WO2011071141A1 - Agent for maintaining surface temperature of molten steel and method for maintaining surface temperature of molten steel - Google Patents

Agent for maintaining surface temperature of molten steel and method for maintaining surface temperature of molten steel Download PDF

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WO2011071141A1
WO2011071141A1 PCT/JP2010/072211 JP2010072211W WO2011071141A1 WO 2011071141 A1 WO2011071141 A1 WO 2011071141A1 JP 2010072211 W JP2010072211 W JP 2010072211W WO 2011071141 A1 WO2011071141 A1 WO 2011071141A1
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Prior art keywords
molten steel
mass
steel surface
heat insulating
melting point
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PCT/JP2010/072211
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French (fr)
Japanese (ja)
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利明 溝口
大輔 三木
徳彦 内山
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新日本製鐵株式会社
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Priority to BR112012013501-5A priority Critical patent/BR112012013501B1/en
Priority to CN201080055433.7A priority patent/CN102762320B/en
Priority to JP2011514929A priority patent/JP4855552B2/en
Publication of WO2011071141A1 publication Critical patent/WO2011071141A1/en

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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
    • 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
    • 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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D7/00—Casting ingots, e.g. from ferrous metals
    • B22D7/06—Ingot moulds or their manufacture
    • B22D7/10—Hot tops therefor
    • 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
    • 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

