C51000 Phosphor Bronze (5% Sn): High-Fatigue Spring Alloy
ASTM B103 · Published: 2026-06-03 · Updated: July 2026
C51000 Phosphor Bronze (5% tin, 0.2% phosphorus) offers an exceptional combination of high fatigue strength, excellent spring properties, and good corrosion resistance. It is the standard material for electrical switch contacts, relay springs,...
C51000 Phosphor Bronze (5% tin, 0.2% phosphorus) offers an exceptional combination of high fatigue strength, excellent spring properties, and good corrosion resistance. It is the standard material for electrical switch contacts, relay springs, bellows, and flexible metal hose. The phosphorus addition acts as a deoxidizer and improves wear resistance.
Quick Facts
| Category | Brass & Bronze |
| Standard | ASTM B103 |
| Density | 8.86 g/cm³ |
| Yield Strength | 130-550 MPa |
| Tensile Strength | 340-690 MPa |
Global Equivalents & Cross-Reference
| Alternative Standard / Grade | Action |
|---|---|
| CuSn5 | Compare |
| EN CW451K | Compare |
| JIS C5102 | Compare |
| GB QSn5-0.2 | Compare |
Related Materials
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Frequently Asked Questions
How does phosphor bronze compare to beryllium copper for springs?
Beryllium copper (C17200) has higher strength and better electrical conductivity but costs 5-10× more and requires special handling due to beryllium's toxicity. C51000 phosphor bronze is the economical choice for most spring and contact applications where extreme conductivity is not required.
References & International Standards
- ASTM International. Standard Specifications for Steel & Metal Alloys. astm.org
- International Organization for Standardization (ISO). Metallic Materials — Cross-Reference Database. iso.org
- American Iron and Steel Institute (AISI). Steel Grade Designations & Equivalents. steel.org
- European Committee for Standardization (CEN). EN Steel Standards & Numbering System. cencenelec.eu