In addition to the craft recipes below, there is also a rusty steel plate which can be found only in the creative inventory.

--http://ubuntuone.com/1OvYYC4fMFMNLZ7nXPedbx-- (dead image link)
Download:
From VanessaE's fork: https://github.com/VanessaE/minetest-steel/archive/master.zip
...or browse the code: https://github.com/VanessaE/minetest-steel
Crafting:

Steel plating: Craft four steel ingots in a square. Yields 2. Careful, put it in water and it'll eventually rust!

Steel grating: Actually, it's a fence. Craft four steel ingots in two columns, with empty space in the middle. Yields 3.

Steel strut: Craft five steel ingots in an "X" pattern. Yields 5.

Sheet metal: Craft three steel ingots in a horizontal line. Yields 6.

Corregated steel roof: Craft three sheet metal in a "v" shape. Yields 3. Can be crafted back into sheet metal by placing three back into the grid in an upside-down "v" shape. Yields 3 in that case as well.

Hardened steel plating: Cook a regular steel plate in a furnace.

Hardened steel grating/fence: Cook a regular steel grate in a furnace.

Most of the steel objects can be recycled into steel scraps. Steel plates (regular or hardened) yield 4 scraps per plate. Grates and struts yield 2 per. Corregated roofing yields 1 per. Rusty steel plates can't be recycled.

Steel scraps are then recycled into standard iron lumps by putting two side by side.
your comments are welcome
Thanks!
License:
Code: GPL v2
textures: CC-BY-SA