Non-consumable electrodes for tig welding of the brand. Tungsten electrodes for argon arc welding. Advantages and disadvantages of the manual TIG welding process

A little theory - in order to weld aluminum, you need a source that gives out alternating current, because aluminum cannot be welded with direct current. This applies specifically to argon arc welding. The device must have a non-contact ignition function, a crater filling function and an AC balance adjustment function. This device has all these functions, there is nothing else in it, but this is quite enough to do the job efficiently.

Argon gas should be given special attention. If it is a little dirty, the welding will fail. Aluminum will turn black during the welding process and the seams will be very ugly. Because it happens that you come across cylinders in which a little air from the atmosphere is mixed.

Filler rod

I have come across two main types of filler material - filler rods for welding pure aluminum, for example, like I have here, electrical busbars, pure aluminum is used there.

And filler rods for welding cast aluminum, in which there is a large amount of impurities of other metals. In such rods, a silicon component is added, which makes it much easier to work with aluminum and the seams will be as strong as possible in such cases.

For welding of pure aluminum, rods with the number 5356 are used. For welding of cast aluminum alloys, rod 4043 is used.

Tungsten electrode

Tungsten electrodes must be used either universal or for alternating current welding, such electrodes are colored green. For aluminum welding, I use a universal electrode with a diameter of 2.4. You can weld both thin and thick aluminum, up to 5-6 mm.

The electrode must be sharpened before welding, but it is not necessary that it be very sharp, it is possible to leave a slight dullness on it, because during the welding process it will still be rounded with a hemisphere. During welding, the tungsten electrode should have a clear sphere that resembles a small droplet, but this droplet should be no larger in diameter than the electrode itself. The color should be shiny, the sphere itself should be even. If it is, for example, matte, it means poor protection or bad gas. It all comes down to gas - either there is little gas, or the gas is bad.

If the electrode melts too much, then it can withstand too high temperatures, which means it is not designed for such currents. That is, it is necessary to use a larger electrode in diameter.

And the device also has such a function as an alternating current balance. We will deal with this function in detail. She is also responsible for how tungsten behaves at work.

Gas protection

For aluminum welding, it makes sense to use a gas lens. A gas lens is a collet holder that has an embedded mesh structure inside, through which gas passes. This gas creates a quieter laminar flow and thus provides better protection for the tungsten electrode and weld pool. There are also special nozzles for this gas lens, the diameter of the nozzles can also be different. Specifically for aluminum, the larger the nozzle diameter, the better the protection will be. I have a very small nozzle diameter, only 8 millimeters, but it will be enough for my task.

The protrusion of the tungsten electrode during welding should be done approximately 4-5 mm. If there is more, then tungsten will be very hot on alternating current and will collapse.

The full name of this welding process is as follows: Manual arc welding in inert gas with a tungsten electrode (DSTU 3761.3-98 "Welding and related processes. Part 3 Welding of metals: joints and seams, technology, materials and equipment. Terms and definitions"). The diagram and essence of the TIG welding process is shown in the figure below.

The edges of the work piece to be welded and the filler metal are melted by an arc burning between the non-consumable tungsten electrode and the work piece. In this case, an electrode is used either from pure or from activated tungsten. Filler metal is added to the weld pool, if necessary. As the arc moves, the molten (liquid) metal in the weld pool solidifies (i.e. crystallizes), forming a weld that joins the edges of the parts. The welded joint is formed either only due to the molten base metal, or due to both the base metal and the metal of the filler wire. The arc, weld pool, ends of the tungsten electrode and filler wire, as well as the cooling seam are protected from the environment by an inert gas (argon or helium) supplied to the welding zone by a torch. Welding is carried out either with direct current of direct polarity, when the positive terminal of the power source is connected to the product, and the negative terminal to the torch, or with alternating current (when welding aluminum).

TIG welding applications

This welding method is widely used in chemical, heat and power, oil refining, aerospace, food, automotive and other industries for welding almost all metals and alloys: carbon, structural and stainless steels, aluminum and its alloys, titanium, nickel, copper, brass , silicon bronzes, as well as dissimilar metals and alloys; surfacing of some metals on others.

Welding power source

The welding power source supplies the welding arc with electrical energy. The following are used as a power source for TIG welding:

Welding transformers - when welding with alternating current;
- welding rectifiers and generators - for direct current welding;
- universal power sources providing both AC and DC welding.

Power sources for TIG welding must have a steeply dipping external current-voltage characteristic (). This characteristic ensures the constancy of the set value of the welding current in case of violations of the arc length, for example, due to oscillations of the welder's hand.

Welding torch

The main purpose of the TIG arc welding torch is to rigidly fix the tungsten electrode (W-electrode) in the required position, supply electric current to it and uniformly distribute the flow of shielding gas around the weld pool. It consists of a body (handle) and a head covered with insulating material. Typically, a control button is built into the torch handle for switching the welding current and shielding gas on and off. Some modern torches have a current control button during welding. The collet allows you to rigidly fix the W-electrode in the torch; to do this, screw the back cap all the way down. Typically, the back cap is long enough to accommodate the entire length of the electrode, as shown. However, for work in confined spaces, the burners can also be supplied with short caps.

