Why might a welder choose a larger than necessary tungsten electrode?

Choosing a larger-than-necessary tungsten electrode primarily provides more thermal conduction, which is particularly beneficial when working with thicker materials. The larger electrode has a greater surface area, which allows it to conduct more heat to the workpiece. This increased heat input is essential for achieving proper penetration and fusion when welding thicker sections, ensuring a more effective and robust weld.

Additionally, a larger electrode can maintain a stable arc even under higher amperage settings, which is essential for welding thicker materials that require increased heat. While there are advantages to the other choices, such as potentially speeding up travel or possibly improving contamination resistance, the key rationale behind using a larger electrode is its enhanced thermal capacity that enables effective welding on thicker substrates.