Metals

Copper Ore

Chalcopyrite

Aluminium Ore

Bauxite

Tin Ore

Cassiterite

Zinc Ore

Zink blende

Properties of Aluminium

Non ferrous - lightweight, ductile, malleable, corrosion resistant, electrical and thermal conductor

Properties of copper

Non ferrous - ductile, malleable, tough, corrosion resistant, electrical and thermal conductor, can be soldered and brazed

Properties of zinc

Non ferrous - low melting point, good corrosion resistance

Properties of silver / gold

Non ferrous - malleable, ductile, corrosion resistant, can be soldered

Properties of titanium

Non ferrous - hard, similar strength to steel but more lightweight, high resistance to corrosion

Properties of tin

Non ferrous - ductile, malleable, low melting point, corrosion resistant

Properties of low carbon steel

Ferrous - ductile, high tensile strength, tough, malleable, poor resistance to corrosion - 0.15 to 0.3% carbon

Properties of medium carbon steel

Ferrous - harder than low carbon steel but less ductile, malleable, tough - 0.3 to 0.7% carbon

Properties of cast iron

Ferrous - hard outer skin but brittle core, good under compression - 3.5% carbon

Properties of stainless steel

Ferrous alloy - tough, hard, corrosion resistant - 18% chrome, 8% nickel

Properties of high speed steel (HSS)

Ferrous alloy - hard, tough, high level of resistance to frictional heat - 18% tungsten, 4% chromium, 1% vanadium, 0.5 to 0.8% carbon

Properties of die steel (tool steel)

Ferrous alloy - hard, tough

Properties of bronze

Non ferrous alloy - tough, corrosion resistant, can be cast - 90% copper, 10% tin

Properties of brass

Non ferrous alloy - corrosion resistant, good electrical and thermal conductor, low melting point, casts well - 65% copper, 35% zinc

Properties of duralumin

Non ferrous alloy - equivalent strength to low carbon steel but more lightweight, ductile, becomes harder as it is worked - 4% copper, 1% magnesium and manganese

Properties of pewter

Non ferrous alloy - malleable, low melting point, casts well - 85 to 99% tin, with the remainder consisting of copper and antimony

Uses of pewter

Tankards, flasks, decorative items and trophies

Uses of duralumin

Aircraft and vehicle parts

Uses of brass

Door fittings, cast valves and taps and ornaments

Uses of bronze

Statues, coins and bearings

Uses of die steel (tool steel)

Blanking punches and dies, extruder dies and fine press tools

Uses of high speed steel (HSS)

Tool blades, drill bits, milling cutters and router bits

Uses of stainless steel

Sinks, kitchenware and cutlery

Uses of cast iron

Disk breaks, machine parts and sheet furniture such as bollards and bins

Uses of medium carbon steel

Springs and gardening tools

Uses of low carbon steel

Nuts, bolts, car bodies and outer panels for white goods

Uses of tin

Soft solder, coatings for food cans, rarely used in its pure form

Uses of titanium

Joint replacements, tooth implants, aircraft and golf clubs

Uses of gold

Jewellery, electronic components and switch components

Uses of silver

Jewellery, cutlery and used for plating other materials

Uses of zinc

Galvanising steel as a protective coating, buckets and intricate die castings

Uses of copper

Electrical wiring, PCB, water pipes and central heating pipes

Uses of aluminium

Drinks cans, aircraft bodies and baking foil

Stock forms of metals

Sheets, plates, bars, tubes and structural (such as H and L beams)

Annealing

Makes hardened metals easier to work with - heated and then slowly cooled to allow for the metal crystals to grow and slowly move into place - can be done in a temperature controlled furnace or in a workshop using a brazing hearth

Case hardening usage

Hardening the surface of steels that have less than 0.4% carbon content - outer casing has greater hardness while the inner core retains the original softer properties - improves wear resistance

Case hardening - Carburising

Changes the chemical composition of the surface of the steel so it can absorb more carbon - placed into a ceramic box packed with carbon and then heated for a predetermined length of time - depth of carbon layer is determined by the length of time the material is exposed to the carbon

