C90300 Bronze Bearing Alloy (ASTM B584): A Complete Guide C90300 Alloy, C903 Tin bronze Bearing
Tin bronze alloys like C90300 are generally used in gear and high-strength bushing and bearing applications requiring high strength, low speeds, and heavy loads.
Typical uses
Building: Heavy construction equipment
Fasteners: Swivel
Industrial: Bearings, bushings, gear blanks, gears, piston rings, pump bodies, pump impellers, valve bodies, valves
Plumbing: Steam fittings
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An In-Depth Guide to Alloy C90300: The High-Strength Tin Bronze Workhorse
When industrial applications demand unwavering strength, superior wear resistance, and the ability to withstand harsh environments, material selection is paramount. For engineers, designers, and procurement specialists navigating the world of high-performance alloys, one material consistently proves its mettle: Alloy C90300.
Commonly known as Navy G bronze, this high-strength tin bronze is engineered for the toughest jobs. It’s not a general-purpose alloy; it is a specialist material designed for high-load, low-speed applications where reliability is non-negotiable.
This article provides a deep dive into C90300, moving beyond surface-level data to explore what makes it a premier choice for critical components. We will dissect its properties, compare it to other alloys, and provide the expert insights needed to leverage its full potential.
What Exactly is Alloy C90300?
Alloy C90300 is a copper-based alloy primarily composed of copper, tin, and zinc. It falls under the category of tin bronzes and is a lead-free material, making it a more environmentally sound choice compared to older, leaded bronze alloys. Its specification is governed by several key ASTM standards, which dictate the manufacturing process and ensure material consistency.
Understanding the casting method is crucial, as it directly influences the material’s grain structure and, consequently, its mechanical properties.
| ASTM Standard | Casting Method | Typical Characteristics | Best Suited For |
| ASTM B584 | Sand Casting | Good for complex, intricate shapes. More economical for one-off or low-volume parts. | Custom pump housings, valve bodies, unique structural components. |
| ASTM B271 | Centrifugal Casting | Produces a very dense, fine-grained structure with high integrity and minimal impurities. | Symmetrical parts like rings, bushings, and sleeves requiring maximum strength and wear life. |
| ASTM B505 | Continuous Casting | Creates uniform, consistent bar and tube stock with excellent straightness and tight dimensional tolerances. | High-volume production of bearings, gears, and bushings where material consistency is key. |
For applications like high-integrity bearings, components produced via centrifugal or continuous casting are often preferred due to their superior metallurgical structure.
The Core of Performance: C90300 Chemical Composition
The performance of any alloy begins with its chemical makeup. Each element in C90300 plays a specific role in defining its final properties. It’s not just a recipe; it’s a balanced formula for strength and durability.
| Element | Percentage (%) | Role & Contribution |
| Copper (Cu) | 86.00 – 89.00 | The base metal, providing excellent thermal and electrical conductivity, and inherent corrosion resistance. |
| Tin (Sn) | 7.50 – 9.00 | The primary strengthening element. It forms a hard intermetallic compound within the softer copper matrix, significantly increasing strength and wear resistance. |
| Zinc (Zn) | 3.00 – 5.00 | Acts as a deoxidizer during casting, improving castability and fluidity. It also contributes to strength and slightly enhances corrosion resistance. |
| Lead (Pb) | 0.30 (max) | Intentionally kept to a minimum. Its near-absence makes C90300 a “lead-free” alloy, suitable for applications with environmental or regulatory constraints. |
(Note: Other trace elements like Iron, Nickel, and Phosphorus are tightly controlled to prevent negative impacts on mechanical properties.)
The synergy between copper and a high percentage of tin is what gives C90300 its signature strength and toughness, setting it apart from more common, general-purpose bronzes.
