機械專業(yè)英語董建國第4章

1、Unit 4Unit 4TEXT READING MATERIAL Unit 4TEXTConventional Milling VS Climb Milling There are two methods of milling，i.e. conventional or up milling and climb or down milling In conventional milling，the cutter rotates against the direction of feedThis method has long been regarded as the only practica

2、l way to use milling cutters. Not long ago, climb milling was recognized as an acceptable method of operation. In climb milling，the cutter rotates in the direction of feed Unit 4 The advantages of climb milling are as follows: (1) Feed can frequently be doubled over conventional milling. (2) Metals

3、can be removed fast without vibration. (3) Finish can be considerably improved (4) Tool life may be prolongedUnit 4Fig. 4-1 Two methods of milling(a) Conventional (Up) milling；(b) Climb (Down) milling Unit 4 Both conventional milling and climb milling are being employed，because climb milling is not

4、applicable to any milling jobClimb milling can be applied only when the machine is of a heavy-duty type and backlash has been eliminatedClimb milling is not recommended for use on cast iron or forgings. Therefore, conventional milling remains useful in milling workUnit 4LEARN TO SPEAKMr. Liu: Good a

5、fternoon, Mr. Xiong.Mr. Xiong:Good afternoon, Mr. Liu.Mr. Liu: I have some trouble with heat treatment. Could you tell me?Mr. Xiong:What are the problems?Mr. Liu: Do you know what is the function of heat treatment?Mr. Xiong:Yes. I think I see. Heat treatment is a method by which the heat treater can

6、 change the physical properties of a material.Mr. Liu: How many types of heat treatment are there?Unit 4Mr. Xiong:There are three main operations in the heat treatment of steel: hardening, tempering and annealing.Mr. Liu: How is hardening operation done?Mr. Xiong:The hardening operation consists of

7、heating the steel above its critical range and then quenching it in a suitable medium such as water, brine, oil, or some other liquid. Having been hardened, the metal must be given a tempering treatment which consists of reheating the hardened steel to a temperature below the critical range, thus pr

8、oducing the required physical properties.Mr. Liu: And what is critical temperature?Unit 4Mr. Xiong: It is the temperature at which a certain change takes place in the physical condition of the steel.Mr. Liu: What is the purpose of annealing?Mr. Xiong: It can soften a work-piece and relieve internal

9、stresses produced by machining.Mr. Liu: Thank you telling me about these.Mr. Xiong: Im glad to have been of some service.Unit 4NEW WORDS AND EXPRESSIONSconventional kEn5venFEn(E)l adj. 一般的，常規(guī)的VS=versus 5v:sEs prep. 對，與相對climb klaIm v.&n. 攀登，爬i.e.=that is 即，就是regard rI5B:d v.&n. 認為，考慮recogniz

10、e 5rekEnaIz vt. 承認，認識acceptable Ek5septEb(E)l adj. 可接受的Unit 4frequent 5fri:kwEnt adj. 時常發(fā)生的，頻繁的frequently adv. 常常，屢次double 5dQb(E)l n. 兩倍adj. 兩倍的 vt. 使加倍vi. 加倍vibration vaI5breIF(E)n n. 振動，搖動considerable kEn5sIdErEb(E)l adj. 相當大(或多)的，重要的considerablely 相當大地prolong prE5lBN; (?) prEJ5lC:N vt. 延長，拖延appl

11、icable 5AplIkEb(E)l adj. 可適用的，合適的duty 5dju:tI; (?) 5du:tI n. 責(zé)任，功率，稅Unit 4backlash 5bAklAF n. 間隙，輪齒隙eliminate I5lImIneIt vt. 排除，消除recommend rekE5mend vt. 推薦，介紹cast kB:st; (?) kAst n. 鑄件v. 鑄造casting n. 鑄造，鑄件forge fC:dV n. 鍛工車間Unit 4v. 鍛造forging 鍛造，鍛件tempering v. 回火annealing v. 退火quenching n. 淬火brine

