Which Brazing Filler Metals Should Be Used For Steel?

Brazing is a technique widely used in industries for joining two metal parts. It is a particularly common process in the automotive, construction, aeronautics, shipbuilding and railway, public works, steel and energy sectors. In order to properly braze metal or copper, it is important to use a quality brazing rod.

What is the difference between welding and brazing?

First of all, brazing must be distinguished from soldering. Brazing refers to an operation consisting of assembling two parts by melting a filler metal without melting the base metal. The filler metal in question can be tin or silver. The melting temperature of the brazing alloy must be lower than that of the base metal.

Welding, on the other hand, refers to a process of fusing two metal parts by fusing the base metal and the filler metal. In the majority of cases, the temperatures used are those which ensure that both the material and the filler metal melt.

Whether brazing or welding, the objective is to maintain the mechanical performance of the assembled parts. Here we will consider the specific merits of brazing. Since brazing is carried at lower temperatures, the base metal itself does not melt. Consequently, brazing provides tighter tolerance control. It also allows for a clean joint without the need for secondary finishing. Just like welding, brazing is also strong and resistant. There are two brazing techniques: soft soldering (fusion of the filler metal below 450°C) and strong brazing (fusion of the filler metal ranging from 600°C to 1000°C).

What type of metal rods should be used to braze copper?

To braze copper, there are two solutions available to you: soft brazing with tin and strong brazing with cupro-phosphorus rods.

Tin brazing of copper

Brazing copper is carried out using a tin-based alloy. This can melt between 180°C and 450°C. The advantage of tin solder is that it is easier to make because it does not require high temperatures. During this operation, it is important to wear protective equipment, such as an apron, shoes, gloves, goggles and a helmet.

Strong copper brazing with cupro-phosphor rods

The other alternative for brazing copper is to use cupro-phosphor rods. While the first technique can be performed with a blowtorch, the second requires suitable equipment, such as an oxyacetylene torch. The melting point of cupro-phosphor rods is between 600°C and 900°C. Here again, the wearing of protective equipment is highly recommended.

Which metal rods should be used to braze steel?

For the assembly of pure copper or plumbing, copper alloys, copper and alloys of copper metals and steels, the ideal solution would be to use strong brazing with copper, phosphorus, silver or  40% silver. These rods guarantee a perfect connection between the two elements which require brazing.

They are useful for assembling piping systems, sensors for motorised controls, vehicle bodies, or high quality engine parts. Steel solder is widely used in the measurement and control technology, mechanical engineering, hydraulics and automotive industries. For the automotive industries in particular, steel brazing can be done by laser. Before brazing the metal, it is useful to consider a number of criteria such as the size of the joint, the metals which are to be joined, the thickness of the base metal profiles, the requirements for in-line or relating to seals.