steel mill vs factory

steel mill and factory both are nouns.

Word	Noun	Adjective	Verb	Adverb
steel mill	Yes	No	No	No
factory	Yes	No	No	No

As nouns, factory is a hypernym of steel mill; that is, factory is a word with a broader meaning than steel mill:

steel mill: a factory where steel is made
factory: a plant consisting of one or more buildings with facilities for manufacturing

Other hypernyms of steel mill include manufactory, manufacturing plant, mill.

steel mill (noun)	factory (noun)
a factory where steel is made	a plant consisting of one or more buildings with facilities for manufacturing