Background

Brasses are alloys of copper and zinc. They may also contain small amounts of other alloying elements to impart advantageous properties. Brasses have high corrosion resistance and high tensile strength. They are also suited to fabrication by hot forging. Free machining grades of brass set the standard for machining, by which other metals are compared.
Brass Classes

Brasses are divided into two classes. The alpha alloys, with less than 37% zinc, and the alpha/beta alloys with 37-45% zinc. Alpha alloys are ductile and can be cold worked. Alpha/beta or duplex alloys have limited cold ductility and are harder and stronger. CZ121 is an alpha/beta alloy.
Alloy CZ114

Brass alloy CZ121 is used for machining. It has lead added to the composition to improve machinability. The lead remains insoluble in the microstructure of the brass and the soft particles act as chip breakers.
Alloy CZ121M

The name CZ121M is sometimes used to emphasise its machining properties.
Chemical Composition

Table 1. Typical chemical composition for brass alloy CZ121

%


CZ121

Cu


58

Pb


3

Sn


-

Fe


-

Al


-

Mn


-

Zn


Balance

Si


-

Ni


-

Properties
Mechanical Properties

Table 2. Typical mechanical properties for brass alloy CZ121

Grade


CZ121

Tensile Strength (MPa)


410

Proof Stress 0.2% (MPa)


200

Elongation A5 (%)


20

Hardness VPN


130-150
Physical Properties

Table 3. Typical physical properties for brass alloy CZ121

Property


Value

Density


8.47 g/cm3

Melting Point


875°C

Modulus of Elasticity


97 GPa

Electrical Resistivity


0.062x10-6 Ω.m

Thermal Conductivity


123 W/m.K at 100°C

Thermal Expansion


20.9 x10-6 /K at 100°C
Alloy Designations

CZ121 corresponds to the following designations:

CEN


BS


UNS


ISO

CW614N


BS2874 CZ121


C38500


CuZn39Pb3
Corrosion Resistance

The corrosion resistance of CZ121 is fair to excellent.
Fabrication
Cold Working

Cold working of CZ121 is poor and is not recommended. It can, however, be knurled if required.
Hot Working

Fabrication of CZ121 by hot working is excellent. It is recommended that hot working be done between 630 and 730°C.
Heat Treatment

Solution treatment or annealing can be done by rapid cooling after heating to 430-600°C.
Machinability

The machinability of alloy CZ121 is excellent. It has a machinability rating of 90 where Alloy 360 FC Brass is 100.
Welding and Joining

Soldering of CZ121 is rated as “excellent” and brazing is “good”. Butt welding is fair but all other welding methods are not recommended.
Applications

CZ121 is typically used in:

· High speed machined components

· Architectural extrusions

· Locks

· Hinges
Supplied Forms

CZ121 is typically supplied by Aalco in the following forms:

· Round bar

· Hexagon bar

· Square bar

· Flat bar