1
Aug 16, 2015
2
SUBJECT: Engineering Materials
INSTRUCTOR: Engr. Nazeer Ahmed Anjum
Students Name: Saad Sharif Saleemi UW-13-ME-BSc-002
Haseeb Tariq UW-13-ME-BSc-014
DEPARTMENT OF MECHANICAL ENGINEERING
4
Aluminum
Refining
Introduction to refining of aluminum
Bayer process
Hall process
Properties
Applications
Question/answers
7 Refining of aluminum:
Introduction
Alumina is the common name given to aluminum oxide (Al2O3). Alumina is produced from bauxite, an ore that is mined from topsoil in various tropical and subtropical regions.
The Bayer process is the primary process by which alumina is extracted from bauxite.
To produce pure aluminum, alumina is smelted using the Hall–Héroult electrolytic process. This process is referred to as primary production.
8 Scheme for refining of aluminum
bauxite• Bayer
process
alumina• Product
of Bayer process
aluminum
• Hall heroult
9 Bayer process:
The Bayer process is carried out in four steps
1. Digestion
2. Clarification
3. Precipitation
4. Calcination.
11 Hall–Héroult process
The Hall–Héroult process is the major industrial process for smelting aluminium. It involves dissolving aluminium oxide (alumina) in molten cryolite, and electrolysing the molten salt bath, typically in a purpose-built cell
12 Principle of Hall process
“when the alumina solution is electrolyzed in molten cryolite (), pure aluminium is produced.”
The reduction cell bottom serves as a cathode, and coal bars immersed in cryolite serve as anodes. Molten aluminium is deposited under a cryolite solution with 3-5% alumina. During this process, temperatures reach 950°C, considerably higher than the melting point of the metal itself, which is 660°C
15 Physical Properties
•Symbol: Al•Melting point: 1,221°F (660.3°C)•Electron configuration: [Ne] 3s2 3p1•Atomic number: 13•Boiling point: 4,566°F (2,519°C)•Atomic mass: 26.981539 ± 0.0000008 u•Discoverer: Hans Christian Ørsted
16 Mechanical Properties
Young's modulus 70 GPa Shear modulus 26 GPa Bulk modulus 76 GPa Poisson ratio 0.35 Vickers hardness 160–350 MPa Brinell hardness 160–550 MPa
17 Some Other Properties
Corrosion resistance Thermal expansion 23.1 (at 25°C) Thermal conductivity 237 Electrical resistivity 28.2 nΩ·m (at 20
°C) Light weight Recyclable
20 Air Craft
In aircraft construction, aluminum is used for frames, exteriors, wiring and electrical systems;
21 Automobile
automotive industry it is used for frames, bodies, blocks, pistons, valves, bumpers, wheels and other parts.
22 Pakages
aluminum has few rivals when it comes to the packaging of food, beverages and pharmaceuticals
23 Electrical equipment
Aluminum has almost entirely replaced copper. Aluminum is also increasingly replacing copper in transformers.
Casing, mountings and other parts or equipment used in communications and electronics.
General office equipment, fuse boxes, satellite dishes, household appliances, television sets and sound systems
24 Different products
furniture and household fittings
Transportation containers, gas cylinders, masts, bicycles and caravans