US1645730A

US1645730A - Method of casting

Info

Publication number: US1645730A
Authority: US
Publication date: 1927-10-18
Anticipated expiration: 1944-10-18

Description

C VAUGHAN METHOD OF CASTING "OriginalFiIed Nov. 20; 1922 2 SheetsSheet l Oct. 18, 1927.

- 1,6457% 0 18, 1927., CIVAUGHAN METHOD OF CASTING Original Filed Nov, 20. 19.2.2v 2 Sheets-Sheet 2 50 Had 6 4 patented fiat, 18, 1927.

comm!) VAUGHAN, 0F CLEVELAND, ozaro, nssrenon To THE PER/MOLD COMPANY, or

. CLEVELAND, OHIO, A CORPORATION OF OHIO.

METHOD or CASTING.

Original application fil ed November 20, 1922, Serial No. 602,269.

December 26, 1924.

This invention relates to a method of casting metals in permanent metal molds' While the-invention is obviously of more general application in many of its aspects, it has been developed in connection with the casting of-articles from aluminum or its alloys, but is equally adaptable to any alloys having relatively high crystallization shrinkage and relatively low fusingpoint.

This application is a division of my prior application SerialNo. 602,269, filed November 20, 1922, for molds and method 'of casting. r

The general-object of the invention is to provide a method for castingsuch alloys toyield castings in Which porosity due to crystallization shrinkage or contraction and "too rapidpfouring is eliminated.

A'further object is to provide a process of casting suited to making castings having flanges or promotions or having sudden 'variations in the cross-sectional dimensions.

physicalstructure of the metal is of rela tively fine grain and relatively uniform throughout.

' Another object oflthe invention is to cause the metal to flow at a suitable rate into the 'mold cavity, and to accompany the by simultaneously cooling themolten metal remote from the gate or that in heavy or thick sec-- tions of the casting. Thus the freezing of the metal takes place progressively toward the gate and themetal in the mold cavity remains liquid between the pointwheresolidification is taking place and the gate.

The new metal coming through the gate comes at such a rate into the mold cavity that it will not be filled so rapidly that the metal in the gate orin any thin parts of the casting near the. gate Will be frozenbefore the metal'solldlfies ln the more remote or thicker parts of the mold cavity, andthus prevent feeding of the metal-through the gatewhen solidificationshrinkage is taking place in the metal'iii the mold cavity. 1 This overcomes the objection. sometimes encountered in other molds where the metal of thethin part solidifiesbefore the metal in the I Divided and this application filed Serial No. 758,115.

thicker partof the casting and thus prevents proper feeding-ofthemetal in the thicker part upon solidification and contraction.

WVithout such feeding, the contraction causes 7 a drawing away from the already solid metal ofthe thin part, resulting in cracking of the casting or uneven shrinking of the castmg from themold Walls causing depressions in the casting, or both.

\Vhile it is an object of this invention to provide a relatively small gate to control the rate of flowinto the casting cavity, it is also an ob ect of this inventionto provide agate which, due to its shape, Will prevent plpmg and will improve the physical characteristics of the metal in the casting adjacent the gate.

Another object of the invention is to provide amold in which the amount of molten metal required in the sprue is greatly reduced as a considerable cooling of ,the metal in the mold cavity is accomplished before the hot molten metal fills the sprue cavity. A relatively smaller amount of metal is therefore needed in thesprue cavity to feed the casting on account of the fact that there has been considerable cooling in the mold cavity and part of the shrinkage has already taken place in the mold cavity before the sprue cavity isfilled, and also because the freezing'of the metal in the mold cavity unfrozen parts of the casting in the mold cavity.

Another object of the invention is to provide a relatively simple method of cooling the portions ofthe mold distant from the gate to facilitate freezing.

Other objects will be apparent from the following description and annexed drawings.

Reference should be had to the accompanying drawings forming apart of this specification in which Figure 1 is a top plan view of the casting apparatus. Fig. 2 is "a side elevation'of the apparatus.

Fig. 3 is a section on line 33 of Fig. 1.

Fig. t is a section on line 4-e of Fig. 3. i

. Fig. 5 is a side elevation of a slightly modified form of theinvention.

