The Engineering metals play an important role in an
industry, because the process of all manufacturing starts with the raw
materials. The materials, mainly used in actual practice may be
broadly divided into the following Two Groups:
The metals, which contain a metal
other than iron as their main constituent, are called NonFerrous Metals. The various Non-Ferrous metals used in
industry are
Aluminum , Copper , Zinc , Brass & Etc.
The metals, which contain iron as their main
constituent, are called Ferrous Metals. The various ferrous
metals used in industry are
Pig Iron,
Cast Iron.
Wrought Iron and
Steel
Steel is the generic term for a large family of IronCarbon alloys, which are malleable, within some
temperature range, immediately after solidification form
the molten state. The principle raw materials used in steel
making are Iron ore, Coal, and Limestone
Is steel that owes its distinctive properties chiefly to the carbon
is contains.A steel qualifies as a Carbon Steel while it contains the
following materials at the rated percentage.
Manganese - 1.65 % (maximum)
Silicon
- 0.60 % (maximum)
Copper
- 0.60 % (maximum)
CLASSIFICATION OF CARBON STEEL :
Carbon Steel can be subdivided roughly into Three
groups :
1. LOW CARBON STEEL
: Carbon - 0.05 To 0.25 %
2. MEDIUM CARBON STEEL : Carbon - 0.30 To 0.55 %
3. HIGH CARBON STEEL
: Carbon - 0.60 To 1.30 %
Is steel that owes its distinctive properties chiefly to same
element or elements other that carbon, or jointly to such other elements
and carbon. Alloy steels posses high yield point and high strength. They
are more stronger, tougher and fatigue resistant than carbon steel.
CLASSIFICATION OF ALLOY STEEL:
Alloy Steel can be subdivided roughly into Three groups:
1. LOW ALLOYSTEEL 2. MEDIUM ALLOY STEEL
3. HIGH ALLOY STEEL
1. LOW ALLOY STELL :
Alloy steels contain one or more alloying agents to improve
mechanical and corrosion - resistant properties over those to carbon
steel. A typical low - alloy grade contains
Carbon
Manganese
Nickel
Chromium
Molybdenum
:
:
:
:
:
0.40 %
0.70 %
1.85 %
0.80 %
0.25 %
2. MEDIUM ALLOY STEEL:
A group of (mostly) proprietary alloys with somewhat better
corrosion resistance that stainless steels are called medium alloys. These
alloys have extensive applications in sulfuric acid system. Because of
their increased nickel and molybdenum contents that are more tolerant of
chloride-contamination than standard stainless steels.
3. HIGH ALLOY STEEL:
The groups of materials called high alloys all contain relatively
large percentage of nickel.
EFFECT OF ALLOYING ELEMENTS:
NICKEL: Increases toughness and improves low-temperature properties
and corrosion resistance.
CHROMIUM: Improve hardness, abrasion resistance, corrosion resistance
SILICON :
and resistance to oxidation.
Improve hardness, abrasion resistance, corrosion resistance
and resistance to oxidation.
MOLYBDENUM : Provides strength at elevated temperatures.
STAINLESS STEEL :
Stainless steels are high-alloy steels and have superior
corrosion resistant to the carbon and conventional low-alloy steels
because they contain relatively large amount of Chromium.
Stainless steels are iron base alloy containing Chromium as the
main alloying element with a minimum content of 10.5% to make it
resistant to staining, rusting, scaling in most of the corrosive
environments.
Several other alloying elements like Nickel, Molybdenum,
Manganese, Copper, Titanium, etc. are also added in different grades
in order to improve its Metallurgical, Physical and Mechanical
Properties to suit typical and use requirements.
Most of metals and alloys loose their strength and start scaling
when heated to high temperature and become brittle at low temperature.
Stainless steel retain its strength to great extent and do not scale at high
temperature, and at the same time they maintain their toughness and
ductility even at subzero temperature.
CLASSFICATION OF STAINLESS STEEL :
In the broadest sense the Stainless steels can be divided into
Three basic groups based on their structures:
1. AUSTENITIC
2. FERITIC
3. MARTENSITIC
The crystal structure of the metal depends upon the
configuration of its atoms to form unit cell.

In austenitic steel metal atoms are arranged in
Face Centered Cubic (FCC)

In ferritic steel metal atoms are arranged in
Body Centered Cubic (BCC)

In martensitic steel metal atoms are arranged in
Body Centered Teragonal (BCT)
EFFECT OF ALLOYING ELEMENTS ON THE PROPERTIES OF STEEL
Alloying
Elements
Hardness
Strength
Yield Point
Elongation
Chromium
Nickel In
Pearlite

Nickel In
Austenite
Molybdenum
Manganese In
Pearlite
Manganese In
Austenite
Nitrogen
Silicon
Phosphorous
Sulphur

Corrosion
Resistance
ENGG.MATERIALS
CERAMIC
METALS
FERROUS METALS
PIG IRON
NON-FERROUS METALS
CAST IRON
WROUGHT STEEL
CARBON STEEL
ALLOY STEEL
LOW C.S MEDIUM C.S
HIGH C.S
LOW A.S MEDIUM A.S
HIGH A.S
AUSTENITI
MARTENSITIC
FERITIC
ORGANIC
WROUGHT IRON
STAINLESS STEEL