EP0059550B1 - Procédé de coulée - Google Patents

Procédé de coulée Download PDF

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Publication number
EP0059550B1
EP0059550B1 EP82300767A EP82300767A EP0059550B1 EP 0059550 B1 EP0059550 B1 EP 0059550B1 EP 82300767 A EP82300767 A EP 82300767A EP 82300767 A EP82300767 A EP 82300767A EP 0059550 B1 EP0059550 B1 EP 0059550B1
Authority
EP
European Patent Office
Prior art keywords
mold
molten metal
rate
furnace
dendritic structure
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.)
Expired
Application number
EP82300767A
Other languages
German (de)
English (en)
Other versions
EP0059550A2 (fr
EP0059550A3 (en
Inventor
Constantine Vishnevsky
Thomas Alan Kolakowski
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.)
PCC Airfoils LLC
Original Assignee
PCC Airfoils LLC
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 PCC Airfoils LLC filed Critical PCC Airfoils LLC
Publication of EP0059550A2 publication Critical patent/EP0059550A2/fr
Publication of EP0059550A3 publication Critical patent/EP0059550A3/en
Application granted granted Critical
Publication of EP0059550B1 publication Critical patent/EP0059550B1/fr
Expired legal-status Critical Current

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Classifications

    • 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
    • B22D27/045—Directionally solidified castings

Definitions

  • the present invention relates to a method of making directionally solidified (DS) castings and more specifically to a method which reduces the time required to cast a directionally solidified article without reducing the quality of the cast product.
  • DS directionally solidified
  • a mold In casting directionally solidified articles from nickel-base superalloys, a mold is commonly positioned on a chill plate which is slowly withdrawn from a furnace to provide for controlled solidification of molten metal in the mold in a manner similar to that disclosed in US-A-3,700,023 and 3,714,977.
  • the mold can be withdrawn from the furnace at speeds of up to about 20 in/hr (50.8 cm/h) to generate acceptable columnar grain structures.
  • the specific speeds at which a particular article is withdrawn from the furnace are governed by the geometry of the article.
  • US-A-3,532,155 discloses an apparatus in which the mold and cooling plate are moved through a heat sink which is disposed immediately beneath the furnace.
  • US ⁇ A ⁇ 4,190,094 suggests varying the rate of withdrawal of the mold from a furnace as a function of the geometry of the article to be cast and other factors.
  • US-A-3714977 discloses the use of a radiation baffle which is supported on the chill plate during initial withdrawal of the chill plate and mold thereon from the furnace and thereafter is supported by stop means at the base of the furnace such that on further withdrawal of the chill plate and mold from the furnace the mold passes through the radiation baffle.
  • This US specification also discloses increasing the mold withdrawal speed from a first rate to a second rate and subsequently to the maximum rate permitted by the apparatus. However, no explanation of why the withdrawal rate is increased in this manner nor any indication of the factors which determine when the increases should occur are given.
  • An object of the present invention is to decrease the time required to form a directionally solidified (DS) casting without substantial coarsening of the columnar grains of the casting.
  • the invention relates to a method of casting a directionally solidified article in a mold cavity, said method comprising the steps of heating at least a portion of a mold in a furnace, pouring molten metal into a cavity in the mold, withdrawing the mold from the furnace at a first rate after having performed said step of pouring molten metal into the mold cavity, solidifying the molten metal in the mold cavity while performing said step of withdrawing the mold from the furnace at the first rate, said step of solidifying the metal in the mold cavity including the steps of forming a dendritic structure having molten metal in its interstices, solidifying portions of the molten metal in the interstices and continuing the formation of the dendritic structure until the dendritic structure reaches an upper end of the mold cavity while performing said step of solidifying portions of the molten metal in the interstices, and increasing the rate of solidification of the molten metal in the interstices of the dendritic structure when the dendritic structure reaches the upper end of the mold cavity,
  • a mold is initially withdrawn from a furnace relatively slowly and a dendritic structure grows upwardly toward the upper end of the mold cavity.
  • the uppermost interstices of this dendritic structure are filled with molten metal.
  • this region of the casting in which a skeleton of solid dendrite and liquid metal coexist is called the mushy zone.
  • the rate at which the mold is withdrawn from the furnace may be maintained substantially constant at the first rate until the dendritic structure reaches the upper end of the mold cavity.
  • the second rate of withdrawal may be greater than 30 in/hr (76.2 cm/hr).
  • the invention includes a method of casting an article having a relatively thick base and a relatively thin airfoil, said method comprising the steps of heating in a furnace at least a portion of a mold having a cavity having a configuration corresponding to the configuration of the article, an upper end portion of the cavity having a configuration corresponding to the configuration of the relatively thin airfoil of the article, pouring molten metal into the mold cavity, withdrawing the mold from the furnace at a first rate after having performed said step of pouring molten metal into the mold cavity, solidifying the molten metal in the mold cavity to form the relatively thick base of the blade while performing said step of withdrawing the mold from the furnace at the first rate, solidifying part of the molten metal in the upper end portion of the mold cavity to form a portion of the relatively thin air
  • the mold is slowly withdrawn from the furnace.
  • the rate of withdrawal of the mold from the furnace is increased to increase the speed of solidification of the molten metal remaining in the dendritic structure.
  • a mold 10 (Fig. 1) is preheated in a known furnace assembly 12 prior to pouring of molten metal into the mold.
  • the known furnace assembly 12 is provided with a refractory outer wall 16 which is surrounded by an induction heating coil 18.
  • a graphite susceptor wall 20 is enclosed by the outer wall 16 and is heated by the induction effect of the coil 18.
  • the furnace assembly 12 has a top plate 22 with an opening which may be provided with a funnel 24 through which molten metal is poured into the mold 10. It is contemplated that the entire furnace assembly 12 will be disposed within a vacuum.
  • the mold 10 has a pouring basin 32 through which molten metal enters a plurality of runners or passages 34 which are connected with a plurality of mold cavities 38 which are disposed in a circular array around the pouring basin 32.
  • a cylindrical heat shield 40 may be provided on the inside of the circular array of mold cavities 38.
  • the mold 10 is disposed on a copper chill plate 42.
  • the chill plate 42 promotes the directional solidification of molten metal in the mold cavities to provide a casting having a columnar grain structure with a grain orientation extending generally parallel to the longitudinal central axes (vertical axes) of the mold cavities 38.
  • the furnace 12 is of a known construction and may be constructed in accordance with US ⁇ A ⁇ 3,376,915; 3,700,023 and/or 3,714,977.
  • the rate of withdrawal of the mold is substantially increased. This results in relatively rapid solidification of the molten metal remaining in the interstices of the dendritic structure.
  • the rapid solidification of the molten metal that remains in the so-called mushy zone does not lead to coarsening of the grain structure.
  • the mold 10 is initially lowered from the position shown in Fig. 1 to the position shown in Fig. 2 at relatively slow speeds, that is speeds of approximately 20 in/h (50.8 cm/h) or less.
  • a dendritic structure 56 (Fig. 3) extends from a fully solidified body 58 of metal at the lower end portion of the mold cavity 38 to the upper end 54 of the mold cavity, the rate of downward movement of the chill plate is increased.
  • the interstices of the uppermost portions of the dendritic structure, the so-called mushy zone are filled with molten metal 60.
  • the rate of downward movement of the chill plate will be increased by a substantial extent when the dendritic structure 56 reaches the top of the mold cavity.
