回火的目的是什么,常用的回火操作有哪几种?
参考答案:
回火的目的:
1.获得工件所需的组织。
2.稳定尺寸。
3.消除淬火内应力。
回火的种类:低温回火;中温回火;高温回火
He revisited his home village last month, and everything there _____ his sweet memory of his childhood. [ ]
A. brought about
B. brought up
C. brought back
D. brought in
伴热管敷设时管端应与取压阀或仪表(),不得影响操作、维护和拆卸。
A、远离
B、留出一段距离
C、靠近
D、都可以