Producer
Steel Dynamics, Inc. (SDI)
Third-largest US steel producer; second-largest domestic heavy rail producer via Columbia City, Indiana Structural and Rail Division. Rail capacity: ~300,000 tons/year; heat-treating capacity for 350,000 tons of head-hardened premium rail. Produces 320-foot long rails (same as Pueblo). All major US Class I railroad approvals. SDI's Columbia City facility also produces structural steel (wide-flange beams). SDI expanded Columbia City from 1 million to 1.6 million tons/year total capacity. First domestic US rail producer to receive simultaneous approval from all Class I railroads.
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Goods downstream
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Facilities
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2 facilities
Steel Dynamics -- Columbus, Mississippi (New Millennium Aluminum) →
USColumbus, Lowndes County, Mississippi, USA · manufacturing_plant
SDI's New Millennium Aluminum flat-rolling mill; one of the most significant new entrants to North American flat-rolled aluminum in decades. A major EAF steel company diversifying into aluminum rolling. Targets automotive sheet and can stock markets. Provides meaningful new non-Novelis capacity in a market dominated by Novelis (~40%). Mill construction completed 2024-2025.
Steel Dynamics Columbia City — Structural and Rail Division →
USColumbia City, IN · steel mill
SDI's rail and structural steel mill; ~300,000 tons/year rail capacity with heat-treating for up to 350,000 tons of head-hardened premium rail. Produces 320-foot long rails. All US Class I railroad approvals; first US producer approved by all majors simultaneously. $200M expansion brought total Columbia City capacity to 1.6 million tons. Also produces wide-flange beams (structural) from the same universal rolling mill.
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Steel Operations (EAF Mini-Mills)
70%Aluminum Operations (Columbus, MS)
15%Metals Recycling (OmniSource)
10%Steel Fabrication (New Millennium Building Systems)
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Did you know2023
Steel Dynamics, universally known as a steel Electric Arc Furnace mini-mill company (third-largest US steel producer), is building an aluminum flat-rolling mill in Columbus, Mississippi under its New Millennium Aluminum brand. This makes SDI one of the first major US steel companies to diversify into aluminum production — targeting automotive aluminum sheet and beverage can stock markets. SDI's entry adds meaningful non-Novelis capacity to a North American aluminum flat-rolled market where Novelis controls approximately 40% of supply. A steel recycler is entering the aluminum supply chain that automakers are rapidly expanding into as they replace steel body panels with aluminum for fuel economy compliance.
Steel Dynamics, Inc. ↗Capacity2023
Steel Dynamics operates 38 steel fabrication plants across 24 US states through its New Millennium Building Systems subsidiary, producing open-web steel joists and roof/floor deck panels — consuming SDI's own structural steel output. This creates a fully integrated supply chain from scrap metal (OmniSource) → EAF steelmaking → structural beam production → building component fabrication, all within one public company. SDI is one of few companies that controls its own raw material sourcing, primary steel production, and downstream fabricated component distribution simultaneously.
Steel Dynamics, Inc. ↗Origin2023
Steel Dynamics was founded in 1993 in Fort Wayne, Indiana by Keith Busse, Mark Millett, and Richard Teets — three executives who left Nucor Corporation to replicate its Electric Arc Furnace mini-mill model at a new company. SDI became one of the fastest-growing US steel companies of the 1990s-2000s using the same scrap-based EAF technology Nucor pioneered. By 2024, SDI had become the third-largest US steel producer at ~13 million tons/year capacity. The founders' departure from Nucor was one of the more significant talent exits in US industrial history — it created a direct competitor that has consistently challenged Nucor's dominance.
Steel Dynamics, Inc. ↗