Oxygen is the most common element on earth and is needed by most living creatures. Oxygen is a very reactive gas and plays an important role in corrosion and oxidation processes.
Oxygen can have a harmful effect in metal processing, but can also be beneficial if used in a targeted application.
In a humid environment, oxygen attacks unalloyed or low-alloyed steels and decomposes the surface of the material through oxidation processes. If this process is not counteracted, it will continue. This leads to pitting corrosion and finally to complete decomposition of the material.
However, oxygen can also be introduced into the material during the processing of steel. This can happen during welding and laser cutting if not enough attention is paid to the use of shielding gases (inert gases). A shielding gas, such as nitrogen, prevents oxygen molecules from the ambient air from penetrating into the molten material. If the oxygen is not shielded, rust will form at the weld seam, which can make the welded construction unstable.
The reactive property of oxygen can also have a positive influence on steel production. If there is too much sulphur or phosphorus in the molten steel, these elements can be burned with the help of oxygen. Oxygen is also important during refining (reduction of the carbon content).
In steel processing, oxygen is also used as an active gas. In flame cutting, instead of a shielding gas, oxygen is blown into the processing area to achieve a significantly higher temperature. This allows to process higher material thicknesses. After cutting, the cut edges must be freed from slag and scale.
In 1774, the English natural scientist Joseph Priestley discovered that air is composed of different gases. Heating mercury oxide produced pure mercury and a colourless gas that encouraged the burning process. One year later the French chemist Lavoisier named the gas Oxygen.
In further experiments Priestley discovered that plants could transform bad air into good air in an airtight glass container.
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