Strange purge technique on 304??

By Steve.E (**)

Date 08-15-2009 07:54

Tommy , you must have argon available for your torch , so why not for back purge ?

By Tommyjoking (****)

Date 08-15-2009 09:10

(long story) in a nutshell its my project, someone elses equipment which I cannot modify to bleed off some purge gas (one bottle). any further explanation would bore you to tears as if that did not already. Besides its a legitimate technical question, very cool co2 as a back purge on 304...whats the potential problems and weld quality detriments to using the technique?? I have NEVER used co2 on stainless ever, so ....I ask.

By Shane Feder (****)

Date 08-15-2009 09:39

Tommyjoking,
Is this work in accordance with any code / standard ?
Regards,
Shane

By ssbn727 (*****)

Date 08-15-2009 10:43

Hi Tommy!

In certain circumstances where back purging isn't available ,sometimes the use of "Solar flux" or, a flux coated GTAW filler rod for 304 may be just what the doctor ordered...
However, there are some drawbacks such as: the slag is very hard to remove from the inside and other drawbacks that are explained in detail in the article from http://www.sperkoengineering.com

Here's the specific article I'm referring to:

http://www.sperkoengineering.com/html/Purge.pdf

There's also "Solar flux":

http://www.solarflux.com/index.html

Here's a .pdf on this stuff:

http://www.solarflux.com/Graphics/web%20graphics/WDF_SOLAReprint.pdf

Here's a quicktime video:

http://www.solarflux.com/Pages/Testreport.html

Finally; Why can't you just get a "Y" connection w/valves to both weld as well as purge by also connecting a flowmeter/regulator after the "Y" connection on to one of the valves to control your flow rate on the purge line? simple solution if you can get your hands on a "Y' connection, and another flowmeter/regulator. ;)

Respectfully,
Henry

By Tommyjoking (****)

Date 08-15-2009 21:53

THx Henry that is a route that never even crossed my mind. The leftover flux would not be a real issue except for any corrosive properties it might have (still got to read all that dude!!). How hard might it be to remove with a drill powered SS brush? Anybody got a .032 308 smaw rod?? LOL!!!! Using copper backing is not an option because of the intended joints geometry...a consumable backing might be ok but I would rather not. Basically I am tig poor and the fella helping me out is shall we say rather "eccentric or finicky" about his stuff....still yet if I can convince him I have a ton of gas splitters, hoses, trailers, modified collets for pulling some gas from the cup etc. in my toolbox. I will owe him for probably half a bottle of argon if I get to backpurge.

Shane no code work at all except my own personal code....do the best you can with what you have available. Its a home project for my future flattrack racer. A very elaborate exhaust setup. Copying a set that costs over $1200 I have the already built custom hand rolled megaphones + repackable aluminum silencers with trick threaded baffles. All that's left is the headers themselves, heat shields and brackets. I wanted to use 321 but my local suppliers can not get the size vs. wall thicknesses that I need. I promised my wife that I would have all modifications done for no more then $500 save painting. The stainless tube is very reasonably priced so I am getting that new but I am getting all my billet aluminum from the scrap yard and machining it at work in my spare time...so far I am on budget.

hmmm I still am interested in hearing an opinion on the dry ice trick.....is co2 just flat out incompatable for purge on 304??? I know the moisture content could be a problem but a homespun dryer would be easy to make...... Now I want to try it just for the heck of it to see what happens LOL!!!

Thx for your replies
Tommy

By ssbn727 (*****)

Date 08-15-2009 23:44

Tommy,

Think basic chemistry for a moment... CO2 = Carbon =more carbon migrating into the weld pool which will bring up the carbon content in the stainless, which will in turn increase the potential of forming together with the chromium to create chromium carbides inside of the tubing at the root... Compounded by the fact that there are also two atoms of Oxygen in the CO2 molecule so, you would also increase the amount of oxygen the root of the weld would be exposed to resulting in more oxidation than you would expose the root of the weld if you did not use any back-purging at all and therefore, increasing the potential for increasing the amount of what is known as "sugaring" as well as porosity at the root of the weld and that's just what would happen at the root of the weld!!! I didn't even talk about what would happen to the base metal adjacent to the weld at the root yet!!!

The HAZ or heat Affected Zone will also be exposed to the extra carbon via possible migration, or through absorption, the extra increased amount of Oxygen in the atmosphere in side the tube will be replacing the amount of primarily Nitrogen in the air atmosphere that it will be replacing which in turn, will increase the amount of oxidation which will occur at the heat affected zone if NO CO2 via dry ice - purging were to be used... In other words, you would be doing more damage than with no type of purge at all!!!

Now I could get more in depth as to what would actually occur at the molecular level as well as what specific changes would occur at the metallurgical also but, I do not want to bore you with so much theory, so much research data that supports what would actually happen, or so much data that would literally have you spinning in your seat saying: "Huh???"

In other words, there's no need for me to go anymore in depth than I already have at this time. if there are questions after-wards, I'd be happy to attempt to answer them to the best of my ability but, the main reason I went the basic chemistry route was to rather simplify in terms that you would readily recognize since you already have quite a bit of experience with welding stainless steels as opposed to potentially losing your attention as to what would occur if CO2 were used compared to no purging at all by inundating you with so much data that you would be saying "Huh???"

So that's what would happen in a nut shell Tommy! ;) The two options I mentioned earlier are good options, and the option which includes the use of a "Y" connection with valves as well as a flowmeter/regulator downstream from the "Y" connection could be even more efficient with respect to the amount of purging gas to be used by incorporating into the tube, the use of water dissolving temporary purging dams which could easily be washed away after the welds are cooled down to room temps after-wards! This would more importantly reduce the amount of wasted purging gas tremendously which in turn would leave you owing your friend less Argon after the work is completed!!! :) :) :)

Respectfully,
Henry

By Stephan (***)

Date 08-16-2009 14:45

Henry,

excellent! As always...

I am honest, as I have read Tommy's post the first time I had similar thoughts on this.

But nevertheless, I yet like the basic question: "...a little co2 from some dry ice+water in a bucket and hosed in to the tube is not a bad second option eh?"

This once is a very... hmmm... trying to find the right term... 'unconventional'(?) approach to an existing task. I truly like it - certainly also as I personally have never thought about using CO2 for purging operations.

And honestly spoken as well. From my humble point of view Henry, you should be absolutely right by considering the Carbon dioxide dissociation. But... as well-known a specific amount of energy is needed to separate the first of the two oxygen atoms from the CO2 molecule, or:

CO2 + 1184,87 kJ --> CO + O

As I mean to know, these reactions are taking place, e.g. with GMAW within the arc's "hot" core (please forgive me the casual formulation) as the first of generally two reactions. Here the dissociation of CO to C + O is furthermore another topic as it reqiures more energy than the first one, what's the reason for that the dissociation of Carbon monoxide is in most cases just partial.

So, when considering the GTAW arc as being in direct contact with the CO2, coming from Tommy's dry ice, then I would mean yes, there is a partial dissociation of CO2 - eventually to CO + O. The oxygen again would - as described so excellently by you - lead to oxidation or sugaring etc.

But my question(s) in general would be: "What would happen as the CO2 is not in direct contact with the arc (surely this wouldn't work as far as the root is welded on an open gap)? Would the energy - just based on 'heating up' the rear side - suffice to dissociate the CO2 molecule? And if (most likely) so, how would the rear side really look like?"

I was glad to read Tommy's final comment: (quote): "... Now I want to try it just for the heck of it to see what happens..."

That's great! Please keep us informed on the outcome, Tommy!

All the best,
Stephan

By ssbn727 (*****)

Date 08-16-2009 19:06 Edited 08-16-2009 19:15

Hi Stephan!

