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How to Use Flux Brazing?

Published in Brazing Techniques 3 mins read

One specific method for applying flux in brazing involves a technique known as hot-rodding.

Using flux is a critical step in brazing to prevent oxidation and ensure a strong bond between the base metals and the filler material. While flux can be applied in various ways (like painting it on, using flux-cored rods, or dipping), the provided reference describes a practical method called "hot-rodding."

Understanding Hot-Rodding Flux Application

The hot-rodding technique is particularly useful when working with powdered flux. It allows for precise application of the flux directly into the joint area where it's needed most.

Here's how to perform hot-rodding based on the reference:

  1. Warm the Brazing Rod: Use your torch flame to warm the tip or end of your brazing filler rod. You don't need to melt the rod, just make it warm enough to attract the flux powder.
  2. Dip into Flux Powder: While the rod is warm, dip the heated end directly into your brazing flux powder.
  3. Observe Agglomeration: The warmth from the rod will cause the individual flux particles to stick together and adhere to the end of the brazing rod. This is where the reference states: "Hot-rodding is where a brazing rod is warmed with the torch flame and then dipped into the brazing flux powder. The warmth in the rod causes flux particles to agglomerate and stick to the end of the brazing rod."
  4. Transfer to the Joint: Once the flux has adhered to the rod, you can then transfer it to the joint opening or seam you are preparing to braze.
  5. Apply to the Joint: Carefully apply the flux from the rod directly onto the surfaces within the joint that need protection from oxidation during the heating process.

Benefits of Hot-Rodding

  • Controlled Application: This method allows you to place the flux precisely where you want it, often within narrow joint gaps.
  • Less Waste: By sticking directly to the rod, less flux is wasted compared to just sprinkling it on.
  • Improved Coverage: The slightly molten or sticky flux adheres well to the warm base metal surface when applied.

Summary of Hot-Rodding Steps

Step Action
1. Heat Rod Warm brazing rod with torch flame.
2. Dip in Flux Dip warm rod into flux powder.
3. Observe Adhesion Flux particles stick to rod (agglomeration).
4. Transfer Move rod with flux to the joint.
5. Apply to Joint Deposit flux from rod into the joint opening.

By using the hot-rodding technique, you can effectively apply powdered brazing flux to your joint, preparing it properly for the brazing process.