Basic steps for good brazing

STEP Nº4 HEATING OF THE PARTS

There are many ways to obtain the brazing temperature and resulting fluidity of the alloy through the clearance.

The most common method to reach the brazing temperature is by using a HAND TORCH.There's a huge variety of combustible gases to be used with a hand torch such as Propane, Acetylene, or Butane. They are mixed with air or pressurized oxygen in order to generate high temperatures.

The torch flame is to be regulated at whether an oxidizing, neutral, or reducing level depending on the base material and the brazing filler metal alloy being used.

The heat supplied by the torch flame must heat up the base metals evenly in such way they reach the brazing temperature at the same time. One way to do so is by moving the flame in circles over the parts to be brazed.

In the specific case of a joint for two pipes overlapping the brazing temperature is reached preferably by heating the internal pipe first and then the external one. Through this method, you assure the internal surface gets evenly to the brazing temperature.

The precise heating of the external pipe is determined by a cherry red color on it indicating the right temperature for the brazing filler metal rod to be applied.

Commonly, the flux indicates the proper moment for the filler metal to be applied and start the brazing process as it turns brilliant and glassy. Once this occurs, move the flame backwards a little and put the tip of the brazing filler metal rod in the clearance area. A portion of the rod will melt and flow through the joint gap.

Reaply heat avoiding the flame to get in direct and permanent contact with the rod tip for more than necessary. then apply more heat just to the front of the melted alloy. The alloy will follow the heat so you can make it go as you wish.

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