JP5693904B2

JP5693904B2 - Manufacturing method of superplastic molded product

Info

Publication number: JP5693904B2
Application number: JP2010225853A
Authority: JP
Inventors: 工藤　智行; 智行工藤; 高田　健; 健高田
Original assignee: Nippon Steel Corp; UACJ Corp
Current assignee: Nippon Steel Corp; UACJ Corp
Priority date: 2010-10-05
Filing date: 2010-10-05
Publication date: 2015-04-01
Anticipated expiration: 2030-10-05
Also published as: JP2012076138A

Description

本発明は、超塑性成形品の製造方法に関する。 The present invention relates to a method for producing a superplastic molded product.

従来から、複雑な成形部品をアルミニウム（アルミニウム合金を含む）で成形する際には、アルミニウムを４００℃以上の高温に加熱し、大きな延性を持たせ成形する超塑性成形が用いられてきた。特に、ＪＩＳ５０００系のＡｌ−Ｍｇ系合金（以下、５０００系アルミニウム合金）は結晶粒の微細化が容易であり、超塑性変形が起こりやすく、大きな延性を示すため、自動車のインナー材などに用いられてきた。また、５０００系アルミニウム合金は固溶Ｍｇ量が多いことから、超塑性変形のひずみ速度が高速度域でも比較的大きな延性を示すという利点もある。そのような特性を利用して、これまで多くの高速超塑性成形用５０００系アルミニウム合金が開発されている。 Conventionally, when forming complex molded parts with aluminum (including aluminum alloys), superplastic forming has been used in which aluminum is heated to a high temperature of 400 ° C. or higher to give large ductility. In particular, JIS5000-based Al—Mg-based alloys (hereinafter, 5000-based aluminum alloys) are easy to refine crystal grains, easily undergo superplastic deformation, and exhibit large ductility. I came. In addition, since the 5000 series aluminum alloy has a large amount of dissolved Mg, there is an advantage that the strain rate of superplastic deformation exhibits relatively large ductility even in a high speed region. Many 5000 series aluminum alloys for high-speed superplastic forming have been developed by utilizing such characteristics.

しかしＡｌ−Ｍｇ系合金は強度に乏しいため、特に大きな強度が求められる自動車アウター材等に用いることは困難である。そこで、ＪＩＳ６０００系のＡｌ−Ｍｇ−Ｓｉ系合金をはじめ、超塑性成形能を有し、かつ人工時効硬化により大きな強度を持たせることが可能な、熱処理系アルミニウム合金の超塑性成形品が求められている。熱処理系アルミニウム合金は、例えば塗装焼付け工程における人工時効硬化により、自動車アウター材に求められる１９０ＭＰａ以上の高耐力を得ることが可能である。 However, since Al—Mg-based alloys have poor strength, it is difficult to use them for automobile outer materials that require particularly high strength. Accordingly, there is a need for a superplastic molded product of a heat-treated aluminum alloy, including a JIS6000-based Al-Mg-Si-based alloy, which has superplastic forming ability and can have high strength by artificial age hardening. ing. The heat-treated aluminum alloy can obtain a high yield strength of 190 MPa or more required for an automobile outer material, for example, by artificial age hardening in a paint baking process.

熱処理系アルミニウム合金を用いた従来の超塑性成形品の製造方法を次に示す。 A conventional method for producing a superplastic molded product using a heat-treated aluminum alloy will be described below.

超塑性成形方法としては高温ブロー成形が用いられる。高温ブロー成形は４００℃以上の高温で高圧のガスを材料に噴きつけ、金型に押し付けることで成形する方法であり、プレス成形のように雄型を必要としないという利点がある。熱処理系アルミニウム合金は溶体化処理が必要となるため、工程数の削減を目的として材料や高圧ガス、金型の温度を溶体化処理温度付近に保ち超塑性成形を行う。 High temperature blow molding is used as the superplastic forming method. High-temperature blow molding is a method in which high-pressure gas at a high temperature of 400 ° C. or higher is sprayed onto a material and pressed against a mold, and has an advantage that a male mold is not required unlike press molding. Since the heat-treated aluminum alloy requires solution treatment, superplastic forming is performed with the temperature of the material, high-pressure gas, and mold close to the solution treatment temperature for the purpose of reducing the number of steps.

次に、超塑性成形の直後に、成形品を離型し所定の場所に移動させて、その後大型ファンや冷却水で直ちに強制冷却することで焼き入れを行う。その後、塗装焼付け工程において、成形品に対して人工時効処理を行う。 Next, immediately after superplastic forming, the molded product is released from the mold, moved to a predetermined location, and then quenched by immediate forced cooling with a large fan or cooling water. Thereafter, an artificial aging treatment is performed on the molded product in the paint baking process.

また、人工時効処理による強度向上の効果を大きくするために、焼き入れ直後に予備時効処理を行うことが提案されている（特許文献１参照）。この場合、例えば、焼き入れ直後に成形品をバッチ炉に投入して予備時効処理を行う。 Moreover, in order to increase the strength improvement effect by artificial aging treatment, it has been proposed to perform preliminary aging treatment immediately after quenching (see Patent Document 1). In this case, for example, immediately after quenching, the molded product is put into a batch furnace to perform preliminary aging treatment.

以上のような従来の製造方法では、強制冷却するまでに冷却装置の稼動や移動の工程を要していた。即ち、従来の製造方法では、超塑性成形から強制冷却までに時間がかかり、十分な焼き入れが出来ないという課題があった。また、超塑性成形直後の成形品は溶体化処理温度以上であるために変形抵抗が小さく、焼き入れの際の強制冷却により部分的に歪が生じてしまうという課題があった。 In the conventional manufacturing method as described above, the operation and movement of the cooling device are required before forced cooling. That is, the conventional manufacturing method has a problem that it takes time from superplastic forming to forced cooling, and sufficient quenching cannot be performed. Further, since the molded product immediately after superplastic forming is at a temperature equal to or higher than the solution treatment temperature, there is a problem that deformation resistance is small, and strain is partially generated by forced cooling during quenching.

