May 4, 2009

‘Black Core’ in Refractory Bricks

What is ‘Black Core’?

As the name suggests these are circular or semi-circular shaped black spots forms around the core or middle portion in non-basic refractory bricks containing good percentage of raw clay. The two reasons attributed to the formation of Black Core are:


=> Presence of Carbonaceous matters in plastic / non-plastic fire clay. Sometimes, too much carbonaceous matters have been found to occur in the fireclays which are available particularly around a Coal-belt.

=> Reducing atmosphere in the kiln during firing of bricks.


Precautions

Following are the few steps to avoid the formation of Black Core in refractory bricks:


=> The firing atmosphere (kiln atmosphere) must be kept oxidizing.

=> Soaking time should be prolonged.

=> If it is not eliminated even after taking the above two steps then the raw clay has to be replaced.


Related Posts:

>> How to Prevent Formation of Iron Spots (Crater) in Refractory Bricks as a Measure of Quality Control [Read]

>> Types of Testing of Refractories [Read]

>> Glimpses of the Growth of Refractory Industry in India [Read]




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