Aluminum alloy material for cold working, method for producing aluminum alloy material for cold working, aluminum alloy material for hot working, and method for producing aluminum alloy material for hot working

Abstract

Provided is an aluminum alloy material for cold working or hot working having an alloy composition containing Si in a range of 0.05 mass% to 0.2 mass%, Fe in a range of 0.3 mass% to 0.5 mass%, Cu in a range of 0.01 mass% to 0.20 mass%, Mn in a range of 0.80 mass% to 1.09 mass%, Mg in a range of 0.05 mass% or less, Ti in a range of 0.01 mass% to 0.1 mass%, B in a range of 0.0010 mass% to 0.030 mass%, with the balance being Al and inevitable impurities, in which needle-like Al-Mn-based compounds having a maximum diameter of 2 μm or more are not present in the metal structure and the Rockwell hardness [HRF] is 57.0 or less.

Description

Aluminum alloy material for cold working, Manufacturing method of aluminum alloy material for cold working, Aluminum alloy material for hot working, Manufacturing method of aluminum alloy material for hot working

[0001] The present invention relates to an aluminum alloy material for cold working, a method for manufacturing an aluminum alloy material for cold working, an aluminum alloy material for hot working, and a method for manufacturing an aluminum alloy material for hot working. This application claims priority based on Japanese Patent Application No. 2023-208387, filed on December 11, 2023, the contents of which are incorporated herein by reference.

[0002] In recent years, aluminum alloys have been increasingly used as structural components for various products, taking advantage of their light weight. For example, steel has traditionally been used for general vessels, building materials such as panels, shipbuilding materials, and containers. However, in recent years, aluminum alloys, which are lightweight, have good corrosion resistance, and are high in strength, have come to be used.

[0003] These extrusions require excellent corrosion resistance, high strength, and excellent workability, and therefore Al-Mn alloys and the like are often used as the aluminum material. Al-Mn alloys are aluminum alloys that have improved strength and weldability without reducing workability and corrosion resistance compared to pure aluminum. As a result, they are widely used in vessels, building materials, containers, and the like. For example, they are used as the body material for fire extinguishers and the container material for secondary batteries. These Al-Mn alloys are manufactured by processes such as extrusion, impact forming, deep drawing, and forging. For example, Patent Document 1 discloses an aluminum alloy that exhibits high strain rate formability at elevated temperatures.

[0004] Japanese Patent No. 6402246 (B)

[0005] However, the aluminum alloy composition disclosed in Patent Document 1 has a problem in that the contents of Fe, Si, and Mn are high, and therefore strong AlFeMnSi compounds are produced in large quantities and coarse, resulting in a decrease in machinability and workability.

[0006] The present invention has been made in view of the above technical background, and aims to provide an aluminum alloy material for cold working that has excellent machinability and workability when forming a container or an outer casing by cold working or hot working, a method for manufacturing the aluminum alloy material for cold working, an aluminum alloy material for hot working, and a method for manufacturing the aluminum alloy material for hot working.

[0007] In order to solve the above problems, the present invention provides the following means.

[0008] (1) An aluminum alloy material for cold working, having an alloy composition containing Si in the range of 0.05% by mass to 0.2% by mass, Fe in the range of 0.3% by mass to 0.5% by mass, Cu in the range of 0.01% by mass to 0.20% by mass, Mn in the range of 0.80% by mass to 1.09% by mass, Mg in the range of 0.05% by mass or less, Ti in the range of 0.01% by mass to 0.1% by mass, B in the range of 0.0010% by mass to 0.030% by mass or less, with the balance being Al and unavoidable impurities, wherein the aluminum alloy material for cold working is free of acicular Al-Mn-based compounds having a maximum diameter of 2 μm or more in its metal structure, and has a Rockwell hardness [HRF] of 57.0 or less.

[0009] (2) The aluminum alloy material for cold working according to (1), characterized in that it is for a pressure-resistant container of a fire extinguisher.

[0010] (3) The aluminum alloy material for cold working according to (1), characterized in that it is used for an outer casing of a secondary battery.

[0011] (4) A method for producing an aluminum alloy material for cold working according to any one of (1) to (3), comprising: a molten alloy forming step of forming a molten aluminum alloy having the same alloy composition as the aluminum alloy material for cold working; a casting step of cooling and solidifying the molten aluminum alloy obtained in the molten alloy forming step to form an aluminum alloy cast product; and a homogenization heat treatment step of homogenizing the aluminum alloy cast product obtained in the casting step, wherein the homogenization heat treatment step comprises a first heat treatment stage in which a heat treatment is performed by holding the temperature in a range of 590°C to 615°C for 4 hours or more, and a second heat treatment stage in which a heat treatment is performed by holding the temperature in a range of 500°C to 540°C for 5 hours or more.

[0012] (5) An aluminum alloy material for hot working, having an alloy composition containing Si in the range of 0.05% by mass to 0.2% by mass, Fe in the range of 0.3% by mass to 0.5% by mass, Cu in the range of 0.01% by mass to 0.20% by mass, Mn in the range of 0.80% by mass to 1.09% by mass, Mg in the range of 0.05% by mass or less, Ti in the range of 0.01% by mass to 0.1% by mass, B in the range of 0.0010% by mass to 0.030% by mass, and the balance consisting of Al and unavoidable impurities, wherein the aluminum alloy material for hot working is free of acicular Al-Mn-based compounds having a maximum diameter of 2 μm or more in its metal structure, and has a Rockwell hardness [HRF] of 57.0 or less.

[0013] (6) The aluminum alloy material for hot working according to (5), characterized in that it is for use in automobile parts.

[0014] (7) A method for producing an aluminum alloy material for hot working according to (5) or (6), comprising: a molten alloy forming step of forming a molten aluminum alloy having the same alloy composition as the aluminum alloy material for hot working; a casting step of cooling and solidifying the molten aluminum alloy obtained in the molten alloy forming step to form an aluminum alloy cast product; and a homogenization heat treatment step of homogenizing the aluminum alloy cast product obtained in the casting step, wherein the homogenization heat treatment step comprises a first heat treatment stage in which a heat treatment is performed by holding the temperature in a range of 590°C to 615°C for 4 hours or more, and a second heat treatment stage in which a heat treatment is performed by holding the temperature in a range of 500°C to 540°C for 5 hours or more.

[0015] According to the present invention, it is possible to provide an aluminum alloy material for cold working, a manufacturing method for an aluminum alloy material for cold working, an aluminum alloy material for hot working, and a manufacturing method for an aluminum alloy material for hot working, which have excellent machinability and workability when forming a container or an exterior body by cold working or hot working.

[0016] Fig. 2 is a cross-sectional view showing an example of the vicinity of a mold of a horizontal continuous casting apparatus for producing an aluminum alloy material according to an embodiment of the present invention. Fig. 3 is an enlarged cross-sectional view of a main part of the horizontal continuous casting apparatus shown in Fig. 1 in the vicinity of a cooling water cavity. Fig. 4 is an explanatory view for explaining the heat flux of a cooling wall part of the horizontal continuous casting apparatus. Fig. 5 is a photograph of an SEM-EBSD image of Example 1. Fig. 6 is a photograph of an SEM-EBSD image of Comparative Example 1.

[0017] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the drawings used in the following description may show characteristic portions enlarged for convenience in order to make the features easier to understand, and the dimensional ratios of each component may not necessarily be the same as those in reality. Furthermore, the materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not necessarily limited thereto. Appropriate changes can be made within the scope that does not change the effects of the present invention.

[0018] [Aluminum alloy material for cold working] An aluminum alloy material for cold working (hereinafter simply referred to as aluminum alloy material) according to one embodiment of the present invention is an aluminum alloy material for cold working having an alloy composition containing Si in the range of 0.05% by mass or more and 0.2% by mass or less, Fe in the range of 0.3% by mass or more and 0.5% by mass or less, Cu in the range of 0.01% by mass or more and 0.20% by mass or less, Mn in the range of 0.80% by mass or more and 1.09% by mass or less, Mg in the range of 0.05% by mass or less, Ti in the range of 0.01% by mass or more and 0.1% by mass or less, and B in the range of 0.0010% by mass or more and 0.030% by mass or less, with the balance being Al and unavoidable impurities, characterized in that the aluminum alloy material does not contain any acicular Al-Mn-based compounds having a maximum diameter of 2 μm or more in its metallographic structure, and has a Rockwell hardness [HRF] of 57.0 or less.

[0019] [Aluminum alloy material for hot working] An aluminum alloy material for hot working (hereinafter simply referred to as aluminum alloy material) according to one embodiment of the present invention is an aluminum alloy material for hot working having an alloy composition containing Si in the range of 0.05% by mass or more and 0.2% by mass or less, Fe in the range of 0.3% by mass or more and 0.5% by mass or less, Cu in the range of 0.01% by mass or more and 0.20% by mass or less, Mn in the range of 0.80% by mass or more and 1.09% by mass or less, Mg in the range of 0.05% by mass or less, Ti in the range of 0.01% by mass or more and 0.1% by mass or less, and B in the range of 0.0010% by mass or more and 0.030% by mass or less, with the balance being Al and unavoidable impurities, characterized in that the aluminum alloy material does not contain any acicular Al-Mn-based compounds having a maximum diameter of 2 μm or more in its metallographic structure, and has a Rockwell hardness [HRF] of 57.0 or less.

[0020] The aluminum alloy material of this embodiment corresponds to a 3000 series aluminum alloy in that it contains a large amount of Mn.

[0021] (Si: 0.05% by mass or more and 0.2% by mass or less) Si crystallizes in the aluminum alloy as intermetallic compounds such as Al-Mn-Si and Al-Mn-Fe-Si, thereby improving the tensile strength of the aluminum alloy. By keeping the Si content within the above range, it is possible to produce the desired forged product without reducing the machinability and forgeability of the aluminum alloy material. However, if excessive Si is added to the aluminum alloy, coarse primary crystal Si grains may crystallize, reducing the tensile strength of the aluminum alloy. By keeping the Si content within the above range, it is possible to suppress the crystallization of primary crystal Si.

[0022] (Fe: 0.3% by mass or more and 0.5% by mass or less) Fe has the effect of improving the tensile strength of the aluminum alloy by crystallizing in the aluminum alloy as fine crystals containing intermetallic compounds such as Al-Mn-Fe-Si, Al-Fe-Si, and Al-Mn-Fe. By keeping the Fe content within the above range, it is possible to produce the desired processed product without reducing the machinability and forgeability of the aluminum alloy material.

[0023] (Cu: 0.01% by mass or more and 0.20% by mass or less) Cu has the effect of finely dispersing Mg—Si compounds in the aluminum alloy and improving the tensile strength of the aluminum alloy by precipitating as Al—Cu compounds. If the Cu content is 0.3% by mass or more, workability will decrease, but if the Cu content is 0.01% by mass or more and 0.20% by mass or less, tensile properties can be improved without decreasing workability.

[0024] (Mn: 0.80% by mass or more and 1.09% by mass or less) Mn has the effect of improving the tensile strength of the aluminum alloy by forming fine granular precipitates containing intermetallic compounds such as Al-Mn-Fe-Si, Al-Mn-Fe, Al-Mn, and Al-Mn-Si in the aluminum alloy. When the Mn content is within the above range, the mechanical properties of the aluminum alloy material at room temperature can be improved.

