US2883724A - Casting processes - Google Patents

Casting processes Download PDF

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Publication number
US2883724A
US2883724A US495308A US49530855A US2883724A US 2883724 A US2883724 A US 2883724A US 495308 A US495308 A US 495308A US 49530855 A US49530855 A US 49530855A US 2883724 A US2883724 A US 2883724A
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US
United States
Prior art keywords
pattern
mould
hollow
casting
wax
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US495308A
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English (en)
Inventor
Hancock Ralph Harold
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Rolls Royce PLC
Original Assignee
Rolls Royce PLC
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Rolls Royce PLC filed Critical Rolls Royce PLC
Application granted granted Critical
Publication of US2883724A publication Critical patent/US2883724A/en
Anticipated expiration legal-status Critical
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/02—Sand moulds or like moulds for shaped castings
    • B22C9/04—Use of lost patterns
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23B—TURNING; BORING
    • B23B51/00—Tools for drilling machines
    • B23B51/04—Drills for trepanning
    • B23B51/0486—Drills for trepanning with lubricating or cooling equipment

Definitions

  • This invention relates to casting processes and in particular to processes of the kind in which an expendable pattern is invested in a refractory material to produce a casting mould. Processes of this kind are commonly referred to as lost wax, the expendable pattern normally being of wax which is melted out of the mould after investment of the pattern. In place of wax other materials such as low melting point metals may be used.
  • the article to be cast is of hollow form, and processes of the kind referred to have been used to produce hollow cast articles from hollow patterns, which are obtained by the provision of inserts in the pattern.
  • one or more inserts are positioned in a die in which the pattern is formed, such insert or inserts being removed from the pattern prior to investment.
  • metal inserts have been used which are supported in a die in which the pattern is formed, such inserts being of uniform section or slightly tapered to facilitate their withdrawal from the pattern.
  • a pattern of hollow form is provided which when invested is filled with refractory material, whereby after melting out of the pattern the mould is formed so as to provide for the casting of an article reproducing the hollow formation.
  • the present invention seeks to overcome such difiiculties and to provide a method of producing hollow cast articles by casting processes of the kind referred to which will present accuracy in the finished part.
  • a-casting process of the kind referred to includes the step of supporting a preformed member of material having increased strength as compared with the investment material within a hollow formation in the pattern prior to the investment thereof, such member being supported with clearance from the wall of the hollow formation whereby the investment material flows into the space defined between the surface of the member and the internal surface of the hollow formation, said member being removable from the hollow formation after the part has been cast in the mould.
  • the preformed member is of a ceramic nature, for example being formed of silica.
  • Such preformed member may if desired be hollow, facilitating its destruction where this is necessary to permit its removal.
  • One particular application of the invention is to the casting of blades of gas-turbine engines in high melting point alloys such as nickel-chromium alloys.
  • Such blades commonly have hollow formations permitting the passage of cooling air in operation of the turbine, and when produced by casting it is desirable that the hollow formation is accurately positioned in relation to the outside walls to obtain the designed wall thickness.
  • the preformed member is supported at one end only in the hollow formation and with clearance from the wall of the hollow formation.
  • the preformed strengthening member used in accordance with the present invention may comprise a rod, for example of silica, of substantially uniform section.
  • Figure 1 is a plan view of a split die, with the top half removed, used for forming a wax pattern
  • Figure 2 is a section on the line IIII of Figure 1 with both halves of the die in position
  • Figure 3 is a section through the pattern and wax support with the strengthening insert in position
  • Figure 4 is a similar section to Figure 3 showing the pattern and support invested in a container
  • Figure 5 is a section on the line VV of Figure 4.
  • the wax pattern is formed in a die having an upper half 10 and a lower half 11 into which the wax is injected through a drilling 12 on the line of the split by injection means shown diagrammetically by the syringe 13. Before injecting the wax a metal insert 14 is inserted in the die supported therein at either end but leaving a space between itself and the pattern which is formed in the die and is shown at 15.
  • the metal insert 14 can be drawn out of the die by means of the handle 16 and will then leave a hollow formation in the wax pattern therein.
  • the pattern is next mounted on a wax support 17 which is shaped to provide the hollow required in the eventual mould through which the metal will be poured in.
  • the pattern After being so mounted the pattern may be coated with a refractory coating by spraying or dipping in known manner.
  • a suitable refractory coating may be prepared as follows:
  • 270 cc. of potassium silicate solution having a specific gravity of 1.3 and a K O/SiO ratio of 1:20 by weight were mixed with 1300 cc. of a solution of dioctyl sodium sulphosuccinate, prepared by diluting 650 cc. of a 60% solution of dioctyl sodium sulphosuccinate with 650 cc. of water.
