JP2006305618A - Semi-solid casting method - Google Patents

Semi-solid casting method Download PDF

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JP2006305618A
JP2006305618A JP2005134027A JP2005134027A JP2006305618A JP 2006305618 A JP2006305618 A JP 2006305618A JP 2005134027 A JP2005134027 A JP 2005134027A JP 2005134027 A JP2005134027 A JP 2005134027A JP 2006305618 A JP2006305618 A JP 2006305618A
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cooling plate
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molten metal
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Tetsuichi Mogi
徹一 茂木
Tatsumo Boku
龍雲 朴
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Chiba Institute of Technology
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Abstract

<P>PROBLEM TO BE SOLVED: To make realizable of a semi-solid casting with which fine crystal grain can be obtained in an alloy having extremely narrow temperature interval of a solid-liquid coexisting range, for example, < 50°C, such as 5052 aluminum alloy. <P>SOLUTION: In the semi-solid casting method comprising a process, in which the solid-liquid coexisting state of slurry is obtained by making flow-down molten alloy onto an inclined cooling plate and separating while generating α primary crystal on this inclined cooling plate, and a process, in which the α-phase grains are granulated by holding this slurry to the temperature range in the solid-liquid coexisting range with a tundish having no temperature inclination; a parting material provided with a heat-insulating function is formed on the surface of the inclined cooling plate, and the film thickness of this parting material is adjusted to such relation as to become thicker according to making narrower of the temperature interval of the solid-liquid coexisting range, and for example, the film thickness of the parting material is made to at least ≥105μm at the upstream side, pouring the molten metal onto the inclined cooling plate, and to 30μm at the downstream side therefrom. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明はセミソリッド鋳造方法に関する。さらに詳述すると、本発明は、傾斜冷却板を用いたセミソリッド連続鋳造方法に関する。   The present invention relates to a semi-solid casting method. More specifically, the present invention relates to a semi-solid continuous casting method using an inclined cooling plate.

近年、金属加工技術の一つとして、固体と液体とが共存した状態で成形するセミソリッド加工法が注目を集め、発達してきた。この方法は固液共存状態で成形するために、溶融金属から成形した場合と比較すると、凝固収縮に起因する、ポロシティー、偏析等の内部欠陥が少ないこと、結晶粒ならびに金属間化合物等の晶出物が微細になるなどの特徴があり、そのため、伸びや疲労特性などの機械的特性が向上する。また、固体金属と比較すると加工力の著しい低下により、それに伴う設備の小型化、難加工材への適用といった多くのメリットがある。   In recent years, as one of the metal processing technologies, a semi-solid processing method in which a solid and a liquid are formed in a coexisting state attracts attention and has been developed. Since this method forms in the state of solid-liquid coexistence, it has fewer internal defects such as porosity and segregation due to solidification shrinkage compared to the case of forming from molten metal, and crystals such as crystal grains and intermetallic compounds. There is a feature such as a finer product, which improves mechanical properties such as elongation and fatigue properties. In addition, compared with solid metal, there are many advantages such as downsizing of equipment and application to difficult-to-process materials due to a significant decrease in processing power.

セミソリッド加工法は大別すると、半凝固加工法（Rheocasting）、半溶融加工法（Thixocasting）がある。半凝固加工法は、セミソリッドスラリー（溶湯中に初晶が存在する固液共存状態）を製造後、直接成形機に流入し、ダイカストのように加圧成形を施し製品を得る方法である。半溶融加工法はセミソリッドスラリーを製造し、連続鋳造することによりビレットを作製、これを所要のサイズに切断したスラグを得る。これを再加熱することにより半溶融状態にし、加圧成形をする方法である。ダイカストの様に金型キャビティー内に充填させて成形品を得る方法と、鍛造あるいは押出しのように開放された金型に直接加圧成形する方法がある。   Semi-solid processing methods are roughly classified into semi-solid processing (Rheocasting) and semi-melt processing (Thixocasting). The semi-solid processing method is a method in which a semi-solid slurry (a solid-liquid coexisting state in which primary crystals exist in a molten metal) is manufactured, and then directly flows into a molding machine to perform pressure molding like die casting to obtain a product. In the semi-melt processing method, a semi-solid slurry is produced, and a billet is produced by continuous casting, and a slag obtained by cutting the billet into a required size is obtained. This is a method in which this is reheated to bring it into a semi-molten state and pressure molding. There are a method of obtaining a molded product by filling a mold cavity like a die casting, and a method of directly press-molding into an open mold such as forging or extrusion.

従来の半凝固スラリーの作製方法としては、固液共存状態のスラリーに対して電磁攪拌や機械的攪拌を行い、スラリーに含まれる固相のデンドライトアームを溶断して、当該固相の粒状化を図っている。例えば、現在、工業的に製造されているＡＣ４Ｃアルミニウム合金のチクソキャスト用ビレットは電磁攪拌が用いられている。しかし、この機械撹拌および電磁撹拌法は、設備の大型化、操作の複雑さおよび高コストなどの問題点が挙げられる上に、取り扱える合金の種類もＡＣ４Ｃアルミニウム合金程度であり少ないという問題点を有している。   As a conventional method for preparing a semi-solid slurry, electromagnetic stirring or mechanical stirring is performed on a slurry in a solid-liquid coexistence state, a solid phase dendrite arm contained in the slurry is blown, and the solid phase is granulated. I am trying. For example, an AC4C aluminum alloy billet for thixocasting currently manufactured industrially uses electromagnetic stirring. However, this mechanical stirring method and electromagnetic stirring method have problems such as an increase in equipment size, operational complexity, and high cost, and the types of alloys that can be handled are as small as AC4C aluminum alloys. is doing.

そこで、これらの問題を解決する上で有効な方法として、アルミニウム合金またはマグネシウム合金などの低融点合金の融液を傾斜させた冷却板上に流下させて、多数の固相粒子を結晶遊離現象により生成させて固液共存状態のスラリーとし、その後このスラリーを温度勾配のない鋳型あるいはタンディシュ内に滞留させて固相粒子を粒状化させる技術が提案されている（非特許文献１〜３、特許文献１）。この方法により、現在までに、鍛造用７０７５アルミニウム合金をはじめ、ＡＣ４ＣＨ、６０７０アルミニウム合金においてセミソリッドスラリーを作り出すことに成功し、さらにこのスラリーを水平連続鋳造することによって微細な結晶粒を有する半溶融加工用ビレットの作製に成功している。   Therefore, as an effective method for solving these problems, a melt of a low melting point alloy such as an aluminum alloy or a magnesium alloy is allowed to flow down on a tilted cooling plate, and a large number of solid phase particles are caused by a crystal liberation phenomenon. Techniques have been proposed in which a solid-liquid coexisting slurry is produced, and then the slurry is retained in a mold or tundish without a temperature gradient to granulate solid phase particles (Non-Patent Documents 1 to 3, Patent Documents). 1). By this method, we have succeeded in producing semi-solid slurry in AC4CH, 6070 aluminum alloy, including 7075 aluminum alloy for forging, and semi-molten with fine crystal grains by horizontal continuous casting of this slurry. Succeeded in producing billets for processing.

このスラリーの作製の際には、凝固シェルが一旦生成されると、シェルの厚さが増加してスラリーが得られにくくなるため、銅製傾斜冷却板の表面に窒化ボロン（ＢＮ）の膜を形成して凝固シェルの発生を防止することが提案されている（非特許文献４）。ＢＮは断熱材として機能するため厚すぎると結晶遊離が起き難くなり、微細粒状結晶が形成されずにデンドライト結晶となる。また、薄すぎると、合金が急冷されて張り付き凝固殻が形成され、この凝固殻が断熱層となって冷却が進まずに結晶遊離が起こらない。結果として、このＢＮ膜の傾斜冷却板の表面への形成は、鋳造温度８９７Ｋ、冷却板の長さが１６０ｍｍ、冷却板の角度が６０°である時のＢＮ膜厚は３０μｍが適切であり、その場合に合金溶液（溶湯）の過冷度並びに熱流束が最も大きく、初晶αＡｌの数が最大となり、微細粒状結晶が得られることを明らかにした。   During the preparation of this slurry, once the solidified shell is formed, the thickness of the shell increases, making it difficult to obtain a slurry. Therefore, a boron nitride (BN) film is formed on the surface of the copper inclined cooling plate. Thus, it has been proposed to prevent the formation of a solidified shell (Non-Patent Document 4). Since BN functions as a heat insulating material, if it is too thick, crystal release is difficult to occur, and a fine granular crystal is not formed and a dendrite crystal is formed. On the other hand, if it is too thin, the alloy is rapidly cooled to form a solidified solid shell, and this solidified shell serves as a heat insulating layer, so that cooling does not proceed and crystal release does not occur. As a result, the formation of this BN film on the surface of the inclined cooling plate is appropriately performed at a casting temperature of 897 K, a cooling plate length of 160 mm, and a cooling plate angle of 60 °, and a BN film thickness of 30 μm is appropriate. In this case, it was clarified that the degree of supercooling and heat flux of the alloy solution (molten metal) was the largest, the number of primary crystals αAl was maximized, and fine granular crystals were obtained.

田辺郁、茂木徹一、杉浦英二：日本金属学会誌、53(2003),290-294.Satoshi Tanabe, Teiichi Mogi, Eiji Sugiura: Journal of the Japan Institute of Metals, 53 (2003), 290-294. 田辺郁、茂木徹一、杉浦英二：日本金属学会誌、67(2003),291-294.Satoshi Tanabe, Teiichi Mogi, Eiji Sugiura: Journal of the Japan Institute of Metals, 67 (2003), 291-294. 矢野栄治、和田典也、西川直樹、茂木徹一：日本金属学会誌、66(2002),1131.Eiji Yano, Noriya Wada, Naoki Nishikawa, Tetsuichi Mogi: Journal of the Japan Institute of Metals, 66 (2002), 1131. 朴龍雲、茂木徹一：日本金属学会誌 第68巻第4号(2004)228-231.Park Ryuun, Teppei Mogi: Journal of the Japan Institute of Metals Vol. 68, No. 4 (2004) 228-231. 特開平１０−３４３０７JP 10-34307 A

しかしながら、傾斜冷却板を用いたセミソリッド連続鋳造方法を用いてビレットの製作に成功したＡＣ４ＣＨ、６０７０、７０７５アルミニウム合金は、いずれも固液共存領域の温度幅が６９℃〜１５７℃と比較的広いものであり、5052Ａｌのような固液共存領域の温度幅が極端に狭い（３７℃）合金の場合には、傾斜冷却板での溶湯の急速固化による冷却板への張り付きや凝固シェルの形成により、結晶遊離が起こらず、セミソリッド鋳造が実現できなかった。このことは、電磁攪拌によってスラリーを得る手法においても同様であり、固液共存領域が狭い合金に対しては、傾斜冷却板を用いた方法よりも半凝固スラリーを作り出すことが難しいものである。   However, AC4CH, 6070, and 7075 aluminum alloys that have been successfully manufactured using a semi-solid continuous casting method using an inclined cooling plate have a relatively wide temperature range of 69 ° C to 157 ° C in the solid-liquid coexistence region. In the case of an alloy where the temperature range of the solid-liquid coexistence region such as 5052Al is extremely narrow (37 ° C), due to the sticking to the cooling plate or the formation of a solidified shell due to the rapid solidification of the molten metal in the inclined cooling plate No crystal release occurred and semi-solid casting could not be realized. This also applies to the method of obtaining a slurry by electromagnetic stirring, and it is more difficult to produce a semi-solid slurry than the method using an inclined cooling plate for an alloy having a narrow solid-liquid coexistence region.

また、引用文献４において明らかにされた傾斜冷却板表面のＢＮ膜の膜厚もＡＣ４ＣＨ、６０７０、７０７５アルミニウム合金といった比較的固液共存領域の温度幅が広い合金において最適化されるものであって、5052Ａｌのような固液共存領域の温度幅が極端に狭い（３７℃）合金の場合には、あてはまらないものであった。   Further, the thickness of the BN film on the inclined cooling plate surface disclosed in the cited document 4 is also optimized in an alloy having a relatively wide temperature range in a solid-liquid coexistence region such as AC4CH, 6070, and 7075 aluminum alloys. This is not the case with an alloy such as 5052Al, which has an extremely narrow temperature range in the solid-liquid coexistence region (37 ° C.).

このように、5052アルミニウム合金のように固液共存領域の温度幅が極端に狭い合金の場合には、セミソリッド鋳造が難しいものであった。   Thus, in the case of an alloy having an extremely narrow temperature range in the solid-liquid coexistence region such as 5052 aluminum alloy, semi-solid casting is difficult.

一方、5052アルミニウム合金は５０００系アルミニウム合金の中でもMg含有量が中程度であり、構造用材料として、一般板金、船舶、車両、建築、缶エンド、ハニカムコア等の用途がある。また、５０００系アルミニウム合金に対して傾斜冷却板を用いたセミソリッドスラリーの作製が有効であれば、凝固温度範囲の狭い同様の合金にも適用でき、応用範囲が広がることが期待でき、これらの加工にもセミソッリドプロセスが適用できれば、新しい加工法として発展できる。そこで、固液共存温度領域の狭い合金にも傾斜冷却板を用いたセミソリッド鋳造の適用を可能とすることが望まれている。   On the other hand, the 5052 aluminum alloy has a medium Mg content among the 5000 series aluminum alloys, and has structural uses such as general sheet metal, ships, vehicles, buildings, can ends, and honeycomb cores. In addition, if it is effective to produce a semi-solid slurry using an inclined cooling plate for a 5000 series aluminum alloy, it can be applied to a similar alloy having a narrow solidification temperature range, and the application range can be expected to expand. If the semi-solid process can be applied to processing, it can be developed as a new processing method. Therefore, it is desired that semi-solid casting using an inclined cooling plate can be applied to an alloy having a narrow solid-liquid coexisting temperature region.

本発明は、かかる要望に応えるもので、5052アルミニウム合金のように、固液共存領域の温度幅が極端に狭い合金例えば５０℃未満の合金において、微細結晶粒が得られるセミソリッド鋳造を実現可能とする鋳造方法を提供することを目的とする。   The present invention responds to such a demand, and it is possible to realize semi-solid casting that can obtain fine crystal grains in an alloy having an extremely narrow temperature range in a solid-liquid coexistence region such as 5052 aluminum alloy, for example, an alloy of less than 50 ° C. An object of the present invention is to provide a casting method.

かかる目的を達成するため、本願発明者等が種々実験及び検討を重ねた結果、5052アルミニウム合金のように固液共存温度領域の狭い合金は傾斜冷却板上で凝固殻が生成しやすく、これを抑えるために他の合金の場合よりも厚い断熱機能を有する離型材の膜を塗布することが考えられるが、厚すぎると十分な冷却を行うことができず、初晶αアルミニウムの遊離にも限界があるという二律相反の関係にある。そこで、より効果的な冷却を行うために冷却板の長さ方向の膜厚を変化させる実験を行った結果、冷却板上に合金が張り付き、凝固殻が生成する現象は溶湯が冷却板に流下してから30mm程度の位置で発生しやすいことがわかった。このことから、冷却板の表面の断熱機能を有する離型材の膜厚を冷却板の上流側と下流側とで変化させることによって、どんな合金にもセミソリッド鋳造方法が適用できることを知見するに至った。また、断熱材膜の膜厚を均一とする場合にも5052アルミニウム合金のセミソリッド鋳造を可能とする膜厚が存在することを知見するに至った。   In order to achieve this object, the inventors of the present application have conducted various experiments and studies. As a result, an alloy having a narrow solid-liquid coexistence temperature range, such as 5052 aluminum alloy, tends to generate solidified shells on the inclined cooling plate. In order to suppress it, it is conceivable to apply a release material film having a heat insulation function thicker than that of other alloys, but if it is too thick, sufficient cooling cannot be performed and the release of primary α-aluminum is also limited. There is a contradictory relationship that there is. Therefore, as a result of an experiment in which the thickness of the cooling plate was changed in order to perform more effective cooling, the phenomenon that the alloy stuck to the cooling plate and solidified shells formed was caused by the molten metal flowing down the cooling plate. After that, it was found to occur easily at a position of about 30 mm. This has led to the finding that the semi-solid casting method can be applied to any alloy by changing the film thickness of the release material having the heat insulation function on the surface of the cooling plate between the upstream side and the downstream side of the cooling plate. It was. Moreover, even when the film thickness of the heat insulating material film is made uniform, it has been found that there is a film thickness that enables semi-solid casting of 5052 aluminum alloy.

本発明にかかるセミソリッド鋳造方法は、かかる知見に基づくものであって、合金溶湯を傾斜させた冷却板上に流下させて該傾斜冷却板上でα初晶を生成かつ遊離させて固液共存状態のスラリーを得る工程と、このスラリーを温度勾配のないタンディッシュで固液共存領域内の温度域に保持して前記α相粒子を粒状化させる工程とを含むセミソリッド鋳造方法において、前記傾斜冷却板の表面に断熱機能を備える離型材を形成し、かつ前記離型材の膜厚を固液共存領域の温度幅が狭くなる程厚くなる関係に調整したものである。BN膜厚さは適切な厚さになると溶湯の過冷度が大きくなり、核生成が容易になり、より多くの結晶が遊離され、凝固組織が微細になる。   The semi-solid casting method according to the present invention is based on such knowledge, and causes the molten alloy to flow down on a tilted cooling plate to generate and release α primary crystals on the tilted cooling plate to coexist with solid and liquid. In the semi-solid casting method, including the step of obtaining a slurry in a state and the step of granulating the α-phase particles by maintaining the slurry in a temperature range in a solid-liquid coexistence region with a tundish without a temperature gradient. A release material having a heat insulation function is formed on the surface of the cooling plate, and the film thickness of the release material is adjusted to be thicker as the temperature range of the solid-liquid coexistence region becomes narrower. When the BN film thickness is appropriate, the degree of supercooling of the melt increases, nucleation is facilitated, more crystals are released, and the solidification structure becomes finer.

ここで、合金溶湯の固液共存領域の温度幅が５０℃以下の場合には、傾斜冷却板の表面の離型材の膜厚を傾斜冷却板の下側よりも上側が厚膜としたものであることが好ましく、より好ましくは離型材がＢＮ膜からなり、傾斜冷却板の下流側では膜厚３０μｍであり、溶湯が注がれる上流側では合金溶湯の固液共存領域の温度幅に応じて下流側膜厚よりも厚く形成されていることである。さらには、合金溶湯の固液共存領域の温度幅が５０℃以下の場合における離型材の膜厚は、傾斜冷却板の溶湯が注がれる上流側で１０５μｍ以上、それよりも下流側では膜厚３０μｍであることが好ましく、さらには傾斜冷却板の上流側の厚膜の離型材が溶湯流下方向に少なくとも３０ｍｍの長さ、下流側の薄膜の離型材が１６０ｍｍの長さで形成されていることが好ましい。   Here, when the temperature range of the solid-liquid coexistence region of the molten alloy is 50 ° C. or less, the film thickness of the release material on the surface of the inclined cooling plate is thicker on the upper side than the lower side of the inclined cooling plate. Preferably, the release material is made of a BN film, has a film thickness of 30 μm on the downstream side of the inclined cooling plate, and depends on the temperature range of the solid-liquid coexistence region of the molten alloy on the upstream side where the molten metal is poured. It is formed thicker than the downstream film thickness. Furthermore, when the temperature range of the solid-liquid coexistence region of the molten alloy is 50 ° C. or less, the film thickness of the release material is 105 μm or more on the upstream side where the molten metal of the inclined cooling plate is poured, and the film thickness on the downstream side. It is preferable that the thickness is 30 μm, and further, the thick film release material on the upstream side of the inclined cooling plate is formed in a length of at least 30 mm in the molten metal flow direction, and the thin film release material on the downstream side is formed in a length of 160 mm. Is preferred.

また、合金溶湯の固液共存領域の温度幅が５０℃以下の場合には、傾斜冷却板の表面の全長に１０５μｍの均一膜厚のＢＮ膜を形成することも好ましい。この場合にも、傾斜冷却板の表面に溶湯が貼り付いて凝固殻となるのを防ぎ、半凝固スラリーを得ることができる。   When the temperature range of the solid-liquid coexistence region of the molten alloy is 50 ° C. or less, it is also preferable to form a BN film having a uniform film thickness of 105 μm on the entire length of the surface of the inclined cooling plate. Also in this case, it is possible to prevent the molten metal from sticking to the surface of the inclined cooling plate to become a solidified shell, and to obtain a semi-solid slurry.

さらに、本発明のセミソリッド鋳造方法において、傾斜冷却板の表面での溶湯の流量は、0.018リットル／秒〜0.038リットル／秒の範囲であることが好ましい。この溶湯の流量も溶湯の冷却板上の過冷度に影響して、結晶の遊離する数に影響する。   Furthermore, in the semisolid casting method of the present invention, the flow rate of the molten metal on the surface of the inclined cooling plate is preferably in the range of 0.018 liter / second to 0.038 liter / second. The flow rate of the molten metal also affects the degree of supercooling of the molten metal on the cooling plate and affects the number of crystals released.

さらに、本発明のセミソリッド鋳造方法によって得られたスラリーを用いてビレットを製造する連続鋳造方法においては、連続鋳造装置の鋳型のキャビティに窒化ボロンの膜を形成し、3mm/s以下の鋳造速度でビレットを連続鋳造することが好ましく、さらに好ましくはタンディシュを前記傾斜冷却板の直下のスラリー温度と同じ温度に予熱しておくことである。   Furthermore, in the continuous casting method for producing a billet using the slurry obtained by the semi-solid casting method of the present invention, a boron nitride film is formed in the mold cavity of the continuous casting apparatus, and the casting speed is 3 mm / s or less. It is preferable to continuously cast the billet, and it is more preferable to preheat the tundish to the same temperature as the slurry temperature immediately below the inclined cooling plate.

本発明のセミソリッド鋳造方法によれば、5052Ａｌのような固液共存領域の温度幅が極端に狭い（３７℃）合金に対しても、傾斜冷却板上での溶湯の急速固化による冷却板への張り付き・凝固シェルの形成を防いで、結晶遊離・初晶析出を起こさせて、半凝固スラリーを作り出すことが可能となる。すなわち、傾斜冷却板を利用してスラリーを得るセミソリッド鋳造方法を、5052Ａｌのような固液共存領域の温度幅が極端に狭い（３７℃）合金に対しても適用可能にできる。このことは、5052Ａｌに代表される５０００系Ａｌ合金に限られず、固液共存領域の温度幅が極端に狭いその他の合金種に対しても同様である。   According to the semi-solid casting method of the present invention, an alloy having an extremely narrow temperature range in a solid-liquid coexistence region such as 5052Al (37 ° C.) can be converted into a cooling plate by rapid solidification of a molten metal on an inclined cooling plate. The formation of a semi-solid slurry can be created by preventing the formation of a solidified shell and the formation of a solidified shell, causing crystal release and primary crystal precipitation. That is, the semi-solid casting method for obtaining slurry using an inclined cooling plate can be applied to an alloy such as 5052Al in which the temperature range of the solid-liquid coexistence region is extremely narrow (37 ° C.). This is not limited to the 5000 series Al alloy represented by 5052Al, and the same applies to other alloy types in which the temperature range of the solid-liquid coexistence region is extremely narrow.

さらに、本発明において、傾斜冷却板の表面の離型材の膜厚を傾斜冷却板の下流側よりも溶湯が注がれる上流側が厚膜とした場合には、平均結晶粒径も細かい半凝固スラリーを得ることができる。加えて、BN膜厚さは適切な厚さになると溶湯の過冷度が大きくなり、核生成が容易になり、より多くの結晶が遊離され、凝固組織がより微細になる。   Furthermore, in the present invention, when the film thickness of the release material on the surface of the inclined cooling plate is a thick film on the upstream side where the molten metal is poured from the downstream side of the inclined cooling plate, the semi-solid slurry having a fine average crystal grain size Can be obtained. In addition, when the BN film thickness is an appropriate thickness, the degree of supercooling of the melt increases, nucleation is facilitated, more crystals are released, and the solidification structure becomes finer.

さらに、請求項７記載の発明によると、適切な範囲に調整された溶湯の流量は溶湯の冷却板上で過冷度に影響を与え、結晶遊離に影響することから、即ち傾斜冷却板上での溶湯の流量を過冷度が上がるように制御可能であることから、結晶の平均粒径を小さくすることができる。本発明者等の実験によれば、45μｍの微細結晶が得られた。   Furthermore, according to the invention described in claim 7, the flow rate of the molten metal adjusted to an appropriate range affects the degree of supercooling on the molten metal cooling plate and affects the crystal release, that is, on the inclined cooling plate. Since the flow rate of the molten metal can be controlled so as to increase the degree of supercooling, the average grain size of the crystals can be reduced. According to experiments by the present inventors, fine crystals of 45 μm were obtained.

また、請求項８及び９の連続鋳造方法によると、タンディッシュを加熱することで結晶粒径が４５μｍまで均一かつ微細粒状組織を有するビレット作製することが可能である。そして、本発明の連続鋳造方法によって得られたビレットの外側のチル層は冷却板から遊離する結晶数の増加に従って薄くなり、本発明者等の実験によると２〜３ｍｍまで薄くなって歩留まりを大幅に改善できた。   Further, according to the continuous casting method of claims 8 and 9, it is possible to produce a billet having a uniform and fine grain structure with a crystal grain size of 45 μm by heating the tundish. And the chill layer outside the billet obtained by the continuous casting method of the present invention becomes thinner as the number of crystals released from the cooling plate increases, and according to the experiments by the present inventors, it becomes thinner to 2 to 3 mm, greatly increasing the yield. It was possible to improve.

以下、本発明のセミソリッド鋳造方法を一実施形態に基づいて詳細に説明する。尚、本実施形態では、固液共存領域の温度幅が狭い合金の一例として5052アルミニウム合金を例に挙げ、傾斜冷却板を用いたセミソリッド鋳造方法の実施の一形態を詳細に説明する。   Hereinafter, the semi-solid casting method of the present invention will be described in detail based on one embodiment. In the present embodiment, 5052 aluminum alloy is taken as an example of an alloy having a narrow temperature range in the solid-liquid coexistence region, and an embodiment of the semi-solid casting method using the inclined cooling plate will be described in detail.

本発明のセミソリッド鋳造方法は、合金溶湯を傾斜させた冷却板上に流下させて該傾斜冷却板上でα初晶を生成かつ遊離させて固液共存状態のスラリーを得る工程と、このスラリーを温度勾配のないタンディッシュで固液共存領域内の温度域に保持してα相粒子を粒状化させる工程とを含むものであり、得られた半凝固スラリーは用途に応じて半凝固加工法（Rheocasting）あるいは半溶融加工法（Thixocasting）に供される。   The semi-solid casting method of the present invention includes a step of flowing a molten alloy on a tilted cooling plate to generate and release α primary crystals on the tilted cooling plate to obtain a solid-liquid coexisting slurry, and the slurry. In a solid-liquid coexistence region in a tundish without a temperature gradient and granulating α-phase particles, and the obtained semi-solid slurry is a semi-solid processing method depending on the application. (Rheocasting) or semi-melt processing (Thixocasting).

セミソリッド鋳造を行う設備としては、例えば水平連続鋳造システムの場合には、図１に示すように、合金融液を得る溶解炉１と、合金融液をスラリー化する傾斜冷却板２と、固液共存領域内の温度域でスラリーを等温保持するタンディシュ１３並びに水平連続鋳造設備１４とを備え、傾斜冷却板２で得られたスラリー１０をタンディシュ１３で所定時間等温保持されることによって傾斜冷却板２の上を流れる間にα晶を生成させてスラリーとなった溶湯を、タンディシュ１３で所定時間等温保持される間にデンドライトを種として粒状に結晶を成長させ、連接された水平連続鋳造１４の水冷鋳型で周囲から連続的に急冷凝固させながら引き抜き、柱状のビレットや板材などを製造する。また、図示していないが、タンディシュ１３の代わりに加熱鋳型などを用い、傾斜冷却板２で得られたスラリー１０を直接加熱鋳型で保持した後に急冷により鋳塊を製造することもある。尚、図中の符号５は坩堝、６はプランジャ、７は連絡路、８は合金溶液、１５注水手段である。   As equipment for performing semi-solid casting, for example, in the case of a horizontal continuous casting system, as shown in FIG. 1, a melting furnace 1 for obtaining a combined financial liquid, an inclined cooling plate 2 for slurrying the combined financial liquid, An inclined cooling plate is provided with a tundish 13 that keeps the slurry isothermal in the temperature range within the liquid coexistence region and a horizontal continuous casting facility 14, and the slurry 10 obtained by the inclined cooling plate 2 is kept isothermally in the tundish 13 for a predetermined time. The molten crystal that is formed into a slurry by generating α crystals while flowing over 2 is grown in a granular form using dendrites as seeds while being kept isothermally in the tundish 13 for a predetermined time. Pull out while continuously cooling and solidifying from the surroundings with a water-cooled mold to produce columnar billets and plate materials. Although not shown, a heated mold or the like may be used instead of the tundish 13, and the ingot may be manufactured by rapid cooling after the slurry 10 obtained by the inclined cooling plate 2 is directly held by the heated mold. In the figure, reference numeral 5 is a crucible, 6 is a plunger, 7 is a communication path, 8 is an alloy solution, and 15 water injection means.

ここで、傾斜冷却板２は例えば純銅製であり、傾斜冷却板２の裏面側には、傾斜冷却板２を冷却する冷却手段としての冷却水路９が設けられている。本発明のセミソリッド鋳造方法においては、傾斜冷却板２の表面に断熱機能を備える離型材の膜３を形成し、かつ該離型材膜３の膜厚を固液共存領域の温度幅が狭くなる程厚くなる関係に調整したことに特徴を有する。すなわち、固液共存領域の温度の幅に応じて断熱機能を備える離型材の膜３の膜厚を調整することによって、さまざまな合金をセミソリッド鋳造・加工可能とするものである。5052Ａｌ合金のように、固液共存領域の温度差が極端に狭い合金の場合には、傾斜冷却板によって奪われるエネルギ（抜熱量）が過度となり、接触面で凝固殻（シェル）が形成され易い。そして、一旦凝固殻が傾斜冷却板２の上に形成されると、結晶の遊離がなくなり、セミソリッドスラリーが作れないことになる。そこで、傾斜冷却板２の表面には、流下する溶湯が冷却板上で凝固殻を形成しないように、断熱機能を備える離型材（溶湯の流れを妨げない断熱材・凝固殻生成防御剤）の膜３を、初晶αアルミニウムの遊離を妨げない範囲で形成するようにしている。   Here, the inclined cooling plate 2 is made of, for example, pure copper, and a cooling water passage 9 as a cooling means for cooling the inclined cooling plate 2 is provided on the back side of the inclined cooling plate 2. In the semi-solid casting method of the present invention, a release material film 3 having a heat insulating function is formed on the surface of the inclined cooling plate 2, and the thickness of the release material film 3 is reduced in the temperature range of the solid-liquid coexistence region. The feature is that the relationship is adjusted so as to be thicker. That is, by adjusting the film thickness of the release material film 3 having a heat insulating function according to the temperature range of the solid-liquid coexistence region, various alloys can be semi-solid casted and processed. In the case of an alloy where the temperature difference in the solid-liquid coexistence region is extremely narrow like 5052Al alloy, the energy (heat removal amount) taken away by the inclined cooling plate becomes excessive, and a solidified shell (shell) is likely to be formed on the contact surface. . Once the solidified shell is formed on the inclined cooling plate 2, the crystals are not released and a semi-solid slurry cannot be formed. Therefore, on the surface of the inclined cooling plate 2, a release material having a heat insulating function (a heat insulating material and a solidified shell formation protective agent that does not hinder the flow of the molten metal) is provided so that the molten metal that flows down does not form a solidified shell on the cooling plate. The film 3 is formed in a range that does not hinder the liberation of the primary α-aluminum.

断熱機能を備える離型材としては、固液共存領域の温度幅が狭い溶湯の冷却を緩和して凝固殻の生成・冷却板への貼り付きを防止し得る低熱伝導率、濡れ性、耐火耐熱性などを有する物質の使用が好ましく、例えば窒化ボロン（ＢＮと略称する）の粒子の使用が好ましい。ＢＮは、冷却板の熱伝導率（３８６W/mK）に比べて桁違いに小さな熱伝導率（３０W/mK前後）の高融点（3273Ｋ）材料である。   As a mold release material with a heat insulation function, it has low thermal conductivity, wettability, fire resistance and heat resistance, which can ease the cooling of the molten metal with a narrow temperature range in the solid-liquid coexistence region and prevent the formation of solidified shell and sticking to the cooling plate For example, it is preferable to use particles of boron nitride (abbreviated as BN). BN is a high melting point (3273K) material with a thermal conductivity (around 30 W / mK) that is orders of magnitude smaller than that of the cooling plate (386 W / mK).

このＢＮ膜３は、流下する溶湯によってＢＮ粒子が剥離したり、溶湯８が直に傾斜冷却板に接触することがないように、緻密に密着していることが好ましい。同時に、ＢＮ膜３の断面および表面は、凹凸があり、沢山の空洞が存在することが好ましい。このような表面性状は溶湯との接触面積を増やし、核生成数を増やす。また、接触面での溶湯の温度分布を不安定にし、溶湯によって閉じ込められた空気の膨張、収縮により、溶湯に揺らぎを与えて冷却板からの結晶の遊離を促進すると推測される。このような表面形状は噴射用ガスとしてのブタンガスなどの蒸発とスプレー時のＢＮ粒子がランダムに付着することによってできたものと考えられる。   It is preferable that the BN film 3 is closely adhered so that the BN particles do not peel off due to the molten metal flowing down or the molten metal 8 does not directly contact the inclined cooling plate. At the same time, it is preferable that the cross section and the surface of the BN film 3 have irregularities and there are many cavities. Such surface properties increase the contact area with the molten metal and increase the number of nucleation. Further, it is presumed that the temperature distribution of the molten metal at the contact surface becomes unstable, and the expansion and contraction of the air confined by the molten metal gives the molten metal a fluctuation and promotes the liberation of crystals from the cooling plate. Such a surface shape is considered to be formed by evaporation of butane gas as a jetting gas and random attachment of BN particles during spraying.

このようなＢＮ膜３は、例えば粘結剤を含むＢＮパウダーを傾斜冷却板上に斑無く塗布して、Ａｒガスで保護しながら電気炉中で３００℃〜４００℃まで加熱することによって作製することができる。本実施形態では、表１に示す市販のＢＮスプレーを傾斜冷却板の表面にスプレーして、所定の厚みに塗布してから炉中加熱することで製作している。しかし、ガスバーナなどで加熱することによっても簡易にＢＮ膜を形成することができる。
Such a BN film 3 is produced by, for example, coating BN powder containing a binder on an inclined cooling plate without any spots and heating to 300 ° C. to 400 ° C. in an electric furnace while protecting with Ar gas. be able to. In this embodiment, the commercially available BN spray shown in Table 1 is sprayed on the surface of the inclined cooling plate, applied to a predetermined thickness, and then heated in a furnace. However, the BN film can be easily formed by heating with a gas burner or the like.

ここで、本実施形態において用いたＢＮは六方晶系結晶構造であり、密度ρ：19.2 g/cｍ３、比熱C: 0.885J/gK、熱伝導率λ：28〜33W/mKである。なお、ＢＮパウダーの最も多い粒子径は4〜5μｍである。ブチルジルコネートは粘結剤で、BN同士をお互いに粘着させる役割をしている。シクロペンタン、プロパン、ブタンガスはBNを塗布する際、BNを噴射する役割をしている。これら粘結剤並びに噴射ガス成分は、加熱時に酸素と反応してＨ２Ｏ，ＣＯ２としてなくなってしてしまうが、ブチルジルコネートの一部はＺｒＯ２およびアモルファス状態に存在するブチルジルコネートとなってＢＮ粒子と共に膜内に残るものと推定される。 Here, BN used in the present embodiment has a hexagonal crystal structure, density ρ: 19.2 g / cm3, specific heat C: 0.885 J / gK, and thermal conductivity λ: 28 to 33 W / mK. The most common particle size of BN powder is 4-5 μm. Butyl zirconate is a binder and serves to adhere BN to each other. Cyclopentane, propane, and butane gas play a role of injecting BN when BN is applied. These binders and propellant gas components react with oxygen during heating and disappear as H 2 O, CO 2 , but a part of butyl zirconate is ZrO 2 and butyl zirconate present in an amorphous state. It is estimated that it remains in the film together with the BN particles.

傾斜冷却板２の表面を被覆する断熱機能を備える離型材膜３の膜厚は、固液共存領域の温度の幅が狭くなるほど冷却を緩和して凝固殻の生成を防ぐため、固液共存領域の温度の幅に応じて調整され、温度幅に逆比例して膜厚を厚くすることが好ましい。ここで、合金溶湯の固液共存領域の温度幅が極端に狭い合金例えば温度幅が５０℃以下の合金の場合においては、凝固殻が生成され易く、かつ凝固殻が生成する現象は溶湯が冷却板に流下した直後の位置で発生し易い。他方、デンドライト結晶の成長を防ぎ粒状結晶を得るには、本発明者等の実験から単に溶湯から熱エネルギを奪うだけでなく結晶遊離を起こさせる熱流束が得られる断熱性・膜厚薄さを必要とし、さらに微細な結晶粒を得るには、凝固殻が生成されない範囲で最大の熱流束を得る膜厚であることが必要であることが判明した。そこで、固液共存領域の温度幅が極端に狭い合金例えば温度幅が５０℃以下の合金の場合においては、傾斜冷却板の溶湯が注がれる上流側の膜厚とそれよりも下流側の膜厚とを異ならせた不均一な膜厚とし、上流側の膜厚を下流側の膜厚よりも厚くなるように形成することが好ましく、この場合にはより微細な結晶粒が得られる。   The film thickness of the release material film 3 having a heat insulating function for covering the surface of the inclined cooling plate 2 is reduced in the solid-liquid coexistence region temperature so that the cooling is eased to prevent the formation of solidified shells. It is preferable that the film thickness is adjusted in accordance with the temperature range, and the film thickness is increased in inverse proportion to the temperature range. Here, in the case of an alloy in which the temperature range of the solid-liquid coexistence region of the molten alloy is extremely narrow, for example, an alloy having a temperature range of 50 ° C. or less, a solidified shell is likely to be generated, and the phenomenon that the solidified shell is generated is that the molten metal is cooled. It is likely to occur at a position immediately after flowing down the plate. On the other hand, in order to prevent the growth of dendrite crystals and obtain granular crystals, it is necessary to have heat insulation and thin film thickness that can obtain heat flux that causes crystal liberation as well as taking heat energy from the molten metal from our experiments. In order to obtain finer crystal grains, it has been found that it is necessary to have a film thickness that provides the maximum heat flux within a range in which a solidified shell is not generated. Therefore, in the case of an alloy having an extremely narrow temperature range in the solid-liquid coexistence region, for example, an alloy having a temperature range of 50 ° C. or less, the film thickness on the upstream side where the molten metal of the inclined cooling plate is poured and the film on the downstream side It is preferable to form a non-uniform film thickness that is different from the thickness, so that the upstream film thickness is larger than the downstream film thickness. In this case, finer crystal grains can be obtained.

例えば、5052Ａｌ合金のように固液共存領域の温度幅が極端に狭い合金において、断熱機能を備える離型材としてＢＮを使用する場合でかつ傾斜冷却板の表面に均一膜厚でＢＮを塗布する場合のＢＮ膜厚は、95μmよりも厚く115μmよりも薄いことが好ましく、より好ましくは100μｍから110μｍの範囲、さらに好ましくは105μｍ程度である。ＢＮ膜厚が95μm以下および115μm以上の場合には、ともにαアルミニウムのデンドライトと粒状晶の混ざった組織が観察され、セミソリッド鋳造は実現できるものの、平均結晶粒径のより微細化への効果が少ない。最も良好なＢＮ膜厚105μmの場合には、冷却板上で生成遊離した初晶αアルミニウムが金型内で多数存在し、平均粒径70μm程度まで微細化された粒状組織が得られた。   For example, in the case where BN is used as a mold release material having a heat insulating function in an alloy having an extremely narrow temperature range in the solid-liquid coexistence region such as 5052Al alloy, and when BN is applied with a uniform film thickness on the surface of the inclined cooling plate The BN film thickness is preferably greater than 95 μm and less than 115 μm, more preferably in the range of 100 μm to 110 μm, and even more preferably about 105 μm. When the BN film thickness is 95 μm or less and 115 μm or more, a structure in which α-aluminum dendrite and granular crystals are mixed is observed, and although semi-solid casting can be realized, the effect on the refinement of the average crystal grain size is further improved. Few. In the case of the best BN film thickness of 105 μm, a large amount of primary aluminum α formed and liberated on the cooling plate was present in the mold, and a granular structure refined to an average particle size of about 70 μm was obtained.

また、溶湯の流下方向にＢＮ膜厚を不均一とする場合には、溶湯が注がれる傾斜冷却板の上流側の膜厚は少なくとも95μmよりも厚くすること、好ましくは110μmよりも厚く、より好ましくは105μｍ以上、さらに好ましくは110μｍ以上、さらに好ましくは115μｍ以上とすることであり、より確実に溶湯が注がれる傾斜冷却板上流側での凝固殻の生成・貼り付きを防ぐには120μｍ程度とすることである。また、5052Ａｌ合金よりも固液共存領域の温度幅が狭い合金の場合には、上流側の膜厚は120μmよりもさらに厚くすることによって溶湯の貼り付き・凝固殻の生成を防ぐことができる。ここで、ＢＮ膜厚を厚くする上流域の長さは、冷却板上に合金が張り付き、凝固殻が生成する現象は溶湯が冷却板に流下してから30mm程度の位置で発生しやすいことが本発明者等の実験でわかった。そこで、冷却板上に合金が張り付き、凝固殻が生成する現象が起きうる範囲、例えば溶湯が落下する位置から30mm程度の部分のBN膜厚を120μm程度に調節して塗布することが好ましい。   When the BN film thickness is non-uniform in the flow direction of the molten metal, the film thickness on the upstream side of the inclined cooling plate into which the molten metal is poured should be at least 95 μm, preferably more than 110 μm, Preferably it is 105 μm or more, more preferably 110 μm or more, more preferably 115 μm or more, and about 120 μm to prevent the formation and sticking of the solidified shell on the upstream side of the inclined cooling plate where the molten metal is poured more reliably. It is to do. Further, in the case of an alloy having a temperature range in the solid-liquid coexistence region narrower than that of the 5052Al alloy, it is possible to prevent the adhesion of molten metal and the formation of a solidified shell by making the film thickness on the upstream side further thicker than 120 μm. Here, the length of the upstream region where the BN film thickness is increased is that the phenomenon that the alloy sticks to the cooling plate and the solidified shell is formed tends to occur at a position of about 30 mm after the molten metal flows down to the cooling plate. It was found by experiments by the inventors. Therefore, it is preferable to apply the BN film in a range where the alloy is stuck on the cooling plate and a phenomenon in which a solidified shell is generated, for example, about 30 mm from the position where the molten metal falls, is adjusted to about 120 μm.

他方、下流域においては結晶遊離を積極的に起こさせる必要があることから、ＢＮ膜厚が上流側よりも遙かに薄く形成されることが好ましい。本発明者等の実験の結果、BN膜厚の違いよる結晶粒径の差異は、冷却板上で起こる溶湯の過冷度に起因すると考えられる。そして、３０μｍ〜１２０μｍの間でＢＮ膜厚と熱流束との関係を求めた本発明者等の実験によれば、ＢＮ膜厚は３０μｍの時に最大の熱流束が得られた。ここで、３０μｍよりも薄いＢＮ膜厚でも大きな熱流束は得られるが、薄くなればなるほどＢＮ膜の表面の凹凸が溶湯の流れで剥離する可能性が加速的に高まり溶湯の流れに対する膜強度の低下による破壊の虞が生ずる。また、ＢＮ膜が薄すぎると、凝固殻が生成されて溶湯が貼り付く虞があり、結局それが断熱層となって冷却能力の低下による初晶遊離が起こらない事態が生ずる。このため、下流側の膜厚は、２０μｍよりも厚いこと、好ましくは３０μｍ程度の薄さとすることである。さらに、この下流側の冷却板長さは、結晶の遊離に影響することが本発明者等の実験によって判明した。この実験の結果、冷却板の下流側の長さは160mm程度のときに初晶αＡｌの数が最も多くなり、微細な結晶粒径が得られた。140ｍｍおよび180ｍｍの場合、ともに初晶αアルミニウムは冷却板長さが160mmよりも粗大であった。これは溶湯と冷却板の接触時間が短かすぎると熱エネルギーの移動が少ないために、初晶αアルミニウムの数が少なり、反対に接触時間が長過ぎると熱エネルギー移動が多すぎて凝固殻が生成して、初晶αアルミニウムの数が減り、結果として結晶粒径が大きくなったと考えられる。このことから、凝固殻の生成を妨げる反面、初晶αＡｌの数を増やす熱エネルギの移動を実現する傾斜冷却板の下流長さに設定することが結晶粒径の微細化に効果的であることが理解できる。このことから、冷却板の下流側の長さは140mmよりも長く180mmよりも短いこと、好ましくは145mm〜175mm、より好ましくは150mm〜170mm、さらに好ましくは160mm程度である。   On the other hand, since it is necessary to positively cause crystal release in the downstream region, it is preferable that the BN film thickness be formed much thinner than the upstream side. As a result of experiments by the present inventors, it is considered that the difference in crystal grain size due to the difference in BN film thickness is due to the degree of supercooling of the molten metal that occurs on the cooling plate. And according to the experiments by the present inventors who have obtained the relationship between the BN film thickness and the heat flux between 30 μm and 120 μm, the maximum heat flux was obtained when the BN film thickness was 30 μm. Here, a large heat flux can be obtained even with a BN film thickness smaller than 30 μm. However, the thinner the film thickness, the higher the possibility that the unevenness of the surface of the BN film will be peeled off by the melt flow, and the film strength against the melt flow is increased. There is a risk of destruction due to lowering. On the other hand, if the BN film is too thin, there is a possibility that a solidified shell is formed and the molten metal sticks, and eventually, it becomes a heat insulating layer, and there is a situation in which primary crystal liberation due to a decrease in cooling capacity does not occur. For this reason, the film thickness on the downstream side is thicker than 20 μm, preferably about 30 μm. Furthermore, it has been found by experiments by the present inventors that the downstream cooling plate length affects the liberation of crystals. As a result of this experiment, when the downstream side length of the cooling plate was about 160 mm, the number of primary crystals αAl was the largest, and a fine crystal grain size was obtained. In both cases of 140 mm and 180 mm, the primary α-aluminum had a cooling plate length coarser than 160 mm. This is because if the contact time between the molten metal and the cooling plate is too short, there is little heat energy transfer, so the number of primary α-aluminum is small, and conversely if the contact time is too long, there is too much heat energy transfer and the solidified shell. It is considered that the number of primary α-aluminum decreased, resulting in an increase in crystal grain size. For this reason, while preventing the formation of solidified shells, setting the downstream length of the inclined cooling plate that realizes the transfer of thermal energy to increase the number of primary αAl is effective in reducing the crystal grain size. Can understand. Therefore, the downstream length of the cooling plate is longer than 140 mm and shorter than 180 mm, preferably 145 mm to 175 mm, more preferably 150 mm to 170 mm, and still more preferably about 160 mm.

