GB2599112A

GB2599112A - Foundry filter and a method of manufacturing the same

Info

Publication number: GB2599112A
Application number: GB2015105.6A
Authority: GB
Inventors: Ali Juma Kassim; Leaney Michael
Original assignee: CAT International Ltd
Current assignee: CAT International Ltd
Priority date: 2020-09-24
Filing date: 2020-09-24
Publication date: 2022-03-30
Also published as: GB202015105D0

Abstract

A foundry filter 100 for filtering molten metal, the filter comprising: a porous ceramic filter structure 101 comprising a plurality of pores 101p for filtering molten metal, wherein the porous ceramic filter structure further comprises a plurality of through holes 102. Also disclosed is a method of producing said filter by producing a plurality of through holes in a porous filter structure, impregnating the structure with ceramic material to form a precursor, and firing the precursor. An alternative method of production comprises 3D printing a precursor porous ceramic filter structure comprising a plurality of pores and a plurality of through holes using a 3D ceramic printer, followed by firing the precursor. The filter is preferably a ceramic foam foundry filter. The diameter of at least some of the through holes may be between 15-20% of the thickness of the filter. The filter preferably has 5-15 pores per inch.

Description

TITLE

FOUNDRY FILTER AND A METHOD OF MANUFACTURING THE SAME

TECHNOLOGICAL FIELD

Examples of the present disclosure relate to a foundry filter and a method of manufacturing the same. Some examples, though without prejudice to the foregoing, relate to a ceramic foam foundry filter for filtering molten metal and a method of manufacturing the same.

BACKGROUND

Conventional foundry filters for metal filtration, such as ceramic filters for filtering molten metal prior to casting, are not always optimal.

Typically, for large direct pour castings of greater than 1 tonne, very large foundry filters (e.g. over 200 mm in diameter with a thickness of 50 mm) are used. However, conventional filters used for such high-volume pours/castings may suffer from issues with regards to becoming blocked. For example, inclusions/slag in the molten metal to be filtered may block the filtering pores of the filter structure thereby increasing the filter time and pour time. Such an increase in filter/pour time may also give rise to problems relating to the molten metal cooling and freezing inside the filter -further blocking the pores (and yet further increasing the filter/pour time). Such issues are particularly prevalent for large iron castings of greater than 1 tonne since molten iron for such castings typically has more inclusions/slag than for other types of metal castings such as steel.

It is useful to provide an improved ceramic foundry filter for filtering molten metal. One or more aspects/examples of the present disclosure may or may not at least partially

address one or more of the background issues.

The listing or discussion of any prior-published document or any background in this specification should not necessarily be taken as an acknowledgement that the document or background is part of the state of the art or is common general knowledge.

One or more aspects/examples of the present disclosure may or may not address one

or more of the background issues.

BRIEF SUMMARY

The scope of protection sought for various embodiments of the invention is set out by the independent claims.

Any examples/embodiments and features described in this specification that do not fall under the scope of the independent claims are to be interpreted as examples useful for understanding various embodiments of the invention.

According to at least some examples of the disclosure there is provided a foundry filter for filtering molten metal, the filter comprising: a porous ceramic filter structure comprising a plurality of pores for filtering molten metal, wherein the porous ceramic filter structure further comprises a plurality of through holes.

According to various, but not necessarily all, examples there is provided a method of providing and/or manufacturing a filter described herein.

According to various, but not necessarily all, examples of the disclosure there is provided a method of manufacturing a foundry filter for filtering molten metal, the method comprising: creating a plurality of through holes in a porous filter structure; impregnating the porous filter structure with ceramic material to form a precursor porous ceramic filter structure; firing the precursor porous ceramic filter structure to form a porous ceramic filter structure comprising a plurality of pores for filtering molten metal, wherein the porous ceramic filter structure further comprises a plurality of through holes.

According to various, but not necessarily all, examples of the disclosure there is provided a method of manufacturing a foundry filter for filtering molten metal, the method comprising: 3D printing, with a 3D ceramic printer, a precursor porous ceramic filter structure comprising a plurality of pores, wherein the precursor porous ceramic filter structure further comprises a plurality of through holes; firing the precursor porous ceramic filter structure to form a porous ceramic filter structure comprising a plurality of pores for filtering molten metal, wherein the porous ceramic filter structure further comprises a plurality of through holes.

According to various, but not necessarily all, examples there is provided a method of using a filter as described herein.