TIG torches are designed in a wide variety of designs and sizes, depending on the maximum current required and the conditions of use. Torch size also affects how the torch heats up and cools when welding. Some burners are designed to be cooled by a flow of protective gas (these are the so-called air-cooled burners). The burners also transfer heat to the surrounding area. Water cooled burners are also available. They are usually intended for use at higher welding currents. Water-cooled TIG torches are generally smaller than air-cooled torches for the same welding currents.

Gas nozzle. The function of the gas nozzle is to direct the shielding gas into the weld zone so that it replaces the surrounding air. The gas nozzle is threaded to the TIG burner, which, if necessary, facilitates its replacement. They are usually made of ceramic material in order to withstand intense heat.

Gas lenses... Another type of nozzle is built-in gas lens nozzles, in which the gas flow passes through a metal grating, which gives it more laminarity, which provides better protection, since such a flow is more resistant to the effects of transverse air currents and acts over a greater distance. The advantage of the laminar gas flow nozzle is that a larger stick out can be set, which gives the welder a better view of the weld pool. Gas lenses also reduce gas consumption.

Conventional nozzle (left) and gas lens nozzle (right)

Shielding gas flow shape from a conventional nozzle

Shielding gas flow shape from a gas lens nozzle

Control units (panels) for TIG welding installations

Control units (panels) for TIG welding installations can be either very simple or very complex with various functions. The simplest control unit allows you to control only the welding current. At the same time, the shielding gas flow is adjusted by a regulator built into the TIG burner. Modern control units allow shielding gas to be switched on before the arc strikes and to continue supplying it for some time after the welding current is switched off. The latter protects the tungsten electrode and the cooling weld pool from the ambient air. Control units for TIG welding systems can also provide control of the rise and fall of the welding current, as well as pulsed welding (current ripple). Adjusting the time of the smooth rise of the current to the nominal level when the arc is ignited protects the tungsten electrode from destruction and ingress of tungsten particles into the weld. Controlling the ramp-down time at the end of welding prevents crater and porosity formation.

In the pulse welding mode, two current levels are set: pulse current and base current. The base current value is selected from the condition of maintaining the arc burning. Melting of the base metal is carried out by the pulse current, while during the pause the weld pool cools down (up to complete crystallization, depending on the parameters of the pulse mode). Pulse and pause durations can be adjusted.

In pulse welding, the seam looks like a series of superimposed weld spots, and the degree of overlap depends on the welding speed.

Basic parameters of manual TIG welding mode

The main parameters of the TIG welding mode are:

Tungsten electrode type;
- electrode diameter;
- type of shielding gas;
- welding current strength (Iw);
- arc voltage (Ud);
- welding speed (Vw).

Used welding consumables

Shielding gases

The shielding gas has several functions. One of them is to displace the surrounding air from the welding zone and, thereby, to exclude its contact with the welding bath and a hot tungsten electrode. It also plays an important role in the passage of current and heat transfer through the arc. TIG welding uses two inert gases: argon (Ar) and helium (He), of which the former is more commonly used. They can both be mixed with each other, or each of them with another gas that has a reducing capacity, i.e. enters into a bond with oxygen. TIG welding uses two gases as reducing gases, hydrogen (H2) and nitrogen (N2). The choice of the type of shielding gas depends on the type of material to be welded.

Selecting the correct shielding gas.

It is recommended to use a N 2 / H 2 gas mixture as a shielding gas for the root side of the weld.

For more information on shielding gases and filler rods, see article

Electrodes

Non-consumable tungsten electrodes for gas-shielded arc welding are manufactured in 4 types (according to -80):

EHF - pure tungsten without special additives;
EVL - tungsten with the addition of lanthanum oxide (1.1 - 1.4%);
EVI - tungsten with the addition of yttrium oxide (1.5 - 3.5%);
EWT - tungsten with the addition of thorium dioxide (1.5 - 2%).

The diameter of the tungsten electrode is selected depending on its brand, value and type of welding current. EHF electrodes are used for welding on alternating current, and others for welding on alternating and direct currents of direct and reverse polarity.

The type of current and polarity affect, first of all, the shape of the penetration. This dependence is conventionally shown in the figure.

A - direct current direct polarity; B - direct current reverse polarity; B - alternating current;

In the process of welding, the electrode becomes blunt and, as a result, the penetration depth decreases. It is recommended to sharpen the end of the electrode for AC welding in the form of a sphere, and for DC welding in the form of a cone. The cone angle should be 28 - 30 °, the length of the conical part should be 2 - 3 electrode diameters. The cone after sharpening should be blunt, the blunt diameter should be from 0.2 to 0.5 mm.

The sharpening process of the electrode is shown in the figure below. When sharpening the electrode, portable devices can be used, or stationary ones with or without special guides for the electrode.

Sharpening the W electrode

Consumption of electrodes with a diameter of 8 - 10 mm with continuous operation for 5 hours:

ESP - 8.4 g / h, EVL - 1.2 g / h, EVI - 0.18 g / h, EVT - 1.4 g / h. To reduce the consumption of the electrode, the inert gas supply should be started before turning on the welding current, and stop after turning off the current and cooling the electrode.

