A non-consumable tungsten electrode tig
Tungsten electrodes belong to the group of non-consumable. They have excellent mechanical properties: hardness, wear resistance under strong heating, the minimum thermal expansion coefficient in comparison with other metals, good thermal conductivity, exceptional resistance to thermal creep, and a very high modulus of elasticity. The demand for them increases annually.
|The temperature at which the obtained data the features of t°C||20°C|
|The linear thermal expansion coefficient α [1/Deg]||43x10-6|
|The density of the alloy [g/cm3]||19,3|
|Tensile strength tensile kg/mm2||35|
|Specific heat at 20 °C [kJ/(kg·deg)]||0,134|
|The thermal conductivity K [W/(m·K)]||300,173|
|Electrical resistivity R, Mhmm2/m||0,054|
Tungsten is a rare element in the earth’s lithosphere. Under normal conditions it is very heavy, hard, not enough plastic. The difficulty of obtaining it in its pure form, rather complicated processing because of the unique properties affect the final product cost.
Technological plasticity of tungsten is low, but with increasing temperature is rising, so rental it is obtained from hot treatment under pressure. Initially manufactured with the aid of powder metallurgy to receive the rod billet. When it gets hot, Raskulinecz on a rotary forging machine — get bars with a diameter of 2 — 3 mm, of which after drawing in the hot state get wire ∅0.2 — 0.3 mm.
Tungsten welding electrode is a thin rod with a special coating or without it. Between him and the workpiece occurs Valitova arc — stable electric discharge in the ionized atmosphere having a temperature sufficient for melting metal. Additionally serves filler material and welding wire. The coating of this electrode gives the possibility to stabilize the arc and protects the molten metal from exposure to air, giving the required seam quality. Applies acidic, basic, cellulosic, rutile coating. In the coating composition include slag, razobratsya, alloying, stabilizing, rascislau components.
Optimization of welding technology
Brand EEPS are unimportant zeigeist. To improve and stabilize the arc applies the additive is zirconium. It is also able to facilitate zeigeist additive thorium (mark EVT-15), which also increases the life. Additive of yttrium to the brand EVI-1, 2,3 allows the connection of parts in AC/DC. Power the welding arc when the AC current may be three phase/single phase.
To join parts made of nonferrous metals are applied to electrodes doped Zirconia for high-alloyed steels — doped thorium. The weld seam is very durable, even between parts of different chemical. composition. TIG welding allows to further strengthen the seam, to protect the work area from the atmospheric gas mixture (oxygen, nitrogen, carbon dioxide), thereby not only improving the quality of the seam, but slowing down the burning of the electrode.
Characteristics of domestic electrodes
Brand ml-2, VL are universal for all operating currents DC /AC and grades of alloys. The use of marks VA, VL, SVI gives the seam a high thermal stability, reliability. These brands produce any shape, size according to custom drawings. Brands with oxides of lanthanum brand La2 O3 has a very easy initial launch and re-zeigeist arc, stable arc, low tendency to burn-through. Additive oxide of lanthanum (up 2%) increases the maximum current in half, as well, as well as the carrying capacity of the electrode. Brand containing lanthanum, more durable than thorium, cerium, wear out slower with the working end, making the weld less tungsten. With a uniform distribution of oxide of lanthanum initial working sharpening lasts longer. Brand ml-2, EEP (according to TU 48−19−527−91) are also used for arc cutting, welding and spraying in an inert gas atmosphere.
Marks of EVI-1 / EVI-1 is produced welding of copper alloys, titanium, stainless steel, low alloy steel with DC straight polarity (DC). From all available tungsten electrodes are the most persistent utrirovannye. Oxides of yttrium is not more than 2.2%, is able to stabilize the cathode spot making a very stable arc regardless of the operating current.
