Extruded multi-hole tube and method for manufacturing the same

Abstract

To provide an extrusion multiple hole pipe having high strength, and a method for manufacturing the same.SOLUTION: An extrusion multiple hole pipe 1 has a chemical component comprising one or two or more elements of 0.30 mass% or more and 1.80 mass% or less Si, 0.10 mass% or more and 0.50 mass% or less Cu, 0.30 mass% or more and 1.00 mass% or less Mn, 0.30 mass% or more and 1.00 mass% or less Mg, and the balance Al with inevitable impurities. Tensile strength of the extrusion multiple hole pipe 1 is 290 MPa or more. When the extrusion multiple hole pipe 1 is manufactured, the extrusion multiple hole pipe 1 is manufactured by holding an ingot having the chemical component at a temperature of 450-620°C for 2 or more hours and subjecting the ingot to homogenization treatment, and then subjecting the ingot to hot extrusion. After the hot extrusion has been completed, the extrusion multiple hole pipe 1 is cooled so that average cooling speed becomes 1°C / sec or more until the temperature of the extrusion multiple hole pipe 1 reaches 150°C. Artificial aging treatment is performed by holding the cooled extrusion multiple hole pipe 1 at a temperature of 150-200°C for 2 or more hours.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] An extruded multi-hole pipe has an outer wall portion constituting its outer peripheral portion and a partition portion partitioning a 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 portion. In order to form a complicated cross-sectional shape having such a fine structure by extrusion, the extruded multi-hole pipe is often made of an aluminum alloy having a relatively low content of alloy elements and excellent extrudability.

[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 is composed of Al and inevitable 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, 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, there has been a demand for increased strength in extruded multi-hole tubes. One simple way to increase the strength of extruded multi-hole tubes is to increase the content of alloying elements that have a strength-enhancing effect. However, generally, high-strength aluminum alloys tend to have high deformation resistance during hot extrusion, so attempting to increase the strength of extruded multi-hole tubes leads to a deterioration in extrudeability, making it difficult to manufacture extruded multi-hole tubes with complex cross-sectional shapes by extrusion.

[0006] This invention was made in view of the above background, and aims to provide an extruded multi-hole tube with high strength and a method for manufacturing the same. [Means for solving the problem]

[0007] One aspect of the present invention is a mixture containing Si (silicon): 0.30% to 1.80% by mass, Cu (copper): 0.10% to 0.50% by mass, and Mn (manganese): 0.30% to 1.00% by mass. 、 Mg (Magnesium): 0.30% by mass or more, 1.00% by mass or less And Cr (chromium): greater than 0% by mass and less than or equal to 0.080% by mass. It contains, Furthermore, it contains one or more elements selected from the group consisting of Fe (iron): 0.40 mass% or less, Zn (zinc): 0.60 mass% or less, Ti (titanium): 0.10 mass% or less, Zr (zirconium): 0.10 mass% or less, and B (boron): 0.10 mass% or less. The material is an extruded multi-hole tube having a chemical composition consisting of Al and unavoidable impurities as the remainder, and a tensile strength of 290 MPa or more.

[0008] Another aspect of the present invention is a method for manufacturing an extruded multi-hole tube according to the above aspect, A casting having the aforementioned chemical components is prepared. The ingot is subjected to a homogenization treatment by holding it at a temperature of 450°C to 620°C for 2 hours or more. Subsequently, the ingot is subjected to hot extrusion to produce the extruded multi-hole tube. After the hot extrusion is completed, the extruded multi-hole tube is cooled so that the average cooling rate until the temperature of the extruded multi-hole tube reaches 150°C is 1°C / second or more. The present invention relates to a method for manufacturing an extruded multi-hole tube, wherein the extruded multi-hole tube, after cooling, is kept at a temperature of 150°C to 200°C for 2 hours or more to undergo artificial aging treatment. [Effects of the Invention]

[0009] The extruded multi-hole tube can easily achieve a high tensile strength of 290 MPa or more by having at least the chemical composition within the specified range. Furthermore, because the extruded multi-hole tube has mechanical properties represented by the specified range of tensile strength, it has higher strength than conventional extruded multi-hole tubes.

[0010] Furthermore, in the manufacturing method of the above embodiment, by performing a homogenization treatment on an ingot having a specific range of chemical components under the specific conditions, it is possible to suppress the increase in deformation resistance of the ingot during subsequent hot extrusion. In addition, by subjecting the extruded multi-hole tube after hot extrusion to cooling and artificial aging treatment under the specific conditions, the strength of the extruded multi-hole tube can be improved.

[0011] As described above, according to the above embodiment, it is possible to provide an extruded multi-hole tube having high strength and a method for manufacturing the same. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a perspective view of the extruded multi-hole tube in Example 1. [Modes for carrying out the invention]

[0013] (Extruded multi-hole pipe) The chemical composition, characteristics, and structure of the aforementioned extruded multi-hole tube will be described below.

[0014] [Chemical composition] The aforementioned extruded multi-hole tube contains Si, Cu, Mn, and Mg as essential components.

[0015] ·Si: 0.30 mass% or more and 1.80 mass% or less The extruded multi-hole pipe contains 0.30% to 1.80% by mass of Si as an essential component. In the extruded multi-hole pipe, a part of Si forms intermetallic compounds such as Mg2Si together with Mg, and has the effect of improving the strength of the extruded multi-hole pipe by dispersion strengthening. In addition, Si that does not form second-phase particles dissolves in the Al matrix phase and has the effect of improving the strength of the extruded multi-hole pipe by solid solution strengthening.

[0016] From the viewpoint of further improving the strength of the extruded multi-hole pipe, the Si content is preferably 0.50% by mass or more, more preferably 0.70% by mass or more, and still more preferably 0.90% by mass or more. If the Si content in the extruded multi-hole pipe is less than 0.30% by mass, there is a risk of causing a decrease in the strength of the extruded multi-hole pipe.

[0017] On the other hand, when the Si content becomes excessively high, the amount of Si dissolved in the ingot increases, which may lead to an increase in the deformation resistance during hot extrusion. By setting the Si content to 1.80% by mass or less, preferably 1.70% by mass or less, and more preferably 1.50% by mass or less, it is possible to improve the strength of the extruded multi-hole pipe while suppressing an increase in the deformation resistance of the ingot during hot extrusion.

[0018] ·Mn: 0.30% to 1.00% by mass The extruded multi-hole pipe contains 0.30% to 1.00% by mass of Mn as an essential component. In the extruded multi-hole pipe, a part of Mn forms an Al-Mn-based intermetallic compound in the Al matrix phase and has the effect of improving the strength of the extruded multi-hole pipe by dispersion strengthening. In addition, Mn that does not form second-phase particles dissolves in the Al matrix phase and has the effect of improving the strength of the extruded multi-hole pipe by solid solution strengthening.

[0019] From the viewpoint of further improving the strength of the extruded multi-hole pipe, the Mn content is preferably 0.40% by mass or more, more preferably 0.50% by mass or more, and still more preferably 0.60% by mass or more. If the Mn content in the extruded multi-hole pipe is less than 0.30% by mass, there is a risk of causing a decrease in the strength of the extruded multi-hole pipe.

[0020] On the other hand, if the Mn content is excessively high, the amount of Mn dissolved in the ingot increases, which may lead to an increase in the deformation resistance during hot extrusion. By setting the Mn content to 1.00 mass% or less, preferably 0.95 mass% or less, it is possible to suppress the increase in the deformation resistance of the ingot during hot extrusion while improving the strength of the extruded multi-hole tube.

[0021] · Cu: 0.10 mass% or more and 0.50 mass% or less The extruded multi-hole tube contains 0.10 mass% or more and 0.50 mass% or less of Cu as an essential component. In the extruded multi-hole tube, Cu is dissolved in the Al matrix phase and has the effect of improving the strength of the extruded multi-hole tube by solid solution strengthening. From the viewpoint of further improving the strength of the extruded multi-hole tube, the Cu content is preferably 0.15 mass% or more, more preferably 0.20 mass% or more. If the Cu content in the extruded multi-hole tube is less than 0.10 mass%, there is a risk of reducing the strength of the extruded multi-hole tube. Also, in this case, there is a risk of deterioration of surface properties such as an increase in surface roughness.

[0022] On the other hand, if the Cu content is excessively high, the amount of Cu dissolved in the ingot during the manufacturing process of the extruded multi-hole tube increases, which may lead to an increase in the deformation resistance and a decrease in the extrusion property during hot extrusion. By setting the Cu content to 0.50 mass% or less, preferably 0.40 mass% or less, it is possible to suppress the increase in the deformation resistance during hot extrusion while improving the strength of the extruded multi-hole tube.

[0023] · Mg: 0.30 mass% or more and 1.00 mass% or less The extruded multi-hole tube contains 0.30 mass% or more and 1.00 mass% or less of Mg as an essential component. In the extruded multi-hole tube, a part of Mg forms intermetallic compounds such as Mg2Si together with Si and has the effect of improving the strength of the extruded multi-hole tube by dispersion strengthening. Also, the Mg that did not form the second-phase particles is dissolved in the Al matrix phase and has the effect of improving the strength of the extruded multi-hole tube by solid solution strengthening.

[0024] From the viewpoint of further improving the strength of the extruded multi-hole tube, the Mg content is preferably 0.40% by mass or more, and more preferably 0.45% by mass or more. If the Mg content in the extruded multi-hole tube is less than 0.30% by mass, it may lead to a decrease in the strength of the extruded multi-hole tube.

[0025] On the other hand, if the Mg content is excessively high, the amount of Mg dissolved in the ingot during the manufacturing process of the extruded multi-hole tube will increase, which may lead to an increase in deformation resistance and a decrease in extrudeability during hot extrusion. By setting the Mg content to 1.00% by mass or less, preferably 0.95% by mass or less, and more preferably 0.90% by mass or less, it is possible to improve the strength of the extruded multi-hole tube while suppressing the increase in deformation resistance during hot extrusion.

[0026] In addition to the essential components mentioned above, the extruded multi-hole tube contains: It contains chromium (Cr). The extruded multi-hole tube also contains, Optional components include Fe (iron) and Zn (zinc). 、T It may contain one or more elements selected from the group consisting of i (titanium), Zr (zirconium), and B (boron).

[0027] ·Fe: 0.40% by mass or less The extruded multi-hole tube may contain Fe as an optional component in an amount exceeding 0% by mass and not exceeding 0.40% by mass. Fe has the effect of improving the strength of the extruded multi-hole tube. From the viewpoint of further improving the strength of the extruded multi-hole tube, the Fe content is preferably 0.05% by mass or more, more preferably 0.10% by mass or more, even more preferably 0.15% by mass or more, and particularly preferably 0.20% by mass or more.

[0028] On the other hand, if the Fe content is excessively high, coarse AlFe-based intermetallic compounds tend to form in the ingot during the manufacturing process of the extruded multi-hole tube. Coarse AlFe-based intermetallic compounds in the ingot are undesirable because they may lead to deterioration of the surface properties of the extruded multi-hole tube, such as an increase in surface roughness. By setting the Fe content to 0.40% by mass or less, preferably 0.35% by mass or less, it is possible to improve the strength of the extruded multi-hole tube while avoiding deterioration of the surface properties.

[0029] ·Cr: More than 0 mass% and less than 0.080 mass% The aforementioned extruded multi-hole tube has an optional component exceeding 0% by mass. 0.080% by mass or less Contains Cr There are Cr has the effect of refining the crystal grains in the metal structure of extruded multi-hole tubes. From the viewpoint of further enhancing this effect, the Cr content is preferably 0.005% by mass or more, and more preferably 0.010% by mass or more.

[0030] 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. Cr content to 0 By keeping the amount below 0.080 mass%, it is possible to sufficiently refine the crystal grains in the metal structure of the extruded multi-hole tube while avoiding the formation of coarse AlCr-based intermetallic compounds.

[0031] ·Zn: 0.60% by mass or less The extruded porous tube may contain Zn as an optional component in an amount exceeding 0% by mass and not exceeding 0.60% by mass. Zn forms precipitates together with Mg, and this precipitate strengthening improves the strength of the extruded porous tube. 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.

[0032] 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 porous tube during homogenization treatment or hot extrusion. By setting the Zn content to 0.60% by mass or less, preferably 0.55% by mass or less, it is possible to obtain the beneficial effects of Zn while avoiding partial melting of the ingot or extruded porous tube.

[0033] ·Ti: 0.10% by mass or less The extruded porous tube may contain Ti as an optional component in an amount exceeding 0% by mass and not exceeding 0.10% by mass. Ti has the effect of refining the crystal grains in the metallic structure of the extruded porous tube. From the viewpoint of further enhancing this effect, the Ti content is preferably 0.005% by mass or more, and more preferably 0.010% by mass or more.

[0034] 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 setting the Ti content to 0.10 mass% or less, preferably 0.090 mass% or less, and more preferably 0.080 mass% or less, it is possible to sufficiently refine the crystal grains in the metal structure of the extruded porous tube while avoiding the formation of coarse AlTi intermetallic compounds.

[0035] ·Zr: 0.10% by mass or less The extruded porous tube may contain Zr as an optional component in an amount exceeding 0% by mass and not exceeding 0.10% by mass. Zr has the effect of refining the crystal grains in the metallic structure of the extruded porous tube. From the viewpoint of further enhancing this effect, the Zr content is preferably 0.005% by mass or more, and more preferably 0.010% by mass or more.

[0036] On the other hand, if the Zr content is excessively high, coarse AlZr-based intermetallic compounds tend to form in the ingot. The presence of coarse AlZr-based intermetallic compounds in the ingot is undesirable because it may lead to cracking during hot extrusion or secondary processing after hot extrusion. By setting the Zr content to 0.10% by mass or less, preferably 0.090% by mass or less, and more preferably 0.080% by mass or less, it is possible to sufficiently refine the crystal grains in the metal structure of the extruded multi-hole tube while avoiding the formation of coarse AlZr-based intermetallic compounds.

[0037] ·B: 0.10% by mass or less The extruded porous tube 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 such effects, the B content in the extruded porous tube is preferably 0.005% by mass or more and 0.090% by mass or less, and more preferably 0.010% by mass or more and 0.080% by mass or less.

[0038] Other elements The extruded porous tube may contain elements other than those mentioned above as unavoidable impurities. Examples of such elements include vanadium (V). The content of each element as an unavoidable impurity may be, for example, 0.05% by mass or less. Furthermore, the total content of each element as an unavoidable impurity may be 0.50% by mass or less.

[0039] From the viewpoint of more reliably obtaining the aforementioned effects of improved strength and improved extrudeability in the manufacturing process, it is preferable that the extruded multi-hole tube has a chemical composition containing Si: 0.70% to 1.70% by mass, Fe: 0.15% to 0.40% by mass, Cu: 0.15% to 0.50% by mass, Mn: 0.50% to 1.00% by mass, Mg: 0.40% to 0.95% by mass, Cr: 0.005% to 0.090% by mass, Zn: 0.10% to 0.60% by mass, Ti: 0.005% to 0.090% by mass, Zr: 0.005% to 0.090% by mass, and B: 0.005% to 0.090% by mass, with the remainder being Al and unavoidable impurities.

[0040] From a similar viewpoint, it is preferable that the extruded porous tube has a chemical composition that essentially contains Si: 0.90% to 1.50% by mass, Fe: 0.20% to 0.35% by mass, Cu: 0.20% to 0.40% by mass, Mn: 0.60% to 0.95% by mass, Mg: 0.45% to 0.90% by mass, Cr: 0.010% to 0.080% by mass, Zn: 0.15% to 0.55% by mass, Ti: 0.010% to 0.080% by mass, Zr: 0.010% to 0.080% by mass, and B: 0.010% to 0.080% by mass, with the remainder being Al and unavoidable impurities.

[0041] [Characteristics] The tensile strength of the extruded multi-hole tube is 290 MPa or higher. Extruded multi-hole tubes with a tensile strength within the specified range have higher strength than conventional extruded multi-hole tubes.

[0042] [shape] An extruded multi-hole tube 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. Furthermore, the extruded multi-hole tube 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.

[0043] 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 between 5 and 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 homogenization treatment under the specific conditions, the increase in deformation resistance during hot extrusion can be suppressed, and the extrudeability can be improved. Therefore, an extruded multi-hole tube having a cross-sectional shape that requires such high extrudeability and high strength can be easily obtained.

[0044] 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 0.2 mm or more and 2.0 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 homogenization treatment under the specific conditions, the increase in deformation resistance during hot extrusion can be suppressed and the extrudeability can be improved. Therefore, an extruded multi-hole tube having a cross-sectional shape that requires such high extrudeability and high strength can be easily obtained.

[0045] (Method of manufacturing extruded multi-hole tubes) In manufacturing the aforementioned extruded multi-hole tube, A casting having the aforementioned chemical components is prepared. The ingot is subjected to a homogenization treatment by holding it at a temperature of 450°C to 620°C for 2 hours or more. Subsequently, the ingot is subjected to hot extrusion to produce the extruded multi-hole tube. After the hot extrusion is completed, the extruded multi-hole tube is cooled so that the average cooling rate until the temperature of the extruded multi-hole tube reaches 150°C is 1°C / second or more. The extruded multi-hole tube, after cooling, can be subjected to artificial aging treatment by holding it at a temperature of 150°C to 200°C for at least two hours.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] In contrast, in the method for manufacturing the extruded multi-hole tube described above, by setting the chemical composition of the ingot to the specified range and then performing a homogenization treatment under the specified conditions, 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, it is possible to easily manufacture an extruded multi-hole tube with a complex cross-sectional shape and high strength.

[0050] 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 50% by mass or more, more preferably 75% by mass or more, and particularly preferable to use 100% by mass, that is, to use only aluminum waste as the casting raw material.

[0051] In the method for manufacturing the extruded multi-hole tube described above, after producing the ingot, the ingot is subjected to a homogenization treatment by holding it at a temperature of 450°C to 620°C for 2 hours or more. By setting the holding temperature and holding time in the homogenization treatment to the specified ranges, coarse precipitates in the ingot can be decomposed, granulated, or redissolved in the Al matrix.

[0052] From the viewpoint of further promoting the decomposition of precipitates in the ingot, the holding temperature in the homogenization treatment is preferably 550°C to 600°C. From the same viewpoint, the holding time in the homogenization treatment is preferably 10 hours or more. Furthermore, from the viewpoint of productivity, the holding time in the homogenization treatment is preferably 24 hours or less.

[0053] If the holding temperature during the homogenization process is below 450°C, or if the holding time is less than 2 hours, the decomposition of precipitates may be insufficient. If the holding temperature during the homogenization process exceeds 620°C, the ingot may partially melt.

[0054] In the method for manufacturing the extruded multi-hole tube described above, if necessary, the ingot that has undergone homogenization treatment under the specific conditions described above may be subjected to further homogenization treatment. In the following, when the homogenization treatment is performed in two stages, the first homogenization treatment will be referred to as the "first homogenization treatment," and the second homogenization treatment will be referred to as the "second homogenization treatment."

[0055] In the second homogenization treatment, the holding temperature is preferably between 400°C and 550°C, and the holding time is preferably 2 hours or more. 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 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 into the Al matrix becomes excessively large, it can lead to a decrease in the movement speed of dislocations in the matrix during hot extrusion, making it easier for deformation resistance to increase.

[0056] In contrast, when the ingot is heated under the specific conditions described above during the second homogenization treatment, the Si and Mn 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, further 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 further improved.

[0057] Furthermore, the holding time in the second homogenization process is preferably 24 hours or less, and more preferably 15 hours or less, from the viewpoint of productivity.

[0058] 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.

[0059] 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, for example, after the first homogenization treatment is completed, the ingot may be cooled to a temperature of 200°C or lower, and then the ingot may be heated to perform the second homogenization treatment.

[0060] In the method for manufacturing the extruded multi-hole tube described above, the extruded multi-hole tube can be obtained by hot extrusion of the ingot after the homogenization treatment has been completed. 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 440°C to 560°C. Also, the temperature of the extruded multi-hole tube immediately after the completion of extrusion can be appropriately set from the range of 400°C to 500°C.

[0061] In the method for manufacturing the extruded multi-hole tube described above, immediately after the completion of hot extrusion, the extruded multi-hole tube is cooled so that the average cooling rate until the temperature of the extruded multi-hole tube reaches 150°C is 1°C / second or more. Various methods such as air cooling, fan cooling, and water cooling can be used to cool the extruded multi-hole tube. Furthermore, the temperature of the extruded multi-hole tube upon completion of cooling should be, for example, 150°C or lower.

[0062] By cooling the extruded porous tube immediately after hot extrusion under the specific conditions described above, the precipitation of solute elements such as Si and Mg dissolved in the extruded porous tube can be suppressed, and the state in which the solute elements remain dissolved in the Al matrix can be maintained. By maintaining this state in which the solute elements remain dissolved in the Al matrix, intermetallic compounds such as Mg2Si can be finely precipitated in the Al matrix during the subsequent artificial aging treatment.

[0063] If the average cooling rate of the extruded multi-hole tube after hot extrusion is slower than 1°C / second, solute elements are more likely to precipitate during cooling. This may lead to a decrease in the strength of the extruded multi-hole tube after artificial aging treatment. While there is no upper limit to the average cooling rate of the extruded multi-hole tube from the viewpoint of avoiding a decrease in the strength of the final extruded multi-hole tube, increasing the average cooling rate may lead to an increase in manufacturing costs. From the viewpoint of avoiding an increase in manufacturing costs, it is preferable to set the average cooling rate of the extruded multi-hole tube after hot extrusion to 300°C / second or less.

[0064] In the above manufacturing method, the extruded multi-hole tube is subjected to artificial aging treatment by holding it at a temperature of 150°C to 200°C for 2 hours or more after cooling is complete. By heating the extruded multi-hole tube under the above specific conditions and subjecting it to artificial aging treatment, solute elements dissolved in the Al matrix of the extruded multi-hole tube are precipitated, and fine intermetallic compounds such as Mg2Si can be formed in the Al matrix. As a result, the strength of the extruded multi-hole tube can be improved by dispersion strengthening.

[0065] From the viewpoint of more reliably obtaining the effect of strength improvement through dispersion strengthening, the holding temperature in artificial aging treatment is preferably 160°C to 190°C. Similarly, the holding time in artificial aging treatment is preferably 5 hours or more, and more preferably 8 hours or more. Furthermore, from the viewpoint of productivity, the holding time in artificial aging treatment is preferably 24 hours or less.

[0066] If the holding temperature during artificial aging is below 150°C, or the holding time is less than 2 hours, the precipitation of solute elements may be insufficient, potentially leading to a decrease in the strength of the extruded multi-hole tube. Furthermore, if the holding temperature during artificial aging exceeds 200°C, crystals and precipitates present in the extruded multi-hole tube are more likely to redissolve into the Al matrix, potentially preventing the acquisition of desired properties.

[0067] The extruded multi-hole tubes obtained in this way may be used as is, or they may be used after post-treatment such as drawing to adjust the dimensions and shape, or zinc spraying or painting to improve corrosion resistance. These post-treatments can be appropriately combined depending on the application of the extruded multi-hole tubes. [Examples]

[0068] Examples of the extruded multi-hole tube and its manufacturing method are described below. The extruded multi-hole tube in this example has a chemical composition containing Si: 0.30% to 1.80% by mass, Cu: 0.10% to 0.50% by mass, Mn: 0.30% to 1.00% by mass, and Mg: 0.30% to 1.00% by mass, with the remainder being Al and unavoidable impurities. The tensile strength of the extruded multi-hole tube is 290 MPa or higher.

[0069] 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, 60.0 mm, and the thickness is, for example, 3.0 mm.

[0070] Furthermore, the extruded multi-hole pipe 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 10 passages 12. In this example, the passages 12 of the extruded multi-hole pipe 1 have a circular cross-sectional shape. The thickness of the thinnest part of the outer wall portion 11 is, for example, 1.2 mm, and the thickness of the thinnest part of the partition wall portion 13 is, for example, 0.6 mm.

[0071] The extruded multi-hole tube in this example can be manufactured, for example, by the following method. First, using a casting raw material containing aluminum waste, an ingot having the chemical composition (alloy symbols A1 to A5) 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.

[0072] After the ingot is formed, the ingot is held at a temperature of 560°C for 6 hours to perform the first homogenization treatment. After the first homogenization treatment is completed, the ingot is held at a temperature of 480°C for 8 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.

[0073] After the second homogenization process is completed, the ingot is heated until its temperature reaches 500°C. While maintaining this temperature, the ingot is hot-extruded, and then the extruded perforated tube 1, immediately after hot extrusion, is cooled to an average cooling rate of 1°C / second until it reaches 150°C. After cooling is complete, the extruded perforated tube 1 is held at a temperature of 180°C for 8 hours for artificial aging treatment.

[0074] Based on the above, test materials S1 to S2 shown in Table 2 can be obtained. Test materials R1 to R2 shown in Table 2 are for comparison with test materials S1 to S2. The method for preparing test materials R1 to R2 is the same as that for test materials S1 to S2, except that the chemical composition of the ingot is changed to alloy symbols A3 to A4 shown in Table 1.

[0075] The evaluation methods for the tensile strength and extrudeability of each test material are described below.

[0076] • Tensile strength First, each test material is cut to obtain a 60 mm long specimen. The length and mass of this specimen are precisely measured, and the cross-sectional area of ​​the specimen is calculated based on these values ​​and the density of the aluminum alloy constituting the specimen. Next, the specimen is mounted between the fixed chuck and the movable chuck of a tensile testing machine. Then, the movable chuck is moved at a tensile speed of 2 mm / min, and a load-displacement curve is obtained by applying a tensile force to the specimen. Based on the load-displacement curve obtained in this way and the cross-sectional area of ​​the specimen obtained by the method described above, the tensile strength and 0.2% yield stress are calculated. In addition, the elongation is calculated based on the load-displacement curve. Table 2 shows the tensile strength, 0.2% yield stress, and elongation of each test material.

[0077] • 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.

[0078] [Table 1]

[0079] [Table 2]

[0080] As shown in Tables 1 and 2, test materials S1 and S2 have the aforementioned specific chemical composition. Furthermore, in the manufacturing process of test materials S1 and S2, the ingots having the aforementioned specific chemical composition are subjected to homogenization treatment, hot extrusion, cooling, and artificial aging treatment under the aforementioned specific conditions. Therefore, test materials S1 and S2 have high strength, excellent extrudeability during hot extrusion, and a good appearance.

[0081] On the other hand, test material R1 does not contain Mn. Therefore, the strength of test material R1 is lower than that of test materials S1 and S2.

[0082] Test material R2 does not contain Cu, and its Mn content is less than the specified range. Therefore, the strength of test material R2 is lower than that of test materials S1 and S2.

[0083] Although specific embodiments of the extruded multi-hole tube and its manufacturing method according to the present invention have been described above based on the examples, the specific embodiments of the extruded multi-hole tube and its manufacturing method according to the present invention are not limited to the embodiments described in the examples, and the configuration can be modified as appropriate without impairing the spirit of the present invention. [Explanation of Symbols]

[0084] 1. Extruded multi-hole tube 11 Exterior wall 12 aisles 13 Bulkhead

Claims

1. The chemical composition contains Si: 0.30% to 1.80% by mass, Cu: 0.10% to 0.50% by mass, Mn: 0.30% to 1.00% by mass, Mg: 0.30% to 1.00% by mass, and Cr: greater than 0% to 0.080% by mass, and further contains one or more elements selected from the group consisting of Fe: 0.40% or less by mass, Zn: 0.60% or less by mass, Ti: 0.10% or less by mass, Zr: 0.10% or less by mass, and B: 0.10% or less, with the remainder being Al and unavoidable impurities. An extruded multi-hole tube with a tensile strength of 290 MPa or more.

2. The extruded multi-hole tube according to claim 1, wherein the extruded multi-hole tube has a flattened cross-sectional shape, and the ratio of the width to the thickness of the extruded multi-hole tube is 5 or more and 30 or less.

3. The extruded multi-hole tube according to claim 1 or 2, wherein 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 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 0.2 mm or more and 2.0 mm or less.

4. A method for manufacturing an extruded multi-hole tube according to any one of claims 1 to 3, A casting having the aforementioned chemical components is prepared. The ingot is subjected to a homogenization treatment by holding it at a temperature of 450°C to 620°C for 2 hours or more. Subsequently, the ingot is subjected to hot extrusion to produce the extruded multi-hole tube. After the hot extrusion is completed, the extruded multi-hole tube is cooled so that the average cooling rate until the temperature of the extruded multi-hole tube reaches 150°C is 1°C / second or more. A method for manufacturing an extruded multi-hole tube, comprising holding the extruded multi-hole tube, after cooling, at a temperature of 150°C to 200°C for two hours or more to perform artificial aging treatment.

5. The method for manufacturing an extruded multi-hole tube according to claim 4, wherein at least a portion of the casting raw material is aluminum waste when producing the ingot.

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