JP2004034135A

JP2004034135A - Aluminum alloy with superior formability in semi-molten state and manufacturing method of its cast ingot

Info

Publication number: JP2004034135A
Application number: JP2002198111A
Authority: JP
Inventors: Shigeru Mikubo; 三久保　滋; Masafumi Mizouchi; 溝内　政文; Tsunaki Iwashita; 岩下　綱樹
Original assignee: Kyushu Mitsui Aluminum Industries Inc
Current assignee: Kyushu Mitsui Aluminum Industries Inc
Priority date: 2002-07-08
Filing date: 2002-07-08
Publication date: 2004-02-05
Anticipated expiration: 2022-07-08
Also published as: US20060032559A1; JP3696844B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a semi-molten billet which can employ a simple process, help reduce its cost and produce a homogenous product after forming. <P>SOLUTION: In semi-continuous casting of an aluminum alloy comprising 0.005-0.5 wt% Ti, 0.0001-0.1 wt% B, and the balance consisting substantially of aluminum, the aluminum alloy in a molten state is poured from above into a cylindrical casting mold with forced cooling, generating a solidified surface shell by a first cooling through the casting mold and the ingot with the solidified shell is stripped out of the mold with its bottom supported by the lower die. Then, a second cooling is applied on the ingot surface with a cooling medium, while a distance between the first cooling and the second cooling is set not more than 150 mm and an angle spouting the second cooling medium to the ingot is held at less than 80° but not less than 20° to the casting direction. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、半溶融成型性に優れたアルミニウム合金及びその鋳塊の製造方法に関するものである。
【０００２】
【従来の技術】
半溶融成型ビレットを用いるチクソキャスト法は、従来の金型鋳造法と比較し鋳造偏析やガス巻き込み、引け巣等の内部欠陥が少なく、機械的特性や寸法精度も向上し、しかも金型寿命が長いなどの利点があり、最近注目をあびてきている技術である。
【０００３】
これに使用するビレットの鋳造方法は、ペシネーやアルマックス方式のように、ビレット段階で初晶α（Ａｌ）相を球状化するため、半溶融温度域で電磁撹拌を行う方法（方式Ａ）が良く知られており既に実用化されている。
また、特許第３２１６６８４号には、アルミニウム合金の給湯時に液相線より３０℃を越えない温度領域に限定し、１℃／秒以上の凝固区間冷却速度で冷却固化し、さらに溶解度線から固相線温度までを０．５℃／分以上の速度で昇温し、さらに固相線を越える温度領域まで昇温するとともに５〜６０分間保持して初晶を球状化した後、液相線以下の成型温度まで更に昇温し半溶融状態になった溶湯を成型する方法で、そのアルミニウム合金にはＴｉ，Ｂを添加する方法（方式Ｂ）が開示されている。
【０００４】
【発明が解決しようとする課題】
上記従来の方法の中、方式Ａでは工程が非常に煩雑で、設備費も高価で製造コストが高くなるという問題があった。
また、方式Ｂでは多量のＡｌ−Ｔｉ−Ｂを添加するため、炉内でのＴｉＢ_２沈降による品質不安定が発生し、更に液相線近傍温度で冷却と昇温を行うため温度制御が複雑で、しかも作業工程が煩雑なため量産化や低コスト化が図れないという問題があった。
【０００５】
本発明は、以上の点に鑑みて創案されたものであって、上記従来技術の欠点を解消し、工程が簡素でしかも低コスト化が達成でき、得られる成型品が均質で高品質な半溶融成型性に優れたアルミニウム合金及びその鋳塊の製造方法を提供することを目的とし、特に半溶融成型用アルミニウム合金ビレットの半連続鋳造時に結晶粒微細化剤として添加するＴｉとＢの添加方法を規制し、添加量を適量に配合し、ＴｉＢ_２の形状とサイズと組成比を限定することと、その後アルミニウム合金ビレットを鋳造する際、鋳造条件のコントロールを調整することにより微細化した鋳造組織を得ることを目的とするものである。
【０００６】
【課題を解決するための手段】
上記目的を達成するため本願発明の第１発明は、Ｔｉ０．００５〜０．５ｗｔ％、Ｂ０．０００１〜０．１ｗｔ％を含み、残部が実質的にアルミニウムから成ることを特徴とする半溶融成型性に優れたアルミニウム合金を採用する。
【０００７】
ここで、上記アルミニウム合金には、ＴｉとＢを適量含有するので、合金の結晶粒を微細化できるものである。
【０００８】
また、上記目的を達成するため本願発明の第２発明は、アルミニウム合金の結晶粒微細化のために添加されるＴｉは、Ａｌ−Ｔｉ母合金で添加し、更にＡｌ−Ｔｉ−Ｂ母合金で添加されることを特徴とする第１発明に記載の半溶融成型性に優れたアルミニウム合金を採用する。
【０００９】
ここで、上記アルミニウム合金には、ＴｉをまずＡｌ−Ｔｉ母合金で添加し、次いでＡｌ−Ｔｉ−Ｂ母合金を添加しているので、より微細な鋳造組織とすることができる。
【００１０】
また、上記目的を達成するため本願発明の第３発明は、アルミニウム合金の結晶粒微細化のために添加されるＴｉ，Ｂ量はＴｉ／Ｂ比が３〜４０であり、（Ａｌ_ｘ・Ｔｉ_ｙ）Ｂ_２（ｘ＝１〜７，ｙ＝１〜９）化合物のサイズが１０μｍ以下の粒状で、しかもＡｌ_ｘ／Ｔｉ_ｙの原子量比が０．２〜２．５であることを特徴とする第１発明又は第２発明に記載の半溶融成型性に優れたアルミニウム合金を採用する。
【００１１】
また、上記目的を達成するため本願発明の第４発明は、Ｔｉ０．００５〜０．５ｗｔ％、Ｂ０．０００１〜０．１ｗｔ％を含み、残部が実質的にアルミニウムから成るアルミニウム合金を半連続鋳造するに際し、アルミニウム合金の溶湯を筒形状の強制冷却鋳型内に上方から注湯し、鋳型により一次冷却して表面凝固層を形成すると共に、該凝固層を形成した鋳塊をその下端を支える下型と共に、前記鋳型から引き下ろし、該鋳塊の表面に冷媒を供給し二次冷却する際、一次冷却と二次冷却までの距離を１５０ｍｍ以内とし、二次冷却用冷媒が鋳塊に当たる角度を鋳造方向に対して２０°以上で８０°未満とすることを特徴とする半溶融成型性に優れたアルミニウム合金鋳塊の製造方法を採用する。
【００１２】
また、上記目的を達成するため本願発明の第５発明は、アルミニウム合金のＴｉは、Ａｌ−Ｔｉ母合金で添加し、更にＡｌ−Ｔｉ−Ｂ母合金で添加されることを特徴とする第４発明に記載の半溶融成型性に優れたアルミニウム合金鋳塊の製造方法を採用する。
【００１３】
また、上記目的を達成するため本願発明の第６発明は、アルミニウム合金のＴｉ，Ｂ量は、Ｔｉ／Ｂ比が３〜４０であり、（Ａｌ_ｘ・Ｔｉ_ｙ）Ｂ_２（ｘ＝１〜７，ｙ＝１〜９）化合物のサイズが１０μｍ以下の粒状で、しかもＡｌ_ｘ／Ｔｉ_ｙの原子量比が０．２〜２．５であることを特徴とする第４発明又は第５発明に記載の半溶融成型性に優れたアルミニウム合金鋳塊の製造方法を採用する。
【００１４】
また、上記目的を達成するため本願発明の第７発明は、アルミニウム合金を半連続鋳造するに際し、二次冷却した後、更に鋳塊の冷却を強化するため三次冷却用冷媒を鋳造方向に対して２０°以上で８０°未満の角度で鋳塊に当てることを特徴とする第４発明、第５発明又は第６発明に記載の半溶融成型性に優れたアルミニウム合金鋳塊の製造方法を採用する。
【００１５】
また、上記目的を達成するため本願発明の第８発明は、アルミニウム合金を半連続鋳造するに際し、筒形状の強制冷却鋳型内に上方から注湯し、鋳型により一次冷却して表面凝固層を形成させる際に、鋳型内の給湯面に配設した浮子式溶湯分配器から溶湯を流出させる溶湯レベル制御において、浮子式溶湯分配器からの溶湯の射出角度が鋳造方向に対して２０°以上で８０°未満であることを特徴とする第４発明、第５発明、第６発明又は第７発明に記載の半溶融成型性に優れたアルミニウム合金鋳塊の製造方法を採用する。
【００１６】
【発明の実施の形態】
以下本発明で用いるアルミニウム合金の成分量の数値限定等種々の数値限定理由について詳述し、本発明の理解に供する。
【００１７】
Ｔｉ成分は、鋳塊の組織を微細化し、鋳塊割れの発生を防止するが、０．００５ｗｔ％未満ではその効果は少なく、一方０．５ｗｔ％を越えるとＴｉＡｌ_３の巨大な晶出物の発生を促進させるため、０．００５〜０．５ｗｔ％とした。
【００１８】
Ｂ成分もまたＴｉ成分とともに鋳塊の組織を微細化し、鋳塊割れの発生を防止するが、０．０００１ｗｔ％未満ではその効果が顕著ではなく、一方０．１ｗｔ％を越えて添加してもそれ以上の効果は期待できないので０．０００１〜０．１ｗｔ％とした。
【００１９】
鋳塊の結晶粒微細化のために添加されるＴｉは、まずＡｌ−Ｔｉ母合金で添加することが重要である。一度に所定量をＡｌ−Ｔｉ−Ｂ母合金で添加すると、母合金中のＴｉＢ_２が溶湯中に沈降して添加量に見合った微細化効果が得られない。このため、まずＡｌ−Ｔｉ母合金で添加して結晶粒を微細化させ、次にＡｌ−Ｔｉ−Ｂ母合金を添加することにより微細な鋳造組織を得ることが出来る。このため微細な結晶粒組織を得るための微細化剤添加法は、Ａｌ−Ｔｉ母合金でまず添加し、続いてＡｌ−Ｔｉ−Ｂ母合金で適量添加することとした。
【００２０】
鋳塊の結晶粒微細化のために添加されるＴｉ，Ｂ量はＴｉ／Ｂ比が重要で、Ｔｉ／Ｂ比が３未満では十分な微細化効果は得られず、一方Ｔｉ／Ｂ比が４０を越えると微細化効果は飽和するため、Ｔｉ／Ｂ比を３〜４０とした。
【００２１】
次に添加される（Ａｌ_ｘ・Ｔｉ_ｙ）Ｂ_２化合物のサイズであるが、（Ａｌ_ｘ・Ｔｉ_ｙ）Ｂ_２のサイズも結晶粒の微細化に影響を及ぼし、１０μｍを越えると微細化効果は著しく低下するとともに、結晶粒微細化の核となる（Ａｌ_ｘ・Ｔｉ_ｙ）Ｂ_２の形状が粒状でないと微細化能は低下するため、（Ａｌ_ｘ・Ｔｉ_ｙ）Ｂ_２のサイズは１０μｍ以下でしかも形状を粒状とした。
ここで、（Ａｌ_ｘ・Ｔｉ_ｙ）Ｂ_２のｘ，ｙについてだが、ｘ＝１〜７，ｙ＝１〜９とした。その理由は、ｘ，ｙともにその範囲を外れると得られる鋳塊の結晶粒微細化効果が劣るようになるからである。
（Ａｌ_ｘ・Ｔｉ_ｙ）Ｂ_２化合物を構成するＡｌ_ｘとＴｉ_ｙの原子量比も結晶粒の微細化に大きく寄与し、Ａｌ_ｘ／Ｔｉ_ｙが０．２未満では微細化効果が少なく、一方２．５を越えても微細化効果が劣るためにＡｌ_ｘ／Ｔｉ_ｙ比を０．２〜２．５とした。
【００２２】
鋳塊の結晶粒微細化は微細化剤の添加とともに鋳造時の冷却を強化し、アルミニウム溶湯の凝固速度を早め、結晶成長を抑制することも重要な要因の一つである。
アルミニウム合金の半連続鋳造に当たり、アルミニウム合金溶湯を上下が開放された冷却鋳型（モールド）を使用し、鋳型下部を閉塞するよう下型を配設し、アルミニウム合金溶湯を出湯ノズルから鋳型内に導入して下型上に供給し、鋳型内の溶湯レベルを鋳型内に配設したフロート分配器のような浮子式溶湯分配器により制御しながら、鋳型内壁からの冷却（一次冷却）により鋳塊殻を形成し、下型を降下させて凝固した鋳塊を鋳型から引き出し、鋳型から引き出された鋳塊を更に冷媒で冷却し（二次冷却）鋳塊全体を凝固させる鋳造方法をとっている。溶湯がモールドに接して冷却される一次冷却と冷媒が直接鋳塊に当たって冷却される二次冷却までの距離は短いほど冷却は早まり結晶粒は微細化されるが、１５０ｍｍを越えると一次冷却から二次冷却までの時間が長くなり、鋳造時の冷却が弱くなるため微細な結晶粒組織が得られない。そのため、一次冷却と二次冷却までの距離は１５０ｍｍ以内とした。
また、冷媒が鋳塊表面に当たる角度によっても二次冷却の程度が変動し、鋳造方向に対して２０°未満か８０°以上では冷却水が鋳塊表面にうまく当たらず冷却能が低下するため２０°以上で８０°未満とした。
【００２３】
二次冷却された後、更に冷却を強化するため三次冷媒を鋳塊表面に当てるが、三次冷媒が鋳造方向に対して２０°未満では冷却能が低下する。一方８０°以上の角度で鋳塊に当てると冷媒は鋳塊に沿って当たらないために、三次冷媒は鋳造方向に対して２０°以上で８０°未満とした。
【００２４】
前記アルミニウム合金の半連続鋳造に当たり、鋳型内の給湯面に配設した浮子式溶湯分配器（フロート）から溶湯を流出させて溶湯レベル制御において、浮子式溶湯分配器（フロート）からの鋳型内に溶湯を噴射するが、射出角度により溶湯の冷却能が大きく変化する。鋳造方向に対して２０°未満の射出角度では、溶湯は鋳造方向に強く落下するためズンプが深くなり、冷却が弱くなる。一方、８０°以上では溶湯が鋳型に強く当たるため鋳塊の外観が悪くなる。このため、モールド内に給湯された溶湯のメタルレベル制御に用いるフロートからの溶湯の射出角度は鋳造方向に対して２０°以上で８０°未満とした。
【００２５】
一般的には、鋳造は半連続鋳造で行われ、鋳型内の溶湯レベル制御は浮子式溶湯分配器（フロート）を使用するが、浮子式溶湯分配器（フロート）を用いないＨＯＴ−ＴＯＰ鋳造法を用いると、冷却は強化され凝固速度が速くなり結晶粒は微細化される。
【００２６】
Ｔｉ，Ｂの適量添加及び最適鋳造条件の選択により鋳塊の結晶を微細化するもので、アルミニウム合金は特に限定しないが、アルミニウムに添加される主要添加元素はＭｇ，Ｓｉ，Ｍｎ，Ｚｎ，Ｃｕ，Ｆｅ，Ｃｒ，Ｎｉ，Ｌｉ，Ｖ，Ｚｒ，Ｓｎ，Ｐｂ，Ｂｉ，Ｃｏ，Ｓｒ等である。
【００２７】
【実施例】
以下本発明の具体的な実施例を比較例と共に示す。
【００２８】
鋳塊組成をそれぞれ下記表１に示すような合金組成にＴｉ，Ｂを添加し、半連続鋳造にてアルミニウム合金ビレットを鋳造した。
【００２９】
【表１】

【００３０】
アルミニウム合金ビレットを下記表２に示す条件で鋳造し、半溶融成型時の成型性、半溶融成型後の初晶α（Ａｌ）相の形状を評価した結果も表２に併記した。
【００３１】
【表２】

【００３２】
表２に示した鋳塊の外観評価は表面が引っ掻き、冷接等の欠陥が無くスムースなものを○と判定した。また、鋳塊の結晶粒は３００μｍ以下を○と判定し、それを越える場合を×と判定した。
半溶融成型の成型性は、良好なものを○と判定し、成型性の悪いものを×と判定した。
半溶融成型後の初晶α（Ａｌ）相の形状は、球状化が認められるものを○とし、球状化が不十分であるものを×と判定した。半溶融成型後の初晶α（Ａｌ）相の微細均一化では、初晶α（Ａｌ）相のサイズが５００μｍ以下を○と判定し、５００μｍを越えるサイズのものを×と判定した。
【００３３】
図１は、初晶α（Ａｌ）相の微細均一化が○評価の代表例写真を示し、図２は、初晶α（Ａｌ）相の微細均一化が×評価の代表例写真を示す。
【００３４】
【発明の効果】
以上述べてきた如く、本発明によれば、従来の半溶融ビレットよりも工程が簡素化され、しかも低コスト化が図れる。
また得られる組織も初晶α（Ａｌ）相サイズが平均５００μｍ以下で、かつ面積率５０％の均一球状化組織となっており、広い範囲の用途に使用可能であるという効果を奏するものである。
【図面の簡単な説明】
【図１】初晶α（Ａｌ）相の微細均一化が○評価の代表例の顕微鏡組織写真である。
【図２】初晶α（Ａｌ）相の微細均一化が×評価の代表例の顕微鏡組織写真である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an aluminum alloy excellent in semi-solid moldability and a method for producing an ingot thereof.
[0002]
[Prior art]
The thixocasting method using a semi-molten molded billet has fewer internal defects such as casting segregation, gas entrapment, shrinkage cavities, mechanical properties and dimensional accuracy, and longer mold life than conventional mold casting methods. It has advantages such as long, and is a technology that has attracted attention recently.
[0003]
As a method of casting a billet used in this method, a method of performing electromagnetic stirring in a semi-melting temperature range (method A) is used to form a primary α (Al) phase into a spheroid at a billet stage, as in the case of the Pescine or Almax method. It is well known and has already been put to practical use.
Also, Japanese Patent No. 3216684 discloses that when hot water is supplied from an aluminum alloy, the temperature is limited to a temperature range not exceeding 30 ° C. from the liquidus line, and the aluminum alloy is cooled and solidified at a solidification zone cooling rate of 1 ° C./sec or more. The temperature is increased up to the linear temperature at a rate of 0.5 ° C./min or more, and further raised to a temperature range exceeding the solidus temperature, and is maintained for 5 to 60 minutes to form primary crystals into spheroids. A method of forming a molten metal in a semi-molten state by further raising the temperature to the forming temperature of (a), and adding Ti and B to the aluminum alloy (method B) is disclosed.
[0004]
[Problems to be solved by the invention]
Among the above conventional methods, the method A has a problem that the steps are very complicated, the equipment cost is high, and the manufacturing cost is high.
Further, in order to add a large amount of Al-TiB In mode B, the quality instability occurs due to TiB ₂ precipitation in the furnace, complicated further temperature control for performing cooling and heated at liquidus temperature near In addition, there is a problem that mass production and cost reduction cannot be achieved due to complicated operation steps.
[0005]
The present invention has been made in view of the above points, and solves the above-mentioned drawbacks of the prior art, can achieve simple and low-cost processes, and can obtain a molded product having a uniform and high-quality semi-finished product. A method for producing an aluminum alloy excellent in melt moldability and a method for producing an ingot thereof, particularly a method for adding Ti and B to be added as a grain refiner during semi-continuous casting of an aluminum alloy billet for semi-solid molding regulate, blended amount in an appropriate amount, and to limit the shape and size and the composition ratio of TiB _2, then when casting aluminum alloy billet, the cast structure was refined by adjusting the control of the casting conditions The purpose is to obtain.
[0006]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a semi-solid molding comprising 0.005 to 0.5% by weight of Ti and 0.0001 to 0.1% by weight of B, with the balance substantially consisting of aluminum. Uses an aluminum alloy with excellent properties.
[0007]
Here, since the aluminum alloy contains Ti and B in appropriate amounts, crystal grains of the alloy can be refined.
[0008]
In order to achieve the above object, a second invention of the present invention is directed to a method of manufacturing a semiconductor device, wherein Ti added for refining the crystal grains of an aluminum alloy is added in an Al-Ti master alloy, and further Ti is added in an Al-Ti-B master alloy. The aluminum alloy having excellent semi-solid moldability according to the first invention is characterized by being added.
[0009]
Here, since Ti is first added to the aluminum alloy as an Al-Ti mother alloy and then an Al-Ti-B mother alloy is added, a finer cast structure can be obtained.
[0010]
In order to achieve the above object, a third invention of the present invention is directed to a method of manufacturing a semiconductor device according to the present invention, wherein the amount of Ti and B added for refining the crystal grain of the aluminum alloy is such that the Ti / B ratio is 3 to 40, and (Al _x Ti _{_{y) B 2 (x = 1~7}} , and characterized in that y = 1 to 9) the size of the compounds in the following granular 10 [mu] m, yet the atomic weight ratio of _Al x / Ti _y is 0.2 to 2.5 The aluminum alloy excellent in semi-solid moldability described in the first invention or the second invention is used.
[0011]
In order to achieve the above object, a fourth invention of the present invention is a semi-continuous casting of an aluminum alloy containing 0.005 to 0.5 wt% of Ti and 0.0001 to 0.1 wt% of B and the balance substantially consisting of aluminum. In doing so, a molten aluminum alloy is poured from above into a cylindrical forced cooling mold, and primary cooled by the mold to form a surface solidified layer, and the ingot having the solidified layer formed thereon is supported by the lower end thereof. Along with the mold, it is pulled down from the mold, and when supplying the refrigerant to the surface of the ingot and performing secondary cooling, the distance between the primary cooling and the secondary cooling is set within 150 mm, and the angle at which the secondary cooling refrigerant hits the ingot is cast. A method for producing an aluminum alloy ingot excellent in semi-solid moldability, characterized by being at least 20 ° and less than 80 ° with respect to the direction.
[0012]
In order to achieve the above object, a fifth invention of the present invention is directed to the fourth invention, wherein Ti of the aluminum alloy is added by an Al-Ti mother alloy, and further added by an Al-Ti-B mother alloy. The method for producing an aluminum alloy ingot excellent in semi-solid moldability according to the invention is employed.
[0013]
In order to achieve the above object, according to a sixth aspect of the present invention, the Ti / B ratio of the aluminum alloy is such that the Ti / B ratio is 3 to 40, and (Al _x · Ti _y ) B ₂ (x = 1 to 7, y = 1-9) The fourth invention or the fifth invention, characterized in that the compound is in the form of granules having a size of 10 μm or less and the Al _x / Ti _y atomic ratio is 0.2-2.5. The method for producing an aluminum alloy ingot excellent in semi-solid moldability described above is employed.
[0014]
Further, in order to achieve the above object, the seventh invention of the present invention provides a semi-continuous casting of an aluminum alloy, after secondary cooling, further strengthening the cooling of the ingot with a tertiary cooling refrigerant in the casting direction. The method for manufacturing an aluminum alloy ingot excellent in semi-solid moldability according to the fourth, fifth or sixth invention, wherein the ingot is applied to the ingot at an angle of 20 ° or more and less than 80 °. .
[0015]
