pa1778data.pdf

U.S. STEEL DUQUESNE WORKS
HAER No. PA-115
(Page 187)
for a specified period of time and air cooling. This method of
annealing makes the steel more adaptable to machining and cold
shearing, because less scaling or warping results due to the
lower temperature reached in heating.
Normalizing consists of heating the steel to 100° above its
critical range, holding at this temperature, and cooling in still
air at ordinary temperatures. Commercially, normalizing produces
a uniform physical structure by removing the irregularities
produced by the excessively high or low rolling or forging
temperatures.
Quenching and tempering consists of heating steel to a point
above its critical temperature and cooling it rapidly by
quenching it in a cooling medium such as water, oil, or brine.
Because this operation produces an extreme hardness or
brittleness in the steel it must be followed by tempering.
Tempering consists of re-heating the steel to a point below its
critical temperature for the purpose of regulating its hardness
or brittleness, toughening it, or releasing stresses. These two
operations (i.e. quenching and tempering) are designed to
increase the hardness and the toughness of steel beyond that
which can be achieved by other heat treatment methods.
Constructed by the American Bridge Company with funds from
the Defense Plant Corporation, the original heat treatment plant
at the Duquesne Works was housed within a T-shaped building
consisting of a transfer bay which was laid out on an east-west
axis, forming the cross-member of the T, and a production bay,
running in a north-south direction. The major pieces of
equipment making up the original heat treatment plant consisted
of Car Bottom Furnaces Nos. 1-5, and the Continuous Electric
Heat Treating Line.
The car bottom furnaces were used in all three major heat
treating processes. In the quench and temper process, two car
bottom furnaces had to be used in tandem. After the bars had
been heated to the proper point above the critical temperature
and held for the requisite time, they were quenched in a quench
tank located in the transfer bay and immediately put into a
tempering furnace which had already been brought up to the proper
temperature. The bars would remain in the furnace for the
requisite amount of time.
Continuous electric heat treating was done in specific
periods of time. Steel bars remained in the different furnaces
for the same length of time. The charge was moved into the first
or pre-heat furnace and held at 1200°F for a period of from
twenty to ninety minutes, depending upon the size of the bar. At