Welding refers to the joining of two or more metal parts in order to obtain a single strong and stable body, through the preparation of an alloy whose melting point is lower than the melting point of the alloy of the object to be welded, and which allows the multiple metal parts to be joined in a durable manner using heat.

This operation can be performed using different methods and techniques, the three main ones being:

Autogenous welding: consists of melting the metal parts to be joined, which will have to touch each other and
through heat they will melt and join.

Braze-welding: consists of doing the previous operation, but with the addition between or on the edges of the two parts, of filler metal of the same alloy as the one to be joined, so as to fuse together creating a single body.

Brazing: consists of melting a filler metal alloy, with a lower melting point than the metals of the parts to be joined, so that the latter remain intact without melting with the soldering alloy.

In precious metals, soldering usually takes place by BRAZING, i.e. by melting an alloy that, previously prepared in the form of a sheet or wire, is placed between the parts of the metal to be soldered.

The operation must be carried out with great care in all its steps, so that the weld is stable and strong, as there will be about 25% less resistance in the area of the welded object.

To achieve a good weld, the key factors are: the heat, the solder, i.e. the filler metal and the fluxes.

This is a principle that applies to all types and techniques of welding, both noble metals and all other metals.

Heat: Heat sources for welding can be of various kinds, propane or methane gas, oxygen, hydrogen-oxygen, lasers, etc. etc. In the laboratory, mostly propane gas or hydrogen-oxygen (micro-flame) is used, and in the more high-tech the laser.

The fluxes: the fluxes used are: borax, boric acid, zinc chloride, these allow the metal’s melting point to be lowered while at the same time performing an anti-oxidant function, dissolving any oxides present on the metal.

We have now seen what welding is, in future articles we will look at the various types of welding for various metals, the various formulas and how they are obtained.

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