U.S. Steel Foundries (Except Investment): An Investor Primer

1. Overview

North American Industry Classification System (NAICS) code 331513 covers U.S. plants that manufacture steel castings other than investment castings.[1] These foundries make heavy, complex or safety-critical parts for mining equipment, rail systems, steel mills, energy infrastructure, defense and industrial machinery.

Investors have two routes:

• Public markets: Ampco-Pittsburgh and The Weir Group provide the closest listed exposure, but neither is a pure play and neither discloses U.S. NAICS 331513 revenue separately.
• Private markets: Direct ownership is more accessible through family businesses, employee-owned companies and private-equity carve-outs. Plant condition, environmental liabilities and customer qualifications matter as much as headline earnings.

2. What it is and how it is structured

A steel foundry melts purchased steel or scrap, adjusts the alloy, pours it into a mold, and then cools, cleans, heat-treats, inspects and often machines the casting. Sand molding is common for large or custom parts. The foundry makes a pattern and cores, forms a usually sand-based mold, melts metal in electric-arc or induction furnaces, adjusts chemistry in the ladle, pours the mold, allows it to solidify, and removes the casting. Gates and risers are cut off; the part is then heat-treated, blasted and ground, inspected—often through magnetic-particle, ultrasonic or radiographic testing—and, where specified, welded and machined.[2][3]

The classification excludes:

• Steel investment foundries, NAICS 331512, which use wax patterns and refractory shells.
• Iron foundries, NAICS 331511.
• Nonferrous foundries, including NAICS 331523, 331524 and 331529.
• Iron and steel forging, NAICS 332111.
• Plants that cast steel and then manufacture it into a finished product; Census classifies those plants by the finished product.[1]

That last rule is important: captive casting inside an equipment or vehicle manufacturer is outside this industry even when the physical process looks similar.

This route is attractive for large, complex shapes, internal passages, unusual alloys and components carrying loads in multiple directions. It competes with forging, welded fabrication, machining from plate or billet, iron and nonferrous casting, and increasingly additive manufacturing. Forging can win where directional strength and toughness dominate; fabrication can win at lower volumes or for simpler geometries; casting wins when consolidating a complex assembly into one part creates enough material, machining or performance advantage.

Ownership is mixed but tilted toward private specialists, employee stock ownership plans (ESOPs) and family businesses. Listed companies generally combine foundries with forging, machining, mining equipment or other industrial operations.

3. How big it is

The supplied federal statistics report 141 employer establishments, 9,928 employees and $652.3 million of annual payroll in 2023.[4] Of those establishments, 94 employed at least 20 people, while six were in the 250-to-499 employee class.[4]

The U.S. Small Business Administration (SBA) size standard for this industry is 500 employees, measured across the company and its affiliates rather than plant by plant.[5]

A recent OSHA regulatory analysis provides a revenue proxy, though it must not be mistaken for observed Economic Census sales. OSHA estimated 164 firms and $4.646 billion of revenue in 2022 dollars for NAICS 331513. It extrapolated revenue from the 2017 Statistics of U.S. Businesses, adjusted it with payroll relationships and a GDP deflator, and applied an average profit rate derived from older IRS industry data. The implied profit margin is approximately 4.7%, but this is a modeled regulatory-screening margin, not observed EBITDA or operating income from foundry accounts.[6]

For historical context, the 2002 Economic Census recorded 248 establishments, 230 companies, 16,831 employees, $630.7 million of payroll, $1.166 billion of material cost, $1.368 billion of value added and $2.536 billion of shipments. Those figures establish the historical scale but are not a current market estimate, and the Economic Census and County Business Patterns universes are not perfectly identical.[7]

The Census Bureau's County Business Patterns universe covers establishments with paid employees; it omits nonemployers.[4] That is a smaller concern here than in contractor or sole-proprietor industries. The more meaningful gap is captive foundry activity classified under the finished product.[1]

The Bureau of Labor Statistics added steel foundries to its Producer Price Index (PPI) coverage effective with the February 2025 release, giving investors a useful new indicator of selling-price changes.[8]

4. The investable universe

Public companies

There is no clean U.S.-listed pure play. Caterpillar, Wabtec and other equipment manufacturers can provide end-market read-throughs, but they are customers or integrated manufacturers rather than direct investments in NAICS 331513. Hitachi Construction Machinery provides exposure through Bradken, which it has wholly owned since 2017.[12]

Major private owners and operators

Other relevant specialists include MetalTek International, Ashland Foundry & Machine Works, Sawbrook Steel Castings, Fisher Cast Steel and Southwest Steel Casting.[20]

5. How the money works

Most foundries quote jobs around five economic components:

1. Metal: scrap, purchased steel and alloy additions such as nickel, chromium and manganese.
2. Conversion: melting, molding, pouring, heat treatment and finishing.
3. Engineering and tooling: patterns, casting simulation and process development.
4. Quality assurance: destructive and nondestructive testing, documentation and customer qualification.
5. Value-added work: machining, welding, assembly and inventory programs.

