SOLDERING:
- Soldering requires the lowest temperature of the three joining processes.
- There are a range of solders available from soft solders to hard solders.
- Soft solders are used for joining electronic components to circuit boards, or for small copper or brass components.
- Hard solders are used for products requiring additional strength and in the construction of products requiring the soldering of a number of mating components.
- Softer solder melts at around 200 degrees Celsius.
- Hard (silver) solders are so called because they contain a small amount of silver that is alloyed with copper and zinc. The amount of each material differs to produce a range of hard solders that melt at temperatures between 600 and 800 degrees Celsius. These solders can be used in the manufacture of hand and machine - crafted jewellery.
BRAZING:
- Brazing takes place at a higher temperature than soldering.
- The filler rod in this case is a brass alloy, called brazing 'spelter' and melts at around 880 degrees Celsius.
- The materials that can be joined using this process include copper and steel (in particular mild steel).
- The process is essentially the same as soldering, with the materials being joined, cleaned and kept clean using a flux - in this case Borax is used. Components are held together while being heated.
- When the correct temperature is reached, the brazing rod melts at the joint, filling the joint by capillary action. Again the material is allowed to cool before having excess flux and braze removed.
WELDING:
- Welding differs from soldering and brazing, in that the materials being joined must be the same. If a filler rod is being used then it should be the same material as that being joined.
- This uses a mixture of oxygen and acetylene to create a flame that will burn at a temperature of around 2500 degrees Celsius at the hottest point. This will clearly be sufficient to melt mild steel at the joint, allowing he melting of a filler rod to fuse the joint edges together.
- The red hose (acetylene) is used until the soot disappears and then the oxygen hose is used to heat the area around the joint so that the metals at the joint and the filler rod melts together.
- METAL INERT GAS
- A form of resistance welding, similar to electric arc welding. In the case of MIG welding, an inert gas is used to provide a protective cloud around the joint area as its being joined.
- Along with TIG (Tungsten Inert Gas) welding it is a more refined form of electric arc welding which can be used to join thin sheet material. Both types of welding use a gas jet around the filler wire to prevent oxidation of the material. Different gases are used with different materials, e.g argon is used with aluminium.
- Both spot and seam welding use an electric current as the heat source. Spot welding, as the name suggests provided a spot of heat to fuse the metals together. It is usual to find a series of spot welds in a structure such as a car body shell. A typical application for this type of joining method is tin-coated mild steel for food and drinks cans.
- A form of resistance welding where the metal components being joined are clamped between two electrodes. An electric current is passed between the electrodes causing a build-up of heat at the centre of the joint, fusing the two components together. Used extensively in the assembly of car body panels.
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