JP2020026119A - Aluminum clad material and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material which exhibits excellent thermal conductivity and electrical conductivity in an extremely low temperature environment and also has high strength. A first metal layer made of an aluminum alloy and a second metal layer made of high-purity aluminum having a purity of 99.99% by mass or more and bonded to at least one surface of the first metal layer are included. The thickness t1 of the first metal layer and the thickness t2 of the second metal layer are aluminum clad materials satisfying the following formula (1). 0.2 ≤ t2 ÷ t1 ≤ 5.0 (1) [Selection diagram] Fig. 1

Description

  The present invention relates to an aluminum clad material that exhibits excellent conductivity under a very low temperature environment and has high strength.

High-purity aluminum is used in various applications because it exhibits excellent physical properties such as light weight, high electrical and thermal conductivity, and excellent corrosion resistance.
For example, since high-purity aluminum has high thermal conductivity in a cryogenic environment, use in a cryogenic environment has been proposed (for example, Patent Documents 1 and 2). As a superconducting magnet used for medical MRI, analytical NMR, and the like, a low-temperature superconducting coil cooled to 4.2 K by liquid helium or a high-temperature superconducting coil cooled to about 20 K by a refrigerator is used. In order to cool these superconducting coils efficiently and uniformly, a heat transfer material having high thermal conductivity even in an extremely low temperature environment lower than the boiling point of liquid nitrogen (77 K) is required. Therefore, it has been proposed to use high-purity aluminum having high thermal conductivity (mainly, purity of 99.9999% (6N) or more) as a heat transfer material even in an extremely low temperature environment.

JP 2010-106329 A JP 2007-63671 A

  The high-purity aluminum materials described in Patent Literatures 1 and 2 exhibit high thermal conductivity and electrical conductivity even in a cryogenic environment, so that they can be used as heat conductive parts for equipment used in a cryogenic environment. Further applications are expected as materials for parts and the like. However, since the high-purity aluminum material is soft, there is a problem that its strength is insufficient and its application range may be limited.

  An object of the present invention is to provide a material exhibiting excellent thermal conductivity and electric conductivity in a cryogenic environment and having sufficient strength, and a method for producing the same.

Aspect 1 of the present invention
A first metal layer made of an aluminum alloy;
A second metal layer made of high-purity aluminum having a purity of 99.99% by mass or more and bonded to at least one surface of the first metal layer;
The thickness t1 of the first metal layer and the thickness t2 of the second metal layer are aluminum clad materials satisfying the following expression (1).
0.2 ≦ t2 ÷ t1 ≦ 5.0 (1)

  A second aspect of the present invention is the aluminum clad material according to the first aspect, wherein the second metal layer is made of high-purity aluminum having a purity of 99.999% by mass or more.

  Aspect 3 of the present invention is the aluminum clad material according to Aspect 1 or 2, wherein the surface of the second metal layer has a Vickers hardness of 30 or less.

  In a fourth aspect of the present invention, the second metal layer has a Vickers hardness of more than 30 at a position of 10 μm in a thickness direction from a bonding surface between the first metal layer and the second metal layer, and the bonding surface The aluminum clad material according to one of aspects 1 to 3, wherein a Vickers hardness at a position 50 μm in a thickness direction from the Vickers hardness is 30 or less.

  Embodiment 5 of the present invention is the aluminum clad material according to any one of Embodiments 1 to 4, which is an aluminum clad material for a cryogenic environment used in a temperature environment of 50 K or lower.

Aspect 6 of the present invention includes:
A method for manufacturing an aluminum clad material, comprising: a first metal layer made of an aluminum alloy; and a second metal layer made of high-purity aluminum having a purity of 99.99% by mass or more and bonded to at least one surface of the first metal layer. And
A cladding step of laminating and rolling and joining the first metal material made of the aluminum alloy and the second metal material made of the high-purity aluminum,
This is a method for manufacturing an aluminum clad material in which the thickness t11 of the first metal material and the thickness t22 of the second metal material satisfy the following expression (2).
0.2 ≦ t22 ÷ t11 ≦ 5.0 (2)

  Aspect 7 of the present invention is the method for producing an aluminum clad material according to Aspect 6, further comprising a step of heat-treating the aluminum clad material after the cladding step.

  Aspect 8 of the present invention is the method for manufacturing an aluminum clad material according to Aspect 6 or 7, wherein the second metal material is made of high-purity aluminum having a purity of 99.999% by mass or more.

  Aspect 9 of the present invention according to any one of Aspects 6 to 8, further comprising a polishing step of polishing the bonding surfaces of the first metal material and the second metal material before the cladding step. This is a method for producing an aluminum clad material.

  ADVANTAGE OF THE INVENTION According to the aluminum clad material of this invention and its manufacturing method, it can exhibit the outstanding thermal conductivity and electric conductivity in a cryogenic environment, and can provide the aluminum clad material which has sufficient intensity | strength.

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.

(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 high-purity aluminum having a purity of 99.99% by mass (4N) or more. 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 alloy) can be applied.

  As used herein, “conductive” should be understood to include both electrical and thermal conductivity, unless otherwise indicated. It is generally known that a metal material has a proportional relationship between thermal conductivity and electrical conductivity when the temperature is constant. Therefore, if it is confirmed that one (for example, electrical conductivity) is improved, it can be said that the other (for example, thermal conductivity) is necessarily improved.

  The aluminum clad material 10 of the present invention has a second metal layer made of high-purity aluminum and has high electric conductivity. However, according to the study of the present inventors, the electric conductivity of the aluminum clad material does not increase as long as the layer made of high-purity aluminum is included, but the layer made of high-purity aluminum is made of an aluminum alloy. It is necessary to have a certain thickness or more with respect to the layer.

  According to the formula (1), the value of (t2 ÷ t1) of the aluminum clad material 10 of the present invention is 0.2 or more. When the value of (t2 ÷ t1) is less than 0.2, the thickness t2 of the second metal layer 12 made of high-purity aluminum is too thin, so that the conductivity of the aluminum clad material 10 becomes low. The value of (t2 ÷ t1) is preferably 0.35 or more, and more preferably 0.4 or more. The aluminum clad material 10 of the present invention has a first metal layer made of an aluminum alloy and has higher strength than a material made of high-purity aluminum. In the present invention, the upper limit of the value of (t2 ÷ t1) is not particularly limited as long as the required strength is satisfied. However, in consideration of the balance between the strength and the conductivity and the cost, the value is usually 5.0 or less, preferably Is 3.0 or less, more preferably 2.0 or less, further preferably 1.0 or less, and particularly preferably 0.8 or less.

  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, 0.04 mm (40 μm) to 5.0 mm, and the thickness t2 of the second metal layer 12 is, for example, 0.06 mm (60 μm). It can be 5.0 mm.

  The aluminum clad material 10 satisfying the above formula (1) has sufficiently high conductivity even in an extremely low temperature environment of, for example, 50K or less. Therefore, the aluminum clad material 10 of the present invention is suitable for use in a temperature environment of 50K or less.

  The second metal layer 12 is preferably made of high-purity aluminum having a purity of 99.999 mass% (5N) or more. High-purity aluminum has higher conductivity because the higher the purity, the better the conductivity in an extremely low-temperature environment. Therefore, by forming the second metal layer 12 with higher-purity (5N or more) aluminum, the high-purity aluminum has higher conductivity. The aluminum clad material 10 can be obtained.

  The second metal layer 12 preferably has a Vickers hardness of the surface 12x of 30 or less. In this specification, “the Vickers hardness of the surface 12x of the second metal layer 12” means that the surface 12x of the second metal layer 12 is tested with a micro Vickers hardness tester at a test force of 0.01 kgf (= 0.09806N). It refers to the measured Vickers hardness (HV 0.01 (10 gf)). The Vickers hardness is measured according to JIS Z 2244: 2009 "Vickers hardness test-test method".

