BS 1400 PB1 Phosphor Bronze: Modern Equivalent and Composition

BS 1400 PB1 is a cast phosphor bronze from the withdrawn British standard. BS 1400:1985 was replaced on 15 March 1999 by BS EN 1982, so PB1 now survives only as a legacy designation on older drawings. Its modern equivalent is EN 1982 CuSn11P-C, code CC481K. Drawings that still call for PB1 should be updated to the EN designation with the casting process code stated.

Cross-reference at a glance

Standard system	Designation	Relationship	Evidence
BS 1400	PB1 — withdrawn 1999-03-15, replaced by BS EN 1982	Legacy	A
BS EN 1982	CuSn11P-C — CC481K (ingot CB481K)	Equivalent	B
DIN (withdrawn)	CuSn10P / G-CuSn10 — W-Nr 2.1050	Equivalent	B
UNS / ASTM	C90700 — nearest, not equivalent (tin ranges differ)	Nearest only	B
SAE	65 / 65c — historical	Historical	C
JIS H5121	CAC502 (PBC2) — approximate	Approximate	B
AS 1565	C90710 / 904D — historical	Historical	C
GB/T 1176	ZCuSn10P1 — approximate	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 — CC481K (castings)	Evidence
Cu	87.0 – 89.5	B
Sn	10.0 – 11.5	B
P	0.5 – 1.0	B
Pb	0.25 max.	B
Zn	0.05 max.	B
Ni	0.10 max.	B
Fe	0.10 max.	B
Al	0.01 max.	B
Mn	0.05 max.	B
Si	0.01 max.	B
S	0.05 max.	B
Sb	0.05 max.	B

Element	EN 1982 — CB481K (ingot)	Evidence
Sn	10.2 – 11.5	C
P	0.6 – 1.0	C

The phosphorus range of 0.5 – 1.0 % is what defines this as a phosphor bronze. It acts as a deoxidiser during melting and raises hardness and fatigue strength in the finished casting.

Mechanical properties

EN 1982 — CC481K, minimum values

Condition	Tensile R_m MPa, min.	Yield R_p0.2 / R_p0.5 MPa, min.	Elongation A %, min.	Hardness HBW, min.	Evidence
GS — sand cast	250	130	5	60	B
GM — permanent mould	310	170	2	85	B
GC — continuous	350	170	5	85	Q
GZ — centrifugal	330	170	4	85	B

Yield shown as R_p0.2.

Physical properties

Property	Value	Evidence
Density	8.8 g/cm³	C
Thermal conductivity	47 W/(m·K)	C

Selection notes

This is a high-tin, high-hardness bearing alloy used for worm wheels, heavily loaded bearings and valve components. The 85 HB minimum for continuously and centrifugally cast material is well above the leaded tin bronzes.
The low lead content means it depends on a reliable lubricant film. It is not the choice for marginal lubrication or shafts that deflect.
When converting legacy drawings, state the casting process code (GS, GM, GZ or GC) alongside CC481K. The mechanical minimums differ materially between processes — elongation ranges from 2 % to 5 % and hardness from 60 to 85 HB.
PB1 is frequently confused with PB2. PB2 corresponds to CuSn12 (CC483K), a different alloy. See the CuSn12 page.

Limitations of the data

The tensile strength for continuous cast is given as 350 MPa by two sources and 330 MPa by another. The 350 MPa figure is shown with the lower alternative noted.
One widely circulated set of figures — tensile 420 MPa, yield 190 MPa, elongation 20 %, hardness 120 HB — is supplier indicative data and is a different quantity from the standard minimums. It is not valid as an acceptance criterion and is not used here.
C90700 is the nearest UNS grade rather than an equivalent: its tin range of 9 – 11 % only partly overlaps the CC481K range of 10.0 – 11.5 %.
Density and thermal conductivity come from a single source.

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