JP2002348630A - Aluminum forged component and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aluminum forged component having a fine and uniform crystal structure, and superior mechanical properties free from spread, and to provide a method for manufacturing the same. SOLUTION: This manufacturing method comprises heating an aluminum alloy material which includes 0.40-1.30% Si, 0.60-1.20% Mg, 0.15-0.50% Cu, 0.04-0.35% Cr, 0.7% or less Fe, 0.25% or less Zn, 0.15% or less Ti, and 1.0% or less Mn, at a temperature (t) in a range of 450-560 deg.C, then hot-forging it while keeping the die at 50-400 deg.C, further making solution treatment for 0.5-12 hours at a temperature T in a range of 520-560 deg.C, having a relationship with (t) of T<=0.025t<2> -24t+6280, and then artificially aging it at 140-200 deg.C for 0.5-12 hours to make the crystal grain sizes so fine as 100 μm or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology for forging aluminum alloys, and more specifically, to an aluminum forging having excellent mechanical properties and applicable to various mechanical parts such as automobile parts. The present invention relates to a component and a method for manufacturing such an aluminum forged component.

[0002]

2. Description of the Related Art In recent years, the shift to aluminum parts has been progressing for automobile parts in response to the demand for vehicle weight reduction, and especially for suspension parts, aluminum forged parts have been adopted in consideration of their reliability. Is increasing. Among such forged parts, from the viewpoint of high strength and high corrosion resistance, hot forged parts of Al-Mg-Si alloys are frequently used, and the conventional aluminum forging production conditions include: Material heating temperature of 4
Generally, the temperature was set to about 50 ° C.

[0003]

However, in the conventional forging technique in which the heating temperature of the material at the time of forging is set to about 450 ° C., coarse grains are formed during hot forging and subsequent heat treatment (T6 treatment). This causes a problem that the mechanical properties are reduced and uneven due to the coarsening. Particularly, in a material having a 0.2% proof stress exceeding 300 MPa and an elongation value exceeding 10%, it is difficult to obtain stable quality, and it is necessary to design parts based on low material characteristic values. At present, it has been a problem in conventional aluminum forged parts or forging methods to solve such problems and to improve mechanical properties and to make them stable.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in a conventional aluminum forged part, and has a fine and uniform crystal structure and excellent mechanical properties without variation. It is an object of the present invention to provide a forged aluminum part and a method for manufacturing the same.

[0005]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventor has studied the effects of the material heating temperature during forging, the solution treatment temperature, and the forging reduction rate on the mechanical performance of an Al-Mg-Si alloy. As a result of intensive examination of the effects, the interdependencies between them were found, and by optimizing these relationships together with the above temperature range, the crystal structure after the aging treatment could be made fine and uniform, It has been found that stable mechanical performance without variation can be ensured.

The present invention is based on such findings, and the aluminum forged part according to the present invention has a mass ratio of Si: 0.40 to 1.30%, Mg: 0.60 to 0.60.
1.20%, Cu: 0.15 to 0.50%, Cr: 0.
04-0.35%, Fe: 0.7% or less, Zn: 0.2
5% or less, Ti: 0.15% or less, Mn: 1.0% or less, an aluminum alloy containing the balance of aluminum and unavoidable impurities, and has a microstructure with a crystal grain size of 100 μm or less; The present invention is characterized in that such a structure in an aluminum forged part is used as means for solving the above-mentioned conventional problems.

The method for manufacturing an aluminum forged part according to the present invention is suitable for manufacturing the above-described aluminum forged part, and has a mass ratio of Si: 0.40 to 1.30%;
Mg: 0.60 to 1.20%, Cu: 0.15 to 0.5
0%, Cr: 0.04 to 0.35%, Fe: 0.7% or less, Zn: 0.25% or less, Ti: 0.15% or less, M
n: an aluminum alloy material containing 1.0% or less, the balance of aluminum and unavoidable impurities is 450 ° C. or more and 5
Hot forging is performed by heating to a temperature t of 60 ° C. or less, and 52
A solution heat treatment at a temperature T of 0 ° C. or more and 560 ° C. or less, followed by artificial aging, wherein the material heating temperature t
T ≦ 0.025t ² −24t +
The manufacturing method is characterized in that the aluminum alloy material is heated to a temperature t, and then subjected to rough forging using a mold held at 50 to 400 ° C. After hot forging until finishing, and after solution treatment for 0.5 to 12 hours, 14
It is characterized by being subjected to artificial aging at 0 to 200 ° C. for 0.5 to 12 hours, and as still another preferred embodiment, a reduction ratio r (%) from rough forging to finish forging in the hot forging. , Heating temperature (t) and solution temperature T
(° C.), T ≦ 0.025 (tr−410) ² +
520, and such a configuration in a method for manufacturing an aluminum forged part is a means for solving the above-mentioned conventional problem.

[0008]

The aluminum forged part according to the present invention is based on an Al-Mg-Si alloy, that is, a 6000 alloy widely used as a forging material. High strength is obtained by applying. And, while optimizing the component composition including Mg and Si, the crystal grain size is 100 μm.
0.2% because of the following microstructure
Stable quality having high strength such that the proof stress is 300 MPa or more is obtained.

Further, in the method for manufacturing an aluminum forged part according to the present invention, the method comprises the steps of:
-Hot forging is performed by heating the Si-based alloy material to a predetermined temperature t (° C.), and a solution at a predetermined temperature T (° C.) having a predetermined relationship with the heating temperature t (° C.) during forging. After the aging treatment, artificial aging is performed (T6 treatment), so that the crystal grain size becomes as fine as 100 μm or less, and the strength of the aluminum forged part is improved without variation.

Next, the reasons for limiting the alloy components, forging conditions, and heat treatment conditions after forging in the present invention will be described. In addition, the content of the alloy component means mass%.

Si: 0.40 to 1.30% Si is a component which coexists with Mg described below to form an Mg ₂ Si-based precipitate to improve the strength of the aluminum alloy. If less than the above, the effect of improving the strength cannot be sufficiently obtained, and if it exceeds 1.30%, the forgeability of the alloy may be impaired.

Mg: 0.60 to 1.20% Mg, as described above, forms a Mg ₂ Si-based precipitate together with Si to improve the strength of the alloy. The effect is not sufficiently obtained, and conversely 1.20%
0.60 to 1.20%
Must be within the range.

Cu: 0.15 to 0.50% Cu not only contributes to the improvement of the matrix strength by precipitation hardening, but also has the function of finely and uniformly dispersing the precipitates during aging treatment. If the Cu content is less than 0.15%, such an effect is difficult to obtain, while if it exceeds 0.50%, forgeability and corrosion resistance are deteriorated.
% Range.

Cr: 0.04 to 0.35% Cr has an effect of preventing the crystal grains from becoming coarse and contributes to high strength and high toughness of the aluminum alloy.
If it is less than 04%, such an effect cannot be expected, and 0.35%
%, The forgeability may be impaired.
０．３0.35%.

Fe: 0.7% or less Fe is treated as an impurity.
Since the elongation is reduced by the system crystallization, the content is set to 0.7% or less.

Zn: 0.25% or less Zn is treated as an impurity, and if it exceeds 0.25%, the stress corrosion cracking resistance deteriorates.

Ti: 0.15% or less Ti is an element that contributes to the refinement of crystal grains, but if contained in a large amount, the toughness is impaired. Therefore, the upper limit is set to 0.15%.

Mn: 1.0% or less Like Cr and Fe, Mn is effective in suppressing the coarsening of crystal grains, but if contained excessively, the forgeability may be impaired. Must be added within a range not exceeding.

Crystal grain size: 100 μm or less In a forged part of an aluminum alloy containing the above alloy component, by setting the crystal grain size to 100 μm or less, the mechanical strength with 0.2% proof stress exceeding 300 MPa is stable. Will be obtained.

Material heating temperature t: 450 to 560 ° C. As the material heating temperature during forging increases, the deformation resistance during forging decreases, and the strain introduced into the material is reduced.
This has the effect of suppressing the coarsening of crystal grains generated during the solution treatment. Such an effect cannot be obtained at a temperature lower than 450 ° C. Conversely, when the temperature exceeds 560 ° C., local melting of the aluminum alloy starts, causing problems such as burning and a decrease in ductility. Temperature range.

Solution treatment temperature T: 520-560 ° C. In the solution treatment, it is necessary to raise the temperature to 520 ° C. or higher in order to dissolve Mg ₂ Si in the aluminum matrix. 560 ° C. or less. Further, since the strain introduced into the material at the time of forging is released by this solution treatment and the crystal grains are coarsened, the material heating temperature t and, more desirably, the material heating temperature t and the forging pressure as described later will be described later. Rate r
It is necessary to set the upper limit of the solution temperature T according to (%). Note that the solution treatment time was determined using Mg ₂ S
From the viewpoint of sufficiently dissolving i in the matrix and avoiding wasteful energy consumption, it is desirable to set it to about 0.5 to 12 hours.

Forging conditions: mold temperature, reduction ratio r The temperature of the mold used for forging must be kept within a temperature range of 50 to 400 ° C., because it affects the life of the mold and coarsening of crystal grains. Is desirable. That is, when the mold temperature is 50
If the temperature is lower than 0 ° C., the crystal grains become coarse due to a decrease in the life of the mold and the actual temperature of the material. In addition, when the rolling reduction r (%) by forging increases, a fiber structure is introduced and the mechanical properties are improved, but the forging reduction r is 50 to 50%.
Even at 80%, when the material heating temperature t is low, strain is generated during forging, which is a factor of causing coarse grains of crystals during solution treatment. The rolling reduction r is defined as in the following equation. r (%) = (1- (dimension after forging) / (initial material dimension))
× 100

Artificial aging: 140-200 ° C. × 0.5-1
The artificial aging for 2 hours is performed to improve the strength of the matrix by precipitating Mg ₂ Si-based precipitates finely and uniformly, and if the heating temperature is lower than 140 ° C., it takes a long time for the precipitation. If the temperature exceeds 200 ° C., the precipitates may be coarsened, making it difficult to improve the strength. When the holding time is less than 0.5 hour, M
When g ₂ Si cannot be precipitated, and when the time exceeds 12 hours, the precipitation proceeds excessively, and the Mg ₂ Si precipitate tends to be coarsened, and similarly, there is a tendency that the strength cannot be stably improved. .

Material heating temperature t, rolling reduction r, solution temperature T
As described above, the material heating temperature t, the rolling reduction r, and the solution temperature T each affect the strength and structure of the forged aluminum part, but are manufactured in a series of steps in the manufacturing process of the part. Therefore, these influence not only independently but also mutually. That is, in order to realize a fine structure having a crystal grain size of 100 μm or less so as to stably obtain high strength by preventing coarsening of the crystal grains, the upper limit value of the solution temperature T is set to the material heating temperature t. Must be calculated as Tu1 = 0.025t ² −24t + 6280, and further, Tu2 = 0.025 (t) calculated from the material heating temperature t and the reduction ratio r (%).
-R-410) ² +520 is desirable.
FIG. 1 shows these condition ranges.

[0025]

EXAMPLES The present invention will be described below more specifically based on examples.

First, an aluminum alloy having the chemical components shown in Table 1 was melted and semi-continuously cast to cast a billet having a diameter of 60 mm.

[0027]

[Table 1]

This billet is subjected to a homogenization treatment at 470 ° C. × 7 hours, then cut to a predetermined length, and the billet is chamfered to remove a segregated structure near a casting surface of the cast billet. A round bar having a diameter of 56 mm and a length of 447 mm was obtained to obtain a forging material.

Using the above forging material, hot forging is performed under the conditions that the material heating temperature t during forging is changed to three levels and the solution heat temperature T is changed to two levels, and the forged product after artificial aging is performed. Table 2 shows the results obtained by examining the mechanical performance of the sample, observing the macrostructure and microstructure, and measuring the crystal grain size. 2 to 5 show the macrostructure of each forged product, and FIG. 6 shows the microstructure of Sample 1 according to the present invention.

[0030]

[Table 2]

The material heating time in the first forging step was 55 minutes, and the mold temperature was 175 ° C. In the first forging, the material for forging is bent in the length direction in consideration of the shape of the final part, and in the second forging, a mold heated and held at 175 ° C. is used, and the lengthwise direction is reduced at an average reduction rate r of 70%. Forged against. Then, in the third forging, forging was similarly performed using a mold heated to 175 ° C. to obtain a final product shape. The solution treatment time was 2.5 hours, and the artificial aging was 1 hour.
The condition of 80 ° C. × 6 hours was adopted.

The material heating temperature t is 540 ° C. and r = 70% (therefore, 0.025t ² -24t + 6280 = 61)
0, 0.025 (tr-410) ² + 520 = 61
0) In sample 1 in which the solution temperature T was 550 ° C., the front surface had a fine and uniform macrostructure, and it was confirmed that the forged product was excellent in mechanical properties, particularly in proof stress-elongation balance. . FIG. 6 also shows the microstructure.
Shows a fine structure as shown in FIG.
Met.

The material heating temperature t is reduced to 500 ° C., and r
= 70% (0.025t ² -24t + 6280 = 5
30, 0.025 (tr−410) ² + 520 = 53
0), Sample 2 in which strain was introduced during forging exhibited a macrostructure of coarse grains grown by recrystallization, and resulted in low mechanical properties, particularly low elongation values. Further, the material heating temperature t was lowered to 450 ° C. (0.025 t ² −24 t + 62).
80 = 542.5, 0.025 (tr−410) ² +
520 = 542.5) In sample 3, since the amount of strain introduced during forging is even larger, a macrostructure of coarse grains grown by recrystallization is obtained as in sample 2, and forged products having low mechanical properties, particularly low elongation values. It became.

The material heating temperature t is set to 500 ° C. (Accordingly,
0.025t ² -24t + 6280 = 530, 0.02
5 (tr−410) ² + 520 = 530), the solution temperature T was lowered to 510 ° C. with respect to the samples 1 to 3,
In Sample 4 in which the release of the strain introduced during forging was suppressed, although the front surface had a fine and uniform macrostructure, the mechanical properties, particularly the tensile strength and the proof stress, were reduced. This is considered to be due to insufficient solid solution of the strengthening element that contributes to precipitation hardening.

