Metal composite material

Abstract

The present disclosure is a metal composite material having two or more layers composed of a first metal and a second metal, the metal composite material having, on the bonding surface of either or both of the first metal and the second metal, a surface-treatment film formed of a metal different from the first metal and the second metal. The first metal and the second metal are bonded via the surface-treatment film. The mechanical strength of the bonding interface between the first metal and the second metal is higher than the mechanical strength of either the first metal or the second metal.

Description

metal composite material

[0001] The present invention relates to a metal composite material in which a first metal and a second metal are bonded together.

[0002] Metal composite materials made of dissimilar metals with significantly different physical properties, such as aluminum and stainless steel, are used in a wide range of applications, including reducing the weight of structures and as joints.

[0003] Generally, it is difficult to directly bond metal composites made of dissimilar metals with significantly different physical properties by metallurgical methods such as rolling, friction welding, diffusion bonding, and explosive bonding. Therefore, metal composites are obtained by sandwiching an intermediate material between the bonding surfaces of either the first metal or the second metal, or both, and then performing a surface treatment on the bonding surfaces before bonding.

[0004] For example, in Patent Document 1 below, a steel sheet is coated with hot-dip aluminum, heated to 450° C., and then roll-bonded by overlapping an aluminum sheet on top of the steel sheet. However, there is a concern that the properties of the materials may be altered due to the thermal load caused by heating during the bonding process.

[0005] In addition, in the following Patent Document 2, a metal composite material is obtained by forming an aluminum undercoat on the surface of various steel plates and non-ferrous metals as substrates, and then forming a thin aluminum layer on the undercoat by pressure rolling, thermal spraying, vapor deposition, or hot-dip impregnation plating. On the other hand, although the undercoat formed on the surface of the above-mentioned substrate is coated by pressure rolling, thermal spraying, or vapor deposition, it cannot be said that the bondability with the substrate is high, and therefore there is a concern that the bond strength of the obtained bonded body will be lower than the strength of the material.

[0006] In addition, in the following Patent Document 3, a clad material of an aluminum alloy and stainless steel is produced by explosive pressure bonding via an intermediate material made of pure aluminum, nickel, a nickel alloy, titanium, a titanium alloy, copper, a copper alloy, and silver. However, Patent Document 3 does not mention a method for joining an aluminum alloy and stainless steel without using an intermediate material.

[0007] Furthermore, in the following Patent Document 4, a pure aluminum layer is interposed between the aluminum alloy and silver in a clad material of aluminum alloy, silver, and stainless steel. Patent Document 4 mentions an explosively bonded product in which a silver or silver alloy layer is interposed between pure aluminum and stainless steel to strengthen the bonding strength. However, if an attempt is made to interpose a silver or silver alloy layer by explosive bonding, silver or silver alloy having a certain thickness must be prepared, which increases the number of explosive bonding operations, raising concerns about high costs.

[0008] Japanese Patent No. 1100170 Japanese Patent Publication No. 10-058591 Japanese Patent No. 6346888 Japanese Patent No. 3431358

[0009] In view of the level of the prior art described above, the problem that the present invention aims to solve is to provide a metal composite material having two or more layers in which a first metal and a second metal are bonded via a surface treatment film without using an intermediate material, and in particular to provide a metal composite material that can avoid thermal load, has excellent strength at the bonded interface, and is low cost.

[0010] As a result of intensive research and repeated experiments to solve the above-mentioned problems, the present inventors have discovered a new metal composite material in which a first metal and a second metal are firmly bonded via a coating formed by surface treatment, as schematically shown in Figure 1. [1] A metal composite material having two or more layers composed of a first metal and a second metal, wherein a surface treatment coating formed of the first metal and a metal different from the second metal is provided on the bonding surface of either or both of the first metal and the second metal, the first metal and the second metal are bonded via the surface treatment coating, and the mechanical strength of the bonding interface between the first metal and the second metal is higher than the mechanical strength of either the first metal or the second metal. [2] The metal composite material according to [1], wherein the surface treatment coating is a plating coating. [3] The plating coating has a linear expansion coefficient of 8.0 x 10 －６ / K or more. [4] The metal composite material according to [2] or [3], wherein the plating film has an elongation of 5% or more. [5] The metal composite material according to any one of [1] to [4], wherein a thin film formed by strike plating or zincate treatment is used as a base for the surface treatment film. [6] The metal composite material according to any one of [1] to [5], wherein the surface treatment film is composed of at least one metal or alloy selected from the group consisting of silver, nickel, copper, zinc, platinum, gold, and tin. [7] The metal composite material according to any one of [1] to [6], wherein the surface treatment film has a thickness of 0.5 μm or more and less than 1000 μm. [8] The metal composite material according to any one of [1] to [7], wherein the second metal is at least one selected from the group consisting of an aluminum alloy, pure aluminum, a titanium alloy, and titanium, and the first metal is stainless steel or steel. [9] The metal composite material according to any one of [1] to [8], wherein the metal composite material has a structure of three or more layers, one outermost end being an aluminum alloy and the other outermost end being stainless steel or steel, the aluminum alloy being joined to pure aluminum, and the pure aluminum and the stainless steel or steel being joined via a surface treatment coating.

[10] The metal composite material according to any one of [1] to [9], wherein the joining interface has a wavy shape with a wave height of 1 mm or less.

[11] A dissimilar metal joint formed from the metal composite material according to any one of [1] to

[10] .

[12] The dissimilar metal joint according to

[11] , wherein the indication patterns detected by JIS Z 2343-1-II Cd-2 penetrant testing at the joining interface of each metal are all 1 mm or less.

[13] The dissimilar material joint according to

[11] or

[12] , wherein the dissimilar material joint has a pipe shape having a predetermined circumferential length, and the total length of the indication patterns detected by the penetrant testing at each of the joint interfaces is 3% or less of the circumferential length.

[14] The dissimilar material joint according to any one of

[11] to

[13] , wherein the impact absorption energy at each of the joint interfaces in a Charpy impact test according to JIS Z 2242 is 15 J or more.

[15] A piping component having a metal joint made of the metal composite material according to any one of [1] to

[10] .

[16] A cryogenic container having a metal joint made of the metal composite material according to any one of [1] to

[10] .

[17] A pressure vessel having a metal joint made of the metal composite material according to any one of [1] to

[10] .

[18] A transportation machinery part having a metal joint made of the metal composite material according to any one of [1] to

[10] .

[19] A method for producing a metal composite material, comprising the steps of: performing a surface treatment on a joining surface of one or both of a first metal and a second metal, and forming a surface treatment film made of a metal different from the first metal and the second metal; and joining the first metal and the second metal via the surface treatment film by explosive bonding.

[20] The method according to

[19] , wherein the surface treatment film is a plating film.

