RAU, III, Charles, B. (6223 Cromwell Drive Nw, Gig Harbor, WA, 98335-7554, US)
CLAIMS
1. A reinforced wheel, comprising: a wheel member having a tire-mounting area having at least one rim-bead portion or flange, the wheel member further comprising a wheel-face portion having a wheel flange sub- portion; and at least one porous rim-bead 'preform' integral with the at least one rim bead portion, or with a portion thereof.
2. The reinforced wheel of claim 1, comprising: two rim bead portions or flanges positioned on opposite sides of the tire-mounting area; and respective rim-bead 'preforms' integral with the rim bead portions, or with respective portions thereof.
3. The reinforced wheel of claim 1, further comprising at least one porous wheel- face 'preform' integral with the wheel-face portion, or with a portion thereof.
4. The reinforced wheel of claim 2, further comprising at least one porous wheel- face 'preform' integral with the wheel-face portion, or with a portion thereof.
5. The reinforced wheel of claim 1, wherein the at least one integrated porous rim- bead 'preform' comprises a ceramic-based 'preform'.
6. The reinforced wheel of claim 5, wherein the ceramic-based 'preform' comprises at least one material selected from the group consisting of silicon carbide, aluminum carbide, tungsten carbide, nickel, chromium, iron, silicon, boron, chromium, chromium carbide, cobalt, and tungsten chrome carbide (optionally including cobalt, or a nickel-based superalloy).
7. The reinforced wheel of claim 2, wherein the integrated porous rim-bead 'preforms' comprises a ceramic-based 'preform'.
8. The reinforced wheel of claim 7, wherein the ceramic-based 'preforms' comprise at least one material selected from the group consisting of silicon carbide, aluminum carbide, tungsten carbide, nickel, chromium, iron, silicon, boron, chromium, chromium carbide, cobalt, and tungsten chrome carbide (optionally including cobalt, or a nickel-based superalloy).
9. The reinforced wheel of claim 3, wherein the integrated porous wheel-face 'preform' comprises a ceramic-based 'preform' or a carbon graphite foam-based 'preform.'
10. The reinforced wheel of claim 9, wherein the ceramic-based 'preform' comprises at least one material selected from the group consisting of silicon carbide, aluminum carbide, tungsten carbide, nickel, chromium, iron, silicon, boron, chromium, chromium carbide, cobalt, and tungsten chrome carbide (optionally including cobalt, or a nickel-based superalloy).
11. The reinforced wheel of claim 4, wherein the integrated porous wheel- face 'preform' comprises a ceramic-based 'preform' or a carbon graphite foam-based 'preform.'
12. The reinforced wheel of claim 11, wherein the ceramic-based 'preform' comprises at least one material selected from the group consisting of silicon carbide, aluminum carbide, tungsten carbide, nickel, chromium, iron, silicon, boron, chromium, chromium carbide, cobalt, and tungsten chrome carbide (optionally including cobalt, or a nickel-based superalloy).
13. The reinforced wheel of claim 1, wherein the integrated porous rim-bead 'preform' comprises aporsity gradient 'preform.'
14. The reinforced wheel of claim 2, wherein the integrated porous rim-bead 'preforms' comprise a porsity gradient 'preform.'
15. The reinforced wheel of claim 3, wherein the integrated porous wheel face 'preform' comprises a porsity gradient 'preform.'
16. The reinforced wheel of claim 4, wherein the integrated porous wheel face 'preform' comprises aporsity gradient 'preform.'
17. A method for producing a reinforced wheel, comprising: a) obtaining at least one rim-bead 'preform'; b) placing the at least one rim-bead 'preform' in a die cast mold cavity, the cavity having a rim-bead casting portion, wherein the rim-bead 'preform' is positioned within the rim-bead casting portion, or within a portion thereof; and c) integrating the at least one rim-bead 'preform' into a wheel by introducing liquid infiltration material into the cavity, wherein the rim-bead 'preform' is infiltrated.
18. The method for producing a reinforced wheel of claim 17, comprising: placing two rim bead portions in the die cast mold cavity; wherein the rim-bead 'preforms' are positioned within respective opposed rim-bead casting portions, or within respective portions thereof; and integrating the two rim-bead 'preforms' into the wheel by introducing liquid infiltration material into the cavity, wherein the rim-bead 'preforms' are infiltrated.
19. The method for producing a reinforced wheel of claim 17, further comprising placing at least one porous wheel-face 'preform' in the die cast mold cavity, the cavity having a wheel-face casting portion, wherein the at least one wheel-face 'preform' is positioned within the wheel-face casting portion, or within a portion thereof; and integrating the at least one wheel- face 'preform' into the wheel by introducing liquid infiltration material into the cavity, wherein the wheel-face 'preform' is infiltrated.
20.. The method for producing a reinforced wheel of claim 19, wherein in least one of: the rim-bead 'preform'; and the wheel- face 'preform' is a porosity gradient 'perform.' |
IMPROVED CAST WHEEL COMPRISING PRE-FORM REINFORCEMENT IN HIGH- DENSITY DIE CASTING
FIELD OF THE INVENTION
Aspects of the present invention relate generally to improved, reinforced wheels including reinforced heavy-duty aluminum commercial truck wheels. More particular aspects relate to novel commercial aluminum truck wheel compositions, and to cost-effective methods of manufacturing same, comprising the strategic use of reinforcement 'preform' materials including, but not limited to ceramics, carbon graphite foam, and other fibrous composites.
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims the benefit of priority to U.S. Provisional Patent Application Serial Number 60/672,574, filed 18 April 2005 and of same tile, and which is incorporated by reference herein in its entirety.
BACKGROUND
Typical commercial heavy-duty truck wheels are 11x22.5 or 11x24.5 inches in size. Lightweight commercial heavy duty truck wheels (e.g., aluminum) are highly prized in light of fuel savings and increased profitability relating to lighter weight commercial wheels. However, benefits such as fuel savings, increased payload, increased profitability, and reduction of green house gasses, are significantly offset by the high wheel cost to the end user. Additionally, the inherent strength of an aluminum wheel is significantly less than its steel counterparts. Therefore, despite numerous potential advantages, economic and strength factors remain a large deterrent to mass marketing and wide spread usage of such lightweight wheels.
Forged aluminum truck wheels became popular in the early 1960s, and traditional means for crafting highly stressed aluminum components (e.g., such as forged aluminum wheels developed by Alcoa Aluminum, Inc.), such as commercial wheels for heavy duty trucks, comprises a time consuming and expensive nine-step forging craft process (FIGURE 1 shows typical prior art commercial aluminum truck wheel). Material and manufacture costs associated with this forging process, result in the production of relatively expensive commercial truck wheels (e.g., as of the date of the present application filing, approximately U.S. $360.00 each, or greater). At this cost, the wheel provides for twenty pounds saved, compared to a steel wheel in the same size (typically costing about U.S. $70.00).
Additionally, aside from the decreased strength relative to steel, typical high wear and rim bead deterioration on aluminum wheels can cause dangerous conditions and safety issues that have resulted in fatalities. Moreover, the increased use of radial-type tires, as opposed to more traditional bias or cross-ply tires, has caused higher wear in the rim-bead area. This is because radial tires flex more, making the tire bead wiggle (chaffing) against the rim bead area. Thus, bead wear has increased, and given the high cost of typical forged aluminum wheels, niche companies have emerged that specialize in repairing wheel rim-bead surfaces. Typically, the worn surfaces are built up with 'mig' welding methods, and then re-machined (lathed), sanded and polished. However, such repair typically takes several days, must be done in specialized shops, and adds substantial expense and down-time.
Recently, a method of coating a forged aluminum wheel, and in particular coating the tire bead retaining area (rim bead) thereof, with a wear-resistant coating (e.g., tungsten carbide, optionally including cobalt or chrome) to increase wear and corrosion resistance has been described (U.S. 6,872,425 to Kaufold et al, 29 March 2005). However, in practical terms and experience, regardless of the particular type or method of coating, the coating must be sprayed on by one method or another, and the thickness is limited (e.g., between about 0.004 to about 0.01 inch) and eventually wears away, necessitating purchase of new wheels and/or repairing
and/or recoating the rim bead area. Additionally, such repairing or coating does not enhance the inherent strength of the aluminum wheel, which is less than its steel counterparts.
