JP3872753B2 - Aluminum alloy for hole expansion processing and manufacturing method - Google Patents
Aluminum alloy for hole expansion processing and manufacturing method Download PDFInfo
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Description
【０００１】
【発明の属する技術分野】
本発明は、自動車用ボディパネル、構造材料等に使用されるアルミニウム合金、特に剪断加工により形成した打ち抜き穴を有し、その後穴拡げ加工されるアルミニウム合金において、穴拡げ性に優れたアルミニウム合金及び製造方法に関する。
【０００２】
【従来の技術】
近年、自動車の車体を軽量化するために、ボディパネル及び構造材料にアルミニウム合金を適用する検討が進められている。自動車部材等の用途には、優れたプレス成形性が要求され、これまでに張出成形性及び深絞り成形性に優れたアルミニウム合金が開発されている。ところが実際の自動車部材には張出及び深絞りのような成形を行った後に、伸びフランジ加工及びバーリング加工等の穴拡げ加工が施される。特に、足廻り部品等の構造材料にアルミニウム合金を適用する際には、穴拡げ性の改善が重要な課題である。
【０００３】
一般に、金属材料の穴拡げ性を向上させるには、材料の局部延性を向上させるか、又は穴内表面を平滑化することが有効である。材料の延性は、温度の上昇とともに向上するため、高温で穴拡げ加工を施す方法が、特許文献１、特許文献２、特許文献３、特許文献４及び特許文献５に開示されている。しかし、このような方法は特別な加工設備が必要である。
【０００４】
また、穴内表面を平滑化するために、レーザーで穴加工を施す方法が特許文献６に、剪断加工によって形成した穴（以下、打抜き穴）を、さらに切削加工する方法が特許文献７に開示されている。しかし、アルミニウム合金にレーザーによる穴加工を施すと、穴内面近傍が凝固組織となるため局部延性が低下し、穴拡げ性の改善効果は小さいことが判明した。また、打抜き穴の内表面をさらに剪断加工して平滑化しても、穴拡げ性が大幅に改善しないという問題があった。
【０００５】
【特許文献１】
特開昭５９−２２５８１３号公報
【特許文献２】
特開昭６０−１２１０１８号公報
【特許文献３】
特開昭６０−１７７９１３号公報
【特許文献４】
特開昭６０−１７７９１４号公報
【特許文献５】
特開昭６３−１１５６１４号公報
【特許文献６】
特開平１０−２７７７６６号公報
【特許文献７】
特開平６−３９４５０号公報
【０００６】
【発明が解決しようとする課題】
本発明は、高温での穴拡げ加工のように特別な装置を必要とせず、レーザーによる穴加工又は打抜き後の剪断加工による穴内表面の平滑化よりも極めて効果的に穴拡げ性を改善した、アルミニウム合金及び製造方法を提供することを目的とする。
【０００７】
【課題を解決するための手段】
本発明者は、剪断加工により打抜き穴を形成したアルミニウム合金の穴拡げ性を詳細に調査した。その結果、打抜き穴の板厚断面において、打抜き穴内表面より１ｍｍの範囲が加工硬化していることが穴拡げ性低下の原因であることを明らかにした。この知見から、少なくとも加工硬化している部分の塑性歪みを回復させる熱処理を施すことが穴拡げ性の向上に極めて有効であることを見出した。
【０００８】
本発明はこのような知見に基づいたものであり、その要旨は以下のとおりである。
【０００９】
（１） 剪断加工による打抜き穴を有するアルミニウム合金において、質量％で、
Ｍｇ：０．２〜６．０％、 Ｓｉ：１．０％以下、
を含有し、
Ｆｅ：０．００１〜１．０％、 Ｍｎ：０．０１〜２．０％、
Ｃｒ：０．００１〜１．０％、
の１種又は２種以上を含有し、残部Ａｌ及び不可避不純物からなり、打抜き穴内表面より１ｍｍの範囲内の硬化率が２０％以下であることを特徴とする穴拡げ加工用アルミニウム合金。
【００１０】
ただし、
硬化率（％）＝（打抜き穴加工部の硬さ−母材の硬さ）×１００／母材の硬さ
ここで、打抜き穴加工部の硬さは、打抜き穴の中心を通る板厚断面における打抜き穴内表面より１ｍｍ範囲内の硬さであり、母材及び打抜き穴加工部の硬さはビッカース硬さである。
【００１１】
（２）剪断加工による打抜き穴を有するアルミニウム合金において、質量％で、
Ｍｇ：０．２〜１．５％、 Ｓｉ：０．４〜２．０％、
を含有し、
Ｆｅ：０．００１〜１．０％、 Ｍｎ：０．０１〜２．０％、
Ｃｒ：０．００１〜１．０％、
の１種又は２種以上を含有し、残部Ａｌ及び不可避不純物からなり、打抜き穴内表面より１ｍｍの範囲内の硬化率が２０％以下であることを特徴とする穴拡げ加工用アルミニウム合金。
【００１２】
ただし、
硬化率（％）＝（打抜き穴加工部の硬さ−母材の硬さ）×１００／母材の硬さ
ここで、打抜き穴加工部の硬さは、打抜き穴の中心を通る板厚断面における打抜き穴内表面より１ｍｍ範囲内の硬さであり、母材及び打抜き穴加工部の硬さはビッカース硬さである。
【００１３】
（３） 質量％で、さらに、
Ｃｕ：０．０１〜１．０％（０．０４％及び０．７％を除く）、
Ｚｎ：０．１〜２．０％、 Ｖ ：０．０１〜０．５％、
Ｚｒ：０．０１〜０．５％、 Ｔｉ：０．００１〜０．５％、
Ｂ ：０．０００１〜０．０５％
の１種又は２種以上を含有することを特徴とする（１）記載の穴拡げ加工用アルミニウム合金。
（４） 質量％で、さらに、
Ｃｕ：０．０１〜１．０％（０．０１％及び０．７％を除く）、
Ｚｎ：０．１〜２．０％、 Ｖ ：０．０１〜０．５％、
Ｚｒ：０．０１〜０．５％、 Ｔｉ：０．００１〜０．５％、
Ｂ ：０．０００１〜０．０５％
の１種又は２種以上を含有することを特徴とする（２）記載の穴拡げ加工用アルミニウム合金。
【００１４】
（５）（１）〜（４）のいずれか１項に記載の成分からなるアルミニウム合金を、２００℃未満で打抜き穴加工後、穴拡げ加工前に、少なくとも打抜き穴内表面より１ｍｍの範囲内を、２００〜６００℃に加熱し、２時間以下保持する熱処理を施すことを特徴とする（１）〜（４）のいずれか１項に記載の穴拡げ加工用アルミニウム合金の製造方法。
【００１５】
（６） 加熱炉内で熱処理することを特徴とする（５）記載の穴拡げ加工用アルミニウム合金の製造方法。
【００１６】
（７）剪断加工による打抜き穴を有し、打抜き穴内表面より１ｍｍの範囲内の硬化率が２０％以下である穴拡げ加工用アルミニウム合金の製造方法であって、（１）又は（２）に記載の成分からなるアルミニウム合金を、２００℃未満で打抜き穴加工後、穴拡げ加工前に、少なくとも打抜き穴内表面より１ｍｍの範囲内を、誘導加熱により熱処理する２００〜６００℃に加熱し、２時間以下保持する熱処理を施すことを特徴とする穴拡げ加工用アルミニウム合金の製造方法。
ただし、
硬化率（％）＝（打抜き穴加工部の硬さ−母材の硬さ）×１００／母材の硬さ
ここで、打抜き穴加工部の硬さは、打抜き穴の中心を通る板厚断面における打抜き穴内表面より１ｍｍ範囲内の硬さであり、母材及び打抜き穴加工部の硬さはビッカース硬さである。
【００１７】
（８）剪断加工による打抜き穴を有し、打抜き穴内表面より１ｍｍの範囲内の硬化率が２０％以下である穴拡げ加工用アルミニウム合金の製造方法であって、（１）又は（２）に記載の成分からなるアルミニウム合金を、２００℃未満で打抜き穴加工後、穴拡げ加工前に、少なくとも打抜き穴内表面より１ｍｍの範囲内を、２００〜６００℃に加熱した高温体を接触させ、２００〜６００℃に加熱し、２時間以下保持する熱処理を施すことを特徴とする穴拡げ加工用アルミニウム合金の製造方法。
ただし、
硬化率（％）＝（打抜き穴加工部の硬さ−母材の硬さ）×１００／母材の硬さ
ここで、打抜き穴加工部の硬さは、打抜き穴の中心を通る板厚断面における打抜き穴内表面より１ｍｍ範囲内の硬さであり、母材及び打抜き穴加工部の硬さはビッカース硬さである。
【００１８】
（９）剪断加工による打抜き穴を有し、打抜き穴内表面より１ｍｍの範囲内の硬化率が２０％以下である穴拡げ加工用アルミニウム合金の製造方法であって、（１）又は（２）に記載の成分からなるアルミニウム合金を、２００℃未満で打抜き穴加工後、穴拡げ加工前に、少なくとも打抜き穴内表面より１ｍｍの範囲内を、バーナーで２００〜６００℃に加熱し、２時間以下保持する熱処理を施すことを特徴とする穴拡げ加工用アルミニウム合金の製造方法。
ただし、
硬化率（％）＝（打抜き穴加工部の硬さ−母材の硬さ）×１００／母材の硬さ
ここで、打抜き穴加工部の硬さは、打抜き穴の中心を通る板厚断面における打抜き穴内表面より１ｍｍ範囲内の硬さであり、母材及び打抜き穴加工部の硬さはビッカース硬さである。
（１０） アルミニウム合金が、質量％で、さらに、
Ｃｕ：０．０１〜１．０％、 Ｚｎ：０．１〜２．０％、
Ｖ ：０．０１〜０．５％、 Ｚｒ：０．０１〜０．５％、
Ｔｉ：０．００１〜０．５％、 Ｂ ：０．０００１〜０．０５％
の１種又は２種以上を含有することを特徴とする（７）〜（９）のいずれか１項に記載の穴拡げ加工用アルミニウム合金の製造方法。
【００１９】
【発明の実施の形態】
本発明者は、アルミニウム合金板を剪断加工して打抜き穴を形成した後、穴広げ性が低下する原因を明らかにするため、以下の検討を行った。まず、３．５ｍｍ厚の５０５２アルミニウム合金より９０ｍｍ角の試験片を切り出し、１０ｍｍφのポンチと１０．２〜１１．０ｍｍφのダイスを用いてクリアランスを変化させ、プレス加工機によって剪断加工により打抜き穴を室温で形成した。打抜き穴径の測定は、拡大鏡を用いて穴径を１０倍に拡大して行った。クリアランスは、ダイス直径とポンチ直径との差を２で除し、さらに板厚で除した百分率である。
【００２０】
打抜き穴の内面は、剪断加工の際のポンチの入側が金属光沢を呈する剪断面であり、出側が光沢のない破断面である。打抜き穴内面の圧延方向２箇所及び圧延方向に直交する幅方向２箇所の４箇所において、板厚方向の剪断面の長さを測定し、板厚で除した百分率として剪断面比率を算出し、さらに４箇所の平均値を求めた。剪断面の長さは、ノギスを用いて側定した。なお比較材として、ボール盤によって１０ｍｍφの穴を切削加工により形成した試験片を作製した。
【００２１】
これらの試験片を用いて、６０°の円錐ポンチを用いて穴拡げ加工を施した後、試験前と同様に穴径を測定した。この測定値から穴拡げ試験前の穴径を減じて、これを試験前の穴径で除した百分率として、穴拡げ率を算出した。その結果、比較材の穴拡げ率は約１３０％であり、これに対して剪断加工により打抜き穴を形成した材料の穴拡げ率は約４０％と大幅に低下することがわかった。また、剪断加工により打抜き穴を形成した材料の穴拡げ率は剪断面比率に依らずほぼ同等であることがわかった。このことから、打抜き穴加工により穴拡げ率が低下する原因は従来知見と異なり、打抜き穴内表面の性状よりも、剪断加工による加工硬化の影響の方が大きいという知見を得た。
【００２２】
そこで、打抜き穴内表面近傍の板厚断面の加工硬化を以下のようにして確認した。まず試験片は、打抜き穴加工後、打抜き穴の中心を通った圧延方向に切断し、切断面である板厚断面を鏡面研磨して作製した。この打抜き穴内表面より０．１〜２ｍｍの範囲のビッカース硬さを、板表面より０．１ｍｍ、板厚中心部及び板表面より１／４板厚の位置で、０．１ｍｍ間隔で測定した。同様の測定を２〜５枚の試料を用いて行い、それぞれ同じ位置での測定値の平均値を算出し、打抜き穴加工部の硬さとした。なお、ビッカース硬さ試験は、ＪＩＳ Ｚ ２２４４に準じて、硬さ記号ＨＶ０．０１に対応する、試験力０．０９８７Ｎで行った。打抜き穴加工を行っていない試験片のビッカース硬さを同様にして測定し、母材の硬さとした。この測定値から硬化率を、
硬化率（％）＝（打抜き穴加工部の硬さ−母材の硬さ）×１００／母材
として求めた。
【００２３】
その結果、打抜き穴内表面より０．１ｍｍの部位では、硬化率は５０〜８０％であり、打抜き穴内表面より離れるに従って硬化率は低下して、打抜き穴内表面より１ｍｍの位置での硬化率はほぼ０％になることがわかった。
【００２４】
打抜き穴内表面より１ｍｍの範囲が加工硬化していることから、塑性歪みを熱処理によって回復させて穴拡げ性の向上を試みた。上述の試験と同条件で打抜き穴加工して穴径を測定し、３５０℃で２時間保持する熱処理を加熱炉内にて施し、室温まで空冷した。穴拡げ試験を上述の試験と同条件で行い、穴拡げ率を評価した。
【００２５】
その結果、打抜き穴性状の指標である剪断面比率の影響は小さく、熱処理によって穴拡げ率が大幅に向上し、切削加工材と同等になることを確認した。これは、（１）アルミニウム合金の穴拡げ性は、打抜き穴内表面の剪断面比率とともに低下し、（２）アルミニウム合金は、局部変形能が小さく、穴拡げ率は著しく低いため、（３）剪断加工により打抜き穴を形成した場合、穴拡げ率を向上させることは困難である、という従来知見を覆すものである。本発明者は、このようにして、室温で剪断加工し、打抜き穴を形成したアルミニウム合金の穴拡げ率を著しく改善させることに成功した。
【００２６】
以下、本発明について詳細に説明する。
本発明では、剪断加工によって打抜き穴内表面近傍に生じた加工硬化が、穴拡げ性低下の原因であることから、加工硬化が生じている打抜き穴内表面より１ｍｍの範囲の硬化率を限定する。
【００２７】
硬化率が２０％を超えると穴拡げ性が低下するため、２０％以下を上限とする。下限は低いほど良く、母材とほぼ同等である場合には０％となる。なお、５０００系アルミニウム合金において、冷間加工歪みが残留している場合、熱処理によって歪みが回復し、母材よりも硬さが低下することがある。また６０００系アルミニウム合金において、Ｔ５及びＴ６処理を施した場合、析出硬化により強度が大きくなっているため、熱処理の条件によっては、析出物が固溶して強化能を失い、母材よりも硬さが低下することがある。例えば、Ｔ５及びＴ６処理を施した６０００系アルミニウム合金に、４９０〜５５０℃で０〜６０ｓの熱処理を施すと、析出物が溶解してＭｇ及びＳｉが固溶するため、熱処理を施した部分の硬さは、母材よりも低下する。このような場合、硬化率の下限は−３０％程度である。
【００２８】
硬化率の測定は以下のようにして行うことができる。まず試験片は、打抜き穴加工後、打抜き穴の中心を通った圧延方向に切断し、切断面である板厚断面を鏡面研磨して作製する。この試験片の打抜き穴内表面より０．１〜２ｍｍの範囲のビッカース硬さを、板表面より０．１ｍｍ、板厚中心部及び板表面より１／４板厚の位置で、０．１ｍｍ間隔で測定する。このようにして、それぞれの測定位置においてビッカース硬さ測定し、この測定値を打抜き穴加工部の硬さとして、それぞれの測定位置における硬化率を求める。
【００２９】
なお、ビッカース硬さ試験は、ＪＩＳ Ｚ ２２４４に準じて行えば良いが、試験力が０．９８０７よりも大きいとビッカースくぼみが大きいため、測定の間隔を０．１ｍｍとすることが難しくなる。したがって、ビッカース硬さ試験は、試験力を０．０９８０７〜０．９８０７の範囲で行うことが好ましい。
【００３０】
打抜き穴加工を行っていない試験片のビッカース硬さを同様にして測定し、母材の硬さとする。母材の硬さの測定は、打抜き穴加工部の硬さを測定した試験片を用いて、打抜き穴内表面より２０ｍｍ以上離れた位置で測定しても良い。母材の硬さは、３点以上の測定値の平均値とすることが好ましい。
【００３１】
この打抜き穴内表面から０．１ｍｍ間隔で測定したビッカース硬さの、それぞれの測定値と母材の硬さの測定値から硬化率を、
硬化率（％）＝（打抜き穴加工部の硬さ−母材の硬さ）×１００／母材の硬さとして求める。打抜き穴内表面から離れた位置での硬化率は低下するが、内抜き穴内表面から１ｍｍ以内の各位置において測定した硬化率が全て２０％以下であることが必要である。
【００３２】
なお、硬さの測定は複数の試験片を用いて測定することが好ましい。試料の採取方向は、圧延方向でも良いが、圧延方向と直交する幅方向及び４５°方向において行っても良い。また、複数の試料にから試験片を採取する場合は、方向に依らず、測定した打抜き穴内表面からの距離に対応するそれぞれの位置で測定したビッカース硬の平均値を算出することが好ましい。
【００３３】
次に本発明のアルミニウム合金の成分について説明する。
【００３４】
本発明は、自動車の足廻り部品等の構造材料に好適な、穴拡げ性に優れたアルミニウム合金である。この用途には強度、成形性及び耐食性に優れたＡｌ−Ｍｇ系の５０００系合金とＡｌ−Ｍｇ−Ｓｉ系の６０００系合金の適用が好ましい。これらの合金において、Ｍｇ量及びＳｉ量の規定は必須であり、Ｆｅ、Ｍｎ及びＣｒは１種又は２種以上を含有するものである。
【００３５】
５０００系合金におけるＭｇ及びＳｉの効果並びに含有量の範囲について説明する。
【００３６】
Ｍｇ：Ｍｇは固溶強化により強度を向上させ、さらに成形性及び加工性も向上させる元素であるが、０．２％未満ではその効果が不十分であるため、０．２％以上をＭｇ量の下限とする。一方、Ｍｇを６．０％を超えて添加すると、熱間加工性が大幅に劣化し、また耐応力腐食割れ性も著しく低下するため、Ｍｇ量の上限を６．０％とする。なお、製造性、加工性及び耐応力腐食割れ性の点から好ましいＭｇ量の範囲は０．５〜５．５％であり、最適範囲は１．５〜３．５％の範囲である。
【００３７】
Ｓｉ：Ｓｉは不純物であり、１．０％を超えて過剰に含有すると、粗大な晶出物及び析出物を生じて延性が低下するため、Ｓｉ量の上限を１．０％とした。なお、好ましい上限は、０．２％以下である。Ｓｉ量の下限は規定しないが、通常、不純物として０．０１％以上を含有する。
【００３８】
次ぎに６０００系合金におけるＭｇ及びＳｉの効果並びに含有量の範囲について説明する。
【００３９】
Ｍｇ：ＭｇはＳｉと複合添加することにより、Ｍｇ−Ｓｉ系の微細な析出物を生じて強度及びプレス成形性を向上させる元素であるが、Ｍｇ量が０．２％未満ではその効果が不十分である。一方、１．５％超のＭｇを添加すると粗大な晶出物及び析出物を形成し、延性が低下する。従って、Ｍｇ量の範囲を０．２〜１．５％の範囲とする。さらに、強度、プレス成形性及び延性が良好な、好ましいＭｇ量の範囲は、０．３〜１．０％である。
【００４０】
Ｓｉ：ＳｉもＭｇとの複合添加により、強度及びプレス成形性を向上させる元素であるが、その効果はＳｉ量が０．４％未満では不十分である。一方、２．０％超のＳｉ量を添加すると、粗大な晶出物及び析出物を生じて延性が低下する。従って、Ｓｉ量を０．４〜２．０％の範囲とする。さらに、強度及び延性が良好な好ましいＳｉ量の範囲は、０．５〜１．５％である。
【００４１】
５０００系及び６０００系合金における、Ｆｅ、Ｍｎ及びＣｒの効果並びに含有量の範囲について説明する。
【００４２】
Ｆｅ：Ｆｅは組織を微細化する元素であるが、その効果は０．００１％未満では不十分であるため、Ｆｅ量の下限を０．００１％以上とする。一方、Ｆｅ量が１．０％を超えると粗大な晶出物及び析出物を生じて延性が低下するため１．０％以下をＦｅ量の上限とする。さらに、組織の微細化と微細析出物の生成の抑制による穴拡げ性の向上を両立するための好ましいＦｅ量の範囲は０．０１〜０．２％であり、最適範囲は０．０１〜０．１％である。
【００４３】
Ｍｎ：Ｍｎは組織を微細化する元素であるが、その効果は０．０１％未満では不十分であり、２．０％を超えると粗大な晶出物及び析出物を生じて延性が低下するため。従って、Ｍｎ量の範囲を０．０１〜２．０％の範囲とする。さらに、微細な析出物の生成を抑制して穴拡げ性を向上するための好ましいＭｎ量の範囲は０．０１〜０．１％であり、最適範囲は０．０１〜０．０７％である。
【００４４】
Ｃｒ：Ｃｒも組織を微細化する元素であるが、その効果は０．００１％未満では不十分であるり、１．０％を超えると粗大な晶出物及び析出物を生じて延性が低下する。従って、Ｃｒ量の範囲を０．０００１〜１．０％の範囲とする。さらに、組織の微細化と微細析出物の生成の抑制による穴拡げ性の向上を両立するための好ましいＣｒ量の範囲は０．０１〜０．１％であり、最適範囲は０．０１〜０．０５％である。
【００４５】
さらに、必要に応じてＣｕ、Ｚｎ、Ｖ、Ｚｒ、Ｔｉ及びＢの１種又は２種以上を含有しても良い。
【００４６】
Ｃｕ：Ｃｕは固溶強化により板材、押出形材ともに加工性を向上させる元素であるが、０．０１％未満ではその効果が小さく、１．０％を超えて添加すると耐食性、応力腐食割れ性が低下する。従って、０．０１〜１％の添加が好ましい。さらに好ましい範囲は、０．１〜０．８％であり、最適範囲は０．２〜０．７％である。
【００４７】
Ｚｎ：Ｚｎは、強度向上により成形性を向上させる効果を有する。その効果は０．１％未満では小さく、２．０％を超えて過剰に添加すると逆に成形性が低下する。従って、０．１〜２．０％の添加が好ましい。
【００４８】
Ｖ：Ｖは、組織を微細化する元素であるが、その効果は０．０１％未満では効果が小さく、０．５％を超えると粗大な晶出物及び析出物を生じて延性が低下する。従って、０．０１〜０．５％の添加が好ましい。
【００４９】
Ｚｒ：Ｚｒは、組織を微細化する元素であるが、その効果は０．０１％未満では不十分であり、０．５％を超えると粗大な晶出物及び析出物を生じて延性が低下する。従って、０．０１〜０．５％の添加が好ましい。
【００５０】
Ｔｉ：Ｔｉは、凝固組織を微細化する元素であるが、その効果は０．００１％未満では小さく、０．５％を超えると粗大な晶出物及び析出物を生じて延性が低下する。従って、０．００１〜０．５％の添加が好ましい。
【００５１】
Ｂ：Ｂは、組織を微細化する元素であるが、その効果は０．０００１％未満では小さく、０．０５％を超えると粗大な晶出物及び析出物を生じて延性が低下する。従って、０．０００１〜０．０５％の添加が好ましい。
【００５２】
次に製造方法について説明する。
【００５３】
穴拡げ加工前の素材は板材、押出形材ともに、常法の製造方法でよい。剪断加工による打抜き穴の形成は、作業性から２００℃未満で行うものとする。また、アルミニウム合金板を液体窒素に浸漬し、−１９６℃以上で行っても良いが、室温が好ましい。
【００５４】
本発明において重要な製造方法は剪断加工後の熱処理であり、これによって打抜き穴内表面近傍の加工硬化の原因である塑性歪みを回復させる。従って、加工硬化している、少なくとも打抜き穴内表面より１ｍｍの範囲の部位を熱処理することが必要である。加熱温度は２００℃より低いと塑性歪みが回復しないため、２００℃以上を下限とする。一方、６００℃を超えると結晶粒径が粗大化して穴拡げ性が低下するため６００℃以下を上限とする。なお、熱処理温度の好ましい範囲は、３００〜５７０℃であり、最適範囲は、３５０〜５５０℃である。保持時間は、加熱温度に到達後、直ちに冷却しても良い。一方、２時間を超えて保持しても効果が飽和するため、２時間を上限とする。
【００５５】
なお、６０００系合金は、４９０〜５５０℃で０〜６０ｓの熱処理を施し、Ｍｇ2Ｓｉを固溶させることが好ましい。この後、強度を上昇させるために、１５０〜２００℃で、２０分〜２時間の熱処理を施しても良い、
この熱処理は、加熱炉内で行っても良い。この場合には打ち抜き穴周辺だけではなく、アルミニウム合金全体が熱処理を受けることになる。５０００系合金の場合は、穴拡げ加工前に受けた加工歪も回復するために、二次加工性も向上させることができる。一方６０００系合金の場合、熱処理により析出物の存在状態が変化して強度が低下することがある。そこで、強度が必要とされる場合には打ち抜き穴周辺のみの部分的な加熱とする方が望ましい。
【００５６】
加熱炉内での熱処理は、昇温に時間を要するため、電磁コイルによる高周波加熱などの誘導加熱によって行っても良い。また、特別な設備を必要とせず、熱処理を行うために２００〜６００℃に加熱した高温体を接触させることでも良い。また、部分的な加熱で良いため、作業効率の点からバーナーで加熱しても良い。
【００５７】
【実施例】
表１に示す合金組成からなる３．５ｍｍ厚のアルミニウム合金板を以下の方法により作製した。Ａ、Ｂ及びＣは５０００系合金であり、鋳造後、熱延、冷延により板厚を３．５ｍｍとし、３５０〜４００℃で２時間保持する熱処理を施し、調質はＯ材とした。Ｄ、Ｅ及びＦは６０００系合金であり、熱間押出により板厚を３．５ｍｍとし、Ｄ及びＥは５３０℃に昇温し、保持せずにそのまま水冷し、さらに１７０〜１８０℃で８時間の熱処理を施してＴ６材としＦは押出し後１７０〜１８０℃で８時間の熱処理を施してＴ５材とした。
【００５８】
【表１】
これらのアルミニウム合金より９０ｍｍ角の試験片を切り出し、１０ｍｍφのポンチと１１．０ｍｍφのダイスを用いてプレス加工機によって室温で打抜き穴加工した。これらの試験片に表２に示す条件で熱処理を施した。熱処理は、熱電対を装着した試験片を用いて、加熱炉、誘導加熱、バーナー加熱、高温体接触の条件による温度変化を調査して、最高温度での保持時間が表２に示す条件になるように調整して行った。熱処理後の試験片の打抜き穴内表面より０．１ｍｍのビッカース硬さを、板厚中心部及び板表面より１／４板厚の位置で測定した。ビッカース硬さ試験はＪＩＳ Ｚ ２２４４に準じて、試験力０．０９８７Ｎで行った。なお、打抜き穴加工を行っていない試験片のビッカース硬さを同様にして測定し、母材の硬さとし、硬化率を算出した。
【００６０】
さらに、６０°の円錐ポンチを用いて穴拡げ加工を施し、穴拡げ試験前後の穴径の変化から穴拡げ率を算出した結果を表２に示す。表２に示すように、本発明の熱処理を施すことにより、優れた穴拡げ性が得られることがわかる。
【００６１】
【表２】
【発明の効果】
本発明によれば、アルミニウム合金の穴拡げ性の向上により、高穴拡げ性打ち抜き穴を有するアルミニウム合金板及びその高穴広げ性打ち抜き穴の加工方法を提供することができ、アルミニウム合金の自動車への適用が工業的に容易になるなど、産業上有用な顕著な効果を奏する。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an aluminum alloy used for automobile body panels, structural materials, etc., in particular, an aluminum alloy having a punched hole formed by shearing and subsequently expanding the hole. It relates to a manufacturing method.
[0002]
[Prior art]
In recent years, in order to reduce the weight of an automobile body, studies are being made to apply aluminum alloys to body panels and structural materials. For applications such as automobile parts, excellent press formability is required, and aluminum alloys having excellent stretch formability and deep drawability have been developed so far. However, an actual automobile member is subjected to forming such as overhang and deep drawing, and then subjected to hole expansion processing such as stretch flange processing and burring processing. In particular, when applying an aluminum alloy to a structural material such as an undercarriage part, improvement of hole expansibility is an important issue.
[0003]
Generally, in order to improve the hole expansibility of a metal material, it is effective to improve the local ductility of the material or to smooth the inner surface of the hole. Since the ductility of the material is improved as the temperature rises, Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4 and Patent Document 5 disclose methods of performing hole expansion at a high temperature. However, this method requires special processing equipment.
[0004]
Moreover, in order to smooth the inner surface of the hole, Patent Document 6 discloses a method of drilling with a laser, and Patent Document 7 discloses a method of further cutting a hole formed by shearing (hereinafter referred to as a punched hole). ing. However, when laser drilling was performed on an aluminum alloy, it was found that the local ductility decreased because the vicinity of the inner surface of the hole became a solidified structure, and the effect of improving the hole expandability was small. Further, there is a problem that even if the inner surface of the punched hole is further sheared and smoothed, the hole expandability is not significantly improved.
[0005]
[Patent Document 1]
JP 59-225813 A [Patent Document 2]
JP-A-60-121018 [Patent Document 3]
JP-A-60-177913 [Patent Document 4]
JP 60-177914 A [Patent Document 5]
JP 63-115614 A [Patent Document 6]
JP-A-10-277766 [Patent Document 7]
Japanese Patent Laid-Open No. 6-39450 [0006]
[Problems to be solved by the invention]
The present invention does not require a special device as in the hole expanding process at a high temperature, and has improved the hole expandability much more effectively than laser hole drilling or smoothing the inner surface of a hole by shearing after punching. An object is to provide an aluminum alloy and a manufacturing method.
[0007]
[Means for Solving the Problems]
The inventor has investigated in detail the hole expandability of an aluminum alloy having punched holes formed by shearing. As a result, it has been clarified that, in the plate thickness cross section of the punched hole, the work hardening in the range of 1 mm from the inner surface of the punched hole is the cause of the hole expandability deterioration. From this knowledge, it has been found that heat treatment for recovering plastic strain at least at a work-hardened portion is extremely effective in improving hole expansibility.
[0008]
The present invention is based on such knowledge, and the gist thereof is as follows.
[0009]
(1) In an aluminum alloy having a punched hole by shearing, in mass%,
Mg: 0.2-6.0%, Si: 1.0% or less,
Containing
Fe: 0.001 to 1.0%, Mn: 0.01 to 2.0%,
Cr: 0.001 to 1.0%,
An aluminum alloy for hole expansion processing, characterized by comprising one or more of the following, comprising the balance Al and inevitable impurities, and having a hardening rate within a range of 1 mm from the inner surface of the punched hole is 20% or less.
[0010]
However,
Curing rate (%) = (Hardness of punched hole processed portion−Hardness of base material) × 100 / Hardness of base material Here, the hardness of the punched hole processed portion is a plate thickness section passing through the center of the punched hole. The hardness of the base material and the punched hole processed portion is Vickers hardness.
[0011]
(2) In an aluminum alloy having punched holes by shearing, in mass%,
Mg: 0.2-1.5%, Si: 0.4-2.0%,
Containing
Fe: 0.001 to 1.0%, Mn: 0.01 to 2.0%,
Cr: 0.001 to 1.0%,
An aluminum alloy for hole expansion processing, characterized by comprising one or more of the following, comprising the balance Al and inevitable impurities, and having a hardening rate within a range of 1 mm from the inner surface of the punched hole is 20% or less.
[0012]
However,
Curing rate (%) = (Hardness of punched hole processed portion−Hardness of base material) × 100 / Hardness of base material
Here, the hardness of the punched hole processed portion is a hardness within a range of 1 mm from the inner surface of the punched hole in the thickness cross section passing through the center of the punched hole, and the hardness of the base material and the punched hole processed portion is Vickers hardness. is there.
[0013]
( 3 ) In mass%,
Cu: 0.01 to 1.0% (excluding 0.04% and 0.7%) ,
Zn: 0.1 to 2.0%, V: 0.01 to 0.5%,
Zr: 0.01 to 0.5%, Ti: 0.001 to 0.5%,
B: 0.0001 to 0.05%
One or containing two or more, characterized in (1) Symbol placement of hole expansion processing aluminum alloys.
(4) In mass%,
Cu: 0.01 to 1.0% (excluding 0.01% and 0.7%),
Zn: 0.1 to 2.0%, V: 0.01 to 0.5%,
Zr: 0.01 to 0.5%, Ti: 0.001 to 0.5%,
B: 0.0001 to 0.05%
1 type or 2 types or more are contained, The aluminum alloy for hole expansion processing of (2) description characterized by the above-mentioned.
[0014]
(5) The aluminum alloy composed of the component according to any one of (1) to (4) is at least within a range of 1 mm from the inner surface of the punched hole after punched hole processing at less than 200 ° C. and before the hole expanding process. The method for producing an aluminum alloy for hole expansion according to any one of (1) to (4), wherein the heat treatment is performed at 200 to 600 ° C. and maintained for 2 hours or less.
[0015]
(6) The method for producing an aluminum alloy for hole expansion according to (5), wherein heat treatment is performed in a heating furnace.
[0016]
(7) A method for producing an aluminum alloy for hole expansion processing having a punched hole by shearing and having a hardening rate within a range of 1 mm from the inner surface of the punched hole of 20% or less, wherein (1) or (2) An aluminum alloy composed of the components described above is heated to 200 to 600 ° C., which is heat- treated by induction heating at least within a range of 1 mm from the inner surface of the punched hole after punching at less than 200 ° C. and before hole expansion, for 2 hours. method for producing a hole expansion processing aluminum alloy you characterized by a heat treatment which holds less.
However,
Curing rate (%) = (Hardness of punched hole processed portion−Hardness of base material) × 100 / Hardness of base material
Here, the hardness of the punched hole processed portion is a hardness within a range of 1 mm from the inner surface of the punched hole in the thickness cross section passing through the center of the punched hole, and the hardness of the base material and the punched hole processed portion is Vickers hardness. is there.
[0017]
(8) A method for producing an aluminum alloy for hole expansion processing having a punched hole by shearing and having a hardening rate within a range of 1 mm from the inner surface of the punched hole of 20% or less, wherein (1) or (2) an aluminum alloy consisting of components described, after punching drilling below 200 ° C., before hole expansion processing, at least 1mm the range of from perforations in the surface, contacting the high-temperature body heated to 200 to 600 ° C., 200 to 600 was heated to ° C., hole expansion you characterized by a heat treatment of holding more than 2 hours manufacturing method of processing an aluminum alloy.
However,
Curing rate (%) = (Hardness of punched hole processed portion−Hardness of base material) × 100 / Hardness of base material
Here, the hardness of the punched hole processed portion is a hardness within a range of 1 mm from the inner surface of the punched hole in the thickness cross section passing through the center of the punched hole, and the hardness of the base material and the punched hole processed portion is Vickers hardness. is there.
[0018]
(9) A method for producing an aluminum alloy for hole expansion processing having a punched hole by shearing and having a hardening rate within a range of 1 mm from the inner surface of the punched hole of 20% or less, wherein (1) or (2) After punching the aluminum alloy composed of the components described below at 200 ° C. and before expanding the hole, at least within 1 mm from the inner surface of the punched hole is heated to 200 to 600 ° C. with a burner and held for 2 hours or less. method for producing a hole expansion processing aluminum alloy you characterized by a heat treatment.
However,
Curing rate (%) = (Hardness of punched hole processed portion−Hardness of base material) × 100 / Hardness of base material
Here, the hardness of the punched hole processed portion is a hardness within a range of 1 mm from the inner surface of the punched hole in the thickness cross section passing through the center of the punched hole, and the hardness of the base material and the punched hole processed portion is Vickers hardness. is there.
(10) The aluminum alloy is in mass%, and
Cu: 0.01 to 1.0%, Zn: 0.1 to 2.0%,
V: 0.01 to 0.5%, Zr: 0.01 to 0.5%,
Ti: 0.001 to 0.5%, B: 0.0001 to 0.05%
The method for producing an aluminum alloy for hole expansion processing according to any one of (7) to (9), comprising one or more of the following.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
The present inventor conducted the following investigation in order to clarify the cause of the decrease in hole expansibility after shearing an aluminum alloy plate to form punched holes. First, a 90 mm square test piece is cut out of a 3.5 mm thick 5052 aluminum alloy, the clearance is changed using a 10 mmφ punch and a 10.2 to 11.0 mmφ die, and a punching hole is formed by shearing with a press machine. Formed at room temperature. The punched hole diameter was measured by enlarging the hole diameter 10 times using a magnifying glass. The clearance is a percentage obtained by dividing the difference between the die diameter and the punch diameter by 2, and further dividing by the plate thickness.
[0020]
The inner surface of the punched hole is a sheared surface having a metallic luster on the entrance side of the punch during shearing, and a broken surface having no gloss on the exit side. In four places of the rolling direction two places on the inner surface of the punched hole and two places in the width direction perpendicular to the rolling direction, the length of the shear face in the thickness direction is measured, and the shear face ratio is calculated as a percentage divided by the thickness, Furthermore, the average value of 4 places was calculated | required. The length of the shear plane was determined using a caliper. As a comparative material, a test piece in which a 10 mmφ hole was formed by cutting with a drilling machine was produced.
[0021]
Using these test pieces, after performing hole expansion using a 60 ° conical punch, the hole diameter was measured in the same manner as before the test. The hole expansion ratio was calculated by subtracting the hole diameter before the hole expansion test from this measured value and dividing this by the hole diameter before the test. As a result, it was found that the hole expansion ratio of the comparative material was about 130%, whereas the hole expansion ratio of the material in which the punched holes were formed by shearing was significantly reduced to about 40%. It was also found that the hole expansion rate of the material in which the punched holes were formed by shearing was almost the same regardless of the shearing surface ratio. From this, it was found that the cause of the decrease in the hole expansion rate by punching hole processing is different from the conventional knowledge, and that the effect of work hardening by shearing is greater than the properties of the inner surface of the punched hole.
[0022]
Then, the work hardening of the plate | board thickness cross section of the punch hole inner surface vicinity was confirmed as follows. First, a test piece was manufactured by cutting a punched hole, cutting it in the rolling direction through the center of the punched hole, and mirror-polishing the plate thickness section as the cut surface. The Vickers hardness in the range of 0.1 to 2 mm from the inner surface of the punched hole was measured at intervals of 0.1 mm at positions 0.1 mm from the plate surface and 1/4 plate thickness from the plate thickness center and the plate surface. The same measurement was performed using 2 to 5 samples, and the average value of the measured values at the same position was calculated to be the hardness of the punched hole processed portion. The Vickers hardness test was conducted at a test force of 0.0987 N corresponding to the hardness symbol HV0.01 in accordance with JIS Z 2244. The Vickers hardness of the test piece that was not punched was measured in the same manner as the hardness of the base material. From this measurement, cure rate
Curing rate (%) = (hardness of punched hole processed portion−hardness of base material) × 100 / base material.
[0023]
As a result, at a portion 0.1 mm from the inner surface of the punched hole, the curing rate is 50 to 80%. The curing rate decreases as the distance from the inner surface of the punched hole decreases, and the curing rate at a position 1 mm from the inner surface of the punched hole is almost equal. It was found to be 0%.
[0024]
Since a range of 1 mm from the inner surface of the punched hole was work-hardened, an attempt was made to improve hole expandability by recovering plastic strain by heat treatment. Punched holes were processed under the same conditions as in the above test, the hole diameter was measured, heat treatment was held at 350 ° C. for 2 hours in a heating furnace, and air-cooled to room temperature. A hole expansion test was performed under the same conditions as the above test, and the hole expansion rate was evaluated.
[0025]
As a result, it was confirmed that the influence of the shear surface ratio, which is an index of the punched hole properties, was small, and the hole expansion rate was greatly improved by heat treatment, which was equivalent to that of the cut material. This is because (1) the hole expandability of the aluminum alloy decreases with the shear surface ratio of the inner surface of the punched hole, and (2) the aluminum alloy has a small local deformability and a significantly low hole expansion rate. When the punched hole is formed by processing, the conventional knowledge that it is difficult to improve the hole expansion rate is overturned. In this way, the present inventor has succeeded in remarkably improving the hole expansion rate of an aluminum alloy that has been sheared at room temperature to form punched holes.
[0026]
Hereinafter, the present invention will be described in detail.
In the present invention, the work hardening generated in the vicinity of the inner surface of the punched hole due to the shearing process causes the hole expandability to be lowered. Therefore, the hardening rate is limited to a range of 1 mm from the inner surface of the punched hole where the work hardening has occurred.
[0027]
When the curing rate exceeds 20%, hole expansibility decreases, so 20% or less is the upper limit. The lower limit is better, and it is 0% when it is almost equal to the base material. In addition, in the 5000 series aluminum alloy, when the cold work strain remains, the strain is recovered by the heat treatment, and the hardness may be lower than that of the base material. In addition, when the T5 and T6 treatments are applied to the 6000 series aluminum alloy, the strength is increased by precipitation hardening, so that depending on the conditions of the heat treatment, the precipitates dissolve and lose the strengthening ability, which is harder than the base metal. May decrease. For example, if a 6000 series aluminum alloy that has been subjected to T5 and T6 treatments is subjected to heat treatment at 490 to 550 ° C. for 0 to 60 seconds, the precipitates are dissolved and Mg and Si are solid-dissolved. The hardness is lower than that of the base material. In such a case, the lower limit of the curing rate is about −30%.
[0028]
The curing rate can be measured as follows. First, after the punched hole is processed, the test piece is cut in the rolling direction passing through the center of the punched hole, and the plate thickness section which is the cut surface is mirror-polished. Vickers hardness in the range of 0.1 to 2 mm from the inner surface of the punched hole of this test piece, 0.1 mm from the plate surface, and at a position of 1/4 plate thickness from the plate thickness center and the plate surface at intervals of 0.1 mm taking measurement. In this way, the Vickers hardness is measured at each measurement position, and the measured value is used as the hardness of the punched hole processed portion to determine the curing rate at each measurement position.
[0029]
The Vickers hardness test may be performed in accordance with JIS Z 2244. However, if the test force is greater than 0.9807, the Vickers dent is large, and it becomes difficult to set the measurement interval to 0.1 mm. Therefore, the Vickers hardness test is preferably performed in the range of 0.09807 to 0.9807 test force.
[0030]
The Vickers hardness of a test piece that has not been punched is measured in the same manner as the hardness of the base material. The hardness of the base material may be measured at a position separated by 20 mm or more from the inner surface of the punched hole, using a test piece whose hardness of the punched hole processed portion is measured. The hardness of the base material is preferably an average value of three or more measured values.
[0031]
From the measured values of the Vickers hardness measured at 0.1 mm intervals from the inner surface of the punched hole and the measured values of the hardness of the base material,
Hardening rate (%) = (Hardness of punched hole processed portion−base material hardness) × 100 / base material hardness. Although the curing rate at a position away from the inner surface of the punched hole is lowered, all the curing rates measured at each position within 1 mm from the inner surface of the punched hole are required to be 20% or less.
[0032]
The hardness is preferably measured using a plurality of test pieces. The sample collection direction may be the rolling direction, but may be performed in the width direction and 45 ° direction orthogonal to the rolling direction. Further, when collecting test pieces from a plurality of samples, it is preferable to calculate the average value of Vickers hardness measured at each position corresponding to the distance from the measured inner surface of the punched hole, regardless of the direction.
[0033]
Next, the components of the aluminum alloy of the present invention will be described.
[0034]
The present invention is an aluminum alloy excellent in hole expansibility suitable for a structural material such as an automobile undercarriage part. For this purpose, it is preferable to apply Al-Mg-based 5000 alloy and Al-Mg-Si-based 6000-based alloy having excellent strength, formability and corrosion resistance. In these alloys, the definition of the amount of Mg and the amount of Si is essential, and Fe, Mn, and Cr contain one or more.
[0035]
The effect and content range of Mg and Si in the 5000 series alloy will be described.
[0036]
Mg: Mg is an element that improves the strength by solid solution strengthening, and further improves the formability and workability, but its effect is insufficient if it is less than 0.2%, so 0.2% or more is the amount of Mg The lower limit of. On the other hand, if Mg is added in excess of 6.0%, the hot workability is significantly deteriorated and the stress corrosion cracking resistance is remarkably lowered. Therefore, the upper limit of Mg content is 6.0%. In addition, the range of preferable Mg amount from the point of manufacturability, workability, and stress corrosion cracking resistance is 0.5 to 5.5%, and the optimal range is the range of 1.5 to 3.5%.
[0037]
Si: Si is an impurity, and if it exceeds 1.0% and excessively contained, coarse crystallized products and precipitates are produced and the ductility is lowered. Therefore, the upper limit of the Si amount is set to 1.0%. A preferred upper limit is 0.2% or less. Although the lower limit of the amount of Si is not specified, it usually contains 0.01% or more as an impurity.
[0038]
Next, the effect and content range of Mg and Si in the 6000 series alloy will be described.
[0039]
Mg: Mg is an element that, when added in combination with Si, produces fine Mg-Si-based precipitates to improve strength and press formability. However, if the amount of Mg is less than 0.2%, the effect is not good. It is enough. On the other hand, when Mg of more than 1.5% is added, coarse crystals and precipitates are formed, and ductility is lowered. Therefore, the range of Mg amount is set to a range of 0.2 to 1.5%. Furthermore, the range of preferable Mg amount with favorable strength, press formability, and ductility is 0.3 to 1.0%.
[0040]
Si: Si is an element that improves strength and press formability by complex addition with Mg, but the effect is insufficient when the Si content is less than 0.4%. On the other hand, when an Si amount of more than 2.0% is added, coarse crystallized products and precipitates are produced and ductility is lowered. Therefore, the Si amount is set to a range of 0.4 to 2.0%. Furthermore, the range of the preferable amount of Si with favorable intensity | strength and ductility is 0.5 to 1.5%.
[0041]
The effects of Fe, Mn, and Cr and the range of contents in 5000 series and 6000 series alloys will be described.
[0042]
Fe: Fe is an element that refines the structure, but its effect is insufficient if it is less than 0.001%, so the lower limit of the amount of Fe is made 0.001% or more. On the other hand, if the amount of Fe exceeds 1.0%, coarse crystals and precipitates are produced and ductility is lowered, so 1.0% or less is made the upper limit of the amount of Fe. Furthermore, the preferable range of Fe content for achieving both the refinement of the structure and the improvement of hole expansibility by suppressing the formation of fine precipitates is 0.01 to 0.2%, and the optimum range is 0.01 to 0. .1%.
[0043]
Mn: Mn is an element that refines the structure, but its effect is insufficient if it is less than 0.01%, and if it exceeds 2.0%, coarse crystals and precipitates are produced and ductility is lowered. For. Therefore, the range of the amount of Mn is made 0.01 to 2.0%. Furthermore, the range of the preferable amount of Mn for suppressing the production | generation of a fine precipitate and improving hole expansibility is 0.01 to 0.1%, and the optimal range is 0.01 to 0.07%. .
