JP3886270B2

JP3886270B2 - High corrosion resistance aluminum alloy with excellent machinability

Info

Publication number: JP3886270B2
Application number: JP33137198A
Authority: JP
Inventors: 伸二吉原; 正和平野; 宏岩村
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 1995-03-30
Filing date: 1998-11-20
Publication date: 2007-02-28
Anticipated expiration: 2016-03-29
Also published as: JP3107517B2; JPH11217647A; JPH09249931A

Description

【０００１】
【発明の属する技術分野】
本発明は、製造の過程で切削加工を多用する機械部品等に適する切削性に優れた高耐食アルミニウム合金押出材に関する。
【０００２】
【従来の技術】
アルミニウム合金のうち特に３０００系のＡｌ−Ｍｎ系合金を中心とした非熱処理型合金は、中程度の機械的性質を持ち耐食性と冷間鍛造性に優れ、低コストで成形が可能なため、機械部品などへの使用実績が多く、その際、一般に冷間鍛造した後切削加工や穴あけ加工を施して製品化されている。しかし、この系の合金は、切削時に発生する切粉が分断され難く切削性に劣るため、複雑な切削や穴あけ加工を必要とする機械部品への採用は困難であった。
【０００３】
また、アルミニウム合金のうち５０００系のＡｌ−Ｍｇ系合金を中心とした非熱処理型合金は、中程度の機械的性質（３０００系より強度レベルがやや高い）を持ち耐食性と冷間加工性に優れ、低コストで加工が可能なため、カメラや顕微鏡の筒材のような光学機器その他の機械部品などへの使用実績が多く、その際、一般に冷間鍛造した後切削加工や穴あけ加工を施して製品化されている。しかし、この系の合金は、切削時に発生する切粉が分断され難く切削性に劣り、複雑な切削や穴あけ加工を必要とする機械部品への採用は困難であった。
【０００４】
一方、従来の高切削性アルミニウム合金は、展伸材の分野ではＡＡ６２６２合金（Ｓｉ：０．４〜０．８質量％、Ｍｇ：０．８〜１．２質量％、Ｃｕ：０．１５〜０．４質量％、Ｐｂ：０．４〜０．７質量％、Ｂｉ：０．４〜０．７質量％、残部Ａｌ）に代表されるように、有効添加元素としてＰｂ、Ｂｉ、Ｓｎ等の低融点金属を含有する（特開昭５４−１４３７１４号公報、特開平３−３９４４２号公報参照）。これら低融点金属はアルミニウム中にほとんど固溶せず、アルミニウム合金中に粒状にミクロ偏析し、その低融点金属粒子が切削加工時の加工発熱により溶融して切粉を分断し、アルミニウム合金の切削性を向上させる。
【０００５】
なお、上記ＡＡ６２６２合金は、製造の過程で切削加工、特にドリル加工が多用される機械部品、例えば自動車のアンチスキッド・ブレーキ・システムのハウジングの素材として従来より使用されている熱処理型アルミニウム合金であるが、このようなＰｂ、Ｂｉ、Ｓｎ等の低融点金属の添加による切削性向上効果は、上記熱処理型合金に限らず非熱処理型合金においても等しく得られることが予想される（例えば上記特開平３−３９４４２号公報参照）。
【０００６】
【発明が解決しようとする課題】
ところが、これらの低融点金属が添加されたアルミニウム合金は切削性が向上する反面耐食性が低下し、また、低融点金属は熱脆性を引き起こす欠点もあり、使用環境に十分な注意を払う必要があった。さらに、合金をスクラップとしてリサイクルする場合、Ｐｂ、Ｂｉ等を必要とする比較的少ない合金種にしか転用ができず、転用範囲が狭まるためにリサイクル性に不利であるという問題を有する。
【０００７】
また、機械部品は耐食性、耐摩耗性又は装飾効果を高めるために、表面にアルマイト処理を施す場合があるが、ＰｂやＢｉが添加されたアルミニウム合金の場合、表面にＰｂやＢｉが露出した箇所において酸化皮膜が形成されず、不均質で光沢のないアルマイト皮膜しか得られないという問題がある。
【０００８】
このような低融点金属を含有せずに切削性を高めた非熱処理型アルミニウム合金は、特開昭６０−１８４６５８号公報に提案されてはいるが、Ｐｂ、Ｂｉ、Ｓｎ等の低融点金属を含有したアルミニウム合金に比べて切削性が十分でなかった。
【０００９】
本発明は上記従来技術の問題点に鑑みてなされたもので、包括的にいえば、切削性と耐食性の双方に優れるアルミニウム合金押出材を得ること、また、リサイクル性を備え、均質なアルマイト皮膜を形成することのできる切削性に優れたアルミニウム合金押出材を得ることを目的とする。個別具体的にいえば、従来の３０００系あるいは５０００系非熱処理型アルミニウム合金と同程度の機械的性質、冷間鍛造性、耐食性、及びリサイクル性を備えるとともに、切削性が改善された非熱処理型アルミニウム合金押出材を得ること、従来のＡＡ６２６２合金と同等以上の切削性を備え、より改善された耐食性を有する熱処理型アルミニウム合金押出材を得ること、を目的とする。
【００１０】
【課題を解決するための手段】
本発明者らは、前記課題を解決するため鋭意研究を重ねた結果、従来切削性を向上させる目的で添加されていたＰｂ、Ｂｉ、Ｓｎなどの低融点金属を添加せず、リサイクル性を阻害しないＳｉ及びＭｇなどを用いることで上記目的を達成できることを見い出し、その知見を基に本発明を完成するに至った。なお、以下に示すように、本願は強度レベルの異なる２系統の非熱処理型アルミニウム合金押出材に関する発明（参考発明）と、熱処理型アルミニウム合金押出材に関する発明（請求項１〜４）を包含する。
【００１１】
［参考発明１］
この発明に関わる切削性に優れる高耐食アルミニウム合金は、Ｓｉ：１．５〜１２．０質量％、Ｍｇ：０．５〜６．０質量％、Ｔｉ：０．０１〜０．１質量％をそれぞれ含有し、残部がＡｌ及び不可避不純物からなる。また、この発明に関わる切削性に優れる高耐食アルミニウム合金は、必要に応じて、上記合金元素に加え、（１）Ｍｎ：０．５〜２．０質量％又はＣｕ：０．１〜１．０質量％のいずれか一方又は双方を含有し、あるいは、（２）Ｆｅ：０．５〜１．０質量％、Ｃｒ：０．１〜０．５質量％、Ｚｒ：０．１〜０．５質量％のうちいずれか１種以上を含有し、あるいは、（３）上記（１）、（２）の双方に挙げた元素を自由に組み合わせて含有する。
【００１２】
上記切削性に優れる高耐食アルミニウム合金は、鍛造性が優れるものの切削性が劣るため多くの機械部品などへの適用ができなかった従来の３００３合金や３００４合金と比較すると、強度、耐食性、及び冷間鍛造性が同等で、切削性が著しく改善された非熱処理型アルミニウム合金であり、低コストの冷間鍛造が可能で、かつ複雑な切削加工が可能となる。そして、切粉の分断性がよく、長い切粉による工具への切粉の巻き付き等のトラブルが発生しない。また、切削性向上のためＰｂ、Ｂｉ等の低融点金属を添加していないので、高耐食であり熱脆性も生じ得ず、リサイクル性も阻害されていない。
なお、このアルミニウム合金は、常法に従って製造することができ、例えば溶解、鋳造、均質化熱処理を施した後押出加工を行い、この押出材を鍛造加工用の素材とすることができる。
【００１３】
次に、上記アルミニウム合金における各元素の添加理由及び添加量の限定理由を説明する。
【００１４】
Ｓｉ：１．５〜１２．０質量％
Ｓｉはアルミニウム組織中にＳｉ系の化合物を形成し切粉の分断性をよくし切削性を向上させる。これはＳｉ系化合物が切粉を分断する起点となるためである。Ｓｉ添加下限値はアルミニウム中での固溶限である１．５％を越えていることが必要であり、Ｓｉによる効果を明確にさせるためには２．０％を越える添加が望ましく、さらに４．０％以上の添加により顕著な効果を得ることができる。従って、優れた切削性を得るとの観点からは、Ｓｉは２．０〜１２．０（２．０を含まず）％、あるいは４．０〜１２．０％とするのがよい。一方、Ｓｉの添加上限は、粗大な初晶Ｓｉが生じ変形抵抗が増加することによる押出性の低下や押出材の脆化を招かないために、共晶点の１２．０％以下とする必要がある。特に押出性が良好な６％以下が望ましい。
【００１５】
Ｍｇ：０．５〜６．０質量％
Ｍｇは歪硬化能を向上させるため切粉分断性を向上させ、また固溶体化して素材の強度を高める効果がある。Ｍｇ含有量が０．５％未満では十分その効果が得られず、６．０％を越えて添加すると変形抵抗が増し押出性が低下する。強度と良好な押出性を確保するとの観点から、概ね１．０％以上、３．０％以下が好ましいが、専ら押出加工時の変形抵抗を抑えて押出性を向上させるとの観点からすれば、１．０％未満、特に０．９％以下とすることで顕著な効果を得ることができる。従って、その場合はＭｇは０．５〜１．０（１．０を含まず）％、あるいは０．５〜０．９％とすればよい。
【００１６】
Ｔｉ：０．０１〜０．１質量％
Ｔｉは鋳造組織を微細化して機械的性質を安定化する。しかし、Ｔｉ含有量が０．０１％未満ではその効果が得られず、一方、０．１％を越えて添加してもその効果は飽和する。
【００１７】
Ｍｎ：０．５〜２．０質量％
Ｍｎは固溶体化して素材の強度を高める効果があり、また、歪硬化能を向上させるため切粉分断を助長する効果を持つ。しかし、Ｍｎ含有量が０．５％未満では十分な効果が得られず、一方、２．０％を越えて添加すると押出性が低下する。特に強度と良好な押出性を確保するとの観点から、０．７％以上、１．５％以下が望まれる。
【００１８】
Ｃｕ：０．１〜１．０質量％
Ｃｕは固溶体化して素材の強度を高めるとともに、歪硬化能を向上させるため切粉分断も助長する効果を持ち、Ｍｎに代えて又はＭｎとともに添加される。しかし、Ｃｕ含有量が０．１％未満ではその効果に乏しく、一方、１．０％を越えて添加すると耐食性が低下し、また押出性も低下する。特に強度と良好な耐食性及び押出性を確保するとの観点から、０．３％以上、０．８％以下が望まれる。
【００１９】
Ｆｅ：０．５〜１．０質量％、
Ｃｒ：０．１〜０．５質量％、
Ｚｒ：０．１〜０．５質量％
Ｆｅ、Ｃｒ、ＺｒはそれぞれＡｌとの化合物を形成し、切粉分断の起点となって切削性を向上させる。本発明においてそれぞれ不可避不純物として下限値未満の含有が許容されるが、下限値未満ではその効果が十分でなく、一方、上限値を越えると粗大な化合物を生成し押出性が低下する。
