US3543284A - Process for casting single crystal shapes - Google Patents

Process for casting single crystal shapes Download PDF

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Publication number
US3543284A
US3543284A US714743A US3543284DA US3543284A US 3543284 A US3543284 A US 3543284A US 714743 A US714743 A US 714743A US 3543284D A US3543284D A US 3543284DA US 3543284 A US3543284 A US 3543284A
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United States
Prior art keywords
mold
smaller
single crystal
rate
chill plate
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Expired - Lifetime
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US714743A
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English (en)
Inventor
Larry W Sink
Bernard H Kear
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RTX Corp
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United Aircraft Corp
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Publication date
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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
    • 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

  • ABSTRACT OF THE DISCLOSURE A process for use in casting materials of single crystal in single and complex shapes wherein the process produces an increased heat extraction rate from the cast part, the rate also being compatible with a rate wh ch promotes the fastest growth consistent with forming sound single crystal materials.
  • This invention relates to a process for the casting of materials of simple or complex single crystal shapes.
  • the present invention herein described provides a process for casting alloy single crystal shapes while satisfying the foregoing criteria.
  • the process of the present invention is employed in a preferred mold construction wherein at least one smaller mold is positioned within a main mold.
  • the main mold comprises a ceramic tube, one open end of which is placed on a chill plate.
  • the geometry of this smaller mold is such that it contains a small opening therein, this opening generally being positioned at the bottom of the smaller mold and providing a communication means between the smaller mold and the main mold.
  • any shape mold can be used; that is a simple shape such as bars, rods, sheets, or wires; or a complex shape such as blades, vanes, or hollow components.
  • the smaller molds are positioned within the main mold such that the small opening in the smaller mold is above the chill plate, a preferred distance being one-half inch.
  • the axis of orientation of material within the smaller mold is a function of the axis of orientation of the directionally solidified metal, the orientation of the opening in the smaller mold and/or the orientation of the smaller mold within the main mold.
  • the process herein described By employing the process herein described, it becomes clear that the only restriction to heat transfer from the molten metal exists in the material forming the smaller mold. More specifically, the material forming the small opening in the small mold is a restriction to heat transfer from the metal in the mold to the chill plate.
  • the process described to this point provides an improvement in heat extraction over previously used methods of casting single crystals because of much simplified heat flow path. However, the process provides a further increase in the rate of heat extraction from the smaller mold. The upward advance of the liquid-solid interface within the smaller mold will lag behind that of the larger mold since there is no restriction to vertical heat extraction in the larger mold.
  • the metal in the larger mold is in direct contact with the outside of the smaller mold, heat flows through the walls of the smaller mold and then downward to the chill through the unrestricted volume of the larger mold.
  • the rate of growth of the solid metal in the larger mold can then be adjusted by regulating the heat input through the heater at the top of the mold to control the heat extraction from the smaller mold to provide the fastest growth rate consistent with the growth of sound single crystal material, largely independent of the shape or cross-section of the smaller mold.
  • the volume or mass within the main mold is greater than the volume or mass Within the smaller molds. Since the liquid-solid interface within the main mold initially moves at a faster rate than the liquid-solid interface within the smaller mold, the latter is at a higher temperature at any point along its length.
  • heat from the smaller mold is transferred to the larger mass within the main mold, establishing a relationship between the growth rate of the single crystal within the smaller mold and the growth rate of the directionally solidified alloy in the main mold. Since this mass is substantial with respect to the mass within the smaller mold, a more efiicient rate of heat extraction is possible, this rate being largely independent of the shape of the specimen being cast in the smaller mold.
  • the process described herein provides a method of efficiently extracting heat from a mold for casting materials in simple or complex single crystal shapes.
  • FIG. -1 is a schematic top sectional view of the preferred FIG. 2 is a vertical section of a preferred mold construction for use with the present invention.
  • FIGS. 1 and 2 a novel form of mold geometry is shown in FIGS. 1 and 2.
  • the mold construction described herein is particularly suited for use with any of the so-called super alloys as described for example in the VerSnyder patent, US. No. 3,260,505 and having the same assignee as this application. As therein noted, these alloys are generally adapted for the process known as directional solidification.
  • the mold construction herein described in adddition to the disclosure contained in the VerSnyder patent, employs the technique of forming Monocrystaloys as described in Piearcey Pat. 3,494,709.
  • tubular mold 4 compatible for use with the procedure described in the VerSnyder patent, is placed on a relatively cool, heat conductive and preferably water cooled plate 6.
  • Tubular mold is preferably made from a ceramic material from a conventional slurry of alumina or other high melting point refractory material in accordance with standard shell-molding techniques; and water for the chill plate 6 is carried through conduits 8.
  • one end of tube 4 rests on chill plate 6 and cooperates to form an enclosed cavity 10.
  • the end of tube 4 opposite chill plate 6 is open to receive molten metal.
  • the means for heating the mold to the desired temperature for casting are the means for heating the mold to the desired temperature for casting.
  • the cavity is surrounded by an electrical resistance heating coil 12 supplied with variable electrical current.
  • the cavity is surrounded by a graphite susceptor, not shown, and this in turn is surrounded by an induction coil supplied with high frequency electric current as is usual in an induction furnace.
  • the mold Prior to casting, the mold is heated to a desired temperature by supplying current to coil 12 and when the desired temperature has been attained, molten metal, heated to the proper temperature for casting, is poured into cavity 10.
  • the chill plate 6 is maintained at a relatively cool temperature by means of water circulating through conduits 8 so as to etsablish a temperature gradient within the molten metal filling cavity 10 as the metal solidifies.
  • a plurality of individual molds 16, 18, and 22 are positioned around the inner periphery of surface 23 of tube 4.
  • Each of these molds has a small opening 24, herein illustrated to be at the bottom of each mold, and is spaced above chill plate 6.
  • the metal begins to solidify it has a controlled columnar structure and by providing a small opening such as 24 in each of the individual molds 16, 18, 20 and 22, growth of a single crystal is promoted therein. Therefore, what is produced is in effect a large mass of controlled columnar structure surrounding relatively smaller masses of single crystal.
  • a significant feature about the construction of the individual molds is that the small opening 24 in each of the molds is the only restriction to heat transfer from each of the molds to chill plate 6. As a result of this, this type mold geometry would permit the heat Within the mold to be extracted at a faster rate than the previous mold constructions which use a double turn restriction as illustrated in the Piearcey Pat. 3,494,709.
  • the volume of tube 4 is substantially greater than the volume within each of molds 16, 18, 20 and 22. Therefore, a relatively greater mass surrounds molds 16, 18, 20 and 22 than is interior thereof. Now as the directional solidification proceeds, the liquidto-solid interface moves away from chill plate 6. As a result of the restriction to heat transfer from the individual molds 16, 18, 20 and 22 to chill plate 6 caused by opening 24, the liquid-solid interface interior of molds 16, 18, 20 and 22 is slower moving than that of the mass surrounding the molds.
  • any distance from the chill plate the solidification of the substantial mass within the tube will be higher than the solidification within molds 16, 18, 20 and 22.
  • the mass surrounding the molds is at a lower temperature, and heat will be extracted laterally from molds 16, 18, 20 and 22.
  • the individual molds are shown positioned above the chill plate. This is of importance in that it has been found that during the directional solidification process, the solidified metal adjacent the chill plate has a random crystal orientation. Accordingly, to get a single crystal with a preferred orientation, the individual molds should be positioned above the chill plate a distance sufiicient to avoid this growth zone. It is clear that individual molds may be positioned at the same height above the chill plate or they may be placed in a stepped arrangement thereabove. However, it has been found that an optimum spacing from the chill plate to the lowest individual mold should be about one-half inch.
  • a main mold comprising a ceramic tube on a chill plate; positioning at least one smaller mold in the interior of the main mold, the smaller mold having restriction means in communication with the main mold; spacing the restriction means above the chill plate; filling the main mold and smaller mold With molten metal; cooling the molten metal and unidirectionally solidifying the molten metal in a direction away from the chill plate;
  • a main mold comprising a ceramic tube on a chillplate
  • positioning the restriction means at the bottom of the smaller mold positioning the bottom of the smaller mold above the chill plate

