US3545524A - Method of casting a wheel - Google Patents

Description

United States Patent Inventors Robert 11. Beetle Mountain Lakes;

4 John B. Delaney, Ridgewood, New Jersey Appl. No. 833,213 Filed Feb. 24, 1969 Division of Ser. No. 616,570, Feb, 16, 1967. Patent No. 3,480,070. 6 Dec; 8, 1970 Abex Corporation New York, New York a corporation of Delaware Patented Assignee METHOD OF CASTING A WHEEL 2 Claims, 2 Drawing Figs.

U.S. Cl. 164/33, 164/137 Int. Cl. BZZd 25/02, B220 9/28 Field olSearch 164/23, 22,

[I'll 3,545,524

References Cited UNITED STATES PATENTS 971,604 10/1910 Griffith 164/356 1,025,438 5/1912 West 164/356 1,908,740 5/1933 Fahrenwald... l64/356X 2,838,816 6/1958 Strom 249/56 3,302,919 2/ l 967 Beetle et a1 249/56 Primary ExaminerJ. Spencer Overholser AssistanLExaminer-R. Spencer Annear Attorney-Kinzer, Dom and Zickert ABSTRACT: A railroad wheel having an inner hub portion and an outer tread portion joined by a thinner plate is cast in a permanent mold having a yieldable and relatively thick lining at the fillets near the tread portion of the wheel. As the casting cools and contracts, the lining yields which allows wheels with fillets of sharp radii to be produced.

I I I I PATENTEU on: 8I97D INVENTORS. ROBERT H. BEETLE JOHN B. DABNEY METHOD OF CASTING A WHEEL This application is a division of application Ser. No. 616,5 70, filed Feb. 16, 1967, now U.S. Pat. No. 3,480,070.

This invention relates to the production of railroad wheels which have a central hub portion and an outer tread portion joined by a so-called plate which is comparatively thin.

It has been proposed to cast'railroad wheels in a permanent mold. U.S. Pat. Nos. 2,779,075 and 2,819,501 are examples, but satisfactory production on-a commercial scale is realized only by casting under pressure as shown by U.S., Pat. Nos. 2,847,739 and 2,990,592. A railroad wheel may weigh almost half a ton. It is perhaps one of the most difficult castings known because its use requires great precision, soundness and freedom fromdefectsin the cast wheel which might otherwise contributeto a failed wheel on the train. I

The geometry of the wheel is also importannand in fact the shape of the fillets at the tread end of the plate of the wheel is recognized as contributing to .superior wheels and is important in wheels having a specialized purpose. In the process of the above identified patents,-the shape of the fillets is severely limited. A sharp radius isnot attainable for the fillets. This is so for the reason that as the casting cools and solidifies, the permanentmold material (e.g. graphite) resists contraction of the fillets. Unless. the fillet design is one'of a large radius of curvature, the contraction of the casting will be soseverely resisted by; the. corresponding mold surfaces as' to create stressing within the, casting giving rise to imperfections in the finished wheel. In fact, in U.S. PaLNo. 2,819,501 means are of necessity provided to enable the cope (upped-portion of the mold to float, upwards as the designated fillets contract against the corresponding graphite mold surfaces. In this way, by resort to mold accessories of a mechanical nature, the problem of the contracting and solidifying fillet is proposed to be handled; Even this result, however, cannot be realized with a sharply curved fillet, becausea sharply curved or abrupt fillet will not apply the wedge or lever effect necessary to theliftingofthecope.

The objects of ourinvention are to enablevirtually any contour to be realized at the fillets of a railroad wheel adjacent the tread of the wheel, and to accomplish this without having to resort to accessory equipment. Theseobjects are realized by lining the fillet areas of the permanent mold with a temporary,

yieldable or frangible mold material such as a bonded, sand or a solidified ceramic slurry which, as the fillet part-ofthe wheel contracts thereagainst, will yield or even crumble allowing contraction to continue unimpeded. 3 u u Thus, we achieve almost" 100 percent flexibility in the contour of the critical filletof a railroad car wheel, and we do not need to incorporate mechanical means in the mold equipment to allow the copeto float during cooling of the casting.

Other and further objects of the present invention will'be apparent from the following description andclaims and are illustrated in the accompanying drawing which, by way of illustration, shows preferred embodiments of the present invention The graphite mold material 111 and 12 constitutes a permanent mold material, butthe principles of the present invention are equally applicable to other kinds of permanent mold material. In any event, the mold 19 is for thecasting of a railroad car wheel, and the moldcavity 20, which spans both sides of the partingline'Zl where the surfaces of the cope anddrag abut, presents the contour of the railroad car wheel to be cast therein. v p H u u Thus, the mold cavity'zflpresen'ts opposed surfaces 32 and 33 which will correspond. to theso-called plate of the wheel. These surfaces are of graphitelbut preferably atypicalmold wash isapplied thereto asa thincoating prior to pouring the molten metal into 'thelmold cavity.CA mold wash may also be applied to any othersurface of: thernold which defines a contourofthewheel. .fi

The mold cavity includes frontand back rim fillet surfaces 36 and 37. These fillet surfaces are those that play a critical role under the present invention, as will be described hereinafter. p H

In addition,.the wheelto be cast has a front rim surface 40, a tread surface 41, a flange 42 and a so-called back rim 43. Of course it'willbe appreciated that the wheel is of 360 form, so that the surfaces thus far described. are continuous about the entirety of the mold cavity 20.

The wheel tobe cast also includeisa hub 45 and corresponding front and'back hub fillets 48 and. 49. u

The moltenmetal, a steel of suitable metallurgy, is admitted 'to the mold cavity through a central riser 50, and in this connection itwill be observed that the riser opening-50, in the preferred embodiment of the invention, islocated at th'e central portion or hub area ofthe mold, especially if the practices in our aforesaid patent are followed. The riser opening 50 is preferably lined with a replaceable ceramic core 51 which may be a conventional sand core or a rnore sopl'iisticated'solid body obtained from a suitable slurry or kyaniteor the like as hereinafter specified. This isj"equally\tme of thexhub core which serves to-define the hub ope tliin'gofthe' wheel.

It will be apparent from FIGQIthatthecourseof molten metal admitted into the riser is downward around the-hub core 60 and thence. radially. outward throughthe plate area 32-33 of. the cavity, past the fillet surfaces 36 and 37 that are adjacent the rim of the wheel, andfinally into contact with the tread surface 41 which, it will be observed, is presented by the permanent mold material which is graphite, in this instance.

The graphite at the tread surface 41 serves as a chill, such that solidification of the molten metal proceeds radially inward from the tread surface 41 in the direction of the hub core FIG. 1 is a sectional view of a mold for a railroad car wheel in accordance with the present invention; and

F IG. 2 shows a typical modification of our invention.

formed from an annular block of "graphite; The cope 11 is disposed on a lower annular-graphite block 12 constituting the drag of the mold.

The cope ll-and the drag 12 may be clamped together by suitably spaced clamps 15 of any desired character, and in this connection the clamping structure herein illustrated cor-' responds to that disclosed in our U.S. Pat. No. 3,302,919,

granted Feb. 7, 1.9 67.

60. As'the molten metal solidifies, itcontracts against the fillet-defining surfaces 36 and 37, and in accordance with the present invention'the fillet surfaces 36 and 3 7 are presented by separate liners 55 and 56 of any yieldable or impermanent mold material such as bonded sand as heretofore used in molds or a ceramic which will also yield or even crumble as the molten metal pushes ther'eagainst. The liners 55 and 56 are, of course, thick enough to yield or crumble as the solidifyingmetalexertsforce.

By using yieldable or frangible liners 55 and 56, we can achieve virtually any contour we want for the fillets of the wheel which are adjacent the rim. Thus, because of their im- 1 permanent or yieldable nature, the liners 55 and 56, unlike the trated in FIG. 1 but showing a typical modification of our invention. Thus, the mold 10A of FIGQZ has additional riser openings 50A formed in the cope 11A. These riser openings 50A may be of any preferred number and'themselves lined I with a sleeve 51A in the nature of a sand core or the like similar tothe lining 51for the central riser 50. The sleeve 51A extends to the mold cavity 20 and the lower end of the sleeve is formedwith anopening 51B allowing excess molten metal to'rise upward therein so that additional molten metal is available within the riser SOA in the course of cooling and contraction of the casting in the mold cavity 20.

The lower end of the auxiliary riser sleeve 51A presents a contour 36A eorresponding to the front rim fillet mold surface 36'of FlGal". In the cope of the mold of-FIG. 2, the frangible or yieldableline'r of the front fillet adjacent the rim of the wheel will be continuous about the entire circumference of the cope, with the exception of the openings 518 where the auxiliary risers 50A are located, Thus, in the cope of FIG. 2 the portion of the mold betweenthe secondary or auxiliary risers, which may be 'ofany desired number, will have a solid or uninterrupted extension corresponding to the liner 55 of FIG. 1.

The liner'which presents the surface 37A, FIG. 2, will be altogether identical to theliner 56 presenting the surface 37 illustrated in FIG. 1, and the sameadvantageous results are realized with the, mold A as above described in connection with the mold l0 ofFlG. l. In the actual construction of the mold, the graphite blocks will bemachined to enable the various cores and sleeves to be set therein. Similarly, the graphite blocks will be machined at the fillet areas MI and M2 to enable the separate liners to be set therein, and .whichlof. course present outer or exposed faces that completethe contour of the wheel. in this regard,

the cores or linersQSS and 56 may be secured adhesively in .place, they may be formed by blowing sand into the machined cavities M1 and M2 while using a suitably shaped pattern, and of course in theins'tanceof FIG. 2 the so-called front fillet liner will be formed as an incident to formation of the riser sleeve 51A.

i Referring to FIG. 1, the liners 55 and 56 may be formed by a sweeping operation; as described in our aforesaid patent, or "may be formedand'positioned by a typical mold jolting operation particularly in the instance where the liners are of sand I which may be thus mechanically bonded in place as described in our aforesaid patent.

