TIG Tungsten

TIG (tungsten inert gas) welding, also known as Gas Tungsten Arc Welding (GTAW), uses tungsten electrodes to produce the weld. Tungsten has an extremely high melting point (around 3,422 °C or 6,192 °F), which means it can sustain the intense heat generated in the welding arc without melting. The tungsten electrode itself does not become part of the weld, making it ideal for precise, high-quality welds on metals like stainless steel, aluminium, and titanium.

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Types of tungsten electrodes for TIG welding

Different types of tungsten electrodes are chosen based on the material being welded, the type of welding power source, and the welding conditions. The main types are:

1. Pure Tungsten (Green, WP):

   • Composed of 99.5% tungsten.

   • Ideal for AC welding, especially on aluminium and magnesium.

   • Produces a stable, balled tip when exposed to the AC current.

   • Limited current-carrying capacity and shorter lifespan compared to other tungsten types.

2. Thoriated Tungsten (Red, WT-2):

   • Contains 1-2% thorium oxide.

   • Offers improved arc stability and higher current-carrying capacity.

   • Mostly used for DC welding on carbon steel, stainless steel, nickel, and titanium.

   • Radioactive (due to thorium), so extra care is needed for ventilation and handling.

3. Ceriated Tungsten (Grey or Orange, WC-20):

   • Contains about 2% cerium oxide.

   • Suitable for both AC and DC welding.

   • Good arc stability, making it ideal for lower-amperage work.

   • Less radioactive than thoriated tungsten and often preferred for light work or delicate welds.

4. Lanthanated Tungsten (Blue or Gold, WL-15 or WL-20):

   • Contains 1.5% or 2% lanthanum oxide.

   • Known for its excellent arc start and stability in both AC and DC welding.

   • Performs well in lower amperage ranges and lasts longer due to better heat resistance.

   • Commonly used as a non-radioactive alternative to thoriated tungsten.

5. Zirconiated Tungsten (White, WZ-8):

   • Contains around 0.7-0.8% zirconium oxide.

   • Primarily used for AC welding, particularly on aluminium and magnesium.

   • Produces a highly stable arc with minimal tungsten spitting.

   • Not recommended for DC welding as it can be less stable in these applications.

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Choosing the Right Tungsten for the Job

• AC Welding (e.g., aluminium and magnesium): Pure tungsten (green) or zirconiated (white) works well due to their balling properties.

• DC Welding (e.g., steel, titanium): Thoriated (Red), Ceriated (Grey), and Lanthanated (Blue) tungsten are preferred as they provide a stable arc and better performance under high heat.

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Tungsten electrode preparation

1. Sharpening: For DC welding, a sharpened tip is often ground to a point, which helps focus the arc on a specific spot for precision. For AC welding, a balled tip is generally preferred for better arc stability.

2. Grinding Direction: Always grind tungsten electrodes longitudinally, not across, as this allows electrons to flow along the grind lines, creating a stable arc.

3. Avoiding Contamination: Tungsten can easily pick up contaminants, so it should be handled with clean tools and gloves. If it becomes contaminated during welding, it should be reground.

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Tips for Tungsten Selection

• For general-purpose TIG welding, 2% Thoriated (Red) is often preferred for DC work.

• For more versatile applications (both AC and DC), 2% lanthanated (Blue) is a popular choice.

• For light-duty or delicate welding, ceriated (Grey) is a good option.

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In summary, tungsten electrodes in TIG welding allow for a controlled, stable arc that is ideal for precision welding applications. Each type has its own unique properties and applications, so choosing the right tungsten depends on the metal being welded, the welding process, and the power source.