BACKGROUND O F THE INVENTION

Field of the I nvention

[0001] This invention relates generally to a system, material and method for producing components such as ax i symmetric components and, more particularly, to a system and method for producing high performance components that includes squeeze c asting and flow-forming.

Discussion of the Related Art

[0002] When producing components such as vehicle components, it is desirable to produce one piece c omponents, for example vehicle wheels, from a lightweight alloy in a manner that is both economical and efficient. It is also desirable to minimize the material used in low stress areas and increase the material used in high stress areas to provide a stronger component while minimizing the weight, which improves fuel efficiency.

[0003] M any high performance vehicle components, such as wheels and other axisymmetric components, are formed from a c ast log or ingot, from which a billet is severed and thereafter subjected to a series of hot forging operations that form, for example, a forged blank. The wheel is then machined, subjected to flow-forming, heat treating, and finally machined a sec ond time to create the final shape. This process is time c onsuming and can be costly.

[0004] Squeez e c asting is a known proc ess that includes pouring a liquid material into a mold and solidifying the liquid under pressure to create a c omponent. However, there are size and material thic kness limitations that prevent squeeze casting from creating c omponents that meet specification requirements of high performance components.

[0005] There is a need in the art for a more cost-effective and efficient way to produce components with the desired specification requirements, partic ularly axisymmetric components and high performance components for vehicles. SUM MARY OF THE INVENTI ON

[0006] In accordance with the teachings of the present invention, a material and method for manufacturing components is disclosed. The method includes squeeze casting the material into a c ompon ent of a desired shape and flow-forming the component that has been squeeze cast to refine the shape of the component. The method also includes heat treating the component to enhance the microstructure of the c omponent and machining the component to further refine the shape.

[00071 Additional features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.

BRIEF DESCRI PTIO N OF THE DRAWINGS

[0008] Figure 1 is a flow diagram of a known process for manufacturing components;

[0009] Figure 2 is an isometric view of a forged blank that will bec ome a vehicle wheel;

[0010] Figure 3 is an isometric view of a vehicle wheel formed from a forged blank;

[0011] Figure 4 is a flow diagram of a proc ess for manufacturing components that includes squeeze c asting and flow-forming;

[0012] Figure 5 is a cut-away, cross-sectional side view of a squeez e c ast blank that will bec ome a vehicle wheel;

[0013] Figure 6 is a cut- away side view of a vehicle wheel formed from a squeeze c ast blank;

[0014] Figure 7 is a front cross- sectional type view of an exemplary squeeze casting press;

[0015] Figure 8 illustrates front views of vehicle wheels made from a forged blank and squeeze cast blank;

[0016] Figure 9 is an exemplary proc ess showing semi-solid forging; and [0017] Figure 1 0 is an exploded view of a mi c restructure of the rim portion and spoke portion of a vehicle wheel.

DETAILED DESCRIPTION O F THE EM BODIM ENTS

[0018] The following discussion of the embodiments of the invention directed to a method for producing c omponents employing a squeez e casting process is merely exemplary in nature, and is in no way intended to limit the invention or its applications or uses.

[0019] Figure 1 is a flow diagram of one known method 10 for producing high performance components. To start, ing ots are provided at box 1 2, which are transformed into billets at box 1 4. M ultiple forging steps are performed at boxes 1 6-20, which are hot forming steps as is known to those skilled in the art. At the end of the forging steps, a forged blank 30, such as a blank that will become a vehicle wheel, is formed. For example, Figure 2 is an isometric view of a forged blank 30 that will become a vehic le wheel. The forged blank 30 is mac hined a first time at box 22 to remove material to create a desired shape or design. In the example of creating the vehicle wheel, machining is performed to create wheel spokes. Next, flow-forming is performed at box 24 that includes applying forc e to both elongate and reduc e the thickness of portions of the component being created. I n the vehicle wheel example, flow-forming at the box 24 is performed on the rim portion of the forged blank 30 that is being formed into the wheel. F low-forming may be performed at high temperature depending on the material used. A heat treatment is performed at box 26 to achieve balanced mechanical properties of the c omponent. Thereafter, a second round of machining is performed at box 28 to ac hieve the final product with the final dimensions of the c omponent and with balanc ed mec hanical properties. F igure 3 is an isometric view of a vehicle wheel 32 that is produc ed by the proc ess discussed above.

[0020] Using multiple forging steps to create a component is time c onsuming and has signific ant costs associated therewith. M ultiple forging dies are needed and the amount of starting material that is machined away to make the final product c an be as much as two-thirds. For example, the forged blank 30 may be 22.5 kg, but after machining the finished wheel 32 may only be 7.5 kg.