There is, therefore, a pronounced need in the art for improved aluminum wheels (e.g., commercial aluminum truck wheels) and for more cost-effective ways to manufacture same. There is a pronounced need in the art for improvements in the aluminum wheel rim-bead areas, which currently wear out and substantially reduce wheel life. There is a pronounced need in the art for wheel strength reinforcement methods to enhance overall wheel safety. There is a pronounced need in the art for method to substantially improve the coefficient of thermal expansion (CTE) problems that give rise to stress-fractures in aluminum wheels and in aluminum castings in general, and which limit the scope of current die casting crafts.
SUMMARY OF THE INVENTION
Aspects of the present invention provide for novel and improved aluminum wheels comprising: at least one 'preform' portion for wheel rim-bead flange reinforcement to afford additional strength and wear-resistance at the rim-bead area; and/or at least one 'preform' portion for wheel-face reinforcement to afford additional strength in the face and wheel locating hole (bolt circle) area. The wheel rim bead 'preform', and/or the wheel- face 'preform' are made intregal to the wheel by infiltration casting of the 'preforms.'
Additional aspects provide infiltratable 'preforms' for use in infiltration casting, the 'preforms' preferably comprising altered porosity gradients (e.g., porosity size gradients) to eliminate abrupt transitions between materials having different coefficient of thermal expansion (CTE) values to reduce or eliminate residual stress commonly produced in the die casting craft. Preferably, such porosity gradient 'preforms' are used in the inventive reinforced aluminum wheels.
Particular preferred embodiment provide a reinforced wheel, comprising: a wheel member having a tire-mounting area having at least one rim-bead portion or flange, the wheel member further comprising a wheel-face portion having a wheel flange sub-portion; and at least one porous rim-bead 'preform' integral with the at least one rim bead portion, or with a portion thereof. Preferably, the wheels comprise two rim bead portions or flanges positioned on opposite sides of the tire-mounting area; and respective rim-bead 'preforms' integral with the rim bead portions, or with respective portions thereof. Preferably, the wheels further comprise at least one porous wheel-face 'preform' integral with the wheel-face portion, or with a portion thereof. Preferably, the integrated porous rim-bead 'preforms', and/or the wheel- face performs, comprise a ceramic-based 'preform'. In particular embodiments, the ceramic-based 'preform' comprises at least one material selected from the group consisting of silicon carbide, aluminum carbide, tungsten carbide, nickel, chromium, iron, silicon, boron, chromium, chromium carbide, cobalt, and tungsten chrome carbide (optionally including cobalt, or a nickel-based superalloy). In particular embodiments, the integrated porous wheel-face 'preform' comprises a ceramic-based 'preform' or a carbon graphite foam-based 'preform.' Preferably, the integrated porous rim-bead 'preform', and/or the integrated porous wheel face 'preform', comprises a porsity gradient 'preform.'
Additional aspects provide a method for producing a reinforced wheel, comprising: obtaining at least one rim-bead 'preform'; placing the at least one rim-bead 'preform' in a die cast mold cavity, the cavity having a rim-bead casting portion, wherein the rim-bead 'preform' is positioned within the rim-bead casting portion, or within a portion thereof; and integrating the at least one rim-bead 'preform' into a wheel by introducing liquid infiltration material into the cavity, wherein the rim-bead 'preform' is infiltrated. Preferably the method comprises: placing two rim bead portions in the die cast mold cavity; wherein the rim-bead 'preforms' are positioned within respective opposed rim-bead casting portions, or within respective portions thereof; and integrating the two rim-bead 'preforms' into the wheel by introducing liquid infiltration material into the cavity, wherein the rim-bead 'preforms' are infiltrated. Preferably, the method further comprises placing at least one porous wheel-face 'preform' in the die cast mold cavity, the cavity having a wheel-face casting portion, wherein the at least one wheel-face 'preform' is positioned within the wheel-face casting portion, or within a portion thereof; and integrating the at least one wheel-face 'preform' into the wheel by introducing liquid infiltration
material into the cavity, wherein the wheel-face 'preform' is infiltrated. Preferably, the rim-bead 'preform', and/or the wheel-face 'preform' is a porosity gradient 'perform.
