Patent Application
20200332806
This disclosure relates in general to a composite metal component and a method of producing same.
Various process steps in the minerals processing industry involve erosive contact with components of equipment which results in significant wear to the extent that frequent replacement is required. However, often the wear of a component is uneven depending on the nature of the process step.
For example, in the process of pumping abrasive slurries, a limiting factor on pump wet end component wear life can be localized wear in the form of deep gouging or very high wear rates in certain locations even though other parts of the same component may be wearing at a relatively low rate. Specific examples include (but are not limited to) the leading edge of a slurry pump impeller and the cutwater of a slurry pump liner (also known as a volute).
One approach to address this issue in the example of pump impellers is to fabricate an impeller which involves positioning specially shaped highly wear resistant materials at certain locations during the manufacture of the impeller that are subject to high wear conditions during operation; while retaining relatively lower cost metal in non-critical areas of the impeller. However, this approach can add significant cost, particularly if the wear resistant component is made from an expensive wear resistant material and requires the manufacture of complex three dimensional shapes to conform to the impeller's hydraulic design requirements.
Another attempt to provide localized wear protection for wear components is the application of welded overlays or other cladding type methods where a thin layer of wear resistant material is overlaid onto the metal component composed of the lower cost metal material. However, while these methods may work when applying a thin layer of wear resistant material to wear components with flat surfaces, wear components in the form of complex shapes such as a pump impeller or a pump liner are not readily amenable to this method.
It is also the case that many other wear components used in mineral processing equipment, such as crushers and grinding mills also suffer from premature failure due to localized wear. It is envisaged that the present invention will also benefit these types of equipment as well.
The present invention seeks to provide a relatively low cost composite metal wear component and a method for producing same that provides a wear component that includes localized wear protection for use in the minerals processing industry.
According to one aspect there is provided a method of producing a composite metal article including the following steps:
In certain embodiments, the casting step (i) includes the following steps:
In certain embodiments, the one or more cavity forming portions is composed of a material that has a coefficient of thermal expansion that is similar, or substantially the same, as the coefficient of thermal expansion of the host metal composition.
In certain embodiments, the one or more cavity forming portions is removed from the host metal composition to reveal the one or more cavities after step (ic).
In certain embodiments, the one or more cavity forming portions is removed from the host metal composition by drilling and/or otherwise machining the component composed of the host metal composition after step (ic).
In certain embodiments the one or more cavity forming portions is composed of a material selected from steel or another metal alloy, carbon or graphite.
In certain embodiments, the one or more cavity forming portions is at least partially fragmented as the host metal composition in the mould solidifies due to shrinkage of the host metal composition during step (ic).
In certain embodiments, the one or more cavity forming portions includes a hollow centre.
In certain embodiments, the one or more cavity forming portions has a higher softening point temperature than the liquid pouring temperature of the host metal composition.
In certain embodiments, the one or more cavity forming portions are cylindrical or cuboid in shape.
In certain embodiments, the component composed of the host metal composition is heat treated and/or undergoes a tempering treatment to remove any residual stresses resulting from the formation of the one or more cavities after the one or more cavity forming portions is removed from the component composed of the host metal composition.
In certain embodiments, the host metal composition is selected from a high chromium white cast iron.
In certain embodiments, the wear resistant composition has an increased wear resistance than the host metal composition.
In certain embodiments, the wear resistant composition is selected from tungsten carbide. In one form the tungsten carbide includes a coarse grain size. In a further form the grain size of the tungsten carbide is 2 to 6 micrometers.
In certain embodiments, the wear resistant composition is cylindrical, cuboid or button shaped.
In certain embodiments, the wear resistant composition is bonded into the one or more cavities in the host metal using an adhesive or by using a brazing method.
In certain embodiments, the composite metal article is a wear component.
In certain embodiments the one or more cavities are located within the body of the composite metal article adjacent to a wear surface of the wear component.
In certain embodiments, the wear component is part of an apparatus used in mineral processing. In this form, the apparatus used in mineral processing may be selected from a centrifugal slurry pump, grinding mill, crusher or wear plate.
In certain embodiments, the wear component is selected from a slurry pump impeller or a liner for a centrifugal slurry pump.