Definitions

  • 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.
  • 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.
  • a molten steel surface heat insulating agent 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.
  • 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 .
  • 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.
  • 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.
  • the present invention employs the following configurations and methods.
  • 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, and a low melting point raw material having a melting point lower than the molten steel surface temperature of 50% by mass or more.
  • a high melting point raw material having a melting point higher than the surface temperature of the molten steel and less than 50% by mass, and having an average composition of 10 to 60% by mass of CaO, 10 to 70% by mass of Al 2 O 3 , 3 and ⁇ 30 wt% of MgO, 0 - 10 wt% and SiO 2 contained a total of 70 mass% or more, the CaO and the Al 2 O 3 and the ratio CaO / Al 2 O 3 0.5-2.
  • This is a molten steel surface heat insulating agent having a melting point lower than the molten steel surface temperature and 70% by mass or more being a powder having a particle size of 200 to 1000 ⁇ m.
  • 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.
  • 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.
  • 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.
  • 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.
  • the melting point is lower than the molten steel surface temperature, which is produced by mixing a low melting point raw material having a melting point of 50% by mass or more lower than the molten steel surface temperature and a high melting point material having a melting point of less than 50% by mass higher than the molten steel surface temperature. It has been found that when a molten steel surface heat insulating agent is used, a melt is generated at the initial stage of melting of the molten steel surface heat insulating agent, and the molten steel surface heat insulating agent can be rapidly melted.
  • 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.
  • the surface temperature of the molten steel in a continuous casting tundish or ladle is 1550 ° C to 1650 ° C. Since the liquid phase molten steel surface heat insulating agent uniformly coats the molten steel surface, generation of Al 2 O 3 -based inclusions due to the molten steel surface coming into contact with the outside air can be prevented.
  • the low-melting-point raw material generates a melt at an initial stage, and the high-melting-point raw material is brought into contact with the melt, thereby promoting diffusion of the high-melting-point raw material into the melt and increasing the melting rate of the high-melting-point raw material.
  • the ratio of the low melting point raw material is prescribed
  • 90 mass%, 80 mass%, or 80 mass% may be sufficient.
  • 70 mass% or more of the molten steel surface heat insulating material is made into a powder having a particle size of 200 to 1000 ⁇ m, whereby the low melting point raw material is rapidly melted and the high melting point raw material is It can be quickly diffused into the melt. More preferably, 70 mass% or more of the molten steel surface heat insulating agent is a powder having a particle size of 300 to 900 ⁇ m, and more preferably 70 mass% or more of the molten steel surface heat insulating agent is a powder having a particle size of 500 to 800 ⁇ m.
  • the particle size here is a dimension of the opening of the sieve, and is a dimension that can pass through the sieve having the predetermined opening.
  • 70% by mass or more is larger than the particle size of 1000 ⁇ m, the low melting point raw material is not rapidly melted, and the diffusion rate of the high melting point raw material into the melt is further reduced, so that the surface of the molten steel is in contact with the outside air. As a result, Al 2 O 3 -based inclusions are generated.
  • 70 mass% or more of the molten steel surface heat insulating agent is a powder having a particle size of 200 ⁇ m or less, the cost of making the raw material fine becomes enormous.
  • the powder having a particle size of 200 to 1000 ⁇ m occupies less than 70% by mass of the molten steel surface heat insulating agent, the amount of solution produced is not sufficient, and the high melting point raw material is introduced into the melt. Because the diffusion rate of the steel decreases, 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 with which the low melting-point raw material and the high melting-point raw material 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.
  • the particle diameters of the low melting point raw material and the high melting point raw material are greatly different, for example, when a raw material having a surface temperature of 200 to 1000 ⁇ m and a raw material of less than 200 ⁇ m or more than 1000 ⁇ m are mixed in the bag, The low melting point raw material and the high melting point raw material are unevenly distributed, and if the high melting point raw material first comes into contact with the molten steel surface, the molten steel surface is not rapidly generated, and the molten steel surface is exposed to the outside air. Contact.
  • 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 completely 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
  • the molten steel surface heat insulating agent When using a molten steel surface heat insulating agent that is completely melted, 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. If the amount of magnesia contained is less than 3% by mass, the rate of erosion of the ladle or tundish coating material will be 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. Therefore, in the molten steel surface heat insulating agent according to the present embodiment, the magnesia content is regulated to 3 to 30% by mass. More preferably, it is 5 to 30% by mass, and still more preferably 7 to 25% by mass.
  • the molten steel surface heat insulating agent according to this embodiment has a composition after mixing (average composition) of 10 to 60% by mass, preferably 15 to 55% by mass, more preferably 25 to 50% by mass of CaO, 10 to 70% by mass.
  • the main components are preferably 20 to 65% by mass, more preferably 40 to 60% by mass of Al 2 O 3 , 3 to 30% by mass of MgO, and 0 to 10% by mass or less of SiO 2 .
  • 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.
  • Examples of the low melting point raw material include B 2 O 3 , Li 2 O, Na 2 O, CaO—Al 2 O 3 , CaO—SiO 2 , SrO—SiO 2 , Al 2 O 3 whose melting point is lower than the molten steel surface temperature.
  • Composite oxides such as —CaO—MgO, Al 2 O 3 —CaO—SiO 2 , Al 2 O 3 —CaO—ZrO 2 , Al 2 O 3 —MgO—SiO 2 , and CaF 2 can be used.
  • this composite oxide a solid obtained by solidifying an arbitrary multi-component melt such as one obtained by pre-melting quick lime and alumina, or alumina cement obtained by pre-melting quick lime and bauxite can be used.
  • 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, CaO—MgO can be used.
  • composition of the specific low melting-point raw material and high melting-point raw material which comprise a molten steel surface heat retention agent, the combination and mixture ratio of a low-melting-point raw material and a high melting-point raw material are shown as an Example later.
  • the above-described molten steel surface thermal insulation agent is arranged on the molten steel surface 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 the heat source is cooled, so that the temperature of the ladle or tundish is lower than that of the molten steel.
  • 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.
  • 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.
  • the molten steel surface heat insulating agent may be arranged on the molten steel surface so that the average melt thickness is in the range of 7 to 25 mm, or 9 to 20 mm.
  • the present invention will be described based on examples, but the conditions in the examples are one example of conditions adopted to confirm the feasibility and effects of the present invention, and the present invention is an example of these conditions. It is not limited to only.
  • 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.
  • the molten steel with 1 charge of 280 t was subjected to hot metal preliminary treatment, 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.
  • the molten steel surface temperature was 1560 to 1580 ° C.
  • 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.
  • 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 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.
  • Al 2 O 3 —CaO—ZrO 2 in Table 1 is 50% by mass of Al 2 O 3 , 45% by mass of CaO and 5% by mass of ZrO 2 .
  • * 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 is 75% by mass of Al 2 O 3 and 25% by mass of MgO.
  • * 9 CaO—MgO 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.
  • 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 to 2 pans of continuous continuous casting.
  • the number of defects 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 pans of continuous continuous casting. It is.
  • the total oxygen amount in the tundish molten steel is 1 to 2 pans of continuous continuous casting, compared to the total oxygen amount in the molten steel after RH treatment (after vacuum degassing treatment). is decreasing.
  • 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.
  • 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

Abstract

Disclosed is an agent for maintaining the surface temperature of molten steel, which is applied over the surface of molten steel that has a predetermined surface temperature. The agent for maintaining the surface temperature of molten steel contains not less than 50% by mass of a low melting point material that has a melting point lower than the surface temperature of the molten steel and less than 50% by mass of a high melting point material that has a melting point higher than the surface temperature of the molten steel, while containing 10-60% by mass of CaO, 10-70% by mass of Al2O3, 3-30% by mass of MgO and 0-10% by mass of SiO2 so that the total is not less than 70% by mass and the ratio of CaO to Al2O3, namely CaO/Al2O3 is 0.5-2.0. The agent for maintaining the surface temperature of molten steel has a melting point lower than the surface temperature of the molten steel, and is composed of a powder that contains particles having a particle diameter of 200-1000 μm in an amount of not less than 70% by mass.

Description

溶鋼表面保温剤と溶鋼表面保温方法Molten steel surface thermal insulation and molten steel surface thermal insulation method
　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２００９－２８０２０５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 based on Japanese Patent Application No. 2009-280205 filed in Japan on Dec. 10, 2009, the contents of which are incorporated herein by reference.
　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 .
特公平３－４８１５２号公報Japanese Examined Patent Publication No. 3-48152
　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低い、５０質量％以上の低融点原料と、融点が前記溶鋼表面温度より高い、５０質量％未満の高融点原料とを含有し、平均組成として、１０～６０質量％のＣａＯと、１０～７０質量％のＡｌ２Ｏ３と、３～３０質量％のＭｇＯと、０～１０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２００～１０００μｍ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, and a low melting point raw material having a melting point lower than the molten steel surface temperature of 50% by mass or more. And a high melting point raw material having a melting point higher than the surface temperature of the molten steel and less than 50% by mass, and having an average composition of 10 to 60% by mass of CaO, 10 to 70% by mass of Al 2 O 3 , 3 and ~ 30 wt% of MgO, 0 - 10 wt% and SiO 2 contained a total of 70 mass% or more, the CaO and the Al 2 O 3 and the ratio CaO / Al 2 O 3 0.5-2. This is a molten steel surface heat insulating agent having a melting point lower than the molten steel surface temperature and 70% by mass or more being a powder having a particle size of 200 to 1000 μm.
（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.
連続連続鋳造での１～２鍋でのタンディッシュ入側溶鋼中の全酸素量に対するタンディッシュ出側溶鋼中の全酸素量の変化量である。This is the amount of change in the total oxygen amount in the tundish outlet side molten steel relative to the total oxygen amount in the tundish inlet side molten steel in one or two pans in continuous continuous casting. 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。It is the average number of surface defects due to oxide inclusions present in one cold-rolled steel sheet coil obtained from steel slabs produced in 1-2 pans of continuous continuous casting.
　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低い５０質量％以上の低融点原料と融点が溶鋼表面温度より高い５０質量％未満の高融点原料とを混合して製造された、融点が溶鋼表面温度より低い溶鋼表面保温剤を用いた場合に、溶鋼表面保温剤の溶融初期において融液が生成し、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。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。 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, the melting point is lower than the molten steel surface temperature, which is produced by mixing a low melting point raw material having a melting point of 50% by mass or more lower than the molten steel surface temperature and a high melting point material having a melting point of less than 50% by mass higher than the molten steel surface temperature. It has been found that when a molten steel surface heat insulating agent is used, a melt is generated at the initial stage of melting of the molten steel surface heat insulating agent, and the molten steel surface heat insulating agent can be rapidly melted. 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.
　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。液相の溶鋼表面保温剤は、溶鋼表面を均一に被覆するため、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。 The surface temperature of the molten steel in a continuous casting tundish or ladle is 1550 ° C to 1650 ° C. Since the liquid phase molten steel surface heat insulating agent uniformly coats the molten steel surface, generation of Al 2 O 3 -based inclusions due to the molten steel surface coming into contact with the outside air can be prevented.
　低融点原料は、初期に融液を生成し、この融液に高融点の原料が接触することにより、高融点原料の前記融液中への拡散を促進して高融点原料の溶融速度を大きくする効果がある。なお、低融点原料の割合が５０質量％を下回ると、高融点原料の拡散が十分に促進されず、溶融速度が上がらず、高融点原料が長時間溶解しない状態が続き、溶鋼表面の外気との遮断が不十分となってしまう。このため、本実施形態に係る溶鋼表面保温剤では、低融点原料の割合を、５０質量％以上に規定される。上限に関しては、９０質量％、８０質量％、又は８０質量％であってもよい。 The low-melting-point raw material generates a melt at an initial stage, and the high-melting-point raw material is brought into contact with the melt, thereby promoting diffusion of the high-melting-point raw material into the melt and increasing the melting rate of the high-melting-point raw material. There is an effect to. When the ratio of the low melting point raw material is less than 50% by mass, the diffusion of the high melting point raw material is not sufficiently promoted, the melting rate does not increase, and the high melting point raw material does not dissolve for a long time. Will be insufficiently blocked. For this reason, in the molten steel surface heat insulating agent which concerns on this embodiment, the ratio of a low melting-point raw material is prescribed | regulated to 50 mass% or more. Regarding an upper limit, 90 mass%, 80 mass%, or 80 mass% may be sufficient.
　更に、本実施形態に係る溶鋼表面保温剤では、溶鋼表面保温剤の７０質量％以上を粒径２００～１０００μｍの粉体とすることにより、低融点原料を速やかに融解させるとともに、高融点原料を前記融液中へ速やかに拡散させることができる。溶鋼表面保温剤の７０質量％以上を粒径３００～９００μｍ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％以上を粒径５００～８００μｍの粉体とする場合は更に好ましい。なお、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。また、７０質量％以上が粒径１０００μより大きくなると、低融点原料が速やかに融解することなく、更に、高融点原料の前記融液中への拡散速度が低下するため、溶鋼表面が外気と接触することにより、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２００μｍ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。また、粒径２００～１０００μｍ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、溶液の生成量が十分でなく、また、高融点原料の前記融液中への拡散速度が低下するため、溶鋼表面が外気と接触してしまう。
　溶鋼表面保温剤は、低融点原料と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。低融点原料と高融点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２００～１０００μｍの原料と２００μｍ未満、あるいは１０００μｍを超える原料を混合した場合には、袋内で、低融点原料と高融点原料が偏在してしまい、もし、高融点原料が最初に溶鋼表面と接触してしまう場合には、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。 Furthermore, in the molten steel surface heat insulating material according to the present embodiment, 70 mass% or more of the molten steel surface heat insulating material is made into a powder having a particle size of 200 to 1000 μm, whereby the low melting point raw material is rapidly melted and the high melting point raw material is It can be quickly diffused into the melt. More preferably, 70 mass% or more of the molten steel surface heat insulating agent is a powder having a particle size of 300 to 900 μm, and more preferably 70 mass% or more of the molten steel surface heat insulating agent is a powder having a particle size of 500 to 800 μm. In addition, the particle size here is a dimension of the opening of the sieve, and is a dimension that can pass through the sieve having the predetermined opening. Further, when 70% by mass or more is larger than the particle size of 1000 μm, the low melting point raw material is not rapidly melted, and the diffusion rate of the high melting point raw material into the melt is further reduced, so that the surface of the molten steel is in contact with the outside air. As a result, 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 200 μm or less, the cost of making the raw material fine becomes enormous. Also, when the powder having a particle size of 200 to 1000 μm occupies less than 70% by mass of the molten steel surface heat insulating agent, the amount of solution produced is not sufficient, and the high melting point raw material is introduced into the melt. Because the diffusion rate of the steel decreases, 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 with which the low melting-point raw material and the high melting-point raw material 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 diameters of the low melting point raw material and the high melting point raw material are greatly different, for example, when a raw material having a surface temperature of 200 to 1000 μm and a raw material of less than 200 μm or more than 1000 μm are mixed in the bag, The low melting point raw material and the high melting point raw material are unevenly distributed, and if the high melting point raw material first comes into contact with the molten steel surface, the molten steel surface is not rapidly generated, and the molten steel surface is exposed to the outside air. Contact.
