CuSn6 — lower tin phosphor bronze. Excellent spring properties and corrosion resistance. For connectors, springs, sliding contacts and bushings.
Standards
| Standard Body |
Designation |
Country |
| EN |
CuSn6 / CW452K |
EU |
| UNS |
C51900 |
USA |
| ASTM |
B103 / B139 Alloy C51900 |
USA |
| BS EN |
PB102 / CW452K |
UK |
| JIS |
C5191 |
Japan |
| GOST |
BrOF6.5-0.15 (BrOF6.5-0.15) |
Russia |
| Trade |
Phosphor Bronze Grade C / Spring Bronze |
Global |
| JUS |
C.Sn6P |
Yugoslavia |
Composition (wt.%)
| Element |
Symbol |
Min % |
Max % |
Typical % |
| Copper |
Cu |
93.000 |
— |
93.500 |
| Tin |
Sn |
5.500 |
6.500 |
6.000 |
| Phosphorus |
P |
0.100 |
0.250 |
0.150 |
Physical
Melting Range
975 – 1025
°C
Thermal Conductivity
71
W/mK
Thermal Expansion
18
×10⁻⁶/K
Machinability
| Rating |
45.0% (B1112=100%) |
| Turning HSS |
175.0 m/min |
| Turning Carbide |
775.0 m/min |
| Surface Finish |
Ra 0.4-1.6 um |
| Coolant |
Soluble oil 5-8% |
Mechanical
| Condition |
Rm (MPa) | Re (MPa) | A (%) |
HB | HRC | KV (J) | E (GPa) |
| Annealed (O) (+O) |
350 – 480 |
≥140 |
≥45 |
80 – 120 |
— |
— |
115 |
| Half Hard (H02) (H02) |
480 – 640 |
≥380 |
≥20 |
130 – 165 |
— |
— |
115 |
| Hard (H04) (H04) |
590 – 750 |
≥510 |
≥10 |
165 – 205 |
— |
— |
115 |
| Extra Hard (H06) (H06) |
680 – 830 |
≥620 |
≥5 |
195 – 230 |
— |
— |
115 |
Heat Treatment
| Process |
Temperature |
Medium |
Duration |
Hardness After |
| Annealing |
450 – 700°C |
Inert or reducing atmosphere |
20-60 min |
HB 80-120 |
| Stress Relief |
130 – 200°C |
Air oven |
1-2 h |
Minimal |
Applications
Electrical Springs: Precision connector springs, relay springs and contact springs — primary application.
Electrical Connectors: Socket contacts, crimp contacts and edge connector fingers.
Bearings: Plain bearing bushes in corrosive environments where steel would corrode.
Musical Instruments: Cymbals, bells and tambourines (80% of professional cymbals are CuSn8-12).
Notes
CuSn6 vs CuBe2 springs: CuSn6: 40% IACS conductivity, Rm 750 MPa H04, no hazard, low cost. CuBe2: 22% IACS, Rm 1400 MPa — 2x strength. Use CuBe2 when spring loads demand >750 MPa; CuSn6 for most electrical springs at lower load.
P content: P (0.10-0.25%) deoxidises the melt (preventing tin oxide porosity) and slightly hardens — essential for spring properties. Specify phosphor bronze (not just tin bronze) for spring applications.