US2313517A - Foundry mold insert and method of making castings - Google Patents

Description

March 9, 1943.

FOUNDRY MOLD INSERT AND METHOD OF MAKING CASTINGS s. 1.. CAMERON 2,313,517

Filed Jan. 21, 1942 loooo-o '0 000 ioooooooj Z7 A 7 '00 I I O OZ INVENTOR. 5ru4er Z, Cami/ 0M BY Y/IWJZ? i/zrwa ATTORNEYS Patented Mar. 9, 1943 FOUNDRY MOLD msm'r AND METHOD or MAKING CASTINGS Stuart L. Cameron, St. Paul, Minn, assignor to Meehanite Metal Corporation, a corporation of Tennessee Application January 21, 1942, Serial No. 427,602

12 Claims.

My invention relates to the foundry molding art and more particularly to an insert member to be positioned in the port connecting the casting cavity and the riser cavity of a foundry mold and to an improved method of feeding the shrinkage void of a casting during the cooling of the casting with the molten metal supplied by a riser and for facilitatin the removal of the riser from the casting after cooling.

In the foundry art such as in the making of castings of iron and the like, it is well known that the metal of the casting shrinks in volume during the cooling of the casting in the mold from the molten state to the solid state. To avoid the presence of shrinkage voids and to assure the production of castings of solid metal in full volume it has been the practice to provide a reservoir of molten metal to feed the casting with molten metal during cooling and shrinkage. This reservoir of molten metal is commonly termed a riser. The foundry flask has formed therein, generally impressed or built up in sand or similar suitable material contained in the mold flask, a casting cavity, a gating system, a riser cavity, and a port interconnecting the casting cavity and the riser cavity. Upon solidification and removal from the mold, the riser, being a superfluous appendage on the casting proper, must be removed. This is usually done by the laborious and time consuming process of chipping with a chisel or otherwise cutting and breaking the neck connecting the casting and riser, the neck being that portion of metal solidifying in the port or throat that connects the casting cavity and the riser cavity'of the mold. The port being made relatively large in cross-section to assure the complete feedin of the casting during cooling and shrinkage produces a riser neck on the solidified casting that is relatively thick and difficult to sever from the casting. Moreover, there is a tendency in breaking the thick riser neck from the casting to cause the fracture to run into the casting proper and to thus form a pocket or recess extending into the casting, the larger the riser neck being in cross-section the deeper the pocket or recess that may be produced in the casting from the fracture running into the casting.

If the riser neck is reduced in cross-sectional size by merely reducing the cross-sectional area of the port between riser cavity and casting cavity, removal of the riser is facilitated but the reduction in cross-sectional area of the port ordinarily induces an early freezing or solidification of the riser neck and consequent hindering or preventing of a complete feeding of the casting during cooling with metal from the riser.

It has not been possible to overcome the above described difiiculties of removal of the riser from the casting by merely reducing the size of the port or throat between the casting cavity and riser cavity and a consequent reduction in crosssectional dimension of the riser neck. By reason of the normal isothermal lines of the metal in the port during cooling it has been necessary to have a relatively large port to assure that the metal in the port does not completely solidify or freeze before solidification and shrinkage of themetal of the casting is completed. This necessity required a minimum size in the port and consequent minimum size of the riser neck for a casting of particular volume and design. Therefore the port, and riser neck formed therein, could not be reduced in size and at the same time assure proper feeding of the casting with fluid metal from the riser by reason of the problem of assuring a free flow of fluid metal in the port during cooling of the casting.

It is an object of my invention to provide for the overcoming of the above described difi'iculties of removal of the riser and at the same time to provide for the assurance of a free flow of fluid metal through the port from the riser to the casting during cooling of the casting.

Another object is the provision for causing a relatively weak part in the riser neck to permit ready removal of the riser from the casting after solidification.

Another object is the provision for providing connections of relatively small cross-sectional dimension between the casting and riser.

