JP2001288547A - Aluminum alloy casting parts, and manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide inexpensive aluminum alloy casting parts capable of stably providing high strength and high elongation even in a high strain rate region on the supposition of collision in the case where the parts are applied, e.g. to automobile body parts, and also to provide a method for manufacturing such aluminum alloy casting parts. SOLUTION: An aluminum alloy casting, which has a composition consisting of 2.0-6.0% Si, 0.15-0.34% Mg, <=0.20% Fe, 0.003-0.01% Sr and the balance Al with inevitable impurities and containing, if necessary, 0.01-0.25% Ti and 0.0001-0.001% B, is subjected to solution heat treatment (at 540-570 deg.C for 15 min to 1 hr and quenching) and two-stage aging treatment (consisting of standing for 5-36 h at room temperature, heating at 140-180 deg.C for 1-12 h, and air cooling).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat treatment technology for an aluminum alloy casting, and more particularly, to a joint for an A-pillar, a B-pillar, a C-pillar, a roof, a space frame, etc., which is a body part of an automobile, at the time of high speed deformation. The present invention relates to an aluminum alloy cast part having excellent dynamic characteristics applicable to a member requiring high strength and large elongation, and a method for producing the same.

[0002]

SUMMARY OF THE INVENTION Aluminum castings are:
Utilizing its features such as high degree of freedom in shape, low manufacturing cost, and light weight, it is widely used for engine parts and transmission parts for automobiles.

In recent years, a joint of a space frame constituting a vehicle body is cast by a vacuum die-casting method and then subjected to heat treatment to improve mechanical properties such as tensile strength, 0.2% proof stress and elongation. Aluminum alloy die castings have begun to be used.

Further, according to the JIS standard, AC4CH, A
According to the STM standard, an aluminum alloy with excellent toughness such as A356 is cast by gravity casting, low pressure casting, molten metal forging, etc., and then subjected to heat treatment, thereby toughness of road wheels, undercarriage parts, cross members, etc. of automobiles. It is widely used to apply to parts that require.

For measures to improve the strength and toughness of such an aluminum alloy casting, see, for example, Japanese Patent Application Laid-Open No. 5-51.
No. 48, JP-A-6-65666, JP-A-7-6247
No. 9, JP-A-9-272942 and the like. In vehicle body parts such as the A-pillar, B-pillar, C-pillar, and roof described above, in order to ensure safety at the time of collision, high strength and large elongation are stably obtained even under a high strain rate range. Although it is important that the static strength and elongation of aluminum castings and aluminum die castings are mentioned in the prior art described in
No mention is made of the strength or elongation in the high strain rate region of the 00 / s level, that is, the dynamic characteristics of these cast parts.

As a method of reducing the weight by applying an aluminum alloy to the A-pillar, B-pillar, C-pillar, roof, etc., a pressed aluminum plate or an extruded aluminum material is applied to these members. Attempts have been made, but these methods have problems with low degree of freedom and high cost, and solving these problems is a problem in reducing the weight of body parts as described above. Had become.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems in the conversion of the above-mentioned automotive body parts into aluminum alloys, and includes, for example, A pillars, B pillars, C pillars, roofs, joints for space frames, and the like. When applied to automotive body parts, even under high strain rate range such as during collisions,
It is an object of the present invention to provide an inexpensive aluminum alloy cast part capable of stably obtaining high strength and high elongation, and a method of manufacturing such an aluminum alloy cast part.

Further, when a core of a sandwich panel using the above-mentioned aluminum alloy casting is defined with xy coordinates perpendicular to each other on the core surface, a convex shape is alternately formed on the upper surface and the lower surface in each of the x direction and the y direction. By providing a sandwich panel using the core, the sandwich panel is excellent in three-dimensional curved surface forming, has no anisotropy, and does not require dimensional accuracy with respect to the core height. It is in.

[0009]

According to a first aspect of the present invention, there is provided a method for manufacturing an aluminum alloy cast part, comprising:
Si: 2.0 to 6.0%, Mg: 0.15 to 0.34
%, Fe: 0.20% or less, Sr: 0.003 to 0.0
An aluminum alloy casting containing 1%, with the balance being Al and unavoidable impurities, is cast, and then subjected to a solution treatment in which it is heated to 540 to 570 ° C., held for 15 minutes to 1 hour, and quenched, and then cooled to room temperature at 5 to 36 ° C. Leave for a while, then 140 ~
The aging treatment of heating to 180 ° C., holding for 1 to 12 hours, and air cooling is performed, and the method for manufacturing an aluminum alloy cast part according to claim 2 of the present invention is characterized in that And Si: 2.0 to 6.0%,
Mg: 0.15 to 0.34%, Fe: 0.20% or less,
Sr: 0.003 to 0.01%, Ti: 0.01 to 0.
25%, B: 0.0001 to 0.001, including the balance A
and an aluminum alloy casting comprising unavoidable impurities and then heated to 540 to 570 ° C. for 15 minutes to 1
After a solution treatment in which the solution is quenched after holding for 5 hours,
３６36 hours, then heated to 140-180 ° C., held for 1-12 hours, and air-cooled to perform the aging treatment. This is a means for solving the above-mentioned conventional problem.

An aluminum alloy casting according to a third aspect of the present invention is an aluminum alloy casting manufactured by the method according to the first or second aspect, wherein the average value of the circle-equivalent diameter of eutectic Si is as follows. Eutectic Si
The average value of the circularity coefficient is 0.85 or more,
In the aluminum alloy cast part according to claim 4, the maximum value of the circle equivalent diameter of eutectic Si is 6.0 μm or less,
6. The aluminum alloy casting according to claim 5, wherein the circularity coefficient of eutectic Si has a minimum circularity coefficient of 0.30 or more, and the area ratio of voids including shrinkage cavities and gas defects is 4%.
The maximum value of the equivalent circle diameter of these holes is 250 μm.
m or less, and in the cast aluminum alloy part according to claim 6, the value obtained by dividing the total elongation at a strain rate of 1000 / s by the total elongation at a strain rate of 0.001 / s is 0.1. In the cast aluminum alloy part according to claim 7, the maximum stress after yielding at a strain rate of 1000 / s is changed to the maximum stress after yielding at a strain rate of 0.001 / s (tensile strength). ) Is 1.15 or more, and such a configuration in the cast aluminum alloy part is a means for solving the above-mentioned conventional problem.

Further, in the aluminum alloy cast part according to claim 8, the Si content and the Mg content are desirably in the range of 2.0 to 4.5% and 0.15 to 0.30%, respectively. In the aluminum alloy cast part according to claim 9, the aluminum alloy cast part is an A-pillar, a B-pillar, which is a vehicle body part.
It is desirable to apply to any of the joints of the C pillar, the roof, and the space frame.

In the sandwich panel according to the tenth aspect of the present invention, when the xy coordinates of the core of the sandwich panel are defined on the core surface so as to be perpendicular to each other, the core is alternately arranged on the upper surface and the lower surface in each of the x direction and the y direction. By manufacturing a sandwich panel using the core, it is excellent in three-dimensional curved surface forming, has no anisotropy, and does not require dimensional accuracy for the height of the core. Has become.

[0013] In the sandwich panel according to claim 11 of the present invention, the xy coordinates of the core of the sandwich panel are defined on the core surface so as to be perpendicular to each other, and the core is alternately arranged on the upper surface and the lower surface in each of the x direction and the y direction. When the convex shape is repeated, the concave / convex shape is a sine wave at the cut surface passing through the apex, and one wavelength / core height ratio = 0.2 to 10, core thickness =
The configuration is 0.5 to 10 mm.

In a sandwich panel according to a twelfth aspect of the present invention, xy coordinates perpendicular to each other are defined on the core surface of the core of the sandwich panel, and the core is alternately arranged on the upper surface and the lower surface in each of the x direction and the y direction. When the convex shape is repeated, the trapezoids are continuously arranged in a wavy shape on the cut surface where the concave / convex shape passes through the vertex, and the hypotenuse angle of the trapezoid is 90 to 150.
°, and the core thickness is 0.5 to 10 mm.

[0015]

The reasons for limiting the alloy components and heat treatment conditions of the present invention will be described below together with the function.

(1) Si: 2.0 to 6.0% Si is an element that greatly affects the flowability of the molten metal during casting, casting cracks, elongation, and toughness.
%, Cast cracking is liable to occur, and if it exceeds 6.0%, the crystallization amount of eutectic Si increases and elongation and toughness decrease. Therefore, the content of Si is 2.0 to 6.
Limited to the range of 0%. In addition, it is desirable to set it in the range of 2.0 to 4.5% from the viewpoint of elongation and toughness.

(2) Mg: 0.15 to 0.45% Mg is an element that precipitates Mg ₂ Si by aging treatment after solution treatment and contributes to improvement in strength. But,
If it is less than 0.15%, the effect is small, and if it exceeds 0.45%, the precipitation amount of Mg ₂ Si increases, and elongation and toughness decrease. Therefore, the range is 0.15 to 0.45%. . From the viewpoint of elongation and toughness, it is desirable to set the range of 2.0 to 4.5%.

