molten surface

例句：

1. 1.The molten metal flowed into the mold.
   熔融金属流入模具。
2. 2. The molten metal was poured into a mold.
   熔融金属被倒入一个模具中。
3. 3. The molten metal had to be cooled quickly to prevent cracking.
   熔融金属必须迅速冷却以防止开裂。