CHICAGO — Reliance Steel & Aluminum Co. reported first-quarter net income of $116.2 million—a nearly 26 percent year-on-year increase—on sales that grew 19.6 percent to $2.29 billion.

Earnings for the Los Angeles-based service center chain were also up 71.1 percent from $67.9 million in the fourth quarter of 2011 on sales that rose 12.5 percent from $2.03 billion in the same comparison.

Tons sold grew 13.8 percent year-over-year to 1.1 million tons, rising 11.2 percent from the preceding quarter. Average prices per ton sold increased 5.3 percent.

Calling the quarter’s results "better than we originally anticipated," Reliance chairman and chief executive officer David H. Hannah said that demand was strongest in January and February, due in part to a more favorable pricing environment, and that sales dollars per day fell slightly in March due to carbon steel pricing uncertainties and decreasing stainless-steel surcharges.

The energy, aerospace, farm and heavy machinery, and automotive markets continued to provide the most growth during the first quarter, the company reported.

Semiconductor and general manufacturing also remained strong, but non-residential construction and related business remains 20 percent below where it was in the first half of 2008, Hannah said during the company’s quarterly conference call.

For the first quarter of 2012, carbon steel sales represented 52 percent of net sales, aluminum and stainless sales were 15 percent each, and alloy sales were 12 percent.