  • 1300 cc. of a non-ionic wetting agent prepared by reacting ethylene oxide with octyl cresol, and sold under the British registered trademark of Lissapol as Lissapol NDB. were added to the mixture, followed by 1800 cc. of a soap solution prepared by mixing 56.5 gms.
  • compositions suitable for forming the initial coating of finely divided refractory of the pattern are known, and may be used, such as those using ethyl silicate as a binding agent.
  • silica rod or tube 18 which passes through the hollow formation in the pattern and is secured at one end to the wax support 17 by additional wax shown at 18A.
  • This rod or tube forms the strengthening insert and is supported with clearance from the wall of the hollow formation in the pattern.
  • the silica rod or tube may be prepared in known manner.
  • the usual method is to fuse the silica in an electric aseayrac furnace after which articles of fused silica may be blown or drawn in similar manner to glass.
  • Rods can be cut to length by Carborundum or emery wheels and polished if desired on Wheels fed with Wet sand.
  • Pattern, support and insert are then placed on a base plate 19 onto which is placed a flask or container 20 secured to the bottom of the base plate by wax shown at 21.
  • the container 20 may advantageously be extended in length by a sheet of waxed paper attached to it.
  • a suitable investment material may be prepared from a fireclay grog containing at least 40% of alumina, and having a particle size distribution such that not less than 26% by weight and not more than 30% by weight is retained on a 200 mesh British Standard 410, 1943, sieve, using as binding liquid an acid sodium silicate solution prepared by adding dilute nitric acid to sodium silicate, as described in British Patent No. 650,532, and containing as gelation accelerator 3.1% by volume of a hexamine solution prepared by dissolving 107 lbs. of hexamine in 30 gallons (British) of water.
  • the investment slurry is prepared by mixing 400 lbs. of the fireclay grog with gallons (British) of the binding liquid.
  • the packing of the investment may be accelerated in known manner by placing the container on a vibrating table. When the refractory material has been packed round the coated pattern any fine material on the top of the mould is trimmed off level with the top of the container and the mould is allowed to gel.
  • the base plate 19 is then removed and the pattern and wax support melted out. At the same time the mould is dried.
  • the mould may then be fired to a temperature of between 1000 C. and 1100 C. in the course of 10 hours and held at this temperature for 2 hours to harden the same.
  • the mould is then inverted and sufficient metal poured in to fill the space therein previously occupied by the pattern.
  • the mould After the cast has cooled the mould is removed by destruction, the investment being cleared from the hollow interior by sand blasting.
  • the silica rod may be broken up during this process.
  • Adoption of the invention presents accuracy in the finished part, it being appreciated that during the casting operation the part of the mould providing the hollow formation is supported by the strengthening member, i.e., the silica rod, extending within its length.
  • the strengthening member may be provided by materials other than silica, such as alumina, mullite or metal rods such as stainless steel, or rod of a nickelchromium alloy, for example that sold under the British registered trade-mark Nimonic.
  • a casting process for precision casting which includes providing a pattern of the article to be cast formed from an expendable material and having a hollow formation therein, supporting same on an expendable pedestal in a container, supporting a preformed strengthening member at one end from said pedestal within the hollow formation with a clearance from the wall thereof, investing the pattern simultaneously internally and externally with a refractory material to form a mould whereby said material simultaneously flows around the said pattern, into the space defined between said strengthening-member and the internal surface of said hollow formation, and about the opposite end of said strengthening-member forming a core integral with said mould, said strengthening member having increased strength compared with said investment material, causing the investment material to set, causing removal of the expendable pattern forming the mould, casting the article and removing the mould therefrom together with said strengthening member.
  • a casting process for a blade for an internal combustion turbine engine which includes casting in a die a pattern of the blade in expendable material, said die containing a removable insert corresponding to the hollow formation to be found in the blade, removing pattern from the die, supporting same in a container on an expendable base support corresponding to the hollow required in the mould to introduce the blade metal, supporting one end only of a preformed strengtheningmember from said base support within the hollow formation with a clearance from the wall thereof and with the opposite end extending beyond the hollow formation, simultaneously investing the pattern internally and externally with a refractory material to form a mould whereby said material flows around the said pattern and into the space defined between said strengthening-member and the internal surface of said hollow formation and around said extending end of said strengthening member, said strengthening member having increased strength compared with said investment material, causing the investment material to set, causing removal of the expendable pattern forming the mould, casting the article and removing the mould therefrom together with said strengthening member.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)
US495308A 1954-04-01 1955-03-18 Casting processes Expired - Lifetime US2883724A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB9649/54A GB771316A (en) 1954-04-01 1954-04-01 Improvements relating to metal casting processes

