×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

High porosity in A356 after welding

High porosity in A356 after welding

High porosity in A356 after welding

(OP)
Need advice from an aluminum welding specialist.
We have a part that is 5.5" by 12" and 5/32" thick, and we have to build up a lug at three opposite locations that is about 1/2" in diameter.  After performing at least a dozen tests, we still have high porosity in the interface and in the weld areas.  We have to follow the Vought spec (CVA 17-12F), which states that the minimum porosity spacing should be greater then 2 times the largest adjacent defect (between voids).  During welding the following was done:
- Pre-heating the part before welding to 350°F
- Cleaning the welding rods and the part before welding
- Covering the part with ceramic fiber wool to keep the heat
- Welding in an argon filled chamber
- Standard Practice: Tig Weld, 100% Ar shield gas, AC current, more cleaning action.

RE: High porosity in A356 after welding

Do you have to use fusion welding to "build up" the lug?  Can you take a pre-made lug and use friction welding to attach it?  This should avoid porosity problems.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: High porosity in A356 after welding

What type Aluminum are you working with?

RE: High porosity in A356 after welding

(OP)
CoryPad,
Unfortunately we don't do friction welding in house.  The pre-made lug is not a bad idea, but we still have to weld it to the rest of the part.
Thank you,

RE: High porosity in A356 after welding

(OP)
unclesid,

We are working with A356-T6 casting, re-heat treated to T6 condition after welding.  I could have sworn I wrote it down!
Thank you,

RE: High porosity in A356 after welding

COKA,

Perhaps your company can "learn" to do friction welding with this project.  Presumably you have spare material (scrapped parts due to excessive porosity).  Do you have a milling machine?  Can you fixture a piece of the casting and then use the rotating machine head to create the friction?  With a simple setup, you could probably determine a procedure that will work.  The benefit is that you have no porosity, and you have a full cross-sectional area weld.  

If the above isn't possible, perhaps you can use a pre-made lug and the GTAW process to create a line weld around the lug perimeter.  This is a relatively simple weld geometry, with a lot less metal requiring solidification, so it may reduce the porosity to manageable levels.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

RE: High porosity in A356 after welding

You did, it's in the title, my problem was I copied the post and not the title lines.

Is your power supplied a high frequency machine with a stabilizing current, meant to weld AL?
Have you tried different welders?
As you are in box keep the torch shielding gas flow as low as possible?  
Have you checked the parts for porosity?
Is the lug also 356?

With all our welding of Aluminum shielding was the biggest problem once we got the high frequency machines.

Keep the arc as short(very important) as possible.

Sounds like you have got the cleaning covered.

I have 2 fillers list by ALCOA 716 (4143) and 4043. We used the 4043 to repair Al die cast parts by the hundreds.  We did have a little porosity.   The 716 did work but was not readily available.  We had some larger injection molded 356 parts that were almost impossible to weld on.    

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources