金属分为黑色金属和有色金属。前者含铁，后者不含铁。

Metals are divided into ferrous and non-ferrous metals. The former contain iron and the latter do not contain iron.

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焊接中，氩作为保护气防止金属氧化。惰性气体焊接是连接几种含铁和不含铁的合金的首选方法。

Argon serves as a shielding gas to protect metals from oxidation during welding. Inert gas welding is the preferred method of joining several ferrous and nonferrous alloys.

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