Situation 1 Mechanical P rinciple

1. Situation 1 Mechanical Principle

2. Task 1Steeland Heat Treatment of Metals • Task 2Introduction to Common Mechanical Parts • Bearings • Gears • Cams • Springs • Properties of Materials • Task 3 Dimensions and Tolerances • Task4 Introduction to Important Parts of Port Machinery • ICE • Four Stroke Gasoline Engine • Common Chassis

3. Task1 Steel and Heat Treatment • I Why to learn? • Steel is the major material used in machines, the students should master the basic knowledge about it. • Heat Treatment is the major process employed in treating steel and other metals.

4. Task1 Steel and Heat Treatment • II How to learn? • Seminar (讨论和任务教学法为主） • Organize the students in groups and provide with some tasks to complete including answering the questions and translating the corresponding paragraphs. • Lecture（讲授法为辅） • III Content • lesson1 Steel • Lesson2 Heat Treatment

5. Lesson 1 Steel Lead-in （communication methods交际法) New Words（lecture +selfstudy 讲授法和自学法） Text Analysis（任务教学法） Exercise

6. Lead-in • What do you know about steel?

7. New Words • steel n. 钢, 钢铁 • plain carbon steel 碳素钢 • alloy steel 合金钢 • low-carbon steel 低碳钢 • medium-carbon steel 中碳钢 • high-carbon steel 高碳钢 • content n. 含量

8. New Words • case-harden 表面硬化 • hardness n. 硬度 • characteristic n. 特性 • tensile strength 抗拉强度

9. New Words • toughness n. 韧性 • antiwear property 抗磨性能 • corrosion resistance 耐蚀性 • red-hardness 红硬性

10. Text AnalysisLesson 1 steel • Para1Generally speaking, there are two kinds of steels in common use: plain carbon steels and alloy steels. Firstly, let’s look at plain carbon steels. • Para2Plain carbon steels are the steels that contain only carbon and no other major alloying elements. This kind of steel has 3 types which are low-carbon steel, medium-carbon steel and high-carbon steel. They get their special names from their content of carbon.

11. Para3If the carbon content is lower than 0.25%, it is called low-carbon steel. It cannot be hardened but can be case-hardened. It has these characteristics which are easy machining & forming, comparatively less strength, least expensive, comparatively less hardness and largest quantity produced. In practice use, bolts, nuts, washers, sheet steel, and shafts use low-carbon steel.

12. Para4Medium-carbon steel contains from 0.25-0.60 percent carbons. This kind of steel is mostly used in situation where greater tensile strength is required. This kind of steel may be hardened for it has higher carbon content. Its haracteristics are as follows, hard & strong after heat treating; medium depth of hardness and more expensive than low carbon steel. Tools such as wrenches, hammers, and screwdrivers are drop-forged from medium-carbon steel and later heat treated.

13. Para5High-carbon steel (also named as tool steel) contains over 0.60 percent carbon, and it can contain as high as 1.7 percent. It has these characteristics: hard & strong after heat treating; depth of hardness increases and more expensive than low & medium carbon steels .Cutting tools, punches, taps, dies, drills and reamers usually use this kind of steel.

14. Para6Then is the alloy steels. Alloy steel is the steel whose characteristics are determined by the addition of other elements in addition to carbon. Alloy steels have some special characteristics which are not found in plain carbon steels, so alloy steels are widely used in practice. That is to say, sometime we prefer alloy steel to plain steel. • Para7Alloy steel has these following characteristics: it increases in tensile strength, hardness, toughness, antiwear property, corrosion resistance and red-hardness.

15. Para1 • Q What are the two kinds of steels in common use? • Key • plain carbon steels and alloy steels

16. Para2 • Q1What is plain carbon steel? • Key: • Plain carbon steels are the steels that contain only carbon and no other major alloying elements. • Cn • 碳素钢指的是只含有碳元素没有其它主要合金元素的钢。 • Q2 How many types of steel can plain carbon steel be divided into according to the carbon content ? • Key: • This kind of steel has 3 types which are low-carbon steel, medium-carbon steel and high-carbon steel.

17. Para3 Q1 What is low-carbon steel? Key:If the carbon content is lower than 0.25%, it is called low-carbon steel. Q2 what are its characteristics? Key:It cannot be hardened but can be case-hardened. It has these characteristics which are easy machining & forming, comparatively less strength, least expensive, comparatively less hardness and largest quantity produced. Q3 what is its usage? Key:Bolts, nuts, washers, sheet steel, and shafts use low-carbon steel.

18. Para4 Q1 What is medium-carbon steel? Key:Medium-carbon steel contains from 0.25-0.60 percent carbons. Q2 what are its characteristics? Key:This kind of steel may be hardened for it has higher carbon content. Its characteristics are as follows, hard & strong after heat treating; medium depth of hardness and more expensive than low carbon steel. Q3 what is its usage? Key:Tools such as wrenches, hammers, and screwdrivers are drop-forged from medium-carbon steel and later heat treated.

19. Para5 Q1 What is high-carbon steel? Key:High-carbon steel (also named as tool steel) contains over 0.60 percent carbon, and it can contain as high as 1.7 percent. Q2 what are its characteristics? Key:It has these characteristics: hard & strong after heat treating; depth of hardness increases and more expensive than low & medium carbon steels . Q3 what is its usage? Key:Cutting tools, punches, taps, dies, drills and reamers usually use this kind of steel.

20. Para6 Q1 What is alloy steel? Key:Alloy steel is the steel whose characteristics are determined by the addition of other elements in addition to carbon.

21. Para7 Q1 What are the characteristics of alloy steel? Key:it increases in tensile strength, hardness, toughness, antiwear property, corrosion resistance and red-hardness.

22. Exercises • 1. Words Matching • 2.Translation

23. 1. Words Matching • toughness n. 耐蚀性 韧性 • antiwear property • corrosion resistance 红硬性 • red-hardness 抗磨性能

24. 2. Translation • 1) It has these characteristics which are easy machining & forming, comparatively less strength, least expensive, comparatively less hardness and largest quantity produced. • Key • 它具有下列特点：容易加工和成形，相对来说强度不足，最便宜，硬度弱，但是可以大批量生产。 • 2) Its characteristics are as follows, hard & strong after heat treating; medium depth of hardness and more expensive than low carbon steel. Tools such as wrenches, hammers, and screwdrivers are drop-forged from medium-carbon steel and later heat treated. • Key • 该钢的特点是：经过热处理后硬度和强度更大，具有中等硬度，但比低碳钢更贵些。

25. Lesson 2 Heat Treatment of Metals Lead-in New Words Text Analysis Exercise

26. Lead-in Q1 What are the major types of heat treatment? Key: Normalizing (正火）， quencing(淬火), tempering(回火）and annealing (退火） Q2 What are their differences? Key

27. key • （1）退火：将工件加热到工艺要求的温度，经过适当的保温以后，再缓慢冷却下来的热处理工艺过程。 • 退火目的：降低硬度，提高塑性，以利于切削和冷变形加工；细化晶粒，均匀钢的组织成分，改善钢的性能，为以后的热处理作准备；消除钢中的残余应力，防止变形开裂。 • 常用的退火方法有完全退火、球化退火、去应力退火等几种。 • （2）正火：将钢加热到上临界点（Ac3、Acm）以上，进行完全奥氏体化，然后在空气中冷却（有时吹风或喷雾冷却）的热处理过程。正火冷却速度比退火快。 • 对于低碳钢（c%小于0.25%），正火加热温度Ac3+（100-150）℃，目的细化组织，提高强、硬度，便于切削加工。因为低碳钢退火硬度太低，切削时易“粘刀”，粗糙度高，效率低。 • 对于中碳钢（0.25％-0.60％），正火加热温度Ac3+（50-100）℃正火代替调质处理，为高频淬火作组织准备。 • 对于高碳钢（大于0.6％），正火加热温度Acm +（30-50）℃，目的消除网状渗碳体，为球化退火作组织准备。

