Aluminum alloy structure, heat bonding method, and aluminum alloy extruded material and method for producing same

Abstract

This aluminum alloy structure is obtained by heat-joining one member to be joined and another member to be joined, and is characterized in that: the one member to be joined contains 1.80-3.00 mass% of Si, 0.10-1.60 mass% of Mn, 0.01-0.70 mass% of Fe, and the remainder being Al and unavoidable impurities; the average crystal grain diameter of the outermost layer of the one member to be joined at the joining part of the one member to be joined and the other member to be joined is 200 [mu] m or less, and the average crystal grain diameter is 400 [mu] m or more in a cross-section at a depth of 100 [mu] m of the smallest-width portion of the one member to be joined. According to the present invention, it is possible to provide an aluminum alloy structure, an aluminum alloy extruded material, and a method for manufacturing the aluminum alloy extruded material, whereby bonding can be performed in a single layer, the manufacturing process can be simplified, bonding properties are good, and deformation during heat bonding can be suppressed.

Description

TECHNICAL FIELD

[0001] The present application relates to an aluminum alloy structure, a heating joining method, and an aluminum alloy extruded material and a manufacturing method thereof, and more particularly, to an aluminum alloy structure capable of being joined to other members by its own action without using a joining member such as a filler metal or a manufacturing method of an aluminum alloy extruded material. BACKGROUND

[0002] In manufacturing a structure such as a heat exchanger using aluminum alloy materials as constituent members, it is necessary to join the aluminum alloy materials to each other. As a joining method of the aluminum alloy materials, various methods are known, and among them, a brazing method is used most frequently.

[0003] As a method of manufacturing a heat exchanger or the like using a joining method of an aluminum alloy material based on a brazing method, for example, there is a method of using a brazing sheet of a clad material in which a filler material composed of an Al-Si alloy is clad (Patent Document 1). However, in manufacturing the clad material, there are manufacturing difficulties such as the need to manufacture each layer separately, further the need to stack and join them, and the manufacturing process becomes complicated.

[0004] In addition, as another method of manufacturing a heat exchanger or the like using a joining method of an aluminum alloy material based on a brazing method, there are known methods of using an aluminum alloy material coated with a powder filler material, a method of separately providing or coating a filler material such as a placed brazing material or a brazing paste to the portion to be joined after assembling each material, and the like (Patent Documents 2 and 3). However, even in these methods, in addition to the aluminum alloy material, a process of separately preparing and providing or coating the filler material is required, and there are manufacturing difficulties such as the manufacturing process becoming complicated.

[0005] Therefore, instead of the above-described method of using a brazing sheet of a clad material, a method of using an aluminum alloy material coated with a powder filler material, which makes the manufacturing process of the aluminum alloy material and the manufacturing process of the aluminum alloy structure complicated, as a method of making the manufacturing process of the aluminum alloy material and the manufacturing process of the aluminum alloy structure more simple, there is a method of using a single-layer brazing sheet (Patent Document 4).

[0006] PRIOR ART DOCUMENTS

[0007] PATENT DOCUMENTS

[0008] Patent Document 1: Japanese Patent Application Laid-Open No. 2008-303405

[0009] Patent Document 2: Japanese Patent Application Laid-Open No. 2011-136358

[0010] Patent Document 3: Japanese Patent Application Laid-Open No. H09-047892

[0011] Patent Literature 4: International Publication No. 2014 / 184880 SUMMARY

[0012] PROBLEMS TO BE SOLVED BY THE INVENTION

[0013] However, a single-layer brazing sheet is able to be joined by partially melting by itself, and thus there is a concern that the deformation of the material becomes significant at the time of heating.

[0014] In addition, a single-layer brazing sheet is joined to other members by the action of itself (liquid phase exuded from the base material) without using a joining member such as a filler metal or a filler metal, and thus the amount of liquid phase used in the brazing joint is small compared to the conventional method using a brazing sheet covered with a filler metal or the method using an aluminum alloy material coated with a powder filler metal, and thus there is a concern that the heating jointability is low.

[0015] Therefore, an object of the present application is to provide an aluminum alloy structure and an aluminum alloy extruded material which are able to be joined in a single layer, thereby enabling a manufacturing process to be simplified, the jointability to be good, and the deformation at the time of heating jointing to be suppressed.

[0016] SOLUTION TO THE PROBLEM

[0017] The present inventors and others have conducted intensive studies, and as a result, have invented an aluminum alloy structure and an aluminum alloy extruded material which are able to be joined in a single layer by controlling the alloy composition and the crystal structure as a joined member, thereby enabling a manufacturing process to be simplified, the jointability to be good, and the deformation at the time of heating jointing to be suppressed, and a manufacturing method thereof.

[0018] That is, the present application (1) provides an aluminum alloy structure which is obtained by heating joining one joined member composed of an aluminum alloy and another joined member composed of either one of an aluminum alloy and pure aluminum, characterized in that

[0019] The aforementioned one joined member contains 1.80 to 3.00 mass% of Si, 0.10 to 1.60 mass% of Mn, 0.01 to 0.70 mass% of Fe, the balance being Al and unavoidable impurities,

[0020] In the outermost layer of the aforementioned one joined member at the joint portion with the aforementioned another joined member, the average grain diameter is 200 μm or less, and in the cross section at the position of 100 μm in depth of the thinnest portion of the wall thickness of the aforementioned one joined member, the average grain diameter is 400 μm or more.

[0021] In addition, the present application (2) provides a heating joining method characterized in that it is a heating joining method of the aluminum alloy structure of (1), in which

[0022] The average grain diameter of the outermost layer of the surface to be joined at 575°C during heating and joining is 200 μm or less, and the average grain diameter of the cross section at a position 100 μm deep from the thinnest portion of the wall thickness is 400 μm or more.

[0023] Further, the present application (3) provides an aluminum alloy extruded material characterized by being an aluminum alloy extruded material having a heating and joining function in a single layer,

[0024] The aluminum alloy extruded material contains 1.80 to 3.00 mass% of Si, 0.10 to 1.60 mass% of Mn, 0.01 to 0.70 mass% of Fe, the balance being Al and unavoidable impurities,

[0025] The width of the thinnest portion of the wall thickness in a cross section orthogonal to the extrusion direction is 0.6 mm or more,

[0026] The average grain diameter of the outermost layer of the surface to be joined after a heating test of raising the temperature from 450°C to 575°C in 4 to 15 minutes and maintaining the temperature at 575 to 615°C for 5 to 40 minutes is 200 μm or less, and the average grain diameter of the cross section at a position 100 μm deep from the thinnest portion of the wall thickness is 400 μm or more.

[0027] Further, the present application (4) provides a manufacturing method of an aluminum alloy extruded material characterized by being a manufacturing method of the aluminum alloy extruded material of (3), the manufacturing method having the following steps:

[0028] a casting step of casting an ingot containing 1.80 to 3.00 mass% of Si, 0.10 to 1.60 mass% of Mn, 0.01 to 0.70 mass% of Fe, the balance being Al and unavoidable impurities; and

[0029] a hot extrusion step of performing hot extrusion on the ingot while the temperature of the ingot is 400°C or higher and 550°C or lower, to shape the width of the thinnest portion of the wall thickness in a cross section orthogonal to the extrusion direction to be 0.6 mm or more.

