JP4406164B2 - Cooling drum for twin drum type continuous casting apparatus and casting method using the same - Google Patents
Cooling drum for twin drum type continuous casting apparatus and casting method using the same Download PDFInfo
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Description
【0001】
【発明の属する技術分野】
本発明は、双ドラム式連続鋳造用冷却ドラムに関するもので、特に、周面に微細な凹凸状の窪み(以下ディンプルという。)を形成し、表面品質の良好な薄鋳片を安定して鋳造するための双ドラム式連続鋳造用冷却ドラムとそれを用いた鋳造方法に関する。
【0002】
【従来の技術】
金属の連続鋳造分野において、最終形状に近い薄帯を連続鋳造する方法として一対の冷却ドラムを用いた双ドラム式ストリップ連続鋳造方法があるが、この鋳造方法は図1に示すように、一対の冷却ドラム1−a、1−bとこれら冷却ドラム間をシールするためのサイド堰2−a、2−bとの間に形成された湯溜まり3に溶融金属Rを供給し、溶融金属Rは、冷却ドラム1−a、1−bを介して抜熱され、冷却ドラム1−a、1−bの周面で凝固シェルg、g’を形成し、凝固シェルg、g’は冷却ドラム間のロールギャップKp間で圧着されて一体化された薄帯Cとなって送り出される。
【0003】
前記薄肉鋳造方法では、鋳造された鋳片は最終製品の形状に近似した形状であるため、鋳造後に表面欠陥を研削などの手段によって除去することは非能率であると共に、歩留りが大幅に低下するが故に、鋳造時に割れや亀裂などの表面欠陥を皆無にすることが必須の技術的課題となっている。一方、前記薄肉鋳造では凝固シェルが急冷されるために急冷に伴う熱収縮応力によって鋳片表面に割れや亀裂等の欠陥が発生し易いという問題がある。そこで、鋳片の表面欠陥を安定的に防止するために様々な提案がなされている。例えば、特公平4−33537号公報では冷却ドラム周面に円形または楕円形のディンプルを多数形成する方法、特開平3−174956号公報では冷却ドラム周面をローレット加工、サンドブラスト加工によって粗面化する方法、特開平9−136145号公報では冷却ドラム周面をショットブラスト加工により最大直径≦平均直径+0.30mmを満足するディンプルを形成する方法、或いは特開平11−179494号公報では冷却ドラム周面をフォトエッチング、レーザー加工等の手段によって直径0.2〜1.0mmの円柱状、楕円柱状の突起を多数形成し、表面の最大凹凸高さが15μm以下である鋳片を得る方法が提案されている。これらの方法は、いずれも冷却ドラム周面にディンプルや突起を多数形成することによって冷却ドラムと溶鋼の間に空気層を導入し、冷却ドラム周面と溶鋼との実効接触面積を減少させることによって凝固シェルの冷却を緩和し、急冷による熱収縮応力を軽減させること、およびディンプルの窪み(凹部)の周縁部(凸部)から凝固を安定的に開始させることにより割れ、亀裂の発生を防止な表面性状の鋳片を得ることを目的としている。
【0004】
【発明が解決しようとする課題】
しかしながら、特公平4−33537号公報や特開平3−174956号公報で提案された方法では、冷却ドラム周面に形成したディンプルに溶鋼が差し込み鋳片表面に高い凸転写が形成されるために後工程での圧延等の加工でスケールの巻き込み、線状ヘゲ等の圧延疵が発生する。また、特開平9−136145号公報、特開平11−179494号公報では、ディンプルが大きく接触表面積が大き過ぎ、凝固シェル形成時に過冷却部と緩冷却部が混在するために鋳片割れが発生する。そこで、本発明者らは、前述したディンプルより更に接触表面積を小さくすれば前記鋳片表面の高い凸転写および割れが発生しないのではないか、また、前述したディンプルより更に多くの凹凸を付与すれば多くの凸部から凝固をより安定的に開始させることにより割れが防止できるのではないかとの発想の下に冷却ドラム周面に従来のディンプルに更に微小な凹および突起を付与することで高い凸転写、鋳片割れ、亀裂等を極力減少する方法を開発した。
【0005】
【課題を解決するための手段】
本発明は、双ドラム式連続鋳造装置に用いる冷却ドラムに関するもので、通常のディンプル内に更に微小な凹およびグリッド破片を喰い込ませた微小な突起を付与することにより、凝固開始点を通常ディンプルよりも微細分散させることにより高い凸転写、鋳片割れ、亀裂等がなく、表面性状に優れた鋳片を安定的に製造するための冷却ドラム及び該冷却ドラムを用いた鋳造方法を提供するものである。その要旨は以下の通りである。
(1)双ドラム式連続鋳造装置用冷却ドラムの周面に平均直径:1.0〜4.0mm、平均深さ:40〜200μmを有する凹凸状ディンプル内に、平均直径:10〜50μm、平均深さ:1〜50μmの微小凹と高さ:1〜50μmのアルミナグリッドの破片が喰い込んだ微小突起を有することを特徴とする双ドラム式連続鋳造装置用冷却ドラム。
(2)双ドラム式連続鋳造装置用冷却ドラムの周面に平均直径:1.0〜4.0mm、平均深さ:40〜170μmのディンプルをショットブラスト加工、フォトエッチング加工またはレーザー加工の何れかの加工手段で形成し、次いで、アルミナグリッド吹付けにより平均直径:10〜50μm、平均深さ:1〜50μmの微小凹を形成し、更に、高さ:1〜50μmのアルミナグリッドの破片が喰い込んだ微小突起を形成した冷却ドラムを用い、溶鋼に可溶な非酸化性ガスまたは溶鋼に可溶な非酸化性ガスと溶鋼に非可溶な非酸化性ガスとの混合ガスの雰囲気中で鋳造することを特徴とする双ドラム式連続鋳造装置用冷却ドラムを用いた鋳造方法。
【0006】
【発明の実施の形態】
薄鋳片の表面割れを防止するためには、冷却ドラムと凝固シェルとの間にガスギャップを形成させて凝固シェルを緩冷却させること、鋳片表面にディンプルによる凸転写を形成させることにより凸転写の周縁部から凝固を開始させ、かつ凝固を鋳片幅方向で均一にする必要がある。一方、鋳造後の薄鋳片をインラインで圧延する場合には圧延後の薄鋳片にはスケール噛込み疵が発生し、この疵は冷延後の薄板製品でも残存する。スケール噛込み疵は凸転写部のうち高い凸転写の部分、すなわち冷却ドラム周面に加工したディンプルのうち深い窪みと対応する部分で優先的に発生する。また、鋳造後にインラインで圧延しない場合にはスケール噛込み疵の発生はないが冷延後でも凸転写が消えずに痕跡が残存する。
【0007】
また、冷却ドラム周面に加工したディンプルは、長時間の鋳造により磨耗して寿命が低下する。上記凸転写によるスケール噛み込み疵および窪みの磨耗による寿命低下を抑制するためには、最大深さと平均深さの差の小さいディンプルが有効であるとの知見から、ショット粒の粒径分布範囲(最大直径−平均直径)を小さくすること、すなわち、上記粒径分布範囲を小さくすることでディンプル深さの分布範囲も小さくなることが判明した。ショットブラスト加工においては、最大直径≦平均直径+0.30mmを満足するショット粒を使用し、所望の平均深さを得るために、冷却ドラム周面の硬度が高い程、使用するショット粒の平均直径を大きく、或いは施工時のブラスト圧力を高くしていた。
【0008】
しかしながら、上述の事実に基づいてディンプルを加工した冷却ドラムを用いて製造した鋳片の表面には依然として微小な表面割れが発生している。そこで、本発明者らは現状のディンプルの状態を詳細に観察した。その結果を図2に示す。この図2および図3は、従来法として最も一般的なショットブラスト加工を行い、冷却ドラムの周面に平均直径:2.1mm、平均深さ:130μmのディンプルを付与し、この冷却ドラム周面のディンプルの状態をレプリカ採取後、45°斜めから電子顕微鏡で15倍(図2)、50倍(図3)で観察(撮影)した表面凹凸形状を示したものである。図2、図3においては窪みの凹凸が明瞭で、ディンプル4の直径は4000ミクロン、深さで100ミクロンを越える深さに達している。このようなディンプルにおいては、ディンプルの直径および深さともに大きいため、凝固シェル形成時に急冷却部と緩冷却部が混在することになる。これでは、冷却ドラム周面に形成したディンプルの凹部では緩冷却過ぎ、一方、凸部では急冷却現象が発生するのは当然である。更に、鋳造時の凝固現象は、ディンプルとの接触部位から凝固が開始するので、ディンプル径が大きい部分や深さが大きい部分では、急冷・緩冷の差が大きくなり過ぎてディンプル単位での微小割れが発生し易くなる。
【0009】
本発明者らは、冷却ドラムの周面に平均直径:1.0〜4.0mm、平均深さ:40〜170μmのディンプルを付与した後、このディンプルに更に、平均直径数十〜数百ミクロンという非常に小さいアルミナグリッドを吹付け、平均直径:10〜50μm、平均深さ:1〜50μmの微小凹および高さ1〜50μmのアルミナグリッド破片喰い込みによる微小突起を形成した。この場合において、前記アルミナグリッドは、ドラム周面に衝突して窪みを形成するものや、衝突した瞬間に破砕してその破片が冷却ドラム周面に突き刺さり、そのまま破片としてドラム周面に喰い込んで鋭角または鈍角状の微小突起を形成する。従って、従来の大径で、深さの大きなディンプル内に更に微小な凹及び突起が形成されることになる。この微小凹は、平均直径:10〜50μm、平均深さ:1〜50μmで、微小突起の高さは1〜50μmである。
【0010】
図4、図5、図6は、このようにして形成した冷却ドラム周面のディンプルの状態をレプリカを採取して電子顕微鏡で45°斜めから15倍(図4)、50倍(図5)、100倍(図6)で観察(撮影)した表面凹凸形状を示したものである。図4(15倍)、図5(50倍)ではディンプル内に微小な凹が形成されている状態が見える。また、図6(100倍)の矢印部で示す様にアルミナグリッドの破片が喰い込んでいる部分が見える。このようなディンプルにおいては、大きなディンプルだけでなく、微小凹の周縁部、微小突起からも凝固が開始するので、凝固シェル形成時に急冷却部と緩冷却部の分布が小さいことになり、より均一冷却が可能になるものである。
【0011】
本発明において、上記サイズの微小凹を形成するためには数十〜数百μmのアルミナグリッドを使用するものであるが、前記アルミナグリッドのサイズが数十μm以下では微小凹の形成が困難であること、またグリッド破片が小さ過ぎても突起形成の効果がなく、一方、数百μm以上のグリッドでは先に形成したディンプルサイズ(平均深さ40〜170μm)を越えたり、グリッドの破片も大き過ぎるのでアルミナグリッドの直径は数十〜数百μmとした。好ましくは50〜100μm前後のサイズのアルミナグリッドが最も効果を発揮できる。また、本発明で最初に形成するディンプルのサイズは、通常のショットブラスト法、フォトエッチング法或いはレーザー加工等のいずれかの手段で形成されるディンプルサイズで十分であり、そのサイズは平均直径:1.0〜4.0mm、平均深さ:40〜170μmが好ましい。そして、このようなサイズで形成したディンプルの表面に更に数十〜数百μmの直径を有するアルミナグリッドを吹き付けて形成する微小凹のサイズは、平均直径:10〜50μm、平均深さは1〜50μmで、しかも通常ディンプルの平均深さ以下が好ましい。
【0012】
また、本発明において形成する微小突起は、高さが1〜50μmである。更に、微小凹凸の形成には、アルミナグリッドを使用したが、Ni、Co、Co−Ni合金、Co−W合金、Co−Ni−W合金のいずれか1種以上からなる溶液をめっきすることや、或いは溶射する方法でも良い。
