JP2005336568A - High toughness aluminum-alloy casting and its production method - Google Patents

High toughness aluminum-alloy casting and its production method Download PDF

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JP2005336568A
JP2005336568A JP2004158757A JP2004158757A JP2005336568A JP 2005336568 A JP2005336568 A JP 2005336568A JP 2004158757 A JP2004158757 A JP 2004158757A JP 2004158757 A JP2004158757 A JP 2004158757A JP 2005336568 A JP2005336568 A JP 2005336568A
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alloy casting
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alloy
elongation
tensile strength
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JP4238180B2 (en
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Yusuke Toyoda
裕介 豊田
Katsuhiro Shibata
勝弘 柴田
Takahiro Mizukami
貴博 水上
Ryoichi Murakashi
良一 村樫
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Honda Motor Co Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a high toughness Al-alloy casting in which all of tensile strength, 0.2% proof stress and elongation can be obtained at high levels in a well balance. <P>SOLUTION: The high toughness Al-alloy casting contains, by mass, 2 to 4% Si, 0.2 to 0.5% Mg, 0.4 to 0.8% Cu, 0.1 to 0.4% Zr, and the balance Al with inevitable impurities. The casting has the tensile strength of ≥280 MPa, the 0.2% proof stress of ≥220 MPa, and the elongation of ≥10%. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、高靱性Ａｌ合金鋳物及びその製造方法に係り、特に、種々の機械的特性に優れたＡｌ合金鋳物の製造技術に関する。   The present invention relates to a high toughness Al alloy casting and a method for producing the same, and more particularly to a technique for producing an Al alloy casting having various mechanical characteristics.

Ａｌ合金鋳物は、車体、サスペンション部材、サブフレーム部材、各種継手部材、及びアルミホイール等のシャーシ構成部品等に使用して好適であり、このような合金については種々の技術が開示されている。   Al alloy castings are suitable for use in chassis components such as vehicle bodies, suspension members, subframe members, various joint members, and aluminum wheels, and various techniques are disclosed for such alloys.

このようなＡｌ合金鋳物としては、伸び、衝撃値、引張強さ、耐力、及び耐食性を向上させることを目的として、質量比で、Ｓｉ：１．６５〜４．０％、Ｍｇ：０．２〜０．４％、Ｆｅ：０．２％以下であり、残部が実質的にＡｌ及び不可避的不純物の組成からなり、Ａｌ基地中の共晶Ｓｉの面積率が１５％以下、伸びが１５％以上、且つ衝撃値が３０〜４０×１０４Ｊ／ｍ２以上である高靱性Ａｌ鋳物が提案されている（特許文献１参照）。この高靱性Ａｌ鋳物は、Ｓｉ含有量を低く抑えた組成で、鋳造後、共晶温度近傍の高温に急冷する高温溶体化処理を行い、しかる後に時効処理を適切に施すことで、優れた伸び及び衝撃値を実現することができる。また、このＡｌ鋳物は、同様に、高温溶体化処理を行い、しかる後に長時間時効処理を行うことで、優れた引張強さ、耐力、及び耐食性を実現することができる。このような技術によれば、部品の薄肉化に伴う軽量化を図ることでき、しかも低圧鋳造又は重力鋳造を適用することができるため、生産性を向上させることができる。 Such an Al alloy casting has a mass ratio of Si: 1.65 to 4.0% and Mg: 0.2 for the purpose of improving elongation, impact value, tensile strength, yield strength, and corrosion resistance. -0.4%, Fe: 0.2% or less, the balance is substantially composed of Al and inevitable impurities, the area ratio of eutectic Si in the Al base is 15% or less, and the elongation is 15%. As described above, a high toughness Al casting having an impact value of 30 to 40 × 10 4 J / m 2 or more has been proposed (see Patent Document 1). This high toughness Al casting has a composition with a low Si content, and after casting it is subjected to a high temperature solution treatment that is rapidly cooled to a high temperature close to the eutectic temperature, and then an aging treatment is appropriately applied to achieve excellent elongation. And impact values can be realized. In addition, this Al casting can be similarly subjected to a high-temperature solution treatment, and then an aging treatment for a long time, thereby realizing excellent tensile strength, yield strength, and corrosion resistance. According to such a technique, it is possible to reduce the weight accompanying the thinning of the parts, and to apply low-pressure casting or gravity casting, so that productivity can be improved.

また、優れた靱性を実現するとともに、金型への焼き付きの発生を防止することを目的として、質量比で、２％≦Ｓｉ≦４％、０．２％≦Ｍｇ≦０．５％、０．４％≦Ｃｕ≦０．８％、０．２％≦Ｆｅ≦０．５％、０．１％≦Ｔｉ≦０．３％、及び不可避的不純物を含み、残部がＡｌであり、金属組織におけるα相の粒径ｄが５０μｍ以下である高靱性Ａｌ合金鋳物が提案されている（特許文献２参照）。この技術では、高靱性Ａｌ鋳物の組成を上記特許文献１と同等の組成とした上で、Ｆｅの含有量を画期的な０．２質量％を超えるものとすることにより、優れた靱性と金型への焼き付き防止とを共に実現することができる。なお、特許文献２に記載の高靱性Ａｌ合金鋳物は、上記組成のＡｌ合金溶湯を加圧下で金型のキャビティに充填し、次いで溶湯の凝固が完了するまで冷却速度を５℃／Ｓに制御して得られるものであり、靱性等の物性は、特許文献１に記載の鋳物と同等であるが、生産性がさらに改善されている。   Further, for the purpose of realizing excellent toughness and preventing the occurrence of seizure on the mold, the mass ratio is 2% ≦ Si ≦ 4%, 0.2% ≦ Mg ≦ 0.5%, 0 .4% ≦ Cu ≦ 0.8%, 0.2% ≦ Fe ≦ 0.5%, 0.1% ≦ Ti ≦ 0.3%, and unavoidable impurities, the balance being Al, There has been proposed a high toughness Al alloy casting in which the particle size d of the α phase is 50 μm or less (see Patent Document 2). In this technique, the composition of the high toughness Al casting is made the same composition as that of the above-mentioned Patent Document 1, and the excellent toughness is achieved by making the content of Fe more than epoch-making 0.2% by mass. Both prevention of seizing on the mold can be realized. In addition, in the high toughness Al alloy casting described in Patent Document 2, the molten aluminum alloy having the above composition is filled into the mold cavity under pressure, and then the cooling rate is controlled to 5 ° C./S until the solidification of the molten metal is completed. The physical properties such as toughness are equivalent to those of the casting described in Patent Document 1, but the productivity is further improved.

特開平９−２７２９４２号公報（要約書）Japanese Laid-Open Patent Publication No. 9-272942 (Abstract) 特願２００３−４２０４０５号Japanese Patent Application No. 2003-420405

しかしながら、上記特許文献１、２に記載された技術では、得られる鋳物の機械的諸性質のうち、特に伸びや衝撃強度等の靱性について、十分な値が得られているとは言い難い。例えば、特許文献１の請求項４に記載の鋳物では、引張強さが２４０ＭＰａ以上であり、しかも０．２％耐力が１４０ＭＰａ以上であるが、衝撃値が１９×１０４と低い。よって、近年においては、抗張力、０．２％耐力及び伸びの全てがバランス良く高いレベルで得られるＡｌ合金鋳物の技術開発が要請されていた。 However, in the techniques described in Patent Documents 1 and 2, it is difficult to say that sufficient values are obtained for toughness such as elongation and impact strength among mechanical properties of the obtained casting. For example, in the casting according to claim 4 of Patent Document 1, the tensile strength is 240 MPa or more and the 0.2% proof stress is 140 MPa or more, but the impact value is as low as 19 × 10 4 . Therefore, in recent years, there has been a demand for the technical development of Al alloy castings in which all of tensile strength, 0.2% proof stress and elongation can be obtained at a high level with good balance.

本発明は、上記要請に鑑みてなされたものであり、抗張力、０．２％耐力及び伸びの全てがバランス良く高いレベルで得られる高靱性Ａｌ合金鋳物及びその製造方法を提供することを目的としている。   The present invention has been made in view of the above requirements, and aims to provide a high-toughness Al alloy casting in which all of tensile strength, 0.2% proof stress and elongation can be obtained in a well-balanced and high level and a method for producing the same. Yes.

本発明者らは、上記のように、抗張力、０．２％耐力及び伸びが、バランス良く高いレベルで得られる、高靱性Ａｌ合金鋳物について、鋭意、研究を重ねた。その結果、上記特許文献２に示すように合金成分中のＦｅ及びＴｉ含有量を限定する代わりに、Ｚｒ含有量を限定することで、上記課題を解決することができるとの知見を得た。本発明は、このような知見に鑑みてなされたものである。   As described above, the present inventors diligently researched a high toughness Al alloy casting in which tensile strength, 0.2% proof stress and elongation can be obtained at a high level in a balanced manner. As a result, as shown in the above-mentioned Patent Document 2, instead of limiting the Fe and Ti contents in the alloy components, the inventors have found that the above problem can be solved by limiting the Zr content. The present invention has been made in view of such knowledge.

