Exhibit 99.1

Steel Dynamics Reports First Quarter 2013 Diluted Earnings Per Share of $0.21

FORT WAYNE, INDIANA, April 17, 2013 / PRNewswire / Steel Dynamics, Inc. (NASDAQ/GS: STLD) today announced first quarter 2013 net income of $48 million, or $0.21 per diluted share, on net sales of $1.8 billion.  By comparison, prior year first quarter net income was $46 million, or $0.20 per diluted share, on net sales of $2.0 billion; and sequential fourth quarter 2012 net income was $61 million, or $0.27 per diluted share, on net sales of $1.7 billion.  Prior quarters included the following items—first quarter 2012 earnings were reduced by $0.03 per diluted share due to refinancing costs and fourth quarter 2012 earnings were increased by $0.07 per diluted share due to positive tax adjustments.

“The first quarter remained challenging from a market perspective, as customer confidence and buying patterns continued to be impacted by global economic uncertainty;” said President and Chief Executive Officer, Mark Millett, “but the team did a great job.  We hit several production records, and did so safely, as safety records improved from levels already better than industry standards.  We are pleased the first quarter financial performance was at the upper range of our March guidance.  Operating income improved slightly to $96 million compared to last quarter’s results.

“Compared to the fourth quarter, operating income from our steel operations improved four percent to $122 million, as increased long product volumes more than offset weaker sheet steel shipments and somewhat lower overall metal spreads,” stated Millett.  “An oversupplied northeastern U.S. galvanized sheet market pressured first quarter shipments from The Techs.  However, increased shipments of wide flange beams, rail and engineered bar products more than offset the decrease.  Despite the slow growth of the commercial construction market, we have seen increased wide flange beam shipments for several consecutive quarters, albeit still very low in relative historical terms, and our fabrication business continues to be profitable.

“Operating income from our metals recycling operations decreased three percent to $25 million when compared to the fourth quarter, as increased volumes were more than offset by decreased ferrous and nonferrous margins,” said Millett. “We noted in our fourth quarter 2012 earnings release that we were anticipating potential challenges in the metals recycling market during the first quarter 2013.  Due to ongoing slow U.S. growth and inclement weather, the availability of unprocessed scrap was limited, particularly in the Midwest and along the northeastern corridor, resulting in increased costs to purchase unprocessed material.

“The company’s continued solid performance in a difficult market environment is driven by our ongoing commitment to provide exceptional value to our customers, while taking advantage of our innovative, low-cost operating culture.  We remain committed to leveraging the full complement of our competitive strengths to sustain and grow shareholder value,” Millett concluded.

First Quarter Review

First quarter shipments were higher across the company’s operating segments when compared to the fourth quarter of 2012, and to the prior year first quarter, aside from metals recycling which decreased year over year.  Operating income increased slightly when compared to the fourth quarter of last year, but declined 20 percent from prior year’s first quarter, primarily due to reduced steel metal spreads, as steel product pricing decreased more than scrap raw material costs.

The company’s steel mill utilization rate improved to 89 percent in the first quarter from 80 percent in the fourth quarter of 2012.  There was a shift toward higher valued-added products in the company’s steel shipments during the first quarter of 2013, when compared to the fourth quarter of 2012.  This change helped offset decreased metal spread, resulting in increased operating income of $4 million.  The average

selling price per ton shipped increased $5 to $789 in the first quarter, and the average ferrous scrap cost per ton melted increased $8 per ton.   Operating income attributable to the company’s long product operations increased 16 percent when compared to the sequential quarter, while earnings from sheet operations decreased four percent.

The impact of losses from the company’s Minnesota operations on first quarter 2013 consolidated net income was approximately $14 million, or $0.06 per diluted share, which included a unique loss of $2 million (after taxes), or $0.01 per diluted share, related to the sale of excess iron concentrate reserves purchased from third parties.  In addition, despite achieving record production levels, the use of higher cost iron concentrate during the quarter also resulted in increased operating losses.  Comparatively, the impact of losses on fourth quarter 2012 earnings was $10 million, or approximately $0.04 per diluted share.  As previously indicated and according to plan, the installation of additional oxygen-burners and other equipment modifications will be made at the iron nugget facility in April.  These modifications are expected to further improve production volumes.

Production at the company’s iron concentrate facility continues to proceed well, and the plant is operating at a cash-cost of less than $50 per metric ton, which is substantially less than current market prices in excess of $135 per metric ton.  As iron concentrate is the primary raw material for the iron nugget facility, this is a pivotal achievement in lowering the raw material input cost of iron nuggets.

The company plans to start solely using its lower-cost iron concentrate for nugget production in May.  However, due to costs related to the outage, the company still anticipates second quarter 2013 losses associated with the Minnesota operations to be similar to those recorded in the fourth quarter of 2012.

During the first quarter the company issued $400 million of new 5¼% senior notes due in 2023 and offered to repay $500 million of its existing 6¾% senior notes due in 2015.  At March 31, 2013, the company had repaid $302 million of the existing senior notes, repaying the remaining amount of $198 million on April 9, 2013.  After giving effect to the April repayment, total debt decreased $100 million and liquidity remained strong with $1.4 billion in unrestricted cash and available funding under the revolving credit facility. These transactions, along with the resulting repayment of debt with available cash, not only extended the company’s overall debt maturity profile, but should also provide an estimated annual interest savings of approximately $13 million.

