U.S. Ferrous Metal Foundries (NAICS 33151): An Investor Primer

1. Overview

North American Industry Classification System (NAICS) code 33151 groups the three U.S. industries that pour ferrous (iron- and steel-based) metal into molds: iron foundries (331511), steel investment foundries (331512), and steel foundries except investment (331513).[1] Together they make the castings inside vehicles, farm and construction machinery, water and sewer systems, aircraft engines, mining equipment, rail cars, power turbines, and defense platforms.

The three children share a common physics — melt metal, pour it into a mold, then cool, clean, heat-treat, inspect, and often machine the part — but they are very different businesses. One is a fragmented, freight-sensitive, high-tonnage world of vehicle and municipal castings; one is a small, highly concentrated precision niche riding the aerospace cycle; and one is a specialist trade in heavy, safety-critical steel parts for mining, rail, and energy. The value of this rollup is the contrast among them, because who owns each child, how each makes money, how profitable each is, and how an outside investor can gain exposure diverge sharply.

A common thread runs through all three: there is no U.S.-listed pure play in any of them. Listed access did widen in 2026 — a precision caster (Doncasters) went public in June 2026,[4] and a small holding company (Air T) carries a direct minority stake in an iron foundry[3] — but both are partial, and most of the actual industry still sits in private, family-owned, employee-owned, and private-equity (PE) hands. The subsector is capital-intensive, cyclical, and operationally unforgiving: utilization, casting yield, energy cost, and defect rates often matter more than headline revenue.

2. What's inside — the three children and how they differ

The children are close cousins in process but different animals as investments. Shares below are by employment and payroll because those two reconcile exactly to the level totals; receipts are only partly available at the child level, and on inconsistent bases (see Section 3).

Two takeaways this level can give that no child can. First, iron foundries dominate the headcount, payroll, and footprint, but the steel-investment niche is where concentration, value-density, and the clearest public proxies live — and the three do not rise and fall together, so a soft farm-equipment year can hurt iron while aerospace lifts investment casting. Second, the federal statistical system sees these three industries very unevenly: only 331512 has published concentration ratios, only 331512 has a current Economic Census receipts line, and the government's own small-business ceiling is more than twice as high for investment casting as for heavy steel. Any market study that treats "ferrous foundries" as one measured thing is papering over those gaps.

3. How big it is

Our ground-truth federal statistics for NAICS 33151 as a whole:

The children reconcile on people, not on money. Establishments (269 + 106 + 141 = 516), employment (32,020 + 15,144 + 9,928 = 57,092), and payroll ($2.316bn + $1.00bn + $0.652bn ≈ $3.97bn) all tie to the level totals.[2] Revenue does not — see below. One derived contrast is worth noting: payroll per employee works out to roughly $72,300 in iron, about $66,300 in steel investment,[4] and roughly $65,700 in other steel (all derived from CBP 2023).[2] Value-density per part is highest in investment casting, but pay per head is not — do not read one as a proxy for the other.

Concentration — the headline contrast of this level. For the subsector as a whole, the four largest firms hold 29.1% of receipts, the top eight 46.3%, the top 20 63.8%, and the top 50 78.5%; the Herfindahl-Hirschman Index (HHI — the sum of squared market shares, on a 0–10,000 scale where regulators generally treat readings below ~1,000 as an unconcentrated market) is 337.4.[6] That low aggregate HHI says the ferrous foundry subsector overall is fragmented. But it is a badly misleading headline. It is dragged down by the many small, regional iron and heavy-steel foundries, and it masks the highly concentrated steel-investment child, where the top four firms alone control 73.5% of receipts and the top 20 control 89%.[4] Worse, the level HHI is the only HHI available at all: Census suppressed the HHI for 331512, no publishable concentration ratio exists for 331513, and no 2022 Economic Census concentration row for 331511 was accessible.[3][4][5] So the one clean-looking concentration number for this subsector is the one that describes the market structure least well. Always look one level down.

