JP2020026570A - Aluminum clad material - Google Patents

Abstract

To provide an aluminum clad material having excellent durability against repeated stress load.SOLUTION: An aluminum clad material has a first metal layer containing an aluminum alloy, and a second metal layer containing pure aluminum and joined to at least one side of the first metal layer, satisfying the following formula (1) and formula (2). HVα≥30 (1) and HVβ÷HVα≤0.3 (2), where HVα is a Vickers hardness of the first metal layer on a cross section containing the first metal layer and the second metal layer, and HVβ is a Vickers hardness of the second metal layer on the cross section.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an aluminum clad material having excellent durability against repeated stress loads.

  When an aluminum alloy plate is used for a member for a heat exchanger, a member for an automobile, or the like, corrosion resistance (particularly pitting corrosion resistance) may become a problem. Therefore, there is known an aluminum clad material having an improved corrosion resistance by using an aluminum alloy plate as a core material and coating one or both surfaces thereof with a skin made of a pure aluminum layer having excellent corrosion resistance (pitting corrosion resistance) ( For example, Patent Documents 1 and 2).

Japanese Patent No. 5537103 JP-A-57-158350

In the case of aluminum clad materials as disclosed in Patent Literatures 1 and 2, when a repeated forming process (bending process or the like) is performed, cracks may occur in the skin material due to fatigue.
Further, there is a difference in the coefficient of thermal expansion between the core material made of an aluminum alloy and the skin material made of pure aluminum. When an aluminum clad material as in Patent Documents 1 and 2 is placed in an environment where heating and cooling are repeated, a difference occurs between the deformation amount of the core material and the deformation amount of the skin material. Cracks were sometimes formed in the skin material due to stress caused by the difference in the amount of deformation.
As described above, the conventional aluminum clad material does not have sufficient durability in an environment in which a repeated stress load (for example, repeated molding, repeated heating and cooling, and the like) occurs.

  An object of the present invention is to provide an aluminum clad material having excellent durability against repeated stress loads.

Aspect 1 of the present invention
A first metal layer made of an aluminum alloy;
A second metal layer made of pure aluminum and joined to at least one surface of the first metal layer;
An aluminum clad material satisfying the following formulas (1) and (2).

HVα ≧ 30 (1)
HVβ ÷ HVα ≦ 0.3 (2)

Here, HVα is the Vickers hardness of the first metal layer in a cross section including the first metal layer and the second metal layer, and HVβ is the Vickers hardness of the second metal layer in the cross section. .

A second aspect of the present invention is the aluminum clad material according to the first aspect, which satisfies the following formula (3).

0.02 ≦ t2 ÷ t1 ≦ 1.0 (3)

Here, t1 is the thickness of the first metal layer, and t2 is the thickness of the second metal layer.

An aspect 3 of the present invention is the aluminum clad material according to the aspect 1 or 2, which satisfies the following formulas (4) and (5).

RRR2 ÷ RRR1 ≧ 5 (4)
RRR2 ≧ 5 (5)

Here, RRR1 is a residual resistance ratio of the first metal layer, and RRR2 is a residual resistance ratio of the second metal layer.

In a fourth aspect of the present invention, the first metal layer is made of an aluminum alloy containing at least one of Mn and Mg,
The aluminum clad material according to any one of aspects 1 to 3, which satisfies the following formula (6).

0.5 ≦ (Cmn1 + Cmg1) ≦ 5.0 (6)

Here, Cmn1 is the Mn content (% by mass) in the first metal layer, and Cmg1 is the Mg content (% by mass) in the first metal layer.

Aspect 5 of the present invention includes:
The second metal layer is the aluminum clad material according to any one of aspects 1 to 4, wherein the number of intermetallic compounds having a diameter of 1 μm or more is 10 or less per 100 μm ² .

  The aluminum clad material of the present invention can exhibit excellent durability against repeated stress loads.

FIG. 1 is a schematic sectional view of an aluminum clad material according to an embodiment of the present invention. FIG. 2 is a partially enlarged schematic sectional view of the aluminum clad material shown in FIG. FIGS. 3A and 3B are schematic cross-sectional views illustrating a method for manufacturing an aluminum clad material according to an embodiment of the present invention. FIG. 4 is a schematic sectional view of an aluminum clad material according to a modification of the embodiment of the present invention. FIG. 5 is a schematic diagram for explaining a test method of a repeated bending test. FIG. 6 is a schematic diagram for explaining a test method of a repeated bending test. FIG. 7 is a schematic diagram for explaining a test method of a repeated bending test.

(Embodiment 1)
FIG. 1 is a schematic sectional view of an aluminum clad material 10 according to an embodiment of the present invention. FIG. 2 is a partially enlarged schematic cross-sectional view of the second metal layer 12 of the aluminum clad material 10.
Aluminum clad material 10 includes a first metal layer 11 and a second metal layer 12 bonded to at least one surface of first metal layer 11. The first metal layer 11 is made of an aluminum alloy, and the second metal layer 12 is made of pure aluminum. In the present specification, “pure aluminum” refers to 1000-series aluminum (for example, A1050, A1070, and the like) defined in JIS H4000: 2014, and intends aluminum having an Al content of 99% by mass or more. . The purity of the pure aluminum forming the second metal layer 12 is preferably at least 99.999% by mass (5N), more preferably at least 99.9999% by mass (6N).

  Although the composition of the aluminum alloy forming the first metal layer 11 is not particularly limited, for example, a 3000-based aluminum alloy (Al-Mn-based alloy), a 5000-based aluminum alloy (Al-Mg-based alloy), and a 6000-based aluminum alloy (Al- Mg-Si based alloy) can be applied.

  The aluminum clad material 10 of the present invention secures strength by the first metal layer 11 and secures corrosion resistance by the second metal layer 12. Therefore, by appropriately adjusting the composition and thickness of the first metal layer 11, the strength of the aluminum clad material 10 can be adjusted to a strength suitable for the intended use (for example, a member for a heat exchanger, a member for an automobile, and the like). .

  In the aluminum clad material 10, the corrosion resistance of the aluminum clad material 10 is improved by cladding the first metal layer 11 having relatively low corrosion resistance with the second metal layer 12 having high corrosion resistance. Improves durability. When cracks occur in the first metal layer 11, the corrosion resistance of the aluminum clad material 10 is reduced, and the durability of the aluminum clad material 10 is reduced.

Here, when the aluminum clad material 10 is subjected to a forming process such as a bending process, the second metal layer 12 is deformed along with the deformation of the first metal layer 11. When the aluminum clad material 10 is repeatedly formed, cracks may occur in the second metal layer 12.
Further, the first metal layer 11 and the second metal layer 12 may have different coefficients of thermal expansion. When the aluminum clad material 10 is placed in an environment where heating and cooling are repeated, cracks may occur in the second metal layer 12 due to deformation (expansion and contraction) of the first metal layer 11.

In order to suppress the occurrence of cracks in the second metal layer 12 while maintaining the strength of the aluminum clad material 10, the present inventors set the Vickers hardness HVα of the first metal layer 11 and the second metal layer It has been found that it is important that the Vickers hardness HVβ of No. 12 satisfies the following formulas (1) and (2).

HVα ≧ 30 (1)
HVβ ÷ HVα ≦ 0.3 (2)

Here, HVα is the Vickers hardness of the first metal layer in a cross section including the first metal layer and the second metal layer (the cross section illustrated in FIG. 1), and HVβ is the second metal layer in the cross section. Vickers hardness.

The strength of the metal layer depends on hardness, thickness, and the like. In the present invention, the strength of the first metal layer 11 is increased by increasing the Vickers hardness (HVα) of the first metal layer 11 to 30 or more, as defined by the formula (1), so that the aluminum clad material 10 The overall strength can be improved. HVα is preferably 40 or more, particularly preferably 50 or more.
HVα is usually 120 or less, and the preferable upper limit varies depending on the use of the aluminum clad material 10. For example, in the aluminum clad material 10 used for a member for a heat exchanger, a member for an automobile, or the like, it is preferable that HVα is 100 or less in order to secure appropriate moldability.

In the formula (2), the ratio of the Vickers hardness of the second metal layer 12 to the Vickers hardness of the first metal layer 11 (HVβ ÷ HVα) is determined by the relative value of the second metal layer 12 to the first metal layer 11. It is an index of the hardness. That is, the smaller the value of (HVβ ÷ HVα), the higher the relative flexibility of the second metal layer 12 with respect to the first metal layer 11. By setting the value of (HVβ ÷ HVα) to 0.3 or less as defined in Expression (2), the relative flexibility of the second metal layer 12 is sufficiently ensured, and Deformability can be increased. Thereby, even in an environment in which a repeated stress load occurs, the occurrence of cracks in the second metal layer 12 can be suppressed, and the durability of the aluminum clad material 10 can be improved.
The lower limit of the value of (HVβ ÷ HVα) is not particularly limited, but (HVβ ÷ HVα) is usually 0.1 or more from the practical hardness of the material.

  As described above, the aluminum clad material 10 that satisfies the expressions (1) and (2) has high strength and excellent durability.

The Vickers hardness (HVα) of the first metal layer 11 is in the thickness direction (the direction of the arrow A in FIG. 2) from the joint surface 15 between the first metal layer 11 and the second metal layer 12 to the first metal layer 11. The measurement is performed at a position of 0.1 mm (position P11 in FIG. 2). The Vickers hardness (HVβ) of the second metal layer 12 is 0.1 mm in the thickness direction (the direction of arrow B in FIG. 2) from the bonding surface 15 to the first metal layer 12 (position P12 in FIG. 2). Perform the measurement.
In the present specification, the Vickers hardness of the second metal layer 11 and the second metal layer 12 (Vickers hardness at the position P11 and the position P12) is 0.01 kgf (= 0.09806N) using a micro Vickers hardness meter. ) Refers to the Vickers hardness (HV0.01 (10 gf)). The Vickers hardness is measured according to JIS Z 2244: 2009 "Vickers hardness test-test method".

The aluminum clad material 10 preferably satisfies the following expression (3).

0.02 ≦ t2 ÷ t1 ≦ 1.0 (3)

Here, t1 is the thickness of the first metal layer 11, and t2 is the thickness of the second metal layer 12 (see FIG. 1).

As defined in the equation (3), the ratio (t2 比 t1) of the thickness t2 of the second metal layer 12 to the thickness t1 of the first metal layer 11 is preferably 0.02 or more and 1.0 or less. .
When the value of (t2 ÷ t1) is 0.02 or more, the thickness of the second metal layer 12 can be secured, so that the corrosion resistance of the second metal layer 12 can be further improved. The value of (t2 ÷ t1) is more preferably 0.05 or more and 0.8 or less, further preferably 0.2 or more and 0.7 or less, and more preferably 0.1 or more and 0.5 or less. Particularly preferred.

  The thickness of the aluminum clad material 10 can be appropriately changed depending on the use, but for general use, the thickness is preferably 0.2 to 6.0 mm. In such an aluminum clad material 10, the thickness t1 of the first metal layer 11 is, for example, 0.1 mm (100 μm) to 5.0 mm, and the thickness t2 of the second metal layer 12 is, for example, 0.1 mm (100 μm) to It can be 5.0 mm.

Further, the aluminum clad material 10 preferably satisfies the following expressions (4) and (5).

RRR2 ÷ RRR1 ≧ 5 (4)
RRR2 ≧ 5 (5)

Here, RRR1 is the residual resistance ratio of the first metal layer 11, and RRR2 is the residual resistance ratio of the second metal layer 12.

The significance of equations (4) and (5) will be described in detail below.
The residual resistance ratio (RRR) is the ratio of the conductivity at low temperature (generally 4.2K) to the conductivity at room temperature. In addition, the deformation resistance of the metal material decreases as the residual resistance ratio (RRR) increases. Therefore, the deformation resistance of the metal material can be estimated from the value of the residual resistance ratio (RRR).

Equation (4) defines the ratio of the residual resistance ratio (RRR2) of the second metal layer 12 to the residual resistance ratio (RRR1) of the first metal layer 11. A large ratio of RRR2 to RRR1 means that the deformation resistance of the second metal layer 12 is smaller than the deformation resistance of the first metal layer 11, in other words, the second metal layer 12 deforms more than the first metal layer 11. Suggests that it is easier.
As defined in equation (4), the ratio of RRR2 to RRR1 is preferably 5 or more, whereby the deformation resistance of the second metal layer 12 is sufficiently smaller than that of the first metal layer 11. Thus, the deformability of the second metal layer 12 can be further improved. As a result, the effect of suppressing the occurrence of cracks in the second metal layer 12 can be improved even under an environment where a repeated stress load is applied.

  RRR2 ÷ RRR1 is more preferably 100 or more, and particularly preferably 1000 or more. The upper limit of RRR2 ÷ RRR1 is not particularly limited, but may be, for example, 10,000 or less.

Equation (5) specifies that the residual resistance ratio (RRR2) of the second metal layer 12 is 5 or more. The high residual resistance ratio (RRR2) of the second metal layer 12 suggests that the amount of impurity atoms contained in the second metal layer 12 is small and that the purity of pure aluminum forming the second metal layer 12 is high. are doing. By satisfying the expression (5), the corrosion resistance function of the second metal layer 12 can be further improved.
RRR2 is more preferably 100 or more, and particularly preferably 1000 or more. The upper limit of RRR2 is not particularly limited, but may be, for example, 100,000 or less.

The respective residual resistance ratios (RRR1 and RRR2) are obtained as follows. Two pieces of the obtained aluminum clad material are prepared. One is polished from the second metal layer 12 side to leave only the first metal layer 11 (first measurement sample). The other is polished from the first metal layer 11 side to leave only the second metal layer (second measurement sample). For each of the first measurement specimen and the second measurement sample, and the electrical resistivity ρ _rt (Ω · m) at room temperature, the electrical resistivity [rho _{4.2 K} in liquid He temperature (4.2K) (Ω · m ) Is measured by the four probe method. Using the obtained electric resistivity, the residual resistance ratio (RRR1 and RRR2) is obtained from the following equation (7).

RRR = ρ _rt ÷ ρ _4.2K (7)

The first metal layer 11 is made of an aluminum alloy containing at least one of Mn and Mg, and the contents of Mn and Mg preferably satisfy Expression (6).

0.5 ≦ (Cmn1 + Cmg1) ≦ 5.0 (6)

Here, Cmn1 is the Mn content (% by mass) in the first metal layer, and Cmg1 is the Mg content (% by mass) in the first metal layer.

  All of the alloy elements Mn and Mg have an effect of improving the strength of the aluminum alloy. When the total content of these alloy elements (Cmn1 + Cmg1) is 0.5% by mass or more, the effect of improving the strength of the first metal layer 11 becomes remarkable, and the strength of the aluminum clad material 10 can be further improved. When the total content of Mn and Mg (Cmn1 + Cmg1) is 5.0% by mass or less, the strength of the first metal layer 11 is appropriately controlled, and the aluminum clad material 10 is easily formed into a component shape. The total content of Mn and Mg (Cmn1 + Cmg1) is preferably 0.8 or more and 4.0 or less, more preferably 1.2 or more and 3.5 or less, still more preferably 1.8 or more and 3.3 or less, and 2.0 or more. Particularly preferred is 3.0 or less.

In the second metal layer 12, the number of intermetallic compounds having a diameter of 1 μm or more is preferably 10 or less per 100 μm ² (10/100 μm ² or less).
A coarse intermetallic compound having a diameter of 1 μm or more tends to be a starting point of cracks when a metal material is formed into a desired part shape. By reducing the number density of the intermetallic compound having a diameter of 1 μm or more in the second metal layer 12 to 10/100 μm ² or less, it is possible to suppress the occurrence of cracks in the second metal layer 12 during molding.

The detection of an intermetallic compound having a diameter of 1 μm or more is performed by mirror-polishing the surface 12x of the second metal layer 12 of the aluminum clad material 10 by buffing, and then taking a photograph by magnifying 500 times with an optical microscope. Image processing is performed on a 0.022 mm ² (0.13 mm × 0.17 mm) range in the photograph, the number of intermetallic compounds having a diameter of 1 μm or more is counted, and the number density per 100 μm ² (pieces / 100 μm ²⁾ ) Is calculated. Here, the “diameter” means that the diameter passing through the center of gravity is measured at intervals of 2 ° for each of the intermetallic compounds observed on the photograph (measured values of 90 diameters are obtained), and the measured values are averaged. It is the value obtained.

Next, an example of a method for manufacturing the aluminum clad material 10 will be described with reference to FIG.
The method for manufacturing the aluminum clad material 10 according to the embodiment of the present invention includes a clad process. Furthermore, a heat treatment step may be included after the cladding step, and a surface polishing step may be included before the cladding step.

(Clad process)
The cladding step is a step in which the first metal material 110 made of an aluminum alloy and the second metal material 120 made of pure aluminum are stacked and roll-bonded. The first metal material 110 becomes the first metal layer 11 of the aluminum clad material 10 after rolling and joining, and the second metal material 120 becomes the second metal layer 12. The second metal material 120 is preferably formed from high-purity aluminum having a purity of 99.999% by mass (5N) or more, and more preferably formed from high-purity aluminum having a purity of 99.9999% by mass (6N) or more.
First, a first metal material 110 and a second metal material 120 are prepared by a conventionally known method. For example, the first metal material 110 can be prepared by casting and rolling an aluminum alloy having a predetermined composition, and the second metal material 120 can be prepared by casting and rolling pure aluminum having a predetermined purity. If necessary, a homogenization treatment may be performed between casting and rolling.

As shown in FIG. 3A, the first metal material 110 and the second metal material 120 are stacked with the upper surface of the first metal material 110 and the lower surface of the second metal material 120 facing each other. The upper surface of the first metal material 110 becomes the bonding surface 110b of the first metal material 110 (the surface to be joined to the second metal material 120), and the lower surface of the second metal material 120 becomes the bonding surface 120b of the second metal material 120. (The surface to be joined to the first metal material 110).
Thereafter, the first metal material 110 and the second metal material 120 are rolled, so that the first metal material 110 and the second metal material 120 are rolled and joined. Thereby, an aluminum clad material 10 as shown in FIG. 3B is obtained.