Referring to the annexed drawings, the mold and actuat ng members tor the mold parts are mounted upon a base 'me'ii'iher oi bed plate 1; The mold may be made'of any suitable material and consists of a fixed'se'c-" provide the casting cavities '5'and a sprue' cavity =6 and IT-shaped feed openings on gates? leading frointhe sprue cavity to the casting cavity. The movable section has a'flat face on theside thereof toward the fixed section which fits against the re'- A. Core 81 maybe attached, to the faceotthe movable section 8 to project into the casting recesses cessed face of the fixed section.

5. -A threaded bar 9 is pivoted to the'outer side of the movable mold section 3, adjacent the base thereof -and; carries a nut 10;;uponits outer end, wh ch l ashandles'llfixed thereto and-1s formed with awide bearing groove '12 having side walls or "opposing, shoulders 12? and d2 An open yoke .13 is fixed to the end of the base member 1 ands adapted; to receive the gro0vedportion-12 of-the nut 10. Yhen the nut 10 is seated inthe yokel3, the yoke forms a thrust bearing for the nut so that by turning the nut in one direction -the shoulder 12 bears against theyoke and forces the bar 9 to move the section 3 until -it is clamped tightly against? the fixed sectionQ. After a casting has been made, thenut 1- 0 caii be turned in the *opposite direction by means of the handles L1 so that the-shoulder'12% bears against the yoke and pulls the mold section 3 away from the section 2, freeing it of-gthecasting. Thenut may then --be rotated or thesecjtion- 3:; moved so that the screw Q may be lifted freeof} the yoke 13in order that: the movable" sectioni} can be quickly pulled entirely away v a a x pipes 2a; and. 25-011 opposite sides of the ma fifonithefixed section 2. The fixed section 2 is provided with an ejecting mechanism consisting of aseries of pl ungers l4 slidably fittedin 'the rear wall: thereofand at the back; otfleach cast ng re-'- cess 5. Durin the 'o aeration of castin these plungersare in withdrawn position so that their ends are flush with thewall oi Th the recess and form a part thereof. plungers 14 in t'hepresent d sclosure are rigidly securedto across: bar 15 which ca1'-- ries a pair of rearwardly extending rack bars 16. These are engaged by an elongated pinion l7 journaled in a'suitable bracket-18;-

atthe rear endotthebase'member. A suit able OPGl'tltlIlQ lever 18 connected to one end 0f the" pinion to actuate the same. By

swinging the leverforwardly after'the movable mold section 3 has been moved away from the fixed section, the plungers 14 are caused to move in the same direction and eject'the castings fron'i' the mold." ln case the'r'e be""tl'1'e"sa'me numberof p'lu'nger's desired as'rack bars, the plungers themselves may beformed wlt-h' rack 1 teeth in t'liein a; be directl y ngaged by a pinion and thus do away with the connecting bar 01' plate 15. In tl'i'eniol'd herein disclosed by way of example, the movable section 3 is the one shown with; a fiat face as a matter o'f'cenvenienee, whereas it"isbbvious that either of the mold section's may'be movable but preferably the one is stationary which will retain cast ing until. it is ejected'by the ejector mechanism herein: described.

- kn important feature of the invention is the chilling of certainportions'o f the mold. While this :may hie accomplished inyarious ways, circulation of 'any suitable fluid, but preferably a liquid such as water orfloil, through the portions of the'moldfwhich are to be chilled has been foundtogive excel-v lentresnlt s. such chilling the rate of cooling of the metal of the thick parts of the casting is increased to such an. extent that the freezing if such-thick parts may be made to occur sooner" than the freezing or; the thinner metal parts between $11011 thick parts and the gate. i' the use of such chill; ing the metal: in the tiick parts o f'the cast ingor in those parts: having sudden v ne tions in cros ssectional dimensions is cooled so as to prevent crackingduringfreezing;

