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CuSn8 (Phosphor Bronze)

Phosphor bronze with 8% tin. Excellent wear resistance, spring properties and seawater corrosion resistance. For bearings, springs and connectors.

Copper Alloys Tin Bronze ENCuSn8 / CW453K ISOCuSn8 (ISO 1187) UNSC52100 ASTMB103 / B139 +5
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Description

CuSn8 per EN 1652 (CW453K). Tin bronze with 8% tin and phosphorus deoxidant. Exceptional spring properties, fatigue resistance, wear resistance and seawater corrosion resistance. Used for precision springs, connectors, bushings, bearings and ship propellers.

Key Properties — Annealed (O)
Rm (Tensile Strength)
380 – 490
MPa
Re / Rp0.2 (Yield)
150
MPa
A₅ (Elongation)
≥ 40.0
%
Hardness
85 – 110
HB
E (Young's Modulus)
110
GPa
Density
8.80
g/cm³
Main Designations (9)
Standard BodyDesignationCountry / RegionNote
EN CuSn8 / CW453K EU
ISO CuSn8 (ISO 1187) International
UNS C52100 USA
ASTM B103 / B139 USA
BS EN PB104 / CW453K UK
JIS C5210 Japan
GOST BrO8 (BrO8) Russia
JUS C.Sn8 Yugoslavia Phosphor bronze 8% Sn; JUS B.C5.400
GB QSn8-0.3 China
Standards (9)
#Standard BodyDesignationCountry / RegionNote
1 EN CuSn8 / CW453K EU —
2 ISO CuSn8 (ISO 1187) International —
3 UNS C52100 USA —
4 ASTM B103 / B139 USA —
5 BS EN PB104 / CW453K UK —
6 JIS C5210 Japan —
7 GOST BrO8 (BrO8) Russia —
8 JUS C.Sn8 Yugoslavia Phosphor bronze 8% Sn; JUS B.C5.400
9 GB QSn8-0.3 China —
All values in wt.%
Cu
Copper
91.0000 – 92.5000
Sn
Tin
7.5000 – 8.5000
P
Phosphorus
0.0200 – 0.4000
ElementSymbolMin %Max %Typical %
Copper Cu 91.0000 92.5000 91.8000
Tin Sn 7.5000 8.5000 8.0000
Phosphorus P 0.0200 0.4000 0.1500
Mechanical Properties
ConditionCode Rm min
MPa		Rm max
MPa		 Re min
MPa		Re max
MPa		 A₅ min
%		 Z
%		 KV
J		 HB minHB max HRC minHRC max E
GPa
Annealed (O) +O 380 490 150 — 40.0 — — 85 110 — — 110.0
Half Hard (H02) H02 540 660 430 — 12.0 — — 145 175 — — 110.0
Spring Hard (H06) H06 700 820 650 — 2.0 — — 200 230 — — 110.0
Physical Properties
Density
8.800
g/cm³
Melting Point
780–830
°C
Young's Modulus
110.0
GPa
Poisson's Ratio
0.340
—
Thermal Conductivity
63.0
W/m·K
Thermal Expansion
18.00
×10⁻⁶ /K
Specific Heat
380
J/kg·K
Electrical Resistivity
0.1100
µΩ·m
Magnetic
No
 
Heat Treatment
Stress Relief (mandatory after cold work)
Temperature:100°C – 200°C
Medium:Air oven
Duration:1-2 h
Cooling:Air cool
Hardness After:Minimal change
Prevents season cracking.
Anneal
Temperature:450°C – 650°C
Medium:Inert or H2/N2 atmosphere
Duration:30-60 min
Cooling:Air or water cool
Hardness After:HB 85-110
Full softening for re-working.
Machinability
Machinability Rating
relative to AISI B1112 = 100%
25.0%
Very Difficult
Turning Speed (HSS)
85
m/min
Turning Speed (Carbide)
380
m/min
Feed Rate (Turning)
0.210
mm/rev
Drilling Speed (HSS)
68
m/min
Milling Speed (Carbide)
395
m/min
CoolantLight oil or soluble oil 5-8%
Chip FormationMedium chips (soft); short (spring)
Tool MaterialHSS M2; carbide K20
Surface FinishRa 0.4-1.6 um
Good machinability. Slightly more difficult than CuSn6 due to higher Sn.
Applications
Springs
Precision springs, wave springs, Belleville washers and high-fatigue spring contacts.
Connectors
High-load electrical connector contacts and high-cycle relay springs.
Bearings
High-duty bearing bushings and thrust washers for moderate-speed, high-load service.
Technical Notes
✅
CuSn8 vs CuSn6
CuSn8: higher strength (700 vs 600 MPa spring hard), lower conductivity (9 vs 13% IACS). Use CuSn8 for mechanical springs requiring maximum stress; CuSn6 for electrical contacts where conductivity matters.
💧
Seawater Resistance
Excellent seawater and salt-spray corrosion resistance. No dezincification risk.