According to various, but not necessarily all, examples of the disclosure there are provided examples as claimed in the appended claims.

The following portion of this 'Brief Summary' section describes various features that can be features of any of the examples described in the foregoing portion of the 'Brief

Summary' section.

In some but not necessarily all examples, the plurality of through holes are substantially straight.

In some but not necessarily all examples, the plurality of through holes form an array of substantially parallel apertures from one surface of the porous ceramic filter structure to an opposite surface of the porous ceramic filter structure.

In some but not necessarily all examples, the filter structure defines a first major surface, and the plurality of through holes extend substantially perpendicularly to the first major surface.

In some but not necessarily all examples, a diameter of at least some of the plurality of through holes is between 15% -20% of the thickness of the filter structure.

In some but not necessarily all examples, a total area of the plurality of through holes is: between 20% -60%, or between 30% -50%, of an area of an ingate or runner that, in use, provides the molten metal to the filter.

In some but not necessarily all examples, the filter structure has: 5-15 pores per inch, or 7-10 pores per inch.

In some but not necessarily all examples, the porous filter structure comprises one or more of: an open cell structure, and a foam structure.

In some but not necessarily all examples, the filter is a ceramic foam foundry filter.

While the various examples and optional features may be described separately, it is to be understood that their provision in all possible combinations and permutations is

contained within the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of various examples of the present disclosure that are useful for understanding the detailed description and certain examples of the present disclosure, reference will now be made by way of example only to the accompanying drawings in which: FIG. 1 shows a schematic plan view of an example of a filter according to the present disclosure, along with an enlarged view of a the same; FIG. 2 shows a schematic perspective view of the filter of FIG. 1; FIG. 3 shows an example of a method of manufacturing a filter according to the present disclosure; FIG. 4 shows a further example of a method of manufacturing a filter according to the present disclosure; FIG. 5 shows a schematic plan view of a further example of a filter according to the

present disclosure; and

FIG. 6 shows a schematic plan view of a yet further example of a filter according to the present disclosure.

The figures are not necessarily to scale. Certain features and views of the figures may be shown schematically or exaggerated in scale in the interest of clarity and conciseness. For example, the dimensions of some elements in the figures can be exaggerated relative to other elements to aid explication. Similar reference numerals are used in the figures to designate similar features. For clarity, all reference numerals are not necessarily displayed in all figures.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a plan view of a foundry filter 100 for filtering molten metal (not shown).

The filter comprises a porous ceramic filter structure 101. As shown in the enlarged zoomed in section of the porous ceramic filter structure, the porous ceramic filter structure comprises a plurality of pores 101p for filtering molten metal.

The pores define a foam structure. In some examples the foam structure may have an open cell/pore structure that provides a plurality of convoluted passageways that enable filtration of molten metal passing therethrough.

In this example, the porous ceramic filter structure is ceramic foam filter suitable for filtering molten metal (not least, for example, ferrous metals such as iron or steel or non-ferrous metals such as aluminium, copper, bronze, etc.). The ceramic filter structure may be made from a ceramic material not least such as: alumina, zirconia, silica, silicon carbide, carbon or carbon composite or ceramic fibres.

The filter structure may have a pore density of: 5-15 pores per inch (2.0 -5.9 pores per cm), or 7-10 pores per inch (2.8 -3.9 pores per cm).

The porous ceramic filter structure further comprises a plurality of through holes 102.

The through holes are apertures/bores that pass straight through the porous ceramic filter structure, e.g. from a first face straight through to an opposing second face of the porous ceramic filter structure. In some examples, the through hole is substantially cylindrical. However, in other examples, the through holes are formed with other cross-sectional shapes, not least for example: square, rectangular or polygonal cross sections.

FIG. 2 shows a schematic perspective view of the filter 100 of FIG. 1. As is indicated in this figure, via the exemplary dotted lines, the though holes 102 are substantially straight and form an array of substantially parallel apertures from one surface of the porous ceramic filter structure 101 to an opposite surface of the porous ceramic filter structure.

The filter (and filter structure) has a first major surface, e.g. upper face 100u -the filtering surface onto which, in use, molten metal is provided/poured onto to be filtered. The plurality of through holes extend substantially perpendicularly to the first major surface, i.e. from the upper face 100u to the lower face 1001.

The filter of FIGs 1 and 2, has a generally circular form factor having an upper major surface 100u and a lower major surface 1001 through which molten metal may pass through so as to be filtered. It is to be appreciated that the shape and dimensions of the filter and filter structure could be duly set so as to be appropriate for the intended use/application, e.g. for integration into a direct pour casting system, a gated system, a die cast system or any other casting system. For example, the filter/filter structure may be of other shapes and form factors, not least for example: square, rectangular or polygonal cross sections.

The diameter 102d of the through holes is greater than 15% of the thickness of the filter structure and/or less than 20% of the thickness of the filter structure. If the diameter of the through holes were too low i.e. < 15% of the thickness of the filter structure (e.g. such that the diameter of the through holes were of the order of the diameter of the pores or < 2 times the pore diameter) such sized through holes would gradually get blocked by inclusions/slag (as per the pores of the filter) during a filtration process/pour/casting. This would slow down the flow rate of the molten metal through the filter and prolong the filtration process/pour/casting time -thereby increasing the risk of the metal cooling and freezing in the filter. Conversely, if the diameter of the through holes is too great, whilst the through holes would be less susceptible to blocking, this would compromise the integrity/strength of the filter and weaken it -thereby making it susceptible to cracking/breaking (not least such as upon initial metal impart at the beginning of a pouring/casting). Moreover, it would also adversely affect the filtering efficiently/filtering effect of the filter.

The provision of a diameter of the through holes between 15% to 20 % of the thickness of the filter structure has been found to be an optimal dimension of the through holes that is neither too small or too large and which optimally reduces the above-mentioned disadvantages whilst still providing the advantages of enabling a relatively constant flow rate of metal through the filter (i.e. through both the pores and the through holes) during the filtration process/casting/pour giving rise to a sufficient degree of filtration efficiency whilst also providing enhanced throughput of molten metal/ filtering flow rate (thereby reducing the filter/pour time may and reducing the risk of molten metal cooling and freezing inside the filter). By carefully configuring the size and number of through holes as per examples of the present disclosure, optimal filter characteristics can be provided that reduce the above disadvantages whilst maximising the above advantages.

By way of an example, for a 50mm thick foam filter, each hole diameter = 50mm x 16% = 8mm The total area of the plurality of through holes is between 20% to 60%, or between 30% to 50%, of an area of an ingate or runner that, in use, provides the molten metal to the filter.

Advantageously, the above ratios and constraints in the dimensions of the through holes ensure that: 1/ There is no 'jetting' or overly high metal velocities occurring through the straight through holes (which could lead to erosion of the filter or increase in metal turbulence of the metal exiting the filter) 2/ The combined area of the holes provides a pressure balance in the system and an increased tolerance in metal variables, i.e. flow rate (namely enabling the provision of a relatively constant flow rate of metal through the filter during the filtration process/casting/pour), that may lead to blockage 3/ a high degree of filtration efficiency is maintained whilst also providing enhanced throughput of molten metal/ filtering flow rate (thereby reducing the filter/pour time may and reducing the risk of molten metal cooling and freezing inside the filter), and also whilst providing turbulence reduction efficiency.

In the illustrated example, the filter has a diameter 100d of 200mm and a thickness 100t of 50mm, the array of through holes each have a diameter 102d of 8mm, and the array of through holes have a separation distance 102s of 20mm.

Where the filter is incorporated into a gating system with 100mm diameter runner prior to the filter housing, the area of runner/ingate = Trr2 = TE X (50mm)2 = 7,850 mm2.

The total area of holes is 40% of the area of runner/ingate = 0.4 x 7,850mm2 = 3,140 mm2 For a hole with a diameter of 8mm, the area of each hole = Tr x (4mm)2 = 50mm2 Accordingly, the total number of holes = total hole area / area of each hole = 3,140 5 mm2/ 50mm2= 62 holes.

By adhering to such design criteria, the filter can provide double the filtering rate/capacity of a conventional foam filter (i.e. such a conventional foam filter being devoid of straight through holes as per examples of the present disclosure) for use with Ductile Iron/Spheroidal Graphite Iron (i.e. Irons treated with Magnesium to generate Carbon in the form of spheres, giving rise to high strength and high ductility).

Examples of the disclosure may thereby provide an improved foundry filter with an increased flow rate / velocity of molten metal therethrough (thereby reducing the potential for metal flow related issues) whilst maintaining adequate filtration efficiency and filtration characteristics/quality. Examples may thereby provide optimal performance in terms of metal/filtration flow rate and filtration efficiency.

FIG. 3 shows a flow chart of an example of a method 200 of manufacturing a filter according to the present disclosure.

In block 201 a plurality of through holes are created in a porous filter structure. The porous filter structure may be a Reticulated Polyurethane Foam (RPF) or any other suitable foam structure that provides an open cell/pore structure providing a plurality of convoluted passageways that enable filtration of molten metal passing therethrough. Though holes may be created in the same by any suitable technique, not least via die pressing or cutting In block 202, the porous filter structure is impregnated (e.g. soaked, coated, sprayed, infused) with a ceramic material (e.g. a ceramic slurry, not least such as Silicon Carbide based slurry or Zirconia based slurry) to form a precursor porous ceramic filter structure, wherein the precursor porous ceramic filter structure comprises a plurality of through holes.

After a drying step in block 203, in block 204, the precursor porous ceramic filter structure is fired to form a porous ceramic filter structure comprising a plurality of pores for filtering molten metal, wherein the porous ceramic filter structure further comprises a plurality of through holes.

The flowchart of FIG. 3 represents one possible scenario among others. The order of the blocks shown is not absolutely required, so in principle, the various blocks can be performed out of order. Not all the blocks are essential. In certain examples one or more blocks can be performed in a different order or overlapping in time, in series or in parallel. One or more blocks can be omitted or added or changed in some combination of ways.

FIG. 4 shows a further example method 300 of manufacturing a filter according to the present disclosure.

In block 301 a precursor porous ceramic filter structure comprising a plurality of through holes is 3D printed with a 3D ceramic printer.

3D printing technologies, also known as Additive Manufacturing technologies, encompass various differing techniques and processes, using differing printing materials, for synthesizing a three-dimensional object. Typically, in 3D printing, successive layers of a material are formed under computer control, for example based on a virtual 3D model or CAD design, which may enable the creation of an object of almost any shape or geometry.

Any 3D printing/additive manufacturing process suitable for forming/synthesising the precursor porous ceramic filter structure may be used, not least for example: 3D printing based on: powder bed, ceramic jet printing, extrusion deposition, fusion deposition modelling, or lithographic ceramic 3D printing.

The 3D ceramic printer prints an initial 3D ceramic model, i.e. the precursor porous ceramic filter structure, which, in effect, forms a precursor to a resultant ceramic object (i.e. the porous ceramic filter structure) once it has undergone firing.

In block 302, the precursor porous ceramic filter structure is fired to form a porous ceramic filter structure comprising a plurality of pores for filtering molten metal, wherein the porous ceramic filter structure further comprises a plurality of through holes.

As used herein, a "precursor" may be used to refer to a substance/structure from which another substance/structure is formed. For example, a ceramic based precursor, which, following firing, forms a resultant ceramic product. The precursor may, for instance, comprise: a porous structure/open cell foam structure/reticulated foam structure, comprising a plurality of through holes, impregnated in a ceramic material/slurry, or a 3D printed ceramic porous structure/open cell foam structure/reticulated foam structure.

The method and processes described above may be used for manufacturing a resultant ceramic object, namely a foundry filter for filtering molten metal, the filter comprising a porous ceramic filter structure comprising a plurality of pores for filtering molten metal, wherein the porous ceramic filter structure further comprises a plurality of through holes.

FIG. 5 schematically illustrates a plan view of an example of foundry filter according to the present disclosure. In the illustrated example, the filter has a diameter of 200mm, the array of through holes has a separation distance of 28mm, and each through hole has a diameter of 6mm.

FIG. 6 schematically illustrates a plan view of a yet further example of foundry filter according to the present disclosure. In the illustrated example, the filter has a diameter of 255mm, the array of through holes has a separation distance of 31mm, and each through hole has a diameter of 8mm.

Although specific terms (and indeed dimensions) have been employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Features described in the preceding description can be used in combinations other than the combinations explicitly described.

Although functions have been described with reference to certain features, those functions can be performable by other features whether described or not.

Although features have been described with reference to certain examples, those features can also be present in other examples whether described or not. Accordingly, features described in relation to one example/aspect of the disclosure can include any or all of the features described in relation to another example/aspect of the disclosure, and vice versa, to the extent that they are not mutually inconsistent.

Although various examples of the present disclosure have been described in the preceding paragraphs, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as set out in the claims The term 'comprise' is used in this document with an inclusive not an exclusive meaning. That is any reference to X comprising Y indicates that X can comprise only one Y or can comprise more than one Y. If it is intended to use 'comprise' with an exclusive meaning then it will be made clear in the context by referring to "comprising only one..." or by using "consisting".

