EP3335817A1 - Casting method and cast article - Google Patents
Casting method and cast article Download PDFInfo
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- EP3335817A1 EP3335817A1 EP17205764.8A EP17205764A EP3335817A1 EP 3335817 A1 EP3335817 A1 EP 3335817A1 EP 17205764 A EP17205764 A EP 17205764A EP 3335817 A1 EP3335817 A1 EP 3335817A1
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- European Patent Office
- Prior art keywords
- partially
- mold
- withdrawal
- withdrawing
- casting method
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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
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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
- B22D27/20—Measures not previously mentioned for influencing the grain structure or texture; Selection of compositions therefor
Definitions
- the present invention is directed to a casting method and cast article. More specifically, the present invention is directed to a casting method for reducing or eliminating freckle grains and a cast article formed therefrom.
- Various components such as turbine buckets for gas turbine engines, are often formed by directional solidification (DS)/single crystal (SC) casting techniques. More specifically, many components are often formed by a casting "withdrawal" technique where a melt-filled investment mold is withdrawn from a casting furnace. Withdrawing the melt-filled investment mold from the casting furnace permits a molten metal or alloy in the mold to cool and solidify, forming the component within the mold.
- DS solidification
- SC single crystal
- Freckle grains are formed due to interdendritic fluid flow, which may result in equiaxed phases surrounded by eutectic phases. Freckle grains are considered undesirable features and may have unacceptable weakness, particularly in the form of reduced fatigue strength.
- a casting method including providing a casting furnace, the casting furnace comprising a withdrawal region in a lower end, positioning a mold within the casting furnace, positioning a molten material in the mold, partially withdrawing the mold a withdrawal distance through the withdrawal region in the casting furnace, the withdrawal distance providing a partially withdrawn portion, at least partially solidifying the partially withdrawn portion, then reinserting at least a portion of the partially withdrawn portion into the casting furnace through the withdrawal region, at least partially re-melting the partially withdrawn portion, and then completely withdrawing the mold from the casting furnace through the withdrawal region to produce a directionally solidified or single crystal cast article.
- the at least partially re-melting the partially withdrawn portion reduces or eliminates freckle grains from the partially withdrawn portion.
- a casting method includes providing a casting furnace, the casting furnace comprising a withdrawal region in a lower end, positioning a mold within the casting furnace, positioning a molten material in the mold, partially withdrawing the mold through the withdrawal region in the casting furnace for a withdrawal time to provide a partially withdrawn portion, at least partially solidifying the partially withdrawn portion, reinserting at least a portion of the partially withdrawn portion into the casting furnace through the withdrawal region, at least partially re-melting the partially withdrawn portion, and then completely withdrawing the mold from the casting furnace through the withdrawal region to produce a directionally solidified or single crystal cast article.
- the at least partially re-melting the partially withdrawn portion reduces or eliminates freckle grains from the partially withdrawn portion.
- a directionally solidified or single crystal cast article includes a directionally solidified or single crystal microstructure and an occurrence of freckle grains corresponding to being formed by a process comprising partially withdrawing to solidify a portion of a withdrawn portion, reinserting to at least partially re-melt the withdrawn portion, and completely withdrawing a mold from a casting furnace to form the directionally solidified or single crystal cast article.
- Embodiments of the present disclosure in comparison to casting methods and cast articles not using one or more of the features disclosed herein, decrease or eliminate freckle grains in cast articles, increase efficiency of casting article, decrease casting costs, or a combination thereof.
- a casting method 100 includes providing a casting furnace 200 (step 110), positioning a mold 210 within the casting furnace 200 (step 120), and positioning a molten material 220 in the mold 210 (step 130).
- step 140 partially withdrawing the mold 210 including the molten material 220 a withdrawal distance 217 through a withdrawal region 205, for example, according to one embodiment, in a lower end 201 of the casting furnace 200, provides a partially withdrawn portion 213.
- the molten material 220 in the partially withdrawn portion 213 at least partially solidifies to form a solidified portion 215.
- the casting method 100 includes holding the mold 210 at the withdrawal distance 217 for a partial withdrawal hold time, then reinserting (step 150) at least a portion of the partially withdrawn portion 213 into the casting furnace 200 through the withdrawal region 205 to form a reinserted portion.
- the partial withdrawal hold time includes any suitable duration, such as, but not limited to, up to about 5 minutes, between about 15 seconds and about 5 minutes, between about 30 seconds and about 5 minutes, or any combination, sub-combination, range, or sub-range thereof.
- the reinserting (step 150) at least partially re-melts the solidified portion 215 to reduce or eliminate freckle grains 214 (see FIG.
- the reinserting (step 150) is followed by holding the reinserted portion within the casting furnace 200 for a reinsertion hold time, then completely withdrawing (step 160) the mold 210 from the casting furnace 200 to crystallize the molten material 220 and form a cast article 300.
- the reinsertion hold time includes any suitable duration, such as, but not limited to, up to about 5 minutes, between about 15 seconds and about 5 minutes, between about 30 seconds and about 5 minutes, or any combination, sub-combination, range, or sub-range thereof.
- the partial withdrawal hold time and the reinsertion hold time are the same, similar, substantially similar, or different.
- the casting furnace 200 includes any suitable casting furnace for receiving the mold 210 (see FIG. 2 ), and maintaining a temperature of the molten material 220 (see FIG. 3 ) at or above a molten material crystallization temperature.
- One suitable casting furnace includes, but is not limited to, a directional solidification casting furnace.
- the casting furnace 200 receives and/or pre-heats the mold 210 prior to positioning the molten material 220 in the mold 210 (step 130).
- the casting furnace 200 receives and/or pre-heats a plurality of molds 210.
- gaps are formed between the plurality of molds 210 within the casting furnace 200.
- positioning of the molds 210 includes, but is not limited to, vertical indexing, calculated guiding, thermally semi-insulating the gaps, or a combination thereof.
- the molten material 220 is then introduced into the mold 210 through an aperture 206 in the casting furnace 200.
- the aperture 206 includes any suitable aperture, such as, but not limited to, a hole in an upper end 202 of the furnace 200, a pipe, a funnel, or a combination thereof.
- the mold 210 includes any suitable mold for receiving the molten material 220 and forming the cast article 300.
- the mold 210 includes a ceramic investment shell mold having a pour cup in communication with one or more cavities corresponding to a shape of the cast article 300.
- the molten material 220 includes any material suitable for casting, and is selected based upon the cast article 300 to be formed.
- the molten material 220 for forming a turbine bucket includes any material capable of directional solidification and/or single crystal formation. Suitable materials include, but are not limited to, metals, superalloys (for example, nickel, cobalt, or iron base superalloys), or a combination thereof.
- the molten material 220 has a composition, by weight, of about 9.8% Cr, about 7.5% Co, about 1.5% Mo, about 6% W, about 4.8% Ta, about 0.5% Nb, about 4.2% Al, about 3.6% Ti, about 0.08% C, about 0.01% B, about 0.1% Hf, and a balance of Ni.
- the partially withdrawing (step 140) of the mold 210 the withdrawal distance 217 exposes the molten material 220 in the partially withdrawn portion 213 to reduced temperatures outside of the casting furnace 200.
- the reduced temperatures outside the casting furnace 200 cool the molten material 220 within the partially withdrawn portion 213.
- Cooling the molten material 220 at least partially solidifies the molten material 220 to form the solidified portion 215 within the partially withdrawn portion 213.
- the solidification shrinks the molten material 220, increasing a density of the solidified material and forming the freckle grains 214 within the solidified portion 215.
- interdendritic fluid flow forms the freckle grains 214.
- Various characteristics, such as, but not limited to, size and/or shape of the mold 210 facilitate increases or decreases in the occurrence of freckle grains 214 in the solidified portion 215.
- the withdrawal distance 217 is selected to correspond with at least one area of the cast article 300 that includes increased freckle grain forming characteristics, such as, but not limited to, initially withdrawn sections, sections including increased thickness, uninterrupted sections, or a combination thereof.
- the withdrawal distance 217 corresponds to a bucket tip shroud of the turbine bucket.
- the withdrawal distance 217 includes, but is not limited to, between about 0.250 inches (about 0.635 cm) and about 6 inches (about 15.24 cm), between about 0.250 inches (about 0.635 cm) and about 3 inches (about 7.62 cm), between about 0.250 inches (about 0.635 cm) and about 1 inch
- the partially withdrawn portion 213 is reinserted (step 150) into the casting furnace 200.
- the reinserting (step 150) of the partially withdrawn portion 213 at least partially re-melts the solidified material formed in the solidified portion 215 to reduce or eliminate the freckle grains 214.
- the molten material 220 which previously had formed the freckle grains 214 solidifies during the completely withdrawing (step 160) of the mold 210 so as to reduce or eliminate the occurrence of freckle grains 214 in the cast article 300.
- the casting method 100 reduces or eliminates the occurrence of freckle grains 214 without post casting freckle grain treatments, such as, but not limited to, blending away the freckle grains 214.
- Suitable partial withdrawal rates include, but are not limited to, between about 1 inch/hour (about 2.54 cm/hour) and about 30 inches/hour (about 76.2 cm/hour), between about 1 inch/hour (about 2.54 cm/hour) and about 15 inches/hour (about 38.1 cm/hour), between about 1 inch/hour (about 2.54 cm/hour) and about 10 inches/hour (about 25.4 cm/hour), between about 1 inch/hour (about 2.54 cm/hour) and about 7 inches/hour (about 17.8 cm/hour), or any combination, sub-combination, range, or sub-range thereof.
- the partial withdrawal rate facilitates a type and/or amount of crystallization formed during the solidification of the solidified portion 215.
- decreasing the partial withdrawal rate increases a duration for exposure of the partially withdrawn portion 213 to the reduced temperature outside of the casting furnace 200. The increased exposure increases the amount of crystallization formed during the solidification of the solidified portion 215.
- the mold 210 is withdrawn from the casting furnace 200 at a complete withdrawal rate.
- Suitable complete withdrawal rates include, but are not limited to, between about 1 inch/hour (about 2.54 cm/hour) and about 30 inches/hour (about 76.2 cm/hour), between about 1 inch/hour (about 2.54 cm/hour) and about 15 inches/hour (about 38.1 cm/hour), between about 1 inch/hour (about 2.54 cm/hour) and about 10 inches/hour (about 25.4 cm/hour), between about 1 inch/hour (about 2.54 cm/hour) and about 7 inches/hour (about 17.8 cm/hour), or any combination, sub-combination, range, or sub-range thereof.
- the complete withdrawal rate facilitates a type and/or rate of crystallization in the cast article 300.
- the complete withdrawal rate facilitates increased amounts of either directional or single-crystal solidification.
- the reinsertion rate is equivalent to any of the suitable partial or complete withdrawal rates disclosed herein.
- the rate of reinsertion is less than the suitable partial or complete withdrawal rates disclosed herein.
- the rate of reinsertion is greater than the suitable partial or complete withdrawal rates disclosed herein.
- suitable reinsertion rates include, but are not limited to, between about 1 inch/hour (about 2.54 cm/hour) and about 30 inches/hour (about 76.2 cm/hour), between about 1 inch/hour (about 2.54 cm/hour) and about 15 inches/hour (about 38.1 cm/hour), between about 1 inch/hour (about 2.54 cm/hour) and about 10 inches/hour (about 25.4 cm/hour), between about 1 inch/hour (about 2.54 cm/hour) and about 7 inches/hour (about 17.8 cm/hour), or any combination, sub-combination, range, or sub-range thereof.
- the partial withdrawal rate, the complete withdrawal rate, and/or the reinsertion rate are automated by any suitable technique throughout the casting method 100.
- Suitable techniques of the automation include, but are not limited to, providing transitions between the partially withdrawing (step 140), the reinserting (step 150), and/or the completely withdrawing (step 160), automatically reversing the partially withdrawing (step 140) to provide the reinserting (step 150), automatically reversing the reinserting (step 150) to provide the completely withdrawing (step 160), varying the partial withdrawal rate, the reinsertion rate, and/or the complete withdrawal rate, adjusting for variations in temperature within the casting furnace 200, adjusting for the area of the cast article 300 that includes increased freckle grain 214 forming characteristics, or a combination thereof.
- the partial withdrawal rate, the reinsertion rate, and/or the complete withdrawal rate are maintained throughout each step (with the exception of an acceleration to begin each step and a deceleration to end each step).
- the partial withdrawal rate, the reinsertion rate, and the complete withdrawal rate are about 5 inches/hour (about 12.7 cm).
- at least one of the partial withdrawal rate, the reinsertion rate, and the complete withdrawal rate is varied throughout the casting method 100.
- Varying throughout the casting method 100 includes, but is not limited to, between steps (for example, between the partially withdrawing (step 140), the reinserting (step 150), and/or the completely withdrawing (step 160)), during at least one step, corresponding to the area of the cast article 300 that includes increased freckle grain 214 forming characteristics, or a combination thereof.
- the partial withdrawal rate and the complete withdrawal rate are about 3 inches/hour (about 7.6 cm/hour), while the reinsertion rate is about 10 inches/hour (about 25.4 cm/hour).
- the casting method 100 includes repeating (step 155) of the partially withdrawing (step 140) and/or the reinserting (step 150) of the mold 210.
- the partially withdrawing (step 140) exposes a previously-unexposed portion 413
- the reinserting (step 150) at least partially re-melts the solidified portion 215 within a reinsertion segment of the previously-unexposed portion 413.
- the reinsertion segment includes, but is not limited to, all, or substantially all, of the previously-unexposed portion 413, less than the entire previously-unexposed portion 413, the area of the cast article 300 that includes increased freckle grain 214 forming characteristics, or a combination thereof.
- the partially withdrawing (step 140) exposes the previously-unexposed portion 413 of about 1 inch (about 2.54 cm), including the reinsertion segment of about 0.5 inches (about 1.27 cm) corresponding to an area of increased thickness.
- the re-melting of solidified portion 215 within the reinsertion segment reduces or eliminates the freckle grains 214 formed therein.
- the partially withdrawing (step 140) exposes the partially withdrawn portion 213 of about 0.5 inches (about 1.27 cm), and the reinserting (step 150) partially re-melts the solidified portion 215 within the partially withdrawn portion 213.
- the repeating (step 155) of the partially withdrawing (step 140) exposes the partially withdrawn portion 213 of about 0.5 inches (about 1.27 cm), including the solidified portion 215 that has been partially re-melted, as well as the previously-unexposed portion 413 of about 0.5 inches (about 1.27 cm).
- step 155) of the reinserting (step 150) then re-melts the solidified portion 215 formed within the previously-unexposed portion 413 without re-melting the solidified portion 215 within the partially withdrawn portion 213 that has been partially re-melted.
- the casting method 100 includes partially withdrawing (step 140) the mold 210 with the molten material 220 for a withdrawal time.
- the withdrawal time includes any suitable amount of time corresponding to formation of the solidified portion 215. Suitable amounts of time include, but are not limited to, up to about 2 hours, up to about 1.5 hours, up to about 1 hour, between about 1 hour and about 2 hours, up to about 0.5 hours, or any combination, sub-combination, range, or sub-range thereof.
- the partial withdrawal rate during the withdrawal time includes any suitable partial withdrawal rate disclosed herein.
- the partial withdrawal rate during the withdrawal time includes, but is not limited to, a constant rate, a pre-set variation in the rate of withdrawal, a progressive rate, or a combination thereof.
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Abstract
Description
- This application relates to and claims the benefit of
U.S. Patent Application No. 14/165,719, filed January 28, 2014 - The present invention is directed to a casting method and cast article. More specifically, the present invention is directed to a casting method for reducing or eliminating freckle grains and a cast article formed therefrom.
- Various components, such as turbine buckets for gas turbine engines, are often formed by directional solidification (DS)/single crystal (SC) casting techniques. More specifically, many components are often formed by a casting "withdrawal" technique where a melt-filled investment mold is withdrawn from a casting furnace. Withdrawing the melt-filled investment mold from the casting furnace permits a molten metal or alloy in the mold to cool and solidify, forming the component within the mold.
