JP2000144296A - High-strength and high-toughness aluminum alloy forged material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-strength and high-toughness Al alloy forged material suitable for the parts of a transport such as automotive suspension parts or the like. SOLUTION: This aluminum alloy forged material has a compsn. contg., by mass, 0.6 to 1.6% Mg, 0.6 to 1.8% Si and 0.05 to 1.0% Cu, furthermore, in which the content of Fe is controlled to <=0.30, contg. one or >= two kinds among 0.15 to 0.6% Mn, 0.1 to 0.2% Cr and 0.1 to 0.2% Zr, moreover, in which the content of hydrogen is controlled to <=0.25 cc/100 g Al, and the balance Al with inevitable impurities. In this case, the aluminum alloy ingot cast at 530 to 600 deg.C is subjected to homogenizing heat treatment at 530 to 600 deg.C and is thereafter subjected to hot forging to form into a forged material, and the total area ratio of Mg2Si (2 in Fig.) and Al-Fe-Si-(Mn, Cr, Zr) crystallized products (3 in Fig.) in the aluminum alloy structure in the forged material is controlled to <=1.5% per unit area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to Al-Mg-Si
The present invention relates to a high-strength, high-toughness aluminum alloy forged material (hereinafter, aluminum is simply referred to as Al).

[0002]

2. Description of the Related Art As is well known, JIS 6000, which is excellent in formability and bake hardenability, for the purpose of weight reduction, for structural materials of transportation equipment such as automobiles and vehicles or for suspension parts such as knuckles, lower arms, upper arms and the like. System (Al-Mg
Al alloys such as -Si) are used. This JIS 6000
Aluminum alloys have excellent mechanical properties such as elongation, corrosion resistance, and stress corrosion cracking, which are other required properties.Also, the amount of alloys such as Mg is small, and scrap can be melted using JIS 6000 series aluminum alloys. It is also excellent in terms of recyclability, which can be reused as a raw material.

[0003] Taking the above-mentioned suspension parts for automobiles as an example, cast aluminum alloys and forged aluminum alloys are used from the viewpoint of reduction in manufacturing cost and processing into parts having complicated shapes. Of these, forged parts requiring higher mechanical strength and mechanical properties such as high toughness use an Al alloy forging. These Al alloy forgings are manufactured by subjecting an Al alloy casting to a homogenizing heat treatment, followed by a hot forging such as a mechanical forging, a tempering treatment such as T6, and an aging treatment.

In recent years, there has been a demand for thinner and higher-strength parts including these automotive suspension parts.
There is a need for the Al alloy forging to have higher strength and higher toughness. However, JIS 6000 series Al alloys currently used for these applications inevitably have insufficient strength.

For this reason, improvement of the Al alloy material has been conventionally performed. For example, in Japanese Patent Application Laid-Open No. 06-256880, a JIS 6000 series (A) is used as a casting material for an aluminum alloy forging used as a component such as a suspension for an automobile.
(l-Mg-Si system) Define the components such as Mg and Si of the cast material, reduce the average particle size of the crystallized substance to 8 μm or less, and finely reduce the dendrite secondary arm spacing (DAS) to 40 μm or less. Thus, it has been proposed to improve the strength and toughness of the forged Al alloy material.

[0006]

However, Japanese Patent Laid-Open Publication No.
As shown in the examples of JP-256880-A, the aluminum alloy forged material obtained by this prior art has a dendrite secondary arm spacing (DAS) of at most about 30 μm, even if it is small. characteristics of wood, in the forged test results upsetting round bar, working rate - if [(original ingot height d ₀ height d _t crack occurred) / d _0] is 75%, the strength
(σ _B ) is about 39.2-39.3kgf / mm ² (384-385N / mm ² )
The toughness (I _C ) is about 2.2 to 2.3 kgf / mm ² (Charpy impact value is about 22 J / cm ² ).

That is, in the upsetting forging test of a round bar as in the prior art, each portion of the round bar is uniformly processed, so that the mechanical characteristics of each portion of the round bar become uniform. However, as shown in Fig. 2, an example of an Al alloy forged material for automotive suspension parts is that the working ratio of an actual Al alloy forged material is low depending on the part of the part even by hot forging such as mechanical forging. In some cases, the mechanical properties of each part of the forged material are not uniform. For example, Figure 2
For shapes such as, such as T ₂ portions of FIG. 2, even when T ₁ part of processing rate is 75%, not only the working ratio of 50%. The toughness of the part with a low working ratio tends to be necessarily lower than that of other parts with a high working ratio because the cast structure remains even after forging.

Therefore, although the strength and toughness of the Al alloy forged material obtained by this conventional technique are higher than those of Al alloys such as JIS 6061 and 6151, a portion with a low processing rate is formed, and this portion is formed. In particular, the average toughness of an Al alloy forged material is insufficient for an Al alloy forged material having low toughness. That is, in the prior art, in a portion where the working ratio is less than 75%, and even 50% or less, the level of the toughness is further reduced, and the high yield strength and high toughness value of the whole part required as a part are reduced. I can't get it.