As described above, from the relationship between the material heating temperature t, the condition of the solution temperature T, and the macrostructure, r = 70%
In the case of T ≦ 0.025t ² −24t + 6280, it was confirmed that the macrostructure exhibited a fine and uniform structure.

[0036]

As described above, the aluminum forged part according to the present invention has a Si content of 0.40 to 1.30.
%, Mg: 0.60 to 1.20%, Cu: 0.15
0.50%, Cr: 0.04 to 0.35%, Fe: 0.
It is made of an aluminum alloy containing 7% or less, Zn: 0.25% or less, Ti: 0.15% or less, and Mn: 1.0% or less, and has a fine structure with a crystal grain size of 100 μm or less. This is an extremely excellent effect that a high-strength component having a 0.2% proof stress exceeding 300 MPa can be stably obtained without variation.

In the method for manufacturing an aluminum forged part according to the present invention, the Al-Mg-Si
The system alloy material is heated to a temperature t in the range of 450 to 560 ° C., and desirably hot forged using a mold maintained at 50 to 400 ° C., and further in a range of 520 to 560 ° C. At a temperature T having a predetermined relationship (T ≦ 0.025t ² −24t + 6280) with the heating temperature t at the time of forging, the solution aging is preferably performed for 0.5 to 12 hours, and then the artificial aging is performed. , Preferably 140-200
Since artificial aging is performed at 0.5 ° C. for 0.5 to 12 hours (T6 treatment), the crystal grain size can be made as fine as 100 μm or less, and the strength of aluminum forged parts can be improved without variation. The excellent effect that it can do is brought.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an appropriate range of a material heating temperature and a solution heat temperature in a method for manufacturing an aluminum forged part according to the present invention.

FIG. 2 is a photograph showing a macrostructure of a forged aluminum part of Sample 1 obtained in an example of the present invention.

FIG. 3 is a photograph showing a macrostructure of a forged aluminum part of Sample 2 obtained in a comparative example.

FIG. 4 is a photograph showing a macrostructure of a forged aluminum part of Sample 3 obtained in a comparative example.

FIG. 5 is a photograph showing a macrostructure of a forged aluminum part of Sample 4 obtained in a comparative example.

FIG. 6 is a photograph showing a microstructure of an aluminum forged part obtained in an example of the present invention.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (Reference) C22F 1/00 604 C22F 1/00 604 610 610 630 630 630A 683 683 691 691B 691C 694 694A (72) Inventor Yukihiro Mujo Kanagawa Nissan Motor Co., Ltd. (2) Takaracho, Kanagawa-ku, Yokohama-shi (72) Inventor Eiji Eguchi 2, Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa F-term (reference) 4E087 AA00 BA04 CA11 CB01 DB14 HA31 HA82

Claims (4)

[Claims] 1. A mass ratio of Si: 0.40 to 1.30.
%, Mg: 0.60 to 1.20%, Cu: 0.15
0.50%, Cr: 0.04 to 0.35%, Fe: 0.
7% or less, Zn: 0.25% or less, Ti: 0.15% or less, Mn: 1.0% or less, microstructure composed of aluminum alloy containing aluminum and unavoidable impurities, and having a crystal grain size of 100 μm or less An aluminum forged part comprising: 2. The mass ratio of Si: 0.40 to 1.30.
%, Mg: 0.60 to 1.20%, Cu: 0.15
0.50%, Cr: 0.04 to 0.35%, Fe: 0.
Aluminum alloy material containing 7% or less, Zn: 0.25% or less, Ti: 0.15% or less, Mn: 1.0% or less, aluminum and inevitable impurities at 450 ° C.
A hot forging by heating to a temperature t of not less than 560 ° C. and a solution heat treatment at a temperature T of not less than 520 ° C. and not more than 560 ° C., followed by artificial aging. ^{2. The} method for manufacturing an aluminum forged part according to claim 1, wherein T has a relationship of T ≦ 0.025t ² −24t + 6280. 3. After the aluminum alloy material is heated to a temperature t, hot forging from rough forging to finishing is performed using a mold held at 50 to 400 ° C.
The method for producing an aluminum forged part according to claim 2, wherein after the solution treatment for a time, artificial aging is performed at 140 to 200C for 0.5 to 12 hours. 4. A method according to claim 1, wherein: T ≦ 0.025 (t−r−) between the reduction ratio r (%) from the rough forging to the finish forging in the hot forging, the heating temperature (t) and the solution temperature (T). 410) The method for manufacturing an aluminum forged part according to claim 2, wherein the method has a relationship of ² + 520.