また、傾斜冷却板上での溶湯の流速は、BN膜と溶湯との間の温度境界層に影響を与え、溶湯の過冷度に影響することが本発明者等の実験によって明らかになった。ここで、溶湯の流速は、離型材の膜例えばＢＮ膜の表面状態や溶湯の粘性などにも影響されるが、同一条件下では傾斜冷却板の傾きの大きさに影響される。そこで、傾斜冷却板の傾きが凝固組織に与える影響について本発明者等が実験した結果、初晶の生成および遊離に最適な冷却板の角度は60°前後、溶湯の流速としては１．４ｍ／ｓ前後であることが最適であることが判明した。冷却板の角度を60°よりも大きくするに従って溶湯の流速が大きくなり、BN表面と溶湯の間の温度境界層が薄くなって、BNと溶湯の間の温度勾配が小さくなり、遊離する初晶αAlも少なくなったと推定される。逆に冷却板の角度が６０°よりも小さくなるに従って、BNと溶湯の間の温度境界層が厚くなるが、溶湯の流速が小さいためにより多くの熱エネルギーが奪われ、ただちに初晶による凝固殻が生成され、そのために生成遊離する結晶が少なくなり、結晶が粗大化されると考えられる。このことから、冷却板の傾斜角度は、50°よりも急で70°よりも緩やか、好ましくは55°〜65°、より好ましくは60°程度である。   Further, it has been clarified through experiments by the present inventors that the flow velocity of the molten metal on the inclined cooling plate affects the temperature boundary layer between the BN film and the molten metal and affects the degree of supercooling of the molten metal. . Here, the flow rate of the molten metal is affected by the surface condition of the release material film, for example, the BN film, the viscosity of the molten metal, and the like, but under the same conditions, it is influenced by the inclination of the inclined cooling plate. Accordingly, as a result of experiments conducted by the present inventors on the influence of the inclination of the inclined cooling plate on the solidification structure, the optimum cooling plate angle for the formation and release of primary crystals is around 60 °, and the molten metal flow rate is 1.4 m / It has been found that it is optimal to be around s. As the angle of the cooling plate is increased from 60 °, the flow rate of the molten metal increases, the temperature boundary layer between the BN surface and the molten metal becomes thinner, the temperature gradient between the BN and the molten metal decreases, and the primary crystal that is liberated. It is estimated that αAl has also decreased. On the contrary, as the angle of the cooling plate becomes smaller than 60 °, the temperature boundary layer between BN and the molten metal becomes thicker, but because the molten metal flow rate is small, more heat energy is taken away and immediately the solidified shell due to the primary crystal. Therefore, it is considered that the crystals that are generated and liberated are reduced and the crystals are coarsened. From this, the inclination angle of the cooling plate is steeper than 50 ° and gentler than 70 °, preferably 55 ° to 65 °, more preferably about 60 °.

尚、5052Al合金の場合における鋳造温度は、本発明者の実験の結果、液相線温度＋１０〜１２Ｋ程度が好ましく、より好ましくは液相線温度＋１０〜１１Ｋ、さらに好ましくは液相線温度＋１０Ｋである。液相線温度＋１２Ｋ以上では冷却板上で生成遊離する結晶の数も少なくなり、金型内での結晶粒径が大きくなり、液相線温度＋９Ｋでは冷却板表面に凝固殻が生成して初晶αAlの遊離を妨害して粗大化したαAlとデンドライト組織が混在する虞がある。このことから、5052Ａｌ合金の場合には929Kが最適である。また、5052Al合金の場合における傾斜冷却板２の直下での溶湯温度は、液相線温度直下の−１．５〜２．０Ｋであることが好ましい。この範囲に収まる抜熱量の冷却下に傾斜冷却板上で流下させて結晶遊離を生じさせる条件とすることによって、即ち傾斜冷却板の長さや、傾斜角度、材質、冷却板上での溶湯流量などの諸条件を適宜調整することで、セミソリッド鋳造を可能とする半凝固スラリーが安定して得られる。   The casting temperature in the case of 5052Al alloy is preferably about liquidus temperature +10 to 12K, more preferably liquidus temperature +10 to 11K, and more preferably liquidus temperature + 10K as a result of the inventor's experiment. is there. When the liquidus temperature is + 12K or higher, the number of crystals generated and liberated on the cooling plate decreases, the crystal grain size in the mold increases, and at the liquidus temperature of + 9K, solidified shells are generated on the surface of the cooling plate. There is a possibility that αAl and the dendrite structure which are coarsened by disturbing the liberation of crystal αAl are mixed. For this reason, 929K is optimal for the 5052Al alloy. Moreover, it is preferable that the molten metal temperature just under the inclination cooling plate 2 in the case of 5052Al alloy is -1.5-2.0K right under a liquidus temperature. By setting the conditions to cause crystal release by flowing down on the inclined cooling plate under cooling of the heat removal amount falling within this range, that is, the length of the inclined cooling plate, the inclination angle, the material, the flow rate of the molten metal on the cooling plate, etc. By appropriately adjusting these conditions, a semi-solid slurry that enables semi-solid casting can be stably obtained.

さらに、本発明者等の実験により、傾斜冷却板上での溶湯の流量も溶湯の過冷度に影響することが明らかとなった。流量が少ないとより多く過冷が起こるが、流量が0.018L/s未満では、溶湯が冷却板上に張り付く現象が起こった。また、溶湯の流量が0.038/sの場合、ビレットのミクロ組織はタンディシュの加熱あり、なしに関係なく結晶の平均粒径はいずれも６０μｍ程度まで微細化されたが、円形度係数は小さくなっていた。しかし、溶湯の流量が0.018L/sである場合、ビレットの鋳肌も綺麗であり、結晶の平均粒径は45μｍになった。これは、溶湯の流量が少なくなるに従って、溶湯の過冷が大きく発生したためたと考えられる。このことから、傾斜冷却板上での溶湯の流量は、結晶粒径を微細化する上ではより遅くして0.018L/sに近づけることであるが、過冷却を防いで溶湯が冷却板上に張り付く現象を回避する上では、あまり流量を少なくしないことが好ましい。そこで、溶湯の流量は0.018L/s〜0.038L/s、好ましくは0.02L/s〜0.034L/s、より好ましくは0.02L/s〜0.031L/s程度にすることである。尚、ビレットの外側のチル層も冷却板から遊離するαＡｌの数の増加に従って、２〜３ｍｍまで薄くなった。   Furthermore, experiments by the present inventors have revealed that the flow rate of the molten metal on the inclined cooling plate also affects the degree of supercooling of the molten metal. When the flow rate is small, more cooling occurs, but when the flow rate is less than 0.018 L / s, the phenomenon that the molten metal sticks to the cooling plate occurred. When the flow rate of the molten metal was 0.038 / s, the billet microstructure was heated by tundish, and regardless of whether the average grain size of the crystal was refined to about 60 μm, the circularity coefficient was small. It was. However, when the flow rate of the molten metal was 0.018 L / s, the billet casting surface was also beautiful, and the average grain size of the crystal was 45 μm. This is considered to be because the supercooling of the molten metal greatly occurred as the flow rate of the molten metal decreased. For this reason, the flow rate of the molten metal on the inclined cooling plate is slower and closer to 0.018 L / s in order to reduce the crystal grain size. In order to avoid the phenomenon of sticking, it is preferable not to reduce the flow rate too much. Therefore, the flow rate of the molten metal is 0.018 L / s to 0.038 L / s, preferably 0.02 L / s to 0.034 L / s, more preferably about 0.02 L / s to 0.031 L / s. The chill layer on the outside of the billet also became thinner to 2-3 mm as the number of αAl released from the cooling plate increased.

ここで、セミソリッド鋳造方法によって得られたスラリーを用いてビレットを連続鋳造法において製造する場合には、連続鋳造装置の鋳型のキャビティに窒化ボロンを塗布し、ＢＮ膜を形成しておくことが好ましい。連続鋳造用銅鋳型にBN膜を塗布しない場合、銅鋳型の冷却能力が強すぎたり、凝固界面の移動速度が速すぎることがあり、凝固殻がタンディシュの中に侵入して、スラリーの供給通路が塞がれてしまって、鋳造速度を変化させてもビレットを作製することができなくなる場合がある。鋳造速度が3mm/sの場合、タンディシュの加熱なしの時はビレットを作製することができなかったが、それを加熱した場合はビレットの作製には成功したが、鋳造速度が2mm/sの場合、タンディシュの加熱あり、なしのいずれもビレットの作製には成功した。このことから、ビレットの連続鋳造の際の鋳造速度は、3mm/s以下、好ましくは2mm/s程度とすることである。尚、ビレットの連続鋳造の際の鋳造速度が4mm/s以上になると、ビレットの作製が困難となった。   Here, when a billet is manufactured in a continuous casting method using a slurry obtained by a semi-solid casting method, boron nitride is applied to a mold cavity of a continuous casting apparatus to form a BN film. preferable. If the BN film is not applied to the copper mold for continuous casting, the cooling capacity of the copper mold may be too strong, or the movement speed of the solidification interface may be too fast, and the solidification shell will enter the tundish and the slurry supply passage May be blocked, making it impossible to produce billets even if the casting speed is changed. When the casting speed was 3 mm / s, the billet could not be made without heating the tundish, but when it was heated, the billet was successfully produced, but when the casting speed was 2 mm / s. The billet was successfully produced with and without tundish heating. For this reason, the casting speed during continuous casting of the billet is 3 mm / s or less, preferably about 2 mm / s. When the casting speed during continuous casting of the billet was 4 mm / s or more, it became difficult to produce the billet.

尚、タンディシュは、5052Al合金の場合で６００℃程度（固相線温度−９Ｋ程度）に予熱していることが結晶の粒状化を図る上で好ましい。タンディシュのスラリー温度と同じ温度への加熱は、ビレット作製が困難であった鋳造速度でのビレット作製を可能とする。タンディシュを加熱することによって、その中の初晶αアルミニウムの成長が抑制され、スラリーの流動性が改善され、充填性がよくなるためと考えられる。さらに、タンディシュの予熱は、固相率を変化させる。さらに、タンディシュでのスラリー１０の等温保持も、固相率を変化させるので、保持時間を調整することによってもタンディシュ内での固相率を調整できる。これらの調整によって、具体的には４０％〜５５％の固相率範囲とすることが好ましい。この場合には、ビレットのチル層の厚さを２〜３ｍｍに薄くすることができる。タンディシュの予熱は、固液共存領域の温度幅が狭くなるほど高い温度とすることが好ましい。また、傾斜冷却板の直下でスラリーを金型に鋳造して鋳塊を作製する場合には、金型の予熱は傾斜冷却板の直下のスラリー温度とほぼ同じ温度例えば９１６Ｋ（液相線温度−３Ｋ）程度にして、鋳造したセミソリッドスラリーの熱移動を少なくすることが結晶の粒状化を図る上で好ましい。   In the case of the 5052Al alloy, the tundish is preferably preheated to about 600 ° C. (solidus temperature of about −9 K) in order to achieve crystal granulation. Heating to the same temperature as the slurry temperature of the tundish enables billet production at a casting speed at which billet production was difficult. It is considered that heating the tundish suppresses the growth of primary crystal α-aluminum therein, improves the fluidity of the slurry, and improves the filling property. Furthermore, tundish preheating changes the solid fraction. Furthermore, isothermal holding of the slurry 10 in the tundish also changes the solid phase rate, so that the solid phase rate in the tundish can also be adjusted by adjusting the holding time. Specifically, it is preferable to adjust the solid phase ratio range from 40% to 55% by these adjustments. In this case, the thickness of the billet chill layer can be reduced to 2 to 3 mm. The preheating of the tundish is preferably performed at a higher temperature as the temperature range of the solid-liquid coexistence region becomes narrower. In addition, in the case of producing an ingot by casting the slurry into a mold immediately below the inclined cooling plate, the preheating of the mold is substantially the same as the slurry temperature immediately below the inclined cooling plate, for example, 916K (liquidus temperature − It is preferable to reduce the heat transfer of the cast semi-solid slurry to about 3K) in order to achieve crystal granulation.

以上のようにして、断熱機能を備える離型材の膜を固液共存領域の温度幅が狭くなる程厚くなる関係に調整して表面に形成した傾斜冷却板に、合金溶湯を流下させて該傾斜冷却板上でα初晶を生成かつ遊離させて固液共存状態のスラリーを得ると共に、このスラリーを温度勾配のないタンディッシュあるいは鋳型で固液共存領域内の温度域に保持してα相粒子を粒状化させることにより、従来実現できなかった5052Al合金のセミソリッド鋳造が可能となった。そして、本方法により得られた半凝固スラリーは用途に応じて半凝固加工法（Rheocasting）あるいは半溶融加工法（Thixocasting）に供される。   As described above, the molten alloy is allowed to flow down on the inclined cooling plate formed on the surface by adjusting the relationship between the release material film having a heat insulation function to be thicker as the temperature range of the solid-liquid coexistence region becomes narrower. The α primary crystals are generated and liberated on the cooling plate to obtain a slurry in the solid-liquid coexistence state, and this slurry is maintained in the temperature range in the solid-liquid coexistence region with a tundish or mold without a temperature gradient, and the α phase particles By granulating, semi-solid casting of 5052Al alloy, which could not be realized previously, became possible. The semi-solid slurry obtained by this method is subjected to a semi-solid processing method (Rheocasting) or a semi-melt processing method (Thixocasting) depending on the application.

（実施例１）
表２に示す化学組成の市販の5052Ａｌ合金を溶解して図１に示す溶解炉、傾斜冷却板および連続鋳造装置を用いてセミソリッド水平連続鋳造によってビレットを製造した。 Example 1
A commercial 5052Al alloy having the chemical composition shown in Table 2 was melted, and billets were produced by semisolid horizontal continuous casting using the melting furnace, the inclined cooling plate and the continuous casting apparatus shown in FIG.

このセミソリッド水平連続鋳造において、鋳造条件の一つである鋳造温度は極めて重要である。そこで、まず鋳造温度を決定するために選定した供試材の熱分析実験を行った。この熱分析実験では、断熱材を巻いた3号黒鉛るつぼに約500ｇの5052合金を入れ、電気炉で1073Kまで加熱し、溶解させた。電気炉からるつぼを取り出し、溶解させた5052合金にあらかじめ温度補正を行ったシースK型熱電対を挿入し、温度測定を行った。冷却曲線を記録して、液相線温度および固相線温度を決定した。この結果、液相線温度は919K、固相線温度は882Kであり、凝固温度範囲は37Kであることが確認できた。 In this semi-solid horizontal continuous casting, casting temperature, which is one of casting conditions, is extremely important. Therefore, a thermal analysis experiment was first performed on the specimen selected to determine the casting temperature. In this thermal analysis experiment, about 500 g of 5052 alloy was placed in a No. 3 graphite crucible wrapped with a heat insulating material, heated to 1073 K in an electric furnace and melted. The crucible was taken out from the electric furnace, and a sheathed K-type thermocouple that had been previously corrected for temperature was inserted into the melted 5052 alloy, and the temperature was measured. A cooling curve was recorded to determine the liquidus and solidus temperatures. As a result, it was confirmed that the liquidus temperature was 919K, the solidus temperature was 882K, and the solidification temperature range was 37K.

ビレットの製作は以下のようにして行った。まず、30号黒鉛るつぼに約8ｋｇの5052アルミニウム合金インゴットを入れ、シリコニット電気炉にて溶解させ所定の温度で保持した。次に溶湯の温度低下防止のためにヒーターで加熱してある湯面制御棒を一定速度で降下させて湯面を上昇させ、るつぼの側面に接続した給湯管を通して溶湯を傾斜冷却板上に流下させた。そして、傾斜冷却板の直下で水平連続鋳造装置のタンディシュにより半凝固スラリーを受けた。そして、溶湯が一定量溜まった後、ダミーバーを水平方向に移動させて連続鋳造を開始してφ６０ｍｍの円柱状のビレットを作製した。得られたビレットをダミーバーから２００ｍｍのところで高さ１０ｍｍの円柱を切り出して研磨を行い、光学顕微鏡で写真を撮影し、結晶粒径を計測した。溶湯の流量は湯面制御棒の降下速度で調節し、ビレットの引き抜き速度はモーターの回転数で調節した。尚、傾斜冷却板へのBN膜塗布方法はBN入りスプレーを用いて所定膜厚の±5μｍになるように膜厚計を用いて測定しながら行った。塗布後にはガスバーナーで焼き付けた。   The billet was produced as follows. First, about 8 kg of 5052 aluminum alloy ingot was placed in a No. 30 graphite crucible and melted in a siliconite electric furnace and maintained at a predetermined temperature. Next, in order to prevent the temperature of the molten metal from decreasing, the molten steel level control rod heated by the heater is lowered at a constant speed to raise the molten metal surface, and the molten metal flows down on the inclined cooling plate through the hot water pipe connected to the side of the crucible. I let you. And the semi-solid slurry was received by the tundish of the horizontal continuous casting apparatus just under the inclination cooling plate. Then, after a certain amount of molten metal was accumulated, the dummy bar was moved in the horizontal direction, and continuous casting was started to produce a φ60 mm cylindrical billet. The obtained billet was polished by cutting out a cylinder having a height of 10 mm at 200 mm from the dummy bar, photographed with an optical microscope, and the crystal grain size was measured. The flow rate of the molten metal was adjusted by the descent speed of the molten metal control rod, and the billet drawing speed was adjusted by the number of rotations of the motor. The BN film coating method on the inclined cooling plate was carried out while measuring with a film thickness meter using a spray containing BN so that the predetermined film thickness was ± 5 μm. After application, it was baked with a gas burner.

(Ｉ)均一 BN膜厚の粒状結晶化と微細化に与える影響
(1)BN膜厚の影響
まず、予備実験に基づいて溶湯がスムーズに流れるBN膜厚を調べ、その膜厚を中心にBN膜厚が凝固組織に与える影響を表３に示す実験条件で調べた。以後の実験は得られた最適BN膜厚を適用し他の鋳造条件を変化させて実験を行った。尚、予備実験では、融液の流れが凝固殻を形成しないで、スムーズに流れるＢＮ膜厚を調べるために、その膜厚を０μｍから１１５μｍまで、１０μｍずつ増加しながら実験を行った。その結果、１０５μｍの場合に融液がスムーズに流れることがわかった。そこでＢＮ膜厚を１０５μｍを中心として凝固組織を調べることとした。ここで、半凝固スラリーはそのまま連続鋳造せずに、冷却板直下に設置した金型に鋳造して、そこで１０ｓ等温保持した後、氷水を用いて急冷を行って鋳塊を作製した。金型は傾斜冷却板の直下のスラリー温度（液相線温度直下−１．５〜２．０Ｋ）とほぼ同じ温度例えば９１６Ｋ（液相線温度−３Ｋ）程度に予熱し、鋳造したセミソリッドスラリーの熱移動を少なくした。その金型の予熱は当該金型にあらかじめ断熱材を巻いて加熱した。そして、断熱材は水冷する前に取り除いた。 (I) Effect of uniform BN film thickness on granular crystallization and refinement
(1) Influence of BN film thickness First, the BN film thickness through which the molten metal flows smoothly is investigated based on preliminary experiments, and the influence of the BN film thickness on the solidified structure is investigated with the experimental conditions shown in Table 3 centering on the film thickness. It was. In the subsequent experiments, the optimum BN film thickness obtained was applied and other casting conditions were changed. In the preliminary experiment, an experiment was performed while increasing the film thickness from 0 μm to 115 μm by 10 μm in order to examine the BN film thickness that smoothly flows without forming a solidified shell. As a result, it was found that the melt flows smoothly in the case of 105 μm. Therefore, the solidified structure was examined with the BN film thickness centered at 105 μm. Here, the semi-solid slurry was not continuously cast as it was, but cast into a mold placed directly under the cooling plate, and kept isothermal for 10 s there, and then rapidly cooled with ice water to produce an ingot. Mold is semi-solid slurry that is preheated to about 916K (liquidus temperature -3K), for example, approximately the same temperature as the slurry temperature directly below the inclined cooling plate (directly below the liquidus temperature -1.5 to 2.0K) Less heat transfer. For the preheating of the mold, a heat insulating material was previously wound around the mold and heated. And the heat insulating material was removed before water-cooling.

傾斜冷却板の表面に均一膜厚でＢＮを塗布する場合における膜厚と金型鋳造組織との関係は、図２に示す通りである。またそれらの結晶粒径とBN膜厚の関係は図３に示す通りである。 The relationship between the film thickness and the mold casting structure when BN is applied to the surface of the inclined cooling plate with a uniform film thickness is as shown in FIG. The relationship between the crystal grain size and the BN film thickness is as shown in FIG.

図２から明らかなように、ＢＮ膜厚が95μmおよび115μmの場合は、ともにαアルミニウムのデンドライトと粒状晶の混ざった組織が観察された。その理由はＢＮ膜厚が95μｍの時は105μｍより冷却板の熱伝導が大きいため、冷却板の表面に凝固殻が生成して、冷却板からの結晶の遊離が妨害されるために結晶の数が少なくなり、初晶αアルミニウムが粗大化し、一部はデンドライト組織となったと考えられる。反対に115μｍの場合には冷却板の熱伝導が小さくなったために、同様に遊離した結晶の数が少なくなり、金型内に液相が多く存在してデンドライト状に成長し、粗大化したものと推定される。最も良好なＢＮ膜厚105μmの場合には、冷却板上で生成遊離した初晶αアルミニウムが金型内で多数存在し、平均粒径70μm程度まで微細化された粒状組織が得られた。   As apparent from FIG. 2, when the BN film thickness was 95 μm and 115 μm, a structure in which α-aluminum dendrite and granular crystals were mixed was observed. The reason for this is that when the BN film thickness is 95 μm, the heat conduction of the cooling plate is larger than 105 μm, so that solidified shells are formed on the surface of the cooling plate and the liberation of crystals from the cooling plate is hindered. The primary α-aluminum is coarsened and a part of the dendritic structure is considered. On the other hand, in the case of 115 μm, the heat conduction of the cooling plate was reduced, so the number of free crystals was similarly reduced, there were many liquid phases in the mold, and it grew like a dendrite and became coarse It is estimated to be. In the case of the best BN film thickness of 105 μm, a large amount of primary aluminum α formed and liberated on the cooling plate was present in the mold, and a granular structure refined to an average particle size of about 70 μm was obtained.

このことから、傾斜冷却板の表面に均一膜厚でＢＮを塗布する場合のＢＮ膜厚は、95μmよりも厚く115μmよりも薄いことが好ましく、より好ましくは100μｍから110μｍの範囲、さらに好ましくは105μｍ程度であることが明らかとなった。
また、ＢＮ膜厚が95μｍでは凝固殻の生成の虞があるが、105μｍでは冷却板上で多数の初晶αＡｌが生成され遊離していることから、少なくとも95μmよりも厚くすること、好ましくは110μmよりも厚く、より好ましくは105μｍ以上、さらに好ましくは110μｍ以上、さらに好ましくは115μｍ以上とすることであり、より確実に溶湯が注がれる傾斜冷却板上流側での凝固殻の生成・貼り付きを防ぐには120μｍ程度とすることであるものと推定される。 Therefore, the BN film thickness when BN is applied to the surface of the inclined cooling plate with a uniform film thickness is preferably greater than 95 μm and less than 115 μm, more preferably in the range of 100 μm to 110 μm, and even more preferably 105 μm. It became clear that it was about.
Further, when the BN film thickness is 95 μm, solidified shells may be formed. However, when 105 μm, a large number of primary crystals αAl are generated and liberated on the cooling plate, so that the thickness should be at least 95 μm, preferably 110 μm. It is thicker, more preferably 105 μm or more, more preferably 110 μm or more, and even more preferably 115 μm or more, so that the solidified shell can be generated and stuck on the upstream side of the inclined cooling plate where the molten metal is poured more reliably. It is estimated that the thickness is about 120 μm to prevent.

(2) 鋳造温度の影響
次ぎに、均一膜厚の場合に最適と判断された105μｍのＢＮ膜を施した傾斜冷却板を用いて、鋳造温度を液相線温度＋９Ｋ，１０Ｋ，１２Ｋ，１４Ｋの４温度（928、 929、931、933K）に変化させて実験を行い、凝固組織に与える影響を表４に示す実験条件で調査した。 (2) Influence of casting temperature Next, using an inclined cooling plate with a 105 μm BN film that was judged to be optimal for uniform film thickness, the casting temperature was set to the liquidus temperature + 9K, 10K, 12K, 14K. Experiments were performed while changing the temperature to 4 temperatures (928, 929, 931, 933 K), and the influence on the solidified structure was investigated under the experimental conditions shown in Table 4.

実験結果を図４に示す。鋳造温度が931K 以上では鋳造温度が高いために冷却板上で生成遊離する結晶の数も少なくなり、金型内での結晶粒径が大きくなったと推定される。鋳造温度が低い928Kでは粗大化したαAlとデンドライト組織が混在したが、これは冷却板に凝固殻が生成して初晶αAlの遊離を妨害した結果であると推定される。このことから本実験では、最適鋳造温度は929K（液相線温度＋１０K）であることが分かった。 The experimental results are shown in FIG. When the casting temperature is 931 K or higher, the casting temperature is high, so the number of crystals generated and liberated on the cooling plate is reduced, and it is presumed that the crystal grain size in the mold has increased. At 928K, where the casting temperature is low, coarse αAl and dendrite structures coexist, which is presumed to be the result of the formation of solidified shells on the cooling plate and hindering the release of primary αAl. From this, it was found that the optimum casting temperature was 929K (liquidus temperature + 10K) in this experiment.

(3) 冷却板長さの影響
また、傾斜冷却板の長さを140mm、160mm、180mmと変化させて実験を行い、凝固組織に与える影響を表５に示す実験条件で調査した。 (3) Effect of cooling plate length In addition, the experiment was conducted by changing the length of the inclined cooling plate to 140 mm, 160 mm, and 180 mm, and the influence on the solidified structure was investigated under the experimental conditions shown in Table 5.

図５に凝固組織に及ぼす冷却板長さの影響を調べた結果を示す。冷却板長さが140ｍｍおよび180ｍｍの場合、ともに初晶αアルミニウムは冷却板長さが160mmよりも粗大であることが分かる。これは溶湯と冷却板の接触時間が短かすぎると熱エネルギーの移動が少ないために、初晶αアルミニウムの数が少なり、反対に接触時間が長過ぎると熱エネルギー移動が多すぎて凝固殻が生成して、初晶αアルミニウムの数が減り、結果として結晶粒径が大きくなったと考えられる。 FIG. 5 shows the results of examining the influence of the cooling plate length on the solidified structure. It can be seen that when the cooling plate length is 140 mm and 180 mm, the primary crystal α aluminum is coarser than the cooling plate length of 160 mm. This is because if the contact time between the molten metal and the cooling plate is too short, there is little heat energy transfer, so the number of primary α-aluminum is small, and conversely if the contact time is too long, there is too much heat energy transfer and the solidified shell. It is considered that the number of primary α-aluminum decreased, resulting in an increase in crystal grain size.

(4) 冷却板角度の影響
さらに、傾斜冷却板角度を50°、60°、70°と変化させて実験を行い、凝固組織に与える影響を表６に示す実験条件で調査した。 (4) Effect of cooling plate angle Further, the experiment was conducted by changing the inclined cooling plate angle to 50 °, 60 °, and 70 °, and the influence on the solidified structure was investigated under the experimental conditions shown in Table 6.

(5)溶湯の流速測定
さらに、表６に示す実験条件でアルミニウム溶湯の傾斜冷却板上での平均流速を測定した。平均流速は、冷却板の上下に熱電対を設定して、冷却板上を流れる溶湯の先端が熱電対に当たる時間差を計測して算出した。ここで使用した記録計の応答速度は0.02ｓである。熱電対は直径0.5mmのシースK型熱電対を用いた。 (5) Measurement of molten metal flow velocity Further, the average flow velocity of the molten aluminum on the inclined cooling plate was measured under the experimental conditions shown in Table 6. The average flow velocity was calculated by setting a thermocouple above and below the cooling plate and measuring the time difference when the tip of the molten metal flowing on the cooling plate hits the thermocouple. The response speed of the recorder used here is 0.02 s. As the thermocouple, a sheath K type thermocouple having a diameter of 0.5 mm was used.

冷却板角度と冷却板上を流下する溶湯の流速の関係を調べた結果を図６に示す。また結晶粒径と冷却板角度の関係を調べた結果を図７に示す。これらの図から明らかなように、溶湯の流速は角度が大きくなるにしたがって大きくなった。冷却板角度が70°の場合、溶湯の流速が大きくなるとBN表面と溶湯の間の温度境界層が薄くなって、BNと溶湯の間の温度勾配が小さくなり、遊離する初晶αAlも少なくなったと推定される。逆に冷却板の角度が50°の場合、BNと溶湯の間の温度境界層が厚くなるが、溶湯の流速が小さいためにより多くの熱エネルギーが奪われ、ただちに初晶による凝固殻が生成され、そのために生成遊離する結晶が少なくなり、結晶が粗大化されたと考えられる。このことから、平均結晶粒径を小さくするには、傾斜冷却板の角度を６０°に近づけること、換言すれば傾斜冷却板上における溶湯の流速を約1.4ｍ／ｓに近づけることが好ましい。   FIG. 6 shows the result of examining the relationship between the cooling plate angle and the flow velocity of the molten metal flowing down the cooling plate. Moreover, the result of investigating the relationship between the crystal grain size and the cooling plate angle is shown in FIG. As is apparent from these figures, the flow rate of the molten metal increased as the angle increased. When the cooling plate angle is 70 °, as the molten metal flow rate increases, the temperature boundary layer between the BN surface and the molten metal becomes thin, the temperature gradient between the BN and the molten metal decreases, and the free primary crystal αAl decreases. It is estimated that Conversely, when the angle of the cooling plate is 50 °, the temperature boundary layer between the BN and the molten metal becomes thick, but more heat energy is lost due to the low flow rate of the molten metal, and a solidified shell is formed immediately by the primary crystal. Therefore, it is considered that the crystals generated and liberated are reduced and the crystals are coarsened. Therefore, in order to reduce the average crystal grain size, it is preferable that the angle of the inclined cooling plate is close to 60 °, in other words, the flow rate of the molten metal on the inclined cooling plate is close to about 1.4 m / s.

(6) 冷却板裏面の温度測定
さらに、溶湯の流速が結晶の遊離および冷却板の熱伝達に与える影響を調べるために、表６に示す実験条件で、冷却板裏面の下端から10mm、30mm、60mm、90mm、120mm、150ｍｍのところに設置して温度測定を行った。 (6) Temperature measurement on the back side of the cooling plate Furthermore, in order to investigate the influence of the flow rate of the molten metal on the liberation of crystals and the heat transfer of the cooling plate, 10 mm, 30 mm, Temperature measurement was performed by installing at 60 mm, 90 mm, 120 mm, and 150 mm.

図８は角度が50°、60°、70°の場合、冷却板裏面の温度を示したものである。図から明らかなように傾斜角度が小さいほど溶湯の流速が小さくなり、冷却板裏面の温度は高くなっていることを示している。これは溶湯が冷却板上を流れる間に初晶の生成から遊離して移動する速度が冷却板と溶湯の熱移動にも影響されるものと推測される。この結果から初晶の生成および遊離に最適な冷却板の角度は60°、換言すれば傾斜冷却板上における溶湯の流速を約1.4ｍ／ｓにすることであることが明らかになった。   FIG. 8 shows the temperature of the back surface of the cooling plate when the angle is 50 °, 60 °, and 70 °. As is apparent from the figure, the smaller the inclination angle, the smaller the flow rate of the molten metal and the higher the temperature of the back surface of the cooling plate. It is presumed that the speed at which the molten metal moves away from the formation of primary crystals while flowing on the cooling plate is also affected by the heat transfer between the cooling plate and the molten metal. From this result, it was clarified that the optimum cooling plate angle for the formation and release of primary crystals was 60 °, in other words, the flow rate of the molten metal on the inclined cooling plate was about 1.4 m / s.

(7) 以上の結果から、均一膜の塗布による結晶粒微細化条件としては、ＢＮ膜厚さ105μm、鋳造温度929K、冷却板長さ160ｍｍ、冷却板角度60°であり、その場合の結晶の平均粒径が70μmであることが明らかになった。 (7) From the above results, the crystal grain refinement conditions by applying a uniform film are as follows: BN film thickness 105 μm, casting temperature 929 K, cooling plate length 160 mm, cooling plate angle 60 °. The average particle size was found to be 70 μm.

（II）不均一 BN膜厚の粒状結晶化と微細化に与える影響
(1) 冷却板の塗布長さの影響
5052アルミニウム合金は傾斜冷却板上で凝固殻が生成しやすく、これを抑えるためには他の合金の場合と比べて、厚いBN膜を塗布しなければならない。しかし、これにより十分な冷却を行うことができず、初晶αアルミニウムの遊離にも限界がある。そこで、より効果的な冷却を行うために冷却板の長さ方向の膜厚を変化させる実験を行った。冷却板上に合金が張り付き、凝固殻が生成する現象は溶湯が冷却板に流下してから30mm程度の位置で発生しやすいことがわかった。これを防ぐためには冷却板上端から30mmの部分（以下冷却板上部と表記する）のBN膜厚を120μmに調節して塗布し、それ以下の部分（以下冷却板下部と表記する）を30μmの厚さにした。この条件で冷却板下部の長さは 140 mm、 150 mm、 160mmと変化させ実験を表７に示す実験条件で行った。 (II) Effect of non-uniform BN film thickness on granular crystallization and refinement
(1) Effect of cooling plate application length
5052 aluminum alloy tends to form solidified shells on the inclined cooling plate, and in order to suppress this, a thick BN film must be applied compared to other alloys. However, this makes it impossible to perform sufficient cooling, and there is a limit to the liberation of primary α-aluminum. Therefore, an experiment was conducted in which the film thickness in the length direction of the cooling plate was changed in order to perform more effective cooling. It was found that the phenomenon of alloy sticking to the cooling plate and the formation of solidified shells is likely to occur at a position of about 30 mm after the molten metal flows down to the cooling plate. To prevent this, adjust the BN film thickness of 30mm from the top of the cooling plate (hereinafter referred to as the upper part of the cooling plate) to 120μm, and apply the smaller part (hereinafter referred to as the lower part of the cooling plate) to 30μm. I made it thick. Under these conditions, the length of the lower part of the cooling plate was changed to 140 mm, 150 mm, and 160 mm, and the experiment was performed under the experimental conditions shown in Table 7.

傾斜冷却板の120μｍのＢＮ膜を形成した上流側の長さは３０ｍｍ一定とし、３０μｍのＢＮ膜を形成した下流側の長さを変更するようにして、不均一にBN膜を塗布した場合における傾斜冷却板下流側長さの影響を調べた結果を図９に示す。これらの結果から明らかなように、鋳造温度および冷却板長さは均一膜と同じように結晶の遊離に影響すると考えられる。結晶が微細になる条件は鋳造温度929K、冷却板角度60°、冷却板下方の長さ150mmにＢＮ膜厚を30μm塗布した場合であり、この時の結晶粒の平均粒径は60μmで、粒状かつ微細な組織が得られた。 The length of the upstream side of the inclined cooling plate on which the 120 μm BN film is formed is constant 30 mm, and the length on the downstream side on which the 30 μm BN film is formed is changed. The result of investigating the influence of the length on the downstream side of the inclined cooling plate is shown in FIG. As is clear from these results, it is considered that the casting temperature and the cooling plate length influence the liberation of crystals in the same manner as the uniform film. The conditions for the crystal to become fine are when the casting temperature is 929K, the cooling plate angle is 60 °, the length of the cooling plate is 150mm and the BN film thickness is 30μm. The average grain size of the crystal is 60μm. And a fine structure was obtained.

(2) 冷却板上の溶湯の温度分布測定
表８の示す実験条件における冷却板上の溶湯の温度分布を求めた。温度分布は、溶湯を傾斜冷却板上に流下させ、熱電対を冷却板端部のBN膜から2mm突出させた所と冷却板直下に設置した断熱鋳型の中にもセットして、温度測定を行い、二つの値から、溶湯の平均温度を算出した。また冷却板の長さは60mm、100ｍｍ、160mm、200mmに変化させた。 (2) Measurement of temperature distribution of molten metal on cooling plate The temperature distribution of molten metal on the cooling plate under the experimental conditions shown in Table 8 was obtained. The temperature distribution is measured by letting the molten metal flow down on the inclined cooling plate and setting the thermocouple in a place where it protrudes 2mm from the BN film at the end of the cooling plate and also in the heat insulating mold installed directly under the cooling plate. The average temperature of the molten metal was calculated from the two values. The length of the cooling plate was changed to 60 mm, 100 mm, 160 mm, and 200 mm.

冷却板上の溶湯の温度分布を膜厚の違いにより比較した結果を図１０に示す。鋳造温度は929Kで同じであるが、膜厚105μmは均一に塗布した場合であり、30μmは不均一塗布のものである。この図から明らかなように、BN膜厚が薄いほど、溶湯の過冷度が大きく起こっている。したがって、BN膜厚の違いよる結晶粒径の差異は、冷却板上で起こる溶湯の過冷度に起因すると考えられる。なお、溶湯の流量も溶湯の過冷度に影響すると考えられる。流量が少ないと図に示すようにより多く過冷が起こるが、流量が0.018L/sを下回ると、溶湯が冷却板上に張り付く現象が起こった。 The result of comparing the temperature distribution of the molten metal on the cooling plate according to the difference in film thickness is shown in FIG. The casting temperature is the same at 929 K, but the film thickness of 105 μm is for uniform coating, and 30 μm is for non-uniform coating. As is apparent from this figure, the thinner the BN film, the greater the degree of supercooling of the melt. Therefore, the difference in crystal grain size due to the difference in BN film thickness is considered to be caused by the degree of supercooling of the molten metal that occurs on the cooling plate. In addition, it is thought that the flow rate of the molten metal also affects the degree of supercooling of the molten metal. When the flow rate is small, more cooling occurs as shown in the figure, but when the flow rate is less than 0.018 L / s, a phenomenon that the molten metal sticks to the cooling plate occurred.

(3) 冷却水の温度測定
傾斜冷却板の冷却水の温度測定を行なうために、まず溶湯を流さずに冷却水のみを流して冷却水の温度を測定した後、溶湯を傾斜冷却板上に流下させて冷却水の上昇温度を測定した。なお、温度を測定するための熱電対は、水冷管の中心に設置した。熱電対は直径0.5mmのシースK型熱電対を用いた。実験条件は表７に示す通りである。 (3) Cooling water temperature measurement In order to measure the cooling water temperature of the inclined cooling plate, first measure the cooling water temperature by flowing only the cooling water without flowing the molten metal, and then put the molten metal on the inclined cooling plate. The rising temperature of the cooling water was measured. A thermocouple for measuring the temperature was installed at the center of the water-cooled tube. As the thermocouple, a sheath K type thermocouple having a diameter of 0.5 mm was used. The experimental conditions are as shown in Table 7.

冷却水の上昇温度およびそれによる熱流束の計算を行って、温度冷却板の冷却能力を求めた。その結果を図１１および図１２に示した。冷却板から抜熱された熱エネルギー量は冷却水の上昇温度から、Ｑ＝Cm△Ｔにより計算して求めた。ここでＣは水の比熱、ｍは水の流量よって計算した冷却水の質量、△Ｔは冷却水の上昇温度である。熱流束qはq＝Q/(n×Ｓ)によって計算した。ｎは冷却管の本数、Ｓは溶湯と冷却管が接触する面積である。この計算は冷却板の裏面および表面の温度が定常状態と考えて行なったものである。計算結果から分かるように、BN膜厚が薄いとき、熱流束が最も大きいことを示している。   The cooling temperature of the temperature cooling plate was calculated by calculating the rising temperature of the cooling water and the resulting heat flux. The results are shown in FIG. 11 and FIG. The amount of heat energy extracted from the cooling plate was calculated from the rising temperature of the cooling water by Q = CmΔT. Here, C is the specific heat of water, m is the mass of the cooling water calculated by the flow rate of water, and ΔT is the rising temperature of the cooling water. The heat flux q was calculated by q = Q / (n × S). n is the number of the cooling pipes, and S is an area where the molten metal and the cooling pipes are in contact. This calculation was performed assuming that the temperature of the back surface and the front surface of the cooling plate was in a steady state. As can be seen from the calculation results, the heat flux is the largest when the BN film thickness is thin.

(III)ビレットの水平連続鋳造とサンプ形状の観察
水平連続鋳造を行った場合のビレットが、どのような凝固過程を経て形成されるかを調べるために、ビレットの凝固界面、すなわちサンプ形状の観察を行った。実験方法はビレットの連続鋳造中に5052 アルミニウム溶湯の供給を止め、トレーサーであるAl−33％Cu溶湯をタンディシュ内に注ぎ込んで、連続鋳造を再開し、ビレットを作製した。作製されたビレットのトレーサーが鋳造されている部分を長さ10ｃｍの円柱状に切り出し、さらに、長手方向に切断し、エメリー紙により研磨を行った後、腐食液0.5％フッ酸によりマクロ腐食を行った。 (III) Observation of billet horizontal continuous casting and sump shape Observation of billet solidification interface, ie sump shape, in order to investigate what kind of solidification process billet is formed through horizontal continuous casting Went. In the experimental method, the supply of the 5052 aluminum melt was stopped during the continuous casting of the billet, and the Al-33% Cu molten metal as a tracer was poured into the tundish, and the continuous casting was resumed to produce the billet. The billet tracer produced is cut into a 10 cm long column, further cut in the longitudinal direction, polished with emery paper, and then subjected to macro corrosion with 0.5% hydrofluoric acid. It was.

ここで、5052アルミニウム合金の連続鋳造は金型鋳造実験にて得られた結晶粒が最も微細になる条件を用いた。またタンディシュは加熱(873K)あり、なしを用いた。タンディシュは電気炉中で加熱して、鋳造直前に連続鋳造設備に取り付けた。鋳造速度は2、3、4mm/sとし、溶湯の流量は0.034L /s、0.018L/s両条件で行った。実験条件は表９に示す通りである。   Here, the continuous casting of the 5052 aluminum alloy was performed under the condition that the crystal grains obtained in the mold casting experiment were the finest. The tundish used was heated (873K) and none. Tundish was heated in an electric furnace and attached to a continuous casting facility just before casting. The casting speed was 2, 3, and 4 mm / s, and the flow rate of the molten metal was 0.034 L / s and 0.018 L / s. The experimental conditions are as shown in Table 9.

(1) タンディシュ加熱の有無の影響
連続鋳造用銅鋳型にBNを塗布なしの場合、鋳造速度を変化させてもビレットを作製することができなかった。それは銅鋳型の冷却能力が強すぎて凝固界面の移動速度が速すぎ、凝固殻がタンディシュの中に侵入して、スラリーの供給通路が塞がれてしまったためである。銅鋳型にBNを塗布した際の鋳造速度とビレットの形状の写真を図１３（ａ）〜（ｄ）に示す。鋳造速度が4mm/sの場合（（ａ），（ｂ））、タンディシュの加熱あり、なしに関わらず、ビレットの作製に成功することができなかった。鋳造速度が3mm/sの場合（（ｃ），（ｄ））、タンディシュの加熱なしの時はビレットを作製することができなかったが、それを加熱した場合はビレットの作製には成功した。しかし、成功率は50％であった。これに対して、鋳造速度が2mm/sの場合、ビレットの表面形状を示す図１４（ａ）〜（ｃ）に明らかなように、タンディシュの加熱あり、なしにかかわらずいずれの場合でもビレットの作製には成功したが、加熱なしの場合（ａ）にはビレットの表面に凹凸ができて粗くなった。これに対し、タンディシュの加熱ありの場合（（ｂ），（ｃ））、表面が綺麗なビレットを作製することができた。これは、タンディシュを加熱することによって、その中の初晶αアルミニウムの成長が抑制され、スラリーの流動性が改善され、充填性がよくなったためと考えられる。 (1) Effect of presence or absence of tundish heating When BN was not applied to a continuous casting copper mold, billets could not be produced even if the casting speed was changed. This is because the cooling capacity of the copper mold is too strong, the moving speed of the solidification interface is too fast, the solidified shell penetrates into the tundish, and the slurry supply passage is blocked. FIGS. 13A to 13D show photographs of casting speed and billet shape when BN is applied to a copper mold. When the casting speed was 4 mm / s ((a), (b)), the billet could not be successfully produced regardless of whether or not the tundish was heated. When the casting speed was 3 mm / s ((c), (d)), the billet could not be produced without heating the tundish, but the billet was successfully produced when it was heated. However, the success rate was 50%. On the other hand, when the casting speed is 2 mm / s, as apparent from FIGS. 14 (a) to 14 (c) showing the billet surface shape, the billet is heated regardless of whether or not the tundish is heated. Production was successful, but without heating (a), the billet surface was rough and rough. On the other hand, when the tundish was heated ((b), (c)), a billet with a clean surface could be produced. This is presumably because heating the tundish suppresses the growth of primary α-aluminum therein, improves the fluidity of the slurry, and improves the filling property.

