Aluminum Casting Processes http://www.totalmateria.com/pag http://www.totalmateria.com/page.aspx?ID=CheckArticle&site=kt e.aspx?ID=CheckArticle&site=ktn&N=!" n&N=!" Rezumat:
Aluminum Aluminum is one o# the #ew metals that can $e cast $% all o# the processes processes use in castin casting g metals metals.. 'hese 'hese proc processe esses( s( in ecrea ecreasin sing g orer orer o# amount amount o# alumin aluminum um casting( are: ie casting( permanent mol casting( san casting )green san an r% san*( plaster casting( in+estment casting( an continuous casting. ,ther processes such as lost #oam( s-ueee casting( an hot isostatic pressing are also mentione. Aluminum is one o# the #ew metals that can $e cast $% all o# the processes use in casting metals. 'hese processes( in ecreasing orer o# amount o# aluminum casting( are: ie casting( permanent mol casting( san casting )green san an r% san*( plaster casting( in+estment casting( an continuous casting. ,ther processes such as lost #oam( s-ueee casting( an hot isostatic pressing are also mentione. 'here are are man% #actors #actors that aect selection o# a casting process process #or #or proucing proucing a speci0c speci0c aluminum allo% part. 'he most important #actors #or all casting processes are: 1easi$ilit% an cost #actors 2ualit% #actors.
In terms o# #easi$ilit%( man% aluminum allo% castings can $e prouce $% an% o# the a+aila$l a+aila$le e methos. methos. 1or 1or a consie consiera$l ra$le e num$er num$er o# casting castings( s( howe+er( howe+er( imensions imensions or esign #eatures automaticall% etermine the $est casting metho. 3ecause metal mols weigh #rom 45 to 455 times as much as the castings the% are use in proucing( most +er% large cast proucts are mae as san castings rather than as ie or permanent mol castings. 6mall castings usuall% are mae with metal mols to ensure imensional accurac%. 2ualit% #actors are also important in the selection o# a casting process. process. 7hen applie to castings( the term -ualit% re#ers to $oth egree o# sounness )#reeom #rom porosit%( cracking( an sur#ace imper#ections* an le+els o# mechanical properties )strength an uctilit%*. 8owe+er( it shoul $e kept in min that in ie casting( although cooling rates are +er% high( air tens to $e trappe in the casting( which gi+es rise to apprecia$le amounts o# porosit% porosit% at the center. center. 9xtensi+e research research has $een conucte to 0n wa%s o# reucing reucing such porosit% howe+er( it is i;cult i# not impossi$le to eliminate completel%( an ie castings o#ten are lower in strength than low
Die Casting
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Allo%s o# aluminum are use in ie casting more extensi+el% than allo%s o# an% other $ase metal. In the nite 6tates alone( a$out >.! $illion ollars worth o# aluminum allo% ie castings is prouce each %ear. 'he ie casting process consumes almost twice as much tonnage o# aluminum allo%s as all other casting processes com$ine. Die casting is especiall% suite to prouction o# large -uantities o# relati+el% small parts. Aluminum ie castings weighing up to a$out ! kg are common( $ut castings weighing as much as !5 kg are prouce when the high tooling an casting
7ith ie casting( it is possi$le to maintain close tolerances an prouce goo sur#ace 0nishes. Die castings are $est esigne esigne with uni#orm uni#orm wall thickness: thickness: minimum practical wall thickness #or aluminum allo% ie castings is epenent on casting sie. Die castings are mae $% inection o# molten metal into metal mols uner su$stantial press pressur ure. e. Eapi Eapi inect inection ion an an rapi rapi solii solii0c 0cati ation on une unerr high high pres pressur sure e com$in com$ine e to prouce prouce a ense( ense( 0ne
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Allo% !4.5 is occasionall% speci0e when highest corrosion resistance is re-uire. 'his allo%( howe+er( has low Guiit% an some tenenc% to hot shortness. It is i;cult to cast( which is reGecte in higher cost per casting.
Permanent mol casting Perman ermanent ent mol mol )gra+ )gra+it% it% ie* ie* casti casting( ng( like like ie ie casti casting( ng( is suite suite to high< high<+ol +olum ume e prouction. Permanent mol castings t%picall% are larger than ie castings. aximum weight o# permanent mol castings usuall% is a$out 45 kg( $ut much larger castings sometimes are mae when costs o# tooling an casting e-uipment are usti0e $% the -ualit% re-uire #or the casting. Perma Permanent nent mol casting castings s are gra+it%<#e gra+it%<#e an pouring pouring rate is relati+ relati+el% el% low( low( $ut the metal metal mol mol prouc prouces es rapi rapi solii0c solii0cati ation. on. Perma Permanent nent mol castings castings exhi$it exhi$it excell excellent ent mechanic mechanical al propert properties. ies. Casting Castings s are generall generall% % soun( soun( pro+ie pro+ie that that the allo%s allo%s use exhi$it goo Guiit% an resistance to hot tearing. echanical properties o# permanent mol castings can $e #urther impro+e $% heat treatment. I# maximum properties are re-uire( the heat treatment consists o# a solution treatment at high temperature #ollowe $% a -uench an then natural or arti0cial aging. 1or small castings in which the cooling rate in the mol is +er% rapi or #or less critical parts( the solution treatment an -uench ma% $e eliminate eliminate an the #ast cooling in the mol relie on to retain in solution the compouns that will prouce age harening. 6ome common aluminum permanent mol casting allo%s( an t%pical proucts cast #rom them( are presente $elow. Allo% @.5 < Automoti+e pistons Allo%s Allo%s @!!.5 @!!.5(( C@!!. C@!!.5( 5( A@!H.5 A@!H.5 < 'imin 'iming g gears gears(( impell impellers ers(( compr compress essors ors(( an an aircr aircra# a#tt an missil missile e components re-uiring high strength Allo%s @!.5( A@!.5 < achine tool parts( aircra#t wheels( pump parts( marine harware( +al+e $oies ,ther aluminum allo%s commonl% use #or permanent mol castings inclue >".5( @4".5( an @@@.5.
6an casting 6an casting( which in a general sense in+ol+es the #orming o# a casting mol with san( inclues con+entional san casting an e+aporati+e pattern )lost<#oam* casting. In con+entional san casting( the mol is #orme aroun a pattern $% ramming san( mixe with the proper $oning agent( onto the pattern. 'hen the pattern is remo+e( lea+ing a ca+it% in the shape o# the casting to $e mae. I# the casting is to ha+e internal internal ca+ities or unercuts( san cores are use to make them. olten metal is poure into the mol( an a#ter it has solii0e the mol is $roken to remo+e the casting. In making mols an cores( +arious agents can $e use #or $oning the san. 'he agent most o#ten use is a mixture o# cla% an water.
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Casting -ualit% is etermine to a large extent $% #ounr% techni-ue. Proper metal< hanlin hanling g practice practice is necessar necessar% % #or o$taini o$taining ng soun soun casting castings. s. Complex Complex casting castings s with +ar%ing wall thickness will $e soun onl% i# proper techni-ues are use.
9+aporati+e )lost<#oam* pattern casting 9+aporati+e pattern casting )9PC* is a san casting process that uses an un$oune san mol with an expena expena$le $le pol%st%ren pol%st%rene e pattern pattern place insie o# the mol. 'his 'his process is somewhat similar to in+estment casting in that an expena$le material can $e use to #orm relati+el% intricate patterns in a surrouning mol material. nlike in+estment casting( howe+er( e+aporati+e pattern casting )9PC* in+ol+es a pol%st%rene #oam pattern that +apories uring the pouring o# molten metal into a surrouning mol o# un$oune san.
6hell ol Casting In shell mol casting( the molten metal is poure into a shell o# resin<$one san onl% 45 to >5 mm thick < much thinner than the massi+e mols commonl% use in san #ounrie #ounries. s. 6hell 6hell mol castings castings surpass surpass orinar% orinar% san san casting castings s in sur#ace sur#ace 0nish 0nish an imen imensio sional nal accur accurac% ac% an an cool cool at sligh slightl% tl% high higher er rates rates howe+ howe+er( er( e-uip e-uipmen mentt an an prouction are more expensi+e.