The fixed section'of-the mold is provided beneath the casting recesses Eifwith a, series otpassages 2Q extendinglengthwise thereof, the co're'8 has a passage'Q-L adjacent its bottom; extending lengthwise thereof, andthe plungers 1t arev hollow, and have axially disposed inlet pipes extending from the rear end thereof to the front end or 'fa ce engaging the casting. An outlet nipple 23 is located adjacent the rear end. Liquid is ciru' ats tli 'aus t e fix m dfs tioa 0 7 andejectors by means oft'eed and discharge chine. The feed pipe 2% has a connection 26 at its upper end from which short pipe sections 27 extend :to the passages 20 in the base portion of the fixed section A flexible conduitQS connects one end of the connection Qti with the passage 'Ql in the core 8, and a branch conduit 29 extends rearwardly and. across the rearend of the machine. Branch pipes-3,0with valves 30?; therein for regulatingt'he flow are in line with each of the ejector; plunge-rs14, extendingf-rom the pipe 2-9 to-a point: over the {rear ends of the plungers 1a and are connected to the inlet pipes 22 0f the plnngers by means of flexible hose sections 3l.- "Th? discharge pipe'25 is connected at its upper end with; a connection 32 similar to the connection 26, from which short pipe sections 33 extendto the outlet ends of the passages in the base of the fixed mold section 2. A flexible hose section 34: connects one end of the connection 32 with the outlet end of the passage 21 in the core 8, and a flexible conduit 35 extends rearwardly from the opposite end of the connection 32 and connects with a cross pipe 36, connected to the discharge nipples 23 of the plungers 14.

By means of the liquid circulating system above described the parts of the mold adjacent the lower portions of the casting cavities 5 are chilled so that metal in the casting cavities is frozen progressively towardthe gate and before the metal freezes in the gates 7. The gates are of relatively smaller cross-sectional area than in 'molds heretofore used, so that the flow of metal continues while a relatively larger portion of the casting is cooled or frozen, and so that the metal does notfreeze in the gates 7 until after all the metal necessary to replace the crystallization shrinkage of the casting isfed to the mold cavity.

In addition to being of'relatively smaller cross-sectional area, the gate has a large periphery with respect to its cross-sectional area, that is instead of being circular or.

ellipticahas is common practice, I have found that it is beneficial to form the gate of a cross-sectional shape such that all parts of the gate are relatively narrow and that there are no wide or. heavy sections of metal inthe gate. I have found that for this purpose a gate of T-shape is advantageous. With a' gate of such shape the tendency to form pipes extending down into the casting is prevented and it is not necessary to extend the gate upwardly a considerable distance to provide a large spruecavity to furnish sufiicient head toprevent the piping formed upon solidification from extending down into the casting. Moreover, with a gate of T or similar cross-sectional shape, namely, a gate having a relatively long and narrow cross sectional portion and having a laterally ex tending cross-sectional portion communicating with saidlong and narrow portion, de pressions inthe surface of the casting may in many cases be substantially eliminated, as previously mentioned, such advantageous results being probably due in part to escape of air from within the mold being more readily facilitated by gates of such shape, as the flow of part of the molten metal is directedaway. from the parting line of the mold.

narrow gate portion and the lateral gate portion adjacent their intersection receives heat from the molten casting metal disposed'withisnot readily dissipated from said bordering mold metal. The said mold metal therefore exerts less chilling action on the molten casting metal than the mold metal adjacent the other portions of the gate. As a result, the casting metal disposed adjacent the inter section ofthe gate portions remains molten longer than the remainder of the casting metal in the gate, thereby increasing the time of feeding of molten metal through the gate to' the castingcavity adjacent said intersection.

Heretofore it has usually been considered necessary to apply heat to portions of the mold to prevent freezing in the gate, or to use metallic inserts of high heat conductivity to chill the thicker parts of the casting. The heating of the mold is expensive and I have found that it is not necessary andin fact slows down the casting operation. It is ad perature of the mold, thus producing a casting of better physical characteristics. In View of the greater rapidity of operation and-also in view of the shape of the gate, the sprue cavity can be relatively small and the 'sprue metal required is much less than heretofore, when the volume of metal in the sprue was about one half the volume of metal in the casting, which was considered good general practice. By the present method the volume of metal'in the sprue need not be more than a maximum of approximately 25% of the volume of metal in the casting, which eil'ects a considerable saving in melting costs.

The cooling of the ejector plunger causes the metal of the castings to be chilled at the points where they are engaged by the plungers, so that the relatively hot castings are not deformed by the pressure exerted thereon bythe plungers.

