JP4274674B2 - Aluminum alloy member excellent in crushability and manufacturing method thereof - Google Patents
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Description
【０００１】
【発明の属する技術分野】
本発明は自動車のサイドメンバー等に使用される圧壊性に優れたアルミニウム合金部材及びそれを使用した部材の製造方法に関し、特に、成形性が優れ、且つ強度が高く、衝突等により衝撃が加わったときに破断せずに変形しやすい圧壊性に優れたアルミニウム合金部材及びその製造方法に関する。
【０００２】
【従来の技術】
近時、自動車の骨格部材及び外板パネル材には、軽量化の要求により鋼材に替わってアルミニウム合金材の使用が検討されつつある。
【０００３】
アルミニウム合金材の中でも、耐食性及び成形性のいずれについても、比較的良好なＪＩＳ ６０００系アルミニウム合金が注目されており、この６０００系アルミニウム合金の押出し型材を使用したフレーム構造が検討されている。また、６０００系アルミニウム合金からなる板材が自動車の外板パネルに採用されつつある。
【０００４】
しかし、自動車の外観の多様化及び居住スペースの増加の要求等から、自動車の制約された空間内に部材を配置しなければならなくなっている。その反面、安全面での基準も厳しくなっており、従来以上に衝突時の衝撃を吸収するように部材には圧壊性の向上も求められている。
【０００５】
従って、狭いスペースに高い圧壊性を有する部材を配置しなければならなくなってきており、複雑な形状に加工することができ、且つ高い強度を有し、更に圧壊性にも優れた自動車用部材が必要とされている。
【０００６】
自動車用部材として使用されている６０００系アルミニウム合金材としては、例えば、自動車のパネル材として使用されるアルミニウム合金板材が特開昭６２−２７８２４５号公報に開示されている。また、自動車のフレームに使用される押出し材が特開平６−２５７８３号公報及び特開平９−２５６０９６号公報に開示されている。
【０００７】
また、Ｍｇ及びＳｉを含むアルミニウム合金の凝固速度を制御して晶出物の形状を制御し、耐衝撃性を高めたアルミニウム合金板が特開平９−２６３８６９号公報に開示されている。
【０００８】
【発明が解決しようとする課題】
しかし、上述の特開平６−２５７８３号公報及び特開平９−２５６０９６号公報に開示されている押出し材は衝撃吸収性が優れているものの、押出し材は形状の制約があり、押出した後、更に複雑な形状の部材に加工することが困難であるという問題点がある。
【０００９】
一方、特開昭６２−２７８２４５号公報に開示されているパネル材に使用されるアルミニウム合金板材を使用して成形した自動車部材では、圧壊性が十分ではないという問題点がある。このように、自動車部材として、適性なアルミニウム合金材はこれまで存在しなかった。
【００１０】
また、特開平９−２６３８６９号公報に開示されているアルミニウム合金板は、熱間圧延加工後に冷間加工を施すものであり、結晶粒は等軸粒になっている。従って、衝撃時にアルミニウム合金板にかかる荷重をうまく分散することができないため、充分な圧壊性が得られないという問題点がある。
【００１１】
本発明はかかる問題点に鑑みてなされたものであって、複雑な形状に加工することができ、圧壊性が優れていると共に、高い強度を有する圧壊性に優れたアルミニウム合金板及びそれを使用した部材の製造方法を提供することを目的とする。
【００１２】
【課題を解決するための手段】
本願発明に係る圧壊性に優れたアルミニウム合金部材は、Ｓｉ：０．４乃至０．８質量％、Ｍｇ：０．４乃至０．８質量％、Ｆｅ：０．３質量％以下、Ｍｎ：０．３質量％以下を含有し、残部が不可避的不純物及びＡｌからなる組成を有し、溶体化処理されたアルミニウム合金部材であって、圧延方向と平行な板厚方向断面における結晶粒の板厚方向の粒径を［ｒt］とし、前記結晶粒の前記圧延方向の粒径を［ｒl］とするとき、［ｒt］の平均値が１００μｍ以下であると共に、前記［ｒl］と前記［ｒt］との比［ｒl］／［ｒt］の平均値が２以上であり、プレス成形時にネッキング及び割れが発生せず、人工時効処理により耐力が２３０ＭＰａ以上としたものであることを特徴とする。
【００１３】
本願発明に係る圧壊性に優れたアルミニウム合金部材の製造方法は、Ｓｉ：０．４乃至０．８質量％、Ｍｇ：０．４乃至０．８質量％、Ｆｅ：０．３質量％以下、Ｍｎ：０．３質量％以下を含有し、残部が不可避的不純物及びＡｌからなる組成を有するＡｌ合金を溶解鋳造後、均質化処理し、更に熱間圧延し、溶体化処理して、冷間圧延することなく、圧延方向と平行な板厚方向断面における結晶粒の板厚方向の粒径を［ｒt］とし、前記結晶粒の前記圧延方向の粒径を［ｒl］とするとき、［ｒt］の平均値が１００μｍ以下であると共に、前記［ｒl］と前記［ｒt］との比［ｒl］／［ｒt］の平均値が２以上であるアルミニウム合金板を得、このアルミニウム合金板を所定の形状にプレス成形した後、人工時効処理を施すことによって耐力が２３０ＭＰａ以上である部材を製造することを特徴とする。
【００１５】
本発明においては、アルミニウム合金の組成及び結晶粒の形態を適切に制御することにより、前述の本発明の課題を解決したものである。
【００１６】
【発明の実施の形態】
以下、本発明について詳細に説明する。本発明においては、特許請求の範囲の組成と結晶粒の形態を有するアルミニウム合金板を、自動車用骨格部材のような所定の形状にプレス成形し、その後、人工時効処理して耐力が２３０ＭＰａ以上である部材を製造する。これにより、プレス成形時は耐力が低くて成形しやすく、プレス成形後に人工時効処理を施して耐力を向上させることにより所定の強度を得ることができる。また、本発明においては、結晶粒の形態はプレス成形が人工時効処理前ではなく、その後に所定の範囲に入ればよい。
【００１７】
以下、上述の本発明の圧壊性に優れたアルミニウム合金板の組成及び結晶粒形態の限定理由並びに本発明の圧壊性に優れたアルミニウム合金部材の製造方法における数値限定理由について詳細に説明する。
【００１８】
Ｓｉ：０．４乃至０．８質量％
Ｓｉは時効処理時にＭｇと共に、Ｍｇ2Ｓｉ等の化合物相を形成し、この化合物相が析出して強度を高める。しかし、Ｍｇ2Ｓｉ等の化合物相及びＳｉ相は鋳造時及び溶体化焼入れ処理時に、粗大な粒子として晶出又は析出して微小な破壊の起点として働くため、圧壊性を大きく低下させる。
【００１９】
また、この晶出及び析出状態はＳｉの含有量に依存する。Ｓｉの含有量が０．４質量％未満では十分な強度を得ることができない。一方、Ｓｉの含有量が０．８質量％を超えると、鋳造時及び焼入れ処理時に粗大粒子として晶出又は析出し、圧壊性が著しく低下する。従って、Ｓｉの含有量は０．４乃至０．８質量％とする。
【００２０】
Ｍｇ：０．４乃至０．８質量％
Ｍｇは時効処理時にＳｉと共に、Ｍｇ2Ｓｉ等の化合物相を形成し、この化合物相が析出して強度を高める。しかし、Ｍｇ2Ｓｉ等の化合物相は鋳造時及び溶体化焼入れ処理時に、粗大な粒子として晶出又は析出して微小な破壊の起点として働くため、圧壊性を大きく低下させる。
【００２１】
また、この晶出状態又は析出状態はＭｇの含有量に依存する。Ｍｇの含有量が０．４質量％未満では、十分な強度を得ることができない。一方、Ｍｇの含有量が０．８質量％を超えると、鋳造時及び焼入れ処理時に粗大粒として晶出又は析出し、圧壊性が著しく低下する。従って、Ｍｇの含有量は０．４乃至０．８質量％とする。
【００２２】
Ｆｅ：０．３質量％以下、Ｍｎ：０．３質量％以下
Ｆｅ及びＭｎは均質化熱処理時に分散粒子を形成し、結晶粒を微細且つ伸長粒化させ、これにより圧壊性の向上に寄与する。しかし、Ｆｅ及びＭｎが過剰に添加されると粗大な化合物相を形成し、この化合物相が微小な破壊の起点として働くため、成形性を低下させると共に、圧壊性も低下させる。従って、Ｆｅの含有量を０．３質量％以下とし、Ｍｎの含有量を０．３質量％以下とする。
【００２３】
圧延方向と平行な板厚方向断面における結晶粒の板厚方向の粒径を［ｒ t ］とし、結晶粒の圧延方向の粒径を［ｒ l ］とするとき、［ｒ t ］の平均値が１００μｍ以下
図１は本発明の結晶粒組織の位置を示す模式図である。図１に示すように、アルミニウム合金板１の圧延方向Ｌと平行な板厚方向断面をＡとする。この断面Ａにおいて、１つの結晶粒ｇの板厚方向ｔにおける結晶粒径を［ｒt］とし、圧延方向Ｌにおける結晶粒径を［ｒl］とする。ＪＩＳ ６０００系アルミニウム合金（Ａｌ−Ｍｇ−Ｓｉ系合金）においては、人工時効処理を加えた場合に、結晶粒界に粗大に析出した粒界析出物及び結晶粒界に沿って形成された無析出物帯（以下、ＰＦＺ：Precipitation Free Zoneという）が微小な破壊の起点及び破壊の伝播を助長する点として働くため、粒界に沿って破壊が進展しやすい。従って、これらの粒界析出及びＰＦＺの状態と共に、結晶粒形態も圧壊性に大きく影響する。即ち、板厚方向ｔにおける結晶粒径［ｒt］が１００μｍを超える粗大な結晶粒が存在する場合には、この粒界に沿って板厚方向ｔに破壊が進展しやすくなり、圧壊性が低下する。従って、圧延方向と平行な板厚方向断面における［ｒt］の平均値は１００μｍ以下とする。