このように、本発明においては、通常の方法で形成した通常のディンプル内に更に微小凹凸或いは微小グリッド破片を喰い込ませることにより、溶鋼の凝固開始点を通常窪み(ディンプル)よりも微細分散させるとにより冷却時の鋳片の微小割れを確実に防止できる。
【0013】
【実施例】
次に、実施例について説明する。本発明においては、前述したような冷却ドラムを用い、鋳造は溶鋼に可溶な非酸化性雰囲気下または、溶鋼に可溶な非酸化性ガスと溶鋼に非可溶な非酸化性ガスの混合雰囲気下で鋳造し、鋳片に本発明による冷却ドラムのディンプルを転写させることにより実施した。
【0014】
表1に示すように、直径:1000mmφのCu製冷却ドラム周面にベースディンプルとして、通常のショットブラスト法により、平均直径:1.5〜3.0mm、平均深さ:30〜250μmを形成した。比較例としての冷却ドラムは、このショットブラスト法によるベースディンプルのままの例、またはベースディンプル深さが小さ過ぎる例、大き過ぎる例、或いは微小凹が形成されても微小凹直径、微小凹深さ、或いは微小突起高さが本発明の範囲に満たないものである。一方、本発明による実施例においては、前記ベースディンプルの上に更に、50〜100μm前後のサイズのアルミナグリッドを吹き付け、平均直径:10〜50μm、平均深さ:1〜50μmの微小凹を形成し、同時に前記アルミナグリッド破片が喰い込み、1〜50μmの高さを有する微小突起を形成した。上記表1にその結果を併せて示した。
【0015】
表1において、実施例No.2およびNo.8は本発明例で、残るNo.1、3〜7、9、10は何れも比較例である。本発明例No.2、No.8においては鋳片割れ発生が皆無であった。一方、比較例である通常のベースディンプルのままのNo.1、No.7の例では、割れ発生量として0.2mm/m2、0.3mm/m2の鋳片割れが発生した。No.3の例では微小凹径が小さ過ぎたために微小凹が形成されても0.1mm/m2の鋳片割れが発生した。No.4の例では微小凹深さが小さ過ぎ、また微小突起高さが小さ過ぎ、0.1mm/m2の鋳片割れが発生した。No.5の例ではベースディンプル深さが小さ過ぎ、しかも微小凹、微小突起も形成していないために17.0mm/m2の大きな鋳片割れが発生した。これはベースディンプル深さが小さ過ぎたことにより緩冷却効果が不足したものと考えられる。また、同様に、No.6の例では微小凹、微小突起を形成してもベースディンプル深さが小さ過ぎ、15.0mm/m2の大きな鋳片割れが発生した。この例ではベースディンプル深さが小さ過ぎ、微小凹、微小突起の効果が発揮されなかったものと考えられる。更に、No.9の例ではベースディンプルの平均深さが250μmと大き過ぎ、微小凹、微小突起がないことと相まって5.0mm/m2の鋳片割れが発生した。No.10の例では、深さが250μmという大きなディンプル内に微小凹、微小突起を付与したが、ベースディンプルが深過ぎて微小凹、微小突起付与の効果が発揮されず3.0mm/m2の鋳片割れが発生した。
【0016】
【表1】
【0017】
【発明の効果】
以上説明したように、本発明による双ドラム式連続鋳造装置用冷却ドラムは、従来のサイズを有する凹凸状のディンプルを形成後、更に前記ディンプル内に数十〜数百μmのサイズを有するアルミナグリッドを吹付け微小凹、微小突起を形成させることにより、凝固開始点の分散による均一冷却を行うことで鋳片表面の微小割れ、亀裂発生を防止し、また、凸転写によるスケール噛込み疵を防止して表面品質の良好な薄鋳片を安定して鋳造することが可能になる。
【図面の簡単な説明】
【図1】本発明を実施するための双ドラム式連続鋳造装置を示す一部断面側面図である。
【図2】従来の冷却ドラムの周面のディンプルをレプリカ採取後電子顕微鏡で45°斜めから観察(撮影)(15倍)した状態を示す拡大図。
【図3】従来の冷却ドラム周面のディンプルをレプリカ採取後電子顕微鏡で45°斜めから観察(撮影)(50倍)した状態を示す拡大図である。
【図4】本発明による冷却ドラムの周面のディンプルをレプリカ採取後電子顕微鏡で45°斜めから観察(撮影)(15倍)した状態を示す拡大図である。
【図5】本発明による冷却ドラムの周面のディンプルをレプリカ採取後電子顕微鏡で45°斜めから観察(撮影)(50倍)した状態を示す拡大図である。
【図6】本発明による冷却ドラムの周面のディンプルをレプリカ採取後電子顕微鏡で45°斜めから観察(撮影)(100倍)した状態を示す拡大図である。
【符号の説明】
1−a、1−b…冷却ドラム
2−a、2−b…サイド堰
3…湯溜まり
4…凹凸状ディンプル
5…微小凹凸
6…微小突起
R…溶融金属
g、g’…凝固シェル
Kp…ロールギャップ
C…薄鋳片[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a twin-drum type continuous casting cooling drum, and in particular, a fine concavo-convex depression (hereinafter referred to as a dimple) is formed on a peripheral surface to stably cast a thin slab having a good surface quality. The present invention relates to a twin drum type continuous casting cooling drum and a casting method using the same.
[0002]
[Prior art]
In the field of continuous casting of metal, there is a twin-drum strip continuous casting method using a pair of cooling drums as a method for continuously casting a ribbon that is close to the final shape. As shown in FIG. Molten metal R is supplied to the
[0003]
In the thin-wall casting method, the cast slab has a shape that approximates the shape of the final product. Therefore, it is inefficient to remove surface defects by means such as grinding after casting, and the yield is greatly reduced. Therefore, it is an indispensable technical problem to eliminate all surface defects such as cracks and cracks during casting. On the other hand, in the thin-wall casting, since the solidified shell is rapidly cooled, there is a problem in that defects such as cracks and cracks are likely to occur on the surface of the slab due to heat shrinkage stress accompanying rapid cooling. Therefore, various proposals have been made to stably prevent surface defects of the slab. For example, Japanese Patent Publication No. 4-33537 discloses a method in which a large number of circular or elliptical dimples are formed on the circumferential surface of the cooling drum, and Japanese Patent Laid-Open No. 3-174957 discloses that the circumferential surface of the cooling drum is roughened by knurling or sandblasting. In Japanese Patent Laid-Open No. 9-136145, a method of forming dimples satisfying the maximum diameter ≦ average diameter + 0.30 mm by shot blasting on the peripheral surface of the cooling drum, or in Japanese Patent Laid-Open No. 11-179494, the peripheral surface of the cooling drum is formed. A method has been proposed in which a large number of cylindrical and elliptical columnar projections having a diameter of 0.2 to 1.0 mm are formed by means such as photoetching and laser processing, and a slab having a maximum unevenness of 15 μm or less on the surface is obtained. Yes. Each of these methods introduces an air layer between the cooling drum and molten steel by forming a large number of dimples and protrusions on the circumferential surface of the cooling drum, thereby reducing the effective contact area between the circumferential surface of the cooling drum and the molten steel. Reduces the cooling of the solidified shell, reduces the heat shrinkage stress due to rapid cooling, and prevents the occurrence of cracks and cracks by starting solidification stably from the peripheral edge (convex part) of the dimple depression (concave part). The object is to obtain a surface texture slab.
