Hi Joe!

"WELDCOME TO THE WORLD'S GREATEST WELDING FORUM!!! :) :) :)"

Can you be more specific? What is your shielding gas flow rate??? What size cup are you using and are you using a trailing shield of some type, and are you purging??? Also, what are your pre-welding cleaning/prep procedures??? In other words, you need to come forth with a heck of a lot more information and specific details that what you're currently describing in order for any of us to be helpful to you! ;)

Respectfully,
Henry

Minimize heat  

Extra large cup,  Many Ti welders construct their own cups... Kinda like a lightsaber  :)

trailing shield usually helps but it would have to be a custom job for 1" pipe.

The work is very doable without a purge box...  Just gonig to take some trials or an experienced helper with the tools.

And as Henry suggested... say more

Get in touch with the kings of titanium: The Titanium Company of America
www.timet.com
They'll be pleased to help you.
Giovanni S. Crisi
Sao Paulo - Brazil

Are you doing this manual or using automatic orbital equipment?

Joe.

If you have a WPS than somebody at one point must have qualified that procedure...  If possible find them and get there gas shield data.   If it's an option is sure is the easiest one.

Edit:

10 CFH on a 5/16 id. cup is starving...   A gas lens with something around 20 cfh for that cup is reasonable.

Hi Joe,
First and foremost especially with Titanium, "Cleanliness is Godliness!!!" So make sure you remove even the slightest oxide layer just prior to actual welding by using a dedicated Stainless steel wire brush just for Titanium... And this is to be done regardless of whether or not prior cleaning was performed beforehand because it doesn't take long for a thin film of Ti oxide to form over the weld surface - CAPECHE??? This MUST be done in order to ensure that there will be no Ti Oxide contamination within the weld area...

Then you need to make sure that when welding Titanium, you have a higher than normal purity percentage in both the shielding as well as the backing gas, and the trailing shield gas also... Typical specifications suggest that shielding gas be at least 99.995-percent pure with no more than 20 parts-per-million (ppm) of oxygen and a dew point greater than -50- to -76-degrees Fahrenheit. Other applications require a 99.999-percent pure flow of argon.

Outfitting your welding torch with a trailing shield is critical—otherwise the risk of oxygen contamination rises, and with it the potential for cracking. Some people fabricate their own trailing shield but there are also fixtures available for purchase. Trailing shields conform to the shape of the tube and follow the TIG welding torch around the pipe. The shields provide an extra protection of argon over the weld after the torch and its argon flow have passed. Setting the torch and trailing shield gas flow at 20-25 cubic-feet/hour (cfh) provides the best coverage. Now if one cannot use a trailing shield, then a really large bore gas nozzle cup is definitely recommended along with the use of a gas lens collet body that has a large enough diameter for the oversized gas cup one is going to use for Ti.

Back purging is also required when welding titanium tubing. This process eliminates the oxygen contained within the pipe by using any variety of a back purge dam: water soluble purges, non-rubber gaskets, specialty tape or inflatable bladders. Argon flows into the dammed area to replace the oxygen contained within the tubing. Allow the argon to flow long enough to replace the oxygen ten times over to ensure the purest welding environment. Always use a clean, nonporous plastic hose to transport the shielding gas to the torch, trailing shield and back purge. Rubber absorbs oxygen that could contaminate the weld.

Does the WPS have a post flow amount written in it???? Because if your post flow is less than 20 seconds, then this could be the cause of getting so much color in the weld... What you do not want to do is to remove the gas shielding prematurely - before the temperature of the weld cools down below the 800-degree Fahrenheit threshold. This is the point at which oxygen can no longer react with the titanium. Some codes may require that post-flow remain until the temperature drops below 500-degrees Fahrenheit, so always follow procedure, and if the procedure isn't sufficient, then revise it, so it does give the desired results-PERIOD!!!

Titanium offers the benefit of showing its true colors once the weld is finished. The final color of the weld joint indicates how well the shielding gas protected the weld from contaminants and how thick the oxide layer is. ;)

Respectfully,
Henry

It sure does read as if those folks are clueless when it comes to Titanium and Aluminum also for cryin out loud! ;) I'm glad you understand, and now it's up to them to open their own minds so that they can do the same... Hang in there Joe!!! :) :) :)

Respectfully,
Henry

Ok Joe

If your on an airbase.. It sounds like a NARF or at least an "I" level airbase if your doing that kind of work..   You should have tech reps from GE, Pratt, Allison, Boeing etc.. All the engine and structure makers.  These tech reps should have access to the standard practice manuals for Aerospace welding, prolly located in your tech library...

