Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D13/00—Centrifugal casting; Casting by using centrifugal force
  • B22D13/06—Centrifugal casting; Casting by using centrifugal force of solid or hollow bodies in moulds rotating around an axis arranged outside the mould
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
  • B22D27/02—Use of electric or magnetic effects
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D13/00—Centrifugal casting; Casting by using centrifugal force
  • B22D13/02—Centrifugal casting; Casting by using centrifugal force of elongated solid or hollow bodies, e.g. pipes, in moulds rotating around their longitudinal axis
  • B22D13/026—Centrifugal casting; Casting by using centrifugal force of elongated solid or hollow bodies, e.g. pipes, in moulds rotating around their longitudinal axis the longitudinal axis being vertical
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D13/00—Centrifugal casting; Casting by using centrifugal force
  • B22D13/06—Centrifugal casting; Casting by using centrifugal force of solid or hollow bodies in moulds rotating around an axis arranged outside the mould
  • B22D13/066—Centrifugal casting; Casting by using centrifugal force of solid or hollow bodies in moulds rotating around an axis arranged outside the mould several moulds being disposed in a circle
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D21/00—Casting non-ferrous metals or metallic compounds so far as their metallurgical properties are of importance for the casting procedure; Selection of compositions therefor
  • B22D21/002—Castings of light metals
  • B22D21/005—Castings of light metals with high melting point, e.g. Be 1280 degrees C, Ti 1725 degrees C

Definitions

• the present invention relates to the manufacture of metal alloy blanks by centrifugal casting of a molten metal alloy, and in particular blade blanks for turbomachines, in particular blades for aeronautical turbojet engines.
• Figure 1 shows a known manufacturing device that can be used for this manufacture.
• the manufacturing device 100 comprises, in a chamber 150 closed and sealed, a crucible 110 and a centrifugal casting wheel 120.
• the crucible 110 is adapted to perform the melting of the metal alloy, which is for example provided in the form of a metal alloy ingot 116. Once this fusion has been performed, the molten metal alloy is poured into the wheel centrifugal casting 120.
• the centrifugal casting wheel 120 is rotatable about an axis of rotation A and comprises a mold 122 for receiving the molten metal alloy.
• the mold 122 extends in a radial direction R with respect to the axis of rotation A.
• the centrifugal casting wheel 120 is rotated about its axis of rotation A. During this rotation, the molten metal alloy is rapidly driven by the centrifugal force at the bottom of the mold 122.
• the rotational speed of the casting wheel Centrifugal 120 is chosen such that this centrifugal force is significantly greater than the force of gravity.
• the molten metal alloy solidifies gradually, at a solidification rate lower than the filling rate of the mold 122; thus, the solidification takes place on the entire mold 122, until the desired metal alloy blank.
• the blank metal alloy is then extracted from the mold 122, and can subsequently undergo subsequent industrial steps (heat treatment, machining, forging ...) to reach a final piece.
• the foundry step that has just been described has the advantage of reducing the porosity due to the removal of the metal alloy during the solidification of the metal alloy blank. However, it also has drawbacks, which will be understood with reference to FIGS. 2 and 3.
• FIG. 2 schematically represents the solidified metal blank in section along the plane C-C of Figure 1 and allows to observe the metallurgical microstructure (the walls of the mold 122 and the centrifugal wheel 120 have been omitted to simplify the drawing).
• the solidified metal blank 146 has a central region B1 consisting of coarsely equiaxed grains.
• the blank 146 Near its walls, the blank 146 has a "skin" B3 consisting of equiaxial grains of smaller dimensions than in the central region B1.
• the blank 146 has an intermediate region B2 consisting of columnar grains (also known as basaltic grains).
• This intermediate region B2 is better visible in FIGS. 3A and 3B, which are photographs of cuts in the radial direction R of two metal blanks made of TA6V (titanium-based alloy comprising by weight 6% of aluminum and 4% of vanadium ) obtained according to the method just described, and where the regions B1, B2 and B3 have been indicated.
• TA6V titanium-based alloy comprising by weight 6% of aluminum and 4% of vanadium
• the columnar grains of the intermediate region B2 induce a very strong anisotropy, which is problematic for subsequent industrial stages.
• the mechanical and dynamic properties of the blank in the intermediate region B2 are very different in the direction considered (perpendicular to the axis of the columnar grains or parallel to their axis), the responses of the material to the forces of the different machining as a function of the angle of cut with respect to the columnar grain axis.
• the relaxations of the constraints of the machining are also anisotropic.
• the machining of the blank must be designed to take into account the foregoing factors, which tends to complicate it.
• the parts that one wishes to achieve by machining the blank must also be sized to take into account the factors that above, which frequently leads to a non-optimal use of the material of the blank.
• the directions of the axes of the columnar grains may vary from one region of the blank to the other (as can be seen for example in FIG. 3B): in this case, the mechanical and dynamic properties of the The blank, even in a given direction, may differ from one region to another of the same blank and / or blank to another. The design of the machining is then even more complex. It may even be that some of the blanks are totally unusable for machining, in which case they must be discarded.
• the blank since the blank has a complex and varied metallurgical microstructure, its use properties (especially mechanical) are widely dispersed. Parts made from this blank must be dimensioned accordingly, which tends to weigh them down. This is particularly undesirable when the part to be manufactured is a dawn for an aeronautical turbojet, because such vanes must be as light as possible in the interest of the turbojet engine's performance.
• the anisotropy induced by the columnar grains of the intermediate region B2, and the interfaces between the intermediate region B2 with columnar grains and the regions B1 and B3 with equiaxial grains make it very difficult or even impractical to perform simple operations. hot shaping of the blank, such as forging, rolling or extruding. However, these operations can bring new mechanical properties to the material of the blank. There is therefore a need for a new process for manufacturing a metal alloy blank by centrifugal casting which makes it possible to reduce the anisotropy of the blank and to simplify and make less costly the subsequent operations to be performed on the blank.
• the present invention provides 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 rotatable about an axis of rotation and comprising a mold for receiving the molten metal alloy, the mold extending in a radial direction relative to the axis of rotation, the device comprising at least one magnet arranged to induce a electric current in the mold during the rotation of the centrifugal casting wheel about the axis of rotation.
• the electrical current induced by the magnet creates a Laplace force that tends to stir the molten metal alloy within the mold. Thanks to this stirring, the metal alloy blank has, after solidification, a homogeneous macrostructure, almost free of columnar grains, and therefore almost isotropic, which eliminates the disadvantages described above.
• the blank has virtually no residual porosity after cooling. This avoids having to subject the blank to a hot isostatic pressing (HIP) step, which also makes it possible to reduce these residual porosities but has the disadvantage of being long and very expensive.
• HIP hot isostatic pressing
• the centrifugal casting wheel comprises a winding surrounding an internal volume of the mold and configured so that the magnet induces an electric current in the winding during said rotation of the centrifugal casting wheel around the axis of rotation.
• an induced current is generated not only in the molten metal alloy (and possibly in the structure of the centrifugal casting wheel), but also in the winding.
• the Laplace force acting on the molten metal alloy is more intense.
• the mixing of the molten metal alloy inside the mold is more intense, which further improves the homogeneity of the metal alloy blank.
• it is not necessary to connect the winding to a source of electricity since an induced current is generated remotely in the winding. This avoids providing a particular connection of the winding to a source of electricity not secured to the centrifugal casting wheel, which would be complex from the mechanical point of view (risk of blocking the centrifugal casting wheel by the supply son).
• the magnet is an annular or circular magnet whose axis is parallel to the axis of rotation.
• the magnetic field generated by the magnet is substantially uniform over the entire volume swept by the mold during the rotation of the centrifugal casting wheel.
• the device comprises a plurality of magnets arranged spaced around the axis of rotation.
• the magnetic field acting on the mold varies during the rotation of the centrifugal casting wheel. It follows that the electric current induced in the mold, and thus the Laplace force acting on the molten metal alloy, is variable during the rotation of the centrifugal casting wheel, which improves the stirring of the molten metal alloy within the mold.
• the magnets are even in number, and the polarities of said magnets alternate regularly around the axis of rotation.
• the magnetic field acting on the mold periodically changes direction during the rotation of the centrifugal casting wheel, which further improves the stirring of the molten metal alloy within the mold.
• the magnet is not secured to the centrifugal casting wheel, and the device further comprises a permanent magnet integral with the centrifugal casting wheel and extending partly through the coil.
• the magnet is an annular or circular magnet whose axis is parallel to the axis of rotation.
• the poles of the permanent magnet and the magnet facing each other have opposite names.
