Welding Titanium

Date 02-07-2005 03:21

I would recomend the Miller Dynasty 200DX with the advanced wave shaping features. For particulars try the Miller motorsports forum ASKANDY.

The D200DX is a bit pricy but it is the easiest way to learn tig. The pulse will help achieve the quality you need. I have been tigging for about 4 monthes and it has helped me more than I can describe.

Good luck,

By LarryL

Date 02-07-2005 14:20

Your project may be an extremely challenging one for you because it will require you to learn several skills simultaneously: Tig welding, structural tube welding, and titanium welding. That doesn't mean that you shouldn't attempt it. Just be prepared for a moderate amount of frustration if you've never Tigged before. If you're proficient at oxyacetylene welding, however, transitioning to Tig shouldn't take very long.

I'm curious as to why you stated that no other material besides titanium will work for the wheelchair you intend to fabricate? Your design only calls for supporting a 250 lb. person on it. Won't an aluminum alloy such as 6061-T6 allow you to fabricate a sufficiently light wheelchair? Your design could incorporate higher strength alloys like 7075 if you used joining methods such as resistance welding and riveting. If ease of portability is a design requirement, you might consider a wheelchair that breaks down into several manageable pieces. I've seen aluminum wheelchairs that can readily be taken apart (and reassembled) so that they can be transported in the trunk of an automobile.

LarryL

By Racefan Date 02-07-2005 22:52

My welding skills are very limited but I have ~4yrs with a Millermatic wire machine.
I acknowledge the steep learning curve but I'm up fr the challenge.
The genesis of the project is two-fold with completing a patent the principal. This is where the requirement for "me" to learn the skills is founded. The second motivation is cost reduction by limiting the out-of-house welding costs.
The material is required due to several mechanical properties. Titanium transfers energy very well limiting the "jolts" to the body which can manifest itself in several ways. You mention titanium bicycles. Ti-bikes are made just for this reason. If you speak with anyone that has ridden a`Ti bike, they will likely mention the "soft" ride quality of the bike.
T6 is a great material for wheelchairs and is used extensively. As you suggest, there are several chairs that fold and can be placed in a trunk. Most of those were likely aluminum but as in an aluminum bike, a very firm or "stiff ride" .
Thank you for the info.

By chall

Date 02-07-2005 14:46

Welding Titanium is more challenging than other metals because of the shielding requirements. Titanium must be kept shielded until it cools more than other metals may require. For that reason, trailing gas is required or the weld must be done inside a glove bag with a controlled inert gas atmosphere.

We don't do a lot of Titanium. When we do it, the welders involved usually get several days of training ahead of time.

Charles Hall

By SWP

Date 02-07-2005 15:46

Racefan,
shielding, shielding, shielding, and cleanliness. Excellent argon shielding is absolutely needed and the weld area must be protected from atmosphere until it has cooled. The color of the finished weld and heat affected zone should ideally be shiny silver, a slight gold tint is acceptable, but any more towards the blue range and you will begin to severely embrittle the weld. The very best method is to weld inside of an inert gas chamber, see an inexpensive example at this site, www. chworldwide.com. The experts go to extreme lengths to ensure the ultimate pure argon atomshere, less than 10 parts per million oxygen and moisture (dew point -60 F), don't use rubber gas hose, purge the lines for a few minutes prior to welding, use ultra-high purity gas.
I would recommend using the largest diameter gas lens you can. Also, since you need to shield the weld while it is cooling, you will need to improvise some kind of trailing shield. Also, don't forget about protecting the weld melt-thru on the inside of the tubing, you need to purge the tubing I.D. during welding. Check out CK Worldwide for the gas lens and trailing shield, http://www.ckworldwide.com. As you'll see, the CK trailing shield is nothing more than a secondary gas lens attached to the torch on a simple bracket. You can do this yourself and maybe add a nozzle, and maybe have another one of these hand held by a helper. Weldhugger also has a trailing shield system, www.weldhugger.com.
Also, don't forget cleanliness, no moisture or oils, dry machine, grind/cut with a fresh wheel (not used on any other metal), handle with white cotton gloves, etc.
You won't need any special TIG power supply, you will use DC electrode negative, and can probably get by with 150 amps for the thickness you are talking about.
Hope this is helpful in getting you started.

By Racefan Date 02-14-2005 10:03

Wow.
Sorry for the late reply but thanks for the very helpful info.
I was hoping to get by w/o having to weld in a totally inert environment but I do not want to compromise the integrity of the material.
I also appreciate the website and they'll likely end-up with some of my money...I've not known a hobby or sport that likes my money so well!...again, thanks for the info.

By TimGary (****)

Date 02-14-2005 13:18

Hi Racefan

Your project could be welded outside of a purge box, if you have the appropriate trailing shields. I could send you a drawing of a shield that I used a while back for TI welding of 3/4" pipe. It works well, and could be easily modified for your application. You just have to maintain filler metal discipline by not allowing the end of the rod to leave the sheilding gas.
If you wish, send me an address or fax# and I'll forward a couple of drawings plus some useful Ti info.

Tim Gary

By Lawrence (*****)

Date 02-07-2005 20:29

Patrick,

Try that google search on "Titanium Wheelchairs" there are plenty of folks making them with lots of good pictures and examples of progressive design.

