2023年全國碩士研究生考試考研英語一試題真題(含答案詳解+作文范文)_第1頁
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1、<p><b>  附:外文翻譯 </b></p><p><b>  電火花加工</b></p><p>  電火花加工法對加工超韌性的導(dǎo)電材料(如新的太空合金)特別有價值。這些金屬很難用常規(guī)方法加工,用常規(guī)的切削刀具不可能加工極其復(fù)雜的形狀,電火花加工使之變得相對簡單了。在金屬切削工業(yè)中,這種加工方法正不斷尋找新的應(yīng)用領(lǐng)域。塑料

2、工業(yè)已廣泛使用這種方法,如在鋼制模具上加工幾乎是任何形狀的模腔。</p><p>  電火花加工法是一種受控制的金屬切削技術(shù),它使用電火花切除(侵蝕)工件上的多余金屬,工件在切削后的形狀與刀具(電極)相反。切削刀具用導(dǎo)電材料(通常是碳)制造。電極形狀與所需型腔想匹配。工件與電極都浸在不導(dǎo)電的液體里,這種液體通常是輕潤滑油。它應(yīng)當(dāng)是點的不良導(dǎo)體或絕緣體。 用伺服機構(gòu)是電極和工件間的保持0.0005~0.001英寸(

3、0.01~0.02mm)的間隙,以阻止他們相互接觸。頻率為20000Hz左右的低電壓大電流的直流電加到電極上,這些電脈沖引起火花,跳過電極與工件的見的不導(dǎo)電的液體間隙。在火花沖擊的局部區(qū)域,產(chǎn)生了大量的熱量,金屬融化了,從工件表面噴出融化金屬的小粒子。不斷循環(huán)著的不導(dǎo)電的液體,將侵蝕下來的金屬粒子帶走,同時也有助于驅(qū)散火花產(chǎn)生的熱量。</p><p>  在最近幾年,電火花加工的主要進步是降低了它加工后的表面粗糙

4、度。用低的金屬切除率時,表面粗糙度可達2—4vin.(0.05—0.10vin)。用高的金屬切除率[如高達15in3/h(245.8cm3/h)]時,表面粗糙度為1000vin.(25vm)。</p><p>  需要的表面粗糙度的類型,決定了能使用的安培數(shù),電容,頻率和電壓值??焖偾谐饘伲ù智邢鳎r,用大電流,低頻率,高電容和最小的間隙電壓。緩慢切除金屬(精切削)和需獲得高的表面光潔度時,用小電流,高頻率,低

5、電容和最高的間隙電壓。</p><p>  與常規(guī)機加工方法相比,電火花加工有許多優(yōu)點。</p><p>  1 . 不論硬度高低,只要是導(dǎo)電材料都能對其進行切削。對用常規(guī)方法極難切削的硬質(zhì)合金和超韌性的太空合金,電火化加工特別有價值。</p><p>  2 . 工件可在淬火狀態(tài)下加工,因克服了由淬火引起的變形問題。</p><p>  3

6、 . 很容易將斷在工件中的絲錐和鉆頭除。</p><p>  4 . 由于刀具(電極)從未與工件接觸過,故工件中不會產(chǎn)生應(yīng)力。</p><p>  5 . 加工出的零件無毛刺。</p><p>  6 . 薄而脆的工件很容易加工,且無毛刺。</p><p>  7 . 對許多類型的工件,一般不需第二次精加工。</p><

7、p>  8 .隨著金屬的切除,伺服機構(gòu)使電極自動向工件進給。</p><p>  9 .一個人可同時操作幾臺電火花加工機床。</p><p>  10.能相對容易地從實心坯料上,加工出常規(guī)方法不可能加工出來的極復(fù)雜的形狀。</p><p>  11.能用較低價格加工出較好的模具。</p><p>  12.可用沖頭作電極,在陰模板上復(fù)制

8、其形狀,并留有必須的間隙。</p><p>  Electrical discharge machining</p><p>  Electrical discharge machining has proved especially valuable in the machining of super-tough, electrically conductive materials su

9、ch as the new space-age alloys. These metals would have been difficult to machine by conventional methods, but EDM has made it relatively simple to machine intricate shapes that would be impossible to produce with conven

10、tional cutting tools. This machining process is continually finding further applications in the metal-cutting industry. It is being used extensively </p><p>  Electrical discharge machining is a controlled m

11、etal removal technique whereby an electric spark is used to cut (erode) the workpiece, which takes a shape opposite to that of the cutting tool or electrode. The cutting tool (electrode) is made from electrically conduct

12、ive material, usually carbon. The electrode, made to the shape of the cavity required, and the workpiece are both submerged in a dielectric fluid, which is generally a light lubricating oil. This dielectric fluid should

13、be a noncond</p><p>  In the last few years, major advances have been made with regard to the surface finishes that can be produced. With the low metal removal rates, surface finishes of 2 to 4 um. (0.05 to

14、0.10um) are possible. With high metal removal rates finishes of 1 000uin. (25um) are produced.</p><p>  The type of finish required determines the number of amperes which can be used, the capacitance, freque

15、ncy, and the voltage setting. For fast metal removal (roughing cuts), high amperage, low frequency, high capacitance, and minimum gap voltage are required. For slow metal removal (finish cut) and good surface finish, low

16、 amperage, high frequency, low capacitance, and the highest gap voltage are required.</p><p>  Electrical discharge machining has many advantages over conventional machining processes.</p><p>  

17、1. Any material that is electrically conductive can be cut, regardless of its hardness. It is especially valuable for cemented carbides and the new supertough space-age alloys that are extremely difficult to cut by conve

18、ntional means.</p><p>  2. Work can be machined in a hardened state, thereby overcoming the deformation caused by the hardening process.</p><p>  3. Broken taps or drills can readily be removed

19、from workpieces. </p><p>  4. It does not create stresses in the work material since the tool (electrode) never comes in contact with the work.</p><p>  5. The process is burr-free.</p>&

20、lt;p>  6. Thin, fragile sections can be easily machined without deforming.</p><p>  7. Secondary finishing operations are generally eliminated for many types of work.</p><p>  8. The process

21、is automatic in that the servomechanism advances the electrode into the work as the metal is removed.</p><p>  9. One person can operate several EDM machines at one time.</p><p>  10. Intricate

22、shapes, impossible to produce by conventional means, are cut out of a solid with relative ease.</p><p>  11. Better dies and molds can be produced at lower costs.</p><p>  12. A die punch can be

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