WO1997046742A9 - Procede et dispositif pour la fabrication de fonte en solidification dirigee - Google Patents

Procede et dispositif pour la fabrication de fonte en solidification dirigee

Info

Publication number
WO1997046742A9
WO1997046742A9 PCT/US1997/009716 US9709716W WO9746742A9 WO 1997046742 A9 WO1997046742 A9 WO 1997046742A9 US 9709716 W US9709716 W US 9709716W WO 9746742 A9 WO9746742 A9 WO 9746742A9
Authority
WO
WIPO (PCT)
Prior art keywords
mold
casting
pouring
molten superalloy
suspender
Prior art date
Application number
PCT/US1997/009716
Other languages
English (en)
Other versions
WO1997046742A1 (fr
Filing date
Publication date
Priority claimed from RU96111520A external-priority patent/RU2093305C1/ru
Priority claimed from RU97104513A external-priority patent/RU2118230C1/ru
Application filed filed Critical
Priority to EP97931043A priority Critical patent/EP0904430A1/fr
Priority to JP50084298A priority patent/JP2001505175A/ja
Publication of WO1997046742A1 publication Critical patent/WO1997046742A1/fr
Publication of WO1997046742A9 publication Critical patent/WO1997046742A9/fr

Links

Definitions

  • This invention relates to a method and apparatus for making directionally solidified castings, and the articles made therefrom. More particularly, the invention relates to making parts greater than 200 mm in length for gas turbine engines. The invention further relates to a method and apparatus that provide improved reliability of the ceramic molds used in the casting process for the articles.
  • Directionally solidified castings including single crystal and polycrystalline, are manufactured by a unidirectional solidification process in which a casting shell mold containing molten superalloy material is withdrawn downward from a heated furnace. The molten superalloy is solidified gradually from the lower end of the casting mold to the upper end.
  • a crystal seed with a crystallographic direction such as ⁇ 011>, is planted in the base of the casting mold.
  • One process of manufacturing directionally solidified castings comprises the pouring of molten metal into a mold within a heated zone, with the base of the mold being cooled by a chill plate, and subsequent crystallization of the molten metal occurring by gradually withdrawing the mold from the heated zone so that the bottom of the mold and upward are cooled by convective radiation to solidify the cast article.
  • This process is discussed in U.S. Patent No. 3.857,436.
  • Another process for making directionally solidified cast articles comprises pouring molten metal into a superheated mold situated in a heated zone and withdrawing the mold from the furnace into a liquid coolant bath, where the coolant bath has a temperature lower than the solidus temperature of the cast metal. This process is described in U.S. Patent No. 3,915,761. Additional variants of these methods are described in Russian Federation Patent N 2010672 and Russian Author Certificate USSR N 1061926.
  • This invention satisfies the above-mentioned need by providing a method of making directionally solidified cast articles, distinguished by having improved reliability of a casting mold, said method comprising the steps of: heating the casting mold to a predetermined temperature in a heating zone in a casting furnace; pouring molten superalloy into the casting mold in the heating zone in an initial amount sufficient to maintain a level of the molten superalloy above a solidification front of the cast article to prevent disturbance of a crystalline growth of the directionally solidified cast article; simultaneously directionally solidifying the molten superalloy in the casting mold by withdrawing the mold from the heating zone into a cooling zone while further pouring of the molten superalloy into the casting mold at a rate to maintain the level of the molten superalloy above the solidification front; and finishing the pouring of the molten superalloy into the casting mold so that a height of the solidified portion of the cast article is greater than one half of an overall height of the cast article.
  • a suspender system to improve the reliability of the mold during the casting process.
  • the suspender system is comprised of horizontal load-bearing beams or rods which closely embrace the casting mold in the casting furnace.
  • Another embodiment of the suspender system includes incorporating the beams or rods into the manufacture of the mold itself. This is accomplished by making a pattern from wax or resinous material for the shape of the mold.
  • a pouring riser that is attached to the mold along the height of the mold's vertical side.
