This application is a non-provisional application claiming priority from German Patent Application No. DE 10 2015 116 520.1, filed Sep. 29, 2015, entitled “Vorrichtung and Verfahren zur Herstellung eines rotationssymmetrischen, hohlen, metallischen Werkstücks” or, as translated, “Device and Method for Producing a Rotationally Symmetrical, Hollow Metallic Workpiece,” which is hereby incorporated by reference in its entirety.
The present disclosure relates generally to devices and methods for producing a rotationally symmetrical, hollow metallic workpiece by way of rotating a casting mould and introducing a melt into the casting mould.
Austrian Patent Publication No. AT 407 646 B discloses a centrifugal casting method and a corresponding device for producing a rotationally symmetrical, hollow metallic workpiece, wherein a casting mould is rotated about a rotation axis. A liquid metallic melt is introduced into the casting mould along with grains or particles of a metallic compound that influence the wear properties of the material that is produced. As a result of the rotation of the casting mould, centrifugal forces act on the melt and on the particles. The density of the particles can be chosen to determine whether they concentrate in the outer area or in the inner area of the rotating casting mould. It is thus possible to adapt the workpiece to the local wear conditions.
In centrifugal casting methods of this kind, the melt is compacted by centrifugal forces, such that a workpiece is obtained with relatively high density and only a few casting defects such as voids or pores. This means that the workpieces produced are of a weight that is too great for many applications, for example, in the manufacture of cars. Therefore, a need exists for reducedweight workpieces.
Although certain example methods and apparatuses have been described herein, the scope of coverage of this patent is not limited thereto. On the contrary, this patent covers all methods, apparatus, and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents. Moreover, those having ordinary skill in the art will understand that reciting “a” element or “an” element in the appended claims does not restrict those claims to articles, apparatuses, systems, methods, or the like having only one of that element.
That said, one example object of the present disclosure is to reduce the weight of manufactured workpieces. This object and others may be achieved by the devices and the methods disclosed herein for producing a rotationally symmetrical, hollow metallic workpieces. In one example, a method may comprise rotating a casting mould about a rotation axis and introducing a melt into the casting mould. The melt may be thrown towards an inner contour of the casting mould by a centrifugal force.
Further, hollow bodies may be added to the melt. The hollow bodies that are added to the melt may become incorporated as the melt solidifies. In this respect, a workpiece can be obtained with cavities formed by the hollow bodies. Because the hollow bodies have a lower density compared to the material of the melt, the weight of the workpiece is reduced.
The material of the hollow bodies, in particular the material of an outer skin of the hollow bodies, may have a higher melting point than the material of the melt. As a result, there is no need to fear fusion of the hollow bodies in the melt. The melting point of the hollow bodies, in particular of the outer skin of the hollow bodies, may be above 700° C. in some examples, above 1500° C. in other examples, and above 2000° C. in still further examples. The melt may be advantageously liquid and/or metallic. The material of the melt may be a steel. Alternatively or in addition, the material of the melt can include aluminum, titanium, zinc, copper, or magnesium.
In some examples, the hollow bodies may be designed as hollow spheres. The hollow spheres can have a diameter of below 5 mm in some examples, below 1 mm in other examples, and below 250 μm in still further examples.
It may be advantageous if the hollow bodies comprise an inorganic, in particular ceramic material. For instance, the hollow bodies can comprise aluminum oxide (Al2O3), zirconium dioxide (ZrO2), silicon carbide (SiC), boron carbide (B4C), silicon nitride (Si3N4), titanium boride (TiB2), tungsten carbide (WC), titanium carbide (TiC), silicon dioxide (SiO2), or some combination of these materials. Alternatively or in addition, the hollow bodies can comprise a metallic material such as, for example, iron or an iron alloy.
In some cases, it has proven advantageous if the hollow bodies are pre-heated before being added to the melt. By way of the pre-heating, the hollow bodies can be brought to an increased temperature at which the danger of the melt setting upon initial contact with the hollow bodies is reduced. The hollow bodies can be pre-heated, for instance, to a temperature above 900° C. in some examples, above 1000° C. in other examples, or above 1100° C. in still further examples.
According to some examples, the hollow bodies may be added to the melt, which has been introduced into the casting mould, only when the melt has at least partially solidified in the casting mould. The at least partial solidification of the melt inside the rotating casting mould can be brought about by the effect of the centrifugal force. Alternatively or in addition, the melt can be cooled, for example, by cooling the casting mould. The mobility of the hollow bodies decreases in the partially solidified melt such that it is possible to reduce the effect whereby the hollow bodies and the melt separate through the different centrifugal forces acting on them. In this respect, a migration of the hollow bodies towards the rotation axis of the casting mould or towards the rotation axis of the produced workpiece can be reduced.
In this connection, it may be advantageous if, after the addition of hollow bodies, additional melt is introduced into the casting mould. The additional melt may be thrown by the effect of the centrifugal force towards the melt that has already at least partially solidified on the inner contour of the casting mould. The introduction of the additional melt permits the production of a layered structure of the workpiece. In some cases, it is possible to adjust the distribution of the hollow bodies through the choice of the quantity of melt and/or hollow bodies. The additional melt may be added only when the melt first introduced has already completely solidified, such that movements of the hollow bodies inside the melt are no longer possible. In this respect, it is possible to produce a workpiece with a layered structure, wherein an edge area of the workpiece directed towards the rotation axis of the workpiece has few hollow bodies or, in particular, is free of hollow bodies. Moreover, the inner contour of the workpiece can be smooth, thereby improving weldability.
