How did Andrew Carnegie's innovations/inventions transform the steal industry?

Andrew Carnegie, known as the "richest man in the world" at the time--made his fortune by buying up a series of steel manufacturing outfits, together known as Carnegie Steel...the process he used to make the steel out of pig iron was known as the "Besemer" process... eventually he sold to JP Morgan...and it became US Steel...this sale was worth billions...and was a record breaker at the time...