Manufacturing method for extruded multi-hole tubes

Abstract

To provide a method for manufacturing an extrusion multiple hole pipe which can easily perform hot extrusion even when contents of elements other than aluminum are comparatively large.SOLUTION: A method for manufacturing an extrusion multiple hole pipe 1 includes manufacturing an ingot having a chemical component comprising one or two or more elements of 2.0 mass% or less Si, 0.6 mass% or less Fe, 0.6 mass% or less Cu, 2.0 mass% or less Mn, 0.4 mass% or less Mg, 0.1 mass% or less Cr, 1.5 mass% or less Zn, 0.1 mass% or less Ti, and 0.1 mass% or less B, and the balance Al with inevitable impurities, in which the total of a content of Si and a content of Mn is 3.2 mass% or less, and a content of Si is smaller than a content of Mn. The method includes holding the ingot at a temperature of 550-650°C for 2 or more hours and subjecting the ingot to first homogenization treatment, and then holding the ingot at a temperature of 450-540°C for 3 or more hours and subjecting the ingot to second homogenization treatment. Then, the method includes subjecting the ingot to hot extrusion.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an extruded multi-hole pipe.

Background Art

[0002] An extruded multi-hole pipe has an outer wall portion that constitutes its outer peripheral portion and a partition wall portion that partitions the space surrounded by the outer wall portion, and is configured such that a fluid can flow through a passage surrounded by the outer wall portion and the partition wall portion. In order to form such a complex cross-sectional shape with such a fine structure by extrusion, the extruded multi-hole pipe is often composed of an aluminum alloy with a relatively low content of alloy elements and excellent extrusion properties.

[0003] For example, in Patent Document 1, it contains Si: 0.01 to 0.3%, Fe: 0.01 to 0.3%, Cu: 0.05 to 0.4%, Mn: 0.05 to 0.3%, Zr: 0.05 to 0.25%, Ti: 0 to 0.15% by mass%, the total of Zr and Ti is 0.3% or less, and the balance consists of Al and unavoidable impurities, and the particle area 1.0 μm dispersed in the matrix 2 Among the above particles, an extruded flat multi-hole pipe for a heat exchanger excellent in corrosion resistance is described, which is characterized in that the area ratio occupied by the AlFeSi stable phase is 0.1% or more and less than 0.5%.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, with growing environmental awareness, the importance of technology for reusing aluminum waste as a casting raw material has increased. However, aluminum waste contains various elements other than aluminum. In some cases, it may also contain other metal materials such as iron. Therefore, when reusing aluminum waste as a casting raw material, the content of elements other than aluminum increases, leading to various problems such as increased deformation resistance during hot extrusion and a decrease in extrusion speed. Consequently, with the level of technology at the time, it was considered difficult to manufacture extruded multi-hole tubes with complex cross-sectional shapes when using aluminum waste as a casting raw material.

[0006] This invention has been made in view of the above background, and aims to provide a method for manufacturing extruded multi-hole tubes that can be easily hot-extruded even when the content of elements other than aluminum is relatively high. [Means for solving the problem]

[0007] One aspect of the present invention is Si (silicon): 0.80% by mass or more 2.00% by mass or less (however, 0.80% by mass) %of A casting is produced that contains (excluding) and Mn (manganese): 0.40% to 2.00% by mass, and further contains as an optional component one or more elements selected from the group consisting of Fe (iron): 0.10% to 0.60% by mass, Cu (copper): 0.05% to 0.60% by mass, Mg (magnesium): 0.03% to 0.40% by mass, Cr (chromium): 0.01% to 0.10% by mass, Zn (zinc): 0.05% to 1.50% by mass, Ti (titanium): 0.005% to 0.10% by mass, and B (boron): 0.005% to 0.10% by mass, with the remainder being Al (aluminum) and unavoidable impurities, and the sum of the Si content and Mn content is 3.20% by mass or less, with the Si content being less than the Mn content. The ingot is subjected to a first homogenization treatment by holding it at a temperature of 550°C to 650°C for 2 hours or more. Subsequently, the ingot is held at a temperature of 450°C to 540°C for 3 hours or more to perform a second homogenization treatment. The present invention relates to a method for manufacturing an extruded multi-hole tube, which involves hot extrusion of the ingot to produce an extruded multi-hole tube. [Effects of the Invention]

[0008] In the method for manufacturing the extruded multi-hole tube, a casting having a specific range of chemical components is subjected to a first homogenization treatment and a second homogenization treatment. By performing the homogenization treatment in two stages and setting the holding temperature and holding time of each stage of the homogenization treatment to the specific range, it is possible to suppress the increase in deformation resistance during hot extrusion, even when the content of elements other than aluminum is relatively high.

