Heat treating and inspection of metals Page: 22
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10-12 AIR CORPS
ening operation represents a variable factor in each case, and may be
approximated by reference to table V.
TABLE V.-Soaking period for steels
Thickness of largest section Approximate weight unit Approximate Approximate
of unit (inches) (pounds) time of heating time of holding
Sto 1 Up to 100 _______-----------_
1 to 2__ 100 to 300__ _______ 1%4
2 to 3_ 300 to 500__ _____ 1= 4%
3 to 4 _ 500 to 1,000 2________2% 1
4 to 5 1,000 to 1,500_ 2/4 1
5 to 8 1,500 to 2,000_ ____32 1%
11. Mild carbon steel (SAE 1025).-Mild carbon steel is used
extensively in the untreated condition for minor forgings and low
stressed fittings. This steel responds to heat treatments in thin sec-
tions satisfactorily. The only physical property appreciably affected
in heavier sections by heat treatment is toughness. This steel re-
sponds readily to heat treatment.
a. Annealing.-Annealing and normalizing require a temperature
of between 1,5750 and 1,650 F. The furnace should be brought to not
more than 1,100 F. before the parts are inserted, then increased
gradually to the annealing heat. Holding at this temperature should
be continued for from 20 to 45 minutes depending upon the mass of the
parts. After the heating operation, the parts are removed from the
furnace and allowed to cool in still air.
b. Hardening.-The hardening temperature for mild steel is from
1,575 to 1,650' F. Upon removal from the furnace, the parts should
be quenched in water or brine at 65 F. The ultimate tensile strength
for this material is 55,000 pounds per square inch.
c. Tempering.-Mild carbon steel, or steel containing less than 0.30
percent carbon, does not harden sufficiently to require tempering except
for thin sections.
12. Medium carbon steel (SAE 1035).-Medium carbon steel
possesses good machining properties but is suitable for many small
and medium size foPgings where moderate physical properties are
desired. This material is often referred to as structural steel.
a. Annealing.-The annealing and normalizing procedure for me-
dium carbon steel is practically the same as that for mild steel. The
upper limit of the annealing temperature in this case, however, may
be as high as 1,6750 F.
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United States. War Department. Heat treating and inspection of metals, book, September 10, 1941; Washington D.C.. (digital.library.unt.edu/ark:/67531/metadc96657/m1/24/: accessed April 29, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.