What is FCAW-G and its meaning?
FCAW-G stands for Flux-cored arc welding-Gas Shielded& is the most used FCAW technique in the industries. In FCAW-G, external shielding gas is used similar to GMAW (MIG-MAG) welding. As the flux-cored wire also has flux coating to create shielding gases, they are not sufficient enough to provide full shielding and external shielding gas (Mainly CO2 as it’s cheaper) is supplied. Argon + CO2 mixtures are also used as shielding gas. The arrangement of FCAW-G is shown in the below figure. Usually, FCAW-G indicates or refers to CO2 as a shielding gas to be used for welding.
Flux-cored wire electrodes are more expensive than solid wire electrodes. Therefore they are used only where good welding properties and/or high weld qualities provide an advantage.
Click here to learn about Flux Cored Arc Welding (FCAW)
The actual 3D sketch of the FCAW-G equipment setup is shown below.
What is FCAW-S and its meaning?
FCAW-S is also known as flux-cored arc welding- Self Shielded. The flux-cored self-shielded wires are used in the FCAW-S technique. The wire is similar to a Stick welding rod but internally filled with flux and in the form of a roll. The coating elements in the wire have enough flux to create sufficient gas shielding without the need for any external shielding gas like required in FCAW-G. The flux in the coating burns and produces the shielding gases and the slag which solidify.
Click here to learn about Shielding gases for MIG-MAG, TIG, and FCAW welding and shielding gases purity
FCAW-S vs. FCAW-G
Both FCAW-S and FCAW-G type of flux-cored arc welding. The only difference between the both is the type of Cored wire. FCAW-S produce shielding gases required for the weld in sufficient quantity and FCAW-G requires additional externally supplied shielding gases to protect the weld pool.
Both FCAW-S & FCAW-G can be welded using the same welding machine and no separate welding machine is required.
FCAW-G vs. MIG welding
When comparing FCAW-G to MIG-MAG welding only difference is the type of the welding wire. While the MIG welding uses a solid wire spool, the FCAW-G are cored wires with internally filled flux. Both the process can be used with the same welding machine without any modification. As, we know MIG stands for Metal inert gas so the shielding gas is used in pure argon, while in FCAW-G, we usually use CO2 or a mixture of Argon + CO2 gases as shielding.
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Types of flux coating in FCAW wire
The flux filling in FCAW wire consists of several raw materials and among other things including arc stabilizers for achieving high process stability, alloying elements for the use of metallurgy, and partly micro-alloyed elements to improve the quality of the metal weld through nucleation. These micro-alloyed elements also provide a fine grain structure in the weld deposit.
The flux coating also includes gas-forming agents and deoxidizers.
The main coating element defines the type of FCAW wire for example a rutile coating or acidic type. In rutile coating, Titanium Oxide (TiO2) is found as the main coating element along with calcium carbonated which produces shielding gas such as Co2 and CO after burning during welding. Alloying elements are added using their ferro products such as ferrosilicon, Ferromanganese, Ferro boron, etc. which provides weld deposit with Si, Mn, and Bo respectively for example.
Cross section of flux cored wires
According to the construction of the wire cross-sections, seamless and shape-closed flux-cored wire
electrodes exist, which also differ in the way they are manufactured. Various types of the cross-section are used in the manufacturing of the flux cored wires along with the latest seamless wire technology adapted by many new manufacturers. The various cross-sections of FCAW wires are shown in the below diagram.
How flux cored wire is made?
The flux-cored wire is manufactured by the welding companies and as a pre-material, for enclosed types, a narrow strip with a slightly more than 10 mm width and less than 1 mm thick is used and brought fist into a U-shape by bending rollers. After this a continuous filling of the mostly dry mixed flux takes place. Subsequently, the cross-section is closed to form the wire and is usually reduced and compressed by rolling.
In the next operation, the complete semi-finished product is drawn and rolled to the final dimension as shown in the below diagram.
How seamless flux-cored wire is manufactured?
The classic production of the seamless flux-cored wires uses a strip of approx. 50 mm width and about 2 mm thickness, from which continuous tubes are manufactured using high-frequency welding. After the recrystallization annealing process, the tube is drawn to the filling diameter. The filling flux, in this case, agglomerated, is inserted into the pipe by vibration and pre-compressed.
Next, the semi-finished product is drawn to the annealing diameter. During this heat treatment, the strain strengthened casing is soft-annealed, reducing the hydrogen originating from the filling flux to far below 5 ml/100 g. Next, the wire is drawn to its final dimensions by several steps, repeatedly wet-cleaned and finally copper-plated and polished. The flux-cored wire electrode manufactured by this method is absolutely protected against moisture absorption and can be stored without limitation. Re-drying is not necessary. As the coating does not contain any stiffness changes, the wires do not twist and ensure no disruptions during feeding. The coppered wire surface improves current transmission and reduces nozzle wear.
Advantages of Flux Cored Wire Welding
Flux-cored wire offers numerous advantages compared to solid wire. They are:
More secure sidewall fusion, tolerant of incomplete fusion
- Good wetting, notch-free transitions, smooth surface
- High crack resistance
- Low spatter droplet transfer
- High process stability
- X-ray-safe welds
- Applicability of micro-alloy elements
- Good suitability for out-of-position welding
- Economic manufacturing