Where the receipts sit — and why you cannot add them up. Of the level's $19.51 billion of 2022 receipts, the steel-investment child accounted for $3.95 billion — about 20% — spread across just 84 firms of the level's 411.[4][6] For the other two children, the available revenue evidence is not on the same basis and must not be summed with it or against the level total:

• Iron (331511): the most recent directly reported Economic Census benchmark is 2017, not 2022 — $8.584 billion of shipments, $4.346 billion of value added, and $338.7 million of capital expenditure on 31,968 employees.[3] Note that 2017 headcount is essentially unchanged from CBP's 32,020 in 2023 (different surveys, so treat as directional): iron's employment base has been flat, not shrinking.
• Steel except investment (331513): there is no observed Economic Census sales figure. The only recent revenue estimate is a modeled one from an OSHA regulatory analysis — 164 firms and $4.646 billion of revenue in 2022 dollars, extrapolated from 2017 business statistics using payroll relationships and a GDP deflator.[5] That is a regulatory-screening estimate, not measured sales.

Different vintages, different universes, different methods. What the evidence does support is the ordering: iron is the largest child by revenue as well as by headcount and payroll, steel investment is the smallest by revenue at roughly a fifth of the level, and steel-except-investment sits in between — while investment casting commands by far the highest value-add per part.

The base has shrunk over two decades. Where child data reaches back, both steel children are materially smaller and more concentrated than in 2002: 331512 has gone from 130 companies with a CR4 of 59.2% and an HHI of 1,662 to 84 firms with a CR4 of 73.5%,[4] and 331513 from 248 establishments and 16,831 employees to 141 and 9,928.[5] This is a mature subsector consolidating and attriting, not one adding capacity.

Undercount caveat. These are employer-establishment figures. County Business Patterns omits nonemployers, but that is a minor issue in this capital-intensive subsector — this is not a sole-proprietor or government-dominated field.[3][5] The material gap is classification scope, not tiny operators: (a) captive foundries run inside vehicle, machinery, engine, and firearm makers are counted under the parent's finished-product industry, not here, so the true physical foundry footprint is larger than 516 plants;[1][3][5] and (b) the marquee aerospace product — the single-crystal superalloy turbine blade — is nonferrous and sits in NAICS 331529, so 331512 understates the economic weight of the companies that lead precision casting.[4] No suppressed value is stated as if known.

4. The investable universe — where value concentrates

Value concentrates unevenly across the three children, and the public and private routes differ by child. Listed access widened during 2026, but every route remains partial.

Iron (331511). No listed pure play. The closest operating proxy is Mueller Water Products ($1.430 billion of fiscal-2025 sales), which runs two U.S. iron foundries for valves and hydrants but reports no standalone foundry results. The only direct listed ownership of a merchant iron foundry is tiny: Air T holds a 20.1% equity-method interest in privately held Cadillac Casting on an original investment of $2.8 million, buried inside an aviation-dominated holding company. Caterpillar ($67.589 billion of 2025 sales; its Mapleton, Illinois, captive foundry can melt as much as 1,000 tons of iron per day) and Deere ($45.684 billion of fiscal-2025 sales; Waterloo, Iowa) operate captive foundries but are better treated as end-market indicators.[3] For a listed foundry P&L in this child you have to leave the U.S.: UK-listed Castings plc reported £171.746 million of external foundry revenue and just £6.378 million of foundry segment profit for the year to March 2026 — under 4%, and a useful warning about how thin iron economics get when volumes or execution disappoint.[3] The real ownership sits private: Waupaca Foundry (Monomoy Capital Partners, 2024; more than 4,000 employees, five iron foundries, 1.4 million tons of capacity — the clearest scaled independent), Grede (Gamut Capital Management, 2019; seven North American facilities, 3,000 employees), Charlotte Pipe and Foundry (which bought Neenah Enterprises in 2022 and now owns the Neenah Foundry, US Foundry, and Bingham & Taylor brands), family-owned McWane (three U.S. pipe foundries), employee-owned AMERICAN Cast Iron Pipe Company, and family-owned Metal Technologies.[3]

