Steel company Nucor is buying Gallatin Steel Co. for about $770 million, which will expand Nucor's footprint in the Midwest.

Taking out an anticipated tax benefit, the purchase price is approximately $630 million, the company said on Monday.

Nucor is purchasing ArcelorMittal and Gerdau's respective 50 percent stakes in Gallatin Steel. Gallatin's flat-rolled products mill is in Ghent, Kentucky. It has an annual capacity of about 1.8 million tons.

Aditya Mittal, chief financial officer of ArcelorMittal, said in a statement that the transaction is part of the company's strategy of selectively divesting non-core assets. Gerdau CEO Andre B. Gerdau Johannpeter said that Gerdau was selling its stake so that it could concentrate on core assets in North America.

Nucor Chairman, President and CEO John Ferriola said that the acquisition will help the company's current position serving flat-rolled customers in the pipe and tube segment.

The acquisition of Gallatin Steel's mill will give Charlotte, North Carolina-based Nucor Corp. five flat-rolled mills in total and will boost its total flat-rolled product annual capacity by 16 percent to about 13 million tons.

The deal is expected to close by the end of the year.