Due to its properties, tungsten is well-suited for use as an electrode material in TiG welding and other similar applications. Adding rare earth oxides to metallic tungsten to stimulate its electron work function improves the welding performance of tungsten electrodes: better arc initiation, higher arc column stability, and lower electrode burn-off rate. Common rare earth additives include cerium oxide, lanthanum oxide, zirconium oxide, yttrium oxide, and thorium oxide.
Application of tungsten electrodes in TIG welding and selection of electrode shape
Tungsten electrodes are used in TIG welding. They are tungsten alloy bars made by powder metallurgy, incorporating approximately 0.3%-5% rare earth elements such as cerium, thorium, lanthanum, zirconium, and yttrium into a tungsten matrix. These bars are then pressure-processed and come in diameters ranging from 0.25 to 6.4 mm, with standard lengths from 75 to 600 mm. The most commonly used specifications are diameters of 1.0, 1.6, 2.4, and 3.2 mm. The shape of the electrode tip is a crucial factor for TIG welding. When using DCSP (Dielectric-Content Suction Spray), the electrode tip must be ground into a pointed shape, and the tip angle varies depending on the application, electrode diameter, and welding current. Narrow joints require a smaller tip angle. When welding very thin materials, a low current and a needle-like small electrode are required to stabilize the arc. A properly grounded electrode ensures easy arc ignition, good arc stability, and an appropriate weld bead width. When welding with AC power, it is unnecessary to grind the electrode tips. With appropriate welding current, the electrode tips will form a hemispherical shape. Increasing the welding current will cause the electrode tips to become bulb-shaped and may melt, contaminating the molten metal.
I.What color tungsten electorde should I use for tig? Application?
Characteristics of Various Tungsten Electrodes:
Pure Tungsten Electrode: High melting and boiling points, not easily melted or evaporated, less prone to burn-off, less tip contamination, but poor electron emission, which is not conducive to stable arc combustion. (Green)
Thorium Tungsten Electrode: Strong electron emission capability, high allowable current density, more stable arc combustion, but thorium has some radioactivity, limiting its use. (Red)
Cerium Tungsten Electrode: Low electron work function, high chemical stability, high allowable current density, non-radioactive, and currently a widely used electrode. (Gray)
Zirconium Tungsten Electrode: This electrode can be selected for base metals where electrode contamination must be prevented and under specific conditions. The tip of this electrode easily maintains a hemispherical shape, suitable for AC welding. (White)
II. Shapes and Applications of Tungsten Electrodes
1. Conical Shape: Suitable for low-current welding of thin plates and butt welds with bent edges.
2. Arc-shaped: Suitable for AC power welding, but the arc is unstable with DC positive polarity.
3. Cylindrical: Suitable for welding aluminum and magnesium alloys. However, it cannot be used with DC positive polarity.
4. Flat-bottomed: Suitable for DC positive polarity, the arc is more concentrated, combustion is stable, and the weld formation is good.
After grinding the tungsten electrode into a cone shape, the tip diameter should be appropriate. If it is too large, the arc will be unstable; if it is too small, it will easily melt. It generally depends on the welding current. The grinding length is generally 3-5 times the tungsten electrode diameter, and the minimum diameter of the end should be 1/2 the tungsten electrode diameter.
III. Tungsten Electrode Extension Length
1. The longer the tungsten electrode extends, the worse the protection effect. If the extension is too small, it will affect visibility and make operation inconvenient. Generally, when the nozzle inner diameter is 8mm, the tungsten electrode extension should be 2-4mm; when the nozzle inner diameter is 10mm, the extension should be 4-6mm.
In summary, tungsten electrodes possess unique advantages in TIG welding. Their high melting point, excellent stability, and corrosion resistance make them an indispensable material in the welding field. Adding rare earth elements such as cerium, thorium, and lanthanum to tungsten can effectively improve the electrode’s arc-starting performance, stability, and lifespan, meeting diverse welding requirements. Tungsten electrodes come in a wide variety of types, suitable for different welding environments and conditions, such as DC and AC power supply welding. The electrode shape, tipping angle, and extension length significantly affect weld quality; therefore, in practical applications, the appropriate tungsten electrode type and parameters should be selected based on the welding current, material thickness, and welding power source type.
Tungsten electrodes, due to their excellent physical properties, are widely used in various precision welding applications. By rationally selecting and adjusting the electrode’s shape and specifications, more stable and efficient welding results can be achieved, providing a solid guarantee for the welding of various metallic materials.