- As the molten metal or alloy cools a thermal gradient across the solid/liquid interface which is too low, or an incline of the interface compared to the horizontal which is too high, may lead to the formation of freckle grains. Freckle grains are formed due to interdendritic fluid flow, which may result in equiaxed phases surrounded by eutectic phases. Freckle grains are considered undesirable features and may have unacceptable weakness, particularly in the form of reduced fatigue strength.
- In one exemplary embodiment, a casting method including providing a casting furnace, the casting furnace comprising a withdrawal region in a lower end, positioning a mold within the casting furnace, positioning a molten material in the mold, partially withdrawing the mold a withdrawal distance through the withdrawal region in the casting furnace, the withdrawal distance providing a partially withdrawn portion, at least partially solidifying the partially withdrawn portion, then reinserting at least a portion of the partially withdrawn portion into the casting furnace through the withdrawal region, at least partially re-melting the partially withdrawn portion, and then completely withdrawing the mold from the casting furnace through the withdrawal region to produce a directionally solidified or single crystal cast article. The at least partially re-melting the partially withdrawn portion reduces or eliminates freckle grains from the partially withdrawn portion.
- In another exemplary embodiment, a casting method includes providing a casting furnace, the casting furnace comprising a withdrawal region in a lower end, positioning a mold within the casting furnace, positioning a molten material in the mold, partially withdrawing the mold through the withdrawal region in the casting furnace for a withdrawal time to provide a partially withdrawn portion, at least partially solidifying the partially withdrawn portion, reinserting at least a portion of the partially withdrawn portion into the casting furnace through the withdrawal region, at least partially re-melting the partially withdrawn portion, and then completely withdrawing the mold from the casting furnace through the withdrawal region to produce a directionally solidified or single crystal cast article. The at least partially re-melting the partially withdrawn portion reduces or eliminates freckle grains from the partially withdrawn portion.
- In another exemplary embodiment, a directionally solidified or single crystal cast article includes a directionally solidified or single crystal microstructure and an occurrence of freckle grains corresponding to being formed by a process comprising partially withdrawing to solidify a portion of a withdrawn portion, reinserting to at least partially re-melt the withdrawn portion, and completely withdrawing a mold from a casting furnace to form the directionally solidified or single crystal cast article.
- Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
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FIG. 1 is a flow chart of a casting method according to an embodiment of the disclosure. -
FIG. 2 shows a process view of a casting method according to an embodiment of the disclosure. -
FIG. 3 shows an enhanced view of a casting method according to an embodiment of the disclosure. -
FIG. 4 shows an enhanced view of a casting method including multiple reinsertions according to an embodiment of the disclosure. - Wherever possible, the same reference numbers will be used throughout the drawings to represent the same parts.
- Provided are a casting method and a cast article. Embodiments of the present disclosure, in comparison to casting methods and cast articles not using one or more of the features disclosed herein, decrease or eliminate freckle grains in cast articles, increase efficiency of casting article, decrease casting costs, or a combination thereof.
- Referring to
FIGS. 1-3 , acasting method 100 includes providing a casting furnace 200 (step 110), positioning amold 210 within the casting furnace 200 (step 120), and positioning amolten material 220 in the mold 210 (step 130). Next, partially withdrawing (step 140) themold 210 including the molten material 220 awithdrawal distance 217 through awithdrawal region 205, for example, according to one embodiment, in alower end 201 of thecasting furnace 200, provides a partially withdrawnportion 213. Themolten material 220 in the partially withdrawnportion 213 at least partially solidifies to form asolidified portion 215. - After the partially withdrawing (step 140), in one embodiment, the
casting method 100 includes holding themold 210 at thewithdrawal distance 217 for a partial withdrawal hold time, then reinserting (step 150) at least a portion of the partially withdrawnportion 213 into thecasting furnace 200 through thewithdrawal region 205 to form a reinserted portion. The partial withdrawal hold time includes any suitable duration, such as, but not limited to, up to about 5 minutes, between about 15 seconds and about 5 minutes, between about 30 seconds and about 5 minutes, or any combination, sub-combination, range, or sub-range thereof. The reinserting (step 150) at least partially re-melts thesolidified portion 215 to reduce or eliminate freckle grains 214 (seeFIG. 3 ), for example, formed in thesolidified portion 215 during the partially withdrawing (step 140). The reinserting (step 150) is followed by holding the reinserted portion within thecasting furnace 200 for a reinsertion hold time, then completely withdrawing (step 160) themold 210 from thecasting furnace 200 to crystallize themolten material 220 and form acast article 300. The reinsertion hold time includes any suitable duration, such as, but not limited to, up to about 5 minutes, between about 15 seconds and about 5 minutes, between about 30 seconds and about 5 minutes, or any combination, sub-combination, range, or sub-range thereof. The partial withdrawal hold time and the reinsertion hold time are the same, similar, substantially similar, or different. - Referring to
FIGS. 2-3 , thecasting furnace 200 includes any suitable casting furnace for receiving the mold 210 (seeFIG. 2 ), and maintaining a temperature of the molten material 220 (seeFIG. 3 ) at or above a molten material crystallization temperature. One suitable casting furnace includes, but is not limited to, a directional solidification casting furnace. In one embodiment, thecasting furnace 200 receives and/or pre-heats themold 210 prior to positioning themolten material 220 in the mold 210 (step 130). In another embodiment, thecasting furnace 200 receives and/or pre-heats a plurality ofmolds 210. In a further embodiment, gaps are formed between the plurality ofmolds 210 within thecasting furnace 200. To facilitate increased control of temperatures within the plurality ofmolds 210, positioning of themolds 210 includes, but is not limited to, vertical indexing, calculated guiding, thermally semi-insulating the gaps, or a combination thereof. Themolten material 220 is then introduced into themold 210 through anaperture 206 in thecasting furnace 200. Theaperture 206 includes any suitable aperture, such as, but not limited to, a hole in anupper end 202 of thefurnace 200, a pipe, a funnel, or a combination thereof. - The
mold 210 includes any suitable mold for receiving themolten material 220 and forming thecast article 300. For example, in one embodiment, themold 210 includes a ceramic investment shell mold having a pour cup in communication with one or more cavities corresponding to a shape of thecast article 300. Themolten material 220 includes any material suitable for casting, and is selected based upon thecast article 300 to be formed. For example, themolten material 220 for forming a turbine bucket includes any material capable of directional solidification and/or single crystal formation. Suitable materials include, but are not limited to, metals, superalloys (for example, nickel, cobalt, or iron base superalloys), or a combination thereof. In another example, themolten material 220 has a composition, by weight, of about 9.8% Cr, about 7.5% Co, about 1.5% Mo, about 6% W, about 4.8% Ta, about 0.5% Nb, about 4.2% Al, about 3.6% Ti, about 0.08% C, about 0.01% B, about 0.1% Hf, and a balance of Ni. - Referring to
FIG. 3 , the partially withdrawing (step 140) of themold 210 thewithdrawal distance 217 exposes themolten material 220 in the partially withdrawnportion 213 to reduced temperatures outside of thecasting furnace 200. The reduced temperatures outside thecasting furnace 200 cool themolten material 220 within the partially withdrawnportion 213. Cooling themolten material 220 at least partially solidifies themolten material 220 to form thesolidified portion 215 within the partially withdrawnportion 213. The solidification shrinks themolten material 220, increasing a density of the solidified material and forming thefreckle grains 214 within the solidifiedportion 215. As solidification continues, interdendritic fluid flow forms thefreckle grains 214. Various characteristics, such as, but not limited to, size and/or shape of themold 210 facilitate increases or decreases in the occurrence offreckle grains 214 in thesolidified portion 215. - In one embodiment, the
withdrawal distance 217 is selected to correspond with at least one area of thecast article 300 that includes increased freckle grain forming characteristics, such as, but not limited to, initially withdrawn sections, sections including increased thickness, uninterrupted sections, or a combination thereof. For example, in another embodiment, thewithdrawal distance 217 corresponds to a bucket tip shroud of the turbine bucket. Thewithdrawal distance 217 includes, but is not limited to, between about 0.250 inches (about 0.635 cm) and about 6 inches (about 15.24 cm), between about 0.250 inches (about 0.635 cm) and about 3 inches (about 7.62 cm), between about 0.250 inches (about 0.635 cm) and about 1 inch - (about 2.54 cm), between about 0.250 inches (about 0.635 cm) and about 0.750 inches (about 1.910 cm), between about 0.250 inches (about 0.635 cm) and about 0.500 inches (about 1.270 cm), or any combination, sub-combination, range, or sub-range thereof. After the
withdrawal distance 217 is reached, the partially withdrawnportion 213 is reinserted (step 150) into thecasting furnace 200. - The reinserting (step 150) of the partially withdrawn
portion 213 at least partially re-melts the solidified material formed in the solidifiedportion 215 to reduce or eliminate thefreckle grains 214. Themolten material 220 which previously had formed thefreckle grains 214 solidifies during the completely withdrawing (step 160) of themold 210 so as to reduce or eliminate the occurrence offreckle grains 214 in thecast article 300. By reducing or eliminating the occurrence offreckle grains 214 during the partially withdrawing (step 140) and the reinserting (step 150), thecasting method 100 reduces or eliminates the occurrence offreckle grains 214 without post casting freckle grain treatments, such as, but not limited to, blending away thefreckle grains 214. - During the partially withdrawing (step 140), the
mold 210 is withdrawn from the castingfurnace 200 at a partial withdrawal rate. Suitable partial withdrawal rates include, but are not limited to, between about 1 inch/hour (about 2.54 cm/hour) and about 30 inches/hour (about 76.2 cm/hour), between about 1 inch/hour (about 2.54 cm/hour) and about 15 inches/hour (about 38.1 cm/hour), between about 1 inch/hour (about 2.54 cm/hour) and about 10 inches/hour (about 25.4 cm/hour), between about 1 inch/hour (about 2.54 cm/hour) and about 7 inches/hour (about 17.8 cm/hour), or any combination, sub-combination, range, or sub-range thereof. In another embodiment, the partial withdrawal rate facilitates a type and/or amount of crystallization formed during the solidification of the solidifiedportion 215. For example, during the partially withdrawing (step 140) of themold 210, decreasing the partial withdrawal rate increases a duration for exposure of the partially withdrawnportion 213 to the reduced temperature outside of the castingfurnace 200. The increased exposure increases the amount of crystallization formed during the solidification of the solidifiedportion 215. - During the completely withdrawing (step 150), the
mold 210 is withdrawn from the castingfurnace 200 at a complete withdrawal rate. Suitable complete withdrawal rates include, but are not limited to, between about 1 inch/hour (about 2.54 cm/hour) and about 30 inches/hour (about 76.2 cm/hour), between about 1 inch/hour (about 2.54 cm/hour) and about 15 inches/hour (about 38.1 cm/hour), between about 1 inch/hour (about 2.54 cm/hour) and about 10 inches/hour (about 25.4 cm/hour), between about 1 inch/hour (about 2.54 cm/hour) and about 7 inches/hour (about 17.8 cm/hour), or any combination, sub-combination, range, or sub-range thereof. The complete withdrawal rate facilitates a type and/or rate of crystallization in thecast article 300. For example, during the completely withdrawing (step 160) of themold 210, the complete withdrawal rate facilitates increased amounts of either directional or single-crystal solidification. - During the reinserting (step 150), at least a portion of the partially withdrawn