In this description, reference has been made to various examples. The description of features or functions in relation to an example indicates that those features or functions are present in that example. The use of the term 'example' or for example', 'can' or 'may' in the text denotes, whether explicitly stated or not, that such features or functions are present in at least the described example, whether described as an example or not, and that they can be, but are not necessarily, present in some or all other examples. Thus 'example', 'for example', 'can' or 'may' refers to a particular instance in a class of examples. A property of the instance can be a property of only that instance or a property of the class or a property of a sub-class of the class that includes some but not all of the instances in the class.

In this description, references to "a/an/the" [feature, element, component, means...] are to be interpreted as "at least one" [feature, element, component, means...] unless explicitly stated otherwise. That is any reference to X comprising a/the Y indicates that X can comprise only one Y or can comprise more than one Y unless the context clearly indicates the contrary. If it is intended to use 'a' or 'the' with an exclusive meaning then it will be made clear in the context. In some circumstances the use of 'at least one' or 'one or more' can be used to emphasise an inclusive meaning but the absence of these terms should not be taken to infer any exclusive meaning.

The presence of a feature (or combination of features) in a claim is a reference to that feature (or combination of features) itself and also to features that achieve substantially the same technical effect (equivalent features). The equivalent features include, for example, features that are variants and achieve substantially the same result in substantially the same way. The equivalent features include, for example, features that perform substantially the same function, in substantially the same way to achieve substantially the same result.

In this description, reference has been made to various examples using adjectives or adjectival phrases to describe characteristics of the examples. Such a description of a characteristic in relation to an example indicates that the characteristic is present in some examples exactly as described and is present in other examples substantially as described.

Whilst endeavouring in the foregoing specification to draw attention to those features of examples of the present disclosure believed to be of particular importance it should be understood that the applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

The examples of the present disclosure and the accompanying claims can be suitably combined in any manner apparent to one of ordinary skill in the art.

Each and every claim is incorporated as further disclosure into the specification and the claims are embodiment(s) of the present invention. Further, while the claims herein are provided as comprising specific dependencies, it is contemplated that any claims can depend from any other claims and that to the extent that any alternative embodiments can result from combining, integrating, and/or omitting features of the various claims and/or changing dependencies of claims, any such alternative embodiments and their equivalents are also within the scope of the disclosure.

Claims

CLAIMSWe claim: 1. A foundry filter for filtering molten metal, the filter comprising: a porous ceramic filter structure comprising a plurality of pores for filtering molten metal, wherein the porous ceramic filter structure further comprises a plurality of through holes.
2. The filter of claim 1, wherein the plurality of through holes are substantially straight.
3. The filter of any previous claim, wherein the plurality of through holes form an array of substantially parallel apertures from one surface of the porous ceramic filter structure to an opposite surface of the porous ceramic filter structure.
4. The filter of any previous claim, wherein the filter structure defines a first major surface, and wherein the plurality of through holes extend substantially perpendicularly to the first major surface.
5. The filter of any previous claim, wherein a diameter of at least some of the plurality of through holes is between 15% -20% of the thickness of the filter structure.
6. The filter of any previous claim, wherein a total area of the plurality of through holes is: between 20% -60%, or between 30% -50%, of an area of an ingate or runner that, in use, provides the molten metal to the filter.
7. The filter of any previous claim, wherein the filter structure has: 5-15 pores per inch, or 7-10 pores per inch.
8. The filter of any previous claim, wherein the porous filter structure comprises one or more of: an open cell structure, and a foam structure.
9. The filter of any previous claim, wherein the filter is a ceramic foam foundry filter.
10. A method of manufacturing a foundry filter for filtering molten metal, the method comprising: creating a plurality of through holes in a porous filter structure; impregnating the porous filter structure with ceramic material to form a precursor porous ceramic filter structure; firing the precursor porous ceramic filter structure to form a porous ceramic filter structure comprising a plurality of pores for filtering molten metal, wherein the porous ceramic filter structure further comprises a plurality of through holes.
11. A method of manufacturing a foundry filter for filtering molten metal, the method comprising: 3D printing, with a 3D ceramic printer, a precursor porous ceramic filter structure comprising a plurality of pores, wherein the precursor porous ceramic filter structure further comprises a plurality of through holes; firing the precursor porous ceramic filter structure to form a porous ceramic filter structure comprising a plurality of pores for filtering molten metal, wherein the porous ceramic filter structure further comprises a plurality of through holes.