NAICS 331511 Quarterly Industry Report
Iron Foundries
Comprehensive industry research for valuation professionals, business owners, buyers, and lenders
NAICS Code: 331511Sector: 33Updated: Q1 2026
About This Report
This industry profile for Iron Foundries (NAICS 331511) draws on data from the U.S. Census Bureau[6], Bureau of Labor Statistics[10], and SBA size standards database[7]. Published by Fair Market Value and updated quarterly, it provides valuation professionals, metals casting analysts, and foundry sector investors with current market data. All quantitative claims are sourced to publicly verifiable databases.
Industry Snapshot
Key metrics for the iron foundries industry.
Industry Definition & Overview
Iron Foundries (NAICS 331511) encompasses establishments primarily engaged in pouring molten pig iron or iron alloys into molds to manufacture castings per the U.S. Census Bureau[5]. Activities include gray iron casting production, ductile iron casting manufacturing, austempered ductile iron processing, sand mold preparation and pouring, shell mold casting, centrifugal casting of iron pipe, and iron casting heat treatment operations. Iron foundries produce castings for automotive powertrain components, municipal water and sewer pipe, industrial machinery bases and housings, agricultural equipment parts, and construction hardware. Gray iron castings offer vibration damping and machinability for engine blocks, brake rotors, and machine tool beds, while ductile iron provides tensile strength and impact resistance for crankshafts, gears, and structural components. Waupaca Foundry operates as the largest independent iron foundry in the world, producing millions of castings annually from multiple Wisconsin facilities. Sand casting remains the dominant production method, with green sand and chemically bonded sand mold systems handling the majority of production volume. Per Census Bureau[6] data, iron foundries serve a diverse customer base where automotive and truck component casting represents the largest single end market by volume and revenue. Based on the SBA Table of Size Standards[7], the size standard is 1,000 employees. The EPA[8] regulates hazardous air pollutant emissions from melting, pouring, and sand handling operations under NESHAP standards for iron and steel foundries. OSHA[9] enforces respirable crystalline silica exposure limits, heat stress prevention protocols, and molten metal handling safety requirements in foundry production environments.
What's Included in This Industry
- Gray iron casting production
- Ductile iron casting manufacturing
- Austempered ductile iron processing
- Sand mold preparation and pouring
- Shell mold casting operations
- Centrifugal iron pipe casting
- Iron casting heat treatment
- Pattern making and core production
- Casting cleaning and finishing
- Iron casting machining services
NAICS Classification Hierarchy
| Level | Description | Code |
|---|---|---|
| Subsector | Primary Metal Manufacturing | 331 |
| Industry Group | Foundries | 3315 |
| NAICS Industry | Ferrous Metal Foundries | 33151 |
| National Industry | Iron Foundries | 331511 |
Related NAICS Codes
| Code | Description | Relationship |
|---|---|---|
| 331512 | Steel Investment Foundries | Steel Investment Foundries produces precision steel castings through lost-wax processes that complement iron foundry sand casting with higher-tolerance components for aerospace, medical, and industrial applications |
| 331513 | Steel Foundries (except Investment) | Steel Foundries produces steel castings through sand and other conventional methods that parallel iron foundry operations in process equipment, melting technology, and end-market customer bases |
| 331110 | Iron and Steel Mills and Ferroalloy Manufacturing | Iron and Steel Mills and Ferroalloy Manufacturing produces pig iron and ferroalloys that iron foundries purchase as charge materials for cupola and electric induction furnace melting operations |
| 331524 | Aluminum Foundries (except Die-Casting) | Aluminum Foundries operates nonferrous casting operations using sand and die casting methods that compete with iron castings in automotive and industrial applications where weight reduction drives material substitution |
| 336310 | Motor Vehicle Gasoline Engine and Engine Parts Manufacturing | Motor Vehicle Gasoline Engine and Engine Parts Manufacturing purchases iron castings for engine blocks, cylinder heads, crankshafts, and brake components representing the largest single end market for iron foundry production output |
| 333120 | Construction Machinery Manufacturing | Construction Machinery Manufacturing consumes heavy iron castings for loader buckets, excavator counterweights, and machinery housings where gray and ductile iron provide mass, wear resistance, and vibration damping properties |
Geographic Concentration
Top states by share of national establishments.