• the device comprises a plurality of magnets not integral with the centrifugal casting wheel and arranged spaced about the axis of rotation.
• the non-integral magnets of the centrifugal casting wheel are even in number, and the polarities of said magnets alternate regularly around the axis of rotation.
• the axis of rotation is vertical.
• the balancing device of the centrifugal casting wheel is simpler.
• the construction and operation of the device are therefore simplified.
• the stirring of the molten metal alloy inside the mold is less disturbed. Indeed, during the rotation of the wheel, the molten metal alloy inside the mold is subjected to the centrifugal force and the force of gravity.
• the centrifugal force is always radial to the axis of rotation. If the axis of rotation is vertical, the direction of the force of gravity also does not vary during the rotation of the wheel, so that the stirring is less disturbed.
• the radial direction is parallel to the horizontal. In this way, the construction of the centrifugal casting wheel is simpler, especially if the axis of rotation is vertical.
• the present invention also provides a method of manufacturing a metal alloy blank comprising the steps of:
• centrifugal casting wheel pouring the molten metal alloy into a centrifugal casting wheel, the centrifugal casting wheel being rotatable about an axis of rotation and comprising a mold for receiving the metal alloy melting, the mold extending in a radial direction relative to the axis of rotation;
• the centrifugal casting wheel comprises a coil surrounding an interior volume of the mold, and during the rotation step, the magnetic field induces an electric current in the coil.
• the method according to the invention provides the same advantages as the device according to the invention.
• the metal alloy is an alloy based on titanium or nickel.
• titanium-based titanium (respectively “nickel-based) is meant that titanium (respectively nickel) is substantially, by weight, the majority element of the alloy.
• Titanium-based or nickel-based metal alloys are among the alloys commonly used to make blanks of mechanically stressed parts, such as blades for a turbomachine, and more particularly blades for an aeronautical turbojet engine.
• the metal alloy blank is a blade blank for a turbomachine, in particular a blade for an aeronautical turbojet engine.
• FIG. 1 shows schematically a known centrifugal casting manufacturing device
• FIG. 2 shows schematically the solidified metal blank obtained by the device of Figure 1, in section along the plane CC of Figure 1;
• FIGS. 3A and 3B are photographs of sections of two metal blanks obtained by the device of FIG. 1, in the direction of FIG. 1;
• FIG. 4 schematically represents a device for manufacturing by centrifugal casting according to the invention
• FIG. 5 is a partial perspective view and cut away of the device of Figure 4.
• FIG. 6 is a top view of the centrifugal casting wheel and the magnet, according to another embodiment of the invention.
• Figure 7 is a top view similar to Figure 6, according to yet another embodiment of the invention.
• FIG. 8 is a top view similar to Figure 7, according to yet another variant of the invention.
• FIG. 9 is a side view of a portion of the centrifugal casting wheel, according to yet another embodiment of the invention.
• FIG. 10 is a perspective view of FIG. 9, showing a first possibility of implementing the variant of FIG. 9;
• FIG. 11 is a perspective view of FIG. 9, showing another possibility of implementing the variant of FIG. 9.
• FIG. 4 schematically represents a device 10 for manufacturing a metal alloy blank by centrifugal casting of a molten metal alloy.
• the manufacturing device 10 comprises, in a closed and sealed enclosure 50, a melting device 610, a centrifugal casting wheel 20 (hereinafter referred to as “the wheel 20" for convenience) and a magnet 40.
• the melter 610 is adapted to provide a molten metal alloy.
• the merge device 610 performs the melting of a metal alloy provided in the form of a metal alloy ingot 616.
• the various constituents of the metal alloy are introduced individually into the melter 610, and then melted together so as to obtain the molten metal alloy.
• the metal alloy is selected from suitable alloys for the final piece to be made from the blank.
• the metal alloy may be, for example, a ceramic-based alloy, a steel, a titanium-based alloy, or a nickel-based alloy.
• Titanium-based alloys include:
• conventional titanium alloys having a crystallographic structure identical to that of pure titanium, for example: TA6V, Ti-17, Ti 10-2-3, Ti-5553, ⁇ 16, ⁇ 21;; and
• titanium-based intermetallic alloys having one or more crystallographic structure phases different from that of pure titanium.
