US2497210A - Method for casting metals - Google Patents

Description

Feb. 14, 1950 R. E. DAY

METHOD FOR CASTING METALS 2 Sheets-Sheet 1 Filed March 6, 1947' Feb. 14, 1950 R. 5. DAY

METHOD FOR CASTING METALS 2 Sheets-Sheet 2 Filed March 6, 1947 Patented Feb. 14, 1950 UNITED STATES PATENT OFFICE METHOD FOR CASTING METALS Ray E. Day, Detroit, Mich.

Application Mar ,6, 1947, Serial No. 732,886

2 Claims. (Cl. 22-134) This invention relates to the art of casting metals and more particularly to an improved foundry mold and an improved method for casting metals.

One of the objects of the present invention is to provide an improved foundry mold whereby high quality castings at relatively low cost are produced and the-usual percentage of scrap is considerably reduced.

All sand molds for casting metals are suitable for a single use and each mold is broken up after a casting operation. Thus, in casting metal in said molds it is necessary to prepare a new mold for each casting to be poured. Since the cost of each sand mold, which is largely labor expense, enters into the cost of the casting produced in the mold, it is apparent that the time involved in preparing the sand mold must be reduced to .a minimum otherwise the cost of the casting may be commercially prohibitive. It is important that sand molds be produced as nearly as possible on a production basis with unskilled labor in order to keep down the cost of the castings. However, this cannot be done in accordance with prior commercial practice and at the same time produce castings of high quality having a minimum of porosity, defects and gas holes. Where the sand molds are complicated and require the expenditure of considerable time in preparing them as well as requiring the use of highly paid skilled labor, many kinds of castings cannot be made commercially except at relatively great expense and even then the castings are seldom of the desired high quality. Such practice either restricts greatly the field of usefulness of green sand molds or enhances materially the cost of the products cast in such molds.

The present invention eliminates the foregoing disadvantages, first, by enabling the mold sections to be prepared rapidly and cheaply on a production basis using unskilled labor, and secnd, by providing a construction which enables uniformly good castings of high quality to be produced with a minimum of scrap loss.

A further object of the present invention is to provide an improved foundry mold for producing superior castings, the mold being composed of two sand mold sections forming when superimposed a parting line and a casting-producing cavity, the upper or cope section having an open top riser disposed between the pouring sprue and the cavity and terminating at the parting line, and the lower or drag section having a runner extending along and parallel to the parting line and a baflie projecting upwardly across the bottom of the runner and disposed immediately below the riser and so constructed as to cause all of the molten metal from the runner to be deflected upwardly into the lower end of the riser at the sprue side thereof and thence to flow across the top of the baflie and down into the runner at the cavity side thereof. This improved sand mold, as well as the improved method of casting metals utilizing such mold, has the important advantages of greatly reducing porosity, gas holes and defects in the casting while at the same time eliminating time and labor expensein preparing the mold, as a result of which the molds can be made cheaply and quickly on a volume basis without increasing the cost of the castings.

A further object of the invention is to provide a sand mold of the foregoing character in which the improved construction is such that the runner, bafile and gating in the drag section may be formed quickly from a single pattern plate, this by reason of the fact that the runner is open throughout its length along the parting line when the mold sections are separated, and further by reason of the fact that the sprue and riser, or risers, in the cope section terminate at the parting line where they communicate directly with the runner. As a consequence of this improved and simplified construction, the mold sections may be made quickly and cheaply, ensuring the production of castings of high quality at a relatively low cost, and reducing to a minimum rejections due to defects.

A still further object of the present invention is to provide an improved foundry mold in which means are provided to control the degree of agitation of the molten metal in the mold as well as the rate of metal flow and the force with which the metal enters the mold.

A still further object of the invention is to provide an improved foundry mold in which means are provided to ensure a predetermined and uniform force and rate of entry of the molten metal into the mold, irrespective of the pouring technique or skill of the operator.

A still further object of the present invention is to provide an improved foundry mold adapted for casting therein gas bearing and gas liberating metals and alloys, means being provided in said mold whereby such gases or fumes may be liberated from the metal before the same enters the casting-producing cavities of the mold.

