TIG question

Date 05-11-2011 00:15

a buddy sent me this question

I have been tig welding for about 25 years. My current rig (Lincoln) I've had for about 4 years and have not had any trouble with it prior to this. I weld about once a month so I get in a fair amount of practice. I have always had consistently good welds with a few exceptions when I try to weld something that is too dirty or oily. When that happened in the past, I stop, do a half-assed clean-up, and that usually fixes it. I just finished a project that I started with Tig but had to finish with stick because of porous welds. Not just a few bubbles but MOSTLY bubbles. I would sometimes be able to weld one section with no problems, then move to another part only to have massive bubble problems. The project was mild steel, cold rolled, all 1/4" thick. Some metal had lubricant used on it and some had primer paint. I used a grinder to remove that paint but it didn't matter. To remove the oil residue, I bought a sand blaster just for this project which I was sure would fix it, followed by solvent cleaning but there was no difference. I want to emphasize that some welds came out just fine (about a third of them). If they started good, they stay good for the whole bead but when it starts bad, it never got better.
The gas bubbles in the weld persisted no matter how long of a bead I laid down and no matter what sort of filler rod I used.
There is no difference when I changed out the tungsten to a new one (I use 1/8" 2% thoriated and a screen gas diffuser on a water-cooled torch)
I used a new gas bottle of pure argon (from Airgas) at 15 cfh flow with preflow and post flow.
The only things that I can think of are: 1) the argon gas bottle is new but can't imagine how a fresh bottle would be contaminated or mislabeled or 2) I didn't clean enough but based on experience, I did a pretty good job - I could have done a little bit better but not much.
Can you diagnose what is happening from what I've told you? Have you ever heard of a bad batch of argon???? I've never had one.

Thanks for your help.

I am thinking that he has a water leak, any other thoughts

By Blaster (***)

Date 05-11-2011 00:39 Edited 05-11-2011 00:46

Any steel contamination on the tungsten can cause porosity.

It is not common, but I have seen some steel (2 or 3 times) were you had to get a dab of deoxidizing filler metal on the base metal before it went liquid, and then keep adding a decent amount of it during welding to prevent porosity. If you first fired up a puddle before adding rod it would instantly go to porosity and once it started, it didn't want to stop when underway. Whether it was actually the chemical makeup of the steel causing the problem or some other obscure factor I am not sure.

It is possible the gas is an issue. We get a bad bottle every couple of years. But it is excedingly unlikely that would happen twice in a row. Of course you don't want the tungstens sticking too far out beyond the end of the cup if you think shielding may be an issue.

Any chance he accidently got a hold of some oxy fill rod instead of TIG rod? That can do it.

By grizzzly (**)

Date 05-11-2011 01:29

He just sent me a little more information

I never have used 6011. I use 7018. I did not take pictures of the welds before I took it to Tucson but they were full of large collapsed bubbles. 7018 seemed to work fine with no problems.
The water: I see no leaks. However, please explain why you suggest this. How can a leak cause this? If there was no water, the tungsten would melt or get way too hot and I would see that. Even if too hot, it shouldn't change the weld. Are you saying the water could be somehow getting into the arc?? The connections are on the handle, away from the head.
The gas: I see no changes in the gas line. Not sure how I would check for a leak

He is talking about a lot of porosity and big stuff
This is an intermittent problem so I think that rules out the gas
He has tried several different tungsten

By DaveBoyer (*****)

Date 05-11-2011 02:51

A friend of Mine had a bad argon cylinder once, but as You mention, it caused a continuous problem, not an intermitent one.

Just a suggestion, You seem to be having all these problems on 1 job. You might try some other material and see how it goes. Same problem different material You can rule out a material issue. Different material no problem, try the filler metal technique Blaster mentioned being sure You have TIG filler.

By grizzzly (**)

Date 05-11-2011 04:16

he did use different filler' and he is going to try welding some SS and let me know

By grizzzly (**)

Date 05-12-2011 02:40 Edited 05-12-2011 02:48

Hi Chris;

I took apart my torch bundle to look for a gas leak today. No leaks. The lines all look brand new and undamaged. I hardly ever unroll it. No gas leak. No water leak. I am pretty sure it has to be a material problem. What do you think? Some steel I can weld just fine. On some steel, I can weld in one place but not another on the same piece. I welded on some stainless steel today and it welded fine. Switched to mild steel and no go.

How do you clean mild steel for welding? I used a bead blaster when I worked at LANL but I cannot afford the floor space now. They are huge. I bought a sand blaster but that is slow, dirty, and often difficult to maneuver the item around to get all angles clean.

I have never had mild steel behave this badly before and even when it did, I could always easily clean it with a wire brush and it welded fine. Now I cannot weld any mild steel. Any other ideas? I am very frustrated!

Jack

Bad weld made today

pic 1

Same Bad weld made today

pic2

Good weld made on same piece of metal. Done two months ago.

pic3

Showing same piece of metal with good weld and a bad weld. The big chunk of metal missing on the upper left was because of porous welds - I cut it out thinking I could use filler rod to replace the bad metal but it didn't work.
pic4
Another Bad weld on two pieces of metal unrelated to the other ones. Made today.

pic 5

GOOD weld on stainless steel made today.
pic 6

By Blaster (***)

Date 05-12-2011 03:34

Looks like a gas shielding issue to me.

What does the electrode look like? Is it oxidizing or erroding?

Tanks of bad gas do get delivered from time to time... I wonder if too if you may have a bottle of blended gas that was misfilled / mislabled?

Any chance you are using a torch with a manual gas valve, not opening it very far, and are accidently pushing on the valve during welding choking off the flow?

By ravi theCobra (**)

Date 05-12-2011 15:45

This is a condition I might have seen before. It looks as though you are trying to weld " rimmed " steel and you do not have sufficient deoxidizers to " kill " the puddle.

This occured in the olden days when steel was " capped " or "rimmed " and contained residual Oxygen.
When you tried to weld these steels ( Usually sheet metal ) they all just " boiled up " into the porous mass you have shown.

I would recomend you get some E 70 S - 2 " Tripple Deoxidized " filler wire and attempt to run a bead on plate -
back in the 1970 's there was a lot of " semi killed " plate around and the use of the E 70 S 2 filler was the only remedy -

Try this and let me know how you do -

By MMyers

Date 05-12-2011 19:44

Grab a different piece of mild steel, clean it (grind to bright metal, acetone, alcohol), and make a weld. Just a bead on plate, no wire. If you get porosity, you have a shielding gas problem. It's either a leak or a bad bottle. If that weld is clean (no porosity), you have a material or cleanliness problem with your part.

By DaveBoyer (*****)

Date 05-13-2011 02:45 Edited 05-14-2011 02:49

Back when I was an apprentice, I got the job of TIG welding pole pieces for street car motors. We specialised in small motor laminations, but We made these too ocasionally. They were made from oily sheet metal stampings stacked up with mild steel pins through holes in the stampings. I would make an autogenous [no filler metal] weld on the ends of the rods at about 300 amps, fusing the last few stampings and the rod ends together. Some would boil up like the pictures You show, most would not. On the ones that boild up, I would add bailing wire as filler, and usually I could get a decent weld after futsing with it a bit. We had no proper filler wire, this was a tool & die shop, not a fab shop.

Having said all that, We never looked for, or found the reason, just dealt with the problem when it arose.

Knowing more now than I did then, I would get whatever rod has the greatest de-oxidizing power, and try it.

Cobra suggest 70 S-2, it might be a good idea to try it.

By Tommyjoking (****)

Date 05-13-2011 01:35

If you welded stainless and had no issues then switched to mild and had problems.....what does that say.....it tells you your rig is fine and your filler is fine on stainless. Therefore your rig is fine and something is wrong material wise on the steel...be it filler or base metal. Steel whether exotic alloy or common A36 is much more temp sensitive in the weld puddle and more prone to show problems with shielding on the weld side. It is just the nature of the beast. If you can weld stainless and all is good then it is a FACT your rig, gas, and filler is working as it should. So eliminate the variables, your rig and your gas if your using straight argon on all of it, what have you. You are left with your base metal and your filler.....I am assuming that you are not trying to weld ridiculously hot or anything like that...thickness for thickness you are in the same ball park parameter wise with stainless welding. Where is this steel coming from???? Brazil, Mexico, Canada, China, Indonesia, the US??? I ask that because I have seen plenty of material come from different sources supposedly meeting a standard and being sub par ....tig welding will bring out the worst in a material that will normally weld "just fine smaw or gmaw". That is just from the hip advice from someone who likes to think they know how to weld most things well. Try some base metals and fillers from a different source and see what you get.

Best regards and good luck'
TOmmy

By gr8tins Date 05-13-2011 03:44

Thanks for all the excellent advice and ideas! I am taking the suggestion to eliminate variables. I brought home a new bottle of 100% Argon courtesy of Airgas this afternoon. I switched tanks and purged gas at 30 cfh for 3 minutes, then tried a weld on one of the same metal pieces shown earlier. It started porous for a quarter inch then went smoothly for 2 inches. Same metal that didn't work earlier. Ah HA! Unfortunately, subsequent welds did not go as well but while I feel like there was some improvement (welds are maybe less porous than before) it's just not what it is supposed to be.

I also bought a new gas hose and torch head today. The old gas hose between the torch and the welder can be tested once I remove it but I don't know how to check the section of gas line between the tank and the welder. (On this Lincoln 275, the gas is routed to a giant twist-plug to get to the torch gas hose). Any suggestions on checking between bottle and twist-plug???? Nothing was moved or altered between the 'good weld' days and now. I am welding at 175-200 amps on 1/4". A short section of SS seemed to weld fine yesterday but need to double check that tomorrow (I would not expect that).

When the new torch head (WP-20) comes in, I'll try that but I see no obvious issues with the old one. The existing head does not have a valve nor will the new one. I use a wide #8 ceramic cup, a new gas lens collet, 1/8" 2% thoriated tungsten, I snug both ends, I let the tip out about 3/8" from the cup end, I sharpen the tungsten often (on the same grinder as before). I do get a lot of spatter with the porous welds but the tip doesn't melt or ball. I hear (and feel) a good amount of gas being emitted from the torch head and that sound changes with the flow setting.

I am interested in trying the filler rod mentioned earlier but I don't think my problem is related to filler because I cannot properly weld even a flat plate. When I use filler, I use ER70S-2 (except on SS of course). Water level was topped off with deionized. The steel I have problems with are a variety of new, rusty, cold-rolled, rebar, bar stock, angle with/without primer, oiled steel, dry, sanded, brushed w/SS, cleaned with acetone, and sand blasted. I have no idea where it was made but China is a good bet. I felt that I had a materials issue but I am getting enough advice to convince me that it may be a gas/leak issue. I need to be really sure the entire length of gas line does not leak so that is next, plus grizzzlys idea of grind/clean/weld on a flat.

I sincerely appreciate all the advice here, especially to grizzzly who got it started for me. I am new to this site and will return!

By gr8tins Date 05-13-2011 21:31

Hi everyone,

I have apparently discovered the CURE to the problem but not the CAUSE of the problem. The cure was to switch from the gas lens collet to a standard 13N29 collet body.

As I mentioned, I set out to systematically make changes one at a time until I found something that makes a difference. The new loaner gas bottle (courtesy of Airgas) was tested with no substantive difference. I made several plates with sanded and cleaned surfaces to test welds on. I made 3 with mild steel from different sources and one of stainless. The stainless plate welded good while none of the other mild steels did. If the ss welds good why didn't anything else?

I tried standard collet bodies 20-some years ago and had minor trouble on the particular application and switched to the gas lens collet. That fixed it and I never wanted to use the standard collet after that because everything worked great with the gas lens collet. Even this week, I changed out the gas lens collet body for a brand new gas lens collet with no change in results so I figured that was not the issue. Today, I dug up an old standard collet and was amazed to find that it fixed my problem! Then I went back and tried 3 other brand new, never used gas lens collets and all produced bad welds.

Now I am trying to understand WHY. Is there some sort of problem with the torch head that the type of collet makes a difference? The guy at Airgas said he had never heard of collet types making much difference in welds. Have any of you experienced anything like this?