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, goodcorrosion 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.
Red Brass: Red brass is an important material used for heat conducting purposes. Itcontains
Cu = 85%
Zn = 15%.
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.
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).
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.
Admiralty Brass: It contains
Cu = 71%
Zn = 29%
Sn = 1%
- Admiralty brass is highly resistant to corrosion.
- It is highly resistant to impingement attack of sea water.
- It is having tensile strength 30 kg/mm2 (approx.).
- It can be cold worked
- It possesses good corrosion resistance to sea water corrosion.
- 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.
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.