They are buying now because they view the prices as being very...

They are buying now because they view the prices as being very cheap. It's human nature (unless you really happen to be dumb).
If the prices were back at their highs- they wouldn't be buying and they certainly wouldn't be stockpiling.

Secondly, they are stockpiling copper, alum, and other materials more so than IO. On a price per tonne basis it is much wiser (and easier) to be able to stockpile the more expensive materials hence why the Gov't is forcing the steel companies to keep producing steel even though they are creating a glut.

It's more manageable to store steel than IO and the steel will eventually be used domestically or exported.
The massive IO stockpiles recently locked up the ports, so to avoid that problem the Gov't is forcing the mills to keep using it even though the mills want to stop as it is hurting their balance sheets doing so. The Gov't though can't buy enough while it is cheap.