US20170239713A1

US20170239713A1 - Method of casting annular member

Info

Publication number: US20170239713A1
Application number: US15/051,189
Authority: US
Inventors: Paul Prest
Original assignee: Caterpillar Inc
Current assignee: Caterpillar Inc
Priority date: 2016-02-23
Filing date: 2016-02-23
Publication date: 2017-08-24

Abstract

A method of casting an annular member is provided. The method includes preparing a sand mold. The method further includes clamping the sand mold between at least two plates. The method further includes rotating the sand mold. The method further includes introducing molten cast material into the sand mold during rotation of the sand mold.

Description

TECHNICAL FIELD

The present disclosure relates to a method of casting an annular member, and more particularly, to a method of casting a metal seal using centrifugal casting process.

BACKGROUND

Metal seals have been widely adopted in various industries and have advantages over non-metallic seals in that they operate over a wider range of temperatures, fluids, and pressures. Metal seals that usually have long and thin portions are, typically, manufactured using casting process. The conventional casting process utilizes sand molds having a gating and rigging system. The gating and rigging system includes gates placed at various strategic locations along the length of cavity of the sand mold. The gates are used to conduct molten metal which compensates for the decrease in the volume of the metal during solidification. The number of gates that are required depends upon the relationship between the length and the thickness of the metal seal being cast. It has been a common practice to provide gates which are spaced apart along the length of a mold by a distance of between 3 to 12 times that of the thickness of the metal seal being cast therein. Such sand mold casting processes have been employed to manufacture large metal seals with up to 37 inches in diameter.
However, such conventional sand mold casting process for manufacturing of the metal seals has certain limitations. The use of gating and rigging system results in extra portions formed with the metal seal which needs to be removed using machining processes. Also, this adds to the cost of re-melting of the removed extra portions to extract the unused metal, so it may be further utilized. Further sometimes during the re-melting process, the metal may get oxidized which can lead to loss of material. It has been observed that the use of the gating and rigging system, among other factors, can lead to a loss of yield of up to 80%, for such conventional sand mold casting process.
One solution known in the art to improve the yield loss is to employ centrifugal casting process using metal molds. Such process generally uses copper molds which are placed in a centrifugal casting machine and do not require an elaborate gating and rigging system. Although such process may help to reduce yield loss, however the centrifugal casting process using metal molds are limited to manufacture metal seals with only up to 10 inches in diameter. Further, the copper molds that are used in the process are generally very expensive, and thus makes the whole process relatively costly.
Chinese Granted Patent Number 202114233, hereinafter referred to as the '233 patent, describes a composite mold for a centrifugal casting floating oil seal ring. The '233 patent provides that the composite mold is formed by compositing the annular metal outer mold with the L-shaped section and the annular resin sand inner mold with the circumferential boss on the inner circumferential surface. The composite mold is simple in structure and easy in casting demolding and fine in circular degree of castings when in centrifugal casting of the annular castings with circumferential grooves on the outer circumferences.

SUMMARY OF THE DISCLOSURE

In one aspect of the present disclosure, a method of casting an annular member is disclosed. The method includes preparing a sand mold. The method further includes clamping the sand mold between at least two plates. The method further includes rotating the sand mold. The method further includes introducing molten cast material into the sand mold during rotation of the sand mold.
In another aspect of the present disclosure, a method of casting a metal seal is disclosed. The method includes preparing a sand mold, having a longitudinal axis, with an annular core and radially extending cavities defining surfaces of the metal seal. The method further includes clamping the sand mold between at least two plates. The method further includes mounting the sand mold in a centrifugal casting machine along an axis of rotation thereof. The axis of rotation of the centrifugal casting machine is parallel to the longitudinal axis of the sand mold. The method further includes rotating the sand mold in the centrifugal casting machine. The method further includes pouring molten cast material, through the annular core, into the sand mold during rotation of the sand mold. The method further includes removing the sand mold from the centrifugal casting machine. The method further includes cooling the sand mold until solidification of the molten cast material. The method further includes removing the plates after solidification of the molten cast material. The method further includes dismantling the sand mold to remove the metal seal.
Other features and aspects of this disclosure will be apparent from the following description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a metal seal, a portion being shown as broken away and in section for clarity, according to an exemplary embodiment of the present disclosure;