そこで、特許文献２では、材料温度及び高圧ガスは溶体化処理温度以上とし、超塑性成形金型の内部に冷却水を流すことで、材料が成形され金型と接触すると同時に材料を強制冷却する方法を提案している。このような特許文献２の技術は、成形から強制冷却までの時間を失くし、十分な焼き入れを可能とするとともに、高圧ガスにより金型に押さえつけることで強制冷却時の歪の発生を抑制しようとするものである。 Therefore, in Patent Document 2, the material temperature and the high-pressure gas are set to a temperature equal to or higher than the solution treatment temperature, and the cooling water is allowed to flow inside the superplastic molding die so that the material is molded and brought into contact with the die and the material is forcibly cooled. Proposed method. Such a technique of Patent Document 2 loses time from molding to forced cooling, enables sufficient quenching, and suppresses the occurrence of distortion during forced cooling by pressing the mold against high pressure gas. It is what.

特開２００８−６２２５５号公報JP 2008-62255 A 特開２００３−１５４４１５号公報JP 2003-154415 A

しかし、特許文献２の方法では、焼き入れまでは迅速に行えるが、予備時効処理を行うためには、成形装置の外に成形品を移動し、別工程で行う必要がある。そのため、焼き入れから予備時効開始までに時間が空き、人工時効の効果が小さくなってしまうという課題がある。 However, in the method of Patent Document 2, quenching can be performed quickly, but in order to perform the pre-aging treatment, it is necessary to move the molded product outside the molding apparatus and perform it in a separate process. For this reason, there is a problem that there is time from quenching to the start of preliminary aging, and the effect of artificial aging is reduced.

本発明は、上記課題に鑑みてなされたものであって、熱処理系アルミニウム合金を用いて高強度の超塑性成形品が得られ、かつ工程の削減が可能な、超塑性成形品の製造方法を提供することを目的とする。 The present invention has been made in view of the above-described problems, and provides a method for producing a superplastic molded product, which can obtain a high-strength superplastic molded product using a heat-treatable aluminum alloy and can reduce the number of processes. The purpose is to provide.

上記目的を達成するため、本発明に係る超塑性成形品の製造方法は、
熱処理系アルミニウム合金の被成形材に対して、溶体化温度以上の温度で予備加熱処理し、前記溶体化温度より低く人工時効処理の温度以上である予備時効温度の金型を用いて超塑性成形し、引き続き前記金型上で保持することで予備時効処理し、その後、前記人工時効処理を施す、ことを特徴とする。 In order to achieve the above object, a method for producing a superplastic molded product according to the present invention comprises:
Against the molded material of the heat treatment aluminum alloy, preheating treatment at a solution temperature or higher, superplastic using a mold of pre-aging temperature the is from solution temperature lower Ku than the temperature of the artificial aging molded, subsequently pre-aging treatment by holding on the mold, then, subjected to the artificial aging treatment, characterized in that.

この場合に、前記熱処理系アルミニウム合金として
質量％で
Ｓｉ：０．８〜１．４％
Ｍｇ：０．４〜１．１％
を含有し、残部はＡｌおよび不可避不純物からなるアルミニウム合金であってもよい。 In this case, Si: 0.8 to 1.4% in mass% as the heat treatment aluminum alloy
Mg: 0.4 to 1.1%
The balance may be an aluminum alloy made of Al and inevitable impurities.

また、前記熱処理系アルミニウム合金として
質量％で
Ｓｉ：０．８〜１．４％
Ｍｇ：０．４〜１．１％
を含有し、さらにＣｕを０．５〜１．０％含有し、残部はＡｌおよび不可避不純物からなるアルミニウム合金であってもよい。 Moreover, Si: 0.8 to 1.4% in mass% as the heat treatment aluminum alloy
Mg: 0.4 to 1.1%
Further, an aluminum alloy containing 0.5 to 1.0% of Cu and the balance of Al and inevitable impurities may be used.

また、前記予備加熱処理の温度を５３０℃〜５８０℃とする、こととしてもよい。 Moreover, it is good also as setting the temperature of the said preheating process to 530 degreeC-580 degreeC.

また、前記金型の温度を１８０℃〜２２０℃とする、こととしてもよい。 Moreover, it is good also as setting the temperature of the said metal mold to 180 to 220 degreeC.

また、前記被成形材の前記金型上における保持時間を８ｍｉｎ以上とする、こととしてもよい。 The holding time of the material to be molded on the mold may be 8 min or longer.

また、前記被成形材の前記金型上における保持時間を３ｍｉｎ以上とする、こととしてもよい。 The holding time of the material to be molded on the mold may be 3 min or longer.

また、前記超塑性成形の方法は高温ブロー成形法である、こととしてもよい。 The superplastic forming method may be a high temperature blow molding method.

また、前記超塑性成形において、前記高温ブロー成形法で用いられる高圧ガスの温度を４００℃〜５００℃とし、前記被成形材の温度を５℃／ｓ〜１４℃／ｓの冷却速度で降温させる、こととしてもよい。 In the superplastic forming, the temperature of the high-pressure gas used in the high-temperature blow molding method is set to 400 ° C. to 500 ° C., and the temperature of the material to be molded is lowered at a cooling rate of 5 ° C./s to 14 ° C./s. It's good.

本発明によれば、熱処理系アルミニウム合金を用いて高強度の超塑性成形品が得られ、かつ工程の削減が可能な、超塑性成形品の製造方法を提供することができる。 ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of a superplastic molded product which can obtain a high-strength superplastic molded product using heat-treatment type aluminum alloy and can reduce a process can be provided.

本発明の実施形態における工程と温度履歴との関係を示すグラフである。It is a graph which shows the relationship between the process in embodiment of this invention, and temperature history. 本発明の実施例で用いられる超塑性成形装置を模式的に示す図である。It is a figure which shows typically the superplastic forming apparatus used in the Example of this invention.

以下に本発明の実施形態について詳細に説明する。 Hereinafter, embodiments of the present invention will be described in detail.

図１に、本実施形態の溶体化処理から予備時効までの工程と温度履歴とを示す。図１に示すように、まず、超塑性成形品の素材である被成形板を溶体化温度以上の温度で予備加熱する。その後、被成形板を溶体化温度より低い予備時効温度に設定された所定の金型上で超塑性成形を行うとともに焼き入れし、引き続き金型上で所定の時間保持することで予備時効を行う。その後、製造された超塑性成形品は所定の温度及び時間で人工時効処理される。 In FIG. 1, the process from the solution treatment of this embodiment to preliminary aging, and temperature history are shown. As shown in FIG. 1, first, a plate to be molded, which is a material of a superplastic molded product, is preheated at a temperature equal to or higher than a solution temperature. Then, pre-aging is performed by performing superplastic forming on a predetermined mold set at a pre-aging temperature lower than the solution temperature and quenching, followed by holding for a predetermined time on the mold. . Thereafter, the manufactured superplastic molded article is artificially aged at a predetermined temperature and time.

