Metrode Products Limited

Hanworth Lane
Chertsey,
Surrey, KT16 9LL
UK

Welding with METRODE Gas Shielded FCW's

Contents
Page
The Flux Cored Arc Welding (FCAW) Process

What is Flux Cored Wire ?

Summary of FCAW Procedural Recommendations

FCAW Process Controls

Welding Current

Arc Voltage

Operability Tolerance Box

Electrical 'Stick-Out'

Gas Shielding

Influence of Travel Speed

10

SMAW, GMAW and FCAW Weld Deposition Rate

11

Welding Techniques

12

Positional Welding

13

ASME IX & BS EN 287 Welding Positions

14

Root Pass Welding

15

Operational Recommendations

16

Metrode Products Limited FCW Welder Booklet Website Copy

Gas Shielded Flux Cored Arc Welding (FCAW)

The Process

Gas nozzle

Contact tip

External gas shield

Arc + slag/gas shield
Flux + alloy powder fill
Weld deposit
Tubular wire sheath
Protective slag cover

Workpiece

Wire 'Stick-out'
carrying current

Supercore and Cormet FCW's are recommended for use with any MIG (GMAW)
equipment, incorporating single or twin drive roll wire feed systems.

The widely popular 1.2mm sized wires are predominantly suitable for welds in
material 5mm thick and above.
Certain applications involving material down to 3mm thickness can also be viably
welded using 1.2mm wire, eg high speed manual seam welding of lap fillet joints,
sealing runs, vessel limpet coil attachments, etc

1.6mm wire is principally suitable for higher current, automatic downhand welding of
thicker wall fabrications.

Metrode Products Limited FCW Welder Booklet Website Copy

page 1

What is Flux Cored Wire ?

Its an inside-out stick electrode!!

(FCAW)
FCW
Flux
Cored
Wire
Flux
Cored
1.2mm Wire

MMA (SMAW)
Flux Coated
Electrode
Flux Coated
4mm Electrode

FCW's thin wall tubular sheath has a comparatively smaller cross-sectional area than solid
wire or manual welding electrodes. Consequently, the current-carrying wire 'stick-out' from
the contact tip shows a higher electrical resistance (R) to passage of the welding current (I).
This has 2 important effects:
1.

Higher current density, Amp/mm2 at the wire tip, eg @ 200A

4mm MMA (SMAW)

eg, @ 150A,

1.2mm FCW

12A / mm2

Current Density

240 A / mm2

Arc intensity and penetrating potential more than x20 that of MMA (SMAW).
2.

Joule Effect (I2R) preheating of the wire is increased. See Section on Electrical 'StickOut'.
Faster wire melt-off; higher weld metal deposition rate.

Metrode Products Limited FCW Welder Booklet Website Copy

page 2

Summary of Procedural Recommendations

Effective application of the FCAW process is maximised by ensuring that operational
procedure follows a number of recommended guidelines, which can be summarised:
1.

Use Welding Current / Arc Voltage combinations which fall within the optimum
operating conditions area of the tolerance box overleaf, to achieve smooth, stable,
minimum spatter arc operability and maximum effective travel speed. See page 6.

2.

Use Argon + 15-25%CO2 at a flow rate between 15 and 20 lpm (30 to 40 cfh).
Other gases are either:
- less expensive, and less effective, or,
- more expensive, and no more effective.
See page 8.

3.

60-70

Use backhand/pulling technique with the gun

at an angle 60 - 70 from the horizontal:-

30-40

The forehand / pushing technique shows

limitations in effectiveness. See page 12.

4.

Operate with an electrode extension from the

contact tip, stick-out, in the range 12 to
20mm:See page 7.

Stick-out
Arc length

5.

Avoid excessively slow travel speed; typically welding at twice the speed normally
associated with operating MMA (SMAW) electrodes.
This will ensure an adequate balance of Fill & Fusion, satisfactory weld profile and
easier / clean slag release.
See page 10.

Metrode Products Limited FCW Welder Booklet Website Copy

page 3

FCAW Process Controls: 1

Welding Current
Standard DC rectifier or inverter power supplies are sufficient.
Pulsed power supplies are also acceptable, though are not essential to ensure
satisfactory arc operability and process stability.
Welding current (Amp), directly controlled via adjustment of Wire Feed Motor speed
setting, is selected to ensure:
-

a level of arc energy / heat input sufficient to achieve weld joint penetration and
fusion, to suit the material thickness being welded.

an appropriate rate of filler metal deposition, to suit the type and size of weld being
deposited.