In some examples, after the introduction of the additional melt, further hollow bodies may be added as soon as the additional melt has at least partially solidified. By the addition of further hollow bodies, a concentration of the hollow bodies can be increased in the edge area of the workpiece directed towards the rotation axis of the workpiece. It is moreover possible to generate a porous inner contour of the workpiece.
In one example method, the casting mould may be rotated about a horizontal rotation axis. In another example, the casting mould may be rotated about a vertical rotation axis.
The example object mentioned above may also be achieved by devices for producing a rotationally symmetrical, hollow metallic workpiece. In some examples, a device may comprise a casting mould that is rotatable about a rotation axis, a feeder device for introducing a melt into the casting mould, and a metering device for adding hollow bodies to the melt that has been introduced into the casting mould.
The example devices disclosed herein permit the same advantages as those that have already been described in connection with the various example methods for producing a rotationally symmetrical, hollow metallic workpiece.
With reference now to the figures, further details, features, and advantages of the present disclosure will become clear from the figures and from the following description with reference to the figures. It should be understood that the figures only depict illustrative examples and do not in any way limit the scope of the present disclosure. Moreover, identical parts are typically provided with like reference signs in the various figures, for which reason said parts are each generally mentioned only once.
In some cases, the material of the melt 4 may be steel. In alternative examples or in addition, the material of the melt 4 can include aluminum, titanium, zinc, copper, or magnesium.
In some examples, the device 1 may comprise a metering device 7 for adding hollow bodies 6 to the melt 4 introduced into the casting mould 2. The hollow bodies 6 may be incorporated into the melt 4 as the latter solidifies and form cavities in the generated workpiece 11. In this respect, a workpiece 11 with desired and defined cavities can be obtained using the device 1, wherein the cavities reduce the weight of the workpiece 11. The hollow bodies 6 may be designed as hollow spheres. The diameter of the hollow spheres may be in a range of below 5 mm in some examples, below 1 mm in other examples, or below 250 μm in still other examples. Hollow bodies 6 made of a ceramic material may be used, as a result of which the stiffness and/or the wear properties of the workpiece 11 can be improved. For example, the hollow bodies 6 can comprise aluminum oxide (Al2O3), zirconium dioxide (ZrO2), silicon carbide (SiC), boron carbide (B4C), silicon nitride (Si3N4), titanium boride (TiB2), tungsten carbide (WC), titanium carbide (TiC), or silicon dioxide (SiO2). Alternatively or in addition, the hollow bodies can comprise a metallic material such as, for example, iron or an iron alloy.
The example production device 1 may further comprise a pre-heating mechanism by which the hollow bodies 6 can be pre-heated, thereby reducing any danger of undesired setting of the melt 4 upon introduction of the hollow bodies 6 into the casting mould 2. The pre-heating means can, for example, be arranged in the metering device 7 and/or can heat the metering device 7. The hollow bodies 6 may be pre-heated to a temperature of above 900° C. in some examples, above 1000° C. in other examples, or above 1100° C. in still further examples.
The feeder device 12 may have, in addition to the casting crucible 5, a casting channel 9 that is arranged in such a way that it passes through a recess in a side cover 3 of the casting mould 2. By way of the casting channel 9, the melt 4 can be introduced into the casting mould 2. Moreover, the metering device 7 for adding the hollow bodies 6 may be arranged in such a way that the hollow bodies 6 can be added to the melt 4 in the casting channel 9. In this respect, a mixture of the melt 4 and the hollow bodies 6 can be introduced jointly into the casting mould 2. Alternatively, it is possible to introduce exclusively the melt 4 or exclusively the hollow bodies 6 into the casting mould 2 via the casting channel 9.
With the example devices described above and shown in
In some examples, the melt 4 and the hollow bodies 6 can be added simultaneously to the casting mould 2. However, in other examples, the melt 4 and the hollow bodies 6 may be added sequentially, as a result of which it is possible to generate a layered structure of the workpiece 11. Example methods resulting in such a layered structure of the workpiece 11 are described below.
In a first step of some example methods, the melt 4 may be exclusively added to the casting mould 2. The melt 4 may be thrown outwards and may partially solidify on the inner contour 8 of the casting mould 2. In a second step of some example methods, the hollow bodies 6 may be added such that the hollow bodies 6 are at least partially enclosed by the melt 4. The mobility of the hollow bodies 6 is reduced in the partially solidified melt 4, and therefore undesired movements of the hollow bodies 6 in the direction of the rotation axis H, V of the casting mould 2 are reduced.
In a third step of some example methods, after hollow bodies 6 have been added, additional melt 4 may be introduced into the casting mould 2. The additional melt 4 introduced in this step may likewise be thrown, by the effect of the centrifugal force, towards the melt 4 that has already partially solidified on the inner contour 8 of the casting mould 2. In some examples, the additional melt 4 may be added only when the melt 4 first introduced has already completely solidified, such that movements of the hollow bodies 6 inside the melt 4 are no longer possible. In this way, a workpiece 11 with a layered structure can be produced in which an edge area of the workpiece 11 directed towards the rotation axis of the workpiece 11 has few hollow bodies or, in particular, is free of hollow bodies.
In a fourth step used in some example methods, further hollow bodies 6 may be added after the introduction of the additional melt 4. If hollow bodies 6 are added last of all in such methods, it is possible to produce a hollow, rotationally symmetrical workpiece 11 with a porous inner contour.
The production of the example workpiece 11 shown in
Number | Date | Country | Kind |
---|---|---|---|
10 2015 116 520.1 | Sep 2015 | DE | national |