EXTRUDING AND FORGING AN ALUMINUM SILICON ALLOY

Abstract: The present invention comprises a method for manufacturing a solid extruded configuration constructed of an Al-Si alloy. Initially, a billet comprising aluminum and silicon is prepared for extrusion. The Al-Si billet is then heated and inserted into an extruding press. Finally, the Al-Si billet is extruded through an extruding die, having a preconfigured die slot configuration resulting in an extruded Al-Si product. The Al-Si product may then be treated for desired tempering or age hardening to produce a final extruded product with improved mechanical and machinability properties as compared to non-extruded Al-Si products. The extruded Al-Si product may further be cold/warm impact extruded or cold/warm/hot forged to achieve a final desired configuration.

Description: TITLE OF THE INVENTION EXTRUDING AND FORGING AN ALUMINUM SILICON ALLOY BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates in general to aluminum-silicon alloys and, more particularly, to a method of extruding an aluminum-silicon alloy toward fabrication of a solid product having improved mechanical and machinability characteristics, as well as, a method of extruding and/or casting an aluminum-silicon alloy for use in association with cold/warm impact extrusion and cold/warm/hot forging applications. 2. Background Art The forming of Aluminum-Silicon ("Al-Si") metal alloys has been known in the art for years, and, Al-Si alloys are conventionally available for cast products. Specifically, the addition of silicon to aluminum in casting alloys has been known as a hardening agent which makes the alloy generally more brittle. Accordingly, Al-Si alloys generally show excellent casting qualities. To date, however, their use in extrusion processes has been limited. Generally, Al-Si alloys were not considered suitable for extrusions due to their hardness and lack of ductility. In addition, Al-Si alloys, such as, for example, 300-series aluminum alloys, have not been considered for cold/warm impact extrusion and cold/warm/hot forging applications. Similarly, such alloys have not been considered inasmuch as they are inherently less ductile in comparison to wrought aluminum alloys, such as the 1000 series, 2000 series, 3000 series, 6000 series and 7000 series alloys which are conventionally utilized for such applications. Accordingly, it would be desirable to utilize Al-Si alloys for the manufacture of extruded products. It is likewise desirable to utilize cast or extruded Al-Si alloys in association with cold/warm impact extruding and cold/warm/hot forging processes. SUMMARY OF THE INVENTION The invention comprises a method for manufacturing a solid extruded configuration constructed of an Al-Si alloy. The method comprises the step of: (a) preparing a billet comprising aluminum and silicon; (b) inserting the Al-Si billet into an extruding press; and (c) extruding the Al-Si billet through an extruding die having a die slot configuration. The resulting extruded Al-Si product comprises a desired extruded configuration. In a preferred embodiment, the method further comprises the step of machining the extruded Al-Si product. The extruded Al-Si product possesses increased machining characteristics relative to machining characteristics of similar Al-Si products formed from a non- extruded method. In such a preferred embodiment, the step of machining may comprise any one or more of drilling, milling and lathe turning. In another preferred embodiment, the method may further include the step of impact extruding the extruded Al-Si configuration into a final desired configuration. In such a preferred embodiment, the method may further include the step of annealing the Al-Si billet prior to the step of impact extruding the extruded Al-Si configuration. In another preferred embodiment, the method may comprise the step of cold/warm/hot forging the extruded Al-Si configuration into a final desired configuration. In such an embodiment, the method may further include the step of annealing the Al-Si billet prior to the step of cold/warm/hot forging the extruded Al-Si configuration. In one such embodiment, the final desired configuration of the Al-Si alloy comprises a compressor scroll. With such a compressor scroll, the Al-Si billet may further include Mn, which billet may comprise a recycled scrap 3000 Al-Mn/Al-Si brazing sheet. In one preferred embodiment, the method may further include the steps of: (a) temporarily maintaining the Al-Si extrusion within a desired temperature range as the Al-Si extrusion exits the extrusion die; (b) quenching the Al-Si extrusion as the Al-Si extrusion exits the extrusion die, to impart desired tempered properties upon the Al-Si extrusion; and (c) age hardening the extruded Al-Si product wherein the age hardened extruded Al-Si product possesses increased strength, ductility and machinability characteristics relative to non-extruded Al-Si products. In such a preferred embodiment, the step of quenching further comprises the step of quenching with a fluid medium and at a desired temperature and time so as to impart a -T6 temper property upon age hardening. In another such preferred embodiment, the step of quenching comprises the step of cooling the Al-Si extrusion with one of forced and/or ambient air to impart a -F or -0 temper property thereto. In another such preferred embodiment, the step of age hardening further comprises the step of age hardening the Al-Si extrusion to at least one of a -T4, -T6 or -T7 temper. In yet another such preferred embodiment, the method may further comprise the step of annealing the Al-Si extrusion. Preferably the step of preparing the Al-Si billet further includes the step of adding a grain refiner. Additionally, the step of preparing may further include the step of modifying the composition of the billet by adding strontium to disperse the eutectic structure of the billet. In one preferred embodiment, the billet may comprise any one of a 300 series Al-Si alloy, a 400 series Al-Si alloy, a eutectic Al-Si alloy, a hypereutectic Al-Si alloy and a hypoeutectic Al- Si alloy. In another preferred embodiment, the step of extruding further comprises the step of homogenizing the Al-Si billet. In yet another preferred embodiment, the extruding press comprises an impact extruding press and the step of extruding comprises the step of impact extruding the Al-Si billet. In another preferred embodiment, the method may further comprise the step of cold drawing the extruded Al-Si alloy configuration. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 of the drawings is a diagram of the process according to a first embodiment of the present invention; Fig. 2 of the drawings is an illustration of the moφhology of an 356.2 Al-Si alloy without strontium modification; Fig 3 of the drawings is an illustration of the moφhology of an 356.2 Al-Si alloy with 0.01% strontium modification; Fig. 4 of the drawings is an illustration of the moφhology of an 356.2 Al-Si alloy with 0.04% strontium modification; Fig. 5 of the drawings is an illustration of the moφhology of the extruded 356 alloy showing the dispersion of the Si particles resulting from hot working of a cast billet; Fig 6 of the drawings is a perspective view of the Al-Si solid extruded configuration in the form of a rod; Fig 7 of the drawings is a perspective view of the Al-Si solid extruded configuration in the form of a bar; Fig. 8 of the drawings is a perspective view of the Al-Si solid extruded configuration in the form of a cup; Fig. 9 of the drawings is a perspective view of the Al-Si solid cold forged configuration in the form of a compressor scroll; and Fig. 10 of the drawings is a cross-sectional view of a brazed sheet which may be recycled into billet form for assembly of the compressor scroll. DETAILED DESCRIPTION OF THE INVENTION While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail, several specific embodiments with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the embodiments so illustrated. Method 10 for manufacturing a solid extruded configuration formed from an Al-Si alloy is shown in Fig. 1 as including several steps. Initially, billet 20 consisting of aluminum and silicon is prepared for extrusion. The Al-Si billet is then heated and inserted into an extruding press 24. Finally, the Al-Si billet is extruded through an extruding die 26, having a preconfigured die slot configuration resulting in an extruded Al-Si product 28. The Al-Si product may then be treated to a desired temper to produce a final extruded product 40. In operation, a 3xx series aluminum alloy melt 13 is prepared by melting alloy 12 to alloy specification. For example, and as will be described for puφoses of explanation of the present disclosure, the 3xx series aluminum alloy may comprise any one of a 356, 356.1, 356.2, A356.0, A356.1 or 357 alloy. Moreover, it will be readily understood by those with ordinary skill in the art, having the present disclosure before them, that other aluminum alloys including Al-Si alloys which include Mg, Mn or other elements. Additionally, other 300 series Al-Si alloys, 400 series Al-Si alloys, eutectic Al-Si alloys, hypereutectic Al-Si alloys, and hypoeutectic Al-Si alloys are likewise contemplated for use. A grain refiner 14 may be added to the Al-Si melt 13 to obtain finer grains in the alloy. Examples of suitable grain refiners include, but are not limited to Al/Ti, Al/Ti/B, and Al/Zr alloys. It is also contemplated that the composition of the billet may modified by adding strontium 16 to disperse the eutectic structure of the billet. Through strontium modification, the resulting alloy includes a finer silicon moφhology, which renders an eventual Al-Si product that is more ductile and formable. In particular, Fig. 2 illustrates a 356.2 cast Al-Si alloy poured at 1300°F with no strontium modification, while Figs. 3 and 4 illustrate the effect of 0.01% and 0.04%) strontium modifications in the same 356.2 cast Al-Si alloy, respectively. The finer silicon moφhology can be seen through a comparison of the material shown in Figs. 3 and 4 with the material shown in Fig. 2. The extrusion process essentially causes the Silicon particles to be broken up and to be finely dispersed within the matrix, as seen in Fig. 5. Additionally, it is also contemplated that other elements such as Na, Ca and/or Sb may also be added for a similar modification. Furthermore, certain trace elements, such as antimony, should be avoided in developing the 300-series aluminum alloy melt as the trace elements promote a silicon moφhology that is increasingly coarse, even with strontium modification. In addition to avoiding certain trace elements, it is further contemplated that the Al-Si melt is fluxed 18 (Fig. 1) to remove hydrogen and oxide impurities, from the melt. Once the appropriate alloy specification is achieved, Al-Si melt 13 is continuously cast in casting step 17 to produce Al-Si logs 18. If necessary, the billets are then homogenized. Homogenization facilitates extrusion and improves ductility of the end Al-Si product. These resulting logs are cut or sheared to form an Al-Si billet 20 which is of a desired size and length. Next, Al-Si billet 20 is heated in heater 22 to a temperature preferably above 700 °F, after which it is inserted into an extrusion press 24. The Al-Si billet is then extruded through an extruding die 26, where extruded Al-Si exits the extrusion die at a temperature preferably in the range of 800-1000 °F. Immediately upon exiting the extrusion die, extruded Al-Si product 28 is quenched with a fluid medium 30 in order to achieve -T4, -T6, -T7, or other desired tempers upon aging of the extruded Al-Si product. The quenching fluid medium may comprise water, air, or spray quench that serves the similar function of rapidly cooling the extruded alloy. Alternatively, the extruded Al-Si product is cooled with either forced or ambient air 32 to impart -F or -O tempers to the extruded product. After quenching, extruded Al-Si product 28 may then be stretched in order to straighten the product if required. Once straight, the extruded Al-Si product is cut to appropriate length and preferably age hardened on racks at a temperature of approximately 350 °F for a period of approximately six hours, or more, to achieve a -T6 temper. This temper imparts both strength and machinability to the extruded Al-Si product. Of course, the final extruded product may likewise be age hardened to other tempers as well, such as a -T4 or -T7 temper, among others. Also, the quenched or aged extruded product may be cold drawn to yield a -T8 or -T9 temper. Final extruded product 40 may then be machined (e.g. drilled, milled, lathe turned, etc.) to meet the requirements of a desired application. The final Al-Si product may take the form of any solid extruded configuration. Examples of solid extruded configurations include a rod 50 as pictured in Fig. 6 and a solid bar 60 as pictured in Fig. 7, although other solid extruded configurations are also contemplated as would be understood by those with ordinary skill in the art. Of course, hollow extruded products are also contemplated. Extrusion is preferred as it results in a process to form Al-Si solid configurations with increased process speed and less expensive post-formation tooling as compared to non-extrusion methods. Extruded Al-Si alloys likewise exhibit desirable characteristics which are superior to cast Al-Si alloys. For example, during testing, in a -T6 condition, extruded 356/357 Al-Si configurations formed according to the above-identified processes produce a material which easily suφasses yield strength, ultimate strength and elongation of a conventionally cast 356/357 Al-Si alloy in the -T6 condition. Moreover, the extruded Al-Si alloy meets and even exceeds the minimum yield strength, ultimate strength and elongation of 6061 -T6 alloy — an alloy generally considered for its superior strength properties. In addition, the extruded Al-Si material achieves machinability approaching that of cast 356/357 alloy. Accordingly, the Al-Si material has the machinability advantages of the 356/357 alloy without the drawbacks with respect to strength and elongation associated with the cast 356/357 alloys. This improved ductility and toughness relative to non-extruded Al-Si alloys allows extruded Al-Si alloys to be used in cold indentation type processes on the machined surfaces of the alloy for added strengthening. Examples of these cold indentation processes include but are not limited to the use of rolled instead of cut threads to increase the bolt pullout force. Moreover, improved ductility and toughness also allow extruded Al-Si alloys to be subjected to cold deformation processes, such as drawing the extruded Al-Si alloys in the solution annealed or even artificially aged condition. In addition, during testing, the extruded Al-Si alloys showed superior chip breaking characteristics during drilling operations ~ as longer chips tend to collect or wrap around tools during machining. These excellent chip breaking characteristics are especially desirable for applications requiring substantial drilling operations, such as ABS valve body machining, high pressure pump housings, engine shafts and bearings, compressor components, and rod stock and forged stock for impact extrusion, among others. In