The inventive 'preform' and the method of using same can be applied to a broad array of components (e.g., essentially any die cast component) that previously could only meet physical application requirements by being manufactured by traditional, expensive forging procedures (e.g., traditional nine-step forging procedures).
BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a traditional commercial aluminum truck wheel.
Figure 2 shows, according to preferred aspects of the present invention, elements of an exemplary embodiment of an improved aluminum wheel, comprising one or more 'preform' reinforcement portions or members incorporated into the wheel during die casting (infiltration casting). In this exemplary embodiment, a pair of ceramic rim-bead reinforcement 'preform' portions (hoops), and a wheel-face area reinforcement 'preform' portion (e.g., ceramic or carbon graphite foam) that are integrated into the finished where, are shown in an exploded view for illustrative purposes.
Figures 3 A and 3B show microscopic views of an exemplary suitable 'preform' material. The material shown is carbon graphite foam, which not only has extremely high thermal conductivity, but also comprises interconnecting porosity suitable for infiltration casting.
Figure 4 shows, according to preferred conceptual aspects of the present invention, an exemplary preferred 'preform' material embodiment having a gradient of porosity sizes (window holes). The porosity size is greater (B) adjacent to the interface with the unreinforced material (A) (the material, which in molten form, is infiltration cast into the 'preform'), and decreases going to the inside area of the 'preform' (from B to C to D).
DETAILED DESCRIPTION OF THE INVENTION
Aspects of the present invention solve a long-standing need in the art for aluminum wheels having improved strength and durability, and that are less susceptible to stress fractures and attendant wheel failure, particularly in the rim bead area.
DEFINITIONS "Infiltration casting" as used herein refers to various art recognized methods of introducing liquid matrix materials (e.g., metals, etc.) into porous matrices of reinforcement material (e.g., rigid porous 'preforms,' fabric, etc.). The inventive methods encompass any appropriate means for such introduction of liquid matrix material, including but not limited to centrifugal casting; high pressure die casting; vacuum die casting; squeeze casting; high vacuum permanent mold casting; low vacuum permanent mold casting; vacuum riserless/pressure riserless casting, surface spray and deposition methods, etc.
A "porous 'preform' as used herein refers various art-recognized 'preforms' suitable for infiltration casting and include, but are not limited to: porous ceramic preforms that contain ceramic particles; porous ceramic hybrid preforms that contain ceramic fibers and particles; ceramic matrix composites; carbon graphite foam 'preforms', pre-cast Duralcan or other MMC materials formed into a wear liner, etc. In particular aspects, ceramic 'preforms' will comprise ceramic particles to reinforce, strengthen, and increase the wear/abrasive resistance of the cast part. Hybrid ceramic 'preforms' may contain both ceramic particle and fibers, which preferably should not shrink during the firing process (the sintering process that completes the manufacture of the preform). Carbon graphite foam 'preforms' may contain silicon carbide particles, and may be produced so that carbon nanotubes are created during manufacturing thereof to increase the ultimate strength of the final part. 'Preforms' may be created with functional gradient porosity, which means that during the preform forming process, pores of varying sizes are created within the structure of the preforms. The purpose of the functional gradient porosity is to facilitate complete infiltration of the preform and to reduce the abrupt decrease in CTE at the intersection of the unreinforced and reinforced area. This would be accomplished by forming larger pores on