【００２４】
［ｒ l ］／［ｒ t ］の平均値：２以上
圧延方向と平行な方向の断面における［ｒl］／［ｒt］の平均値は大きい方が望ましい。しかし、［ｒl］／［ｒt］の平均値が２以上であれば良好な圧壊性を具備させることができる。従って、［ｒl］／［ｒt］の平均値を２以上とする。なお、本発明の結晶粒組織は、圧延及び溶体化処理後に生じたものであり、押出し材で生じるような繊維状組織とは異なる。
【００２５】
人工時効処理後の耐力が２３０ＭＰａ以上
形状が複雑な部材を成形するためには、プレス成形する前において耐力が低い方が好ましい。一方、自動車骨格部材等として使用する部材としては、所定の強度が必要なため、プレス成形後に人工時効処理を施し、耐力を２３０ＭＰａ以上とする。
【００２６】
なお、人工時効処理の条件は結晶粒径及び耐力が本発明の範囲を満たすような条件であれば、特に、制限されるものではなく、当業者が適宜選択することができ、１８０℃乃至２３０℃の温度範囲で１乃至１０時間処理することが好ましい。
【００２７】
【実施例】
以下、本発明の圧壊性に優れたアルミニウム合金板及び本発明方法により製造した圧壊性に優れたアルミニウム合金部材の実施例について、その特性を比較例と比較して具体的に説明する。
【００２８】
先ず、下記表１に示す化学組成を有するアルミニウム合金を溶解鋳造した後、５４０℃の温度で４時間の条件で均質化処理を施し、そのまま引き続いて終了温度が２６０℃乃至３２０℃で、圧延上がりの板厚が２．５ｍｍとなるように熱間圧延を行ない、更に、１００℃／分以上の加熱速度で加熱し、５２０乃至５５０℃の温度で４秒以内保持した後、１００℃／分以上の冷却速度で常温まで冷却し溶体化焼入れした。なお、本発明の結晶粒の形態とするためには、熱間圧延の条件（熱間加工の加工率又は終了温度等）を適宜選択すればよく、例えば熱間圧延の圧延率が９５％を超える場合には、熱間圧延終了温度を２６０乃至３５０℃とすればよい。また、比較例No.１０及び１１は熱間圧延した後、上述の溶体化焼入れ処理を施し、更に、熱処理し、圧延率５０％の冷間圧延を施し、厚さが２．５ｍｍのアルミニウム合金板とした。比較例No.１４は熱間圧延終了温度を３８０℃として圧延を行なった。比較例No.１５は５００℃未満の温度で均質化処理を行なった。
【００２９】
このアルミニウム合金板について、結晶組織を観察し、圧壊性及び耐力を調べた。更に、自動車骨格部材として通常要求される溶接性について調べた。
【００３０】
結晶粒組織は、図１に示すように、製造したアルミニウム合金板１の圧延方向Ｌと平行な板厚方向断面Ａに電解エッチングを施した後、光学顕微鏡を使用して、５０倍の倍率で板厚×０．１ｍｍの範囲を１０視野観察し、この断面Ａの板厚方向ｔにおける［ｒt］の平均値を測定した。更に、この断面Ａの圧延方向Ｌにおける結晶粒径と板厚方向ｔにおける結晶粒径との比［ｒl］／［ｒt］の平均値を測定した。このアルミニウム合金板の結晶粒径［ｒt］及び結晶粒径比［ｒl］／［ｒt］を表２に示す。
【００３１】
プレス成形性については、直径が２２０ｍｍの上述の人工時効処理を施す前のアルミニウム合金板（ブランク）を使用し、直径が１００ｍｍでパンチ角半径が１０ｍｍの円筒ポンチにより絞り高さを２２ｍｍとして成形試験を行い、プレス成形性を評価した。プレス成形性の評価については、成形可能であったものを○、ネッキング又は割れが発生したものを×とした。
【００３２】
圧壊性とは、自動車の衝突等の衝撃的な荷重が加わったときに、部材に割れが生じることなく変形する特性であり、圧壊性が良好な部材は割れが生じることなく蛇腹状に変形することである。即ち、部材がほぼ１８０°に折りたたんだような形態に変形することである。従って、静的な１８０°曲げ試験により圧壊性の評価が可能である。
【００３３】
本実施例では、曲げ半径が２ｍｍの１８０°曲げ試験を行ない、圧壊性を評価した。圧壊性の評価については、割れが生じなかったものを○とし、破断したものを×とした。
【００３４】
耐力については、ＪＩＳ Ｚ２２４１に基づいて引張試験を行い、０．２％耐力を求め、これを耐力とした。なお、圧壊性の評価及び引張試験を行う前に試験片に１９０℃の温度で２時間の条件で熱処理を施した。
【００３５】
溶接性については、各供試材毎に溶接電流が１８０Ａ、溶接電圧が２３Ｖ、溶接速度が８５ｃｍ／分の条件で突き合わせ溶接を行ない、その後溶接部断面の光学顕微鏡観察を行ないミクロ割れの有無を調べ、これを評価した。溶接性の評価については、ミクロ割れのない良好な継手が得られたものを○とし、ミクロ割れが発生したものを×とした。これらの結果を表３に示す。
【００３６】
【表１】
【表２】
【表３】
上記表３に示すように、本発明の範囲にある実施例No.１乃至５は、成形試験、１８０°曲げ試験、０．２％耐力及び溶接性がいずれも良好な結果であり、優れたプレス成形性、圧壊性、強度及び溶接性を得ることができた。
【００４０】
一方、比較例No.６はＳｉの含有量が本発明の上限値を超えているため、１８０°曲げ試験で割れが生じ、圧壊性が劣った。また、溶接性が劣った。
【００４１】
比較例No.７はＳｉの含有量が本発明の下限値未満であるため、０．２％耐力が低く強度が不十分であった。また、［ｒt］の平均値が本発明の上限値を超えているため、１８０°曲げ試験で割れが生じ、圧壊性が劣った。更に、［ｒl］／［ｒt］の平均値が本発明の下限値未満であるため、圧壊性が劣った。更にまた、溶接性が劣った。
【００４２】
比較例No.８はＭｇの含有量が本発明の下限値未満であるため、０．２％耐力が低く強度が不十分であった。また、プレス成形性も劣った。
【００４３】
比較例No.９はＭｎの含有量が本発明の上限値を超えているため、プレス成形性が劣った。
【００４４】
比較例No.１０はアルミニウム合金板の組成及び［ｒt］の平均値は本発明の範囲内にあるが、［ｒl］／［ｒt］の平均値が本発明の下限値未満であるため、１８０°曲げ試験で割れが生じ、圧壊性が劣った。
【００４５】
比較例No.１１はアルミニウム合金板の組成及び［ｒt］の平均値は本発明の範囲内にあるが、［ｒl］／［ｒt］の平均値が本発明の下限値未満であるため、１８０°曲げ試験で割れが生じ、圧壊性が劣った。
【００４６】
比較例No.１２はＭｇの含有量が本発明の上限値を超えているので、１８０°曲げ試験で割れが生じ、圧壊性が劣った。また、プレス成形性も劣った。
【００４７】
比較例No.１３はＦｅの含有量が本発明の上限値を超えているので、１８０°曲げ試験で割れが生じ、圧壊性が劣った。また、０．２％耐力が低く強度が不十分であり、プレス成形性も劣った。
【００４８】
比較例No.１４は［ｒt］の平均値が本発明の上限値を超え、［ｒl］／［ｒt］の平均値が本発明の下限値未満であるため、１８０°曲げ試験で割れが生じ、圧壊性が劣った。
【００４９】
比較例No.１５は０．２％耐力が低く強度が不十分であり、プレス成形性が劣った。
【００５０】
【発明の効果】
以上詳述したように本発明においては、合金組成及び結晶粒の形態を適正に制御することにより、自動車骨格部材に好適な優れたプレス成形性及び強度を有し、特に、圧壊性が優れたアルミニウム合金板を得ることができる。また、このアルミニウム合金板を使用することにより、従来にない高い強度を有し、圧壊性が優れた自動車骨格部材を得ることができる。
【図面の簡単な説明】
【図１】本発明の結晶粒組織の位置を示す模式図である。
【符号の説明】
１；アルミニウム合金板
Ａ；断面
Ｌ；圧延方向
ｇ；結晶粒
ｔ；板厚方向[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an aluminum alloy member having excellent crushability used for automobile side members and the like, and a method for producing a member using the same, and in particular, it has excellent formability and high strength, and an impact is applied by a collision or the like. about excellent aluminum alloy member and a manufacturing method thereof deformable crush resistance without breaking when.
[0002]
[Prior art]
Recently, the use of aluminum alloy materials instead of steel materials is being studied for automobile frame members and outer panel materials due to demands for weight reduction.
