US2819501A

US2819501A - Wheel mold

Info

Publication number: US2819501A
Application number: US189961A
Authority: US
Inventors: Edmund Q Sylvester
Original assignee: Griffin Wheel Co Inc
Current assignee: Griffin Wheel Co Inc
Priority date: 1950-10-13
Filing date: 1950-10-13
Publication date: 1958-01-14
Anticipated expiration: 1975-01-14

Description

1953 E. Q. SYLVESTER 2,819,501

WHEEL MOLD Filed Oct. 13, 1950 4 Sheets-Sheet l IN VEN TOR.

Fa 7122025 Q Weak? Jan. 14, 1958 E. QSYLVESTER 2,819,501

WHEEL MOLD Filed Oct. 15, 1950 4 Sheets-Sheet 2 INVENTOR. Zazzzzuzd 53712265521 Jan. 14, 1958 E. SYLVESTER 2,319,501

WHEEL MOLD Filed 001:. 13. 1950 4 Sheets-Sheet 4 fix. ja?

INV NTORQ I'd Fauna? 53 506356)" nited States atent WHEEL MOLD Edmund Q. Sylvester, Lake Forest, 11]., assignor to Griflin Wheel Company, Chicago, 11]., a corporation of Delaware Application October 13, 1950, Serial No. 189,961

9 Claims. (Cl. 2291) 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.

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.

Another object of the invention is to devise a novel graphite mold and method of making the same by machining the mold cavity in the mating surfaces of the cope and drag mold sections.

A further object of the invention is to devise a novel method of quickly and economically renewing the mold cavity by machining a uniform increment of graphite from the mating surfaces of the cope and drag sections.

Still another object of the invention is to provide one or more risers formed and arranged to accommodate contraction of the cooling cast wheel without rupturing the plate section thereof.

Another object of the invention is to devise a novel riser cup and method of making the same, to prevent any possibility of explosions due to coaction of the graphite and molten steel. The novel n'ser cup is particularly formed and arranged to prevent such action and also to form a part of the mold cavity in the cope section.

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

A different object of the invention is to devise a novel method and means for pouring molten steel into the graphite mold, to prevent erosion in the graphite surfaces defining the mold cavity.

Still another object of the invention is to devisea novel method for forming an axle hole in the hub of the wheel casting.

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;

ring 32.

Figures 3, 4 and 5 are sectional views taken, respectively, on the lines 3--3, 4--4, and 55 of Figure 2;

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

Figures 7, 8, 9 and 10 are sectional views taken, respectively, on the lines 77, 8-8, 9--9 and Ill-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 ins for the cope and drag sections thereof;

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

Figure 13 is a fragmentary vertical sectional view of the cope comparable to the view thereof shown in Figure 11, but illustrating the means for forming a riser cup therein;

Figure 14 is a plan view of the riser cup heater shown in Figure 13; and

Figure 15 is a side elevational view illustrating a preferred form of apparatus for forming an axle hole in the hub of a wheel casting produced according to the invention.

Describing the invention in detail and referring first to Figure 1, the mold comprises a composite top section or cope, which is generally designated 2, and is provided with a trunnion 3 at each side thereof for convenient handling as by a crane or hoist (not shown). The mold also comprises a bottom section or drag .4 having at 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 clainp bar 16 engages an opposed lug 18 of the cape, 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,'afte r 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

30 and 32 are clamped together by bolt and nut assemblies 40 (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 18 is provided with a machined slot 43, as best seen in Figures 12 and 12a. The slot 43 is defined in part by spaced steel bars 44, secured as by screws 46 to the 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 trunnionsfi, for a purpose hereinafter described.

The drag 4, as shown in Figures 6-11, comprises a top ring 48 having a flange 50 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 60 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, and 11 also comprises a plurality of resiliently actuated plungers 64, each of which is supported by a compression spring 66 supported by a bushing 68 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 68. The plungers 64, as shown in Figure 11, support all or a predetermined part of the weight of cope 2 to accommodate uniform contraction of the wheel casting as hereinafter described.

The

graphite blocks

30 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'st eel 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 difiiculty 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 X 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 76 of the mold cavity radially inwardly of the rim section 74, 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.

The riser cup 88, as best seen in Figure 11, isa generally cylindrical gas permeable, noninfia-mmable member formed for example of any desired mixture of core sand and binder baked, as hereinafter described, to provide a ally designated 100, is positioned at the bottom of the opening 92, said heater having a top pattern surface 102 preferably formed of aluminum and corresponding to the shape of the mold cavity across the bottom of the opening 92. Thus, the surface 102 of the heater 100 closes the bottom of the opening 92 along a contour corresponding to the contour of the wheel to be cast in the mold cavity.

With the heater 100 and plug 90 in position, as shown in Figure 13, any suitable mixture such as for example, a mixture of silica sand and about 2% dry phenol binder is poured into the opening 92 around the plug 90 until the opening is entirely filled as shown in Figure 13. The mixture is then baked by the heater and by the residual heat in the graphite block 38 from the casting which has just been removed therefrom. In the case of an initial casting, the block 38 is baked in a furnace and the heater 100 is simultaneously energized to bake the mixture until it solidifies.

