Professional welders consider argon arc welding to be the most effective and reliable way to connect various metal products. This type of joining of parts is popular not only in industrial enterprises, but also in the conditions of a home workshop, as it allows the welding of metals with different mechanical and physical properties.
The argon-arc compound is a melting of metal using tungsten electrodes. Therefore, before proceeding with the welding work, it is necessary to carefully familiarize yourself with the types and marking of tungsten electrodes for welding.
Features
Structurally, tungsten electrodes are made in the form of thin metal rods of pressed particles of this metal. The use of fine pressed particles previously subjected to high heat 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, reduce the acidity of the metal, a special coating is applied to the tungsten electrodes for argon arc welding, which also improves the alloying of the metal.
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 made of various materials. Due to the absence of excess precipitation from the coating, welding with a tungsten electrode in a shielding gas medium is considered to be better than other types of welding.
Electrode composition
Most tungsten rods contain from 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 material consumption during the welding process. Only one hundredth of the material is consumed per meter of the weld. The main thing is that the surface of the electrodes does not contain any traces of contaminants and impurities, as well as lubricating technological materials, shells and cracks. Upon purchase, the surface of the rods is inspected visually.
Marking of tungsten products
The choice of rods for the intended purpose is equally possible in any country in the world, since the marking of tungsten electrodes is determined in accordance with international standards. And this means that the inscription on the body and the color of the tip reflect the chemical composition and type of the selected product.
The first letter W indicates that it 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 the alloying additional components is indicated as follows:
- WP - indicates that the rod is made of pure tungsten;
- C - added cerium oxide component;
- Y - the bar contains yttrium dioxide;
- T - the electrode contains thorium dioxide;
- L - lanthanum oxide is present in the rod;
- Z - indicates the presence of zirconium oxide.
After letter marking, digital inscriptions are indicated. The first indicate 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 produce electrodes with a length of 50, 75 and 100 mm.
Designation of electrodes by color
Choosing a specific brand of tungsten electrode by color is quite simple. Letter 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.
In order to obtain a high-quality and reliable connection of various metals, it is necessary to correctly choose not only the welding mode, but also the tungsten electrode itself. Therefore, among this variety of types of welding consumables, it is easy to navigate by the color of the tip.
Green color (WP)
These electrode models 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 result of the connection is obtained when protecting the place of joining of parts with argon or helium.
High stability of arc burning is achieved using a variable frequency current, preferably using a high-frequency oscillator with a sinusoidal current. A feature of such electrodes is considered to be a spherical shape of the tip, due to the fact that its thermal load is limited.
Red color (WT20)
These electrode models contain thorium oxide, which refers to low level radioactive elements, and greatly affects not only the state of the environment, but also human well-being. Temporary use of these electrodes does not pose a great risk to health, but permanent, long-term use can harm the health of the welder. The main safety requirement when welding with thorium electrode is good ventilation of the room and the use of reliable protective equipment.
Tungsten electrodes with thorium content are considered universal products, as they work perfectly both on alternating and direct current. But in DC welding, it far exceeds the quality indicators of rods without additives, which leads to its widespread use.
Excellent reliability indicators are achieved when welding nickel, copper, titanium, silicon bronze, molybdenum and tantalum.
White color (WZ8)
These electrodes as additives contain zirconium oxide, not more than 0.8%. Such rods are able to withstand a large current load than tungsten electrodes of other brands. 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 connecting parts from magnesium, nickel, aluminum, bronze, as well as their alloys.
Gray color (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, so that the initial start-up is simplified, and the operating current limit expands.
Professional welders consider gray electrodes to be completely universal, since they work on current of any polarity, while it allows you to connect almost all metal alloys.
When operating at minimum currents, it provides excellent stability of the welding arc, which allows connecting 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 be concentrated on the hot end of the rod.
Dark Blue (WY20)
The welding of complex and critical structures made of copper alloys, titanium, low carbon steels is most often carried out with alloying electrodes made of yttrium dioxide (about 2%). Due to the additional addition, these rods are characterized by high stability of the cathode spot, so the arc is stable at any current values.
Professional welders consider the WY20 the most resistant non-consumable tungsten electrode.
Blue and gold color (WL20 and WL15)
These electrodes contain lanthanum oxide as an additive. WL20 contains about 2% of lanthanum and is colored blue, and WL15 contains about 1.5% of the additive and is marked in golden color.
These brands of rods are considered the most durable, since they have a low level of contamination of the weld pool. Due to this quality, sharpening of tungsten electrodes of this type lasts a very long time.
The high potential of lanthanums has a simple ignition of the arc and a low tendency to burn through metal. With the help of such products, a compound of bronze, copper, aluminum, as well as high alloy steels is produced.
Features of sharpening electrodes
Unlike melting type electrodes, which are ready to work at any time, non-consumable tungsten electrodes need to be sharpened. The pressure of the arc on the surface of the metals being welded, as well as the effective distribution of energy, depends on the shape of the tip of this product.
The rules for sharpening rods depend on the type of electrode, as well as on the conditions for the use of argon arc welding.
The shape of the 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);
- the rods WY, WC and WZ are made conical in shape.
Sharpening length 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 grinding process can be performed using a grinder or grinder. But it is best to clamp the rod in an electric drill chuck and sharpen it at low speeds.
Grinding angle is also of great importance. This parameter depends on the applied welding current strength:
- when working at high currents, the sharpening angle is 60-120 degrees;
- at average currents, the angle is 20-30 degrees;
- at minimum currents - 10-20 degrees.
The correct sharpening angle affects the stability of the arc during welding.
Errors made during this operation can lead to the following negative phenomena:
- uneven shape may 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;
- Shallow penetration depth and large rod wear provoke too sharp or obtuse sharpening angles.
If at least one similar symptom appears, the welding process must be urgently stopped and the sharpening defect corrected.
Remember that the right choice of tungsten electrodes greatly increases the performance of work and improves the quality of the connection of metal structures. Strictly observe safety rules when carrying out welding work, because the health of the welder depends on this.