Blue coluration of Ti

By ssbn727 (*****)

Date 10-24-2003 08:01

Hi Ian!

The short answer is YES, and YES!!!
If you want a long answer let us know...
I say this because some people in this forum are getting tired of my long replies so, I'll try to keep it short and simple but, I really do'nt know if I can stick with this new self imposed policy I'm trying to follow...
Respectfully,

SSBN727 Run Silent... Run Deep!!!

By Ian Taylor (*)

Date 10-24-2003 08:22

ssbn727

I would welcome a long reply - if you wish to reply off this forum then I have sent a mail to your hotmail account for you to reply to. Do you have any specs to refer to (MIL etc).

Regards
IanT

By jwright650 (*****)

Date 10-31-2003 19:25

SS,
Keep the posts coming, length is not of concern to someone learning from it. I know absolutely nothing about Ti and find the reading interesting.
John Wright
PS. Who complained of the long post?....just curious.

By ssbn727 (*****)

Date 11-03-2003 20:24

Hi JW!
I'll say one thing that's for sure; anybody that thinks that they do not need to learn anything else is only kidding themselves!!!
I also found out that the more you think you know about something, the more you realize that you need to learn alot more about everything!!!
I really do appreciate your support John Wright!!!
I have a tremendous amount of respect for your experience and knowledge, especially your readiness to share it with anyone that seeks it!!! I'm honored to know you in this forum as a friend!!!
The person that e-mailed their comments about the length of my replies was just stating their opinion and in hindsight, I was little bit upset about it... Since I made my initial self imposed policy proclamation in a previous reply on this thread, I decided to abandon it because of the support from colleagues like yourself, Rodofgod and others...I also came to the conclusion that I cannot let other individuals opinions influence me in the way I should express myself here so, I decided to not change the way I've always expressed myself and that is with sometimes long, yet purposeful explanations in order to promote debate and to seek differing views because after all, I cannot practice humility if I abandon my principle and philosophy to remain teachable!!! Once Again thank you for your support and understanding!!! Oh Yeah I almost forgot, the person that wrote me via e-mail has since "profusely" apologized to me and I replied that "I should apologize to you and myself for taking your opinion so seriously!!!" This person does'nt frequent this forum often anyway!!!
The name is'nt important because as you also know, Forgivness is a practice that should never be lost among ourselves so, let's put that person's opinion to rest... I know that you understand what I mean when I say this... Anywho, how about a category on welding metallurgy or welding physics or even let's say Electric arc welding processes, solid state welding processes, Automation & Robotics, Hybrid & Specialized Joining processes and keep the rest or bundle some of them within some of these categories to save some space???

Respectfully,

SSBN727 Run silent... Run Deep!!!

By Lawrence (*****)

Date 10-24-2003 12:53

Ok, This may start a donnybrook but we will all learn something.

AWS D17.1 2001 (Specification for Fusion Weldng for Aerospace Applications) now puts Ti into 3 classes in its weld bead and reinforcement color table (6.1)

Blue oxide on Class 1 welds : are considered a reject "...on the weld and in the HAZ up to 0.030 in. beyond the weld."

Your coloration is 1/4 inch or 0.250 in. beyond the weld.. if you were working to this doccument you would need mechanical removal of that blue alpha case, and thats all required.

Blue oxide on Class 2 and Class 3 Welds: are considered a reject unless : "Blue discoloration is considered rejectable if additional welding is to be performed. Blue discoloration is acceptable on finish welds but must be removed prior to susequent processing."

Class 2 & 3 make no mention of HAZ However, we can look at the criteria for the more stringent class 1 and see that your within limits there.

I know This flys in the face of common Ti shop practice and the older versions of Mil Std 1595. It also disagrees with my old Pratt Whitney Acceptablity photo chart.

To keep the long story short. Color is a poor indicator of soundness in titanium anyhow. Here is why. The amount of Oxygen/nitrogen (in the molten pool) it takes to embrittle a Ti weld is much less than the amount it takes to produce color, so here color is no indicator to rely on.

After Ti solidifies/freezes, until it reaches about 800 degrees it is still surface soluable and this is where inefficient gas trailing can produce color (alpha case). This stuff is a few thou thick and its brittle. Specs require removal to avoid stress risers or contamination of subsequent passes.

Back to your problem. Blue coloration 1/4 inch away from the weld points to Alpha case.

Are you working to a specific code? Knowing this would further enable board posters to comment.

Lawrence.

By - Date 10-24-2003 14:34

hey ssbn.we never get tired of your long replies so "keep em coming"

=)

By ssbn727 (*****)

Date 10-24-2003 22:46

Hi Oxy!
Thanks for your support!!!

Respectfully,

SSBN727 Run Silent... Run Deep!!!

By ssbn727 (*****)

Date 10-24-2003 22:44

Hi Lawrence!
Can you be more specific as to the amount of O2 (ball park amount in ppm's) it takes to cause embrittlement in a Ti weld assuming that you know what Ti alloy you are using, and then give an amount in ppm's that would cause discoloration? As long as I've been around, when welding Titanium, after completion of the weld upon visually inspecting for discoloration, and finding it almost always meant O2 contamination, even in the HAZ (Heat Affected Zone) unless this was caused by excessive current, and slow tavel speed, provided that work/travel angles, and torch standoff distance were adequate... Even if this (excessive current, slow travel speed) was the root cause for the dicoloration in the HAZ, enbrittlement has occurred so, it all depends on what is acceptable from the code requirements Ian, and the sub is working from. Unless the client specifies further evaluation than what the code or standard requirements call for in order to accept the work from the subcontractor... Btw, Lawrence! You're merely stating your experiences so, I do'nt think you're starting a "donnybrook"... There may be differences in our opinions but, that's why we discuss these issues here... It's like you mentioned, we will all learn something from this, and that's why this forum is such a wonderful place to participate in!!!
Hi Ian!
I'll need to find out some more details from you in order to give you a better answer as far as your query is concerned: Ti Alloy type, and diameter of tubing, you already gave the wall thickness. What code or standard are you and the sub working from? Is the sub purging the tube and monitoring the amount of O2 ppm's in the purge zone repeatedly also, has the root reinforcement and the surrounding surfaces been visually inspected to see if there is any discoloration present? If the sub is purging, how are they doing it? What diameter filler and alloy type is the sub using? Is the sub in fact using a trailing shield with sufficient gas coverage, and if possible, what are the welding parameters being used? Are you working from British standards? What (if you've asked) have you found out in the UK welding forum? Oh yeah, what is the gas being used for shielding, and for purging? What welding process?
Please let us know so that we can assist you further...

Respectfully,

SSBN727 Run Silent... Run Deep!!!

By ssbn727 (*****)

Date 10-25-2003 12:37

Hi Ian!
I did a little websurfing last night and found some interesting websites pertaining to Ti welding issues... I must warn you that the list is not short, so here goes:
http://www.twca.com/WahChang/pages/outlook/html/bkissues/20_03.htm
http://www-cms.llnl.gov/s-t/welding.html
http://www.ewi.org/njc/titanium.asp
http://www.key-to-metals.com/Article28.htm
http://www.key-to-metals.com/Article50.htm
http://www.timet.com/design&fabframe.html
http://www.timet.com/productsframe.html
http://www.tigdepot.com/products/p4.html Ti trailing sheilds & more!!!
http://www.hi-techwelding.com
http://www.alloychange.com/a/6010.html this one is a forum.
http://www.arcraftplasma.com/nonferrous.htm Indian company website that uses info straight from the U. S. Army manual on Ti welding!!!

Some of these websites are more relevant than others, and if you ask me, the first seven are the good ones!!! Especially the first three...