  • the amount by which the rate of withdrawal can be increased will depend upon the article being cast and the specific alloy of which it is formed.
  • the rate of withdrawal of the mold was increased from a speed of less than 20 in/hr (50.8 cm/h) to a speed of more than 34 in/hr (86.36 cm/ h) in casting a turbine blade formed of a nickel-base superalloy. Even though the rate of withdrawal of the mold 10 from the furnace assembly 12 was substantially increased, there was no objectionable coarsening of the grains of the cast article.
  • each of the mold cavities 38 has a lower portion with a configuration corresponding to the configuration of a starter block and the base of the blade.
  • Each of the mold cavities 38 also has a portion which extends upwardly from the base portion of the mold cavity and has a configuration corresponding to the configuration of the airfoil of the blade.
  • the airfoil of the blade has a substantially uniform thickness throughout its axial extent.
  • a mold cavity 38 with a partially cast blade 62 is shown schematically in Fig. 3.
  • the mold cavity 38 includes a lower end portion 64 which extends upwardly from an upper surface 66 of the chill plate 42. This lower end portion 64 of the mold cavity has a generally rectangular configuration.
  • an intermediate portion 68 Directly above the lower end portion 64 of the mold cavity 38 is an intermediate portion 68 having a configuration corresponding to the configuration of the base 70 of the blade 62.
  • An upper portion 72 of the mold cavity 38 extends upwardly from the intermediate portion 69 and has a configuration corresponding to the configuration of an airfoil portion 74 of the blade 62.
  • the mold cavity terminates at the upper end surface 54 which is connected with a runner 34 through which molten metal enters the mold cavity 38.
  • molten metal enters the mold cavity through the runner 34. Molten metal flows downwardly through the mold cavity 38 into engagement with the upper surface 66 of the chill plate 42. The molten metal immediately solidifies in the lower end portion 64 of the mold cavity 38.
  • the initially solidified molten metal has a random columnar grain structure next to the chill plate 42. However, the more favorably oriented grains grow rapidly upwardly from the chill plate 42 through a competitive growth zone from which the most favorably oriented grains emerge. These most favorably oriented grains enter the intermediate portion 68 of the mold cavity and solidify to initiate formation of a base portion 70 of the blade 62.
  • an upwardly extending dendritic structure 56 is formed.
  • This dendritic structure consists of a plurality of most favorably oriented grains which form a plurality of upwardly extending dendrites.
  • the molten metal in the interstices of the uppermost portions of dendritic structure solidifies to continue the formation of the base portion 70 of the blade 62.
  • the formation of the base portion 70 of the blade 62 is completed and continued solidification of the molten metal in the interstices of the dendritic structure initiates the formation of the airfoil 74.
  • the molten metal solidifies to form the lower end portion of the airfoil 74, the dendritic structure grows upwardly to the tip of the airfoil at the surface 54.
  • the base 70 of the airfoil has solidified and the lower portion of the airfoil 74 of the blade is solidified.
  • the upper portion of the airfoil of the blade has not fully solidified.
  • the interstices of the uppermost portions of the basic dendritic structure 56 are filled with molten metal 60.
  • This uppermost portion, containing both solid dendrites and interstices filled with molten metal is known in the art as the mushy zone.
  • the height of the mushy zone can be several inches (several amounts of 2.54 cm), with the specific distance being related to the alloy being cast and how sharp the vertical temperature drop or thermal gradient is in the solidifying metal.
  • the rate of withdrawal of the mold 10 from the furnace assembly 12 is substantially increased. Since the dendritic structure has been formed throughout the length of the airfoil 74 of the blade 62, there is coarsening of the grains at the upper end portion or tip of the airfoil due to the increased speed of withdrawal of the mold 10 from the furnace 12. This is true even though the airfoil 74 has a substantially uniform thickness throughout its length.
  • the blade 62 which results from this casting process has been illustrated schematically in Fig. 4.
  • the grains of the directionally solidified blade extend to the tip end of the airfoil without coarsening of the grains.
  • a mold of the same general construction as the mold 10 was withdrawn at a constant relatively high speed from the furnace assembly 12.
  • the resulting blade 80 had a relatively fine grain structure adjacent to its base 82 and at the lower end portion 84 of the airfoil 86.
  • the upper or airfoil tip portion 88 of the airfoil was very coarse grained and consisted of two or three crystals.
  • the coarse grained outer end portion of the airfoil 86 of the blade 80 makes the casting unacceptable for use in most circumstances.
  • the continuous fine grained structure of the blade 62 (Fig. 4) is quite acceptable for most purposes.
  • the fine grained structure of the blade 62 could have been obtained by withdrawing the mold from the furnace assembly 12 at a constant and relatively low speed.
  • an airfoil with the same fine grained structure as has been illustrated schematically in Fig. 4 for the blade 62 could have been obtained by withdrawing the mold 10 from the furnace 12 at a relatively low speeds of approximately 20 in/h (50.8 cm/h) or less.
  • the above described method embodying the present invention substantially decreases the amount of time required to cast the fine grained blade 62 by increasing the rate of withdrawal of the mold 10 from the furnace 12 when the dendritic structure 56 has grown from the solidified body of metal 58 at the lower end portion of the mold 10 to the upper end surface 54 of the mold.
  • the mold 10 is initially withdrawn at a relatively slow speeds from the furnace 12, that is at a speeds of less than about 20 in/hr (50.8 cm/h).
  • the speed of withdrawal of the mold 10 from the furnace 12 is increased to, for example, a speed of greater than 30 m/hr (76.2 cm/h) for example to 34 in/h (86.36 cm/h).
  • the embodiment decreases the time required to form a directionally solidified (DS) casting without substantial coarsening of the columnar grains of the casting.
  • This is accomplished by initially withdrawing a mold 10 from a furnace 12 at relatively slow speeds. At the mold 10 is slowly withdrawn from the furnace 12, a dendritic structure 56 grows upwardly toward the upper end 54 of the mold cavity 38. The interstices of this dendritic structure 56 are filled with molten metal. When the dendritic structure 56 reaches the upper end 54 of the mold cavity 38, the rate of withdrawal of the mold 10 from the furnace 12 is increased to increase the rate of solidification of the molten metal in the interstices of the dendritic structure 56.
  • a particularly advantageous use of such a method is the casting of blades 62 having relatively thick bases 70 and thin airfoils 74.
  • the mold 10 is slowly withdrawn from the furnace 12.
  • the rate of withdrawal of the mold 10 from the furnace 12 is increased to increase the speed of solidification of the molten metal in the dendritic structure.