As a result, components requiring higher strength and higher toughness as a whole, more specifically, high strength of 315 N / mm ² or more at σ _0.2 and 20 J / cm ² at Charpy impact value as a whole. It cannot be applied to parts and members requiring the above toughness, and has hindered the expansion of the use of the forged Al alloy itself as a suspension part for automobiles.

[0010] The present invention has been made in view of such circumstances, and its purpose is to improve the average mechanical properties of the forged material as a whole, even if there are portions having a low forging rate. It is an object of the present invention to provide a high-strength and high-toughness Al alloy forging that can be applied to parts and members that require high strength and high toughness as a whole forged material.

[0011]

In order to achieve this object, the gist of the forged Al alloy of the present invention is as follows: Mg: 0.6 to 1.6% (mass
%, The same applies hereinafter), Si: 0.6 to 1.8%, Cu: 0.05 to 1.0%, Fe is controlled to 0.30% or less, Mn: 0.15 to 0.6%, C
r: 0.1 to 0.2%, Zr: containing one or more of 0.05 to 0.2%, hydrogen: 0.25 cc / 100 g Al or less, an aluminum alloy forging material consisting of the balance Al and unavoidable impurities, Ten
Al alloy ingot cast at a cooling rate of
After a homogenizing heat treatment at a temperature of ~ 600 ° C, the forged material is hot forged, and the Mg ₂ Si in the Al alloy structure in the forged material is obtained.
And the total area ratio of Al-Fe-Si- (Mn, Cr, Zr) -based crystallized substances is set to 1.5% or less per unit area.

The present inventors have studied the relationship between the crystallized material crystallized by casting and the toughness of the forged Al alloy structure. As a result, the area ratio of the specific crystallized material is reduced to the forged Al alloy structure. It was found that it was closely related to the toughness of steel.

In other words, the inventors of the present invention have found that the starting point of the fracture of the forged Al alloy structure (the starting point of the dimple) is Mg ₂ Si and Al— Fe-Si-M
n, Al-Fe-Si-Cr, Al-Fe-Si-Zr and other Al-Fe-Si- (Mn, C
(r, Zr) system.

More importantly, the fact that these crystallized substances present in the Al alloy structure are dispersed not at a large or long shape but at intervals from each other contributes to the improvement of toughness. I learned. That is, these crystallized substances cannot be simply reduced or eliminated from the viewpoint that they contribute to securing particularly necessary strength. But,
By controlling the morphology of these crystallized substances that are inevitably present or necessary, securing the necessary strength, even if the forging rate is low or there is a part where the forging rate is low,
It has been found that high average toughness can be secured.

For example, morphological control of the crystallized substance as disclosed in JP-A-06-256880, that is, simply reducing the average particle size of the crystallized substance of the ingot does not contribute much to the improvement of toughness. Contrary to the idea as disclosed in JP-A-06-256880, even if the average particle size of the ingot crystallized matter is large, it is dispersed at intervals. ) Is found to contribute to the improvement of toughness.
That is, even if the average particle size of the crystallized product is small, the toughness, particularly the fracture toughness, is deteriorated when the space between the crystallized materials is small and dense or connected. And, on the other hand, in the present invention,
The crystallized amount itself such as Mg ₂ Si and Al—Fe—Si— (Mn, Cr, Zr) based crystallized materials is controlled or reduced except for the necessary strength.

[0016] The control of the amount of the crystallized substance and the coping with the situation where the crystallized substance is dispersed at a distance from each other (the crystallized substance is not in a state where the distance between the crystallized particles is small or dense or connected) are well handled. In the present invention, the total area ratio of Mg ₂ Si and Al—Fe—Si— (Mn, Cr, Zr) -based crystallization per unit area is selected as an index to be used.

The area ratio of these crystallized substances is determined by visual observation or image analysis observation of the structure of the cross section in the thickness direction of the Al alloy ingot or forged material by 800 times scanning electron microscope (SEM). The magnification of the scanning electron microscope does not change much even when measured at a magnification of 400 to 800, but at other magnifications, the number of crystallized substances to be measured is completely different. For this reason, when the magnification is different, the measured area ratio is significantly different, and the reproducibility of the area ratio is lost. Therefore, in the present invention, the magnification of the scanning electron microscope, which is the standard for defining the area ratio of the crystallized substance, is set to 800 times. Also, in order to provide reproducibility of the area ratio measurement, observe the number of visual fields (measurement points) of the target area for measuring the area ratio of the crystallized substance as 5 to 20 visual fields, and measure the crystallized substance in each visual field. It is preferable to take the average of the area ratios.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The definition of a crystallized substance in the present invention will be described. Mg ₂ by visual observation or image analysis observation of 800 times the scanning electron microscope (SEM) Si and Al-Fe-Si- (Mn, C
(r, Zr) is 1.5% per unit area
% Or less, preferably 1.0% or less, higher strength and high toughness required for automotive suspension parts, etc., preferably, the average value of proof stress (σ _0.2 ) is 350N
/ mm ² or more, high toughness with an average value of 30 J / cm ² or more can be obtained.

On the other hand, when the total area ratio of the crystallized substances exceeds 1.5% per unit area, the working ratio is reduced even by hot forging (the working ratio is less than 75%). It is not possible to obtain an average high toughness value for the entire part, including the fact that the toughness of the part of the part is significantly reduced.

[0020] Figure 1 is an Al alloy forged material manufactured in examples described later, in the thickness direction cross section of the T ₁ site in FIG. 2
It is a figure which shows the microstructure by the scanning electron microscope (SEM) of 800 times (micrograph by SEM). In the figure, 2 is the crystallized Mg ₂ Si, 3 is Al-Fe-
It is a Si- (Mn, Cr, Zr) crystallized substance. Here, Figure 1
(a) Al-forged Al alloy according to the present invention Al-Fe-Si- (Mn, Cr, Z
r) The systemic crystals 3 are finely dispersed at intervals. In contrast, Fig. 1 (b)
The Al-Fe-Si- (Mn, Cr, Zr) -based crystallized substance 3 has a shape in which the crystallized substances are long connected.

The forged Al alloy shown in FIG._0.2 so
350N / mm^TwoWith the above high strength, 30J / cm^Twothat's all
In contrast to the high toughness, the forged Al alloy in Fig.
J / cm ^TwoThe toughness is as follows.
You. Further, in addition, each of FIGS. 1 (a) and 1 (b)
The size of the Al-Fe-Si- (Mn, Cr, Zr) -based
According to Kaihei 06-256880, the average particle size is 8 μm or less.
is there. Therefore, the average of the ingot (cast material)
Simply reducing the grain size does not contribute much to improving toughness,
Even if the average particle size of the ingot crystallized matter is large,
If they are open and dispersed (sparsely present), the words
In other words, Mg_TwoSi and Al-Fe-Si- (Mn, Cr, Zr) crystallized material
The lower the total area ratio of the aluminum alloy, the higher the strength and toughness of the aluminum alloy.
This confirms that a gold forging can be obtained.

Of course, the area ratio of other crystals also affects toughness. Typical examples of other crystallized substances include, for example, a crystallized substance of Si alone, Al ₇ Cu ₂ Fe, Al ₁₂ (Fe, Mn) ₃ Cu ₂ , (Fe, Mn) A
l ₆ , Cu or Mg crystallized compound phase with Al, Al ₂ Cu ₂ Mg, Al ₂ C
u _2, and the like. Among them, the crystallized substance of Si alone serves as a starting point of material destruction and significantly lowers toughness. Therefore, Si
It is necessary that there is substantially no single crystallized substance,
More specifically, it is necessary that a crystallized substance of Si alone is not observed by a scanning electron microscope of 800 times. However, in the case of the usual manufacturing method described later, the crystal structure of Si alone does not substantially exist in the structure of the Al alloy ingot or the Al alloy forged material.

Also, other Al ₇ Cu ₂ Fe, Al ₁₂ (Fe, Mn) ₃ Cu ₂ ,
(Fe, Mn) Al ₆ , Al ₂ Cu ₂ Mg, about the crystallized material such as Al ₂ Cu ₂ ,
As in the case of the Mg ₂ Si and Al—Fe—Si— (Mn, Cr, Zr) crystallized materials, it is necessary to reduce the area ratio in order to improve the toughness. However, these crystallized substances are Mg ₂ Si and Al-Fe-Si-
(Mn, Cr, Zr) Absolute amount is smaller than the amount of crystallized material,
Moreover, if the total area ratio of the Mg ₂ Si and Al-Fe-Si- (Mn, Cr, Zr) -based crystallized products is reduced, the area ratio is inevitably reduced. . Therefore, in the present invention, the crystallized substances other than the Mg ₂ Si and Al—Fe—Si— (Mn, Cr, Zr) crystallized substances are not particularly defined.

In order to satisfy the requirements for the crystallized product of the Al alloy forged material in the present invention and to ensure that the Al alloy forged material has high strength and high toughness, the ingot and the ingot that govern the generation of the crystallized product are required. In the stage of heat treatment for ingot homogenization, Mg ₂ Si and Al-Fe-Si-
It is important that the total area ratio of the (Mn, Cr, Zr) -based crystallized material be 1.5% or less per unit area. That is, the control of the area ratio of the crystallized product is substantially impossible in the forging step, and the control of the area ratio of the crystallized material of the forged material in the present invention is as follows.
It is performed in the stage of ingot and homogenizing heat treatment of the ingot.

The average value of proof stress and toughness referred to in the present invention means, for example in FIG. 2, the highest working rate = the T ₁ portion (75% working rate) having the highest proof stress and toughness, and the working rate Is lowest =
It refers to the average of the lowest T ₂ portions strength and toughness (working ratio 50%). Of course, this does not only mean averaging the values of only these two points, but also averaging the values of a plurality of parts that require further assurance of mechanical properties depending on the member or the shape of the member. good.

(Ingot) In the ingot for a forging material according to the present invention, the secondary dendrite arm spacing (DAS) of the ingot is set to 30 μm or less in order to ensure the toughness of the forged Al alloy. . As a result, the crystal grains of the Al alloy ingot and the Al alloy forged material are refined, and Mg ₂ Si and Al-Fe-Si- (Mn,
It lowers the total area ratio of (Cr, Zr) -based crystallization and improves the toughness of the forged Al alloy. When the dendrite secondary arm spacing (DAS) of this ingot becomes larger than 30 μm, the dendrite secondary arm spacing (DAS) of the Al alloy forged material of JP-A-06-256880 is about 30 μm. like,
When there is a portion having a low forging rate, the toughness of the entire Al alloy forging cannot be improved.

The forged material includes a case where the ingot is directly hot forged and a case where the ingot is once extruded and then hot forged. Therefore, the shape of the ingot includes an ingot such as a round bar, a slab shape, and a near net shape close to a product shape, and is not particularly limited.

(Chemical Composition of the Al Alloy of the Present Invention) Next, the chemical composition of the Al alloy of the present invention will be described.
The Al alloy of the present invention has mechanical properties such as strength, elongation, and toughness, as well as corrosion resistance, stress corrosion cracking resistance, or recyclability with a small amount of alloy, for use in transportation equipment such as automobiles and ships, and structural materials or parts. Needs to be satisfied.
Among them, particularly as a suspension component for an automobile, preferably, a high strength of 350 N / mm ² or more at σ _0.2 and 30 J / cm 2
It is necessary to obtain an average high toughness of ² or more.

Therefore, in order to satisfy the above-mentioned properties, the chemical composition of the Al alloy of the present invention must be in accordance with JIS 60 of Al-Mg-Si system.
00 series Al alloy component standard (JIS 6101, 6003, 6151, 6061,
6N01, 6063, etc.)
0.6-1.6%, Si: 0.6-1.8%, Cu: 0.05-1.0%, Fe is controlled to 0.30% or less, Mn: 0.15-0.6%, Cr:
An Al alloy containing one or more of 0.1 to 0.2% and Zr: 0.05 to 0.2%, hydrogen: 0.25 cc / 100 g Al or less, and the balance being Al and unavoidable impurities. Other, Zn:
0.005 to 1.0%, Ti: 0.001 to 0.1%, B: 1. to 300 ppm and the like are selectively contained as necessary. However, even if it does not conform to each component standard of JIS 6000 series Al alloy, as long as it has the above-mentioned basic characteristics, to further improve the characteristics and add other characteristics, change the component composition as appropriate Is acceptable. In this regard, it is permissible to include other elements such as Ni, V, Sc, and Ag as appropriate in accordance with a change in the component range of the above elements and more specific applications and required characteristics. Further, impurities that are inevitably mixed in from the raw material scrap and the like are allowed as long as the quality of the forged material of the present invention is not impaired.

(Elemental Content of Al Alloy of the Present Invention)
Regarding the content of each element in the alloy material, critical significance and preferred ranges will be described.

Mg: 0.6-1.6%. Mg is precipitated by artificial aging as Mg ₂ Si together with Si, and in the case of Cu-containing composition, forms a compound phase with Cu and Al further, and is essential for imparting high strength (proof stress) when using final products Element. Mg 0.
When the content is less than 6%, the amount of work hardening decreases, and even when artificial aging is performed, σ
_{With 0.2} , high strength of 315 N / mm ² or more cannot be obtained. Meanwhile, 1.
If the content exceeds 6%, the strength (proof stress) becomes too high, impairs the forgeability, and the total area ratio of the Mg ₂ Si crystallized product is 1.5% or less per unit area, preferably 1.0% or less. % Or less, the toughness is reduced, and high toughness cannot be obtained. Therefore, the content of Mg is set in the range of 0.6 to 1.6%.

Si: 0.6-1.8%. Si, together with Mg, is precipitated as Mg ₂ Si by artificial aging and is an essential element for imparting high strength (proof stress) when the final product is used. Si
If the content is less than 0.6%, sufficient strength cannot be obtained by artificial aging, and a high strength of 315 N / mm ² or more cannot be obtained at σ _0.2 . On the other hand, if it is contained in excess of 1.8%, it precipitates as coarse single Si particles during casting and quenching, and as described above, lowers toughness. In addition, Mg ₂ Si and Al-Fe-Si- (Mn, Cr, Z
r) The total area ratio of the system crystallization cannot be 1.5% or less per unit area, preferably 1.0% or less, and high toughness cannot be obtained. Further, the moldability is impaired, for example, the elongation is reduced. Therefore, the content of Si is set in the range of 0.6 to 1.8%.

Cu: 0.05-1.0%. Cu forms a compound phase with Mg and Al to precipitate and contributes to the improvement of matrix strength.At the time of aging treatment, it also acts as a nucleus for the precipitation of other alloying elements and finely and uniformly disperses the precipitate. Has the effect of significantly promoting age hardening of the final product. If the Cu content is less than 0.05%, these effects cannot be exhibited. On the other hand, when the content of Cu exceeds 1.0%, these effects are saturated, and on the contrary, the toughness or hot forgeability is reduced. Further, if the Cu content exceeds 0.3%, the corrosion resistance tends to decrease, so from the viewpoint of corrosion resistance, the Cu content is preferably 0.3% or less. Therefore, the content of Cu is 0.05
To 1.0%, preferably 0.05 to 0.3%.

Mn: 0.15 to 0.6%, Cr: 0.1 to 0.2%, Zr: 0.05
~ 0.2% of one or more species. These elements are subjected to Al ₂₀ Cu ₂ Mn ₃ , Al ₁₂ Mg
₂ Cr, and generates dispersed particles such as Al ₃ Zr (dispersed phase). Since these dispersed particles have an effect of hindering the movement of the grain boundary after recrystallization, fine crystal grains can be obtained. Also, among these elements, when Zr is contained in combination with other Mn and Cr, Zr is smaller than dispersed particles of Al-Mn-based or Al-Cr-based having a size of tens to hundreds of angstroms. , More fine
Al-Zr-based dispersed particles precipitate. Therefore, Zr is Mn, Cr
When they are contained together, the effect of inhibiting the movement of crystal grain boundaries and sub-crystal grain boundaries, suppressing the growth of crystal grains is great, and the effect of improving fracture toughness and fatigue properties is great. On the other hand, excessive content of these elements can cause dissolution and coarse Al-Fe-Si-
An (Mn, Cr, Zr) -based intermetallic compound or crystallized substance is easily formed, becomes a starting point of fracture, and causes a decrease in toughness.
Therefore, the total area ratio of the Al-Fe-Si- (Mn, Cr, Zr) crystallized material is 1.5% or less per unit area, preferably 1.0%.
Or less, and high toughness cannot be obtained. Therefore, the content of each of these elements is Mn: 0.15
0.6%, Cr: 0.1 to 0.2%, Zr: 0.05 to 0.2%.

Fe: 0.30% or less. Fe contained as impurities in the Al alloy is Al ₇ Cu ₂ Fe, Al ₁₂ (Fe, Mn) ₃ Cu ₂ , (Fe, Mn) Al ₆ ,
Alternatively, coarse Al-Fe-Si- (Mn, Cr, Z
r) Produces systemic crystals. As described above, these crystals degrade the fracture toughness and the fatigue properties. In particular, when the Fe content exceeds 0.3%, more strictly 0.25%, the total area ratio of Al-Fe-Si- (Mn, Cr, Zr) -based crystallized substances is 1.5% or less per unit area. Preferably, it cannot be 1.0% or less, and it is not possible to obtain higher strength and higher toughness required for suspension parts for automobiles and the like. Therefore, the content of Fe is preferably 0.30% or less, more preferably 0.25% or less.

Hydrogen: 0.25 cc / 100 g Al or less. Hydrogen significantly reduces toughness and significantly degrades impact fracture resistance.
In addition, in the case of a thinned or high-strength automobile suspension part, the influence of hydrogen on the deterioration of impact fracture resistance is particularly large. Therefore, hydrogen is 0.25 cc / 100g A
l Make the content as low as possible.

(Zn, Ti, B, Be, V, etc.) Next, Zn, Ti, B
, Be, V and the like are elements that are selectively contained depending on the purpose. Zn: 0.005 to 1.0%. Zn achieves high strength by precipitating MgZn ₂ finely and at high density during artificial aging. However, if the content of Zn is less than 0.005%, sufficient strength cannot be obtained by artificial aging, whereas if the content exceeds 1.0%, the corrosion resistance is significantly reduced. Therefore, the content of Zn is preferably in the range of 0.005 to 1.0%.

Ti: 0.001 to 0.1%. Ti is an element added to refine the crystal grains of the ingot and improve press formability. However, if the content of Ti is less than 0.001%, this effect cannot be obtained. On the other hand, if the content of Ti exceeds 0.1%, coarse crystals are formed and the formability is reduced. Therefore, Ti
Is preferably in the range of 0.001 to 0.1%.

B: 1 to 300 ppm. B, like Ti, is an element added to refine the crystal grains of the ingot and improve press formability. However, if the content of B is less than 1 ppm, this effect cannot be obtained, while if the content is more than 300 ppm,
Again, coarse crystals are formed and formability is reduced. Therefore, the content of B is preferably in the range of 1 to 300 ppm.

Be: 0.1 to 100 ppm. Be is an element contained to prevent re-oxidation of the Al melt in the air. However, if the content is less than 0.1 ppm, this effect cannot be obtained, while if the content exceeds 100 ppm, the material hardness increases,
Decreases moldability. Therefore, the content of Be is 0.1 to
It is preferable to be in the range of 100 ppm.

V: 0.15% or less. V forms dispersed particles (dispersed phase) during homogenizing heat treatment and subsequent hot forging, like Mn, Cr, and Zr. Since these dispersed particles have an effect of hindering the movement of the grain boundary after recrystallization, fine crystal grains can be obtained. However, an excessive content tends to generate a coarse Al-Fe-Si-V-based intermetallic compound or crystallized substance during melting and casting, becomes a starting point of fracture, and causes a decrease in toughness. Therefore, when V is contained, the content should be 0.15% or less.

Next, a preferred method of manufacturing the forged Al alloy according to the present invention will be described. The production of the forged Al alloy in the present invention itself can be carried out by an ordinary method. For example, when casting an Al alloy melt that has been melt-adjusted within the range of the above-mentioned Al alloy components, for example, a normal melt casting such as a continuous casting rolling method, a semi-continuous casting method (DC casting method), and a hot top casting method. Casting is performed by appropriately selecting a method.

However, in order to improve the toughness of the forged Al alloy, the crystal grains of the ingot of the Al alloy are refined, and
_{2 To} reduce the total area ratio of Si and Al-Fe-Si- (Mn, Cr, Zr) crystallized materials, cast an Al alloy melt at a cooling rate of 10 ° C / sec or more. It is necessary to When the cooling rate of the ingot is less than 10 ° C./sec, the crystal grains become coarse, and the dendrite secondary arm interval (DAS) of the ingot cannot be reduced to 30 μm or less. In addition, Mg ₂ Si and Al-Fe-Si- (Mn, Cr, Z
r) The total area ratio of the crystallized system cannot be 1.5% or less per unit area, preferably 1.0% or less, and higher strength and toughness required for suspension parts for automobiles and the like. Can not get.

Next, the homogenizing heat treatment temperature of the Al alloy ingot (cast material) needs to be in a temperature range of 530 to 600 ° C. The normal homogenization heat treatment temperature of this type of Al alloy casting material is about 470 to 480 ° C., but in the present invention, as described above, one or more of Mn, Cr, and Zr are used to improve toughness. Al ₂₀ Cu ₂ M
Generate dispersed particles (dispersed phase) such as n ₃ , Al ₁₂ Mg ₂ Cr, and Al ₃ Zr to obtain fine crystal grains. Further, in order to increase the yield strength and toughness of the forged Al alloy, it is necessary to sufficiently dissolve the Mg ₂ Si-based crystallized solid in the homogenization heat treatment.

For this purpose, the homogenizing heat treatment at a high temperature of 530 to 600 ° C. is required. If the temperature of the homogenizing heat treatment is lower than 530 ° C., the number of the dispersed particles is insufficient, and the crystal grains are large. Become. In addition, the amount of solid solution of Mg ₂ Si crystallized material was insufficient,
The total area ratio of Mg ₂ Si and Al-Fe-Si- (Mn, Cr, Zr) -based crystallization products cannot be less than 1.5% per unit area, preferably less than 1.0%, and Higher toughness and higher toughness required for suspension parts, etc. More specifically, high toughness with a Charpy impact value of 20 J / cm ² or more when having high strength of 315 N / mm ² or more at σ _0.2 Can not get. On the other hand, even when the homogenization heat treatment temperature exceeds 600 ° C,
The effect does not change, but rather causes problems such as erosion of the Al alloy ingot (cast material).

After the homogenizing heat treatment, hot forging is performed by mechanical forging, hydraulic forging, or the like to form an Al alloy forging in a final product shape (near net shape). After forging, heat treatment and aging treatment such as T6 treatment (hardening after solution treatment) to obtain necessary strength and toughness are performed.

In order to eliminate the cast structure remaining in the Al alloy forged material and to improve the strength and toughness, the forging may be performed after the Al alloy ingot is subjected to a homogenizing heat treatment and then extruded.

