Transcript
DTM-UI
Flux Core Arc Welding (FCAW)
DTM-UI
Flux cored arc welding
FCAW
methods
With gas
shielding -
Outershield
Without gas
shielding -
Innershield
With metal
powder -
Metal core
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Outershield - principle of operation
DTM-UIInnershield - principle of operation
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ARC CHARACTERISTICS
Volts
Amps
OCV
Constant Voltage Characteristic
Small change in voltage =
large change in amperage
The self
adjusting arc.
Large arc gap
Small arc gap
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Insulated extension nozzle
Current carrying guild tube
Flux cored hollow wire
Flux powder
Arc shield composed of vaporized and slag forming compounds
Metal droplets covered
with thin slag coating
Molten weld pool
Solidified weld metal and slag
Flux core
Wire joint
Flux core wires
Flux Core Arc Welding (FCAW)
DTM-UI Flux cored arc welding
FCAW
methods
With gas
shielding -
Outershield
Without gas
shielding -
Innershield (114)
With metal
powder -
Metal core
With active
gas shielding
(136)
With inert gas
shielding (137)
DTM-UI FCAW - differences from MIG/MAG
usually operates in DCEP but some Innershield wires operates in DCEN
power sources need to be more powerful due to the higher currents
doesn't work in deep transfer mode
require knurled feed rolls
Innershield wires use a different type of
welding gun
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Backhand (drag) techniqueAdvantages
preferred method for flat or horizontal position
slower progression of the weld
deeper penetration
weld stays hot longer, easy to remove
dissolved gasses
Disadvantages
produce a higher weld profile
difficult to follow the weld joint
can lead to burn-through on thin sheet plates
DTM-UIForehand (push) technique
Advantages
preferred method for vertical up or overhead
position
arc is directed towards the unwelded joint , preheat
effect
easy to follow the weld joint and control the
penetration
Disadvantages
produce a low weld profile, with coarser ripples
fast weld progression, shallower depth of penetration
the amount of spatter can increase
DTM-UI FCAW advantages
less sensitive to lack of fusion
requires smaller included angle compared to MMA
high productivity
all positional
smooth bead surface, less danger of undercut
basic types produce excellent toughness properties
good control of the weld pool in positional welding especially with rutile wires
seamless wires have no torsional strain, twist free
ease of varying the alloying constituents
no need for shielding gas
DTM-UI FCAW disadvantages
limited to steels and Ni-base alloys
slag covering must be removed
FCAW wire is more expensive on a weight basis than solid wires (exception: some high alloy steels)
for gas shielded process, the gaseous shield may be affected by winds and drafts
more smoke and fumes are generated compared with MIG/MAG
in case of Innershield wires, it might be necessary to break the wire for restart (due to the high amount of insulating slag formed at the tip of the wire)
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Advantages:
1) Field or shop use
2) High productivity
3) All positional
4) Slag supports and
shapes the weld Bead
5) No need for shielding
gas
Disadvantages:
1) High skill factor
2) Slag inclusions
3) Cored wire is
Expensive
4) High level of fume
(Inner-shield)
5) Limited to steels
and nickel alloys
FCAW advantages/disadvantages
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