【０００１】
【産業上の利用分野】
本発明は、Ａｌ基金属鋳造品の熱間等方圧プレス処理法に関し、より詳細には、Ａｌ基金属鋳造品に熱間等方圧プレス処理、溶体化処理およびクエンチ処理を施して所定の強度特性を与えるための熱間等方圧プレス処理法に関し、特に、熱間等方圧プレスと、溶体化および液体クエンチからなる一連の熱処理を簡略化すると共に全体としての工程数を低減し、処理効率を高め得る様に改善された処理技術に関するものである。
【０００２】
なお、本発明において上記Ａｌ基金属鋳造品とは、純Ａｌおよび各種のＡｌ合金よりなる鋳造品が含まれるが、以下の説明では、単にＡｌ鋳造品ということがある。
【０００３】
【従来の技術】
熱間等方圧プレス（ＨＩＰ）法は、鋳造品にしばしばみられる引け巣やガス気孔の除去、セラミックや粉末冶金製品の如き焼結品の内部に残留する気孔の除去などを始めとして広く活用されている。特に鋳造品にＨＩＰ処理を施すと、機械的な強度特性に重大な影響を及ぼす気孔状の欠陥である引け巣やガス気孔を効率よく除去できることから、例えばＮｉ基スーパアロイやＴｉ合金の如き航空機用ジェットエンジンや機体構造部品の製造、軽量化を目標として機体部品や油圧部品などに使用されるＡｌ鋳造品の製造などにも利用されている。
【０００４】
鋳造品の多くは、鋳造後に溶体化処理、クエンチおよび時効処理を施し、鋳造材の微細組織を制御して最適化することで所定の強度特性を与え、最終製品とされる。そして鋳造品にこれらの処理を施す場合は、まずＨＩＰ処理によって引け巣などの内部欠陥をなくした後、溶体化処理やクエンチなどの熱処理を行うのが一般的である。
【０００５】
ところで通常の鋳造材の場合、ＨＩＰ処理温度は溶体化処理温度とほぼ同等であるか、或いはやや低い温度であることから、ＨＩＰ処理のための高温条件下で同時に溶体化処理を済ませることができれば、全体としての熱処理時間を短縮し得ることから、これまでにも幾つかの試みがなされている。ところが実際には、高圧ガスの使用などに起因する様々の問題があり、実現されるまでには至っていない。
【０００６】
技術面での最大の課題は、ＨＩＰ処理で高温に保持した後の冷却速度が遅いため十分なクエンチ（急冷）効果が得られず、冷却過程で合金成分の一部が析出してしまうことである。そのため、ＨＩＰ処理後の冷却速度を高めることによって上記合金成分の析出を回避する方法が検討され、例えば米国特許第５，１２３，８３２号には、１２００℃前後の温度でＨＩＰ処理が行われるＮｉ基あるいはＦｅ基の鋳造品を対象とし、ＨＩＰ装置内での冷却速度を３０〜１００℃／分に高めることによりこの問題を解決すべく、ＨＩＰ装置内で高圧ガスを強制的に対流させる急冷ＨＩＰ装置が開示されている。
【０００７】
こうした急冷ＨＩＰ法をＮｉ基やＦｅ基の合金に適用する場合、クエンチ効果を得るには、ＨＩＰ処理温度である１０００〜１２００℃から４００℃程度までの温度域を急冷すればよく、また合金の種類によっては、３０〜１００℃／分程度の冷却速度でも十分な効果が得られると考えられている。
【０００８】
ところがＡｌ鋳造品の場合は、ＨＩＰ処理温度が５００〜５５０℃程度と低温であるため、ＨＩＰ処理と溶体化処理を兼ねて実施するには、少なくとも１５０℃程度以下の温度域までを１００℃／分以上、好ましくは１０００℃／分以上といった高速で冷却しなければならず、前掲の急冷ＨＩＰ装置では、この様な高レベルの冷却速度を実現することができない。
【０００９】
そこで、ガス以外の圧力媒体を用いた熱間等方圧プレス法も検討されている。たとえば特開２００１−２６２２９５号公報には、Ａｌ鋳造品の如き軽合金鋳物を対象とし、溶体化処理と急冷（クエンチ）および時効処理を組合せて実施する際に、溶体化処理を少なくとも部分的な熱間静水圧プレス法（ＨＩＰ法と同じ）によって同時に行う方法、更には、溶体化処理そのものに熱間静水圧プレス法を採用する方法が開示されている。
【００１０】
ＨＩＰ法は、前述した如く一般に溶体化処理と同等の温度で行われるので、ＨＩＰ処理温度で保持した後の冷却を高速で行うことができれば、ＨＩＰ処理のための熱を利用して同時に溶体化処理を行うことが可能となる。但しこの時に問題となるのは、前述した如く高圧ガスを用いるＨＩＰ法の場合、ＨＩＰ処理温度で保持した後の冷却工程で、熱処理（クエンチ）に必要とされる程の急冷を実現できないことである。
【００１１】
前掲の従来技術では、圧力媒体として溶融塩、即ち液体を使用することで、高圧保持後の減圧（放圧）に要する時間を短縮し、減圧時の温度低下を抑制すると共に、処理品（鋳造品）を収納したバスケットを溶融塩から素早く取り出して急冷工程へ移送する方法が採用されている。なお上記公報では、圧力媒体としてガス加圧も含めた流体を使用し得ることが上位概念で記載されているが、高圧ガスを用いてＨＩＰ処理することの利点と課題については記載されておらず、具体的な条件としては、溶融塩（液状媒体）を用いた液圧ＨＩＰで圧力を７００〜１２００ｂａｒとし、保持時間を１分以内とすることが好ましいと記載されているだけである。換言すると当該公報に開示された方法は、溶融塩（液状媒体）の使用を前提とする熱間等方圧プレス法を開示するだけのものと理解される。
【００１２】
尚、この様な溶融塩を用いたＨＩＰ処理法は、Ａｌ合金の如き軽合金以外の材料も含めて古くから検討されているが、溶融塩の使用に伴う操業上の問題、即ち設備周辺に漏れ出した溶融塩による周辺機器の腐食や環境汚染、更には、処理後の製品の水洗に要する工程数の増大や洗浄排水からの塩の回収、排水の浄化に要する水処理設備の設置などに伴う設備負担など、多くの問題が山積していることもあって、実用化されるまでに至っていない。今後ますます厳しさを増すことが予測される環境問題を考えると、溶融塩の使用を必須とする上記方法は好ましい方法とは言い難い。
【００１３】
【発明が解決しようとする課題】
本発明は上記の様な従来技術に指摘される問題に鑑みてなされたものであり、その目的は、鉄基金属などに較べて比較的低い温度域でＨＩＰ処理や溶体化処理が行われるＡｌ基金属鋳造品を対象とし、圧力媒体として溶融塩の如き液体を使用するのではなく、処理が簡単で環境問題を起こすことのないガスを圧力媒体とするＨＩＰ法によって、引け巣などの解消と溶体化処理、更にはクエンチ処理を含めた一連の工程を簡単に且つ効率よく遂行し得るような技術を確立することにある。
【００１４】
【課題を解決するための手段】
上記課題を解決することのできた本発明にかかるＡｌ基金属鋳造品の熱間等方圧プレス処理法とは、ガスを圧力媒体としてＡｌ基金属鋳造品にＨＩＰ処理を施し、内部の引け巣やガス気孔を消滅させる方法であって、Ａｌ基金属鋳造品を、Ａｌ基金属に対し非反応性で且つ通気・通液性を有する低伝熱性無機材料で被包した状態で加熱・加圧してＨＩＰ処理および溶体化処理を行った後、降圧してＨＩＰ装置から取り出し、クエンチ用冷媒に浸漬して急冷するところに特徴を有している。
【００１５】
この方法を実施する際のより具体的な手法としては、▲１▼上記通気・通液性の低伝熱性無機材料として、セラミック繊維材からなる不織布やフエルト、ウエッブ、シート、ブランケット、マットなどを使用し、Ａｌ基金属鋳造品をこれらのセラミック繊維材で被包した状態でＨＩＰ処理、溶体化処理およびクエンチ処理を行う方法、および、▲２▼前記通気・通液性の低伝熱性無機材料として、低伝熱性のセラミック粒子を使用し、該セラミック粒子を通液性容器内に装入すると共に、該セラミック粒子群にＡｌ基金属鋳造品を埋没させた状態で、ＨＩＰ処理、溶体化処理およびクエンチ処理を行う方法が好ましい方法として推奨される。
【００１６】
【発明の実施の形態および実施例】
上記の様に本発明では、ガスを圧力媒体としてＡｌ基金属鋳造品（以下、再びＡｌ鋳造品という）にＨＩＰ処理を施し、内部の引け巣やガス気孔を消滅させる際に、Ａｌ鋳造品を、Ａｌ基金属に対し非反応性で且つ通気・通液性を有する低伝熱性無機材料で被包した状態でＨＩＰ装置内へ装入し、加熱・加圧してＨＩＰ処理および溶体化処理を行った後、降圧してＨＩＰ装置から取り出し、クエンチ用冷媒に浸漬して急冷するところに特徴を有するもので、具体的な実施態様としては、
▲１▼前記通気・通液性を有する低伝熱性の無機材料として、セラミック繊維からなる不織布、フエルト、ウエッブ、シート、ブランケット、マットなどを用いる方法と、
▲２▼石英ビーズの如き低伝熱性のセラミック粒子を用いる方法
の２つの態様が例示される。
【００１７】
いずれの方法を採用するにしても、ＨＩＰ処理のための高圧ガス雰囲気下では、上記無機材料が有している通気性によって圧縮媒体ガスの十分な自然対流が確保され、処理品（Ａｌ鋳造品）を効率よく加熱することができる。また、ＨＩＰ処理の後に、例えば水の如き冷媒クエンチのために処理品を大気圧下でクエンチ槽へ移送する際には、空隙が多く低伝熱性の無機材料が有している断熱・保温性が活かされ、処理品がＨＩＰ処理温度（溶体化処理温度）から急速に降温するのを可及的に抑制する。
【００１８】
即ち本発明では、Ａｌ鋳造品を通気・通液性の低伝熱性無機材料で被包した状態でＨＩＰ装置内へ装入し、所定温度まで昇温すると共に所定圧力までガス加圧することによってＨＩＰ処理を行うが、このＨＩＰ処理工程では、Ａｌ鋳造品を被包している無機材料は空隙率が高く高通気・通液性であるから、高圧ガスは該無機材料層内で十分に対流し、Ａｌ鋳造品は均一に加熱される。よって、ＨＩＰ処理による圧密化（引け巣や空隙の解消）は効率よく進行する。
【００１９】
また、該ＨＩＰ処理のための加熱を溶体化処理のための熱としても有効に活用することが有効であることは、先に説明した通りである。ところが、前掲の従来技術でも指摘した通り、ＨＩＰ処理や溶体化処理が比較的低い温度域で行われるＡｌ鋳造品の場合は、ＨＩＰ処理後に大気圧まで放圧してからクエンチ設備まで移送するまでの間で放熱によってかなり高温するため、所定の急冷効果が得られ難くなる。
【００２０】
ところが本発明の場合、前述の如くＡｌ鋳造品は、通気・通液性の低伝熱性無機材料で被包した状態でＨＩＰ装置内へ装入されており、ＨＩＰ処理後に放圧して同装置から取り出したときでも、Ａｌ鋳造品は上記低伝熱性無機材料で被包されて保温されているので、移送時の降温が可及的に防止される。そのため、ＨＩＰ処理と並行して当該温度での溶体化処理を施した場合でも、当該処理温度を実質的に保持した状態でクエンチ設備まで移送することができ、その後直ちにクエンチ用液体槽に浸漬することで、十分なクエンチ効果が保証される。尚、Ａｌ鋳造品を被包している前記無機材料は前述の如く空隙率の高い通気・通液性素材であるから、クエンチ用液体に浸漬したときは直ちに液体の浸入を許し、内部のＡｌ鋳造品は急冷される。よって、被包した無機材料がＡｌ鋳造品に対するクエンチ（急冷）効果を損なう恐れもない。
【００２１】
以下、本発明を実施する際のより具体的な構成を、先に掲げた２つの好ましい実施形態を例にとって詳細に説明していく。
【００２２】
本発明における第１の好ましい実施形態では、Ａｌ鋳造品にＨＩＰ処理を施して内部の引け巣やガス気孔を消滅させる際に、Ａｌ鋳造品をセラミック繊維からなる不織布やフエルト、ウエッブ、シート、ブランケット、マットなどで被包しておき、ＨＩＰ処理時に当該処理温度と圧力を保持すると共に、ＨＩＰ装置内の温度を溶体化処理温度に保って同時に溶体化処理を行う。そして、当該温度を保持したままで圧縮媒体ガスを回収・放出して装置内を大気圧に戻し、次いで、セラミック繊維材からなる不織布やフエルトなどで被包されたＡｌ鋳造品をＨＩＰ装置から取り出し、水等のクエンチ用液状冷媒に浸漬することによりクエンチ処理を行う。
【００２３】
液状冷媒としては、水の他、鉱物油等の各種油などを使用することも可能であるが、クエンチ後の処理の簡便性、冷媒に要するコスト、急冷効果等を総合的に考慮して最も一般的なのは水である。しかし本発明は、もとより冷媒として水を用いたクエンチ（急冷）のみに限定されるわけではない。
【００２４】
この方法を実施するに当り「Ａｌ基金属に対し非反応性で且つ通気・通液性を有する低伝熱性無機材料でＡｌ鋳造品を被包する」ことによる作用効果を主体にして説明を進める。
【００２５】
ＨＩＰ処理の圧縮媒体ガスとして一般的に使用されるアルゴンや窒素などは、Ａｌ鋳造品をＨＩＰ処理する際の一般的な条件である例えば５００〜５５０℃、１００ＭＰａといった温度・圧力条件下では極めて流動性に富んだ流体であり、温度による密度変化も大きいことから、少しの温度差でも激しい自然対流現象を生じる。そのため、Ａｌ鋳造品の周囲に部分的な温度分布が生じたとしても、ＨＩＰ装置内でガスの自然対流が保証される限り、Ａｌ鋳造品は確実に灼熱される。
【００２６】
しかも、それらの圧縮媒体ガスは粘性が極めて低いため、大気圧下では気体に対する流動抵抗が問題となる様な状況、例えば連通気孔を有する素材や通気・通液性繊維材などで被包された状態であっても、それら通気性材料によって圧縮媒体ガスの自然対流が阻害する程度は極めて少ない。また、セラミック繊維からなる不織布やフエルトなどは一般に空隙率が非常に高く、全体としての空隙率は通常９０％以上、更には９５％程度以上であり、ガスに対する流動抵抗が小さく且つ繊維自体の熱容量も小さいので、Ａｌ鋳造品をこの様な繊維材で被包したとしても、高圧ガス雰囲気下で内部のＡｌ鋳造品の加熱が大きく阻害されることはない。
【００２７】
一方、大気圧雰囲気下では、外部を被包する空隙率の高い低伝熱性のセラミック繊維材が、高温に保持された内部のＡｌ鋳造品に対して優れた保温効果を発揮する。本発明に係る第１の発明では、この様な高圧ガスの特性と、セラミック繊維材料からなる不織布やマットなどが有する特徴を活用するところに最大の特徴を有している。
【００２８】
以下、図を参照しつつ上記実施形態について具体的に説明していく。
【００２９】
