Nucor Corp. (NUE), the largest U.S. steel producer, on Friday said second-quarter earnings fell sharply due to higher-than-expected scrap metal and energy costs.

The company, which makes steel by melting scrap in electric arc furnaces, also said it expects third-quarter earnings to be well below analysts' estimates due to depressed levels of nonresidential construction.

Nucor reported second-quarter earnings of $8.4 million, or 11 cents per share, down from $59.7 million, or 76 cents per share, a year earlier.

The Charlotte, North Carolina-based company said costs from the unanticipated shutdown of a mill, lost sales from equipment downtime and curtailed production reduced earnings by about 6 cents per share.

Sales in the quarter rose to $1.52 billion from $1.20 billion a year earlier.

Nucor said it expects third-quarter earnings of 15 cents to 20 cents per share. Analysts' average estimate is 39 cents, according to Reuters Research, a unit of Reuters Group Plc.

The difficult environment for steel companies in the United States — including a surge in health-care and pension costs — has pushed more than 35 steelmakers into bankruptcy since 1997 and led to a wave of consolidation within the industry.

Shares of Nucor closed at $50.18 on the New York Stock Exchange on Thursday. The stock rose about 28 percent during the second quarter, compared with a rise of nearly 15 percent in the Standard and Poor's 500 index, of which Nucor is a component.