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Re: Tungsten

Original poster: "Mike" <mike.marcum@xxxxxxxxxxxx>

So I wonder what's mixed with the tungsten in light bulb filaments that gets white hot (around 4000F) and is quite brittle? I always thought it was pure tungsten but I guess not.

----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Friday, April 08, 2005 2:02 PM
Subject: Re: Tungsten

Original poster: Steve Ward <steve.ward@xxxxxxxxx>

With a bit of googling:



"Very pure tungsten can be cut with a hacksaw,  forged, spun, drawn,
and extruded. The impure metal is brittle and can be worked only with
difficulty. Tungsten has the highest melting point of all metals, and
at temperatures over 1650oC has the highest tensile strength. The
metal oxidizes in air and must be protected at elevated temperatures.
It has excellent corrosion resistance and is attacked only slightly by
most mineral acids. The thermal expansion is about the same as
borosilicate glass, which makes the metal useful for glass-to-metal
seals. "

Looks like Jared was correct.

Steve Ward

On Apr 8, 2005 9:37 AM, Tesla list <tesla@xxxxxxxxxx> wrote:
> Original poster: DRIEBEN@xxxxxxxxxxxxxxx
> Jared, Gary,
> I'm sorry, but I'm gonna have to go with Gary
> on this. "Pure" tungsten has a melting point
> of ~6170*F and a specific gravity of 19.3 and
> I just can't see anything with those properties
> being "softer than lead" which has a melting
> point of a mere 621*F, BTW. Of course mercury
> has a specific gravity of 13.5 but is liquid
> at room temp (-38*F is its melting point, I believe).
> Maybe some of the more chemically inclined list
> members could jump in on settling the hardness
> scale that pure tungsten would fall into.
> David Rieben
> ----- Original Message -----
> From: Tesla list <tesla@xxxxxxxxxx>
> Date: Thursday, April 7, 2005 6:28 pm
> Subject: Re: Tungsten
>  > Original poster: jdwarshui@xxxxxxxxx
>  >
>  > Hi: Gary
>  > From: Jared
>  >
>  > Yes: I have worn deep ruts in grinding wheels dressing TIG rods.
>  > It is
>  > hard to believe that in its pure form, tungsten should be so soft.
>  >
>  > Carbon is also soft, unless of course it is perfectly covalently
>  > bonded then you get diamonds.
>  >
>  > Iron is considered soft as well, but again in it's pure crystaline
>  > form it exceeds the strength of the strongest alloy steel.
>  >
>  > My understanding is that it only takes a handfull of boron to produce
>  > tons of high strength steel. Boron has a real tiny atomic radius
>  > so it
>  > gets wedged between crstals making it nearly impossible for
>  > dislocations to move.
>  >
>  >
>  >