JP7396105B2 - Manufacturing method for aluminum alloy forgings - Google Patents

Description

The present invention relates to an aluminum 6000 series alloy forged material suitable for use as an undercarriage member for supporting the body of a transportation machine, such as a four-wheeled vehicle.

In recent years, due to the demand for improved fuel efficiency in the automobile industry, various parts used in automobiles, such as suspension parts that support the car body, especially suspension arms, upper arms, lower arms, tie rod ends, etc., have been increasing. Aluminum 6000 series alloys (Al-Mg-Si series), which have excellent strength, high toughness, and corrosion resistance, are used, and there is a demand for further weight reduction of automobiles.

In order to satisfy this requirement, it has become necessary to further improve the strength of JIS standard 6000 series alloys. In other words, it is necessary to make the members thinner by increasing their strength. In addition, in addition to strength, there is a need for further quality improvements in undercarriage components in terms of corrosion resistance such as stress corrosion cracking.

In order to meet these demands, proposals have been made to solve the problem by controlling the composition and manufacturing process to obtain the desired metal structure as a high-strength aluminum 6000 series alloy for automobile suspension parts. (See Patent Document 1 below)

JP 2017-179413 Publication

However, in the manufacturing process, there has been no discussion regarding the angular velocity of the product during quenching. If this angular velocity is not appropriate, air will be drawn in during hardening and the desired hardening speed will not be obtained, resulting in the problem of insufficient mechanical properties, that is, hardness, which are required for automobile suspension parts. Ta.

The present invention has been made in view of this technical background, and is an aluminum alloy that can provide a sufficient hardening rate by controlling the angular velocity of the product during hardening, and has excellent mechanical properties. The purpose of the present invention is to provide a method for manufacturing forged materials.

In order to achieve the above object, the present invention provides the following means.

[1] A method for producing an aluminum alloy forged material including a quenching process as a heat treatment process,
A method for producing an aluminum alloy forged material, wherein in the quenching process, the forged material is brought into contact with quenching water while being rotated, and the angular velocity at the time of contact is 10°/sec or more and 180°/sec or less.

[2] The method for producing an aluminum alloy forged material according to item 1 above, wherein the aluminum alloy is an Al-Mg-Si alloy.

[3] The method for producing an aluminum alloy forged material according to the above item 1 or 2, wherein the solution treatment step includes temperature raising in a hot forging step.

[4] The method for producing an aluminum alloy forged material according to any one of items 1 to 3 above, wherein the temperature of the water in the quenching step is 40° C. to 90° C.

According to the invention [1], the quenching process is performed by bringing the aluminum alloy forged material into contact with quenching water while rotating, and at the time of contact, the angular velocity is 10°/sec or more and 180°/sec or less. Since air entrainment can be suppressed during hardening, quenching can be performed with sufficient contact with quenching water, which can give sufficient quenching speed to aluminum alloy forgings and provide excellent mechanical properties. Obtainable. Therefore, it is possible to provide a high-strength aluminum alloy forged material suitable for automobile suspension members and the like.

According to the invention [2], by using an Al-Mg-Si alloy as the aluminum alloy, it is possible to provide a high-strength Al-Mg-Si alloy forged material suitable for automobile suspension parts, etc. .

According to the invention [3], since the solution treatment process uses temperature raising in the hot forging process, it is possible to provide a high-strength aluminum alloy forged material suitable for automobile suspension parts etc. at a low cost. .

According to the invention [4], by setting the water temperature in the quenching process to 40°C to 90°C, an aluminum alloy forged material suitable for use as a higher quality and stronger automobile suspension member, etc. is provided. be able to.

FIG. 1 is a plan view showing an L-shaped arm, which is an example of the aluminum alloy forged material manufactured in this embodiment. FIG. 2 is a plan view showing an A-type arm, which is an example of the aluminum alloy forged material manufactured in this embodiment. FIG. 3 is a plan view showing a straight arm which is an example of the aluminum alloy forged material manufactured in this embodiment. FIG. 4 is an explanatory diagram showing the locations where Vickers hardness is measured in the L-shaped arm of FIG. 1.

A method for manufacturing an aluminum alloy forged material of the present invention will be explained.

Note that the embodiments shown below are merely illustrative, and the present invention is not limited to these illustrated embodiments, and can be modified as appropriate without departing from the technical idea of the present invention.

In this embodiment, an aluminum alloy forged product is manufactured by performing a molten metal forming process, a casting process, a homogenizing heat treatment process, a hot forging process, a solution treatment process, a quenching process, and an artificial age hardening process in this order. It is. Each of these steps will be explained below.

(Molten metal formation process)
The molten metal forming step is a step in which raw materials are melted to obtain a molten aluminum alloy whose composition has been adjusted.

In this embodiment, Si: 0.80 mass% to 1.40 mass%, Fe: 0.15 mass% to 0.50 mass%, Cu: 0.20 mass% to 0.60 mass%, Mn: 0 .30 mass% to 0.60 mass%, Mg: 0.50 mass% to 1.20 mass%, Cr: 0.05 mass% to 0.25 mass%, the balance being dissolved in a composition consisting of Al and inevitable impurities. The prepared Al-Mg-Si alloy molten metal is obtained.

(Casting process)
The casting process is a process of obtaining a cast material (forging billet) by casting the molten aluminum alloy obtained in the molten metal forming process.

The casting method is not particularly limited, and conventionally known methods may be used, such as continuous casting and rolling, semi-continuous casting (DC casting), and the like.

Further, the diameter of the cast material is not particularly limited, but is set to, for example, a diameter of 30 mm to 80 mm. Furthermore, the cast material may be extruded with an extruder to obtain a billet for forging, and in this case as well, the diameter is set to, for example, 30 mm to 80 mm.

Further, in the casting process, it is preferable to set the cooling rate of the cast material to 10°C/min to 50°C/min. This is because by doing so, it is possible to manufacture an aluminum alloy product with sufficiently high tensile strength at room temperature. In particular, the cooling rate of the cast material is preferably set to 15°C/min to 30°C/min.

(Homogenization heat treatment process)
In the homogenization heat treatment process, the cast material obtained in the casting process is subjected to homogenization heat treatment to homogenize the micro-segregation caused by solidification, to precipitate supersaturated solid solution elements, and to transform the metastable phase into an equilibrium phase. It is a process of making changes.

By performing this homogenization heat treatment, the size of the intermetallic compound can be reduced, fracture originating from the intermetallic compound can be suppressed, and the tensile strength can be further improved.

Furthermore, by performing the homogenization heat treatment, each element contained in the intermetallic compound is uniformly diffused into the base material, making it possible to further improve the tensile strength through solid solution strengthening and precipitation.

Further, the treatment temperature in the homogenization heat treatment is preferably set in the range of 450°C to 570°C. By heat-treating at a temperature of 450°C or higher, intermetallic compounds such as crystallized substances in the cast material dissolve into solid solution and can be sufficiently homogenized, and by heat-treating at a temperature of 570°C or lower, burning can be prevented. It is.

After performing such a homogenization heat treatment step, the cast material is cut into predetermined lengths to obtain a billet for forging.

(hot forging process)
The hot forging process is a process in which the forging billet obtained after the homogenization heat treatment process is heated and molded into a mold by applying pressure with a press machine.

The temperature conditions of the hot forging process are relevant in that they allow the characteristics of the aluminum alloy to be expressed with better reproducibility. That is, it becomes possible to make the microstructure of the aluminum alloy after the solution treatment step described below into equiaxed crystal grains. In particular, it is preferable that the hot forging process be performed with the mold temperature set at 100°C to 250°C and the material temperature set at 400°C to 550°C. This is because by performing hot forging under such conditions, the tensile strength of the aluminum alloy forged material can be further improved.

In the hot forging process of this embodiment, an aluminum alloy forged material having an L-shaped arm (FIG. 1), an A-shaped arm (FIG. 2), or a straight arm (FIG. 3) is obtained.

Next, a solution treatment process, a quenching treatment process, and an artificial age hardening treatment process will be explained.

(Solution treatment process)
The solution treatment process is a heat treatment in which the aluminum alloy forged material obtained in the hot forging process is held at a high temperature and then rapidly cooled to form a supersaturated solid solution.

In the solution treatment process, it is preferable to set the heating temperature to 500°C to 560°C and the holding time to 0.5 to 6 hours. By setting such conditions, the balance between cost and properties can be better achieved. This is because it can improve the quality.

Further, the solution treatment step may be a step in which heating in a hot forging step is also used. In other words, by making the hot forging process double as a solution treatment process, the aluminum alloy forged material kept at a high temperature immediately after the hot forging process is subjected to the quenching process described later, thereby rapidly cooling it and achieving supersaturation. A solid solution may also be formed.

In the hot forging step that uses temperature elevation, it is preferable to set the temperature immediately after the hot forging step to 500° C. to 560° C., and set the time from immediately after the hot forging step to quenching to 1 second to 30 seconds. This is because, by setting such conditions, it is possible to achieve a better balance between cost and characteristics even in this step in which temperature elevation is used in conjunction with the solution treatment step, as well as in the solution treatment step.

By using temperature elevation in the hot forging process in this way, compared to the conventional case where the product is slowly cooled once after the hot forging process, then heated again in a continuous heating furnace or a single furnace and subjected to a solution treatment process, An aluminum alloy of the same quality is obtained, which not only saves the energy required for reheating, but also significantly improves the production time.

Furthermore, it is possible to provide a high-strength aluminum alloy forged material suitable for automobile suspension members and the like at a low cost.

(Quenching treatment process)
Next, the quenching treatment step, which is a feature of the present invention, is a heat treatment in which the solid solution state obtained by the solution treatment step is rapidly cooled to form a supersaturated solid solution.

In the quenching process of the present invention, after the solution treatment process or the hot forging process that also serves as solution treatment, the aluminum alloy forged material is brought into contact with quenching water while rotating, and the angular velocity at the time of contact is 10°/sec or more. Hardening is performed so that the temperature becomes 180°/sec or less.

By bringing the aluminum alloy forging into contact with the quenching water while rotating, the entire surface of the aluminum alloy forging can be brought into contact with the quenching water that has not been warmed by the aluminum alloy forging.

Furthermore, the direction of rotation of the aluminum alloy forged material is not particularly limited, and may be vertical rotation (rotation axis is horizontal) or horizontal rotation (rotation axis is vertical); Rotation is more preferable. This is because vertical rotation increases the speed at the interface between the surface of the aluminum alloy forged material and water.

If the angular velocity is less than 10°/sec, there will be differences in the cooling rate of the aluminum alloy forging at different locations when submerged in water, and mechanical properties will vary depending on the location of the aluminum alloy forging.

If the angular velocity is greater than 180°/sec, air (bubbles) will be drawn in when submerged in water, and the presence of these bubbles on the surface of the aluminum alloy forged material will cause contact between the surface of the aluminum alloy forged material and the quenching water. The area becomes smaller and the cooling rate decreases.

In this embodiment, the aluminum alloy forged material is grasped by a robot, rotated so that the angular velocity is 10°/sec or more and 180°/sec or less upon contact with the quenching water, and allowed to fall freely, and submerged in the quenching water. Quenching is performed in

In addition, the method is not limited to the method using a robot, and quenching may be performed by placing the aluminum alloy forged material on a belt conveyor, moving it, rotating and dropping it at the end to give an angular velocity, and submerging it in quenching water.

Further, in the quenching treatment step of this embodiment, it is preferable to perform rapid cooling with water at 40° C. to 90° C. (water quenching treatment).

This is because by quenching with water at 40° C. to 90° C. in this way, it is possible to provide an aluminum alloy forged material of higher quality and higher strength suitable for use as an automobile suspension member, etc.

As described above, in the quenching treatment process of the present invention, the aluminum alloy forged material is brought into contact with quenching water while rotating, and the angular velocity at the time of contact is 10°/sec to 180°/sec, so that no air is generated during quenching. Since it is possible to suppress the entrainment of aluminum alloy, it is possible to perform quenching with sufficient contact with quenching water, so it is possible to give sufficient quenching speed to aluminum alloy forgings and obtain excellent mechanical properties. can. Therefore, it is possible to provide a high-strength aluminum alloy forged material suitable for automobile suspension members and the like.

(Artificial aging hardening process)
The artificial age hardening process is a heat treatment for imparting appropriate hardness to an aluminum alloy forged product by heating and holding it at a relatively low temperature to precipitate supersaturated solid solution elements.

In this embodiment, it is preferable to set the heating temperature to 160° C. to 250° C. and the holding time to 10 minutes to 8 hours. This is because such conditions provide a better balance between cost and characteristics.

In this embodiment, by performing the above heat treatment (solution treatment process, quenching treatment process, and artificial age hardening treatment process), fine precipitates are uniformly dispersed, and the aluminum alloy has a highly balanced strength, ductility, and toughness. Forged materials can be obtained.

Aluminum alloy products manufactured in this way (castings, forgings, etc.) have excellent mechanical properties at room temperature, so they can be used for example in automobile suspension parts (suspension arms, upper arms, etc.). It is suitably used as a material for lower arms, tie rod ends, etc.).

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

<Example 1>
Contains Si: 1.10% by mass, Fe: 0.25% by mass, Cu: 0.40% by mass, Mn: 0.50% by mass, Mg: 0.85% by mass, and Cr: 0.15% by mass. A molten aluminum alloy was obtained by heating an aluminum alloy, the remainder of which consisted of Al and unavoidable impurities, and then continuous casting was performed using the molten aluminum alloy to obtain a continuously cast material. The obtained continuous cast material was subjected to homogenization heat treatment and then air cooled.

Next, the continuously cast material after air cooling was hot forged at a material temperature of 530°C and a mold temperature of 180°C. The obtained forged material was subjected to solution treatment at 530 ° C., water quenched by placing it in water at 50 ° C., and then heated at 180 ° C. for 6 hours to perform artificial age hardening treatment to obtain forged product 1. Ta.

When performing this water quenching, an angular velocity of 15°/sec was applied using a robot to perform the quenching.

<Example 2>
Contains Si: 1.10% by mass, Fe: 0.25% by mass, Cu: 0.40% by mass, Mn: 0.50% by mass, Mg: 0.85% by mass, and Cr: 0.15% by mass. A molten aluminum alloy was obtained by heating an aluminum alloy, the remainder of which consisted of Al and unavoidable impurities, and then continuous casting was performed using the molten aluminum alloy to obtain a continuously cast material. The obtained continuous cast material was subjected to homogenization heat treatment and then air cooled.

Next, the continuously cast material after air cooling was hot forged at a material temperature of 530°C and a mold temperature of 180°C, and immediately after forging, it was placed in water at 50°C for water quenching, and then at 180°C for 6 hours. A forged product 1 was obtained by heating and performing artificial age hardening treatment.

When performing this water quenching, an angular velocity of 15°/sec was applied using a robot to perform the quenching.

<Example 3>
Forged product 1 was obtained in the same manner as in Example 1 except that the angular velocity was 50°/sec.

<Example 4>
Forged product 1 was obtained in the same manner as in Example 2 except that the angular velocity was 50°/sec.

<Example 5>
Forged product 1 was obtained in the same manner as in Example 1 except that the angular velocity was 100°/sec.

<Example 6>
Forged product 1 was obtained in the same manner as in Example 2 except that the angular velocity was 100°/sec.

<Example 7>
Forged product 1 was obtained in the same manner as in Example 1 except that the angular velocity was 150°/sec.

<Example 8>
Forged product 1 was obtained in the same manner as in Example 2 except that the angular velocity was 150°/sec.

<Comparative example 1>
Contains Si: 1.10% by mass, Fe: 0.25% by mass, Cu: 0.40% by mass, Mn: 0.50% by mass, Mg: 0.85% by mass, and Cr: 0.15% by mass. A molten aluminum alloy was obtained by heating an aluminum alloy, the remainder of which consisted of Al and unavoidable impurities, and then continuous casting was performed using the molten aluminum alloy to obtain a continuously cast material. The obtained continuous cast material was subjected to homogenization heat treatment and then air cooled.

Next, the continuously cast material after air cooling was hot forged at a material temperature of 530°C and a mold temperature of 180°C. The obtained forged material was subjected to solution treatment at 530°C, water quenched by placing it in water at 50°C, and then heated at 180°C for 6 hours to perform artificial age hardening treatment to obtain a forged product. .