(3) Fe: 0.2% or less When the content of Fe increases, the amount of crystallization of acicular intermetallic compounds containing iron increases, and the toughness decreases. .

(4) Sr: 0.003 to 0.01% Sr is an element that contributes to improvement of toughness by granulating eutectic Si crystallized when an Al-Si alloy is cast.
If it is less than 0.003%, the effect is small.
%, The flowability of the molten metal decreases, and when applied to large-sized, thin-walled aluminum alloy castings such as car body parts, casting defects such as hot junctions and poor running around are likely to occur. Therefore, the content is in the range of 0.003 to 0.01%.

(5) Ti: 0.01 to 0.25% B: 0.0001 to 0.001% Ti and B crystallize out a TiB ₂ compound, which becomes a heterogeneous nucleus to form a primary crystal α (Al ) It is an element effective for refining the phase and improving the mechanical properties of the aluminum casting. However, Ti: less than 0.01%, B:
If it is less than 0.0001%, the effect is small, and Ti: 0.
Exceeding 25%, B: Exceeding 0.001%
Al ₃ particles and TiB ₂ particles become coarse and primary α (Al)
Since the phase refining effect is reduced, Ti
~ 0.25%, B is 0.0001 ~ 0.0
01% range.

(6) Solution treatment temperature: 540 ° C. to 570
℃ Solution holding time: 15 minutes to 60 minutes Since the eutectic Si granulation is a phenomenon based on the diffusion of the Si element, the higher the solution treatment temperature and the longer the solution holding time, the more granular the eutectic Si becomes. You will get closer. However, when the processing temperature is high or the holding time is long, the eutectic Si is coarsened at the same time, so that it is difficult to achieve both fine and granular eutectic Si. That is,
When the solution treatment temperature is lower than 540 ° C., a long solution holding time is required in order to set the average value of the circularity coefficient of eutectic Si to 0.85 or more, and the circle equivalent diameter of eutectic Si becomes large. Exceeding the desired value results in reduced elongation. Similarly, when the solution treatment is performed at a solution treatment temperature of 570 ° C. for 60 minutes or more, the circle equivalent diameter of the eutectic Si exceeds a desired value, and the elongation decreases. And the solution treatment temperature is 5
If the temperature exceeds 70 ° C., there is a possibility that a partial melting portion may be generated due to the influence of segregation of impurities and the like.
C is the upper limit of the solution treatment temperature.

As described above, the solution treatment conditions that can satisfy both the circle equivalent diameter of eutectic Si and the circularity coefficient necessary for obtaining excellent dynamic characteristics include the solution treatment temperature: 5
The conditions of 40 ° C. to 570 ° C. and the solution holding time: 15 minutes to 60 minutes are selected.

(7) Aging treatment conditions: After the solution treatment, the mixture is left at room temperature for 5 to 36 hours and then at 140 to 180 ° C. for 1 hour.
Holding for 12 hours to 12 hours In the aluminum alloy casting of the present invention, it is possible to improve static and dynamic strength and elongation by performing aging treatment after solution treatment. However,
In the present invention, emphasis is placed on ensuring elongation under a high strain rate region such as a body part, and after solution treatment, natural aging is performed by leaving at room temperature for 5 to 36 hours, and furthermore, 140 ° C to 18 ° C.
Two-stage aging treatment is performed in which artificial aging is performed at 0 ° C. for 1 hour to 12 hours. By applying such a two-stage aging treatment, the elongation under a high strain rate region is improved as compared with a case where ordinary artificial aging treatment is performed.

(8) Average value of the circle equivalent diameter of eutectic Si:
0 μm or less Average value of the circularity coefficient of eutectic Si: 0.85 or more As described above, in order to improve elongation and toughness while achieving both refinement and granulation of eutectic Si, circles of eutectic Si are required. The mean value of the equivalent diameter is 2.0 μm or less, and at the same time, the eutectic Si
Is preferably 0.85 or more.

(9) Maximum value of the circle equivalent diameter of eutectic Si: 6.
0 μm or less Minimum value of circularity coefficient of eutectic Si: 0.30 or more To make eutectic Si finer, as described above, eutectic Si
It is desirable that the average value of the circle-equivalent diameter of the above is 2.0 μm or less, and the maximum value is also preferably 6.0 μm or less. For further granulation of eutectic Si,
More preferably, the average value of the circularity coefficient of eutectic Si is 0.85 or more, and the minimum value is 0.30 or more.

(10) Area ratio of pores: 4% or less Maximum value of equivalent circle diameter of pores: 250 μm or less If shrinkage cavities or gas defects (blow holes) exist in a part, stress concentration due to notch effect causes In particular, it has a serious effect on elongation and toughness at high strain rates. In the cast aluminum alloy part according to the present invention, if the area ratio of the voids including shrinkage cavities and gas defects is 4% or less and the maximum value of the equivalent circle diameter is 250 μm or less, it does not significantly affect the elongation and toughness. Has been confirmed, and it is desirable that the content be in this range.

(11) The ratio of the total elongation at a high strain rate to the total elongation at a low strain rate: 0.90 or more In order to stably obtain a large elongation even under a high strain rate range such as at the time of collision of a car. The value obtained by dividing the total elongation at a strain rate of 1000 / s (dynamic tension) by the total elongation at a strain rate of 0.001 / s (static tension) is preferably 0.90 or more. .

(12) The ratio of the tensile strength at a high strain rate to the tensile strength at a low strain rate: 1.15 or more Similarly, it is stable even in a high strain rate range in which a car collision is considered. In order to obtain a high strength, a strain rate of 10
The maximum stress (tensile strength) after yielding of 00 / s is calculated by setting the strain rate to 0.
It is desirable that the value divided by the maximum stress (tensile strength) after yielding at 001 / s is 1.15 or more.

(13) One wavelength of the convex shape of the sandwich panel core surface / core height: 0.2 to 10 The xy coordinates of the core of the sandwich panel perpendicular to each other on the core surface are defined, and the x direction and the y direction are defined. In each of the directions, when the convex shape is alternately formed on the upper surface and the lower surface, when the concave / convex shape is a sine wave at the cut surface passing through the vertex, the ratio of 1 wavelength / core height is set to 0.2 to 10. The reason is that when the ratio of 1 wavelength / core height is less than 0.2, the core height for securing sufficient rigidity is easily secured, but the weight increases due to the close core interval, and the 1 wavelength / core height ratio increases. / Core height ratio is 10
If it exceeds, the core shape becomes a state close to a flat plate,
This is because sufficient rigidity cannot be exhibited.

(14) Core thickness of sandwich panel:
The reason for setting the core thickness to 0.5 to 10 mm is that when the core is made of an aluminum alloy die casting, the core thickness is 0.5 to 10 mm.
Those with a diameter of less than mm cannot be produced due to manufacturing. When the core thickness exceeds 10 mm, the internal defects specific to the casting increase.

(15) Angle of oblique side of trapezoidal convex shape of the sandwich panel core surface: 90 to 150 ° The xy coordinates of the sandwich panel core perpendicular to each other on the core surface are defined, and each of the x direction and the y direction is defined. When the convex shape is repeated alternately on the upper surface and the lower surface, if the trapezoids are continuously arranged in a wavy shape at the cut surface passing through the apex, the hypotenuse angle of the trapezoid is 90 to 150 ° The reason is that when the oblique angle of the trapezoid exceeds 150 °, the core shape becomes close to a flat plate, and sufficient rigidity cannot be exhibited.

[0032]

According to the method for manufacturing an aluminum alloy cast part according to claim 1 of the present invention, the mass ratio of Si:
2.0-6.0%, Mg: 0.15-0.34%, F
e: Cast an aluminum alloy casting containing 0.20% or less, Sr: 0.003 to 0.01%, the balance being Al and unavoidable impurities, then heating to 540 to 570 ° C and holding for 15 minutes to 1 hour After performing a solution treatment of quenching after that, the mixture is left at room temperature for 5 to 36 hours, and then 140 to 180 hours.
Aging treatment by heating to 1 ° C. and holding for 1 to 12 hours, and air cooling, so that eutectic Si is refined and granulated by optimizing the solution treatment conditions, and the two-stage aging treatment is applied. Since the optimization of the precipitation state of Mg ₂ Si is compatible, an aluminum alloy cast part having high strength and elongation can be obtained at a low cost even under a high strain rate range in consideration of a collision of an automobile. Can be obtained, and in the method for manufacturing an aluminum alloy cast part according to claim 2 of the present invention, the mass ratio of S
i: 2.0 to 6.0%, Mg: 0.15 to 0.34%,
Fe: 0.20% or less, Sr: 0.003 to 0.01
%, Ti: 0.01 to 0.25%, B: 0.0001 to
After casting an aluminum alloy casting containing 0.001 and the balance Al and unavoidable impurities,
Since the solution treatment and the two-stage aging treatment are performed, in addition to the effect of the above-described claim 1, a more excellent effect of improving mechanical properties based on the primary crystal refining effect by Ti and B is brought about. .

The cast aluminum alloy part according to claim 3 of the present invention is manufactured by the above manufacturing method, wherein the average value of the circle equivalent diameter of eutectic Si is 2.0 μm or less, The average circularity coefficient of eutectic Si is 0.
Since it is 85 or more, it is possible to improve the dynamic characteristics of the component by simultaneously refining and granulating eutectic Si, and the aluminum alloy cast component according to claim 4 is
Since the maximum value of the circle-equivalent diameter of eutectic Si is 6.0 μm or less and the minimum value of the circularity coefficient of eutectic Si is 0.30 or more, the eutectic Si can be more reliably refined and granulated. And the dynamic characteristics can be further improved. The aluminum alloy cast part according to claim 5 has an area ratio of voids including shrinkage cavities and gas defects of 4% or less, The maximum value of the circle equivalent diameter of these holes is 250 μm
Because of the following, it is possible to further improve the dynamic characteristics of the component by minimizing the extent of the decrease in elongation and toughness due to voids under a high strain rate range.

Further, the cast aluminum alloy part according to claim 6 has a value obtained by dividing a total elongation at a strain rate of 1000 / s by a total elongation at a strain rate of 0.001 / s of 0.90 or more. Therefore, a high elongation can be obtained even under a high strain rate range in consideration of the collision of the automobile. The aluminum alloy cast part according to claim 7 has a strain rate of 1
The maximum stress after yielding at a rate of
Since the value divided by the maximum stress after yielding at / s is 1.15 or more, high strength can be obtained even under a high strain rate range, and the dynamic characteristics can be more reliably improved. Can be. In the aluminum alloy cast part according to claim 8, the Si content is 2.0 to 4.5%,
Since the g content is in the range of 0.15 to 0.30%, the elongation and toughness of the part can be further improved, and the aluminum alloy casting part according to claim 9 is the aluminum alloy casting part. Parts are especially A pillar, B
Since it is applied to joints of pillars, C-pillars, roofs, and space frames, it has an extremely excellent effect of being able to provide inexpensively vehicle body parts having excellent dynamic characteristics and excellent collision safety. Things.

According to the sandwich panel according to the tenth to twelfth aspects of the present invention, even if a panel has a complicated curved surface in which a plurality of curved surfaces are continuous or a panel having a three-dimensional curved surface, it depends on the elasticity of the core. Due to the excellent degree of freedom of deformation, secondary processing can be performed easily and with high precision. In addition, it can be used as a conventional hexagonal core honeycomb panel or a corrugated core (corrugated cardboard structure) in which trapezoidal shapes are two-dimensionally arranged. There is no anisotropy as seen, and in the conventional hexagonal core honeycomb panel, severe core height control was required at the time of joining the core and the face plate, but in this sandwich panel, the core and the At the time of face plate joining, applying a load and sandwiching the core causes the core to expand and contract in the in-plane direction, uniform core height, and complete joining of the core and face plate. It is possible to obtain a sandwich panel with high joint quality Te.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments.

(1) Melting and Casting First, two kinds of aluminum alloys having the compositions shown in Table 1 were melted at 750 ° C., and then bubbling treatment with argon gas was performed for the purpose of removing inclusions and degassing. did.

[0038]

[Table 1]

Next, using the above two kinds of aluminum alloys, twelve plate-shaped castings of 150 mm × 200 mm × 3 mm as shown in FIG. 1 were cast by a sand type gravity casting method using No. 7 silica sand. did. The temperature of the molten metal during casting was 745 ° C.

(2) Heat Treatment A solution casting treatment and an aging treatment were performed on each of the twenty-four plate castings obtained by sand casting under the respective conditions shown in Table 2. Here, the holding time of the solution treatment and the aging treatment means the time from when the casting reaches a predetermined temperature.

The casting after the solution treatment was immediately quenched by being immediately poured into water. The casting after the artificial aging was immediately air-cooled in the atmosphere.

[0042]

[Table 2]

(3) Investigation of Structure After observing the cross-sectional structure of each of the heat-treated castings with an optical microscope, and performing image analysis,
The circle equivalent diameter and circularity coefficient of eutectic Si were measured. Table 3 shows the results. In addition, FIGS. 2 and 3 show representative cross-sectional structure photographs of the examples and the comparative examples.

[0044]

[Table 3]

From the results shown in Table 3, the equivalent circle diameter of eutectic Si is
It can be seen that if the solution heat-retention time is the same, the solution heat treatment temperature is higher, and if the solution heat treatment temperature is the same, the solution heat-retention time longer is more likely.

Further, the circularity coefficient of eutectic Si is larger when the solution treatment temperature is higher when the solution treatment holding time is the same, and is longer when the solution treatment temperature is the same. It can be seen that it tends to be larger.

Both the coarsening and the graining of eutectic Si
Such a result is obtained because the phenomenon is based on the diffusion of the i element.

From these results, it can be seen that, under the solution treatment conditions of the present invention, both refinement and grain formation of eutectic Si are compatible.

(4) Tensile Test A test piece having the shape shown in FIG. 4 was cut out from each of the flat plate castings after the heat treatment and subjected to a tensile test. Strain rate 0.0
For the tensile test at 01 / s (hereinafter referred to as “static”), a universal testing machine of Instron type was used, and the strain rate was 1000 / s.
For the tensile test at s (hereinafter referred to as “dynamic”), a One-Bar Method high-speed tensile tester shown in FIG. 5 was used.

Table 4 shows the results of both static and dynamic tensile tests. Here, a stress-strain diagram in the case of a dynamic tensile test is shown in FIG. 6, where the yield stress is the maximum stress after yield (corresponding to the tensile strength in the case of a static tensile test). ), The strength of the material was represented by the expression “maximum stress after yielding”.

[0051]

[Table 4]

From the results in Table 4, it is clear that the maximum stress after the yield increases in the dynamic tensile test but the elongation tends to decrease in comparison with the static tensile test. It became. However, in the aluminum alloy casting according to the present invention, the rate of increase of the maximum stress after yielding in the case of dynamic compared to the case of static is larger than that of the aluminum alloy casting of the comparative example, and the rate of decrease in elongation is smaller. . To make this easier to understand, the static-dynamic ratio (value in the case of dynamic / value in the case of static) is shown in Table 4.

Thus, in the aluminum alloy casting according to the present invention, both excellent strength (maximum stress after yielding) and elongation are achieved even in a high strain rate region assuming an automobile collision. I understand.

This is because, since the eutectic Si is made finer and more granular, breakage originating from eutectic Si particles existing between grain boundaries and dendrite arms is less likely to occur, or This is considered to be due to both the effect of the slip of the crystal grains during high-speed deformation due to eutectic Si being hardly alienated and the effect of the change in the precipitation state of Mg ₂ Si due to the two-stage aging treatment.

(5) Volume fraction and maximum diameter of vacancies Alloy No. 1 shown in Table 1 750 aluminum alloy
After melting at ° C., the degassing conditions were variously changed, and a plate casting having the shape and dimensions shown in FIG. 1 was cast in the same manner. Next, heat treatment is applied to each plate casting (heating at 565 ° C. for 30 minutes followed by rapid cooling—leave at room temperature for 24 hours—air cooling after heating at 150 ° C. × 8 hours).
Then, the tensile test piece shown in FIG. 4 was sampled, and a dynamic tensile test was similarly performed.

Then, for the fracture surface of each tensile test piece, S
EM observation was performed, and based on the SEM observation photograph, the area ratio of pores (both shrinkage cavities and gas defects) that appeared on the fractured surface and the maximum equivalent circle diameter were measured by image analysis.

FIGS. 7 and 8 show the relationship between the measured void area ratio and the maximum equivalent circle diameter and the elongation during the dynamic tensile test, where the void area ratio was 4%. Below,
When the maximum equivalent circle diameter was 250 μm or less, it was confirmed that excellent dynamic elongation of 10% or more was obtained even in a high strain rate region where the strain rate was about 1000 / s.

(Embodiment 11) FIG. 9 shows the configuration of Embodiment 11. 300mm width, 300mm length, 1.0mm thickness
Manufactured using the material of the present invention between upper and lower plate materials 1 and 3 made of aluminum alloy wrought material 6951-T6 having a width of 300
mm, length 300 mm, plate thickness 1.0 mm, x-y coordinates perpendicular to each other on the core surface, and z axis defined in a direction perpendicular to the core surface, and upper and lower surfaces in each of the x and y directions When the convex shape 4 is alternately repeated, as shown in FIG. 10, the concave / convex shape 4 is a sine wave at the cut surface passing through the vertex, the core height H in the z direction is 15 mm, and the wavelength W is 3
A sandwich panel with a core 2 of 0 mm was inserted.