What I got out of the first seven was the fact that in order to verify soundness of not only the weld but, also the adjacent HAZ, one must not rely completely on coloration via visual inspection as the method of determining whether or not to accept the work...
Discoloration does give you a relatively good indicator of contamination but, to what extent is the key as to whether or not the work is acceptable!!! The Lawrence Livamore website above shows us the differences in the size and pattern of grain structures beginning from the weld itself all the way out to a specific distance from the weld in the heat affected zone (HAZ)... The photos clearly show the difference between the two HAZ on either side of the weld, and as you can see, as you go further away from the axis of the weld especially in the secondary HAZ, you'll see that there still is embrittlement occurring!!!
One of the other websites show color photos of what is acceptable as far as discoloration is concerned, and is also a good visual source of reference... Now I do'nt know what grade of Ti you are using so you'll have refer to these sites for guidance in NDE and/or DE, and to improve the welding procedure...
As stated in a few of thes sites is that the only way to verify that the work is acceptable. One must use destructive and NDT methods in order to rule out any contamination/embrittlement or both!!!
Some of the destructive tests include: Tensile samples, notch toughness and impact tests or both because, ductility or lack of is the key here... NDT methods can also be employed such as: Portable hardness testing, Eddy current, UT, and I doubt that most of us could afford it but also, the real time enhanced RT (x-ray diffraction) method which is the best for looking at the changes in the grain structures in the as welded condition that Lawrence Livamore used for their research via Stanford's Synchrotron Radiation Lab...
TIMET has a good book in .pdf format that covers basic design and fabrication of Ti that also covers welding and evaluation of the welds, and a corrosion resistance chart for Ti which you can also download in .pdf...The other sites have some useful info also...
All in all, these websites, the opinions offered, and the examples shown should be able to give you a better understanding as to what has occured in the tube welds, and what is the next course of action for you to take!!! I hope everybody learns something out of this because, I certainly did!!! Good Luck and feel free to ask for further assistance...
I just love that Lawrence Livamore site!!!
Respectfully,

SSBN727 Run Silent... Run Deep!!!

By Lawrence (*****)

Date 10-25-2003 15:08

SSBN

1st off I wasn't stating opinion or experience; rather, I was referencing a newly established AWS standard that differs significantly from the past in several areas. (It surprised me the first read, and my boss was on the D17 committee)

I think I can get you the info on contamination in ppm. next week when I have my desk reference handy. As far as embrittlement is concerned both oxygen and nitrogen will embrittle Ti. This is nothin new datawise, EWI and TWI have published extensively about this over the last decade. They simply ran GTAW welds on Ti with controlled amounts of contaminants in the shield gas. They discovered that the welds were embrittled long before color was observed. Than they ran good shielding gas and contaminated the trailing gas to different degrees to discover the Alpha Case phenomena. The moral of the story is that welds with perfect color can be unsound due to low level contamination, and that welds colored by insufficient trailing gas that display Alpha Case can be sound if the Alpha Case is removed.

The alpha beta alloys (6AL4V being a good example) are naturally at maximum solubility when they are molten, however, even after solidification, that contamination will migrate in solid solution (I need my notes to give the temps involved.) quite some distance, following the heat source (first phase). From initial solidification to the next transformation it’s still deep soluble; this is why it’s vital to have no contamination in shielding gas. From the next transformation down to about 800 degrees Ti is vulnerable to thin layer alpha case coloration and embrittlement, which is a trailing gas issue.

So we have two vulnerable periods with Ti, with different consequences for contamination during each. First is deep embrittlement caused by contamination during the molten state down to a specific temperature range and requires heavy rework/material removal, and the second is the Alpha Case which is a surface condition, requiring less drastic measures.

This explains the reason for rejection in the 0.030 in. range away from the weld in a Class 1 weld. Color forming in an area subjected to melting or critical heat risks deep embrittlement. As you get further from the melt zone, issues of alpha case are found.

Now it’s certainly my "opinion" that the above example, which is a substantial 1/4 inch from the melt zone, is alpha case. And it surely should have been removed before shipment to the client, and I suppose can be rejected on those grounds, however I would argue against the assumption that that color 1/4 inch from the melt zone is deep embrittlement that would require significant rework.

Great thread

PS. Those complaining about long threads are missing the point of the forum. I say pour the coals to it SSBN!

Lawrence

By rodofgod (**)

Date 10-25-2003 20:48

As I've already posted my thought's on this same question on the http://www.ukwelder.com/
forum, I'll refrain from repeating myself!!! BUT anyone who thinks todays welding problems can be answered in four or five lines of narrative is sadly out or date!!

Keep 'em coming SSBN!!!!!

Glenn Webb

By ssbn727 (*****)

Date 10-25-2003 22:19

Hi Ian, Lawrence, Rodofgod!

