6061-T6 porosity

By welder_guy2001 (***)

Date 07-22-2003 03:23

even when you weld on dirty aluminum it's not the cleanest weld, but it's definitely not filled w/ porosity. I'd look at the gas flow and tungsten stickout. it could be that you're holding the gas cup too far away from the material. or there's not enough gas flow. are you on AC current w/ the high frequency on continuously? are you using pure tungsten?

does DI stand for deionized water? if so, then that could very well be reacting w/ the aluminum. and w/ the nitric acid in that same area there could be some interesting chemistry going on. try cleaning the weld area w/ a stainless steel toothbrush and then weld it. if you have some scrap aluminum laying around, try cleaning that up w/ the brush and see how that welds. eliminate all the variables and you will find your answer.

By jeffc Date 07-22-2003 04:23

Thanks for the reply. I am using about 20 lpm Ar. Using a Dynasty 300 on AC with a 1/8 2% Thoriated electrode. 195 amps 80% neg polarity and about 180 Htz output. I did start out with a scrubing using SST brush. Didn't see any difference with or without brushing. The parts were wraped in papeer towels and sealed in plastic bags. I tried a 25%-75% He Ar mix and it seamed reduce the posity some, but not totally eliminating it. This is a problem I see from this customer off and on. Today I asked if they could rinse with plane water after prep. So we will see if eliminating the DI will help. It makes sense to me as the DI being striped of ions will try to react with the Alu. We'll see. Thanks again.
JC

By Michael Sherman (***)

Date 07-22-2003 11:25

I have a couple of suggestions. 1) Turn your gas pressure down. You should be at 10 lpm, not 20 lpm. This high pressure may well be causing turbulance. 2) Although it is possible to use thoriated tungsten on aluminum, you will like the results of pure tungsten better. 3) Balance your sine wave or use more positive on it, for better cleaning action. 4) Switch back to all Argon, you will get better cleaning action with that than a mix. 5) Use the stainless brush. 6) Make certain the parts are 100% dry. If you are cleaning them, rinsing, wrapping in towels and then locking them in a plastic bag, I wonder, are they dry when you weld them? Good luck and if you solve your problem, please let us know how you did it.

Respectfully,
Mike Sherman

By Lawrence (*****)

Date 07-22-2003 18:59

Just to fortify the other good advice.

At 195 amps you will need a good sized cup and argon flow at or above 25 cfh (I you will need to convert to lpm yourself :).

Rember your balence control on *Dynasty* at 80% is a Real-time 80%. By this I mean that it is equivilant to the dial pegged to 10 (or absolute max pen.) on a synchrowave. In most cases this provides insufficient cathodic action. I would suggest taking it down to 70% or even 65. This may mean moving up in tungsten dia. so be it.

Next. at amperages as high as your working your increased frequency is only making more noise. You will have fine arc stability and directional control at 60 Hz. and alot less noise.

Abrasive prep: Immedatly prior to welding I like an 80 grit aluminum oxide disc 1 or 3 inch on a mandrel driven by an 18,000 rpm pnumatic 90 degree die grinder.

6061 likes to be welded fast! Overly slow travel speeds also contribute to hydrogen entrapment and subsequent porosity. You can help this to a small extent by using a larger dia. filler wire to help cool the puddle along with positioning your body to move at maximum speed (within reason) along the joint.

By jeffc Date 07-23-2003 02:08

Thankyou all very much! I think I will have a batch of parts for this weekend. You all have given me excellent leads. I will write back after the next batch and give a update.

Jeff Currier