（被成形板の材料）
本実施形態に用いられる被成形板の材料は、熱処理系アルミニウム合金とする。熱処理系アルミニウム合金とは、溶体化処理を行い直ちに急冷することで過飽和固溶状態とした後、焼き戻し処理を行うことで第二相を微細析出させ、所望の強度を得ることが出来るアルミニウム合金である。例えば、ＪＩＳ２０００系のＡｌ−Ｃｕ−Ｓｉ系合金（以下、２０００系合金）、ＪＩＳ６０００系のＡｌ−Ｍｇ−Ｓｉ系合金（以下、６０００系合金）、ＪＩＳ７０００系のＡｌ−Ｚｎ−Ｍｇ系合金（以下、７０００系合金）などが熱処理系アルミニウム合金として広く利用されている。以下、本実施形態では６０００系アルミニウム合金の例について説明する。 (Material of molded board)
The material of the forming plate used in this embodiment is a heat-treated aluminum alloy. A heat-treated aluminum alloy is an aluminum alloy that can obtain a desired strength by finely precipitating the second phase by performing a solution treatment and immediately quenching to obtain a supersaturated solid solution state and then performing a tempering treatment. It is. For example, JIS 2000 Al-Cu-Si alloy (hereinafter 2000 alloy), JIS 6000 Al-Mg-Si alloy (hereinafter 6000 alloy), JIS 7000 Al-Zn-Mg alloy (hereinafter 6000 alloy) 7000 series alloys) are widely used as heat treatment aluminum alloys. Hereinafter, in this embodiment, an example of a 6000 series aluminum alloy will be described.

６０００系合金は、自動車のアウターおよびインナー部品用途等、量産性が求められる超塑性成形品に適している。その理由を以下に示す。６０００系合金は比較的添加合金元素量が少なく、同じ６０００系合金パネルのスクラップを溶解した後、再利用しやすくリサイクル性にも優れている。そのため、同じ熱処理系アルミニウム合金である２０００系合金や７０００系合金に比べて材料費が安くすむ。加えて、６０００系合金はＭｇを含むために、高ひずみ速度域で比較的大きな延性を示す。その理由としては、高ひずみ速度域では変形の際に、転位がＭｇを引き摺りながら動くため、粘性抵抗となり板厚均一性が向上するからであると考えられている。Ｍｇは、Ａｌ中でサイズミスフィットが非常に大きい元素であるため、転位の周りに集中しやすい。このような、転位がＭｇを引き摺りながら移動する現象を溶質ドラッグ現象と呼んでいる。したがって、生産性の点で優れる高速成形には、Ｍｇを含有している６０００系アルミニウム合金が適している。本発明者らの知見によれば、１０^−３／ｓほどの低ひずみ速度では粒界すべりが主な変形機構となるため、４０μｍほどの比較的大きな結晶粒を持つ６０００系アルミニウム合金は粒界三重点で大きなキャビテーションが発生しやすく延性に劣る。しかし、１０^−２／ｓ以上の高ひずみ速度になると前述の溶質ドラッグのような粒内変形が主となることからキャビテーションの発生は抑えられ延性が向上し、２００％近くの大きな延性を示すようになることが分かっている。 The 6000 series alloy is suitable for superplastic molded products that require mass productivity, such as automotive outer and inner parts. The reason is as follows. The 6000 series alloy has a relatively small amount of additive alloy elements, and after melting the same 6000 series alloy panel scrap, it is easy to reuse and excellent in recyclability. Therefore, the material cost can be reduced as compared with 2000 series alloy and 7000 series alloy which are the same heat treatment type aluminum alloy. In addition, since the 6000 series alloy contains Mg, it exhibits a relatively large ductility in a high strain rate region. The reason for this is considered to be that the dislocation moves while dragging Mg during deformation in the high strain rate region, resulting in viscous resistance and improved plate thickness uniformity. Mg is an element that has a very large size misfit in Al, so it tends to concentrate around dislocations. Such a phenomenon in which dislocations move while dragging Mg is called a solute drag phenomenon. Therefore, a 6000 series aluminum alloy containing Mg is suitable for high speed forming which is excellent in productivity. According to the knowledge of the present inventors, grain boundary sliding becomes a main deformation mechanism at a strain rate as low as 10 ⁻³ / s. Therefore, a 6000 series aluminum alloy having a relatively large crystal grain of about 40 μm has a grain boundary. Large cavitation is likely to occur at the triple point, and the ductility is poor. However, at a high strain rate of 10 ⁻² / s or more, intragranular deformation such as the above-mentioned solute drag becomes the main, so that the occurrence of cavitation is suppressed and the ductility is improved, and a large ductility of nearly 200% is exhibited. I know that

ＪＩＳ６０００系アルミニウム合金として特に質量％でＳｉ：０．８〜１．４％、Ｍｇ：０．４〜１．１％のものを用いると大きな強度と良好な成形性が得られる。また、Ｃｕを０．５〜１．０％含有させると、さらに大きな強度を得ることが可能である。Ｓｉ量が０．８％未満、Ｍｇ量が０．４％未満、Ｃｕが０．５％未満の場合、人工時効硬化が小さく大きな強度が得られない。一方でＳｉ量が１．４％もしくはＭｇ量が１．１％より多い場合、第二相粒子が多くなり、キャビテーションの起因となることから大きな延性が得られない。また、Ｃｕ量が１．０％よりも多い場合、糸さびが発生し、耐食性が悪化する。被成形板は鋳造-均熱-熱延-冷延-熱処理の工程により製造する。ただし合金種にもよるが、場合により、均熱や熱処理は省略可能であり、一方で、冷延の間に一回以上の熱処理を設けても良い。 When a JIS 6000 series aluminum alloy having a mass percentage of Si: 0.8 to 1.4% and Mg: 0.4 to 1.1% is used, large strength and good formability can be obtained. Further, when Cu is contained in an amount of 0.5 to 1.0%, a greater strength can be obtained. When the Si content is less than 0.8%, the Mg content is less than 0.4%, and the Cu content is less than 0.5%, the artificial age hardening is small and a large strength cannot be obtained. On the other hand, when the Si content is 1.4% or the Mg content is more than 1.1%, the second phase particles increase and cavitation is caused, so that large ductility cannot be obtained. Moreover, when there is more Cu content than 1.0%, a thread rust will generate | occur | produce and corrosion resistance will deteriorate. The plate to be formed is manufactured by a process of casting, soaking, hot rolling, cold rolling, and heat treatment. However, depending on the type of alloy, depending on the case, soaking and heat treatment may be omitted. On the other hand, one or more heat treatments may be provided during cold rolling.

