Identifying Titanium

[island911]

Originally posted by Pors911E
. . . whereas Ti begins to lose strength around 100F. At operating temp (200F), Ti strength would be at roughly 85%.

Seriously Steve; what Ti looses that kind of strength?

Ti13V11Cr3Al Ti-alloy, for example, is going from room temp Yeild strenth at 160ksi to 128ksi . . .at 800°F! Even at 128ksi it out performs most steels.

[Pors911E]

Island911,

Not noodles, titanium, ASTM B-265.

Commercial grade titanium really only has two things going for it. A high strength to weight ratio, and superior corrosion resistance in some pretty severe services. Other than that, it's weaker than steel per unit volume (requires larger/thicker parts for similar service), not particularly ductile (won't bend far before cracking), and can't be used in an oxidizing atmosphere at high temps. Only the F1/Indy cars can really justify its use - but they have bigger budgets than many small countries.

There are a few ti alloys that can stand up to heat. My understanding that the parts which experience the greatest temeratures are are typically constructed of heat-resistant nickel based alloys. At those temeratures, commercial grade titanium would oxidize itself into oblivion.

You crack me up. I was just trying to shed a little light on a topic I know a little about. Not an expert, I just know a thing or two. (I know, a little knowledge can be a dangerous thing) Thanks for your constructive comments.

[jpachard]

Titanium would be an odd choice for head studs since it has the tendency to gall quite easily. It is also rather elastic compared to steel, depending on the alloy. Machining Titanium is not actually that bad once you know what tools to use. I have worked with titanium extensively( I used to weld and fabricate Ti bicycles and I used to work in the foundry that makes Callaway Ti golf clubs). Welding TI is a whole other story. It must be done in a completely oxygen free environment since Ti starts to absorb oxygen at about 600 deg. which causes it to become very brittle. Ti can be extruded but it must be done in a vacuum. Boeing orders approx 35 miles of extruded tubing a year which they use for hard hydraulic lines on aircraft.

Cheers, James

[Pors911E]

DR. Isl

Just saw your last post. What does that stuff go for per lb.?

[nostatic]

3/2.5 can be extruded, but 6/4 can't, so instead the "tubing" is made from flat sheets that are rolled and welded.

James, didn't you work for Merlin (I seem to recall this conversation)?

See, all that knowledge from the bike industry has some application around here...

[jpachard]

Nostatic, I did work for Merlin and Fat City Cycles. I forgot that detail about the 3-2.5 vs 6-4. You are correct. 6al 4v is veeerrry hard...They tried to extrude it but it just chewed up the mandrels.

Cheers, James

[island911]

What's it cost? . . I have no idea. I just pick one that had a good spread on the strength effected by temp.
The point being, it's no where near 85% over 100°F. . . .That is huge -- like pasta

[jluetjen]

Curt - You've got a TAG block??? How long have you had that? So what are some of the features that you are finding so interesting on it (aside from the mystery metal studs)?

- John

[911pcars]

"Ti head studs would have to be at least twice the dia. of steel studs to be capable of exerting the same clamping load..."

Steve,
You might be referring to CP (commercially pure) grade of Ti which is almost never used to make fasteners. The highest grade of aerospace fasteners are alloyed ti (about 230 ksi UTS), and lighter too. There are steel fasteners that are equivalent, but these are pretty esoteric super alloys and they still don't have the anti-corrosion properties that ti has unless special coatings are applied. Besides, they won't use them in an airplane because it has to get off the ground.

Again, not sure about the type of ti you're referring to for strength at elevated temperatures. Like steel, there are many versions of ti. Porsche race cars use/used ti for many light weight, high strength parts including front wheel spindles and connecting rods that typically operate in a high temperature environment. The ti connecting rods in the Honda NSX are 30% lighter than an equivalent steel rod. I don't think their strength is compromised at all by heat (in that application anyway).

Honda also showed they could produce a ti con rod cheaper than a comparable steel rod by using recycled aerospace machining scraps. When the industry discovers new methods to inexpensively produce and fabricate this plentiful material, look out. Imagine the performance of your current car if it weighed 30% less - a huge impact in all areas of the transportation industry.

BTW, I gleaned a lot of this info from Forbes Aird's Racer's Encyclopedia of Metals, Fibers & Materials. A must read for techies.

