EP0343401A2 - Moule de précision - Google Patents
Moule de précision Download PDFInfo
- Publication number
- EP0343401A2 EP0343401A2 EP89107893A EP89107893A EP0343401A2 EP 0343401 A2 EP0343401 A2 EP 0343401A2 EP 89107893 A EP89107893 A EP 89107893A EP 89107893 A EP89107893 A EP 89107893A EP 0343401 A2 EP0343401 A2 EP 0343401A2
- Authority
- EP
- European Patent Office
- Prior art keywords
- alumina
- slurry
- 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- Withdrawn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
Images
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
Definitions
- the present invention relates to a mould and to a method for the manufacture of moulds for investment casting.
- 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) or of single crystal structure (SX), however, known mould materials have certain disadvantages.
- the casting procedure for the production of DS and SX components requires that the mould be maintained for several hours above the liquidus temperature of the alloy being cast. Such temperatures may exceed 1500 o C. 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 phase.
- An object of the present invention is to provide a mould having improved high temperature strength and creep resistance than known moulds.
- 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 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, repeatting 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.
- a "flour” is defined as a ceramic powder wherein substantially all particles are less than 100 micro metres in diameter.
- 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 (3Al2O3.2SiO2) 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 1400 o C are preferred.
- the alumina in the slurry should be in the form generally known as "reactive alumina".
- alumina has a high specific surface area and a very small particle size.
- 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).
- 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.
- a ceramic shell mould when made by the method of the first aspect.
- 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.
- 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 contain only synthetic "starting" materials which are both readily available and of relatively high purity compared to naturally occuring minerals such as zircon.
- the accompanying figure shows a graph of creep displacement against time for conventional mould materials and for materials according to the present invention.
- 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.
- 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.
- the colloidal silica contained approximately 30 wt% of silica.
- 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 A2′ material over the Y.D.S material is in creep resistance as shown by the creep tests in the accompanying figure. Conditions for the tests were; test temperature 1420 o C; test bars fired at 1500 o 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.
- the thermal diffusivity of the A2 and A2′ materials was 4.24 mm2 sec ⁇ 1 compared with 1.74 mm2 sec ⁇ 1 for the Y.D.S. material.
- Mullite was detected by X-ray diffraction analysis in A2′ but not in A2 material.
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)
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB888811799A GB8811799D0 (en) | 1988-05-19 | 1988-05-19 | Investment casting mould |
| GB8811799 | 1988-05-19 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0343401A2 true EP0343401A2 (fr) | 1989-11-29 |
| EP0343401A3 EP0343401A3 (fr) | 1990-12-19 |
Family
ID=10637123
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP19890107893 Withdrawn EP0343401A3 (fr) | 1988-05-19 | 1989-05-02 | Moule de précision |
Country Status (2)
| Country | Link |
|---|---|
| EP (1) | EP0343401A3 (fr) |
| GB (2) | GB8811799D0 (fr) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1996022849A1 (fr) * | 1995-01-25 | 1996-08-01 | Aetc Limited | Moule pour moulage a modele perdu |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB9104728D0 (en) * | 1991-03-06 | 1991-04-17 | Ae Turbine Components | Casting mould |
Family Cites Families (3)
| 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 |
| JPS6146346A (ja) * | 1984-08-09 | 1986-03-06 | Agency Of Ind Science & Technol | 超合金の一方向性凝固鋳型に用いるインベストメントシエル鋳型の製造法 |
| 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/fr not_active Withdrawn
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1996022849A1 (fr) * | 1995-01-25 | 1996-08-01 | Aetc Limited | Moule pour moulage a modele perdu |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2218705A (en) | 1989-11-22 |
| EP0343401A3 (fr) | 1990-12-19 |
| GB8811799D0 (en) | 1988-06-22 |
| GB8909624D0 (en) | 1989-06-14 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
| AK | Designated contracting states |
Kind code of ref document: A2 Designated state(s): CH DE FR IT LI |
|
| 17P | Request for examination filed |
Effective date: 19900226 |
|
| PUAL | Search report despatched |
Free format text: ORIGINAL CODE: 0009013 |
|
| AK | Designated contracting states |
Kind code of ref document: A3 Designated state(s): CH DE FR IT LI |
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| STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN |
|
| 18D | Application deemed to be withdrawn |
Effective date: 19910620 |