JP4855554B2 - Molten steel surface thermal insulation and molten steel surface thermal insulation method - Google Patents
Molten steel surface thermal insulation and molten steel surface thermal insulation method Download PDFInfo
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/005—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 using exothermic reaction compositions
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/10—Supplying or treating molten metal
- B22D11/108—Feeding additives, powders, or the like
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D1/00—Treatment of fused masses in the ladle or the supply runners before casting
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
- B22D11/10—Supplying or treating molten metal
- B22D11/11—Treating the molten metal
- B22D11/111—Treating the molten metal by using protecting powders
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
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Description
本発明は、取鍋や連続鋳造用タンディッシュなどにより溶鋼を移送、又は精錬処理を行う際に、断熱・保温あるいは空気酸化防止を目的として溶鋼表面を被覆する溶鋼表面保温剤に関する。
本願は、２００９年１２月１０日に、日本に出願された特願２００９−２８０２０６号に基づき優先権を主張し、その内容をここに援用する。TECHNICAL FIELD The present invention relates to a molten steel surface heat insulating agent that coats a molten steel surface for the purpose of heat insulation / heat retention or air oxidation prevention when the molten steel is transferred or refined by a ladle or a tundish for continuous casting.
This application claims priority on December 10, 2009 based on Japanese Patent Application No. 2009-280206 for which it applied to Japan, and uses the content here.
従来から、連続鋳造用タンディッシュや取鍋などにより溶鋼を移送、又は精錬処理を行う際に、溶鋼表面保温剤で溶鋼の表面を被覆し、溶鋼からの熱放散と外気の侵入を防止している。溶鋼表面保温剤として、ＳｉＯ２とＣを主成分とする焼籾が広く使用されている。焼籾を溶鋼表面保温剤として使用した場合、ＳｉＯ２は溶鋼中のＡｌと反応してＡｌ２Ｏ３系の介在物を生成するため、製品の表面欠陥が増大するという問題がある。Conventionally, when transporting or refining molten steel using a tundish or ladle for continuous casting, the surface of the molten steel is covered with a molten steel surface heat insulating agent to prevent heat dissipation from the molten steel and intrusion of outside air. Yes. As a molten steel surface heat insulating agent, shochu containing SiO 2 and C as main components is widely used. When shochu is used as a molten steel surface heat insulating agent, SiO 2 reacts with Al in the molten steel to generate Al 2 O 3 -based inclusions, which increases the surface defects of the product.
そこで、ＳｉＯ２の少ない保温剤として、特許文献１に示されるように、ＭｇＯ系の溶鋼表面保温剤が開発されている。Therefore, as shown in Patent Document 1, an MgO-based molten steel surface heat insulating agent has been developed as a heat insulating agent with a small amount of SiO 2 .
しかしながら、ＭｇＯを主成分とする溶鋼表面保温剤は融点が高く、使用温度では主に固相であるため、溶鋼表面を均一に被覆することができず、外気と溶鋼表面との反応により、Ａｌ２Ｏ３系の介在物が生成する。However, since the molten steel surface heat insulating agent mainly composed of MgO has a high melting point and is mainly a solid phase at the operating temperature, the molten steel surface cannot be uniformly coated, and the reaction between the outside air and the molten steel surface causes Al 2 O 3 inclusions are produced.
本発明は、上記問題を解決し、溶鋼表面保温剤由来の成分により、溶鋼中にアルミナ系の介在物が生成されることが無く、且つ、溶鋼表面での溶融速度が速く、溶鋼表面を均一に被覆することができる溶鋼表面保温剤を提供することを目的とする。 The present invention solves the above-mentioned problems, and does not produce alumina inclusions in the molten steel due to the components derived from the molten steel surface heat insulating agent, and has a high melting rate on the molten steel surface, making the molten steel surface uniform. An object of the present invention is to provide a molten steel surface heat insulating agent that can be coated on the surface.
上記課題を解決するため、本発明は以下の構成及び方法を採用する。 In order to solve the above problems, the present invention employs the following configurations and methods.
（１）本発明の第１の態様は、所定の溶鋼表面温度を有する溶鋼表面に配置される溶鋼表面保温剤であって、融点が前記溶鋼表面温度より高い、２種以上の高融点原料からなり、１０〜７０質量％のＣａＯと、１０〜６０質量％のＡｌ２Ｏ３と、５〜２５質量％のＭｇＯと、０．５〜１０質量％のＳｉＯ２とを合計７０質量％以上含有し、前記ＣａＯと前記Ａｌ２Ｏ３との比ＣａＯ／Ａｌ２Ｏ３が０．５〜２．０であり、融点が前記溶鋼表面温度より低く、７０質量％以上が粒径３０〜１００μｍの粉体である、溶鋼表面保温剤である。 (1) A first aspect of the present invention is a molten steel surface heat insulating agent disposed on a molten steel surface having a predetermined molten steel surface temperature, wherein two or more kinds of high melting point raw materials having a melting point higher than the molten steel surface temperature. 10 to 70% by mass of CaO, 10 to 60% by mass of Al 2 O 3 , 5 to 25 % by mass of MgO, and 0.5 to 10% by mass of SiO 2 are contained in total of 70% by mass or more. and, wherein the CaO and is said Al 2 O 3 ratio of CaO / Al 2 O 3 is 0.5 to 2.0, a melting point lower than the molten steel surface temperature more than 70% by mass of the particle diameter 30~100μm It is a molten steel surface heat insulating agent that is a powder.
（２）本発明の第２の態様は、上記（１）に記載の前記溶鋼表面保温剤を、平均溶融層厚さが５〜３０ｍｍの範囲となるように前記溶鋼表面に配置する、溶鋼表面保温方法である。 (2) A second aspect of the present invention is a molten steel surface in which the molten steel surface heat-retaining agent according to (1) is disposed on the molten steel surface so that the average molten layer thickness is in the range of 5 to 30 mm. It is a heat retention method.
上記（１）に記載の構成によれば、溶鋼表面保温剤の成分により、溶鋼中にアルミナ系の介在物が生成されることが無く、溶鋼表面保温剤が速やかに溶融して溶鋼表面を均一に被覆し、溶鋼と大気の接触によるアルミナ系介在物の生成を抑えることが可能となる。 According to the configuration described in (1) above, alumina inclusions are not generated in the molten steel due to the components of the molten steel surface heat insulating agent, and the molten steel surface heat insulating agent quickly melts to make the molten steel surface uniform. It is possible to suppress the formation of alumina inclusions due to contact between the molten steel and the atmosphere.
上記（２）に記載の方法によれば、溶鋼表面保温剤が、速やかに溶融して溶鋼表面を均一に確実に被覆し、棚つりの発生を防止することができるので、溶鋼と大気との接触によるアルミナ系介在物の生成を抑えることが可能となる。 According to the method described in the above (2), the molten steel surface heat insulating agent can be melted quickly and the molten steel surface can be coated uniformly and surely, and the occurrence of shelves can be prevented. Generation of alumina inclusions due to contact can be suppressed.
発明者らは、溶鋼表面保温剤で溶鋼表面を均一に被覆するために、溶鋼表面保温剤の溶融速度を速くするための方法を検討した。その結果、融点が溶鋼表面温度より高い２種以上の高融点原料を混合することにより製造された、融点（混合後の融点）が溶鋼表面温度より低い溶鋼表面保温剤であって、その７０質量％以上が粒径３０〜１００μｍの粉体である溶鋼表面保温材を用いた場合に、異なる高融点原料間の固体拡散が促進されるため、溶鋼表面と接触する溶鋼表面保温剤の速やかな溶融が可能となることを発見した。このため、溶解した溶鋼表面保温剤は、溶鋼表面を均一に被覆し、溶鋼表面が外気と接触することによるＡｌ２Ｏ３系の介在物の生成を防止することができる。以下、上記発見に基づく本発明の実施形態に係る溶鋼表面保温剤について詳細に説明する。尚、溶鋼表面保温材の融点とは、物質の温度を上昇させたときに溶融を始める温度であり、多元系物質の場合には固相線温度に相当する平均組成での融点である。尚、連続鋳造用タンディッシュや取鍋などにおける溶鋼表面温度は１５５０℃〜１６５０℃である。The inventors examined a method for increasing the melting rate of the molten steel surface heat insulating agent in order to uniformly coat the molten steel surface with the molten steel surface heat insulating agent. As a result, it is a molten steel surface heat insulating agent having a melting point (melting point after mixing) produced by mixing two or more high melting point raw materials having a melting point higher than the molten steel surface temperature. When a molten steel surface heat insulating material that is a powder having a particle size of 30 to 100 μm is used, the solid diffusion between different high melting point raw materials is promoted, so that the molten steel surface heat insulating material that contacts the molten steel surface is rapidly melted. Discovered that it would be possible. Therefore, the molten steel surface insulation agent dissolved can be uniformly coat the surface of molten steel, the molten steel surface to prevent the formation of Al 2 O 3 based inclusions due to contact with the outside air. Hereinafter, the molten steel surface heat insulating agent which concerns on embodiment of this invention based on the said discovery is demonstrated in detail. The melting point of the molten steel surface heat insulating material is a temperature at which melting starts when the temperature of the substance is raised, and in the case of a multi-component substance, it is a melting point with an average composition corresponding to the solidus temperature. In addition, the molten steel surface temperature in the tundish for continuous casting, a ladle, etc. is 1550 to 1650 degreeC.
本実施形態に係る溶鋼表面保温剤は、その７０質量％以上が粒径３０〜１００μｍの粉体であることを特徴とする。ここでの粒径は、篩いの目開きの寸法であり、前記所定の目開き寸法の篩いを通過することができる寸法である。溶鋼表面保温剤の７０質量％以上が粒径１００μより大きくなると、溶鋼表面保温剤が速やかに融解しないので、溶鋼表面が外気と接触して、Ａｌ２Ｏ３系の介在物が生成されてしまう。一方で、溶鋼表面保温剤の７０質量％以上を粒径３０μｍ以下の粉体とすると、原料を細かくするコストが莫大となってしまう。溶鋼表面保温剤の７０質量％以上が粒径４０〜９０μｍの粉体とする場合はより好ましく、溶鋼表面保温剤の７０質量％以上が粒径５０〜８０μｍの粉体とする場合は更に好ましい。また、粒径３０〜１００μｍの粉体が、溶鋼表面保温剤の７０質量％より少ない割合しか占めない場合にも、溶解速度が速い溶鋼表面保温剤が少ないため、溶鋼表面を速やかに溶液で覆うことができず、溶鋼表面が外気と接触してしまう。
溶鋼表面保温剤は、異なる高融点原料が均一に混ぜられた状態で袋に入れられていればよい。この袋に入れられた状態の溶鋼表面保温剤を、袋ごと溶鋼表面に投入することができる。原料の粒径が大きく違う場合、例えば本実施形態に係る溶鋼表面保温剤の３０〜１００μｍの高融点原料と３０μｍ未満、あるいは１００μｍを超える異なった種類の高融点原料を混合した場合には、袋内で原料が偏在してしまい、異なる原料が接触し難くなり反応が遅くなるため、溶鋼表面で速やかに融液が生成されず、溶鋼表面が外気と接触してしまう。The molten steel surface heat insulating agent according to the present embodiment is characterized in that 70 mass% or more thereof is a powder having a particle size of 30 to 100 μm. The particle size here is a dimension of the sieve opening, and is a dimension that can pass through the sieve having the predetermined opening dimension. When 70 mass% or more of the molten steel surface heat insulating agent is larger than the particle size of 100 μm, the molten steel surface heat insulating agent does not melt quickly, so that the molten steel surface comes into contact with the outside air and Al 2 O 3 -based inclusions are generated. . On the other hand, if 70 mass% or more of the molten steel surface heat insulating agent is a powder having a particle size of 30 μm or less, the cost of making the raw material fine becomes enormous. More preferably, 70% by mass or more of the molten steel surface heat insulating agent is a powder having a particle size of 40 to 90 μm, and more preferably 70% by mass or more of the molten steel surface heat insulating agent is a powder having a particle size of 50 to 80 μm. Moreover, even when the powder having a particle size of 30 to 100 μm occupies less than 70% by mass of the molten steel surface heat retention agent, the molten steel surface is quickly covered with the solution because there are few molten steel surface heat retention agents having a high dissolution rate. The surface of the molten steel comes into contact with the outside air.
The molten steel surface heat insulating agent should just be put in the bag in the state in which different high melting-point raw materials were mixed uniformly. The molten steel surface heat insulating agent in the state of being put in the bag can be put into the molten steel surface together with the bag. When the particle size of the raw material is greatly different, for example, when the high-melting-point raw material of 30 to 100 μm of the molten steel surface heat-retaining agent according to this embodiment is mixed with different types of high-melting-point raw materials of less than 30 μm or more than 100 μm Since the raw materials are unevenly distributed in the inside, it becomes difficult for different raw materials to come into contact with each other and the reaction is slowed down, so that the melt is not rapidly generated on the molten steel surface, and the molten steel surface comes into contact with the outside air.
溶鋼表面保温剤の融点（平均組成での融点）が溶鋼表面温度よりも高い場合には、溶鋼表面保温剤が完全な溶融状態に到らず、溶鋼表面での拡がり性が悪化し、溶鋼表面が外気と接触してしまう。このため、本実施形態に係る溶鋼表面保温剤の融点は溶鋼表面温度より低く設定されている。 When the melting point (melting point in average composition) of the molten steel surface heat insulating agent is higher than the molten steel surface temperature, the molten steel surface heat insulating agent does not reach a complete molten state, and the spreadability on the molten steel surface deteriorates, and the molten steel surface Will come into contact with outside air. For this reason, melting | fusing point of the molten steel surface heat insulating agent which concerns on this embodiment is set lower than molten steel surface temperature.
完全に溶融した溶鋼表面保温剤を使用した場合には、取鍋やタンディッシュなどの耐火物の溶損が問題となる。そこで、本実施形態に係る溶鋼表面保温剤では、取鍋やタンディッシュのコーティング材に用いられているマグネシア（ＭｇＯ）を含む原料を用いることにより、タンディッシュの溶損を防止している。含有するマグネシアの量が５質量％よりも少ない場合には、取鍋やタンディッシュのコーティング材の溶損速度が速くなり、操業に支障をきたす。一方で、含有するマグネシアの量が３０質量％よりも高い場合には、融点が上昇するため、溶鋼を均一に被覆することができなくなる。そこで、本実施形態に係る溶鋼表面保温剤では、マグネシアの含有率を５〜３０質量％に規定する。マグネシアの含有率は、７〜２５質量％であればより好ましい。 When a completely molten molten steel surface heat insulating agent is used, melting of refractories such as ladle and tundish becomes a problem. Therefore, in the molten steel surface heat insulating agent according to the present embodiment, melting of the tundish is prevented by using a raw material containing magnesia (MgO) used in a ladle or a tundish coating material. When the amount of magnesia contained is less than 5% by mass, the melting rate of the ladle or tundish coating material is increased, which hinders operation. On the other hand, when the amount of magnesia contained is higher than 30% by mass, the melting point increases, so that the molten steel cannot be uniformly coated. Then, in the molten steel surface heat insulating agent which concerns on this embodiment, the content rate of magnesia is prescribed | regulated to 5-30 mass%. The content of magnesia is more preferably 7 to 25% by mass.
本実施形態に係る溶鋼表面保温剤は、混合後組成（平均組成）が、１０〜７０質量％、好ましくは１５〜６５質量％、尚好ましくは２０〜６０質量％のＣａＯ、１０〜６０質量％、好ましくは１５〜５５質量％、尚好ましくは２０〜５０質量％のＡｌ２Ｏ３、５〜２５質量％のＭｇＯ、０．５〜１０質量％のＳｉＯ２を主成分としている。ただし、ＣａＯ／Ａｌ２Ｏ３＝０．５〜２．０とする。これは、ＣａＯ／Ａｌ２Ｏ３＝０．５〜２．０の範囲で溶鋼表面保温剤の融点（平均組成での融点）が極小となるためである。また、溶鋼表面保温剤に占めるＳｉＯ２の質量が、１０質量％を超えると、溶鋼中のＡｌとの反応により、Ａｌ２Ｏ３系の介在物を生成し、製品の表面欠陥が増大してしまう。ＭｇＯの含有量については、上記した通りである。尚、「主成分とする」とは、該当する成分が全体の７０質量％以上を占める場合を指す。本実施形態に係る溶鋼表面保温剤においては、上述の成分の合計が全体の８０質量％、又は９０質量％以上であってもよい。 The molten steel surface heat insulating agent according to the present embodiment has a composition after mixing (average composition) of 10 to 70% by mass, preferably 15 to 65% by mass, more preferably 20 to 60% by mass of CaO, and 10 to 60% by mass. The main component is preferably 15 to 55% by mass, more preferably 20 to 50% by mass of Al 2 O 3, 5 to 25 % by mass of MgO, and 0.5 to 10% by mass of SiO 2 . However, the CaO / Al 2 O 3 = 0.5~2.0 . This is because the melting point (melting point of the average composition) of the molten steel surface heat insulating agent is minimized in the range of CaO / Al 2 O 3 = 0.5 to 2.0. Moreover, if the mass of SiO 2 occupying the molten steel surface heat insulating agent exceeds 10 mass%, the reaction with Al in the molten steel generates Al 2 O 3 -based inclusions, which increases the surface defects of the product. End up. The content of MgO is as described above. “Containing as a main component” means that the corresponding component occupies 70% by mass or more of the whole. In the molten steel surface heat insulating agent according to the present embodiment, the total of the above components may be 80% by mass or 90% by mass or more of the whole.
前記した高融点原料としては、マグネサイトを焼成して製造したＭｇＯや、電融品ＭｇＯ、あるいは、ＣａＯ、Ａｌ２Ｏ３、ＳｉＯ２、ＳｒＯ、ＺｒＯ２、Ａｌ２Ｏ３−ＭｇＯ、ＣａＯ−ＭｇＯを用いることができる。Examples of the high melting point raw material include MgO produced by firing magnesite, electromelted MgO, CaO, Al 2 O 3 , SiO 2 , SrO, ZrO 2 , Al 2 O 3 —MgO, and CaO—. MgO can be used.
溶鋼表面保温方法としては、上記説明した溶鋼表面保温剤を、平均溶融厚さが５〜３０ｍｍの範囲となるように溶鋼の表面に配置することが望ましい。これは、平均溶融厚さが５ｍｍを下回る場合には、溶鋼表面の外気との遮断が不十分となるからである。また、平均溶融厚さが３０ｍｍを上回る場合には、熱源である溶鋼から離れた位置にある溶鋼表面保温剤の上部が冷却されることにより、溶鋼よりも温度が低い取鍋やタンディッシュの耐火物表面に、溶鋼表面保温剤が固化して付着し、溶鋼と溶鋼表面保温剤との間に隙間ができてしまうからである。これを棚つりという。棚つりが発生すると、溶鋼と溶鋼表面保温剤との間に隙間ができるので、溶鋼表面が外気と接触してしまう。溶鋼表面保温剤を、平均溶融厚さが７〜２５ｍｍ、又は９〜２０ｍｍの範囲となるように溶鋼表面に配置してもよい。 As the molten steel surface heat retaining method, it is desirable to dispose the above-described molten steel surface heat insulating agent on the surface of the molten steel so that the average melt thickness is in the range of 5 to 30 mm. This is because when the average melt thickness is less than 5 mm, the molten steel surface is not sufficiently blocked from the outside air. In addition, when the average melt thickness exceeds 30 mm, the upper part of the molten steel surface heat insulating agent located at a position away from the molten steel as a heat source is cooled, so that the temperature of the ladle or tundish is lower than that of the molten steel. This is because the molten steel surface heat insulating agent solidifies and adheres to the surface of the object, and a gap is formed between the molten steel and the molten steel surface heat insulating agent. This is called shelving. When shelving occurs, a gap is formed between the molten steel and the molten steel surface heat insulating agent, so that the molten steel surface comes into contact with the outside air. You may arrange | position a molten steel surface heat insulating agent on the molten steel surface so that an average melt thickness may become the range of 7-25 mm, or 9-20 mm.
次に、本発明を実施例に基づいて説明するが、実施例における条件は、本発明の実施可能性および効果を確認するために採用した一条件例であり、本発明はこれらの条件例のみに限定されない。
本発明は、本発明の要旨を逸脱せず、本発明の目的を達成する限りにおいて、種々の条件ないし条件の組合せを採用し得るものである。Next, the present invention will be described based on examples, but the conditions in the examples are one condition example adopted for confirming the feasibility and effects of the present invention, and the present invention is limited to these condition examples. It is not limited to.
The present invention can adopt various conditions or combinations of conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.
１チャージ２８０ｔの溶鋼を溶銑予備処理、転炉脱炭、ＲＨによる真空脱ガス処理を行い、極低炭素鋼を溶製した。これを、容量６０ｔのタンディッシュを用いて連続鋳造法により鋳片を製造した。鋳造は、１５チャージ分の溶鋼を連続して行った。溶鋼表面温度は１５６０〜１５８０℃とした。本発明、あるいは比較例の溶鋼表面保温剤は、鋳造初期からタンディッシュ内の溶鋼の保温に用いた。溶鋼表面保温剤は、実施例、比較例の場合ともにタンディッシュに対して５００ｋｇを袋ごと添加した。一枚の鋳片は、厚み２５０ｍｍ、長さ７０００ｍｍ、幅１５００ｍｍである。鋳片は、通常用いられる熱間圧延、冷間圧延工程を経て厚さ０．７ｍｍ、幅１５００ｍｍの冷延鋼板にした。なお、表１〜表４に実施例、参考例および比較例のデータを示す。レイアウトの都合上４つの表に分割したが、表２は表１の続きであり、表３は表２の続きであり、表４は表３の続きである。 The molten steel of 1 charge 280t was subjected to hot metal pretreatment, converter decarburization, and vacuum degassing treatment with RH to produce ultra low carbon steel. A slab was produced by continuous casting using a tundish having a capacity of 60 t. Casting was performed continuously for 15 charges of molten steel. Molten steel surface temperature was 1560-1580 degreeC. The molten steel surface heat-retaining agent of the present invention or the comparative example was used to keep the molten steel in the tundish from the beginning of casting. As for the molten steel surface heat insulating agent, 500 kg of the bag was added to the tundish in both the examples and comparative examples. One slab has a thickness of 250 mm, a length of 7000 mm, and a width of 1500 mm. The slab was made into a cold-rolled steel sheet having a thickness of 0.7 mm and a width of 1500 mm through a commonly used hot rolling and cold rolling process. Tables 1 to 4 show data of examples , reference examples, and comparative examples . Although divided into four tables for the sake of layout, Table 2 is a continuation of Table 1, Table 3 is a continuation of Table 2, and Table 4 is a continuation of Table 3.
表１中の※１ ＣａＯ―Ａｌ２Ｏ３は、ＣａＯが５０質量％、Ａｌ２Ｏ３が５０質量％である。
表１中の※２ ＣａＯ−ＳｉＯ２は、ＣａＯが５５質量％、ＣａＯ−ＳｉＯ２が４５質量％である。
表１中の※３ ＳｒＯ−ＳｉＯ２は、ＳｒＯが５０質量％、ＳｉＯ２が５０質量％である。
表１中の※４ Ａｌ２Ｏ３−ＣａＯ−ＭｇＯは、Ａｌ２Ｏ３が５０質量％、ＣａＯが４５質量％、ＭｇＯが５質量％である。
表１中の※５ Ａｌ２Ｏ３−ＣａＯ−ＳｉＯ２は、Ａｌ２Ｏ３が５０質量％、ＣａＯが４５質量％、ＳｉＯ２が５質量％である。
表１中の※６ Ａｌ２Ｏ３−ＣａＯ−ＺｒＯ２は、Ａｌ２Ｏ３が５０質量％、ＣａＯが４５質量％、ＺｒＯ２が５質量％である。
表１中の※７ Ａｌ２Ｏ３−ＭｇＯ−ＳｉＯ２は、Ａｌ２Ｏ３が２５質量％、ＭｇＯが２５質量％、ＳｉＯ２が５０質量％である。
表２中の※８ Ａｌ２Ｏ３−ＭｇＯは、Ａｌ２Ｏ３が７５質量％、ＭｇＯが２５質量％である。
表２中の※９ ＣａＯ−ＭｇＯは、ＣａＯが７０質量％、ＭｇＯｓが３０質量％である。
表４中の※１０ 溶融層厚さは、鉄棒を溶鋼に浸漬させ、付着した溶鋼表面保温剤の厚みを溶融層厚みとした。
表４中の※１１ ΔＴ．Ｏは、連続連続鋳造の１〜２鍋における、ＲＨ処理後（真空脱ガス処理後）溶鋼中の全酸素量に対する、タンディッシュ溶鋼中の全酸素量の変化量である。
表４中の※１２ 欠陥発生個数は、連続連続鋳造の１〜２鍋で製造された鋼片から得られる冷延鋼板コイル１本当たり中に存在する酸化物系介在物による表面欠陥の平均個数である。In Table 1, * 1 CaO—Al 2 O 3 is 50% by mass of CaO and 50% by mass of Al 2 O 3 .
Table 1 in ※ 2 CaO-
* 3 SrO—SiO 2 in Table 1 is 50% by mass of SrO and 50% by mass of SiO 2 .
Table 1 in ※ 4 Al 2 O 3 -CaO- MgO is, Al 2 O 3 is 50 wt%, CaO 45% by weight,
Table 1 in ※ 5 Al 2 O 3 -CaO-
Table 1 in ※ 6 Al 2 O 3 -CaO-
* 7 Al 2 O 3 —MgO—SiO 2 in Table 1 is 25% by mass of Al 2 O 3 , 25% by mass of MgO, and 50% by mass of SiO 2 .
* 8 Al 2 O 3 —MgO in Table 2 is 75% by mass of Al 2 O 3 and 25% by mass of MgO.
* 9 CaO-MgO in Table 2 is 70% by mass of CaO and 30% by mass of MgOs.
The thickness of the molten layer * 10 in Table 4 was obtained by immersing an iron bar in molten steel and setting the thickness of the molten steel surface heat insulating agent attached thereto as the molten layer thickness.
* 11 ΔT. In Table 4 O is a change amount of the total oxygen amount in the tundish molten steel with respect to the total oxygen amount in the molten steel after RH treatment (after vacuum degassing treatment) in 1-2 pans of continuous continuous casting.
* 12 In Table 4, the number of defects generated is the average number of surface defects due to oxide inclusions present in each cold-rolled steel sheet coil obtained from steel slabs produced in 1-2 continuous pans. It is.
図１に示されるように、実施例及び参考例では、連続鋳造の１〜２鍋における、ＲＨ処理後（真空脱ガス処理後）溶鋼中の全酸素量に対し、タンディッシュ溶鋼中の全酸素量は減少している。これは、溶鋼表面保温剤が、速やかに溶融してタンディッシュ表面を均一に被覆したため、溶鋼と大気の接触によるアルミナ系介在物の生成が抑えられるとともに、溶鋼中のアルミナ系介在物が浮上して、溶鋼から除去されたからである。
また、図２に示されるように、実施例及び参考例では、連続鋳造の１〜２鍋で製造された鋼片から得られる冷延鋼板コイル１本当たり中に存在する酸化物系介在物による表面欠陥の平均個数が、従来の比較例に比べて大幅に減少している。これも、溶鋼表面保温剤が、速やかに溶融してタンディッシュ表面を均一に被覆したため、溶鋼と大気の接触によるアルミナ系介在物の生成が抑えられたからである。
As shown in FIG. 1, in the examples and reference examples , the total oxygen in the tundish molten steel with respect to the total oxygen amount in the molten steel after RH treatment (after vacuum degassing treatment) in 1 to 2 pans of continuous casting. The amount is decreasing. This is because the molten steel surface heat insulating agent melts quickly and uniformly coats the tundish surface, so that the formation of alumina inclusions due to contact between the molten steel and the atmosphere is suppressed, and the alumina inclusions in the molten steel surface. This is because it was removed from the molten steel.
In addition, as shown in FIG. 2, in the examples and the reference examples , the oxide inclusions exist in one cold-rolled steel sheet coil obtained from a steel piece produced in a 1-2 pan of continuous casting. The average number of surface defects is greatly reduced as compared with the conventional comparative example. This is also because the molten steel surface heat insulating agent quickly melts and uniformly coats the tundish surface, thereby suppressing generation of alumina inclusions due to contact between the molten steel and the atmosphere.
本発明によれば、溶鋼表面保温剤由来の成分により、溶鋼中にアルミナ系の介在物が生成されることが無く、且つ、溶鋼表面での溶融速度が速く、溶鋼表面を均一に被覆することができる溶鋼表面保温剤を提供することができる。 According to the present invention, due to the component derived from the molten steel surface heat insulating agent, there is no generation of alumina inclusions in the molten steel, and the melting rate on the molten steel surface is high, and the molten steel surface is uniformly coated. It is possible to provide a molten steel surface heat insulating agent capable of
Claims (2)
融点が前記溶鋼表面温度より高い、２種以上の高融点原料からなり、
１０〜７０質量％のＣａＯと、１０〜６０質量％のＡｌ２Ｏ３と、５〜２５質量％のＭｇＯと、０．５〜１０質量％のＳｉＯ２とを合計７０質量％以上含有し、
前記ＣａＯと前記Ａｌ２Ｏ３との比ＣａＯ／Ａｌ２Ｏ３が０．５〜２．０であり、
融点が前記溶鋼表面温度より低く、
７０質量％以上が粒径３０〜１００μｍの粉体である
ことを特徴とする溶鋼表面保温剤。A molten steel surface heat insulating agent disposed on a molten steel surface having a predetermined molten steel surface temperature,
Melting point is higher than the surface of molten steel temperature, it consists of two or more refractory materials,
10 to 70% by mass of CaO, 10 to 60% by mass of Al 2 O 3 , 5 to 25 % by mass of MgO, and 0.5 to 10% by mass of SiO 2 are contained in total of 70% by mass or more,
The ratio CaO / Al 2 O 3 of the Al 2 O 3 and the CaO is 0.5 to 2.0,
The melting point is lower than the surface temperature of the molten steel,
A molten steel surface heat-retaining agent, wherein 70 mass% or more is a powder having a particle size of 30 to 100 μm.
ことを特徴とする溶鋼表面保温方法。The molten steel surface heat-retaining agent according to claim 1 is disposed on the molten steel surface so that the average molten layer thickness is in the range of 5 to 30 mm.
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| JPH06170507A (en) * | 1992-12-02 | 1994-06-21 | Nippon Steel Corp | Surface insulating material for molten steel |
| JPH10263768A (en) * | 1997-03-24 | 1998-10-06 | Sumitomo Metal Ind Ltd | Method for reusing converter slag |
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| JPH06170507A (en) * | 1992-12-02 | 1994-06-21 | Nippon Steel Corp | Surface insulating material for molten steel |
| JPH10263768A (en) * | 1997-03-24 | 1998-10-06 | Sumitomo Metal Ind Ltd | Method for reusing converter slag |
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