【００２０】
また、上記アルミニウム合金の不可避不純物としては、ＪＩＳＨ４０４０に規定する化学成分に準じ、Ｐｂ、Ｂｉ、Ｓｎは各々０．０５質量％以下が許容される。これらの低融点金属は多く含まれるとアルミニウム合金の耐食性を劣化させるが、この範囲内であればその特性に影響を与えない。また、他の不可避不純物も個々に０．０５質量％以下が許容される。
【００２１】
［参考発明２］
この発明に関わる切削性に優れる高耐食アルミニウム合金は、Ｓｉ：１．５〜１２．０質量％、Ｍｇ：２．０〜６．０質量％をそれぞれ含有し、残部がＡｌ及び不可避不純物からなる。また、この発明に関わる切削性に優れる高耐食アルミニウム合金は、必要に応じて、上記合金元素に加え、（１）Ｍｎ：０．３〜１．２質量％、Ｔｉ：０．０１〜０．１質量％のいずれか一方又は双方を含有し、あるいは、（２）Ｆｅ：０．５〜１．０質量％、Ｃｒ：０．１〜０．５質量％、Ｚｒ：０．１〜０．５質量％のうちいずれか１種以上を含有し、あるいは、（３）上記（１）、（２）の双方に挙げた元素を自由に組み合わせて含有する。
【００２２】
上記切削性に優れる高耐食アルミニウム合金は、冷間加工性が優れるものの切削性が劣るため多くの機械部品などへの適用ができなかった従来の５０５２合金や５０５６合金と比較すると、強度、耐食性、及び冷間鍛造等の冷間加工性が同等で、切削性が著しく改善された非熱処理型アルミニウム合金であり、複雑な切削加工を可能とする合金である。そして、切粉の分断性がよく、長い切粉による工具への切粉の巻き付き等のトラブルが発生しない。また、切削性向上のためＰｂ、Ｂｉ等の低融点金属を添加していないので、高耐食であり熱脆性も生じ得ず、リサイクル性も阻害されていない。
なお、このアルミニウム合金は、常法に従って製造することができ、例えば溶解、鋳造、均質化熱処理を施した後押出加工を行い、この押出材を切削加工用の素材とすることができる。
【００２３】
次に、上記アルミニウム合金における各元素の添加理由及び添加量の限定理由を説明する。
【００２４】
Ｓｉ：１．５〜１２．０質量％
Ｓｉはアルミニウム組織中にＳｉ系の化合物を形成し切粉の分断性をよくし切削性を向上させる。これはＳｉ系化合物が切削時に発生する切粉を分断する起点となるためである。Ｓｉ添加下限値はアルミニウム中での固溶限である１．５％を越えていることが必要であり、Ｓｉによる効果を明確にさせるためには２．０％を越える添加が望ましく、さらに４．０％以上の添加により顕著な効果を得ることができる。従って、優れた切削性を得るとの観点からは、Ｓｉは２．０〜１２．０（２．０を含まず）％、あるいは４．０〜１２．０％とするのがよい。一方、Ｓｉの添加上限は、粗大な初晶Ｓｉが生じ変形抵抗が増加することによる押出性の低下や押出材の脆化を招かないために、共晶点の１２．０％以下とする必要がある。特に押出性が良好な６％以下が望ましい。
【００２５】
Ｍｇ：２．０〜６．０質量％
Ｍｇは歪硬化能を向上させるため切粉分断性を向上させ、また固溶体化して素材の強度を高める効果がある。Ｍｇ含有量が２．０％未満では十分な効果が得られず、６．０％を越えて添加すると変形抵抗が増し押出性が低下する。特に強度と良好な押出性を確保するとの観点から、２．５％以上、５．５％以下が望まれる。
【００２６】
Ｔｉ：０．０１〜０．１質量％
Ｔｉは鋳造組織を微細化して機械的性質を安定化する。しかし、Ｔｉ含有量が０．０１％未満ではその効果が得られず、一方、０．１％を越えて添加してもその効果は飽和する。
【００２７】
Ｍｎ：０．３〜１．２質量％
Ｍｎは固溶体化して素材の強度を高める効果があり、また、歪硬化能を向上させるため切粉分断を助長する効果を持つ。しかし、Ｍｎ含有量が０．３％未満では十分な効果が得られず、一方、１．２％を越えて添加すると押出性が低下する。特に強度と良好な押出性を確保するとの観点から、０．５％以上、１．０％以下が望まれる。
【００２８】
Ｆｅ：０．５〜１．０質量％、
Ｃｒ：０．１〜０．５質量％、
Ｚｒ：０．１〜０．５質量％
Ｆｅ、Ｃｒ、ＺｒはそれぞれＡｌとの化合物を形成し、切粉分断の起点となって切削性を向上させる。本発明においてそれぞれ不可避不純物として下限値未満の含有が許容されるが、含有量がそれぞれ下限値未満ではその効果が十分でなく、一方、上限値を越えると粗大な化合物を生成し押出性が低下する。
【００２９】
また、上記アルミニウム合金の不可避不純物としては、ＪＩＳＨ４０４０に規定する化学成分に準じ、Ｐｂ、Ｂｉ、Ｓｎは各々０．０５質量％以下が許容される。これらの低融点金属は多く含まれるとアルミニウム合金の耐食性を劣化させるが、この範囲内であればその特性に影響を与えない。また、他の不可避不純物も個々に０．０５質量％以下が許容される。
【００３０】
［請求項１〜４の発明］
この発明に関わる切削性に優れる高耐食アルミニウム合金は、Ｓｉ：１．５〜１２．０質量％、Ｍｇ：０．２〜１．２質量％、Ｃｕ：０．１５〜３．０質量％をそれぞれ含有し、残部がＡｌ及び不可避不純物からなる。また、この発明に関わる切削性に優れる高耐食アルミニウム合金は、必要に応じて、上記合金元素に加え、Ｃｒ：０．０４〜０．３５質量％又はＴｉ：０．００１〜０．０５質量％のいずれか一方又は双方を含有する。
【００３１】
上記切削性に優れる高耐食アルミニウム合金の最大の特徴は、ＡＡ６２６２合金のようにＰｂ、Ｂｉ、Ｓｎ等の低融点金属を添加せずに、切削性を向上させていることである。このアルミニウム合金押出材は、低融点金属を添加していないことからＡＡ６２６２合金に比べ高耐食性であり、さらに、熱脆性も生じ得ず、リサイクル性も高い。そして、切粉の分断性がよく、長い切粉による工具への切粉の巻き付き等のトラブルが発生しない。
なお、上記アルミニウム合金は、常法に従い、例えば、溶解、鋳造、均質化処理を施した後押出加工を行い、この押出材を溶体化、焼入れ、人工時効処理を施し所定の強度を与えた後、切削加工に供することができる。
【００３２】
次に、上記アルミニウム合金における各元素の添加理由及び添加量の限定理由を説明する。
【００３３】
Ｓｉ：１．５〜１２．０質量％
Ｓｉはアルミニウム組織中にＳｉ系の化合物を形成させ、切粉分断をよくし、切削性を向上させる。これはＳｉ相が歪み伝播の起点となり、切削時に工具から受ける歪の伝播速度を速くしているためである。よってＳｉ添加下限値は、アルミニウム中での固溶限である１．５％を越えていることが必要であり、Ｓｉによる効果を明確にさせるためには２．０％を越える添加が望ましく、さらに４．０％以上の添加により顕著な効果を得ることができる。従って、優れた切削性を得るとの観点からは、Ｓｉは２．０〜１２．０（２．０を含まず）％、あるいは４．０〜１２．０％とするのがよい。一方、Ｓｉの添加上限は、粗大な初晶Ｓｉが生じ変形抵抗が増加することによる押出性の低下や押出材の脆化を招かないために、共晶点の１２．０％以下とする必要があり、特に押出生産性が良好な６％以下が望ましい。
【００３４】
Ｍｇ：０．２〜１．２質量％
ＭｇはＳｉとの共存によって熱処理時にＭｇ_２Ｓｉとなって析出し、強度を高める効果がある。Ｍｇ含有量が０．２％未満ではその効果が得られず、一方、１．２％を越えて添加するとＭｇ単体の固溶強化により変形抵抗が増加し押出性が低下する。強度と良好な押出性を確保するとの観点から、概ね０．４％以上、１．０％以下が好ましいが、専ら押出加工時の変形抵抗を抑えて押出性を向上させるとの観点からすれば、１％未満、特に０．９％以下とすることで顕著な効果を得ることができる。従って、その場合はＭｇは０．２〜１．０（１．０を含まず）％、あるいは０．２〜０．９％とすればよい。
【００３５】
Ｃｕ：０．１５〜３．０質量％
Ｃｕは熱処理により強度を高めるとともに、歪み硬化能を向上させるため切粉分断を助長する。Ｃｕ含有量が０．１５％未満ではその効果に乏しく、一方３．０％を越えて添加すると耐食性が低下し、また押出性も低下する。特に強度と良好な耐食性及び押出性を確保するとの観点から、０．２％以上、２．５％以下が望まれる。
【００３６】
Ｃｒ：０．０４〜０．３５質量％
Ｃｒは押出加工時の加工発熱過程での再結晶による強度低下を抑える効果があるが、０．０４％未満ではその効果がない。一方、０．３５％を越えて添加するとＡｌ−Ｃｒ系の粗大な化合物を生成し押出材を脆化させる。特に再結晶防止と押出材脆化を防止するとの観点から、０．０７％以上、０．３％以下が望まれる。
【００３７】
Ｔｉ：０．００１〜０．０５質量％
Ｔｉは鋳造組織を微細化して機械的性質を安定化する。しかし、Ｔｉ含有量が０．００１％未満ではその効果が得られず、一方０．０５％を越えて添加してもそれ以上微細化効果は向上しない。
【００３８】
Ｆｅ：０．５〜１．０質量％
Ｚｒ：０．１〜０．５質量％
Ｆｅ、ＺｒはそれぞれＡｌと化合物を形成し、切粉の分断の起点となって切削性を向上させるため、必要に応じて添加することができる。本発明合金においてそれぞれ不可避不純物として下限値未満の含有が許容されるが、下限値未満ではその効果が十分でなく、一方、上限値を越えると粗大な化合物を生成し、押出性が低下する。
【００３９】
また、上記アルミニウム合金の不可避不純物としては、ＪＩＳＨ４０４０に規定する化学成分に準じ、Ｐｂ、Ｂｉ、Ｓｎは各々０．０５質量％以下、Ｍｎは０．１５質量％以下が許容される。これらの成分は多く含まれると上記アルミニウム合金の耐食性（Ｐｂ、Ｂｉ、Ｓｎ）又は切削性（Ｍｎ）を劣化させるが、上記範囲内であればこれらの特性に影響を与えない。
【００４０】
［請求項５の発明］
この発明に関わるアルマイト処理用アルミニウム合金は、これまで述べた切削性に優れる高耐食アルミニウム合金の用途を特定したものである。このアルミニウム合金の母材中に微細に分散したＳｉやＳｉＭｇ_２は、従来の高切削性アルミニウム合金中に分散するＰｂやＢｉと異なり、酸化皮膜の均質な形成を妨げず、表面に均質で光沢のあるアルマイト皮膜が形成された機械部品等を得ることができる。
【００４１】
【実施例】
以下、本発明の実施例等について、比較例と比較して具体的に説明する。なお、［参考例１］は参考発明１に対応し、［参考例２］は参考発明２に対応し、［実施例１］は請求項１〜４の発明に対応し、［実施例２］は請求項５の発明に対応する。
【００４２】
［参考例１］
表１〜表３に示した化学組成の合金を溶解し半連続鋳造により１６０ｍｍ径の押出ビレットを作製し、５２０℃で４時間均質化熱処理を施した後、５００℃の押出温度で６０ｍｍ径に押し出した。
【００４３】
【表１】