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the interior side of the preform than those formed in the interior of the preform or at the area that will be wear surface side of the preform. Or the pore size could be consistent throughout the preform, but larger than normal pore size would assist in accomplish the softening of the changes in CTE. Particular aspects provide novel selectively reinforced composite materials and methods for making same involving infiltration casting of liquid continuous phase matrix material (e.g., non-ferrous metals such as aluminum, aluminum alloys, magnesium, magnesium alloys, titanium, titanium alloys, zinc alloys, copper, or resins/epoxies, polymers, plastics, various blends of concrete/cement, etc.) into porous 'preforms' (e.g., with defined shapes ) comprising one or more reinforcement constituents (e.g., SiC, Al 2 O 3 , etc.). Additional exemplary materials for particles (reinforcement constituents) include, but are not limited to: Silicon Carbide (SiC); Silicon; Alumina Oxides (A12O3); Mangesium oxide; Tungsten Carbides; Chromium Carbide; Carbon Diamond; Polycrystalline Diamond; Nickel; Copper; Zinc; Titanium Boride; fibrous material (e.g., acrylic fibers, aramid fibers, glass fibers, silica fibers, carbon fibers, metallic fibers, mineral fibers and mixtures thereof); carbonaceous material (e.g., petroleum coke, metallurgical coke, natural carbon, synthetic carbon and mixtures thereof); iron powder; inert fillers (e.g., whiting, talc, barytes, clays and mixtures thereof) and binders (e.g., resinous binders); metal sulfide-iron powder alloy; metal sulfides, including but not limited to ZnS, FeS, MoS 2 , CuS 2 , TiS, CdS, Sb 2 S 3 , MnS, CoS, Co 3 S 4 , CaS, BaS, SrS, FeS 2 , ZrS 2 , Cu 2 S, Ni 3 S 2 , NiS, Ni 3 S 4 , MnS 2 , CoS 2 , Co 2 S 3 , SnS; etc.
Various art-recognized means can be used to infiltrate the continuous phase matrix material, in a liquid state, into the porous pre-forms, and such means include but are not limited to use of low/high vacuum, low/high pressure, gravity, or induced centrifugal force (e.g., centrifugal casting, high pressure die casting, vacuum die casting, squeeze casting, high vacuum permanent mold casting, low vacuum permanent mold casting, vacuum riserless/pressure riserless casting, etc.). Exemplary porous rigid perform materials (reinforcement) include but are not limited to ceramics, carbon graphite foam, metallic foam, concrete and other fibrous
composites. Typical preferred porous rigid pre-forms comprise a material system comprised of binders and multiphase (discrete reinforcement constituent(s)) materials in various volume fractions. Preferred porous rigid 'preforms' contain open-cell porosity (window holes). In particularly preferred porous 'preform' embodiments, at least one porosity (window hole) gradient (or a series of stepped, functionally gradient porosity (FGP) layers) is present with either the pore number or pore size, or both generally increasing toward at least one 'preform' surface, so that there are significantly larger pores on one or more outer surfaces of the 'preform' (e.g.,. the surface next to the interface boundaries between 'preform' surface and the un- reinforced continuous phase matrix material) relative to, for example, the 'preform' interior.
Preferred Embodiments
Preferred aspects provide for a novel aluminum wheel comprising, in one or more particular locations thereof, reinforcement materials. Preferably, the reinforcement materials are 'preforms' (e.g., ceramic-based 'preforms' or carbon graphite foam-based 'preforms') having a percentage of open-cell porosity and a predetermined percentage of reinforcing perform structure (e.g., carbon graphite foam, silicon carbide, and other materials and/or composite fibers within the 'preform' structure as ingredients). Exemplary suitable reinforcement 'preform' materials are ceramic, carbon graphite foam, or other fibrous composites that are typically used in applications that utilize resin, aluminum and other materials to provide for enhanced strength properties.
Preferred embodiment use two types of 'preforms': carbon graphite foam 'preforms'
(e.g., for the wheel flange area pre-form) that have high heat conductivity relative to ceramic
'preforms' to, for example, transfer heat form brake; and ceramic 'preforms' (e.g., MMC with ceramic-based particles and composite fiber, such as "super wool fiber" mineral deposit fiber) (e.g., for the rim-bead area 'preforms'). Both preferred 'preform' types preferably have wear
resistant reinforcement material (e.g., silicon carbide) and porosity/windows to allow for infiltration casting with metals or resins, to provide physical strength and wear resistance (ceramic wear plates are best for wear resistance).
Ih particular reinforced wheel aspects 10 (FIGURE 2), 'preform' annular members 2 (hoops) provide wear-resistant portions (e.g., comprising wear resistant particles) to reduce rim- bead wear (e.g., increase resilience of rim to wear). In particular manufacturing embodiments, the porous reinforcement rim bead 'preforms' 2 are placed in a die-cast mold cavity and infiltrated (pressure, or force-filled) during the casting process (e.g., high pressure aluminum die casting). Preferably, a special high-pressure die casting process (high-density — extra pressure) is used, utilizing pre-forms to create more physical strength in selected areas, and to provide high wear-resistant factors.
Figure 2 shows an exemplary improved wheel 10 comprising (Bl and B2), for example, two ceramic based 'preform' hoop rings 2 to provide strength reinforcement and to extend rim bead area 8 life through high wear resistance. Another 'preform' (e.g., carbon graphic foam based perform) 6 (C) provides additional strength to the wheel-face area 4, and in some embodiments (e.g., using carbon graphite foam 'preforms') provides substantial improvements in thermal conductivity. Preferably, both types of 'preform' portions (e.g., rim-bead and wheel- face, and ceramic or carbon graphite foam) contain functional gradient porosity (window holes) (see FIGURE 4) to facilitate improved infiltration during the casting procedure, and provide a substantially improved coefficient of thermal expansion (CTE) for reduced residual stress potentialities or issues by a gradual transition at the interface where reinforcement ends and the non-reinforcement material begins. As shown in the example, sub-assemblies Bl, B2, and C are inserted in the die mold cavity and infiltrated with aluminum during a casting procedure.
With further reference to FIGURE 2, on the wheel-face there is a flat bolt circle 4 (ten bolt holes plus pilot hole) (e.g., flange- 1/2 inch thick). During manufacture, a wheel-face
reinforcing 'preform' 6 (e.g., roughly planar, with corresponding holes) is optionally placed in the die casting mold cavity at a position corresponding to wheel-face position. The 'preform' 6 may be limited in scope to the bolt circle area, or may extend over all or a portion of the wheel face. The wheel-face reinforcing 'preform' 6 is thereby integrated into the finished wheel structure. Preferably, both at least one wheel-face 'preform' 6 and one or more rim bead 'preforms' 2 are placed in a die-cast mold cavity and infiltrated (pressure, or force-filled) during the casting process (e.g., high pressure aluminum die casting) to provide an integrated, reinforced wheel that has enhanced strength and wear resistance, particularly in the rim-bead area 8. As will be obvious to one skilled in the relative art, a variety of sizes and shapes of wheel-face 'preforms' 6 and/or rim bead 'preforms' 2 can be used to provide for essentially any dimension of reinforced wheel. Preferably, regardless of the shape, size and number of 'preforms' used they are positionable within a die-cast mold cavity and infiltrated (pressure, or force-filled) during the casting process (e.g., high pressure aluminum die casting) to provide for integrated wheels having enhanced strength and wear characteristics.
Aluminum drums, relative to steel, are by nature more deficient in strength, have less satisfactory wear characteristics and are more subject to stress problems. Accordingly, a time- consuming, relatively expensive nine-step forging method has been used to produce them (hammering is used to make the material denser and stronger). By contrast, the inventive commercial wheels are manufactured using special high-pressure die casting equipment, instead of the traditional nine-step forging method. The aluminum alloys utilized in the high-pressure die casting technique may comprise low cost, or even recycled aluminum stocks. The inventive pre-forms are infiltration cast, or force-filled with the liquefied aluminum alloy during casting. The inventive wheels comprising, for example, ceramic-based 'preforms', and/or carbon graphite foam-based 'preforms' are substantially different in the base structure, and offer substantial improvements in strength and wear compared with prior art forged wheels and forged, coated wheels. " While carbon graphite foam 'preforms' offer enhanced thermal (and electrical)
conductivity, the strongest wheels are formed using ceramic or ceramic-based 'preforms' for both the rim-bead and wheel-face areas. The selected perform(s) provide an increase in mechanical strength and improved wear resistance in areas such as the wheel rim-bead areas, and the wheel face, where a pilot-hole and bolt-circle holes (typically ten) benefit from the inventive reinforcement.