Mechanical Properties: A Foundation of Strength
Mechanical properties are the tangible metrics that define an alloy’s ability to perform under stress. For C90300, these numbers confirm its suitability for high-load environments.
| Property | Minimum Value | Typical Value | What This Means in Practice |
| Tensile Strength | 44 ksi (303 MPa) | 45 ksi (310 MPa) | High load capacity. This is the maximum stress the material can withstand before fracturing, critical for structural and load-bearing components. |
| Yield Strength | 22 ksi (152 MPa) | 21 ksi (145 MPa) | Resistance to permanent deformation. The material will not permanently bend or deform until this stress level is reached, ensuring components maintain their shape under design loads. |
| Elongation | 18% | 30% | Good ductility and toughness. The alloy can stretch and deform significantly before breaking, making it resistant to fracture from impact or sudden overloads. |
| Brinell Hardness | – | 70 BHN | Excellent wear resistance. Hardness directly correlates to resistance against scratching, abrasion, and wear, which is essential for bearings and bushings. |
| Machinability Rating | – | 30 (vs. 100 for free-cutting brass) | Moderately difficult to machine. Its toughness requires sharp tooling and slower speeds. This is the trade-off for its superior strength and wear properties. |
The combination of high strength, good ductility, and significant hardness makes C90300 an ideal material for components that experience pounding, heavy pressure, and abrasive forces.
C90300 vs. A Common Alternative: The Strength vs. Machinability Trade-Off
To truly understand C90300, it’s helpful to contrast it with another widely used bronze, such as a common leaded bearing bronze (e.g., C93200). This comparison highlights their distinct engineering purposes.
| Feature | Alloy C90300 (Navy G) | Common Leaded Bearing Bronze | The Deciding Factor |
| Primary Advantage | High Strength & Wear Resistance | Excellent Machinability & Lubricity | Choose C90300 for heavy loads and abrasion. Choose the other for general-purpose bearings where ease of manufacturing is key. |
| Key Alloying Element | Tin (Sn) for strength | Lead (Pb) for lubricity and machinability | Tin creates a harder, tougher matrix. Lead creates a softer, self-lubricating one but reduces ultimate strength. |
| Load Capacity | High. Ideal for heavy, pounding loads at low speeds. | Moderate. Best for medium loads and higher speeds where lead’s properties are beneficial. | Application pressure and impact loading will dictate the choice. C90300 excels under extreme pressure. |
| Environmental Profile | Lead-Free. Compliant with modern environmental regulations. | Contains Lead. Restricted in potable water and other environmentally sensitive applications. | C90300 is the clear choice where lead is prohibited or undesirable. |
This contrast is crucial: C90300 is engineered for strength, while many other bronzes are engineered for machinability. You choose C90300 when performance cannot be compromised.
Industry Application Spotlight: The Movable Bridge Bearing
Imagine the immense forces at play in a movable bridge or a large industrial turntable. These structures involve slow, intermittent motion under colossal loads. This is a perfect case study for C90300.
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The Challenge: The bearings must support millions of pounds, endure constant pressure, and resist environmental corrosion from rain, salt, and pollution. They must operate smoothly without galling or seizing after long periods of being static.
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Why C90300 Excels:
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High Compressive Strength: It withstands the immense static load without deforming.
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Low Friction & Anti-Galling: The tin bronze composition prevents the metal surfaces from welding together under pressure, ensuring smooth movement.
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Fatigue Resistance: It handles the cyclical stress of movement and vibration over decades of service.
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Corrosion Resistance: It performs reliably in outdoor, marine, or industrial-chemical environments, far outlasting steel components.
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In this scenario, a material with lower strength might deform, and one with poor corrosion resistance would fail prematurely, leading to catastrophic structural failure. C90300 provides the necessary long-term reliability.
Frequently Asked Questions (FAQ) about Alloy C90300
Q: Is C90300 bronze magnetic?
A: No, Alloy C90300 is non-magnetic. Its high copper content gives it a magnetic permeability of 1, meaning it is not attracted to magnets and will not interfere with magnetic fields.
Q: How difficult is it to weld C90300?
A: Welding C90300 is considered fair. While soldering is excellent and brazing is good, arc welding methods require care due to the material’s thermal conductivity. Preheating and proper technique are essential to avoid cracking. It is not as easily welded as steel.
Q: What is the difference between C90300 and “Navy G” bronze?
A: They are the same material. “Navy G” is the common trade name for Alloy C90300, originating from its historical use in naval applications for its strength and resistance to saltwater corrosion.
Q: Why is C90300 a superior choice for marine applications?
A: Its high copper and tin content provides excellent resistance to corrosion from seawater, brine, and steam. Unlike many ferrous metals, it will not rust and maintains its structural integrity for years in harsh marine environments, making it ideal for steam fittings, marine hardware, and pump components.
Conclusion: The Expert’s Choice for Demanding Applications
Alloy C90300 is far more than just another bronze. It is a highly engineered material designed for specific, demanding roles. Its profile is defined by high strength, excellent wear resistance, and robust corrosion resistance, all within a lead-free composition.
While it may not be the easiest material to machine, its performance in high-load, low-speed applications is virtually unmatched. For critical components in heavy machinery, movable structures, and marine environments, understanding the deep properties of C90300 is the first step toward building systems that are not only powerful but also enduringly reliable.
C90300 bronze, compliant with ASTM B584, is a high-performance tin bronze alloy widely used in marine, industrial, and heavy machinery applications. Known for its balanced corrosion resistance, wear properties, and cost-effectiveness, this cast bronze alloy excels in demanding environments. Below, we break down its composition, mechanical properties, and ideal use cases.
What is C90300 Bronze?
C90300 is a cast tin bronze alloy containing copper, tin, and zinc. Its unique composition delivers:
- High corrosion resistance in seawater and acidic environments
- Excellent wear resistance for bearings, gears, and bushings
- Good machinability and castability for complex components
C90300 Bronze Composition (ASTM B584)
| Element | Percentage | Role in Alloy Performance |
|---|---|---|
| Copper (Cu) | 86.0–89.0% | Base metal for structural integrity |
| Tin (Sn) | 7.5–8.5% | Enhances strength and corrosion resistance |
| Zinc (Zn) | 3.0–5.0% | Improves castability and reduces cost |
| Others (Pb, P) | <0.5% | Trace elements for specialized needs |
Key Takeaway: The tin-zinc balance makes C90300 ideal for moderately loaded bearings and marine hardware.
Mechanical & Physical Properties
| Property | Value |
|---|---|
| Density | 8.8 g/cm³ |
| Tensile Strength | 275–345 MPa |
| Yield Strength | ~125 MPa |
| Elongation (Cast State) | 15–25% |
| Hardness | HB 70–100 |
| Thermal Conductivity | Moderate (lower than pure copper) |
Why It Matters: C90300’s combination of strength and ductility supports dynamic loads in bearings and gears.
Key Advantages of C90300 Bronze
C90300 vs. Similar Bronze Alloys
| Alloy | Composition | Strengths | Limitations | Best For |
|---|---|---|---|---|
| C90300 | Cu-Sn-Zn | Balanced cost/performance | Moderate load limits | Marine bearings, valves |
| C90500 | Higher Sn (10%) | Higher strength | Brittle | High-load bearings |
| C93200 | Leaded tin bronze | Self-lubricating | Poor corrosion resistance | Low-speed bearings |
Design Tip: C90300 is optimal for applications requiring both corrosion resistance and moderate wear resistance.
Machining & Fabrication Tips
- Casting: Preheat molds to 200–300°C to minimize porosity.
- Machining: Use sharp carbide tools to prevent material adhesion.
- Welding: Avoid arc welding; opt for brazing or gas-shielded welding.
- Heat Treatment: Anneal at 600–650°C if post-casting machining is required.
Is C90300 Right for Your Project?