The hardness of the surface 12x of the second metal layer 12 is an index for knowing the purity of the high-purity aluminum forming the second metal layer 12 and the heat treatment conditions applied to the aluminum clad material 10.
When the impurity element in the high-purity aluminum forming the second metal layer 12 increases, the hardness of the second metal layer 12 increases, and the conductivity decreases. That is, when the purity of the high-purity aluminum increases, the hardness decreases and the conductivity improves.
Further, when processing strain is introduced into the second metal layer 12 by rolling or the like, the hardness of the second metal layer 12 increases, and the conductivity decreases. This processing strain can be removed by subjecting the second metal layer 12 to heat treatment under appropriate conditions. When the aluminum clad material 10 is heat-treated to remove the processing strain of the second metal layer 12, the hardness of the second metal layer 12 is reduced, and the conductivity is improved.

  From these facts, the low Vickers hardness of the surface 12x of the second metal layer 12 means that the high purity aluminum of the second metal layer has high purity and / or heat treatment under appropriate conditions during the production of the aluminum clad material 10. Suggest that it was. The Vickers hardness of the surface 12x of the second metal layer 12 being 30 or less means that high purity aluminum having a purity of 99.99% by mass or more is used for the second metal layer, and / or that the aluminum clad material 10 Is an index to indirectly know that heat treatment was performed under appropriate conditions.

As described above, the high purity of the high-purity aluminum and the heat treatment of the aluminum clad material 10 under appropriate conditions all contribute to the improvement of the conductivity of the second metal layer 12. Therefore, the Vickers hardness of the surface 12x of the second metal layer 12 of 30 or less is an index for indirectly knowing that the conductivity of the second metal layer 12 is high and that the conductivity of the aluminum clad material 10 is high. Becomes
The Vickers hardness of the surface 12x of the second metal layer 12 is more preferably 25 or less, and particularly preferably 20 or less.

  When the purity of the high-purity aluminum forming the second metal layer 12 is extremely high (for example, 99.999% by mass (5N) or more), the high-purity aluminum is extremely soft, so that the second metal layer 12 has a processing strain. The Vickers hardness of the surface 12x of the second metal layer 12 may be 30 or less even if it remains (that is, even if heat treatment is not performed). This suggests that when the high-purity aluminum of the second metal layer 12 is extremely high-purity, it exhibits sufficiently high conductivity without heat treatment.

  In the cross section of the second metal layer 12, the hardness in the vicinity of the joint surface 15 between the first metal layer 11 and the second metal layer 12 is preferably a predetermined hardness. In the cross section of the aluminum clad material 10 shown in FIG. 2, the second metal layer 12 has a Vickers hardness at a position (position P10 in FIG. 2) 10 μm away from the bonding surface 15 in the thickness direction (the direction of arrow A in FIG. 2). Is more than 30, and the Vickers hardness at a position 50 μm away from the joining surface 15 in the thickness direction (position P50 in FIG. 2) is preferably 30 or less. The significance of these rules will be described below.

  As described above, in the second metal layer 12 into which the processing strain has been introduced, when the processing strain is removed by the heat treatment, the hardness is reduced and the conductivity is improved. However, when the heat treatment is performed in a state where the second metal layer 12 and the first metal layer 11 made of another metal (aluminum alloy) are joined, the vicinity of the joint surface (for example, in the range of 0 to 20 μm from the joint surface). 2), the hardness of the second metal layer 12 may increase and the conductivity may decrease. Further, when the heat treatment temperature is too high and / or the heat treatment time is too long, the hardness of the high-purity aluminum increases even at a position away from the joint surface (for example, at a position about 50 μm away from the joint surface). In some cases, conductivity may decrease.

From these findings, the fact that the hardness of the second metal layer 12 at a position 50 μm away from the bonding surface 15 of the aluminum clad material 10 (position P50) is suppressed to be low indicates that an excessive amount of It can be an index to know that heat treatment was not performed under the conditions (high temperature, long time).
Therefore, in the cross section of the second metal layer 12, the Vickers hardness at a position P10 of 10 μm in the thickness direction from the bonding surface 15 is more than 30, and the Vickers hardness at a position P50 of 50 μm in the thickness direction from the bonding surface 15 is 30. If it is below, it can be indirectly known that the heat treatment was performed under suitable conditions. The Vickers hardness at the position P50 is more preferably 27 or less, and particularly preferably 25 or less.

In this specification, the Vickers hardness of the cross section of the second metal layer 12 (Vickers hardness at the position P10 and the position P50) is measured with a test force of 0.01 kgf (= 0.09806N) using a micro Vickers hardness meter. Vickers hardness (HV0.01 (10 gf)). The Vickers hardness is measured according to JIS Z 2244: 2009 "Vickers hardness test-test method".
The joining surface 15 is specified by observing the cross section of the aluminum clad material 10 with an optical microscope, and a position P10 of 10 μm and a position P50 of 50 μm (FIG. 2) are determined in the thickness direction therefrom. Measure the length.

  The hardness of the cross section is measured by the following procedure. First, the aluminum clad material 10 is cut into a predetermined shape. At this time, cutting is performed at a cross section substantially perpendicular to the joint surface 15 between the first metal layer 11 and the second metal layer 12. The cut aluminum clad material is embedded with an acrylic resin so that its cross section is exposed. Thereafter, the exposed cross section is mirror-polished by buffing, and the hardness is measured.

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. Further, 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 high-purity 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 formed from high-purity aluminum having a purity of 99.99% by mass (4N) or more, more preferably from high-purity aluminum having a purity of 99.999% by mass (5N) 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 high-purity 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 set so as to satisfy the following equation (2).

0.2 ≦ t22 ÷ t11 ≦ 5.0 (2)

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 0.2 or more and 5.0 or less (that is, satisfying Expression (2)), the thickness ratio after rolling is set to 0.2 or more and 5.0 or less (that is, The aluminum clad material 10 satisfying the following formula (1) can be obtained.

0.2 ≦ t2 ÷ t1 ≦ 5.0 (1)

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)
The aluminum clad material 10 (FIG. 3B) obtained by the clad process may be heat-treated. The heat treatment step has an effect of removing the processing strain introduced into the first metal layer 11 and the second metal layer 12 by the rolling in the cladding step. In particular, since the processing strain of the second metal layer 12 may cause the conductivity of the second metal layer 12 to decrease, the conductivity of the second metal layer 12 is improved by the heat treatment step, and the conductivity of the aluminum clad material 10 is further reduced. The effect of improvement can be expected.
The conditions of the heat treatment may be, for example, a heat treatment temperature of 150 ° C. or more and 400 ° C. or less, and a heat treatment time of 2 hours or more and 10 hours or less.

  The aluminum clad material 10 thus obtained has high strength and excellent conductivity under an extremely low temperature environment.

(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 and 12b may be made of high-purity aluminum of the same purity, or may be made of high-purity aluminum of another purity. For example, the second metal layer 12a covering the upper surface of the first metal layer 11 is made of high-purity aluminum having a purity of 99.99% by mass (4N), and the second metal layer 12b covering the lower surface is 99.999% by mass (5N). ) May be made of high-purity 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 effect of improving conductivity can be enhanced as compared with the case where the second metal layers 12a and 12b are formed only on one surface.

When the aluminum clad material 20 has two layers of the second metal layers 12a and 12b, the total thickness (total thickness) of the second metal layers 12a and 12b may satisfy the above formula (1). Required. That is, in the example of FIG. 4, the aluminum clad material 20 needs to satisfy the following expression (3).

0.2 ≦ (t2a + t2b) ÷ t1 ≦ 5.0 (3)

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 50 μm. Is preferred.
Thereby, the aluminum clad material 20 having both good strength and good conductivity in a low-temperature environment can be obtained.

  Further, the second metal layer 12 having a large thickness (in FIG. 4, the second metal layer 12a) also has a surface hardness, a hardness in the vicinity of the interface, and other specifications of the second metal layer 12 specified in the first embodiment. By satisfying those provisions, 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. Preparation of Measurement Sample Aluminum was cast and rolled to prepare an aluminum plate (second metal material 120) having the purity shown in Table 1. 2N-Al, 4N-Al, 5N-Al and 6N-Al in Table 1 refer to aluminum having a purity of 99% by mass, 99.99% by mass, 99.999% by mass and 99.9999% by mass, respectively.
Further, an aluminum alloy (A5052) was 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 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 1 means that the chemical component was not detected.

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: 2.0-3.0mm × 125mm × 190mm
-Dimensions of the second metal material 120: 0.3 to 1.0 mm x 125 mm x 190 mm
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. ". In Table 3, the sample No. Sample No. 11 is composed of only the first metal layer 11 (that is, does not include the second metal layer 12). Numeral 12 means that the second metal layer 12 is formed only (that is, the first metal layer 11 is not included).

  The thickness t11 of the first metal material 110 before rolling and the thickness t22 of the second metal material 120 are determined by the thickness of the first metal layer described in Table 3 after rolling (after hot rolling and finish rolling). It is selected to be t1 and the thickness t2 of the second metal layer. The ratio of the thickness t22 of the second metal material 120 to the thickness t11 of the first metal material 110 before rolling (the thickness ratio before rolling) is the thickness of the first metal layer after rolling. The thickness (the thickness ratio after rolling) of “the thickness t2 of the second metal layer” to “the thickness t1” is substantially equal. Therefore, the thickness t11 of the first metal material 110 and the thickness t22 of the second metal material 120 before rolling are set so that the thickness ratio before rolling is equal to the thickness ratio after rolling shown in Table 3. The distance was adjusted between 2.0 to 3.0 mm and 0.3 to 1.0 mm, respectively.

Sample No. 1 of the aluminum clad material 10 manufactured under the above conditions was used. 2 to 5, 7, 9, and 11 to 12 were held at the heat treatment temperature shown in Table 3 for 3 hours to carry out heat treatment to obtain a measurement sample.
In Table 3, the sample No. Material of the second metal layer of Sample No. 10 and Sample No. 10 The underlined values of the thickness ratio after rolling of 9 to 10 indicate that they do not meet the requirements of the present invention.

2. Hardness Measurement Hardness of the second metal layer (hardness at the surface 12x and at the position P10 at 10 μm from the joint surface 15 and at the position P50 at 50 μm (FIG. 2))
The Vickers hardness (HV0.01) of the second metal layer 12 of the measurement sample (aluminum clad material) manufactured under the conditions shown in Table 3 was measured using a micro Vickers hardness meter. 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.

In the hardness measurement of the surface 12x of the second metal layer 12, a 10 mm x 20 mm sample piece was cut out from the prepared measurement sample, and the surface 12x was buff-polished and mirror-polished to perform measurement.
In the hardness measurement at a position P10 at a distance of 10 μm from the bonding surface 15 and at a position P50 at a distance of 50 μm, a 10 mm × 20 mm sample piece was cut out from the manufactured measurement sample in a cross section orthogonal to the bonding surface 15. 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 confirmed with an optical microscope, the joint surface 15 between the first metal layer 11 and the second metal layer 12 is specified, and a position P10 separated by 10 μm from the joint surface 15 and a position P50 separated by 50 μm are determined. Identified. Micro Vickers hardness was measured at each position.

Table 4 shows the measurement results of the Vickers hardness.
The measurement of the hardness of the surface 12x of the second metal layer 12 is performed using the sample No. Performed in all of 1-12. The sample No. Since 11 was formed only of the first metal layer, the surface hardness of the first metal layer 11 was substantially measured.
The hardness measurement at the positions P10 and P50 (FIG. 2) of the second metal 1 to 4.

