JP2006037190A - Aluminum alloy, method for molding aluminum alloy casting and chassis structural member for vehicle molded with aluminum alloy - Google Patents

Aluminum alloy, method for molding aluminum alloy casting and chassis structural member for vehicle molded with aluminum alloy Download PDF

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JP2006037190A
JP2006037190A JP2004221225A JP2004221225A JP2006037190A JP 2006037190 A JP2006037190 A JP 2006037190A JP 2004221225 A JP2004221225 A JP 2004221225A JP 2004221225 A JP2004221225 A JP 2004221225A JP 2006037190 A JP2006037190 A JP 2006037190A
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molten metal
semi
aluminum alloy
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JP4510541B2 (en
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Takahiro Mizukami
貴博 水上
Yusuke Toyoda
裕介 豊田
Katsuhiro Shibata
勝弘 柴田
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 an aluminum alloy capable of obtaining high toughness by a semi-melting casting method, to provide a method for molding an aluminum alloy casting, and to provide a chassis structural member for a vehicle molded with the aluminum alloy. <P>SOLUTION: A semi-molten metal having a composition comprising, by weight, 2.0 to 4.0% Si, and the balance substantially Al with inevitable impurities and having a solid phase ratio of 25 to 45% is rapidly cooled, so as to obtain a high toughness aluminum alloy or a high toughness aluminum alloy casting. In the method for molding an aluminum alloy casting, a semi-molten metal is charged to a vessel 1 at a temperature in the vicinity of an eutectic point to control its solid phase ratio to the objective one, the semi-molten metal and the vessel 1 are charged to an injection sleeve 3 from the split face of a casting die 2, the casting die 2 is closed, and thereafter, the vessel 1 and the semi-molten metal are pressed by a plunger 4, are packed into the cavity 5 of the casting mold 2 and are rapidly cooled at a cooling rate of ≥5°C/s. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、アルミニウム合金、アルミニウム合金鋳物の成形方法、及びアルミニウム合金で成形した車両用シャーシ構造部材に関する。   The present invention relates to an aluminum alloy, a method for forming an aluminum alloy casting, and a vehicle chassis structure member formed from the aluminum alloy.

自動車の軽量化のため、サスペンション部材、サブフレーム部材、各種継手部材、アルミホイール等の車両用シャーシ構造部材にアルミニウム合金(以下Ａｌ合金と記す)鋳物が使用されている。
Ａｌ合金鋳物の成形には複雑な形状でも容易に成形できる半溶融鋳造法が用いられている。半溶融鋳造法に用いるビレットには、半溶融状態アルミニウム組成物の流動性を確保するために、特許文献１に示されているように、Ｓｉ６．０〜８．０ｗｔ％の高Ｓｉ材料が一般的に用いられている。しかし、特許文献１にも指摘されているようにＳｉの含有量が多いと靭性が低下し、含有量が不足すると溶湯の流動性が低下する。
低Ｓｉ含有量のアルミニウムで半溶融鋳造法が可能になれば、高靭性の鋳造品が得られるが、靭性と流動性は前記のように二律背反の関係にあるため、実現していない。
これまでも、低Ｓｉ含量のＡｌ合金で高靭性を得る検討がなされており、例えば特許文献２にＡｌ合金鋳物を高温溶体化処理後、時効処理する技術が開示されている。
特許文献２に開示された技術は、Ｓｉが１．６５〜４．０％のＡｌ合金鋳物を５５０〜５７５℃に加熱した後急冷して溶体化処理し、次いで１４０〜２００℃で時効処理するものである。
特開２００１−２５２７５４号公報（段落００１４） 特開平９−２７２９４２号公報（段落００１４〜００１９） In order to reduce the weight of automobiles, aluminum alloy castings (hereinafter referred to as Al alloys) are used for vehicle chassis structural members such as suspension members, subframe members, various joint members, and aluminum wheels.
For the molding of Al alloy castings, a semi-molten casting method is used which can be easily molded even with complicated shapes. In order to ensure the fluidity of the semi-molten aluminum composition, the billet used in the semi-molten casting method is generally made of a high Si material of Si 6.0 to 8.0 wt% as shown in Patent Document 1. Has been used. However, as pointed out in Patent Document 1, if the Si content is large, the toughness is lowered, and if the content is insufficient, the fluidity of the molten metal is lowered.
If a semi-molten casting method can be performed with aluminum having a low Si content, a cast product with high toughness can be obtained. However, since toughness and fluidity are in a trade-off relationship as described above, it has not been realized.
So far, studies have been made to obtain high toughness with an Al alloy having a low Si content. For example, Patent Document 2 discloses a technique in which an Al alloy casting is subjected to an aging treatment after a high-temperature solution treatment.
In the technique disclosed in Patent Document 2, an Al alloy casting having Si of 1.65 to 4.0% is heated to 550 to 575 ° C., and then rapidly cooled to form a solution treatment, and then an aging treatment at 140 to 200 ° C. Is.
JP 2001-252754 A (paragraph 0014) JP-A-9-272742 (paragraphs 0014 to 0019)

しかし、特許文献２に開示されたような鋳物を通常の鋳造方法で鋳造すると溶湯温度が高くなり、鋳型寿命が短くなるような問題があることから、半溶融鋳造法で低Ｓｉ含有量のＡｌ合金鋳物を生産することを可能にすることが望まれている。   However, since casting such as disclosed in Patent Document 2 is cast by a normal casting method, there is a problem that the molten metal temperature becomes high and the mold life is shortened. It is desired to be able to produce alloy castings.

そこで、本発明では、前記した問題を解決し、半溶融鋳造法で高靭性が得られるＡｌ合金、Ａｌ合金鋳物の成形方法、及びＡｌ合金で成形した車両用シャーシ構造部材を提供することを目的とする。   Accordingly, the present invention aims to solve the above-described problems and provide an Al alloy that can obtain high toughness by a semi-molten casting method, a method for forming an Al alloy casting, and a vehicle chassis structure member that is formed using an Al alloy. And

請求項１に記載の発明は、Ｓｉ２．０〜４．０ｗｔ％、残部実質的にＡｌ及び不可避不純物を含有する組成からなり、固相率２５〜４５ｗｔ％の半溶融溶湯を急冷してなるＡｌ合金の構成とした。
請求項１に記載の発明によれば、Ｓｉ含有量が２．０〜４．０ｗｔ％と、従来の半溶融鋳造法に用いられるＡｌ合金のＳｉ含有量（５．５〜８．０ｗｔ％）より低いため、従来の半溶融鋳造法よりも高靭性のＡｌ合金が得られる。 The invention according to claim 1 is composed of a composition containing Si 2.0 to 4.0 wt%, the balance substantially containing Al and inevitable impurities, and is obtained by quenching a semi-molten molten metal having a solid phase ratio of 25 to 45 wt%. The composition of the alloy was adopted.
According to invention of Claim 1, Si content is 2.0-4.0 wt%, and Si content (5.5-8.0 wt%) of Al alloy used for the conventional semi-molten casting method Since it is lower, an Al alloy having higher toughness than the conventional semi-molten casting method can be obtained.

