The large majority of Materials needing welding for being manufactured in items of useful shapes are metals.
Pure metals are individual chemical elements represented in the Periodic Table.
Their specific properties qualify them for being designated as showing metallic qualities.
Among their characteristic properties, besides an opaque lustrous surface reflecting light, are the property of good conductor of heat and electricity, because of their atomic binding and electron availability to carry an electric current.
Most metals are solid, but mercury (Hg) is known as being a liquid metal at normal temperature.
Pure metals are used for very specific purposes where their purity confers them special properties.
They cannot be employed for building useful everyday items, because their mechanical properties are insufficient to sustain the required stresses developing in normal use.
Most metallic materials in current use are in the forms of alloys, that means mixtures of different elements, combined to display useful properties.
The science studying properties and technology of metals and alloys is called Metallurgy and is essential knowledge to anyone wanting to use welding for constructing any required item.
Process metallurgy is concerned with the extraction of metals from their ores and with refining of metals.
Physical metallurgy, with the physical and mechanical properties of metals as affected by composition, processing, and environmental conditions.
And Mechanical metallurgy, with the response of metals to applied forces.
Plastic is material consisting of any of a wide range of synthetic or semi-synthetic organic compounds that enjoyed extraordinary development in the last century.
Plastic materials are malleable and so can be molded into solid objects.
Plastic materials are commonly classified as thermo-plastic or thermo-setting, depending on their behavior in the presence of heat.
Of these, only those of the first class can be welded or joined by using heat in special processes designed not to destroy their useful properties.
When heat cannot be used, adhesives are generally employed to connect firmly plastic items.
Among recent developments of non metallic materials, carbon fibers of exceptional tensile properties are being produced for use in composite panels and other structures built for resisting loads in demanding applications for aerospace.
Traditional welding is not an option in this case.
A ceramic is an inorganic, non-metallic, solid material comprising metal, non-metal or metalloid atoms primarily held in ionic and covalent bonds.
Ceramic materials in powder form are thermally sprayed on metallic surfaces to provide special properties like exceptional wear resistance or thermal insulation.
The technology is derived from that used primarily for spraying metals to rebuild worn surfaces or to provide selected surface properties.
For welding different materials, the usual processes must be adapted to suit the procedures that experience proved as the most successful for reaching the results sought.
The list of some of the pages of this website describing the most common combinations is given in the Index-Welding-Page under the same heading as here above.
There, one can find a long list of welding processes applied to different materials, whose title describes the content of the relevant page, displayed by clicking on the active link.