tungstin smear

Date 03-06-2010 21:39

Mike,

First off, Welcome to the AWS Welding Forum.

This is a new term to me but I am in no way a GTAW expert. Especially on titanium.

Maybe some of the guys who do similar work will be able to understand your description of the problem and jump in here.

Sounds more like a way to keep wages down, tell people their welds are below standard using a non-standard term that doesn't truly apply to anything.

But, the reason I jumped in besides welcoming you, after you enter a post you should see a tab at the bottom of your entered post that allows for 'attach' ments. Use that to go to your pictures files and attach the photo. Now, getting a pic of the 'film' from RT is a different problem. If you have the film, you maybe able to get a pic with standard camera with back light and download to your files. Or, do they copy off a scanner with enough clarity to attach for viewing. Just a couple of options. I haven't had the need to try either. Hopefully others can shed more light.

edit: Yep, its still there. Wasn't sure since they changed the format of the forum a short time ago and I don't use it often.

Have a Great Day, Brent

By Tommyjoking (****)

Date 03-07-2010 00:16

Mike while you get a film posted, you might want to include info like what grade of tungsten you are using, general size of cup, general amperage range and gas flow rates. Sounds like tungsten degradation to me but........that info will help these guys give more definitive answers to the cause.

Good luck
TOmmy

By welderbrent (*****)

Date 03-07-2010 00:32

!!HIJACK!!

HAPPY BIRTHDAY TOMMY!!

End Hijack.

Have a Great Day, Brent

By Tommyjoking (****)

Date 03-07-2010 17:31

THank you Brent!!! Good ale and a stack of ribeyes and shrimp and friends and family....it was a wonderful birthday. The weather was perfect too.

By mike wiebe 3 (*)

Date 03-08-2010 18:04

All of the welding is done in welding chambers so there is no worry about gas flow or cup size. We buy tungsten in 18" lengths and have used all of it sticking out to get to where need to weld. As far as amps not more than 125 to 150.

By Metarinka (****)

Date 03-08-2010 23:19

just like mig wire, if you stick out a tungsten too far you can burn it out from stick out. It can't handle as much current as copper so running 3-4 inches of tungsten stick out in a purge chamber can cause it to overheat.

Sounds like you need a low profile torch or flex head torch or something to get where you need to go.

By mike wiebe 3 (*)

Date 03-09-2010 03:26

We work on castings so most of our welding is to repair gas pockets or shrinks so most of the time tungsten does not have that problem, (overheating) We sometimes have to have tungsten out that far to get to weld. Often times it may stick out 10"with a 90 degree bend and 3" of tungsten beyond that, not to mention the bend in the wire. There seems to be no correlation as to how far tungsten is sticking out and the tungsten smear.

By Lawrence (*****)

Date 03-08-2010 06:14

Jeff

I gotta be brief so I'll just note a few things.

Pure tungsten is 20 years out of date and should not be used for any application in my opinion.. There are better alternatives.

If you were welding steel with a pure tungsten it most likely could not handle the current you were using and just roasted.

Any tungsten. No matter what the alloy can overheat if too much current is run through it... Different alloyed electrodes will behave/degrade differently.

Rule of thumb... If the pointed tip changes from perfectly pointed in any way... no matter what kind of electrode your using.. you better pay attention.

If a thorium electrode tip changes shape while welding... Assume you are transferring contamination into the weld.

By mike wiebe 3 (*)

Date 03-09-2010 03:29

What type of tungsten do you suggest for aluminum? It has been close to fifteen years since I have done aluminum and that is what we were told to use. thanks

By Lawrence (*****)

Date 03-09-2010 04:50

I prefer lanthanum 1.5% (gold) for a multi purpose AC/DC electrode.

Cerium is also excellent for multi purpose use.

Zirconium is great for a dedicated AC electrode.

By js55

Date 03-09-2010 13:37

I'm still wondering how you can a get a high density result from anything to do with tungsten.
Geralds input here might be helpful.

By welderbrent (*****)

Date 03-09-2010 14:39

JS,

You have mentioned this twice. I think you have something backwards in your mind at the moment unless you are reading something different than I am.

For your consideration:
1) WIT manual module 9 page 9-12 states "Since tungsten has a much greater density than steel or aluminum, it will show up as a difinite light area on the radiographic film." Figure 9.22 shows an image of a Tungsten Inclusion as light spots on the film.
2) The Certification Manual for Welding Inspectors on page 228 states "These tungsten inclusions appear as light areas on radiographs, because tungsten is highly opaque to radiation. This is opposite from most other discontinuities, which show up as dark regions on the radiographic film." Figure 11.8 pg 233 illustrates the same as the WIT book.

Now, my question in light of these statements from two separate sources is why are you having a problem with 'high density result from anything to do with tungsten'? It seems that that is exactly the result one SHOULD expect. Did I miss something? It would appear this is correct for steel and aluminum. How about Titanium? Are you saying Titanium is more dense than tungsten and thus the tungsten inclusion should appear darker and less dense instead of lighter and more dense? I know little about Titanium and didn't look it up. Just started typing because I am wondering what you saw that I may have missed.

Please do not take this question wrong. I'm just trying to increase my own knowledge base here. Wondering what the rest of us may have missed. But it appears to me that the tungsten is 'MORE' dense and would show up as a light spot on RT.

Have a Great Day, Brent

By js55

Date 03-09-2010 15:00 Edited 03-09-2010 15:02

Definition:
density, radiographic,
The degree of darkening of exposed and processed photographic or radiographic film.

Therefore, material density is inversely proportional to developed film density.
The description in the post (that of comparing it in appearance to LOP, a definate lower density phenomena since LOP reduces the thickness of the material being radiographed and resulting in a darkening of the radiogrpahic film as opposed to a lightening) led me to believe we were talking film density not material density.

By welderbrent (*****)

Date 03-09-2010 16:43

Okay, I see what you are talking about.

So, tungsten inclusion would be indicated by a light spot on the RT, but, when Mike compared it to LOP, which would be a darker indication, you were 'confused' (my word/description) as to rather he had tungsten inclusion or some other kind of indication.

And, now I am as well. If it truly shows as a LOP then it is darker which tungsten inclusion would not be.

Some clarification should be in order in order to truly start coming to proper answers to the problem.

Thank you for responding. I didn't put that part of it together till now.

Have a Great Day, Brent

By Lawrence (*****)

Date 03-09-2010 17:29

Now were getting down to what is really wrong.

By Tommyjoking (****)

Date 03-10-2010 03:24

You betcha Law

By Metarinka (****)

Date 03-09-2010 18:02

you guys beat me to it, I was about to comment on the difference between material density and xray film density and how they opposite and often used interchangebly to much confusion. Less dense material will create a "denser" spot on film, more dense material will create a less dense spot on x ray film. As measured by a densitometer. If it's not specifically clear what one is talking about it's very easy to create confusion.

By ssbn727 (*****)

Date 03-10-2010 00:12

Hi Mike wiebe 3!

First off, "WELDCOME TO THE WORLD"S GREATEST WELDING FORUM!!! :) :) :)"

Man! That weld pool must be really hot enough to melt the W so much that it actually "swirls" in the molten pool!!! :) :) ;) Remember that W (tungsten) will melt @ approximately 6000 degrees F, or slightly less! ;)

Is the temperature of the molten pool that hot that the W inclusion will almost instantaneously melt and "swirl" around within the shape of the molten pool??? Hmmm... ;) Theoretically this could occur if the conditions were just right, and from what I read in previous posts regarding the welding being performed in completely inert enclosures, the possibility of the arc plasma itself causing the W to partially melt is plausible and it could indeed become a droplet that could quite possibly be stirred within the molten pool if the molten pool is agitated enough and the droplet doesn't have enough time within the temperature of the pool to solidify enough to prevent it from "swirling" around within the pool and resulting in "tungsten smear."

However, the conditions must be just right for this to actually occur IMHO. ;)

Respectfully,
Henry

By Shane Feder (****)

Date 03-10-2010 00:34

Hi all,
Agree totally with js55 regarding the density.
I still have a graph I have kept for years that has a perfectly symetrical 6 mm (1/4") long tungsten inclusion. Have no idea how the welder broke it off because the point of the tungsten looks as if it has just been sharpened.
On the crescent / half moon indications - the only time I have ever heard of those shapes on radiographs is fingernail marks on the film which show up as very dense.
Regards,
Shane

By Tommyjoking (****)

Date 03-10-2010 03:29

One small thought.....Every material has electrical resistance....there are limits to how long we can run a certain size wire or any conductor really...that resistance usually rears it's head in feet not inches...however it all revolves around diameter.....it is a remote chance but is the length of the tungsten vs diameter exceeding that limit (a full purge does not matter in this regard).
Tommy

interesting thread to say the least

By ssbn727 (*****)

Date 03-10-2010 16:02 Edited 03-10-2010 17:01

The GTA weld pool, and the arc plasma in a totally inert atmosphere does indeed behave differently than being surrounded by air, but I think your point regarding the length of the tungsten vs the diameter is a valid one. ;) the only problem is to explain how the weld pool was so darn hot enough to "swirl" the tungsten droplet and maintain the temperaturehot enough within the pool to actually "smear" the tungsten in such a manner when we all know that W has a significantly higher melting temperature than whatever it was that Mike was welding inside the chamber...

What bothers me most about this thread is that the OP expects us to give a comprehensive answer to his query without providing us with ALL of the necessary information we need in order to give the OP as comprehensive an answer as possible!!! :( :( :( So how about giving us ALL of the relevant information that you can muster together Mike, and then we can give you a better informed group of probabilities, or reasoning as to what your superiors are calling "Tungsten Smear"???

I mean, even if you did provide a picture of the RT film, without saying what the thickness of the Aluminum? Or the actual geometry of the "business end" of the tungsten, the diameter of the tungsten... Was it a casting or not (you mention a casting in one of your later posts,but you're not being specific enough in one post and instead, are just feeding us little bits of data as this thread grows longer and longer!). Was the shielding gas 100% argon, or were you using an argon/helium mix for more penetration (this could be really important as to how the weld pool was hot enough to enable the tungsten droplet(s) to "swirl" around in a very hot molten pool)... Also, how oxidized was the Aluminum casting, was the thickness of the Aluminum surface oxide layer greater than normal???

So if you have anymore information to share with us Mike, now would be the time to do so if you want to receive a pretty good explanation as to why your superiors, and specifically the metallurgist is calling these indications as "tungsten smear." Without ALL of the pieces to the puzzle revealed, the only thing you will get is a bunch of different opinions based on conjecture and incomplete speculation on the same level junk bond traders sell their own wears in the stock market!!! :( :( :(

I mean no disrespect when write this, but if you want us to help in figuring this out for you, then you need to give us ALL of the information available including data which you may not even think is relevant - CAPECHE??? :) :) ;)

Now if they are insisting on using pure W for welding Aluminum, then the metallurgist is either a dinosaur with no understanding that zirconiated W as Larry mentioned earlier, is far superior than pure W for use with Aluminum AC GTAW, or the company is too set in their ways to "weldcome" any change for the better when it comes to solving a problem they claim is actually cutting into their own profits which gives them justification for denying the welders a raise!!! Yet in reality, it is their own ignorance as the real reason why this is happening in the first place!!! There!!! I finished with my rant!!! :) :) ;)

I do hope that it turns out that the fault lies in your company's own "horse blinders" mentality for not being open to changing the type of W they're using to perform these welds!

Respectfully,
Henry

Respectfully,
Henry

By js55

Date 03-10-2010 12:59 Edited 03-10-2010 14:19

Not just to be argumentative but to explore a little deeper, I still have problems with the theory. If the tungsten were to be small enough to escape low film density detection then I find it difficult to believe it can create a void large enough to create a high density crescent moon effect that is detectable. Somehow, right at the point of solidification the void would have to exist ostensibly caused by surface tension in the void and its inability to melt together. That is a lot of surface tension for a puddle hot enough to melt tungsten. And if the surface tension is that high how is it a lack of fusion isn't also associated.
Also, if the tungsten were actually large enough to do something of this sort, IMO, it would then be large enough to be seen.
Worm tracks porosity (not a standard term) can create a similar phenomena but then worm tracks are caused by the existence of a gas which is trying to escape right at the moment of solidification, though it of course is not crescent moon shaped.
The only way I can see this as possible is a dissociation of the tungsten/thoria oxide, etc. creating an oxygen gas that is captured like worm tracks. But thats a hot fricken puddle!!

By welderbrent (*****)

Date 03-10-2010 14:46

With the info provided by Mike, JS and Henry my mind is still trying to figure this out as well.

If the tungsten is so TOTALLY disintegrated that it shows the 'opposite' kind of a weld discontinuity as to density then it should no longer be a 'tungsten' discontinuity at all. Right? or not? And if one were running hot enough and slow enough to totally breakdown the tungsten then how and/or why did they end up with an area with a fusion problem?

And either way, is this a discontinuity that makes a part (I know we haven't seen the film yet nor exactly how this fits into which code) rejectable?

Bottom line to me still appears to be a bogus way of keeping from giving welders a raise. My own opinion based upon how it is being used according to the OP, Mike, earlier in this thread.

I guess I'm not helping, just trying to figure this out for my own understanding. I'll just wait for the experts here to figure this out.

Very interesting subject matter to me. Thanks Mike for asking about it and JS, Shane, Henry, Lawrence, and whoever I forgot names of, for contributing. Hope it gets figured out.

Have a Great Day, Brent

By mike wiebe 3 (*)

Date 03-11-2010 02:20

Let me try to get all info out. It is an aerospace titanium casting plant. The thickness may be from .040" to .500". It is all done in a weld chamber. Due to casting complexity we may have tungsten sticking way out there, using up to three dental mirrors to see weld area. Most of our welding is to take care of gas pockets or shrinks, with some welding to take care of undersize dim's. We use 3/32" 2% thoriated tungsten for most of welds. It is 100% argon atmosphere. Amperage is 125 to 175. I have been there as a welder for 9 years and have since become a machinist for last two years.
this tungsten smear has been called out the whole time I have been there, but as stated I wasn't real concerned with it until they started to keep track of our pass rate out of x-ray. All of us welders do our best to put out quality welds and improve our skills. Now that i am a machinist I guess it should not bother me at all but it does. I am just trying to improve my knowledge. And it would be nice to know what may cause this so that a different technique could be used. Tungsten is hand ground to spec. The material is ti 6-2-4-2 and ti 6-4. Sorry if I confused people but I was worried about letting out to much info without approval if you know what I mean. If there is other info that I left out please let me Know. I have a hard time saying everything let alone trying to type what I am thinking. I will not be able to post an rt until later next week. Have to quit now because my fingers hurt from all this typing. Also we have had this smear appear when tungsten was only sticking out 1/4". Hopefully this helps and thanks again guys.