Welding brass

By Stephan (***)

Date 06-23-2007 19:43

Hey cp!

Brass as a copper-zinc alloy is a bit tricky to be welded. Zinc has a relatively low boiling point (906°C = 1662,8F) . Thus it can likely be supposed that a larger amount of zinc is being vaporized while welding. Hereby again the base material can be deteriorated in its mechanical properties.

Therefore I would like to recommend you to consider soldering instead of welding.

Due to lower working temperature ranges (< the boiling point of zinc) you can avoid to vaporize zinc and thus to conserve the original properties of the base material as far as possible.

I did a quick search for you and have found:

http://www.muggyweld.com/1clip11.html

Perhaps soldering could be an alternative to welding, in particular under considering that you want to "rework" flaw areas and re-machine the part.

Kind regards,
Stephan

By cp1969 Date 06-23-2007 20:27

Thanks for the response. My original post left out some key info as to why soldering won't work.

This part is for a physics experiment. It is a conductor and has sixteen wire termination slots machined into it. One of the slots is off location by about .200". Now, knowing what we all know about electricity, what possible difference could it make that one slot is off by .200" when all the wires are ultimately joined together upstream, carrying current from the same source? None that we normal people could see.

But it matters big time to the physicists. That mislocation means the symmetry of the piece is disrupted and that early-terminated wire will deliver its current just a tiny, tiny bit sooner (I have it off by 1.7 x 10^-11 sec) than the others and all sixteen conductors have to deliver their current at exactly the same time for the experiment to yield valid results.

If they are that picky about location because it affects timing can you imagine how picky they are about part material uniformity?

By Stephan (***)

Date 06-24-2007 00:15

Hey cp,

hmmm, that sounds great and truly extraordinary...

I once had the honour to accomplish some pretty fine welding- and brazing trials for the Wendelstein 7X project, which is a thermonuclear reactor experiment, see also:

http://www.ipp.mpg.de/eng/for/projekte/w7x/for_proj_w7x.html

and I can remember well, they had the highest levels of joint-quality I have ever experienced.

O.K. this is an important fact you have described and thus I suppose you have to get approximately the same chemical composition in weld deposit as in the base material.

Interesting task...

As far as I assume you won't - with reservation - find a standardized filler for the base metal you have to process. On the other hand I don't know the geometrical dimensions of the part you are talking about.

Under the presumption the part is a large dimensioned one you would need a welding process having a higher arc power density, e.g. Gas Shielded Metal Arc Welding (GMAW) which however needs a specific coiled wire electrode, having the necessary (standardized) composition.

Gas Tungsten Arc Welding (GTAW) would be an alternative but having - compared with the GMAW - an only lower density of arc power.

Thus I would think that Plasma-Welding may be a possible to use welding process. In combination with a flux - perhaps standardized available(?) - which is improving the wetting-properties and a piece of your original base material it could lead to success. At least I would suppose to attain the most similar chemical composition and thus the most similar properties compared with the untreated base material.

Or you can try to find a brass-filler having a higher zinc-content for compensating the zinc-vaporization which probably will occur, to attain a nearly similar composition. Honestly I have never tried it by myself but from the physics side I guess it could work.

Perhpas has another one of the appreciated fellows in the forum personal experiences with PAW of brass and is thus able to point us in the right direction.

Really interesting matter, cp!

Regards,
Stephan

By billvanderhoof (****)

Date 06-24-2007 04:15

It might be best to talk to the end user on this. It may be better to tune the length of the wire than to meddle with this part. I doubt that an electrical pulse will travel through this part in all directions with the same velocity anyway so some tuning of the wire length may be intended already.

If you weld it you may introduce some difference in the velocity of an electrical pulse either from different chemistry or crystal orientation in the weld metal.

Bill

By Stephan (***)

Date 06-24-2007 16:38

Bill,

pretty good points...

In particular the changing of the physical-chemical properties of the base material after welding is a point which surely should be considered.

Always hard to recommend something reasonable under not knowing the entire details but this "Experiment" is - though sounding interesting- certainly tough.

Best,
Stephan

By CWI555

Date 06-24-2007 16:59

Stephan, Bill,

Having seen some "experiments" with similiar requirements At some of the U.S. National Labs, I have to agree with the idea of leaving it alone. The electrical timing on "experiments" like that are super critical, and therefore the part should really be remade all together. There are just to many things that can go wrong trying to fix it.
My opinion for what it's worth.

Regards,
Gerald

By Stephan (***)

Date 06-24-2007 17:23

Gerald,

hmmm, I agree, most likely You and Bill are right.

I guess the calculated delay time in a magnitude of 10^-11 seconds speaks an own speech.

By the way, I truly don't want to be the culprit for not finding the answer on the fundamental questions of the universe by having given a wrong recommendation ;-) .

Best to you all,
Stephan

By cp1969 Date 06-25-2007 23:08

As of today, there will be no repair attempt. Higher-paid people that me have ruled it out. I haven't ruled it out yet, though. Sometimes people change their minds.

Thanks for all the responses!

By Stephan (***)

Date 06-26-2007 07:01

cp,

as already guessed - Bill and Gerald were right by supposing that it would likely come so...

However, thanks for the information!

Regards,
Stephan