FYI: As far as I am aware, the only photos that relate to Loizeaux's claims are the famous red-hot chunks of broken steel beams being pulled out by excavators/demolition claws. Molten metal doesn't look like chunks of broken steel beams, red-hot or otherwise. Obviously. You can't pick up melted steel with a claw. You need a ladle. You wouldn't even try to pick up melted steel with an excavator, because the risk of severe damage to the excavator. There is a long-standing confusion between "red-hot" and "melted", and the the truthers encourage this confusion elsewhere.Yes, he's not a steel foundry worker or a materials scientist. And this is getting off topic.
I think the cool down time of molten steel to non-flowable is a bit of a red-herring here, because much of the steel ended up in smoldering piles that, IIRC, were measured at up to about 1000F more than a month after the event.
My father-in-law died about a year ago, after retiring from shift-supervisor on a major steel company (rolling mill, not structural channel/other). He'd know melt-to-solidify times. My wife had to copy his "little black book" for heating times to bring ingots (of sizes up to 20 tons, and of various types of steel) up from room temperature to rolling temperature - with coke-gas furnaces, it'd take 18-24 hours to bring them up to rolling heat.
Her best guess (should be a pretty good one because she worked there as a student), of molten to solid/de-moldable is about a day. In 20 ton ingots. But remember, this is second hand from 30 years ago. Also remember that they would be trying to speed this process up to keep the amount of super-hot inventory/molds necessary on hand to a reasonable minimum.
I did see the unit in operation - at the time the most advanced hot roll mill in the world.
Oh heck, I'll just ask the company and see what they say.