BS 1400 LG2 Gunmetal: Modern Equivalent and Composition
BS 1400 LG2 is the classic 85-5-5-5 leaded gunmetal: roughly 5 % each of tin, zinc and lead with the balance copper. Like PB1 it comes from the withdrawn BS 1400, and its modern equivalent is EN 1982 CuSn5Zn5Pb5-C, code CC491K. It is a general-purpose pressure-tight casting alloy used for valve bodies, pump casings and light to medium duty bearings.
Cross-reference at a glance
| Standard system | Designation | Relationship | Evidence |
|---|---|---|---|
| BS 1400 | LG2 — withdrawn 1999-03-15, replaced by BS EN 1982 | Legacy | A |
| BS EN 1982 | CuSn5Zn5Pb5-C — CC491K | Equivalent | B |
| DIN 1705 (withdrawn) | G-CuSn5ZnPb / RG5 — W-Nr 2.1096 | Equivalent | B |
| UNS / ASTM | C83600 — approximate, not fully equivalent | Approximate | B |
| SAE | 40 | Historical | C |
| JIS | CAC406 (formerly BC6) — approximate | Approximate | C |
| GB/T 1176 | ZCuSn5Pb5Zn5 (formerly ZQSn5-5-5) — approximate | Approximate | B |
| ISO | CuSn5Zn5Pb5 / CuPb5Sn5Zn5 | Approximate | C |
“Equivalent” means the specifications cover substantially the same composition range. “Nearest only” and “Approximate” mean the ranges overlap partially and a substitution needs checking against the composition table.
Chemical composition
| Element | EN 1982 — CC491K | Evidence |
|---|---|---|
| Cu | 83.0 – 87.0 | B |
| Sn | 4.0 – 6.0 | B |
| Pb | 4.0 – 6.0 | B |
| Zn | 4.0 – 6.0 | B |
| Ni | 2.0 max. | Q |
| P | 0.10 max. | B |
| Fe | 0.30 max. | B |
| Sb | 0.25 max. | B |
| Al | 0.01 max. | B |
| Si | 0.01 max. | B |
| S | 0.10 max. | B |
| Element | ASTM — C83600, for comparison | Evidence |
|---|---|---|
| Cu | 84.0 – 86.0 | B |
| Sn | 4.0 – 6.0 | B |
| Pb | 4.0 – 6.0 | B |
| Zn | 4.0 – 6.0 | B |
| Ni (incl. Co) | 1.0 max. | Q |
| P | 0.05 max. | B |
| Fe | 0.30 max. | B |
| Sb | 0.25 max. | B |
| Al | 0.005 max. | B |
| Si | 0.005 max. | B |
| S | 0.08 max. | B |
The tin, lead and zinc ranges are identical across the two systems, at 4.0 – 6.0 % each. They differ in the copper window (83.0 – 87.0 % under EN against 84.0 – 86.0 % under ASTM) and in the nickel and phosphorus limits.
lg2 gunmetal Mechanical properties
EN 1982 — CC491K, minimum values
| Condition | Tensile Rm MPa, min. |
Yield Rp0.2 / Rp0.5 MPa, min. |
Elongation A %, min. |
Hardness HBW, min. |
Evidence |
|---|---|---|---|---|---|
| GS — sand cast | 200 | 90 | 13 | 60 | B |
| GM — permanent mould | 220 | 110 | 6 | 65 | B |
| GZ — centrifugal | 250 | 110 | 13 | 65 | B |
| GC — continuous | 250 | 110 | 13 | 65 | B |
Yield shown as Rp0.2.
Physical properties
| Property | Value | Evidence |
|---|---|---|
| Density | 8.7 g/cm³ (EN-side) against 8.83 g/cm³ (ASTM-side) | Q |
| Machinability rating | 84 – 85 % (free-cutting brass C36000 = 100) | C |
Selection notes
- Pressure tightness is the reason this alloy dominates valve bodies, pump casings and steam fittings. The combination of tin, zinc and lead gives sound castings with good machinability.
- As a bearing material it suits light to medium loads at low speeds. For higher loads, C93200 or CuSn12 carry more. See the C93200 page for the comparison.
- It is more forgiving of poor lubrication than the high-tin alloys, and machines readily.
- ZCuSn5Pb5Zn5 is also the nearest GB grade to C93200. That means the same Chinese designation is used as a substitute for two different Western alloys, which is a common source of confusion on drawings and should be resolved by naming the standard.
Limitations of the data
- The Werkstoff number is 2.1096, not 2.1098.
- C83600 is approximate rather than equivalent: the copper window is narrower and the nickel limit lower than under EN.
- The nickel limits in both systems (2.0 % under EN, 1.0 % under ASTM) come from single sources and are marked accordingly.
- A tensile figure of 255 MPa, yield 117 MPa, elongation 30 % and hardness 60 HB circulates for C83600 as typical values. These are not standard minimums and are not valid as acceptance criteria.
- Density differs by about 1.5 % between the EN-side and ASTM-side sources.
Related grade pages
Leaded tin bronze (bearing bronze)
Cast aluminium bronze
Manganese bronze / high-tensile brass
High-lead tin bronze
Wrought phosphor bronze
Cast tin bronze
High-tensile brass (special brass)
Cast nickel aluminium bronze
Sintered (powder metallurgy) bronze
Wrought nickel aluminium bronze
Cast phosphor bronze
