Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
  • B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
  • B22C1/18—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of inorganic agents
  • B22C1/181—Cements, oxides or clays
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
  • B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
  • B22C1/165—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents in the manufacture of multilayered shell moulds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
  • B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
  • B22C1/18—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents of inorganic agents
  • B22C1/183—Sols, colloids or hydroxide gels
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C9/00—Moulds or cores; Moulding processes
  • B22C9/02—Sand moulds or like moulds for shaped castings
  • B22C9/04—Use of lost patterns
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C9/00—Moulds or cores; Moulding processes
  • B22C9/12—Treating moulds or cores, e.g. drying, hardening
• • 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 presentation relates to the field of foundry, in particular the foundry processes of the lost-wax type, and more particularly the slip used in such processes, in particular for the manufacture of foundry shell molds.
• the first step is normally the manufacture of a shell mold, which generally includes the production of a model of material with a comparatively low melting temperature, such as for example a wax or resin, around which is then made a shell of refractory material.
• a molten metal is poured into this mold, in order to fill the cavity formed by the model. in the mold after its evacuation. Once the metal cools and solidifies, the mold can be opened or destroyed in order to recover a metal part conforming to the shape of the model.
• the wax model is generally
• contact slip plays a key role in the quality of the molded metal parts.
• this contact slip makes it possible to form the internal surface of the shell mold, coming directly into contact with the metal of the metal part to be molded.
• the present disclosure relates to a foundry slip for the manufacture of shell molds for the molding of a part comprising an alloy
• the slip comprising powder particles and a binder, the binder comprising colloidal yttrin, and the powder particles comprising zirconia stabilized by calcium oxide.
• a foundry slip is a slip suitable for being used for the formation of a shell mold in which molten metal will be cast.
• a slip comprises a binder, that is to say a compound ensuring cohesion between the powder particles and giving the shell mold its mechanical strength in raw and after sintering.
• the binder can be inorganic.
• the powder particles can be sand particles (also known as “flour”), in particular refractory particles, generally having a diameter between 1 micrometer and 100 micrometers.
• the foundry slip used in this presentation comprises a binder comprising colloidal yttrin, and powder particles comprising zirconia.
• CSZ from the English “calcia stabilized zirconia”, that is to say zirconia stabilized by calcium oxide
• CSZ from the English “calcia stabilized zirconia”, that is to say zirconia stabilized by calcium oxide
• the viscosity of a slip of the state of the art does not have the composition of the present description, that is to say that is, a binder comprising colloidal yttrin and powder particles comprising zirconia stabilized by calcium oxide (CSZ), tends to increase over time, causing gelation of the slip.
• a binder comprising colloidal yttrin and powder particles comprising zirconia stabilized by calcium oxide (CSZ) tends to increase over time, causing gelation of the slip.
• the use of zirconia stabilized by calcium oxide makes it possible to modify the interaction between the binder and the powder particles to stabilize the slip, while retaining a low reactivity with the metals to be molded, such as for example titanium aluminide alloys (TiAI), or even a lower reactivity than a slip comprising an yttrin powder and a binder comprising colloidal ytrin.
• TiAI titanium aluminide alloys
• the slip thus obtained therefore has an increased service life and can be reused.
• the baths used can also be larger, without causing loss.
• the slip is a contact slip configured to come into contact with the metal of the part to be molded.
• Called slip is the first slip used, which comes directly into contact with the metal of the part at the time of molding, as opposed to the following slip, called reinforcement slip and
• a Contact slip is configured to follow the shape of the part and not alter it.
• a contact slip is often kept for longer periods of time than a reinforcing slip which is consumed more quickly, hence an increased need for stability for a contact slip.
• the slip according to the present disclosure is therefore particularly suitable for use as a contact slip, due to its stability over time and its non-reactivity with certain metals such as TiAI.
• the mass content of calcium oxide in the zirconia stabilized by calcium oxide is between 1 and 30%, preferably between 3 and 20%, more preferably between 5 and 10 %.
