Gōngjiàng bǎ shāohóng de gāngtiáo fàngrù shuǐ zhōng cuìhuǒ.
The craftsman plunged the red-hot steel rod into water to quench it.
Tips
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淬 (cuì) means 'to dip / temper' — note the water radical 氵; 火 = 'fire.' Together: water meets fire, the classic forge process. Often used metaphorically: 经过淬火的意志 = 'a will tempered by hardship.'