JP6033757B2 - Aluminum alloy clad plate and method for producing aluminum alloy clad structure member - Google Patents

Description

  The present invention relates to an aluminum alloy clad plate and an aluminum alloy clad structure member (hereinafter, aluminum is also referred to as aluminum or Al). Here, the clad plate is a laminated plate in which aluminum alloy layers are laminated with each other and joined together by rolling or the like.

  In the structural members of transport aircraft that use aluminum alloy plates as materials for weight reduction, such as the body of an automobile or aircraft body, there is a contradiction between high alloying for high strength and formability to structural members. Cheap.

  For example, 7000 series aluminum alloys for structural members and ultra-super duralumin (Al-5.5% Zn-2.5% Mg alloy) are used as a typical means for increasing the strength of elements such as Zn and Mg. Although increased, there is a problem that ductility is lowered and it is difficult to form a structural member. In addition, there is a problem that the corrosion resistance is lowered, or the strength is increased by aging (aging hardening) at room temperature during storage, and the moldability to a structural member is significantly lowered. In addition, there is a problem that the production efficiency of the plate such as a rolling process is low.

  Such a contradictory problem between high strength and formability can be solved only by the composition and structure of the aluminum alloy plate alone, such as the 7000 series aluminum alloy plate and ultra-duralumin plate, or the manufacturing method. difficult.

  As a method for solving this problem, an aluminum alloy clad plate (laminated plate) in which two to four aluminum alloy layers (plates) having different compositions and characteristics are laminated is known.

  A typical example of this is an aluminum alloy brazing sheet for a heat exchanger having a three-layer to four-layer structure in which a core material of a 3000 series aluminum alloy is clad with a sacrificial anode material of a 7000 series aluminum alloy and a brazing material of a 4000 series aluminum alloy. .

  In addition to this, in Patent Document 1, an aluminum alloy material for an automobile fuel tank comprising a core material of 5000 series aluminum alloy material for increasing strength, a skin material of 7000 series aluminum alloy material for improving corrosion resistance, and a clad material, respectively. Proposed.

  Further, in Patent Document 2, the aluminum alloys are maximized by continuous casting using twin rolls utilizing the melting point difference of 1000 series, 3000 series, 4000 series, 5000 series, 6000 series, 7000 series, etc. aluminum alloys. A method for manufacturing a clad plate in which four layers are laminated and integrated is proposed.

  Further, in Patent Document 3, when a plurality of aluminum alloy layers are stacked, a Cu anticorrosion layer is interposed between the aluminum alloy layers, and Cu of the Cu anticorrosion layer is joined by high-temperature heat treatment. It has also been proposed to improve the corrosion resistance of the clad plate by diffusing up to.

JP 2004-285391 A Japanese Patent No. 5083862 JP 2013-95980 A

  However, none of these conventional aluminum alloy clad plates solves the contradiction with formability at a high strength level such as the above-mentioned 7000 series aluminum alloy plates for structural members of the above-mentioned transport aircraft.

  In order to solve such problems, the object of the present invention is to solve the contradiction with formability at a high strength level such as the 7000 series aluminum alloy plate, and to provide both high strength and high formability. Is to provide.

In order to achieve this object, the gist of the present invention is an aluminum alloy clad plate that is press-formed and used as a structural member,
An aluminum alloy clad plate that is press-formed and used as a structural member, in which a plurality of aluminum alloy layers are laminated,
A plurality of aluminum alloy layers containing one or more of Mg: 1.5 to 14% by mass, Zn: 2 to 30% by mass, Cu: 1.5 to 6% by mass, and at least Mg Are laminated so that aluminum alloy layers having different contents of either Zn or Cu or Cu are joined together,
The aluminum alloy clad plate is a value obtained by averaging the contents of Mg, Zn, and Cu in each of the laminated aluminum alloy layers, and at least two of Mg, Zn, and Cu are within the content range. Including
Among the laminated aluminum alloy layers, an aluminum alloy layer containing Zn and Cu in the respective content ranges is laminated inside the aluminum alloy clad plate,
Among the laminated aluminum alloy layers, Mg is contained in the content range, and Zn: 2% by mass or less (including 0% by mass), Cu: 1.5% by mass or less (including 0% by mass) Are respectively laminated on both outer sides of the aluminum alloy clad plate,
The total number of laminated aluminum alloy layers of the aluminum alloy clad plate is 3 to 7, and the overall plate thickness is 1 to 5 mm.
As the characteristics of the aluminum alloy clad plate, the laminated aluminum after the clad plate was subjected to diffusion heat treatment at 450 ° C. for 1 hour, held at room temperature for 1 week, and further subjected to aging treatment at 120 ° C. for 2 hours. The hardness of each bonded interface portion between the alloy layers has a structure that is all higher than the hardness of each of the laminated aluminum alloy layers constituting this bonded interface portion,
That is.

  The gist of the aluminum alloy clad structure member of the present invention is that the aluminum alloy clad plate is press-molded, subjected to diffusion heat treatment at 450 ° C. × 1 hour, held at room temperature for 1 week, and further subjected to T6 treatment. By applying, it has a 0.2% proof stress of 400 MPa or more.

  In order to make the aluminum alloy clad plate have both high strength and high formability, the present invention is based on the above-described number of layers and plate thickness, and the aluminum alloy layers clad with each other are specified to contain a large amount of Mg and Zn. The composition. Thereby, first, the ductility of the material clad plate is increased to ensure press formability to the structural member. This increase in strength at the material stage is unnecessary because it hinders press formability.

  Then, after press forming the structural member, Mg, Zn, Cu, or the like contained in the aluminum alloy layers clad with each other is diffused into the texture of the laminated plates by heat treatment. Then, by diffusion of such elements, new composite precipitates (aging precipitates) formed of these Mg, Zn, Cu, or the like are precipitated at the joint interface portions to increase the strength. In this respect, the specific composition containing a large amount of Mg, Zn, etc. of the aluminum alloy layer to be clad is not only from the viewpoint of ductility, but also by the heat treatment, the composite precipitates due to the diffusion of the elements are formed at the joint interface portions. It is also a composition for increasing the strength by precipitation.

  In the present invention, in order to guarantee high strength due to the manifestation of such a mechanism, the clad plate at the material stage is subjected to diffusion heat treatment at 450 ° C. for 1 hour on the clad plate and then kept at room temperature for one week. Furthermore, the structure or characteristics after the artificial aging treatment at 120 ° C. for 2 hours is defined. And as this structure | tissue thru | or characteristic, it prescribes | regulates that the hardness of each joining interface part of the said laminated | stacked aluminum alloy layers is all higher than the hardness of the said laminated | stacked aluminum alloy layers. This is because when the composite precipitates are deposited at the joint interface portion, the hardness of the joint interface portion is higher than that of the inner structure of the plate.

  Therefore, if this hardness difference is measured by a method that can measure the hardness at a pinpoint, such as micro-Vickers hardness, the dispersion state such as the density of the composite precipitate (nano-sized fine precipitate) at the joint interface Even if it is not time-consumingly measured by TEM or the like, it becomes a standard that directly correlates with a desired increase in strength.

It is sectional drawing which shows the one aspect | mode of this invention clad board. It is sectional drawing which shows the other aspect of this invention clad board. It is sectional drawing which shows the other aspect of this invention clad board. It is sectional drawing which shows the other aspect of this invention clad board.

FIG. 1 shows the best mode for carrying out an aluminum alloy clad plate of the present invention (hereinafter also simply referred to as a clad plate) and an aluminum alloy clad structure member (hereinafter also simply referred to as a clad structure member) using the same. 2, 3 will be used for explanation. 1 to 3 only show a partial cross section in the width direction or rolling direction (longitudinal direction) of the clad plate of the present invention, and such a cross-sectional structure is the width direction or rolling direction of the clad plate of the present invention. It extends uniformly (uniformly) throughout.
In the following description of the embodiment of the present invention, a plate before cladding is referred to as an aluminum alloy plate, and a layer in the cladding plate after the plate is rolled and thinned is referred to as an aluminum alloy layer. Therefore, the significance of the definition of the aluminum alloy layer in the clad plate, such as the composition and the way of lamination, can be read as the significance of the definition of the aluminum alloy plate or ingot before being clad.

(Clad plate)
The clad plate of the present invention is an aluminum alloy layer including Mg, Zn, or Cu in a range that defines one or more of them, and the content of at least one of Mg, Zn, or Cu is different from each other. The aluminum alloy layers are laminated (cladded) with 3 to 7 layers (sheets). And the plate | board thickness of the whole laminated | stacked clad board is an aluminum alloy clad board which is the range of 1-5 mm.

  The layers to be laminated (the number of ingots or plates described later, the number of laminated layers) are more effective as multilayers in order to exhibit the characteristics of the clad plate, and should be three layers (three or more). is necessary. Two layers are not much different from a single plate, and there is no point in stacking them. On the other hand, as the characteristics of the clad plate, even if it is laminated more than 7 layers (7 sheets), a great improvement can not be expected, conversely, the production efficiency of the clad plate in the plate thickness range is greatly reduced, Not practical.

  In the case of a normal single plate such as the 7000 series, when ductility is increased as in the present invention, such as up to 14% by mass of Mg and up to 30% by mass of Zn, the ductility is extremely reduced and rolling cracks occur. Etc., and rolling becomes impossible. On the other hand, in the present invention, since it is a laminated plate (laminated ingot) of thin plates with different compositions, the ductility is high even if the alloy is made high, so cold rolling to the clad of the thin plate Can be hot-rolled. In other words, the clad plate of the present invention can be manufactured as a rolled clad plate by a normal rolling process.

