Gunmetal Casting Foundry

Gunmetal is a copper-tin-zinc alloy family encompassing leaded gunmetal (LG grades: LG1, LG2, LG4), unleaded gunmetal (G grades), and high-tin gunmetal grades, all conforming to BS 1400, EN 1982, ASTM B584, and DIN 1705 international standards. Historically named for its original use in cannon manufacture, gunmetal today is a critical engineering material for pressure-retaining castings in fluid service. Brass & Copper Parts operates a dedicated gunmetal casting foundry producing sand castings, centrifugal castings, and investment castings in standard grades LG2 (C83600), LG4 (C83800), G1 (C90500), AB1, and custom compositions for valve manufacturers, pump OEMs, marine engineering, power generation, and general engineering customers worldwide.

Product Overview

Gunmetal castings combine the pressure tightness and machinability of leaded alloys with the corrosion resistance and mechanical reliability of tin-bronze compositions. The Brass & Copper Parts gunmetal casting foundry handles the complete casting production chain from pattern manufacture, mold preparation, melt chemistry control, casting, fettling, heat treatment (where required), machining, NDT, and pressure testing to final inspection and certification. Our foundry is equipped for both low-volume prototype casting (1–5 pieces) and series production (500–10,000 pieces per year), with rapid pattern manufacture capability for new component introductions. Casting weights from 50 grams to 500 kilograms are accommodated across all gunmetal grades.

Key Features

• Full gunmetal alloy range – LG1, LG2, LG4, G1, G3, AB1, and custom alloy grades available
• Pressure-tight castings – Hydrostatic tested to PN10, PN16, PN25 ratings as applicable
• In-house pattern shop – Rapid pattern manufacture for new components, pattern storage for repeat orders
• Complete machining capability – CNC turning, milling, boring, and grinding for finished components
• Full material certification – EN 10204 Type 3.1 certificates with every heat
• Classification society capability – Marine castings approved by DNV, Lloyd’s Register, Bureau Veritas, ABS
• Global export experience – Supply to UK, USA, Germany, Australia, UAE, Singapore from India

Technical Specifications – Gunmetal Alloy Grades

International Grade Equivalents

Product Types and Variants

Gunmetal Sand Castings for Industrial Valves

Gunmetal LG2 and LG4 are the industry-standard materials for industrial valve bodies, bonnets, gland nuts, and stuffing box components in water, steam, gas, and compressed air service. Sand cast gunmetal valve bodies are produced from ½” (DN15) to 12″ (DN300) nominal bore, conforming to BS EN 1982, ASTM B584, and BS 1400 material specifications. End-connection patterns for BSP, NPT, and flanged (PN10/16, ANSI Class 150/300) configurations are maintained in our pattern library. Brass & Copper Parts manufactures and machines gunmetal valve bodies to finished condition, including seat lapping, thread cutting, and hydrostatic testing per BS EN 12266 or API 598, delivering valve-ready castings for assembly with trim components.

Gunmetal Pump Castings

Gunmetal pump bodies, impellers, back covers, and bearing brackets for horizontal and vertical centrifugal pumps handling freshwater, seawater, industrial chemicals, and fire water are a core product of the Brass & Copper Parts foundry. Pump castings are produced in LG2 (C83600) for general water service, LG4 (C83800) for higher-pressure or slightly more aggressive fluid service, and G1 (C90500/PB2) for pump components requiring improved wear resistance. Casting weights range from 0.3 kg (small submersible pump parts) to 300 kg (large industrial centrifugal pump volutes). Pump castings are supplied as rough castings, semi-machined to bore and flange, or fully machined and balanced impellers per customer drawings and pump hydraulic design specifications.

Gunmetal Marine Castings

Marine gunmetal castings for hull fittings, propulsion, and deck hardware are produced at Brass & Copper Parts with classification society material approval for vessels certified by DNV, Lloyd’s Register, Bureau Veritas, ABS, and RINA. Marine gunmetal castings include sea chest flanges, seacocks, through-hull fittings, propeller shaft stern tube bearings, tiller heads, bollard bases, capstan housings, and anchor chain stopper components. Material grades LG2 (C83600) and G1 (C90500) are specified for different marine applications depending on seawater exposure intensity and mechanical load requirements. All marine castings are supplied with foundry material certificates conforming to the relevant classification society type approval requirements.