In order to achieve the above object, an eighth invention of the present invention is directed to a semi-continuous casting of an aluminum alloy, in which a molten metal is poured into a cylindrical forced cooling mold from above and primary cooled by the mold to form a surface solidified layer. In this case, in the molten metal level control for causing the molten metal to flow out of the floating molten metal distributor disposed on the molten metal supply surface in the mold, the injection angle of the molten metal from the floating molten metal distributor is not less than 20 ° with respect to the casting direction, and The method for producing an aluminum alloy ingot excellent in semi-solid moldability according to the fourth, fifth, sixth or seventh invention, wherein the angle is less than 0 ° is adopted.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, various reasons for limiting the numerical values, such as limiting the numerical values of the components of the aluminum alloy used in the present invention, will be described in detail to provide an understanding of the present invention.
[0017]
The Ti component refines the structure of the ingot and prevents the occurrence of cracks in the ingot, but the effect is small when the content is less than 0.005 wt%, while when it exceeds 0.5 wt%, a large crystallized substance of TiAl ₃ is formed. In order to promote the generation, the content was made 0.005 to 0.5 wt%.
[0018]
The B component also refines the structure of the ingot together with the Ti component and prevents the occurrence of cracks in the ingot. However, if the content is less than 0.0001% by weight, the effect is not remarkable. Since no further effect can be expected, the content is set to 0.0001 to 0.1 wt%.
[0019]
It is important that Ti added for refining the crystal grains of the ingot is first added in an Al-Ti master alloy. The addition of a predetermined amount of Al-TiB master alloys at once, TiB ₂ in the matrix alloy can not be obtained refining effect commensurate with the added amount is settled in the melt. For this reason, a fine cast structure can be obtained by first adding an Al-Ti master alloy to refine the crystal grains and then adding an Al-Ti-B master alloy. For this reason, as a method of adding a refiner for obtaining a fine crystal grain structure, an Al-Ti mother alloy is first added, and then an appropriate amount is added using an Al-Ti-B mother alloy.
[0020]
The Ti / B ratio is important for the amounts of Ti and B added for refining the crystal grains of the ingot, and if the Ti / B ratio is less than 3, a sufficient refining effect cannot be obtained. If it exceeds 40, the effect of miniaturization is saturated, so the Ti / B ratio is set to 3 to 40.
[0021]
Next, the size of the (Al _x · Ti _y ) B ₂ compound to be added, the size of the (Al _x · Ti _y ) B ₂ also affects the refinement of the crystal grains. Is remarkably reduced, and the refining ability is reduced unless the shape of (Al _x · Ti _y ) B ₂ , which is the core of grain refinement, is not granular, so that the size of (Al _x · Ti _y ) B ₂ is 10 μm. Below, the shape was granular.
Here, _x and _{y of} (Al _x · Ti _y ) B ₂ were set as x = 1 to 7, and y = 1 to 9. The reason is that if both x and y are out of the range, the effect of refining the crystal grain of the obtained ingot becomes inferior.
The atomic weight ratio of Al _x to Ti _y constituting the (Al _x .Ti _y ) B ₂ compound also greatly contributes to the refinement of the crystal grains. When Al _x / T _y is less than 0.2, the effect of the refinement is small, while Even if it exceeds 2.5, the Al _x / T _y ratio is set to 0.2 to 2.5 because the effect of miniaturization is inferior.
[0022]
One of the important factors for the refinement of the crystal grain size of the ingot is to enhance the cooling during casting together with the addition of a refining agent, increase the solidification rate of the aluminum melt, and suppress the crystal growth.
In semi-continuous casting of aluminum alloy, a lower mold is used to close the lower part of the mold using a cooling mold (mold) with an open top and bottom, and the molten aluminum alloy is introduced into the mold from a tapping nozzle. The molten metal in the mold is supplied to the lower mold, and the molten metal level in the mold is controlled by a float type molten metal distributor such as a float distributor disposed in the mold, while the ingot shell is cooled by cooling from the inner wall of the mold (primary cooling). Is formed, the lower mold is lowered, the solidified ingot is drawn out of the mold, and the ingot drawn from the mold is further cooled with a refrigerant (secondary cooling) to solidify the entire ingot. The shorter the distance between the primary cooling, in which the molten metal is in contact with the mold and cooling, and the secondary cooling, in which the refrigerant directly hits the ingot, the faster the cooling and the finer the crystal grains. The time until the next cooling becomes longer and the cooling during casting becomes weaker, so that a fine grain structure cannot be obtained. Therefore, the distance between the primary cooling and the secondary cooling was set to within 150 mm.
Also, the degree of secondary cooling varies depending on the angle at which the refrigerant hits the ingot surface, and if it is less than 20 ° or more than 80 ° with respect to the casting direction, the cooling water does not come into contact with the ingot surface, and the cooling capacity is reduced. At least 80 ° and less than 80 °.
[0023]
After the secondary cooling, a tertiary refrigerant is applied to the surface of the ingot to further enhance the cooling. However, when the tertiary refrigerant is less than 20 ° with respect to the casting direction, the cooling capacity is reduced. On the other hand, when the refrigerant is applied to the ingot at an angle of 80 ° or more, the refrigerant does not hit along the ingot. Therefore, the tertiary refrigerant is set at 20 ° or more and less than 80 ° with respect to the casting direction.
[0024]
In the semi-continuous casting of the aluminum alloy, the molten metal flows out from a float type molten metal distributor (float) disposed on a hot water supply surface in the mold to control the molten metal level. When the molten metal is injected, the cooling ability of the molten metal changes greatly depending on the injection angle. At an injection angle of less than 20 ° with respect to the casting direction, the molten metal drops strongly in the casting direction, so that the zump becomes deep and the cooling becomes weak. On the other hand, at 80 ° or more, the appearance of the ingot deteriorates because the molten metal hits the mold strongly. For this reason, the angle of injection of the molten metal from the float used for controlling the metal level of the molten metal supplied into the mold was set to 20 ° or more and less than 80 ° with respect to the casting direction.
[0025]
Generally, casting is performed by semi-continuous casting, and the level of molten metal in the mold is controlled using a float type molten metal distributor (float), but the HOT-TOP casting method without using the float type molten metal distributor (float) is used. With the use of, the cooling is enhanced, the solidification rate is increased, and the crystal grains are refined.
[0026]
It is to refine the crystal of the ingot by adding appropriate amounts of Ti and B and selecting the optimal casting conditions. The aluminum alloy is not particularly limited, but the main additive elements added to aluminum are Mg, Si, Mn, Zn, and Cu. , Fe, Cr, Ni, Li, V, Zr, Sn, Pb, Bi, Co, Sr and the like.
[0027]
【Example】
Hereinafter, specific examples of the present invention will be described together with comparative examples.
[0028]
Ti and B were added to the ingot compositions shown in Table 1 below, and aluminum alloy billets were cast by semi-continuous casting.
[0029]
[Table 1]

