Brasses

Brasses are widely used alloy of copper (main constituent) and zinc. They also contain small amounts of lead or tin or aluminium. The most commonly used copper-zinc alloy is brass. There are various types of brasses, depending upon the proportion of copper and zinc. The fundamental a binary alloy comprises 50% copper and 50% zinc. By adding small quantities of other elements, properties of brass may be greatly changed. For example addition of lead (1 to 2%) improves the machining quality of brass. It has a greater-strength than that of copper, but has a lower thermal and electrical conductivity. Brasses alloys are very resistant to atmospheric corrosion and can be easily soldered. They can be easily fabricated by processes like spinning and can also be electroplated with metals like nickel and chromium. Some of common phases of brass are discussed as under.

Alpha Phase

If the copper crystal structure is face centered cubic (FCC), there will be up to 36% of zinc. This solid solution is known as alpha brass. It has good mechanical properties, good corrosion resistance but it possesses lower electrical conductivity than copper.

Beta Phase

If the amount of zinc increases beyond 36%, beta brass will appear in the microstructure of the slowly cooled brass. This has body centered cubic structure (BCC). This phase is hard but quite tough at room temperature.

Gamma Phase

When zinc content is increased in brass beyond 45%, then gamma phase is appeared in its structure. This structure is extremely brittle, rendering an alloy which makes it unsuitable for general engineering purposes. The various types of brasses are discussed as under.

1 Red Brass

Red brass is an important material used for heat conducting purposes. Itcontains

Cu = 85%

Zn = 15%.

Properties

Red brass is having excellent corrosion resistance and workability. It possesses tensile strength ranging from 27-31 kg/mm 2. Percentage elongation of this brass is 42-48.

Applications

Red brass is mainly utilized for making, heat exchanger tubes, condenser, radiator cores, plumbing pipes, sockets, hardware, etc.

2 Yellow Brass or Muntz Metal

Yellow brass is also known as muntz metal. It contains

Cu = 60%

Zn = 40%

Muntz metal is having high strength and high hot workability. It is having tensile strength 38 Kg/mm2 (approximately). The percentage elongation of this brass is 45%.

Applications

Yellow brass or muntz metal is suitable for hot working by rolling, extrusion and stamping. It is utilized for making small various components of machine and electrical equipment such as bolts, rods, tubes, valves and fuses. This metal is utilized for making for pump parts, valves, taps, condenser tubes, sheet form for ship sheathing (because of excellent corrosion resistance).

3 Cartridge Brass

It contains 70% Cu and 30% Zn. It is having good combination of strength and ductility. It is having tensile strength between 31-37 kg/mm2. Percentage elongation of this brass is 55-66%. It is generally processed into rolled sheets. The metal alloy can be easily cold worked using cold working processes such as wire drawing, deep drawing and pressing.

Applications

It is utilized for making for making tubes, automotive radiator cores, hardware fasteners, rivets, springs, plumber accessories and in tube manufacture.

4 Admiralty Brass

It contains

Cu = 71%

Zn = 29%

Sn = 1%

Properties

1. Admiralty brass is highly resistant to corrosion.

2. It is highly resistant to impingement attack of sea water.

3. It is having tensile strength 30 kg/mm2 (approx.).

4. It can be cold worked

5. It possesses good corrosion resistance to sea water corrosion.

6. The percentage elongation of admiralty brass is 65%.

Applications

Admiralty brass is utilized for making condenser tubes in marine and other installations. It is used for making plates used for ship building. It is utilized also for making bolts, nuts, washers, condenser plant and ship fittings parts, etc.

5 Naval Brass

Navel brass is commonly used for making marine components. It contains

Cu = 59%

Zn = 40%

Sn = 1%

Properties

Properties of naval brass are similar to muntz metal. As 1% zinc is replaced by 1% tin in Muntz metal to make navel brass, corrosion resistance of this material to sea water is significantly improved. The percentage elongation of navel brass is 47% and its tensile strength is 38 kg/mm2 (approx.).

Applications

Navel brass is commonly utilized for making marine hardware casting, piston rods, propeller shafts, welding rods etc.

6 Manganese Brass

Manganese brass is sometimes also called manganese bronze. It contains

Cu = 60%

Zn = 38%

Mn = 0.5%

Fe = 1.0%

Sn = 0.5%

Properties

Manganese brass possesses sufficient toughness and good corrosion resistance. It is very active in reducing the oxides of other metals.

Applications

Manganese brass is utilized for making hydraulic rams, valves and cylinders, tubes, pump rods, propellers, bolts, nuts etc.

7 Iron Brass or Delta Metal

Iron brass or delta brass contains

Cu = 60%

Zn = 37%

Fe = 3%

Iron brass or delta metal is hard, strong, tough, and having good corrosion resistance. It can be casted easily.

Applications

If corrosion is to be resisted in mild steel, then some amount of iron brass or delta metal is added in mild steel.

8 Gilding Brass

Gilding brass is a very cheap metal for making jewellery, decorative and ornamental products. It generally contains

Cu = 85%

Zn = 15%

Applications

Because of better appearance this metal is commonly used for jewellery, decorative and ornamental work.

9 Free Cutting Brass

Free cutting brass contains

Cu = 57.5%

Zn = 40%

Pb = 2.5%

Free cutting brass is highly machinable and it does not allow bending.

Applications

Free cutting brass is used for making cast, forged or stamped blanks to be used for further machining such as high speed turning and screwing.

10 Lead Brass

Lead brass is also known as cloak brass which contains

Cu = 65%

Zn = 34%

Pb = 1%

Applications

Lead brass or cloak brass is used in making small gears and pinions for clock work.

Reference Introduction to basic Manufacturing Processes and Workshop Technology by Rajender Singh.

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