UNS C90300 Tin Bronze — Casting Copper Alloy

1. Introduction

NOUS C90300 is a widely used tin-bronze casting alloy that delivers a practical combination of good castability, résistance à la corrosion (surtout dans les environnements marins), bearing/wear behavior and satisfactory mechanical strength.

It is specified for bushings, Pump Pièces, vannes, gears and other components where service loading, sliding contact and corrosion resistance are primary drivers.

2. What is Bronze UNS C90300?

UNS C90300 is a cast tin bronze alloy in the UNS (Système de numérotation unifiée) Famille d'alliages de cuivre.

It is formulated for foundry use and is widely specified where a balance of coulée, résistance à la corrosion (particularly in marine and water-handling environments), good bearing/wear behavior and reasonable mechanical strength est requis.

In practice C90300 is chosen for components such as bushings, manches, pump and valve parts, small gears and marine fittings where sliding contact, embedability and resistance to seawater or wet corrosion are important.

Key features and metallurgical character

• Bonne coulée. C90300 pours and fills molds predictably in sand, shell and investment processes, enabling reasonably thin sections and good surface detail when processed correctly.
• Tin-strengthened matrix. Tin acts as a substitutional alloying element in copper, raising hardness, wear resistance and strength relative to plain copper while preserving ductility sufficient for many bearing and structural uses.
• Bearing and tribological performance. Les expositions d'alliage conformability and embedability—it will accept small contaminant particles into the softer bronze matrix rather than score a harder mating shaft, making it suitable for plain bearings and bushings under boundary or mixed lubrication.
• Excellent wet-environment corrosion resistance. Tin bronzes resist general corrosion and perform well in seawater and many industrial aqueous environments; they are less prone to dezincification or rapid localized attack than many brasses.
• Not precipitation-hardening. Mechanical properties are established primarily by composition and solidification/microstructure; C90300 is not normally subject to strengthening by solution/aging treatments.
  Stress-relief or annealing operations are used mainly for dimensional stability or ductility adjustments.
• Machinabilité modérée. Tin improves chip formation and machinability relative to many high-strength copper alloys; carbide tooling and standard bronze machining practices are appropriate for production work.

3. Alloy identity and typical chemistry

Values are presented as typical weight-percent ranges used for design and procurement; always confirm exact limits with the foundry’s mill/certified analysis for any critical application.

4. Physical and mechanical properties

Below are representative as-cast values for C90300 drawn from typical supplier and material-data references.

Actual properties vary with casting process, épaisseur de section, gating strategy and melting practice — always validate with cast coupons from your foundry.

Physical properties

Propriétés mécaniques (typical as-cast)

5. Casting behavior and foundry practice

Suitable casting processes

C90300 is adaptable to the major casting methods used for bronzes:

• Coulée de sable — economical for large or heavy sections.
• Moulage de précision (casting de la cire perdue) — best surface finish and dimensional accuracy for thinner, pièces détaillées.
• Moulage en coquille and permanent-mold casting — intermediate options offering improved surface finish and tolerance.
• Continuous and centrifugal casting are also used for bars, rings and certain shapes.

Critical casting parameters

• Température de versement / surchauffer: respect the alloy liquidus and avoid excessive superheat;
  Concast data indicate liquidus near ~1000 °C and solidus near ~854 °C — control within a narrow window to balance fluidity and avoid oxidation/dross.
• Faire fondre la propreté: degassing and filtration are essential; tin bronzes are sensitive to hydrogen porosity and oxide inclusions — ceramic filters and rotary degassers reduce risks.
• Déclenchement & alimentation: design feeders to supply shrinkage in heavy sections and use gradual sectional transitions to avoid hot-spots and hot-tears.
  Simulation (fill/solidification) is recommended for complex geometries.
• Contrôle de solidification: directional solidification with chills or chills/risers helps reduce shrinkage defects and refines microstructure in thicker portions.

Traitement thermique post-tour

C90300 is not a precipitation-hardening alloy; it does not respond to solution-age heat treatments to raise strength.

Typical thermal steps are stress-relief anneals (to remove casting stresses and improve machinability) or moderate anneals to improve ductility where required.

Practical foundry practice relies on casting control — not heat treatment — for most mechanical property objectives.

6. Machinabilité, adhésion & finition

Machinabilité

• Machinabilité modérée — tin content enhances chip formation and machinability relative to many high-strength copper alloys;
  common machinability rating values place C90300 in a practical class for routine turning, milling and drilling with carbide tooling.
• Recommended practice: use rigid fixturing, outillage en carbure (coated grades for production), conservative feeds to avoid built-up edge, and light finishing passes for critical surfaces.
  Sulfur and lead contents in other alloys (not C90300 lead-free variants) can alter chip control — verify composition before selecting cutting parameters.

Adhésion

• Effrontement is the preferred joining method for bronze castings when required (filler metals and flux selected for bronze compatibility).
• Soudage is generally avoided for large castings because bronze tends to suffer from thermal cracking and property changes; localized welding can be used with specialist procedures and post-weld stress relief where unavoidable.

Finition de surface

• Polissage, placage (Dans, Agir), lacquering or patination are commonly applied depending on functional or aesthetic requirements.
  For bearing surfaces, honing or lapping produces the required surface texture for lubricant film formation.

(Select finishing and joining processes in consultation with the foundry to avoid galvanic compatibility issues and finish adhesion problems.)

7. Corrosion, wear and tribological performance

• Résistance à la corrosion: Tin bronzes such as C90300 exhibit excellent resistance in fresh and seawater environments and are commonly used for marine hardware and pump components.
  Their tin content promotes a stable surface film and reduces susceptibility to certain localized corrosion mechanisms.
• Tribology and bearing behavior: C90300 is valued for good conformability and embedability — under mixed or boundary lubrication it tends to accept small hard particles into the softer bronze matrix rather than scoring the harder shaft.
  This makes it a favored material for bushings, plain bearings and sleeves running against hardened steel. Proper lubrication and surface finish are still necessary for long service life.

Note de conception: for high-load rotating bearings consider tested bearing geometry, lubrication regime and possible use of lined or composite bearings if duty exceeds bronze’s capability.

8. Typical applications of UNS C90300 alloy

Common service areas where UNS C90300 is specified:

• Bagues, sleeves and plain bearings (hydraulic pumps, boîtes de vitesses).
• Pump and valve components (échange, corps de valve, sièges) — especially in marine and water-handling equipment.
• Engrenages, worm wheels and small structural castings where castability and wear resistance are needed.
• Marin fittings and propeller components where seawater corrosion resistance is required.
• Decorative castings and architectural elements where patina and aesthetics matter.

9. Comparisons with related copper alloys

10. Conclusion

UNS C90300 tin bronze is a éprouvé, high-value cast copper alloy that excels in balancing mechanical strength, se résistance à l'usure, corrosion durability, et la coulée.

Its carefully engineered chemical composition and uniform microstructure deliver consistent performance in moderate-load, low-to-medium speed service environments, making it indispensable in marine, manipulation des fluides, mechanical power transmission, and general engineering sectors.

 

FAQ

What is the typical tin content in C90300?

Typical tin is ~7.5–9.0 wt% with copper as the balance; zinc is commonly present at ~3–5 wt%. Always check the mill certificate for the lot you receive.

Can C90300 be heat treated to increase strength?

No — C90300 is not a precipitation-hardening alloy.

Strength and ductility are primarily controlled through composition, section size and solidification rate; stress-relief anneals are used for dimensional stability.

Is UNS C90300 suitable for seawater service?

Yes — tin bronzes such as C90300 are routinely used in marine environments and pump components because of good seawater corrosion resistance and anti-fouling behavior relative to many steels.

What casting process should I specify?

Utiliser casting d'investissement for thin, detailed parts and tight tolerances; sand or shell casting for larger or economy parts.

Specify desired surface finish, tolerance band and NDT requirements up front.