Tungsten is a crucial component in TIG (Tungsten Inert Gas) welding, responsible for providing precise control over the welding arc. However, with various types of tungsten electrodes available, selecting the right one for the job can be challenging, especially for beginners. This guide will cover everything you need to know about the types of tungsten, their selection, and how to use them effectively in TIG welding.
Table of Contents
What is Tungsten and Why is it Important in TIG Welding?
Tungsten is a metal with the highest melting point of any element, making it ideal for handling the high temperatures involved in TIG welding. Unlike consumable electrodes used in other welding processes, tungsten electrodes are non-consumable, meaning they don’t melt into the weld puddle. Instead, they conduct the electric arc that creates the weld, providing greater control and stability.
Benefits of Using Tungsten in TIG Welding:
- Precise heat control for intricate welds.
- Stable arc that leads to high-quality welds.
- Durability due to high melting point, leading to less frequent electrode replacement.
Types of Tungsten Electrodes
Choosing the correct tungsten electrode depends on the type of material you are welding, the current (AC or DC), and the desired weld quality. Each type of tungsten is color-coded for easy identification.
1. Pure Tungsten (Green)
Pure tungsten electrodes (99.5% tungsten) are one of the oldest types of electrodes used in TIG welding. They are mainly used for welding aluminum and magnesium with AC (alternating current). The balled tip that forms when using AC helps stabilize the arc, making it suitable for these softer metals. However, pure tungsten has largely fallen out of favor with the advent of more advanced tungsten alloys.
Advantages:
- Inexpensive and readily available.
- Ideal for AC welding on aluminum and magnesium.
Disadvantages:
- High consumption rate compared to alloyed tungstens.
- Not suitable for DC welding or materials requiring precision.
Use Case: Pure tungsten is best used in simple welding applications where the metal’s softness (like aluminum) benefits from a wide, balled arc.
2. Thoriated Tungsten (Red)
Thoriated tungsten electrodes (2% thorium) are one of the most popular choices for DC welding, particularly when working with stainless steel, carbon steel, and nickel alloys. Thoriated electrodes offer a stable arc, high current-carrying capacity, and excellent durability, making them a go-to choice for many welders.
Advantages:
- Superior arc starting capabilities.
- Long lifespan due to high heat tolerance.
- Stable at both high and low current levels.
Disadvantages:
- Thorium is radioactive, so handling requires safety precautions.
- Not recommended for AC welding.
Use Case: Ideal for DC welding, especially when working with steel, stainless steel, and nickel alloys.
3. Ceriated Tungsten (Gray)
Ceriated tungsten electrodes contain 2% cerium and are used for both AC and DC welding. They are especially favored in applications that require low-current welding, such as welding thin materials or delicate metals like titanium and stainless steel. Ceriated tungsten provides excellent arc starts, making it a good option for beginners.
Advantages:
- Performs well at lower currents.
- Suitable for both AC and DC applications.
- Less radioactive compared to thoriated tungsten.
Disadvantages:
- Less durable at high temperatures.
- Not as effective in high-amperage applications.
Use Case: Excellent for low-current, precision welding in delicate applications, particularly in automotive and aerospace industries.
4. Lanthanated Tungsten (Blue/Gold)
Lanthanated tungsten electrodes contain around 1-2% lanthanum oxide and are often considered a great alternative to thoriated tungsten. They provide excellent arc stability and performance for both AC and DC welding. Lanthanated tungsten is durable, has a slow burn-off rate, and works well across a wide range of amperages.
Advantages:
- Versatile, suitable for both AC and DC welding.
- High arc stability, even at low currents.
- Non-radioactive, making it safer to handle than thoriated tungsten.
Disadvantages:
- Slightly lower current-carrying capacity compared to thoriated tungsten.
Use Case: This is a highly versatile option, ideal for welding stainless steel, copper, and nickel alloys.
How to Select the Right Tungsten for Your Project
When selecting tungsten, consider the following factors:
1. Type of Material
Different materials require different types of tungsten. For instance, aluminum and magnesium generally work best with pure or zirconiated tungsten when using AC, while steel and nickel alloys are best welded with thoriated or lanthanated tungsten when using DC.
2. Welding Current (AC vs. DC)
The type of current you use also dictates the tungsten you should choose. Pure and zirconiated tungsten works better for AC, especially in aluminum welding, while thoriated, ceriated, and lanthanated tungsten excel in DC applications.
3. Electrode Diameter
Tungsten electrodes come in various diameters, typically ranging from 0.020 inches to 0.25 inches. Thinner electrodes are ideal for low-current welding on delicate materials, while thicker electrodes are necessary for high-amperage welding.
4. Current Capacity and Arc Stability
Tungsten electrodes with additives like thorium or lanthanum tend to offer better arc starts, greater arc stability, and higher current capacity. These are critical factors if you’re working on precision welding projects or require more control.
Preparing and Sharpening Tungsten Electrodes
The performance of a tungsten electrode in TIG welding depends not only on the type of tungsten but also on how it is prepared and maintained. Proper sharpening and handling of tungsten electrodes ensure a stable arc and a higher-quality weld. The next section will cover key steps for sharpening, handling, and troubleshooting.
