Metal Forming and Pressworking Review

Vocabulary definitions derived from lecture review questions covering metal forming, rolling, extrusion, forging, wire drawing, and pressworking processes.

Metal Forming

Plastic deformation processes performed on ductile and malleable metals and alloys.

Bloom

A hot-rolled ingot with a square cross-sectional area produced above $225\,\text{cm}^2$.

Slab

A hot-rolled ingot with a cross-sectional area greater than $100\,\text{cm}^2$.

Sheet

A rolled product having a thickness less than $6\,\text{mm}$.

A rolled product having a thickness less than $6\,\text{mm}$ and a width less than $300\,\text{mm}$.

Strip

Hot Working Processes

Metal forming processes carried out at temperatures above the re-crystallization temperature.

Re-crystallization Temperature (Metal Alloys)

The re-crystallization temperature for metal alloys, which is $\frac{1}{2}$ of their melting temperature.

Re-crystallization Temperature (Pure Metals)

The re-crystallization temperature for pure metals, which is $\frac{1}{3}$ of their melting temperature.

Lead (Re-crystallization)

A metal whose re-crystallization temperature is room temperature.

Seamless Tubing

The forming process in which tubes are produced without a joint.

Extrusion

A simple compressive metal forming process used to produce structural shapes, rails, frames, doors, and windows.

Isothermal Forming

A metal forming process in which pre-heating of the tools is performed.

Friction in Metal Forming

An interaction that causes defects, increased force, and retarded work flow in metal forming operations.

Sticking

The tendency of two surfaces in relative motion to adhere to each other rather than slide, yielding a coefficient of friction of approximately $0.7$ in rolling.

Annealing

An operation used to interrupt the rolling sequence in order to prevent material fracture.

Three-High Rolling Mill

A rolling mill setup where the middle roller is rotated by friction.

Four-High Rolling Mill

A rolling mill configuration generally used for sheet rolling with reduced power requirements.

Cluster Rolling Mill

A rolling mill used for the cold rolling of thin sheets of high-strength metal.

Continuous Rolling Mill

A rolling mill system also known as a Tandem mill.

Planetary Rolling Mill

A rolling mill used to reduce slabs to coiled hot-rolled strips in a single pass.

Universal Rolling Mill

A mill with two pairs of rollers whose axes are perpendicular to each other, used for beams and I-sections that require finished edges.

Skew Rolling Mill

A specialized rolling mill used to produce steel balls for ball bearings.

Transverse Rolling Mills

Rolling mills also referred to as Roll Forging Mills.

Ring Rolling Mill

A rolling mill in which a donut-shaped workpiece is placed between rollers.

Edge Cracks

A rolling defect caused by poor material ductility at the rolling temperature.

Alligatoring

A rolling defect caused by non-uniform material deformation during rolling.

Neutral Point

The point along roll contact where strip velocity equals roll velocity; also known as the no-slip point.

Direct and Hydrostatic Extrusion

Extrusion types where the direction of movement of both the ram and work material is the same.

Impact Extrusion

An extrusion process used to produce collapsible tubes such as toothpaste tubes.

Hydrostatic Extrusion

An extrusion process where fluid pressure is applied to deform the metal.

Center Burst

An extrusion defect caused by high die angle, low extrusion ratio, or impurities; also called center cracking, arrow head fracture, or chevron cracking.

Fishtailing

An extrusion defect characterized by the formation of a sink hole in the end of a billet.

Cemented Carbide

A material used for cold extrusion dies when long die life, dimensional control, and high production rates are required.

Barreling Effect

A common deformation defect encountered in open-die forging.

Tool Steel

The standard material used to make forging dies.

Hammer Forging

A forging method that requires multiple impact blows to shape the material.

Cold Heading & Upset Forging

Forging operations extensively used for the production of bolt and screw heads.

Swaging & Radial Forging

Processes used to reduce the diameter of a tube or rod at the end to form a tapered section.

Orbital Forging

A forging method in which one of the dies is tilted to a preset angle.

Isothermal Forging

A specialized forging process used to eliminate processing problems in superalloys and titanium.

Sizing

A cold working process used to accurately establish dimensional tolerances.

Coining

A cold working squeezing process used to produce very fine and intricate surface details.

Mandrel

A component in metal spinning that serves as a support structure for the workpiece.

Wire Drawing

A cold working process similar to extrusion used for making wheel spokes, with a maximum theoretical single-pass reduction of $63\%$.

Diamond

The die material used for fine wire drawing operations.

Tube Drawing & Tube Sinking

Operations used to reduce the diameter or wall thickness of tubes.

Deep Drawing

A sheet metal press forming operation that produces vessel-shaped or cup-like cylindrical parts.

Earing

A deep drawing defect resulting in cup walls with uneven peaks and valleys.

Tearing

A deep drawing defect resulting in a crack formed in the cup near its base.

Spring Back

An elastic recovery distortion in bending processes, compensated for by over-bending or bottoming.

Edge Bending

A bending operation that employs cantilever loading.

V-Bending

The most common sheet metal bending method.

Stretch Forming

A process used to manufacture large contoured sheet components such as aircraft wing panels, typically using vertically oriented presses.

Piercing

A sheet metal cutting operation used to make required holes.

Lancing

A sheet metal cutting operation in which a hole is partially cut and one side is bent down.

Nibbling

A press cutting operation utilized as an alternative or substitute to blanking.

Stripper

A plate used to remove the sheet metal from a cutting or non-cutting punch.

Knockout

The mechanism used to eject a formed or cut workpiece from the die.

Center of Pressure

An imaginary point in the blank at which the resultant shear force acts.

Clearance

The space provided between die and punch in press working, which is increased when working with hard materials.

Penetration

The depth to which the punch enters the sheet before shear fracture occurs.

Shear (Punch/Die)

An angular bevel provided on a punch or die to reduce required cutting forces in press working.