Professional welders consider argon arc welding to be the most effective and reliable way to join various metal products. This type of joining of parts is popular not only in industrial enterprises, but also in home workshop conditions, as it allows welding metals with different mechanical and physical properties.
Argon-arc connection is a metal melting using tungsten electrodes. Therefore, before you start welding, you must carefully read the types and markings of tungsten electrodes for welding.
Features
Structurally, tungsten electrodes are made in the form of thin metal rods from pressed particles of this metal. The use of small pressed particles, previously subjected to high temperature treatment, rather than pieces of solid metal, is based on the high refractoriness of this material.
Such rods in appearance almost do not differ from cast metal. To stabilize the arc, reduce gas formation, reduceacidity of the metal, a special coating is applied to tungsten electrodes for argon arc welding, which also improves metal alloying.
Of course, the use of argon arc welding for home use is considered an expensive technology, but industrial enterprises widely use it to work with complex metal structures from various materials. Due to the absence of excess deposits from the coating, welding with a tungsten electrode in a shielding gas environment is considered to be of higher quality than other types of welding.
Electrode composition
Most tungsten rods are composed of 97% pure metal, as well as various additives that effectively activate the welding process. The amount of additives can be from 1.5% to 3%.
The main additives are:
- zirconium oxide;
- cerium oxide;
- lanthanum oxide;
- thorium oxide;
- yttrium oxide.
Due to this composition, tungsten electrodes for argon welding are characterized by high refractoriness (about 3000℃) and high boiling point (almost 5800℃). These properties imply a very low consumption of material during the welding process. Only hundredths of the material is consumed per meter of welding seam. The main thing is that the surface of the electrodes does not contain any traces of contamination and foreign inclusions, as well as technological lubricants, shells and cracks. Upon purchase, the surface of the rods is visually inspected.
Marking of tungsten products
Select bars bydestination is equally possible in any country of the world, since the marking of tungsten electrodes is determined in accordance with international standards. And this means that it is the inscription on the body and the color of the tip that reflect the chemical composition and type of the selected product.
The first letter W indicates that this is a tungsten electrode. The characteristics of the product in its pure form are not very high, so alloying components are added to improve them.
The letter designation of alloying additional components is indicated as follows:
- WP - indicates that the rod is made of pure tungsten;
- C – cerium oxide component added;
- Y - the rod contains yttrium dioxide;
- T – electrode contains thorium dioxide;
- L – lanthanum oxide is present in the bar;
- Z - indicates the presence of zirconium oxide.
After the lettering, there are digital inscriptions. The first denote the percentage of alloying additives. The second group of numbers indicates the length of the bar in millimeters. The most common length is 175 mm, but manufacturers also produce electrodes with lengths of 50, 75 and 100 mm.
Designation of electrodes by color
Choosing a certain brand of tungsten electrode by color is quite simple. Alphabetic and digital inscriptions indicate the presence of impurities and the chemical composition of the electrodes, which is easy to determine by reading the markings on the metal.
To obtain a high-quality and reliable connection of various metals, it is necessary to correctly select not only the welding mode, but alsodirectly to the tungsten electrode. Therefore, among this variety of types of welding consumables, it is easy to navigate by the color of the tip.
Green color (WP)
These models of electrodes have the highest content of pure tungsten, the proportion of impurities here is only 0.5%. Such electrodes are used for welding aluminum, as well as pure magnesium and its alloys. The best joint result is obtained when the joint is protected with argon or helium.
High arc stability is achieved using a variable frequency current, preferably using a high-frequency oscillator with a sinusoidal current. A feature of such electrodes is the spherical shape of the tip, due to the fact that its thermal load is limited.
Red (WT20)
These models of electrodes contain thorium oxide, which belongs to low-level radioactive elements, and greatly affects not only the environment, but also the well-being of a person. Temporary use of these electrodes does not pose a great he alth risk, but permanent, long-term use can harm the he alth of the welder. The main safety requirement when welding with an electrode with thorium is good ventilation of the room and the use of reliable protective equipment.
