Steel is John Henry Irons. His first appearance was in THE ADVENTURES OF SUPERMAN #500 back in 1993. Doctor Irons was a college football star and bright engineer. After college he went to work for AmerTek Industries. He faked his own death when he found out that the military weapons he had designed were sold to street gangs. He moved from Washington DC to Metropolis where he worked under the radar as a construction worker..
One day while working on top of a skyscraper he fell off during a rescue of a fellow riveter. He was then rescued by Superman. While thanking Superman, he was told to “live a life worth saving”. Later while Superman was fighting Doomsday John Henry Irons repaid Superman’s heroism and helped out using only a Sledgehammer. He was injured and buried alive during the brawl.
When he recovered from his injuries he found that Superman had been killed by Doomsday. He decided that the world needed a Superman. He would payback The Man of Steel by becoming a man of steel. He went to work building a suit of armor. The armor would protect him and hide his identity. He included rocket boots for flight and rivet guns to subdue his enemies. He integrated in his arsenal the sledgehammer to honor his namesake John Henry, of American folklore.
Later when Superman returned he gave Steel permission to wear the Superman emblem. Saying he would be proud if John Henry Irons continued as a Superman. He then proceeded to tell Steel that Superman is more of an idea than a person and that he has earned the right to wear the S.