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
  • Ceramic Products (AREA)
US714743A 1968-03-20 1968-03-20 Process for casting single crystal shapes Expired - Lifetime US3543284A (en)

Applications Claiming Priority (1)

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US71474368A 1968-03-20 1968-03-20

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US3543284A true US3543284A (en) 1970-11-24

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US714743A Expired - Lifetime US3543284A (en) 1968-03-20 1968-03-20 Process for casting single crystal shapes

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US (1) US3543284A (enrdf_load_stackoverflow)
DE (1) DE1912379A1 (enrdf_load_stackoverflow)
FR (1) FR1602773A (enrdf_load_stackoverflow)
GB (1) GB1250842A (enrdf_load_stackoverflow)
SE (1) SE347178B (enrdf_load_stackoverflow)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3598172A (en) * 1969-10-30 1971-08-10 United Aircraft Corp Process of casting with downward-unidirectional solidification
US4683936A (en) * 1984-05-16 1987-08-04 Trw Inc. Controlled solidification, method of distributing strengthening additives and maintaining a constant melt level
US5899257A (en) * 1982-09-28 1999-05-04 Societe Nationale D'etude Et De Construction De Moteurs D'aviation Process for the fabrication of monocrystalline castings
CN110695332A (zh) * 2019-10-17 2020-01-17 邳州市政隆建设有限公司 一种半自动化铸造机

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3260505A (en) * 1963-10-21 1966-07-12 United Aircraft Corp Gas turbine element
US3342455A (en) * 1964-11-24 1967-09-19 Trw Inc Article with controlled grain structure
US3376915A (en) * 1964-10-21 1968-04-09 Trw Inc Method for casting high temperature alloys to achieve controlled grain structure and orientation
US3417809A (en) * 1965-07-16 1968-12-24 United Aircraft Corp Method of casting directionally solidified articles

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3260505A (en) * 1963-10-21 1966-07-12 United Aircraft Corp Gas turbine element
US3376915A (en) * 1964-10-21 1968-04-09 Trw Inc Method for casting high temperature alloys to achieve controlled grain structure and orientation
US3342455A (en) * 1964-11-24 1967-09-19 Trw Inc Article with controlled grain structure
US3417809A (en) * 1965-07-16 1968-12-24 United Aircraft Corp Method of casting directionally solidified articles

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3598172A (en) * 1969-10-30 1971-08-10 United Aircraft Corp Process of casting with downward-unidirectional solidification
US5899257A (en) * 1982-09-28 1999-05-04 Societe Nationale D'etude Et De Construction De Moteurs D'aviation Process for the fabrication of monocrystalline castings
US4683936A (en) * 1984-05-16 1987-08-04 Trw Inc. Controlled solidification, method of distributing strengthening additives and maintaining a constant melt level
CN110695332A (zh) * 2019-10-17 2020-01-17 邳州市政隆建设有限公司 一种半自动化铸造机

Also Published As

Publication number Publication date
GB1250842A (enrdf_load_stackoverflow) 1971-10-20
SE347178B (enrdf_load_stackoverflow) 1972-07-31
DE1912379A1 (de) 1969-10-02
FR1602773A (enrdf_load_stackoverflow) 1971-01-25

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