[0030]
The aluminum alloy billet was cast under the conditions shown in Table 2 below, and the results of evaluation of the moldability during semi-solid molding and the shape of the primary α (Al) phase after semi-solid molding are also shown in Table 2.
[0031]
[Table 2]

[0032]
In the appearance evaluation of the ingot shown in Table 2, the surface was scratched, and a smooth ingot free from defects such as cold welding was judged as ○. The crystal grain size of the ingot was determined to be ○ when the grain size was 300 μm or less, and was determined to be × when the grain size exceeded 300 μm.
Regarding the moldability of the semi-solid molding, good ones were judged to be good, and poor moldability were judged to be bad.
The shape of the primary crystal α (Al) phase after semi-solid molding was evaluated as もの when spheroidization was observed, and as × when spheroidization was insufficient. In the fine homogenization of the primary crystal α (Al) phase after semi-solid molding, the primary crystal α (Al) phase was determined to be ○ when the size of the primary crystal α (Al) phase was 500 μm or less, and was determined to be × when the size exceeded 500 μm.
[0033]
FIG. 1 shows a photograph of a typical example in which fine uniformization of the primary crystal α (Al) phase was evaluated as ○, and FIG. 2 shows a photograph of a typical example in which fine uniformity of the primary crystal α (Al) phase was evaluated as x.
[0034]
【The invention's effect】
As described above, according to the present invention, the process can be simplified and the cost can be reduced as compared with the conventional semi-molten billet.
Also, the obtained structure is a uniform spheroidized structure having an average primary crystal α (Al) phase size of 500 μm or less and an area ratio of 50%, and has an effect that it can be used for a wide range of applications. .
[Brief description of the drawings]
FIG. 1 is a photomicrograph of a representative example of the evaluation of o for fine uniformity of the primary α (Al) phase.
FIG. 2 is a photomicrograph of a representative example of a case where fine homogenization of a primary crystal α (Al) phase is evaluated as x.

