Wikipedia defines welding as "a fabrication process that joins materials, usually metals." This is done by melting the part of the materials to be joined and adding some additional molten joining material. When the molten material cools, it forms a strong bond or joint.

Welding is the most widely practiced way of joining metals together due to the efficiency and economy of the process. It has been estimated that approximately 50% of the Gross National Product of the USA arises from activities that are in some for or another related, perhaps remotely, to welding. As an example, farming may appear to have nothing to do with welding, but the equipment the framer uses to grow and harvest his crops will have used welding in their manufacturing process.

Until the advent of the 20th century, welding was confined to blacksmith shops where two pieces of metal were heated to very high temperatures in a forge and then hammered together until the joining occurred. This is what is called forge welding.

With the introduction of electricity into industrial processes, welding became both quicker and easy, and also more economical. Today there are 4 types of welding techniques that are commonly used.

* The most basic for is Arc Welding where the parts to be joined together are brought into contact with strong electrical current and heated. The molten parts are then joined together to form a weld. This is the low technology end of welding in its cheapest and least sophisticated form. * Gas Welding is generally used for repair work especially in the case hollow items like tubes and pipes. Hot gas is forced onto the surfaces to be welded. This procedure requires the parts to be subjected to less heat and is suitable for material that may be damaged by exposure to high temperature. For this reason it is used in the jewellery industry which has to work with soft metal with low melting points. * Resistance Welding requires that an additional sheet of material is used to cover the pieces that are to be welded together. This provides great strength to a weld, but the process requires expensive equipment and also the use of additional material to encase the weld which makes it expensive and not suitable for all applications. * Laser Welding is the most modern technology available. High intensity lasers can be tightly focused and produce controllable heat on the surfaces to be welded very quickly. This is perfect for material which can be damaged by prolonged exposure to extreme heat. Laser welding is very accurate and can be used to produce even the smallest of welds. However, because of the high capital cost involved in purchasing this equipment, the cost of welding is also high.

Although the perception of welding is that of a simple process of heating and joining, it is a high technology industry with huge amounts being spent of research and development to find stronger, more accurate and cheaper methods. The welding process plays a big role in metallurgy with a constant effort underway to find newer and more weld friendly alloys.

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