With respect to any material thickness being welded, use of excessively high welding
currents, to speed up weld deposition, risks loss of bead shape control and finished weld
appearance.
Use Wire Feed Speed (WFS) control to fine tune arc length during welding. Increased
WFS reduces arc length, and vice versa.
Typical Wire Feed Speed relationship with Welding Current:
Amps, DC+

Wire Feed Speed Control

WFS

Metrode Products Limited FCW Welder Booklet Website Copy

page 4

FCW Welding Process Controls: 2

Arc Voltage
! Arc voltage directly influences the length of the welding arc, ie the distance between the
tip of the wire and the weld pool surface:

Low arc volts

Short arc length

High arc volts

Long arc length

! Arc length control is the key to maximum welding operability:

Arc voltage too low

- wire tip contacting weld pool
- harsh arc condition
- excessive weld spatter
- narrow, peaky bead profile

Arc voltage too high

- excessively long arc
- weak arc directionality
- wide low penetration beads
- inconsistent weld bead profile

! Correct selection of arc voltage results in:

Metrode Products Limited FCW Welder Booklet Website Copy

uniformly smooth arc operability

minimum weld spatter
maximum weld pool control & travel
speed
clean easy slag release
maximum weld appearance
maximum weld quality

page 5

FCAW Welding Process Controls: 3

Operability Tolerance Box
for
Downhand Welding Applications
Effective operation of the FCAW process is maximised via selection of a balanced
combination of amps & arc volts. At any particular current level, there is an arc voltage
range, within which tolerable arc operability can be experienced. The limits of these
combinations form an 'Operability Tolerance Box'.
However, over the full recommended current range for Supercore and Cormet FCW's, a
narrower 'Power Band' within the tolerable operability limits, approximately 2V wide,
defines the limits within which "optimum welding operability" performance will be
experienced.
Operation outside this 'Power Band' will result in progressively inferior process
performance, as arc voltage is increased or reduced.

Supercore & Cormet FCW's: 1.2mm, Ar +15-25%CO2

-

40.0
Tolerance Box

Excessively long arc

Wider, low penetration beads
Weaker arc directionality
Loss of bead profile uniformity
Slag release difficulties

Optimum operating
conditions

35.0

30.0

Volts

Increasingly difficult manual welding

operability
270A: HV fillet welding limit
300A: Gravity fillets only

25.0

20.0

15.0

90

Unsatisfactory arc operability

Poor globular metal transfer
Excessive weld spatter
110

130

150

170

190

210

230

Excessively short arc length

Wire tip contacting weld pool
Coarser arc condition
Excessive weld spatter

250

270

290

310

330

Amps

Metrode Products Limited FCW Welder Booklet Website Copy

page 6

FCAW Process Controls: 4

Electrical 'Stick-Out'

typically 5mm

The length of wire electrode protruding from the contact tip during welding, termed the
electrical 'stick-out' (ESO) plays an important role in FCAW process effectiveness.
The 'stick-out', carrying welding current, becomes electrically preheated prior to it being
fed into the arc zone. This usefully:
-

increases efficiency of wire tip 'melt-off', and overall weld metal deposition rate.

ensures that any wire surface 'contaminant' is effectively burned-off before it enters
the arc, and avoids risk of gas porosity.

Welding with a fixed 'stick-out' in the range of 12 to 20mm is recommended.

Fluctuations in 'stick-out' during welding can lead to excessive changes in welding
current and arc operability. For example:
ESO, mm
Current
Arc Voltage

8
202
27

12
187
27.8

16
172
28.1

20
162
28.4

24
154
28.6

Any variations should be restricted to the practical limits of manual welding.

Metrode Products Limited FCW Welder Booklet Website Copy

page 7

FCAW Process Controls: 5

Gas Shielding
Supercore and Cormet FCW's are designed for maximum performance under standard
Argon + 20% CO2 type gas shielding.
However, with a slight adjustment in arc voltage level, they operate satisfactorily under
the range of Ar + 15-20%CO2 type shielding gases, with and without a residual O2
component, used in many other countries around the world.
Eg

At, typically, 200A:

Ar + 25%CO2 (+/- 2%O2)

30V
Ar + 20%CO2 (+/- 2%O2)
29V
Ar + 12%CO2 (+ 2%O2)
27V
Ar + 5%CO2 (+ 2%O2)
26V
Ar + 38%He* + 2%CO2
25V
100%CO2 **
32V
* Proprietary gas mixtures, containing proportions of Helium, can be used, though
offer no technical advantages.
** Not recommended for use with Supercore P' grade positional welding wires.

The change in effective arc voltage results in a slight upward or downward shift in the
optimised 'power band'. See page 9.
Gas flow rate selected should be sufficient to ensure adequately effective shielding
under the prevailing environmental conditions.
Excessively high flow rates are both wasteful and conducive to turbulence, with a
consequent loss of effectiveness and overall arc stability.
Welding outdoors, eg on-site, will require higher flow rates, and should involve
essential precautions (eg tent enclosure) to protect welding from adverse windy
conditions, to avoid excessive influence of oxygen and nitrogen pick-up, and
consequent weld porosity.
Typical gas flow rate recommendations:
Protected workshop:
Draughty workshop:
Welding outdoors:

10 15 lpm
15 20 lpm
20 25 lpm

(20 30 cfh)
(30 40 cfh)
(40 50 cfh)

Both CO2 and Argon/CO2 gas shielding result in suitably low carbon weld metal, for
corrosion resistance purposes.
Argon-based gases promote slightly lower C,
increased alloy transfer and weld Ferrite phase level:
Supercore 316L
CO2
Argon+20%CO2

C
0.03
0.024

Mn Si
1.60 0.63
1.67 0.63

Metrode Products Limited FCW Welder Booklet Website Copy

S
0.010
0.008

P
0.022
0.027

Cr
Ni
Mo
19.2 12.3 2.6
19.6 12.4 2.7

Cu
0.07
0.09

page 8

Ferrite
8FN
10FN

Supercore FCW: Optimum Operating Conditions

Influence of shielding gas composition on 'power band' optimised settings

100% CO2
Ar + 15-20% CO2 (O2)
Ar + 12% CO2 (O2)

Page 9

FCAW Process Controls: 6

Influence of Travel Speed
! Operating using optimum 'power band' Amps / Arc Volts enables welder to control and
maximise travel speed.
! Supercore and Cormet FCW deposition rate is approximately twice as fast as that
with MMA (SMAW) electrodes, at the same current. See page 11. Consequently,
travel speed must be increased proportionately to maintain control of the weld pool,
bead shape and balance of deposited metal versus weld fusion,
ie a balanced FILL / FUSION ratio.
Torch angle also becomes, ultimately, a related factor.
Eg:

- too slow, heavier build-up

- welding torch angled lower to control
weld pool slag
- arc operating in wrong position to
secure fusion/penetration

- faster travel speed, reduced build-up

- weld torch can be angled to arc nearer
leading edge of weld pool to maximise
fusion/penetration

Under balanced current/voltage volts conditions, travel speed can be increased to

achieve smaller size weld beads, whilst maintaining requisite bead shape, eg mitre
profile fillet welds of reduced leg length.
However, excessively slow or fast travel speeds result in loss of essential FILL /
FUSION balance:

Excessive fill
Poor profile
Lack of corner fusion

Effective operating range

Travel Speed
Page 10

Reduced:
- bead size
- penetration
- bead quality

MMA, MIG & FCW Weld Metal Deposition Rates

kg/h

lb/h

Deposition rate

FCAW

12.5

MIG
(GMAW)

10

4
7.5
3

MMA
(SMAW)

2
Supercore
Supermet
Supermig

1
0
0

50

100

150

200

250

Welding Current Amps DC+

Eg @ 200A

Supercore 316L
Supermig 316L
Supermet 316L

Page 11

1.2mm:
1.2mm
5mm

3.6 kg/h
2.7 kg/h
2.2 kg/h

2.5
0
300

Welding Technique
Downhand Welding
Welding torch angle influences weld pool/slag control, weld bead profile and the degree of
penetration depending on whether a backhand/pulling or a forehand/pushing technique is
used.
Backhand/Pulling Technique
As with the other important slag shielded process,
60-70
MMA (SMAW), the backhand technique is both a
natural and a recommended mode of torch
operation for most applications:
30-40
- Arc forces control the weld pool and slag,
preventing cold laps and slag entrapment.
- Penetration is maximised
- With horizontal-vertical fillet welds, the wire tip should be aimed directly into the joint corner.
A 30-40 torch angle ensures that equi-leg length fillets are achieved. A 60-70backhand
torch angle, typical of MMA (SMAW) welding practice, produces slightly convex fillet weld
profiles. Steeper, almost upright, torch angles may be used to produce flat, mitre profile
fillets without loss of essential slag control.
For weld cladding applications, the backhand
technique is employed to produce high build-up
weld deposits and ensure essential fusion
between
adjacent
beads.
To
minimise
penetration into the base material, and associated
dilution effects, the technique of aiming the wire tip
in-board of the 'toe' of the previous bead is
recommended. This results in approx 50% bead
overlap, full fusion and a neat tie-in between
adjacent beads to give a uniformly flat clad layer.
Forehand/Pushing Technique

