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Welding in Space
Name: Dennis B.
Status: Educator
Age: 40s
Location: N/A
Country: N/A
Date: N/A
Question:
Will it be possible to weld steel, alum.,
titanium, etc., using conventional electrical welding sources like an arc welder
we use here on earth,in space with zero gravity? I assume the orbiting
space station would have a minimal amount of gravity from simply
orbiting the earth but say, on a long trip to Mars or other location where
there's virtually zero gravity, would the molten metal from the weld zone
stay intact from capillary action or would it 'blast' off into the
surrounding atmosphere (or lack of it) around the "astronaut" that's doing the
welding?
Also, would there still be the need for a protective
'envelope' of inert gas surrounding the weld zone like argon, or helium, etc.
as it is required on earth with the oxygen-nitrogen atmosphere? Is the
vacuum of space really empty?
Replies:
Hi, Dennis !!
It is possible to weld steel, alum, titanium, etc
using conventional electrical welding sources, despite of
zero gravity. There are several types of welding, as you
know. They can be divided into two groups :
1 - by pressure
2 - by fusion
To the first group belong processes using ultra-sound,
electrical diffusion, electrical resistance, explosion, etc.
Some processes are not very well defined, and are
classified between both 1 and 2, like the process
named point resistance.
To the second group belong most of the used industrial
processes, and one of them is welding by arc. As source
of heat to the fusion may be used electrical discharge
from an electrode and the metal ( by using negative and
positive charges ). Gravity is only necessary when a molten
metal must be deposited over the surface of another one.
In this case, it is necessary to use an appropriated welding
method that doesn´t use gravity.
The second part of your question refer to the use of an
envelop of inert gas. Well, in the space such measure is
not necessary, just because there are not oxygen molecules
present.
And, as an answer to your third question : " is the vacuum in
space really empty ? ". Yes, it is possible to be considered like
this. In reality, the concentration is said to be about 1 hydrogen
atom per cubic meter of space !!!
Regard
Alcir Grohmann
One issue I am not too sure about here is if you could even form an arc in
space. In a truly hard vacuum, you could not form an arc plasma, because
there would be no gas atoms to ionize. So it might be necessary to use at
least a small amount of gas, not as a protective anti-corrosion envelope,
but as a charge carrier.
If an arc would form, arc welding in space would be a lot easier than on
earth. Gravity will not be much of an issue: even on earth, you can weld a
joint from all directions. Vertical or overhead joints are a pain for the
welder, but that's an issue of positioning himself rather than an issue of
which direction the metal flows. In space, any direction would be as good
as any other. The lack of oxygen and nitrogen in space would eliminate the
need for the protective gas envelope used in TIG and MIG welding. In the
Space Shuttle's orbit, there is a little bit of atmosphere remaining, but it
is so much less than at the surface that it shouldn't adversely affect weld
quality. (This might not be true for difficult metals such as titanium and
tantalum that need to be worked in special inert-gas boxes on earth; even
the gas envelope from a TIG torch can't exclude enough air for a weld to
work down here.)
Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
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Update: June 2012
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