さらに、Ｓｉ含有量が２．０〜４．０ｗｔ％のＡｌ合金の固相率を２５〜４５ｗｔ％に調製すると、半溶融溶湯の液相はＡｌリッチの亜共晶組成となる。
このため、前記した半溶融溶湯を急冷すると、Ａｌ合金鋳物の金属組織中には、半溶融状態で生成したＡｌ結晶相（これを第一のα相と記す）とは別の微細なＡｌ結晶相（これを第二のα相と記す）が、Ａｌ−Ｓｉ共晶相の中に析出する。この微細な第二のα相の存在により、Ａｌ結晶相とＡｌ−Ｓｉ共晶相の界面（以下、粒界と記す）を通じた亀裂の進展が阻止される結果、Ａｌ合金の靭性等の機械的性質が向上する。 Further, when the solid phase ratio of the Al alloy having a Si content of 2.0 to 4.0 wt% is adjusted to 25 to 45 wt%, the liquid phase of the semi-molten molten metal has an Al-rich hypoeutectic composition.
For this reason, when the above-mentioned semi-molten molten metal is rapidly cooled, in the metal structure of the Al alloy casting, a fine Al crystal different from the Al crystal phase generated in the semi-molten state (this is referred to as the first α phase). A phase (referred to as the second α phase) precipitates in the Al—Si eutectic phase. The presence of this fine second α-phase prevents crack growth through the interface between the Al crystal phase and the Al-Si eutectic phase (hereinafter referred to as grain boundaries), resulting in a machine such as toughness of the Al alloy. The physical properties are improved.

請求項２に記載の発明は、円相当径が２０μｍ以上で、かつ平均円相当径が５０μｍ以上の第一のα相と、円相当径が２０μｍ未満の第二のα相とを含むことを特徴とする請求項１に記載のＡｌ合金の構成とした。   The invention according to claim 2 includes a first α phase having an equivalent circle diameter of 20 μm or more and an average equivalent circle diameter of 50 μm or more, and a second α phase having an equivalent circle diameter of less than 20 μm. It was set as the structure of Al alloy of Claim 1 characterized by the above-mentioned.

請求項２に記載の発明によれば、円相当径が２０μｍ以上で、かつ平均円相当径が５０μｍ以上の第一のα相よりも微細な粒径の第二のα相の存在により、粒界を通じた亀裂の進展がより有効に阻止される結果、Ａｌ合金の靭性が向上する。
なお、円相当径とは、顕微鏡で観察されるα相の粒子面積から算出した擬似円の直径であり、平均円相当径とは円相当径の数平均値である。 According to the second aspect of the present invention, the presence of the second α phase having a finer particle diameter than the first α phase having an equivalent circle diameter of 20 μm or more and an average equivalent circle diameter of 50 μm or more, As a result of the more effective prevention of crack propagation through the boundary, the toughness of the Al alloy is improved.
The equivalent circle diameter is a pseudo circle diameter calculated from the particle area of the α phase observed with a microscope, and the average equivalent circle diameter is a number average value of equivalent circle diameters.

請求項３に記載の発明は、第二のα相の平均円相当径は、第一のα相の平均円相当径の５分の１以下であることを特徴とする請求項１または請求項２に記載のＡｌ合金の構成とした。
第二のα相の平均円相当径が第一のα相の平均円相当径の１／５以下のとき、微細な第二のα相の存在によって亀裂の進展をより有効に阻止できる結果、更に靭性の優れたＡｌ合金が得られる。 The invention according to claim 3 is characterized in that the average equivalent circle diameter of the second α phase is one fifth or less of the average equivalent circle diameter of the first α phase. 2 was used.
When the average equivalent circle diameter of the second α phase is 1/5 or less of the average equivalent circle diameter of the first α phase, the result of being able to more effectively prevent the growth of cracks due to the presence of the fine second α phase, Furthermore, an Al alloy having excellent toughness can be obtained.

請求項４に記載の発明は、前記半溶融溶湯を冷却速度５℃／秒以上で急冷することを特徴とする請求項１から請求項３のいずれか１項に記載のＡｌ合金の構成とした。
請求項４の発明によれば、半溶融溶湯を冷却速度５℃／秒以上で急冷するため、結晶化が促進される結果、前記した微細な第二のα層を確実に形成することができる。 The invention according to claim 4 is the structure of the Al alloy according to any one of claims 1 to 3, wherein the semi-molten molten metal is rapidly cooled at a cooling rate of 5 ° C / second or more. .
According to the invention of claim 4, since the semi-molten molten metal is rapidly cooled at a cooling rate of 5 ° C./second or more, crystallization is promoted, and as a result, the fine second α layer can be reliably formed. .

請求項５に記載の発明は、請求項１から請求項４のいずれか１項に記載のＡｌ合金で成形したことを特徴とする車両用シャーシ構造部材である。
請求項１から請求項４のいずれか１項に記載のＡｌ合金を用いれば、高靭性のサスペンション部材、サブフレーム部材、各種継手部材、アルミホイール等の車両用シャーシ構造部材を容易に成形することができる。 A fifth aspect of the present invention is a vehicle chassis structure member formed by the Al alloy according to any one of the first to fourth aspects.
When the Al alloy according to any one of claims 1 to 4 is used, a vehicle chassis structural member such as a tough suspension member, a subframe member, various joint members, and an aluminum wheel is easily formed. Can do.

請求項６に記載の発明は、容器にＳｉ２．０〜４．０ｗｔ％、残部実質的にＡｌ及び不可避不純物を含有する組成からなる溶湯を流し込み、共晶点近傍の温度で前記溶湯を目的の固相率を有する半溶融溶湯に調整し、前記半溶融溶湯を前記容器と共に鋳造金型の割り面より射出スリーブに装填し、前記鋳造金型を閉止した後、前記容器及び前記半溶融溶湯をプランジャにより押圧して前記半溶融溶湯を前記鋳造金型のキャビティに充填し、次いで前記鋳造金型のキャビティに充填した前記半溶融溶湯を冷却速度５℃／秒以上で急冷することを特徴とするＡｌ合金鋳物の成形方法とした。
請求項６の発明によれば、半溶融溶湯を容器ごと鋳造金型の割り面より射出スリーブに装填するため、装填から射出するまでの時間が短くなり温度低下を最小限にできる結果、凝固し易い半溶融溶湯、または流動性が悪い半溶融溶湯であっても一工程で成形することが可能になる。さらに、冷却速度５℃／秒以上で急冷するため、前記した微細な第二のα相を確実に形成することができる。 The invention according to claim 6 is directed to pouring a molten metal having a composition containing Si 2.0 to 4.0 wt%, the balance substantially containing Al and inevitable impurities into a container, and using the molten metal at a temperature near the eutectic point. The semi-molten molten metal having a solid phase ratio is adjusted, and the semi-molten molten metal is loaded onto the injection sleeve from the split surface of the casting mold together with the container, and the casting mold is closed, and then the container and the semi-molten molten metal are Pressing with a plunger fills the cavity of the casting mold with the molten metal, and then quenches the molten metal filled in the cavity of the casting mold at a cooling rate of 5 ° C./second or more. The Al alloy casting was formed.
According to the invention of claim 6, since the semi-molten molten metal is loaded into the injection sleeve from the split surface of the casting mold together with the container, the time from loading to injection can be shortened and the temperature drop can be minimized. Even a semi-molten molten metal that is easy or a semi-molten molten metal having poor fluidity can be molded in one step. Furthermore, since the quenching is performed at a cooling rate of 5 ° C./second or more, the fine second α-phase can be reliably formed.

