Work Safe and Stay Safe
Whenever using tools, always think safety first, there is nothing more important than your personal safety and if tools (both hand and power) are used incorrectly you can hurt yourself (in the extreme - fatally).
Always follow equipment and workshop instructions, including the use of recommended personal protection equipment. Accidents only take a moment to occur but can take a lifetime to recover from. You are responsible for your safety so remember
Work Safe and Stay Safe.
Carbon-alloy
When carbon and other materials are alloyed with iron it forms steel.
The amount of carbon is very small, it can be less than 1%.
Changing the amount of carbon, even by such small amounts, will dramatically change such properties as hardness, ductility and toughness.
Different properties mean different uses. Generally, low-carbon steels are used where toughness is needed.
Increasing the amount of carbon increases hardness, so high-carbon steels are used where hardness is needed.
It means that materials can be designed for special uses.
Hardening & tempering
In ancient times, it was thought a sword could be hardened by plunging it into the newly-decapitated body of a slave and stirring vigorously.
Modern metallurgy tells us that the secret of hardening certain kinds of steel is to heat them, then cool them rapidly. Swift cooling changes the way the elements in the alloy are arranged, especially the iron and carbon. The effect is to produce a harder material. In the case of this steel, the harder material consists of a mass of uniform needle-shaped crystals.
Induction hardening is done by inducing a high current flow into the component that needs hardening. This is done with an induction coil. After the component has been heated enough, it is quenched, usually in oil. A process called flame hardening can also be used, but in contrast the material is water-quenched.
The shape of the component may require different methods of heating and cooling but the principle is the same.
The process of quenching can make a material harder but it can also make it brittle. This brittleness can be reduced to make the steel more ductile and tougher by tempering.
Tempering means heating to a certain temperature, depending on the material, holding it at that temperature for a time, then letting it cool at a controlled rate. The temperature needed, how long it's held, and how the material is cooled all depend on the material, and the properties that are wanted.