（予備加熱温度）
被成形板に６０００系アルミニウム合金を用いる場合、成形前に被成形板を５３０〜５８０℃の温度域に保つと十分な溶体化処理が可能である。望ましくは、出来るだけ高い温度に保つのが良いが、５８０℃以上とすると被成形板に局部融解が生じてしまうため、予備加熱温度は５８０℃以下とする。また、予備加熱の際の昇温速度は、速いほど結晶粒の粗大化及び熱延母結晶の粗大化を抑えるため、肌荒れやリジングの防止につながる。望ましくは、昇温速度は１０℃／ｓ以上であると良い。 (Preheating temperature)
When a 6000 series aluminum alloy is used for the forming plate, a sufficient solution treatment is possible if the forming plate is kept in a temperature range of 530 to 580 ° C. before forming. Desirably, the temperature should be kept as high as possible, but if it is 580 ° C. or higher, local melting occurs in the plate to be molded. Therefore, the preheating temperature is 580 ° C. or lower. Further, the higher the temperature raising rate during the preheating, the more the coarsening of crystal grains and the coarsening of hot-rolled mother crystals are suppressed, leading to prevention of rough skin and ridging. Desirably, the heating rate is 10 ° C./s or more.

（予備加熱方法）
被成形板の予備加熱の方法は特に規定しないが、大きな昇温速度が得られ、かつ迅速に成形を開始出来る方法でなければならない。つまり、予備加熱後、成形までに時間が空くと自然冷却により粗大な第二相粒子が析出し、十分な人工時効の効果が得られない。加えて、被成形板の温度が下がりすぎると、変形抵抗が大きくなり成形が出来なくなる。具体的には、バッチ炉を超塑性成形機に隣接させ、このバッチ炉で被成形板に対して予備加熱を行い、その後直ちに被成形板を金型の位置までスライド等の方法で移動させ、成形を開始する方法を取ると良い。 (Preheating method)
The method for preheating the plate to be molded is not particularly defined, but it must be a method that can obtain a large temperature increase rate and can start forming quickly. That is, if there is time before molding after preheating, coarse second-phase particles are precipitated by natural cooling, and a sufficient artificial aging effect cannot be obtained. In addition, if the temperature of the plate to be molded is too low, the deformation resistance increases and molding becomes impossible. Specifically, the batch furnace is placed adjacent to the superplastic forming machine, preliminarily heating the plate to be molded in this batch furnace, and immediately after that, the plate to be molded is moved to the position of the mold by a method such as sliding, It is good to take a method to start molding.

（超塑性成形方法）
超塑性成形方法には高温ブロー成形法を用いることが出来る。高温ブロー成形法によれば、成形用の高圧ガス温度による被成形板の温度調節や、成形用のガス圧によるひずみ速度の制御が可能である。成形用の高圧ガスには窒素ガスなどの不活性ガスを用いる必要がある。これは高圧ガスと被成形板が反応しないようにするためである。また、金型はプレス成形のように雄型を必要とせず、雌型のみで良い。したがって金型費は安価で済み、また装置の稼動が少ないという利点がある。金型の内部にはヒーターを配置し、金型を独立で温度制御できることが好ましい。 (Superplastic forming method)
A high temperature blow molding method can be used as the superplastic molding method. According to the high temperature blow molding method, it is possible to adjust the temperature of the plate to be molded by the high pressure gas temperature for molding and to control the strain rate by the gas pressure for molding. It is necessary to use an inert gas such as nitrogen gas as the high-pressure gas for molding. This is to prevent the high-pressure gas and the molded plate from reacting. In addition, the die does not need a male die unlike press molding, and only a female die may be used. Therefore, there is an advantage that the mold cost is low and the operation of the apparatus is small. It is preferable that a heater is disposed inside the mold so that the temperature of the mold can be controlled independently.

（高圧ガス圧力）
高圧ガスの圧力は、超塑性成形の金型形状に合わせて適宜変更しても良いが、成形が開始されると被成形板は急速に冷却されるので、出来るだけ高圧にすることが望ましい。本実施形態のような６０００系アルミニウム合金を用いれば、高ひずみ速度域でも２００％以上の比較的大きな伸びを示し、また変形機構が粒界すべり変形より粒内変形が主となるため、キャビテーションの発生を極わずかに抑えることが可能である。具体的には、１．０ＭＰａ以上のガス圧で成形することにより、板厚減少率が５０％の箇所でもキャビテーションの面積率を１．０％以下に抑えられることが分かっている。 (High pressure gas pressure)
The pressure of the high-pressure gas may be changed as appropriate according to the shape of the superplastic forming mold. However, since the forming plate is rapidly cooled when the forming is started, it is desirable to make the pressure as high as possible. When a 6000 series aluminum alloy as in this embodiment is used, a relatively large elongation of 200% or more is exhibited even in a high strain rate region, and the deformation mechanism is mainly intragranular deformation rather than intergranular sliding deformation. Occurrence can be minimized. Specifically, it has been found that by molding at a gas pressure of 1.0 MPa or more, the area ratio of cavitation can be suppressed to 1.0% or less even at a location where the plate thickness reduction rate is 50%.

（高圧ガス温度）
高圧ガスの温度は、被成形板の温度以下とすると、超塑性成形が行えると同時に被成形板の温度勾配を持たせることが出来、焼き入れ性が向上する。ただし、高圧ガスの温度を低くしすぎると、成形が完了する前に被成形板の変形抵抗が大きくなりすぎ、変形がそれ以上進まなくなり、また延性も落ちるため成形が出来ない場合もある。具体的には、６０００系アルミニウム合金を用いる場合、高圧ガスの温度を４００℃〜５００℃の範囲内にすると良い。そうすることで被成形板を５℃／ｓ〜１０℃／ｓの冷却速度で降温させることが可能である。ただし、５００℃以下とするとＭｇの固溶量が減少し、前述の溶質ドラッグ現象の効果が小さくなるため、延性が下がる。そのため比較的大きな変形量を要する場合は、高圧ガスの温度を５００℃とするのが望ましい。 (High pressure gas temperature)
If the temperature of the high-pressure gas is set to be equal to or lower than the temperature of the plate to be molded, superplastic forming can be performed and a temperature gradient of the plate to be molded can be provided, and the hardenability is improved. However, if the temperature of the high-pressure gas is too low, the deformation resistance of the plate to be molded becomes too large before the molding is completed, so that the deformation does not progress further, and the ductility is also lowered, so that molding may not be possible. Specifically, when a 6000 series aluminum alloy is used, the temperature of the high pressure gas is preferably in the range of 400 ° C to 500 ° C. By doing so, it is possible to cool down a to-be-formed board with the cooling rate of 5 degree-C / s-10 degree-C / s. However, if the temperature is 500 ° C. or lower, the solid solution amount of Mg is reduced, and the effect of the solute drag phenomenon is reduced, so that the ductility is lowered. Therefore, when a relatively large amount of deformation is required, it is desirable to set the temperature of the high-pressure gas to 500 ° C.

（金型温度）
金型の温度は予備時効温度に保持するものとする。予備時効温度とは、用いられる熱処理系アルミニウム合金に対して予備時効の効果の大きい温度である。そうすることにより、被成形板は金型と接触した部分から大きな焼き入れが入り、金型と同じ温度に冷却された時点で、予備時効処理温度に保持される。すなわち溶体化処理、超塑性成形、焼き入れ、予備時効処理の工程を全て連続的に行うことが可能である。６０００系アルミニウム合金を用いる場合、金型の温度は１８０℃〜２２０℃の範囲内で保持することが望ましい。本発明者らの知見から前記温度内で予備時効処理を行うと人工時効による強度向上が最も大きいことが分かっている。 (Mold temperature)
The mold temperature is maintained at the pre-aging temperature. The pre-aging temperature is a temperature at which the pre-aging effect is large for the heat-treated aluminum alloy used. By doing so, a to-be-molded board is hold | maintained at the preliminary aging treatment temperature, when big quenching enters from the part which contacted the metal mold | die, and it cooled to the same temperature as a metal mold | die. That is, the steps of solution treatment, superplastic forming, quenching, and preliminary aging treatment can all be performed continuously. When using a 6000 series aluminum alloy, it is desirable to hold | maintain the temperature of a metal mold | die within the range of 180 to 220 degreeC. From the knowledge of the present inventors, it is known that the strength improvement by artificial aging is the greatest when the preliminary aging treatment is performed within the temperature.

本実施形態の成形温度は、予備加熱温度に比べて非常に低い温度であるため、離型性が向上するという利点がある。熱処理系アルミニウム合金は溶体化処理温度以上に加熱する必要があるため、金型も同じ温度とすると超塑性成形品と金型で強い固着が起こり、離型の際に歪が生じてしまう。そのような課題に対し、本発明によれば金型温度は低温であるため、超塑性成形品と金型の間で強い固着は起きず、離型が容易となる。また、金型を高温に上げる必要がないため、エネルギーコストを削減することが可能である。 Since the molding temperature of the present embodiment is very lower than the preheating temperature, there is an advantage that the mold release property is improved. Since the heat-treated aluminum alloy needs to be heated to a temperature equal to or higher than the solution treatment temperature, if the mold is set to the same temperature, strong fixation occurs between the superplastic molded product and the mold, and distortion occurs during the mold release. In order to solve such a problem, according to the present invention, since the mold temperature is low, strong fixation does not occur between the superplastic molded product and the mold, and the mold release becomes easy. In addition, since it is not necessary to raise the mold to a high temperature, it is possible to reduce energy costs.

（金型で保持する時間）
最後に、超塑性成形品を金型で保持する時間は、所望の予備時効の効果が出る時間とする。一般的に予備時効処理の時間が長いほど強度の向上は大きいが、サイクルタイムを考慮すると保持時間は１０ｍｉｎ以内にすることが望ましい。本発明者の知見によれば、本発明の請求の範囲に記載の合金を用いれば８ｍｉｎの予備時効を行えば大きく強度が向上することが分かっている。さらには請求の範囲に記載のように、Ｃｕを０．５〜１．０％含有の合金では、３ｍｉｎの予備時効処理を行えば大きく強度が向上することが分かっており、サイクルタイムを短くすることも可能である。 (Time to hold in the mold)
Finally, the time for holding the superplastic molded product with the mold is set to the time when the desired preliminary aging effect is produced. In general, the longer the preliminary aging treatment, the greater the improvement in strength. However, considering the cycle time, the holding time is preferably within 10 minutes. According to the knowledge of the present inventor, it has been found that if the alloy described in the claims of the present invention is used, the strength is greatly improved by performing preliminary aging for 8 minutes. Furthermore, as described in the claims, it has been found that the alloy containing 0.5 to 1.0% of Cu greatly improves the strength by performing the pre-aging treatment for 3 minutes, and shortens the cycle time. It is also possible.

なお、上記実施形態では６０００系合金を例としたが、本発明は、例えば、２０００系合金や７０００系合金等の熱処理系アルミニウム合金に対しても好適に利用することができる。この場合において、各工程における温度及び時間等の条件は、合金の種類によって適宜実験的に定めることが好ましい。 In the above-described embodiment, the 6000 series alloy is taken as an example, but the present invention can be suitably used for a heat treatment aluminum alloy such as a 2000 series alloy or a 7000 series alloy. In this case, it is preferable to experimentally determine conditions such as temperature and time in each step depending on the type of alloy.

次に、本発明に係る超塑性成形品の製造方法の実施例について、その特許請求の範囲から外れる比較例と比較して具体的に説明するが、本発明はこれに制限されるものではない。 Next, examples of the method for producing a superplastic molded product according to the present invention will be specifically described in comparison with comparative examples that are out of the scope of the claims, but the present invention is not limited thereto. .

