High-Performance Bronze Investment Casting: NAB, Aluminium Bronze, Silicon Bronze, Tin Bronze, Phosphor Bronze and CuNi

The Bottom Line

• Bronze investment casting isn't one material - it's four distinct alloy families (aluminium bronze, silicon bronze, tin bronze/gunmetal, and copper-nickel), each with its own grades, standards, and service envelope.

  
  

• Aluminium bronze alone spans nine ASTM grades, from general-purpose C95400 to the marine-standard C95800 to the aerospace-grade C95520, with properties driven almost entirely by aluminium content, nickel addition, and heat treatment condition. Specifying "bronze" or even "aluminium bronze" without the grade number and heat treatment condition is not a real specification.

• Grade selection is a service-environment decision, not a cost decision - the savings from under-specifying a grade disappear the moment the part fails in service.

  
  

• Heat treatment condition matters as much as the grade number - C95800 in seawater service and C95520 for its rated strength both require it explicitly stated on the purchase order, since as-cast supply is a specification error for both.

  
  

• Beyond aluminium bronze, silicon bronze, tin bronze/gunmetal, and copper-nickel each have a genuine, non-overlapping service niche - field-weldable corrosion resistance, wear/bearing duty, and long-life seawater piping respectively.

Nine Grades of Aluminium Bronze for Lost Wax Casting

Each grade in the aluminium bronze family is defined by its aluminium content and by its iron and nickel additions, which together determine where the grade sits on the strength-corrosion resistance-heat treatment spectrum. The grade selection decision is a service environment decision, not a cost decision. The material saving from specifying C95400 where C95800 is required disappears entirely when the casting fails in service and must be replaced.

C95200 - Cast Aluminium Bronze

C95200 - approximately 9% aluminium, iron addition for grain refinement, no nickel - is the entry point of the aluminium bronze family. Its value is in castability: good fluidity, predictable shrinkage, and a low tendency toward hot cracking make it the most straightforward grade to cast with consistent quality.

Yield strength in the as-cast condition is approximately 140 MPa, and corrosion resistance is adequate for general industrial service in non-aggressive environments - bearings, bushings, and wear parts in dry or mildly corrosive conditions.

What C95200 cannot do is protect itself reliably in seawater or high-chloride environments. The alloy lacks the nickel that stabilises the kappa phase and makes the protective oxide film coherent under sustained aggressive attack. Specifying C95200 for seawater service to save material cost is a decision that typically results in premature failure through dealuminification - a failure mode discussed in detail below. European equivalent: CC330G under EN 1982.

C95200's high ductility as-cast also makes it the grade most sensitive to a different, process-level defect: oxide bifilms entrained during turbulent mould filling. Because C95200 is specified partly for its 20% elongation potential, a casting that comes back from testing with poor or scattered elongation results despite meeting tensile spec is showing a casting-process defect, not a metallurgical shortfall - covered in detail in why your aluminium bronze casting is failing mechanical testing.

C95300 - High-Strength Aluminium Bronze

C95300 (approximately 10% Al, 0.8-1.5% Fe) is the least discussed grade in the aluminium bronze family, which is a missed opportunity - because when heat-treated to the TQ50 temper, it delivers yield strength of approximately 310 MPa at a cost point below the nickel-bearing grades. Bearing segments for the steel industry, cams, mining machine components, high-strength clamps, and electrical connectors are the primary applications.

The critical point for buyers: as-cast C95300 does not deliver these properties. A purchase order without a specified heat treatment condition will result in a casting at roughly half the grade's strength potential. European designation: CC331G (EN 1982); DIN: G-CuAl10Fe3.

C95400 - Aluminium Bronze Bearing Alloy (AB1)

C95400 (approximately 10.5% Al, 3-5% Fe) is the most widely cast aluminium bronze grade. Known in British and European specifications as the AB1 equivalent under BS 1400, it delivers reliable yield strength of approximately 205 MPa as-cast, rising with annealing, at a cost and castability point that makes it the default choice for general industrial applications.

Pump bodies, valve housings, butterfly valve discs and stems, gear blanks, bearing sleeves, and fluid-handling components across chemical processing and heavy engineering are the core C95400 market.