| # | State | % Est. | Total Est. |
|---|---|---|---|
| 1 | Wisconsin | 12.6% | 33 |
| 2 | Ohio | 11.5% | 30 |
| 3 | Indiana | 8.8% | 23 |
| 4 | Michigan | 8.8% | 23 |
| 5 | Pennsylvania | 8.1% | 21 |
| 6 | Alabama | 6.1% | 16 |
| 7 | California | 5.4% | 14 |
| 8 | Minnesota | 5.0% | 13 |
| 9 | Texas | 3.8% | 10 |
| 10 | Illinois | 3.5% | 9 |
% Of Establishments
0%
13%
Source: County Business Patterns, U.S. Census Bureau[3]
SBA Lending Summary
32
Total SBA Loans
$56.1M
Total Loan Volume
$1.8M
Average Loan Size
9 yrs
Average Loan Term
7.89%
Average Interest Rate
1,056
Jobs Supported
Source: SBA 7(a) Program Data, U.S. Small Business Administration — FY 2025[4]
Key Insight: Per the SBA Table of Size Standards[7], Iron Foundries (NAICS 331511) has a size standard of 1,000 employees for federal small business contracting purposes. SBA lending programs[11] support qualifying iron foundry operations including melting equipment, molding lines, emission control systems, and facility modernization investments. Eligible businesses can access SBA 7(a) loans[12] for working capital, equipment, and acquisition financing, while 504 loans[13] support major fixed-asset purchases including real estate and heavy machinery.
Top SBA Lenders
| # | Lender | Loans | Volume | Avg Loan |
|---|---|---|---|---|
| 1 | Availa Bank | 16 | $36.9M | $2.3M |
| 2 | Newtek Bank, National Association | 8 | $18.4M | $2.3M |
| 3 | Unity Bank | 8 | $800K | $100K |
Frequently Asked Questions
Common questions about this industry.
What is the NAICS code for iron foundries?
NAICS 331511 covers iron foundries that pour molten iron or iron alloys into molds to manufacture gray iron, ductile iron, and other ferrous castings per the U.S. Census Bureau[5].
What is the SBA size standard?
Per the SBA size standard[7], the threshold is 1,000 employees for federal small business contracting eligibility and SBA lending products for iron foundry operations.
What is the difference between gray iron and ductile iron?
Gray iron contains graphite flakes providing vibration damping and machinability, while ductile iron contains nodular graphite providing tensile strength and impact resistance per Bureau of Labor Statistics[10] product classification.
Who is the largest U.S. iron foundry?
Waupaca Foundry operates as the largest independent iron foundry globally per Census Bureau[6] establishment data, producing gray iron, ductile iron, and austempered ductile iron castings from multiple facilities in Wisconsin.
What is the largest end market?
Automotive and truck component casting represents the largest single end market per Census Bureau[6] shipment data, with engine blocks, cylinder heads, brake rotors, and crankshafts accounting for major production volume.
What environmental regulations apply?
The EPA[8] enforces National Emission Standards for Hazardous Air Pollutants under 40 CFR Part 63 Subpart ZZZZZ for iron and steel foundries, regulating particulate, organic, and metallic emissions from melting and pouring operations.
What is sand casting?
Sand casting packs chemically bonded or clay-bonded sand around a pattern to create mold cavities, which receive molten iron poured from ladles per Census Bureau[6] process classification. Green sand molding remains the most common production method by volume.
What safety hazards exist in foundries?
OSHA[9] identifies respirable crystalline silica exposure from sand handling, heat stress from molten metal proximity, burn hazards from pouring operations, and noise exposure from shakeout and cleaning as primary foundry workplace hazards.
Sources & References
Government datasets and editorial sources used in this report.
- [1]U.S. Bureau of Labor Statistics, Quarterly Census of Employment and Wages bls.gov
- [2]U.S. Census Bureau, Economic Census census.gov
- [3]U.S. Census Bureau, County Business Patterns census.gov
- [4]U.S. Small Business Administration, SBA 7(a) Loan Program Data data.sba.gov
- [5]U.S. Census Bureau census.gov
- [6]Census Bureau data.census.gov
- [7]SBA Table of Size Standards sba.gov
- [8]EPA epa.gov
- [9]OSHA osha.gov
- [10]Bureau of Labor Statistics bls.gov
- [11]SBA lending programs sba.gov
- [12]SBA 7(a) loans sba.gov
- [13]504 loans sba.gov
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