• stabilized by calcium oxide in the slip is between 65 and 75%, preferably between 68% and 72%, more preferably equal to 70%.
• a mass ratio of the binder in the slip is between 20 and 40%, preferably between 25 and 35%, more preferably equal to 29.8%.
• a mass ratio of additives in the slip is less than 10%, preferably between 0.1 and 5%, more preferably still between 0.5 and 2%.
• the viscosity of the slip is a hydrophiliosity of the slip.
• the viscosity of the slip is maintained at a value between 0.1 and 2 Pa.s for a duration at least equal to 24 hours. These values make it possible in particular to facilitate the accessibility of the slip to certain narrow areas of the model.
• the foundry slip is
• the slip according to the present disclosure is particularly suitable for use as a contact slip, due to its stability over time. and its non-reactivity with metallic alloys based on titanium aluminide (T'AI).
• the present presentation also relates to the use of a foundry slip according to any one of the preceding embodiments for the manufacture of a shell mold.
• the present presentation also relates to a method of manufacturing a shell mold for molding a part, the method comprising steps of:
• the reinforcing slip comprises a binder and powder particles, the binder being chosen from: ethyl silicate, sodium silicate or colloids among which, in particular, colloidal silica, colloidal alumina, colloidal yttrin or colloidal zirconia.
• the powder particles are sized. In some embodiments, the powder particles
• mullite-zirconia composites include at least one compound from alumina, mullite, zirconia, mullite-zirconia composites.
• the present presentation also relates to a shell mold obtained by a process according to any one of the preceding embodiments.
• the shell mold obtained by the process according to the present description makes it possible to limit the oxygen-rich reaction layer which forms on the surface of a metal part, for example a blade of an aeronautical engine, molded in this mold. shell.
• the reaction layer is defined here as the thickness for which the oxygen concentration is greater than at least twice the concentration measured in the base alloy. In particular, for an isothermal contact at 1600 ° C. for a period of 5 min, this reaction flask remains less than 15 ⁇ m for the part thus obtained.
• FIG. 1 schematically represents the steps of a process for manufacturing a shell mold for foundry processes
• Figure 2 is a graph illustrating the evolution of the viscosity of a control slip, and of the slip of the present presentation, as a function of a shear stress.
• the process for manufacturing aeronautical parts is a foundry process.
• the various stages of this process are described for example in the document FR3031921.
• a first step in this process consists in manufacturing a wax cluster model called still 'non-permanent cluster'.
• the shell mold is made from the wax cluster.
• the wax constituting the cluster model is removed from the mold. This removal of the wax is carried out by bringing the shell mold in an autoclave oven (or other) to a temperature higher than the melting temperature of the wax.
• the metal cluster of blades is formed in the shell mold by pouring molten metal into it.
• the cluster is released from the shell mold.
• each of the blades is separated from the rest of the cluster and finished by finishing processes, for example machining processes.
• the invention relates in particular to the manufacture of the shell mold in which the casting of the metal will be carried out, and more specifically the contact slip used for the manufacture of this mold.
• the different steps of this process are illustrated in Figure 1.
• the first step includes the provision of a wax model, or other equivalent material that can be easily removed later, of the part.
• the wax model is dipped in a first slip, the contact slip (step S2), comprising powder particles and a binder.
• Sandblasting in other words a deposit of sand particles called contact stucco, is then carried out, followed by drying of the layer obtained (step S3). This sanding step makes it possible to strengthen the layer and facilitate the attachment of the next layer.
• step S4 A deposit of sand particles called reinforcing stucco is then carried out, followed by drying of the layer obtained (step S5). Steps S4 and S5 are repeated N times, until a determined shell thickness is obtained. Finally, when the desired thickness is reached, a dewaxing step, consisting of removing the wax model from the model, then heat treatment, is carried out (step S6). After elimination of the wax model, we obtain a ceramic shell mold whose cavity reproduces in negative all the details of the part to be molded.
• the heat treatment comprises cooking the mold obtained, the cooking temperature preferably being between 1000 and 1200 ° C.
• the slip used is composed of particles of materials
• ceramics in particular alumina, mullite, zirconia or the like, with a mineral colloidal binder and additives if necessary, such as wetting agents or anti-foaming agents.
• the contact slip used in step S2 comprises yttrin.
• the contact stucco used in step S3 may also include yttrin.
• the reinforcing slip and the reinforcing stucco used in steps S4 and S5 can comprise mullite, alumina, silico-aluminous, silica, zircon, zirconia or yttrine, for example.
• the invention relates more particularly to the contact slip used in step S2, and in particular the presence of colloidal yttrin and of zirconia stabilized by calcium oxide (CSZ) in the powder particles which comprises that -this.
• CSZ calcium oxide
• slip A intended to be used as contact slip for the manufacture of a shell mold.
• Slip A may have the following composition, expressed in percentages by mass:
• slip B which the inventors have determined that it exhibits reactivity with TiAI similar to that of slip A, and whose powder particles comprise zirconia stabilized by calcium oxide (CSZ), CaO acting as a stabilizing agent.
• the CSZ can for example be obtained by reactive sintering.
• the level of CaO in percentage by mass present in the powder is between 1 and 20%. Slip B thus obtained has the following mass percentages:
• Slip B also includes unavoidable impurities.
• unavoidable impurities mention may, for example, be made of silicon dioxide (Si02), titanium dioxide (Ti02), iron oxide (Fe203) or alumina (AI203). Elements which are not intentionally added to the composition and which are provided with other elements are defined as inevitable impurities.
• the curves illustrated in Figure 2 illustrate the influence of the composition used for the contact slip according to this presentation on the stability thereof.
• This figure shows the evolution of the dynamic viscosity h in Pa.s of the slip, as a function of a shear applied to this slip.
• These measurements are carried out using a rotary rheometer having coaxial cylindrical geometries, making it possible to apply to the slip a shear of between 0.1 and 100 s 1 .
• Curve (a) represents the viscosity of slip A after 0.5 h
• curve (b) represents the viscosity of slip A after 2 h
• curve (c) represents the viscosity of slip A after 3.5 h
• curve (d) represents the viscosity of the slip B of the invention after 24 h.
• the durations mentioned above are determined from an instant t0 corresponding to the end of the manufacture of the slip.
• Curves (a) and (b) illustrating the viscosity of slip A after 0.5 h and after 2 h are substantially combined.
• the viscosity of slip A is approximately equal to 4 Pa.s after 2 h. This viscosity then increases very rapidly over time, and reaches a value greater than 25 Pa.s after 3.5 h. In other words, the slip quickly becomes very viscous, and tends to gel.
• slip B shows that the viscosity of slip B remains below 1 Pa.s after 24 h, whatever the shear applied to it.
• Slip B therefore has increased stability compared to slurry A, and remains fluid while retaining a low viscosity even 24 hours after the preparation of this slurry.
• the composition of slip B makes it possible to maintain a low reactivity with TiAI alloys, equivalent to or even less than that of slip A.
• references to a process can be transposed, alone or in combination, to a device, and conversely, all the characteristics described with reference to a device can be transposed, alone or in combination, to a process.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Materials Engineering (AREA)
• Dispersion Chemistry (AREA)
• Mold Materials And Core Materials (AREA)
• Molds, Cores, And Manufacturing Methods Thereof (AREA)

Applications Claiming Priority (2)

Publications (1)

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• 2018
  • 2018-12-11 FR FR1872711A patent/FR3089438B1/fr active Active
• 2019
  • 2019-12-05 CN CN201980082228.0A patent/CN113165053B/zh active Active
  • 2019-12-05 EP EP19868215.5A patent/EP3894107A1/fr active Pending
  • 2019-12-05 WO PCT/FR2019/052940 patent/WO2020120882A1/fr unknown
  • 2019-12-05 JP JP2021533241A patent/JP2022512205A/ja active Pending
  • 2019-12-05 US US17/309,616 patent/US20220048097A1/en active Pending

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