How Hard is Titanium to Weld?

[icemaker]

My buddy is an avid powered paraglider. This is basically an engine with prop straped to your back and a parachute overhead - and then you go flying (yeah, I know - but he doesn't question my hobbies). Anyway he has a bent up prop cage that is supposedly made of Ti (I haven't inspected it yet, so don't know for sure if it is or isn't) he wants me to straighten out and reweld for him. The welds are non-critical from a flight safety point of view, but quality is still important. I have a Tig machine (Miller Synchrowave 250) and have welded aluminum, SS, and mild steel using Tig, however, I have never attempted Ti. What filler metal is usually used and is it readily available from local welding supply houses? What tungsten is recommended for Ti? Is argon appropriate, or is a mix needed? DC EN, EP, or AC? Where can I find recommended Amp settings based on material thickness, etc., etc., etc.? Any and all assistance would be appreciated. Thanks, Bill.

[MikeC]

I have not actually welded titanium yet, but... From what I know you will need an inert atmoshpere. That means a glove box big enough to put the entire prop shroud into and a spare argon bottle to purge all the air out of the box. If you don't have that on hand, the repair is pretty much out of the question on something like this. You can use a trailer cup on sheet or something, but not on wire.

That said, it's kind of hard for me to believe they would put a titanium shroud on the prop. That's a ton of money. It may be aluminum or even stainless instead. If it's Ti, you'll know it just by looking at it.

[artk]

I don't do TIG welding at all and don't consider myself a welder. However, the books I have studied show that Titanium requires a backing gas or inert atmosphere on both sides of the weld. Your TIG gun will provide that on the outside of the tubing, but you will need to rig up something to purge the inside of the tube at least in the area of the weld.

The information I have seen shows that this doesn't have to be too elaborate and I even thought you could use the same gas bottle if you could tap the gas into the two different ways and still have enough flow. If heat isn't a local problem I have seen suggestions that you could use duct tape and cardboard to help close off the input end. You just have to provide an inert atmosphere on both sides of the weld.

Now the people with real knowledge can educate me. [img]/ubb/images/graemlins/crazy.gif"%20alt="[/img]

Regards,
-Art K

[mrb37211]

It it is titanium, don't use "Magic Markers" on it. In the SR-71 Blackbird program, mechanics circled places to be repaired with marker, fixed them, and a bit later found the whole area which was circled had fallen out. Charles

[artk]

I don't remember anything about magic markers, but didn't Ben Rich in his book, "Skunk Works", mention that high concentrations of chlorine made the titanium skin brittle? I seem to recall that they stopped using city water to wash down the birds. I wonder if the magic marker thing was after the metal temperature cycled during flight or was it just a chemical reaction at normal temps?

Regards,
-Art K

[MikeC]

I haven't heard about the marker thing, but I KNOW you can stop drill a crack in a titanium jet tailpipe with a graphite pencil dot. Apparently when the metal comes up to temp, it burns out the dot. The ink in the marker may do essentially the same thing. Ti is WEIRD stuff.

[gradstdnt]

Titanium is actually a very easy metal to weld. It doesn't conduct heat well so it forms a puddle easily with the TIG torch. Surface tension of the puddle allows for easy addition of filler as well as easy to get a nice smooth clean fillet between parts welded. I''ve messed around with it but haven't done any big jobs.

Now the hard part. As always with TIG, parts need to be very clean. Ti when heated is very reactive with oxygen and hydrogen. This means the parts need to be under a shielding gas when at elevated temps. Glovebox is one solution. You may get by with a gas lense and a trailing gas shield to cover the welding area. There are plenty of people who weld titanium without gloveboxes. The opportunities for failure are higher in that a small draft can contaminate the weld area. The weld area will discolor if not properly shielded.

One way to test if the material is titanium. If you rub titanium up against glass, the ti will leave a mark on the glass.

[wlbrown]

SIR,
before i did anything, i would contact the company that made the
frame, and ask them what type of material it is made from. then
go from there. like the other post said, i doubt if it is made from ti,
because the cost would be very high.
good luck with your projects.
wlbrown

[icemaker]

Hello,
I have the frame in my shop currently and it is Ti. I have obtained repair tubing and welding rod from the manufacturer and will give it a try when I get a break. I am going to make a temp glove box with argon purge and put the sections that will require welding in it so that it will be totally inert. I guess I'll see how it works out. Bill

[MikeC]

Do report back on your results. I have some tubing, sheet and plate laying around and I am just itching to try it. I just don't want to ruin what little stock I have.