Gunmetal Centrifugal Castings for Bearing and Sleeve Applications

Centrifugal casting of gunmetal alloys produces cylindrical rings, bushings, bearing sleeves, and hollow cylinders with superior density and mechanical integrity compared to static sand castings. G1 (C90500) and LG4 (C83800) centrifugal cast rings are used for pump shaft bearing sleeves, hydraulic cylinder guide rings, stern tube bearing liners, and worm gear bearing bushings. The dense, porosity-free microstructure achievable through centrifugal casting improves load capacity and extends service life compared to equivalent static castings. Brass & Copper Parts operates vertical and horizontal centrifugal casting machines producing gunmetal rings in OD from 50 mm to 700 mm, wall thicknesses from 8 mm to 120 mm, and lengths up to 1200 mm.

Investment Cast Gunmetal Precision Components

Investment casting of gunmetal alloys (LG2, G1, G3) produces intricate near-net-shape components for valve internals, instrument housings, manifold bodies, specialty fittings, and precision mechanical assemblies. Investment cast gunmetal achieves surface finish Ra 1.6–6.3 μm and dimensional tolerance CT5–CT7 (ISO 8062-3), enabling significant reduction in secondary machining versus sand cast components of equivalent complexity. This process is well-suited for small, complex gunmetal components (5 grams to 2 kg) in batch sizes of 50 to 50,000 pieces per year. Brass & Copper Parts offers wax tooling design and manufacture, ceramic shell investment casting, and CNC finishing as an integrated service for investment cast gunmetal components.

Custom Alloy Gunmetal Castings to Specification

Beyond standard BS and ASTM gunmetal grades, Brass & Copper Parts casts gunmetal components to proprietary customer alloy specifications, defense material standards (DEF STAN 02-834), classification society type-approved alloys, and legacy British Admiralty specifications (DTD, BA grades). Custom alloy development services are available for applications requiring specific combinations of corrosion resistance, strength, machinability, or conductivity not achievable with standard commercial grades. Each custom alloy melt is verified by optical emission spectrometry (OES) against the specified composition limits before pouring, and mechanical test coupons are cast integrally with the production casting for destructive tensile and hardness testing.

Applications by Industry

Manufacturing Process

The Brass & Copper Parts gunmetal foundry operates coreless induction furnaces in 250 kg and 500 kg capacities for melting all gunmetal grades. Charge materials — copper cathode, tin ingot, zinc ingot, lead ingot, and returns — are weighed by electronic load cell scales accurate to ±0.1 kg. Melt chemistry is verified by optical emission spectrometer (OES) during the melt stage, with correction additions made before pouring approval. Pattern storage exceeds 500 active wooden and aluminum patterns for valve, pump, and marine casting geometries, enabling same-week mold preparation for repeat orders. No-bake (furan resin) sand system is used for dimensional accuracy on machined surfaces; green sand is used for high-volume production casting runs. Post-casting operations include vibratory fettling, shot blasting to Sa 2.5 cleanliness, dimensional inspection to drawing, 100% spectrometric analysis per heat, and hydrostatic pressure testing per specification.

Quality Standards and Certifications

• BS 1400 (LG1, LG2, LG4, G1, G3) – British standard for gunmetal castings
• ASTM B584 (C83600, C83800, C90500, C92200) – American standard for copper alloy sand castings
• EN 1982 (CC491K, CC492K, CC480K, CC493K) – European copper alloy casting standard
• DIN 1705 – German standard for gunmetal and tin bronze castings
• IS 318 – Indian standard for copper alloy castings
• ISO 9001:2015 – Quality management system certification
• DNV / Lloyd’s Register / Bureau Veritas / ABS – Marine casting type approvals
• EN 10204 Type 3.1 – Material test certificates with every heat

Why Choose Brass & Copper Parts Gunmetal Foundry

Brass & Copper Parts is a full-service gunmetal casting foundry with in-house pattern making, melting, casting, machining, pressure testing, and certification capabilities under one roof. This integrated approach eliminates supply chain complexity for valve and pump OEM customers who require machined, tested, and certified castings ready for assembly. Our pattern library of over 500 active casting patterns enables rapid delivery of repeat components. Technical support from our foundry engineers covers alloy selection, casting geometry optimization, dimensional tolerance feasibility, and post-casting processing recommendations for new product introductions. We export to over 25 countries with full documentation including EN 10204 3.1 certificates, classification society certificates, packing lists, CITES-compliant origin declarations, and customs-ready export documentation.

Frequently Asked Questions

What is gunmetal and how does it differ from bronze?

“Gunmetal” refers specifically to copper-tin-zinc alloys (typically BS 1400 LG or G grades), while “bronze” is a broader term for any copper-tin alloy family. In commercial practice, gunmetal usually implies leaded copper-tin-zinc grades (LG2, LG4) used for castings, whereas “bronze” may refer to unleaded tin bronze (C90500, C90700), phosphor bronze, or aluminum bronze. The distinction is primarily historic and commercial — both are copper alloy castings and are often used interchangeably in specifications.

