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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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l b ll d l b ll d Can also be called Can also be called

Manual Metal Arc Welding Manual Metal Arc Welding gg

(MMAW) or (MMA)(MMAW) or (MMA)(MMAW) or (MMA)(MMAW) or (MMA)

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Arc is established between Arc is established between

electrode and base metal electrode and base metal

Heat is generated by the arc to Heat is generated by the arc to

melt with electrode and base metalmelt with electrode and base metal

Molten metal is protected by both Molten metal is protected by both

solidified slag and fumes6

solidified slag and fumesKCWONG

P AC DC Power source, AC or DC

El t d h ldElectrode holder

Protective helmetCan be AC or DCProtective helmet

Other accessories

or DC

Other accessories

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Electrode HolderAC or DC Power Source

Electrode

AC or DC Power SourceAnd Controls

ArcArc

WorkElectrode LeadWorkpiece Lead

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Operation Electrode Size (mm)

Arc Current

(A)

Min. Protective

Sh d

SuggestedShade No.

(A) ShadeShielded M t l A

Less than 2.5 Less than 60 7 -

Metal Arc Welding 2.5 - 4 60 - 160 8 10

4 6 4 160 250 10 124 – 6.4 160 – 250 10 12

More than 6.4 250 - 550 11 14

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Grinder

Electrode HolderHolder

Wire Brush

W ldi

Chipping Hammer Welding

Tong

Hammer

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National Standards (BS EN ISO)National Standards (BS EN ISO)

BS EN 499 (Covered electrodes for BS EN 499 (Covered electrodes for manual metal arc welding of non-alloyed and fire grain steels)and fire grain steels)

EN ISO 2560:2005 (Classification of ( f fWelding Consumables for Covered Electrodes for Manual Metal Arc (111) Electrodes for Manual Metal Arc (111) Welding of Non-Alloy and Fine Grain Steels)

Welding and Cutting Processes 12

Steels)CASTCO

Supersede BS EN 499

Applies a dual approach to classification of electrode using gmethods A and B

Welding and Cutting Processes 13CASTCO

Welding and Cutting Processes 14CASTCO

Welding and Cutting Processes 15CASTCO

N i l S d d (AWS)National Standards (AWS)

AWS A5 1 (Specification for carbon AWS A5.1 (Specification for carbon steel electrodes for shielded metal

ldi )arc welding)

AWS A5 5 (Specification for lowAWS A5.5 (Specification for low-alloy steel electrodes for shielded metal arc welding)metal arc welding)

Welding and Cutting Processes 16CASTCO

E XXXXE – Electrode XX - Tensile strength x 1000 (psi)X X - Welding position

1 - all position1 - all position2 - flat or horizontal fillet position4 d hill iti

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4 - down hill positionKCWONG

X - coating characteristicsX coating characteristicsChemical composition of the coating,p g,current type, and operatingcharacteristic of the electrodecharacteristic of the electrode.Number can be from 0 to 8For example, 5, 6, 8 are low hydrogenelectrode that required keeping inelectrode that required keeping insealed container or preheat prior

ldi t li i t i t l lwelding to eliminate moisture level

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Si l d t Simple and easy set up

P t blPortable

Low cost equipmentLow cost equipment

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Productivity relatively slow

Slag removal

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Electrode (low hydrogen type) must be Electrode (low hydrogen type) must be

appropriately storage pp p y g

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Porosity Arc blow Arc blow SpatterSpatterSlag inclusion Incomplete fusion

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Welding ElectrodeM ti fi ld d d

Welding Electrode

F d Bl

Magnetic field produced Around electrode

Forward Blow

Back BlowBack Blow

Welding Direction

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Welding Direction

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l ll d l ll d Can also be called Can also be called

Metal Inert Gas Welding Metal Inert Gas Welding gg

(MIG)(MIG)(MIG)(MIG)

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Heat is generated by arc (between filler Heat is generated by arc (between filler wire and work-piece) to melt and fuse

rk pi c t th rwork-piece togetherMolten metal is protected by either inert Mo t n m ta s prot ct y th r n rt or active gas (MAG)S lid fill i i ti l f d t Solid filler wire is continuously fed to welding gun through wire feeding unitg g g gCommonly employed as a semi-automatic process

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processKCWONG

Power source (DC prefer) Power source (DC prefer) Electrode wire feed unitControl console

hi ldi l Shielding gas supply systemWelding gunWelding gunWater cooling system if necessary

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Wire Feeding UnitWire Feeding UnitWire Feeding UnitWire Feeding Unit

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Cable AssemblyCable Assembly

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Welding GunWelding GunWelding GunWelding Gun

