gray cast iron

例句：

1. 1.The old bridge is made of gray cast iron, which is sturdy and durable.
   这座老桥是用灰色铸铁建造的，非常坚固耐用。
2. 2. The construction crew used gray cast iron to reinforce the foundation of the new building.
   建筑队使用灰色铸铁加固了新建筑的基础。
3. 3. The gray cast iron door was a popular choice for its durability and resistance to corrosion.
   灰色铸铁门因其耐久性和抗腐蚀性而受到广泛欢迎。