Method of production of component from metal foam, component produced by said method and mould for the realization of said method

Abstract

Foamable semifinished product (1) in the form of granules produced from the metal alloy and the foam agent is inserted into the cavity of the closable mould (2) and the liquid (3) with the density that is higher than the apparent (or bulk) density of the resulting foam is led to it. The liquid has a temperature which is higher than the temperature of the melting of the metal alloy; the transfer of the heat to the particles of the foamable semifinished product (1) takes place; it subsequently expands, whereby it is supported by the liquid (3). During the expansion at least part of the liquid (3) is pushed by the expansion itself out of the mould (2) through the opening. The liquid (3) allows the regulation of the pressure of the environment of the foam agent, too, which helps to set exactly the moment of expansion. The metal melt can be advantageously used as liquid (3). The melt can partially remain in the mould (2) so the hybrid structure of the component is created. The new method makes the foaming significantly quicker, it secures the homogeneity of the metal foam, simplifies the moulds and diminishes the energy demands for the whole process.

Claims

1. A method of making a component from a metal foam, the method comprising the steps of: inserting inside a cavity of a closable and/or one-off mould (2) a solid foamable semi-finished product (1) in the form of granules produced from a metal alloy and a foam agent; heating the foamable semi-finished product (1) inside the mould; flooding a cavity of the mould (2) with an amount of a liquid (3) having a temperature that is higher than a temperature at which the foamable semi-finished product (1) melts; transferring a heat from the liquid (3) to the foamable semi-finished product (1) to heat the foamable semi-finished product (1), which produces gases in pores of the foamable semi-finished product to expand the foamable semi-finished product; wherein the expanded foamable semi-finished product (1) is supported by the liquid (3), and wherein during the expansion, at least part of the liquid (3) goes out of the mould (2) through a respective opening in the mould (2); the liquid (3) is pushed out by the expansion of the foamable semi-finished product (1).

2. The method according to the claim 1, wherein the liquid (3) is placed into the mould (2) by injection through an opening in a bottom or the bottommost part of the mould (2) and later is also pushed out through the opening.

3. The method according to claim 1, wherein during the expansion, more than 75% of the amount of the liquid (1) is pushed out of the mould (2).

4. The method according to claim 1, wherein a part of the liquid (3) remains in the mould (2), the part of the liquid (3) remaining in the mould solidifies on the mould together with the foam and creates a hybrid casting combining a solidified foam and a solidified liquid into a single monolithic component.

5. The method according to claim 1, wherein a free space remaining in the cavity of the mould (2) after placing the foamable semi-finished product is partially filled with the liquid (3), wherein a volume of the liquid (3) and the foamable semi-finished product (1) before the expansion step is smaller than an inner volume of the cavity of the mould (2).

6. The method according to claim 5, wherein the amount of the liquid (3) is determined on basis of the weight and granulometry of the foamable semi-finished product (1).

7. The method according to claim 1, wherein during the contacting step of the foamable semi-finished product (1) with the liquid (3), the liquid (3) is exposed to a pressure, which at a given temperature, is higher than a pressure preventing the foam agent from releasing a gas necessary for foaming and the expansion, wherein before the decrease in the temperature of the liquid (3) to the temperature of a solidification of the foam, a pressure of the liquid (3) diminishes below the value preventing the foam agent from releasing the gas at the given temperature.

8. The method according to claim 1, wherein: the liquid (3) is a melt of a metal with a temperature of melting that is lower than the temperature of a solidification of the metal foam; or the liquid (3) is a melt of a metal with a temperature of melting that is higher than the temperature of the solidification of the metal foam.

9. The method according to claim 1, wherein the liquid (3) is a melt of a metal alloy having an identical chemical composition as the metal alloy of the foamable semi-finished product (1).

10. The method according to claim 1, wherein before the flooding of the liquid (3), a metal and/or a ceramic reinforcement (5) is inserted into the cavity of the mould (2), wherein the shape of the metal and/or the ceramic reinforcement (5) is selected from the group consisting of nets, grids, rods, hollow profiles, wires, fibers, and mixtures thereof; the reinforcement (5) is inserted adjacently at a distance to an inner surface of the mould (2).

11. The method according to claim 10, wherein a perforation in the reinforcement (5) constitutes a sieve for a separation of the foam from the liquid on a surface of a finished casting.

