spongy iron

例句：

1. 1. The new steel mill uses sponge iron as a raw material.
   新的钢铁厂使用海绵铁作为原材料。
2. 2. The sponge iron is used to make steel.
   海绵铁被用来制造钢铁。
3. 3. The sponge iron was found in the mine.
   海绵铁在矿井中被发现。