US 4,905,752 AGranted

Method of casting a metal article

AssigneePCC Airfoils, Inc.

InventorT. V. Rama Prasad

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Abstract

A long thin article having an enlarged end portion, such as a vane having a long thin airfoil and a shroud at the end of the airfoil, is cast by using a chill at the enlarged end portion of an article mold cavity. The chill is engaged by molten metal at the enlarged end portion of the article mold cavity. The molten metal quickly solidifies adjacent to the chill to eliminate the formation of defects. The chill is advantageously located in a pocket disposed at one end of the article mold cavity. The chills are placed in the pockets with the molds in an up-side-down orientation. The mold is then turned right-side-up and placed on a chill plate. The chills project from the mold and support the mold above the chill plate. During casting of an article, heat is transmitted from the enlarged end portion of the article through chill to the chill plate.

Claims41

Dependent claims

A method of casting a metal article having a long thin airfoil portion with a length which is more than four inches and which is at least twenty times the thickness of the airfoil portion and having a shroud portion connected to one end of the airfoil portion, said method comprising the steps of forming a mold having an article mold cavity with a long thin airfoil forming portion and with a shroud forming portion at one end of the airfoil forming portion, the long thin airfoil forming portion of the article mold cavity having a length which is more than four inches and which is at least twenty times its thickness, the long thin airfoil forming portion of the article mold cavity being free of gating along its length, the shroud forming portion of the article mold cavity being disposed at the one end of the airfoil forming portion and having a relatively wide platform forming portion which extends transversely outwardly from the long thin airfoil forming portion and having a rail forming portion which is narrower than the platform forming portion and which projects from the platform forming portion in a direction away from the airfoil forming portion, the rail forming portion having an open end which is spaced from the wide platform forming portion of the article mold cavity, blocking the open end of the rail forming portion of the article mold cavity with a chill, said step of blocking the open end of the rail forming portion of the article mold cavity includes locating a chill in a position in which the chill extends across an opening in the rail forming portion of the article mold cavity and in which the chill is spaced from the platform forming portion of the article mold cavity, positioning the mold in a furnace with the long thin airfoil forming portion of the article mold cavity extending upwardly from the shroud forming portion of the article mold cavity and with the chill blocking the opening which is at the lower end of the rail forming portion of the article mold cavity and with the chill disposed beneath and spaced from the platform forming portion of the article mold cavity, heating the mold, thereafter, conducting molten metal into the article mold cavity, said step of conducting molten metal into the article mold cavity including engaging an upper side surface of the chill with the molten metal, solidifying the molten metal in the article mold cavity with an equiaxed grain structure, said step of solidifying the molten metal including simultaneously solidifying molten metal in the shroud forming portion and the long thin airfoil forming portion of the article mold cavity, said step of solidifying molten metal in the shroud forming portion including initially solidifying the molten metal in the rail forming portion of the article mold cavity at a first rate and initially solidifying the molten metal in the platform forming portion of the article mold cavity at a second rate which is less than the first rate.

A method of casting a plurality of metal articles, said method comprising the steps of providing a mold structure having a plurality of article molds with openings at their lower end portions, blocking the openings at the lower end portions of the article molds with a plurality of chill members, positioning the chill members on a chill plate, supporting the weight of the mold structure on the chill members with the mold structure spaced from the chill plate, thereafter, conducting molten metal into the article molds, and transmitting heat from the molten metal through the chill members to the chill plate.