You know something? I was probably thinking about the disassociation with respect to the GMAW process also when I first wrote what I did, and now I realize after reading you response that you're probably right in saying that there would need to be more arc energy at the root of the weld for the carbon to "coalesce" with the root of the weld because as I forgot to mention that the only disassociation would be with the two atoms of oxygen and as a result, one would instead have a molecule of carbon monoxide as well as an "orphan" atom of oxygen which would more than likely increase the amount of oxygen content in the atmosphere already in the tube which would nonetheless, increase the amount of oxygen - the root of the weld would be exposed to because, even though the arc energy isn't in itself - enough to disassociate all of the atoms in the CO2 molecule, there is enough energy created by other means to separate oxygen atoms in the atmosphere as well as in the CO2 molecule via the increased bombardment of electrons as these elements in their gaseous state are ionized from the arc although at a much lesser degree when compared to GMAW

Thank you for reminding me the differences in the amounts of energy required in order to disassociate carbon atoms from oxygen compared to oxygen from another oxygen atom. :)

However, my point was also considering the potential for a significant amount of condensation of CO2 within the tube to accumulate on the inner wall surface of the tube also via the dry ice Tommy was considering to use as the source of the CO2 so, disassociation wasn't so much a consideration in what I was thinking would occur as a result of using this method of delivering the CO2 in to the tube for use as a purging mechanism in itself... So, my main concern was the entrapment of CO2 in the root of the weld as a result of solidification which would result in porosity in itself as well as coalescing with the chromium in the stainless steel to form chromium carbides which would therefore destroy the passivation, or self healing, corrosion prevention mechanism that makes stainless steel unique to other types of steels exposed to the atmosphere as well as moisture over a period of time.

Mind you, I haven't even mentioned yet the physical phenomena of gravity, or the fluid dynamics with respect to the mass comparisons between air in the atmosphere, and CO2 which would inevitably have Tommy saying Huh??? This is exactly what I was attempting to avoid by simplifying my explanation... I guess I should have been more thorough. ;)

Respectfully,
Henry

By Stephan (***)

Date 08-17-2009 06:02

Hi Henry,

thanks again!

Quote: "I guess I should have been more thorough."

No, as usual you were thorough in the absolute widest extent!

Of course, from the pure practical side to fixing the issue, all the responses, like those ones coming from yourself, from Lawrence, Dave, Steve and Shane are stringently pathbreaking.

My response whereas was more a bit more pointing to the general physical feasibility of using CO2 as a purge gas in general - at least as it may have no direct contact to the arc or W-electrode respectively, in a first order.

You know, there are so many investigations on purge gases like Argon, Nitrogen + H2,..., etc. But I personally have never seen an investigation by now, dealing with CO2. Of course the assumption of dissociation and both electrode destruction and surface oxidation lies near, but anyway, how would it appear as far as the gas does really only 'purge' the surface and displacing hereby the pure Oxygen? Hmmm... yet perhaps a bit of a too 'academic' question for the forum - at least as I interpret the 'rating'. But this, I know, we are fortunately having the same opinion about... ;-)

Certainly however, I also wish that Tommy may go to solve his application most properly and therefore your and the other replies are far more suitable. I guess anyway, that Tom would have not conducted his announced test using the final and expensive part.

All the best,
Stephan

By ssbn727 (*****)

Date 08-17-2009 08:12 Edited 08-21-2009 22:15

Hey Stephan,

Please do not concern yourself with the silly rating system... Whoever it is that's intentionally doing this to both you and I are the ones showing their true colors - YELLOW!!!
As in COWARDS!!!

It reminds me how for some participants seem to think as if they were still back in High school as adolescents holding grudges, seeking revenge in such a petty manner by giving someone, anyone, especially you, or myself a "Low numerical" rating all because, they cannot seem to act in a mature manner past the ninth grade level after kindergarten!!! ;)

Das ist aber schade!!! (That's a shame!) Es macht nichts!!! (It doesn't matter!!!) because, I do not participate in here to win any popularity contests, and I might as well repeat myself so that the entire forum understands why I do participate in the first place... But before I do, I would like to say that whoever it is that is attempting to lower my own IMHO, silly numerical rating which has dropped ever since I had an exchange with another participant recently...

