WO2025126920A1 - 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 - Google Patents

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

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.

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 utensils, building materials such as panels, marine materials, and containers. However, in recent years, aluminum alloy materials, which are light, have good corrosion resistance, and are high in strength, have begun to be used.

These shaped materials require excellent corrosion resistance, high strength, and excellent workability, and therefore Al-Mn alloys and the like are often used as the aluminum material. Compared to pure aluminum, Al-Mn alloys are aluminum alloys that have improved strength and weldability without reducing workability and corrosion resistance. For this reason, they are widely used in utensils, building materials, containers, and the like. For example, they are used as the body material of fire extinguishers and the container material of secondary batteries. These Al-Mn alloys are manufactured by processing such as extrusion, impact molding, deep drawing, and forging.
For example, US Pat. No. 5,399,633 discloses an aluminum alloy that exhibits high strain rate formability at elevated temperatures.

Japanese Patent No. 6402246 (B)

However, the aluminum alloy composition disclosed in Patent Document 1 has a high content of Fe, Si, and Mn, which causes the formation of large and strong AlFeMnSi compounds, resulting in problems with reduced machinability and workability.

The present invention has been made in consideration of this technical background, and aims to provide an aluminum alloy material for cold working that has excellent machinability and workability when forming containers or exterior bodies by cold working or hot 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.

To solve the above problems, the present invention provides the following means.

(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 to 0.05% by mass, 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, with the balance being Al and unavoidable impurities, characterized in that there are no acicular Al-Mn-based compounds with a maximum diameter of 2 μm or more in the metal structure, and the Rockwell hardness [HRF] is 57.0 or less.

(2) An aluminum alloy material for cold working as described in (1), characterized in that it is for use in pressure-resistant containers for fire extinguishers.

(3) An aluminum alloy material for cold working as described in (1), characterized in that it is for use in exterior containers of secondary batteries.

(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 for forming an aluminum alloy molten having the same alloy composition as the aluminum alloy material for cold working; a casting step for 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 for homogenizing the aluminum alloy casting obtained in the casting step, the homogenization heat treatment step comprising 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, which contains 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 to 0.05% by mass, 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, characterized in that there are no acicular Al-Mn-based compounds having a maximum diameter of 2 μm or more in the metal structure, and the Rockwell hardness [HRF] is 57.0 or less.

(6) An aluminum alloy material for hot working as described in (5), characterized in that it is for use in automotive parts.

(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 an aluminum alloy molten 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, the homogenization heat treatment step comprising a first heat treatment stage in which the heat treatment is performed at a temperature range of 590°C to 615°C for 4 hours or more; and a second heat treatment stage in which the heat treatment is performed at a temperature range of 500°C to 540°C for 5 hours or more.

The present invention makes it possible to provide an aluminum alloy material for cold working that has excellent machinability and workability when forming containers or exterior bodies by cold working or hot 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.

1 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. 2 is an enlarged cross-sectional view of a main portion near a cooling water cavity of the horizontal continuous casting machine shown in FIG. 1 . FIG. 2 is an explanatory diagram illustrating a heat flux in a cooling wall portion of a horizontal continuous casting apparatus. 1 is a photograph of an SEM-EBSD image of Example 1. 1 is a photograph of an SEM-EBSD image of Comparative Example 1.

Below, an embodiment 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 parts in an enlarged scale for the sake of convenience in order to make the features easier to understand, and the dimensional ratios of each component may not necessarily be the same as in reality. Furthermore, the materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not necessarily limited to them, and may be modified as appropriate within the scope that does not change the effects of the present invention.

[Aluminum alloy material for cold working]
An aluminum alloy material for cold working according to one embodiment of the present invention (hereinafter simply referred to as "aluminum alloy material") 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, 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 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.

[Aluminum alloy material for hot working]
An aluminum alloy material for hot working according to one embodiment of the present invention (hereinafter simply referred to as "aluminum alloy material") 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, 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 has 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.

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

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

(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 crystallized products including intermetallic compounds such as Al-Mn-Fe-Si, Al-Fe-Si, Al-Mn-Fe, etc. By keeping the Fe content within the above range, it is possible to manufacture the desired processed product without deteriorating the machinability and forgeability of the aluminum alloy material.

