High‑Strength Copper Tin Alloy UNS C51900 (R720) – Ideal for Springs & Flexible Tubes

CuSn6 provides an excellent combination of strength, cold formability and hardness. It is wear resistant, has good corrosion resistance and soldering properties. Due to its high strength and good spring properties combined with good machining properties it is used for all kind of springs, Bourdon tubes or flexible metal tubes.

Quantity: 4 TonnesAdditional services: Slitting center, Electro Plating, Electro Plating Reflow, Multilayer Advanced barrier Sn.

Properties

General

Property	Temperature	Value
Density	23.0 °C	8.8 g/cm³

Mechanical

Property	Temperature	Value	Comment
Bendability 90°, gw	23.0 °C	1 [-]	r = x t, t <0.5mm
Elastic modulus	23.0 °C	102 - 118 GPa	depending on the condition
Elongation A50	23.0 °C	4 %
Hardness, Vickers	23.0 °C	210 [-]	min.
Tensile strength	23.0 °C	720 MPa	min
Yield strength Rp0.2	23.0 °C	650 MPa	min.
Bendability 90°, bw	r = x t, t <0.5mm

Thermal

Property	Temperature	Value	Comment
Coefficient of thermal expansion	100.0 °C	1.8E-5 1/K	for 20°C to the mentioned temperature
	200.0 °C	1.85E-5 1/K	for 20°C to the mentioned temperature

Specific heat capacity	23.0 °C	377 J/(kg·K)
Thermal conductivity	23.0 °C	75 W/(m·K)

Electrical

Property	Temperature	Value	Comment
Electrical conductivity	23.0 °C	9.00E+6 - 1.00E+7 S/m	min.
Specific Electrical conductivity		15.5 % IACS	min.

Chemical properties

Property	Value	Comment
Copper	Balance
Iron	0.1 %	max.
Lead	0 - 0.02 %
Nickel	0 - 0.2 %
Other	0 - 0.2 %
Phosphorus	0.01 - 0.4 %
Tin	5.5 - 7 %
Zinc	0 - 0.2 %

Technological properties

Property
Application areas	Electrical: Miniaturized Connectors, Contact Springs, Relais Springs, Electrical Flexing Contact Blades, Terminals, Switch Parts, Fuse Clips, Electronic Connectors, Resistance Wire, Electromechanical Spring Components, Electrical Flexing Contact Blades, Wire Brushes, Switch Parts, Electronic and Precision Instrument Parts. Fasteners: Lock Washers, Cotter Pins, Fasteners. Industrial: Bourdon Tube, Bellows, Textile Machinery, Perforated Sheets, Springs, Sleeve Bushing, Clutch Disks, Beater Bar, Chemical Hardware. General: Stamped parts, Connectors, Contact springs, Spring elements, Ultra high strength spring elements, Membranes, Switch elements, Fixed contacts.
Brazing	Good
Cold Forming	Max. 70 % between annealings, excellent
Corrosion properties	CuSn6 has a good resistance to seawater, different agents and industrial atmosphere and has a good resistance to tarnishing. It is in a large extend resistant to pitting corrosion. Even in seawater the laminar attack is higher than localized corrosion.
Heat Treatment	Temper: R720
Hot forming	at 750-850°C, limited
Machining	Rating 20, less suitable
Other	This alloy is in accordance with RoHS 2002/96/CE for electric & electronic equipments and 2002/53/CE for automotive industry.
Plating	Electroplating is excellent
Welding	Gas Shielded Arc Welding: Good, Laser Welding: Good

CuSn6 (UNS C51900 R640) – High Strength, Wear‑Resistant Spring Metal CuSn6 (UNS C51900 R850) – High-Strength, Wear-Resistant Spring Alloy

Metal