Quality
Control - All aspects of the control of the spraying process
including the surface preparation, spraying, control of thickness
deposited and the oxide and porosity levels, surface finish and
NDE checks as specified.
Quarter
hard – A temper
of nonferrous alloys and some ferrous alloys characterized by
tensile strength about midway between that of dead
soft and half
hard tempers.
Quench-age
embrittlement – of low-carbon steels resulting from precipitation
of solute carbons at existing dislocations and from precipitation
hardening of the steel caused by differences in ferrite at different
temperatures. Quench-age embrittlement usually is caused by rapid
cooling of the steel from temperatures slightly below embrittlement
Ac1 (the temperature at which austenite begins to form) and can
be minimized by quenching from lower temperatures.
Quench
aging – Aging induced by rapid cooling after solution
heat treatment.
Quench
annealing – Annealing an austenitic ferrous alloy by solution
heat treatment followed by rapid quenching.
Quench
Crack - A crack resulting from thermal stress induced during
rapid cooling or quenching, or from stresses induced by delayed
transformations some time after the article has been fully quenched.
Quench
cracking – Fracture of a metal during quenching from elevated
temperature. Most frequently observed in hardened carbon steel,
alloy steel, or tool steel parts of high hardness and low toughness.
Cracks often emanate from fillets, holes, corners, or other stress
raisers and result from high stresses due to the volume changes
accompanying transformation to martensite.
Quench
hardening – (1) Hardening suitable alpha-beta alloys (most
often certain copper to titanium alloys) by solution treating
and quenching to develop a martensitic-like structure. (2) In
ferrous alloys, hardening by austenitizing and then cooling at
a rate such that a substantial amount of austenite transforms
to martensite.
Quenching
– Rapid cooling. When applicable, the following more specific
terms should be used: brine
quenching, caustic
quenching, cold
die quenching, forced-air
quenching, intense
quenching, oil
quenching, press
quenching, spray
quenching, direct
quenching, fog
quenching, hot
quenching, interrupted
quenching, and water
quenching.
Racking
– A term used to describe the placing of parts to be heat treated
on a rack or tray. This is done to keep parts in a proper position
to avoid heat-related distortions and to keep parts separated.
See fixturing.
Recalescence
– A phenomenon, associated with the transformation of gamma iron
to alpha iron on cooling (supercooling) of iron or steel, revealed
by the brightening (reglowing) of the metal surface owing to the
sudden increase in temperature caused by the fast liberation of
the latent heat of transformation. Contrast with decalescence.
Recarburize
– (1) To increase the carbon content of molten cast iron or steel
by adding carbonaceous material, high-carbon pig iron, or a high-carbon
alloy. (2) To carburize a metal part to return surface carbon
lost in processing; also known as carbon
restoration.
Recovery
– Reduction or removal of work-hardening effects, without motion
of large-angle grain boundaries.
Recrystallization
– (1) The formation of a new, strain-free grain structure from
that existing in cold-worked metal, usually accomplished by heating.
(2) The change from one crystal structure to another, as occurs
on heating or cooling through a critical temperature.
Recrystallization
annealing – Annealing cold-worked metal to produce a new grain
structure without phase change.
Recrystallization
temperature – The approximate minimum temperature at which
complete recrystallization of a cold-worked metal occurs within
a specified time.
Recuperator
– Equipment for transferring heat from gaseous products of combustion
to incoming air or fuel. The incoming material passes through
pipes surrounded by a chamber through which the outgoing gases
pass.
Reducing
Agent - A substance that causes reduction, thereby itself
becoming oxidized.
Reducing
flame – A gas flame produced with excess fuel in the inner
flame.
Reduction
- A reaction in which electrons are added to the reactant. More
specifically, the addition of hydrogen or the abstraction of oxygen.
Reduction
of area – (1) Commonly, the difference, expressed as a percentage
of original area, between the original cross-sectional area of
a tensile test specimen and the minimum cross-sectional area measured
after complete separation. (2) The difference, expressed as a
percentage of original area, between original cross-sectional
area and that after straining of the specimen.
Refractory
– (1) A material of very high melting point with properties that
make it suitable for such uses as furnace linings and kiln construction.
(2) The quality of resisting heat.
Regenerator
– Same as recuperator except the
gaseous products of combustion heat brick checkerwork in a chamber
connected to the exhaust side of the furnace while the incoming
air and fuel are being heated by the brick checkerwork in a second
chamber, connected to the entrance side. At intervals, the gas
flow is reversed so that incoming air and fuel contact hot checkerwork
while that in the second chamber is being reheated by exhaust
gases.
Residual
stress – An internal stress not depending on external forces
resulting from such factors as cold working, phase changes, or
temperature gradients.
Resin
- A synthetic or naturally occurring polymer.
Retort
– A vessel used for distillation of volatile materials, as in
separation of some metals and in destructive distillation of coal.
Reverberatory
furnace – A furnace with a shallow hearth, usually nonregenerative,
having a roof that deflects the flame and radiates heat toward
the hearth or the surface of the charge.
RFI Shielding
- Thermal spray coatings of electrically conductive metals such
as zinc, aluminum and copper are used on non-conducting composite
casing materials to shield sensitive electronic devices from radio
frequency electromagnetic interference.
Rhodium
plating - The electrodeposition of rhodium for oxidation resistance
combined with surface hardness.
Rimmed steel - A low carbon steel having enough iron oxide
to give a continuous evolution of carbon monoxide during solidification
giving a rim of material virtually free of voids.
Rockwell hardness test – An indentation
hardness test based on the depth of penetration of a specified
penetrator into the specimen under certain arbitrarily fixed conditions.
Rotary
retort furnace – A continuous-type furnace in which the work
advances by means of an internal spiral, which gives good control
of the retention time within the heated chamber.
Runout
- A casting defect caused by incomplete filling of the mold due
to molten metal draining or leaking out of some part of the mold
cavity during pouring; escape of molten metal from a furnace,
mold or melting crucible.
Rutherford
Backscattering Spectrometry (RBS) - A relevant ion beam technique
for surface composition analysis (analyzed depth: up to 1 micrometer).
It is widely used in thin film science.
