|
Back to Part One
|
The engine intakes and some fairings on the B-25 were joined by oxy-fuel welding. |
|
TOOLS
Virtually any torch may be considered viable, but this author tends to avoid giant ``railway" torches, and,
conversely, small jewelry torches. Most are fine, some are really good and comfortable, and a few might
be considered for specialty work.
Hoses of choice are light and flexible, enabling both out-of-position work, and long periods requiring a
steady hand.
Regulators, because of the low pressures required, may not be accurate at the low end, and so must be
twiddled with the torch lit to establish the best flame. Do this with the torch valves open, setting the
largest, best flame for the tip. A glance
|
This oxy-fuel welding on 3003 sheet was simply planished on the wheel without any metal finishing. |
back at the gauges will show the approximate right pressure. Set the flame neutral, or if the regs creep,
slightly feathered (carburizing) so as to avoid an oxidizing flame completely.
Aluminum OFW flux must be of the highest quality, and strictly specified as a welding flux, not as a brazing
or soldering flux. Brazing fluxes, while providing a very poor weld appearance, also re-alloy the weld
area with zinc from the zinc chloride they contain. The presence of zinc in this manner, makes the
aluminum parent metal weak and brittle.
The proper aluminum OFW fluxes from the old days have mostly disappeared, but a few years ago TM Technologies
had the original ALCOA formula revived, and it is now sold under the TM Technologies label.
(see TM fluxes)
Special safety eye wear must also be used, both to protect the welder, and to provide a clear view
through the yellow-orange flare given off by the incandescing flux.
In the 1920s, cobalt melter's glasses were borrowed from steel foundries and were still available until the
1980s. However, the lack of protection from impact, ultra-violet, infrared, and blue light caused severe
eyestrain and eye damage.
Didymium eyewear, developed for glassblowers in the 1960s, was also borrowed, until many complained of eye
problems from excessive infrared, blue light, and insufficient shading.
In 1989 TM Technologies patented a new green glass, designed especially for aluminum OFW. It cuts the flare
and provides required protection from ultraviolet, infrared, blue light, and impact, according to ANSI
Z87-1989 safety standards. As of this writing, this eyewear has no known peer, and no complaints.
(see TM 2000 High Accuracy Safety Eyewear)
A stainless ``tooth" brush is essential for scrubbing off the invisible oxide film, just prior to welding.
Continue
|
