Choosing the right tungsten is essential for successful TIG welding. You must ensure that the right tungsten is used for the right type of power source, the material to be welded and the thickness of the material. With many different types of tungsten electrodes available, learning how to correctly select the right tungsten for each application can greatly improve welding performance and save time and money.
Principal Oxide: 0.7– 0.9% Zirconium Oxide
Non-Radioactive. Best for use in alternating current (a/c) for aluminum alloys and magnesium alloys using inverter or transformer based constant current power sources. Balls well, handles higher amperage than pure tungsten with less spitting, better arc starts and arc stability than pure tungsten.
Principal Oxide: 1.3 –1.7% Lanthanum Oxide
Non-Radioactive. Best for use in direct current (d/c) as an alternative to 2% thoriated using inverter or transformer based constant current power sources. Best for non corroding steels, titanium alloys, nickel alloys, copper alloys. Best d/c arc starts and stability, low erosion rate, wide amperage range, no spitting.
Principal Oxide: 1.8–2.2% Cerium Oxide
Non-Radioactive. Best for use in alternating current (a/c) or direct current (d/c) applications using inverter or transformer based constant current power sources. Good for low-alloyed steels, non corroding steels, aluminum alloys, magnesium alloys, titanium alloys, nickel alloys, copper alloys. Good ignition and re-ignition properties, long service life, excellent arc stability. Low erosion rate, best at low amperage range, no spitting, good d/c arc starts and stability.
Principal Oxide: None
Non-Radioactive. Contains 99.50% tungsten. Good for use in alternating current (a/c) for aluminum alloys and magnesium alloys in low to medium amperage applications using transformer based constant current power sources only. Balls easy, tends to spit at higher amperages. Used for non-critical welds only.
Principal Oxide: 1.8 – 2.2% Lanthanum Oxide
Non-Radioactive. Best general purpose electrode for both alternating current (a/c) or direct current (d/c) using inverter or transformer based constant current power sources. Good for low-alloyed steels, non corroding steels, aluminum alloys, magnesium alloys, titanium alloys, nickel alloys, copper alloys. Good arc starts and stability, medium to high amperage range, low erosion rate.
Depending on the type of tungsten electrode, tungsten can be prepared in spherical, pointed or truncated shapes. Spherical tips are most commonly used for pure tungsten electrodes and are recommended for use with the AC process for both sine wave and conventional square wave TIG welders. To properly ball the end of the tungsten, apply the recommended AC amperage to the electrode diameter and the end of the tungsten will form a ball. The diameter of the spherical end should not exceed 1.5 times the diameter of the electrode (e.g. a 1/8" electrode should form a 3/16" diameter end) as having a large spherical rod at the tip of the electrode will reduce arc stability and/or fall off and contaminate the weld.
In any application, the type and shape of tungsten you use will help determine the quality of the arc and the weld performance to be achieved. Each of these types of tungsten brings with it certain advantages and disadvantages. This is why, regardless of the material or process you use for TIG welding, it is always important to choose wisely when selecting tungsten for your application. In any case, it will take some time to learn how to prepare and select a tungsten electrode for the application being used.
By following the above and with some practice, you will be able to learn how to select the best tungsten electrode for your application and the correct method of tungsten preparation.
