John Futter wrote:
> Derek
> In my opinion you should listen to Jerry
> From my limited knowledge moving fast on Al with mig on small parts tends to leave microcracks especially at the start and finish of the weld -fine if you are building a boat but no good for high vac work.
> All the people I have seen doing this type of small work including myself use TIG and even then it takes a bit of trial and error to get the DC offset on the AC setting right.
> have a go anyway and report back
I will
btw a circle a doesnt have a start or a finish.- hence the turntable and if there are cracks or porosity there's always Technoweld
mig (ARGON) welding Alu pipework
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Linda Haile
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Re: mig (ARGON) welding Alu pipework
As I stated in my first post in this thread, heat the parts to be welded first. This will considerably reduce the risk of cracks.
A hot air gun is ideal for this, and can heat to 500 degrees C.
You then need a lot less power for welding, so you can also use a slower wire feed rate.
This also drives out any moisture which reduces porosity as well.
(Melting point of ally is six to eight hundred degrees C. The hotter it is before welding the less the distortion and cracking due to localized heating.)
A hot air gun is ideal for this, and can heat to 500 degrees C.
You then need a lot less power for welding, so you can also use a slower wire feed rate.
This also drives out any moisture which reduces porosity as well.
(Melting point of ally is six to eight hundred degrees C. The hotter it is before welding the less the distortion and cracking due to localized heating.)
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Jerry Biehler
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Re: mig (ARGON) welding Alu pipework
On the outside of something yes you can mig it, but the ID of a 16mm hole like a vacuum fitting is supposed to be welded, good luck.
Problem with aluminum mig is I have seen weeping even on fluid tanks. I cant imagine what it would be like on vacuum.
But its still worth a try. Nothing to loose but a little aluminum.
Problem with aluminum mig is I have seen weeping even on fluid tanks. I cant imagine what it would be like on vacuum.
But its still worth a try. Nothing to loose but a little aluminum.
Re: mig (ARGON) welding Alu pipework
Had some lessons from a professional welder on both TIG and Mig with Al (about 15 hours). he showed its quite possible to produce good welds with cheap MIG welders with Al. And then he got me to do it. The first thing he did was to modify the shroud so that the tip protruded 4mm from the shroud. then a few runs to get the power and feed right. On my set that was quite low power and a high feed rate. Then the crucial part was tilting the torch to ensure the shield gas stayed ahead of the arc. Get that right and it was then quite easy.