Different types of metal and their properties

Design & Technology students often learn about ferrous metals, non-ferrous metals and their alloys. This article summarises the properties, stock forms, and uses of common metals, helping students to revise these topics.

Students selecting different types of metal

Metals are separated into two categories: ferrous and non-ferrous.

Ferrous Metals

Contain iron (“ferrous” comes from the Latin word “ferrum,” meaning iron – this is why the symbol of iron is Fe)
Magnetic (although some alloys, like stainless steel are not always magnetic)
Generally have high tensile strength (hence valuable for construction and manufacturing)
Prone to rust when exposed to oxygen and moisture due to iron content
Become less malleable as more carbon is added

An alloy is a mixture of two or more elements, where at least one of these is a metal. Many alloys are mixtures of 2 or more metals. These are combined to improve appearance or properties.

FERROUS METALS & THEIR ALLOYS

Cast iron

Properties

Uses

2-4% carbon

Hard and resistant to deformation (good under compression)

Cast – poured molten into moulds

Brittle – cannot be bent or forged

Poor tensile strength

Can’t be welded – cracks under heat stress (can be bolted, or joined using brazing – melting brass/bronze rod)

Cookware (i.e. frying pans)

Manhole / drain covers

Lamp posts / fence railings

Gym weights

Wood stoves

Wrought iron is different (has less carbon) and is hammered/forged into shape

Mild steel

Properties

Uses

Most common steel (also known as low-carbon steel)

Cheap and readily available

Versatile – easy to weld, bend, cut

Reasonably tough

Rusts easily (if used outdoors, needs to be galvanised with a zinc coating to prevent rust)

Construction beams

Trusses

Body panels on cars

Nails / bolts

General usage

High-carbon steel

Properties

Uses

Hard and strong tool steel

Costs more than mild steel, but still relatively inexpensive

Difficult to form and cut

More expensive

Brittle – easy to crack

Rusts easily

Knives

Chisels

Files

Hand tools / low-speed tools

Medium carbon steel is useful for things like a woodworking vise etc

High-speed steel

Properties

Uses

An alloy – has added tungsten, molybdenum, chromium, vanadium, and sometimes cobalt, in addition to carbon

Specialised tool steel

Withstands high temperatures without losing hardness, allowing faster cutting speeds

Excellent abrasion resistance, so doesn’t wear out with use

Ground to very sharp, precise cutting edges

Expensive and complex to manufacture

Difficult to repair (so hard it requires specialised tools)

High speed machining and cutting tools

Drill bits

Power saw blades

Stainless steel

Properties

Uses

An alloy – has chromium and nickel added

High resistance to corrosion

Shiny and attractive

Tough and hard

Difficult to cut

More expensive than mild steel

Cutlery (knives / forks etc)

Taps and sinks

Door handles

Screws

Non-ferrous metals

Do not contain iron
Not magnetic
Generally more corrosion resistant than ferrous metals
Often more expensive

NON-FERROUS METALS & THEIR ALLOYS

Aluminium

Properties

Uses

Very light

Malleable and ductile

Durable

Corrosion resistant

Conducts heat and electricity

Not magnetic

Drink and food cans

Baking foil / baking trays

Aircraft bodies

Window frames

Malleable – hammered and pressed into shape without breaking

Ductile – stretches into wire without breaking

Copper

Properties

Uses

Relatively soft and malleable

Ductile

High resistance to corrosion

Great conductor of heat and electricity

Quite expensive

Roofing

Pots

Electrical wiring

Pipes

Copper is a self-finishing material – obtains a green patina with age as oxidises upon exposure to air / moisture

Lead

Properties

Uses

Dense, soft, and very malleable

Excellent corrosion resistance

High toxicity – being phased out due to health risks

Radiation shielding

Historically used in plumbing, roofing nails / roofing flashings

Tin

Properties

Uses

Ductile

Hammered into shape

Corrosion resistant

Magnetic

Coatings for food cans (typically mild steel coated with a thin layer of tin to protect against corrosion – can also be enamel lined for use with food)

Rarely used in pure form as it is very soft

Zinc

Properties

Uses

Corrosion-resistant

Malleable

Long life-span

Recyclable

Self-healing (scratches re-coat naturally)

Relatively expensive

Galvanizing (coating to prevent rust – most common usage)

Pure zinc sheets used as roofing and cladding

Gutters / downpipes

Titanium

Properties

Uses

Extremely high strength-to-weight ratio

Excellent corrosion resistant

Very high melting point

Very durable

Very expensive

Difficult to cut, weld, and fabricate (requires specialised tools)

Coastal marine structures

Roofing / cladding on high-end, prestigious projects (i.e. the Guggenheim museum by architect Frank Gehry)

Nickel-titanium (an alloy made from from nickel and titanium) is the most common shape memory alloy

Tungsten

Properties

Uses

Highest melting point of all metals

Very durable and hard-wearing / scratch resistant

Brittle and difficult to machine

Very heavy

Cutting tools, saw blades, and drill bits

Mining / excavation equipment

Fishing weights

Lightbulb filaments (because of the very high melt point)

Duralumin

Properties

Uses

Alloy comprised of aluminium, copper, magnesium, and manganese

Lightweight and strong (and gets stronger with age = age hardenable)

Nearly as light as pure aluminium but much stronger

Relatively affordable

Easy to machine

Less corrosion-resistant than pure aluminium (needs protective coating)

Aerospace industry

Spacecraft components

High-performance vehicles

Electronic equipment bodies

Portable ladders

Common stock forms of metals

Environmental Considerations

Most metals can be repeatedly recycled without quality loss (unlike plastic and paper which degrade each time)

Steel, aluminium & copper are often recycled

Long lifespan reduces replacement needs

Metals are made from elements in the earth’s crust (non-renewable)

Mining/extraction can result in habitat / landscape destruction

Energy-intensive to shape / process (but recycled metals use far less energy)

Heavy metals can be toxic if released into environment

Are not biodegradable, but corrode/oxidize instead (rust, or develop a patina coating like copper)

Learn about other modern materials that contain metals (including metal foams and super alloys), as well as smart materials (including shape-memory alloys).

Sample examination questions (AS Design & Technology)

Examiner comment: Generally, this was answered well and most candidates could give two reasons why stainless steel had been used for the figure.

Examiner comment: Most candidates were able to name a non-ferrous metal that could be used to make the support for the desk tidy. Frequently seen correct answers included aluminium, brass and copper. Candidates who gave an incorrect answer often named a ferrous metal, such as iron.

Examiner comment: Most candidates gave at least one reason for using aluminium for the parts of the model wind turbine, with ‘lightweight’ being a very popular answer.

Examiner comment: Generally, this was answered well and most candidates could give at least one reason why stainless steel was suitable.

Amiria Gale

Amiria has a Bachelor of Architectural Studies, Bachelor of Architecture (First Class Honours) and a Graduate Diploma of Teaching. She is a CIE Accredited Art & Design and Design & Technology Coursework Assessor. Amiria now teaches Art, Design & Technology at ACG Parnell College.