Another object is the provision for maintaining the metal in the port between casting cavity and riser cavity at the temperature of fluidity after pouring and until cooling and shrinkage of the casting is completed.

Another object is the provision for retaining heat from the molten metal passing through the port during pouring of the casting and restoring the heat to metal in the port during cooling of the casting.

Another object is the provision for insulating the molten metal in the port between casting cavity and riser cavity to maintain fluidity of the metal during cooling of the casting.

Another object is the provision for taking advantage of the heat reaction characteristics of sand and similar refractory material, and particularly core sand, in the feeding of a casting from a riser during solidification and shrinkage.

Another object is the provision of an improved insert to be positioned in a foundry mold within the port connecting a riser cavity and casting cavity and next adJacent the casting cavity.

Another object is the provision of an improved method of feeding a casting from a riser during solidification and shrinkage of the casting.

Other objects and a fuller understanding of my invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawing, in which:

Figure 1 is a longitudinal cross-sectional view taken lengthwise of a foundry mold embodying my invention and is taken along the line i-l of Figure 2;

Figure 2 is a plan view looking down on the bottom portion of the mold of Figure 1 and is taken along the line 22 of Figure 1;

Figure 3 is an enlarged fragmentary view of a portion of the mold of Figures 1 and 2 and particularly showing the mounting of my improved insert therein, and is a view looking in the direction of the arrows 3--3 of Figure 2;

Figure 4 is another enlarged fragmentary view of a portion of the mold of Figures 1 and 2 and particularly showing the mounting of my improvedinsert therein, and is a view looking in the direction of the arrows 4-4 of Figure 2;

Figure 5 is a detail view of a preferred form of insert embodying features of my invention;

Figure 6 is a cross-sectional view through the line 56 of Figure 5;

Figure '7 is a detail view of a modified form of insert embodying features of my invention;

Figure 8 is a cross-sectional view through the line 8-8 of Figure 7;

Figure 9 is a detail view of another modified form of insert embodying features of my invention; and

Figure 10 is a cross-sectional view through the line l|0 of Figure 9.

With referenceto the several views of the drawing, there is shown a foundry mold comprised of a cope II and drag H. The sand mold part IS in the cope and the sand mold part l4 in the drag meet along the common line 2-2 of Figure 1. The pin holders: 25 are provided at opposite ends of the mold. Impressed or otherwise formed in the sand mold l4 of drag I2 is the casting cavity l for containing the casting to be produced. A riser cavity I5 is formed in the assembled parts of the mold, as shown in.

Figure 1, to provide an upwardly rising reservoir for molten metal. A box 23 on the top of the mold provides for upward extension of the riser cavity.

For pouring molten metal into the casting cavity there is provided a pouring basin or cup 2| formed in the box 22 upon the top of the mold. A sprue 20 extending down through the mold communicates with the runner 18 disposed horizontally in the mold. The plurality of gates l9 connect the runner I8 with the casting cavity l5.

Providing communication between the casting cavity l5 and riser cavity I 6 there is a port or throat I! cut or formed in the sand part [4 of drag 12. The port I! forms a channel through which molten metal may flow between the casting cavity and riser cavity.

Next adjacent to the casting cavity I5 there is cut or impressed a stepped portion to form a largement of the port H for a short distance from the casting cavity proper.

My improved insert 21 is positioned in this enlargement of the port I! intermediate of the casting cavity l5 and the shoulders 24 and 25 The insert snugly fits between the parts I3 and H of the mold and is held in upright position therebetween. The shoulders 24 and 25 provide a backing for the insert 21 and prevent it from being moved longitudinally of the port ll between the casting cavity and riser cavity. The tight engagement of the insert and the walls of the port I I when the cope i i is mounted over the drag l2 firmly holds the insert in place. If desired, nails may be used to help hold the insert in place before the cope is placed over the drag. Also, an appropriate binding agent applied to the peripheral edges of the insert may be used to secure the insert in position.

