JP4501236B2 - Continuous casting method - Google Patents
Continuous casting method Download PDFInfo
- Publication number
- JP4501236B2 JP4501236B2 JP2000197459A JP2000197459A JP4501236B2 JP 4501236 B2 JP4501236 B2 JP 4501236B2 JP 2000197459 A JP2000197459 A JP 2000197459A JP 2000197459 A JP2000197459 A JP 2000197459A JP 4501236 B2 JP4501236 B2 JP 4501236B2
- Authority
- JP
- Japan
- Prior art keywords
- ratio
- equiaxed
- value
- equiaxed crystal
- casting
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Images
Landscapes
- Continuous Casting (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、溶融金属合金の連続鋳造方法に関する。
【０００２】
【従来の技術】
厚板用鋼や線材用鋼、構造用鋼、さらにはマルテンサイト系ステンレス鋼等では、連鋳鋳片の中心部に溶質偏析やミクロキャビティーが連なった収縮孔が発生しやすく、製品においてこれらに起因する欠陥が発生することがある。また、フェライト系ステンレス鋼においては、鋳片内部の柱状凝固組織に起因した冷延板表面の加工性不良（リジング）が発生しやすい。
【０００３】
ところで、等軸晶率に影響を及ぼす連続鋳造の操業条件に関して、例えば、鋼の連続鋳造の場合では、溶鋼過熱度や鋳造速度、電磁攪拌強度の等軸晶率への影響は、ある限られた条件内でしか理解されておらず、そのため、操業条件を大幅に変更した時に等軸晶率がどのように変化するかは、鋳造後に鋳片断面を調査して初めて解るという、まったくの経験に頼っていた。そのため、等軸晶率に大きく影響する鋳片の中心偏析や中心断面割れ、加工性といった鋳片単位の製品特性のバラツキがおおきくなり、品質管理上問題が発生していた。
【０００４】
このような欠陥は、鋳片中心部の凝固組織を柱状晶から等軸晶に変えるか、あるいは等軸晶率を増大することによって軽減できることが知られており、従来から、凝固組織が柱状晶から等軸晶に遷移する位置を予測する方法が開発されている。
これらの予測方法として、凝固・伝熱の数値シミュレーションにより凝固組織が柱状晶から等軸晶に遷移する位置を予測する方法が紹介されている。例えば、Ｊ．Ｄ．Ｈｕｎｔらの理論解析的モデル（Material Science and Eng.,vol.65（I984）,pp74-83）を適用した例（例えば、Arlette Etienne:steel Research,61(10,472) ）が提案されており、この提案は、固相率０の柱状晶先端位置における温度勾配Ｇ′がある臨界値を下回った時に柱状晶から等軸晶に選移するという考えで、柱状晶先端における等軸晶粒の体積率が或る臨界値を上回ったら柱状晶の成長が停止するという背景に基づくものである。
【０００５】
また、凝固解析により凝固組織が柱状晶から等軸晶に遷移する位置を予測する方法（例えば、International Journal of Numerical Methods for Heat ＆ Fluid Flow,vol.9,No.3,1999,pp.296-317, 或いはAppl Math Phys Model Iron steel Ind,pp.271-272,1982 ) も提案されており、この提案は、溶湯内に分散する多数の生成核密度、その分散度、生成場所、溶鋼過冷度等を仮定してそれぞれの核について凝固解析するようにしたものである。
【０００６】
更に、等軸晶率Ｒｅが最大値を示す溶鋼攪拌位置、或いは攪拌部の固相率、更には等軸晶率に及ぼす鋳造速度Ｖｃの影響に関して、下記のような関係式が提案されている。
Ｒｅ＝ＡＰB Ｖｃ-0.5ｆ（η） （ブルームの場合） …（１）
（日本鉄鋼協会編、鉄と鋼，１９８３年，Ｓ２６９に記載）
Ｒｅ＝−ａ（ΔＴＶｃ／Ｕ0.4 ）＋ｂ （ビレットの場合） …（２）
（日本鉄鋼協会編、材料と性質、１９８８年，１２９１に記載）
ここで、Ａ，Ｂ，ａ，ｂは定数、ｆ（η）は凝固率ηの関数、Ｐは溶鋼流速を示す攪拌力の指標としての凝固前面推力、Ｔはタンディッシュ内溶鋼過熱度（°Ｃ）、Ｖｃは鋳造速度（ｍ／ｍｉｎ）、Ｕは溶鋼攪拌流速（ｃｍ／ｓｅｃ）である。
【０００７】
つまり、（１），（２）式は、等軸晶率Ｒｅが鋳造速度Ｖｃの増加に対して減少することを示しており、また、（１）式は等軸晶率Ｒｅが最大になる最適な攪拌位置があるとしている。
更に、特開昭５３−８３２７号公報では、高等軸晶率スラブを得るために、メニスカスから鋳造方向に８ｍを越える位置の４０〜９０ｍｍの未凝固部で電磁攪拌する方法が提案されている。
【０００８】
【発明が解決しようとする課題】
しかしながら、上述した凝固組織が柱状晶から等軸晶に遷移する位置を予測する方法においては、いずれも、計算方法が複雑で、非常に限られた微小領域での予測方法であり、しかも、決定すべきパラメーターが多いため、連続鋳造に適用するには計算機のメモリー不足から実用が困難である。
【０００９】
また、考慮すべき操業条件（鋳造速度、溶鋼過熱度、二次冷却条件、スラブサイズ、溶鋼攪拌速度、溶鋼攪拌位置、鋼種）を全て考慮したものではなく、溶鋼温度や二次冷却条件を考慮する程度に止まり、連続鋳造に即適用できるものではない。
本発明はこのような不都合を解消するためになされたものであり、任意の等軸晶率を簡単且つ正確に予測することができるようにして、鋳片の中心偏析や中心断面割れ、加工性といった鋳片単位の製品特性のバラツキを少なくすることができる溶融金属合金の連続鋳造方法を提供することを目的とする。
【００１０】
【課題を解決するための手段】
上記目的を達成するために、請求項１に係る溶融金属合金の連続鋳造方法は、溶融金属合金の連続鋳造方法において、金属合金の固液共存領域における固相率ｆｓが特定の固相率ｆｅである鋳片厚み方向の位置を鋳造方向にわたって計算するとともに、該計算により得られた位置における鋳片厚み方向の温度勾配Ｇおよび凝固速度Ｒを計算により算出し、前記温度勾配Ｇと前記凝固速度Ｒのべき乗Ｒｎとの比Ｇ／Ｒｎを、前記特定の固相率ｆｅを０．１〜０．３の間、前記凝固速度Ｒのべき乗Ｒｎの指数ｎを０〜１．０の間の範囲で計算により求め、このＧ／Ｒｎが所定の閾値よりも小さくなる範囲を等軸晶形成域と判定し、該判定結果に基づいて前記等軸晶形成域の鋳片断面に占める鋳片厚み方向の割合を求めて等軸晶率を予測し、予測した前記等軸晶率の最大値を目標等軸晶率とし、鋳造速度を、前記目標等軸晶率での鋳造速度の予測値に近づけて鋳造することを特徴とする。
ただし、前記所定の閾値は、Ｇ／Ｒｎの臨界値であり、このＧ／Ｒｎの臨界値は、前記特定の固相率ｆｅおよび前記凝固速度Ｒのべき乗Ｒｎの指数ｎを選定・固定して解析して得られたＧ／Ｒｎ値に対応する等軸晶率の計算値と実測された等軸晶率の実測値とが対応一致した場合におけるＧ／Ｒｎ値で決定される。
【００１１】
ここで、固相率ｆｅは金属種により経験的に決まる定数で０．１〜０．３間の間の値であり、また、ｎは金属種により経験的に決まる定数で、０．１〜１．０の間の値である。
【００１２】
請求項２に係る溶融金属合金の連続鋳造方法は、溶融金属合金の連続鋳造方法において、金属合金の固液共存領域における固相率ｆｓが特定の固相率ｆｅである鋳片厚み方向の位置を鋳造方向にわたって計算するとともに、該計算により得られた位置における鋳片厚み方向の温度勾配Ｇおよび凝固速度Ｒを計算により算出し、前記温度勾配Ｇと前記凝固速度Ｒのべき乗Ｒ ｎ との比Ｇ／Ｒ ｎ を、前記特定の固相率ｆｅを０．１〜０．３の間、前記凝固速度Ｒのべき乗Ｒ ｎ の指数ｎを０〜１．０の間の範囲で計算により求め、このＧ／Ｒ ｎ が所定の閾値よりも小さくなる範囲を等軸晶形成域と判定し、該判定結果に基づいて前記等軸晶形成域の鋳片断面に占める鋳片厚み方向の割合を求めて等軸晶率を予測し、予測した前記等軸晶率の最大値を目標等軸晶率とし、前記目標等軸晶率に最も近くなる位置に電磁攪拌設備を設置して鋳造することを特徴とする。
ただし、前記所定の閾値は、Ｇ／Ｒ ｎ の臨界値であり、このＧ／Ｒ ｎ の臨界値は、前記特定の固相率ｆｅおよび前記凝固速度Ｒのべき乗Ｒ ｎ の指数ｎを選定・固定して解析して得られたＧ／Ｒ ｎ 値に対応する等軸晶率の計算値と実測された等軸晶率の実測値とが対応一致した場合におけるＧ／Ｒ ｎ 値で決定される。
【００１３】
【発明の実施の形態】
以下、本発明の実施の形態を説明する。
本発明者等は、簡便に凝固組織が柱状晶から等軸晶に遷移する位置を予測する方法を見い出すべく、種々の溶鋼の連続鋳造鋳片の凝固組織調査から得られる柱状晶から等軸晶に遷移する位置と、凝固・伝熱解析により求められるその位置での温度勾配Ｇと凝固速度Ｒの関係を調査・解析した。
【００１４】
凝固・伝熱解析手法は、下記（３）式に示す一次元伝熱基礎方程式を前進差分近似して繰り返し計算する一般的な方法を用い、凝固潜熱の取り扱いはエンタルピー法とし、温度と固相率の関係は一般的なClyne-Kurzらの式から計算し、溶質の凝固点降下と拡散を考慮して与えた。
ρ（∂Ｈ／∂ｔ）＝（λ∂Ｔ 2／∂ｘ 2） …（３）
ここで、Ｈ：鋼の含熱量，Ｔ：鋼の温度，ρ：鋼の密度，λ：鋼の熱伝導率，x ：鋳片厚み方向距離，t ：時間
バルク内の見かけの熱伝導率λＬ（= 有効熱伝導率）は、溶鋼流動により上昇するため、溶鋼の熱伝導率λＬ0 よりも大きくし、実現象に一致するように与えた。
【００１５】
ここで、鋼の熱伝導率λは、バルク内（特定固相率ｆｅ＞固相率ｆｓ）でλＬ、特定固相率ｆｅから固相率１までの間では液相率（１−ｆｓ）に比例して増加するとすればよい。つまり、
ｆｅ＞ｆｓ： λ＝λＬ
ｆｅ≦ｆｓ＜１：
λ＝[ λＬ(1−ｆｓ) ／(1−ｆｅ)]＋[ λｓ( ｆｓ−ｆｅ）／(1−ｆｅ）]
ここで、λｓは固相温度における鋼の熱伝導率である。
【００１６】
この際、バルク内の見かけの熱伝導率λＬをメニスカスからの距離ｚに依存して変化させることにより、λを予測できることを見い出した。つまり、電磁力による溶鋼撹絆部分のλは、その中央部位置Ｌｓが溶鋼熱伝導率λＬ0 の１０倍、それよりもメニスカス方向の溶鋼攪拌影響領域ｕＬ、及び鋳片引き抜き方向の溶鋼攪拌影響領域ｄＬでは距離に比例して減少する。メニスカスから１ｍ下までは溶綱熱伝導率の５倍、それ以外の溶鋼攪拌の影響の殆ど及ばない位置では溶鋼熱伝導率の２倍として与えた。
【００１７】
ｕＬ，ｄＬは、溶鋼攪拌条件に依存し、柱状晶の傾斜している長さ、ホワイトバンド部位置等、凝固組織を観察することにより決定する事ができる。本発明では、攪拌強度を増加させても等軸晶率（等軸晶厚み／鋳片厚み×１００％）が増加しない飽和条件において、ｕＬ＝１．５ｍ，ｄＬ＝１．５ｍと与えたが、これらの値は電磁攪拌装置の仕様、設置状況、鋳片サイズ、等により変わり得る値である。
【００１８】
上記の数値は、一般的な流動解析結果から同様の値を求めても良く、条件により変更すべき定数である。
本発明における解析条件の例を以下に示す。
・シェル刻みメッシュ＝１ｍｍ，刻み時間＝０．０１ｓｅｃ
・鋳型内初期の溶鋼過熱度ΔＴM は、実測に基づき、タンディッシュ内溶鋼過熱度ΔＴT の関数として次式で与えた。
【００１９】
ΔＴM ＝０．５９ΔＴT −５．８
・ΔＴT ＝１５〜６３°Ｃ
・鋳造速度Ｖｃ＝０．６〜１．５ｍ／ｍｉｎ
・二次冷却水比（溶鋼１ｋｇあたりの冷却水量）ＩW ＝０．６〜１．４Ｌ／ｋｇ
・溶鋼電磁攪拌装置中央位置のメニスカスからの距離Ｌｓ＝3.0,4.6,5.3,7.2 ｍ
・鋳型内長辺抜熱量は、鋳造速度Ｖｃに依存させて平均的実測値を与えた。
・特定固相率ｆｅ位置における温度勾配（°Ｃ／ｍｍ）Ｇは、鋳片厚み方向温度分布のラグランジュ補間多項式を固相率ｆｓ＝特定固相率ｆｅとなる温度位置で微分して求めた。・特定固相率ｆｅ位置における凝固速度Ｒ（ｍｍ／ｍｉｎ）は、５ｓｅｃ間のシェル厚の差で算出した。
【００２０】
その結果、柱状晶から等軸晶、或いは等軸晶から柱状晶へ遷移する位置は、特定固相率ｆｅが０．１〜０．３であるとした場合の、その位置での温度勾配Ｇと凝固速度Ｒのべき乗Ｒn との比Ｇ／Ｒn （ｎ＝０〜１．０）が、ある臨界値に対応し、等軸晶率はその臨界値を下回った領域の総和にほぼ一致することを見いだした。
【００２１】
臨界値は、鋼種により、また、等軸晶形成域の判定計算に適用する特定固相率ｆｅ，Ｇ／Ｒn のｎ値により異なる値を示し、ｆｅ＝０．３，ｎ＝０．５とすると、ＳＵＳ４３０の場合で０．３６（°Ｃｍｉｎ1/2 ／ｍｍ3/2 ）、ＳＵＨ409 Ｌの場合で０．２７（°Ｃｍｉｎ1/2 ／ｍｍ3/2 ）、ＳＳ４１の場合で０．２２（°Ｃｍｉｎ1/2 ／ｍｍ3/2 ）であった。特定固相率ｆｅ＝０．１〜０．３、ｎ＝０〜１．０の範囲では、それによる柱状晶から等軸晶に遷移する位置の差は５％の誤差範囲で一致した。それ以外の範囲の値では、誤差が大きくなることを見いだしたので、特定固相率ｆｅ＝０．１〜０．３、ｎ＝０〜１．０の範囲が最適と考えられる。
【００２２】
なお、Ｇ／Ｒn の臨界値、つまり、しきい値の決定方法は、特定固相率ｆｅ，ｎ値を適当に選定・固定して解析し、その時の実測等軸晶率に対応するＧ／Ｒn 値を臨界値と決定すればよく、特別な実験や調査を実施する必要はない。
図１の（イ）は特定固相率ｆｅである鋳片厚み方向の位置をメニスカスから鋳造方向にわたって計算した結果をプロットしたものであり、また、（ロ−１）は特定固相率ｆｅの位置での温度勾配Ｇと凝固速度のべき乗Ｒn との比Ｇ／Ｒn をメニスカスから鋳造方向にわたって計算した結果をプロットしたものである。
【００２３】
計算条件は次の通りである。
特定固相率ｆｅ：０．３
ｎ値：０．５（∴Ｇ／Ｒn ＝Ｇ／√Ｒ）
鋼種：ＳＵＳ４３０
鋳造速度Ｖｃ：１．０ｍ／ｍｉｎ
メニスカスから溶鋼電磁攪拌装置の中央部位置までの距離Ls：５．３ｍ
二次冷却水比（溶鋼１ｋｇあたりの冷却水量）ＩW ：０．９３Ｌ／ｋｇ
タンディッシュ内溶鋼過熱度ΔＴT ：４０°Ｃ
なお、固相率ｆｓが特定固相率ｆｅである鋳片厚み方向の位置は、図２を参照して、鋳辺長辺方向内面から鋳片中心までの距離をＤ／２（鋳片厚みの半分）とし、特定固相率ｆｅ位置から鋳型中心までの距離をｄとした場合に、ｄ／（Ｄ／２）×１００％として表す。
【００２４】
ここで、ＳＵＳ４３０の場合のＧ／√Ｒの臨界値（閾値）は、上述したように０．３６（°Ｃｍｉｎ1/2 ／ｍｍ3/2 ）であるので、柱状晶から等軸晶に遷移する位置は、図１から、ｄ／（Ｄ／２）×１００ ＝４０％となり、Ｇ／√Ｒは単調に減少しているので該位置よりも鋳片の内部側に位置する範囲を等軸晶形成域と判定し、該判定結果に基づいて等軸晶形成域の鋳片断面に占める鋳片厚み方向の割合を求めて等軸晶率を予測する。この時の柱状晶から等軸晶に遷移する位置の実測値は３８〜４５％であるので、判定精度は良好であることが解る。
【００２５】
なお、この例の（ロ−１）のようにＧ／√Ｒが単調に減少する場合は、Ｒe0を等軸晶率として算出すればよいが、鋳造条件によっては図１の（ロ−２）のように減少後一旦上昇した後に再度減少する場合もある。この場合の等軸晶率はＲe0−（Ｒe1−Ｒe2）として算出すればよい。
そして、このように、操業条件のなかでも、鋳造速度、溶鋼過熱度、二次冷却条件、スラブサイズ、溶鋼攪拌位置、鋼種等の殆どの要因を考慮して予測した等軸晶率の鋳造速度Ｖｃに対する影響や、該等軸晶率の溶鋼電磁攪拌装置の設置位置に対する影響を現工程、或いは次工程の操業に反映させることにより、鋳片の中心偏析や中心断面割れ、加工性といった鋳片単位の製品特性のバラツキを少なくすることができ、また、予測計算も簡単で且つ決定すべきパラメーターも少ないため既設の計算機でも連続鋳造への実用化を可能にすることができる。
【００２６】
なお、上記実施の形態では、凝固・伝熱解析手法として、一次元伝熱解析による手法を例に採ったが、これに限る必要はなく、上記（３）式を２次元、あるいは３次元の伝熱方程式に変更して予測を行っても差し支えない。また、流動解析と伝熱凝固解析とをリンクして解析すればより精度のある予測ができるが、品質管理上、本実施形態の手法でも十分である。
【００２７】
更に、上記実施の形態では、鋼の連続鋳造を例に採ったが、これに限定されず、例えばアルミニウムや銅の連続鋳造にも本発明を適用可能である。
【００２８】
【実施例１】
厚み２００ｍｍ、幅１０００〜１３００ｍｍのＳＵＳ４３０、ＳＵＨ４０９Ｌ、ＳＳ４１を鋳造し、それぞれ鋳片断面（鋳造方向に垂直面）の等軸晶率（等軸晶形成域厚み／鋳片厚み×１００％、幅方向５カ所平均値）を調査した。柱状晶から等軸晶に遷移する位置の決定は、マクロ凝固組織の結晶粒の全部の径の縦横比が２以下になる位置とした。
【００２９】
操業条件は、鋳造速度Ｖｃ＝０．６〜１．５ｍ／ｍｉｎ、タンディッシュ内溶鋼過熱度ΔＴT ：１５〜６３°Ｃ、二次冷却水比ＩW ：０．６〜１．４Ｌ／ｋｇ、溶鋼電磁攪拌装置の中央位置のメニスカスからの距離Ｌｓ＝３．０，４．６，５．３，７．２ｍ、２相式交流電磁攪拌装置は、起磁力である印加電流が１相７００Ａ，２相１０００Ａ、磁場周波数は２．５Ｈｚとした。浸漬ノズル吐出口は上向き５度，浸漬深さは２００ｍｍとした。
【００３０】
このようにして求めた等軸晶率の実測値と、本発明による等軸晶形成域の判定法から得られた等軸晶率の予測値との比較を図３に示す。なお、図中の記号と鋼種、Ｌｓ、スラブ厚との関係は表１によるものとする。
【００３１】
【表１】
表１及び図３から明らかなように、等軸晶率の実測値と本発明による等軸晶率の予測値とは略一致しており、また、寄与率ｒ2 も０．９４であり、予測精度は十分であることが判る。
【００３３】
【実施例２】
実施例１で溶鋼電磁攪拌装置の中央位置のメニスカスからの距離Ｌｓ＝５．３ｍｍで鋳造したＳＵＳ４３０（２００ｍｍ厚み）鋳片で、本発明による等軸晶形成域の判定法から等軸晶率５０±５％となるスラブを予測し、その冷延鋼板１．０ｍｍ厚みのリジング特性を評価した。比較例として、ランダムに抽出したスラブを対象とした。
【００３４】
リジング特性値（５段階；５：最良，３：５と１の中間，１：最悪）の標準偏差１σを調査（ｎ＝３０）したところ、比較材が平均値３．８，１σ0 ．5 ，に対し、本発明で等軸晶率を予測したスラブの場合、平均値４．８，１σ0 ．2 ，であった。これにより、品質管理上、本発明の等軸晶形成域の判定法を用いることにより、品質バラツキの少ない製品を選別できることが判った。
【００３５】
【実施例３】
本発明の等軸晶形成域の判定法を用いて予測した連続鋳造鋳片の等軸晶率（特定固相率ｆｅ＝０．３，ｎ値＝０．５の場合）に及ぼす鋳造速度Ｖｃの影響を厚み２００ｍｍ、幅１０００〜１３００ｍｍのＳＵＳ４３０及びＳＵＨ４０９Ｌの場合で予測した結果を図４に示す。
【００３６】
図から、ＳＵＳ４３０の場合は約１．０ｍ／ｍｉｎ、ＳＵＨ４０９Ｌの場合は０．８〜０．９ｍ／ｍｉｎ近傍が、等軸晶率が最大値を示す鋳造速度Ｖcpであることが判る。
また、実測した等軸晶率に及ぼす鋳造速度Ｖｃの影響を同図中に示す。
このときの鋳造：調査条件は次の通りとした。厚み２００ｍｍ、幅１０００〜１３００ｍｍのＳＵＳ４３０、ＳＵＨ４０９Ｌを鋳造し、鋳片断面（鋳造方向に垂直面）の等軸晶率（等軸晶厚み／鋳片厚み×１００％、幅方向５カ所平均値）を調査した。柱状晶から等軸晶に遷移する位置の決定は、マクロ凝固組織の結晶粒径の縦横比が２以下になる位置とした。操業条件は、タンディッシュ内溶鋼過熱度ΔＴT ：４０〜６３°Ｃ、二次冷却水比ＩW ：０．７〜１．２Ｌ／ｋｇ、溶鋼電磁攪拌装置中央位置のメニスカスからの距離Ｌｓ＝５．３ｍ、２相式交流電磁攪拌装置は起磁力である印加電流が１相７００Ａ，２相１０００Ａ、磁場周波数は２．５Ｈｚとした。浸漬ノズル吐出口は上向き５度，浸漬深さは２００ｍｍとした。
【００３７】
等軸晶率が最大値を示す鋳造速度の予測値Ｖcpは、図４から実測値と、傾向及び絶対値ともにほぼ一致することが判る。等軸晶率が最大値を示す鋳造速度の予測値Ｖcpに近づけて鋳造した鋳片と従来法によって鋳造した鋳片の等軸晶率は、本発明材が平均５４％、標準偏差５％（Ｖｃ＝０．９０〜１．１５ｍ／ｍｉｎ，平均１．０３ｍ／ｍｉｎ）に対して、従来材は平均４３％、標準偏差１２％（Ｖｃ＝０．６０〜１．５ｍ／ｍｉｎ，平均１．１４ｍ／ｍｉｎ）であった。このようにして鋳造速度をＶcpに近づけて鋳造した鋳片が最も高等軸晶率を持つことはいうまでもない。従って、低等軸晶率に起因する鋳片欠陥や製品での特性劣化、ばらつき等の品質上の問題点が軽減される。
【００３８】
【実施例４】
本発明の等軸晶形成域の判定法を用いて予測した連続鋳造鋳片の等軸晶率（ＳＵＳ４３０，鋳造速度Ｖｃ＝１．０ｍ／ｍｉｎ，特定固相率ｆｅ＝０．３，ｎ値＝０．５の場合）に及ぼす溶鋼電磁攪拌装置中央位置のメニスカスからの距離Ｌｓの影響を厚み２００ｍｍ、幅１０００〜１３００ｍｍのＳＵＳ４３０について予測した結果を図５に示す。
【００３９】
また、実測した等軸晶率に及ぼす溶鋼電磁攪拌装置中央位置のメニスカスからの距離Ｌｓの影響を同図中に示す。
なお、このときの鋳造条件，調査方法は次の通りとした。
厚み２００ｍｍ、幅１０００〜１３００ｍｍのＳＵＳ４３０を鋳造し、鋳片断面（鋳造方向に垂直面）の等軸晶率（等軸晶厚み／鋳片厚み×１００％、幅方向５カ所平均値）を調査した。柱状晶から等軸晶に遷移する位置の決定は、マクロ凝固組織の結晶粒径の縦横比が２以下になる位置とした。
【００４０】
操業条件は、タンディッシュ内溶鋼過熱度ΔＴT ：４０〜６３°Ｃ、二次冷却水比ＩW ：１．０〜１．２Ｌ／ｋｇ、溶鋼電磁攪拌装置は２相式交流電磁攪拌装置で起磁力である印加電流は１相７００Ａ，２相１０００Ａとし、磁場周波数は２．５Ｈｚとした。浸漬ノズル吐出口は上向き５度、浸漬深さは２００ｍｍとした。
【００４１】
等軸晶率の予測値が最大値を示すＬｓ（Ｌsp）は、図５から、ＳＵＳ４３０で約４．６ｍであり、実測値と傾向及び絶対値ともほぼ一致した。なお、連続鋳造機の構造上、溶鋼電磁攪拌装置はロールセグメントに組み込むのが一般的であり、任意の位置に設置できない。よって、等軸晶率が最大値を示すＬsp＝４．６ｍ近傍のセグメントの中央位置５．３ｍに溶鋼電磁攪拌装置を設置するものとし、この数値は、実施例３のＬｓに一致する。
【００４２】
【発明の効果】
上記の説明から明らかなように、本発明によれば、任意の等軸晶率を簡単且つ正確に予測することができるので、鋳片の中心偏析や中心断面割れ、加工性といった鋳片単位の製品特性のバラツキを少なくすることができるという効果が得られる。
【図面の簡単な説明】
【図１】メニスカスからの距離ＺとＧ／√Ｒとｄ／（Ｄ／２）との関係を示すグラフ図である。
【図２】等軸晶形成域の判定方法の説明に用いる説明図である。
【図３】本発明法によって得られた等軸晶率の予測値と実測値との関係を示すグラフ図である。
【図４】鋳造速度と本発明法によって得られた等軸晶率の予測値及び実測値との関係を鋼種別に比較したグラフ図である。
【図５】電磁攪拌装置中央位置のメニスカスからの距離と本発明法によって得られた等軸晶率の予測値及び実測値との関係を示すグラフ図である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for continuously casting a molten metal alloy.
[0002]
[Prior art]
In steel for thick plates, steel for wire rods, structural steel, martensitic stainless steel, etc., shrinkage holes with solute segregation and microcavities are likely to occur in the center of continuous cast slabs. Defects due to the occurrence may occur. Further, in ferritic stainless steel, workability defects (ridging) on the surface of the cold-rolled sheet due to the columnar solidified structure inside the slab are likely to occur.
[0003]
By the way, regarding the operating conditions of continuous casting that affect the equiaxed crystal ratio, for example, in the case of continuous casting of steel, the influence on the equiaxed crystal ratio of the molten steel superheat degree, casting speed, and electromagnetic stirring strength is limited. As a result, it is only possible to understand how the equiaxed crystal ratio changes when the operating conditions are changed drastically after investigating the cross section of the slab after casting. Relied on. For this reason, the product characteristics of the slab unit such as center segregation, center cross-section cracking, and workability of the slab, which greatly affect the equiaxed crystal ratio, vary greatly, causing problems in quality control.
[0004]
It is known that such defects can be reduced by changing the solidification structure at the center of the slab from columnar crystals to equiaxed crystals or by increasing the equiaxed crystal ratio. A method has been developed for predicting the position of transition from an equiaxed crystal to an equiaxed crystal.
As these prediction methods, a method for predicting the position where the solidification structure transitions from a columnar crystal to an equiaxed crystal is introduced by a numerical simulation of solidification and heat transfer. For example, J. et al. D. An example (for example, Arlette Etienne: steel Research, 61 (10,472)) to which the theoretical analysis model of Hunt et al. (Material Science and Eng., Vol. 65 (I984), pp74-83) is applied has been proposed. The proposal is based on the idea that when the temperature gradient G ′ at the tip of the columnar crystal with a solid fraction of 0 falls below a certain critical value, the columnar crystal transitions to the equiaxed crystal. This is based on the background that the growth of columnar crystals stops when the value exceeds a certain critical value.
[0005]
Also, a method for predicting the position where the solidification structure transitions from columnar crystals to equiaxed crystals by solidification analysis (for example, International Journal of Numerical Methods for Heat & Fluid Flow, vol. 9, No. 3, 1999, pp. 296- 317, or Appl Math Phys Model Iron steel Ind, pp.271-272, 1982) .This proposal is based on the density of many nuclei dispersed in the molten metal, its degree of dispersion, its location, Coagulation analysis is performed for each nucleus assuming the degree.
[0006]
Furthermore, the following relational expression has been proposed regarding the influence of the casting speed Vc on the molten steel stirring position where the equiaxed crystal ratio Re has the maximum value, or the solid fraction of the stirring section, and further on the equiaxed crystal ratio. .
Re = AP B Vc -0.5 f (η) (in the case of Bloom) (1)
(Described in Japan Iron and Steel Institute, Iron and Steel, 1983, S269)
Re = −a (ΔTVc / U 0.4 ) + b (in the case of billet) (2)
(Listed in Japan Iron and Steel Institute, Materials and Properties, 1988, 1291)
Here, A, B, a, b are constants, f (η) is a function of the solidification rate η, P is a solidification front thrust as an index of stirring force indicating the molten steel flow velocity, and T is a superheat degree of molten steel in the tundish (° C) and Vc are casting speeds (m / min), and U is the molten steel stirring flow rate (cm / sec).
[0007]
That is, the equations (1) and (2) indicate that the equiaxed crystal ratio Re decreases as the casting speed Vc increases, and the equation (1) maximizes the equiaxed crystal ratio Re. It is said that there is an optimal stirring position.
Furthermore, Japanese Patent Laid-Open No. 53-8327 proposes a method of electromagnetic stirring in an unsolidified portion of 40 to 90 mm at a position exceeding 8 m from the meniscus in the casting direction in order to obtain a high equiaxed crystal slab.
[0008]
[Problems to be solved by the invention]
However, any of the above-described methods for predicting the position where the solidification structure transitions from a columnar crystal to an equiaxed crystal has a complicated calculation method and is a prediction method in a very limited micro region, and is determined. Since there are many parameters to be used, it is difficult to apply to continuous casting due to a lack of computer memory.
[0009]
Also, not all operating conditions that should be considered (casting speed, molten steel superheat, secondary cooling conditions, slab size, molten steel stirring speed, molten steel stirring position, steel grade) are considered, but the molten steel temperature and secondary cooling conditions are considered. However, it cannot be immediately applied to continuous casting.
The present invention has been made to eliminate such inconveniences, and can easily and accurately predict an arbitrary equiaxed crystal ratio so that the center segregation, center cross-section cracking, and workability of a slab can be performed. An object of the present invention is to provide a continuous casting method of a molten metal alloy that can reduce the variation in product characteristics of each slab unit.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the molten metal alloy continuous casting method according to
However, the predetermined threshold is the critical value of G / R n, the critical value of the G / R n is, and selection of the index n of the power R n of the particular solid fraction fe and the solidification rate R Found fixed calculated value of equiaxed Akiraritsu corresponding to G / R n values obtained by analyzing the actually measured equiaxed Akiraritsu and is determined by the G / R n value when corresponding match The
[0011]
Here, the solid phase ratio fe is a constant empirically determined by the metal species and is a value between 0.1 and 0.3, and n is a constant empirically determined by the metal species, A value between 1.0 .
[0012]
The molten metal alloy continuous casting method according to
However, the predetermined threshold is the critical value of G / R n, the critical value of the G / R n is, and selection of the index n of the power R n of the particular solid fraction fe and the solidification rate R Found fixed calculated value of equiaxed Akiraritsu corresponding to G / R n values obtained by analyzing the actually measured equiaxed Akiraritsu and is determined by the G / R n value when corresponding match The
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
In order to find a method for easily predicting the position at which a solidified structure transitions from a columnar crystal to an equiaxed crystal, the present inventors have determined that the equiaxed crystal is obtained from a columnar crystal obtained from a solidified structure investigation of a continuous cast slab of various molten steels. The relationship between the temperature transition position and the temperature gradient G and the solidification rate R at the position determined by solidification / heat transfer analysis was investigated and analyzed.
[0014]
The solidification / heat transfer analysis method uses a general method that repeatedly calculates the forward one-dimensional approximation of the one-dimensional heat transfer basic equation shown in the following equation (3). The solidification latent heat is handled by the enthalpy method, and the temperature and solid phase The rate relationship was calculated from the general Clyne-Kurz et al. Equation and was given considering the freezing point depression and diffusion of the solute.
ρ (∂H / ∂t) = (λ∂T 2 / ∂x 2 ) (3)
Here, H: heat content of steel, T: temperature of steel, ρ: density of steel, λ: thermal conductivity of steel, x: slab thickness direction distance, t: apparent thermal conductivity λL in time bulk Since (= effective thermal conductivity) increases due to the flow of molten steel, it was made larger than the thermal conductivity λL 0 of the molten steel so as to match the actual phenomenon.
[0015]
Here, the thermal conductivity λ of steel is λL in the bulk (specific solid fraction fe> solid fraction fs), and the liquid phase fraction (1-fs) between the specific solid fraction fe and the
fe> fs: λ = λL
fe ≦ fs <1:
λ = [λL (1-fs) / (1-fe)] + [λs (fs-fe) / (1-fe)]
Here, λs is the thermal conductivity of steel at the solid phase temperature.
[0016]
At this time, it was found that λ can be predicted by changing the apparent thermal conductivity λL in the bulk depending on the distance z from the meniscus. That is, λ of the molten steel stirring portion due to electromagnetic force is 10 times the molten steel thermal conductivity λL 0 at the center position Ls, the molten steel stirring influence region uL in the meniscus direction, and the molten steel stirring effect in the slab drawing direction. In the region dL, it decreases in proportion to the distance. It was given as 5 times the molten steel thermal conductivity up to 1 m below the meniscus, and twice the molten steel thermal conductivity at other positions where the influence of stirring of the molten steel was hardly affected.
[0017]
uL and dL depend on the molten steel stirring conditions, and can be determined by observing the solidified structure such as the tilted length of columnar crystals and the position of the white band. In the present invention, uL = 1.5 m and dL = 1.5 m are given under saturation conditions where the equiaxed crystal ratio (equal crystal thickness / slab thickness × 100%) does not increase even when the stirring strength is increased. These values are values that can vary depending on the specifications, installation status, slab size, etc. of the electromagnetic stirring device.
[0018]
The above numerical values may be obtained from general flow analysis results, and are constants that should be changed depending on conditions.
Examples of analysis conditions in the present invention are shown below.
-Shell increment mesh = 1 mm, increment time = 0.01 sec
The initial molten steel superheat degree ΔT M in the mold was given by the following equation as a function of the molten steel superheat degree ΔT T in the tundish based on actual measurements.
[0019]
ΔT M = 0.59 ΔT T −5.8
・ ΔT T = 15 ~ 63 ° C
Secondary cooling water ratio (cooling water amount per kg of molten steel) I W = 0.6 to 1.4 L / kg
・ Distance Ls = 3.0, 4.6, 5.3, 7.2 m from the meniscus at the center of the molten steel magnetic stirrer
-The amount of heat extracted from the long side in the mold was given an average measured value depending on the casting speed Vc.
The temperature gradient (° C / mm) G at the specific solid fraction fe position is obtained by differentiating the Lagrangian interpolation polynomial of the slab thickness direction temperature distribution at the temperature position where the solid fraction fs = the specific solid fraction fe. . The solidification rate R (mm / min) at the specific solid fraction fe position was calculated by the difference in shell thickness for 5 seconds.
[0020]
As a result, the transition from the columnar crystal to the equiaxed crystal or the transition from the equiaxed crystal to the columnar crystal has a temperature gradient G at that position when the specific solid phase ratio fe is 0.1 to 0.3. the ratio G / R n of the power R n of solidification rate R (n = 0~1.0) is corresponding to a certain critical value, equiaxed Akiraritsu almost coincides with the sum of the areas below the critical value I found something to do.
[0021]
Critical value, the steel grade, also certain solid fraction fe is applied to the determination calculation of equiaxed formation region, it shows different values of n values of G / R n, fe = 0.3 , n = 0.5 Then, 0.36 (° Cmin 1/2 / mm 3/2 ) in the case of SUS430, 0.27 (° Cmin 1/2 / mm 3/2 ) in the case of SUH409L, and 0. 22 (° C min 1/2 / mm 3/2 ). In the specific solid phase ratio fe = 0.1 to 0.3 and n = 0 to 1.0, the difference in the position of transition from the columnar crystal to the equiaxed crystal coincided within an error range of 5%. Since it was found that the error is larger in the other range values, the specific solid phase ratio fe = 0.1 to 0.3 and n = 0 to 1.0 are considered to be optimal.
[0022]
The critical value of G / R n , that is, the threshold value is determined by selecting and fixing a specific solid fraction fe, n value appropriately, and analyzing G corresponding to the measured equiaxed crystal ratio at that time. / R n value may be determined as a critical value, it is not necessary to conduct special experiments and investigations.
(A) in FIG. 1 is a plot of the result of calculation of the position in the slab thickness direction having a specific solid fraction fe from the meniscus over the casting direction, and (b-1) is the specific solid fraction fe. FIG. 5 is a plot of the results of calculating the ratio G / R n between the temperature gradient G at the position and the power R n of the solidification rate from the meniscus over the casting direction.
[0023]
The calculation conditions are as follows.
Specific solid fraction fe: 0.3
n value: 0.5 (∴G / R n = G / √R)
Steel type: SUS430
Casting speed Vc: 1.0 m / min
Distance Ls: 5.3m from meniscus to center position of molten steel electromagnetic stirrer
Secondary cooling water ratio (cooling water amount per kg of molten steel) I W : 0.93 L / kg
Tundish molten steel superheat ΔT T : 40 ° C
The position in the slab thickness direction at which the solid phase rate fs is the specific solid phase rate fe refers to the distance from the inner surface in the casting side long side direction to the slab center with reference to FIG. When the distance from the specific solid fraction fe position to the template center is d, it is expressed as d / (D / 2) × 100%.
[0024]
Here, since the critical value (threshold value) of G / √R in the case of SUS430 is 0.36 (° Cmin 1/2 / mm 3/2 ) as described above, it transitions from a columnar crystal to an equiaxed crystal. From FIG. 1, the position to perform is d / (D / 2) × 100 = 40%, and G / √R is monotonously decreasing, so the range positioned on the inner side of the slab from the position is equiaxed. The crystal formation region is determined, and the ratio of the slab thickness direction in the cross section of the slab of the equiaxed crystal formation region is obtained based on the determination result to predict the equiaxed crystal ratio. At this time, since the actual measurement value at the position where the transition from the columnar crystal to the equiaxed crystal is 38 to 45%, it is understood that the determination accuracy is good.
[0025]
In the case where G / √R as in this example (b -1) decreases monotonically, it may be calculated R e0 as equiaxed Akiraritsu, but by casting condition of FIG. 1 (b -2 In some cases, once it rises after the decrease, then decreases again. The equiaxed crystal ratio in this case may be calculated as R e0 − (R e1 −R e2 ).
And, among the operating conditions, the casting speed of the equiaxed crystal ratio predicted in consideration of most factors such as casting speed, molten steel superheating degree, secondary cooling conditions, slab size, molten steel stirring position, steel type, etc. By reflecting the influence on Vc and the influence of the equiaxed crystal ratio on the installation position of the molten steel electromagnetic stirring device on the operation of the current process or the next process, the slab such as center segregation of the slab, center cross section crack, workability, etc. The variation in unit product characteristics can be reduced, and the prediction calculation is simple and the number of parameters to be determined is small. Therefore, even existing computers can be put to practical use for continuous casting.
[0026]
In the above embodiment, as a solidification / heat transfer analysis method, a one-dimensional heat transfer analysis method is used as an example. However, the present invention is not limited to this, and the above equation (3) is expressed in two dimensions or three dimensions. The prediction can be made by changing to the heat transfer equation. Further, if the flow analysis and the heat transfer solidification analysis are linked and analyzed, a more accurate prediction can be made. However, the method of the present embodiment is sufficient for quality control.
[0027]
Furthermore, in the said embodiment, although continuous casting of steel was taken as an example, it is not limited to this, For example, this invention is applicable also to continuous casting of aluminum and copper.
[0028]
[Example 1]
Casting SUS430, SUH409L, SS41 with a thickness of 200mm and a width of 1000-1300mm, respectively, the equiaxed crystal ratio (thickness of equiaxed crystal formation zone thickness / slab thickness x 100%, width direction) The average value of 5 places) was investigated. The position of transition from the columnar crystal to the equiaxed crystal was determined at a position where the aspect ratio of all the diameters of the crystal grains of the macro-solidified structure was 2 or less.
[0029]
Operating conditions are casting speed Vc = 0.6 to 1.5 m / min, superheat degree of molten steel in tundish ΔT T : 15 to 63 ° C., secondary cooling water ratio I W : 0.6 to 1.4 L / kg The distance Ls = 3.0, 4.6, 5.3, 7.2 m from the meniscus at the center of the molten steel electromagnetic stirrer is applied to the two-phase AC electromagnetic stirrer with an applied current of magnetomotive force of 700 A per phase. , 2-phase 1000 A, magnetic field frequency was 2.5 Hz. The immersion nozzle outlet was 5 degrees upward, and the immersion depth was 200 mm.
[0030]
FIG. 3 shows a comparison between the actually measured value of the equiaxed crystal ratio thus obtained and the predicted value of the equiaxed crystal ratio obtained from the method for determining the equiaxed crystal formation region according to the present invention. The relationship between the symbols in the figure and the steel type, Ls, and slab thickness is as shown in Table 1.
[0031]
[Table 1]
As is apparent from Table 1 and FIG. 3, the measured value of the equiaxed crystal ratio and the predicted value of the equiaxed crystal ratio according to the present invention are substantially the same, and the contribution ratio r 2 is 0.94, It can be seen that the prediction accuracy is sufficient.
[0033]
[Example 2]
In Example 1, the SUS430 (200 mm thickness) slab was cast at a distance Ls = 5.3 mm from the meniscus at the center of the molten steel electromagnetic stirring device, and the
[0034]
When the standard deviation 1σ of the ridging characteristic values (5 steps; 5: best, 3: 5 and 1 in between, 1: worst) was investigated (n = 30), the comparative material had an average value of 3.8, 1σ0. 5, in the case of the slab in which the equiaxed crystal ratio is predicted in the present invention, the average value is 4.8,
[0035]
[Example 3]
Casting speed Vc affecting the equiaxed crystal ratio (in the case of specific solid fraction fe = 0.3, n value = 0.5) of the continuous cast slab predicted using the method for determining the equiaxed crystal formation region of the present invention. FIG. 4 shows the results of predicting the influence of SUS430 and SUH409L having a thickness of 200 mm and a width of 1000 to 1300 mm.
[0036]
From the figure, it can be seen that the casting speed Vcp is about 1.0 m / min in the case of SUS430 and around 0.8 to 0.9 m / min in the case of SUH409L, at which the equiaxed crystal ratio shows the maximum value.
In addition, the influence of the casting speed Vc on the measured equiaxed crystal ratio is shown in FIG.
Casting at this time: Investigation conditions were as follows. SUS430 and SUH409L with a thickness of 200 mm and a width of 1000 to 1300 mm were cast, and the equiaxed crystal ratio of the slab cross section (plane perpendicular to the casting direction) (equal axis thickness / slab thickness x 100%, average value in 5 width directions) investigated. The position of transition from columnar crystals to equiaxed crystals was determined at a position where the aspect ratio of the crystal grain size of the macro-solidified structure was 2 or less. The operating conditions are as follows: molten steel superheat degree in the tundish ΔT T : 40 to 63 ° C, secondary cooling water ratio I W : 0.7 to 1.2 L / kg, distance Ls from the meniscus at the center of the molten steel electromagnetic stirrer In the 5.3 m, two-phase AC magnetic stirring device, the applied current, which is magnetomotive force, was 700 A for one phase, 1000 A for two phases, and the magnetic field frequency was 2.5 Hz. The immersion nozzle outlet was 5 degrees upward, and the immersion depth was 200 mm.
[0037]
It can be seen from FIG. 4 that the predicted value Vcp of the casting speed at which the equiaxed crystal ratio has the maximum value almost coincides with the measured value and the tendency and absolute value. As for the equiaxed crystal ratio of the slab cast close to the predicted casting speed Vcp at which the equiaxed crystal ratio is the maximum, and the slab cast by the conventional method, the present invention material has an average of 54% and a standard deviation of 5% ( In contrast to Vc = 0.90-1.15 m / min, average 1.03 m / min), the conventional material has an average of 43% and a standard deviation of 12% (Vc = 0.60-1.5 m / min,
[0038]
[Example 4]
The equiaxed crystal ratio (SUS430, casting speed Vc = 1.0 m / min, specific solid fraction fe = 0.3, n value) predicted using the method for determining the equiaxed crystal formation region of the present invention. FIG. 5 shows the result of predicting the influence of the distance Ls from the meniscus at the center position of the molten steel electromagnetic stirring device on the SUS430 having a thickness of 200 mm and a width of 1000 to 1300 mm.
[0039]
Further, the influence of the distance Ls from the meniscus at the central position of the molten steel electromagnetic stirring device on the measured equiaxed crystal ratio is shown in FIG.
The casting conditions and survey method at this time were as follows.
Cast SUS430 with a thickness of 200mm and a width of 1000-1300mm, and investigate the equiaxed crystal ratio (equal axis thickness / slab thickness x 100%, average value at 5 locations in the width direction) of the slab cross section (plane perpendicular to the casting direction). did. The position of transition from columnar crystals to equiaxed crystals was determined at a position where the aspect ratio of the crystal grain size of the macro-solidified structure was 2 or less.
[0040]
The operating conditions are as follows: molten steel superheat ΔT T in the tundish: 40 to 63 ° C., secondary cooling water ratio I W : 1.0 to 1.2 L / kg, the molten steel electromagnetic stirrer is a two-phase AC electromagnetic stirrer The applied current, which is magnetomotive force, was 1
[0041]
Ls (Lsp) at which the predicted value of the equiaxed crystal ratio shows the maximum value is about 4.6 m in SUS430 from FIG. 5, and the measured value, the tendency, and the absolute value almost coincided. Note that the molten steel electromagnetic stirring device is generally incorporated in the roll segment because of the structure of the continuous casting machine, and cannot be installed at an arbitrary position. Therefore, it is assumed that the molten steel electromagnetic stirrer is installed at the center position 5.3 m of the segment in the vicinity of Lsp = 4.6 m where the equiaxed crystal ratio has the maximum value, and this value corresponds to Ls in Example 3.
[0042]
【The invention's effect】
As is clear from the above description, according to the present invention, an arbitrary equiaxed crystal ratio can be predicted easily and accurately. The effect that variation in product characteristics can be reduced is obtained.
[Brief description of the drawings]
FIG. 1 is a graph showing a relationship among a distance Z from a meniscus, G / √R, and d / (D / 2).
FIG. 2 is an explanatory diagram used for explaining a method of determining an equiaxed crystal formation region.
FIG. 3 is a graph showing the relationship between the predicted value and the measured value of equiaxed crystal ratio obtained by the method of the present invention.
FIG. 4 is a graph comparing the relationship between the casting speed and the predicted value and measured value of the equiaxed crystal ratio obtained by the method of the present invention for each steel type.
FIG. 5 is a graph showing the relationship between the distance from the meniscus at the central position of the electromagnetic stirring device and the predicted and measured values of the equiaxed crystal ratio obtained by the method of the present invention.
Claims (2)
ただし、前記所定の閾値は、Ｇ／Ｒｎの臨界値であり、このＧ／Ｒｎの臨界値は、前記特定の固相率ｆｅおよび前記凝固速度Ｒのべき乗Ｒｎの指数ｎを選定・固定して解析して得られたＧ／Ｒｎ値に対応する等軸晶率の計算値と実測された等軸晶率の実測値とが対応一致した場合におけるＧ／Ｒｎ値で決定される。In the continuous casting method of the molten metal alloy, the position in the slab thickness direction where the solid phase ratio fs in the solid-liquid coexistence region of the metal alloy is a specific solid phase ratio fe is calculated over the casting direction and obtained by the calculation. the temperature gradient G and the solidification rate R of the slab thickness direction at a position calculated by calculation, the ratio G / R n of the power R n of the temperature gradient G and the solidification rate R, the specific solid fraction fe between 0.1 and 0.3, the determined by calculation indices n a power R n of solidification rate R in a range between 0 to 1.0, range in which the G / R n becomes smaller than a predetermined threshold value Is determined as the equiaxed crystal formation region, and the ratio of the slab thickness direction in the slab cross section of the equiaxed crystal formation region is calculated based on the determination result to predict the equiaxed crystal ratio, and the predicted equiaxed axis The maximum value of the crystallinity is the target equiaxed crystal ratio, and the casting speed is the target equiaxed crystal. A method for continuously casting a molten metal alloy, characterized in that casting is performed close to a predicted value of a casting speed at a rate .
However, the predetermined threshold is the critical value of G / R n, the critical value of the G / R n is, and selection of the index n of the power R n of the particular solid fraction fe and the solidification rate R Found fixed calculated value of equiaxed Akiraritsu corresponding to G / R n values obtained by analyzing the actually measured equiaxed Akiraritsu and is determined by the G / R n value when corresponding match The
ただし、前記所定の閾値は、Ｇ／Ｒ ｎ の臨界値であり、このＧ／Ｒ ｎ の臨界値は、前記特定の固相率ｆｅおよび前記凝固速度Ｒのべき乗Ｒ ｎ の指数ｎを選定・固定して解析して得られたＧ／Ｒ ｎ 値に対応する等軸晶率の計算値と実測された等軸晶率の実測値とが対応一致した場合におけるＧ／Ｒ ｎ 値で決定される。 In the molten metal alloy continuous casting method, the position in the slab thickness direction where the solid phase ratio fs in the solid-liquid coexistence region of the metal alloy is a specific solid phase ratio fe is calculated over the casting direction and obtained by the calculation. the temperature gradient G and the solidification rate R of the slab thickness direction at a position calculated by calculation, the ratio G / R n of the power R n of the temperature gradient G and the solidification rate R, the specific solid fraction fe between 0.1 and 0.3, the determined by calculation indices n a power R n of solidification rate R in a range between 0 to 1.0, range in which the G / R n becomes smaller than a predetermined threshold value Is determined as the equiaxed crystal formation region, and the ratio of the slab thickness direction in the slab cross section of the equiaxed crystal formation region is calculated based on the determination result to predict the equiaxed crystal ratio, and the predicted equiaxed axis The maximum value of the crystallinity is the target equiaxed crystal ratio, which is closest to the target equiaxed crystal ratio. Continuous casting method to that molten metal alloy, wherein the casting installed an electromagnetic stirring equipment comprising position.
However, the predetermined threshold is the critical value of G / R n, the critical value of the G / R n is, and selection of the index n of the power R n of the particular solid fraction fe and the solidification rate R Found fixed calculated value of equiaxed Akiraritsu corresponding to G / R n values obtained by analyzing the actually measured equiaxed Akiraritsu and is determined by the G / R n value when corresponding match The
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2000197459A JP4501236B2 (en) | 2000-06-30 | 2000-06-30 | Continuous casting method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2000197459A JP4501236B2 (en) | 2000-06-30 | 2000-06-30 | Continuous casting method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2002011556A JP2002011556A (en) | 2002-01-15 |
| JP4501236B2 true JP4501236B2 (en) | 2010-07-14 |
Family
ID=18695785
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2000197459A Expired - Fee Related JP4501236B2 (en) | 2000-06-30 | 2000-06-30 | Continuous casting method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP4501236B2 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100793559B1 (en) | 2006-07-10 | 2008-01-14 | 주식회사 포스코 | Method for estimating equiaxied grain ratio of ferritic stainless steel |
| JP6384447B2 (en) * | 2015-10-15 | 2018-09-05 | Ｊｆｅスチール株式会社 | Continuous casting method |
| CN113798463B (en) * | 2021-08-18 | 2023-08-18 | 鞍钢股份有限公司 | Method for evaluating cooling water distribution of continuous casting blank by utilizing isometric crystal width of continuous casting blank |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001259812A (en) * | 2000-03-22 | 2001-09-25 | Nkk Corp | Method for evaluating and reducing center segregation in continuously cast slab |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS538327A (en) * | 1976-07-12 | 1978-01-25 | Nippon Steel Corp | Method of continuous casting |
| JPS63281764A (en) * | 1987-05-12 | 1988-11-18 | Nissan Motor Co Ltd | Production of valve seat |
| JPH0611888B2 (en) * | 1989-10-06 | 1994-02-16 | 住友軽金属工業株式会社 | Manufacturing method of rare earth-iron giant magnetostrictive alloy ingot |
| JP2677070B2 (en) * | 1991-09-12 | 1997-11-17 | 住友金属工業株式会社 | Horizontal continuous casting method |
| JP2664572B2 (en) * | 1991-11-06 | 1997-10-15 | 株式会社神戸製鋼所 | Temperature prediction method for unsolidified part of slab in continuous casting |
| JP3119203B2 (en) * | 1997-06-27 | 2000-12-18 | 住友金属工業株式会社 | Unsolidified rolling method of slab |
-
2000
- 2000-06-30 JP JP2000197459A patent/JP4501236B2/en not_active Expired - Fee Related
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001259812A (en) * | 2000-03-22 | 2001-09-25 | Nkk Corp | Method for evaluating and reducing center segregation in continuously cast slab |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2002011556A (en) | 2002-01-15 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US20120012274A1 (en) | Method for continuous casting of steel and electromagnetic stirrer to be used therefor | |
| JP4865944B2 (en) | Method and apparatus for controlling metal flow in continuous casting using electromagnetic fields | |
| Shen et al. | Dendrite growth behavior in directionally solidified Fe–C–Mn–Al alloys | |
| Zeng et al. | Improving inner quality in continuous casting rectangular billets: comparison between mechanical soft reduction and final electromagnetic stirring | |
| Sivesson et al. | Improvement of inner quality of continuously cast billets using electromagnetic stirring and thermal soft reduction | |
| JP2008260045A (en) | Solidification delay suppressing method | |
| Mostafapoor et al. | Effects of Zr addition on solidification characteristics of Al–Zn–Mg–Cu alloy using thermal analysis | |
| JP4501236B2 (en) | Continuous casting method | |
| Li et al. | Solidification structure simulation and casting process optimization of GCr15 bloom alloy | |
| Zhang et al. | Numerical and experimental investigation of solidification structure and macrosegregation in continuously cast 2311 die steel slab | |
| Marcandalli et al. | A thermomechanical model for simulation of carbon steel solidification in mould in continuous casting | |
| Davis et al. | Segregation behaviour in Nb microalloyed steels | |
| JP5429139B2 (en) | Steel continuous casting method | |
| KR100524628B1 (en) | Method for predicting the characteristics of solidfied hook in the continuous casting, using the maximum acceleration of mold and cooling index | |
| M’Hamdi et al. | Modelling of heat transfer coupled with columnar dendritic growth in continuous casting of steel | |
| Ganguly et al. | Quantification of the solidification microstructure in continuously-cast high-carbon steel billets | |
| JP2664572B2 (en) | Temperature prediction method for unsolidified part of slab in continuous casting | |
| Drożdż | The influence of the superheat temperature on the slab structure in the continuous steel casting process | |
| Mizukami et al. | Prediction of solid-liquid interfacial energy of steel during solidification and control of dendrite arm spacing | |
| JP2008260044A (en) | Continuous casting method of steel slab for preventing breakout caused by solidification delay | |
| Isaev | Effectiveness of using large cooling elements to alleviate axial segregation in continuous-cast ingots | |
| Chen et al. | Numerical modeling of centerline segregation by a combined 3-D and 2-D hybrid model during slab continuous casting | |
| JP3151918B2 (en) | Continuous casting method | |
| JPH08276258A (en) | Method for estimating solidified shell thickness of continuously cast slab | |
| Mehrara et al. | Modeling of primary dendrite arm spacing variations in thin-slab casting of low carbon and low alloy steels |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20070426 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20071023 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20091006 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20091204 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20100119 |
|
| A521 | Written amendment |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20100217 |
|
| TRDD | Decision of grant or rejection written | ||
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 20100330 |
|
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20100412 |
|
| R150 | Certificate of patent or registration of utility model |
Free format text: JAPANESE INTERMEDIATE CODE: R150 |
|
| FPAY | Renewal fee payment (event date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20130430 Year of fee payment: 3 |
|
| LAPS | Cancellation because of no payment of annual fees |