図１は、処理品（Ａｌ鋳造品）１をセラミック繊維材２からなる不織布やフエルト、ブランケットなどで覆った状態を模式的に示したものである。セラミック繊維材２としては、Ａｌ鋳造品の一般的なＨＩＰ処理温度である５００〜５５０℃の温度域でＡｌ基金属に対して非反応性で且つ耐熱性を有し、更に低伝熱性の素材であれば特に制限なく使用できるが、好ましいものとしては、アルミナ−シリカ系のガラス状繊維、珪酸カルシウム繊維、純アルミナ繊維やジルコニア繊維の如き各種セラミック繊維、石綿などが挙げられる。
【００３０】
これらのうち市販品として入手することのできる好ましいセラミック繊維材としては、例えばイソライト工業社製の商品名「カオウール」等が挙げられる。これらは、厚さ６ｍｍ程度の繊維質ブランケットが標準品として入手可能であるが、これを薄く削いで３ｍｍ程度の厚さとすれば、本発明の目的に十分適合できる。
【００３１】
この様なセラミック繊維材で処理品（Ａｌ鋳造品）を被包し、例えばステンレス等の針金で縛って固定する。この様にして準備した多数のＡｌ鋳造品をバスケット内へ装入し、ＨＩＰ処理に供される。
【００３２】
セラミック繊維材の空隙率は大きいが、前述した如く大気圧条件下では、空気または圧縮媒体ガスの密度が低く且つ単位体積当りの比熱も小さいため、温度差があっても生じるガスの自然対流は弱く、また低伝熱性であるため、大気圧条件下では高い断熱効果を発揮する。一方、該セラミック繊維材は空隙率が高く通気・通液性に富んでおり、高圧ガス雰囲気下では温度差による自然対流を起こすため、断熱効果は大きく低下する。本発明では、こうしたセラミック繊維材が有している伝熱特性をうまく活用する点に大きな特徴がある。
【００３３】
実際に採用される処理工程の代表例は、例えば図２に示す通りであり、本例では、溶体化処理をＨＩＰ処理工程で併せて実施する。一般に、Ａｌ鋳造品の溶体化処理は５３０℃前後の温度で６〜１０時間程度保持することによって行われ、この溶体化処理では、鋳造時に析出した成分を均質化すること、特に、鋳造時の冷却で析出した針状析出物の尖った部分を丸く鈍化させることに主眼が置かれる。
【００３４】
一般に、Ａｌ鋳造品中に含まれる析出物の母材（マトリックス）への固溶量は高圧力下で増大する傾向があるので、ＨＩＰ処理のための高圧条件下で同時に溶体化処理を行うと、大気圧条件下で溶体化処理を行う場合に較べると処理時間を短縮することが可能となる。たとえばＡｌ−Ｓｉ系合金の場合、大気圧下でのＳｉの固溶量は最大で１．５原子％であるが、１００ＭＰａでは１．９原子％、２００ＭＰａでは２．４原子％にまで増加する。このため、溶体化処理を大気圧（常圧）で行う場合、上記の様に５３０℃前後の温度で６〜１０時間程度保持しなければならないが、１００〜２００ＭＰａといった通常のＨＩＰ処理圧力で溶体化処理を行うと、同程度の温度（５３０℃前後）でも２〜３時間程度で十分な溶体化処理効果を得ることが可能となる。
【００３５】
図２に例示した処理工程について説明すると、先ず、例えば前記図１に示した如くセラミック繊維材で被包した複数の処理品（Ａｌ鋳造品）を、バスケットなど任意の通気・通液性容器に入れてＨＩＰ装置内へ装入し、真空引き・ガス置換を行う。次いでＨＩＰ装置内を昇温しつつ高圧ガスを吹き込んで昇圧し、例えば５００〜５３０℃、５０〜２００ＭＰａの保持条件で１〜４時間程度保持する。高圧ガスとしては、アルゴンや窒素などが一般的に使用されるが、これらに限られるわけではなく、これらの混合ガスや乾燥空気等を使用することも可能である。
【００３６】
このとき、Ａｌ鋳造品を被包しているセラミック繊維材は、前述の如く空隙率が高く且つ通気・通液性の高いものであり、また高圧力条件下では熱伝達を阻害することもないので、内部のＡｌ鋳造品に対する高圧ガスの加圧（圧密化）作用や均熱作用が損なわれることもなく、Ａｌ鋳造品は通常の方法と実質的に同程度の時間で十分に圧密化され、引け巣や空孔欠陥は解消される。
【００３７】
この温度・圧力の保持期間中、Ａｌ鋳造品の圧密化が進行すると共に、前述した如く高圧の高温条件下で溶体化処理も同時に進行するので、該温度・圧力での保持時間を例えば２〜３時間程度に設定すれば、この間に圧密化と溶体化のための加熱処理を同時に進めることができる。
【００３８】
その後、例えば５００〜５３０℃のＨＩＰ処理温度（および溶体化処理温度）を保持したままで、高圧ガスを抜いてＨＩＰ装置内の圧力を大気圧まで降下させる。その後、直ちにＨＩＰ装置からＡｌ鋳造品を取り出し、クエンチのための液状冷媒槽の上方へ素早く移送して液状冷媒中にＡｌ鋳造品を落下・浸漬させてクエンチ（急冷）を行う。
【００３９】
ところで、高圧ガスを用いたＨＩＰ処理を終えたＡｌ鋳造品を大気に曝したままの状態でＨＩＰ装置から取り出して移送すると、特に薄肉の鋳造品ではこの移送作業を素早く行ったとしても、Ａｌ鋳造品の表面温度は直ぐに５０℃程度は低下し、表面と内部で温度差ができる。そのため、該温度差を有する状態で液状冷媒槽内へ投入してクエンチを行うと、急冷開始温度の違いによってクエンチ効果に差異が生じ、クエンチ後の物性の均質性が損なわれる。また薄物のＡｌ鋳造品では、上記搬送工程での放熱によって鋳造品全体の温度が大幅に低下し、クエンチ効果自体が著しく損なわれる恐れも生じてくる。
【００４０】
ところが、上記の様にＡｌ鋳造品をセラミック繊維材で被包しておくと、大気雰囲気中で当該セラミック繊維材が発揮する断熱・保温作用によって移送時の温度降下が抑えられ、Ａｌ鋳造品の表面と内部の温度差が低減する他、鋳造品全体としての降温も可及的に抑えられるので、冷媒クエンチ後の物性を可及的に均質に保持し得ると共に、安定して十分な急冷クエンチ効果を確保することが可能となる。尚セラミック繊維材は、低密度で通気・通液性（水の浸透性）が大きく且つ熱容量も小さいので、液状冷媒を用いたクエンチの際の急冷効果も殆ど損なわれることがない。
【００４１】
図３は本発明の他の処理パターンを例示するもので、この例では、溶体化処理の大半を大気圧下の溶体化処理炉で行う。即ち、前記と同様にしてＡｌ鋳造品をセラミック繊維材で被包しておき、この状態で溶体化処理炉へ装入してから昇温し所定時間（たとえば５時間程度）保持する。その後、Ａｌ鋳造品を高温に保った状態で溶体化処理炉から取り出してＨＩＰ装置方向へ移送し、該装置内へ装入する。この時も、移送中におけるＡｌ鋳造品の温度降下は、被包したセラミック繊維材の有する断熱・保温効果によって最小限に抑えられる。もっとも、移送時間を極力短縮することが望ましいことは当然である。
【００４２】
次いで、直ちにＨＩＰ装置内へＨＩＰ用ガスを注入してＨＩＰ処理を行う。この時、ＨＩＰ用ガスの断熱圧縮によって温度が若干変動する恐れもあるので、こうした温度変動を極力抑えて均一な溶体化処理温度を確保するには、例えばＨＩＰ装置の処理室内に均熱化用のガス撹拌ファンを設けてガスを撹拌することが望ましい。そして、加圧状態で例えば１〜１５分程度保持してＡｌ鋳造品を圧密化した後、前記図２の場合と同様に溶体化処理温度およびＨＩＰ処理温度を保ったままで放圧してＡｌ鋳造品を取り出し、冷媒クエンチ処理を行う。この間のＡｌ鋳造品は、前記と同様セラミック繊維材で保温されているため移送時の温度降下は可及的に抑えられ、且つ該セラミック繊維材は高い通気・通液性と空隙率を有しているので冷媒クエンチ時は直ちに液状冷媒の浸入を許し急冷効果を損なうこともない。
