机电工程专业英语 教学课件 ppt 作者 马佐贤 主编 张雪娟 副主编Unit 5.pptVIP

Heat treatment is a method by which the heat treatment can change the physical properties of a material. There are four main operations: annealing normalizing hardening tempering Assignment * * * Unit 5 Heat Treatment of Steels Dialogue 5.1 Heat Treatment of Steels 5.2 Dialogue 5.1 What is NC? Do you know heat treatment? How many types of heat treatment are there? What is critical temperature? It is the temperature at which a certain change takes place in the physical condition of the steel. Practice Read the dialogue again and translate some important sentences. Heat Treatment of Steels 8.2 Discuss “Heat Treatment of Steels” the heating and cooling operations performed on a metal for the purpose of altering such characteristics as hardness strength ductility A tool steel intended to be machined into a punch may first be softened so that it can be machined． 要想把一块工具钢加工成一只冲头，可先使其变软， 以便能进行机械加工 When a steel part is to be either hardened or softened , its temperature must be taken above the critical temperature line； Temperature 50--100 When the heating time is completed，the steel must be cooled down to room temperature． room temperature 常温，室温 Annealing leaves the steel in the softest possible condition (dead soft)． dead soft 极软 * *