即ち、本発明の高靱性Ａｌ合金鋳物は、質量比で、２％≦Ｓｉ≦４％、０．２％≦Ｍｇ≦０．５％、０．４％≦Ｃｕ≦０．８％、０．１％≦Ｚｒ≦０．４％、及び不可避的不純物を含み、残部がＡｌであり、抗張力が２８０ＭＰａ以上、０．２％耐力が２２０ＭＰａ以上、且つ伸びが１０％以上であることを特徴としている。なお、本発明の高靱性Ａｌ合金鋳物には、Ｓｒ、Ｎａ等の共晶Ｓｉ微細化剤を含有させることができる。   That is, the high toughness Al alloy casting of the present invention has a mass ratio of 2% ≦ Si ≦ 4%, 0.2% ≦ Mg ≦ 0.5%, 0.4% ≦ Cu ≦ 0.8%, 0.8%. 1% ≦ Zr ≦ 0.4% and containing inevitable impurities, the balance being Al, tensile strength is 280 MPa or more, 0.2% proof stress is 220 MPa or more, and elongation is 10% or more. . The high toughness Al alloy casting of the present invention can contain a eutectic Si refiner such as Sr or Na.

また、本発明の高靱性Ａｌ合金鋳物の製造方法は、質量比で、２％≦Ｓｉ≦４％、０．２％≦Ｍｇ≦０．５％、０．４％≦Ｃｕ≦０．８％、０．１％≦Ｚｒ≦０．４％、及び不可避的不純物を含み、残部がＡｌであり、抗張力が２８０ＭＰａ以上、０．２％耐力が２２０ＭＰａ以上、且つ伸びが１０％以上である高靱性Ａｌ合金鋳物を製造するにあたり、上記組成の合金を鋳造し、５００〜５４０℃の高温熱処理を施した後、急冷処理を施し、次いで１６０〜１８５℃の温度で時効処理を施すことを特徴としている。   Moreover, the manufacturing method of the high toughness Al alloy casting of this invention is 2% <= Si <= 4%, 0.2% <= Mg <= 0.5%, 0.4% <= Cu <= 0.8% by mass ratio. 0.1% ≦ Zr ≦ 0.4% and inevitable impurities, the balance being Al, the tensile strength is 280 MPa or more, the 0.2% proof stress is 220 MPa or more, and the elongation is 10% or more In producing an Al alloy casting, an alloy having the above composition is cast, subjected to high-temperature heat treatment at 500 to 540 ° C., then subjected to rapid cooling treatment, and then subjected to aging treatment at a temperature of 160 to 185 ° C. .

本発明の高靱性Ａｌ合金鋳物によれば、合金中のＺｒ含有量の適正化を図ることにより、Ａｌ合金鋳物の、優れた抗張力、０．２％耐力及び伸びをバランス良く高いレベルで実現することができる。   According to the high toughness Al alloy casting of the present invention, by optimizing the Zr content in the alloy, the Al alloy casting achieves excellent tensile strength, 0.2% proof stress and elongation at a high level in a balanced manner. be able to.

以下に、本発明の好適な実施形態を説明する。
本発明の高靱性Ａｌ合金鋳物は、質量比で、２％≦Ｓｉ≦４％、０．２％≦Ｍｇ≦０．５％、０．４％≦Ｃｕ≦０．８％、０．１％≦Ｚｒ≦０．４％、及び不可避的不純物を含み、残部がＡｌであり、抗張力が２８０ＭＰａ以上、０．２％耐力が２２０ＭＰａ以上、且つ伸びが１０％以上である。このような合金中の各元素の含有理由、及びその含有量限定理由は、以下のとおりである。 The preferred embodiments of the present invention will be described below.
The high toughness Al alloy casting of the present invention has a mass ratio of 2% ≦ Si ≦ 4%, 0.2% ≦ Mg ≦ 0.5%, 0.4% ≦ Cu ≦ 0.8%, 0.1%. ≦ Zr ≦ 0.4%, and inevitable impurities are contained, the balance is Al, the tensile strength is 280 MPa or more, the 0.2% proof stress is 220 MPa or more, and the elongation is 10% or more. The reasons for the inclusion of each element in such an alloy and the reasons for limiting its content are as follows.

Ｓｉは、溶湯の流動性を良好にし、またＡｌ合金鋳物の機械的特性を向上させる効果を有する。但し、Ｓｉ含有量が２質量％未満の場合には、溶湯の流動性が悪化するため、Ａｌ合金鋳物において鋳造欠陥の発生が著しく増大する。一方、Ｓｉ含有量が４質量％を超える場合には、α−Ａｌ相の結晶粒界に分布するＳｉ結晶の量が増大するため、Ａｌ合金鋳物の靱性が低下する。従って、Ｓｉの含有量は、２〜４質量％とした。   Si has the effect of improving the fluidity of the molten metal and improving the mechanical properties of the Al alloy casting. However, when the Si content is less than 2% by mass, the fluidity of the molten metal is deteriorated, so that the occurrence of casting defects is remarkably increased in the Al alloy casting. On the other hand, when the Si content exceeds 4% by mass, the amount of Si crystals distributed at the crystal grain boundaries of the α-Al phase increases, so that the toughness of the Al alloy casting decreases. Therefore, the content of Si is set to 2 to 4% by mass.

Ｍｇは、Ｔ６処理によりＭｇ２Ｓｉを微細に分散析出させてＡｌ合金鋳物の強度を向上させる効果を有する。但し、Ｍｇ含有量が０．２質量％未満の場合には、上記効果が不十分である。一方、Ｍｇ含有量が０．５質量％を超える場合には、Ｍｇ２Ｓｉの析出量が過多となるため、Ａｌ合金鋳物の靱性が低下する。従って、Ｍｇの含有量は、０．２〜０．５質量％とした。 Mg has the effect of improving the strength of the Al alloy casting by finely dispersing and precipitating Mg 2 Si by T6 treatment. However, when the Mg content is less than 0.2% by mass, the above effect is insufficient. On the other hand, when the Mg content exceeds 0.5% by mass, the amount of Mg 2 Si precipitated becomes excessive, and the toughness of the Al alloy casting is lowered. Therefore, the content of Mg is set to 0.2 to 0.5% by mass.

Ｃｕは、Ａｌへの高い固溶限に基づいてＡｌ合金鋳物の金属組織を固溶強化し、また、Ｔ６処理による分散析出により上記金属組織を分散強化する効果を有する。但し、Ｃｕ含有量が０．４質量％未満の場合には、Ａｌ合金鋳物における強度向上効果が十分でない。一方、Ｃｕ含有量が０．８質量％を超える場合には、Ａｌ合金鋳物の耐応力腐食割れ性が低下するのみならず、耐食性も悪化する。従って、Ｃｕ含有量は、０．４〜０．８質量％とした。   Cu has the effect of solid-solution strengthening the metal structure of the Al alloy casting based on the high solid solubility limit in Al, and also has the effect of dispersion strengthening the metal structure by dispersion precipitation by T6 treatment. However, when the Cu content is less than 0.4 mass%, the strength improvement effect in the Al alloy casting is not sufficient. On the other hand, when the Cu content exceeds 0.8% by mass, not only the stress corrosion cracking resistance of the Al alloy casting is lowered but also the corrosion resistance is deteriorated. Therefore, the Cu content is set to 0.4 to 0.8 mass%.

Ｚｒは、結晶粒を微細化する効果を有する。但し、Ｚｒの含有量が０．１質量％未満の場合には、上記効果が不十分である。一方、Ｚｒの含有量が０．４質量％を超える場合には、ＺｒＡｌ系高温晶出物であるＡｌ３Ｚｒが粗大に成長するため、溶湯の流動性が悪化して鋳造欠陥が生じ易くなる。従って、Ｚｒの含有量は、０．１〜０．４質量％とした。 Zr has the effect of refining crystal grains. However, when the Zr content is less than 0.1% by mass, the above effect is insufficient. On the other hand, when the Zr content exceeds 0.4% by mass, Al 3 Zr which is a ZrAl-based high-temperature crystallized product grows coarsely, so that the fluidity of the molten metal is deteriorated and casting defects are likely to occur. . Therefore, the content of Zr is set to 0.1 to 0.4% by mass.

次に、本発明の高靱性Ａｌ合金鋳物の製造方法についての、各限定理由を詳細に説明する。
即ち、上記高靱性Ａｌ合金鋳物を製造する場合には、質量比で、２％≦Ｓｉ≦４％、０．２％≦Ｍｇ≦０．５％、０．４％≦Ｃｕ≦０．８％、０．１％≦Ｚｒ≦０．４％、及び不可避的不純物を含み、残部がＡｌであり、抗張力が２８０ＭＰａ以上、０．２％耐力が２２０ＭＰａ以上、且つ伸びが１０％以上である高靱性Ａｌ合金鋳物を製造するにあたり、上記組成の合金を鋳造し、５００〜５４０℃の高温熱処理を施した後、急冷処理を施し、次いで１６０〜１８５℃の温度で時効処理を施す。 Next, each limitation reason is demonstrated in detail about the manufacturing method of the high toughness Al alloy casting of this invention.
That is, when manufacturing the above-mentioned high toughness Al alloy casting, the mass ratio is 2% ≦ Si ≦ 4%, 0.2% ≦ Mg ≦ 0.5%, 0.4% ≦ Cu ≦ 0.8%. 0.1% ≦ Zr ≦ 0.4% and inevitable impurities, the balance being Al, the tensile strength is 280 MPa or more, the 0.2% proof stress is 220 MPa or more, and the elongation is 10% or more In producing an Al alloy casting, an alloy having the above composition is cast, subjected to high-temperature heat treatment at 500 to 540 ° C., then subjected to rapid cooling treatment, and then subjected to aging treatment at a temperature of 160 to 185 ° C.

