Brazing

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Brazing

Brazing is a special type of soldering and is one of the manufacturing processes . It is a joining process with hard solder as an additional material for the material connection of metallic workpieces. The brazing temperature is defined as about 450 ° C .

properties

Brazed joints are generally less strong than welded joints , but almost always stronger than soft soldered joints. The materials used make hard soldered connections conductive to heat and electricity . The Peltier effect occurs through the use of different materials .

Materials that are suitable for brazing:

Alloys are usually used as solders which, on the one hand, have a favorable melting point and, on the other hand, contain metal components that enable a good connection with the workpieces. If small gaps have to be soldered, the viscosity of the melt must be low on the one hand and the surface tension must allow a capillary effect on the other. This often makes the use of fluxes necessary, which also remove disruptive oxide layers from workpieces.

Usual solders are, for. B. according to DIN EN 1044:

  • silver and phosphorus- containing solders for soldering copper and other non-ferrous metals
  • Copper-phosphorus brazing alloys for creating pure copper connections
  • solders with a high silver content (45%) with a low melting point
  • silicon -containing aluminum alloys for the sole soldering of aluminum
  • Brass hard solders for joining all types of steel, copper and many materials containing nickel
  • Nickel-based solders with melting points around 1000 degrees Celsius for temperature-resistant joining of steels

Solders based on bronze are uncommon.

commitment

Transportable device (in case) for brazing with propane and oxygen

Brazed connections can be found:

In general, brazing is suitable for joining surfaces, since larger contact surfaces again achieve good load-bearing capacity. A particularly popular use is the connection of pipes with fittings , because the hard solder quickly and reliably fills the space between the fitting and the pipe, making it very easy to establish a material-to-material, gas and liquid-tight connection. The lower temperature than that required for welding reduces the load on the workpieces, which can otherwise be expressed by distortion of the workpieces.

The main advantage of the low temperature required, however, is the reduced requirement on the heat source. A simple propane torch ( blowtorch ) is often enough to achieve a good connection quality. The dangerous handling of pure oxygen as with oxy-fuel welding and the radiation that is harmful to the eyes and skin with electric welding are no longer necessary .

Bicycle frames used to be mainly hard-soldered. Today, also because of the increasing popularity of aluminum as a material, they are more likely to be welded. The main purposes of brazing are still likely to be in cold and hot water installations with copper pipes and in refrigeration technology. Copper pipes can be connected with brass or copper-phosphorus solder.

The use of different metals and alloys within a soldered joint has a disadvantageous effect. Galvanic elements are often formed here, which can lead to rapid corrosion .

literature

  • Herbert Littnanski: Brazing with silver solders , Westdeutscher Verlag, Cologne 1966.
  • Dieter Miedek: Brazing is not a book with seven seals. Guide for practice, Verlag für Technik und Handwerk, 2012, ISBN 978-3-8818-0437-0 .
  • Eduard Scharkus, Franz Findeisen: The mechanical engineer. A textbook for apprentices - journeymen and masters, Coleman Verlag, 1955.

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