Method for producing an aluminium alloy foam by moulding
View Patent ↗A method for producing an aluminum alloy foam wherein an aluminum alloy, in molten form, infiltrates the interstices of a preform of silicon elastomer elements, by means of a conventional molding process, typically a low-pressure process, followed by the elimination of the preform broken down into silica powder during the molding cycle and/or an additional baking cycle.
1. A method for manufacturing an aluminium alloy foam having open cells with a porosity of from 60% to 80%, wherein the method comprises:
extruding a silicone elastomer through a die to form silicone elastomer elements;
cutting each of the extruded silicone elastomer elements into portions of silicone elastomer elements, each of said portions having a similar length;
agglomerating the portions of silicone elastomer elements;
polymerizing the agglomerated portions of silicone elastomer elements in a moulding tool to form a preform;
removing the preform from the moulding tool;
storing the preform at a temperature of from 80° C. to 150° C.;
placing the preform into a mould;
casting an aluminium alloy in the mould at a temperature of from 800° C. to 820° C., and at a pressure of from 700 mbar to 1.5 bar, to allow the alloy to penetrate into interstices of the preform, thereby forming an aluminium alloy foam and silica powder; and
removing the aluminium alloy foam from the mould.
2. The method according to claim 1 , wherein the portions are formed as substantially spherical balls before the agglomeration step.
3. The method according to claim 1 , wherein the silicone elastomer elements extruded from the die have a circumscribed outside diameter of from 2 mm to 10 mm.
4. The method according to claim 1 , wherein the portions have a length of from 2 mm to 10 mm.
5. The method of claim 1 , wherein the portions are agglomerated by mixing the portions in the presence of a binder, and forming the preform in a core box mould.
6. The method according to claim 5 , wherein the binder is a liquid silicone binder.
7. The method according to claim 6 , wherein the liquid silicone binder is used in an amount of from 1% to 3% expressed as a percentage by mass.
8. The method according to claim 5 , wherein the binder is a liquid polyurethane resin binder.
9. The method according to claim 8 , wherein the liquid polyurethane resin binder is used in an amount of from 2% to 4% expressed as a percentage by mass.
10. The method according to claim 1 , wherein the preform has a density of from 0.5 to 0.8.
11. The method according to claim 1 , further comprising introducing a tube into the preform during the agglomerating step.
12. The method according to claim 11 , wherein the tube is made from aluminium alloy or borosilicate glass.
13. The method according to claim 1 , wherein the preform is preheated to a temperature of from 150° C. to 250° C. before being placed into the mould.
14. The method according to claim 1 , wherein the preform has a minimum size of 50 mm×50 mm, and a thickness of from 10 to 100 mm, and a maximum size of 350 mm×350 mm, and a thickness of from 15 to 80 mm.
15. The method of claim 1 , wherein the polymerizing step is a natural polymerizing step or a forced polymerizing step.
16. The method of claim 15 , wherein the forced polymerizing step is carried out by stoving at a temperature of from 50° C. to 100° C.
17. The method of claim 1 , wherein the portions are agglomerated by directly clamping in a core box mould tool or in a press forming tool.
18. The method of claim 1 , comprising casting the aluminium alloy at a pressure of from 700 mbar to 1.0 bar.
19. The method of claim 1 , further comprising stoving aluminium alloy foam at a temperature of from 400° C. to 450° C., and discharging the silica powder.
20. The method of claim 1 , wherein the silica powder is discharged by a member selected from the group consisting of manual knocking out, vibrating, blowing, water under pressure, and a combination thereof.