Btw, where's Ti-6Al-4v? I'm sure that his comments would round out the discussion on this thread... I wonder if Dr. Weld visits this forum?
So now that we know (my Fault for not checking your posts there Ian, rodofgod) that the tubing is in fact Ti-6Al-4v, we can rule out the characteristics of any other grade of Ti. Am I correct here Ian??? Micro-fissures can be problematic in the HAZ with Ti when talking about the purity level of the shielding/purging gas itself which in itself has to be either ruled in or out in order to find the root cause of the blue coloration in the HAZ as Lawrence, and rodofgod has pointed out...
I apologize (what was I thinking! must've been the Duplex situation) when I only mentioned that O2 contamination would be the cause of embrittlement in the HAZ!!! Thanks for reminding me Lawrence, Rodofgod!!! Nitrogen exposure is another source of contamination that also results in embrittlement to a lesser degree nonetheless, Very bad for Ti also!!! However, Nitrogen can be beneficial when mixed with Argon as a shielding gas for welding Duplex, and Super-Duplex Stainless stls. but, that's another story!!!
I love that phrase from Rodofgod when he mentions to "bin it!" in the UK welding forum, and I have to agree with him!!! Just on principle I'd reject it, because if the subcontractor was "worth their salt" so to speak, their QA dept. should've caught the "alpha case" prior to delivery, and subsquently removed it, rework the order if possible (which I'd be hesitant to accept), then testing it with an established NDT method PRIOR to shipment, in other words, the subcontractor blew it!!!
Straight and simple!!! Now if the subcontractor wants to redeem themselves, then they have to provide Ian with an acceptable replacement!!! Otherwise, it's their problem Ian!!! Not yours!!!
My advice to you is to reject the work, and not release payment until a suitable replacement is provided by the sub!!! Yeah that's going to cost them but, they should've thought about that in the first place!!!
If your going by British Standards, then do what your supposed to do...
REJECT THE TUBES!!! As Rodofgod said: "Bin IT!!!" Are you going to take the heat, and the loss of not only the costs, but also of your prestige when the tubes are rejected by the customer???
I do'nt think so, if I were you so, "BIN IT!!!" Demand the subcontractor for a suitable replacement PERIOD!!! What it comes down to is a business decision that you have to make in this situation!!!
That would be my opinion... This is a very educational thread!!!

Respectfully to all,

SSBN727 Run Silent... Run Deep!!!

By Lawrence (*****)

Date 10-25-2003 22:36

Here is another good one, I know were bouncing around a bit, but that comes when you swim with big fish, or submarines, to mix a metaphore.

Micro fissures, What many folks interpret as micro fissures in 6AL4V is more often grain boundries, or the faces of of excessively sized single crystals. Thsese crystals are born during over fast solidification. The EWI folks say this is less than optimum, but NOBODY cares to speak directly to the issue in the form of inspection criteria, since they won't show up during RT or FPI.

The appearence is just about like crazing or a shattered window effect over the surface of the weld and sometimes into the heat affected zone. Again it has to do with the multiple phase transformations and the speed of cooling.

Rod of G is sure right that you can't get far in just a few lines.

By rodofgod (**)

Date 10-25-2003 22:58

HI all,

Lawrence, Wish I had your way with words!!!
Gotta say,My only actual experience WELDING Ti was with the R.A.F but then I guess that's a pretty high standard!!! Never had a Tornado crash cause of MY welding!!!Had plenty of experience with it since (condensers etc...) but that military expereience kind of sticks to you with Ti!!!

Glenn Webb

By ssbn727 (*****)

Date 11-01-2003 01:28

Hi Glenn!

Yeah those Tornados can fly!!!
The F-14 Tomcats Ti fuselages are EB welded in a Vaccum chamber that's an oldie but still the best Naval Air superiority Jet Fighter In the WORLD!!! Their motto is a picture of a tomcat leaning on something and looking straight at you with a devilish grin!!! I ca'nt remember what it is that the tomcat was leaning against but, underneath this logo that's unique to the F-14, it says: "ANYTIME BABY!!!"
I personally did some work on that vaccum chamber one time back in the early eighties at the Bethpage plant when we supplied them with welding equipment and supplies... That plant was buzzing with work back then!!!
Nowadays, things are sadly alot different at the Long Island facility...
The F-14 still runs circles around almost every fighter out there except for maybe the F-15 Strike Eagle and F-22 Raptor!!!
USN! SECOND TO NONE!!! No disrespect to the Royal Navy Glenn!!!

By rodofgod (**)

Date 11-02-2003 01:23

Hi ssbn727,
What about the F-4 Phantom! I worked on those, and they where WAY ahead of their time!
The good old days!!!

Glenn Webb

By ssbn727 (*****)

Date 11-02-2003 16:36

Hi Rodofgod!

