What does cast iron mean?

Tizh explained that it was cast with molten iron. Behind the synonym casting and pouring sentence is a continuous iron-cast castle peak. The source is Chen's "A Willow on the Qinghai Plateau". 、

It means as strong as iron, indicating the strength of will or body.

Ex.: I stand here and look around. Behind me is a continuous iron-cast castle peak, and there are ochre ups and downs nearby. There are no trees at all.

-"A willow tree in Qinghai Plateau"