(2) タンディシュ加熱の有無と溶湯流量の結晶組織に与える影響
上述の実験条件で製作されたビレットのミクロ組織を図１５に示す。溶湯の流量が0.034/sの場合、ビレットのミクロ組織はタンディシュの加熱あり、なしに関係なく結晶の平均粒径はいずれも６０μｍ程度（まで微細化されたが、円形度係数は小さくなっていた）であった。しかし、溶湯の流量が0.018L/sである場合、（ビレットの鋳肌も綺麗であり、）結晶の平均粒径は45μｍになった。これは、溶湯の流量が少なくなるに従って、溶湯の過冷が大きく発生したためだと考えられる。（尚、ビレットの外側のチル層も冷却板から遊離するαＡｌの数の増加に従って、２〜３ｍｍまで薄くなった） (2) Effect of Tundish Heating and Melting Flow Rate on Crystal Structure Figure 15 shows the microstructure of the billet manufactured under the above experimental conditions. When the flow rate of the molten metal was 0.034 / s, the billet microstructure was heated by tundish, and regardless of whether the average grain size of crystals was reduced to about 60 μm (although it was refined, the circularity coefficient was small) )Met. However, when the flow rate of the molten metal was 0.018 L / s, the average grain size of the crystal was 45 μm (the billet's cast skin was also clean). This is thought to be due to the fact that as the flow rate of the molten metal decreases, the molten metal is greatly cooled. (The chill layer on the outside of the billet also became thinner to 2 to 3 mm as the number of αAl released from the cooling plate increased.)

(3) ビレットの冷却速度およびサンプ形状
ビレットのサンプ形状を図１６に示す。図から明らかなように5052アルミニウム合金の凝固界面の深さはかなり浅く17mmになっている。これはスラリーが鋳型に注入されてから、鋳型の中で17mm移動するとビレットが中心部まで凝固されていることを意味している。鋳造速度が2mm/sであることから、中心まで凝固するのに8.5sかかると考えられる。ビレットの直径が60mmであることから、ビレットの凝固速度が3.53mm/sであることが分かる。ビレットの冷却曲線を図１７に示す。図に示すようにビレットの中心部がスラリー（916K）状態から固相線温度（910K）まで下がるのに8sかかることからビレットの冷却速度が0.75K/sであると考えられる。 (3) Billet cooling rate and sump shape The billet sump shape is shown in FIG. As is clear from the figure, the depth of the solidification interface of the 5052 aluminum alloy is considerably shallower and 17 mm. This means that the billet is solidified to the center when it is moved 17 mm in the mold after the slurry is poured into the mold. Since the casting speed is 2 mm / s, it is considered that it takes 8.5 s to solidify to the center. Since the billet diameter is 60 mm, the solidification rate of the billet is found to be 3.53 mm / s. The cooling curve of the billet is shown in FIG. As shown in the figure, it takes 8 s for the billet center to drop from the slurry (916 K) state to the solidus temperature (910 K), so the cooling rate of the billet is considered to be 0.75 K / s.

(IV) 以上、冷却板へのＢＮ塗布の条件や鋳造条件を変化させて実験を行った結果、次のことが明らかとなった。
(1) 傾斜冷却板は固液共存領域が狭い合金のセミソリッド鋳造に対しても有効であり、平均粒径が４５μm程度に微細化されたビレットを作製することができる。
(2) BN膜厚さは適切な厚さになると溶湯の過冷度が大きくなり、核生成が容易になり、より多くの結晶が遊離され、凝固組織が微細になる。
(3) 溶湯の流速はBNと溶湯との間の温度境界層に影響を与え、溶湯の過冷度に影響する。
(4) 溶湯の流量も溶湯の冷却板上の過冷度に影響して、結晶の遊離する数に影響する。
(5) 傾斜冷却板に塗布するBN膜厚を板の長さ方向に沿って変化させるとより微細な結晶粒が得られる。 (IV) As a result of experiments conducted while changing the conditions for applying BN to the cooling plate and the casting conditions, the following became clear.
(1) The inclined cooling plate is also effective for semi-solid casting of an alloy having a narrow solid-liquid coexistence region, and can produce a billet with an average particle size reduced to about 45 μm.
(2) When the BN film thickness is appropriate, the degree of supercooling of the melt increases, nucleation is facilitated, more crystals are released, and the solidification structure becomes finer.
(3) The flow rate of the molten metal affects the temperature boundary layer between BN and the molten metal, and affects the degree of supercooling of the molten metal.
(4) The flow rate of the molten metal also affects the degree of supercooling on the molten metal cooling plate and affects the number of crystals released.
(5) Finer crystal grains can be obtained by changing the BN film thickness applied to the inclined cooling plate along the length direction of the plate.

（実施例２）
表２に示す組成の5052アルミニウム合金を用いて、傾斜冷却板を用いたセミソリッド鋳造を行った。このセミソリッド鋳造は、実施例１の装置の水平連続鋳造装置の代わりに重力鋳造するための温度勾配のほとんど無い鋳型を用いたものである。尚、実験に使う合金は超音波洗浄するとともに、融液と直接接触するすべての実験用器具には、不純物の混入を防ぐために、特級試薬のＴｉＯ２を塗布した。 (Example 2)
Using a 5052 aluminum alloy having the composition shown in Table 2, semi-solid casting using an inclined cooling plate was performed. In this semi-solid casting, a mold having almost no temperature gradient for gravity casting is used instead of the horizontal continuous casting apparatus of the apparatus of the first embodiment. The alloy used in the experiment was ultrasonically cleaned and a special grade reagent, TiO 2, was applied to all experimental instruments in direct contact with the melt in order to prevent contamination with impurities.

実施例１と同様の方法で得た5052アルミニウム合金の溶湯を、傾斜冷却板上に流下させた。この融液を冷却板直下に設置した金型に鋳造して、そこで１０ｓ等温保持した。金型は傾斜冷却板の直下のスラリー温度とほぼ同じ温度例えば９１６Ｋ（液相線温度−３Ｋ）程度に予熱し、鋳造したセミソリッドスラリーの熱移動を少なくした。その後、氷水を用いて急冷を行い、鋳塊を作製した。金型の予熱は当該金型にあらかじめ断熱材を巻いて加熱した。そして、断熱材は水冷する前に取り除いた。組織観察のために、鋳塊の底部より１０ｍｍの位置から１０×１０×１０ｍｍ３の大きさの試料を切り出して研磨を行い、光学顕微鏡で写真撮影をして結晶粒径を計測した。なお、試料の他にも、鋳造条件、傾斜冷却板の材質、冷却方法、冷却速度、ＢＮ膜の組成、計測装置などにおいて実施例１と同じものを用いた。また膜厚は実施例１と同じ予備実験から得た膜厚情報に基づいて、１０５μｍ均一膜厚と、長さ方向で膜厚を変化させた不均一膜（上流側長さ３０ｍｍの膜厚は１２０μｍ、下流側長さ１６０ｍｍの膜厚は３０μｍ）との２種類に分けて、実施例１と同様の実験を行った。 The molten 5052 aluminum alloy obtained by the same method as in Example 1 was allowed to flow down on the inclined cooling plate. This melt was cast into a mold placed directly under the cooling plate, where it was kept isothermal for 10 s. The mold was preheated to approximately the same temperature as the slurry temperature directly below the inclined cooling plate, for example, about 916 K (liquidus temperature—3 K), thereby reducing the heat transfer of the cast semi-solid slurry. Then, it cooled rapidly using ice water and produced the ingot. For the preheating of the mold, a heat insulating material was previously wound around the mold and heated. And the heat insulating material was removed before water-cooling. For structure observation, a sample having a size of 10 × 10 × 10 mm 3 was cut out from a position 10 mm from the bottom of the ingot, polished, and photographed with an optical microscope to measure the crystal grain size. In addition to the sample, the same casting conditions, material of the inclined cooling plate, cooling method, cooling rate, BN film composition, measuring device, etc. were used as in Example 1. Also, the film thickness is 105 μm uniform film thickness and non-uniform film in which the film thickness is changed in the length direction based on the film thickness information obtained from the same preliminary experiment as in Example 1 (the film thickness of the upstream length is 30 mm. The same experiment as in Example 1 was performed by dividing into two types of 120 μm and a downstream length of 160 mm having a film thickness of 30 μm.

その結果、均一膜の塗布による結晶粒微細化条件としては、ＢＮ膜厚さ１０５μｍ、鋳造温度９２９Ｋ、冷却板長さ１６０ｍｍ、冷却板角度６０°であり、結晶の平均粒径が７０μｍであることが明らかになった。また、不均一膜の塗布による結晶微細化条件としては、冷却板上方の長さ３０ｍｍにＢＮ膜厚を１２０μｍ、冷却板下方の長さ１５０ｍｍにＢＮ膜厚を３０μｍ塗布し、鋳造温度９２９Ｋ、冷却板角度６０°であり、このときの結晶粒の平均粒径は６０μｍで、粒状かつ微細化された組織が得られるという結果が得られた。ＢＮ膜厚が薄いとき、熱流束が最も大きくなり傾斜冷却板の上で生成される初晶αＡｌの数が多くなるという実施例１と同じ実験結果が示すように、ＢＮ膜厚さは適切な厚さになると融液の過冷度が大きくなり、核生成が容易になり、より多くの結晶が遊離され、凝固組織が微細になる。   As a result, crystal grain refinement conditions by applying a uniform film are as follows: BN film thickness 105 μm, casting temperature 929 K, cooling plate length 160 mm, cooling plate angle 60 °, and average crystal grain size is 70 μm. Became clear. Also, as the crystal refining conditions by application of the non-uniform film, a BN film thickness of 120 μm is applied to a length of 30 mm above the cooling plate, a BN film thickness of 30 μm is applied to a length of 150 mm below the cooling plate, a casting temperature of 929 K, cooling The plate angle was 60 °, and the average grain size of the crystal grains at this time was 60 μm, and the result was obtained that a granular and refined structure was obtained. When the BN film thickness is thin, the BN film thickness is appropriate as shown in the same experimental results as in Example 1 that the heat flux becomes the largest and the number of primary crystals αAl generated on the inclined cooling plate increases. When the thickness is increased, the degree of supercooling of the melt increases, nucleation is facilitated, more crystals are released, and the solidified structure becomes finer.

以上の実験結果から、傾斜冷却板を用いたセミソリッド鋳造法は、固液共存領域が狭い合金のセミソリッド鋳造に対しても有効であり、水平連続鋳造によりビレットを製造する場合も、重力鋳造によりインゴットを製造する場合も、同じ結果が得られることが明らかとなった。   From the above experimental results, the semi-solid casting method using an inclined cooling plate is also effective for semi-solid casting of alloys where the solid-liquid coexistence area is narrow, and even when manufacturing billets by horizontal continuous casting, gravity casting It was revealed that the same results can be obtained when manufacturing an ingot.

（実施例３）
表１０に示す5052Ａｌアルミニウム合金を用いてセミソリッド水平連続鋳造によりビレットを作製し、表１１に示す実験条件即ち実施例１において得られた傾斜冷却板とＢＮ膜厚に関する最適な条件下でのタンディシュ加熱の有無、引き抜き速度並びに傾斜冷却板上における溶湯の流量の変化が結晶の微細化に与える影響について検討した。 (Example 3)
Billets were produced by semisolid horizontal continuous casting using the 5052Al aluminum alloy shown in Table 10, and the experimental conditions shown in Table 11, that is, the inclined cooling plate obtained in Example 1, and the tundish under the optimum conditions regarding the BN film thickness. The effects of the presence or absence of heating, the drawing speed, and the change in the flow rate of the molten metal on the inclined cooling plate on the refinement of the crystal were investigated.

実施例１と同じ手順により、市販の5052アルミニウム合金インゴットを溶解させ所定温度で保持してから溶湯を傾斜冷却板上に流下させ、さらにタンディシュ内に溜めた。溶湯が一定量溜まった後、ダミーバーを水平方向に移動させて連続鋳造を開始してφ６０ｍｍの円柱状のビレットを作製した。得られたビレットをダミーバーから２００ｍｍのところで高さ１０ｍｍの円柱を切り出して研磨を行い、光学顕微鏡で写真を撮影し、結晶粒径を計測した。溶湯の流量は湯面制御棒の降下速度で調節し、ビレットの引き抜き速度はモーターの回転数で調節した。 In the same procedure as in Example 1, a commercially available 5052 aluminum alloy ingot was melted and maintained at a predetermined temperature, and then the molten metal was allowed to flow down on the inclined cooling plate and further stored in the tundish. After a certain amount of molten metal was collected, the dummy bar was moved in the horizontal direction to start continuous casting to produce a cylindrical billet with a diameter of 60 mm. The obtained billet was polished by cutting out a cylinder having a height of 10 mm at 200 mm from the dummy bar, photographed with an optical microscope, and the crystal grain size was measured. The flow rate of the molten metal was adjusted by the descent speed of the molten metal control rod, and the billet drawing speed was adjusted by the number of rotations of the motor.

まず、溶湯の流量を0.038リットル／秒に一定し、ビレットの引き抜き速度を４ｍｍ／秒、３ｍｍ／秒、２ｍｍ／秒と変化させ、タンディッシュの加熱有無による実験を行った。その結果、タンディッシュの加熱の有無にかかわらず、引き抜き速度が４ｍｍ／秒の場合にはビレットが破断して作製することができなかった。しかし、引き抜き速度が３ｍｍ／秒の場合にはタンディッシュの加熱の有無にかかわらずビレットが作製できたが、成功率が５０％であった。この原因は5052アルミニウム合金の固液共存領域が狭いためにサンプの深さが浅くて凝固界面の移動速度と引き抜き速度の釣り合いが合わなかったためと考えられる。さらに、引き抜き速度が２ｍｍ／秒の場合、タンディッシュの加熱の有無にかかわらず、ビレットの成功率がほぼ１００％だった。この際、ビレットの冷却速度は５．５℃／秒である。また、タンディッシュを加熱しなかった場合、溶湯の流量が0.038リットル/秒の場合には、ビレットの表面に溝があることが観察できた。それは冷却板から遊離した初晶αＡｌがタンディシュ中で成長して、スラリーの固相率が高くなって、流動性が悪くなったことに原因があると推測される。しかし、ビレットの組織は丸くなって、平均粒径が６０μｍ程度であった。同じ溶湯流量でも、タンディシュを６００℃（固相線温度−９Ｋ）まで加熱した場合には、ビレットの鋳肌は綺麗になり、結晶組織も６０μｍまで微細化されたが、円形度係数が小さくなっていることが分かった。これは冷却板から遊離した初晶αＡｌが鋳型の中で急冷されて形成した組織だと考えられる。このことから、タンディシュの加熱の有無は、タンディシュ内での固相率を変動させて鋳肌に影響を与えるが、平均結晶粒径の微細化には影響ないことが判明した。   First, the experiment was performed with and without heating of the tundish while the flow rate of the molten metal was fixed at 0.038 liter / second and the billet drawing speed was changed to 4 mm / second, 3 mm / second, and 2 mm / second. As a result, regardless of whether or not the tundish was heated, when the drawing speed was 4 mm / second, the billet was broken and could not be produced. However, when the drawing speed was 3 mm / sec, billets could be produced regardless of whether or not the tundish was heated, but the success rate was 50%. This is probably because the solid-liquid coexistence region of the 5052 aluminum alloy is narrow and the sump depth is so shallow that the balance between the moving speed of the solidification interface and the drawing speed does not match. Furthermore, when the drawing speed was 2 mm / second, the success rate of the billet was almost 100% regardless of whether or not the tundish was heated. At this time, the cooling rate of the billet is 5.5 ° C./second. Further, when the tundish was not heated, it was observed that there was a groove on the surface of the billet when the flow rate of the molten metal was 0.038 liter / second. It is presumed that this is because the primary crystal αAl released from the cooling plate grows in the tundish, the solid phase ratio of the slurry increases, and the fluidity deteriorates. However, the billet structure was round and the average particle size was about 60 μm. When the tundish was heated to 600 ° C (solidus temperature -9K) even with the same molten metal flow rate, the cast surface of the billet became clean and the crystal structure was refined to 60 µm, but the circularity coefficient decreased. I found out. This is considered to be a structure formed by rapidly cooling the primary αAl released from the cooling plate in the mold. From this, it was found that the presence or absence of heating of the tundish affects the casting surface by changing the solid phase ratio in the tundish, but does not affect the refinement of the average crystal grain size.