Consider C90300 bronze if your application requires:
✅ Resistance to saltwater/chemical corrosion
✅ Moderate-load sliding or rotating components
✅ Cost-effective alternatives to high-tin bronzes
Common Use Cases:
- Shipbuilding bearings exposed to seawater
- Industrial pump parts in corrosive fluids
- Mining equipment requiring impact resistance
| Property | ASTM-B143-70 (Alloy 903) | ASTM-B271-54 |
|---|---|---|
| Casting Method | Centrifugal | Centrifugal |
| Primary Composition | Tin Bronze (C90300) | Likely Tin Bronze or Similar |
| Applications | Bearings under heavy loads | Marine systems, bushings |
| Corrosion Resistance | Moderate | High |
| Wear Resistance | High | High |
| Machinability | Fair | Good |
C90300 Tin Bronze (ASTM B584): In-Depth Analysis of Properties and Marine Applications
C90300, a high-performance phosphor tin bronze alloy compliant with ASTM B584, is prized for its exceptional corrosion resistance, mechanical strength, and versatility in demanding environments. Widely used in shipbuilding, heavy machinery, and industrial systems, this alloy combines copper, tin, zinc, and trace elements to deliver unmatched reliability. Below, we dive into its composition, performance data, and specialized marine engineering applications.
C90300 Bronze Composition: Key Elements & Roles
C90300 is a multicomponent tin bronze with precise elemental ratios for optimized performance:
| Element | Percentage Range | Function in Alloy |
|---|---|---|
| Copper (Cu) | 86–89% | Base metal for structural integrity and thermal/electrical conductivity |
| Tin (Sn) | 7.5–9.0% | Enhances strength, hardness, and corrosion resistance |
| Zinc (Zn) | 3.5–5.0% | Improves castability and cost efficiency |
| Lead (Pb) | 0.25–0.3% | Enhances machinability and anti-seizure properties |
| Nickel (Ni) | 0.8–1.0% | Boosts corrosion resistance and high-temperature stability |
| Iron (Fe) | 0.15–0.2% | Strengthens grain structure |
| Phosphorus (P) | Trace | Acts as a deoxidizer, improving casting fluidity |
| Silicon (Si) | Trace | Enhances wear resistance |
Why It Matters: The addition of nickel and phosphorus refines its microstructure, making C90300 ideal for marine and high-stress applications.
Mechanical Properties of C90300 Bronze
| Property | Value |
|---|---|
| Tensile Strength | ≥400 MPa (varies with heat treatment) |
| Yield Strength (0.2%) | ≥124 MPa |
| Elongation | ≥20% |
| Hardness (Brinell) | ~70 HB |
| Density | 8.8 g/cm³ |
Key Strengths:
- Retains tensile strength under dynamic loads.
- Balances ductility with wear resistance for bearings and gears.
C90300 Bronze: 5 Standout Characteristics
- Superior Corrosion Resistance
- Resists pitting and crevice corrosion in seawater, brackish water, and acidic environments (pH 4–8).
- High Load-Bearing Capacity
- Withstands shock loads and cyclic stresses in marine engines and hydraulic systems.
- Self-Lubricating Properties
- Low friction coefficient (0.08–0.15) reduces wear in bushings and bearings.
- Thermal Stability
- Maintains performance up to 260°C (500°F).
- Electrical Conductivity
- ~15% IACS (International Annealed Copper Standard), suitable for marine electrical components.
C90300 in Shipbuilding: Critical Marine Applications
1. Marine Structural Components
- Hull Fittings & Deck Hardware
Used for seawater-exposed parts like hull plates, keel bolts, and deck cleats due to resistance to biofouling and saltwater corrosion. - Desalination Systems
Ideal for evaporator tubes and condenser plates in onboard desalination units, where it combats scaling and chloride-induced degradation.
2. Ship Propulsion & Mechanical Systems
- Propeller Shaft Bearings & Bushings
Handles high thrust loads and abrasive wear in propeller assemblies. - Piston Rings & Cylinder Liners
Withstands high-pressure, high-temperature conditions in marine diesel engines.