Zirconium and hafnium electrodes are used in plasma welding torches. Welding with a graphite electrode is used very rarely - mainly for the production of non-critical welded joints in the manufacture of products from low-carbon steel, welding of defects on cast iron and when welding copper in nitrogen with direct current of direct polarity.

Influence of current polarity on the welding process

The polarity of the welding current significantly affects the nature of the arc welding process in an inert gas with a tungsten electrode. Unlike consumable electrode welding (which includes MMA and MIG / MAG welding), when welding with a non-consumable electrode in a shielded inert gas atmosphere, the differences in the nature of the welding process on reverse and direct polarity are of the opposite nature.

So, when using reverse polarity, the TIG welding process is characterized by the following features:

Reduced heat input into the product and increased heat input into the electrode (therefore, when welding with reverse polarity, the non-consumable electrode must be of a larger diameter at the same current; otherwise, it will overheat and quickly collapse);
- the zone of melting of the base metal is wide, but shallow;
- the effect of cathodic cleaning of the surface of the base metal is observed, when, under the influence of the flow of positive ions, the oxide and nitride films are destroyed (the so-called cathodic sputtering), which improves the fusion of the edges and the formation of the weld.

Whereas when welding on straight polarity, the following is observed:

Increased heat input into the product and reduced heat input into the electrode;
- the zone of melting of the base metal is narrow, but deep.

As in the case of MMA and MIG / MAG welding, the differences in arc properties at forward and reverse polarity in TIG welding are associated with the asymmetry of energy release at the cathode and anode. This asymmetry, in turn, is determined by the difference in the values ​​of the voltage drop in the anodic and cathodic regions of the arc. In the conditions of welding with a non-consumable electrode, the cathode voltage drop is much lower than the anode voltage drop, therefore, less heat is generated at the cathode than at the anode.

Below is an approximate amount of heat release in different parts of the arc for TIG welding at a welding current of 100 A and when using straight polarity (as the product of the voltage drop in the corresponding arc region by the welding current):

In the cathode region: 4 V x 100 A = 0.4 kW at a length of ≈ 0.0001 mm
- in the arc column: 5 V x 100 A = 0.5 kW at a length of ≈ 5 mm
- in the anode area: 10 V x 100 A = 1.0 kW at a length of ≈ 0.001 mm.

Due to the fact that when welding on straight polarity, there is an increased input of heat into the product and reduced into the electrode, when welding on direct current, direct polarity is used. In this case, due to the fact that heat is released mainly in the anode region, only those portions of the base metal melt to which the arc is directed, i.e. where the anode is located.

Basic international designations related to TIG welding

TIG- This abbreviation of the name of this process is accepted in Europe. TIG - Tungsten Inert Gas (tungsten - tungsten in English).

WIG- So it is customary to call this process in Germany for brevity. WIG - Wolfram-Inertgasschweiβen (wolfram - tungsten in German).

TIG-DC- TIG method on direct current (DC - direct current - direct current in English).

TIG-AC- TIG method on alternating current (AC - alternating current - alternating current in English).

TIG-HF- TIG method with a system of non-contact arc excitation by high-voltage and high-frequency discharge; HF - high frequency - high frequency in English.

In this case, an oscillator is used, which generates a short-term voltage pulse, which provides a breakdown and sequential development of a spark discharge up to an arc discharge. Due to the high frequency and low power of the oscillator, the high voltage is harmless to humans. High-frequency ignition ensures the highest quality of the welded seam, since it does not contact the tungsten electrode with the workpiece, and, therefore, excludes the ingress of tungsten particles into the weld pool. With this ignition, there is also no destruction of the end face of the tungsten electrode. However, the use of oscillators can lead to failure of devices that are sensitive to electromagnetic influences.

TIG-Contact or SCRATCH START - a TIG method with contact arc initiation by touching the tungsten electrode of the workpiece ("striking" the end of the tungsten electrode over the surface of the workpiece, similar to how it is done when welding with coated electrodes). With this method of arc ignition, it is possible for tungsten particles to enter the weld pool, as well as destruction of the end of the tungsten electrode, since at the moment of contact of the electrode with the product, a short-circuit current flows.

TIG-LIFT ARC(TIG-LIFT IGNITION, LIFTIG) - TIG method with contact arc excitation when at the moment of a short circuit a previously reduced current flows.

This method of ignition of the arc, although it does not exclude contact of the electrode with the product, does not have the disadvantages of the previous method, since at the moment of short circuit, a previously reduced current flows.

Setting the TIG welding parameters

The figure below shows the sequence for defining and adjusting the TIG welding parameters.

TIG welding technique

In TIG welding, the side angle of the torch must always be maintained at 90 degrees. The torch should be held at an angle. While the angle of inclination of the torch to the surface of the product in the direction of reverse welding should be 70… 80 degrees. The additive is fed as the burner moves at an angle of 15 to 30 ° to the base metal.