(Embodiment 12) FIG. 11 shows the configuration of Embodiment 12. As in Example 11, the width is 300 mm and the length is 30
0mm, 1.0mm thick aluminum alloy wrought material 6951-
Between the upper and lower plate members 5 and 7 made of T6, manufactured using the material of the present invention, a width of 300 mm, a length of 300 mm, a plate thickness of 1.0 mm, xy coordinates perpendicular to each other on the core surface, and a core surface When the z-axis is defined in a direction perpendicular to the direction, and the convex shape 8 is repeated alternately on the upper surface and the lower surface in each of the x direction and the y direction, as shown in FIG. , The trapezoids are continuously arranged in a wave shape, the core height H in the z direction is 15 mm, and the inclination angle θ of the trapezoid is 1
20 °, trapezoid upper side L (joint length between core and face plate) = 8 mm
A sandwich panel sandwiching the core 6 was prepared.

(Comparative Example 15) A structure similar to that of FIG.
It is manufactured by using an aluminum alloy casting AC4CH-T6 widely applied to a portion where high ductility and high toughness are required between the upper and lower plate materials 1 and 3 of the same size and the same material. A sandwich panel was prepared in which a core having the same shape as the core 4 was inserted.

(Comparative Example 16) The same structure as that of FIG. 11 is applied to a portion where high ductility and high toughness are required between upper and lower plate members 5 and 7 of the same size and the same material. An aluminum alloy casting AC4CH-T6 was used to produce a sandwich panel in which a core having the same shape as the core 6 of Example 12 was inserted.

(Comparative Example 17) As a conventional example, a width of 300 m
m, a 300 mm long, 1.0 mm thick aluminum alloy wrought material with a cell size of 20 mm, a core height of 15 mm, and a cell foil thickness of 0.2 mm between upper and lower plate materials made of aluminum alloy wrought material 6951-T6 Regarding the honeycomb panel having a hexagonal core made of 6951-T6, the following curved surface molding was performed under the same conditions together with the sandwich panels according to the above-described Examples and Comparative Examples. An adhesive was used for bonding the cores and the core and the face plate.

Using the molding die composed of the punch 9 and the die 11 as shown in FIG. 13, the first embodiment is so arranged that the center line of the cross section of each panel is spherical with a curvature of 250 mm.
Each of the sandwich panels obtained in Examples 1 and 12 and Comparative Examples 15 and 16 and the honeycomb panel of Comparative Example 17 were subjected to press working to form a three-dimensional curved surface.

As a result, in the honeycomb panel according to Comparative Example 17 (conventional example), buckling occurred in the core portion inside the panel, and peeling of the face plate and the core occurred near the buckling portion. In addition, an aluminum alloy casting material AC4 is used as a core.
In the sandwich panels according to Comparative Examples 15 and 16 using CH-T6, although the molding itself was good, cracks occurred in the core at the center of the panel. On the other hand, in the sandwich panels according to Examples 11 and 12 using the core to which the material of the present invention was applied, neither the core portion was cracked, and a good three-dimensional curved panel was obtained.

From the results of the molding process described above, the use of a core-shaped panel having irregularities continuous in two directions perpendicular to each other as described above improves the curved formability of the panel, but causes cracks, and By using the core of the material of the present invention, it is possible to realize a sandwich panel excellent in moldability in which the joint between the core and the face plate does not peel and does not crack even in the case of three-dimensional curved surface molding, as in the case of the curved surface molding. It was confirmed that it was possible.

[Brief description of the drawings]

FIG. 1 is a plan view (a) and a side view (b) showing the shape of a casting obtained by sand casting in an embodiment of the present invention.

FIG. 2 is a photograph showing an example of a cross-sectional structure of an aluminum alloy casting according to an example of the present invention.

FIG. 3 is a photograph showing an example of a cross-sectional structure of an aluminum alloy casting according to a comparative example of the present invention.

FIG. 4 is a plan view showing the shape of a test piece subjected to static and dynamic tensile tests.

FIG. 5 is a schematic view showing a configuration of a One-Bar Method high-speed tensile tester.

FIG. 6 is a graph showing a typical example of a stress-strain diagram in a dynamic tensile test.

FIG. 7 is a graph showing the relationship between the area ratio of holes and elongation during a dynamic tensile test.

FIG. 8 is a graph showing the relationship between the maximum circle equivalent diameter of holes and elongation during a dynamic tensile test.

FIG. 9 is a perspective view showing the sandwich panel according to the present invention, in which the concave-convex shape of the core is a sine wave at a cut surface passing through a vertex.

FIG. 10 is a sectional view taken along lines AA and BB in FIG. 9;

FIG. 11 is a perspective view showing a sandwich panel according to the present invention, in which the concave-convex shape of the core is trapezoidal at a cut surface passing through a vertex.

