CA1304561C - Tube having filter therein for use in the casting of metals - Google Patents
Tube having filter therein for use in the casting of metalsInfo
- Publication number
- CA1304561C CA1304561C CA000605807A CA605807A CA1304561C CA 1304561 C CA1304561 C CA 1304561C CA 000605807 A CA000605807 A CA 000605807A CA 605807 A CA605807 A CA 605807A CA 1304561 C CA1304561 C CA 1304561C
- Authority
- CA
- Canada
- Prior art keywords
- tube
- filter
- mould
- sprue
- casting
- 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
Links
Landscapes
- Casting Support Devices, Ladles, And Melt Control Thereby (AREA)
Abstract
ABSTRACT
TUBE HAVING FILTER THEREIN FOR
USE IN THE CASTING OF METALS
A tube of refractory material for use in the casting of molten metals has a filter located on one or more ledges at or adjacent the base of the tube and held in position by one or more projections on the inner surface of the tube or on the lateral surface of the filter. The filter may be a honeycomb type of structure having cells which extend from one face to an opposite face, or a structure having interconnecting cells such as a ceramic foam. In use the tube is inserted in a mould sprue which communicates directly with the mould cavity.
TUBE HAVING FILTER THEREIN FOR
USE IN THE CASTING OF METALS
A tube of refractory material for use in the casting of molten metals has a filter located on one or more ledges at or adjacent the base of the tube and held in position by one or more projections on the inner surface of the tube or on the lateral surface of the filter. The filter may be a honeycomb type of structure having cells which extend from one face to an opposite face, or a structure having interconnecting cells such as a ceramic foam. In use the tube is inserted in a mould sprue which communicates directly with the mould cavity.
Description
~3C~5~
TUBE HAVING FILTER THEREIN
FOR USE IN THE CASTING OF METALS
This invention relates to a tube of refractory material having a filter therein for use in the casting of metals, and to a mould containing the tube.
Our copending Canadian Patent Application No. 588962 describes a method of casting a molten metal in which a tube of refractory material having a filter therein is located in the sprue (defined as a passage which provides the sole means of entry of molten metal) of a mould and the molten is poured through the filter into the mould cavity. The method is particularly useful in the gravity die-casting or low pressure diecasting of non-ferrous metals in permanent moulds such as metal dies.
It has now been found that a tube in which the filter is located on one or more ledges adjacent the base of the tube and is held in position by one or more projections on the inside of the tube or on the lateral surface of the filter, is particularly useful in the method described above.
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TUBE HAVING FILTER THEREIN
FOR USE IN THE CASTING OF METALS
This invention relates to a tube of refractory material having a filter therein for use in the casting of metals, and to a mould containing the tube.
Our copending Canadian Patent Application No. 588962 describes a method of casting a molten metal in which a tube of refractory material having a filter therein is located in the sprue (defined as a passage which provides the sole means of entry of molten metal) of a mould and the molten is poured through the filter into the mould cavity. The method is particularly useful in the gravity die-casting or low pressure diecasting of non-ferrous metals in permanent moulds such as metal dies.
It has now been found that a tube in which the filter is located on one or more ledges adjacent the base of the tube and is held in position by one or more projections on the inside of the tube or on the lateral surface of the filter, is particularly useful in the method described above.
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According to the invention there is provided a tube of refractory material having a filter fixed therein wherein the filter is located on one or more ledges at or adjacent the base of the tube and is held in position by one or more projections on the inner surface of the tube or on the lateral surface of the filter.
According to a further feature of the invention there is provided a mould for metal casting comprising a mould cavity and a sprue communicating directly with the cavity and having located in the sprue a tube of refractory material having a filter fixed therein as described above.
Although a plurality of ledges spaced apart around the perimeter of the tube at or adjacent its base may be used, it is preferable that the tube has a single ledge extending completely around the perimeter. A ledge extending completely around the perimeter of the tube not only locates the filter in the desired position but it also prevents metal from bypassing the filter when the tube is inserted in the sprue of a mould and has molten metal poured through it.