The mistake buyers make with C95400 is treating it as a universal aluminium bronze. It is excellent in its range - general industrial service, moderate corrosion environments, wear and strength requirements. It is not adequate for continuous seawater immersion or high-chloride environments.

Upgrading to C95500 or C95800 for seawater applications is not a luxury - it is what prevents dealuminification. European designation: CC331G (EN 1982); DIN: G-CuAl10Fe3.

C95500 and C95520 - Nickel Aluminium Bronze

The nickel addition in C95500 (approximately 11% Al, 3-5.5% Ni, 3-5% Fe) does two things simultaneously: it raises yield strength to approximately 275 MPa as-cast, and it meaningfully improves the alloy's resistance to dealuminification in moderately aggressive environments.

The nickel stabilises the kappa phase and makes the protective oxide film more coherent under sustained chloride attack. C95500 is the correct choice when C95400 is borderline on strength or when the service environment is more aggressive than general industrial conditions but does not require the full seawater specification of C95800. European designation: CC332G (EN 1982). The full comparison between C95500 and C95800 - composition, ASTM B148 property minimums, and which grade to specify for which service condition - is covered in nickel aluminium bronze investment casting grades: C95500 vs C95800.

C95520 - designated AMS 4881 in aerospace and defence procurement - is the high-performance heat-treated variant of the C95500 family, and it occupies a different category entirely. Solution treated and tempered, it achieves yield strengths above 480 MPa - comparable to medium-carbon steel - while retaining the corrosion resistance and low magnetic permeability of the nickel aluminium bronze family.

Developed for aircraft landing gear bushings and bearings, it has extended into BOP components, high-pressure oil and gas fittings, and heavy-load defence bearings. There is one rule for C95520: specifying it without a heat treatment condition is a meaningless specification. The properties are entirely a product of the solution treatment and temper cycle. C95520 doesn't carry a single, universally-cited EN 1982 designation the way C95500 and C95800 do - CC333G is the EN equivalent most consistently associated with C95800 specifically, so European buyers specifying C95520-equivalent performance should confirm the closest CC designation by composition and heat-treated properties directly with the foundry rather than assuming a one-to-one standard cross-reference.

C95600 - Silicon Nickel Aluminium Bronze

C95600 takes a different approach to the aluminium bronze composition: rather than high aluminium with iron and nickel additions, it uses a silicon addition (approximately 6% Si, 7% Al) that improves castability and machinability while maintaining useful corrosion resistance.

The result is a grade well-suited to components that are difficult to cast or machine in the higher-strength grades - cable connectors, terminals, valve stems, gears, and worm drives in electrical and industrial applications. C95600 is not a marine or high-corrosion grade; its protective film is less robust than the nickel-bearing grades in aggressive seawater, and it should not be specified where C95500 or C95800 properties are required. It also shouldn't be confused with the separate silicon bronze alloy family covered later in this guide - C95600 is an aluminium bronze with a silicon addition, not a true silicon bronze.

C95700 - Manganese Nickel Aluminium Bronze

C95700 (approximately 8% Al, 11-14% Mn, 1.5-3% Ni, 2-4% Fe) is the high-manganese variant of the nickel aluminium bronze family. Understanding why manganese is present requires a brief metallurgical note: in aluminium bronze, six percent manganese is metallurgically equivalent to one percent aluminium in its strengthening effect.

The high manganese content acts as a beta phase stabiliser and strengthener, producing yield strengths of approximately 310 MPa as-cast in a grade that is less sensitive to section thickness variation than the higher-aluminium grades. C95700 occupies a similar application space to C95800 for heavy-duty pump impellers, marine hardware, and valve bodies in moderately aggressive environments where maximum strength is the primary driver and the full seawater corrosion resistance of C95800 is secondary.

C95800 - Marine Nickel Aluminium Bronze (AB2)

C95800 (approximately 9% Al, 4-5.5% Ni, 3-5% Fe, 0.8-1.5% Mn) is the grade that defines what aluminium bronze can do at its best. Known as AB2 under BS 1400 and CC333G (CuAl10Ni5Fe4-C) under EN 1982, produced to MIL-B-24480 for naval applications - it is the standard material for marine hardware, seawater pump internals, offshore valve bodies, naval components, and industrial fire suppression systems, and it is essentially irreplaceable in those applications.

