JP6345016B2 - Aluminum alloy plate for hot forming and manufacturing method thereof - Google Patents
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本発明は、高い時効硬化性を有するだけでなく、高歪み速度域において高い高温延性を有し、熱間成形に好適なＡｌ−Ｍｇ−Ｓｉ系の熱間成形用アルミニウム合金板及びその製造方法に関する。 The present invention provides an Al-Mg-Si hot-forming aluminum alloy sheet suitable for hot forming and not only having high age-hardening properties but also high high-temperature ductility in a high strain rate region, and a method for producing the same About.
近年、構造部品の軽量化手段の一つとして、アルミニウム合金の適用が進んでいる。しかしながら、一般的にアルミニウム合金は鋼板に比べて成形性が低く、様々な加工法の検討が必要である。そのような加工法の一つとして、超塑性変形を利用した熱間成形が挙げられる。このような熱間成形の代表的な例として、ブロー成形が挙げられる。 In recent years, application of aluminum alloys has been progressing as one of means for reducing the weight of structural parts. However, aluminum alloys generally have lower formability than steel plates, and various processing methods need to be studied. One of such processing methods is hot forming using superplastic deformation. A typical example of such hot forming is blow molding.
ブロー成形とは、特にアルミニウムが高温で超塑性と呼ばれる著しく大きな延性を示すことを利用した成形方法である。具体的には、加熱された上下金型でアルミニウム板材を挟持し、アルミニウム板材を加熱した後に高圧ガスで加圧して、アルミニウム板材を成形金型形状に成形する方法が一般的である。ブロー成形は、アルミニウム材の大きな高温延性を利用して冷間プレス成形では不可能な複雑形状の成形を可能とするだけでなく、高温での変形抵抗が小さいために、金型への転写性に優れ高意匠性部品に適する。加えて、基本的には片方の金型だけで成形が可能なため、冷間プレス成形に比べて金型費を低減でき、少量多品種の部品の成形に用いられている。 Blow molding is a molding method that makes use of the fact that aluminum exhibits a remarkably large ductility called superplasticity at high temperatures. Specifically, a method is generally used in which an aluminum plate is sandwiched between heated upper and lower molds, and the aluminum plate is heated and then pressurized with a high-pressure gas to form the aluminum plate into a molding die shape. Blow molding not only makes it possible to mold complex shapes that are impossible with cold press molding by utilizing the high-temperature ductility of aluminum materials, but also has low deformation resistance at high temperatures, so transferability to molds is possible. Excellent for high design parts. In addition, since molding is basically possible with only one mold, the mold cost can be reduced as compared with cold press molding, and it is used for molding a small variety of parts.
特にアルミニウム合金に関しては、優れた超塑性特性を示す材料が積極的に開発されている。中でもＡｌ−Ｃｕ系及びＡｌ−Ｚｎ−Ｍｇ−Ｃｕ系のアルミニウム合金は、高温で著しく大きな延性を示すことに加え、ブロー成形後の熱処理により高強度が得られるために、幾つかのブロー成形用合金が開発されている。 Particularly for aluminum alloys, materials exhibiting excellent superplastic properties have been actively developed. Among them, Al-Cu-based and Al-Zn-Mg-Cu-based aluminum alloys exhibit remarkably large ductility at high temperatures and high strength can be obtained by heat treatment after blow molding. Alloys have been developed.
しかしながら、Ａｌ−Ｃｕ系やＡｌ−Ｚｎ−Ｍｇ−Ｃｕ系のアルミニウム合金は、耐食性と溶接性に劣り、また製造コストが高価になるために航空機などの特殊部品への適用に限られている。一方で、Ｍｇが多量に固溶したＡｌ−Ｍｇ系合金は高温で大きな延性を示すことは勿論であるが、中程度の強度と溶接性、ならびに、耐食性に優れており、一般部品向けの熱間成形用材料として広く用いられている。特にその需要の大部分は、自動車部品用途に占められている。しかしながら、自動車部品への軽量化の需要が増大するにつれ、高強度の一般部品用途の熱間成形用材料が求められるようになってきた。 However, Al-Cu-based and Al-Zn-Mg-Cu-based aluminum alloys are inferior in corrosion resistance and weldability, and are expensive to manufacture, and thus are limited to application to special parts such as aircraft. On the other hand, an Al-Mg alloy with a large amount of Mg in solid solution exhibits high ductility at a high temperature, but it has excellent medium strength, weldability, and corrosion resistance. Widely used as an inter-molding material. In particular, most of the demand is occupied by automobile parts. However, as the demand for weight reduction of automobile parts increases, a hot molding material for general parts with high strength has been demanded.
そのため、近年では特許文献１、２のような熱間成形用Ａｌ−Ｍｇ−Ｓｉ系合金が開発されている。しかしながら、これらの熱間成形用Ａｌ−Ｍｇ−Ｓｉ系合金の成形性は必ずしも十分ではなかった。特に生産性の点において、実用的な歪み速度域である１０−２〜１０−１／秒での高温延性は十分とは言えず、高速成形ができないため量産性に劣るという問題があった。 Therefore, in recent years, Al-Mg-Si alloys for hot forming like Patent Documents 1 and 2 have been developed. However, the formability of these Al-Mg-Si alloys for hot forming is not always sufficient. In particular, in terms of productivity, the high temperature ductility at 10 −2 to 10 −1 / sec, which is a practical strain rate range, is not sufficient, and there is a problem in that it is inferior in mass productivity because high-speed molding cannot be performed.
本発明は上記問題を解決すべくなされたもので、高い時効硬化性を有するだけでなく、１０−２〜１０−１／秒の高歪み速度域における高温延性が高く、高速成形による量産性に優れる熱間成形用アルミニウム合金板及びその製造方法の提供を目的とする。 The present invention has been made to solve the above-mentioned problems, and not only has high age-hardening properties, but also has high high-temperature ductility in a high strain rate range of 10 −2 to 10 −1 / sec. An object is to provide an excellent aluminum alloy plate for hot forming and a method for producing the same.
上記問題に対して本発明者は、高歪み速度域における熱間成形性と材料組織の関係を種々種検討した結果、高歪み速度域においても成形中に発生する欠陥が成形性の低下を招くことを突き止めた。更に、この欠陥を抑制するためには１５°未満の小角粒界の存在確率を大きくすることが効果的であることを見出した。また、高い成形性を維持しつつ、時効硬化により高強度が得られる成分範囲を特定した。具体的には、一般部品用途として十分な強度である引張強度３００ＭＰａ以上を、時効後の引張強度として設定した。これにより、高い時効硬化性を有するだけでなく、高歪み速度域における成形性の向上を達成することができ、本発明を完成するに至った。 As a result of various studies on the relationship between the hot formability and the material structure in the high strain rate region, the present inventors have found that the defects generated during molding cause the moldability to deteriorate even in the high strain rate region. I found out. Furthermore, in order to suppress this defect, it has been found effective to increase the existence probability of a small-angle grain boundary of less than 15 °. Moreover, the component range in which high strength is obtained by age hardening while maintaining high moldability was specified. Specifically, a tensile strength of 300 MPa or more, which is a sufficient strength for general parts, was set as the tensile strength after aging. Thereby, not only has high age-hardening property, but also improvement in formability in a high strain rate region can be achieved, and the present invention has been completed.