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

Claims (4)

1. Un procédé de coulée d'un article solidifié directionnellement (62) dans une cavité de moule (38), ledit procédé comprenant les opérations consistant à chauffer au moins une partie d'un moule (10) dans un four (12), à verser du métal fondu dans une cavité du moule (38), à retirer le moule du four à une première vitesse après avoir réalisé ladite opération de versage du métal fondu dans la cavité du moule, à solidifier le métal fondu dans la cavité du moule tout en effectuant l'opération de retrait du moule du four à la première vitesse, ladite opération de solidification du métal dans le four comprenant les étapes consistant à former une structure dendritique (56) comportant du métal fondu dans ses interstices, à solidifier des parties du métal fondu dans les interstices et à poursuivre la formation de la structure dendritique jusqu'à ce que la structure dendritique atteigne l'extrémité supérieure (54) de la cavité du moule tout en effectuant ladite étape de solidification de parties du métal fondu dans les interstices, et à augmenter la vitesse de solidification du métal fondu dans les interstices de la structure dendritique lorsque la structure dendritique atteint l'extrémité supérieure de la cavité du moule, ladite étape d'augmentation de la vitesse de solidification du métal fondu comprenant l'étape consistant à augmenter la vitesse à laquelle le moule est retiré du four depuis une première vitesse jusqu'à une seconde vitesse quand la structure dendritique atteint l'extrémité supérieure de la cavité du moule.
2. Un procédé de coulée d'un article (62) ayant une base (70) relativement épaisse et un plan aérodynamique (74) relativement mince,, ledit procédé comprenant les opérations consistant à chauffer dans un four (12) au moins une partie d'un moule (10) comprenant une cavité (38) ayant une configuration correspondant à la configuration de l'article, une partie d'extrémité supérieure (72) de la cavité ayant une configuration correspondant à la configuration du plan aérodynamique relativement mince (74) de l'article, à verser du métal fondu dans la cavité du moule, à retirer le moule du four à une première vitesse après avoir effectuer ladite opération de versage du métal fondu dans la cavité du moule, à solidifier le métal fondu dans la cavité du moule pour former la base relativement épaisse de l'article tout en effectuant ladite opération de retrait du moule à partir du four à la première vitesse, à solidifier une partie du métal fondu dans la partie d'extrémité supérieure de la cavité du moule pour former une partie du plan aérodynamique relativement mince de l'article tout en poursuivant ladite opération de retrait du moule à partir du four, ladite opération de solidification du métal fondu pour former une partie du plan aérodynamique relativement mince comprenant l'étape consistant à étendre la structure dendritique (56) avec du métal fondu dans ses interstices vers le haut à partir du métal solidifié faisant partie du plan aérodynamique relativement mince tout en effectuant ladite opération de retrait du moule du four, à augmenter la vitesse à laquelle le moule est retiré du four à une seconde vitesse qui est supérieure à la première vitesse quand la structure dendritique s'étend en direction de l'extrémité supérieure (54) de la cavité du moule, et à solidifier le métal fondu dans les interstices de la structure dendritique pour terminer la formation du plan aérodynamique relativement mince tout en retirant le moule du four à une seconde vitesse.
3. Procédé selon la revendication 1 ou 2, comprenant en outre l'opération consistant à maintenir la vitesse à laquelle le moule est retiré du four sensiblement constante à la première vitesse, jusqu'à ce que la structure dendritique atteigne l'extrémité supérieure de la cavité du moule.
4. Procédé selon la revendication 1, 2 ou 3, dans lequel ladite seconde vitesse de retrait est supérieure à trente pouces par heure (76,2 cm/h).
EP82300767A 1981-02-27 1982-02-16 Procédé de coulée Expired EP0059550B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US23914381A 1981-02-27 1981-02-27
US239143 1994-05-06