What makes C95800 the marine standard is not any single property but the combination: superior seawater corrosion resistance exceeding C95500, cavitation erosion resistance that protects pump impellers and propellers under high-velocity flow, biofouling resistance - the biostatic surface deters barnacle and algae attachment without coatings - and magnetic permeability below 1.05, which makes it the naval standard for sonar housings, mine countermeasure vessels, and submarine hardware. C95800 must be heat-treated for seawater service - this is discussed in detail in the section below.

C95800's total-cost case against sand casting - machining allowance, NDT rejection rate, and rework cost - is covered in nickel aluminium bronze investment castings cost advantage, and how it compares directly against duplex stainless steel for seawater service - on cost, weight, and proven track record - is covered in NAB vs duplex stainless steel for seawater service.

C95900 - Manganese Aluminium Bronze

C95900 has the highest aluminium content of the standard casting grades - approximately 11-12% Al with 4-5.5% Fe - producing maximum hardness and wear resistance in the aluminium bronze family, with as-cast yield strengths approaching 380 MPa. The high aluminium content requires careful heat treatment to avoid retained beta phase, which reduces toughness. Applications are dominated by wear resistance requirements: forming dies, heavy wear plates, tooling components, and parts subject to abrasive wear where the alloy's extreme hardness is the primary selection driver.

Grade Comparison - US, British and European Designations

The table below cross-references all nine ASTM aluminium bronze grades with their British (BS 1400), European (EN 1982), and common name equivalents, together with typical as-cast yield strength and heat treatment requirement, for quick orientation across the family. These are typical figures, not a substitute for the full ASTM B148 minimum property table for the specific grade and temper being ordered - always confirm exact minimum tensile, yield, and elongation requirements against the current B148 revision on the purchase order itself.

UNS Grade	BS 1400	EN 1982	Common Name	Al %	Ni %	Yield As-Cast	Heat Treatment
C95200	-	CC330G	Cast Aluminium Bronze	~9	-	~140 MPa	Optional - anneal for stress relief
C95300	-	CC331G	High-Strength Al Bronze	~10	-	~170 / 310 MPa (TQ50)	Recommended - TQ50 for full strength
C95400	AB1	CC331G	Al Bronze Bearing Alloy	~10.5	-	~205 MPa	Recommended - annealed standard supply
C95500	-	CC332G	Cast NAB	~11	~4	~275 MPa	Recommended - anneal or solution treat
C95520	-	see note above	High-Perf. NAB (AMS 4881)	~11	~5	>480 MPa (HT)	Mandatory - solution treat + temper
C95600	-	-	Silicon NAB	~7Al/6Si	-	~205 MPa	Optional
C95700	-	-	Manganese NAB	~8	~2	~310 MPa	Recommended
C95800	AB2	CC333G	Marine NAB (MIL-B-24480)	~9	~5	~250 MPa	Mandatory - seawater service
C95900	-	-	Manganese Al Bronze	~12	-	~380 MPa	Recommended - solution treat + temper

What Heat Treatment Does - and Why As-Cast Is Often the Wrong Specification

Heat treatment of aluminium bronze is where the most avoidable procurement mistakes happen. The issue is a failure mode called dealuminification: the selective leaching of aluminium from the alloy surface in aggressive seawater and acid environments, which leaves behind a porous, mechanically weak copper matrix with no structural integrity. The part looks intact from the outside. Inside, it has been hollowing out from the moment it entered service.

Dealuminification happens because the protective alumina film relies on a coherent, homogeneous microstructure to be reliable. In an as-cast aluminium bronze, the kappa phase distribution is uneven - driven by variable cooling rates through the mould.

This unevenness produces a film that is less coherent and more susceptible to sustained attack in aggressive seawater environments. Heat treatment produces the homogeneous, fine kappa phase distribution that makes the protective film reliable and eliminates dealuminification susceptibility.

For C95800 in seawater service, an as-cast supply condition is a specification error, not a cost saving. For C95520, the situation is more direct: without solution treatment and temper, the casting simply does not achieve its rated strength. No inspection process corrects a heat treatment that was not performed. The practical implication: the heat treatment condition must appear on the purchase order. Specifying the UNS grade alone leaves the foundry free to supply as-cast material.

Lost Wax Casting vs Sand Casting for Aluminium Bronze

The manufacturing route decision for an aluminium bronze component comes down to geometry first, then production volume.

Investment casting - the lost wax casting process - is the route for components where geometric complexity, thin walls, and near-net-shape output matter. The ceramic shell process fills intricate passages, multi-port valve geometries, butterfly valve profiles, and wall thicknesses down to approximately 2mm for aluminium bronze, with dimensional accuracy and surface consistency that sand casting cannot match. The near-net-shape output also reduces downstream machining - significant for aluminium bronze, which machines more slowly than steel and requires more tool wear management.

The specific mechanism behind that quality and consistency advantage - controlled, low-turbulence mould filling versus sand casting's open pouring basins - is covered across the whole marine bronze family in marine bronze investment casting vs sand casting.

Sand casting is the route for large-section, straightforward-geometry components above the practical range of the investment casting process - large propeller blades, heavy flanges, and thick-section structural parts. The geometry of the component, not the alloy or the production volume, is the primary deciding factor.

A complex geometry at any production volume favours lost wax casting; a simple geometry at large section size favours sand casting. Where that geometric freedom matters most - draft-angle-free mating faces, valve seats, and hub geometries on complex marine bronze components that a permanent-mould or sand process simply cannot release without redesign - is covered in draft angle elimination for complex marine bronze components. Process overview is covered on the investment casting process page, including dimensional capabilities on the dimensions, tolerances and weights page.

Silicon Bronze: A Genuinely Different Alloy Family

Silicon bronze deserves its own section rather than a mention alongside C95600, because it's a genuinely different alloy family, not a variant of aluminium bronze - and because the name "silicon bronze" gets applied loosely across the industry to two chemically different things.

True silicon bronze (sometimes sold under the trade name Everdur), such as C87200 and C87300, is a copper-silicon alloy with little to no zinc - C87300 runs roughly 94% copper, 4% silicon, and about 1% manganese, with iron added in C87200 for extra strength and casting fluidity. What's commonly sold in the market as "silicon brass" - C87500 and C87600 - is a related but distinct composition that includes a meaningful zinc addition (12-16% in C87500), which is why it's more accurately called silicon brass, not silicon bronze, even though the two names get used interchangeably in casual specification.

Silicon bronze's defining advantage is a combination that few copper alloys offer together: good corrosion resistance approaching that of the nickel aluminium bronzes, high fluidity and low melting point that make it genuinely easy to cast cleanly, and excellent weldability - silicon bronze is a common welding filler rod material precisely because it welds cleanly to itself and to other copper alloys. It's also non-sparking and non-magnetic, the same properties that make aluminium bronze useful in ATEX and defence-adjacent applications.

Typical applications lean toward marine hardware, architectural fittings, and components that combine a corrosion-resistant, good-looking as-cast finish with genuine weldability - deck hardware, boat fittings, and valve stems and bodies where the part may need field welding or repair. Silicon bronze is not the strength leader of the bronze family - C95500, C95520, and C95800 all outperform it on yield strength - and it's not the first choice for the most aggressive continuous-immersion seawater service, where C95800's proven track record and heat-treated microstructure still lead.

Where silicon bronze, aluminium bronze, and nickel aluminium bronze actually sit relative to each other on the strength-corrosion resistance spectrum, and which one to specify for a given seawater valve body application, is worked through directly in aluminium bronze vs NAB vs silicon bronze alloy selection guide. Governing standards are ASTM B584 and ASTM B271 for the US market, with EN 1982's CC series covering the European equivalents.

Tin Bronze, Phosphor Bronze and Gunmetal

Tin bronze is the oldest branch of the bronze family - copper alloyed with tin, with phosphorus added in phosphor bronze grades as a deoxidiser that improves castability, grain refinement, and wear performance. Where aluminium bronze's defining metallurgical characteristic is its narrow freezing range (it solidifies compactly, closer to a pure metal), tin bronze's defining characteristic is the opposite: a genuinely wide freezing range, meaning it solidifies gradually over a broad temperature spread rather than all at once.

That wide freezing range makes tin bronze more prone to shrinkage porosity distributed through thicker sections if gating and feeding aren't designed around it - a real process consideration, not a reason to avoid the alloy family, since investment casting's controlled solidification and feeding design manage it well.

C90300 (Navy G bronze, approximately 88% Cu, 8% Sn, 4% Zn) is the classic marine tin bronze - corrosion-resistant in seawater and a traditional choice for ship propeller shaft sleeves and offshore rig components. C90500 (gun metal, approximately 88% Cu, 10% Sn, 2% Zn) trades some corrosion resistance for wear endurance, making it the standard choice for gears, thrust washers, and mining equipment bushings under sustained sliding load.

C90700 (approximately 89% Cu, 11% Sn, no zinc) pushes tin content higher still for the best fatigue resistance in the family, suited to heavy-load gears, worm wheels, and industrial machinery bearings that see cyclic loading rather than steady-state wear. C92200 (leaded tin bronze, "Navy M", ASTM B584) adds a small lead addition for machinability and anti-galling performance, and is a long-established choice for marine propeller shaft sleeves and hydraulic system components where a low-friction, non-galling bearing surface against a rotating shaft matters more than maximum strength.

Tin bronze and gunmetal grades don't compete with aluminium bronze on strength or with copper-nickel on pure seawater corrosion resistance - their advantage is wear performance and bearing behaviour under sliding contact, which is why they dominate gear, bushing, and thrust-washer applications rather than structural or high-corrosion marine hardware. ASTM B584 (sand and centrifugal castings) and ASTM B148-adjacent copper-tin specifications govern the US market; EN 1982's CC series (CC491K for gunmetal, for example) covers Europe.

Copper-Nickel (CuNi): The Seawater Piping and Desalination Specialist

Copper-nickel is the odd alloy out in this guide, in a useful way: where aluminium bronze, silicon bronze, and tin bronze are all copper-plus-a-strengthening-element systems, copper-nickel (CuNi) is copper alloyed directly with nickel, in two standard ratios - 90/10 (C96200, approximately 90% copper, 10% nickel) and 70/30 (C96400, approximately 70% copper, 30% nickel). Neither grade is chasing strength the way the aluminium bronzes do; both are built around one job: long-term, low-maintenance performance in continuous seawater flow.

CuNi's seawater corrosion rate is both extremely low and unusually predictable - commonly cited in the low single-digit to low double-digit micrometres-per-year range - and unlike several other copper alloys, it isn't particularly susceptible to stress corrosion cracking, which matters for pressure-retaining piping that sees sustained mechanical stress alongside corrosive exposure. Both grades share the copper-alloy family's biofouling resistance, with 90/10 showing a slight edge over 70/30 in some service comparisons; 70/30 in turn generally holds up better under higher-velocity flow and more aggressive erosion-corrosion conditions, which is why it's the more common choice in the highest-flow-velocity sections of a seawater system.

This is why CuNi's application list looks different from the rest of the bronze family: seawater piping systems, heat exchanger and condenser tubing and tube sheets on ships, desalination plant piping and components, offshore platform seawater systems, and ship hull sheathing.

Aluminium bronze - C95800 and C95500 - remains the default for pump impellers and structural valve bodies where maximum strength is the priority, but 70/30 CuNi (C96400) does see real use in pump components and valve bodies of its own, particularly in defence and offshore applications where its erosion-corrosion resistance under aggressive, high-velocity seawater flow is the deciding factor over raw strength.

For the piping, tubing, and heat-transfer surfaces that move seawater around a vessel or a desalination plant for decades with minimal intervention, CuNi is very hard to beat on total lifecycle cost even where its raw material cost or strength doesn't compete with the aluminium bronzes. Governing standards are ASTM B369 (castings) and ASTM B271, with EN 1982's CC380H (90/10) and CC382H (70/30) as the European equivalents.

Applications by Industry

Bronze investment castings - across aluminium bronze, silicon bronze, tin bronze, and copper-nickel - serve a wider range of demanding applications than any single copper casting alloy family could on its own. The industries served span marine and naval, oil and gas, aerospace, chemical processing, water treatment, general manufacturing, and defence - each sector driven by a distinct combination of properties, and often by more than one alloy family working together in the same system.