さらに、タンディッシュを加熱した場合、流量が0.018 リットル/秒のビレットの鋳肌は綺麗であり、平均結晶粒径も４０μｍまで微細化された。これは溶湯の流量が少なくなるに従って、溶湯の過冷度がより大きくなり、より多くの初晶αが遊離され、鋳型の中で凝固され微細化したと考えられる。この場合、ビレットの外側のチル層も冷却板から遊離するαＡｌの数の増加に従って、２〜３ｍｍまで薄くなることが判明した。このことから、傾斜冷却板上での溶湯流量は小さくするほど、結晶粒径が微細化することが明らかとなった。   Furthermore, when the tundish was heated, the casting surface of the billet with a flow rate of 0.018 liter / second was clean, and the average crystal grain size was refined to 40 μm. It is considered that as the flow rate of the molten metal decreases, the degree of supercooling of the molten metal increases and more primary crystal α is liberated and solidified and refined in the mold. In this case, it has been found that the chill layer outside the billet also becomes thinner to 2-3 mm as the number of αAl released from the cooling plate increases. From this, it became clear that the crystal grain size becomes finer as the molten metal flow rate on the inclined cooling plate is reduced.

つまり、固液共存領域が狭い合金に対しても傾斜冷却板は有効であり、ダンディッシュを加熱することで結晶粒径が４５μｍまで均一かつ微細粒状組織を有するビレット作製することが可能であること、溶湯の流量は溶湯の冷却板上で過冷度に影響を与え、結晶遊離に影響すること、更にはビレットの外側のチル層は冷却板から遊離する結晶数の増加に従って薄くなることが明らかになった。   In other words, the inclined cooling plate is effective even for alloys with a narrow solid-liquid coexistence region, and it is possible to produce billets having a uniform and fine grain structure up to a crystal grain size of 45 μm by heating the dundish. It is clear that the flow rate of the molten metal affects the degree of supercooling on the cooling plate of the molten metal and affects crystal release, and that the chill layer outside the billet becomes thinner as the number of crystals released from the cooling plate increases. Became.

なお、上述の実施形態は本発明の好適な実施の一例ではあるがこれに限定されるものではなく、本発明の要旨を逸脱しない範囲において種々変形実施可能である。本実施形態並びに実施例では５０５２Ａｌ合金を例に挙げて主に説明しているが、これに特に限定されるものではなく、固液共存領域の温度幅が狭い他の合金種においても適用可能である。例えば、本発明者等の実験によると、合金元素０．３質量％を含む９９．７％ＡｌのＡｌ合金でもセミソリッド鋳造が可能であった。また、本実施形態並びに各実施例において明らかにされた好適な傾斜冷却板の長さや、傾斜角度、材質、冷却板上での溶湯流量などの諸条件は、４〜８kg/minまでは同一条件で成立することを本発明者等の実験によって確認したが、さらに生産規模を拡大する場合あるいは他の合金に適用する場合にも、傾斜冷却板２の直上での溶湯の温度（鋳造温度）を液相線温度＋１０〜１５Ｋ程度、傾斜冷却板２の直下での溶湯温度を液相線温度直下の−０．１〜５．０Ｋの範囲に収まる抜熱量の冷却下に傾斜冷却板上で流下させて結晶遊離を生じさせる条件とすることによって、セミソリッド鋳造を可能とする半凝固スラリーが安定して得られる。さらに、傾斜冷却板２に注ぐときの溶湯の断面を自然放出による円形とせずに、厚みが薄く幅広の扁平な断面とすることにより比表面積を増大させることで、冷却板・ＢＮ膜にかかる単位面積当たりの熱容量を少なくすることでＢＮ膜厚を限界のままでも微細化を可能とすることができる。   The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention. In the present embodiment and examples, the 5052Al alloy is mainly described as an example. However, the present invention is not particularly limited to this, and can be applied to other alloy types having a narrow temperature range in the solid-liquid coexistence region. is there. For example, according to experiments by the present inventors, semi-solid casting was possible even with an Al alloy of 99.7% Al containing 0.3% by mass of alloy elements. In addition, various conditions such as the preferred length of the inclined cooling plate, the inclination angle, the material, and the flow rate of the molten metal on the cooling plate, which are clarified in this embodiment and each example, are the same for 4 to 8 kg / min. In the case where the production scale is further increased or when the present invention is applied to other alloys, the temperature of the molten metal (casting temperature) immediately above the inclined cooling plate 2 is confirmed. The liquidus temperature is about +10 to 15K, and the molten metal temperature immediately below the inclined cooling plate 2 flows down on the inclined cooling plate while cooling the heat removal amount within the range of -0.1 to 5.0K immediately below the liquidus temperature. By setting the conditions to cause crystal liberation, a semi-solid slurry that enables semi-solid casting can be stably obtained. Furthermore, the unit of the cooling plate / BN film is increased by increasing the specific surface area by making the cross-section of the molten metal when pouring into the inclined cooling plate 2 into a thin and wide flat cross-section without spontaneously discharging the circular cross-section. By reducing the heat capacity per area, it is possible to miniaturize even if the BN film thickness remains at the limit.

本発明のセミソリッド鋳造方法を実施する水平連続鋳造システムの概略構成を示す模式図である。It is a schematic diagram which shows schematic structure of the horizontal continuous casting system which implements the semisolid casting method of this invention. 凝固組織に及ぼすＢＮ膜厚の影響を示す金属組織を示す写真である。It is a photograph which shows the metal structure which shows the influence of the BN film thickness which acts on a solidification structure. ＢＮ膜厚と結晶粒径との関係を示すグラフである。It is a graph which shows the relationship between a BN film thickness and a crystal grain diameter. 結晶粒径に及ぼす鋳造温度の影響を示すグラフである。It is a graph which shows the influence of the casting temperature on a crystal grain size. 結晶粒径に及ぼす冷却板長さの影響を示すグラフである。It is a graph which shows the influence of the cooling plate length which acts on a crystal grain size. 冷却板角度と流速の関係を示すグラフである。It is a graph which shows the relationship between a cooling plate angle and a flow velocity. 冷却板角度と結晶粒径の関係を示すグラフである。It is a graph which shows the relationship between a cooling plate angle and a crystal grain diameter. 溶湯の流速と冷却板裏面の温度のの関係を示すグラフであるIt is a graph which shows the relationship between the flow rate of a molten metal, and the temperature of the cooling plate back surface. 不均一膜における鋳造温度と結晶の粒径の関係を示すグラフである。It is a graph which shows the relationship between the casting temperature and the grain size of a crystal | crystallization in a nonuniform film | membrane. 冷却板上の溶湯の温度分布を示すグラフである。It is a graph which shows the temperature distribution of the molten metal on a cooling plate. ＢＮ厚さと冷却板の冷却水の上昇温度関係を示すグラフである。It is a graph which shows BN thickness and the rising temperature relationship of the cooling water of a cooling plate. ＢＮ膜厚と熱流束との関係を示すグラフである。It is a graph which shows the relationship between a BN film thickness and a heat flux. ビレット表面形状に及ぼす鋳造速度の影響を示す図で、（ａ）は４ｍｍ／ｓ時におけるタンディシュ加熱有り、（ｂ）は４ｍｍ／ｓ時におけるタンディシュ加熱なし、（ｃ）は３ｍｍ／ｓ時におけるタンディシュ加熱有り、（ｄ）は３ｍｍ／ｓ時におけるタンディシュ加熱なしの状態をそれぞれ示す。It is a figure which shows the influence of the casting speed on billet surface shape, (a) with tundish heating at 4 mm / s, (b) without tundish heating at 4 mm / s, and (c) tundish at 3 mm / s. With heating, (d) shows the state without tundish heating at 3 mm / s. 鋳造速度が２ｍｍ／ｓ時におけるビレット表面形状に及ぼす影響を示す図で、（ａ）は傾斜冷却板上での溶湯流量０．０３４Ｌ／ｓにおけるタンディシュ加熱なし、（ｂ）は傾斜冷却板上での溶湯流量０．０３４Ｌ／ｓにおけるタンディシュ加熱あり、（ｃ）は傾斜冷却板上での溶湯流量０．０１８Ｌ／ｓにおけるタンディシュ加熱有りの状態をそれぞれ示す。It is a figure which shows the influence which the casting speed has on the billet surface shape at the time of 2 mm / s, (a) without tundish heating at a molten metal flow rate of 0.034 L / s on the inclined cooling plate, (b) on the inclined cooling plate (C) shows a state with tundish heating at a molten metal flow rate of 0.018 L / s on the inclined cooling plate. ビレットのミクロ組織を示す写真であり、（ａ）ビレットの上部、（ｂ）中心から上方２０ｍｍ、（ｃ）中心、（ｄ）中心から下方へ２０ｍｍ、（ｅ）下部のそれぞれについて、傾斜冷却板上での溶湯流量０．０３４Ｌ／ｓにおけるタンディシュ加熱なし、溶湯流量０．０３４Ｌ／ｓにおけるタンディシュ加熱あり、溶湯流量０．０１８Ｌ／ｓにおけるタンディシュ加熱有りの状態をそれぞれ示す。It is a photograph showing the microstructure of the billet, (a) the upper part of the billet, (b) 20 mm upward from the center, (c) center, (d) 20 mm downward from the center, (e) the inclined cooling plate The states of no tundish heating at the molten metal flow rate 0.034 L / s, the tundish heating at the molten metal flow rate 0.034 L / s, and the tundish heating at the molten metal flow rate 0.018 L / s are shown. ビレットのサンプ形状を示す図である。It is a figure which shows the sump shape of a billet. ビレットの冷却曲線を示す図である。It is a figure which shows the cooling curve of a billet.

符号の説明Explanation of symbols

１ 溶解炉
２ 傾斜冷却板
３ ＢＮ膜（断熱機能を有する離型材）
８ 合金融液
１０ スラリー
１３ タンディシュ
１４ 水平連続鋳造機 DESCRIPTION OF SYMBOLS 1 Melting furnace 2 Inclined cooling plate 3 BN film | membrane (mold release material which has a heat insulation function)
8 Combined financial liquid 10 Slurry 13 Tundish 14 Horizontal continuous casting machine

Claims (9)

合金溶湯を傾斜させた冷却板上に流下させて該傾斜冷却板上でα初晶を生成かつ遊離させて固液共存状態のスラリーを得る工程と、このスラリーを温度勾配のないタンディッシュまたは鋳型で固液共存領域内の温度域に保持して前記α相粒子を粒状化させる工程とを含むセミソリッド鋳造方法において、前記傾斜冷却板の表面に断熱機能を備える離型材を形成し、かつ前記離型材の膜厚を固液共存領域の温度幅が狭くなる程厚くなる関係に調整したものであるセミソリッド鋳造方法。   A step of flowing a molten alloy on a tilted cooling plate to generate and release α primary crystals on the tilted cooling plate to obtain a slurry in a solid-liquid coexistence state; and this slurry is a tundish or mold having no temperature gradient In a semi-solid casting method including a step of granulating the α-phase particles while maintaining a temperature range in a solid-liquid coexistence region, forming a release material having a heat insulating function on the surface of the inclined cooling plate, and A semi-solid casting method in which the film thickness of the release material is adjusted so as to increase as the temperature range of the solid-liquid coexistence region decreases. 前記合金溶湯の固液共存領域の温度幅が５０℃以下の場合には、前記傾斜冷却板の表面の離型材の膜厚を傾斜冷却板の下流側よりも溶湯が注がれる上流側が厚膜としたものである請求項１記載のセミソリッド鋳造方法。   When the temperature range of the solid-liquid coexistence region of the molten alloy is 50 ° C. or less, the thickness of the release material on the surface of the inclined cooling plate is thicker on the upstream side where the molten metal is poured than on the downstream side of the inclined cooling plate. The semi-solid casting method according to claim 1, wherein 前記離型材はＢＮ膜からなり、前記傾斜冷却板の下流側では膜厚３０μｍであり、前記溶湯が注がれる上流側では前記合金溶湯の固液共存領域の温度幅に応じて前記下流側膜厚よりも厚く形成されているものである請求項２記載のセミソリッド鋳造方法。   The release material is made of a BN film, and has a film thickness of 30 μm on the downstream side of the inclined cooling plate, and on the upstream side where the molten metal is poured, the downstream film according to the temperature range of the solid-liquid coexistence region of the molten alloy. The semi-solid casting method according to claim 2, wherein the method is formed thicker than the thickness. 前記離型材の膜厚は、前記傾斜冷却板の溶湯が注がれる上流側で１０５μｍ以上、それよりも下流側では３０μｍである請求項２記載のセミソリッド鋳造方法。   3. The semi-solid casting method according to claim 2, wherein a film thickness of the mold release material is 105 μm or more on the upstream side where the molten metal of the inclined cooling plate is poured, and 30 μm on the downstream side. 前記傾斜冷却板の上流側の厚膜の離型材は溶湯流下方向に少なくとも３０ｍｍの長さ、下流側の薄膜の離型材は１６０ｍｍの長さで形成されているものである請求項２から４のいずれかに記載のセミソリッド鋳造方法。   The thick film release material on the upstream side of the inclined cooling plate is formed with a length of at least 30 mm in the downward direction of the molten metal, and the thin film release material on the downstream side is formed with a length of 160 mm. The semisolid casting method according to any one of the above. 前記合金溶湯の固液共存領域の温度幅が５０℃以下の場合には、前記傾斜冷却板の表面の全長に１０５μｍの均一膜厚のＢＮ膜を形成したものである請求項１記載のセミソリッド鋳造方法。   2. The semi-solid according to claim 1, wherein a BN film having a uniform film thickness of 105 μm is formed on the entire surface of the inclined cooling plate when the temperature range of the solid-liquid coexistence region of the molten alloy is 50 ° C. or less. Casting method. 前記傾斜冷却板の表面での前記溶湯の流量は0.018リットル／秒〜0.038リットル／秒の範囲である請求項１から６のいずれかに記載のセミソリッド鋳造方法。   The semi-solid casting method according to any one of claims 1 to 6, wherein a flow rate of the molten metal on a surface of the inclined cooling plate is in a range of 0.018 liter / second to 0.038 liter / second. 請求項１から７のいずれかに記載のセミソリッド鋳造方法によって得られたスラリーを用いてビレットを製造する連続鋳造方法において、連続鋳造装置の鋳型のキャビティに窒化ボロンの膜を形成し、3mm/s以下の鋳造速度でビレットを連続鋳造するものであるセミソリッド連続鋳造方法。   8. A continuous casting method for producing a billet using the slurry obtained by the semi-solid casting method according to claim 1, wherein a boron nitride film is formed in a mold cavity of a continuous casting apparatus, Semi-solid continuous casting method in which billets are continuously cast at a casting speed of s or less. 前記連続鋳造装置のタンディシュを前記傾斜冷却板の直下のスラリー温度と同じ温度に予熱しているものである請求項８記載のセミソリッド連続鋳造方法。
The semisolid continuous casting method according to claim 8, wherein the tundish of the continuous casting apparatus is preheated to the same temperature as the slurry temperature directly below the inclined cooling plate.
JP2005134027A 2005-05-02 2005-05-02 Semi-solid casting method Pending JP2006305618A (en)

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