Manufacturing Knowledge Menu | Forging Manufacturing Services
Forging Manufacturing Review
Courtesy of Forging Industry Association
design information see our Forging Design Review.
Alloy 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 response.
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.
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.
raw material or forging stock from which a forging is made.
same as a
billet, but with a cross-sectional area greater than 36 sq. in.
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.
one held to closer-than-conventional
Closed die forging:
see impression die forging.
a post-forging process
- on hot or cold parts - to attain closer tolerances or improved surfaces.
one that is restruck cold to improve
selected tolerances or reduce a specific section thickness.
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.
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 longitudinal axis.
imparting plastic deformation to a metal or alloy at a temperature below
recrystallization to produce hardness and strength increases via strain hardening.
one that, by design, requires a
specified amount of finish (or machining) to reach the final dimensional requirements.
one made by equipment
incorporating two opposed rams, which simultaneously strike repeated blows on the workpiece.
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.
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.
"pancake" shaped forging (flat with a round cross-section); e.g., a blank for gears, rings and flanged hubs.
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.
a forging with zero draft on vertical walls.
(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
forcing metal through a die orifice in the same direction as the applied force (forward extrusion) or in the
opposite direction (backward extrusion).
(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.
amount of stock left on the surface of a
forging to be removed by subsequent machining.
excess metal that extends out from the body of the forging to ensure complete
filling of the finishing impressions.
"true" closed die forging in which metal deformed in a die cavity
permits virtually no excess metal to escape.
patterns that reveal how the grain structure follows the direction of working in
relative ability of a material to deform without rupture.
ratio of the cross-sectional area before and after forging; sometimes refers to percentage reduction in thickness.
rod, bar, etc. used as the raw material or stock in forging.
those made from steels with special
alloying-element additions to facilitate machining.
fiberlike 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 mechanical properties.
one produced on a forging hammer, usually between impression dies but sometimes flat dies; the process of forging in a drop hammer (see
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.
heating or cooling operations, sometimes
isothermal, to produce desired properties in forgings.
forgings made on equipment that utilizes very high ram
product machined from bar, plate, slab, etc.
a cylindrical open
die forging, e.g., thick-walled tubes or rings.
a process in which dies are heated close to the forging temperature of
the alloy being forged/ used for difficult-to-forge alloys.
same as hot working - plastically deforming an alloy at a
temperature above its recrystallization point, i.e., high enough to avoid strain hardening.
a boss in the center of a forging that
forms an integral part of the body.
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.
is most commonly conducted at about 2000 degrees F under a controlled atmosphere or
vacuum to prevent oxidation while forging superalloys.
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.
see saddle/mandrel forging.
aligning a point in one die half with the corresponding point in the opposite die half.
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.
structure of metals/alloys as seen on a mounted, ground, polished and etched specimen to reveal grain size, constituent phases, etc.
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.
the plane that divides the two die halves used in forging; also applies to the resulting forging and impression dies.
enlarging a hole via a tapered or cylindrical punch.
permanent distortion of a material without fracturing it.
a flat, hot-rolled metal or alloy product whose thickness is much less than its width.
any forging process that
produces parts to closer tolerances than conventional forging processes.
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.
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.)
a salvage operation following a primary forging operation rehitting forgings in the same die in which they were last forged.
forged wall or vertical section generally projecting in a direction parallel to the ram stroke.
one whose basic
configuration consists of ribs and webs.
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 parts.
an initial machining operation that leaves adequate stock for subsequent finish
rolling and forging a pierced disc over a mandrel to yield a seamless ring or tube.
a flat-shaped semifinished, rolled metal ingot with a width not less than 10 in. and a cross-sectional area not less than 16 sq. in.
an established tolerance for a certain class of product; preferred over "commercial" or "published" tolerance.
a finishing operation for correcting misalignment in a forging or between different sections of a forging.
microstructural 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.
reducing the size of forging stock; alternately, forging in semicontoured
dies to lengthen a blank.
incorporating a "target" (benchmark or gage point) on a forging to facilitate
machining; coined locating surfaces and drilled centers are commonly used.
the specified permissible deviation from a specified
or nominal dimension; the permissible variation in the size of a part.
performed hot or cold, the mechanical shearing of flash
or excess material from a forging by use of a trimmer in a trim press.
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):
machine with horizontal action used to produce upset forgings.
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.
a relatively flat, thin portion of a forging -
generally parallel to the forging plane - that connects ribs and bosses.
any special tolerance wider than