pa1778data.pdf
pa1778data.pdf
pa1778data.pdf
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U.S. STEEL DUQUESNE WORKS<br />
HAER No. PA-115<br />
(Page 187)<br />
for a specified period of time and air cooling. This method of<br />
annealing makes the steel more adaptable to machining and cold<br />
shearing, because less scaling or warping results due to the<br />
lower temperature reached in heating.<br />
Normalizing consists of heating the steel to 100° above its<br />
critical range, holding at this temperature, and cooling in still<br />
air at ordinary temperatures. Commercially, normalizing produces<br />
a uniform physical structure by removing the irregularities<br />
produced by the excessively high or low rolling or forging<br />
temperatures.<br />
Quenching and tempering consists of heating steel to a point<br />
above its critical temperature and cooling it rapidly by<br />
quenching it in a cooling medium such as water, oil, or brine.<br />
Because this operation produces an extreme hardness or<br />
brittleness in the steel it must be followed by tempering.<br />
Tempering consists of re-heating the steel to a point below its<br />
critical temperature for the purpose of regulating its hardness<br />
or brittleness, toughening it, or releasing stresses. These two<br />
operations (i.e. quenching and tempering) are designed to<br />
increase the hardness and the toughness of steel beyond that<br />
which can be achieved by other heat treatment methods.<br />
Constructed by the American Bridge Company with funds from<br />
the Defense Plant Corporation, the original heat treatment plant<br />
at the Duquesne Works was housed within a T-shaped building<br />
consisting of a transfer bay which was laid out on an east-west<br />
axis, forming the cross-member of the T, and a production bay,<br />
running in a north-south direction. The major pieces of<br />
equipment making up the original heat treatment plant consisted<br />
of Car Bottom Furnaces Nos. 1-5, and the Continuous Electric<br />
Heat Treating Line.<br />
The car bottom furnaces were used in all three major heat<br />
treating processes. In the quench and temper process, two car<br />
bottom furnaces had to be used in tandem. After the bars had<br />
been heated to the proper point above the critical temperature<br />
and held for the requisite time, they were quenched in a quench<br />
tank located in the transfer bay and immediately put into a<br />
tempering furnace which had already been brought up to the proper<br />
temperature. The bars would remain in the furnace for the<br />
requisite amount of time.<br />
Continuous electric heat treating was done in specific<br />
periods of time. Steel bars remained in the different furnaces<br />
for the same length of time. The charge was moved into the first<br />
or pre-heat furnace and held at 1200°F for a period of from<br />
twenty to ninety minutes, depending upon the size of the bar. At