A method of casting a metal article having a long thin airfoil portion with a length which is more than four inches and which is at least twenty times the thickness of the airfoil portion and having a shroud portion connected to one end of the airfoil portion, said method comprising the steps of forming a ceramic mold having an article mold cavity with a long thin airfoil forming portion and with a shroud forming portion at one end of the airfoil forming portion and having a pocket disposed on a side of the shroud forming portion opposite from the airfoil forming portion, the long thin airfoil forming portion of the article mold cavity having a length which is more than four inches and which is at least twenty times its thickness, the long thin airfoil forming portion of the article mold cavity being free of gating along its length, said step of forming a mold including providing a pattern having a long thin airfoil pattern portion, a shroud pattern portion and a pocket pattern portion, the long thin airfoil pattern portion being free of gating along its length, covering the long thin airfoil pattern portion, the shroud pattern portion and the pocket pattern portion of the pattern with a wet coating of ceramic mold material, drying the coating of ceramic mold material, and removing the pattern from within the dried coating of ceramic mold material to form the article mold cavity with the airfoil forming portion and the shroud forming portion and to form the pocket, said method further including placing a chill member in the pocket, positioning the mold in a furnace with the long thin airfoil forming portion of the article mold cavity extending upwardly from the shroud forming portion of the article mold cavity and with the chill member disposed in the pocket beneath the shroud forming portion of the article mold cavity, heating the mold, thereafter, conducting molten metal into the article mold cavity, said step of conducting molten metal into the article mold cavity including conducting molten metal into the long thin airfoil forming portion at a location other than along the length of the airfoil forming portion, solidifying the molten metal in the article mold cavity with an equiaxed grain structure, said step of solidifying the molten metal including transmitting heat from the shroud forming portion to the chill member in the pocket.

A method of casting a metal article at least a portion of which is long and thin and has a length which is more than four inches and which is at least twenty times its thickness and having an enlarged end portion connected to the long thin portion, said method comprising the steps of forming a mold having an article mold cavity having a long thin portion which has a length which is more than four inches and is at least twenty times its thickness and having an enlarged end portion at one end of the long thin portion, the long thin portion of the article mold cavity being free of gating along its length, positioning a chill member on a side of the enlarged end portion of the article mold cavity opposite from the long thin portion of the article mold cavity, positioning the mold in a furnace with the chill member engaging a chill plate, heating the mold, said step of heating the mold including heating a lower half of the portion of the mold defining the long thin portion of the article mold cavity into a first temperature range, the highest temperature of the first temperature range being close to but less than the solidus temperature of the metal of the article, said step of heating the mold including heating an upper half of the portion of the mold defining the long thin portion of the article mold cavity into a second temperature range containing temperatures which are greater than the first temperature range, conducting molten metal into the article mold cavity, said step of conducting molten metal into the article mold cavity including conducting molten metal into the long thin portion of the article mold cavity at a location other than along the length of the long thin portion of the article mold cavity and conducting molten metal into the enlarged end portion of the article mold cavity, said step of conducting molten metal into the article mold cavity being initiated while the lower half of the portion of the mold defining the long thin portion of the article mold cavity is in the first temperature range and the upper half of the portion of the mold defining the long thin portion of the article mold cavity is in the second temperature range, and solidifying the molten metal in the article mold cavity with an equiaxed grain structure, said step of solidifying the molten metal including transmitting heat from the molten metal through the chill member to the chill plate.

A method of casting a metal article at least a portion of which is long and thin and has a length which is more than four inches and which is at least twenty times its thickness and having an enlarged end portion connected to the long thin portion, said method comprising the steps of forming a mold having an article mold cavity having a long thin portion with a length which is more than four inches and is at least twenty times its thickness and having an enlarged end portion at one end of the long thin portion, the long thin portion of the article mold cavity being free of gating along its length, positioning a chill member on a side of the enlarged end portion of the article mold cavity opposite from the long thin portion of the article mold cavity, positioning the mold in a furnace with the chill member engaging a chill plate, heating the mold, conducting molten metal into the article mold cavity, said step of conducting molten metal into the article mold cavity including conducting molten metal into the long thin portion of the article mold cavity at a location other than along the length of the long thin portion of the article mold cavity and conducting molten metal into the enlarged end portion of the article mold cavity, solidifying the molten metal in the article mold cavity, said step of solidifying the molten metal including transmitting heat from the molten metal through the chill member to the chill plate, and completing solidification of the molten metal in a lower half of the long thin portion of the article mold cavity and the enlarged end portion of the article mold cavity prior to completion of solidification of the molten metal in an upper half of the long thin portion of the article mold cavity and after a major portion of the molten metal in the upper half of the long thin portion of the article mold cavity has solidified.

Dependencies are inferred from the claim text.