TIG welding is performed "angled forward" (ie the torch is tilted towards the forming weld) with regular addition of additive in small steps. When welding, it is very important that the end of the filler wire is not pulled out of the gas shielded zone; otherwise, when molten or heated, it will oxidize on contact with ambient air. Any degree of oxidation or contamination of the filler wire will inevitably cause contamination of the weld pool. Therefore, it is very important that the welder uses the filler ponds clean of dirt, grease or moisture. Typically, dirt and grease will get onto the filler metal from dirty gloves. Therefore, immediately before welding, it is highly desirable to process the rods, for example, with acetone. Lubrication and moisture, both on the filler rod and on the base metal, can cause serious weld defects such as porosity, hydrogen cracking, etc.

Features of welding aluminum and aluminum alloys

TIG welding of most metals uses direct current, direct polarity. However, these welding conditions are unacceptable when it comes to aluminum and magnesium. This is due to the presence of a strong and refractory oxide film on the surface of these metals. Aluminum is highly reactive. It easily interacts with atmospheric oxygen, i.e. oxidizes. This forms a thin dense film of aluminum oxide (Al 2 O 3). Aluminum owes its high corrosion resistance to this very film. The melting point of pure aluminum is 660 ºС, and the melting point of aluminum oxide is more than three times higher - 2030 ºС. Alumina is a ceramic material that is hard and non-conductive. When aluminum melts, it spreads out in large drops kept from fusion by an oxide film. If the fragments of the film end up in the crystallized weld metal, then its mechanical properties deteriorate. Thus, in order to weld two aluminum parts together, first of all, this oxide film must be destroyed. This can be done:

Mechanically (however, this is practically impossible, since due to the high chemical activity of aluminum, it immediately enters into a bond with oxygen, and a new layer of aluminum oxide begins to form. Moreover, under conditions of arc welding at high temperatures, aluminum oxidation and the formation of an oxide film occurs even more intensely);
- chemical treatment (rather difficult and time-consuming);
- welding on reverse polarity;
- welding on alternating current.

When the electrode is connected to the negative pole (straight polarity welding), a significant amount of heat will be transferred to the workpiece, but the film will not break. If the polarity is changed and the electrode is connected to the positive pole (welding with reverse polarity), then less heat will be transferred to the product, however, as soon as the arc is excited, the oxide film begins to break (so-called cathodic cleaning occurs).

There are two theories explaining the mechanism of the destruction of the oxide film on reverse polarity.

The cathode spot, moving along the surface of the weld pool, leads to the evaporation of aluminum oxides, while the emission of electrons from active cathode spots repels fragments of the oxide film to the edges of the weld pool, where they form thin stripes.

The ion flow has sufficient kinetic energy to destroy the oxide film when it collides with the cathode surface (a similar effect occurs during sandblasting). This theory is supported by the fact that the cleaning effect is higher when using inert gases with a higher atomic weight (argon)

However, along with this positive phenomenon, such negative consequences of welding with reverse polarity as overheating of the electrode, on which too much heat will be generated (causing it to overheat), and low penetration of the base metal will be observed. The solution to these problems is AC welding. The combination of forward and reverse polarity allows you to take advantage of both polarities; we obtain both the necessary heat input (i.e., penetration of the base metal) in half-periods of direct polarity and cleaning the surface from aluminum oxide (in half-periods of reverse polarity). Welding with alternating current at this frequency is the ideal process for joining all types of aluminum and magnesium alloys.

Advantages and disadvantages of the manual TIG welding process

Compared to other welding methods (MMA, MIG / MAG, submerged arc welding), TIG welding has the following advantages:

Allows to obtain high quality welded seams in relation to almost all metals and alloys (including difficult-to-weld and dissimilar ones, for example, aluminum with steel);
- provides a good visual control of the weld pool and arc;
- due to the absence of metal transfer through the arc, there is no metal spatter;
- practically no treatment of the seam surface after welding is required;
- as in the case of MIG / MAG and MMA welding processes, TIG welding can be performed in all spatial positions;
- as in the case of MIG / MAG welding, there is no slag in TIG welding, which means that there are no slag inclusions in the weld metal.

The disadvantages of this welding method include low productivity, complexity and high cost of the power source (compared to consumable electrode welding).

Health and safety in relation to the TIG welding process

Tungsten electrodes are used in argon arc welding, that is, welding with a non-consumable electrode in an argon shielding gas environment.

The melting point of tungsten is 3410 ° C, the boiling point is 5900 ° C. It is the most refractory metal in existence. Tungsten remains hard even at very high temperatures. This allows you to make non-consumable electrodes out of it. In nature, tungsten occurs mainly in the form of oxidized compounds - wolframite and scheelite.

In argon arc welding, an arc burns between the work piece and the tungsten electrode. The electrode is located inside the welding torch. For gas-shielded welding, direct current of direct polarity is usually used. Reverse polarity current or alternating current is sometimes used. In such cases, it is advisable to use tungsten electrodes with alloy additions, which increase the stability and stability of the welding arc.

To improve the quality of the electrode (for example, resistance to high temperatures, increase the stability of the arc), rare-earth metal oxides are added to pure tungsten as an additive. There are a number of varieties of tungsten electrodes, depending on the content of these additives. This determines the brand of the electrode. Nowadays, the brand of the electrode is easy to remember by the color in which one end is painted. Tungsten electrodes are divided into three types: Fixed (WT, WY), Variable (WP, WZ) and Universal (WL, WC).

