Welding problems (hydrogen from the air moisture) in an aluminium vessel 2

[drodrig]

Hi,

Some supplier is having problems welding an aluminium vacuum vessel.

The hydrogen from the air moisture is diluting into the melted aluminium during the welding process. There are large bubbles when it solidifies.

X-rays are showing the problem.

The new approach is pre heating the welded parts.

Does anybody have any tips to get a proper welding for a tight vacuum vessel?

The porous seam will be a problem for the vacuum

thanks

 

[EdStainless]

What material is their gas hose? When was it last replaced?
Most hoses become more permeable with age.
Is the weld filler filler kept warm in a very low humidity environment?
If the wire isn't dry you are out of luck.
We used to measure oxygen (down to sub-ppm) at the torch when we were setting up.
Are they cleaning with the correct solvents?
That are clean and dry themselves?
preheat may help but it is just one factor.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[drodrig]

I don't know details, I was looking for some guidelines since the problem is impacting in the project time line

The oxygen measurement is a good idea.

Preheat is one of their next steps

I found this post and there are very nice recommendations:

https://www.eng-tips.com/viewthread.cfm?qid=343947

 

[weldstan]

Check the dew point at the torch in addition to addressing Ed's comments.

 

[mfgenggear]

Drodrig

no mention on the type of welding method.
porosity, and welding cracks are a major issue.
what type od aluminum also comes into play,
I forgot a lot, but here are some tips as well
welding rod or spools need to be store in a container dry as possible.
pre scraping if the welded edges, "areas" have to be prepped in advanced. but can not sit longer than 15 minutes.
due to oxide on the surfaces. all the scrapping tools have to be free of contamination.

clean the areas with acetone to remove debris and contamination.

Important: preheating the parts to a safe temperature, may ask here or a welding engineer'

post weld heat treat may be required, verify with a weld engineer.

and lst if your supplier is not use to or have a proper procedure, stop all work and consult and hire pro welding engineer.
because the more they try to repair, the more damage will be caused and prts will be scrap. seen this happen a lot in the past.
aluminum can be easy or it can be a nightmare.

 

[Tmoose]

"aluminum can be easy or it can be a nightmare."

I worked at a company that made, and also had made some complicated aluminum vacuum vessels and structures.
As I recall the New England weather, especially in summer, could single handedly make well developed aluminum welding processes performed by extremely talented welders impossible on some days. Porosity from atmospheric moisture would result despite best weld prep and process control efforts. Even on some fairly non-tricky alloys.

 

[mfgenggear]

tmoose

that's part of the reason to bake the parts prior to weld.