What happened
Shares of United States Steel (X -5.83%) surged more than 10% by noon EST on Tuesday. Driving up the steel company's stock was the acquisition of the remaining stake in a joint venture.
So what
U.S. Steel has exercised its option to acquire the remaining 50.1% stake in Big River Steel that it doesn't already own for $774 million. The deal will give it full ownership of one of the newest, most advanced flat-rolled mini-mills in the country. The company previously bought a stake in the three-year-old mill that makes steel by melting scrap in an electric furnace for $700 million in October.

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The purchase is part of the steelmaker's plan to remake the company by focusing on a "best of both" approach that incorporates new mini-mill technologies with its legacy blast furnace facilities. That will enable the company to compete against rivals Nucor and Steel Dynamics, which both focus on operating lower-cost mini-mills.
Now what
U.S. Steel is laying the cornerstone of its new "best of both" strategy by acquiring full control of Big River Steel. The mill will enable the company to better compete against rival U.S. steelmakers, which have outperformed it in recent years thanks to their focus on operating lower-cost mills. However, with today's rally, shares of the steel company are up more than 70% on the year as investors seem to have priced in the benefits. Because of that, it's not the best metals stock to buy these days.