【００４４】
【表２】

【００４５】
【表３】

【００４６】
この押出材から押出方向に径２０ｍｍ×高さ２０ｍｍの試験片を採取し、これを冷間で軸方向に据込み鍛造し、側面に微小割れが発生する限界据込み率を求め、各々の冷鍛性（据込み鍛造性）を下記の要領で評価した。また、この押出材から高さ６０ｍｍの試験片を切り出し、これを冷間で軸方向に据込み鍛造（限界据込み率が５０％以上のものは５０％、限界据込み率が５０％未満のものはその限界据込み率まで）し、その据込み鍛造材を用いて各々の機械的性質、切削性及び耐食性を下記の要領で測定した。なお、押出性を調べるため上記押出では押出荷重を一定（６００トン）とし、押出速度（押出材が出てくるときの速度）を計測し、各押出材の押出性を下記の要領で評価した。
【００４７】
冷鍛性；限界据込み率が５０％を越えるとき◎（優れている）、３０〜５０％のとき○（使用可能である）、３０％未満のとき×（使用に耐えない）と評価した。
機械的性質；据込み鍛造材から据込み方向に垂直な方向に径６ｍｍ、平行部長さ４０ｍｍの引張試験片を採取し、その引張強さ、耐力、及び伸びを測定した。切削性；市販の高速度鋼製の４ｍｍ径ドリルを用い、回転数１５００ｍｍ／分、送り速度３００ｍｍ／分の条件にて切削し、ドリルへの巻き付き発生の有無を観察するとともに、切粉分断性を調べるため切粉１００個当りの重量を測定した。
耐食性；７２時間のＣＡＳＳ試験（５％食塩水に塩化第二銅を１００ｐｐｍ添加し、さらに酢酸にてｐＨ＝３に調整した液を５０℃にて噴霧）による単位面積当りの重量減少を測定した。
押出性；押出速度の値が５ｍ／分より大のとき◎（優れている）、２〜５ｍ／分のとき○（使用可能である）、２ｍ／分より小のとき×（使用に耐えない）と評価した。
【００４８】
これらの試験結果を表４〜表６に示す。
この発明の実施例に相当する合金１〜３２は、いずれも優れた切削性と耐食性を示し、これを比較例の合金４５（従来の３００３合金に相当）や合金４６（従来の３００４合金に相当）と比較すると、切削性において著しく優れ、機械的性質や耐食性は同等であり、冷鍛性でもほぼ同等である。また、押出材にはむしれや焼き付き痕はなく表面性状は良好で、押出性の値も十分使用可能な範囲内にある。
【００４９】
【表４】