Steel investment (331512) — the concentration story. The global leader, Precision Castparts Corp. (PCC) (~$10.4 billion of revenue, ~33,000 employees; divisions include PCC Structurals, PCC Airfoils, and Wyman-Gordon), is wholly owned by Berkshire Hathaway, which bought it for ~$37.2 billion in 2016 — one holding among many. The clear No. 2 in aero castings, Howmet Aerospace (~$8.3 billion FY2025 revenue, ~$109 billion market capitalization), remains the cleanest large-cap precision-casting proxy, though much of its highest-value work is nonferrous superalloy. New since the last version of this page: Doncasters (DPC Holdings) listed on the NYSE on June 25, 2026 — a genuine investment caster with disclosed casting economics, but primarily a nickel- and cobalt-superalloy producer rather than a NAICS 331512 steel foundry. No. 3, Consolidated Precision Products (CPP), is PE-owned (Warburg Pincus and Berkshire Partners). Below them: high-volume Signicast (Form Technologies), Hitchiner, MetalTek International, Stainless Foundry & Engineering, Avalon Precision Casting (acquired by Sigma Electric), captive casters such as Sturm, Ruger's Pine Tree Castings, and a long private tail serving medical and valve niches. Impro Precision Industries (HKEX: 1286) offers an international comparable — its investment-casting segment ran HK$1.91 billion in 2025, 37.5% of the group — but it is global and alloy-mixed.[4]

Steel except investment (331513). The two nearest listed exposures are Ampco-Pittsburgh, whose Forged and Cast Engineered Products segment did $292.6 million of 2025 sales (up from $286.6 million in 2024, with cast versus forged not separated), and the UK-listed The Weir Group, whose ESCO division generated £709 million of 2025 revenue with North America at 56% of orders — neither breaks out U.S. steel-casting revenue. Hitachi Construction Machinery offers indirect exposure through Bradken, wholly owned since 2017. The private roster is deep: employee-owned Amsted Industries (100% employee-owned since 1998), WHEMCO/Park, Vulcan Metals (TerraMar Capital, which bought Bradken's North American specialty foundries and machining operations in 2025), Harrison Steel Castings (a 700,000-square-foot Indiana plant casting parts from 400 to 18,000 pounds), employee-owned Eagle Alloy, family-controlled Stainless Foundry & Engineering, and American Steel Castings.[5]

Three patterns visible only from this level. Employee ownership is a recurring structure across all three children, not a 331513 quirk — Amsted, Eagle Alloy, and AMERICAN Cast Iron Pipe are all employee-owned, which shapes both deal availability and price expectations.[3][5] The child boundary is a process boundary, not a company boundary: Stainless Foundry & Engineering pours both sand and investment castings and appears in the rosters of two children, a reminder that firm-level screens will straddle these codes.[4][5] And across all three, the biggest and best assets are private; public tickers give diluted, blended exposure. Tickers, valuations, and yields are in Section 10.

5. How the money works

All three children run the same core economics, with different emphasis:

• Revenue ≈ parts (or tons) shipped × negotiated price, plus tooling, machining, coating, and assembly. Iron foundries think in tons and price-per-pound; investment foundries think in parts and price-per-part; heavy-steel foundries quote custom jobs around five components — metal, conversion, engineering and tooling, quality assurance, and value-added machining.[3][4][5]
• High fixed cost, high operating leverage. Furnaces, molding lines, shell rooms, heat treatment, and pollution controls are expensive whether busy or idle, so capacity utilization is the master dial — modest volume swings produce large margin swings. Iron-and-steel-product capacity utilization (a broad proxy, not a foundry-only measure) ran 72.2% in 2025, implying available slack.[3]
• Metal is largely a pass-through; the foundry keeps a conversion margin. Scrap, pig iron, and alloy (nickel, chromium, manganese) content is often passed to customers via surcharges. Aerospace and turbine agreements increasingly add index-linked protection for energy, labor, tariffs, and inflation — but timing, index basis, and fixed-price contracts leave real exposure.[4] Pass-throughs lag everywhere.
• Energy is a first-order cost, and the melt decision is a capital decision. Iron-foundry fuel consumption measured 1,444.6 million Btu per employee and 4.1 thousand Btu per dollar of shipments in 2022. Furnace choice follows: AMERICAN Cast Iron Pipe is spending $285 million through 2029 to replace a cupola with four coreless induction furnaces, expecting 25% more melting capacity and a 50% reduction in on-site greenhouse-gas emissions — but trading combustion exposure for electricity-price and grid exposure.[3]
• Yield and quality are the profit levers. Casting yield (good metal out vs. metal poured) and first-pass/scrap rates decide unit economics; a defect found after pouring, heat treatment, and machining destroys nearly all the cost accumulated to that point, not just the metal.[4][5]
• Stickiness and switching costs — with the bill attached. Patterns, tooling, and customer qualifications make relationships durable; in aerospace and defense, a certified sole-source position is a genuine moat. Doncasters derived roughly 70% of 2025 sales from long-term agreements — and its ten largest customers were 69% of sales, its two largest 38%. The moat and the concentration risk are the same fact.[4]
• Aftermarket smooths the cycle. Replacement/wear parts are higher-margin and steadier than original-equipment volume — at Weir's ESCO division, aftermarket was 94% of 2025 revenue (a company example, not an industry average).[5]