If sand is used for the fillet liners, these may be typical core I sands, iand abonidingagent such as a core paste, sodium silicate,'a resin binder and so on can be used to hold the liner in place. ln fact, adhesive bonding of the liner may be combined mechanical bonding in 'ajolting operation as mentioned above. The sand grains themselves may be internally bonded by sodium silicate, resins, oil, clay or other sand core binders well knownin the art. As mentionedabeve, it is also possible to have the liners solidified from a ceramicslurry, particularly in the instance of preferencefor a precision finish in the cast wheel. Thus, the

fillet liners 55 and56; or those described in connection with F IG. 2, may conform tothe following specification:

Colloidal silica (30% Slob-2160 00.

Citric acid (One molar solution)34 cc.

Kyanite (100 mesh or finer)16.5 lbs.

sulphate solution (600 gm./ 1000 cc. H O) The above quantities are approximate figures and may be varied slightly depending upon humidity, temperature and .other environmental conditions which would effect gelling of the slurry within apredetermined time.

The colloidal silic'afcitric acid and kyanite are mixed thoroughly, kyanite being added until the viscosity reaches approximately 8258c. The sulfate solution is added and mixed 7 well. Theslurry is then readyfor use. The amount of sulfate The initial gelling of ceramic linings 55 and 56; which-is in the form of a slurry when the lining is formed by. the sweep method or by an injection method, is accelerated by the heat of the cope and, the drag. On a production basis, the copea'nd drag will be at elevated temperatures because of the residual heat of previous casting operations. Where the cope and drag are being used initially, the cope and drag are preheated to approximately l50-l80 F. to facilitate the gelling of the refractory ceramic linings 55 and 56. r

After the linings 55 and 56 are gelled or solidified,v the linings are cured. For example, the cope and drag may be broughttogether to form a complete mold and heated at a temperature and for a timesufficient to cure the linings 55 and 56 in an oven at about 400-F. for a period of several hours. Also, as much moisture as possible is driven from the mold during this backing operation. Shortly before the mold is to receive the molten metal, the mold is removed from the oven, vent holes (if used in the graphite blocks) are lined with sand, and a central opening may be formed in the vent holes. The hub core 60 is pasted in position, and the unlined areas of the mold cavity are preferably sprayed with a mold wash made of a mixture of zircon flour, bentonite and water. The mold wash is sprayed or brushed on to form a very light layer of about one sixty-fourth of an inch or less in thickness. The function of the mold wash is to protect the graphite surfaces. The mold is then closed with the cope 11 superimposed on the drag'1-2 by the usual pins and holes on the respective flasks and 31. Next the clamps 16 are applied, and the mold is tilted as described in our U.S. Pat. No. 3,302,919.

Metal is poured into the mold through the central combined gate and riser means 50 to till the entire mold cavity and the riser cavity. The pouring temperature and time of pour will depend upon. the composition of the metal and the size and shape of the wheel.

, As soon as the mold is filled, the mold is leveled that is, un tilted. After'a skin is formed onathe metal, the clamps 16 are loosened and there may be some lifting of the cope 11 relative to the wheel casting as the latter solidifies. After the casting is cooled to a desired temperature, the cope 11 is lifted. and the wheel casting is separated therefrom. The riser having been knocked off, the wheel casting is immersed in a soaking pit. The wheel casting is taken from the soaking pit and subjected to heat treatment.

The cope anddrag have their casting cavities cleaned, particularly to, remove any remaining portions of the linings-'55 and 56 and the riser sleeve 51. The cope and drag are then ready to receive a new lining 55 and 56 and a new riser sleeve 51. for the next casting operation when using the mold of FIG. 1.

It will be seen fromthe foregoing that the liners 55 and 56, or their equivalent, in effect interpose a yieldable mold surface between the solidifying metal and the unyieldable permanent mold 11-12. The permanent mold material, how ever, is used to present an outer chill surface 41. The molten metal solidifies radially inward encountering the contours 36 and 37, which are enlarged in comparison to the inner plate portion of the casting. However, the liners 55 and 56 are purposely expendable, yieldable or even frangible and hence interpose no resistance to sharp radii of the solidifying casting.

Hence, while preferred embodiments of the invention have been described and illustrated, it is to be understood that they are capable of variation and modification.

We claim:

l. A method of casting a wheel or the like having thin and thick sections joined along an enlarging contour comprising: affording a mold of permanent mold material presenting opposed walls defining a mold cavity having thick and thin sections joined by opposed enlarging contours and conforming generally to the section of the casting to be formed therein, said permanent mold material itself presenting a chill for the thick section of the casting, and lining the opposed walls of said mold cavity only at said enlarging contours with an impermanent liner of a mold material whieh will yieldas the casting solidifies inward from the chill and cbntracts a ainst said liner.

conforming to the wheel rim, and in which the liner at the enlarging contours has a radius conforming to a fillet of the wheel which joins the plate and rim.

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