metals

Steel is the most common metal used by man. It is used in the construction of

our buildings, bridges, aircraft, cars, ships and many everyday items. Without steel,

our modern industrial world would not exist.

In order to produce steel, iron ore is required, in large quantities. Iron ore is dug out

of the ground from open cast mines or mined deep underground.

The ore is crushed into a fine powder, mixed with water, making a slurry.

Clay is added to the slurry and the mixture shaped into pellets and baked,

forming a hard shell. The pellets are sent to a steel mill in order to extract the

iron which is normally converted into steel.

A simplified diagram of a Blast Furnace is drawn below. A typical blast furnace may be

up to 32 metres in height and 10 metres in diameter. They have thick steel sides,

lined with refractory bricks, to ensure that heat is not lost. Blast furnaces are used

continuously and are only shut down when their

brick lining needs replacing.
As the mixture of iron ore, coke and limestone heats, the hot waste gases are

collected and cleansed. They are then used to help heat the air blast, required if

blast furnace is to reach the high temperatures needed to produce molten iron.

The stock level is constantly ‘topped up’. Molten iron ore is ‘tapped’ at the bottom

of the blast furnace, poured into the iron ladle and removed for use.

The **** is removed at the tap hole. Although generally regarded as waste, it is used

in road making.

FERROUS METALS - IRON

Wrought Iron was used by the Romans. Roman iron weapons were forged, not cast. Iron was forged by heating it to high temperatures (to red heat) and hammering it into shape.
Britain had numerous Roman iron ore mines. It also had large forests, which provided the wood required for smelting (extracting the iron form the ore).

FERROUS METALS - IRON -
INDUSTRIAL REVOLOUTION

Abraham Darby 1st (1678 –1717)

Developed a technique of producing ‘pig iron’ in large quantities, through casting molten iron, crucial to the industrial revolution. He developed sand casting techniques, making it possible to produce cast products of a high standard.

Cast iron has a carbon content higher than 2.1%. Cast iron is brittle and can snap. Cast iron is likely to break/shatter if dropped or when it receives a ‘blow’.

FERROUS  AND  NON-FERROUS METALS

Ferrous metals contain IRON

These are metals that contain iron. Consequently they tend to rust / suffer from corrosion. They need protecting with paint, oil or a surface finish. They react to a magnet.

Non-ferrous metals do not contain IRON

Non-ferrous metals do not contain iron. Consequently, they do not to rust or suffer unduly from contact with moisture. They do not react to a magnetNON-FERROUS METALS
ALUMINIUM

Light grey in colour. Smelted from bauxite ore. Aluminium 95%, Copper 4%, Manganese 1%

Ductile, soft, malleable, machines well on lathes and milling machines. Very light and resists corrosion. Can be cast into products from ingots.

MANUFACTURE - NYLON FIBRE

Produced when equal volumes of a diamine acid and a dicarboxylic acid are carefully and slowly poured together.

Oil based (diamine) and floats on the top of the other, water based chemical dicarboxylic. A delicate film forms where the two chemicals meet (called the ‘interface’).

Film removed using tweezers, producing a continuous nylon thread.

Nylon is now used in a wide and varied range of products. These include nylon nuts, bolts, washers, screws, tools, packaging and even parts for cars. The list is endless and includes clothing / textiles

These plastics can be re-heated and re-shaped in various ways. They become mouldable after reheating as they do not undergo significant chemical change. Reheating and shaping can be repeated. The bond between the molecules is weak and becomes weaker when reheated, allowing reshaping. These types of plastics can be recycled.Acrylic. (Known also as PERSPEX) This is the most common plastic in a school workshop. Purchased in the form of sheets and comes in a range of colours. It can be translucent (e.g. smoked), transparent or opaque. It is resistant to most acids and weather conditions. Easy to cut shape. Polishes well.

Baths, safety glasses, signs.
LDPE - Low Density Polythene is tough and flexible. Softer than HDPE.

Can be moulded into almost any form. Flexible, comes in range of colours.
Bottles and plastic bags are made from the low density polystyrene.
HDPE - High Density Polythene which is rigid and hard. Less flexible than LDPE.

Machine parts, bowls and crates are generally made from high density polystyrene.

Can be moulded into almost any form. Flexible, comes in range of colours.