  • the pouring riser has at least one passageway, and preferably more than one passageway into the interior cavity of the mold, with a stationary pouring cup telescopically connected to the pouring riser.
  • the pouring cup is located near the top of the furnace.
  • Figure 1 is a schematic view of a ceramic shell mold for a cast article blade with its base upward in a suspender system.
  • Figure 2 is a schematic view of a ceramic shell mold for a cast article blade with its base downward in a suspender system.
  • Figure 3 is a schematic side view of the ceramic shell mold for a cast article blade from points A to A of Figures 1 and 2.
  • Figure 4 is a schematic view of a ceramic shell mold with a pouring riser, at least one passageway into the cavity of the mold, and a stationary pouring cup.
  • Figure 5 is a schematic view of the casting pattern of the shell mold, the skeleton design of the mold with the suspender system incorporated in the mold pattern, the flanges of the suspender system and the starting zone in the mold for the onset of the directional solidification of the molten superalloy.
  • the instant invention is directed towards a method and apparatus for producing large, directionally solidified cast articles having a cast height greater than 200 mm, and preferably greater than 300 mm.
  • the casting mold reliability, as well as the casting equipment is improved.
  • the cast articles made by the inventive method are of particular interest to aircraft and power generation equipment, and include, but are not limited to, components such as blades, airfoils, buckets, nozzles, and the like.
  • the invention can be described as heating a mold, shell, shell mold, or casting mold, herein all terms mean mold, which usually contains a ceramic material, to a predetermined temperature in a heating zone in a casting furnace.
  • the predetermined temperature is a temperature of the mold that is sufficient to accept the molten superalloy material before crystallization or solidification of the superalloy begins.
  • a preheat temperature for the mold that is above the melting temperature of the superalloy is recommended.
  • the casting furnace atmosphere is generally maintained under vacuum conditions.
  • the mold may have a starter crystal seed in its cavity to initiate the growth of a desired crystallographic oriented single crystal article. As a result, the mold can be designed for polycrystalline or single crystal cast articles.
  • the molten superalloy (herein also referred to as melt) is poured into the mold.
  • the superalloy metal may be heated and melted in a separate furnace or in a separate compartment of the casting furnace.
  • the temperature of the molten superalloy (melt) at the instant of its pouring into the mold may be about 100° to 120° C higher than the temperature corresponding to the beginning of crystallization, but somewhat lower than the temperature of the mold.
  • the method of the invention is further characterized in that the directional solidification of the molten superalloy starts after a sufficient amount of molten superalloy has been poured into the mold so that a level or height of the molten superalloy above the solidification front is adequate to prevent turbulence or disturbance of the crystal formation during the directional solidification process.
  • a sufficient initial amount of molten superalloy that is poured into the mold may be about 10 to 40 % of the volume of the mold, and preferably, is about 20 to 30 % of the mold volume.
  • the cooling zone may be a chill plate or liquid metal cooling bath, or other suitable cooling method.
  • the invention herein will be described in terms of the cooling zone being a liquid metal cooling bath, such as liquid tin or aluminum. It is also noted that a baffle may exist between the heating and cooling zones to further increase the temperature gradient when directionally solidifying the cast article.
  • the further pouring of the molten superalloy into the mold is performed simultaneously with the directional solidification process through a poring cup in such a way that a required level of the molten superalloy would be provided above the solidification front of the cast superalloy metal to prevent disturbance of the crystal growth of the cast article.
  • solidification takes place simultaneously with the proportioned pouring of the molten superalloy at a rate which provides the progressive raising of the molten superalloy level above the solidification front in such a way that when the melt pouring finishes, the height of the solidified portion of the cast article should be greater than about one half (1/2) of the total casting height of the article. This also serves to decrease the mechanical load on the ceramic mold.
