• 鋼はがね — steel
• 鋼鉄こうてつ — steel (used technically)
• 精鋼せいこう — refined steel
• 製鋼せいこう — steel manufacturing
• 軟鋼なんこう — soft steel

This kanji is composed of 金 (“metal”) and 岡 (“hill”) as the phonetic element. It refers to iron that has been further refined to become stronger – what we call steel.

鋼はがねのように強つよい心こころを 持もちたい。
I want to have a heart as strong as steel.

この橋はしは 鋼鉄こうてつでできている。
This bridge is made of steel.

はがね is commonly used in daily Japanese to refer to steel materials. コウ appears in compound and technical words like 製鋼 (steel production).