Inventive wheel rim-bead reinforcement. As stated above, typical high wear and rim bead deterioration can cause dangerous conditions and safety issues that have resulted in fatalities. Likewise, wheel-face areas 4 need to be made stronger. The inventive, cost-effective aluminum commercial truck wheel 10 provides durable, wear-resistant rim-beads 8 by the incorporation of 'preform' portions (e.g., hoops or rings) installed in the high-pressure die casting mold cavity. Preferred embodiment comprise a pair of ceramic-based 'preforms' 2 for the rim bead areas that have approximately a 10% to 30% amount of silicon carbide particles (e.g., in the 11-14 micron range), the pre-form being infiltrated during the casting procedure.
Inventive wheel face reinforcement. In preferred embodiments, a separate roughly planar 'preform' 6 (e.g., based on ceramic or on carbon graphite foam, with a similar percentage of silicon carbide) (e.g., shaped much like a plate with holes) is placed into the die cavity to afford additional strength in the wheel-face area 4 and wheel locating hole area (bolt circle), providing a reinforced wheel-face or bolt circle that also facilitates machining operations. In alternate embodiments, at least one rim-bead 'preform' is integral with, or attached to, the wheel-face 'preform' such that a single 'preform' is placed into the die cavity to afford additional strength in the face- flange, and rim-bead areas.
Preferably, by design, the 'preforms,' whether ceramic, carbon graphite foam-based (or other composite fiber based) have a porosity (window holes) characteristic. Significantly, according to preferred aspects of the present invention (as described below), the manufacturing procedure for the 'preform' material is altered to provide areas or gradients of higher or lower
quantity or percentage of porosity (window holes). A denser 'preform' comprises less porosity (smaller window holes).
Improved coefficient of thermal expansion (CTE) properties. According to preferred aspects of the present invention, the inventive high-pressure die-cast wheels comprising the inventive 'preforms' equal or exceed the desired physical strengths normally associated with the traditional nine-step forging technique. Additionally, and significantly, the inventive wheels comprise additional improvements to address coefficient of thermal expansion (CTE) issues, which could result in residual stress at the interface between an abrupt edge or end of a reinforcement 'preform' and the un-reinforced aluminum. Therefore, in particularly preferred embodiments a porosity (window holes) gradient is present in the 'preform', which have larger pores on the outer surface of the 'preform' {i.e. the surface next to the interface with the un- reinforced aluminum) (see FIGURE 4). FIGURE 4 shows a conceptual rendering of a porosity gradient 'preform' having an interior to exterior porosity (window holes) gradient with larger pores on the outer surface 12 of the 'preform' {i.e. the surface next to the interface with the un- reinforced aluminum 14) (A = unreforced material {e.g., aluminum or aluminum alloy); B = exterior areas of 'preform' with LARGEST window holes (porosity); C = interior area of 'preform' with smaller window holes (porosity); D = interior area of 'preform' with smallest window holes (porosity).
Preferred aspects of the invention thus provides for a gradual, smoothed transition from more porous, less dense 'preform' material (larger window holes) to more dense 'preform' material (larger window holes). This smoothed porosity gradient is associated with a complementary gradient of infiltrated aluminum. The materials gradients created, therefore, obviate the "residual stresses" otherwise encountered at an abrupt interface between the
'preform' and the un-reinforced aluminum (or other infiltration material). The gradual change in window hole porosity provides for particularly beneficial CTE properties in high temperature applications involving substantial heat cycling (e.g., truck wheels). The potential of crack
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formations from residual stress due to abrupt transitions between materials having mismatched CTE values is substantially reduced or eliminated. Additionally, the 'preform' porosity gradient provides for less capillary action resistance during infiltration casting of the metal or resin that is forced under pressure during casting procedures.
Significantly, aspects of the present invention allow for manufacturing with, for example, a reduced number of steps relative to conventional methods (e.g., only four steps to a finished component (e.g., a commercial aluminum truck wheel) having improved physical strength and wear resistance, and have reduced residual stress from CTE differences in materials. Such inventive components will save fuel, create increased profitability and lower green house gas production. Moreover, the inventive wheels may comprise recycled aluminum.
Further aspects of the invention allow for reinforcement of essentially any die cast applications to provide low cost reinforced components that equal or exceed the strength and/or wear properties of traditionally manufactured components, such as nine-step forged manufactured components.