Device and method for manufacturing a metal alloy blank by centrifugal casting

Abstract

A device (10) for manufacturing a metal alloy blank by centrifugal casting of a molten metal alloy, comprising a centrifugal casting wheel (20), the centrifugal casting wheel (20) being rotary about an axis of rotation (A) and comprising a mold (22) for receiving the molten metal alloy, the mold extending in a radial direction (R1) with respect to the axis of rotation (A). The device (10) comprises at least one magnet arranged in such a way as to induce an electric current in the mold (22) during the rotation of the centrifugal casting wheel (20) about the axis of rotation (A).

Claims

1. A device for manufacturing a metal alloy blank by centrifugal casting of a molten metal alloy, comprising a centrifugal casting wheel, the centrifugal casting wheel being rotary about an axis of rotation and comprising a hub and a plurality of molds fixed to the hub for receiving the molten metal alloy, each mold of the plurality of molds extending in a radial direction with respect to the axis of rotation evenly spaced about the axis, the device comprising at least one magnet arranged in such a way as to induce an electric current in the mold during the rotation of the centrifugal casting wheel about the axis of rotation, each mold being provided with a coil comprising windings that surround an internal volume of the mold, the windings extending parallel to the radial direction.

2. The device according to claim 1, wherein the coil is configured in such a way that the at least one magnet induces an electric current in the coil during said rotation of the centrifugal casting wheel about the axis of rotation.

3. The device according to claim 1, wherein the at least one magnet is an annular or circular magnet, an axis of which is parallel to the axis of rotation.

4. The device according to claim 1, comprising a plurality of magnets arranged in a spaced manner about the axis of rotation.

5. The device according to claim 4, wherein the magnets are even in number, and polarities of said magnets alternate evenly about the axis of rotation.

6. The device according to claim 2, wherein the at least one magnet does not form a single part with the centrifugal casting wheel, and further comprising a permanent magnet forming a single part with the centrifugal casting wheel and extending partly across the coil.

7. The device according to claim 6, wherein the at least one magnet is an annular or circular magnet, an axis of which is parallel to the axis of rotation, and the poles of the permanent magnet and of the at least one magnet facing it have opposite names.

8. The device according to claim 6, comprising a plurality of magnets not forming a single part with the centrifugal casting wheel and arranged in a spaced manner about the axis of rotation.

9. The device according to claim 8, wherein the magnets not forming a single part with the centrifugal casting wheel are even in number, and polarities of said magnets alternate evenly about the axis of rotation.

10. The device according to claim 6, wherein the permanent magnet is disposed under the plurality of molds and extends in plane perpendicular to the axis.

11. The device according to claim 1, wherein the plurality of molds are superimposed in such a way as to form several levels of mold.

12. The device according to claim 1, wherein the device comprises a motor for rotationally driving the centrifugal casting wheel about the axis.

13. A method for manufacturing a metal alloy blank using the device according to claim 1, comprising the following steps: melting of the metal alloy; pouring of the molten metal alloy into the centrifugal casting wheel, the centrifugal casting wheel being rotary about the axis of rotation and comprising the plurality of molds for receiving the molten metal alloy, each mold extending in the radial direction with respect to the axis of rotation; rotation of the centrifugal casting wheel about its axis of rotation and solidification of the molten metal alloy inside each mold, in such a way as to obtain the metal alloy blank; and extraction of the metal alloy blank from each mold, a magnetic field being applied to each mold during the rotation step in such a way as to induce an electric current in each mold.

14. The method according to claim 13, wherein, during the rotation step, the magnetic field induces an electric current in the coil.

