課件參考留德hot processe

1、Hot ProsMetal CastingFundamentals of Metal-Casting1. Definition: The Casing pros basically involves pouring molten metal o a mold patterned after the part to be manufactured, allowing itto cool, and removing the metal from the mold.Important considerations in casting operations are as follows:1).2).

2、3).the the theflow of the molten metal o solidification and cooling of influence of the type of moldthe mold the metal materialhe mold2. The significant factors affecting castings sh, size, uniformity,and chemical comition are the type of metal; the thermal propertiesof both the metal and the mold;

3、the geometric relationship betn volumeand surface area of the casting; and the shof themold.3. Produce of solidification,Metaldropstofreezing erface)pothesolidificationfront(solid-liquid metalsolidifyingmovesthrough owardthe the centermoltenfrom the mold walls4. As the driving force of the heat tran

4、sfer is reduced away from the moldwalls, the grainse equiaxed and coarse. Such grain development isknown as homogenous cleation.5. The width of the mushy zone, where both liquid and solid phases are present, is an important factor during solidification. This zone isdescribedermsof a temperature diff

5、erence, FR=TL-TS.TS= temp of solidknown as the freezingrange, as follows: TL= temp of liquid6. The type of solidification depends on the comition of the eutectic.7. Casting is a solidification pros in whiolten metal is pouredo a mold and allowed to cool. Bernoullis theorem, the continuity law,and th

6、e Reynolds number are theytical tools used in designing, withthe goal of an appropriate flow rate and the elimination of defectsassoted with fluid flow.8. Solidification of pure metals takes placeonstant temperature,alloys occurs over a range of temperature. Phase diagrams are importanttoolsforident

7、ifyingthesolidificationpoorposfortechnologically important materials.9There are 7 kind of casting defects have been identified: 1)Blow 2)Scar 3)Blister 4)Scab 5)Wash 6)Misrun 7)Cold shut10. New and advanced technology for modern casting industry: Argon-oxygen decarburization and deoxidation, electro

8、slag remelting, ladle metallurgy, plasma refining, calcium wire injection.KEYWORDSAspiration抽吸 Bernoullis theorem Casing 鑄件，鑄造定律Chills 金屬型，冷鐵，白口層，激冷 Columnar dendrites 柱狀枝晶 Columnar grains 柱狀晶Cored dendrites 芯部枝晶Fluidity性Freezing range 凝固區(qū)間，凝固范圍Gate 澆道口Gating system 澆鑄系統(tǒng)Heterogeneous nucleation 異質(zhì)結(jié)核

9、，多相成核 Homogenous nucleation 均質(zhì)結(jié)核，單相成核 Macrosegregation 宏觀偏析Microsegregation 微觀偏析Mold 鑄型，錠模Mushy zone 固液相混合區(qū)，糊狀區(qū)Reynlods number 雷諾數(shù)Re=vd/，其中 v、 分別為流體的流速、密度與黏性系數(shù)，d 為一特征長度Risers 冒口Runners 橫澆口，流槽 Segregation 偏析 Shrinking 縮孔，收縮 Skin 鑄造表面 Solidification 凝固 Sprue 直澆口 Turbulence 湍流，紊流Metal-Casting Proses1.

10、Type of casting and their advantages and limiions Sand: A: almost any metal cast, no limit to size, shor weight, lowtooling cost; L: some finishing required, somewhat coarse finish, wide tolerance.Smold: A: Good dimenal accuracy and surface finish, highproduction rate. L: part size limited, expensiv

11、e patterns and equipment required.Expendable pattern: A: Most metals cast with no limit to size, complexsh. L: pattern have low strengnd can be costly for lowties.Plaster mold A:ricate shs, good dimenal accuracy and finish,low porosity. L: limited to nonferrous metals, limited size and volume of pro

12、duction, mold making time relatively long.Ceramic mold: A: ricate sh s, close tolerance parts, good surface finish. L: limited size.Investment: A: ricate size, excellent surface finish and accuracy, almost any metal cast. L: part size limited, expensive patterns, mold, and labor.Permanent mold: A: g

13、ood surface finish and dimen al accuracy, low porosity, high production rate. L: High mold cost, limited sh andricacy, not suitable for high-melting po metals.Die: A: excellent dimenal accuracy and surface finish, highproduction rate. L: Die cost is high, part size limited, usually limited to nonfer

14、rous metals, long lead time.Centrifugal: A: production rate.large cylindrical parts with good quality, highL:equipment is expensive, parts shlimited.2. Casting proses are generally classified as expendable-mold orpermanent-mold casting.3.Benefit of permanent casting; economical for large production

15、runs,scrap loss is low and dimen surface details.al accuracy is relative high, with good4.Environmental impact of foundry operations is an important aspect of casting metals.KEYWORDSBinders 粘結(jié)劑Centrifugal casting 離心鑄造 Ceramic-mold casting 陶瓷鑄造 Chaplets 芯撐Comite 復(fù)合型Core prs 芯頭，芯座Cores 型芯Crystal growi

16、ng 晶體長大 Die casting 壓鑄 Expendable-pattern casting Foundry 鑄造，鑄造廠一次模鑄造Investment casting 熔模鑄造Leviion melting 懸浮鑄造Lost-wax pros 失蠟法Permanent-mold casting型鑄造Preci Pre Racasting 精密鑄造，熔模鑄造，精密鑄件re casting 壓力鑄造prototy快速母模成型Sand Scasting 砂型鑄造-mold casting 殼型鑄造Squeeze casting 擠壓鑄造Vacuum casting 真空鑄造Metal Cas

17、ting：Design， Materials, and Economics1.Conditions affect casting: Characteristics of the metals and alloys casting, the method of casting, the mold and die materials, the molddesign, and various pros parameters, the molten metal in thecavities, the gating system, the rate of cooling, the rate of coo

18、ling, the gases evolved.2.It is important to considert these factors in the casting:weldability,bility, and surface conditions.3.These factors influence the overall cost are: materials, molds, dies, equipment, labor.Cast stainless steels with improved corro4.KEYWORDSCast iron 鑄鐵Compacted graphite ir

19、on儒墨鑄鐵Nodular cast iron 球墨鑄鐵 Machining allowance 加工余量 Porosity 氣孔率Shrinkage cavities 縮孔，縮穴Forming and Sha Rolling of MetalsProses and Equipment1. Rolling is the pros of reducing the thickness of a long workpieceby compressive force appd through a set of rolls. Plates, which aregenerally regarded as

20、having greatern 6mm, and sheets are generallylessn 6mm thick.2. Rolling mills have a variety of roll configurations, such as two-high, three high, four-high, cluster, and tandem.KEYWORDSCast structure 鑄造組織Wrought structure 鍛造組織F1.ing of MetalsFing is a pros in which the workpiece is shd by compressi

21、veforappd though various dies and tools.2.Typical fed products are bolts and rivets, connecting rods, shaftsfor turbines, gears, hand tools, and structural components formachinery, aircraft, railroads, and a variety of other transpor equipment.ion3.Metal flow and grain structure can be controlled, s

22、o fed parts havegood strengnd toughness, they can be used reliably for highly stressed and critical applications.4.5.Catalogs: cold fing, warm fing, hot fing., and the workpiece good surfaceCold fing: requires greater forand dimenal accuracy. Hot fing: requires smaller for surface are not as good.it

23、produdimenal accuracy and6.Ingots or billets -Heating and heat protectFreefing, Open die fing, closed die fing, etcMachinery,heat treatment, clear, inspection.Workpiece materials behavior during deformation, friction, heat7.transfer, and material-flow characteristicshe dieareimportant considerations

24、, as are the proper selection of die materials, lubricants, workpiece and die temperatures, speeds, and equipment.8.Fing denotes a family ofmetalworking proses in whichdeformation of the workpiece iscarried out by compressive for ing is capable of producing a wideappd through a set of dies. Fvariety

25、 of structural parts with favorable characteristicch asstrength, toughness, dimenal accuracy, and reliability in service.9.Thercing force depends on the cross-sectional area and the tipgeometry of the punch, on the strength of material, and on the magnitudeof friction at the slidingerfa. The pre to

26、five times the strength of the material.re may rang from threeKEYWORDSClosed-die f Cogging 開坯ing 閉式模鍛Coining 壓印，精壓Edging 修邊End grain 端面晶粒Flash 飛邊Feability 可鍛性Hammers 鍛錘熱實驗Incremental f Isothermal fing 步進(jìn)鍛造 ing 等溫鍛造 ing 凈成形鍛造Net-sh Open-die Piercing Preciffing 開式模鍛沖孔fing 精密鍛造Presses 壓力機(jī)Hydraulic pres

27、ses 水壓機(jī)Oil hydraulic presses 油壓機(jī)Manipulator 操作機(jī)Roll fing 滾鍛Sheet-Metal Forming ProShearing 沖裁sesCommon Bending Operations 普通彎曲工藝Stretch Forming 拉伸成形Deep Drawing 深拉Rubber Forming 橡膠成形1.Compared to those made by casting and fing, sheet-metal parts offerthe advantages of light weight and versatile sh.2

28、.Characteristics of sheet-metal forming prosesRoll forming: long parts with constant complex cross-section, goodsurface Stretch low-finish, high production rates, high tooling costs. forming: large parts with shallow contours, suitable forty production, high tooling and equipment costs depend onpart

29、 size.Drawing: Shallow or deep parts with relatively simple sh production rates, high tooling and equipment costs.s, highSt eming: Includes a variety of operations, such as punching, bling,sing, bending, flanging, and coining, simple or complex shs beformed at high production rates, tooling and equi

30、pment costs canhigh, but lalow.Rubber forming: Drawing and emsing of simple or complex shs,sheetrface protected by rubber membranes, flexibility of operation,low tooling costs.Spinning: Small or large axisymmetric parts, good surface finish, lowtooling costs, but labor costs can be hig automated.les

31、s operations areSuplastic forming: Complex shs, fine details and closetoleran, forming times are ling, hence forming production rates arelow, parts not suitable for high-temperature use.Peen forming: Shallow contours on large sheets, flexibility ofoperation, equipment costs can be high, pros is also

32、 used forstraightening parts.Explosive forming: Very large sheets with relatively complex shs,although usually axisymmetric, low tooling cost, but high labor cost,suitable for low-ty production, long cycle times.Magnetic-pulse forming: Shallow forming, bulging, and emsingoperations on relatively for

33、ming low-strength sheets, most suitablefor tubular shs, high production rates, requires spel tooling.3.Sheet-metal forming proses are among the most versatile of alloperations. They ate generally used on workpiehaving high ratiosof surface area to thickness. Unlike in bulk deformation prosechas fing

34、 and extru, the thickness of the metal in sheet formingis generally prevented from being reduced, to avoid necking and tearing.Important material parameters are the quality of the sheared edge of the sheet metal prior to forming, the capability of the sheet to stretch4.uniformly, and the materialsto

35、 thinning, its normal andplanar anisotropy, its grain size, and its yield-poelongation(for low-carbon steels)5.Because of the relatively thaterials used, spring back, buckling,and wrinking are significant problems in sheet forming. Springback is a function of the yield stress, the elastic modulus, a

36、nd the ratio of bend radius to thickness. These problem can be reduced or eliminated by proper tool and die design. By minimizing the unsupported lengthof the sheet during pro ing sheet and its Several test methodssing and by controlling the thickness of the mechanical properties.have been developed for predicting the6.formability