Nippon Steel, which completed its $14.1 billion purchase of U.S. Steel last year after a contentious political fight, said it expects to spend $2 billion to $2.5 billion over three years to replace the equipment that rolls steel at Mon Valley Works, a complex of three plants in towns south of Pittsburgh. The investment is more than double Nippon Steel’s original cost estimate for the project, according to company executives.
U.S. Steel Chief Executive David Burritt said in an interview that the company on its own could not afford the costly upgrades and maintenance the mill required. Two years ago, U.S. Steel said it might cease making steel at Mon Valley and move its corporate headquarters from Pittsburgh, the company’s home for 125 years.
In early 2025, then-President Biden blocked the sale to Nippon Steel, citing potential national-security risks. President Trump resurrected the deal and approved it on the condition that Nippon Steel invest $11 billion in U.S. Steel’s existing plants. As part of the agreement, Trump received a so-called “golden share” in U.S. Steel that allows him and future presidents to veto plant closings, the transfer of production out of the country, and other operational changes.
“The Mon Valley project will go a long way to make people feel like there’s a future here,” Burritt said. “We’ve got great partners with Nippon Steel. These investments would not have been able to happen without it.”
The centerpiece of the renovation is the replacement of a hot-strip mill in West Mifflin, Pennsylvania, that dates to 1938. The hot-strip mill flattens thick slabs of heated steel into long, thin ribbons of sheet steel that are wound into coils and shipped to customers. Burritt said the new line will produce higher-value sheet steel for auto bodies and pipe used in pipelines, making Mon Valley more competitive against rival mills, including a new Nucor mill under construction in West Virginia.
The new hot-strip mill will be built at the company’s plant in Braddock, Pennsylvania, where Mon Valley’s steel is made, eliminating a six-mile rail trip that currently adds several hours to production time. The new equipment will be able to produce coils three times larger than the old equipment, according to Ron Ferchak, the project’s operations and technical lead. “It’ll be a much faster process now,” Ferchak said.
U.S. Steel had previously attempted to replace the mill. The company announced plans to build a new line in 2019 but abandoned them a couple of years later after failing to obtain government permits, executives said.
Leaders of the United Steelworkers Union had opposed the Nippon Steel purchase and helped turn Biden and other pro-union Democrats against the deal. Trump, as a candidate, also opposed it. Burritt said individual union workers who broke with their leadership to support the deal helped change Trump’s mind.
The company is adding workers at Mon Valley to maintain steel production while construction proceeds. Between 20 and 40 new employees are being added each month to the hourly workforce of about 3,000, according to the steelworkers union.
Jason Zugai, 48, a 29-year steelworker at the West Mifflin plant, said the hiring and signs that the company is moving forward have improved employees’ morale. “They can see the investments being made,” said Zugai, who backed the Nippon Steel purchase. “We’re hoping that everything will be on track.”