Why is high-purity argon essential for welding aluminum, titanium, and other non-ferrous metals?

Why is high-purity argon essential for welding aluminum, titanium, and other non-ferrous metals?
The market distinguishes three argon grades: standard argon (~99.6%), pure argon (~99.9%), and high-purity argon (99.99%+). For carbon steel and stainless steel welding, the first two grades suffice. But for aluminum, aluminum alloys, titanium, and titanium alloys, high-purity argon is mandatory. Impurities in lower grades cause oxidation of the weld and heat-affected zone, making proper fusion impossible. This purity requirement directly impacts pricing: a standard 40L cylinder at 15MPa sells around RMB 200, while 5N (99.999%) high-purity argon costs roughly double at RMB 400. The gap reflects both purification costs and the criticality of impurity control for demanding applications. Buyers should verify purity certificates and match grade to application to avoid weld defects and rework costs.