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Shielded Metal Arc Welding (SMAW)
Gas Metal Arc Welding (GMAW/MIG)
Flux-cored Arc Welding (FCAW)
Gas Tungsten Arc Welding (GTAW/TIG)
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Working Principle
Equipment
Filler metals
Advantages
Limitation
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Can also
l be
b called
ll d
Manual Metal Arc Welding
g
(MMAW) or (MMA)
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Arc is established between
electrode and base metal
Heat is generated by the arc to
melt with electrode and base metal
Molten metal is protected by both
solidified slag and fumes
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P
Power
source, AC or DC
El t d holder
h ld
Electrode
Protective helmet
Can be AC
or DC
Other accessories
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AC or DC Power Source
And Controls
Electrode
Electrode Holder
Arc
Workpiece Lead
Operation Electrode
Size (mm)
Shielded
M t l Arc
Metal
A
Welding
Work
Electrode
Lead
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Less than 2.5
Arc
Current
(A)
9
Min.
Suggested
Protective Shade No.
Sh d
Shade
Less than 60
7
-
2.5 - 4
60 - 160
8
10
4 – 6.4
64
160 – 250
10
12
More than 6.4
250 - 550
11
14
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Grinder
Electrode
Holder
Wire
Brush
Chipping
Hammer
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Welding
W
ldi
Tong
11
National Standards (BS EN ISO)
BS EN 499 (Covered electrodes for
manual metal arc welding of non-alloyed
and fire grain steels)
EN ISO 2560:2005 ((Classification
f
of
f
Welding Consumables for Covered
Electrodes for Manual Metal Arc (111)
Welding of Non-Alloy and Fine Grain
Steels)
Welding and Cutting Processes
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Supersede BS EN 499
Applies a dual approach to
classification of electrode using
g
methods A and B
Welding and Cutting Processes
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Welding and Cutting Processes
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Welding and Cutting Processes
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National
Standards
N i
lS
d d (AWS)
AWS A5
A5.11 (Specification for carbon
steel electrodes for shielded metal
arc welding)
ldi )
AWS A5.5
A5 5 (Specification for low
lowalloy steel electrodes for shielded
metal arc welding)
Welding and Cutting Processes
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E XXXX
E – Electrode
XX - Tensile strength x 1000 (psi)
X - Welding position
1 - all position
2 - flat or horizontal fillet position
4 - down
d
hill position
iti
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X - coating characteristics
p
g,
Chemical composition
of the coating,
current
type,
and
operating
electrode
characteristic of the electrode.
Number can be from 0 to 8
For example, 5, 6, 8 are low hydrogen
electrode that required keeping in
sealed container or preheat prior
welding
ldi to
t eliminate
li i t moisture
i t
l
level
l
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Si l and
Simple
d easy sett up
P t bl
Portable
Low cost equipment
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Productivity relatively slow
Slag removal
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Electrode (low hydrogen type) must be
appropriately
pp p
y storage
g
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Porosity
Arc blow
Spatter
Slag inclusion
Incomplete fusion
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Magnetic
M
ti field
fi ld produced
d
d
Around electrode
Welding Electrode
F
Forward
d Bl
Blow
Back Blow
Welding Direction
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24
Can also
l be called
ll d
Metal Inert Gas Welding
g
(MIG)
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Heat is generated by arc (between filler
wire and work-piece) to melt and fuse
work-piece
rk pi c together
t
th r
Mo t n metal
Molten
m ta iss prot
protected
ct by
y either
th r inert
n rt
or active gas (MAG)
S lid fill
i iis continuously
ti
l f
d tto
Solid
filler wire
fed
welding
g gun
g through
g wire feeding
g unit
Commonly employed as a semi-automatic
process
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Power source (DC prefer)
Electrode wire feed unit
Control console
Shielding
hi ldi gas supply
l system
Welding gun
Water cooling system if necessary
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Wire Feeding Unit
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Cable Assembly
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Welding Gun
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Some typical standards for specification
of steel wire are
BS EN 12534 (Welding consumables – wire
electrodes, wires, rods and deposits for gas
shielded metal arc welding of high strength
steels – Classification)
AWS A5.18 (Specification for carbon steel
filler m
f
metals f
for Gas Shielded Arc Welding)
g)
A01T09-pp1-dt_ndt_II.ppt
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ER XXS-X
XXS X
ER - Electrode Rod
XX - Tensile strength x 1000 (psi)
S lid Wi
S - Solid
Wire
X - Chemical Composition (2-7,
(2 7 G)
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Spray Transfer
Globular Transfer
Short Circuiting Transfer
Pulse Transfer
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Hi h
Higher-current
td
density
it and
d iis
considered
id
d to
t be
b th
the h
hottest
tt t one
V
Very
fine
fi d
droplets
l t
B tf
Best
for h
heavier
i section
ti material
t i l
G d for
Good
f f
full
ll penetration
t ti weld
ld jjoint
i t
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L
Less
stable,
bl increase
i
spatter
L ss heat
h t than
th spray
sp
t
sf mode
m d
Less
transfer
Droplets of filler wire is significantly
larger than spray transfer mode
Only
y on down hand position
p
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The least amount of heating
Excellent for welding of sheet metal and
having excessive gap
Incomplete fusion (insufficient heat)
Allows for all position welding
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Protect molten pool against atmosphere
Argon, Helium and their mixtures
CO2 or argon mixture are commonly used
for welding of carbon steel
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C
Capable
bl of
f welding
ldi most alloys
ll
N slag
sl to
t be
b removed
m
d
No
Higher productivity
Lower labour cost
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Less smoke generated,
generated improve workshop
environment
easily
y observe the action of molten puddle
p
to improve arc control
no flux contamination, lowest hydrogen
problems
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Not suitable for field work
Complexity and high cost of equipment
Unstable w
wire
re feed due to worn lliner
ner and
contact tube
Easy to contaminate with working
environment
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Porosity due to
Lack of shielding
contamination
Incomplete fusion
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Very similar to GMAW
Tubular electrode (granular flux contains)
M l
Molten
metall is
i covered
db
by a layer
l
of
f flux
fl
as was the case for SMAW
45
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May not need shielding gas depend on
the
h type of
f filler
f ll wire
S
Some
fill
filler wire
i capable
bl of
f providing
idi
sufficient protection to the molten
pu
f
g
puddle and so called “self-shielding”
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E XXT-X
47
(AWS A5
A5.20)
20)
E
- Electrode
X
- Tensile strength x 10000 (psi)
X
-Welding
g position
p
“0” (flat or horizontal fillet position)
“1” (all position)
T
- Tubular Wire
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X - Chemical Composition and operating
characteristics , such as
Type
yp of current
Polarity
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Similar
l to GMAW
G
Hi h current capacity
i power source as
High
compared to GMAW
Lack of shielding gas supply system if
self-shielding is used
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Suitable for field welding
Good performance on contaminated
surface
Higher deposition rate,
rate increase
p
productivity
y
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Advantages
g
Well penetration
Less skill required for operator
compared with SMAW
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Require slag removal
Fumes and gases hazards
Complexity in equipment set up as
d iincrease iinitial
iti l costt
GMAW and
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Slag inclusion
Porosity
Incomplete fusion
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Can also
l be called
ll d
Tungsten
g
Inert Gas
Welding (TIG)
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Non consumable electrode
Non-consumable
El t d iis made
Electrode
d of
f pure or
alloyed
ll
d tungsten
Arc is created between tungsten
electrode and work piece
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Filler metal must be added manually or
b mechanical
by
h i lf
feed
d if necessary
Arc and molten metal is shielded by
using of inert gas
g is required
q
no slag
to remove
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W ldi
Welding
direction
di
ti
Gas Nozzle
Filler
Rod
Weld meta
Protective
Gas
Arc
Tungsten
Electrode
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P
Power
source
s
(AC and/or
d/ DC)
Control console
Shielding gas supply system
Welding
Weld
ng torch
Water cooling
g system
y
if necessary
y
Electrode wire feed unit if necessary
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High frequency generator aids to
initiate welding
g arc especially
p
y for
welding reactive material, such as
aluminum and magnesium
Remote control (foot pedal or some
devices mounted on the torch)
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Type
Tip Colour
EWP
P
Pure
Tungsten
T
t
G
Green
EWCe-2
EWCe
2
1 8-2
1.8
2.2
2 % Ceria
Orange
EWLa-1
1 % Lanthanum Oxide
Black
EWTh-1
0.8 – 1.2 % Thoria
Yellow
EWTh-2
1.7 – 2.2 % Thoria
Red
EWZr
0.15 -0.4 % Zirconia
AWS Code
Brown
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Excellence for welding thin section
material
t i l
Usually used for welding root pass
Capable of welding most materials
Perform high quality and excellence visual
appearance
pp
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No slag to be removed
Process is a clean and controllable
no filler metal is added if the joint
design is permitted
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Tolerance for contamination is quite low,
High level required by the operator
Not suitable for windy situation
Low productivity as the process is too
slow
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Porosity
p
Incomplete
fusion
Tungsten inclusion
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