After the mixture has been baked sufficiently to solidify the riser cup 88, the heater 100 and plug 90 are removed, and a hole or opening 104 (Figure 11) is drilled in the bottom of the riser cup 88 at a point radially inwardly of the rim section 74 of the mold cavity. If desired, either the surface of plug 90 or the heater surface 102 may be provided with a dowel or projection corresponding to the shape of the opening 102 and bearing against the other surface to avoid the necessity of drilling the hole 104. g

It may also be noted that preferably the plug 90 and heater surface 102 are coated with a suitable parting medium such as acetylene black to prevent sticking of the binder.

Referring again to Figure l, 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 dragsections 2 and 4 are then assembled as shown in Figure 11, with the pins 60 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 10 is then actuated by the hydraulic jack 12 and, acting against the top lug 14, 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 11, 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 84 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 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 88 and the gate 82.

As soon as the mold cavity, the riser cup 88 andthe gate 82 are filled with molten metal, the lever 10 is released b means of the hydraulic jack '12, and the spring 20 tilts the drag 4 downwardly ag; inst the stop 26, thereby facilitating flow of metal from the riser cup 38 to the casting cavity, inasmuch as the riser cup 88, 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 11) 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 104 radially inwardly of the rim mold section 74, such contraction of the wheel casting is uniform, resulting in a substantially perfectly round casting. The metal within the opening 104, during contraction of thewheel casting, normally breaks off so that upon removal of the casting from the mold, the riser and riser cup 88 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 section 76; Furthermore, the hole 104 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 104 cracks off after the casting has solidified and begins to contract during cooling thereof as above described.

It will be understood that after the casting has solidified, the cope 2 is removed by the trunnions 3 to accom modate removal of the casting from the drag 4.

After removal of the casting from the mold, the casting is supported on a rotatable table 106, as shown in Fig ure 15, wherein the casting is indicated at 108, and the sprue or gate portion of the casting is indicated at 110.

An oxy-acetylene lance 112 is used with approximately 60 lbs. oxygen pressure to lance a hole indicated at 114 through the hub of the wheel casting 108 into the shrinkage cavity 116 extending into the hub of the casting from the sprue portion 110 thereof. This operation normally takes about three seconds. The casting is then permitted to cool for about twenty minutes, until the hub has cooled to about 1400 F., whereupon the table 106 is rotated by any suitable motor means (not shown) and the lance 112, starting from the hole 114, is utilized to cut a cylindrical axle hole, diagrammatically indicated at 118 in Figure 15. This operation simultaneously removes the :sprue portion 110 of the casting and provides the necessary axle hole through the hub.

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.--l.65-1.80 Electrical resistivity (ohm-in.).00020.00040 Thermal conductivity (B. t. u./ft. /ft./hr. F.)--100 Thermal expansion coefficient (in./in./ C.)--

10 X 10 -30 X 10- Transverse breaking strength-4500 1500 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 con tent of the molten steel to a value of from about .6% to about 1.0%, a considerable reduction in shinkage is achieved over that which normally occurs when the molten steel contains a normal carbon content of from about 1.5% to about 3.5%. 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:

1. Casting apparatus comprising a mold including cope and drag sections, a riser opening through the cope section means pivotally supporting the drag section, means at one side of the pivotal axis of said drag section and engageable with the cope section for clamping the latter against the drag section and for urging the drag section to a level position, and spring means at the opposite side of said axis and engaged with the cope section for clamping it against the drag section, said spring means being operative upon release of the first-mentioned clamping means to pivot the sections to a tilted position, whereat the riser opening is above the position thereof prior to release of the first mentioned clamping means.

2. A wheel mold comprising top and bottom sections, each having a mass of graphite with a recess partly defining a wheel shaped casting cavity between said sections, a plurality of springs carried by the bottom section and spaced around said cavity, said springs supporting part of the weight of the top section, and releasable means for clamping said sections together, whereby upon .release of said clamping means said springs afford a floating action of the top section seated against the top of a cooling wheel casting within the cavity.

3. Casting apparatus comprising a mold including cope and drag sections, a gate and a riser opening through the cope section, means for holding said mold in a level position and for locking the sections to each other, and spring means for tilting the mold to raise the level of the riser opening after the mold has been filled with molten metal poured into the gate.

4. Casting apparatus comprising a mold including cope and drag sections, means pivotally supporting the drag section, means at one side of the pivotal axis of said drag section and engageable with the cope section for clamping the latter against the drag section and for urging the drag section to a level position, and spring means at the opposite side of said axis and engaged with the cope section for clamping it against the drag section, said spring 7 means being operative upon release of the first-mentioned clamping means to pivot the sections to a tilted position.