What profitability actually looks like — read the ordering, not the gaps. No audited margin data exists for these NAICS codes themselves, and the three children's best available proxies are measured on incompatible bases, so they cannot be compared decimal-for-decimal:

• Steel investment: Howmet's Engine Products segment ran a 33.3% adjusted EBITDA (earnings before interest, taxes, depreciation, and amortization) margin in 2025 as volumes climbed. Doncasters — primarily superalloy, but the clearest investment-casting disclosure available — reported 2025 gross margin of 23.1% and adjusted EBITDA margin of 16.5%, split 18.0% in its North American aerospace segment, 22.0% in European industrial gas turbines, and just 6.5% in transportation turbo wheels.[4]
• Steel except investment: the only industry-wide figure is a modeled ~4.7% pre-tax profit rate from an OSHA regulatory analysis — a screening estimate, not observed EBITDA.[5] Actual results can be far worse: Ampco-Pittsburgh's casting-related segment posted a $44.7 million operating loss in 2025 on $292.6 million of sales, though $41.4 million of that was a deconsolidation charge and $10.8 million exit charges.[5]
• Iron: Castings plc's £6.378 million of foundry segment profit on £171.746 million of revenue — under 4%, and before other operating income and pension cost.[3]

Even allowing for the incompatible measures, the pattern is hard to miss: margin rises steeply with qualification difficulty and value density, from low-single-digit iron conversion work, through high-single-digit-to-teens heavy steel, to twenties-and-above aerospace precision casting — and the same spread reappears inside the investment child, where Doncasters' turbo-wheel segment earns a third of what its gas-turbine segment does.

Metrics owners and analysts watch across all three: utilization, tons or parts shipped and price, casting yield and scrap/rework, energy and labor cost per ton, on-time delivery, backlog and book-to-bill, long-term-agreement and aftermarket coverage, and maintenance capital. Two of the three children now have a public price read: the producer price index for iron foundries rose roughly 2.6% in the year to May 2026, and steel foundries entered producer-price-index coverage with the February 2025 release.[3][5]

6. Demand drivers

Because the children point at different end markets, the subsector is diversified in aggregate even though each child is cyclical on its own:

• Iron (331511): light and commercial vehicles, agricultural and construction machinery, pumps and compressors, rail, and — steadier — municipal water pipe and castings. EV adoption reduces demand for some engine-block, cylinder-head, and transmission castings but not for brakes, hubs, suspension, chassis, machinery, or water infrastructure; the net effect is plant- and part-mix specific. Infrastructure is the clearest secular support.[3]
• Steel investment (331512): commercial aerospace is the largest single driver (over 45% of global investment-casting demand in 2024), amplified by defense rearmament — Howmet's defense-aerospace revenue rose 21% in 2025 — and by industrial gas turbines pulled up by data-center electricity demand, where Howmet's revenue grew 25%. Medical implant volumes add a steady base.[4]
• Steel except investment (331513): mining and aggregates (crusher and ground-engaging parts, mill liners), rail, steel-mill rolls and slag pots, energy (pumps, valves, turbines, nuclear-qualified parts), and defense. The strongest secular argument here is not volume growth but scarcity of qualified domestic capacity: Defense Department industrial strategy emphasizes resilient capacity and skilled workforce, and the Steel Founders' Society has framed steel-casting capability as a national-security concern — though that last is an industry-advocacy position, not a neutral forecast.[5]