It will be seen that any number of castings may be made in one mold, each casting cavity having a gate connecting it to the commonv sprue. Furthermore by having the molds designed so that the gates come on the ends of the'casting, a series of castings may.

be easily. trimmed simultaneously by sliding them on their flat faceson the table of the trimming machine. Also as the metal com ing from the gate is thin in cross-sectional shape it is more easily and quickly cut through than when a circular or elliptical gate is need; i

In the inoditied construction shown in Fig.6 the base '1? aiid tiir'ed and movable sectio 2 and 3f are constructed in siib y the same winner as the cori spoliding'parte in the modification lirstde sc'ribed. ln'thie modification, 'howei er, we movable sect-ion core pins ltl sl dably" nioniited in openings therethrough andproeet' ng into the c'astln recesses; The core pins 40 are for the purpbse'ot' forming aper:

three seems bolt'heles or thelike" in de siredfportions' of the casting. The" pins 401 arehxedto a plate ll which is adapted to 'bear against the outer face of the moi able mold section 3f"; A liracket 42 is attached tfithe baseotthe movable section and has stop' pin's'"43 detaehably secured thereto and projecting toward the plate 41'." Ascre 9 similar 'tdthe ScreWfQ ab V'e' described is pivetall attadh edfte the pita 4i; "lhe'ieections 2 and S are held in pos tion after they are in Close contz tbysuithble catch 44 iiivot'ed to one oitthenl. When the shew" base, which will prevent "small pieces or scraps of metal which'tall between the sec tio'ns of the mold from keeping the mold seetionsiou t of close contact.

It Will thna be seen that I have provided a method 01" Casting aluminum allo'ye ari'dfthe i |1\.-" A J- i .v like whereby the ireezing of irregularly shaped castings may be caused to take'place progressivelytoiyard the gate. By my method, moreover, the freezing ot the casting metal may take place relatively rapidly. Thus" the time required lreae casting operationis materially reduced and the reduction of castin s reatliv increased.

Fureaennore, by ieason'ot the progre'i and relatively rapid freezing of a casting as accomplished by my improved method, less nielte'n metal to compensate for crystallizw tion shrinkage of the casting metal remains to be 'tedfro'ni the spree cavity'thrbugh the gate the casting'cai ity after the filling of? the Listing cavity, and hence asmiille'r 'spru'e cavity may be employed "with, attendant advanta dnction'.

Furthermore, it is to be understood that the particular forms of apparatusshown and described, and theparticnlar procedure set forth are presented for purposes 0t expla-' nation and illustration and that various modifications of said apparatiis and proce} dure'can be made 'witheut depart ng l' IO TDj dy'the core bins 410 are iirstpa'rti'ally" inclndingdecreased cost oi pm y nv ntive as efi d n heeppe del;

claime.

"'W hat I claim is: li 'l' he method 0ft castinga metallic alloy of relatively high, crystallizati on shrinkage and 7Q of 'r'elatiwly low flisi ngjjoiiit which consists 1 in eeri g sn(:h"metal into a."n'ietal mold (if substantially uniform heat condiictivity hat?" irw' a iiiolid cavity, a i l'atiyely small sprne cavity, alid 'a i-elatively narrow gate between their controlling the lfl Q X V of metal through tl i e'gate hem the spru cavity ahd chilling the metal in the mold cavity insu'cl'i" a manner that f're'ezih is progresiye mwair'd 1 the gate, whereby the surplus of metal 'i'ifthe so gate and spriie j cavity is maintained "molten fine b tant ally he solidification 5' if} a; otthe'n'ietalin the mold cavity.

The method of casting ametallic alloy of relatively" high 'cry stallization shrinkage and lbw fusing pbint which consists inpoiir ten metal into a'mold of Substantially unifoi-i'n heat condi'i'ctivity; the sprue cavity; 0t which has a gate communicatingyiiththe' 111;: "cavity, and 00011110 such" portions of W ni'old about the casting"cavityithichare ed by thethick part the casting." he process of making light alloy castings \"vhich consists in ponrihg molten metal into nietfal ii'i'cilds of' 'snbstantiallyuniform heat" conductivity haying a mold cavity; a relatively small gate a relatively small" sprite cavity, and cooling the meld" adjacent manna; parts" of the cast'ing to insurathe ti jezi g of the metal in the mold'cai ity and Q thick parts oft' h e casting before the metal in the gate orsprne cavity is frozen.