According to another aspect there is provided a composite metal article produced by the method described herein.
According to another aspect there is provided a composite metal wear component including:
In certain embodiments the one or more cavities are located within the main body portion of the composite wear component adjacent to a wear surface of the composite metal wear component.
In certain embodiments, the composite metal wear component is part of an apparatus used in mineral processing. The apparatus used in mineral processing may be selected from a centrifugal slurry pump, grinding mill, crusher or wear plate.
According to another aspect there is provided a composite metal wear component for use with a centrifugal slurry pump, the composite metal wear component including:
In certain embodiments, the one or more cavities is/are formed during casting of the main body portion, or the one or more cavities is/are machined into the main body portion.
In certain embodiments, the composite metal wear component is a slurry pump impeller or a liner for a centrifugal slurry pump.
According to another aspect there is provided a slurry pump impeller including a back shroud with an inner main face with an outer peripheral edge and a central axis, a plurality of pumping vanes extending away from the inner main face of the back shroud, the pumping vanes being disposed in spaced apart relation, each pumping vane including opposed main side faces, a leading edge in the region of the central axis and a trailing edge in the region of the outer peripheral edge of the back shroud with a passageway between adjacent pumping vanes, wherein the pumping vanes include one or more cavities located therein and wherein a wear resistant composition is bonded at least partially within the one or more cavities.
In certain embodiments, the slurry pump impeller includes a front shroud having an inner main face wherein the plurality of pumping vanes extend between the inner main faces of the back and front shrouds.
In certain embodiments, each of the plurality of pumping vanes includes at least one cavity. In certain embodiments, the one or more cavities are located within a body portion of each of the plurality of pumping vanes whereby the wear resistant composition is not exposed to the passageway between adjacent pumping vanes.
In certain embodiments, the one or more cavities each include an opening located in a top surface of the plurality of pumping vanes between the opposed main side faces and remote from the back shroud.
In certain embodiments, the one or more cavities extend through the body portion of each of the plurality of pumping vanes from the opening towards the back shroud.
In certain embodiments, the one or more cavities extend through the body portion of each of the plurality of pumping vanes from the opening until in line with where the plurality of the pumping vane meets the back shroud.
In certain embodiments, the one or more cavities are located proximal to the leading edge of the plurality of pumping vanes.
In certain embodiments, the one or more cavities are located within about 5 mm to about 25 mm from the leading edge of the plurality of pumping vanes.
In certain embodiments the wear resistant composition is gradually exposed as the pumping vanes are subjected to wear in use.
According to another aspect there is provided a pump liner for a centrifugal slurry pump, the pump liner including a main pumping chamber having:
In certain embodiments the one or more cavities are located within a body portion of the region of the transition surface whereby the wear resistant composition is not exposed to the main pumping chamber.
In certain embodiments the one or more cavities each include an opening located in an outside surface of the pump liner in the region of the transition surface.
In certain embodiments the pump liner includes at least one cavity which includes two openings located on an outside surface on opposite sides of the pump liner wherein the wear resistant composition is located proximal to the cutwater.
In certain embodiments, the one or more cavities are located within about 5 mm to about 25 mm from transition surface.
In certain embodiments, the wear resistant composition is gradually exposed as the cutwater and/or the transition surface is subjected to wear in use.
Other aspects, features, and advantages will become apparent from the following detailed description when taken in conjunction with the accompanying drawings, which are a part of this disclosure and which illustrate, by way of example, principles of the inventions disclosed.
The accompanying drawings facilitate an understanding of the various embodiments.
By means of the method described herein, it was found that a composite metal article may be produced which finds application as a wear component for use in the minerals processing industry. In particular, it was found that when one or more cavities were formed during the casting process of a metal component, the one or more cavities did not significantly effect the structural integrity of the metal component and also allowed for a wear resistant composition in solid form to be bonded into the one or more cavities to produce a composite metal article with increased wear resistance properties.