FIG. 2 is a cross-sectional view of the metal seal of FIG. 1, according to an exemplary embodiment of the present disclosure;

FIG. 3 is a planar view of a sand mold, according to an embodiment of the present disclosure;

FIG. 4 is a planar view of a pattern, according to an embodiment of the present disclosure;

FIG. 5 is a planar view of the pattern of FIG. 4 with the sand mold of FIG. 3, according to an embodiment of the present disclosure;

FIG. 6 is a planar view of the pattern of FIG. 4 with the sand mold of FIG. 3 being lifted therefrom, according to an embodiment of the present disclosure;

FIG. 7 is a perspective view of a mold assembly, according to an embodiment of the present disclosure;

FIG. 8 is a top view of the mold assembly of FIG. 7, according to an embodiment of the present disclosure;

FIG. 9 is a sectional view of the mold assembly of FIG. 7, according to an embodiment of the present disclosure;

FIG. 10 is a diagrammatic view of a centrifugal casting machine including the mold assembly, according to an embodiment of the present disclosure; and

FIG. 11 is a flowchart depicting a method of casting the metal seal, according to yet another embodiment of the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Wherever possible, corresponding or similar reference numbers will be used throughout the drawings to refer to the same or corresponding parts.
The present disclosure provides a method for manufacturing an annular member. As illustrated in FIG. 1, the annular member, generally represented by numeral 100, may be any metallic ring-shaped member which can be employed for a variety of applications. In an embodiment, the annular member 100 is a metal seal. Hereinafter the terms “annular member” and the “metal seal” have been interchangeably used. Also as used herein, the term “metal” includes single element metals as well as metallic alloys. It may be understood that the metal seal 100, as described, may generally be part of an O-ring metal seal which is a commonly used seal in machine design as it is inexpensive, easy to make, and reliable and has simple mounting requirements.
As illustrated in FIG. 1, the metal seal 100 may include a relatively long internal, cylindrical surface 102. A first end 104 of the metal seal 100 has a rounded comer 106 extending from the cylindrical surface 102 and then curves radially away from the cylindrical surface 102. It may be seen from the cross-sectional view of the metal seal 100, as illustrated in FIG. 2, that the rounded corner 106 is formed at a junction of the central opening of the metal seal 100. The metal seal 100 also has an external, annular inclined surface 108 which diverges in an axial direction away from the first end 104. The inclined surface 108 is inclined radially outwardly in a direction away from the cylindrical surface 102, as shown in FIG. 1. In one example, the angle of this inclination of the inclined surface 108 is about 15 degrees with respect to a vertical axis ‘V’ of the metal seal 100.
It may be contemplated by a person skilled in the art that a flexible O-ring (not shown) may be mounted on the inclined surface 108 of the metal seal 100, so that when assembled the metal seal 100 is pushed against some component to be coupled to, and thereby urge into a sealing position. The metal seal 100 also includes a generally radially extending flange 110 which extends beyond a portion of the inclined surface 108 and functions to hold the flexible O-ring on the metal seal 100 until final assembly of the parts.
FIG. 3 illustrates a sectional view of an exemplary sand mold 300, in accordance with an embodiment of the present disclosure. The sand mold 300 may be utilized for casting of an annular member, such as the annular member 100 of the present disclosure. In other words, the sand mold 300 has been designed to manufacture the metal seal 100 as has been shown in FIG. 1. In one example, the sand mold 300 may be made of green sand which is widely known to be used in the casting process. In some example, the sand mold 300 may be made by mixing some binders in order to prevent the collapse of the sand mold 300 due to high forces during the casting process.
As illustrated in FIG. 3, the sand mold 300 may include an annular core 302 extending along a depth of the sand mold 300. In one example, the annular core 302 may be located in a radial center ‘C’ and extending along a longitudinal axis ‘L’ of the sand mold 300. The sand mold 300 may include a cavity, generally represented by the numeral 304, which may be radially extending inside the sand mold 300. It may be understood that the boundaries of the cavity 304 defines the surfaces of the metal seal 100, when removed, after casting, out from the sand mold 300. Further, FIG. 3 shows a channel 306 which connects the annular core 302 and the cavity 304, in the sand mold 300. In one example, the channel 306 may have taper in the range of 3 to 5 degrees extending in a downward slope from the annular core 302 to the cavity 304. It may be understood that the sand mold 300 may include a plurality of channels 306 separated by a certain distance and ending at a circumferential periphery of the sand mold 300, as more clearly illustrated in a subsequent FIG. 7.
