JP5387508B2

JP5387508B2 - Continuous casting method, continuous casting control device and program

Info

Publication number: JP5387508B2
Application number: JP2010126226A
Authority: JP
Inventors: 祐二平本; 新一福永; 淳一中川
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Priority date: 2010-06-01
Filing date: 2010-06-01
Publication date: 2014-01-15
Anticipated expiration: 2030-06-01
Also published as: JP2011251308A

Description

本発明は、溶鋼から鋳型用の冷却水までの間に凝固シェル、モールドパウダー層、鋳型の各熱伝導体が存在する連続鋳造において、鋳型内状態を支配する主要因である伝達係数を決定する手法を利用して、鋳型内における浸漬ノズルの左右での溶鋼の偏流状態を診断し、鋳造状態を適正な条件に制御する連続鋳造方法、連続鋳造の制御装置及びプログラムに関する。 The present invention determines the transfer coefficient, which is the main factor governing the state in the mold, in continuous casting where the solidified shell, mold powder layer, and mold thermal conductors exist between the molten steel and the cooling water for the mold. The present invention relates to a continuous casting method, a continuous casting control apparatus, and a program for diagnosing the drift state of molten steel on the left and right of an immersion nozzle in a mold and controlling the casting state to an appropriate condition.

図１３に連続鋳造設備の概要を示す。転炉及び二次精錬で作られた溶鋼は取鍋５１に入れられ、タンデッシュ５２を介して鋳型５３へと注がれる。鋳型５３に接触した溶鋼は冷やされて凝固し、鋳造速度がコントロールされながらロール５４で運ばれて、ガス切断機５５で適当な長さに切断される。かかる鋼の連続鋳造においては、鋳型５３内の溶鋼流動状態や凝固状態が鋳片の性状の悪化トラブルによる鋳造停止を招くことがあり、安定鋳造や欠陥のない鋳片を製造するためには、鋳型内状態をオンラインで推定し、制御することが必要である。 FIG. 13 shows an outline of the continuous casting equipment. Molten steel produced by the converter and secondary refining is put into a ladle 51 and poured into a mold 53 through a tundish 52. The molten steel that has come into contact with the mold 53 is cooled and solidified, and is carried by a roll 54 while the casting speed is controlled, and is cut to an appropriate length by a gas cutter 55. In such continuous casting of steel, the molten steel flow state and solidification state in the mold 53 may cause casting stoppage due to the deterioration of the properties of the slab, and in order to produce stable casting and slabs without defects, It is necessary to estimate and control the in-mold state online.

鋳型内での溶鋼の流動は、浸漬ノズルへの付着や溶損、鋳造速度の変化により時々刻々変化する。特に浸漬ノズルの吐出孔への介在物の付着による吐出孔の閉塞は、鋳型の左右短辺に向かう吐出流量の不均等を生じせしめる。その結果、吐出流量が増大した側では短辺への吐出流速の増大に起因したストランド内下降流速の増加、気泡や介在物の侵入量の増加を招く他、メニスカスへの流速の増加によりモールドパウダーの巻き込みを招きやすくなるという問題がある。そのため、鋳片の品質低下を招き、ひいては製品歩留まりの低下やユーザからのクレームの増加につながることが多い。 The flow of molten steel in the mold changes from time to time due to adhesion to the immersion nozzle, melting damage, and changes in casting speed. In particular, the clogging of the discharge hole due to the inclusion of inclusions on the discharge hole of the immersion nozzle causes an uneven discharge flow rate toward the left and right short sides of the mold. As a result, on the side where the discharge flow rate is increased, the increase in the flow rate in the strand due to the increase in the discharge flow rate to the short side, the increase in the amount of invading bubbles and inclusions, and the increase in the flow rate to the meniscus, the mold powder There is a problem that it becomes easy to invite. For this reason, the quality of the slab is deteriorated, which often leads to a decrease in product yield and an increase in complaints from users.

ここで、鋳型内の状態を推定する方法として、例えば特許文献１には、鋳型銅板の溶鋼側表面の法線上の１点で鋳型銅板に埋設された測温素子にて鋳型鋼板内温度を測定し、この測温値から凝固シェルに沿った溶鋼の流速を求める手法が開示されている。 Here, as a method for estimating the state in the mold, for example, in Patent Document 1, the temperature in the mold steel plate is measured by a temperature measuring element embedded in the mold copper plate at one point on the normal line of the molten steel side surface of the mold copper plate. And the method of calculating | requiring the flow velocity of the molten steel along a solidification shell from this temperature measurement value is disclosed.

具体的には、測温値から鋳型銅板を通過する熱流束を求め、その熱流束から総括熱抵抗（溶鋼から冷却水までの熱伝導体の熱抵抗を合成したもの）Ｒを決定して、下式（１０１）より、溶鋼と凝固シェルとの間の対流熱伝達係数βを求める。なお、λ_sは凝固シェルの熱伝導率、λ_pはモールドパウダー層の熱伝導率、λ_mは鋳型銅板の熱伝導率、ｈ_mはモールドパウダー層と鋳型銅板との間の熱伝達係数、ｈ_wは鋳型銅板と冷却水との間の熱伝達係数、ｄ_sは凝固シェル厚み、ｄ_pはモールドパウダー層厚み、ｄ_mは鋳型銅板厚みである。
Ｒ＝（１／β）＋（ｄ_s／λ_s）＋（ｄ_p／λ_p）＋（１／ｈ_m）＋（ｄ_m／λ_m）＋（１／ｈ_w）・・・（１０１） Specifically, the heat flux passing through the mold copper plate is obtained from the temperature measurement value, and the overall heat resistance (the synthesized heat resistance of the heat conductor from the molten steel to the cooling water) R is determined from the heat flux, From the following equation (101), the convective heat transfer coefficient β between the molten steel and the solidified shell is obtained. The heat transfer coefficient between the lambda _s is the thermal conductivity of the solidified shell, lambda _p is the thermal conductivity of the mold powder layer, lambda _m is the thermal conductivity of the mold copper plate, h _m is a mold powder layer and the mold copper plate, h _w is the heat transfer coefficient, d _s is solidified shell thickness, d _p is the mold powder layer thickness, d _m is the mold copper plate thickness between mold copper plate and cooling water.
R = (1 / β) + (d _s / λ _s ) + (d _p / λ _p ) + (1 / h _m ) + (d _m / λ _m ) + (1 / h _w ) (101) )

式（１０１）から求めた熱伝達係数βを用いて、下式（１０２）より、ヌッセルト数Ｎｕを求め、このヌッセルト数Ｎｕを下式（１０３）又は（１０４）に代入してレイノルズ数Ｒｅを求める。そして、レイノルズ数Ｒｅを下式（１０５）に代入して溶鋼流速Ｕを求める。なお、λ₁は溶鋼の熱伝導率、Ｘ₁は伝熱代表長さ、Ｐｒはプラントル数、νは溶鋼の動粘性係数、Ｘ₂は溶鋼流代表長さである。
β＝Ｎｕ×λ₁×Ｘ₁・・・（１０２）
Ｎｕ＝０．６６４×Ｐｒ^1/3×Ｒｅ^4/5（Ｕ＜Ｕ₀）・・・（１０３）
Ｎｕ＝０．０３６×Ｐｒ^1/3×Ｒｅ^1/2（Ｕ≧Ｕ₀）・・・（１０４）
Ｒｅ＝Ｕ×Ｘ₂／ν・・・（１０５） Using the heat transfer coefficient β obtained from the equation (101), the Nusselt number Nu is obtained from the following equation (102), the Nusselt number Nu is substituted into the following equation (103) or (104), and the Reynolds number Re is obtained. Ask. Then, the Reynolds number Re is substituted into the following equation (105) to obtain the molten steel flow velocity U. Note that λ ₁ is the thermal conductivity of the molten steel, X ₁ is the heat transfer representative length, Pr is the Prandtl number, ν is the kinematic viscosity coefficient of the molten steel, and X ₂ is the molten steel flow representative length.
β = Nu × λ ₁ × X ₁ (102)
Nu = 0.664 × Pr ^1/3 × Re ^4/5 (U <U ₀ ) (103)
Nu = 0.036 × Pr ^1/3 × Re ^1/2 (U ≧ U ₀ ) (104)
Re = U × X ₂ / ν (105)

特許第３２３０５１３号公報Japanese Patent No. 3230513 特開平１０−２７７７１６号公報Japanese Patent Laid-Open No. 10-277716 特開２００８−２６００４６号公報（段落［００２０］）JP 2008-260046 A (paragraph [0020]) 特開平０８−２７６２５７号公報（段落［０００８］）Japanese Patent Laid-Open No. 08-276257 (paragraph [0008]) 特開２０００−３１７５９４号公報JP 2000-317594 A 特開２００１−２３９３５３号公報JP 2001-239353 A

ここで、凝固シェルと鋳型銅板との間の熱伝達係数αは、下式（１０６）で記述できる（式（１０１）の右辺第３項及び第４項）。特許文献１では、モールドパウダー層厚みｄ_pは、モールドパウダーの種類と鋳型振動の振幅、周波数、及び振動波形と、鋳造速度が決まれば一定に決まる数値であり、また、モールドパウダー層の熱伝導率λ_pは、モールドパウダーの種類によらず、ほぼ一定であることが知られており、また、モールドパウダー層と鋳型銅板との間の熱伝達係数ｈ_mも、モールドパウダーの種類が決まればほぼ一定の値に決まるとしている。
１／α＝（ｄ_p／λ_p）＋（１／ｈ_m）・・・（１０６） Here, the heat transfer coefficient α between the solidified shell and the mold copper plate can be described by the following formula (106) (the third and fourth terms on the right side of the formula (101)). In Patent Document 1, the mold powder layer thickness d _p is a numerical value that is fixed when the type of mold powder, the amplitude, frequency, and vibration waveform of the mold vibration and the casting speed are determined, and the heat conduction of the mold powder layer. rate lambda _p, regardless of the type of mold powder, is known to be substantially constant, also the heat transfer coefficient h _m between the mold powder layer and the mold copper plate, once the type of mold powder It is determined to be almost constant.
1 / α = (d _p / λ _p ) + (1 / h _m ) (106)

つまり、特許文献１の手法において、凝固シェルと鋳型銅板との間の熱伝達係数αは、時間的に変化しない一定値として取り扱うことが前提条件となっている。 That is, in the method of Patent Document 1, it is a precondition that the heat transfer coefficient α between the solidified shell and the mold copper plate is handled as a constant value that does not change with time.

