THE CARBON CONTENT OF STEEL)

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THE CARBON CONTENT OF STEEL

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The carbon content of steel, often determines its hardness, ability to resist wear and consequently, its practical application. For instance, a screw driver blade requires a hardwearing surface, to resist wear whilst in use. However, a screwdriver blade that is hardened throughout its cross-section, will be too brittle / inflexible and eventually snap / break. Therefore, retaining a measure of durability / flexibility throughout its cross-section, is a vital characteristic. For this reason, the screwdriver blade has been hardened at its surface (increased carbon content), whilst having a lower carbon content throughout its cross-section.

The commercial industrial process called ‘Gas Carbonising’ is seen below. A number of steel gear wheels, for a train, have been set up in a special furnace. The gears are heated to a constant temperature of 1000 degrees centigrade, then a gas rich in carbon is introduced. This process is monitored over a number of hours, until the right amount of carbon is absorbed into the surface of the steel. The surface depth of absorbed carbon will vary and depend on the components being carbonised, their thickness / density and the work they are to perform, when in use.

In a school workshop, CASE HARDENING is carried out using a brazing hearth and a tin of case hardening compound. Follow this link for the process.

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