[0004]
[Problems to be solved by the invention]
However, in the methods proposed in Japanese Patent Publication No. 4-33537 and Japanese Patent Laid-Open No. 3-174957, the molten steel is inserted into the dimples formed on the peripheral surface of the cooling drum, and a high convex transfer is formed on the surface of the cast slab. Rolling wrinkles such as scale entrainment and linear shaving are generated by processing such as rolling in the process. Further, in JP-A-9-136145 and JP-A-11-179494, a dimple is large and a contact surface area is too large, and a supercooled part and a slow-cooled part coexist at the time of forming a solidified shell. Therefore, the present inventors may not cause high convex transfer and cracks on the slab surface if the contact surface area is made smaller than that of the dimples described above, or more unevenness than that of the dimples described above. if by giving many more small concave contact and protrusions of the conventional dimple convex portion to the cooling drum circumference under the idea of that it would be possible to prevent cracking by starting coagulation more stably We have developed a method to reduce high convex transfer, slab cracks, cracks, etc. as much as possible.
[0005]
[Means for Solving the Problems]
The present invention relates to a cooling drum used in the twin drum type continuous casting apparatus, by imparting minute projections were bite more minute concave contact and grid debris within normal dimple, the solidification starting point Provided is a cooling drum for stably producing a slab having excellent surface properties without causing high convex transfer, slab cracking, cracking, etc. by fine dispersion than ordinary dimples, and a casting method using the cooling drum Is. The summary is as follows.
( 1 ) In an uneven dimple having an average diameter of 1.0 to 4.0 mm and an average depth of 40 to 200 μm on the peripheral surface of a cooling drum for a twin drum type continuous casting apparatus, an average diameter of 10 to 50 μm and an average A cooling drum for a twin-drum type continuous casting apparatus, characterized in that it has minute protrusions with a depth of 1 to 50 μm and a height: 1 to 50 μm of alumina grid fragments.
( 2 ) Dimples having an average diameter of 1.0 to 4.0 mm and an average depth of 40 to 170 μm on the peripheral surface of the cooling drum for the twin-drum type continuous casting apparatus, either shot blasting, photoetching or laser processing Next, micro- concaves having an average diameter of 10 to 50 μm and an average depth of 1 to 50 μm are formed by spraying alumina grid, and further, pieces of alumina grid having a height of 1 to 50 μm are eaten. In a mixed gas atmosphere of non-oxidizing gas soluble in molten steel or non-oxidizing gas soluble in molten steel and non-oxidizing gas insoluble in molten steel A casting method using a cooling drum for a twin-drum type continuous casting apparatus, characterized by casting.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
In order to prevent the surface crack of the thin slab, a gas gap is formed between the cooling drum and the solidified shell to slowly cool the solidified shell, and a convex transfer by dimples is formed on the surface of the slab. It is necessary to start solidification from the peripheral edge of the transfer and make the solidification uniform in the slab width direction. On the other hand, when the thin slab after casting is rolled in-line, scale-engaging flaws are generated in the thin slab after rolling, and these wrinkles remain even in the thin plate product after cold rolling. Scale biting occurs preferentially in the high convex transfer portion of the convex transfer portion, that is, in the portion corresponding to the deep depression in the dimple processed on the peripheral surface of the cooling drum. Further, when rolling is not performed in-line after casting, no scale biting flaws occur, but the convex transfer remains without disappearing even after cold rolling.
[0007]
Further, the dimples processed on the peripheral surface of the cooling drum are worn out by casting for a long time and the life thereof is reduced. Based on the knowledge that dimples with a small difference between the maximum depth and the average depth are effective for suppressing the reduction of the life due to the wear of the scale bite and dent due to the convex transfer, the particle size distribution range of shot grains ( It has been found that the distribution range of the dimple depth is reduced by reducing the maximum diameter-average diameter), that is, by reducing the particle size distribution range. In shot blasting, shot grains satisfying the maximum diameter ≦ average diameter + 0.30 mm are used, and in order to obtain a desired average depth, the higher the hardness of the cooling drum peripheral surface, the higher the average diameter of the shot grains used. Or increased blast pressure during construction.