[0030] Further, the present application (5) provides the manufacturing method of an aluminum alloy extruded material of (4), characterized by further having a homogenization step of performing homogenization treatment of keeping the ingot at a temperature of 570°C or lower after the casting step.

[0031] Effects of the Invention

[0032] According to the present application, it is possible to provide an aluminum alloy structure and an aluminum alloy extruded material which can be joined in a single layer, thereby enabling simplification of the manufacturing process, good joining properties, and suppression of deformation during heating and joining. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the state of Al-Si alloy, a representative binary eutectic alloy.

[0034] Figure 2 This is an explanatory diagram illustrating the formation mechanism of the liquid phase in the aluminum alloy in the aluminum alloy used in the bonding of the aluminum alloy extrusion material of the present invention.

[0035] Figure 3 This is an explanatory diagram illustrating the formation mechanism of the liquid phase in the aluminum alloy in the aluminum alloy used in the bonding of the aluminum alloy extrusion material of the present invention.

[0036] Figure 4 This is a schematic diagram of the state of Al-Si alloy, a representative binary eutectic crystal.

[0037] Figure 5 The results are observed in the cross-sectional microstructure along the wall thickness direction after a heating test simulating the heating bonding of the aluminum alloy extruded material of the present invention.

[0038] Figure 6 The results are microstructural observations of the outermost layer of the aluminum alloy extruded material after a heating test simulating the heating bonding of the aluminum alloy extruded material of the present invention, with the cross-section perpendicular to the depth direction.

[0039] Figure 7 The microstructure observation results are obtained from a section perpendicular to the depth direction at a depth of 100 μm after a heating test simulating the heating bonding of the aluminum alloy extruded material of the present invention.

[0040] Figure 8 This is a diagram of the inverted T-shaped joint test. Detailed Implementation

[0041] The aluminum alloy structure of the present invention is characterized in that it is formed by thermally joining one bonding member made of aluminum alloy with another bonding member made of either aluminum alloy or pure aluminum. The aforementioned bonding member contains 1.80 to 3.00% by mass of Si, 0.10 to 1.60% by mass of Mn, 0.01 to 0.70% by mass of Fe, with the balance being Al and unavoidable impurities. In the outermost layer of the aforementioned bonding member at the joint between the aforementioned bonding member and the aforementioned other bonding member, the average grain diameter is 200 μm or less. In the cross-section at a depth of 100 μm in the thinnest part of the aforementioned bonding member, the average grain diameter is 400 μm or more.

[0042] The aluminum alloy structure of the present application is an aluminum alloy structure in which one joined member composed of an aluminum alloy is heat joined with another joined member composed of either an aluminum alloy or pure aluminum.

[0043] One joined member of the aluminum alloy structure of the present application is composed of an aluminum alloy. That is, one joined member is an aluminum alloy material formed of an aluminum alloy.

[0044] The aluminum alloy forming one joined member contains 1.80 to 3.00 mass% of Si, 0.10 to 1.60 mass% of Mn, 0.01 to 0.70 mass% of Fe, the balance being Al and unavoidable impurities.

[0045] Si is an element that generates a liquid phase of Al-Si system at the time of heat joining and contributes to joining. If the content of Si of the aluminum alloy is less than 1.80 mass%, a sufficient amount of liquid phase cannot be generated, and the joinability is reduced, and in addition, if the content of Si exceeds 3.00 mass%, a large amount of elemental Si is contained, and in the manufacturing process of the aluminum alloy material, the fear of tool wear becomes significant. Therefore, the content of Si of the aluminum alloy forming one joined member is specified to be 1.80 to 3.00 mass%. The lower limit value of the content of Si of the aluminum alloy forming one joined member is preferably 2.00 mass%. In addition, the upper limit value of the content of Si of the aluminum alloy forming one joined member is preferably 2.80 mass%. The content of Si can be set to a range combining the above upper limit value and lower limit value.

[0046] Mn is an element that adjusts the crystal structure of the aluminum alloy material and contributes to improvement of heat joinability and suppression of deformation at the time of heat joining. If the content of Mn of the aluminum alloy is less than 0.10 mass%, the grain diameter of the present application cannot be obtained, and the deformation at the time of heat joining becomes large, and in addition, if the content of Mn exceeds 1.60 mass%, the deformation resistance of the aluminum alloy material becomes large, and the fear of difficulty in processing in the manufacturing process of the aluminum alloy material arises. Therefore, the content of Mn of the aluminum alloy forming one joined member is specified to be 0.10 to 1.60 mass%. The lower limit value of the content of Mn of the aluminum alloy forming one joined member is preferably 0.20 mass%, more preferably 0.30 mass%. In addition, the upper limit value of the content of Mn of the aluminum alloy forming one joined member is preferably 1.40 mass%, more preferably 1.20 mass%, more preferably 1.00 mass%, more preferably 0.80 mass%. The content of Mn can be set to a range combining the above upper limit value and lower limit value.

[0047] Fe is an element that contributes to improvement in strength of the aluminum alloy material. If the content of Fe in the aluminum alloy is less than 0.01 mass%, an aluminum base metal of extremely high purity needs to be used for the production, and the cost increases. In addition, if the content of Fe exceeds 0.70 mass%, an Al-Fe-Si compound is generated, and the amount of Si that contributes to the generation of liquid phase at the time of heat bonding decreases, thereby reducing the heat bonding property. Therefore, the content of Fe in the aluminum alloy that forms one bonded member is specified to be 0.01 to 0.70 mass%. The lower limit value of the content of Fe in the aluminum alloy that forms one bonded member is preferably 0.05 mass%, more preferably 0.10 mass%, and even more preferably 0.15 mass%. In addition, the upper limit value of the content of Fe in the aluminum alloy that forms one bonded member is preferably 0.60 mass%, more preferably 0.50 mass%, and even more preferably 0.40 mass%. The content of Fe can be set to a range combining the above-described upper limit value and lower limit value.

[0048] The other bonded member of the aluminum alloy structure of the present application is composed of an aluminum alloy or pure aluminum. That is, the other bonded member is an aluminum alloy material or a pure aluminum material, and is formed of an aluminum alloy or pure aluminum. In the case where the other bonded member is composed of an aluminum alloy, the other bonded member can be of the same alloy composition as the aluminum alloy material that forms one bonded member, or can be of a different alloy composition.

[0049] Next, the metallographic structure of the aluminum alloy structure of the present application is described.

[0050] In the metallographic structure of one bonded member of the aluminum alloy structure of the present application, in order to improve the heat bonding property, the crystal grains are made fine at the bonding surface, and in order to suppress deformation at the time of heat bonding, the crystal grains inside the material are made coarse. These metallographic structures should actually be achieved just before the liquid phase is generated. However, the aforementioned metallographic structures are generally maintained after the heat bonding is completed, and therefore the aforementioned metallographic structures can be confirmed by any one of the structure after the heat bonding, the material on which a heat test simulating the heat bonding is performed, and the material that is heated to just before the liquid phase is generated and then cooled. One mode of heat treatment is a mode in which heating at an average temperature increase rate of 5 to 100°C / minute to 580 to 620°C is performed, and then heating at 580 to 620°C for about 0 to 20 minutes is performed, and then cooling is performed.

[0051] In the joining portion of one joined member to another joined member of the aluminum alloy structure of the present application, the average grain diameter of the outermost layer of one joined member is 200 μm or less. The average grain diameter of the outermost layer is measured in a section at a depth of 0 to 10 μm from the surface of the joining surface of one joined member, that is, a section perpendicular to the depth direction at a depth of 0 to 10 μm. However, in the joining portion, the position of the surface of one joined member is sometimes not clearly determined due to the presence of a liquid phase generated from one joined member. In this case, the average grain diameter of the outermost layer can also be measured in a section at a depth of 0 to 10 μm from the surface of one joined member in a region near the joining portion, which is considered to be equivalent to the joining surface of one joined member.

[0052] The average grain diameter of the outermost layer affects the heating jointability at the time of production of the aluminum alloy structure. In the case where the average grain diameter of the outermost layer is greater than 200 μm, the heating jointability at the time of production of the aluminum alloy structure is reduced. That is, at the time of heating jointing, a liquid phase of Al-Si system is generated at the grain boundaries of one joined member, the liquid phase is supplied to the joining portion as a path of the grain boundaries, whereby the liquid phase is filled into the joining portion and solidified, thereby performing jointing, but in the case where the average grain diameter of the outermost layer of one joined member is large, the grain boundaries are few, and thus the amount of supply of the liquid phase to the joining portion is reduced, and there is a concern that jointing becomes insufficient. For the above reason, the average grain diameter of the outermost layer of one joined member is specified to be 200 μm or less. The average grain diameter of the outermost layer of one joined member is preferably 180 μm or less, more preferably 160 μm or less, and still more preferably 140 μm or less.

[0053] In the section at a depth of 100 μm of the thinnest portion of one joined member of the aluminum alloy structure of the present application, the average grain diameter is 400 μm or more. The average grain diameter of the section at a depth of 100 μm of the thinnest portion is measured in a section at a depth of 100 μm from the surface of one joined member, that is, a section perpendicular to the depth direction at a depth of 100 μm.

[0054] The average grain diameter of the cross section at the position of 100 μm in depth of the thinnest wall thickness portion affects deformation at the time of heating bonding. When the average grain diameter of the cross section at the position of 100 μm in depth of the thinnest wall thickness portion is less than 400 μm, deformation at the time of heating bonding becomes significant. That is, when Al-Si-based liquid phase is generated at the grain boundary at the time of heating bonding, a large amount of grain boundary slip is generated in the case where the average grain diameter is small, and the deformation amount becomes large in the thinnest wall thickness portion where the rigidity is particularly low, and thus the deformation amount is greatly affected, and there is a concern that the dimensional specifications are not satisfied. For the above reasons, the average grain diameter of the cross section at the position of 100 μm in depth of the thinnest wall thickness portion is specified to be 400 μm or more.

[0055] Note that the bonding surface of one bonded member of the aluminum alloy structure of the present application and the thinnest wall thickness portion can be the same position or different positions.

[0056] From the viewpoint of deformation resistance, the width of the thinnest wall thickness portion of one bonded member of the aluminum alloy structure of the present application is preferably 0.6 mm or more. When the width is less than 0.6 mm, the rigidity of the material decreases, and there is a concern that the metallographic structure of the present application cannot be obtained.

[0057] The heating bonding method of the present application is characterized in that it is a heating bonding method of the aluminum alloy structure of the present application, in which the average grain diameter of the outermost layer of the surface to be bonded of the metallographic structure at 575°C at the time of heating bonding is 200 μm or less, and the average grain diameter of the cross section at the position of 100 μm in depth of the thinnest wall thickness portion is 400 μm or more.

[0058] That is, the heating bonding method of the present application is a heating bonding method in which one bonded member and another bonded member are heated and bonded in order to obtain the aluminum alloy structure of the present application, and in the heating for the heating bonding of the one bonded member and the another bonded member, the average grain diameter of the outermost layer of the surface to be bonded of the metallographic structure of the one bonded member is 200 μm or less when the temperature of the one bonded member reaches 575°C, and the average grain diameter of the cross section at the position of 100 μm in depth of the thinnest wall thickness portion is 400 μm or more.

[0059] In the heat bonding method of the present application, 575°C is the temperature before a liquid phase is about to be generated in a member to be bonded. Thus, the heat bonding method of the present application is a heat bonding method in which, with respect to a metallographic structure before a liquid phase is about to be generated, the average grain diameter of the outermost layer of the surface to be bonded is made 200 μm or less, thereby forming many liquid phase supply paths in the surface layer, making the solderability good, and the average grain diameter of the cross section at a position 100 μm deep from the thinnest portion of the wall thickness is made 400 μm or more, thereby preventing grain boundary sliding in the interior of the material and reducing deformation. Also, the metallographic structure formed at 575°C is substantially maintained even after subsequent heating and cooling.

[0060] In the heat bonding method of the present application, for example, by heating a member to be bonded manufactured by the manufacturing method of a member to be bonded described later at an average temperature increase rate of 5 to 100°C / min to 580 to 620°C and maintaining it at 580 to 620°C for about 0 to 20 minutes, the average grain diameter of the outermost layer of the surface to be bonded of the metallographic structure of the member to be bonded can be made 200 μm or less, and the average grain diameter of the cross section at a position 100 μm deep from the thinnest portion of the wall thickness can be made 400 μm or more.

[0061] The aluminum alloy extruded material of the present application is an aluminum alloy extruded material characterized by being an aluminum alloy extruded material having a heat bonding function in a single layer, containing 1.80 to 3.00 mass% of Si, 0.10 to 1.60 mass% of Mn, 0.01 to 0.70 mass% of Fe, the balance being Al and unavoidable impurities, having a width of the thinnest portion of the wall thickness in a cross section at right angles to the extrusion direction of 0.6 mm or more, having an average grain diameter of the outermost layer of the surface to be bonded of 200 μm or less after a heating test of increasing the temperature from 450°C to 575°C in 4 to 15 minutes and maintaining it at 575 to 615°C for 5 to 40 minutes, and having an average grain diameter of the cross section at a position 100 μm deep from the thinnest portion of 400 μm or more.

[0062] The aluminum alloy extruded material of the present application is composed of an aluminum alloy. That is, the aluminum alloy extruded material of the present application is an aluminum alloy material, formed of an aluminum alloy.

