SUMMARY
Each metal or alloy has properties, qualities, or characteristics
that make it desirable for a particular use.
Undesirable qualities
are toned down or compensated for by enhancing the desirable ones.
This is done with alloys and metal processing.
Hardness is a metal's characteristic to resist penetration, cutting,
or distortion.
This quality can be enhanced by alloying, heat
treatment, and cold working. Brittleness in a metal causes cracking
or breaking under stress.
Metal that can be shaped by hammering,
rolling, or pressing is malleable.
Ductility permits a metal to be
drawn, bent, or twisted into various permanent shapes without
breaking.
This is a desirable quality in metal used for tubing or
wire.
Elasticity allows metal to return to its original shape when
the force causing the change in shape is removed.
Metal that
conducts heat or electricity is conductive. Density is the mass per
unit volume of a substance, and the preferred unit of volume
expression is the cubic inch.
Contraction and expansion are the
qualities that describe a substance's reaction when heated or cooled.
Strength is the measure of a metal's ability to hold loads or
withstand an applied load.
Toughness measures a metal's ability to
withstand tearing, shearing, or stretching stresses.
Stress,
measured in pounds per square inch (psi), is the force or forces
placed upon a metal, substance, or body.
The different ways that
stress forces can be applied are tension, compression, torsion,
bending, and shear.
Tension pulls or stretches a material, and
resistance to tension is tensile strength.
Compression describes a
substance's decrease in volume under pressure. Torsion is the force
that produces a twisting motion. Bending is a combination of tension
and compression forces. Shear is a cutting force.
PART C:
METAL-WORKING PROCESSES
GENERAL
Man's search for tools and better materials to make them from has led
him from the random use of pieces of wood, bone, and stone through
the Bronze and Iron Ages to the Industrial Age. Along the way, man
discovered many metal-working processes and uses for the finished
metals.
One of the earliest processes discovered was alloying copper with
tin.
This produced bronze and ushered in the Bronze Age.
Practicable and economical ways to smelt iron ore and produce usable
iron brought man into the Iron Age. Step by step, the way led to the
Industrial Age.
We now have many ways to process metal for
particular uses.
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