請求項７に記載の発明は、前記目的の固相率が２５〜４５ｗｔ％であることを特徴とする請求項６に記載のＡｌ合金鋳物の成形方法とした。
請求項７の発明によれば、固相率を２５〜４５ｗｔ％に調整することにより、凝固し易く流動性の悪いＳｉ２．０〜４．０ｗｔ％のアルミニウム半溶融溶湯でも、一工程で成形することが可能になる。 The invention according to claim 7 is the method for forming an Al alloy casting according to claim 6, wherein the target solid phase ratio is 25 to 45 wt%.
According to the invention of claim 7, by adjusting the solid phase ratio to 25 to 45 wt%, even an aluminum semi-molten molten metal of Si 2.0 to 4.0 wt% which is easy to solidify and has poor fluidity is formed in one step. It becomes possible.

本発明のＡｌ合金によれば、従来の半溶融鋳造法よりも高靭性のＡｌ合金が得られる。
また、本発明のＡｌ合金鋳物の成形方法によれば、凝固し易く流動性の悪いＳｉ２．０〜４．０ｗｔ％のアルミニウム半溶融溶湯であっても成形することができる。さらに、本発明のＡｌ合金を用いれば、高靭性の車両用シャーシ構造部材を得ることができる。 According to the Al alloy of the present invention, an Al alloy having higher toughness than the conventional semi-molten casting method can be obtained.
Further, according to the method for molding an Al alloy casting of the present invention, even an aluminum semi-molten molten metal of Si 2.0 to 4.0 wt% that is easy to solidify and poor in fluidity can be molded. Furthermore, if the Al alloy of the present invention is used, a tough vehicle chassis structural member can be obtained.

次に、本発明の実施形態について、適宜図面を参照しながら説明する。
本実施形態のＡｌ合金はＳｉ２．０〜４．０ｗｔ％、残部実質的にＡｌ及び不可避不純物を含有する組成からなり、固相率２５〜４５ｗｔ％の半溶融溶湯の状態から急冷して得られる。
得られるＡｌ合金は、円相当径が２０μｍ以上で、かつ平均円相当径が５０μｍ以上の第一のα相と、円相当径が２０μｍ未満の第二のα相とを含む。
急冷条件としては、冷却速度を５℃／秒以上とすることが好ましい。 Next, embodiments of the present invention will be described with reference to the drawings as appropriate.
The Al alloy of this embodiment has a composition containing Si 2.0 to 4.0 wt%, the balance substantially containing Al and inevitable impurities, and is obtained by quenching from the state of a semi-molten molten metal having a solid phase ratio of 25 to 45 wt%. .
The obtained Al alloy includes a first α phase having an equivalent circle diameter of 20 μm or more and an average equivalent circle diameter of 50 μm or more, and a second α phase having an equivalent circle diameter of less than 20 μm.
As the rapid cooling condition, the cooling rate is preferably 5 ° C./second or more.

Ａｌ合金を構成するＳｉの含有理由、及び含有量の限定理由は下記のとおりである。   The reason for containing Si constituting the Al alloy and the reason for limiting the content are as follows.

Ｓｉ：２．０〜４．０ｗｔ％
Ｓｉは、溶湯の流動性を良好にし、Ａｌ合金鋳物の靭性に影響する。Ｓｉ＜２．０ｗｔ％では溶湯の流動性が不足するため、Ａｌ合金鋳物に巣やヒケと呼ばれる鋳造欠陥が著しく増大する。一方、Ｓｉ＞４．０ｗｔ％では、α相の粒界に分布するＳｉ共晶の量が過多となるため、Ａｌ合金鋳物の靭性が低下する。 Si: 2.0 to 4.0 wt%
Si improves the fluidity of the molten metal and affects the toughness of Al alloy castings. When Si <2.0 wt%, the fluidity of the molten metal is insufficient, so that casting defects called nests and sink marks are remarkably increased in the Al alloy casting. On the other hand, when Si> 4.0 wt%, the amount of Si eutectic distributed in the α phase grain boundaries becomes excessive, and the toughness of the Al alloy casting is lowered.

このＡｌ合金は、さらに以下の成分を含有していてもよい。各成分の含有理由、及び含有可能量を以下に説明する。   This Al alloy may further contain the following components. The reason for the inclusion of each component and the amount that can be contained will be described below.

Ｍｇ：０．２〜０．５ｗｔ％
ＭｇはＭｇ2ＳｉとなってＡｌ合金鋳物の強度に影響する。Ｍｇ＜０．２ｗｔ％では強度の向上が不十分である。一方、Ｍｇ＞０．５ｗｔ％では、Ｍｇ2Ｓｉの析出が過多となり靭性が低下する。 Mg: 0.2 to 0.5 wt%
Mg becomes Mg 2 Si and affects the strength of the Al alloy casting. If Mg <0.2 wt%, the strength is not sufficiently improved. On the other hand, if Mg> 0.5 wt%, Mg 2 Si is excessively precipitated and the toughness is lowered.

Ｃｕ：０．４〜０．８ｗｔ％
ＣｕはＡｌ合金鋳物の金属組織を固溶強化して強度向上に寄与するが、耐食性を低下させる。Ｃｕ＜０．４ｗｔ％では強度向上が不十分である。一方、Ｃｕ＞０．８ｗｔ％では耐食性が低下し、耐応力腐食割れ性が低下する。 Cu: 0.4 to 0.8 wt%
Cu contributes to improving the strength by solid-solution strengthening the metal structure of the Al alloy casting, but reduces the corrosion resistance. When Cu <0.4 wt%, the strength improvement is insufficient. On the other hand, when Cu> 0.8 wt%, the corrosion resistance is lowered and the stress corrosion cracking resistance is lowered.

Ｔｉ：０．１〜０．３ｗｔ％
ＴｉはＡｌ合金鋳物の結晶を微細化し強度を向上させる。Ｔｉ＜０．１ｗｔ％では前記した結晶を微細化し強度を向上させる効果が不十分である。一方、Ｔｉ＞０．３ｗｔ％では、Ａｌ3Ｔｉが生成して溶湯の流動性を悪化させるため、鋳造欠陥が生じやすくなる。 Ti: 0.1 to 0.3 wt%
Ti refines the crystal of the Al alloy casting to improve the strength. When Ti <0.1 wt%, the above-described effect of reducing the size of the crystal and improving the strength is insufficient. On the other hand, when Ti> 0.3 wt%, Al 3 Ti is generated and the fluidity of the molten metal is deteriorated, so that casting defects are likely to occur.