Claims

Ｔｉ０．００５〜０．５ｗｔ％、Ｂ０．０００１〜０．１ｗｔ％を含み、残部が実質的にアルミニウムから成ることを特徴とする半溶融成型性に優れたアルミニウム合金。An aluminum alloy having excellent semi-solid moldability, characterized by containing 0.005 to 0.5 wt% of Ti and 0.0001 to 0.1 wt% of B, and the balance substantially consisting of aluminum.

前記アルミニウム合金の結晶粒微細化のために添加されるＴｉは、Ａｌ−Ｔｉ母合金で添加し、更にＡｌ−Ｔｉ−Ｂ母合金で添加されることを特徴とする請求項１に記載の半溶融成型性に優れたアルミニウム合金。2. The half-finished metal according to claim 1, wherein the Ti added for refining the crystal grains of the aluminum alloy is added by an Al—Ti master alloy, and further added by an Al—Ti—B master alloy. 3. Aluminum alloy with excellent melt moldability.

前記アルミニウム合金の結晶粒微細化のために添加されるＴｉ，Ｂ量は、Ｔｉ／Ｂ比が３〜４０であり、（Ａｌ_Ｘ・Ｔｉ_ｙ）Ｂ_２（ｘ＝１〜７，ｙ＝１〜９）化合物のサイズが１０μｍ以下の粒状で、しかもＡｌ_Ｘ／Ｔｉ_ｙの原子量比が０．２〜２．５であることを特徴とする請求項１又は２に記載の半溶融成型性に優れたアルミニウム合金。The amounts of Ti and B added for refining the crystal grains of the aluminum alloy are such that the Ti / B ratio is 3 to 40 and (Al _X .Ti _y ) B ₂ (x = 1 to 7, y = 1 9) The semi-solid moldability according to claim 1 or 2, wherein the compound has a particle size of 10 μm or less and an atomic ratio of Al _x / T _y is 0.2 to 2.5. Excellent aluminum alloy.

