Every ingot, when cast, contains within itself a considerably larger
store of heat than is necessary for the rolling operation. Some of this
heat is, of course, lost by passing into the mould, some is lost by
radiation before the ingot enters into the soaking pit, and some is lost
after it enters, by being conducted away by the brickwork; but in the
ordinary course of working, when there is no undue loss of time in
transferring the ingots, after allowing for this loss, there remains a
surplus, which goes into the brickwork of the soaking pits, so that this
surplus of heat from successive ingots tends continually to keep the
pits at the intense heat of the ingot itself. Thus, occasionally it
happens that inadvertently an ingot is delayed so long on its way to the
pit as to arrive there somewhat short of heat, its temperature will be
raised by heat from the walls of the pit itself; the refractory mass
wherein the pit is formed, in fact, acting as an accumulator of heat,
giving and taking heat as required to carry on the operation in a
continuous and practical manner.

[Illustration: GJERS' SOAKING PITS FOR STEEL INGOTS.]

During the soaking operation a quantity of gas exudes from the ingot and
fills the pit, thus entirely excluding atmospheric air from entering;
this is seen escaping round the lid, and when the lid is removed
combustion takes place.

It will be seen by analyses given hereinafter that this gas is entirely
composed of hydrogen, nitrogen, and carbonic oxide, so that the ingots
soak in a perfectly non-oxidizing medium. Hence loss of steel by
oxidation does not take place, and consequently the great loss of
yield which always occurs in the ordinary heating furnace is entirely
obviated.