[0008]
However, minute surface cracks still occur on the surface of the slab manufactured using a cooling drum in which dimples are processed based on the above-described facts. Therefore, the present inventors have observed the current dimple state in detail. The result is shown in FIG. 2 and 3 show the most common shot blasting as a conventional method, and dimples having an average diameter of 2.1 mm and an average depth of 130 μm are imparted to the peripheral surface of the cooling drum. The surface irregularities of the dimples were observed (photographed) at 45 times (FIG. 2) and 50 times (FIG. 3) with an electron microscope from 45 ° obliquely after sampling. In FIGS. 2 and 3, the depressions and projections are clear, and the dimple 4 has a diameter of 4000 microns and a depth exceeding 100 microns. In such a dimple, since both the diameter and the depth of the dimple are large, a rapid cooling part and a slow cooling part are mixed when forming the solidified shell. In this case, it is natural that the dimple recess formed on the peripheral surface of the cooling drum is excessively cooled, while the convex portion causes a rapid cooling phenomenon. Furthermore, the solidification phenomenon during casting starts from the point of contact with the dimple, so the difference between quenching and slow cooling becomes too large at the part where the dimple diameter is large or the part where the depth is large. Cracks are likely to occur.
[0009]
The inventors of the present invention applied dimples having an average diameter of 1.0 to 4.0 mm and an average depth of 40 to 170 μm to the peripheral surface of the cooling drum, and then further added this dimple to an average diameter of several tens to several hundreds of microns. only spray very small alumina grid that, the average diameter: 10 to 50 [mu] m, average depth: to form a minute projection by embedding alumina grid debris minute concave contact and height 1 to 50 [mu] m of 1 to 50 [mu] m. In this case, the alumina grid collides with the drum peripheral surface to form a dent, or crushes at the moment of collision, and the fragments stab into the peripheral surface of the cooling drum. A sharp or obtuse minute projection is formed. Thus, the conventional large diameter, so that the further small 凹及 beauty projections to a depth greater the dimple is formed. The minute recesses have an average diameter of 10 to 50 μm, an average depth of 1 to 50 μm, and the height of the minute protrusions is 1 to 50 μm.
[0010]
4, 5, and 6, the dimple state on the circumferential surface of the cooling drum formed in this way is taken as a replica, and 15 times (FIG. 4) and 50 times (FIG. 5) from an angle of 45 ° with an electron microscope. The surface uneven | corrugated shape observed (photographed) by 100 time (FIG. 6) is shown. In FIG. 4 (15 times) and FIG. 5 (50 times), it can be seen that a minute recess is formed in the dimple. Moreover, as shown by the arrow part of FIG. 6 (100 times), the part which the piece of the alumina grid bites in can be seen. In such dimples, solidification starts not only from the large dimples, but also from the peripheral edge of the micro- concave and the micro-protrusions, so the distribution of the rapid cooling part and the slow cooling part is small when forming the solidified shell, and more uniform Cooling is possible.
[0011]
In the present invention, an alumina grid with a size of several tens to several hundreds of μm is used to form the micro- concave of the above size. However, when the size of the alumina grid is several tens of μm or less, it is difficult to form the micro- concave. In addition, if the grid pieces are too small, there will be no effect of protrusion formation. On the other hand, if the grid is several hundred μm or more, it will exceed the previously formed dimple size (average depth 40 to 170 μm), or the grid pieces will be large. Therefore, the diameter of the alumina grid was set to several tens to several hundreds μm. An alumina grid having a size of about 50 to 100 μm is most effective. The dimple size initially formed in the present invention may be a dimple size formed by any means such as a normal shot blasting method, a photo etching method, or laser processing, and the size has an average diameter of 1 0.0-4.0 mm and average depth: 40-170 micrometers are preferable. And the size of the micro- concave formed by spraying an alumina grid having a diameter of several tens to several hundreds μm on the surface of the dimple formed in such a size has an average diameter of 10 to 50 μm and an average depth of 1 to 1. It is preferably 50 μm and usually less than the average depth of the dimples.
[0012]
Moreover, the microprotrusions formed in the present invention have a height of 1 to 50 μm. Furthermore, although the alumina grid was used for the formation of minute irregularities, plating with a solution composed of at least one of Ni, Co, Co—Ni alloy, Co—W alloy, and Co—Ni—W alloy, Alternatively, a thermal spraying method may be used.
As described above, in the present invention, the solidification start point of the molten steel is more finely dispersed than the normal depressions (dimples) by further encroaching the fine irregularities or fine grid fragments into the normal dimples formed by the usual method. Thus, micro-cracking of the slab during cooling can be surely prevented.
[0013]
【Example】
Next, examples will be described. In the present invention, the cooling drum as described above is used, and casting is performed in a non-oxidizing atmosphere soluble in molten steel or a mixture of a non-oxidizing gas soluble in molten steel and a non-oxidizing gas insoluble in molten steel. The casting was carried out under an atmosphere, and the dimples of the cooling drum according to the present invention were transferred to the slab.
