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Hardening tungsten?

NewGunPlumber

Aluminum
Joined
Dec 18, 2019
I'm in the process of designing a fixture which uses a piece of 3.2mm tungsten rod approx 150mm long as a stylis to follow a contour.

I chose to use tungsten looking for something with a small diameter that would give me minimal flex over the 150mm length. What I got was 3.2mm. 0.3% zirconiated TIG welding tungsten but it's been supplied as "annealed and flexible".

Is there any realistic way to harden this to make it rigid as possible? It won't see any form of impact and I have 10 to play with
 

gbent

Diamond
Joined
Mar 14, 2005
Location
Kansas
I don't know about tungsten, but with iron based alloys the hardness has nothing to do with the flexibility. The hardness does affect the amount of bending a part can sustain before permanent deformation, but hardening does nothing to stiffness (a property described by Young's modulus).
 

bosleyjr

Diamond
Joined
Sep 30, 2006
Location
SE PA, Philly
Different definitions of flexible here, I think. True flexibility relates to modulus of elasticity. This is how much a bar deflects under different loads. Steel of any HT status, has about the same modulus.

Another definition of flexible is the abilty to be deformed plastically, without breaking. Kind of the opposite of brittle. Tungsten is often used because it is ductile and will deform without breaking.

Another definition is the ability to be easily bent. This is a low yield stress.

Hardess is another thing. Not related to modulus of elasticity. Often related to tensile strength in steel.

To answer your question, though, if you are using a pure W (EWP) welding eletrode, I don't think that there's any heat treatment you can use to make it stiffer.

If you want a stiffer structure, perhaps uses tungsten carbide? This is a completely different animal. It has about twice the elastic modulus (twice as rigid/stiff) of pure tungsten, and about 4 times that of steel.
 
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Joe Gwinn

Stainless
Joined
Nov 22, 2009
Location
Boston, MA area
For this application, we are talking about Young's Modulus, which is all about spring constants and not about how easy it is to bend. Heat treating has little effect on Young's Modulus. Nor does hardening by mechanical means such as hammering.

Here is some more information, plus a table of moduli.


https://www.thoughtco.com/youngs-modulus-4176297

For a practical demonstration, take two pieces of pre-hardened steel spring stock, and clamp both side by side in a big vise, with protruding lengths adjusted to get the same audio tone when plucked. Then take a torch to one spring, heating it to red hot, and let it cool. The plucked tones will still be about the same.
 
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Robert R

Cast Iron
Joined
Aug 27, 2005
Location
Raymond , CA

I chose to use tungsten looking for something with a small diameter that would give me minimal flex over the 150mm length. What I got was 3.2mm. 0.3% zirconiated TIG welding tungsten but it's been supplied as "annealed and flexible".

Tungsten wire or bar cannot be hardened or annealed by thermal processing. It is manufactured by sintering tungsten powder at 3100 deg C.
Items fabricated from tungsten are often heated to 1000 deg C to relieve stresses caused during hot forming. The parts would be too brittle to handle without this operation
If a tungsten wire is heated above 1500 deg C it will recrystallize and become very brittle.

Tungsten manufactures use the word anneal when the actual thermal process is stress relief.
 

jscpm

Stainless
Joined
May 4, 2010
Location
Cambridge, MA
Man, tungsten isn't hard enough for you? Jeesh, no pleasing some people. What do you want? Diamond? Adamantite? Whatever Thor's hammer is made out of?
 

bosleyjr

Diamond
Joined
Sep 30, 2006
Location
SE PA, Philly
I think he's talking about nearly pure (0.3% zirconium) tungsten alloy, not "heavy alloy" which is tungsten carbide in a matrix of other metals. The metal itself has a Brinell hardness of 30, about the same as ferrite, IIRC.

Tungsten "Heavy alloy" aka tungsten carbide aka carbide is indeed hard and stiff. You can buy 3mm carbide rod. But you have to figure out how to cut it!
 

NewGunPlumber

Aluminum
Joined
Dec 18, 2019
Thanks for the education guys and in particular Jo for the link.

Looking at pure tungsten vs steel vs tungsten carbide I think I'll stick with what I have for now!
 

cyanidekid

Titanium
Joined
Jun 4, 2016
Location
Brooklyn NYC
I think he's talking about nearly pure (0.3% zirconium) tungsten alloy, not "heavy alloy" which is tungsten carbide in a matrix of other metals. The metal itself has a Brinell hardness of 30, about the same as ferrite, IIRC.

Tungsten "Heavy alloy" aka tungsten carbide aka carbide is indeed hard and stiff. You can buy 3mm carbide rod. But you have to figure out how to cut it!
not difficult, notch with diamond and snap. sharpen with diamond. yes, a welding electrode, of any flavor is quite hard, as in similar to hardened steel, but if you want less deflection tungsten carbide is what you want.
 








 
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