I recently observed early life (30-40 heats) cracking and chip out of magnesia carbon bricks(especially in metal zone) of 50 ton capacity ladle in a steel plant where 30-40% heats are routed thru VD and alloy steel is produced.
I have found that plant operation is intermittent and sometimes,after every 2-3 days,a ladle is kept out of circulation and in cold condition for 8-24 hours before being heated for 3-4 hrs and brought to circulation once again.This is done to accomodate some other ladle which is in circuit.This is done on rotation basis.
So,why this chip out is happening ?
Is it due to expansion of the bricks ?
Is it due to spalling ?
Is it due to very tight refractory lining ?
Is it due to lower residual carbon % (presently residual carbon is 10% metal zone and 14 % slag zone )?
Does it depend on purity of magnesia (presently 97.5% FM with C/S ratio 1.7-1.9 and 98 % FM with C/S ratio 1.9 are used in metal and slag zone respectively) ?
Can it happen due to entry of any foreign element in the batch?
Will addition of DBM reverse the trend ?
Will using a single 2 mm thick mortar paste between two bricks in each ring to provide expansion gap help ?
Can it happen due to size/location of the key (piece of brick which is cut out from the mother brick and inserted to tighten each ring).I mean if keys of several rings fall in the same line,or keys are too small to get eroded and come out of the lining) or keys fall on the purging side of the lining!
Can step formation in the lining result in faster damage of the bricks ? I have observed 10-20 mm steps between two rings in few cases in a ladle which was being lined.
Can spiral lining in place of present straight lining reduce such chip outs ?
Is chip out a quality issue of the lining or of the product?
I have found that plant operation is intermittent and sometimes,after every 2-3 days,a ladle is kept out of circulation and in cold condition for 8-24 hours before being heated for 3-4 hrs and brought to circulation once again.This is done to accomodate some other ladle which is in circuit.This is done on rotation basis.
So,why this chip out is happening ?
Is it due to expansion of the bricks ?
Is it due to spalling ?
Is it due to very tight refractory lining ?
Is it due to lower residual carbon % (presently residual carbon is 10% metal zone and 14 % slag zone )?
Does it depend on purity of magnesia (presently 97.5% FM with C/S ratio 1.7-1.9 and 98 % FM with C/S ratio 1.9 are used in metal and slag zone respectively) ?
Can it happen due to entry of any foreign element in the batch?
Will addition of DBM reverse the trend ?
Will using a single 2 mm thick mortar paste between two bricks in each ring to provide expansion gap help ?
Can it happen due to size/location of the key (piece of brick which is cut out from the mother brick and inserted to tighten each ring).I mean if keys of several rings fall in the same line,or keys are too small to get eroded and come out of the lining) or keys fall on the purging side of the lining!
Can step formation in the lining result in faster damage of the bricks ? I have observed 10-20 mm steps between two rings in few cases in a ladle which was being lined.
Can spiral lining in place of present straight lining reduce such chip outs ?
Is chip out a quality issue of the lining or of the product?
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