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Welding and soldering are two operations widely used in the industrial carpentry sector, but they are confused all too often: what are the differences between the two processes? When are one or the other used? Let us answer these questions.

Autogenous welding and heterogeneous welding

To obtain welded joints there are several techniques that can be used, each one characterized by advantages and disadvantages when applied. A first subdivision is between autogenous and heterogeneous welding techniques.

Autogenous welding occurs by fusion or pressure, characterized by the participation of the base metal in the constitution of the welded joint. It can be performed with or without filler material.

It is what, in common parlance, is simply called welding: the result is the union of two compatible materials, after careful cleaning of the surfaces to be welded. To perform it correctly, the materials must be placed in the final position and then melted.

The best known techniques involve the use of gas or the electric arc formed between the electrode and metal. The greatest advantage is the maximum tightness of the joint, with a high risk of deformation.

Soldering and brazing are, instead, heterogeneous welds: in this case the fusion concerns only the filler material, as the base metal is only heated to allow the sliding of the soldering alloy.

To allow this, the melting point of the filler metal must necessarily be lower than that of the base material.

During the soldering process, the parts to be soldered are joined together, facilitating the capillary penetration of the soldering metal: during the process, the base material is heated evenly until the correct temperature is reached, allowing the filler material to melt and fill the fillers (between 0.05 and 0.2 mm wide).

Soldering techniques

Soldering techniques can be divided into three categories:

  • Hard soldering: performed at a maximum temperature of 450°C, using tin and lead alloys. Much used in the electronics sector.
  • Soft soldering: carried out over 450°C with silver, gold, copper, brass or nickel alloys.
  • Brazing : the metals used reach a melting point above 900°C.

Soldering : advantages and disadvantages

The use of soldering techniques involves a large number of advantages: the possibility of joining different materials is a unique feature, not totally possible during classical welding. Furthermore, it is not just metallic materials.

The distortions caused are imperceptible, resulting in an impeccable aesthetic appearance, but must be performed with particular care: the joint, at the end of soldering, has little elasticity and mechanical strength compared to when the edges to be joined melt. This leads to an increase in fragility and the risk of breakage.

It is very important to highlight the low energy cost of the process, making it more sustainable and less burdensome to the budget invested.

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