EP0311203A2 - Foundry core material - Google Patents
Foundry core material Download PDFInfo
- Publication number
- EP0311203A2 EP0311203A2 EP88202172A EP88202172A EP0311203A2 EP 0311203 A2 EP0311203 A2 EP 0311203A2 EP 88202172 A EP88202172 A EP 88202172A EP 88202172 A EP88202172 A EP 88202172A EP 0311203 A2 EP0311203 A2 EP 0311203A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- titania
- core
- oxide
- core material
- ions
- 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.)
- Granted
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
- B22C1/02—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives
- B22C1/10—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by additives for special purposes, e.g. indicators, breakdown additives for influencing the hardening tendency of the mould material
Definitions
- the present invention relates to ceramic materials for use in ceramic cores particularly, though not exclusively for use in the manufacture of precision cast components.
- Components such as blades and nozzle guide vanes, for example, for gas turbine engines frequently have complex shaped hollow internal passages for cooling purposes. Such passages allow the component to operate at much higher gas inlet temperature than would otherwise be the case.
- the passages are generally formed by the use of leachable ceramic cores cast in situ during a vacuum precision casting process.
- Such cores have generally comprised silica-based materials.
- the high temperature strength of a core depends on the devitrification of vitreous silica to the crystalline phase, cristobalite. Heretofore this has generally been accomplished by alkali metal ions such as sodium, for example, added to the silica glass as catalysts in minor additions. Although alkali metal ions do promote devitrification of silica they also lower the high temperature strength of the core by lowering the melting temperature of the bond.
- Both types of component are made by an essentially similar process wherein any cores used have to withstand temperatures exceeding 1500°C, sometimes for several hours. The result of this may be extensive plastic deformation of the core which tends to deform under its own weight and deflect when metal is poured into the mould in which the core is located.
- Outer dimensional tolerances for precision cast gas turbine components are stringent, also the position, size and orientation etc. of cored passages within the components are subject to equally stringent tolerances.
- a core material for foundry use comprises silica having therein ions selected from the group comprising titanium, zirconium, phosphorous, vanadium, chromium, molybdenum and tungsten.
- the ions may be added in the form of a finely divided oxide powder, or as a compound containing the element, preferably an organic compound which is miscible with the binder used during core manufacture.
- An organic compound miscible with the binder allows homogeneous dispersal throughout the mixture.
- the addition may lie in the range from 0.05 to 10wt%.
- a preferred addition is titania.
- a preferred range of titania may be 0.1 to 5wt%.
- a more preferred range of titania may be 0.1 to 2.5wt%.
- the silica is of purity greater than 99.5%.
- a method of making a core for foundry use comprises the steps of mixing silica with material containing ions selected from the group comprising titanium, zirconium, phosphorous, vanadium, chromium, molybdenum and tungsten and organic binder material, moulding a desired core shape, heating to remove the organic binder and then firing in excess of 1180°C.
- the firing temperature is in excess of 1200°C.
- the content of organic binder material may be in the range of 15 to 40wt% of the mixture.
- Titania may be added as titania or as a titanium compound which decomposes to the oxide during processing.
- a series of core material compositions were made by mixing fused silica with 0.1wt%, 0.25wt%, 1.0wt% and 2.5wt% titania of substantially submicron particle size. These compositions were pressed into pellets and fired at temperatures from 1150°C to 1300°C. The extent of devitrification was then assessed by means of thermal expansion measurements. The results showed that titania over the whole range of concentrations tested promoted detrification when fired at and above 1200°C. The extent of crystallisation increased with firing temperature, soak time at temperature and with increasing concentration of titania.
- mix 52 A mix was made of a normal production core material containing sodium ions. This material was designated mix 52.
- Test bars of mixes L69 and 52 were injection moulded and heated slowly to a temperature of 700°C to drive off the organic binder materials.
- the mix 52 bars were dipped in ethyl silicate solution prior to firing in order to fill some of the porosity in the material.
- the dipped material was designated A52.
