TL-FCAW

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

DTM-UI

Outershield - principle of operation

DTM-UIInnershield - principle of operation

DTM-UI

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

DTM-UI

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

DTM-UI

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)

DTM-UI

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