Since this is about a type of business, I think that "iron&steel manufacturing" is enough to explain this industry. Steel manufacturing could also work for this translation, but I desided to add "Iron" to it. I agree with Cinefil-san that the manufacturing includes the processing / machining of products.

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Note added at 1 hr (2010-06-02 03:22:28 GMT)
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http://www.ifc.org/ifcext/enviro.nsf/AttachmentsByTitle/gui_...$FILE/ironsteel_PPAH.pdf

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Note added at 1 hr (2010-06-02 03:27:21 GMT)
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http://www.ibisworld.com.au/industry/default.aspx?indid=222
"ACTIVITIES

The primary activities of companies in this industry are:
•ferroalloy production (including alloys of manganese, silicon or chrome)
•pig iron production
•sheet or strip tinplate production
•stainless steel production
•steel alloy production
•the manufacture of iron or steel bars
•the manufacture of iron or steel flat-rolled products
•the manufacture of rail fastenings or other rail accessories
•the manufacture of steel roof decking
•the manufacture of structural steel shapes (not fabricated)"

http://www.ibisworld.com.au/industry/default.aspx?indid=569&...
"ACTIVITIES

The primary activities of companies in this industry are:
•Direct reduction of iron ore
•Making and/or manufacturing steel products
•Manufacturing and/or converting pig iron"