Which gunmetal grade should I specify for a water service gate valve?

For standard potable water or industrial water service gate valves (PN10/PN16), LG2 (C83600, CC491K) is the standard specification. For higher tin content and improved bearing properties in pump service, LG4 (C83800) or G1 (C90500) is preferred. For potable water contact compliance (NSF/ANSI 61), a lead free grade must be specified — standard LG2 contains 4–6% lead and is not NSF 61 compliant. Brass & Copper Parts can advise on appropriate alloy selection for specific service conditions.

What is the maximum casting weight your foundry can produce?

Brass & Copper Parts’ gunmetal foundry handles casting weights from 50 grams (precision investment castings) to 500 kilograms (large sand castings for pump casings, mooring hardware, and industrial valve bodies). For castings above 500 kg, we partner with specialist heavy copper foundries. Most standard valve and pump castings fall in the 0.1–100 kg range, which is our highest-efficiency production zone.

How long does it take to produce a new gunmetal casting from drawing?

For new castings requiring new pattern equipment: 4–6 weeks for pattern manufacture + 2–3 weeks for first casting and approval = 6–10 weeks total to first approved casting. For repeat castings from existing patterns: 3–5 weeks production lead time from order confirmation. Investment castings (new wax tooling): 5–8 weeks to first samples. Rush delivery services are available at premium for urgent project or maintenance requirements.

Do you carry stock of common gunmetal castings?

Brass & Copper Parts maintains inventory of commonly requested standard valve body and pump body castings in LG2 (C83600) for ½” to 4″ gate valve, globe valve, and check valve bodies, enabling off-the-shelf delivery for urgent requirements. Custom and non-standard castings are produced to order. Contact our sales team for current stock availability and pricing for standard valve casting sizes.

Can gunmetal castings be repaired by welding?

Yes. LG2 and LG4 gunmetal castings can be weld-repaired using GTAW (TIG) or GMAW (MIG) with ERCuSn-A or matching gunmetal filler wire. Pre-heat to 100–150°C prevents thermal cracking in thicker sections. Weld repair acceptability for pressure-retaining castings requires re-testing (hydrostatic) and may require classification society or quality plan approval for marine or critical-service applications. Brass & Copper Parts provides welding repair services for casting defect remediation with full documentation.

What surface finish do gunmetal sand castings typically achieve?

As-cast sand castings achieve surface finish Ra 12.5–25 μm (N10–N11) depending on sand system and pouring conditions. Shot-blasted finish is approximately Ra 6.3–12.5 μm. CNC-machined surfaces achieve Ra 0.8–3.2 μm depending on operation type and tooling. Ground surfaces achieve Ra 0.4–0.8 μm. Investment cast gunmetal achieves as-cast Ra 1.6–6.3 μm without secondary finishing.

What is the typical dimensional tolerance for gunmetal sand castings?

Gunmetal sand castings conform to CT8–CT10 (ISO 8062-3 / DCTG 8–10 per ASTM A802) for as-cast dimensions, depending on casting size and geometry. Post-casting CNC machining achieves tolerances of ±0.05 to ±0.25 mm on critical dimensions including bore diameters, face-to-face lengths, and flange hole pitch circles. Tight tolerance features such as bearing bores and valve seat diameters are machined to IT7 or better as standard.

Do you supply gunmetal castings with classification society certificates for marine vessels?

Yes. Brass & Copper Parts holds manufacturing facility approval with DNV and Lloyd’s Register for gunmetal casting production under foundry approval conditions. Marine gunmetal castings for seawater service, hull fittings, and propulsion components are supplied with individual cast-unit certificates referencing the applicable classification society type approval. Additional survey and witness requirements by the relevant classification society surveyor can be accommodated at our foundry facility.

What is the difference between LG2 and G1 gunmetal for pump impellers?

LG2 (C83600) contains 5% tin, 5% zinc, and 5% lead, making it more machinable and pressure-tight but softer (60–85 HB). G1 (C90500) contains 9–11% tin with 1–3% zinc and minimal lead — higher tin provides greater hardness (70–90 HB) and improved wear and cavitation resistance. For pump impellers handling sandy or erosive fluids, G1 is preferred over LG2 due to better erosion resistance. For valve bodies handling clean water, LG2 is the standard choice due to its superior pressure tightness and machinability.

Request a Quote from Our Gunmetal Foundry

Brass & Copper Parts is an experienced gunmetal casting foundry supplying valve, pump, marine, and general engineering castings in all standard and custom alloy grades. Send us your drawings, alloy grade, quantity, and delivery requirements for a comprehensive technical and commercial proposal.

Contact us: sales@brass-copper-parts.com | +91-22-43449300