(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 the effect of improving the tensile strength of the aluminum alloy by precipitating as an Al-Cu compound. When Cu is 0.3 mass% or more, the workability is reduced, but when Cu is 0.01 mass% or more and 0.20 mass% or less, the tensile properties can be improved without reducing the workability.

(Mn: 0.80 mass% or more and 1.09 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, Al-Mn-Si, etc. When the Mn content is within the above range, the mechanical properties of the aluminum alloy material at room temperature can be improved.

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

(Ti: 0.01% by mass or more, 0.1% by mass or less)
Ti has the effect of refining the crystal grains of the aluminum alloy and improving the wrought workability. If the Ti content is less than 0.01% by mass, the effect of refining the crystal grains may not be sufficiently obtained. On the other hand, if the Ti content exceeds 0.1% by mass, coarse crystallized products may be formed, and the wrought workability may be reduced. In addition, if a large amount of coarse crystallized products 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.

(B: 0.0010% by mass or more, 0.030% by mass or less)
B has the effect of refining the crystal grains of the aluminum alloy and improving the wrought workability. By adding B to the aluminum alloy together with the above-mentioned Ti, the effect of refining the crystal grains is improved. If the content of B is less than 0.0010 mass%, the effect of refining the crystal grains may not be sufficiently obtained. On the other hand, if the content of B exceeds 0.030 mass%, coarse crystallized matter may be formed and mixed into the aluminum alloy material as inclusions. In addition, if a large amount of coarse crystallized matter containing B is mixed into the final product of the aluminum alloy, the toughness may decrease. Therefore, the content of B is set to 0.0010 mass% or more and 0.030 mass% or less. The content of B is preferably 0.0050 mass% or more and 0.025 mass% or more.

(Inevitable impurities)
Inevitable impurities are impurities that are inevitably mixed into the aluminum alloy from the raw materials or manufacturing process. Examples of inevitable impurities include Ni, Sn, Be, etc. The content of these inevitable impurities is preferably not more than 0.1 mass%.

(There are no needle-shaped Al-Mn compounds with a maximum diameter of 2 μm or more in the metal structure.)
In the alloy structure in the cross section of the aluminum alloy material, acicular Al-Mn compounds of 2 μm or more are not allowed to precipitate. If such acicular Al-Mn compounds are present, they may hinder cutting work, and may deteriorate machinability, cold workability, and hot workability.

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

As described above, according to the aluminum alloy material for cold working and the aluminum alloy material for hot working of this embodiment, the respective compositions are within the above-mentioned ranges, there are no acicular Al-Mn compounds with a maximum diameter of 2 μm or more in the metal structure, and the Rockwell hardness [HRF] is 57.0 or less, so that, for example, Al-Fe-Mn-Si compounds are unlikely to form and an aluminum alloy material for cold working and an aluminum alloy material for hot working that have excellent machinability can be realized.

Since such aluminum alloy materials for cold working have excellent machinability and cold workability, they can be used, for example, as the processed material for the pressure-resistant containers of fire extinguishers that contain the extinguishing agent that constitutes the fire extinguisher under pressurized conditions, or as the processed material for the exterior containers that contain the power generation stacks of secondary batteries, such as lithium-ion batteries.

In addition, the aluminum alloy material for hot working of this embodiment has excellent machinability, hot workability, and forgeability, so it can be used as a processed material for automobile parts, such as suspension arms.

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

(Molten metal forming process)
The molten metal forming process is a process of obtaining a molten aluminum alloy by melting raw materials and adjusting the composition. The composition of the molten aluminum alloy may be the same as that of the aluminum alloy material. That is, the molten aluminum alloy is adjusted to have an alloy composition containing Si in the range of 0.05 mass% to 0.2 mass%, Fe in the range of 0.3 mass% to 0.5 mass%, Cu in the range of 0.01 mass% to 0.20 mass%, Mn in the range of 0.80 mass% to 1.09 mass%, Mg in the range of 0.05 mass% or less, Ti in the range of 0.01 mass% to 0.1 mass%, B in the range of 0.0010 mass% to 0.030 mass%, and the remainder being Al and inevitable impurities, to obtain a molten aluminum alloy of 3000 series.
By carrying out the subsequent steps using a molten aluminum alloy having the above composition, it is possible to obtain an aluminum alloy material suitable for cold working or 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.

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 elemental elements or compounds containing two or more elements that are the raw materials for the aluminum alloy in a ratio that produces the desired aluminum alloy. For example, Ti and B may be mixed as grain refiners such as Al-Ti-B rods in order to control the grain size of the aluminum alloy during the casting process.

Also, the raw material for the molten aluminum alloy may be 10% or more of scrap material of 1000 series, 2000 series, 3000 series, 4000 series, 5000 series, 6000 series, or 7000 series aluminum alloys, with the remainder being new aluminum ingots and the above-mentioned additive elements, which may be melted to obtain a molten aluminum alloy having an adjusted composition. Note that 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.

(Casting process)
In the casting process, the molten aluminum alloy (liquid phase) is cooled and solidified into a solid (solid phase) to obtain an aluminum alloy cast product. The casting process can be, for example, a horizontal continuous casting method.

Here, a horizontal continuous casting apparatus that can be used for producing the aluminum alloy material of this embodiment is shown in Figs. 1 and 2.
1 is a cross-sectional view showing an example of the vicinity of a mold 12 of a horizontal continuous casting apparatus 10. FIG 2 is an enlarged cross-sectional view showing a main portion of the horizontal continuous casting apparatus 10 near a cooling water cavity 24.

The horizontal continuous casting device 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 (insulating member) 13 arranged between one end side 12a of the mold 12 and the molten metal receiving portion 11.

The molten metal receiving section 11 is composed of a molten metal inlet section 11a that receives the molten aluminum alloy M obtained in the above-mentioned molten metal forming process, a molten metal holding section 11b, and an outlet section 11c into the hollow section 21 of the mold 12.

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, distributes the molten aluminum alloy M stably to each mold 12.

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 the pouring passage 13a provided in the refractory plate body 13. The molten aluminum alloy M supplied into the hollow portion 21 is then cooled and solidified by the cooling device 23 described below, and is drawn out from the other end side 12b of the mold 12 as an aluminum alloy rod B, which is a solidified ingot.

A pull-out drive device (not shown) that pulls out the cast aluminum alloy rod B at a constant speed may be installed on the other end 12b of the mold 12. It is also preferable to install a synchronized cutter (not shown) that cuts the continuously pulled aluminum alloy rod B to any length.

The refractory plate 13 is a member that blocks heat transfer between the molten metal receiving portion 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.

In this embodiment, the mold 12 is a hollow cylindrical member, and is 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 can be selected from the optimal combination in terms of thermal conductivity, heat resistance, and mechanical strength.

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

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 central axis C of the mold toward the casting direction of the aluminum alloy bar B (see FIG. 1). In other words, the inner peripheral surface 21a is configured in a tapered shape that opens out like a cone toward the casting direction. The angle of the taper is the elevation angle.

If the elevation angle is less than 0°, when the aluminum alloy rod B is pulled out of the mold 12, it encounters resistance at the other end 12b, which is the mold outlet, and casting may become difficult. On the other hand, if the elevation angle exceeds 3°, the contact of the inner peripheral surface 21a with the molten aluminum alloy M may become insufficient, and the effect of removing heat from the molten aluminum alloy M and its solidified shell to the mold 12 may decrease, resulting in insufficient solidification. As a result, a remelted skin may appear on the surface of the aluminum alloy rod B, or unsolidified molten aluminum alloy M may erupt from the end of the aluminum alloy rod B, which is not preferable, as this may lead to casting problems.

The cross-sectional shape of the hollow portion 21 of the mold 12 (the planar shape of the hollow portion 21 of the mold 12 when 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 polygon, a semicircle, an ellipse, or an irregular cross-sectional shape that does not have an axis or plane of symmetry, other than the circular shape of this embodiment.

A fluid supply pipe 22 is disposed on one end side 12a of the mold 12 to supply 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 types of lubricating fluid 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 the annular lubricant supply port 22a.

In this embodiment, the pressurized lubricating fluid is supplied from the lubricating material supply port 22a to the inner peripheral surface 21a of the mold 12. The liquid lubricating material may be heated to decompose into a gas and supplied to the inner peripheral surface 21a of the mold 12. Alternatively, a porous material may be disposed in the lubricating material supply port 22a, and the lubricating fluid may be allowed to seep out onto the inner peripheral surface 21a of the mold 12 through the porous material.

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

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

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 through 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.

The cooling water injection passage 25 also sprays cooling water W from a shower opening 25a facing the hollow portion 21 directly toward the aluminum alloy rod B at the other end side 12b of the mold 12 to cool the aluminum alloy rod B. The vertical cross-sectional shape of the cooling water injection passage 25 may be, for example, semicircular, pear-shaped, or horseshoe-shaped, in addition to the circular shape of this embodiment.

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 surface 21a 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 bar B from the cooling water spray passage 25. However, it is also possible to configure the configuration so that each of these is supplied through a separate cooling water supply pipe.

The length from the position where the extension line of the central axis of the shower opening 25a of the cooling water injection passage 25 hits the surface of the cast aluminum alloy bar B to the contact surface between the mold 12 and the refractory plate-like body 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, casting is not possible because a good film is not formed, and 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 aluminum alloy molten metal M or aluminum alloy bar B increases, which may cause cracks on the casting surface or tearing inside the mold, making the casting unstable, and is not preferable.

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

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

Note that "parallel" in this context also includes cases 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., where the inner bottom surface 24a is inclined from 0° to 3° relative to the inner peripheral surface 21a.

As shown in Figure 1, the cooling wall portion 27 of the mold 12, which is the portion where the inner bottom surface 24a of the cooling water cavity 24 faces the inner peripheral surface 21a of the hollow portion 21 of the mold 12, is formed so that 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, for example, in the range of 10 x ¹⁰⁵ W/ ^m2 or more and 50 x ¹⁰⁵ W/ ^m2 or less.

The mold 12 is formed so that the thickness t of the cooling wall 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, and preferably 0.5 mm to 2.5 mm. The material for forming the mold 12 is selected so that the thermal conductivity of at least the cooling wall 27 of the mold 12 is within a range of 100 W/m·K to 400 W/m·K.

In FIG. 1, the molten aluminum alloy M in the molten metal receiving section 11 is supplied from one end 12a of a mold 12, which is held so that the central axis C of the mold is nearly horizontal, via a refractory plate 13, and is forcibly cooled at the other end 12b of the mold 12 to become an aluminum alloy rod B.

The aluminum alloy rod B is pulled out at a constant speed by a pull-out drive device (not shown) installed near the other end 12b of the mold 12, so that it is cast continuously to form a long aluminum alloy rod B. The pulled aluminum alloy rod B is then cut to the desired length, for example, by a synchronous cut-off machine (not shown).

The composition ratio of the cast aluminum alloy rod B can be confirmed, for example, by a method using a photoelectric emission spectrophotometric analyzer (example: Shimadzu Corporation, PDA-5500) as described in "JIS H 1305."

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

The liquid lubricant can be a vegetable oil, which is a lubricating oil. Examples include rapeseed oil, castor oil, and salad oil.

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 and may leak from the mold 12 due to insufficient lubrication. If the supply rate is too high, the surplus may get mixed into the aluminum alloy rod B and cause internal defects.

The casting speed, which is the speed at which the aluminum alloy rod B is pulled out of 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, at a casting speed within this range, the network structure of the crystals 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.

The amount of cooling water sprayed from the shower opening 25a of the cooling water spray passage 25 is, for example, preferably 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, the molten aluminum alloy M may not solidify and may leak from the mold 12. In addition, the surface of the cast aluminum alloy bar 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 more than this range, the mold 12 may lose too much heat, causing it to solidify midway.

The average temperature of the molten aluminum alloy M flowing from the molten metal receiving portion 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, there is a risk that coarse crystals will form in the mold 12 or in front of it and will be incorporated into the aluminum alloy bar B as internal defects. On the other hand, if the temperature of the molten aluminum alloy M is too high, a large amount of hydrogen gas will be easily incorporated into the molten aluminum alloy M, which will be incorporated into the aluminum alloy bar B as porosity and may cause internal cavities.

Furthermore, by setting 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 in the cooling wall portion 27 of the mold 12 to a range of 10 x 10 ⁵ W/m ² or more and 50 x 10 ⁵ W/m ² or less, the occurrence of seizure of the aluminum alloy rod B can be prevented.

The cooling wall 27 of the mold 12 receives heat from the molten aluminum alloy M and exchanges the heat by cooling it with the cooling water W contained in the cooling water cavity 24. Regarding the state of this heat exchange, attention is focused on the heat flux per unit area as shown in the explanatory diagram in Fig. 3. The heat flux per unit area is expressed by the following formula (1) according to Fourier's law.
Q=-k×(T1-T2)/L...(1)
Q: heat flux k: thermal conductivity (W/m·K) of the portion through which heat passes (the cooling wall portion 27 of the mold 12 in this embodiment)
T1: Low temperature side temperature of the portion through which heat passes (in this embodiment, the inner bottom surface 24a of the cooling water cavity 24)
T2: High temperature side temperature of the portion through which heat passes (in this embodiment, the inner circumferential surface 21a of the hollow portion 21 of the mold 12)
L: Length (mm) of the section where heat passes through (in this embodiment, the thickness t of the cooling wall portion 27 of the mold 12)

Based on the mold material, thickness, and temperature measurement data that show good results even when the amount of lubricating oil is reduced during casting, the cooling wall portion 27 of the mold 12 is configured so that the heat flux value per unit area is 10×10 ⁵ W/m ² or more, thereby making it possible to prevent seizure of the cast aluminum alloy bar B. In addition, it is preferable that the heat flux value per unit area is 50×10 ⁵ W/m ² or less.

In order to set the cooling wall portion 27 of the mold 12 within this range of heat flux values, 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 or more and 3.0 mm or less. In addition, 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 or more and 400 W/m·K or less.

When manufacturing the aluminum alloy rod B, the above-mentioned horizontal continuous casting device 10 is used to continuously supply the aluminum alloy molten metal M stored in the molten metal receiving portion 11 into the hollow portion 21 from one end side 12a of the mold 12. In addition, cooling water W is supplied to the cooling water cavity 24, and a lubricating fluid, such as lubricating oil, is supplied from the fluid supply pipe 22.

The molten aluminum alloy M supplied into the hollow portion 21 is then cooled and solidified under conditions where the heat flux value per unit area in the cooling wall portion 27 is 10× ¹⁰⁵ W/ ^m2 or more, to cast the aluminum alloy bar B. When casting the aluminum alloy bar B, it is preferable to set the wall surface temperature of the cooling wall portion 27 of the mold 12, which is cooled by cooling water W, to 100° C. or less.

The aluminum alloy rod B thus obtained is cooled and solidified under conditions where the heat flux value per unit area in the cooling wall 27 is 10×10 ⁵ W/m ² or more, thereby suppressing adhesion of reaction products, such as carbides, caused by contact between the lubricating oil gas and the molten aluminum alloy M. This makes it unnecessary to cut and remove carbides, etc., on the surface of the aluminum alloy rod B, and allows the aluminum alloy rod B to be produced with a high yield.

The casting process for obtaining a cast product from the molten aluminum alloy M is not limited to the horizontal continuous casting method described above, and any known continuous casting method 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 mold 12), but the following will briefly explain the case where the hot top method is used.

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 spout and through the header, where the flow rate is adjusted, and enters a cylindrical mold that is installed almost horizontally, where it is forcibly cooled and a solidified shell is formed on the outer surface of the molten metal.

In addition, cooling water is sprayed directly onto the casting as it is pulled out of the mold, and the solidification of the metal progresses all the way to the inside of the casting as it is continuously pulled out. Molds are generally made of metal components with good thermal conductivity, and have a hollow structure to allow the introduction of a coolant inside.

The refrigerant to be used can be selected from those that are industrially available, but water is recommended from the viewpoint of ease of use.

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 on the upper side of the mold. There are no particular restrictions on the material and size of the header, and it can be appropriately selected depending on the composition range of the alloy to be cast and the dimensions of the cast product.

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 that is typical for horizontal continuous casting, such as 200 to 600 mm/min.

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.

(Homogenization heat treatment process)
The homogenization heat treatment step is a step in which homogenization heat treatment is performed on the aluminum alloy casting obtained in the casting step to homogenize microsegregation caused by solidification, precipitate supersaturated solid solution elements, and change metastable phases to equilibrium phases.

In this embodiment, the homogenization heat treatment process is performed by two stages of heat treatment. First, the casting obtained in the casting process is heat treated by holding it in a temperature range of 590°C to 615°C for 4 hours or more (first heat treatment stage). Next, the casting is heat treated by holding it in a temperature range of 500°C to 540°C for 5 hours or more (second heat treatment stage). In this way, by performing the homogenization heat treatment process by two stages of heat treatment with different temperature ranges and holding times, the precipitation of acicular Al-Mn compounds is prevented. This makes it possible to improve the machinability, cold workability, and hot workability during cutting processing.