すなわち、本発明は請求項１において、Ｍｇ：０．３〜２．０ｍａｓｓ％、Ｓｉ：０．６〜２．０ｍａｓｓ％を含有し、Ｍｎ：０．０４％〜０．５０ｍａｓｓ％及びＣｒ：０．０４％〜０．３０ｍａｓｓ％の１種又は２種を更に含有し、残部Ａｌ及び不可避的不純物からなるアルミニウム合金からなり、昇温速度６０℃／分で５３０℃まで昇温後において、隣接する結晶粒の粒界が１５°未満の小角粒界である存在確率が５０％以上であることを特徴とする熱間成形用アルミニウム合金板とした。 That is, this invention contains Mg: 0.3-2.0mass%, Si: 0.6-2.0mass% in Claim 1, Mn: 0.04% -0.50mass% and Cr: 0 It further comprises one or two kinds of 0.04% to 0.30 mass%, and consists of an aluminum alloy composed of the balance Al and unavoidable impurities, and is adjacent after being heated up to 530 ° C. at a heating rate of 60 ° C./min. The aluminum alloy plate for hot forming was characterized in that the existence probability that the grain boundaries of the crystal grains were small-angle grain boundaries of less than 15 ° was 50% or more.
本発明は請求項２では請求項１において、熱間成形用アルミニウム合金板が、Ｓ方位の方位密度が２０以上、５μｍ以上の第２相粒子の密度が１００〜１０００個／ｍｍ２の未再結晶組織からなるものとした。 The present invention is the second aspect of the present invention, wherein the hot-formed aluminum alloy sheet is not re-reproduced in which the orientation density of the S orientation is 20 or more and the density of second phase particles of 5 μm or more is 100 to 1000 / mm 2 . It consisted of a crystal structure.
更に本発明は請求項３では請求項１又は２において、前記アルミニウム合金がＣｕ：０．１０〜０．８０ｍａｓｓ％、Ｚｎ：０．３ｍａｓｓ％以下及びＴｉ：０．１５ｍａｓｓ％以下から選択される１種又は２種以上を更に含有するものとした。 Furthermore, in the present invention, the present invention is the first aspect, wherein the aluminum alloy is selected from Cu: 0.10 to 0.80 mass%, Zn: 0.3 mass% or less, and Ti: 0.15 mass% or less 1 The seeds or two or more kinds were further contained.
本発明は請求項４では請求項１〜３のいずれか一項において、ブロー成形用に用いられるアルミニウム合金板とした。 According to a fourth aspect of the present invention, in any one of the first to third aspects, the aluminum alloy plate is used for blow molding.
本発明は請求項５において、請求項１〜４のいずれか一項に記載の熱間成形用アルミニウム合金板の製造方法であって、Ｍｇ：０．３〜２．０ｍａｓｓ％、Ｓｉ：０．６〜２．０ｍａｓｓ％を含有し、Ｍｎ：０．０４％〜０．５０ｍａｓｓ％及びＣｒ：０．０４％〜０．３０ｍａｓｓ％の１種又は２種を更に含有し、残部Ａｌ及び不可避的不純物からなるアルミニウム合金溶湯を鋳造する鋳造工程と、得られた鋳塊を５００℃以上で、かつ前記アルミニウム合金の融点未満の温度で１〜１２時間熱処理する均質化処理工程と、均質化処理した鋳塊が３００〜４００℃のときの圧下率を８０％以上とする熱間圧延工程とを含むことを特徴とする熱間成形用アルミニウム合金板の製造方法とした。 This invention is the manufacturing method of the aluminum alloy plate for hot forming as described in any one of Claims 1-4 in Claim 5, Comprising: Mg: 0.3-2.0mass%, Si: 0.00. 6 to 2.0 mass%, Mn: 0.04% to 0.50 mass% and Cr: 0.04% to 0.30 mass%, or further containing one or two types, the balance Al and inevitable impurities A casting process for casting a molten aluminum alloy comprising: a homogenization process in which the obtained ingot is heat treated at a temperature of 500 ° C. or higher and lower than the melting point of the aluminum alloy for 1 to 12 hours; And a hot rolling step for reducing the rolling reduction when the lump is 300 to 400 ° C. to 80% or more.
本発明は請求項６では請求項５において、前記アルミニウム合金がＣｕ：０．１０〜０．８０ｍａｓｓ％、Ｚｎ：０．３ｍａｓｓ％以下及びＴｉ：０．１５ｍａｓｓ％以下から選択される１種又は２種以上を更に含有するものとした。 According to a sixth aspect of the present invention, in the sixth aspect, the aluminum alloy is one or two selected from Cu: 0.10 to 0.80 mass%, Zn: 0.3 mass% or less and Ti: 0.15 mass% or less. More than seeds were included.
本発明は請求項７では請求項５又は６において、前記熱間圧延工程の後に、圧延板を７０％以下の圧下率で冷間圧延する冷間圧延工程を更に含むものとした。 According to a seventh aspect of the present invention, in the fifth or sixth aspect, the present invention further includes a cold rolling step of cold rolling the rolled sheet at a reduction rate of 70% or less after the hot rolling step.
本発明により、高歪み速度域における高温延性が高く、高速成形による量産性に優れたる熱間成形用アルミニウム合金板が得られる。 According to the present invention, it is possible to obtain an aluminum alloy plate for hot forming that has high ductility at high strain rates and is excellent in mass productivity by high speed forming.
本発明に係る熱間成形用アルミニウム合金板は、所定の合金組成を有し、所定条件の昇温後において、隣接する結晶粒の小角粒界である確率を５０％以上とした。また、所定のＳ方位密度と第２相粒子密度を有する。なお、本発明に係る熱間成形用アルミニウム合金板は、ブロー成形用、熱間プレス成形用などに適用可能である。以下、本発明について詳細に説明する。 The aluminum alloy plate for hot forming according to the present invention has a predetermined alloy composition, and the probability of being a small-angle grain boundary between adjacent crystal grains after a temperature increase under a predetermined condition is set to 50% or more. Moreover, it has a predetermined S orientation density and second phase particle density. The aluminum alloy plate for hot forming according to the present invention can be applied to blow forming, hot press forming, and the like. Hereinafter, the present invention will be described in detail.
１．金属組織
１−１．小角粒界の存在確率
まず、本発明のアルミニウム合金の金属組織について説明する。
１０−２〜１０−１／秒の高歪み速度域において、数十μｍの平均結晶粒径を有するＡｌ−Ｍｇ−Ｓｉ系合金を高温ブロー成形などの超塑性成形する際には、変形機構は粒内変形が主体となる。しかしながら、粒内変形と同時に粒界すべりも変形機構に寄与しているものと考えられる。特に粒界すべり変形は、粒界の三重点において空洞欠陥が発生し易く、同時に粒内変形を伴うと空洞欠陥の合体・拡大により破断の起点となり成形性低下の要因となる。
1. Metallographic structure 1-1. First, the metal structure of the aluminum alloy of the present invention will be described.
When an Al—Mg—Si based alloy having an average crystal grain size of several tens of μm is subjected to superplastic forming such as high temperature blow molding in a high strain rate region of 10 −2 to 10 −1 / sec, the deformation mechanism is Intragranular deformation is the main component. However, it is considered that the intergranular deformation and the grain boundary sliding contribute to the deformation mechanism. In particular, the grain boundary sliding deformation is likely to cause a cavity defect at the triple point of the grain boundary. At the same time, when the intragranular deformation is accompanied, the cavity defect is coalesced and expanded, which becomes a starting point of breakage and causes a decrease in formability.
図１に示すように、本発明者は、Ａｌ−Ｍｇ−Ｓｉ系合金の成形後の金属組織を調査した結果、上記超塑性成形中に発生する欠陥は、粒界の角度が１５°以上の大角粒界に沿って拡大することが観察され、一方で、粒界角度が１５°未満の小角粒界上では大角粒界上ほど欠陥の発生、拡大が無いことを見出した。そこで、本発明の熱間成形用アルミニウム合金板では、熱間成形温度に加熱後において、隣接する結晶粒の粒界が１５°未満の小角粒界の存在を大きくすることで欠陥の発生を抑制し、高速成形性の向上を図るものである。 As shown in FIG. 1, as a result of investigating the metal structure after forming the Al—Mg—Si based alloy, the inventor found that the defects generated during the superplastic forming had a grain boundary angle of 15 ° or more. On the other hand, it has been observed that expansion along the large-angle grain boundary is observed, and on the other hand, on the small-angle grain boundary where the grain boundary angle is less than 15 °, there is no defect generation and expansion on the large-angle grain boundary. Therefore, in the aluminum alloy sheet for hot forming of the present invention, after heating to the hot forming temperature, the occurrence of defects is suppressed by increasing the presence of small-angle grain boundaries where the grain boundaries of adjacent crystal grains are less than 15 °. In addition, high-speed moldability is improved.
具体的には、隣接する結晶粒の粒界が１５°未満である小角粒界の存在確率を５０％以上と規定する。この存在確率が５０％未満であると、大角粒界の確率が大きくなるために欠陥の発生、拡大を抑制できず、成形性向上効果が得られない。なお、この存在確立の上限値は特に限定されるものではないが、本発明では７０％とするのが好ましく、６０％とするのがより好ましい。また、金属組織観察前の加熱条件は、実際のブロー成形条件に近い昇温速度６０℃／分で５３０℃まで加熱するものとする。隣接する結晶粒の粒界が１５°未満である小角粒界の存在確率は、上記条件で加熱後のアルミニウム合金板の圧延方向に沿った縦断面（厚さ方向に沿った断面）を切り出して断面を研磨後、ＥＢＳＰを用いて
２００μｍ×２００μｍの視野について、１５°未満の小角粒界の個数と１５°以上の大角粒界の個数を測定し、〔小角粒界の個数／（小角粒界の個数＋大角粒界の個数）〕×１００をもって小角粒界の存在確率とした。
Specifically, the existence probability of small-angle grain boundaries in which the grain boundaries of adjacent crystal grains are less than 15 ° is defined as 50% or more. If the existence probability is less than 50%, the probability of large-angle grain boundaries increases, so that the occurrence and expansion of defects cannot be suppressed, and the effect of improving formability cannot be obtained. The upper limit value for the establishment of existence is not particularly limited, but in the present invention, it is preferably 70% and more preferably 60%. Moreover, the heating conditions before metal structure observation shall be heated to 530 degreeC with the temperature increase rate of 60 degree-C / min close | similar to actual blow molding conditions. The existence probability of the small-angle grain boundary where the grain boundary of the adjacent crystal grain is less than 15 ° is obtained by cutting a longitudinal section (cross section along the thickness direction) along the rolling direction of the aluminum alloy sheet after heating under the above conditions. After the cross section was polished, the number of small-angle grain boundaries of less than 15 ° and the number of large-angle grain boundaries of 15 ° or more were measured for a field of view of 200 μm × 200 μm using EBSP. Number + number of large-angle grain boundaries)] × 100 was defined as the existence probability of small-angle grain boundaries.
１−２．未再結晶組織におけるＳ方位密度
小角粒界の存在確率を大きくするためには、未再結晶組織において、方位の近い結晶粒の方位密度を大きくすることが有効である。アルミニウム合金の場合は、特にＣｕｂｅ方位｛００１｝＜１００＞の結晶粒が優先的に成長し易く、その存在密度は熱間圧延条件に大きく左右される。熱間成形時の加熱によってＣｕｂｅ方位を成長させ、方位密度を大きくするためには、加熱前、すなわち熱間圧延後又は冷間圧延後において、Ｓ方位｛１２３｝＜６３４＞の方位密度を大きくしておくことが有効である。Ｓ方位の方位密度を大きくすることが、再結晶時のＣｕｂｅ方位の生成、成長を促進する。
1-2. S orientation density in non-recrystallized structure In order to increase the existence probability of a small-angle grain boundary, it is effective to increase the orientation density of crystal grains having a close orientation in the non-recrystallized structure. In the case of an aluminum alloy, crystal grains having a Cube orientation {001} <100> tend to grow preferentially, and the density of the presence is greatly influenced by hot rolling conditions. In order to grow the Cube orientation by heating at the time of hot forming and increase the orientation density, the orientation density of the S orientation {123} <634> is increased before heating, that is, after hot rolling or after cold rolling. It is effective to keep it. Increasing the orientation density of the S orientation promotes the generation and growth of the Cube orientation during recrystallization.
本発明では、未再結晶組織におけるＳ方位｛１２３｝＜６３４＞の方位密度を２０以上とするのが好ましい。この方位密度が２０未満であると、Ｃｕｂｅ方位の生成率が小さくなり、小角粒界の存在確率を大きくできない場合がある。なお、この方位密度の上限値は特に限定されるものではないが、本発明では４０とするのが好ましく、３０とするのがより好ましい。なお、Ｓ方位の測定は、ＥＢＳＰを用いて２００μｍ×２００μｍの視野について測定した。 In the present invention, the orientation density of the S orientation {123} <634> in the unrecrystallized structure is preferably 20 or more. If the orientation density is less than 20, the generation rate of the Cube orientation becomes small and the existence probability of the small-angle grain boundary may not be increased. The upper limit value of the orientation density is not particularly limited, but is preferably 40 and more preferably 30 in the present invention. In addition, the measurement of S orientation was measured about the visual field of 200 micrometers x 200 micrometers using EBSP.
