FCAW: Flux-cored arc welding
FCAW introduced in 1950. This is a modified version of the MIG welding process. In which solid wire is replaced by a flux-cored (tubular) wire, inside with flux and alloy additions.
It is a commonly used high deposition rate welding process that adds the benefits of flux to the welding.
Definition
The Fcaw is a process, in which coalescence is produced by heating with an electric arc between a continuous tubular consumable electrode and work
.the electrode is flux-cored, the flux is contained within the electrode which is hollow.
In addition to flux mineral and ferroalloys,
the core can provide additional protection and composition control.
the flux inside the wire provides the necessary shielding of the weld pool
It’s used, eliminates the need for gas shielding equipment and gas costs.
The flux inside the wire provides the shielding of the weld pool to avoid atmospheric contamination of the molten weld pool.
it gives a dipper weld penetration and it may give a better performance with thicker base metals.
WELDING EQUIPMENT
- For power feed roll required a variable speed motor and controller which drive the electrode at a preset and uniform rate.
- A gun which houses a trigger to initiate and stop the electrode feed and flow of gas, electrical current to the arc, and if used water for cooling the torch
- Nozzle which directs the shielding gas to the arc and weld pool
- Contact tube at the axis of the nozzle to transfer welding current to the electrode.
- A system of cable houses electrical connections and casings to direct the gas, electrode, power and water if used
- The amount for the spooled of the coiled electrode
- A control station containing the relays, solenoid and timers needed to integrate the system
- A source of shielding gas, if needed, and a device for metering the flow rate of the gas
- A water supply for cooling if necessary
MATERIAL TO BE WELD
- Low to Medium Carbon steels
- Low alloy high strength steels
- Quenched and tempered steels
- Cast iron
- (Certain) stainless steel
- Mild and low alloy steels
- Some high nickel alloys
- Some surfacing alloys
Advantage of FCAW
- There is an economic advantage of fcaw is that the feed wire is not much costly.
- The capability of welding in all positions.
- The fcaw provides high-quality weld metal at a lower cost with less effort as compare with SMAW welding operators.
- FCAW has excellent Weld appearance and smooth uniform welds, less liable to weld defect(Porosity).
- A void range of welding materials.
All these advantages are making this process, a preferred welding process.
Disadvantage of FCAW
- Carbon dioxide gas produced a harsh arc and it’s spattering is excessive.
- irregular wire feed – typically a mechanical problem.
- More costly filler material/wire as compared to GMAW.
- The amount of smoke generated can far exceed that of SMAW, GMAW, or GTAW.
- Creates more fumes than Shielded metal Arc Welding.
- Need to properly adjust the power supply.
Possible welding defect
- Undercut
- Lack of fusion
- Lack of penetration
- Slag inclusion
- Porosity
- Cracks
Welding process variables
In this process, welding variables are as follows:
- Wire feed speed
- Arc voltage
- Electrode extension
- Travel speed and angle
- Electrode angles
- Electrode wire type
- Shielding gas composition (if required)
Electrode wires
FCAW process is using mostly in ferrous metals, primarily steels.
Today, various electrode wires are available some of them are :
E60T-7,E60T-8,E70T-1,E70T,2,E70T-3,E70T-4,E70T-5,E70T-6