Through the above steps, the aluminum alloy material of this embodiment can be manufactured, in which there are no acicular Al-Mn compounds with a maximum diameter of 2 μm or more in the metal structure, and the Rockwell hardness [HRF] is 57.0 or less.

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

[Examples 1 to 8 and Comparative Examples 1 to 8]
(Production of continuous cast products)
First, an aluminum alloy material was prepared having the alloy composition (the balance being aluminum) shown in the following Table 1. Using the prepared aluminum alloy material, a continuous cast product having a circular cross section and a diameter of 82 mm was produced.

(Manufacturing of aluminum alloy materials)
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 the following Table 2. In Examples 1-8, a two-stage heat treatment was performed, and in Comparative Examples 1-8, a one-stage heat treatment was performed.

[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 the following Table 3. Moreover, a photograph of an SEM-EBSD image of Example 1 is shown in FIG. 4A, and a photograph of an SEM-EBSD image of Comparative Example 1 is shown in FIG. 4B.

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

<Distribution of needle-shaped 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 a 7 mm square to prepare a test piece for microstructure evaluation of 7 mm x 7 mm x 2 mm thick. The distribution of acicular Al-Mn compounds having 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).
(Judgment criteria)
"Satisfied": No acicular Al--Mn compounds are present.
"Not Satisfied": Needle-like Al--Mn compounds are present.

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

As shown in Table 3, it has been 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 has a Rockwell hardness [HRF] of 57.0 or less, is free of acicular Al-Mn compounds with a maximum diameter of 2 μm or more, and has excellent machinability and workability.

The present invention makes it possible to provide an aluminum alloy material for cold working that has excellent machinability and workability, and a manufacturing method thereof, and an aluminum alloy material for hot working, and a manufacturing method thereof.

10 Horizontal continuous casting device 11 Molten metal receiving part (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 (thermal insulation member)
Reference Signs List 13a: Passage for pouring molten metal 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 jet 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 (7)

An aluminum alloy material for cold working, having an alloy composition containing Si in the range of 0.05 mass % or more and 0.2 mass % or less, Fe in the range of 0.3 mass % or more and 0.5 mass % or less, Cu in the range of 0.01 mass % or more and 0.20 mass % or less, Mn in the range of 0.80 mass % or more and 1.09 mass % or less, Mg in the range of 0.05 mass % or less, Ti in the range of 0.01 mass % or more and 0.1 mass % or less, B in the range of 0.0010 mass % or more and 0.030 mass % or less, with the balance being Al and unavoidable impurities,
An aluminum alloy material for cold working, characterized in that it has no needle-like Al-Mn compounds with a maximum diameter of 2 μm or more in its metal structure and has a Rockwell hardness [HRF] of 57.0 or less. The aluminum alloy material for cold working described in claim 1, characterized in that it is for use in pressure containers for fire extinguishers. The aluminum alloy material for cold working described in claim 1, characterized in that it is for use in exterior containers of secondary batteries. A method for producing an aluminum alloy material for cold working according to any one of claims 1 to 3, comprising the steps of:
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;
a homogenization heat treatment step of subjecting the aluminum alloy cast product obtained in the casting step to a homogenization heat treatment,
The homogenization heat treatment process includes a first heat treatment stage in which a heat treatment is performed by holding the temperature in the range of 590°C or more and 615°C or less for 4 hours or more, and then a second heat treatment stage in which a heat treatment is performed by holding the temperature in the range of 500°C or more and 540°C or less for 5 hours or more. 1. An aluminum alloy material for hot working, comprising: 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; and the balance consisting of Al and unavoidable impurities,
An aluminum alloy material for hot working, characterized in that it has no needle-like Al-Mn compounds with a maximum diameter of 2 μm or more in its metal structure and has a Rockwell hardness [HRF] of 57.0 or less. The aluminum alloy material for hot working described in claim 5, characterized in that it is for use in automotive parts. The method for producing an aluminum alloy material for hot working according to claim 5 or 6,
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;
a homogenization heat treatment step of subjecting the aluminum alloy cast product obtained in the casting step to a homogenization heat treatment,
The homogenization heat treatment process includes a first heat treatment stage in which a heat treatment is performed by holding the temperature in the range of 590°C or more and 615°C or less for 4 hours or more, and then a second heat treatment stage in which a heat treatment is performed by holding the temperature in the range of 500°C or more and 540°C or less for 5 hours or more.

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