15. The method according to claim 13, wherein the metal alloy is a titanium-based alloy.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be clearly understood, and its advantages will be more apparent, on reading the following detailed description of several embodiments, shown by way of non-limiting example. The description refers to the appended drawings wherein:

(2) FIG. 1 schematically shows a known device for manufacturing by centrifugal casting;

(3) FIG. 2 schematically shows the solidified metal blank obtained by the device of FIG. 1, in section along the plane C-C of FIG. 1;

(4) FIGS. 3A and 3B are photographs of sections of two metal blanks obtained by the device of FIG. 1, in the direction R of FIG. 1;

(5) FIG. 4 schematically shows a device for manufacturing by centrifugal casting according to the invention;

(6) FIG. 5 is a partial perspective and stripped-down view of the device of FIG. 4;

(7) FIG. 6 is a top view of the centrifugal casting wheel and of the magnet, according to another variant of the invention;

(8) FIG. 7 is a top view similar to FIG. 6, according to yet another variant of the invention;

(9) FIG. 8 is a top view similar to FIG. 7, according to yet another variant of the invention;

(10) FIG. 9 is a side view of a part of the centrifugal casting wheel, according to yet another variant of the invention;

(11) FIG. 10 is a perspective view of FIG. 9, showing a first possibility of implementation of the variant of FIG. 9;

(12) FIG. 11 is a perspective view of FIG. 9, showing another possibility of implementation of the variant of FIG. 9.

DETAILED DESCRIPTION OF THE INVENTION

(13) FIG. 4 schematically shows a device 10 for manufacturing a metal alloy blank by centrifugal casting of a molten metal alloy.

(14) The manufacturing device 10 comprises, in a closed and airtight chamber 50, a melting device 610, a centrifugal casting wheel 20 (which will subsequently be referred to as “the wheel 20” for convenience) and a magnet 40.

(15) The melting device 610 is suitable for providing a molten metal alloy. In an example, the melting device 610 carries out the melting of a metal alloy provided in the form of an ingot 616 of metal alloy. In another example, the different constituents of the metal alloy are introduced individually into the melting device 610, then melted together in such a way as to obtain the molten metal alloy.

(16) The metal alloy is chosen from among the alloys suitable for the finished part to be manufactured from the blank.

(17) Without wishing to limit the scope of the present disclosure, the metal alloy can be, for example, a ceramic-based alloy, a steel, a titanium-based alloy, or else a nickel-based alloy.

(18) Among titanium-based alloys, the following can notably be envisioned: conventional titanium alloys having a crystallographic structure identical to that of pure titanium, such as for example: TA6V, Ti-17, Ti 10-2-3, Ti-5553, β16, β21S; and titanium-based intermetallic alloys, having one or more phases of crystallographic structure different from that of pure titanium.

(19) Among titanium-based intermetallic alloys, titanium aluminides may particularly be envisioned, including: titanium aluminides with columnar γ and α.sub.2 phases, such as: Ti-48Al-1V-0,3C, Ti-48Al-2Cr-2Nb (also known by the name “GE 48-2-2”) or Ti-48Al-2Nb-0,75Cr-0,3Si (also known by the name “Daido RNT650”); titanium aluminides with equiaxed γ and α2 phases, such as Ti-45Al-2Nb-2Mn+0,8TiB.sub.2 (also known by the name “Howmet 45XD”), Ti-47Al-2Nb-2Mn+0,8TiB.sub.2 (also known by the name “Howmet 47XD”), Ti-47Al-2W-0,5Si-0,5B (also known by the name “ABB-23”) or Ti-48Al-1,3Fe-1,1V-0,3B; aluminides with equiaxed β, γ and α.sub.2 phases, such as Ti-47,3-Al-2, 2N b-0,5Mn-0,4W-0,4Mo-0,23Si, Ti-46,5Al-3Nb-2Cr-0,2W-0,2Si-0,1C (also known by the name “K5SC”), TI-46Al-5Nb-1W, Ti-47Al-3,7(Cr,Nb,Mn,Si)-0,5B (also known by the name “GKSS-TAB”), Ti-45Al-8(Nb,B,C) (also known by the name “GKSS TNB”), Ti-46,5Al-1,5Cr-2Nb-0,5Mo-0,13B-0,3C (also known by the name “395M”), Ti-46Al-2,5Cr-1Nb-0,5Ta-0,01B (also known by the name “Plansee γ-MET”), Ti-47Al-1Re-1W-0,2Si (also known by the name “Onera G4”), Ti-43Al-9V-0,3Y, Ti-42Al-5Mn, Ti-43Al-4Nb-1Mo-0,1B, or Ti-45Al-4Nb-4Ta.