Sherwood Lee
http://members.rennlist.org
Early 911S Registry

[Superman]

In my experience, pipe is usually made using a method other than extrusion. Candidly, I'm usually dealing with large pipe, but the fabrication method starts with a sheet that is folded and a straight weld joint is made. The other method is where a narrower sheet is folded into a spiral, and welded. The Boeing folks I spoke with reported that machinists HATE Ti, or at least the Ti that is sold from the Boeing Surplus store. It dulls and breaks their machines. Pipe or angle-stock is rarely found at the Surplus store. They sometimes have small blocks of it, and often have sheets, typically .040". I believe they get $8 per pound. The sheets weigh more than they look, as do the blocks. This stuff is not exactly feather-light.

[nick-moss]

A great thread on the techinical qualiies of ti, but how does a layman identify it as being ti, not steel or alumium?

[Bill Verburg]

The high strength to weight ratio as well as properties such as good elasticity, high temp strength and stability, low thermal conductivity, corrosion resistance etc. make Ti very desireable. There are alloys such as the 6al/4v that are equally at home as rotating parts in jet engines or as bicycle frames. Other alloys are used for everything from springs(Ti can be verty elastic and non fatigue prone) to valves, to con rods and crankshafts. Skin of the Sr-71 is made of Ti due to its high temp strength.

My personal use has been limited to my bicycle frame where the lightness and ride qualities(elasticity) are very much appreciated after 100 mi. or so in the saddle, and which still has polished frame pieces that look like new despite all the abuse heaped on it.

Ti hardware will gall easily and needs to have an anti-sieze used on it, that is one of the reasons Ti valves haven't caught on yet, though the new Infinity V8s do have them.

My new engine will have Ti valve spring retainers which should be good for a few rpm.

[Early_S_Man]

The entire airframe (90% Ti alloys) of the A-12/SR-71A reaches a sustained temp of 600°F and selected parts get even hotter ... for a typical flight of 8+ hours, so loss of strength evidently wasn't ever a factor during their 40+ year lifetime. The typical flight profile acted as heat treatment for the entire airframe, according to Lockheed engineers! There was never any fatigue problems or aging due to Ti's excellent corrosion resistance and the heat treatment effect!

[Pors911E]

The original point I was trying to make was, Titanium Grade 2, garden variety and most readily available, if there is such a thing for Titanium, didn't seem to me like it would make sense for use in head studs. It starts losing strength at relatively low temperatures. That’s it.

Ti13V11Cr3Al or many other aerospace Ti based alloys sound great, in theory, but it is not the kind of thing that is on the shelf anywhere. Might make great head studs… the melt would probably have to be special ordered, lead time could be months and they might cost $__,000/ea. don’t know.

That'll teach a brother to speak up...

[Bill Verburg]

Ti fasteners are available from any # of places, heres one source that I have used.

Redmist Motorsports

[jpachard]

Superman,
I have been to the facility where they draw the tubing for Boeing in Dearborn, MI and they draw it through a mandrel. They can also butt the tubing now( vary the wall thickness by changing the ID). Machinists usually dislike Ti because they have not been given the proper tols to machine it. 17-4ph stainless is actually alot more difficult to machine than most Ti Grades. I crank away through Ti all day on my CNC..

Cheers, James

[claptrap]

James, did you know Gary Helfrich? I learned to weld Ti from him.

Scott.

[jpachard]

Scott, There is a blast from the past, Gary had just left Fat City when I started....many moons ago. He is quite a piece of work...Funny guy
Cheers, James

[Rouxzy]

As far and heat goes titanium is used for the tubes in steam generaters in nuclear power plants. Needless to say it gets pretty hot and for long periods of time, like about 14 to 18 months at a time, so I can't see ti losing strength properties due to heat.

[cegerer]

Well, the headstuds are magnetic. However, there're also 10 bellhousing studs that aren't magnetic - and these have even more of a Ti appearance. I've tried to remove both the head and bell studs without success. These babies seem to be in to stay!

Here's a few photos. The headstuds appear much blacker in the photos than in real life:

This is inside the cylinder opening. Check out the crude casting of the hole (for oil??) and is that an oil squirter in the bottom left corner??



More crude casting on top of the block - apparently not important to the performance of this World Championship winning motor, just surprising to see!!!