FERROUS METALS
Most ferrous metals have a high strength. They are versatile materials.
They conduct heat and electricity. They are easily joined by a variety of
methods, however they are likely to rust unless treated. The more commonly
used examples in school are:
MILD
STEEL
General:
A very useful general purpose material - relatively easy to work with. It
can be surface hardened. Available in a wide range of sizes. These steels
have a high tensile strength, are ductile, tough fairly malleable. It can
only be case hardened. Many uses a general purpose steel - gates,
railings, car bodies etc.
Strengths
: High strength-to-weight ratio; High stiffness-to-weight
ratio; Good strength with high toughness; High stiffness; Very cheap; Easy
to shape; Easy to weld; Easy to recycle.
weaknesses:
High density; Poor electrical and thermal conductivity.
Common applications :
Large structures - bridges, buildings, oil rigs; Car body panels, trains;
Machine tools; Pressure vessels; Food packaging; Nails.
Manufacturing
Information:
Forming
- Die
casting is the most commonly used casting process.; Rolling is important
for structural sections like I-beams; Easily extruded for pipes, tubes,
wire.
Machining
- Readily
machined.
Environmental
Information: Steel production uses a lot of energy, but
less than most metals; Steel is easily recycled - as it is usually
magnetic it is easily sorted from mixed waste. Mild steel rusts easily,
and must be protected by painting, galvanising or other coatings.
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HIGH
CARBON STEEL
General: This is the hardest of all the
carbon steels, it can be heat treated to make it very hard and tough - it
is relatively difficult to work with. Its main uses are for hammers and
cutting tools.
Strengths
: High strength-to-weight ratio; High stiffness-to-weight
ratio; Good strength with high toughness; High stiffness; Very cheap; Easy
to shape; Easy to weld; Easy to recycle.
weaknesses:
High density; Poor electrical and thermal conductivity.
Common applications :
Railway track; Bearings, gears, shafts; Cutting tools; Pressure vessels;
Hand tools (spanners, hammers etc).
Manufacturing
Information:
Forming
- Powder
Metal Forming is most commonly used with high strength alloy steels;
Rolling, extrusion and sheet forming are only used with low alloy (lower
strength) alloys.
Machining
- Readily
machined, but Gets more difficult for the stronger alloys (usually those
with higher alloy content).
Environmental
Information: Steel production uses a lot of energy, but less
than most metals; Steel is easily recycled - as it is usually magnetic it is
easily sorted from mixed waste; Mild steel rusts easily, and must be
protected by painting, galvanising or other coatings.
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STAINLESS
STEEL
General:
A non rusting steel. A strong tough material - hygienic but is harder to
work. Can be highly polished.
Strengths
: High strength-to-weight ratio; High stiffness-to-weight ratio;
Good strength with high toughness; High stiffness; Very cheap; Easy to shape;
Easy to weld; Easy to recycle.
weaknesses:
High density; Poor electrical and thermal conductivity.
Common applications :
Used for sinks, kitchenware, tanks, pipes
and parts of aircraft.
Manufacturing
Information:
Forming
- Sheet
forming.
Machining
- Readily
machined.
Joining
- Suitable for use with most techniques, although not very suitable
for soldering or brazing.
Environmental
Information: Steel production uses a lot of energy.
All steels melt at about 14000C
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NON
FERROUS METALS
They usually have very good working properties. They
are very resistant to corrosion and are good conductors of heat and
electricity. They are usually easily joined by heat. They can be softened
by annealing or hardened by cold working. They have a lower melting point
than ferrous metals. Some common ones include:
ALUMINIUM
General
: A greyish white, soft metal, can easily be cast but is hard
to weld. Has good corrosion resistance, is light, soft, malleable, ductile
and highly conductive to both heat and electricity.
Strengths
: High strength-to-weight ratio, High
stiffness-to-weight ratio, High electrical and thermal conductivity, Easy to
shape, Easy to recycle
weaknesses:
Difficult to arc weld
Common applications :
kitchen utensils, kitchen foil, cans and engine parts, aircraft, boats,
railway coaches, window frames, power cables. Melting point - about 6500C.
Manufacturing
Information:
Forming
- Easy
to use with most metal forming processes, Some difficulties with powder
processing as it tends to oxidise, Very suitable for rolling at all
thicknesses down to foil, Die casting is the most commonly used casting
process, Usually comparatively soft, so readily extruded, Sheet forming is
important use for cans.
Machining
- Relatively
soft, so readily machined.
Joining
- Suitable
for use with most techniques, although difficult to arc-weld and an inert
gas is needed.
Environmental
Information: Aluminium production uses lots of energy.
Aluminium is easily recycled - this only uses 1% of the energy needed to
produce the metal from ore. Aluminium use in cars is growing rapidly - low
weight means good fuel economy and low emissions metal.
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BRASS
General
: Very attractive yellow metal - machines well and is easy to
join. Corrosion resistant, but tarnishes quickly, harder than copper.
Casts well, easily machined and easily joined by hard or soft soldering.
Good heat and electrical conductivity. Melting point - about 9800C.
Strengths
: Reasonable
strength , Corrosion resistant, Easy to shape
weaknesses:
Quite expensive
Common applications :
electrical components, tap castings, plumbing components, ornaments,
propellors.
Manufacturing
Information:
Forming
-
Fairly
easily extruded because it is quite soft; Difficult to roll, forge or use in
sheet form; Not used much with powder metallurgy as it tends to oxidise.
Machining
- Relatively
easily machined.
Joining
- Soldering and brazing are the main methods. Environmental
Information: Production uses quite a lot of energy; easy to
recycle, but the amount recycled is small.