[0003]
Among aluminum alloy materials, a relatively good JIS 6000 series aluminum alloy has attracted attention in terms of both corrosion resistance and formability, and a frame structure using an extruded mold material of this 6000 series aluminum alloy has been studied. Further, a plate material made of a 6000 series aluminum alloy is being adopted for an outer panel of an automobile.
[0004]
However, due to the diversification of the appearance of automobiles and the demand for an increase in living space, members have to be arranged in the restricted space of automobiles. On the other hand, standards for safety are becoming stricter, and members are also required to have improved crushability so as to absorb impacts at the time of collision.
[0005]
Therefore, it has become necessary to arrange a member having high crushability in a narrow space, and an automotive member that can be processed into a complicated shape, has high strength, and is excellent in crushability. is needed.
[0006]
As a 6000 series aluminum alloy material used as a member for automobiles, for example, an aluminum alloy plate material used as a panel material for automobiles is disclosed in Japanese Patent Application Laid-Open No. 62-278245. Also, extruded materials used for automobile frames are disclosed in Japanese Patent Application Laid-Open Nos. 6-25783 and 9-256096.
[0007]
Japanese Patent Laid-Open No. 9-263869 discloses an aluminum alloy plate in which the solidification rate of an aluminum alloy containing Mg and Si is controlled to control the shape of a crystallized product and the impact resistance is improved.
[0008]
[Problems to be solved by the invention]
However, although the extruded materials disclosed in the above-mentioned JP-A-6-25783 and JP-A-9-256096 are excellent in impact absorption, the extruded material has a shape restriction, and after being extruded, There is a problem that it is difficult to process a member having a complicated shape.
[0009]
On the other hand, an automobile member formed by using an aluminum alloy plate material used for a panel material disclosed in Japanese Patent Laid-Open No. 62-278245 has a problem that the crushability is not sufficient. Thus, no suitable aluminum alloy material has existed as an automobile member.
[0010]
Moreover, the aluminum alloy plate disclosed in JP-A-9-263869 is subjected to cold working after hot rolling, and crystal grains are equiaxed grains. Accordingly, the load applied to the aluminum alloy plate at the time of impact cannot be well dispersed, and there is a problem that sufficient crushability cannot be obtained.
[0011]
The present invention has been made in view of such problems, and can be processed into a complicated shape, has excellent crushability, has high strength, and has excellent crushability and uses the same. An object of the present invention is to provide a method for manufacturing the member.
[0012]
[Means for Solving the Problems]
Aluminum alloy member which is excellent in crush resistance of this gun onset Ming, Si: 0.4 to 0.8 mass%, Mg: 0.4 to 0.8 wt%, Fe: 0.3 wt% or less, Mn : 0.3 mass% or less, the balance being a composition composed of inevitable impurities and Al, and a solution-treated aluminum alloy member , the crystal grains in the plate thickness direction cross section parallel to the rolling direction When the grain size in the plate thickness direction is [r t ] and the grain size in the rolling direction of the crystal grains is [r l ], the average value of [r t ] is 100 μm or less, and the [r l] ] and has a the [r t] the ratio of the [r l] / [average value of r t] is 2 or more, necking and cracks are not generated at the time of press molding, which strength is not less than 230MPa by artificial aging It is characterized by being.
[0013]
Method of manufacturing an aluminum alloy member which is excellent in crush resistance of this gun onset Ming, Si: 0.4 to 0.8 mass%, Mg: 0.4 to 0.8 wt%, Fe: 0.3 wt% hereinafter, Mn: containing 0.3 wt% or less, after the melting and casting an Al alloy have a composition the balance being inevitable impurities and Al, and homogenized, further hot rolling, and solution treatment Without cold rolling, the grain size in the thickness direction of the crystal grains in the cross section in the thickness direction parallel to the rolling direction is [r t ], and the grain size in the rolling direction of the crystal grains is [r l ] to time, the average value of [r t] is 100μm or less, the [r l] and the [r t] and the ratio [r l] / der average value of 2 or more [r t] Rua give the aluminum alloy plate, depending after press-molding the aluminum alloy plate into a predetermined shape, an artificial aging treatment facilities Succoth Strength is characterized by producing member is not less than 230 MPa.
[0015]
In the present invention, the above-mentioned problems of the present invention are solved by appropriately controlling the composition of aluminum alloy and the form of crystal grains.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail. In the present invention, an aluminum alloy plate having the composition and crystal grain form of the claims is press-formed into a predetermined shape such as an automobile skeleton member, and then subjected to artificial aging treatment so that the yield strength is 230 MPa or more. A certain member is manufactured. As a result, the yield strength is low during press molding and it is easy to mold, and a predetermined strength can be obtained by performing artificial aging treatment after press molding to improve the yield strength. In the present invention, the form of the crystal grains may be within a predetermined range after the press molding is not before the artificial aging treatment but after that.
[0017]
Hereinafter, the reasons for limiting the composition and crystal grain shape of the aluminum alloy plate having excellent crushability according to the present invention and the reasons for limiting the numerical values in the method for producing an aluminum alloy member having excellent crushability according to the present invention will be described in detail.
[0018]
Si: 0.4 to 0.8 mass%
Si forms a compound phase such as Mg 2 Si together with Mg during aging treatment, and this compound phase precipitates to increase the strength. However, the compound phase such as Mg 2 Si and the Si phase are crystallized or precipitated as coarse particles at the time of casting and solution hardening and quenching, and thus serve as a starting point for minute fractures.
[0019]
The crystallization and precipitation state depends on the Si content. If the Si content is less than 0.4% by mass, sufficient strength cannot be obtained. On the other hand, when the Si content exceeds 0.8% by mass, crystallization or precipitation occurs as coarse particles during casting and quenching, and the crushability is significantly reduced. Accordingly, the Si content is set to 0.4 to 0.8 mass%.
[0020]
Mg: 0.4 to 0.8 mass%
Mg forms a compound phase such as Mg 2 Si together with Si during aging treatment, and this compound phase precipitates to increase the strength. However, a compound phase such as Mg 2 Si crystallizes or precipitates as coarse particles during casting and solution hardening and serves as a starting point for minute fractures, so that the crushability is greatly reduced.
[0021]
Further, the crystallization state or precipitation state depends on the content of Mg. If the Mg content is less than 0.4% by mass, sufficient strength cannot be obtained. On the other hand, if the Mg content exceeds 0.8% by mass, the crystals crystallize or precipitate as coarse particles during casting and quenching, and the crushability is significantly reduced. Therefore, the Mg content is set to 0.4 to 0.8 mass%.
[0022]
Fe: 0.3% by mass or less, Mn: 0.3% by mass or less Fe and Mn form dispersed particles during the homogenization heat treatment to make crystal grains fine and elongated, thereby contributing to the improvement of the crushability. . However, when Fe and Mn are added excessively, a coarse compound phase is formed, and this compound phase acts as a starting point of minute fracture, so that the moldability is lowered and the crushability is also lowered. Therefore, the Fe content is set to 0.3% by mass or less, and the Mn content is set to 0.3% by mass or less.
[0023]
The average value of [r t ] when the grain size in the plate thickness direction of the cross section in the plate thickness direction parallel to the rolling direction is [r t ] and the grain size in the rolling direction of the crystal grains is [r l ]. Is 100 μm or less . FIG. 1 is a schematic diagram showing the position of the grain structure of the present invention. As shown in FIG. 1, let A be a cross section in the plate thickness direction parallel to the rolling direction L of the aluminum alloy plate 1. In the cross section A, the crystal grain size in the plate thickness direction t of one crystal grain g is [r t ], and the crystal grain size in the rolling direction L is [r l ]. In JIS 6000 series aluminum alloy (Al-Mg-Si series alloy), when artificial aging treatment is applied, grain boundary precipitates coarsely precipitated at the grain boundaries and non-precipitation formed along the grain boundaries Since a material zone (hereinafter referred to as PFZ: Precipitation Free Zone) serves as a starting point for minute fractures and a point for promoting propagation of fractures, fractures easily progress along grain boundaries. Therefore, together with the grain boundary precipitation and the state of PFZ, the crystal grain shape greatly affects the crushability. That is, when there are coarse crystal grains having a crystal grain size [r t ] in the plate thickness direction t exceeding 100 μm, the breakage tends to progress along the grain boundary in the plate thickness direction t, and the crushability is improved. descend. Therefore, the average value of [r t ] in the cross section in the thickness direction parallel to the rolling direction is 100 μm or less.
[0024]
Average value of [r 1 ] / [r t ]: 2 or more It is desirable that the average value of [r 1 ] / [r t ] is larger in the cross section in the direction parallel to the rolling direction. However, if the average value of [r 1 ] / [r t ] is 2 or more, good crushability can be achieved. Therefore, the average value of [r 1 ] / [r t ] is set to 2 or more. The crystal grain structure of the present invention is generated after rolling and solution treatment, and is different from a fibrous structure generated in an extruded material.
[0025]
The yield strength after the artificial aging treatment is 230 MPa or more. In order to mold a member having a complicated shape, it is preferable that the yield strength is low before press molding. On the other hand, a member used as an automobile skeleton member or the like needs a predetermined strength, and therefore is subjected to an artificial aging treatment after press molding to have a yield strength of 230 MPa or more.
[0026]
The conditions for the artificial aging treatment are not particularly limited as long as the crystal grain size and the proof stress satisfy the scope of the present invention, and can be appropriately selected by those skilled in the art. It is preferable to perform the treatment for 1 to 10 hours in a temperature range of ° C.
[0027]
【Example】
Hereinafter, the characteristics of the aluminum alloy plate excellent in the crushability of the present invention and the aluminum alloy member excellent in the crushability manufactured by the method of the present invention will be specifically described in comparison with the comparative examples.
[0028]
First, after melting and casting an aluminum alloy having the chemical composition shown in Table 1 below, a homogenization treatment was performed at a temperature of 540 ° C. for 4 hours, followed by rolling at a finish temperature of 260 ° C. to 320 ° C. The steel sheet is hot-rolled to a thickness of 2.5 mm, further heated at a heating rate of 100 ° C./min or more and held at a temperature of 520 to 550 ° C. within 4 seconds, and then 100 ° C./min or more. The solution was cooled to room temperature at a cooling rate of 5 and then solution-quenched and quenched. In order to obtain the form of the crystal grains of the present invention, the hot rolling conditions (such as the hot working rate or end temperature) may be appropriately selected. For example, the hot rolling rolling rate is 95%. In the case of exceeding, the hot rolling end temperature may be 260 to 350 ° C. Comparative Examples No. 10 and 11 were hot-rolled, then subjected to the above-mentioned solution hardening treatment, further heat-treated , cold-rolled at a rolling rate of 50%, and an aluminum alloy having a thickness of 2.5 mm. A board was used. Comparative Example No. 14 was rolled at a hot rolling end temperature of 380 ° C. Comparative Example No. 15 was homogenized at a temperature of less than 500 ° C.
[0029]
About this aluminum alloy plate, the crystal structure was observed and the crushability and yield strength were investigated. Furthermore, the weldability normally required for automobile frame members was investigated.
[0030]
As shown in FIG. 1, the crystal grain structure was subjected to electrolytic etching on the plate thickness direction cross section A parallel to the rolling direction L of the manufactured aluminum alloy plate 1 and then at a magnification of 50 times using an optical microscope. the range of thickness × 0.1 mm and 10 field observation to measure the mean value of [r t] in the thickness direction t of the cross-section a. Furthermore, the average value of the ratio [r 1 ] / [r t ] of the crystal grain size in the rolling direction L and the crystal grain size in the sheet thickness direction t of the cross section A was measured. Table 2 shows the crystal grain size [r t ] and the crystal grain size ratio [r l ] / [r t ] of this aluminum alloy plate .
[0031]
For press formability, the aluminum alloy plate (blank) before the artificial aging treatment with a diameter of 220 mm was used, and a draw height was set to 22 mm with a cylindrical punch having a diameter of 100 mm and a punch angle radius of 10 mm. The press formability was evaluated. Regarding the evaluation of press formability, the case where molding was possible was marked with ◯, and the case where necking or cracking occurred was marked with x.
[0032]
Crushability is a property that deforms without cracking when a shocking load such as an automobile collision is applied. A member with good crushability deforms into a bellows without cracking. That is. That is, the member is deformed into a shape that is folded at approximately 180 °. Therefore, the crushability can be evaluated by a static 180 ° bending test.
[0033]
In this example, a 180 ° bending test with a bending radius of 2 mm was performed to evaluate the crushability. For the evaluation of the crushability, the case where no crack was generated was marked with ◯, and the broken piece was marked with x.
[0034]
As for the proof stress, a tensile test was performed based on JIS Z2241, and a 0.2% proof stress was obtained, which was defined as the proof stress. In addition, before performing crushability evaluation and a tensile test, the test piece was heat-processed on the conditions for 2 hours at the temperature of 190 degreeC.
[0035]
For weldability, butt welding was performed for each specimen under the conditions of a welding current of 180 A, a welding voltage of 23 V, and a welding speed of 85 cm / min, and then the presence of microcracks was observed by optical microscope observation of the welded section. Investigated and evaluated this. For the evaluation of weldability, the case where a good joint without microcracking was obtained was rated as ◯, and the case where microcracking occurred was marked as x. These results are shown in Table 3.
[0036]
[Table 1]
[Table 2]
[Table 3]
As shown in Table 3 above, Examples Nos. 1 to 5 within the scope of the present invention are excellent results in the molding test, 180 ° bending test, 0.2% proof stress and weldability. It was possible to obtain press formability, crushability, strength and weldability.
[0040]
On the other hand, in Comparative Example No. 6, since the Si content exceeded the upper limit of the present invention, cracking occurred in the 180 ° bending test and the crushability was inferior. Moreover, the weldability was inferior.
[0041]
In Comparative Example No. 7, the Si content was less than the lower limit of the present invention, so the 0.2% proof stress was low and the strength was insufficient. Further, since the average value of [r t] exceeds the upper limit of the present invention, cracking at 180 ° bending test occurred, was poor crush resistance. Furthermore, since the average value of [r 1 ] / [r t ] is less than the lower limit of the present invention, the crushability is inferior. Furthermore, the weldability was inferior.
[0042]
In Comparative Example No. 8, the Mg content was less than the lower limit of the present invention, so the 0.2% yield strength was low and the strength was insufficient. Moreover, the press formability was also inferior.
[0043]
Comparative Example No. 9 was inferior in press formability because the Mn content exceeded the upper limit of the present invention.
[0044]
In Comparative Example No. 10, the composition of the aluminum alloy plate and the average value of [r t ] are within the range of the present invention, but the average value of [r l ] / [r t ] is less than the lower limit value of the present invention. Therefore, cracking occurred in the 180 ° bending test, and the crushability was inferior.
[0045]
In Comparative Example No. 11, the composition of the aluminum alloy plate and the average value of [r t ] are within the range of the present invention, but the average value of [r l ] / [r t ] is less than the lower limit value of the present invention. Therefore, cracking occurred in the 180 ° bending test, and the crushability was inferior.
[0046]
In Comparative Example No. 12, since the Mg content exceeded the upper limit of the present invention, cracking occurred in the 180 ° bending test, and the crushability was poor. Moreover, the press formability was also inferior.
[0047]
In Comparative Example No. 13, since the Fe content exceeded the upper limit of the present invention, cracking occurred in the 180 ° bending test, and the crushability was poor. Further, the 0.2% proof stress was low and the strength was insufficient, and the press formability was also inferior.
[0048]
In Comparative Example No. 14, the average value of [r t ] exceeds the upper limit value of the present invention, and the average value of [r l ] / [r t ] is less than the lower limit value of the present invention. Cracking occurred and the crushability was poor.
[0049]
Comparative Example No. 15 had a low 0.2% yield strength and insufficient strength, and was inferior in press formability.
[0050]
【The invention's effect】
As described above in detail, in the present invention, by appropriately controlling the alloy composition and the form of crystal grains, it has excellent press formability and strength suitable for automobile frame members, and in particular, excellent crushability. An aluminum alloy plate can be obtained. Further, by using this aluminum alloy plate, an automobile skeleton member having unprecedented high strength and excellent crushability can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the position of a crystal grain structure of the present invention.
[Explanation of symbols]
1; Aluminum alloy plate A; Section L; Rolling direction g; Crystal grain t; Plate thickness direction
Claims (2)
Priority Applications (1)
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| JP2000110884A JP4274674B2 (en) | 2000-04-12 | 2000-04-12 | Aluminum alloy member excellent in crushability and manufacturing method thereof |
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| JP2000110884A JP4274674B2 (en) | 2000-04-12 | 2000-04-12 | Aluminum alloy member excellent in crushability and manufacturing method thereof |
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| JP2002275567A (en) * | 2001-03-19 | 2002-09-25 | Asahi Tec Corp | PRECIPITATION-HARDENING Al ALLOY, AND METHOD OF HEAT TREATMENT FOR PRECIPITATION-HARDENING ALLOY |
| CA2971618C (en) | 2015-01-12 | 2020-08-25 | Novelis Inc. | Highly formable automotive aluminum sheet with reduced or no surface roping and a method of preparation |
| JP6810508B2 (en) * | 2015-05-28 | 2021-01-06 | 株式会社神戸製鋼所 | High-strength aluminum alloy plate |
| JP2017125240A (en) * | 2016-01-14 | 2017-07-20 | 株式会社神戸製鋼所 | Aluminum alloy structural member, manufacturing method thereof, and aluminum alloy sheet |
| CN109072355A (en) * | 2016-07-13 | 2018-12-21 | 古河电气工业株式会社 | Aluminum alloy materials and use its conductive member, battery component, fastenings, spring part and structure part |
| JP7244407B2 (en) | 2019-12-13 | 2023-03-22 | 株式会社神戸製鋼所 | Aluminum alloy sheet for automobile structural member, automobile structural member, and method for producing aluminum alloy plate for automobile structural member |
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| JP2614686B2 (en) * | 1992-06-30 | 1997-05-28 | 住友軽金属工業株式会社 | Manufacturing method of aluminum alloy for forming process excellent in shape freezing property and paint bake hardenability |
| JP2823797B2 (en) * | 1994-02-16 | 1998-11-11 | 住友軽金属工業株式会社 | Manufacturing method of aluminum alloy sheet for forming |
| JPH083702A (en) * | 1994-06-17 | 1996-01-09 | Furukawa Electric Co Ltd:The | Production of aluminum alloy sheet material excellent in formability and heating hardenability |
| JP3253244B2 (en) * | 1996-03-15 | 2002-02-04 | 株式会社神戸製鋼所 | Extruded Al-Mg-Si aluminum alloy material for shock absorbing members with excellent axial crushing performance. |
| JP3734317B2 (en) * | 1996-10-09 | 2006-01-11 | 古河スカイ株式会社 | Method for producing Al-Mg-Si alloy plate |
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