Plaster Casting In this metho( either a permea$le )aerate* or impermea$le plaster is use #or the mol. 'he plaster in slurr% #orm is poure aroun a pattern( the pattern is remo+e an the plaster mol is $ake $e#ore the casting is poure. 'he high insulating +alue o# the plaster allows castings with thin was to $e poure. inimum wall thickness o# aluminum plaster castings t%picall% is 4.! mm. Plaster mols ha+e high reprouci$ilit%( permitting castings to $e mae with 0ne etails an close tolerances. echanical properties an casting -ualit% epen on allo% composition an #ounr% techni-ue. 6low cooling ue to the highl% insulating nature o# plaster mols tens tens to magni magni#% #% solii solii0c 0cati ation on
"!.5( @!!.5( C@!!.5( @!.5 an A@!.5.
In+estment casting In+e In+est stme ment nt cast castin ing g o# alum alumin inum um most most comm common onl% l% empl emplo% o%s s plas plaste terr mol mols s an an expena expena$le $le pattern patterns s o# wax or other other #usi$le #usi$le materials. materials. Plaster Plaster slurr% slurr% is in+este in+este aroun patterns #or se+eral castings( an the patterns are melte out as the plaster is $ake.
In+estment casting prouces precision parts aluminum castings can ha+e walls as thin as 5.5 to 5.H! mm. 8owe+er( in+estment moling is o#ten use to prouce large -uantities o# intricatel% shape parts re-uiring no #urther machining so internal porosit% selom is a pro$lem. 3ecause o# porosit% porosit% an slow solii0cation( solii0cation( mechanical properties are low. In+estment castings usuall% are small( an it is especiall% suite to prouction o# ewelr% an parts #or precision precision instruments. Eecent strong strong interest $% the aerospace inustr% in the in+estment casting process has resulte in limite use o# impro+e technolog% to prouce premium -ualit% castings. Com$ining this accurate imensional control with the high an care#ull% controlle mechanical properties can( at times( usti#% casting costs an prices normall% not consiere practical. Aluminu Aluminum m allo%s allo%s commonl% commonl% use #or in+estme in+estment nt casting castings s are >5.5( >5.5( >"!.5( >"!.5( @5.5( @5.5( @!!.5( @!.5( @(5( !4.5( !@!.5 an H4>.5.
Centri#ugal Casting Centri#uging is another metho o# #orcing metal into a mol. 6teel $ake san( plaster( cast iron( or graphite mols an cores are use #or centri#ugal casting o# aluminum. etal etal ies ies or mols mols pro+i pro+ie e rapi rapi chilli chilling( ng( resul resultin ting g in a le+el le+el o# soun sounn ness ess an mechanical properties compara$le or superior to that o# gra+it%
Continuous Casting Bong shapes o# simple cross section )such as roun( s-uare( an hexagonal ros* can $e prouce $% continuous casting( which is one in a short( $ottomless( water
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Hot isostatic pressing Hot isostatic pressing of aluminum castings reduces porosity and can thus decrease the scatter in mechanical properties. The method also makes possible the salvaging of castings that have been scrapped for reasons of internal internal porosity porosity,, thereby thereby achievin achieving g improved improved foundry foundry recovery recovery.. This This advantag advantagee is of more significa significant nt importan importance ce in the manufacture manufacture of castings castings subject to radiograp radiographic hic inspecti inspection on hen re!uired re!uired levels levels of soundness are not achieved in the casting process. The development of hot isostatic pressing is pertinent to the broad range of premium castings, but is especially relevant for the more difficult-to-cast difficult-to-cast aluminum-copper aluminum-copper series.
Hybrid "ermanent Mold "rocesses #lthough die casting, centrifugal casting, and gravity die casting constitute, on a volume basis, the major permanent mold processes, there are also some hybrid processes that use permanent molds. This includes s!uee$e casting and semisolid metal processing.
%vervie The manufacturing manufacturing process of pistons pistons has changed changed considera considerably bly since the inception inception of the internal combustion motor. Modern piston manufacturing is fully automated ith little or no human intervention. This is not the case ith &" "istons. &" "istons strength lies in our ability to manufacture very lo numbers numbers of pistons pistons at a time 'for example, example, ()-*)+. This This ability means means that e do not, and cannot, cannot, compete ith the massive automated facilities of the manufacturers of mass produced pistons for modern vehicles. t also means that they cannot do hat e do either. hat is laid out belo is the ay that e make pistons. pistons. e use many modern manufactur manufacturing ing processes processes,, but also older older methodolo methodologies gies hich ensures our position as a niche manufacturer. oundry
The foundry is the beginning of the piston. #t the foundry the die is prepared by heating it to operating temperature for approximately one hour. This process allos the die to readily accept the molten material hen it is poured.
The material The material used is a ()/ silicon content aluminium.
The die The dies used are 0 piece and three piece. These dies are made from cast iron ith steel inserts for the gudgeon pin holes and the cores. The cores dictate the placement of the gudgeon pin and can be located to give offset pins or s!uare pins. H
The process The process starts by heating the material to 1)) degrees Celsius. This is ell above the melting point of the aluminium, aluminium, but belo its boiling point. point. The material material is then scooped up ith a ladle from the crucible 'the pot that holds the molten material+. This is then poured into the die through the sprue. The material is then alloed to cool before it is removed re moved from the die and placed into a bin of hot ater. This ater is used to facilitate a more even settling of the hot metal. #fter the castings have had time to cool they are placed into a heat treatment plant overnight. This process tempers the casting and ensures the piston ill have improved !ualities.
#fter it is removed from the heat treatment the casting has its runner removed. This process takes little time and is fully automated.
Pin Boring
#t this stage of the piston manufacturing process the casting has the gudgeon pin hole rough machined machined and the locating bung machined. The bung This process is here the casting is machined on the base to allo placement of the casting in other machines. This is carried out on a simple lathe.
The pin bore "
Pin $oring is one in conunction with the $ung turning( as one casting is remo+e #rom ha+ing the $ung #ace machine it is place on the pin $orer. $orer. 'he pin $orer is onl% onl% a rough machining process process which allows the the reamer to enter the gugeon hole later. CNC Turning
'urning o# the casting is carrie out on CNC )Computer Numeric Control* machin machiner% er%.. 'his 'his e-uipm e-uipment ent is the most most accura accurate te an #astes #astestt a+aila a+aila$le $le #or this this application with +er% tight tolerances an extremel%#astspinlespees.(the castings are place in the lathe on a $ung an hel in place $% a soli ro through the gugeon pin hole. A raw $olt is acti+ate in the chuck which raws the ro towar the chuck an hols the piston in(place.
'he lathe is then starte an the machining c%cle $egun. 'his c%cle is programme programme into the lathe in a $asic language language calle J!55 means spinle spee spee >!55 >!55rp rpm* m*(( at part partic icula ularr #ee #ee rate rates s )eg )eg J54 J54 rapi rapi tra+ tra+ers erse* e* an an othe otherr commans such as 54 )repeat programme* an others. As %ou can see this is a simple s%stem to learn an implement. A#ter the piston is machine it is remo+e #rom the lathe lathe an the part part num$er stampe on on the crown piston. piston.
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The piston is no ready for the finishing processes.
Drilling 'he 0rst stages o# the 0nishing process inclue rilling( slotting( +al+e an crank relie+ing. Drilling Drilling Drilling inclues inclues all oil holes in places places such as the gugeon gugeon pin $osses an oil ring groo+es. Slotting
6lot 6lotti ting ng is wher where e slot slots s are are plac place e in the the skir skirtt or in the the oil oil ring ring groo groo+e +e.. Valve,relieving 'his process is one on a mill an in+lo+es setting the machine up #or the process( choosing the correct cutter an completing the o$. 6ince there are so man% ierent t%pes o# +al+e relie#s it is impossi$le to ha+e a specialise machine set up to o one o$. Crank Relieving Crank relei+ing is carrie out on a specialise machine which scallops the skirt o# the piston to the re-uire shape an epth $% using two oppose cutters place on a common sha#t. 44
Grinding 'his process in+ol+es the 0nal sie $eing machine on the piston. 'he
griner machines the skirt o# the piston onl% an in the maorit% o# cases is cam groun groun. . Cam grining grining ensures ensures the pisto piston n will will grow grow e+enl% e+enl% in the $ore $ore o# the engine. A per#ectl% roun piston will expan une+enl% uring use $ecause o# the une+en placement o# material in the casting )gugeon pin $osses an ri$$ing use #or strenghtening*.
