FLUX-CORED ARC WELDING (FCAW)
CARBON STEEL FLUX CORED ELECTRODES CLASSIFICATION, SFA NO-5.20
CHEMICAL COMPOSITION
LOW ALLOY ELECTRODES FOR FCAW, SFA NO-5.29
LOW ALLOY ELECTRODES FOR FCAW, SFA NO-5.29
Suffix T1,T4,T5 and T8 indicates a general
grouping of electrodes that contain similar flux
or core components that produce distinctive
welding characteristics and similar slag system.
FLUX-CORED ARC WELDING (FCAW)
An arc welding process that uses an arc between a continuous filler metal electrode and the weld pool with shielding from a flux contained within the tubular electrode or from an externally supplied gas and without the application of pressure
FLUX-CORED ARC WELDING (FCAW)
Flux-cored arc welding (FCAW) 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 electric current.
An externally supplied shielding gas is sometimes used, but often the flux itself is relied upon to generate the necessary protection from the atmosphere.
The process is widely used in construction because of its high welding speed and portability.
FCAW overcomes many of the restrictions associated with SMAW.
SCHEMATIC ILLUSTRATION FOR FCAW PROCESS
Welding Direction
TYPES OF FCAW
Self shielding type - that requires no shielding gas
Flux core in the tubular consumable electrode
This core contains more than just flux; it also contains various ingredients that when exposed to the high temperatures of welding generate a shielding gas for protecting the arc.
This type of FCAW is preferable because it is portable and the conditions of air flow do not need to be considered.
Gas shielding type
Uses a shielding gas that must be supplied by an external supply
This type was developed primarily for welding steels
Since it uses both a flux cored electrode and an external shielding gas, one might say that it is a combination of gas metal (GMAW) and flux-cored arc welding
This particular style of FCAW is preferable for welding thicker and out-of-position metals.
However, it cannot be used in a windy environment
GAS SHIELD SELF SHIELD
Advantages• FCAW may be an "all-position" process with the right
filler metals.
• No shielding gas needed making it suitable for outdoor
welding and/or windy conditions.
• A high-deposition rate process.
• Some "high-speed" (e.g., automotive applications).
• Low operator skill is required.
• High quality weld deposit
DISADVANTAGES
• Melted Contact Tip – happens when the electrode actually contacts the base metal, thereby fusing the two.
• 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.
CIRCUIT DIAGRAM
FLUX CORED ELECTRODE CONFIGURATIONS
BUTT LAP HEART
Metal
Flux
FLUX CORED ELECTRODE FORMING OPERATION
Strip steel
Flux Hooper
Flux Fill“U” – Forming Rolls
Closing RollsTo drawing operation
METHODS OF APPLICATIONS & POSITION CAPABILITIES
Semiautomatic
Automatic
No manual process possible
All position welding
WELDABLE METALS & ALLOYS
• Best wieldable are• Low carbon steels• Low alloy steels• High and medium carbon steels• Alloy steels• Certain grades of stainless steels
• Using spl electrodes• Cast irons• Nickel alloys
WELDABLE THICKNESS RANGES
# Depends on the type of shielding
# Self shielding = Less penetration Max penetration is 6 mm
# Gas shielding = Deep penetration Max penetration is 13 mm
WELDING CURRENT
Similar to GMAW DCEP is most used DCEN is sometimes used
DC – CV is the power source Current = 50 A – 750 A
AC can used with spl flux formulations
CC power supply is then used
Shielding Gases
Gas can be Inert, Reactive, or Mixtures of both
Gas flow rate is between 35- 45 CFH
Argon and Carbon Dioxide are the main three gases used in GMAW
Carbon Dioxide most used
Carbon Dioxide + Argon mixture sometimes used
DEPOSITION RATES & QUALITY OF WELDS
High deposition rates
High quality welds
LIMITATIONS & APPLICATIONS Only for ferrous alloys Removal of slag Expensive
Replacing SMAW, GMAW (CO2 version) and SAW for thinner materials
Automotive industry, Pipe industry, Tank industry, General construction industries
ELECTRODES
# SELF-SHIELDED ELECTRODES
Self-shielded electrodes rely solely on the materials in the core of the wire for shielding the arc from the atmosphere, purifying the weld metal and providing the slag formers necessary to protect the molten weld puddle
These electrodes do not rely on gas shielding as the gas shielded types do; therefore, they can operate more effectively in outdoor environments without a windscreen
Best suited for welding low carbon steels and low alloy steels
Uses a long electrical stick-out commonly from one to four inches
Enables the electrode to burn off at a faster rate and increases deposition
The preheating also decreases the heat available for melting the base metal, resulting in a more shallow penetration than the gas shielded process
# A major drawback of the self shielded process is the metallurgical quality of the deposited weld metal
# Deoxidizing and denitrifying alloys, primarily aluminum, will reduce ductility and impact strength at low temperatures
# For this reason, the self shielding method is usually restricted to less critical applications
# The self shielding electrodes are more suitable for welding in drafty locations than the gas shielded types
FUNCTIONS OF THE FLUX INGREDIENTS
# METAL CORED WIRES (GAS SHIELDED)
Metal cored electrodes are fabricated tubularwires having a metallic sheath with the core ingredients predominantly iron powder
Iron powder serves to increase the electrodes deposition efficiency, while improving the
speed of travel
Because the slagging ingredients have been replaced with iron powder, the slag residue makes up
less than 5% of the deposit
This feature provides the user the capability to multipass without deslagging
# A major advantage is very good shielding
# No need for core ingredients such as aluminum
# The weld metallurgy is cleaner
# Suitable for welding not only mild steels, but also low alloy steels in a wide range of strength and impact levels
# The gas shielded method uses a shorter electrical stickout than the self shielded process
# Extensions from 1/2" to 3/4" are common on all diameters, and 3/4" to 1-1/2" on larger diameters
# Higher welding currents are also used with this process, enabling high deposition rates
# The auxiliary shielding helps to reduce the arc energy into a columnar pattern
# The combination of high currents and the action of the shielding gas contributes to the deep penetration inherent with this process
# Both spray and globular transfer are utilized with the gas shielded process
SLAG SYSTEMS