CISX 500, a depressed centre flat car.

[doctorwayne]

Yes, it does make sense to some degree, but the size of the ingot is still puzzling me. The steel company at which I worked also produced armour plate and the ingots were similar in shape, but less than 30 tons. I'd estimate that we produced at least two dozen grades of steel suitable for use as armour plate, the particular grade dependent upon the particular use and the particular customer - the U.S. military was the biggest customer of those grades from our company. This type of steel, in ingot or slab form at least, is very sensitive to sudden changes in temperature. For that reason, there were special procedures (time constraints) for stripping the ingots from their moulds and for re-heating ingots for rolling (soaking pit charging temperatures and graduated temperature increases dependent on the temperature of the steel at charging). Rolling temperature, as I recall, was about 2400°F, which is 50°-100°F hotter than most grades. Much of what we rolled was not put though the hot scarfer (a machine with adjustable torch heads through which a slab would pass, the torches playing on the entire circumference of the slab as it moved at slow speed along the roller line. These torches burned natural gas with oxygen, and were used to remove surface imperfections). Most of these ingots were rolled to thicknesses beyond the capacity of the crop shear, which could handle slabs up to 500 sq. in. in cross-section, so most of these ingots left our mill as one-piece "blooms" (semi-finished slabs).
Once rolled, the blooms were stacked, then placed under steel covers lined with firebricks. When they reached a specific temperature, they were shipped to the plate mill for re-heating and rolling into plate, again using procedures similar to those outlined for ingots. The chemical make-up of the steel, coupled with the heating and cooling cycles, and the rolling operations all contributed to the durability of the resultant plate.

Wayne