Bronze
Bronze band consists of a copper/tin alloy: CuSn. There are various alloy compositions, such as CuSn6. The number 6 indicates the tin percentage of the alloy (copper 94%, tin 6%). The higher the tin content, the stronger the material will be.
Tin is more expensive than copper as a raw material. CuSn bands with a higher tin content are therefore traded on the market at a higher price.
Bronze strips
CuSn (bronze) is a rather brittle material compared to brass. CuSN alloys are therefore suitable for products with good spring properties and high corrosion resistance, i.e. they retain the shape they were given when the band was shaped in the punching/bending process under defined mechanical strain, bounce back and do not corrode. Bronze alloys have almost the same spring characteristics and strength of steel, but are more resistant to corrosion. Their high copper content also makes them very good electrical conductors.
The alloy to be used is normally specified by an engineer during the development of a punched and bent part, as he knows the mechanical and electrical requirements for the final product and will take into account the market prices for the raw material.
Application examples:
Application examples:
CuSn 4= Damping pipes for machine and device construction, vibration dampers for cooling compressors, bellows, spring contacts for relays or switches.
CuSn 5-6: Springs and spring contacts for electrical use in relays or switches, leaf springs, coil springs
CuSn8: As CuSn5-6 and additionally also sliding bearings, sliding tracks and bolts
Physical properties
Physical properties
| Alloy | Density g/cm3 | Electrical conductivity MS/m - %IACS | Heat conductivity W/mk | Heat expansion coefficient 106/k | Modulus of elasticity KN/mm2 |
|---|---|---|---|---|---|
| CuSn4 | 8.9 | 11.0 - 20 | 84 | 17.8 | 110 |
| CuSn5 | 8.9 | 10.0 - 20 | 82 | 17.8 | 110 |
| CuSn6 | 8.8 | 9.0 - 20 | 84 | 17.8 | 110 |
| CuSn8 | 8.8 | 7 - 13 | 62 | 18.2 | 110 |
Chemical composition
Chemical composition
| Aloy | Cu % | Zn % | Sn % | P % |
|---|---|---|---|---|
| CuSn4 | Rest | <0,2 | 3,5 – 4,5 | 0,01 – 0,40 |
| CuSn5 | Rest | <0,2 | 4,5 – 5,5 | 0,01 – 0,40 |
| CuSn6 | Rest | <0,2 | 5,5 – 7,0 | 0,01 – 0,40 |
| CuSn8 | Rest | <0,2 | 7,5 – 8,5 | 0,01 – 0,40 |