TIG welding is an arc process whereby you create the arc with an electrode and add the filler wire by hand. The electrode used is made of tungsten which is a rare metallic element. Tungsten has the highest melting point of any metal, 3,410 °C
Tungsten electrodes come in a varying degree of sizes depending on the material you want to weld and the welding current you want to use.
Each electrode is colour coded to eliminate any confusion and it appears at the end of the electrode.
Typically used for AC Aluminium welding. Pure has a higher consumption ration when compared to thoriated or ceriated electrodes but they form a clean balled tip easily with good arc stability.
THORIATED 2%- RED
Best for use in direct current DC applications. They can be used on thin aluminium (AC) also. They stay sharp longer and so are ideal for thin steels. Thorium is radioactive; therefore, you must always follow the manufactures, instructions on correct use and sharpening.
These are best in DC mode at low amperage. They give excellent starting and so are popular with steel pipe fabricating and thin plate. Its best on carbon steel, stainless steel titanium and nickel alloys. Using at high temperatures isn't recommended. Ceriated electrodes can also be used in AC mode although I prefer White Zirconiated.
The Gold Lanthanated electrodes contain less than the blue electrodes Work well in either AC or DC electrode negative with a pointed end. They can also ball when used in AC Mode. Lanthanated tungstens maintain a sharpened point well, so are good for production welding of steel and stainless steel in DC mode.
Best general purpose electrode for both alternating current AC or direct current DC. The blue lanthanated electrodes are popular due to the relative ease of striking an arc and lower amperage required. They perform exceptionally well in both AC & DC applications and are a popular general use electrode.
Best for use in alternating current (a/c) for aluminum alloys. Zirconiated electrodes are recommended for AC aluminium welding as they ball easily and have a high resistance to contamination.
Depending on the type of tungsten electrode, preparation of the tungsten consists of eithera balled, pointed, or truncated shape.
A balled tip is most commonly used on a pure tungsten electrode and is suggested for use with the AC process on sine wave and conventional Square Wave TIG welders.
AC TUNGSTEN PREPARATION
To properly ball the end of the tungsten, apply the AC amperage recommended for the electrode diameter and the ball on the end of the tungsten will form itself. The diameter of the balled end should not exceed 1.5 times the diameter of the electrode (for example, a 3.2mm. electrode should form a 4.5mm diameter end. Having a larger sphere at the tip of the electrode can reduce arc stability and fall off which may contaminate the weld.
In any application, the type and shape of tungsten you use helps determine the arc quality and welding performance you will achieve.
DC TUNGSTEN PREPARATION
To prepare a tungsten for DC welding it needs to be sharpened to a point.
The grind marks MUST run along the tungsten to the point NOT around.
If you have the grind marks going around this can create arc wander and instability.
The finer and longer the point the finer the arc.
The fatter and shorter the point the bigger the arc
Each of the above types of tungsten will bring certain advantages and disadvantages. That’s why, regardless of type of material or process you are using to TIG weld,it is always important to be wise when choosing the tungsten for your application. With anything, it takes time to learn how to prepare and select tungsten electrodes for the application you are using.
By following the above and with some practice, you will be able to learn how to pick the best tungsten electrode for your application and proper tungsten preparation.