Machining Titanium

[Chris HeapyParticipant @chrisheapy71135]

Thanks Trevor. I chipped a carbide endmill trying to cut out the hardened area so I gave up on it. I note for future reference your comment about 'never pilot drill' because indeed that is what I did.

[joeyParticipant @joey]

Hi guys, is there no heat treatment that will soften the titanium?

[Jesse Hancock 1Participant @jessehancock1]

Hi, I have very few particulars on the 20mm thick Titanium 6"x4" blocks I worked on once and once only for Aero Space in Bristol. They gave us a few samples to experiment on and the long and short of it all was I burnt an ID profile in them using oxy propane. It cut like butter and later Aero space gave us about 100 parts to profile.

There were no issues with fire or anything…from a profiling point of view it was easy peasy.

As I say I've no idea what the spec was but the customer sure was happy with the result.

Jesse

[VicParticipant @vic]

I turned some commercially pure Titanium rod on my 8 x 14 lathe with HSS tooling. Worked fine until I let it rub as the tool dulled and the swarf caught fire! Best not to look at burning Titanium I understand due to UV given off. The part was saved though and looked nice after sand blasting to match the other parts. I have a couple of billets of 6Al 4V titanium and it's a bit tougher to cut. Sawing it by hand is hard work and takes ages.

[Peter BondParticipant @peterbond14804]

I've hand-sawn grade 5 and I'd rather not do that again. It can be hammer formed cold (0.7mm sheet), but it takes some effort to get it to take a permanent set and the stuff hits you back. Grade 1 is far more forgiving.

Hot forging is much easier. Some US smiths have rather snazzy forging tongs made of Ti, the lower heat conduction is supposed to be a boon (although in reality I suspect it's for bragging rights).

A laser welder will join Ti happily (under argon), but a) it's only good for thin pieces, say up to 2mm, and b) the weld can still end up brittle – I need to see if I can anneal it successfully. Can't do vacuum annealing, but I can use tool wrap and some charcoal to scavenge O2.

I also have a few small blocks of aero origin, no idea what alloy though.

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Peter Bond on 23/01/2015 10:51:42:

Some US smiths have rather snazzy forging tongs made of Ti, the lower heat conduction is supposed to be a boon (although in reality I suspect it's for bragging rights).

I hope not. Ti forging tongs would be very dangerous. Pure Ti is highly inflamable at temperatures over about 600 C. I suspect they are made from one of the high temperature alloys.

Russell.

[Peter BondParticipant @peterbond14804]

Solid section bar is not going to spontaneously combust at 600C given the MP is 1668C. Turnings will go up with less encouragement due to their greater surface area. I can get steel to ignite at room temperature, never mind any of the pyrophoric metals.

As for precisely which alloy of Ti they're using, no idea. Probably whatever could be scavenged.

For more information on hand forging titanium, may I suggest this as a possible starting point – http://www.iforgeiron.com/topic/22934-help-with-forging-titanium/

On combustion (specific to aero engines) – http://www.fire.tc.faa.gov/pdf/fsr-0457.pdf

[Neil WyattModerator @neilwyatt]

[Neil LickfoldParticipant @neillickfold44316]

There are Ti specific soluble cutting fluid. Like others have said, sharp tools, low speeds and relatively high feeds.The centre cut point drills work a lot better than regular drills. Sharp positive rake carbide turning and boring tools also work very well. HSS works well , but does dull a lot quicker than HSS. As soon as heat starts to build, resharpen the tool or go to a slower speed. When drilling through plate, I put a piece of steel underneath for the drill to break into. On the lathe I try to avoid breaking through where possible and prefer to part off or face off the back end. Ti also expands quite a lot, and is a slow conductor of heat. When drilling the common problem is the material getting hot, and then contracting as the drill is either retracted or when more coolant is poured down the hole.

Neil

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Peter Bond on 23/01/2015 12:17:58:

Solid section bar is not going to spontaneously combust at 600C given the MP is 1668C. Turnings will go up with less encouragement due to their greater surface area. I can get steel to ignite at room temperature, never mind any of the pyrophoric metals.

Ignition temperature has nothing to do with melting point or surface area. Increased surface area increases the rate of combustion. Many materials will burn well below their melting point.

Yes, there are many different alloys of titanium but Ti is the chemical symbol for the element titanium and refers to the pure element rather than any alloy. I was referring, somewhat tongue in cheek, to the misuse of the symbol – should have used a smiley.

Russell

PS. How do you get steel to burn at room temperature?

[Peter BondParticipant @peterbond14804]

Steel wool, drop it in pure O2

*Technically* constitutes burning it at room temp, but obviously it's the rate of reaction on oxidation that bumps the heat up locally.

[MuzzerParticipant @muzzer]

The ultimate coolant! And here.

Edited By Muzzer on 25/01/2015 17:47:44

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