18 Storing
and Re-Drying Submerged Arc Fluxes Unionmelt
bags are designed to reduce the amount of moisture intrusion, when they are completely
closed. They are
provided with layers of paper, as well as a film of plastic to help retard moisture
penetration. However,
when the bags are opened or if they become punctured, they should be kept in a
closed container in
order to ensure that the products remain low in moisture.
If the flux becomes exposed to humidity,
it can be re-dried. Re-drying flux can often restore it to its original,
as-manufactured condition. In the case
of fused submerged arc fluxes, a re-drying temperature of a
minimum of 300°F (149°C) is
recommended to assure the moisture is reduced to its original levels. For
bonded fluxes, a minimum of 500°F.
(260°C) is recommended. For bonded flux, it is important not to exceed
1000°F (538°C), or the welding
characteristics of the flux may suffer. When
re-drying the flux, it is important that the complete mass be brought up to the
temperature designed. If
the flux is held in large containers, this can take a very long time - perhaps
over 24 hours. In thin layers, reduction
in moisture can be accomplished in as little as one hour, for example, in layers
one or two inches thick.
The re-drying temperature and time, therefore, are dependent on the amount of
moisture contamination
and the thickness of the flux bed being dried. Flux
Handling Condition* Holding
Baking
Type (Opened
Bags) (Reconditioning)
Fused 250°F
(121°C) Min.
300°F (149°C)
Bonded 250°F
(121°C) Min.
500°F (260°C)
Max.1000°F
(538°C) *
The actual baking time and temperatures
are a function of the amount of moisture.
