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BRAZING RODS AND FLUXES

Fluxes for Brazing

A flux must possess the following properties: • It must dissolve oxides • It must prevent the formation of new oxide skin • It must reduce the surface tension of the filler metal • It must act as a heat indicator • It must remain active for a time at melting temperature, without burning.

Unitor fluxes are normally in paste form, but may also be supplied as powders. Flux powder may be mixed with distilled water or methylated spirits if a paste is required. Always replace the cap on the flux tin after use to prevent drying out and contamination.

When handling flux, avoid direct contact with the skin, especially if you have scratches or open cuts. Always wash your hands afterwards. Good ventilation is necessary wherever welding or brazing takes place.

3.05

The different types of fluxes are formulated to melt at a temperature just below the bonding temperature of the filler metal. In this way the flux medium acts as a temperature indicator and shows when the correct bonding temperature has been reached.

Surplus flux remaining on the workpiece after brazing should be removed by rinsing in clean water and brushing.

Fluxes for welding are dealt with in the chapter on welding rods.

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