FIG. 12 is a sectional view taken along lines CC and DD of FIG. 11;

FIG. 13 is a perspective view showing a curved surface forming procedure of the sandwich panel according to the present invention.

[Explanation of symbols]

 1,5 Sandwich panel top plate 2 Sandwich panel core (sinusoidal cross section) 3,7 Sandwich panel bottom plate 6 Sandwich panel core (trapezoid cross section)

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Claims (12)

[Claims] 1. A mass ratio of Si: 2.0 to 6.0%, M
g: 0.15 to 0.34%, Fe: 0.20% or less, S
r: An aluminum alloy casting containing 0.003 to 0.01%, the balance being Al and unavoidable impurities is cast, then heated to 540 to 570 ° C., held for 15 minutes to 1 hour, and then quenched. After that, the method is left at room temperature for 5 to 36 hours, then heated to 140 to 180 ° C., held for 1 to 12 hours, and air-cooled to perform an aging treatment. 2. Si: 2.0 to 6.0% by mass ratio, M
g: 0.15 to 0.34%, Fe: 0.20% or less, S
r: 0.003 to 0.01%, Ti: 0.01 to 0.2
5%, B: 0.0001 to 0.001, containing Al
And an aluminum alloy casting composed of unavoidable impurities, and then subjected to a solution treatment in which it is heated to 540 to 570 ° C., held for 15 minutes to 1 hour, then rapidly cooled, and then cooled to room temperature.
Leave for 36 hours and then heat to 140-180 ° C for 1
A method for producing an aluminum alloy cast part, comprising performing an aging treatment of holding for 12 hours and air cooling. 3. An aluminum alloy cast part manufactured by the method according to claim 1 or 2, wherein an average value of a circle equivalent diameter of eutectic Si is 2.0 μm or less, and eutectic Si
Wherein the average value of the circularity coefficient is 0.85 or more. 4. The maximum value of the circle-equivalent diameter of eutectic Si is 6.0 μm.
The cast aluminum alloy part according to claim 3, wherein the minimum value of the circularity coefficient of eutectic Si is 0.30 or more when m or less. 5. The area ratio of pores including shrinkage cavities and gas defects is 4% or less, and the maximum value of the circle-equivalent diameter of these pores is 250 μm or less. Item 5. An aluminum alloy casting part according to Item 4. 6. The value obtained by dividing the total elongation at a strain rate of 1000 / s by the total elongation at a strain rate of 0.001 / s is 0.90 or more. 5. The cast aluminum alloy part according to any one of 5. 7. A value obtained by dividing the maximum stress after yielding at a strain rate of 1000 / s by the maximum stress (tensile strength) after yielding at a strain rate of 0.001 / s is 1.15 or more. The cast aluminum alloy part according to any one of claims 3 to 6, characterized in that: 8. The method according to claim 3, wherein the content of Si is 2.0 to 4.5%, and the content of Mg is 0.15 to 0.30%. Aluminum alloy casting parts. 9. The cast aluminum alloy part according to claim 3, wherein the part is a joint of an A-pillar, a B-pillar, a C-pillar, a roof or a space frame, which is an automobile body part. . 10. When defining xy coordinates perpendicular to each other on the core surface of the core of the sandwich panel, the x direction, y direction
For each of the directions, it is manufactured to repeat the convex shape alternately on the upper surface and the lower surface, and by making a sandwich panel using the core, it is excellent in three-dimensional curved surface molding,
The sandwich panel using an aluminum alloy casting according to claim 1, wherein there is no anisotropy and no dimensional accuracy is required for the height of the core. 11. The sandwich panel core is defined by mutually perpendicular xy coordinates on the core surface, and when the convex shape is alternately repeated on the upper surface and the lower surface in each of the x direction and the y direction, the uneven shape is determined. Sinusoidal wave at the cut surface passing through the apex, 1 wavelength / core height ratio = 0.2 to 10, core thickness =
The sandwich panel using the aluminum alloy casting according to claim 1, wherein the thickness is 0.5 to 10 mm. 12. The xy coordinates of the core of the sandwich panel, which are perpendicular to each other on the core surface, are defined. When the convex shape is alternately formed on the upper surface and the lower surface in each of the x direction and the y direction, the uneven shape is determined. The trapezoids are continuously arranged in a wavy shape at the cutting plane passing through the vertex, and the hypotenuse angle of the trapezoid is 90 to 15
The sandwich panel using an aluminum alloy casting according to claim 1, wherein the core has a thickness of 0 ° and a core thickness of 0.5 to 10 mm.