What is the property of helium as a shielding gas in GMAW?

Helium, as a shielding gas in Gas Metal Arc Welding (GMAW), is characterized by being much lighter than air, which allows it to dissipate quickly into the atmosphere. This property can influence the behavior of the weld pool and the arc stability. The lighter nature of helium means that it can rise rapidly during the welding process, unlike heavier gases that might stay close to the weld and potentially create an unstable shielding environment. This quick escape can be beneficial as it reduces the chances of contamination and helps maintain a clean weld area.

In addition to affecting coverage, the rapid dissipation of helium can help in controlling the cooling rates of the weld, contributing to the overall quality of the weld. While helium may have higher thermal conductivity and may assist in achieving higher arc temperatures, the primary relevance in this context focuses on its lightweight nature that influences the shielding process.