JP6741208B2 - Hypereutectic Al-Si based aluminum alloy, cast member made of the same, and method for producing the aluminum alloy - Google Patents

Hypereutectic Al-Si based aluminum alloy, cast member made of the same, and method for producing the aluminum alloy Download PDF

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JP6741208B2
JP6741208B2 JP2015255992A JP2015255992A JP6741208B2 JP 6741208 B2 JP6741208 B2 JP 6741208B2 JP 2015255992 A JP2015255992 A JP 2015255992A JP 2015255992 A JP2015255992 A JP 2015255992A JP 6741208 B2 JP6741208 B2 JP 6741208B2
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aluminum alloy
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慶之 大窪
慶之 大窪
信裕 新井
信裕 新井
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Proterial Ltd
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本発明は、過共晶Al−Si系アルミニウム合金、及びそれからなる鋳造部材、並びに前記アルミニウム合金の製造方法に関するものである。 The present invention relates to a hypereutectic Al—Si based aluminum alloy, a cast member made of the same, and a method for producing the aluminum alloy.

軽量化、複雑形状の加工容易性、製造コスト低減等の点で有利なアルミニウム合金の鋳造部材は各種の部品に広く使用されている。特に自動車等では、ケースやカバー類の材料としてAl−Si−Cu−Mg系のJIS AC4B、ADC12等が、また足回り部品やロードホイールの材料としてAl−Si−Mg系のJIS AC4CH、ADC3等が使用されているが、省エネルギーおよび燃費改善が要求されており、それらを構成するアルミニウム合金鋳造部材にも一層の軽量化および高品質化が望まれている。 Aluminum alloy cast members, which are advantageous in terms of weight reduction, easiness of processing of complicated shapes, reduction of manufacturing cost, etc., are widely used for various parts. Particularly in automobiles, Al-Si-Cu-Mg-based JIS AC4B, ADC12, etc. are used as materials for cases and covers, and Al-Si-Mg-based JIS AC4CH, ADC3, etc. are used as materials for undercarriage parts and road wheels. However, there is a demand for energy saving and improvement in fuel consumption, and further weight reduction and quality improvement are demanded for the aluminum alloy cast members constituting them.

近年は、熱処理の適正化やCAEを活用した構造解析により、必要な強度を確保しつつ減肉や薄肉化することによって上記軽量化の要求に応じてきたが、以下に述べるように材料がもつ特性が原因で、さらなる軽量化要求に対応できる余地が少なくなってきている。 In recent years, through the optimization of heat treatment and structural analysis utilizing CAE, the demand for weight reduction has been met by reducing the thickness and reducing the thickness while ensuring the required strength. Due to the characteristics, there is less room to meet the demand for further weight reduction.

ケース、カバー類に多用されている上記Al−Si−Cu−Mg系アルミニウム合金は、強度は十分あるものの、原子量が大きく耐食性を阻害する元素でもあるCuを含むため、過度に薄肉化すると腐食により気密性が損なわれやすくなるおそれがある。また、上記Al−Si−Cu−Mg系アルミニウム合金は破断伸びが2.0%以下と延性が小さいので、変形能を要求される部材には適用し難く、適用範囲が限られている。 The Al-Si-Cu-Mg-based aluminum alloy, which is often used in cases and covers, has sufficient strength, but contains Cu, which has a large atomic weight and is also an element that hinders corrosion resistance, and therefore excessively thinning causes corrosion. Airtightness may be easily impaired. Further, since the Al-Si-Cu-Mg-based aluminum alloy has a small elongation at break of 2.0% or less, it is difficult to apply it to a member which is required to have deformability, and its application range is limited.

足回り部品やロードホイール等に適用されている上記Al−Si−Mg系アルミニウム合金は、Al−Si−Cu−Mg系アルミニウム合金よりも延性が大きいため、変形能も大きい。そしてCuを実質的に含まないため耐食性が良好である。強度の指標である0.2%耐力も車両等に適用できる100MPa以上あり、さらに熱処理によってさらに大きくすることが可能であるので、鋳造部材の軽量化のための薄肉設計が可能である。ところが、上記のアルミニウム合金は亜共晶組成でありヤング率が76GPa以下のため、強度および延性を確保できても、薄肉にすると鋳造部材として必要な剛性を確保することができなくなってしまう。従って、さらなる薄肉設計での軽量化は困難になりつつある。 The Al-Si-Mg-based aluminum alloy applied to underbody parts, road wheels, and the like has a higher ductility than the Al-Si-Cu-Mg-based aluminum alloy, and therefore has a high deformability. And since it does not substantially contain Cu, the corrosion resistance is good. The 0.2% proof stress, which is an index of strength, is 100 MPa or more applicable to vehicles and the like, and can be further increased by heat treatment, so that a thin design for weight reduction of cast members is possible. However, since the above aluminum alloy has a hypoeutectic composition and a Young's modulus of 76 GPa or less, even if strength and ductility can be secured, if it is made thin, the rigidity required as a cast member cannot be secured. Therefore, it is becoming difficult to reduce the weight with a thinner design.

ヤング率の高いアルミニウム合金として過共晶Al-Si系合金が注目されているが、初晶Si粒子が粗大に晶出しやすく延性は著しく低い。過共晶Al−Si系合金の初晶Siを微細化する先行技術として、例えば特許文献1に、過共晶Al-Si合金溶湯中のP含有量を1massppm以上、50massppm以下に調整するとともに、金属Na又は金属Naを含む金属Na合金部材を前記過共晶Al-Si合金溶湯に添加する添加ステップを備えることを特徴とする過共晶Al−Si合金の製造方法と、アルミニウムマトリクス中に分散している初晶Si粒子の平均粒径が100μ未満であり、丸みを帯びた外郭形状に形成されている過共晶Al−Si合金が開示されている。 A hypereutectic Al—Si alloy has attracted attention as an aluminum alloy having a high Young's modulus, but primary crystal Si particles tend to coarsely crystallize, and the ductility is extremely low. As a prior art for refining primary crystal Si of a hypereutectic Al-Si alloy, for example, in Patent Document 1, while adjusting the P content in the hypereutectic Al-Si alloy molten metal to 1 massppm or more and 50 massppm or less, A method for producing a hypereutectic Al-Si alloy, comprising the step of adding metallic Na or a metallic Na alloy member containing metallic Na to the hypereutectic Al-Si alloy melt, and dispersing in an aluminum matrix. Disclosed is a hypereutectic Al-Si alloy in which the average particle size of the primary crystal Si particles is less than 100 μm and which is formed in a rounded outer shape.

特開2012−62501号公報JP 2012-62501 A

本発明者らは特許文献1に記載のようなMg、PおよびNaを含む過共晶Al-Si系アルミニウム合金について、その組成、ミクロ組織および機械的性質との関係を検討したところ、Naの添加を適切に行わないとアルミニウム合金に含有する水素が増大してしまい、その結果、気泡(ガス欠陥)が多数生じて、機械的性質、特に延性を確保しにくくなってしまうことがわかった。 The inventors of the present invention have studied the relationship between the composition, microstructure and mechanical properties of a hypereutectic Al-Si based aluminum alloy containing Mg, P and Na as described in Patent Document 1, and It was found that the hydrogen contained in the aluminum alloy increases if the addition is not performed properly, and as a result, a large number of bubbles (gas defects) are generated, and it becomes difficult to secure the mechanical properties, particularly ductility.

本発明は、微細な初晶Si粒子を有し、高い強度と延性を有する過共晶Al-Si系アルミニウム合金、及びそれからなる鋳造部材、並びに前記アルミニウム合金を製造するのに好適な製造方法を提供することを目的としている。 The present invention has fine primary crystal Si particles, a hypereutectic Al-Si-based aluminum alloy having high strength and ductility, a cast member made of the same, and a production method suitable for producing the aluminum alloy. It is intended to be provided.

本発明の一形態は、質量基準で、12.6〜16.0%のSi、0.1〜0.6%のMg、0.0001〜0.0200%のP、0.0100〜0.0400%のNa、0.05〜0.3%のTi、残部がAl及び不可避的不純物からなり、100gあたりの含有水素量が水素ガス基準で0.05〜1.0cmであって、切断面に観察される最大の初晶Si粒子の最大幅が1〜90μmであり、切断面に観察される共晶Si粒子同士の平均距離が0μmを超え5μm以下であることを特徴とする過共晶Al−Si系アルミニウム合金である。 One form of the present invention is, on a mass basis, 12.6 to 16.0% Si, 0.1 to 0.6% Mg, 0.0001 to 0.0200% P, 0.0100 to 0. 0400% of Na, 0.05 to 0.3 percent of Ti, the balance being a l及 beauty unavoidable impurities, the hydrogen content per 100g is 0.05~1.0Cm 3 Tsu der hydrogen gas standards Te, the maximum width of the largest primary Si particles observed on the cut surface is 1~90Myuemu, characterized der Rukoto below 5μm beyond the average distance of the eutectic Si particles are observed on the cut surface is 0μm Is a hypereutectic Al-Si aluminum alloy.

さらに加えて、切断面に観察される円相当径で20μm以上の気泡の数が1個/mm以下であることが好ましい。 In addition, it is preferable that the number of bubbles having a circle equivalent diameter of 20 μm or more observed on the cut surface is 1/mm 2 or less.

また、本発明の過共晶Al-Si系アルミニウム合金においては、破断伸びが5%以上、シャルピー衝撃値が15J/cm以上であることが好ましい。 Further, in the hypereutectic Al—Si based aluminum alloy of the present invention, it is preferable that the breaking elongation is 5% or more and the Charpy impact value is 15 J/cm 2 or more.

加えて、0.2%耐力が100MPa以上であることが好ましい。 In addition, the 0.2% proof stress is preferably 100 MPa or more.

本発明の他の一形態は、本発明の過共晶Al−Si系アルミニウム合金からなる鋳造部材である。 Another embodiment of the present invention is a cast member made of the hypereutectic Al-Si based aluminum alloy of the present invention.

そして、本発明のさらに他の一形態は、脱水素処理工程とNa添加工程とを含み、前記Na添加工程の前に前記脱水素処理工程を実施して、質量基準で、12.6〜16.0%のSi、0.1〜0.6%のMg、0.0001〜0.0200%のP、0.0100〜0.0400%のNa、0.05〜0.3%のTi、残部がAl及び不可避的不純物からなる溶湯を、前記Na添加工程の後の30分以内に注湯して、600℃から580℃の間の冷却速度を15℃/s以上で冷却し凝固させることにより、100gあたりの含有水素量が水素ガス基準で0.05〜1.0cm であって、切断面に観察される最大の初晶Si粒子の最大幅が1〜90μmであり、切断面に観察される共晶Si粒子同士の平均距離が0μmを超え5μm以下である過共晶Al-Si系アルミニウム合金製造する方法である。 Then, still another embodiment of the present invention includes a dehydrogenation treatment step and a Na addition step, wherein the dehydrogenation treatment step is performed before the Na addition step, and the mass reference is 12.6 to 16. 0.0% Si, 0.1-0.6% Mg, 0.0001-0.0200% P, 0.0100-0.0400% Na, 0.05-0.3% Ti, the molten metal and the balance being a l及 beauty unavoidable impurities, and poured within 30 minutes after the Na addition step, cooling the cooling rate between 580 ° C. from 600 ° C. at 15 ° C. / s or more coagulation the Rukoto is, a 0.05~1.0Cm 3 hydrogen content per 100g is hydrogen gas basis, the maximum width of the largest primary Si particles observed on the cut surface is 1~90Myuemu, the average distance of the eutectic Si particles are observed on the cut surface is a process for preparing der Ru hypereutectic Al-Si-based aluminum alloy below 5μm exceed 0 .mu.m.