  • the molten superalloy level above the solidification front should be a sufficient height so that turbulence does not effect the solidification of the cast article.
  • a suggested height may be about 30 to 70mm. Again, one skilled in the art may deteremine without undue experimentation the appropriate height level depending on the mold size and shape.
  • the suspender system comprises suspender components or elements which comprise horizontal load-bearing beams that closely embrace or surround the shell mold at points or positions spaced about ⁇ A section of the mold height.
  • the beams bear the hydrostatic pressure of the molten superalloy when it is poured into the mold.
  • the beams or rods are made of molybdenum, graphite, a graphite-based composite material, or mixtures thereof.
  • the shell mold 1 is suspended on two upper horizontal load-bearing beams 2 which are positioned in the openings of the upper graphite inserts 3.
  • the next pair of horizontal beams 4 are then positioned in place.
  • the beams closely embrace the mold side surfaces and they are fastened with wedges of graphite, molybdenum, graphite-based composites, or mixtures thereof, to provide a fixed position of the shell mold in the suspender system.
  • the amount of beams that are used depends upon the height, width and cross-sectional dimensions of the mold. For instance, the horizontal beams should be positioned at about every 100 ⁇ 50 mm when the width of the casting is ⁇ 200 mm.
  • FIG. 1 is a cross-sectional view of figures 1 and 2.
  • the shell mold is 9 is suspended on two upper horizontal load-bearing beams 0 which are positioned in the openings of the upper graphite inserts 11.
  • the next pair of horizontal beams 12 are then positioned in place.
  • suspender components or elements such as beams, bars, or rods, incorporated as part of the mold itself.
  • the suspender components or elements are positioned in the casting pattern of the mold on the exterior of the mold.
  • the mold is first made from a wax or plastic pattern, which later receives a ceramic slurry coating to eventually form the ceramic mold for casting of articles.
  • the horizontal beams and vertical support beams are placed as a skeleton in the casting pattern for the mold.
  • the skeleton is shaped for instance with cylindrical members with flanges on their butt ends on the outer surface or exterior of the mold.
  • the skeleton section for the suspender elements form exterior cavities on the mold.
  • the suspender components are placed inside the skeleton on the mold and the butt ends of the skeleton are sealed with a ceramic slurry.
  • the skeleton members are positioned above the starting zone on the mold and are distributed uniformly along the entire height of the mold.
  • the mold is then positioned on a hanger in the casting furnace to be heated to a predetermined temperature as mentioned above in the method of this invention.
  • Figure 5 shows the casting pattern 19 and the pattern of the skeleton 20 with flanges 21 and the starting zone 22.
  • a pouring cup is placed into the mold in the heating zone of the casting furnace.
  • the pouring cup has an elongated side portion which enters a base of the mold, if there are no inner cores within the mold. If inner cores are present in the mold, then the cup enters a special pouring channel.
  • a pouring riser is positioned to one lateral side of the mold.
  • the pouring riser is connected along the entire height of the pattern and with the casting cavity by the passageways inclined at the angles of about -70 to +70 to the horizontal plane.
  • the cross-section of each passageway may be about 1-3mm if they also play the role of filtration when the molten superalloy is poured into the mold.
  • both the pouring riser and the suspender system may be incorporated into the pattern and subsequently, become part of the final mold.
  • the ceramic shell mold 13 has a pouring riser 14 positioned on the lateral side of the mold with passageways 15 of small cross-section.
  • the pouring cup 16 is stationary and is place near the top of the furnace.
  • the stationary cup 17 for simultaneous pouring of the molten superalloy into two clusters of molds is also shown.
  • the molten superalloy is poured into the mold through a stationary cup located at the top section of the furnace.
  • the cup telescopically enters the pouring riser.
  • a stationary pouring cup is used which has a pouring member for each pouring riser.
  • the molten superalloy pouring into the mold cavity from a riser through the passageways which are inclined at proper angles to the horizontal plane, as described above, provides smooth movement of the molten superalloy without any turbulent stream which may cause the parasitic grain growth in the cast article. Further, the passageways that have small enough cross-section, help to eliminate the formation of nonmetallic inclusions in the cast article.
