Exotic Metals Heat-treat

[Anonymous]

Have been thinking of kicking out a set of one off titanium rods. Machine, material, tools, etc. will not be a problem. What is a problem is that I have no idea what if any heat-treat should be applied to them. I thought to find a broken (read "cheap") rod on E-bay and have it rockwelled, but I have not been able to locate one.

Does anyone know what would be an appropriate hardness/heat-treat process? Would I even want them heat-treated?

 

[xctasy]

I don't know about heat treating.

Any one with a 250 should consider NSX Honda rods.

For the 200, use Jet's titanium rods, as used on early DFX 2.65 Turbo engines, or some wild Pinto/Lima 2.0/2.3 race engines. They are special order items from 5.15 to 5.3", but you can get down to 5". Some 911 Turbos have very short titanium rods about the 5 inch mark.


Can't help anymore than that, sorry.

 

[Anonymous]

the cryo treatment is a much better alternative

 

[Anonymous]

I guess it was stupid not to include the link for the cryo huh?....These are the people I used...they do good work with a quick turnaround[http://www.300below.com/][/url]

 

[Anonymous]

the heat treatment process varies widely depending on the titanium alloy contents. there is a wide range of alloys. diferent alloys for different uses. the 6Al-4V is often used for structural rotating components that can be machined from billet. it can be solution heat treated and should be aged. in the annealed state it yields at 120-130kpsi. and in the typical solution heat treat/aged condition yield would be at 170kpsi.
titanium is similar to aluminum in that it work-hardens easily. you could design a lighter rod with the heat treat but it would be limited by a very definite fatigue cycle. it would become very important to have a finite element stress analisys so you know what and where the stress risers are and how many cycles it will see in service. you would have to work-up some figures on the dynamics of the rod during use.
an annealed rod has a lower yield point but would be much less prone to critical fatigue failure. it would be a heavier rod( but approx 2/3 the weight of the steel rod)
a note of caution "hardness is not a good measure of the adequacey of.......heat treatment of titanium alloys" paraphrased from ASM Non-ferrous Handbook. The reading belies that there are usually skin properties
that are significantly inconsistent. you would need to cut through the rod and test the core for hardness and preferrably perferm a fracture test on a core segment. Also since someone else has done the homework on the original rod , you could verify the alloy used.
interesting idea.......you want to buzz your 200 incher up to 10,000!!!!

 

[Anonymous]

What stude3 said.
It has often been said the heat treatment of steel is proof that there is a God, but steel it the only metal that behaves the way it does. When getting into non-ferrous metals, heat-treatment becomes a confusing subject, to say the least. It would be important to realise that you probably cannot expect indefinate service from these rods unless very carefull design consideration is given, as is the case with aluminum rods.
As for the heat treatment, you need to talk to someone that heat treats titanium. Ti has a very strong affinity for nitrogen when it get good and hot, and this will cause nitrogen embrittlement. The items would need to be treated in a vaccum furance. Heat treat companys can give you alot of help in detemining what you will need, and they have the equipment to do it accuratly. If anything, they will help clear up the muddled mess that the books can sometimes seem to cause, because they know where to look and exactly what to look for.

 

[Anonymous]

What is it that you think titanium rods will acomplish?

 

[Anonymous]

changing to titanium would reduce the reciprocating mass which reduces the stresses on all the rotating and bearing parts. it also raises the lateral critical speeds. so it makes it physically possible to wind your engine to higher rpm's and delelop more HP. The valve timing , harmonic balancing, flywheel etc would have to be redone in order to make use of this improvement. this upgrade would be more practical for racing application like formula 1 where high rpms are used to gain huge HP's out of small displacements.( In formula 1 they regularly demand 700HP out of 3 liter
engines.)

 

[Anonymous]

I intend to build to the edge of the envelope. Titanium rods will permit higher R's By virtue of lower mass. Granted the pistons will need to be slightly heavier to allow for reinforcment neccessary for the Ti rods. But it should still be a signifigantly lighter assembly.

The desire to build them myself is just that. However given the lack of cut and dry info on metal treatment I will probably have them made for me by someone who knows what they are doing. That way I can avoid puking an engine with a huge cash investment in it. Crower is the most likely source for me to go through. But I'll cross that bridge when I get there. I'm going to build this motor right, so it's not going to happen overnight.

 

[Anonymous]

Having found this thread, I now have another document to search for among my piles of ancient tech articles. This one is a 15-20-year-old issue of Bike Tech, a small periodical for bicycle builders.

As I remember it, the article was by a frame-builder who was experimenting with titanium frames. He put two welded frames in a heat-treat oven, evacuated it of air, and back-filled with argon, then started the oven and timer. When he returned the next morning and took the cool frames out of the oven, they were covered with an irridescent blue scale. He realized that he had mistakenly back-gassed the heat-treat oven with nitrogen, and he set the two frames aside as ruined. Some time later he ran some tests on the frames and found to his amazement that every mechanical property he tested for had been markedly enhanced!

This is one item I think I can find in short order . . . .