The DC TIG welder, as we saw before, is useful for metallurgical tasks on steel, nickel, titanium and other metals other than aluminum and magnesium. Now, what factors need to be taken into account? buy welding equipment What is really useful to us? The answer depends, as always, on the jobs we have planned.
In this article we will see a practical guide for choosing a DC TIG welder according to the type of work and materials.
TIG DC welding machine: choice according to the materials and work envisaged
metals
Being a direct current TIG (or GTAW) welder, we know that it will be useful in the event that we plan to work with steel, nickel, titanium and other metals other than aluminum and magnesium, since the latter have a particular tendency to develop an inert oxide layer on the surface as soon as they come into contact with air. Although it is still possible to weld these metals with direct current equipment in automatic mode, this implies the use of a powerful current of argon, or the use of some other mechanism (provided for by automated machines).
Material thickness
A secondary factor in choosing a DC TIG welder is the thickness of the materials with which we will work.
As a general rule, the greater the thickness range, the greater the amperage range that the equipment must handle. As an example, for a device with a current range between 5 A and 230 A, it will be able to Weld materials as thin as 24 stainless steel sheet (0.6 mm thick) and as thick as 6.35 mm aluminum plates.
Make sure that the equipment shows a stable behavior in the arc when working with currents lower than 10 A.
Types of works
The TIG technique is mainly used for jobs that require maximum neatness and safety; That is why TIG welders are widely used in the automotive and aeronautical industries and for welding bicycle frames, for example.
In the case of DC TIG welder, the most frequent jobs are those of artistic and decorative ironwork, repair of bodywork, bicycles and motorcycles, repair of industrial machines and, of course, manufacture of mechanical metal parts. The most common materials are steel, iron, copper and titanium.
If you plan to perform any of these jobs, with the materials described, the DC TIG welder It is the recommended equipment.
Aspects to consider
low amperage
To be able to work with thin materials, it is necessary that the equipment can work correctly with low levels of electrical current; As stated before, this responds to the need to control the temperature without cutting the electric arc.
This feature is extremely important for welding thin materials, especially copper or stainless steel sheets.
heat control
In a complementary way to the amperage control, the temperature control avoids the problem of torsion in the sheets due to stress due to overheating of the parts.
The heat control consists of a pulsed system that regulates the time destined to circulate a high current between the electrode and the mass; the rest of the time a low intensity current is used for the sole purpose of keeping the arc active.
arc start
The main problem with early direct current TIG welders was the start Of the arc. To achieve this, a much higher current was launched during the first milli-seconds, in order to ionize the air and create the necessary electric arc. As soon as this happened, the current dropped to the usual level. This system was called hot start.
Another principle is currently used, which avoids burning or perforating the material and also allows the stability of the archwire to be maintained throughout the entire process.
Ramp
An additional control factor is the so-called ramp of current, which allows the amperage to be reduced shortly before the end of the welding, in order to avoid the crater at the end of the seam, which can often cause cracks.
Investment
“Picking” (etching) observable in the welding of 6061 aluminum in the alternating current (AC) regime. This phenomenon can be completely eliminated by using a DC TIG welder, but to achieve this it is necessary to have great skill in the use of the equipment, or to use an automated cycle.
The DC TIG welder often provides polarity reversal control. Normally, in a direct current regime, the electrode is negatively charged; this is represented by the acronym DCEN in English (Direct Current, Electrode Negative). In this regime, the electrode emits electrons and heats the material, while the inert gas ionizes and travels towards the electrode. This causes that the material is not completely protected by the inert atmosphere, and oxides are produced in the seam.
With the reverse regime, DCEP, it is the material that emits electrons, which travel towards the electrode, which is heated; the inert atmosphere tends to settle on the material, protecting it at the cost of losing heat in the electrode.
So far, then, the variables to consider before choose to buy a TIG DC welding machine, now it only remains to decide and start enjoying!
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