JP5004032B2 - Aluminum-based alloy having excellent high-temperature strength and low thermal expansibility and method for producing the same - Google Patents
Aluminum-based alloy having excellent high-temperature strength and low thermal expansibility and method for producing the same Download PDFInfo
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本発明は、高温強度に優れたアルミニウム基合金に関し、エンジンのピストンやコンプレッサー部品、真空ポンプ部品などに必要な優れた高温強度と低熱膨張性を発現可能とするアルミニウム基合金およびその製造方法に関する。 The present invention relates to an aluminum-based alloy having excellent high-temperature strength, and relates to an aluminum-based alloy capable of exhibiting excellent high-temperature strength and low thermal expansion required for engine pistons, compressor parts, vacuum pump parts, and the like, and a method for producing the same.
従来、ピストン母材に使用されるアルミニウム基合金には、優れた高温強度と低熱膨張性が要求されており、一般的にAl‐Si系の合金が用いられている。
そして、高温強度の向上を目途に、Cu，Mg，Mn，Ni等の第三成分量の調整や、製造条件の調整による組織のコントロールを図っている（例えば、特許文献１参照）。
しかしながら、共晶温度が比較的低いAl‐Si系の鋳造材を基本としているため、高い温度での溶体化処理ができず、十分な析出強化が得られない。したがって、第三成分量の調整や組織のコントロールによっても、高温強度の向上には限界がある。
そこで、例えば特許文献２に見られるように、Al‐Cu‐Mg系の鍛造材を用いることも試みられている。
Then, with the aim of improving the high-temperature strength, the organization is controlled by adjusting the amount of third components such as Cu, Mg, Mn, Ni, and the manufacturing conditions (see, for example, Patent Document 1).
However, since it is based on Al-Si cast material having a relatively low eutectic temperature, solution treatment at a high temperature cannot be performed, and sufficient precipitation strengthening cannot be obtained. Therefore, there is a limit to improving the high temperature strength even by adjusting the amount of the third component and controlling the structure.
Thus, for example, as seen in Patent Document 2, attempts have been made to use Al-Cu-Mg based forgings.
特許文献２で提案されているアルミニウム合金材は、Cu：1.5〜7.0％、Mg：0.01〜2.0％を含む鍛造材であり、高温強度の点からは極めて有用な素材である。しかしながら、その線膨張係数は23〜24×10-6／℃程度である。このため、例えばエンジン用ピストンとして用いようとすると、シリンダーとのクリアランス制御に困難を伴うことになる。例えばエンジン用ピストンとして用いるに当たっては、シリンダーとのクリアランス制御を容易にすべく、22×10-6／℃以下の線膨張係数が求められる。
本発明は、このような問題を解消すべく案出されたものであり、高温特性に優れたAl‐Cu系合金を基本にして、線膨張係数が小さいアルミニウム基合金を提供することを目的とする。
The aluminum alloy material proposed in Patent Document 2 is a forging material containing Cu: 1.5 to 7.0% and Mg: 0.01 to 2.0%, and is an extremely useful material in terms of high temperature strength. However, the linear expansion coefficient is about 23 to 24 × 10 −6 / ° C. For this reason, for example, if it is used as an engine piston, it will be difficult to control the clearance with the cylinder. For example, when used as a piston for an engine, a linear expansion coefficient of 22 × 10 −6 / ° C. or less is required in order to facilitate clearance control with the cylinder.
The present invention has been devised to solve such problems, and an object of the present invention is to provide an aluminum-based alloy having a low linear expansion coefficient based on an Al-Cu alloy superior in high temperature characteristics. To do.
本発明の高温強度に優れ、低熱膨張性を有するアルミニウム基合金は、その目的を達成するため、Cu：5.0〜12.0質量％、Mg：0.1〜1.0質量％、Mn：0.1〜1.0質量％、Fe：0.1〜1.5質量％およびNi：0.5〜4.0質量％を、Fe+Ni：1.7質量％以上の関係で含有するとともに、Si含有量を1質量％以下に規制し、残部がAlと不可避不純物からなる成分組成と、200℃×100時間保持後の200℃での引張強さが250MPa以上、および250℃×100時間保持後の250℃での引張強さが150MPa以上なる機械的特性と、室温〜200℃の範囲での平均線膨張係数が22×10-6／℃以下なる熱膨張特性を有することを特徴とする。 In order to achieve the object, the aluminum-based alloy having excellent high-temperature strength and low thermal expansibility of the present invention includes Cu: 5.0 to 12.0 mass%, Mg: 0.1 to 1.0 mass%, Mn: 0.1 to 1.0 mass%, Fe : 0.1-1.5% by mass and Ni: 0.5-4.0% by mass in relation to Fe + Ni: 1.7% by mass or more, and the Si content is regulated to 1% by mass or less, and the balance is from Al and inevitable impurities. Composition, mechanical properties such that the tensile strength at 200 ° C after holding at 200 ° C x 100 hours is 250 MPa or more, and the tensile strength at 250 ° C after holding at 250 ° C x 100 hours is 150 MPa or more, and room temperature It has a thermal expansion characteristic that an average linear expansion coefficient in a range of ˜200 ° C. is 22 × 10 −6 / ° C. or less.
前記アルミニウム基合金は、さらに、V：0.05〜0.20質量％、Zr：0.05〜0.25質量％、Ti：0.05〜0.20質量％の少なくとも一種以上を含んでいてもよい。
また、前記アルミニウム基合金中のFeが0.6質量％以上で、Ni／Fe比が0.5〜3となるように成分調整されていることが好ましい。
さらに、9%以上の占有面積率で金属間化合物を晶出させていることが好ましい。
The aluminum-based alloy may further contain at least one or more of V: 0.05 to 0.20 mass%, Zr: 0.05 to 0.25 mass%, and Ti: 0.05 to 0.20 mass%.
Moreover, it is preferable that the component is adjusted so that Fe in the aluminum-based alloy is 0.6% by mass or more and the Ni / Fe ratio is 0.5 to 3.
Furthermore, it is preferable to crystallize the intermetallic compound with an occupied area ratio of 9% or more.
そのような高温強度に優れ、低熱膨張性を有するアルミニウム基合金は、上記の成分組成を有するアルミニウム基合金の押出材に510〜545℃×1時間以上の溶体化処理を施し、その後に185〜235℃で1〜20時間の時効処理を施すことにより得られる。 Such an aluminum-based alloy having excellent high-temperature strength and low thermal expansibility is subjected to a solution treatment of 510 to 545 ° C. for 1 hour or more on the extruded material of the aluminum-based alloy having the above component composition, and thereafter 185 to It is obtained by applying an aging treatment at 235 ° C. for 1 to 20 hours.
本発明により提供されるアルミニウム基合金は、線膨張係数が小さく、しかも高温強度にも優れている。したがって、例えばエンジン用ピストンに用いることにより、シリンダーとのクリアランス制御も容易に行え、エネルギー効率に優れた自動車用エンジンを低コストで提供することが可能になる。 The aluminum-based alloy provided by the present invention has a low coefficient of linear expansion and is excellent in high temperature strength. Therefore, for example, when used for an engine piston, clearance control with a cylinder can be easily performed, and an automobile engine having excellent energy efficiency can be provided at low cost.
本発明者等は、高温特性に優れたAl‐Cu系合金において、機械的特性を低下させることなく、線膨張係数を小さくする手段について、鋭意検討を重ねてきた。
その過程で、適量のFe，Niを複合添加しAl‐Ni系，Al‐Cu‐Ni系，Al‐Cu‐Ni‐Fe系の化合物を９％以上、晶出させるとともに、比較的高温で人工時効処理を施すことが有効であることを見出し、特許請求の範囲に記載したような事項の選定に到達したものである。
The inventors of the present invention have intensively studied a means for reducing the linear expansion coefficient without deteriorating the mechanical characteristics in an Al—Cu alloy having excellent high temperature characteristics.
In the process, a proper amount of Fe and Ni are added in combination to crystallize more than 9% of Al-Ni, Al-Cu-Ni, and Al-Cu-Ni-Fe compounds, and at a relatively high temperature, The inventors have found that it is effective to apply an aging treatment, and have reached the selection of items as described in the claims.