The principal inputs are purchased steel and scrap, ferroalloys, electricity, natural gas, molding sand, binders, refractories, consumables and skilled labor. Electricity drives melting; natural gas is important in heat treatment. Freight matters because many products are exceptionally heavy. The Department of Energy describes steelmaking and steel melting as energy-intensive, high-temperature processes.[21]

The critical operating metric is good-casting yield, not simply tons melted. Gating and risers are needed to feed metal during solidification but are not saleable product; defects discovered after pouring, heat treatment and machining destroy all the cost accumulated to that point. Other critical metrics include plant utilization, furnace productivity, scrap and rework, energy per ton, on-time delivery, backlog quality and maintenance capital spending. Foundries have high fixed costs, so modest volume changes can produce large margin swings.

Specialty alloys, difficult geometries, large casting capacity and customer certifications support better pricing. Commodity castings compete more directly on delivered cost. Metal and energy surcharges can protect margins, but price-cost timing remains a risk. Customer qualifications and pattern ownership can create sticky relationships, but long-lived contracts become unattractive when metal, energy or wage escalators lag actual cost inflation.

Replacement wear parts can create recurring revenue. At Weir's ESCO division, aftermarket products represented 94% of 2025 revenue, although that is a company example rather than an industry average.[10]

6. Demand drivers

The principal demand channels are:

• Mining and aggregates: crusher parts, ground-engaging tools, mill liners and undercarriage components. Wear parts also create replacement demand based on operating hours and material abrasiveness.
• Rail: truck components, couplers and other high-load parts. Demand follows freight volumes, fleet age, new-car construction and maintenance requirements.
• Steel and aluminum mills: cast rolls, slag pots and mill equipment.
• Energy: pumps, valves, turbine and hydroelectric components, oil-and-gas equipment and nuclear-qualified castings.
• Defense: naval, armored-vehicle and other specification-intensive parts. Defense and naval demand can be unusually durable because qualification, domestic-source requirements and inspection standards restrict the supplier base.
• Heavy equipment: construction, agriculture, material handling and industrial machinery.[22]

Useful leading indicators include mining production, steel-mill capital spending, railcar orders, heavy-equipment production, oil-and-gas investment and defense procurement. Replacement parts and defense work can be steadier than new equipment, but the overall industry remains cyclical.

The strongest positive secular argument is not broad volume growth but scarcity of qualified domestic capacity. The Defense Department's industrial strategy emphasizes resilient capacity and a sufficiently skilled workforce.[23] The Steel Founders' Society of America has warned that steel-casting capability and capacity have become national-security concerns, although that is an industry-advocacy position rather than a neutral demand forecast.[24]

The Bureau of Labor Statistics projects employment across the broader foundry industry, NAICS 3315, to fall from 106,000 in 2024 to 90,400 in 2034, a 14.7% decline, while real output falls from $26.9 billion to $24.8 billion. That is a broader-foundry projection, not a forecast specifically for 331513.[25]

7. Regulation

Major emitting facilities are covered by the U.S. Environmental Protection Agency's (EPA) National Emission Standards for Hazardous Air Pollutants (NESHAP). Regulated emissions can include particulate matter, lead, manganese, chromium, nickel and organic pollutants from binders and other processes.[26] Smaller "area source" foundries face a separate federal air-toxics standard.[27]

The Occupational Safety and Health Administration (OSHA) regulates respirable crystalline silica from foundry sand. Its general-industry standard sets an action level of 25 micrograms per cubic meter and a permissible exposure limit of 50 micrograms per cubic meter, each averaged over an eight-hour shift.[28] Molten metal, heat, noise, grinding, fumes, machine guarding and hazardous-energy control add further safety obligations. The Bureau of Labor Statistics reported a 2023 recordable injury and illness rate of 5.6 cases per 100 full-time workers for NAICS 331513, including 3.2 cases involving days away, restriction or transfer.[29]

