This unit surveys the most commonly used ferrous and non- ferrous metals and their principal alloys for engineering applications.
REVIEW AND SUMMARY
✓ This unit surveys the most commonly used ferrous and non- ferrous metals and their principal alloys for engineering applications.
✓ Ferrous alloys (steels and cast irons) are those in which iron is novig the prime constituent.
✓ Steels can be classified as follows:
1. Plain carbon steels
(i) Low-carbon steels - Those contain less than 0.25% carbon.
(ii) Medium-carbon steels - Those containing between 0.25 and 0.60% carbon.
(iii) High-carbon steels - Those containing more than 0.60% carbon.
2. Alloy steels
(i) Low alloy steels - Those contain upto 3 to 4% of alloying elements.
(ii) High alloy steels - Those contain more than 5% of alloying elements.
✓ The alloying elements are added to enhance properties such as ole increased strength, toughness, hardenability, corrosion and wear resistance, etc.
✓ Some of the commonly used alloying elements include Mn, Si, Cr, Ni, W, Mo, V, Ti, Co, Cu and Pb.
✓ In this unit, we have discussed designation, composition, properties and typical applications of the following four important alloy steels.
1. Stainless steels,
2. Tool steels,
3. HSLA steels, and
4. Maraging steels.
✓ Stainless steels are alloys of iron, chromium, and other elements that resist corrosion from many environments.
✓ Three classes of stainless steels, on the basis of its micro- structure, are:
1. Austenitic stainless steels,
2. Ferritic stainless steels, and
3. Martensitic stainless steels.
✓ Tool steels are high-carbon alloys used to make tools and dies for cutting, forming, or otherwise shaping a material into a component or part for a specific application.
✓ HSLA (High-Strength Low-Alloy steels), also known as micro- alloyed steels, are low-carbon steels containing small amounts of alloying elements. Its primary purpose is weight reduction through increased strength.
✓ Maraging steels are low-carbon, highly alloyed steels. They are used in applications where very high tensile strength is desired.
✓ Cast irons can be defined as the ferrous alloys with greater than 2% carbon.
✓ In this unit, we have presented the designation, composition, properties, and typical applications of the following five major types of cast irons.
1. Grey cast iron,
2. White cast iron,
3. Malleable cast iron,
4. Spheroidal graphite (or nodular or ductile) cast iron, and
5. Alloy cast iron.
✓ The microstructure of grey cast iron contains graphite flakes, which tend to be brittle. But in spheroidal graphite cast iron these graphite flakes present as spheroidal nodules, which increases toughness. The white cast iron contains the cementite structure in the pearlitic matrix. The malleable irons may be produced by heat treating certain white cast irons, which contains graphite nodules (temper carbon).
✓ Alloy cast irons have been developed to have improved or special properties, such as high corrosion resistance.
✓ All the metallic elements other than iron are referred to as non-ferrous materials.
✓ The important non-ferrous materials used in engineering practice are aluminium, copper, lead, magnesium, nickel, tin, titanium, and zinc.
✓ Copper is a highly ductile metal with high electrical conduc- tivity and the pure metal is used in many electrical and electronics applications.
✓ The important copper alloys are:
1. Brasses Cu-Zn alloys),
2. Bronzes (Cu-Sn alloys),
3. Gun metals (Cu-Sn-Zn alloys), and
4. Cupronickels (Cu-Ni alloys).
✓ Aluminium is a soft, ductile metal of low density and with a high resistance to corrosion.
✓ Types of aluminium alloys:
1. Heat-treatable aluminium alloys:
Al-Cu, Al-Cu-Ni, Al-Mg-Si, etc. alloys.
2. Non-heat-treatable aluminium alloys:
Al-Mn, Al-Mg, Al-Si, alloys.
✓ At the end of this unit, the designation, composition, properties, and typical applications of alloys of copper and aluminium were discussed.
✓ Precipitation hardening, also known as age hardening, is the most important method of strengthening i.e., hardening the most of non-ferrous alloys by solid state reaction.
✓ Bearing materials are those materials used for making bearings.
✓ A bearing material should be hard, wear resistant; and should have a low coefficient of friction.
✓ The widely used bearing materials are:
1. White metals,
2. Copper-base alloys,
3. Aluminium-base alloys,
4. Plastic materials, and
5. Ceramics.
KEY TERMS YOU SHOULD REMEMBER
Ferrous Metals
Steels
Plain carbon steels
Low carbon steels
Medium carbon
steels
High carbon steels
Alloy steels
Low alloy steels
High alloy steels
AISI-SAE designation
system
Mild steels
AISI steels
HSLA steels
Alloying elements
Tool steels
Stainless steels
Austenitic stainless
steels
Ferritic stainless
steels
Martensitic
stainless steels
Maraging steels
Cast iron
Grey cast iron
White cast iron
Malleable cast iron
Ferritic
Pearlitic
Spheroidal graphite
cast iron
Alloy cast iron
Nodular cast iron
Ductile cast iron
Non-ferrous Metals
Copper
Copper alloys
Brasses
Gliding metal
Cartridge brass
Standard brass
Muntz metal
Naval brass
Admiralty brass
High tensile brass
Free cutting brass
Leaded gun metal
Monel metal
Bronzes
Bell bronze
Cupronickels
Phosphor bronze
Cupronickel
Silicon bronze
Coinage bronze
Leaded bronze
Aluminium bronze
Gun metals
'K' monel
Aluminium
Aluminium alloys
Al-Cu alloys
Precipitation (or age)
hardening
Natural ageing
Artificial ageing
Overageing
Bearing materials
White metals
Admiralty gun metal
Duralumin
Y-alloy
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