Water is not safe with molten metals. Physical contact will result in steam and a "boiler" explosion. Or, physical contact with certain metals (e.g., lithium, aluminum, zirconium) will result in the metals combusting with the water, liberating hydrogen gas, which can then explode. So, why do they use water for cooling? Nothing else is more effective or safer or as inexpensive.
Water is not safe with molten metals. Physical contact will result in steam and a "boiler" explosion. Or, physical contact with certain metals (e.g., lithium, aluminum, zirconium) will result in the metals combusting with the water, liberating hydrogen gas, which can then explode. So, why do they use water for cooling? Nothing else is more effective or safer or as inexpensive.