Tungsten in TIG Welding: Types, Selection and Use Guide

Tungsten is a key component of TIG (tungsten inert gas) welding, a process that uses an electric arc to create a strong and precise weld between different metals. Tungsten electrodes are responsible for delivering the current that generates the arc, and they come in various types, sizes, and shapes. Choosing the right tungsten electrode for your TIG welding project can make a big difference in the quality and appearance of your weld. In this article, we will explain the different types of tungsten electrodes, how to select them based on the material and current type, and how to use them properly.

I. Types of Tungsten Electrodes

Tungsten electrodes are usually alloyed with small amounts of other metals to improve their performance and durability. The most common types of tungsten electrodes are:

1. Pure tungsten (green): This is the original type of tungsten electrode that was used for TIG welding aluminum and magnesium with alternating current (AC). It has the highest melting point of all metals, and it forms a smooth ball at the tip when heated. However, it is not recommended for modern inverter power sources, as it can cause instability and spitting of the arc.
   
   

2. 2% thoriated tungsten (red): This is the most popular type of tungsten electrode for TIG welding with direct current (DC). It contains 2% thorium, which enhances the arc stability, current carrying capacity, and electrode life. It also produces a sharp tip that allows for better control and penetration of the weld. However, it is slightly radioactive, and it can cause health and environmental hazards if not handled properly.
   

   
   

3. 2% lanthanated tungsten (blue): This is a versatile type of tungsten electrode that can be used for both AC and DC TIG welding. It contains 2% lanthanum, which improves the arc starting, stability, and electrode life. It also maintains a sharp tip that is suitable for thin and delicate materials. It is not radioactive, and it is considered a safe and effective alternative to thoriated tungsten.
   

   
   

4. 2% ceriated tungsten (grey): This is another type of tungsten electrode that can be used for both AC and DC TIG welding. It contains 2% cerium, which enhances the arc starting, especially at low amperages. It also forms a sharp tip that is ideal for small and intricate welds. It is not radioactive, and it is preferred for welding stainless steel, titanium, and nickel alloys.
   

   
   

5. 1.5% lanthanated tungsten (gold): This is a newer type of tungsten electrode that is similar to 2% lanthanated tungsten but with less lanthanum content. It has a lower work function, which means it requires less energy to start and maintain the arc. It also has a longer electrode life and a higher resistance to contamination. It can be used for both AC and DC TIG welding, and it is suitable for a wide range of materials and applications.
   

II.  Selection of Tungsten Electrodes

The selection of the right tungsten electrode for your TIG welding project depends on several factors, such as:

1) The material to be welded:

Different metals have different characteristics and requirements for TIG welding. For example, aluminum and magnesium require AC welding, while steel and copper require DC welding. Some metals, such as stainless steel and titanium, are more sensitive to heat and contamination and require a sharper and cleaner electrode tip. You should choose a tungsten electrode that matches the material type and thickness, and that can produce a stable and consistent arc.

2) The current type and polarity:

TIG welding can be done with either AC or DC, and with either electrode negative (EN) or electrode positive (EP) polarity. AC welding is used for aluminum and magnesium, as it alternates between EN and EP, which helps to clean the oxide layer and penetrate the base metal. DC welding is used for most other metals, as it provides a steady and concentrated arc.

• EN polarity is used for most DC welding, as it provides more heat to the electrode and less to the workpiece, resulting in a deeper and narrower weld.
  

  
  

• EP polarity is used for some DC welding, such as when welding thin materials or using filler metal, as it provides more heat to the workpiece and less to the electrode, resulting in a wider and shallower weld.

You should choose a tungsten electrode that can handle the current type and polarity, and that can deliver the desired heat and penetration.

3) The amperage range:

TIG welding can be done with a wide range of amperages, depending on the material, thickness and speed of the weld. Generally, the higher the amperage, the larger the electrode diameter and the shorter the electrode length. The lower the amperage, the smaller the electrode diameter and the longer the electrode length. You should choose a tungsten electrode that can operate within the amperage range of your weld, and that can provide a stable and smooth arc.