[0044]
Cr: Cr is also an element that refines the structure, but its effect is insufficient if it is less than 0.001%, and if it exceeds 1.0%, coarse crystals and precipitates are produced and ductility is lowered. To do. Therefore, the range of Cr amount is set to a range of 0.0001 to 1.0%. Furthermore, the preferable Cr amount range for achieving both improvement of hole expansion by miniaturization of the structure and suppression of formation of fine precipitates is 0.01 to 0.1%, and the optimal range is 0.01 to 0. .05%.
[0045]
Furthermore, you may contain 1 type, or 2 or more types of Cu, Zn, V, Zr, Ti, and B as needed.
[0046]
Cu: Cu is an element that improves the workability of both the plate and the extruded shape by solid solution strengthening. However, the effect is small if it is less than 0.01%, and if it exceeds 1.0%, the corrosion resistance and the stress corrosion cracking property. Decreases. Therefore, addition of 0.01 to 1% is preferable. A more preferable range is 0.1 to 0.8%, and an optimal range is 0.2 to 0.7%.
[0047]
Zn: Zn has the effect of improving formability by improving strength. The effect is small if it is less than 0.1%, and if it is added in excess of 2.0%, the moldability is lowered. Therefore, addition of 0.1 to 2.0% is preferable.
[0048]
V: V is an element that refines the structure, but its effect is small if it is less than 0.01%, and if it exceeds 0.5%, coarse crystals and precipitates are produced and ductility is lowered. . Therefore, addition of 0.01 to 0.5% is preferable.
[0049]
Zr: Zr is an element that refines the structure, but its effect is insufficient if it is less than 0.01%, and if it exceeds 0.5%, coarse crystals and precipitates are produced and ductility is lowered. To do. Therefore, addition of 0.01 to 0.5% is preferable.
[0050]
Ti: Ti is an element that refines the solidification structure, but its effect is small if it is less than 0.001%, and if it exceeds 0.5%, coarse crystals and precipitates are produced and ductility is lowered. Therefore, the addition of 0.001 to 0.5% is preferable.
[0051]
B: B is an element for refining the structure, but its effect is small if it is less than 0.0001%, and if it exceeds 0.05%, coarse crystals and precipitates are produced, and ductility is lowered. Therefore, the addition of 0.0001 to 0.05% is preferable.
[0052]
Next, a manufacturing method will be described.
[0053]
The raw material before the hole expansion process may be a conventional manufacturing method for both the plate material and the extruded shape material. The punching hole is formed by shearing at less than 200 ° C. in view of workability. Moreover, although an aluminum alloy plate may be immersed in liquid nitrogen and it may carry out at -196 degreeC or more, room temperature is preferable.
[0054]
An important production method in the present invention is a heat treatment after shearing, thereby recovering plastic strain that is the cause of work hardening in the vicinity of the inner surface of the punched hole. Therefore, it is necessary to heat-treat at least a portion in the range of 1 mm from the inner surface of the punched hole, which is work hardened. When the heating temperature is lower than 200 ° C., plastic strain does not recover, so 200 ° C. or higher is set as the lower limit. On the other hand, if the temperature exceeds 600 ° C., the crystal grain size becomes coarse and the hole expansibility decreases, so the upper limit is 600 ° C. In addition, the preferable range of heat processing temperature is 300-570 degreeC, and the optimal range is 350-550 degreeC. The holding time may be cooled immediately after reaching the heating temperature. On the other hand, since the effect is saturated even if it is maintained for more than 2 hours, the upper limit is 2 hours.
[0055]
Note that 6000 series alloy, heat-treated at 0~60s at four hundred ninety to five hundred and fifty ° C., it is preferred to solid solution of Mg 2 Si. Thereafter, in order to increase the strength, heat treatment may be performed at 150 to 200 ° C. for 20 minutes to 2 hours.
This heat treatment may be performed in a heating furnace. In this case, not only the periphery of the punched hole but the entire aluminum alloy is subjected to heat treatment. In the case of a 5000 series alloy, secondary workability can be improved because the processing strain received before the hole expansion processing is recovered. On the other hand, in the case of a 6000 series alloy, the presence of precipitates may change due to heat treatment, resulting in a decrease in strength. Therefore, when strength is required, it is preferable to perform partial heating only around the punched hole.
[0056]
Since the heat treatment in the heating furnace takes time to raise the temperature, it may be performed by induction heating such as high-frequency heating using an electromagnetic coil. In addition, a high temperature body heated to 200 to 600 ° C. may be brought into contact without performing special equipment and performing heat treatment. Moreover, since partial heating is sufficient, you may heat with a burner from the point of work efficiency.
[0057]
【Example】
A 3.5 mm-thick aluminum alloy plate having the alloy composition shown in Table 1 was produced by the following method. A, B, and C are 5000 series alloys. After casting, the plate thickness was 3.5 mm by hot rolling and cold rolling, and heat treatment was performed for 2 hours at 350 to 400 ° C., and the tempering was O material. D, E, and F are 6000 series alloys, the plate thickness is set to 3.5 mm by hot extrusion, D and E are heated to 530 ° C., water-cooled without being held, and further at 170 to 180 ° C., 8 Heat treatment was performed for a time period to obtain a T6 material, and F was subjected to a heat treatment at 170 to 180 ° C. for 8 hours after extrusion to obtain a T5 material.
[0058]
[Table 1]
A test piece of 90 mm square was cut out from these aluminum alloys and punched at room temperature with a press machine using a 10 mmφ punch and a 11.0 mmφ die. These test pieces were heat-treated under the conditions shown in Table 2. In the heat treatment, a test piece equipped with a thermocouple is used to investigate temperature changes depending on the conditions of the heating furnace, induction heating, burner heating, and hot body contact, and the holding time at the maximum temperature becomes the conditions shown in Table 2. It was adjusted as follows. The Vickers hardness of 0.1 mm from the inner surface of the punched hole of the test piece after the heat treatment was measured at a position at a thickness of 1/4 from the center of the plate thickness and the plate surface. The Vickers hardness test was performed according to JIS Z 2244 with a test force of 0.0987 N. In addition, the Vickers hardness of the test piece which has not performed the punching hole processing was measured in the same manner, and the hardness was calculated as the hardness of the base material.
[0060]
Further, Table 2 shows the results of calculating the hole expansion rate from the change in the hole diameter before and after the hole expansion test by performing hole expansion using a 60 ° conical punch. As shown in Table 2, it can be seen that excellent hole expandability can be obtained by performing the heat treatment of the present invention.
[0061]
[Table 2]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the improvement of the hole expansibility of an aluminum alloy can provide the aluminum alloy plate which has a high hole expansibility punching hole, and the processing method of the high hole expansibility punching hole, and the aluminum alloy to the motor vehicle. As a result, industrially useful remarkable effects can be obtained.
Claims (10)
Ｍｇ：０．２〜６．０％、
Ｓｉ：１．０％以下、
を含有し、
Ｆｅ：０．００１〜１．０％、
Ｍｎ：０．０１〜２．０％、
Ｃｒ：０．００１〜１．０％
の１種又は２種以上を含有し、残部Ａｌ及び不可避不純物からなり、打抜き穴内表面より１ｍｍの範囲内の硬化率が２０％以下であることを特徴とする穴拡げ加工用アルミニウム合金。
ただし、
硬化率（％）＝（打抜き穴加工部の硬さ−母材の硬さ）×１００／母材の硬さ
ここで、打抜き穴加工部の硬さは、打抜き穴の中心を通る板厚断面における打抜き穴内表面より１ｍｍ範囲内の硬さであり、母材及び打抜き穴加工部の硬さはビッカース硬さである。 In aluminum alloy having punched holes by shearing, in mass%,
Mg: 0.2-6.0%,
Si: 1.0% or less,
Containing
Fe: 0.001 to 1.0%,
Mn: 0.01 to 2.0%,
Cr: 0.001 to 1.0%
One or comprise two or more, Ri Do the balance Al and inevitable impurities, hole expansion processing aluminum alloy hardening rate in the range of 1mm from the punched hole surface you characterized der Rukoto than 20% of .
However,
Curing rate (%) = (Hardness of punched hole processed portion−Hardness of base material) × 100 / Hardness of base material
Here, the hardness of the punched hole processed portion is a hardness within a range of 1 mm from the inner surface of the punched hole in the thickness cross section passing through the center of the punched hole, and the hardness of the base material and the punched hole processed portion is Vickers hardness. is there.
質量％で、
Ｍｇ：０．２〜１．５％、
Ｓｉ：０．４〜２．０％、
を含有し、
Ｆｅ：０．００１〜１．０％、
Ｍｎ：０．０１〜２．０％、
Ｃｒ：０．００１〜１．０％
の１種又は２種以上を含有し、残部Ａｌ及び不可避不純物からなり、打抜き穴内表面より１ｍｍの範囲内の硬化率が２０％以下であることを特徴とする穴拡げ加工用アルミニウム合金。
ただし、
硬化率（％）＝（打抜き穴加工部の硬さ−母材の硬さ）×１００／母材の硬さ
ここで、打抜き穴加工部の硬さは、打抜き穴の中心を通る板厚断面における打抜き穴内表面より１ｍｍ範囲内の硬さであり、母材及び打抜き穴加工部の硬さはビッカース硬さである。 In an aluminum alloy having punched holes by shearing,
% By mass
Mg: 0.2 to 1.5%
Si: 0.4-2.0%,
Containing
Fe: 0.001 to 1.0%,
Mn: 0.01 to 2.0%,
Cr: 0.001 to 1.0%
One or comprise two or more, Ri Do the balance Al and inevitable impurities, hole expansion processing aluminum alloy hardening rate in the range of 1mm from the punched hole surface you characterized der Rukoto than 20% of .
However,
Curing rate (%) = (Hardness of punched hole processed portion−Hardness of base material) × 100 / Hardness of base material
Here, the hardness of the punched hole processed portion is a hardness within a range of 1 mm from the inner surface of the punched hole in the thickness cross section passing through the center of the punched hole, and the hardness of the base material and the punched hole processed portion is Vickers hardness. is there.
Ｃｕ：０．０１〜１．０％（０．０４％及び０．７％を除く）、
Ｚｎ：０．１〜２．０％、
Ｖ ：０．０１〜０．５％、
Ｚｒ：０．０１〜０．５％、
Ｔｉ：０．００１〜０．５％、
Ｂ ：０．０００１〜０．０５％
の１種又は２種以上を含有することを特徴とする請求項１記載の穴拡げ加工用アルミニウム合金。In mass%,
Cu: 0.01 to 1.0% (excluding 0.04% and 0.7%) ,
Zn: 0.1 to 2.0%,
V: 0.01 to 0.5%
Zr: 0.01 to 0.5%,
Ti: 0.001 to 0.5%,
B: 0.0001 to 0.05%
The aluminum alloy for hole expansion processing according to claim 1, comprising one or more of the following.
Ｃｕ：０．０１〜１．０％（０．０１％及び０．７％を除く）、Cu: 0.01 to 1.0% (excluding 0.01% and 0.7%),
Ｚｎ：０．１〜２．０％、Zn: 0.1 to 2.0%,
ＶV ：０．０１〜０．５％、: 0.01 to 0.5%
Ｚｒ：０．０１〜０．５％、Zr: 0.01 to 0.5%,
Ｔｉ：０．００１〜０．５％、Ti: 0.001 to 0.5%,
ＢB ：０．０００１〜０．０５％: 0.0001-0.05%
の１種又は２種以上を含有することを特徴とする請求項２記載の穴拡げ加工用アルミニウThe aluminum for hole expansion processing according to claim 2, comprising one or more of ム合金。Alloy.
ただし、
硬化率（％）＝（打抜き穴加工部の硬さ−母材の硬さ）×１００／母材の硬さ
ここで、打抜き穴加工部の硬さは、打抜き穴の中心を通る板厚断面における打抜き穴内表面より１ｍｍ範囲内の硬さであり、母材及び打抜き穴加工部の硬さはビッカース硬さである。 A method for producing an aluminum alloy for hole expansion processing having a punched hole by shearing and having a hardening rate of 20% or less within a range of 1 mm from the inner surface of the punched hole, comprising the components according to claim 1 or 2. After punching a hole at less than 200 ° C. and before expanding the hole, the aluminum alloy is heated to 200 to 600 ° C. by induction heating at least within a range of 1 mm from the inner surface of the punched hole and subjected to heat treatment for 2 hours or less. method for producing a hole expansion processing aluminum alloy you characterized.
However,
Curing rate (%) = (Hardness of punched hole processed portion−Hardness of base material) × 100 / Hardness of base material
Here, the hardness of the punched hole processed portion is a hardness within a range of 1 mm from the inner surface of the punched hole in the thickness cross section passing through the center of the punched hole, and the hardness of the base material and the punched hole processed portion is Vickers hardness. is there.
ただし、
硬化率（％）＝（打抜き穴加工部の硬さ−母材の硬さ）×１００／母材の硬さ
ここで、打抜き穴加工部の硬さは、打抜き穴の中心を通る板厚断面における打抜き穴内表面より１ｍｍ範囲内の硬さであり、母材及び打抜き穴加工部の硬さはビッカース硬さである。 A method for producing an aluminum alloy for hole expansion processing having a punched hole by shearing and having a hardening rate of 20% or less within a range of 1 mm from the inner surface of the punched hole, comprising the components according to claim 1 or 2. After punching the aluminum alloy at a temperature of less than 200 ° C. and before expanding the hole, at least within a range of 1 mm from the inner surface of the punched hole, a high-temperature body heated to 200 to 600 ° C. is contacted and heated to 200 to 600 ° C. a method for producing a hole expansion processing aluminum alloy you characterized by a heat treatment of holding more than 2 hours.
However,
Curing rate (%) = (Hardness of punched hole processed portion−Hardness of base material) × 100 / Hardness of base material
Here, the hardness of the punched hole processed portion is a hardness within a range of 1 mm from the inner surface of the punched hole in the thickness cross section passing through the center of the punched hole, and the hardness of the base material and the punched hole processed portion is Vickers hardness. is there.
ただし、
硬化率（％）＝（打抜き穴加工部の硬さ−母材の硬さ）×１００／母材の硬さ
ここで、打抜き穴加工部の硬さは、打抜き穴の中心を通る板厚断面における打抜き穴内表面より１ｍｍ範囲内の硬さであり、母材及び打抜き穴加工部の硬さはビッカース硬さである。 A method for producing an aluminum alloy for hole expansion processing having a punched hole by shearing and having a hardening rate of 20% or less within a range of 1 mm from the inner surface of the punched hole, comprising the components according to claim 1 or 2. After the punching of the aluminum alloy at a temperature of less than 200 ° C., and before the hole expanding process, at least 1 mm from the inner surface of the punched hole is heated to 200 to 600 ° C. with a burner and subjected to heat treatment for 2 hours or less. method for producing a hole expansion processing aluminum alloy you characterized.
However,
Curing rate (%) = (Hardness of punched hole processed portion−Hardness of base material) × 100 / Hardness of base material
Here, the hardness of the punched hole processed portion is a hardness within a range of 1 mm from the inner surface of the punched hole in the thickness cross section passing through the center of the punched hole, and the hardness of the base material and the punched hole processed portion is Vickers hardness. is there.
Ｃｕ：０．０１〜１．０％、Cu: 0.01 to 1.0%,
Ｚｎ：０．１〜２．０％、Zn: 0.1 to 2.0%,
ＶV ：０．０１〜０．５％、: 0.01 to 0.5%
Ｚｒ：０．０１〜０．５％、Zr: 0.01 to 0.5%,
Ｔｉ：０．００１〜０．５％、Ti: 0.001 to 0.5%,
ＢB ：０．０００１〜０．０５％: 0.0001-0.05%
の１種又は２種以上を含有することを特徴とする請求項７〜９のいずれか１項に記載の穴拡げ加工用アルミニウム合金の製造方法。1 or 2 types of these are contained, The manufacturing method of the aluminum alloy for hole expansion processes of any one of Claims 7-9 characterized by the above-mentioned.
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