Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology FLUX CORED ARC WELDING TWI...
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Transcript of Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology FLUX CORED ARC WELDING TWI...
Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology
FLUX CORED ARC WELDING
TWI Training & Examination TWI Training & Examination ServicesServices
EWF/IIW Diploma CourseEWF/IIW Diploma Course
Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology
Flux cored arc welding
FCAW FCAW methodsmethods
With gas With gas shielding - shielding - “Outershiel“Outershiel
d”d”
Without gas Without gas shielding - shielding -
“Innershield“Innershield”(114)”(114)
With metal With metal powder - powder - “Metal “Metal core”core”
With active With active gas gas
shielding shielding (136)(136)
With inert With inert gas gas
shielding shielding (137)(137)
Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology
“Outershield” process
Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology
“Innershield” process
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Structure of the cored wires
• provide form stability to the wire
• serves as current transfer during welding
Functions of metallic sheath:
Function of the filling powder:
• stabilise the arc• add alloy
elements• produce gaseous
shield• produce slag• add iron powder
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Core elements and their function
• Aluminium Aluminium - deoxidize & denitrify- deoxidize & denitrify
• Calcium - provide shielding & form slagCalcium - provide shielding & form slag
• Carbon - increase hardness & strengthCarbon - increase hardness & strength
• Manganese - deoxidize & increase strengthManganese - deoxidize & increase strength
• Molybdenum - increase hardness & strengthMolybdenum - increase hardness & strength
• Nickel - improve hardness, strength, Nickel - improve hardness, strength, toughness toughness & corrosion resistance& corrosion resistance
• Potassium - stabilize the arc & form slagPotassium - stabilize the arc & form slag
• Silicon - deoxidize & form slagSilicon - deoxidize & form slag
• Sodium - stabilize arc & form slagSodium - stabilize arc & form slag
• Titanium - deoxidize, denitrify & form slagTitanium - deoxidize, denitrify & form slag
Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology
Types of cored wire
• not sensitive to not sensitive to moisture pick-upmoisture pick-up
• can be copper coated can be copper coated better current transferbetter current transfer
• thick sheath thick sheath good good form stability form stability 2 roll 2 roll drive feeding possibledrive feeding possible
• difficult to manufacturedifficult to manufacture
• good resistance good resistance to moisture to moisture pick-uppick-up
• can be copper can be copper coatedcoated
• thick sheaththick sheath• difficult to seal difficult to seal
the sheaththe sheath
Seamless cored wire
Butt joint cored wire
Overlapping cored wire
• sensitive to sensitive to moisture moisture pick-uppick-up
• cannot be cannot be copper copper coatedcoated
• thin sheaththin sheath• easy to easy to
manufacturmanufacturee
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Cored wire manufacturing process
Str
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Th
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Flu
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Dra
w d
ie
Clo
sin
g
roll
ers
Fo
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g
roll
ers
Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology
FCAW wire designation
Wire designation acc. BS EN 758:Wire designation acc. BS EN 758:
Standard Standard numbernumber
Tubular cored Tubular cored electrodeelectrode
Tensile Tensile propertiesproperties
Impact Impact propertiesproperties
Light alloy Light alloy additionsadditions
Type of electrode coreType of electrode core
Shielding gasShielding gas
Welding position Welding position (optional)(optional)
Diffusible hydrogen content Diffusible hydrogen content (optional)(optional)
EN 758 - T 46 3 1Ni B M 4 H5EN 758
T 46 3 1Ni MB 4 H5
Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology
FCAW wire designation
Wire designation acc. AWS A-5.20:Wire designation acc. AWS A-5.20:
Welding position (0 - F/H only; Welding position (0 - F/H only; 1- all positions)1- all positions)
Electrode usability (polarity, Electrode usability (polarity, shielding and KV); can range shielding and KV); can range from 1 to 14from 1 to 14
E 71 T-6 M J H8
Designates an electrodeDesignates an electrode
Minimum UTS of weld metal (ksi x Minimum UTS of weld metal (ksi x 10)10)Flux cored electrodeFlux cored electrode
E 71 T-6
Shielding gas for classificationShielding gas for classification
M
27J at -40°C requirement 27J at -40°C requirement (optional)(optional)
Diffusible hydrogen content Diffusible hydrogen content (optional); can be 4, 8 or 16(optional); can be 4, 8 or 16
J H8
Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology
FCAW - differences from MIG/MAG
• usually operates in usually operates in DCEP but some DCEP but some “Innershield” wires “Innershield” wires operates in DCENoperates in DCEN
• power sources need power sources need to be more powerful to be more powerful due to the higher due to the higher currentscurrents
• doesn't work in deep doesn't work in deep transfer modetransfer mode
• require knurled feed require knurled feed rollsrolls
• ““Innershield” Innershield” wires use a wires use a different type of different type of welding gun welding gun
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FCAW - differences from MIG/MAG
350 Amps self shielded welding gun350 Amps self shielded welding gun
Courtesy of Lincoln Courtesy of Lincoln ElectricElectric
Contact tip
Thread protector
Conductor tube
Trigger
Handle
Hand shield
24V insulated switch lead
Welding gun cable
Close wound stainless steel spring wire liner (inside welding gun cable)
Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology
FCAW - differences from MIG/MAG
Self shielded Self shielded electrode nozzleelectrode nozzle
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Travel Angle
75° 75°90°
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Backhand (“drag”) technique
AdvantagesAdvantages• preferred method for flat or horizontal preferred method for flat or horizontal
positionposition• slower progression of the weldslower progression of the weld• deeper penetrationdeeper penetration• weld stays hot longer weld stays hot longer easy to remove easy to remove
dissolved gassesdissolved gasses
DisadvantagesDisadvantages• produce a higher weld profileproduce a higher weld profile• difficult to follow the weld jointdifficult to follow the weld joint• can lead to burn-through on thin sheet can lead to burn-through on thin sheet
platesplates
Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology
Forehand (“push”) technique
AdvantagesAdvantages• preferred method for vertical up or preferred method for vertical up or
overhead positionoverhead position• arc is directed towards the unwelded arc is directed towards the unwelded
joint joint preheat effect preheat effect• easy to follow the weld joint and control easy to follow the weld joint and control
the penetrationthe penetration
DisadvantagesDisadvantages• produce a low weld profile, with coarser produce a low weld profile, with coarser
ripplesripples• fast weld progression fast weld progression shallower depth shallower depth
of penetrationof penetration• the amount of spatter can increasethe amount of spatter can increase
Copyright © 2005, TWI Ltd World Centre for Materials Joining Technology
FCAW advantages
• less sensitive to lack of fusionless sensitive to lack of fusion• requires smaller included angle compared to MMArequires smaller included angle compared to MMA• high productivityhigh productivity• all positionalall positional• smooth bead surface, less danger of undercutsmooth bead surface, less danger of undercut• basic types produce excellent toughness basic types produce excellent toughness
propertiesproperties• good control of the weld pool in positional good control of the weld pool in positional
welding especially with rutile wireswelding especially with rutile wires• seamless wires have no torsional strain seamless wires have no torsional strain twist twist
freefree• ease of varying the alloying constituentsease of varying the alloying constituents• no need for shielding gasno need for shielding gas
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FCAW advantages
Deposition rate for carbon steel weldingDeposition rate for carbon steel welding
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FCAW disadvantages
• limited to steels and Ni-base alloyslimited to steels and Ni-base alloys• slag covering must be removedslag covering must be removed• FCAW wire is more expensive on a weight FCAW wire is more expensive on a weight
basis than solid wires (exception: some basis than solid wires (exception: some high alloy steels)high alloy steels)
• for gas shielded process, the gaseous for gas shielded process, the gaseous shield may be affected by winds and draftsshield may be affected by winds and drafts
• more smoke and fumes are generated more smoke and fumes are generated compared with MIG/MAGcompared with MIG/MAG
• in case of Innershield wires, it might be in case of Innershield wires, it might be necessary to break the wire for restart necessary to break the wire for restart (due to the high amount of insulating slag (due to the high amount of insulating slag formed at the tip of the wire)formed at the tip of the wire)