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Soldering – The AWS defines soldering as a group of joining processes that produce coalescence of materials by heating them to the soldering temperature and by using a filler metal (solder) having a liquidus not exceeding 840ºF (450ºC), and below the solidus of the base metals.
Brazing – Brazing joins materials by heating them in the presence of a filler metal having a liquidus above 840ºF (450ºC) but below the solidus of the base metal.
Welding – In welding, fusion takes place with melting of both the base metal and usually a filler metal.
2.The difference between soldering and brazing is temperature. The American Welding Society defines soldering as metal coalescence below 800 °F and brazing as metal coalescence above 800 °F. Both processes bond adjoining metal surfaces by completely wetting the surfaces with molten filler metal and maintaining that bond until solidified. The bond is only as strong as the filler metal, but some braze metals can be very strong indeed.
3.Welding melts the metals at the joint using very high temperatures. Essentially the metal from the two parts is blended by heat. However, if the metal melts too easily it will become a liquid and run out of the weld area. Properly executed, a weld is just as strong as the metal being joined. However, the higher heat of welding can change the material properties if you aren’t careful. This change in the metal’s properties can make the weld weak. Therefore, welds are commonly performed on like materials only.
Brazing uses a braze alloy that become liquid at a moderate temperature to join two other metals. These metals can be the same or dissimilar. The joined materials are NOT molten as they are in welding, but the braze alloy is liquid and flows between the joint. Properly performed brazed joints can possibly be stronger than the work pieces they joined. Unlike welding, brazing only has minimal impact on material properties. Braze alloys can also be expensive. Copper alloys are commonly brazed, particularly since copper’s properties make it very difficult to weld.
Soldering uses an alloy that is liquid at relatively low temperatures to join two other metals. It has the least impact on the base materials, and also provides the weakest joint. It is particularly useful when heat can damage or distort the materials being joined. Electrical components are commonly soldered to avoid heat damage. This method is more delicate than that of the other two described here. Various metals can be soldered together, such as gold and sterling silver in jewelry, brass in watches and clocks, copper in water pipes, or iron in leaded glass stained windows.