The main reasons for the high number of waste products and low product rates are as follows:
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. The body will be shortened after it is boring, which will result in the addition of boring shortening cracks, or the slight boring cracks will become large, resulting in a low boring product rate.
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 after the dullness is fully shown, the cracks are fully exposed to people's sight;
Third, because the grading of the materials is unreasonable, the distribution principle of the tightest packing has not been reached, and 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, leading to boring cracks.
According to the various causes of the low incidence of boring rate, choosing a certain coping method can deal with the problems in production.
Regardless of the use of coal gangue, shale, fly ash, or one or more of other industrial waste residues as production materials, if the moisture content of the material is not in a reasonable condition, regardless of the high moisture content of the material, 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, it is necessary to control the molding moisture 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 during molding. From 13% to 15%, when using a semi-rigid plastic extruder, the molding moisture content is controlled at 15% to 17%. When using a general extruder, 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, adjusting the unevenness of the moisture in the molding of the material must also determine the amount of water added based on the unevenness of the natural moisture content of the material. When the natural moisture content of the material is high, add less water, and add more water when the natural moisture content of the material is low.
Strengthen material processing and improve material forming function
When the material forming function is uniform, the moisture content, compactness, and shortening function of the clay bars after extrusion are common. As long as this, the molded clay bars will not have internal injuries. After cutting into wet billets, each piece The body has outstanding overall functions, and the boring functions on the surface, left, right, and top of the body 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. The condition of the cracks started.
The sludge is internally damaged and the body is cracked after drying. Most of it is because the material processing is not in place, or the size of the broken material does not meet the production requirements, or because of two or more materials. The mixing is uneven, or the water content in the mud flow is uneven after adding water. Some local water content is high, and some local water content is low, so that some of the particles in the quality are coarse, while the other are fine and some are The seed material content is high, 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 very low water content is less plastic. 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 particle size required for the production process. For coal gangue material, the particle size of the largest particle in the quality 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. . In addition, according to the natural moisture content of the material, the amount of water added in the qualitative analysis of the fault is that 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 fine, and whether the gradation of the material particles is reasonable is not only related to the connotation quality of the clay sticks 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, and the shortening rate is basically the same. After boring, the modification of each part is generally appropriate, and boring cracks do not easily 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, plastic molding is still used. The particle accumulation during quality guessing is still the basis for molding. The same principle is carried out. When stacked, large particles of material are placed in a regular order to form a large skeleton structure.
Secondly, the medium-sized material fills the large open 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 joint effect. This is the principle of the tightest accumulation of materials. In the process of the most tightly packed materials, the three materials of coarse, medium and fine components are all lacking. If all the 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. Are fine particles, although the space between the particles is small and strong,
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 an affirmative share, it may form a semi-finished product and a product brick with low strength and brittleness. What is the distribution of coarse, medium and fine 3 kinds of particles in the guess? According to theoretical calculations and experimental results, the percentage of each component should be coarse: medium: fine = large: small: large, which is generally called "The two ends are large and the center is small", that is to say, in the course of the most tightly packed materials, the percentage of coarse particles and fine particles is greater than the percentage of medium particles. When it comes to the actual production details, if the material particles are too fine, it is necessary to add a certain amount of coarse grain materials to the quality guess. Often, the quality guess can participate in the required amount of mature and inferior material particles. Add coal gangue particles.
Some manufacturers participate in a small amount of fine sand in the quality guess, which can also have the effect of changing the particle gradation of the material. If fine powder does not work in quality guessing, one method is to strengthen the crushing and crushing of the material to produce a certain amount of fine powder, and the other method is to mix a certain amount of fly ash or swelling soil, clay in the quality guessing. And other fine particles.
Some manufacturers participate in a small amount of fine sand in the quality guess, which can also have the effect of changing the particle gradation of the material. If fine powder does not work in quality guessing, one method is to strengthen the crushing and crushing of the material to produce a certain amount of fine powder, and the other method is to mix a certain amount of fly ash or swelling soil, clay in the quality guessing. And other fine particles. Some manufacturers participate in a small amount of fine sand in the quality guess, which can also have the effect of changing the particle gradation of the material. If fine powder does not work in quality guessing, one method is to strengthen the crushing and crushing of the material to produce a certain amount of fine powder, and the other method is to mix a certain amount of fly ash or swelling soil, clay in the quality guessing. And other fine particles.
The boring process is that the body and the boring medium conduct thermal and wet communication in the authentic boring. The heat medium transfers its own heat to the body and absorbs the water dispersed from the 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, and the temperature rises, and the moisture in it is discharged, and the amount decreases. From low temperature, high temperature, and heavy wet billet, it gradually becomes higher temperature, lower moisture content and 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, the heat medium temperature is higher, and 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 to disperse and transpiration the water in the green body. Without sufficient heat, it can be used for other purposes. In addition, because the temperature of the green body is the same as the temperature of the heat medium, there is no temperature ladder, which can not continue to increase the temperature of the green body. In the deceleration and boring stage, most of the water in the green body has been swept away, and the water content is small. At the same time, because of the decrease in the heat supply at this time, the boring speed has decreased significantly compared to the constant 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. It is very important to improve the rate of boring products. In the detailed operation, great attention should be paid to the timely discharge of moisture from the entry end of the authentic boring room to avoid the dampness of the green body, and the waste rate will be very high when it is boring.
Strictly control the boring speed at 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 many cracks will occur. . In the constant-speed boring process, although the blank temperature does not increase, if the boring speed is too fast, the bulk will be shortened. If the shortening speed exceeds the ability of the blank to eliminate its internal stress, the blank will also Cracks simply occur, reducing the rate of boring products. 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 using high temperature and large air volume methods, 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 summary, when the rate of boring products in the local boring room is low, it must be distinguished because the problem of the material is still 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 to the guess. Amount of fine sand. And because the invisible cracks and boring cracks caused by the irrational gradation of the material particles should be adjusted by the method of the gradation of the material particles to reach a situation of simple molding and not showing boring cracks.
If the proportion of coarse particles in the quality guess exceeds the agreed scale, the content of coarse particles should be reduced, and the grinding method should be used, or another fine material must be quantified to adjust the particle gradation. If the gradation caused by the excessive content of fine particles and the lack of coarse particles in the quality guess is unreasonable, you should participate in the coarse particles in the quality guess, and the amount of participation should be determined based on the results required for the adjustment. Regarding the molding crack caused by the low plasticity of the material, the material can be processed through physical methods. For example, the weathering or aging method is adopted. After the weathering effect, the water is distributed evenly 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 is evenly dispersed, 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 be added only after adding water. It is the same as the physical method. Chemical methods can be used to improve the plasticity of the material. For example, if you mix basic organic or inorganic materials in the quality guess, you can improve the plasticity of the material. For 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 method of processing is to participate in a certain amount of inferior materials in the high-plasticity guess, increase the conflict between layers, and reduce the layer and Velocity of relative movement between layers. Properly reduce the speed of the reamer, and keep the gap between the reamer blade and the mud bushing at a minimum interval to reduce the occurrence of cracks.