１−３．未再結晶組織における５μｍ以上の第２相粒子の密度
また、上記小角粒界の存在確立が高い組織を形成するためには、未再結晶組織における第２相粒子の分布を制御することが有効である。粗大な第２相粒子は成形中の欠陥の起点となるため成形性を低下させる一因となることに加えて、再結晶の際に周囲の方位と異なる方位を有する結晶粒を生成する起点となりうる。このような周囲の方位と異なる方位を有する結晶粒を囲む粒界は大角粒界となるため、結果として第２相粒子が多いと小角粒界の確率を大きくすることが困難となる。一方で第２相粒子が適量分布していると、熱間成形時の粒成長を抑制できるという側面がある。これらの観点から、５μｍ以上の円相当直径を有する第２相粒子の分布密度は、１００〜１０００個／ｍｍ２とするのが好ましく、
１００〜５００個／ｍｍ２とするのがより好ましい。第２相粒子の分布密度を１００個／ｍｍ２以上とすることで熱間成形時の粒成長抑制効果を大きくすることがでる。すなわち、１００個／ｍｍ２未満ではこのような粒成長抑制効果を大きくし難い。一方、１０００個／ｍｍ２以下とすることで小角粒界の密度向上に有効に作用する。すなわち、１０００個／ｍｍ２を超える場合には、このような小角粒界の密度向上を有効に得られない場合がある。なお、５μｍ以上の第２相粒子の密度測定は、（株）ニレコ社製画像解析装置「ルーゼックスＦＳ」を用いて０．２ｍｍ２の視野について測定した。
1-3. The density of second phase particles of 5 μm or more in the non-recrystallized structure In order to form a structure in which the existence of the small-angle grain boundary is highly established, it is effective to control the distribution of the second phase particles in the non-recrystallized structure. It is. Coarse second phase particles serve as a starting point for defects during molding, which contributes to a decrease in formability and, in addition, a starting point for generating crystal grains having an orientation different from the surrounding orientation during recrystallization. sell. Since the grain boundary surrounding the crystal grains having an orientation different from the surrounding orientation becomes a large-angle grain boundary, as a result, if there are many second-phase grains, it is difficult to increase the probability of the small-angle grain boundary. On the other hand, when the second phase particles are distributed in an appropriate amount, there is an aspect that grain growth during hot forming can be suppressed. From these viewpoints, the distribution density of the second phase particles having an equivalent circle diameter of 5 μm or more is preferably 100 to 1000 particles / mm 2 ,
More preferably, the number is 100 to 500 / mm 2 . By setting the distribution density of the second phase particles to 100 particles / mm 2 or more, the effect of suppressing grain growth during hot forming can be increased. That is, if it is less than 100 pieces / mm 2, it is difficult to increase the effect of suppressing such grain growth. On the other hand, when it is set to 1000 pieces / mm 2 or less, it effectively acts to improve the density of the small-angle grain boundaries. That is, when it exceeds 1000 particles / mm 2 , there is a case where such small-angle grain boundary density improvement cannot be effectively obtained. The density measurement of 5μm or more second phase particles were measured for the field of view of 0.2 mm 2 with Co. Nireco Corp. image analyzer "Luzex FS".
１−４．平均結晶粒径
更に、結晶組織における平均結晶粒径を３０〜５０μｍとすることにより、１０−２〜１０−１／秒の高歪み速度域における成形性を向上させることができる。一般に、結晶粒径が１０μｍ以下のような非常に微細粒であると、１０−５〜１０−３／秒の低歪み速度域においては粒界すべりが変形機構の主体となり、粒界すべりに伴う欠陥も縮小して成形性が向上する。一方、粒内変形が主体的となる１０−２〜１０−１／秒の高歪み速度域においては、平均結晶粒径が３０μｍ未満の場合、変形機構に占める粒界すべりの寄与が大きくなり、欠陥の拡大につながる。すなわち、平均結晶粒径は３０μｍ以上にすることが、高歪み速度域においては成形性の向上に有効である。また、平均結晶粒径を５０μｍ以下とすると成形後の肌荒れを有効に抑制できる。すなわち、５０μｍを超えると成形後の肌荒れを有効に抑制できない。以上により本発明では、結晶組織における平均結晶粒径を３０〜５０μｍとするのが好ましく、３０〜４０μｍとするのがより好ましい。なお、結晶組織における平均結晶粒径の測定は、ＥＢＳＰを用いて８００μｍ×１６００μｍの視野について１５°以上の高角粒界の囲まれる結晶粒の平均結晶粒径を測定した。
1-4. Average crystal grain size Further, by setting the average crystal grain size in the crystal structure to 30 to 50 μm, the formability in a high strain rate region of 10 −2 to 10 −1 / sec can be improved. In general, when the crystal grain size is very fine such as 10 μm or less, the grain boundary slip becomes a main component of the deformation mechanism in the low strain rate region of 10 −5 to 10 −3 / sec, and accompanying the grain boundary slip. Defects are also reduced to improve moldability. On the other hand, in the high strain rate region of 10 −2 to 10 −1 / sec, in which intragranular deformation is dominant, when the average crystal grain size is less than 30 μm, the contribution of grain boundary sliding to the deformation mechanism increases. It leads to the expansion of defects. That is, setting the average crystal grain size to 30 μm or more is effective for improving formability in a high strain rate region. Further, when the average crystal grain size is 50 μm or less, rough skin after molding can be effectively suppressed. That is, when the thickness exceeds 50 μm, rough skin after molding cannot be effectively suppressed. As described above, in the present invention, the average crystal grain size in the crystal structure is preferably 30 to 50 μm, and more preferably 30 to 40 μm. The average crystal grain size in the crystal structure was measured by measuring the average crystal grain size of crystal grains surrounded by a high-angle grain boundary of 15 ° or more for a field of view of 800 μm × 1600 μm using EBSP.
２．アルミニウム合金の成分組成
次に、本発明の熱間成形用アルミニウム合金板の成分組成とその限定理由を以下に示す。
2. Next, the component composition of the aluminum alloy plate for hot forming according to the present invention and the reasons for its limitation are shown below.
