03-12-2017, 12:09 PM
Great-looking results, Bear! 
You're right about larger ingots retaining heat longer, Mark, but the longer an ingot of this type of steel was allowed to cool, the longer and more involved was the practice to re-heat it. Usually, a cold ingot (not cold in the usual sense of the word, but likely under 500°F) would be placed in a cooled soaking pit (similar definition of "cool"), and the cover left off of the pit for a specified time period related to the time the ingot was stripped (had its mould removed or was removed from the mould). After that, the pit would be closed, but the burner not started until another specified time had elapsed. When firing of the pit began, the BTU input would be closely monitored, and the process was usually in steps rather than a continuous heating to rolling temperature. So heat to a certain temperature, then allow the entire ingot to soak to that temperature, then heat to the next step, and so-on.
While steels like this are extremely durable once they've gone through the entire manufacturing process, they can be very fragile at various points in that process.
I recall one incident where we had a heat of such steel coming to our mill,along with with a couple of other heats of more common grades. The other heats had been stripped first, so were cooler than the special one, but still visibly orange in their centres. The specialty steel, out of the stripper building last would be first into the mill and was destined to go into two somewhat separated soaking pits at the north end of the mill, while the other, cooler, grades needed to be spotted elsewhere. As the locomotive was pulling the two cooler heats from the stripper, the switchman 'phoned: "Hey pal, whereya gonna want this stuff spotted?" "Gimme three buggies at 18 row and the balance of that one at 14 , then 4 buggies at 11, 4 at 8, and the rest at 1." I replied. As I spoke, I was looking out the open side of the mill, to the stripper where the crane was removing the last couple of moulds from the heat.
I turned away to attend to something else, and when I looked again, the switchman, not wanting to get cooked while making that first cut, had a firehose trained on the two ingots on the adjacent buggies where the first cut needed to be made.
As the water hit the ingots, the thermal shock caused the surface to begin spalling off, almost instantly turning them into two very expensive pieces of scrap! 
I never did hear what became of him (he wasn't, as I recall, one of the regular switchmen...which might explain his actions).
Wayne
Mr Fixit Wrote:.....As I understand it, a larger ingot would retain it's heat longer following its pouring and then during transit between one plant and the next and, so reduce the amount of "soaking" time and energy required to bring it back up to heat prior to rolling at the next plant.
You're right about larger ingots retaining heat longer, Mark, but the longer an ingot of this type of steel was allowed to cool, the longer and more involved was the practice to re-heat it. Usually, a cold ingot (not cold in the usual sense of the word, but likely under 500°F) would be placed in a cooled soaking pit (similar definition of "cool"), and the cover left off of the pit for a specified time period related to the time the ingot was stripped (had its mould removed or was removed from the mould). After that, the pit would be closed, but the burner not started until another specified time had elapsed. When firing of the pit began, the BTU input would be closely monitored, and the process was usually in steps rather than a continuous heating to rolling temperature. So heat to a certain temperature, then allow the entire ingot to soak to that temperature, then heat to the next step, and so-on.
While steels like this are extremely durable once they've gone through the entire manufacturing process, they can be very fragile at various points in that process.
I recall one incident where we had a heat of such steel coming to our mill,along with with a couple of other heats of more common grades. The other heats had been stripped first, so were cooler than the special one, but still visibly orange in their centres. The specialty steel, out of the stripper building last would be first into the mill and was destined to go into two somewhat separated soaking pits at the north end of the mill, while the other, cooler, grades needed to be spotted elsewhere. As the locomotive was pulling the two cooler heats from the stripper, the switchman 'phoned: "Hey pal, whereya gonna want this stuff spotted?" "Gimme three buggies at 18 row and the balance of that one at 14 , then 4 buggies at 11, 4 at 8, and the rest at 1." I replied. As I spoke, I was looking out the open side of the mill, to the stripper where the crane was removing the last couple of moulds from the heat.
I turned away to attend to something else, and when I looked again, the switchman, not wanting to get cooked while making that first cut, had a firehose trained on the two ingots on the adjacent buggies where the first cut needed to be made.
As the water hit the ingots, the thermal shock caused the surface to begin spalling off, almost instantly turning them into two very expensive pieces of scrap! I never did hear what became of him (he wasn't, as I recall, one of the regular switchmen...which might explain his actions).
Wayne