|Mark’s electrode||Percentage composition|
|Lanthanum oxide||Tungsten||The admixture of Fe, Al, Ca, Si, to|
|Ml-2||1.6 — 2||more than 99.9||0.1|
|EEPS||-||97,9 — 98,3|
The parameters of the electrodes
|Mark’s electrode||Tolerance||Diameter, mm||Tolerance||Length, mm|
|Ml-2||±0.1||1, 1.6, 2, 2.5, 3, 4||±2.0||75; 150; 200|
|EEPS||±0.1||1, 1.6, 2, 2.5, 3, 4|
|±0.2||5, 6, 8|
The length of the electrodes of 1000 mm and ∅: 1.6; 2; 3; 4 mm. Surface polished, smooth, without cracks, grease, burrs, chips, stains grease. It needs to be polished, smooth, and the surface of the rod ∅1; 2; 2.5; 1.6 mm is etched. Allowed on the surface of the shell, secovi, the color of a tint, in the limits of permissible deviations. Electrodes should be cut off the ends. Allowed at the ends of the chips are not more than 1 mm. Straightness of the rod may have deviations not more than 0.25% of the total length. Electrodes EVL-2 have markings in black color with oil paint.
Characteristics of imported electrodes
Stamps WP, WL-20, WC-20, WT-20, WZ8, WY-20 — widely used in arc welding in an inert gas atmosphere. For Tungsten Insert Gas (TIG welding) are applied ADS, WIG, GTA -semi-automatic, automatic, manual arc welding in a protective atmosphere. Use: inert argon, helium, active -oxygen, hydrogen, carbon dioxide, nitrogen or their mixture (A+ Ah, 2+ Ah, 2+ Ah).
For argon arc welding electrodes in canisters
|color code (mark)||quantity in 1 kg||additives||diameter, in mm||Note|
|grey (WC-20)||151||1.8−2.2% (dioxide of cerium)||1.6||Stainless, heat-resistant and acid-resistant steel and metals (niobium, molybdenum, Nickel, titanium, tantalum, their alloys, bronze, copper, silicon bronze.|
|blue (WL-20)||151||1.8−2.2% (lanthanum dioxide)||1.6||Connection high-alloy steel thin sheets, surfacing for valves, shapes, cutting of aluminium, copper, bronze and high alloy steels.|
|red (WT-20)||151||1.8−2.2% (thorium dioxide)||1.6||Direct current for welding. The arc ignition is easy. Shape stability at high currents. You can change the sharpening angle. Durable.|
|white (WZ8)||151||0.8% (zirconium dioxide)||1.6||Identical pure tungsten. Arc stability and easy arc start. Welding of important connections with alternating current.|
|green (WP)||96||Clean W without alloying additives||2||Welding of aluminum, manganese, alloys AC. Sufficient service life. Good zeigeist arc.|
|dark blue (WY-20)||151||1.8−2.2% (yttrium oxide)||1.6||Welding is the most critical connections DC. Long service life, easy arc ignition.|
Mark WL-20 (containing an admixture of an oxide of lanthanum to 2.2%) has easy arc ignition, easy re-zeigeist, very stable arc, low probability of burn-through. Rises one and a half times the carrying capacity of the electrode and the maximum voltage at the alternating current. In comparison with stamps WT-20, WC-20 (a mixture of thorium and cerium), lanthanum — more durable, have less wear on the working end, less contamination of the weld. Lanthanum oxide with a uniform distribution in the electrode can long keep its original sharpening.
For a sinusoidal AC current required spherical sharpening of the working end of the electrode. From WC-20 to 2.2% cerium oxide (the most common non-radioactive rare earth element), facilitates the initial start of the arc, increases the maximum welding current, and improves emissions. This brand is designed to work with alternating and with direct current straight polarity. Mark WC-20 has a greater arc stability (even at low values of current. They are used for connecting pipelines, sheet steel, orbital welding of pipes. The disadvantage is that when working with high voltage oxide of cerium starts to concentrate on the working end.
The optimal value of the current at alonedown welding for tungsten electrodes.
|electrode diameter, mm||A constant current, And||Alternating current, And|
|Reverse polarity||Straight polarity||Negative more positive half-wave||The negative and positive half-wave is equal to|
|4||40 — 55||400 — 500||300 — 400||200 — 320|
|3.2||25 — 40||250 — 400||225 — 325||160 — 250|
|3||20 — 35||220 — 350||200 — 300||140 — 230|
|2.4||15 — 30||150 — 250||140 — 235||100 — 180|
|2||12 — 25||100 — 200||80 — 160||70 — 130|
|1.6||10 — 20||70 — 150||70 — 150||60 — 120|
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