結晶を微細化するという効果はＺｒ及びＢによっても得られる。この場合Ｚｒは０．１〜０．３ｗｔ％、Ｂは０．２〜０．４ｗｔ％の範囲で添加することが好ましい。なお、ＢはＴｉ，Ｚｒと協働して結晶を微粒子化する効果を発揮する。   The effect of refining the crystal can also be obtained with Zr and B. In this case, it is preferable to add Zr in the range of 0.1 to 0.3 wt% and B in the range of 0.2 to 0.4 wt%. B exhibits the effect of making crystals finer in cooperation with Ti and Zr.

Ａｌ合金鋳物は、前記した組成のＡｌ合金を固相率２５〜４５ｗｔ％の半溶融溶湯とし、これを急冷して得られる。
固相率２５ｗｔ％未満では液状の金属の量が過多のためハンドリングが難しく、実質的に成形することは極めて困難である。また、固相率が４５ｗｔ％を超えると、固形分が多く成形が難しくなる。 The Al alloy casting is obtained by rapidly cooling the Al alloy having the above composition into a semi-molten molten metal having a solid phase ratio of 25 to 45 wt%.
If the solid phase ratio is less than 25 wt%, the amount of liquid metal is excessive, so that handling is difficult, and it is extremely difficult to form. On the other hand, if the solid phase ratio exceeds 45 wt%, the solid content is large and molding becomes difficult.

固相率は、共晶点近傍の温度、好ましくは液相線温度に対して５０℃未満の過熱温度に保持されている溶湯を容器中に注ぎ、この容器の中で所定時間保持することによって除冷しながらＡｌ結晶を晶出させて調整する。容器へ溶湯を注ぐ際は、容器を傾け、溶湯が暴れないように静かに注ぐ必要がある。溶湯が暴れてしまうと酸化膜等を巻き込み、製品の品質が低下してしまうためである。注湯後は、例えば、容器に部分的な断熱を施す等して容器内の均熱を図ることが好ましい。
冷却速度は５〜３０℃／秒の範囲が好ましい。冷却速度が３０℃／秒を超えると容器の搬送、セット時に温度が下がりすぎて、目標の固相率で成形できなくなる。５℃／秒未満であると、第一のα相が異常成長してＡｌ合金の靭性が低下する。 The solid phase ratio is determined by pouring a molten metal maintained at a temperature near the eutectic point, preferably at a superheating temperature of less than 50 ° C. with respect to the liquidus temperature, into the container, and holding the molten metal in the container for a predetermined time. Adjust by crystallizing Al crystal while cooling. When pouring molten metal into the container, it is necessary to tilt the container and pour it gently so that the molten metal does not get out of control. This is because if the molten metal becomes violent, an oxide film or the like is involved and the quality of the product is deteriorated. After pouring, for example, it is preferable to achieve uniform temperature in the container by, for example, partially insulating the container.
The cooling rate is preferably in the range of 5 to 30 ° C./second. When the cooling rate exceeds 30 ° C./second, the temperature is lowered too much during the transportation and setting of the container, and it becomes impossible to mold at the target solid phase rate. If it is less than 5 ° C./second, the first α phase grows abnormally and the toughness of the Al alloy decreases.

図１は、ＡｌとＳｉとの共晶平衡図に基づき作成したもので、Ｓｉ含有量と共晶時の固相率の関係を示す図である。すなわち、図1の右下がりの線は、半溶融溶湯から晶出し得るＡｌ結晶（α相）の最大の割合を示し、この線より上ではＡｌ結晶（α相）は晶出しないことを表している。
図1に示したように、本実施形態は、Ｓｉ含有量２．０〜４．０ｗｔ％、固相率２５〜４５ｗｔ％の領域にある。これに対して、従来の半溶融鋳造法で使用される合金はＳｉ含有量６．０〜８．０ｗｔ％、固相率４０〜６０ｗｔ％の領域にある。 FIG. 1 is created based on the eutectic equilibrium diagram of Al and Si, and shows the relationship between the Si content and the solid fraction during eutectic. That is, the lower right line in FIG. 1 indicates the maximum proportion of Al crystal (α phase) that can be crystallized from the molten metal, and above this line, the Al crystal (α phase) does not crystallize. Yes.
As shown in FIG. 1, the present embodiment is in a region where the Si content is 2.0 to 4.0 wt% and the solid phase ratio is 25 to 45 wt%. On the other hand, the alloy used in the conventional semi-molten casting method is in a region where the Si content is 6.0 to 8.0 wt% and the solid phase ratio is 40 to 60 wt%.

図１から明らかなように、本実施形態のＳｉ含有量２．０〜４．０ｗｔ％、固相率２５〜４５ｗｔ％の範囲は、図１の線より下にあり、冷却によりさらにＡｌが晶出可能な亜共晶組成になっている。このため、急冷することによりにより半溶融状態で生成した第一のα相とは別の、図２に示した微細な粒径の第二のα相が析出する。
図２から明らかなように、本実施形態のＡｌ合金には円相当径が２０μｍ以上で、かつ平均円相当径が５０μｍ以上の第一のα相と、円相当径が２０μｍ未満の第二のα相とが含まれている。
なお、図２はＳｉ３ｗｔ％のＡｌ合金の半溶融溶湯を、固相率３０ｗｔ％から冷却速度１０℃／秒で急冷したときの金属組織の顕微鏡写真の写図である。 As is clear from FIG. 1, the Si content range of 2.0 to 4.0 wt% and the solid phase ratio of 25 to 45 wt% of the present embodiment is below the line in FIG. It has a hypoeutectic composition. For this reason, the second α phase having a fine particle size shown in FIG. 2 separates from the first α phase generated in the semi-molten state by rapid cooling.
As apparent from FIG. 2, the Al alloy of the present embodiment has a first α phase having an equivalent circle diameter of 20 μm or more and an average equivalent circle diameter of 50 μm or more, and a second α phase having an equivalent circle diameter of less than 20 μm. α phase is included.
FIG. 2 is a photomicrograph of the metallographic structure when a semi-molten molten metal of 3 wt% Si alloy is rapidly cooled at a cooling rate of 10 ° C./sec from a solid phase ratio of 30 wt%.

これに対して、従来のＡｌ合金は、ほぼ図１の右下がりの線上にあるため、液相中に晶出可能なＡｌが殆ど存在せず、図３に示したように、急冷しても微細な粒径の第二のα相は晶出しない。さらに詳しくは、成形直前の液相はＡｌ−Ｓｉの共晶組成になっているため、急冷過程においても余剰のＡｌが存在せず、微細な粒径の第二のα相は析出し得ない。そして、成形後には冷却過程で生じたＡｌ−Ｓｉの共晶相と、半溶融溶湯中で生成していた粒径の大きい球状α相が混在した金属組織構造となる。
なお、図３は従来の成形領域にあるＡｌ合金の半溶融溶湯を、冷却速度１０℃／秒で急冷したときの金属組織の顕微鏡写真の写図である。 On the other hand, since the conventional Al alloy is almost on the right-downward line in FIG. 1, there is almost no Al that can be crystallized in the liquid phase, and even if it is rapidly cooled as shown in FIG. The second α phase having a fine particle size does not crystallize. More specifically, since the liquid phase immediately before forming has an eutectic composition of Al-Si, there is no surplus Al even in the rapid cooling process, and the second α phase having a fine particle size cannot be precipitated. . And after shaping | molding, it becomes the metal structure which the eutectic phase of Al-Si produced in the cooling process and the spherical alpha phase with the large particle size produced | generated in the semi-molten molten metal were mixed.
FIG. 3 is a photomicrograph of the metallographic structure when the Al alloy semi-molten molten metal in the conventional forming region is rapidly cooled at a cooling rate of 10 ° C./second.

