ME8491 ENGINEERING METALLURGY - UNIT 1

1. ME 8491 ENGINEERING METALLURGY
M.KARTHIKEYAN
ASSISTANT PROFESSOR
DEPARTMENT OF MECHANICAL ENGINEERING
AAA COLLEGE OF ENGINEERING & TECHNOLOGY, SIVAKASI
karthikeyan@aaacet.ac.in

2. Constitution of alloys – Solid solutions, substitutional
and interstitial – phase diagrams, Isomorphous, eutectic,
eutectoid, peritectic, and peritectoid reactions, Iron –
carbon equilibrium diagram. Classification of steel and
cast Iron microstructure, properties and application.
UNIT I ALLOYS AND PHASE DIAGRAMS

3. CLASSIFICATION OF STEELS

4. Carbon percentage: 0.008 to 0.25 %
Microstructure: Ferrite, Pearlite
Properties:
 Low hardness and cost.
 High ductility,
 Toughness,
 Machinability and
 Weldability
LOW-CARBON STEEL (OR MILD-CARBON STEEL)

5. Description:
 Low-carbon steel is the most widely used form of carbon steel.
 These steels usually have a carbon content of less than 0.25 wt.%.
 They cannot be hardened by heat treatment (to form martensite) so
this is usually achieved by cold work.
 Carbon steels are usually relatively soft and have low strength.
 They do, however, have high ductility, making them excellent for
machining, welding and low cost.
 High-strength, low-alloy steels (HSLA) are also often classified as
low-carbon steels, however, also contain other elements such
as copper, nickel, vanadium and molybdenum.

6. Applications:
 Automobile panels,
 nails,
 wire,
 Pipes,
 structural steel,
 sheet steel,
 Low-temperature pressure vessels

7. Carbon percentage: 0.25 to 0.60 %
Microstructure: Martensite
Properties:
 Low hardenability,
 Medium strength,
 Ductility and
 Toughness
MEDIUM-CARBON STEEL

8. Description:
 Medium-carbon steel has a carbon content of 0.25 – 0.60 wt.% and a
manganese content of 0.60 – 1.65 wt.%.
 The mechanical properties of this steel are improved via heat
treatment involving autenitising followed by quenching and
tempering, giving them a martensitic microstructure.
 Heat treatment can only be performed on very thin sections,
however, additional alloying elements, such as
chromium, molybdenum and nickel, can be added to improve the
steels ability to be heat treated and, thus, hardened.
 Hardened medium-carbon steels have greater strength than low-
carbon steels, however, this comes at the expense of ductility and
toughness.

9. Applications:
 Machinery parts,
 gears,
 shifts,
 axles,
 bolts,
 Crankshafts,
 couplings,
 cold headed parts.

10. Carbon percentage: 0.60 to 2 %
Microstructure: Pearlite
Properties:
 High hardness,
 Strength,
 Low ductility
HIGH-CARBON STEEL

11. Description:
 High-carbon steel has a carbon content of 0.60– 2 wt.% and a
manganese content of 0.30 – 0.90 wt.%.
 It has the highest hardness and toughness of the carbon steels and
the lowest ductility. High-carbon steels are very wear-resistant as a
result of the fact that they are almost always hardened and
tempered.
 Tool steels and die steels are types of high-carbon steels, which
contain additional alloying elements including chromium,
vanadium, molybdenum and tungsten.
 The addition of these elements results in the very hard wear-
resistant steel, which is a result of the formation of carbide
compounds such as tungsten carbide (WC).

12. Applications:
 Music wire,
 Springs,
 cutting tools

13. 1. What is steel?
2. Explain the various classifications of steel with microstructure,
properties and applications.
QUESTIONS