The following table summarizes the recommended types and sizes of tungsten electrodes for different materials and current types:

III. Use of Tungsten Electrodes

The use of tungsten electrodes for TIG welding involves the following steps:

1) Preparation:

Before welding, you should prepare the tungsten electrode by grinding it to a suitable shape and cleaning it with a solvent. The shape of the electrode tip affects the arc characteristics and the weld quality. Generally, there are two main shapes of electrode tips: balled and pointed.

1. Balled tips are used for AC welding, as they provide a wider and softer arc that can clean the oxide layer and penetrate the base metal.
   

   
   

2. Pointed tips are used for DC welding, as they provide a narrower and sharper arc that can control the heat and penetration of the weld.

To grind the electrode tip, you should use a dedicated tungsten grinder or a fine-grit abrasive wheel, and grind along the length of the electrode, not across it. This will create a smooth and even surface that will reduce the risk of arc wandering and contamination. To clean the electrode, you should use a clean cloth and a solvent, such as acetone or alcohol, and wipe the electrode from the tip to the end. This will remove any dust, oil or grease that could affect the arc quality and the weld purity.

2) Installation:

After preparing the tungsten electrode, you should install it in the TIG torch by loosening the collet and inserting the electrode through the back cap. You should make sure that the electrode is aligned with the center of the torch, and that it protrudes enough from the nozzle to create a sufficient arc gap. The length of the electrode protrusion depends on the electrode diameter, the amperage, and the shielding gas flow rate.

Generally, the electrode protrusion should be about 1.5 to 2 times the electrode diameter for DC welding, and about 3 to 4 times the electrode diameter for AC welding. You should tighten the collet and the back cap securely, but not too much, as this could damage the electrode or the torch components.

3) Operation:

Once the tungsten electrode is installed in the TIG torch, you should set the power source and the gas regulator to the appropriate settings for your weld. You should also wear the proper protective equipment, such as gloves, helmet, and clothing, and make sure that the work area is well-ventilated and free of flammable materials. To start the arc, you should either use a high-frequency (HF) start or a lift start. An HF start uses a high-voltage spark to initiate the arc without touching the workpiece, while a lift start uses a gentle contact and lift motion to create the arc. You should avoid using a scratch start, which involves dragging the electrode across the workpiece, as this could damage the electrode and contaminate the weld.

To maintain the arc, you should keep a constant arc length and a steady travel speed, and adjust the amperage and the torch angle as needed. You should also use a filler metal if required, and feed it into the weld pool with your other hand. To end the arc in TIG welding, you should use one of the following methods, depending on the current type and the electrode type:

• For AC welding with balled electrodes, you should reduce the amperage gradually with the pedal or the finger slider, and then pull the torch away quickly. This will prevent the electrode from sticking to the workpiece and creating a crater.
  

  
  

• For DC welding with pointed electrodes, you should either use a post-flow or a crater-fill technique. A post-flow uses a continuous flow of shielding gas after stopping the arc, to protect the weld pool from oxidation and contamination. A crater fill adds one last dab of filler metal to the weld pool, to fill the crater and prevent cracking.
  

  
  

  You should also reduce the amperage gradually with the pedal or the finger slider, and then break the arc softly.

4) Cleaning the electrode:

After ending the arc, you should clean the electrode with a clean cloth and a solvent, to remove any residue or contamination that could affect the next weld. You should also inspect the electrode tip for any damage or wear, and re-grind it if necessary.

IV. Conclusion

Tungsten electrodes are essential for TIG welding, as they deliver the current that creates the arc and the weld. There are different types of tungsten electrodes, each with its own advantages and disadvantages. You should choose the right type and size of tungsten electrode for your TIG welding project, based on the material, the current type, and the amperage range. You should also prepare, install, operate, and clean the tungsten electrode properly, to ensure a stable, smooth, and quality weld. TIG welding is a skill that requires practice and patience, but with the right tungsten electrode and technique, you can achieve impressive results.

Related articles

1. Identifying and solving tungsten electrode and arc issues

2. TIG Welding Tips for Beginner and Intermediate Welders

3. How to Solve 10 Common TIG Welding Problems [Guide]

4. TIG Welding: A Guide to Top-Quality Connections

5. MIG/MAG, MMA, TIG Welding: Choosing the Right Technique