铸造和铸造过程外文文献翻译中英文翻译材料加工铸造外文翻译.docx

1、铸造和铸造过程外文文献翻译中英文翻译材料加工铸造外文翻译铸造和铸造过程外文文献翻译、中英文翻译、材料加工铸造外文翻译 外文原文Casting and its processes IntroductionManufacturing process can be classified into two general groups known as primary and secondary processes The primary processes namely casting forging cold heading cold extruding brake forming and so

2、on are those that convert raw material into shapes These forming methods include both hot and cold working processes and in general will still require further finishing operations in order to obtain an end productThe secondary processes are those that bring the part to the dimensions and surface fin

3、ish specified One may also include in the secondary processes such operations as heat treating and surface treatments for corrosion resistance hardness and appearance Secondary processes are planning turning milling drilling boring reaming broaching grinding honing lapping polishing and special meth

4、ods of metal removal such as electrochemical machining Operations like screw cutting tapping thread milling gear cutting and so on are secondary processes that are merely adaptations of one of the aforementioned processes that are merely adaption of one of the aforementioned processes A complete dis

5、cussion of these procedures is beyond the scope of this text Therefore we will confine ourselves to succinct descriptions of the most prominent techniques12 Castings Castings are identified by the type of mold or the force required toy fill the mold Molds are either permanent or expendable The patte

6、rn of sand shell and plaster molds however can be used repeatedly for making new molds As the metal cools it takes the shape of the cavity The basic casting methods are described below Sand castings1 The green sand process is one in which most bonded sands packed around a wood or metal pattern The p

7、attern is then removed and molten metal is poured into the cavity When the metal solidifies the mold is broken and the casting is removed Almost any metal can be used with virtually no limit as to the size or shape of the part The method permits casting complex components at a low tooling cost and i

8、s the most direct route from pattern to casting Some machining is always necessary with the green sand process and large castings have rough surface finish Close tolerances are difficult to achieve and long thin projections should not be cast It is possible however to design for bosses undercuts and

9、 inserts The minimum core hole diameter advisable are aluminum3 1614 in and the minimum section thicknesses advisable are aluminum 316 in cooper 332 in iron 332 in magnesium5332 in and steel 1412 in 2 The dry sand process is similar to the green sand process except that core boxes are used in place

10、of patterns This method is usually limited to smaller parts than method 1 The sand is bonded with a setting binder and the core is then oven baked at 300400 to remove the moisture 3The carben dioxide sand process is one in which the sand molds are bonded whit sodium silicate solutions and set by for

11、cing carbon dioxide gas through the sand This type of mold is strong and permits the production of better dimensionally controlled castings than either method 1 or 2 4 The coresand mold process is one where the molds are put together completely from oven baked cores set with organic binders such as

12、oil or dextrines Shell Mold Casting This is a process where the molds are made by coating the sand with a thermosetting plastic The mold is then supported on the outsaid by sand or shot and molten metal is poured When the metal has solidified the mold is broken away from the finished casting Shell m

13、olding produces casting with smooth surfaces uniform grain structure high dimensional accuracy rapid production rate and minimal amount of finishing operations The minimum section thickniss castable is 11614 in but section differences where the imum minimum ratio is greater than 5 to 1 should be avo

14、ided Bosses undercuts and inserts are easily cast and the minimum cored hole diameter is 1814 in The method is relatively costly is limited to few metals Full-Mold Casting A process in which a green sand or cold-setting resin bonded is packed around a foamed plastic pattern for example polystyrene T

15、he plastic pattern is vaporized with the pouring of the molten metal into the mold An improved casting surface can be obtained by putting a refractory type of coating on the pattern surface before sand packing The pattern can be one piece or several pieces depending upon the complexity of the part t

16、o be cast The plastic patterns are handled easily They do not require any draft and produce no flash on the casting For small quantity production this method can be expensive depending upon the size and complexity of the casting The minimum recommended section thickness is 0 1 in and the imum sectio

17、n thickness is unlimited Bosses undercuts and inserts present no problem in this type of casting The minimum cored hole diameter is 14 in Permanent Mold Castings These are formed by a mold that can be used repeatedly Some applications have reported as many as 25 000 castings being made from the same

18、 mold Usually the mold requires some redressing after about 3000 uses The molds are machined of metal for example gray iron for casting nonferrous metals and cast itons Machined graphite molds are used to cast steel This method produces castings that have a good surface finish as well as a good grai

19、n structure low porosity and high dimensional accuracy The initial mold cost is relatively expensive but castings weighing as little as several ounces to castings are limited to relatively simple shapes and forms The imum recommended section thickness is about 20 in The minimum thickness however dep

20、endsuoon the material being cast as follows 316 in for iton 33218 in for aluminum 532 in for magnesium and 332 516 in for copper The minimum castable holes are 31614 in in diameter Die Casting A process used extensively in the quantity production of intricately shaped zinc alumimum lead and magnesiu

21、m alloys The method is limited in use with tin and copper alloys Castings are formed by forcing molten metal under pressures of 1500-25 000 psi into an accurately machined steel die The steel die which is water cooled is held together by a hydraulic press until the metal casting s solidifies To ease

22、 the ejection of the cast parts a lubricant is sprayed on the die forming surface and the ejection pins For small die cast components multiple cavity dies are used The surface finish of the resulting castings is quite smooth and has excellent dimensional accuracy Although the cost of production is r

23、elatively cheap the initial die cost is high Diecasting is limited to nonferrous metals and by the size of the part that can be cast The imum wall section thickness is usually restricted to 316 in but certainly to no greater than 050 in Plaster Mold Casting These are made by pouring a nonferrous all

24、oy for example aluminum copper or zinc alloy into a plaster mold which is then broken to remove the solidified casting The castings produced by this process are smooth have high dimensional accuracy low porosity and can be made in many intricate shapes The method however has disadvantages in that is

25、 limited to nonferrous metals small castings and also requires a relatively long time to make the molds The minimum wall section thickness is 0040-0060 in for a cast area that is less than 2 sq in For larger cast areas the minimum wall thickness increased accordingly The show process developed withi

26、n the last decade is a cost promising method It employs the use of plaster molds This procedure produces castings with fine detail and excellent dimensional accuracy and surface finish Ceramic Mold Casting This process uses a mold made of a ceramic powder binder and gelling agent The mold can also b

27、e made of a ceramic facing reinforced with a sand backing The method is restricted to casting intricate parts requiring fine detail close tolerances and smooth finishes The minimum wall thickness recommended is 0025-0050 in There is however no limit to the imum wall thickness Investment Casting Thes

28、e are made when parts are desired that are intricate in shape have excellent surface finish and require a high degree of dimensional accuracy In addition this method of casting permits the use of a variety of metal alloys and does not have In addition this method of casting permits the use of a vari

29、ety of metal alloys and does not have any metal flashing to be removed from the finishes castingThe technique of investment casting requires careful workmanship and expensive patterns and moths The minimum castable wall thickness is about 0025-0050 in and the imum thickness should not exceed 3 in Ce

30、ntrifugal Casting This is a method of casting a shape by pouting the molten metal into a rotating fladk containing the mold The molds are made of sand metal or graphite depending on the metal cast and are rotated about their axial centers either in a horizontal or vertical position Relatively large

31、diameter and bulky components are made are pipe gun barrels hollow shafts machinery drive rolls long sleeves tubing and so on Where the diameter to length ratio is rather large the rotational axis can be vertically mounted molds the method is called semmicentrifugal casting and it is used to make pa

32、rts such as wheels turbosupercharger diaphragms disks flywheels and so on Figure 1-5-2 shows a schematic section of a semicentrifugal casting of a cored flywheel Generally the method of centrifugal casting is expensive and is also limited in the shapes which can be cast However the castings made by

33、this mehod are very sound and have good dimensional accuracy It should also be noted that this method is the only way to obtain a large cylindrical part Continuous Casting This is a method whereby a molten metal is continuously gravity fed from a ladle into an ingot mold of a desired shape which is open at both ends As