portion 213 is reinserted into the castingfurnace 200 at a reinsertion rate proceeding in a direction opposite or substantially opposite a direction of the partially withdrawing (step 140). In one embodiment, the reinsertion rate is equivalent to any of the suitable partial or complete withdrawal rates disclosed herein. In another embodiment, the rate of reinsertion is less than the suitable partial or complete withdrawal rates disclosed herein. In yet another embodiment, the rate of reinsertion is greater than the suitable partial or complete withdrawal rates disclosed herein. For example, suitable reinsertion rates include, but are not limited to, between about 1 inch/hour (about 2.54 cm/hour) and about 30 inches/hour (about 76.2 cm/hour), between about 1 inch/hour (about 2.54 cm/hour) and about 15 inches/hour (about 38.1 cm/hour), between about 1 inch/hour (about 2.54 cm/hour) and about 10 inches/hour (about 25.4 cm/hour), between about 1 inch/hour (about 2.54 cm/hour) and about 7 inches/hour (about 17.8 cm/hour), or any combination, sub-combination, range, or sub-range thereof. - Additionally, in one embodiment, the partial withdrawal rate, the complete withdrawal rate, and/or the reinsertion rate are automated by any suitable technique throughout the
casting method 100. Suitable techniques of the automation include, but are not limited to, providing transitions between the partially withdrawing (step 140), the reinserting (step 150), and/or the completely withdrawing (step 160), automatically reversing the partially withdrawing (step 140) to provide the reinserting (step 150), automatically reversing the reinserting (step 150) to provide the completely withdrawing (step 160), varying the partial withdrawal rate, the reinsertion rate, and/or the complete withdrawal rate, adjusting for variations in temperature within the castingfurnace 200, adjusting for the area of thecast article 300 that includes increasedfreckle grain 214 forming characteristics, or a combination thereof. - In one embodiment, the partial withdrawal rate, the reinsertion rate, and/or the complete withdrawal rate, are maintained throughout each step (with the exception of an acceleration to begin each step and a deceleration to end each step). For example, the partial withdrawal rate, the reinsertion rate, and the complete withdrawal rate are about 5 inches/hour (about 12.7 cm). In another embodiment, at least one of the partial withdrawal rate, the reinsertion rate, and the complete withdrawal rate is varied throughout the
casting method 100. Varying throughout thecasting method 100 includes, but is not limited to, between steps (for example, between the partially withdrawing (step 140), the reinserting (step 150), and/or the completely withdrawing (step 160)), during at least one step, corresponding to the area of thecast article 300 that includes increasedfreckle grain 214 forming characteristics, or a combination thereof. For example, in one embodiment, the partial withdrawal rate and the complete withdrawal rate are about 3 inches/hour (about 7.6 cm/hour), while the reinsertion rate is about 10 inches/hour (about 25.4 cm/hour). - Referring to
FIG. 4 , in another embodiment, thecasting method 100 includes repeating (step 155) of the partially withdrawing (step 140) and/or the reinserting (step 150) of themold 210. In one embodiment, during the repeating (step 155), the partially withdrawing (step 140) exposes a previously-unexposed portion 413, and the reinserting (step 150) at least partially re-melts the solidifiedportion 215 within a reinsertion segment of the previously-unexposed portion 413. The reinsertion segment includes, but is not limited to, all, or substantially all, of the previously-unexposed portion 413, less than the entire previously-unexposed portion 413, the area of thecast article 300 that includes increasedfreckle grain 214 forming characteristics, or a combination thereof. For example, in another embodiment, during the repeating (step 155), the partially withdrawing (step 140) exposes the previously-unexposed portion 413 of about 1 inch (about 2.54 cm), including the reinsertion segment of about 0.5 inches (about 1.27 cm) corresponding to an area of increased thickness. The re-melting of solidifiedportion 215 within the reinsertion segment reduces or eliminates thefreckle grains 214 formed therein. - In another example, the partially withdrawing (step 140) exposes the partially withdrawn
portion 213 of about 0.5 inches (about 1.27 cm), and the reinserting (step 150) partially re-melts the solidifiedportion 215 within the partially withdrawnportion 213. Next, the repeating (step 155) of the partially withdrawing (step 140) exposes the partially withdrawnportion 213 of about 0.5 inches (about 1.27 cm), including the solidifiedportion 215 that has been partially re-melted, as well as the previously-unexposed portion 413 of about 0.5 inches (about 1.27 cm). The repeating (step 155) of the reinserting (step 150) then re-melts the solidifiedportion 215 formed within the previously-unexposed portion 413 without re-melting the solidifiedportion 215 within the partially withdrawnportion 213 that has been partially re-melted. - In one embodiment, the
casting method 100 includes partially withdrawing (step 140) themold 210 with themolten material 220 for a withdrawal time. The withdrawal time includes any suitable amount of time corresponding to formation of the solidifiedportion 215. Suitable amounts of time include, but are not limited to, up to about 2 hours, up to about 1.5 hours, up to about 1 hour, between about 1 hour and about 2 hours, up to about 0.5 hours, or any combination, sub-combination, range, or sub-range thereof. The partial withdrawal rate during the withdrawal time includes any suitable partial withdrawal rate disclosed herein. In a further embodiment, the partial withdrawal rate during the withdrawal time includes, but is not limited to, a constant rate, a pre-set variation in the rate of withdrawal, a progressive rate, or a combination thereof. - While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
- Various aspects and embodiments of the present invention are defined by the following clauses:
- 1. A casting method in a casting furnace, the casting furnace comprising a withdrawal region in a lower end, the method comprising:
- positioning a mold within the casting furnace;
- positioning a molten material in the mold;
- partially withdrawing the mold a withdrawal distance through the withdrawal region in the casting furnace, the withdrawal distance providing a partially withdrawn portion, at least partially solidifying the partially withdrawn portion; then
- reinserting at least a portion of the partially withdrawn portion into the casting furnace through the withdrawal region, at least partially re-melting the partially withdrawn portion; and then
- completely withdrawing the mold from the casting furnace through the withdrawal region to produce a directionally solidified or single crystal cast article;
- wherein at least partially re-melting the partially withdrawn portion reduces or eliminates freckle grains from the partially withdrawn portion.
- 2. The casting method of clause 1, comprising varying a partial withdrawal rate during the partially withdrawing of the mold, the varying corresponding to portions of the mold including increased freckle grain forming characteristics.
- 3. The casting method of clause 1, comprising varying a complete withdrawal rate during the completely withdrawing of the mold, the varying corresponding to portions of the mold including increased freckle grain forming characteristics.
- 4. The casting method of clause 1, comprising decreasing at least one of a partial withdrawal rate and a complete withdrawal rate corresponding to a portion of the mold including increased thickness.
- 5. The casting method of clause 1, wherein the partially withdrawing of the mold comprises a partial withdrawal rate of between about 1 inch per hour and about 10 inches per hour, the completely withdrawing of the mold comprises a complete withdrawal rate of between about 1 inch per hour and about 10 inches per hour, and the reinserting comprises a reinsertion rate of between about 1 inch per hour and about 20 inches per hour.
- 6. The casting method of clause 5, wherein the partial withdrawal rate differs from the complete withdrawal rate.
- 7. The casting method of clause 5, wherein the reinsertion rate is greater than the partial withdrawal rate and the complete withdrawal rate.
- 8. The casting method of clause 5, wherein the reinsertion rate, the partial withdrawal rate, and the complete withdrawal rate are equivalent.
- 9. The casting method of clause 1, further comprising a partial withdrawal hold time prior to the reinserting, and a reinsertion hold time prior to the completely withdrawing.
- 10. The casting method of clause 1, further comprising positioning one or more additional molds within the casting furnace.
- 11. The casting method of clause 10, wherein the positioning of the one or more additional molds is selected from the group consisting of vertical indexing, calculated guiding, thermally semi-insulating gaps formed between the one or more additional molds, and combinations thereof.
- 12. The casting method of clause 1, wherein the withdrawal distance is between about 0.250 inches and about 6.0 inches.
- 13. The casting method of clause 1, further comprising repeating the partially withdrawing and the reinserting of the mold prior to the completely withdrawing.
- 14. The casting method of clause 13, wherein the repeating of the partially withdrawing exposes a previously-unexposed portion of the mold, and the repeating of the reinserting partially re-melts the solidified portion in the previously-unexposed portion of the mold.
- 15. The casting method of clause 1, wherein at least partially re-melting the partially withdrawn portion eliminates freckle grains from the cast article.
- 16. The casting method of clause 1, wherein the partially withdrawn portion comprises a turbine bucket tip shroud, and the cast article comprises a turbine bucket.
- 17. A casting method in a casting furnace, the casting furnace comprising a withdrawal region in a lower end, the method comprising:
- positioning a mold within the casting furnace;
- positioning a molten material in the mold;
- partially withdrawing the mold through the withdrawal region in the casting furnace for a withdrawal time to provide a partially withdrawn portion, at least partially solidifying the partially withdrawn portion;
- reinserting at least a portion of the partially withdrawn portion into the casting furnace through the withdrawal region, at least partially re-melting the partially withdrawn portion; and then
- completely withdrawing the mold from the casting furnace through the withdrawal region to produce a directionally solidified or single crystal cast article;
- wherein at least partially re-melting the partially withdrawn portion reduces or eliminates freckle grains from the partially withdrawn portion.
- 18. A directionally solidified or single crystal cast article, comprising:
- a directionally solidified or single crystal microstructure and an occurrence of freckle grains corresponding to being formed by a process comprising partially withdrawing to solidify a portion of a withdrawn portion, reinserting to at least partially re-melt the withdrawn portion, and completely withdrawing a mold from a casting furnace to form the directionally solidified or single crystal cast article.
- 19. The cast article of clause 18, wherein the microstructure is directional solidification.
- 20. The cast article of clause 18, wherein the microstructure is single-crystal.
Claims (15)
- A casting method (100) in a casting furnace (200), the casting furnace (200) comprising a withdrawal region (205) in a lower end (201), the method comprising:positioning (120) a mold (210) within the casting furnace (200);positioning (130) a molten material (220) in the mold (210);partially withdrawing (140) the mold (210) a withdrawal distance (217) through the withdrawal region (205) in the casting furnace (200), the withdrawal distance (217) providing a partially withdrawn portion (213), at least partially solidifying the partially withdrawn portion (213); thenreinserting (150) at least a portion of the partially withdrawn portion (213) into the casting furnace (200) through the withdrawal region (205), at least partially re-melting the partially withdrawn portion (213); and thencompletely withdrawing (160) the mold (210) from the casting furnace (200) through the withdrawal region (205) to produce a directionally solidified or single crystal cast article (300);wherein at least partially re-melting the partially withdrawn portion (213) reduces or eliminates freckle grains (214) from the partially withdrawn portion (213).
