Carbon is a black powder with the symbol C and the atomic no 6 on the periodic table. It is one of the few elements that have been known since antiquity.
Carbon is one of the least abundant elements in the earth's crust, but the 4th most abundant element in the universe, after Hydrogen, Helium and Oxygen. It is present in all known life forms, and in the human body it is the 2nd most abundant element, after Oxygen.
The different forms of Carbon include, most importantly: braai charcoal; diamond and graphite, and its uses are just as varied, including, writing and drawing, lubricant, pigment, electrodes, electroplating, jewellery, industrial cutting etc.
Naturally the use that we are most interested in, is its ability to form alloys with iron. Carbon is added to iron to increase hardness, i.e. increased resistance to shape change when force is applied.
Carbon has an extremely powerful affect on alloy, in relatively small amounts. Notice in the definitions below how small the relative difference in Carbon % separates the different alloys:
- Low Carbon Steel - + - 0.05 - 0.15% C
- Mild Steel - + - 0.16 - 0.29% C
- Medium Carbon Steel - 0.3 - 0.59% C
- High Carbon Steel - 0.6 - 0.99% C
- Ultra High Carbon Steel - 1.0 - 2.0% C, although anything over 1.2% usually made as powdered metallurgical steel
Stainless Steel is defined as steel with + - 10% Chromium content by mass, and as such can vary in Carbon content, e.g. 0.6% C - 12C27, to S90V - 2.3% C.
High Carbon content usually equals high Hardness, but low toughness, i.e. As the Carbon and therefore hardness increases, propensity to brittleness also increases. This somewhat canceled out in the manufacturing process of the S90V.
Precautions:
Although pure Carbon has a low toxicity, inhalation of coal dust or soot in large quantitiescan be dangerous, causing congestive lung disease. In a different form, diamond dust, it is also harmful if ingested or inhaled. Call to mind the silent danger of Carbon Monoxide gas poisoning too. Carbon will also burn vigorously in the presence of air at high temperatures.
