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Engineering
Welding
Term | Definition |
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Multi-runs | This is a method of welding two pieces of thick metal together. A number of welding runs are necessary to build up the gaps in between the two pieces. |
Flash back arrestor | This is a safety device used in gas welding. It prevents the flame from burning gas travelling through the hose and into the tanks |
Dissolved acetylene | This is the from that acetylene is stored in the tank. The tank is similar to a sponge, it absorbs the acetylene. Liquid acetylene would explode in the tank. |
Shielded-arc | This is protection of the weld pool by an inert gas preventing oxidation of the weld |
Edge preparation | This is the preparation of the edges to be welded. They should be free of rust and oil to allow for a quality weld and should be tapered slightly to allow for a good joint. |
Slag inclusion | This is a fault where the slag drops into the weld pool and becomes part of it weakening the weld. This is caused by moving the apparatus to slowly. Welding at the correct place will prevent this. |
Porosity | Porosity is the presence of air bubbles in the weld. This is caused by moving the apparatus to quickly not giving the weld pool a chance to form properly. This is controlled by welding at the correct place |
Lack of penetration | This is again a problem with the weld pool. Due to lack of temperature the edges to be joined do not melt to form the weld pool and fuse together. This can be prevented by setting the welder to the correct power setting. |
Neutral Flame | Equal mix, most commonly used welding flame. Used for welding steel, stainless steel and cast iron |
Oxidising Flame | Excess oxygen in the mix. Flame makes a 'hissing' sound. Used for welding brass as it prevents fuming and loss of zinc. Also acts as a decarburising flame for steels |
Carburising Flame | Excess acetylene in the mix. Used in special welding to ensure good protection against oxidization |
Step-down Transformer | In this circuit, the transformer takes AC at a high voltage and produces AC at a lower voltage. This ensures that the output current will be higher than the input current |
Smoothing capacitor | A more uniform direct current is produced by smoothing surges produced by the rectifier |
Benefits of multi-runs | Multi-run welds produce a finished weld that is more refined in structure than single run welds. Each run of the weld has a post heating effect on the previous |