すなわち、請求項１〜４に記載したような、Cu：5.0〜12.0質量％、Mg：0.1〜1.0質量％、Mn：0.1〜1.0質量％、Fe：0.1〜1.5質量％、およびNi：0.5〜4.0質量％を、さらに必要に応じてV：0.05〜0.20質量％、Zr：0.05〜0.25量％、Ti：0.05〜0.20質量％の少なくとも一種以上を、Fe+Ni：1.7質量％以上の関係で含有するとともに、Si含有量が1質量％以下に規制されたアルミニウム基合金であって、均質化処理の後押出加工された押出材に510〜545℃×1時間以上の溶体化処理とその後の185〜235℃で1〜20時間の時効処理を施したものが、200℃×100時間保持後の引張強さが250MPa以上および250℃×100時間保持後の引張強さが150MPa以上なる機械的特性と、室温〜200℃の範囲での平均線膨張係数が22×10-6／℃以下なる熱膨張特性を有するようになることを見出したものである。
特にFeが0.6質量％以上で、Ni／Fe比が0.5〜3となるように成分調整されているものが好ましい。
That is, as described in claims 1 to 4, Cu: 5.0 to 12.0 mass%, Mg: 0.1 to 1.0 mass%, Mn: 0.1 to 1.0 mass%, Fe: 0.1 to 1.5 mass%, and Ni: 0.5 to 4.0% by mass, further as required: V: 0.05-0.20% by mass, Zr: 0.05-0.25% by mass, Ti: 0.05-0.20% by mass, Fe + Ni: 1.7% by mass or more And an aluminum-based alloy whose Si content is regulated to 1% by mass or less, and after the homogenization treatment, the extruded material is subjected to a solution treatment of 510 to 545 ° C. × 1 hour or more and a subsequent solution treatment. Mechanically treated with aging treatment at 185 to 235 ° C for 1 to 20 hours, with a tensile strength after holding at 200 ° C for 100 hours of 250 MPa or more and a tensile strength after holding at 250 ° C for 100 hours of 150 MPa or more It has been found that the thermal expansion characteristics are such that the characteristics and the average linear expansion coefficient in the range of room temperature to 200 ° C. are 22 × 10 −6 / ° C. or less.
In particular, it is preferable that the component is adjusted so that Fe is 0.6 mass% or more and the Ni / Fe ratio is 0.5 to 3.
まず、本発明アルミニウム基合金の成分組成から説明する。
アルミニウム基合金において低熱膨張化を図るに当たっては、Si添加が最も代表的な手法である。しかしながら、Siを添加すると、溶体化温度を低くせざるを得ず、十分な析出組織が得られなくなる。このため、本発明ではSiに替え、Fe，Niの添加により優れた高温強度を維持した状態で低熱膨張化を図ることができた。
機械的特性は、基本的には、添加されたCuの固溶強化と時効処理時に析出するAl2Cuによる析出強化に依存するものである。また必要に応じてZr，V，Tiを添加して固溶強化を図っている。
以下、各成分の作用、好ましい含有量等について説明する。
First, the component composition of the aluminum-based alloy of the present invention will be described.
Si addition is the most typical method for reducing the thermal expansion of aluminum-based alloys. However, when Si is added, the solution temperature must be lowered, and a sufficient precipitation structure cannot be obtained. For this reason, in the present invention, it was possible to achieve low thermal expansion while maintaining excellent high-temperature strength by adding Fe and Ni instead of Si.
The mechanical properties basically depend on the solid solution strengthening of the added Cu and the precipitation strengthening by Al 2 Cu precipitated during the aging treatment. If necessary, Zr, V, and Ti are added to enhance solid solution.
Hereinafter, the action of each component, the preferred content, etc. will be described.
Si：1質量％以下
Siを多量に含有し、Si粒子を晶出させることで低熱膨張化が図れるが、マトリックス中への固溶量も増加するため固相線温度が低下し、高強度を得るための析出強化が得られない。溶体化温度が510℃を達成するために添加量は1質量％以下に規制する。
Si: 1% by mass or less
Low thermal expansion can be achieved by containing a large amount of Si and crystallizing Si particles, but the amount of solid solution in the matrix also increases, so the solidus temperature decreases and precipitation strengthening to obtain high strength is achieved. I can't get it. In order to achieve a solution temperature of 510 ° C., the amount added is restricted to 1% by mass or less.
Cu：5.0〜12.0質量％
Cuは機械的強度の向上に資する。添加されたCuは、Al相中に固溶して強度向上に資する他、時効処理時にθ’‐Al2Cuを形成して、あるいはさらに含まれるMgと、S’‐Al2CuMgを形成して、析出強化による高強度化に貢献する。その含有量が5.0質量％に満たないと所望の強化は達成できない。通常CuはAl相中に5.8質量％程度しか固溶しないため、Cu量を、5.8質量％を超えて添加しても強度アップは期待できないが、本発明では低熱膨張化のためにFe、Ni等を含有させており、含ませたCuがFe，Ni系の金属間化合物に取り込まれるため、5.8質量％を超えて含有させても強度に寄与することになる。ただし、12.0質量％を超えると、再なる強度アップに寄与しない。したがって、本発明では、Cu含有量は5.0〜12.0質量％とする。
Cu: 5.0 to 12.0 mass%
Cu contributes to improvement of mechanical strength. The added Cu forms a solid solution in the Al phase to contribute to strength improvement, and forms θ'-Al 2 Cu during aging treatment, or further contains Mg and S'-Al 2 CuMg. Contributes to high strength by precipitation strengthening. If the content is less than 5.0% by mass, the desired strengthening cannot be achieved. Usually, Cu only dissolves about 5.8% by mass in the Al phase, so even if the amount of Cu exceeds 5.8% by mass, an increase in strength cannot be expected. However, in the present invention, Fe, Ni are used for low thermal expansion. Etc., and the contained Cu is incorporated into the Fe, Ni-based intermetallic compound. Therefore, even if the content exceeds 5.8% by mass, it contributes to the strength. However, if it exceeds 12.0% by mass, it will not contribute to the increase in strength. Therefore, in this invention, Cu content shall be 5.0-12.0 mass%.