【００４３】
この様にＡｌ鋳造品をセラミック繊維材で被包しておけば、冷媒クエンチに際し冷媒槽へＡｌ鋳造品を落下投入するときにも、該セラミック繊維材が緩衝材として機能するため、Ａｌ鋳造品の機械的な損傷や傷の発生が抑制されるという副次的な効果も期待される。
【００４４】
次に、本発明を実施する際のもう一つの態様である「無機材料として低伝熱性のセラミック粒子を使用し、該セラミック粒子を通液性容器内に装入すると共に、該セラミック粒子群にＡｌ鋳造品を埋没させた状態で、ＨＩＰ処理、溶体化処理およびクエンチ処理を行う方法」を実施する際にも、高圧ガスによるＡｌ鋳造品の加熱・加圧作用、および大気圧下でＡｌ鋳造品を移送する際の保温効果、更には、液状冷媒クエンチ時における急冷効果などについては、前掲のセラミック繊維材でＡｌ鋳造品を被包して行う場合と実質的に同じ作用効果が得られる。しかしこの態様では、下記の付加的作用も得ることができるので好ましい。
【００４５】
即ちこの態様を実施する場合、通常は、例えば金網製のバスケット等にＡｌ鋳造品を装入し、その周りに低伝熱性のセラミック粒子を充填するという形態で実施されるため、常にバスケット等で多数のＡｌ鋳造品を搬送することとなり、多数個のＡｌ鋳造品の処理を同時に行うことができるので極めて効率的である。
【００４６】
尚この際に使用されるセラミック粒子としては、低伝熱性で且つ集合体として十分な通気・通液性を有するものであれば、その種類や形状などは特に制限されないが、中でも特に好ましいのは直径１ｍｍ弱から数ｍｍの球体であり、この様なサイズの球体であれば、充填率が高くてＨＩＰ処理時の余分な空間（デッドスペース）を低減でき、圧縮媒体ガスの使用量を低減し得るといった利点も享受できる。
【００４７】
また、セラミック粒子として石英ビーズを使用すると、▲１▼当該石英ビーズの卓越した低伝熱性が有効に活かされて優れた保温効果が得られる、▲２▼比重が２．２程度と軽量でハンドリングが容易である、▲３▼熱容量が他のセラミック粒子よりも小さいためクエンチ時の過大な冷媒（水など）の蒸発を回避できる、▲４▼熱膨張率が小さいため５００℃程度の温度から例えば水クエンチしても熱衝撃によるビーズの破損が少なく繰返し使用が可能である、といった数々の利点が有効に発揮されるので特に好ましい。
【００４８】
尚セラミック粒子としては、上述したビーズ状（球状）のものが一般的であるが、この他、例えば蒸留などで充填材として使用されるセラミック質のラシヒリングや鞍なども、通気性と通液性を有し且つ大気雰囲気で断熱作用を発揮する点ではセラミックビーズと同様の効果を有するので、同様に活用できる。
【００４９】
【発明の効果】
本発明は以上の様に構成されており、Ａｌ合金鋳造品のＨＩＰ処理を、（溶体化処理＋クエンチ＋時効処理）からなる一連の組合せとして実施することができ、ＨＩＰ処理後に再加熱して溶体化処理を行っていた従来法に較べて、再加熱による溶体化処理が不要になるばかりか、高圧下のＨＩＰ処理で併せて溶体化処理を行うことで溶体化処理時間を大幅に短縮できる。
【００５０】
また、ＨＩＰ処理による通常の作用効果として、引け巣や気孔の消滅による延性・疲労寿命などの改善は勿論のこと、針状析出物の存在が原因と考えられている疲労寿命の低下を効果的に防止することができ、極めて信頼性の高いＡｌ鋳造品を提供できる。更に、ＨＩＰ処理＋溶体化処理＋急冷クエンチの一連の作業に要する時間を著しく短縮することができ、ひいては生産性の大幅な向上と製造コストの低減が可能となる。
【００５１】
より具体的には、本発明を活用したＡｌ鋳造品専用のＨＩＰ装置を使用することで、従来から実施されている［ＨＩＰ処理＋溶体化処理＋急冷クエンチ］の一連の作業に要する処理コストの１／５程度以下、更には１／１０程度以下にまで低減することも可能となる。その結果、従来は処理コスト面の制約から実用化が困難とされてきた自動車用Ａｌ鋳造品に対しても、上記［ＨＩＰ処理＋溶体化処理＋急冷クエンチ］からなる改質技術の適用の道が拓けることとなる。
【００５２】
更には、前述したＡｌ鋳造品の物性改善効果により、Ａｌ鋳造部品の安全設計面も考慮した部品の薄肉化が容易になり、自動車部品の軽量化およびこれに関連する省エネルギー化や排気ガス低減などにも寄与できる。また本発明は、自動車部品に限らず、車両、船舶、航空機材料、更には家電製品用のパネル材等として利用されるＡｌ鋳造品の製造に幅広く有効に活用できる。
【００５３】
加えて本発明によれば、従来例では［ＨＩＰ処理＋溶体化処理＋急冷クエンチ］からなる一連の処理効果を確保することの必要上、その採用を余儀なくされていた溶融塩の使用に伴う作業の煩雑性や環境問題、廃液処理などの問題を起こす恐れもなく、ガスを圧縮媒体とする非常にクリーンなプロセスであることから、今後の環境問題への要請にも応え得る極めて有用な方法である。
【図面の簡単な説明】
【図１】本発明を実施する際に、繊維質ブランケットを用いたＡｌ鋳造品の被包例を示す説明図である。
【図２】本発明の一実施例を示す工程説明図である。
【図３】本発明の他の実施例を示す工程説明図である。
【符号の説明】
１ Ａｌ基金属鋳造品
２ セラミック繊維材[0001]
[Industrial applications]
The present invention relates to a hot isostatic pressing method for an Al-based metal casting, and more specifically, to a hot isostatic pressing, a solution treatment, and a quench treatment for an Al-based metal casting to perform a predetermined process. Regarding the hot isostatic pressing method to give strength properties, in particular, hot isostatic pressing, and simplify the series of heat treatment consisting of solution and liquid quench and reduce the number of steps as a whole, The present invention relates to an improved processing technique so as to increase processing efficiency.