The thickness t11 of the first metal material 110 and the thickness t22 of the second metal material 120 are preferably set so as to satisfy the following equation (8).

0.02 ≦ t22 ÷ t11 ≦ 1.0 (8)

The ratio of the “thickness t22 of the second metal material 120” to the “thickness t11 of the first metal material 110” before rolling (this is referred to as “the thickness ratio before rolling”) is the “first thickness ratio before rolling”. It is almost equal to the ratio of the “thickness t2 of the second metal layer” to the “thickness t1 of the metal layer” (this is called “thickness ratio after rolling”). Therefore, by setting the thickness ratio before rolling to 0.02 or more and 1.0 or less (that is, satisfying Expression (8)), the thickness ratio after rolling is set to 0.02 or more and 1.0 or less (that is, The aluminum clad material 10 satisfying the following expression (3) can be obtained.

0.02 ≦ t2 ÷ t1 ≦ 1.0 (3)

When rolling joining (cladding) between the first metal material 110 and the second metal material 120 is performed by hot rolling, the adhesion between the first metal layer 11 and the second metal layer 12 of the aluminum clad material 10 is easily improved. It is preferable because it is possible. The heating temperature at the time of hot rolling can be appropriately set, and is, for example, 250 ° C. or more and 600 ° C. or less. When performing a surface treatment (polishing step) as described later, the first metal layer 11 and the second metal layer 12 may be used even if the hot rolling is performed at a lower temperature (for example, 250 ° C. or more and 300 ° C. or less). Can be sufficiently improved.
Finish rolling (cold rolling) may be further performed on the aluminum clad material 10 after the hot rolling.

(Polishing process)
Before the cladding step, a polishing step of polishing the bonding surface 110b of the first metal material 110 and the bonding surface 120b of the second metal material 120 may be included. When the oxide film on the bonding surfaces 110b and 120b is removed by polishing, there is an effect that the first metal material 110 and the second metal material 120 are easily joined in the cladding process.

In the polishing step, the above effects can be obtained if at least a part of the oxide film on the bonding surfaces 110b and 120b is removed. In particular, the bonding surface 110b of the first metal material 110 and the bonding surface 120b of the second metal material 120 each have an arithmetic average roughness Ra (JIS B 0601: 2013) of 0.5 μm or more and 3 μm or less. Polishing is preferable because the above effect becomes more remarkable. It is more preferable to perform polishing so that Ra is 0.5 μm or more and 2 μm or less.
Polishing of the bonding surfaces 110b and 120b can be performed, for example, by buff polishing using an abrasive.

(Heat treatment process)
It is preferable to heat-treat the aluminum clad material 10 (FIG. 3B) obtained by the clad process. The heat treatment step has an effect of reducing the hardness of the second metal layer 12 by removing the processing strain introduced into the second metal layer 12 by the rolling in the cladding step. However, since the processing strain of the first metal layer 11 is also removed by the heat treatment, if the heat treatment conditions (heat treatment temperature and heat treatment time) are not appropriate, the hardness of the first metal layer 11 is excessively reduced, and the aluminum clad There is a possibility that the strength of the material 10 cannot be secured.

  The preferred heat treatment conditions are such that the hardness of the second metal layer 12 is reduced and the hardness of the first metal layer 11 is not excessively reduced. Depends on the material.

When the Mn content contained in the first metal layer 11 is Cmn1 (% by mass) and the Mg content contained in the first metal layer 11 is Cmg (% by mass), the first metal layer 11 is (Cmn + Cmg). When ≦ 2.0 is satisfied and the second metal layer 12 is pure aluminum, the heat treatment temperature can be set to 150 ° C. to 250 ° C., and the heat treatment temperature can be set to 2 hours to 10 hours.
For example, when the first metal layer 11 is made of an A3000 series aluminum alloy (A3003 or the like) and the second metal layer 12 is made of 99.999% by mass (5N) of pure aluminum, the heat treatment temperature is set to 150 ° C. or more and 250 ° C. or less. The heat treatment time can be set to 2 hours to 10 hours.

When the first metal layer 11 satisfies (Cmn + Cmg)> 2.0 and the second metal layer 12 is pure aluminum, the heat treatment temperature is 150 ° C. or more and 500 ° C. or less, and the heat treatment temperature is 2 hours or more and 10 hours or less. Can be.
For example, when the first metal layer 11 is made of an A5000-based aluminum alloy (such as A5052) and the second metal layer 12 is made of 99.999% by mass (5N) of pure aluminum, the heat treatment temperature is set to 150 ° C. or more and 500 ° C. or less. The heat treatment time can be set to 2 hours to 10 hours.

