关羽是三国里最受欢迎的武将,他凭一把“青龙偃月刀”过五关斩六将,驰骋疆场。相传“青龙偃月刀”又名“冷艳锯”,重41公斤,削铁如泥,头发放在刀刃上,吹口气就会断为两截。当然,传说毕竟是传说,难免有夸大之处,但是锋利的“宝刀”确实存在。19世纪中叶,科学家就已经知道,古代的工匠制造 Guan Yu is the most popular military commander in the Three Kingdoms. He used the “Qinglong Haoyue knife” to pass five battles and six generals to ride the battlefield. According to legend, “Qinglong Haoyue knife,” also known as “cold saw”, weighs 41 kg, cut iron like mud, hair on the blade, the breath will be cut into two parts. Of course, legend is a legend after all. It is inevitable that there are exaggerations, but sharp “swords” do exist. In the middle of the 19th century, scientists already knew that ancient craftsmen made