机械毕业设计英文外文翻译163钢.docx

1、机械毕业设计英文外文翻译163钢英文原文: SteelsSteel is one of the most valuable metals known to man; approximately 200 million tons can be produced in the United States annually. In 1900, US capacity was but 21 million tons. Although the process of steelmaking is familiar to most engineers, a review of this process w

2、ould be appropriate at this time.Iron ore, limestone, and coal are the principal raw materials used in making iron and steel. Coke is produced by heating bituminous coal in special ovens. Skip cars go up the skip hoist with loads of iron ore, coke, and limestone and dump them into the top of the bla

3、st furnace. Hot air from the stove is blown into the furnace near the bottom. This causes the coke to burn at temperatures up to 3000F. The ore is changed into drops of molten iron that settle to the bottom of the blast furnace. The limestone that has been added joins with impurities to form a slag

4、that floats on top of the pool of liquid iron. Periodically , the molten iron is drained into a ladle for transporting to either the Bessemer converter, electric furnace or open-hearth furnace. The slag is removed separately so as mot to contaminate the iron.The making of steel from iron involves a

5、further removal of impurities. Regardless of which process is used for making steel-open-hearth, Bessemer-converter, or electric-furnace-steel scrap is added along with desired alloying elements and the impurities are burned out.Liquid steel removed from the furnace is poured into ingot molds. The i

6、ngots are then removed to “soaking pits” where they are brought to a uniform rolling temperature.At the rolling mill, the white-hot steel passes through rolls that form the plastic steel into the desired shape: blooms, slabs, or billets. These three semifinished shapes then go to the finishing mills

7、 where they are rolled into finished forms as structural steel, plates and sheets, rods, and pipes.Steel is the basic and most valuable material used in apparatus manufactured today. Its application is based on years of engineering experience, which serves as a guide in choosing a particular type of

8、 steel. Each variable, such as alloy, heat treatment, and processes of fabrication has its influence on the strength, ductility, machinability, and other mechanical properties, and affects the type of steel selected. The following basic concepts also assist in determining which steel should be used:

9、1. The modulus of elasticity in tension falls within the range of 28106to 30106lb/in2, regardless of composition or form; therefore, sizes as determined by deflection remain the same regardless of the steel chosen.2. Carbon content determines the maximum hardness of steel regardless of alloy content

10、. Therefore, the strength desired, which is proportional to hardness, can determine the carbon content.3. The ability of the steel to be uniformly hardened throughout its volume depends on the amount and kind of alloy. This is more complex, but does not necessarily change the calculation of the size

11、 of the part. 4.Ductility decreases as hardness increases.The preliminary choice of steel for a part as well as for other factors, such as notch sensitivity, shrinkage, blowholes, corrosion, and wear, is simplified when based on the above principles. The final selection is made by matching the mater

12、ial with the process of manufacture used in order to obtain the shape, surface, and physical requirements of the part. The selection may be made from among low-carbon steels, low-alloy steels, high-carbon steels, and high-alloy steels.Steel is one of the few common metals that has an endurance limit

13、. You will recall that fatigue is the failure of a material due to repeated loading. Most metals become tired as they are subjected to stress over and over again. The stress a material can withstand under constant loading is much less than under static loading. As steel is continually loaded, it wil

14、l reach a lower limit of strength. This property is quite pronounced in wire shapes. Common copper and aluminum wire can easily be broken by flexing the wire in a local spot. Normally after a few dozen flexes, the wire breaks. Steel wire, however, is very tough and flexing the wire simply cold works

15、 the material making the process futile for the unknowing person trying to break a steel wire. At some point steel will resist weakening due to repeated loading. This is known as an “endurance limit”. The endurance limit of steel is around 60% of its original strength.This property of having an endu

16、rance limit makes steel invaluable for use in structural applications like bridges, springs, struts, beams, etc. Of course, there are many factors that effect the endurance limit of a material. A primary factor is the surface quality of the material and/or the manufacturing process used to produce t

17、he specimen.Fatigue is attributable to the initial material mot being an ideal homogeneous solid. In each half cycle, irreversible minute strains are produced. Fatigue failure usually develops from:1.Repeated cyclic stresses that cause incremental slip and cold working locally in the material.2.Grad

