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One of many open die forging options, hollow forging starts
with a punched or pierced disc on a tapered draw bar. Progressive
reduction of the outside diameter increases the overall length
of the sleeve, while the inside diameter remains constant.
Open die forging of rings starts with a preform on saddle/mandrel.
Progressive reduction of the wall thickness to increase the diameter
achieves the required dimensions. Subsequent machining then delivers
the near-net shape.
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Forging Terms and Definitions
From Flow lines to Isothermal forging
Courtesy of Forging Industry Association
Flow lines: patterns that reveal how the grain structure
follows the direction of working in a forging.
Forgeability: relative ability of a material to deform
without rupture.
Forging reduction: ratio of the cross-sectional area before
and after forging; sometimes refers to percentage reduction in
thickness.
Forging stock: wrought rod, bar, etc. used as the raw
material or stock in forging.
Free-machining-steel forgings: those made from steels
with special alloying-element additions to facilitate machining.
Grain flow: fiberlike lines that show (via macroscopic
etching) the orientation of the microstructural grain pattern
of forgings achieved by working during forging processes. Optimizing
grain flow orientation maximizes mechanical properties.
Hammer forging: one produced on a forging hammer, usually
between impression dies but sometimes flat dies; the process
of forging in a drop hammer (see drop forging).
Hand forging: one made by manually controlled manipulation
in a press without impression dies, usually between flat dies
with progressive forging of the workpiece; also referred to as
flat-die forging.
Heat treatment: heating or cooling operations, sometimes
isothermal, to produce desired properties in forgings.
High-energy-rate forging: forgings made on equipment that
utilizes very high ram velocities.
Hog-out: product machined from bar, plate, slab, etc.
Hollow forging: a cylindrical open die forging, e.g.,
thick-walled tubes or rings.
Hot-die forging: a process in which dies are heated close
to the forging temperature of the alloy being forged/ used for
difficult-to-forge alloys.
Hot forging: same as hot working - plastically deforming
an alloy at a temperature above its recrystallization point,
i.e., high enough to avoid strain hardening.
Hub: a boss in the center of a forging that forms an integral
part of the body.
Impact extrusion: a reverse extrusion process in which
metal is displaced backwards between a punch and a die to form
a hollow part.
Impression die forging: one formed to shape and size in
die cavities or impressions; also commonly referred to as closed
die forging.
Isothermal forging: is most commonly conducted at about
2000 degrees F under a controlled atmosphere or vacuum to prevent
oxidation while forging superalloys.
Continue Terms and Definitions
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