JP2021143375A - Aluminum alloy forged article and method for producing aluminum alloy forged article - Google Patents

Abstract

To provide an aluminum alloy forged article that has excellent mechanical property at ordinary temperature and is less likely to generate recrystallized grain, and to provide a method for producing the same.SOLUTION: An aluminum alloy forged article 1 of the present invention contains Cu: 0.15 mass% to 1.0 mass%, Mg: 0.6 mass% to 1.15 mass%, Si: 0.95 mass% to 1.25 mass%, Mn: 0.4 mass% to 0.6 mass%, Fe: 0.2 mass% to 0.3 mass%, Cr: 0.11 mass% to 0.25 mass%, Ti: 0.012 mass% to 0.035 mass%, and B by 0.0001 mass% to 0.03 mass%, the Zn content is 0.25 mass% or less, the Zr content is 0.05 mass% or less, the balance is Al and unavoidable impurities, and, in the cross-section structure of the forged article 1, the fraction of Mg2Si phase present in the visual field area of 500×500 μm2 as measured by SEM-EBSD method is 0.1% or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing an Al-Mg-Si based aluminum alloy forged product having excellent mechanical properties at room temperature.

In recent years, aluminum alloys are being used more and more as structural members of various products by taking advantage of their light weight. For example, high-strength steel has been used for undercarriage and bumper parts of automobiles, but in recent years, high-strength aluminum alloy materials have been used. Iron-based materials have been used exclusively for automobile parts, for example, suspension parts, but they are often replaced with aluminum materials or aluminum alloy materials mainly for the purpose of weight reduction.

Since these automobile parts are required to have excellent corrosion resistance, high strength and excellent workability, Al—Mg—Si based alloys, especially A6061 are often used as aluminum alloy materials. Then, in order to improve the strength, such automobile parts are manufactured by forging, which is one of plastic working, using an aluminum alloy material as a processing material.

In addition, recently, since it is necessary to reduce costs, suspension parts obtained by forging cast members as they are without extrusion and then performing T6 treatment have begun to be put into practical use. Development of high-strength alloys to replace the conventional A6061 is underway (see Patent Documents 1 to 3 below).

Japanese Unexamined Patent Publication No. 5-59477 Japanese Unexamined Patent Publication No. 5-247574 Japanese Unexamined Patent Publication No. 6-256880

However, the above-mentioned Al-Mg-Si-based high-strength alloy has a problem that a sufficiently high strength cannot be obtained because the processed structure is recrystallized in the forging and heat treatment steps and coarse crystal grains are generated. rice field. Therefore, in order to prevent the formation of coarse recrystallized grains, Zr is added to prevent recrystallization (for example, Patent Documents 1 and 2 above).

However, although the addition of Zr is effective in preventing recrystallization, it has the following problems.

(1) The addition of Zr weakens the grain refinement effect of the Al-Ti-B alloy, coarsens the grain of the ingot itself, and causes a decrease in the strength of the processed product (forged product) after plastic working. ..

(2) Since the effect of grain refinement of the ingot itself is weakened, ingot cracks are likely to occur, internal defects increase, and the yield deteriorates.

(3) Zr forms a compound with an Al—Ti—B based alloy, and the compound is deposited on the bottom of the furnace for storing the molten alloy, contaminating the furnace and at the same time, these compounds are also ingots produced. It crystallizes coarsely inside and reduces the strength.

As described above, although the addition of Zr is effective in preventing recrystallization, it has been difficult to maintain the stability of the strength.

The present invention has been made in view of such a technical background, and an object of the present invention is to provide an aluminum alloy forged product having excellent mechanical properties at room temperature and less likely to generate recrystallized grains, and a method for producing the same. ..

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

[1] Cu: 0.15% by mass to 1.0% by mass, Mg: 0.6% by mass to 1.15% by mass, Si: 0.95% by mass to 1.25% by mass, Mn: 0.4 Mass% to 0.6% by mass, Fe: 0.2% by mass to 0.3% by mass, Cr: 0.11% by mass to 0.25% by mass, Ti: 0.012% by mass to 0.035% by mass , B is contained in an amount of 0.0001% by mass to 0.03% by mass, the Zn content is 0.25% by mass or less, the Zr content is 0.05% by mass or less, and the balance is composed of Al and unavoidable impurities. It is an aluminum alloy forged product
An aluminum alloy forged product having an Mg ₂ Si phase fraction of 0.1% or less ^{present in a viewing area of 500 × 500 μm 2} measured by the SEM-EBSD method in the cross-sectional structure of the forged product.

[2] The method for manufacturing an aluminum alloy forged product according to item 1 above.
The molten metal formation process to obtain the molten metal,
A casting step of obtaining a cast product by casting the molten metal obtained in the molten metal forming step, and
A homogenization heat treatment step of performing a homogenization heat treatment on the cast product obtained in the casting step, and a homogenization heat treatment step.
A forging step of forging a cast product after the homogenizing heat treatment step to obtain a forged product,
A solution treatment step of performing a solution treatment on the forged product obtained in the forging step, and a solution treatment step.
A quenching treatment step of quenching after the solution treatment step and a quenching treatment step.
A method for producing an aluminum alloy forged product, which comprises an aging treatment step of performing an aging treatment on the forged product after the quenching treatment step.

[3] In the homogenization heat treatment step, the cast product obtained in the casting step is subjected to a homogenization heat treatment in which the cast product is held at a temperature of 370 ° C. to 560 ° C. for 4 hours to 10 hours.
In the forging step, the cast product after the homogenizing heat treatment step is forged at a heating temperature of 450 ° C. to 560 ° C.
In the solution treatment step, the forged product obtained in the forging step is heated at a heating rate of 5.0 ° C./min or more from 20 ° C. to 500 ° C. at 530 ° C. to 560 ° C. for 0.3 hours to 3 Perform solution treatment to hold for less than an hour,
In the quenching treatment step, all the surfaces of the forged product come into contact with the quenching water within 5 to 60 seconds after the solution treatment step, and quenching is performed in the water tank for more than 5 minutes and within 40 minutes.
The aluminum according to item 2 above, wherein the aging treatment step is performed by heating the forged product after the quenching treatment step at a temperature of 180 ° C. to 220 ° C. for 0.5 hours to 1.5 hours. Manufacturing method of forged alloy products.

According to the invention of [1], the content of each element is set within a predetermined range, and Mg ₂ ^{present in a field area of 500 × 500 μm 2 measured by the SEM-EBSD method in the cross-sectional structure of the forged product.} When the Si phase fraction is 0.1% or less, it is possible to provide an aluminum alloy forged product which has excellent mechanical properties at room temperature and is less likely to generate recrystallized grains.

According to the invention of [2], the molten metal forming step, the casting step, the homogenizing heat treatment step, the forging step, the solution treatment step, the quenching treatment step and the aging treatment step are included, so that the mechanical properties are excellent at room temperature. It is possible to produce an aluminum alloy forged product which has a above-mentioned structure and is less likely to generate recrystallized grains.

According to the invention of [3], by setting the treatment conditions in each treatment step within a predetermined range, the aluminum alloy has further excellent mechanical properties at room temperature and is less likely to generate recrystallized grains. Forged products can be manufactured.

FIG. 1 is a perspective view showing an aluminum alloy forged product obtained by the production method of the present invention.

The aluminum alloy forged product and the method for producing the aluminum alloy forged product of the present invention will be described.

The embodiments shown below are merely examples, and the present invention is not limited to these illustrated embodiments, and can be appropriately modified without departing from the technical idea of the present invention.

The aluminum alloy forged product 1 of the present embodiment has Cu: 0.15% by mass to 1.0% by mass, Mg: 0.6% by mass to 1.15% by mass, and Si: 0.95% by mass to 1.25% by mass. Mass%, Mn: 0.4% by mass to 0.6% by mass, Fe: 0.2% by mass to 0.3% by mass, Cr: 0.11% by mass to 0.25% by mass, Ti: 0.012 It contains mass% to 0.035 mass%, B 0.0001 mass% to 0.03 mass%, Zn content of 0.25 mass% or less, Zr content of 0.05 mass% or less, and the balance. Is composed of Al and unavoidable impurities, and in the cross-sectional structure of this forged product 1, the Mg ₂ ^{Si phase fraction present in the field area of 500 × 500 μm 2} measured by the SEM-EBSD method is 0.1% or less. It is a feature.

In this way, the content of each element is set within a predetermined range, and in the cross-sectional structure of the forged product 1, the Mg ₂ Si phase fraction ^{present in the field area of 500 × 500 μm 2 measured by the SEM-EBSD method is determined.} When it is 0.1% or less, it is possible to provide an aluminum alloy forged product which has excellent mechanical properties at room temperature and is less likely to generate recrystallized grains.

The method for producing the aluminum alloy forged product 1 of the present embodiment is, for example, by performing a molten metal forming step, a casting step, a homogenizing heat treatment step, a forging step, a solution treatment step, a quenching treatment step, and an aging treatment step in this order, for example. The aluminum alloy forged product 1 as shown in FIG. 1 is manufactured. Hereinafter, each step will be described.

(Melted metal forming process)
The molten metal forming step is a step of melting a raw material to obtain an aluminum alloy molten metal having a prepared composition.

In this embodiment, Cu: 0.15% by mass to 1.0% by mass, Mg: 0.6% by mass to 1.15% by mass, Si: 0.95% by mass to 1.25% by mass, Mn: 0. .4% by mass to 0.6% by mass, Fe: 0.2% by mass to 0.3% by mass, Cr: 0.11% by mass to 0.25% by mass, Ti: 0.012% by mass to 0.035 It contains 0.0001% by mass to 0.03% by mass of B and 0.0001% by mass, Zn content is 0.25% by mass or less, Zr content is 0.05% by mass or less, and the balance is Al and unavoidable impurities. A molten metal of a 6000 series aluminum alloy consisting of the above is obtained (prepared). In the molten aluminum alloy, the Zn content may be 0% by mass (Zn-free), or the Zr content may be 0% by mass (Zr-free).

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

The continuous casting method for obtaining a cast product is not particularly limited, and various known continuous casting methods (vertical continuous casting method, horizontal continuous casting method, etc.) can be mentioned. As the vertical continuous casting method, a hot top casting method or the like is used. In the following, as an example of the continuous casting method, a case where an aluminum alloy continuous casting material is manufactured by a hot top casting method using a hot top casting device (that is, a molten aluminum alloy is continuously cast by a hot top casting method to continuously cast an aluminum alloy. (When manufacturing materials) will be briefly described.

The hot-top casting apparatus includes a mold, a molten metal receiver (header), and the like. The mold is cooled by the cooling water filled in the mold. Receptors are generally made of refractory and are located above the mold. The molten aluminum alloy in the receiver is injected downward into the cooled mold, cooled by the cooling water ejected from the mold at a predetermined cooling rate and solidified, and further water in the water tank (its temperature). : Immerse in (about 20 ° C) to completely solidify. As a result, a long continuous cast material such as a rod can be obtained.

(Homogenization heat treatment process)
In the homogenization heat treatment step, the cast material obtained in the casting step is subjected to homogenization heat treatment to homogenize the microsegregation generated by solidification, precipitate hypersaturated solid-dissolved elements, and transfer the semi-stable phase to the equilibrium phase. This is the process of making changes.

In the present embodiment, a homogenizing heat treatment is performed in which the cast product obtained in the casting step is held at a temperature of 370 ° C. to 560 ° C. for 4 hours to 10 hours. By performing the homogenization heat treatment in this temperature range, the ingot is sufficiently homogenized and the solute atoms are sufficiently incorporated, so that sufficient strength required by the subsequent aging treatment can be obtained.

(Forging process)
The forging step is a step of heating the forging billet obtained after the homogenizing heat treatment step and applying pressure with a press to mold the die.

In the present embodiment, the ingot after the homogenization heat treatment is forged at a heating temperature of 450 ° C. to 560 ° C. to obtain a forged product (for example, a suspension arm part of an automobile). At this time, the starting temperature for forging the forging material is 450 ° C to 560 ° C. This is because if the starting temperature is less than 450 ° C., the deformation resistance becomes high and sufficient processing cannot be performed, and if it exceeds 560 ° C., defects such as forging cracks and eutectic melting are likely to occur.

(Solution processing process)
The solution treatment step is a step of alleviating the strain introduced in the forging step and solid-solving the solute element.

In the present embodiment, after the temperature of the forged product after the forging step is lowered to 20 ° C., heating is started after the temperature reaches room temperature, and the temperature rising rate is always 5.0 ° C. over the entire temperature range from 20 ° C. to 500 ° C. The solution treatment is performed by raising the temperature at / min or more and holding the temperature at 530 ° C. to 560 ° C. for 0.3 hours to 3 hours or less.

If the temperature rise rate is less than 5.0 ° C./min, Mg ₂ Si is coarsely precipitated, and if the treatment temperature is less than 530 ° C., solution hardening does not proceed and high strength due to aging precipitation cannot be realized, resulting in a treatment temperature of less than 5.0 ° C./min. This is because if the temperature exceeds 560 ° C., the solid solution of the solute element is further promoted, but eutectic melting and recrystallization are likely to occur.

(Quenching process)
The quenching treatment step 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 present embodiment, all the surfaces of the forged product come into contact with the quenching water within 5 to 60 seconds after the solution treatment, and the quenching treatment is performed in the water tank for more than 5 minutes and within 40 minutes.

(Aging process)
The aging treatment step is a heat treatment for heating and holding an aluminum alloy forged product at a relatively low temperature to precipitate elements that are supersaturated and solid-solved to impart appropriate hardness.

In the present embodiment, the forged product after the quenching treatment step is heated at a temperature of 180 ° C. to 220 ° C. for 0.5 hours to 1.5 hours for aging treatment. If the treatment temperature is less than 180 ° C or the treatment time is less than 0.5 hours, the Mg ₂ Si-based precipitate that improves the tensile strength cannot grow sufficiently, and if the treatment temperature exceeds 220 ° C, the Mg ₂ Si-based precipitate becomes coarse. This is because the tensile strength cannot be sufficiently improved.

As described above, in the method for producing an aluminum alloy forged product of the present invention, the content of each element is set within a predetermined range, and the treatment conditions in each treatment step are set within a predetermined range. It is possible to produce an aluminum alloy forged product which has excellent mechanical properties at room temperature and is less likely to generate recrystallized grains.

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

<Examples 1 to 13>
A continuous cast material having a diameter of 54 mm and a circular cross section was prepared from an aluminum alloy having an alloy composition shown in Table 1, and homogenized heat treatment was performed under the conditions shown in Table 1. The obtained cast material was forged under the conditions shown in Table 1 and plastically worked into the shape of the suspension arm component of the automobile shown in FIG.

Next, the temperature was raised and solution treatment was performed under the conditions shown in Table 1, then the quenching treatment shown in Table 1 was performed, and then the aging treatment was performed to obtain an aluminum alloy forged product 1.

<Comparative Examples 1 to 9>
A continuous cast material having a diameter of 54 mm and a circular cross section was prepared from an aluminum alloy having an alloy composition shown in Table 2, and homogenized heat treatment was performed under the conditions shown in Table 2. The obtained cast material was forged under the conditions shown in Table 2 and plastically worked into the shape of the suspension arm component of the automobile shown in FIG.

Next, the temperature was raised and solution treatment was performed under the conditions shown in Table 2, then the quenching treatment shown in Table 2 was performed, and then the aging treatment was performed to obtain an aluminum alloy forged product 1.

Quenching starts when the entire forged product is submerged in water.

Each aluminum alloy forged product obtained as described above was evaluated based on the following evaluation method.

<Proof stress evaluation method at room temperature>
From the obtained forged aluminum alloy, a tensile test piece having a distance between reference points of 25.4 mm and a parallel portion diameter of 6.4 mm is collected, and the tensile test piece is subjected to a normal temperature (25 ° C.) tensile test to obtain proof stress. It was measured and evaluated based on the following criteria.

(criterion)
“○”… The proof stress at room temperature is 370 MPa or more “Δ”… The proof stress at room temperature is 360 MPa or more and less than 370 MPa “×”… The proof stress at room temperature is less than 360 MPa.

As is clear from Table 1, the aluminum alloy forged products of Examples 1 to 13 produced by the production method of the present invention were excellent in proof stress at room temperature.

On the other hand, as shown in Table 2, the forged aluminum alloys of Comparative Examples 1 to 9 outside the specified range of the present invention were inferior in yield strength at room temperature.

<Measurement method of _{Mg 2} Si phase fraction obtained by SEM-EBSD method of forged aluminum alloy>
_{The Mg 2} Si phase fraction was measured for each aluminum alloy forged product using an SEM-EBSD device. A plate-shaped body having a size of 10 mm × 10 mm × thickness 2 mm was collected from the forged product and used as an SEM-EBSD measurement sample. The measurement conditions were an acceleration voltage of 15 kV, a measurement pitch of 0.5 μm / px, an analysis region of 500 × 500 μm ^2, and a grain boundary definition angle of 15 °. These results are shown in Tables 1 and 2.

As shown in Table 1, in Examples 1 to 13, the Mg ₂ Si phase fraction was 0.1% or less.

On the other hand, as shown in Table 2, in Comparative Examples 1 to 9, the Mg ₂ Si phase fraction was larger than 0.1%.

The forged product obtained by the method for producing an aluminum alloy forged product according to the present invention has excellent mechanical strength at room temperature, and is therefore suitably used as a suspension material for, for example, suspension arm parts of automobiles. It is not limited to such applications.

1: Aluminum alloy forged product

Claims (3)

Cu: 0.15% by mass to 1.0% by mass, Mg: 0.6% by mass to 1.15% by mass, Si: 0.95% by mass to 1.25% by mass, Mn: 0.4% by mass to 0.6% by mass, Fe: 0.2% by mass to 0.3% by mass, Cr: 0.11% by mass to 0.25% by mass, Ti: 0.012% by mass to 0.035% by mass, B Forged aluminum alloy containing 0.0001% by mass to 0.03% by mass, Zn content of 0.25% by mass or less, Zr content of 0.05% by mass or less, and the balance consisting of Al and unavoidable impurities. It ’s a product,
An aluminum alloy forged product having an Mg ₂ Si phase fraction of 0.1% or less ^{present in a viewing area of 500 × 500 μm 2} measured by the SEM-EBSD method in the cross-sectional structure of the forged product. The method for manufacturing an aluminum alloy forged product according to claim 1.
The molten metal formation process to obtain the molten metal,
A casting step of obtaining a cast product by casting the molten metal obtained in the molten metal forming step, and
A homogenization heat treatment step of performing a homogenization heat treatment on the cast product obtained in the casting step, and a homogenization heat treatment step.
A forging step of forging a cast product after the homogenizing heat treatment step to obtain a forged product,
A solution treatment step of performing a solution treatment on the forged product obtained in the forging step, and a solution treatment step.
A quenching treatment step of quenching after the solution treatment step and a quenching treatment step.
A method for producing an aluminum alloy forged product, which comprises an aging treatment step of performing an aging treatment on the forged product after the quenching treatment step. In the homogenization heat treatment step, the cast product obtained in the casting step is subjected to a homogenization heat treatment in which the cast product is held at a temperature of 370 ° C. to 560 ° C. for 4 hours to 10 hours.
In the forging step, the cast product after the homogenizing heat treatment step is forged at a heating temperature of 450 ° C. to 560 ° C.
In the solution treatment step, the forged product obtained in the forging step is heated at a heating rate of 5.0 ° C./min or more from 20 ° C. to 500 ° C. at 530 ° C. to 560 ° C. for 0.3 hours to 3 Perform solution treatment to hold for less than an hour,
In the quenching treatment step, all the surfaces of the forged product come into contact with the quenching water within 5 to 60 seconds after the solution treatment step, and quenching is performed in the water tank for more than 5 minutes and within 40 minutes.
The second aspect of claim 2, wherein the aging treatment step is performed by heating the forged product after the quenching treatment step at a temperature of 180 ° C. to 220 ° C. for 0.5 hours to 1.5 hours. Manufacturing method of forged aluminum alloy products.

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