[0002]
In the present invention, the above-mentioned Al-based metal casting includes a casting made of pure Al and various Al alloys, but in the following description, may be simply referred to as an Al casting.
[0003]
[Prior art]
The hot isostatic pressing (HIP) method is widely used for removing shrinkage cavities and gas porosity often found in cast products, and removing pores remaining inside sintered products such as ceramics and powder metallurgy products. Have been. In particular, when a cast product is subjected to HIP treatment, shrinkage cavities and gas pores, which are pore-like defects that have a significant effect on mechanical strength properties, can be efficiently removed. For example, for aircraft such as Ni-based superalloys and Ti alloys It is also used in the manufacture of jet engines and airframe structural parts, and in the manufacture of aluminum castings used in airframe parts and hydraulic parts for the purpose of weight reduction.
[0004]
Many cast products are subjected to a solution treatment, a quench and an aging treatment after casting to give a predetermined strength characteristic by controlling and optimizing a microstructure of a cast material, thereby being a final product. When these processes are performed on a cast product, it is common to first remove internal defects such as shrinkage cavities by a HIP process and then perform a heat treatment such as a solution treatment or a quench.
[0005]
By the way, in the case of a normal cast material, since the HIP treatment temperature is almost equal to or slightly lower than the solution treatment temperature, if the solution treatment can be completed simultaneously under high temperature conditions for the HIP treatment. Some attempts have been made to reduce the heat treatment time as a whole. However, in practice, there are various problems caused by the use of high-pressure gas and the like, and they have not been realized yet.
[0006]
The biggest technical problem is that the cooling rate after holding at a high temperature in the HIP process is slow, so that a sufficient quenching (quenching) effect cannot be obtained, and some of the alloy components precipitate during the cooling process. is there. Therefore, a method of avoiding the precipitation of the alloy component by increasing the cooling rate after the HIP processing has been studied. For example, in US Pat. No. 5,123,832, Ni is used in which the HIP processing is performed at a temperature of about 1200 ° C. In order to solve this problem by increasing the cooling rate in the HIP apparatus to 30 to 100 ° C./min, the quenching HIP in which the high-pressure gas is forcibly convected in the HIP apparatus is intended for the base material or the Fe-based casting. An apparatus is disclosed.
[0007]
When such a quenching HIP method is applied to a Ni-based or Fe-based alloy, a quenching effect can be obtained by quenching the temperature range from 1000 to 1200 ° C., which is the HIP processing temperature, to about 400 ° C. Depending on the type, it is considered that a sufficient effect can be obtained even at a cooling rate of about 30 to 100 ° C./min.
[0008]
However, in the case of an Al casting, since the HIP processing temperature is as low as about 500 to 550 ° C., in order to carry out both the HIP processing and the solution treatment, the temperature must be at least 100 ° C./150° C. or less. Cooling must be performed at a high speed of at least 1000 ° C./minute or more, and preferably at a high speed of 1000 ° C./minute or more.
[0009]
Therefore, a hot isostatic pressing method using a pressure medium other than gas is also being studied. For example, Japanese Patent Application Laid-Open No. 2001-262295 discloses that, when a light alloy casting such as an Al casting is used and a solution treatment, a quenching, and an aging treatment are combined, the solution treatment is performed at least partially. There is disclosed a method which is performed simultaneously by a hot isostatic pressing method (same as the HIP method), and a method which employs a hot isostatic pressing method for the solution treatment itself.
[0010]
As described above, since the HIP method is generally performed at the same temperature as the solution treatment, if the cooling at a high temperature after holding at the HIP treatment temperature can be performed at a high speed, the heat treatment for the HIP treatment is used to simultaneously perform the solution treatment. Processing can be performed. However, a problem at this time is that in the case of the HIP method using a high-pressure gas as described above, in the cooling step after holding at the HIP processing temperature, rapid cooling required for heat treatment (quenching) cannot be realized. is there.
[0011]
In the above-mentioned prior art, by using a molten salt, that is, a liquid as a pressure medium, the time required for decompression (pressure release) after holding at a high pressure is reduced, the temperature decrease at the time of decompression is suppressed, and the processed product (casting) is reduced. Is quickly removed from the molten salt and transferred to a quenching step. In the above-mentioned publication, although it is described in a general concept that a fluid including gas pressurization can be used as a pressure medium, the advantages and problems of performing the HIP treatment using a high-pressure gas are not described. As specific conditions, it is only described that it is preferable to set the pressure to 700 to 1200 bar by a hydraulic HIP using a molten salt (liquid medium) and to keep the holding time within 1 minute. In other words, it is understood that the method disclosed in this publication only discloses a hot isostatic pressing method based on the use of a molten salt (liquid medium).
[0012]
The HIP treatment method using such a molten salt has been studied for a long time, including materials other than light alloys such as Al alloys. Corrosion of peripheral equipment and environmental pollution due to leaked molten salt, as well as increase in the number of steps required for washing products after treatment, recovery of salt from washing wastewater, installation of water treatment equipment required for purification of wastewater, etc. Many problems, such as the associated equipment burden, are piled up and have not yet been put to practical use. Given the environmental problems that are expected to become increasingly severe in the future, the above-mentioned method, which requires the use of a molten salt, cannot be said to be a preferable method.