- The casting method (100) of claim 1, comprising varying a partial withdrawal rate during the partially withdrawing of the mold (210), the varying corresponding to portions of the mold (210) including increased freckle grain (214) forming characteristics.
- The casting method (100) of claim 1 or 2, comprising varying a complete withdrawal rate during the completely withdrawing of the mold (210), the varying corresponding to portions of the mold (210) including increased freckle grain (214) forming characteristics.
- The casting method (100) of any one of claims 1 to 3, comprising decreasing at least one of a partial withdrawal rate and a complete withdrawal rate corresponding to a portion of the mold (210) including increased thickness.
- The casting method (100) of any one of claims 1 to 4, wherein the partially withdrawing of the mold (210) comprises a partial withdrawal rate of between 1 inch per hour and 10 inches per hour, the completely withdrawing of the mold (210) comprises a complete withdrawal rate of between 1 inch per hour and 10 inches per hour, and the reinserting comprises a reinsertion rate of between 1 inch per hour and 20 inches per hour.
- The casting method (100) of claim 5, wherein the partial withdrawal rate differs from the complete withdrawal rate.
- The casting method (100) of claim 5 or 6, wherein the reinsertion rate is greater than the partial withdrawal rate and the complete withdrawal rate.
- The casting method (100) of any one of claims 1 to 7, further comprising a partial withdrawal hold time prior to the reinserting, and a reinsertion hold time prior to the completely withdrawing.
- The casting method (100) of any one of claims 1 to 8, wherein the withdrawal distance (217) is between 0.250 inches and 6.0 inches.
- The casting method (100) of any one of claims 1 to 9, further comprising repeating the partially withdrawing and the reinserting of the mold (210) prior to the completely withdrawing.
- The casting method (100) of claim 10, wherein the repeating of the partially withdrawing exposes a previously-unexposed portion (413) of the mold (210), and the repeating of the reinserting partially re-melts the solidified portion (215) in the previously-unexposed portion (413) of the mold (210).
- The casting method (100) of any one of claims 1 to 11, wherein the partially withdrawn portion (213) comprises a turbine bucket tip shroud, and the cast article (300) comprises a turbine bucket.
- A directionally solidified or single crystal cast article (300), comprising:a directionally solidified or single crystal microstructure and an occurrence of freckle grains (214) corresponding to being formed by a process comprising partially withdrawing to solidify a portion of a withdrawn portion (213), reinserting to at least partially re-melt the withdrawn portion (213), and completely withdrawing a mold (210) from a casting furnace (200) to form the directionally solidified or single crystal cast article (300).
- The cast article of claim 13, wherein the microstructure is directional solidification.
- The cast article of claim 13 or 14, wherein the microstructure is single-crystal.
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US15/383,384 US10265764B2 (en) | 2014-01-28 | 2016-12-19 | Casting method and cast article |
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EP1076118A1 (en) * | 1999-08-13 | 2001-02-14 | ABB (Schweiz) AG | Method and an apparatus for casting a directionally solidified article |
US20130022803A1 (en) * | 2008-09-25 | 2013-01-24 | General Electric Company | Unidirectionally-solidification process and castings formed thereby |
EP2902135A2 (en) * | 2014-01-28 | 2015-08-05 | General Electric Company | Casting method and cast article |
WO2015130371A2 (en) * | 2013-12-30 | 2015-09-03 | United Technologies Corporation | Directional solidification apparatus and related methods |
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US5275227A (en) * | 1990-09-21 | 1994-01-04 | Sulzer Brothers Limited | Casting process for the production of castings by directional or monocrystalline solidification |
US6217286B1 (en) * | 1998-06-26 | 2001-04-17 | General Electric Company | Unidirectionally solidified cast article and method of making |
WO2007122736A1 (en) * | 2006-04-25 | 2007-11-01 | Ebis Corporation | Casting method and apparatus |
US20100034692A1 (en) * | 2008-08-06 | 2010-02-11 | General Electric Company | Nickel-base superalloy, unidirectional-solidification process therefor, and castings formed therefrom |
US20100071812A1 (en) * | 2008-09-25 | 2010-03-25 | General Electric Company | Unidirectionally-solidification process and castings formed thereby |
US10082032B2 (en) * | 2012-11-06 | 2018-09-25 | Howmet Corporation | Casting method, apparatus, and product |
-
2017
- 2017-12-06 EP EP17205764.8A patent/EP3335817A1/en not_active Withdrawn
- 2017-12-07 JP JP2017234773A patent/JP6986945B2/en active Active
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
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EP1076118A1 (en) * | 1999-08-13 | 2001-02-14 | ABB (Schweiz) AG | Method and an apparatus for casting a directionally solidified article |
US20130022803A1 (en) * | 2008-09-25 | 2013-01-24 | General Electric Company | Unidirectionally-solidification process and castings formed thereby |
WO2015130371A2 (en) * | 2013-12-30 | 2015-09-03 | United Technologies Corporation | Directional solidification apparatus and related methods |
EP2902135A2 (en) * | 2014-01-28 | 2015-08-05 | General Electric Company | Casting method and cast article |
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JP2018122355A (en) | 2018-08-09 |
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