SES clean and choked

these pics show the SESs (Sub Entry Shrouds) of the same tundish, photographed immediately after end of casting from adjacent strands.

if we take a look at these 2 tundish shrouds, the easily distinguishable feature is the deposition at the bottom end of the shroud on the first pic.

not something strange to steel making, that is a mass of inclusions( most likely alumina, silica, MnO, CaO and other complex oxides).

with this level of depositions, that particular strand got chocked during casting unexpectedly which is undesirable for a planned smooth casting. unplanned closures of strands, and in turn machines in somecases, may upset the dynamics of the shopfloor.

this is evident when 1 strand is getting smoothly cast, another strand of the same tundish may develop a lof of inclusion buildup which eventually may choke that strand.

the reason for buildup in one strand could be air-ingression through the seating area of the SES; likely, it is combined with a sufficient supply of inclusions from the steel.

in any case, one of the important responsibilities of LF is to prepare heats with least amount of inclusions before sending heats to caster. it is not just the ingression of air that could build up that much of inclusions to choke SES without the indigenous inclusions from secondary metallurgy units.

casting personnel has little to no control over inclusions of steel. the pic above speaks about the critical responsibility that lies with the LF personnel.

further more, the mild red color of SES in the second pic indicates this tundish was just taken out of casting hence the SES is still red hot; the SES in first pic is cold and black that indicates that strand has been closed much earlier.