GB2218705A - Investment casting mould - Google Patents
Investment casting mould Download PDFInfo
- Publication number
- GB2218705A GB2218705A GB8909624A GB8909624A GB2218705A GB 2218705 A GB2218705 A GB 2218705A GB 8909624 A GB8909624 A GB 8909624A GB 8909624 A GB8909624 A GB 8909624A GB 2218705 A GB2218705 A GB 2218705A
- Authority
- GB
- United Kingdom
- Prior art keywords
- slurry
- alumina
- mould
- pattern
- firing
- 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.)
- Withdrawn
Links
- 238000005495 investment casting Methods 0.000 title description 4
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 26
- 239000002002 slurry Substances 0.000 claims description 24
- 238000000034 method Methods 0.000 claims description 22
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 11
- 239000000919 ceramic Substances 0.000 claims description 10
- 239000002245 particle Substances 0.000 claims description 10
- 238000001035 drying Methods 0.000 claims description 9
- 235000013312 flour Nutrition 0.000 claims description 8
- 239000011159 matrix material Substances 0.000 claims description 8
- 238000010410 dusting Methods 0.000 claims description 7
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 6
- 238000010304 firing Methods 0.000 claims description 6
- 238000004519 manufacturing process Methods 0.000 claims description 6
- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 claims description 5
- 238000007598 dipping method Methods 0.000 claims description 5
- 229910052863 mullite Inorganic materials 0.000 claims description 5
- 239000008119 colloidal silica Substances 0.000 claims description 4
- 239000011248 coating agent Substances 0.000 claims description 2
- 238000000576 coating method Methods 0.000 claims description 2
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical compound [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 claims 1
- 238000005058 metal casting Methods 0.000 claims 1
- 239000000463 material Substances 0.000 description 24
- 238000012360 testing method Methods 0.000 description 9
- 229910052845 zircon Inorganic materials 0.000 description 6
- GFQYVLUOOAAOGM-UHFFFAOYSA-N zirconium(iv) silicate Chemical compound [Zr+4].[O-][Si]([O-])([O-])[O-] GFQYVLUOOAAOGM-UHFFFAOYSA-N 0.000 description 6
- 239000008186 active pharmaceutical agent Substances 0.000 description 5
- 238000005266 casting Methods 0.000 description 5
- 235000013339 cereals Nutrition 0.000 description 4
- 238000006073 displacement reaction Methods 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- 239000000377 silicon dioxide Substances 0.000 description 3
- 239000000956 alloy Substances 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 238000000605 extraction Methods 0.000 description 2
- 229910052500 inorganic mineral Inorganic materials 0.000 description 2
- 239000011707 mineral Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000007711 solidification Methods 0.000 description 2
- 230000008023 solidification Effects 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- 229910000323 aluminium silicate Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 238000000399 optical microscopy Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 239000005368 silicate glass Substances 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
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
- B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
- B22C1/165—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents in the manufacture of multilayered shell moulds
-
- 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
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Mold Materials And Core Materials (AREA)
- Molds, Cores, And Manufacturing Methods Thereof (AREA)
- Dental Preparations (AREA)
Description
., et 1.7 05 i- -I- Investment Casting Mould The present invention relates
to a mould and to a method for the manufacture of moulds for investment casting.
In the manufacture of components such as, for example, blades and nozzle guide vanes for gas turbine engines the well known technique of precision investment casting is frequently employed. This technique employs a ceramic shell mould formed around, for example, a wax pattern of the component to be cast. Heretofore, the bulk of such ceramic shell. moulds have normally comprised coarse alumina or aLumino-siLicate particles within a zircon flour matrix bonded with silica.
Generally speaking, known ceramic moulds are adequate for the casting of components with microstructures of equiaxed grains. Where the components are required to be of directionally solidified, columnar grain structure (DS) k or of single crystal structure (SX), however, known mould materials have certain disadvantages.
of The casting procedure for the production of DS and SX cordponents requires that the mould be maintained for several hours above the liquidus temperature of the alloy being cast. Such temperatures may exceed 15000C. At these temperatures the strength and stiffness of the mould may be inadequate to withstand the prolonged metallostatic pressure of the molten alloy without either rupture or unacceptable distortion. This limitation is primarily associated with viscous creep of the siliceous binder p h a s e.
Existing DS and SX shell moulds generally use a zircon flour filler material i.e. crushed zircon sand; a natural mineral which is becoming scarce and consequently increasingly expensive.
An object of the present invention i having improved high temperature resistance than known moulds.
s to provide a mould strength and creep According to a first aspect of the present invention a method for the the manufacture of a ceramic shell mould comprises the steps of making a slurry comprising colloidal silica having alumina flour therein, coating a i :Z pattern of a component to be cast with the slurry, dusting the coated pattern with alumina particles, drying the coated and dusted pattern, dipping the pattern into a slurry for a second time, redusting with alumina particles and drying again, repeating the slurry dipping, dusting and drying stages.at Least one further time, removing the pattern and then firing the shell mould.
For the purpose of this specification a "flour" is defined as a ceramic powder wherein substantially all particles are less than 100 micro metres in diameter.
In a preferred embodiment of the method of the present invention the dried shell mould so formed is fired at a temperature sufficiently high to allow at Least a part of the silica to combine with the alumina flour. to form muLLite (3AL 2 0 3" 2SiO 2) in the matrix binder phase.
The shell may be fired either in a specific firing operation after drying and removal of the pattern or during preheating and "soaking" of the mould prior to the casting operation. Temperatures in excess of 14000C are preferred.
Preferably at Least part of the alumina in the slurry should be in the form generally known as "reactive aLumina". Such alumina has a high specific surface area and a very small particle size. Examples of suitable commerciaLLy available aLumina powders are those of the "RA" series (trademark) produced by British ALcan ALuminium Limited and those by Alcoa under the code CT9 (trade mark). PreferabLy the slurry may contain from 1 to 25 wt% of reactive alumina and up to 70 wt% of other alumina fLour. More preferably the matrix slurry may contain from 10 to 20 wt% of reactive alumina.
The matrix slurry may optionally contain up to 5 wt% of fine titania powder which may act as a catalyst in the formation of mullite in the matrix. It has been found that additions greater than 5 wt% confer no additional practical benefit.
According to a second aspect of the present invention there is provided a ceramic shell mould when made by the method of the first aspect.
It has been found that the new mould material possesses greater thermal diffusivity than conventional materials. This is advantageous, especially in the case of DS and SX castings in that it allows more precise control of heat extraction thereby reducing the risk of nucleating stray grains in the so-called "mushy" region ahead of the solidification front.
t, 0 1 C_ - 5 A further advantage conferred by the greatly improved high temperature strength properties of the new material is that thinner shell moulds may be used. This in turn also enhances control of heat extraction during solidification.
Shell moulds of -the present invention synthetic "starting" materials which are available and of relatively high purity naturally occuring minerals such as zircon.
contain only bot h readily compared to In order that the present invention may be more fully understood examples will now be described by way of illustration only.
The accompanying figure shows a graph of creep displacement against time for conventional mould materials and for materials according to the present invention.
Examples
Moulds for testing were prepared by the following method.
A wax pattern was dipped in a slurry of the first composition shown in Table 1 The dipped pattern was then dusted with 80's mesh (B.S.) fused alumina and dried.
The coated pattern was then dipped in a more dilute version of the same slurry and then dusted with 28/48's mesh (B.S.) Tabular Alumina and then dried.
The sample was then dipped in a slurry of the second composition given in Table 1, dusted with 28/48's mesh (B.S.) Tabular ALumina and dried.
This last dipping, dusting and drying sequence was repeated as required.
The final stage in building the shell mould was a slurry dip only followed by drying.
Each sample had seven slurry and six dusting coats.
The wax pattern was removed by a known method.
Some of the moulds were fired at 9600C for 30 minutes. These were designated material "AV'.
Others were fired at 1500 0 C for 2 hours. These were designated material "A2".
rl a 1 - 7 -1; 1 Table 1
Slurry Colloidal 325 s i I i ca a 1 u m i n a suspension 28/48 Reactive Titania alumina alumina 1st Comp 25.4 58.6 - 14.6 1.4 2nd " 20.3 50.7 15.1 12.7 1.2 All the above figures are in weight %. The colloidal silica contained approximately 30 wt% of silica.
Further moulds were made using conventional colloidal silica/zircon flour slurry by conventional current methods and given the same number of slurry and dusting coats as A2 and AV. These moulds were fired at 9600C for 30 minutes. This material was designated "Y.D.S."
Modulus of rupture tests were carried out at 10500C on the prepared samples. The results are given in Table 2 below.
Table 2
Eaterial MOR 10500C Av.ShelC Av.Fail Load /MPa Thickness (mm) 10500C/N Y.D.S. 15.0 4.6 67.5 A2 24.2 4.7 108.9 A2' 30.0 4.7 135.0 As may be seen from Table 2 the strength of the A2 material under equivalent processing conditions is about 60% greater than the Y.D.S material and the A2' material is 100% stronger than the Y.D.S. material.
The important improvement of the A21 material over Y.D.S material is in creep resistance as shown by creep tests in the accompanying figure. Conditions for the tests were; test temperature 14200c; test bars fired at 15000 for approximately 2 hours and soaked at the test temperatures for approximately 6 minutes prior to testing; test bar section was 4.6 x 25.0 mm and a 750g static load was used. The conventional Y.D.S. material failed in under 20 seconds with a displacement of 0.6 mm whereas the A2' material showed steady creep with a displacement of 0.33 mm after 7 minutes. In casting DS and SX components creep resistance of the shell mould is of greater importance.
t h e t h e 1; 1 The thermal diffusivity of the A2 and A21 materials was 4.24 mm 2 sec -1 compared with 1.74 mm 2 sec- 1 for the Y.D.S. material.