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Some typical standards for specification 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 metals for Gas Shielded Arc Welding)f m f g)

A01T09-pp1-dt_ndt_II.ppt 33

ER XXS XER XXS-XER - Electrode RodXXXX - Tensile strength x 1000 (psi)S S lid WiS - Solid WireX Chemical Composition (2 7 G)X - Chemical Composition (2-7, G)

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Spray Transfer

Globular Transfer

Short Circuiting Transfer

Pulse Transfer

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Hi h t d it d i Higher-current density and is

id d t b th h tt t considered to be the hottest one

V fi d l t Very fine droplets

B t f h i ti t i lBest for heavier section material

G d f f ll t ti ld j i tGood for full penetration weld joint

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L bl i Less stable, increase spatter

L ss h t th sp t sf m dLess heat than spray transfer mode

Droplets of filler wire is significantly Droplets of filler wire is significantly

larger than spray transfer modelarger than spray transfer mode

Only on down hand positiony p

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The least amount of heating 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 bl f ldi llCapable of welding most alloys

N sl t b m dNo slag to be removed

Higher productivity Higher productivity

Lower labour costLower labour cost

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Less smoke generated improve workshop Less smoke generated, improve workshop

environmentenvironment

easily observe the action of molten puddle y p

to improve arc control

no flux contamination, lowest hydrogen

problems

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Not suitable for field work Not suitable for field work

Complexity and high cost of equipment Complexity and high cost of equipment

Unstable wire feed due to worn liner and Unstable w re feed due to worn l 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 l i d b l f fl Molten metal is covered by a layer of flux

as was the case for SMAWas was the case for SMAW

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May not need shielding gas depend on

h f f ll the type of filler wire

S fill i bl f idi Some filler wire capable of providing

sufficient protection to the molten sufficient protection to the molten

puddle and so called “self-shielding”pu f g

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E XXT-X (AWS A5 20)E XXT-X (AWS A5.20)E - Electrode E - Electrode

X - Tensile strength x 10000 (psi)X Tensile strength x 10000 (psi)

X -Welding positiong p

“0” (flat or horizontal fillet position)

“1” (all position)

48T - Tubular Wire

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X Chemical Composition and operating X - Chemical Composition and operating

characteristics , such as characteristics , such as

Type of currentyp

Polarity

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l GSimilar to GMAW

Hi h i High current capacity power source as

compared to GMAWcompared to GMAW

Lack of shielding gas supply system if Lack of shielding gas supply system if

self-shielding is usedself-shielding is used

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Suitable for field weldingSuitable for field welding

Good performance on contaminated Good performance on contaminated

surface surface

Higher deposition rate increase Higher deposition rate, increase

productivityp y

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AdvantagesAdvantagesgg

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

GMAW d i i iti l tGMAW and increase initial cost

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Slag inclusion

Porosity

Incomplete fusion

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l ll d l ll d Can also be called Can also be called

Tungsten Inert Gas Tungsten Inert Gas gg

Welding (TIG)Welding (TIG)Welding (TIG)Welding (TIG)

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Non consumable electrodeNon-consumable electrode

El t d i d f Electrode is made of pure or

ll d alloyed tungsten

Arc is created between tungsten

electrode and work piece

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Filler metal must be added manually or

b h i l f d if by mechanical feed if necessary

Arc and molten metal is shielded by Arc and molten metal is shielded by

using of inert gasusing of inert gas

no slag is required to removeg q

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W ldi di tiWelding directionGas Nozzle

Filler

ProtectiveTungsten

Filler Rod Weld meta

ProtectiveGas

Electrode

Arc

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P s (AC d/ DC) Power source (AC and/or DC)

Control consoleControl console

Shielding gas supply systemShielding gas supply system

Welding torchWeld ng torch

Water cooling system if necessaryg y y

Electrode wire feed unit if necessary

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High frequency generator aids to High frequency generator aids to

initiate welding arc especially for g p y

welding reactive material, such as

aluminum and magnesium

Remote control (foot pedal or some

devices mounted on the torch)

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AWS Code Type Tip Colour

EWP P T t GEWP Pure Tungsten Green

EWCe-2 1 8-2 2 % Ceria OrangeEWCe 2 1.8 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

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EWZr 0.15 -0.4 % Zirconia BrownKCWONG

Excellence for welding thin section

t i lmaterial

Usually used for welding root passUsually used for welding root pass

Capable of welding most materialsCapable of welding most materials

Perform high quality and excellence visual Perform high quality and excellence visual

appearance

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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

Incomplete fusionp

Tungsten inclusion Tungsten inclusion

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