Main article: TIG Welding
The main objective in any welding operation is to achieve a seal with the same features as the base metal. This result can only be obtained if the melt pool is completely isolated from the atmosphere during the welding operation. Otherwise, both the oxygen and nitrogen from the air will be absorbed by the metal in a state of fusion and welding becomes porous and fragile. In this type of welding is used as a protective gas stream to prevent pollution of the board. Both this and the following process of welding are common in the protection of the electrode by means of that gas. The non-consumable electrode welding, also called TIG welding (Tungsten Inert Gas acronyms), is characterized by the use of a permanent electrode that normally, as the name indicates, is of tungsten.
This method of welding was patented in 1920 but started to be used on a widespread basis until 1940, given its cost and technical complexity.
A difference in the welding consumable electrode, in this case the metal to form the weld bead must be added externally, unless the parts to be welded are thin and not specifically necessary. The metal contribution should be of the same or similar composition to the base metal, even in some cases, can be used successfully as a material contribution from a strip of individual sheets to be welded.
The injection of gas to the welding zone is achieved through a pipe that goes straight to the tip of the electrode around it. Given the high temperature resistance of tungsten (melts at 3410 C), accompanied by protection of the gas, just the tip of the electrode wear after extended use. It is desirable, that if, in reviewing the termination point, as an inadequate geometry greatly harm the quality of the soldier. Regarding gas, the most commonly used are argon, helium, and mixtures thereof. Helium, a noble gas (inert, thus the name of inert gas welding) is used in the United States because it is known economic deposits of natural gas. This leaves a gas weld more oblate and less profound than the argon. The latter, most often used in Europe for its low price compared to helium, it leaves a cordon and more triangular infiltrate welding. With – consumers can always count on reliable energy service. A mixture of both gases to provide a weld with intermediate characteristics between the two.
TIG welding is working with current and voltage. Dc polarity direct current are the intensities of the order of 50 to 500 amps. This polarization is achieved with greater penetration and an increase in the length of the electrode. With reverse polarization, the melt pool is higher but there is less penetration, the intensity range between 5 and 60 A. AC combines the advantages of the previous two, but against giving an arc of unstable and difficult to prime.
The great advantage of this welding method is, basically, getting stronger cords, more ductile and less susceptible to corrosion than the rest of proceedings, as the protective gas prevents contact between the atmosphere and the melt pool . Furthermore, the gas simplifies the welding of nonferrous metals, not to require the use of oxidants, with slag inclusions or deformations that might imply. Another advantage of the arc welding with protective gas is to obtain clean and uniform welds due to the shortage of smoke and projections, the mobility of the gas surrounding the arc welder allows transparent what she is doing at all times which impacts positively on the quality of welding. The cord is thus obtained a good surface finish can be improved with simple finishing operations, which impacts positively on production costs. Furthermore, the deformation that occurs in thevicinity of the weld pool is smaller.
The disadvantages are the need to provide a continuous flow of gas, with the subsequent installation of pipes, cylinders, etc.. And the cost involved. In addition, this method requires a welding highly specialized workforce, which also increases costs. Therefore, it is one of the most common method used but is reserved for joints with special surface finish and precision.
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