Outlook

“Demand for high-quality steel products has not abated,” Millett said. “We remain optimistic. The team is on track to complete the organic growth projects scheduled to start at the end of this year, including the engineered special-bar-quality capacity expansion and the premium rail product addition.  The automotive market remains strong, and we believe there is potential for manufactured goods to continue to build momentum in 2013.   Housing start data also suggests an increasingly higher potential for a recovery in residential construction. We continue to be cautiously optimistic about the nonresidential construction market in 2013, as market indices continue to trend higher. We also view the increase in our long product and fabrication sales as a positive sign, even though they are improving from historically low levels. We are confident that with our exceptional team, and our superior, low-cost operating culture, we are uniquely prepared to capitalize on the opportunities ahead.”

Summary First Quarter Operating Segment Information

The following tables highlight operating results for each of the company’s primary operating platforms. References to operating income in the following paragraphs exclude profit-sharing expenses and amortization pertaining to intangible assets.  Dollar amounts are in thousands, excluding per ton data.

Steel Operations

This segment includes five electric-arc-furnace steel mills and related steel finishing and processing facilities, including The Techs. The company’s steel operations produce flat-rolled steel, structural steel, merchant bars, engineered special-bar-quality steel, rebar, rail, and specialty shapes.

Metals Recycling and Ferrous Resources Operations

This segment principally includes the company’s metals recycling operations (OmniSource Corporation), a liquid pig iron production facility (Iron Dynamics), and the company’s Minnesota iron producing operations.

Steel Fabrication Operations

Steel fabrication operations include New Millennium Building Systems, which fabricates steel joists, trusses, and decking used in the construction of non-residential buildings.

About Steel Dynamics, Inc.

Steel Dynamics, Inc. is one of the largest domestic steel producers and metals recyclers in the United States based on estimated annual steelmaking and metals recycling capability, with annual sales of $7.3 billion in 2012, over 6,600 employees, and manufacturing facilities primarily located throughout the United States (including five steel mills, six steel processing facilities, two iron production facilities, over 70 metals recycling locations and six steel fabrication plants).

Forward-Looking Statement

This press release contains some predictive statements about future events, including statements related to conditions in the steel and metallic scrap markets, Steel Dynamics’ revenues, costs of purchased materials, future profitability and earnings, and the operation of new or existing facilities. These statements are intended to be made as “forward-looking,” subject to many risks and uncertainties, within the safe harbor protections of the Private Securities Litigation Reform Act of 1995. These statements speak only as of this date and are based upon information and assumptions, which we consider reasonable as of this date, concerning our businesses and the environments in which they operate. Such predictive statements are not guarantees of future performance, and we undertake no duty to update or revise any such statements. Some factors that could cause such forward-looking statements to turn out differently than anticipated include: (1) the effects of a recurrent slowing economy on industrial demand; (2) changes in economic conditions, either generally or in any of the steel or scrap-consuming sectors which affect demand for our products, including the strength of the non-residential and residential construction, automotive, appliance, and other steel-consuming industries; (3) fluctuations in the cost of key raw materials (including steel scrap, iron units, and energy costs) and our ability to pass-on any cost increases; (4) the impact of domestic and foreign import price competition; (5) risks and uncertainties involving product and/or technology development; and (6) occurrences of unexpected plant outages or equipment failures.

More specifically, we refer you to SDI’s more detailed explanation of these and other factors and risks that may cause such predictive statements to turn out differently, as set forth in our most recent Annual Report on Form 10-K, in our quarterly reports on Form 10-Q or in other reports which we from time to time file with the Securities and Exchange Commission. These are available publicly on the SEC Web site, www.sec.gov, and on the Steel Dynamics Web site, www.steeldynamics.com.

Conference Call and Webcast

On Thursday, April 18, 2013, at 10:00 a.m. Eastern Time, Steel Dynamics will host a conference call with investors and analysts to discuss the company’s first quarter 2013 operating and financial results.  We invite you to listen to the live audiocast of the conference call accessible from our website (http://www.steeldynamics.com), or via telephone (the conference call number may also be obtained on our website).   A replay of the discussion will be available on our website until midnight on  April 25, 2013.  A downloadable podcast and an MP3 file of the event will also be available on our website.

Contact:  Marlene Owen, Director Investor Relations —+1.260.969.3500

Steel Dynamics, Inc.

CONSOLIDATED STATEMENTS OF INCOME (UNAUDITED)

(in thousands, except per share data)

Steel Dynamics, Inc.

UNAUDITED SUPPLEMENTAL OPERATING INFORMATION

(dollars in thousands)

(Note 1) Segment operating income (loss) excludes profit sharing expense.

Steel Dynamics, Inc.

CONSOLIDATED BALANCE SHEETS

(in thousands)

Steel Dynamics, Inc.

CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED)

(in thousands)