[0025] (Mg: 0.05% by mass or less) Mg is mainly dissolved in 3000 series aluminum alloys and acts as a solid solution strengthener. If a large amount of Mg is added, it reduces workability. If the Mg content is 0.05% by mass or less, it can provide good mechanical properties without reducing workability. Furthermore, the Mg content is preferably 0.001% by mass or more.

[0026] (Ti: 0.01% by mass or more, 0.1% by mass or less) Ti has the effect of refining the crystal grains of an aluminum alloy and improving its wrought workability. If the Ti content is less than 0.01% by mass, the effect of refining the crystal grains may not be sufficient. On the other hand, if the Ti content exceeds 0.1% by mass, coarse crystals may be formed, which may reduce the wrought workability. Furthermore, if a large amount of coarse crystals containing Ti are mixed into the aluminum alloy material, the toughness may be reduced. Therefore, the Ti content is preferably 0.012% by mass or more, and 0.035% by mass or less, more preferably 0.015% by mass or more, and 0.050% by mass or less.

[0027] (B: 0.0010% by mass or more, 0.030% by mass or less) B has the effect of refining the crystal grains of an aluminum alloy and improving its wrought workability. Adding B to an aluminum alloy together with the above-mentioned Ti improves the effect of refining the crystal grains. If the B content is less than 0.0010% by mass, the effect of refining the crystal grains may not be sufficient. On the other hand, if the B content exceeds 0.030% by mass, coarse crystals may be formed and may be mixed into the aluminum alloy material as inclusions. Furthermore, if a large amount of coarse crystals containing B are mixed into the final aluminum alloy product, the toughness may be reduced. Therefore, the B content is set to 0.0010% by mass or more, and 0.030% by mass or less. The B content is preferably 0.0050% by mass or more, and 0.025% by mass or more.

[0028] (Inevitable Impurities) Inevitable impurities are impurities that are inevitably mixed into the aluminum alloy from raw materials or the manufacturing process. Examples of inevitable impurities include Ni, Sn, and Be. The content of these inevitable impurities preferably does not exceed 0.1 mass%.

[0029] (No acicular Al—Mn compounds with a maximum diameter of 2 μm or more are present in the metal structure) No acicular Al—Mn compounds with a diameter of 2 μm or more are allowed to precipitate in the alloy structure in the cross section of the aluminum alloy material. The presence of such acicular Al—Mn compounds may hinder cutting, and may result in deterioration of machinability, cold workability, and hot workability.

[0030] (Rockwell hardness [HRF] after homogenization treatment is 57.0 or less) When measuring the hardness of an aluminum alloy material that has been subjected to a homogenization treatment described later, if the Rockwell hardness using the HRF scale (60 kg-1 / 16" steel ball) is 60.0 or more, cold workability is reduced, and reheat treatment (O material treatment) is required. Therefore, in order to ensure cold workability, the Rockwell hardness [HRF] needs to be 57.0 or less. Although not particularly limited, the Rockwell hardness [HRF] may be 55.5 or less, or may be 54.0 or less. Furthermore, although not particularly limited, the Rockwell hardness [HRF] may be 1.0 or more, 10 or more, or 30 or more.

[0031] As described above, according to the aluminum alloy material for cold working and the aluminum alloy material for hot working of the present embodiment, the respective compositions are within the above-mentioned ranges, no acicular Al-Mn compounds having a maximum diameter of 2 μm or more are present in the metallographic structure, and the Rockwell hardness [HRF] is 57.0 or less. This makes it possible to realize an aluminum alloy material for cold working and an aluminum alloy material for hot working that are, for example, less likely to produce Al-Fe-Mn-Si compounds and have excellent machinability.

[0032] Such an aluminum alloy material for cold working has excellent machinability and cold workability, and can therefore be used, for example, as a processed material for a pressure-resistant container of a fire extinguisher that contains a fire extinguishant under pressure, or as a processed material for an outer container that contains a power generation laminate of a secondary battery, such as a lithium-ion battery.

[0033] Furthermore, the aluminum alloy material for hot working according to this embodiment has excellent machinability, hot workability, and forgeability, and can therefore be used as a processed material for automobile parts, for example, suspension arms.

[0034] [Methods for manufacturing an aluminum alloy material for cold working, and an aluminum alloy material for hot working] Next, an example of a method for manufacturing an aluminum alloy material for cold working and an aluminum alloy material for hot working according to the present embodiment will be described. The method for manufacturing an aluminum alloy material according to the present embodiment includes a molten metal forming step, a casting step, and a homogenization heat treatment step.

[0035] (Molten Metal Forming Step) The molten metal forming step is a step of melting raw materials to obtain a molten aluminum alloy having a composition adjusted. The composition of the molten aluminum alloy may be the same as that of the aluminum alloy raw material. That is, a molten aluminum alloy of a 3000 series is obtained by adjusting the alloy composition to contain Si in the range of 0.05 mass% to 0.2 mass% inclusive, Fe in the range of 0.3 mass% to 0.5 mass% inclusive, Cu in the range of 0.01 mass% to 0.20 mass% inclusive, Mn in the range of 0.80 mass% to 1.09 mass% inclusive, Mg in the range of 0.05 mass% to 0.1 mass% inclusive, Ti in the range of 0.01 mass% to 0.1 mass% inclusive, and B in the range of 0.0010 mass% to 0.030 mass% inclusive, with the balance being Al and unavoidable impurities. By carrying out the subsequent steps using a molten aluminum alloy having the above composition, it is possible to obtain an aluminum alloy material that is suitable for cold working and hot working, in which no acicular Al—Mn-based compounds having a maximum diameter of 2 μm or more are present in the metal structure and the Rockwell hardness [HRF] is 57.0 or less.

