Brazing is a method in which two metals can be joined together by using a filler metal. Most filler metals are silver and copper based.

The parent metals are heated to a temperature which lies above the filler metal's melting temperature, but which is below the parent metal's melting point. Despite this, the brazing process is a metalic bonding  - the filler metal and the parent metals join together in a thin layer to form the so called bonding zone.

A brazing process in which the elements to be joined are found in the solid state is called fusion. It is the brazing alloy's composition and diffusion depth which determines the strength of the brazed joint.

In all brazing situations, it is important that the brazing gap is metallically clean in order for diffusion and the metalic bonding to take place.

Metallic oxides are the main obstacle for the brazing alloys smooth flowing and metallic bonding qualities.

It is not enough that these metallic oxides are removed before brazing; it is also necessary to prevent further oxidation during the heating process. This is best achieved by using a suitable brazing flux, or by brazing in a protective atmosphere or vacuum.

Choosing the correct brazing alloy is important:
The brazing alloy should have a composition which fulfils the necessary requirements.

Furthermore, it should be resilient and flexible, and at the same time be capable of a metallic bonding with the parent metals without corrosion and other metallurgical difficulties. Brazing can be applied in many different product areas, in manual brazing and in connection with automation.

In recent years, brazing has become a more automative process and with this, the brazing process will cover increasingly larger product areas.

First and foremost brazing is used when:

• complicated joints arise
• there are parent metals which cannot endure extreme heat
• there is a need to join different types of metals
• the parent metals have different dimensions (from thick to very thin)
• the cost of extra finishing treatments is too high (eg. after welding)

As well as copper, brass and hardmetals (eg. tungsten carbides), different types of steel (plain, stainless etc.) can also be brazed with excellent results.