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COPPER
General
: Red/pink in colour. Malleable, ductile, tough, corrosion
resistant, very good heat and electrical conductivity. Very soft, easy to
form and join by hard or soft soldering, but work hardens quickly and
needs frequent annealing. Can be enamelled easily. Melting point - about
11000C.
Strengths
: High electrical and thermal conductivity;
Corrosion resistant; Easy to shape
weaknesses:
Low strength; Quite expensive.
Common applications
:
electrical wires and components, decorative work, plumbing pipes and
components, printed circuits, roofing, castings.
Manufacturing
Information:
Forming
- Easily
cast; Readily extruded because it is quite soft; Rarely rolled, forged or
used in sheet forming; Not used much with powder metallurgy as it tends to
oxidise
Machining
- Readily
machined..
Joining
- Difficult to arc weld; Soldering is the main method used.
Environmental
Information: Copper production uses quite a lot of energy;
Copper is easy to recycle, but the amount recycled is small and it can be
difficult to retrieve (e.g. most copper wiring has a plastic sleeve).
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TIN
General
: White,
very soft, excellent corrosion resistance in damp conditions. Melting
point - about 2300C.
Strengths
: Corrosion resistant; Easy to cast and form
weaknesses:
Low strength
Common applications
:
Plating for steel (tinplate), alloying with copper to make bronze, soft
solders.
Manufacturing
Information:
Forming
- Easy
to use with most metal forming processes.
Machining
- Relatively
soft, so readily machined.
Joining
- Commonly used as an alloy for solder. Environmental
Information: Production uses quite a lot of energy.
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LEAD
General
:
Bright and shiny when new, but rapidly tarnishes to a dull grey. The
heaviest of the common metals, it is soft, malleable, corrosion resistant
and immune to many chemicals, very easy to work. Melting point - about 3300C.
Strengths
: Low melting point; High density; Corrosion resistant; Easy
to shape.
weaknesses:
Low strength; Low stiffness; High cost; Environmental
concerns (particularly with young children).
Common applications
:
coverings for power and telephone cables, protection against X-rays and
radiation. Soft solders, bearing metals, roof coverings and flashings.
Manufacturing
Information:
Forming
- Most
commonly die cast; Can easily be deformed to shape, e.g. by
forging.
Machining
- Usually
easy to machine, but caution needed because of toxicity
Joining
- Not suitable for arc welding; Commonly used as an alloy for
solder
Environmental
Information: Lead production uses quite a lot of energy,
but the volume in use is small; Lead in paint and petrol is being reduced
or eliminated due to health concerns.
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ZINC
General
: Zinc has a good resistant
to corrosion, low density and low melting point.
Strengths
: Corrosion resistant; Easy to cast.
weaknesses:
Low strength; Difficult to form.
Common applications :
Zinc alloys are used for simple castings of low strength. It is often used
to protect steels from rusting by galvanising
(e.g corrugated sheet, car bodywork and motorway crash barriers).
Manufacturing
Information:
Forming
- Most
commonly die cast; Poor formability, so rarely forged, rolled, extruded or
used in sheet forming; Not used much with powder metallurgy as it tends to
ignite!
Machining
- Usually
easy to machine.
Joining
- Difficult
to arc weld and inert gas required.
Environmental
Information: Zinc production uses quite a lot of energy,
but the volume in use is small.
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NICKEL
ALLOYS
General
: Very hard for non ferrous metals. Attractive grey colour.
Nickel alloys are dense, stiff, strong alloys used primarily for their
strength and corrosion resistance at high temperatures (jet engines). Pure
nickel has moderate strength, like iron, but alloying with Cr, Co, Mo, W
gives the high strength needed in a jet engine. Nickel is also alloyed
with copper to make coins.
Strengths
: High strength at high temperature; High corrosion
resistance; High stiffness; Easy to shape.
weaknesses:
High density.
Common applications :
ideal for jewellery (nickel silver); decorative kitchen utensils; coins
Manufacturing
Information:
Forming
- Not
used in sheet forming; Forging is important for coins and jet engine parts;
Special die casting processes are used for jet engine blades.
Machining
- Usually
easily machined
Joining
- Arc
welding only with inert gas or in vacuum.
Environmental
Information: Nickel production uses quite a lot of energy,
but the volume in use is small.
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SILVER
General : A very expensive but attractive material it is ideal to
fashion into any shape, can be cast and enamelled.
Strengths
: Corrosion resistant; Easy to cast
weaknesses:
Low strength
Common applications :
ideal for jewellery, as a plating for kitchen utensils.
Manufacturing
Information:
Forming
-
All casting and forming processes can be used
Machining
- Usually easy to machine - though because of high cost care
is taken to minimise waste.
Joining
- soldering or ultrasonic welding may be used.
Environmental
Information: mined from rocks containing very small
quantities of the metal - it is therefore an energy intensive metal to
produce. Its recycling value is of course very high.
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GOLD
General
: A very expensive but attractive material it is ideal to
fashion into any shape; used for jewellery due to its natural
appearance, but also its chemical stability - it does not oxidise at room
temperature. In engineering gold is used in small quantities in electronics for
making electrical contacts since it has a very high electrical conductivity, and
does not oxidise
Strengths
: Corrosion resistant; Easy to cast
weaknesses:
Low strength
Common applications :
ideal for jewellery, as a plating for electrical components.
Manufacturing
Information:
Forming
-
All casting and forming processes can be used
Machining
- Usually easy to machine - though because of high cost care
is taken to minimise waste.
Joining
- soldering or ultrasonic welding may be used.
Environmental
Information: mined from rocks containing very small
quantities of the metal - it is therefore an energy intensive metal to
produce. Its recycling value is of course very high.
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