Why is a water-cooled copper mold used to cast molybdenum?

Molybdenum has an extremely high melting point of 2,610 °C (4,730 °F), which makes it impossible to cast into high-quality ingots using conventional methods.12

To overcome this, the metal is melted using an electric arc. During this process, the molten molybdenum is cast into a water-cooled copper mold to facilitate immediate and controlled solidification. This technique is necessary because the intense heat required to melt the metal would otherwise damage standard casting equipment, and the water-cooled mold ensures the structural integrity of the resulting ingot.13