Steel Forging : One made from a steel containing
additional alloying elements other than carbon
(e.g.. Ni, Cr, Mo) to enhance physical and
mechanical properties and/or heat-treat
Bar : A section hot rolled from a billet to a
round, square, rectangular, hexagonal or other
shape with a cross-section less than 16 sq. in.
Billet : A semi finished section (width <2X
thickness), hot rolled from a metal ingot,
generally having a cross-section ranging from 16
to 64 sq. in. Also applies to a hot-worked
forged, rolled or extruded round or square.
Blank : Raw material or forging stock from
which a forging is made.
Bloom : Same as a billet, but with a
cross-sectional area greater than 36 sq. in.
Blocker-type forging : One with the general
shape of the final configuration, but featuring
a generous finish allowance, large radii, etc.
Carbon steel forging : One made from a steel
whose major alloying element, carbon, produces
the resultant properties and hardness.
Close-tolerance forging : One held to
closer-than-conventional dimensional tolerances.
Closed die forging : See impression die
Coining : A post-forging process - on hot or
cold parts - to attain closer tolerances or
Cold-coined forging : One that is re-struck
cold to improve selected tolerances or reduce a
specific section thickness.
Cold forging : Various forging processes
conducted at or near ambient temperatures to
produce metal components to close tolerances and
net shape. These include bending, cold drawing,
cold heading, coining extrusion (forward or
backward), punching, thread rolling and others.
Cold heading : Plastically deforming metal at
ambient temperatures to increase the
cross-sectional area of the stock (either solid
bar or tubing) at one or more points along the
Cold working : Imparting plastic deformation
to a metal or alloy at a temperature below re-crystallization to produce hardness and
strength increases via strain hardening.
Conventional forging : One that, by design,
requires a specified amount of finish (or
machining) to reach the final dimensional
Counterblow forging : One made by equipment
incorporating two opposed rams, which
simultaneously strike repeated blows on the work
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
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.
Draft Less Forging : A forging with zero
draft on vertical walls.
Drawing : (1) reducing the cross-section of
forging stock while simultaneously increasing
(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
(2) The surface condition of a forging after
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
Flash : Excess metal that extends out from
the body of the forging to ensure complete
filling of the finishing impressions.
Flash Less Forging : "True" closed die
forging in which metal deformed in a die cavity
permits virtually no excess metal to escape.
Flow Lines : Patterns that reveal how the
grain structure follows the direction of working
in a forging.
Forge ability : 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
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 : Fiber like lines that show (via
macroscopic etching) the orientation of the
micro structural grain pattern of forgings
achieved by working during forging processes.
Optimizing grain flow orientation maximizes
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 work piece; 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
Hog-Out : Product machined from bar, plate,
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
Hot Forging : Same as hot working -
plastically deforming an alloy at a temperature
above its re-crystallization 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 super alloys. From
Machine forging to Rib-and-web forging
Machine Forging (Upsetter Forging) : One made
in a forging machine or upsetter, in which a
horizontally moving die in the ram forces the
alloy into the die cavities.
Mandrel Forging : See saddle/mandrel forging.
Match : Aligning a point in one die half with
the corresponding point in the opposite die
Micro alloyed-Steel Forging : One made from a mircroalloyed steel requiring only controlled
cooling to reach optimum properties, which is in
contrast to conventional quenched-and-tempered
steels that require traditional heat treatments
to achieve the same results.
Microstructure : The microscopic structure of
metals/alloys as seen on a mounted, ground,
polished and etched specimen to reveal grain
size, constituent phases, etc.
Near-Net-Shape Forging : Forging components
as close as possible to the required dimensions
of the finished part.
Open Die Forging : One produced by working
between flat or simply contoured dies by
repetitive strokes and continuous manipulation
of the workpiece; sometimes called hand forging.
Parting Line : The plane that divides the two
die halves used in forging; also applies to the
resulting forging and impression dies.
Piercing : Forming or enlarging a hole via a
tapered or cylindrical punch.
Plastic Deformation : Permanent distortion of
a material without fracturing it.
Plate : A flat, hot-rolled metal or alloy
product whose thickness is much less than its
Precision Forging : Any forging process that
produces parts to closer tolerances than
conventional forging processes.
Perform : Forging operation in which stock is
preformed or shaped to a predetermined size and
contour prior to subsequent die forging
operations; also, ring blanks of a specific
shape for profile (contour) ring rolling.
Press Forging : The shaping of metal between
dies on a mechanical or hydraulic press.
Quenched-And-Tempered Steel Forging : One
that is quenched and tempered to produce the
required hardness and properties; should more
accurately be referred to as
hardened-and-tempered. (Hardening and tempering
are heat treatments that follow austenitizing,
which is usually the first heat treatment
performed on carbon- and alloy-steel forgings.)
Re-striking : A salvage operation following a
primary forging operation rehitting forgings in
the same die in which they were last forged.
Rib : A forged wall or vertical section
generally projecting in a direction parallel to
the ram stroke.
Rib-And-Web Forging : One whose basic
configuration consists of ribs and webs.
Ring Rolling : Forming seamless rings from
pierced discs or thick-walled, ring-shaped
blanks between rolls that control wall
thickness, ring diameter, height and contour.
Roll Forging : Shaping stock between power
driven rolls that incorporate contoured dies;
used for preforming and to produce finished
Rough Machining : An initial machining
operation that leaves adequate stock for
subsequent finish machining.
Saddle/Mandrel Forging : Rolling and forging
a pierced disc over a mandrel to yield a
seamless ring or tube.
Slab : A flat-shaped semi finished, rolled
metal ingot with a width not less than 10 in.
and a cross-sectional area not less than 16 sq.
Standard Tolerance : An established tolerance
for a certain class of product; preferred over
"commercial" or "published" tolerance.
Straightening : A finishing operation for
correcting misalignment in a forging or between
different sections of a forging.
Structural Integrity : Inherent micro
structural soundness of forgings as a
result of achieving 100% density, uniform
metallurgical structure and grain size, as well
as the absence of porosity, segregation, large
inclusions and other non-forged part defects.
Swaging : Reducing the size of forging stock;
alternately, forging in semi-contoured dies to
lengthen a blank.
Target Machining : Incorporating a "target"
(benchmark or gage point) on a forging to
facilitate machining; coined locating surfaces
and drilled centers are commonly used.
Tolerance : The specified permissible
deviation from a specified or nominal dimension;
the permissible variation in the size of a part.
Trimming: Performed hot or cold, the
mechanical shearing of flash or excess material
from a forging by use of a trimmer in a trim
Upset Forging : One made by upset of an
appropriate length of bar, billet or bloom;
working metal to increase the cross-sectional
area of a portion or all of the stock.
Upsetter (Forging Machine) : A machine with
horizontal action used to produce upset
Warm Forging : Forging of steel at
temperatures ranging from about 1000 degrees F
to just below the normal hot working range of
1900 to 2300 degrees F.
Web : A relatively flat, thin portion of a
forging - generally parallel to the forging
plane - that connects ribs and bosses.
Wide Tolerance : Any special tolerance wider
Drawing : (1)
Reducing the cross-section of forging stock
while simultaneously increasing the length;
(2) In heat treating, the same as tempering