被成形板の材料には、表１に示す組成の６０００系アルミニウム合金を用いた（合金番号１〜１３）。なお、表１において残部とは不可避的不純物を含む。 A 6000 series aluminum alloy having a composition shown in Table 1 was used as the material of the plate to be molded (Alloy Nos. 1 to 13). In Table 1, the balance includes inevitable impurities.

工程及び温度履歴は、図１で前述したとおりである。予備加熱にはバッチ炉を用い、超塑性成形にはブロー成形を用いた。また被成形板の板厚を１．３ｍｍとした。予備加熱した被成形板を速やかに超塑性成形出来るようにバッチ炉と図２に示す金型２とは隣接させた。予備加熱温度は５００℃、５３０℃、５５０℃とし、被成形板が十分に溶体化する温度とした。 The process and temperature history are as described above with reference to FIG. A batch furnace was used for preheating, and blow molding was used for superplastic forming. The plate thickness of the plate to be molded was 1.3 mm. The batch furnace and the mold 2 shown in FIG. 2 were placed adjacent to each other so that the preheated plate can be quickly superplastically formed. The preheating temperature was 500 ° C., 530 ° C., and 550 ° C., and the temperature at which the plate to be molded was sufficiently formed into solution.

図２に本実施例で超塑性成形、焼入れ、予備時効を行う超塑性成形装置の主要部を模式的に示す。前述の如く予備加熱した被成形板１を金型２の上に移動させ、押さえ型３を下降させ、速やかにシーリングし、高圧ガスにより超塑性成形を行った。超塑性成形品は３５０ｍｍ×３５０ｍｍ、高さ９０ｍｍの角筒とした。金型２の温度はヒーター３を用いて制御し、表２に示すように、実験条件１〜１１について１７０℃、２００℃又は２３０℃とした。また、押さえ型４の温度はヒーター５で制御し、金型２の温度と同じ温度になるように制御した。 FIG. 2 schematically shows a main part of a superplastic forming apparatus that performs superplastic forming, quenching, and preliminary aging in this embodiment. As described above, the preliminarily heated plate 1 was moved onto the mold 2, the presser mold 3 was lowered, quickly sealed, and superplastic forming was performed with high-pressure gas. The superplastic molded product was a square tube of 350 mm × 350 mm and a height of 90 mm. The temperature of the mold 2 was controlled using the heater 3, and as shown in Table 2, the experiment conditions 1 to 11 were set to 170 ° C., 200 ° C., or 230 ° C. Further, the temperature of the presser mold 4 was controlled by the heater 5 so as to be the same temperature as that of the mold 2.

超塑性成形の方法として高温ブロー成形法を使用した。この成形方法に用いられる高圧ガスは、通路６を通り押さえ型４の内側に供給されるようにした。図には示していないが、供給源は例えば７ｍ^３の高圧のガスボンベとし、高圧ガスには窒素ガスを用いた。断熱材７を挟んで高圧ガス加熱室８を設け、ヒーター９により成形前に高圧ガスを加熱した。加熱されたガスは開閉弁１０を伴ったバルブ１１により加熱室８に保持され、成形開始時には開いて高圧ガスを供給出来るようにした。本実験では、高圧ガスの温度は各実験条件について５１０℃又は４００℃とし、圧力は５ＭＰａとした。また昇圧時間を１０秒とし、その後２０秒間５ＭＰａで一定とした。成形後、超塑性成形品を金型上で各実験条件について２ｍｉｎ、３ｍｉｎ、６ｍｉｎ、８ｍｉｎ又は３２ｍｉｎ保持した。 A high temperature blow molding method was used as a superplastic molding method. The high-pressure gas used in this molding method was supplied to the inside of the holding die 4 through the passage 6. Although not shown in the figure, the supply source was a high-pressure gas cylinder of, for example, 7 m ³ , and nitrogen gas was used as the high-pressure gas. A high pressure gas heating chamber 8 was provided with the heat insulating material 7 interposed therebetween, and the high pressure gas was heated by the heater 9 before molding. The heated gas was held in the heating chamber 8 by a valve 11 with an on-off valve 10 and opened at the start of molding so that high-pressure gas could be supplied. In this experiment, the temperature of the high-pressure gas was 510 ° C. or 400 ° C. for each experimental condition, and the pressure was 5 MPa. The pressurization time was 10 seconds, and then was kept constant at 5 MPa for 20 seconds. After molding, the superplastic molded product was held on the mold for 2 min, 3 min, 6 min, 8 min or 32 min for each experimental condition.

次に、超塑性成形品に１８０℃で３５ｍｉｎの人工時効処理を行った後、底面中央付近（板厚減少率約３０％）からＪＩＳ５号引張試験片を採取し、０．２％耐力の測定を行った。引張方向は圧延方向に平行とした。 Next, after superplastic molding was subjected to an artificial aging treatment at 180 ° C. for 35 min, a JIS No. 5 tensile test piece was collected from the vicinity of the bottom center (plate thickness reduction rate of about 30%), and the 0.2% yield strength was measured. Went. The tensile direction was parallel to the rolling direction.

表２の実験条件１〜１１は表１の合金１に対して、予備加熱温度、高圧ガス温度、金型温度、金型上の保持時間に対する超塑性成形品の０．２％耐力を示したものである。０．２％耐力は、自動車用アウター材に必要な１９０ＭＰａを目標値とした。 Experimental conditions 1 to 11 in Table 2 show the 0.2% proof stress of the superplastic molded product with respect to the alloy 1 of Table 1 with respect to the preheating temperature, the high-pressure gas temperature, the mold temperature, and the holding time on the mold. Is. The target value of 0.2% proof stress was 190 MPa required for the outer material for automobiles.

実験条件１〜３の比較により予備加熱温度の影響を調査した。その結果５３０℃、５５０℃では１９０ＭＰａ以上の強度を得ることが出来たが、５００℃では大きな強度を得ることが出来なかった。これは５００℃では溶体化が不十分であると考えられ、予備加熱温度は５３０℃以上が望ましい。なお予備加熱温度を５８０℃より大きくすると局部融解が生じた。 The effect of preheating temperature was investigated by comparing experimental conditions 1 to 3. As a result, a strength of 190 MPa or more could be obtained at 530 ° C. and 550 ° C., but a large strength could not be obtained at 500 ° C. It is considered that the solution is insufficient at 500 ° C., and the preheating temperature is desirably 530 ° C. or higher. When the preheating temperature was higher than 580 ° C., local melting occurred.