Marine and Naval - Seawater, Biofouling and Magnetic Permeability

C95800 (AB2) is the dominant grade for structural and rotating marine hardware, and understanding why requires understanding what marine service actually demands of a casting. Ship propellers, pump shafts, underwater fastenings, seawater pump impellers, valve bodies, manifolds, and hull fittings operate in an environment that simultaneously demands corrosion resistance, cavitation erosion resistance, biofouling resistance, and - for naval vessels - controlled magnetic signature. No other copper casting alloy delivers all four in a structural casting the way C95800 does.

The biofouling resistance of C95800 is particularly significant in long-service applications: the biostatic surface of nickel aluminium bronze deters barnacle and algae attachment, reducing fouling accumulation that increases hull drag and fuel consumption. For the piping and heat-transfer side of the same vessel - seawater cooling lines, condenser tubing - copper-nickel takes over as the preferred material, and the two families are routinely specified together on the same ship or platform rather than competing for the same parts list.

For naval and defence applications, C95800 produced to MIL-B-24480 covers submarine valves, sonar equipment housings, mine countermeasure vessel hardware, and periscope components - all specifications requiring magnetic permeability below 1.05 that no ferrous material meets.

Oil and Gas - Offshore Valves, Wellhead Components and Fire Suppression

The oil and gas sector asks aluminium bronze to do several things simultaneously that no other material achieves as a combination: resist corrosive fluids and sour gas (H2S-containing environments), perform in seawater-exposed offshore conditions, and comply with ATEX non-sparking requirements in explosive-atmosphere zones.

Valve bodies, pump parts, pipe fittings, and wellhead components across offshore installations are cast in C95500 and C95800. Standard C95400 is not adequate for sour service - the nickel addition in C95500 and above provides the dealuminification and corrosion resistance that H2S-containing environments demand.

Offshore fire suppression systems are a specific application area - manifold valve bodies, nozzle bodies, and breaching adapters (hose coupling adapters that connect suppression lines of different diameters in offshore and industrial installations) are cast in C95800, delivering seawater resistance and non-sparking compliance simultaneously. BOP components requiring yield strengths beyond C95800 capability are specified in C95520 to AMS 4881.

Aerospace - Landing Gear, Actuators and Non-Magnetic Structural Components

C95520 in the AMS 4881 heat-treated condition earns its place in aerospace by solving a problem that neither steel nor standard aluminium alloys can resolve simultaneously: delivering the strength of medium-carbon steel with the corrosion resistance and low magnetic permeability of a copper alloy, in complex geometries that would require extensive machining from bar if produced any other way. Aircraft landing gear bushings and bearings, actuator components, and heavy-duty structural bearings subject to combined cyclic fatigue loading and corrosion are the primary investment casting applications.

For non-magnetic aerospace and defence components - avionics housings, sonar equipment enclosures, and structural components on magnetically sensitive platforms - C95800 investment castings provide the structural integrity of a precision casting with controlled magnetic permeability that steel cannot match.

Chemical Processing - Heat Exchangers and Corrosive Fluid Systems

Chemical processing plants impose conditions that eliminate most copper alloys from consideration: sustained exposure to acids, chlorides, and industrial process chemicals at elevated temperatures, combined with the mechanical demands of pump and valve service. Aluminium bronze's resistance to stress corrosion cracking - a failure mode that removes many other copper alloys from aggressive chemical service - is as important as its general corrosion resistance in this sector.

Heat exchanger tube sheets and bonnets, chemical storage vessel fittings, corrosive fluid pump impellers and housings, and valve bodies handling acid process streams are cast in C95400 for moderate chemical environments and C95500 or C95800 for aggressive chloride-containing or acidic process fluids. Silicon bronze also earns a place here on components that need field weldability alongside corrosion resistance - piping fittings and valve bodies that may need to be repaired or modified in service without the heat-treatment sensitivity of the nickel aluminium bronzes.

Water Treatment and Desalination

Desalination and water treatment plants impose some of the most demanding operating conditions for pump and valve components - high-pressure seawater or brackish water, continuous cavitation in pump impellers, and chloride concentrations that corrode unprotected ferrous materials within months.

C95800 investment castings for pump impellers, valve bodies, and pipework fittings in seawater desalination service deliver the erosion and cavitation resistance from high-velocity flow that extends component life and reduces plant downtime. For freshwater treatment systems, C95400 provides the required performance at a lower material cost. And for the piping and heat-transfer runs that move seawater through the plant rather than pumping or valving it, copper-nickel - 90/10 for general piping, 70/30 where flow velocity is highest - is the specialist material of choice, on the same total-lifecycle-cost logic that makes it standard on ships and offshore platforms.

General Industrial - Butterfly Valves, Pumps and Process Equipment

C95400 (AB1) covers the majority of general industrial aluminium bronze investment casting demand. Butterfly valve discs, stems and seat rings, centrifugal pump impellers and casings, bearing housings, gear blanks, and worm drive components across chemical processing, food processing, HVAC, and heavy engineering are the core applications.

The combination of wear resistance, strength, and predictable mechanical properties makes C95400 the cost-effective choice for components that do not face the corrosion demands of marine or offshore service. For pure wear and bearing duty - gears, thrust washers, worm wheels under sustained sliding contact - tin bronze and gunmetal grades (C90500, C90700) are frequently the better-suited and more cost-effective choice than aluminium bronze, since they're purpose-built for that duty rather than general-purpose. Dimensional capabilities and near-net-shape tolerances achievable for these component geometries are covered on the dimensions, tolerances and weights page.

Tooling, ATEX Compliance and Wear-Resistant Components

At the high-hardness end of the aluminium bronze range, C95900 is the grade for forming dies, heavy wear plates, and tooling components where abrasive wear resistance is the primary requirement. C95700 and C95800 cover worm drives, gears, and wear components in magnetic-sensitive environments where non-magnetic properties are required alongside high hardness.

Across the grade range, aluminium bronze's ATEX Zone 1 and Zone 2 compliance - non-sparking under friction in environments containing flammable gases, vapours, or combustible dusts - makes it the material of choice for components in explosive atmosphere environments: non-sparking hand tools, valve components in refineries and petrochemical plants, and equipment in paint manufacturing, grain handling, and mining. Silicon bronze shares this non-sparking, non-magnetic profile and is a common alternative where its easier weldability outweighs aluminium bronze's higher strength. In offshore environments, seawater resistance and non-sparking compliance are inseparable requirements - which is why C95800 is specified even where ATEX compliance alone would permit a lower grade.

How to Specify Bronze on an Investment Castings Drawing

A correctly specified purchase order for any bronze investment casting - aluminium bronze, silicon bronze, tin bronze, or copper-nickel - is built on five elements, and every one of them matters. The UNS grade number is the foundation - C95200, C95400, C95800, C87300, C90500, C96400, or whichever grade the application requires, not just "bronze" or "aluminium bronze." The heat treatment condition sits alongside the grade number and is equally important for the grades that respond to it: annealed, TQ50 temper, solution treated, or AMS 4881 heat treated for aluminium bronze; as-cast is standard for most silicon bronze, tin bronze, and copper-nickel grades, but this should still be stated explicitly rather than assumed.

The applicable standard - ASTM B148 for aluminium bronze, ASTM B584/B271 for silicon bronze, ASTM B584 for tin bronze and gunmetal, ASTM B369/B271 for copper-nickel, in each case for US procurement, or EN 1982 with the relevant CC designation for European procurement - sets the acceptance criteria. Inspection requirements must be stated explicitly: visual inspection as the mandatory baseline; radiographic testing per ASTM E155 (or EN 12681) for pressure-containing components; dye penetrant test per ASTM E165 on all machined surfaces; hydrostatic pressure test for pump bodies, valve bodies, and manifolds.

Finally, EN 10204 Type 3.1 material certification with heat number traceability confirms what was poured and whether the heat treatment was performed to specification.

Source Bronze Investment Castings Across the Full Alloy Family

Pahwa MetalTech's copper alloys investment casting capability covers all nine aluminium bronze grades from C95200 to C95900, including C95520 to AMS 4881, alongside silicon bronze, tin bronze and gunmetal, and copper-nickel - within our wider investment casting process capability and our marine parts and propellers industry focus, with in-house heat treatment and full material certification.

If you are specifying a bronze component for marine, offshore, aerospace, chemical processing, water treatment, or industrial service and want to confirm grade, heat treatment condition, and inspection requirements before raising a purchase order, contact us or email info@pahwametaltech.co.in.