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TIG welding machine


TIG Welders - Welding Equipment

There are 16 products in category TIG welding machine.



TIG TUNGSTEN INERT GAS WELDING

Tungsten inert gas arc welding is a process in which the heat required to weld is provided by an electric arc maintained between an infusible electrode and the workpiece; the electrode used to transfer the current is a tungsten or tungsten alloy electrode. The welding area, the molten metal and the non-consumable electrode are protected from outside air and atmospheric agents by inert gas passing through the torch. TIG welding can be carried out with filler material, weld rod, or with the fusion of the base material due to the heat produced by the electric arc.

TIG WELDER: types

a) AC alternating current tig welding machine

The current/voltage output from the generator has a typically square waveform, which changes its polarity at regular intervals, with frequencies from 20 to 200 cycles per second (Hertz) or even higher, depending on the type of generator used. This frequency is obtained thanks to one or more devices, whose function is to transform the sinusoidal current of the mains into an alternating current suitable for soldering.

b) DC direct current tig welding machine

The output current from the generator has a continuous waveform, obtained through devices that allow the conversion of the current from AC to DC.

PULSED WELDING MACHINE

There is another family of generators, called direct current generators, regardless of the polarity of the connection, namely modulated or pulsed direct current generators.

The pulsed current tig welding machine is a direct current generator with special devices that allow the amplitude of the welding current to vary. The pulsed current is obtained by superimposing another component, usually with square waves, on the direct current, producing an arc pulse. This system produces a weld bead formed by a continuous alternation of welding points which, one after the other, form a single bead. It is normally used on thin pieces, where the heat input must be controlled to avoid puncturing the workpiece without compromising the penetration of the weld.

TIG WELDING MACHINE: PROTECTIVE GAS

The protective gases used in TIG welding are: argon, helium, argon-helium mixtures and argon-hydrogen mixtures.

During tig welding that uses argon as the shielding gas, the arc is quite stable but the pool is less hot; consequently this gas is more suitable for welding thin thicknesses.

It is well known that argon is a widely used gas due to its much lower cost than helium; this factor is the major motivation in the choice of shielding gas.

Helium arcs develop greater heat than argon; its use is therefore recommended for welding materials with greater thermal conductivity, allowing for a faster welding speed.

Since helium is lighter than air, it is essential to use it in higher quantities than those used for argon in order to effectively protect the pool.

Argon and helium mixtures are used to have protective gases with intermediate characteristics.

TIG WELDING MACHINE: TUNGSTEN ELECTRODE

There are different types of tungsten electrodes on the market:

  • Pure tungsten electrodes. They are used with low current intensities and in alternating current because the arc is more stable. As for the economic aspect, they are the least expensive.
  • Thoriated tungsten electrodes. They withstand high current intensities. The arc is easy to ignite and once triggered remains very stable. The use of these electrodes is suitable for direct current direct polarity steel welding.
  • Tungsten electrodes with zirconium. They are used in manual welding on aluminum, magnesium and its alloys with a medium-low current intensity.
  • Cerium electrodes. Its characteristics are the high emission of electrons that allow good penetration and good resistance to wear.

TIG WELDING: TYPES OF ELECTRIC ARC IGNITION

There are several types of arch triggers most frequently used:

  • HF trigger (high frequency)
    The spark is created by a high-frequency generator that superimposes a high voltage impulse on the welding voltage; the power of this device is minimal, but sufficient to allow the remote triggering of the electric arc.
    The HF trigger requires the use of a special TIG welding torch, which also has a button to control the trigger.
  • LIFT trigger

It is obtained thanks to a device that provides a very low value current so as not to damage the tungsten electrode tip when it is in contact with the material to be welded.

As soon as you move the electrode away from the workpiece, a spark is created that causes the arc to ignite; the generator then increases the welding current to the value set on the adjustment panel. LIFT ignition, due to the lack of high frequency, has the property of not creating electromagnetic disturbances; the contact of the electrode tip with the material to be welded pollutes the melting pool.

  • Scratch ignition

This ignition occurs by rubbing the tungsten electrode on the workpiece, with the consequent ignition of the arc. Unfortunately, due to the contact between the electrode and the workpiece, there are tungsten inclusions at the beginning of the bead that lower the quality of the weld.

TIG WELDING: THE MATERIALS

TIG welding is mainly encountered in the welding of stainless steels, aluminum and its alloys, nickel, copper, titanium and their alloys.

Stainless steel

Stainless steels are welded with a direct current (DC) tig welding machine with direct polarity.

Workpieces up to 2.5 mm can be welded without filler material; in addition to this thickness, the two joints must be smoothed out and the use of filler material is recommended, which must be particularly suitable for the quality of the stainless steel. Before welding, it is recommended to carefully clean the piece with a stainless steel brush.

Aluminum

Aluminum and its alloys are welded with an alternating current (AC) tig welding machine and require the use of a high frequency generator with suitable characteristics for a good bead finish. If there is high oxidation, it is important to eliminate it with a brush or pickling (chemical process to eliminate the oxide present on the piece).

In this case too, it is possible to weld without filler material up to 2.5 mm; beyond this thickness, the joints must be smoothed out and the use of filler material is recommended.

Argon gas shield welding, with tungsten electrode, is also used with mild and alloy steel, nickel and its alloys; copper and its alloys, titanium and noble metals. For all these metals and alloys direct current (DC) in direct polarity is used.

TIG WELDING: ADVANTAGES

TIG welding has therefore countless advantages in terms of finishing and aesthetics of the bead, an excellent mechanical seal and a certified guarantee for applications in the food industry and beyond. In the presence, for example, of pipes or tanks containing liquids or gases, the TIG process allows all the necessary certifications. In spite of this, welding is extremely slow and thus if the thicknesses are greater or there are no particular needs of the sector, Mig welding is still the best choice, for a definitely higher productivity.

HOW TO CHOOSE A TIG WELDING MACHINE

Tig welding is a professional process, but it is also in increasingly high demand in DIY thanks to its excellent mechanical seal and the high aesthetics of the weld bead. However, it is important to know how to choose the right product according to the work to be done.

First of all, there are two types of Tig welding machines: DC and AC. The first allows to weld iron, stainless steel, copper and cast iron (if preheated). The second allows the welding of aluminum and its alloys.

The second important thing for the choice of the welding machine is the ignition of the electric arc; there are mainly two types of ignition: Lift and HF. With the first, the operator must touch the electrode on the workpiece and lift up quickly to be able to ignite the electric arc; with the second, on the other hand, simply press the torch button to trigger immediately without touching the electrode on the workpiece. This second option is certainly the most common and professional because it allows not to ruin the tungsten and to trigger very quickly and repeatedly.

We can therefore say that when talking about professional Tig welders, we must consider those with an HF trigger, while the choice of DC or AC must be made simply according to the material to be welded. Remember that the price of an AC/DC welding machine is normally much higher than a simple DC machine.

There are also other considerations to be made according to the functions of the welding machine; most Tig machines have the Pulsed function that allows to weld with two different alternating currents and to deform the piece less; it is certainly a very interesting and valid function, but for DIY use and with little experience, it could be difficult to adjust because, in addition to the two currents, we often have to adjust the frequency and other functions connected to it. Therefore, sometimes it is recommended to use a welding machine with simpler adjustments to facilitate a less experienced user.

 


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