【００５０】
【表５】

【００５１】
【表６】

【００５２】
これに対し、比較例の合金３３〜４７は組成がこの発明の範囲外の合金であり、いずれも何らかの特性が実施例合金１〜３２に比べ劣っている。すなわち、合金３３、３５、３７、３９は、それぞれＳｉ、Ｍｇ、Ｃｕ、Ｍｎの含有量が不足のため切削性に劣る（切粉の分断性が劣り、切粉の巻き付きがある）。合金３４、３６、３８、４０、４２〜４４は、それぞれＳｉ、Ｍｇ、Ｃｕ、Ｍｎ、Ｆｅ、Ｃｒ、Ｚｒが過剰なため押出性と冷鍛性に劣り、合金３８は耐食性にも劣る。合金４１はＴｉを有効量含有しないため、伸びが悪く冷鍛性に劣る。また、従来の合金４５及び合金４６は切削性に劣り、合金４６にＰｂ及びＢｉを添加してなる合金４７は切削性は改善されたが、耐食性が悪くなっている。
【００５３】
［参考例２］
表７及び表８に示した化学組成の合金を溶解し半連続鋳造により１６０ｍｍ径の押出ビレットを作製し、５２０℃で４時間均質化熱処理を施した後、５００℃の押出温度で６０ｍｍ径に押し出した。
【００５４】
【表７】

【００５５】
【表８】

【００５６】
この押出材から［参考例１］と全く同じ要領で試験片を採取し、かつ全く同じ要領で冷鍛性、機械的性質、切削性、耐食性、押出性の測定及び評価を行った。これらの試験結果を表９及び表１０に示す。
この発明の実施例に相当する合金４８〜６０は、いずれも優れた切削性と耐食性を示し、これを比較例の合金６９（従来の５０５６合金に相当）、合金７０（従来の５０５２合金に相当）及び合金７１（従来の５０８３合金に相当）と比較すると、切削性において著しく優れ、機械的性質や耐食性は同等であり、冷鍛性でもほぼ同等である。また、押出材にはむしれや焼き付き痕はなく表面性状は良好で、押出性の値も十分使用可能な範囲内にある。
【００５７】
【表９】

【００５８】
【表１０】

【００５９】
これに対し、比較例の合金６１〜７２は組成がこの発明の範囲外の合金であり、いずれも何らかの特性が実施例合金４８〜６０に比べ劣っている。すなわち、合金６２、６４はそれぞれＳｉ、Ｍｇの含有量が不足のため切削性に劣る（切粉の分断性が劣り、切粉の巻き付きがある）。合金６１、６３、６５〜６８はそれぞれＳｉ、Ｍｇ、Ｃｕ、Ｆｅ、Ｃｒ、Ｚｒが過剰なため押出性と冷鍛性に劣り、合金６５は耐食性にも劣る。また、従来の合金６９、合金７０及び合金７１は切削性に劣り、合金６９にＰｂ及びＢｉを添加してなる合金７２は切削性は改善されたが、耐食性が悪くなっている。
【００６０】
［実施例１］
表１１及び表１２に示した化学組成の合金を溶解し半連続鋳造により１６０ｍｍ径の押出ビレットを作製し、４７５℃で４時間均質化熱処理を施した後、５００℃の押出温度で６０ｍｍ径に押し出し、これを５２０℃で１時間溶体化処理して水中に焼入れた。さらに１７０℃で６時間の人工時効処理を施して供試材とし、各々の機械的性質、切削性及び耐食性を下記の要領で測定及び評価を行った。
【００６１】
【表１１】

【００６２】
【表１２】

【００６３】
機械的性質；押出方向に採取したＪＩＳ４号試験片を用い、ＪＩＳＺ２２４１に規定する金属材料試験方法に準じ、引張強さ、耐力、及び伸びを測定した。
切削性、耐食性、押出性；［参考例１］と同じ要領。
【００６４】
これらの試験結果を表１３及び表１４に示す。
この発明の実施例に相当する合金７３〜９８は、いずれも優れた切削性と耐食性を示し、これを比較例合金１０５（従来のＡＡ６２６２合金に相当）と比較すると、耐食性に優れ、切削性でも同等ないし優れている。また、押出材にはむしれや焼き付き痕はなく表面性状は良好で、押出性と機械的性質の値も十分使用可能な範囲内にある。
【００６５】
【表１３】

【００６６】
【表１４】

【００６７】
これに対し、比較例合金９９〜１０５は組成がこの発明の範囲外の合金であり、いずれも何らかの特性が実施例合金７３〜９８に比べ劣っている。すなわち、合金１００、１０１はＳｉ量が不足のため切削性に劣り（切粉の分断性が劣り、切粉の巻き付きがある）、合金１０４はＣｕ量が過剰のため耐食性に劣り、合金１０５（ＡＡ６２６２相当）はＰｂ、Ｂｉを含有するためさらに耐食性が劣る。また、合金９９はＳｉ量が過剰のため、合金１０２はＭｇ量が過剰のため、合金１０３はＣｒ量が過剰のため、合金１０４はＣｕが過剰なため、合金１０６はＦｅが過剰なため、合金１０７はＺｒが過剰なため、それぞれ押出性に劣る。
【００６８】
［実施例２］
参考例１，２及び実施例１の供試材の表面を研磨したのち硫酸アルマイトを施し、酸化皮膜の厚さを１０μｍにして表面の光沢を観察した。表面の光沢が優れているものを◎、劣るものを×と評価し、その結果を表４〜６、９、１０、１３、１４に併せて記載した。本発明の実施例及び参考発明の実施例に相当する合金は、いずれも表面の光沢が優れアルマイト処理性に優れている。
【００６９】
【発明の効果】
このように、参考発明１に関わるアルミニウム合金は、Ｐｂ、Ｂｉ等の低融点金属を使用していないにも関わらず、従来の３００３合金や３００４合金に比べて切削性が著しく優れ、機械的性質、耐食性、冷間鍛造性、押出性についてもほぼ同等で優れる非熱処理型合金である。
また、参考発明２に関わるアルミニウム合金は、Ｐｂ、Ｂｉ等の低融点金属を使用していないにも関わらず、従来の５０５６合金、５０５２合金及び５０８３合金に比べて切削性が著しく優れ、機械的性質、耐食性、冷間鍛造性、押出性についてもほぼ同等で優れる非熱処理型合金である。
そして、いずれも長い切粉による工具への切粉の巻き付き等のトラブルも発生せず、冷間鍛造の採用及び熱処理の省略により工程の低コスト化を達成できるものであり、さらにリサイクル性にも難がないことから、工業的価値が極めて大きいものである。
【００７０】
一方、本発明に関わるアルミニウム合金（請求項１〜４）は、耐食性及び切削性について従来技術のＡＡ６２６２合金を凌駕する。そして、長い切粉による工具への切粉の巻き付き等のトラブルも発生しないため、特に自動工作機械を用いた無人運転で作成される機械部品用素材として適しており、加えて低融点金属に起因する熱脆性も生じ得ず、リサイクル性も高いので、ＡＡ６２６２合金が用いられていた各用途に適用できる切削性に優れた高耐食アルミニウム合金として工業的価値がきわめて大きいものである。
また、上記アルミニウム合金（請求項１〜４及び参考発明１，２）は、ＰｂやＢｉを添加することなく切削性を高めていることから、アルマイト処理性に優れ、均質で光沢のあるアルマイト皮膜を形成することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention is a highly corrosion-resistant aluminum alloy having excellent machinability suitable for machine parts and the like that frequently use cutting in the manufacturing process. Extruded material About.
[0002]
[Prior art]
Among aluminum alloys, non-heat-treatable alloys centered on 3000 series Al-Mn series alloys have medium mechanical properties, excellent corrosion resistance and cold forgeability, and can be formed at low cost. There are many uses for parts, and in that case, it is generally commercialized by cold forging and then cutting and drilling. However, this type of alloy is difficult to cut off the chips generated during cutting and has poor machinability, so it has been difficult to employ it for machine parts that require complicated cutting and drilling.
[0003]
In addition, non-heat-treatable alloys centered on 5000 series Al-Mg series alloys among aluminum alloys have moderate mechanical properties (slightly higher strength level than 3000 series) and excellent corrosion resistance and cold workability. Because it can be processed at low cost, it has many uses for optical equipment such as cameras and microscope tubes, and other mechanical parts. In that case, it is generally cold forged and then subjected to cutting and drilling. It has been commercialized. However, this type of alloy is difficult to cut off the chips generated at the time of cutting and has poor machinability, and it has been difficult to adopt it for machine parts that require complicated cutting and drilling.
[0004]
On the other hand, the conventional high machinability aluminum alloy is an AA6262 alloy (Si: 0.4 to 0.8% by mass, Mg: 0.8 to 1.2% by mass, Cu: 0.15 to 5%) in the field of wrought material. 0.4% by mass, Pb: 0.4 to 0.7% by mass, Bi: 0.4 to 0.7% by mass, balance Al), and the like as effective additive elements such as Pb, Bi, Sn, etc. (See Japanese Patent Laid-Open Nos. 54-143714 and 3-39442). These low-melting-point metals hardly dissolve in aluminum, but microsegregate in an aluminum alloy in the form of particles. The low-melting-point metal particles melt due to processing heat generated during cutting and cut off the chips, thereby cutting the aluminum alloy. Improve sexiness.
[0005]
The AA6262 alloy is a heat-treatable aluminum alloy that has been conventionally used as a material for a housing of an automotive anti-skid brake system, for example, a machine part that is frequently used in machining, particularly drilling. However, it is expected that the effect of improving the machinability by adding such a low-melting point metal such as Pb, Bi, or Sn is equally obtained not only in the above heat treatment type alloy but also in a non heat treatment type alloy (for example, the above-mentioned Japanese Patent Application Laid-Open No. 3-39442).
[0006]
[Problems to be solved by the invention]
However, aluminum alloys to which these low melting point metals are added have improved machinability, but also have low corrosion resistance, and low melting point metals also have the drawback of causing thermal embrittlement, so it is necessary to pay sufficient attention to the usage environment. It was. Furthermore, when the alloy is recycled as scrap, it can be diverted only to relatively few alloy types that require Pb, Bi and the like, and the diversion range is narrowed, which is disadvantageous for recyclability.
[0007]
In addition, in order to improve the corrosion resistance, wear resistance or decorative effect, mechanical parts may be anodized on the surface, but in the case of an aluminum alloy to which Pb or Bi is added, the part where Pb or Bi is exposed on the surface In this case, there is a problem that an oxide film is not formed and only a non-homogeneous and glossy alumite film is obtained.
[0008]
A non-heat-treatable aluminum alloy having improved machinability without containing such a low melting point metal has been proposed in Japanese Patent Laid-Open No. 60-184658, but a low melting point metal such as Pb, Bi, Sn or the like is used. The machinability was not sufficient as compared with the contained aluminum alloy.
[0009]
The present invention has been made in view of the above-mentioned problems of the prior art, and comprehensively speaking, an aluminum alloy excellent in both machinability and corrosion resistance. Extruded material Aluminum alloy with excellent machinability that can form a uniform anodized film with recyclability Extruded material The purpose is to obtain. Individually speaking, the non-heat-treatable type has the same mechanical properties, cold forgeability, corrosion resistance, and recyclability as the conventional 3000-type or 5000-type non-heat-treatable aluminum alloy, and improved machinability. Aluminum alloy Extruded material A heat-treatable aluminum alloy having a machinability equivalent to or better than that of a conventional AA6262 alloy and having improved corrosion resistance Extruded material It aims to obtain.
[0010]
[Means for Solving the Problems]
As a result of intensive studies to solve the above problems, the present inventors have not added low-melting point metals such as Pb, Bi, and Sn, which have been added for the purpose of improving machinability, and hindered recyclability. It has been found that the above-mentioned object can be achieved by using Si, Mg, etc. that are not used, and the present invention has been completed based on the knowledge. As shown below, the present application is a non-heat-treatable aluminum alloy of two systems with different strength levels. Extruded material Inventions related to ( Reference invention ) And heat-treatable aluminum alloy Extruded material Inventions related to ( Claims 1-4 ).
[0011]
[ Reference invention 1 ]
The highly corrosion-resistant aluminum alloy having excellent machinability according to the present invention includes Si: 1.5 to 12.0 mass%, Mg: 0.5 to 6.0 mass%, Ti: 0.01 to 0.1 mass%. Each is contained, and the balance consists of Al and inevitable impurities. In addition, the high corrosion resistance aluminum alloy excellent in machinability related to the present invention, if necessary, in addition to the above alloy elements, (1) Contains either one or both of Mn: 0.5-2.0% by mass or Cu: 0.1-1.0% by mass, or (2) Fe: 0.5-1.0% by mass, Cr: 0.1-0.5% by mass, Zr: containing any one or more of 0.1-0.5% by mass, or (3) the above (1), (2) The elements listed in both are included in any combination.
[0012]
The high corrosion resistance aluminum alloy having excellent machinability is superior in forgeability but poor in machinability, so compared with the conventional 3003 alloy and 3004 alloy, which could not be applied to many machine parts, the strength, corrosion resistance, It is a non-heat-treatable aluminum alloy that has the same hot forgeability and markedly improved machinability, and can be cold-forged at low cost and complex cutting. And the cutting | disconnection property of a chip is good and troubles, such as winding of the chip around a tool with a long chip, do not generate | occur | produce. Moreover, since low melting point metals such as Pb and Bi are not added for improving machinability, they have high corrosion resistance, cannot cause thermal brittleness, and do not hinder recyclability.
The aluminum alloy can be produced according to a conventional method. For example, the aluminum alloy can be melted, cast, and subjected to a homogenization heat treatment, and then subjected to extrusion, so that the extruded material can be used as a material for forging.
[0013]
Next, the reason for adding each element in the aluminum alloy and the reason for limiting the addition amount will be described.
[0014]
Si: 1.5-12.0 mass%
Si forms a Si-based compound in the aluminum structure to improve the cutting performance of the chips and improve the cutting performance. This is because the Si-based compound serves as a starting point for dividing the chips. The lower limit of Si addition needs to exceed 1.5% which is the solid solubility limit in aluminum, and in order to clarify the effect of Si, addition of more than 2.0% is desirable. A remarkable effect can be obtained by addition of 0.0% or more. Therefore, from the viewpoint of obtaining excellent machinability, Si is preferably 2.0 to 12.0% (not including 2.0)%, or 4.0 to 12.0%. On the other hand, the upper limit of addition of Si needs to be 12.0% or less of the eutectic point so as not to cause deterioration of extrudability and embrittlement of the extruded material due to the generation of coarse primary crystal Si and increase in deformation resistance. There is. In particular, 6% or less with good extrudability is desirable.
[0015]
Mg: 0.5-6.0 mass%
Mg has the effect of improving the chip breaking property because it improves the strain hardening ability, and increasing the strength of the material by forming a solid solution. If the Mg content is less than 0.5%, the effect cannot be obtained sufficiently. If the Mg content exceeds 6.0%, the deformation resistance increases and the extrudability decreases. From the standpoint of ensuring strength and good extrudability, 1.0% or more and 3.0% or less are generally preferred, but from the standpoint of improving extrudability exclusively by suppressing deformation resistance during extrusion processing. If the content is less than 1.0%, particularly 0.9% or less, a remarkable effect can be obtained. Therefore, in that case, Mg may be 0.5 to 1.0 (not including 1.0)%, or 0.5 to 0.9%.
[0016]
Ti: 0.01 to 0.1% by mass
Ti refines the cast structure and stabilizes the mechanical properties. However, if the Ti content is less than 0.01%, the effect cannot be obtained. On the other hand, the effect is saturated even if the content exceeds 0.1%.
[0017]
Mn: 0.5 to 2.0% by mass
Mn has the effect of increasing the strength of the material by forming a solid solution, and also has the effect of promoting chip breaking in order to improve strain hardening ability. However, if the Mn content is less than 0.5%, a sufficient effect cannot be obtained. On the other hand, if it exceeds 2.0%, the extrudability is lowered. In particular, from the viewpoint of securing strength and good extrudability, 0.7% or more and 1.5% or less are desired.
[0018]
Cu: 0.1 to 1.0% by mass
Cu has a solid solution to increase the strength of the material and also has an effect of promoting chip breaking in order to improve strain hardening ability, and is added in place of Mn or together with Mn. However, if the Cu content is less than 0.1%, the effect is poor. On the other hand, if the Cu content exceeds 1.0%, the corrosion resistance decreases and the extrudability also decreases. In particular, from the viewpoint of securing strength and good corrosion resistance and extrudability, 0.3% or more and 0.8% or less are desired.
[0019]
Fe: 0.5 to 1.0% by mass,
Cr: 0.1 to 0.5% by mass,
Zr: 0.1 to 0.5% by mass
Fe, Cr, and Zr each form a compound with Al and serve as a starting point for chip cutting to improve machinability. In the present invention, the content of each unavoidable impurity is less than the lower limit, but if the content is less than the lower limit, the effect is not sufficient. On the other hand, if the upper limit is exceeded, a coarse compound is produced and the extrudability is lowered.
[0020]
Moreover, as an inevitable impurity of the said aluminum alloy, 0.05 mass% or less of Pb, Bi, and Sn is respectively accepted according to the chemical component prescribed | regulated to JISH4040. If these low melting point metals are contained in a large amount, the corrosion resistance of the aluminum alloy is deteriorated, but if it is within this range, the characteristics are not affected. In addition, 0.05% by mass or less of other inevitable impurities is allowed individually.
[0021]
[ Reference invention 2 ]
The highly corrosion-resistant aluminum alloy having excellent machinability according to the present invention contains Si: 1.5 to 12.0% by mass, Mg: 2.0 to 6.0% by mass, and the balance is made of Al and inevitable impurities. . In addition, the high corrosion resistance aluminum alloy excellent in machinability related to the present invention, if necessary, in addition to the above alloy elements, (1) Mn: 0.3 to 1.2% by mass, Ti: 0.01 to 0.1% by mass, or both, or (2) Fe: 0.5-1.0% by mass, Cr: 0.1-0.5% by mass, Zr: containing any one or more of 0.1-0.5% by mass, or (3) the above (1), (2) The elements listed in both are included in any combination.
[0022]
The high corrosion-resistant aluminum alloy having excellent machinability is superior in cold workability but has poor machinability, so compared with the conventional 5052 alloy and 5056 alloy that could not be applied to many machine parts, the strength, corrosion resistance, In addition, it is a non-heat-treatable aluminum alloy that has the same cold workability such as cold forging and has a remarkably improved machinability, and is an alloy that enables complex cutting work. And the cutting | disconnection property of a chip is good and troubles, such as winding of the chip around a tool with a long chip, do not generate | occur | produce. Moreover, since low melting point metals such as Pb and Bi are not added for improving machinability, they have high corrosion resistance, cannot cause thermal brittleness, and do not hinder recyclability.
The aluminum alloy can be manufactured in accordance with a conventional method. For example, the aluminum alloy can be melted, cast, and subjected to a homogenization heat treatment, followed by extrusion, and the extruded material can be used as a cutting material.
[0023]
Next, the reason for adding each element in the aluminum alloy and the reason for limiting the addition amount will be described.
[0024]
Si: 1.5-12.0 mass%
Si forms a Si-based compound in the aluminum structure to improve the cutting performance of the chips and improve the cutting performance. This is because the Si-based compound serves as a starting point for cutting off chips generated during cutting. The lower limit of Si addition needs to exceed 1.5% which is the solid solubility limit in aluminum, and in order to clarify the effect of Si, addition of more than 2.0% is desirable. A remarkable effect can be obtained by addition of 0.0% or more. Therefore, from the viewpoint of obtaining excellent machinability, Si is preferably 2.0 to 12.0% (not including 2.0)%, or 4.0 to 12.0%. On the other hand, the upper limit of addition of Si needs to be 12.0% or less of the eutectic point so as not to cause deterioration of extrudability and embrittlement of the extruded material due to the generation of coarse primary crystal Si and increase in deformation resistance. There is. In particular, 6% or less with good extrudability is desirable.
[0025]
Mg: 2.0-6.0 mass%
Mg has the effect of improving the chip breaking property because it improves the strain hardening ability, and increasing the strength of the material by forming a solid solution. When the Mg content is less than 2.0%, a sufficient effect cannot be obtained. When the Mg content exceeds 6.0%, the deformation resistance increases and the extrudability decreases. In particular, from the viewpoint of securing strength and good extrudability, 2.5% or more and 5.5% or less are desired.
[0026]
Ti: 0.01 to 0.1% by mass
Ti refines the cast structure and stabilizes the mechanical properties. However, if the Ti content is less than 0.01%, the effect cannot be obtained. On the other hand, the effect is saturated even if the content exceeds 0.1%.
[0027]
Mn: 0.3 to 1.2% by mass
Mn has the effect of increasing the strength of the material by forming a solid solution, and also has the effect of promoting chip breaking in order to improve strain hardening ability. However, if the Mn content is less than 0.3%, a sufficient effect cannot be obtained. On the other hand, if it exceeds 1.2%, the extrudability decreases. In particular, from the viewpoint of securing strength and good extrudability, 0.5% or more and 1.0% or less are desired.
[0028]
Fe: 0.5 to 1.0% by mass,
Cr: 0.1 to 0.5% by mass,
Zr: 0.1 to 0.5% by mass
Fe, Cr, and Zr each form a compound with Al and serve as a starting point for chip cutting to improve machinability. In the present invention, it is allowed to contain less than the lower limit as an unavoidable impurity in each case, but if the content is less than the lower limit, the effect is not sufficient, while if the content exceeds the upper limit, a coarse compound is produced and the extrudability decreases. To do.
[0029]
Moreover, as an inevitable impurity of the said aluminum alloy, 0.05 mass% or less of Pb, Bi, and Sn is respectively accepted according to the chemical component prescribed | regulated to JISH4040. If these low melting point metals are contained in a large amount, the corrosion resistance of the aluminum alloy is deteriorated, but if it is within this range, the characteristics are not affected. In addition, 0.05% by mass or less of other inevitable impurities is allowed individually.
[0030]
[ Claims 1-4 Invention of]
The highly corrosion-resistant aluminum alloy having excellent machinability according to the present invention includes Si: 1.5 to 12.0% by mass, Mg: 0.2 to 1.2% by mass, and Cu: 0.15 to 3.0% by mass. Each is contained, and the balance consists of Al and inevitable impurities. In addition, the high corrosion resistance aluminum alloy having excellent machinability according to the present invention, if necessary, Cr: 0.04 to 0.35 mass% or Ti: 0.001 to 0.05 mass% in addition to the above alloy elements. Either or both of these are contained.
[0031]
The greatest feature of the high corrosion resistance aluminum alloy having excellent machinability is that machinability is improved without adding a low melting point metal such as Pb, Bi, Sn, etc. like the AA6262 alloy. This aluminum alloy extruded material has a high corrosion resistance compared to the AA6262 alloy because no low melting point metal is added, and further, heat embrittlement cannot occur and recyclability is also high. And the cutting | disconnection property of a chip is good and troubles, such as winding of the chip around a tool with a long chip, do not generate | occur | produce.
In addition, the aluminum alloy is subjected to, for example, melting, casting, homogenization treatment, and extrusion processing according to a conventional method, and the extruded material is subjected to solution treatment, quenching, and artificial aging treatment to give a predetermined strength. It can be used for cutting.
[0032]
Next, the reason for adding each element in the aluminum alloy and the reason for limiting the addition amount will be described.
[0033]
Si: 1.5-12.0 mass%
Si forms a Si-based compound in the aluminum structure, improves chip breaking and improves machinability. This is because the Si phase serves as a starting point for strain propagation and increases the propagation speed of strain received from the tool during cutting. Therefore, the Si addition lower limit value needs to exceed 1.5% which is the solid solubility limit in aluminum, and in order to clarify the effect of Si, addition exceeding 2.0% is desirable, Further, a remarkable effect can be obtained by addition of 4.0% or more. Therefore, from the viewpoint of obtaining excellent machinability, Si is preferably 2.0 to 12.0% (not including 2.0)%, or 4.0 to 12.0%. On the other hand, the upper limit of addition of Si needs to be 12.0% or less of the eutectic point so as not to cause deterioration of extrudability and embrittlement of the extruded material due to the generation of coarse primary crystal Si and increase in deformation resistance. In particular, 6% or less is preferable because the extrusion productivity is good.
[0034]
Mg: 0.2-1.2% by mass
Mg coexists with Si during heat treatment ₂ It is precipitated as Si and has the effect of increasing strength. If the Mg content is less than 0.2%, the effect cannot be obtained. On the other hand, if the Mg content exceeds 1.2%, deformation resistance increases due to solid solution strengthening of Mg alone, and the extrudability decreases. From the standpoint of ensuring strength and good extrudability, it is generally preferably 0.4% or more and 1.0% or less, but from the standpoint of improving extrudability exclusively by suppressing deformation resistance during extrusion processing. If the content is less than 1%, particularly 0.9% or less, a remarkable effect can be obtained. Therefore, in that case, Mg may be 0.2 to 1.0 (not including 1.0)%, or 0.2 to 0.9%.
[0035]
Cu: 0.15-3.0 mass%
Cu enhances the strength by heat treatment and promotes chip breaking in order to improve strain hardening ability. When the Cu content is less than 0.15%, the effect is poor. On the other hand, when the Cu content exceeds 3.0%, the corrosion resistance is lowered and the extrudability is also lowered. In particular, from the viewpoint of securing strength and good corrosion resistance and extrudability, 0.2% or more and 2.5% or less are desired.
[0036]
Cr: 0.04-0.35 mass%
Cr has an effect of suppressing a decrease in strength due to recrystallization in the process of heat generation during extrusion, but if less than 0.04%, there is no effect. On the other hand, if added over 0.35%, a coarse compound of Al-Cr type is formed and the extruded material is embrittled. In particular, from the viewpoint of preventing recrystallization and preventing embrittlement of the extruded material, 0.07% or more and 0.3% or less are desired.
[0037]
Ti: 0.001 to 0.05 mass%
Ti refines the cast structure and stabilizes the mechanical properties. However, if the Ti content is less than 0.001%, the effect cannot be obtained. On the other hand, the addition of more than 0.05% does not further improve the miniaturization effect.
[0038]
Fe: 0.5 to 1.0% by mass
Zr: 0.1 to 0.5% by mass
Fe and Zr each form a compound with Al and serve as a starting point for cutting the chips to improve the machinability. Therefore, Fe and Zr can be added as necessary. Each alloy of the present invention is allowed to contain less than the lower limit as an unavoidable impurity. However, if the content is less than the lower limit, the effect is not sufficient. On the other hand, if the upper limit is exceeded, a coarse compound is produced and the extrudability is lowered.
[0039]
Moreover, as an inevitable impurity of the said aluminum alloy, according to the chemical component prescribed | regulated to JISH4040, 0.05 mass% or less for Pb, Bi, and Sn respectively and Mn 0.15 mass% or less are accept | permitted. If these components are contained in a large amount, the corrosion resistance (Pb, Bi, Sn) or machinability (Mn) of the aluminum alloy is deteriorated. However, if it is within the above range, these properties are not affected.
[0040]
[ Claim 5 Invention of]
The aluminum alloy for alumite treatment according to the present invention specifies the use of the high corrosion resistance aluminum alloy having excellent machinability described so far. Si or SiMg finely dispersed in the base material of this aluminum alloy ₂ Unlike Pb and Bi dispersed in a conventional high machinability aluminum alloy, it is possible to obtain a machine part or the like in which a uniform and glossy alumite film is formed on the surface without disturbing the uniform formation of an oxide film. .
[0041]
【Example】
Examples of the present invention etc Will be specifically described in comparison with a comparative example. In addition, [ Reference example 1 ] Reference invention 1 Corresponding to [ Reference example 2 ] Reference invention 2 Corresponding to [ Example 1 ] Claims 1-4 Corresponding to the invention of [ Example 2 ] Claim 5 This corresponds to the invention.
[0042]
[ Reference example 1 ]
An alloy having the chemical composition shown in Tables 1 to 3 was melted and an extruded billet having a diameter of 160 mm was prepared by semi-continuous casting, and subjected to a homogenization heat treatment at 520 ° C. for 4 hours. Extruded.
[0043]
[Table 1]

[0044]
[Table 2]

[0045]
[Table 3]

[0046]
A test piece having a diameter of 20 mm × height of 20 mm in the extrusion direction was collected from the extruded material, and this was subjected to upsetting forging in the axial direction while cold, and the limit upsetting rate at which microcracks were generated on the side surface was determined. Forgeability (upset forgeability) was evaluated in the following manner. In addition, a test piece having a height of 60 mm was cut out from the extruded material, and this was upset in the axial direction in the cold direction (the limit upsetting rate is 50% or more and the limit upsetting rate is less than 50%). Then, the mechanical properties, machinability and corrosion resistance of each of the upset forging materials were measured in the following manner. In order to investigate the extrudability, in the above extrusion, the extrusion load was set constant (600 tons), the extrusion speed (speed when the extruded material comes out) was measured, and the extrudability of each extruded material was evaluated as follows. .
[0047]
Cold forgeability: evaluated as ◎ (excellent) when the limit upsetting rate exceeds 50%, ○ (can be used) when 30 to 50%, x (not withstand use) when less than 30% .
Mechanical properties: Tensile test pieces having a diameter of 6 mm and a parallel part length of 40 mm were taken from the upset forged material in a direction perpendicular to the upsetting direction, and the tensile strength, yield strength, and elongation were measured. Cutting performance: Using a commercially available 4 mm diameter drill made of high-speed steel, cutting was performed under the conditions of a rotation speed of 1500 mm / min and a feed rate of 300 mm / min. The weight per 100 chips was measured.
Corrosion resistance: The weight loss per unit area was measured by a CASS test for 72 hours (100 ppm of cupric chloride added to 5% saline solution and sprayed with a solution adjusted to pH = 3 with acetic acid at 50 ° C.). .
Extrudability: When the value of the extrusion speed is greater than 5 m / min, ◎ (excellent), when 2-5 m / min, ○ (can be used), when less than 2 m / min, x (not useable) ).
[0048]
These test results are shown in Tables 4-6.
Alloys 1 to 32 corresponding to the examples of the present invention all showed excellent machinability and corrosion resistance, which were compared to alloy 45 (corresponding to conventional 3003 alloy) and alloy 46 (corresponding to conventional 3004 alloy) of comparative examples. ) Is remarkably excellent in machinability, mechanical properties and corrosion resistance are equivalent, and cold forgeability is almost equivalent. In addition, the extruded material has no peeling or burn-in traces, has a good surface property, and the value of extrudability is within a usable range.
[0049]
[Table 4]

[0050]
[Table 5]

[0051]
[Table 6]

[0052]
On the other hand, the alloys 33 to 47 of the comparative examples are alloys whose compositions are out of the range of the present invention, and any characteristics are inferior to those of the examples alloys 1 to 32. That is, the alloys 33, 35, 37, and 39 are inferior in machinability due to insufficient contents of Si, Mg, Cu, and Mn (inferior chip breaking property and chip winding). The alloys 34, 36, 38, 40, and 42 to 44 have excessive amounts of Si, Mg, Cu, Mn, Fe, Cr, and Zr, respectively, so that the extrudability and cold forgeability are inferior, and the alloy 38 is also inferior in corrosion resistance. Since the alloy 41 does not contain an effective amount of Ti, the elongation is poor and the cold forgeability is poor. Further, the conventional alloy 45 and alloy 46 are inferior in machinability, and the alloy 47 obtained by adding Pb and Bi to the alloy 46 has improved machinability but has poor corrosion resistance.
[0053]
[ Reference example 2 ]
An alloy having the chemical composition shown in Table 7 and Table 8 was melted and an extruded billet having a diameter of 160 mm was produced by semi-continuous casting. After homogenizing heat treatment at 520 ° C. for 4 hours, the extrusion billet was heated to 500 ° C. to a diameter of 60 mm. Extruded.
[0054]
[Table 7]

[0055]
[Table 8]

[0056]
From this extruded material [ Reference example 1 The test specimens were collected in exactly the same manner, and the cold forgeability, mechanical properties, machinability, corrosion resistance, and extrudability were measured and evaluated in exactly the same manner. The test results are shown in Table 9 and Table 10.
Alloys 48 to 60 corresponding to the examples of the present invention all showed excellent machinability and corrosion resistance, which were compared with alloy 69 (corresponding to conventional 5056 alloy) and alloy 70 (corresponding to conventional 5052 alloy) of comparative examples. ) And alloy 71 (corresponding to conventional 5083 alloy), the machinability is remarkably excellent, the mechanical properties and the corrosion resistance are equivalent, and the cold forgeability is almost equivalent. In addition, the extruded material has no peeling or burn-in traces, has a good surface property, and the value of extrudability is within a usable range.
[0057]
[Table 9]

[0058]
[Table 10]

[0059]
On the other hand, the alloys 61 to 72 of the comparative example are alloys whose compositions are out of the range of the present invention, and any characteristics are inferior to those of the examples alloys 48 to 60. That is, the alloys 62 and 64 are inferior in machinability due to insufficient contents of Si and Mg, respectively (the severing property of the swarf is inferior and there is wrapping of the swarf). Alloys 61, 63, and 65 to 68 are inferior in extrudability and cold forgeability because Si, Mg, Cu, Fe, Cr, and Zr are excessive, respectively, and alloy 65 is also inferior in corrosion resistance. Further, the conventional alloy 69, alloy 70 and alloy 71 are inferior in machinability, and the alloy 72 obtained by adding Pb and Bi to the alloy 69 has improved machinability but has poor corrosion resistance.
[0060]
[ Example 1 ]
An alloy having the chemical composition shown in Tables 11 and 12 was melted and an extruded billet having a diameter of 160 mm was prepared by semi-continuous casting. After homogenizing heat treatment at 475 ° C. for 4 hours, the extrusion billet was heated to 500 ° C. to a diameter of 60 mm. Extruded, solution treated at 520 ° C. for 1 hour and quenched in water. Further, an artificial aging treatment was performed at 170 ° C. for 6 hours to obtain a test material, and the mechanical properties, machinability and corrosion resistance were measured and evaluated in the following manner.
[0061]
[Table 11]

[0062]
[Table 12]

[0063]
Mechanical properties: Tensile strength, proof stress, and elongation were measured in accordance with a metal material test method specified in JISZ2241, using a JIS No. 4 test piece collected in the extrusion direction.
Machinability, corrosion resistance, extrudability; [ Reference example 1 ] Same procedure.
[0064]
These test results are shown in Tables 13 and 14.
Alloys 73 to 98 corresponding to the examples of the present invention all showed excellent machinability and corrosion resistance. When compared with Comparative Example Alloy 105 (corresponding to the conventional AA6262 alloy), the alloys 73 to 98 have excellent corrosion resistance and machinability. Equal or excellent. Further, the extrudate has no peeling or seizure marks, and the surface properties are good, and the values of extrudability and mechanical properties are within a usable range.
[0065]
[Table 13]

[0066]
[Table 14]

[0067]
On the other hand, the comparative example alloys 99 to 105 are alloys whose compositions are out of the range of the present invention, and any characteristics are inferior to those of the example alloys 73 to 98. That is, alloys 100 and 101 have inferior machinability due to insufficient amount of Si (inferior chipping ability and wrapping of chips), and alloy 104 has inferior corrosion resistance due to excessive amount of Cu, and alloy 105 ( Since AA6262) contains Pb and Bi, the corrosion resistance is further inferior. Further, since the alloy 99 has an excessive amount of Si, the alloy 102 has an excessive amount of Mg, the alloy 103 has an excessive amount of Cr, the alloy 104 has an excessive amount of Cu, and the alloy 106 has an excessive amount of Fe. Each of the alloys 107 is inferior in extrudability because of excessive Zr.
[0068]
[ Example 2 ]
Reference Examples 1 and 2 and Example 1 After polishing the surface of the test material, alumite sulfate was applied, the thickness of the oxide film was 10 μm, and the gloss of the surface was observed. Those having excellent surface gloss were evaluated as ◎, and those having inferior surface were evaluated as ×, and the results were also shown in Tables 4 to 6, 9, 10, 13, and 14. Examples of the present invention and Example of reference invention All the alloys corresponding to the above have excellent surface gloss and excellent anodizing ability.
[0069]
【The invention's effect】
in this way, Aluminum alloy related to Reference Invention 1 Despite the fact that low melting point metals such as Pb and Bi are not used, the machinability is remarkably superior to the conventional 3003 and 3004 alloys, and the mechanical properties, corrosion resistance, cold forgeability, and extrudability Is a non-heat-treatable alloy that is almost equivalent and excellent.
Also, Aluminum alloy related to Reference Invention 2 Is excellent in machinability compared to conventional 5056 alloy, 5052 alloy and 5083 alloy, although it does not use low melting point metals such as Pb and Bi, mechanical properties, corrosion resistance, cold forgeability, It is a non-heat-treatable alloy that is almost equivalent and excellent in extrudability.
In addition, troubles such as wrapping of chips around the tool due to long chips do not occur, and it is possible to achieve cost reduction of the process by adopting cold forging and omitting heat treatment, and also in recyclability Since there is no difficulty, the industrial value is extremely large.
[0070]
On the other hand, the aluminum alloy ( Claims 1-4 ) Outperforms the prior art AA6262 alloy in terms of corrosion resistance and machinability. And since troubles such as wrapping of chips around tools due to long chips do not occur, it is particularly suitable as a material for machine parts created by unmanned operation using automatic machine tools, and in addition, due to low melting point metal Therefore, the industrial value is extremely high as a highly corrosion-resistant aluminum alloy having excellent machinability that can be applied to each application in which the AA6262 alloy was used.
In addition, the aluminum alloy ( Claims 1 to 4 and Reference Inventions 1 and 2) Since the machinability is enhanced without adding Pb or Bi, it is excellent in anodizing ability and can form a homogeneous and glossy anodized film.

Claims

Si: 1.5 to 12.0 mass%, Mg: 0.2 to 1.2 mass%, Cu: 0.15 to 0.25 mass%, respectively, Pb, Bi, and Sn are each 0.05 A highly corrosion-resistant aluminum alloy extruded material excellent in machinability, characterized in that it is not more than mass% and the balance is made of Al and inevitable impurities.

Furthermore, Cr: 0.04-0.35 mass% is contained, The highly corrosion-resistant aluminum alloy extrusion material excellent in the machinability described in Claim 1 characterized by the above-mentioned.

Furthermore, Ti: 0.001-0.05 mass% is contained, The highly corrosion-resistant aluminum alloy extrusion material excellent in the machinability described in Claim 1 or 2 characterized by the above-mentioned.

Furthermore, it contains 1 or more types of Fe: 0.5-1.0 mass%, Zr: 0.1-0.5 mass%, The cutting described in any one of Claims 1-3 characterized by the above-mentioned. High corrosion resistance aluminum alloy extruded material with excellent properties .

An aluminum alloy extruded material for alumite treatment having the chemical composition according to any one of claims 1 to 4.