temperature at 450 is necessary to precipitate the
Q6-84.
What is the process of producing a hard case
over a tough core known as?
soluble constituents from solid solution.
Q6-85.
The process of hardening steel by introducing
The annealing of solution heat-treated material
carbon to the heated metal is known by what
should be avoided whenever possible if subsequent
term?
forming and drawing operations are to be formed.
If such operations are not severe, it is generally
Q6-86.
The process of hardening alloy steel by hold-
advantageous to repeat the solution heat treatment
ing it at temperatures below the critical point
and form the material in the freshly quenched con-
in anhydrous ammonia is known by what
dition.
term?
Q6-72.
What is the only metal that cannot be
Q6-87.
The carbon in steel, which exists as particles
hardened by heat-treatment?
of iron carbide, scattered throughout the iron
mixture is known by what term?
Q6-73.
Uneven heating of metal often causes what
actions to occur?
Q6-88.
If the cooling is slow, the carbon particles are
relatively course and few. In what condition
Q6-74.
The slow heating of metal ensures what con-
will this leave the steel?
dition?
Q6-89.
Before steel can be hardened completely, it
Q6-75.
The heating rate for hardened tools and parts
must be heated to a certain point, before it is
should be slower than metals that are in what
rapidly quenched. What is this point called?
condition?
Q6-90.
If you don't have an instrument to determine
Q6-76.
What is the process of holding a metal at a
the temperature of steel being heated, you can
temperature until it is heated throughout and
judge it by what factor?
changes have had time to take place?
Q6-91.
What term describes an aluminum alloy with
Q6-77.
How can you reduce the distortion and
a protective coating of aluminum?
cracking of metal?
Q6-92.
What increases artificially aged alloys' resis-
Q6-78.
The process for rapidly cooling heated metal
tance to corrosion?
is known by what term?
Q6-93.
What is the recommended time interval be-
Q6-79.
Alloy steels are generally hardened by
tween removal from the heat and immersion
cooling with what substance?
during the quenching process?
Q6-80.
The form of heat-treatment used to reduce
Q6-94.
Small aluminum parts are normally quenched
residual stresses, induce softness, and alter
in what substance to ensure good resistance
ductility is known by what term?
to corrosion?
Q6-81.
The process in which an iron-based metal is
Q6-95.
What quenching method is used to quench
allowed to cool at room temperature, in still
large forgings to prevent cracking and mini-
air, after being heated to approximately
mize distortions?
100F is known by what term?
Q6-96.
The process of removing the effects of
Q6-82.
The process of quenching a metal after it is
heat-treatment in alloys is referred to by what
heated to a temperature slightly above the
term?
critical temperature is known by what term?
Q6-97.
It takes a 2-hour soak at 750 to 800F,
Q6-83.
The process by which steel is heated to just
followed by a maximum cooling rate of 50
below critical and held there for a period of
per hour to 500F to remove the effects of a
time, and then cooled with oil, water, or brine
partial or full heat-treatment and obtain what
is known by what term?
condition?
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