FCAW

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

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.


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) 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

FCAW

Documents

Transcript of FCAW