A still further object of the invention is to provide an improved method of casting aluminum I and aluminum alloys in green sand molds to secure strong and sound castings relatively free from various common defects and particularly from the defect of pin point porosity."

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

Fig. l is a sectional view illustrating a foundry mold embodying the present invention.

Fig. 2 is a plan view of the structure shown in Fig. 1.

Fig. 3 is a sectional view illustrating a modified construction of a foundry mold embodying the present invention.

Fig. 4 shows in perspective a workpiece, namely, a frame which can be cast in accordance with applicant's improved method.

Fig. 5 shows two cast workpieces similar to one shown in Fig. 4, as said pieces are taken out from the mold with all risers and gates as well as communicating channels being represented by frozen metal still connected to the workpiece.

Before explaining in detail the present invention it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. This application is a continuation in part of my application Serial No. 425,268, filed January 1, 1942, now abandoned.

In casting metals and particularly in the process of pouring the molten metal from ladies air bubbles become incorporated or trapped in the metal mass and are carried into the castingproducing cavities of molds. In addition, when sand molds and particularly sand molds with green sand are used, the-effect of the molten metal on the moisture contained in the sand is responsible for producing various gases and vapors which become mixed with the metal and are carried therewith into the casting-producing cavities. Such air and gases may remain in the metal in the form of fine bubbles and gas holes and frequently cause the very common defect in metal castings known as pin point porosity.

The above dimculties are particularly serious when aluminum or its alloys are cast in "green sand" molds.

One of the theories, which has been offered to explain the cause of pin point porosity," particularly in green san molds, is to the effect that the molten metal contacting at very high temperature the moisture contained in the molding sand causes decomposition of water vapor into oxygen and hydrogen. The oxygen may then combine with the metal, producing the corresponding metal oxide, while the hydrogen remaining in a free state mixes with the metal in the form of minute bubbles, causing formation of pores in the metal. 1

Whatever may be the causes of various defects in castings and particularly aluminum castings, I have found that it before permitting the molten metal to enter the casting-producing cavity of the mold all of this metal is caused to flow into a riser in the cope section which is open to atmosphere and is caused to circulate or agitate therein before flowing back into the runner, rectification of the molten metal occurs and castings of much higher quality are produced.

The mold hereinafter described is of the green 5 sand type and has a character and proportion adapting it for casting aluminum. It will be understood, however, that the invention is not limited to molds of such character and use, and that dry sand molds adapted for casting metals may be constructed in accordance with the invention.

Referringto the drawings and particularly to Figs. 1 and 2 thereof, the improved mold illustrated thereby comprises generally a lower section or drag I and an upper section or cope ii connected together in the assembled position of the mold with the aid of pins l2. The entire mold is supported on a board i3. Both the drag H) and cope ll comprise outside flasks or shells Illa and Ila, respectively. Such shells or flasks may be of any suitable construction and be made of wood or metal. In the present embodiment of the invention the shells or flasks [0a and Ila are made of metal by stamping. The flasks Illa and Ha are designed and adapted to hold a body of molding and fillings lb and ilb, respectively. The drag and the cope are formed separately by the use of patterns, and when put together the compacted sand fillings thereof contact each other along the parting line" It. Because of the character of the patterns used and the aligning function of the pin l2, the cavities formed in the sand fillings of the drag and cope register with each other when the mold is assembled, as can be clearly seen from the drawings.

In accordance with the present invention the cavities in the mold are so arranged as to carry out my improved process. The mold comprises, first, a casting-producing cavity 15 which, depending upon its character, may be formed either in the drag ill, the cope II, or in both, as is the case in the present instance. A pouring sprue i is provided in the cope, and it is adapted to receive the molten metal usually poured into the sprue opening manually from a ladle. A connecting channel or runner I1 is provided and is adapted to receive the molten metal from the sprue l6 and to convey it toward the casting-producing cavity l5. In conventional molds the molten metal is allowed to pass directly into the casting-producing cavity, carrying with it gases which may be contained in the molten metal, the air which may become entrapped in the metal when the same enters the sprue 16, the vapors produced when the molten metal contacts the moisture of the molding sand as well as the products of decomposition of such moisture, if the same takes place. In accordance with my invention there is provided in the mold a rectifying or pop-up riser l8 arranged in such a manner that all metal issuing from the channel or runner l'l must first enter said riser l8 and circulate therein before it is allowed to enter the castingproducing cavity l5.

