1. The following heat treatments alter the properties of metals
Steel can be treated by intense heat to give it different properties of hardness and softness. (only high carbon steel can be hardened and tempered).

2. Hardening
If steel is heated until it glows red and is quenched (dipped) in clean water immediately, it becomes very hard but also brittle.
This means it is likely to break or snap if put under great pressure.
In a school workshop most heat treatment of metals takes place on a brazing hearth

3. is a heat process where is metal is heated to a specific temperature /colour and then allowed to cool slowly
Annealing
a heat treatment that alters the microstructure of a material causing changes in properties such as strength and hardness and ductility
This softens the metal which means it can be cut and shaped more easily.
Mild steel, is heated to a red heat and allowed to cool slowly. Aluminium will melt if heated for too long.

4. As a rule they are heated and allowed to cool slowly
are relatively soft
can be cut and shaped more easily They bend easily when pressure is applied.
As a rule they are heated and allowed to cool slowly
Difficult to cut and shape.
Very difficult if not impossible to bend.
As a rule they are heated and cooled very quickly by quenching in clean, cold water.

5. TEMPERING
Tempering is a heat treatment technique for metals, alloys and glass
Tempering is achieved by a controlled reheating of the material piece to a temperature below its lower critical temperature (melts)
The temperatures used in tempering are often too low to be gauged by the colour of the workpiece. In this case, the blacksmith will heat the work piece for a known amount of time.

6. heated again to a red colour
is a simple method of hardening steel. It is less complex than hardening and tempering.
Case Hardening
Carbon is added to the outer surface of the steel.
One advantage of this method of hardening steel is that the inner core is left untouched and so still processes properties such as flexibility and is still relatively soft.
steel is heated to red heat
heated again to a red colour
plunged into case hardening compound (high in carbon )
and allowed to cool a little.
plunged into cold,
clean water