28. （3）淬火：将钢加热到临界点以上，保温一定的时间进行奥氏体化，然后以大于临界冷却速度冷却，以得到介稳态马氏体组织或下贝氏体组织的热处理工艺。（3）淬火：将钢加热到临界点以上，保温一定的时间进行奥氏体化，然后以大于临界冷却速度冷却，以得到介稳态马氏体组织或下贝氏体组织的热处理工艺。 • 淬火的目的：提高工具、渗碳零件和其他高强度耐磨机器零件的硬度、强度和耐磨性。 • 淬火冷却介质：水、各种水溶液、各种油和熔化的盐、碱及金属等。 • 淬透性：表征钢在淬火时所能达到的淬硬层深度。 • 常用的淬火方式：单液淬火，在一种冷却介质中一直冷却到室温；双液淬火：先在水中冷到Ms温度再快速转移到油中冷却到室温；分级淬火：先置于温度为Ms点的盐浴或碱浴中冷却，待内外温度一致后，在取出在油中或空气中冷却；等温淬火：置于温度为Ms点的盐浴或碱浴中，长时间等温最终获得下贝氏体的热处理工艺。（作业） • （4）回火：将淬火后的工件，再加热到Ac1以下某一温度，保温一定时间，然后冷却到室温的热处理工艺。 • 回火目的：消除内应力；获得所需的力学性能；稳定组织和尺寸。

29. New Words • heat treatment 热处理 • manufacturability 可制造性 • formability n. 成型性能 • ductility n. 延展性, 柔软性 • internal stress 内应力 • soften v. 软化 • hardening n. 硬化 • material modification 材料改性

30. New Words • tempering n. 回火 • quench hardening 淬火硬化 • stress relieving 应力消除 • quenching n. 淬火 • Troostite n. 屈氏体 • Sorbite n. 索氏体 • machinability n. 可加工性 • spheroidizing n. 球化(处理)

31. Text AnalysisLesson 2 Heat Treatment of Metals • Para1Heat treatment is the operation of heating and cooling a metal in its solid state to change its properties. • Para2Heat treatment is often associated with increasing the strength of material, but it can also be used to alter certain manufacturability objectives such as improve machining, improve formability, restore ductility after a cold working operation. Thus it is a very enabling manufacturing process that can not only help other manufacturing process, but can also improve product performance by increasing strength or other desirable characteristics.

32. Para3With the proper heat treatment, internal stresses may be removed, grain size reduced, toughness increased, or a hard surface produced on a ductile interior. Steels are particularly suitable for heat treatment, since they respond well to heat treatment and the commercial use of steels exceeds that of any other materials. Steels are heat treated for one of the following reasons: • 1softening • 2hardening • 3material modification

33. Common Heat Treatments • Softening: • Para4Softening is done to reduce strength or hardness, remove residual stresses, improve toughness, restore ductility, refine grain size or change the electromagnetic properties of the steel. • Para5Restoring ductility or removing residual stresses is a necessary operation when a large amount of cold working is to be performed, such as in a cold-rolling operation or wiredrawing. Annealing — full Process, spheroid zing, normalizing and tempering — austempering, martempering are the principal ways by which steel is softened.

34. Para6Hardening: Hardening of steels is done to increase the strength and wear properties. One of the pre-requisites for hardening is sufficient carbon and alloy content. If there is sufficient carbon content, then the steel can be directly hardened. Otherwise the surface of the part has to be carbon enriched using some diffusion treatment hardening techniques. • Para7Material Modification: Heat treatment is used to modify properties of materials in addition to hardening and softening. These processes modify the behavior of the steels in a beneficial manner to maximize service life, e.g., stress relieving, or strength properties, e.g., cryogenic treatment, or some other desirable properties, e.g., spring aging.

35. Para8Tempering is a process done subsequent to quench hardening. Tempering is done immediately after quench hardening. When the steel cools to about 40 ºC (104 ºF) after quenching, it is ready to be tempered. The part is reheated to a temperature of 150 to 400 ºC (302 to 752 ºF). In this region a softer and tougher structure Troostite is formed. Alternatively, the steel can be heated to a temperature of 400 to 700 ºC (752 to 1292 ºF) that results in a softer structure known as Sorbite. This has less strength than Troostite but more ductility and toughness.