The insert 21 is positioned across the port I1 and athwart the fiow of molten metal in the port. As outer portions of the insert are engaged by the shoulders 24 and 25 there is a reduced area of the fiat surface of the insert which is met by the molten metal in the port IT. This area of the insert within the confine of the minimum dimensionv of the port, that is, at the edge of the shoulders, is designated as the eflective area of insert and is shown in broken lines identified by the reference character 28. It is the effective area 28 of the insert which contacts, and controls the flow of, molten metal through the port between the riser cavity and casting cavity.

In the preferred form of insert, shown in Figures 1, 2, 3, 4, 5 and 6, there are a plurality of relatively small round openings 29 extending through the insert and uniformly distributed over the effective area 28. The edges of the openings 29 are somewhat champfered as shown in the drawing to avoid sharp corners of sand material to be encountered by the molten metal.

The insert is made of a frangible refractory material of high heat insulating nature and is preferably made of core sand. The insert is formed in the usual manner of making foundry cores, in which sand is mixed with linseed oil or other binder, molded to shape in the cavity of a core box, and baked in a core oven. By reason of the preferred material from which it is made and the manner in which it is formed, my insert may be referred to as a core or core-sand insert.

The disposition of the openings in the insert is such that the insert constitutes a grid or network of alternate open spaces and solid portions. Ihzcept for the outer peripheral portions of the insert, the solid portions of the insert are embraced or bounded on opposite sides by the openings. This grid of divided solid portions is thus brought into intimate heat exchange relationship with molten metal in the port and passing through the openings. A relatively large surface area is provided by this structure for contact and heat exchange between thev sand of the insert and the molten metal in the port. All of the solid portions of the insert within the effective area 28 are in relatively close contact with the molten metal and particularly those intermediate solid portions of the insert that have openings 29 disposed on opposite sides thereof whereby heat may be exchanged with the metal in more than one lateral direction across the insert.

Refractory material such as sand and particularly core sand possesses the characteristics of being a good heat insulator. It can absorb heat at the point of contact with molten metal but cannot conduct or transmit the heat very far away through the sand. It has been found that such material and particularly core sand will heat up relatively slowly and also cool down relatively slowly in relationship with metal, such as cast iron. In tests with pyrometer readings it has been determined that core sand lags behind metal in going to a high temperature and in returning to a low temperature. It is capable of storing latent heat and imparting this heat to metal in the immediate vicinity and to slow up the cooling rate of the metal. By dividing up the sand and metal into relatively small portions or sub-divisions so as to bring them into intimate heat exchange relationship it is possible to take advantage of the different heating and cooling characteristics of the sand and the metal notwithstanding the low heat conductivity of the sand.

The useful and novel character of my invention may be illustrated by a description of an operation utilizing the new insert. With reference to Figure 1, molten iron is poured into the basin 2i, down the sprue 20 and into the casting cavity i 5 through the runner I8 and gates IS. The molten iron also flows from the casting cavity l5 out the port I! and up into the riser cavity l6 until the riser cavity i6 is substantially filled. During the progressive movement of molten iron from the casting cavity, through the port l1, and up into the riser cavity, the molten iron has passed relatively rapidly through the openings 29 and in intimate heat exchange relationship with the solid portions of the insert 21. The solid portions of the insert thus become super-heated by reason of the rapid addition of heat to the large contact area of sand material encountered by the moving molten iron. The super-heated insert then holds a large quantity of heat that it is capable of imparting to iron in close heat exchange relationship with it.

After pouring, there is a short period in which there is substantially no movement of metal through the mold cavities. Soon thereafter the casting begins to cool and to solidify. Upon cooling, the iron casting begins to progressively shrink in volume and will contain shrinkage voids unless constantly fed with another iron through the period of solidification from the communicating reservoir or riser of molten iron. It is essential that the iron in the port through which the metal is fed from the riser is kept at a high temperature to assure fluidity of the iron. If the iron in the port freezes or solidifies too soon the casting is starved or deprived of the necessary surplus iron required to produce a sound casting.