　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 completely 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３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３～３０質量％に規定する。より好ましくは、５～３０質量％であり、更に好ましくは、７～２５質量％である。 When using a molten steel surface heat insulating agent that is completely melted, 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. If the amount of magnesia contained is less than 3% by mass, the rate of erosion of the ladle or tundish coating material will be 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. Therefore, in the molten steel surface heat insulating agent according to the present embodiment, the magnesia content is regulated to 3 to 30% by mass. More preferably, it is 5 to 30% by mass, and still 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、１０～６０質量％、好ましくは１５～５５質量％、尚好ましくは２５～５０質量％のＣａＯ、１０～７０質量％、好ましくは２０～６５質量％、尚好ましくは４０～６０質量％のＡｌ２Ｏ３、３～３０質量％のＭｇＯ、０～１０質量％以下の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 this embodiment has a composition after mixing (average composition) of 10 to 60% by mass, preferably 15 to 55% by mass, more preferably 25 to 50% by mass of CaO, 10 to 70% by mass. The main components are preferably 20 to 65% by mass, more preferably 40 to 60% by mass of Al 2 O 3 , 3 to 30% by mass of MgO, and 0 to 10% by mass or less of SiO 2 . However, CaO / Al 2 O 3 = 0.5 to 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.
　前記した低融点原料としては、融点が溶鋼表面温度以下であるＢ２Ｏ３、Ｌｉ２Ｏ、Ｎａ２Ｏ、ＣａＯ－Ａｌ２Ｏ３、ＣａＯ－ＳｉＯ２、ＳｒＯ―ＳｉＯ２、Ａｌ２Ｏ３－ＣａＯ－ＭｇＯ、Ａｌ２Ｏ３－ＣａＯ－ＳｉＯ２、Ａｌ２Ｏ３－ＣａＯ－ＺｒＯ２、Ａｌ２Ｏ３－ＭｇＯ－ＳｉＯ２、ＣａＦ２などの複合酸化物を用いることができる。この複合酸化物としては、生石灰とアルミナを予備溶融した後に粉砕したもの、または生石灰とボーキサイトを予備溶融した後に粉砕したアルミナセメント等、任意の多元系融体を凝固した固体を使用することができる。また、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。なお、溶鋼表面保温剤を構成する具体的な低融点原料と高融点原料の組成、低融点原料と高融点原料の組み合わせや配合比率は、後で実施例として示す。 Examples of the low melting point raw material include B 2 O 3 , Li 2 O, Na 2 O, CaO—Al 2 O 3 , CaO—SiO 2 , SrO—SiO 2 , Al 2 O 3 whose melting point is lower than the molten steel surface temperature. Composite oxides such as —CaO—MgO, Al 2 O 3 —CaO—SiO 2 , Al 2 O 3 —CaO—ZrO 2 , Al 2 O 3 —MgO—SiO 2 , and CaF 2 can be used. As this composite oxide, a solid obtained by solidifying an arbitrary multi-component melt such as one obtained by pre-melting quick lime and alumina, or alumina cement obtained by pre-melting quick lime and bauxite can be used. . 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, CaO—MgO can be used. In addition, the composition of the specific low melting-point raw material and high melting-point raw material which comprise a molten steel surface heat retention agent, the combination and mixture ratio of a low-melting-point raw material and a high melting-point raw material are shown as an Example later.
　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表面に配置することにしている。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 thermal insulation method, the above-described molten steel surface thermal insulation agent is arranged on the molten steel surface 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 the 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. The molten steel surface heat insulating agent may be arranged on the molten steel surface so that the average melt thickness is in the range of 7 to 25 mm, or 9 to 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み合わ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 example of conditions adopted to confirm the feasibility and effects of the present invention, and the present invention is an example of these conditions. It is not limited to only.
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に実施例と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 with 1 charge of 280 t was subjected to hot metal preliminary treatment, 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. The molten steel surface temperature was 1560 to 1580 ° C. 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 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.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
　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 .
In Table 1, * 2 CaO—SiO 2 is 55% by mass of CaO and 45% by mass of CaO—SiO 2 .
* 3 SrO—SiO 2 in Table 1 is 50% by mass of SrO and 50% by mass of SiO 2 .
* 4 Al 2 O 3 —CaO—MgO in Table 1 is 50% by mass of Al 2 O 3 , 45% by mass of CaO and 5% by mass of MgO.
* 5 Al 2 O 3 —CaO—SiO 2 in Table 1 is 50% by mass of Al 2 O 3 , 45% by mass of CaO and 5% by mass of SiO 2 .
* 6 Al 2 O 3 —CaO—ZrO 2 in Table 1 is 50% by mass of Al 2 O 3 , 45% by mass of CaO and 5% by mass of ZrO 2 .
* 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 .
In Table 2, * 8 Al 2 O 3 —MgO is 75% by mass of Al 2 O 3 and 25% by mass of MgO.
In Table 2, * 9 CaO—MgO 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 to 2 pans of continuous continuous casting.
* 12 In Table 4, the number of defects 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 pans of continuous continuous casting. It is.
　図１に示されるように、実施例では、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 example, the total oxygen amount in the tundish molten steel is 1 to 2 pans of continuous continuous casting, compared to the total oxygen amount in the molten steel after RH treatment (after vacuum degassing treatment). 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 example, surface defects caused by oxide inclusions present in one cold-rolled steel sheet coil obtained from a steel piece produced by continuous casting in one or two pans are used. The average number 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)

  1. 　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低い、５０質量％以上の低融点原料と、融点が前記溶鋼表面温度より高い、５０質量％未満の高融点原料とを含有し、
    　１０～６０質量％のＣａＯと、１０～７０質量％のＡｌ２Ｏ３と、３～３０質量％のＭｇＯと、０～１０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２００～１０００μｍ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,
    A low melting point raw material having a melting point lower than the molten steel surface temperature of 50% by mass or more and a high melting point raw material having a melting point higher than the molten steel surface temperature of less than 50% by mass;
    10 to 60% by mass of CaO, 10 to 70% by mass of Al 2 O 3 , 3 to 30% by mass of MgO, and 0 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 insulating agent characterized in that 70 mass% or more is a powder having a particle size of 200 to 1000 μm.
  2. 　請求項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
    ことを特徴とする溶鋼表面保温方法。     The molten steel surface heat insulating agent according to claim 1, wherein the molten steel surface heat insulating agent is disposed on the molten steel surface so that an average molten layer thickness is in a range of 5 to 30 mm.
PCT/JP2010/072211 2009-12-10 2010-12-10 Agent for maintaining surface temperature of molten steel and method for maintaining surface temperature of molten steel WO2011071141A1 (en)

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CN105108089A (en) * 2015-07-31 2015-12-02 铜陵市大明玛钢有限责任公司 Preparation method for molten steel surface heat preservation agent

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CN105200186A (en) * 2015-09-02 2015-12-30 铜陵翔宇商贸有限公司 Preparing method for liquid steel surface heat preserving agent
CN114262765A (en) * 2021-12-23 2022-04-01 上海盛宝冶金科技有限公司 Environment-friendly tundish molten steel heat-insulating agent and preparation method thereof

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JPH01317667A (en) * 1988-06-16 1989-12-22 Yoshizawa Sekkai Kogyo Kk Heat holding material for molten metal and production thereof
JPH06170507A (en) * 1992-12-02 1994-06-21 Nippon Steel Corp Surface insulating material for molten steel
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