Porosity in mild steel GTAW

Date 10-25-2004 20:16

In addition to grinding or sanding followed by brushing, you might try wiping the joint with acetone or alcohol. The same wipe goes for your filler, maybe you are contaminating it by handling. Also remove any scale on the surface of each pass.

By TimGary (****)

Date 10-26-2004 11:29

It sounds to me like you're having a shielding gas problem.
Check for gas line for leaks and propper pressure.
Do you have an old beat up flowmeter that isn't working properly?
Are there any drafts, wind or fan blowing your gas away?
Are you or someone else standing on your gas line?
Is you cup nice and clean?
Are the gas holes in the collet clogged?
What does you instructor suggest?

The last time I was in welding school one of my "friends" was jealous because I was doing better than he was. So, as a "practical joke" he would turn off my gas while I was welding test plates, and then, when I would would stop to try and figure out what was going on, he would turn it on again.

Good luck and have fun,
Tim

By RonG

Date 10-26-2004 13:08

Believe it or Not!
I have witnessed a fellow standing on his gas hose wandering why he could not get it to flow. Same guy often parks is safty glasses on top of his head and then searches for them.

If you loose your gas coverage you will see lots of sparks (4th of July). If you have insuffient gas you will get things like you discribed but it could also be from angleing your torch to much or wrong size cup but most likely loose cup or cap. Any of the above will let Oxygen in.

By _TJ

Date 10-26-2004 14:11

Well I know the regulator(not the flow meter) has a leak and we have to turn the Argon off when we're done so it don't all leak out over night. Maybe I'll try to get him to change it out. No drafts that I'm aware of. The problem occurs in my booth and the one next to mine, so I don't think it's the flow meter. Each machine has it's own. It's on a manifold system so it looks like the culprit might be the regulator on the bottle.
Collet is clean, cup is clean.
I wonder if we're getting bad gas? Like I said, one bead will run perfect, the next will be all screwed up. Very frustrating. It puts any improvement I might make on hold that's for sure.
My instructor doesn't know what's going on, he's not really a TIG welder, says its pu$$y welding.

Thanks for the replies, I'll see what I can come up with.

Edit* Oh yeah I'll also make sure the cup is tight and I'm not angling the torch too much.

By Lawrence (*****)

Date 10-26-2004 14:53

Nice,

Well, welder$ that can combo GTAW root with $MAW fill on pipe and do a little fitting make darned good money, and are in such demand that the only time off they get is the time they refuse OT, furthermore, most of them would also quickly convince $omebody who $uggested they were $issies that they were wrong.

Maybe your school is using some donated steel? Sometimes unknown batches of steel turn out not to be deoxidized (a good time to complain about imported steel) the stuff will bubble as soon as it begins to melt, If this is the case try to dip a little of your welding rod into the puddle before it jumps onto your electrode. Situations like this are a good time to try some ER70-6 right off the mig roll and see if this helps a little.

By _TJ

Date 10-28-2004 04:50

The steel we use for practice is scrap, my instructor says they havn't had any problem with the test stuff. I think maybe I just needed to turn the flow meter up. Did that today and didn't have any problems. We'll see how it goes tomorrow.

Interesting about dipping the rod into the puddle, not sure I understand what you mean. I have been getting stuff bubbling up around the edges of the puddle, only on certain areas of a given piece of steel.

By Lawrence (*****)

Date 10-28-2004 15:22

TJ,

In situations where mild steel appears to boil as it begins to melt;

The weld wire I mentioned (ER70-6) is formulated with deoxidzers which when you dab even a little bit of it into a turbulant puddle of low quality mild steel it will often make it a little easier to work with. If you ever work on old farm equipment or are forced to GTA weld on mild steel material that you cannot remove all the corrosion from, this little trick will save alot of frustration.

Tig and rust are enemies, if your material is rusted to the point of pitting, the wire brush needs to be replaced with a more agressive abrasive, and if there is exfoliation than it's prolly a lost cause.

Same with Mill Scale, it hates to be tigged over. Grind the stuff back at least 1/4inch from the weld and things get alot better.

By _TJ

Date 10-29-2004 02:26

I actually have been literally grinding every inch of the plate in one direction, then grinding it down again in a different direction. I'm telling you this metal is clean as I can get it, shiny and bright, no pitting or scale left whatsoever. And I thought the problem was solved, but it isn't. We have discovered there is a rather large leak in the regulator or the manifold system, potentially sucking air in with the Argon. That's all we can figure at this point.

By agong

Date 10-29-2004 01:39

I guess you solved your problem by increasing gas flow rate.
Other possible way to solve this problem: 1) Keep the arc length short when you move. Too long arc causes air traps into puddle. 2) Practice ...

By the way, a good instructor does not need to be a good welder, just like a good basketball coach does not have to be a good player.
Discuss with your instructor about your questions.

By _TJ

Date 10-29-2004 02:34

Thanks for the replys everyone.

I would just like to withdraw my previous comments about my instructor. He DOES know his stuff, worlds more than me with my little single year of experience. I can be struggling with something for days and he'll come in and show me something and it gets me right back on track. I have learned a hell of alot from this guy and in the future I'll try to keep my comments in check.

I think we're gonna check the system for leaks tomorrow...

By magodley (**)

Date 10-29-2004 12:34

Are you by any chance using oxy-acetylene filler RG 60?
Andy

By _TJ

Date 10-29-2004 13:59

I'll check today.

*edit* No it's E70S-2. We got the leaks %99 percent fixed today. There is a tiny one still, new reg is on order. Didn't get a chance to test it out much, spent the whole day tracking and fixing the leaks. We shall see on Monday.

By ssbn727 (*****)

Date 10-31-2004 06:28

Welcome to the forum!

I've been reading this post for awhile now and, I have to say that you're one step away from solving the problem...

Change the faulty regulator & recheck for any other leaks that might appear after the new regulator is installed just for good measure.

On another note; Your instructor may well be knowledgable enough to teach but, I do'nt agree with his comments regarding the GTAW process! I must concurr with Lawrence that thi$ proce$$ i$ well worth becoming proficient in... Heck, I know a few good welders out there that I know for a fact are anything but, what your instructor referred to so, learn as much as you can about this process because, later on in your career, you'll be glad that you did... Btw, It's always good to read your comments Larry!!! I hope everything is well and all the best!!!

Anywho, Buono fortuno (good fortune or some people mean good luck) and keep practicing so that when you become tired, you practice some more!!! Most important of all,
Never stop learning and, never stop seeking to learn more because, a true craftsman or craftsperson, is always seeking more knowledge in order to improve their skill sets and always remains teachable.

Respectfully,
SSBN727 Run Silent... Run Deep!!!

By billvanderhoof (****)

Date 10-31-2004 07:09

If you don't get a win, it could be the metal. Sometimes it seems like a dozer blade, for example, will get dirt embedded right into the metal (or I might be making excuses for a bad day). Still a little new metal for test purposes will not cost much.
Bill

By _TJ

Date 11-03-2004 02:03

Just to cap this thing off, it looks like is was a combination of 5 or so leaks in the system causing my porosity. I thought we'd gotten all of them but went back over all the joints and found a couple more. Now that the system is pretty much leak-free, we haven't had any more issues with porosity in the last couple days.

Thanks for the comments, info and the welcome!