U.S. Iron Foundries (NAICS 331511): An Investor Primer

1. Overview

Iron foundries melt purchased iron and scrap, pour the metal into molds, and sell castings used in vehicles, machinery, water systems, construction products and cookware.[1] The industry is capital-intensive, cyclical and operationally unforgiving: utilization, casting yield, energy use and defect rates can matter more than headline revenue growth.

Public-market access is limited and mostly indirect through manufacturers with captive foundries. Private investors can obtain more direct exposure through independent foundries, private-equity portfolios, family businesses, private credit and equipment financing.

2. What it is and how it is structured

North American Industry Classification System (NAICS) code 331511 covers gray, ductile, malleable and related iron castings, including cast-iron pipe, fittings, manhole covers, cookware and unfinished industrial parts. Establishments that cast and then manufacture a finished product are classified by that finished product instead.[1]

A typical foundry receives steel scrap, foundry returns and sometimes pig iron; blends the charge to a required chemistry; melts it in a cupola, electric-arc furnace or, increasingly, an induction furnace; adjusts carbon, silicon, magnesium and other alloying elements; and pours the metal into sand molds. After cooling, the mold is broken at shakeout, gates and risers are removed, and the casting is blasted, ground, heat-treated, inspected and sometimes machined or assembled. The Environmental Protection Agency identifies melting, pouring, cooling and shakeout as the major emissions points.[2][3]

Gray iron is valued for damping, machinability and low cost; ductile iron, made by magnesium treatment, has materially greater strength and toughness. Part geometry and chemistry are customer-specific. Patterns and core boxes, process qualification, metallurgy, machining fixtures and quality history create switching costs even though the underlying iron is a commodity.

Excluded adjacent industries include steel investment foundries (331512), other steel foundries (331513), nonferrous die-casting foundries (331523), aluminum foundries other than die casting (331524), other nonferrous foundries (331529), and forging and stamping operations.[1]

Independent producers are predominantly privately held or sponsor-owned. Public manufacturers such as Caterpillar and Deere operate captive foundries, while Mueller Water Products combines foundry operations with finished water-infrastructure products.

Federal statistics understate the physical footprint because captive operations may be classified with machinery or vehicle manufacturing. County Business Patterns also excludes nonemployers and most government activity, although this is not a government- or tiny-operator-dominated industry.[4][5]

3. How big it is

County Business Patterns reported 269 employer establishments, 32,020 employees and $2.316 billion of annual payroll in 2023.[4]

The most recent detailed NAICS 331511 operating benchmark from the Economic Census is 2017, which reported 31,968 employees, $1.813 billion of payroll, $8.584 billion of shipments, $4.198 billion of materials cost, $4.346 billion of value added and $338.7 million of capital expenditure.[6] A directly reported 2022 Economic Census revenue or concentration row for NAICS 331511 was not accessible.

The Small Business Administration (SBA) uses 1,000 employees as the size ceiling for certain small-business programs in this industry, but that administrative threshold does not describe the actual ownership mix.[7]

4. Investable universe

There is no clean U.S.-listed pure play. Air T, Inc. (NASDAQ: AIRT) accounts for a 20.1% equity-method interest in privately held Cadillac Casting, with an original investment of $2.8 million. Cadillac makes ductile-iron automotive and industrial castings, but its results are embedded in a diversified holding company dominated by aviation-related businesses.[8][9]

The closest New York Stock Exchange (NYSE) exposures are integrated manufacturers:

As an international public comparator—not a U.S. benchmark—UK-listed Castings plc reported £171.746 million of external foundry revenue and £6.378 million of foundry segment profit before other operating income and pension cost for the year ended March 2026, illustrating how thin margins can be when volumes, pricing or operating execution disappoint.[15]

Major private operators include:

• Waupaca Foundry, acquired by Monomoy Capital Partners in 2024. At the time of the transaction it reported more than 4,000 employees, five iron foundries and 1.4 million tons of capacity, making it the clearest scaled independent producer.[16][17]
• Grede, owned by funds managed by Gamut Capital Management following its 2019 purchase from American Axle & Manufacturing. Its current company history reports seven North American facilities and 3,000 employees.[18][19]
• Charlotte Pipe and Foundry, privately held, which acquired Neenah Enterprises in 2022 and now owns the Neenah Foundry, US Foundry and Bingham & Taylor brands.[20][21]
• McWane, a family-owned producer of ductile-iron pipe, valves, hydrants and fittings, with three U.S. pipe foundries under McWane Ductile.[22][23]
• AMERICAN Cast Iron Pipe Company, employee-owned, manufacturing ductile-iron pipe, valves, hydrants and large machinery castings.[24]
• Metal Technologies, a family-owned gray- and ductile-iron casting and machining group.[25]

5. How the money works

Revenue usually equals casting volume multiplied by a negotiated price per part or pound, plus tooling, machining, coating and assembly. Customer qualification and dedicated patterns make relationships sticky, but major vehicle and machinery programs can also create customer concentration.

