LOOKING TO IMPROVE
Try fluxes for tube, pipe production
By Yehuda Baskin, Ph.D.
improvements often are simple concepts that can
have profound effects on existing processes. New technologies and process efficien-cies allow manufacturers to improve products or increase throughput. For example,
developments in high-frequency power
supplies allow tube and pipe manufacturers to select the optimal frequency for the
application. Consumables also continue to
evolve and find new applications. Welding
flux is one such consumable. Many tube
and pipe manufacturers have found that
using a flux reduces defects, thereby
Fluxes for tube welding processes are
available in two forms: paste and liquid.
Both have pros and cons, and the choice
depends on several factors. Introducing
fluxes is easy in the tube and pipe production process, and the result often is a
cost-effective return in quality, efficiency,
consistency, and time management.
Before choosing a paste or a liquid, it
is necessary to learn about the chemical
makeup and vitreous (glassy) nature of
tube and pipe welding fluxes; the chemical mechanisms whereby the flux
removes refractory oxides from the surfaces of 409 stainless steel, 409 aluminized stainless steel (MO), and 439
stainless steel; and the role of fluorine.
Fluxes are essential when joining metals in
ambient air, whether by soldering,
brazing, or welding. When heated, fluxes
perform four tasks:
1. Dissolve or react with surface
2. Protect the cleaned surfaces against
3. Transfer heat from the heat source
to the joint.
Photo courtesy of Abbey International Ltd., Perrysburg, Ohio.
4. Remove surface oxides, allowing
surface or filler metals to flow and wet
the joining surfaces.
It is important to distinguish brazing
fluxes from welding fluxes. The difference is a matter of temperature: Brazing
takes place from 900 degrees F to 2,200
degrees F; welding is from 1,500 degrees
F to 3,000 degrees F.
Tube and pipe mill weld boxes develop very high temperatures ( 2,600 to
2,800 degrees F), so a welding flux seems
to be appropriate for this application.
However, the heat cycle used in tube and
pipe production is too short and too
intense to activate welding fluxes.
Moreover, the fluoride content of these
fluxes is quite low. High fluoride content
is critical in tube and pipe welding
In fact, various silver brazing flux
formulations are suitable for this