[0009] As described above, according to the above embodiment, it is possible to provide a method for manufacturing an extruded multi-hole tube that can be easily hot-extruded even when the content of elements other than aluminum is relatively high. [Brief explanation of the drawing]

[0010] [Figure 1] Figure 1 is a perspective view of the extruded multi-hole tube in Example 1. [Modes for carrying out the invention]

[0011] In the method for manufacturing the extruded multi-hole tube, first, an ingot having the specific chemical composition is produced. The ingot contains one or more elements selected from the group consisting of Si, Fe, Cu, Mn, Mg, Cr, Zn, Ti, and B. These elements are contained in casting raw materials such as aluminum ingots, aluminum waste, and intermediate alloys. When aluminum waste is used as the casting raw material, the aforementioned elements may mainly originate from the aluminum waste.

[0012] ·Si: 2.00% by mass or less The ingot contains more than 0% by mass and less than or equal to 2.00% by mass of Si. There areSi is an element found in aluminum ingots, aluminum alloys containing Si in aluminum waste (e.g., 4000 series alloys and 6000 series alloys), and intermediate alloys. Si has the effect of improving the strength of extruded multi-hole tubes. From the viewpoint of further improving the strength of extruded multi-hole tubes, the Si content is preferably 0.20% by mass or more, more preferably 0.40% by mass or more, even more preferably 0.60% by mass or more, particularly preferably 0.70% by mass or more, and most preferably 0.80% by mass or more.

[0013] On the other hand, if the Si content is excessively high, the deformation resistance of the ingot during hot extrusion will increase, which may lead to a decrease in extrudeability. By setting the Si content to 2.00% by mass or less, preferably 1.50% by mass or less, more preferably 1.40% by mass or less, and even more preferably 1.30% by mass or less, it is possible to improve the strength of the extruded multi-hole tube while suppressing the increase in the deformation resistance of the ingot during hot extrusion.

[0014] ·Mn: 2.00% by mass or less The ingot contains more than 0% by mass and less than or equal to 2.00% by mass of Mn. There are Mn is an element found in aluminum ingots, aluminum alloys containing Mn in aluminum waste (e.g., 3000 series alloys), and intermediate alloys. Mn has the effect of improving the strength of extruded multi-hole tubes. From the viewpoint of further improving the strength of extruded multi-hole tubes, the Mn content is preferably 0.40% by mass or more, more preferably 0.60% by mass or more, even more preferably 0.80% by mass or more, particularly preferably 0.90% by mass or more, and most preferably 1.00% by mass or more.

[0015] On the other hand, if the Mn content is excessively high, the deformation resistance of the ingot during hot extrusion will increase, which may lead to a decrease in extrudeability. By setting the Mn content to 2.00% by mass or less, preferably 1.80% by mass or less, and more preferably 1.70% by mass or less, it is possible to improve the strength of the extruded multi-hole tube while suppressing the increase in the deformation resistance of the ingot during hot extrusion.

[0016] Also, the total content of Si and Mn in the ingot is 3.20 mass% or less, and the content of Si is less than the content of Mn. In the chemical composition of the ingot, in addition to making the contents of Si and Mn within the specific ranges respectively, by satisfying the relationship between the content of Si and the content of Mn as described above, the increase in the deformation resistance of the ingot during hot extrusion can be more effectively suppressed, and it becomes possible to easily produce an extruded multi-hole tube having a complex cross-sectional shape. From the viewpoint of further enhancing the above-described effects, the total content of Si and Mn is preferably 3.00 mass% or less.

[0017] When the total content of Si and Mn exceeds 3.20 mass%, there is a risk of causing a decrease in the extrudability during hot extrusion. Also, when the content of Si is equal to or more than the content of Mn, it becomes difficult to precipitate fine AlMnSi-based intermetallic compounds in the ingot, which may cause deterioration of the extrudability. Also, in this case, the extrusion limit speed is likely to decrease, which may cause a decrease in the productivity of the extruded multi-hole tube. When producing the ingot, when the total amount of Mn contained in the aluminum ingot and aluminum waste materials is equal to or less than the total amount of Si, the chemical composition can be adjusted by methods such as adding an intermediate alloy containing Mn.

[0018] ·Fe: 0.60 mass% or less The ingot may contain Fe exceeding 0 mass% and 0.60 mass% or less. Fe is an element contained in aluminum ingots and aluminum waste materials, etc. In particular, parts made of Fe-based alloys may be contained in aluminum waste materials. When such aluminum waste materials are used as casting raw materials, the content of Fe in the ingot tends to increase. By setting the content of Fe to preferably 0.10 mass% or more, more preferably 0.15 mass% or more, still more preferably 0.20 mass% or more, and particularly preferably 0.25 mass% or more, it becomes easier to increase the ratio of aluminum waste materials in the casting raw materials.

[0019] On the one hand, when the Fe content is excessively high, coarse AlFe-based intermetallic compounds are likely to form in the ingot. Coarse AlFe-based intermetallic compounds in the ingot are not preferable because they may cause deterioration of the surface properties of the extruded multi-hole tube, such as an increase in surface roughness. By setting the Fe content to 0.60% by mass or less, preferably 0.50% by mass or less, deterioration of the surface properties can be avoided.

[0020] · Cu: 0.60% by mass or less The ingot may contain more than 0% and 0.60% by mass or less of Cu. Cu is an element contained in aluminum ingots and aluminum waste materials, etc. In particular, aluminum waste materials may contain parts made of aluminum alloys (such as 2000 series alloys) containing a large amount of Cu. When such aluminum waste materials are used as casting raw materials, the Cu content in the ingot tends to increase. Cu has the effect of nobilizing the natural potential of the extruded multi-hole tube and improving the corrosion resistance of the extruded multi-hole tube. From the perspective of further improving the corrosion resistance of the extruded multi-hole tube, the Cu content is preferably 0.05% by mass or more, more preferably 0.10% by mass or more, still more preferably 0.15% by mass or more, and particularly preferably 0.20% by mass or more. Also, in this case, the ratio of aluminum waste materials in the casting raw materials can be more easily increased.

[0021] On the other hand, when the Cu content is excessively high, the amount of Cu dissolved in the ingot increases, which may lead to an increase in the deformation resistance of the ingot during hot extrusion and a decrease in the extrudability. By setting the Cu content to 0.60% by mass or less, preferably 0.40% by mass or less, it is possible to suppress the increase in the deformation resistance of the ingot during hot extrusion while improving the corrosion resistance of the extruded multi-hole tube.

[0022] · Mg: 0.40% by mass or less The ingot may contain more than 0% by mass and up to 0.40% by mass of Mg. Mg is an element found in aluminum ingots and aluminum waste materials. In particular, aluminum waste materials may contain parts made of aluminum alloys that contain a large amount of Mg (for example, 5000 series alloys and 6000 series alloys, etc.), and when such aluminum waste materials are used as casting raw materials, the Mg content in the ingot tends to be high. Mg has the effect of improving the strength of extruded multi-hole tubes. From the viewpoint of further improving the strength of extruded multi-hole tubes, the Mg content is preferably 0.03% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.07% by mass or more. In this case, it is also possible to increase the proportion of aluminum waste materials in the casting raw materials.

[0023] On the other hand, if the Mg content is excessively high, the amount of Mg dissolved in the ingot will increase, which may lead to an increase in the deformation resistance of the ingot during hot extrusion and a decrease in extrudeability. By setting the Mg content to 0.40% by mass or less, preferably 0.30% by mass or less, the increase in the deformation resistance of the ingot during hot extrusion can be suppressed.

[0024] ·Cr: 0.10% by mass or less The ingot may contain more than 0% by mass and up to 0.10% by mass of Cr. Cr is an element found in aluminum ingots and aluminum waste materials. In particular, aluminum waste materials may contain parts made of aluminum alloys that contain a large amount of Cr (for example, 5000 series alloys and 7000 series alloys, etc.), and when such aluminum waste materials are used as casting raw materials, the Cr content in the ingot tends to be high. By setting the Cr content to preferably 0.01% by mass or more, more preferably 0.02% by mass or more, and even more preferably 0.03% by mass or more, it is possible to increase the proportion of aluminum waste materials in the casting raw materials.

[0025] On the other hand, if the Cr content is excessively high, coarse AlCr intermetallic compounds are more likely to form in the ingot. The presence of coarse AlCr intermetallic compounds in the ingot is undesirable because it may increase the likelihood of cracking during hot extrusion or secondary processing after hot extrusion. By limiting the Cr content to 0.10 mass% or less, the formation of coarse AlCr intermetallic compounds can be avoided.

[0026] ·Zn: 1.50% by mass or less The ingot may contain more than 0% by mass and 1.50% by mass or less of Zn. Zn is an element found in aluminum ingots and aluminum waste materials. In particular, aluminum waste materials may contain parts made of aluminum alloys (e.g., 7000 series alloys) that contain a large amount of Zn, and when such aluminum waste materials are used as casting raw materials, the Zn content in the ingot tends to be high. Zn has the effect of improving corrosion resistance by weakening the surface oxide film of extruded multi-hole tubes and dispersing the occurrence of pitting corrosion. From the viewpoint of further enhancing this effect, the Zn content is preferably 0.05% by mass or more, more preferably 0.10% by mass or more, and even more preferably 0.15% by mass or more. In this case, it is also possible to increase the proportion of aluminum waste materials in the casting raw materials.

[0027] On the other hand, if the Zn content is excessively high, the solidus temperature of the aluminum alloy decreases, which may lead to partial melting of the ingot or extruded perforated tube during homogenization treatment or hot extrusion. By setting the Zn content to 1.50% by mass or less, preferably 1.00% by mass or less, it is possible to obtain the beneficial effects of Zn while avoiding partial melting of the ingot or extruded perforated tube.

[0028] ·Ti: 0.10% by mass or less The ingot may contain more than 0% by mass and 0.10% by mass or less of Ti. Ti has the effect of refining the crystal grains in the metallic structure of the ingot. From the viewpoint of further enhancing this effect, the Ti content is preferably 0.005% by mass or more, more preferably 0.007% by mass or more, and even more preferably 0.010% by mass or more.

[0029] On the other hand, if the Ti content is excessively high, coarse AlTi intermetallic compounds tend to form in the ingot. The presence of coarse AlTi intermetallic compounds in the ingot is undesirable because it may lead to cracking during hot extrusion or secondary processing after hot extrusion. By limiting the Ti content to 0.10 mass% or less, the formation of coarse AlTi intermetallic compounds can be avoided while sufficiently refining the crystal grains in the ingot's microstructure.

[0030] ·B: 0.10% by mass or less The ingot may contain more than 0% by mass and 0.10% by mass or less of B. By setting the B content in the extruded porous tube to the above-mentioned specific range, the crystal grains in the metal structure of the extruded porous tube can be sufficiently refined. From the viewpoint of more reliably obtaining this effect, it is preferable that the B content in the ingot be 0.005% by mass or more and 0.10% by mass or less.

[0031] Other elements The ingot may contain elements other than those mentioned above as unavoidable impurities. Examples of such elements include Zr (zirconium) and V (vanadium). The content of each element as an unavoidable impurity may be 0.05 mass% or less. Furthermore, the total content of each element as an unavoidable impurity may be 0.50 mass% or less.

[0032] From the viewpoint of more reliably obtaining the aforementioned effect of improving extrudeability, it is preferable that the ingot contains Si: 0.60% to 1.40% by mass and Mn: 0.80% to 1.80% by mass, with the remainder being Al and unavoidable impurities, and that the total of the Si content and Mn content is 3.20% by mass or less, and that the Si content is less than the Mn content. In this case, the ingot may further contain as an optional component one or more elements selected from the group consisting of Fe: 0.10% to 0.50% by mass, Cu: 0.05% to 0.40% by mass, Mg: 0.05% to 0.30% by mass, Cr: 0.01% to 0.10% by mass, Zn: 0.10% to 1.00% by mass, Ti: 0.005% to 0.10% by mass, and B: 0.005% to 0.10% by mass.

[0033] From a similar viewpoint, it is preferable that the ingot contains, as an essential component, Si: 0.70% to 1.30% by mass, Fe: 0.10% to 0.50% by mass, Cu: 0.05% to 0.40% by mass, Mn: 0.90% to 1.70% by mass, Mg: 0.05% to 0.30% by mass, Cr: 0.01% to 0.10% by mass, Zn: 0.10% to 1.00% by mass, Ti: 0.005% to 0.10% by mass, and B: 0.005% to 0.10% by mass, with the remainder being Al and unavoidable impurities, and the total of the Si content and Mn content being 3.00% by mass or less, and the Si content being less than the Mn content.

[0034] For the production of the ingot, known casting methods such as DC casting and CC casting can be employed. As the casting material for producing the ingot, for example, new aluminum ingots or aluminum waste can be used.

[0035] In the method for manufacturing the extruded multi-hole tube, it is preferable to use aluminum waste material in at least a portion of the casting raw material. Here, aluminum waste material includes scraps and chips generated during the manufacturing process of aluminum products, used aluminum products, and aluminum parts separated from used products.

[0036] As mentioned above, when aluminum waste is reused as a casting material, the content of elements other than aluminum increases, leading to various problems such as increased deformation resistance during hot extrusion and a decrease in extrusion speed. Therefore, with the current level of technology, it was considered difficult to manufacture extruded multi-hole tubes with complex cross-sectional shapes when using aluminum waste as a casting material.

[0037] In contrast, in the method for manufacturing the extruded multi-hole tube described above, by setting the chemical composition of the ingot to the specific range and then performing a two-stage homogenization treatment described later, it is possible to suppress the increase in deformation resistance during hot extrusion even when the content of elements other than aluminum is relatively high. Therefore, according to the manufacturing method of the above embodiment, even when aluminum waste material is used in at least a portion of the casting raw material and the content of elements other than aluminum is relatively high, extruded multi-hole tubes with complex cross-sectional shapes can be easily manufactured.

[0038] Furthermore, by using aluminum waste as at least a portion of the casting raw material, the amount of new aluminum ingot used can be reduced. As a result, the environmental burden in the manufacturing process of extruded multi-hole tubes can be further reduced, and the material cost of extruded multi-hole tubes can be further reduced. From the viewpoint of further enhancing these effects, it is preferable that the proportion of aluminum waste in the casting raw material be 35% by mass or more, more preferably 45% by mass or more, and particularly preferable 60% by mass or more.

[0039] In the method for manufacturing the extruded multi-hole tube described above, after producing the ingot, the ingot is held at a temperature of 550°C to 650°C for 2 hours or more to perform a first homogenization treatment. By setting the holding temperature and holding time in the first homogenization treatment to the specified ranges, coarse precipitates in the ingot can be decomposed, granulated, or redissolved in the Al matrix.

[0040] From the viewpoint of further promoting the decomposition of precipitates in the ingot, the holding temperature in the first homogenization treatment is preferably 580°C to 620°C. From the same viewpoint, the holding time in the first homogenization treatment is preferably 10 hours or more. Furthermore, from the viewpoint of productivity, the holding time in the first homogenization treatment is preferably 24 hours or less.

[0041] If the holding temperature in the first homogenization treatment is below 550°C, or if the holding time is less than 2 hours, the decomposition of precipitates may be insufficient. If the holding temperature in the first homogenization treatment exceeds 650°C, the ingot may partially melt.

[0042] In the method for manufacturing the extruded multi-hole tube described above, a second homogenization treatment is performed on the ingot after the first homogenization treatment. The holding temperature in the second homogenization treatment is set to 450°C or higher and 540°C or lower, and the holding time is set to 3 hours or longer. As mentioned above, the first homogenization treatment is performed primarily for the decomposition, granulation, and re-solution of coarse precipitates that crystallized in the ingot during casting. However, if the holding temperature and holding time in the first homogenization treatment are set within the specified range, the solid solution of solute elements such as Mn and Si into the Al matrix is ​​also promoted along with the decomposition, granulation, and re-solution of precipitates. If the amount of solute elements dissolved in the Al matrix becomes excessively large, it can lead to a decrease in the movement speed of dislocations in the matrix during hot extrusion, and the deformation resistance tends to increase.

[0043] In contrast, when the ingot is heated under the specific conditions described above during the second homogenization treatment, the Si and Mn that were dissolved in the Al matrix during the first homogenization treatment can be finely precipitated as AlMnSi intermetallic compounds. As a result, the amount of solute elements dissolved in the Al matrix can be reduced, thereby lowering the deformation resistance during hot extrusion. Therefore, by heating the ingot after the first homogenization treatment under the specific conditions described above and performing the second homogenization treatment, the extrudeability during hot extrusion can be improved.

[0044] From the viewpoint of further enhancing the effect of improving extrudeability, the holding temperature in the second homogenization treatment is preferably 480°C to 520°C. From the same viewpoint, the holding time in the second homogenization treatment is preferably 5 hours or more. Furthermore, from the viewpoint of productivity, the holding time in the second homogenization treatment is preferably 24 hours or less, and more preferably 15 hours or less.

[0045] If the holding temperature in the second homogenization treatment is less than 450°C, or the holding time is less than 3 hours, the amount of AlMnSi intermetallic compound precipitated tends to be small, which may lead to a deterioration in extrudeability during hot extrusion. If the holding temperature in the second homogenization treatment exceeds 540°C, the Si and Mn dissolved in the Al matrix phase become less likely to form intermetallic compounds, which may lead to a deterioration in extrudeability during hot extrusion.

[0046] In the above manufacturing method, the first homogenization treatment and the second homogenization treatment can be performed consecutively. Here, performing the first homogenization treatment and the second homogenization treatment consecutively means that after the completion of the first homogenization treatment, the temperature of the ingot is lowered to the holding temperature for the second homogenization treatment, and the second homogenization treatment is started when the temperature of the ingot reaches the holding temperature for the second homogenization treatment.

[0047] When the first homogenization treatment and the second homogenization treatment are performed consecutively, it is preferable to cool the ingot to the holding temperature for the second homogenization treatment at an average cooling rate of 20°C / hour or more and 60°C / hour or less after the completion of the first homogenization treatment.

[0048] Furthermore, in the above manufacturing method, after the first homogenization treatment is completed, the ingot may be cooled to a temperature lower than the holding temperature in the second homogenization treatment, and then the second homogenization treatment may be performed. In this case, the temperature of the ingot at the completion of cooling can be, for example, 200°C or less. When heating the ingot after cooling to the holding temperature in the second homogenization treatment, it is preferable to heat the ingot to the holding temperature in the second homogenization treatment at an average heating rate of 20°C / hour or more and 60°C / hour or less.

[0049] In the method for manufacturing the extruded multi-hole tube described above, the extruded multi-hole tube can be obtained by hot extrusion of an ingot that has undergone a second homogenization treatment. The temperature of the ingot at the start of extrusion and the temperature of the extruded multi-hole tube at the completion of extrusion can be appropriately set according to the chemical composition of the extruded multi-hole tube. For example, the temperature of the ingot at the start of extrusion can be appropriately set from the range of 450°C to 550°C. The extruded multi-hole tube obtained in this way may be used as is, or it may be used after post-treatment such as straightening work or cutting to adjust the dimensions and shape, heat treatment for strength adjustment, zinc spraying to improve corrosion resistance, or painting. These post-treatments can be appropriately combined according to the application of the extruded multi-hole tube.

[0050] The extruded multi-hole tube obtained by the above manufacturing method has an outer wall portion that separates the external space from the interior of the extruded multi-hole tube, and a plurality of partition walls that separate the internal space of the outer wall portion. The extruded multi-hole tube also has a plurality of passages surrounded by the outer wall portion and the partition walls, and is configured so that liquids, gases, etc., can flow through these passages. The cross-sectional shape of the extruded multi-hole tube is not particularly limited and can take various shapes such as oval or rectangular. Similarly, the cross-sectional shape of the passages in the extruded multi-hole tube is not particularly limited and can take various shapes such as circular, triangular, or square.

[0051] The extruded multi-hole tube may have a flattened cross-sectional shape. In this case, the ratio of the width to the thickness of the extruded multi-hole tube can be 2 to 50, preferably 3 to 30. Generally, when an extruded multi-hole tube has a flattened shape, the higher the ratio of the width to the thickness, the more difficult the extrusion process becomes, and the higher the extrudeability tends to be required. In the manufacturing process of the extruded multi-hole tube, by subjecting the aluminum alloy ingot having the specific chemical components to a two-stage homogenization treatment, the increase in deformation resistance during hot extrusion can be suppressed and the extrudeability can be improved. Therefore, an extruded multi-hole tube with a cross-sectional shape that requires such high extrudeability can be easily obtained.

[0052] Furthermore, the extruded multi-hole tube has an outer wall portion that separates the external space from the inside of the extruded multi-hole tube, and a plurality of partition walls that separate the internal space of the outer wall portion, and the thickness of the outer wall portion and the partition walls may be 0.10 mm or more and 2.0 mm or less, preferably 0.15 mm or more and 1.5 mm or less. Similar to the width-to-thickness ratio described above, in the extruded multi-hole tube, the thinner the thickness of the outer wall portion and partition walls, the more difficult the extrusion process becomes, and the higher the extrudeability tends to be. In the manufacturing process of the extruded multi-hole tube, by subjecting the aluminum alloy ingot having the specific chemical components to a two-stage homogenization treatment, the increase in deformation resistance during hot extrusion can be suppressed and the extrudeability can be improved. Therefore, an extruded multi-hole tube with a cross-sectional shape that requires such high extrudeability can be easily obtained. [Examples]

[0053] An example of the method for manufacturing the extruded multi-hole tube described above is explained below. In the method for manufacturing the extruded multi-hole tube in this example, an ingot is produced that contains one or more elements selected from the group consisting of Si: 2.00 mass% or less, Fe: 0.60 mass% or less, Cu: 0.60 mass% or less, Mn: 2.00 mass% or less, Mg: 0.40 mass% or less, Cr: 0.10 mass% or less, Zn: 1.50 mass% or less, Ti: 0.10 mass% or less, and B: 0.10 mass% or less, with the remainder being Al and unavoidable impurities, and the sum of the Si content and Mn content being 3.20 mass% or less, with the Si content being less than the Mn content. After that, the ingot is subjected to a first homogenization treatment by holding it at a temperature of 550°C to 650°C for 2 hours or more. After the first homogenization treatment is completed, the ingot is subjected to a second homogenization treatment by holding it at a temperature of 450°C to 540°C for 3 hours or more. Then, by hot extrusion of the ingot after the second homogenization treatment is completed, an extruded multi-hole tube can be manufactured.

[0054] The extruded multi-hole tube 1 in this example has a flattened cross-sectional shape, as shown in Figure 1. More specifically, the extruded multi-hole tube 1 has an oval cross-sectional shape. The width of the extruded multi-hole tube 1 is, for example, 14.0 mm, and the thickness is, for example, 2.5 mm.

[0055] Furthermore, the extruded multi-hole tube 1 has an outer wall portion 11 that separates its external space from its interior, and a partition wall portion 13 that divides the space enclosed by the outer wall portion 11 into 19 passages 12. In this example, the passages 12 of the extruded multi-hole tube 1 have a circular cross-sectional shape. The thickness of the thinnest parts of the outer wall portion 11 and the partition wall portion 13 is, for example, 0.4 mm.

[0056] The manufacturing method for the extruded multi-hole tubes in this example will be explained in more detail below. First, using casting raw materials including aluminum waste, an ingot having the chemical composition (alloy symbols A1 to A3) shown in Table 1 is produced by DC casting. In Table 1, "Bal." is a symbol indicating that the element in question is the remainder.

[0057] After the ingot is prepared, the ingot is held at a temperature of 600°C for 10 hours to perform the first homogenization treatment. After the first homogenization treatment is completed, the ingot is held at a temperature of 500°C for 10 hours to perform the second homogenization treatment. The first and second homogenization treatments may be performed consecutively, or the temperature of the ingot may fall below the holding temperature for the second homogenization treatment between the completion of the first homogenization treatment and the start of the second homogenization treatment.

[0058] After the second homogenization treatment is completed, the ingot is hot-extruded at a temperature of 500°C to produce the extruded multi-hole tube 1. This yields the test materials S1 to S3 shown in Table 2. Note that test materials R1 to R4 shown in Table 2 are for comparison with test materials S1 to S3. The preparation method for test materials R1 to R3 is the same as for test materials S1 to S3, except that the chemical composition of the ingot is changed to alloy symbols A4 to A6 shown in Table 1. The preparation method for test material R4 is also the same as for test materials S1 to S3, except that the chemical composition of the ingot is changed to alloy symbol A7 shown in Table 1, and the second homogenization treatment is omitted.

[0059] The method for evaluating the extrudeability of each test material is described below.

[0060] • Extrusion Extrudeability can be evaluated based on the appearance of the test material. More specifically, the appearance of the test material is observed visually, and the presence or absence of cracks and streaks along the extrusion direction is evaluated. Table 2 shows the presence or absence of cracks and streaks at the ends of each test material.

[0061] [Table 1]

[0062] [Table 2]

[0063] As shown in Tables 1 and 2, in the manufacturing process of test materials S1 to S3, the ingots having the specified chemical components are subjected to a first homogenization treatment and a second homogenization treatment under the specified conditions, thereby reducing the deformation resistance of the ingots during hot extrusion. Therefore, test materials S1 to S3 have a good appearance.

[0064] On the other hand, since test material R1 has a Si content greater than or equal to its Mn content, it has inferior extrudeability compared to test materials S1 to S3, and streaky patterns appear on the surface of the test material. Because the combined Si and Mn content of test material R2 is excessively high, it exhibits inferior extrudeability compared to test materials S1 to S3, resulting in cracking at the widthwise edges of the test material and the formation of streaky patterns on the surface of the test material.

[0065] Test material R3 has an excessively high Mn content, resulting in inferior extrudeability compared to test materials S1 to S3, and causing streaky patterns to appear on the surface of the test material. Because test material R4 did not undergo a second homogenization treatment during its manufacturing process, it has inferior extrudeability compared to test materials S1 to S3, and streaky patterns appear on the surface of the test material.

[0066] Although specific embodiments of the method for manufacturing an extruded multi-hole tube according to the present invention have been described above based on the examples, the specific embodiments of the method for manufacturing an extruded multi-hole tube according to the present invention are not limited to the embodiments, and the configuration can be modified as appropriate without impairing the spirit of the present invention. [Explanation of Symbols]

[0067] 1. Extruded multi-hole tube 11 Exterior wall 12 aisles 13 Bulkhead

Claims

1. It contains Si: 0.80% by mass or more and 2.00% by mass or less (excluding 0.80% by mass) and Mn: 0.40% by mass or more and 2.00% by mass or less, and further contains Fe: 0.10% by mass or more and 0.60% by mass or less, Cu: 0.05% by mass or more and 0.60% by mass or less, Mg: 0.03% by mass or more and 0.40% by mass or less, Cr: 0.01% by mass or more and 0.10% by mass or less, and Zn: 0.05% by mass or more and 1.5% by mass or less. A casting is prepared that contains, as an optional component, one or more elements selected from the group consisting of 0% by mass or less, Ti: 0.005% by mass or more and 0.10% by mass or less, B: 0.005% by mass or more and 0.10% by mass or less, with the remainder being Al and unavoidable impurities, the sum of the Si content and Mn content being 3.20% by mass or less, and having a chemical composition in which the Si content is less than the Mn content. The ingot is subjected to a first homogenization treatment by holding it at a temperature of 550°C to 650°C for 2 hours or more. Subsequently, the ingot is held at a temperature of 450°C to 540°C for 3 hours or more to perform a second homogenization treatment. A method for manufacturing an extruded multi-hole tube, comprising then hot extruding the ingot to produce an extruded multi-hole tube.

2. The method for manufacturing an extruded multi-hole tube according to claim 1, wherein, after the completion of the first homogenization treatment, the ingot is cooled to the holding temperature in the second homogenization treatment at an average cooling rate of 20°C / hour or more and 60°C / hour or less.

3. A method for manufacturing an extruded multi-hole tube according to claim 1, wherein, after the completion of the first homogenization treatment, the ingot is cooled to a temperature lower than the treatment temperature in the second homogenization treatment, and then the ingot is heated to the holding temperature in the second homogenization treatment at an average heating rate of 20°C / hour or more and 60°C / hour or less.

4. A method for manufacturing an extruded multi-hole tube according to any one of claims 1 to 3, wherein at least a portion of the casting raw material is aluminum waste when producing the ingot.

5. A method for manufacturing an extruded multi-hole tube according to any one of claims 1 to 4, wherein the extruded multi-hole tube having a flat cross-sectional shape and a width-to-thickness ratio of 2 to 50 is produced by the hot extrusion method.

6. A method for manufacturing an extruded multi-hole tube according to any one of claims 1 to 5, wherein the extruded multi-hole tube is manufactured by hot extrusion, having an outer wall portion that separates the external space from the inside of the extruded multi-hole tube, and a plurality of partition wall portions that separate the internal space of the outer wall portion, and the thickness of the outer wall portion and the partition wall portions is 0.10 mm or more and 2.0 mm or less.

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