Because of the non setting refractory material is used in the field of baking and burning, will appear dry shrinkage and firing shrinkage.
It is necessary to consider the measures to compensate the shrinkage in the design of
composition, that is, the total molar volume of the reaction product is greater than the total molar volume of the reaction product, and the volume expansion of the matrix is matched with the sintering shrinkage. The main methods are as follows:
composition, that is, the total molar volume of the reaction product is greater than the total molar volume of the reaction product, and the volume expansion of the matrix is matched with the sintering shrinkage. The main methods are as follows:
(1) Thermal decomposition method, a mineral which is decomposed at high temperature and the molar volume of the product of its in situ thermal decomposition is more than the molar volume of the original mineral to compensate for the sintering shrinkage of the material. Such as in the A1203-SiO2 system unshaped refractory materials added a certain amount of kyanite, after high temperature calcinations into mullite and free silica (quartz), volume expansion and produces about 16% ~ 18% (calculated). There are sillimanite, andalusite and sillimanite minerals. The volume expansion after the decomposition of Kyanite is the largest, so it has been widely used.
(2) High temperature chemical reaction method is used to compensate for the volume expansion effect of the in-situ chemical reaction occurring during high temperature use. In the 
aluminum matrix such as magnesium or magnesium aluminum castables, ramming material or vibratory ramming material in. With high temperature MgO and in situ reaction to generate spinel and produce about 7.5% of the volume expansion, can be part of the compensation of the sintering shrinkage.
aluminum matrix such as magnesium or magnesium aluminum castables, ramming material or vibratory ramming material in. With high temperature MgO and in situ reaction to generate spinel and produce about 7.5% of the volume expansion, can be part of the compensation of the sintering shrinkage.
(3) In the process of heating, the transformation method of the crystal type can be used to produce the mineral, and the molar volume of the crystal is larger than the molar volume of the transformation. As in the trough of blast furnace A1203- SiC-C matter ramming material is added with appropriate amount of silica particles with quartz transformation of tridymite and cristobalite volume expansion effect (respectively 12.7% and 17.4% to compensate matrix of sintering shrinkage, reduce or eliminate the trough of the shrinkage cracking phenomenon.
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