次に、実験条件３〜６の比較により高圧ガス温度と冷却速度の影響を調査した。実験４のように高圧ガス温度を５１０℃とすると、被成形板の冷却速度はおよそ４℃／ｓとなり十分な焼入れを行うことが出来ず、強度が得られないことが分かる。一方で、実験条件５のように高圧ガス温度を３５０℃とすると、冷却速度はおよそ１５℃／ｓとなり成形が完了する前に材料の変形抵抗が非常に大きくなり変形が進まなくなってしまった（表２の「成形未完了」）。これらの結果から、高圧ガスの温度は本発明に示すように４００℃〜５００℃の間が望ましい。 Next, the influence of the high-pressure gas temperature and the cooling rate was investigated by comparing experimental conditions 3 to 6. When the high-pressure gas temperature is set to 510 ° C. as in Experiment 4, it can be seen that the cooling rate of the plate to be molded becomes approximately 4 ° C./s, and sufficient quenching cannot be performed, and the strength cannot be obtained. On the other hand, when the high-pressure gas temperature is set to 350 ° C. as in the experimental condition 5, the cooling rate is about 15 ° C./s, and the deformation resistance of the material becomes very large before the molding is completed and the deformation does not progress ( “Molding incomplete” in Table 2). From these results, the temperature of the high-pressure gas is preferably between 400 ° C. and 500 ° C. as shown in the present invention.

次に、実験条件３、７、８の比較により金型温度の影響を調査した。実験条件７、８のように金型温度を１７０℃、２３０℃とすると、１９０ＭＰａを超える強度は得られなかったが、本発明例である実験条件３のように金型温度を２００℃とすると１９０ＭＰａを超える大きな強度を得た。本発明者らの知見から、金型の温度を１８０℃〜２２０℃にすれば、金型上の保持時間を８ｍｉｎで１９０ＭＰａ以上の大きな強度を得ることが分かっている。 Next, the influence of the mold temperature was investigated by comparing the experimental conditions 3, 7, and 8. When the mold temperature was 170 ° C. and 230 ° C. as in experimental conditions 7 and 8, strength exceeding 190 MPa was not obtained, but when the mold temperature was 200 ° C. as in experimental condition 3 which is an example of the present invention. A large strength exceeding 190 MPa was obtained. From the knowledge of the present inventors, it is known that if the temperature of the mold is set to 180 ° C. to 220 ° C., a large strength of 190 MPa or more is obtained at a holding time on the mold of 8 min.

最後に、実験条件３、９、１０、１１の比較により金型上の保持時間の影響を調査した。本発明のように金型上の保持時間を８ｍｉｎ以上とすれば、１９０ＭＰａを超える大きな強度を得ることが出来るが、金型上の保持時間が２ｍｉｎ、６ｍｉｎでは大きな強度は得られなかった。この結果から、合金１を被成形板として用いる場合、予備時効の効果を得るためには少なくとも金型上の保持時間を８ｍｉｎ以上とする必要があることが分かる。 Finally, the effect of holding time on the mold was investigated by comparing experimental conditions 3, 9, 10, and 11. When the holding time on the mold is 8 min or more as in the present invention, a large strength exceeding 190 MPa can be obtained, but no large strength was obtained when the holding time on the mold was 2 min and 6 min. From this result, it can be seen that, when using the alloy 1 as a plate to be molded, at least the holding time on the mold needs to be 8 min or more in order to obtain the effect of preliminary aging.

表３の実験条件１２〜２４は本発明の合金組成の範囲内外にＳｉ、Ｍｇ、Ｃｕ量を振り、それらの合金の人工時効後の０．２％耐力を示したものである。予備加熱温度、高圧ガス温度、金型温度は、それぞれ５３０℃、４００℃、２００℃とし、表２において最も人工時効後に強度を得た条件に統一した。 Experimental conditions 12 to 24 in Table 3 show the 0.2% yield strength after artificial aging of these alloys by varying the amounts of Si, Mg and Cu within and outside the range of the alloy composition of the present invention. The preheating temperature, the high-pressure gas temperature, and the mold temperature were set to 530 ° C., 400 ° C., and 200 ° C., respectively.

まず実験条件３および１２〜１５の比較によりＳｉ量の影響を調査した。その結果、Ｓｉ量が０．８％以上のときに１９０ＭＰａを超える強度を得ることが出来たが、０．６９％では得ることが出来なかった。またＳｉ量１．５％では成形品に破断が生じた。このことからＳｉ量は０．７５〜１．４％の範囲内が望ましい。 First, the influence of the amount of Si was investigated by comparing experimental conditions 3 and 12-15. As a result, it was possible to obtain a strength exceeding 190 MPa when the Si amount was 0.8% or more, but not 0.69%. When the Si amount was 1.5%, the molded product was broken. For this reason, the Si content is desirably in the range of 0.75 to 1.4%.

次に実験条件３および１６〜１９の比較によりＭｇ量の影響を調査した。その結果、Ｍｇ量が０．４％以上のときに１９０ＭＰａを超える強度を得ることが出来たが、０．２％では得ることが出来なかった。またＭｇ量１．２％では成形品に破断が生じた。このことからＭｇ量は０．４〜１．１％の範囲内が望ましい。 Next, the influence of the amount of Mg was investigated by comparing experimental conditions 3 and 16-19. As a result, it was possible to obtain a strength exceeding 190 MPa when the Mg content was 0.4% or more, but not 0.2%. When the Mg content was 1.2%, the molded product was broken. For this reason, the amount of Mg is preferably in the range of 0.4 to 1.1%.

最後に実験条件２０〜２４の比較によりＣｕ含有量と金型上の保持時間の影響を調査した。その結果実験条件２０、２１のようにＣｕ含有量が０．６％以上でかつ金型上の保持時間が３分であれば１９０ＭＰａを超える強度を得ることが出来た。しかし、実験条件２２のようにＣｕ含有量が０．６％であっても金型上の保持時間が２分であれば１９０ＭＰａを超える強度を得ることは出来なかった。また実験条件２３のようにＣｕ含有量が０．４％の場合、金型上の保持時間を３分としても１９０ＭＰａを超える強度を得ることは出来なかった。なおＣｕ含有量が１．１％となると糸錆が生じ、耐食性が悪化した。このことからＣｕ含有量は０．５〜１．０％が望ましく、金型上の保持時間を３分としても１９０ＭＰａを超える強度を得ることが可能である。 Finally, the effects of Cu content and holding time on the mold were investigated by comparing experimental conditions 20-24. As a result, when the Cu content was 0.6% or more and the holding time on the mold was 3 minutes as in the experimental conditions 20 and 21, a strength exceeding 190 MPa could be obtained. However, even if the Cu content is 0.6% as in the experimental condition 22, if the holding time on the mold is 2 minutes, a strength exceeding 190 MPa could not be obtained. Further, when the Cu content was 0.4% as in the experimental condition 23, it was not possible to obtain a strength exceeding 190 MPa even when the holding time on the mold was 3 minutes. In addition, when the Cu content was 1.1%, yarn rust was generated and the corrosion resistance was deteriorated. From this, the Cu content is desirably 0.5 to 1.0%, and it is possible to obtain a strength exceeding 190 MPa even if the holding time on the mold is 3 minutes.

以上により、本発明によれば、熱処理系アルミニウム合金の溶体化処理、溶体化処理より低い温度での超塑性成形及び焼き入れ、並びに予備時効を一連の工程で行うので、人工時効の効果を高めて高強度の超塑性成形品が得られるとともに工程の削減を行うことができる。 As described above, according to the present invention, the solution treatment of the heat-treated aluminum alloy, superplastic forming and quenching at a lower temperature than the solution treatment, and preliminary aging are performed in a series of steps, so that the effect of artificial aging is enhanced. In addition, a high-strength superplastic molded product can be obtained and the number of processes can be reduced.

１被成形板
２金型
３ヒーター
４押さえ型
５ヒーター
６通路
７断熱材
８加熱室
９ヒーター
１０開閉弁
１１バルブ DESCRIPTION OF SYMBOLS 1 Molding board 2 Mold 3 Heater 4 Holding mold 5 Heater 6 Passage 7 Heat insulating material 8 Heating chamber 9 Heater 10 On-off valve 11 Valve

Claims

熱処理系アルミニウム合金の被成形材に対して、溶体化温度以上の温度で予備加熱処理し、前記溶体化温度より低く人工時効処理の温度以上である予備時効温度の金型を用いて超塑性成形し、引き続き前記金型上で保持することで予備時効処理し、その後、前記人工時効処理を施す、ことを特徴とする超塑性成形品の製造方法。 Against the molded material of the heat treatment aluminum alloy, preheating treatment at a solution temperature or higher, superplastic using a mold of pre-aging temperature the is from solution temperature lower Ku than the temperature of the artificial aging molded, subsequently pre-aging treatment by holding on the mold, then the artificial aging treatment is performed, a manufacturing method of superplastic forming article, characterized in that.

前記熱処理系アルミニウム合金は、質量％で
Ｓｉ：０．８〜１．４％
Ｍｇ：０．４〜１．１％
を含有し、残部はＡｌおよび不可避不純物からなるアルミニウム合金であることを特徴とする請求項１に記載の超塑性成形品の製造方法。 The heat-treatable aluminum alloy is Si: 0.8 to 1.4% by mass.
Mg: 0.4 to 1.1%
The method for producing a superplastic molded product according to claim 1, wherein the balance is an aluminum alloy comprising Al and inevitable impurities.

前記熱処理系アルミニウム合金は、質量％で
Ｓｉ：０．８〜１．４％
Ｍｇ：０．４〜１．１％
を含有し、さらにＣｕを０．５〜１．０％含有し、残部はＡｌおよび不可避不純物からなるアルミニウム合金であることを特徴とする請求項１に記載の超塑性成形品の製造方法。 The heat-treatable aluminum alloy is Si: 0.8 to 1.4% by mass.
Mg: 0.4 to 1.1%
2. The method for producing a superplastic molded product according to claim 1, further comprising 0.5 to 1.0% of Cu, the balance being an aluminum alloy composed of Al and inevitable impurities.

前記予備加熱処理の温度を５３０℃〜５８０℃とする、ことを特徴とする請求項２又は３に記載の超塑性成形品の製造方法。 The method for producing a superplastic molded product according to claim 2 or 3, wherein the temperature of the preheating treatment is set to 530C to 580C.

前記金型の温度を１８０℃〜２２０℃とする、ことを特徴とする請求項２又は３に記載の超塑性成形品の製造方法。 The method for producing a superplastic molded product according to claim 2 or 3, wherein a temperature of the mold is set to 180 ° C to 220 ° C.

前記被成形材の前記金型上における保持時間を８ｍｉｎ以上とする、ことを特徴とする請求項２に記載の超塑性成形品の製造方法。 The method for producing a superplastic molded product according to claim 2, wherein the holding time of the molding material on the mold is 8 min or more.

前記被成形材の前記金型上における保持時間を３ｍｉｎ以上とする、ことを特徴とする請求項３に記載の超塑性成形品の製造方法。 The method for producing a superplastic molded product according to claim 3, wherein a holding time of the molding material on the mold is set to 3 minutes or more.

前記超塑性成形の方法は高温ブロー成形法である、ことを特徴とする請求項１乃至７のいずれか１項に記載の超塑性成形品の製造方法。 The method for producing a superplastic molded product according to any one of claims 1 to 7, wherein the superplastic molding method is a high temperature blow molding method.

前記超塑性成形において、前記高温ブロー成形法で用いられる高圧ガスの温度を４００℃〜５００℃とし、前記被成形材の温度を５℃／ｓ〜１４℃／ｓの冷却速度で降温させる、ことを特徴とする請求項１乃至８のいずれか１項に記載の超塑性成形品の製造方法。 In the superplastic molding, the temperature of the high-pressure gas used in the high-temperature blow molding method is set to 400 ° C. to 500 ° C., and the temperature of the material to be molded is lowered at a cooling rate of 5 ° C./s to 14 ° C./s. The method for producing a superplastic molded product according to any one of claims 1 to 8.