Although a filter having one or more projections may be used, elongate projections on the inside of the tube are preferred so that the filter can be located on the ledge or ledges centrally over the aperture in the base of the tube.
i3a~6~
According to a further feature of the invention there is provided a mould for metal casting comprising a mould cavity and a sprue communicating directly with the cavity and having located in the sprue a tube of refractory material having a filter fixed therein as described above.
Although a plurality of ledges spaced apart around the perimeter of the tube at or adjacent its base may be used, it is preferable that the tube has a single ledge extending completely around the perimeter. A ledge extending completely around the perimeter of the tube not only locates the filter in the desired position but it also prevents metal from bypassing the filter when the tube is inserted in the sprue of a mould and has molten metal poured through it.
Although a filter having one or more projections may be used, elongate projections on the inside of the tube are preferred so that the filter can be located on the ledge or ledges centrally over the aperture in the base of the tube.
i3a~6~
The projections on the inner surface of the tube may be small knife-edges but they are preferab1y ribs of a more substantial size. The projections are preferably equally spaced apart 5 around the perimeter of the inner surface of the tube and are tapered from bottom to top.
The filter is inserted into the tube from the top. located on the ledge or ledges and held in position by the projections, the presence of the projections ensures that small size variations which occur in filters of the same nominal size can be tolerated, because filters of slightly different- size can still be held firmly in place.
The combination of the ledge or ledges and the projections allows transportation of the tubes without the filters being dislodged and prevents the filters from floating when molten metal is poured into moulds in which they are 1ocated.
For ease of manufacture the tube is preferably cylindrical but if desired, the outer and/or the inner perimeter may be of an alternative shape such as oval or square.
If desired to aid filling of the tube with molten metal, the top end of the tube may be flared in the shape of a funnel.
. .
~3~4561 The material from which the tube is made must be sufficiently refractory to withstand the temperature of the metal to be cast in the mould.
Suitable materials include silica sand and heat-S -insulating materials containing fibrous and/or particulate refractory materials. The preferred tubes are made by dewatering on to a suitable former an aqueous slurry containing the fibrous and/or particulate refractory material and a binder, removing the tube from the former and then heating the tube to remove water and to harden or cure the binder. Such tubes can be manufactured accurately to close tolerances on both their inner and outer surfaces. This is important because the outer surface must be such that the tube fits snugly in the sprue of a die or sand mould without being crushed and without floating of the tube occuring when metal is cast into the die or sand mould. Accuracy in the size of the inner surface is important in order to guarantee insertion and location of the filter. Such tubes are also erosion resistant and this ensures that particles and fibres are not washed from the surface by metal poured into the tube and through. the filter into the mould cavity.
The filter may be a honeycomb type of structure having cells which extend from one face to an opposite face, or a structure having inter-connecting cells such as a ceramic foam.
~3~4561 Ceramic foam filters are preferred because molten metal flows through such filters much less turbulently than it does through other types of filter. Ceramic foam filters may be made using a known method of making a ceramic foam, in which an organic foam, usually polyurethane foam, is impregnated with an aqueous slurry of ceramic material containing a binder, the impregnated foam is dried to remove water and the dried impregnated foam is fired to burn off the organic foam to produce a ceramic foam.
As used herein the term sprue means any passage which is used to provide the sole means of entry of molten metal into a mould.
The mould of the invention has no running system apart from the sprue. In addition to the mould cavity and the sprue the mould may also have one or more feeder cavities.
The mould of the invention may be used for the casting of a variety of non-ferrous metals, for example, aluminium and aluminium alloys, aluminium bronze, magnesium and its alloys, zinc and its alloys and lead and its alloys, or for the casting of ferrous metals such as iron and steel.
The mould may be a sand mould prepared to conventional foundry practice or a permanent mould, such as a metal die, for producing castings by gravity diecasting or by low pressure die-casting.
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13(1 4561 The preferred application of the tube and mould of the invention is the gravity diecasting of aluminium or aluminium alloys.
