EP2158987A1 - Präzisionsgussverfahren und verlorenes Modell für dieses Verfahren - Google Patents

Präzisionsgussverfahren und verlorenes Modell für dieses Verfahren Download PDF

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Publication number
EP2158987A1
EP2158987A1 EP09166187A EP09166187A EP2158987A1 EP 2158987 A1 EP2158987 A1 EP 2158987A1 EP 09166187 A EP09166187 A EP 09166187A EP 09166187 A EP09166187 A EP 09166187A EP 2158987 A1 EP2158987 A1 EP 2158987A1
Authority
EP
European Patent Office
Prior art keywords
lost
block
thermal properties
mold
metal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP09166187A
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English (en)
French (fr)
Inventor
Marie Fecourt
Mario Dufloux
Freddy Jacques
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
PSA Automobiles SA
Original Assignee
Peugeot Citroen Automobiles SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Peugeot Citroen Automobiles SA filed Critical Peugeot Citroen Automobiles SA
Publication of EP2158987A1 publication Critical patent/EP2158987A1/de
Withdrawn legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D15/00—Casting using a mould or core of which a part significant to the process is of high thermal conductivity, e.g. chill casting; Moulds or accessories specially adapted therefor
    • 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
    • B22C9/046—Use of patterns which are eliminated by the liquid metal in 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
    • B22D27/04—Influencing the temperature of the metal, e.g. by heating or cooling the mould

Definitions

  • the invention relates to a lost pattern molding method and a mold for this method, to promote certain properties of the molded part.
  • one of the ways to evaluate the metallurgical health of a part is to examine the grain size. It is recalled that when a metal is examined under a microscope, the surface of the metal appears to be composed of juxtaposed crystalline polyhedra. Each of these polyhedra is commonly called the "grain" of the metal. These grains correspond, at their origin, that is to say each one or more nuclei or germs from which the crystallization of the metal occurred during its solidification. It's grain are also known as "crystallite".
  • the Applicant is aware of lost pattern casting methods including casting in a mold of a molten metal which sublimates or liquefies the lost pattern so that the volume occupied by the lost pattern is progressively replaced by the molten metal, the mold comprising at least one refrigerant block in thermal contact with the lost model.
  • Such a mold equipped with a refrigerant block is for example described in the French patent application published under No. FR 2,685,229 .
  • These cooling blocks can accelerate the cooling of the metal and thus promote the appearance of small metal grains.
  • the measurement of the grain size is performed by image analysis under an optical microscope or with a scanning electron microscope.
  • the largest grain width is typically between 1 and 100 microns.
  • the size of grains and their shape have consequences on the mechanical characteristics of the solid phase metal. For example, coarse grains that is to say grains whose size is close to 100 microns correspond to fragile and brittle metals. Conversely, small grains, that is to say, the largest width is less than 50 microns and preferably less than 10 microns, correspond to more solid metals.
  • the cooling rate of the metal therefore has a direct impact on the mechanical characteristics of the molded part and on its functional strength.
  • the object of the invention is to remedy this disadvantage by proposing a lost pattern molding process in which a more precise control of the grain size is made possible. More generally, the present invention aims to make it possible to modify certain characteristics of a molded part in a fine and precise manner.
  • It therefore relates to a lost model molding process comprising, after the start of casting, adjusting the thermal properties of the refrigerant block according to the stage reached in the molding process to change the cooling rate of the cast metal.
  • the adjustment of the thermal properties of the refrigerant block makes it possible to adapt the rate of cooling of the metal at each stage of the molding process. Thus, it becomes possible to control more precisely the grain size of the solidified metal and therefore better control the mechanical characteristics of the molded part.
  • the figure 1 represents a mold 2 for a lost pattern molding process.
  • this mold 2 is designed for the production of molded parts for motor vehicles.
  • the molded part is a cylinder head.
  • the metal used to cast this part is, for example, an aluminum alloy such as AlSi7Cu3Mg.
  • the mold 2 comprises a lost model composed here of two parts 6 and 8.
  • the lost model is the reflection of the molded part to obtain.
  • This lost model is made of a sublimable material when in contact with the molten metal.
  • this sublimable material is a pyrolyzable cellular polymer.
  • this material is polystyrene.
  • Each portion 6, 8 is integral with several casting attacks 18 through which the molten metal will be introduced within these parts 6 and 8 of the lost model.
  • the end of each casting stroke 18, opposite to the lost pattern, is connected to a casting chute.
  • One end of the descent 20 is connected to a casting cup 22 made of refractory material.
  • the descent 20 and each attack 18 is initially formed of a sublimable material when it comes into contact with the molten metal.
  • this sublimable material is polystyrene.
  • the assembly formed by the lost model, the casting attacks 18 and the pouring down 20 is incorporated inside a tank 26 containing vibrated sand 28.
  • the lost model, the casting attacks and the pouring down are coated with a layer (not shown) suitable for isolating the molten metal from the sand 28 when it is introduced into the mold 2.
  • layer is, for example, made of refractory material whose melting temperature is much higher than the temperature of the molten metal. Typically, this layer has a thickness of between 1 mm and several millimeters.
  • the mold 2 comprises one or more cooling blocks for controlling the cooling rate of the metal cast in this mold.
  • a refrigerant block 30 has been shown. This refrigerating block 30 is connected to an apparatus 32 adapted to adjust at least one thermal property of the refrigerant block according to the stage reached in the molding process.
  • the refrigerating block 30 is able to cool locally the cast metal in the lost model. For this, it has a front face 34 turned to the lost model and thermally coupled to a portion of this lost model. This front face is crossed by a heat flow. Heat flow is the amount of heat that passes through this front face per unit of time. For example, the heat flux is expressed in J / s. The intensity of this heat flux is a function of the thermal properties of the block 30. Thus, by the term "thermal property of the block 30" is meant any physical characteristic of the block 30 able to modify the intensity of this heat flux. .
  • the refrigerating block 30 is a parallelogram whose front face 34 is directly in contact with the layer of refractory material enveloping the lost model.
  • Block 30 is for example made of a good thermal conductor material, that is to say whose thermal conductivity at 20 ° C is strictly greater than 10 Wm-1.K-1 and preferably greater than 200 Wm-1 .K-1.
  • block 30 is made of stainless steel.
  • the block 30 is integral with the tank 26.
  • it came integrally with a wall of the tank and thus forms with this wall only one block.
  • Block 30 also comprises a cavity 36 ( Figure 2 ) intended to receive a coolant, and orifices 38 and 40 ( Figure 2 ) for connecting respective ends of the cavity 36 to heat-transfer fluid supply conduits.
  • the cavity 36 forms a serpentine which winds in a plane parallel to the front face 34.
  • an arrow represents the direction of circulation of a coolant in the cavity 36.
  • the thermal properties of the block 30 are, for example, the thermal conductivity and the specific heat capacity of the heat transfer liquid present in the cavity 36, as well as the temperature, the circulation velocity or the pressure of the heat transfer liquid present in the cavity. 36.
  • the specific heat capacity is the amount of energy to be supplied by heat exchange to a unit of mass of a material to raise its temperature of 1 ° C.
  • the thermal capacities are given for a temperature of 25 ° C. and under atmospheric pressure.
  • the apparatus 32 comprises ducts 44 and 46 fluidically connected respectively to the orifices 38 and 40.
  • the duct 44 is a heat transfer fluid supply duct inside the cavity 36.
  • the duct 46 is, on the contrary, a conduit for discharging the coolant from the cavity 36.
  • the end of the conduit 44 opposite the orifice 38 is connected to controllable valves 48, 50 and 51 for fluidically and selectively connecting the conduit 44 to a first and second reservoir 52, 54 of heat transfer fluids and a plug air. More specifically, the valve 48 connects the conduit 44 to the reservoir 52 when it is open and the valve 50 connects the conduit 44 to the reservoir 54 when it is open.
  • the reservoir 52 is filled with a thermally insulating heat transfer liquid.
