Many users have doubts when consulting ceramic fiber products. It is clearly a 1260 ℃ standard ceramic fiber module. Why is the service temperature only about 1100? Did you use degraded materials? Xiaobian cried out in his heart that he was wronged. At the same time, he felt that it was necessary to popularize the knowledge about the use temperature of ceramic fiber modules.
In the continuous flame atmosphere heating furnace as the lining, the long-term service temperature of domestic aluminum silicate fiber can also be said to be the safe service temperature: 950 ℃ for 1050 ordinary type; 1050 degrees for 1260 standard type; 1100 ℃ for 1260 high purity type; 1200 ℃ for 1400 high aluminum type; 1430 zirconium containing type is about 1350 ℃; Chrome containing aluminum silicate products or polycrystalline alumina fibers can be selected for kilns greater than 1250 ℃.
This is because during the long-term heating process, once the aluminum silicate fiber exceeds its own acceptable temperature, crystallization will occur. Generally speaking, the internal fiber is broken and crushed, resulting in product pulverization, loss of thermal insulation performance, production loss and even potential safety hazards.
What is crystallization?
The crystallization process is the orderly arrangement of atoms in the metastable glass phase to form a lattice structure with the lowest internal energy. Aluminum silicate fiber belongs to amorphous refractory fiber. No matter what composition and structure, there is crystallization in the process of heating.
Aluminum silicate fiber is divided into five conventional types, namely ordinary type, standard type, high purity type, high aluminum type and zirconium containing type. These models have different degrees of crystallization when heated at 1100 ℃ for 500h. This crystallization is directly proportional to the heating time. The crystallization temperature of aluminum silicate fiber heated for a long time is 1100 ℃, and the crystallization temperature heated for a short time is about 1200 ℃.
Crystallization heating process
After mullite crystals are precipitated from aluminum silicate fiber during heating, the amount of crystallization increases with the increase of temperature or time.
During the crystallization process, the fine grains precipitated first need to grow gradually, and some grain growth processes are also the process of shrinkage or elimination of other grains. As a result, the average grain size increases. This grain growth is not the bonding of small grains, but the result of grain boundary movement. With the continuous growth of mullite grains, the microstructure of the fiber further shrinks, and the shrinkage of the microstructure will appear in the macro. There is an uneven “shrinkage” in the diameter of the refractory fiber rod. When the refractory fiber grains merge with each other and grow close to the diameter of the fiber rod, the shrinkage here is enough to break the fiber, that is, pulverize. This temperature is the service limit temperature of the refractory fiber.
Heating crystallization of different grades of aluminum silicate fibers
Due to the high impurity content and low A1203 content of ordinary refractory fiber, the grain grows faster at the beginning of crystallization. It is the lowest service temperature of glassy refractory fiber. The impurity content of high-purity refractory fiber is less than 1%, the crystallization temperature lags behind that of ordinary refractory fiber, and the precipitated grain grows slowly. Therefore, the service temperature of high-purity refractory fiber is higher than that of ordinary aluminum silicate fiber.
The crystallization temperature of high alumina refractory fiber lags behind that of high purity refractory fiber, and the grain growth rate is slower. Its long-term service temperature is slightly higher than that of high purity refractory fiber. ZrO2 in the microstructure of zirconium containing refractory fiber (or chromium containing fiber) is eliminated in the matrix of high-purity refractory fiber. Its main function is to inhibit the crystallization and grain growth of refractory fiber during heating. However, at about (1200 ℃), ZrO2 will gradually and slowly burn or volatilize. With the extension of time, its inhibition will become smaller and smaller, and the crystallization and grain growth will also accelerate. Finally, the service temperature is basically the same as that of high alumina refractory fiber.
It can better achieve the effect of energy saving and heat insulation when the equipment is put into operation and ensure the service life of the equipment. Materials must be selected in strict accordance with the service temperature of the product. According to the working condition and operating temperature of the equipment, plus a certain temperature range, select the corresponding grade of aluminum silicate fiber products.
For more details or questions, please call the company’s hotline + 0531 85800088 or through the online customer service website, or leave your contact information. We have technicians to solve the problems related to high temperature materials for you at any time.
Shandong redon high temperature materials Co., Ltd. has domestic high-end production equipment and reliable production technology, with an annual output of 1050 ceramic fiber series products, 1260 ceramic fiber series products, 1400 ceramic fiber series products and 1600 polycrystalline series products of more than 10000 tons. There are more than 30 kinds of products in different forms, such as cotton, blanket, felt, board, paper, various textiles, profiled products, modules, folding blocks, castables, spraying and so on, which can meet the heat insulation requirements of different situations in the high temperature field. Welcome to click the online service at the bottom right of the website or submit an online inquiry. We will contact you as soon as possible.