BS643 Rope Capping Alloy
Product Overview
BS643 Rope Capping Alloy is the industry standard for capping steel wire ropes, providing excellent fluidity at low pouring temperatures and high holding resistance. It was the basis for the B.S.S. 643 specification introduced by the British Standards Institute in 1935, and remains a trusted alloy for wire rope applications.
Physical and Mechanical Properties
| Property | Value |
|---|---|
| Ultimate Tensile Strength | 3.8 tons/sq. inch |
| Elongation | 2% |
| Brinell Hardness | 25.6 (10mm ball, 500kg load, 15s) |
| Density | 9.96 g/cubic centimetre |
| Weight | 0.36 lb./cubic inch |
| Solidus | 240°C |
| Liquidus | 265°C |
| Pouring Range | 335°C – 363°C |
| Ingot Weight | 3 kg |
Chemical Composition
| Element | Percentage (%) |
|---|---|
| Tin (Sn) | 4.75 – 5.25 |
| Lead (Pb) | Balance |
| Antimony (Sb) | 14.5 – 15.5 |
| Copper (Cu) | 0.05 (Max) |
| Zinc (Zn) | 0.005 (Max) |
| Arsenic (As) | 0.005 (Max) |
| Total Impurities | 0.2 (Max) |
Casting and Application
BS643 Rope Capping Alloy melts at a temperature below 350°C, which does not significantly affect the fatigue resistance of hard drawn steel ropes when poured correctly. Its high fluidity allows it to penetrate to the narrow ends of the socket, creating a strong mechanical bond with the wires.
When wires are tinned, the holding resistance can reach 700 lb. per sq. inch; twisted or bent wires further increase this resistance threefold. The alloy relies on frictional resistance developed by shrinkage around the wire for strength.
Recommended Socketing Method (B.S.S. 643)
The rope should be securely bound with soft iron seizing wire, with individual wires unwound and cleaned before inserting into the socket. The socket must be heated evenly to approximately 100°C before pouring the molten alloy at 335–363°C. Powdered rosin dusted among wires helps metal flow, and careful pouring ensures complete fill without overflow.
After solidification, the socket should cool gradually, remaining undisturbed, before cleaning and treating the rope with preservative dressing.
Learn More!
*Learn More About DKL Metals*
Wikipedia – Wire Rope[Poured Sockets]