12. The method according to claim 1, wherein before the flooding of the liquid (3) to the mould (2), the mould (2) is heated to a temperature higher than the temperature of the melting of the foamable semi-finished product (1).

13. The method according to claim 1, wherein during the pushing of the liquid (3) out of the mould (2), part of the liquid (3) remains in folds of the mould (2), wherein the part of the liquid (3) solidifies into shapes having different shapes than shapes on the mould (2).

14. A component containing the metal foam produced by the method according to claim 1; wherein the component is a single piece component including a framework and an outer surface of a transportation device.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The invention is further disclosed by drawings 1 to 43. The used scale and the particular shape of the mould and the respective product are not binding; they are informative or adjusted for the purposes of clarity. This is why there is a mould with the simply shaped cavity on the drawings, even in cases where a particular example verbally describes different shape character of the casting.

(2) FIGS. 1 to 6 gradually depict the basic steps in one cycle of foaming in the divided mould.

(3) FIG. 1 depicts the placement of the foamable semifinished product into the mould before the pouring of the liquid;

(4) FIG. 2 shows the foamable semifinished product into the mould when pouring of the liquid;

(5) FIG. 3 shows the activation of the foaming;

(6) FIG. 4 shows the continuation of the activation of the foaming;

(7) FIG. 5 subsequently depicts the expansion of the foamable semifinished product, whereby the expansion pushes the liquid into the collecting vessel;

(8) FIG. 6 shows on a lower left corner a pictogram showing the recyclation of the liquid, which is moved from the collecting vessel and used once again;

(9) FIGS. 7 to 17 disclose the use of the separating reinforcement from the stainless expanded metal.

(10) FIG. 7 shows that the reinforcement is placed into the mould in such a way that its perforated surface is adjacently placed at the distance from the inner walls of the mould;

(11) FIGS. 8 to 12 show the steps similarly to FIGS. 2 to 6;

(12) FIG. 13 depicts the mould with the casting in the solidified state. The black color marks the solidified liquid without the foam structure.

(13) FIG. 14 shows the casting without the mould;

(14) FIG. 15 shows the casting with the removed intake system;

(15) FIG. 16 is spatially depicted cross-section of the mould, whereby the view shows the bare reinforcement from the expanded metal, which—through its perforation—creates a boundary between the foamed mass and the solidified melt;

(16) FIG. 17 is a cross-sectional view of the partially cut-out reinforcement;

(17) FIGS. 18 to 26 depict the method where the mould has a shape elements which effectively prevent the pushing of the liquid out from certain areas of the mould.

(18) FIG. 18 shows the placement of the foamable semifinished product inside the mould before the pouring of the liquid;

(19) FIG. 19 shows foamable semifinished product inside the mould while pouring of the liquid;

(20) FIG. 20 depicts the activation of the foaming;

(21) FIG. 21 shows the continuation pf the activation of the foaming;

(22) FIG. 22 then depicts the expansion of the foamable semifinished product where this expansion pushes the liquid into the collecting vessel.

(23) FIG. 23 shows in the lower left corner a pictogram meaning the recyclation of the liquid which is moved from the collecting vessel and is repeatedly used;

(24) FIG. 24 depicts the mould with the casting in the solidified state. Full black color marks the solidified liquid without the foam structure;

(25) FIG. 25 shows a casting without the mould;

(26) FIG. 26 shows the casting with the removed intake system where the ribs and the lower part of the casting are created by the solidified liquid;

(27) FIGS. 27 to 32 depict the steps of the foaming in the mould, where at the end the pressure of the liquid is increased; the latter event is depicted on the FIG. 32.

(28) FIG. 33 shows the effect of the pressure on the foam. P1 to P5 denote the increasing pressure. The figures under the individual pressure represent an example of the structure.

(29) FIGS. 34 to 36 depict the steps with the gradual regulation of the pressure. The circle depicts the pressure vessel—for example autoclave—in which the mould is placed. The arrows heading from the circumference of the circle and the sign Pn depict the produced inner overpressure. The crossed-out letter P in the FIG. 36 denotes the ceasing of the overpressure.

(30) FIG. 34 depicts the foamable semifinished product inside the mould before the pouring of the liquid;

(31) FIG. 35 shows the foamable semifinished product inside the mould during the pouring of the liquid;

(32) FIG. 36 depicts the pushing of the liquid out to the collecting vessel after the decrease in pressure and subsequent expansion;

(33) FIG. 37 depicts the usage of the undivided ceramic mould;

(34) FIGS. 38 to 43 depict the steps of the foaming when the foamable semifinished product is placed into the mould which is already filled with the liquid.

(35) FIG. 38 depicts the mould at the start of the process;

(36) FIG. 39 the mould is filled with liquid;

(37) FIG. 40 depicts the step where the foamable semifinished product is put into the contact with the liquid, whereby the mould closes at the same time;

(38) FIG. 41 depicts the beginning of the expansion of the foamable semifinished product, which correlates with the pushing of the liquid out of the mould;

(39) FIG. 42 shows the continuing expansion;

(40) FIG. 43 shows the filling out of the cavity of the mould.

EXAMPLES OF THE REALIZATION

Example 1

(41) In this example according to FIGS. 1 to 6 the foamable semifinished product 1 in form of granules is produced from the powder metal alloy AlSi10 and 0.8 weight % powder of the foam agent TiH.sub.2. The granules are inserted into the cavity of the two-piece foundry graphite mould 2, which in its bottommost part has an intake for the melt, whereby the pouring opening into the intake leads out above the highest point of the cavity of the mould 2. The volume of the foamable semifinished product 1 takes up approximately 20% of the inner space of the mould 2. The closed mould 2 with the foamable semifinished product 1 is—in the protective atmosphere of the nitrogen—heat to 550° C., where there is no expansion of the foamable semifinished product 1. After the evening out of the temperature of the mould 2 and granules the melted alloy AlSi10 pre-heated to 900° C. has been—according to the FIG. 2—poured into the mould 2 from outside of the furnace through the intake in such a way that at least 80% of the free space in the cavity of the mould 2 is filled in. Immediately, that is, approximately 2 seconds after the pouring of the melt into the mould 2, the foamable semifinished product 1 is melted and expands according to FIGS. 3 and 4, which is manifested by reverse flow of the liquid 3, that is, the melt flows out of the intake to the collecting vessel 4 under the mould 2. The outflow of the melt ceases after approximately 20 seconds which is a signal that the expansion of the granules (or granulate) is finished. The mould 2 which has been already placed outside the furnace is left for cooling to temperature of approximately 450° C. After the opening the finished component is taken out of the mould 2; the component is completely produced by the aluminum foam with the overall porosity being 83%. Whole melt poured into the mould 2 has been pushed by the expansion of the foamable semifinished product 1 outside the cavity of the mould 2; part of the foam is in the intake opening.

Example 2

(42) The granules of the foamable semifinished product 1 were in this case according to the FIG. 33 prepared from the powder aluminum alloy AlMgSi and 1 weight % of the powder of the foam agent TiH.sub.2. The granules were inserted into the cavity of the thin-walled mould 2 welded from the steel metal sheet. The volume of the semifinished product 1 occupied approximately 20% of the inner space of the mould 2. In the upper part the mould 2 has circular air vents with diameter 0.2 mm and in lower part it has a circular opening with diameter 15 mm. The mould 2 together with the foamable semifinished product 1 has been hanged in the special autoclave above the pot with the melted lead whose temperature is 950° C. After the closing of the autoclave its inner space has been pressurized by the nitroged to 1 MPa (10 atm). Subsequently the mould 2 has been completely dipped into the melted lead which has flowed slowly into the cavity of the mould 2, which is allowed by the air vents in it upper part which lead above the level of the molten lead.

(43) After the mould 2 is completely filled in with the liquid lead (approximately 30 s) and after 1 minute the whole granules are melted in the mould 2, which manifests itself by the decrease of the temperature in the mould 2 to approximately 680° C., but the granules practically do not expand due to the pressure. The pressure in the autoclave is subsequently diminished to 0.15 MPa (1.5 atm), which causes the immediate expansion of the granules and the pushing of the lead out of the mould 2 through the bottom opening. The aluminum foam does not get out through the upper air vents because they are too small for the foam and moreover they lead to the part that is cooler than the molten lead, where the used aluminum alloy solidifies and closes the air vents. During the expansion the mould 2 was pulled out of the pot with the lead in such a way that the bottom opening remains dipped in the lead melt. After the putting out of the mould 2 from the pot the aluminum foam solidifies under the influence of the lower temperature in the space, whereby until the expansion of the granules takes place until their total solidification. The outflow of the foam through the bottom opening is prevented by the cap from the lead melt. After the total solidification of the aluminum foam at approximately 580° C. almost whole cavity of the mould 2 is filled in by the aluminum foam; only the area in the bottom opening contains the molten lead with the temperature of solidification temperature below 400° C., which after the complete pulling out of the mould out of the pot flows back into the pot.

(44) With regard to the remaining overpressure of 0.15 MPa in the autoclave the apparent diameter of the pores in the aluminum alloy is limited to 2 mm at maximum, whereby the apparent density of the foam was 0.55 g/cm.sup.3.

Example 3

(45) In this example according to FIGS. 7 to 17 the foamable semifinished product 1 in form of granules is prepared from the powder aluminum alloy AlMg1Si0.6 and 0.6 weight % of the powder of the foam agent TiH.sub.2. The granules are poured in the silicone mould 2 into the wax model of the shape component. The grid from the stainless expanded metal with the mesh size of approximately 1.5 mm is placed into the silicone mould 2 in such a way that it copies the surface of the mould 2 while keeping the distance from the inner wall. The grid in the finished product fulfills the function of the reinforcement 5, too. The volume of the foamable semifinished product 1 occupies approximately 20% of the volume of the wax model. The wax model has been dipped into the ceramic suspension by the known methods and dried by the known methods, too, until the continuous ceramic shell with thickness of approximately 4 mm is produced on the model. After the drying of the shell with the wax the opening has been created in its lower part and the wax has been melted away from it completely at the temperature of approximately 100° C. The foamable granules and the stainless grid remain in the cavity of the shell mould 2, though, whereby the grid copies the mould's 2 surface. The intake produced from the material similar to the shell is placed onto the opening in the bottom part in such a way that it leads into the cavity at the height of approximately 20 mm above the lowest part of the cavity of the mould 2.

(46) The shell with the intake, granules and stainless grid are subsequently heated to the temperature 550° C. and then the melted aluminum alloy AlMg1Si0.6 heated to the temperature 850° C. is poured into the cavity in such a way that it fills the whole free space of the cavity of the mould 2. After the filling of the mould 2 the cavity is gradually deaerated through the finely porous ceramic wall of the shall. Basically immediately after the pouring of the melt to the form the melting of the foamable semifinished product 1—granules takes place, as well as its expansion, which is manifested by the reverse flow of the liquid 3—melt out of the intake. The outflow of the melt stops after approximately 15 seconds, which gives a signal that the expansion of the granules is finished. The mould 2 is left to cool to approximately 400° C. After the removal of the ceramic shell the finished component is taken out, whereby this component has a core produced by the aluminum foam with porosity approximately 80%. The foam is on the whole surface—which have been in the cavity covered by the stainless grid—covered by approximately 1 mm thick layer of the compact alloy AlMg1Si0.6 in which the grid has been welded, because the foam could not have reached the surface of the cavity of the mould 2 due to the grid and therefore has been unable to push out the melted alloy. In the same way the poreless metal appears in the bottom of the component, because the foam was not able to push out the melt from the area about the intake/outtake. The hybrid casting with the core from AlMg1Si0.6 foam and the poreless 1 mm thick surface layer produced by the same alloy results. The surface layer has been reinforced by the stainless expanded metal similarly to reinforced concrete. In the bottom part of the component the poreless layer of the alloy AlMg1Si0.6 with thickness approximately 20 mm, which is designed for the drilling of the fixing threads of the component, is produced.

Example 4

(47) The rods according to FIGS. 38 to 43, produced from the aluminum technically pure powder and 0.4% weight of the powder of the foam agent TiH.sub.2, were connected by the aluminum wires to the cap of the two-part foundry mould 2 produced from HBN in such a way that the dividing plane of the mould 2 is in the topmost part. The mould 2 basically constitutes a vessel covered by the cap. In the lowest part of the mould 2 (in the vessel) an intake is placed, whereby the pouring opening to the intake leads above the level of the dividing plane. The volume of the foamable semifinished product 1 takes up approximately 20% of the space of the cavity of the mould 2. The open lower part of the mould 2 (vessel) is heated to 850° C. and filled with the melted lead of the same temperature to at least ⅘ of the height of the vessel. the ccap of the mould 2 with the attached foamable semifinished product 1 is at the same time heated in the furnace to 550° C. where the expansion of the foamable semifinished product 1 does not take place, yet.