  • the reservoir 58 is filled with a heat transfer fluid capable of capturing and transporting large amounts of heat.
  • the liquid 56 has a thermal conductivity at 20 ° C, strictly less than 10 Wm-1.K-1 and preferably strictly less than 1 Wm-1.K-1.
  • the liquid 56 also has a low specific heat capacity, that is to say a heat capacity of less than 900 J.Kg-1.K-1.
  • the liquid 56 is silica or pieces of solid silica mixed in a liquid.
  • the liquid 58 has a high mass capacity, that is to say greater than 1000 J.Kg-1.K-1 and, preferably, greater than 1500 J.Kg-1.K- 1.
  • the liquid 58 is water.
  • the end of the conduit 46 opposite the port 40 is fluidly connected to a controllable pump 60.
  • the position of this pump 60 is for illustrative purposes only. Other appropriate positions of this pump may be determined by those skilled in the art.
  • the output of this pump 60 is connected via a conduit 62 to an inlet of a radiator 64.
  • the radiator 64 is able to cool the coolant which is currently circulating in the conduit 62.
  • An output of the radiator 64 is fluidly connected to two controllable valves 66 and 68 for selectively reinjecting the coolant either in the reservoir 52 or in the reservoir 54.
  • the apparatus 32 also comprises a control unit 70 able to control the various equipment of the apparatus 32 and in particular the pump 60 and the valves 48, 50, 51, 66 and 68. More specifically, the unit 70 is suitable for control the valves 48, 50, 51, 66 and 68 to replace the flow of liquid 56 that currently flows in the conduits 44 and 46 by the liquid 58 and vice versa.
  • the figure 3 shows in more detail the front face 34 of the refrigerant block 30.
  • This front face has several grooves 80 allowing the sand 28 to be inserted between this face 34 and the lost model on which it is supported.
  • the lost model is realized. More precisely, during this step 90, the two parts 6 and 8 of this lost model are realized.
  • this assembly is called "cluster". Then, during a step 94, this cluster is coated with refractory material to obtain the layer to prevent the molten metal from mixing with the sand 28.
  • the cluster covered with the layer of refractory material is placed inside the tank 26. More specifically, during this installation, the refrigerating block 34 is used as a stop allowing a precise positioning of the cluster.
  • the sand 28 is added to the tank 26 and vibrated to fill all the interstices of the lost model.
  • the vibrations enable the sand 28 to be inserted in the grooves 80 of the refrigerating block 30, which allows to fill interstices or recesses of the lost model whose openings open opposite the face 34.
  • the unit 70 controls the filling of the cavity 36 with the liquid 56.
  • the valves 48 and 66 are open and the pump 60 is actuated to draw the liquid 56 into the cavity 36.
  • the molten metal is cast inside the mold 2. More specifically, the molten metal is poured into the cup 22 and then flows inside the pouring chute 20 . When the molten metal comes into contact with the polystyrene, the polystyrene turns into gas and the gas is evacuated through the same channels that allowed the arrival of the molten metal. Gradually, the molten metal fills the entire descent 20 and flows into the casting attacks. Once all the polystyrene present in the attacks 18 and in the descent 20 has been sublimed, the molten metal continues to flow inside the lost model. Thus, progressively, during step 102, the molten metal replaces the polystyrene of parts 6 and 8 of the lost model.
  • the apparatus 32 permanently maintains liquid 56 in the cavity 36 so as to reduce the heat flow through the face 34.
  • the pump 46 is stopped to maintain the cavity 36 filled without circulating the liquid 56 inside the cavity 36.
  • the casting of the molten metal is stopped.
  • the interval T1 is determined experimentally and corresponds to the time necessary for the footprints in which parts 6 and 8 of the lost model were housed to be completely filled by the molten metal.
  • the unit 70 controls the evacuation of the liquid 56 from the cavity 36.
  • the valve 48 is closed, the valve 51 is open, the valve 66 remains open and the pump 60 is actuated until the liquid 56 has completely evacuated the cavity 36.
  • the unit 70 controls the filling of the cavity 36 with the liquid 58.
  • the valves 50 and 68 are open.
  • the valve 44 is closed and the pump 60 is actuated.
  • the liquid 58 is sucked until the cavity 36 is completely filled.
  • the pump 60 is kept in action so that the liquid 58 circulates continuously in the cavity 36. This increases the intensity of the heat flow through the face 34 which allows to cool more effectively the metal during its solidification. The appearance of small metal grains is favored.
  • the circulation of the liquid 58 in the cavity 36 is maintained at a constant speed V1 during a predetermined time interval T2.
  • the interval T2 is determined experimentally to correspond to the time required for the molten metal to be completely solidified while having a temperature as close as possible to its melting temperature.
  • the speed V1 is not the maximum speed of circulation of the fluid in the cavity 36 and therefore does not correspond to the fastest possible cooling of the molten metal. Indeed, here, we do not try to reach the smallest possible size of metal grains.
  • the unit 70 accelerates the speed of circulation of the liquid 58 in the cavity 36 to reach a speed V2 strictly greater than the speed V1.
  • the unit 70 controls the pump 60.
  • This acceleration of the flow velocity of the liquid 58 in the cavity 36 further increases the intensity of the heat flow through the face 34.
  • the cooling of the metal so accelerates.
  • the unit 70 maintains the circulation of the liquid 58 with this accelerated speed for a predetermined time interval T3.
  • the interval T3 is determined experimentally to correspond to the time necessary for the temperature of the molded part reaches a demolding temperature. This step 112 accelerates the cooling of the molded part.
  • step 114 when the molded part has reached the demolding temperature, the sand and the layer of refractory material are removed.
  • a metal casting having a shape identical to that of the lost model is obtained.
  • the refrigerant block is in direct contact with the lost model.
  • the cooling block can be mechanically isolated from the lost model by a layer of sand.
  • the mold 2 may comprise more than one refrigerant block.
  • the materials used to create the liquid 56 or 58 may be endothermic materials such as for example a material containing iron oxide. Such materials can absorb heat very effectively.
  • One of the liquids 56 or 58 may also include a good thermal conductive material such as iron shot.
  • the thermal properties of the refrigerant block 30 can be varied continuously or stepwise.
  • the modification of the thermal properties of the refrigerating block 30 can be carried out, no longer according to a time elapsed since the beginning of the casting but according to data measured in real time using sensors.
  • at least one of these sensors measures a physical quantity representative of the temperature of the metal present in the mold 2.
  • one of these sensors measures the temperature of the heat transfer liquid.
  • a coolant gas can also be used such as air.
  • the radiator 64 may be omitted.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)
EP09166187A 2008-08-29 2009-07-23 Präzisionsgussverfahren und verlorenes Modell für dieses Verfahren Withdrawn EP2158987A1 (de)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
FR0855823A FR2935276B1 (fr) 2008-08-29 2008-08-29 Procede de moulage a modele perdu et moule pour ce procede