第一のα相は、円相当径が２０μｍ以上で、かつ平均円相当径が５０μｍ以上となるよう、前記した方法で容器中の溶湯の冷却速度を調整することによって生成させる。円相当径が２０μｍ未満または平均円相当径５０μｍ未満では容器内のＡｌ合金の形状保持が困難で搬送セットが不可能という問題が起きる。   The first α phase is generated by adjusting the cooling rate of the molten metal in the container by the above-described method so that the equivalent circle diameter is 20 μm or more and the average equivalent circle diameter is 50 μm or more. If the equivalent circle diameter is less than 20 μm or the average equivalent circle diameter is less than 50 μm, there is a problem that it is difficult to maintain the shape of the Al alloy in the container and the conveyance set is impossible.

円相当径が２０μｍ未満の第二のα相は、半溶融溶湯を５℃／秒以上の冷却速度で冷却することによって生成させる。冷却速度が５℃／秒未満では、図２(冷却速度５℃／秒)と図４（冷却速度１℃／秒)との比較で明らかなように、第二のα相はごく僅かしか形成されない。冷却速度の調整は、鋳造金型を用いて成形する場合には、例えば鋳造金型の冷却水温度、あるいは鋳造金型の設計等、公知の方法によって調整することができる。
また、第二のα相の平均円相当径は、第一のα相の平均円相当径の１／５以下であることが良好な靭性を有するＡｌ合金を得る上で好ましい。更に、第二のα相の平均円相当径は、第一のα相の平均円相当径の１／７以下であることが、より優れた靭性を有するＡｌ合金を得る上で好ましい。
なお、図４は図２と同一のＳｉ含量、固相率のＡｌ合金を用い、冷却速度を遅くした場合の金属組織の顕微鏡写真の写図である。 The second α phase having an equivalent circle diameter of less than 20 μm is generated by cooling the semi-molten molten metal at a cooling rate of 5 ° C./second or more. When the cooling rate is less than 5 ° C./second, the second α-phase is only slightly formed as is apparent from the comparison between FIG. 2 (cooling rate 5 ° C./second) and FIG. 4 (cooling rate 1 ° C./second). Not. In the case of molding using a casting mold, the cooling rate can be adjusted by a known method such as the cooling water temperature of the casting mold or the design of the casting mold.
The average equivalent circle diameter of the second α phase is preferably 1/5 or less of the average equivalent circle diameter of the first α phase in order to obtain an Al alloy having good toughness. Furthermore, the average equivalent circle diameter of the second α phase is preferably 1/7 or less of the average equivalent circle diameter of the first α phase in order to obtain an Al alloy having better toughness.
FIG. 4 is a photomicrograph of the metallographic structure when an Al alloy having the same Si content and solid phase ratio as in FIG. 2 is used and the cooling rate is slow.

顕微鏡下で観察される第二のα相の占める面積は、第一のα相の面積を含む総面積に対して５％以上、より好ましくは２０％以上の面積であることがＡｌ合金物の靭性を向上させる上で好ましい。更に、より良好な靭性を有するＡｌ合金を得るためには、第二のα相の面積が総面積に対して２０％〜５０％の範囲内にあることが好ましい。   The area occupied by the second α phase observed under the microscope is 5% or more, more preferably 20% or more of the total area including the area of the first α phase. It is preferable when improving toughness. Furthermore, in order to obtain an Al alloy having better toughness, the area of the second α phase is preferably in the range of 20% to 50% with respect to the total area.

従来の半溶融鋳造法では、成形後のＡｌ合金鋳物の金属組織は、前記したようにＡｌ−Ｓｉの共晶相と、粒径の大きい球状α相（Ａｌ結晶相）が混在した構造となっている（図３参照）。Ａｌ−Ｓｉの共晶相と、アルミニウムの球状α相とでは結晶構造が異なるため、粒界を通って亀裂が進展し易いことが知られている。
しかし、金属組織中に微細な第二のα相を生成させることにより、粒界を通じた亀裂の進展が阻止される結果、Ａｌ合金の靭性等、機械的性質が向上する。 In the conventional semi-molten casting method, the metal structure of the Al alloy casting after forming has a structure in which an Al—Si eutectic phase and a spherical α phase having a large particle size (Al crystal phase) are mixed as described above. (See FIG. 3). It is known that the crystal structure is different between the Al—Si eutectic phase and the spherical α phase of aluminum, so that cracks easily propagate through the grain boundaries.
However, by generating a fine second α-phase in the metal structure, the progress of cracks through the grain boundary is prevented, and as a result, mechanical properties such as toughness of the Al alloy are improved.

次に、Ａｌ合金鋳物の製造方法について、適宜図を参照しながら説明する。
図５は、Ａｌ合金鋳物を製造する方法を模式的に表した図である。 Next, a method for producing an Al alloy casting will be described with reference to the drawings as appropriate.
FIG. 5 is a diagram schematically showing a method for producing an Al alloy casting.

図示しない溶融炉から、液相線温度に対して５０℃未満の過熱度に保持されている溶湯を容器１に注入する。容器１には、本発明者らが特開２００２−３０７１５３号公報に開示したような、底部（鋳造金型２のゲートに対向する面）に脆弱部７が設けられた容器１を好適に用いることができる。
また、溶湯を容器１へ注入するとき、特開平１１−１３８２４８号公報に開示した方法を用いることができる（図６）。この方法を用いた場合、溶湯を一旦汲取り容器Ｃに受け、容器１を傾けておき、傾けた容器１を起こしながら、傾斜した容器１の内周面に沿って溶湯を注入する。これにより、容器１へ溶湯を静かに注ぐことができ、酸化膜等の巻き込みによる製品の品質の低下を防止することができる。 From a melting furnace (not shown), molten metal maintained at a degree of superheat of less than 50 ° C. with respect to the liquidus temperature is poured into the container 1. As the container 1, a container 1 having a fragile part 7 provided on the bottom (the surface facing the gate of the casting mold 2) as disclosed in Japanese Patent Application Laid-Open No. 2002-307153 is suitably used. be able to.
Moreover, when pouring a molten metal into the container 1, the method disclosed in JP-A-11-138248 can be used (FIG. 6). When this method is used, the molten metal is once received in the container C, the container 1 is inclined, and the molten metal is injected along the inner peripheral surface of the inclined container 1 while raising the inclined container 1. Thereby, a molten metal can be poured gently into the container 1, and the fall of the quality of the product by involvement of an oxide film etc. can be prevented.

溶湯には、Ｓｉ２．０〜４．０ｗｔ％、残部実質的にＡｌ及び不可避不純物を含有する組成からなるものを用いることができる。この組成ではないアルミニウム溶湯であっても、本実施形態の製造方法を用いてＡｌ合金鋳物を製造することは可能である。
この容器１を周囲が断熱された断熱容器に入れる等の方法によって、溶湯を所定の冷却速度に保ちつつ所定の時間冷却して目標の固相率を有する半溶融溶湯６を調整することができる。固相率は２５〜４５ｗｔ％の範囲内になるよう調整する。 A molten metal having a composition containing Si 2.0 to 4.0 wt%, the balance substantially containing Al and inevitable impurities can be used. Even if it is a molten aluminum which does not have this composition, it is possible to manufacture an Al alloy casting using the manufacturing method of this embodiment.
A semi-molten molten metal 6 having a target solid phase ratio can be adjusted by cooling the molten metal for a predetermined time while keeping the molten metal at a predetermined cooling rate by a method such as putting the container 1 in a heat insulating container whose periphery is insulated. . The solid phase ratio is adjusted to be in the range of 25 to 45 wt%.

所定時間経過後、半溶融溶湯６の入った容器１を断熱容器から取り出し、図５に示すように半溶融溶湯６を容器１ごと鋳造金型２の割り面より射出スリーブ３に装填する。
この時、半溶融溶湯６の固相率が２５ｗｔ％以上であれば、空気と触れる面の半溶融溶湯６は凝固しているため、半溶融溶湯６が容器１からこぼれることはなく、容器１ごと射出スリーブ３に装填することができる。
射出スリーブ３は半溶融溶湯６の固化を防ぐため、断熱材で保温されていることが好ましい。また、装填は手動で行っても良いし、搬送装置により自動的に行なうこともできる。 After a predetermined time has elapsed, the container 1 containing the semi-molten molten metal 6 is taken out from the heat insulating container, and the semi-molten molten metal 6 is loaded into the injection sleeve 3 from the split surface of the casting mold 2 together with the container 1 as shown in FIG.
At this time, if the solid phase ratio of the semi-molten molten metal 6 is 25 wt% or more, the semi-molten molten metal 6 on the surface that comes into contact with air is solidified. Can be loaded into the injection sleeve 3 together.
The injection sleeve 3 is preferably kept warm with a heat insulating material in order to prevent the semi-molten molten metal 6 from solidifying. In addition, the loading may be performed manually or automatically by a transport device.

容器１を射出スリーブ３に装填したら、直ちに鋳造金型２を閉止し、容器１内の半溶融溶湯６を容器１と共にプランジャ４により押圧する。これにより、容器１の底部に設けられた脆弱部７が破断して、半溶融溶湯６が鋳造金型２のキャビティ５に充填される。   When the container 1 is loaded on the injection sleeve 3, the casting mold 2 is immediately closed, and the semi-molten molten metal 6 in the container 1 is pressed together with the container 1 by the plunger 4. Thereby, the weak part 7 provided in the bottom part of the container 1 is broken, and the molten metal 6 is filled in the cavity 5 of the casting mold 2.

なお、容器１の材質はアルミニウムであることが好ましく、特にＪＩＳ称呼１０８０、１０７０等の１０００系純アルミニウムを好適に用いることができる。
次いで、キャビティ５内部の半溶融溶湯６を冷却速度５℃／秒以上で急冷してＡｌ合金鋳物を得る。キャビティ５内部の半溶融溶湯６の冷却は、鋳造金型２に設けた冷却水路１１に冷却水を循環させる等、公知の手段によって行なうことができる。 In addition, it is preferable that the material of the container 1 is aluminum, and 1000 series pure aluminums, such as JIS name 1080 and 1070, can be used especially suitably.
Next, the semi-molten molten metal 6 inside the cavity 5 is rapidly cooled at a cooling rate of 5 ° C./second or more to obtain an Al alloy casting. The semi-molten molten metal 6 inside the cavity 5 can be cooled by known means such as circulating cooling water through a cooling water channel 11 provided in the casting mold 2.

本実施形態のＡｌ合金を用いれば、高靭性のＡｌ合金鋳物を得ることができる。さらに、本実施形態のＡｌ合金鋳物の成形方法を適用すれば、例えば車両用シャーシ構造部材のように複雑な形状の部材であっても、高靭性を損なうことなく成形することができる。   If the Al alloy of this embodiment is used, a high toughness Al alloy casting can be obtained. Furthermore, by applying the Al alloy casting molding method of the present embodiment, even a member having a complicated shape such as a vehicle chassis structural member can be molded without impairing high toughness.

以上、実施形態について説明したが、本発明は前記した実施形態には限定されない。
例えば、固相率の調整方法として、周囲が断熱された断熱容器を例に説明したが、一定温度に保たれた炉やトンネルに所定時間置く方法を用いてもよい。
また、本実施形態では、射出スリーブ３は半溶融溶湯６の固化を防ぐため、断熱材で保温されていることが好ましいとしたが、半溶融溶湯６を撹拌するために、射出スリーブ３に機械撹拌、あるいは電磁撹拌手段を設けても良い。また、射出スリーブ３に装填した空の容器１に、溶融炉から直接半溶融溶湯６を注入して、射出スリーブ３で所定時間保持して目標とする固相率に調整することもできる。 As mentioned above, although embodiment was described, this invention is not limited to above-described embodiment.
For example, as a method for adjusting the solid phase ratio, a heat-insulated container having a thermally insulated periphery has been described as an example, but a method of placing it in a furnace or tunnel maintained at a constant temperature for a predetermined time may be used.
In the present embodiment, the injection sleeve 3 is preferably kept warm by a heat insulating material in order to prevent the semi-molten molten metal 6 from solidifying. However, in order to agitate the semi-molten molten metal 6, Stirring or electromagnetic stirring means may be provided. Alternatively, the semi-molten molten metal 6 can be directly injected from the melting furnace into the empty container 1 loaded in the injection sleeve 3 and held for a predetermined time in the injection sleeve 3 to adjust the target solid phase ratio.

本発明のＡｌ合金に適した物として、車両用シャーシ構造部材を取り上げたが、これに限られるもので無く、例えばブロワのファン等の回転する部材や、機械装置筐体等、各種の鋳物製品に適用することができる。特に、鉄製の鋳物製品に対して本発明のＡｌ合金を適用すると、軽量化の効果を顕著に奏することができる。   The chassis structural member for a vehicle is taken up as an object suitable for the Al alloy of the present invention. However, the present invention is not limited to this. For example, various casting products such as a rotating member such as a blower fan, a machine housing, etc. Can be applied to. In particular, when the Al alloy of the present invention is applied to a cast iron product, the effect of weight reduction can be remarkably exhibited.

次に、本発明の効果を確認した実施例について説明する。前記した実施形態のＡｌ合金及びＡｌ合金鋳物の成形方法を用いて、Ｓｉ含有量及び固相率が本発明の範囲に入る場合を実施例とし、入らない場合を比較例として、靭性、引張強度、及び成形性を比較した。   Next, examples in which the effects of the present invention have been confirmed will be described. Using the Al alloy and Al alloy casting method of the above-described embodiment, the case where the Si content and the solid phase ratio fall within the scope of the present invention is taken as an example, and the case where it does not enter is a comparative example, toughness, tensile strength And the moldability were compared.

実施例及び比較例に用いたシャルピー試験片、及び引張試験片は、固相率を前記した方法により調整した半溶融溶湯を用いて、２００ｔダイカスト機により作製した。その鋳造条件は、鋳造金型温度９０〜２５０℃、初速０．１５ｍ／秒、射出スピード０．３ｍ／秒、鋳造圧力９０ＭＰａに設定した。
引張試験片は平板状をなし、標点距離が２５ｍｍ、厚さｔが３ｍｍ、幅ｗが６ｍｍであり、シャルピー試験片はＪＩＳ３号試験片に相当する。 The Charpy test piece and the tensile test piece used in Examples and Comparative Examples were prepared by a 200 t die casting machine using a semi-molten molten metal whose solid phase ratio was adjusted by the method described above. The casting conditions were set to a casting mold temperature of 90 to 250 ° C., an initial speed of 0.15 m / second, an injection speed of 0.3 m / second, and a casting pressure of 90 MPa.
The tensile test piece has a flat plate shape, the gauge distance is 25 mm, the thickness t is 3 mm, and the width w is 6 mm. The Charpy test piece corresponds to a JIS No. 3 test piece.

表１に、各実施例及び比較例に用いた合金のＳｉ濃度、成形条件及び評価結果を示す。
（なお、表１中の「固相率調整温度」とは、溶湯を容器に注ぐときの温度のことであり、前記した液相線温度に対して５０℃未満の過熱度の温度のことである。平均円相当径は、サンプル数１０以上について円相当径を求めその数平均を算出した。
また、「成形性」の評価は、鋳造金型のキャビティに合金が完全に充填され、かつ合金の内部に微小欠陥が無い場合を「○」とした。 Table 1 shows the Si concentration, molding conditions, and evaluation results of the alloys used in the examples and comparative examples.
(Note that “solid phase ratio adjustment temperature” in Table 1 refers to the temperature when pouring the molten metal into the container, and refers to the temperature of the degree of superheat below 50 ° C. with respect to the liquidus temperature described above. For the average equivalent circle diameter, the equivalent circle diameter was obtained for 10 or more samples, and the number average was calculated.
The evaluation of “formability” was “◯” when the cavity of the casting mold was completely filled with the alloy and there was no minute defect inside the alloy.

Figure 2006037190
Figure 2006037190

＜Ｓｉ含有量の影響＞
実施例１〜３と比較例１、２に、Ｓｉ含有量のみを変更し、他の条件は同一にした場合の成形性、靭性等の評価結果を示す。
Ｓｉ含有量が本発明の範囲（２．０〜４．０ｗｔ％）より少ないと（比較例２）、合金の内部に微小欠陥が多く見られた。また、この微小欠陥ために衝撃値、耐力のバラツキが大きく、正当な評価を行なえない成形品しか得られなかった。一方、Ｓｉ含有量が本発明の範囲より高い６．５％の場合は（比較例１）、合金の内部に第二のα相の生成が認められず、衝撃値、耐力等が低い成形品しか得られなかった。
これに対し、Ｓｉ含有量が本発明の範囲内（２．０〜４．０ｗｔ％）にある実施例１〜３では、成形性は良好で、衝撃値、伸び共に従来合金（比較例１）より高い靭性に優れた合金となった。また、抗張力、耐力も従来合金より優れていた。 <Influence of Si content>
In Examples 1 to 3 and Comparative Examples 1 and 2, only the Si content is changed and the other conditions are the same.
When the Si content was less than the range of the present invention (2.0 to 4.0 wt%) (Comparative Example 2), many micro defects were observed inside the alloy. Further, due to this minute defect, the impact value and the proof stress varied greatly, and only a molded product that could not be properly evaluated was obtained. On the other hand, when the Si content is 6.5% higher than the range of the present invention (Comparative Example 1), the formation of the second α phase is not recognized in the alloy, and the molded product has a low impact value, yield strength, and the like. Only obtained.
On the other hand, in Examples 1 to 3 in which the Si content is within the range of the present invention (2.0 to 4.0 wt%), the formability is good, and both the impact value and the elongation are conventional alloys (Comparative Example 1). The alloy has higher toughness. Also, the tensile strength and proof stress were superior to those of conventional alloys.

＜固相率の影響＞
実施例２，４と比較例３〜５に、固相率のみを変更し、他の条件は同一にした場合の、伸び及び衝撃値で表される靭性、成形性等の評価結果を示す。
固相率が本発明の範囲より低い比較例３では、液状金属が過多となり半溶融溶湯のハンドリングが困難なため、成形を行なうことができなかった。一方、固相率が本発明よりも高い５０％以上の比較例４，５の場合は、Ｓｉ含有量が低いために半溶融溶湯の流動性が劣った。このため、固相率５０ｗｔ％及び６０ｗｔ％では鋳造金型のキャビティが完全に充填されない部分が残っていた。
これに対し、固相率が本発明の範囲内にある実施例２，４（固相率３０ｗｔ％、４０ｗｔ％）では、鋳造金型のキャビティの充填は良好であった。 <Influence of solid fraction>
In Examples 2 and 4 and Comparative Examples 3 to 5, evaluation results of toughness and formability represented by elongation and impact values when only the solid phase ratio is changed and the other conditions are the same are shown.
In Comparative Example 3 where the solid phase ratio was lower than the range of the present invention, the liquid metal was excessive, and it was difficult to handle the semi-molten molten metal, so that molding could not be performed. On the other hand, in Comparative Examples 4 and 5 having a solid phase ratio of 50% or higher higher than that of the present invention, the fluidity of the semi-molten molten metal was inferior because the Si content was low. For this reason, when the solid phase ratio is 50 wt% and 60 wt%, there remains a portion in which the cavity of the casting mold is not completely filled.
On the other hand, in Examples 2 and 4 (solid phase ratios of 30 wt% and 40 wt%) in which the solid phase ratio is within the range of the present invention, the filling of the cavity of the casting mold was good.

＜冷却速度の影響＞
実施例２と比較例６に、冷却速度のみを変更し、他の条件は同一にした場合の成形性、靭性等の評価結果を示す（図２、図４参照）。
いずれの場合も、成形性は良好であった。しかし、冷却速度が本発明の範囲外である比較例６では、第二のα相の生成は認められなかった。このため、伸び、衝撃値だけでなく、抗張力、耐力も実施例２より劣っていた。 <Influence of cooling rate>
Example 2 and Comparative Example 6 show the evaluation results of formability, toughness, etc. when only the cooling rate is changed and the other conditions are the same (see FIGS. 2 and 4).
In any case, the moldability was good. However, in Comparative Example 6 in which the cooling rate was outside the range of the present invention, the generation of the second α phase was not observed. For this reason, not only the elongation and impact values, but also the tensile strength and proof stress were inferior to those of Example 2.

＜第二のα相の影響＞
Ｓｉ含有量が本発明の範囲内にあり、冷却速度が５℃／秒の場合は第二のα相の生成が認められ良好な靭性等をしめしたが、冷却速度が本発明の範囲外である１℃／秒のとき（比較例６）、及びＳｉ含有量が本発明の範囲外である従来合金（比較例１）のときは、第二のα相は生成せず、靭性も劣っていた。
また、実施例１〜４の本発明に係るＡｌ合金は、第一のα相の平均円相当径が５０μｍ以上で、更に、第二のα相の平均円相当径は第一のα相の平均円相当径の５分の１以下の値であり、本実施例では約１／７以下であった。
なお、比較例３では前記のように成形ができなかったため、平均円相当径の測定は不能であった。比較例２，４，５では良好な第一及び第二のα相が認められたものの、前記のように成形上の問題で靭性等の評価は行なえなかった。このことは、加工条件の適正化により、比較例２〜５の範囲のもでも高靭性を有するＡｌ合金として使用可能であることを示唆している。 <Influence of second alpha phase>
When the Si content is within the range of the present invention and the cooling rate is 5 ° C./second, the formation of the second α-phase is recognized and good toughness is shown, but the cooling rate is outside the range of the present invention. At a certain 1 ° C./second (Comparative Example 6) and a conventional alloy (Comparative Example 1) whose Si content is outside the scope of the present invention, the second α phase is not formed and the toughness is also inferior. It was.
Further, in the Al alloys according to the present invention of Examples 1 to 4, the average equivalent circle diameter of the first α phase is 50 μm or more, and the average equivalent circle diameter of the second α phase is that of the first α phase. It is a value of 1/5 or less of the average equivalent circle diameter, and in this example, it was about 1/7 or less.
In Comparative Example 3, since the molding could not be performed as described above, the average equivalent circle diameter could not be measured. In Comparative Examples 2, 4, and 5, good first and second α phases were observed, but as described above, evaluation of toughness and the like could not be performed due to molding problems. This suggests that it can be used as an Al alloy having high toughness even in the range of Comparative Examples 2 to 5 by optimizing the processing conditions.

Ｓｉ含有量と共晶時の固相率の関係を示す図である。It is a figure which shows the relationship between Si content and the solid-phase rate at the time of eutectic. 本発明のＡｌ合金の半溶融溶湯を冷却速度１０℃／秒で急冷したときの金属組織を示す顕微鏡写真の写図である。It is a copy of the microscope picture which shows a metal structure when the semi-molten molten metal of Al alloy of this invention is rapidly cooled with the cooling rate of 10 degree-C / sec. 従来の成形領域にあるＡｌ合金の半溶融溶湯を冷却速度１０℃／秒で急冷したときの金属組織を示す顕微鏡写真の写図である。It is a copy of the microscope picture which shows a metal structure when the semi-molten molten metal of Al alloy in the conventional shaping | molding area | region is rapidly cooled with the cooling rate of 10 degree-C / sec. 本発明のＡｌ合金の半溶融溶湯を冷却速度１℃／秒で冷却した場合の金属組織を示す顕微鏡写真の写図である。It is a copy of the microscope picture which shows the metal structure at the time of cooling the semi-molten molten metal of Al alloy of this invention at the cooling rate of 1 degree-C / sec. Ａｌ合金鋳物を製造する方法の模式図である。It is a schematic diagram of the method of manufacturing an Al alloy casting. 溶湯を容器へ注入する方法の模式図である。It is a schematic diagram of the method of injecting molten metal into a container.

符号の説明Explanation of symbols

１ 容器
２ 鋳造金型
３ 射出スリーブ
４ プランジャ
５ キャビティ
６ 半溶融溶湯 DESCRIPTION OF SYMBOLS 1 Container 2 Casting die 3 Injection sleeve 4 Plunger 5 Cavity 6 Semi-molten molten metal

Claims (7)

Ｓｉ２．０〜４．０ｗｔ％、
残部実質的にＡｌ及び不可避不純物を含有する組成からなり、
固相率２５〜４５％の半溶融溶湯を急冷してなることを特徴とするアルミニウム合金。 Si 2.0-4.0 wt%,
The balance substantially consists of a composition containing Al and inevitable impurities,
An aluminum alloy characterized by quenching a semi-molten molten metal having a solid phase ratio of 25 to 45%. 円相当径が２０μｍ以上で、かつ平均円相当径が５０μｍ以上の第一のα相と、
円相当径が２０μｍ未満の第二のα相とを含むことを特徴とする請求項１に記載のアルミニウム合金。 A first α phase having an equivalent circle diameter of 20 μm or more and an average equivalent circle diameter of 50 μm or more;
The aluminum alloy according to claim 1, further comprising a second α phase having an equivalent circle diameter of less than 20 μm. 前記第二のα相の平均円相当径は、前記第一のα相の平均円相当径の５分の１以下であることを特徴とする請求項１または請求項２に記載のアルミニウム合金。   3. The aluminum alloy according to claim 1, wherein an average equivalent circle diameter of the second α phase is 1/5 or less of an average equivalent circle diameter of the first α phase. 前記半溶融溶湯を冷却速度５℃／秒以上で急冷することを特徴とする請求項１から請求項３のいずれか１項に記載のアルミニウム合金。   The aluminum alloy according to any one of claims 1 to 3, wherein the semi-molten molten metal is rapidly cooled at a cooling rate of 5 ° C / second or more. 請求項１から請求項４のいずれか１項に記載のアルミニウム合金で成形したことを特徴とする車両用シャーシ構造部材。   A vehicle chassis structural member formed of the aluminum alloy according to any one of claims 1 to 4. 容器にＳｉ２．０〜４．０ｗｔ％、残部実質的にＡｌ及び不可避不純物を含有する組成からなる溶湯を流し込み
共晶点近傍の温度で前記溶湯を目的の固相率を有する半溶融溶湯に調整し、
前記半溶融溶湯を前記容器と共に鋳造金型の割り面より射出スリーブに装填し、
前記鋳造金型を閉止した後、
前記容器及び前記半溶融溶湯をプランジャにより押圧して前記半溶融溶湯を前記鋳造金型のキャビティに充填し、
次いで前記鋳造金型のキャビティに充填した前記半溶融溶湯を冷却速度５℃／秒以上で急冷する
ことを特徴とするアルミニウム合金鋳物の成形方法。 Pour molten metal having a composition containing Si 2.0 to 4.0 wt%, the balance substantially containing Al and inevitable impurities into the container, and adjust the molten metal to a semi-molten molten metal having a desired solid fraction at a temperature near the eutectic point. And
The semi-molten molten metal is loaded into the injection sleeve from the split surface of the casting mold together with the container,
After closing the casting mold,
The container and the semi-molten molten metal are pressed by a plunger to fill the semi-molten molten metal into a cavity of the casting mold,
Next, the aluminum alloy casting molding method characterized by quenching the semi-molten molten metal filled in the cavity of the casting mold at a cooling rate of 5 ° C./second or more. 前記目的の固相率が２５〜４５ｗｔ％であることを特徴とする請求項５に記載のアルミニウム合金鋳物の成形方法。   The method for forming an aluminum alloy casting according to claim 5, wherein the target solid phase ratio is 25 to 45 wt%.
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