Near-term optimism sits against a long-run decline, and both are in the child evidence. An American Foundry Society survey projects overall casting sales up 4.2% in 2026 — 52% of that from pricing and 48% from tonnage — with 95% of surveyed foundries making capital investments, and 72% of respondents positive on the year.[3][5][15] Over a decade, the Bureau of Labor Statistics projects employment across the broader foundry industry (NAICS 3315, which is wider than this level) falling from 106,000 in 2024 to 90,400 in 2034, a 14.7% decline, with real output slipping from $26.9 billion to $24.8 billion.[5][14] These are not contradictory so much as different horizons: a pricing-led cyclical upswing inside a structurally shrinking, automating, consolidating industry.

Useful leading indicators: vehicle and ag/construction-equipment build rates, aircraft build rates and airline backlogs, defense procurement, mining production and steel-mill capital spending, railcar orders, and interest rates (which drive the rate-sensitive vehicle and equipment cycles).

7. Regulation

Regulation is largely common across all three children, since they run similar high-heat, dusty processes:

• Air emissions. The Environmental Protection Agency (EPA) regulates major iron and steel foundries under the National Emission Standards for Hazardous Air Pollutants (NESHAP), 40 Code of Federal Regulations (CFR) Part 63, Subpart EEEEE; smaller "area sources" fall under Subpart ZZZZZ.[8][9] Controls target particulate matter and hazardous air pollutants (HAPs) — manganese, lead, chromium, nickel, and organics released during melting, molding, and cooling. High-alloy and stainless work raises the chromium and nickel burden.[4] Tighter ambient particulate standards can constrain permits or expansions even when NESHAP limits do not change.[3]
• Worker safety. The Occupational Safety and Health Administration (OSHA) limits respirable crystalline silica from foundry sand: an eight-hour permissible exposure limit (PEL) of 50 micrograms per cubic meter and an action level of 25.[10] Molten metal, heat, noise, grinding, fume, machine guarding, and hazardous-energy control add further obligations.[5]
• Water and waste — with a partial offset. Clean Water Act effluent guidelines cover foundry wastewater; spent sand, baghouse dust, and slag require characterization and disposal or reuse compliance.[5] The reuse channel is real: EPA estimates roughly 2.6 million tons of foundry sand are beneficially used outside foundries each year, with iron, steel, and aluminum sands accounting for 96% of that volume — so spent sand can be a cost or a modest recovery depending on state rules, contamination, and local end markets.[3][11]
• Trade — protective and costly at the same time. As of July 2026, some unfinished cast-steel articles remained subject to an additional 50% Section 232 duty, with other metal products treated differently by tariff classification, origin, and product type.[5][16] Product-specific antidumping and countervailing-duty orders add targeted shelter in individual niches — iron construction castings for the iron child, slag pots from China for the heavy-steel child.[3][5] But the U.S. International Trade Commission found that Section 232 and Section 301 tariffs, while reducing imports and raising U.S. production and prices, left U.S. importers bearing nearly the full tariff cost[5][17] — and duties on castings do not stop imported finished machinery that already contains foreign castings. Verify each product's Harmonized Tariff Schedule treatment rather than assuming uniform protection.