FIGS. 4-6 illustrate exemplary intermediate steps for preparing the sand mold 300. As may be seen, the preparation of the sand mold 300 involves a pattern 400 which defines the profiles for the annular core 302 and the cavity 304 of the sand mold 300, as illustrated in FIG. 4. The preparation process includes ramming the sand into a pattern 500, as diagrammatically illustrated in FIG. 5, and then removing the completed sand mold 300 out from the pattern 500, as diagrammatically illustrated in FIG. 6. Such process of preparing a sand mold can be contemplated by a person skilled in the art of casting, and hence has not been described in detail for the brevity of the disclosure.
Referring back to FIG. 3, in one example, the sand mold 300 may further include a base part 308. Like the sand mold 300, the base part 308 may also be made of green sand which is widely known to be used in the casting process. Further, the base part 308 may be made by mixing some binders in order to prevent the collapse of the base part 308 due to high forces during the casting process. It may be understood that the base part 308 may be formed separate and joined with an upper part 310 of the sand mold 300, to complete the sand mold 300. In one example, the base part 308 may be interlocked with the upper part 310 using projections 312, in the base part 308, and corresponding grooves (not shown) in upper part 310, of the sand mold 300.
Referring now to FIG. 7, a perspective view of a mold assembly 700, including the sand mold 300, is illustrated. The dashed lines in FIG. 7 show the internal profile of the sand mold 300, representing the outlines of the cavity 304. Although the sand mold 300 is shown to have a circular shape, it may be contemplated that the sand mold 300 may be of any other shape depending on the requirements of the casting process. Also, the channels 306 have been shown to have a leaf like shape, however such shape is exemplary only and these channels may have any other suitable shape.
Further, the mold assembly 700 of FIG. 7 may include two plates, an upper plate 702 and a bottom plate 704. In the mold assembly 700, the sand mold 300 may be sandwiched between the upper plate 702 and the bottom plate 704. In one example, the plates 702, 704 may be formed of steel or some other high strength material. Further, the upper plate 702 may be provided with a hole 706 aligned with the annular core 302 of the sand mold 300, as more clearly illustrated in top view illustration of the mold assembly 700 in FIG. 8. In one example, the upper plate 702 may also include one or more grips 708 provided close to its periphery, which can be used to lift the upper plate 702 and separate from the sand mold 300, when required. In one example, some grips may also be provided on the bottom plate 704.
Further referring to FIG. 9, a sectional view of the mold assembly 700 is illustrated. As shown, the upper plate 702 and the bottom plate 704 may be coupled with the sand mold 300 by use of a fastening arrangement 900, including a screw 902 and a washer 904, or any other type of fastening arrangement known in the art.
In an embodiment of the present disclosure, the casting process for manufacturing the metal seal 100 utilizes a centrifugal casting machine, such as a centrifugal casting machine 1000 as diagrammatically illustrated in FIG. 10. The centrifugal casting machine 1000 may include a stand 1002 suitably shaped to hold the mold assembly 700. The centrifugal casting machine 1000 may also include a spindle 1004 attached to a lower part of the stand 1002. The spindle 1004 is in connection with a motor 1006 and rotatable by driving of the motor 1006, in the centrifugal casting machine 1000. As shown, the stand 1002 may be so positioned and shaped, such that an axis of rotation ‘A’ of the centrifugal casting machine 1000 is parallel to the longitudinal axis ‘L’ of the sand mold 300. In some examples, the spindle 1004 may be connected to the motor 1006, via a gear 1008. It may also be understood that any other type of centrifugal casting machine may be used for the purpose of the present disclosure.
FIG. 10 also representatively shows a crucible 1010 containing a molten cast material 1012 which may be poured into the mold assembly 700, through the hole 706, and thereby enters the sand mold 300 via the annular core 302. In some examples, the process of pouring the molten cast material 1012 into the sand mold 300 may be automated using some arrangement in the centrifugal casting machine 1000, such as a robotic arm, a supply conduit or the like. In one example, the molten cast material 1012 includes stelite. In other examples, the molten cast material 1012 may be some other cast iron alloy with high tensile strength and durability.
In one example, the centrifugal casting machine 1000 may further include a heating arrangement 1014 for heating the sand mold 300 placed in the stand 1002. It may be contemplated by a person skilled in the art that for this purpose, the heating arrangement 1014 may include a highly resistive coil wrapped around the stand 1002 and further connected to a high voltage electric current source.