These should be very informative... And you and your supervisors should have access to them...

Details about surface prep, purge rates, backup fixturing etc. can be found in the standard practice manuals.. 

1595 and D17 are minimalist for a reason...  The reason is the wealth and diversity of standard practices founded by each of these major aerospace players...

As Professor Crisi noted the Ti institutes and EWI/TWI  have great data... much of that data was gathered collaberatively with the aerospace folks who publish the standard practices I've mentioned...  

Hunt down the Tech Reps...  They are paid to help you do your job...  You are the reason they exist and mostly they are quite helpful.  These tech reps, through their tier one employers, shoud also have membership in EWI, TWI and the Ti institute and be able to to the legwork of finding the tools you need...  The research has been done for about 20 years... Ti is nothing new to these folks... Use em

Let us know what you find out.

Hello Joe;

You have already received some good advice. All I can do is add my confirmation on a couple of points.

Shielding Gas: Argon purchased to AWS A5.32 is "pure" enough for welding titanium. Use the largest gas nozzle you can and if possible, use a gas lens to permit higher flow rates than would be possible without the gas lens. A trailing cup can be easily fabricated using thin gage stainless steel, a diffuser, and a "cape" made from a piece of "fire blanket.” The idea is to contain the argon gas to displace all oxygen and nitrogen, as well as hydrogen from the weld puddle (gas nozzle's function) and the weld as it cools to a temperature sufficiently low that it no longer reacts with atmospheric gases (the function of the trailing cup). You can also build a "bubble" or a chamber out of plastic film stretched over a wire frame constructed from welding rod. The larger volume of the chamber will require extensive purge and it will require a good volume of argon to lower the oxygen/nitrogen content to less than 0.5%.

Purge: You most definitely need to purge the ID of the tube. Block the ends with stainless steel wool that has been rinsed in 90% isopropyl alcohol and air-dried. You need to allow the air in the tube to be completely displaced by the argon. The (flow x time) should be sufficient to displace the system volume about 7 times to reduce the oxygen content to less than 0.5% (maximum). Air is less dense than argon, so there needs to be venting at the high points in the system to allow the air and excess purge gas (argon) to vent. I would use too high a flow rate with the thin wall tubing. Initial purge flow can be about 10 cfh and then it can be reduced to about 5 cfh if the vents are small. You do not want a positive pressure inside the system that will "blow-out" the molten weld puddle leaving a gaping hole where the weld puddle once was. 

Cleaning: Wire brush all the joints with a stiff bristle brush that has austenitic stainless steel bristles after the piece and the wire brush have been cleaned in isopropyl alcohol to remove all traces of oils (including fingerprints). Do not handle the piece with your bare hands or using gloves that are not perfectly clean. Wipe down any fixturing or tools with the alcohol before using them.

Sweat or the use of chlorinated solvents can contaminate the titanium and it will cause it to crack if the part is reheated (as in the case of stress relief or annealing).

Rods, filler metal: Wipe down all filler metals with the alcohol before using them. It would be a good idea to clean them using stainless steel wool that has also been cleaned in alcohol and air-dried before using it.

Henry said it all when he addressed cleaning and the need to keep everything clean.

If you do everything correctly, the weld, exterior and root side, will be as silver as a new quarter. The discoloration will occur if there is contamination. It will go from silver to a light straw (pale yellow), to gold, to purple, blue, black, and finally gray ash. You need to strive for silver. Any more than a hint of yellow is a kiss of death unless you are doing a sculpture and you are looking for pretty colors for an entirely different reason.

Nearly anything will contaminate titanium. Sweat, fingerprints, oils, chlorinated solvents, dirty rags or welding gloves, dust in the air, etc. Some of the shops I have worked with have people tasked with vacuuming and cleaning all day long just to reduce the possibility of contamination. Adhesive tape will give off fumes when it is heated which will be absorbed by the weld puddle and it will cause contamination.

Grinding disks and other tooling must not be used on anything other than the titanium. Carbide rotary files are usually preferred over grinding disks.

This sample shows the affects of varying levels of atmospheric contamination. Wire brushing the weld will remove the colors derived from oxidation, but the damage is done and it is permanent. Once contaminated, the weld and adjacent base metal has to be removed before a structually sound weld can be made.

Best regards - Al