Steel investment carries extra gatekeepers. Aerospace and defense work adds de facto barriers — AS9100 quality certification and Nadcap special-process accreditation, plus program-specific OEM and FAA source qualification — alongside ITAR/EAR export controls and the DFARS specialty-metals clause, which generally requires U.S.-melted specialty metals for defense parts and structurally favors domestic foundries.[4]

8. Consolidation

Consolidation has been real but uneven across the children, and the aggregate HHI of 337.4 understates how concentrated parts of the subsector already are.[6]

• Steel investment (331512) is the most consolidated and still consolidating — and now the change is measurable: from 130 companies with a CR4 of 59.2% and an HHI of 1,662 in 2002 to 84 firms with a CR4 of 73.5% today, with the HHI suppressed.[4] Original-equipment makers prefer fewer, fully qualified suppliers; Berkshire's 2016 PCC purchase (~$37.2 billion) was the defining deal; PE roll-ups (CPP, Signicast) gathered smaller shops into platforms. High qualification, capital, and metallurgical barriers keep new entrants scarce.[4]
• Iron (331511) has seen assets pass among industrial groups, families, and PE sponsors (Waupaca to Monomoy in 2024; Grede to Gamut in 2019; Neenah Enterprises to Charlotte Pipe in 2022), but competition stays regional for freight-heavy municipal products and more national for high-volume vehicle parts. The antitrust ceiling is real: in the 2021 Neenah Enterprises/US Foundry municipal-castings deal, 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.[3]
• Steel except investment (331513) consolidates selectively — and has shrunk more by attrition than by roll-up, from 248 establishments and 16,831 employees in 2002 to 141 and 9,928 today.[5] Plants are hard to relocate, environmental liabilities can be large, and customer qualifications may not transfer, so buyers pursue focused carve-outs (TerraMar's 2025 purchase of Bradken's North American specialty operations) rather than sweeping platforms. Note also that establishment counts are a poor proxy for share here: one company can own several plants, while a single foundry can dominate a narrow casting size or qualification.[5]

Across all three, patterns, tooling, environmental permits, skilled labor, rare furnace and lifting capacity, and customer qualifications are the barriers that protect incumbents and deter new plants.

9. Risks

The children share most risks, differing mainly in which end-market cycle bites:

• Cyclicality: vehicle, ag, mining, rail, oilfield, and aerospace volumes can fall quickly — though the three children's cycles are only partly correlated, giving the aggregate some diversification.
• Fixed-cost leverage: low utilization sharply compresses margins and cash flow. Ampco-Pittsburgh's casting-related segment posted a $44.7 million operating loss in 2025 — mostly a $41.4 million deconsolidation charge plus $10.8 million of exit charges, so read it as evidence that restructuring and plant economics can overwhelm revenue scale rather than as a run-rate loss.[5]
• Input and energy volatility: scrap, alloys, electricity, coke, gas, binders, refractories, and freight can move faster than customer pricing; pass-throughs lag. Even in the best-contracted child, stainless prices eased about 11% across 2025 as nickel oversupplied — volatility cuts both ways on conversion margin.[4]
• Substitution and technology: EV adoption and shifts toward aluminum, forgings, weldments, or fabricated assemblies can strand product-specific iron/steel capacity; metal additive manufacturing is a long-term watch item, already widely adopted for intermediate patterns — complementary today more than substitutive, and least economic as a replacement for ordinary large steel castings.[3][4][5]
• Quality escapes: defects on safety-critical parts trigger scrap, warranty, stoppages, or customer loss; a single defect or furnace interruption can block an OEM's far larger assembly.[4]
• Environmental and safety liabilities — and they are quantified. Old plants carry air-control, waste, remediation, silica, and molten-metal exposure, and every child records injury rates well above the private-industry benchmark of 2.3 recordable cases per 100 full-time workers: iron foundries 5.5 (2024), steel foundries except investment 5.6 with a 3.2 days-away/restricted/transferred rate (2023), and steel investment foundries 4.0 with a 2.4 DART rate (2024).[3][4][5][12][13] Note the mismatched years. The ranking is intuitive — sand molding and heavy handling are more hazardous than lost-wax work — but even the safest child runs roughly 1.7× the private-industry rate.
• Labor: experienced metallurgists, molders, welders, patternmakers, and maintenance techs are hard to replace amid an aging skilled-trades base, and qualification work cannot simply be shifted to inexperienced labor.[4][5]
• Customer concentration: losing one qualified program can idle specialized capacity — Doncasters' two largest customers alone were 38% of 2025 sales.[4]
• Trade volatility: the same tariffs that protect domestic casting pricing raise steel, alloy, refractory, and equipment costs, and importers have historically absorbed most of the duty.[5][17]
• Private-company leverage: sponsor-owned businesses add refinancing and exit-timing risk on top of operating cyclicality.