(48) After the regularization (or evening out) of the temperature of the mould 2 and of the lead melt the cap with the attached foamable semifinished product 1 is pushed into the bottom part of the mould 2 by means of the pneumatic piston and the mould 2 is closed by the pressure. Immediately after the closure of the mould 2 and dipping of the foamable semifinished product 1 to the lead an expansion takes place, which manifests itself by the pushing of the lead out of the intake. The outflow of the lead stops after approximately half a minute, which gives a signal that the expansion of the granules is finished. The bottom mould 2—which after the closing by the cap and the beginning of the foaming basically immediately cools by approximately 150° C.—is left to cool to approximately 500° C. After the opening the finished component—completely produced by the aluminum foam with the overall porosity 78%—is taken out. All lead that had poured into the bottom part of the mould 2 has been pushed out by the expansion of the foamable semifinished product 1 outside the cavity of the mould 2 through the intake, whereby the intake is wholly filled by the foam, too.

Example 5

(49) The process in this example according to FIGS. 18 to 26 is similar to the example 1. The mould 2 is different; here it has shape elements 6 preventing the pushing of the liquid 3 out of the mould 2 during the expansion of the foamable semifinished product 1. The liquid 3 in this example has an identical basis as foamable semifinished product 1.

(50) The shape elements 6 are, for example, ribs into which the liquid 3 flows but is not supposed to flow out. On FIGS. 24 to 26 these zones are marked by the full black, which denotes the poreless mass of the solidified liquid 3 or—more precisely—solidified melt with the identical material basis as foam's basis. It is preferable if the cooling or reinforcing ribs have a full structure without the pores.

Example 6

(51) The method in this example according to FIGS. 27 to 32 is similar as the example 1 until the moment of the flowing of the liquid 3 out of the mould 2 where the pressure acts against the outflowing liquid 3 according to FIG. 32. The piston acting directly in the intake system is depicted schematically; various mechanical or hydraulic systems can be used in actual operation to created pressure. The structure of the foam can be controlled by means of the pressure. The mould 2 has an adequately firm construction in this example.

Example 7

(52) The usage of the autoclave according to FIGS. 34 to 36 in this example provides an important disposition for the launching of the expansion and influencing the resulting structure of the foam according to FIG. 33. The method according to FIGS. 27 to 32 is similar as in the example 1, but during the placement of the liquid 3 into the mould 2 the outside pressure Pn acts upon the mould 2 and the liquid 3 and prevents the launching of the expansion. The pressure acting upon the liquid 3 acts, at the same time, from the outside of the mould 2, so that the mould 2 does not need to be resistant to the overpressure Pn.

(53) After the release of the pressure according to FIG. 36 the expansion and the outflow of the liquid 3 to the collecting vessel 4 starts.

Example 8

(54) The mould 2 is undivided and one-off as depicted on the FIG. 37. The shell of the mould 2 is created by the non-metal, ceramic material; in particular the mould 2 is produced by the drying of the suspension containing ceramic particles applied onto the meltable wax model of the component. The common method known from the preparation of the wax model is supplemented by the fact that before the application of the layers of the shell the foamable semifinished product 1—and alternatively the reinforcement 5, too—is placed into the wax model or onto its surface. The foamable semifinished product 1 is not introduced into the mould 2 after its production, but during its production; the mould 2 basically grows around the mass of the foamable semifinished product 1.

INDUSTRIAL APPLICABILITY

(55) The industrial applicability is obvious. According to this invention it is possible to industrially and repeatedly produce the components from the metal foam, including complex and large, sizable components, whereby the heat necessary for the foaming does not need to be transferred through the walls of the mould, which significantly diminishes the overall energy demands and production costs. The possibility of using cheap, one-off, but also complex and enduring moulds allow the effective production of different serial nature, ranging from prototypes to industrial mass production with high degree of automatization.

LIST OF RELATED ELEMENTS

(56) 1—foamable semifinished product 2—mould 3—liquid 4—collective vessel 5—reinforcement 6—shape element in the mould HBN—Hexagonal Bornitrid