Mullite was detected by X-ray diffraction analysis in A21 but not in A2 material.
Examination of the AV material by optical microscopy showed extensive bonding of the Large alumina grains with the matrix which consisted of the small alumina particles bonded with muLLite. In the Y.D.S material, in contrast, there was very Little bonding of the Large alumina particles to the matrix of small zircon particles bonded with silicate glass.
-
Claims (1)
- C 1 a i m s1.. A method for the manufacture of a ceramic sheLL mould, the method comprising the steps of making a slurry comprising colloidal silica having alumina fLour therein, coating a pattern of a component to be cast the slurry, dusting the coated pattern with a particles, drying the coated and dusted dipping the dried pattern into a slurry for a time. redusting with alumina particles and w i t h alumin patterr second drying again, repeating the slurry dipping, dusting and drying stages at least one further time, removing the pattern and then firing the shell mould.2.A method according to Claim 1 wherein the mould is fired at a temperature sufficiently high to form mullite in the matrix.3. A method according to either Claim 1 or Claim 2 wherein the firing temperature is above 14000C.A method according to any one preceding claim wherein the firing of the mould is carried out as a specific operation.i 11 7 - 11 1 5. A method according to any one of Claims- 1 to 3 wherein the firing of the mould is performed during preheating immediately prior to metal casting.6. A method according to any one preceding claim wherein at Least a part of the alumina in the slurry is in the form of reactive alumina.7. A method according to Claim 6 wherein the slurry contains from 1 to 25 wt% of reactive alumina.8. A method according to Claim 7 wherein the slurry contains from 10 to 20 wt% of reactive alumina.A meth6d according to any one preceding claim wherein the slurry contains up to 5 wt% of titania.10. A ceramic shell mould when made by any one of the method claims from Claim 1 to Claim 9.11.A method for the manufacture of a ceramic shell mould substantially as hereinbefore described with reference to the accompanying specification.12. A ceramic shell mould substantially as hereinbefore described with reference to the accompanying specification.Published 1989 at The Patent Office. State House, 6673.HighHolborn. London WC1R4TP Further copies maybe obtained from The Patent office. Sales Branch, St Mary Cray. Orpington, Kent BRS 3RD. Printed by Multiplex techniques ltd. St Mary Cray, Kent, Con. 1/87
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB888811799A GB8811799D0 (en) | 1988-05-19 | 1988-05-19 | Investment casting mould |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8909624D0 GB8909624D0 (en) | 1989-06-14 |
| GB2218705A true GB2218705A (en) | 1989-11-22 |
Family
ID=10637123
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB888811799A Pending GB8811799D0 (en) | 1988-05-19 | 1988-05-19 | Investment casting mould |
| GB8909624A Withdrawn GB2218705A (en) | 1988-05-19 | 1989-04-27 | Investment casting mould |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB888811799A Pending GB8811799D0 (en) | 1988-05-19 | 1988-05-19 | Investment casting mould |
Country Status (2)
| Country | Link |
|---|---|
| EP (1) | EP0343401A3 (en) |
| GB (2) | GB8811799D0 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2253400A (en) * | 1991-03-06 | 1992-09-09 | Ae Turbine Components | Casting mould |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2297285A (en) * | 1995-01-25 | 1996-07-31 | T & N Technology Ltd | Investment casting mould |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4664172A (en) * | 1984-08-09 | 1987-05-12 | Agency Of Industrial Science And Technology | Method for production of investment shell mold for grain-oriented casting of super alloy |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4188450A (en) * | 1976-06-23 | 1980-02-12 | General Electric Company | Shell investment molds embodying a metastable mullite phase in its physical structure |
| GB2168060B (en) * | 1984-12-04 | 1988-08-10 | Ohara Kk | Mold material and process for casting of pure titanium or titanium alloy |
-
1988
- 1988-05-19 GB GB888811799A patent/GB8811799D0/en active Pending
-
1989
- 1989-04-27 GB GB8909624A patent/GB2218705A/en not_active Withdrawn
- 1989-05-02 EP EP19890107893 patent/EP0343401A3/en not_active Withdrawn
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4664172A (en) * | 1984-08-09 | 1987-05-12 | Agency Of Industrial Science And Technology | Method for production of investment shell mold for grain-oriented casting of super alloy |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2253400A (en) * | 1991-03-06 | 1992-09-09 | Ae Turbine Components | Casting mould |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8909624D0 (en) | 1989-06-14 |
| GB8811799D0 (en) | 1988-06-22 |
| EP0343401A2 (en) | 1989-11-29 |
| EP0343401A3 (en) | 1990-12-19 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |