Ceramic fiber as the third generation of refractory material after the traditional heavy firebrick and monolithic refractoriness, it not only has the excellent insulation performance as general thermal conductivity materials, and has excellent heat-resistant properties under high temperature continuous work. Due to the crystallization of glass fiber, polycrystalline crystal fiber morphology transformation, harmful impurities and fiber in the fiber used in corrosive material to promote fiber crystal, polycrystalline and contact of sintering, high temperature creep and other factors, there appears the change of the structure of the fiber shrinkage deformation, fiber loss, brittle broken, fiber strength and densification, therefore, the use of all kinds of ceramic fiber temperature has a limit temperature which is called the highest using temperature, also known as the "classification temperature" or "level temperature", which is also considered as a symbol of fiber heat resistance. Internationally divide ceramic fiber products into four grades temperature: 1000 ℃, 1260 ℃, 1260 ℃ and 1600 ℃.
The highest operating temperature of ceramic fiber refers to the limited temperature ceramic fiber can bear within short time, which represents
ceramic fiber products heat resistance index. Ceramic fiber products allowed long time temperature is generally around 200℃ lower than the highest use temperature. Take domestic 1260℃ fiber products, for example, its long using temperature is 1000℃. Therefore, the highest temperature concept is very important, which has close relation with the long time using temperature and is applied in the process of fiber main reference basis. In the past, some people take the highest temperature as a long-term use of temperature, which is wrong and will cause unnecessary loss.
In addition, the same kind of ceramic fiber products using under different conditions also have different long-term temperature. Such as industrial kiln operation system (continuous or intermittent kiln), fuel type, furnace atmosphere and other technological conditions are all the factors affecting the service life of ceramic fiber. There is no ideal method for determination of ceramic fiber heat resistance index. Usually these products will be heated to a certain temperature, and evaluate the difference between operating and the highest temperature according to the sample plus hotline shrinkage and crystallization degree
1. Refractory insulation fiber classification temperature: it refers to the highest operating temperature. It is the test temperature when refractory fiber product is kept heating for 24h and gets 4% high temperature line shrinkage. This kind of product will have short service life under the temperature, so it is seldom applied.
2. Operating temperature: it means safety using temperature for a long time. It is the test temperature when refractory fiber product is kept heating under fixed temperature for 24h and high temperature line shrinkage is less than 2.5%. Under the temperature, crystal fiber and non-crystal fiber transmission and grain growth speed is slow with stable property.
