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Changes of graphite electrodes during the firing stage
Views: 836 Update date: Oct 12,2020

During the roasting process, the external dimensions of the raw product are constantly changing. In general, its volume is shrinking, but sometimes the size may also increase. The uneven shrinkage of the volume of the green product will cause internal and external defects until cracks are formed. Shrinkage is related to the degree of compaction, pressing method, binder quality and dosage, aggregate calcination temperature, heating rate and, calcination degree. These factors are usually intertwined.

Shrinkage occurs gradually as the firing temperature increases. Cold-pressed molded products have a low shrinkage temperature, and hot-pressed and low-porosity raw products do not shrink when they are heated. The volume starts to increase at 100 degrees Celsius, and reaches the maximum value at 400 degrees Celsius, and starts to shrink from 400 degrees Celsius and then the shrinking temperature increased sharply, until after 800 degrees Celsius, the shrinking speed decreased.
The lower the bulk density of the raw product and the lower the unit pressure during molding, the greater the shrinkage of the product.

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