International brands of electrodes

WP(green) - Pure tungsten electrode (content not less than 99.5%). The electrodes provide good arc stability when welding on alternating current, balanced or unbalanced with continuous high frequency stabilization (with an oscillator). These electrodes are preferred for sinusoidal AC welding of aluminum, magnesium and their alloys, as they provide good arc stability in both argon and helium environments. Due to the limited thermal load, the working end of the pure tungsten electrode is formed into a ball.

Aluminum, magnesium and their alloys.

Check out the prices for WP(green) electrodes, please follow the link.

WZ-8(white) - Zirconium oxide electrodes are preferred for AC welding where even minimal contamination of the weld pool is not tolerated. The electrodes produce an extremely stable arc. The permissible current load on the electrode is slightly higher than on cerium, lanthanum and thorium electrodes. The working end of the electrode when welding with alternating current is machined in the shape of a sphere.

Main materials to be welded: aluminum and its alloys, bronze and its alloys, magnesium and its alloys, nickel and its alloys.

Check out the prices for WZ-8(white) electrodes, please follow the link.

WT-20(red) - Thorium oxide added electrode. The most common electrodes, since they were the first to show significant advantages of composite electrodes over pure tungsten electrodes when welding with direct current. However, thorium is a low level radioactive material, so the fumes and dust generated when sharpening the electrode can affect the welder's health and the safety of the environment.
The relatively small release of thorium during episodic welding, as practice has shown, are not risk factors. But, if welding is carried out in confined spaces regularly and for a long time, or the welder is forced to inhale the dust generated when sharpening the electrode, it is necessary for safety reasons to equip the work area with local ventilation.
Thorinated electrodes work well when welding with direct current and with improved power sources, while, depending on the task, you can change the angle of the electrode sharpening. Thorized electrodes retain their shape well at high welding currents, even in cases where a pure tungsten electrode begins to melt with the formation of a spherical surface at the end.
WT-20 electrodes are not recommended for AC welding. The end of the electrode is machined in the form of a platform with protrusions.

Main materials to be welded: stainless steels, metals with a high melting point (molybdenum, tantalum), niobium and its alloys, copper, silicon bronze, nickel and its alloys, titanium and its alloys.

Check out the prices for WT-20(red) electrodes, please follow the link.

WY-20(dark blue) - Yttrium tungsten electrode, the most durable non-consumable electrode in use today. It is used for welding critical joints at direct current of direct polarity, the content of the oxide additive is 1.8-2.2%, yttrium tungsten increases the stability of the cathode spot at the end of the electrode, as a result of which the arc stability is improved in a wide range of operating currents.

Main materials to be welded: welding of especially critical structures made of carbon, low-alloy and stainless steels, titanium, copper and their alloys at direct current (DC).

Check out the prices for WY-20(dark blue) electrodes, please follow the link.

WC-20(gray) - Alloy tungsten with 2% cerium oxide (cerium is the most abundant non-radioactive rare earth element) improves electrode emission. Improves the initial arc start and increases the allowable welding current. WC-20 electrodes are universal, they can be successfully welded on alternating current and on constant straight polarity.
Compared to a pure tungsten electrode, the cerium electrode provides greater arc stability even at low currents. The electrodes are used in orbital welding of pipes, welding of pipelines and sheet steel. When welding with these electrodes with high current values, a concentration of cerium oxide occurs at the glowing end of the electrode. This is a disadvantage of cerium electrodes.

Main materials to be welded: metals with a high melting point (molybdenum, tantalum), niobium and its alloys, copper, silicon bronze, nickel and its alloys, titanium and its alloys. Suitable for all types of steels and alloys on AC and DC

Check out the prices for WC-20(gray) electrodes, please follow the link.

WL-20, WL-15 (blue, gold) - Tungsten Lanthanum Oxide electrodes have very easy initial arc start, low burn-through tendency, stable arc and excellent re-arc characteristics.
The addition of 1.5% (WL-15) and 2.0% (WL-20) lanthanum oxide increases the maximum current, the carrying capacity of the electrode is about 50% more for a given size when welding with AC than pure tungsten. Compared to cerium and thorium, lanthanum electrodes have less wear on the tip of the electrode.
Lanthanum electrodes are more durable and less tungsten contamination of the weld. Lanthanum oxide is evenly distributed along the length of the electrode, which allows maintaining the original sharpening of the electrode for a long time during welding. This is a significant advantage when welding with direct current (straight polarity) or alternating current from advanced welding power sources such as steels and stainless steels. When welding with alternating sinusoidal current, the working end of the electrode must have a spherical shape.

Main materials to be welded: high-alloy steels, aluminum, copper, bronze. Suitable for all types of steels and alloys in AC and DC.

Check out the prices for WL-20 and WL-15 link .

