Method of making metal castings

• US 4,804,032 A
• Filed: 07/27/1987
• Issued: 02/14/1989
• Est. Priority Date: 11/29/1985
• Status: Expired due to Term

• Current Assignee: Cosworth Research & Development Limited Hylton Road Worcester WR2 5JS United Kingdom
• Original Assignee: Cosworth Research & Development Limited
• Inventors: Wilkins, Philip S. A.
• Primary Examiner(s): Jordan, M.
• Assistant Examiner(s): Batten, Jr., J. Reed
• Application Number:
  US07/097,970
• Time in Patent Office: 568 Days
• Field of Search: 164/34, 164/35, 164/36, 164/119, 164/246, 164/365
• US Class Current: 164/34
• CPC Class Codes: B22C 9/046 Use of patterns which are eliminated by the liquid metal in the mould
• CPC Class Codes: B22D 18/04 Low pressure casting, i.e. making use of pressures up to a few bars to fill the mould

Abstract

Method of and apparatus for making metal castings using a polystyrene pattern 10 embedded in unbonded sand 20 which is consolidated to form a mould M in which is defined a mould cavity C. Molten metal is fed into the cavity C and permitted to solidify to form a casting 11. The metal is aluminum or an aluminum alloy and at least part of the mould is formed of sand which comprises at least 50% zircon sand, or other particulate material suitable for making a mould and having a bulk density lying in the range 2-3 grams/cc. The mould M may have a moulding feature 9 having upper and lower surfaces for contact with the metal and which projects inwardly of the mould cavity C from the main wall thereof and the length of any one section of the molding feature 9 being at least twice the thickness of the thinnest part thereof by which the section is connected to the main wall of the mould cavity.

Claims

1. A method of making metal castings comprising the steps of providing an in situ destroyable pattern, then embedding the pattern in unbonded sand and consolidating the sand to form a mould in which is defined a mould cavity comprising at least one preformed moulding feature which is included in said pattern, then feeding a molten metal selected from the group consisting of aluminum and aluminum alloys into the cavity and permitting the metal to solidify within the cavity to form a casting and interrupting the feed of metal to the cavity and removing the casting from the cavity, wherein at least part of the mould is formed of sand which comprises at least substantially wholly sand selected from the group consisting of zircon sand and other particulate material suitable for making a mould having a bulk density lying in the range 2-3 gm/cc.

2. A method according to claim 1 wherein said preformed moulding feature has upper and lower surfaces for contact with the metal and projects inwardly of the mould cavity from a main wall thereof and has a configuration such that a mould made of 100% silica sand, except for usual impurities, and LM25 aluminum alloy is the metal cast, a part of the casting resulting from the moulding feature is displaced by at least 5% from its designed position relative to the nearest part of the casting defined by the main wall of the cavity.

3. A method according to claim 1 wherein the whole of the mould, except the or each preformed moulding feature, comprises unbonded said which comprises at least substantially wholly sand, selected from the group consisting of zircon sand and other particulate material suitable for making a mould having a bulk density lying in the range 2-3 gm/cc.

4. A method according to claim 1 wherein said part comprises at least one moulding feature which has upper and lower surfaces for contact with the metal and which projects inwardly of the mould cavity from a main wall thereof and has a configuration such that the length of any one section of the moulding feature is at least twice the thickness of the thinnest part thereof by which the section is connected to the main wall of the mould cavity.

5. A method of making metal castings comprising the steps of providing an in situ destroyable pattern, then embedding the pattern in unbonded sand and consolidating the sand to form a mould in which is defined a mould cavity, then feeding a molten metal selected from the group consisting of aluminum and aluminum alloys into the cavity and permitting the metal to solidify within the cavity to form a casting and interrupting the feed of metal to the cavity and removing the casting from the cavity, wherein the mould cavity comprises a moulding feature which has upper and lower surfaces for contact with the metal and which projects inwardly of the mould cavity from a main wall thereof and has a configuration such that a mould made of 100% silica sand, except for usual impurities, and LM25 aluminum alloy is the metal cast, a part of the casting resulting from the moulding feature is displaced by at least 5% from its designed position relative to the nearest part of the casting defined by the main wall of the cavity made of sand which comprises at least substantially wholly sand selected from the group consisting of zircon sand and other particulate material suitable for making a mould having a bulk density lying in the range 2-3 gm/cc.

6. A method according to claim 5 wherein the moulding feature is formed of unbonded sand.

7. A method according to claim 6 wherein the unbonded sand comprises at least substantially wholly zircon sand, except for usual impurities.

8. A method according to claim 5 wherein at least substantially the whole of the moulding feature is preformed of sand bonded with a bonding agent.

9. A method according to claim 8 wherein the bonded sand comprises at least substantially wholly zircon sand and bonding agent except for usual impurities.

10. A method according to claim 5 wherein the pattern is supported within a container, by means of a feed member which is mounted within the container, introducing the sand into the container to embed the pattern therein, and feeding metal into the mould cavity through a passage provided by the feed member into the mould cavity, an ingate part of the pattern being disposed in casting relationship with an orifice in the container and the metal being fed generally upwardly against the force of gravity to the orifice from a reservoir of molten metal which is at a level which is below the level of the cavity.

11. A method according to claim 5 wherein the moulding feature has upper and lower surfaces for contact with the metal and which projects inwardly of the mould cavity from a main wall thereof and has a configuration such that the length of any one section of the moulding feature is at least twice the thickness of the thinnest part thereof by which the section is connected to the main wall of the mould cavity.

12. A mould for making metal castings comprising consolidated unbonded sand in which is embedded an in situ destroyable pattern to define a mould cavity, there being provided in the mould cavity a moulding feature which has upper and lower surfaces for contact with the metal and which projects inwardly of the mould cavity from a main wall thereof and has a configuration such that a mould made of 100% silica sand, except for usual impurities, and LM25 aluminum alloy is the metal cast, a part of the casting resulting from the moulding feature is displaced by at least 5% from its designed position relative to the nearest part of the casting defined by the main wall of the cavity and comprising at least substantially wholly sand selected from the group consisting of zircon sand and other particulate material suitable for making a mould having a bulk density lying in the range 2-3 gm/cc.

13. A mould according to claim 12 wherein the moulding feature is formed of unbonded sand.

14. A mould according to claim 13 wherein the unbonded sand comprises at least substantially wholly zircon sand, except for usual impurities.

15. A mould according to claim 12 wherein at least substantially the whole of the moulding feature is preformed of sand bonded with a bonding agent.

16. A mould according to claim 15 wherein the bonded sand comprises at least substantially wholly zircon sand and bonding agent except for usual impurities.

17. A method of making metal castings comprising the steps of providing an in situ destroyable pattern, then embedding the pattern in unbonded sand and consolidating the sand to form a mould in which is defined a mould cavity, then feeding a molten metal selected from the group consisting of aluminum and aluminum alloys into the cavity and permitting the metal to solidify within the cavity to form a casting and interrupting the feed of metal to the cavity and removing the casting from the cavity, with at least part of the mould comprising at least one preformed moulding feature which is included in said pattern and being formed of sand which comprises at least substantially wholly sand selected from the group consisting of zircon sand and other particulate material suitable for making a mould having a bulk density lying in the range of 2-3 gm/cc.