[0021] Figure 4 is a flow diagram of a process 40 for producing high performanc e components that uses squeeze c asting via any suitable squeez e casting apparatus known to those skilled in the art, where like reference numerals identify the same steps as in the process 10. I ngots, or a starting material, are used at the box 2, but instead of transforming the ingots into billets, the ingots are melted and poured into a c asting or mold at box 42 to c reate a squeeze cast blank 48, shown in F igure 5, that is the start of the shape of a component, such as a vehicle wheel 50, shown in Figure 6. During squeeze c asting, the melted ingot material is solidified under pressure to c reate a component with a refined mi c restructure that exhibits strength and ductility that is superior to c omponents made by known methods, such as low pressure die c asting. I n this way, the ingots from the box 12 are squeeze cast at the box 42 such that the c omponent being produc ed is quickly made to be close to the final desired shape. For example, in the case of a vehicle wheel, the wheel may be squeeze cast such that the spokes are created without the need for multiple forging steps followed by mac hining that cuts away a significant amount of material to create the spokes. During flow-forming at the box 24, the thick rim section of the squeeze c ast blank 48 is flow-formed by a rotated roller 72 at room temperature or elevated temperatures depending on the material used to make a thin and elongated rim of the vehicle wheel 50, as shown in F igure 6.

[0022] Figure 7 is a front cross- sectional type view of an exemplary squeeze casting press 52 that is suitable for use in the squeeze casting proc ess at the box 42. A mold 74 is positioned between an upper platen 76 and a lower platen 78. As disc ussed above, the squeeze cast blank 48 is created within the mold 74. To create the squeeze cast blank 48, melted ingot material is transferred through a melt transfer 80 to a shot sleeve 82. A punch 84 moves upwards and pushes the melted ingot material into the mold 74. The punch 84 subsequently provi des high squeeze pressure during solidific ation of the liquid, which is some predetermined time that depends on the material used and the c ooling rate desired, to create the squeeze c ast blank 48. After the squeeze c ast blank 48 is created, the upper platen 76 and an upper portion of the mold 74 move upward such that the squeeze cast blank 48 can be removed from the mold 74. Squeeze c asting molds may be of any design desired, and may be, for example, made of high strength tool steel or other metals. Typically the molds are two or more parts that c an be affixed together and then taken apart when squeeze c asting is c omplete to remove the component therein.

[0023] While squeeze casting is able to get the c omponent being made close to its final form, additional steps such as flow-forming are required to meet spec ific ation requirements nec essary for high performanc e components. F or example, flow-forming at the box 24 is nec essary for a wheel bec ause the thickness required for the rim portion is smaller than what is achievable by squeeze c asting alone. By way of example, a vehicle wheel rim portion may have a thickness requirement of 3 mm, which is not ac hiev able by squeeze casting alone. Thus, the steps at the boxes 24- 28 are used to refine the c omponent that has been squeeze c ast at the box 42 such that spec ific ation requirements may be met.

[0024] Once the cooled component, i. e., the squeeze cast blank 48, is removed from the squeeze c asting mold, flow-forming is performed at the box 24 to produce the desired annular or ring shape. Additional steps may be performed prior to flow-forming, as is described in detail below. Flow- forming may be performed at room temperature. Next, heat treatment is performed at the box 26 to ac hieve the final product with balanced mec hanic al properties. Thereafter, machining is performed at the box 28 to produce the final desired dimensions of the component being produced, such as the wheel 50. Heat treatment at the box 26 may be varied in temperature and time to suit the material being used for the c omponent. The heat treatment typic ally causes particles to dissolve such that the desired particles may be precipitated out in a c ontrolled manner, as is known to those skilled in the art.

[0025] Figure 8 illustrates front views of vehicle wheels 60 and 66. The wheel 60 is made from the proc ess 1 0 that includes forging. Areas 62 must be machined away to create spokes 64. The wheel 66 is made from the process 40 that includes squeeze casting, where hollow spac es 68 and spokes 70 are created by squeez e casting from the proc ess 40 without the need for machining. The process 40 also allows for more design flexibility as well. For example, the spokes 70 that c an be any shape desired.