- Test bars of each of the compositions were then placed from ambient into the hot zone of a Modulus of Rupture (MOR) testing apparatus which had been allowed to stabilise at 1450°C, and soaked for periods of 30 minutes and 60 minutes. After the completion of each soak period the bars were loaded to failure at 55 N/min to failure. After testing physical measurements of porosity and density were made (see Table). Physical and Mechanical Properties of Compositions No. 52, A52, L69 tested at 1450°C. Mix No. Test No. Soak Time/ min.
- MOR Modulus of Rupture
- the L69 material soaked for 30 and 60 minutes at 1450°C has achieved MOR values of 37.8 and 39.8 MPa.
- the level of crystallisation of mix 52 and A52 materials is comparable to the L69 material but the MOR values are greatly reduced at averages of 6.8 and 11.8 MPa respectively.
Abstract
Description
- The present invention relates to ceramic materials for use in ceramic cores particularly, though not exclusively for use in the manufacture of precision cast components.
- Components such as blades and nozzle guide vanes, for example, for gas turbine engines frequently have complex shaped hollow internal passages for cooling purposes. Such passages allow the component to operate at much higher gas inlet temperature than would otherwise be the case. The passages are generally formed by the use of leachable ceramic cores cast in situ during a vacuum precision casting process.
- Such cores have generally comprised silica-based materials. The high temperature strength of a core depends on the devitrification of vitreous silica to the crystalline phase, cristobalite. Heretofore this has generally been accomplished by alkali metal ions such as sodium, for example, added to the silica glass as catalysts in minor additions. Although alkali metal ions do promote devitrification of silica they also lower the high temperature strength of the core by lowering the melting temperature of the bond.
- In recent years gas turbine components having metallic grain structures comprising either columnar grains, produced by a directional solidification process (DS), or a single crystal (SC) have gained increased prominence. This is due to the higher stresses and temperatures which may be withstood by components having such structures.
- Both types of component are made by an essentially similar process wherein any cores used have to withstand temperatures exceeding 1500°C, sometimes for several hours. The result of this may be extensive plastic deformation of the core which tends to deform under its own weight and deflect when metal is poured into the mould in which the core is located.
- Outer dimensional tolerances for precision cast gas turbine components are stringent, also the position, size and orientation etc. of cored passages within the components are subject to equally stringent tolerances.
- It is an object of the present invention to provide a material for cores which will devitrify without the presence of alkal imetal ions and not suffer from distortion at high temperatures.
- According to one aspect of the present invention a core material for foundry use comprises silica having therein ions selected from the group comprising titanium, zirconium, phosphorous, vanadium, chromium, molybdenum and tungsten.
- The ions may be added in the form of a finely divided oxide powder, or as a compound containing the element, preferably an organic compound which is miscible with the binder used during core manufacture. An organic compound miscible with the binder allows homogeneous dispersal throughout the mixture.
- Where the element is added as the oxide the addition may lie in the range from 0.05 to 10wt%.
- A preferred addition is titania.
- A preferred range of titania may be 0.1 to 5wt%.
- A more preferred range of titania may be 0.1 to 2.5wt%.
- Preferably the silica is of purity greater than 99.5%.
- According to a second aspect of the present invention a method of making a core for foundry use comprises the steps of mixing silica with material containing ions selected from the group comprising titanium, zirconium, phosphorous, vanadium, chromium, molybdenum and tungsten and organic binder material, moulding a desired core shape, heating to remove the organic binder and then firing in excess of 1180°C.
- Preferably the firing temperature is in excess of 1200°C.
- The content of organic binder material may be in the range of 15 to 40wt% of the mixture.
- After firing it is preferred that less than 50% of the silica has transformed to crystobalite, further devitrification continuing during mould preheat so that at casting the crystobalite content approaches 100%.
- Titania may be added as titania or as a titanium compound which decomposes to the oxide during processing.
- In order that the invention may be more fully understood examples will now be described by way of illustration only.