[0014]
As shown in Table 1, diameter as the base dimples on the Cu-made cooling drum peripheral surface of 1000Mmfai, by conventional shot blasting method, average diameter: 1.5 to 3.0 mm, average depth: forming a 30~250μm did. Cooling drum as a comparative example, an example of leaving the base dimples by the shot blasting method or the base dimples examples depth is too small, eg too large, or small 凹直 diameter even small concave is formed, a micro 凹深 Alternatively, the height of the minute protrusion is less than the scope of the present invention. On the other hand, in an embodiment according to the present invention, an alumina grid having a size of about 50 to 100 μm is further sprayed on the base dimple to form minute recesses having an average diameter of 10 to 50 μm and an average depth of 1 to 50 μm. At the same time the narrowing had alumina grid debris Eating to form minute projections having a height of 1 to 50 [mu] m. It is shown together with the results in Table 1 above.
[0015]
In Table 1, Examples No. 2 and No. 8 are examples of the present invention, and the remaining Nos. 1, 3 to 7, 9, and 10 are comparative examples. In Invention Examples No. 2 and No. 8, no slab cracking occurred. On the other hand, remains No.1 conventional base dimples is a comparative example, in the example No.7, 0.2 mm / m 2, is 0.3 mm / m 2 of cast halves occurs as cracking amount. The cast halves 0.1 mm / m 2 be small concave is formed for fine concave diameter is too small is generated in the example no.3. In the example of No. 4, the depth of the minute recess was too small, the height of the minute protrusion was too small, and a slab crack of 0.1 mm / m 2 occurred. In the case of No. 5, the base dimple depth was too small, and the micro- concave and micro-projections were not formed, so a large slab crack of 17.0 mm / m 2 occurred. This is considered that the slow cooling effect is insufficient because the base dimple depth is too small. Similarly, in the case of No. 6, even when the micro- recesses and micro-protrusions were formed, the base dimple depth was too small and a large slab crack of 15.0 mm / m 2 occurred. In this example, it is considered that the base dimple depth is too small, and the effect of the minute recesses and minute protrusions was not exhibited. Furthermore, in the example of No. 9, the average depth of the base dimples was too large, 250 μm, and coupled with the absence of minute recesses and protrusions, a slab crack of 5.0 mm / m 2 occurred. In the example of No. 10, the minute dimples and minute protrusions were provided in the large dimple having a depth of 250 μm, but the effect of providing the minute depressions and minute protrusions was not exhibited because the base dimple was too deep, and 3.0 mm / m 2. The slab crack occurred.
[0016]
[Table 1]
[0017]
【The invention's effect】
As described above, the cooling drum for a twin-drum type continuous casting apparatus according to the present invention has an alumina grid having a size of several tens to several hundreds of μm in the dimple after forming an uneven dimple having a conventional size. By forming a micro- recess and micro-projection, uniform cooling is achieved by dispersing the solidification start point, thereby preventing micro cracks and cracks on the surface of the slab, and preventing scale clogging due to convex transfer. Thus, it becomes possible to stably cast a thin slab having a good surface quality.
[Brief description of the drawings]
FIG. 1 is a partially sectional side view showing a twin-drum type continuous casting apparatus for carrying out the present invention.
FIG. 2 is an enlarged view showing a state in which dimples on the peripheral surface of a conventional cooling drum are observed (photographed) (15 times) from a 45 ° angle with an electron microscope after replica collection.
FIG. 3 is an enlarged view showing a state in which dimples on a peripheral surface of a conventional cooling drum are observed (photographed) (magnified by 50 times) from an angle of 45 ° with an electron microscope after replica collection.
FIG. 4 is an enlarged view showing a state in which dimples on the peripheral surface of the cooling drum according to the present invention are observed (photographed) (15 times) from a 45 ° angle with an electron microscope after replica collection.
FIG. 5 is an enlarged view showing a state in which dimples on the peripheral surface of the cooling drum according to the present invention are observed (photographed) (50 times) from a 45 ° angle with an electron microscope after replica collection.
FIG. 6 is an enlarged view showing a state in which dimples on the peripheral surface of the cooling drum according to the present invention are observed (photographed) (100 times) from a 45 ° angle with an electron microscope after replica collection.
[Explanation of symbols]
1-a, 1-b ... cooling drums 2-a, 2-b ...
Claims (2)
Priority Applications (23)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2000306753A JP4406164B2 (en) | 2000-10-05 | 2000-10-05 | Cooling drum for twin drum type continuous casting apparatus and casting method using the same |
AU56712/01A AU777752B2 (en) | 2000-05-12 | 2001-05-11 | Cooling drum for continuously casting thin cast piece and fabricating method and device therefor and thin cast piece and continuous casting method therefor |
CA002377876A CA2377876C (en) | 2000-05-12 | 2001-05-11 | Cooling drum for thin slab continuous casting, processing method and apparatus thereof, and thin slab and continuous casting method thereof |
ES05006811T ES2333232T3 (en) | 2000-05-12 | 2001-05-11 | A COOLING DRUM FOR CONTINUOUS COLADA OF THICK IRON. |
EP05006813A EP1595622A1 (en) | 2000-05-12 | 2001-05-11 | A method of processing a cooling drum for metal cast strip by continuous casting and an apparatus therefor |
AT01930090T ATE361167T1 (en) | 2000-05-12 | 2001-05-11 | COOLED CASTING ROLL FOR CONTINUOUS CASTING OF THIN PRODUCTS AND CONTINUOUS STRONG CASTING PROCESS |
EP05006812A EP1602424B2 (en) | 2000-05-12 | 2001-05-11 | A cooling drum for thin slab continuous casting and continuous casting method thereof |
AT05006812T ATE375833T1 (en) | 2000-05-12 | 2001-05-11 | COOLED CASTING ROLL FOR CONTINUOUS CASTING OF THIN PRODUCTS AND CONTINUOUS CASTING PROCESSES |
ES05006812T ES2291995T5 (en) | 2000-05-12 | 2001-05-11 | A cooling drum for continuous thin plate casting and a continuous casting method with it |
DE60140321T DE60140321D1 (en) | 2000-05-12 | 2001-05-11 | COOLED CASTING ROLL FOR CONTINUOUS CASTING OF THIN PRODUCTS |
EP05006814A EP1582279A1 (en) | 2000-05-12 | 2001-05-11 | A continuous cast thin slab |
KR1020057016119A KR100668126B1 (en) | 2000-05-12 | 2001-05-11 | Apparatus for processing cooling drum for continuously casting thin cast piece |
DE60128217T DE60128217T2 (en) | 2000-05-12 | 2001-05-11 | COOLED CASTING ROLL FOR THE CONTINUOUS CONTINUOUS CASTING OF THIN PRODUCTS AND CONTINUOUS CASTING METHOD |
EP01930090A EP1281458B1 (en) | 2000-05-12 | 2001-05-11 | Cooling drum for continuously casting thin cast piece and continuous casting method therefor |
US10/031,349 US6896033B2 (en) | 2000-05-12 | 2001-05-11 | Cooling drum for continuously casting thin cast piece and fabricating method and device therefor and thin cast piece and continuous casting method therefor |
KR1020057016118A KR100692499B1 (en) | 2000-05-12 | 2001-05-11 | Method of processing cooling drum for continuously casting thin cast piece |
PCT/JP2001/003965 WO2001085369A1 (en) | 2000-05-12 | 2001-05-11 | Cooling drum for continuously casting thin cast piece and fabricating method and device therefor and thin cast piece and continuous casting method therefor |
AT05006811T ATE446814T1 (en) | 2000-05-12 | 2001-05-11 | COOLED CASTING ROLL FOR CONTINUOUS CASTING OF THIN PRODUCTS |
KR1020027000450A KR100668123B1 (en) | 2000-05-12 | 2001-05-11 | Cooling drum for continuously casting thin cast piece and fabricating method and device therefor and thin cast piece and continuous casting method therefor |
EP05006811A EP1595621B1 (en) | 2000-05-12 | 2001-05-11 | A cooling drum for thin slab continuous casting |
DE60131034T DE60131034T3 (en) | 2000-05-12 | 2001-05-11 | COOLED CASTING ROLL FOR THE CONTINUOUS CONTINUOUS CASTING OF THIN PRODUCTS AND CONTINUOUS CASTING METHOD |
ES01930090T ES2287125T3 (en) | 2000-05-12 | 2001-05-11 | COOLING DRUM FOR CONTINUOUS COLADA OF MOLDED THIN PIECES AND CONTINUOUS COLADA PROCEDURE FOR THE SAME. |
US11/044,561 US7159641B2 (en) | 2000-05-12 | 2005-01-26 | Cooling drum for thin slab continuous casting, processing method and apparatus thereof, and thin slab and continuous casting method thereof |
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JP2000306753A JP4406164B2 (en) | 2000-10-05 | 2000-10-05 | Cooling drum for twin drum type continuous casting apparatus and casting method using the same |
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JP2006231347A (en) * | 2005-02-23 | 2006-09-07 | Mitsubishi-Hitachi Metals Machinery Inc | Twin roll type continuous caster |
KR100779574B1 (en) * | 2006-08-02 | 2007-11-29 | 주식회사 포스코 | Casting roll for twin roll strip caster |
WO2010104032A1 (en) * | 2009-03-11 | 2010-09-16 | 新東工業株式会社 | Method of processing cavity surface of casting mold |
US8424588B2 (en) | 2009-08-08 | 2013-04-23 | Sintokogio, Ltd. | Casting die |
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