Direct current welded (steel, stainless steel, titanium, brass, copper, cast iron, as well as dissimilar joints). Each material needs its own filler wire, and the better you choose the one that matches the chemical composition, the stronger, more beautiful and more reliable the connection will be. The burner must connect to "-" and the earth clamp to "+". This gives us a straight polarity, which gives us a more stable directional arc and deeper penetration. When choosing a tungsten electrode, you need to pay attention to its diameter, since it is selected based on the thicknesses of the parts to be welded.

For DC welding, the most important requirement must be remembered, the tungsten electrode must be sharpened very accurately and sharply. At large enterprises, special machines and machines with a diamond wheel are used to sharpen tungsten electrodes, but without one, you can use a regular flap wheel with fine grain or a grinding machine. Sharpening is carried out to the tip of the electrode while preventing it from overheating. tungsten becomes more brittle and begins to simply crumble. You also need to remember about the shielding gas, it must be high-frequency argon (the volume fraction of argon must be at least 99.998%).

If the gas is bad, then it will immediately make itself felt, the most important sign is the darkening of the weld. A regulator must be installed on the cylinder; it can be either with pressure gauges or of a float type. Increasingly, most serious enterprises use imported gearboxes with two rotameters and the second is used for blowing. This in turn gives protection to the reverse bead of the seam (sheet and pipe welding).

The welding itself is carried out from right to left, in the right hand the torch, in the left hand the filler material (if necessary). If the machine has the functions "current decay" and "gas after welding", then you should not forget about them, the first will give you a smooth current decay at the end of welding, and the second will continue to protect the weld during cooling. The burner should be at an angle of 70 0 to 85 0, the additive is fed at approximately an angle of 20 0 smoothly and progressively. At the end of welding, there is no need to rush and tear the torch away from the welding place, since this will result in a lengthening of the arc and poor seam protection.

Aluminum is welded on alternating current, tungsten is not sharpened during preparation like a needle, but only slightly rounded. When welding aluminum, an important part must be given to the preparation of both the material and the additive. First, the surface must be cleaned and degreased. Secondly, remove chamfers if the thickness does not allow full penetration. Due attention is also paid to the additive, it is necessary to correctly select the chemical. composition, it can be pure AL 99%, AlSi (silumin) or AlMg (duralumin). For the rest, only practice is needed.

How to protect yourself

And in the end, I would like to note that with this type of welding, you need to properly treat the means of protection. Choose only those protective equipment in which it will be not only comfortable but also safe. when TIG welding is very strong ultraviolet radiation, and we are given only one eye.
We recommend that you consider a modern highly effective means of protection -

Tungsten electrodes are a common term among welders and other metalworking professionals. They are small rods designed to supply current to welded products. Of course, like any object, they have their own varieties and types. For convenience and symbolic designation, the established markings are used, which directly indicate the technical characteristics of the welding material used.

Tungsten electrodes are required to transfer current to the workpieces being welded.

Types of tungsten electrodes and their purpose

Tungsten is a metal that is almost impossible to find in its pure form. Often it is used in the process, since this metal is quite refractory, so it is able to maintain its own strength even during prolonged welding. Tungsten metal is economical. During welding, the amount used is negligible.

The largest supplier of the presented metal is China. It is on their territory that huge reserves of tungsten are observed. In connection with this fact, when purchasing tungsten electrodes in a store, pay attention to the manufacturer. If you find a European country, then you can be sure that you will overpay when buying. European countries release electrodes only after purchasing the metal in China.

The welding consumable is classified into three types, which include:

1. AC electrodes. The main materials that are welded when exposed to current are magnesium, aluminum and their varieties, alloys. The presented variety is widely used in cases where it is necessary to protect the welding from contamination.
2. DC electrodes. Here, metals such as yttrium or thorium are added to the tungsten electrode. In the case of the latter, one should remember about its radioactivity, which can significantly harm people in a closed room. Therefore, thorium-based electrodes are used for welding in open areas or in warehouses where there is reliable effective ventilation. These products are used for welding the following metals:

• copper;
• titanium;
• nickel;
• tantalum;
• bronze;
• steel that is not subject to rust during operation;
• carbon alloys.

Safety precautions should be noted here when welding.

Important! Since some alloys and metals can emit toxic substances during combustion, the welder must wear protective equipment, where the respiratory system and eyes will be closed.

It is also necessary to use argon shielding gas.

Universal electrodes. Universal tungsten electrodes are used when it is necessary to weld products from copper, aluminum, bronze, tantalum, nickel, titanium and almost all types of steel. These electrodes work perfectly on AC and DC currents, which simplifies the task somewhat. Frequent use can be observed in pipeline welding, since they can be used to join thin sheets of metal and make the seam invisible.

Using a particular type for welding requires the right choice when purchasing. Therefore, in order to carry out welding, it is necessary to have a basic knowledge of the behavior and properties of the metal being welded. Often, professional welders have the appropriate specialization and education.

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Tungsten Electrode Marking

Important! The marking of tungsten electrodes is necessary for specialists, since it contains the entire list of characteristics and metals used both in the manufacture of an electrode and suitable for welding.

The established and accepted markings for convenience differ in designation and color.