if, The r cesse-r making castingshil ving shapes with sudden Va iations in their cross sectional Adimehs'ions, from light 'allo'ysj havrelati el higli' crystallizatibn shrinkage and relative y low fusing p'oint'whic'h consis'ts in ll ltlbtlt lclllq siic'h me't'al'int'o a metal" mold ar substantially uniform heat con'chic and chillingthe iiietal inthe thicker part of the casting, whereby the metal inthe cas ngiza'vity" i3 solidifietlif"prbgressively tmyatdthe gate and spri e cayity.

5. Themethod 0t castin which consists in introducingmolten mmf ine; a mold c'ayit'y, agate, and a spine ca le ming the heat from the heavier sections of the inetal'i'n/the castg by cireulatingfliqnid"through the adj: part of the mOldtoiinsni'e soliditieatioiibf the metal ,9

in the mold progressively toii'ard the gate;

6. The method ofcasting an alloy of relatively high crystallizationshrinkage and a relatively low melting" point 'which 'coneists in"inti'cdncing molten metal oftsu'ch char-' 2?. acterietics into a 'Iiermanent m olc l having a I gate oif such shape" that 'ea'chfa'rt' oi the molten n' etalsolidiifyingin the gate is 'relatively close to themes-1 otthe' mold.

7. The method ot'.nasti ng an alloy ofrela in metal molds 7 3 tively high crystallization shrinkage and a relatively low melting point which consists in introducing molten metal of such characteristics into a permanent mold having a gate of such shape that each part of the molten metal solidifying in the gate is relatively close to the metal of the mold, and cooling the mold adjacent the thicker or more remote parts of the casting.

8. Theprocess of making light alloy castings in permanent molds of substantially uniform heat conductivity having a relatively small gate and sprue cavity which consists in introducing molten metal into the sprue cavity and cooling the mold at points remote from the gate, whereby substantially all of r the metal in the mold cavity solidifies before the surplus metal in the sprue cavity.

9. The method of casting metals having a relatively highcrystallization shrinkage and a relatively low melting point which con sists in/introducing molten metal into a mold of substantially uniform heat conductivity having a relatively small gate and sprue cavity and chilling portions of the mold adjacent the heavier sections of molten metal, whereby relatively rapid solidification of the casting is accomplished and such solidification is progressive toward the gate to insure the casting receiving fresh molten metal to compensate for shrinkage.

10. The method of casting, relatively rapidly, metals having a relatively high crystallization shrinkage and a relatively low melting point which consists in introducing such molten metal into a permanent mold of substantially uniform heat conductivity through a relatively small gate and cooling the portions of the mold adjacent the heavier sections of the casting, whereby a relatively smaller volume of metal is needed in the sprue cavity to furnish molten metal to compensate for shrinkage losses and a relatively quick total solidification is obtained.

11. The method of casting metal alloys having a relatively high crystallization shrinkage and a relatively low melting point which consists in introducing such metal into a permanent mold of substantially uniform heat conductivity having a mold cavity shaped to form a casting having an irregular distribution of metal, such mold having a relatively small gate, and cooling portions of the mold adjacent the heavier sections of casting metal.

12. The method of casting which consists in pouring molten metal into a permanent mold ;of substantially uniform heat conductivity and maintaining the fluidity of such metal through the gate into the casting cavity during the freezing of the casting by chilling only those portions of the mold adjacent the heavier sections of metal and permitting the metal in the thin sections to remain'fluid between such heavy sections and the gate.

13. The method of simultaneously making a plurality of castings from metal of relatively high crystallization shrinkage and relatively low melting point which consists in introducing molten metal of such characteristics into a permanent mold of substantially uniform heat conductivity having a plurality of mold cavities with gates leading thereto from a sprue cavity and causing the solidificationtof the heavy sections of such castings by cooling the mold adjacent thereto, so that solidification of the metal of the castings is progressive toward the gate to insure a constant supply of fresh metal to compensate for shrinkages.

In testimony whereof, I hereunto afiix my signature.

CONRAD VAUGHAN.