When performing this water quenching, an angular velocity of 0°/sec was applied using a robot to perform the quenching.

<Comparative example 2>
A forged product was obtained in the same manner as Comparative Example 1 except that the angular velocity was 5°/sec.

<Comparative example 3>
A forged product was obtained in the same manner as Comparative Example 1 except that the angular velocity was 190°/sec.

<Comparative example 4>
A forged product was obtained in the same manner as Comparative Example 1 except that the angular velocity was 200°/sec.

<Comparative example 5>
Contains Si: 1.10% by mass, Fe: 0.25% by mass, Cu: 0.40% by mass, Mn: 0.50% by mass, Mg: 0.85% by mass, and Cr: 0.15% by mass. A molten aluminum alloy was obtained by heating an aluminum alloy, the remainder of which consisted of Al and unavoidable impurities, and then continuous casting was performed using the molten aluminum alloy to obtain a continuously cast material. The obtained continuous cast material was subjected to homogenization heat treatment and then air cooled.

Next, the continuously cast material after air cooling was hot forged at a material temperature of 530°C and a mold temperature of 180°C, and immediately after forging, it was placed in water at 50°C for water quenching, and then at 180°C for 6 hours. A forged product was obtained by heating and undergoing artificial age hardening treatment.

When performing this water quenching, an angular velocity of 0°/sec was applied using a robot to perform the quenching.

<Comparative example 6>
A forged product was obtained in the same manner as Comparative Example 5 except that the angular velocity was 5°/sec.

<Comparative example 7>
A forged product was obtained in the same manner as in Comparative Example 5 except that the angular velocity was 190°/sec.

<Comparative example 8>
A forged product was obtained in the same manner as Comparative Example 5 except that the angular velocity was 200°/sec.

Various evaluations were performed on each of the forged products obtained as described above based on the following evaluation methods.

<Measurement of angular velocity>
Angular velocity was measured using a gyro sensor. Specifically, a gyro sensor measured the angular velocity when a forged material was grabbed by a robot, rotated, and dropped.

<Hardness measurement>
Hardness measurements were performed on each of the forged products of Examples 1 to 8 and Comparative Examples 1 to 8. Specifically, the forged product was cut into 10 mm squares, filled with resin, and the target surface was polished to #2000 with emery paper, and then the Vickers hardness was measured using a Vickers hardness meter. The Vickers hardness was measured at 10 points with a load of 10 g, and the average Vickers hardness was calculated.

Furthermore, Vickers hardness was measured using an L-shaped arm at measurement points P1 to P5 shown in FIG. Table 1 shows the measurement results of Vickers hardness. The judgment criteria in Table 1 are: ○ when the error (hardness difference) in the measurement results at 5 locations is 4 HV or less, and × when it is 5 HV or more.

From Table 1, it can be seen that in Examples 1 to 8, the error (difference in hardness) was 3HV or 4HV or less, and sufficient mechanical properties were obtained.

On the other hand, in Comparative Examples 1 to 8, the error (difference in hardness) was 5HV or more, indicating that sufficient mechanical properties were not obtained.

The forged products for suspension parts obtained by the manufacturing method of the present invention have high strength and are therefore suitable for use as materials for suspension arms, upper arms, lower arms, tie rod ends, etc. of automobile suspension parts, but in particular, this forged product has high strength. It is not limited to such uses.

1: Aluminum alloy forged material

Claims (4)

A method for producing an aluminum alloy forged material including a quenching process as a heat treatment process,
A method for producing an aluminum alloy forged material, wherein in the quenching process, the forged material is brought into contact with quenching water while being rotated, and the angular velocity at the time of contact is 10°/sec or more and 180°/sec or less. The method for producing an aluminum alloy forged material according to claim 1, wherein the aluminum alloy is an Al-Mg-Si alloy. 3. The method for producing an aluminum alloy forged material according to claim 1, wherein the solution treatment step includes temperature raising in a hot forging step. The method for producing an aluminum alloy forged material according to any one of claims 1 to 3, wherein the temperature of the water in the quenching treatment step is 40°C to 90°C.

Images