I cannot stop you from what you are doing so my point is simple, If you have something to say to me, then send me a PM instead of making anyone else feel as if they are being punished for communicating with me in this forum!!! If you have a resentment with me, then keep it with me, and no one else, because nobody else deserves to be targeted with your rather childish manner in which you seek to extract revenge on me!!!

I remember when this numerical ratings system was first implemented some time ago, and I said it then to deaf ears that someone, or even more than one individual would become a potential victim of silly, immature, mean spirited retribution towards the individual(s) via the use of the numerical rating system, and now it seems that my prediction has come to fruition as a result!!! :(

Das ist aber schade!!!, Das ist aber schade!!!

This is my own personal opinion of this attempt to defame my character, and to intimidate anyone else that attempts to communicate with me also...

I mean, it's like being in high school all over again, (Forgive me for not remembering the appropriate term for high school level in the German Education system, my friend.) and it just encourages a lot of false rating towards individuals like myself for speaking my mind and as a result, or towards anyone else who communicates with me as they are punished by childish individuals who seem to think that this is their way of seeking revenge at me...

The origin of my spiraling ratings for which I really do not take so seriously, and I'm dead serious when I speak for myself - comes from recent disputes I've had with one or more participants in here, and they are a likely source as to why only recently my ratings have plummeted so suddenly, and since I cannot prove this accusation, I can only speculate at this time as the root cause for my own ratings to drop from an average of 2.78 to it's current low of 1 point something so suddenly!!!

For me: "Es macht nichts" (It doesn't matter) but, it does bother me that whoever else communicates with me should also become victims of this malicious behavior, and I only hope that Ross & the rest of the administrators would take a look into it and seriously reprimand whoever it is that is abusing the ratings system.

However, I'm not going to lose any sleep over it because I do not participate in the forum so that I can win a popularity contest as you know also... We both particpate to share in our collective experiences as well as our collective wisdom in order to learn from each other and in the process of doing so, forge friendships, collaborate on projects, and find commaraderie amongst each other as people who go through life on life's terms for the most part as well as share our personal difficulties in coping with the struggles one encounters in living in this very complicated age of human existence. This is the reason I participate in this forum!!! so like it or not, you're not going to get rid of me with your silly games!!!

That is all I'm going to say about this matter as I leave it up to the administrators to investigate this matter as well as administer the appropriate amount of justice to the individual(s) who are guilty of this vile behavior. I rest my case!!! ;)

Respectfully,
Henry

By Stephan (***)

Date 08-17-2009 12:41

Henry!

Thanks for your kind reply.

It makes me sad to see, that my return to the forum appears to cause such a kind of random. And much more it makes me sad to see the 'ratings' of highly appreciated fellows in particular you, but also many others, have been dropped down meanwhile and this partially dramatically.

However, I can't help myself. If this, what you are assuming to being the root cause, were right, I wish to say: "At any time again I would confess my unreserved sympathy for you... at any time! Also for paying the price to fall down to an average rating of 1."

The rating could certainly be used as a means of expressing somebody's opinion about somebody's else disrespectful post(s) without stirring the pot additionally. I mean however, when it comes to different perceptions on technical issues everybody has the choice to express his/her different opinion - what is at least in my opinion the deeper sense of e.g. this great welding forum.

This to lead finally and at the end of the day to your outstanding statement:

We both particpate to share in our collective experiences as well as our collective wisdom in order to learn from each other and in the process of doing so, forge friendships, collaborate on projects, and find commaraderie amongst each other as people who go through life on life's terms for the most part as well as share our personal difficulties in coping with the struggles one encounters in living in this very complicated age of human existence. This is the reason I participate in this forum!!!