• titanium aluminides are particularly contemplated, among which:
• phase titanium aluminides and ⁇ 2 columnar such as:
• Ti-48AI-1V-0.3C Ti-48AI-2Cr-2Nb (also known as “GE 48-2-2") or Ti-48AI-2Nb-0.75Cr-0.3Si (also known as “Daido RNT650");
• titanium aluminas with ⁇ and 2 equiaxed phases such as T-45Al-2Nb-2Mn + 0.8TiB 2 (also known as "Howmet
• aluminides with ⁇ , ⁇ and ⁇ 2 equiaxed phases such as Ti-47.3-Al-2,2Nb-0,5Mn-0,4W-0,4Mo-0,23Si, Ti-46,5AI -3Nb-2Cr-0.2W-0,2Si-0, IC
• the Ti-48Al-2 Cr-2 NB alloy comprises, in atomic percentage, 48% of Al, 2% of Cr, 2% of Nb, and titanium (Ti) in addition to 100%.
• nickel-based alloys conventional nickel alloys such as René 77 or DS 200, or nickel superalloys such as AMI, are particularly contemplated.
• the fusion device 610 can be, for example:
• VAR Vacuum Arc Remelting
• VIM Vacuum Induction Melting
• EB Electro Bombardment
• the enclosure 50 is controlled to provide the required atmosphere:
• the molten metal alloy leaving the melting device 610 is poured into the wheel 20.
• the wheel 20 comprises a hub 30 at least one mold 22 fixed to the hub 30.
• the hub 30 comprises a central channel 32 and several supply channels 33 each communicating with a mold 22.
• the hub 30 may be provided with a funnel 31 opening onto the central channel 32.
• the hub 30 is capable of being rotated about an axis of rotation A, for example by means of a motor (not shown).
• the wheel 20 is rotatable about the axis of rotation A.
• the axis A is preferably vertical.
• FIG. 5 shows in perspective a mold 22 fixed to the hub 30
• the mold 22 extends in a radial direction R1 with respect to the axis A (see FIG. 4).
• this radial direction RI is perpendicular to the axis A.
• the radial direction RI is parallel to the horizontal.
• the mold 22 is adapted to receive the molten metal alloy, here in a cavity 22B.
• the mold 22 is typically made of a metal, a metal alloy or a ceramic sufficiently resistant to withstand the thermal stresses associated with contact with the molten mechanical alloy.
• the cavity 22B may have a rectangular or cylindrical section. This section may advantageously be constant over the entire length of the cavity 22B.
• the cavity 22B typically has a length substantially 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.
• the metal alloy blank After solidification, the metal alloy blank then has the general shape of a bar.
• the cavity 22B communicates with a supply channel 33 via a feed 22A, which is optionally of smaller section than the cavity 22B.
• molds 22 may be attached to the hub 30 as can be seen in FIGS. 4 and 5. For example, several molds 22 may be evenly spaced about the axis A. The molds 22 may also be superimposed to form a plurality of molds 22. (two in FIGS. 4 and 5) mold levels 22. The molds 22 can be separable from the hub 30, so that they can be replaced individually and / or separated one by one from the hub 30 in order to extract the metal alloy blank after solidification.
• the manufacturing device 10 also comprises at least one magnet.
• the magnet designated by the reference 40; it should be noted, however, that the features presented in the following with respect to the magnet 40 may be applied to a single, all or some of the magnets.
• the magnetic field generated by the magnet 40 is denoted H.
• magnet includes both permanent magnets and electromagnets, unless otherwise stated.
• 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 a metal alloy), and also in the molten metal alloy contained in the cavity 22B.
• This electric current generates a magnetic field induced in the mold 22.
• this induced magnetic field creates a Laplace force.
• This Laplace force tends to stir the molten metal alloy being solidified in the cavity 22B.
• the stirring of the molten metal alloy in the cavity 22B has the following effects:
• the stirring of the molten metal alloy considerably favors the formation of equiaxial grains with respect to the formation of columnar grains. Therefore, the alloy metal blank has a homogeneous macrostructure, almost without of columnar grains, and therefore almost isotropic, which eliminates the disadvantages discussed above.
• 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 level of the solidification front. This makes it possible to avoid any local segregation, and consequently any aligned positive segregation or exudation in the blank.
• the manufacturing device 10 thus 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 forming operations (forging, rolling, extrusion, etc.). Furthermore, the subsequent operations to be performed on the blank are less expensive because the hot isostatic pressing step is no longer necessary.