Mg：0.1〜1.0質量％
Mgの添加によりS’‐Al2CuMgを形成して、析出強化による高強度化に貢献する。室温から200℃までの高強度化に有効である。一方で200℃を越える温度域に対してはθ’‐Al2Cu形成が有効であり、よって、上下限を規制する必要がある。200℃以下で高強度を得るにはMg：0.1質量％が必要であり、250℃以上で高強度を得るには1.0質量％以下の添加に抑える必要がある。
Mg: 0.1-1.0 mass%
By adding Mg, S'-Al 2 CuMg is formed and contributes to high strength by precipitation strengthening. Effective for increasing strength from room temperature to 200 ° C. On the other hand, θ′-Al 2 Cu formation is effective for the temperature range exceeding 200 ° C. Therefore, it is necessary to regulate the upper and lower limits. In order to obtain high strength at 200 ° C. or lower, Mg: 0.1% by mass is necessary, and to obtain high strength at 250 ° C. or higher, it is necessary to suppress the addition to 1.0% by mass or less.
Mn：0.1〜1.0質量％
Mnは鋳造時にマトリックスに固溶し、HO処理時にMn系の析出物（Al‐Cu‐Mn系）を生成する。その析出物は押出や鍛造後のT6処理時に粒界の移動を妨げ、結晶粒の粗大化を防止する効果がある。強度，靭性，耐食性を高める効果がある。また、高温の引張強さを高める効果があり添加する。0.1質量％未満では効果が得られない。一方で1.0質量％を超えて添加すると粗大な晶出物を形成し、熱間加工性やT6処理後の部品の靭性を阻害する。
Mn: 0.1 to 1.0 mass%
Mn forms a solid solution in the matrix during casting and produces Mn-based precipitates (Al-Cu-Mn system) during HO treatment. The precipitates have the effect of preventing the grain boundary from moving during the T6 treatment after extrusion or forging and preventing the coarsening of the crystal grains. It has the effect of increasing strength, toughness and corrosion resistance. Also, it has the effect of increasing the tensile strength at high temperatures and is added. If it is less than 0.1% by mass, the effect cannot be obtained. On the other hand, if it exceeds 1.0 mass%, a coarse crystallized product is formed, which hinders hot workability and toughness of parts after T6 treatment.
Ni：0.5〜4.0質量％
Al‐Ni系金属間化合物を形成し、低熱膨張化に寄与する。目標とする線膨張係数（22×10-6／℃）を得るには0.5質量％以上の添加が必要である。但し、Niは高価な元素であり、素材のコストアップとなるので4.0％質量以下とする。
Ni: 0.5-4.0% by mass
Forms Al-Ni intermetallic compounds and contributes to low thermal expansion. In order to obtain the target linear expansion coefficient (22 × 10 −6 / ° C.), it is necessary to add 0.5% by mass or more. However, Ni is an expensive element and increases the cost of the material.
