COPPER & ITS ALLOYS

COPPER & ITS ALLOYS

1 Introduction:-

Copper is red in colour and has a crystalline structure and it possesses the following properties

1)      Excellent resistance to corrosion

2)      High thermal and electrical conductivity

3)      Non magnetic properties

4)      It is ductile and malleable

5)      Very good mach inability

6)      Resistance to fatigue, abrasion and corrosion

7)      It can be soldered, brazed or welded

8)      It can be easily polished, plated and possesses a pleasing appearance

9)      Ease of forming alloys with other elements like zinc, tin, aluminum, lead, silicon, nickel etc.

10)    Melting point of copper is  1080^°C.           

2.Uses of copper

     Copper is used for the following

(1)     Electrical parts, Condensers, heat exchangers, household utensils, bus bars etc.

(2)     Automobile radiators, pressure vessels.

(3)     For bolts, studs, welding tips,

3  Types of Copper Alloys:-

1)       Copper zinc alloy (Brass)

      Brass is an alloy of copper and zinc it has high resistance to corrosion and is easily machinable.  It also acts as good bearing material.  Zinc in the brass increase ductility along with strength. Brass possesses greater strength than copper.  However it has a lower thermal and electrical conductivity. The properties of brass varies with the percentage of zinc varies from 5 - 45%.

Types of Brasses

Brasses are classified based on

1)            Structure- alpha brasses, alpha –beta brasses

2)            Colour- red brass and yellow brass.

Alpha brass contain zinc less than 30% and alpha-beta brass contain zinc between 30-44%.

Alpha Brass-They are soft, ductile, malleable and have good corrosion resistance. These are suitable for cold working.

Types of Alpha-Brass

1)            Cap Copper-contains zinc between 2-5%. It is very ductile. Used for caps of detonators.

2)            Gilding Metal- contains zinc 5-15%. Used for bullet envelopes, containers, condenser tubes, coins, emblems, jewellery.

3)            Cartridge brass (70-30 Brass) contains zinc 30%. Used for cartridge cases, radiator fins, lamp fixtures, rivets, springs.

4)            Admiralty Brass-contains zinc 30% and Tin 1%. Used for condensor tubes and heat exchangers.

Alpha-Beta Brass

They contain zinc between 30-40%, they are hard, strong, compared to alpha brasses, and they are hot worked.

Types of Alpha-Beta Brasses

1. Muntz Metal (60-40 Brass)- contain zinc 40%. Used for utensils, shafts, nuts, bolts, pump parts, condensor tubes.
2. Naval Brass (Also called Tobin Brass)- Contain zinc 39% and Tin 1%, used for marine hardware, propeller shafts, piston rods, nuts and bolts, welding rods.
3. Leaded Brass-contain zinc 39% and lead 1-3%. Used for parts requiring high machinability.
4. High Tensile Brass-contain zinc 39%, Fe 2%, Mn 1%, used for marine engine pumps, ships, propellers, gears, and valve bodies.
5. Brazing Brass- contains Zinc 50% and is very brittle. Used for brazing purpose.

2) Copper Tin alloy (Bronze)

     Bronze is basically an alloy of copper and tin.  It possesses superior mechanical property and corrosion resistance than brass.  It is comparatively hard and it resists surface wear.  It can be shaped in to various forms. The tin content varies from 10 -15%.

Types Of Bronze and uses:

1. Aluminium Bronze-contain aluminium 4 to 11%, Fe, Ni, Mn, Si are added in small amount.

Properties:

a.            Good Strength, ductility and toughness.

b.            Good bearing properties.

c.            Good Corrosion resistance.

d.            Good fatigue resistance

e.            Good lustre

Uses:

For jewelry, heat exchangers, chemical plants, pimp castings, valve fittings, cylinder heads, gears, dies, bearings, spark plug bodies and electrical parts,

2. Tin Bronzes-contain tin 8-25%, zinc 1-2%

Properties:

a)            Good ductility and malleability

b)            Good corrosion resistance.

Uses:

For making coins, pumps, gears, bearings, bells, statues, pipe fittings, ornamental fixtures, gun barrels.

3. Beryllium Bronzes-contain beryllium 2%

Properties:

a)            Good corrosion and fatigue resistance.

b)            Good bearing properties.

c)            High resilience.

Uses:

Used for springs, diaphragms, bellows, gears, bearings, and electrical contacts.

4. Silicon Bronze-contain silicon 1-5%

Properties:

a)            High resistance to corrosion.

b)            High tensile strength

c)            High toughness.

Uses:

For high strength bolts, rivets, springs, propeller shafts, bells.