Case hardening - Quenching

The hot metal is quenched in water to seal the carbon layer without affecting the properties of the inner core

Hardening

Heating medium and high carbon steels to alter the crystalline structure, holding them at this temperature for a given time and quenching them in water, oil or salt water baths - increases hardness but increases brittleness

Tempering

Process for medium and high carbon steels that have been hardened - metal heated to below the critical point and given time to be air cooled - exact temperature dictates hardness removed - reduction in hardness but an increase in toughness

Tempering colour

The colour seen on the metal that indicates the temperature at which brittleness is removed

Critical point

The temperature at which the atoms of carbon and steel mix freely before bonding together to become a solid

Press forming

Mass manufacture as expensive - sheet metal is clamped over a die of the product - hydraulic press pushes the due into the sheet metal - die is lowered and the pressed component is removed

Spinning

Mass manufacture of products with radial symmetry - former (mandrel) placed into the chuck and the sheet metal blank is placed between the mandrel and the tail stock - roller tool stretched the metal around the mandrel - product is removed and finished

Cupping and deep drawing

Mass or continuous production - pressing blank is clamped over a deep drawing die - hydraulic press moves the deep drawing punch to be in contact with the blank - die pushed into the blank - blank pressed further down to make the cup shape

Difference between cupping and deep drawing

Becomes deep drawing when the depth of the pressing exceeds the diameter of the press blank

Drop forging

Mass manufacture - die is made from cast tool steel with each half attached on the anvil and ram - metal is heated to above its recrystallisation temperature to prevent brittleness - heated metal is placed onto the anvil die - ram is brought down to spread the metal into the dies - product is removed and finished

Wrought iron forging

One off / limited batch production - metal is heated - shaped by tongs and hammering / twisting it

Bending

One off or batch - sheet metal is pressed between the die and punch - pressure is applied to force the metal into the correct shape

Press brake

Industrial machine used to bend metals - has a back gauge to ensure that the metal is in the correct place

Hot rolling

Metal that is heated to above its recrystallisation temperature and pressed between rollers to reduce its thickness

Advantages of hot rolling

Uniform material properties throughout the material, no stresses or deformation that could result in a fault

Disadvantages of hot rolling

Surface is usually coated with carbon deposits that require acid pickling to remove, less tight to the tolerance

Cold pressing

Metal that is heated to below its recrystallisation temperature and pressed between rollers to reduce its thickness

Advantages of cold rolling

Tighter tolerances as no carbon deposits on the surface

Disadvantages of cold rolling

Expensive, can create warping from internal stress

Sand casting

Pattern made as a replica of the product and placed into the bottom box (drag) and surrounded by tightly packed sand - drag is turned around and cope is clamped into position - top half of pattern is placed on top of the top design and wooden stakes are placed near the mould - sand is packed around it - cope and drag are separated and connecting channels are made - placed back together and metal is poured back down them - cooled, removed and finished

Die casting

Steel mould is made and clamped together - metal is poured into mould and allowed to cool (pressure may be applied to force metal in) - cooled, removed and finished

Investment / lost wax casting

One off - replica of product is made from wax - wax model is dipped in clay and fired in kiln (wax melts away) - metal is poured into the mould - clay is broken away once metal has cooled and finished

Low temperature pewter casting

MDF mould is made - mould is sandwiched between two pieces of MDF and clamped - pewter is poured into the mould - cooled, removed and finished

MIG welding

Electric arc is made to create heat which melts the join area - a wire electrode of the same metal also melts to fill the gap between the metals - electrode advances when the trigger is pressed

MIG welding shielding gas

CO2 or argon used to prevent oxidation at the join site, which would prevent the weld from forming properly

TIG welding

Weld metals such as stainless steel and non ferrous metals - same as MIG welding but electrode of tungsten does not melt in the process - separate filler rod used

TIG welding shielding gas

Argon or helium is used to protect the area from oxidation, which would prevent the weld from joining properly