[0063] The aluminum alloy extruded material of the present invention has a single-layer heat-bonding function. That is, the aluminum alloy extruded material of the present invention can be bonded using the liquid phase generated inside the aluminum alloy material by heating. Therefore, although it is a single layer, it is an aluminum alloy extruded material that can be bonded to other components without using pre-applied brazing filler metal or other bonding materials (hereinafter, it is also described as a single-layer bonded aluminum alloy extruded material). In detail, the aluminum alloy extruded material of the present invention is an aluminum alloy extruded material with a single-layer heat-bonding function at a temperature where the liquid phase fraction is 5.0% or more and 35.0% or less (an aluminum alloy extruded material with a single-layer heat-bonding function).

[0064] Single-layer bonded aluminum alloy extrusions must be bonded at a temperature where the ratio of the mass of the liquid phase generated within the aluminum alloy to the total mass of the aluminum alloy (hereinafter referred to as the "liquid phase ratio") is 5% or more and 35% or less. If the liquid phase ratio exceeds 35%, the amount of liquid phase generated is excessive, and the aluminum alloy cannot maintain its shape, resulting in large deformation. On the other hand, when the liquid phase ratio is less than 5%, bonding becomes difficult. A preferred liquid phase ratio is 5% to 30%, and a more preferred liquid phase ratio is 10% to 20%.

[0065] The formation mechanism of the liquid phase is explained. Figure 1 The diagram schematically illustrates the phase diagram of an Al-Si alloy, a representative binary eutectic alloy. When an aluminum alloy with a Si concentration of c1 is heated, liquid phase formation begins at a temperature T1 near the eutectic temperature (solid line temperature) Te. Below the eutectic temperature Te, as... Figure 2 As shown in (a), the precipitates are distributed within the matrix separated by grain boundaries. Here, if the formation of the liquid phase begins, then as... Figure 2 As shown in (b), the grain boundaries with higher segregation of precipitates melt and become a liquid phase. Then, as... Figure 2 As shown in (c), Si precipitates, which are the main additive element, dispersed in the aluminum alloy matrix, and the periphery of the intermetallic compounds melt into spherical shapes to form a liquid phase. Furthermore, as... Figure 2 As shown in (d), the spherical liquid phase generated in the matrix, due to interfacial energy, undergoes resolution in the matrix over time and with increasing temperature, and then migrates towards the grain boundaries and surface through diffusion within the solid phase. Next, as... Figure 1 As shown in the diagram, when the temperature rises to T2, the amount of liquid phase increases according to the phase diagram. Figure 1 As shown, in an aluminum alloy material where the Si concentration is less than the maximum solid solution limit concentration c2, liquid phase formation begins near the solidus temperature Ts2. However, unlike the case of c1, the microstructure before melting is as follows... Figure 3 As shown in (a), sometimes no crystals are present in the matrix. In this case, as... Figure 3(b) of FIG. 1, melting first occurs in the grain boundary to become a liquid phase, and then, as shown in (c) of FIG. 1, a liquid phase is generated from a portion where the solute element concentration is locally high in the matrix. As shown in (d) of FIG. 1, the spherical liquid phase generated in the matrix is re-dissolved in the matrix over time and with a temperature rise due to the interfacial energy, and moves toward the grain boundary and the surface by intragranular diffusion. When the temperature rises to T3, the amount of liquid phase increases according to the phase diagram. Thus, the joining in the present application utilizes the liquid phase generated by partial melting inside the single-layer joining aluminum alloy extruded material, and can achieve a balance between joining and shape maintenance. Figure 3 Figure 3

[0066] The behavior of the metallographic structure from the generation of the liquid phase to the joining will be described. The single-layer joining aluminum alloy extruded material in which the liquid phase is generated and the aluminum alloy object material to be joined are combined, and they are heated at a temperature at which the liquid phase ratio is 5.0% or more and 35.0% or less. Then, when the joint portion is observed with a microscope, as described above, the small amount of liquid phase generated on the surface of the single-layer joining aluminum alloy extruded material in the joining fills the gap of the aluminum alloy object material in which the oxidation film is destroyed due to the action of flux or the like. Next, the liquid phase located near the joining interface of the two alloy materials gradually moves into the aluminum alloy object material, and along with this, the grains of the solid phase α phase of the single-layer joining aluminum alloy extruded material which is in contact with the joining interface gradually grow into the aluminum alloy object material. On the other hand, the grains of the aluminum alloy object material also gradually grow toward the single-layer joining aluminum alloy extruded material side. Then, the structure of the single-layer joining aluminum alloy extruded material becomes the structure of the aluminum alloy object material into which the single-layer joining aluminum alloy extruded material enters, and is joined. Therefore, no metallographic structure other than the single-layer joining aluminum alloy extruded material and the aluminum alloy object material is generated at the joining interface.

[0067] On the other hand, in the case of joining the aluminum alloy object material by brazing heating using the brazing sheet coated with the filler material, a fillet is formed at the joint portion, and eutectic structures are observed, and a joining structure different from the case of joining the aluminum alloy object material by brazing heating using the single-layer joining aluminum alloy extruded material is formed. That is, in the case of joining the aluminum alloy object material by brazing heating using the brazing sheet coated with the filler material, the liquid phase filler material fills the joint portion to form a fillet, and therefore, a eutectic structure different from the surrounding portion is formed at the joint portion. In addition, in the welding method, melting occurs locally at the joint portion, and therefore, a metallographic structure different from other portions is formed.

[0068] Thus, in the case of joining the aluminum alloy object material by heating using the single-layer joining aluminum alloy extruded material, the metallographic structure of the joint portion is composed of only the metallographic structures of the two joined members, or the metallographic structure in which the two joined members are integrated, and in this respect, the joining structure is different from the case of using the brazing sheet coated with the filler material and the case based on welding.​​

[0069] Moreover, due to such joining behavior, in the case where the single-layer joining aluminum alloy extruded material is used to perform heat joining with the aluminum alloy object material, shape change in the vicinity of the joining portion after the joining process hardly occurs. That is, in the case where the single-layer joining aluminum alloy extruded material is used to perform heat joining with the aluminum alloy object material, shape change after joining such as a weld bead in a welding method, a fillet in a brazing method hardly occurs.

[0070] In the present application, it is extremely difficult to measure the actual liquid phase ratio of the single-layer joining aluminum alloy extruded material in heating. Therefore, the liquid phase ratio prescribed in the present application is calculated by equilibrium calculation. Specifically, it is calculated from the alloy composition and the maximum temperature reached at the time of heating by a thermodynamic equilibrium calculation software such as Thermo-Calc (registered trademark) manufactured by Thermo-Calc Software AB Co.

[0071] Based on Figure 4 , the relationship between the liquid phase ratio and the temperature is explained. Figure 4 is a graph obtained by deforming Figure 1 . In Figure 4 , both a line (hereinafter, referred to as "solidus line 1") extending in parallel with the horizontal axis at the temperature Te and a line (hereinafter, referred to as "solidus line 2") dividing the boundary with the α phase and extending from the left end portion of the solidus line 1 to the vertical axis at 660°C indicate the solidus. In addition, both a line (hereinafter, referred to as "liquidus line 1") extending from 660°C of the vertical axis to the lower right and meeting the aforementioned solidus line 1 and a line dividing the boundary with (Si + liquid phase) and extending to the upper right from the aforementioned meeting position indicate the liquidus.