本発明によれば、微細な初晶Si粒子を有し、高い強度と延性を有する過共晶のAl-Si系アルミニウム合金及びそれからなる鋳造部材、並びに前記アルミニウム合金の好適な製造方法が提供される。 According to the present invention, there is provided a hypereutectic Al-Si-based aluminum alloy having fine primary crystal Si particles, having high strength and ductility, a cast member made of the same, and a suitable method for producing the aluminum alloy. It

実施例1の過共晶Al-Si系アルミニウム合金のミクロ組織である。3 is a microstructure of the hypereutectic Al—Si-based aluminum alloy of Example 1. 過共晶Al-Si系アルミニウム合金の初晶Si粒子と共晶Si粒子を示すミクロ組織の一例である。It is an example of a microstructure showing primary crystal Si particles and eutectic Si particles of a hypereutectic Al-Si based aluminum alloy. 図2における初晶Si粒子の最大幅の測定方法を説明する部分拡大図である。FIG. 3 is a partially enlarged view illustrating a method for measuring the maximum width of primary crystal Si particles in FIG. 2. 図2における共晶Si粒子同士の距離の測定方法を説明する部分拡大図である。FIG. 3 is a partially enlarged view illustrating a method of measuring a distance between eutectic Si particles in FIG. 2. 比較例1の過共晶Al-Si系アルミニウム合金のミクロ組織である。3 is a microstructure of a hypereutectic Al-Si-based aluminum alloy of Comparative Example 1. 本発明の実施形態に係るアルミニウム合金の鋳造に用いた第1の種類の鋳型の概略図である。It is a schematic diagram of the 1st kind of mold used for casting of aluminum alloy concerning the embodiment of the present invention. 第1の種類の鋳型に鋳造された鋳造部材の形状と各種試験片を採取した位置を示す概略図である。It is a schematic diagram showing the shape of the casting member cast in the mold of the 1st kind, and the position where various test pieces were sampled. 本発明を実施形態に係るアルミニウム合金の鋳造に用いた第2の種類の鋳型の概略図である。FIG. 3 is a schematic view of a second type of mold used for casting the aluminum alloy according to the embodiment of the present invention. 第2の種類の鋳型に鋳造された鋳造部材の形状と各種試験片を採取した位置を示す概略図である。It is a schematic diagram showing the shape of the cast member cast in the mold of the 2nd kind, and the position where various test pieces were sampled. 本発明の実施の形態に係る引張試験片の概略形状である。It is a schematic shape of the tensile test piece which concerns on embodiment of this invention. 冷却速度の定義を説明する図である。It is a figure explaining the definition of a cooling rate.

以下に、本発明を実施するための形態を、図表を参照しつつ詳細に説明する。 Hereinafter, modes for carrying out the present invention will be described in detail with reference to the drawings.

(Mg)
MgはSiとMgSiを形成し、引張強さと0.2%耐力を向上させる働きがある。この効果を得るには、Mgは質量基準で0.1%以上含有することが好ましい。しかし、Mgは0.6%を超えて含有するとMgSiが過剰となり、破断伸びが低下する。また、MgSiは強固な電子化合物であり、それ自体が高いヤング率を有するため、アルミニウム合金のヤング率の向上にも寄与する。Mgの含有量は質量基準で0.1〜0.6%とする。なお、好ましくは0.2〜0.4%であり、より好ましくは0.25〜0.35%である。以下、他の合金成分の成分値も質量基準とする。
(Mg)
Mg forms Si and Mg 2 Si and has a function of improving tensile strength and 0.2% proof stress. In order to obtain this effect, Mg is preferably contained in an amount of 0.1% or more based on the mass. However, when Mg exceeds 0.6%, Mg 2 Si becomes excessive and the elongation at break is reduced. Further, since Mg 2 Si is a strong electronic compound and has a high Young's modulus by itself, it also contributes to the improvement of the Young's modulus of the aluminum alloy. The content of Mg is 0.1 to 0.6% by mass. In addition, it is preferably 0.2 to 0.4%, and more preferably 0.25 to 0.35%. Hereinafter, the component values of other alloy components are also based on mass.

(P)
Pは過共晶Al−Si系アルミニウム合金における初晶Si粒子を微細化する効果がある。初晶Si粒子を微細化させるために必要な含有量は0.0001%(1ppm)であり、これに満たない場合は初晶Si粒子の微細化は困難である。また、0.0200%(200ppm)を超えると初晶Si粒子が粗大化するようになる。従ってPの含有量は0.0001%(1ppm)〜0.0200%(200ppm)である。好ましくは0.0020%(20ppm)〜0.0100%(100ppm)である。より好ましくは0.0020%(20ppm)〜0.0050%(50ppm)である。
(P)
P has an effect of refining primary crystal Si particles in a hypereutectic Al-Si-based aluminum alloy. The content necessary for refining the primary crystal Si particles is 0.0001% (1 ppm), and if the content is less than this, it is difficult to refine the primary crystal Si particles. Further, when it exceeds 0.0200% (200 ppm), the primary crystal Si particles become coarse. Therefore, the content of P is 0.0001% (1 ppm) to 0.0200% (200 ppm). It is preferably 0.0020% (20 ppm) to 0.0100% (100 ppm). It is more preferably 0.0020% (20 ppm) to 0.0050% (50 ppm).

(Na)
Naはアルミニウム合金中のSiの拡散を抑制するため、Pの効果によって微細に晶出した初晶Si粒子の成長を抑制する効果がある。このため、適当な量のNaをPと共にアルミニウム合金中に含有させることが好ましい。ただし、Na含有量が0.0400%(400ppm)を超えると、P含有による初晶Siの微細化効果が低下するようになるので好ましくない。また、Naはアルミニウム合金の共晶Si粒子を微細化する効果もある。共晶Si粒子を微細化するために必要なNa含有量は0.0100%(100ppm)であり、これに満たない場合は共晶Si粒子が微細化しないために十分な機械的性質、特に延性を得ることが困難になる。このため、Naの含有量は0.0100%(100ppm)〜0.0400%(400ppm)とする。好ましくは0.0150%(150ppm)〜0.0350%(350ppm)であり、より好ましくは0.0180%(180ppm)〜0.0350%(350ppm)である。
(Na)
Since Na suppresses the diffusion of Si in the aluminum alloy, it has the effect of suppressing the growth of finely crystallized primary crystal Si particles due to the effect of P. Therefore, it is preferable to add an appropriate amount of Na together with P in the aluminum alloy. However, if the Na content exceeds 0.0400% (400 ppm), the effect of refining the primary crystal Si due to the P content will decrease, which is not preferable. Further, Na also has the effect of refining the eutectic Si particles of the aluminum alloy. The Na content necessary for refining the eutectic Si particles is 0.0100% (100 ppm), and if the Na content is less than this, sufficient mechanical properties, especially ductility, are obtained because the eutectic Si particles are not refined. Will be difficult to obtain. Therefore, the content of Na is set to 0.0100% (100 ppm) to 0.0400% (400 ppm). It is preferably 0.0150% (150 ppm) to 0.0350% (350 ppm), and more preferably 0.0180% (180 ppm) to 0.0350% (350 ppm).

Naのアルミニウム合金への添加方法はNaのハロゲン化物を含有するフラックスをアルミニウム合金溶湯(以下、溶湯ともいう。)の表面に撒いて撹拌する方法だけでなく、アルミニウムまたはアルミニウム合金で金属ナトリウムを密封した形態のNa添加剤を、溶湯に浸漬して添加する方法などがある。なお、Naは雰囲気中の水分(HO)から酸素(O)を奪うことによって酸化減耗するため、溶湯に添加してからの経過時間が過大になると、共晶Si粒子の微細化効果を得にくくなる。加えて、雰囲気中の水分がNaに還元されて生じる水素ガス(H)が溶湯に多量に溶解して、これが鋳造後に多数の気泡として出現するようになりアルミニウム合金の機械的性質を損ねる原因となる。Naは添加するときの溶湯の温度が高いほど効率よく溶湯に溶け込む傾向がある。しかし一方で、溶湯が高温であるほど上述した酸化減耗が急速に進行し、水素ガスの溶湯への溶け込みも助長されてしまう。このため、Naを溶湯に添加する溶湯温度と添加方法、およびその時期を適切にすることが望ましい。特にNaの添加後に後述する脱ガス処理を行うと、Naの酸化減耗が助長されるだけでなく脱ガス効率も低下しやすくなるので好ましくない。また、鋳造にあたっては、Naの溶湯へ溶け込みが十分に達した時期のできるだけ早期に行うことが好ましい。 The method of adding Na to the aluminum alloy is not only a method of sprinkling a flux containing a halide of Na on the surface of a molten aluminum alloy (hereinafter, also referred to as molten metal) and stirring, but also sealing metallic sodium with aluminum or an aluminum alloy. There is a method in which the Na additive having the above-mentioned form is added by immersing it in a molten metal. Since Na is oxidized and depleted by removing oxygen (O) from moisture (H 2 O) in the atmosphere, if the elapsed time after addition to the molten metal becomes excessive, the effect of refining the eutectic Si particles will be reduced. Hard to get. In addition, a large amount of hydrogen gas (H 2 ) generated by reducing the moisture in the atmosphere to Na is dissolved in the molten metal and appears as a large number of bubbles after casting, which impairs the mechanical properties of the aluminum alloy. Becomes The higher the temperature of the molten metal when Na is added, the more efficiently Na tends to dissolve into the molten metal. On the other hand, however, the higher the temperature of the molten metal, the more rapidly the above-described oxidative wear progresses, which promotes the penetration of hydrogen gas into the molten metal. Therefore, it is desirable to appropriately set the temperature of the molten metal for adding Na to the molten metal, the method for adding the molten metal, and the timing. In particular, if the degassing treatment described below is performed after the addition of Na, not only the oxidation loss of Na is promoted but also the degassing efficiency tends to decrease, which is not preferable. Further, it is preferable that the casting is carried out as early as possible when the melting of Na into the molten metal has sufficiently reached.