[0013]
[Problems to be solved by the invention]
The present invention has been made in view of the problems pointed out in the prior art as described above, and an object of the present invention is to provide an HIP treatment or solution treatment in a relatively low temperature range as compared with an iron-based metal or the like. For the base metal castings, instead of using a liquid such as a molten salt as a pressure medium, it is possible to eliminate shrinkage cavities and the like by using the HIP method that uses a gas that is easy to process and does not cause environmental problems as a pressure medium. It is an object of the present invention to establish a technique that can easily and efficiently perform a series of steps including a solution treatment and a quench treatment.
[0014]
[Means for Solving the Problems]
The hot isostatic pressing method for an Al-based metal casting according to the present invention, which has been able to solve the above-mentioned problems, is to perform a HIP treatment on an Al-based metal casting using a gas as a pressure medium and to form an internal shrinkage cavity or the like. A method for eliminating gas pores, in which an Al-based metal casting is heated and pressurized in a state of being covered with a low heat conductive inorganic material that is non-reactive with an Al-based metal and has ventilation and liquid permeability. It is characterized in that after performing HIP treatment and solution treatment, the pressure is lowered and taken out from the HIP device, immersed in a quenching refrigerant and rapidly cooled.
[0015]
As a more specific method for carrying out this method, (1) nonwoven fabrics, felts, webs, sheets, blankets, mats, etc. made of ceramic fiber material are used as the above-mentioned air-permeable and liquid-permeable low heat conductive inorganic materials. A HIP treatment, a solution treatment, and a quenching treatment in a state in which an Al-based metal casting is covered with these ceramic fiber materials, and (2) the low-heat-conductive inorganic material having air permeability and liquid permeability. HIP treatment and solution treatment in a state where ceramic particles having low heat conductivity are used, and the ceramic particles are charged into a liquid-permeable container, and an Al-based metal casting is buried in the ceramic particles. And a method of performing a quench treatment is recommended as a preferable method.
[0016]
Embodiments and Examples of the Invention
As described above, in the present invention, an Al-based metal casting (hereinafter, again referred to as an Al casting) is subjected to HIP processing using a gas as a pressure medium to eliminate internal shrinkage cavities and gas pores. In a state of being encapsulated with a low heat conductive inorganic material that is non-reactive with an Al-based metal and has air permeability and liquid permeability, it is charged into a HIP device, and heated and pressurized to perform HIP treatment and solution treatment. After that, the pressure is reduced and taken out of the HIP device, and it is characterized in that it is immersed in a quenching refrigerant and quenched, and as a specific embodiment,
(1) A method using a nonwoven fabric, felt, web, sheet, blanket, mat, or the like made of ceramic fiber as the low heat conductive inorganic material having air permeability and liquid permeability;
(2) Method using ceramic particles having low heat conductivity such as quartz beads
Are exemplified.
[0017]
Regardless of which method is adopted, in the high-pressure gas atmosphere for the HIP treatment, sufficient natural convection of the compression medium gas is secured by the air permeability of the inorganic material, and the treated product (Al cast product) ) Can be efficiently heated. In addition, after the HIP treatment, when the treated product is transferred to the quench tank under atmospheric pressure for the purpose of quenching a refrigerant such as water, for example, the heat insulating and heat insulating properties of the inorganic material having many voids and having low heat conductivity are possessed. Is used to suppress the temperature of the treated product from rapidly decreasing from the HIP treatment temperature (solution treatment temperature) as much as possible.
[0018]
That is, in the present invention, the Al casting is charged into the HIP device in a state of being wrapped with a low heat conductive inorganic material having ventilation and liquid permeability, and is heated to a predetermined temperature and gas-pressurized to a predetermined pressure. In this HIP process, the inorganic material enclosing the Al casting has a high porosity and high air permeability and liquid permeability, so that the high-pressure gas is sufficiently convected in the inorganic material layer. , Al castings are uniformly heated. Therefore, the compaction (elimination of shrinkage cavities and voids) by the HIP process proceeds efficiently.
[0019]
As described above, it is effective to effectively utilize the heating for the HIP treatment also as the heat for the solution treatment. However, as pointed out in the above-mentioned prior art, in the case of an Al cast product in which the HIP treatment and the solution treatment are performed in a relatively low temperature range, after the HIP treatment, the pressure is released to the atmospheric pressure and then transferred to the quench equipment. Since the temperature rises considerably due to heat radiation between them, it is difficult to obtain a predetermined quenching effect.
[0020]
However, in the case of the present invention, as described above, the Al casting is charged into the HIP device in a state of being wrapped with the air-permeable and liquid-permeating low-thermal-conductivity inorganic material. Even when the aluminum casting is taken out, the aluminum casting is covered with the low-heat-conductivity inorganic material and kept warm, so that the temperature during transfer is prevented as much as possible. Therefore, even when the solution treatment at the temperature is performed in parallel with the HIP treatment, the solution can be transferred to the quench facility while substantially maintaining the processing temperature, and immediately thereafter, immersed in the quench liquid tank. This ensures a sufficient quench effect. Since the inorganic material enclosing the Al casting is a gas-permeable and liquid-permeable material having a high porosity as described above, when immersed in a quench liquid, the liquid is immediately allowed to enter, and the internal Al The casting is quenched. Therefore, the encapsulated inorganic material does not impair the quench (quenching) effect on the Al casting.
[0021]
Hereinafter, a more specific configuration for carrying out the present invention will be described in detail by taking the two preferred embodiments described above as examples.
[0022]
In the first preferred embodiment of the present invention, when an Al casting is subjected to HIP treatment to eliminate shrinkage cavities and gas pores therein, the Al casting is made of a nonwoven fabric made of ceramic fiber, a felt, a web, a sheet, a blanket. And a mat or the like, and the processing temperature and pressure are maintained during the HIP processing, and the solution treatment is performed simultaneously while maintaining the temperature in the HIP apparatus at the solution processing temperature. Then, while maintaining the temperature, the compressed medium gas is recovered and released to return the inside of the apparatus to the atmospheric pressure. Then, the Al cast product wrapped with the nonwoven fabric made of ceramic fiber material or felt is taken out of the HIP apparatus. The quenching treatment is performed by immersing in a quench liquid refrigerant such as water.
[0023]
As the liquid refrigerant, it is possible to use various oils such as mineral oil in addition to water, but it is most preferable to comprehensively consider the simplicity of processing after quenching, the cost required for the refrigerant, the quenching effect, and the like. Common is water. However, the present invention is not necessarily limited to quench (quenching) using water as a cooling medium.
[0024]
In implementing this method, description will be made mainly on the operation and effect of "encapsulating the Al casting with a low heat conductive inorganic material which is non-reactive with the Al-based metal and has air permeability and liquid permeability". .
[0025]
Argon, nitrogen, and the like generally used as a compression medium gas in the HIP process flow extremely under the temperature and pressure conditions of 500 to 550 ° C. and 100 MPa, which are the general conditions for the HIP process of an Al casting. Since it is a highly fluid and its density changes greatly with temperature, even a slight temperature difference causes severe natural convection. Therefore, even if a partial temperature distribution occurs around the Al casting, the Al casting is surely burned as long as natural convection of gas is ensured in the HIP device.