By the use of my insert in the manner described, the insert acts as a heat reservoir, holding the large amount of heat progressively imparted thereto during the pouring of the iron into the mold. The construction of the insert is such that the sand material thereof is disposed in intimate heat exchange relationship with the iron substantially all through the cross-sectional area of the port. During the feeding movement of the iron from the riser to the casting the insert imparts heat to the more rapidly cooling iron and thus prevents the formation of the normal isothermal lines which would exist if the insert were not there.

The influence of the insert is therefore such that the port or neck of the riser is held open longer than if the insert were absent. The sand being heated to a high temperature by the molten iron but having a lower heat conductivity than the iron, remains at the temperature of fluidity of iron much longer than if the insert had not been used and the neck of iron in the port had been permitted to solidify through its natural isothermal lines. Therefore, by the utilization of my invention the port I! remains open and the iron therein continues to be fluid until such time as the casting in the cavity i5 is completely solidified. The casting being fed from the riser throughout the period of solidification is sound and without shrinkage voids.

Upon shaking out of the casting from the mold, the riser is readily severed from the casting by chipping or otherwise breaking the relatively weak connections of solid iron within the openings 29 of the frangible sand insert. It is apparent that removal of the riser is thus greatly facilitated by providing these many weak connections rather than having to cut or break a solid neck of iron. Likewise, the fact that the danger of the fractures extending into the casting proper is very much diminished, will be readily apparent. The economy in foundry practice made possible by the utilization of my invention will be fully appreciated by those acquainted in theindustry.

'In Figures 7 and 8, there is shown a modified form of insert. In this modified form there are three relatively large openings 32 centrally disposed in the effective area of the insert, and grouped around the openings 32 are a large number of smaller openings 33. As in the previously described preferred form of insert, the molten iron first flows through all the openings and in turn the contacted surfaces of solid portions of the insert impart heat to the adjacent iron, and particularly the iron in the plurality of openings. There is emphasized, however,- in the modified form of Figures 7 and 8, the fact that the outerly arranged openings 33 provide for the superheating of the solid portions of the insert around the centrally disposed openings 32. The centrally disposed openings 32 may thus be made somewhat larger than the other openings to permit a more rapid and free flow of metal therethrough and the solid portions of insert around the openings 32 will be sufliciently heated to maintain the fluidity of the metal therein during the feeding from the riser to the casting.

In Figures 9 and 10, there is shown another modified form of insert somewhat similar to that of the insert shown in Figures '7 and 8. In Figures 9 and 10 the three relatively large rectangular openings 30 are substantially surrounded by the smaller rectangular openings 3|. While all of the openings and separated solid portions function as described in connection with the preferred form of insert shown in Figures 1 to 6, there is emphasized here the particular advantage of the surrounding openings permitting the molten iron to impart heat to the outer of the opposite sides of the fingers of solid sand adjacent the centrally disposed openings and thus providing for the thorough and concentrated heating of the sand around the centrally disposed openings.

My invention includes the method herein suggested of-dividing up the metal in the port of the riser into a plurality of separate portions and of maintaining these portions of metal in intimate heat exchange relationship with core sand or similar material placed in close contact with, and surrounding, all the said separate portions of metal during the period of pouring the casting and during the period of feeding the casting during solidification and shrinkage.

The present disclosure includes the'description contained in the appended claims as well as the above contained description and the description stated in the appended claims is incorporated by reference in this specification.

Although I have described my invention with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts and modifications in the steps of the disclosed method may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

I claim as my invention:

1. In a foundry sand mold having a casting cavity, a riser cavity for feeding surplus molten metal to the casting cavity during shrinkage in the casting and a connecting open space between the casting cavity and the riser cavity, the connecting open space having a set-back at said casting cavity to provide a shoulder portion spaced from the casting cavity, the improvement of a core-sand insert adapted to be placed in said connecting open space next adjacent and intermediate, the casting cavity and said shoulder portion, said insert being comprised of a substantially flat body of molded core sand having a plurality of closely spaced openings extending therethrough, said openings being distributed over the effective area of said insert defined by the said connecting open space through which molten metal moves, some of the openings being positioned around, and in close proximity to, other of the openings whereby molten metal moving through said some of the openings stores heat in the insert around the other of the openings and molten metal moving through the other of said openings stores heat in the adjacent portions of the insert, the heat stored in said insert retarding the normal cooling rate of the molten metal in said open space to assure the feeding of said surplus molten metal from the riser cavity into the casting cavity during shrinkage of the casting.