- A series of core material compositions were made by mixing fused silica with 0.1wt%, 0.25wt%, 1.0wt% and 2.5wt% titania of substantially submicron particle size. These compositions were pressed into pellets and fired at temperatures from 1150°C to 1300°C. The extent of devitrification was then assessed by means of thermal expansion measurements. The results showed that titania over the whole range of concentrations tested promoted detrification when fired at and above 1200°C. The extent of crystallisation increased with firing temperature, soak time at temperature and with increasing concentration of titania.
- Further material was made of a single composition containing 1wt% titania in the mix to give 1.3wt% in the fired material. The mix comprised 68.50wt% fused silica, 1wt% titania and the balance being an organic binder based in polyethylene glycol. The mix was made in a Z-blade mixer. The organic components were mixed dry with the titania and then the Z-blade mixer heated until the organic components were molten. Mixing of the molten components and titania was continued for 1 hour and then the silica added in portions. When all the silica had been added mixing continued for 2 hours, the heaters were then switched off and the material granulated in situ. This material was designated mix L69.
- A mix was made of a normal production core material containing sodium ions. This material was designated mix 52.
- Test bars of mixes L69 and 52 were injection moulded and heated slowly to a temperature of 700°C to drive off the organic binder materials.
- Some of the mix 52 bars were dipped in ethyl silicate solution prior to firing in order to fill some of the porosity in the material. The dipped material was designated A52.
- All three types of material were then fired under similar conditions at 1150°C for 5 hours. Test bars of each of the compositions were then placed from ambient into the hot zone of a Modulus of Rupture (MOR) testing apparatus which had been allowed to stabilise at 1450°C, and soaked for periods of 30 minutes and 60 minutes. After the completion of each soak period the bars were loaded to failure at 55 N/min to failure. After testing physical measurements of porosity and density were made (see Table).
Physical and Mechanical Properties of Compositions No. 52, A52, L69 tested at 1450°C. Mix No. Test No. Soak Time/ min. Bulk Density/ g cm⁻³ Apparent Solid Density/ g cm⁻³ Apparent Porosity /% MOR / MPa Deflection at Failure / mm 52 *AMB AMB 1.453 2.21 34.1 7.5 0.34 T129 30 1.483 2.27 34.7 6.4 0.80 T128 60 1.467 2.27 35.4 7.2 0.72 A52 *AMB AMB 1.579 2.21 28.6 14.1 0.33 T135 30 1.580 2.26 30.1 11.2 0.80 T134 60 1.598 2.27 29.6 12.4 0.67 L69 *T120 AMB 1.431 2.17 34.1 11.0 0.36 T132 30 1.673 2.28 26.6 37.8 0.52 T131 60 1.680 2.31 27.3 39.8 0.58 *As fired bars tested at ambient temperature. - Referring now to the Table and where Mix 52 as fired has a bulk density of 1.45 g/cm³, porosity of 34,1% and a MOR of 7.5 MPa. The effect of dipping in ethyl silicate prior to firing is to increase the bulk density to 1.58 g/cm³ with a decrease in porosity to 28.6% and a consequent doubling of MOR. The L69 bars as fired have a bulk density of 1.43 g/cm³, a porosity of 34.1% and a MOR of 11.0 MPa. The deflection at failure for all compositions is similar at 0.35mm.
- It may be seen that the L69 material soaked for 30 and 60 minutes at 1450°C has achieved MOR values of 37.8 and 39.8 MPa. The level of crystallisation of mix 52 and A52 materials is comparable to the L69 material but the MOR values are greatly reduced at averages of 6.8 and 11.8 MPa respectively.