[0048]

Next, embodiments of the present invention will be described. Al alloy ingots shown in Table 1 (Al alloy castings, all φ68 mm diameter × 580 m
m) with the casting method (DC casting method, hot-top casting method) and cooling rate (° C / sec) shown in Tables 2 and 3, and at the temperature shown in Table 2, A time-homogenized heat treatment was carried out, and hot-forging was performed by mechanical forging on the shape of an automobile suspension component at a processing rate shown in Tables 2 and 3 to produce an Al alloy forged material 1 having a shape shown in FIG. Next, this Al alloy forging 1 was subjected to a solution treatment at 560 ° C. for 1 hour using a nitrite furnace, followed by water cooling (water quenching).
Aging treatment was performed at 180 ° C for 5 hours. The ingot of Invention Example No. 5 in Table 3 was subjected to the extrusion ratio after the homogenization heat treatment was performed.
After performing the extrusion process in 6, hot forging was performed.

Then, test pieces were taken from the Al alloy ingot and the Al alloy forged material 1, respectively, and the ingot and the Al alloy forged material were obtained.
1 in the thickness direction of the cross section of the tissue, the 800-fold magnification of a scanning electron microscope (SEM), field number of the specimen (measurement points) performs observation and image analysis as 10 field, Mg ₂ Si
And total area of Al-Fe-Si- (Mn, Cr, Zr) crystallized material
The area ratio per (0.0127 mm ² ) (average of each visual field) was determined. Also, the dendrite secondary arm spacing (D
AS, μm) were also determined from the microstructure photograph of the ingot by the crossing method specified in “Method for measuring aluminum dendrite arm spacing and cooling rate” (1988.8, Research Committee of the Institute of Light Metals). The results are shown in Tables 2 and 3.

Further, the test piece taken from the Al alloy forged material 1
Tensile strength (σ_B, N / mm^Two), Proof stress (σ _0.2, N / mm^Two), Elongation
 (δ,%), toughness = Charpy impact value (J / cm^Two) Etc. mechanical
The properties were measured. At this time, each part of the forged aluminum alloy 1
The variation in mechanical properties due to differences in forging rate
As can be seen, the sampled area was the same as the forging rate in Fig. 1.
The highest T₁And the lowest forging rate T_Twoage
Was. The forging rate is calculated as the cross-sectional area reduction rate.
Was. And the average of the mechanical properties of these parts is also found,
Al alloy forging 1 Determine the average mechanical properties of the whole
Was. These results are also shown in Tables 2 and 3.

As is clear from Table 2, the Fe content was 0.30%
In the following, using Al alloy No. 1 in Table 1 with a chemical composition within the scope of the present invention, such as keeping the hydrogen content to 0.25 cc / 100 g Al or less, and the casting cooling rate and homogenization treatment temperature were Inventive Examples Nos. 1 and 5 that satisfy the inventive manufacturing method have a forging rate of
Even at 50 percent the lowest T _2, which ensure high strength and high toughness, the average mechanical properties of the entire Al alloy forging, in particular yield strength (σ _{0. 2)} is 350 N / mm ² or more And an average toughness value of 30 J / cm ² or more. And, the Al alloy forged material structure of these invention examples is A as shown in FIG.
The l-Fe-Si- (Mn, Cr, Zr) -based crystallized substance 3 had a structure in which it was finely dispersed at intervals.

Among the invention examples shown in Table 2, invention example No.
In contrast to Examples 1 and 5, Invention Example No. 2 has a relatively low casting cooling rate and a relatively large dendrite secondary arm spacing (DAS). In addition, Invention Example No. 4 has a relatively low homogenization treatment temperature, little generation of dispersed particles such as Mn, Cr, and Zr, and relatively coarse crystal grains. In addition, Invention Example No. 3 uses the Al alloy of No. 2 in Table 1 having relatively high Si content, Fe content, and Mg content, and Mg ₂ Si and Al-Fe-Si- (Mn, Cr, Zr). The total area ratio of the system crystallization is relatively high. As a result, these inventive examples, Al average mechanical properties of the entire alloy forging, in particular, the average yield strength (σ _{0. 2)} is 315N / mm ² or more, and an average toughness value of 20 J / cm ² or more although ensuring the strength and toughness in the T ₂ where the forging ratio becomes the lowest 50% have inferior to the invention examples Nanba1,5.

Invention Example No. 1 containing Zr together with Mn and Cr
Invention Example No. 6 having almost the same composition except that it does not contain Zr (Table
In comparison with 3), the toughness value of Invention Example No. 1 is higher.
From this result, it can be seen that the above-mentioned excellent effect of improving the toughness of Zr.

On the other hand, as is clear from Table 3, in particular, Comparative Example No. 7 using the No. 3 Al alloy of Table 1 in which the amount of Fe deviated from the range of the present invention was higher than that of Mg ₂ Si and Al-Fe The total area ratio of -Si- (Mn, Cr, Zr) -based crystallization is out of the range of the present invention. Further, Comparative Example No. 8 in which the casting cooling rate is lower than the production method of the present invention,
Dendrite secondary arm spacing (DAS) is outside the scope of the present invention. Further, in Comparative Example No. 9, the homogenization treatment temperature was lower than that of the production method of the present invention, the generation of dispersed particles such as Mn, Cr, and Zr was small, and the crystal grains were relatively coarse. Therefore, all of these comparative examples have a forging rate of 50%, in particular.
The strength and toughness are low in the lowest becomes T _2, the average mechanical properties of the entire Al alloy forged material 1, proof stress (sigma
_0.2 ) is 315 N / mm ² or less, and the average toughness value is 20 J / cm ² or less. And, the amount of hydrogen deviated from the range of the present invention to a higher level
Comparative Example No. 10 using Al alloy of No. 5 of No. 1 also has the same average mechanical properties as Al alloy forged material 1 as the other comparative examples, except that the proof stress (σ _0.2 ) is 315 N / mm ² or less, and an average toughness value of 20 J / cm ² or less and extremely low.

The Al-Fe-Si- (Mn, Cr,
As shown in FIG. 1 (b), the Zr) -based crystallized product had a shape in which the crystallized products were long connected.

According to the present invention, according to the present invention, in particular, forged materials of various shapes, such as structural materials of transportation equipment such as automobiles and vehicles or suspension parts such as knuckles, lower arms, and upper arms, are used. As a whole, σ _0.2 is 315 N / mm ² or more and 20 J / cm ²
It can be seen that the above-mentioned high strength and high toughness aluminum alloy forged material can be obtained. Therefore, the critical significance of each requirement in the method for manufacturing the high-strength high-toughness aluminum alloy forged material of the present invention, the aluminum alloy material for processing, and the aluminum alloy forged material is supported.

[0057]

[Table 1]

[0058]

[Table 2]

[0059]

[Table 3]

[0060]

According to the present invention, σ _0.2 is 350 N / mm ² or more and toughness is 30 even when the working ratio of hot forging is low.
It is possible to provide a high-strength and high-toughness Al alloy forged material having a strength of J / cm ² or more and which can be applied to parts and members requiring higher strength and higher toughness. Therefore, the use of forged Al-Mg-Si-based Al alloys in automobiles, vehicles, ships, and other transporting equipment can be expanded, which is of great industrial value.

[Brief description of the drawings]

FIG. 1 (a) is an explanatory view showing a microstructure of an Al alloy forged material according to the present invention, and FIG. 1 (b) is a prior art, respectively.

FIG. 2 is an explanatory view showing an example of an Al alloy forging material for a suspension component for an automobile.

[Explanation of symbols]

1: Al alloy forging, 2: Mg ₂ Si crystallization, 3: Al-Fe-Si- (Mn, C
r, Zr)

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Claims (9)

[Claims] (1) Mg: 0.6 to 1.6% (mass%, hereinafter the same), S
i: 0.6 to 1.8%, Cu: 0.05 to 1.0%, and 0.3% Fe
Mn: 0.15 to 0.6%, Cr: 0.1 to 0.2%, Zr:
One or more of 0.05 to 0.2%, and hydrogen:
0.25 cc / 100gAl or less, aluminum alloy forging material consisting of the balance Al and unavoidable impurities, the aluminum alloy ingot cast at a cooling rate of 10 ° C. / sec or more, 53
After a homogenizing heat treatment at a temperature of 0 to 600 ° C., the forged material is hot forged, and Mg ₂ Si and Al—Fe—Si— (Mn, Cr, Zr) in the aluminum alloy structure of the forged material are used. A high-strength, high-toughness aluminum alloy forged material, characterized in that the total area ratio of the crystallized product of the above is 1.5% or less per unit area. 2. The high-strength and toughness according to claim 1, wherein the area ratio of the Mg ₂ Si and Al—Fe—Si— (Mn, Cr, Zr) crystallized material is 1.0% or less per unit area. Forged aluminum alloy. 3. The method according to claim 1, wherein the content of Fe is regulated to 0.25% or less.
Or a high-strength, high-toughness aluminum alloy forging according to item 2. 4. The high-strength, high-toughness aluminum alloy forging according to claim 1, wherein a dendrite secondary arm interval (DAS) of the aluminum alloy ingot is 30 μm or less. 5. The high-strength, high-toughness aluminum alloy forged material according to claim 1, wherein the aluminum alloy ingot is cast and then extruded. 6. The high strength according to claim 1, wherein the average value of the proof stress (σ _0.2 ) is 350 N / mm ² or more and the average value of the Charpy impact value is 30 J / cm ² or more. High toughness aluminum alloy forging. 7. The high-strength, high-toughness aluminum alloy forging according to claim 1, wherein the aluminum alloy forging has a portion where the hot forging rate is less than 75%. 8. The high-strength, high-toughness aluminum alloy forging according to claim 1, wherein the aluminum alloy forging is used for parts of a transport machine. 9. The high-strength and high-toughness aluminum alloy forging according to claim 1, wherein the aluminum alloy forging is used for suspension parts of automobiles.