Thet were except that they relied too heavily on their missiles which were not as consistently accurate as the newer generation air to air missiles used today... Their biggest vulnerability was the fact that in the Vietnam conflict, The Air force F-4's were not capable of dogfighting because of the lack of machine gun or cannon fire capability!!!
To summarize, the F-4 phantom was misused in the role as a fighter and in my opinion, whoever decided to use these planes as such even after continuous complaints from the fighter pilots themselves should've been COURT-MARTIALED!!! All those young men that had to die because some bone-head assumption that the missiles would work all of the time so they did'nt need more fire power makes me MADDER and ANGRIER than I would like to express!!! Forgive me for being so blunt!!! I hope that this does'nt open any new wounds for any of the heroes that served in that god for saken war!!!I also hope that I'm not looked upon as not being patriotic because, nothing could be further from the Truth regarding my comments, which by the way were confirmed when I saw a History Channel presentation this week about the events that led to the development of our F-15 Strike Eagle Fighter for which they got it right in the design for it's intended use!!! They spent alot of time in the presentation pointing the vulnerabilities of the F-4 Phantom used in Vietnam and why so many were shot down!!! I hope we never again lose sight of the lessons learned from that bloody conflict!!!

Respectfully,

SSBN727 Run Silent... Run Deep!!!

By billvanderhoof (****)

Date 11-03-2003 02:57

http://www.wpafb.af.mil/museum/research/fighter/f4e.htm
If you're an airplane buff you'll spend hours here. The F-4E had a gun, 20mm vulcan M61A1, for the very reasons you state. There was also a 20mm vulcan in a pod that could be hung under the wing of most anything. I don't know when in the war that became available. If you had only one I bet you had to tramp on the rudder pedal a little when you touched that thing off. They say the 30mm in an A-10 darn near stops the plane when the switch is in rapid fire mode.
Bill

By jwright650 (*****)

Date 11-03-2003 11:53

Bill,
Is that why they added 900lbs more thrust to each engine on the F-4E? :)
John Wright

By billvanderhoof (****)

Date 11-05-2003 05:32

http://www.vogue-web.ch/f4/f4_11.html
This is a site for phantom buffs, this page discusses the development of the E model. No mention is made of complaints about insufficient power (I doubt that any fighter pilot ever complained about a modification that added power though). Apparently the more powerful engine was available so it was included. The pod mount M61A1 had been available but was disliked (inaccurate, lots of drag, took up a hard point that could have carried other things, and the biggie- made spin recovery difficult, even unlikely under 10000 feet)
Bill

By Lawrence (*****)

Date 10-31-2003 18:33

SSBN

The amount of Air it takes to contaminate GTA welds in 6AL4V in the research I have available is 0.21 %. This amount was enough to cause falure during destructive testing, but not enough to cause any color reaction on the surface.

A few days ago I sent you a bit more information at the email address you have listed on the site here. I'm hoping to hear from you soon about that stuff.

Best

Lawrence

By ssbn727 (*****)

Date 10-31-2003 20:23

Hi Lawrence!
Sorry I did'nt get back to you yet about recieving that info from you!
I'll e-mail the particulars to you ASAP...
Did some of that research have the cooperation of TIMET, Titanium Industries, Titanium Fabrication Corporation which cooperates with ASME code revisions and the International Titanium association which I believe establishes these grade numbers, by any chance?
I ask this because I got an interesting e-mail to send you regarding some of the findings in the research done by the AWS D17.1 committee in case you want to check it out...
So then the total percentage of allowable oxygen present would be 0.21 %? Hmm, that's funny because there's already 0.25% in Grade 5 Ti6AL-4V are you sure you're talking about Grade 5 Ti6AL-4V? and not Grade 23 which is the ELI variant or Grade 29 which is another ELI variant but also has small amounts of ruthenium also for increased corrosion resistance???
I guess during the actual welding, the already small amounts of Oxygen present in the parent or base metal dissolves into the inert atmosphere but then, would'nt that also increase the total amount of oxygen in that shield and/or in the trailing or purging shield??? The Oxygen has got to go somewhere!!! (unless it becomes the interstitial or "stranger" atom in the lattice which would cause the lattice to distort)
I guess maybe I'm grasping at "thin air" here??? Get it???
Likewise, It's always a pleasure discussing these and other mutual issues with you.

Respectfully,

SSBN727 Run Silent... Run Deep!!!