２−１．Ｍｇ：０．３〜２．０ｍａｓｓ％、Ｓｉ：０．６〜２．０ｍａｓｓ％
Ｍｇ及びＳｉは、本発明に用いるアルミニウム合金の基本成分である。両元素は、超塑性成形性の確保及び成形後の時効硬化処理により、Ａｌ−Ｍｇ系アルミニウム合金以上の大きな強度を得るための必須添加元素である。Ｍｇ含有量が０．３ｍａｓｓ％（以下、単に「％」と記す）未満、或いは、Ｓｉ含有量が０．６％未満では、上述の効果が十分に得られない。一方、Ｍｇ含有量が２．０％を超え、或いは、Ｓｉ含有量が２．０％を超える場合には、粗大な第２相粒子が発生する。その結果、粗大な第２相粒子が成形中の欠陥の起点となる。これに加えて、最終圧延後の加熱で起こる再結晶において、第２相粒子を起点として周囲の方位と異なる方位を有する結晶粒が生成し易くなる。このような周囲の方位と異なる方位を有する結晶粒を囲む粒界は大角粒界となるため、結果として小角粒界の存在確率を大きくすることが困難となる。以上により、Ｍｇ含有量を０．３〜２．０％、ならびに、Ｓｉ含有量を０．６〜２．０％に規定した。なお、Ｍｇ含有量は、好ましくは
０．６〜１．４％、ならびに、Ｓｉ含有量は、好ましくは０．８〜１．４％である。
2-1. Mg: 0.3-2.0 mass%, Si: 0.6-2.0 mass%
Mg and Si are basic components of the aluminum alloy used in the present invention. Both elements are essential addition elements for obtaining a strength greater than that of the Al—Mg-based aluminum alloy by ensuring superplastic formability and age hardening after forming. If the Mg content is less than 0.3 mass% (hereinafter simply referred to as “%”) or the Si content is less than 0.6%, the above-described effects cannot be obtained sufficiently. On the other hand, when the Mg content exceeds 2.0% or the Si content exceeds 2.0%, coarse second phase particles are generated. As a result, coarse second-phase particles serve as starting points for defects during molding. In addition, in the recrystallization that occurs by heating after the final rolling, crystal grains having an orientation different from the surrounding orientation starting from the second phase particles are easily generated. Since the grain boundary surrounding the crystal grains having an orientation different from the surrounding orientation is a large-angle grain boundary, it is difficult to increase the existence probability of the small-angle grain boundary as a result. As described above, the Mg content was regulated to 0.3 to 2.0%, and the Si content was regulated to 0.6 to 2.0%. The Mg content is preferably 0.6 to 1.4%, and the Si content is preferably 0.8 to 1.4%.
２−２．Ｍｎ：０．０４〜０．５０％、Ｃｒ：０．０４〜０．３０％
Ｍｎ及びＣｒは、ブロー成形などの超塑性成形後の粒成長を抑制する効果を有するため少なくともいずれか一方を添加する。Ｍｎ含有量が０．０４％未満、或いは、Ｃｒ含有量が０．０４％未満の場合には、上記効果が十分に得られない。一方、Ｍｎ含有量が０．５０％を超え、或いは、Ｃｒ含有量が０．３０％を超える場合には、時効硬化性が低下だけでなく、粗大な第２相粒子の形成、および結晶粒の安定化により粒界すべりを起こりやすくし、成形中に欠陥を誘発して成形性が低下する。以上のように、Ｍｎの含有量は０．０４〜０．５０％、Ｃｒの含有量は０．０４〜０．３０％である。なお、ＭｎとＣｒは、両方を含有してもよく、或いは、いずれか一方のみを含有してもよい。Ｍｎ含有量は、好ましくは０．０４〜０．２０％であり、Ｃｒ含有量は、好ましくは０．０４〜０．１０％である。
2-2. Mn: 0.04 to 0.50%, Cr: 0.04 to 0.30%
Since Mn and Cr have an effect of suppressing grain growth after superplastic forming such as blow molding, at least one of them is added. When the Mn content is less than 0.04% or the Cr content is less than 0.04%, the above effects cannot be obtained sufficiently. On the other hand, when the Mn content exceeds 0.50% or the Cr content exceeds 0.30%, not only the age-hardening property is lowered but also the formation of coarse second phase particles and crystal grains Grain boundary slip is likely to occur due to stabilization, and defects are induced during molding, thereby reducing moldability. As described above, the Mn content is 0.04 to 0.50%, and the Cr content is 0.04 to 0.30%. In addition, Mn and Cr may contain both, or may contain only any one. The Mn content is preferably 0.04 to 0.20%, and the Cr content is preferably 0.04 to 0.10%.
２−３．Ｃｕ：０．１０〜０．８０％
Ｃｕは時効硬化性を向上させるため、必要に応じて選択的に添加してもよい。Ｃｕ含有量が０．１０％未満では十分な強度向上の効果が得られない。一方、Ｃｕ含有量が０．８０％を超えると、粗大な第２相粒子が形成され成形性の低下を招く。以上により、Ｃｕ含有量は０．１０〜０．８０とし、好ましくは０．３０〜０．５０％である。
2-3. Cu: 0.10 to 0.80%
Cu may be selectively added as necessary to improve age hardening. If the Cu content is less than 0.10%, sufficient strength improvement effect cannot be obtained. On the other hand, if the Cu content exceeds 0.80%, coarse second-phase particles are formed, resulting in a decrease in formability. Accordingly, the Cu content is set to 0.10 to 0.80, preferably 0.30 to 0.50%.
２−４．Ｚｎ：０．３％以下
Ｚｎを添加することで強度を増加することができるため、必要に応じて選択的に添加してもよい。しかしながら、Ｚｎを添加すると耐食性が損なわれるため、Ｚｎ含有量は０．３０％以下に規制するのが好ましく、０．１０％以下に規制するのがより好ましい。なお、Ｚｎ含有量は０％であってもよい。
2-4. Zn: 0.3% or less Since the strength can be increased by adding Zn, it may be selectively added as necessary. However, since corrosion resistance is impaired when Zn is added, the Zn content is preferably regulated to 0.30% or less, and more preferably regulated to 0.10% or less. The Zn content may be 0%.
２−５．Ｔｉ：０．１５％以下
Ｔｉを添加することで鋳塊組織を微細化することが可能となるため、必要に応じて選択的に添加してもよい。しかしながら、Ｔｉを添加すると粗大な金属間化合物の生成に繋がるため、Ｔｉ含有量は０．１５％以下に規制するのが好ましく、０．１０％以下に規制するのがより好ましい。なお、Ｔｉ含有量は０％であってもよい。
2-5. Ti: 0.15% or less Since the ingot structure can be refined by adding Ti, it may be selectively added as necessary. However, since addition of Ti leads to the formation of coarse intermetallic compounds, the Ti content is preferably regulated to 0.15% or less, and more preferably regulated to 0.10% or less. The Ti content may be 0%.
２−６．不可避的不純物
Ｆｅは、一般的なアルミニウム合金に不可避的不純物として含まれる可能性がある。Ｆｅ含有量が０．３％を超えると、粗大な第２相粒子が形成され、小角粒界の存在確率の低下を招く場合がある。以上により、Ｆｅ含有量は０．３％以下に規制するのが好ましく、０．２％以下に規制するのがより好ましい。なお、Ｆｅ含有量は０％であってもよい。
また、Ｆｅの他の不可避的不純物として、Ｚｒ、Ｂ、Ｂｅなどを各々０．０５％以下、全体で０．１５％以下が含んでいても、本発明の効果を損なわないので許容される。
2-6. Inevitable impurities Fe may be included as an inevitable impurity in general aluminum alloys. If the Fe content exceeds 0.3%, coarse second-phase particles are formed, which may lead to a decrease in the existence probability of small-angle grain boundaries. As described above, the Fe content is preferably regulated to 0.3% or less, and more preferably regulated to 0.2% or less. The Fe content may be 0%.
Further, as other unavoidable impurities of Fe, even if they contain 0.05% or less of Zr, B, Be, etc., respectively, and 0.15% or less in total, it is allowed because the effects of the present invention are not impaired.
３．製造方法
次に、本発明の熱間成形用アルミニウム合金板の好適な製造方法について説明する。
3. Manufacturing Method Next, a preferable manufacturing method of the aluminum alloy plate for hot forming according to the present invention will be described.
３−１．溶解鋳造工程
まず、上記合金成分の合金溶湯を溶製し、これを鋳造する。鋳造は例えばＤＣ鋳造のような一般的な方法によって行われる。その際、冷却速度を大きくすることにより、粗大な第２相粒子の形成を抑制することが好ましい。本発明では、ＤＣ鋳造における冷却速度として、５０℃／分以上とするのが好ましく、１００℃／分以上とするのがより好ましい。
3-1. Melting and casting process First, the molten alloy of the above alloy components is melted and cast. Casting is performed by a general method such as DC casting. At that time, it is preferable to suppress the formation of coarse second phase particles by increasing the cooling rate. In this invention, it is preferable to set it as 50 degreeC / min or more as a cooling rate in DC casting, and it is more preferable to set it as 100 degreeC / min or more.
３−２．均質化処理工程
溶解鋳造によって得られたアルミニウム合金の鋳塊は、必要に応じて面削を施してから、均質化処理工程にかけられる。均質化処理温度は、５００℃以上で、かつ、本発明の実施形態に係るアルミニウム合金の融点温度（例えば約５８０℃）未満と規定する。加熱温度が５００℃未満では、成形性の劣化を招く第２相粒子の再固溶の促進が図れない。また、均質化処理温度を本発明の実施形態に係るアルミニウム合金の融点温度未満とすることによって、アルミニウム合金の溶解を防ぐことができる。従って、均質化処理温度は、５００℃以上でアルミニウム合金の融点未満とし、５３０〜５６０℃とするのが好ましい。均質化処理時間については、１〜１２時間とし、２〜８時間とするのがより好ましい。１時間未満では、成形性の劣化を招く第２相粒子の再固溶の促進が図れず、１２時間を超えても均質化処理効果が飽和して不経済となる。
3-2. Homogenization treatment process The ingot of the aluminum alloy obtained by melt casting is subjected to a homogenization treatment process after chamfering as necessary. The homogenization treatment temperature is specified to be 500 ° C. or higher and lower than the melting point temperature (eg, about 580 ° C.) of the aluminum alloy according to the embodiment of the present invention. When the heating temperature is less than 500 ° C., the re-solution of the second phase particles that causes deterioration of the moldability cannot be promoted. Moreover, melt | dissolution of an aluminum alloy can be prevented by making homogenization process temperature less than melting | fusing point temperature of the aluminum alloy which concerns on embodiment of this invention. Therefore, the homogenization treatment temperature is 500 ° C. or more and less than the melting point of the aluminum alloy, and preferably 530 to 560 ° C. The homogenization treatment time is 1 to 12 hours, and more preferably 2 to 8 hours. If it is less than 1 hour, the re-solution of the second phase particles that causes deterioration of moldability cannot be promoted, and if it exceeds 12 hours, the homogenization effect is saturated and uneconomical.
３−３．熱間圧延工程
上述のように、小角粒界の確率を大きくするためには、方位の近い結晶粒の方位密度を大きくすることが有効であり、その存在密度は熱間圧延条件に大きく左右される。本発明では、Ｓ方位の方位密度を大きくして、再結晶時のＣｕｂｅ方位の生成、成長を促進するために、熱間圧延の条件が設定される。具体的には、熱間圧延における材料温度が３００〜４００℃のときの圧下率を８０％以上とする。これにより、Ｃｕｂｅ方位を生成、成長させるために好適な金属組織となり、熱間成形時の加熱によって、より一層小角粒界の存在確率が高い金属組織を得ることができる。上記材料温度が３００〜４００℃に限定した理由は、３００℃未満では変形抵抗が大きくなって熱間圧延が困難となり、４００℃を超えるとＣｕｂｅ方位の生成率が減少するからである。また、上記圧下率が８０％未満では、Ｃｕｂｅ方位が十分に生成しない。なお、圧下率の上限値は特に限定されるものではないが、本発明では９５％とするのが好ましい。
3-3. Hot rolling process As described above, in order to increase the probability of a small-angle grain boundary, it is effective to increase the orientation density of crystal grains that are close in orientation, and the existence density greatly depends on the hot rolling conditions. The In the present invention, the hot rolling conditions are set in order to increase the orientation density of the S orientation and promote the generation and growth of the Cube orientation during recrystallization. Specifically, the rolling reduction when the material temperature in hot rolling is 300 to 400 ° C. is 80% or more. Thereby, it becomes a suitable metal structure for generating and growing the Cube orientation, and a metal structure having a higher probability of existence of small-angle grain boundaries can be obtained by heating during hot forming. The reason why the material temperature is limited to 300 to 400 ° C. is that if it is less than 300 ° C., deformation resistance becomes large and hot rolling becomes difficult, and if it exceeds 400 ° C., the production rate of Cube orientation decreases. Further, when the rolling reduction is less than 80%, the Cube orientation is not sufficiently generated. The upper limit of the rolling reduction is not particularly limited, but is preferably 95% in the present invention.
３−４．冷間圧延工程
本発明においては、熱間圧延工程を経た圧延板は、そのままの状態でも、熱間圧延工程の加熱によって小角粒界の存在確率が高い組織が形成されている。従って、熱間圧延工程後において、冷間圧延工程を必ずしも設けなくてもよく、熱間圧延板をそのまま熱間ブロー成形などの熱間成形に供することが可能である。
3-4. Cold Rolling Process In the present invention, the rolled plate that has undergone the hot rolling process has a structure in which a small-angle grain boundary has a high probability of existence due to heating in the hot rolling process even if it is as it is. Therefore, it is not always necessary to provide a cold rolling step after the hot rolling step, and the hot rolled plate can be directly subjected to hot forming such as hot blow forming.
一方で、板厚の精度を向上させるために、熱間圧延工程後に冷間圧延工程を設けてもよい。但し、冷間圧下率が大きくなると第２相粒子を起点として周囲の方位と異なる方位を有する結晶粒が生成し易い。そのような周囲の方位と異なる方位を有する結晶粒を囲む粒界は大角粒界となるため、結果として小角粒界の存在確率を大きくすることが困難となる。冷間圧延工程を設ける場合において、このような小角粒界の存在確率の低下を防止するには、冷間圧下率を好ましくは７０％以下、より好ましくは６０％以下とする。また、冷間圧延工程の途中又は後に焼鈍工程を設けることもできる。但し、冷間圧延工程途中の焼鈍はＣｕｂｅ量が減少するので設けないのが好ましい。 On the other hand, in order to improve the accuracy of the plate thickness, a cold rolling process may be provided after the hot rolling process. However, when the cold rolling reduction increases, crystal grains having an orientation different from the surrounding orientation are likely to be generated starting from the second phase particles. Since the grain boundary surrounding the crystal grains having an orientation different from the surrounding orientation becomes a large-angle grain boundary, it is difficult to increase the existence probability of the small-angle grain boundary as a result. In the case of providing the cold rolling step, in order to prevent such a decrease in the existence probability of the small-angle grain boundaries, the cold rolling reduction is preferably 70% or less, more preferably 60% or less. Further, an annealing step can be provided during or after the cold rolling step. However, it is preferable not to provide annealing during the cold rolling process because the amount of Cube decreases.
本発明の実施形態に係る熱間成形用アルミニウム合金板においては、熱間成形時の加熱によって溶体化処理を施すことが可能である。従って、最終焼鈍工程を省略して、熱間圧延工程後、或いは、その後の冷間圧延工程後に、圧延板をそのまま熱間成形に供してもよい。これにより製造コストの低減が図られる。 In the aluminum alloy plate for hot forming according to the embodiment of the present invention, it is possible to perform a solution treatment by heating during hot forming. Therefore, the final annealing step may be omitted, and the rolled sheet may be directly subjected to hot forming after the hot rolling step or after the subsequent cold rolling step. Thereby, the manufacturing cost can be reduced.
以下に、本発明の実施例について説明する。表１に示すアルミニウム合金（合金番号１〜１６）をそれぞれ溶解し、ＤＣ鋳造法によって鋳造した。ＤＣ鋳造における冷却速度は、およそ８０℃／分とした。得られた鋳塊を面削し、表２に示す条件で均質化処理した。次いで、鋳塊の温度を４００℃として熱間圧延を行った。このとき、材料温度が３００〜４００℃における圧下率を表２に示すように制御した。最後に、熱間圧延後の圧延板を冷間圧延に供試して、最終板厚１ｍｍの圧延板試料を得た。なお、冷間圧下率も表２に示す。 Examples of the present invention will be described below. Aluminum alloys (alloy numbers 1 to 16) shown in Table 1 were melted and cast by the DC casting method. The cooling rate in DC casting was about 80 ° C./min. The obtained ingot was chamfered and homogenized under the conditions shown in Table 2. Next, hot rolling was performed at a temperature of the ingot of 400 ° C. At this time, the rolling reduction at a material temperature of 300 to 400 ° C. was controlled as shown in Table 2. Finally, the rolled sheet after hot rolling was subjected to cold rolling to obtain a rolled sheet sample having a final sheet thickness of 1 mm. The cold rolling reduction is also shown in Table 2.
４．試料の評価
４−１．小角粒界の存在確率
上記試料を、バッチ炉にて昇温速度６０℃／分で５３０℃まで昇温した後に、室温まで冷却した。この冷却した試料について、走査電子顕微鏡（日本電子株式会社製ＪＳＭ−６５１０）に取り付けた結晶方位解析装置（ＴＳＬ社製ＭＳＣ−２２００）により小角粒界の存在確率を測定した。２００μｍ×２００μｍの測定視野を５箇所選択し、各視野の存在確立を下記式から求め、全視野の算術平均をもって存在確立（％）とした。
存在確立（％）＝〔小角粒界の個数／（小角粒界の個数＋大角粒界の個数）〕×１００
4). Evaluation of sample 4-1. Presence probability of small-angle grain boundaries The sample was heated to 530 ° C. at a heating rate of 60 ° C./min in a batch furnace, and then cooled to room temperature. About this cooled sample, the existence probability of the small angle grain boundary was measured by the crystal orientation analyzer (MSC-2200 made by TSL) attached to the scanning electron microscope (JSM-6510 made by JEOL Ltd.). Five measurement fields of 200 μm × 200 μm were selected, the presence of each field was established from the following formula, and the arithmetic mean of all fields was defined as the presence (%).
Existence establishment (%) = [number of small-angle grain boundaries / (number of small-angle grain boundaries + number of large-angle grain boundaries)] × 100
４−２．Ｓ方位密度
上記試料を機械研磨して板断面中心を通るＲＤ‐ＴＤ面を露出させた後、鏡面研磨を行った。この研磨面を走査電子顕微鏡（日本電子株式会社製ＪＳＭ−６５１０）に取り付けた結晶方位解析装置（ＴＳＬ社製ＭＳＣ−２２００）により観察し、Ｓ方位密度を測定した。２００μｍ×２００μｍの測定視野を５箇所選択し、各視野におけるＳ方位密度を測定し、全視野の算術平均をもってＳ方位密度とした。
4-2. S orientation density The sample was mechanically polished to expose the RD-TD plane passing through the center of the plate cross section, and then mirror polished. The polished surface was observed with a crystal orientation analyzer (MSC-2200 manufactured by TSL) attached to a scanning electron microscope (JSM-6510 manufactured by JEOL Ltd.), and the S orientation density was measured. Five measurement fields of 200 μm × 200 μm were selected, the S orientation density in each field was measured, and the arithmetic average of all fields was taken as the S orientation density.
４−３．５μｍ以上の金属間化合物の密度
上記Ｓ方位密度を測定した研磨面について、（株）ニレコ社製画像解析装置ルーゼックスＦＳを用いて５μｍ以上の金属間化合物の密度を測定した。０．２ｍｍ２の測定視野を２２箇所選択し、各視野における密度を測定し、全視野の算術平均をもって５μｍ以上の金属間化合物の密度とした。
Density of intermetallic compound of 4-3.5 μm or more The density of the intermetallic compound of 5 μm or more was measured using an image analysis apparatus Luzex FS manufactured by Nireco Corporation on the polished surface where the S orientation density was measured. 22 measurement fields of 0.2 mm 2 were selected, the density in each field was measured, and the arithmetic average of all fields was taken as the density of the intermetallic compound of 5 μm or more.
４−４．ブロー張出成形試験
上記試料を５３０℃まで加熱した後、１００φの円筒金型を用いてブロー張出成形試験を行った。ガス圧は２．６ｋｇｆ／ｃｍ２まで６０秒で昇圧し、以後はこの圧力を保持した。破断後に成形を止め、成形品の張出高さを測定した。張出高さが５０．０ｍｍを超えるものを合格とし、それ以下を不合格とした。なお、同一試料を用いて２個の試験を行い、それらの算術の平均値をもって張出高さとした。
4-4. Blow-extrusion molding test After the sample was heated to 530 ° C., a blow-extrusion molding test was conducted using a 100φ cylindrical mold. The gas pressure was increased to 2.6 kgf / cm 2 in 60 seconds, and this pressure was maintained thereafter. After breaking, the molding was stopped and the overhang height of the molded product was measured. A projecting height exceeding 50.0 mm was regarded as acceptable, and less than that was regarded as unacceptable. Two tests were performed using the same sample, and the average value of the arithmetic was used as the overhang height.
４−５．時効後の引張強度
上記試料から３ｃｍ×２０ｃｍの試験片を３個切り出し５３０℃で１時間溶体化処理を行った。これを室温まで水冷して焼き入れ処理した後に、連続して１８０℃×１時間のバッチ時効処理を行った。バッチ時効処理したものを用いて、ＪＩＳ５号引張試験に準拠した引張強度を測定した。各試験片の算術平均値をもって引張強度とした。引張強度が３００ＭＰａ以上を合格とし、それ未満を不合格とした。
4-5. Tensile strength after aging Three test pieces of 3 cm × 20 cm were cut out from the sample and subjected to solution treatment at 530 ° C. for 1 hour. This was water-cooled to room temperature and quenched, and then batch-aged at 180 ° C. for 1 hour. The tensile strength based on the JIS No. 5 tensile test was measured using the batch aging treatment. The arithmetic average value of each specimen was taken as the tensile strength. A tensile strength of 300 MPa or more was accepted and less than that was rejected.
４−６．成形後の結晶粒
ＥＢＳＰを用いて、上記ブロー張出成形成した成形品における結晶粒を観察した。板厚減少率が５０％以上の箇所で６００μｍ×１５００μｍの視野において，１００μｍ以上の粗大な結晶粒の存在の有無を観察した。このような粗大な結晶粒が存在した場合は粗大化とし、存在しなかった場合は正常粒とした。
4-6. Crystal grains after molding The crystal grains in the molded article formed by blow-extrusion were observed using EBSP. The presence or absence of coarse crystal grains of 100 μm or more was observed in a field of view of 600 μm × 1500 μm at a location where the plate thickness reduction rate was 50% or more. When such coarse crystal grains existed, they were coarsened, and when they did not exist, they were regarded as normal grains.
以上の評価結果を表３に示す。成形高さ及び時効後の引張強度が共に合格の場合、総合評価が合格（○）とし、それ以外を不合格（×）とした。 The above evaluation results are shown in Table 3. When the molding height and the tensile strength after aging were both acceptable, the overall evaluation was acceptable (◯), and the others were unacceptable (x).
本発明例１〜１３では、良好な熱間成形性及び時効硬化性を有しており、総合評価が合格であった。特に本発明例７〜９では、より高い時効硬化性を有していた。 In Invention Examples 1 to 13, it had good hot formability and age-hardening properties, and the overall evaluation was acceptable. In particular, Invention Examples 7 to 9 had higher age-hardening properties.
これに対して、比較例１では、Ｍｇ含有量が少な過ぎたために時効硬化性に劣った。また、比較例２では、Ｍｇ含有量が多過ぎたために小角粒界の存在確率が小さくなった。その結果、熱間成形性が低下した。 On the other hand, in comparative example 1, since there was too little Mg content, it was inferior to age-hardening property. Moreover, in Comparative Example 2, since the Mg content was too large, the existence probability of the small-angle grain boundaries was reduced. As a result, hot formability decreased.
比較例３では、Ｓｉ量が少な過ぎたために時効硬化性に劣った。また、比較例４では、Ｓｉ量が多過ぎたために小角粒界の存在確率が小さくなった。その結果、熱間成形性が低下した。 In Comparative Example 3, the age hardening was inferior because the amount of Si was too small. Further, in Comparative Example 4, the existence probability of the small-angle grain boundaries was reduced because of the excessive amount of Si. As a result, hot formability decreased.
比較例５では、Ｍｎ及びＣｒの含有量が共に少な過ぎたために、熱間成形後に結晶粒の異常粒成長による粗大化が確認された。また、比較例６では、Ｍｎ含有量が多過ぎ、Ｃｒ含有量が少な過ぎたために、小角粒界の存在確率が小さくなった。その結果、熱間成形性が低下した。 In Comparative Example 5, since both the contents of Mn and Cr were too small, coarsening due to abnormal grain growth of crystal grains was confirmed after hot forming. In Comparative Example 6, since the Mn content was too high and the Cr content was too low, the existence probability of small-angle grain boundaries was reduced. As a result, hot formability decreased.
比較例７では、Ｃｒ含有量が多過ぎ、Ｍｎ含有量が少な過ぎたために、小角粒界の存在確率が小さくなった。その結果、熱間成形性が低下した。 In Comparative Example 7, since the Cr content was too high and the Mn content was too low, the existence probability of the small-angle grain boundaries was reduced. As a result, hot formability decreased.
比較例８では、材料温度が３００〜４００℃における熱間圧下率が低過ぎたために、小角粒界の存在確率が小さくなった。その結果、熱間成形性が低下した。 In Comparative Example 8, since the hot rolling reduction at the material temperature of 300 to 400 ° C. was too low, the existence probability of the small-angle grain boundaries was reduced. As a result, hot formability decreased.
比較例９では、冷間圧下率が大き過ぎたために、小角粒界の存在確率が小さくなった。その結果、熱間成形性が低下した。 In Comparative Example 9, since the cold rolling reduction was too large, the existence probability of small-angle grain boundaries was reduced. As a result, hot formability decreased.
比較例１０では、均質化処理温度が低過ぎたために、小角粒界の存在確率が小さくなった。その結果、熱間成形性が低下した。 In Comparative Example 10, since the homogenization temperature was too low, the existence probability of the small-angle grain boundaries was reduced. As a result, hot formability decreased.
比較例１１では、均質化処理時間が短過ぎたために、小角粒界の存在確率が小さくなった。その結果、熱間成形性が低下した。 In Comparative Example 11, since the homogenization time was too short, the existence probability of small-angle grain boundaries was reduced. As a result, hot formability decreased.
本発明に係る熱間成形用アルミニウム合金板は、高歪み速度域における高温延性が高く、高速成形による量産性に優れる。 The aluminum alloy plate for hot forming according to the present invention has high hot ductility in a high strain rate region and is excellent in mass productivity by high speed forming.
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