(20) It is specified that in the list above, all the numerical values designate the atomic percentage (at %) of the element that they precede. Thus, the alloy Ti-48Al-2Cr-2Nb comprises, in atomic percentage, 48% of Al, 2% of Cr, 2% of Nb, and titanium (Ti) in addition to 100%.

(21) Among the nickel-based alloys, conventional nickel alloys may particularly be envisioned such as René 77 or DS 200, or else nickel superalloys such as AM1.

(22) The melting device 610 can be, for example: a furnace for the melting by electrical arc of a metal electrode in a cold crucible in a vacuum or under reduced pressure, more commonly known by the terms “Vacuum Arc Remelting (VAR) furnace” or “Skull VAR furnace”; a furnace for melting by induction in a vacuum or under reduced pressure, more commonly known by the term “Vacuum Induction Melting (VIM) furnace”; a furnace for melting by plasma burner under reduced pressure, more commonly known by the term “Plasma Arc Melting (PAM) furnace”; a furnace for melting by electronic bombardment in a vacuum, more commonly known by the term “Electronic Bombardment (EB) furnace”; or a combination of these.

(23) According to the type of melting device 610 chosen, the chamber 50 is controlled to provide the required atmosphere: vacuum; or reduced and controlled pressure of an inert gas in relation to the metal alloy; or reduced and controlled pressure of a gas reacting with the metal alloy, in order to modify the chemical composition of the metal alloy during its melting.

(24) The molten metal alloy exiting the melting device 610 is poured into the wheel 20.

(25) The wheel 20 comprises a hub 30, at least one mold 22 attached to the hub 30.

(26) The hub 30 comprises a central channel 32 and several intake channels 33 each communicating with a mold 22.

(27) In order to facilitate the pouring of the molten metal alloy, the hub 30 can be provided with a funnel 31 opening onto the central channel 32.

(28) The hub 30 is liable to be rotationally driven about an axis of rotation A, for example using a motor (not shown). Thus, the wheel 20 is rotary about the axis of rotation A.

(29) In order to simplify the device for balancing the wheel 20, the axis A is preferably vertical.

(30) FIG. 5 shows in perspective a mold 22 attached to the hub 30 (the funnel 31 has been left out to avoid crowding the drawing).

(31) The mold 22 extends in a radial direction R1 with respect to the axis A (see FIG. 4). Preferably, in order to simplify the construction of the wheel 20, this radial direction R1 is perpendicular to the axis A. Thus, if the axis A is vertical, the radial direction R1 is parallel to the horizontal.

(32) The mold 22 is able to receive the molten metal alloy, here in a cavity 22B. To do this, the mold 22 is typically made of metal, a metal alloy or a ceramic resistant enough to resist the thermal stresses linked to contact with the molten metal alloy.

(33) The cavity 22B can have a rectangular or cylindrical section. This section can advantageously be constant over the entire length of the cavity 22B.

(34) Along the radial direction R1, the cavity 22B typically has a length considerably greater than the maximum dimension of its section, for example at least 3 times, and preferably at least 5 times greater than the maximum dimension of its section. After solidification, the metal alloy blank then has the general shape of a bar.

(35) The cavity 22B communicates with an intake channel 33 via an intake 22A, which is where applicable of smaller section than the cavity 22B.

(36) Several molds 22 can be attached to the hub 30 as can be seen in FIGS. 4 and 5. For example, several molds 22 can be evenly spaced about the axis A. The molds 22 can also be superimposed in such a way as to form several (two in FIGS. 4 and 5) levels of molds 22.

(37) The molds 22 can be separable from the hub 30, such that they can be individually replaced and/or separated one by one from the hub 30 in order to extract the metal alloy blank from it after solidification.

(38) As mentioned above, the manufacturing device 10 also comprises at least one magnet. In the remainder of the text, for convenience, the term “magnet” will be used, denoted by the reference 40; it should however be noted that the features shown in the remainder of the text in relation to the magnet 40 can be applied to only one, to all or to some of the magnets.

