Torches Processes

Assembly obtained by using a filler metal that is different from the basic metal of the parts to be assembled.
Brazing is performed at the melting temperature of the filler metal, lower than that of the base metal.
Due to a capillary effect, the brazing alloy penetrates between the surfaces to be assembled (e.g. joins of copper pipes).
The assembly point, or in some cases the entire part to be assembled, must be brought up to temperature.

Brazing is divided into
1) low-temperature brazing (in which the temperature is below 450°C)
2) high-temperature brazing (in which the temperature is above 450°C)
When is it used?
■ For very dissimilar joint section thicknesses, as the high temperature required by autogenous welding can deform the thin thickness.
■ Irregular and non-flat join, as the brazing filler material can easily flow across irregular paths.
■ Metals or other materials to be joined with significantly different melting temperatures.

Procedure in which the assembly is obtained using similar techniques to welding. The surface anchoring occurs between the deposited metal bead and the surfaces to be assembled which have not been brought to melting point. The filler metal, based on brass, melts between 800°C and 930°C (depending on the alloy): at these temperatures, deformations are limited to thin sections and there is less zinc evaporation when assembling galvanised parts. Fluxes need to be used to promote the flow of the filler metal on the part (powder, paste or coated rods).


Assembly procedure in which the metal of the parts to be assembled, known as the base metal, is melted to form the weld joint. Depending on the thicknesses in question, the weld is done with or without filler metal, generally the same as the base metal.

The flame is useful for heating sheets and pipes, in order to easily modify their shape for bending or cambering. It can also be used to separate shrink fitted parts. (The outer part is heated, so it dilates and expands and it can then be dismantled).
There are also multi-flame heating torches with tips comprising a set of holes which produce a gentler and wider flame, which is therefore less concentrated.

Oxy cutting is a procedure for cutting metal sheets or sections, that uses an oxyacetylene flame and a jet of pure oxygen.
It is based on the principle that when ferrous materials are heated to incandescence, they burn if they are in an oxygen atmosphere.
It is done by using a special torch which emits two concentric gas flows:
■ an outer jet shaped as a ring, which forms a flame similar to that used in oxyacetylene welding, and serves to make the metal red hot;
■ a central jet of pressurised oxygen which makes the cut by means of a process of combustion and fusion of the metal, and removes the cutting slag by pressure. To start the cut, you first heat to incandescence the starting point with only the flame. You then open the oxygen jet without moving until the entire thickness of the sheet is perforated. You can then start the advance movement to continue the cut.