12、braIn n. 鹽水reheating ri:5hi:tIN n. 重新加熱Unit 4conventional milling 逆銑climb milling 順銑up milling 逆銑down milling 順銑regardas 認為是in a similar way 同樣in this way 這樣be recognized as 被認為是tool life 刀具壽命，刀具耐用度Unit 4heavy-duty 重型的cast iron 鑄鐵as follows 如下twist drill 麻花鉆high-speed steel 高速鋼heat treatment 熱處理Unit

13、 4heat treater 熱處理工作者physical properties of a material 材料的物理性能hardened steel 淬硬鋼critical range 臨界點internal stress 內(nèi)應(yīng)力critical temperature 臨界溫度Unit 4NOTES 1There are two methods of milling，i.e. conventional or up milling and climb or down milling 銑削方法有兩種：逆銑(即反向銑削)與順銑(即同向銑削)。 “or”可以表示“即”的意義，引出一個同位語。例如

14、: The cutting speed must be reduced in the first, or roughing cut 在初切(即粗切)時，切削速度必須降低。Unit 4 2In conventional milling，the cutter rotates against the direction of feed 逆銑時，銑刀旋轉(zhuǎn)方向與進給方向相反。 “against the direction of”的含義是“與的方向相反”。Unit 4 3This method has long been regarded as the only practical way to use

15、milling cutters. 這種銑削方法長期以來一直被認為是使用銑刀的惟一切實可行的方法。 to v 短語可以用來修飾名詞。這里的“to use”用來修飾前面的“way”。又例如: Conventional milling is not the only way to use milling cutters.逆銑不是使用銑刀的惟一方法。Unit 4 4In climb milling，the cutter rotates in the direction of feed 順銑時，銑刀順著進給方向旋轉(zhuǎn)。 “in the direction of ”的含義是“沿著的方向”。 5Climb m

16、illing can be applied only when the machine is of a heavy-duty type and backlash has been eliminated 只有在機床具有相當?shù)膭傂郧议g隙也已消除的情況下，才能使用順銑。 “be + of + 抽象名詞”可以表示“具有”或“屬于”等意義。句中“is of a heavy-duty type”的含義是“是重型的(剛性好的)”。再看下面兩個句子： Unit 4These supports are of great rigidity.這些支架具有很大的剛性。This machine is not of a

17、heavy-duty type.這臺機器不屬于重型的。 Unit 4EXERCISES 1Discuss the following questions in English: (1) What is the conventional milling? (2) What is the climb milling? (3) What are the differences between the conventional milling and the climb milling?Unit 4 2Use English for replacing Chinese or use Chinese f

18、or replacing English. (1) 進給方向 (2) 銑刀 (3) 粗切 (4) Method of operation (5) The direction of feed (6) Practical wayUnit 4READING MATERIALRoughing and Finishing Cut It is customary，in shop practice, to take at least two cuts make a job smooth and accurate The first cut to take is to remove excess metal

19、from the surface of the work-piece as rapidly as possibleTo do this，the cut should be as deep and the feed as coarse as the work-piece and the machine tool will standCutting speed should be adjusted downward, if necessary，to permit thisThe first，or roughing，cut should be deep enough to size the job,

20、 with a suitable allowance for a finishing cut, in one pass whenever possible Unit 4 When you intend to adjust the cutting speed or the feed to increase the rate of the of the production on a machine tool, it is advisable to increase the feed even though the speed must be reduced somewhatTo increase

21、 the feed rather than the cutting speed will increase production without a corresponding increase in power consumption and tool wearUnit 4 The purpose of the last，or finishing，cut is to finish a work-piece smooth and accurate. To accomplish this，the cut should be shallow and the feed fine and cuttin

22、g speed should be increased much higher than for the roughing cut. Roughing and finishing operations are usually not performed on the same machine. It is a common practice，for example，to rough-turn work-pieces on a lathe, and to finish them on a grinderSome machines, abrasive machines for instance, are known to perform both roughing and finishing operations Unit 4PROFESSIONAL WORDS AND PHRASES customary 5kQstEmErI; (?) 5kQstEmerI adj. 習(xí)慣的，通常的 least li:st adj. 最小的，