5mm
50-60

2-3mm

50-60

The forehand technique associated with MIG

(GMAW) solid wire welding produces flat/ concave
60-70
cosmetically attractive fillet welds and/or low
reinforcement butt welds. Penetration is minimised,
and the technique may be preferred in situations
where improved visibility and seam following are
important, eg high speed sealing run along the back
side of a 2-run double side weld in thin material, eg
3mm thick. However, the technique is not
recommended for thicker material where the lower travel speed involved could result in loss of
slag control and full fusion with the base material. This applies also to weld cladding where
the gains of minimal penetration, important to reduced dilution in first layer cladding on the CMn steel, may be offset by the risk of incomplete fusion.

Page 12

Welding Technique
Positional Welding
Standard Supercore Wires
These are designed to show maximum operating
smoothness, productivity and finished weld appearance when used in the downhand or
horizontal/vertical positions, eg ASME 1G/2G (BS EN PA/PC) positions. A degree of
operability in inclined positions is possible. For example, for vertical up position:
Single bead: Not recommended. Difficult to optimise arc
operability and finished weld quality.
Multi-pass: Weave welding, eg 160A, 24V,
opportunity for flatter profiles, in thicker material.

offers

Control of bead shape limits range of optimum settings,

with fillet sizes up to 8mm leg maximum.
6mm leg length:
7mm leg length:
8mm leg length:

130A, 21-22V
140A, 23-24V
160A, 24-25V

Downhill and vertically-down welding can be used to achieve good appearance, concave
profile fillet welds and sealing runs, with low penetration, eg:

170A, 24-25V
400-500mm/min

180A, 24V
Short ESO 6-8mm
500-600mm/min

Positional Supercore Wires ('P') These wires are intended primarily for welding
structures and pipework in all positions, including the challenging ASME 5G/6G (BS EN
PF/H-LO45).
An optimum balance of weld pool control, easy, clean slag release and flat weld profiles is
achieved operating in the region of 140-170A, 22-25V.

Page 13

Welding Positions
According to ASME IX and (BS EN 287) specifications

1G (PA)

1G Rotated (PA)

2G (PC)

2G (PC)

3G (PF)

4G (PE)

5G (PF)

6G (H-LO45)

45

1F (PA)

2F (PB)

45

3F (PF)

4F (PD)

Page 14

Root Pass Welding

The viable application of FCW's for root pass welding operations is subject to a number of
requirements;
1.

Double-side V and J-butts

Provided that joint alignment can be maintained, an initial joint-sealing run can be
deposited without encountering excessive penetration and need for extensive backgrinding prior to back-filling. Typical open or closed joint configurations would involve:
Root face:

2.

2 0.5mm

Root gap:

2 1mm

Single-side V and J-butts

To achieve consistently uniform, fully penetrating root beads, joint gap and alignment
maintenance is essential. Typical joint configurations would involve:
Root face:

1.5 2.0mm

Root gap:

2.5 0.5mm

The slag shielded root underbead surface does not require additional inert gas protection.
It is recommended that FCAW in this context is confined to those joints in pipework or
small vessels where the thin layer of underbead slag is acceptable, or, can be adequately
flushed away.
3.

Single-side welding on to ceramic backing

This higher productivity approach to single or double-sided V-butts, welding on to hard
baked ceramic tiles that fuse to support and mould the weld underside, can be applied
effectively to alloy FCAW, producing uniformly smooth weld profiles. Typical joint
configurations would involve:
Root face:

4.

1.0 0.5mm

Root gap:

6 8mm

Single-side welding on to solid steel backing

Single bead root pass welding into this type of 'blind' joint configuration is not
recommended. Full penetration and fusion of the joint corners and backing bar may be
prevented by slag trapped at the root of the joint.
The alternative, a 2-bead root layer - involves excessive joint opening, eg a 12mm wide
root gap, and overall joint volume.
It is recommended that the typical 5mm wide root gap joint is welded, initially, using an
'Ultramet B' grade basic coated type SMAW (MMA) electrode, to secure reliable fusion
and freedom from entrapped slag.