しかしながら、エアーギャップの発生等の報告事例から判るように、モールドパウダー層の厚みは時間的に大きく変動する可能性が高く、凝固シェルと鋳型銅板との間の熱伝達係数αを一定値として取り扱うことは、実用上、同手法の適用領域を、平均的な正常操業領域に限定したものにしている。また、特許文献１では凝固シェルの厚みも一定としているので、鋳型の左右短辺に向かう溶鋼の偏流状態を検知するために必要な熱伝達係数の時間変動の推定精度が悪く、十分な偏流状態の検知精度を得ることができない。 However, as can be seen from reported cases such as the occurrence of an air gap, the thickness of the mold powder layer is highly likely to fluctuate over time, and the heat transfer coefficient α between the solidified shell and the mold copper plate is treated as a constant value. This practically limits the application area of the method to the average normal operation area. In Patent Document 1, since the thickness of the solidified shell is also constant, the estimation accuracy of the time variation of the heat transfer coefficient necessary for detecting the drift state of the molten steel toward the left and right short sides of the mold is poor, and the sufficient drift state The detection accuracy cannot be obtained.

本発明は上記の点に鑑みてなされたものであり、鋳型内における浸漬ノズルの左右での溶鋼の偏流に伴う操業及び品質トラブルを回避できるようにすることを目的とする。 The present invention has been made in view of the above points, and it is an object of the present invention to avoid operation and quality problems associated with the drift of molten steel on the left and right of the immersion nozzle in the mold.

本発明の連続鋳造方法は、鋳型の中央に配置された浸漬ノズルから左右の鋳型短辺に向かって溶鋼を吐出し、溶鋼から鋳型用の冷却水までの間に凝固シェル、モールドパウダー層、鋳型の各熱伝導体が存在する連続鋳造において、凝固シェルと鋳型との間の熱伝達係数α、及び、溶鋼と凝固シェルとの間の熱伝達係数βを求めて、これら熱伝達係数α、βに基づいて連続鋳造を制御する連続鋳造方法であって、前記浸漬ノズルを挟む左右位置それぞれにおいて鋳型長辺内に鋳造方向に位置をずらして埋設された複数の測温手段を用いて、鋳型を通過する熱流束を取得する熱流束取得手順と、熱伝達係数α及び熱伝達係数βを含み、鋳型を通過する熱流束を表わす式と、前記熱流束取得手順で取得した熱流束とを用いて、前記右位置での熱伝達係数α_R及び熱伝達係数β_Rを同時に決定し、また、前記左位置での熱伝達係数α_L及び熱伝達係数β_Lを同時に決定する熱伝達係数決定手順と、前記熱伝達係数決定手順で決定した熱伝達係数α_R及びα_Lが共に５００〜５００００Ｗ／ｍ²・Ｋの場合であって、熱伝達係数β_Rと熱伝達係数β_Lとの比、又は、熱伝達係数β_Rから求めた溶鋼の流速と熱伝達係数β_Lから求めた溶鋼の流速との比が所定の値を超えて異なるとき、鋳造速度を減少させる制御手順とを有することを特徴とする。
また、本発明の連続鋳造方法の他の特徴とするところは、前記左右位置の測温手段は前記浸漬ノズルを挟んで左右対称に配置されており、前記浸漬ノズルの中心から左右の鋳型短辺までの鋳型幅方向距離をそれぞれＷ／２とした場合に、前記左右位置は、それぞれ前記浸漬ノズルの中心からＷ／６以上離れた位置で、かつ、鋳型のコーナから４０ｍｍ以上離れた位置である点にある。
また、本発明の連続鋳造方法の他の特徴とするところは、前記制御手順では、熱伝達係数β_R、β_Lのうち大きい方を小さい方で除した値が１．５以上となったとき、鋳造速度を減少させる点にある。
また、本発明の連続鋳造方法の他の特徴とするところは、前記制御手順では、鋳造速度を２０％以上減少させる点にある。
また、本発明の連続鋳造方法の他の特徴とするところは、前記熱伝達係数決定手順では、Ｔを凝固シェルの温度、Ｔ₀を溶鋼の温度、Ｔ_sを溶鋼と凝固シェルとの界面温度、ｕを鋳造速度、λ_sを凝固シェルの熱伝導率、ｃ_sを凝固シェルの比熱、ρ_sを凝固シェルの密度、Ｌを凝固シェルの潜熱、ｄを鋳型の凝固シェル側の表面から測温手段までの距離、λ_mを鋳型の熱伝導率として、鋳造方向をｚ軸、鋳造方向に直交する方向をｘ軸とする２次元座標上で、凝固シェルの厚みｓ(ｚ，ｔ)及び凝固シェルの鋳型側の表面温度Ｔ(０，ｚ，ｔ)を表わす式（Ａ）、（Ｂ）と、凝固シェルの鋳型側の表面−モールドパウダー層−熱電対間の熱収支に基づいて、鋳型を通過する熱流束ｑ_m(ｚ，ｔ)を表わす式（Ｃ）とを用いて、熱伝達係数α及び熱伝達係数βを同時に決定し、凝固シェルの厚みｓ(ｚ，ｔ)を計算する点にある。

また、本発明の連続鋳造方法の他の特徴とするところは、前記熱流束取得手順では、ｄ_wを測温手段から水冷位置までの距離、ｈ_wを鋳型と冷却水との間の熱伝達係数、Ｔ_wを冷却水温度、λ_mを鋳型の熱伝導率として、前記複数の測温手段の温度計測値Ｔ_{m_obs}(ｚ，ｔ)に基づいて、式（Ｄ）より、鋳型を通過する熱流束ｑ_m(ｚ，ｔ)を計算する点にある。

本発明の連続鋳造の制御装置は、鋳型の中央に配置された浸漬ノズルから左右の鋳型短辺に向かって溶鋼を吐出し、溶鋼から鋳型用の冷却水までの間に凝固シェル、モールドパウダー層、鋳型の各熱伝導体が存在する連続鋳造において、凝固シェルと鋳型との間の熱伝達係数α、及び、溶鋼と凝固シェルとの間の熱伝達係数βを求めて、これら熱伝達係数α、βに基づいて連続鋳造を制御する連続鋳造の制御装置であって、前記浸漬ノズルを挟む左右位置それぞれにおいて鋳型長辺内に鋳造方向に位置をずらして埋設された複数の測温手段を用いて、鋳型を通過する熱流束を取得する熱流束取得手段と、熱伝達係数α及び熱伝達係数βを含み、鋳型を通過する熱流束を表わす式と、前記熱流束取得手段で取得した熱流束とを用いて、前記右位置での熱伝達係数α_R及び熱伝達係数β_Rを同時に決定し、また、前記左位置での熱伝達係数α_L及び熱伝達係数β_Lを同時に決定する熱伝達係数決定手段と、前記熱伝達係数決定手段で決定した熱伝達係数α_R及びα_Lが共に５００〜５００００Ｗ／ｍ²・Ｋの場合であって、熱伝達係数β_Rと熱伝達係数β_Lとの比、又は、熱伝達係数β_Rから求めた溶鋼の流速と熱伝達係数β_Lから求めた溶鋼の流速との比が所定の値を超えて異なるとき、鋳造速度を減少させる制御手段とを備えることを特徴とする。
本発明のプログラムは、鋳型の中央に配置された浸漬ノズルから左右の鋳型短辺に向かって溶鋼を吐出し、溶鋼から鋳型用の冷却水までの間に凝固シェル、モールドパウダー層、鋳型の各熱伝導体が存在する連続鋳造において、凝固シェルと鋳型との間の熱伝達係数α、及び、溶鋼と凝固シェルとの間の熱伝達係数βを求めて、これら熱伝達係数α、βに基づいて連続鋳造を制御するためのプログラムであって、前記浸漬ノズルを挟む左右位置それぞれにおいて鋳型長辺内に鋳造方向に位置をずらして埋設された複数の測温手段を用いて、鋳型を通過する熱流束を取得する熱流束取得処理と、熱伝達係数α及び熱伝達係数βを含み、鋳型を通過する熱流束を表わす式と、前記熱流束取得処理で取得した熱流束とを用いて、前記右位置での熱伝達係数α_R及び熱伝達係数β_Rを同時に決定し、また、前記左位置での熱伝達係数α_L及び熱伝達係数β_Lを同時に決定する熱伝達係数決定処理と、前記熱伝達係数決定処理で決定した熱伝達係数α_R及びα_Lが共に５００〜５００００Ｗ／ｍ²・Ｋの場合であって、熱伝達係数β_Rと熱伝達係数β_Lとの比、又は、熱伝達係数β_Rから求めた溶鋼の流速と熱伝達係数β_Lから求めた溶鋼の流速との比が所定の値を超えて異なるとき、鋳造速度を減少させる制御処理とをコンピュータに実行させる。 In the continuous casting method of the present invention, molten steel is discharged from the immersion nozzle disposed in the center of the mold toward the left and right mold short sides, and between the molten steel and the cooling water for the mold, a solidified shell, a mold powder layer, a mold In the continuous casting in which each heat conductor is present, the heat transfer coefficient α between the solidified shell and the mold and the heat transfer coefficient β between the molten steel and the solidified shell are obtained, and these heat transfer coefficients α, β are obtained. A continuous casting method for controlling the continuous casting based on the plurality of temperature measuring means embedded in the long side of the mold in each of the left and right positions sandwiching the immersion nozzle and embedded in the casting direction. Using a heat flux acquisition procedure for acquiring a heat flux passing through, an expression including a heat transfer coefficient α and a heat transfer coefficient β, representing a heat flux passing through a mold, and a heat flux acquired in the heat flux acquisition procedure , Heat transfer coefficient at the right position Determine the _R and heat transfer coefficient beta _R simultaneously, also the heat transfer coefficient determination procedure for determining simultaneously the heat transfer coefficient alpha _L and the heat transfer coefficient beta _L at the left position, determined by the heat transfer coefficient determination procedure The heat transfer coefficient α _R and α _L are both 500 to 50000 W / m ² · K, and the ratio of the heat transfer coefficient β _R to the heat transfer coefficient β _L or the molten steel obtained from the heat transfer coefficient β _R And a control procedure for reducing the casting speed when the ratio between the flow rate of the molten steel and the flow rate of the molten steel obtained from the heat transfer coefficient β _L exceeds a predetermined value.
Another feature of the continuous casting method of the present invention is that the temperature measuring means at the left and right positions are arranged symmetrically with respect to the immersion nozzle, and the left and right mold short sides from the center of the immersion nozzle. When the distance in the mold width direction is W / 2, the left and right positions are positions that are separated from the center of the immersion nozzle by W / 6 or more, and are positions that are separated from the corner of the mold by 40 mm or more. In the point.
Another feature of the continuous casting method of the present invention is that, in the control procedure, a value obtained by dividing the larger one of the heat transfer coefficients β _R and β _L by the smaller one is 1.5 or more. The point is to reduce the casting speed.
Another feature of the continuous casting method of the present invention is that the control procedure reduces the casting speed by 20% or more.
Another feature of the continuous casting method of the present invention is that in the heat transfer coefficient determination procedure, T is the temperature of the solidified shell, T ₀ is the temperature of the molten steel, T _s is the interface temperature between the molten steel and the solidified shell. , U is the casting speed, λ _s is the thermal conductivity of the solidified shell, c _s is the specific heat of the solidified shell, ρ _s is the density of the solidified shell, L is the latent heat of the solidified shell, and d is measured from the surface of the solidified shell side of the mold. The thickness s (z, t) of the solidified shell on a two-dimensional coordinate with the casting direction as the z-axis and the direction orthogonal to the casting direction as the x-axis, the distance to the temperature means, λ _m as the thermal conductivity of the mold, and Based on the formulas (A) and (B) representing the surface temperature T (0, z, t) on the mold side of the solidified shell, and the heat balance between the mold side surface of the solidified shell, the mold powder layer, and the thermocouple, Using the equation (C) representing the heat flux q _m (z, t) passing through the mold, the heat transfer coefficient α and the heat transfer coefficient β Are simultaneously determined, and the thickness s (z, t) of the solidified shell is calculated.

Another feature of the continuous casting method of the present invention is that, in the heat flux acquisition procedure, d _w is a distance from the temperature measuring means to the water cooling position, and h _w is a heat transfer between the mold and the cooling water. Based on the temperature measurement values T _{m — obs} (z, t) of the plurality of temperature measuring means, the _coefficient passes through the mold according to formula (D), where T _w is the cooling water temperature and λ _m is the thermal conductivity of the mold. The point is to calculate the heat flux q _m (z, t).

The control device for continuous casting according to the present invention discharges molten steel from the immersion nozzle arranged in the center of the mold toward the left and right mold short sides, and between the molten steel and the cooling water for the mold, a solidified shell, a mold powder layer In the continuous casting in which each heat conductor of the mold exists, the heat transfer coefficient α between the solidified shell and the mold and the heat transfer coefficient β between the molten steel and the solidified shell are obtained, and these heat transfer coefficients α , A continuous casting control device for controlling the continuous casting based on β, using a plurality of temperature measuring means embedded in the mold long side shifted in the casting direction at each of the left and right positions sandwiching the immersion nozzle A heat flux acquisition means for acquiring a heat flux passing through the mold, an expression representing the heat flux passing through the mold, including the heat transfer coefficient α and the heat transfer coefficient β, and the heat flux acquired by the heat flux acquisition means And at the right position Determining the heat transfer coefficient alpha _R and the heat transfer coefficient beta _R simultaneously, also the heat transfer coefficient determining means for determining the heat transfer coefficient alpha _L and the heat transfer coefficient beta _L at the left position simultaneously, the heat transfer coefficient determination The heat transfer coefficients α _R and α _L determined by the means are both 500 to 50000 W / m ² · K, and the ratio of the heat transfer coefficient β _R and the heat transfer coefficient β _L or the heat transfer coefficient β _R And a control means for reducing the casting speed when the ratio of the flow rate of the molten steel obtained from the above and the flow rate of the molten steel obtained from the heat transfer coefficient β _L exceeds a predetermined value.
The program of the present invention discharges molten steel from the immersion nozzle arranged in the center of the mold toward the left and right mold short sides, and each of the solidified shell, mold powder layer, and mold between the molten steel and the cooling water for the mold. In continuous casting in which a heat conductor is present, a heat transfer coefficient α between the solidified shell and the mold and a heat transfer coefficient β between the molten steel and the solidified shell are obtained and based on these heat transfer coefficients α and β. A program for controlling continuous casting, and passes through the mold using a plurality of temperature measuring means embedded in the long side of the mold at different positions in the casting direction at the left and right positions sandwiching the immersion nozzle. Using the heat flux acquisition process for acquiring the heat flux, the formula representing the heat flux passing through the mold, including the heat transfer coefficient α and the heat transfer coefficient β, and the heat flux acquired in the heat flux acquisition process, Heat transfer unit in the right position Determine alpha _R and the heat transfer coefficient beta _R simultaneously, also the heat transfer coefficient determining process of determining the heat transfer coefficient alpha _L and the heat transfer coefficient beta _L at the left position simultaneously determined by the heat transfer coefficient determining process The heat transfer coefficients α _R and α _L were both 500 to 50000 W / m ² · K, and were obtained from the ratio of the heat transfer coefficient β _R and the heat transfer coefficient β _L or the heat transfer coefficient β _R. When the ratio between the molten steel flow rate and the molten steel flow rate obtained from the heat transfer coefficient β _L exceeds a predetermined value, the computer is caused to execute a control process for reducing the casting speed.

本発明によれば、鋳型内状態を支配する２つの主要因である凝固シェルと鋳型との間の熱伝達係数α、及び、溶鋼と凝固シェルとの間の熱伝達係数βを求めて、これら熱伝達係数α、βに基づいて連続鋳造を制御することにより、鋳型内における浸漬ノズルの左右での溶鋼の偏流に伴う操業及び品質トラブルを回避でき、連続鋳造の鋳片品質及び操業性向上に寄与する。 According to the present invention, the heat transfer coefficient α between the solidified shell and the mold, which is the two main factors governing the state in the mold, and the heat transfer coefficient β between the molten steel and the solidified shell are obtained. By controlling the continuous casting based on the heat transfer coefficients α and β, it is possible to avoid operation and quality problems associated with the drift of molten steel on the left and right of the immersion nozzle in the mold, and to improve the slab quality and operability of continuous casting. Contribute.

連続鋳造設備の鋳型の断面の一部を示す図である。It is a figure which shows a part of cross section of the casting_mold | template of a continuous casting installation. 凝固シェルの外表面−モールドパウダー層−熱電対間の熱収支の概念を示す図である。It is a figure which shows the concept of the heat balance between the outer surface of a solidification shell-mold powder layer-thermocouple. 実施例での各熱電対の温度計測値及び各熱電対位置での熱流束を示す特性図である。It is a characteristic view which shows the temperature measurement value of each thermocouple in an Example, and the heat flux in each thermocouple position. 実施例での鋳造速度の変化を示す特性図である。It is a characteristic view which shows the change of the casting speed in an Example. 実施例での溶鋼温度の変化を示す特性図である。It is a characteristic view which shows the change of the molten steel temperature in an Example. 実施例において本発明を適用して求めたモールドパウダー層の総括熱伝達係数α及び溶鋼側熱伝達係数βを示す特性図である。It is a characteristic view which shows the general heat transfer coefficient (alpha) and the molten steel side heat transfer coefficient (beta) of the mold powder layer which calculated | required applying this invention in the Example. 本発明を適用して求めた凝固シェルの厚み、時間、ｚ方向位置を軸とする特性図である。It is a characteristic view which makes the axis | shaft the thickness of solidified shell calculated | required by applying this invention, time, and a z direction position. 実施形態に係る連続鋳造設備の鋳型を示す図である。It is a figure which shows the casting_mold | template of the continuous casting installation which concerns on embodiment. 実施形態に係る連続鋳造の制御装置の機能構成を示すブロック図である。It is a block diagram which shows the function structure of the control apparatus of the continuous casting which concerns on embodiment. 実施形態に係る連続鋳造方法を示すフローチャートである。It is a flowchart which shows the continuous casting method which concerns on embodiment. 実施形態に係る連続鋳造方法を示すフローチャートである。It is a flowchart which shows the continuous casting method which concerns on embodiment. 本発明の連続鋳造の制御装置として機能しうる情報処理装置のハードウェアの概略構成の一例を示すブロック図である。It is a block diagram which shows an example of schematic structure of the hardware of the information processing apparatus which can function as a control apparatus of the continuous casting of this invention. 連続鋳造設備の概要を説明するための図である。It is a figure for demonstrating the outline | summary of a continuous casting installation.

以下、添付図面を参照して、本発明の好適な実施形態について説明する。
まず、本発明において利用する、凝固シェルと鋳型との間の熱伝達係数α、及び、溶鋼と凝固シェルとの間の熱伝達係数βの決定手法について説明する。
図１は、鋳型内凝固状態を示す概念図であり、連続鋳造設備の鋳型の断面の一部を示す。図１において、１は溶鋼である。２は鋳片たる凝固シェル（凝固層）である。３はモールドパウダー層である。４は鋳型銅板（単に鋳型とも呼ぶ）であり、冷却水を流すための水冷溝が形成されている。図１に示すように、溶鋼１から鋳型用の冷却水までの間に凝固シェル２、モールドパウダー層３、鋳型銅板４の各熱伝導体が存在する。 Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.
First, a method for determining the heat transfer coefficient α between the solidified shell and the mold and the heat transfer coefficient β between the molten steel and the solidified shell used in the present invention will be described.
FIG. 1 is a conceptual diagram showing a solidified state in a mold, and shows a part of a cross section of a mold of a continuous casting facility. In FIG. 1, 1 is molten steel. Reference numeral 2 denotes a solidified shell (solidified layer) as a slab. 3 is a mold powder layer. Reference numeral 4 denotes a mold copper plate (also simply referred to as a mold), in which a water cooling groove for flowing cooling water is formed. As shown in FIG. 1, the respective heat conductors of the solidified shell 2, the mold powder layer 3, and the mold copper plate 4 exist between the molten steel 1 and the cooling water for the mold.

また、鋳型銅板４には複数の熱電対５が鋳造方向に位置をずらして埋設されている。熱電対５は、鋳造方向（図１に示すｚ軸方向）に一列に並べるのが好ましいが、鋳造方向に直交する方向（図１に示すｘ軸方向）にずれている場合でも、以下に説明する演算の際に補間演算等を行って位置補正すればよい。 A plurality of thermocouples 5 are embedded in the mold copper plate 4 while being shifted in the casting direction. The thermocouples 5 are preferably arranged in a line in the casting direction (z-axis direction shown in FIG. 1), but even when they are shifted in the direction orthogonal to the casting direction (x-axis direction shown in FIG. 1), they will be described below. The position may be corrected by performing an interpolation calculation or the like during the calculation.