各合金元素の含有理由、及びその含有量限定理由は、上記したとおりである。鋳造法としては、例えば、金型重力鋳造法や一般的なダイカスト法を適用することができ、鋳造温度は７２０〜７３０℃、金型温度は金型重力鋳造法では２５０〜３００℃、ダイカスト法では１５０〜２５０℃が好ましい。   The reason for containing each alloy element and the reason for limiting its content are as described above. As the casting method, for example, a die gravity casting method or a general die casting method can be applied, the casting temperature is 720 to 730 ° C., the die temperature is 250 to 300 ° C. in the die gravity casting method, and the die casting method. Then, 150-250 degreeC is preferable.

また、上記高温熱処理（溶体化処理）温度が５００℃未満では、強化相と核サイト原子との均質化が十分進まない一方、５４０℃を超える場合には、部分的なバーニングが発生し、粒界強度が著しく低下するので好ましくない。従って、熱処理温度は５００〜５４０℃とした。なお、この高温熱処理時間は、製品の寸法によるが、概して４〜１０時間で十分な均質化が実現される。   When the temperature of the high-temperature heat treatment (solution treatment) is less than 500 ° C., homogenization between the strengthening phase and the nucleus site atoms does not proceed sufficiently, whereas when it exceeds 540 ° C., partial burning occurs, This is not preferable because the field strength is significantly reduced. Therefore, the heat treatment temperature was set to 500 to 540 ° C. In addition, although this high temperature heat processing time is based on the dimension of a product, sufficient homogenization is generally implement | achieved in 4 to 10 hours.

さらに、時効処理温度が１６０℃未満では、強化相の析出が十分に得られないばかりでなく、処理時間が増大するため、不経済的である一方、１８５℃を超える場合には、析出時の強化相が成長し過ぎて、Ｚｒによって微細化核サイトを形成した効果がなくなるため好ましくない。従って、時効処理温度は１６０〜１８５℃とした。なお、時効処理時間は、概して５〜１４時間が好ましい。   Furthermore, if the aging treatment temperature is less than 160 ° C, not only the precipitation of the strengthening phase is not sufficiently obtained, but also the treatment time is increased, which is uneconomical. This is not preferable because the strengthening phase grows too much and the effect of forming fine nucleation sites by Zr is lost. Therefore, the aging treatment temperature was set to 160 to 185 ° C. In general, the aging treatment time is preferably 5 to 14 hours.

以下、本発明を実施例により、さらに詳細に説明する。
表１に示す各組成の合金に、表１，２に示す熱処理を施して、比較例１〜９及び発明例１〜１０のＡｌ合金鋳物をそれぞれ得た。なお、各比較例のＡｌ合金鋳物は、上記特許文献２に示す成分組成を適用したものであり、各発明例のＡｌ合金鋳物は、本発明の成分組成を適用したものである。また、各比較例及び発明例の鋳物中のＦｅ含有量は０．２質量％未満である。比較例１〜９及び発明例１〜１０の各Ａｌ合金鋳物についての、抗張力、０．２％耐力及び伸びを測定した結果を表１に併記するとともに、図１，２に示す。 Hereinafter, the present invention will be described in more detail with reference to examples.
The alloys having the compositions shown in Table 1 were subjected to the heat treatments shown in Tables 1 and 2 to obtain Al alloy castings of Comparative Examples 1 to 9 and Invention Examples 1 to 10, respectively. In addition, the Al alloy casting of each comparative example applies the component composition shown in the above-mentioned patent document 2, and the Al alloy casting of each invention example applies the component composition of the present invention. Moreover, Fe content in the casting of each comparative example and invention example is less than 0.2% by mass. The results of measuring the tensile strength, 0.2% proof stress and elongation of the Al alloy castings of Comparative Examples 1 to 9 and Invention Examples 1 to 10 are shown in Table 1 and shown in FIGS.

Figure 2005336568
Figure 2005336568

Figure 2005336568
Figure 2005336568

図１は、比較例１〜９及び発明例１〜１０の各Ａｌ合金鋳物についての、伸びと０．２％耐力との関係を示すグラフであり、図２は、同様に、伸びと抗張力との関係を示すグラフである。これらの結果から、発明例は全て、各比較例よりも、抗張力、０．２％耐力及び伸びの全てがバランス良く高いレベルで得られていることが判る。以上より、本発明のＡｌ合金鋳物の組成、及びＡｌ合金鋳物の製造方法における熱処理の限定根拠の有効性が実証された。   FIG. 1 is a graph showing the relationship between elongation and 0.2% proof stress for each Al alloy casting of Comparative Examples 1 to 9 and Invention Examples 1 to 10, and FIG. It is a graph which shows the relationship. From these results, it can be seen that all of the inventive examples were obtained in a high level with good balance of tensile strength, 0.2% proof stress and elongation, as compared with the comparative examples. From the above, the composition of the Al alloy casting of the present invention and the effectiveness of the grounds for limiting the heat treatment in the method for producing the Al alloy casting were proved.

次に、本発明の合金組成及び上記特許文献２の合金組成において、晶出するＡｌ３Ｔｉ及びＡｌ３Ｚｒの、溶湯の流動性への影響を比較検討する。Ａｌ−３Ｓｉ−０．４Ｍｇ−０．６Ｃｕの組成中に、下記の表３に示すように、Ｔｉ又はＺｒを含有させて、Ａｌ３ＴｉとＡｌ３Ｚｒとの各晶出温度を測定した。その結果を表３に併記するとともに、図３に示す。 Next, the effects of the crystallized Al 3 Ti and Al 3 Zr on the fluidity of the molten metal in the alloy composition of the present invention and the alloy composition of Patent Document 2 will be compared. As shown in Table 3 below, Ti or Zr was contained in the composition of Al-3Si-0.4Mg-0.6Cu, and the crystallization temperatures of Al 3 Ti and Al 3 Zr were measured. The results are shown in Table 3 and shown in FIG.

Figure 2005336568
Figure 2005336568

さらに、Ａｌ−３Ｓｉ−０．４Ｍｇ−０．６Ｃｕの組成中に、Ｔｉを０．１５質量％含有させたＡｌ合金鋳物と、Ｚｒを０．２質量％含有させたＡｌ合金鋳物とについて、溶湯温度７１５℃及び７３０℃でのＭＩＴ式流動長を測定した。なお、本測定は各５回行い、その平均値を算出した。その結果を図４に示す。   Furthermore, in the composition of Al-3Si-0.4Mg-0.6Cu, an Al alloy casting containing 0.15% by mass of Ti and an Al alloy casting containing 0.2% by mass of Zr, The MIT flow length at temperatures of 715 ° C. and 730 ° C. was measured. In addition, this measurement was performed 5 times each and the average value was computed. The result is shown in FIG.

図３及び図４から明らかなように、含有元素としてＺｒを用いた場合には、Ｔｉを用いた場合よりも晶出温度が低く、これにより、流動性が向上するので、鋳造性及び鋳造品の品質が向上する。また、低Ｓｉ合金にＺｒを含有させると、粒界のまだらなＳｉ共晶の間にＺｒ化合物が微細析出するため、強度及び靱性が向上する。このような作用は、従来技術としてＴｉを含有させた鋳物では実現されない。また、この作用は、ＴｉとＺｒとが同じ微細化効果を生じさせる元素であっても、ＴｉとＡｌとの原子半径の差が小さく、ＺｒとＡｌとの原子半径の差が大きいことに起因する。以上より、鋳造性及び鋳造品の品質、並びに鋳造品の靱性を向上させるためには、Ａｌ合金中にＴｉを含有させるよりも、Ｚｒを含有させる方が有効であることが実証された。   As is apparent from FIGS. 3 and 4, when Zr is used as the contained element, the crystallization temperature is lower than when Ti is used, thereby improving the fluidity. Improve the quality. Further, when Zr is contained in the low Si alloy, the Zr compound is finely precipitated between the mottled Si eutectics at the grain boundaries, so that the strength and toughness are improved. Such an effect is not realized in a casting containing Ti as a conventional technique. In addition, this action is caused by the fact that the difference in atomic radius between Ti and Al is small and the difference in atomic radius between Zr and Al is large even when Ti and Zr are elements that produce the same refinement effect. To do. From the above, it has been proved that inclusion of Zr is more effective than inclusion of Ti in the Al alloy in order to improve castability, cast product quality, and cast product toughness.

さらに、Ａｌ−３Ｓｉ−０．４Ｍｇ−０．６Ｃｕの組成中に、Ｔｉを０〜０．３質量％含有させたものと、Ｚｒを０〜０．５質量％含有させたものとについて、抗張力、０．２％耐力及び伸びを測定した。その結果を図５，６に示す。   Furthermore, in the composition of Al-3Si-0.4Mg-0.6Cu, the tensile strength of those containing 0 to 0.3% by mass of Ti and those containing 0 to 0.5% by mass of Zr. 0.2% proof stress and elongation were measured. The results are shown in FIGS.

