JP2010209374A - Foamed aluminum fitted with outer surface coating and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide foamed aluminum fitted with an outer surface coating in which variation in a bubble ratio and bubble size is reduced, and which has suitable compressive strength (compressive stress), and to provide a method for producing the same. <P>SOLUTION: The outer surface of foamed aluminum 5 or 5A is coated and fused with a coating 2 made of aluminum or an aluminum alloy having a melting point higher than that of the foamed aluminum so as to be foamed aluminum 4 or 4A fitted with the outer surface coating. In the method for producing the same, when an aluminum metal body (precursor) for foaming is heated and foamed in a die so as to obtain foamed aluminum, a coating made of an aluminum or aluminum alloy material having a melting point higher than that of the aluminum metal body (precursor) for foaming is arranged at the inner surface of the die, and heating and foaming are performed. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to foamed aluminum with an outer surface skin excellent in energy absorption and rigidity and a method for producing the same.

  Foamed aluminum is a foam in which a large number of independent bubbles are dispersed in a metal matrix. For example, it can be used as an energy absorber that absorbs impact energy.

  As a method for producing foamed aluminum, in a method for producing foamed aluminum in which an unfoamed precursor (precursor) containing aluminum powder as a matrix is heated and foamed, finer bubbles having a melting point higher than that of the aluminum powder are not added. The thing characterized by including in the foaming precursor (precursor) is disclosed (for example, refer patent document 1).

  According to the thing of patent document 1, the adhesion | attachment of bubbles can be prevented by including the bubble refinement | miniaturization particle | grains whose melting | fusing point is higher than the aluminum powder as a matrix in an unfoamed precursor (precursor).

Japanese Patent Laid-Open No. 2007-100196 (Claims)

  However, since the skin of the outer surface of the foamed aluminum obtained by the technique described in Patent Document 1 is as thin as less than 0.5 mm and has a variation, the strength is low for use in a structure such as an automobile bumper. There was concern that it was not enough. Here, the reason why the skin of the outer surface of the foamed aluminum is less than 0.5 mm is that when the precursor is in a molten state, the foaming agent is decomposed to generate gas (hydrogen gas) and the foaming phenomenon occurs. It depends. When these bubbles increase, the volume expands and sticks to the mold wall to solidify. Therefore, the thickness of the approximate skin is 0.1 to 0.5 mm.

  An object of the present invention is to provide a foamed aluminum with an outer surface skin having a small variation in bubble ratio and bubble diameter and having an appropriate compressive strength (compressive stress), and a method for producing the same.

  The invention according to claim 1 for solving the above-mentioned problems is characterized in that the outer surface of foamed aluminum is coated and fused with a skin material of aluminum or aluminum alloy having a melting point higher than that of the foamed aluminum. It is a foamed aluminum with an outer surface skin, which is intended to greatly improve the compressive stress that cannot be achieved with conventional foamed aluminum.

  In the present invention, examples of the skin material include those made of a hollow extruded shape (Claim 2), those formed by welding a plurality of plate materials (Claim 3), and bending the plate material. For example, a hollow plate that is formed by welding the end portions of the plate material can be used.

  In the present invention, the melting point of the aluminum or aluminum alloy skin of the foamed aluminum with the outer surface skin is higher by 10 ° C to 170 ° C, preferably 10 ° C to 70 ° C higher than the melting point of the foamed aluminum ( Claim 5).

  Here, the temperature range is set because the heating temperature is difficult to control when the melting point of the skin material is higher than the melting point of the foamed aluminum is less than 10 ° C., and the aluminum that can be selected at a value exceeding 170 ° C. This is because no longer exists. Further, in terms of adhesion, it is better that the temperature difference is small. That is, since the inner surface side of the skin material comes into contact with the molten aluminum metal body for foaming (precursor) and approaches a semi-molten state, both are firmly bonded during solidification. Therefore, the melting point of the skin material is preferably in the range of 10 ° C. to 70 ° C. higher than the melting point of the foamed aluminum.

  In the present invention, the thickness of the aluminum or aluminum alloy skin material of the foamed aluminum with the outer surface skin is preferably 0.5 mm or more that can give the required compressive stress.

  Here, when the skin material is not installed on the inner surface of the mold, the skin of the outer surface of the foamed aluminum varies from about 0.1 mm to about 0.3 mm, and it is not stable as the skin material, so that sufficient compressive stress can be obtained. Can not. Further, even when the skin material is arranged on the inner surface of the mold, if the skin material thickness is less than 0.5 mm, the inner surface side surface layer portion of the skin material is in a semi-molten state as described above, so the skin material is thin. As a result, the strength of the skin material itself varies, and as a result, the effect of improving the compressive strength of the entire foamed aluminum with skin material becomes poor. Therefore, the thickness of the skin material to be applied needs to be 0.5 mm or more.