Publications (1)

Publication Number Publication Date
EP2158987A1 true EP2158987A1 (de) 2010-03-03

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EP09166187A Withdrawn EP2158987A1 (de) 2008-08-29 2009-07-23 Präzisionsgussverfahren und verlorenes Modell für dieses Verfahren

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EP (1) EP2158987A1 (de)
FR (1) FR2935276B1 (de)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011161347A1 (fr) * 2010-06-24 2011-12-29 Peugeot Citroën Automobiles SA Cuve de moulage en modele perdu
EP3539687A1 (de) * 2017-12-27 2019-09-18 Casa Maristas Azterlan Vorrichtung und verfahren zur verbesserten kühlung einer metallischen legierung in einer sandform
FR3123579A1 (fr) * 2021-06-08 2022-12-09 Psa Automobiles Sa Dispositif de moulage au sable avec procede a modele perdu

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB663479A (en) * 1949-05-23 1951-12-19 H A Howard Ltd Improvements relating to heating and cooling metal moulds
FR2685229A1 (fr) 1991-12-20 1993-06-25 Peugeot Procede de moulage en modele perdu et element refrigerant pour la mise en óoeuvre de ce procede.
DE102005032324A1 (de) * 2005-07-08 2007-01-11 gwk Gesellschaft Wärme Kältetechnik mbH Vorrichtung zur kontinuierlichen Temperierung der Spritzgieß- oder Druckgießform einer Spritzgieß- oder Druckgussanlage
US20070277952A1 (en) * 2006-05-30 2007-12-06 Vulcan Engineering Company Rapid localized directional solidification of liquid or semi-solid material contained by media mold

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB663479A (en) * 1949-05-23 1951-12-19 H A Howard Ltd Improvements relating to heating and cooling metal moulds
FR2685229A1 (fr) 1991-12-20 1993-06-25 Peugeot Procede de moulage en modele perdu et element refrigerant pour la mise en óoeuvre de ce procede.
DE102005032324A1 (de) * 2005-07-08 2007-01-11 gwk Gesellschaft Wärme Kältetechnik mbH Vorrichtung zur kontinuierlichen Temperierung der Spritzgieß- oder Druckgießform einer Spritzgieß- oder Druckgussanlage
US20070277952A1 (en) * 2006-05-30 2007-12-06 Vulcan Engineering Company Rapid localized directional solidification of liquid or semi-solid material contained by media mold

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2011161347A1 (fr) * 2010-06-24 2011-12-29 Peugeot Citroën Automobiles SA Cuve de moulage en modele perdu
FR2961724A1 (fr) * 2010-06-24 2011-12-30 Peugeot Citroen Automobiles Sa Cuve de moulage en modele perdu
EP3539687A1 (de) * 2017-12-27 2019-09-18 Casa Maristas Azterlan Vorrichtung und verfahren zur verbesserten kühlung einer metallischen legierung in einer sandform
FR3123579A1 (fr) * 2021-06-08 2022-12-09 Psa Automobiles Sa Dispositif de moulage au sable avec procede a modele perdu

Also Published As

Publication number Publication date
FR2935276A1 (fr) 2010-03-05
FR2935276B1 (fr) 2011-11-04

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