The refractoriness of castable refractory and the softening temperature under load are two different kind of data, the difference of these two data is as follows:
(1) Refractoriness
Refractoriness refers to the ability of a sample to resist melting under high temperature. It is different from the melting point, which is the temperature at which the crystalline phase of a pure substance and its liquid phase are in equilibrium. Unshaped refractories and their raw materials are aggregates composed of a variety of different compounds, so they have no melting point, only their melting temperature range. The refractoriness is measured by the comparison method.
The chemical mineral composition and microstructure of the material are the most basic factors affecting its refractoriness. Various impurity components, especially those of strong fluxes, will seriously reduce its refractoriness. Therefore, material selection and high purification are very important. It should be pointed out that it is wrong to use the refractoriness index as the use temperature of general materials. Because when it reaches the refractoriness temperature, the material has been softened and has no mechanical strength. The operating temperature is comprehensively evaluated by performance indicators such as refractoriness and load softening temperature.
(2) Load softening temperature
The load softening temperature refers to the temperature at which the sample undergoes constant load under continuous heating conditions and deforms. It characterizes the resistance of the material under the combined action of high temperature and load, and also characterizes the softening temperature at which the material exhibits obvious plastic deformation. Therefore, this index is one of the important basis for determining the use temperature of monolithic refractories.
When testing, the sample size is a cylinder with a diameter of 50mm and a height of 50mm. Apply a static pressure of 0.2MPa, and continuously increase the temperature to expand the sample to the highest point and then compress to 0.6% of the original height. This is the load softening starting temperature. When the deformation is 4% It is the load softening temperature of 4% deformation. Unshaped refractory materials can be regarded as the sintering process of materials due to the large critical particle size of refractory aggregates and unfired conditions. Therefore, compared with shaped fired products, their load softening temperature is different. Unshaped refractories measured the load softening temperature of 0.6% deformation and 4% deformation, and the results only reported the temperature of deformation 4%. The temperature is more reproducible, that is, more accurate. It should be pointed out that due to the addition of additives, the measured load softening temperature is lower, such as low cement high alumina castable refractory, etc., the actual use temperature is indeed higher.
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