Plasma and argon arc welding difference
Argon arc welding technology is based on the principle of ordinary arc welding, the use of argon on the protection of the metal welding consumables, through the high current so that the welding consumables in the welded substrate melted into a liquid state to form a pool of weld metal and weld metal to achieve the metallurgical combination of a welding technology, due to the high temperature melt welding constantly send up the welding consumables can not and oxygen in the air, thus preventing the oxidation of welding copper, aluminum, alloy, therefore can be welded. A kind of welding technology, due to the high temperature melt welding in the continuous delivery of argon, so that the welding consumables can not be in contact with the oxygen in the air, thus preventing the oxidation of the welding consumables, so you can weld copper, aluminum, alloy steel and other non-ferrous metals.
Plasma welding, plasma jet through the entire weld and the formation of a small hole (i.e., small hole effect) gas also passes through. Of course, this small hole with the arc forward and closed. Plasma welding can be welded than TIG welding thicker steel plate in the operation of the technical and economic benefits of both have undeniable advantages.
Root Channel Manual Arc Welding Manual TIG Welding Plasma Welding (PAW)
Plate Preparation Bevel + Blunt Edge Bevel + Blunt Edge 2.5-8mm
No Bevel + Blunt Edge Required
Fitting Relatively Difficult (Gap) Difficult (Small Gap) Easy
Welder's Skill Requirements Skilled Skilled Skilled General
Welding speed Very slow Very slow Quite fast
Operating difficulty Difficulty Very difficult Easier
Post-weld quality Good/but unattractive in appearance Good Excellent
Special problems Overheating of the welding electrode, easy fatigue of the welder None
Difficulty in controlling the quality, Difficulty in controlling the quality,
Distortion of the workpiece Deformation of the workpiece
Because of its high welding speed, the seam is fast, beautiful, and the seam quality is good. Because of its fast welding speed, beautiful weld, weld quality, low cost, plasma welding has been widely used in equipment manufacturing industry on a variety of types of joints for welding, medical equipment, vacuum devices, thin plate processing, bellows, instrumentation, sensors, automotive parts, chemical seals and so on.
Micro-beam plasma welding is more in the actual use of the huge advantages revealed, the quality of the weld can be compared with the laser welding. Micro-beam plasma technology has been successfully applied to the welding of most metals, such as steel, stainless steel, various alloy steels, copper, nickel, titanium, molybdenum, tungsten, gold, platinum, rhodium, palladium and other metals and their alloy materials. Typical application products are sensor membrane box, welded bellows, micro-motor stator core, electronic products, stainless steel pot
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★Process Characteristics
Plasma welding is very similar to TIG welding. They both have an arc formed between a pointed tungsten electrode and the workpiece. However, by placing an electrode in the torch, the plasma arc can be separated from the shielding gas pocket, and the plasma is then pushed through a well-bored copper nozzle to compress the arc. By varying the diameter of the hole and the speed of the plasma gas flow, three types of operation can be realized:
1. Microbeam plasma: 0.1 to 15A
A microbeam plasma arc can be used even at very low welding currents. The column arc remains stable even when the arc length does not vary more than 20mm.
2, medium current: 15 ~ 200A
In the larger 15 ~ 200A current, the plasma arc process characteristics similar to the TIG arc, but because the plasma is compressed, the arc is more straight. Although the plasma flow rate can be increased to increase the depth of the weld pool, it creates a risk of mixing air and shielding gas in the turbulent shielding gas flow.
3, small hole type plasma: more than 100A
By increasing the welding current and plasma flow rate, can produce a strong plasma beam, as with laser or electron beam welding, it can form a full depth of fusion in the material. During welding, as the weld pool flows, the metal is cut through small holes to form weld passes under surface tension. The process can be used to weld thicker materials (stainless steel up to 10mm thick) when welding in a single pass.
★Power source
When using a plasma arc, a DC current and droop characteristic power source is usually used. Due to the unique operating characteristics obtained from the special torch arrangement and the respective separated plasma and shielding gas streams, a common TIG power supply can be added to the plasma console, and specially assembled plasma systems can also be used. It is not easy to stabilize the plasma arc when using sinusoidal AC power. The plasma arc is difficult to function when the electrode and workpiece are spaced far apart and the plasma is compressed, and the overheated electrode interferes with the stabilization of the arc by causing the conductive nozzle to become spherical during the positive half-cycle.
A dedicated DC switching power supply can be used. Reducing the duration of the positive electrode by adjusting the balance of the waveform allows the electrode to be cooled sufficiently to maintain the pointed conductive nozzle shape and form a stable arc.
★Arc Starting
Although the plasma arc is generated by employing high frequency, it is first formed between the electrode and the plasma nozzle. This dimensional arc is contained in the torch and transferred to the workpiece when welding is required. As with the dimensional arc held between the welds, the dimensional arc system ensures stable arc initiation, which avoids the need for high frequencies that generate electronic interference.
★Electrodes
Used for the plasma process is a tungsten electrode containing 2% thorium oxide and a copper plasma nozzle. Unlike the nozzles used for TIG welding, the diameter of the electrode nozzle is less stringent in the plasma process, but the compression angle must be maintained at about 30° to 60°. The diameter of the plasma nozzle hole is very important, under the same current intensity and plasma gas flow rate, the hole diameter is too small will lead to excessive corrosion or even melting of the nozzle. In the operating current, need to be careful to use the diameter of the plasma nozzle is too large.
Note: A hole diameter that is too large may cause difficulties in arc stabilization and hole maintenance.
★Plasma and Protective Gases
The usual combination gas for plasma is argon with 2% to 5% argon as a protective gas. Helium can also be used as a plasma gas, but because of its higher temperature, it reduces the current rise rate of the nozzle. The lower the hydrogen content, the more difficult it is to perform small-hole type plasma welding.
★Applications
☆Microbeam Ion Welding
Microbeam Ion is commonly used for welding thin plates (0.1mm thick), wires, and mesh sections. The needle-straightened arc minimizes arc deviation and distortion. While the equivalent TIG arc is more diffuse, newer transistorized (TIG) power sources produce very stable arcs at low currents.
☆Medium Current Welding
This method can be chosen for conventional TIG welding in the melting mode. Its advantages are that it produces a deeper depth of fusion (thanks to the higher plasma flow) and allows for greater surface contamination including the flux coat (electrode in the torch). The main disadvantage is that the torch is bulky, making manual welding more difficult. In mechanized welding, more attention should be paid to torch maintenance to ensure stable performance.
☆Small Hole Type Welding
A few of the advantages available are: deeper melt depth and faster welding speed. Compared to the TIG arc, it can weld through plates up to 10mm thick, but when using a single-pass welding technique, the plate thickness is usually limited to 6mm. The usual method is to use small holes with filler to ensure a smooth weld pass section (no tooth edges). As the thickness reaches 15mm, a 6mm thick blunt edge is used for V-joint preparation. It is also possible to use the two-pass welding technique, whereby the first and second passes are automatically generated by adding filler wires in the melting mode.
The welding parameters, plasma flow rate, and filler wire addition (to fill the hole) must be precisely balanced to maintain the stability of the hole and weld pool, and this technique is only suitable for mechanized welding. Although the technique can be used for positional welding through the use of pulsed current, it is typically used for high-speed flat welding of thicker plate materials (over 3mm). When performing pipe welding, the overflow current and plasma gas flow rate must be precisely controlled to ensure small hole closure.