C655
A silicon bronze
Typical values for the temper in the title
C655 ("High Silicon Bronze A") contains about 3% silicon and about 1% manganese. It combines good strength, corrosion resistance (also in marine and chemical environments) and excellent weldability, which is relatively rare among copper alloys.
It is used for marine bolts and fasteners, chemical tanks and piping, welded parts and sculpture. Silicon bronze wire is also used for arc brazing of galvanized steel.
Mechanical and physical properties
| Property | Value | Note |
|---|---|---|
| Tensile strength Rm | 370–650 MPa | |
| Yield strength Rp0.2 | 105–490 MPa | |
| Elongation A | 3–60% | |
| Hardness | 75–180 HB | |
| Modulus of elasticity E | 100 GPa | |
| Density ρ | 8.53 g/cm³ | |
| Machinability | 30% | relative rating in the site database |
Chemical composition (wt %)
| Element | Range | Role |
|---|---|---|
| Si silicon | 2.8–3.8 | strength and corrosion resistance |
| Mn manganese | 0.50–1.3 | |
| Zn zinc | max 1.5 | |
| Fe iron | max 0.8 | |
| Ni nickel | max 0.6 | |
| Pb lead | max 0.05 | |
| Cu copper | balance |
Per copper.org tables.
Tempers and heat treatment
Ordinary copper and brass are not hardened by heat treatment. Strength comes from cold work, marked as the temper: annealed (O) is soft, up to "hard" (H) is strong. Annealing returns the material to the soft condition.
| Condition | Properties | When to choose it |
|---|---|---|
| Annealed (O) | soft and ductile, lowest strength in the range | deep drawing and bending |
| Half hard (H02) | medium strength | general parts |
| Hard (H04 and up) | high strength, low ductility | springs and contacts |
Applications
- Marine bolts and fasteners
- Chemical tanks and piping
- Welded parts
- Sculpture
- Arc brazing wire
Fabrication
Welding
Excellent, among the best of the copper alloys.
Corrosion
Resistant in the atmosphere, water and many chemicals.
Machining
Moderate.
Compared with similar materials
| Material | Rm / Rp0.2 | Welding | When it is the better choice |
|---|---|---|---|
| C614 | 550–600 / 280 MPa | Excellent | aluminum bronze: stronger · material page |
| C510 | 330–690 / 130–550 MPa | Medium | phosphor bronze: for springs · material page |
| 316 / 316L | 485–620 / 170–310 MPa | Excellent — ER316L | stainless: strong, costly to machine · material page |
Common mistakes
Choosing brass instead when welding is needed
Brass is hard to weld because of the zinc. Silicon bronze welds well.
Expecting aluminum bronze strength
It is weaker.
Using it for loaded bearings
For bearings, tin or aluminum bronzes.
Equivalents, standards and supply
| EN | CW116C |
|---|---|
| DIN | CuSi3Mn1 |
| JIS | C6561 |
| Standards | ASTM B98 / EN 12163 |
| Forms | rod · wire · welding |
| Producers | Wieland · Diehl |
Learn more
Values are typical and for comparison only. For design, rely on the standard and the mill certificate. Sources: Copper Development Association (copper.org), ASTM B111 and B124, producer data sheets, and the METAL HUB materials database.
Updated: October 31, 2026