INDUSTRIAL APPLICABILITY

The present disclosure relates to a method 1100 for manufacturing the annular member 100, such as the metal seal 100. The conventionally known casting processes for manufacturing the metal seal 100 includes stacking up multiple sand molds provided with large and elaborate gating and rigging systems. The use of gates in the sand mold result in the extra portions formed along with the casted metal seals which leads to loss of yield and further adds to additional steps of machining away those extra portions. In some cases, the loss of yield has been reported up to 80%. This significantly limits the efficiency of such conventional casting processes. Other centrifugal casting methods using copper molds have limitation for size of the metal seals that could be manufactured, and require high initial capital.
The present method 1100 for casting the metal seal 100 is depicted by means of a flowchart as illustrated in FIG. 11. The method 1100 of the present disclosure includes a step 1102 of preparing the sand mold 300. The process of preparing the sand mold 300 has already been described in reference to FIGS. 4-6. Further, the method 1100 includes a step 1104 involving, clamping the sand mold 300 between two plates 702, 704 to support the sand mold 300. As discussed, the sand mold 300 is clamped by means of the fastening arrangement 900. Further, the method 1100 includes a step 1106 involving, mounting the sand mold 300 in the centrifugal casting machine 1000. The sand mold 300 is placed in the stand 1002 of the centrifugal casting machine 1000, such that the longitudinal axis ‘L’ of the sand mold 300 is parallel to the axis of rotation ‘A’ of the centrifugal casting machine 1000. In some examples, the mold assembly 700, including the sand mold 300, is lifted via the grips 708 provided on the upper plate 702 and then placed inside the stand 1002.
Further, the method 1100 includes a step 1108 involving, rotating the sand mold 300 along the axis of rotation ‘A’ in the centrifugal casting machine 1000. It may be understood that the motor 1006 of the centrifugal casting machine 1000 is driven to rotate the spindle 1004, which in turn rotate the stand 1002 and the sand mold 300 placed therein. Further, the method 1100 includes a step 1110 involving, pouring the molten cast material 1012, via the annular core 302, into the sand mold 300. The molten cast material 1012 may be poured from the crucible 1010. In one example, the molten cast material 1012 may be poured while the sand mold 300 is being rotated in order to hurl the molten cast material 1012 into the cavity 304 of the sand mold 300. Further, the molten cast material 1012 may be poured in a direction of rotation ‘R’ of the sand mold 300 in order to minimize spillage. In one example, the sand mold 300 is rotated in a range of 500 to 2000 revolutions per minute. More specifically, in one example, the sand mold 300 is rotated in a range of 1000 to 1200 revolutions per minute. Further, in one example, the sand mold 300 is rotated for a time period ranging from 30 minutes to 180 minutes, or specifically in the range of 60 to 90 minutes.
In one example, the method 1100 further involves, heating the sand mold 300 in the centrifugal casting machine 1000 during its rotation to keep the molten cast material 1012 in the molten liquid state, so that the molten liquid can flow through the channels 306 to the cavity 304. The sand mold 300 is heated using the heating arrangement 1014, in the centrifugal casting machine 1000. In one example, the sand mold 300 is heated to a temperature between 100 to 500 degrees Celsius. More specifically, the sand mold 300 is heated to a temperature between 200 to 300 degrees Celsius.
Further, the method 1100 includes a step 1112 involving, removing the sand mold 300 from the centrifugal casting machine 1000. The step 1112 may include decelerating the rotation of the sand mold 300, in the centrifugal casting machine 1000, after a predetermined time period depending on the molten cast material 1012 among other casting process characteristics. For this purpose, the rotation of the sand mold 300 is decelerated in a range of 200 to 500 revolutions per minute, by stopping the motor 1006. The step 1112 may further include lifting the mold assembly 700 out of the stand 1002 by using the grips 708 and using some kind of a lifting device, such as a gantry or the like.
Further, the method 1100 includes a step 1114 involving, cooling the sand mold 300 until solidification of the molten cast material 1012. For this purpose, the mold assembly 700, removed from the centrifugal casting machine 1000, is kept in a cool place. In one example, the sand mold 300 is cooled using natural draft of air.
Further, the method 1100 includes a step 1116 involving, removing the plates 702, 704, from the mold assembly 700, after solidification of the molten cast material 1012, to remove the sand mold 300. Finally, the method 1100 includes a step 1118 involving, dismantling the sand mold 300 to remove the casted metal seal 100 therefrom.
The present method 1100 can be used to cast metal seals 100 without the use of gating and rigging systems, as are required in a conventional casting process. The elimination of the gating and rigging system may lead to significant increase in the yield of the casting process, as the molten cast material that is required to fill up the gates and runners is not required anymore using the method 1100 of the present disclosure. Further, the present method 1100 significantly reduces the extra cost and effort required to machine off the extra portions formed with the metal seals in the conventional casting process. Also, the present method 1100 reduces the possibility of contamination and/or oxidation of the molten cast material which can occur during the re-melting of the extra portions to reuse the material.
While aspects of the present disclosure have been particularly shown and described with reference to the embodiments above, it will be understood by those skilled in the art that various additional embodiments may be contemplated by the modification of the disclosed machines, systems and methods without departing from the spirit and scope of what is disclosed. Such embodiments should be understood to fall within the scope of the present disclosure as determined based upon the claims and any equivalents thereof.

Claims

We claim:

1. A method of casting an annular member, the method comprising:

preparing a sand mold;

clamping the sand mold between at least two plates;

rotating the sand mold; and

introducing molten cast material into the sand mold during rotation Thereof.

2. The method of claim 1 further comprising, mounting the sand mold in a centrifugal casting machine for rotation thereof.

3. The method of claim 1 further comprising, heating the sand mold during rotation thereof.

4. The method of claim 2 further comprising, removing the sand mold from the centrifugal casting machine after rotation thereof.

5. The method of claim 4 further comprising, cooling the sand mold until solidification of the molten cast material, after removal from the centrifugal casting machine.

6. The method of claim 5 further comprising, removing the plates after solidification of the molten cast material.

7. The method of claim 6 further comprising, dismantling the sand mold to remove the annular member.

8. A method of casting a metal seal, the method comprising:

preparing a sand mold, having a longitudinal axis, with an annular core and radially extending cavities defining surfaces of the metal seal;

clamping the sand mold between at least two plates;

mounting the sand mold in a centrifugal casting machine along an axis of rotation thereof, wherein the axis of rotation of the centrifugal casting machine is parallel to the longitudinal axis of the sand mold;

rotating the sand mold in the centrifugal casting machine;

pouring molten cast material, through the annular core, into the sand mold during rotation thereof;

removing the sand mold from the centrifugal casting machine;

cooling the sand mold until solidification of the molten cast material;

removing the plates after solidification of the molten cast material; and

dismantling the sand mold to remove the metal seal.

9. The method of claim 8, wherein the annular core is located substantially at a radial center of the sand mold.

10. The method of claim 8, wherein the sand mold includes a channel connecting the annular core and the cavity.

11. The method of claim 10, wherein the channel includes a taper extending in a downward slope from the annular core to the cavity.

12. The method of claim 8, wherein at least one of the plates provides a hole aligning with the annular core of the sand mold, when clamped therewith.

13. The method of claim 8, wherein the sand mold is removed from the centrifugal casting machine using one or more grips provided on the plates.

14. The method of claim 8, wherein the molten cast material is introduced in a direction of rotation of the sand mold.

15. The method of claim 8, wherein the sand mold is rotated in a range of 500 to 2000 revolutions per minute.

16. The method of claim 15, wherein the sand mold is rotated in a range of 1000 to 1200 revolutions per minute.

17. The method of claim 8, wherein the sand mold is rotated for a time period ranging from 30 minutes to 180 minutes.

18. The method of claim 17, wherein the sand mold is rotated for a time period ranging from 60 minutes to 90 minutes.

19. The method of claim 8 further comprising, heating the sand mold in the centrifugal casting machine during rotation thereof.

20. The method of claim 19, wherein the sand mold is heated to a temperature in a range of 100 to 500 degrees Celsius.