Publications (1)

Publication Number Publication Date
US2883724A true US2883724A (en) 1959-04-28

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Application Number Title Priority Date Filing Date
US495308A Expired - Lifetime US2883724A (en) 1954-04-01 1955-03-18 Casting processes

Country Status (4)

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US (1) US2883724A (cs)
BE (1) BE536963A (cs)
FR (1) FR1121390A (cs)
GB (1) GB771316A (cs)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102581220A (zh) * 2011-01-04 2012-07-18 私立中原大学 中空蜡胚成型方法及其装置
CN103406492A (zh) * 2013-08-22 2013-11-27 中国南方航空工业(集团)有限公司 注蜡模具
CN111590019A (zh) * 2020-07-14 2020-08-28 衢州市东港机械制造有限公司 一种精密铸件壳用涂料制作工艺及检验方法

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2994931A (en) * 1958-09-12 1961-08-08 Misco P C Inc Mold element and method for manufacture of same
US4930703A (en) * 1988-12-22 1990-06-05 General Electric Company Integral fuel nozzle cover for gas turbine combustor
CN104439071A (zh) * 2014-11-21 2015-03-25 柳州金特机械有限公司 一种精铸件制壳工艺

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1303785A (en) * 1919-05-13 Method of forming cores for hollow castings
US1663455A (en) * 1925-07-09 1928-03-20 John B Lukomski Molding apparatus
US2517902A (en) * 1944-08-31 1950-08-08 George C Luebkeman Molding process and means
GB678035A (en) * 1950-03-17 1952-08-27 Rolls Royce Improvements in processes for precision castings
GB685857A (en) * 1950-03-14 1953-01-14 Idoson Motor Cylinder Company Improved method of preparing moulds for metal castings more particularly for air cooled cylinders
DE903135C (de) * 1951-10-02 1954-02-01 Walter U Schmitt Fa Dr Verfahren zum Einformen von Zahnbruecken fuer Stiftzaehne
US2749586A (en) * 1952-08-14 1956-06-12 Mercast Corp Process of forming shell mold
US2752653A (en) * 1954-03-09 1956-07-03 Rolls Royce Method of and dies for forming hollow expendable patterns for casting
US2752652A (en) * 1954-09-28 1956-07-03 Central States Ind Supply Comp Method of reinforcing cores, utilizing glass tubes

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1303785A (en) * 1919-05-13 Method of forming cores for hollow castings
US1663455A (en) * 1925-07-09 1928-03-20 John B Lukomski Molding apparatus
US2517902A (en) * 1944-08-31 1950-08-08 George C Luebkeman Molding process and means
GB685857A (en) * 1950-03-14 1953-01-14 Idoson Motor Cylinder Company Improved method of preparing moulds for metal castings more particularly for air cooled cylinders
GB678035A (en) * 1950-03-17 1952-08-27 Rolls Royce Improvements in processes for precision castings
DE903135C (de) * 1951-10-02 1954-02-01 Walter U Schmitt Fa Dr Verfahren zum Einformen von Zahnbruecken fuer Stiftzaehne
US2749586A (en) * 1952-08-14 1956-06-12 Mercast Corp Process of forming shell mold
US2752653A (en) * 1954-03-09 1956-07-03 Rolls Royce Method of and dies for forming hollow expendable patterns for casting
US2752652A (en) * 1954-09-28 1956-07-03 Central States Ind Supply Comp Method of reinforcing cores, utilizing glass tubes

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102581220A (zh) * 2011-01-04 2012-07-18 私立中原大学 中空蜡胚成型方法及其装置
CN103406492A (zh) * 2013-08-22 2013-11-27 中国南方航空工业(集团)有限公司 注蜡模具
CN103406492B (zh) * 2013-08-22 2015-07-15 中国南方航空工业(集团)有限公司 注蜡模具
CN111590019A (zh) * 2020-07-14 2020-08-28 衢州市东港机械制造有限公司 一种精密铸件壳用涂料制作工艺及检验方法

Also Published As

Publication number Publication date
FR1121390A (fr) 1956-08-13
GB771316A (en) 1957-03-27
BE536963A (cs)

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