Which of the following gas mixes tends to produce low-crowned weld beads on stainless steels?

The gas mix that produces low-crowned weld beads on stainless steels is Argon-Helium-Carbon Dioxide. This combination is effective because the use of argon provides excellent arc stability and reduces spatter, while helium contributes to a hotter arc and improved penetration. The addition of carbon dioxide further enhances the arc characteristics and facilitates better fluidity in the weld pool, which leads to flatter weld beads with a low crown.

Flat weld beads are desirable in many applications, particularly in stainless steel welding, as they reduce the risk of defects such as undercutting and provide a cleaner appearance. The specific interaction of argon and helium also aids in better heat distribution, allowing for a more controlled bead shape.

Other mixes, like those containing oxygen or significant amounts of air, tend to introduce oxidation or create higher crown profiles due to varied arc characteristics, which can detract from the desired finish and structural integrity of the weld. Similarly, pure argon or different gas mixes do not produce the same low crown effect due to their differing thermal and fluid dynamics properties.