(Si)
Siはそのアルミニウム合金中の含有量の増加に伴って、アルミニウム合金のヤング率を高める元素である。また、Alに対しての共晶元素であるため、鋳造性を良好にする元素である。特に共晶組成である12.6%を超える、すなわち過共晶になると、共晶Siだけでなく初晶Siも晶出しやすくなる。これらの晶出Siは高いヤング率をもつだけでなく、アルミニウム合金の母相(α相)よりも低密度であるため、アルミニウム合金全体の質量に対するヤング率の比、すなわち比剛性の向上にも寄与する。このため、剛性を確保しつつ鋳造部材の軽量化を一層図ることができる。Si含有量は、過共晶となる12.6%以上であるとヤング率を76GPa以上に確保できるので好ましい。好ましくは12.8%以上、より好ましくは12.8〜16%、さらにより好ましくは12.8〜14%である。
(Si)
Si is an element that increases the Young's modulus of the aluminum alloy as the content of the aluminum alloy increases. Further, since it is a eutectic element for Al, it is an element that improves the castability. In particular, when the eutectic composition exceeds 12.6%, that is, when hypereutectic, not only eutectic Si but also primary Si is likely to crystallize. These crystallized Si not only have a high Young's modulus, but also have a lower density than the parent phase (α phase) of the aluminum alloy, so that the ratio of the Young's modulus to the mass of the entire aluminum alloy, that is, the specific rigidity can be improved. Contribute. Therefore, the weight of the cast member can be further reduced while ensuring the rigidity. It is preferable that the Si content is 12.6% or more, which is hypereutectic, because the Young's modulus can be secured to 76 GPa or more. It is preferably 12.8% or more, more preferably 12.8 to 16%, and even more preferably 12.8 to 14%.

(Ti)
Tiは結晶粒を微細化させてアルミニウム合金の強度および延性を向上させるのみならず、アルミニウム合金溶湯が凝固収縮する際に発生する応力に抗して鋳造割れを防止する作用を有する。必須ではないが、これらの作用を効果的に発揮させるためには、Tiを質量基準で0.05%以上含有させるのが好ましい。高純度Al地金に不可避的不純物として含まれるTiは0.05%未満であるので、高純度Al地金を原料に用いる場合、上記の効果を得るためにはTiを付加的に含有させる必要がある。ただし、Tiの含有量が0.3%を超えるとAl−Ti系の金属間化合物が晶出し、アルミニウム合金の延性はかえって低下するので、Tiを付加的に含有させる場合は0.05〜0.3%とし、より好ましくは0.1〜0.3%とする。また例えば、Ti源として、展伸材の6000系合金、AC4CH合金等のアルミニウム合金スクラップ材、低純度Al地金等を使用とした場合、通常不可避的不純物として0.05%以上のTiが混入してくるので、それに応じて付加的に含有させるTi量を調節するのが好ましい。
(Ti)
Ti not only improves the strength and ductility of the aluminum alloy by refining the crystal grains, but also acts to prevent casting cracks against the stress generated when the molten aluminum alloy solidifies and shrinks. Although not essential, it is preferable that Ti is contained in an amount of 0.05% or more by mass in order to effectively exhibit these effects. Since Ti contained as an unavoidable impurity in the high-purity Al ingot is less than 0.05%, when using the high-purity Al ingot as a raw material, it is necessary to additionally contain Ti in order to obtain the above effect. There is. However, when the content of Ti exceeds 0.3%, the Al-Ti-based intermetallic compound crystallizes, and the ductility of the aluminum alloy rather decreases. Therefore, when Ti is additionally contained, it is 0.05 to 0. 0.3%, and more preferably 0.1 to 0.3%. Further, for example, when a 6000 series alloy of wrought material, aluminum alloy scrap material such as AC4CH alloy, low-purity Al ingot, etc. are used as the Ti source, 0.05% or more of Ti is usually mixed as unavoidable impurities. Therefore, it is preferable to adjust the amount of Ti to be additionally contained accordingly.

(不可避的不純物)
リサイクルの観点から、6000系合金やその他のアルミニウム合金のスクラップ材、低純度Al地金等を溶解原料として多量に使用する場合があり、上述した以外の元素が不可避的不純物として混入する可能性がある。これらの不純物元素については、例えば検出限界以下に低減することは多大なコストアップの要因となるので、本発明の目的を阻害しない含有範囲であれば許容されるものとする。基本的にはJIS規格等に沿った各不純物の許容含有量とすればよく、本発明においては、0.10%以下のCu、0.10%以下のZn、0.17%以下のFe、0.10%以下のMn、0.05%以下のNi、0.05%以下のCr、0.05%以下のPbおよび0.05%以下のSnとするのが好ましい。特にCuは耐食性を低下させ、FeはAl−Fe−Si系の金属間化合物またはMnと共にAl−Fe−Mn−Si系の金属間化合物を形成して延性の低下をきたすので、上記の値を超えたCuおよびFeを含有させるのは好ましくない。
(Inevitable impurities)
From the viewpoint of recycling, scrap materials of 6000 series alloys and other aluminum alloys, low-purity Al ingots, etc. may be used in large amounts as melting raw materials, and elements other than those mentioned above may be mixed as unavoidable impurities. is there. For these impurity elements, for example, reducing below the detection limit causes a great increase in cost, so the content range that does not impair the object of the present invention is allowed. Basically, the permissible content of each impurity may be in accordance with JIS standards, and in the present invention, 0.10% or less of Cu, 0.10% or less of Zn, 0.17% or less of Fe, Preferably, Mn is 0.10% or less, Ni is 0.05% or less, Cr is 0.05% or less, Pb is 0.05% or less, and Sn is 0.05% or less. In particular, Cu lowers the corrosion resistance, and Fe forms an Al—Fe—Mn—Si intermetallic compound together with the Al—Fe—Si based intermetallic compound or Mn to cause a decrease in ductility. It is not preferable to contain excess Cu and Fe.

(含有水素量)
大気中、ガス炉等に由来する燃焼ガス、溶解炉、保持炉を構成する耐火物、およびその他の雰囲気中の水分がAlと反応して水素ガスが生成され、これがアルミニウム合金溶湯中に溶け込むため、アルミニウム合金は水素を含有する。さらに前述したように、Naを溶湯に添加してからの経過時間が過大になると、溶湯への水素の溶け込みが助長される。水素を多量に含んだアルミニウム合金溶湯は、凝固する際に固溶しきれない水素が気体として放出されるが、その一部が鋳造部材中に留って気泡として残留するため、機械的性質、特に破断伸びや衝撃値の低下をもたらす。また、溶体化熱処理を施した場合、過飽和に溶解している水素が粗大な気泡となって鋳造部材中に再び現れることもある。このような有害な気泡を抑制するために必要な含有水素量は、水素ガス基準でアルミニウム合金100gあたり0.05〜1.0cm(以下、単位をcm/100gAlと表記することがある。)である。すなわち、1.0cm/100gAlを超えると気泡により機械的性質、特に破断伸びや衝撃値が低下するので好ましくない。また、後述する実用的な脱ガス処理方法では0.05cm/100gAl未満にすることは困難であって生産上好ましくない。好ましい含有水素量は0.05〜0.5cm/100gAlであり、より好ましくは0.05〜0.3cm/100gAlである。なお、凝固したアルミニウム合金の含有水素量は、真空溶融抽出法など公知の方法で測定することができる。
(Amount of contained hydrogen)
In the atmosphere, the combustion gas derived from the gas furnace, the melting furnace, the refractories forming the holding furnace, and the moisture in the other atmosphere react with Al to generate hydrogen gas, which melts into the molten aluminum alloy. The aluminum alloy contains hydrogen. Further, as described above, if the elapsed time from the addition of Na to the molten metal becomes too long, the dissolution of hydrogen into the molten metal is promoted. Aluminum alloy molten metal containing a large amount of hydrogen, hydrogen that is not completely dissolved when solidified is released as a gas, but a part of it remains in the cast member and remains as bubbles, mechanical properties, In particular, it causes elongation at break and reduction in impact value. In addition, when solution heat treatment is performed, hydrogen that is dissolved in supersaturation may reappear in the cast member as coarse bubbles. Such hydrogen content required to suppress an undesirable bubbles, aluminum alloy 100g per 0.05~1.0Cm 3 with hydrogen gas standards (hereinafter, sometimes the unit denoted as cm 3/100 gal. ). That is, if it exceeds 1.0 cm 3 /100 g Al, bubbles are not preferable because mechanical properties, particularly elongation at break and impact value are lowered. In addition, it is difficult to reduce the pressure to less than 0.05 cm 3 /100 gAl by a practical degassing method described later, which is not preferable in production. The preferred hydrogen content is 0.05 to 0.5 cm 3 /100 g Al, and more preferably 0.05 to 0.3 cm 3 /100 g Al. The hydrogen content of the solidified aluminum alloy can be measured by a known method such as a vacuum melting extraction method.

含有水素量を低減する方法のひとつは、溶湯の段階で十分に脱ガス処理(脱水素処理)を行うことである。すなわち、アルゴンガスを溶湯に吹き込む方法や、ハロゲン化合物を含むフラックスを溶湯に添加して撹拌するなどの公知の方法を用いることができる。脱ガス処理の時期は、前述したようにNa添加の前に実施することが望ましい。また、脱ガス処理後の水素ガスの再溶解を避けるために、前述したように、Na添加後の鋳造は可能な限り早期に行うことが好ましい。 One of the methods for reducing the amount of hydrogen contained is to sufficiently perform degassing treatment (dehydrogenation treatment) at the stage of molten metal. That is, a known method such as a method of blowing argon gas into the molten metal or a method of adding a flux containing a halogen compound to the molten metal and stirring the mixture can be used. It is desirable that the degassing treatment be performed before the addition of Na as described above. Further, in order to avoid re-dissolution of hydrogen gas after the degassing treatment, as described above, it is preferable that the casting after the addition of Na is performed as early as possible.

(最大の初晶Si粒子とその最大幅)
過共晶Al-Si系アルミニウム合金において、初晶Si粒子が粗大であると機械的性質、特に延性が阻害されるので好ましくない。引張応力や衝撃力に対しては、少数であっても、初晶Si粒子が粗大であるほど脆弱になる。初晶Si粒子の大きさは、切断面に観察される最大の初晶Si粒子の最大幅が1〜90μmであることが好ましい。
(Maximum primary Si particles and their maximum width)
In the hypereutectic Al-Si based aluminum alloy, if the primary crystal Si particles are coarse, mechanical properties, particularly ductility are impaired, which is not preferable. Even if the number is small, the larger the primary crystal Si particles are, the more vulnerable they are to tensile stress and impact force. Regarding the size of the primary crystal Si particles, the maximum width of the maximum primary crystal Si particles observed on the cut surface is preferably 1 to 90 μm.

ここで最大の初晶Si粒子の最大幅の定義を図面を参照しつつ説明する。図2は過共晶Al-Si系アルミニウム合金の初晶Si粒子と共晶Si粒子を示すミクロ組織の一例である。図2の視野を第1の視野とよぶことにすると、図3は第1の視野における一の初晶Si粒子1の近傍の領域X1を拡大した図である。図3において初晶Si粒子1の輪郭上の最も離間した2点間の長さW1を、初晶Si粒子1の最大幅W1と定義する。そして、第1の視野に観察される他の初晶Si粒子(例えば、図2における初晶Si粒子11)についても同様に最大幅を測定して比較して、第1の視野における最も大きな最大幅をもつものが初晶Si粒子1であるとき、第1の視野における最大の初晶Si粒子の最大幅はW1であると定義する。以下、他の任意の第2の視野、第3の視野、・・・、第Nの視野についても同様に測定し、各視野における最大の初晶Si粒子の最大幅がW2、W3、・・・、WNであった場合、W1、W2、W3、・・・、WNのうち最も大きい値を有する初晶Si粒子を最大の初晶Si粒子と定義し、その最大幅を最大の初晶Si粒子の最大幅Wpと定義する。観察する倍率にもよるが、視野数Nは多い方がWpの値はより確からしくなるので好ましい。視野数Nは3以上が好ましく、より好ましくは5以上である。 Here, the definition of the maximum width of the maximum primary Si particles will be described with reference to the drawings. FIG. 2 is an example of a microstructure showing primary crystal Si particles and eutectic Si particles of a hypereutectic Al—Si based aluminum alloy. When the field of view of FIG. 2 is called a first field of view, FIG. 3 is an enlarged view of a region X1 in the vicinity of one primary crystal Si particle 1 in the first field of view. In FIG. 3, the length W1 between the two points on the contour of the primary crystal Si particle 1 that are most distant from each other is defined as the maximum width W1 of the primary crystal Si particle 1. Then, the maximum widths of the other primary crystal Si particles (for example, the primary crystal Si particles 11 in FIG. 2) observed in the first visual field are similarly measured and compared, and the largest maximum width in the first visual field is measured. When it is the primary Si particles 1 that have a large degree, the maximum width of the maximum primary Si particles in the first field of view is defined as W1. Hereinafter, other arbitrary second visual field, third visual field,..., Nth visual field are similarly measured, and the maximum width of the maximum primary crystal Si particles in each visual field is W2, W3,... ., WN, the primary crystal Si particles having the largest value among W1, W2, W3,..., WN are defined as the maximum primary crystal Si particles, and the maximum width thereof is the maximum primary crystal Si. It is defined as the maximum width Wp of the particles. Although it depends on the magnification of observation, it is preferable that the number N of visual fields is large because the value of Wp becomes more accurate. The visual field number N is preferably 3 or more, and more preferably 5 or more.

(共晶Si粒子同士の平均距離)
Al−Si系アルミニウム合金の機械的性質は共晶Si粒子の大きさと分布によっても大きく左右される。共晶Si粒子が微細かつ密に分散しているほど強度および延性、靭性が大きくなるので好ましい。ここで、共晶Si粒子とは粒子状の形態のみをいうのではなく、円形状、楕円形状、板状、棒状、樹枝状、その他の形態も含む。
(Average distance between eutectic Si particles)
The mechanical properties of Al-Si-based aluminum alloys are also greatly influenced by the size and distribution of eutectic Si particles. It is preferable that the eutectic Si particles are finely and densely dispersed because the strength, the ductility, and the toughness increase. Here, the eutectic Si particles are not limited to a particulate form, but include a circular form, an elliptical form, a plate form, a rod form, a dendrite form, and other forms.

共晶Si粒子が微細かつ密に分散している状態は、例えば共晶Si粒子同士の平均距離で表すことができる。ここで、共晶Si粒子同士の距離とは、切断面に観察される一の共晶Si粒子の輪郭と、該共晶Si粒子の近傍にある他の共晶Si粒子の輪郭との間の距離である。次に、切断面に観察される共晶Si粒子同士の平均距離の測定方法を、図面を参照しつつ説明する。図4は図2に示す領域X2を拡大したものであり、共晶Si粒子同士の距離の測定方法を説明する図である。まず、予め長さを定めた任意の線分3を複数の共晶Siを横切るように引く。図4の例では組織写真上で50μmに相当する長さの線分3としている。この線分3と、線分3が横切る3つの共晶Si粒子21、22、23の輪郭との交点をs1、s2、・・・、s6とするとき、s2とs3との距離d1を共晶Si粒子21と22との距離とし、s4とs5との距離d2を共晶Si粒子22と23との距離として測定する。以下、このようにして線分3を複数引いて共晶Si粒子同士の距離を測定し、これらの平均値を共晶Si粒子同士の平均距離と定義する。なお、線分3の長さは共晶Si粒子を3個以上横切る長さとすることが好ましく、より好ましくは5個以上とする。また線分3は3本以上引いて測定することが好ましく、また線分の方向も観察面上において縦、横、斜めの任意の方向で引くことが好ましい。さらに、1視野だけでなく複数の視野において測定し、それらの平均値を採用することがより確からしい値を得ることができて好ましい。測定する際の倍率は、観察される共晶Si粒子の大きさや分布に応じて任意に設定してよい。また、光学顕微鏡では解像度が不足する場合は、SEM(走査型電子顕微鏡)など、より高倍率の顕微鏡で観察すれば、より正確な値を得ることができる。 The state in which the eutectic Si particles are finely and densely dispersed can be represented by, for example, the average distance between the eutectic Si particles. Here, the distance between the eutectic Si particles means the distance between the contour of one eutectic Si particle observed on the cut surface and the contour of another eutectic Si particle in the vicinity of the eutectic Si particle. It is a distance. Next, a method for measuring the average distance between the eutectic Si particles observed on the cut surface will be described with reference to the drawings. FIG. 4 is an enlarged view of the region X2 shown in FIG. 2 and is a diagram illustrating a method for measuring the distance between the eutectic Si particles. First, an arbitrary line segment 3 having a predetermined length is drawn so as to cross a plurality of eutectic Si. In the example of FIG. 4, the line segment 3 has a length corresponding to 50 μm on the structure photograph. When the intersections of this line segment 3 and the contours of the three eutectic Si particles 21, 22, 23 that line segment 3 crosses are s1, s2,..., S6, the distance d1 between s2 and s3 is The distance between the crystal Si particles 21 and 22 is measured, and the distance d2 between s4 and s5 is measured as the distance between the eutectic Si particles 22 and 23. Hereinafter, a plurality of line segments 3 are drawn in this way to measure the distance between the eutectic Si particles, and the average value of these is defined as the average distance between the eutectic Si particles. The length of the line segment 3 is preferably a length that crosses three or more eutectic Si particles, and more preferably five or more. In addition, it is preferable to draw three or more line segments 3 for measurement, and it is also preferable to draw the line segment in any of vertical, horizontal, and diagonal directions on the observation surface. Furthermore, it is preferable to measure not only in one visual field but in a plurality of visual fields, and to use the average value thereof, because a more probable value can be obtained. The magnification at the time of measurement may be arbitrarily set depending on the size and distribution of the observed eutectic Si particles. Further, when the resolution is insufficient with the optical microscope, more accurate value can be obtained by observing with a microscope having a higher magnification such as SEM (scanning electron microscope).

共晶Si粒子同士の平均距離は、5μmを超えると破断伸びが低下するので好ましくない。従って共晶Si粒子同士の平均距離は0μmを超え5μm以下とする。ここで、共晶Si粒子同士の平均距離が0μm、すなわち切断面に観察される共晶Si粒子の全てが周囲の共晶Si粒子と互いに隣接し合う形態は、金属学的にあり得ないので除外される。 If the average distance between the eutectic Si particles exceeds 5 μm, the elongation at break decreases, which is not preferable. Therefore, the average distance between the eutectic Si particles is more than 0 μm and 5 μm or less. Here, the average distance between the eutectic Si particles is 0 μm, that is, a form in which all of the eutectic Si particles observed on the cut surface are adjacent to the surrounding eutectic Si particles is metallurgically impossible. Excluded.

なお、この測定方法によれば、共晶Si粒子の平均粒径も定義することができる。すなわち図4において、s1とs2との距離を共晶Si粒子21の粒径、s3とs4との距離を共晶Si粒子22の粒径、s5とs6との距離を共晶Si粒子23の粒径、と定義しこれらの平均値を共晶Si粒子の平均粒径として算出できる。もちろん、上述した共晶Si同士の平均距離の算出方法と同様に、線分3を複数、好ましくは任意の方向で引いて測定し、またこれを複数の視野で行った平均値を採用すれば、より確からしい値が得ることができる。 According to this measuring method, the average particle size of the eutectic Si particles can also be defined. That is, in FIG. 4, the distance between s1 and s2 is the particle diameter of the eutectic Si particles 21, the distance between s3 and s4 is the particle diameter of the eutectic Si particles 22, and the distance between s5 and s6 is the eutectic Si particles 23. The grain size is defined as, and the average value of these is calculated as the average grain size of the eutectic Si particles. Of course, similar to the method of calculating the average distance between the eutectic Si described above, if a plurality of line segments 3 are drawn, preferably in an arbitrary direction, measurement is performed, and an average value obtained by performing this in a plurality of visual fields is adopted. , You can get more probable value.

(気泡の数)
切断面に観察される円相当径で20μm以上気泡の数が1個/mmを超えると、機械的性質、特に破断伸びと衝撃値が低下するので好ましくない。従って、切断面に観察される円相当径で20μm以上の気泡の数が1個/mm以下であることが好ましい。なお、円相当径で20μm以上の気泡が観察されない場合の気泡の数は0個/mmとして測定される。図5は円相当径で20μm以上の気泡4が観察された視野の一例を示すミクロ組織写真である。
(Number of bubbles)
When the number of bubbles of 20 μm or more in the equivalent circle diameter observed on the cut surface exceeds 1/mm 2 , the mechanical properties, particularly the elongation at break and the impact value decrease, which is not preferable. Therefore, it is preferable that the number of bubbles having a circle-equivalent diameter of 20 μm or more observed on the cut surface is 1/mm 2 or less. The number of bubbles is measured as 0/mm 2 when bubbles having a circle equivalent diameter of 20 μm or more are not observed. FIG. 5 is a microstructure photograph showing an example of a visual field in which bubbles 4 having a circle equivalent diameter of 20 μm or more are observed.

気泡の数の測定方法は、切断面の1視野に観察される円相当径20μm以上の気泡の数を測定する方法とし、この方法で任意の5視野について測定した値の平均値とする。気泡の大きさは画像解析装置等を用いて計測できる。なお、鋳造部材の空洞欠陥の種類には気泡の他に引け巣もある。ただし、引け巣の内面にはデンドライトの凹凸が観察されるのに対して、気泡の内面にはデンドライトの凹凸は観察されないので、これらは容易に識別し、区別できる。 The method for measuring the number of bubbles is to measure the number of bubbles having an equivalent circle diameter of 20 μm or more observed in one visual field of the cut surface, and use the average value of the values measured in any five visual fields by this method. The size of bubbles can be measured using an image analysis device or the like. In addition to air bubbles, there are shrinkage cavities as types of cavity defects in the cast member. However, since the concavity and convexity of the dendrites are observed on the inner surface of the shrinkage cavity, the concavity and convexity of the dendrites are not observed on the inner surface of the bubbles, and therefore these can be easily identified and distinguished.

(破断伸び)
引張試験における破断伸び(以下、伸びともいう。)は5%以上であることが好ましい。伸びが5%以上であれば、例えば自動車用部品として必要な延性が確保される。好ましくは7%以上、より好ましくは10%以上、さらに好ましくは12%以上である。伸びを高める方法として、溶体化処理を施すT4熱処理、時効処理のみを施すT5熱処理、溶体化処理と時効処理とを組み合わせるT6熱処理、またはT6熱処理において過時効処理を施すT7熱処理など、各種熱処理を実施することができる。ただし、破断伸びは強度、例えば後述する0.2%耐力と背反する性質があるので、破断伸びを25%超とすると0.2%耐力が不足するので好ましくない。従って破断伸びは25%以下、好ましくは20%以下である。
(Elongation at break)
The breaking elongation (hereinafter also referred to as elongation) in the tensile test is preferably 5% or more. When the elongation is 5% or more, the ductility required for automobile parts is ensured. It is preferably at least 7%, more preferably at least 10%, further preferably at least 12%. As a method for increasing elongation, various heat treatments such as T4 heat treatment for solution treatment, T5 heat treatment for aging treatment only, T6 heat treatment for combining solution treatment and aging treatment, or T7 heat treatment for overaging treatment in T6 heat treatment are performed. It can be carried out. However, since the elongation at break has a property that is contrary to the strength, for example, 0.2% proof stress described later, if the breaking elongation exceeds 25%, the 0.2% proof stress becomes insufficient, which is not preferable. Therefore, the elongation at break is 25% or less, preferably 20% or less.

(シャルピー衝撃値)
衝撃値は、無ノッチの試験片におけるシャルピー衝撃試験で15J/cm以上であることが好ましい。この値に満たない場合は例えば自動車用足回り部品には採用され難い。また、自動車用ロードホイールに適用するためには20J/cm以上が好ましく、より好ましくは25J/cm以上である。シャルピー衝撃値(以下、衝撃値ともいう。)を高める方法として、溶体化処理を施すT4熱処理、時効処理のみを施すT5熱処理、溶体化処理と時効処理とを組み合わせるT6熱処理、または溶体化処理と過時効処理とを組み合わせるT7熱処理などを実施してもよい。
(Charpy impact value)
The impact value is preferably 15 J/cm 2 or more in the Charpy impact test on the unnotched test piece. If the value is less than this value, it is difficult to use it as an underbody part for automobiles, for example. Further, in order to be applied to a road wheel for automobiles, it is preferably 20 J/cm 2 or more, more preferably 25 J/cm 2 or more. As a method of increasing the Charpy impact value (hereinafter, also referred to as an impact value), T4 heat treatment for performing solution treatment, T5 heat treatment for performing only aging treatment, T6 heat treatment for combining solution treatment and aging treatment, or solution treatment You may implement T7 heat processing etc. which combine with overaging treatment.

(0.2%耐力)
強度の指標として、引張試験における0.2%耐力(以下、耐力ともいう。)は100MPa以上であることが好ましい。100MPaに満たない場合は、特に自動車用の鋳造部材として必要な強度を確保しにくいため好ましくない。特に自動車用足回り部品に採用されるためには、耐力は120MPa以上であることが好ましく、自動車用ロードホイールに採用されるためには160MPa以上がより好ましく、さらにより好ましくは180MPa以上である。耐力を高める方法として、溶体化処理を施すT4熱処理、時効処理のみを施すT5熱処理、溶体化処理と時効処理とを組み合わせるT6熱処理、またはT6熱処理において過時効処理を施すT7熱処理など、各種熱処理を実施することができる。ただし、0.2%耐力は前述したように破断伸びと背反する性質があるので、0.2%耐力を300MPa超とすると破断伸びが不足するので好ましくない。従って0.2%耐力は300MPa以下、好ましくは280MPa以下である。
(0.2% proof stress)
As an index of strength, 0.2% proof stress (hereinafter, also referred to as proof stress) in a tensile test is preferably 100 MPa or more. If it is less than 100 MPa, it is difficult to secure the strength required as a cast member for automobiles in particular, which is not preferable. In particular, the proof stress is preferably 120 MPa or more in order to be adopted in the undercarriage parts for automobiles, more preferably 160 MPa or more, still more preferably 180 MPa or more in order to be adopted in the road wheels for automobiles. As a method for increasing the yield strength, various heat treatments such as T4 heat treatment for solution treatment, T5 heat treatment for aging treatment only, T6 heat treatment for combining solution treatment and aging treatment, or T7 heat treatment for overaging treatment in T6 heat treatment are performed. It can be carried out. However, since 0.2% proof stress has a property contrary to the elongation at break as described above, if the 0.2% proof stress exceeds 300 MPa, the elongation at break becomes insufficient, which is not preferable. Therefore, the 0.2% proof stress is 300 MPa or less, preferably 280 MPa or less.

(鋳造部材)
本発明の鋳造部材は、重力鋳造法、低圧鋳造法、高圧鋳造法、ダイカスト鋳造法等の公知の鋳造法により製造したものであり、特に今後さらなる薄肉軽量化が要求される車両等の構成部品に好適である。例えば自動車や自動二輪車のロードホイール、シャシ部材、パワートレイン部材(スペースフレーム、ステアリングホイールの芯金、シートフレーム、サスペンションメンバー、エンジンブロック、シリンダヘッドカバー、チェーンケース、ミッションケース、オイルパン、プーリ、シフトレバー、インスツルメントパネル、吸気用サージタンク、ペダルブラケット等)等に使用するのに適している。
(Casting member)
The cast member of the present invention is manufactured by a known casting method such as a gravity casting method, a low pressure casting method, a high pressure casting method, and a die casting method. Suitable for For example, road wheels of automobiles and motorcycles, chassis members, power train members (space frames, cores of steering wheels, seat frames, suspension members, engine blocks, cylinder head covers, chain cases, mission cases, oil pans, pulleys, shift levers) , Instrument panels, intake surge tanks, pedal brackets, etc.).

(冷却速度)
鋳造にあたっては溶湯の冷却速度を大きくすることが好ましい。冷却速度が大きいほど、初晶Si粒子は小さく、また共晶Si粒子も緻密になるので、強度および延性をより高めることができる。特に初晶Siが晶出し始める温度から共晶温度までの温度範囲の冷却速度を大きくすることが好ましく、例えば600℃から580℃までの冷却速度を15℃/s以上とすることが好ましい。冷却速度を大きくする手段としては、鋳造部材の形状を薄肉にする、鋳型を冷却する、鋳型と溶湯との密着度を高めて鋳型への抜熱を促進する等の方法を適用することができる。
(Cooling rate)
In casting, it is preferable to increase the cooling rate of the molten metal. The higher the cooling rate, the smaller the primary crystal Si particles and the denser the eutectic Si particles, so that the strength and ductility can be further increased. In particular, it is preferable to increase the cooling rate in the temperature range from the temperature at which the primary crystal Si begins to crystallize to the eutectic temperature, and for example, the cooling rate from 600° C. to 580° C. is preferably 15° C./s or more. As a means for increasing the cooling rate, methods such as thinning the shape of the casting member, cooling the mold, and enhancing the adhesion between the mold and the molten metal to promote heat removal to the mold can be applied. ..

[実施例]
次に、本発明の実施例を図および表を参照しつつさらに詳細に説明する。なお、本発明はこれらに限定されるものではない。
[Example]
Next, embodiments of the present invention will be described in more detail with reference to the drawings and tables. The present invention is not limited to these.

(溶解)
後述する各実施例の溶解工程は共通の方法とした。すなわち、原料として工業用の純Al、純Si、純Mgおよび必要に応じて含有させる金属元素を含むAl母合金を黒鉛製るつぼに装入し、るつぼの外側から電気ヒータで加熱する方式の電気炉を用いて大気中で溶解して溶湯を得た。溶解温度は表2におけるP添加の溶湯温度に示す値とした。また、溶解量は各実施例とも35〜40kgの範囲とした。
(Dissolution)
The dissolution process in each of the examples described below was a common method. In other words, an industrial method in which pure Al, pure Si, pure Mg for industrial use as a raw material, and an Al mother alloy containing a metal element to be contained as necessary are charged into a graphite crucible and heated by an electric heater from the outside of the crucible. A molten metal was obtained by melting in the atmosphere using a furnace. The melting temperature was the value shown in Table 2 for the temperature of the molten metal with P added. In addition, the amount of dissolution was set in the range of 35 to 40 kg in each example.

(Pの添加)
添加するPの形態として粉末状の赤リンを用いた。溶湯1kgあたり0.75gの赤リンをアルミニウム箔に包んだ状態で、フォスフォライザを用いて溶湯中に浸漬することにより添加した。P添加時の溶湯温度は表2に示す値とした。
(Addition of P)
Powdered red phosphorus was used as the form of P to be added. 0.75 g of red phosphorus per 1 kg of molten metal was added by being immersed in the molten metal using a phosphorizer in a state of being wrapped in aluminum foil. The temperature of the molten metal when P was added was the value shown in Table 2.

(脱ガス処理)
Pを添加して0.5h後に、フラックス(商品名N408H、日本金属化学(株)製)処理を行って溶湯の清浄度を高める操作を行い、次いでArガスを溶湯中に吹き込むバブリング操作で脱ガス処理を行った。溶湯中の水素量は、プロトン導電性セラミックスセンサーによる方法(TYK社製、NOTORP KYHS−A2型)で計測し、0.15cm/100gAl以下となるまで脱ガス処理を行った。脱ガス処理に要する時間も含めて、P添加からNa添加までの溶湯保持時間は表2のP添加の保持時間に示す値とした。
(Degassing treatment)
After 0.5 hours from the addition of P, a flux (trade name N408H, manufactured by Nippon Metal Chemical Co., Ltd.) treatment is performed to increase the cleanliness of the molten metal, and then degassing is performed by bubbling operation in which Ar gas is blown into the molten metal. Gas treatment was performed. The amount of hydrogen in the molten metal was measured by a method using a proton conductive ceramics sensor (manufactured by TYK, NOTORP KYHS-A2 type), and degassed until 0.15 cm 3 /100 g Al or less. The molten metal holding time from P addition to Na addition, including the time required for the degassing treatment, was the value shown in Table 2 for the P addition holding time.

(Naの添加)
脱ガス処理の後にNaを添加した。Naはアルミニウム缶に封入された金属Na(商品名ナバック、フォセコ社製、以下缶入りNaともいう。)を用いた。添加量は缶入りNa(1個あたりのNa量が25g)をアルミニウム箔で包み、これを2個、フォスフォライザを用いて溶湯中に浸漬することにより添加した。Na添加時の溶湯温度およびNa添加後から注湯までの保持時間は表2に示す条件とした。鋳造直前における各実施例の溶湯の合金成分は表1に示す値であった。なお、合金成分の分析には固体発光分光分析装置(ThermoScientific社製)を使用した。
(Addition of Na)
Na was added after degassing. As Na, a metal Na (trade name: Nabac, manufactured by Foseco Co., Ltd., hereinafter also referred to as Na in a can) enclosed in an aluminum can was used. The addition amount was such that Na in a can (the amount of Na per piece was 25 g) was wrapped in aluminum foil, and two pieces of this were added by immersing them in a molten metal using a phosphorizer. The molten metal temperature when Na was added and the holding time from the addition of Na to the pouring were the conditions shown in Table 2. The alloy composition of the molten metal of each example immediately before casting had the values shown in Table 1. A solid-state emission spectroscopic analyzer (Thermo Scientific) was used to analyze the alloy components.

(鋳型)
以上の工程で得られた溶湯を鋳造する鋳型は、大別して2つの種類を使用した。図6は第1の種類の鋳型の概略図であり、図6(a)は正面、図6(b)は側面の概略図である。第1の種類の鋳型(以下、舟型ともいう。)は、上側の幅w1と下側の幅w2の寸法と、鋳鉄製または銅製の異なる鋳型材料を組み合わせた、さらに3種類の舟型を用いた。幅w1および幅w2の寸法と鋳型材料との組み合わせを示した舟型の仕様を表1に示す。舟型Aはw1=33mm、w2=23mmの鋳鉄製、舟型B1はw1=33mm、w2=23mmの純銅製、舟型B2はw1=28mm、w2=18mmの純銅製、舟型B3はw1=20mm、w2=10mmの純銅製とした。
(template)
The molds for casting the molten metal obtained in the above steps were roughly classified into two types. 6A and 6B are schematic views of the first type of mold, FIG. 6A is a front view, and FIG. 6B is a side view. The first type of mold (hereinafter, also referred to as a boat type) has three types of boat types in which dimensions of an upper width w1 and a lower width w2 and different mold materials made of cast iron or copper are combined. Using. Table 1 shows the boat-shaped specifications showing the combinations of the width w1 and width w2 dimensions and the mold material. The boat type A is made of cast iron with w1=33 mm and w2=23 mm, the boat type B1 is made of pure copper with w1=33 mm and w2=23 mm, the boat type B2 is made of pure copper with w1=28 mm and w2=18 mm, and the boat type B3 is w1. =20 mm and w2=10 mm made of pure copper.

図8は第2の種類の鋳型の概略図であり、図8(a)は正面、図8(b)は側面の概略図である。第2の種類の鋳型(以下、金型Cともいう。)は図8(b)中のPLで示される鉛直方向の縦見切りの鋳型である。材質は純銅とし、上記した舟型の仕様と併せて表1に示す。 FIG. 8 is a schematic view of the second type of mold, FIG. 8(a) is a front view, and FIG. 8(b) is a side view. The second type of mold (hereinafter, also referred to as a mold C) is a vertical parting mold in the vertical direction indicated by PL in FIG. 8B. The material is pure copper and is shown in Table 1 together with the above-mentioned boat type specifications.

(鋳造部材)
第1の種類の鋳型(舟型)および第2の種類の鋳型(金型C)に溶湯を重力鋳造して鋳造部材を作製した。図7は第1の種類の鋳型に鋳造された鋳造部材の形状と各種試験片を採取する位置を示す概略図であり、図7(a)は正面、図7(b)は側面の概略形状である。また、図9は第2の種類の鋳型に鋳造された鋳造部材と各種試験片を採取する位置を示す概略図であり、図9(a)は正面、図9(b)は側面の概略形状である。以下、舟型Aに鋳造された鋳造部材を部材Aとよぶ。また、舟型B1、B2、B3に鋳造された鋳造部材をそれぞれ部材B1、B2、B3とよび、これらを舟型材と総称する。また金型Cに鋳造された鋳造部材を部材Cとよぶ。以上の鋳造部材の名称を前述した鋳型の名称と併せて表1に示す。また、各実施例における注湯温度と注湯した鋳型を表2に示す。
(Casting member)
A molten metal was gravity-cast into a first type mold (boat type) and a second type mold (die C) to produce a cast member. FIG. 7 is a schematic view showing the shape of a casting member cast in a first type of mold and the position for collecting various test pieces. FIG. 7(a) is a front view, and FIG. 7(b) is a schematic side view. Is. Further, FIG. 9 is a schematic view showing a casting member cast in a second type of mold and a position for collecting various test pieces. FIG. 9A is a front view, and FIG. 9B is a side view. Is. Hereinafter, the cast member cast into the boat shape A is referred to as a member A. Further, the cast members cast into the boat shapes B1, B2, B3 are referred to as members B1, B2, B3, respectively, and are collectively referred to as boat-shaped members. Further, a cast member cast in the mold C is referred to as a member C. The names of the above cast members are shown in Table 1 together with the names of the above-mentioned casting members. Table 2 shows the pouring temperature and the casting mold in each example.

(含有水素量の測定)
溶湯が凝固した後の含有水素量の測定は、真空溶融抽出法によるガス量測定装置((株)共立製)を用いて測定した。
(Measurement of hydrogen content)
The amount of hydrogen contained after the molten metal was solidified was measured using a gas amount measuring device by vacuum melting extraction method (manufactured by Kyoritsu Co., Ltd.).

(冷却速度の測定方法)
舟型、および金型Cへの溶湯の鋳造にあたっては熱電対を挿入して、凝固過程における溶湯の温度を測定した。各鋳造部材における熱電対の位置TCを図7および図9に示す。舟型材においては略中央部であって底面BLを基準として10mmの高さ位置、部材Cにおいてはφ13mmの略丸棒形状の部位Y2の略中央であって底面BLを基準として6.5mmの位置とした。また、図11は溶湯の冷却曲線から冷却速度を算出する方法を説明する図である。冷却速度は、測定された冷却曲線5において鋳込み後に溶湯が600℃に到達してから580℃まで低下するまで区間の冷却速度とした。すなわち600℃と580℃の温度差Δθ(=20℃)を、600℃到達から580℃到達までの経過時間Δt(s)で除したΔθ/Δt(℃/s)として求めた。各実施例の冷却速度の測定結果は表2に示す。
(Measuring method of cooling rate)
When casting the molten metal into the boat shape and the mold C, a thermocouple was inserted to measure the temperature of the molten metal during the solidification process. The position TC of the thermocouple in each cast member is shown in FIGS. 7 and 9. In the boat-shaped material, it is at a substantially central portion and at a height position of 10 mm with reference to the bottom surface BL, and with member C, at a substantially center of a substantially round bar-shaped portion Y2 having a diameter of 13 mm and at a position of 6.5 mm with respect to the bottom surface BL. And Further, FIG. 11 is a diagram illustrating a method of calculating the cooling rate from the cooling curve of the molten metal. The cooling rate was the cooling rate of the section in the measured cooling curve 5 from when the molten metal reached 600°C after casting to when it decreased to 580°C. That is, the temperature difference Δθ (=20° C.) between 600° C. and 580° C. was calculated as Δθ/Δt (° C./s) divided by the elapsed time Δt(s) from reaching 600° C. to reaching 580° C. The measurement results of the cooling rate of each example are shown in Table 2.

(熱処理)
舟型材および部材Cは、大気雰囲気中でT6熱処理を行った。T6熱処理の溶体化処理温度と時間、および時効処理温度と時間は表2に示す条件とした。
(Heat treatment)
The boat shape member and the member C were subjected to T6 heat treatment in the air atmosphere. The solution treatment temperature and time of the T6 heat treatment and the aging treatment temperature and time were set to the conditions shown in Table 2.

(機械的性質の評価方法)
図7および図9に示すこれらの鋳造部材から以下の所定の形状の試験片を採取し、機械的性質として、ヤング率、シャルピー衝撃値、引張試験による0.2%耐力と破断伸びを評価した。試験片の採取部位は網掛けで示す領域とした。すなわち舟型材からは図7における底面BLを基準として5mmから20mmまでの高さの部位Y1から採取し、部材Cでは図9におけるφ13mmの略丸棒形状の部位Y2から採取した。
(Mechanical property evaluation method)
From these cast members shown in FIGS. 7 and 9, test pieces having the following predetermined shapes were sampled, and as mechanical properties, Young's modulus, Charpy impact value, 0.2% proof stress by tensile test and elongation at break were evaluated. .. The sampling site of the test piece was a shaded area. That is, from the boat-shaped material, it was sampled from the site Y1 having a height of 5 mm to 20 mm with reference to the bottom surface BL in FIG. 7, and the member C was sampled from the site Y2 having a substantially round bar shape of 13 mm in FIG.

ヤング率は幅10mm×長さ80mm×厚さ4mmの試験片とし、自由共振式弾性率測定装置(型式JE2−RT、日本テクノプラス製)を用いて測定した。シャルピー衝撃値は幅10mm×長さ55mm×厚さ3mmのノッチ無しの試験片を、シャルピー衝撃試験機(藤井精機製、50J)を用いて、室温において衝撃速度3.4m/sで行った。図10は引張試験片の概略形状である。図10(a)は上面図であり、全長を80mm、全幅を10mm、平行部の長さを32mm、平行部の幅を6.5mmとした。図10(b)は側面図であり、厚さは4mmとした。引張試験は万能試験機(インストロン社製、50kN)を用いて、標点距離25mmとし、室温において2mm/min.のクロスヘッドスピードで行った。 The Young's modulus was a test piece having a width of 10 mm, a length of 80 mm, and a thickness of 4 mm, and was measured using a free resonance type elastic modulus measuring device (model JE2-RT, manufactured by Nippon Technoplus). For the Charpy impact value, a notched test piece having a width of 10 mm, a length of 55 mm and a thickness of 3 mm was used at room temperature at an impact speed of 3.4 m/s using a Charpy impact tester (manufactured by Fujii Seiki Co., Ltd., 50J). FIG. 10 is a schematic shape of a tensile test piece. FIG. 10A is a top view, where the total length is 80 mm, the total width is 10 mm, the parallel portion length is 32 mm, and the parallel portion width is 6.5 mm. FIG. 10B is a side view, and the thickness is 4 mm. In the tensile test, a universal tester (manufactured by Instron Co., Ltd., 50 kN) was used, the gauge length was set to 25 mm, and the room temperature was 2 mm/min. I went at crosshead speed.

(ミクロ組織観察)
また、舟型材および部材Cのミクロ組織観察を行った。舟型材は図7において底部位置BLから10mmの位置の面、部材Cは図7において底部BLから5mmの位置の面が観察面となるように小片を採取して樹脂に埋め込み、SiC研磨紙にて粗研磨後、ダイヤモンドペーストを用いて鏡面研磨してミクロ組織観察用試料を調製した。観察は光学顕微鏡(倒立型金属顕微鏡、オリンパス製)を用い、必要に応じて走査型電子顕微鏡(型番SU70、日立ハイテクノロジーズ製)を用いて行った。また、円相当径などのミクロ組織の定量測定には、必要に応じて画像解析装置(商品名「A像くん」、旭化成エンジニアリング製)を使用して行った。最大の共晶Si粒子の最大幅、共晶Si粒子同士の平均距離、および気泡の数は任意の5視野で測定した。特に共晶Si粒子同士の平均距離の算出にあたっては十分に計測できる倍率(例えば1000倍)で観察し、図4で説明した線分3は、少なくとも3個以上の共晶Si粒子を横切る長さで縦、横、斜めに合計5本引いて計測した。
(Microstructure observation)
Further, the microstructure of the boat-shaped material and the member C was observed. The boat-shaped material is a surface 10 mm from the bottom position BL in FIG. 7, and the member C is a small piece that is embedded in resin so that the surface 5 mm from the bottom BL in FIG. After rough polishing, mirror polishing was performed using diamond paste to prepare a sample for microstructure observation. The observation was performed using an optical microscope (inverted metal microscope, made by Olympus) and, if necessary, a scanning electron microscope (model SU70, made by Hitachi High Technologies). In addition, an image analyzer (trade name “A image-kun”, manufactured by Asahi Kasei Engineering Co., Ltd.) was used for the quantitative measurement of the microstructure such as the equivalent circle diameter, if necessary. The maximum width of the maximum eutectic Si particles, the average distance between the eutectic Si particles, and the number of bubbles were measured in any 5 visual fields. In particular, in calculating the average distance between the eutectic Si particles, observation is performed at a sufficiently measurable magnification (for example, 1000 times), and the line segment 3 described in FIG. 4 is a length across at least three eutectic Si particles. In total, 5 pieces were drawn vertically, horizontally, and diagonally for measurement.

表2に本発明の実施例1〜10の合金成分の組成と含有水素量、ミクロ組織および製造条件および機械的性質を示す。 Table 2 shows the composition, hydrogen content, microstructure, manufacturing conditions and mechanical properties of the alloy components of Examples 1 to 10 of the present invention.

(実施例1)
実施例1はSi=12.9%、Mg=0.33%、Ti=0.13%、P=0.0036%(36ppm)、Na=0.0247%(247ppm)、Alおよび不可避的不純物からなり、含有水素量=0.17cm/100gAlであって、Pの添加条件は溶湯温度700℃、保持時間60min.、Naの添加条件は溶湯温度700℃、保持時間は30min.以下、注湯温度は670℃で舟型Aに冷却速度22℃/sで注湯された部材Aである。最大の初晶Si粒子の最大幅は60μm、共晶Si同士の平均距離は3.6μm、円相当径20μm以上の気泡の数は観察されない、すなわち0個/mmであった。また、溶体化処理540℃×4.0h、時効処理180℃×0.3hのT6熱処理で、0.2%耐力は194MPa、破断伸びは12.4%、シャルピー衝撃値は36J/cmであった。図1は実施例1のミクロ組織写真である。
(Example 1)
Example 1 has Si=12.9%, Mg=0.33%, Ti=0.13%, P=0.0036% (36 ppm), Na=0.0247% (247 ppm), Al and inevitable impurities. The hydrogen content was 0.17 cm 3 /100 g Al, and the P addition conditions were as follows: melt temperature 700° C., holding time 60 min. , Na was added at a molten metal temperature of 700° C. for a holding time of 30 min. Hereinafter, the pouring temperature is 670° C. and the member A is poured into the boat A at a cooling rate of 22° C./s. The maximum width of the maximum primary crystal Si particles was 60 μm, the average distance between the eutectic Si particles was 3.6 μm, and the number of bubbles having a circle equivalent diameter of 20 μm or more was not observed, that is, 0/mm 2 . Also, T6 heat treatment of solution treatment 540° C.×4.0 h, aging treatment 180° C.×0.3 h, 0.2% yield strength 194 MPa, elongation at break 12.4%, Charpy impact value 36 J/cm 2 . there were. FIG. 1 is a microstructure photograph of Example 1.

(実施例2)
実施例2は冷却速度が18℃/s、時効処理が150℃×0.5hであった以外は実施例1と同様の条件で製造した部材Aである。最大の初晶Si粒子の最大幅は48μm、共晶Si同士の平均距離は3.7μm、円相当径20μm以上の気泡の数は観察されない、すなわち0個/mmであった。また、0.2%耐力は139MPa、破断伸びは12.0%、シャルピー衝撃値は23J/cmであった。
(Example 2)
Example 2 is a member A manufactured under the same conditions as in Example 1 except that the cooling rate was 18° C./s and the aging treatment was 150° C.×0.5 h. The maximum width of the maximum primary crystal Si particles was 48 μm, the average distance between the eutectic Si particles was 3.7 μm, and the number of bubbles having an equivalent circle diameter of 20 μm or more was not observed, that is, 0/mm 2 . The 0.2% proof stress was 139 MPa, the elongation at break was 12.0%, and the Charpy impact value was 23 J/cm 2 .

(実施例3)
実施例3は冷却速度が22℃/s、時効処理が150℃×0hであった以外は、実施例2と同様の条件で製造した部材Aである。ここで時効処理の時間が0hとは、時効温度到達直後に放冷したことを表す。実施例3の最大の初晶Si粒子の最大幅は62μm、共晶Si同士の平均距離は3.4μm、円相当径20μm以上の気泡の数は観察されない、すなわち0個/mmであった。また、0.2%耐力は129MPa、破断伸びは15.0%、シャルピー衝撃値は20J/cmであった。
(Example 3)
Example 3 is a member A manufactured under the same conditions as in Example 2 except that the cooling rate was 22° C./s and the aging treatment was 150° C.×0 h. Here, the time of the aging treatment being 0 h means that the aging treatment was allowed to cool immediately after reaching the aging temperature. In Example 3, the maximum width of primary crystal Si particles was 62 μm, the average distance between eutectic Si particles was 3.4 μm, and the number of bubbles having a circle equivalent diameter of 20 μm or more was not observed, that is, 0/mm 2 . .. The 0.2% proof stress was 129 MPa, the elongation at break was 15.0%, and the Charpy impact value was 20 J/cm 2 .

(実施例4)
実施例4は金型Cに鋳造され、冷却速度が45℃/s、時効処理時間が0.5hであった以外は実施例1と同様の条件で製造した部材Cである。最大の初晶Si粒子の最大幅は8μm、共晶Si同士の平均距離は0.3μm、円相当径20μm以上の気泡の数は観察されない、すなわち0個/mmであった。また、0.2%耐力は246MPa、破断伸びは13.1%、シャルピー衝撃値は45J/cmであった。
(Example 4)
Example 4 is a member C cast in a mold C and manufactured under the same conditions as in Example 1 except that the cooling rate was 45° C./s and the aging treatment time was 0.5 h. The maximum width of the maximum primary crystal Si particles was 8 μm, the average distance between the eutectic Si particles was 0.3 μm, and the number of bubbles having a circle equivalent diameter of 20 μm or more was not observed, that is, 0/mm 2 . The 0.2% proof stress was 246 MPa, the elongation at break was 13.1%, and the Charpy impact value was 45 J/cm 2 .

(実施例5)
実施例5はSi=14.0%、Mg=0.32%、Ti=0.14%、P=0.0020%(20ppm)、Na=0.0320%(320ppm)、Alおよび不可避的不純物からなり、含有水素量=0.21cm/100gAlであって、冷却速度20℃/sで注湯された以外は実施例1と同様の条件で製造した部材Aである。最大の初晶Si粒子の最大幅は90μm、共晶Si同士の平均距離は2.9μm、円相当径20μm以上の気泡の数は観察されない、すなわち0個/mmであった。また、0.2%耐力は198MPa、破断伸びは5.2%、シャルピー衝撃値は17J/cmであった。
(Example 5)
In Example 5, Si=14.0%, Mg=0.32%, Ti=0.14%, P=0.020% (20 ppm), Na=0.0320% (320 ppm), Al and inevitable impurities. The member A was manufactured under the same conditions as in Example 1 except that the hydrogen content was 0.21 cm 3 /100 g Al and the molten metal was poured at a cooling rate of 20° C./s. The maximum width of the maximum primary crystal Si particles was 90 μm, the average distance between the eutectic Si particles was 2.9 μm, and the number of bubbles having an equivalent circle diameter of 20 μm or more was not observed, that is, 0/mm 2 . The 0.2% proof stress was 198 MPa, the elongation at break was 5.2%, and the Charpy impact value was 17 J/cm 2 .

(実施例6)
実施例6はSi=12.8%、Mg=0.31%、Ti=0.15%、P=0.0029%(29ppm)、Na=0.0274%(274ppm)、Alおよび不可避的不純物からなり、含有水素量=0.14cm/100gAlであって、冷却速度17℃/sで注湯され、時効処理180℃×0.5hとした以外は実施例1と同様の条件で製造した部材Aである。最大の初晶Si粒子の最大幅は77μm、共晶Si同士の平均距離は4.0μm、円相当径20μm以上の気泡の数は観察されない、すなわち0個/mmであった。また、0.2%耐力は185MPa、破断伸びは6.9%、シャルピー衝撃値は24J/cmであった。
(Example 6)
In Example 6, Si=12.8%, Mg=0.31%, Ti=0.15%, P=0.0029% (29 ppm), Na=0.0274% (274 ppm), Al and inevitable impurities. It was produced under the same conditions as in Example 1 except that the hydrogen content was 0.14 cm 3 /100 g Al, the melt was poured at a cooling rate of 17° C./s, and the aging treatment was 180° C.×0.5 h. It is member A. The maximum width of the maximum primary crystal Si particles was 77 μm, the average distance between the eutectic Si particles was 4.0 μm, and the number of bubbles having an equivalent circle diameter of 20 μm or more was not observed, that is, 0/mm 2 . The 0.2% proof stress was 185 MPa, the breaking elongation was 6.9%, and the Charpy impact value was 24 J/cm 2 .

(実施例7)
実施例7は舟型B1に冷却速度が21℃/sで鋳造された以外は、実施例6と同様の条件で製造した部材B1である。最大の初晶Si粒子の最大幅は68μm、共晶Si同士の平均距離は3.6μm、円相当径20μm以上の気泡の数は観察されない、すなわち0個/mmであった。また、0.2%耐力は208MPa、破断伸びは8.9%、シャルピー衝撃値は30J/cmであった。
(Example 7)
Example 7 is a member B1 manufactured under the same conditions as in Example 6 except that the boat type B1 was cast at a cooling rate of 21° C./s. The maximum width of the maximum primary crystal Si particles was 68 μm, the average distance between the eutectic Si particles was 3.6 μm, and the number of bubbles having an equivalent circle diameter of 20 μm or more was not observed, that is, 0/mm 2 . The 0.2% proof stress was 208 MPa, the elongation at break was 8.9%, and the Charpy impact value was 30 J/cm 2 .

(実施例8)
実施例8はMg=0.30%、Ti=0.14%、P=0.0027%(27ppm)、Na=0.0281%(281ppm)、含有水素量0.16cm/100gAl、舟型B2に冷却速度が30℃/sで鋳造され、時効処理165℃×0.8hとした以外は、実施例6と同様の条件で製造した部材B2である。最大の初晶Si粒子の最大幅は45μm、共晶Si同士の平均距離は2.2μm、円相当径20μm以上の気泡の数は観察されない、すなわち0個/mmであった。また、0.2%耐力は185MPa、破断伸びは12.5%、シャルピー衝撃値は39J/cmであった。
(Example 8)
In Example 8, Mg=0.30%, Ti=0.14%, P=0.0027% (27 ppm), Na=0.0281% (281 ppm), hydrogen content 0.16 cm 3 /100 g Al, boat shape The member B2 was manufactured under the same conditions as in Example 6 except that the cooling rate was 30° C./s in B2 and the aging treatment was 165° C.×0.8 h. The maximum width of the maximum primary crystal Si particles was 45 μm, the average distance between the eutectic Si particles was 2.2 μm, and the number of bubbles having an equivalent circle diameter of 20 μm or more was not observed, that is, 0/mm 2 . The 0.2% proof stress was 185 MPa, the breaking elongation was 12.5%, and the Charpy impact value was 39 J/cm 2 .

(実施例9)
実施例9は舟型B3に冷却速度が35℃/sで鋳造され、時効処理180℃×0.3hとした以外は、実施例6と同様の条件で製造した部材B3である。最大の初晶Si粒子の最大幅は31μm、共晶Si同士の平均距離は1.5μm、円相当径20μm以上の気泡の数は観察されない、すなわち0個/mmであった。0.2%耐力は202MPa、破断伸びは14.5%、シャルピー衝撃値は45J/cmであった。
(Example 9)
Example 9 is a member B3 manufactured under the same conditions as in Example 6 except that the boat type B3 was cast at a cooling rate of 35° C./s and the aging treatment was 180° C.×0.3 h. The maximum width of the maximum primary crystal Si particles was 31 μm, the average distance between eutectic Si particles was 1.5 μm, and the number of bubbles having an equivalent circle diameter of 20 μm or more was not observed, that is, 0/mm 2 . The 0.2% proof stress was 202 MPa, the elongation at break was 14.5%, and the Charpy impact value was 45 J/cm 2 .

(実施例10)
実施例10は金型Cに冷却速度が39℃/sで鋳造された以外は、実施例8と同様の条件で製造した部材Cである。最大の初晶Si粒子の最大幅は20μm、共晶Si同士の平均距離は0.5μm、円相当径20μm以上の気泡の数は観察されない、すなわち0個/mmであった。また0.2%耐力は185MPa、破断伸びは16.4%、シャルピー衝撃値は52J/cmであった。
(Example 10)
Example 10 is a member C manufactured under the same conditions as in Example 8 except that the mold C was cast at a cooling rate of 39° C./s. The maximum width of the maximum primary crystal Si particles was 20 μm, the average distance between eutectic Si particles was 0.5 μm, and the number of bubbles having a circle equivalent diameter of 20 μm or more was not observed, that is, 0/mm 2 . The 0.2% proof stress was 185 MPa, the elongation at break was 16.4%, and the Charpy impact value was 52 J/cm 2 .

[比較例]
次に、比較例ついても表2に示す。特に記載のない製造条件等は実施例に同じである。
[Comparative example]
Next, Table 2 also shows comparative examples. Manufacturing conditions and the like that are not particularly described are the same as those in the examples.

(比較例1)
比較例1はSi=13.2%、Mg=0.31%、Ti=0.14%、P=0.0129%(129ppm)、Na=0.0091%(91ppm)、Alおよび不可避的不純物からなり、含有水素量=1.20cm/100gAlであって、Pの添加条件は溶湯温度800℃、保持時間60min.、Naの添加条件は溶湯温度750℃、保持時間は120min.、注湯温度は700℃で舟型Aに冷却速度24℃/sで注湯された部材Aである。最大の初晶Si粒子の最大幅は65μm、共晶Si同士の平均距離は1.3μm、円相当径20μm以上の気泡の数は1.75個/mmであった。また、溶体化処理540℃×4.0h、時効処理180℃×0.5hのT6熱処理で、0.2%耐力は220MPa、破断伸びは3.0%、シャルピー衝撃値は10J/cmであった。図5は比較例1のミクロ組織写真である。
(Comparative Example 1)
Comparative Example 1 is Si=13.2%, Mg=0.31%, Ti=0.14%, P=0.129% (129 ppm), Na=0.0091% (91 ppm), Al and inevitable impurities. The hydrogen content was 1.20 cm 3 /100 g Al, and the addition conditions of P were the melt temperature 800° C. and the holding time 60 min. , Na is added under the conditions of a molten metal temperature of 750° C. and a holding time of 120 min. The pouring temperature is 700° C. and the member A is poured into the boat A at a cooling rate of 24° C./s. The maximum width of the maximum primary crystal Si particles was 65 μm, the average distance between eutectic Si particles was 1.3 μm, and the number of bubbles having a circle equivalent diameter of 20 μm or more was 1.75 cells/mm 2 . In addition, T6 heat treatment of solution treatment 540° C.×4.0 h, aging treatment 180° C.×0.5 h, 0.2% proof stress 220 MPa, elongation at break 3.0%, Charpy impact value 10 J/cm 2 . there were. FIG. 5 is a microstructure photograph of Comparative Example 1.

(比較例2)
比較例2はNaを添加しなかった例である。すなわちSi=12.8%、Mg=0.33%、Ti=0.14%、P=0.0090%(90ppm)、Naは0.0001%(1ppm)未満、Alおよび不可避的不純物からなり、含有水素量=0.10cm/100gAlであって、Pの添加条件は溶湯温度800℃、保持時間45min.、注湯温度は770℃で、舟型Aに冷却速度23℃/sで注湯された部材Aである。最大の初晶Si粒子の最大幅は40μm、共晶Si同士の平均距離は14.8μm、円相当径20μm以上の気泡の数は観察されない、すなわち0個/mmであった。また、溶体化処理540℃×4.0h、時効処理180℃×0.5hのT6熱処理で、0.2%耐力は227MPa、破断伸びは2.0%、シャルピー衝撃値は8J/cmであった。
(Comparative example 2)
Comparative Example 2 is an example in which Na was not added. That is, Si=12.8%, Mg=0.33%, Ti=0.14%, P=0.0090% (90 ppm), Na less than 0.0001% (1 ppm), consisting of Al and inevitable impurities. , Hydrogen content=0.10 cm 3 /100 g Al, and the addition conditions of P are as follows: melt temperature 800° C., holding time 45 min. The pouring temperature is 770° C., and the member A is poured into the boat shape A at a cooling rate of 23° C./s. The maximum width of the maximum primary crystal Si particles was 40 μm, the average distance between the eutectic Si particles was 14.8 μm, and the number of bubbles having a circle equivalent diameter of 20 μm or more was not observed, that is, 0/mm 2 . Further, in T6 heat treatment of solution treatment 540° C.×4.0 h, aging treatment 180° C.×0.5 h, 0.2% proof stress is 227 MPa, elongation at break is 2.0%, Charpy impact value is 8 J/cm 2 . there were.

表1

Figure 0006741208
Table 1
Figure 0006741208

表2

Figure 0006741208
Table 2
Figure 0006741208

注:(1)残部はAlおよび不可避的不純物である。
(2)Naの欄における「−」は不可避的不純物として0.0001%未満のNaを含む。
Note: (1) The balance is Al and inevitable impurities.
(2) "-" in the column of Na contains less than 0.0001% Na as an unavoidable impurity.

表2(つづき)

Figure 0006741208





Table 2 (continued)
Figure 0006741208





表2(つづき)

Figure 0006741208
Table 2 (continued)
Figure 0006741208

表2(つづき)

Figure 0006741208
Table 2 (continued)
Figure 0006741208

注:(3)時効処理の時間の欄における値「0」は時効処理温度に到達した直後に放冷したことを表す。
Note: (3) The value "0" in the column of aging treatment time means that the aging treatment temperature was allowed to cool immediately.

1(11) 初晶Si粒子
2(21、22、23) 共晶Si粒子
3 線分
4 気泡
5 冷却曲線
1 (11) Primary Si particles 2 (21, 22, 23) Eutectic Si particles 3 Line segment 4 Bubble 5 Cooling curve

Claims (8)

質量基準で、12.6〜16.0%のSi、0.1〜0.6%のMg、0.0001〜0.0200%のP、0.0100〜0.0400%のNa、0.05〜0.3%のTi、残部がAl及び不可避的不純物からなり、100gあたりの含有水素量が水素ガス基準で0.05〜1.0cmであって、切断面に観察される最大の初晶Si粒子の最大幅が1〜90μmであり、切断面に観察される共晶Si粒子同士の平均距離が0μmを超え5μm以下であることを特徴とする過共晶Al−Si系アルミニウム合金。 On a mass basis, 12.6 to 16.0% Si, 0.1 to 0.6% Mg, 0.0001 to 0.0200% P, 0.0100 to 0.0400% Na, 0. from 05 to 0.3% of Ti, the balance being a l及 beauty unavoidable impurities, the hydrogen content per 100g is I 0.05~1.0Cm 3 der hydrogen gas basis, was observed on the cut surface largest maximum width of the primary crystal Si particles are 1~90Myuemu, hypereutectic the average distance of the eutectic Si particles are observed on the cut surface is characterized der Rukoto below 5μm exceed 0μm that Al- Si-based aluminum alloy. 前記Siが質量基準で12.6〜14.0%である請求項1に記載の過共晶Al−Si系アルミニウム合金。The hypereutectic Al-Si system aluminum alloy according to claim 1, wherein the Si is 12.6 to 14.0% on a mass basis. 切断面に観察される円相当径で20μm以上の気泡の数が1個/mm以下である請求項1又は請求項に記載の過共晶Al−Si系アルミニウム合金。 Hypereutectic Al-Si based aluminum alloy according to claim 1 or claim 2 yen number of equivalent diameter 20μm or more bubbles is one / mm 2 or less observed on the cut surface. 破断伸びが5%以上、シャルピー衝撃値が15J/cm以上である請求項1乃至請求項のいずれかに記載の過共晶Al-Si系アルミニウム合金。 The hypereutectic Al-Si system aluminum alloy according to any one of claims 1 to 3 , which has a breaking elongation of 5% or more and a Charpy impact value of 15 J/cm 2 or more. 0.2%耐力が100MPa以上である請求項1乃至請求項のいずれかに記載の過共晶Al−Si系アルミニウム合金。 The hypereutectic Al-Si system aluminum alloy according to any one of claims 1 to 4 , which has a 0.2% proof stress of 100 MPa or more. 請求項1乃至請求項のいずれかに記載の過共晶Al-Si系アルミニウム合金からなる鋳造部材。 A cast member made of the hypereutectic Al-Si-based aluminum alloy according to any one of claims 1 to 5 . 脱水素処理工程とNa添加工程とを含み、前記Na添加工程の前に前記脱水素処理工程を実施して、質量基準で、12.6〜16.0%のSi、0.1〜0.6%のMg、0.0001〜0.0200%のP、0.0100〜0.0400%のNa、0.05〜0.3%のTi、残部がAl及び不可避的不純物からなる溶湯を、前記Na添加工程の後の30分以内に注湯して、600℃から580℃の間の冷却速度を15℃/s以上で冷却し凝固させることにより、100gあたりの含有水素量が水素ガス基準で0.05〜1.0cm であって、切断面に観察される最大の初晶Si粒子の最大幅が1〜90μmであり、切断面に観察される共晶Si粒子同士の平均距離が0μmを超え5μm以下である過共晶Al-Si系アルミニウム合金製造する方法。 A dehydrogenation treatment step and a Na addition step are included, the dehydrogenation treatment step is performed before the Na addition step , and 12.6 to 16.0% Si on a mass basis, 0.1 to 0. 6% Mg, 0.0001 to .0200 percent P, .0100-0.0400 percent Na, molten metal from 0.05 to 0.3 percent of Ti, balance being a l及 beauty unavoidable impurities and then poured within 30 minutes after the Na addition step, the Rukoto allowed to cool to solidify the cooling rate between 580 ° C. from 600 ° C. at 15 ° C. / s or higher, the hydrogen content per 100g is It is 0.05 to 1.0 cm 3 on the basis of hydrogen gas, the maximum width of the maximum primary crystal Si particles observed on the cut surface is 1 to 90 μm, and the maximum width of the eutectic Si particles observed on the cut surface is how the average distance to produce der Ru hypereutectic Al-Si-based aluminum alloy below 5μm exceed 0 .mu.m. 前記溶湯のSi含有量は、質量基準で12.6〜14.0%である請求項7に記載の過共晶Al−Si系アルミニウム合金を製造する方法。The method for producing a hypereutectic Al-Si based aluminum alloy according to claim 7, wherein the Si content of the molten metal is 12.6 to 14.0% on a mass basis.
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