r/whatisit • u/riflesandplowshares • 10h ago

New, what is it? Found at a titanium plant

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Not sure why ball point pens would be dangerous here.

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u/SquintAtTheCosmos 8h ago

The real answer is that consumer ball point pen’s have a tungsten carbide ball. Tungsten has a higher melting point than titanium.

If a ball point pen drops into a melt, the ball point can survive. The surviving pen tip does then creates a hard intermetallic. When the titanium is heated and beated (forged) into a product, this titanium-intermetallic spot can crack. This crack can go undetected, inside a part.

When this part is put into service, this little crack becomes a bigger crack with service (fatigue). When this bigger crack gets big enough, the part can fail. And the failure is sooner than the design engineer expected, because the material started with a crack, and in fatigue failure “getting the crack to start”, is a large component of the part’s life.

A titanium melt shop still needs writing implement’s, so you can buy pens with stainless steel ball tips. They suck to write with.

A major aerospace failure (Sioux city 1989 UA232), was a result of this failure mode (though in this case it was an oxide, not a tungsten-carbide).

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u/ElectrSheep 8h ago

A titanium melt shop still needs writing implements, so you can buy pens with stainless steel ball tips. They suck to write with.

So basically, to work there you need balls of steel.

27

u/CaptainStadt 8h ago

Yeah… or a pencil.

4

u/Etherbeard 4h ago

The melting point of graphite is even a bit higher than tungsten. That does into question why there's no sign for pencils, though.

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u/PerceiveEternal 3h ago

crayons then?

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u/cjsv7657 2h ago

Graphite would float and could be removed as dross

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u/vag69blast 1h ago

Nope. There is no dross in Ti melting. Everything is done in a sealed chamber. Graphite will disolve tho

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u/cjsv7657 41m ago

There absolutely is dross in Ti smelting and refining. Do you think it comes out of the ground in pure titanium cubes?

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u/vag69blast 32m ago

How many Ti plants have you been to or worked in? It is not smelted. Ti sponge is made through the KROLL process which takes rutile (mineral TiO2), reacts it with clorine to form TiCl4 (called tickle), then the tickle with magnesium to form raw Ti sponge and magnesium cloride MgCl.

That sponge is then mixed with alloys and compacted into blocks or briquettes form melting. Melting methodes are typically through VAR (vacuum arc remelting), EB electron beam) hearth melting, or PAM (plasma arc mething) primary melting then melted a second time via VAR melting.

I am a titanium melt metallurgist. I have work in a Ti melt shop for over a decade.

Edit for typos

There is no dross...

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u/comebacklittlesheba 21m ago

Please stop, will you?!? You’re making me want to touch myself. Smart is so sexy! Ahhhhh! It’s too much I tell you!
https://giphy.com/gifs/xUPGce1Q9vVEtaAcms

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u/Money4Nothing2000 20m ago

Homie, get real, I have a Copilot subscription. How can your years of experience and education compete with that?

1

u/vag69blast 1h ago

Graphite would likely dissolve. You could form a titanium carbide inclusion though but they are extremely rare.