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Comment by Animats | Hacker News Reader

That's a hot rolling mill. They're not making steel, just forming it. The old, messy plant next door makes the steel.

Better hot rolling mills have been mechanized for a long time. Here's a plain rebar mill in Delhi that's for sale.[1] There must be some people around somewhere, but they're not near the machinery when it's working. The machinery is huge, but not computerized. On the other hand, here's a rolling mill in India that has lots of people handling hot metal with tongs.[2] That's about where the US was in 1935.

[1] https://www.youtube.com/watch?v=eW0jAMxAN3Y [2] https://www.youtube.com/watch?v=q-lGaC8OJGs

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HN has reached some kind of wonderful critical mass when it gets such a well-informed comment about steel production almost instantly after the post appears. Thanks for an answer that radically changed my view of the original post. My life is complete.

I've started browsing by user name instead of topic. Animats is consistently good.

Animats stands for "ambulatory encyclopedia". Also John Nagle https://en.wikipedia.org/wiki/Nagle%27s_algorithm

I'm just old. I lived in Cleveland when it looked like this.[1] City streets ran through the steel mills. Switch engines pulled short trains of red-hot ingots on tracks on city streets. You could see the ingots make the trip from caster to rolling mill. In a steel town, everybody knows the basic process.

[1] http://timkovach.com/wp/wp-content/uploads/2014/05/clark-ave...

THAT JOHN NAGLE? Whoa. My life really is complete. Please excuse me while I stalk his HN history ...

Even the automated ones are dangerous to be close to, apparently. There's a characteristic type of snarl-up known as a "cobble" where white-hot steel rod flies everywhere: https://youtu.be/uxbsgWOjX5o

Well a 1001 ways to die now.

Every American steel mill I've been in or heard about has cages that people have to stay inside if they are near the part of the line where this can happen. (Presumably an OSHA requirement, but I'm not 100% on that.)

Not the one I worked in back in the early 90's. You could walk along to rolling line and had to hit a pause button to stop the feeding of billets in the reheat furnace to cross the line to the other side of the plant. Nucor Plymouth.

I was a Nucor engineer in the early 2010s, and all their rolling mills had them by then. Things had changed a lot since the '90s, though. The old guys talked about having to manually replace the electrodes in the arc furnaces, which has been done with a robot arm since the late '90s or early 2000s.

(For those of you who don't know what this is, each electrode is a graphite column one or two feet in diameter and about 20 feet long. Replacing them took two guys, selected for their resemblance to linebackers, and had to be done multiple times each day.)

They now have a walkway to be able to cross over safely. Cobbles sure still happen and it's scary to see hot steel spaghetti fly into the air from within the pulpit.

Steel manufacturing seems to have a large number of "that's going to suck to clean up" failure modes.

https://m.youtube.com/watch?v=Q9zW4BcomQo

That's metalwork in general. A friend of mine worked in a copper mill as an engineering intern and he told me all kinds of horror stories like having to clear out a chimney with a shotgun and scraping several tons of copper off the floor.

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