On the contrary, non-consumable electrode supplies no filler on weld bead. Thus if filler is required then it must be supplied separately. Thus its length gradually shortens with welding time. If this filler length is short then it has to be replaced frequently by a new one.
This reduces rate of production and interrupts the process. On the other hand, a long filler can be continuously fed to the welding zone for longer duration without any interruption. Such method is productive but requires bulk storage of costly filler. Preferable welding mode: Arc welding can be performed in three different modes. As mentioned earlier, filler is not necessary to supply when root gap is very small or base materials are thin.
When welding is carried out without applying any filler, it is termed as autogenous mode. However, if filler is applied and metallurgical composition of filler is similar to that of parent component, then it is termed as homogenous mode. If metallurgical composition of filler substantially differs from that of parent component, it is termed as heterogeneous mode. Different welding processes are suitable for different modes.
Electrode material: Electrode material of every arc welding process must possesses few basic characteristics like good electrically conductive, good electron emissivity, desired melting point, etc. It is worth mentioning that filler metal must be compatible with parent metal otherwise they will not mix up properly leading defective welding.
Thus with consumable electrode, electrode material should be chosen based on compatibility with base metal. With non-consumable electrode, filler material should be chosen based on compatibility with base metal, whereas electrode should be made of such material with high melting. Coated or bare electrode: Electrode can be coated to protect it from oxidation or atmospheric contamination.
Apart from protection against oxidation, coating also provides other advantages such as supplying shielding gas, reducing spatter, stabilizing arc, inducing chemical elements into weld bead, etc. However, a coated electrode is costly and prone to damage with time. Different processes utilize different types of coating, each having desired function. Shielding gas supply: Shielding gas is supplied in arc welding to dispense the oxygen from welding zone and create an envelope of inert gases surrounding the weld bead.
Its primary function is to protect hot weld bead from oxidation. Such shielding gas can be supplied directly from a gas cylinder or indirectly by disintegrating other chemical elements during welding. Spatter problem: Spatter is small droplets of molten filer metal that is produced due to scattering of arc and comes out from the welding zone.
This spatter causes loss of filler metal and thus non-uniform filler deposition rate that sometime leads to various welding defects including negative reinforcement and dimensional inaccuracy.
It also hampers appearance and requires grinding after welding for its removal. Manual and automation: Shielded metal arc welding is carried out manually and thus it is also called manual metal arc welding MMAW. And no matter which welding process you use, always make sure to abide by welding safety standards to keep yourself injury-free. Flux cored-arc welding or FCAW is a type of semi-automatic welding process that uses an arc between the consumable electrode or filler wire and the metal workpiece.
The heat from the arc melts both the filler and the workpiece, fusing them together and filling any gaps if present. Flux-cored arc welding is very similar to GMAW or MIG welding with one key difference — the electrode in FCAW is shielded by the flux core removing the need for a shielding gas which protects the electrode from the wind and the air.
FCAW also enables higher wire deposition rates and greater arc stability which makes it a better alternative for welding alloys than MIG. They are:. The students learn and experience the different processes, which makes them better qualified for a job.
Gas metal arc welding GMAW , also known as metal inert gas MIG welding, uses a continuous solid wire electrode that travels through the welding gun, which is accompanied by a shielding gas to protect it from contaminants.
GMAW is one of the most common welding processes and can be used indoors to weld materials for industries like construction, vehicle production, manufacturing and aerospace.
Shielded metal arc welding SMAW is a welding technique that can be used on all ferrous materials in all welding positions. Another name for SMAW is stick welding. A flux-coated electrode which is a metal stick in an electrode holder is connected to a power source and touches the base metal to produce the weld. The flux shields the electric arc to prevent contamination. SMAW can be used to weld low- and high-alloy steels, carbon steel, cast iron and nickel alloys for industries like construction, shipbuilding and manufacturing.
It can be done indoors and outdoors. SMAW produces slag, which is a layer of byproduct welders chip off after the weld for a clean look. Flux-cored arc welding FCAW uses a continuous hollow wire electrode with a flux compound that protects the weld pool by forming a gas.
FCAW is often used for thick materials because the flux-core wire can penetrate thick weld joints. FCAW can be used on cast iron, stainless steel, carbon steel, high-nickel alloys and low-alloy steel.
Such shielding is indispensably necessary to obtain defect-free welding. If electrode is bare then shielding gas is required to supply from external source such as gas cylinder with the help of suitable accessories. SMAW utilizes a flux-coated electrode and thus flux supplies shielding gas during welding.
Contrary to this, TIG welding employs a bare tungsten electrode and thus shielding gas is required to supply externally. Welding spatter: In context of arc welding, spatter is the tiny droplets of molten filler metal that come out of the welding zone mostly due to scattering of electric arc.
This spatter causes loss of costly filler metal as well as reduces filler deposition rate. It also tend to make the arc unstable causing difficulty in maintaining it. Unwanted deposition of metal droplets surrounding the weld bead also hampers appearance and sometimes requires additional post-processing like grinding. Certain arc welding processes are inherent to spatter formation, even with optimum set of parameters.
Shielded metal arc welding is one such method that is always associated with spatter. However, spatter level can be minimized using optimum process parameters, properly cleaning parent metal surface and controlling environment in a desirable way.
TIG welding is usually free from spatter and spatter related defects. Manual and automatic operation and joint quality: Shielded metal arc welding is carried out manually and thus it is also called manual metal arc welding. Therefore maintaining constant arc length, weld direction, feed rate etc. Accordingly weld quality depends on experience and capability of welder.
However, initiation and maintaining the arc is quite easy. No filler is also required to supply additionally. Thus the process is comparatively easier. Tungsten inert gas welding can be carried out manually else an automated system can be employed. Feeding filler metal at a constant rate is a bit difficult; but maintaining the arc is more complicated. Although process is quite difficult and requires experienced welder, TIG welding can easily produce sound, reliable and defect-free joint.
The author also suggests you to go through the following references for better understanding of the topic.
0コメント