Foundry wastewater is subject to Clean Water Act effluent guidelines.[30] Spent sand, baghouse dust and sludge require waste characterization and state-level disposal or reuse compliance. Spent sand may be reused beneficially in some applications, but mixed or contaminated waste remains subject to state requirements.[31]

Trade policy also matters. As of July 2026, some unfinished cast-steel articles remained subject to an additional 50% Section 232 tariff, while other metal products received different treatment based on tariff classification, origin and product type.[32][33] Investors should verify the Harmonized Tariff Schedule classification rather than assume every casting receives identical protection. Separate U.S. trade orders on Chinese slag pots illustrate the importance of import pricing in individual niches.[34]

Trade protection creates two-sided risk. Duties on castings may improve domestic competitiveness, while higher tariffs on steel, ferroalloys, refractories or machinery raise input and capital costs. Imported finished machinery containing foreign castings can also bypass protection applied only to the casting itself. The U.S. International Trade Commission found that Section 232 and Section 301 tariffs reduced imports and raised U.S. production and prices in covered steel and aluminum markets, while U.S. importers bore nearly the full tariff cost.[35]

8. Competitive dynamics and consolidation

The strongest competitive advantages are:

• Approved alloys, processes and welding procedures.
• Low defect rates and reliable delivery.
• Rare furnace, lifting and machining capacity for large castings.
• Pattern ownership and long customer histories.
• Integrated engineering, testing and machining.
• Defense, nuclear, rail or pressure-equipment qualifications.

Switching suppliers can be slow because a new foundry may need patterns, sample castings, testing and customer approval. That supports incumbent relationships, especially in safety-critical applications. Once a safety-critical casting has qualified tooling, metallurgy and inspection procedures, switching suppliers can be costly and slow.

Consolidation remains selective rather than sweeping. Foundries are difficult to relocate, environmental liabilities can be substantial and customer qualifications may not transfer easily. Recent transactions—such as TerraMar's acquisition of Bradken's North American specialty operations—show private capital pursuing carve-outs where focused ownership may improve utilization and investment discipline.[15]

No publishable federal concentration ratio was available for this industry. Establishment count alone should not be treated as market share: one company may own several plants, while individual foundries may dominate narrow casting sizes or qualifications. The available evidence supports a fragmented, predominantly private market, but not a precise concentration claim.

9. Risks

• Cyclicality: mining, rail, oilfield and heavy-equipment orders can fall sharply.
• Low utilization: fixed labor, furnace and environmental costs remain when production declines.
• Input inflation: scrap, alloys, electricity, gas, binders and freight can move faster than customer pricing.
• Quality failures: defects can require expensive rework, scrapping or warranty payments.
• Equipment outages: furnace or heat-treatment failures can interrupt an entire plant.
• Safety and environmental liabilities: silica, molten metal, historic waste and air emissions create recurring compliance costs.
• Labor: experienced metallurgists, molders, welders, patternmakers and maintenance technicians are difficult to replace.
• Customer concentration: losing one qualified program can leave specialized capacity idle.
• Substitution: forgings, weldments, ductile iron and redesigned fabricated assemblies can replace cast steel. Direct metal additive manufacturing is also a threat for prototypes, low-volume spares and small high-value components, though it is not yet an economic replacement for ordinary large steel castings.
• Trade volatility: tariffs may protect domestic pricing while also increasing steel, alloy or equipment costs.

Ampco-Pittsburgh's casting-related segment reported a $44.7 million operating loss in 2025, including a $41.4 million deconsolidation charge and $10.8 million of exit charges, demonstrating how restructuring, utilization and plant economics can overwhelm revenue scale.[9]

10. How to invest and outlook

Public investors should treat Ampco-Pittsburgh and Weir as different propositions. Ampco offers smaller, more operationally sensitive exposure; Weir offers a diversified mining-aftermarket platform in which U.S. foundries are only one component. Compare backlog, utilization, margins, free cash flow, maintenance spending and end-market mix—not group revenue alone.

Private buyers should prioritize:

• Environmental and worker-safety records.
• Furnace, crane and heat-treatment condition.
• Normalized yield, scrap and rework.
• Customer and end-market concentration.
• Ownership of patterns and intellectual property.
• Qualification-transfer risk.
• Maintenance backlog and working-capital needs.
• Ability to pass through metal and energy costs.
• Backlog cancellation terms and metal-price escalators.
• Union exposure and insurance.
• Replacement cost and permitting difficulty of melt capacity.