(39) In the remainder of the text, the magnetic field generated by the magnet 40 is denoted H.

(40) In the present description, “magnet” encompasses both permanent magnets and electromagnets, unless otherwise specified.

(41) When the wheel 20 turns about the axis A (the direction of rotation D is indicated in FIGS. 6 to 11), the magnetic field H induces an electric current in the mold 22. This electric current is induced in the walls 23 of the mold 22 (especially if it is made of a metal or metal alloy), and also in the molten metal alloy contained in the cavity 22B. This electric current generates an induced magnetic field in the mold 22. As is known, this induced magnetic field creates a Laplace force.

(42) This Laplace force tends to stir the molten metal alloy in the method of solidification in the cavity 22B.

(43) The stirring of the molten metal alloy in the cavity 22B has the following effects: in front of the solidification front of the metal alloy (in other words in its still-melting part), allowing the grain seeds to grow in three dimensions, which promotes the formation of equiaxed grains; at the solidification front, breaking the tips of any columnar grains, which adversely affects the formation of columnar grains and also has the advantage of providing new seeds of equiaxed grains.

(44) It will therefore be understood that the stirring of the molten metal alloy considerably promotes the formation of equiaxed grains with respect to the formation of columnar grains. As a consequence, the metal alloy blank has a homogenous, and therefore virtually isotropic, structure, which eliminates the drawbacks discussed above.

(45) In addition, the stirring makes it possible to constantly re-homogenize the chemical composition of the molten metal alloy, both in front of the solidification front and at the solidification front. This makes it possible to avoid any local segregation, and consequently any aligned positive segregation or exudation into the blank.

(46) In addition, at the solidification front, the stirring makes it possible to improve the supply of molten metal alloys during the solidification shrinkage. The blank consequently has virtually no residual porosity after cooling. This avoids the need to subject the blank to a step of Hot Isostatic Pressing (HIP).

(47) The manufacturing device 10 therefore makes it possible to obtain a metal blank with improved mechanical and structural properties, which can be more easily machined and/or subjected to hot shaping operations (forging, rolling, extrusion etc.) Moreover, subsequent operations to be carried out on the blank are less expensive since the hot isostatic compression step is no longer necessary.

(48) In order to reinforce the stirring of the molten metal alloy, the mold 22 can be provided with a coil 60, as seen in FIG. 5.

(49) The coil 60 comprises one, or more typically several, windings electrically connected together. The windings of the coil 60 surround an internal volume of the mold 22. In the example shown in FIG. 5, this internal volume is the entire cavity 22B. It could also be only a part of the cavity 22B.

(50) In the meaning of the present description, the fact that the windings of the coil 60 surround an internal volume of the mold 22 means that said internal volume is contained in the volume delimited by the windings of the coil 60. Thus, the windings of the coil 60 can be sunk into the walls 23 of the mold 22 as shown in FIG. 5, or else arranged on the external surface of the walls 23.

(51) When the wheel 20 turns about the axis A, an electric current I is induced in the coil 60, in addition to the current induced in the walls 23 of the mold 22 and in the molten metal alloy. The Laplace force exerted on the molten metal alloy is therefore more intense, which improves the stirring of the molten metal alloy.

(52) Preferably, the windings extend parallel to the radial direction R1. This maximizes the area swept by the coil during the rotation of the wheel 20, in particular if the cavity 22B has a length considerably greater than the maximum dimension of its section as explained above.

(53) As shown in FIG. 6, the magnet 40 can be an annular magnet 40C the axis of which is parallel to the axis A. It can also be a circular magnet.

(54) The magnet 40C makes it possible to obtain a magnetic field H substantially uniform over the whole volume swept by the mold 22 during the rotation of the wheel 20.

(55) Preferably, the axis of the magnet 40C is colinear with the axis A. The magnetic field H is then more uniform over the whole of the volume swept by the mold 22 during the rotation of the wheel 20.

(56) In a variant, as shown in FIG. 7, the device comprises a plurality (here three) magnets 40-1, 40-2, 40-3 each arranged in such a way as to induce an electric current in the mold 22 and where applicable in the coil 60.

