Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C9/00—Moulds or cores; Moulding processes
  • B22C9/10—Cores; Manufacture or installation of cores
  • B22C9/105—Salt cores

Definitions

• the present invention relates to the production of hollow, superalloy parts by investment casting techniques and more particularly to the production of metal parts formed of cobalt or nickel superalloys and containing small and narrow apertures and passages in the castings.
• a disposable pattern which is a replica of the part to be cast and which includes any necessary gates and risers, is usually dipped in a refractory slurry which hardens to form a smooth coating that serves as the mold face.
• the precoating or dipcoating of the pattern usually is carried out by immersing the pattern in a suspension of a fine refractory powder in a suitable liquid binder that is capable of hardening during drying at room conditions. Following dipping, the excess slurry is drained from the pattern and the coating is stuccoed while wet with coarser refractory particles which help to set the coating.
• a ceramic shell mold is usually prepared by repeating the dipping and stuccoing operations described above until a shell having a sufficient thickness to resist the stresses occuring in subsequent operations is built up around the pattern.
• the usual thickness range is from one-eighth of an inch to one-half of an inch, although thinner or heavier shells may be formed for special situations.
• the disposable pattern is removed from the mold which is then prepared for the casting operation.
• the typical pattern materials used in the process have been either wax blends or plastics such as polystyrene and, occasionally, polyethylene.
• a ceramic core usually formed of pressed silica, is disposed within the mold at an appropriate location. While these silica cores are quite useful, they are difficult to remove with a non-corrosive leaching media after the casting has been made. It can be appreciated that when very small or fine apertures or interstices are filled with an insoluble core material that difficulty can be encountered when attempting to totally remove the material with a non-corrosive leaching medium.
• an aqueous solution of 12 to 30 w/o magnesium chloride is mixed with w/o magnesium oxide powder to form a thick slurry.
• the slurry is poured into a plastic or rubber die having the configuration which is desired.
• the components react to form a complex magnesium oxychloride cement which is relatively rigid, even in the unfired state.
• the body is fired to convert the oxychloride to the oxide, generally at temperaturesbetween about 2,200 to 2,700 F.
• a solid, rugged magnesium oxide core is produced which can be subsequently incorporated in an investment casting process.
• the core which was formed is generally coated by dipping it in a slurry of finely divided zirconium oxide (having an average particle size below. microns) to prevent the reaction of the magnesium with any silicates from the exterior shell of the investment casting.
• the core of magnesium oxide may be removed by playing a jet of live steam upon it or placing the part in an autoclave filled with water at a relatively high temperature. The magnesium oxide dissolves in the steam and other leaching agents need not be added for its removal.
• the apertures or interstices are disposed within it.
• magnesium chloride MgCl 6H O
• magnesium oxide were added to 55 grams of solution and a magnesium oxychloride cement (plus MgO) was formed. This cement was poured into a plastic die to solidify. When solid, it was removed from the die and fired at a temperature of 2,700F. to convert the oxychloride to the oxide.
• a method of forming a water-soluble core for use in the manufacture of hollow articles in investment casting processes said core being adapted to be disposed within the casting so that, upon removal, hollow passages remain, said method including the steps of: admixing an aqueous solution of magnesium chloride with magnesium oxide powder to form a slurry; pouring said slurry into a die of the desired shape and allowing said slurry to harden to form a body corresponding to the shape of said die; thing said body at a temperature of 2,2002,70()F. to oxidize said magnesium chloride and form a solid magnesium oxide core, said core being useful in said investment casting process.
• a method of forming a water-soluble core for use in the manufacture of hollow articles in investment casting processes said core being adapted to be I disposed within the casting so that, upon removal, hollow passages remain, said method including the steps of: admixing an aqueous solution of magnesium chloride with magnesium oxide powder to form a slur-

Landscapes

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

Applications Claiming Priority (1)

Publications (1)

Family

ID=22566794

Family Applications (1)

Country Status (12)

Cited By (10)

Families Citing this family (1)

Citations (4)

• 1971
  • 1971-06-29 US US00158128A patent/US3722574A/en not_active Expired - Lifetime
• 1972
  • 1972-02-02 CA CA133,814A patent/CA972920A/en not_active Expired
  • 1972-03-21 GB GB1317872A patent/GB1325412A/en not_active Expired
  • 1972-03-24 IL IL39070A patent/IL39070A/en unknown
  • 1972-03-28 FR FR7211411A patent/FR2143646B1/fr not_active Expired
  • 1972-04-14 SE SE7204854A patent/SE399371B/xx unknown
  • 1972-04-14 AU AU41149/72A patent/AU464359B2/en not_active Expired
  • 1972-04-21 CH CH599272A patent/CH538434A/fr not_active IP Right Cessation
  • 1972-04-24 DE DE2220060A patent/DE2220060C3/de not_active Expired
  • 1972-06-08 IT IT25385/72A patent/IT956344B/it active
  • 1972-06-23 BE BE785335A patent/BE785335A/fr unknown
  • 1972-06-24 JP JP6361772A patent/JPS5524982B1/ja active Pending

Patent Citations (4)

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