Classifications

• • 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

Definitions

• the present invention relates to the manufacture of parts such as blading complex geometries according to the technique known as lost wax foundry.
• a model wax or other equivalent material easily removable by the following. If necessary we group together several models into one cluster. We made around this model a ceramic mold by soaking in a first slip to form a first layer of material in contact with its area. Sand the surface of this layer to reinforce and facilitate the hanging of the next layer, and we dry the whole: what constitutes respectively the stuccage and drying operations. We then repeat the soaking operation in slip of possible compositions different, operation always associated with the successive operations of stuccage and drying. Thus, a ceramic shell consisting of a plurality of layers.
• the slips are composed of particles of ceramic materials, flour, such as alumina, mullite, zircon or the like, with a mineral colloidal binder and adjuvants, if any, depending on the rheology desired.
• These adjuvants make it possible to control and stabilize characteristics of the different types of layers, while avoiding the effects of different physicochemical characteristics of raw materials constituting the slips. It can be a wetting agent, a plasticizer or a texturizer based, for the latter, the desired thickness for the deposit.
• the carapace mold is then dewaxed, which is an operation by which eliminates the material constituting the original model. After elimination of the model, we obtain a ceramic mold whose cavity reproduces all the details of the model. The mold then undergoes heat treatment at high temperature or "cooking", which gives it the mechanical properties required.
• the carapace mold is thus ready for the manufacture of the metal part by casting.
• the step The next step is to sink a molten metal into the mold cavity and then to the solidify.
• solidification techniques In the field of lost-wax foundry, there is currently a distinction several solidification techniques, therefore several casting techniques, according to the nature of the alloy and the expected properties of the part resulting from the casting. It may be directed solidification with columnar structure (DS), directed solidification with monocrystalline structure (SX) or solidification equiaxe (EX) respectively.
• DS columnar structure
• SX directed solidification with monocrystalline structure
• EX solidification equiaxe
• the shell is broken by a shaking operation, and we complete the manufacture of the metal part.
• shells can be made at through several processes. Each carapace must have properties specific to ensure the desired type of solidification. For example, for equiaxed solidification, several different processes can be one using a silicate binder of ethyl, another using a silica binder colloid. For directed solidification, shells can be made from different fillers, based on silico-aluminous, silica-zircon or silica.
• the invention achieves these objectives with the following method.
• the method is characterized by the fact that ceramic particles of the slips comprise a refractory oxide or a a mixture of refractory oxides without zircon, none of the layers comprising zircon.
• the slip for the formation of the reinforcement layers is much more fluid than the second slip.
• the binder for different slips is a solution colloidal mineral such as colloidal silica.
• the stucco grains for the layers of contact, intermediate and reinforcement are made from mullite grains and no zircon.
• the stuccage operations are carried out with stucco grains covering a size range between 80 and 1000 microns.
• stucco is preferably applied by dusting to the first layers, and is preferably applied by fluidized bed, for layers from the fourth.
• Stucco is applied automatically, so that the movements of the robot can make a carapace mold having a porosity after baking, between 20 and 35%. More shell is porous, the more it reduces its sensitivity to thermal shocks such as those products during different types of pouring.
• the baking cycle of the mold comprises a heating up to a temperature between 1000 and 1150 ° C, preferably between 1030 ° C and 1070 ° C.
• the first slip can be formed from mullite flours and of alumina without zircon, with or without germinating.
• the contact is composed mainly of mullite flour in quantity between 40 and 80% by weight, possibly of alumina flour, a binder based on colloidal silica, and organic adjuvants.
• the contact layer is composed of a mixture of alumina flours and mullite in quantities between 40 and 80% by weight and between 2 and 30% by weight, remainder comprising a binder based on colloidal silica, a germinant, and organic adjuvants.
• the second and third slip are common to any solidification process, and comprise a mixture of alumina and mullite flours in an amount of between 45 and 95% by weight, and mullite grains in an amount of between 0 and 25% by weight.
• the mold structure thus defined finds, indifferently, a use for the manufacture of a part with solidification of directed type with a columnar structure, the contact layer being formed mainly from a mullite flour, for the manufacture of a monocrystalline structured type solidification-type part, the contact layer being formed predominantly from a mullite flour or else for producing a piece with equiaxed type solidification, the contact layer being formed from a mixture of alumina flour and mullite.
• the invention also relates to a method for manufacturing parts by casting molten metal that, irrespective of the type of solidification, directed to columnar structure, directed at monocrystalline or equiaxed structure, molds with a common shell skeleton: intermediate layer and common reinforcement layer.
• the invention also relates to an installation for the production of parts by casting a molten metal in a shell mold comprising a station of manufacture of molds and casting stations for different solidifications, said stations being fed with molds having reinforcement layers identical.
• the method of manufacturing shell molds for use common to all types of parts includes a first step of manufacturing the model in wax or other equivalent material known in the field.
• wax or other equivalent material known in the field.
• the models are shaped to the dimensions of the final pieces, alloys.
• the carapace manufacturing steps are preferably carried out by a robot whose movements are common to all types of parts, programmed to have an optimal action on the quality of the deposits made, and to free oneself the geometric aspect of the various blades.
• slips are prepared in which they are quenched successively the models or the cluster to make a deposit of matter ceramic.
• layer # 1 contact, once the model removed from the first slip after an immersion phase, the covered model undergoes a dewatering phase then topping. Then, sprinkles of stucco are applied to do not disturb the thin layer of contact.
• mullite whose granulometry in this first layer is fine. It is between 80 and 250 microns. The surface condition of the pieces in final depends in part.
• the No. 1 layer is dried.
• the dipping is then carried out in a second slip to form a layer N ° 2, called intermediate.
• the composition is the same regardless of the solidification mode adopted.
• a stucco is deposited by dusting and dried.
• mullite whose particle size is average. It can be between 120 and 1000 microns.
• the state of porosity final shells depend in part on it.
• the model is then quenched in a third slip to form the layer No. 3 which is the first so-called reinforcement layer.
• the same stucco is then applied to layer 2 by dusting, and dried.
• the soaking operations are repeated in the third slip, stuccage and drying to form the layers of "reinforcement".
• the stuccage is carried out by fluidized bed.
• a glazing operation is performed which does not include a stuccage operation.
• the carapace in final can consist of 5 to 12 layers.
• Soak programs are optimized for each type of layer, in order to to overcome the geometrical aspect of the different types of pieces, and are therefore common to all references.
• the interlayer drying range is optimized for each type of layer, to overcome the geometric aspect of the different types of parts.
• the range is therefore common.
• the range allows indeed for each type of layer, a drying of molds with geometries as different as vanes movers, distributors, or structural parts.
• the baking cycle of molds is the same for all types of solidification, and thus free from the type of room. It includes a rising phase in temperature, a plateau at the cooking temperature and a phase of cooling.
• the cooking cycle is chosen to optimize the properties mechanical shells so as to allow cold handling without risk of breakage, and in order to minimize sensitivity to thermal shock that can be generated during the different stages of casting.

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

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• 2004
  • 2004-05-12 FR FR0405143A patent/FR2870147B1/fr not_active Expired - Fee Related
• 2005
  • 2005-05-11 CA CA2507170A patent/CA2507170C/fr not_active Expired - Lifetime
  • 2005-05-11 EP EP05103958A patent/EP1595620B1/de not_active Expired - Lifetime
  • 2005-05-11 JP JP2005138394A patent/JP4937528B2/ja not_active Expired - Lifetime
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