[0036] A molten aluminum alloy can be obtained by heating and melting an aluminum alloy. Alternatively, the aluminum alloy may be formed by melting a mixture containing the elements or compounds containing two or more elements that are raw materials for the aluminum alloy, in proportions that produce the desired aluminum alloy. For example, to control the grain size of the aluminum alloy during the casting process, Ti and B may be mixed as grain refiners, such as Al-Ti-B rods.

[0037] Alternatively, the molten aluminum alloy may be prepared by melting 10% or more of scrap aluminum alloys of 1000 series, 2000 series, 3000 series, 4000 series, 5000 series, 6000 series, or 7000 series, with the remainder being new aluminum ingots and the above-mentioned additive elements, as raw materials for the molten aluminum alloy. The new aluminum ingots referred to here are aluminum with a concentration of 99% by mass or more obtained by subjecting alumina produced from minerals to electrolysis, a process known as electrolytic refining.

[0038] (Casting Step) In the casting step, a molten aluminum alloy (liquid phase) is cooled and solidified into a solid (solid phase) to obtain an aluminum alloy cast product. The casting step can be performed by, for example, horizontal continuous casting.

[0039] A horizontal continuous casting apparatus that can be used to produce an aluminum alloy material according to this embodiment is shown in Figures 1 and 2. Figure 1 is a cross-sectional view showing an example of the vicinity of the mold 12 of the horizontal continuous casting apparatus 10. Figure 2 is an enlarged cross-sectional view of a main portion of the horizontal continuous casting apparatus 10 near the cooling water cavity 24.

[0040] The horizontal continuous casting apparatus 10 shown in Figures 1 and 2 has a molten metal receiving portion (tundish) 11, a hollow cylindrical mold 12, and a refractory plate-like body (thermal insulating member) 13 arranged between one end side 12a of the mold 12 and the molten metal receiving portion 11.

[0041] The molten metal receiving portion 11 is composed of a molten metal inlet portion 11 a that receives the molten aluminum alloy M obtained in the molten metal forming process described above, a molten metal holding portion 11 b, and an outlet portion 11 c that flows into the hollow portion 21 of the mold 12.

[0042] The molten metal receiving portion 11 maintains the upper liquid level of the molten aluminum alloy M at a position higher than the upper surface of the hollow portion 21 of the mold 12, and in the case of multiple casting, stably distributes the molten aluminum alloy M to each mold 12.

[0043] The molten aluminum alloy M held in the molten metal holding portion 11b in the molten metal receiving portion 11 is poured into the hollow portion 21 of the mold 12 through a pouring passage 13a provided in the refractory plate 13. The molten aluminum alloy M supplied into the hollow portion 21 is then cooled and solidified by a cooling device 23 (described later) and drawn out from the other end 12b of the mold 12 as an aluminum alloy rod B, which is a solidified ingot.

[0044] A drawing drive device (not shown) that draws out the cast aluminum alloy rod B at a constant speed may be installed at the other end 12b of the mold 12. It is also preferable that a synchronized cutting machine (not shown) that cuts the continuously drawn aluminum alloy rod B to a desired length be installed.

[0045] The refractory plate 13 is a member that blocks heat transfer between the molten metal receiver 11 and the mold 12, and may be made of materials such as calcium silicate, alumina, silica, a mixture of alumina and silica, silicon nitride, silicon carbide, graphite, etc. Such a refractory plate 13 may also be made up of multiple layers made of different materials.

[0046] In this embodiment, the mold 12 is a hollow cylindrical member made of, for example, one or a combination of two or more materials selected from aluminum, copper, or alloys thereof. The materials for the mold 12 may be selected from an optimum combination in terms of thermal conductivity, heat resistance, and mechanical strength.

[0047] The hollow portion 21 of the mold 12 is formed to have a circular cross section in order to cast the aluminum alloy rod B into a cylindrical rod shape, and the mold 12 is held so that the mold central axis (central axis) C passing through the center of this hollow portion 21 is aligned approximately horizontally.

[0048] The inner peripheral surface 21a of the hollow portion 21 of the mold 12 is formed at an elevation angle of 0° to 3° (more preferably 0° to 1°) with respect to the mold central axis C toward the casting direction of the aluminum alloy bar B (see FIG. 1). That is, the inner peripheral surface 21a is configured in a tapered shape that opens like a cone toward the casting direction. The angle of this taper is the elevation angle.

[0049] If the elevation angle is less than 0°, the aluminum alloy rod B encounters resistance at the other end 12b, which is the mold outlet, when it is drawn out of the mold 12, which may make casting difficult. On the other hand, if the elevation angle exceeds 3°, the inner peripheral surface 21a will not be in sufficient contact with the molten aluminum alloy M, which may reduce the heat transfer effect from the molten aluminum alloy M and the solidified shell formed by cooling and solidifying it to the mold 12, which may result in insufficient solidification. As a result, this is not preferable because it may lead to casting problems such as the formation of a remelted skin on the surface of the aluminum alloy rod B or the ejection of unsolidified molten aluminum alloy M from the end of the aluminum alloy rod B.

[0050] The cross-sectional shape of the hollow portion 21 of the mold 12 (the planar shape when the hollow portion 21 of the mold 12 is viewed from the other end side 21b) may be selected to match the shape of the aluminum alloy rod to be cast, such as a triangular or rectangular cross-sectional shape, a polygonal, semicircular, elliptical, or an irregular cross-sectional shape having no axis or plane of symmetry, in addition to the circular shape of this embodiment.

[0051] A fluid supply pipe 22 is disposed at one end 12a of the mold 12 to supply a lubricating fluid into the hollow portion 21 of the mold 12. The lubricating fluid supplied from the fluid supply pipe 22 can be one or more lubricating fluids selected from a gas lubricant and a liquid lubricant. When supplying both a gas lubricant and a liquid lubricant, it is preferable to provide separate fluid supply pipes for each. The lubricating fluid supplied under pressure from the fluid supply pipe 22 is supplied into the hollow portion 21 of the mold 12 through an annular lubricant supply port 22a.

[0052] In this embodiment, the lubricating fluid is supplied under pressure from the lubricant supply port 22a to the inner circumferential surface 21a of the mold 12. Note that the liquid lubricant may be heated to decompose into a gas and then supplied to the inner circumferential surface 21a of the mold 12. Alternatively, a porous material may be disposed in the lubricant supply port 22a, and the lubricating fluid may be allowed to seep out onto the inner circumferential surface 21a of the mold 12 through the porous material.

[0053] A cooling device 23, which is a cooling means for cooling and solidifying the molten aluminum alloy M, is formed inside the mold 12. The cooling device 23 of this embodiment has a cooling water cavity 24 that accommodates cooling water W for cooling the inner circumferential surface 21 a of the hollow portion 21 of the mold 12, and a cooling water injection passage 25 that connects the cooling water cavity 24 with the hollow portion 21 of the mold 12.

[0054] The cooling water cavity 24 is formed in a ring shape surrounding the hollow portion 21 outside the inner circumferential surface 21 a of the hollow portion 21 inside the mold 12 , and cooling water W is supplied to the cavity 24 via a cooling water supply pipe 26 .

[0055] The inner surface 21a of the mold 12 is cooled by the cooling water W contained in the cooling water cavity 24, which removes heat from the molten aluminum alloy M filling the hollow portion 21 of the mold 12 from the surface in contact with the inner surface 21a of the mold 12, forming a solidified shell on the surface of the molten aluminum alloy M.

[0056] The cooling water jetting passages 25 spray cooling water W directly from shower openings 25a facing the hollow portion 21 toward the aluminum alloy rods B at the other end 12b of the mold 12 to cool the aluminum alloy rods B. The vertical cross-sectional shape of the cooling water jetting passages 25 may be, for example, semicircular, pear-shaped, or horseshoe-shaped, in addition to the circular shape of this embodiment.

[0057] In this embodiment, the cooling water W supplied through the cooling water supply pipe 26 is first stored in the cooling water cavity 24 to cool the inner peripheral surface 21 a of the hollow portion 21 of the mold 12, and then the cooling water W in the cooling water cavity 24 is sprayed toward the aluminum alloy rod B through the cooling water spray passage 25. However, it is also possible to configure these to be supplied by separate cooling water supply pipes.

[0058] The length from the position where the extension of the central axis of the shower opening 25a of the cooling water injection passage 25 hits the surface of the cast aluminum alloy rod B to the contact surface between the mold 12 and the refractory plate 13 is called the effective mold length L, and this effective mold length L is preferably, for example, 10 mm or more and 40 mm or less. If this effective mold length L is less than 10 mm, a good coating cannot be formed, making casting impossible. If it exceeds 40 mm, the effect of forced cooling is reduced, solidification by the mold wall becomes dominant, and the contact resistance between the mold 12 and the molten aluminum alloy M or the aluminum alloy rod B increases, which may cause cracks on the casting surface or tearing inside the mold, making casting unstable.

[0059] It is preferable that the supply of the cooling water W to the cooling water cavity 24 and the spray of the cooling water W from the shower opening 25a of the cooling water spray passage 25 can be controlled by control signals from a control device (not shown).

[0060] The cooling water cavity 24 is formed so that an inner bottom surface 24 a near the hollow portion 21 of the mold 12 is parallel to the inner peripheral surface 21 a of the hollow portion 21 of the mold 12 .

[0061] Note that "parallel" here also includes the case where the inner peripheral surface 21a of the hollow portion 21 of the mold 12 is formed at an elevation angle of 0° to 3° relative to the inner bottom surface 24a of the cooling water cavity 24, i.e., the case where the inner bottom surface 24a is inclined from 0° to 3° relative to the inner peripheral surface 21a.

[0062] As shown in FIG. 1 , the cooling wall portion 27 of the mold 12, which is the portion where the inner bottom surface 24 a of the cooling water cavity 24 faces the inner peripheral surface 21 a of the hollow portion 21 of the mold 12, has a heat flux value per unit area from the molten aluminum alloy M in the hollow portion 21 to the cooling water W in the cooling water cavity 24 of, for example, 10×10 ５ W / m ２ That's it, 50 x 10 ５ W / m ２ It is formed so as to fall within the following range.

[0063] The mold 12 may be formed so that the thickness t of the cooling wall portion 27 of the mold 12, i.e., the distance between the inner bottom surface 24a of the cooling water cavity 24 and the inner peripheral surface 21a of the hollow portion 21 of the mold 12, is within a range of, for example, 0.5 mm to 3.0 mm, preferably 0.5 mm to 2.5 mm. The material for forming the mold 12 may be selected so that the thermal conductivity of at least the cooling wall portion 27 of the mold 12 is within a range of 100 W / m·K to 400 W / m·K.

[0064] In FIG. 1 , molten aluminum alloy M in a molten metal receiving portion 11 is supplied through a refractory plate 13 to one end 12 a of a mold 12, which is held so that the central axis C of the mold is substantially horizontal, and is forcibly cooled at the other end 12 b of the mold 12 to form an aluminum alloy rod B.

[0065] The aluminum alloy rod B is drawn out at a constant speed by a drawing drive device (not shown) installed near the other end 12b of the mold 12, and is continuously cast to form a long aluminum alloy rod B. The drawn aluminum alloy rod B is then cut to a desired length by, for example, a synchronous cutting machine (not shown).

[0066] The composition ratio of the cast aluminum alloy rod B can be confirmed, for example, by a method using a photoelectric emission spectrophotometer (e.g., PDA-5500 manufactured by Shimadzu Corporation, Japan) as described in "JIS H 1305".

[0067] The difference in height between the liquid level of the molten aluminum alloy M stored in the molten metal receiver 11 and the upper inner circumferential surface 21a of the mold 12 is preferably 0 mm to 250 mm (more preferably 50 mm to 170 mm). By setting the difference in height within this range, the pressure of the molten aluminum alloy M supplied into the mold 12 and the lubricating oil and the gas produced by vaporizing the lubricating oil are suitably balanced, resulting in stable castability.

[0068] The liquid lubricant may be a vegetable oil, such as rapeseed oil, castor oil, or salad oil.

[0069] The lubricating oil supply rate is preferably 0.05 mL / min to 5 mL / min (more preferably 0.1 mL / min to 1 mL / min). If the supply rate is too low, the molten aluminum alloy M in the aluminum alloy rod B may not solidify due to insufficient lubrication and may leak from the mold 12. If the supply rate is too high, the excess may get mixed into the aluminum alloy rod B and cause internal defects.

[0070] The casting speed, which is the speed at which the aluminum alloy rod B is withdrawn from the mold 12, is preferably 200 mm / min or more and 1500 mm / min or less (more preferably 400 mm / min or more and 1000 mm / min or less). This is because, if the casting speed is within this range, the network structure of the crystallized matter formed by casting becomes uniform and fine, which increases the resistance of the aluminum matrix to deformation at high temperatures and improves the high-temperature mechanical strength.

[0071] The amount of cooling water sprayed from the shower openings 25a of the cooling water spray passages 25 is preferably, for example, 10 L / min to 50 L / min (more preferably 25 L / min to 40 L / min) per mold. If the amount of cooling water is less than this range, the molten aluminum alloy M may not solidify and leak from the mold 12. Furthermore, the surface of the cast aluminum alloy rod B may remelt, forming an uneven structure that may remain as an internal defect. On the other hand, if the amount of cooling water is greater than this range, the mold 12 may lose too much heat, causing it to solidify prematurely.

[0072] The average temperature of the molten aluminum alloy M flowing from the molten metal receiver 11 into the mold 12 is preferably, for example, 650°C or higher and 750°C or lower (more preferably 680°C or higher and 720°C or lower). If the temperature of the molten aluminum alloy M is too low, coarse crystallized products may be formed in the mold 12 or before that, and may be incorporated as internal defects inside the aluminum alloy rod B. On the other hand, if the temperature of the molten aluminum alloy M is too high, a large amount of hydrogen gas may be easily incorporated into the molten aluminum alloy M, which may be incorporated as porosity in the aluminum alloy rod B and cause internal cavities.

[0073] In the cooling wall portion 27 of the mold 12, the heat flux value per unit area from the molten aluminum alloy M in the hollow portion 21 to the cooling water W in the cooling water cavity 24 is 10×10 ５ W / m ２ That's it, 50 x 10 ５ W / m ２ By keeping the temperature within the following range, it is possible to prevent the aluminum alloy rod B from seizing.

[0074] The cooling wall 27 of the mold 12 receives heat from the molten aluminum alloy M and performs heat exchange by cooling this heat with the cooling water W contained in the cooling water cavity 24. Regarding the state of this heat exchange, attention was focused on the heat flux per unit area, as shown in the explanatory diagram in Figure 3. The heat flux per unit area is expressed by the following equation (1) using Fourier's law. Q = -k × (T1 - T2) / L (1) Q: heat flux k: thermal conductivity (W / m·K) of the location through which heat passes (in this embodiment, the cooling wall 27 of the mold 12) T1: low-temperature side temperature of the location through which heat passes (in this embodiment, the inner bottom surface 24 a of the cooling water cavity 24) T2: high-temperature side temperature of the location through which heat passes (in this embodiment, the inner circumferential surface 21 a of the hollow portion 21 of the mold 12) L: section length (mm) of the location through which heat passes (in this embodiment, the thickness t of the cooling wall 27 of the mold 12)

[0075] Good results were obtained even when the amount of lubricating oil was reduced during casting. Based on the mold material, thickness, and temperature measurement data, the heat flux value per unit area was 10 × 10 ５ W / m ２ By configuring the cooling wall portion 27 of the mold 12 so that the heat flux value per unit area is 50×10 or more, it is possible to prevent the cast aluminum alloy rod B from seizing. ５ W / m ２ It is preferable to do the following:

[0076] To set the heat flux value of the cooling wall portion 27 of the mold 12 within this range, the mold 12 may be formed so that the thickness t of the cooling wall portion 27 of the mold 12 is, for example, in the range of 0.5 mm to 3.0 mm. Also, the thermal conductivity of at least the cooling wall portion 27 of the mold 12 may be set in the range of 100 W / m·K to 400 W / m·K.

[0077] When producing the aluminum alloy rod B, the horizontal continuous casting apparatus 10 described above is used to continuously supply the molten aluminum alloy M stored in the molten metal receptacle 11 from one end 12a of the mold 12 into the hollow portion 21. In addition, cooling water W is supplied to the cooling water cavity 24, and a lubricating fluid, for example, lubricating oil, is supplied from the fluid supply pipe 22.

[0078] The molten aluminum alloy M supplied into the hollow portion 21 is cooled to a temperature at which the heat flux value per unit area of ​​the cooling wall portion 27 is 10×10 ５ W / m ２ The aluminum alloy rod B is cooled and solidified under the above conditions to be cast. During casting of the aluminum alloy rod B, it is preferable to set the wall surface temperature of the cooling wall portion 27 of the mold 12, which is cooled by the cooling water W, to 100° C. or less.

[0079] The aluminum alloy rod B thus obtained has a heat flux value per unit area in the cooling wall portion 27 of 10×10 ５ W / m ２ Cooling and solidification under the above conditions suppresses adhesion of reaction products, such as carbides, that occur due to contact between the lubricating oil gas and the molten aluminum alloy M. This eliminates the need to remove carbides and the like from the surface of the aluminum alloy rod B by cutting, and allows the aluminum alloy rod B to be produced with a high yield.

[0080] The casting process for obtaining a cast product from the molten aluminum alloy M is not limited to the above-mentioned horizontal continuous casting method, and known continuous casting methods such as vertical continuous casting can be used. Vertical continuous casting methods are classified into the float method and the hot top method depending on the method of supplying the molten aluminum alloy M to the mold (casting die 12), and the following will briefly explain the case where the hot top method is used.

[0081] The casting equipment used in the hot top method is equipped with a mold, a molten metal receiving vessel (header), etc. The molten metal supplied to the molten metal receiving vessel passes through a tapping port and then through the header, where the flow rate is adjusted, and enters a cylindrical mold placed almost horizontally, where it is forcibly cooled and a solidified shell is formed on the outer surface of the molten metal.

[0082] Furthermore, cooling water is sprayed directly onto the casting as it is pulled out of the mold, allowing the solidification of the metal to progress throughout the casting as it is continuously pulled out. Molds are generally made of metal materials with good thermal conductivity and have a hollow structure to allow the introduction of a coolant inside.

[0083] The refrigerant to be used may be selected from among those that are industrially available, but water is recommended from the viewpoint of ease of use.

[0084] The mold used in this embodiment is appropriately selected from metals such as copper and aluminum, or graphite, from the viewpoint of heat transfer performance and durability at the contact point with the molten metal. The header is generally made of a refractory material and is installed above the mold. The material and size of the header may be appropriately selected depending on the composition range of the alloy to be cast and the dimensions of the cast product, and are not particularly limited.

[0085] The average cooling rate during casting may be appropriately selected from a generally recommended range, such as 10 to 300°C / sec. The casting speed may be appropriately selected from a range generally used in horizontal continuous casting, such as 200 to 600 mm / min.

[0086] The casting method described above makes it possible to obtain a uniform metal structure even in medium to large castings. There are no particular restrictions on the diameter of the castings, and the method is suitable for use with rods with diameters of 30 to 100 mm.

[0087] (Homogenization Heat Treatment Step) The homogenization heat treatment step is a step in which the aluminum alloy casting obtained in the casting step is subjected to homogenization heat treatment to homogenize microsegregations caused by solidification, precipitate supersaturated solid solution elements, and transform metastable phases into equilibrium phases.

[0088] In this embodiment, the homogenization heat treatment process is performed by a two-stage heat treatment. First, the casting obtained in the casting process is heat-treated by holding it at a temperature range of 590°C to 615°C for at least four hours (first heat treatment stage). Next, the casting is heat-treated by holding it at a temperature range of 500°C to 540°C for at least five hours (second heat treatment stage). In this way, by performing the homogenization heat treatment process by two heat treatment stages with different temperature ranges and holding times, the precipitation of acicular Al-Mn compounds is prevented. This can improve the machinability, cold workability, and hot workability during cutting.

[0089] Through the steps as described above, it is possible to produce the aluminum alloy material of the present embodiment in which no acicular Al—Mn-based compounds having a maximum diameter of 2 μm or more are present in the metallographic structure and the Rockwell hardness [HRF] is 57.0 or less.

[0090] Next, specific examples of the present invention will be described, but the present invention is not particularly limited to these examples.

[0091] [Examples 1 to 8 and Comparative Examples 1 to 8] (Production of Continuously Cast Products) First, aluminum alloy materials were prepared having the alloy compositions (the balance being aluminum) shown in Table 1 below. Continuously cast products having a circular cross section and a diameter of 82 mm were produced using the prepared aluminum alloy materials.

[0092]

[0093] (Production of Aluminum Alloy Material) Next, the obtained continuous cast product was subjected to a homogenization heat treatment process to obtain an aluminum alloy material. The conditions of the homogenization heat treatment process are shown in Table 2 below. In Examples 1-8, a two-stage heat treatment was performed, and in Comparative Examples 1-8, a one-stage heat treatment was performed.

[0094]

[0095] [Evaluation] The aluminum alloy materials of Examples 1 to 8 and Comparative Examples 1 to 8 obtained as described above were subjected to the following evaluations. The evaluation results are shown in Table 3 below. Also, a photograph of an SEM-EBSD image of Example 1 is shown in Figure 4A, and a photograph of an SEM-EBSD image of Comparative Example 1 is shown in Figure 4B.

[0096] <Rockwell hardness [HRF]> The Rockwell hardness [HRF] was measured using the HRF scale on the cross section of the aluminum alloy material obtained through the homogenization heat treatment process 10 times per sample, and the average value was used as the measurement result for each sample. (Evaluation criteria) "Satisfied": Rockwell hardness [HRF] is 57.0 or less. "Not Satisfied": Rockwell hardness [HRF] is greater than 57.0.

