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CuZn31Si1 (Silicon Brass -- Lead-Free Free-Machining)

CuZn31Si1 -- lead-free free-machining brass using silicon in place of lead for chip control. Rm 400-550 MPa, machinability approaching standard leaded brass. For plumbing fittings and drinking water components in jurisdictions restricting lead content (EU, California, and similar low-lead regulations).

Copper Alloys Lead-Free Free-Machining Brass EN 12164CuZn31Si1 / CW724R (nearest) Trade NamesEcoBrass (Sanbo Shindo) / Envirobrass / C69300 (nearest US lead-free) NSF/ANSI 61Drinking water system components -- compliance target composition EU Drinking Water DirectiveLow-lead potable water contact compliance +1
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Description

CuZn31Si1 (Eco-Brass / EnviroBrass type, CW724R nearest) per EN 12164. Si addition (0.7-1.3%) creates a fine, hard silicide phase that provides chip-breaking action analogous to lead, without the toxicity concerns -- developed specifically to meet increasingly strict low-lead and lead-free regulations for potable water contact components (EU Drinking Water Directive, US "lead-free" definitions under the Reduction of Lead in Drinking Water Act). Standard for plumbing fittings, potable water valves and drinking water system components in regulated jurisdictions.

Key Properties — Extruded/Drawn (H02)
Rm (Tensile Strength)
420 – 560
MPa
Re / Rp0.2 (Yield)
280
MPa
A₅ (Elongation)
≥ 15.0
%
Hardness
110 – 145
HB
E (Young's Modulus)
105
GPa
Density
8.40
g/cm³
Main Designations (5)
Standard BodyDesignationCountry / RegionNote
EN 12164 CuZn31Si1 / CW724R (nearest) EU
Trade Names EcoBrass (Sanbo Shindo) / Envirobrass / C69300 (nearest US lead-free) Global
NSF/ANSI 61 Drinking water system components -- compliance target composition USA
EU Drinking Water Directive Low-lead potable water contact compliance EU
JUS Bezolovni Si-mesing za pitku vodu; nema JUS Yugoslavia/BiH
Standards (5)
#Standard BodyDesignationCountry / RegionNote
1 EN 12164 CuZn31Si1 / CW724R (nearest) EU —
2 Trade Names EcoBrass (Sanbo Shindo) / Envirobrass / C69300 (nearest US lead-free) Global —
3 NSF/ANSI 61 Drinking water system components -- compliance target composition USA —
4 EU Drinking Water Directive Low-lead potable water contact compliance EU —
5 JUS Bezolovni Si-mesing za pitku vodu; nema JUS Yugoslavia/BiH —
All values in wt.%
Cu
Copper
68.0000 – 71.0000
Zn
Zinc
27.0000 – 31.0000
Si
Silicon
0.7000 – 1.3000
Pb
Lead (residual only)
≤ 0.0900
ElementSymbolMin %Max %Typical %
Copper Cu 68.0000 71.0000 69.5000
Zinc Zn 27.0000 31.0000 29.0000
Silicon Si 0.7000 1.3000 1.0000
Lead (residual only) Pb — 0.0900 0.0300
Mechanical Properties
ConditionCode Rm min
MPa		Rm max
MPa		 Re min
MPa		Re max
MPa		 A₅ min
%		 Z
%		 KV
J		 HB minHB max HRC minHRC max E
GPa
Extruded/Drawn (H02) H02 420 560 280 — 15.0 — — 110 145 — — 105.0
Annealed (O) +O 380 480 180 — 25.0 — — 85 115 — — 105.0
Physical Properties
Density
8.400
g/cm³
Melting Point
880–900
°C
Young's Modulus
105.0
GPa
Poisson's Ratio
0.350
—
Thermal Conductivity
55.0
W/m·K
Thermal Expansion
20.00
×10⁻⁶ /K
Specific Heat
380
J/kg·K
Electrical Resistivity
0.1200
µΩ·m
Magnetic
No
 
Heat Treatment
Annealing
Temperature:500°C – 650°C
Medium:Inert or reducing atmosphere
Duration:20-60 min
Cooling:Air or water cool
Hardness After:HB 85-115
Stress Relief
Temperature:150°C – 200°C
Medium:Air oven
Duration:1 h
Cooling:Air cool
Hardness After:Minimal
After machining or forming.
Hot working characteristics
Temperature:650°C – 750°C
Medium:Hot extrusion/forging
Duration:N/A
Cooling:Air cool
Hardness After:Good hot workability
Si-brass hot works well, similar to conventional leaded brass.
Regulatory compliance note
Medium:Residual Pb typically held below 0.25% (US) or 0.09% (stricter EU/California) depending on target market
Duration:N/A
Cooling:N/A
Hardness After:N/A
Confirm exact target specification against the applicable jurisdiction before specifying.
Machinability
Machinability Rating
relative to AISI B1112 = 100%
65.0%
Moderate
Turning Speed (HSS)
175
m/min
Turning Speed (Carbide)
780
m/min
Feed Rate (Turning)
0.340
mm/rev
Drilling Speed (HSS)
150
m/min
Milling Speed (Carbide)
790
m/min
CoolantSoluble oil 5-8%
Chip FormationShort chips due to Si-phase chip breaking -- approaches leaded brass performance
Tool MaterialHSS M2; carbide K20
Surface FinishRa 0.8-3.2 um
Good machinability -- meaningfully better than plain unleaded brass, though still somewhat behind full-lead CuZn39Pb3.
Applications
Plumbing Fittings
Potable water plumbing fittings in low-lead regulated markets.
Drinking Water Valves
Valve bodies and components for drinking water systems.
Water Meters
Water meter bodies and components requiring NSF/ANSI 61 or equivalent compliance.
Technical Notes
✅
Si-brass vs standard leaded brass for plumbing
CuZn39Pb3 (standard leaded brass): excellent machinability, but Pb content exceeds low-lead drinking water regulations in the EU, California (AB 1953) and under the US Reduction of Lead in Drinking Water Act. CuZn31Si1: purpose-developed lead-free alternative achieving most of the machinability benefit via Si rather than Pb, meeting modern low-lead potable water regulations. Increasingly the mandatory choice for new plumbing fitting designs in regulated markets, regardless of historical leaded-brass practice.