introduction to welding, soldering and brazing

 

Welding is a process of joining a metal into one due to heat with or without pressure effect or it can also be defined as a metallurgical bond generated by the attraction force between atoms. Soldering and brazing is a process of grafting metal which is used other metal connector in a liquid state which then frozen.

Soldering is the process of connecting two pieces of metal with different metals which are poured in a liquid state with a temperature not exceeding 430 o C between the two pieces. The most widely used alloy / filler metal alloys are lead and lead alloys having a liquid point between 180 – 370 °C. The composition of 50% Pb and 50% Sn is mostly used for solder tin where this alloy has a liquid point at 220 °C.

 

Brazing of the filler metal has a liquid point above 430 °C but is still below the molten point of the parent metal. The most commonly used metals and alloys are:

  1. Copper: liquid point 1083 °C.
  2. Copper alloy: brass and bronze having a liquid point between 870 °C – 1100 °C.
  3. Silver alloy: which has a liquid point between 630 °C – 845 °C.
  4. Aluminum Alloy: which has a liquid point between 570 °C – 640 °C.

The advantages of the brazing process are the possibility of joining of metals that are difficult to weld, joining of different metals and joining of thin materials. In addition the brazing process is fast and
resulting in a tidy connection that does not require any more completion work.

 

In brazing the most important thing is cleaness, the surface must be free of dirt, grease, or oxides and the part of the joint must be exactly the size or shape with the gap for the filler. The desoldering process is grouped by way of heating. There are four ways in which to heat the metal in connection.

  • Dyeing of objects to be connected in fill metal or liquid flux.
  • Brazing by using the furnace. Here the object is clamped with a jig and inserted into a temperature controlled furncae according to the point of molten metal.
  • Brazing with flame. The flame heat is taken from the flame of acetylene or oxihydrogen and the filler metal in the form of a melted wire in the connection gap.
  • Brazing with electric energy. Heat comes from electic resistance, induction or electric arc.

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