3. Residual resistance ratio (RRR)
The residual resistance ratio (RRR) was measured in order to study the conductivity in a cryogenic environment.
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 4 shows the measured values of RRR of each sample. In addition, RRRs of 1000 or more were classified as excellent (◎), 500 or more and less than 1000 were classified as good (○), and less than 500 were classified as poor (×).

4. Tensile strength The tensile strength of the measurement sample was examined by a tensile test.
A JIS No. 13B tensile test piece was prepared from the measurement sample, and the tensile test piece was determined based on JIS Z 2241: 2011 using a tensile tester conforming to JIS standards. Table 4 shows the measured values of the tensile strength of each sample. Further, the tensile strength was classified as good (（) when the tensile strength was 100 MPa or more, and poor (x) when the tensile strength was less than 100 MPa, and shown in the column of “Evaluation” in Table 4.

  Sample No. In Nos. 1 to 8, the first metal layer 11 is made of an aluminum alloy, the second metal layer 12 is made of high-purity aluminum having a purity of 99.99% by mass (4N) or more, and the thickness ratio (t2 ÷ t1) is 0.1 mm. Since it was 2 to 5.0, the RRR was 100 or more, and the tensile strength was 100 MPa or more. In addition, the sample No. of high purity aluminum (5N-Al) having a purity of 99.999% by mass was used for the second metal layer. Comparing the results of Sample Nos. 1 to 4, Sample No. Sample No. 1 in which the heat treatment temperature was as high as 500 ° C. Sample No. 4 heat-treated at a heat treatment temperature of 150 ° C. or more and 400 ° C. or less as compared with No. 4 Some of the samples had an RRR exceeding 1000, and were significantly improved. As described above, even when the high-purity aluminum has high purity, the heat treatment at a temperature of 150 ° C. or more and 400 ° C. or less has an effect of improving the RRR.

On the other hand, sample No. In No. 9, since the thickness ratio (t2 ÷ t1) was as small as 0.10, the second metal layer 12 made of high-purity aluminum was thin and the RRR was low.
Sample No. In No. 10, the RRR was extremely low because the purity of aluminum forming the second metal layer 12 was as low as 99% by mass (2N-Al).
Sample No. In No. 11, since the second metal layer 12 was not present, the conductivity in an extremely low temperature environment was low, and the RRR was extremely low.
Sample No. In No. 12, the tensile strength was low because the first metal layer 11 made of an aluminum alloy was not present.

(Example 2)
The bonding surfaces 110b and 120b of the first metal material 110 and the second metal material 120 were polished, and hot-rolled at different temperatures to perform roll joining (cladding).
Sample No. of Example 1 With respect to the first metal material 110 (size: 2.0 mm × 125 mm × 190 mm) and the second metal material 120 (size: 1.0 mm × 120 mm × 190 mm) prepared in the same manner as in Example 1, each of the entire surfaces of the bonding surfaces 110 b and 120 b is A sample which was rubbed 10 times in the longitudinal direction with a commercially available stainless steel wire brush to roughen the surface and a sample which was polished 10 times in the longitudinal direction with a commercially available metal polishing agent were prepared.
The arithmetic mean roughness Ra (JIS B 0601: 2013) of the bonding surfaces 110b and 120b of each sample was measured in a range of 1.0 × 1.4 mm square using a laser microscope. The measurement was performed near the center of each sample. Table 5 shows the measured values of Ra.

Thereafter, the bonding surface 110b of the first metal material 110 and the bonding surface 110b of the second metal material 120 were brought into contact with each other, and hot-rolled to perform roll joining (cladding). The temperature (hot rolling temperature) of each metal material before rolling was as shown in Table 5, and five passes were performed at a rolling reduction of 15 to 20% per pass. The final total reduction was 80%.
A peeling test was performed on the obtained sample (aluminum clad material). In the peeling test, a sample cut into a size of 10 mm × 20 mm was bent at 90 degrees near the center in the longitudinal direction (at a position 10 mm from the end), and then returned to 180 degrees (this was referred to as “90-degree bending”). ). After repeating the 90-degree bending at the same position ten times, it was visually confirmed whether or not peeling occurred between the first metal layer 11 and the second metal layer 12. The case where peeling did not occur was evaluated as “complete bonding (）)”, the case where partial peeling was performed was evaluated as “partially peeling (△)”, and the case where the film was completely peeled was evaluated as “complete peeling (×)”. Table 5 shows the evaluation results.

  In the polishing with a wire brush, the surface roughness Ra of the bonding surface 110b of the first metal material 110 exceeds 3 μm, which is out of the preferable range of the surface roughness of the present invention (Ra = 0.5 to 3 μm). Was. On the other hand, the surface roughness Ra of the bonding surface 120b of the second metal material 120 was in the range of 0.5 to 3 μm. In this case, in order to completely join the first metal material 110 and the second metal material 120, it is necessary to set the hot rolling temperature to 320 ° C. or higher (320 ° C. to 400 ° C. in this embodiment).

  On the other hand, in the polishing with the polishing powder, the surface roughness Ra of the bonding surfaces 110b and 120b was both in the range of 0.5 to 3 μm. In this case, the first metal material 110 and the second metal material 120 could be completely joined at a hot rolling temperature of 260 ° C. or higher (260 ° C. to 400 ° C. in this example). That is, it was found that when the surface roughness Ra of the bonding surfaces 110b and 120b was within the preferable range, the metal materials 110 and 120 could be completely bonded even at a low hot rolling temperature of 260 ° C to 280 ° C.

10, 20 aluminum clad material 11 first metal layer 12, 12a, 12b second metal layer 12x surface of second metal layer 15, 150 bonding surface 110 first metal material 110b bonding surface of first metal material 120 second metal Material 120b Laminated surface of second metal material

Claims (9)

A first metal layer made of an aluminum alloy;
A second metal layer made of high-purity aluminum having a purity of 99.99% by mass or more and bonded to at least one surface of the first metal layer;
An aluminum clad material in which the thickness t1 of the first metal layer and the thickness t2 of the second metal layer satisfy the following expression (1).
0.2 ≦ t2 ÷ t1 ≦ 5.0 (1)   The aluminum clad material according to claim 1, wherein the second metal layer is made of high-purity aluminum having a purity of 99.999% by mass or more.   The aluminum clad material according to claim 1 or 2, wherein the surface of the second metal layer has a Vickers hardness of 30 or less.   The second metal layer has a Vickers hardness of more than 30 at a position of 10 μm in a thickness direction from a bonding surface between the first metal layer and the second metal layer, and a Vickers hardness of 50 μm in a thickness direction from the bonding surface. The aluminum clad material according to any one of claims 1 to 3, wherein the Vickers hardness at the position is 30 or less.   The aluminum clad material according to any one of claims 1 to 4, which is an aluminum clad material for a cryogenic environment used in a temperature environment of 50K or less. A method for manufacturing an aluminum clad material, comprising: a first metal layer made of an aluminum alloy; and a second metal layer made of high-purity aluminum having a purity of 99.99% by mass or more and bonded to at least one surface of the first metal layer. And
A cladding step of laminating and rolling and joining the first metal material made of the aluminum alloy and the second metal material made of the high-purity aluminum,
A method for manufacturing an aluminum clad material in which a thickness t11 of the first metal material and a thickness t22 of the second metal material satisfy the following expression (2).
0.2 ≦ t22 ÷ t11 ≦ 5.0 (2)   The method for producing an aluminum clad material according to claim 6, further comprising a step of heat-treating the aluminum clad material after the cladding step.   The method for manufacturing an aluminum clad material according to claim 6, wherein the second metal material is made of high-purity aluminum having a purity of 99.999 mass% or more.   The manufacturing of the aluminum clad material according to any one of claims 6 to 8, further comprising, before the cladding step, a polishing step of polishing each of the bonding surfaces of the first metal material and the second metal material. Method.

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