(57) The magnets 40-1, 40-2, 40-3 are arranged in a spaced manner about the axis A. In other words, between the magnets 40-1, 40-2, 40-3, there are spaces without magnets. Consequently, the magnetic field H varies according to the angular position of the mold 22. It follows that the electric current induced by the magnet in the mold 22, and therefore the Laplace force, in the mold 22 is variable during the rotation of the wheel 30, which improves the stirring of the molten metal alloy inside the mold 22.

(58) Preferably, in order to simplify the construction of the manufacturing device 10, the magnets 40-1, 40-2, 40-3 are all identical.

(59) It is also preferable that the magnets 40-1, 40-2, 40-3 be evenly spaced apart.

(60) The magnets 40-1, 40-2, 40-3 can have the shape of annular segments, the axis of which is parallel to the axis A as shown in FIG. 7. It can also be circular segments. As in the variant of FIG. 6, it is preferable that the axis of the annular or circular segments be colinear with the axis A.

(61) Preferably, as shown in FIG. 8, the magnets are even in number (here, four magnets 40-1 to 40-4), and the polarities of the magnets alternate evenly about the axis A. In other words, following the direction of rotation of the wheel 20, the pole of the magnets 40-1 to 40-4 facing the wheel 20 is alternatively North, South, North, South etc.

(62) Thus, the magnetic field H applied to the mold 22 changes direction periodically during the rotation of the wheel 20, which further improves the stirring of the molten metal alloy inside the mold 22. If the magnets 40-1 to 40-4 are evenly spaced and identical, the magnetic field H is alternating.

(63) According to yet another variant schematically shown in FIG. 9, the device 10 further comprises a permanent magnet 40M forming a single part with the wheel 20. The magnet 40 itself has the form of a magnet 40S not forming a single part with the wheel 20. Typically, the magnet 40S is fixed with respect to the chamber 50. The permanent magnet 40M extends partly across the coil 60 of the mold 22.

(64) Preferably, the poles of the permanent magnet 40M and the magnet 40S facing one another have opposite names (i.e. if one of the poles is North, the other is South). Thus, at the level of the windings located between the permanent magnet 40M and the magnet 40S, the magnetic field H is virtually uniform, as schematically shown in FIG. 9. This increases the intensity of the induced electric current in the coil 60 and therefore the intensity of the stirring.

(65) Furthermore, if the windings of the coil 60 extend parallel to the radial direction R1, the lines of the magnetic field Hare aligned with the windings of the coil, which further increases the intensity of the current induced in the coil 60 and therefore the intensity of the stirring.

(66) As shown in FIG. 10, the magnet 40S can be an annular magnet, the axis of which is parallel to the axis A. It can also be a circular magnet.

(67) Such an annular or circular magnet makes it possible to obtain a magnetic field H substantially uniform over the whole volume swept by the mold 22 during the rotation of the wheel 20. As shown in FIGS. 9 and 10, it is preferable that the poles of the permanent magnet 40M and the annular or circular magnet 40S facing one another have opposite names.

(68) In a variant, as shown in FIG. 11, the device comprises a plurality (here three) magnets 40S-1, 40S-2, 40S-3 not forming a single part with the wheel 20 and each arranged in such a way as to induce an electric current in the mold 22 and where applicable in the coil 60.

(69) In the variant shown in FIG. 11, the magnets 40S-1, 40S-2, 40S-3 are such that their poles all have a name opposite to that of the magnet 40M which they face (i.e. if the poles of the magnets 40S-1, 40S-2, 40S-3 are North, the pole of the magnet 40M they face is South).

(70) In another variant (not shown), the magnets not forming a single part with the wheel (20) are even in number, and the polarities of said magnets alternate evenly about the axis A. In other words, following the direction of rotation of the wheel 20, the pole of these magnets facing the wheel 20 is alternatively North, South, North, South etc.

(71) Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. Furthermore, individual features of the different embodiments described can be combined in additional embodiments. Consequently, the description and the drawings must be considered in an illustrative sense rather than a restrictive one.