JPH06285606A - Method for continuously casting steel - Google Patents

Abstract

PURPOSE:To make possible the uniform growth of solidified shell at an initial period for any kind of steel and to produce a cast slab without surface defect. CONSTITUTION:Plural heaters 2 are arranged in the necessary range of the casting direction containing the neighborhood of meniscus in a mold 1. Plural thermocouples 3 are arranged between these heaters 2 and the inner surface of the mold 1. During continuous casting operation, while allowing high temp. and high pressure cooling water to flow in a mold 1, the temps. in the inner surface of the mold 1 are measured with the thermocouples 3 and these measured values are outputted to a control panel 4. The calorific quantity of the heater 2 is controlled through the control panel 4 so as to become the optimum heat flux decided in advance according to the kind of steel based on the temp. distribution in the casting direction in the inner surface of the mold 1 obtd. from the measured values.

Description

【発明の詳細な説明】Detailed Description of the Invention

【０００１】[0001]

【産業上の利用分野】本発明は、鋳片における表面欠陥
の発生を可及的に防止可能な鋼の連続鋳造方法に関する
ものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous casting method for steel capable of preventing the occurrence of surface defects in a slab as much as possible.

【０００２】[0002]

【従来の技術】鋼の連続鋳造において、鋳片の表面品質
を向上させるためには、鋳片の表面縦割れや横割れとい
った表面欠陥の発生を防止する必要がある。これには、
鋳片における表面形成を支配する初期凝固の制御技術を
確立する必要があり、従来、高融点モールド・パウダの
使用、セラミック等の低熱伝導率材料の鋳型表面めっ
き、鋳型材料として低熱伝導材料の採用、鋳型内に発熱
体を埋設する等による鋳型の緩冷却化技術が実施され、
また提案されてきた。2. Description of the Related Art In continuous casting of steel, in order to improve the surface quality of a slab, it is necessary to prevent surface defects such as surface vertical cracks and lateral cracks of the slab. This includes
It is necessary to establish a technique for controlling the initial solidification that controls the surface formation in the slab. Conventionally, high melting point mold powder was used, mold surface plating of low thermal conductivity material such as ceramics, adoption of low heat conductive material as mold material , Gentle mold cooling technology by embedding a heating element in the mold, etc.,
It has also been proposed.

【０００３】例えば、特開昭６２−２２４５５号公報で
提案された技術は、鋳型冷却板内あるいはその裏面のメ
ニスカス近傍にヒータ及び熱電対を設置し、鋳型メニス
カス部の加熱温度を制御しようとするものである。すな
わち、メニスカス部近傍の鋳型抜熱量をヒータへの印加
電流の増減により調節することにより、鋳型全体の抜熱
量を低下させることなく鋳型内における抜熱量の調整を
可能とし、鋳造状況の変化に即時に対応させようとする
のである。For example, in the technique proposed in Japanese Patent Laid-Open No. 62-22455, a heater and a thermocouple are installed in the mold cooling plate or near the meniscus on the back surface of the mold to control the heating temperature of the mold meniscus. It is a thing. That is, by adjusting the heat removal amount of the mold near the meniscus by increasing or decreasing the current applied to the heater, it is possible to adjust the heat removal amount in the mold without lowering the heat removal amount of the entire mold, and to immediately respond to changes in the casting situation. It tries to correspond to.

【０００４】[0004]

【発明が解決しようとする課題】ところで、鋼の初期凝
固形態は、通常デンドライト状であるが、このデンドラ
イト組織で形成される凝固殻の固相率が０．６以下の範
囲では凝固殻に強度がないので、鋳片表面の縦割れや横
割れの原因とはならず、固相率が０．６〜０．８となっ
て初めて凝固殻に強度が出現する。この場合、凝固殻の
成長が不均一であると、鋳片の表面割れが発生する。し
たがって、特開昭６２−２２４５５号公報で提案されて
いる技術のように、鋳型内のメニスカス近傍のみを単に
加熱して抜熱量を低下させるものでは、鋳片表面割れの
発生防止の根本的な対策とは言いがたい。The initial solidification morphology of steel is usually dendrite-like, but when the solid fraction of the solidified shell formed by this dendrite structure is 0.6 or less, the strength of the solidified shell is high. Since it does not exist, it does not cause vertical cracking or lateral cracking on the surface of the slab, and the strength appears in the solidified shell only when the solid fraction reaches 0.6 to 0.8. In this case, if the growth of the solidified shell is uneven, surface cracking of the slab occurs. Therefore, as in the technique proposed in Japanese Patent Application Laid-Open No. 62-22455, when only the vicinity of the meniscus in the mold is heated to reduce the heat removal amount, it is fundamental to prevent the occurrence of slab surface cracking. It is hard to say that it is a countermeasure.

【０００５】また、鋳型内メニスカス近傍で形成される
初期凝固殻は溶質再配分及び相変態を伴いながら成長す
るので、溶質再配分あるいは相変態が完了し、初期凝固
殻が均一な溶質濃度あるいは晶出相となるように鋼種に
対応した初期凝固殻成長時の鋳型抜熱量を最適化する必
要もある。Since the initial solidified shell formed near the meniscus in the mold grows with solute redistribution and phase transformation, solute redistribution or phase transformation is completed and the initial solidified shell has a uniform solute concentration or crystal. It is also necessary to optimize the amount of heat removed from the mold during the initial solidified shell growth corresponding to the steel type so as to be in the phase.

【０００６】さらに、包晶鋼やステンレス鋼に代表され
るような、凝固過程でδ／γ変態が介在する鋼種におい
ては、δ相とγ相の凝固収縮率及び機械的性質が異なる
ため、初期凝固を制御することは困難である。Further, in steel types such as peritectic steel and stainless steel in which the δ / γ transformation is involved in the solidification process, the solidification shrinkage ratio and mechanical properties of the δ phase and the γ phase are different from each other. Controlling coagulation is difficult.

【０００７】本発明は上記した従来の連続鋳造方法にあ
った問題点に鑑みてなされたものであり、初期凝固殻の
均一成長が可能となるように鋳型内抜熱量を最適に制御
できる連続鋳造方法を提供することを目的としている。The present invention has been made in view of the problems in the above-mentioned conventional continuous casting method, and continuous casting capable of optimally controlling the heat removal amount in the mold so that the initial solidified shell can be uniformly grown. It is intended to provide a way.

【０００８】[0008]

【課題を解決するための手段】上記した目的を達成する
ために、本発明の連続鋳造方法は、鋳型内におけるメニ
スカス近傍を含む鋳込み方向所要範囲内にヒータを複数
設置するとともに、これらヒータと鋳型内面の間に複数
の熱電対を設け、連続鋳造中、鋳型内に高温高圧の冷却
水を流しつつ、前記熱電対で鋳型内面の温度を測定し、
これら測定値によって求められる鋳型内面鋳込み方向の
温度分布に基づき、鋼種によって予め求めてある最適熱
流束となるようにヒータの発熱量を制御することとして
いるのである。In order to achieve the above-mentioned object, the continuous casting method of the present invention is to install a plurality of heaters within a required casting direction range including the vicinity of a meniscus in a mold, and to provide the heater and the mold. Providing a plurality of thermocouples between the inner surface, during continuous casting, while flowing high-temperature high-pressure cooling water in the mold, measuring the temperature of the mold inner surface with the thermocouple,
Based on the temperature distribution in the casting direction of the inner surface of the mold obtained from these measured values, the heat generation amount of the heater is controlled so that the optimum heat flux is obtained in advance depending on the steel type.

【０００９】[0009]

【作用】本発明の連続鋳造方法では、連続鋳造中、鋳型
内に高温高圧の冷却水を流しつつ、鋼種によって予め求
めてある最適熱流束となるようにヒータの発熱量を制御
するので、鋼種に応じた最適の鋳型内鋳込み方向の熱流
束で連続鋳造がおこなえる。In the continuous casting method of the present invention, during continuous casting, while the cooling water of high temperature and high pressure is made to flow in the mold, the calorific value of the heater is controlled so as to obtain the optimum heat flux previously determined by the steel type. Continuous casting can be performed with the optimum heat flux in the casting direction according to the above.