In certain embodiments, the method as described herein may be used to produce a composite metal wear component which includes the wear resistant composition inserted and bonded within the component adjacent or proximal to regions of the wear component that are subject to significant wear in use. For example, the method as herein described may be used to produce a composite metal slurry pump impeller which may be composed of a host metal composition including a wear resistant material bonded within cavities formed during the casting process of the host metal composition. The wear resistant material may be bonded within cavities that may be located in within the body of the slurry pump impeller composed of the host metal composition adjacent, or proximal to the leading edge of the pumping vanes of the slurry pump impeller, and/or located in the body of the impeller at other locations that may be subject to significant wear in use
In certain embodiments other types of composite metal wear components may be produced where the wear resistant material may be bonded within cavities located adjacent, or proximal to areas subject to significant wear. For example, a metal liner for a centrifugal slurry pump may be produced from a host metal composition which includes a wear resistant material bonded within cavities located adjacent or proximal to the cutwater of the metal liner. Further examples of types of metal wear components may be produced in accordance with the method described which may find application for use with grinding mills, crushers and wear plates.
In certain embodiments, the wear resistant material is located such that it is encased within the main body of the metal wear component where the main working surfaces of the metal wear component are composed of the host metal composition. This allows that the working surfaces of the wear component are not hydrodynamically altered by the inclusion of the wear resistant material. It this embodiment, when the main body of the metal wear component begins to wear during use, the metal wear component becomes exposed which then slows down the rate of wear experienced by the metal wear component.
In an embodiment there is provided a method of producing a composite metal article that may be used as a composite metal wear component. The method includes the following steps:
In the method as herein described, casting step (i) may include positioning one or more cavity forming portions into a mould for the component. The mould for the component may be in the shape of the composite metal article which may be for a composite metal wear component. The cavity forming portions provide that when a host metal composition is introduced into the mould in liquid form, the host metal composition surrounds the cavity forming portions providing that the locations of the mould taken up by the cavity forming portions are not filled with the liquid host metal composition. It is at these locations that the cavities are formed. As a result, the cavity forming portions are shaped to provide the subsequent interior surface shape of the cavities. In a preferred form, the cavity forming portions are cylindrical or cuboid in shape which results in cavities having an interior surface shape that is cylindrical or cuboid in form.
The host metal composition in the mould is allowed to cool and solidify forming the component composed of the host metal composition. The cavity forming portions may be located within the host metal composition once the component has cooled and solidified. Alternatively, the cavity forming portions may be formed of a material that fractures, or otherwise structurally degrades due to the shrinkage of the host metal composition as it cools and solidifies.
To provide the cavities in the host metal component after the liquid host metal has cooled and solidified, the one or more cavity forming portions or remaining fragments thereof may be removed from the host metal composition. Suitable removal techniques may involve drilling and/or otherwise machining the component.
In an embodiment the one or more cavity forming portions may be formed from a material that has a coefficient of thermal expansion that is similar, or substantially the same, as the coefficient of thermal expansion of the host metal composition. In addition, the cavity forming portions may have a higher softening temperature than the liquid pouring temperature of the host metal composition. For example, the one or more cavity forming portions may be composed of a material selected from steel or another metal alloy, or the one or more cavity forming portions may be composed of carbon or graphite.
In an embodiment the one or more cavity forming portions include a hollow centre. Such a form may encourage the one or more cavity forming portions to fracture or otherwise structurally degrade due to the host metal composition shrinking as it cools and solidifies during the casting step. The cavity forming portions including a hollow centre may be cylindrical or cuboid in shape and may be formed from materials such as glass or quartz glass. Prior to inserting the cavity forming portions with a hollow centre into the mould, the cavity forming portions may be pre-weakened, for example, by scratching the surface of the cavity forming portion. The pre-weakening may further encourage the one or more cavity forming portions to fracture or otherwise structurally degrade during the casting process which facilitates the removal during the method as described.
Following the removal of the cavity forming portions from the component formed from the host metal composition, the component may be heat treated or subjected to a tempering treatment to remove any residual stresses resulting from the formation of the one or more cavities.
The host metal composition may be selected from any suitable metal or metal alloy that is appropriate for casting wear components, such as for example high chromium white cast iron. The wear resistant composition would ideally have an increased wear resistance than the host metal composition and may be chosen from a material with a very high wear resistance such as tungsten carbide. The tungsten carbide may be sintered and/or may have a grain size of 2 to 6 micrometers. In a preferred form, the wear resistant composition is cylindrical, cuboid or button shaped or is of another form that is commonly manufactured. A commonly manufactured form such as cylindrical, cuboid or button shape has been found to be generally less expensive than other more irregular shapes which reduces the cost of producing the composite metal wear component as herein described.
In an embodiment the wear resistant composition is bonded into the one or more cavities in the host metal using an adhesive. The adhesive may have high gap filling capabilities and high tensile strength. For example, the adhesive may be selected from LOCTITE EA 9497 or 3M Scotch-weld 7236 B/A or other structural epoxy adhesive; or a high strength retaining compound such as Loctite 620, Loctite 638 or Loctite 660. As an alternative the wear resistant composition is bonded into the one or more cavities by using a brazing method. As a further alternative, or in addition to the above mentioned bonding examples, the wear resistant component may be bonded into the one or more cavities via a mechanical locking arrangement such as for example a threaded plug, a shrink-fit plug or a close-fit plug secured by a high-strength retaining compound; these measures being employed to prevent the wear resistant component from coming out of the cavity in which it is secured during operation of the equipment.
Referring to
Referring to
Referring to
The cavities 20 shown in
A wear resistant material that may be in the form of a cylinder which may be slightly smaller in diameter to the cavities 20 may be inserted into the cavities after the impeller has been cast. The wear resistant material may be composed of any suitable material that has an increased wear resistance compared to the metal composition used to cast the body of the impeller. In a preferred form the wear resistant material may be selected from cylinders of sintered tungsten carbide that are of a cylindrical shape that is slightly smaller than the cavities 20. The wear resistant material may be bonded within the cavities by use of an adhesive or by using a brazing method. In
The impeller 10 as shown in
In use, the metal composition of the impeller 10 will begin to wear in certain locations such as the leading edge 14 of the pumping vane 12. This will eventuate in the enhanced wear resistant material becoming exposed to the abrasive process conditions in the operation of the centrifugal slurry pump. At this time, the rate of wear will decrease due to the increased wear resistance of the wear resistant material bonded within the cavities 20. This has the advantageous effect of reducing the overall wear rate of the impeller 10 and increasing its working life.
FIG.5 depicts an alternative embodiment of a wear component which is in the form of a liner 50 for a centrifugal slurry pump. The liner 50 is in the form of a volute and includes a pumping chamber 52 and an outlet 51. The liner 50 includes a transition surface 70 extending between an inner peripheral surface 71 of the main pumping chamber and an inner peripheral surface of the discharge outlet 72, where the transition surface includes a cutwater 53. A cutwater 53 is a portion of the liner 50 which separates the flow of slurry from the pumping chamber 52 and the outlet 51 when in use during the operation of a centrifugal slurry pump. The cutwater 53 is often the location of significant impact erosion wear during the slurry pumping operation.
A further advantage of the method described herein is the modification required to the original wear component casting is the location of cavity forming portions in a standard wear component mould. This will result in a final casting that is in appearance exactly the same as the original part, except that it will have cavities provided for insertion of the wear resistant material.
In the foregoing description of certain embodiments, specific terminology has been resorted to for the sake of clarity. However, the disclosure is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes other technical equivalents which operate in a similar manner to accomplish a similar technical purpose. Terms such as “left” and right”, “front” and “rear”, “above” and “below” and the like are used as words of convenience to provide reference points and are not to be construed as limiting terms.
In this specification, the word “comprising” is to be understood in its “open” sense, that is, in the sense of “including”, and thus not limited to its “closed” sense, that is the sense of “consisting only of”. A corresponding meaning is to be attributed to the corresponding words “comprise”, “comprised” and “comprises” where they appear.
In addition, the foregoing describes only some embodiments of the invention(s), and alterations, modifications, additions and/or changes can be made thereto without departing from the scope and spirit of the disclosed embodiments, the embodiments being illustrative and not restrictive.
Furthermore, invention(s) have described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention(s). Also, the various embodiments described above may be implemented in conjunction with other embodiments, e.g., aspects of one embodiment may be combined with aspects of another embodiment to realize yet other embodiments. Further, each independent feature or component of any given assembly may constitute an additional embodiment.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017905071 | Dec 2017 | AU | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/AU2018/051364 | 12/19/2018 | WO | 00 |