Reaming 'he 0nal machining process #or the piston is that o# reaming. 'his
process in+ol+es the piston $eing place in a $ath o# oil an reame at ierent sies to reach the 0nal sie re-uire. 6ince the pin $oring process is onl% rough it is necessar% to ream the pin $ore a num$er o# times to achie+e the sur#ace 0nish an sie re-uire. Eeaming is not a #ast process an is onl% partiall% automate )there are automatic #ees on the reaming machines*. 'olerances achie+e on the 0nishe reame sur#ace is 5.Ea.
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Pin Fitting and Final Inspection
#t this stage the piston is cleaned, fitted ith the appropriate gudgeon pin, stamped ith the pistons2 oversi$e and any other markings, and then sent to despatch.
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inally, inally, the piston is rapped and placed in the shipping container ith the ring set and sent to the customer.
Aluminium casting processes are classified as Ingot casting or Mould casting. During the first process, primary or secondary aluminium is cast into rolling ingot (slab), extrusion ingot (billet) and wire bar ingot which are subsequently transformed in semi and finished products. !he second process is used in the foundries for producing cast products. !his is the oldest and simplest (in theory but not in practice) means of manufacturing shaped components. !his section describes exclusi"ely Mould casting which can be di"ided into two main groups # $
%and casting
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Die casting
&ther tec &ther techni hniques ques such as 'lo 'lost st foa foam' m' or 'wa 'wax x pat patter tern' n' pro proces cesses ses are als also o use used d but their economical importance is considerably lower than both listed techniques. %and asting In san sand d cas castin ting, g, re reusa usable ble,, per perman manent ent pat patter terns ns are use used d to ma mae e the san sand d mou moulds lds.. !h !he e preparation and the bonding of this sand mould are the critical step and "ery often are the rate controlling step of this process. !wo main routes are used for bonding the sand moulds# $
!he 'green sand' consists of mixtures of sand, clay and moisture.
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!he 'dry sand' consists of sand and synthetic binders cured thermally or chemically.
!he sand cores used for forming the inside shape of hollow parts of the casting are made using dry sand components. !his "ersatile technique is generally used for high"olume production. An example of half sand mould is gi"en in *igure +.
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Figure 1. alf mould with cores and an example of a cast air intae for a turbocharger.
-ormally, such moulds are filled by pouring the melted metal in the filling system. Mould designing is a particularly complex art and is based on the same principle as gra"ity die casting illustrated in *igure . In the 'low pressure' sand casting technique, the melted metal is forced to enter the mould by low pressure difference. !his more complicated process allows the production of cast products with thinner wall thicness. Die asting In this technique, the mould is generally not destroyed at each cast but is permanent, being made of a metal such as cast iron or steel. !here are a number of die casting processes, as summarised in *igure /. igh pressure die casting is the most widely used, representing about 012 of all light alloy casting production. 3ow pressure die casting currently accounts for about /12 of produc production tion and its use is increa increasing. sing. 4ra"ity 4ra"ity die casti casting ng accounts for the rest rest,, with the exception excep tion of a small but growing contr contributi ibution on from the recen recently tly introduced introduced "acuu "acuum m die casting and squee5e casting process.
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Figure 2. lassifications of die casting processes.
4ra"ity asting A schematic "iew in *igure 6 shows the main parts constituting a classical mould for gra"ity die casting. ores (inner parts of the mould) are generally made of bonded sand.
Figure 3. %chematic "iew of the components of a casting mould (gra"ity die casting).
4ra"ity die casting is suitable for mass production and for fully mechanised casting. igh 7ressure Die asting In this process, the liquid metal is in8ected at high speed and high pressure into a metal mould. A schematic schematic "iew of high pressure die die casting is gi"en in *igure .
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Figure 4. %chematic "iew of a high pressure die casting machine.
!his equipment consists of two "ertical platens on which bolsters are located which hold the die hal"es. &ne platen is fixed and the other can mo"e so that the die can be opened and closed. A measured amount of metal is poured into the shot slee"e and then introduced into the mould ca"ity using a hydraulicallydri"en piston. &nce the metal has solidified, the die is opened and the casting remo"ed. In this process, special precautions must be taen to a"oid too many gas inclusions which cause blistering during subsequent heattreatment or welding of the casting product. 9oth the machine and its dies are "ery expensi"e, and for this reason pressure die casting is economical only for high"olume production. 3ow 7ressure Die asting As schematised in *igure 0, the die d ie is filled from a pressurised crucible below, and pressures of up to 1.: bar are usual. 3owpressure die casting is especially suited to the production of components that are symmetric about an axis of rotation. 3ight automoti"e wheels are normally manufactured by this technique.
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Figure 5. %chematic "iew of a low pressure die casting machine.
;acuum Die asting !he principle is the same as lowpressure die casting. !he pressure inside the die is decreased by a "acuum pump and the difference of pressure forces the liquid metal to enter the die. !his transfer is less turbulent than by other casting techniques so that gas inclusions can be "ery limited. As a consequence, this new technique is specially aimed to components which can subsequently be heattreated. %quee5e asting or %quee5e *orming As shown in *igure <, liquid metal is introduced into an open die, 8ust as in a closed die forging process. !he dies are then closed. During the final stages of closure, the liquid is displaced into the further parts of the die. -o great fluidity requirements are demanded of the liquid, since the displa dis placem cement ents s are sma small. ll. !hu !hus s for forgin ging g all alloy oys, s, whi which ch gen general erally ly ha" ha"e e poo poorr flu fluidi iditie ties s whi which ch normally precludes the casting route, can be cast by this process.
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Figure 6. !he squee5e casting principle.