Publications (3)

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EP0059550A2 EP0059550A2 (fr) 1982-09-08
EP0059550A3 EP0059550A3 (en) 1984-03-28
EP0059550B1 true EP0059550B1 (fr) 1987-07-01

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Family Applications (1)

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EP82300767A Expired EP0059550B1 (fr) 1981-02-27 1982-02-16 Procédé de coulée

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EP (1) EP0059550B1 (fr)
JP (1) JPS57199558A (fr)
CA (1) CA1196470A (fr)
DE (1) DE3276658D1 (fr)
IL (1) IL65013A (fr)

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60158970A (ja) * 1984-01-27 1985-08-20 Kawachi Alum Kogyo Kk 薄肉大面積の板状長尺製品の鋳造用鋳込み装置
DE69423061T2 (de) * 1993-08-06 2000-10-12 Hitachi, Ltd. Gasturbinenschaufel, Verfahren zur Herstellung derselben sowie Gasturbine mit dieser Schaufel
US5577547A (en) * 1994-04-28 1996-11-26 Precision Castparts Corp. Method of casting a metal article
GB0304327D0 (en) * 2003-02-26 2003-04-02 Rolls Royce Plc Component casting
US20090293994A1 (en) * 2008-05-30 2009-12-03 Konitzer Douglas G High thermal gradient casting with tight packing of directionally solidified casting
GB201601898D0 (en) 2016-02-03 2016-03-16 Rolls Royce Plc Apparatus for casting multiple components using a directional solidification process
CN111451485B (zh) * 2020-05-22 2021-11-16 安徽省繁昌县皖南阀门铸造有限公司 一种金属铸造用水冷设备

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3714977A (en) * 1971-07-23 1973-02-06 United Aircraft Corp Method and apparatus for the production of directionally solidified castings
US3895672A (en) * 1973-12-26 1975-07-22 United Aircraft Corp Integrated furnace method and apparatus for the continuous production of individual castings
JPS513307A (en) * 1974-06-29 1976-01-12 Minoru Nishizawa Kinzokuno kyureisochi
US3931847A (en) * 1974-09-23 1976-01-13 United Technologies Corporation Method and apparatus for production of directionally solidified components
JPS514186A (en) * 1974-12-20 1976-01-14 Nippon Soda Co 2*33 jihidoro 4hh1*33 benzookisajinkeikagobutsuno seizohoho

Also Published As

Publication number Publication date
JPS57199558A (en) 1982-12-07
CA1196470A (fr) 1985-11-12
EP0059550A2 (fr) 1982-09-08
IL65013A (en) 1986-08-31
IL65013A0 (en) 1982-04-30
DE3276658D1 (en) 1987-08-06
EP0059550A3 (en) 1984-03-28

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