2. In a foundry mold having a casting cavity, a riser cavity for feeding the casting cavity during shrinkage of the casting in cooling, and a port connecting the casting cavity and the riser cavity to permit molten metal to flow therethrough, the improvement of a core-sand insert positioned in said port adjacent the casting cavity and athwart the port in the path of said molten metal, said insert being comprised of a substantially fiat body of core sand having peripheral edge portions and having open spaces and solid portions alternately disposed therein intermediate of said edge portions at close intervals across the cross-sectional area of the port to form a plurality of spaced solid portions of sand next adjacent to, and on opposite sides of, bodies of molten metal in said open spaces, and in intimate heat exchange relationship with said molten metal, the said solid portions being heatable to a high degree of temperature by the said molten metal and being capable of maintaining the adjacent molten metal in said port at a high degree of temperature during the cooling and shrinkage of the casting to assure fluidity of the molten metal in said port and the feeding of the shrinking casting with metal from said riser,

3. In a foundry mold having a casting cavity, a riser cavity for feeding the casting cavity during shrinkage of the casting, and a port connecting the casting cavity and the riser cavity to permit molten metal to flow therethrough, the improvement of a core-sand insert mounted in said port, said insert having a plurality of interstices extending therethrough to form a grid having interconnecting solid portions, the interstices and solid portions alternating across the insert intermediate the peripheral edges thereof, said peripheral edges of the insert being engageable by the walls of said port and the alternating interstices and solid portions of the insert being extended across said port, the alternating solid portions .being heatable to a high temperature by the molten metal passing through the adjacent interstices in moving through the port during pouring of the casting and the molten metal in said interstices being maintainable at a high temperature by the heat in said solid portions during cooling of the casting to assure the fluidity of molten metal in the port and the feeding of the shrinking casting by the riser.

4. A core insert positioned in the port connecting a casting cavity and a riser cavity in a foundry mold, said core insert comprising a substantially flat plate formed of refractory material of low heat conductivity capable of absorbing heat from molten metal immediately adjacent thereto and restoring the absorbed heat to molten metal immediately adjacent thereto, said insert having a plurality of openings extended therethrough, said openings being distributed at recurring intervals in a plurality of directions across the fiat plate intermediate the opposite edges thereof, the portions of the fiat plate adjacent said openings being heated by molten metal passing therethrough during pouring of the casting, the portions of the flat plate intermediate of said openings being heated on both of the opposite sides thereof by said molten metal, the said molten metal being retained at a fluid temperature in said openings, and particularly in those openings bound by said portions of the fiat plate heated on both opposite sides thereof, during cooling of the casting to assure feeding of the shrinking casting through the said port from the said riser.

5. A frangible body of molded refractory material of low heat conductivity capable of absorbing heat from molten metal immediately adjacent thereto and of restoring the absorbed heat to molten metal immediately adjacent thereto, said body having a plurality of openings extended therethrough to form a grid-work of solid portions embraced by said openings, the said body being inserted in the port connecting the casting cavity and riser cavity in a foundry mold to provide for the flow of the molten metal in said port through said openings during pouring of the casting whereby the grid-work of solid portions becomes super-heated by the said flow of molten metal through said openings and thereafter restores heat to the molten metal in said port during cooling of the casting to-assure fluidity of metal feeding into the shrinking casting from the riser.

6. In a foundry mold having a casting cavity, a riser cavity, and a port connecting said cavities, the improvement of a flat molded body of frangible refractory material having a plurality of openings extended therethrough and distributed in both lateral directions across the flat face thereof, said body being engaged by the walls of said port and held in said port adjacent the casting cavity and athwart the flow of molten metal through the port, the flow of molten metal through the port upon pouring of the casting being divided into a plurality of rods of metal in said openings separated in both lateral directions across the flat face of the body by solid portions of the body, the separate rods of metal exposed upon breaking away the said body after cooling of the casting facilitating the removal of the riser from the casting by the breaking of the said separate rods of metal.

\ 7. In a foundry mold having a casting cavity, a riser cavity for feeding the casting cavity during shrinkage of the casting and a port connecting the casting cavity and the riser cavity to permit molten metal to flow therethrough, the improvement of a refractory insert adapted to be positioned in said port next adjacent to said casting cavity, said insert having a frame portion engaged by the walls of the port and extending around an open space for accommodating the flow of metal through said port, said insert having a plurality of spaced solid portions extended in a plurality of directions laterally of the insert and into said open space from the surrounding frame portion and positioned in intimate heat exchange relationship with metal in said open space, said spaced solid portions of the insert upon being heated by the adjacent molten metal passing through the port during pouring of the casting maintaining the metal in the port at a temperature of fluidity during cooling and shrinking of the casting and said spaced solid portions of the insert dividing the metal in said port into a plurality of spaced and relatively narrow portions of solid metal after cooling to facilitate the ready separation of the riser from the casting.

8. In a foundry mold having a casting cavity,

a riser cavity and a port therebetween, a flat plate molded of core sand or the like inserted in said port next adjacent the casting cavity, said flat plate having a plurality of openings extended therethrough and distributed at intervals across the face of the fiat plate in a plurality of lateral directions, said openings accommodating molten metal in said port, the solid portions of said flat plate intermediate of said openings dividing the molten metal in the port into a plurality of portions accommodated in said openings and surrounding each of said portions of metal, the separate portions of surrounded metal upon solidification providing relatively weak connections between the casting and riser to facilitate the removal of the riser from the casting.

9. In the foundry casting art, the improvement of separating the molten stream of metal intermediate the casting cavity and riser cavity into a plurality of separate streams of metal spaced apart in a plurality of directions and surrounding each of said separate streams of metal with an insulating material capable of storing heat from the metal during pouring of the casting and imparting heat to the metal during cooling of the casting with relatively no conduction of heat away from the metal whereby the separated streams of metal are maintained at a temperature of fluidity until solidification of the casting is completed.

10. In the foundry casting art, the improved method of dividing up the metal in the port intermediate a casting cavity and riser cavity into a plurality of separate portions of metal, intermediate said casting cavity and said riser cavity, and of maintaining these separate portions of metal in intimate heat exchange relationship with core sand or similar insulating material placed in close contact with, and surrounding, all of the said separate portions of metal during the period of pouring the casting and during the period of feeding the casting during solidification and shrinkage.

11. The combination of a foundry mold having a casting cavity, a riser cavity and a port connecting said cavities, and a core-sand insert member mounted in said port next-adjacent the cast- I ing cavity and athwart the flow of metal therethrough, said insert member having a. plurality of small openings distributed in a plurality of directions over the face of the insert member and extending therethrough for providing communication between the casting cavity and the riser cavity, the arrangement of the mold and insert member providing for the imparting of heat to the insert member by molten metal in said port and for the maintaining of the temperature of said molten metal by said imparted heat.

12. In the foundry casting art, the improved method comprising: forming a mold having a casting cavity, a riser cavity and a port connecting the casting cavity and riser cavity; mounting in said port and adjacent to the casting cavity a refractory insert member having a plurality of small openings extended therethrough and distributed in a plurality of directions across the face of the insert member; and introducing molten metal into said casting cavity, riser cavity and port to impart heat from said molten metal to said insert member during initial movement of molten metal through said openings and to transmit the imparted heat to said molten metal during subsequent movement of the molten metal through said openings.

STUART L. CAMERON.

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