  • a casting furnace with a liquid coolant bath ( Russian commercial model unit UVNK-8P) was used to make targe castings in accordance with the present invention.
  • the shell mold was for a large- sized airfoil having dimensions of height equal to 400 mm, chord or cross-section of 180 mm, and the width of the base being 200 mm.
  • the shell mold had a thickness of about 8-10 mm and was solidified with its base upward.
  • the mold had a single crystal seed in a starting cavity and was positioned inside a special suspender, as shown in figures 1 and 3.
  • the suspender system included two vertical molybdenum hangers consisting of rods with a diameter of 20 mm and interconnected by graphite inserts (wedges) having two openings. The distance between the openings is equal to about the shell mold's thickness.
  • the load is transferred to the horizontal beams of the suspender. These beams closely embrace the mold along its perimeter and effectively prevent its distortion.
  • the horizontal load- bearing beams are made of molybdenum and have a cross-section of 10 times 20 mm.
  • the pouring cup has a gauged hole and is placed inside the mole cavity in such a way that the pouring hole is positioned at the level of about 200 mm from the mold's upper edge.
  • the airfoil was solidified with its base 5 downward.
  • the method of its position in the suspender system is shown in figure 2.
  • the horizontal load-bearing beams were made of sintered graphite.
  • the directional solidification process was started after about 30% of the volume of the mold ( about 7-7.5 kilograms of molten superalloy) was filled with the nickel-base o superalloy, Russian type ZhS.
  • the method of proportioning the pouring of the molten superalloy and the conditions of the directional solidification process, are as describe in Example 1.
  • the large size airfoil casting thus produced had a single crystal structure along the entire height.
  • Example 3 This example is further illustrative of the present invention.
  • a pouring riser which was interconnected with the casting cavity along the entire height by about eight (8) passageways of 2 mm in diameter, in which the passageways were inclined at the angle of about 70° to the horizontal plane.
  • a skeleton for the suspender's components was prepared where the skeleton had flanges on the butt ends.
  • the ceramic shell was made according to a slurry dipping technique known in the art and was then fired at 1250°C for about 4 hours.
  • the molybdenum suspender components were positioned into the cooled mold inside the ceramic skeleton.
  • the skeleton butt ends were then sealed with a ceramic slurry.
  • the mold and suspender were placed in the casting furnace, Russian commercial model UVNK-8P, and the heating chamber was evacuated to 1 x 10 "3 mm m.c.
  • the nickel-base superalloy of Russian type ZhS was melted in an induction furnace.
  • the molten superalloy was poured into the mold through the stationary cup via the inclined passageways.
  • the stationary cup was telescopically inserted into the pouring riser.
  • the pouring procedure was performed in two steps. First, about 20% by volume of the mold of the molten superalloy was poured into the mold, and solidification begun by lowering the mold into the coolant at the rate of 10mm/min. After the solidification had begun in a starting zone of the mold, the pouring of the molten superalloy was continued, while the withdrawal of the mold from the heating zone into a cooling zone was continued. At the moment when the pouring of the molten superalloy was completed, the mold was withdrawn one half its height into the cooling zone. The mold with the molten superalloy had then been completely lowered until it was fully immersed into a liquid metal coolant bath.
  • the mold was removed from the coolant, the solidified casting was removed from the suspender and from the ceramics, and the macrostructure of the cast article was revealed .
  • the cast article was 450 mm in height and had the single crystal structure of [001] orientation alone the entire height. In the course of the directional solidification process, the ceramic mold was absolutely free of distortion.
  • the suspender components were protected from the coolant metal bath.
  • the inventive methods allow the casting of large articles, single crystal and polycrystalline, of required geometric dimensions.
  • the suspender components are reusable in the directional solidification process.

