POSCO continuous caster roll refurbishment

Football-field-sized refurbishment shop with lathes restoring caster rolls by weld deposition. Tom's central example that metal additive manufacturing has industrial precedent going back a hundred years.

Then people have been trying to use it for all kinds of things, but they had a lot of problems trying to do it with metals. That's what — if you watch that video of my one-hour lecture, why metals are a problem in trying to make the whole process work. But in fact, we have been doing it for a hundred years with metals. I've been to steel plants where they're rebuilding the steel rolls to roll the steel for continuous casting — size of a football field, nothing but a bunch of lathes with the rolls being refurbished and just laying metal down to resurface them. This is additive manufacturing. You can't afford to throw away these huge rolls. So we've been doing it for years.

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Twelve-foot, foot-diameter caster rolls refurbished by lathe-cutting damaged surface, preheating to 600–800°F with flames, and laying down weld metal. Stress relief happens in-process from flame temperature. Used as another long-standing example of industrial additive manufacturing.

I visited POSCO Steel when it was the largest steel plant in the world, in Pohang, Korea. They took me through a facility where they refurbished the rolls for the continuous caster. These rolls are about twelve feet long, a foot in diameter. A molten band of hot steel comes down out of the casting machine — about seven or eight stories tall — and gets bent ninety degrees, and these rolls, hundreds of them, are bending this hot steel. They wear out — they're touching steel at above a thousand degrees centigrade. They're water-cooled in service, but the surface is touching something basically 1200 degrees centigrade, so they get thermal cracking. So they take them into the shop — about half the size of a football field, lots of lathes. They'd have this twelve-foot roll, do a pass and cut off the bad stuff on the surface. Then they'd preheat the whole thing. There were flames all over the shop — I think I was there in August, it was pretty hot — great big flames preheating to six, seven, eight hundred degrees Fahrenheit. Then just laying down weld metal. They got around the residual stresses because with the flame temperatures they're stress-relieving as they go. They're building up massive metal on the outside of these rolls. They have to replace them periodically, probably after two weeks of service, and this machine runs continuously for two or three years. So we do lots of buildup of metal parts.