【００１０】[0010]

【実施例】以下、本発明方法を添付図面に示す１実施例
に基づいて説明する。図１は本発明方法を実施する鋳型
の構造の１例を模式的に示す図面である。図１におい
て、１は鋳型であり、その内部におけるメニスカス近傍
を含む鋳込み方向所要範囲に、小径の金属シース型ヒー
タ２を多数設置し、さらにこの多数のヒータ２と鋳型１
の内面の間には、鋳型１の内面温度を測定するための熱
電対３を設置している。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method of the present invention will be described below with reference to an embodiment shown in the accompanying drawings. FIG. 1 is a drawing schematically showing an example of the structure of a mold for carrying out the method of the present invention. In FIG. 1, reference numeral 1 denotes a mold, in which a large number of small-diameter metal sheath type heaters 2 are installed in a required range in the casting direction including the vicinity of a meniscus.
A thermocouple 3 for measuring the temperature of the inner surface of the mold 1 is installed between the inner surfaces of the.

【００１１】そして、これら多数のヒータ２と熱電対３
はそれぞれ鋳型１外部の制御盤４に接続されている。こ
の制御盤４には、予め連続鋳造する溶鋼５の鋼種ごとの
鋳型１内鋳込み方向における最適熱流束が入力されてお
り、鋳型内に高温高圧の冷却水を流しつつ連続鋳造する
際に、タンディッシュから浸漬ノズル６を介して鋳型１
内に鋳込まれる鋼種を入力されることにより、熱電対３
から入力されてくる測定温度からの温度分布に基づい
て、鋳型１内が連続鋳造される鋼種の最適熱流束と成る
ようにヒータ２の発熱量を制御するのである。Then, these many heaters 2 and thermocouples 3
Are respectively connected to the control panel 4 outside the mold 1. The optimum heat flux in the casting direction in the mold 1 for each steel type of the molten steel 5 to be continuously cast in advance is input to the control board 4, and when the continuous casting is performed while the high-temperature and high-pressure cooling water is allowed to flow in the mold, the Mold 1 from dish through immersion nozzle 6
By inputting the type of steel to be cast inside, the thermocouple 3
The heat generation amount of the heater 2 is controlled so that the inside of the mold 1 has the optimum heat flux of the continuously cast steel type based on the temperature distribution from the measured temperature input from the.

【００１２】本発明は上記したようにして連続鋳造する
方法であり、次に、本発明方法の効果を確認するために
行った実験結果について説明する。先ず、本発明方法及
び従来方法の双方を対象として、溶鋼５と鋳型１間を通
過する熱流束に及ぼす鋳型１内に設置したヒータ２の加
熱量、冷却水の温度、微細凹凸処理めっきの影響を熱伝
導計算によって評価した。The present invention is a method of continuous casting as described above. Next, the results of experiments conducted to confirm the effect of the method of the present invention will be described. First, for both the method of the present invention and the conventional method, the influence of the heating amount of the heater 2 installed in the mold 1, the temperature of the cooling water, and the fine unevenness treatment plating on the heat flux passing between the molten steel 5 and the mold 1. Was evaluated by heat conduction calculation.

【００１３】図２に定常状態時の熱流束と冷却水温度の
関係を示す。図２に示す結果は、計算条件として、鋳型
厚み１５ｍｍ、シース型ヒータ２の設置位置は、鋳型１
の上端より５０ｍｍの位置から鋳込み方向に５０ｍｍピ
ッチで４個づつで、かつ、鋳型内面から５ｍｍの位置、
熱電対３の設置位置は、前記した設置位置のヒータ２の
鋳型内面寄り３ｍｍの位置、溶鋼５の温度は１５５０
℃、鋳型１の背面は水冷されているものとし、定常状態
になるまで計算したものである。また、ヒータ２の加熱
量は０Ｗ／ｍ³ 及び４．２×１０⁹ Ｗ／ｍ³ の場合の結
果であり、冷却水は６ｋｇ／ｃｍ² の圧力で、その温度
は３０〜１００℃の間で変化させた。なお、溶鋼５と鋳
型１間の熱伝達係数は、一般に連続鋳造の凝固解析で用
いられている４．２×１０² Ｗ／ｍ² ℃を使用して試算
した。FIG. 2 shows the relationship between the heat flux and the cooling water temperature in the steady state. The results shown in FIG. 2 show that, as calculation conditions, the mold thickness is 15 mm, the installation position of the sheath type heater 2 is the mold 1
From the position 50 mm from the upper end of the mold, four at a pitch of 50 mm in the casting direction, and 5 mm from the inner surface of the mold.
The installation position of the thermocouple 3 is 3 mm closer to the inner surface of the mold of the heater 2 at the installation position described above, and the temperature of the molten steel 5 is 1550.
C., the back of the mold 1 is assumed to be water-cooled, and calculations are performed until a steady state is reached. The heating amount of the heater 2 is the result when the heating amount is 0 W / m ³ and 4.2 × 10 ⁹ W / m ³ , and the cooling water has a pressure of 6 kg / cm ² and the temperature is between 30 and 100 ° C. Changed. The heat transfer coefficient between the molten steel 5 and the mold 1 was calculated by using 4.2 × 10 ² W / m ² ° C which is generally used in solidification analysis of continuous casting.

【００１４】従来の鋳型冷却の場合に相当するヒータ２
の加熱量０Ｗ／ｍ³ で、冷却水温度を３０℃とした場
合、定常状態時の熱流束は６．２×１０⁵ Ｗ／ｍ² とな
る。そして、この場合、冷却水温度を上げると熱流束は
減少し、冷却水温度が１００℃の時熱流束は６．０×１
０⁵ Ｗ／ｍ² となる。A heater 2 corresponding to the conventional mold cooling case.
When the heating amount is 0 W / m ³ and the cooling water temperature is 30 ° C., the heat flux in the steady state is 6.2 × 10 ⁵ W / m ² . Then, in this case, when the cooling water temperature is increased, the heat flux decreases, and when the cooling water temperature is 100 ° C., the heat flux is 6.0 × 1.
It becomes 0 ⁵ W / m ² .

【００１５】冷却水温度を３０℃とし、ヒータ２の加熱
量を４．２×１０⁹ Ｗ／ｍ³ とすると、熱流束は５．６
×１０⁵ Ｗ／ｍ² となり、ヒータ２で加熱しない場合と
比較して１０％程度小さくなる。また、ヒータ２の加熱
量を４．２×１０⁹ Ｗ／ｍ³とし、冷却水温度を１００
℃とすると、熱流束は５．４×１０⁵ Ｗ／ｍ² となる。When the cooling water temperature is 30 ° C. and the heating amount of the heater 2 is 4.2 × 10 ⁹ W / m ³ , the heat flux is 5.6.
× 10 ⁵ W / m ² , which is about 10% smaller than the case where the heater 2 does not heat. Further, the heating amount of the heater 2 is set to 4.2 × 10 ⁹ W / m ³ , and the cooling water temperature is set to 100
At a temperature of ℃, the heat flux is 5.4 × 10 ⁵ W / m ² .

【００１６】上記した試算結果に基づき、鋳型１内に６
ｋｇ／ｃｍ² の圧力で７０℃の冷却水を流しつつ、表１
に示す化学成分の包晶鋼を鋳込んだ。そして、その際、
熱電対３で鋳型１内面の鋳込み方向の温度を測定し、こ
れら温度を制御盤４に出力して制御盤４で鋳型内面鋳込
み方向の温度分布を求め、上記したような試算によって
予め求めてある表１の包晶鋼の最適熱流束となるよう
に、ヒータの発熱量を０〜４．２×１０⁹ Ｗ／ｍ³ の範
囲で制御した。なお、鋳造速度は２ｍ／ｍｉｎで行っ
た。Based on the above-mentioned trial calculation results, 6 pieces are placed in the mold 1.
While flowing cooling water of 70 ° C at a pressure of kg / cm ² ,
Peritectic steel with the chemical composition shown in was cast. And at that time,
The temperature in the casting direction on the inner surface of the mold 1 is measured by the thermocouple 3, these temperatures are output to the control panel 4, and the temperature distribution in the casting direction on the inner surface of the mold is determined by the control panel 4, and is calculated in advance by the trial calculation as described above. The heat value of the heater was controlled in the range of 0 to 4.2 × 10 ⁹ W / m ³ so that the optimum heat flux of the peritectic steel in Table 1 was obtained. The casting speed was 2 m / min.