18、ual reduction of ductility of the strain hardened areas that develop into cracks.3.A notching effect from submicroscopic cracks.The endurance limits of steels create some very desirable physical properties. These properties can be detrimental to the manufacturability of the material. For instance, i

19、n the cold rolling of steel the endurance limit creates a limitation on the amount of cold working that can be input to any part. After this limit has been reached the material must be heated above its critical temperature to permit further cold working.Plain carbon steels represent the major propor

20、tion of steel production. Carbon steels have a wide diversity of application, including castings, forgings, tubular products, plates, sheets and wire products, structural shapes, bars, and tools. Plain carbon steels, generally, are classified in accordance with their method of manufacture as basic o

21、pen hearth, acid open hearth, or acid Bessemer steels, and by carbon content.The principal factors affecting the properties of the plain carbon steels are the carbon content and the microstructure. The microstructure is determined by the composition of the steel (carbon, manganese, silicon, phosphor

22、us, and sulfur, which are always present, and residual elements including oxygen, hydrogen, and nitrogen) and by the final rolling, forging, or heat-treating operation. However, most of the plain carbon steels are used without a final heat treatment and , consequently, the rolling and forging operat

23、ions influence the microstructure.Carbon steels are predonminantly pearlitic in the cast, rolled, or forged conditions. The constituents of the hypoeutectoid steels are therefore ferrite and pearlite, and of the hypereutectoid steels are cementite and pearlite.Alloy steel is an alloy of iron and car

24、bon containing alloying elements, one or more of which exceeds the following: manganese, 1.65 percent; silicon, 0.60 percent; copper, 0.60 percent; and/or specified amounts of other alloying elements, including aluminum, boron , and chromium up 3.99 percent; cobalt, niobium, molybdenum, nickel, tung

25、sten, vanadium, zirconium, or other elements added in sufficient quantity to give the desired properties of the steel.Since there are more elements , some expensive, to be kept within the specified ranges in alloy steel than are required in carbon steel , alloy steel requires more involved technique

26、s of quality control and, consequently, is more expensive.Alloy steel can give better strength, ductility, and toughness properties than can be obtained in carbon steel. Consequently, the engineer should consider alloy steels I designs subject go high stresses and/or impact loading.Almost all alloy

27、steels are produced with fine-grain structures. A steel is considered to be fine-grained if its grain size is rated 5, 6, 7, or 8. Number1 grain size shows 1 .5 grains/in. of steel area examined at 100diameters magnification. Fine-grain steels have less tendency to crack during heat treatment and ha

28、ve better toughness and shock-resistance properties. Coarse grained steels exhibit better machining properties and may be hardened more deeply than fine-grained steels.To select the alloy steel that is best suited for a given design, the effects of the principal alloying elements must be taken into

29、account. They are as follows.1. Nickel provides toughness, corrosion resistance, and deep hardening.2. Chromium improves corrosion resistance, toughness, and hardenability.3. Manganese deoxidizes, contributes to strength and hardness, decreases the critical-cooling rate.4. silicon deoxidizes, promot

30、es resistance to high-temperature oxidation, raises the critical temperature for heat treatment, increases the susceptivity of steel to decarburization and graphitization.5. Molybdenum promotes hardenability, increases tensile and creep strengths at high temperatures.6. vanadium deoxidizes, promotes

31、 fine-grained structure.7. Copper provides resistance to corrosion and acts as strengthening agent.8. Aluminum deoxidizes, promotes fine-grained structure, and aids nitriding.9. boron increases hardenability.The term “stainless steel” denotes a large family of steels containing at least 11.5percent

32、chromium. They are not resistant to all corroding media.Stainless steel competes with nonferrous alloys of copper and nickel on a corrosion-resistance and cost basis and with light metals such as aluminum and magnesium on the basis of cost and strength-weight ratio. Stainless steel has a number of a

33、lloy compositions and there are many supplies. Information on its properties and fabrication can be obtained readily. Sound techniques have been evolved for casting, heat treating, forming, machining, welding, assembling, and finishing stainless steel. It will be found that this material usually work-hardens(which make