Welding
| Introduction A weld occurs when pieces of metal are joined by causing the interface to melt and blend prior to solidifying as a uniform metal joint. This process may be caused by heat, pressure or a combination of both. When heat alone is used the process is called fusion welding. Pressure welding usually involves heating the surfaces to a plastic state and then forcing the metal together. The heating can be by electric current of by friction resulting from moving one surface relative to the other. The methods and equipment used for welding metal are also associated with cutting metal. There are a large number of welding and allied processes including the following.
Calculation relating to welded joints can be found on webpage... Weld Stress Calculations Notes on drawing representations of welds can be found on webpage .. Drawing of Weld Symbols. Manual Metal Arc Welding Process Electric Arc welding is based on providing an electric circuit comprising the Electric current source the feed and return path, the electrode and the workpiece. The arc welding process involves the creation of a suitable small gap between the electrode and the workpiece. When the circuit is made a large current flows and an arc is formed between the electrode and the workpiece. The resulting high temperatures causing the workpiece and the electrode to melt The electrode is consumable. It includes metal for the weld, a coating which burns off to form gases which shield the weld from the air and flux which combines with the nitrides and oxide generated at the weld. When the weld solidifies a crust is formed from the impurities created in the weld process (Slag). This is easily chipped away. MIG & TIG WeldingThe Metal Inert Gas Process uses a consumable electrode of wire form and an inert gas shield of carbon dioxide when welding carbon steel.. The wire electrode provides a continuous feed of filler metal allowing welds of any length without stopping. The inert gas shield eliminates slag and allows cleaner and stronger weld.. This process is used widely for automated welding using robots.  The Tungsten Inert gas (TIG) system uses a non-consumable electrode of tungsten and also provides an inert gas shield of argon or helium. This process was orginally developed for welding magnesium and it is now used for welding aluminium, copper, stainless steel, and a wide range of other metals that are difficult to weld. Consumable rods may be used depending on the type of weld and the thickness of weld.  The welding process designations provided below are based on BS EN ISO 4063 and are used when identifying welds to BS EN 22553
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