!his technique is especially suited for maing fibrereinforced castings from fibre cae preform. %quee5e casting forces liquid aluminium to infiltrate the preform. In comparison with non reinforced aluminium alloy, aluminium alloy matrix composites manufactured by this technique can double the fatigue strength at 611=. ence, such reinforcements are commonly used at the edges of the piston head of a diesel engine where solicitations are particularly high. onclusions Aluminium castings are "ery powerful and "ersatile techniques for manufacturing semi or finish fin ished ed pro produc ducts ts wit with h int intric ricate ate sha shapes pes.. !h !hose ose tec techni hnique ques s are con contin tinuou uously sly imp impro" ro"ed ed and de"eloped to satisfy the user needs and to penetrate new marets. Inno"ations are mainly oriented to the automobile sector which is the most important maret for castings. !his continual impro"ement and de"elopment will ensure that aluminium castings continue to play a "ital role in this field. .a$om.com3article.aspx4#rticle56(78* cle56(78* http://.a$om.com3article.aspx4#rti is con consid sidere ered d a fund fundame amenta ntall rul rulee in in man manufa ufactu cturin ring g an an alu alumi minum num all alloy oy not to all allo o the temperature, during the melting operation, to go beyond the point re!uired for pouring into the particular molds mol ds emp employ loyed, ed, to pre preven ventt oxi oxida datio tion n and gassing gassing the met metal. al. 9ut in mak making ing my all alloy oy,, fin find d it advantageous to heat beyond this point re!uired for pouring, in order to have the alloy absorb the various gases gas es pre presen sentt in the pro produc ducts ts of the fue fuell com combus bustio tion. n. Th Thus, us, by :ov :overh erheat eating ing:: mea mean n rai raisin sing g the temperature beyond that re!uired for pouring. t is to be noted that the pouring temperature varies ith the particular type of mold employed as is knon in the art. or a aluminum piston manufacture find that a prac- o tical temperature to hich the molten mass is to s be raised is approximately ;1(: C. '(<))) .+. . +. n r casting the piston from this molten alloy allo t the most highly stressed parts of the piston, vi$., a the hanger members, to solidify at such a rate as t to allo the gas to escape during solidification. o The parts of the piston, such as the bearing sur- faces, are chilled sufficiently so that the gas s cannot escape, but is entrapped in minute pores p uniformly disseminated throughout these bearing p portions of the piston. find that due to the n presence of, tfese pores, the outermost of hich el are exposed during the machining of the piston, a the surface is capable of absorbing and maintain- ir ing a continuous film of oil. a The alloy embodying my invention may be im- m proved ith respect to increased tensile strength,
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fr increased yield point, and increased hardness by lo a heat treating process. This process consists if of heatin hea ting g cas castin tings gs mad madee from the all alloy oy to a al tem temper peratu ature re of app approx roxima imately tely 0(<= C., '8< '8<)) )) . .+, +, th depending upon the si$e and form of the casting, or the period being longer for the larger than for the fl smaller casting, and holding at this temperature for a period from one to three hours, folloing by a rapid cooling in a blast of air at room temperature, and then :artificially ageing: it from to to eight hours. n artificially ageing raise the temperature to (*( to *00) C., '*0) to >))) .+, depending upon the form, si$e, thickness of section and nature of the casting. #fter holding the product at this temperature for to to eight hours, it is alloed to cool at room temperature. have stated in the above that allo my alloy, hile in the presence of the gaseous furnace products, to become overheated. hile this is advantageous from the point of vie of absorbing these gases, it has one disadvantage that can be readily appreciated by anyone skilled in the art. This disadvantage arises from the danger of oxygen becoming absorbed into the body of the molten alloy ith the resultant formation of aluminum oxide. ?ince aluminum oxide is an abrasive material, its presence in a piston is very undesirable, both from a machining and an operating standpoint. have found that by b y introducing antimony trichloride trichloride into the body of the molten alloy before pouring, am able to greatly facilitate the removal of such aluminum oxide as it actually is formed. n explaining the mechanics of this oxide removal ill confine myself for the present to the action of the aluminum trichloride hich is formed hen the antimony trichloride is decomposed by the molten aluminum and ill later describe the effect of the liberated antimony upon the silicon. can summari$e the reaction into hich the antimony trichloride enters ith the aluminum as follos@ ?bCl7A#-?bA#C(7 The aluminum trichloride hich is formed in the above reaction is useful by virtue of the effect >) it has n reducing the surface tension of the aluminum-aluminum oxide interface, and thereby alloing the oxide to coagulate and rise to the surface here it may be skimmed off. The other useful gases, carbon monoxide, carbon dioxide, and nitrogen, are in solution in the molten alloy and are not greatly affected, or, at any rate, are iot completely removed by the antimony trichlo. ide treatment. The antimony that is produced by the above reuction becomes uniformly disseminated throughnut the molten alloy. have found that metallic antimony, hen introduced into a molten alumikum-silicon alloy, as antimony trichloride, has he property of :modifying: the alloy. ithout ithout ttempting a necessarily lengthy explanation of he modifying process in aluminum-silicon alloys, r ithout confining myself to any one particuar theory regarding modification, ill simply tate that it is accompanied by the folloing henomena 'a+ an increase in the eutectic comosition from ((.< per cent silicon to approxiuately (7 per cent siliconB 'b+ a decrease in the utectic temperature from 011) C., '()1(: ".+ to p"roximately 0<0) C., '()>8) .+B 'c+ a definite nprovement in the physical properties of the loy, including elongationB 'd+ a change in the lcrostructure of the hypoeutectic silicon itself om the acicular structure of the unmodified aly to the colloidally dispersed silicon of the modDed alloy. n forming binary aluminum silicon loys, the customary custo mary agents used to bring abou aboutt iese changes are the alkali metal metalss and their fluri flurides, des, hydroxides, hydroxides, chlorides, "eroxides, and the uorides and peroxides of the alkaline earth met- 1 < *,(7( als as ell as various mixtures of these substances. t can be readily appreciated that a modifier that can be introduced into the body of the molten alloy, as have succeeded in doing ith the antimony by adding it as the trichloride in the form of a gas has very definite advantages oing to its uniform dispersion throughout the alloy. n the case of adding the customary agents in the form of salts, the uniformity of their dispersion depends upon the degree of mechanical mixing. n adding the antimony trichloride, volatili$e the same, and thereby it forms a very active dispersing agent in and of itself as contrasted ith being mechanically dispersed throughout the mass. #lso, the antimony has one further advantage that have not dealt ith,
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namely, that of increasing the resistance of aluminum alloys to corrosion, especially salt ater corrosion. #s e!uivalent of antimony trichloride give the folloing@ #ntimony #ntimony tribromide, antimony pentachloride, antimony trifluoride, and antimony pentafluoride. The process by hich make my alloy follos. The eights given are sufficient for one hundred pounds of the finished alloy less a slight melting loss. do not limit myself to the particularcompositions of the starting materials that described, but my invention includes the use of other materials that are knon to those skilled in the art to be e!ual or e!uivalent. or example, may add copper as the metal, in combination ith aluminum in the form of an aluminum rich alloy, in combination ith both nickel and aluminum as an aluminum rich ternary alloy, or in any other manner that ill give the desired analysis in the finished alloy. This applies e!ually ell to the other alloying ingredients. or example, may ma y add vanadium either as the ten per cent vanadium aluminum alloy, or by introducing a volatile salt of vanadium hich ill decompose to liberate vanadium. urther, it is to be understood that fifteen pounds of a thirtythree per cent silicon aluminum alloy is the e!uivalent of ten pounds of the fifty per cent alloy plus five pounds of substantially substantially pure aluminum, etc. i n the crucible of a conventional conventional oilfired tilting crucible furnace, melt together the folloing materials@ #s one of the starting materials, an alloy consisting of fifty per cent silicon, the balance substantially pure aluminum-->* pounds. ?ubstantially pure aluminum->< pounds. #n alloy consisting of tenty per cent nickel, ten per cent copper, and the balance substantially pure aluminum-() pounds. #n alloy consisting of ten per cent vanadium the balance substantially pure aluminum-( aluminum-( pound. #fter the above ingredients are thoroughli melted together, add one pound of metallic mag. nesium. no allo the temperature of the moltel alloy to increase to approximately ;1(= C., '(<)) . .+, +, hile it is in the presence of the products o combustion of the fuel, so that it ill absorb car bon monoxide, carbon dioxide and nitroger hen this temperature is reached, introduc antimony trichloride into the molten alloy as have before described. hen have added abou ).* pound of antimony trichloride, allo th temperature to drop to about ;(<= C., '(0))= .@ and the alloy is ready to be poured into piston piston rings, castings, or into ingots for remeltini The aluminum alloy thus formed embodyin ,)1< my invention comprises *) to **/ silicon, */ nickel, (/ copper, (/ magnesium, ).(/ vanadium, ).(/ antimony, the balance substantially pure aluminum, i. e., aluminum plus impurities, other than silicon and copper. or purposes here tensile 7trength can be sacrificed for better bearing !ualities, as in the case here the alloy is to be used for a lightly stressed bearing, provide an alloy having the folloing analysis@ ?ilicon *0 to 70/, nickel */, copper (/, magnesium ).0/, vanadium ).(/, antimony ).(/,, and the balance substantially pure aluminum, i. e., aluminum plus impurities, other than silicon and copper. Eelative limits of range of ingredients@ t is impractical for the alloy to contain silicon to more than 0)/ by eight of the total alloy, because such an alloy ould have a very high melting point, and because the oxidi$ation of aluminum at such high temperature ould be so great as to be prohibitive. 9elo (0/ the
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coefficient of expansion is so great as to render the alloy subject to the customary disadvantages of the alloys no commonly in use. Fickel@ This ingredient cannot be belo (/ because no appreciable hardening of the matrix results. f more than 0/ is added, segregation becomes too great and the alloy becomes brittle. rom the point of vie of economics, its cost at present prices ould be prohibitive. The amount of nickel must be sufficient to prevent precipitation of any copper aluminum compound as such from the copper aluminum solid solution. The nickel serves to purposes '(+, to provide hardening, and '*+, to provide against again st permanent volume volume gro groth. th. The rule rule,, there therefore, fore, for dete determini rmining ng the amoun amountt of nick nickel el to be employed in the alloy of my invention, characteri$ed by having a relatively high silicon content, is that there must be just sufficient nickel to combine ith the copper aluminum compound and precipitate as ternary copper nickel aluminum compound and prevent the precipitation of copper aluminum as such. The amount of nickel, therefore, is critical for the alloy embodying my invention. Copper@ There must be at least ).0/ present to get any hardening and strengthening of the matrix effect, and if there is present more than *.0/, then there is an undue tendency for permanent volume groth. To be sure, if there should be present more than *.0/, then it ould re!uire a sufficiently larger amount of nickel present to prevent precipitation, precipitation, hich ould result result in an alloy hich ould ould be too brittle. brittle. Magnesium@ #t #t least (/ is re!uired to obtain the necessary degree of hardness hile above 7/ excessive oxidi$ation results. Ganadium@ # trace is necessary to get any effect, and serious segregation occurs over (/. r have found that hen the amount of vanadium - is increased, a point may be reached here segregation of crystals of vanadi van adium um alu alumi minum num com comii pou pound nd occ occurs urs.. Th Thee seg segreg regati ation on beg begins ins abo above ve o abo about ut t tenty enty-fiv -fivee one one-hundredths of one per f cent, and hen the amount of vanadium reaches - one per cent, segregation is serious. #mounts . above tenty-five one hundredths of one per e cent are increasingly disadvantageous for the rea reason son of inc increa reasin sing g seg segreg regati ation. on. %ne-tent %ne-tenth h of it one per cen centt has been fou found nd to giv givee satisfactory .e results both economically and practically practically.. +, #ntimony@ ?ome effect is obtained ith a trace s, and ith more than ).0/ very coarse crystals of g. antimony are formed, hich are objectionable because they eaken the alloy. f #luminum-impurities@ 9alance of alloy is aluminum plus its impurities, other than silicon and copper. The use of antimony as an alloying element in aluminum alloys is knon for the purpose of increasing the corrosion resistance. obtain the advantage of using antimony in the form of antimony trichloride to get the more intimate intermixing, but principally to get the effect of the chlorine hich is liberated. The same advantage of intermixing is obtained ith vanadium hen it is employed in the form of its volatile salts. This application is a continuation-in-part of my application ?erial Fo. 1><,>** filed %ctober (, (87>, and my application ?erial Fo. ;0,0>* filed &une (<, (87<. %bviously, changes may be made in the forms, dimensions and arrangement of the parts of my invention, ithout departing from the principle thereof, the above setting forth only preferred forms of embodiment.
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claim@ (. #n aluminum alloy comprising substantially silicon tenty to fifty per cent, nickel one to five per cent, copper five-tenths per cent to to and five tenths per cent, magnesium one to three per cent, vanadium in an effective amount up to (/, antimony in an effective amount up to (/, and the balance aluminum plus impurities. *. The process of making an aluminum alloy characteri$ed by having a lo coefficient of expansion comprising the steps of 'a+ forming a hypereutectic aluminum silicon alloy containing nickel, copper, and vanadi van adiumB umB 'b+ add adding ing mag magnes nesium ium to sai said d all alloy oy hi hile le in a mol molten ten sta stateB teB and 'c+ sup superh erheat eating ing sa said id composition in the presence of gases readily absorbable by said composition composition.. 7. The process of making an aluminum alloy characteri$ed by having a lo coefficient of expansion comprising the steps of 'a+ forming an aluminum silicon alloy containing silicon *) to0)/,nickel ( to 0/,, cop 0/ copper per ).0 to *.0 *.0/, /, van vanadi adium um in an eff effect ective ive amount amount up to (/, the bal balanc ancee alu alumi minum num plus impuritiesB 'b+ adding magnesium to said alloy hile in a molten state in an amount of ( to 7/B and 'c+ superheating said composition in the presence of gases readily absorbable by said composition. >. The process of making an aluminum alloy characteri$ed by having a lo coefficient of expansion comprising the steps of 'a+ forming a hypereutectic aluminum silicon alloy containing nickel, copper, and vanadi van adiumB umB 'b+ add adding ing mag magnes nesium ium to sai said d all alloy oy hi hile le in a mol molten ten sta stateB teB and 'c+ sup superh erheat eating ing sa said id composition to approximately ;1( C. in. the presence of gases readily absorbable by said composition. 0. The process of making an aluminum alloy characteri$ed by having a lo coefficient of expansion comprising the steps of 'a+ forming an aluminum silicon alloy containing silicon *) to 0)/, nickel ( to 0/, copper ).0 to *.0/, vanadium in an effective amount up to (/, and the balance substantially all aluminumB 'b+ adding magnesium to said alloy hile in a molten state in an amount of ( to 7/B and 'c+ superheating said composition to approximately ;1() C. in the presence of gases readily absorbable by said composition. <. #n aluminum alloy comprising substantially silicon *) to 0)/, nickel ( to 0/, copper ).0 to *.0/, magnesium ( to 7/, vanadium in an effective amount up to (/ and the balance substantially all aluminum. 1. The process of making an aluminum alloy characteri$ed by having a lo coefficient of expansion comprising the steps of 'a+ forming a hypereutectic aluminum silicon alloy containing nickel, copper, and vanadiumB 'b+ adding magnesium to said alloy hile in a molten stateB 'c+ adding antimony trichlorideB and 'd+ superheating said composition in the presence of gases readily absorbable by said composition. ;. The method of dispersing silicon in an aluminum alloy, hich consists in the step of adding to the aluminum mix antimony trichloride. 8. The method of dispersing silicon in an aluminum alloy, hich consists in the step of adding to the aluminum mix antimony trichloride in effective amounts up to (/. (). The aluminum alloy containing from *) to **/ of silicon, copper about (/, nickel about tice the copper cop per,, mag magnes nesium ium abo about ut (/, and van vanadi adium um in eff effect ective ive amo amount unt up to (/, the rem remain ainder der bei being ng essentialy aluminum. ((. The aluminum alloy containing from *) to **/ of silicon, copper about (/, nickel about tice the copper, magnesium about (/, and vanadium about # of (/, the remainder being essentially aluminum.
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(*. # piston suitable for use in internal combustion engines, hich piston is formed of a cast aluminum alloy containing silicon *) to 0)/, nickel ( to 0/, copper ).0 to *.0/, vanadium in an effective amount up to (/, magnesium ( to 7/ and the balance aluminum plus impurities. (7. # piston suitable for use in internal combustion engines, hich piston is formed of a cast aluminum alloy containing from *) to **/ of silicon, copper about (/, nickel about tice the copper, magnesium about (/, and vanadium in effective amount up to (/, the remainder being essentially aluminum. (>. # piston ring for use in high speed, high compression internal combustion engines, hich ring is formed of a cast aluminum alloy containing silicon *) to 0)/, nickel ( to 0/, copper ).0 to *.0/, vanadium in an effective amount up to (/, magnesium ( to 7/ and the balance 0 aluminum plus impurities. (0. # piston ring for use in high speed, high compression internal combustion engines, hich piston ring is formed of a cast aluminum alloy containing from *) to **/ of silicon, copper about (/, nickel about tice the copper, magnesium about (/, and vanadium in effective amount up to (/, the remainder being essentially aluminum. ?char ?ch ar$, $, Ha Harv rvey ey . (87; (8 7; formed from said alloy
#lum #l umin inum um all alloy oy and and pro proce cess ss for for mak makin ing g the the same same,, pist piston on and and pis pisto ton n ring ring
# technology for forged aluminum pistons and their mass production that enables lighteight design. irst adopted on the I8< model JK())) Thunder#ce. Lsed since on large-displacement sports models from the JK-E series to the Midnight ?tar. ?ummary This is an aluminum piston forging technology and its mass production method that involves heating aluminum alloy to a set temperature and putting it in a temperature-controlled metal mold and forging it under pressure into the piston shape. t can make use of strong aluminum alloy material hich does not have to be heated until it melts so that it maintains its original even solidification matrix. This makes possible a thinner-alled thinner-alled piston design, thus reducing the pistonIs pistonIs reciprocating inertial eight. The primary merit is that stronger aluminum alloys can be used in the forging process.
urthermore, a program as developed by hich the aluminum alloy is heated to a specified temperature, inserted into the mold ith the best timing and forged ith just the right amount of pressure.
This This is called called our Contr Controll olled ed orgin orging g Techno echnolog logyN yN.. t invol involves ves compre comprehen hensiv sivee contro controll of optimum optimum heating of the the aluminum alloy, alloy, the temperature of of the metal mold, optimum use of of the mold freeing agent and control of the pressure applied. n this ay it is possible to achieve mass production of aluminum forged pistons that until no had proved difficult.
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9ect 4* Design o# thinner* reuction o# reci
https@33.yamaha-motor.eu
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Aluminium cast allo%s #or high per#ormance pistons In the course o# engine ownsiing( the automoti+e inustr% e+elops more e;cient engines with higher power ensities. Conse-uentl%( the re-uirements on the use materials increase.
%eparately cast 7D specimen in the !M*>* testing de"ice
'he currentl% use aluminum pistons in moern iesel engines can stan maximum com$ustion pressures up to 45$ar an maximum operating temperatures up to 55OC. 'his is( with a +alue o# 5."( alrea% the highest applie homologous material temperature occurring in technical application )' homolog = 5." "5F ' 6*. As part part o# a 331<# 331<#un une e 7INJ 7INJ pro proect ect(( new cast alumin aluminum um piston piston allo%s allo%s are are e+elope #or prouction $% two( #or this application( new casting processes. Bow pressure ie casting )BPDC* an high pressure ie casting )8PDC* oer a smoother melt Gow an a signi0cantl% higher rate o# solii0cation( respecti+el%( which are a+antageous compare to the gra+it% ie casting )JDC* process use in mass prouction toa%. 'his a+antages( together with appropriate allo% e+elopment( is expec expecte te to lea lea to a #urthe #urtherr incre increase ase o# the possi$ possi$le le operat operating ing parame parameter ters s to com$ustion pressures up to >55$ar maximum temperatures up to 5OC )' homolog = 5."!*.
!emperature !e mperature and mechanical strain profile of a !M*>* test
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asting defect as crac initiation of a !M*
!he research wor of the department of materials mechanics at I?@/ include the characteri5ation of the microstructure using 3M, %?M and !?M, as well as thermomechanical fatigue (!M*) experiments with and without superimposed highcycle fatigue (*) loading. In the !M* tests, due to the different manufacturing processes, two different sample geometries are used. !he thinner samples with only .0 mm ha"e a "ery small cross section in the gauge length. In order to a"oid bucling of these samples, a special glass holder was in"ented which minimi5es bendin ben ding g forc force e cau caused sed by att attach aching ing the ext extens ensome ometer ter.. !he basic !M* tests are per perform formed ed wit with h a min minimu imum m temperature of !min /11=, a maximum temperature !max 1= and a dwell time at !max of tdwell <1s. !he mechanical strain amplitude is 012 of the thermal strain amplitude (B a, t me 012 Ba, therm). !he superimposed * loading with different amplitudes (Ba, t * 1.16 to 1.102 Bmech) is applied at a frequency of f*+15. 9y using this test method, the thermally induced stresses at the combustion chamber side of the piston during startstop operation as well as the superimposed fatigue loading caused by ignition pressure and inertial forces are simulated. *rom the resulting lifetime, the cyclic deformation cur"e, the fracture mode and metallographic cross sections, conclusions can be drawn about the damage mechanisms ser"ing as an important contribution to alloy and process de"elopment.
Institute of ?nergy and limate Cesearch (I?@)
Aluminum Sand Casting Process Dependable. Long lasting. eliable. !"e #oose Aluminum $a%. $a%. 7roduct quality is one of your top concerns. ou ou need to now that e"ery step of the aluminum sand casting process is executed by an expert team with the latest technology and an eye toward perfection. hoose 9oose Aluminum for your aluminum sand casting needs. -o matter the si5e of your pro8ect or the industry you ser"e, 9oose Aluminum deli"ers quality aluminum sand castings e"ery time. *or insight into the basic steps of our aluminum sand casting process, tae a quic loo at the steps we employ. !o discuss the unique approach that the 9oose team brings to e"ery 8ob and the industrybest customer ser"ice for which we are nown, call us at :+:66<00E+ or clic here to request an appointment.
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#asic Steps in Aluminum Sand Casting Process A pattern is built from your print or model. !he !he pattern is a positi"e shape of your your part.
A sand mold is made using using your pattern. !he sand mold is a negati"e. If your part is a solid aluminum sand casting, the pattern is all thatFs required. If your casting is hollow, a separate component called a core must be used. ores are the shape of the inside of your part. A second tool component will be required, called a core box. %and is put into the core box and cured to produce a core.
!he core is set into the mold before it is closed. Metal is poured into the mold tra"eling through a GgatingH system and into the "oid left by the pattern and core. After the metal metal solidifies the mold is Gdumped.H Gdumped.H our our aluminum aluminum sand castings still still attached to to the gating system are pulled from the sand. !he core is "ibrated out of the aluminum sand casting and the casting is cut off of the gating. !he aluminum sand casting then needs ground. !he gating contacts and any excess metal fins are remo"ed from the casting lea"ing only the shape you required.
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he Process
'he ol Dike in all permanent mold manufacturing processes, the first step in die casting is the production of the mold. mold. The mold must must be accurately created as to halves that can be opened and closed for removal of the metal casting, similar to the basic the basic permanent mold casting process. The mold for die casting is commonly commonly machined from steel and and contains all the components of the gating system. Multi-cavity die are die are employed in manufacturing industry to produce several castings ith each cycle. Unit dies hich dies hich are a combination of smaller dies are also used to manufacture metal castings in industry. n a die casting production setup, the mold, 'or die+, is designed so that its mass is far greater than that of the casting. Typically Typically the mold ill have ())) times the mass of the metal casting. ?o a * pound part ill re!uire a mold eighing a tonO 5ue to the extreme pressures and the continuous exposure to thermal gradients from the molten metal, earing of the die can be a problem. Hoever in a ell maintained manufacturing process, a die can last hundreds of thousands of cycles before needing to be replaced.
Die Casting achines n addition to the opening and closing of the mold to prepare for and remove castings, it is very important that there is enough force that can be applied to hold the to halves of the mold together during the injection of the molten metal. lo of molten metal under such pressures ill create a tremendous force acting to separate the die halves during the process. 5ie casting machines are large and strong, designed to hold the mold together against such forces.
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Figure:81
n manufacturing industry, die casting machines are rated on the force ith hich they can hold the mold closed. Clamping forces for these machines vary from around *0 to 7))) tons.
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Inection ,# olten etal n industrial manufacture the process of die casting falls into to basic categories, hot chamber die casting and cold chamber die casting. Pach process ill be discussed specifically in more detail later. #lthough #lthough these processes vary from each other, both employ a piston or plunger to force molten metal to travel in the desired direction.
Figure:82
The pressure at hich the metal is forced to flo into the mold in die casting manufacture is on the order of ()))psi to 0))))psi '1M"a to 70)M"a+. This pressure is accountable for the tremendously intricate surface detail and thin alls that are often observed in metal castings manufactured by this techni!ue. @4
%nce the mold has been filled ith molten metal, the pressure is maintained until the casting has hardened. The mold is then opened and the casting is removed. Pjector pins built into the mold assist in the removal of the metal casting. n most manufacturing operations, the internal surfaces of the mold are sprayed ith a lubricant before every cycle. The lubricant ill assist in cooling don the dies as ell as preventing the metal casting from sticking to the mold. #fter the casting has been removed re moved and the lubricant applied to the mold surfaces, the die are clamped together again then the cycle ill repeat itself. Cycle times ill differ depending upon the details of each specific die casting manufacturing techni!ue. n some instances, very high rates of production have been achieved using this metal casting process.
Insert oling ith the die casting process, shafts, bolts, bushings and other parts can be inserted into the mold and the metalcasting may be formed around these parts. This is called insert molding, once solidified these parts become one ith the casting. To help ith the integration of the part into the casting, the part may be grooved or knurled providing a stronger contact contact surface beteen the part and the the molten metal.