図５，６によれば、抗張力、０．２％耐力及び伸びの向上には、Ｚｒの含有量は０．１質量％以上が好ましいことが判る。また、Ｚｒの含有量が０．４質量％を超えると、実用鋳造温度域で化合物（Ａｌ３Ｚｒ）が生成されるため、この化合物が坩堝内で沈殿し、溶湯の流動性を悪化させ鋳造欠陥が生じ易くなる。また、図５，６から明らかなように、Ｚｒの含有量が０．３質量％を超えれば、各機械的性質はほぼ飽和状態に達し、０．４質量％を超えても、各性質は向上しない。以上により、本発明のＺｒ含有量（０．１％≦Ｚｒ≦０．４％）の限定根拠の有効性が実証された。 5 and 6, it can be seen that the Zr content is preferably 0.1% by mass or more for improvement of tensile strength, 0.2% proof stress and elongation. Further, if the content of Zr exceeds 0.4% by mass, a compound (Al 3 Zr) is generated in a practical casting temperature range, so that this compound precipitates in the crucible and deteriorates the fluidity of the molten metal. Defects are likely to occur. Further, as apparent from FIGS. 5 and 6, if the Zr content exceeds 0.3 mass%, each mechanical property reaches a substantially saturated state, and even if it exceeds 0.4 mass%, each property is Does not improve. From the above, the effectiveness of the grounds for limiting the Zr content (0.1% ≦ Zr ≦ 0.4%) of the present invention was proved.

最後に、本発明の高靱性Ａｌ合金鋳物の構成元素である、Ｓｉ、Ｍｇ、及びＣｕについての好適範囲を実証する。
表４に示す各組成の合金を鋳造し、５２５℃で４時間の高温熱処理を施した後、急冷処理を施し、次いで１７５℃で５時間の時効処理を施して各比較例１０〜１９、及び発明例１１〜１８のＡｌ合金鋳物をそれぞれ得た。これらの各Ａｌ合金鋳物について、抗張力、０．２％耐力及び伸びを測定し、さらに応力腐食割れについて調査した。これらの結果を表４に併記するとともに、図７〜９に示す。なお、応力腐食割れの調査については、Ｃリングをクロム酸へ浸漬することにより行い、応力は耐力の９０％とした。 Finally, the preferred ranges for Si, Mg, and Cu, which are constituent elements of the high toughness Al alloy casting of the present invention, will be demonstrated.
Each alloy shown in Table 4 was cast and subjected to high-temperature heat treatment at 525 ° C. for 4 hours, followed by quenching treatment, and then aging treatment at 175 ° C. for 5 hours. The Al alloy castings of Invention Examples 11 to 18 were obtained. For each of these Al alloy castings, tensile strength, 0.2% proof stress and elongation were measured, and further stress corrosion cracking was investigated. These results are shown in Table 4 and shown in FIGS. The stress corrosion cracking was investigated by immersing the C ring in chromic acid, and the stress was 90% of the proof stress.

Figure 2005336568
Figure 2005336568

表４及び図７〜９から明らかなように、質量比で、２％≦Ｓｉ≦４％、０．２％≦Ｍｇ≦０．５％、０．４％≦Ｃｕ≦０．８％、０．１％≦Ｚｒ≦０．４％の範囲（本発明の範囲）である、発明例１１〜１８では、抗張力、０．２％耐力及び伸びについて、バランス良く高い値が得られた。これに対し、本発明の範囲外である、比較例１１〜１９では、抗張力、０．２％耐力及び伸びの少なくとも一方について好適な結果が得られていない。以上により、本発明のＳｉ，Ｍｇ，Ｃｕ含有量の限定根拠の有効性が実証された。   As is apparent from Table 4 and FIGS. 7 to 9, the mass ratio is 2% ≦ Si ≦ 4%, 0.2% ≦ Mg ≦ 0.5%, 0.4% ≦ Cu ≦ 0.8%, 0 In Invention Examples 11 to 18 in the range of 0.1% ≦ Zr ≦ 0.4% (the range of the present invention), high values were obtained with good balance in terms of tensile strength, 0.2% proof stress and elongation. On the other hand, in Comparative Examples 11 to 19, which are outside the scope of the present invention, no suitable results have been obtained for at least one of tensile strength, 0.2% proof stress, and elongation. From the above, the effectiveness of the grounds for limiting the Si, Mg, and Cu contents of the present invention was proved.

以上説明したように、本発明の高靱性Ａｌ合金鋳物では、特に、Ｚｒの含有量の適正化を図ることにより、高靱性Ａｌ合金鋳物の、優れた抗張力、０．２％耐力及び伸びをバランス良く高いレベルで実現することができる。従って、本発明は、今後益々高度な機械的諸性質が要求されることが予想される、車体、サスペンション部材等に適用することができる点で、有用である。   As described above, the high toughness Al alloy casting of the present invention balances the excellent tensile strength, 0.2% proof stress and elongation of the high toughness Al alloy casting, particularly by optimizing the content of Zr. It can be realized at a high level. Therefore, the present invention is useful in that it can be applied to a vehicle body, a suspension member, and the like, which are expected to require more advanced mechanical properties in the future.