Sharpening Tungsten Electrodes
Tungsten electrodes must be sharpened before use, and the sharpening process can affect the quality of your weld. Here are the best practices for sharpening:
1. Using the Right Grinder
It’s essential to use a dedicated tungsten grinder or a grinding wheel reserved specifically for tungsten to avoid contamination. The grinder should have a fine-grit, diamond wheel to prevent tungsten particles from embedding in the electrode.
2. Grinding Direction
Always grind tungsten electrodes lengthwise, parallel to the axis. Grinding the electrode in a circular motion around its circumference can result in arc instability, as the tungsten will not provide a focused arc. Grinding lengthwise ensures that the sharpening lines direct the arc down toward the weld.
3. Creating a Sharp Point
For DC welding, you will need a sharp point. The sharp tip concentrates the arc and provides better arc control, especially for materials like stainless steel or carbon steel. Aim for a taper length of about 2-3 times the diameter of the tungsten electrode.
For AC welding (typically aluminum), tungsten is typically balled at the end. The ball can be created by briefly applying a higher current, which melts the end of the electrode, creating a rounded shape. The size of the ball should be about 1-1.5 times the diameter of the tungsten.
4. Cleaning the Electrode
After sharpening, it’s important to clean the electrode to remove any potential contaminants. Use a clean cloth to wipe the electrode before welding.
Best Practices for Storing Tungsten Electrodes
Contamination can be a major issue for tungsten electrodes, especially when working on projects that require high precision. Follow these tips to avoid contamination:
- Keep electrodes in a sealed container when not in use. This helps prevent them from picking up dust, dirt, or oils that could negatively impact the weld.
- Avoid touching the sharpened tip with bare hands, as skin oils can transfer to the tungsten and cause contamination.
- If using multiple types of tungsten electrodes, store them separately, preferably labeled with their color codes, to prevent cross-contamination.
Troubleshooting Common Issues with Tungsten Electrodes
Even with careful preparation and handling, issues can arise with tungsten electrodes during TIG welding. Here are common problems and how to address them:
1. Tungsten Contamination
If the tungsten electrode becomes contaminated (for example, if it touches the weld puddle or filler material), it can cause arc instability and defects in the weld.
Solution: Stop welding immediately, remove the contaminated part of the electrode by grinding it down, and re-sharpen it properly before resuming welding.
2. Unstable Arc
An unstable arc can result in poor weld quality and can occur due to improper electrode sharpening or contamination.
Solution: Ensure the electrode is sharpened properly along its length, clean the tungsten thoroughly, and check for any contamination that may have occurred during grinding or handling.
3. Burnback of Tungsten Tip
Burnback occurs when the tip of the tungsten electrode melts back due to excessive heat. This can happen when the amperage is too high or if the wrong type of tungsten is used for the material being welded.
Solution: Lower the amperage setting or switch to a higher-amperage-rated tungsten, such as thoriated or lanthanated tungsten for DC applications.
4. Short Tungsten Life
Some types of tungsten, such as pure tungsten, tend to wear out more quickly than others. However, short tungsten life can also result from improper handling or excessive heat.
Solution: Choose a tungsten alloy suited for the job, such as lanthanated or ceriated tungsten for AC or DC welding. Make sure to use the right amperage settings and avoid overheating the tungsten.
5. Arc Wandering
Arc wandering occurs when the arc drifts from the desired welding point, often due to a blunt tungsten tip or contamination.
Solution: Ensure that the electrode is properly sharpened to a fine point for DC welding, and keep the tip clean and free from contamination.
FAQs
Q1: Can I use pure tungsten electrodes for DC welding?
A1: No, pure tungsten electrodes are typically used for AC welding, especially for aluminum and magnesium. They are not suitable for DC welding due to their poor arc stability and lower current-carrying capacity compared to other alloyed tungstens.
Q2: How do I know which tungsten electrode diameter to use?
A2: The electrode diameter should match the current range of your welding project. For low-current applications, smaller diameters like 1/16 inch work best. For high-current projects, you can use thicker electrodes like 3/32 inch or 1/8 inch.
Q3: How should I dispose of thoriated tungsten electrodes?
A3: Thoriated tungsten is radioactive, so it must be disposed of following local hazardous waste regulations. Avoid grinding in poorly ventilated areas, and use specific guidelines for safe handling and disposal.
Q4: Why does my tungsten electrode keep contaminating the weld pool?
A4: Tungsten contamination usually occurs if the electrode touches the filler metal or the workpiece during welding. Ensure proper technique and distance between the electrode and workpiece to avoid contamination. Also, regrind the electrode if it becomes contaminated.
Q5: What is the difference between lanthanated and ceriated tungsten?
A5: Lanthanated tungsten provides better arc stability at higher currents, making it versatile for both AC and DC welding. Ceriated tungsten, on the other hand, is ideal for low-current applications and is particularly suited for precision welding on thin metals.
Q6: What color code corresponds to rare earth tungsten electrodes?
A6: Rare earth tungsten electrodes are typically purple in color. These electrodes offer a high current-carrying capacity and are versatile for both AC and DC welding on materials like aluminum, steel, and titanium.