The following markings apply to tungsten electrodes:

1. WP (green) - here the electrode is almost entirely tungsten. Its content is 99.5%. Used for welding magnesium and aluminum. A possible use of the electrode for the marking provided is sinusoidal welding. Two types of gas are used for protection: argon and helium.
2. WC-20 (gray) - 2% cerium oxide. They are referred to as universal electrodes, since they are used in welding with alternating current and with the use of positive polarity. They are used in the connection of pipelines in fixed joints.
3. WL-15, WL-20 (blue) - there is an admixture of lanthanum, which allows you to achieve a stable arc, and re-ignition, which makes the electrode of this brand often used in industry. In addition, the use of lanthanum in the electrode can increase the operating current and reduce wear by half. The seams made with the presented type of electrode are durable and less dirty. For the electrode to work, it is necessary to give a spherical end.
4. WT-20 (red) - Thorium is included here. As already described above, its dust during work is somewhat hazardous to human health. Despite this fact, the presented markings are sometimes used more often than electrodes, which are almost entirely composed of tungsten. This feature is explained by the excellent properties of thorium, which can combine the most "finicky" metals in a matter of seconds. It is recommended to use direct current during work, since with a sinusoidal use of current, the resulting arc can jump over the surface to be welded. Such troubles should not be allowed.
5. WZ-8 (White) - Less than a percent of zirconium oxide is present. When working, you must carefully monitor the cleanliness. It is recommended to use alternating current. Before use, the electrode should be spherical at the tip. Best used for aluminum welding.
6. WY-20 (dark blue) - Tungsten electrodes with a thin yttrium coating. They are considered to be the most stable electrodes, therefore they are often used for welding critical and important structures.

When choosing electrodes, it is necessary to determine the welding method and the properties of the metal being welded, because several types and markings of tungsten electrodes may be required to connect one structure.

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Argon arc welding: its features and technology

Argon arc welding is a combination of metals protected by argon. The presented process is carried out in two ways, each of which should be considered in detail.

Manual welding with a tungsten electrode protected by argon. This method includes several stages:

1. Argon and the required current are supplied to the burner. The second phase of the current is brought to the surface, where the welding will take place. An arc is created between the electrode attached to the torch and the surface. The filler wire is fed to it.
2. Next, you need to ignite the arc. To do this, it is better to use a carbon plate so as not to spoil the surface to be welded, since such an oversight can lead to contamination of the seam.
3. Then the arc is excited. An oscillator is often used here.
4. We follow the movement of the electrode, since its trajectory should be laid exactly along the seam, in any other case, we should stop working, because this nuisance can signal the beginning of melting of the electrode.

Here, the use of alternating current is allowed, because during welding, a direct current component will be formed.

Automatic tungsten electrode welding. This method is often used to weld pipelines in fixed joints.

Automatic welding is carried out by special units with different designs, which independently carry out the entire welding process.

Here, the welding arc occurs between the metal surface and the end of the wire, which is the electrode.

Often the presented devices cannot be applied in some areas. This is especially due to the inability to make a short seam.

Tungsten electrodes for argon arc welding contain the following markings: WP, WZ, WT, WY. This is due to their reliability and versatility in use. Many of the presented types of electrodes are used for welding thin metal sheets. In this case, a fine conical sharpening of the electrode is often required.

In the case when particularly stringent requirements are imposed on the weld seam regarding its purity and accuracy, TIG welding is indispensable. Such qualities should be possessed by a seam performed, for example, in the manufacture of automobiles. Used in this situation, tungsten electrode welding allows not only to fulfill all the necessary conditions, but also to significantly save the consumption of scrap materials, that is, directly to the electrodes themselves.

Features of tungsten electrodes and their welding.

Tungsten is the most refractory of all metals used for the manufacture of electrodes. Its melting point is 3422 degrees Celsius. As a result, the consumption of electrodes when performing argon welding is reduced to minimum values.

Such welding can be carried out both in manual and semi-automatic or automatic modes. In this case, it is possible not to use an additive at all, using metal from the melted edges of the part as a material for forming the weld. This approach further increases the cost-effectiveness of welding.

Tungsten non-consumable electrodes are used for welding metal products, the thickness of which can start from 0.1 mm. The maximum thickness in this case is not limited.

One of the main conditions for obtaining a high-quality and accurate weld seam is thorough preparation of the edges and assembly of the parts to be welded. This is especially important in the event that the joining of blanks made of thin sheet metal is being carried out. Here it is necessary to pre-assemble the product using tacks made with the same tungsten electrode. In industrial production, in this case, special assembly machines are usually used.

Another important condition is the displacement of air from the welding zone. For this, work is carried out in an environment of protective gases (most often argon). The amount of gas required depends on many factors: on the thickness of the metal, on its chemical composition, on the size of the parts to be welded, on the type of welded joint. In addition, the speed of welding also affects the gas consumption - the faster it is carried out, the more powerful the shielding gas flow should be. It is important that the entire weld pool is exposed to argon, as well as the heated end of the additive (if used) and the electrode itself.

An essential feature of welding with a tungsten electrode is that the arc must be ignited without touching its end to the metal of the workpiece to be welded. This can be done using an oscillator. The fact is that at the moment of ignition of the arc, when the electrode and the base metal are in contact, tungsten at its end is alloyed with the metal, that is, a composition appears whose melting point is much lower than that of pure tungsten. And this leads to a decrease in the quality of the welded joint. It is also very important to choose the right welding current - this will allow you to minimize the consumption of the electrode during welding and maintain the shape of the sharpening of its end for a long time.

