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Open die forging of shafts consists of manipulating the stock
and progressively forging the component to shape. Turning on
a lathe brings the shaft to near-net shape.
Open die forging of disc shapes involves progressive upsetting/forging
to reach desired dimensions. Pierced discs are often used as
preforms for saddle/mandrel rings and hollow forgings.
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Forging Terms and Definitions
From Cold working to Flashless forging
Courtesy of Forging Industry Association
Cold working: imparting plastic deformation to a metal
or alloy at a temperature below recrystallization to produce
hardness and strength increases via strain hardening.
Controlled cooling of forgings is used to attain required properties
and/or corresponding microstructural phase changes; applies to
heat-treatable steels (e.g., quenching) and to microalloyed steels,
which require no heat treatment, but only controlled cooling
to attain final properties.
Conventional forging: one that, by design, requires a
specified amount of finish (or machining) to reach the final
dimensional requirements.
Counterblow forging: one made by equipment incorporating two opposed rams, which simultaneously strike repeated blows on the workpiece.
Cross forging: the practice of working stock in one or
more directions to make resultant properties more isotropic (equal
in three directions) - e.g., by upsetting and redrawing the material.
Directional properties: refers to the inherent directionality
within a forging such that properties are optimally oriented
to do the most good under in-service conditions. Typically, maximum
strength is oriented along the axis that will experience the
highest loads.
Disc: "pancake" shaped forging (flat with a
round cross-section); e.g., a blank for gears, rings and flanged
hubs.
Draft: the necessary taper on the side of a forging to
allow removal from the dies; also applies to the die impression.
Commonly expressed in degrees as the draft angle.
Draftless forging: a forging with zero draft on vertical
walls.
Drawing: (1) reducing the cross-section of forging stock
while simultaneously increasing the length; (2) in heat treating,
the same as tempering.
Drop forging: one produced by hammering metal in a drop
hammer between impression dies.
Extrusion: forcing metal through a die orifice in the
same direction as the applied force (forward extrusion) or in
the opposite direction (backward extrusion).
Finish: (1) the material remaining after forging that
is machined away to produce the final part; (2) the surface condition
of a forging after machining.
Finish all over (F.A.O.): designates that forgings be
made sufficiently larger than dimensions shown to permit machining
on all surfaces to given sizes.
Finish allowance: amount of stock left on the surface
of a forging to be removed by subsequent machining.
Flash: excess metal that extends out from the body of
the forging to ensure complete filling of the finishing impressions.
Flashless forging: "true" closed die forging
in which metal deformed in a die cavity permits virtually no
excess metal to escape.
Continue Terms and Definitions
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