In order to insert and locate the tube in the sprue of the mould it is preferred that the outer surface of the tube tapers from one end of the tube to the other end and that the sprue has a corresponding taper, the direction of taper depending on whether the tube is to be inserted in the sprue from above or below. The outeP surface of the tube or the mould surface surrounding the sprue may have means for holding the tube firmly in position once it has been inserted in the sprue.
The means may be for example protrusions such as ribs on the lateral surface of the tube or protrusions such as ribs formed on the sprue of a sand mould by the use of a recessed former during mould production or in the case of a metal mould or die protrusions such as ribs machined on the mould or die surface surrounding the sprue.
The refractory tube is preferably located in the sprue such that the lower end of the tube and the filter are not in contact with the casting.
This can be achieved for example by incorporating a ledge above the base of the sprue and seating the tube on the ledge.
~3Q4561 When a casting requiring a feeder is produced using the tube and mould of the invention it is possible to locate the tube contain~ng the filter in the feeder cavity and to utilise the feeder as the sprue. In such applications it will be usual to use a tube wich has exothermic and/or heat-insulating properties as well as being refractory in order to achieve satisfactory feeding of the casting.
After pouring and as the metal in the mould cavity solidifies and contracts, molten ~etal is fed from the tube cavity through the filter to compensate for the contraction and to produce a sound casting. After solidification the casting is removed from the mould and the sprue/
feeder is removed.
In order to mak-e it easy to remove the sprue/feeder a breaker core may be located between the lower end of the tube and the mould cavity in accordance with normal practice. The breaker core may be fixed to the base of the tube if desired, for example by means of an adhesive or by shaping the breaker core so that part of the breaker core can be push fitted into the tube.
Alternatively the breaker core may be formed integrally with the tube.
13~S~,i By the use of a tube of refractory material having a filter therein and a mould according to the invention, having no running system, apart from the sprue, it is possible to produce castings more economically compared with conventional practices of sand casting or gravity diecasting metals because elimination of the running system significantly reduces the weight of metal which must be cast to produce a particular 1~ casting and less fettling of the casting is needed.
The construction of a sand mould or the design of a die for gravity diecasting is simplified and both can be made smaller compared to conventional sand moulds or dies. An existing die may be modified to produce a mould according to the invention by blocking off its running system and if necessary, machining the sprue of the die to allow insertion of the tube.
Furthermore, metal can be cast at lower melt temperatures and in the case of gravity die-casting, at lower die temperatures.
Castings produced in moulds according to the invention have improved directional solidifi--cation characteristics and are substantially free from porosity and inclusions and as a result, have good mechanical properties such as elongation and good machinability and are pressure tight.
1.3~ 56ii The invention is illustrated with reference to the accompanying drawings in which Figure 1 is a vertical cross-section of a tube of refractory material having a filter therein according to the invention and Figure 2 is a half horizontal cross--section of the tube of Figure 1.
Referring to the drawings a tube 1 of circular horizontal cross-section and made from refractory material has a ledge 2 at its base 3 extending around the perimeter of the tube 1. The tube 1 also has five elongate ribs 4, equally spaced apart around its inner surface 5 adjacent the base 3. The ribs 4 taper from their bottom end 6 to their top end 7, and the tube 1 tapers from the top 8 to the base 3. The tube 1 contains a ceramic foam 9 of a circular horizontal cross-section which is inserted in the tuhe 1 at the top 8, located on the ledge 2 and held in place by the ribs 4.
In use the tube 1 is inserted into the sprue of a mould and molten non-ferrous metal poured into the top 8 of the tube 1, passes through the filter 9 into the mould cavity.
The filter is inserted into the tube from the top. located on the ledge or ledges and held in position by the projections, the presence of the projections ensures that small size variations which occur in filters of the same nominal size can be tolerated, because filters of slightly different- size can still be held firmly in place.
The combination of the ledge or ledges and the projections allows transportation of the tubes without the filters being dislodged and prevents the filters from floating when molten metal is poured into moulds in which they are 1ocated.
For ease of manufacture the tube is preferably cylindrical but if desired, the outer and/or the inner perimeter may be of an alternative shape such as oval or square.
