机电专业英语
2009-9
北京理工大学
刘云 编
137
本书内容共13章，即机械基础知识与部件、机械加工工具、机械加工、公差拟合与测量、钢铁及其制造、电的常识、电与电路、无线电通信与电器维修、电焊、能源、微机组装与维护、自动化与机器人、电脑制图。为便于读者更好地利用本书，编者在每节后面都附有详细的课文注释和词汇，希望对读者有所帮助。 《机电专业英语》内容新颖、图文并茂、通俗易懂、门类齐全、适应面广，适合中等职业学校学生的实际水平。
Part One：Basic Knowledge of Machine and Mechanical Components 1.Basic Knowledge of Machine 2.Shaft 3.Shaft Accessories--Keys and Pins 4.Bearings 5.Screws 6.Worms．Worm Gears 7.Cam 8.GearsPart Tw0：Machine Tools 1.Fixture and Jig 2.Reamer 3.Grinding Wheel 4.Boring Tbol 5．Turning Tool 6.Cutting Tool Part Three：Machining 1．Turning 2.ne Lathe and Its Construction 3.Milling 4.Milhng Machine 5.Grinding 6. Bench Work ……
Most metallic materials allow phase transformation in the mud state after the shaping processwithout changing the general geometry， which makes it possible to control the structure and thus theproperties within rather wide limits， practical technical operations， which are associated with suchphase transformations， are called heat treatment. There are three main operations in the heat treat-ment of steel ： hardening， tempering， and annealing. The hardening operation consists of heating the steel above its critical range and then quenchingit， that is rapidly cooling in a suitable medium such as water， brine， oil， or some other liquid. Havingbeen hardened，the metal must be given a tempering treatment which consists of reheating the hard-ened steel to a temperature below the critical range， holding at this temperature for some time andthen followed by cooling in water， oil or air. The critical points or temperatures are the temperatures at which a certain change takes place inthe physical condition of the steel. These points are very important because in order to properlyharden a piece of steel， it must be heated to a temperature above the upper critical point. Havingknown the critical points for certain steel， we can easily control the heat in the furnace.Gas， oil，and electric furnaces are the most commonly used for heat treating metals. Annealing is the uniform heating of a metal above usual hardening temperatures， followed byvery slow cooling. Annealing may be carried out either to soften a piece that is too hard to machineor to remachine a piece that has already been hardened. Annealing also relieves internal stressesproduced by machining. Nomalizing is to heat the steel slowly to about 30℃ above its upper critical temperature， thenfollowed by cooling in still air. The process is applied to achieve the best combination of mechanicalproperties when it is undesirable for the material to be in the softest possible condition.
