Subject: Re: Exotic Hi-temp alloys

From: [email-masked]
Date: Thu, 22 Feb 1996 07:30:39 -0500

To All,
Titanium has the oxidation resistance of a piece of coal. It is ok for the
leading edge of an F-16's wing but the only time it gets over 1200*F is at
Mach-2 and 25,000 ft. It also burns with the zeal of magnesium and zirconium,
think flares or flash bulbs. It has to be welded by TIG. It will alloy with
the iron in the pan of the forge as it is welded which will only lower its
oxidation resistance. Besides titanium costs about $30 a pound anyway.

Regards,

Bill Hochella

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From: [email-masked]
Date: Fri, 23 Feb 1996 00:12:42 -0500

I think some of you may be getting carried away.  

Yes, Titanium may work to line a forge.  It maintains 20-50% of its room
temp. strength at 1000 degrees F, but drops off quickly after that.  I expect
that some parts of the forge do get hotter than 1000 F.  Also, Ti tends to
oxidize above 800 degrees.  In the bottom of the forge, there should be a
reducing environment, so this may not be too much of a problem.

But really, you can get just about the same properties with stainless steel
at lots less cost.  Any of the precipitation hardening grades (15-5PH,
15-7PH, 17-4PH, etc.) are fine for service to 600-800 degrees, and even hold
40-50% of their strength to 1000 degrees.  These alloys are also readily
forgeable and weldable with common equipment (usually gas shielded arc).  I
haven't tried heat treating these in a blacksmith's setting yet, but I'm
considering it.  Note that the process is entirely different than tool steel
- if anyone is interested, I'll post a sample process.  Don't ignore the 300
series (austenitic) stainless, either.  They have excellent corrosion
resistance and maintain their strength to 1000-1200 degrees, but the
unstabilized grades tend to become brittle with prolonged exposure over 750
degrees.  It appears that they are also slightly more difficult to forge than
the precipitation hardening grades in the annealed condition.

I think this string started when someone asked what to use in or near a
(wood?) fire.  For my money, I'd go with stainless.

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From: [email-masked]
Date: Fri, 23 Feb 96 17:08:21 PST

>Mach-2 and 25,000 ft. It also burns with the zeal of 
magnesium and zirconium,

I have used and forged titanium.  To my knowledge, there 
are several different alloys of titanium and only a few of 
them contain magnesium.  It is the addition of this 
element (Mg++) that causes the stuff to go up like a 
flare. Rob Gunter had a piece ignite and burn it's way 
through his fire pot and then proceed to burn through a 6" 
concrete slab.  YIKES!!!

Test the Titanium first.  Hit a carner of it with a torch 
and if it lights up the shop, forget about forging it.  
The fumes from some grades of Ti can also make you feel 
very ill (24hr flu symptoms).

Otherwise the stuff is great fun and makes really cool 
tongs (light as aluminum, stronger than steel, Super 
Tongs!)

-----------------------------------------------------
Name: Franklyn D. Garland        A Hobby Is Hard work
E-mail: [email-masked]          You wouldn't Do For
Date: 02/23/96                     A Living.
Time: 17:08:21

http://www.mcs.net/~frnklyn/homepage/
-----------------------------------------------------

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From: [email-masked] (MR WILLIAM A HOCHELLA)
Date: Sat, 24 Feb 1996 01:41:47 EST

To All,
Continuing the discussion on Titanium.....
Titanium will burn all on its own regardless of the alloy content. I 
have access to CP Titanium and have not played around with any of the 
other alloys. 6Al-4V, 8Sn and a Manganese bearing alloy were popular 
aircraft alloys a while back. Vanadiun Oxide is fairly nasty stuff if 
it gets up into the air. Does anyone really know what alloy has the 
potential for making you sick?

regards,
Bill Hochella

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From: "Szucs" <[email-masked]>
Date: Thu, 29 Feb 1996 10:55:25 -0500

On Feb 28,  6:12am, [email-masked] wrote:

> If you are relying on forged titanium for strength, some caveats, from the
> bicycle frame building industry. Pure titanium must be welded in an inert gas
> atmosphere: put it in a box, replace the air with inert gas, use glove/sleeve
> setup like a beed blasting cabinet. For welding Ti-6Al-4V: Fill the inside of
> the tubes with inert gas and TIG weld, shielded with inert gas. If you don't
> do thes things you get hydrogen and oxygen imbrittlement. My guess is that
> you risk some of these problems when forging titanium.

	Actually, the biggest pest is nitrogen.  Ti has a grand affinity
	for N, readily forming nitrides.  Nitrogen free atmospheres should
	be used when hot working Ti.  I have not read that O2 or H pose
	any major troubles, but I may have just not been paying attention
	that day :).

	-Andy V.