Reported signals are cautiously positive but mixed. Ampco-Pittsburgh said first-half 2026 customer orders reached approximately $268 million, up 32% from about $204 million, with improving North American roll demand.[36] A broader American Foundry Society survey—not specific to steel foundries—found 72% of respondents positive about 2026 and projected 4.2% sales growth.[37]

The most commonly misreported point is the industry boundary. "Steel foundry" is not synonymous with steel mill; "steel casting" does not include investment casting, forging or continuous casting of slabs and billets; and owning a foundry does not mean the facility is counted in 331513. Market reports that ignore those distinctions routinely overstate both the addressable market and the number of investable companies.

Forward-looking judgment: defense, mining wear, infrastructure replacement and trade protection should support qualified domestic foundries. The best assets are likely to be plants with recurring replacement demand, difficult-to-replicate casting capability and strong process control. The weakest are commodity jobbing shops with aging equipment, poor utilization and limited pricing power.

Sources

1. U.S. Census Bureau, 2022 NAICS Manual: Steel Foundries (except Investment), 2022.
2. Steel Founders' Society of America, Casting Process Overview, current.
3. U.S. Environmental Protection Agency, AP-42: Steel Foundry Process Description, 2020.
4. U.S. Census Bureau, County Business Patterns: NAICS 331513, 2023.
5. U.S. Small Business Administration, Table of Small Business Size Standards, 2023.
6. Occupational Safety and Health Administration, Final Economic Analysis: NAICS 331513, 2024.
7. U.S. Census Bureau, 2002 Economic Census: Steel Foundries (except Investment), 2002.
8. U.S. Bureau of Labor Statistics, Producer Price Index News Release—February 2025, 2025.
9. U.S. Securities and Exchange Commission, Ampco-Pittsburgh 2025 Form 10-K, 2026.
10. The Weir Group, Annual Report and Financial Statements 2025, 2026.
11. The Weir Group, Weir Increases Investment in Newton, Mississippi, 2019.
12. Bradken, Management and Governance: Hitachi Construction Machinery, current.
13. Amsted Industries, History and Employee Ownership, current.
14. WHEMCO, Melting and Casting Capabilities, current.
15. Bradken, TerraMar Capital Acquires Specialty Products North America, 2025.
16. Harrison Steel Castings, About Us, current.
17. Eagle Alloy, About Eagle Alloy, current.
18. Stainless Foundry & Engineering, About Us, current.
19. American Steel Castings, About American Steel Castings, current.
20. MetalTek International, Manufacturing Critical Metal Components, current.
21. U.S. Department of Energy, Iron and Steel Manufacturing, current.
22. Steel Founders' Society of America, 2024 Industry Market Forecast, 2024.
23. U.S. Department of Defense, DOD Releases First Defense Industrial Strategy, 2024.
24. Steel Founders' Society of America, Casteel Reporter—February 2024, 2024.
25. U.S. Bureau of Labor Statistics, Industry Employment and Output Projections, current.
26. U.S. Environmental Protection Agency, Iron and Steel Foundries: National Emission Standards for Hazardous Air Pollutants, 2026.
27. U.S. Environmental Protection Agency, Air-Toxics Regulation for Iron and Steel Foundry Area Sources, 2026.
28. Occupational Safety and Health Administration, General Industry and Maritime Silica Standard, current.
29. U.S. Bureau of Labor Statistics, Injury and Illness Rates by Industry, 2023, 2023.
30. U.S. Environmental Protection Agency, Metal Molding and Casting Effluent Guidelines, 2026.
31. U.S. Environmental Protection Agency, Beneficial Uses of Spent Foundry Sands, current.
32. The White House, Annex I-A: 50% Section 232 Tariff on Full Value, 2026.
33. The White House, Further Adjusting the Tariff Regimes for Imports of Aluminum, Steel and Copper, 2026.
34. U.S. International Trade Commission, Slag Pots from China Injure U.S. Industry, 2025.
35. U.S. International Trade Commission, Economic Impact of Section 232 and Section 301 Tariffs, current.
36. Ampco-Pittsburgh Corporation, First-Half 2026 Customer Order Activity, 2026.
37. American Foundry Society, Quarterly Metalcasters Outlook Survey, 2026.