The main costs are scrap and pig iron, alloy additions, electricity or coke, natural gas, sand and binders, labor, machining, freight, maintenance and environmental controls. Raw-material surcharges can reduce commodity exposure, but pricing formulas may lag actual costs. Yield is as important as purchase price: metal in defective castings, gates and risers can be remelted, but it consumes furnace energy, molding capacity and labor without producing revenue.

Energy exposure is material. The Energy Information Administration's 2022 Manufacturing Energy Consumption Survey measured iron-foundry fuel consumption at 1,444.6 million Btu per employee, 7.4 thousand Btu per dollar of value added and 4.1 thousand Btu per dollar of shipments.[26] Furnace choice consequently matters: induction melting reduces direct combustion emissions and permits better chemistry control but raises sensitivity to electricity prices and grid reliability. AMERICAN Cast Iron Pipe Company is investing $285 million through 2029 to replace one cupola with four coreless induction furnaces, expecting 25% more melting capacity and a 50% reduction in on-site greenhouse-gas emissions.[27]

Foundries have substantial fixed costs. Furnaces, molding lines, pollution-control equipment and maintenance teams remain expensive when volumes fall. Important operating measures include:

• melt and molding-line utilization;
• tons shipped and price per pound;
• casting yield, scrap and rework rates;
• labor and energy cost per ton;
• furnace and line uptime;
• machining content and contribution margin;
• backlog, program launches and customer concentration.

As a broad proxy, iron-and-steel-product capacity utilization—not a foundry-only measure—was 72.2% in 2025, suggesting available industrial capacity.[28] The Producer Price Index (PPI) for iron foundries was approximately 2.6% higher in May 2026 than a year earlier, based on Bureau of Labor Statistics index data.[29]

6. Demand drivers

The largest demand pools are light and commercial vehicles, agricultural and construction machinery, pumps and compressors, rail equipment, municipal castings, ductile-iron water pipe and consumer cookware.[1][10][17][18] Grede's current product portfolio includes suspension, chassis and drivetrain parts; heavy-truck engine and chassis parts; and axle housings for agricultural and heavy equipment.[30]

Vehicle, truck and heavy-equipment demand is cyclical and sensitive to interest rates, dealer inventories, construction activity and farm income. Municipal water products are typically steadier because installed systems require continuing repair and replacement.

Electric vehicles (EVs) reduce demand for some engine-block, cylinder-head and transmission castings. They do not eliminate demand for brakes, hubs, suspension parts, industrial machinery or water infrastructure. Grede explicitly identifies brakes, suspension, chassis and powertrain as its automotive opportunity set.[31] The net effect depends heavily on each plant's customer and part mix.

Infrastructure is the clearest secular support. Ductile-iron pipe, hydrants, valves, manhole frames and drainage castings benefit from replacement of aging water systems and publicly funded construction. Transportation, defense and reshoring can support engineered domestic castings because qualification, weight, freight cost and supply-chain security reduce the appeal of distant sourcing.

The American Foundry Society projected overall casting sales—not iron-foundry sales alone—to rise 4.2% in 2026, with 52% of the projected growth coming from pricing and 48% from tonnage; 95% of surveyed foundries said they were making capital investments.[32]

7. Regulation

The Environmental Protection Agency (EPA) regulates major iron and steel foundries under National Emission Standards for Hazardous Air Pollutants (NESHAP) requirements in 40 Code of Federal Regulations (CFR) Part 63, Subpart EEEEE. Smaller area sources fall under Subpart ZZZZZ.[33][34] Controls address particulate matter and hazardous air pollutants (HAP), including manganese, lead and organic compounds released during melting, molding and cooling. Tighter ambient particulate standards can constrain permits or expansions even when the underlying NESHAP limits do not change.