比較例１〜９及び発明例１〜１０についての、伸びと０．２％耐力との関係を示すグラフである。It is a graph which shows the relationship between elongation and 0.2% yield strength about Comparative Examples 1-9 and Invention Examples 1-10. 比較例１〜９及び発明例１〜１０についての、伸びと抗張力との関係を示すグラフである。It is a graph which shows the relationship between elongation and tensile strength about Comparative Examples 1-9 and Invention Examples 1-10. Ａｌ３Ｔｉ及びＡｌ３Ｚｒの晶出温度とＴｉ又はＺｒ含有量との関係を示すグラフである。Al 3 is a graph showing the relationship between the crystallization temperature of the Ti and Al 3 Zr and Ti or Zr content. ＭＩＴ式流動長と溶湯温度との関係を示すグラフである。It is a graph which shows the relationship between MIT type | mold flow length and molten metal temperature. Ａｌ−３Ｓｉ−０．４Ｍｇ−０．６Ｃｕの組成中に、Ｔｉを０〜０．３質量％含有させたＡｌ合金鋳物と、Ｚｒを０〜０．５質量％含有させたＡｌ合金鋳物とについての、抗張力及び０．２％耐力と、Ｔｉ又はＺｒ含有量との関係を示すグラフである。About the Al alloy casting in which 0 to 0.3% by mass of Ti is contained in the composition of Al-3Si-0.4Mg-0.6Cu and the Al alloy casting in which 0 to 0.5% by mass of Zr is contained It is a graph which shows the relationship between tensile strength and 0.2% yield strength, and Ti or Zr content. Ａｌ−３Ｓｉ−０．４Ｍｇ−０．６Ｃｕの組成中に、Ｔｉを０〜０．３質量％含有させたＡｌ合金鋳物と、Ｚｒを０〜０．５質量％含有させたＡｌ合金鋳物とについての、伸びとＴｉ又はＺｒ含有量との関係を示すグラフである。About the Al alloy casting in which 0 to 0.3% by mass of Ti is contained in the composition of Al-3Si-0.4Mg-0.6Cu and the Al alloy casting in which 0 to 0.5% by mass of Zr is contained It is a graph which shows the relationship between elongation and Ti or Zr content. 抗張力及び伸びとＳｉ含有量との関係を示すグラフである。It is a graph which shows the relationship between tensile strength and elongation, and Si content. 抗張力及び伸びとＭｇ含有量との関係を示すグラフである。It is a graph which shows the relationship between tensile strength and elongation, and Mg content. 抗張力及び伸びとＣｕ含有量との関係を示すグラフである。It is a graph which shows the relationship between tensile strength and elongation, and Cu content.

Claims (2)

質量比で、２％≦Ｓｉ≦４％、０．２％≦Ｍｇ≦０．５％、０．４％≦Ｃｕ≦０．８％、０．１％≦Ｚｒ≦０．４％、及び不可避的不純物を含み、残部がＡｌであり、抗張力が２８０ＭＰａ以上、０．２％耐力が２２０ＭＰａ以上、且つ伸びが１０％以上であることを特徴とする高靱性Ａｌ合金鋳物。   In mass ratio, 2% ≦ Si ≦ 4%, 0.2% ≦ Mg ≦ 0.5%, 0.4% ≦ Cu ≦ 0.8%, 0.1% ≦ Zr ≦ 0.4%, and inevitable A high-toughness Al alloy casting characterized by containing a general impurity, the balance being Al, a tensile strength of 280 MPa or more, a 0.2% proof stress of 220 MPa or more, and an elongation of 10% or more. 質量比で、２％≦Ｓｉ≦４％、０．２％≦Ｍｇ≦０．５％、０．４％≦Ｃｕ≦０．８％、０．１％≦Ｚｒ≦０．４％、及び不可避的不純物を含み、残部がＡｌであり、抗張力が２８０ＭＰａ以上、０．２％耐力が２２０ＭＰａ以上、且つ伸びが１０％以上である高靱性Ａｌ合金鋳物を製造するにあたり、前記組成の合金を鋳造し、５００〜５４０℃の高温熱処理を施した後、急冷処理を施し、次いで１６０〜１８５℃の温度で時効処理を施すことを特徴とする高靱性Ａｌ合金鋳物の製造方法。   In mass ratio, 2% ≦ Si ≦ 4%, 0.2% ≦ Mg ≦ 0.5%, 0.4% ≦ Cu ≦ 0.8%, 0.1% ≦ Zr ≦ 0.4%, and inevitable In producing a high toughness Al alloy casting containing a general impurity, the balance being Al, the tensile strength is 280 MPa or more, the 0.2% proof stress is 220 MPa or more, and the elongation is 10% or more, an alloy having the above composition is cast. A method for producing a high toughness Al alloy casting, characterized by performing a high-temperature heat treatment at 500 to 540 ° C., followed by a rapid cooling treatment and then an aging treatment at a temperature of 160 to 185 ° C.
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