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1、机械加工类中英文翻译、外文翻译关于可机加工性的论述 英文原文：On the discussion of the machinabilityAbstract: The paper is about the concept of mamufacturing engineering and the ways of processing it.It explains the foundamental concept of manufacturing engineeing from the way of example and also offer us some konds of materials
2、can be used in manifacturing engineering.Keywords: manufacturing engineering、mterial、concept译文：20.9 MACHINABILITYThe machinability of a material usually defined in terms of four factors:Surface finish and integrity of the machined part;Tool life obtained;Force and power requirements;Chip control. Th
3、us, good machinability good surface finish and integrity, long tool life, and low force And power requirements. As for chip control, long and thin stringy cured chips, if not broken up, can severely interfere with the cutting operation by becoming entangled in the cutting zone.Because of the complex
4、 nature of cutting operations, it is difficult to establish relationships that quantitatively define the machinability of a material. In manufacturing plants, tool life and surface roughness are generally considered to be the most important factors in machinability. Although not used much any more,
5、approximate machinability ratings are available in the example below. Machinability Of SteelsBecause steels are among the most important engineering materials as noted in Chapter 5 , their machinability has been studied extensively. The machinability of steels has been mainly improved by adding lead
6、 and sulfur to obtain so-called free-machining steels.Resulfurized and Rephosphorized steels. Sulfur in steels forms manganese sulfide inclusions second-phase particles , which act as stress raisers in the primary shear zone. As a result, the chips produced break up easily and are small; this improv
7、es machinability. The size, shape, distribution, and concentration of these inclusions significantly influence machinability. Elements such as tellurium and selenium, which are both chemically similar to sulfur, act as inclusion modifiers in resulfurized steels.Phosphorus in steels has two major eff
8、ects. It strengthens the ferrite, causing increased hardness. Harder steels result in better chip formation and surface finish. Note that soft steels can be difficult to machine, with built-up edge formation and poor surface finish. The second effect is that increased hardness causes the formation o
9、f short chips instead of continuous stringy ones, thereby improving machinability.Leaded Steels. A high percentage of lead in steels solidifies at the tip of manganese sulfide inclusions. In non-resulfurized grades of steel, lead takes the form of dispersed fine particles. Lead is insoluble in iron,
10、 copper, and aluminum and their alloys. Because of its low shear strength, therefore, lead acts as a solid lubricant Section 32.11 and is smeared over the tool-chip interface during cutting. This behavior has been verified by the presence of high concentrations of lead on the tool-side face of chips
11、 when machining leaded steels.When the temperature is sufficiently high-for instance, at high cutting speeds and feeds Section 20.6 the lead melts directly in front of the tool, acting as a liquid lubricant. In addition to this effect, lead lowers the shear stress in the primary shear zone, reducing
12、 cutting forces and power consumption. Lead can be used in every grade of steel, such as 10xx, 11xx, 12xx, 41xx, etc. Leaded steels are identified by the letter L between the second and third numerals for example, 10L45 . Note that in stainless steels, similar use of the letter L means “low carbon,”
13、 a condition that improves their corrosion resistance. However, because lead is a well-known toxin and a pollutant, there are serious environmental concerns about its use in steels estimated at 4500 tons of lead consumption every year in the production of steels . Consequently, there is a continuing
14、 trend toward eliminating the use of lead in steels lead-free steels . Bismuth and tin are now being investigated as possible substitutes for lead in steels.Mental pipe cutting machine is the one mainly be used in the production of cars,industry and some work of putting materials.The work need to be
15、 finished is the design of body of the machine and the roll of it.It includes the design and calculate of the slowing speed box,.The choose of the electromotor,the design of the gearing,the rev,the measure design of the main deliver parts.Than do the emandation work.After all ,get the data and drawi
16、ng the engineering picture.It includes one final assembling picture,two assembling pictures of each parts,some small pictures of the important accessary.The design work we do this time is to the purpose of be used at the place of fanning pipe and draining pipe.This product also can be used at the si