3. Marine Piping & Pump Systems
- Seawater Valves & Pump Casings
Resists cavitation erosion in ballast pumps and cooling systems. - Heat Exchanger Tubes
Performs reliably in condensers and oil coolers exposed to turbulent seawater.
4. Offshore Platform Components
- Subsea Connectors & Mooring Hardware
Used in riser bolts and chain links for corrosion resistance in splash zones. - Hydraulic Actuators
Ensures leak-free operation in dynamic positioning systems.
C90300 vs. Competing Bronze Alloys
| Alloy | Best For | Limitations |
|---|---|---|
| C90300 | Marine bearings, valves | Limited to moderate loads |
| C95500 | High-speed bearings | Higher cost (Ni-Al added) |
| C93700 | Low-cost bushings | Poor saltwater resistance |
Design Tip: Pair C90300 with stainless steel shafts to minimize galvanic corrosion.
Fabrication Guidelines for Marine Components
- Casting: Use sand casting for large hull fittings; centrifugal casting for precision pump impellers.
- Machining: Employ carbide tools with cutting speeds of 60–100 SFM (surface feet per minute).
- Welding: Opt for TIG welding with ECuSn-C (AWS A5.6) filler metal.
- Post-Processing: Stress-relieve at 290–320°C (550–600°F) for seawater-exposed parts.
Why Engineers Choose C90300 for Marine Projects
- Longevity: Outperforms stainless steel in splash zones with a service life exceeding 25 years.
- Cost Savings: Reduces maintenance downtime in offshore oil rigs and cargo ships.
- Regulatory Compliance: Meets ASTM, MIL-B-17971, and DNV GL standards for marine alloys.
Correspondence between C90300 (ASTM B584) and Domestic Grades
1. Chemical Composition Comparison
| Element | C90300 (ASTM B584) | QSn7-0.2 (GB) | QSn6.5-0.4 (GB) |
|---|---|---|---|
| Copper (Cu) | 86.0–89.0% | Balance | Balance |
| Tin (Sn) | 7.5–8.5% | 6.0–7.5% | 6.0–7.0% |
| Zinc (Zn) | 3.0–5.0% | ≤0.3% | ≤0.3% |
| Phosphorus (P) | Trace (about 0.1%) | 0.10–0.25% | 0.26–0.40% |
| Lead (Pb) | ≤0.3% | ≤0.02% | ≤0.02% |
| Other Elements | Nickel (Ni) ≤1.0% | Iron (Fe) ≤0.1% | Iron (Fe) ≤0.1% |
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Zinc (Zn) Content: C90300 contains 3–5% Zn to improve castability, while the domestic grades contain almost no zinc.
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Phosphorus (P) Content: QSn6.5-0.4 has a higher phosphorus content (0.26–0.40%), enhancing deoxidation and elasticity.
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Impurity Control: Domestic grades have stricter limits on lead (Pb) and iron (Fe).
2. Mechanical Property Comparison
| Property | C90300 (As-Cast) | QSn7-0.2 (Cold-Rolled) | QSn6.5-0.4 (Cold-Rolled) |
|---|---|---|---|
| Tensile Strength | 275–345 MPa | ≥450 MPa | ≥550 MPa |
| Yield Strength | ≥125 MPa | ≥350 MPa | ≥400 MPa |
| Elongation | 15–25% | ≥10% | ≥5% |
| Hardness (HB) | 70–100 | 160–200 | 180–220 |
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C90300: High toughness, suitable for casting complex parts (e.g., bearings, valves).
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QSn7-0.2/QSn6.5-0.4: Strengthened by cold working, higher strength but lower ductility, designed for elastic components.