The use of direct polarity of the welding current allows to achieve minimal heating of tungsten, and therefore, to reduce the consumption of the electrode. This is also facilitated by the argon protection of the electrode from oxidation by atmospheric oxygen. As a result, for an hour of the welder's work, the tungsten electrode is reduced by tenths, and sometimes by hundredths of a gram. In other words, one such product can be enough for several full work shifts.

Technological characteristics of tungsten electrode welding.

The tungsten electrode is successfully used for welding products from various types of metals, the thickness of which varies from the smallest values ​​to 6-8 mm. It is also allowed to use these types of electrodes for making thicker connections, but in practice this is rare. The use of consumable electrodes in this case makes it possible to obtain a seam with higher technical and physical characteristics and to increase labor productivity.

The choice of welding technology depends on whether it is performed manually or in an automatic mode.

For manual welding, the following requirements must be observed:

• welding is carried out in the direction from right to left;
• when welding products of small thickness, the torch is located at an angle of 60 degrees to the surface of the product to be welded;
• if parts of large thickness are being welded, the torch is positioned as when welding fillet welds, that is, at an angle of 90 degrees to the surface of the part;
• the method of filler rod guidance also depends on the thickness of the product. If we are talking about parts made of thin sheet metal, the bar is introduced to the side of the arc column while performing reciprocating vibrations. When welding parts of significant thickness, the movement of the bar should be translational and transverse.

If welding is performed in automatic or semi-automatic mode, then the direction is selected so that the filler rod goes in front of the arc. In this case, the tungsten electrode should be located at an angle of 90 degrees to the surface of the workpieces to be welded. The angle between the electrode and filler rod must also be right.

Distinctive features of argon-arc welding of aluminum with a tungsten electrode.

Argon arc welding is used today when performing permanent joining of parts made of a wide variety of metals: steel, nickel, copper, and their alloys. But it received the greatest popularity when welding aluminum products, especially when it comes to the manufacture of critical structures for aircraft construction or mechanical engineering.

Theoretical recommendations state that welding of aluminum with a tungsten electrode should be carried out on a direct current of reverse polarity (with a "plus" on the electrode). But practice shows that in this case it is almost impossible to achieve stable, even burning of the arc. And this leads to the fact that the edges of the parts to be welded are not melted well enough, and the consumption of an expensive tungsten electrode increases significantly. That is why most often practicing welders work with aluminum at normal frequency alternating current.

In this case, the welding period is divided into two half periods:

• in one of them the current is less, and there is a "plus" on the electrode,
• in the other, the current is greater, but on the electrode it is "minus".

In the half-period when the electrode has a positive charge, the surface of the metal to be welded is cleaned. When the electrode is negatively charged, the metal is intensely melted, while the heating of the tungsten itself decreases. The property of the metal to be cleaned during welding makes it possible to carry out work without the use of special fluxes.

Some nuances of argon-arc welding with a tungsten electrode.

One of the important conditions for obtaining a high-quality welded joint is a stable arc. A direct current of direct polarity helps to achieve a continuous, even burning from the arc. In this case, the current values ​​can be very small - from 5 A, and the voltage - from 12 V. Direct current is used to weld steel, copper, brass, cast iron, titanium and their alloys.

Sharpening of the tungsten electrode is of great importance in direct current welding - its end must be sharp and clearly defined. In industrial welding, electrodes are sharpened using special equipment - diamond wheel machines. If they are absent, a regular grinding machine or a fine-grained wheel will do. Sharpening is done towards the end of the electrode. In this case, it is necessary to carefully monitor that the electrode does not overheat during the preparation process. Exceeding the temperature of tungsten above the permissible values ​​makes it very brittle - such an electrode will simply crumble during the welding process.

In addition, to perform argon-arc welding, a high-purity shielding gas is required - it must contain at least 99.99% argon. Otherwise, there is no need to talk about the high quality of the weld. By the way, it is the weld that will help determine the quality of argon - if the gas contains a large amount of foreign impurities, the material of the weld will darken.

Note! The use of argon reliably protects products from the appearance of an oxide film on their surface during the welding process. But at the same time, argon does not remove the oxides that were on the metal initially. Therefore, before starting welding, it is necessary to carefully clean the edges of the workpieces to be welded.

Welding of aluminum and its alloys, as already mentioned, is carried out on alternating current. The sharpening of the electrode is also of great importance here. True, in this case, the electrode is not sharpened sharply, like a sting - it is enough to slightly round its end. In addition, it is very important to properly prepare the parts and select the correct filler material before welding aluminum. As for preparation, this is, first of all, cleaning and degreasing the surfaces to be welded, as well as chamfering them if the parts are made of thick metal. Both pure aluminum (Al 99%) and its alloys - silumin (an alloy of aluminum with silicon AlSi) or duralumin (aluminum plus magnesium AlMg) can be used as an additive for welding with a tungsten electrode of aluminum.