Foundry sand also creates respirable crystalline-silica exposure. Occupational Safety and Health Administration (OSHA) rules set an eight-hour permissible exposure limit of 50 micrograms per cubic meter and an action level of 25 micrograms per cubic meter.[35]

Spent sand is both a cost and an opportunity. EPA estimates that approximately 2.6 million tons of foundry sand are beneficially used outside foundries annually and that iron, steel and aluminum sands account for 96% of that volume. State waste rules, contamination and local end markets determine whether reuse produces savings or the foundry pays landfill costs.[36]

Other obligations include state air permits, wastewater and stormwater controls, site remediation and worker protection around molten metal and heavy equipment. Product-specific antidumping and countervailing-duty orders protect some construction castings from certain foreign suppliers; investors should verify the treatment of each product rather than assume that broad steel tariffs apply.[37]

8. Competitive dynamics and consolidation

Scale improves scrap purchasing, customer reach, engineering support and the ability to spread compliance costs. Yet competition remains regional for freight-heavy municipal products and more national or international for high-volume vehicle parts.

Patterns, tooling and customer approvals create real barriers to switching. In a municipal-castings transaction, the Department of Justice found the parties were two of only three significant suppliers across 11 states and required divestiture of rights to more than 500 patterns.[38]

Consolidation has transferred assets among industrial groups, families and private-equity sponsors. New entry remains difficult because plants require heavy capital, environmental permits, skilled labor and enough customer volume to fill a molding line.

9. Risks

• Cyclicality: vehicle, agricultural, truck and construction volumes can fall quickly.
• Fixed-cost leverage: low utilization can sharply compress margins and cash flow.
• Input volatility: scrap, alloys, electricity, coke and natural-gas costs may move faster than customer pricing.
• Technology and substitution: EV adoption and substitution toward aluminum, plastics, forgings or fabricated parts can strand product-specific capacity.
• Quality: defects can trigger scrap, warranty costs, production stoppages or customer loss.
• Environmental liabilities: old plants may carry costly air-control, waste or remediation obligations.
• Labor and safety: foundries need experienced workers and face material heat, silica and molten-metal hazards. The Bureau of Labor Statistics reported a 2024 total-recordable injury and illness rate of 5.5 cases per 100 full-time workers in iron foundries, versus 2.3 for private industry overall.[39]
• Customer concentration: losing one qualified program can leave specialized equipment underused.
• Private-company leverage: sponsor-owned businesses add refinancing and exit-timing risk to normal operating cyclicality.

10. How to invest and outlook

Public investors seeking the closest operating exposure should examine Mueller Water Products (MWA), while recognizing that its valuation reflects the broader water-products business. Caterpillar (CAT) and Deere (DE) offer only diluted, captive exposure and are better treated as end-market indicators. Air T (AIRT) provides a small equity-method stake in Cadillac Casting, though it is not a foundry pure play.[8]

Private investors can pursue control acquisitions, minority stakes, private credit, equipment leases or sale-leasebacks. Diligence should focus on saleable tons rather than melt capacity; utilization by molding line; scrap and rework rates; contribution per machine or mold hour; surcharge mechanics; customer and program concentration; pattern ownership; remaining program life; union and skilled-labor exposure; environmental permits and legacy sites; maintenance backlog; and the capital required to move from cupola to electric melting.

A common misunderstanding is that this is a commodity iron business. It is actually a collection of qualified, process-specific conversion franchises whose economics depend more on utilization, yield, tooling, customer programs and environmental capital than on owning iron ore.

Outlook: selective rather than broadly bullish. Municipal water replacement, domestic-content requirements and supply-chain localization support well-positioned plants.[40] Large-equipment and agricultural demand remain more vulnerable. Waupaca's decision to close a finishing operation after softer agricultural demand, while continuing a $100 million-plus modernization program, captures the industry's central divide: older or poorly loaded capacity is at risk, while efficient plants with durable customer programs can still justify investment.[41]

This is a forward-looking judgment, not a reported forecast. The best opportunities are likely to be plant-specific turnarounds and specialized infrastructure franchises rather than a uniform industry recovery.

