fundamentals of welding
DESCRIPTION
Manufacturing ProcessesTRANSCRIPT
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1MAJU,ISLAMABAD 11/26/2013
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211/26/2013MAJU,ISLAMABAD
MANUFACTURING PROCESSES- I
P R O J E C T N A M E : W E L D I N G P R O C E S S E S
G R O U P M E M E B E R S :
1. A B U B A K R AY U B
2. W A Q A S A S H R A F
3. H A F E E Z - U R - R E H M A N
4. B I L A L J A V E D
5. S A L M A N A Z I Z
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CLASSIFICATION OF ASSEMBLY PROCESSES
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What is Welding?
Welding is a materials joining process in which two or
more parts are coalesced at their contacting surfaces by a
suitable application of heat and/or pressure
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T E R M S
1) Filler Material: Facilitate coalescence, Increase bulk and strength.
2) Weldment: The assemblage of parts that are joined by welding is called a
weldment.
3) Faying Surfaces: Surfaces in contact or in close proximity that are to be
joined.
4) Welding Fixture: Holds and clamps the components in fixed position for
welding.
5) Welding positioner: Hold the parts, can also moves the assemblage to the
desired position for welding.11/26/2013
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TY
PE
S O
F W
EL
DIN
G
PR
OC
ES
SE
S
FUSION WELDING
ARC (AW)
RESISTANCE (RW)
OXYFUEL (OFW)
OTHER
ELECTRON BEAM
LASER BEAM
SOLID STATE WELDING
DIFFUSION (DFW)
FRICTION (FRW)
ULTRASONIC (USW)
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The principal applications of welding are:
1. Construction, such as buildings and bridges
2. Piping, pressure vessels, boilers, and storage
tanks
3. Shipbuilding
4. Aircraft and Aerospace
5. Automotive and Railroad
6. They can be performed at construction sites, in
shipyards, at customers’ plants, and in
automotive repair shops
VERSATILITY OF WELDING
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The Weld Joint: It is the junction of the edges or surfaces of
parts that have been joined by welding.
Types of Joints
• Butt Joint
• Corner
Joint
• Lap Joint
• Tee Joint
• Edge Joint
Types of Welds
• Fillet Weld
• Groove Weld
• Plug Weld
• Slot Weld
• Spot Weld
• Seam Weld
• Flange Weld
• Surfacing Weld11/26/2013
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(a) butt, (b) corner, (c) lap, (d) tee, and (e) edge
Variousforms of fillet welds
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Some typical groove welds
Plug and Slot Welds
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a) SPOT WELD and
b) SEAM WELD
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PHYSICS OF WELDING
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Physical relationships
Power Density
“ Power transferred to the work per unit surface
area ”
PD = P/A (Watt/mm^2)
Heat Balance
Equations
Hw (net heat used by the welding
operation)=Um*V (Joules)
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PHYSICAL RELATIONSHIPS
There are two physical relationships that allow fusion welding to
be performed.
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• Inverse Relation (PD is inversely proportion to time of
melting)
• If power density is too low, the heat is conducted into the
work as rapidly as it is added at the surface, and melting
never occurs.
• The minimum power density required to melt most metals
in welding is about 10 W/mm^2.
• Differences in the range of PD among different welding
processes.(See Table on next slide)
EFFECT OF TIME
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• For metallurgical reasons, it is desirable to melt the metalwith minimum energy, and high power densities are generally preferable.
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Heat required to melt depends upon:
• Metal’s volumetric specific heat
• The melting point of metal
• Metals heat of fusion
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The unit Energy for melting is given by,
Not a l l the energy Generated by Heat source is used to melt the weld meta l
Eq # A
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HEAT BALANCE EQUATION and Heat Transfer Mechanism
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• Heat Energy available for welding is given by:
Hw= f 1*f 2*H
• f1 and f2 are proportions
• H = total Heat generated by the welding process
• Heat balance will be (from Eq # A)
Hw= Um*V
• Rate form
RHw=f 1*f 2*RH= Um*Aw*v
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FUSION WELDED JOINT, ZONES AND GRAIN STRUCTURE
Figure (a)
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Figure(b)
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• Fusion Zone (Completely Melted)
• Epitaxial Grain Growth (Atoms from the molten pool solidify
on preexisting lattice sites)
• Weld Interface (Narrow boundary)
• Heat Effected Zone (Welding failures occur)
• Unaffected Base Metal (residual stresses)
Cont.
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