G'day to you Sir. It all depends if you are using UTC or TRS2004/06. It would be unwise of me to offer any new-ish buildings if you are still using the UTC version...:hehe:
From memory, I know that built-in to the games were a Sintering Plant, a Blast Furnace and an Open Hearth, which may be useful. I have also downloaded off the DLS a few Steel Mills, which may also be helpful to you, do a search under the category Buildings/Structures, and type in Steel Mill, slag, etc, etc. I was playing with the JPK SteelMill Annexe yesterday and I know for a fact that PhilSkene also has a Steel Works named after him, both are excellent creations.
Just a few ideas mate....

Cheerz. ex-railwayman.
Check out my thread in screen shots called Bethlehem Steel Shortline Railroad C&BL lasted posted January 5, 2008 for ideas.:wave: