Torch Brazing

Torch brazing is considered to be the most versatile among all the brazing processes as its application can be found in almost any industry, be it the vast fabrication or repair work. Torch brazing is done in air. In torch brazing process, the necessary heat is provided by ordinary gas welding equipment by burning gas combinations such as air and acetylene, oxygen and acetylene, oxygen and hydrogen and air and propane. Torch brazing has some essential applications which as well hold importance in the brazing sector. They are commonly applied for small assemblies and low-volume applications.

Use of Torch Brazing
Torch brazing is generally used to join comparatively small assemblies which are made from materials that do not oxidize at the brazing temperature or can be protected from oxidation with brazing fluxes. The most commonly used filler metals while using torch brazing include aluminum-silicon alloys, silver-base alloys, and copper-zinc alloys. If a protective brazing atmosphere is not being used then flux is also needed with these filler metals. Self-fluxing copper-phosphorus alloys are also used.

Process of Applying Torch Brazing Flame
Torch brazing is usually conducted with handheld oxyfuel gas torches using various fuels. Depending upon the size of the torch, lowest flame temperature & less heat can be provided by air gas torches. For aluminum brazing and for brazing other non ferrous alloys, oxy hydrogen torches are often used. In case of brazing, torch flames are played upon thoroughly cleaned parts by the operator. These flames are neutral or slightly reducing and are used to heat the heavier sections.

While heating, flux is applied to the joint area which prevents oxidation of the parts. Further, this flux prepares the surface for wetting by the filler metal once it cleans the joint area of oxides after it gets melted. The metal is later handfed to the joint area once these joints reaches a particular brazing temperature. Usually, instead of being handfed, the filler brazing rods are preplaced to fit the joint contour in the form of a ring, washer, or insert. The most often used filler metals rather need a joint clearance (at brazing temperature) of 0.05 to 0.125 mm for capillary flow. Lap joints are usually preferred.

One can achieve uniform heating through the employment of multiflame torches. The torch can be directed more on the heavier members having greater thermal conductivity in order to bring all members of the assembly to brazing temperature simultaneously.

Torch Brazing Equipment
There are varied kinds of equipment required for torch brazing which makes this brazing process quite convenient. Torch brazingequipment basically include :

Torch Brazing Advantages
Whenever advantages of torch brazing is discussed, it is essentially compared with welding. Torch brazing as a process has its own set of advantages which need to be taken into consideration to prove the worth of brazing over welding. Advantages of torch brazing can be widely categorized into the following pointers :

Torch brazing requires a very small investment especially when the joint quality is largely dependent on operator skill having a consistency issue.