[0026]
Moreover, since these compressed medium gases have extremely low viscosity, they are wrapped with a material that has a problem of flow resistance to the gas under the atmospheric pressure, for example, a material having continuous ventilation holes or a gas-permeable / liquid-permeable fiber material. Even in the state, the degree to which the natural convection of the compressed medium gas is hindered by these air-permeable materials is extremely small. Non-woven fabrics and felts made of ceramic fibers generally have a very high porosity, and the porosity as a whole is usually 90% or more, more preferably about 95% or more, the flow resistance to gas is small, and the heat capacity of the fibers themselves is small. Therefore, even if the Al casting is covered with such a fibrous material, the heating of the Al casting inside in a high-pressure gas atmosphere is not greatly hindered.
[0027]
On the other hand, under the atmospheric pressure atmosphere, the ceramic fiber material having a high porosity and enclosing the outside and having a high porosity exerts an excellent heat retaining effect on the internal Al castings held at a high temperature. The first invention according to the present invention has the greatest feature in utilizing the characteristics of such a high-pressure gas and the features of a nonwoven fabric or mat made of a ceramic fiber material.
[0028]
Hereinafter, the above embodiment will be described in detail with reference to the drawings.
[0029]
FIG. 1 schematically shows a state in which a processed product (Al cast product) 1 is covered with a nonwoven fabric, felt, blanket, or the like made of a ceramic fiber material 2. The ceramic fiber material 2 is a material which is non-reactive and heat-resistant to Al-based metals in a temperature range of 500 to 550 ° C., which is a general HIP processing temperature of an Al casting, and has a low heat conductivity. As long as it is used, there is no particular limitation, but preferred examples include alumina-silica-based glassy fibers, calcium silicate fibers, various ceramic fibers such as pure alumina fibers and zirconia fibers, and asbestos.
[0030]
Among these, as a preferable ceramic fiber material which can be obtained as a commercial product, for example, Kao Wool (trade name, manufactured by Isolite Industries, Ltd.) and the like can be mentioned. Although a fiber blanket having a thickness of about 6 mm is available as a standard product, it can be adequately adapted to the object of the present invention by shaving it into a thickness of about 3 mm.
[0031]
The processed product (Al cast product) is wrapped with such a ceramic fiber material, and tied and fixed with a wire such as stainless steel. A large number of Al castings prepared as described above are charged into a basket and subjected to HIP processing.
[0032]
Although the porosity of the ceramic fiber material is large, as described above, under atmospheric pressure conditions, since the density of air or compressed medium gas is low and the specific heat per unit volume is small, the natural convection of the gas generated even if there is a temperature difference is Since it is weak and has low heat conductivity, it exhibits a high heat insulating effect under atmospheric pressure conditions. On the other hand, the ceramic fiber material has a high porosity and is rich in air permeability and liquid permeability, and causes natural convection due to a temperature difference in a high-pressure gas atmosphere, so that the heat insulating effect is greatly reduced. A major feature of the present invention is that the heat transfer characteristics of such a ceramic fiber material are effectively utilized.
[0033]
A typical example of the processing steps actually employed is, for example, as shown in FIG. 2. In this example, the solution treatment is performed together with the HIP processing step. Generally, the solution treatment of an Al casting is performed by maintaining the temperature at about 530 ° C. for about 6 to 10 hours. In this solution treatment, the components precipitated during casting are homogenized, and in particular, during the casting, The main focus is on rounding and blunting the sharp portions of the needle-like precipitates precipitated by cooling.
[0034]
In general, the amount of precipitates contained in an Al casting in the matrix (matrix) tends to increase under high pressure. Therefore, when solution treatment is performed simultaneously under high pressure conditions for HIP treatment. The processing time can be reduced as compared with the case where the solution treatment is performed under atmospheric pressure conditions. For example, in the case of an Al-Si alloy, the amount of solid solution of Si under atmospheric pressure is 1.5 atomic% at maximum, but increases to 1.9 atomic% at 100 MPa and 2.4 atomic% at 200 MPa. . Therefore, when the solution treatment is performed at atmospheric pressure (normal pressure), the solution must be maintained at a temperature of about 530 ° C. for about 6 to 10 hours as described above, but the solution is treated at a normal HIP treatment pressure of 100 to 200 MPa. When the solution treatment is performed, a sufficient solution treatment effect can be obtained in about two to three hours even at the same temperature (around 530 ° C.).
[0035]
The process illustrated in FIG. 2 will be described. First, for example, a plurality of processed products (Al castings) wrapped with ceramic fiber material as shown in FIG. Then, it is charged into the HIP device and evacuated and replaced with gas. Next, the inside of the HIP apparatus is heated to increase the pressure by blowing high-pressure gas, and is kept at, for example, 500 to 530 ° C. and 50 to 200 MPa for about 1 to 4 hours. As the high-pressure gas, argon, nitrogen, or the like is generally used, but is not limited thereto. It is also possible to use a mixed gas of these, dry air, or the like.
[0036]
At this time, the ceramic fiber material enclosing the Al casting has a high porosity and high air permeability and liquid permeability as described above, and does not hinder heat transfer under high pressure conditions. Therefore, the pressurizing (consolidating) action of the high-pressure gas and the soaking action on the internal Al casting are not impaired, and the Al casting is sufficiently compacted in substantially the same time as the ordinary method. In addition, shrinkage cavities and void defects are eliminated.
[0037]
During the holding period of the temperature and the pressure, the consolidation of the Al casting proceeds, and the solution treatment also proceeds simultaneously under the high pressure and high temperature conditions as described above. If it is set to about 3 hours, heat treatment for consolidation and solution treatment can be performed simultaneously during this time.
[0038]
After that, while maintaining the HIP processing temperature (and solution treatment temperature) of, for example, 500 to 530 ° C., the high-pressure gas is removed and the pressure in the HIP apparatus is reduced to atmospheric pressure. Thereafter, the Al casting is immediately taken out of the HIP device, quickly transferred to a position above the liquid refrigerant tank for quench, and the Al casting is dropped and immersed in the liquid refrigerant to be quenched (quenched).
[0039]
By the way, when the Al cast product after the HIP treatment using the high-pressure gas is taken out of the HIP device while being exposed to the atmosphere and transferred, especially in the case of a thin cast product, even if this transfer operation is performed quickly, the Al cast product may be used. The surface temperature of the product immediately drops by about 50 ° C., causing a temperature difference between the surface and the inside. For this reason, when quenching is performed by charging the quenched liquid in a state having the temperature difference, the difference in the quenching start temperature causes a difference in the quenching effect, thereby impairing the uniformity of physical properties after quenching. Further, in the case of a thin aluminum casting, there is a possibility that the temperature of the entire casting is significantly reduced due to the heat radiation in the transporting step, and the quench effect itself may be significantly impaired.
[0040]
However, when the Al cast product is wrapped with the ceramic fiber material as described above, the temperature drop during transfer is suppressed by the heat insulating and heat retaining action exerted by the ceramic fiber material in the air atmosphere, and the Al cast product is wrapped. In addition to reducing the temperature difference between the surface and the inside, the temperature drop of the entire cast product is suppressed as much as possible, so that the physical properties after the quenching of the refrigerant can be kept as homogeneous as possible, and the quench quench is stable and sufficient The effect can be secured. Since the ceramic fiber material has a low density, a large air permeability / liquid permeability (water permeability), and a small heat capacity, the quenching effect at the time of quench using a liquid refrigerant is hardly impaired.
[0041]
FIG. 3 illustrates another processing pattern of the present invention. In this example, most of the solution treatment is performed in a solution treatment furnace under atmospheric pressure. That is, the Al casting is wrapped in a ceramic fiber material in the same manner as described above, and in this state, the aluminum casting is charged into a solution treatment furnace, and then heated and maintained for a predetermined time (for example, about 5 hours). Thereafter, the Al cast product is taken out of the solution treatment furnace while being kept at a high temperature, transported toward the HIP device, and charged into the device. Also at this time, the temperature drop of the Al casting during transfer is minimized by the heat insulating and heat retaining effect of the encapsulated ceramic fiber material. However, it is natural that it is desirable to reduce the transfer time as much as possible.
[0042]
Next, the HIP gas is immediately injected into the HIP device to perform the HIP process. At this time, the temperature may slightly fluctuate due to the adiabatic compression of the HIP gas. In order to secure such a uniform solution treatment temperature by suppressing such temperature fluctuation as much as possible, for example, the temperature in the processing chamber of the HIP apparatus is reduced. It is desirable to provide a gas stirring fan for stirring the gas. Then, for example, after maintaining the pressurized state for about 1 to 15 minutes to consolidate the Al casting, the pressure is released while maintaining the solution treatment temperature and the HIP processing temperature in the same manner as in FIG. And perform a refrigerant quench process. During this time, the temperature of the Al cast product is kept low by the ceramic fiber material as described above, so that the temperature drop during transfer is suppressed as much as possible, and the ceramic fiber material has high air permeability / liquid permeability and porosity. Therefore, when the refrigerant is quenched, the liquid refrigerant is immediately allowed to enter and the quenching effect is not spoiled.
[0043]
If the Al casting is wrapped with the ceramic fiber material in this manner, the ceramic fiber material functions as a buffer even when the Al casting is dropped into the refrigerant tank during refrigerant quenching. It is also expected to have a secondary effect of suppressing the occurrence of mechanical damage and scratches on the surface.
[0044]
Next, another embodiment of the present invention, "using low heat conductive ceramic particles as an inorganic material, while charging the ceramic particles into a liquid container, the ceramic particles in the group Method of performing HIP treatment, solution treatment and quench treatment with Al casting buried in the state ", heat and pressurize Al casting with high pressure gas, and perform Al casting under atmospheric pressure. With respect to the heat retaining effect at the time of transferring the product and the quenching effect at the time of quenching the liquid refrigerant, substantially the same operation and effect as when the Al casting is covered with the ceramic fiber material described above can be obtained. However, this embodiment is preferable because the following additional effects can be obtained.
[0045]
That is, when this mode is implemented, usually, for example, an Al casting is charged into a basket made of wire mesh and the like, and the surroundings are filled with low heat conductive ceramic particles. Since a large number of Al castings are conveyed and the processing of a large number of Al castings can be performed simultaneously, it is extremely efficient.
[0046]
The type and shape of the ceramic particles used in this case are not particularly limited as long as they have low heat conductivity and have sufficient gas permeability and liquid permeability as an aggregate. It is a sphere having a diameter of less than 1 mm to several mm. If the sphere has such a size, the filling rate is high, an extra space (dead space) during the HIP processing can be reduced, and the amount of compressed medium gas used can be reduced. You can also enjoy the benefits of gaining.
[0047]
In addition, when quartz beads are used as ceramic particles, (1) the excellent low heat conductivity of the quartz beads can be effectively utilized to obtain an excellent heat retaining effect. (2) The specific gravity is as light as 2.2, and the handling is low. (3) Since the heat capacity is smaller than that of other ceramic particles, it is possible to avoid excessive evaporation of the refrigerant (such as water) at the time of quenching. (4) Since the coefficient of thermal expansion is small, a temperature of about 500 ° C. Even if water quenching is used, it is particularly preferable because many advantages such as less damage to beads due to thermal shock and repetitive use are effectively exhibited.
[0048]
The above-mentioned bead-shaped (spherical) ceramic particles are generally used. In addition, ceramic Raschig rings and saddles used as fillers in distillation and the like also have gas permeability and liquid permeability. And has the same effect as ceramic beads in that it has a heat insulating effect in the air atmosphere.
[0049]
【The invention's effect】
The present invention is configured as described above, and the HIP treatment of the Al alloy casting can be performed as a series of combinations of (solution treatment + quenching + aging treatment). Compared with the conventional method in which solution treatment is performed, not only the solution treatment by reheating is not necessary, but also the solution treatment time can be significantly reduced by performing the solution treatment together with the HIP treatment under high pressure. .
[0050]
In addition, as a normal function and effect of the HIP treatment, not only the improvement of ductility and fatigue life due to the disappearance of shrinkage cavities and pores, but also the reduction of fatigue life, which is considered to be caused by the presence of needle-like precipitates, is effectively performed. And a highly reliable Al casting can be provided. Further, the time required for a series of operations of the HIP treatment + the solution treatment + the quenching quenching can be remarkably reduced, and thus the productivity can be greatly improved and the production cost can be reduced.
[0051]
More specifically, the use of a HIP device dedicated to Al castings utilizing the present invention reduces the processing cost required for a series of operations of [HIP treatment + solution treatment + quenching quench] conventionally performed. It can be reduced to about 1/5 or less, and further to about 1/10 or less. As a result, the method of applying the reforming technology consisting of the above [HIP treatment + solution treatment + quench quench] is also applied to Al castings for automobiles, which were conventionally considered to be difficult to put into practical use due to processing cost restrictions. Can be developed.
[0052]
Furthermore, the effect of improving the physical properties of the Al cast product described above makes it easy to reduce the thickness of the Al cast component in consideration of the safety design aspect as well, thereby reducing the weight of automobile parts and the related energy saving and exhaust gas reduction. Can also contribute. In addition, the present invention can be widely and effectively used for manufacturing not only automotive parts but also Al castings used as materials for vehicles, ships, aircrafts, and panel materials for home electric appliances.
[0053]
In addition, according to the present invention, it is necessary to secure a series of processing effects of [HIP processing + solution treatment + quenching quench] in the conventional example, so that the operation associated with the use of the molten salt has been forced to be employed. It is a very clean process that uses gas as the compression medium without the complications of environmental problems and the risk of waste liquid treatment.It is a very useful method that can respond to future environmental issues. is there.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an example of encapsulation of an Al casting using a fibrous blanket when implementing the present invention.
FIG. 2 is a process explanatory view showing one embodiment of the present invention.
FIG. 3 is a process explanatory view showing another embodiment of the present invention.
[Explanation of symbols]
1 Al-based metal castings
2 Ceramic fiber materials