  For this reason, before forming a clad plate by rolling, it is an aluminum alloy ingot or plate that includes one or more of Mg, Zn, and Cu, and includes at least Mg, Zn, or Cu. 3-7 pieces of aluminum alloy ingots or plates having different contents are laminated (clad). And like a normal rolling process, after performing a homogenization heat treatment as needed, it can be hot-rolled to make a clad plate. In order to further reduce the thickness within the plate thickness range, in addition to this, cold rolling is performed while performing intermediate annealing as necessary. These rolled clad plates are subjected to tempering (heat treatment such as annealing and solution treatment) as necessary to produce the clad plates of the present invention. Here, after each aluminum alloy ingot is separately homogenized and heat-treated, the ingots laminated and laminated may be hot-rolled after being reheated to the hot rolling temperature. Alternatively, each aluminum alloy ingot is separately homogenized and heat-rolled separately, and then individually hot-rolled, and if necessary, each intermediate-annealed or cold-rolled, and each individually has an appropriate thickness. Then, the plate materials laminated and laminated may be further cold-rolled to form a clad plate.

  The plate thickness of the entire clad plate of the present invention is in the range of 1 to 5 mm merely defines the plate thickness range that is widely used in the structural members of the above-mentioned transport aircraft. If the plate thickness is less than 1 mm, the required properties such as rigidity, strength, workability, and weldability required as a structural member are not satisfied. On the other hand, if the plate thickness exceeds 5 mm, it becomes difficult to press-form the structural member of the transport aircraft, and the weight reduction required as the structural member of the transport aircraft cannot be achieved due to the increase in weight.

Of course, the thickness (plate thickness) of the ingot to make the final clad plate thickness 1-5 mm by the rolling clad method depends on the number of layers (number of layers), the rolling rate, and the like. However, it is about 50-200 mm. Further, when the final clad plate has a thickness of 1 to 5 mm, the thickness of each laminated alloy layer depends on the number of laminated layers (number of layers) but is 0.1 to 2.0 mm (100 to 100 mm). About 2000 μm).
In addition, in the case of a process in which a homogenized heat treatment, hot rolling, or cold rolling is performed alone and then laminated to form a clad plate in the cold rolling process, the thickness of each plate material at the stage of lamination is the number of laminated sheets Although it depends on the number of layers and the rolling rate, it is about 0.5 to 5.0 mm.

(Aluminum alloy plate before being clad, ingot composition, composition of aluminum alloy layer after being clad and thinned, and composition of clad plate)
The composition of the aluminum alloy plate or ingot before being clad (laminated) or the aluminum alloy layer after being clad is Mg: 1.5 to 14% by mass, Zn: 2 to 30% by mass, Cu: 1. 5-6 mass% of 1 type or 2 types or more (1 type-3 types) shall be included. Among these, aluminum alloy layers (plates) containing one or two of Mg and Zn in the above-mentioned content range, and aluminum alloy layers (plates) having different contents of at least either Mg or Zn. It is particularly preferable from the viewpoint of combining formability and strength that the aluminum alloy clad plates are laminated together and contain either Mg or Zn in the content range.

  These aluminum alloy layers containing one or more of Mg: 1.5-14% by mass, Zn: 2-30% by mass, and Cu: 1.5-6% by mass are Al—Zn-based, Al— An Mg-based or Al-Cu-based binary aluminum alloy may be used. Further, it may be an Al—Zn—Mg-based, Al—Zn—Cu-based, Al—Mg—Cu-based ternary aluminum alloy, or an Al—Zn—Mg—Cu-based quaternary system. . By combining these, the final clad plate is laminated in a predetermined number so that Mg and Zn are included in the content range.

  The clad plate of the present invention may contain Si and Li which are selectively contained in the composition of the 7000 series aluminum alloy plate, ultra-super duralumin plate, 2000 series aluminum alloy plate and 8000 series aluminum alloy plate for the structural member. . Therefore, in the binary, ternary, and quaternary aluminum alloys referred to in the present invention, the balance other than the main elements of Mg, Zn, and Cu to be defined may be inevitable impurities and aluminum. In addition, after containing an impurity element or less that will be described below in an allowable amount or less, the remainder is selectively contained Si: 0.5 mass% or less, Li: 0.1 mass% or less, unavoidable impurities and aluminum It is also good.

  The present invention contemplates alternatives such as 7000 series aluminum alloy plates and ultra-duralumin plates (Al-5.5% Zn-2.5% Mg alloy), 2000 series aluminum alloy plates and 8000 series aluminum alloy plates for structural members. That is, at the stage of the material clad plate, the main objective is to greatly improve the ductility of these high strength materials and to increase the strength to the same level as these high strength materials after forming into a structural member. Therefore, the final composition of the clad plate is the same as the composition of the 7000 series aluminum alloy plate, ultra-super duralumin plate, 2000 series aluminum alloy plate and 8000 series aluminum alloy plate for the structural member as the composition of the entire clad plate. It is necessary to make the composition close to this.

  Accordingly, one or more of Mg, Zn, Cu, which are the main elements (essential elements) of the 7000 series aluminum alloy plate, ultra-duralumin plate, 2000 series aluminum alloy plate and 8000 series aluminum alloy plate for the structural member ( 2 or 3), Mg: 1.5 to 14% by mass, Zn: 2 to 30% by mass, Cu: 1.5 to 6% by mass, respectively. And as a final clad board, in order to guarantee these compositions, Mg: 1.5-14 mass%, Zn: 2-30 mass%, Cu: 1.5-6 mass%, 2 types or more (2 types or 3 types) shall be included. That is, at least two of Mg, Zn, and Cu as average values of the Mg, Zn, and Cu contents of the laminated aluminum alloy layers, which are average compositions of the entire aluminum alloy clad plate, respectively. A seed shall be included in each said content range. Here, the value obtained by averaging the contents of Mg, Zn, and Cu in each of the laminated aluminum alloy layers is the Mg, Zn of each aluminum alloy plate that constitutes each aluminum alloy layer of the clad plate. In the Cu content, the weighted arithmetic mean values of the Mg, Zn, and Cu contents obtained by weighting corresponding to the cladding ratio are used. For example, in a four-layer aluminum alloy clad plate, the clad ratio is 25% for each aluminum alloy layer if the aluminum alloy layers have an equal thickness. A weighted arithmetic mean value is calculated using this cladding ratio.

Significance of composition of clad aluminum alloy layer and clad plate:
In the present invention, after press forming the structural member, Mg, Zn, Cu, or the like contained in the aluminum alloy layers clad with each other is diffused into the texture of the laminated plates by heat treatment. And, by diffusion of such elements, new fine composite precipitates (aging precipitates) such as Zn—Mg and Zn—Mg—Cu based on these Mg, Zn or Cu are joined together. Interfacial structure control (ultra-high-density dispersion of nano-sized fine precipitates) is performed in order to increase the strength by precipitating at high density on the interface. Thus, the clad plate was subjected to diffusion heat treatment at 450 ° C. for 1 hour, held at room temperature for 1 week, and further laminated as a structure after being subjected to artificial aging treatment at 120 ° C. for 2 hours as T6 treatment. The strength of the clad plate is increased by having a structure in which the hardness of each joint interface between the aluminum alloy layers is higher than the hardness of each laminated aluminum alloy layer.

  In this respect, the layers to be laminated are aluminum alloy layers each including one or more of Mg, Zn, and Cu, and at least the contents of each of Mg, Zn, and Cu are included. Different aluminum alloy layers need to be present. That is, when the contents of Mg, Zn, and Cu are the same as each other, even if the contents of other elements in the layers are different, the mutual diffusion of the bonded layers of Mg, Zn, and Cu occurs. Since it does not occur, a new fine composite precipitate (aging precipitate) of Mg, Zn, and Cu cannot be deposited at a high density at each joint interface portion, and the strength cannot be increased.

  The specific composition containing a large amount of Mg, Zn, Cu, etc. in the aluminum alloy layer to be clad, and the layers laminated and joined to each other are made of aluminum alloy layers having different contents of at least Mg, Zn, or Cu. This is not only from the viewpoint of ductility, but is also a composition for increasing the strength by precipitating composite precipitates by diffusion of the elements at the joint interface portions by heat treatment.

  In the present invention, in order to guarantee high strength due to the manifestation of such a mechanism, the clad plate at the material stage is subjected to diffusion heat treatment at 450 ° C. for 1 hour on the clad plate and then kept at room temperature for one week. Then, as a structure after further performing an artificial aging treatment at 120 ° C. for 2 hours, the hardness of each bonded interface portion between the laminated aluminum alloy layers is all higher than the hardness of the laminated aluminum alloy layers. It is specified as high. This is because when the composite precipitates are deposited at the joint interface portion, the hardness of the joint interface portion is higher than that of the inner structure of the plate.

Therefore, for example, by measuring the hardness difference in a pinpoint manner, the hardness of the interfacial structure between the alloy layers, such as the commonly used micro Vickers hardness, and the internal structure of the other plate, It is a measure that directly correlates with the desired increase in strength. There is also a means to directly measure the high density dispersion state of nano-size sized fine precipitates at the bonding interface by TEM, but even if it is examined, the strength and density of nano-size sized fine precipitates, Factors such as size do not always correlate directly, but there is a difficulty in finding and identifying the correlated factors. In addition, the TEM measurement has a problem that requires a lot of effort, including the number of measurements. On the other hand, the measurement of the micro Vickers hardness is relatively simple, above all, the hardness of the interface portion or the hardness difference between the interface portion and the inside of the plate, even if the interface portion is a part of the clad plate, It correlates directly with the strength of the entire clad plate with good reproducibility.

  In the present invention, the average composition of the entire clad plate was also determined by weighting the Mg, Zn, and Cu contents of each laminated aluminum alloy layer corresponding to the clad ratio. As an arithmetic average value of each content of Cu, at least two of Mg, Zn, and Cu are in the content range, Mg: 1.5 to 14 mass%, Zn: 2 to 30 mass %, Cu: 1.5 to 6% by mass. Here, the composition of the entire clad plate is a value obtained by averaging the contents of Mg, Zn, and Cu of each laminated aluminum alloy layer for each element. Even if at least two of Mg, Zn, and Cu are included as an average composition of the entire clad plate, if the amount of each element is less than the lower limit and deviates from the prescribed composition, the clad plate diffuses at 450 ° C. for 1 hour. After heat treatment, after holding at room temperature for 1 week and further after artificial aging treatment at 120 ° C for 2 hours, the diffusion of Mg, Zn, Cu, etc. to the structure of each other laminated plate is insufficient To do.

  As a result, due to this diffusion, the amount of precipitation of these new composite precipitates (aging precipitates) formed of Mg, Zn, Cu, or the like at the joint interface portion is insufficient. For this reason, the hardness of each joining interface part of the laminated | stacked aluminum alloy layers does not become all higher than the hardness of each said laminated | stacked aluminum alloy layer. Therefore, an aluminum alloy clad structural member formed by press-molding this aluminum alloy clad plate cannot have a 0.2% proof stress of 400 MPa or more.

  On the other hand, as an average composition of the entire clad plate, the content of each Mg, Zn, Cu in each of the laminated aluminum alloy layers is determined even if it contains at least two of Mg, Zn, and Cu. When the arithmetic average value of the contents of Mg, Zn, and Cu obtained by weighting corresponding to the ratio exceeds the upper limit and deviates from the specified composition, the ductility of the clad plate is remarkably lowered. Accordingly, the press formability is reduced to a level equivalent to that of the 7000 series aluminum alloy plate or ultra-super duralumin plate, 2000 series aluminum alloy plate or 8000 series aluminum alloy plate for the structural member, and the meaning of the clad plate is lost.

(How to laminate the clad plates)
The clad plate of the present invention includes one or more of Mg: 1.5 to 14% by mass, Zn: 2 to 30% by mass, and Cu: 1.5 to 6% by mass, which are combined at the time of lamination. It is necessary to change the way of lamination depending on the composition of the aluminum alloy layers. A method of stacking will be described with reference to FIGS.

  FIG. 1 shows that an Al—Mg-based plate is used as both outermost layers (two outermost layers), and an Al—Zn-based plate is laminated inside each of them, and an Al—Mg-based plate is arranged at the center. This is an example in which a total of five layers are stacked.

  FIG. 2 also shows that Al—Mg-based plates are both outermost layers (two outermost layers), Al—Zn—Mg-based plates are stacked on the inner side, and an Al—Mg-based plate is arranged at the center. This is an example in which five layers are laminated in total.

  FIG. 3 shows that an Al—Mg-based plate is used as both outermost layers (two outermost layers), and an Al—Cu-based plate is laminated on each inner side, and an Al—Mg-based plate is arranged at the center. This is an example in which a total of five layers are stacked.

  FIG. 4 shows an Al—Mg-based plate as both outermost layers (two outermost layers), and an Al—Cu—Mg-based plate is laminated inside each, and an Al—Mg-based plate is arranged at the center. This is an example in which a total of five layers are laminated.

  Each of these FIGS. 1 to 4 is an aluminum alloy layer that includes plates stacked on each other within a range that defines one or more of Mg, Zn, and Cu, and is at least Mg, Zn, or Cu. This is an example of the present invention in which the aluminum alloy layers having different contents are used.

  In addition, in FIGS. 1 to 4, the Al—Zn system in FIG. 1 and the Al—Zn—Mg system in FIG. The aluminum alloy layers such as Al-Cu-based in FIG. 3 and Al-Cu-Mg-based in FIG. 4 are inferior in corrosion resistance. Therefore, in order to ensure the corrosion resistance of the cladding plate, the aluminum alloy layers are laminated so as to be inside the cladding plate. ing. When these aluminum alloy layers containing Zn and / or Cu are laminated so as to be on the outer side (surface side, surface layer side) of the clad plate, the clad plate and the content of Zn and Cu are large, so the clad As a result, the corrosion resistance of the clad structure member is lowered.

  Accordingly, in FIGS. 1 to 4, a clad plate containing Mg in the content range, such as an Al—Mg system, is laminated on both outer sides (both surface side and both surface layer sides) of the clad plate. However, even in the case of such an Al—Mg system or the like, when Zn and Cu are included in addition to Mg, the corrosion resistance is also lowered, so that the corrosion resistance is not greatly reduced. Zn: 2 mass% or less (0 mass%) And Cu: 1.5% by mass or less (including 0% by mass), respectively.

(Aluminum alloy composition)
Hereinafter, the meaning of the inclusion or regulation of each element as the composition of the aluminum alloy layer to be clad or the final clad plate will be individually described. In the case of the composition as the final clad plate, the content of each element is determined from the content of each element of a single plate, and the content of each element of each laminated plate (all plates). It is read as an average value of. The following% indication regarding content is the meaning of the mass%.

Mg: 1.5-14%
Mg, which is an essential alloy element, together with Zn, forms clusters (fine precipitates) in the structure of the clad plate or clad structure member to improve work hardening characteristics. Moreover, an aging precipitate is formed in the structure | tissue of a clad board or a clad structure member, or a joining interface part, and intensity | strength is improved. If the Mg content is less than 1.5%, the strength is insufficient, and if it exceeds 14%, casting cracks occur, the rollability of the clad plate (ingot) decreases, and the production of the clad plate becomes difficult.

Zn: 2 to 30%
Zn, which is an essential alloying element, together with Mg, forms clusters (fine precipitates) in the structure of the clad plate or clad structure member to improve work hardening characteristics. Moreover, an aging precipitate is formed in the structure | tissue of a clad board or a clad structure member, or a joining interface part, and intensity | strength is improved. If the Zn content is less than 2%, the strength is insufficient, and the balance between strength and formability also decreases. On the other hand, if Zn exceeds 30%, casting cracks occur, and the rollability of the clad plate (ingot) decreases, making it difficult to produce the clad plate. Even when it can be produced, the grain boundary precipitate MgZn ₂ increases and intergranular corrosion easily occurs, the corrosion resistance is remarkably deteriorated, and the moldability is also lowered.

Cu: 1.5-6%
Cu has an effect of improving the strength of the clad plate and the clad structure member. If the Cu content is less than 1.5%, this strength improvement effect is small. On the other hand, if the Cu content exceeds 6%, casting cracks occur, the rollability of the clad plate (ingot) decreases, and the production of the clad plate becomes difficult. Even when it can be manufactured, the corrosion resistance such as SCC resistance is significantly reduced.

Other elements:
Other elements other than those described are impurities. In addition to pure aluminum ingots, the inclusion of these impurity elements by using aluminum alloy scrap is assumed (allowed) as a melting raw material. Specifically, Fe: 0.5% or less, Si: 0.5% or less, Li: 0.1% or less, Zr: 0.3% or less, Mn: 1.0% or less, Cr: 0.3 %, Sn: 0.1% or less, and Ti: 0.1% or less, the inclusion is allowed without deteriorating the ductility and strength characteristics of the clad plate according to the present invention.

  Hereinafter, the present invention will be described more specifically with reference to examples. An aluminum alloy clad plate was produced by a rolling clad method under the production conditions described later on an ingot obtained by combining and laminating ingots having compositions corresponding to the aluminum alloy layers having the compositions shown in Table 1. The amount of Mg, Zn and Cu as the above-mentioned average composition of this clad plate was measured and calculated. Further, in order to evaluate the moldability of the clad plate, the clad plate is held at an average temperature rising rate of 20 ° C./second and an ultimate temperature of 450 ° C. for 1 second, and then rapidly cooled at a cooling rate of 30 ° C./second. The elongation (%) after the application was investigated. These results are shown in Table 2.

  The aluminum alloy clad plate was subjected to diffusion heat treatment at 450 ° C. for 1 hour, then held at room temperature for 1 week, and then subjected to artificial aging treatment at 120 ° C. for 2 hours. The internal hardness (HV) of each laminated board was investigated. The hardness is a commercially available micro Vickers hardness tester, and the hardness (HV) at any five locations of each joint interface and any five locations inside each laminated plate in the cross-section in the width direction of the clad plate. Each was measured and averaged. In each example, the thickness of each junction interface portion of the clad plate is about 30 to 50 μm or less from the diffusion distance of each element at the junction interface at 450 ° C. × 1 hour. In order to make the diagonal length of the indentation formed at the site where the hardness evaluation is performed at about 30 μm or less, the load was set to 10 g as the measurement condition of the micro Vickers.

  Assuming when used as a structural member, as shown in Table 2, after diffusion treatment at 450 ° C. × 1 hour, hold at room temperature for 1 hour, and then perform T6 treatment (artificial aging treatment), respectively, The 0.2% yield strength (MPa) of the alloy clad plate was investigated. These results are also shown in Table 2 (in Table 2, the aluminum alloy clad plate is also abbreviated as a clad plate).

(Manufacture of aluminum alloy clad plate)
The production of the aluminum alloy clad plate laminate was as follows. Aluminum alloy ingots having the compositions A to S shown in Table 1 were melted and cast, and separately subjected to homogenous heat treatment and hot rolling by a conventional method, and cold rolling as necessary, and the plate thicknesses were each 0.5. Each plate was adjusted to a range of ˜5.0 mm. These plate materials were superposed and laminated in each combination shown in Table 2, and after the reheating of the laminated plate material at 400 ° C. for 30 minutes, hot rolling was started at that temperature to obtain a clad plate. The clad plate was further cold-rolled while being subjected to intermediate annealing at 400 ° C. for 1 second, and finally subjected to final annealing at 400 ° C. for 1 second to obtain each clad plate thickness shown in Table 2 (total thickness of each layer) ) Clad plate. When the plate thickness of these final clad plates was 1 to 5 mm, the thickness of each laminated alloy plate was in the range of about 0.1 to 2.0 mm (100 to 2000 μm). Moreover, the clad ratio of the final clad plate was manufactured so that the thicknesses (cladding ratios) of the respective aluminum alloy layers were equal for the inventive examples 1 to 15 and comparative examples 16 to 25 in Table 2. On the other hand, the inventive examples 26 and 27 in Table 2 were manufactured so that the thicknesses of the respective aluminum alloy layers were different as described later.

  In the column of the aluminum alloy clad plate in Table 2, the total number of the plates of Table 1 was laminated together with the contents of Mg, Zn, and Cu, which are the above-mentioned average composition, as the entire aluminum alloy clad plate. The types of plates A to S shown in Table 1 as combinations of the plates are shown in the order from the top of the stacked layers. Here, each content of Mg, Zn, and Cu, which is an average composition of the aluminum alloy clad plate, was obtained by weighting corresponding to the cladding ratio, and each weighted arithmetic average of the contents of Mg, Zn, and Cu Value. In the case of Invention Examples 1 to 15 and Comparative Examples 16 to 25 in Table 2 where the thickness of each aluminum alloy layer is equal, the cladding ratio of each aluminum alloy layer is set to an equal ratio corresponding to the number of layers, and each of the above elements The weighted arithmetic mean value of the amount content was calculated. On the other hand, in Invention Examples 26 and 27 in Table 2, the weighted arithmetic mean value of the content of each element amount was calculated as the ratio of the uneven cladding ratio described later according to the different thickness of each aluminum alloy layer. .

  For example, with AEA or AGA, aluminum alloy layers of A in Table 1 are laminated on both outer sides of three clad plates, respectively, and each of the aluminum alloy layers of E or G in Table 1 is It means that it is laminated on one inner layer. In the other three-layer examples, if the symbols of the respective aluminum alloy layers are replaced with the symbols shown in Table 2, the same combination is obtained.

  In AIJA or LQRL, aluminum alloys layers of A or L in Table 1 are laminated on both outer sides of the four clad plates, respectively, and aluminum alloys of I and J or Q and R of Table 1 It means that the layers are laminated on the inner two layers of the clad plate in the order of description of I, J or Q, R from the top. In the other four-layer examples, if the symbols of the respective aluminum alloy layers are replaced with the symbols shown in Table 2, the same combination is obtained.

  In ADAEA or LNLNL, A or L aluminum alloy layers in Table 1 are respectively laminated on both outer sides of the five clad plates, and D, A, E or N, L, N in Table 1 It means that each aluminum alloy layer is laminated on the inner three layers of the clad plate from the top in the order of D, A, E or N, L, N. In the other five-layer examples, if the symbols of each aluminum alloy layer are replaced with the symbols shown in Table 2, the same combination is obtained.

  ADAEADA or AHAHAHA is the aluminum alloy layer of A in Table 1 laminated on both outer sides of the seven clad plates, and the aluminum alloy layers of D, A, E or H, A in Table 1 It means that it is laminated on the inner five layers of the clad plate from the top in the order of D, A, E, A, D or H, A, H, A, H. In the other seven-layer examples, if the symbols of each aluminum alloy layer are replaced with the symbols shown in Table 2, the same combination is obtained.

  Here, Invention Example 26 in Table 2 has the same number of laminations and lamination order as the three AEA layers of Invention Example 1, but the cladding ratio of each aluminum alloy layer is not equal to that of Invention Example 1. , [A plate thickness]: [E plate thickness]: [A plate thickness] are adjusted to have a clad ratio of 2: 3: 2, respectively, and the thickness of each aluminum alloy layer is adjusted to obtain a clad plate Is manufacturing. Inventive Example 27 in Table 2 has the same number of layers and the same stacking order as the five ADAEA layers of Inventive Example 7, but the clad ratio of each aluminum alloy layer is the same as that of Inventive Example 7. Rather, [A thickness]: [D thickness]: [A thickness]: [E thickness]: [A thickness] is 1: 3: 1: 1: 2 respectively. The clad plate is manufactured by adjusting the thickness of each aluminum alloy layer so that the clad ratio is obtained.

  In the view of the micro Vickers average hardness in Table 2, for example, in the interface portion, AE is a bonding interface portion in a plate of A and E, BH is a bonding interface portion in a plate of B and H, and LN is The joining interface part in the board of L and N is shown. In other examples, if the symbols of each aluminum alloy plate are replaced with the symbols shown in Table 2, the same combination is obtained.

  Moreover, in the micro Vickers average hardness of Table 2, for example, A: 65 in the inside is a measurement hardness of 65 HV inside the plate of A in Table 1, and E: 91 is a measurement inside the plate of E in Table 1. The hardness is 91 HV, which is smaller than the hardness 112 HV of the bonding interface AE. In other examples, if the symbols of each aluminum alloy plate are replaced with the symbols shown in Table 2, the same combination is obtained.

In Table 2, with respect to the hardness of the bonding interface, the same stacking combination (joining interface parts with the same combination of aluminum alloy layers) has the same hardness regardless of the upper and lower sides and the stacking order. It was.
For example, the hardness of the two interface portions in the AEA 3 layer of Invention Example 1 was the same value for the upper interface AE and the lower interface EA, which is the same combination of laminations, as shown in Table 2. Is representatively described only in the case of AE.
This is another example of the invention, for example, BH, HB (Invention 2), AG, GA (Invention 4), CG, GC (Invention 5), AE, EA (Invention 7, 13) , AH, HA (Invention Examples 8, 14), AD, DA (Invention Examples 7, 13, 15), CE, EC (Invention Examples 3, 15), AI, IA (Invention Example 9), AJ The same applies to JAs (Invention Example 10), AKs and KAs (Invention Example 11).
Further, for example, LN and NL (comparative examples 16, 24, and 25), LQ and QL (comparative example 17), LR and RL (comparative example 18), LS and SL (comparative example 19). MN, NM (Comparative Example 20), LO, OLs (Comparative Example 21), LP, PLs (Comparative Example 22) are the same.

  Invention Examples 1 to 15, 26, and 27 in Table 2 include one or more of Mg: 1.5 to 14% by mass, Zn: 2 to 30% by mass, and Cu: 1.5 to 6% by mass. Aluminum alloy layers, which are different from each other in content of at least either Mg, Zn, or Cu, are stacked on each other. And as a whole clad board, at least 2 sort (s) of Mg, Zn, Cu is included in the said content range. Moreover, the aluminum alloy layer containing Zn and Cu in the respective content ranges is laminated on the inner side of the clad plate, contains Mg in the content range, and Zn: 2 mass% or less, Cu: 1.5 mass % Are respectively laminated on both outer sides of the clad plate. Moreover, the total number of laminated clad plates is 3 to 7, and the overall plate thickness is 1 to 5 mm.

  The clad plate was subjected to diffusion heat treatment at 450 ° C. for 1 hour, held at room temperature for 1 week, and further subjected to aging treatment at 120 ° C. for 2 hours. , All the layers have a structure higher than the hardness of each of the laminated aluminum alloy layers constituting the bonded interface portion.

  As a result, the clad plate has an elongation of the clad plate after the heat treatment of 20% or more and exhibits high formability. In addition, the aluminum alloy clad plate has a high strength with a 0.2% proof stress of 400 MPa or more after the diffusion heat treatment, room temperature aging, and T6 treatment assuming a heat treatment after press forming the structural member.

  On the other hand, Comparative Examples 16 to 25 in Table 2 contain Mg, Zn, and Cu in the laminated aluminum alloy layer, although the lamination conditions such as the number of laminations, clad plate thickness, and lamination order are within the specified range. The amount is too small as specified in Table 1. As a result, as shown in Table 2, the content of Mg, Zn, and Cu as the whole clad plate is too much less than specified. For this reason, there are many cases where the average hardness of the bonding interface is smaller than the average hardness inside each layer and is out of specification. As a result, in these comparative examples, the elongation of the clad plate after the heat treatment is also 20% or more, but the 0.2% proof stress after the diffusion heat treatment, room temperature aging, and T6 treatment is also less than 300 MPa. Further, Comparative Examples 20 and 22 were not able to be produced due to cracking during rolling.

  ADVANTAGE OF THE INVENTION According to this invention, the contradiction with the formability in high intensity | strength levels, such as said 7000 series aluminum alloy board, can be solved, and the aluminum alloy clad board which combines high strength and high formability can be provided. For this reason, this invention is used suitably for the structural member for transport aircraft.

Claims (2)

An aluminum alloy clad plate in which a plurality of aluminum alloy layers are laminated,
Mg: from 1.5 to 14 mass%, Zn: 2 to 30 wt%, Cu: 1.5 to 6 wt% observed including one or more of the balance, and aluminum, the content range of A plurality of aluminum alloy layers that are Mg, Zn or Cu (including 0% by mass) and unavoidable impurities are laminated,
Or at least Mg, Zn or are stacked in such a manner that the content of either Cu different aluminum alloy layer is bonded to each other,
The aluminum alloy clad plate is a value obtained by averaging the contents of Mg, Zn, and Cu in each of the laminated aluminum alloy layers, and at least two of Mg, Zn, and Cu are within the content range. Including
Among the laminated aluminum alloy layers, an aluminum alloy layer containing Zn and Cu in the respective content ranges is laminated inside the aluminum alloy clad plate,
Among the laminated aluminum alloy layers, Mg is contained in the content range, and Zn: 2% by mass or less (including 0% by mass), Cu: 1.5% by mass or less (including 0% by mass) Are respectively laminated on both outer sides of the aluminum alloy clad plate,
The total number of laminated aluminum alloy layers of the aluminum alloy clad plate is 3 to 7, and the overall plate thickness is 1 to 5 mm.
As the characteristics of the aluminum alloy clad plate, the laminated aluminum after the clad plate was subjected to diffusion heat treatment at 450 ° C. for 1 hour, held at room temperature for 1 week, and further subjected to aging treatment at 120 ° C. for 2 hours. The hardness of each bonded interface portion between the alloy layers has a structure that is all higher than the hardness of each of the laminated aluminum alloy layers constituting this bonded interface portion,
An aluminum alloy clad plate characterized by the above. The aluminum alloy clad plate according to claim 1 is press-molded , subjected to diffusion heat treatment at 450 ° C. for 1 hour, held at room temperature for 1 week, and further subjected to T6 treatment, whereby 0.2% proof stress of 400 MPa or more is obtained. A method for producing an aluminum alloy clad structure member for producing an aluminum alloy clad structure member .

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