[0097] <Distribution of acicular Al-Mn compounds with a maximum diameter of 2 μm or more in the metal structure> A plate (2 mm thick) for preparing a test piece for microstructure evaluation was taken from a cross section perpendicular to the longitudinal direction of the aluminum alloy material obtained through the homogenization heat treatment process. The obtained plate was cut into 7 mm squares to prepare a 7 mm x 7 mm x 2 mm thick test piece for microstructure evaluation. The distribution of acicular Al-Mn compounds with a maximum diameter of 2 μm or more was measured on the surface of the obtained test piece for microstructure evaluation using a SEM-EBSD (scanning electron microscope-electron backscatter diffraction) device. (Evaluation criteria) "Satisfied": No acicular Al-Mn compounds are present. "Not Satisfied": Acicular Al-Mn compounds are present.

[0098] <Overall Evaluation> The evaluation results of Rockwell hardness and distribution of acicular Al-Mn compounds were evaluated based on the following evaluation criteria. (Evaluation criteria) "Satisfied": Both evaluation items are "Satisfied". "Not Satisfied": At least one of the two evaluation items is "Not Satisfied".

[0099]

[0100] As shown in Table 3, it was confirmed that the aluminum alloy material of this embodiment can realize an aluminum alloy material for cold working and an aluminum alloy material for hot working that have a Rockwell hardness [HRF] of 57.0 or less, are free of acicular Al—Mn compounds with a maximum diameter of 2 μm or more, and have excellent machinability and workability.

[0101] According to the present invention, it is possible to provide an aluminum alloy material for cold working, which has excellent machinability and workability, a manufacturing method thereof, an aluminum alloy material for hot working, and a manufacturing method thereof.

[0102] DESCRIPTION OF SYMBOLS 10 Horizontal continuous casting apparatus 11 Molten metal receiving portion (tundish) 11a Molten metal inlet portion 11b Molten metal holding portion 11c Outlet portion 12 Mold 12a One end side 12b Other end side 13 Refractory plate body (heat insulating member) 13a Molten metal pouring passage 21 Hollow portion 21a Inner peripheral surface 21b Other end side 22 Fluid supply pipe 22a Lubricant supply port 23 Cooling device 24 Cooling water cavity 24a Inner bottom surface 25 Cooling water injection passage 25a Shower opening 26 Cooling water supply pipe 27 Cooling wall portion B Aluminum alloy rod M Molten aluminum alloy W Cooling water

Claims

1. An aluminum alloy material for cold working having an alloy composition containing Si in the range of 0.05% by mass or more and 0.2% by mass or less, Fe in the range of 0.3% by mass or more and 0.5% by mass or less, Cu in the range of 0.01% by mass or more and 0.20% by mass or less, Mn in the range of 0.80% by mass or more and 1.09% by mass or less, Mg in the range of 0.05% by mass or less, Ti in the range of 0.01% by mass or more and 0.1% by mass or less, B in the range of 0.0010% by mass or more and 0.030% by mass or less, with the balance being Al and unavoidable impurities, wherein the aluminum alloy material for cold working has an alloy composition containing no acicular Al-Mn-based compounds having a maximum diameter of 2 μm or more in the metal structure, and has a Rockwell hardness [HRF] of 57.0 or less.

2. The aluminum alloy material for cold working according to claim 1, which is used for a pressure vessel of a fire extinguisher.

3. The aluminum alloy material for cold working according to claim 1, which is used for the outer casing of a secondary battery.

4. A method for producing an aluminum alloy material for cold working according to any one of claims 1 to 3, comprising: a molten alloy forming step of forming a molten aluminum alloy having the same alloy composition as the aluminum alloy material for cold working; a casting step of cooling and solidifying the molten aluminum alloy obtained in the molten alloy forming step to form an aluminum alloy casting; and a homogenization heat treatment step of homogenizing the aluminum alloy casting obtained in the casting step, wherein the homogenization heat treatment step comprises a first heat treatment stage in which a heat treatment is performed by holding the temperature in the range of 590°C to 615°C for 4 hours or more, and a second heat treatment stage in which a heat treatment is performed by holding the temperature in the range of 500°C to 540°C for 5 hours or more.

5. An aluminum alloy material for hot working having an alloy composition containing Si in the range of 0.05% by mass or more and 0.2% by mass or less, Fe in the range of 0.3% by mass or more and 0.5% by mass or less, Cu in the range of 0.01% by mass or more and 0.20% by mass or less, Mn in the range of 0.80% by mass or more and 1.09% by mass or less, Mg in the range of 0.05% by mass or less, Ti in the range of 0.01% by mass or more and 0.1% by mass or less, B in the range of 0.0010% by mass or more and 0.030% by mass or less, with the balance being Al and unavoidable impurities, wherein the aluminum alloy material for hot working has an alloy composition containing no acicular Al-Mn-based compounds having a maximum diameter of 2 μm or more in the metal structure, and has a Rockwell hardness [HRF] of 57.0 or less.

6. The aluminum alloy material for hot working according to claim 5, which is for use in automobile parts.

7. A method for producing an aluminum alloy material for hot working according to claim 5 or 6, comprising: a molten alloy forming step of forming a molten aluminum alloy having the same alloy composition as the aluminum alloy material for hot working; a casting step of cooling and solidifying the molten aluminum alloy obtained in the molten alloy forming step to form an aluminum alloy casting; and a homogenization heat treatment step of homogenizing the aluminum alloy casting obtained in the casting step, wherein the homogenization heat treatment step comprises a first heat treatment stage in which a heat treatment is performed by holding the temperature in the range of 590°C to 615°C for 4 hours or more, and a second heat treatment stage in which a heat treatment is performed by holding the temperature in the range of 500°C to 540°C for 5 hours or more.

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