FCA welding uses the heat generated by a DC electric arc to fuse the metal being welded. The arc is struck between a continuously fed consumable filler wire and the workpiece, melting both the filler wire and the workpiece in the immediate vicinity. A wire feed unit takes the filler wire from a spool or bulk pack, and feeds it through the welding gun to the arc. The consumable wire used in FCAW is tubular and contains a core of flux and metal powder. The flux fill is also used to provide alloying, arc stability, slag cover, de-oxidation and - in the case of some wires - gas shielding.
As with MIG - another common arc welding method, direct current power sources with constant voltage output characteristics are normally employed to supply the welding current. With flux-cored wires, the terminal that the filler wire is connected to depends on the specific product being used; some wires running electrode positive, others running electrode negative. The work return is then connected to the opposite terminal. It has also been found that the output characteristics of the power source can have an effect on the quality of the welds produced.
FCAW welding uses three types of filler wires: rutile gas-shielded, basic gas-shielded, and self-shielded. Rutile, gas-shielded wires are easy to use with good slag removal and positional capabilities. Basic, gas-shielded wires give better mechanical properties, but tend to be less user-friendly and slag removal can be difficult. Self-shielded wires are ideal for site work but tend to compromise operability and deposition rates as the flux must serve a dual function.
The wire feed unit takes the filler wire from a spool or bulk pack, and feeds it through the welding gun to the arc at a predetermined and accurately controlled speed. Normally, special knurled feed rolls are used with flux-cored wires to assist feeding and to prevent crushing the consumable.
Metal transfer modes with FCAW are similar to those obtained in MIG welding, but here the mode of transfer is heavily dependent on the composition of the flux fill, as well as on current and voltage. The filler metal composition also plays a crucial role in determining transfer characteristics.
The most common modes of transfer in FCAW are:
With FCAW, the entire arc area is covered by a shielding gas, which protects the molten weld pool and filler metal against adverse atmospheric effects. This protective atmosphere can be supplied in two different ways:
Pure carbon dioxide or mixtures of argon (Ar) and carbon dioxide (CO2) are ideal for FCAW auxiliary shielding gas applications. The CO2 composition in argon is typically specified at 20% or 25%. We deliver a range of tried-and-tested cored welding gases with these components under families such as CORGON®, CRONIGON®, VARIGON®, FORMIER® and STARGOLD™. These mixes have been designed to bring you the full benefits of FCAW welding. These include improved productivity combined with high quality across a range of plain carbon, alloy, stainless and duplex steels. Our application experts can advise you on the mixture and operating mode best suited to your needs, also supporting you with the equipment and gas management services you need.
Contact your local Linde representative to check availability in your region.
FCAW is a variant of the metal inert gas (MIG) process. Although there are many common features, there are also several fundamental differences. The main one relates to the consumable. Unlike MIG, which uses a solid consumable filler wire, FCAW uses a tubular consumable where the outer metal sheath is filled with fluxing agents plus metal powder.The flux fill is also used to provide alloying, arc stability, slag cover, de-oxidation, and, with some wires, gas shielding effects. See below for some of the other core similarities and differences.
Similarities between FCAW and MIG welding
Differences between FCAW and MIG welding
Like FCAW, stick welding - also known as manual metal arc (MMA) welding - has the ability to form a slag over the weld metal. This slag supports and shapes the weld bead. FCA welding is typically associated with higher productivity levels than MMA. In addition, flux-cored electrodes can enable a range of metallurgical and physical characteristics that may be difficult or impossible to achieve with traditional stick welding.
Similarities between FCAW and MMA welding
Differences between FCAW and MMA welding
FCAW stands for flux-cored arc welding. This welding process uses the heat generated by an arc struck between a continuously fed consumable filler wire and the workpiece to fuse the metal in the joint area. It is a popular choice for many different welding applications as FCAW welders can achieve improvements in productivity and weld quality relative to MMA (stick) welding and MIG welding.
FCAW is a variant of the MIG (metal inert gas) process. Common features include the use of a direct current power source with constant voltage output characteristics to supply the welding current. However, MIG uses a solid consumable filler wire whereas FCAW uses a tubular consumable consisting of an outer metal sheath filled with fluxing agents plus metal powder. The flux fill provides alloying, arc stability, slag cover, de-oxidation, and, with some wires, gas shielding effects. The electrical resistance of flux-cored wires is higher than that of solid MIG wires, and this higher electrical resistance gives the FCAW welding method some of its novel properties.
With FCA welding, the entire arc area must be covered by a shielding gas to protect the molten weld pool against the effects of atmospheric contamination. This can be achieved in two different ways:
Linde offers a wide portfolio of shielding agents tailored to the specific requirements of FCAW.
The auxiliary shielding gas depends on the specific type of wire used. Pure carbon dioxide (CO2) and mixtures of argon (Ar) and CO2 are most frequently specified for FCAW. Linde offers these gases in different blending ratios to support individual application requirements.
The equipment required for the FCAW process is essentially the same as that used in MIG welding, namely a power source, a wire feed system, and a welding gun. In addition, an auxiliary shielding gas is required for gas-shielded operations.
The right filler metal in FCA welding can help the operator produce welds of high metallurgical and radiographic quality with good mechanical properties, and to overcome typical welding problems such as high hydrogen levels, lack of fusion and porosity, as well as hot or cold cracking defects. Gas-shielded welding wires are available for alloys such as carbon steels, alloy steels, austenitic stainless steels and nickel alloys.
Self-shielded welding wires with filler metal and flux are available for carbon steel and alloy steels. Hardfacing wires depositing weld metal over a wide composition and hardness range are available in gas-shielded or self-shielded versions.
Like all welding methods, FCAW can present occupational health and safety issues if best practices are not observed. The extent and nature of these hazards depends on the material being welded and the consumables in use. FCAW does tend to generate more particulate fume than MIG or MMA welding. Whilst most of this fume is considered fairly inert and not a potentially great hazard, some of the metallic and flux constituents of certain products give rise to pollutants which can present a risk to health. These include chromium from stainless steel and some surfacing wires, barium oxide from some self-shielded wires, and high levels of manganese or nickel from some surfacing wires.
Appropriate fume extraction equipment and the correct personal protective equipment (PPE) can mitigate or eliminate these risks. Linde has developed a comprehensive three-level gas portfolio to help welders increase sustainability performance and occupational safety. Building on the proven potential of PPE, organizational change and learning, and technical extraction/purification technologies, this portfolio extends all the way to less-emissive welding gases with the ability to reduce fume emission rates (FER) directly at the source. Click here for more information on our COMPETENCE, PERFORMANCE and PREVENTION Lines.