addition, these extruded Al-Si alloys are particularly resistant to corrosion. In particular, samples of an extruded Al-Si alloy were tested by submerging samples in a corrosive brake fluid mixture (760 ml GM brake fluid and 40 ml distilled water) at 140° C for 75 hours. The samples were weighed before submersion and then again after submersion. Any change in weight would be indicative of some corrosion of the Al-Si alloy. At the end of the test period, the samples (which originally weighed 2.432 oz) were weighed again, with none of the alloy weights changing. Moreover, a visual inspection of each test piece revealed no visual signs of corrosion. Accordingly, the extruded Al-Si alloy proved highly resistant to corrosion. In one embodiment, as shown in Fig. 1, such an Al-Si, after extrusion, may further undergo a cold/warm impact extrusion process 44 and/or a cold/warm/hot forging process 46. In such an embodiment, a standard casting alloy of the Al-Si-Mg class containing approximately 7%> Si and 0.20-0.45% Mg may be used, however, other Al-Si alloys, such as those disclosed above, are also contemplated. For maximum ductility, a relatively dilute hypoeutectic 300-series alloy is recommended. After a desired Al-Si billet is formed and the Al-Si billet is extruded into a desired configuration, the extruded Al-Si product is annealed 42 to impart desired temper properties on the end Al-Si product. For cold/warm impact extrusion applications, as well as cold/warm/hot forging, it is preferred that the Al-Si product is annealed to an -O condition, however, other tempers are contemplated. Once annealed, the extruded Al-Si configuration is cold/warm impact extruded 44, or, cold/warm/hot forged 46into the desired final configuration. Again, once cold/warm impact extruded or cold/warm/hot forged, the resulting Al-Si product may be age hardened as desired. The final product may take the configuration of an impact extruded cup as shown in Fig. 8. As shown in Fig. 9, compressor scroll 90 for use with a scroll compressor, is particularly well suited for manufacture according to the above-described cold/warm/hot forging process. In particular, while other alloys are contemplated, an Al-Si billet containing 3 to 8%> Si and up to 1% Mn may be prepared. The lower silicon content of the billet of such an embodiment facilitates the dispersion of silicon during the step of extruding the billet, thereby increasing the ductility thereof. The addition of Mn increases strength and lessens galling, which may be an important consideration where, as with the compressor scroll, the final product encounters excessive contact with other parts. Such an Al-Si alloy having the desired Si and Mn content may be obtained through recycling of brazing sheets, such as the brazing sheet shown in Fig. 10. The brazing sheet includes core 200 comprising a 3000 Al-Mn alloy , top layer 202 and bottom layer 204 comprising an Al-Si alloy. Such a material is largly recycled inasmuch as the production of sheets requires substantial trimming, and, in turn, substantial excess scrap. Once the Al-Si alloy is prepared according to the specification and processed using a suitable grain refiner, strontium modification, if required, and control of unwanted trace elements, the alloy is cast into a billet. It is subsequently extruded into a general desired configuration and annealed to achieve the desired properties for a particular application. Once annealed, the extruded configuration may be cold/warm/hot forged into a final desired configuration, such as the configuration shown in Fig. 8. In yet another embodiment of the invention, a 300-series Al-Si alloy is provided for cold/warm impact extrusion in the form of a cast and annealed rod, bar, or billet. In this embodiment, a 300-series alloy is again melted to alloy specification and processed using a suitable grain refiner, possible strontium modification, and control of unwanted trace elements. Once the melt processing has produced the desired alloy composition, Al-Si billets are cast from the melt using control on the vertical and/or horizontal casting conditions. Finally, the cast Al-Si billets are annealed to an appropriate temper condition, and then used in desired cold/warm impact extrusion and/or cold/warm hot forging applications. The final annealed Al-Si product formed through extrusion and/or casting possess increased ductility and thus increased formability in cold/warm impact extrusion and cold/warm/hot forging applications. Moreover, because a 300-series Al-Si alloy is used instead of the more common wrought aluminum alloys, it is anticipated that the contemplated cold/warm impact extrusion or cold/warm hot forged product will have increased wear resistance and machinability characteristics. The foregoing description and drawings merely explain and illustrate the invention and the invention is not limited thereto except insofar as the appended claims are so limited, as those skilled in the art who have the present disclosure before them will be able to make modifications and variations therein without departing from the scope of the invention.

Claims: WHAT IS CLAIMED IS: 1. A method for manufacturing a solid extruded configuration constructed of an Al-Si alloy comprising the steps of: preparing a billet comprising aluminum and silicon; inserting the Al-Si billet into an extruding press; and extruding the Al-Si billet through an extruding die having a die slot configuration which will result in an extruded Al-Si product having a desired extruded configuration. 2. The method according to claim 1 further comprising the step of machining the extruded Al-Si product, wherein the extruded Al-Si product possesses increased machining characteristics relative to machining characteristics of similar Al-Si products formed from a non-extruded method. 3. The method according to claim 2 wherein the step of machining comprises at least one of the steps of drilling, milling and lathe turning. 4. The method according to claim 1 further comprising the step of impact extruding the extruded Al-Si configuration into a final desired configuration. 5. The method according to claim 4 further comprising the step of annealing the Al-Si billet prior to the step of impact extruding the extruded Al-Si configuration. 6. The method according to claim 1 further comprising the step of cold/warm/hot forging the extruded Al-Si configuration into a final desired configuration. 7. The method according to claim 6 further comprising the step of annealing the Al-Si billet prior to the step of cold/warm/hot forging the extruded Al-Si configuration. 8. The method according to claim 6 wherein the final desired configuration of the Al-Si alloy comprises a compressor scroll. 9. The method according to claim 8 wherein the Al-Si billet further includes Mn. 10. The method according to claim 9 wherein the Al-Si billet comprises recycled scrap 3000 Al-Mn Al-Si brazing sheets. 11. The method according to claim 1 furthering including the steps of: temporarily maintaining the Al-Si extrusion within a desired temperature range as the Al-Si extrusion exits the extrusion die; quenching the Al-Si extrusion as the Al-Si extrusion exits the extrusion die, and after the step of temporarily maintaining the desired temperature range, to impart desired tempered properties upon the Al-Si extrusion; and age hardening the extruded Al-Si product wherein the age hardened extruded Al- Si product possesses increased strength, ductility, and machinability characteristics relative to non-extruded Al-Si products. 12. The method according to claim 11 wherein the step of quenching the Al-Si extrusion further comprises the step of quenching with a fluid medium, and at a desired temperature and time so as to impart -T6 temper properties to the extruded Al-Si product, upon appropriate age hardening. 13. The process according to claim 11 wherein the step of quenching the Al-Si extrusion fiirther comprises the step of cooling the Al-Si extrusion with at least one of forced air or ambient air to impart -F or -O temper properties upon the Al-Si extruded product. 14. The method according to claim 11 wherein the step of age hardening further includes the step of age hardening the Al-Si extrusion to at least one of a -T4, -T6, or -T7 temper. 15. The method according to claim 11 further comprising the step of annealing the Al-Si to impart increased ductility on the Al-Si extrusion. 16. The method according to claim 1 wherein the step of preparing the Al-Si billet further includes the step of adding a grain refiner. 17. The method according to claim 1 wherein the step of preparing the Al-Si billet further includes the step of modifying the composition of the billet by adding strontium to disperse the eutectic structure of the Al-Si billet. 18. The method according to claim 1 wherein the step of preparing a billet further comprises preparing the Al-Si billet from one of the alloys from the group consisting of: a 300 series Al-Si alloy, a 400 series Al-Si alloy, a eutectic Al-Si alloy, a hypereutectic Al-Si alloy and a hypoeutectic Al-Si alloy. 19. The method according to claim 1 wherein the step of extruding the Al-Si billet further includes extruding the Al-Si product to at least one of the following configurations from the group of rods, bars or combinations thereof. 20. The method according to claim 1 further comprising the step of homogenizing the Al-Si billet. 21. The method according to claim 1 wherein the extruding press comprises a extruding press, and, the step of extruding comprises the step of impact extruding of the Al-Si billet. 22. The method according to claim 1 further comprising the step of cold drawing the extruded Al-Si alloy configuration.

Inventors: BENEDYK JOSEPH C, BENEDYK, JOSEPH, C.
Applicants: ALUMAX INC, BENEDYK JOSEPH C, ALUMAX, INC., BENEDYK, JOSEPH, C.
Application year: 1998
Main classification: C22F1
IPC codes: C22F1