17、tuation of enhancing the efficiency of production.Make the working effection upon and low down the labor force.Calcium-Deoxidized Steels. An important development is calcium-deoxidized steels, in which oxide flakes of calcium silicates CaSo are formed. These flakes, in turn, reduce the strength of t
18、he secondary shear zone, decreasing tool-chip interface and wear. Temperature is correspondingly reduced. Consequently, these steels produce less crater wear, especially at high cutting speeds.Stainless Steels. Austenitic 300 series steels are generally difficult to machine. Chatter can be s problem
19、, necessitating machine tools with high stiffness. However, ferritic stainless steels also 300 series have good machinability. Martensitic 400 series steels are abrasive, tend to form a built-up edge, and require tool materials with high hot hardness and crater-wear resistance. Precipitation-hardeni
20、ng stainless steels are strong and abrasive, requiring hard and abrasion-resistant tool materials.The Effects of Other Elements in Steels on Machinability. The presence of aluminum and silicon in steels is always harmful because these elements combine with oxygen to form aluminum oxide and silicates
21、, which are hard and abrasive. These compounds increase tool wear and reduce machinability. It is essential to produce and use clean steels.Carbon and manganese have various effects on the machinability of steels, depending on their composition. Plain low-carbon steels less than 0.15% C can produce
22、poor surface finish by forming a built-up edge. Cast steels are more abrasive, although their machinability is similar to that of wrought steels. Tool and die steels are very difficult to machine and usually require annealing prior to machining. Machinability of most steels is improved by cold worki
23、ng, which hardens the material and reduces the tendency for built-up edge formation.Other alloying elements, such as nickel, chromium, molybdenum, and vanadium, which improve the properties of steels, generally reduce machinability. The effect of boron is negligible. Gaseous elements such as hydroge
24、n and nitrogen can have particularly detrimental effects on the properties of steel. Oxygen has been shown to have a strong effect on the aspect ratio of the manganese sulfide inclusions; the higher the oxygen content, the lower the aspect ratio and the higher the machinability.The mechanical seal i
25、s depends on a pair of relative motion link end surface A fixed, another revolves together with axis the mutual fitting forms the small axial play plays the seal role, this kind of equipment is called the mechanical seal. The mechanical seal usually by moves the link, the static link, contracts the
26、part and the seal part is composed. Moves the link and the static link end surface composes a pair to rub, moves the link to depend on in the sealed chamber the liquid pressure to cause its shoulder up on the static link end surface, and produces on two links end surfaces suitable compared to presse
27、s and maintains an extremely thin liquid membrane to achieve the seal the goal. Contracts the part pressurize, may cause to pump under the operating condition, also maintains the end surface fitting, guaranteed the seal medium nothing more than leaks, and prevented the impurity enters seals the end
28、surface. Seals the part to play the seal to move the link and axis gap B, the static link and the gland gap C role, simultaneously to the vibration which pumps, attacks the cushioning effect. The mechanical seal in the actual movement is not an isolated part, it is with other spare parts which pumps
29、 combines the movement together, simultaneously may see through its basic principle, the mechanical seal normal operation has the condition, for instance: Otherwise fleeing measures a pump spindles being not able to very big, friction subsidiary end face can not form the ratio pressure demanding reg
30、ularly; The pump spindle that machinery hermetic sealing gets along can not have boundary very big deflection , end face waits a minute otherwise than pressure will be uneven. Besides only when satisfying similar such external condition, fine machinery seals off oneself function, ability reaches ide
31、al hermetic sealing effect. In selecting various elements to improve machinability, we should consider the possible detrimental effects of these elements on the properties and strength of the machined part in service. At elevated temperatures, for example, lead causes embrittlement of steels liquid-
32、metal embrittlement, hot shortness; see Section , although at room temperature it has no effect on mechanical properties.Sulfur can severely reduce the hot workability of steels, because of the formation of iron sulfide, unless sufficient manganese is present to prevent such formation. At room tempe
33、rature, the mechanical properties of resulfurized steels depend on the orientation of the deformed manganese sulfide inclusions anisotropy . Rephosphorized steels are significantly less ductile, and are produced solely to improve machinability. Machinability of Various Other Metals Aluminum is gener
34、ally very easy to machine, although the softer grades tend to form a built-up edge, resulting in poor surface finish. High cutting speeds, high rake angles, and high relief angles are recommended. Wrought aluminum alloys with high silicon content and cast aluminum alloys may be abrasive; they requir
35、e harder tool materials. Dimensional tolerance control may be a problem in machining aluminum, since it has a high thermal coefficient of expansion and a relatively low elastic modulus.Beryllium is similar to cast irons. Because it is more abrasive and toxic, though, it requires machining in a contr
36、olled environment.Cast gray irons are generally machinable but are. Free carbides in castings reduce their machinability and cause tool chipping or fracture, necessitating tools with high toughness. Nodular and malleable irons are machinable with hard tool materials.Cobalt-based alloys are abrasive
37、and highly work-hardening. They require sharp, abrasion-resistant tool materials and low feeds and speeds.Wrought copper can be difficult to machine because of built-up edge formation, although cast copper alloys are easy to machine. Brasses are easy to machine, especially with the addition pf lead
38、leaded free-machining brass . Bronzes are more difficult to machine than brass.Magnesium is very easy to machine, with good surface finish and prolonged tool life. However care should be exercised because of its high rate of oxidation and the danger of fire the element is pyrophoric .Molybdenum is d
39、uctile and work-hardening, so it can produce poor surface finish. Sharp tools are necessary.Nickel-based alloys are work-hardening, abrasive, and strong at high temperatures. Their machinability is similar to that of stainless steels.Tantalum is very work-hardening, ductile, and soft. It produces a
40、poor surface finish; tool wear is high.Titanium and its alloys have poor thermal conductivity indeed, the lowest of all metals , causing significant temperature rise and built-up edge; they can be difficult to machine.Tungsten is brittle, strong, and very abrasive, so its machinability is low, altho
41、ugh it greatly improves at elevated temperatures.Zirconium has good machinability. It requires a coolant-type cutting fluid, however, because of the explosion and fire. Machinability of Various MaterialsGraphite is abrasive; it requires hard, abrasion-resistant, sharp tools.Thermoplastics generally
42、have low thermal conductivity, low elastic modulus, and low softening temperature. Consequently, machining them requires tools with positive rake angles to reduce cutting forces , large relief angles, small depths of cut and feed, relatively high speeds, and proper support of the workpiece. Tools sh
43、ould be sharp.External cooling of the cutting zone may be necessary to keep the chips from becoming “gummy” and sticking to the tools. Cooling can usually be achieved with a jet of air, vapor mist, or water-soluble oils. Residual stresses may develop during machining. To relieve these stresses, mach
44、ined parts can be annealed for a period of time at temperatures ranging from to to , and then cooled slowly and uniformly to room temperature.Thermosetting plastics are brittle and sensitive to thermal gradients during cutting. Their machinability is generally similar to that of thermoplastics.Becau
45、se of the fibers present, reinforced plastics are very abrasive and are difficult to machine. Fiber tearing, pulling, and edge delamination are significant problems; they can lead to severe reduction in the load-carrying capacity of the component. Furthermore, machining of these materials requires c
46、areful removal of machining debris to avoid contact with and inhaling of the fibers.The machinability of ceramics has improved steadily with the development of nanoceramics Section and with the selection of appropriate processing parameters, such as ductile-regime cutting Section .Metal-matrix and c
47、eramic-matrix composites can be difficult to machine, depending on the properties of the individual components, i.e., reinforcing or whiskers, as well as the matrix material. Thermally Assisted MachiningMetals and alloys that are difficult to machine at room temperature can be machined more easily a
48、t elevated temperatures. In thermally assisted machining hot machining , the source of heata torch, induction coil, high-energy beam such as laser or electron beam , or plasma arcis forces, b increased tool life, c use of inexpensive cutting-tool materials, d higher material-removal rates, and e red
49、uced tendency for vibration and chatter.It may be difficult to heat and maintain a uniform temperature distribution within the workpiece. Also, the original microstructure of the workpiece may be adversely affected by elevated temperatures. Most applications of hot machining are in the turning of high-strength metals and alloys, although experiments are in progress to machine ceramics such as silicon