Ｔｉ０．００５〜０．５ｗｔ％、Ｂ０．０００１〜０．１ｗｔ％を含み、残部が実質的にアルミニウムから成るアルミニウム合金を半連続鋳造するに際し、アルミニウム合金の溶湯を筒形状の強制冷却鋳型内に上方から注湯し、鋳型により一次冷却して表面凝固層を形成すると共に、該凝固層を形成した鋳塊をその下端を支える下型と共に、前記鋳型から引き下ろし、該鋳塊の表面に冷媒を供給し二次冷却する際、一次冷却と二次冷却までの距離を１５０ｍｍ以内とし、二次冷却用冷媒が鋳塊に当たる角度を鋳造方向に対して２０°以上で８０°未満とすることを特徴とする半溶融成型性に優れたアルミニウム合金鋳塊の製造方法。When semi-continuously casting an aluminum alloy containing 0.005 to 0.5 wt% of Ti and 0.0001 to 0.1 wt% of B, and the balance being substantially aluminum, a molten aluminum alloy is placed in a cylindrical forced cooling mold. Pouring from above, forming a surface solidified layer by primary cooling with a mold, and pulling down the ingot with the solidified layer from the mold, together with a lower mold supporting the lower end thereof, and placing a coolant on the surface of the ingot. When supplying and performing secondary cooling, the distance between primary cooling and secondary cooling is set to 150 mm or less, and the angle at which the secondary cooling refrigerant strikes the ingot is set to 20 ° or more and less than 80 ° with respect to the casting direction. A method for producing an aluminum alloy ingot having excellent semi-solid moldability.

前記アルミニウム合金のＴｉは、Ａｌ−Ｔｉ母合金で添加し、更にＡｌ−Ｔｉ−Ｂ母合金で添加されることを特徴とする請求項４に記載の半溶融成型性に優れたアルミニウム合金鋳塊の製造方法。5. The aluminum alloy ingot having excellent semi-solid moldability according to claim 4, wherein Ti of the aluminum alloy is added as an Al-Ti mother alloy and further added as an Al-Ti-B mother alloy. 6. Manufacturing method.

前記アルミニウム合金のＴｉ，Ｂ量は、Ｔｉ／Ｂ比が３〜４０であり、（Ａｌ_ｘ・Ｔｉ_ｙ）Ｂ_２（ｘ＝１〜７，ｙ＝１〜９）化合物のサイズが１０μｍ以下の粒状で、しかもＡｌ_ｘ／Ｔｉ_ｙの原子量比が０．２〜２．５であることを特徴とする請求項４又は５に記載の半溶融成型性に優れたアルミニウム合金鋳塊の製造方法。The Ti / B content of the aluminum alloy is such that the Ti / B ratio is 3 to 40, and the size of the (Al _x .Ti _y ) B ₂ (x = 1 to 7, y = 1 to 9) compound is 10 μm or less. in granular, moreover manufacturing method of semi-molten molding excellent in aluminum alloy ingot of claim 4 or 5, wherein the atomic weight ratio of Al x _/ Ti _y is 0.2 to 2.5.

前記アルミニウム合金を半連続鋳造にするに際し、二次冷却した後、更に鋳塊の冷却を強化するため三次冷却用冷媒を鋳造方向に対して２０°以上で８０°未満の角度で鋳塊に当てることを特徴とする請求項４、５又は６に記載の半溶融成型性に優れたアルミニウム合金鋳塊の製造方法。In the semi-continuous casting of the aluminum alloy, after secondary cooling, a tertiary cooling refrigerant is applied to the ingot at an angle of 20 ° or more and less than 80 ° with respect to the casting direction to further enhance the cooling of the ingot. The method for producing an aluminum alloy ingot excellent in semi-solid moldability according to claim 4, characterized in that:

前記アルミニウム合金を半連続鋳造するに際し、筒形状の強制冷却鋳型内に上方から注湯し、鋳型により一次冷却して表面凝固層を形成させる際に、鋳型内の給湯面に配設した浮子式溶湯分配器から溶湯を流出させる溶湯レベル制御において、浮子式溶湯分配器からの溶湯の射出角度が鋳造方向に対して２０°以上で８０°未満であることを特徴とする請求項４、５、６又は７に記載の半溶融成型性に優れたアルミニウム合金鋳塊の製造方法。When the aluminum alloy is semi-continuously cast, it is poured from above into a cylindrical forced cooling mold, and when a primary cooling is performed by the mold to form a surface solidified layer, a floating type disposed on a hot water supply surface in the mold. In the molten metal level control for causing the molten metal to flow out of the molten metal distributor, an injection angle of the molten metal from the float type molten metal distributor is 20 ° or more and less than 80 ° with respect to a casting direction. 8. The method for producing an aluminum alloy ingot having excellent semi-solid moldability according to 6 or 7.