Metals

Metals are poly crystalline bodies which are having number of different oriented fine crystals. Normally major metals are in solid states at normal temperature. However, some metals such as mercury are also in liquid state at normal temperature. All metals are having high thermal & electrical conductivity. All metals are having positive temperature coefficient of resistance. Means resistance of metals increase with increase of temperature. Examples of metals – Silver, Copper, Gold, Aluminum, Iron, Zinc, Lead, etc. Metals can be further divided into two groups-

1. Ferrous Metals – All ferrous metals are having iron as common element. All ferrous materials are having very high permeability which makes these materials suitable for construction of core of electrical machines. Examples: Cast Iron, Wrought Iron, Steel, Silicon Steel, High Speed Steel, Spring Steel etc.
2. Non-Ferrous Metals- All non-ferrous metals are having very low permeability. Example: Silver, Copper, Gold, Aluminum etc.for further details.

Ferrous Metals

The following are ferrous metals and the kind of uses to which they are usually put:
• Mild Steel – Carbon content of 0.1 to 0.3% and Iron content of 99.7 – 99.9%. Used for engineering purposes and in general, none specialised metal products.
• Carbon steel – Carbon content of 0.6 to 1.4% and Iron content of 98.6 to 99.4 %.  Used to make cutting tools such as drill bits.
• Stainless Steel – Made up of Iron, nickel and chromium. Resists staining and corrosion and is therefore used for the likes of cutlery and surgical instrumentation. See our infographic celebrating 100 years of stainless steel usage in buildings or the different types of stainless steel.
• Cast Iron – carbon 2 – 6% and Iron at 94 to 98%. Very strong but brittle. Used to manufacture items such as engine blocks and manhole covers.
• Wrought Iron – Composed of almost 100% iron. Used to make items such as ornamental gates and fencing. Has fallen out of use somewhat.

Non Ferrous Metals

These are the non ferrous metals and their uses:
• Aluminium – An alloy of aluminium, copper and manganese. Very lightweight and easily worked. Used in aircraft manufacture, window frames and some kitchen ware.
• Copper – Copper is a natural occurring substance. The fact that it conducts heat and electricity means that it is used for wiring, tubing and pipe work.
• Brass – A combination of copper and zinc, usually in the proportions of 65% to 35% respectively. Is used for ornamental purposes and within electrical fittings.
• Silver – Mainly a natural substance, but mixing with copper creates sterling silver. Used for decorative impact in jewellery and ornaments, and also to solder different metals together.
• Lead – Lead is a naturally occurring substance. It is heavy and very soft and is often used in roofing, in batteries and to make pipes.