• 鋼鉄こうてつ — steel (technical term)
• 精鋼せいこう — refined steel
• 製鋼せいこう — steel manufacturing
• 軟鋼なんこう — mild steel
• 鋼材こうざい — steel materials
• 鋼はがね — steel

This kanji combines 金 (“metal”) with 岡 (phonetic), giving the sense of durable and fortified iron. It represents steel — stronger than iron alone — often used as a metaphor for resilience and toughness.

鋼はがねのように強つよい意志いしを 持もちたい。
I want to have a will as strong as steel.

この橋はしは 鋼鉄こうてつで 建たてられています。
This bridge is built of steel.