If you need just one wheelchair, you really might want to consider simply buying one. Your investment in a good welding machine (pjseaman's choice is excellent) tube bending, notching and face prep equipment will be way above the cost of a Ti chair somebody else made.

On the other hand if your going into buisness making these things for a living than don't skimp on equipment. I would imagine the liability for making wheelchairs is pretty high. Fitups, purge, shielding and welds will have to be aerospace perfect. If your not already an expert fabricator/GTA welder than this is a pretty complex project to start learning on.

Another place to get ideas is from makers of welded tubular titanium bicycle frames.

By Racefan Date 02-14-2005 10:38

Thank you for the reply.
Actually the makers of wheelchairs do have a few sporty designs and as you say, are readily available.
A properly fitted Ti chair will set you back ~$6000 which is criminal. If you look over the sites note they price the "chair". Now if you want one with wheels...tires...you get the picture... The obvious question is "why so much"?! It's right along the line of a $25 aspirin in the hospital.
I hope to introduce a high quality chair that people can afford. If I can pull-it-off, I'll make them affordable to own, hopefully make a little money, recover my costs and get the satisfaction of improving someone’s life. All this while showing the medical "extortionist" the gig is up.
Again as you mention, liability is a paramount issue. Fortunately an attorney-colleague is giving pro-bono advice which I’m not at liberty to discuss. Point well taken though!
I’m an engineer for a fortune fifty non-air framer aerospace firm and appreciate your suggestion about purchasing good quality gear. I know the value of good tools and such.
Thanks again for the reply.

By metals406 Date 02-19-2005 18:30

Just got done watching a show on the History Channel about manufacture of the F-14 Tomcat. The main structure is fabed out of pure Titanium. They had a segment about welding Titanium, and how difficult it is. They used a welding process I'm not familiar with, but is flawless. They recover planes that went down, and the main body of the Tomcat is virtually untouched. You might do some searching in the Aero-Space industry, and find out what the process is, wish I could remember what it was called. It may be that the Aero-Space contractor may even want to work with/buy your design, you sit back and get a tidy profit, and people recieve a product for less. They would already be set up for mass production, which hopefully could keep cost down. I don't know? This might be just a brain fart:) Good Luck!

By ssbn727 (*****)

Date 02-20-2005 12:59

Hey Metals!

The process they (Grumman Aircraft of Bethpage, NY out on Long Island) used on the "Tomcat's" fuselage was EBW.
Otherwise known as Electron Beam Welding.

The process was totally automated (customized one of a kind system) and, the welding was performed in a "clamshell" type vacuum chamber. Do'nt worry about the "brainfart" because your intentions were good!!!

I know first hand about this system at Grumman because, I had the honor (seems like many) years ago to actually see how this system performed and MAN-O-MAN, did it ever!!! Perhaps one of the GREATEST Fighter aircraft EVER produced in the WORLD!!! GO NAVY!!! SECOND TO NONE!!!
The F-14's motto is "ANYTIME - BABY"!!! Too bad they're being retired!!!

Anywho, getting back to your situation "Racefan"... As TimGary mentioned, with the appropriate trailing shields, the need for a vacuum chamber can be avoided. SWP also had some good advice also as did Lawrence...

I've personally welded a variety of Titanium.
From CP (commercially Pure) grades to a variety of Ti alloys when I worked for company in New Jersey and, the key words to successful weldments were: Cleanliness & backpurge and monitor the heck out of the joints before during & after welding for gas purity!!! I say this because even if everything else was strictly followed such as mentioned in the previous posts, if the joints were'nt clean (white glove treatment) & backpurged properly - it did'nt matter if everything else was correctly done... The welds would turn out to have some CONTAMINATION and they would not consistently pass NDT or NDE (Non Destructive Testing or Non Destructive Evaluation, they both mean the same)... Just as important is to make sure not to contaminate the joint with arc strikes or tungsten contamination...
Color is also an important factor in understanding how to set up your current, travel angle, travel speed, work angles, tip to work distance, etc. Cross contamination is critical also. Meaning that the machine tool bits used in fabrication, the grinding/cutting wheels, the wire wheels must be of the type that does NOT leave any residue or impregnate any of it's materials into the Ti base metal and, must be used exclusively on ONLY the specific Ti base metal!!! NOT on any other metal PERIOD!!! I cannot stress this enough!!!

I could go on and on but, the only way you're going to learn how to weld Ti properly is to learn from someone who has already done so successfully on a consistent basis because, even though the metal is relatively easy to weld, it is far more difficult to produce consistent high quality welds with this metal without knowing and experiencing firsthand - ALL of the factors & variables, ALL of the necessary precautions that are required to ensure success due to the very nature of this reactive metal... Not to mention that Ti is'nt a relatively inexpensive metal to fabricate and weld compared to lets say, Aluminum... I hope this helps!!!

Respectfully,

SSBN727 Run Silent... Run Deep!!!

By olmpkwelder474 (*)

Date 02-25-2005 01:59

U can get buy with using an extremely big gaslens and lots of post flow. I recomend the biggest cup CKworldwide makes. It's clear and u can totally see through it so u can keep the tungsten tight or stick it out a bit and still get good gas coverage. Its about an inch in diam maybe a bit bigger. Do some research on the color of titanium after it's been welded. U can get buy with more then u think for ur application. Alittle color in the weld won't hurt your application.