[0011] One aspect of the present invention is as follows: [1A] A metal composite material having two or more layers composed of a plate of a first metal and a plate of a second metal, wherein the joining surfaces of either or both of the first metal and the second metal have a surface treatment film coated with a thin film of a metal different from the first metal and the second metal, the first metal and the second metal are directly joined via the surface treatment film, and the mechanical strength of the joining interface between the first metal and the second metal is higher than the mechanical strength of either the first metal or the second metal. [2A] The metal composite material according to [1A], wherein the surface treatment film is a plating film. [3A] The plating film has a linear expansion coefficient of 8.0 x 10 －６ / K or more. [4A] The metal composite material according to [2A] or [3A], wherein the plating film has an elongation of 5% or more. [5A] The metal composite material according to any one of [1] to [4A], wherein the base of the surface treatment film is strike plated or zincated. [6A] The metal composite material according to any one of [1A] to [4A], wherein the first metal and the second metal are not subjected to a temperature load equal to or higher than their recrystallization temperature during the joining process. [7A] The metal composite material according to any one of [1A] to [4A], wherein the first metal and the second metal are joined via the surface treatment film by explosive bonding.

[0012] Further, another aspect belonging to the technical field of the present invention is as follows. [1B] A dissimilar metal joint in which one outermost end is an aluminum alloy and the other outermost end is stainless steel or steel, the aluminum alloy is joined to pure aluminum, and the pure aluminum and the stainless steel or steel are joined via a silver-plated film, characterized in that the joint interface between the aluminum alloy and the pure aluminum and the joint interface between the pure aluminum and the stainless steel or steel are each wavy joint interfaces with a wave height of 1 mm or less. [2B] The dissimilar metal joint according to [1B], which has a strike-plated layer as a base for the silver plating. [3B] The dissimilar metal joint according to [1B] or [2B], in which, at each joint interface, indication patterns detected by JIS Z 2343-1-II Cd-2 penetrant testing are 1 mm or less. [4B] The dissimilar material joint according to any one of [1B] to [3B], wherein the dissimilar material joint has a piping shape with a predetermined circumferential length, and the total length of the indication pattern detected by the penetrant testing at each joint interface is 3% or less of the circumferential length. [5B] The dissimilar material joint according to any one of [1B] to [4B], wherein the impact absorption energy at each joint interface in a Charpy impact test according to JIS Z 2242 is 15 J or more. [6B] The dissimilar material joint according to any one of [1B] to [5B], which is for joining aluminum piping and stainless steel piping, and wherein an aluminum alloy, pure aluminum, and stainless steel are joined, and the pure aluminum and stainless steel are joined via a silver-plated coating. [7B] The dissimilar material joint according to any one of [1B] to [6B], wherein the layers are joined by explosive welding.

[0013] According to the present invention, even when metal combinations are difficult to join, by using a surface treatment film without using an intermediate material, it is possible to provide a low-cost metal composite material that has excellent strength at the joining interface and does not require application of a temperature load that exceeds the recrystallization temperature of the metal.

[0014] Fig. 1 is a cross-sectional view of a metal composite material according to the present embodiment; Fig. 2 is a cross-sectional view of a dissimilar metal joint according to the present embodiment; Fig. 3 is a photograph explaining the definition of wave height at a joint interface; Fig. 4 is a photograph explaining a joint interface between pure aluminum and stainless steel or steel; Fig. 5 is a photograph of an indication pattern in a penetrant flaw test; Fig. 6 is a photograph explaining the definition of a fracture position in a shear test; Fig. 7 is a schematic diagram of a dissimilar metal joint according to an example; Fig. 8 is a photograph of a dissimilar metal joint according to an example after a penetrant flaw detection test.

[0015] Hereinafter, an embodiment of the present invention (hereinafter referred to as "the present embodiment") will be described in detail.

[0016] [First embodiment] This embodiment is a metal composite material having two or more layers composed of a first metal and a second metal, wherein a surface treatment film formed of the first metal and a metal different from the second metal is provided on a joining surface of either or both of the first metal and the second metal, the first metal and the second metal are joined via the surface treatment film, and the mechanical strength of the joining interface between the first metal and the second metal is higher than the mechanical strength of either the first metal or the second metal.

[0017] For example, this embodiment is a metal composite material of two or more layers, as shown in Figure 1, composed of a plate 10 of a first metal and a plate 20 of a second metal. The joining surfaces of either or both of the first metal and the second metal have a surface treatment film 30 coated with a thin film of a metal different from the first metal and the second metal. Here, the first metal and the second metal are directly joined via the surface treatment film 30, and the mechanical strength of the joining interface between the first metal and the second metal is higher than the mechanical strength of either the first metal or the second metal.

[0018] <Surface treatment processing> In this specification, "surface treatment processing" means applying a coating to the surface of either the first metal plate or the second metal plate, or both metal surfaces, by plating, thermal spraying, or vapor deposition.

[0019] <Recrystallization Temperature> In this specification, the "recrystallization temperature" refers to the temperature at which recrystallization occurs as defined in JIS G 0201. This temperature is significantly affected by the purity or composition of the metal or alloy, the degree of plastic strain within the crystal, the heating time, etc., and the physical properties of the metallic material change. For example, the recrystallization temperature of A1100-H112 in JIS H 4000 is approximately 180°C, and the recrystallization temperature of SUS304L in JIS G 4305 is approximately 530°C.

[0020] <Bonding Interface> When the metal composite material of this embodiment is subjected to a shear test according to JIS G 0601, either the first or second metal fractures. That is, it is preferable that the metal plate with lower mechanical strength fractures first before delamination occurs at the bonding interface between the first metal plate and the second metal plate in the shear test. In other words, the mechanical strength of the bonding interface in the shear test according to JIS G 0601 is higher than the mechanical strength of either the first or second metal. This feature strengthens the bonding between the first metal plate and the second metal plate.

[0021] <Plating> In this specification, "plating" refers to the "electroplating method" defined in JIS H 0400. Within this standard, "electroplating method" is defined as a method of electrochemically depositing (electrodepositing) a metal on a metal or non-metal surface. Furthermore, "plating film" includes not only the film deposited by electroplating described above, but also a base for improving the adhesion strength of the plating. In this specification, "silver plating" refers to silver electroplating with an effective surface thickness of 0.5 μm or more applied to metal in accordance with JIS H 8621 or an equivalent standard. In this specification, "silver plating film" refers to not only the film deposited by silver electroplating described above, but also a state including a base for strike plating described below. In this specification, "strike plating" refers to plating performed to obtain a thin film of electrodeposited metal to promote the deposition of a plating film performed in a subsequent process defined in JIS H 0400. Applying a strike plating primer to the surface of stainless steel or steel can improve the adhesion of silver plating to the surface in a subsequent process. In this specification, "zincate treatment" refers to a zinc substitution treatment, a method of forming a zinc film on the surface of an object through a substitution reaction, and is generally performed as a pretreatment before plating aluminum or an aluminum alloy. Plating a different metal after one zincate treatment does not significantly improve adhesion. Therefore, double zincate treatment, in which zincate treatment is performed twice, is commonly used.

[0022] <Linear expansion coefficient> The linear expansion coefficient is measured in accordance with JIS Z 2285, and is a value specific to the material determined from the temperature difference of the sample and the change in length of the sample. In order to prevent cracking and peeling due to heat generated during joining, the linear expansion coefficient of the plating film is preferably 8.0 × 10 －６ / K or more, more preferably 8.5 × 10 －６ / K or more. The linear expansion coefficient is 8.0 × 10 －６ If the coefficient of linear expansion of the plating film is lower than 40.0 × 10 / K, cracking or peeling due to heat generated during bonding is likely to occur. －６ / K or less is preferred.

[0023] <Elongation> The elongation is determined from the breaking elongation defined in JIS Z 2241. In order to prevent cracking and peeling due to plastic deformation caused by pressure generated during joining, the elongation of the plating film is preferably 5% or more, more preferably 10% or more. If the elongation is lower than 5%, cracking and peeling due to plastic deformation caused by pressure generated during joining are likely to occur. Furthermore, although there is no particular upper limit, from the viewpoint of bondability to metal, the elongation of the plating film is preferably 60% or less.

[0024] <Explosive welding> Explosive welding is a metal joining method that utilizes the high pressure of explosives, and is a technology that can firmly join dissimilar metals in particular. A major feature of this technology is that it can be joined with almost no heat load on the metal materials, so it can firmly join combinations of metals that cannot be joined by conventional methods. Furthermore, as a mechanism for achieving strong joining, it is known that the bonded interface of metals joined by explosive welding exhibits a unique wavy shape.

[0025] The explosive used in explosive bonding is a gunpowder that generates a detonation wave. In order to firmly bond metal plates, it is preferable to use an explosive with an explosion velocity of 1,000 m / s or more. For a more optimal bonding force, it is even more preferable to use an explosive with an explosion velocity of 1,500 m / s to 3,000 m / s, which is 1 / 3 to 1 / 2 times the speed of sound. Specific examples of explosives include ammonium nitrate; nitrate esters such as PETN (pentaerythritol tetranitrate); nitroglycerin; nitro compounds such as TNT (trinitrotoluene); nitramines such as cyclotrimethylenetrinitramine and cyclotetramethylenetetranitramine; and the like. These may be used alone or in combination with other explosive components or other components other than explosives.

[0026] Furthermore, the bonded interface between the first metal and the second metal preferably has a wavy shape in cross section. The wave height can be measured by observing the bonded cross section using a microscope or a magnifying glass. When the bonded interface has a wavy shape, better bond strength is easily obtained. The wave height is preferably 1 mm or less. When the wave height is 1 mm or less, gas leakage when a dissimilar material is joined is easily suppressed. The wave height is preferably 0.8 mm or less, and more preferably 0.5 mm or less. There is no particular restriction on the lower limit of the wave height, but from the viewpoint of practical measurement accuracy, the lower limit is preferably 0.1 μm or more. From the viewpoint of bond strength, it is preferably 1 μm or more, more preferably 10 μm or more, even more preferably 15 μm or more, and particularly preferably 20 μm or more.

[0027] [Second Embodiment] A second embodiment of the present invention will be described below. This embodiment may be implemented in combination with the first embodiment, and some of the components of this embodiment may be implemented in combination with the first embodiment.

[0028] [Background Art Related to the Second Embodiment] Industrial facilities and equipment use a variety of metal materials, resulting in numerous joints between dissimilar metals. When joining these dissimilar metal materials, those that cannot be welded are primarily joined mechanically using flanges and bolts. However, flange fastening requires the use of a huge number of bolts during equipment assembly, which requires a significant amount of time during assembly and also requires time for periodic maintenance such as retightening. Furthermore, this method has problems such as low reliability in terms of performance, such as a tendency for leakage.

[0029] On the other hand, in the case of weldable dissimilar metals, the process is very simple and inexpensive. However, welding metals with different properties requires difficult setting and management of the welder's skills and welding conditions. This can lead to problems such as a high likelihood of welding defects, and also to problems such as performance degradation due to the alloy formed at the weld. Therefore, when used in harsh environments or when extremely high joining properties are required, dissimilar metal joints, in which dissimilar metals are metallurgically joined together in advance so that the same metals can be welded together, are becoming more common.

[0030] Methods for manufacturing dissimilar metal joints made of dissimilar metal materials include explosive welding, HIP, brazing, etc. Both ends of the joint material are made of the same material that can be welded, but some joints have a structure in which another material is inserted between the two ends to facilitate joining the metal materials at both ends and to improve performance.

[0031] In recent years, liquefied natural gas (LNG) and shale gas liquefaction and vaporization plants, air separation units, and other facilities have been installed around the world, and these facilities and devices contain many joints between dissimilar metals that are exposed to cryogenic temperatures. These gas-related facilities require highly reliable joint materials, even in cryogenic environments. These gas-related facilities require high joint performance, even in cryogenic environments. Therefore, poor joint conditions at the joint interface of joint materials can lead to leakage, which can reduce the mechanical properties of the joint interface and ultimately lead to a serious accident.

[0032] Furthermore, in carriers that transport these gases, the gas is liquefied by cooling it to cryogenic temperatures and then transported in a small volume. This requires a cryogenic container for storing the liquefied gas and a joint to connect the hull. In particular, Moss-type carriers require a joint to connect the aluminum spherical tank to the steel hull. If the bonding condition of the joint interface between these joint materials is poor, peeling will occur, which will reduce the mechanical properties of the joint interface, potentially causing the spherical tank weighing nearly 1,000 tons to fall off and ultimately leading to a major accident.

[0033] For example, in the above-mentioned Patent Document 1, as described above, there is a thermal load due to heating during the joining process, which may cause a deterioration in the properties of the material, the plating layer, or the joining interface.Furthermore, there is a concern that the impact absorption energy may decrease.

[0034] Furthermore, as described above, the bonding strength to the substrate in Patent Document 2 is not high, and therefore there is a concern that the impact absorption energy of the resulting bonded body will be significantly low.

[0035] Furthermore, as mentioned above, Patent Document 3 does not mention a method for joining aluminum alloy and stainless steel without using an intermediate material.

[0036] Furthermore, in Patent Document 4, as described above, when attempting to interpose a silver or silver alloy layer by explosive bonding, silver or a silver alloy having a certain thickness must be prepared, which increases the number of times explosive bonding is performed, raising concerns about increased costs.

[0037] The object of the second embodiment is to provide a dissimilar metal joint material having an aluminum alloy at one outermost end and stainless steel or steel at the other outermost end, which has high joining characteristics without leakage even in an extremely low temperature environment, and a method for manufacturing the joint material. [Effects Related to the Second Embodiment]

[0038] The dissimilar material joint according to the second embodiment is leak-free and has high joining characteristics even in an extremely low temperature environment.

[0039] [Specific Configuration of Second Embodiment] This embodiment will be described in detail below. This embodiment is a dissimilar material joint in which one outermost end is made of aluminum alloy and the other outermost end is made of stainless steel or steel, the aluminum alloy is joined to pure aluminum, and the pure aluminum and the stainless steel or steel are joined via a coating (surface treatment coating).