10. How to invest and outlook

Public routes (all indirect; tickers and figures reserved for here):

Private routes are where most of the industry sits: control or minority stakes, private credit, equipment finance, and sale-leasebacks in the family-, employee-, and PE-owned foundries named in Section 4. Diligence should center on saleable tons rather than melt capacity; utilization by line; normalized yield, scrap, and rework; contribution per mold or machine hour; surcharge and escalator mechanics; customer, program, and end-market concentration; pattern and tooling ownership; qualification-transfer risk; remaining program life; environmental condition and legacy sites; maintenance backlog; union and skilled-labor exposure; and the capital required for melt modernization.

Outlook (forward-looking judgment, not a reported forecast). The three children point in different directions, so a blanket call misleads:

• Steel investment (331512) has the strongest tailwind — record aircraft backlogs, the narrowbody ramp, defense budgets, data-center-driven gas-turbine demand, and Buy-American/DFARS content rules; Howmet guided to roughly $9.1 billion of 2026 revenue, about 10% growth. But the one large-cap proxy already prices in much of that optimism, and the child's own headwinds — skilled labor, energy and alloy volatility, aerospace air-pocket risk — are unresolved.[4]
• Steel except investment (331513) is cautiously positive on defense, mining wear, infrastructure replacement, and trade protection; Ampco-Pittsburgh reported first-half 2026 orders of about $268 million, up 32% from roughly $204 million, with improving North American roll demand. The best assets are plants with recurring replacement demand and hard-to-replicate capability; the weakest are commodity jobbing shops with aging equipment and no pricing power.[5]
• Iron (331511) is the most selective story: municipal-water replacement and domestic-content rules support well-positioned plants, while EV adoption and soft large-equipment/ag demand pressure others. Waupaca's simultaneous closure of a finishing operation and $100 million-plus modernization captures the divide — older or poorly loaded capacity is at risk while efficient plants with durable programs still justify investment.[3]

Net: the best opportunities are plant-specific and child-specific — a qualified precision caster riding aerospace, a heavy-steel foundry with recurring wear-part demand, or an efficient iron plant anchored to water infrastructure — rather than a uniform "ferrous foundry" recovery. Two cautions this level exists to deliver. The subsector's low aggregate HHI should not be mistaken for a level playing field; the money and the moats are unevenly distributed, and the federal data hides that unevenness rather than revealing it. And the near-term casting upcycle sits inside a decade-long projected contraction of the broader foundry base — so the durable returns are more likely to come from taking share in a shrinking, qualification-protected market than from riding volume growth.

Sources

1. U.S. Census Bureau, "2022 NAICS Manual" — definitions and scope rules for Iron Foundries (331511), Steel Investment Foundries (331512), and Steel Foundries except Investment (331513), including the rule classifying establishments that cast and then finish a product under the finished-product industry, 2022. https://www.census.gov/naics/reference_files_tools/2022_NAICS_Manual.pdf
2. Reconciliation of child-industry figures to the level total (269+106+141 = 516 establishments; 32,020+15,144+9,928 = 57,092 employees; $2.316bn+$1.00bn+$0.652bn ≈ $3.97bn annual payroll), and payroll-per-employee derived from those figures, from the child primers below.[3][4][5]
3. Histometrics child primer, "U.S. Iron Foundries (NAICS 331511)," drawing on U.S. Census Bureau County Business Patterns (2023) and 2017 Economic Census data via the Steel Founders' Society of America; Mueller Water Products, Caterpillar, Deere, Air T, and Castings plc filings; Monomoy Capital Partners, Gamut Capital Management, and Charlotte Pipe transaction releases; Waupaca Foundry, McWane, AMERICAN Cast Iron Pipe, and Grede company sources; U.S. Energy Information Administration Manufacturing Energy Consumption Survey (2022); Federal Reserve Bank of St. Louis capacity-utilization and producer-price series; U.S. International Trade Commission and Department of Justice sources; EPA and OSHA sources.
4. Histometrics child primer, "Steel Investment Foundries (NAICS 331512)," drawing on U.S. Census Bureau 2022 Economic Census concentration ratios, 2002 Economic Census concentration data, and County Business Patterns (2023); Howmet Aerospace results; Doncasters (DPC Holdings) IPO and SEC filings; Berkshire Hathaway/Precision Castparts; Warburg Pincus and Berkshire Partners (CPP); Impro Precision results; Grand View Research investment-casting market study; Investment Casting Institute; EPA, OSHA, and BLS sources.
5. Histometrics child primer, "U.S. Steel Foundries, Except Investment (NAICS 331513)," drawing on U.S. Census Bureau County Business Patterns (2023) and the 2002 Economic Census; an OSHA final economic analysis (modeled firm count, revenue, and profit rate); Ampco-Pittsburgh and The Weir Group filings; Amsted, WHEMCO, Bradken/TerraMar, Harrison Steel, Eagle Alloy, Stainless Foundry, and American Steel Castings sources; Steel Founders' Society of America and Department of Defense industrial-base sources; BLS producer-price, injury, and employment-projection data; EPA, OSHA, White House, and U.S. International Trade Commission sources.
6. Histometrics ground-truth federal statistics, NAICS 33151: U.S. Census Bureau County Business Patterns (2023) — establishments, employment, payroll; U.S. Census Bureau 2022 Economic Census — receipts, firm count, and concentration ratios (CR4 29.1%, CR8 46.3%, CR20 63.8%, CR50 78.5%, HHI 337.4). https://www.census.gov/programs-surveys/cbp.html
7. U.S. Small Business Administration, "Table of Small Business Size Standards," 2023. https://www.sba.gov/document/support-table-size-standards
8. U.S. Environmental Protection Agency, "Iron and Steel Foundries: NESHAP for Major Sources (40 CFR Part 63, Subpart EEEEE)," 2026. https://www.epa.gov/stationary-sources-air-pollution/iron-and-steel-foundries-national-emissions-standards-hazardous
9. U.S. Environmental Protection Agency, "Iron and Steel Foundries: NESHAP for Area Sources (Subpart ZZZZZ)," 2026. https://www.epa.gov/stationary-sources-air-pollution/iron-and-steel-foundries-national-emission-standards-hazardous-air
10. Occupational Safety and Health Administration, "Respirable Crystalline Silica — General Industry and Maritime," current. https://www.osha.gov/silica-crystalline/general-industry-maritime
11. U.S. Environmental Protection Agency, "Beneficial Uses of Spent Foundry Sands," 2026. https://www.epa.gov/smm/beneficial-uses-spent-foundry-sands
12. U.S. Bureau of Labor Statistics, "Survey of Occupational Injuries and Illnesses: Industry Rates," 2024 (iron foundries 5.5; steel investment foundries 4.0 with 2.4 DART; private industry 2.3). https://www.bls.gov/web/osh/table-1-industry-rates-national.htm
13. U.S. Bureau of Labor Statistics, "Injury and Illness Rates by Industry, 2023" (steel foundries except investment 5.6, with 3.2 days away, restricted, or transferred). https://www.bls.gov/iif/nonfatal-injuries-and-illnesses-tables/table-1-injury-and-illness-rates-by-industry-2023-national.htm
14. U.S. Bureau of Labor Statistics, "Industry Employment and Output Projections" (NAICS 3315 foundries, 2024–2034), current. https://www.bls.gov/emp/tables/industry-employment-and-output.htm
15. 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
16. The White House, "Further Adjusting the Tariff Regimes for Imports of Aluminum, Steel and Copper into the United States," 2026. https://www.whitehouse.gov/presidential-actions/2026/06/further-adjusting-the-tariff-regimes-for-imports-of-aluminum-steel-and-copper-into-the-united-states/
17. U.S. International Trade Commission, "Economic Impact of Section 232 and Section 301 Tariffs," current. https://www.usitc.gov/keywords/301_tariffs