[0026] In another embodiment, a semi-solid forging step at box 46 may be included in the process 40. Thus, after the ingot from the box 1 2 has been squeeze c ast at the box 42, but before the material in the mold has cooled enough to be in a completely solid state, the semi-solid forging step may be used so that the component may be manipulated when it is in a semisolid state. Figure 9 illustrates an exemplary semi-solid forging process. The squeez e cast component is in a liquid state 90 at high temperatures. As the temperature begins to drop over time, the component transitions to a semisolid state 92 where there are solid portions 94 and liquid portions 96. The semi-solid forging temperature used depends on the alloy used. F or ex ample, the temperature may be 50-1 00K lower than that at 100% liquid portions 96, or forging at a temperature at 40-1 00% volume fraction of solid portions 94 and 60-0% of liquid portions 96. O ne or more hammers 98, depending on the number of spokes, may be used during the semi-solid state 92 to forge the component. Thus, when a solid state 1 00 of the component is achieved, there will be forged portions of the component. This may be desirable for creating pockets in the spokes andf or for thinning the spokes of the component. Thus, semi-solid forging at the box 46 provides for additional design options to be created that are not possible from squeeze c asting alone.

[0027] Semi-solid forging is a volume c onstant proc ess, thus the process itself does not remove material. M ec hanic al strength of the component is increased after semi-solid forging, therefore less material is needed for the spoke portion(s) to meet required performance specifications. Furthermore, an in-die forging proc ess may be performed at a temperature such that the material in the mold has cooled enough to be in a fully solid state. The temperature at which in- die forging is performed depends on the alloy used. For example, the temperature may be at 0-1 00K lower than that at 1 00% solid portions 94. Hot deformation is introduc ed into the material, thus mechanic al properties are increased, which allows for less material to be used in the spokes, as stated above.

[0028] In another embodiment, rapid c ooling of the squeeze c ast component may be performed at box 44 to create a rricrostructure of the component that is better than what is achieved without rapid cooling. The processes of boxes 44 and 46 may be used together by c ooling the component at the box 44 followed by semi-solid forging at the box 46. As shown in Figure 1 0, rapid cooling of a rim portion 1 1 2 of the c omponent illustrates a finer microstructure than spoke portion 1 1 0, whic h is not rapidly cooled ac cording to this example. Elements 1 1 4 and 1 1 6 are particles that are removed during heat treatment before box 24 and re- pre ipitated out at the box 26, leaving an even finer microstructure. A better, or finer, microstructure is beneficial bec ause it imparts greater strength and ductility of the component that is required for flow-forming at the box 24. Rapid cooling may be achieved by any suitable means, such as by using c ooling channels 1 18 that are embedded within the mold and that use, for example, water or pressurized gas to rapidly c ool the component or portions of the c omponent.

[0029] The material used for the ingots of the proc ess 40 can be any suitable alloy. I n particular, special alloys of reasonable c ast ability for squeez e casting at the box 42 may be used that provides the strength and formability required in the flow-forming step at the box 24 and provides a desired Si and M g/CufZn content. F or example, a special alloy that includes a high Si content, similar to the common casting aluminum alloy A31 9/A356, and also a high Mg content, similar to the common wrought aluminum alloy 6082 6061 is desirable. An exemplary spec ial alloy includes 3-6 wt.% (weight percent) of silicon to retain castability during the squeeze casting process at the box 42 and also to maximiz e formability for flow-forming at the box 24. A Cu+M g+Zn c ontent of 2-5 wt.% is also desired to make the material heat- treatable. In addition, a T4 treatment (a solution heat treatment) is desired to dissolve Cu, M g and Zn to increase ductility to obtain a flow-form able structure, and a T5 treatment (a proc ess of artific ial aging at elevated temperature after c ooling from previous hot working steps) is desired to balance strength and ductility. F urther, an Fe content of 0.1 - 0.3 wt. is desired to prevent die-sticking during squeeze c asting, and a Cr+M n c ontent of 0.2 - 0.4 wt. % is desired to prevent the harmful p-AIF eSi phase and for better formability.

[0030] The T4 treatment described above is performed before the flowforming step at the box 42 and the T5 treatment is performed during the heat treatment step at the box 26. The heat treatment temperature and time period depend on the specific alloy composition used. F or example, a T4 temperature in the range of 673- 823K for a time period of 1 to 5 hours may be used. The T5 treatment may be, for example, in the temperature range of 393-523K for a time period of 2 to 24 hours.

[0031] The foregoing disc ussion disclosed and desc ribes merely exemplary embodiments of the present invention. One skilled in the art will readily recognize from sue h discussion and from the acc ornpanying drawings and claims that various changes, modifications and variations c an be made therein without departing from the spirit and scope of the invention as defined in the following claims.