Oxy - acetylene welding

Used on low carbon steel when other welding processes are not suitable - oxygen and acetylene mixed together to form an intense flame - metals to be joined are grinded at an angle to ensure that the weld runs through the entire join - area is heated to form a melt pool - filler metal rod is introduced and melted to fill the gap - torch is moved along the metal to ensure a continuous seam is produced (molten metal flows to the hottest point)

Brazing

Materials are cleaned and clamped together - flux is applied to prevent oxidation - joint is heated - brazing rod (made of brass) is applied to the area and melts to fill the join

Soldering

Materials are cleaned and clamped together - joint is heated with a soldering iron - solder is applied to the area and melts to fill the join - area is cleaned to remove any excess flux

Riveting

Rivet is inserted into drilled hole - non curved end is hammered to squeeze the materials together

Pop riveting

Rivet head is pushed through the drilled hole - steel pin is pulled out of the rivet body pulling the two pieces of material closer

Self tapping screws

Joining thin sheet metals - pilot hole is drilled - screw is inserted - cuts its own thread - used on products where the panels need to be removed such as on white goods or battery compartments

Machine screws

Used to join thicker pieces of materials together - typically tightened with an Allen key or spanner

Nut and bolt

Bold placed through entire hole with nut tightened on the end - washer placed to spread out the tension of the joint - spring washer used to prevent the join from coming undone after a sudden movement / vibration - nyloc nut helps to prevent it coming undone by elasticslly deforming over the thread

Milling

Metal is clamped and can be cut away in all directions to create the product - type of cutter used dictates the cut made (cut away, shape edge or drill holes)

Turning

Metal placed on a centre lathe - cutting tool is moved to create the cuts needed

Flame cutting

Intense flame is used to cut low carbon and alloy steel place - metal is melted and then blown away by the slag jet to finish the cut

Advantages of flame cutting

Cheap to set up as equipment is readily available, can be set up with CNC machining

Disadvantages of flame cutting

Difficult to keep a straight line with high levels of tolerance due to the deformation on the cutting edge

Plasma cutting

Used on conductive materials - jet of plasma is produced by the electrical arc and the gas - heat generated by the plasma burns the material and blows wastage away

Laser cutting

Laser is focussed on the metal to melt it - high pressure air blows wastage away

Advantage of laser cutting

High tolerance, less warping and a high surface finish

Disadvantages of laser cutting

Not able to cut to the same thickness as plasma cutting

Punching / stamping

Stamps out sections of material using a stamp (upper) and die (lower)

Cellulose and acrylic paints

Colour and texture finish to a metal - acts as a barrier against corrosion - surface must be cleaned

Electroplating

A metal is used to coat another (usually cheaper) metal - provides both a protective layer and a greater aesthetic appeal - product and donor metal is placed into electrolyte solution - dc current applied to move the donor ions to the product

Dip coating (general)

Product is dipped in a tank of another material for it to be coated in (such as polymer or metals)

Dip coating - polymers

Metal product is heated and dipped into tank of polymer powder - powder melts and covers the product evenly - left to air dry

Dip coating - metals

Cleaned product is passed through a tank of molten metal and left to cool

Galvanising

Dip coating steel in zinc

Powder coating

Product is negatively charged while a positively charged thermoset polyester resin is sprayed onto it - product baked into an oven to give an even coating

Varnishing (metals)

Clear finish to protect the metal while allowing the colour of the natural metal to be seen

Sealants

Polymer based sealant that protect polished surfaces from decay and tarnishing - applied and allowed to cure for 15 minutes

Preservatives

Provides protection to metals during and manufacturing - applied with cloth, spray or immersion

Anodising

Aluminium products are positively charged in an electrolyte bath - builds up the aluminium oxide layer - finished with a clear lacquer or varnish to protect the surface

Cathodic protection

Anode (more corrosive) will corrode faster than the cathode (less corrosive) when water is near the join (creates an electrochemical cell) - makes the product metal the cathode while the sacrificial metal anode erodes instead - used to protect steel structures buried in soil or immersed in water