C51000 Phosphor Bronze (5% Sn): High-Fatigue Spring Alloy vs C26000 Cartridge Brass (70/30): The Cold-Workable Standard
Side-by-side engineering comparison of C51000 Phosphor Bronze (5% Sn): High-Fatigue Spring Alloy (ASTM B103) and C26000 Cartridge Brass (70/30): The Cold-Workable Standard (ASTM B36). Compare mechanical properties, chemical composition, density, yield strength, international equivalents, and typical applications to select the right material for your project.
Quick Verdict
Choose C51000 phosphor bronze when the application requires fatigue strength, spring performance, or wear resistance under sliding contact — its 5% tin content provides exceptional elastic behavior and fatigue life. Choose C26000 cartridge brass when deep-drawability, formability, and cost matter more than spring performance — its 70/30 Cu-Zn composition offers unmatched cold-working capability....
Fatigue strength and spring performance for electrical contacts
Deep-drawability and formability for decorative and plumbing parts
Quick Comparison
| Property | C51000 Phosphor Bronze (5 | C26000 Cartridge Brass (7 |
|---|---|---|
| Standard | ASTM B103 | ASTM B36 |
| Category | Brass & Bronze | Brass & Bronze |
| Density | 8.86 g/cm³ | 8.53 g/cm³ |
| Yield Strength | 130-550 MPa | 75-420 MPa |
| Tensile Strength | 340-690 MPa | 300-650 MPa |
| Key Applications | C51000 Phosphor Bronze (5% tin, 0.2% phosphorus) offers an exceptional combination of high fatigue strength, excellent s... | C26000 Cartridge Brass (70% Cu, 30% Zn) is the most ductile brass composition — it can be deep-drawn, spun, and cold-for... |
International Equivalents
| C51000 Phosphor Bron Equivalents | C26000 Cartridge Bra Equivalents |
|---|---|
| CuSn5 | CuZn30 |
| EN CW451K | EN CW505L |
| JIS C5102 | JIS C2600 |
| GB QSn5-0.2 | GB H70 |
How to Choose
| Choose C51000 Phosphor Bronze (5 when... | C51000 phosphor bronze (5% Sn) provides exceptional fatigue strength and spring properties for electrical switch contacts, relay springs, and bellows. |
| Choose C26000 Cartridge Brass (7 when... | C26000 cartridge brass (70/30) offers unmatched deep-drawability for ammunition cases, radiator cores, and plumbing fittings at lower cost. |
Decision Checklist: Which Is Right for You?
| Criterion | C51000 Phosphor Bron | C26000 Cartridge Bra |
|---|---|---|
| Fatigue Strength And Spring Performance For Electrical Contacts | ✓ | |
| Deep-Drawability And Formability For Decorative And Plumbing Parts | ✓ | |
| Fatigue/spring requirement — C51000's 5% tin provides superior elastic... | ✓ | |
| Formability — C26000 offers unmatched deep-drawability; C51000 has goo... | ✓ | |
| Cost — C51000 costs $10-15/kg vs C26000 at $6-10/kg (1.5-2x premium fo... | ✓ |
Selection Guide
Choose C51000 phosphor bronze when the application requires fatigue strength, spring performance, or wear resistance under sliding contact — its 5% tin content provides exceptional elastic behavior and fatigue life. Choose C26000 cartridge brass when deep-drawability, formability, and cost matter more than spring performance — its 70/30 Cu-Zn composition offers unmatched cold-working capability. C51000 costs 1.5-2x more than C26000 but provides 3-5x better fatigue life and superior wear resistance. Phosphor bronze for springs and contacts; cartridge brass for formed parts.
Key Decision Factors
- Fatigue/spring requirement — C51000's 5% tin provides superior elastic limit and fatigue life (up to 550 MPa cold-worked); C26000 has lower elastic limit (~420 MPa full-hard) and poorer fatigue resistance
- Formability — C26000 offers unmatched deep-drawability; C51000 has good formability but cannot match C26000's extreme draw capability
- Cost — C51000 costs $10-15/kg vs C26000 at $6-10/kg (1.5-2x premium for phosphor bronze); specify C51000 only when spring or wear performance justifies the cost
- Wear resistance — C51000's tin content and phosphorus deoxidation provide better sliding wear resistance than C26000; for bearing applications, consider C93200 bearing bronze instead
- Corrosion resistance — both resist freshwater and atmospheric corrosion; C51000 has slightly better saltwater resistance due to its tin content
When to Use Each
Use C51000 Phosphor Bron for:
C51000's 5% tin content provides high fatigue strength (up to 550 MPa cold-worked) and excellent elastic limit, making it the standard for switch contacts, relay springs, and connector terminals requiring millions of flex cycles.
C51000's combination of fatigue resistance and formability enables hydroformed bellows for hydraulic and gas systems. The tin bronze microstructure resists fatigue cracking during flex cycles.
Phosphor bronze's wear resistance (enhanced by phosphorus deoxidation) suits it for light-duty bushings, wear strips, and guide components where the higher cost of bearing bronze (C93200) is not justified.
C51000's tonal properties and corrosion resistance make it standard for guitar strings (phosphor bronze wound strings), reed organs, and precision instrument springs.
Use C26000 Cartridge Bra for:
C26000's 70/30 Cu-Zn composition provides maximum deep-drawing capability — standard for ammunition cases, radiator cores, lamp fixtures, and any component requiring extreme draw depths.
C26000 provides 300-650 MPa tensile strength, good freshwater corrosion resistance, and moderate machinability. Standard for faucet bodies, valve stems, and compression fittings.
C26000's warm gold color, polishability, and ability to be stamped and formed make it the standard for decorative door hardware, lighting fixtures, and consumer products.
C26000's 28% IACS conductivity and low cost suit it for terminal lugs, connector bodies, and general electrical hardware where spring performance is not required.
Frequently Asked Questions
What is the main difference between C51000 Phosphor Bronze (5% Sn) and C26000 Cartridge Brass (70/30)?
C51000 Phosphor Bronze (5% Sn): High-Fatigue Spring Alloy (ASTM B103) provides 130-550 MPa yield strength at 8.86 g/cm³ density, while C26000 Cartridge Brass (70/30): The Cold-Workable Standard (ASTM B36) delivers 75-420 MPa at 8.53 g/cm³. The choice depends on whether your application prioritizes fatigue strength and spring performance for electrical contacts or deep-drawability and formability for decorative and plumbing parts.
Can C51000 Phosphor Bronze (5% Sn) be substituted for C26000 Cartridge Brass (70/30)?
In many applications, these materials can be cross-referenced, but direct substitution should always be verified against specific project specifications, especially for fatigue strength and spring performance for electrical contacts, deep-drawability and formability for decorative and plumbing parts, and operating environment. Consult your engineer of record.
Can C26000 brass be used for spring contacts instead of phosphor bronze?
Not recommended for critical springs. C26000 has lower elastic limit (~420 MPa full-hard) and significantly poorer fatigue life than C51000. Under repeated flex cycles, C26000 springs will take a permanent set (lose spring force) or crack far sooner than phosphor bronze springs. For low-cycle, low-stress applications (battery contacts in consumer devices, low-force terminals), C26000 may be adequate. For relay springs, switch contacts, or any safety-critical spring requiring millions of cycles, C51000 phosphor bronze (or C17200 beryllium copper for the highest performance) is essential. The cost premium for phosphor bronze is typically justified by the longer service life and reliability.
What does 'phosphor' mean in phosphor bronze?
The 'phosphor' refers to a small phosphorus addition (0.03-0.35%) during melting. Phosphorus serves two purposes: (1) it acts as a deoxidizer, removing oxygen from the molten bronze to prevent brittle copper oxide inclusions, and (2) it improves wear resistance and hardness by forming fine copper phosphide particles in the microstructure. The phosphorus content is small enough that it does not significantly affect corrosion resistance or electrical conductivity, but it noticeably improves the alloy's wear and fatigue properties — which is why phosphor bronze is specified for springs and sliding contacts. Without the phosphorus addition, the alloy would be plain tin bronze (CuSn5), which has inferior wear properties.
Why is C51000 more expensive than C26000?
Two factors: (1) Tin content — C51000 contains 5% tin, which costs $25-35/kg, versus C26000's 30% zinc at $2-3/kg. Although C26000 has a higher alloying content by percentage, zinc is far cheaper than tin, making C51000's raw material cost 1.5-2x higher. (2) Processing — phosphor bronze requires more careful melting and deoxidation (phosphorus addition), and its lower ductility means more frequent annealing during cold working. The total premium of 1.5-2x reflects both raw material and processing cost differences. For applications where C51000's spring or wear properties are essential, the premium is easily justified by performance and reliability.
Which material is better for a bushing?
Neither C51000 nor C26000 is ideal for heavy-duty bushings. For light-duty, low-speed bushings with moderate loads, C51000 phosphor bronze is acceptable due to its wear resistance. For heavier loads and higher speeds, specify C93200 bearing bronze (SAE 660, with 7% lead for solid lubrication) or C95400 aluminum bronze. C26000 cartridge brass is NOT suitable for bushings — it has poor bearing properties and will gall and seize under sliding load due to its zinc content and lack of solid lubricant phase. For instrument bushings and low-load pivot points, C51000 is the standard choice; for industrial machinery, C93200 or C95400 is required.
Can C51000 phosphor bronze be deep-drawn like cartridge brass?
Yes, but to a more limited extent. C51000 has good formability in the annealed condition and can be moderately deep-drawn, stamped, and formed. However, its 5% tin content increases strength and reduces ductility compared to C26000, meaning it cannot be drawn to the extreme depths possible with cartridge brass without intermediate annealing. For deep-drawn components requiring high final strength and fatigue resistance (such as bellows or diaphragms), the process is: anneal → draw → anneal → draw → strain harden to final temper. C26000 can typically be drawn to full depth without intermediate annealing, which is why it is preferred for high-volume deep-drawn production like ammunition cases.