  The upper limit of the thickness of the skin material is determined by the shape of the foamed aluminum and the required strength, and is not limited.

  According to the seventh aspect of the invention, when a foamed aluminum metal body (precursor) is heated and foamed in a mold to obtain foamed aluminum, aluminum or aluminum having a melting point higher than that of the foamed aluminum metal body (precursor) on the inner surface of the mold A method for producing foamed aluminum with an outer surface skin, wherein a skin material made of an alloy material is placed, heated to foam the foamed aluminum metal body and fused to the skin material.

  In this invention, the foaming aluminum metal body (precursor) is obtained by mixing a foaming agent powder with aluminum or an aluminum alloy powder and extruding the preformed body obtained by isostatic pressing (CIP molding). What is obtained (Claim 8) or that obtained by further rolling the one obtained by extrusion is preferred (Claim 9).

  According to this invention, it is possible to obtain an energy absorber that absorbs impact energy, that is, a foamed aluminum with an outer surface skin that is excellent in compressive stress.

It is a flowchart which shows the manufacturing method of the aluminum foam with an outer surface skin which concerns on this invention. It is sectional drawing which shows the different form of the aluminum metal body for foaming in this invention (precursor). Sectional drawing (a) which shows one form of the skin material in this invention, sectional drawing (b) which shows another form, I section expanded sectional view (c) of (b), sectional view (d) which shows another form It is a II section expanded sectional view (e) of () and (d). It is a perspective view which shows another form of the aluminum foam with an outer surface skin which concerns on this invention. It is a photograph which shows the cross section of Example 4 of the foaming aluminum which concerns on this invention. 6 is a photograph showing a cross section of foamed aluminum in Comparative Example 4.

  Embodiments of foamed aluminum with an outer surface skin and a method for producing the same according to the present invention will be described below with reference to the accompanying drawings.

  (1) Raw material powder, (2) Aluminum or aluminum alloy skin material and (3) Foamed aluminum with outer surface skin and manufacturing method thereof, (a) Powder mixing step, (b) Hydrostatic press molding (CIP forming step) ), (C) precursor molding process, (d) mold assembling process, and (e) heating / foaming process.

(1) Raw material powder As aluminum powder, aluminum or various aluminum alloy powders can be used. The particle diameter of the aluminum powder used in the present invention is not particularly limited, but usually a powder having a particle diameter of 5 to 350 μm, preferably 20 to 100 μm may be used. When the particle size exceeds 350 μm, it becomes difficult to uniformly mix the aluminum powder and the foaming agent powder. On the other hand, when the particle size is smaller than 5 μm, aggregation occurs between the aluminum powders, and it becomes difficult to uniformly mix with the foaming agent powder. The aluminum powder may be a heat treatment type alloy.

  The foaming agent powder is not particularly limited as long as it generates a gas at a certain temperature or higher, but in order to foam aluminum having a strong bond with oxygen, titanium hydride (TiH2) containing hydrogen having a strong reducing power, Hydroxides such as sodium hydrogen carbonate (NaHCO 3), calcium carbonate (CaCO 3) that releases carbon dioxide, and the like are used. The foaming agent powder used in the present invention is preferably 0.3% by mass or more and 5% by mass or less. When the amount of the foaming agent powder exceeds 5% by mass, the variation in the bubble ratio and bubble diameter of the foamed aluminum becomes large. Further, when the foaming agent powder is less than 0.3% by mass, the density of the foamed aluminum is increased and the foam is not foamed. That is, when the foaming agent powder is less than 0.3% by mass, the amount of gas generated is small even when the precursor is in a molten state, and the amount of bubbles that become cavities is also reduced. For this reason, the density of the manufactured foamed aluminum is increased, and the effect of improving the energy absorption characteristics is also decreased.

  The particle size of the blowing agent powder used in the present invention is not particularly limited, but a powder having a particle size of 10 to 50 μm may be used. When the particle diameter exceeds 50 μm, it becomes difficult to uniformly mix the aluminum powder and the foaming agent powder. On the other hand, if the particle size is smaller than 10 μm, aggregation occurs between the foaming agent powders, and it becomes difficult to uniformly mix with the aluminum powder.

  In addition, the particle size in this invention shows the value by the laser diffraction type particle size analysis measuring method. In addition, the shape of any powder is not limited, and may be any shape such as a teardrop shape, a true spherical shape, a spheroid shape, a flake shape, or an indefinite shape.

(2) Aluminum or aluminum alloy skin material The aluminum or aluminum alloy skin material is not particularly limited as long as it has a higher melting point than aluminum foam or aluminum alloy, but for example, aluminum metal for foaming. It is preferably applicable when the body (precursor) is JISA6061 and the skin material is JISA1000 series. That is, the temperature difference between the melting points of JISA6061 and JISA1000 series is in the range of 60 ° C to 90 ° C.

  The adhesion between the foamed aluminum and the skin material is more excellent as the temperature difference between the melting points of the foamed aluminum and the skin material is closer to 10 ° C.

  Further, when a heat-treatable alloy such as JIS A6000 is used for the outer surface skin material and the foaming aluminum metal body (precursor), the mechanical properties of the foamed aluminum with the outer surface skin can be improved by performing an appropriate heat treatment. Good.

(3) Foamed aluminum with outer skin and manufacturing method thereof For producing foamed aluminum with outer skin, as shown in FIG. 1, (a) powder mixing step → (b) isostatic pressing (CIP forming step) ) → (c) Precursor molding process → (d) Mold assembly process → (e) Foamed aluminum with outer skin can be produced in the order of heating / foaming process.

(A) Powder mixing step Aluminum or various aluminum alloy powders and foaming agent powder such as titanium hydride are mixed as the aluminum powder. A known mixing means may be employed as a mixing method. For example, a mixer such as a V blender or a cross rotary mixer, a vibration mill, a planetary mill or the like may be used and mixed for about 1 to 6 hours.

(B) Hydrostatic press molding process (CIP molding process)
The obtained mixture is cold compacted by a hydrostatic pressure method at a pressure of 98.07 MPa to 294.21 MPa at room temperature to obtain a preform with a filling degree of 60 to 80%. When the cold compacting pressure is lower than 98.07 MPa, the filling degree is 60% or less, the strength of the preform is not sufficient, and there is a possibility that the preform is cracked during conveyance. Further, in terms of strength, a filling degree of 80% is sufficient, and it is not necessary to apply a pressure of 294.21 MPa or more.

(C) Precursor molding step Next, the obtained preform is different depending on the composition, but after being heated to a temperature of 200 to 500 ° C. in advance, the extrusion is performed by an extrusion method as shown in FIGS. 2 (a) and 2 (b). An aluminum metal body for foaming 1 (precursor) made of an actual material, an aluminum metal body for foaming 1A (precursor) made of a hollow material or an aluminum metal body for foaming 1B (precursor) is obtained. At this time, the heating atmosphere of the preform is not particularly limited, and an atmosphere such as air, nitrogen gas, argon gas, or vacuum can be set.

  Further, a plate-shaped aluminum metal body for foaming obtained by extrusion may be used as a foaming aluminum metal body (precursor) whose thickness is adjusted by rolling.

(D) Mold assembly step Next, after placing a skin material of aluminum or aluminum alloy having a melting point higher than that of foamed aluminum on the inner surface of a mold having a target shape, an aluminum metal body for foaming (precursor) is placed in the skin material. ) Is loaded. In this case, the skin material 2 made of a hollow extruded shape as shown in FIG. 3A, the skin material 2A formed by welding W of a plurality of plate materials to form a hollow shape, or the plate material is bent to form a hollow shape. And the skin material 2B etc. which welded the edge parts of a board | plate material can be used.

(E) Heating / foaming step After the foaming aluminum metal body (precursor) is loaded in the skin material, it is heated at 500 ° C. or more depending on the capacity and composition of the precursor in a heating furnace such as a far infrared heating furnace or a high frequency induction heating furnace Heating is performed at a temperature of 800 ° C., and immediately after reaching the foaming temperature, the mold is taken out of the heating furnace and forcedly air-cooled to obtain foamed aluminum 4 with an outer surface skin as shown in FIG. In the foamed aluminum 4 with the outer surface skin, the foamed aluminum 5 in which the foaming aluminum metal body (precursor) is foamed is fused in the skin material 2. The capacity of the precursor loaded in the skin material is adjusted according to the required density.

  Further, by filling the plate-like aluminum metal body for foaming 1B (precursor) obtained by extrusion or rolling into a sheath-like skin material and heating it, a plate-like outer surface as shown in FIG. 4A of foamed aluminum with a surface skin can be manufactured. Such foamed aluminum with an outer surface skin has advantages such as ease of physical and chemical surface treatment since it has a skin material having a thickness sufficient for various processing treatments. In FIG. 4B, reference numeral 5A denotes aluminum in which a plate-like foaming aluminum metal body 1B (precursor) is foamed.

  Next, the result of evaluating the characteristics of the foamed aluminum with outer skin of the present invention and the conventional foamed aluminum will be described.

  A preformed body obtained by CIP molding of the aluminum mixed powder shown in Table 1 was obtained by extrusion at 450 ° C. to obtain an aluminum metal body for foaming (precursor). This was placed and foamed in a far-infrared heating furnace to obtain a foamed aluminum with an outer surface skin having a quadrangular prism shape (height 40 mm × width 57 mm × length 200 mm).

A test piece having a width of 40 mm × 57 mm × a height of 70 mm, with both ends in the length direction of the obtained quadrangular prism-shaped foamed aluminum with an outer surface skin being cut off leaving a length of 70 mm, with the cut surfaces without skin material as the upper and lower surfaces Table 1 also shows values obtained by converting the plateau region up to 50% strain from the displacement-load curve into energy absorption and average compressive stress.

  As shown in Table 1, when Examples 1 to 3 and Comparative Examples 1 and 2 in which the aluminum mixed powder is JISA 4045 + 1% TiH2 are compared, in Examples 1 to 3, energy absorption amounts are 1439J, 1360J, 1200J, While the average compressive stress is 17.0 MPa, 15.8 MPa, and 14.8 MPa, in Comparative Examples 1 and 2, the energy absorption amounts are 1152 J and 1120 J, and the average compressive stress is 14.3 MPa and 14.1 MPa, respectively. there were.

  Further, when Examples 4 to 7 and Comparative Examples 3 to 5 in which the aluminum mixed powder is JISA6061 + 1% TiH2 are compared, in Examples 4 to 7, the energy absorption amounts are 2162J, 2067J, 1820J, and 2091J, respectively, and the average compressive stress. Are 26.6 MPa, 25.1 MPa, 22.3 MPa, and 25.5 MPa, while in Comparative Examples 3 to 5, the energy absorption amounts are 1637 J, 1573 J, and 1884 J, and the average compressive stress is 20.2 MPa and 19 respectively. .5 MPa and 22.2 MPa.

  As is clear from the results in Table 1, Examples 1 to 7 are generally compared to Comparative Example 1 based on comparison between Examples 1 to 3 and Comparative Examples 1 and 2 and Examples 4 to 7 and Comparative Examples 3 to 5. It can be seen that it is superior in energy absorption and compressive stress compared to ˜5.

  5 is a cross-sectional photograph of the foamed aluminum produced under the conditions of Example 4, and FIG. 6 is a cross-sectional photograph of the foamed aluminum produced under the conditions of Comparative Example 4.

  The foamed aluminum with outer skin according to the present invention can be used for a bumper for an automobile, and can also be used for a structure such as a guardrail or a protective wall of a road.

1,1A, 1B Precursor (foaming aluminum metal body)
2,2A, 2B Skin material 3 Gap 4,4A Foamed aluminum with outer surface skin 5,5A Foamed aluminum W Welding

Claims (9)

  A foamed aluminum with an outer surface skin, wherein the outer surface of foamed aluminum is coated and fused with a skin material of aluminum or aluminum alloy having a melting point higher than that of the foamed aluminum.   2. The foamed aluminum with an outer surface skin according to claim 1, wherein the skin material is made of a hollow extruded profile.   The foamed aluminum with outer surface skin according to claim 1, wherein the skin material is formed by welding a plurality of plate materials into a hollow shape.   2. The foamed aluminum with outer surface skin according to claim 1, wherein the skin material is formed by bending a plate material into a hollow shape and welding the end portions of the plate material.   The outer surface skin according to any one of claims 1 to 4, wherein the melting point of the aluminum or aluminum alloy skin material of the foamed aluminum with the outer surface skin is 10 to 170 ° C higher than the melting point of the foamed aluminum. With foamed aluminum.   The foamed aluminum with outer surface skin according to any one of claims 1 to 5, wherein the thickness of the aluminum or aluminum alloy skin material of the foamed aluminum with outer surface skin is 0.5 mm or more.   When the foamed aluminum metal body is heated and foamed in the mold to obtain foamed aluminum, a skin material made of aluminum or an aluminum alloy material having a melting point higher than that of the foamed aluminum metal body is disposed on the inner surface of the mold and heated to A method for producing foamed aluminum with an outer surface skin, comprising foaming an aluminum metal body for foaming and fusing it to the skin material.   The foaming aluminum metal body is obtained by mixing a foaming agent powder with aluminum or aluminum alloy powder and hot extruding a preform formed by isostatic pressing. The manufacturing method of the aluminum foam with an outer surface skin of Claim 7.   The above aluminum metal body for foaming is obtained by further rolling a product obtained by mixing a foaming agent powder with aluminum or aluminum alloy powder and hot extruding a preform obtained by isostatic pressing. The method for producing foamed aluminum with an outer surface skin according to claim 7, wherein: