JP2006192439A - Method for preventing clogging of nozzle in continuous casting for steel - Google Patents

Method for preventing clogging of nozzle in continuous casting for steel Download PDF

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JP2006192439A
JP2006192439A JP2005003481A JP2005003481A JP2006192439A JP 2006192439 A JP2006192439 A JP 2006192439A JP 2005003481 A JP2005003481 A JP 2005003481A JP 2005003481 A JP2005003481 A JP 2005003481A JP 2006192439 A JP2006192439 A JP 2006192439A
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femn
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fesi
fecr
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JP4460462B2 (en
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Toshiaki Mizoguchi
利明 溝口
Yu Watanabe
祐 渡辺
Hiroyoshi Nakajima
弘喜 中島
Jun Yamaguchi
純 山口
Shigekazu Matsuba
繁和 松葉
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Nippon Steel Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for achieving a stable continuous casting operation without clogging a ladle nozzle and an immersion nozzle. <P>SOLUTION: A method for preventing the clogging of the nozzle, is performed as the followings, by which FeSi, FeMn, FeP, FeCr alloys are added into molten steel exceeding 50 ppm soluble oxygen concentration so as to become ≥80% of the aimed concentration shown with mass% in each element to the aimed Si, Mn, P, Cr concentrations in a molten steel in a tundish or a cast slab. Further, the method for preventing the clogging of the nozzle, is performed as the followings, in which total Ca mixed quantity from these alloys is limited so that the charging quantity of the added FeSi, FeMn, FeP, FeCr alloys satisfies the following formula (A) after Al-deoxidation. That is, the above (A) formula is Total Ca mixed quantity=(0.5×W<SB>FeSi</SB>×Ca<SB>FeSi</SB>/100+0.01×W<SB>FeMn</SB>×Ca<SB>FeMn</SB>/100+0.02×W<SB>FeP</SB>×Ca<SB>FeP</SB>/100+0.005×W<SB>FeCr</SB>×Ca<SB>FeCr</SB>/100)/W<SB>steel</SB>×10<SP>6</SP>≤6. Wherein, W<SB>i</SB>(kg) is added quantity of i alloy after Al deoxidation, W<SB>steel</SB>(kg) is molten steel quantity and Ca<SB>i</SB>(mass%) is Ca concentration in the ferro-alloy i. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は鋼の連続鋳造において、鍋ノズルや浸漬ノズルで発生するノズル詰りを防止する方法に関するものである。   The present invention relates to a method for preventing nozzle clogging generated in a pan nozzle or an immersion nozzle in continuous casting of steel.

ノズルの詰まり防止については従来から様々な検討がなされており、多数の特許が出願されている。例えば特許文献１には、ノズル内壁からの不活性ガスの吹き込みによりノズルの詰まりを防止する方法が開示されている。また特許文献２には、ノズルの材質を工夫することにより、ノズルの詰まりを防止する方法が開示されている。また特許文献３には、浸漬ノズル耐火物を透過する空気を遮断することにより、ノズルの詰まりを防止する方法が開示されている。また特許文献４には、介在物の組成を制御することにより、ノズルの詰まりを防止する方法が開示されている。また特許文献５には、浸漬ノズル近傍の溶鋼中Ｓ低減により溶鋼の界面張力を制御し、ノズルの詰まりを防止する方法が開示されている。しかしそのような多くの工夫がなされてきたにもかかわらず、溶鋼の種類や操業方法によってはノズル詰まりが発生し、生産に支障を来たすことがある。
特開昭５２−５７０２４号公報 特開平５−９６３４８号公報 特開２０００−２０５１５１号公報 特開２００１−６４７１８号公報 特開２００３−２９０８８６号公報 特開平９−１９２７９９号公報 Various studies have been made to prevent nozzle clogging, and many patents have been filed. For example, Patent Document 1 discloses a method of preventing nozzle clogging by blowing inert gas from the nozzle inner wall. Patent Document 2 discloses a method for preventing nozzle clogging by devising the material of the nozzle. Patent Document 3 discloses a method for preventing clogging of the nozzle by blocking the air that passes through the immersion nozzle refractory. Patent Document 4 discloses a method for preventing nozzle clogging by controlling the composition of inclusions. Patent Document 5 discloses a method for preventing clogging of the nozzle by controlling the interfacial tension of the molten steel by reducing S in the molten steel near the immersion nozzle. However, in spite of many such efforts, nozzle clogging may occur depending on the type of molten steel and the operation method, which may hinder production.
JP-A 52-57024 JP-A-5-96348 JP 2000-205151 A JP 2001-64718 A JP 2003-290886 A JP-A-9-192799

従って本発明の目的は、鍋ノズルや浸漬ノズルでの詰まりのない安定した連続鋳造操業を達成するための方法を提供することである。   Accordingly, an object of the present invention is to provide a method for achieving a stable continuous casting operation free from clogging with a pan nozzle or an immersion nozzle.

本発明者はノズル詰まりの発生メカニズムについて検討し、溶鋼中のCa濃度が６ppmよりも高まると溶鋼中のアルミナ粒子表面が固液共存状態となり、これがバインダーとなってクラスター状の粗大介在物が生成され、ノズル内壁に付着してノズル詰まりを招くことを解明した。さらにアルミキルド鋼での実鋳造の詳細な解析を行った結果、ノズル内壁付着物はアルミナであり、アルミナ内部に微量のCaOを含有する場合が多いこと、Caの起源が成分調整用に溶鋼に添加されるフェロ合金に不可避的に含まれる微量Caであることを知った。   The present inventor examined the mechanism of nozzle clogging, and when the Ca concentration in the molten steel was higher than 6 ppm, the alumina particle surface in the molten steel became a solid-liquid coexistence state, which became a binder and produced cluster-like coarse inclusions. It was elucidated that it adhered to the inner wall of the nozzle and caused nozzle clogging. Furthermore, as a result of detailed analysis of actual casting with aluminum killed steel, the deposit on the inner wall of the nozzle is alumina, and the alumina often contains a small amount of CaO, and the origin of Ca is added to the molten steel for component adjustment I learned that it is a trace amount of Ca inevitably contained in ferroalloys.

なお溶鋼中のCa濃度とノズル詰まりとの間に関係があることは、特許文献６にも開示されているが、特許文献６に記載の発明はアルミナ粒子のバインダーとなるP2O5をCaで還元するという内容であり、成分調整用に溶鋼に添加されるフェロ合金に着目したものでも、Caによるアルミナ粒子のクラスター化を防止しようとするものでもない。 The relationship between the Ca concentration in molten steel and nozzle clogging is also disclosed in Patent Document 6, but the invention described in Patent Document 6 uses P 2 O 5 as a binder for alumina particles as Ca. It is not intended to prevent clustering of alumina particles due to Ca, nor is it focused on ferroalloys added to molten steel for component adjustment.

上記の知見に基づいてなされた請求項１の発明は、タンディッシュ溶鋼または鋳片における目標Si、Mn、P、Cr濃度に対し、各元素の質量%で表される目標濃度の80%以上になるように、不可避不純物として0.5質量%以上のCaを含有するFeSi、FeMn、FeP、FeCr合金の内、添加合金量の多いほうから少なくとも2つ以上の合金を、溶存酸素濃度が50ppmを超える溶鋼に添加することを特徴とするものである。   The invention according to claim 1 made based on the above knowledge is more than 80% of the target concentration expressed by mass% of each element with respect to the target Si, Mn, P, Cr concentration in the tundish molten steel or slab. As such, at least two of the FeSi, FeMn, FeP, and FeCr alloys containing 0.5 mass% or more of Ca as unavoidable impurities in the larger amount of alloy added, the molten steel having a dissolved oxygen concentration exceeding 50 ppm It is characterized by adding to the above.

また同一の課題を解決するためになされた請求項２の発明は、Al脱酸後に添加するFeSi、FeMn、FeP、FeCr合金の投入量が下記(A)式を満足するように、当該合金からのCa総混入量を制限することを特徴とするものである。
Ca総混入量=(0.5・WFeSi・CaFeSi/100 + 0.01・WFeMn・CaFeMn/100 + 0.02・WFeP・CaFeP/100 + 0.005・WFeCr・CaFeCr/100）/Wsteel ×106≦6 ・・・ (A)
ここで、Wi（kg）はAl脱酸後のi合金の添加量、Wsteel（kg）は溶鋼量、Cai（質量%）はフェロ合金i中のCa濃度で0.5質量%以上である。 In order to solve the same problem, the invention of claim 2 is based on the fact that the amount of FeSi, FeMn, FeP, FeCr alloy added after Al deoxidation satisfies the following formula (A). The total amount of Ca mixed is limited.
Total Ca content = (0.5 · W FeSi · Ca FeSi / 100 + 0.01 · W FeMn · Ca FeMn / 100 + 0.02 · W FeP · Ca FeP / 100 + 0.005 · W FeCr · Ca FeCr / 100) / W steel × 10 6 ≦ 6 ・ ・ ・ (A)
Here, W i (kg) is the added amount of the i alloy after Al deoxidation, W steel (kg) is the molten steel amount, and Ca i (mass%) is 0.5 mass% or more in terms of the Ca concentration in the ferroalloy i. .

請求項１の発明では、不可避不純物としてCaを含有するFeSi、FeMn、FeP、FeCr合金を、溶存酸素濃度が50ppmを超える溶鋼に添加する。通常、溶鋼中の溶存酸素濃度を50ppm未満とするためにはAlによる脱酸が必要であり、アルミナが溶鋼中に存在することとなるため、Caを含有するFeSi、FeMn、FeP、FeCr合金を投入するとアルミナ粒子のクラスター化が発生する。しかし溶存酸素濃度が50ppmを超える溶鋼、すなわちAlによる脱酸前の溶鋼中にこれらの合金を添加しても、アルミナが存在しないので粗大介在物が生成されることがなく、ノズル詰まりを防止できる。   In the invention of claim 1, FeSi, FeMn, FeP, and FeCr alloy containing Ca as an inevitable impurity is added to molten steel having a dissolved oxygen concentration exceeding 50 ppm. Usually, deoxidation with Al is necessary to make the dissolved oxygen concentration in molten steel less than 50 ppm, and alumina exists in the molten steel. Therefore, FeSi, FeMn, FeP, FeCr alloys containing Ca When added, alumina particles are clustered. However, even if these alloys are added to molten steel with a dissolved oxygen concentration exceeding 50 ppm, that is, molten steel before deoxidation with Al, since no alumina is present, coarse inclusions are not generated and nozzle clogging can be prevented. .

また請求項２の発明では、溶鋼中のCa濃度が６ppmよりも高まると溶鋼中のアルミナ粒子がクラスター化してノズル詰まりを招くとの知見に基づき、Al脱酸後に添加するFeSi、FeMn、FeP、FeCr合金から持ち込まれる総Ca混入量を６ppm以下に規制し、これによってノズル詰まりを防止することができる。   In the invention of claim 2, FeSi, FeMn, FeP added after Al deoxidation based on the knowledge that if the Ca concentration in the molten steel is higher than 6 ppm, the alumina particles in the molten steel cluster and cause nozzle clogging. The total amount of Ca introduced from the FeCr alloy is restricted to 6 ppm or less, which can prevent nozzle clogging.

前記したように、請求項１の発明では溶存酸素濃度が50ppmを超える溶鋼、すなわちAlによる脱酸前の溶鋼中に、タンディッシュ溶鋼または鋳片における目標Si、Mn、P、Cr濃度に対し、各元素の質量%で表される目標濃度の80%以上になるように、不可避不純物として0.5質量%以上のCaを含有するFeSi、FeMn、FeP、FeCr合金の内、添加合金量の多いほうから少なくとも2つ以上の合金を添加する。Alを添加する前の溶鋼にこれらの合金を添加しても、合金中Caを無害化することができる。   As described above, in the invention of claim 1, the dissolved oxygen concentration exceeds 50 ppm, that is, in the molten steel before deoxidation with Al, the target Si, Mn, P, Cr concentration in the tundish molten steel or slab, From FeSi, FeMn, FeP, and FeCr alloys containing 0.5% by mass or more of Ca as inevitable impurities so that the target concentration expressed by mass% of each element is 80% or more At least two or more alloys are added. Even if these alloys are added to the molten steel before the addition of Al, Ca in the alloy can be made harmless.

ここで不可避不純物としてのCa含有率を0.5質量%以上としたのは、FeSi、FeMn、FeP、FeCr合金には0.5〜7質量%のCaが混在していることが分析により確認されたためである。またノズル閉塞を完全に防止するためには、目標Si、Mn、P、Cr濃度に対し、各元素の質量%で表される目標濃度の80%以上になるように、Al添加前に合金を添加する必要がある。80%未満ではAl脱酸後に投入する合金量が多くなるため、フェロ合金中のCaによるアルミナ粒子表面の局所溶解が発生し、ノズル閉塞を招くおそれがある。   The reason why the Ca content as an unavoidable impurity was set to 0.5 mass% or more is that the analysis confirmed that Fe-7, FeMn, FeP, and FeCr alloy contained 0.5 to 7 mass% Ca. . In order to completely prevent nozzle clogging, the alloy should be added before Al addition so that the target concentration expressed by mass% of each element is 80% or more of the target Si, Mn, P, Cr concentration. It is necessary to add. If it is less than 80%, the amount of alloy to be added after Al deoxidation increases, so that local dissolution of the alumina particle surface by Ca in the ferroalloy may occur, leading to nozzle clogging.

請求項１の発明によれば、成分調整用合金の投入タイミングを変えるだけで、連続鋳造におけるノズル詰まりを確実に防止して生産性を向上させることができる。このため特別な設備や合金中の不純物規制を必要としないので、操業時の作業負荷が小さく、低コストで優れた効果が得られる。   According to the first aspect of the present invention, it is possible to reliably prevent nozzle clogging in continuous casting and improve productivity only by changing the timing of introducing the component adjusting alloy. For this reason, no special equipment or impurity regulation in the alloy is required, so that the workload during operation is small, and an excellent effect can be obtained at low cost.

請求項２の発明は、合金毎の脱酸溶鋼へのCa歩留まりを解析した結果、FeSi合金では50％、FeMn合金では1％、FeP合金では2％、FeCr合金では0.5％であることに基づきなされたものである。各フェロ合金中Caの溶鋼への混入量はこれらの歩留まり％/100×合金添加量(kg)×合金中Ca濃度（質量％）/100で求めることができる。またノズル閉塞を防止するためには、前記したようにフェロ合金からのCa総混入量を6ppm以下とする必要がある。これらの関係から、(A)式を規定したものである。この請求項２の発明はAl添加後に添加されるフェロ合金からのCa総混入量を規制したもので、この発明によっても連続鋳造におけるノズル詰まりを確実に防止して生産性を向上させることができる。   The invention according to claim 2 is based on the analysis of the Ca yield in the deoxidized molten steel for each alloy, which is 50% for the FeSi alloy, 1% for the FeMn alloy, 2% for the FeP alloy, and 0.5% for the FeCr alloy. It was made. The amount of Ca mixed in the molten steel in each ferroalloy can be determined by these yield% / 100 × alloy addition amount (kg) × Ca concentration (mass%) / 100 in the alloy. In order to prevent nozzle clogging, the total amount of Ca mixed from the ferroalloy needs to be 6 ppm or less as described above. From these relationships, the formula (A) is defined. The invention of claim 2 regulates the total amount of Ca mixed from the ferroalloy added after the addition of Al, and this invention can also reliably prevent nozzle clogging in continuous casting and improve productivity. .

溶鋼約280トンの鋼種A〜D（表1）を、転炉-RHで溶製し、垂直曲げ型連鋳機を使って、厚さ250mm、幅1200〜2200mmの鋳片を製造した。鋳造速度は1.0〜1.7m/min、タンディッシュ温度は1520〜1580℃とした。浸漬ノズル1本当たり7連々鋳を実施し、ノズル閉塞状況を評価した。   Steel grades A to D (Table 1) of about 280 tons of molten steel were melted in a converter-RH, and a slab having a thickness of 250 mm and a width of 1200 to 2200 mm was manufactured using a vertical bending type continuous casting machine. The casting speed was 1.0 to 1.7 m / min, and the tundish temperature was 1520 to 1580 ° C. Seven consecutive castings per immersion nozzle were carried out, and the nozzle clogging situation was evaluated.

請求項１の発明に基づいてフェロ合金を添加した結果を、比較例とともに表２に示す。また請求項２の発明によりフェロ合金からのCa総混入量を規制した結果を、比較例とともに表３に示す。いずれの発明の実施例においても、ノズル閉塞が生じないことが確認された。   The result of adding the ferroalloy based on the invention of claim 1 is shown in Table 2 together with the comparative example. Table 3 shows the result of regulating the total amount of Ca mixed from the ferroalloy according to the invention of claim 2 together with the comparative example. It was confirmed that no nozzle clogging occurred in any of the inventive examples.

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Claims (2)

タンディッシュ溶鋼または鋳片における目標Si、Mn、P、Cr濃度に対し、各元素の質量%で表される目標濃度の80%以上になるように、不可避不純物として0.5質量%以上のCaを含有するFeSi、FeMn、FeP、FeCr合金の内、添加合金量の多いほうから少なくとも2つ以上の合金を、溶存酸素濃度が50ppmを超える溶鋼に添加することを特徴とする鋼の連続鋳造におけるノズル詰り防止方法。   Containing 0.5% by mass or more of Ca as an inevitable impurity so that it becomes 80% or more of the target concentration expressed by mass% of each element with respect to the target Si, Mn, P, Cr concentration in tundish molten steel or slab Nozzle clogging in continuous casting of steel, characterized in that at least two of the FeSi, FeMn, FeP, and FeCr alloys to be added are added to the molten steel having a dissolved oxygen concentration exceeding 50 ppm. Prevention method. Al脱酸後に添加するFeSi、FeMn、FeP、FeCr合金の投入量が下記(A)式を満足するように、当該合金からのCa総混入量を制限することを特徴とする鋼の連続鋳造におけるノズル詰り防止方法。
Ca総混入量=(0.5・WFeSi・CaFeSi/100 + 0.01・WFeMn・CaFeMn/100 + 0.02・WFeP・CaFeP/100 + 0.005・WFeCr・CaFeCr/100）/Wsteel ×106≦6 ・・・ (A)
ここで、Wi（kg）はAl脱酸後のi合金の添加量、Wsteel（kg）は溶鋼量、Cai（質量%）はフェロ合金i中のCa濃度で0.5質量%以上である。 In continuous casting of steel characterized by limiting the total amount of Ca mixed from the alloy so that the amount of FeSi, FeMn, FeP, FeCr alloy added after Al deoxidation satisfies the following formula (A) How to prevent nozzle clogging.
Total Ca content = (0.5 · W FeSi · Ca FeSi / 100 + 0.01 · W FeMn · Ca FeMn / 100 + 0.02 · W FeP · Ca FeP / 100 + 0.005 · W FeCr · Ca FeCr / 100) / W steel × 10 6 ≦ 6 ・ ・ ・ (A)
Here, W i (kg) is the added amount of the i alloy after Al deoxidation, W steel (kg) is the molten steel amount, and Ca i (mass%) is 0.5 mass% or more in terms of the Ca concentration in the ferroalloy i. .
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JP7087727B2 (en) 2018-06-26 2022-06-21 日本製鉄株式会社 Steel manufacturing method
JP7087728B2 (en) 2018-06-26 2022-06-21 日本製鉄株式会社 Steel manufacturing method
JP7087725B2 (en) 2018-06-26 2022-06-21 日本製鉄株式会社 Steel manufacturing method
JP7087723B2 (en) 2018-06-26 2022-06-21 日本製鉄株式会社 Steel manufacturing method
JP7087724B2 (en) 2018-06-26 2022-06-21 日本製鉄株式会社 Steel manufacturing method
JP7087726B2 (en) 2018-06-26 2022-06-21 日本製鉄株式会社 Steel manufacturing method
JP7119642B2 (en) 2018-06-26 2022-08-17 日本製鉄株式会社 steel manufacturing method
JP7119641B2 (en) 2018-06-26 2022-08-17 日本製鉄株式会社 steel manufacturing method
JP7256381B2 (en) 2018-06-26 2023-04-12 日本製鉄株式会社 Manufacturing method of killed steel

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