Abstract

L'invention concerne un procédé et un dispositif pour la fabrication de grosses pièces de fonte, en solidification dirigée, dont la hauteur de coulage est supérieure à 200 mm, et de préférence à 300 mm. On améliore ainsi la fiabilité du moule et de l'équipement de fonderie, en versant selon les proportions un superalliage en fusion dans un moule protégé par des suspensoirs. Les pièces réalisées revêtent un intérêt particulier pour l'aéronautique et la production d'énergie; la liste non exhaustive comprend des éléments tels que les lames/pales, les profils aérodynamiques, les ailettes ou déflecteurs, les buses et autres.
PCT/US1997/009716 1996-06-05 1997-06-04 Procede et dispositif pour la fabrication de fonte en solidification dirigee WO1997046742A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP97931043A EP0904430A1 (fr) 1996-06-05 1997-06-04 Procede et dispositif pour la fabrication de fonte en solidification dirigee
JP50084298A JP2001505175A (ja) 1996-06-05 1997-06-04 方向性凝固鋳物を作るための方法と装置

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
RU96111520A RU2093305C1 (ru) 1996-06-05 1996-06-05 Способ получения отливок направленной кристаллизацией
RU96111520 1997-03-19
RU97104513A RU2118230C1 (ru) 1997-03-19 1997-03-19 Способ получения монокристаллических отливок
RU97104513 1997-03-19

Publications (2)

Publication Number Publication Date
WO1997046742A1 WO1997046742A1 (fr) 1997-12-11
WO1997046742A9 true WO1997046742A9 (fr) 1998-03-19

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Application Number Title Priority Date Filing Date
PCT/US1997/009716 WO1997046742A1 (fr) 1996-06-05 1997-06-04 Procede et dispositif pour la fabrication de fonte en solidification dirigee

Country Status (6)

Country Link
US (1) US20010001415A1 (fr)
EP (1) EP0904430A1 (fr)
JP (1) JP2001505175A (fr)
KR (1) KR20000016339A (fr)
CN (1) CN1226291A (fr)
WO (1) WO1997046742A1 (fr)

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EP1561536A1 (fr) * 2004-02-03 2005-08-10 Siemens Aktiengesellschaft Procédé de réparation par brasage d'une pièce ayant un matériau de base avec une microstructure orientée
CN100343001C (zh) * 2005-03-24 2007-10-17 北京铝镁泰和铸机设备科技有限公司 一种薄膜金属型结晶器的铸造机及应用方法
US7540919B2 (en) * 2005-04-01 2009-06-02 Gt Solar Incorporated Solidification of crystalline silicon from reusable crucible molds
CN100406161C (zh) * 2005-04-29 2008-07-30 中国科学院金属研究所 一种定向凝固铸造方法
CN100368121C (zh) * 2005-09-02 2008-02-13 哈尔滨工业大学 一种TiAl基合金板件的定向凝固方法
CN1320972C (zh) * 2005-09-02 2007-06-13 哈尔滨工业大学 一种适于连续熔铸定向凝固的矩形冷坩埚系统
US20070051623A1 (en) * 2005-09-07 2007-03-08 Howmet Corporation Method of making sputtering target and target
US8079400B2 (en) * 2008-10-02 2011-12-20 United Technologies Corporation Process for casting columnar grain airfoil with preferential primary orientation
CN102095754B (zh) * 2010-11-16 2014-07-02 昆明理工大学 大型铸件凝固分析方法
CN102019354B (zh) * 2010-12-27 2012-11-07 沈阳黎明航空发动机(集团)有限责任公司 带冠超薄细长叶片的定向凝固方法
CN102166643B (zh) * 2011-03-30 2013-07-24 江苏中欧材料研究院有限公司 一种防止单晶叶片杂晶缺陷的方法
US8752611B2 (en) 2011-08-04 2014-06-17 General Electric Company System and method for directional casting
CN102389966B (zh) * 2011-11-18 2013-06-19 大连船用推进器有限公司 大型船用定距螺旋桨铸造轴孔水冷装置
US8708031B2 (en) * 2012-09-25 2014-04-29 Babcock & Wilcox Technical Services Y-12, Llc Method and mold for casting thin metal objects
CN108080604B (zh) * 2017-12-27 2019-09-13 大连船用推进器有限公司 螺旋桨铸件成形凝固顺序控制装置及其控制步骤
CN114273610B (zh) * 2021-12-01 2024-06-25 东方电气集团东方汽轮机有限公司 一种用于定向结晶叶片熔模铸造的型壳及制备方法

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US3857436A (en) * 1973-02-13 1974-12-31 D Petrov Method and apparatus for manufacturing monocrystalline articles
US3927710A (en) * 1974-08-21 1975-12-23 United Technologies Corp Joining of multi-section ceramic molds
US5309976A (en) * 1993-03-16 1994-05-10 Howmet Corporation Continuous pour directional solidification method

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