  The aluminum clad material 10 thus obtained has high strength and excellent durability against repeated stress loads.

(Modification)
FIG. 4 is a schematic sectional view of an aluminum clad material 20 according to a modification of the embodiment of the present invention. The aluminum clad material 20 according to the modification includes the second metal layers 12a and 12b on both surfaces of the first metal layer 11. The two second metal layers 12a, 12b may be made of pure aluminum of the same purity or may be made of pure aluminum of another purity. For example, the second metal layer 12a covering the upper surface of the first metal layer 11 is made of pure aluminum having a purity of 99.999% by mass (5N), and the second metal layer 12b covering the lower surface is 99.9999% by mass (6N). Of pure aluminum. The thickness t2a of one second metal layer 12a and the thickness t2b of the other second metal layer 12b may be the same or different.
When the second metal layers 12a and 12b are formed on both surfaces of the first metal layer 11, the corrosion resistance is superior to the case where the second metal layers 12a and 12b are formed only on one surface.

When the aluminum clad material 20 has two second metal layers 12a and 12b, the total thickness (total thickness) of the second metal layers 12a and 12b satisfies the above expression (3). preferable. That is, in the example of FIG. 4, the aluminum clad material 20 preferably satisfies the following expression (9).

0.02 ≦ (t2a + t2b) ÷ t1 ≦ 1.0 (9)

Here, t2a is the thickness of one second metal layer 12a, and t2b is the thickness of the other second metal layer 12b.
When the thickness t2a of one second metal layer 12a is larger than the thickness t2b of the other second metal layer 12b (that is, t2a> t2b), the thickness t2a of the second metal layer 12a is more than 100 μm. Is preferred. This makes it possible to obtain an aluminum clad material 20 having both good strength and good corrosion resistance.

  Also, regarding the hardness, residual resistance ratio, and other specifications of the second metal layer 12 specified in the first embodiment, the thick second metal layer (the second metal layer 12a in FIG. By satisfying the rules, the aluminum clad material 20 according to the modification can have the same effect as the aluminum clad material 10 of the first embodiment.

(Example 1)
1. Production of Measurement Sample Pure aluminum was cast and rolled to prepare a pure aluminum plate (second metal material 120) having the purity shown in Table 1. 5N-Al in Table 1 refers to pure aluminum having a purity of 99.999% by mass.
Further, an aluminum alloy (A3003 and A5052) was cast and rolled to prepare an aluminum alloy plate (first metal material 110) having a composition shown in Table 2.
Tables 1 and 2 show the results of composition analysis of the obtained first metal material 110 and second metal material 120 by solid-state emission spectroscopy. A line (-) in Table 2 means that the chemical component was not detected. Table 2 also shows the total content of Mn and Mg (Cmn1 + Cmg1).

After cutting the obtained first metal material 110 and second metal material 120 into the following dimensions, a surface treatment step, a cladding step (hot rolling) and a finish rolling (cold rolling) are performed under the following conditions, and aluminum A clad material 10 was prepared.
・ Dimensions of the first metal material 110: 2.0mm × 125mm × 190mm
・ Dimensions of the second metal material 120: 1.0mm × 125mm × 190mm
Surface treatment step: The entire bonding surface 110b of the first metal material 110 and the entire bonding surface 120b of the second metal material 120 were polished with a commercially available metal polishing agent by reciprocating 10 times in the longitudinal direction.
Cladding step (hot rolling): Each of the first metal material 110 and the second metal material 120 before rolling is heated to 300 to 350 ° C., and at that temperature (hot rolling temperature), the rolling reduction per pass. Five passes of hot rolling were performed at 15 to 20%. The final total reduction was 50-75%.
Finish Rolling (Cold Rolling): As finish rolling, cold rolling is performed for 1 to 10 passes at a rolling reduction of 10 to 20% per pass to obtain a predetermined thickness (“thickness of aluminum clad material in Table 3”). ").

  The combination of the material of the first metal material 110 and the material of the second metal material 120 used in the production of each aluminum clad material 10 is the “material” of the first metal layer and the “material” of the second metal layer described in Table 3. ".

  Sample No. 1 of the aluminum clad material 10 manufactured under the above conditions was used. Samples for measurement were obtained by holding the samples Nos. 1, 4, 6, and 7 at the heat treatment temperature shown in Table 3 for 3 hours. The thickness of each measurement sample was as described in “Thickness of aluminum clad material” in Table 3.

2. Hardness measurement The Vickers hardness (HV0.01) of the first metal layer 11 and the second metal layer 12 of the measurement sample (aluminum clad material 10) manufactured under the conditions shown in Table 3 was measured using a micro Vickers hardness meter. It was measured. In accordance with JIS Z 2244: 2009 "Vickers hardness test-Test method", a regular square pyramid diamond indenter is pushed into the surface of the test piece, and after the test force is released, the diagonal length of the hollow remaining on the surface. Was used to calculate Vickers hardness. In this standard, the hardness symbol is changed according to the test force, and here, the Vickers hardness (HV0.01) at the test force of 0.01 kgf (= 0.09806N) is adopted.

The Vickers hardness HVα of the first metal layer 11 was measured at a position 0.1 mm from the joint surface 15 between the first metal layer 11 and the second metal layer 12 (position P11 in FIG. 2). The Vickers hardness HVβ of the second metal layer 12 was measured at a position 0.1 mm from the joint surface 15 (position P12 in FIG. 2).
In the measurement of HVα and HVβ, a 10 mm × 20 mm sample piece was cut out from the prepared measurement sample. An acrylic resin was embedded so that the cross section of the sample piece was exposed, and the exposed cross section was mirror-polished by buff polishing. The mirror-polished cross section is checked with an optical microscope to specify the joint surface 15 between the first metal layer 11 and the second metal layer 12, and is separated from the joint surface 15 by 0.1 mm in the direction A toward the first metal layer 11. And a position P12 separated by 0.1 mm in the direction B from the bonding surface 15 to the second metal layer 12 (FIG. 2). At each position, Vickers hardness was measured.

  Table 4 shows the measurement results of the Vickers hardness HVα of the first metal layer 11 and the Vickers hardness HVβ of the second metal layer 12. The hardness ratio (HVβ ÷ HVα) was calculated from the measurement results, and is shown in Table 4. In Table 4, the sample No. The underlined values of the hardness ratios (HVβ ÷ HVα) of 5 to 8 indicate that they do not meet the requirements of the present invention.

3. Repeat bending test A test piece 40 (FIGS. 5A and 5B) having a width of 10 mm and a length of 100 mm was cut out from the created measurement sample to obtain a sample for a repeated bending test.
In the repeated bending test, at least one of the four corners of an aluminum alloy rectangular parallelepiped block of 85 mm × 85 mm × 50 mm was chamfered with R10 to form a jig 50 for the repeated bending test (FIGS. 5A and 5B). )).
The test piece 40 was arranged so that the center 40C in the length direction of the test piece 40 was in contact with the arc center 52C of the corner 52 of the jig 50 with the chamfered corner R10 (FIG. 6A). At this time, the test piece 40 was arranged so that the first metal layer 41 was in contact with the jig 50 and the second metal layer 42 was not in contact with the jig 50.

As shown in FIG. 6B, the test piece 40 was bent so as to follow the arc of R10 at the corner 52 of the jig 50 (referred to as “bending work”). At this time, both ends 40E, 40E of the test piece 40 were pressed with a 50 mm × 50 mm × 10 mm aluminum alloy plate (holding jig 60) so that a force could be evenly applied to the test piece 40.
As shown in FIG. 7, the test piece 40 after the bending was placed on a flat work table 70, pressed down from above with a holding jig 60, and the test piece 40 was stretched flat (referred to as “return operation”). At this time, the test piece 40 is arranged so that both ends 40E, 40E of the test piece 40 are in contact with the upper surface of the worktable 70, and the upwardly curved portion (the center 40C of the test piece 40) is pressed downward by the holding jig 60. did.

  One set of the bending test was performed by the bending operation and the subsequent returning operation, and the bending test was repeated 30 sets for each test piece 40. After the end of the repeated bending test, the surface of the sample piece 40 on the side of the second metal layer 42 was visually observed to confirm the presence or absence of cracks having a length in the width direction of 5 mm or more. When there was the crack, "Yes" was described in "Repeated bending test (presence or absence of crack)" in Table 4. When no crack was observed, or when only a crack having a length of less than 5 mm in the width direction was observed, "none" was described in Table 4.

4. Residual resistance ratio (RRR)
Two samples for each measurement (aluminum clad material 10) were prepared. One was polished from the second metal layer 12 side to leave only the first metal layer 11 (first measurement sample). The other was polished from the first metal layer 11 side to leave only the second metal layer 12 (second measurement sample). The residual resistance ratio (RRR1 and RRR2) was measured for each of the first measurement sample and the second measurement sample.
Using a measurement sample, and the electrical resistivity ρ _rt (Ω · m) at room temperature, the electrical resistivity ρ _4.2K (Ω · m) of the four-terminal method in liquid He temperature (4.2 K) It was measured. Using the obtained electric resistivity value, a residual resistance ratio (RRR) was obtained from the following equation (4).