5 Directing the molten metal into the rectifying riser I8 is efl'ected with the aid of a baflle is provided in the channel I'l. When the molten metal flows through the channel 11 and strikes the baflle l9, it is deflected upward and flows into the riser l8 nearly to the upper end thereof. The molten metal rises in the rectifying riser It only until it is about to reach the upper end thereof and therefrom the metal flows down into the casting-producing cavity 15. Thus, the metal progressively directed into the rectifying or ventilating riser I3 is in a state of continuing turbulence, and the gases contained in the metal are permitted to escape because of the churning action in this riser.

In addition to the above described metalrectifying function, the riser I8 has another very important function. When a casting is being poured in ordinary practice without the rectifying riser, a considerable variation in the rate of filling and degree of agitation in the casting cavity may be caused by varying the technique of the operator or the height of the ladle above the mold. With the use of the riser I8, the force of pouring caused by the flow of metal from, the ladle into the sprue I6 is spent or dissipated in the riser I8. Thus, the rate of flow and the resultant agitation in the casting-producing cavity I can be controlled substantially independently of the operators skill. By controlling the force with which the molten metal enters the casting-producing cavity, such as cavity I5, the molten metal may be introduced in the casting-producing cavity in such a manner as not to damage most intricate and tender cavity formations which are quite usual when intricate or thin castings are produced.

In the structure illustrated in Figs. 1 and 2 the riser It also combines in itself the function of a conventional feeding riser such as the riser 20. It is well known in the art that provision of a number of feeding risers around the castingproducing cavity is necessary, particularly when casting metals having high shrinkage, in order to supply metal to the casting-producing cavity when the metal filling the same freezes and decreases in volume. When the mold of Figs. 1 and 2 is filled, the molten metal fills the sprue Hi, the channel or runner I1, the rectifying riser I8, the casting-producing cavity I5 and the feeding riser 20, substantially reaching the upper ends of said sprue I6 and risers I8 and 20. As the metal freezes, the casting-producing cavity I5 is fed both from the feeding riser and the rectifying riser I8.

The structure illustrated in Fig. 3 is substantially similar to the structure illustrated in Figs. 1 and 2, the difference being in providing in the structure of Fig. 3 a rectifying riser which is arranged substantially midway between the sprue 2i and the casting-producing cavity 22. Said riser indicated in the drawings by the numeral 23 is adapted to receive and to circulate therein all metal issuing from the channel or runner 25. This is effected by provision of a baiile 2d interrupting the flow of metal in'the channel and directing it into the riser 23 for circulation therein. It will be understood that unless the baffle 24 is provided, the metal from the sprue 2! would fiow through the channel 25 and directly into the casting-producing cavity 22 without filling the riser 23 which would be filled only after the metal fills the entire mold and rises to the surface of the mold in all cavities or risers following the law of behavior of liquids in communicating vessels.

Figs. 4 and 5 illustrate the application of the present invention in a. multiple piece mold adapted for casting simultaneously a plurality, in the present instance two, of workpieces such as illustrated in perspective in Fig. 4.

Fig. 5 illustrates in perspective the metal formation or cluster as the frozen metal is removed from the mold, all feeding risers, sprues, gates, as well as rectifying risers, being still connected to the workpieces 28. By tracing the pouring and flow of metal in the formation of Fig. 5, application of the invention to a practical use may be best understood. In the mold from which the structure of Fig. 5 is taken, the metal 5 is poured simultaneously from two ladies into the sprues and 3|. From the sprue 30 the metal flows in two directions to the rectifying risers 32a and 321) wherein it is circulated to permit liberation of gases and is passed into the workpiece-producing cavities 28a and 28b, meeting therein the metal flowing from'the sprue 3| approximately in places indicated by the numeral 33 and thereupon filling the feeding risers 34a and 34b. From the sprue 31 the metal flows in two directions through rectifying risers 36a and 36b into the casting-producing cavities 28a and 28b, meeting the metal from the sprue 30 at places 33 and thereupon filling the feeding risers 31a and 31b. Depressions 38a and 381) under the feeding risers 32a and 32b should be noted. which depressions are produced by the bailles adapted to direct the flowing metal into the rectifying risers 32a. and 32b and to ensure proper circulation of metals therein. Similar depressions 39a and 39b can be seen in Fig. 5 under the feeding risers 36a and 36b. It will be understood that after removal from the mold, a formation such as shown in Fig. 5 is broken into several parts and all excess metal including the sprues and.- risers is cut away.

There is thus produced an improved method of casting metals in an improved foundry mold whereby it is possible to produce better and stronger castings free from various common defects, as Well as to attain other objects of the present invention listed above. Where it has been quite common and usual for scrap and defective castings due to air and gas bubbles and pin point porosity to be at least fifteen percent and greater, I have found that in practicing my method and using my improved mold the amount of scrap and defective castings has been reduced to a negligible figure. Thus, better articles and great economy are effected with the aid of the present improved method and foundry mold.

It is of great importance to note that the cope and drag sections of the mold may be made very easily with a minimum expenditure of time without requiring such skill as necessitates utilizing the services of high paid bench molders. The drag is made with the use of a pattern plate which forms the runner I1 or 25, the baflie I9 or 24,

the gating at the end of the runner and the drag portion of the casting cavity I5 or 22. This can be accomplished by forming the runner entirely open along the parting line- The cope section is also formed by the use of a pattern plate since the sprue I6 or 2I, the rectifying riser I8 or 23,

the cope portion of the casting cavity as well as any other risers terminate at'the parting line.

In preparing the drag section of the mold, for example, thesand is rammed down into the flask against the pattern plate which is provided with raised members forming impressions in the sand corresponding to the runner or runner portiom, the gating and a part of the casting cavity. The pattern is also provided with a portion which forms the solid baffle of sand. The construction, therefore, is such that the sand mold may be easily separated from the pattern plate and then inverted. Thus, the drag section, and this also applies to the cope section, can be readily made by the simple operation of ramming the sand in the flask. No particular skill or extra labor is required in making the present mold nor in assembling the cope and drag for the pouring operation.

I claim:

1. The method of making a sand mold and casting metal therein, comprising forming a cope section with a parting line along its bottom and an open top riser terminating at said parting line, forming a portion of a casting cavity in said section and a runner leading therefrom into the lower end of said riser and open at said parting line, ramming sand in a flask against a pattern plate to simultaneously form a drag section having a parting line, a runner extending along said drag parting line which is open throughout its length at such parting line and a solid bailie at the end of said last named runner which baflle is in the form of a wall curving from the botom of the runner and extending uninterruptedly substantially to the drag parting line, also forming at the same time by means of a portion on the pattern plate a casting cavity portion separated from said last named runner by said batlie. placing said cope and drag sections together with the parting lines thereof coincident so as to cause said baflle to form an inlet opening at the sprue side of the bottom of said riser of less horizontal crosssectional area than the horizontal cross-sectional area of the bottom of the riser, and pouring molten metal into the mold to cause the metal to flow along from the runner in the drag section and to be entirely deflected upwardly by said baifle across the parting line into said riser and thence across the top of said baflie into the casting cavity.

2. The method of making a sand mold and casting metal therein, comprising forming a cope section with a parting line along its bottom and an open top riser terminating at said parting line,

forming a portion of a casting cavity in said section communicating with the lower end of said riser, ramming sand in a flask against a pattern I plate to simultaneously form a drag section having a parting line, a runner extending along said drag parting line which is open throughout its length at such parting line and a solid bai'lle at the end of said last named runner which baflle ls in the form of a wall curving from the bottom of the runner and extending uninterruptedly at least to the drag parting line. also forming at the same time by means of a portion on the pattern plate a casting cavity portion entirely separated from said last named runner by said baffle. placing said cope and drag sections together with the parting lines thereof coincident so as to cause said baffle to form an inlet opening at the sprue side of the bottom of said riser of less horizontal cross-sectional area than the horizontal cross-sectional area of the bottom of the riser, and pouring molten metal into said mold to cause the metal to flow along the runner in the drag section and to be entirely deflected upwardly by said bafile across the parting line into said riser and thence across the top of said baffle into the casting cavity.

RAY E. DAY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Lange Jan. 7, 1913

Images