1. TWI Training & Examination Services EWF/IIW Diploma Course
FLUX CORED ARC WELDING
TWI Training & Examination Services
EWF/IIW Diploma Course

2. 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)

3. “Outershield” process

4. “Innershield” process

5. Structure of the cored wires
Functions of metallic sheath:
Function of the filling powder:
provide form stability to the wire
serves as current transfer during welding
stabilise the arc
add alloy elements
produce gaseous shield
produce slag
add iron powder

6. Core elements and their function
Aluminium - deoxidize & denitrify
Calcium - provide shielding & form slag
Carbon - increase hardness & strength
Manganese - deoxidize & increase strength
Molybdenum - increase hardness & strength
Nickel - improve hardness, strength, toughness & corrosion resistance
Potassium - stabilize the arc & form slag
Silicon - deoxidize & form slag
Sodium - stabilize arc & form slag
Titanium - deoxidize, denitrify & form slag

7. Overlapping cored wire
Types of cored wire
Seamless cored wire
Butt joint cored wire
Overlapping cored wire
not sensitive to moisture pick-up
can be copper coated  better current transfer
thick sheath  good form stability  2 roll drive feeding possible
difficult to manufacture
good resistance to moisture pick-up
can be copper coated
thick sheath
difficult to seal the sheath
sensitive to moisture pick-up
cannot be copper coated
thin sheath
easy to manufacture

8. Cored wire manufacturing process
Strip reel
Thin sheet metal
Flux input
Draw die
Closing rollers
Forming rollers

9. FCAW wire designation EN 758 - T 46 3 1Ni B M 4 H5 EN 758 T 46 3 1Ni B
Wire designation acc. BS EN 758:
Diffusible hydrogen content (optional)
Shielding gas
Light alloy additions
Tensile properties
Standard number
EN T Ni B M 4 H5
EN 758 T 46 3
1Ni B M 4 H5
Tubular cored electrode
Impact properties
Type of electrode core
Welding position (optional)

10. FCAW wire designation E 71 T-6 M J H8 E 7 1 T -6 M J H8
Wire designation acc. AWS A-5.20:
27J at -40°C requirement (optional)
Electrode usability (polarity, shielding and KV); can range from 1 to 14
Welding position (0 - F/H only; 1- all positions)
Designates an electrode
E 71 T-6 M J H8 E 7 1 T -6 M J H8
Minimum UTS of weld metal (ksi x 10)
Flux cored electrode
Shielding gas for classification
Diffusible hydrogen content (optional); can be 4, 8 or 16

11. 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

12. FCAW - differences from MIG/MAG
350 Amps self shielded welding gun
Courtesy of Lincoln Electric
Close wound stainless steel spring wire liner (inside welding gun cable)
24V insulated switch lead
Handle
Conductor tube
Welding gun cable
Trigger
Thread protector
Hand shield
Contact tip

13. FCAW - differences from MIG/MAG
Self shielded electrode nozzle

14. Travel Angle
75°
90°

15. Backhand (“drag”) technique
Advantages
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

16. Forehand (“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

17. 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

18. FCAW advantages
Deposition rate for carbon steel welding

19. 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)