[0040] In this embodiment, the term "cryogenic temperature" refers to the extremely low temperatures to which air separation units, which cool, liquefy, and distill air to extract gases such as oxygen, nitrogen, and hydrogen as liquids for use in various plants, such as chemical plants and steel plants, and natural gas liquefaction units, which liquefy natural gas extracted from gas fields through various processes, are exposed, and also includes temperatures down to 4 K (approximately -269°C), the boiling point of helium, which is close to absolute zero (-273.15°C).

[0041] As shown in FIG. 2 , in this embodiment, a first metal 2 and a second metal 3 are joined via a surface treatment film 4. Specifically, this embodiment is a dissimilar metal joint in which one outermost end is an aluminum alloy 1 and the other outermost end is a stainless steel or steel 2, the aluminum alloy 1 is joined to pure aluminum 3, and the first metal (in one embodiment, the stainless steel or steel 2) and the second metal (in one embodiment, the pure aluminum 3) are joined via a surface treatment film (in one embodiment, a silver-plated film 4). Here, it is preferable that the joint interface between the aluminum alloy 1 and the pure aluminum 3 and the joint interface between the pure aluminum 3 and the stainless steel or steel 2 are wavy joint interfaces with a wave height of 1 mm or less. Furthermore, it is preferable that the length of an indication pattern detected at each joint interface by a penetrant testing according to JIS Z 2343-1-II Cd-2 or an equivalent standard is 1 mm or less.

[0042] It is preferable that the dissimilar material joint has a "flange" that starts from the aluminum alloy, stainless steel, or steel and has a thickness greater than the outer diameter of the pipe. By having a fillet (e.g., reference numeral 5 in FIG. 2) with an arc radius of 1 mm or more at the start of the flange (e.g., reference numeral 6 in FIG. 2), stress concentration does not occur when temperature and pressure are applied by the fluid flowing inside the joint, which tends to reduce stress overall.

[0043] Furthermore, it is preferable that the value obtained by dividing the total length of the dissimilar material joint by the length of the flange is 1.5 or more. By cutting the parts other than the flange so that the value obtained by dividing the total length of the dissimilar material joint by the length of the flange is 1.5 or more, the vicinity of the joint between the dissimilar metals can be made more resistant to temperature and pressure loads. In addition, the weight of the entire joint can be reduced. In other words, the load on the entire device is reduced and a structure with good workability is achieved.

[0044] It is also preferable that an aluminum alloy be disposed at one outermost end and stainless steel or steel be disposed at the other outermost end. It is also preferable that the joint interface between the first metal and the second metal has a wavy shape. At the same time, it is preferable that the total length of the defect indication pattern in a penetrant inspection is preferably 3% or less of the circumference. By satisfying any of the above conditions, a welded joint material is provided that minimizes gas leakage even in a cryogenic environment and has high joining characteristics. The preferred range of the wave height is the same as in the first embodiment.

[0045] As described above, this embodiment is a dissimilar metal joint in which a surface treatment film is provided between a first metal (in one embodiment, stainless steel or steel) and a second metal (in one embodiment, pure aluminum). The provision of this surface treatment film (in one embodiment, a silver-plated film) can improve joinability. Furthermore, the provision of a flange starting at the stainless steel or steel and aluminum alloy allows for weight reduction and improved workability while maintaining the performance of a dissimilar metal joint. Furthermore, the provision of an R-shaped flange starting point can prevent stress concentration at the flange starting point. Furthermore, the joint interface between the dissimilar metals has a wavy interface, which allows for controlling the wavelength and wave height of the wavy interface to achieve both high joint strength and high leak resistance.

[0046] In the present embodiment, "aluminum" refers to pure aluminum having alloy numbers 1100, 1080, 1070, 1050 or equivalent in ASME Section II, Part B or JIS standards. The aluminum alloy is an alloy other than the above-mentioned pure aluminum that contains aluminum as a main component and also contains Fe and other components such as Mn and Mg.

[0047] In the present embodiment, "steel, stainless steel" refers to a material containing Fe as a main component and described in ASME Section II, Part A or JIS standard, or a material containing components equivalent to those described in said standard.

[0048] In this embodiment, the "wave height" at the joint interface refers to the difference in height from the crest to the trough of the wave, as shown in Figure 3. The wave height refers to the average value of measurements taken at 10 arbitrary points on the joint interface on the outer circumferential surface of the joint material using a magnifying glass, vernier calipers, or an electron microscope. As shown in Figure 4, the joint interface between pure aluminum 2 and stainless steel or steel 1 is an interface that includes a surface treatment coating (in one embodiment, a silver plating coating 3), and the wave height at the joint interface is measured from the waves formed between the pure aluminum 2 and the surface treatment coating 3.

[0049] The penetrant testing conforms to JIS Z 2343-1-II Cd-2 or an equivalent standard, and the size and number of detected red indicators are measured using a measuring device such as a vernier caliper. Specifically, indicators refer to red patterns that are visually observed using the penetrant used in the penetrant testing, as shown in FIG. 5, due to scratches present on the surface of the material. Here, the size and number of detected patterns are measured using a measuring device such as a vernier caliper. In this embodiment, in the case of a pipe fitting, it is preferable that the length of each indicator is 1 mm or less, or that the total length of the indicators is 3% or less of the circumference. Here, the absence of indicators also falls within the category of 1 mm or less.

[0050] The impact absorption energy is a value obtained from the results of a test conducted using a V-notch test piece in accordance with the Charpy impact test method for metallic materials of JIS Z 2242. In the case of a piping joint, the impact absorption energy is preferably 15 J or more at each joint interface.

[0051] The leakage amount evaluation test is carried out using the vacuum spray method of the helium leakage test method of JIS Z 2331 or an equivalent standard.

[0052] The dissimilar metal joint of this embodiment can be used not only for the various pipes of air separation units used in the aforementioned chemical, steel, and other plants to extract gases such as oxygen, nitrogen, and hydrogen as liquids, and natural gas liquefaction units that liquefy natural gas extracted from gas fields through various processes, but also for welding and joining aluminum or aluminum alloys to various other metals in building structures, transportation equipment, and the like.

[0053] In this embodiment, regarding "explosive bonding," it is known that the bonding interface of metals bonded by explosive bonding exhibits a unique wavy shape as a mechanism for strong bonding. The wave height of the bonding interface can be adjusted by adjusting the energy, amount of explosive, etc. during explosive bonding.

[0054] [Third Embodiment] A third embodiment of the present invention will now be described. This embodiment may be implemented in combination with the first embodiment and / or the second embodiment, and some of the components of this embodiment may be implemented in combination with the first embodiment and / or the second embodiment.

[0055] In this embodiment, the surface treatment film is not limited to the specific configurations described in the first and second embodiments. For example, the surface treatment film according to this embodiment is preferably a plating film, and is preferably made of at least one metal selected from the group consisting of silver, nickel, copper, zinc, platinum, gold, and tin. Either configuration can easily achieve the effects of the present invention.

[0056] In this embodiment, the thickness of the surface treatment film is preferably 0.5 μm or more and less than 1000 μm. A surface treatment film thickness of 0.5 μm or more easily ensures sufficient bonding strength between the first metal and the second metal, and therefore tends to provide excellent leak resistance in dissimilar material joints. Furthermore, a thickness of less than 1000 μm is preferable because it facilitates the formation of the surface treatment film and also contributes to weight reduction by reducing the amount of metal used in the intermediate layer. A more preferred thickness range is 0.5 to 900 μm, and even more preferably 0.5 to 500 μm. The thickness of the surface treatment film can be detected by observing the cross section of the layer on which the film is formed using an optical microscope, electron microscope, or the like.

[0057] In this embodiment, the first metal is not limited to the specific configurations described in the first and second embodiments. For example, the first metal according to this embodiment is preferably at least one selected from the group consisting of copper, stainless steel, and steel, but is not limited thereto. Furthermore, the thickness of the first metal is arbitrary and is not particularly limited. From the viewpoint of achieving both workability and bonding strength, a thickness of 1 mm to 200 mm is preferred, a thickness of 1 mm to 150 mm is more preferred, and a thickness of 1 mm to 100 mm is even more preferred. Regardless of the configuration, the configuration of the present invention can be easily achieved. In the technical field of clad materials, a relatively thick metal among the metals to be joined is sometimes referred to as a "base material" and a relatively thin metal is sometimes referred to as a "clad material." In the present disclosure, the first metal may be the base material and the second metal may be the clad material, or the second metal may be the base material and the first metal may be the clad material.

[0058] In this embodiment, the second metal is not limited to the specific configurations described in the first embodiment and the second embodiment. For example, the second metal according to this embodiment is preferably at least one selected from the group consisting of aluminum alloy, pure aluminum, tungsten, titanium alloy, and titanium. Furthermore, the thickness of the second metal is optional and is not particularly limited. From the viewpoint of achieving both workability and bonding strength, the thickness is preferably 1 mm or more and 200 mm or less, more preferably 1 mm or more and 100 mm or less, and even more preferably 1 mm or more and 50 mm or less. Regardless of the configuration, the configuration of the present invention can be easily achieved.

[0059] In this embodiment, the metal composite material preferably has a three-layer or more structure, one outermost layer being an aluminum alloy and the other outermost layer being stainless steel or steel, the aluminum alloy being bonded to pure aluminum, and the pure aluminum and the stainless steel or steel being bonded via a surface treatment film. Furthermore, the surface treatment film is preferably a plating film. This configuration makes it easier to achieve the features of the present invention.

[0060] In this embodiment, it is preferable that a thin film formed by strike plating or zincate treatment is used as a base for the surface treatment film. With this configuration, the configuration of the present invention can be easily achieved.

[0061] Another aspect of this embodiment is a dissimilar material joint made of a metal composite material. Because this dissimilar material joint is made of the metal composite material of this embodiment, it has excellent strength at the joint interface and can be provided at low cost.

[0062] The metal composite materials and dissimilar material joints described in the first to third embodiments can be used in any machinery, device, equipment, buildings, etc. that have a metal joint where different metals are joined. Metal composite materials are advantageous for reducing the weight of structures and can therefore be suitably used as heat exchangers, heat sinks, welded joint materials, air separation units, chemical tankers, and pressure vessels. Dissimilar material joints are impact resistant and have excellent gas leak resistance, so they can be suitably used as piping components, cryogenic containers for storing liquefied gases, and pressure vessels for high-pressure gases, as well as transportation machinery components for vehicles, railways, aircraft, etc.

[0063] Examples and comparative examples of the present invention will be shown below, but the present invention is not limited to these examples and comparative examples.

[0064] [Example of First Embodiment] <Shear Test> This was specified in accordance with the test method for clad steel of JIS G 0601. As shown in Fig. 6, the test piece after the shear test was observed, and if the first metal 10 was attached, the second metal 20 was determined to be the material fracture at the attached metal side if the first metal 10 was attached, or if the second metal 20 was attached, the first metal 10 was determined to be the material fracture at the attached metal side. On the other hand, in the case of a joint interface fracture, if the first metal 10 was attached, the plating film 30 or the second metal 20 was not attached, or if the second metal 20 was attached, the plating film 30 or the first metal 10 was not attached, and the joint surface was exposed, it was determined to be a joint interface fracture.

[0065] <Ultrasonic flaw detection test> The ultrasonic flaw detection test was carried out in accordance with the ultrasonic flaw detection test specified in the test method for clad steel in JIS G 0601. When the horizontal axis represents the propagation time and the vertical axis represents the sound pressure, and the bottom echo height was set to 80%, if no defect echo was detected with an interface echo height of 40% or more, it was determined that there was no defect.

[0066] <Linear Expansion Coefficient> The linear expansion coefficient was determined in accordance with JIS Z 2285 from a value specific to the material, which is determined from the temperature difference of the sample and the amount of change in length of the sample.

[0067] <Elongation> The elongation was determined from the breaking elongation defined in JIS Z 2241.

[0068] Example 1: Stainless steel (JIS G 4305: SUS304L, thickness: 50 mm) was used as the first metal plate, and commercially pure aluminum (JIS H 4000: A1100P-H112, thickness: 12 mm) was used as the second metal plate. The surface of the first metal plate was subjected to strike nickel plating as a base, and then silver plating was applied, thereby performing surface treatment on the joining surfaces of the first metal plates.

[0069] Next, a predetermined gap was created between the first metal plate and the second metal plate, each coated with a silver plating film, and a powdered explosive containing ammonium nitrate as its main component was placed at a predetermined thickness. The explosive was then detonated using a 6 mm diameter detonator to perform explosive bonding. As a result, the first metal plate and the second metal plate were successfully joined. Ultrasonic testing (JIS G 0601, back surface echo method) confirmed a defect-free full-surface bond.

[0070] Next, a total of four test samples for shear tests were cut out from the metal composite material and subjected to shear tests (JIS G 0601). As a result, as shown in the table below, all of the fracture locations in the shear tests were pure aluminum fractures, meaning that the bonded interface had sufficient strength.

[0071] Example 2: Stainless steel (JIS G 4305: SUS316L, thickness: 30 mm) was used as the first metal plate, and aluminum alloy (JIS H 4000: A3003P-O, thickness: 10 mm) was used as the second metal plate. The surface of the second metal plate was subjected to a double zincate treatment as a base, and then copper plating was applied, thereby performing surface treatment on the joining surface of the second metal plate.

[0072] Next, a predetermined gap was created between the first metal plate and the second metal plate coated with a copper plating film, and a powdered explosive containing ammonium nitrate as the main component was placed at a predetermined thickness. The explosive was then detonated using a 6 mm diameter detonator to perform explosive bonding. As a result, the first metal plate and the second metal plate were successfully bonded. Ultrasonic testing (JIS G 0601, back surface echo method) confirmed a defect-free full-surface bond.

[0073] Next, a total of four test samples for shear tests were cut out from the metal composite material and subjected to shear tests (JIS G 0601). As a result, as shown in the table below, all of the fracture locations in the shear tests were in the aluminum alloy, which means that the bonded interface had sufficient strength.

[0074] Example 3 A general structural rolled steel material (JIS G 3101: SS400, thickness: 5 mm) was used as the first metal plate, and pure tungsten (ASTM B760-07, thickness: 1 mm) was used as the second metal plate. The surface of the first metal plate was nickel-plated to perform surface treatment of the joining surfaces of the first metal plates.

[0075] Next, a predetermined gap was created between the first metal plate and the second metal plate, each coated with a nickel plating film, and a powdered explosive containing ammonium nitrate as its main component was placed at a predetermined thickness. The explosive was then detonated using a 6 mm diameter detonator to perform explosive bonding. As a result, the first metal plate and the second metal plate were successfully bonded. Ultrasonic testing (JIS G 0601, back surface echo method) confirmed a defect-free full-surface bond.

[0076] Next, a total of four test samples for shear tests were cut out from the metal composite material and subjected to shear tests (JIS G 0601). As a result, as shown in the table below, all of the fracture locations in the shear tests were in the structural steel, meaning that the bonded interface had sufficient strength.

[0077] Example 4 Oxygen-free copper (JIS H 3100: C1020P-1 / 4H, thickness: 100 mm) was used as the first metal plate, and pure aluminum (JIS H 4000: A1050P-H112, thickness: 6 mm) was used as the second metal plate. The surface of the second metal plate was subjected to a double zincate treatment as a base, and then platinum plating was applied, thereby performing surface treatment on the joining surface of the second metal plate.

[0078] Next, a predetermined gap was created between the first metal plate and the second metal plate coated with a platinum plating film, and a powdered explosive containing ammonium nitrate as the main component was placed at a predetermined thickness. The explosive was then detonated using a 6 mm diameter detonator to perform explosive bonding. As a result, the first metal plate and the second metal plate were successfully bonded. Ultrasonic testing (JIS G 0601, back surface echo method) confirmed a defect-free full-surface bond.

[0079] Next, a total of four test samples for shear testing were cut out from the metal composite material and subjected to shear testing (JIS G 0601). As a result, as shown in the table below, all of the fracture locations in the shear testing were pure aluminum, meaning that the bonded interface had sufficient strength.

[0080] Example 5: A rolled steel material for welded structures (JIS G 3106: SM400B, plate thickness: 22 mm) was used as the first metal plate, and an aluminum alloy (JIS H 4000: A3003P-O, plate thickness: 13 mm) was used as the second metal plate. The surface of the first metal plate was subjected to a nickel strike plating as a base, and then to a silver plating, thereby performing a surface treatment of the joining surfaces of the first metal plates.

[0081] Next, a predetermined gap was provided between the first metal plate and the second metal plate, each coated with a silver plating film, and a powdered explosive containing ammonium nitrate as the main component was placed at a predetermined thickness. The explosive was then detonated using a 6 mm diameter detonator to perform explosive bonding. As a result, the first metal plate and the second metal plate were successfully joined, and an ultrasonic flaw detection test (JIS G 0601, back surface echo method) determined that the entire surface was joined without any defects.

[0082] Next, a total of four test samples for shear tests were cut out from the metal composite material and subjected to shear tests (JIS G 0601). As a result, as shown in the table below, all of the fracture locations in the shear tests were in the aluminum alloy, indicating sufficient strength of the bonded interface.

[0083] Example 6: Stainless steel (JIS G 4305: SUS304L, thickness: 20 mm) was used as the first metal plate, and commercially pure titanium (JIS H 4600: TP270C, thickness: 2 mm) was used as the second metal plate. The surface of the first metal plate was subjected to nickel strike plating as a base, and then nickel plating was applied, thereby performing surface treatment of the joining surfaces of the first metal plates.

[0084] Next, a predetermined gap was provided between the first metal plate and the second metal plate, both of which were coated with nickel plating films, and a powdered explosive containing ammonium nitrate as the main component was placed at a predetermined thickness. The explosive was then detonated using a 6 mm diameter detonator to perform explosive bonding. As a result, the first metal plate and the second metal plate were successfully joined, and ultrasonic testing (JIS G 0601, back surface echo method) determined that the entire surface was joined without any defects.

[0085] Next, a total of four test samples were cut out from the metal composite material and subjected to shear testing (JIS G 0601). As a result, as shown in the table below, all of the fracture locations in the shear test were in the titanium, indicating sufficient strength at the bonded interface.

[0086] Comparative Example 1: Stainless steel (JIS G 4305: SUS304L, plate thickness: 50 mm) was used as the first metal plate, and industrially pure aluminum (JIS H 4000: A1100P-H112, plate thickness: 12 mm) was used as the second metal plate. A predetermined gap was provided between the first metal plate and the second metal plate, and a powdered explosive mainly composed of ammonium nitrate was placed to a predetermined thickness. The explosive was then detonated using a 6 mm diameter detonator to perform explosive bonding. As a result, the first metal plate and the second metal plate were successfully joined. However, as a result of ultrasonic testing (JIS G 0601, back surface echo method), the joining range was determined to be 30% of the total.

[0087] Next, a total of four test samples for shear tests were cut out from the metal composite material and subjected to shear tests (JIS G 0601). As a result, as shown in the table below, all of the fracture locations in the shear tests were at the bond interface, meaning that sufficient shear strength was not obtained.

[0088] Comparative Example 2: A general structural rolled steel material (JIS G 3101: SS400, plate thickness: 5 mm) was used as the first metal plate, and pure tungsten (ASTM B760-07, plate thickness: 1 mm) was used as the second metal plate. A predetermined gap was provided between the first metal plate and the second metal plate, and a powdered explosive mainly composed of ammonium nitrate was placed at a predetermined thickness. The explosive was then detonated using a 6 mm diameter detonator to perform explosive bonding. As a result, the first metal plate and the second metal plate were successfully joined. However, numerous cracks were observed on the surface of the pure tungsten second metal plate, meaning that it was not suitable for use as a product. Furthermore, as shown in the table below, a shear test could not be performed.

[0089]

[0090] [Examples for the Second and Third Embodiments] Example 1A A three-layer clad consisting of an aluminum alloy (JIS H 4000: A5083P-O, plate thickness: 50 mm), pure aluminum (JIS H 4000: A1100P-H112, plate thickness: 12 mm), and stainless steel (JIS G 4305: SUS304L, plate thickness: 50 mm) was produced by explosive bonding. The surface of the stainless steel was nickel strike plated (thickness: 1 μm) as a base, and then silver plated (thickness: 50 μm) before explosive bonding. This clad was subjected to ultrasonic testing in accordance with JIS G 0601, and a dissimilar material joint with the shape shown in Figure 7 was fabricated from the position where the joining was confirmed, and its performance was evaluated (a = 27 mm, b = 3.9 mm, c = 25 mm, d = 106 mm, e = 49 mm, R = 5 mm, the value obtained by dividing the total length of the dissimilar material joint by the length of the flange was 1.9). The wavelength and wave height at the joining interface were 346 μm and 113 μm, respectively, at the joining interface between the aluminum alloy and pure aluminum, and 627 and 48 μm, respectively, at the joining interface between pure aluminum and stainless steel. A helium leak test was conducted on the resulting joint in accordance with JIS Z 2331 "Helium Leak Test Method," and a leak current of 0.9 × 10 －１０ P.A.M. ３ / sec (at room temperature), which means that the material has excellent leak resistance. A penetrant test was performed on the entire outer peripheral surface in accordance with JIS Z 2343-1-II Cd-2, and the length or diameter of any indications detected was measured. As shown in Figure 8, no indications were detected. A Charpy impact test specimen was prepared in accordance with JIS Z 2242, cooled to -196°C (liquid nitrogen), and subjected to an impact test. The absorbed energy values ​​were 54 J at the interface between the aluminum alloy and pure aluminum, and 57 J at the interface between the pure aluminum and stainless steel.

[0091] Example 2A: A three-layer clad structure consisting of an aluminum alloy (ASME SB-209 3003-O, thickness: 50 mm), pure aluminum (ASME SB-209 1100-H112, thickness: 12 mm), and stainless steel (ASME SA-240 Type 316L, thickness: 50 mm) was fabricated by explosive bonding. The stainless steel surface was first nickel-strike plated (thickness: 1 μm) as a base, and then silver-plated (thickness: 400 μm) before explosive bonding. This clad was subjected to ultrasonic testing in accordance with JIS G 0601, and a dissimilar material joint with the shape shown in Figure 7 was fabricated from the position where welding was confirmed, and its performance was evaluated (a = 33 mm, b = 4.6 mm, c = 25 mm, d = 106 mm, e = 56 mm, R = 5 mm, the value obtained by dividing the total length of the dissimilar material joint by the length of the flange was 1.9). The wavelength and wave height at the joint interface were 252 μm and 81 μm, respectively, at the joint interface between the aluminum alloy and pure aluminum, and 640 μm and 42 μm, respectively, at the joint interface between pure aluminum and stainless steel. A helium leak test was conducted on the obtained joint in accordance with JIS Z 2331 "Helium Leak Test Method," and a leak rate of 1.2 × 10 －１０ P.A.M. ３ / sec (room temperature), which means that it has excellent leak resistance. Furthermore, a penetrant test was performed on the entire outer peripheral surface in accordance with JIS Z 2343-1-II Cd-2, and the length or diameter of any indication patterns detected was measured, but no indication patterns were detected. Furthermore, Charpy impact test specimens were prepared in accordance with JIS Z 2242 and cooled to -196°C (liquid nitrogen), and impact tests were performed. An absorbed energy value of 58 J was obtained at the joint interface between the aluminum alloy and pure aluminum, and 58 J at the joint interface between pure aluminum and stainless steel.

[0092] Example 3A: A four-layer clad consisting of aluminum alloy (JIS H 4000: A5083P-O, plate thickness: 40 mm), pure aluminum (JIS H 4000: A1100P-H112, plate thickness: 12 mm), pure titanium (JIS H 4600: TP270C, plate thickness: 2 mm), and stainless steel (JIS G 4305: SUS304L, plate thickness: 30 mm) was produced by explosive bonding. The stainless steel surface was nickel-strike plated (thickness: 1 μm) as a base, and then nickel-plated (thickness: 50 μm) before explosive bonding. Ultrasonic testing was performed on this clad in accordance with JIS G 0601. Starting from the location where welding was confirmed, a dissimilar joint with the shape shown in Figure 7 was fabricated and its performance evaluated (a = 114.3 mm, b = 6.02 mm, c = 20 mm, d = 78 mm, e = 148 mm, R = 5 mm; the total length of the dissimilar joint divided by the flange length was 2.1). The wavelength and wave height at the joint interface were 711 μm and 255 μm, respectively, at the aluminum alloy / pure aluminum joint interface, 958 μm and 99 μm, respectively, at the pure aluminum / pure titanium joint interface, and 498 μm and 113 μm, respectively, at the pure titanium / stainless steel joint interface. A helium leak test was performed on the resulting joint in accordance with JIS Z 2331, "Helium Leak Test Method," and the result was 1.3 × 10-11 Pa m3 / sec (room temperature), demonstrating excellent leak resistance. Furthermore, a penetrant test was performed on the entire outer peripheral surface in accordance with JIS Z 2343-1-II Cd-2, and the length or diameter of any detected indications was measured, but no indications were detected. Furthermore, Charpy impact test specimens were prepared in accordance with JIS Z 2242 and cooled to -196°C (liquid nitrogen), and an impact test was performed. The absorbed energy values ​​were 51 J at the joint interface between the aluminum alloy and pure aluminum, 55 J at the joint interface between pure aluminum and pure titanium, and 119 J at the joint interface between pure titanium and stainless steel.

[0093] Example 4A A three-layer clad consisting of an aluminum alloy (JIS H 4000: A3003P-O, plate thickness: 13 mm), pure titanium (JIS H 4600: TP270C, plate thickness: 2 mm), and stainless steel (JIS G 4305: SUS304L, plate thickness: 22 mm) was produced by explosive pressure bonding. The stainless steel surface was subjected to nickel strike plating (thickness: 1 μm) as a base, and then nickel plating (thickness: 200 μm) was applied, followed by explosive pressure bonding. This clad was subjected to ultrasonic testing in accordance with JIS G 0601, and a joint material measuring 9 mm x 250 mm in original plate thickness was cut out with a band saw from the position where joining was confirmed. The cut surface of the outer periphery of the joint material was polished to perform a surface finish. The wavelength and wave height at the bonded interface were 812 μm and 116 μm, respectively, at the bonded interface between the aluminum alloy and pure titanium, and 623 μm and 145 μm, respectively, at the bonded interface between the pure titanium and stainless steel. Penetrant testing was performed on the entire surface in accordance with JIS Z 2343-1-II Cd-2, and the length or diameter of any indications detected was measured. No indications were detected. Charpy impact test specimens were prepared in accordance with JIS Z 2242 and cooled to -196°C (liquid nitrogen). An absorbed energy value of 48 J was obtained at the bonded interface between the aluminum alloy and pure titanium, and 106 J at the bonded interface between the pure titanium and stainless steel.

[0094] Comparative Example 1A: A three-layer clad consisting of an aluminum alloy (JIS H 4000: A5083P-O, plate thickness: 50 mm), commercially pure aluminum (JIS H 4000: A1100P-H112, plate thickness: 12 mm), and stainless steel (JIS G 4305: SUS304L, plate thickness: 50 mm) was produced by explosive bonding. Ultrasonic testing was performed on this clad in accordance with JIS G 0601, and a Charpy impact test specimen was prepared from the position where bonding was confirmed in accordance with JIS Z 2242. The specimen was cooled to -196 °C (liquid nitrogen) and subjected to impact testing. The absorbed energy values ​​were 4.4 J at the bonding interface between the aluminum alloy and pure aluminum (fracture location: bonding interface between pure aluminum and stainless steel), and 1.5 J at the bonding interface between pure aluminum and stainless steel. In other words, it was confirmed that this clad fell outside the range of a preferred embodiment of this invention. The maximum length of the indications was 4.5 mm, and the total length of the indications was 60% of the circumference.

[0095] Comparative Example 2A: A three-layer clad consisting of an aluminum alloy (JIS H 4000: A5083P-O, plate thickness: 50 mm), pure aluminum (JIS H 4000: A1100P-H112, plate thickness: 12 mm), and stainless steel (JIS G 4305: SUS304L, plate thickness: 50 mm) was produced by explosive bonding. The surface of the pure aluminum was double zincated as a base, and then copper plated (thickness: 50 μm) before explosive bonding. This clad was subjected to ultrasonic testing in accordance with JIS G 0601, and a Charpy impact test specimen was prepared from the position where bonding was confirmed in accordance with JIS Z 2242. The specimen was cooled to -196°C (liquid nitrogen) and subjected to impact testing. The absorbed energy values ​​were 6.3 J at the bonding interface between the aluminum alloy and pure aluminum (fracture location was the bonding interface between pure aluminum and stainless steel) and 3.3 J at the bonding interface between pure aluminum and stainless steel. This confirms that the clad falls outside the range of a preferred aspect of this embodiment. The maximum length of the indication pattern was 1.8 mm, and the total length of the indication pattern was 25% of the circumference.

[0096] [Industrial Applicability Related to the First Embodiment] According to the present invention, by joining metal composite materials of metals that are difficult to join without using an intermediate material but through a surface-treated coating, it is possible to obtain a strongly joined metal composite material at low cost. Therefore, the present invention is extremely useful industrially. The metal composite material of the present invention may be applicable to reducing the weight of structures, as well as to heat exchangers, heat sinks, welding joint materials, air separation units, chemical tankers, pressure vessels, piping components, cryogenic containers, and transportation machinery components, etc. However, the applicability of the present invention is not limited to these.

[0097] [Industrial Applicability Related to the Second and Third Embodiments] Equipment and devices requiring cryogenic environments and / or high vacuum performance often use high-pressure and hazardous materials as media. Therefore, damage to these components can result in not only economic losses but also personal injury. Therefore, if the joint condition of a dissimilar material joint is poor and the joint performance is low, cracks may develop and progress due to aging, unexpected stress concentration, thermal cycles, and the like, potentially leading to the problems described above. The weld joint material related to the second embodiment can exhibit high reliability and high joint performance even in cryogenic environments, such as liquefied natural gas (LNG), liquid nitrogen, liquid hydrogen, and liquid helium. Therefore, it can be suitably used in equipment and devices requiring cryogenic environments and / or high vacuum performance. Furthermore, the use of silver plating can reduce the amount of expensive silver used as an intermediate material and further reduce the number of joining steps required in conventional joining methods, thereby significantly reducing costs compared to conventional methods.

[0098] (Reference symbols in Fig. 1) 10 First metal plate 20 Second metal plate 30 Surface treatment film (Reference symbols in Fig. 2) 1 Aluminum alloy 2 First metal (stainless steel or steel) 3 Second metal (aluminum) 4 Surface treatment film (silver plating film) 5 Fillet portion 6 Collar portion (Reference symbols in Fig. 4) 1 First metal (stainless steel or steel) 2 Second metal (aluminum) 3 Surface treatment film (silver plating film) (Reference symbols in Fig. 6) 10 First metal 20 Second metal 30 Surface treatment film (plating film) (Reference symbols in Fig. 7) 1 Aluminum alloy 2 Second metal (aluminum) 3 Surface treatment film (silver plating film) 4 First metal (stainless steel or steel)

Claims

1. A metal composite material having two or more layers composed of a first metal and a second metal, wherein a surface treatment film formed of the first metal and a metal different from the second metal is provided on the joining surface of either or both of the first metal and the second metal, the first metal and the second metal are joined via the surface treatment film, and the mechanical strength of the joining interface between the first metal and the second metal is higher than the mechanical strength of either the first metal or the second metal.

2. The metal composite material according to claim 1, wherein the surface treatment film is a plating film.

3. The linear expansion coefficient of the plating film is 8.0 x 10 －６ The metal composite material according to claim 2, wherein the metal composite material has a viscosity of 1000:1 or more.

4. The metal composite material according to claim 2 or 3, wherein the plating film has an elongation of 5% or more.

5. The metal composite material according to any one of claims 1 to 4, which has a thin film formed by strike plating or zincate treatment as a base for the surface treatment film.

6. The metal composite material according to any one of claims 1 to 5, wherein the surface treatment film is composed of at least one metal or alloy selected from the group consisting of silver, nickel, copper, zinc, platinum, gold, and tin.

7. The metal composite material according to any one of claims 1 to 6, wherein the thickness of the surface treatment film is 0.5 μm or more and less than 1000 μm.

8. The metal composite material according to any one of claims 1 to 7, wherein the second metal is at least one selected from the group consisting of an aluminum alloy, pure aluminum, a titanium alloy, and titanium, and the first metal is stainless steel or steel.

9. The metal composite material according to any one of claims 1 to 8, having a structure of three or more layers, one outermost end being an aluminum alloy and the other outermost end being stainless steel or steel, the aluminum alloy being bonded to pure aluminum, and the pure aluminum and the stainless steel or steel being bonded via the surface treatment film.

10. The metal composite material according to any one of claims 1 to 9, wherein the bonding interface has a wavy shape with a wave height of 1 mm or less.

11. A dissimilar material joint made of the metal composite material according to any one of claims 1 to 10.

12. A dissimilar material joint as set forth in claim 11, in which any indication pattern detected by a JIS Z 2343-1-II Cd-2 penetrant inspection at the joint interface between the metals is 1 mm or less.

13. The dissimilar material joint according to claim 11, wherein the dissimilar material joint is in the shape of a pipe having a predetermined circumference, and the total length of the indication pattern detected by the penetrant testing at each of the joint interfaces is 3% or less of the circumference.

14. A dissimilar material joint as set forth in claim 11, wherein the impact absorption energy in a Charpy impact test according to JIS Z 2242 at each of the joint interfaces is 15 J or more.

15. A piping part having a metal joint made of the metal composite material according to any one of claims 1 to 10.

16. A cryogenic vessel having a metal joint made of the metal composite material according to any one of claims 1 to 10.

17. A pressure vessel having a metal joint formed from the metal composite material according to any one of claims 1 to 10.

18. A transportation machine part having a metal joint made of the metal composite material according to any one of claims 1 to 10.

19. A method for producing a metal composite material, comprising the steps of: performing a surface treatment process on a joining surface of either or both of a first metal or a second metal, and forming a surface treatment film composed of a metal different from the first metal and the second metal; and joining the first metal and the second metal via the surface treatment film by explosive bonding.

20. The manufacturing method according to claim 19, wherein the surface treatment film is a plating film.

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