God bless you,
Stephan

By Joseph P. Kane (****)

Date 08-21-2009 19:35 Edited 08-21-2009 20:01

Henry

I am giving you a ZERO rating for your rant. Shame on you for calling the raters cowards and "...YELLOW!!!" You regularly rant about censorship and I agree with you on most of those rants. Here, however, it seems to matter who's "Ox is Being Gored".

I would like to frequently rate the "capitalization and punctuation morons" who pretend they are "English language challenged" or pretend to be "backwoodsy good ole boys" in their posts, but there is no ZERO rating! I would like to force them to stay after school and write on the blackboard "I will use proper capitalization and punctuation on the AWS Forum." - 200 times! Alas, I can't. So why bother? In your case, just to remind you what you profess to stand for.!

Joe Kane

By ssbn727 (*****)

Date 08-21-2009 22:27

Nice to "Hear" from you too Joe!!!

Gotta watch what I say these days... The "Ox" is focusing on "Goring" me at every turn these days by putting entire threads into the OTB&G as PUNISHMENT!!!

Yet at the same time promotes being off topic one second then apologizes the next as if it were just a mistake but, when I do it it's a major violation that warrants threads that weren't even started by me to end up in his new proverbial garbage dump and using me as an example to the rest of the participants not to question the actions from the almighty from marketing??? I shudder to think!!! LOL :) :) :) whoops! we'll probably end up in there after what I just said!!! :) :) ;)
Ohh Well - such is life!

Respectfully,
Henry

By DaveBoyer (*****)

Date 08-17-2009 02:05

Tommy, I used the marine section of FC2002 when I fabricated a replacement water injection exhaust elbow for My sailboat's diesel. I just welded the parts [304 SS] together with a 308-16 stick rod, even where it joined to Sch. 40 steel pipe on the "dry" side of the elbow. I used this part for 7 years, in spite of the sulpher compounds and sea water exposure. It was still working when I layed the boat up.

Do You think this part would hold up if You "just did it" ?

For small diameter filler metal You might use MIG wire cut to lengths You can handle.

By Lawrence (*****)

Date 08-17-2009 03:07

Tommy

Solar flux is a better idea than the Carbon dioxide if you absolutly can't get an argon backing.

Just remember that the solar flux is a one pass backing, so you have to get the weld right the first time..

And best to practice on some scrap first because Solar Flux (with any penetration at all or on a fillet at the root) will make an entirely different arc and puddle. It will be big and green and sluggish and hard to see your filler going in cleanly.

The Carbon dioxide brought up will also bring condenced water moisture with it (as others have mentioned) and that is not a friend of hot stainless.. Better to use nothing at all than the Carbon Dioxide in my opinion.

300 series stainless that your working with is pretty tough stuff.. Have seen some horrible weld profiles last for decades, but your too good for that so half the problem is solved.. Any welding supply will have solar flux. Just follow the directions and do a few trials so you have no surprises when it comes to the money joint!

Clean the back side as best as you can with a rotary wire brush... The Solar Flux is used on short term repairs on aircraft hot sections and even some pressure vessles like LPT and HPT cases with engineering authority. So it is a pretty well vetted procedure.

By Tommyjoking (****)

Date 08-17-2009 07:11

HUH??

LOL Henry LOL

Those are the kind of answers/disscussion that I wanted to hear!!!!!! I have never used it for a shield gas "in this manner" out of a bottle much less dry ice Good reasons why not are brought to light....thank you.

Yep Dave I could just weld it and I know it would be fine. But I just cannot stand not to have a backing gas or a mechanical means of keeping the Oxy away on steels...it irritates me to no end to know the weld is not what it should be.

Yall do not get mad at me please:   After a couple of beers and some negotiating....I get to do as I wish with the borrowed equipment !!!!   YAY!!!! The guy asked me to show him how to braze and "can you make cast iron stick back together and not break??" Things got much more friendly at that point.

Now I will definitely keep in mind the Solar flux for the future....I assume there are some tapes that might be usefull on stainless as well.   I guess it may be a little different then some of the fluxes used in Oxy/Act operations on other metals???   Thanks for the technique advice Lawrence

Stephan no worries    I will still put some dry ice to some scrap tube and weld it out just to see what it looks like......I expect it to end up black and ugly on the inside but it will be neat to see anyway. I will do it with zero gap and make sure I have a full pen joint and a no pen joint    If its interesting I will post you some pics.

THX all
TOMMY

By Stephan (***)

Date 08-17-2009 07:51

Tommy,

it's good to read (quote):

"...Those are the kind of answers/disscussion that I wanted to hear!!!!!!"

And if you may find some time to test it, I'd like to say 'YES!' it would be interesting to see some pictures! ;-)

Thanks and all the best,
Stephan

By Superflux (****)

Date 08-17-2009 17:01

I have been guilty of recommending Solar Flux in the past. HOWEVER! this is a last resort. Far too many swirleys in the puddle!
Rig yourself (and this will take some creative "engineering") a large animal, ie. horse or cattle hypodermic syringe to a purge line. this will fit through most gaps and allow you to aim the purge gas directly to the area, but not too close, needed. Since codes (and I've never seen a proceedure) do not address the volume required of the back purge zone....
CO2 is used in some S/S FCAW and GMAW applications. Seems counterintuitive, but I've been involved with this discussion in the past (CO2 used with Stainless) I think if I were in your predicament, by using your dry ice, it would make for an excellent "Custom Blend" with the aforementioned needle device.

...no such thing as the impossible, just creative solutions to difficult issues....

By ssbn727 (*****)

Date 08-17-2009 17:37

Hi Superflux!

Sure it can be used... However, the root of the weld would not be as sound as a weld root welded with an argon purge, and since Tommy did not initially mention what this application was to be used for, we presumed that the application would be of a more critical nature.

The potential for creating discontinuities as well as defects does increase when one uses CO2 as opposed to Argon for purging 304 stainless steel tubing... Otherwise, just from an economic as well as a quality perspective, CO2 would always be used instead of Argon. ;)

Respectfully,
Henry

By Lawrence (*****)

Date 08-17-2009 19:27

Nitrogen is sometimes used for purging of 300 series stainless

Never heard of CO2 being used.. But I would like to see some technical data about it.

By DaveBoyer (*****)

Date 08-18-2009 02:47

Is nitrogen used on full penetration joints ? It seems that it might cause embritlement if the metal got hot enough [molten ?] to absorb it.

By Lawrence (*****)

Date 08-18-2009 03:46

Yes... I did miles of it in wineries in california in the late 80s.. tight fitups on the butt joints because the N will foul up an arc if there is any leakage. When long runs had to be purged they chose N rather than Argon. Good results, not shiney on the inside but still nice... I guess fit for purpose.

Lots of sch 5 autogenous welds.. The old hands called em brewmaster welds.. I was just learnin back then.

By Tommyjoking (****)

Date 08-19-2009 06:15

No technical data but I will try to get you some seat of the pants trials as soon as I remember to grab a block on the way to work Lawrence. In keeping with the "theme" I will try to make up some quick and dirty dryer to keep as much condensate out of the mix as possible. Preval bottle, couple of tubes, some rice and maybe a cigerette butt on the outlet??? LOL. No make that a beer can thats keeping it more real world.

By fludnor Date 08-18-2009 02:33

truly you're in a dilemma mr. tommy. with all these forum response, i'm sure you have the all the options. but may i ask something...what fluid will flow inside the vessel? if and only if, the fluid will not cause any problem in an oxidized root (an SS weld without back purge), then i guess you can proceed with a no purge SS open root welding. good luck and best regards.

By rodofgod (**)

Date 08-18-2009 21:12

Hi All!

Interesting thread!

Talking of strange purge techniques, have a look at this thread from the UKwelder site!

http://www.ukwelder.com/forum/index.php?showtopic=9236

Anybody else used burning hardwood as a 'purge'?

Regards

By Steve.E (**)

Date 08-19-2009 09:32

Got to try that one... Do you think Iron Bark would be OK....:)