U.S. Steel approves about $3 billion hot strip mill at Mon Valley Works

The Mon Valley project

The project replaces an 87-year-old hot strip mill at the Irvin plant in West Mifflin and is the largest single investment in Nippon Steel's $11 billion U.S. plan through 2028, U.S. Steel said. The new mill will sit at the Edgar Thomson plant in Braddock, part of Mon Valley Works along with Clairton Coke Works and Irvin.

The $3 billion figure is an increase from an earlier pledge of up to $2.5 billion for Mon Valley, which followed an original $1 billion commitment, PublicSource reported. Bloomberg reported the increase came as costs climbed.

Nippon Steel said the installation will include walking-beam reheating furnaces and a sizing press intended to raise productivity, reduce energy use and improve material yield. The company said the mill will let Mon Valley make high-strength steels for automotive customers that the site cannot competitively produce, according to materials shared with community leaders and reported by PublicSource.

Annual capacity will rise to about 3.5 million tons from about 2.2 million, an increase of about 60%, the company said. Output is aimed at automotive, home appliance and energy customers. Construction will begin after permits are granted, with first production targeted for the second half of 2029, about three years after the investment decision.

U.S. Steel estimates the project will preserve about 3,000 jobs at Mon Valley Works and create nearly 3,200 indirect and induced jobs over three years, generating up to $1.7 billion in economic benefit. PublicSource reported those estimates alongside the earlier up-to-$2.5 billion plan.

Nippon Steel's U.S. bet

Nippon Steel completed its $14.9 billion acquisition of U.S. Steel in June 2025 after an 18-month political and regulatory fight, Reuters reported. The Mon Valley mill is the largest single project in the Japanese company's $11 billion commitment to its U.S. subsidiary through the end of 2028.

U.S. Steel has become a growth driver for its parent. Nippon Steel raised U.S. Steel's fiscal 2026 business profit guidance to 180 billion yen ($1.14 billion) from 100 billion yen, citing a blast furnace restart and a U.S. market recovery, Manufacturing Dive reported. The upgrade is part of Nippon Steel's plan to improve U.S. Steel's throughput, energy efficiency, productivity and quality.

Vice Chairman Takahiro Mori said in June that U.S. hot-rolled steel sheet sold above $1,200 a metric ton, more than double the level in Asia, and that U.S. Steel could earn 300 billion to 400 billion yen a year in the long run, Reuters reported. Nippon Steel has said it plans to double steel production in the U.S. within three to five years.