鋳型銅板４に接する溶鋼１の湯面を座標軸の原点（０，０）にとり、鋳造方向をｚ軸、鋳造方向に直交する凝固層成長方向をｘ軸とする２次元座標上で、凝固層成長を記述する偏微分方程式を下式（１）〜（４）のように設定する。Ｔは凝固シェル２の温度、Ｔ₀は溶鋼１の温度、Ｔ_sは溶鋼１と凝固シェル２との界面温度（凝固温度）である。ｓ(ｚ，ｔ)は凝固シェル２の厚みである。β(ｚ，ｔ)は溶鋼１と凝固シェル２との間の対流熱伝達係数（「溶鋼側熱伝達係数」と称する）、α(ｚ，ｔ)は凝固シェル２と鋳型銅板４との間の熱伝達係数（「モールドパウダー層の総括熱伝達係数」と称する）である。ｕは鋳造速度である。λ_s、ｃ_s、ρ_s、Ｌは凝固シェル２の物性値であり、熱伝導率、比熱、密度、凝固潜熱である。Ｔ_m(０，ｚ，ｔ)は鋳型銅板４の凝固シェル２側の表面（鋳型銅板４の内表面）の温度である。 The surface of molten steel 1 in contact with the mold copper plate 4 is taken as the origin (0, 0) of the coordinate axis, the solidified layer growth on a two-dimensional coordinate with the casting direction z-axis and the solidified layer growth direction orthogonal to the casting direction x-axis. Is set as shown in the following equations (1) to (4). T is the temperature of the solidified shell 2, T ₀ is the temperature of the molten steel 1, and T _s is the interface temperature (solidification temperature) between the molten steel 1 and the solidified shell 2. s (z, t) is the thickness of the solidified shell 2. β (z, t) is a convective heat transfer coefficient between the molten steel 1 and the solidified shell 2 (referred to as “molten steel side heat transfer coefficient”), and α (z, t) is between the solidified shell 2 and the mold copper plate 4. (Referred to as “overall heat transfer coefficient of mold powder layer”). u is the casting speed. λ _s , c _s , ρ _s , and L are physical property values of the solidified shell 2, and are thermal conductivity, specific heat, density, and latent heat of solidification. T _m (0, z, t) is the temperature of the surface of the mold copper plate 4 on the solidified shell 2 side (the inner surface of the mold copper plate 4).

すなわち、式（１）は凝固シェル２内での熱収支を表わす。式（２）は凝固シェル２と溶鋼１との境界条件を表わす。式（３）は凝固シェル２と溶鋼１との界面での熱収支を表わす。式（４）は凝固シェル２とモールドパウダー層３との界面での熱収支を表わす。 That is, formula (1) represents the heat balance in the solidified shell 2. Equation (2) represents the boundary condition between the solidified shell 2 and the molten steel 1. Equation (3) represents the heat balance at the interface between the solidified shell 2 and the molten steel 1. Equation (4) represents the heat balance at the interface between the solidified shell 2 and the mold powder layer 3.

ここで、凝固シェル２の温度Ｔがｘの２次式で記述できると仮定し、下式（５）で近似する。 Here, it is assumed that the temperature T of the solidified shell 2 can be described by a quadratic expression of x, and is approximated by the following expression (5).

式（５）を式（１）〜式（４）に代入し、係数ａ(ｚ，ｔ)と係数ｂ(ｚ，ｔ)を決定する。 Equation (5) is substituted into Equations (1) to (4) to determine coefficient a (z, t) and coefficient b (z, t).

係数ａ(ｚ，ｔ)と係数ｂ(ｚ，ｔ)から、凝固シェル２の厚みｓ(ｚ，ｔ)と、凝固シェル２の鋳型銅板４側の表面（凝固シェル２の外表面）の温度Ｔ(０，ｚ，ｔ)は、下式（６）、（７）で記述することができる。 From the coefficients a (z, t) and b (z, t), the thickness s (z, t) of the solidified shell 2 and the temperature of the surface of the solidified shell 2 on the mold copper plate 4 side (the outer surface of the solidified shell 2). T (0, z, t) can be described by the following equations (6) and (7).

ここで、基準となる時刻ｔ₀を任意に固定し、新変数η（≧０）を導入し、ｚ＝ｕ・η、ｔ＝ｔ₀＋ηとおく。これにより、式（６）は、下式（８）、（９）のように変形することができる。 Here, the reference time t ₀ is arbitrarily fixed, a new variable η (≧ 0) is introduced, and z = u · η and t = t ₀ + η are set. Thereby, Formula (6) can be transformed into the following Formulas (8) and (9).

また、式（７）は、下式（１０）のように変形することができる。 Moreover, Formula (7) can be deform | transformed like the following Formula (10).

式（８）の差分近似式は、下式（１１）のようになる。 The difference approximation formula of Formula (8) becomes like the following Formula (11).

一方、式（１０）を離散化すると、下式（１２）のようになる。 On the other hand, when Expression (10) is discretized, the following Expression (12) is obtained.

更に、式（１２）を下式（１３）のように変形する。 Furthermore, the equation (12) is transformed into the following equation (13).

以下の記号で定義し、式（１３）を式（１４）のように書き換える。 It is defined by the following symbols, and equation (13) is rewritten as equation (14).

式（１４）は、下式（１５）のように、ｙに関する２次方程式に書き換えることができる。 Equation (14) can be rewritten as a quadratic equation relating to y as in the following equation (15).

以下に、凝固シェル２の厚みｓ(η_k)を計算する手順を記す。熱伝達係数α(η_k)、β(η_k)が与えられたとする。溶鋼１の湯面上では、ｓ(η₁)＝０である。これを式（１５）に代入して２次方程式を解き、Ｔ(０，η₁)を得る。次に、ｓ(η₁)、Ｔ(０，η₁)を式（１１）に代入して、Ψ(η₂)を求める。（９）式の左辺にΨ（η₂）を代入、右辺にＴ（０，η₁）を代入して、ｓ(η₂)を求め、それを式（１５）に代入して２次方程式を解き、Ｔ(０，η₂)を得る。以下、同様の操作を繰り返すことにより、凝固シェル２の厚みの時間履歴ｓ(η_k)を計算することができる。 The procedure for calculating the thickness s (η _k ) of the solidified shell 2 will be described below. It is assumed that heat transfer coefficients α (η _k ) and β (η _k ) are given. On the surface of the molten steel 1, s (η ₁ ) = 0. By substituting this into equation (15), the quadratic equation is solved to obtain T (0, η ₁ ). Next, s (η ₁ ) and T (0, η ₁ ) are substituted into equation (11) to obtain Ψ (η ₂ ). Substituting Ψ (η ₂ ) into the left side of equation (9) and substituting T (0, η ₁ ) into the right side to obtain s (η ₂ ), substituting it into equation (15), and the quadratic equation To obtain T (0, η ₂ ). Thereafter, the time history s (η _k ) of the thickness of the solidified shell 2 can be calculated by repeating the same operation.

また、特許文献２に示されているように、式（１）〜（４）を差分法等の数値計算手法を用いて計算することも可能であるが、上述した手法を用いることにより格段に演算速度が速くなるので、オンラインで凝固シェル２の凝固状態を推定することが可能になる。 Further, as shown in Patent Document 2, equations (1) to (4) can be calculated using a numerical calculation method such as a difference method, but by using the above-described method, Since the calculation speed is increased, the solidification state of the solidified shell 2 can be estimated online.

次に、熱伝達係数α(η_k)、β(η_k)の決定方法について述べる。図２に示すように、凝固シェル２の鋳型銅板４側の表面（凝固シェル２の外表面）−モールドパウダー層３−熱電対５間の熱収支を擬定常状態と仮定して、下式（１６）で記述する。図２において、点線は温度の変化の関係を示す。ｑ_mは鋳型銅板４をｘ軸方向に通過する熱流束である。ｄは鋳型銅板４の凝固シェル２側の表面（鋳型銅板４の内表面）から熱電対５までの距離である。λ_mは鋳型銅板４の熱伝導率である。式（７）に示すように、Ｔ(０，ｚ_k，ｔ)にはβ(ｚ_k，ｔ)を含んでおり、式（１６）は熱伝達係数α、βを未知数とする式となっている。 Next, a method for determining the heat transfer coefficients α (η _k ) and β (η _k ) will be described. As shown in FIG. 2, assuming that the heat balance between the surface of the solidified shell 2 on the mold copper plate 4 side (the outer surface of the solidified shell 2), the mold powder layer 3 and the thermocouple 5 is a quasi-steady state, 16). In FIG. 2, the dotted line indicates the relationship of temperature change. q _m is a heat flux passing through the mold copper plate 4 in the x-axis direction. d is the distance from the surface of the mold copper plate 4 on the solidified shell 2 side (the inner surface of the mold copper plate 4) to the thermocouple 5. λ _m is the thermal conductivity of the mold copper plate 4. As shown in equation (7), T (0, z _k , t) includes β (z _k , t), and equation (16) is an equation with the heat transfer coefficients α and β as unknowns. ing.

ここで、鋳型銅板４をｘ軸方向に通過する熱流束ｑ_m(ｚ_i，ｔ)は、鋳型銅板４の鋳造方向に埋設した複数の熱電対５の温度計測値Ｔ_{m_obs}(ｚ_i，ｔ)に基づいて、鋳造方向に対し、下式（１７）より計算する（ｉは熱電対を表わす添え字である）。熱流束ｑ_m(ｚ_i，ｔ)を補間計算（内外挿計算）することにより、任意の鋳造方向において鋳型銅板４をｘ軸方向に通過する熱流束ｑ_mを求めることができる。ｄ_wは熱電対５から水冷位置までの距離である。ｈ_wは鋳型銅板４と冷却水との間の熱伝達係数である。Ｔ_wは冷却水温度である。 Here, the heat flux q _m (z _i , t) passing through the mold copper plate 4 in the x-axis direction is a temperature measurement value T _{m_obs} (z _i , t) of the plurality of thermocouples 5 embedded in the casting direction of the mold copper plate 4. ) To calculate the casting direction from the following equation (17) (i is a subscript representing a thermocouple). Heat flux q _m (z _i, t) by an interpolation calculation (interpolation or extrapolation calculation), it is possible to determine the heat flux q _m that passes through the mold copper plate 4 in the x-axis direction in any casting direction. _dw is the distance from the thermocouple 5 to the water cooling position. h _w is a heat transfer coefficient between the mold copper plate 4 and the cooling water. T _w is the cooling water temperature.

式（１６）を、式（８）〜式（１５）に合わせるために、前に定義した変数ηを用い、下式（１８）のように書き換える。 In order to match the equation (16) with the equations (8) to (15), the previously defined variable η is used and rewritten as the following equation (18).

熱伝達係数α(η_k)、β(η_k)は、式（１８）より、下式（１９）で表される最小二乗法による最小化問題として同時に決定されるとともに、凝固シェル２の厚みの時間履歴ｓ(η_k)も計算される。 The heat transfer coefficients α (η _k ) and β (η _k ) are determined simultaneously from the equation (18) as a minimization problem by the least square method represented by the following equation (19), and the thickness of the solidified shell 2 The time history s (η _k ) is also calculated.

以上述べたように、凝固シェル２と鋳型銅板４との間の熱伝達係数α、及び、溶鋼１と凝固シェル２との間の熱伝達係数βを同時に決定し、凝固シェル２の厚みを計算することができる。凝固シェル２と鋳型銅板４との間の熱伝達係数α、及び、溶鋼１と凝固シェル２との間の熱伝達係数βは鋳型内凝固状態を支配する主要因であり、それを同時に決定できるので、これらの要因が鋳型内鋳片の凝固厚みに及ぼす影響を定量的に評価することができる。これにより、パウダー流入状態や溶鋼流動が鋳片凝固厚みに及ぼす影響を見積もることができ、連続鋳造の鋳片品質及び操業性向上に寄与する。 As described above, the heat transfer coefficient α between the solidified shell 2 and the mold copper plate 4 and the heat transfer coefficient β between the molten steel 1 and the solidified shell 2 are simultaneously determined, and the thickness of the solidified shell 2 is calculated. can do. The heat transfer coefficient α between the solidified shell 2 and the mold copper plate 4 and the heat transfer coefficient β between the molten steel 1 and the solidified shell 2 are main factors governing the solidified state in the mold, and can be determined simultaneously. Therefore, it is possible to quantitatively evaluate the influence of these factors on the solidification thickness of the in-mold slab. Thereby, the influence which the powder inflow state and molten steel flow exert on the slab solidification thickness can be estimated, which contributes to the improvement of slab quality and operability of continuous casting.

なお、特許文献５には、鋳造方向に複数点配置された鋳型温度検出手段より伝熱逆問題手法を使って予測した熱流束値を境界条件にした熱伝導方程式を解き、溶融金属の凝固厚みと凝固シェル温度プロフィールを得て、更には鋳造方向に複数点配置された鋳型温度検出手段より伝熱逆問題手法を使って計算した熱流束値と鋳型内面表面温度及び前記凝固シェル温度プロフィール計算結果から、熱伝導方程式を解きパウダー流入厚みを得る構成が開示されている。また、特許文献６には、鋳造方向に間隔をおいて鋳型の複数箇所に埋設した温度計測手段で鋳型温度を計測し、鋳型温度計測値に基づいて鋳型内面での熱流束を伝熱逆問題手法を用いて推定し、熱流束推定値に基づき鋳片内部の熱流束より溶融金属流動起因の対流熱伝達量を推定し、対流熱伝達量推定値により鋳型内溶融金属流動の異常を検出する構成が開示されている。しかしながら、いずれの先行技術も、上述したように凝固シェル２と鋳型銅板４との間の熱伝達係数α、及び、溶鋼１と凝固シェル２との間の熱伝達係数βを同時に決定し、凝固シェル２の厚みを計算するものではない。 In Patent Document 5, a heat conduction equation with a heat flux value predicted using a heat transfer inverse problem method as a boundary condition from a mold temperature detecting means arranged at a plurality of points in the casting direction is solved, and the solidification thickness of the molten metal is obtained. The heat flux value calculated by using the inverse heat problem method from the mold temperature detecting means arranged at a plurality of points in the casting direction and the inner surface temperature of the mold and the calculation result of the solidified shell temperature profile Thus, a configuration for solving the heat conduction equation and obtaining the powder inflow thickness is disclosed. In Patent Document 6, the mold temperature is measured by temperature measuring means embedded in a plurality of locations of the mold at intervals in the casting direction, and the heat flux on the inner surface of the mold is calculated based on the measured temperature of the mold. Estimate using a method, estimate the convective heat transfer due to molten metal flow from the heat flux inside the slab based on the estimated heat flux, and detect abnormalities in the molten metal flow in the mold based on the estimated convective heat transfer A configuration is disclosed. However, in any of the prior arts, as described above, the heat transfer coefficient α between the solidified shell 2 and the mold copper plate 4 and the heat transfer coefficient β between the molten steel 1 and the solidified shell 2 are simultaneously determined and solidified. The thickness of the shell 2 is not calculated.

ここで、上述した凝固シェル２と鋳型銅板４との間の熱伝達係数α、及び、溶鋼１と凝固シェル２の間の熱伝達係数βの決定方法の実施例を説明する。
図３（ａ）は各熱電対Ｌ１〜Ｌ７の温度計測値を示す特性図、図３（ｂ）は各熱電対Ｌ１〜Ｌ７の温度計測値から得られた各熱電対Ｌ１〜Ｌ７位置での熱流束を示す特性図である。熱電対Ｌ１〜Ｌ７は、各々、湯面から１０ｍｍ、３０ｍｍ、４０ｍｍ、７０ｍｍ、１００ｍｍ、１６０ｍｍ、２７０ｍｍの位置に設置されている。また、鋳型銅板の内表面か各熱電対Ｌ１〜Ｌ７までの距離ｄは１０ｍｍ、各熱電対から水冷位置までの距離ｄｗは５ｍｍである。図３（ｂ）に示す熱流束は、式（１７）により求めたものである。 Here, an embodiment of a method for determining the heat transfer coefficient α between the solidified shell 2 and the mold copper plate 4 and the heat transfer coefficient β between the molten steel 1 and the solidified shell 2 will be described.
FIG. 3A is a characteristic diagram showing the temperature measurement values of the thermocouples L1 to L7, and FIG. 3B is the thermocouple L1 to L7 position obtained from the temperature measurement values of the thermocouples L1 to L7. It is a characteristic view which shows a heat flux. The thermocouples L1 to L7 are respectively installed at positions of 10 mm, 30 mm, 40 mm, 70 mm, 100 mm, 160 mm, and 270 mm from the hot water surface. The distance d from the inner surface of the mold copper plate to each of the thermocouples L1 to L7 is 10 mm, and the distance dw from each thermocouple to the water cooling position is 5 mm. The heat flux shown in FIG. 3B is obtained by the equation (17).

凝固シェル２の熱伝導率λ_sは２９Ｗ／ｍ・Ｋ、比熱ｃ_sは０．６７０ｋＪ／ｋｇ・Ｋ、密度ρ_sは７６５０ｋｇ／ｍ₃は、潜熱Ｌは２６８ｋＪ／ｋｇである。また、鋳型銅板の熱伝導率λ_mは２５１Ｗ／ｍ・Ｋである。また、鋳型銅板４と冷却水との間の熱伝達係数ｈ_wは３００００ｋｃａｌ／ｍ³・Ｈｒ・℃である。また、凝固温度Ｔ_sは１４９７度である。 The solidified shell 2 has a thermal conductivity λ _s of 29 W / m · K, a specific heat c _s of 0.670 kJ / kg · K, a density ρ _s of 7650 kg / m ₃ , and a latent heat L of 268 kJ / kg. The mold copper plate has a thermal conductivity λ _m of 251 W / m · K. The heat transfer coefficient h _w between the mold copper plate 4 and the cooling water is 30000 kcal / m ³ · Hr · ° C. The solidification temperature T _s is 1497 degrees.

図４は鋳造速度ｕの変化を示す特性図、図５は溶鋼温度Ｔ₀の変化を示す特性図である。 FIG. 4 is a characteristic diagram showing a change in casting speed u, and FIG. 5 is a characteristic diagram showing a change in molten steel temperature T ₀ .

図６（ａ）は本発明を適用した求めたモールドパウダー層の総括熱伝達係数αを示す特性図、図６（ｂ）は本発明を適用して求めた溶鋼側熱伝達係数βを示す特性図である。本実施例では、鋳造方向において湯面〜９０ｍｍ、９０ｍｍ〜１８０ｍｍ、１８０ｍｍ〜２７０ｍｍに３分割して、それぞれでモールドパウダー層の総括熱伝達係数αと溶鋼側熱伝達係数βを求めている。 6A is a characteristic diagram showing the overall heat transfer coefficient α of the mold powder layer obtained by applying the present invention, and FIG. 6B is a characteristic showing the molten steel side heat transfer coefficient β obtained by applying the present invention. FIG. In the present embodiment, the molten steel surface is divided into three parts, that is, a molten metal surface to 90 mm, 90 mm to 180 mm, and 180 mm to 270 mm in the casting direction, and the overall heat transfer coefficient α and molten steel side heat transfer coefficient β of the mold powder layer are obtained.

また、図７は本発明を適用して求めた凝固シェル２の厚み、時間、ｚ方向位置を軸とする特性図である。１００ｓピッチで演算を行い、その結果をドットで示すとともに、内挿計算を行っている。同図に示すように、凝固シェル２の厚みは鋳造方向に向かうに従って成長していることがわかる。 FIG. 7 is a characteristic diagram about the thickness, time, and z-direction position of the solidified shell 2 obtained by applying the present invention. The calculation is performed at a pitch of 100 s, the result is indicated by dots, and the interpolation calculation is performed. As shown in the figure, it can be seen that the thickness of the solidified shell 2 grows toward the casting direction.

以下では、ここまで説明した凝固シェル２と鋳型銅板４との間の熱伝達係数α、及び、溶鋼１と凝固シェル２との間の熱伝達係数βの決定手法を利用して、鋳型内における浸漬ノズルの左右での溶鋼の偏流状態を診断し、連続鋳造を制御する実施形態を説明する。 In the following, by using the method for determining the heat transfer coefficient α between the solidified shell 2 and the mold copper plate 4 and the heat transfer coefficient β between the molten steel 1 and the solidified shell 2 described so far, An embodiment for diagnosing the drift state of molten steel on the left and right of the immersion nozzle and controlling continuous casting will be described.