Claims (16)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB8723582 | 1987-10-07 | ||
GB878723582A GB8723582D0 (en) | 1987-10-07 | 1987-10-07 | Foundry core material |
Publications (3)
Publication Number | Publication Date |
---|---|
EP0311203A2 true EP0311203A2 (en) | 1989-04-12 |
EP0311203A3 EP0311203A3 (en) | 1990-09-12 |
EP0311203B1 EP0311203B1 (en) | 1993-09-22 |
Family
ID=10624944
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP19880202172 Expired - Lifetime EP0311203B1 (en) | 1987-10-07 | 1988-10-03 | Foundry core material |
Country Status (3)
Country | Link |
---|---|
EP (1) | EP0311203B1 (en) |
DE (1) | DE3884327T2 (en) |
GB (2) | GB8723582D0 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP2740550A4 (en) * | 2011-08-03 | 2015-05-27 | Hitachi Metals Ltd | Ceramic core and method for producing same |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB829447A (en) * | 1956-06-04 | 1960-03-02 | Corning Glass Works | Method of making ceramics and product thereof |
US3002948A (en) * | 1957-09-12 | 1961-10-03 | American Steel Foundries | Shell mold |
US3661829A (en) * | 1970-04-13 | 1972-05-09 | Suddentsche Kalkstickstoff Wer | Aqueous sulfo modified melamine-form-aldehyde resin composition containing multivalent oxides |
EP0179649A2 (en) * | 1984-10-24 | 1986-04-30 | Fairey Industrial Ceramics Limited | Ceramic materials |
Family Cites Families (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3549736A (en) * | 1966-09-02 | 1970-12-22 | Lexington Lab Inc | Process for forming sintered leachable objects of various shapes |
US3859405A (en) * | 1971-02-22 | 1975-01-07 | Precision Metalsmiths Inc | Methods of making molded refractory articles |
US4422496A (en) * | 1982-01-25 | 1983-12-27 | International Minerals & Chemical Corp. | Process for preparing olivine sand cores and molds |
US4522651A (en) * | 1982-01-25 | 1985-06-11 | International Minerals & Chemical Corp. | Foundry mold and core composition |
SU1058704A1 (en) * | 1982-08-06 | 1983-12-07 | Ленинградский Ордена Октябрьской Революции И Ордена Трудового Красного Знамени Технологический Институт Им.Ленсовета | Self-hardening mixture for producing moulds and cores |
FR2569586B1 (en) * | 1984-09-06 | 1986-09-12 | Snecma | PROCESS FOR THE PREPARATION OF FOUNDRY CORES AND CERAMIC COMPOSITION FOR USE IN CARRYING OUT SAID PROCESS |
-
1987
- 1987-10-07 GB GB878723582A patent/GB8723582D0/en active Pending
-
1988
- 1988-10-03 GB GB8823113A patent/GB2210611B/en not_active Expired - Fee Related
- 1988-10-03 EP EP19880202172 patent/EP0311203B1/en not_active Expired - Lifetime
- 1988-10-03 DE DE19883884327 patent/DE3884327T2/en not_active Expired - Fee Related
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB829447A (en) * | 1956-06-04 | 1960-03-02 | Corning Glass Works | Method of making ceramics and product thereof |
US3002948A (en) * | 1957-09-12 | 1961-10-03 | American Steel Foundries | Shell mold |
US3661829A (en) * | 1970-04-13 | 1972-05-09 | Suddentsche Kalkstickstoff Wer | Aqueous sulfo modified melamine-form-aldehyde resin composition containing multivalent oxides |
EP0179649A2 (en) * | 1984-10-24 | 1986-04-30 | Fairey Industrial Ceramics Limited | Ceramic materials |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP2740550A4 (en) * | 2011-08-03 | 2015-05-27 | Hitachi Metals Ltd | Ceramic core and method for producing same |
US9539639B2 (en) | 2011-08-03 | 2017-01-10 | Hitachi Metals, Ltd. | Ceramic core and method for producing same |
Also Published As
Publication number | Publication date |
---|---|
EP0311203A3 (en) | 1990-09-12 |
DE3884327T2 (en) | 1994-02-24 |
EP0311203B1 (en) | 1993-09-22 |
DE3884327D1 (en) | 1993-10-28 |
GB8723582D0 (en) | 1987-11-11 |
GB8823113D0 (en) | 1988-11-09 |
GB2210611A (en) | 1989-06-14 |
GB2210611B (en) | 1991-09-11 |
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