3. Core Characteristics and Application Scenarios
| Grade | Advantages | Typical Application Fields |
|---|---|---|
| C90300 | Excellent castability, wear resistance, seawater corrosion resistance | Ship bearings, pump valves, gears, bushings |
| QSn7-0.2 | High elasticity, good electrical conductivity, fatigue resistance | Springs, contact pieces, electrical connectors |
| QSn6.5-0.4 | Ultra-high strength, wear resistance, stress relaxation resistance | High-load elastic components, precision wear-resistant parts |
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Dynamic Load Components (e.g., ship bearings): Prioritize C90300 for its castability and corrosion resistance.
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Elastic/Electrical Components (e.g., springs, contacts): Choose QSn7-0.2 or QSn6.5-0.4 for higher strength in the cold-rolled state.
4. Processing and Heat Treatment Considerations
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C90300:
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Casting Process: Sand casting or centrifugal casting, preheat molds to 200–300°C.
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Weldability: Poor, requires copper-based filler materials (e.g., BCuP series brazing alloys).
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QSn7-0.2/QSn6.5-0.4:
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Cold Working: Intermediate annealing (600–650°C) is required to prevent cracking.
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Heat Treatment: Cold-rolled state is used directly; annealing will reduce strength.
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5. Substitutability Analysis
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C90300 → QSn7-0.2/QSn6.5-0.4:
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Feasible Scenarios: Static wear-resistant components, elastic components in non-seawater environments.
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Infeasible Scenarios: Components requiring casting or long-term seawater exposure (domestic grades have poor castability and low zinc content).
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Reverse Substitution (QSn → C90300):
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Feasible Scenarios: High-load dynamic bearings, marine engineering components.
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Summary
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C90300: Excellent castability, suitable for complex structures requiring corrosion and wear resistance.
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QSn Series: High strength after cold working, specialized in elastic and electrical components.
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In shipbuilding and marine engineering, prioritize C90300 castings.
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In electronics and mechanical instruments, QSn series offer better cost-effectiveness.
Need Help Selecting Materials? Contact our experts today to discuss your project requirements.
C90300 (ASTM B584) bronze remains a top choice for engineers prioritizing durability, corrosion resistance, and affordability. Its versatility in casting and machining makes it ideal for marine systems, industrial bearings, and hydraulic components. For extreme loads or high-speed applications, consider pairing it with specialized lubricants or upgrading to C90500/C90700 alloys.
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C90300 tin bronze (ASTM B584) is a cornerstone material for marine engineers tackling corrosion, wear, and mechanical stress. From propeller shafts to desalination plants, its blend of strength, castability, and seawater resistance ensures reliable performance in the harshest ocean environments. For projects requiring higher loads or extreme temperatures, consider pairing it with C95400 aluminum bronze or C63000 nickel-aluminum bronze. Contact our metallurgy team for tailored recommendations.
Centrifugal Casting Bronze Bearing C90300
Centrifugally cast bronze Alloy 903 (C90300 tin bronze) is commonly used in gears and high-strength bushings and bearings operating under high strength, low speeds, and heavy loads. It is also found in pump impellers, piston rings, steam fittings, and valve bodies. In addition, C903 tin bronze castings are used for movable bridge components, bridge turntables, and other structures requiring fixed and expansion bearings for slow or intermittent movement under heavy loads.
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Tin Bronzes
Tin bronze offers excellent wear and corrosion resistance, along with high load-carrying capacity, durability, and tensile strength.
Castings & Bearings Designs and variants
We use centrifugal casting to produce bushes, rings, and sleeves from all copper alloys that meet international and local standards (DIN EN 1982:1998-12, PN-EN 1982, DIN 1705, 1709, 1714, PN 91/H-87026, ASTM B271, BS 1400) as well as special alloys. c90300 tin bronze flat plate. C90300 is a high-strength copper-tin alloy, often referred to as cast tin bronze, known for its excellent wear resistance, corrosion protection, and machinability. It conforms to ASTM B584 standards and is commonly used in industrial applications that require durability and performance under heavy loads.