Sources

1. U.S. Census Bureau, "2022 NAICS Definition: 331511 Iron Foundries," 2022, https://www.census.gov/naics/?details=331511&input=331511&year=2022
2. U.S. Environmental Protection Agency, "Iron Foundry Process Description," https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=9100Q6O2.TXT
3. U.S. Environmental Protection Agency, "AP-42 Iron and Steel Foundries Background Document," 2020, https://19january2021snapshot.epa.gov/sites/static/files/2020-11/documents/c12s10_0.pdf
4. U.S. Census Bureau, "331511: Iron Foundries—County Business Patterns Profile," 2023, https://data.census.gov/profile/331511_-_Iron_foundries?codeset=naics~331511
5. U.S. Census Bureau, "County Business Patterns Methodology," 2025, https://www.census.gov/programs-surveys/cbp/technical-documentation/methodology.html
6. Steel Founders' Society of America, "2017 Economic Census Data for Iron Foundries," 2022, https://www.sfsa.org/wp-content/uploads/2022/06/Steel-Casting-2022-SL2022.pdf
7. U.S. Small Business Administration, "Table of Size Standards," 2023, https://www.sba.gov/document/support-table-size-standards
8. Air T, Inc., "Annual Report on Form 10-K," 2025, https://www.sec.gov/Archives/edgar/data/353184/000035318425000057/a2025annualreportforprinti.pdf
9. Air T, Inc., "Form 10-K," December 2025, https://www.sec.gov/Archives/edgar/data/353184/000035318426000016/airt-20251231.htm
10. Mueller Water Products, "Annual Report on Form 10-K," 2025, https://www.sec.gov/Archives/edgar/data/1350593/000135059325000066/mwa-20250930.htm
11. Caterpillar, "Annual Report on Form 10-K," 2025, https://www.sec.gov/Archives/edgar/data/18230/000001823026000008/cat-20251231.htm
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13. Deere & Company, "Fiscal 2025 Fourth-Quarter and Full-Year Results," 2025, https://www.deere.com/en/news/all-news/fy25-fourth-quarter-earnings/
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16. Monomoy Capital Partners, "Monomoy Completes Acquisition of Waupaca Foundry," 2024, https://www.mcpfunds.com/news/monomoy-capital-partners-completes-acquisition-of-waupaca-foundry/
17. Waupaca Foundry, "Waupaca Foundry Announces Acquisition Agreement," 2024, https://waupacafoundry.com/news/Waupaca-Foundry-Announces-Acquisition-Agreement
18. Gamut Capital Management, "Acquisition of Grede Iron Casting Operations," 2019, https://www.gamutcapital.com/news-content/2019/9/18/aam-announces-sale-of-us-iron-casting-operations-to-funds-managed-by-gamut-capital-management
19. Grede, "Company History," 2026, https://grede.com/company/history/
20. Charlotte Pipe and Foundry, "Charlotte Pipe and Foundry Acquires Neenah Enterprises," 2022, https://www.charlottepipe.com/newsroom/press-releases/charlotte-pipe-and-foundry-acquires-neenah-enterprises
21. Charlotte Pipe and Foundry, "Charlotte Pipe and Neenah Foundry Align Operations," 2026, https://www.charlottepipe.com/newsroom/press-releases/charlotte-pipe-and-foundry-neenah-foundry-align-operations-as-part-of-a-new-commercial-structure
22. McWane, "About McWane," 2026, https://pe.mcwane.com/groups/about-mcwane
23. McWane Ductile, "About," 2026, https://www.mcwaneductile.com/about/
24. AMERICAN Cast Iron Pipe Company, "Company History," 2026, https://american-usa.com/about/story
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30. Grede, "Products," 2026, https://grede.com/what-we-do/products/
31. Grede, "Automotive Market," 2026, https://grede.com/markets/automotive/
32. American Foundry Society, "Quarterly Metalcasters Outlook Survey," March 2026, https://www.afsinc.org/news/2026/03/17/quarterly-metalcasters-outlook-survey-shows-increasing-optimism-among-foundry
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34. U.S. Environmental Protection Agency, "Iron and Steel Foundries: NESHAP for Area Sources," 2026, https://www.epa.gov/stationary-sources-air-pollution/iron-and-steel-foundries-national-emission-standards-hazardous-air
35. Occupational Safety and Health Administration, "Respirable Crystalline Silica in General Industry," 2018, https://www.osha.gov/laws-regs/standardinterpretations/2018-06-25
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37. U.S. International Trade Commission, "Iron Construction Castings from Brazil, Canada, and China," 2022, https://www.usitc.gov/press_room/news_release/2022/er0502ll1926.htm
38. U.S. Department of Justice, "Divestitures Required in Neenah Enterprises' Acquisition of US Foundry," 2021, https://www.justice.gov/archives/opa/pr/justice-department-requires-divestitures-neenah-enterprises-inc-s-acquisition-us-foundry
39. U.S. Bureau of Labor Statistics, "Survey of Occupational Injuries and Illnesses: Industry Rates," 2024, https://www.bls.gov/web/osh/table-1-industry-rates-national.htm
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41. Waupaca Foundry, "Press Releases: Plant Closure and Modernization Program," 2025, https://waupacafoundry.com/news/press-releases