pig iron
銑 centers on crude, unrefined iron: pig iron, the raw material produced by a blast furnace before further processing.
銑 combines the metal radical 金 with 先, which likely contributes the sound セン. The character originally referred to raw, unworked metal, specifically pig iron.
The metal radical 金 on the left and 先 (before, ahead) on the right suggest metal in its earliest, unrefined state: pig iron, the raw material that comes before finished steel.
For セン, picture a sen coin (銭, せん) made of crude pig iron: the sen coin cues セン, and the rough metal reminds you of the kanji's meaning.
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