JP7080135B2 - Aluminum clad material - Google Patents

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

Japanese Patent No. 5537103 Japanese Patent Application Laid-Open No. 57-158350

Aluminum clad materials such as Patent Documents 1 and 2 may have cracks in the skin material due to fatigue when repeatedly molded (bending or the like).
Further, there is a difference in the coefficient of thermal expansion between the core material made of aluminum alloy and the skin material made of pure aluminum. When an aluminum clad material such as Patent Documents 1 and 2 is placed in an environment where heating and cooling are repeated, a difference between the amount of deformation of the core material and the amount of deformation of the skin material occurs. The stress caused by the difference in the amount of deformation sometimes caused cracks in the skin material.
As described above, the conventional aluminum clad material has not been sufficiently durable in an environment where repeated stress loads (for example, repeated molding, repeated heating and cooling, etc.) occur.

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 is
The first metal layer made of aluminum alloy and
It comprises a second metal layer made of pure aluminum and bonded to at least one side of the first metal layer.
It is 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 the 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. ..

Aspect 2 of the present invention is the aluminum clad material according to Aspect 1 that 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.

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

RRR2 ÷ RRR1 ≧ 5 (4)
RRR2 ≧ 5 (5)

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

In aspect 4 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 (mass%) in the first metal layer, and Cmg1 is the Mg content (mass%) in the first metal layer.

Aspect 5 of the present invention is
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 cross-sectional view of an aluminum clad material according to an embodiment of the present invention. FIG. 2 is a partially enlarged schematic cross-sectional view of the aluminum clad material shown in FIG. 3A and 3B are schematic cross-sectional views for explaining a method for manufacturing an aluminum clad material according to an embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of an aluminum clad material according to a modified example 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 cross-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.
The aluminum clad material 10 includes a first metal layer 11 and a second metal layer 12 bonded to at least one surface of the 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, etc.) defined in JIS H4000: 2014, and is intended to be 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 99.999% by mass (5N) or more, more preferably 99.9999% by mass (6N) or more.

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

In the aluminum clad material 10 of the present invention, the strength is secured by the first metal layer 11 and the corrosion resistance is secured by the second metal layer 12. Therefore, the composition and thickness of the first metal layer 11 can be appropriately adjusted to make the strength of the aluminum clad material 10 suitable for the intended use (for example, heat exchanger member, automobile member, etc.). ..

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 a relatively low corrosion resistance with the second metal layer 12 having a high corrosion resistance, thereby improving the corrosion resistance of the aluminum clad material 10. The durability is improved. When cracks occur in the first metal layer 11, the corrosion resistance of the aluminum clad material 10 is lowered, and the durability of the aluminum clad material 10 is lowered.

Here, when the aluminum clad material 10 is subjected to a forming process such as bending, the second metal layer 12 is also deformed along with the deformation of the first metal layer 11. When the aluminum clad material 10 is repeatedly molded, 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.

Therefore, 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 have Vickers hardness HVα of the first metal layer 11 and the second metal layer. It was found that it is important that the Vickers hardness HVβ of 12 satisfies the following equations (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 (cross section shown in FIG. 1), and HVβ is the second metal layer in the cross section. Vickers hardness.

The strength of the metal layer depends on the hardness, thickness and the like. In the present invention, as defined in the formula (1), the Vickers hardness (HVα) of the first metal layer 11 is made as hard as 30 or more, thereby increasing the strength of the first metal layer 11 and increasing the strength of the aluminum clad material 10. The overall strength can be improved. HVα is preferably 40 or more, particularly preferably 50 or more.
The HVα is usually 120 or less, and the preferable upper limit thereof depends on the intended use of the aluminum clad material 10. For example, in the aluminum clad material 10 used for heat exchanger members, automobile members, etc., the HVα is preferably 100 or less in order to ensure appropriate molding processability.

In the specification of 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 the relative of the second metal layer 12 to the first metal layer 11. It is an index of 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. As specified in the formula (2), by setting the value of (HVβ ÷ HVα) to 0.3 or less, the relative flexibility of the second metal layer 12 is sufficiently ensured, and the second metal layer 12 has a sufficient relative flexibility. The deformability can be increased. As a result, even in an environment where repeated stress loads occur, it is possible to suppress the occurrence of cracks in the second metal layer 12 and improve the durability of the aluminum clad material 10.
The lower limit of the value of (HVβ ÷ HVα) is not particularly limited, but (HVβ ÷ HVα) is usually 0.1 or more due to the practical hardness of the material.

As described above, the aluminum clad material 10 satisfying the provisions of the formulas (1) and (2) has high strength and excellent durability.

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

The aluminum clad material 10 preferably satisfies the following formula (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 specified in the formula (3), the ratio (t2 ÷ 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 0.1 or more and 0.5 or less. Especially preferable.

The thickness of the aluminum clad material 10 can be appropriately changed depending on the application, but in general applications, 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) or more. It can be 5.0 mm.

Further, the aluminum clad material 10 preferably satisfies the following formulas (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 the equations (4) and (5) will be described in detail below.
The residual resistivity ratio (RRR) is the ratio of the conductivity at low temperature (generally 4.2K) to the conductivity at room temperature. Further, the larger the residual resistance ratio (RRR), the smaller the deformation resistance of the metal material. 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. The 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 is deformed from the first metal layer 11. It suggests that it is easy.
As specified in the formula (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. Therefore, the deformability of the second metal layer 12 can be further improved. As a result, the effect of suppressing the generation of cracks in the second metal layer 12 can be improved even in an environment where repeated stress loads are 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) stipulates that the residual resistance ratio (RRR2) of the second metal layer 12 is 5 or more. The high resistivity (RRR2) of the second metal layer 12 suggests that the amount of impurity atoms contained in the second metal layer 12 is small and the purity of the pure aluminum forming the second metal layer 12 is high. is doing. By satisfying the formula (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.

In addition, each residual resistance ratio (RRR1 and RRR2) is obtained as follows. Two pieces of the obtained aluminum clad material are prepared. One sheet is polished from the second metal layer 12 side to leave only the first metal layer 11 (first measurement sample). The other sheet is polished from the side of the first metal layer 11 to leave only the second metal layer (second measurement sample). For each of the first measurement sample and the second measurement sample, the electric specific resistance value ρ _rt (Ω ・ m) at room temperature and the electric specific resistance value ρ _4.2K (Ω ・ m) at the liquid He temperature (4.2K). ) Is measured by the four-terminal method. Using the obtained electrical resistivity value, 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 preferably made of an aluminum alloy containing at least one of Mn and Mg, and the content of Mn and Mg preferably satisfies the formula (6).

0.5 ≤ (Cmn1 + Cmg1) ≤ 5.0 (6)

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

Both Mn and Mg, which are alloying elements, have an action of improving the strength of the aluminum alloy. When the total content (Cmn1 + Cmg1) of these alloying elements 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. Further, 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 can be 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, further preferably 1.8 or more and 3.3 or less, and 2.0 or more. 3.0 or less is particularly preferable.

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

The detection of an intermetal compound having a diameter of 1 μm or more is carried out 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 at a magnification of 500 times with an optical microscope. Image processing was performed on the range of 0.022 mm ² (length 0.13 mm x width 0.17 mm) in the photograph, the number of intermetallic compounds with a diameter of 1 μm or more was counted, and the number density per 100 μm ² (pieces / 100 μm ² ). ) Is calculated. Here, "diameter" means the diameter passing through the center of gravity of each of the intermetallic compounds observed on the photograph in 2 ° increments (measurements of 90 diameters can be obtained), and the measured values are averaged. It is a value obtained by

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

(Clad process)
The clad step is a step of laminating and rolling and joining a first metal material 110 made of an aluminum alloy and a second metal material 120 made of pure aluminum. 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, the first metal material 110 and the second metal material 120 are prepared by a conventionally known method. For example, an aluminum alloy having a predetermined composition can be cast and rolled to prepare a first metal material 110, and pure aluminum having a predetermined purity can be cast and rolled to prepare a second metal material 120. If necessary, a homogenization treatment may be carried out between casting and rolling.

As shown in FIG. 3A, the upper surface of the first metal material 110 and the lower surface of the second metal material 120 face each other, and the first metal material 110 and the second metal material 120 are laminated. The upper surface of the first metal material 110 is the bonding surface 110b (the surface bonded to the second metal material 120) of the first metal material 110, and the lower surface of the second metal material 120 is the bonding surface 120b of the second metal material 120. (The surface to be joined to the first metal material 110).
Then, the first metal material 110 and the second metal material 120 are rolled and joined by rolling the laminate in which the first metal material 110 and the second metal material 120 are laminated. As a result, the aluminum clad material 10 as shown in FIG. 3 (b) 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 formula (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 "thickness ratio before rolling") is the "first" after rolling. It is substantially equal to the ratio of "thickness t2 of the second metal layer" to "thickness t1 of the metal layer" (this is referred to as "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 the formula (8)), the thickness ratio after rolling is 0.02 or more and 1.0 or less (that is, that is). , An aluminum clad material 10 satisfying the following formula (3)) can be obtained.

0.02 ≤ t2 ÷ t1 ≤ 1.0 (3)

When the first metal material 110 and the second metal material 120 are rolled and joined (clading) 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 can be done. The heating temperature during hot rolling can be appropriately set, and is, for example, 250 ° C. or higher and 600 ° C. or lower. When the surface treatment (polishing step) as described later is performed, the first metal layer 11 and the second metal layer 12 are performed even if the hot rolling is performed at a lower temperature (for example, 250 ° C. or higher and 300 ° C. or lower). Adhesion can be sufficiently improved.
The aluminum clad material 10 after hot rolling may be further subjected to finish rolling (cold rolling).

(Polishing process)
Prior to the clad step, a polishing step of polishing the bonded surface 110b of the first metal material 110 and the bonded surface 120b of the second metal material 120 may be included. When the oxide films on the bonded surfaces 110b and 120b are removed by polishing, there is an effect that the first metal material 110 and the second metal material 120 are easily bonded in the clad step.

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

(Heat treatment process)
It is preferable to heat-treat the aluminum clad material 10 (FIG. 3 (b)) obtained by the clad step. The heat treatment step has the effect of removing the processing strain introduced into the second metal layer 12 by rolling during the clading step and lowering the hardness of the second metal layer 12. 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, heat treatment time) are not appropriate, the hardness of the first metal layer 11 is excessively lowered and the aluminum clad There is a risk that the strength of the material 10 cannot be ensured.

Suitable heat treatment conditions are preferably in a range in which the hardness of the second metal layer 12 is reduced and the hardness of the first metal layer 11 is not excessively reduced, and the first metal layer 11 and the second metal layer 12 are not excessively reduced. It depends on the material of.

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

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

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

(Modification example)
FIG. 4 is a schematic cross-sectional view of the aluminum clad material 20 according to the modified example of the embodiment of the present invention. The aluminum clad material 20 according to the modified example includes the second metal layers 12a and 12b on both surfaces of the first metal layer 11. The two second metal layers 12a and 12b may be made of pure aluminum of the same purity or may be made of pure aluminum of different 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 has a purity of 99.9999% by mass (6N). It may be made of pure aluminum. Further, 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 excellent as compared with the case where the second metal layers 12a and 12b are formed on only 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 formula (3). preferable. That is, in the example of FIG. 4, the aluminum clad material 20 preferably satisfies the following formula (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 thicker 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. It is preferable to do. This makes it possible to obtain an aluminum clad material 20 having good strength and corrosion resistance.

Further, regarding the hardness, the residual resistivity ratio, and other regulations of the second metal layer 12 specified in the first embodiment, the thick second metal layer (second metal layer 12a in FIG. 4) is the same. By satisfying the provisions, the aluminum clad material 20 according to the modified example can have the same effect as the aluminum clad material 10 of the first embodiment.

(Example 1)
1. 1. Preparation of Sample for Measurement 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, aluminum alloys (A3003 and A5052) were cast and rolled to prepare an aluminum alloy plate (first metal material 110) having the composition shown in Table 2.
Tables 1 and 2 show the analysis results obtained by analyzing the composition of the obtained first metal material 110 and second metal material 120 by solid-state emission spectroscopic analysis. 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 to the following dimensions, a surface treatment step, a clad step (hot rolling) and a finish rolling (cold rolling) are performed under the following conditions, and aluminum is used. The clad material 10 was prepared.
-Dimensions of the first metal material 110: 2.0 mm x 125 mm x 190 mm
-Dimensions of the second metal material 120: 1.0 mm x 125 mm x 190 mm
Surface treatment step: The entire bonded surface 110b of the first metal material 110 and the entire bonded surface 120b of the second metal material 120 were polished by reciprocating 10 times in the longitudinal direction with a commercially available metal polishing agent.
Clad process (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 rate per pass. Hot rolling of 5 passes was performed at 15 to 20%. The final total reduction rate was 50-75%.
-Finish rolling (cold rolling): As finish rolling, cold rolling is performed for 1 to 10 passes with a rolling reduction of 10 to 20% per pass, and a predetermined thickness ("Thickness of aluminum clad material" in Table 3). It was rolled to "sa").

The material combinations of the first metal material 110 and the second metal material 120 used in the production of each aluminum clad material 10 are the "material" of the first metal layer and the "material" of the second metal layer shown in Table 3. It was described in.

Among the aluminum clad materials 10 manufactured under the above conditions, the sample No. 1 to 4, 6 and 7 were kept at the heat treatment temperature shown in Table 3 for 3 hours to perform heat treatment, and a sample for measurement was obtained. The thickness of each measurement sample was as described in "Thickness of aluminum clad material" in Table 3.

2. 2. Hardness measurement For the first metal layer 11 and the second metal layer 12 of the measurement sample (aluminum clad material 10) prepared under the conditions shown in Table 3, the Vickers hardness (HV0.01) was measured using a micro Vickers hardness tester. It was measured. According to the provisions of JIS Z 2244: 2009 "Vickers Hardness Test-Test Method", a diamond indenter with a regular quadrangular pyramid is pushed into the surface of the test piece to release the test force, and then the diagonal length of the indentation remaining on the surface. The Vickers hardness was calculated from. In this standard, it is stipulated that the hardness symbol is changed according to the test force, and here, the Vickers hardness (HV0.01) when the test force is 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 sample piece of 10 mm × 20 mm was cut out from the prepared measurement sample. The sample piece was embedded with acrylic resin so that the cross section was exposed, and the exposed cross section was mirror-polished by buffing. The mirror-polished cross section is confirmed with an optical microscope to identify the joint surface 15 between the first metal layer 11 and the second metal layer 12, and the joint surface 15 is separated from the joint surface 15 by 0.1 mm in the direction A. The position P11 and the position P12 separated from the joint surface 15 to the second metal layer 12 by 0.1 mm in the direction B were specified (FIG. 2). Vickers hardness was measured at each position.

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. In addition, the hardness ratio (HVβ ÷ HVα) was calculated from these measurement results and is shown in Table 4. In Table 4, the sample No. The underlined values of the hardness ratio (HVβ ÷ HVα) of 5 to 8 indicate that they do not meet the provisions of the present invention.

3. 3. Repeated 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 prepared measurement sample and used as a repeated bending test sample.
In the repeated bending test, R10 was chamfered at at least one of the four corners of the aluminum alloy rectangular parallelepiped block of 85 mm × 85 mm × 50 mm to obtain a jig 50 for the repeated bending test (FIGS. 5 (a) and 5 (b)). )).
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 portion 52 chamfered from R10 of the jig 50 (FIG. 6A). At this time, the first metal layer 41 of the test piece 40 was arranged so as to be 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 of the corner portion 52 of the jig 50 (referred to as “bending work”). At this time, both ends 40E and 40E of the test piece 40 were pressed with an aluminum alloy plate (pressing jig 60) having a size of 50 mm × 50 mm × 10 mm so that the force could be evenly applied to the test piece 40.
As shown in FIG. 7, the test piece 40 after bending was placed on a flat workbench 70, pressed from above with a holding jig 60, and the test piece 40 was stretched flat (referred to as "return work"). At this time, the test piece 40 is arranged so that both ends 40E and 40E of the test piece 40 are in contact with the upper surface of the workbench 70, and the upwardly curved portion (center 40C of the test piece 40) is pressed downward by the jig 60. did.

The above bending work and the subsequent returning work were used to make one set of bending tests, and the bending test was repeated 30 sets for each test piece 40. After the repeated bending test was completed, the surface of the sample piece 40 on the second metal layer 42 side was visually observed to confirm the presence or absence of cracks having a length of 5 mm or more in the width direction. If there is such a crack, it is described as "Yes" in "Repeat bending test (presence or absence of crack)" in Table 4. When no cracks were confirmed, or when only cracks having a length of less than 5 mm in the width direction were confirmed, "None" was described in Table 4.

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

RRR = ρ _rt ÷ ρ _4.2K (4)

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

5. Number of intermetallic compounds with 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) prepared under the conditions shown in Table 3. For 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. The surface 12x of the second metal layer 12 of the aluminum clad material 10 was mirror-polished by buffing, and then photographed at a magnification of 500 times with an optical microscope. Image processing was performed on the range of 0.022 mm ² (length 0.13 mm x width 0.17 mm) in the photograph, the number of intermetallic compounds with a diameter of 1 μm or more was counted, and the number density per 100 μm ² (pieces / 100 μm ² ). ) Was calculated. Here, "diameter" measures the diameter passing through the center of gravity of each of the intermetallic compounds observed on the photograph in 2 ° increments (measurements of 90 diameters can be obtained), and the measured values are averaged. I asked for it.
The calculated number density is described in the column of "second metal layer (piece / 100 μm ² )" of "intermetallic compound having a diameter of 1 μm or more" in Table 5.

Sample No. In Nos. 1 to 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% by mass (5N) or more, and the Vickers hardness HVα of the first metal layer 11 is 30. As described above, the ratio of 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, large cracks (cracks of 5 mm or more in the width direction) did not occur, and excellent durability against repeated stress loading was shown.

In addition, sample No. In 1 and 2, the ratio of RRR2 to RRR1 (RRR2 ÷ RRR1) 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. Since the hardness ratio (HVβ ÷ HVα) of 5 to 8 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 1st metal layer 12, 12a, 12b 2nd metal layer 12x Surface of 2nd metal layer 15 Bonding surface 110 1st metal material 110b Laminating surface of 1st metal material 120 2nd metal material 120b Bonded surface of second metal material 40 Specimen

Claims (5)

The first metal layer made of aluminum alloy and
It comprises a second metal layer made of pure aluminum and bonded to at least one side of the first metal layer.
An aluminum clad material that 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 the 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, 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. The aluminum clad material according to claim 1 or 2, which satisfies the following formulas (4) and (5).

RRR2 ÷ RRR1 ≧ 5 (4)
RRR2 ≧ 5 (5)

Here, RRR1 is the residual resistance ratio of the first metal layer, and RRR2 is the 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 formula (6).

0.5 ≤ (Cmn1 + Cmg1) ≤ 5.0 (6)

Here, Cmn1 is the Mn content (mass%) in the first metal layer, and Cmg1 is the Mg content (mass%) in the first metal layer. The aluminum clad material according to any one of claims 1 to 4, wherein the second metal layer contains 10 or less intermetallic compounds having a diameter of 1 μm or more per 100 μm ² .

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