図８（ａ）、（ｂ）は本実施形態に係る連続鋳造設備の鋳型を示す。図８（ａ）は鋳型短辺４Ｓの断面図、図８（ｂ）は鋳型４の平面図である。図８（ａ）、（ｂ）では溶鋼１のメニスカス付近のモールドパウダー層３しか図示しないが、モールドパウダーは凝固シェル２と鋳型銅板４の間に流入し、溶鋼１から鋳型用の冷却水までの間には凝固シェル２、モールドパウダー層３、鋳型銅板４の各熱伝導体が存在する。 FIGS. 8A and 8B show a mold for a continuous casting facility according to this embodiment. 8A is a cross-sectional view of the mold short side 4S, and FIG. 8B is a plan view of the mold 4. FIG. 8 (a) and 8 (b), only the mold powder layer 3 near the meniscus of the molten steel 1 is shown, but the mold powder flows between the solidified shell 2 and the mold copper plate 4, and from the molten steel 1 to the cooling water for the mold. In between, there are thermal conductors of the solidified shell 2, the mold powder layer 3, and the mold copper plate 4.

鋳型４の中央には浸漬ノズル６が配置されており、浸漬ノズル６の左右の吐出孔６ａから左右の鋳型短辺４Ｓに向かって溶鋼が吐出される。鋳型長辺４Ｌにおいて、浸漬ノズル６に挟んで右位置に２つの熱電対５ａ、５ｂが鋳造方向に一列に並んで埋設され、また、左位置に２つの熱電対５ｃ、５ｄが鋳造方向に一列に並んで埋設されている。右位置の熱電対５ａ、５ｂと左位置の熱電対５ｃ、５ｄとは浸漬ノズル６を挟んで左右対称に配置される。なお、図８（ａ）、（ｂ）では左右一対の吐出孔６ａしか図示しないが、吐出孔６ａは複数対あってもよい。 An immersion nozzle 6 is disposed at the center of the mold 4, and molten steel is discharged from the left and right discharge holes 6 a of the immersion nozzle 6 toward the left and right mold short sides 4 </ b> S. On the long side 4L of the mold, two thermocouples 5a and 5b are embedded in a row in the casting direction at the right position across the immersion nozzle 6, and two thermocouples 5c and 5d are aligned in the casting direction at the left position. It is buried side by side. The thermocouples 5a and 5b at the right position and the thermocouples 5c and 5d at the left position are arranged symmetrically with the immersion nozzle 6 in between. 8A and 8B, only a pair of left and right discharge holes 6a are shown, but a plurality of pairs of discharge holes 6a may be provided.

図９は、本実施形態に係る連続鋳造の制御装置の機能構成を示す図である。１１は熱流束取得部であり、既述した手法により、熱電対５ａ、５ｂ及び熱電対５ｃ、５ｄを用いて鋳型４の右位置及び左位置を通過する熱流束を取得する。 FIG. 9 is a diagram showing a functional configuration of the continuous casting control apparatus according to the present embodiment. Reference numeral 11 denotes a heat flux acquisition unit that acquires the heat flux passing through the right position and the left position of the mold 4 using the thermocouples 5a and 5b and the thermocouples 5c and 5d by the method described above.

１２は熱伝達係数決定部であり、既述した手法により、熱伝達係数α及び熱伝達係数βを同時に決定し、凝固シェル２の厚みを計算する。本実施形態では、熱電対５ａ、５ｂを用いて右位置におけるメニスカスから所定の深さ位置での熱伝達係数α_R及び熱伝達係数β_Rを決定する。同様に、熱電対５ｃ、５ｄを用いて左位置におけるメニスカスから所定の深さ位置での熱伝達係数α_L及び熱伝達係数β_Lを決定する。この場合に、右位置での熱伝達係数α_R及び熱伝達係数β_Rと、左位置での熱伝達係数α_L及び熱伝達係数β_Lとは、同じ深さ位置での値とするのが好適である。 Reference numeral 12 denotes a heat transfer coefficient determination unit that simultaneously determines the heat transfer coefficient α and the heat transfer coefficient β by the method described above, and calculates the thickness of the solidified shell 2. In the present embodiment, the heat transfer coefficient α _R and the heat transfer coefficient β _R at a predetermined depth position are determined from the meniscus at the right position using the thermocouples 5a and 5b. Similarly, the heat transfer coefficient α _L and the heat transfer coefficient β _L at a predetermined depth position are determined from the meniscus at the left position using the thermocouples 5c and 5d. In this case, the heat transfer coefficient α _R and heat transfer coefficient β _R at the right position and the heat transfer coefficient α _L and heat transfer coefficient β _L at the left position are values at the same depth position. Is preferred.

１３は制御部であり、熱伝達係数決定部１２で決定した熱伝達係数α_R及びα_Lが共に５００〜５００００Ｗ／ｍ²・Ｋの場合であって、熱伝達係数β_Rと熱伝達係数β_Lとの比が所定の値を超えて異なるとき、鋳造速度を減少させる。本実施形態では、熱伝達係数β_R、β_Lのうち大きい方を小さい方で除した値（ξ：「偏流率」と称する）を求めて、偏流率ξが１．５以上となったとき、鋳造速度を減少させる。 Reference numeral 13 denotes a control unit in which the heat transfer coefficients α _R and α _L determined by the heat transfer coefficient determination unit 12 are both 500 to 50000 W / m ² · K, and the heat transfer coefficient β _R and the heat transfer coefficient β _When the ratio with _L differs by more than a predetermined value, the casting speed is decreased. In the present embodiment, when a value obtained by dividing the larger one of the heat transfer coefficients β _R and β _L by the smaller one (ξ: referred to as “flow rate”) is obtained, the flow rate ξ becomes 1.5 or more. , Reduce the casting speed.

図１０は、本実施形態に係る制御装置による連続鋳造方法を示すフローチャートである。図１０に示す一連の処理は、例えば定周期で実行される。熱流束取得部１１は、熱電対５ａ、５ｂ、５ｃ、５ｄを用いて鋳型４の右位置及び左位置を通過する熱流束を取得する（ステップＳ１０１）。 FIG. 10 is a flowchart showing a continuous casting method by the control device according to the present embodiment. The series of processing shown in FIG. 10 is executed at a regular cycle, for example. The heat flux acquisition unit 11 acquires the heat flux that passes through the right position and the left position of the mold 4 using the thermocouples 5a, 5b, 5c, and 5d (step S101).

次に、熱伝達係数決定部１２は、右位置においてメニスカスから所定の深さ位置での熱伝達係数α_R及び熱伝達係数β_Rを同時に決定し、また、左位置においてメニスカスから所定の深さ位置での熱伝達係数α_L及び熱伝達係数β_Lを同時に決定する（ステップＳ１０２）。 Next, the heat transfer coefficient determination unit 12 simultaneously determines the heat transfer coefficient α _R and the heat transfer coefficient β _R at a predetermined depth position from the meniscus at the right position, and also has a predetermined depth from the meniscus at the left position. The heat transfer coefficient α _L and the heat transfer coefficient β _{L at the position} are simultaneously determined (step S102).

次に、制御部１３は、ステップＳ１０２において決定した熱伝達係数α_R及びα_Lが、予め定められている熱伝達係数α_l以上であり、かつ、予め定められている熱伝達係数α_h以下であるか否かを判定する（ステップＳ１０３）。α_l≦（α_R及びα_L）≦α_hであればステップＳ１０４に進み、そうでなければ本処理を抜ける。ここで、α_lは５００Ｗ／ｍ²・Ｋである。凝固シェル２と鋳型４との間の熱伝達係数αが５００Ｗ／ｍ²・Ｋより小さい場合、凝固シェル２に異物が噛み込んで通常とは異なる熱伝導状態となっていることが多く、ここでの目的である鋳型４内での溶鋼の偏流状態の診断には使えないという知見があるからである。一方、α_hは５００００Ｗ／ｍ²・Ｋである。凝固シェル２と鋳型４との間の熱伝達係数αが５００００Ｗ／ｍ²・Ｋを越える場合、モールドパウダー層３の厚みが薄くなり、凝固シェル２と鋳型４との焼き付きが発生する懸念があり、通常操業範囲を外れているので、ここでの目的である鋳型４内での溶鋼の偏流状態の診断から除外するのが妥当であるからである。 Next, the controller 13 determines that the heat transfer coefficients α _R and α _L determined in step S102 are greater than or equal to a predetermined heat transfer coefficient α _{l and} less than or equal to a predetermined heat transfer coefficient α _h. It is determined whether or not (step S103). If α _l ≦ (α _R and α _L ) ≦ α _h , the process proceeds to step S104. Otherwise, the process is exited. Here, α _l is 500 W / m ² · K. When the heat transfer coefficient α between the solidified shell 2 and the mold 4 is smaller than 500 W / m ² · K, foreign matter is caught in the solidified shell 2 and is often in a different heat conduction state. This is because there is a knowledge that it cannot be used for diagnosis of the drift state of molten steel in the mold 4 which is the purpose of the above. On the other hand, α _h is 50000 W / m ² · K. When the heat transfer coefficient α between the solidified shell 2 and the mold 4 exceeds 50000 W / m ² · K, there is a concern that the thickness of the mold powder layer 3 becomes thin and seizure between the solidified shell 2 and the mold 4 occurs. This is because it is appropriate to exclude from the diagnosis of the drift state of the molten steel in the mold 4 which is the object here because it is out of the normal operating range.

次に、制御部１３は、ステップＳ１０２において決定した熱伝達係数β_Rと熱伝達係数β_Lとの比が所定の値を超えて異なるか否かを判定する(ステップＳ１０４)。本実施形態では、偏流率ξ（＝β_R／β_L又はβ_L／β_R（β_R、β_Lのうち小さい値が分母、大きい値が分子））を求め、偏流率ξ≧１．５であるか否かを判定する。その結果、偏流率ξ≧１．５であればステップＳ１０５に進み、そうでなければ本処理を抜ける。上述した式（１０３）〜式（１０５）からもわかるように、溶鋼の流速は溶鋼１と凝固シェル２との間の熱伝達係数βに依存する。換言すれば、浸漬ノズル６の左右で溶鋼の偏流が発生して溶鋼の流速に差が生じている場合、左右位置での熱伝達係数β_Rと熱伝達係数β_Lに差が生じるので、ξ≧１．５となる場合は、浸漬ノズル６の左右で溶鋼の偏流が発生しているものと推定される。 Next, the control unit 13 determines whether or not the ratio between the heat transfer coefficient β _R and the heat transfer coefficient β _L determined in step S102 exceeds a predetermined value (step S104). In the present embodiment, the drift rate ξ (= β _R / β _L or β _L / β _R (the smaller value of β _R and β _L is the denominator and the larger value is the numerator)) is obtained, and the drift rate ξ ≧ 1.5. It is determined whether or not. As a result, if the drift rate ξ ≧ 1.5, the process proceeds to step S105. Otherwise, the process is exited. As can be seen from the equations (103) to (105), the flow rate of the molten steel depends on the heat transfer coefficient β between the molten steel 1 and the solidified shell 2. In other words, when a drift of the molten steel occurs on the left and right of the immersion nozzle 6 and a difference occurs in the flow velocity of the molten steel, a difference occurs between the heat transfer coefficient β _R and the heat transfer coefficient β _L at the left and right positions. When ≧ 1.5, it is presumed that a drift of molten steel occurs on the left and right of the immersion nozzle 6.

なお、熱伝達係数β_Rと熱伝達係数β_Lとの比を偏流率ξと説明したが、ステップＳ１０２において決定した熱伝達係数β_Rと熱伝達係数β_Lとから、例えば上述した式（１０３）〜式（１０５）を用いて浸漬ノズル６の左右での溶鋼の流速を求め、その比を偏流率ξとしてもよい。 Note that the ratio of the heat transfer coefficient β _R and the heat transfer coefficient β _L has been described as the drift rate ξ. From the heat transfer coefficient β _R and the heat transfer coefficient β _L determined in step S102, for example, the above-described formula (103 ) To Expression (105), the flow rate of the molten steel on the left and right of the immersion nozzle 6 may be obtained, and the ratio thereof may be the drift rate ξ.

浸漬ノズル６の左右での溶鋼の偏流への対策として、制御部１３は鋳造速度を減少させる（ステップＳ１０５）。鋳造速度を減少させるときは、２０％以上減少させる。鋳造速度を減少させることにより、鋳型４内での溶鋼の流動を抑え、浸漬ノズル６の左右での溶鋼の偏流を抑えることができる。 As a countermeasure against the drift of molten steel on the left and right of the immersion nozzle 6, the control unit 13 decreases the casting speed (step S105). When reducing the casting speed, reduce it by 20% or more. By reducing the casting speed, the flow of the molten steel in the mold 4 can be suppressed, and the drift of the molten steel on the left and right of the immersion nozzle 6 can be suppressed.

以上のように鋳造速度を減少させたときは、例えば一定時間経過した後に、元の鋳造速度に復帰（増大）させるようにすればよい。 As described above, when the casting speed is decreased, for example, after a predetermined time has elapsed, the original casting speed may be returned (increased).

或いは、鋳造速度を減少させたときは、その後、図１１に示す一連の処理を例えば定周期で実行するようにしてもよい。ステップＳ２０１〜Ｓ２０３までは、図１０のステップＳ１０１〜Ｓ１０３と同じである。そして、偏流率ξが所定の値以上となったか否かを判定する（ステップＳ２０４）。ここでいう所定の数値は、図１０でいう値と同程度の値でなく、浸漬ノズル６の左右での溶鋼の偏流が略確実になくなっていると考えられる値とする。本実施形態では、偏流率ξ≦１．２となっていればステップＳ２０５に進み、元の鋳造速度に復帰させるが、そうでなければ本処理を抜ける。元の鋳造速度に復帰させた後は、再び図１０に示す一連の処理を定周期で実行する。 Alternatively, when the casting speed is decreased, a series of processes shown in FIG. 11 may be executed at regular intervals, for example. Steps S201 to S203 are the same as steps S101 to S103 in FIG. Then, it is determined whether or not the drift rate ξ has become a predetermined value or more (step S204). The predetermined numerical value here is not a value similar to the value shown in FIG. 10, but a value that is considered to ensure that the drift of the molten steel on the left and right of the immersion nozzle 6 is almost certainly eliminated. In the present embodiment, if the drift rate ξ ≦ 1.2, the process proceeds to step S205 to return to the original casting speed. After returning to the original casting speed, the series of processes shown in FIG. 10 is executed again at a constant cycle.

以上のように、浸漬ノズル６を挟む左右位置での熱伝達係数β_Rと熱伝達係数β_Lとを比較することにより、浸漬ノズル６の左右での溶鋼の偏流状態を診断するものである。図１０（ａ）に示すように、浸漬ノズル６の中心から左右の鋳型短辺４Ｓの上端部までの鋳型幅方向距離をそれぞれＷ／２とした場合に、左右位置は、それぞれ浸漬ノズル６の中心からＷ／６以上離れた範囲で設定する。浸漬ノズル６からＷ／６までの範囲では、吐出孔６ａから吐出される溶鋼の流れが鋳型長辺４Ｌから離れており（図１０（ｂ）を参照）、浸漬ノズル６の左右での溶鋼の流速の差を捉えにくくなるためである。また、左右位置は、鋳型４のコーナから４０ｍｍ以上離れた範囲で設定する。鋳型４のコーナから４０ｍｍまでの範囲では、凝固シェル２の凝固遅れ等の外乱が発生しやすく、浸漬ノズル６の左右での溶鋼の流速の差を捉えにくくなるためである。 As described above, by comparing the heat transfer coefficient β _R and the heat transfer coefficient β _L at the left and right positions sandwiching the immersion nozzle 6, the drift state of the molten steel at the left and right of the immersion nozzle 6 is diagnosed. As shown in FIG. 10 (a), when the distance in the mold width direction from the center of the immersion nozzle 6 to the upper ends of the left and right mold short sides 4S is W / 2, the left and right positions are respectively the positions of the immersion nozzle 6. Set within the range of W / 6 or more from the center. In the range from the immersion nozzle 6 to W / 6, the flow of the molten steel discharged from the discharge hole 6a is away from the mold long side 4L (see FIG. 10B), and the molten steel on the left and right of the immersion nozzle 6 This is because it becomes difficult to detect the difference in flow velocity. The left and right positions are set within a range of 40 mm or more away from the corner of the mold 4. This is because in the range from the corner of the mold 4 to 40 mm, disturbance such as solidification delay of the solidified shell 2 is likely to occur, and it becomes difficult to grasp the difference in the flow rate of the molten steel between the left and right of the immersion nozzle 6.

また、熱伝達係数α_R、α_L及び熱伝達係数β_R、β_Lを決定する深さ位置は、メニスカスより１００ｍｍ以上深く、６００ｍｍ以下までの深さ範囲で設定する。メニスカスに近くなると、メニスカスでの反転流れの影響を受け、浸漬ノズル６の左右での溶鋼の流速の差を捉えにくくなるためである。また、浸漬ノズル６から深さ方向に離れると、浸漬ノズル６の左右での溶鋼の流速の差を捉えにくくなるためである。 The depth positions for determining the heat transfer coefficients α _R and α _L and the heat transfer coefficients β _R and β _L are set within a depth range of 100 mm or more and 600 mm or less from the meniscus. This is because when it is close to the meniscus, it is difficult to detect the difference in the flow velocity of the molten steel between the left and right of the immersion nozzle 6 due to the influence of the reverse flow at the meniscus. Moreover, it is because it will become difficult to catch the difference of the flow rate of the molten steel in the right and left of the immersion nozzle 6 if it leaves | separates from the immersion nozzle 6 in the depth direction.

表１に、各条件別の浸漬ノズル６の左右での溶鋼の偏流に起因するヘゲ・スリバー等の製品品質異常の発生率を示す。製品品質異常の発生率は、スラブ本数比率で表している。鋼種は低炭Ａｌ−Ｋ鋼であり、鋳造厚は２５０ｍｍ、鋳造幅は１２５０ｍｍ、鋳造速度は１．４ｍ／ｍｉｎとした。 Table 1 shows the occurrence rate of product quality abnormalities such as hege and sliver due to the drift of molten steel on the left and right of the immersion nozzle 6 for each condition. The incidence of product quality abnormalities is expressed as a ratio of the number of slabs. The steel type was low-carbon Al-K steel, the casting thickness was 250 mm, the casting width was 1250 mm, and the casting speed was 1.4 m / min.

表１に示すように、偏流率ξが１．５より小さければ、鋳造速度を１．４ｍ／ｍｉｎのままとしても製品品質異常の発生率を許容値（０．６％）以下とできるが、偏流率ξが１．５以上では、鋳造速度を１．４ｍ／ｍｉｎのままとすると発生率が許容値（０．６％）を超えてしまう。 As shown in Table 1, if the drift rate ξ is smaller than 1.5, the rate of product quality abnormality can be set to an allowable value (0.6%) or less even if the casting speed is kept at 1.4 m / min. If the drift rate ξ is 1.5 or more, the generation rate exceeds the allowable value (0.6%) if the casting speed is kept at 1.4 m / min.

偏流率ξが１．５以上の場合に、鋳造速度を１．３ｍ／ｍｉｎ（速度ダウン率７．１％）、１．２ｍ／ｍｉｎ（速度ダウン率１４．３％）に減少させると、発生率は低くなるものの、まだ許容値（０．６％）を超えている。それに対して、鋳造速度を１．１ｍ／ｍｉｎ（速度ダウン率２１．４％）、１．０ｍ／ｍｉｎ（速度ダウン率２８．６％）まで減少させると、偏流率ξが１．５、１．６、１．７、１．８いずれの場合でも発生率を許容値（０．６％）以下に抑えることができている。この結果から、偏流率ξが１．５以上の場合に、鋳造速度を２０％以上減少させるのが好適であることがわかる。 Generated when the casting speed is reduced to 1.3 m / min (speed down rate 7.1%) and 1.2 m / min (speed down rate 14.3%) when the drift rate ξ is 1.5 or more. Although the rate is low, it still exceeds the tolerance (0.6%). On the other hand, when the casting speed is reduced to 1.1 m / min (speed down rate 21.4%) and 1.0 m / min (speed down rate 28.6%), the drift rate ξ is 1.5, The occurrence rate can be suppressed to an allowable value (0.6%) or less in any case of .6, 1.7, 1.8. From this result, it is understood that it is preferable to reduce the casting speed by 20% or more when the drift rate ξ is 1.5 or more.

図１２は、本発明の連続鋳造の制御装置として機能しうる情報処理装置１００のハードウェアの概略構成の一例を示すブロック図である。この情報処理装置１００は、上述した演算処理を実行する中央処理装置であるＣＰＵ１０１、各種入力条件や演算結果等を表示する表示部１０２、演算結果等を保存するハードディスク等の記憶部１０３を有する。また、演算プログラム、各種アプリケーションプログラム、データ等を記憶するＲＯＭ（リードオンリーメモリ）１０４を有する。また、演算プログラムに基づいてＣＰＵ１０１が処理を行うときに用いる作業領域であるＲＡＭ（ランダムアクセスメモリ）１０５、及びキーボード、マウス等の入力部１０６等を有する。 FIG. 12 is a block diagram showing an example of a schematic configuration of hardware of the information processing apparatus 100 that can function as the continuous casting control apparatus of the present invention. The information processing apparatus 100 includes a CPU 101 that is a central processing unit that performs the above-described arithmetic processing, a display unit 102 that displays various input conditions, calculation results, and the like, and a storage unit 103 such as a hard disk that stores calculation results and the like. Further, it has a ROM (Read Only Memory) 104 for storing arithmetic programs, various application programs, data and the like. In addition, it has a RAM (Random Access Memory) 105 which is a work area used when the CPU 101 performs processing based on the arithmetic program, and an input unit 106 such as a keyboard and a mouse.

また、コンピュータ装置を連続鋳造の制御装置として機能させるためのプログラムは本発明を構成する。プログラムを供給するための記憶媒体としては、例えば、フレキシブルディスク、ハードディスク、光ディスク、光磁気ディスク、ＣＤ−ＲＯＭ、ＣＤ−Ｒ、磁気テープ、不揮発性のメモリカード、ＲＯＭ等を用いることができる。 Moreover, the program for functioning a computer apparatus as a control apparatus of continuous casting comprises this invention. As a storage medium for supplying the program, for example, a flexible disk, a hard disk, an optical disk, a magneto-optical disk, a CD-ROM, a CD-R, a magnetic tape, a nonvolatile memory card, a ROM, or the like can be used.

以上、本発明を種々の実施形態と共に説明したが、本発明はこれらの実施形態にのみ限定されるものではなく、本発明の範囲内で変更等が可能である。例えば上記実施形態では測温手段として熱電対を用いているが、例えば特許文献３にあるような光ファイバーグレーティングセンサー（ＦＢＧ：ＦｉｂｅｒＢｒａｇｇＧｒａｔｉｎｇ）や特許文献４にあるようなラマン散乱型光ファイバ式分布型温度計測器等を用いてもよい。 As mentioned above, although this invention was demonstrated with various embodiment, this invention is not limited only to these embodiment, A change etc. are possible within the scope of the present invention. For example, in the above embodiment, a thermocouple is used as a temperature measuring means. For example, an optical fiber grating sensor (FBG) as described in Patent Document 3 or a Raman scattering type optical fiber distribution as described in Patent Document 4 is used. A mold temperature measuring instrument or the like may be used.

また、上記実施形態では、鋳型長辺４Ｌのうち一方を対象にして説明したが、他方の鋳型長辺４においても、浸漬ノズル６の左右での溶鋼の偏流状態を診断してもよいことは明らかである。 Moreover, in the said embodiment, although demonstrated considering one side among the mold long sides 4L, it is possible to diagnose the drift state of the molten steel in the left and right of the immersion nozzle 6 also in the other mold long side 4. it is obvious.

１：溶鋼
２：凝固シェル
３：モールドパウダー層
４：鋳型銅板
５、５ａ、５ｂ、５ｃ、５ｄ：熱電対
６：浸漬ノズル
１１：熱流束取得部
１２：熱伝達係数決定部
１３：制御部 1: Molten steel 2: Solidified shell 3: Mold powder layer 4: Mold copper plate 5, 5a, 5b, 5c, 5d: Thermocouple 6: Immersion nozzle 11: Heat flux acquisition unit 12: Heat transfer coefficient determination unit 13: Control unit

Claims

Molten steel is discharged from the immersion nozzle located in the center of the mold toward the left and right mold short sides, and there are solidified shell, mold powder layer, and mold thermal conductors between the molten steel and the cooling water for the mold. In continuous casting, the heat transfer coefficient α between the solidified shell and the mold and the heat transfer coefficient β between the molten steel and the solidified shell are obtained, and the continuous casting is controlled based on these heat transfer coefficients α and β. A continuous casting method,
A heat flux acquisition procedure for acquiring a heat flux passing through the mold by using a plurality of temperature measuring means embedded in the long side of the mold at different positions in the left and right positions sandwiching the immersion nozzle,
The heat transfer coefficient α _R and the heat at the right position are calculated using the equation representing the heat flux passing through the mold, including the heat transfer coefficient α and the heat transfer coefficient β, and the heat flux acquired in the heat flux acquisition procedure. A heat transfer coefficient determination procedure for simultaneously determining the heat transfer coefficient β _R and simultaneously determining the heat transfer coefficient α _L and the heat transfer coefficient β _L at the left position;
The heat transfer coefficient α _R and α _L determined in the heat transfer coefficient determination procedure are both 500 to 50000 W / m ² · K, and the ratio of the heat transfer coefficient β _R and the heat transfer coefficient β _L , or A control procedure for reducing the casting speed when the ratio of the flow rate of the molten steel determined from the heat transfer coefficient β _R and the flow rate of the molten steel determined from the heat transfer coefficient β _L exceeds a predetermined value. Continuous casting method.

The temperature measuring means at the left and right positions are arranged symmetrically across the immersion nozzle,
When the mold width direction distance from the center of the immersion nozzle to the left and right mold short sides is W / 2, respectively, the left and right positions are positions separated from the center of the immersion nozzle by W / 6 or more, and The continuous casting method according to claim 1, wherein the continuous casting method is located at a position 40 mm or more away from a corner of the mold.

In the control procedure, when the value obtained by dividing the larger one of the heat transfer coefficients β _R and β _L by the smaller one becomes 1.5 or more, the casting speed is decreased. The continuous casting method described.

The continuous casting method according to any one of claims 1 to 3, wherein the casting speed is reduced by 20% or more in the control procedure.

In the heat transfer coefficient determination procedure,
T is the temperature of the solidified shell, T ₀ is the temperature of the molten steel, T _s is the interface temperature between the molten steel and the solidified shell, u is the casting speed, λ _s is the thermal conductivity of the solidified shell, c _s is the specific heat of the solidified shell, ρ _s is the density of the solidified shell, L is the latent heat of the solidified shell, d is the distance from the surface of the solidified shell side of the mold to the temperature measuring means, and λ _m is the thermal conductivity of the mold.
The solidified shell thickness s (z, t) and the solidified shell mold-side surface temperature T (0, z, t) on a two-dimensional coordinate with the casting direction z-axis and the direction orthogonal to the casting direction x-axis. And a formula representing the heat flux q _m (z, t) passing through the mold based on the heat balance between the surface of the solidified shell on the mold side, the mold powder layer, and the thermocouple. 5. The heat transfer coefficient α and the heat transfer coefficient β are simultaneously determined using (C) and the thickness s (z, t) of the solidified shell is calculated. The continuous casting method described in 1.

In the heat flux acquisition procedure,
d _w is the distance from the temperature measuring means to the water cooling position, h _w is the heat transfer coefficient between the mold and the cooling water, T _w is the cooling water temperature, and λ _m is the thermal conductivity of the mold.
The heat flux q _m (z, t) passing through the mold is calculated from the equation (D) based on the temperature measurement values T _{m — obs} (z, t) of the plurality of temperature measuring means. 6. The continuous casting method according to any one of 1 to 5.

Molten steel is discharged from the immersion nozzle located in the center of the mold toward the left and right mold short sides, and there are solidified shell, mold powder layer, and mold thermal conductors between the molten steel and the cooling water for the mold. In continuous casting, the heat transfer coefficient α between the solidified shell and the mold and the heat transfer coefficient β between the molten steel and the solidified shell are obtained, and the continuous casting is controlled based on these heat transfer coefficients α and β. A control device for continuous casting,
A heat flux acquisition means for acquiring a heat flux passing through the mold using a plurality of temperature measuring means embedded in the casting mold in the left and right positions sandwiching the immersion nozzle in the casting direction.
The heat transfer coefficient α _R and the heat at the right position are calculated using an expression that includes the heat transfer coefficient α and the heat transfer coefficient β and represents the heat flux passing through the mold and the heat flux acquired by the heat flux acquisition means. A heat transfer coefficient determining means for simultaneously determining the heat transfer coefficient β _R and simultaneously determining the heat transfer coefficient α _L and the heat transfer coefficient β _L at the left position;
The heat transfer coefficients α _R and α _L determined by the heat transfer coefficient determining means are both 500 to 50000 W / m ² · K, and the ratio of the heat transfer coefficient β _R and the heat transfer coefficient β _L , or And a control means for reducing the casting speed when the ratio of the flow rate of the molten steel obtained from the heat transfer coefficient β _R and the flow rate of the molten steel obtained from the heat transfer coefficient β _L exceeds a predetermined value. Continuous casting control device.

Molten steel is discharged from the immersion nozzle located in the center of the mold toward the left and right mold short sides, and there are solidified shell, mold powder layer, and mold thermal conductors between the molten steel and the cooling water for the mold. In continuous casting, the heat transfer coefficient α between the solidified shell and the mold and the heat transfer coefficient β between the molten steel and the solidified shell are obtained, and the continuous casting is controlled based on these heat transfer coefficients α and β. A program for
A heat flux acquisition process for acquiring a heat flux passing through the mold, using a plurality of temperature measuring means embedded in the mold long side with the position shifted in the casting direction in each of the left and right positions sandwiching the immersion nozzle,
The heat transfer coefficient α _R and the heat at the right position are calculated using the equation representing the heat flux passing through the mold, including the heat transfer coefficient α and the heat transfer coefficient β, and the heat flux acquired in the heat flux acquisition process. A heat transfer coefficient determination process for simultaneously determining the heat transfer coefficient β _R and simultaneously determining the heat transfer coefficient α _L and the heat transfer coefficient β _L at the left position;
The heat transfer coefficients α _R and α _L determined in the heat transfer coefficient determination process are both 500 to 50000 W / m ² · K, and the ratio of the heat transfer coefficient β _R and the heat transfer coefficient β _L , or When the ratio of the molten steel flow velocity obtained from the heat transfer coefficient β _R and the molten steel flow velocity obtained from the heat transfer coefficient β _L differs by more than a predetermined value, the computer executes control processing to reduce the casting speed. Program.