There are different ways to connect the parts together. Commonly this can be done by fasten them with rivets or bolts, solder or weld them together. Welding is a process that creates a continuous joint upon wide materials surfaces. This is the main feature of welding, especially for enclosed cans such as boilers, etc.

The quality of weld depends on the base material, filler and flux material, energy and design. The welding method and concentration of energy input, weldability of the base material and type of the filler and flux influence the strength of weld and material. The heat-affected zone has also effect on weld quality. To test the quality of the weld either destructive or nondestructive methods are used. Gas and non-metallic inclusions, cracks, incomplete penetration, distortions, lack of fusion and lamellar tearing are common defects of welds (best welding caps).

Welding is a fabrication that joins materials by causing fusion, which usually melts the base material. Usually, there are fillers that added to joining base materials. The joint is created in the process of cooling the pool of those molten materials. As a rule, a base material is not as strong as a joint. The pressure also can be applied during the welding process.

The fusion technique was developed when mankind discovered the iron forging. People heated small pieces of iron to welding temperature and then hammered or pressed them to create larger useful pieces. The most common today’s welding techniques are arc welding, oxyacetylene welding, resistance, electron-beam, friction, laser welding and other. The shielded metal-arc welding is the most used technique. In this process, an electric arc is used to melt the electrode’s metal and transfer it to the joint. Another technique is gas (usually oxyacetylene) welding. For fusion process heat is supplied by burned acetylene in oxygen. For the resistance welding, the main source of heat is the electrical resistance of the joint. Such welds are made using low-voltage and high current power source with pressure applied. A dense stream of high-velocity electrons bombarding the joint is a source of heat for electron-beam welding. The friction welding is based on heating joining parts by friction. A laser beam is a source of heat when fusing materials in the laser welding.

The most widely used materials in welded constructions are carbon and low-alloy steels. The amount of carbon or alloying content influences the weldability of steels widely. Another good weldable material is Aluminium and its alloys. Despite the high thermal conductivity that makes its welding difficult, copper and its alloys are also well weldable. As a rule, you can easily weld plastic or glass. The most common technique to weld them is heating to melting range and adding pressure on surfaces.

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