If desired to aid filling of the tube with molten metal, the top end of the tube may be flared in the shape of a funnel.
. .
~3~4561 The material from which the tube is made must be sufficiently refractory to withstand the temperature of the metal to be cast in the mould.
Suitable materials include silica sand and heat-S -insulating materials containing fibrous and/or particulate refractory materials. The preferred tubes are made by dewatering on to a suitable former an aqueous slurry containing the fibrous and/or particulate refractory material and a binder, removing the tube from the former and then heating the tube to remove water and to harden or cure the binder. Such tubes can be manufactured accurately to close tolerances on both their inner and outer surfaces. This is important because the outer surface must be such that the tube fits snugly in the sprue of a die or sand mould without being crushed and without floating of the tube occuring when metal is cast into the die or sand mould. Accuracy in the size of the inner surface is important in order to guarantee insertion and location of the filter. Such tubes are also erosion resistant and this ensures that particles and fibres are not washed from the surface by metal poured into the tube and through. the filter into the mould cavity.
The filter may be a honeycomb type of structure having cells which extend from one face to an opposite face, or a structure having inter-connecting cells such as a ceramic foam.
~3~4561 Ceramic foam filters are preferred because molten metal flows through such filters much less turbulently than it does through other types of filter. Ceramic foam filters may be made using a known method of making a ceramic foam, in which an organic foam, usually polyurethane foam, is impregnated with an aqueous slurry of ceramic material containing a binder, the impregnated foam is dried to remove water and the dried impregnated foam is fired to burn off the organic foam to produce a ceramic foam.
As used herein the term sprue means any passage which is used to provide the sole means of entry of molten metal into a mould.
The mould of the invention has no running system apart from the sprue. In addition to the mould cavity and the sprue the mould may also have one or more feeder cavities.
The mould of the invention may be used for the casting of a variety of non-ferrous metals, for example, aluminium and aluminium alloys, aluminium bronze, magnesium and its alloys, zinc and its alloys and lead and its alloys, or for the casting of ferrous metals such as iron and steel.
The mould may be a sand mould prepared to conventional foundry practice or a permanent mould, such as a metal die, for producing castings by gravity diecasting or by low pressure die-casting.
, ' .
:
:. , , .~ , . : :' ': .
.,. :
.
,~: . . .
13(1 4561 The preferred application of the tube and mould of the invention is the gravity diecasting of aluminium or aluminium alloys.
In order to insert and locate the tube in the sprue of the mould it is preferred that the outer surface of the tube tapers from one end of the tube to the other end and that the sprue has a corresponding taper, the direction of taper depending on whether the tube is to be inserted in the sprue from above or below. The outeP surface of the tube or the mould surface surrounding the sprue may have means for holding the tube firmly in position once it has been inserted in the sprue.
The means may be for example protrusions such as ribs on the lateral surface of the tube or protrusions such as ribs formed on the sprue of a sand mould by the use of a recessed former during mould production or in the case of a metal mould or die protrusions such as ribs machined on the mould or die surface surrounding the sprue.
The refractory tube is preferably located in the sprue such that the lower end of the tube and the filter are not in contact with the casting.
This can be achieved for example by incorporating a ledge above the base of the sprue and seating the tube on the ledge.
~3Q4561 When a casting requiring a feeder is produced using the tube and mould of the invention it is possible to locate the tube contain~ng the filter in the feeder cavity and to utilise the feeder as the sprue. In such applications it will be usual to use a tube wich has exothermic and/or heat-insulating properties as well as being refractory in order to achieve satisfactory feeding of the casting.
After pouring and as the metal in the mould cavity solidifies and contracts, molten ~etal is fed from the tube cavity through the filter to compensate for the contraction and to produce a sound casting. After solidification the casting is removed from the mould and the sprue/
feeder is removed.
In order to mak-e it easy to remove the sprue/feeder a breaker core may be located between the lower end of the tube and the mould cavity in accordance with normal practice. The breaker core may be fixed to the base of the tube if desired, for example by means of an adhesive or by shaping the breaker core so that part of the breaker core can be push fitted into the tube.
Alternatively the breaker core may be formed integrally with the tube.
13~S~,i By the use of a tube of refractory material having a filter therein and a mould according to the invention, having no running system, apart from the sprue, it is possible to produce castings more economically compared with conventional practices of sand casting or gravity diecasting metals because elimination of the running system significantly reduces the weight of metal which must be cast to produce a particular 1~ casting and less fettling of the casting is needed.
The construction of a sand mould or the design of a die for gravity diecasting is simplified and both can be made smaller compared to conventional sand moulds or dies. An existing die may be modified to produce a mould according to the invention by blocking off its running system and if necessary, machining the sprue of the die to allow insertion of the tube.
Furthermore, metal can be cast at lower melt temperatures and in the case of gravity die-casting, at lower die temperatures.
Castings produced in moulds according to the invention have improved directional solidifi--cation characteristics and are substantially free from porosity and inclusions and as a result, have good mechanical properties such as elongation and good machinability and are pressure tight.
1.3~ 56ii The invention is illustrated with reference to the accompanying drawings in which Figure 1 is a vertical cross-section of a tube of refractory material having a filter therein according to the invention and Figure 2 is a half horizontal cross--section of the tube of Figure 1.
Referring to the drawings a tube 1 of circular horizontal cross-section and made from refractory material has a ledge 2 at its base 3 extending around the perimeter of the tube 1. The tube 1 also has five elongate ribs 4, equally spaced apart around its inner surface 5 adjacent the base 3. The ribs 4 taper from their bottom end 6 to their top end 7, and the tube 1 tapers from the top 8 to the base 3. The tube 1 contains a ceramic foam 9 of a circular horizontal cross-section which is inserted in the tuhe 1 at the top 8, located on the ledge 2 and held in place by the ribs 4.
In use the tube 1 is inserted into the sprue of a mould and molten non-ferrous metal poured into the top 8 of the tube 1, passes through the filter 9 into the mould cavity.
Claims (12)
1. A tube of refractory material having a filter fixed therein wherein the filter is located on one or more ledges at or adjacent the base of the tube and is held in position by one or more projections on the inner surface of the tube or on the lateral surface of the filter.
2. A tube according to Claim 1 having a single ledge extending around the perimeter of the tube.
3. A tube according to Claim 1 wherein the projections are equally spaced apart around the perimeter of the inner surface of the tube and are tapered from bottom to top.
4. A tube according to Claim 1 having an outer surface which tapers from one end of the tube to the other end.
5. A tube according to Claim 1 wherein the tube has protrusions on its outer surface.
6. A tube according to Claim 1 wherein the top of the tube is flared.
7. A tube according to Claim 1 wherein the filter has cells which extend from one face to an opposite face.
8. A tube according to Claim 1 wherein the filter is a ceramic foam.
9. A mould for metal casting comprising a mould cavity and a sprue communicating directly with the sprue and having located in the sprue a tube of refractory material having a filter fixed therein according to Claim 1.
10. A mould according to Claim 9 formed of sand.
11. A mould according to Claim 9 wherein the mould is a metal die.
12. A mould according to Claim 9 wherein the mould surface surrounding the sprue has protrusions for holding the tube in position.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB888818229A GB8818229D0 (en) | 1988-07-30 | 1988-07-30 | Tube having filter therein for use in casting of non-ferrous metals |
| GB8818229 | 1988-07-30 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1304561C true CA1304561C (en) | 1992-07-07 |
Family
ID=10641418
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000605807A Expired - Lifetime CA1304561C (en) | 1988-07-30 | 1989-07-17 | Tube having filter therein for use in the casting of metals |
Country Status (2)
| Country | Link |
|---|---|
| CA (1) | CA1304561C (en) |
| GB (1) | GB8818229D0 (en) |
-
1988
- 1988-07-30 GB GB888818229A patent/GB8818229D0/en active Pending
-
1989
- 1989-07-17 CA CA000605807A patent/CA1304561C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| GB8818229D0 (en) | 1988-09-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |