Metals
EdExcel Product Design: Graphics
Metals
• Ferrous
– Steel
• Non-ferrous
– Aluminium
– Tin
• Alloys
– Stainless steel
– duralumin
• Aesthetic
• Functional &
mechanical properties
• Application
• Advantages
• Disadvantages
• For graphic products
& commercial
packaging
Properties
• Ductility (being ductile)
– is a solid material's ability to deform under tensile
(pulling/tension) stress; this is often characterized by the
material's ability to be stretched into a wire.
• Malleability
– is a material's ability to deform under compressive stress; this is
often characterized by the material's ability to form a thin sheet
by hammering or rolling.
• Hardness
– is a measure of how resistant solid matter is to various kinds of
permanent shape change when a force is applied.
• Corrosion resistance
– Is the materials ability to not corrode (or rust). Some metals are
more intrinsically resistant to corrosion than others.
Micro-structure of metals
Metals usually have one or two loose electrons in their
outer electron shell and therefore they are likely to
become easily detached, it is this movement of electrons
which accounts for metals high electrical and thermal
conductivity. This ability for movement also leads metals
to have ductile and malleable properties.
All metals are solid at room temperature (with the
exception of mercury).
When in a solid state the atoms energy is reduced and
they arrange themselves in a regular lattice structure in
the form of small seed crystals or grains, there are 3
possible lattice structures;
•Closed-packed hexagonal (CPH)
•Face-centred cubic (FCC)
•Body-centred cubic (BCC)
CPH
FCC
BCC
Structure
Properties
Examples
CPH
Weak, poor strength to
weight ratio.
Zinc, magnesium
FCC
Ductile, good electrical
conductor.
BCC
Hard, tough.
Gold, copper,
silver, aluminium,
tin
Chromium, steel.
Micro-structure of iron:
Iron changes from BCC lattice to FCC lattice at 9100C and
above 14000C it changes back again. In the FCC form it
absorbs carbon which essential for steel making.
Steel
• Dull grey in colour (brown with corrosion)
• Steel is an alloy of iron and other elements, including
carbon.
• Alloys with a higher than 2.1% carbon are known as cast
iron. Because they are not malleable even when hot, they
can be worked only by casting (pouring metal into a mould)
• Magnetic
• Melting point for steel 800-1500 degrees C.
• Usually the least expensive metal
• Corodes easily
• Hardening & tempering can be used
• Key metals: HSS, mild steel, cast iron, carbon steel
Aluminium
• Appearance ranging from silvery to dull gray
• Aluminium is the most abundant metal, in the
Earth's crust.
• Relatively soft, durable, lightweight, ductile and
malleable metal.
• Does not corrode
• It is non-magnetic.
• Melting point: 660°C
• Comes from bauxite in its raw form.
• Once extracted electrolysis is used for processing
Bauxite is difficult to break down and therefore
electrolysis is needed rather than melting so that it can be
processed (this process requires a great deal of electrical
expenditure).
The bauxite (red-brown solid) - aluminium oxide mixed
with impurities - is extracted from the earth.
It is the most used non-ferrous metal:
Automobiles, aircraft, trucks, railway cars, marine vessels,
bicycles, packaging (cans, foil, etc.), cooking utensils,
watches, street lighting poles, sailing ship masts, walking
poles, outer shells of consumer electronics, also cases for
equipment e.g. photographic equipment.
Tin
•
•
•
•
Is malleable & ductile
Silvery-white metal.
Tin melts at a low temperature of about 232 °C
Tin resists corrosion from water but can be attacked by
acids and alkalis. Tin can be highly polished and is used
as a protective coat for other metals.[4] In this case the
formation of a protective oxide layer is used to prevent
further oxidation.
• Mainly mined in china
• About half of tin produced is used in solder. The rest is
divided between tin plating, tin chemicals, brass and
bronze, and niche uses
Stainless Steel
• Stainless steel does not readily corrode, rust or stain with
water as ordinary steel does.
• Magnetic
• Poor conductor of electricity
• Melting point: 1510°C
• Stainless steels are iron alloys with a minimum of 10.5%
chromium. Other alloying elements are added to enhance
their structure and properties such as formability, strength
and cryogenic toughness. These include metals such as:
• Nickel
• Titanium
• Copper
Duralumin
• Aluminium Alloy - The main alloying constituents are
copper, manganese, and magnesium.
• Strong, hard, lightweight alloy of aluminum, widely
used in aircraft construction,
• After heat treatment and aging, these alloys are
comparable to soft steel in strength.
• Duralumin alloys are relatively soft, ductile, and
workable in the normal state; they may be rolled,
forged, extruded, or drawn into a variety of shapes and
products. Their light weight and consequent high
strength per unit weight compared with steel suit them
for aircraft construction.
• Melting point 650°C
Questions
1. Explain what is meant by the term alloy?
2. Explain in detail the difference between ferrous and
non-ferrous metals.
3. Define the terms ductile, malleable and corrosion
resistant.
4. Suggest a use for:
Mild Steel, stainless steel, Aluminium, Copper, Brass &
Lead
Task
• Log onto the computers
• Create a table:
Wood
Aesthetics
Functional &
mechanical
properties
Advantages
Disadvantages
Steel
Aluminium
Tin
Stainless
steel
Duralumin
For aesthetics get an image of the metal and write a brief descrition.
For properties add things like lightweight or malleable etc
Then put some advantages and disadvantages for each
Print off