5. A mold comprising top and bottom blocks of refractory material having recesses on their facing surfaces defining a casting cavity, the recess in the top block being partly defined by a generally conical surface tapering toward the bottom block, spring means carried by the bottom block for supporting the weight of the top block, means for releasably clamping said blocks together, means for maintaining the blocks in alignment with each other during clamping thereof by said clamping means and upon release of said clamping means, whereby upon release of said clamping means after molten metal has been poured into said cavity, the resulting casting acting against said surface may freely urge the top block upwardly while said casting cools with its top surface in contact with said first mentionedfsurface, without imposing excessive mechanical stresses on the casting.

6. A wheel mold comprising top and bottom sections, each having a mass of graphite with a recess partly defining a wheel shaped casting cavity between said sections, a plurality of springs carried by the bottom section and spaced around said cavity, said springs supporting at least part of the weight of the top section, and releasable means for clamping said sections together, means for aligning the blocks during clamping thereof and after release of said clamping means, whereby upon release of said clamping means said springs afford a floating action of the cope in response to contraction of a cooling wheel casting within the cavity; I

7. A mold comprising top and bottom blocks of refractory material having recesses in their mutual facing bottom and top surfaces, respectively, defining a mold cavity, a ringlike member surrounding the top block and seated against an upwardly facing surface thereof, substantially the entire top area of said top block being open to the atmosphere, a plurality of riser openings connected to said cavity and interrupting said top area, a ringlike member recessed in said topblock at its bottom surface, said last mentioned member being entirely disposed above said bottom surface, a ringlike member recessed in the bottom block at its top surface, said last mentioned member being entirely disposed below said top surface, a ringlike member seated against said bottom block at its bottom surface, means releasably interconmeeting the ringlike members associated with the top block for clamping the latter between said last mentioned members, means releasably interconnecting the ringlike members associated with the bottom block for clamping the latter between said last mentioned members, said top and bottom blocks seating directly against each other along said first mentioned surfaces, and interengaging readily releasable means carried by the second mentioned ringlike member and by the third mentioned ringlike member for maintaining said blocks with their recesses in proper mating relationship to define said cavity.

8. A mold according to claim 7, wherein the last mentioned means are characterized by a pair of pins upstanding from the third mentioned ringlike member, an opening in the second mentioned ringlike member complementary to and snugly receiving one of the pins, and a radial slot in the second mentioned ringlike member interrupting its radially outer perimeter and snugly receiving the other of said pins.

9. A mold comprising permanent cope and drag mold blocks having mated recesses defining a wheel shaped castingcavity including-a hub section, an annular plate section thinner in vertical cross section than the hub section and extending radially outwardly therefrom, and a rim section-thicker in vertical cross section than the plate section, said rim section having a portion tapering radially inwardly and merging with the plate section, a gate through one of the blocks connected to the hub section of the cavity, a plurality of riser cavities interrupting the top surface of the cope block and extending downwardly into the plate section of the cavity, a gas permeable riser cup in each riser cavity, said cup having a bottom wall separating said cavities and partly defining the plate section and the tapered portion of the rim section of said cavity, said bottom wall having an opening therethrough which is entirely ofiset from the vertical axis of the riser cavity, the vertical axis of the last mentioned opening intersecting the tapered portion of the rim section at the juncture of said tapered portion with the plate section of the casting cavity and accommodating flow of molten metal from the riser cup to the juncture of the plate and rim sections of the casting cavity, said bottom wall as seen in vertical cross section being substantially thinner around said offset opening than the plate section of the casting cavity, whereby solidification of molten metal in said offset opening is prevented until said metal has solidified in the rim and plate sections of the casting cavity, and whereby, upon solidification of said molten metal, lifting of the cope block is effective to break off the metal in said ofiset opening and to lift the metal constituting a riser in said riser cup.

References Cited in the file of this patent UNITED STATES PATENTS 128,051 Manning June 18, 1872 380,890 Codling Apr. 10, 1888 401,804 Washburn Apr. 23, 1889 760,960 Connolly May 24, 1904 1,157,847 Davis Oct. 26, 1915 1,161,034 Davis Nov. 23, 1915 1,172,506 Vickers Feb. 22, 1916 1,376,602 Cannon May 3, 1921 1,467,112 Lucier Sept. 4, 1923 1,660,966 Hasey Feb. 28, 1928 1,767,055 Devel June 24, 1930 1,925,496 Nichols Sept. 5, 1933 2,054,597 Gathmann Sept. 15, 1936 2,120,700 Gay June 14, 1938 2,181,947 McCarroll Dec. 5, 1939 2,195,402 Baird Apr. 2, 1940 2,299,860 Stoody et al. Oct. 27, 1942 2,368,719 Miller Feb. 6, 1945 2,401,075 Humes May 28, 1946 2,423,151 Miller July 1, 1947 2,497,210 Day Feb. 14, 1950 2,500,097 Soflfel Mar. 7, 1950 FOREIGN PATENTS Great Britain Aug. 12, 1948 OTHER REFERENCES American Foundryman, March 1946, pages 48-68, pages 52 and particularly relied on.