United States Steel Corp. X -1.82% outlined plans Thursday for the biggest upgrade of its steelmaking operations in decades by investing more than a $1 billion in its plants near Pittsburgh.

The centerpiece project aims to reduce the cost and the time to produce sheet steel at the company’s mill in Braddock, Pa.

The company also intends to build a cogeneration plant at its coking coal ovens in nearby Clairton to decrease emissions by using waste gases from the coking process to generate electricity. The coke plant was damaged by a fire on Christmas Eve that has resulted in elevated releases of sulfur and other emissions while repairs have been under way.