2. Welding Definitions :
Welding is the joining of multiple pieces of metal by the use of heat and
or pressure. A union of the parts is created by fusion or recrystallization
across the metal interface. Welding can involve the use of filler material,
or it can involve no filler.
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Purpose:
To become more familiar with the welding process and its effects
on the material
To look at the changes in microstructure and the hardness in the
Heat Affected Zone (HAZ)
Welding defects, their cause and preventative Measures
Industrial radiography techniques
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What commercial and technological importance does welding have?
Provides a permanent joint
Weld joint can be stronger than parent material
( If the filler material has superior strength characteristics and proper
techniques are used)
Usually the most economical way to join components
Can be done in the field away from a factory
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Type of Welding:
Arc Welding
Tig Welding
Arc Welding :
A fusion welding process in which the coalescence of the metals
is achieved by the heat from an electric arc between an electrode
and the work.
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Types of Arc welding :
Shielded Metal Arc Welding (SMAW):
An arc welding process that uses a consumable electrode consisting of a
filler metal rod coated with chemicals that provide flux and shielding.
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Gas Metal Arc Welding (GMAW):
Arc welding process in which the electrode is a consumable bare metal
wire and shielding is accomplished by flooding the area with gas.
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Tig Welding & Gas tungsten Arc Welding (GTAW).
TIG welding is a process where melting is produced by heating
with an arc struck between a non-consumable tungsten electrode
and the work piece. An inert gas is used to shield the electrode
and weld zone to prevent oxidation of the tungsten electrode and
atmospheric contamination of the weld and hot filler wire.
13. Engineering Material:
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.
Metels
Metals
Ferrous Metals Non- Ferrous Metals
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Ferrous Metals :
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
Non-Ferrous Metals :
The metals, which contain a metal other than iron as their main
constituent, are called Non-Ferrous Metals. The various Non-Ferrous
metals used in industry are
Aluminum , Copper , Zinc , Brass
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Steel:
Steel is the generic term for a large family of Iron-Carbon 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
Carbon Steel :
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)
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CLASSIFICATION OF CARBON STEEL :
Low Carbon Steel
(Carbon-0.05 To 0.25 %)
Medium Carbon Steel
(Carbon-0.30 To 0.55 %)
High Carbon Steel
(Carbon-0.60 To 1.30 %)
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Alloy steels:
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:
Low Alloy Steel
Medium Alloy Steel
High Alloy Steel
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1. Low Alloy Steel:
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 : 0.40 %
Manganese : 0.70 %
Nickel : 1.85 %
Chromium : 0.80 %
Molybdenum : 0.25 %
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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.
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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.
CLASSFICATION OF STAINLESS STEEL
Austenitic:
In austenitic steel metal atoms are arranged in Face Centered Cubic (FCC)
Feritic:
In ferritic steel metal atoms are arranged in Body Centered Cubic (BCC)
Martensitic:
In martensitic steel metal atoms are arranged in Body Centered Teragonal (BCT)
