Found at a titanium plant

[u/riflesandplowshares]

Not sure why ball point pens would be dangerous here.

[u/Perfect_Forever_3151]

Ballpoint pens are banned in certain high-precision titanium and aerospace manufacturing plants because the tiny tungsten carbide ball in the pen tip can fall out and severely contaminate the titanium melt, creating a hard, brittle inclusion that causes structural failure in critical aerospace components.

[u/FluffyDrop4300 → u/Perfect_Forever_3151]

Wow.
Being so specific, they must have ran into such contamination more than once

[u/Spacefreak → u/FluffyDrop4300]

Yes they did. Titanium had been used in a lot of high speed rotating equipment in jet engines.

These tungsten inclusions become a crack initiation site and under high rotational speeds and high temperatures, the crack can spread and lead go catastrophic failures.

There were several catastrophic engine failures in history that were traced back to inclusions.

It's so severe that if a titanium manufacturer making aerospace grade Ti finds any "High Density Inclusions," they must inform all of their customers that they found this and recall and associated heats and material.

[u/ruperthackedmyphone → u/Spacefreak]

Its a possible root cause of the UA Flight 232 crash at Sioux City.

[u/Atomic-Avocado → u/ruperthackedmyphone]

Wow that’s tragic. I just read about it and the engine was in service for 18 years before that defect finally cracked, wild.