Call to Talk With A Product Expert - 877-532-WELD (9353)

High Heat Brazing Flux for High-Temperature Applications

High heat brazing flux is selected based on the temperature range required, base metal composition, and joint configuration. Proper selection ensures the flux remains effective throughout the heating cycle and protects metal surfaces during brazing.

Different formulations are used depending on process demands, allowing consistent results when working in elevated temperature conditions.

High Heat Brazing Flux for Demanding, High-Temperature Jobs

High heat brazing flux is used when standard flux cannot maintain performance at elevated temperatures. It enables proper filler metal flow and bonding in conditions where lower-temperature fluxes break down. This high heat brazing flux is suited for thicker materials and demanding applications where joint integrity is critical.

At WeldingMart, you can buy high heat brazing flux in the forms and sizes required for your process. Our in-stock selection is ready to ship, helping you avoid delays. Whether you’re working with higher heat ranges or difficult joint configurations, we stock black brazing flux that delivers consistent results and dependable joint strength.

Shop Shop All Welding Wire & Rod, browse brazing flux, or explore general purpose brazing flux for related applications.

Benefits

  • Maintains performance at elevated temperatures where standard flux breaks down
  • Supports strong, consistent joints in demanding brazing conditions
  • In-stock and ready to ship to keep high-heat jobs on schedule

Frequently Asked Questions

What makes a brazing flux suitable for high-temperature applications?
High-heat brazing fluxes (AWS Type 3B or Type 5) are formulated to remain active at temperatures from about 1350°F to 2200°F (732–1204°C). Type 3B contains boric acid, borates, fluorides, and fluoborates, while Type 5 is a borax/boric acid/borate blend. These are used with high-temperature filler metals such as BCu, BCuP, BAg, BAu, RBCuZn, and BNi, where lighter Type 3A fluxes would burn out before the joint reaches temperature.
What base metals can I use a high-heat brazing flux on?
AWS Type 3B and Type 5 high-heat fluxes are recommended for most metals except aluminum alloys, magnesium alloys, and some titanium or aluminum-bearing alloys. This covers carbon steel, stainless steel, copper, copper alloys, nickel, nickel alloys, and similar metals. For aluminum and magnesium, use AWS Type 1 or Type 2 fluxes, which are specifically formulated for lower temperatures.
Why is this type of flux sometimes called 'black flux'?
High-temperature brazing fluxes based on borax or borate compositions often turn black or dark as they are heated and absorb metal oxides during brazing. 'Black flux' is a common shop term for these dense, high-activity brazing fluxes. The dark color indicates the flux is working — it is dissolving the oxides on the base metal surface to allow the filler metal to wet and flow.
Do I need to remove high-heat brazing flux residue after brazing?
Yes — all brazing flux residues, including high-heat types, must be removed after brazing because they are corrosive and will damage the brazement over time if left in place. Hot water scrubbing removes most residues while the flux is still soft and warm. Stubborn residue can be removed with dilute acid dips, wire brushing, shot blasting, or fiber brushing. Never leave flux residue on pressure-containing parts.