The stake was sold for 428,000 marka ($256,900/218,800 euro) in direct negotiations with the buyer, the privatisation agency said last week.
Zeljezara Zenica is based in Bosnia's fourth-largest city, Zenica.
The operations that remained in government hands are currently highly indebted.
The Federation is one of two entities that make up Bosnia, the other is the Serb Republic.
(1 euro=1.95583 marka)