Fluxes

Fluxes

Procedure

Unfortunately, there is no universal flux that covers the entire temperature range from 600 ° C to 1000 ° C and that satisfies all the above requirements. Boron-based components which are completely satisfactory at the highest temperatures lack flowability and activity below 750 ° C and are therefore ineffective. To solve this problem, a series of compounds containing low melting fluorides have been developed, each of them with specific characteristics of use. The key features of our complete series of fluxes are described in the table below.

The residues of some fluxes disappear during cooling. Others must be eliminated by washing, mechanically or chemically.

Fluxes for silver soldering, for light metals, zinc and its alloys: brush in hot water and rinse (do not use wire brushes). The residues of Pastin 1-2 fluxes are removed with hot water, Pastin 3 with benzuene or thuluol.

Hammer, scraper, metal brushes, grinding wheel, cleaner, emery cloth, sandblasting, etc.

Here are some solutions that can generally be used depending on the base metal.

It is necessary to carry out a thorough cleaning of the faces of the joint to be brazed before brazing, in order to eliminate grease and foreign substances, but also to use a flux to obtain a good brazing.


A flux is a chemical compound based on potassium tetraborate or potassium fluoride, it comes in the form of a paste or powder. Its role is:

  1. facilitate the wetting of the filler metal;
  2. dissolve the metal oxides that form during heating;
  3. protect the joint surfaces against air oxidation.


A flux must possess other qualities according to its composition:

  • it must begin to melt at a temperature lower than that of the solidus of the filler metal used, so as to stick uniformly on the surfaces of the joint;
  • it must not decompose at the maximum brazing temperature;
  • it must be easily eliminated with water or brushing.


The use of potassium components avoids the flare caused by sodium during torch brazing. However, fluxes must be used with caution and it is preferable to avoid contact with the skin for a long time and not to breathe the degassed vapours (fumes). Hence, the need to ventilate the workplace well.


Fluxes are selected based on:

  1. power on the metals to be brazed;
  2. temperature of use;
  3. presentation;
  4. ease of elimination.
Type / description Interval Fluidit Activities Life Available in
C Dust Pasta
N. 1 - FLUX 1 F 530-750 Very good Very good Media And And
N. 2 - FLUX 1100 550-800 Good Good Very long And And
N. 3 - BLACK FLUX 600-1000 Good Good Very long No And
N. 4 - DRY FLUX 550-850 Good High Very long And And
N. 5 - FLUX 751 550-800 Good High Media No And
FLOW 707 180-350 Good High Media No And
Fluxes table 1

New eco fluxes

The new fluxes 16/14, 16/17 and 16/18 for silver alloys replace the old formulation fluxes.


The flux series 16 comply with REACH - CE 1907/2006, Annex II - Rev. 16/01/2012 and do not require ADR transport.

Type Description Interval Fluidit Activities Life Available in
C Dust Pasta
FLOW 16/14 Universal. For metals, copper and its alloys, iron, stainless steel. 530-750 Very good Very high Media And And
FLOW 16/17 Universal. For strong thicknesses, stainless steel, tungsten carbides. 600-1000 Good Good Very long And And
FLUX 16/18 IND. Universal. Induction brazing on heavy metals. 550-850 Good High Very long And And
Fluxes table 2

For information on fluxes, fill out the form and ask for a quote

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