【００１７】[0017]

【表１】 [Table 1]

【００１８】図３は上記した実験時における定常状態時
の熱流束と鋳片表面割れ発生率の関係を示す。図３中の
○印は従来方法による結果を、また、●印は本発明方法
による結果を示す。従来の連続鋳造方法で鋳造された鋳
片表面の縦割れ発生率は０．１％前後であったが、本発
明方法を用いた場合は、０．０３％程度に抑制できた。FIG. 3 shows the relationship between the heat flux and the slab surface crack occurrence rate in the steady state during the above-mentioned experiment. In FIG. 3, ◯ marks show the results by the conventional method, and ● marks show the results by the method of the present invention. The rate of occurrence of vertical cracks on the surface of the slab cast by the conventional continuous casting method was about 0.1%, but when the method of the present invention was used, it could be suppressed to about 0.03%.

【００１９】[0019]

【発明の効果】以上説明したように、本発明方法によれ
ば、鋼種に応じた最適の鋳型内鋳込み方向の熱流束で連
続鋳造がおこなえるので、どのような鋼種であっても初
期凝固殻の均一成長が可能となり、表面欠陥のない鋳片
が製造できる。As described above, according to the method of the present invention, continuous casting can be performed with an optimum heat flux in the casting direction in the mold according to the steel type, so that no matter what kind of steel the initial solidified shell Uniform growth is possible, and a slab with no surface defects can be manufactured.

【図面の簡単な説明】[Brief description of drawings]

【図１】本発明方法を実施する鋳型の構造の１例を模式
的に示す図面である。FIG. 1 is a drawing schematically showing an example of the structure of a mold for carrying out the method of the present invention.

【図２】定常状態時の熱流束と冷却水温度の関係を示す
図である。FIG. 2 is a diagram showing a relationship between a heat flux and a cooling water temperature in a steady state.

【図３】実験時における定常状態時の熱流束と鋳片表面
割れ発生率の関係を示す図である。FIG. 3 is a diagram showing a relationship between a heat flux and a slab surface crack occurrence rate in a steady state during an experiment.

【符号の説明】[Explanation of symbols]

１ 鋳型 ２ ヒータ ３ 熱電対 ４ 制御盤 1 Mold 2 Heater 3 Thermocouple 4 Control panel

Claims (1)

【特許請求の範囲】[Claims] 【請求項１】 鋳型内におけるメニスカス近傍を含む鋳
込み方向所要範囲内にヒータを複数設置するとともに、
これらヒータと鋳型内面の間に複数の熱電対を設け、連
続鋳造中、鋳型内に高温高圧の冷却水を流しつつ、前記
熱電対で鋳型内面の温度を測定し、これら測定値によっ
て求められる鋳型内面鋳込み方向の温度分布に基づき、
鋼種によって予め求めてある最適熱流束となるようにヒ
ータの発熱量を制御することを特徴とする鋼の連続鋳造
方法。1. A plurality of heaters are installed within a required range in the casting direction including the vicinity of the meniscus in the mold, and
A plurality of thermocouples are provided between these heaters and the inner surface of the mold, during continuous casting, while flowing cooling water of high temperature and high pressure in the mold, the temperature of the inner surface of the mold is measured by the thermocouple, and the mold is determined by these measured values. Based on the temperature distribution in the inner surface casting direction,
A continuous casting method for steel, characterized in that the amount of heat generated by a heater is controlled so that the optimum heat flux is obtained in advance depending on the type of steel.