Page 15

Operational Recommendations
Wire Feed System
Supercore and Cormet wires operate effectively on both single and double drive roll systems.
Extreme wire feed roll pressure must be avoided, to prevent distortion of the tubular sheath,
potential flux losses and interference with overall wire feeding smoothness.
It is
recommended that roll pressure adjustment during setting up is just sufficient to ensure that
feeding can positively overcome finger gripping of wire exiting from the contact tip.
The guide tube, which steers wire from the feed rolls into the welding torch liner, should be
fitted very close to the drive roll exit, to ensure that wire delivery is fully supported, and
breakout, 'birdsnesting', problems are prevented.
Use matching sized coiled steel liner for the wire diameter involved, to maintain positive wire
feeding.
Whilst in many cases both 1.2 and 1.6mm wire sizes are available, with stainless steel
fabrication, the 1.2mm size is the most popular, by virtue of:
-

suitably wide ~140 270A operating range, which adequately covers the general
thicknesses of stainless steels welded.

faster melt-off / deposition rate than the larger cross-section 1.6mm size.

The 1.6mm diameter wires generally fit those situations which can take advantage of higher
current/voltage operating conditions, eg mechanised welding applications.
Welding Procedure
Joint surfaces to be welded should be free from excessive oxide, grease and/or paint, to
promote bead 'toe' wetting, general profile uniformity, and effective slag release.
Select wire feed speed (welding current) to suit welding position or material thickness to be
joined.
Select appropriate arc voltage as indicated by the 'power band' of the Operability Tolerance
Box.
Wire tip trimming will ensure effective explosion-free arc striking and a smooth weld start.
Set gas shield flow rate to appropriate level, adjust gas nozzle such that the contact tip is
recessed ~5mm inside.
Operating with a typical 15mm 'stick-out', trim the wire feed speed to optimise arc length and
achieve a smooth, spatter-free, spray arc condition. (See 'Arc Voltage', page 5.)
Welding with a 'pulling' (backhand) technique similar to MMA (SMAW), is recommended for
maximum overall welding performance in the downhand / horizontal-vertical positions. (See
'Welding Techniques', page 12.)
Page 16

Arc extinction, via welding back over the weld pool, 'feeds' the final crater and yields a crackfree weld finish.
Machine Maintenance
Whilst FCAW is characteristically a low weld spatter process, efficient application to high
productivity fabrication will benefit from routine machine maintenance to minimise
unnecessary downtime:
-

cleaning of wire feed roll system, to remove any build-up of debris,

removal of any spatter deposited, in the gas shield nozzle, to ensure continued
effectiveness of weld pool protection

worn contact tips, which ultimately impede smooth wire feeding and can cause 'burnback', should be regularly inspected and replaced, to avoid delays more costly than a new
tip. Use contact tip size designated for the wire diameter.

Wire Protection
Wire reels on the machine should, preferably, be provided with some form of protective
covering, to avoid unnecessary exposure to the airborne contamination and moisture levels
associated with workshop environments. Under these conditions wire reels can be expected
to remain in satisfactory condition on the machine over several days. However, conditions of
unprotected exposure on the machine, and especially in a closed, cold, workshop over the
weekend, risk the possibility of moisture pick-up on the wire surface/seam and subsequent
weld porosity. In these circumstances, spools should be removed from the machine and
stored in a warm, dry cupboard or enclosure.
Welding Fume Control
Welding fumes generated during fabrication of austenitic stainless steels in particular - eg
type 304L/316L are an important aspect of working environment control.
The rate of fume emission per kilo of deposited weld metal is significantly lower than that of
rutile coated MMA (SMAW) electrodes. However, in view of the comparatively higher
deposition rate achieved using the FCAW process:
eg @ 200A

Supercore 316L
Supermet 316L

1.2mm
5mm

3.6 kg/h arc time

2.2 kg/h arc time

the levels of fume generated per unit time, by both MMA and FCW, are broadly similar.
In general, in view of the higher operating duty cycles possible using the FCAW process,
control of welding fume levels, via the use of local fume extraction, is strongly recommended,
especially with welding in confined or poorly ventilated work areas.
For more detailed information on welding fumes, see the appropriate Metrode FCW Data
Sheet, and the Welding Manufacturers' Association publication No 236 "The Arc Welder At
Work".

Page 17