FCAW (FLUX CORED ARC WELDING)

Kunal Parikh, SEPL,Vadodara

Contents
1. Process Definition and Description
2. Advantages of FCAW
3. Limitations of FCAW
4. Process Variables
5. Welding Technique
6. Specifications of FCAW
7. Welding Equipment for FCAW
8. Welding Problems Cause & Remedial Action
 1. Process Definition & Description
Flux-cored arc welding (FCAW or FCA) is a semi-automatic or automatic arc
welding process. FCAW requires a continuously-fed consumable
tubular electrode containing a flux and a constant-voltage or, less commonly, a
constant-current welding power supply. An externally supplied shielding gas is
sometimes used, but often the flux itself is relied upon to generate the necessary
protection from the atmosphere, producing both gaseous protection and
liquid slag protecting the weld. The process is widely used in construction because of its
high welding speed and portability. This process was developed as an alternative to
SMAW.
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Flux Cored Arc Welding
(FCAW)
Operating principle of the process
 2. Advantages of FCAW
 FCAW may be an "all-position" process with the right filler metals (the consumable electrode)
 No shielding gas needed with some wires making it suitable for outdoor welding and/or windy
conditions
 A high-deposition rate process (speed at which the filler metal is applied) in the 1G/1F/2F
 Some "high-speed" (e.g., automotive) applications
 As compared to SMAW and GTAW, there is less skill required for operators.
 Less precleaning of metal required
 Metallurgical benefits from the flux such as the weld metal being protected initially from external
factors until the slag is chipped away
 Porosity chances very low
 Less equipment required, easier to move around (no gas bottle)
3.Limitations of FCAW
 Melted contact tip – when the contact tip actually contacts the base metal, fusing the two and
melting the hole on the end.
 Irregular wire feed – typically a mechanical problem.
 Porosity – the gases (specifically those from the flux-core) don’t escape the welded area
before the metal hardens, leaving holes in the welded metal.
 More costly filler material/wire as compared to GMAW.
 The amount of smoke generated can far exceed that of SMAW, GMAW, or GTAW.
 Changing filler metals requires changing an entire spool. This can be slow and difficult as
compared to changing filler metal for SMAW or GTAW.
 Creates more fumes than SMAW.
4. Process Variables
 Wire feed speed
 Arc voltage
 Electrode extension
 Travel speed and angle
 Electrode angles
 Electrode wire type
 Shielding gas composition (if required)
 Reverse polarity (Electrode Positive) is used for FCAW Gas-
Shielded wire, Straight polarity (Electrode Negative) is used
for self shielded FCAW
 Contact tip to work distance (CTWD)
5. Welding Techniques
Pushing Neutral Dragging
6. Specification of FCAW
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Example:- AWS SFA/A 5.20 E 71TC

AWS= American Welding Society

5.20 = Specification of carbon steel electrode rods

E Designates Electrode with Flux

7 Indicates tensile strength of the weld metal in 10000 psi
1 Position Designator 0 is for flat or horizontal and 1 is for all
position welding
T This designator identifies as Electrodes is flux cored or
tubular electrode
1 Designates Polarity of electrode DCEP M ( Single or Multipass)
C Type of Shielding Gas ( Here it is 100% CO2)
 7. Welding Equipment FCAW

Equipment, Arc Types and Welding Positions

Main Components of the Welding Machine
 9.Weld Problems in FCAW
Sr. Problem Causes Remedial Action
No
1 Lack of Fusion  Low heat input.  Use a sufficiently high welding current with the
 Surface contamination. appropriate arc voltage.
 Electrode angle is incorrect.  Before you begin welding, clean the metal.
 The electrode diameter is incorrect for the material  Avoid molten pool from flooding the arc.
thickness you’re welding.  Use correct electrode diameter and angle.
 Travel speed is too fast.  Reduce deposition rate.
 The weld pool is too large and it runs ahead of the arc.

2 Porosity and Worm Tracking  Inadequate electrode oxidant.  Clean the materials before you begin welding.
 Using a longer arc.  Use dry electrodes and materials.
 The presence of moisture.  Use correct arc distance.
 Improper gas shield.  Check the gas flow meter and make sure that it’s
 Incorrect surface treatment. optimized as required with proper with pressure and
 Use of too high gas flow. flow settings.
 Contaminated surface.  Reduce arc travel speed, which will allow the gases to
 Presence of rust, paint, grease or oil. escape.
 Use the right electrodes.
 Use a proper weld technique.

3 Slag Inclusions  Improper cleaning.  Increase current density.

 The weld speed is too fast.  Reduce rapid cooling.
 Not cleaning the weld pass before starting a new one.  Adjust the electrode angle.
 Incorrect welding angle.  Remove any slag from the previous bead.
 The weld pool cools down too fast.  Adjust the welding speed.
 Welding current is too low.

4 Undercutting  Too high weld current.  Use proper electrode angle.

 Too fast weld speed.  Reduce the arc length.
 The use of an incorrect angle, which will direct more  Reduce the electrode’s travel speed, but it also
heat to free edges. shouldn’t be too slow.
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5 Excessive Penetration or Lack of  There was too much space between the metal you’re  Use proper joint geometry.
Penetration welding together.  Use a properly sized electrode.
 You’re moving the bead too quickly, which doesn’t  Reduce arc travel speed.
allow enough metal to be deposited in the joint.  Choose proper welding current.
 You’re using a too low amperage setting, which  Check for proper alignment.
results in the current not being strong enough to
properly melt the metal.
 Large electrode diameter.
 Misalignment.
 Improper joint.

6 Spatter  The running amperage is too high.  Clean surfaces prior to welding.
 Voltage setting is too low.  Reduce the arc length.
 The work angle of the electrode is too steep.  Adjust the weld current.
 The surface is contaminated.  Increase the electrode angle.
 The arc is too long.  Use proper polarity.
 Incorrect polarity.  Make sure you don’t have any feeding issues.
 Erratic wire feeding.

7 Cracks  Use of hydrogen when welding ferrous metals.  Preheat the metal as required.
 Residual stress caused by the solidification shrinkage.  Provide proper cooling of the weld area.
 Base metal contamination.  Use proper joint design.
 High welding speed but low current.  Remove impurities.
 No preheat before starting welding.  Use appropriate metal.
 Poor joint design.  Make sure to weld a sufficient sectional area.
 A high content of sulphur and carbon in the metal.  Use proper welding speed and amperage current.
 To prevent crater cracks make sure that the crater is
properly filled.