US2779075A - Cast article and method of making - Google Patents

Description

Jan. 29, 1957 E. Q. SYLVESTER 2,779,075

CAST ARTICLE AND METHOD OF MAKING Original Filed Oct. 13, 1950 3 Sheets-Sheet 1 21 g -ZZE/NeTOR.

Jan. 29, 1957 E. SYLVESTER 2,779,075

CAST ARTICLE AND METHOD OF MAKING Original Filed Oct. 13, 1950 3 Sheets-Sheet? INVENTOR.

United I CAST ARTICLE AND METHOD OF MAKING Edmund Q. Sylvester, Chicago, 111., assignor to Griffin Wheel Company, Chicago, 111., a corporation of Delaware 6 Claims. (Cl. 22-413) This invention relates to the art of casting metals and more particularly to the casting of ferrous metal objects such as iron or steel railway car wheels. This application is a division of my copending application Serial No. 189,961, filed October 13, 1950.

A primary object of the invention is to devise a novel method and means for casting steel car wheels having exceptionally fine grain microstructure and unusually small shrinkage voids.

In this connection, it has been discovered, according to the present invention, that by casting steel wheels in a graphite mold, the normal relationship between the shrinkage voids and the carbon content of the steel is reversed due to extremely rapid cooling of the molten steel. in other words, by reducing the carbon content of the steel, shrinkage voids are reduced rather than increased, whereas, according to prior art techniques, reduction of carbon has always resulted in increase of shrinkage voids. It will be understood that this is a very significant factor in the production of steel railway car wheels wherein low carbon content and consequent ductility are highly desirable.

A further object of the invention is to accommodate contraction of the cooling wheel by removing the weight of the cope mold section therefrom.

Another object of the invention is to tilt the mold after pouring to position a riser opening at the highest point of the mold cavity to ensure feeding of the cooling casting.

A further object of the invention is to provide an improved cast steel wheel having improved physical characteristics resulting from the novel casting method.

The foregoing and other objects and advantages of the invention will become apparent from a consideration of the following specification and the accompanying drawings wherein:

Figure l is a side elevational view of a preferred embodiment of apparatus utilized in the practice of the invention;

Figure 2 is a plan view of the cope with its graphite portion removed;

Figures 3, 4 and S are sectional views taken, respectively, on the lines 33, 4-4, and 5-5 of Figure 2;

Figure 6 is a plan view of the drag with its graphite portion removed;

Figures 7, 8, 9 and are sectional views taken, respectively, on the lines 7-7, 8 8, 99 and 10-10 of Figure 6;

Figure 11 is a fragmentary central, vertical, sectional view through the mold;

Figure 12 is a fragmentary vertical, radial sectional view through the mold illustrating one of the aligning pins for the cope and drag sections thereof, and

Figure 12a is a sectional view on the line 12a-12a of Figure 12.

Describing the invention in detail and referring first to Figure l, the mold comprises a composite top section'or tates Paten ICC 5 each side thereof, a trunnion 6 supported by a pedestal 8 to support the mold and accommodate tilting thereof, as hereinafter described in connection with the novel process.

The mold is illustrated in pouring position with the cope 2 clamped against the drag 4, and with the latter clamped against a stop 9 by a lever 10 actuated by an hydraulic jack 12. The lever 10 engages a lug 14 of the cope 2, and a resiliently actuated clamp bar 16 engages an opposed lug 18 of the cope, the bar 16 being connected by a bolt 19 to a compression spring 20 contained within a frame or casing 22 pivotally mounted at 24 adjacent a stop 26 against which the spring 20 urges the drag 4 upon release of the lever 10, after the molten metal, such as steel, has been poured into the cope 2 through a pouring cup 28. The purpose of this arrangement will become apparent in connection with the description of the operation of the device.

Referring now to Figures 2 to 5 and 11, it will be seen that the cope 2 comprises top and bottom annular rings 30 and 32 having annular flanges 34 and 36, respectively, seated against top and bottom shoulders of an annular graphite block 38.

The rings 36 and 32 are clamped together by bolt and nut assemblies dti (Figures 2 and 4), and the ring 32 is formed with the before mentioned lugs 14 and 18. The lug 14 is provided with a precision machine ground bushing 42, as best seen in Figures 2 and 3, and the lug 1% is provided with a machined slot 43, as best seen in Figures 12 and 12a' The slot :3 is defined in part by spaced steel bars 44, secured as by screws 46 to the ring 32. The bushing 42 and slot 43 are diametrically opposed to each other and are preferably arranged so that a vertical plane bisecting them is approximately perpendicular to the axis of the coaxial drag trunnions 6, for a purpose hereinafter described.

The drag 4, as shown in Figures 641, comprises a top ring 48 having a flange 5t) seated against a complementary shoulder of a graphite block 52, the bottom of which is supported in a complementary cylindrical tray 54, which is preferably perforated as at 57 (Figures 6 and 11) and is provided with the above mentioned drag trunnions 6, as shown in Figure 9.

The ring 48, as best seen in Figures 6 and 8, is removably bolted as at 58 to the tray 54 to clamp the graphite block 52 therebetween. The ring 48, as shown in Figures 6, 7 and 12 is provided with a pair of pins 6%) removably bolted thereto as at 62 and adapted for reception within the bushing 42 and the slot 43, respectively, to align the cope and drag.

The ring 48, as best seen in Figures 6, 10 and ll also may comprise a plurality of resiliently actuated plungers 64, each of which is supported by a compression spring 66 supported by a bushing 6h threaded through the ring 48. The spring 66 is adjustably compressed by a nut 70 and a lock nut 72, and the vertical position of the plunger 64 is adjustable by the threaded bushing 63. The

plungers 64, as shown in Figure 11, support all or a pre-' determined part of the weight of cope 2 to accommodate uniform contraction of the wheel casting as hereinafter described.

The graphite blocks 3% and 52 are machined on their mating surfaces to define a mold cavity corresponding to the shape of a Standard A. A. R. wheel, said cavity comprising a rim section 74, a plate section 76, and a hub section '78 for the corresponding parts of a steel wheel to be cast therein, as hereinafter described.

The graphite block 38 of the cope 2 is also provided with a readily removable graphite sleeve 80 (Figure 11) which may, if desired, be secured in any convenient manner, as by a suitable cement, within a complementary hole or opening of the block 38, said sleeve having a gate opening 82 tapering upwardly to communicate with the pouring cup 28. Beneath the gate opening 80 is a fusible, preferably metallic anti-splash cup 84, which, in the illustrated embodiment shown in Figure 11, is formed of thin sheet steel. The anti-splash cup 84 is inserted into the cope cavity 78, prior to assembly of the sleeve 80; and the bottom of the cup 84 is seated on the block 52. The cup 84 is adapted to receive the molten metal from the gate 82, and after the molten metal has filled the cup 84, the latter melts providing a pool of molten metal beneath the gate 82 so that additional molten metal flowing therefrom into the mold cavity does not splash but flows smoothly into the pool which enlarges until the casting cavity is filled with molten metal. This novel arrangement prevents splashing of the molten metal and also prevents rapid erosion and pitting of the graphite surfaces defining the mold cavity, a difficulty which has heretofore rendered maintenance of such molds unduly expensive for the production of large steel castings such as railway wheels.

It may be noted that some erosion of the graphite surfaces defining the mold cavity occurs even with the present arrangement, and I have discovered that by arranging the mold parts as above described, these surfaces and the mating surfaces 86 of the graphite blocks 38 and 52 around the periphery of the mold cavity may be machined to remove an increment of for example of an inch, thereby quickly and economically renewing the mold cavity.

The graphite block 38 of the cope 2 comprises one or more riser cups or sleeves 88 communicating with the plate section '75 of the mold cavity radially inwardly of the rim section 7 5, and it has been discovered, according to the present invention, that the location of these cups 88 is extremely important, preventing distortion of the wheel casting during shrinkage of the cooling steel in the mold cavity. In this connection, it has been discovered that the prior art practice of connecting risers to the rim section of the mold cavity prevents uniform contraction of the cooling wheel casting and causes nonround wheel tread surfaces.

Referring again to Figure 1, a pouring operation will be described as follows. The surfaces of the cope and drag graphite blocks 38 and 52, defining the casting cavity, are preferably coated with acetylene black to prevent sticking of the casting in the mold cavity, and the cope and drag sections 2 and 4 are then assembled as shown in Figure ll, with the pins so received in the bushing 42 and slot 43, respectively, maintaining the cope and drag sections in positive alignment. With the cope 2 and drag 4 in assembled relationship and supported by the drag trunnions 6 and pedestals 8, the bar 16 is engaged with the cope lug 18 and under the action of the spring 20 is effective to tilt the drag 4 against the stop 26. The lever 11 is then actuated by the hydraulic jack 12 and, acting against the top lug i4, urges the drag 4 against the stop 9 to a position wherein the mold is in a level pouring position. Under these conditions, as best seen in Figure ll, molten steel is poured into the cup 28 and flows downwardly through the gate 82 into the antisplash cup 84%, the initial flow of molten metal impinging against the bottom of the anti-splash cup to prevent erosion of the drag graphite block 52. The cup 84-, as above noted, is a thin walled, fusible vessel which melts by the time it is filled with molten metal from the gate 82 so that the molten metal within the cup 34 flows smoothly to the bottom of the hub section 78 of the mold cavity forming a pool of molten metal at that point. Additional molten metal which is continuously poured into the cup 28, flows through the gate 82 and into the 2 pool at the bottom of the hub cavity section 78. Thus, the pool enlarges until it fills the entire mold cavity, as well as the riser cup 83 and the gate 82.

As soon as the mold cavity, the riser cup 88 and the gate 82 are filled with molten metal, the lever 10 is released by means of the hydraulic jack 12, and the spring 20 tilts the drag 4 downwardly against the stop 26, there by facilitating flow of metal from the riser cup E3 to the casting cavity, inasmuch as the riser cup 85, after tilting of the mold by the spring 20, is connected to the mold cavity at approximately its highest point. The clamp bar 16 is then released. Under these conditions, the weight of the cope 2 is entirely, or if desired, partially carried by the springs 66, whereby as the wheel casting within the mold cavity contracts upon cooling, the conical surface of said casting at the inner perimeter of the cavity section 74 (Figure ll) may freely raise the cope 2 without overstressing the plate portion of the wheel within the mold cavity section 76. it has also been found that by positioning the riser opening 1W- radially inwardly of the rim mold section 74, such contraction of the wheel casting is uniform, resulting in a substantially per fectly round casting. The metal Within the opening lid i, during contraction of the wheel casting, normally breaks off so that upon removal of the casting from the mold, the riser and riser cup 83 remain within the cope 2.

It will be noted in this connection that feeding of the solidifying casting within the casting cavity by metal within the riser cup 88 is facilitated by the fact that the bottom wall of the riser cup which partly defines the upper margin of the plate section '76 of the casting cavity, is thinner in cross sectional area than the plate ection 76. Furthermore, the hole H34 in the bottom wall of the riser cup interrupts substantially less than half of the downwardly facing surface of said bottom wall, and the hole 104 is positioned at the radially outermost point of said bottom wall so that the metal in the opening 1% cracks ofi after the casting has solidified and begins to contract during cooling thereof as above described.

It will be understood that after the casting has solidfied, the bar 16 is released, and the cope 2 is removed by the trunnions 3 to accommodate removal of the casting from the drag 4.

The resulting casting is an unusually fine grained structure, due to the rapid cooling of the steel within the graphite mold which must be at least three times the weight of the molten steel therein, in order to achieve this result.

The graphite blocks 38 and 52 are preferably formed of a material composed wholly or in part of carbon with a carbonaceous bond, this carbon being all or in part of a graphitic form with the following corresponding properties:

Apparent density gm./cc. 1.65l.80. Electrical resistivity (ohm-in.) 00020-00040. Thermal conductivity (B. t. u./ ft. 10-100.

2/ft./hr. F.). Thermal expansion coeflicient (in./ l0 l0 3O l0-".

in./ C.). Transverse breaking strength 1500-4500 p. s. i. Maximum particle size 0.1.

The graphite is manufactured by crushing and screening calcined petroleum coke to produce particles which pass through a 20 mesh screen and are retained by a 35 mesh screen, and to produce flour particles which pass through a 200 mesh screen. The flour and larger particles are mixed in any desired proportion, with about 30% pitch at about 300 C., whereupon the mixture is cooled and compressed into briquettes of suitable dimensions. The briquettes are then baked, and after baking are impregnated with pitch in a vacuum chamber, whereupon the briquettes are graphitized by slowly heating them in a furnace to about 3000 C. and then slowly cooling them for about ten to twelve days.

It has also been found that by reducing the carbon content of the molten steel to a value of from about .6% to about 1.0%, a considerable reduction in shrinkage is achieved over that which normally occurs when the molten steel contains a normal carbon content. An example of a steel which has produced these unusual castings is one containing about .111% aluminum, about .51% chromium, about .48% silicon, about .032% sulphur, about .028% phosphorus, about .66% manganese, about .6% to 1.0% carbon, and the balance substantially pure iron. It will be understood that the various elements may be varied, if desired, provided that the carbon content be within the range stated, inasmuch as an increased carbon content will increase shrinkage voids, contrary to the heretofore accepted rule that increase of carbon content reduces shrinkage voids.

This phenomenon is believed to be caused by the unusually rapid rate at which the casting is cooled, due to the relatively great volume of graphite and its excellent heat conducting properties.

I claim:

l. A method of making a steel casting comprising pouring molten steel having a carbon content of from about .6% to about 1.0% into a graphite mold having a weight at least about three times that of the steel poured into said mold.

2. A method of casting a steel wheel comprising pouring molten steel having a carbon content of not more than about 1.0% into a graphite mold having a particle size of not more than about 0.1 inch and having a density of from about 1.65 to 1.80 gm./cc., the weight ratio of graphite to steel being at least about three to one.

3. A steel wheel cast according to claim 2.

4. A method of casting comprising the steps of positioning a mold with its gate in a substantially vertical position while pouring molten metal into the gate until the mold is filled, and then after the mold has filled and after the molten metal in contact with the mold has formed a skin, tilting the mold to a position whereat a n'ser cavity therein is above the level of said gate.

5. A process of casting a Wheel comprising the steps of clamping a cope and drag section together, then filling the mold cavity with molten metal, and then before the molten metal has solidified in said cavity and after the molten metal in contact with the mold has formed a skin preventing flow of molten metal from the mold cavity, relieving at least part of the weight of said cope section from said metal while maintaining said cope section in contact with said metal to accommodate upward floating of the cope section in response to radial contraction of the cooling wheel.

6. A method of casting in a mold having a cope and drag sections defining a mold cavity, said cope section having a gate opening and a riser opening communicating with the mold cavity, said method comprising the steps of positioning the mold with the upper ends of said openings at approximately the same level while pouring molten metal into the gate opening until the cavity and both openings are filled with said molten metal, and then after the metal in contact with said sections has formed a fluid tight envelope around the molten metal tilting the mold to a position whereat the upper end of the riser opening is at a higher level than that of the gate opening until the molten metal has solidified within the mold.

References Cited in the file of this patent UNITED STATES PATENTS 451,575 Richards May 5, 1891 1,415,027 Gebhardt May 9, 1922 2,473,160 Madrigal June 14, 1949 2,618,032 Traenkner Nov. 18, 1952 2,632,216 McQuaid Mar. 24, 1953 FOREIGN PATENTS 535,351 Great Britain Apr. 7, 1941 OTHER REFERENCES Iron and Steel, Boylston, page 31, John Wiley & Sons, 1928.

Graphite Molds for Short Run Castings, by Putchinski, 4 pages, Iron Age, Sept. 6, 1945, pages 83-85 and 174.

Graphite Molds for Casting Vertical Steel Ingots, by House and Killman, 5 pages, Iron Age. Jan. 16. 1947 pages 59-63.

Claims (1)

1. A METHOD OF MAKING A STEEL CASTING COMPRISING POURING MOLTEN STEEL HAVING A CARBON CONTENT OF FROM ABOUT .6% TO ABOUT 1.0% INTP A GRAPHITE MOLD HAVING A WEIGHT AT LEAST ABOUT THREE TIMES THAT OF THE STEEL POURED INTO SAID MOLD.

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