RRR = ρ _rt ÷ ρ _4.2K (4)

Table 5 shows the measured value of RRR of the first metal layer 11 (RRR1), the measured value of RRR of the second metal layer 12 (RRR2), and the value of (RRR2 ÷ RRR1) calculated from the measured values of each sample. Shown in

5. Number of intermetallic compounds having a diameter of 1 μm or more per 100 μm ² (pieces / 100 μm ² )
Sample No. of the measurement sample (aluminum clad material 10) manufactured under the conditions shown in Table 3. Regarding 1 and 2, the number of intermetallic compounds having a diameter of 1 μm or more contained in the second metal layer 12 was measured. After the surface 12x of the second metal layer 12 of the aluminum clad material 10 was mirror-polished by buffing, the photograph was taken at a magnification of 500 times with an optical microscope. Image processing is performed on a 0.022 mm ² (0.13 mm × 0.17 mm) range in the photograph, the number of intermetallic compounds having a diameter of 1 μm or more is counted, and the number density per 100 μm ² (pieces / 100 μm ²⁾ ) Was calculated. Here, the “diameter” is a value obtained by measuring the diameter passing through the center of gravity at intervals of 2 ° for each of the intermetallic compounds observed on the photograph (measured values of 90 diameters are obtained), and averaging the measured values. I asked.
The calculated number density is described in the column of “second metal layer (pieces / 100 μm ² )” of “intermetallic compound having a diameter of 1 μm or more” in Table 5.

  Sample No. In Nos. 1-4, the first metal layer 11 is made of an aluminum alloy, the second metal layer 12 is made of pure aluminum having a purity of 99.999 mass% (5N) or more, and the Vickers hardness HVα of the first metal layer 11 is 30. As described above, the ratio of the Vickers hardness HVβ of the second metal layer 12 to HVα (hardness ratio (HVβ ÷ HVα)) was 0.2 or less. As a result, in the repeated bending test, no large cracks (cracks of 5 mm or more in the width direction) were generated, and excellent durability against repeated stress load was exhibited.

In addition, the sample No. In Examples 1 and 2, the ratio of RRR2 to RRR1 (RRR2ＲRRR1) was 5 or more, and the number of intermetallic compounds having a diameter of 1 μm or more in the second metal layer 12 was 10/100 μm ² or less. Therefore, the sample No. It is considered that Nos. 1 and 2 show particularly excellent durability against repeated stress loads.

  On the other hand, sample No. In Nos. 5 to 8, since the hardness ratio (HVβ０．３HVα) exceeded 0.3, large cracks (cracks of 5 mm or more in the width direction) occurred in the repeated bending test.

10, 20 Aluminum clad material 11 First metal layer 12, 12a, 12b Second metal layer 12x Surface of second metal layer 15 Joining surface 110 First metal material 110b Bonding surface of first metal material 120 Second metal material 120b The bonding surface of the second metal material 40 test piece

Claims (5)

A first metal layer made of an aluminum alloy;
A second metal layer made of pure aluminum and joined to at least one surface of the first metal layer;
An aluminum clad material satisfying the following expressions (1) and (2).

HVα ≧ 30 (1)
HVβ ÷ HVα ≦ 0.3 (2)

Here, HVα is the Vickers hardness of the first metal layer in a cross section including the first metal layer and the second metal layer, and HVβ is the Vickers hardness of the second metal layer in the cross section. . The aluminum clad material according to claim 1, wherein the following formula (3) is satisfied.

0.02 ≦ t2 ÷ t1 ≦ 1.0 (3)

Here, t1 is the thickness of the first metal layer, and t2 is the thickness of the second metal layer. The aluminum clad material according to claim 1 or 2, wherein the following formulas (4) and (5) are satisfied.

RRR2 ÷ RRR1 ≧ 5 (4)
RRR2 ≧ 5 (5)

Here, RRR1 is a residual resistance ratio of the first metal layer, and RRR2 is a residual resistance ratio of the second metal layer. The first metal layer is made of an aluminum alloy containing at least one of Mn and Mg,
The aluminum clad material according to any one of claims 1 to 3, which satisfies the following expression (6).

0.5 ≦ (Cmn1 + Cmg1) ≦ 5.0 (6)

Here, Cmn1 is the Mn content (% by mass) in the first metal layer, and Cmg1 is the Mg content (% by mass) in the first metal layer. 5. The aluminum clad material according to claim 1, wherein the second metal layer has 10 or less intermetallic compounds having a diameter of 1 μm or more per 100 μm ^2. 6.

Images