【简答题】Many people have to work at weekends. Some people do not mind, others think it is terrible. One man thinks that working at weekends can be __21__. He is George Smith. Mr. Smith works in an office, in ...
【简答题】回火的目的是什么?工件淬火后为什么要及时回火? 回火的目的是消除和减小内应力,稳定组织,调整性能,以获得较好的强度和韧性配合。淬火钢的组织主要由马氏体和少量残余奥氏体组成____,其内部存在很大的内应力,脆性大,韧性低,一般不能直接使用,如不及时消除,将会引起工件的变形,甚至开裂。
【单选题】About _________ people are in the People’s Park at the weekends.
【简答题】During the week days,they are luckily busy office people; but on weekends,they are just a brood of(一窝)stay home animals.A recent survey shows that office workers in China prefer quiet and easy ways to...
【简答题】回火的目的是什么?工件淬火后为什么要及时进行回火?
【简答题】汽轮机叶轮的作用是什么?运行中的叶轮会受到哪些力的作用?
【简答题】回火的目的是什么?工件淬火后为什么要及时进行回火?