Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne 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



Click here to return to the Engineering Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory