Extrusion material made of aluminum alloy

Abstract

To provide an extrusion material made of aluminum alloy.SOLUTION: An extrusion material contains Cr by 0.05 mass% or more and 1.00 mass% or less, Fe by 0.05 mass% or more and 1.00 mass% or less, Si by 0.05 mass% or more and 1.50 mass% or less, and the balance consists of Al and inevitable impurities, where Fe and Si satisfy the relation of 0.8Fe≤Si, an intermetallic compound containing Cr having 0.01 μm or more and less than 5.00 μm of diameter on a circle-equivalent diameter is 10 or more in an observation visual field per 10000 μm2 of an ED-TD parallel surface, and furthermore, an intermetallic compound having 10 μm or more of diameter on a circle-equivalent diameter is less than 3 in an observation visual field per 10000 μm2 of an ED-TD parallel surface.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an extruded material made of an aluminum alloy.

Background Art

[0002] Aluminum is known as a metal with relatively good corrosion resistance. However, when exposed to a chloride environment, the oxide film is destroyed and corrosion occurs. In this case, the corrosion tends to progress in the thickness direction of the material plate, and it penetrates the material in a relatively short time, leading to problems such as a decrease in material strength and leakage of the contents. Therefore, when using aluminum, it is necessary to perform some anticorrosion treatment. As general anticorrosion methods, there are surface treatment using a coating film with excellent environmental resistance, and a method of extending the life by controlling the corrosion form in a planar shape by Zn spraying and diffusion treatment.

[0003] Patent Document 1 discloses a method for manufacturing a laminated metal material, in which a surface treatment agent is applied to the surface of an aluminum alloy to form a corrosion-resistant oxide film, and a resin film is further laminated on the oxide film. Patent Document 2 discloses an extruded material of an aluminum-zinc-based alloy, and an anodic oxide film that exhibits excellent corrosion resistance even in an environment where water vapor is present is formed on this extruded material. Patent Document 3 discloses a tube made of a hollow extruded material of aluminum, and the surface of this tube is formed of a diffusion layer of a metal more base than the tube (aluminum).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] Although the performance of conventional anti-corrosion methods is excellent, surface treatments and multi-layer materials are costly. In addition, if there are coating unevennesses in the surface treatment, there is a risk of corrosion. There is also a risk of corrosion when the surface is damaged by external factors during use in the market. Also, from the perspective of realizing a carbon-neutral society, which has attracted attention in recent years, surface treatments and Zn spraying also have the problem of reducing recyclability. From the above points, it has been necessary to develop a highly corrosion-resistant aluminum alloy that can be used in a single layer without using such anti-corrosion methods.

[0006] Therefore, an object of the present invention is to provide a highly corrosion-resistant aluminum alloy.

Means for Solving the Problems

[0007] In the production of an extruded material made of an aluminum alloy added with Cr, Fe, and Si, the inventors have found that by controlling the production conditions to densely distribute the Cr-containing compound, even if corrosion occurs on the alloy surface, the Cr-containing highly corrosion-resistant film uses the corrosion as a driving force to cover the corroded part, thereby suppressing the progress of corrosion.

[0008] The extruded material made of the aluminum alloy of the present invention contains Cr in an amount of 0.05% by mass or more and 1.00% by mass or less, Fe in an amount of 0.05% by mass or more and 1.00% by mass or less, and Si in an amount of 0.05% by mass or more and 1.50% by mass or less, with the balance being Al and inevitable impurities, and Fe and Si satisfy the relationship of 0.8Fe ≦ Si, and the Cr-containing intermetallic compound having a diameter of 0.01 μm or more and less than 5.00 μm in terms of equivalent circle diameter is 10 or more in the observation field of view per 10000 μm 2 in the ED-TD parallel plane, and further, the intermetallic compound having a diameter of 10 μm or more in terms of equivalent circle diameter is less than 3 in the observation field of view. ED is the extrusion direction, and TD is the transverse direction orthogonal to both ED and the normal direction. The ED-TD parallel plane is a plane parallel to both ED and TD formed by shaving the surface of the extruded material.

[0009] Cr: 0.05 mass% or more and 1.00 mass% or less By densely distributing the Cr-containing compound, when the compound is decomposed by slight corrosion, Cr is concentrated on the alloy surface layer to form a corrosion-resistant oxide film containing Cr in the corroded part, thereby improving the corrosion resistance of the alloy. If the Cr content is less than 0.05 mass%, a sufficient corrosion resistance effect (formation of a highly corrosion-resistant oxide film containing Cr) cannot be obtained. If it exceeds 1.00 mass%, coarse intermetallic compounds are generated during casting, resulting in a decrease in extrudability.

[0010] Fe: 0.05 mass% or more and 1.00 mass% or less Fe is distributed as intermetallic compounds such as Al-Fe-based and Al-Fe-Si-based. By devising the manufacturing conditions, these Fe-containing compounds can be doped with Cr at the Fe sites, and the Cr-containing intermetallic compounds can be densely distributed. If the Fe content is less than 0.05 mass%, the manufacturing cost increases. If it exceeds 1.00 mass%, coarse intermetallic compounds are generated during casting, resulting in a decrease in extrudability.

[0011] Si: 0.05 mass% or more and 1.50 mass% or less When Si is contained together with Fe, the formation of Al-Fe-Si-based intermetallic compounds with a smaller cathodic reaction compared to Al-Fe-based intermetallic compounds is favored, and a highly corrosion-resistant oxide film containing Cr is formed against slight corrosion, thereby improving the corrosion resistance of the alloy. If the Si content is less than 0.05 mass%, a sufficient effect (formation of a highly corrosion-resistant oxide film containing Cr) cannot be obtained. If Si exceeds 1.50 mass%, the solidus temperature decreases, resulting in leakage of the molten metal during casting.

[0012] (Relationship between the contents of Fe and Si) Fe and Si have a relationship of 0.8Fe≦Si in terms of mass % in the composition of the aluminum alloy (hereinafter referred to as the relational formula). By satisfying the above relational expression, the formation of Al-Fe-Si intermetallic compounds, which have a smaller cathodic reaction than Al-Fe intermetallic compounds, can be favored, and a highly corrosion-resistant oxide film containing Cr against minor corrosion can be formed, improving the corrosion resistance of the alloy. If the relational expression is not satisfied, the formation of Al-Fe compounds becomes favored, and the corrosion resistance decreases.

[0013] (Distribution of fine intermetallic compounds) ED-TD parallel surface 10000μm 2 Within an observation field per unit area, there are 10 or more intermetallic compounds containing Cr having an equivalent circle diameter of 0.01 μm or more and less than 5.00 μm. By densely distributing fine intermetallic compounds containing Cr, when the intermetallic compounds containing Cr are decomposed by minor corrosion, Cr is concentrated on the surface layer of the alloy, forming an oxide film containing Cr with excellent corrosion resistance in the corroded area, thereby improving the corrosion resistance of the alloy. 2 If the number of particles per observation field is less than 10, it is not possible to form an oxide film containing Cr.

[0014] (Distribution of coarse intermetallic compounds) ED-TD parallel surface 10000μm 2 There are less than three intermetallic compounds with a circle equivalent diameter of 10 μm or more in the observation field per unit area. If a large number of coarse intermetallic compounds having an equivalent circle diameter of 10 μm or more are distributed, they will act as starting points for corrosion and further inhibit the formation of an oxide film containing Cr, thereby reducing the corrosion resistance of the alloy.

[0015] (Corrosion resistance after SWAAT test) The corroded area of ​​the test material subjected to the SWAAT test (Sea Water Acidified Test: conforming to ASTM G85-A) for 24 hours contains Cr in the film. The corrosion resistance of the alloy is improved by generating a film containing Cr using slight corrosion as the driving force.

[0016] The extruded material made of the aluminum alloy of the present invention preferably contains Ti in an amount of 0.05% by mass or more and 1.00% by mass or less. Ti can reduce the progress of corrosion in the thickness depth direction by distributing layers with different Ti concentrations through the peritectic reaction during casting and the extrusion process. When the Ti content is less than 0.05% by mass, the improvement in corrosion resistance is low. When the Ti content exceeds 1.00% by mass, coarse intermetallic compounds are generated during casting, resulting in a decrease in extrudability. The extruded material made of the aluminum alloy of the present invention may further contain any one or a plurality of elements among Mn, Mg, Cu, Zr, V, Sr, Sc, and Mo.

[0017] The extruded material made of the aluminum alloy of the present invention preferably contains Mn in an amount of 0.10% by mass or more and 2.00% by mass or less. Mn precipitates as intermetallic compounds such as Al-Mn-based, Al-Mn-Si-based, and Al-Mn-Si-Fe-based, and can improve the material strength of the extruded material made of the aluminum alloy. When the Mn content is less than 0.10% by mass, the effect of improving the material strength is low. When the Mn content exceeds 2.00% by mass, coarse intermetallic compounds are generated during casting, resulting in a decrease in extrudability.

[0018] The extruded material made of the aluminum alloy of the present invention preferably contains Mg in an amount of 0.01% by mass or more and 3.00% by mass or less. Mg can be dissolved or precipitated as intermetallic compounds such as Mg2Si, and can improve the material strength of the extruded material made of the aluminum alloy. When the Mg content is less than 0.01% by mass, the effect of improving the material strength is low. When the Mg content exceeds 3.00% by mass, the material strength of the extruded material made of the aluminum alloy is too high, making it difficult to manufacture (extrude) the material.

[0019] The extruded material made of the aluminum alloy of the present invention preferably contains Cu in an amount of 0.01% by mass or more and 1.00% by mass or less.

[0020] Cu can improve the material strength of an extruded material made of an aluminum alloy by solid solution. If the content of Cu is less than 0.01% by mass, the effect of improving the material strength is low. If the content of Cu exceeds 1.00% by mass, the material strength of the extruded material made of an aluminum alloy is too high, making it difficult to manufacture (extrude) the material.

[0021] The extruded material made of the aluminum alloy of the present invention preferably contains any one or a plurality of elements of Zr, V, Sr, Sc, and Mo, each in an amount of 0.01% by mass or more and 0.50% by mass or less. Zr, V, Sr, Sc, and Mo can form intermetallic compounds to improve the material strength of the extruded material made of an aluminum alloy. If the content of Zr, V, Sr, Sc, and Mo is less than 0.05% by mass, the effect of improving the material strength is low. If the content of Zr, V, Sr, Sc, and Mo exceeds 0.50% by mass, coarse intermetallic compounds are generated during casting, resulting in a decrease in extrudability.

Advantages of the Invention

[0022] According to the extruded material made of the aluminum alloy of the present invention, intermetallic compounds containing Cr are densely distributed, and a highly corrosion-resistant film containing Cr is formed using slight corrosion as a driving force, so that the corrosion resistance can be maintained for a long period of time.

Embodiments for Carrying Out the Invention

[0023] The extruded material according to the embodiment of the present invention contains 0.05% by mass or more and 1.00% by mass or less of Cr, 0.05% by mass or more and 1.00% by mass or less of Fe, and 0.05% by mass or more and 1.50% by mass or less of Si, and the balance consists of Al and unavoidable impurities.

[0024] Cr: 0.05% by mass or more and 1.00% by mass or less By densely distributing a compound containing Cr, when the compound is decomposed by slight corrosion, Cr can be concentrated on the alloy surface layer to form a corrosion-resistant oxide film containing Cr in the corroded part, thereby improving the corrosion resistance of the alloy. If the Cr content is less than 0.05% by mass, a sufficient corrosion resistance effect (formation of a highly corrosion-resistant oxide film containing Cr) cannot be obtained. If it exceeds 1.00% by mass, coarse intermetallic compounds are formed during casting, resulting in a decrease in extrudability.

[0025] Fe: 0.05% by mass or more and 1.00% by mass or less Fe is distributed as intermetallic compounds such as Al-Fe-based and Al-Fe-Si-based compounds. By devising the manufacturing conditions, these Fe-containing compounds can be doped with Cr at the Fe sites, and the Cr-containing intermetallic compounds can be densely distributed. If the Fe content is less than 0.05% by mass, the manufacturing cost will increase. If it exceeds 1.00% by mass, coarse intermetallic compounds are formed during casting, resulting in a decrease in extrudability.

[0026] Si: 0.05% by mass or more and 1.50% by mass or less When Si is contained together with Fe, it promotes the formation of Al-Fe-Si-based compounds with a smaller cathodic reaction compared to Al-Fe-based compounds, forming an oxide film containing Cr against slight corrosion and improving the corrosion resistance of the alloy. If the Si content is less than 0.05% by mass, a sufficient effect (formation of a highly corrosion-resistant oxide film containing Cr) cannot be obtained. If the Si content exceeds 1.50% by mass, the solidus temperature decreases, resulting in leakage of molten metal during casting.

[0027] (Relationship between the contents of Fe and Si) Fe and Si have a relationship of 0.8Fe ≤ Si with respect to the mass percentage of the composition of the aluminum alloy (hereinafter referred to as the relational expression). By satisfying the above relational expression, the formation of Al-Fe-Si-based compounds with a smaller cathodic reaction than Al-Fe-based compounds can be promoted, forming an oxide film containing Cr against slight corrosion and improving the corrosion resistance of the alloy. If the relational expression cannot be satisfied, the formation of Al-Fe-based compounds becomes dominant, resulting in a decrease in corrosion resistance.

[0028] The extruded material according to an embodiment of the present invention may contain any one or more of Ti, Mn, Mg, Cu, Zr, V, Sr, Sc, and Mo.

[0029] The extruded material made of an aluminum alloy preferably contains Ti in an amount of 0.05% by mass or more and 1.00% by mass or less. Ti can reduce the progress of corrosion in the wall thickness depth direction by distributing layers with different Ti concentrations through the peritectic reaction during casting and the extrusion process. If Ti is less than 0.05% by mass, the improvement in corrosion resistance is low. The extruded material made of an aluminum alloy in which Ti exceeds 1.00% by mass preferably contains Mn in an amount of 0.10% by mass or more and 2.00% by mass or less.

[0030] The extruded material made of an aluminum alloy preferably contains Mn in an amount of 0.10% by mass or more and 2.00% by mass or less. Mn precipitates as intermetallic compounds such as Al-Mn, Al-Mn-Si, and Al-Mn-Si-Fe systems, and can improve the material strength of the extruded material made of an aluminum alloy. If Mn is less than 0.10% by mass, the effect of improving the material strength is low, and if Mn exceeds 2.00% by mass, coarse intermetallic compounds are generated during casting and the extrudability decreases.

[0031] The extruded material made of an aluminum alloy preferably contains Mg in an amount of 0.01% by mass or more and 3.00% by mass or less. Mg can precipitate as a solid solution or as intermetallic compounds such as Mg2Si, and can improve the material strength of the extruded material made of an aluminum alloy. If Mg is less than 0.01% by mass, the effect of improving the material strength is low, and if Mg exceeds 3.00% by mass, the material strength of the extruded material made of an aluminum alloy is too high, making it difficult to manufacture the material (extrusion processing).

[0032] The extruded material made of an aluminum alloy preferably contains Cu in an amount of 0.01% by mass or more and 1.00% by mass or less. Cu can improve the material strength of the extruded material made of an aluminum alloy by solid solution. If the Cu content is less than 0.01% by mass, the effect of improving the material strength is low. If the Cu content exceeds 1.00% by mass, the material strength of the extruded material made of aluminum alloy is too high, making it difficult to manufacture the material (extrusion).

[0033] The extruded material made of aluminum alloy preferably contains any one or a plurality of elements of Zr, V, Sr, Sc, and Mo in an amount of 0.01% by mass or more and 0.50% by mass or less for each element. Zr, V, Sr, Sc, and Mo can form intermetallic compounds to improve the material strength of the extruded material made of aluminum alloy. If the content of Zr, V, Sr, Sc, and Mo is less than 0.05% by mass, the effect of improving the material strength is low. If the content of Zr, V, Sr, Sc, and Mo exceeds 0.50% by mass, coarse intermetallic compounds are generated during casting, resulting in a decrease in extrudability.

[0034] (Distribution of fine intermetallic compounds) 10000 μm of the ED-TD parallel plane 2 In the observation field per 10000 μm, there are 10 or more intermetallic compounds containing Cr with an equivalent circle diameter of 0.01 μm or more and less than 5.00 μm. ED is the extrusion direction, TD is the transverse direction orthogonal to ED and the thickness direction (ND), and the ED-TD parallel plane is a plane parallel to ED and TD formed by shaving the surface of the extruded material.

[0035] Due to the dense distribution of fine intermetallic compounds containing Cr, when the intermetallic compounds containing Cr are decomposed by slight corrosion, Cr is concentrated on the alloy surface layer to form a corrosion-resistant oxide film containing Cr in the corroded part, thereby improving the corrosion resistance of the alloy. If the number of fine intermetallic compounds containing Cr is less than 10 in the observation field per 10000 μm 2 it is impossible to form an oxide film containing Cr.

[0036] (Distribution of coarse intermetallic compounds) 10000 μm of the ED-TD parallel plane 2 In the observation field per 10000 μm, there are less than 3 intermetallic compounds with an equivalent circle diameter of 10 μm or more. The presence of a large number of coarse intermetallic compounds with a diameter of 10 μm or more in terms of equivalent circle diameter serves as a starting point for corrosion and further inhibits the formation of an oxide film containing Cr, resulting in a decrease in the corrosion resistance of the alloy.

[0037] (Corrosion of Extruded Materials Made of Aluminum Alloys) In the extruded material made of aluminum alloy, intermetallic compounds containing Cr are densely distributed, and a film containing Cr is formed using slight corrosion as the driving force. This oxide film containing Cr has high corrosion resistance. The conditions for confirming the oxide film are to conduct the SWAAT test (Sea Water Acidified Test: conforming to ASTM's G85 - A) on a test specimen made of the aluminum alloy with the above composition for 24 hours. In the test specimen that has undergone the SWAAT test, a corroded part is generated, and surface analysis is performed on this corroded part in the thickness direction by X - Ray Photoelectron Spectroscopy (hereinafter referred to as XPS). This XPS measurement is performed every 1.2 nm in terms of the depth converted from the sputtering time in terms of SiO2, and the part from the surface layer to the depth direction until the concentrations (intensities) of O and Al are reversed is defined as the oxide film (O > Al on the surface layer side), and the presence or absence of Cr is confirmed at any measurement point in the oxide film. When Cr is present, a peak appears near 574 eV.

[0038] (Manufacturing Method) The manufacturing method of the extruded material made of aluminum alloy includes an ingot manufacturing process for manufacturing an ingot, a homogenization process for homogenizing the ingot, and an extrusion process for extruding the ingot.

[0039] (Ingot Manufacturing Process) The ingot manufacturing process manufactures an ingot (slab) by melt casting. The ingot is made of an aluminum alloy containing 0.05% by mass or more and 1.00% by mass or less of Cr, 0.05% by mass or more and 1.00% by mass or less of Fe, and 0.05% by mass or more and 1.50% by mass or less of Si, with the balance being Al and inevitable impurities. This aluminum alloy may contain any one or a plurality of Ti, Mn, Mg, Cu, Zr, V, Sr, Sc, and Mo. Preferably, the aluminum alloy contains 0.05% by mass or more and 1.00% by mass or less of Ti. Preferably, the aluminum alloy contains 0.10% by mass or more and 2.00% by mass or less of Mn. Preferably, the aluminum alloy contains 0.01% by mass or more and 3.00% by mass or less of Mg. Preferably, the aluminum alloy contains 0.01% by mass or more and 1.00% by mass or less of Cu. Preferably, the aluminum alloy contains any one or a plurality of the elements Zr, V, Sr, Sc, and Mo, each element in an amount of 0.01% by mass or more and 0.50% by mass or less. The casting temperature is 700°C or more and less than 790°C, preferably 730°C or more and less than 770°C. When the casting temperature during casting is less than 700°C, the time staying in the crystallization temperature range during casting becomes long, and coarse intermetallic compounds that cannot be sufficiently crushed in the extrusion process are generated. When the casting temperature during casting is 790°C or more, it becomes impossible to manufacture due to molten metal leakage. The cooling rate is 0.1°C / s or more, preferably 1°C / s or more. When the cooling rate during casting is less than 0.1°C / s, the time staying in the crystallization temperature range during casting becomes long, and coarse intermetallic compounds that cannot be sufficiently crushed in the extrusion process are generated.

[0040] (Homogenization process) In the homogenization process, the state of heating the ingot to 400°C or more and less than 600°C, preferably 430°C or more and less than 580°C, is maintained. The holding time is 1 hour or more and 12 hours or less, preferably 3 hours or more and 10 hours or less. By performing heat treatment of the ingot at a predetermined temperature, Al-Fe-based and Al-Fe-Si-based intermetallic compounds are precipitated, and further Cr doping into Fe sites is promoted. If the temperature is less than 400 °C, a sufficient effect (homogenization) cannot be obtained. If the temperature is 600 °C or higher, the precipitates coarsen or redissolve, resulting in a sparse distribution.

[0041] (Extrusion process) In the extrusion process, hot extrusion is performed. During extrusion, processing heat is generated due to the friction between the aluminum and the die, causing the material temperature to rise. The maximum temperature reached during extrusion is, for example, less than 620 °C, preferably less than 580 °C. If it exceeds 620 °C, the distribution becomes sparse due to coarsening and redissolution of the compounds. The extrusion speed is 0.5 m / s or more, preferably 0.8 m / s or more. By setting the extrusion speed to 0.5 m / s or more, processing stress can be applied to the material to crush coarse intermetallic compounds.

[0042] Through the extrusion process, an extruded material made of an aluminum alloy with the above composition is completed. The manufacturing method of the extruded material may perform solution treatment, aging treatment, and brazing heat treatment as necessary.

[0043] In the manufacturing method of the extruded material made of an aluminum alloy according to an embodiment of the present invention, by using an aluminum alloy in which the content ratio of Fe and Si is adjusted and added together with Cr as a raw material and controlling the manufacturing conditions of casting, homogenization treatment, and extrusion temperature, a compound with a small cathode reaction can be preferentially generated, and coarse crystallites can be suppressed. As a result, it is possible to prevent coarse intermetallic compounds from becoming the starting point of corrosion and to prevent the formation of the Cr-containing film from being inhibited.

[0044] In the extruded material made of an aluminum alloy according to an embodiment of the present invention, fine intermetallic compounds containing Cr are densely distributed. When the fine intermetallic compounds containing Cr are decomposed by corrosion, an oxide film with high corrosion resistance containing the decomposed Cr is formed. As a result, the extruded material made of an aluminum alloy can be used for a long time even if it is a single layer. Forming the surface of a conventional aluminum alloy as an anodic oxide film or using a multi-layer material containing a sacrificial anticorrosive material incurs high costs. Also, if there are coating irregularities in the surface treatment, there is a risk of corrosion. There is also a risk of corrosion when the surface is damaged by external factors during use in the market. When using Zn spraying, corrosion of the sacrificial anode material inevitably occurs for sacrificial corrosion prevention. If the corrosion products clog the flow path of the device or adhere to the surface of the device material, it may reduce the performance of the device and also damage the appearance of the device. In the case of applications such as air conditioner indoor units, it is not desirable because the corrosion products scatter. Furthermore, conventional surface treatments and multi-layer materials reduce recyclability. On the other hand, according to the extruded material according to an embodiment of the present invention, an oxide film containing Cr is formed using corrosion as a driving force, so that the generation of corrosion products can be suppressed, clogging of the flow path can be prevented, and the function and appearance of the material surface can be maintained well. The extruded material is formed into a cylindrical shape, for example, and used for pipe materials, tubes of heat exchangers, etc.

Examples

[0045] The corrosion resistance of extruded materials extruded by changing the materials and manufacturing conditions was evaluated.

[0046] (Materials) The materials used for manufacturing include those containing Cr, Fe, and Si, with the balance consisting of Al and inevitable impurities, those containing Cr, Fe, and Si, with the balance consisting of Al and inevitable impurities, and those with Ti added. Materials 1 to 9 contain Cr in an amount of 0.05 mass% or more and 1.00 mass% or less, Fe in an amount of 0.05 mass% or more and 1.00 mass% or less, and Si in an amount of 0.05 mass% or more and 1.50 mass% or less, with the balance being Al and inevitable impurities, and the contents of Fe and Si satisfy the relationship of 0.8Fe ≤ Si. The materials 10 to 12 contain 0.05% by mass or more and 1.00% by mass or less of Cr, 0.05% by mass or more and 1.00% by mass or less of Fe, 0.05% by mass or more and 1.50% by mass or less of Si, and 0.05% by mass or more and 1.00% by mass or less of Ti, with the balance being Al and inevitable impurities, and the Fe and Si contents satisfy the relationship of 0.8Fe ≤ Si. Hereinafter, the ranges of 0.05% by mass or more and 1.00% by mass or less of Cr, 0.05% by mass or more and 1.00% by mass or less of Fe, 0.05% by mass or more and 1.50% by mass or less of Si, and 0.05% by mass or more and 1.00% by mass or less of Ti may all be referred to as the first composition ranges. The materials 35 and 36 contain 0.05% by mass or more and 1.00% by mass or less of Cr, 0.05% by mass or more and 1.00% by mass or less of Fe, and 0.05% by mass or more and 1.50% by mass or less of Si, and Ti is outside the range of 0.05% by mass or more and 1.00% by mass or less, with the balance being Al and inevitable impurities, and the Fe and Si contents satisfy the relationship of 0.8Fe ≤ Si. For the materials 28 to 33, the content of any one of Cr, Fe, Si, and Ti is not controlled within the first composition range, and among these, for the material 32, the Fe and Si contents further do not satisfy the relationship of 0.8Fe ≤ Si. For the material 34, the contents of Cr, Fe, and Si are controlled within the first composition range, but the Fe and Si contents do not satisfy the relationship of 0.8Fe ≤ Si. Table 1 shows the mass % of Cr, Fe, Si, and Ti of each material and the relationship of 0.8Fe ≤ Si.

[0047]

Table 1

[0048] (Manufacturing method) The manufacturing method of the extruded material includes an ingot manufacturing process for manufacturing an ingot, a homogenization process for homogenizing the ingot, and an extrusion process for extruding the ingot.

[0049] (Ingot manufacturing process) The ingot manufacturing process manufactures an ingot (slab) by melting and casting. The casting temperature is 700 °C or higher and less than 790 °C. The cooling rate is 0.1 °C / s or higher.

[0050] (Homogenization process) In the homogenization process, the ingot is maintained in a state of being heated to 400 °C or higher and less than 600 °C. The holding time is 5 hours.

[0051] (Extrusion process) In the extrusion process, hot extrusion is performed. During extrusion, processing heat is generated due to the friction between aluminum and the die, the material temperature rises, and the maximum temperature reached during extrusion is less than 620 °C. The extrusion speed is 0.5 m / s or higher.

[0052] Table 2 shows the casting temperature, casting cooling rate, homogenization treatment temperature, extrusion temperature, and extrusion speed of each manufacturing method. Note that for manufacturing methods A to G, the casting temperature, casting cooling rate, homogenization treatment temperature, extrusion temperature, and extrusion speed are controlled within the above ranges, and for manufacturing methods H to L, any one of the casting temperature, casting cooling rate, homogenization treatment temperature, extrusion temperature, and extrusion speed is outside the above ranges.

[0053]

Table 2

[0054] Extruded materials made of aluminum alloy are produced from materials (any one of materials 1 to 12, 28 to 36) and manufacturing conditions (any one of manufacturing methods A to L) to obtain samples 1 to 12, 28 to 36, 41 to 52, 68 to 76, 81 to 100, 121 to 130, and the number of compounds, corrosion weight loss, and corrosion depth of each sample 1 to 12, 28 to 36, 41 to 52, 68 to 76, 81 to 100, 121 to 130 are measured. Note that the extruded material is formed in a cylindrical shape, its cross-section is a rectangular shape with a length of 1.3 mm and a width of 18.0 mm, and the thickness of each part of the cross-section is 0.3 mm.

[0055] i. Number of compounds (distribution state) From the sample, mechanical polishing and electrolytic polishing of the cut-out sample pieces were performed to produce a thin film, and 10,000 μm of the ED-TD parallel plane was observed with a TEM (transmission electron microscope). 2 (100 μm square) was set as the observation field, and fine compounds and coarse compounds were measured. The presence or absence of Cr in the compounds was determined by EPMA for compounds larger than 1 μm and by compositional analysis using EDS for compounds 1 μm or less. Fine compounds are intermetallic compounds having a circle equivalent diameter of 0.01 μm or more and less than 5.00 μm. Coarse compounds are intermetallic compounds having a circle equivalent diameter exceeding 10 μm. Tables 3 and 4 show the numbers of fine compounds and coarse compounds.

[0056] II. Film analysis of the corroded part of the extruded material The film on the corroded part of the test material loaded in the SWAAT test for 24 hours was analyzed. After loading the test material cut out from the extruded material in the SWAAT test for 24 hours, washing with pure water and thoroughly drying the test material, XPS measurement of the material surface layer was performed to determine the presence or absence of Cr in the film. The case where Cr was detected in the film was regarded as good, and the case where it was not detected was regarded as bad. Tables 3 and 4 show the film analysis results of each sample, with good being A and bad being C. The SWAAT test is a cycle test using 5% NaCl at pH 3 as the corrosion solution, spraying at 50 °C for 30 minutes and wetting at 50 °C for 90 minutes as one cycle. XPS measurement was performed every 1.2 nm in depth with the sputtering time converted to SiO2 depth. The oxide film was defined as the depth range from the surface layer until the concentrations of O and Al reversed in the depth direction (O > Al on the surface layer side), and the presence or absence of Cr detection (a peak appearing near 574 eV when Cr is present) at any measurement point in the oxide film was determined. Samples 1 to 9, 28 to 49, 68 to 90, 121 to 130 shown in Table 3 are made of aluminum alloys not containing Ti, and samples 10 to 12, 35, 36, 50 to 52, 75, 76, 91 to 100 shown in Table 4 are made of aluminum alloys containing Ti.

[0057] III. Corrosion weight loss A test specimen was cut out from the cylindrical extruded material with a length of 80 mm, and the range of 180 degrees around the central axis and the cylinder end of the outer peripheral surface were protected by masking, and the unmasked part of the outer peripheral surface was subjected to a corrosion test in an exposed state. The corrosion test was carried out for 1320 hours in the SWAAT test, and it was evaluated by the weight change (corrosion loss) before and after the corrosion test. The corrosion loss less than 5.0 mg / cm 2 was considered good, and the corrosion loss of 5.0 mg / cm 2 or more and less than 10.0 mg / cm 2 was considered slightly good, and 10.0 mg / cm 2 or more was evaluated as bad. Tables 3 and 4 show the evaluation of the corrosion loss of each sample 1 - 12, 28 - 36, 41 - 52, 68 - 76, 81 - 100, 121 - 130, with good being A, slightly good being B, and bad being C.

[0058] II. Corrosion Depth After the test specimen cut out from the extruded material was loaded with SWAAT for 1320 hours, the corrosion depth of the test specimen was evaluated. In this evaluation, first, the deepest corroded part on the exposed surface of the test specimen was identified using a non-contact step measuring instrument, and then the cross-section was exposed by resin embedding and polishing at the identified location, and the thinnest thickness t1 of the test specimen after corrosion was measured by observation. The difference between t1 and the thickness t0 of the test specimen measured in advance before the SWAAT test was defined as the corrosion depth (=t0 - t1). The corrosion depth less than 60 μm was considered good, 60 μm or more and less than 120 μm was considered slightly good, and 120 μm or more was considered bad. Tables 3 and 4 show the evaluation of the corrosion depth of each sample 1 - 12, 28 - 36, 41 - 52, 68 - 76, 81 - 100, 121 - 130, with good being A, slightly good being B, and bad being C.

[0059] III. Evaluation of Corrosion Resistance The corrosion resistance of the samples was evaluated based on the corrosion weight loss and the corrosion depth. When both the evaluation of the corrosion weight loss and the evaluation of the corrosion depth were good (A), it was considered good. When one was good (A) and the other was slightly good (B), or when both were slightly good (B), it was considered slightly good. When either was poor (C), it was considered poor. Tables 3 and 4 show the evaluation of the corrosion resistance of each of the samples 1 to 12, 28 to 36, 41 to 52, 68 to 76, 81 to 100, and 121 to 130, with good being designated as A, slightly good as B, and poor as C.

[0060]

Table 3

[0061]

Table 4

[0062] As shown in Table 3, Samples 1 to 9, 41 to 49, and 81 to 85 contain 0.05% by mass or more and 1.00% by mass or less of Cr, 0.05% by mass or more and 1.00% by mass or less of Fe, and 0.05% by mass or more and 1.50% by mass or less of Si, with the balance being Al and inevitable impurities, and the Fe and Si contents satisfying the relationship of 0.8Fe ≤ Si. They were manufactured by any of Manufacturing Methods A to G in which the manufacturing conditions of casting, homogenization treatment, and extrusion processing (extrusion temperature and extrusion speed) were controlled. As a result, compounds with a small cathodic reaction could be preferentially generated, fine intermetallic compounds containing Cr could be densely distributed, and coarse precipitates could be suppressed thereon. Furthermore, in the corroded part of the surface layer, it was confirmed that the corrosion weight loss was small, the corrosion depth was shallow, and an oxide film containing Cr in which the intermetallic compound was decomposed was formed, and the corrosion resistance was good.

[0063] As shown in Table 4, Samples 10 to 12, 35, 50 to 52, 75, 91 to 95 contain Cr at 0.05 mass% or more and 1.00 mass% or less, Fe at 0.05 mass% or more and 1.00 mass% or less, Si at 0.05 mass% or more and 1.50 mass% or less, and Ti at 0.05 mass% or more and 1.00 mass% or less, with the balance being Al and inevitable impurities, and any of Materials 10 to 12, 35 that satisfy the relationship of 0.8Fe ≤ Si for the contents of Fe and Si are manufactured by any of Manufacturing Methods A to G in which the manufacturing conditions of casting, homogenization treatment, and extrusion processing (extrusion temperature and extrusion speed) are controlled. As a result, a compound with a small cathode reaction can be preferentially generated, and fine intermetallic compounds containing Cr can be densely distributed, and coarse precipitates can be suppressed thereon. Furthermore, in the corroded part of the surface layer, it was confirmed that the corrosion weight loss was small, the corrosion depth was shallow, and an oxide film containing Cr in which the intermetallic compound was decomposed was formed, and the corrosion resistance was good. Samples 35 and 75 use Material 35 with a Ti content less than the first composition range, but it was confirmed that the corrosion resistance is good.

[0064] Samples 28 to 31, 33, 68 to 73, 121 to 125 were manufactured by any of manufacturing methods A to G in which the manufacturing conditions of casting, homogenization treatment, and extrusion (extrusion temperature, extrusion speed) were controlled using any of materials 28 to 31 and 33 whose content of any of Cr, Fe, and Si was outside the first composition range. Samples 32 and 72 were manufactured by any of manufacturing methods A and G in which the manufacturing conditions of casting, homogenization treatment, and extrusion (extrusion temperature, extrusion speed) were controlled using material 32 whose Si content was outside the first composition range and whose Fe and Si contents did not satisfy the relationship of 0.8Fe ≦ Si. Further, samples 34 and 74 were manufactured by any of manufacturing methods A and G in which the manufacturing conditions of casting, homogenization treatment, and extrusion (extrusion temperature, extrusion speed) were controlled, using material 34 whose contents of Cr, Fe, and Si were within the first composition range but whose Fe and Si contents did not satisfy the relationship of 0.8Fe ≦ Si, to produce extruded materials. Regardless of the control of the manufacturing conditions of casting, homogenization treatment, and extrusion (extrusion temperature, extrusion speed), it was confirmed that when the content of any of Cr, Fe, and Si was outside the first composition range or when the Fe and Si contents did not satisfy the relationship of 0.8Fe ≦ Si, the corrosion resistance was low. Also, samples 29, 31, 33, 69, 71, 73 were manufactured by any of manufacturing methods A and G using any of materials 29, 31, and 33 whose content of any of Cr, Fe, and Si was outside the first composition range, and since the manufacturing was difficult, the corrosion resistance was not evaluated. Samples 30 and 70 were manufactured by any of manufacturing methods A and G using material 30 with a low Fe content, and since the cost was high, the corrosion resistance was not evaluated.

[0065] Samples 126 to 130 were manufactured by any of manufacturing methods H to L in which none of the manufacturing conditions of casting, homogenization treatment, and extrusion (extrusion temperature and extrusion speed) were controlled, using material 28 whose Cr content was outside the first composition range. It was confirmed that when none of the manufacturing conditions of casting, homogenization treatment, and extrusion (extrusion temperature and extrusion speed) were controlled, the corrosion resistance of the extruded material was low. Samples 86 to 90 contain 0.05% by mass or more and 1.00% by mass or less of Cr, 0.05% by mass or more and 1.00% by mass or less of Fe, and 0.05% by mass or more and 1.50% by mass or less of Si, with the balance being Al and inevitable impurities, and are made of Material 1 where the Fe and Si contents satisfy the relationship of 0.8Fe ≤ Si, and are manufactured by any one of manufacturing methods H to L that do not control any of the manufacturing conditions of casting, homogenization treatment, and extrusion (extrusion temperature and extrusion speed). It was confirmed that if any of the manufacturing conditions of casting, homogenization treatment, and extrusion (extrusion temperature and extrusion speed) are not controlled, the corrosion resistance of the extruded material is low.

[0066] Samples 96 to 100 contain 0.05% by mass or more and 1.00% by mass or less of Cr, 0.05% by mass or more and 1.00% by mass or less of Fe, 0.05% by mass or more and 1.50% by mass or less of Si, and 0.05% by mass or more and 1.00% by mass or less of Ti, with the balance being Al and inevitable impurities, and are made of Material 10 where the Fe and Si contents satisfy the relationship of 0.8Fe ≤ Si, and are manufactured by any one of manufacturing methods H to L that do not control any of the manufacturing conditions of casting, homogenization treatment, and extrusion (extrusion temperature and extrusion speed). It was confirmed that if any of the manufacturing conditions of casting, homogenization treatment, and extrusion (extrusion temperature and extrusion speed) are not controlled, the corrosion resistance is low.

[0067] Samples 36 and 76 contain 0.05% by mass or more and 1.00% by mass or less of Cr, 0.05% by mass or more and 1.00% by mass or less of Fe, and 0.05% by mass or more and 1.50% by mass or less of Si, and the Ti content is outside the first composition range, with the balance being Al and inevitable impurities, and are made of Material 36 where the Fe and Si contents satisfy the relationship of 0.8Fe ≤ Si, and the extruded materials are manufactured by any one of manufacturing methods A and G that control the manufacturing conditions of casting, homogenization treatment, and extrusion (extrusion temperature, extrusion speed). Since the Ti content is high and the manufacturing is difficult, the corrosion resistance was not evaluated.

Examples

[0068] The tensile strength Rm of the extruded materials manufactured by changing the materials and manufacturing conditions was evaluated.

[0069] (Materials) The material used for manufacturing the extruded material contains Cr, Fe, and Si, and also contains any one or more of the elements Ti, Mn, Mg, Cu, Zr, V, Sr, Sc, and Mo, with the balance consisting of Al and inevitable impurities. Materials 13 to 27 contain 0.05% by mass or more and 1.00% by mass or less of Cr, 0.05% by mass or more and 1.00% by mass or less of Fe, and 0.05% by mass or more and 1.50% by mass or less of Si, with the balance being Al and inevitable impurities, and the contents of Fe and Si satisfy the relationship of 0.8Fe ≤ Si. Also, in Materials 13 to 27, as the contents, Ti is 0.05% by mass or more and 1.00% by mass or less, Mn is 0.10% by mass or more and 2.00% by mass or less, Mg is 0.01% by mass or more and 3.00% by mass or less, Cu is 0.01% by mass or more and 1.00% by mass or less, and any one or more of the elements Zr, V, Sr, Sc, and Mo are 0.01% by mass or more and 0.50% by mass or less for each element. Hereinafter, the range of 0.10% by mass or more and 2.00% by mass or less of Mn and the range of 0.01% by mass or more and 3.00% by mass or less of Mg may both be referred to as the second composition range. In Materials 37 to 40, the content of either Mn or Mg is outside the second composition range. Table 5 shows the mass percentages of Cr, Fe, Si, Ti, Mn, Mg, Cu, Zr, V, Sr, Sc, and Mo in each of Materials 13 to 27 and 37 to 40, and the relationship of 0.8Fe ≤ Si regarding the mass percentages of Fe and Si.

[0070]

Table 5

[0071] (Manufacturing Method) The manufacturing method of the extruded material includes an ingot manufacturing process for manufacturing an ingot, a homogenization process for homogenizing the ingot, and an extrusion process for extruding the ingot. The manufacturing method is any one of Manufacturing Methods A to L in Table 2 above.

[0072] An extruded material was prepared using a material (any one of Materials 13 to 27, 37 to 40) and manufacturing conditions (any one of Manufacturing Methods A to L) to obtain Samples 13 to 27, 37 to 40, 53 to 67, 77 to 80, 101 to 120, and the strength of each of Samples 13 to 27, 37 to 40, 53 to 67, 77 to 80, 101 to 120 was measured. The extruded material is a pipe material with an inner diameter of 27 mm and an outer diameter of 30 mm. From this pipe material, No. 13 Type B test pieces were cut out according to the Metallic Materials - Tensile Testing Method (JIS Z2241:2011), and the tensile strength Rm was measured. A tensile strength Rm of 140 MPa or more was judged as good, a tensile strength Rm of 100 MPa or more and less than 140 MPa was judged as slightly good, and a tensile strength Rm of less than 100 MPa was judged as poor. Table 5 shows the tensile strength Rm of each of Samples 13 to 27, 37 to 40, 53 to 67, 77 to 80, 101 to 120, representing good as A, slightly good as B, and poor as C. Also, the measurement of the number of compounds, the film analysis at the corroded part of the extruded material, the corrosion weight loss, the corrosion depth, and the evaluation of corrosion resistance performed in Example 1 were similarly carried out for each of Samples 13 to 27, 37 to 40, 53 to 67, 77 to 80, 101 to 120 in Example 2, and these measured values and evaluations are shown together in Table 6.

[0073]

Table 6

[0074] Samples 13 - 27, 53 - 67, and 101 - 120 used any of Materials 13 - 27 in which the contents of Cr, Fe, Si, Ti, Mn, Mg, Cu, Zr, V, Sr, Sc, and Mo were all controlled within the second composition range, and their tensile strengths Rm were good or slightly good. Among these, Samples 13 - 27, 53 - 67, 101 - 105, and 111 - 115 were manufactured by any of Manufacturing Methods A - G in which the manufacturing conditions of casting, homogenization treatment, and extrusion (extrusion temperature and extrusion speed) were controlled. In the corroded part of the surface layer, it was confirmed that the corrosion weight loss was small, the corrosion depth was shallow, and an oxide film containing Cr in which the intermetallic compound was decomposed was formed, and the corrosion resistance was good or slightly good. Samples 106 - 110 and 116 - 120 were manufactured by Manufacturing Methods H - L in which any of the manufacturing conditions of casting, homogenization treatment, and extrusion (extrusion temperature and extrusion speed) were not controlled, and their corrosion resistance was poor.

[0075] Samples 37 - 40 and 77 - 80 are manufactured by any of Manufacturing Methods A and G using any of Materials 37 - 40 in which the content of either Mn or Mg is not controlled within the second composition range. Among these, the tensile strength Rm of Samples 37, 39, 77, and 79 was poor, but the corrosion resistance was slightly good because the manufacturing conditions of casting, homogenization treatment, and extrusion (extrusion temperature and extrusion speed) were controlled. Samples 38, 40, 78, and 80 were manufactured by any of Manufacturing Methods A and G using Materials 38 and 40 in which the content of either Mn or Mg exceeded the second composition range, and manufacturing was not performed because the extrudability was poor.

Claims

1. It contains 0.05% by mass or more and 1.00% by mass or less of Cr, 0.05% by mass or more and 1.00% by mass or less of Fe, and 0.05% by mass or more and 1.50% by mass or less of Si, and the balance consists of Al and inevitable impurities. Fe and Si satisfy the relationship of 0.8Fe ≤ Si. Intermetallic compounds containing Cr having a diameter equivalent to a circle of 0.01 μm or more and less than 5.00 μm are present in an observation field of view per 10,000 μm ２ of the ED-TD parallel plane in a number of 10 or more, Furthermore, an extruded material made of an aluminum alloy, characterized in that the number of intermetallic compounds having a diameter of 10 μm or more in terms of equivalent circle diameter is less than 3 in the observation field of view.

2. The extruded material made of an aluminum alloy according to Claim 1, characterized in that it contains 0.05% by mass or more and 1.00% by mass or less of Ti.

3. The extruded material made of an aluminum alloy according to Claim 1 or Claim 2, characterized in that it further contains any one or a plurality of elements among 0.10% by mass or more and 2.00% by mass or less of Mn, 0.01% by mass or more and 3.00% by mass or less of Mg, 0.01% by mass or more and 1.00% by mass or less of Cu, 0.01% by mass or more and 0.50% by mass or less of Zr, 0.01% by mass or more and 0.50% by mass or less of V, 0.01% by mass or more and 0.50% by mass or less of Sr, 0.01% by mass or more and 0.50% by mass or less of Sc, and 0.01% by mass or more and 0.50% by mass or less of Mo.

Images