Fe：0.1〜1.5質量％
Niとの共存により優れた高温強度を維持した状態で低熱膨張化が図れる。この効果はFe：0.1質量％以上の含有で顕著となる。Fe含有量が少ない成分組成で目標の線膨張係数を満足するには多量のNiの添加が必要であり、素材コストが高まる。Feを添加し、Al‐Cu‐Fe‐Ni系金属間化合物を形成させることでNi単独添加よりも効果的に低熱膨張化に寄与させることができる。Feは多量に添加すると粗大な金属間化合物を生成し、熱間加工性やT6処理後の製品の靭性を低下させることから、1.5質量％を上限とする。なお、Niは高価であり多量の添加は素材コストを高める。低コストでより効果的に低熱膨張化が図るために、Feを比較的多く、0.6質量％以上でNi／Fe比を0.5〜3の範囲で調整することが好ましい。
上記したとおり、Fe添加量が少ない場合にはNi量を多くする必要があり、両者は合量で1.7質量％以上含ませる必要がある。
Fe: 0.1-1.5% by mass
Coexistence with Ni enables low thermal expansion while maintaining excellent high-temperature strength. This effect becomes remarkable when Fe is contained by 0.1% by mass or more. In order to satisfy the target linear expansion coefficient with a component composition having a low Fe content, a large amount of Ni must be added, which increases the material cost. Addition of Fe to form an Al—Cu—Fe—Ni intermetallic compound can contribute to lower thermal expansion more effectively than the addition of Ni alone. When Fe is added in a large amount, a coarse intermetallic compound is formed, and the hot workability and the toughness of the product after T6 treatment are reduced. Therefore, the upper limit is 1.5% by mass. Note that Ni is expensive, and adding a large amount increases the material cost. In order to achieve low thermal expansion more effectively at a low cost, it is preferable to adjust the Ni / Fe ratio in the range of 0.5 to 3 at a relatively large amount of Fe and 0.6 mass% or more.
As described above, when the amount of Fe added is small, it is necessary to increase the amount of Ni, and it is necessary to include both in a total amount of 1.7% by mass or more.
Zr：0.05〜0.25質量％
鋳造中に固溶し、HO処理でAl‐Zr系析出物を生成し、押出または鍛造材の溶体化処理後の粒界の移動を妨げ、結晶粒の粗大化を抑止する効果がある。強度，靭性，耐食性を高めるため、必要に応じて添加する。また、Al‐Zr系析出相は微細であり、高温強度にも寄与する。0.05質量％未満では効果は得られず、0.25質量％を超えて添加すると鋳造時に粗大な金属間化合物を生成し、加工性や靭性を阻害する。
Zr: 0.05-0.25 mass%
It has the effect of forming solid solution during casting, producing Al-Zr-based precipitates by HO treatment, preventing the movement of grain boundaries after solution treatment of extrusion or forging, and suppressing the coarsening of crystal grains. Add as necessary to enhance strength, toughness, and corrosion resistance. Moreover, the Al-Zr system precipitation phase is fine and contributes to high temperature strength. If the amount is less than 0.05% by mass, the effect cannot be obtained. If the amount exceeds 0.25% by mass, a coarse intermetallic compound is formed during casting, which impairs workability and toughness.
V：0.05〜0.20質量％
Ti：0.05〜0.20質量％
V，Tiは固溶強化により強度を高める作用を有し、高温での強度維持が図れるので、必要に応じて添加する。いずれも添加量が0.05質量％に満たないと顕著な効果は得られない。逆に0.20質量％を超える程に多く含ませると、鋳造時に粗大な金属間化合物を生成し、加工性や靭性を阻害する。
V: 0.05-0.20 mass%
Ti: 0.05-0.20 mass%
V and Ti have the effect of increasing the strength by solid solution strengthening and can maintain the strength at a high temperature. Therefore, V and Ti are added as necessary. In any case, if the addition amount is less than 0.05% by mass, a remarkable effect cannot be obtained. On the other hand, if it is contained in an amount exceeding 0.20% by mass, a coarse intermetallic compound is produced during casting, and workability and toughness are hindered.
次に製造方法について説明する。
本発明に係るアルミニウム基合金は、所定の成分組成を有する合金の鋳塊に、従来と同様に均質化処理を施した後、必要に応じて押出加工を施し、鋳塊もしくは押出材に、熱間もしくは冷間の鍛造加工を施して所望形状の加工品を得、さらにその後、適正に制御された溶体化処理と時効処理を組み合わせて施されることにより製造される。
すなわち、成分組成と適正に制御された溶体化処理および時効処理の組み合わせにより所望の線膨張係数（室温〜200℃の範囲での平均線膨張係数が22×10-6／℃以下）と高温特性（200℃×100時間保持後の引張強さが250MPa以上、250℃×100時間保持後の引張強さが150MPa以上）を呈するようになる。
Next, a manufacturing method will be described.
The aluminum-based alloy according to the present invention is obtained by subjecting an ingot of an alloy having a predetermined composition to a homogenization treatment in the same manner as in the prior art, and then extruding as necessary. A processed product having a desired shape is obtained by performing a forging process in between or cold, and then manufactured by combining appropriately controlled solution treatment and aging treatment.
That is, the desired linear expansion coefficient (average linear expansion coefficient in the range of room temperature to 200 ° C is 22 × 10 -6 / ° C or less) and high-temperature characteristics by a combination of component composition and appropriately controlled solution treatment and aging treatment (The tensile strength after holding at 200 ° C. for 100 hours is 250 MPa or more, and the tensile strength after holding at 250 ° C. for 100 hours is 150 MPa or more).
Zr，V，Tiを含有する場合には鋳造温度が低い場合にはAl‐Zr系，Al‐V系，Al‐Ti系の粗大な金属間化合物が生成する。粗大な金属間化合物を生成させないように鋳造直前のメタル温度を高温にする必要がある。700℃以上で鋳造することが望ましい。
鋳造は、従来どおりDC鋳造で構わない。
押出加工や鍛造加工に特段の制限はない。従来通りの方法で、押出加工や鍛造加工を行う。
When Zr, V, and Ti are contained, when the casting temperature is low, coarse Al-Zr, Al-V, and Al-Ti intermetallic compounds are formed. It is necessary to increase the metal temperature immediately before casting so as not to generate coarse intermetallic compounds. It is desirable to cast at 700 ° C or higher.
Casting may be DC casting as before.
There are no particular restrictions on extrusion or forging. Extrusion and forging are performed by conventional methods.
本発明にあっては、Al‐Cu系およびAl‐Cｕ‐Mg系の金属間化合物を析出させることにより強化を図っている。したがって溶体化処理とその後の時効処理が重要な工程となる。なお、本発明にあってはMnの含有によっても特性を向上させているが、Mnの効果はHO処理で形成させるAl‐Cu‐Mn系の析出相によるものである。この相は熱に対して、比較的、安定であり、溶体化温度で固溶し、時効温度で析出するものではない。 In the present invention, strengthening is achieved by precipitating Al—Cu and Al—Cu—Mg intermetallic compounds. Accordingly, solution treatment and subsequent aging treatment are important steps. In the present invention, the characteristics are also improved by the inclusion of Mn, but the effect of Mn is due to the Al—Cu—Mn-based precipitated phase formed by the HO treatment. This phase is relatively stable to heat, does not dissolve at the solution temperature, and does not precipitate at the aging temperature.
溶体化処理：510〜545℃×１時間
溶体化処理はCu，Mgを固溶させるために行う。5％以上のCuを固溶させるには510℃以上の溶体化温度が必要である。固溶量を高めることで時効処理後の析出量が高まり、強度に寄与させることができる。一方で545℃を超えて溶体化処理すると局部的に融解し、強度，延性を低下させる。
高温保持後に速やかに室温まで冷却することで過飽和固溶体となり、その後の時効処理で十分な析出強化を得ることができる。望ましくは80℃以下の温水または室温水への焼入れにより、十分な固溶状態を得ることができる。
Solution treatment: 510-545 ° C. for 1 hour The solution treatment is performed to dissolve Cu and Mg. A solution temperature of 510 ° C. or higher is required to dissolve Cu of 5% or higher. By increasing the amount of solid solution, the amount of precipitation after the aging treatment increases, which can contribute to the strength. On the other hand, when the solution treatment exceeds 545 ° C, it melts locally, reducing the strength and ductility.
A supersaturated solid solution is obtained by rapidly cooling to room temperature after holding at a high temperature, and sufficient precipitation strengthening can be obtained by subsequent aging treatment. Desirably, a sufficient solid solution state can be obtained by quenching in warm water or room temperature water of 80 ° C. or less.
時効処理：185〜235℃×1〜20時間
時効処理でθ'‐Al2Cu或いはＳ'‐Al2CuMgの析出物を形成させ、析出強化で強度に寄与する。比較的低い185℃未満で処理すると、析出密度が高まり、比較的低温域では優れた強度が得られるが、高温に曝露されると析出に伴い体積膨張し、製品の寸法変化が大きく、低熱膨張が達成されない。時効時間が１時間未満で短いと、析出物が十分に成長せず、強度が得られない。185℃以上の温度で時効処理すると固溶量を減らすことができ、高温環境化での体積膨張を抑制することが可能である。ただし、235℃超える程に高い温度では析出物が粗大化し、比較的低温域（200℃以下）で強度が得られない、あるいは20時間を超えるほどの長時間の処理を施すと、強度を低下させることになるとともに経済的にも適していない。
Aging treatment: 185-235 ° C. × 1-20 hours aging treatment forms θ′-Al 2 Cu or S′-Al 2 CuMg precipitates and contributes to strength by precipitation strengthening. When treated at a relatively low temperature of less than 185 ° C, the density of precipitation increases and excellent strength is obtained at relatively low temperatures, but when exposed to high temperatures, volume expansion occurs with precipitation, resulting in large dimensional changes in the product and low thermal expansion. Is not achieved. When the aging time is shorter than 1 hour, the precipitate does not grow sufficiently and the strength cannot be obtained. When an aging treatment is performed at a temperature of 185 ° C. or higher, the amount of solid solution can be reduced, and volume expansion in a high temperature environment can be suppressed. However, precipitates become coarser at temperatures higher than 235 ° C, and strength cannot be obtained in a relatively low temperature range (200 ° C or lower), or the strength decreases when treated for a long time exceeding 20 hours. It is not suitable economically.
表１に示す成分組成のアルミニウム合金を溶解炉で溶製し、鋳造温度700℃以上（金型投入直前の温度を700℃以上）でφ254mmにDC鋳造した。続いて保持条件500℃×12hでHO処理し（昇温速度80℃／h、冷却はファン冷却）、その後、ビレット加熱温度380℃、押出速度5m／minでφ40mmに押出加工した。
得られた押出材に表２に示す条件で溶体化処理および時効処理を施した後、30〜200℃の線膨張係数と200℃で100時間保持した後の200℃での高温引張特性および250℃で100時間保持した後の250℃での高温引張特性を調査した。
Aluminum alloys having the composition shown in Table 1 were melted in a melting furnace and DC casted to φ254 mm at a casting temperature of 700 ° C. or higher (the temperature immediately before the mold was introduced was 700 ° C. or higher). Subsequently, HO treatment was performed at a holding condition of 500 ° C. × 12 h (temperature increase rate: 80 ° C./h, cooling was fan cooling), and then extrusion was performed to φ40 mm at a billet heating temperature of 380 ° C. and an extrusion rate of 5 m / min.
The obtained extruded material was subjected to a solution treatment and an aging treatment under the conditions shown in Table 2, followed by a linear expansion coefficient of 30 to 200 ° C., a high-temperature tensile property at 200 ° C. after holding at 200 ° C. for 100 hours, and 250 The high temperature tensile properties at 250 ° C. after holding at 100 ° C. for 100 hours were investigated.
各調査方法は次のとおりである。
線膨張係数の測定方法：
試験片形状φ10mm×長さ50mm、昇温速度約2℃／分で加熱しながら、試験片の長さを測定し、所定の温度範囲における長さの変化／温度で線膨張係数を示した。
引張試験：
試験片形状JIS14A号とし、炉内で試験片を所定の温度に加熱したまま、引張試験を実施した。
Each survey method is as follows.
Method for measuring linear expansion coefficient:
The length of the test piece was measured while heating at a test piece shape of φ10 mm × length of 50 mm and a heating rate of about 2 ° C./min, and the linear expansion coefficient was indicated by the change in length / temperature within a predetermined temperature range.
Tensile test:
The test piece shape was JIS14A, and a tensile test was carried out while the test piece was heated to a predetermined temperature in the furnace.
調査結果を表２に併せて示す。
なお、No.19は粗大晶生成により調査を中止した。
The survey results are also shown in Table 2.
Note that No. 19 was stopped due to the formation of coarse crystals.
Si含有量が規制範囲よりもが高い材料では、目標とする線膨張係数≦22×10-6／℃を達成しているが、200，250℃の高温の引張強さは目標値に満たないことが分かる（No.22，23）。高温強度を満足するには、Al‐Cu系析出物による析出強化が必要であるが、Si添加により、固相線温度が低下し、溶体化温度が高められないためAl‐Cu系析出物による十分な析出強化が得られないことが原因の一つである。 For materials whose Si content is higher than the regulation range, the target linear expansion coefficient ≤ 22 x 10-6 / ° C has been achieved, but the tensile strength at high temperatures of 200 and 250 ° C is less than the target value. (No.22, 23) In order to satisfy the high temperature strength, precipitation strengthening with Al-Cu-based precipitates is necessary. However, due to the addition of Si, the solidus temperature is lowered and the solution temperature cannot be increased. One reason is that sufficient precipitation strengthening cannot be obtained.
成分規制範囲内の合金でも溶体化温度が低いほど強度は低下傾向が認められる。溶体化温度が510℃未満ではAl‐Cu系析出物による析出強化が不十分となり、高温強度が満たない（No.11）。
また、熱処理条件を満たしても、Cu量，Mn量が規制範囲を満たさない場合も高温強度は満足できない（No.21，18）。なお、Mn量を、規定値を超えて添加すると粗大な晶出物を生成し、製品の伸びや靭性を低下させるため好ましくない（No.19）。
さらに高温強度を高める元素としてZr，V，Tiがある。無添加でも目標とする高温強度を得ることはできるので、必要に応じて添加し高温強度を高めることができている（No.25，26）。
Even in alloys within the component regulation range, the lower the solution temperature, the lower the strength. If the solution temperature is lower than 510 ° C, precipitation strengthening due to Al-Cu-based precipitates is insufficient, and high-temperature strength is not satisfied (No. 11).
Even if the heat treatment conditions are satisfied, the high-temperature strength cannot be satisfied even if the Cu content and Mn content do not meet the regulation ranges (No. 21, 18). If the Mn content exceeds the specified value, a coarse crystallized product is formed, and the elongation and toughness of the product are lowered (No. 19).
Furthermore, there are Zr, V, and Ti as elements that increase the high temperature strength. Since the target high-temperature strength can be obtained even without addition, it can be added as necessary to increase the high-temperature strength (No. 25, 26).
高温強度を満足する材料でもFeとNi添加が規制範囲に満たない材料では、目標とする線膨張係数は得られていない（No.17，24）。
目標とする線膨張係数を得るためには低Fe含有の場合にはNi量を2.5％以上添加する必要がある（No.2）。なお、Ni添加量を高めるほど低熱膨張化が得られるが（No.4）、コストが高まるため、本発明では上限を4％以下としている。
Fe，Ni比で0.6〜1.6の範囲でFe，Niを添加すると、Ni添加量が低くても目標の線膨張係数を得ることができる。その場合の添加量は総量で1.7％以上が必要となる（No.8，9，10，12，13，14，15，16）。
高温時効条件により線膨張係数は低下する。成分規制値を満足しても20時間までの時効時間においては、時効温度185℃未満では目標値を満足できないことがわかる（No.1，3，5，7）。
The target linear expansion coefficient is not obtained for materials that satisfy high temperature strength, but for which Fe and Ni additions are not within the regulatory range (Nos. 17 and 24).
In order to obtain the target linear expansion coefficient, it is necessary to add 2.5% or more of Ni when the Fe content is low (No. 2). In addition, although lower thermal expansion can be obtained as the Ni addition amount is increased (No. 4), since the cost is increased, the upper limit is set to 4% or less in the present invention.
When Fe and Ni are added in the range of 0.6 to 1.6 in terms of Fe and Ni ratio, the target linear expansion coefficient can be obtained even if the amount of Ni addition is low. In that case, the total amount added must be 1.7% or more (No. 8, 9, 10, 12, 13, 14, 15, 16).
The linear expansion coefficient decreases due to high temperature aging conditions. It can be seen that even if the component regulation value is satisfied, the target value cannot be satisfied at an aging temperature of less than 185 ° C for aging times of up to 20 hours (No. 1, 3, 5, 7).
線膨張係数に及ぼす晶出物量の影響を把握するために，T6処理後の押出棒のＬ方向断面の組織を観察した（No.1，2，4，8，12）。Ｒ／２部（表面と中心の間）について画像解析でAl‐Cu‐Ni‐Fe系晶出物の占有面積率を測定した結果を表３に示した。線膨張係数が22×10-6／℃を超える材料（No.1）のAl−Cu−Ni−Fe系晶出物の占有面積率が９％未満であるのに対して，線膨張係数が22×10-6／℃以下の材料（No.2，4，8，12）の占有面積率は９％以上である。この様にAl−Cu−Ni−Fe系晶出物の占有面積率が９％以上で線膨張係数22×10-6／℃以下を満たすことが明らかとなった。 In order to grasp the influence of the amount of crystallized substance on the linear expansion coefficient, the structure of the cross section in the L direction of the extruded rod after T6 treatment was observed (No. 1, 2, 4, 8, 12). Table 3 shows the results of measuring the occupied area ratio of the Al-Cu-Ni-Fe-based crystallized material by image analysis for R / 2 part (between the surface and the center). The linear expansion coefficient is less than 9% for the Al-Cu-Ni-Fe crystallized area occupied by the material (No. 1) whose linear expansion coefficient exceeds 22 × 10 -6 / ° C. The occupied area ratio of materials (No.2, 4, 8, 12) below 22 × 10 -6 / ° C is 9% or more. As described above, it was clarified that the Al—Cu—Ni—Fe crystallization area occupied area ratio was 9% or more and the linear expansion coefficient was 22 × 10 −6 / ° C. or less.
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