Flux cored arc welding is a semi-automatic or fully-automatic welding method that is widely used for welding large sections and with materials of great thicknesses and lengths, especially in the flat position. It was actually developed for the purpose of automating welding processes. The flux cored arc welding method using a shielding gas (FCAW-G) was developed to combine the best characteristics of arc welding and CO2welding.
Flux cored arc welding actually comprises two welding processes. One is flux cored arc welding with no shielding gas (FCAW/FCAW-S). This is a self-shielding process that's also called "Innershield". The second process is flux cored arc welding using a gas (FCAW-G), also called "Outershield". This is the most widely used FCAW process.
The filler wires that are used in FCAW are tubular, and the core is filled with a mixture of mineral flux and powder. That's why this process is called 'flux cored'. There are tubular wires for all positions, including welding stainless steel.The flux-cored wire is either rutile or basic, as with most of the coated electrodes used in MMA, but in some ways its design is quite the opposite of the coated electrode: the filler metal is a tubular wire that contains a flux or iron powder.The wires used in FCAW have a smaller diameter than the coated electrodes used in MMA. For this reason, the prepared joints - the grooves - can have a smaller distance, and this reduces the amount of filler metal that's needed.
During welding the flux produces a slag which covers the weld pool as it is solidifying, and its purpose is similar to the coating used on coated electrodes: to protect the weld pool from impurities. The combination of a flux inside the wire and an external shielding gas gives a good weld from a stable arc with very little spatter. This method has been developed rapidly and extensively in recent years. The flux-cored wire is supplied on reels and fed to the welding gun in MIG and TIG welding.
The power sources that are used for flux cored arc welding are almost the same as those used for MIG welding. They are rectifiers of the dc constant voltage type, the CV type with what's called a flat characteristic.
The most widely used shielding gas is CO2, but mixtures of argon and CO2 are becoming more common because the argon gas improves the properties of the weld. It also gives rapid deposition of metal and high-quality welds in steel.
Flux cored arc welding has several advantages. Since the process is machine controlled, the quality of the weld is more even and a number of defects is reduced owing to the fact that the conditions can be more closely controlled than in manual welding processes. The use of higher currents gives increased weld rates and thus increased productivity. Distortion can be reduced because of the lower heat input and higher speeds.
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| © Olav.Talberg@iu.hio.no | Updated 06.03.02 | Comments [ ] |