• the mold 22 may be provided with a coil 60, which is seen in FIG.
• the coil 60 comprises one or more typically several turns electrically connected to each other.
• the turns of the coil 60 surround an interior volume of the mold 22. In the example shown in FIG. 5, this interior volume is the entire cavity 22B. It could also be only part of the cavity 22B.
• the turns of the coil 60 can be embedded in the walls
• the turns extend parallel to the radial direction RI. This maximizes the area swept by the coil during the rotation of the wheel 20, particularly if the cavity 22B has a length significantly greater than the maximum dimension of its section as explained above.
• the magnet 40 may be an annular magnet 40C whose axis is parallel to the axis A. It may also be a circular magnet.
• the magnet 40C makes it possible to obtain a substantially uniform magnetic field H over the entire volume swept by the mold 22 during the rotation of the wheel 20.
• the axis of the magnet 40C coincides with the axis A.
• the magnetic field H is then more uniform over the entire volume swept by the mold 22 during the rotation of the wheel 20.
• the device comprises a plurality (here three) magnets 40-1, 40-2, 40-3 each arranged to induce an electric current in the mold 22 and possibly in the winding 60.
• the magnets 40-1, 40-2, 40-3 are arranged spaced about the axis A. In other words, between the magnets 40-1, 40-2, 40-3, there are gaps devoid of 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.
• the magnets 40-1, 40-2, 40-3 are all identical.
• magnets 40-1, 40-2, 40-3 are regularly spaced from each other.
• the magnets 40-1, 40-2, 40-3 may have the shape of annular segments whose axis is parallel to the axis A as shown in Figure 7. It may also be circular segments. As in the variant of Figure 6, it is preferable that the axis of the annular or circular segments is coincident with the axis A.
• the magnets are even in number (here, four magnets 40-1 to 40-4), and the polarities of the magnets alternate regularly around the axis A.
• the pole of the magnets 40-1 to 40-4 facing the wheel 20 is alternately North, South, North, South, ....
• the magnetic field H applying to the mold 22 periodically changes direction during the rotation of the wheel 20, which further improves the stirring of the molten metal alloy inside the mold
• the magnetic field H is alternating.
• the device 10 further comprises a permanent magnet 40M integral with the wheel 20.
• the magnet 40 is in turn in the form of a magnet 40S not secured to the wheel 20.
• the magnet 40S is fixed relative to the enclosure 50.
• the permanent magnet 40M extends partly through the coil 60 of the mold 22.
• the poles of the permanent magnet 40M and the facing magnet 40S have opposite names (i.e., if one of the poles is North, the other is South).
• the magnetic field H is almost uniform, as shown schematically in FIG. 9.
• the lines of the magnetic field H are aligned with the turns of the winding, which further increases the intensity of the current induced in the winding 60 and therefore the intensity of the brewing.
• the magnet 40S may be an annular magnet whose axis is parallel to the axis A. It may also be a circular magnet.
• annular or circular magnet makes it possible to obtain a substantially uniform magnetic field H over the entire volume swept by the mold 22 during the rotation of the wheel 20.
• poles of the permanent magnet 40M and the annular or circular magnet 40S facing each other have opposite names.
• the device comprises a plurality (here three) of magnets 40S-1, 40S-2, 40S-3 not integral with the wheel 20 and each arranged so as to induce an electric current in the mold 22 and possibly in the coil 60.
• 40S-2, 40S-3 are such that their poles all have a name opposite to that of the 40M magnet they face (that is, if the poles of magnets 40S-1, 40S-2, 40S-3 are North, the pole of magnet 40 they face is South).
• the non-integral magnets are even in number of the wheel 20 are even in number, and the polarities of said magnets regularly alternate around 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 alternately North, South, North,

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
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• Molds, Cores, And Manufacturing Methods Thereof (AREA)

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• 2017
  • 2017-11-07 FR FR1760453A patent/FR3073163B1/fr active Active
• 2018
  • 2018-11-06 EP EP18804376.4A patent/EP3706934B1/de active Active
  • 2018-11-06 CN CN201880075810.XA patent/CN111372703B/zh active Active
  • 2018-11-06 US US16/761,998 patent/US11433453B2/en active Active
  • 2018-11-06 WO PCT/FR2018/052736 patent/WO2019092354A1/fr unknown

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