36. Para9Generally speaking, the purposes of annealing are: alteration of ductility and toughness, induction of softness and refinement of grain structure and removal of gases and stresses. • para10This process of normalizing is very similar to annealing, which improves strength and machinability. • Para11Spheroidizing is a form of annealing consisting of prolonged heating of iron base alloys at a temperature in the neighborhood of, but generally slightly below the critical range, usually followed by a relatively slow cooling. Spheroidizing causes the graphite to assume a spheroidal shape, hence the name.

37. Para1 • Q1What is heat treatment? • Key:Heat treatment is the operation of heating and cooling a metal in its solid state to change its properties. • Cn:热处理指的是对金属在其固态状态下进行加热和冷却以改变其物理特性的一种操作。

38. Para2 • Q1 What is the purpose of heat treatment? • Key: • Heat treatment is often associated with increasing the strength of material, but it can also be used to alter certain manufacturability objectives such as improve machining, improve formability, restore ductility after a cold working operation.

39. Para3 • Q1 What is the result of heat treatment? • key:internal stresses may be removed, grain size reduced, toughness increased, or a hard surface produced on a ductile interior. • Q2 Why steel is particularly suitable for heat treatment? • Key:Because they respond well to heat treatment and the commercial use of steels exceeds that of any other materials. • Q3 What are the major reasons for heat treatment? • Key:1softening • 2hardening • 3material modification

40. Para4 • Q What is the purpose of softening? • Key:Softening is done to reduce strength or hardness, remove residual stresses, improve toughness, restore ductility, refine grain size or change the electromagnetic properties of the steel. • Cn:软化常用来降低强度或硬度，消除残余应力，增加韧性，恢复展延性，细化结晶粒度或改变钢的电磁性。

41. Para5 • QWhat are the principal ways by which steel is softened? • Key: Annealing — full Process, spheroid zing, normalizing and tempering — austempering, martempering are the principal ways by which steel is softened. • Cn:退火-完全退火和球化，正火，淬火，回火包括 奥氏体回火和马氏体回火是软化钢的主要工艺。

42. Para6 • Q What is purpose of hardening? Key: Hardening of steels is done to increase the strength and wear properties.

43. Para7 • Q What is the purpose of mateiral modification? • Key: These processes modify the behavior of the steels in a beneficial manner to maximize service life

44. Para8 • Q What is the difference between Troostite and Sorbite？ • Key:Sorbite has less strength than Troostite but more ductility and toughness.

45. Para9 • Q What is the purpose of annealing？ • Key: the purposes of annealing are: alteration of ductility and toughness, induction of softness and refinement of grain structure and removal of gases and stresses. • Cn一般来说退火的目的是：改变延展性和韧性，增加软度，改善颗粒结构消除气体和应力。

46. Para10 • Q What is the purpose of normalizing？ • Key: It improves strength and machinability.

47. Para11 • What is spheroiziding? • Key: Spheroidizing is a form of annealing consisting of prolonged heating of iron base alloys at a temperature in the neighborhood of, but generally slightly below the critical range, usually followed by a relatively slow cooling. Spheroidizing causes the graphite to assume a spheroidal shape, hence the name.

48. Exercises • 1. Words Matching • 2.Translation

49. 1. Words Matching • heat treatment 软化 • manufacturability 延展性, 柔软性 • formability n. 硬化 成型性能 • ductility n. • internal stress 材料改性 • soften v. 热处理 • hardening n. 可制造性 • material modification 内应力

50. 2.Translation • Spheroidizing is a form of annealing consisting of prolonged heating of iron base alloys at a temperature in the neighborhood of, but generally slightly below the critical range, usually followed by a relatively slow cooling. Spheroidizing causes the graphite to assume a spheroidal shape, hence the name. • 球化是一种退火工序要对铁基合金在接近但一般稍微低于临界范围的温度下进行长期加热，其后进行相对缓慢的冷却。球化使石墨形成球型，因此而得名。