Figure:83
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Properties And Considerations Of Manufacturing By ie Casting •
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etal castings with close tolerances( tremenous sur#ace etail( an thin intricate walls can $e manu#acture using this process.
Due to the rapi cooling at the ie walls smaller grain structures are #orme( resulting in manu#acture metal castings with superior mechanical properties. 'his is especiall% true o# the thinner sections o# the casting. @@
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7hen manu#acturing $% this process( it is o# concern to keep the mol cool. Die ma% ha+e special passages $uilt into them that water is c%cle through in orer to keep own thermal extremes.
8igh prouction rates are possi$le in ie casting manu#acture.
6ince the mol is not permea$le( ae-uate +ents nee to $e pro+ie #or the elimination o# gases uring the metal casting process. 'hese +ents are usuall% place along the parting line $etween the ie.
Due to the high pressures( a thin Gash o# metal is usuall% s-ueee out at the parting line. 'his Gash has to $e trimme latter #rom the casting.
9ector pins will usuall% lea+e small roun marks on the metal casting. 'hese can $e o$ser+e on the sur#aces o# manu#acture parts.
'he nee to open an an close the mol limits limits some o# the shapes an geometries that ma% $e cast using this manu#acturing process.
9-uipment cost #or ie casting are generall% high.
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Die casting manu#acture can $e highl% automate( making la$or cost low.
Die casting is similar to most other permanent mol casting processes in that high set up cost( an high proucti+it% make it suita$le #or larger $atch manu#acture an not small prouction runs.
http://theli$rar%o#manu#acturing.com/ieQcasting.html Pistons are commonl% mae o# a cast aluminum allo% #or excellent an lightweight thermal conucti+it%. ost o st pist istons ons are are mae mae #ro #rom die! die! or gra" gra"it ity! y!ca cast st a#u$ a#u$in inu$ u$ a##o a##oy y. Cast lightw twei eigh ghtt an an has has goo goo stru struct ctur ural al inte integr grit it% % an an low low a#u$in a#u$inu$ u$ a##oy a##oy is ligh manu#acturing costs. 'he light weight o# aluminum reuces the o+erall mass an #orce #orce necessar% necessar% to initiate initiate an maintain maintain acceleration acceleration o# the piston. 'his allows allows the pist piston on to util utili ie e mor more o# the the #or #orce pro prouc uce e $% com$ com$us usti tion on to powe powerr the the application.
Cast A#u$inu$ Pistons
3est suite #or stock engines. Bower price point. 'he t%pical cast piston is mae o# a lower grae aluminum which is molten an Gowe into a mol ha+ing the shape o# the 0nishe prouct. Piston mols are perman permanent ent ies( ies( intric intricate atel% l% mae mae o# multip multiple< le
3est suite #or up to 55 8P in 63 or H55 8P in 33 normall% aspirate engines. i price point. @!
'he h%pereutectic piston is also a cast piston $ut with an ieal amount o# silicon ae )approximatel% 4F* to prouce a much stronger +ersion o# the stanar cast cast pist piston on.. 6ili 6ilico con n itse itsel# l# expa expan ns s less less than than alum alumin inum um(( $ut $ut it also also acts acts as an insulator to pre+ent the aluminum #rom a$sor$ing as much o# the operational heat. Another $ene0t o# aing silicon is that the piston $ecomes harer an is less suscepti$le to scu;ng. Aitionall% the higher silicon content o# the h%pereutectic pistons allows #or a tighter 0t piston impro+ing com$ustion seal ue to reuce rocking o# the piston as it tra+els in the c%liner wall. Although not as ro$ust as #orge pistons( h%pereutectic pistons are an ieal choice #or engines proucing up to 55 8P in small $locks an up to H55 8P in $ig $locks( epening on application. 3ecause o# the higher silicon content( h%pereutectic is a less uctile allo% an is less #orgi+ing when use with $ooste an/or nitrous applications( making them $est suite #or normall% aspirate engines. &'32 Forged A#u$inu$ Pistons
3est suite #or engines proucing up to 4555 horsepower normall% aspirate. 8igher price point. 1orge 1orge pistons are the strongest piston on the market. 'he manu#acturing process is ierent #rom a cast piston. 'he aluminum is not molten like a cast piston( instea a hot slug o# aluminum allo% calle an ingot is place in a #emale mol( an a male ram is poune into it. 'he result is a piston $lank( which must then unergo man% mach machin inin ing g oper operat atio ions ns $e#o $e#orre it $eco $ecome mes s a pist piston on.. 5@> 5@> is a high high4 cousin( ue to reuce rocking o# the piston as it tra+els in the c%liner wall. 5@> is also a more sta$le allo%( so it will retain characteristics such as ring groo+e integrit%( #or longer li#e c%cle applications. 3eca 3ecause use o# the the high higher er sili silico con n cont conten ent( t( 5@> 5@> is a less less uct uctil ile e allo allo% % an an is less less #orgi+ing when use with $ooste an/or nitrous applications( making them $est suite #or normall% aspirate engines. 2(18 Forged A#u$inu$ Pistons
3est suite #or engines proucing up to 4>55 horsepower an is ieal #or engines running power aers. 8igher price point. 1orge 1orge pistons are the strongest piston on the market. 'he manu#acturing process is ierent #rom a cast piston. 'he aluminum is not molten like a cast piston( instea a @
hot slug o# aluminum allo% calle an ingot is place in a #emale mol( an a male ram is poune into it. 'he result is a piston $lank( which must then unergo man% machining operations $e#ore it $ecomes a piston. 'he >4 aluminum material is a lowF*( high4 is a more uctile allo% an grants higher tolerances with higher resistance to etonation. 'he #orgi+ing characteristics allow #or the most extreme conitions( $ut longe+it% is e+entuall% compromise a#ter countless heat c%cles.
Forged versus cast pistons #ugust (0, *)(* * )(*"at "at
hen building an engine for your muscle car, one decision is to use forged versus cast pistons. pistons. hile most people kno that forged pistons are stronger, am not sure if everyone knos hy.
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mage courtesy of matchity, on lickr hen you think about it, it is ama$ing that your pistons donIt end up as a molten pile of aluminum aluminum in your oil pan. #luminum #luminum melts melts at around (*0) degrees , and the combustion combustion temper temperatu atures res can exceed exceed that. Ho the piston piston survives survives is that that since since it is aluminum, aluminum, it can transfer transfer that head rapidly rapidly to keep cool. That ill ill ork for a hile, but after a hile the piston ill no longer be able to transfer enough heat to other parts of the piston and to the cylinder alls. The other thing that helps is the fact that there is a thin thin layer of cooler gas that is next to the piston that acts as a buffer buffer to help keep the piston cool. That is hy detonation or pinging is is so dangerous, the flame front hits the piston to early and ashes aay part or all of that gas layer and can melt the piston. piston. That is hy you see gray flecks on your spark spark plug if you have had enough detonation, the piston melted and droplets of it ended up on your spark plugs. #s mentioned before, automotive pistons are made of aluminum, actually an aluminum alloy that contains silicon as ell. The silicon is added to strengthen the aluminum aluminum as ell as reduce the expansion due to increased temperatures. Cast pistons are made by pouring melted aluminum alloy into a mold that is in the shape of a piston. #fter they have cooled and solidified the pistons are machined to their final shape and dimensions. This is a less expensive ay to manufacture pistons pistons since there is minimal machine ork involved. orged pistons are made by heating a chunk of aluminum alloy and using a press to s!uee$e or forge forge it into a rough piston piston shape by using tons of pressure. pressure. This compacts compacts the structure structure of the aluminum alloy in the piston making making it stronger. t also results results in the piston having more thermal thermal expansion due to the denser structure of the alloy. There is a third type of piston, piston, hypereutectic. hypereutectic. hat that means means is that it has a higher level of silicon that a standard cast piston. t is still a cast piston, but it is stronger, and it has less thermal expansion. expansion. That allos allos it to fit into the cylinder cylinder tighter and have less ring gap since it doesnIt expand as much. That is hy most ne cars have them, it allos a better seal in the cylinder and less emissions emissions.. #ll of this brings us to the !uestion of hat should be used in my car. car. f it is a mild engine ith no boost or nitrous, and it is not routinely running at redline, cast or hypereutectic pistons ould be just fine. "ersonally, if there isnIt much of a price difference ould go ith hypereutectic h ypereutectic pistons. orged pistons are good for running a turbo or a super charger, running nitrous or if it ill often often see high E"Ms. %f course it can also be piece of mind for a milder engine, engine, but it usually usually isnIt needed. needed. 9ut if you are building building an engine and think you may one day ant to run nitrous on it, then definitely go ith forged.
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!&P 1 ' 1 ' Crus"ing and (rinding) Alumina reco"ery begins by passing the bauxite through screens
to sort it by si5e. It is then crushed to produce relati"ely uniformly si5ed material. !his materials is fed into a large grinding mill where it is mixed with a caustic soda solution ( sodium hydroxide) hydroxide) under high temperature and pressure. !he grinding mill rotates lie a huge drum while steel rods, rolling around loose inside the mill, grind the ore to an e"en finer consistency. !he material finally discharged from the mill is called slurr%. !he result resulting ing liquor liquor contai contains ns a soluti solution on of sodium sodium alumina aluminate te and undiss undissol" ol"ed ed bauxit bauxite e residues containing iron iron,, silicon silicon and and titanium titanium.. !hese residues commonly referred to as 'red mud' gradually sin to the bottom of the tan and are remo"ed.
S!&P 2 ' 2 ' Digesting) !he slurry is pumped to a digester where the chemical reaction to dissol"e the
alumina taes place. In the digester the slurry under 01 pounds per square inch pressure is heated to 611= *ahrenheit (+0= elsius). It remains in the digester under those conditions from 61 minutes to se"eral hours. More caustic soda is added to dissol"e aluminum containing compounds in the slurry. Jndesirable compounds either donKt dissol"e in the caustic soda, or combine with other compounds to create a scale on equipment which must be periodically cleaned. !he digestion process produces a sodium aluminate solution. 9ecause all of this taes place in a pressure cooer, the slurry is pumped pumped into a series series of flash tanks to reduce reduce the pressu pressure re and heat heat before before it is transf transferr erred ed into settling tanks
S!&P 3 ' 3 ' Settling) Settling) %ettling is achie"ed primarily by using gra"ity, although some chemicals are
added to aid the process. Lust as a glass of sugar water with fine sand suspended in it will separate out o"er time, the impurities in the slurry things lie sand and iron and other trace elements that do not dissol"e will e"entually settle to the bottom.
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!he liquor at the top of the tan (which loos lie coffee) is now directed through a series of filters. After washing to reco"er alumina and caustic soda, the remaining red mud is pumped into large storage ponds where it is dried by e"aporation.
!he alumina in the still warm liquor consists of tiny, suspended crystals. owe"er there are still some "ery fine, solid impurities that must be remo"ed. Lust as coffee filters eep the grounds out of your cup, the filters here wor the same way. !he giantsi5ed filters consist of a series of 'lea"es' big cloth filters o"er steel frames and remo"e much of the remaining solids in the liquor. !he material caught by the filters is nown as a filter cake and is washed to remo"e alumina and caustic soda. !he filtered liquor a sodium aluminate solution is then cooled and pumped to the precipitators. precipitators.
S!&P 4 ' 4 ' Precipitation) Imagine a tan as tall as a sixstory building. -ow imagine row after row of those tans called precipitators. !he clear sodium aluminate from the settling and filtering operation
is pumped into these precipitators. *ine particles of alumina called seed crystals (alumina hydrate) are added to start the precipitation of pure alumina particles as the liquor cools. Alumina crystals begin to grow around the seeds, then settle to the bottom of the tan where they are remo"ed and transferred to ' t"ic*ening tan*s.' *inally, it is filtered again then transferred by con"eyor to the calcination kilns. kilns.
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S!&P 5 ' 5 ' Calcination) alcination is a heating process to remo"e the chemically combined water
from the alumina hydrate. !hatKs why, once the hydrated alumina is calcined, it is referred to as anhydrous alumina. Anhydrous means without water. *rom precipitation, the hydrate is filtered and washed to rinse away impurities and remo"e moisture. moisture. A continuous continuous con"eyor con"eyor system system deli"ers deli"ers the hydrate into the calcining iln. !he calcining iln is briclined inside and gasfired to a temperature of /,111=* or +,+11=. It slowly rotates (to mae sure the alumina dries e"enly) and is mounted on a tilted foundation which allows the alumina to mo"e through it to cooling eqipment. (-ewer plants use a method called fluid bed calcining where alumina particles are suspended abo"e a screen by hot air and calcined.) !he result is a white powder lie that shown below# pure alumina. !he caustic soda is returned to the beginning of the process and used again.
At this point, the alumina alumina is ready for con"ersion into aluminum aluminum at a smelter. smelter. Alumina is also used in maing chemicals chemicals and ceramics.
%tage / on"erting Alumina to Aluminum Smelting)) In +EE<, two //yearold scientists on opposite sides of the Atlantic, C"arles +all of the Smelting J%A and Paul L.!. L.!. +eroult +eroult of *rance *rance,, made made the same disco" disco"ery ery molten molten cr%olite (a sodium sodium
aluminum fluoride mineral) could be used to dissol"e alumina and the resulting chemical reaction would produce metallic aluminum. !"e +all,+eroult process remains in use today.
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!he alle allerou roult lt proces process s taes taes place place in a large large carbon carbon or or graphite graphite lined steel container container called a reduction pot . In most plants, the pots are lined up in long rows called potlines. !he ey to the chemical chemical reaction necessary necessary to con"ert the alumina to metallic metallic aluminum is the running of an electrical current through the cryolite>alumina mixture. The process requires the use of direct current (DC) – not the alternating current (AC) used in homes . !he immense amounts of power required to produce aluminum is the reason why aluminum plants are almost always located located in areas where affordable affordable electrical electrical power is readily a"ailable. a"ailable. %ome experts experts maintain that one percent of all the energy used in the United States is used in the maing of aluminum . !he electrical "oltage used in a typical reduction pot is only !."! #olts, but the amperage is -& "ig" generally in the range of $%%&%%% to $!%&%%% amperes or more. !he current flows betw betwee een n a carb carbon on anode (pos (posit iti" i"el ely y char charge ged) d),, made made of petr petrol oleu eum m coe coe and and pitc pitch, h, and and a cat"ode (negati"ely charged), formed by the thic carbon or graphite lining of the pot.
hen the electric current passes through the mixture, the carbon of the anode combines with the oxygen in the alumina. !he chemical reaction produces metallic aluminum and carbon dioxide. !he molten aluminum settles to the bottom of the pot where it is periodically syphoned off into crucibles while the carbon dioxide a gas escapes. ;ery little cryolite is lost in the process, and the alumina is constantly replenished from storage containers abo"e the reduction pots. !he metal is now ready to be forged, turned into alloys, or extruded into the shapes and forms necessary to mae appliances, electronics, automobiles, airplanes cans and hundreds of other familiar, useful items. Aluminum is formed at about N11=, but once formed has a melting point of only <<1=. In some smelters this spare heat is used to melt recycled metal, which is then blended with the new metal. 'ecycled metal requires only ! per cent of the energy required to mae new metal . 9lending recycled metal with new metal allows considerable energy sa"ings, as well as the efficient use of the extra heat a"ailable. hen it comes to quality, there is no difference between primary metal and recycled metal. !he smelting process required to produce aluminum from the alumina is continuous the potline is usually ept in production / hours a day yearround. A smelter cannot easily be stopped and restarted. If production is interrupted by a power supply failure of more than four hours, the metal in the pots will solidify, often requiring an expensi"e rebuilding process. !he cost of building a typical, modern smelter is about O+.< billion.
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Most smelters produce aluminum that is NN.:2 pure acceptable for most applications. owe"er, super pure aluminum (NN.NN2) is required for some special applications, typically those where high ductility or conducti"ity is required. It should be noted that what may appear to be marginal differences in the purities of smelter grade aluminum and super purity aluminum can result in significant changes in the properties of the metal.
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