古人是用陨铁制造刀具的,陨铁很纯净而柔软。后来,一个不知道名字的铁匠偶然或者由于天才的猜想将刀具放到燃烧的炭上,意外地发现刀子变得更加坚硬了。从此以后,铁匠就开始往铁中加碳来制造钢。但是,加碳的钢更脆。另—种制造强度更大的钢的方法是用氮取代碳,氮比碳更易溶于钢。在热 The ancients made tools with yttrium iron. The yttrium iron was pure and soft. Later, a blacksmith who did not know the name accidentally or put the cutter on the burning charcoal because of the genius’s guess, unexpectedly discovered that the knife became harder. Since then, blacksmiths have begun to add carbon to iron to make steel. However, the carbon added steel is more brittle. Another way to make stronger steels is to replace carbon with nitrogen, which is more soluble in steel than carbon. In the heat