04-10-2012, 02:24 PM
GAS METAL ARC WELDING
GAS METAL.pptx (Size: 752.42 KB / Downloads: 37)
Gas metal arc welding (GMAW), is a welding process in which an electric arc forms between a consumable wire electrode and the workpiece metal(s), which heats the workpiece metal(s), causing them to melt, and join. Along with the wire electrode, a shielding gas feed through the welding gun, which shields the process from contaminants in the air. The process can be semi-automatic or automatic. A constant voltage, direct current power source is most commonly used with GMAW, but constant current systems, as well as alternating current, can be used. There are four primary methods of metal transfer in GMAW, called globular, short-circuiting, spray, and pulsed-spray, each of which has distinct properties and corresponding advantages and limitations.
Short-circuit transfer occurs when filler metal is deposited from the electrode by short-circuiting to the workpiece surface. Amperage and voltage settings, along with proper shielding gas selection, determine if welds are produced with short-circuit transfer. Short circuit can be easily understood as it is related to what occurs in a circuit of an electrical fuse. If too much current (amperage) is introduced to the circuit, the fuse overheats and blows. The same principles occur when short-circuit welding. The difference is that the electrode (fuse) is being continually fed, and the short circuit occurs over and over again, depositing the electrode on the base metal as weld.
WHAT IS GLOBULAR TRANSFER?
with increased arc voltages in the same amperage range as the short-circuit transfer. The increased arc voltage melts the electrode back away from the weld pool. The electrode forms a balled end approximately 2 times the electrode diameter, and filler metal is deposited when gravity causes the molten droplet to detach from the electrode and fall across an open gap, causing an explosive deposit. The welder will observe an open arc or gap between the electrode and the weld pool.
GAS METAL.pptx (Size: 752.42 KB / Downloads: 37)
Gas metal arc welding (GMAW), is a welding process in which an electric arc forms between a consumable wire electrode and the workpiece metal(s), which heats the workpiece metal(s), causing them to melt, and join. Along with the wire electrode, a shielding gas feed through the welding gun, which shields the process from contaminants in the air. The process can be semi-automatic or automatic. A constant voltage, direct current power source is most commonly used with GMAW, but constant current systems, as well as alternating current, can be used. There are four primary methods of metal transfer in GMAW, called globular, short-circuiting, spray, and pulsed-spray, each of which has distinct properties and corresponding advantages and limitations.
Short-circuit transfer occurs when filler metal is deposited from the electrode by short-circuiting to the workpiece surface. Amperage and voltage settings, along with proper shielding gas selection, determine if welds are produced with short-circuit transfer. Short circuit can be easily understood as it is related to what occurs in a circuit of an electrical fuse. If too much current (amperage) is introduced to the circuit, the fuse overheats and blows. The same principles occur when short-circuit welding. The difference is that the electrode (fuse) is being continually fed, and the short circuit occurs over and over again, depositing the electrode on the base metal as weld.
WHAT IS GLOBULAR TRANSFER?
with increased arc voltages in the same amperage range as the short-circuit transfer. The increased arc voltage melts the electrode back away from the weld pool. The electrode forms a balled end approximately 2 times the electrode diameter, and filler metal is deposited when gravity causes the molten droplet to detach from the electrode and fall across an open gap, causing an explosive deposit. The welder will observe an open arc or gap between the electrode and the weld pool.