[0072] Here, a point of the temperature T2 is set as P0, a line passing through P0 and extending in parallel with the horizontal axis of the graph is drawn, an intersection with the liquidus line 1 is set as P1, and an intersection with the solidus line 2 is set as P2. The Al-Si alloy having the Si concentration of C1 is in a state where the liquid phase and the solid phase coexist at the temperature T2, the Si concentration in the liquid phase becomes the concentration C P1 at the point P1, and the Si concentration in the solid phase becomes the concentration C P2 at the point P2. Moreover, the proportion of the mass of the liquid phase with respect to the total mass at the temperature T2, that is, the liquid phase ratio becomes the ratio of the length of the line segment P0 to P2 to the length of the line segment P1 to P2.

[0073] As described above, based on Figure 1 and Figure 4The phase diagram of the binary alloy is plotted to obtain the liquidus ratio from the alloy composition and temperature. Also, in the multicomponent system of three or more components, the phase diagram is plotted based on the state diagram according to the alloy composition and temperature, and thus the liquidus ratio is obtained even in the multicomponent system of three or more components. Note that the phase diagram of the multicomponent system of three or more components is difficult to obtain with the naked eye, and thus the liquidus ratio is obtained by using the thermodynamic equilibrium calculation software Thermo-Calc. Figure 4 Such a simple X-Y plane diagram is shown, but the liquidus ratio can be obtained by computer calculation by using the thermodynamic equilibrium calculation software Thermo-Calc.

[0074] The joined member combined with the aluminum alloy extruded material of the present application is composed of an aluminum alloy or pure aluminum. That is, the joined member combined with the aluminum alloy extruded material of the present application is an aluminum alloy material or a pure aluminum material, and is formed of an aluminum alloy or pure aluminum. In the case where the aluminum alloy material forming the joined member combined with the aluminum alloy extruded material of the present application is composed of an aluminum alloy, the aluminum alloy material forming the joined member combined with the aluminum alloy extruded material of the present application can be the same alloy composition as the aluminum alloy material forming the aluminum alloy extruded material of the present application, or can be a different alloy composition.

[0075] The aluminum alloy forming the aluminum alloy extruded material of the present application contains 1.80 to 3.00 mass% of Si, 0.10 to 1.60 mass% of Mn, 0.01 to 0.70 mass% of Fe, the balance being Al and inevitable impurities.

[0076] Si is an element that generates a liquid phase of Al-Si system at the time of heating joining, and contributes to joining. If the content of Si in the aluminum alloy is less than 1.80 mass%, a sufficient amount of liquid phase cannot be generated, and the joinability is reduced, and if the content of Si exceeds 3.00 mass%, a large amount of elemental Si is contained, and in the manufacturing process of the aluminum alloy material, the tool wear is worried to become significant. Therefore, the content of Si in the aluminum alloy forming the aluminum alloy extruded material of the present application is specified to be 1.80 to 3.00 mass%. The lower limit value of the content of Si in the aluminum alloy forming the aluminum alloy extruded material of the present application is preferably 2.00 mass%. Also, the upper limit value of the content of Si in the aluminum alloy forming the aluminum alloy extruded material of the present application is preferably 2.80 mass%. The content of Si can be set to the range combined with the above upper and lower limit values.

[0077] Mn is an element that adjusts the crystal structure of the aluminum alloy material, and is useful for improving the heat bonding property and suppressing deformation at the time of heat bonding. If the content of Mn in the aluminum alloy is less than 0.10 mass%, the grain diameter of the present application cannot be obtained, and the deformation at the time of heat bonding becomes large. In addition, if the content of Mn exceeds 1.60 mass%, the deformation resistance of the aluminum alloy material becomes large, and it is feared that the working in the manufacturing process of the aluminum alloy material becomes difficult. Therefore, the content of Mn in the aluminum alloy that forms the aluminum alloy extruded material of the present application is specified to be 0.10 to 1.60 mass%. The lower limit value of the content of Mn in the aluminum alloy that forms the aluminum alloy extruded material of the present application is preferably 0.20 mass%, more preferably 0.30 mass%. In addition, the upper limit value of the content of Mn in the aluminum alloy that forms the aluminum alloy extruded material of the present application is preferably 1.40 mass%, more preferably 1.20 mass%, more preferably 1.00 mass%, more preferably 0.80 mass%. The content of Mn can be set to the range combined with the above upper limit value and lower limit value.

[0078] Fe is an element that is useful for improving the strength of the aluminum alloy material. If the content of Fe in the aluminum alloy is less than 0.01 mass%, an aluminum base metal of extremely high purity needs to be used for the manufacturing, and the cost rises. In addition, if the content of Fe exceeds 0.70 mass%, an Al-Fe-Si-based compound is generated, and the amount of Si that is useful for the generation of liquid phase at the time of heat bonding decreases, and thus the heat bonding property decreases. Therefore, the content of Fe in the aluminum alloy that forms the aluminum alloy extruded material of the present application is specified to be 0.01 to 0.70 mass%. The lower limit value of the content of Fe in the aluminum alloy that forms the aluminum alloy extruded material of the present application is preferably 0.05 mass%, more preferably 0.10 mass%, more preferably 0.15 mass%. In addition, the upper limit value of the content of Fe in the aluminum alloy that forms the aluminum alloy extruded material of the present application is preferably 0.60 mass%, more preferably 0.50 mass%, more preferably 0.40 mass%. The content of Fe can be set to the range combined with the above upper limit value and lower limit value.

[0079] The width of the thinnest portion of the wall thickness in the cross section of the aluminum alloy extruded material of the present application that is perpendicular to the extrusion direction is 0.6 mm or more. In the case where the width is less than 0.6 mm, the rigidity of the material decreases, and it is feared that the metallographic structure of the present application cannot be obtained.

[0080] Next, the metallographic structure of the aluminum alloy extruded material of the present application is described.

[0081] In the metallographic structure of the aluminum alloy extruded material of the present application, in order to improve the heating joint property, the grains are made fine at the joint surface, and in order to suppress deformation at the time of heating joint, the grains inside the material are made coarse. These metallographic structures should actually be achieved just before the liquid phase is generated. However, the aforementioned metallographic structures are generally maintained after the heating joint is completed, and therefore the aforementioned metallographic structures can be confirmed by any one of the structure after the heating joint, the material that has performed a heating test simulating the heating joint, and the material that has been heated to just before the liquid phase is generated and then cooled. One way of the heat treatment that immediately cools after heating to just before the liquid phase is generated is the following: heating to 580°C to 620°C at an average temperature increase rate of 5 to 100°C / minute, then performing heating at 580°C to 620°C for 0 minutes to about 20 minutes, and then performing cooling.

[0082] The average grain diameter of the surface layer of the surface to be joined after the heating test of the aluminum alloy extruded material of the present application, in which the temperature is increased from 450°C to 575°C in 4 to 15 minutes and maintained at 575°C to 615°C for 5 to 40 minutes, is 200 μm or less. The average grain diameter of the surface layer is measured at a cross section of 0 to 10 μm in depth from the surface of the surface to be joined (i.e., a cross section perpendicular to the depth direction at a position of 0 to 10 μm in depth from the surface of the surface to be joined).

[0083] The average grain diameter of the surface layer affects the heating joint property at the time of production of the aluminum alloy structure. In the case where the average grain diameter of the surface layer is greater than 200 μm, the heating joint property at the time of production of the aluminum alloy structure is reduced. That is, at the time of heating joint, a liquid phase of Al-Si is generated at the grain boundaries of the surface to be joined, the liquid phase is supplied to the joint portion using the grain boundaries as a path, and thus the liquid phase is filled into the joint portion and solidified, thereby performing the joint, but in the case where the average grain diameter of the surface layer of the surface to be joined is large, the grain boundaries are few, and therefore the amount of supply of the liquid phase to the joint portion is reduced, and there is a concern that the joint becomes insufficient. For the above reason, the average grain diameter of the surface layer of the surface to be joined is specified to be 200 μm or less. The average grain diameter of the surface layer of the surface to be joined is preferably 180 μm or less, more preferably 160 μm or less, and more preferably 140 μm or less.

[0084] The aluminum alloy extruded material of the present invention, after undergoing a heating test in which the temperature is raised from 450°C to 575°C for 4 to 15 minutes and held at 575 to 615°C for 5 to 40 minutes, has an average grain diameter of 400 μm or more in a cross-section at a depth of 100 μm in the thinnest part. The average grain diameter of the cross-section at a depth of 100 μm in the thinnest part is measured by taking the surface of the surface to be joined as the depth reference (zero position) in a cross-section at a depth of 100 μm along the surface of the surface to be joined (i.e., a cross-section perpendicular to the depth direction at a depth of 100 μm).

[0085] The average grain diameter of the cross-section at a depth of 100 μm in the thinnest part of the wall affects the deformation during heat bonding. When the average grain diameter of the cross-section at a depth of 100 μm in the thinnest part of the wall is less than 400 μm, the deformation during heat bonding becomes significant. That is, during heat bonding, when an Al-Si liquid phase forms at the grain boundaries, a large amount of grain boundary slip occurs when the average grain diameter is small. Since the thinnest part of the wall has particularly low rigidity, it is greatly affected by this slip, resulting in greater deformation and concerns about not meeting dimensional specifications. Based on the above reasons, the average grain diameter of the cross-section at a depth of 100 μm in the thinnest part of the wall is specified to be 400 μm or more.

[0086] Furthermore, the bonding surface of the aluminum alloy extruded material of the present invention and the thinnest part of the wall thickness can be at the same location or at different locations.

[0087] As an example of the metallographic structure of the aluminum alloy extruded material of the present invention, the microstructure of the thinnest part of the aluminum alloy extruded material to be joined after a heating test simulating heat joining is shown below. Figures 5-7 . Figure 5 It is the microstructure of a cross-section parallel to the extrusion direction and the wall thickness direction. The surfaces near the joints exhibit fine recrystallized structures, while the interior of the material has coarse recrystallized structures. Figure 6 It is the microstructure of the outermost layer in a cross-section perpendicular to the depth direction. It is a fine recrystallized structure, suitable for heat bonding. Figure 7 It is the microstructure of a section perpendicular to the depth direction at a depth of 100 μm. It is a coarse recrystallized structure, which is effective in suppressing deformation during heat bonding.

[0088] It should be noted that the average grain diameter in this invention is the average grain diameter measured according to the intercept method of JIS G 0551.

[0089] Thus, the aluminum alloy extruded material of the present application has a metallographic structure in which, when heating from 450°C to 575°C in 4 to 15 minutes and holding at 575 to 615°C for 5 to 40 minutes, the average grain diameter of the surface layer of the surface to be joined is 200 μm or less, and the average grain diameter of the cross section at a position 100 μm deep from the thinnest wall thickness is 400 μm or more.

[0090] Further, the aluminum alloy extruded material of the present application has a metallographic structure as described above, and thus, by performing a heat treatment of heating to immediately before the liquid phase is generated and then cooling, for example, by performing a heat treatment of heating to 580 to 620°C at an average heating rate of 5 to 100°C / min and holding at 580 to 620°C for about 0 to 20 minutes, and then cooling, in the heating joining, a structure in which the average grain diameter of the surface layer of the surface to be joined is 200 μm or less, and the average grain diameter of the cross section at a position 100 μm deep from the thinnest wall thickness is 400 μm or more is formed, and thus, the joining can be performed in a single layer, the joining property is good, and the deformation at the time of heating joining can be suppressed.

[0091] The aluminum alloy material used as one of the members to be joined in the aluminum alloy structure of the present application and the aluminum alloy extruded material of the present application can be produced by appropriately combining a continuous casting method, a DC casting method, an extrusion method, and a rolling method. Further, the aluminum alloy material used as another of the members to be joined in the aluminum alloy structure of the present application and the pure aluminum material can be produced by appropriately combining a continuous casting method, a DC casting method, an extrusion method, and a rolling method. As a casting raw material, an aluminum new base metal, an aluminum recycled base metal, an intermediate alloy, and an aluminum scrap can be used.

[0092] The production method of the aluminum alloy material used as one of the members to be joined in the aluminum alloy structure of the present application and the aluminum alloy extruded material of the present application is characterized by having the following steps:

[0093] a casting step of casting an ingot containing 1.80 to 3.00 mass% of Si, 0.10 to 1.60 mass% of Mn, 0.01 to 0.70 mass% of Fe, the balance being Al and unavoidable impurities; and

[0094] a hot extrusion step of hot-extruding the ingot at a temperature of 400°C or higher and 550°C or lower to form a shape in which the width of the thinnest wall thickness in a cross section perpendicular to the extrusion direction is 0.6 mm or more.

[0095] Further, in the aluminum alloy material for a joined member used in the aluminum alloy structure of the present application and the manufacturing method of the aluminum alloy extrusion material of the present application, a homogenization process of keeping the ingot at a temperature of 570°C or lower, preferably 450 to 570°C, can be further provided after the aforementioned casting process and before the aforementioned hot extrusion process.

[0096] The casting process is a process of casting an ingot containing 1.80 to 3.00 mass% of Si, 0.10 to 1.60 mass% of Mn, 0.01 to 0.70 mass% of Fe, and the balance of Al and inevitable impurities by DC casting, continuous casting, or the like. The lower limit value of the Si content of the ingot is preferably 2.00 mass%, and the upper limit value of the Si content of the ingot is preferably 2.80 mass%. Further, the lower limit value of the Mn content of the ingot is preferably 0.20 mass%, more preferably 0.30 mass%, and the upper limit value of the Mn content of the ingot is preferably 1.40 mass%, more preferably 1.20 mass%, more preferably 1.00 mass%, more preferably 0.80 mass%. Further, the lower limit value of the Fe content of the ingot is preferably 0.05 mass%, more preferably 0.10 mass%, more preferably 0.15 mass%, and the upper limit value of the Fe content of the ingot is preferably 0.60 mass%, more preferably 0.50 mass%, more preferably 0.40 mass%. The contents of Si, Mn, and Fe can be set to the range obtained by combining the upper and lower limit values described above.

[0097] After the casting process is performed, a homogenization treatment of keeping the ingot at a temperature of 570°C or lower, preferably 450 to 570°C, can be performed as needed. The holding time of the homogenization treatment can be appropriately selected, and is preferably 2 hours or more, more preferably 2 to 24 hours. The homogenization treatment has the effect of eliminating the microsegregation of the ingot structure of the small billet and homogenizing the structure. In the case where the temperature of the homogenization treatment is higher than 570°C, the small billet portion is concerned to be partially melted. Further, in the case where the time of the homogenization treatment is shorter than 2 hours, the diffusion energy becomes insufficient, and the microsegregation of the ingot structure of the small billet is concerned to be unable to be eliminated. Further, from the viewpoint of productivity, the time of the homogenization treatment is preferably 24 hours or less.

[0098] The hot extrusion process involves hot extruding an ingot at a temperature of 400°C to 550°C to form a shape in which the width of the narrowest part of the cross-section perpendicular to the extrusion direction is 0.6 mm or more. The hot extrusion temperature is ideally between 400°C and 550°C. If the extrusion temperature is below 400°C, the extrusion pressure becomes high, raising concerns about extrusion difficulties. If the extrusion temperature is above 550°C, the aluminum alloy tube being extruded is prone to cracking defects. Therefore, the extrusion ratio in hot extrusion is preferably 20 to 1000. By maintaining an extrusion ratio of 20 to 1000, the processing strain applied to the surface by hot extrusion becomes sufficient, resulting in the metallographic structure of the present invention. Here, the extrusion ratio refers to the ratio of the cross-sectional area of ​​the extrusion cylinder inserted into the small square billet before extrusion to the cross-sectional area of ​​the extruded material. If the extrusion ratio is less than 20, the processing strain applied by hot extrusion becomes insufficient, raising concerns about obtaining the metallographic structure of the present invention. On the other hand, when the extrusion ratio is greater than 1000, the load during extrusion processing increases, hindering extrudability. The lower limit of the extrusion ratio is preferably 20 or more, more preferably 40 or more, and even more preferably 60 or more.

[0099] Furthermore, the manufacturing method of the aluminum alloy material used as a joined component in the aluminum alloy structure of the present invention and the aluminum alloy extrusion material of the present invention can be exemplified by producing small square billets through continuous casting, DC casting, etc., homogenizing them as needed, and then hot rolling them. As for the hot rolling conditions, it is sufficient to appropriately select conditions that deform the surface of the small square billet to a degree that allows the metallographic structure of the present invention to be obtained.

[0100] The joining method in the manufacture of the aluminum alloy structure of the present invention, and the method for joining the aluminum alloy extruded material of the present invention with other components are described.

[0101] Preferably, bonding is performed at a temperature where the ratio of the mass of the liquid phase generated within the aluminum alloy material to the total mass of the aluminum alloy material (hereinafter referred to as the "liquid phase ratio") is 5% or more and 35% or less. This aluminum alloy material is either an aluminum alloy material used as a bonded component or an aluminum alloy material forming the extruded aluminum alloy material of the present invention. If the liquid phase ratio exceeds 35%, the amount of liquid phase generated is excessive, and the aluminum alloy material becomes unable to maintain its shape, resulting in significant deformation. On the other hand, when the liquid phase ratio is less than 5%, bonding becomes difficult. It should be noted that determining the actual liquid phase ratio during heating is extremely difficult. Therefore, the liquid phase ratio is determined through equilibrium calculations. Specifically, it is calculated using thermodynamic equilibrium calculation software such as Thermo-Calc based on the alloy composition and the highest temperature reached during heating.

[0102] In addition, in order to sufficiently fill the liquid phase to the joining portion, it is preferable to also take into consideration the filling time, and it is preferable that the time for which the liquid phase rate is 5% or more is 30 seconds or more and 3600 seconds or less. More preferably, the time for which the liquid phase rate is 5% or more is 60 seconds or more and 1800 seconds or less, whereby more sufficient filling is performed, and reliable joining is performed. When the time for which the liquid phase rate is 5% or more is less than 30 seconds, sometimes the liquid phase cannot be sufficiently filled to the joining portion. On the other hand, if it exceeds 3600 seconds, sometimes deformation of the aluminum material occurs. Note that in the joining method of the present application, the liquid phase moves only in the vicinity of the joining portion, and thus the time required for this filling is not dependent on the size of the joining portion.

[0103] As a specific example of the ideal joining conditions, it is possible to set 580°C to 620°C as the joining temperature, and set the holding time at the joining temperature to be around 0 minutes to 20 minutes. In addition, the average temperature increase rate up to the joining temperature is 5 to 100°C / minute. Here, a holding time of 0 minutes means that cooling is started immediately after the temperature of the members reaches the prescribed joining temperature. In addition, in order to cause the metallographic structure of the joining portion to form in a suitable state as described later, it is also possible to adjust the heating conditions according to the composition.

[0104] An oxide film is formed on the surface layer of the aluminum alloy material, and thus hinders joining. Therefore, it is necessary to destroy the oxide film in joining. In order to destroy the oxide film, it is preferable to apply a flux at least to the joining portion. As the flux, a fluoride-based flux such as KAlF4, CsAlF4, or a chloride-based flux such as KCl, NaCl, which are used in brazing of aluminum alloys, is used. These fluxes melt before the liquid phase is generated or before the joining temperature is reached, and react with the oxide film to destroy the oxide film. Furthermore, in this method, in order to suppress the formation of the oxide film, joining is performed in a non-oxidizing atmosphere such as nitrogen, argon, or the like. In particular, in the case where a fluoride-based flux is used, it is preferable to perform joining in a non-oxidizing gas atmosphere in which the oxygen concentration is suppressed to 250 ppm or less, and the dew point is suppressed to -25°C or less.

[0105] Hereinafter, an embodiment will be shown, and the present application will be specifically described, but the present application is not limited to the embodiment shown below.

[0106] Example

[0107] (Example and Comparative Example)

[0108] Manufacture of Aluminum Alloy Extruded Material

[0109] First, ingots having chemical compositions shown in Table 1 (alloy Nos. Al to A7) were cast by DC casting. The ingots had a cylindrical shape with a diameter of 90 mm. Then, the ingots were heated to perform homogenization treatment. The holding temperature and the holding time in the homogenization treatment were 530°C for 8 hours. After the homogenization treatment, the ingots were inserted into a preheated container having a diameter of 97 mm while the temperature of the ingots was 520°C, and hot-extruded into a flat strip shape having a width of 35 mm and a thickness of 3.0 mm. In this way, aluminum alloy extruded materials were obtained.

[0110] [Table 1]

[0111]

[0112] Grain diameters after heating test of heating joint

[0113] By the same production method as described above, ingots composed of alloys Al to A7 shown in Table 2 were hot-extruded at the extrusion ratios shown in Table 2 to produce aluminum alloy extruded materials Bl to B5 and Cl to C2 having a width of 35 mm and a thickness of 3.0 mm, and an ingot composed of alloy A3 shown in Table 2 was hot-extruded at the extrusion ratio shown in Table 2 to produce an aluminum alloy extruded material C3 having a width of 60 mm and a thickness of 15 mm.

[0114] Next, after a heating test in which the temperature was raised from 450°C to 575°C in 4 to 15 minutes and held at 575 to 615°C for 5 to 40 minutes, and then cooled to room temperature, test materials Bl to B5 and test materials Cl to C3 after the heating test were obtained. Then, the surface of the material parallel to the extrusion direction and the width direction was assumed to be the surface to be jointed, and the surface and a position 100 μm deep from the surface were cut and polished to adjust the surface. Further, etching was performed, and one field was photographed at 50 times using a polarizing microscope, and the average grain diameter was measured by the intercept method according to JIS G 0551.

[0115] [Table 2]

[0116]

[0117] As shown in Table 2, test materials B1 to B5 have the average grain diameter specified in this invention. On the other hand, test materials C1 and C2 have low Mn content, therefore, the average grain diameter at a depth of 100 μm is smaller than the range specified in this invention. Therefore, there is concern that deformation during heat bonding may become significant. In addition, test material C3 has a low extrusion ratio, therefore, the average grain diameter of the outermost layer is larger than the range specified in this invention. In aluminum alloy materials with heat bonding function in a single layer, grain boundaries become the supply path for the liquid phase, and the average grain diameter of the outermost layer of test material C3 is very large, therefore, it is speculated that the supply path of liquid phase solder is very small. Therefore, there is concern that the heat bonding performance of test material C3 may be reduced.

[0118] <Evaluation of Heat-Jointing Properties and Resistance to High-Temperature Deformation>

[0119] Materials were prepared using the same manufacturing method as described above, resulting in test materials B1~B5 and test materials C1 and C2.

[0120] In the evaluation of heat-bonded properties, the following methods were used: Figure 8 The test pieces shown (reference numeral 1) underwent an inverted T-shaped bonding test. Each test material was cut into 60mm lengths, and a fluoride-based flux was applied to the bonding surfaces. A 1.0mm thick A3003 aluminum alloy plate (reference numeral 2) was erected at the center of the bonding surface of each test material in the width direction, forming an inverted T-shape, and heat treatment for bonding was performed. The heat treatment conditions were: heating from 450°C to 575°C in 4 minutes, holding at 600°C for 3 minutes, and then cooling to room temperature. The presence or absence of bonding was then confirmed by cross-sectional observation; bonded cases were rated as "pass," and unbonded cases were rated as "fail." The results are shown in Table 3.

[0121] To evaluate high-temperature deformation resistance, a sag test was conducted as follows. Each test material was cut into 130mm lengths, with 100mm protruding horizontally from one end, and then subjected to heat treatment for joining. The heat treatment conditions were: heating from 450°C to 575°C over 6 minutes, holding at 600°C for 3 minutes, and then cooling to room temperature. The sag of each test material was then measured. Sags of less than 2mm were rated as "Acceptable / Excellent," sags exceeding 2mm but less than 5mm as "Acceptable / Good," sags exceeding 5mm but less than 20mm as "Unacceptable / Poor," and sags exceeding 20mm as "Unacceptable / Very Poor." The results are shown in Table 3.

[0122] [Table 3]

[0123]

[0124] The heating joint property and the high-temperature deformation resistance of the test materials B1 to B5 were all good. On the other hand, the Si content of the test material Cl was lower than the range defined in the present application, and therefore the heating joint property was poor. In addition, the Mn content of the test material C2 was lower than the range defined in the present application, and therefore the average grain diameter at a depth of 100 μm was smaller than the range defined in the present application, and therefore the deformation after heating was significant, and the high-temperature deformation resistance was poor.

[0125] The above describes examples of the aluminum alloy structure of the present application, and the aluminum alloy extruded material of the present application and the manufacturing method thereof based on the examples, but the specific modes of the aluminum alloy structure of the present application, and the aluminum alloy extruded material of the present application and the manufacturing method thereof are not limited to the modes of the examples, and the constitution can be appropriately changed within a range not impairing the gist of the present application.

Claims

1. An aluminum alloy structural body, characterized in that, It is formed by heating and joining one component made of aluminum alloy to another component made of either aluminum alloy or pure aluminum. The joined component contains 1.80–3.00% by mass Si, 0.10–1.60% by mass Mn, 0.01–0.70% by mass Fe, with the balance being Al and unavoidable impurities. At the junction of the one joined member and the other joined member, the average grain diameter in the outermost layer of the one joined member is less than 200 μm, and the average grain diameter in the cross section at a depth of 100 μm in the thinnest part of the one joined member is greater than 400 μm.

2. A heating bonding method, characterized in that, It is the heating and joining method for the aluminum alloy structure as described in claim 1, wherein, The average grain diameter of the outermost layer of the metallographic structure supplied for bonding at 575°C during heat bonding is less than 200 μm, and the average grain diameter of the cross section at a depth of 100 μm in the thinnest part is greater than 400 μm.

3. An aluminum alloy extrusion material, characterized in that, It is an extruded aluminum alloy material with a single-layer heat-bonding function. The aluminum alloy extruded material contains 1.80~3.00% by mass Si, 0.10~1.60% by mass Mn, 0.01~0.70% by mass Fe, with the balance being Al and unavoidable impurities. The width of the thinnest part of the cross-section perpendicular to the extrusion direction is 0.6 mm or more. After a heating test in which the temperature is raised from 450°C to 575°C over 4 to 15 minutes and held at 575 to 615°C for 5 to 40 minutes, the average grain diameter of the outermost layer of the surface to be bonded is less than 200 μm, and the average grain diameter of the cross section at a depth of 100 μm in the thinnest part of the wall is greater than 400 μm.

4. A method for manufacturing an aluminum alloy extruded material, characterized in that, It is a method for manufacturing the aluminum alloy extruded material according to claim 3, the manufacturing method comprising the following steps: The casting process involves casting ingots containing 1.80–3.00% by mass Si, 0.10–1.60% by mass Mn, 0.01–0.70% by mass Fe, with the balance being Al and unavoidable impurities; and In the hot extrusion process, the ingot is hot-extruded while the temperature of the ingot is above 400°C and below 550°C, forming a shape in which the width of the thinnest part of the cross section perpendicular to the extrusion direction is 0.6 mm or more.

5. The method for manufacturing aluminum alloy extruded material according to claim 4, characterized in that, Following the casting process is a homogenization process, which involves homogenizing the ingot at a temperature below 570°C.

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