placed to form a large skeleton structure;
Secondly, the medium-sized material fills the large vacant space between the large particles. In the end, the fine-grained material occupies the remaining space of the large particles and the medium particles, which plays a connecting effect. This is the principle of the most dense accumulation of materials. In the process of the most tightly packed materials, the coarse, medium and fine three-component materials are indispensable. If all coarse particles are used, the space between the particles is larger, the bonding is not good, and the density of the green body is low. For fine particles, although the space between the particles is small and firmly bonded,
The density is high, but because there is no skeleton effect of coarse particles, the strength of the green body is not high. When the proportion of the material with a certain particle size in the green body occupies a certain proportion, the semi-finished and finished bricks produced may have low strength and become brittle. What was the distribution ratio of coarse, medium and fine 3 kinds of particles in the original guess? According to theoretical calculations and experimental results, it can be concluded that the percentage of each component should be coarse: medium: fine = large: small: large, which is generally called "The two ends are large and the middle is small", that is, in the process of the most tightly packed materials, the percentage of coarse particles and fine particles is greater than the percentage of medium particles. Specifically in production practice, if the material particles are too fine, a certain amount of coarse grained material must be added to the original guess. Often, the required amount of mature and infertile material particles is added to the original guess. If necessary, it can be added to the original guess. Coal Gangue Particles.
Some manufacturers participate in a small amount of fine sand in the original guess, which can also have the effect of changing the particle gradation of the material. If fine powder does not work in the original guess, one method is to strengthen the crushing of the material to produce a certain amount of fine powder, and the other method is to mix the necessary amount of fly ash in the original guess to swell the soil, clay, etc. Other fine particles.
Proper operation of boring process using boring principle
The boring process is that the green body and the boring medium exchange heat and humidity in the authentic dryness. The heat medium transfers its own heat to the green body and absorbs the water diffused from the green body. The temperature itself decreases and the humidity increases. The gas with low moisture content becomes low temperature and high humidity gas with lower temperature and larger moisture content. The green body absorbs the heat transferred from the heat medium, the temperature rises, and the moisture in it is discharged, and the weight decreases. From the low temperature, high temperature, and heavy wet billet, it gradually becomes a higher temperature, a lower moisture content, and a lighter weight. High temperature and low water content body. In the boring heating stage, the heat transferred from the heating medium to the green body is not only used for transpiration of the water in the green body, but also a certain amount of heat. Because the temperature of the green body is lower and the heat medium temperature is higher, the temperature gradient Under the effect, the sufficient heat is used to heat the green body and increase the temperature of the green body.
In the constant-speed boring stage, the heat transferred from the heating medium to the green body is used for the diffusion and transpiration of the water in the green body. Without sufficient heat, it can be used for other purposes. Together, because the temperature of the green body is the same as the temperature of the heat medium, there is no temperature ladder, which may not continue to increase the temperature of the green body. In the deceleration and boring stage, because most of the water in the green body has been swept away, the water content is small. At the same time, because of the decrease in the heat supply at this time, the boring speed is significantly lower than the isokinetic speed. In the boring room, the heating phase and the constant-speed boring phase are the fastest boring dehydration phase and the shortest boring shortening phase. The simplest phase is the boring crack phase. If the operation of this phase is realized, the boring waste rate of the authentic boring room will be reduced. It is very important to improve the boring yield. In the specific operation, great attention should be paid to the timely discharge of moisture from the entry side of the authentic boring room to prevent the body from regaining moisture, and the reject rate will be very high when it is boring.
Strictly control the boring speed in the initial stage of boring. The air volume and temperature sent to the boring room must be accurately detected and strictly controlled. Once the heat and air volume sent is too large, the green body will be quickly dehydrated, shortened and enlarged, and a large number of cracks will occur. In the constant-speed boring process, although the temperature of the green body does not increase, if the boring speed is too fast, the green body still has a large volume shortening. If the shortening speed exceeds the ability of the green body to eliminate its internal stress, the green body also Simple cracks occur, reducing boring yield. Therefore, in these two stages of boring, the temperature of the heat medium entering the boring chamber and the amount of air supply should be strictly controlled. The size of the supply air temperature and volume should be based on the results of theoretical calculations. In the future, the boring operation at the critical point in the boring room should be carried out with high temperature and large air volume as much as possible, so that the boring process is performed at a high speed. This can not only improve the boring output value, but also reduce the boring waste rate.
In short, when the boring yield of the boring room in the local road is low, it must be identified that the problem is caused by the problem of the boring room.
Regarding the formation of invisible cracks and boring cracks caused by the material, the material should be modified. When the plasticity of the material is too high to cause boring cracks, the plasticity of the material should be reduced. A certain amount of slag, coal gangue, fly ash, fly ash, etc. can be added in the original guess. If the above materials are not available, the necessary amount can also be added. Fine sand. And because the invisible cracks and boring cracks caused by the irrational gradation of the material particles should be adjusted by the gradation of the material particles to achieve a state of simple molding without boring cracks.
If the proportion of coarse particles in the original guess exceeds the allowable scale, the content of coarse particles should be reduced, and a fine method should be used, or another fine material must be quantified to adjust the particle gradation. If the grading caused by the excessive content of fine particles and insufficient content of coarse particles in the original guess is unreasonable, you should participate in the coarse particles in the original guess, and the amount of participation is determined according to the results required for adjustment. Regarding the forming crack caused by the low plasticity of the material, the material can be processed through physical methods. For example, weathering or aging methods are adopted. After the weathering effect, the water is distributed uniformly through the capillary tube. The internal seizures are differentiated, cracked, and loosened. The material function is improved and the plasticity is improved.
After aging and adding water for a period of time, the raw materials are naturally matured, the materials are moist and slack, and the water dispersion is uniform, and the plasticity of the materials is also improved. The method of adding fine powder content can also improve the plasticity of the materials. Capillary pores become smaller and their traction increases. The specific surface area increases, and the water film can only be added after adding water. As with physical methods, chemical plasticity can be used to improve the plasticity of the material. For example, if basic organic or inorganic materials are mixed in the original guess, the plasticity of the material is improved. Lactic acid, humic acid, acetic acid, etc. Inorganic substances include sodium carbonate and water glass.
Because the hidden cracks that are most likely to appear during the molding process are spiral lines and S-shaped cracks. The treatment method is to participate in a certain amount of inferior materials in the high-plasticity original guess, increase the friction between layers, and reduce the layer and layer. Velocity of relative movement between layers. Reduce the reamer speed properly and keep the gap between the reamer blade and the mud bush at a minimum interval to reduce the occurrence of cracks.