How to lay high alumina bricks, how to judge the price and quality
The fire resistance of high alumina bricks fluctuates greatly. The load softening temperature of most high alumina bricks is greater than 1400°C. When high alumina bricks contain higher Al2O3, and when there are more mullite and corundum, their thermal conductivity decreases as the temperature increases, but is above 1000°C. High alumina bricks have the characteristics of thermal shock stability and high normal temperature compressive strength, but their resistance to chemical erosion is weak.
High alumina bricks also have the characteristics of high high temperature creep rate. Generally speaking, high alumina bricks are composed of fine-grained corundum, fine columnar mullite and glass phases. The glassy phase is distributed between the granular corundum. Under high-temperature thermal loads, softening of the glass phase can cause sliding and deformation of granular corundum. If a solid matrix is formed from mullite columnar crystals, its creep resistance can be relatively improved. But in general, the performance of ordinary high alumina bricks under the conditions of 1400℃.0.2MPa (50h)
The creep rate is as high as 10%~20%, and even large deformation often occurs before the constant temperature time.
The production process of high alumina bricks is similar to that of multi-clinker clay bricks, but the main difference is that the proportion of clinker in the ingredients is higher, up to 90~95%. broken
Before, the clinker needs to be graded, selected and screened, and then iron removed. The firing temperature is high. For example, when firing in a tunnel kiln, the temperature is generally between 1500 and 1600°C.
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Lightweight high alumina brick
Lightweight high alumina bricks are important insulation materials for thermal furnaces. Rational manufacturing and selection of lightweight high-alumina bricks is of great significance to the rational use of energy. Correctly implement China's energy policy. Among various lightweight thermal insulation materials, lightweight high-alumina bricks have high fire resistance and small bulk density; raw materials are abundant and refractory bricks are cheap, making them ideal thermal insulation materials. Depending on the manufacturing process, lightweight high-alumina bricks can be made using the foam method or the figure method.
How to judge whether the price of high alumina bricks is reasonable?
High alumina bricks come in various specifications and prices. When purchasing high alumina bricks, how to understand the actual price from the company's quotation mainly depends on the following points:
Aluminum content
One of the important working properties of high alumina refractory bricks is the structural strength at high temperatures, which is usually evaluated by the load softening deformation temperature. It also measures its high-temperature creep properties to reflect its high-temperature structural strength. The test results show that as the Al2O3 content increases, the load softening temperature increases. According to aluminum oxide
Al2O3 content, high alumina brick manufacturers are divided into three levels: Level 1 - Al2O3 content >75%; Level 2 - Al2O3 content is 60~75%; Level 3 - Al2O3 content is 48~60%. Generally speaking, high aluminum The price of bricks is divided based on the alumina content of the product.
Size
The sizes of high alumina bricks are generally divided into national standard, special-shaped and special-shaped. The standard size is fixed, the manufacturer can produce it in large quantities, and the price is relatively low; special shapes. Special sizes and shapes are not fixed. Except for general special-shaped bricks, they generally require enterprises to customize production, which requires mold opening costs. The production difficulty increases according to the complexity of the shape, and the price is relatively high.
How to lay high alumina bricks?
High alumina brick linings are divided into four categories according to the size of the brick joints and the fineness of the operation. The categories and brick joint sizes are: Category 1 ≤ 0.5mm; Category 2 ≤ 1mm;
Category 3 ≤ 2mm; Category 4 ≤ 3mm. The fire mud in the brick joints and mortar joints should be full, and the brick joints in the upper and lower layers of the inner and outer layers should be staggered. The preparation of refractory mortar for bricklaying should follow the following principles.
1. Before laying bricks, various refractory muds should be pre-tested and pre-layed to determine the bonding time, initial setting time, consistency and water consumption of different muds. 2. Use different utensils to prepare different muds and clean them in time.
3. Use clean water to prepare mud of different qualities, accurately weigh the amount of water, mix evenly, and use as needed. No more water should be added to the prepared hydraulic and air-hardening mud, and the initial setting mud should not be used further.
4. When combining the prepared phosphate with mud, the specified trapping time should be ensured, and the prepared mud should not be diluted with water at will. Due to its corrosive nature, this slurry cannot come into direct contact with metal shells. Before brick lining construction, the site should be thoroughly inspected and cleaned. Before laying the brick lining, the laying out work should be done, and the size and elevation of the masonry should be checked according to the design drawings. The basic requirements for laying bricks are: bricks must be close to each other, brick joints must be straight, and the bricks must be in circles.
Accurate, the locked bricks are firm, well positioned, and do not sag or become hollow. The masonry should be kept flat and vertical. High-alumina bricks should be laid with staggered joints, the mud in the joints of the masonry bricks should be full, the surface should be pointed, the joints should be horizontal and vertical, the arc surface should be smooth, and the masonry should be dense. Implement the variety layout of different high alumina bricks according to the design plan. When laying bricks, the fullness of the fire mud is required to reach more than 95%. The surface brick joints must be seamed with original slurry, but the excess mud on the surface of the brick lining must be scraped off in time.
When laying bricks, flexible tools such as wooden hammers, rubber hammers or hard plastic hammers should be used. Steel hammers should not be used, and bricks should not be chiseled into the masonry. After the mud has dried and hardened, the masonry should not be struck hard or corrected. Bricks must be selected strictly, bricks of different materials and types must be strictly separated, and bricks of the same quality and type must be even in length. The thickness of the joint steel plate is generally 1~1.2mm, and it must be flat, not curled, not twisted, and free of burrs. The width of each board should be about 10mm smaller than the brick width.
During masonry construction, the steel plates shall not exceed the edge of the bricks, and the steel plates shall not be used for sounding or building bridges. Only one steel plate is allowed per joint. Adjusting narrow steel plates should be used as little as possible. Cardboard used for expansion joints should be placed as designed. When locking bricks, use flat bricks for locking and fine processing, and stagger adjacent brick paths by 1 to 2 bricks. It is strictly prohibited to use castables alone to lock bricks, but the last locking brick can be fixed with castables.
Composition and dosage of mud used for laying high alumina bricks.
High alumina brick refractory slurry is made of refractory fine aggregate and binder, and is mixed with liquid binder in a certain proportion to make slurry of different consistencies. The fire resistance temperature and chemical composition of masonry refractory products should be used.
The fire resistance of refractory products applies to the chemical composition. The prepared high alumina brick refractory slurry should have a certain room temperature bonding strength, high high temperature flexural resistance, shear strength, low temperature shrinkage, good air tightness and good construction performance.
The construction performance of high-alumina brick slurry is mainly reflected in the laying, spreading, water loss and plasticity. Generally speaking, the water retention time of mud is used to identify its construction performance. The so-called water retention time refers to the time required for the mud to be mixed into a suitable consistency and spread on the brick surface with a trowel to a certain thickness for it to be absorbed by the brick surface, which is generally 1 to 2 minutes. Too long or too short is not conducive to operation. After the mud is mixed. There should be no precipitation or segregation after being placed for a short period of time.
How to check the quality of high alumina bricks?
The quality of high alumina bricks can be inspected and identified according to the following methods.
1. Whether the specifications and dimensions of high-alumina refractory bricks meet the requirements and whether the dimensions are consistent
2. Whether the strength meets the requirements can be determined not only through the test report issued by the laboratory, but also by knocking the sound produced by the aluminum brick on site.
Less intense.
3. Are the edges and corners complete and straight, and how smooth is the surface?
4. Whether the color difference can meet the engineering requirements. Are the high alumina bricks blackened by smoke?
5. Is there any undercooked food or even undercooked food? The surface or heart of underfired bricks is dark red, and there is a mute sound when struck.
6. Whether there are overfired bricks. Especially for dry hems and silk seams, if you choose overheated high-alumina bricks, it will be difficult to cut and process. The color of high-alumina bricks is darker than that of normal high-alumina bricks, and they often have bending and deformation. When struck, the sound is crisp and metallic, like a metal sound.
7. Whether there are cracks. Wind cracks can be found through observation, and fire cracks in high-alumina bricks caused by combustion can be identified by knocking sounds. Bricks with cracks on the surface or inside will reduce their strength and easily cause freeze-thaw damage.
8. Density inspection. By inspecting the dried mud brick section and the cross-section identification of the finished high alumina brick, it is possible to influence the holes, blisters, water cut layer, and sand cut section.
layer and impurity density.
9. Whether there is frost (alkali generation). Bricks with frost cannot be used for foundations or wet areas, and bricks with severe frost are unqualified.
10. Other inspections. For example, whether the sand content in the soil is too high, whether it contains slurry particles, whether there are lime particles or even lime bursts, whether the high-aluminum bricks have been exposed to rain, whether the bricks are frozen or contain frozen soil, etc. The existence of these phenomena will lead to a decrease in the quality of the bricks and should be carefully observed and inspected.
11. Check the test report issued by the high alumina brick manufacturer. After the bricks are transported to the site, the project department should select samples and send them to the laboratory for retesting. If the retest results do not meet the relevant standards, it means that the quality of the on-site materials does not match the sample.
How do you know if the price is reasonable when buying high alumina bricks? In addition to the material content, there are also special uses, such as low creep performance, anti-flaking products, etc. The prices are different.
Zhengzhou SNR Refractory Co.,Ltd are professional in producing different kinds of refractory materials for glass industry.Any demands,please don't hesitate contact with me.
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+86-15238007351 |
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+86-371-86039318 |
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annie@snrefractory.com |
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