Tungsten electrodes containing thorium are considered universal products, as they work great ason both AC and DC. But when welding with direct current, it far exceeds the quality indicators of rods without additives, which leads to its wide application.
Excellent joint reliability is achieved when welding nickel, copper, titanium, silicon bronze, molybdenum and tantalum.
White (WZ8)
These electrodes contain zirconium oxide as an additive, not more than 0.8%. Such rods are able to withstand a greater current load than other brands of tungsten electrodes. It is preferable to work with them on alternating current.
Such rods have increased stability of the welding arc. When using them, the weld pool is absolutely not contaminated, which contributes to the formation of a high-quality seam without various defects. They have high quality characteristics when joining parts made of magnesium, nickel, aluminum, bronze, as well as their alloys.
Grey (WC20)
These electrodes contain about 2% cerium oxide, which is a very common non-radioactive rare earth metal. Its main property is a positive effect on the emission of the welding rod, due to which the initial start-up is simplified and the operating current limit is expanded.
Professional welders consider gray electrodes to be completely universal, as they work on current of any polarity, while allowing you to connect almost all metal alloys.
When operating at minimum currents, providesexcellent stability of the welding arc, which allows you to connect thin steel sheets, as well as pipe parts, of almost any diameter. But the operation of such electrodes at high current is undesirable, since cerium oxide can concentrate at the hot end of the rod.
Dark Blue (WY20)
Welding of complex and critical structures made of copper alloys, titanium, low-carbon steels is most often done with electrodes with an alloying additive of yttrium dioxide (about 2%). Thanks to an additional additive, these rods are characterized by a high resistance to the cathode spot, so the arc is stable at any current values.
Professional welders consider WY20 the most durable non-consumable tungsten electrode.
Blue & Gold (WL20 & WL15)
These electrodes contain lanthanum oxide as an additive. WL20 contains about 2% lanthanum and is colored blue, while WL15 contains about 1.5% additive and is marked gold.
These brands of rods are considered the most durable, as they have a low level of contamination of the weld pool. Due to this quality, the sharpening of this type of tungsten electrodes lasts a very long time.
The high potential of lanthanums has a simple ignition of the arc and a low tendency to burn through the metal. With the help of such products, the connection of bronze, copper, aluminum, as well as high-alloy steels is made.
Features of sharpeningelectrodes
Unlike consumable type electrodes, which are ready to use at any time, non-consumable tungsten electrodes must be sharpened. The shape of the tip of this product determines the pressure of the arc on the surface of the metals being welded, as well as the efficient distribution of energy.
The rules for sharpening the rods depend on the brand of the electrode, as well as on the conditions of use of argon arc welding.
The shape of sharpening of various brands of rods is done as follows:
- WT electrodes form a slight bulge;
- the tip of the WP and WL electrodes is made in the form of a sphere (ball);
- rods WY, WC and WZ are made cone-shaped.
The length of the sharpening is calculated by multiplying the diameter of the rod by the number 2.5. So, if the diameter of the electrode is 3 mm, then you need to sharpen it to a length of 7.5 mm. The sharpening process can be performed using a grinder or grinder. But it is best to clamp the rod in the chuck of an electric drill and sharpen at low speeds.
Also of great importance is the angle of sharpening. This parameter depends on the applied welding current:
- when working at high currents, the sharpening angle is 60-120 degrees;
- at average current values, the angle is 20-30 degrees;
- at minimum currents - 10-20 degrees.
The correct sharpening angle affects the stability of the arc during welding.
Mistakes made during this operation can lead to the following negative phenomena:
- uneven shape can deviate the welding arc from the desired direction;
- violation of the sharpening width leads to insufficient heating of the seam;
- Instability of arc burning occurs due to deep scratches and grooves on the tip;
- Small depth of penetration and high wear of the rod provoke too sharp or obtuse sharpening angles.
If at least one similar symptom appears, it is urgent to stop the welding process and correct the sharpening defect.
Remember that the right choice of tungsten electrodes greatly increases the productivity of work and improves the quality of the connection of metal structures. Strictly observe the safety rules when carrying out welding work, because the he alth of the welder depends on this.
