KR100423448B1 - A METHOD FOR MANUFACTURING Mn ADDED ULTRA LOW CARBON BLACK PLATE - Google Patents
A METHOD FOR MANUFACTURING Mn ADDED ULTRA LOW CARBON BLACK PLATE Download PDFInfo
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- KR100423448B1 KR100423448B1 KR10-2000-0071890A KR20000071890A KR100423448B1 KR 100423448 B1 KR100423448 B1 KR 100423448B1 KR 20000071890 A KR20000071890 A KR 20000071890A KR 100423448 B1 KR100423448 B1 KR 100423448B1
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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
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/068—Decarburising
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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
- C21C7/0075—Treating in a ladle furnace, e.g. up-/reheating of molten steel within the ladle
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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
- C21C7/0087—Treatment of slags covering the steel bath, e.g. for separating slag from the molten metal
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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
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/06—Deoxidising, e.g. killing
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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
- C21C7/10—Handling in a vacuum
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Abstract
본 발명은 주로 건전지 케이스, 에어로졸 돔(Dome), 팬시(Fancy) 용품 등의 소재로 널리 사용되는 Mn첨가 극저탄소 블랙플레이트(이하, 'BP재'라 함)의 제조방법에 관한 것으로, Mn첨가 극저탄소 BP재의 제조시 제강단계에서 용강의 재산화 반응을 억제하고 RH 정련시간을 감소시킴으로써, 강의 청정성을 크게 향상시킨 Mn첨가 극저탄소 BP재의 제조방법을 제공하는데, 그 목적이 있다.The present invention relates to a manufacturing method of Mn-added ultra-low carbon black plate (hereinafter referred to as 'BP material'), which is mainly used as a material for battery cases, aerosol domes, and fancy articles. It is an object of the present invention to provide a method for producing Mn-added ultra-low carbon BP material which greatly improves the cleanliness of steel by suppressing the reoxidation reaction of molten steel in the steelmaking step and reducing the RH refining time during the production of the ultra low carbon BP material.
상기한 목적을 달성하기 위한 본 발명은,The present invention for achieving the above object,
중량%로 C: 0.004중량% 이하, Mn: 0.4~0.6중량%인 극저탄소 블랙 플레이트의 제조방법에 있어서,In the manufacturing method of ultra-low carbon black plate which is C: 0.004% by weight or less, Mn: 0.4-0.6% by weight,
용강을 전로 또는 전기로에서 레이들로 출강시 2.0~2.5kg/용강-톤의 Fe-Mn, 1.7~3.3kg/용강-톤의 생석회(CaO), 및 Al이 40% 이상인 슬래그 탈산제를 0.3~0.6kg/용강-톤 첨가하는 단계;2.0 ~ 2.5kg / melt-ton Fe-Mn, 1.7 ~ 3.3kg / melt-ton quicklime (CaO), and slag deoxidizer 0.3 ~ 0.6 when Al is used as ladle in converter or electric furnace adding kg / mol-ton;
상기 레이들을 RH로 이송하여 진공도를 5torr이하로 낮추고, 용강을 환류시키면서 탄소농도가 40ppm 이하에 도달할 때까지 탈탄반응을 행하는 단계;Transferring the ladle to RH to lower the vacuum to below 5 torr, and decarburizing the molten steel until the carbon concentration reaches 40 ppm or less;
상기 RH내에서 탈탄반응이 종료되면 용존산소를 30ppm 이하로 낮추도록, 용강탈산제를 첨가하는 단계;Adding a molten deoxidizer to lower the dissolved oxygen to 30 ppm or less when the decarburization reaction is completed in the RH;
상기 용강탈산제를 첨가한 후 2.5~4.0kg/용강-톤의 금속Mn을 첨가하는 단계;Adding 2.5 to 4.0 kg / melt-ton of metal Mn after adding the molten deoxidizer;
상기 금속 Mn첨가후 진공도를 0.5~50torr로 유지하면서 5~8분간 용강을 환류시키고 RH 정련을 종료하는 단계; 및Refluxing the molten steel for 5 to 8 minutes while maintaining the vacuum degree at 0.5 to 50 torr after adding the metal Mn and terminating the RH refining; And
상기 RH정련 종료직후 용강에 슬래그 탈산제를 0.2~0.6kg/용강-톤 첨가하는 단계를 포함하여 이루어지는 Mn첨가 극저탄소 블랙 플레이트의 제조방법을 기술적 요지로 한다.Method of producing a Mn-added ultra-low carbon black plate comprising the step of adding 0.2 ~ 0.6kg / molten-ton of slag deoxidizer to the molten steel immediately after the completion of the RH refining.
Description
본 발명은 주로 건전지 케이스, 에어로졸 돔(Dome), 팬시(Fancy) 용품 등의 소재로 널리 사용되는 Mn첨가 극저탄소 블랙플레이트(이하, 'BP재'라 함)의 제조방법에 관한 것으로, 보다 상세하게는 제강공정에서 C: 0.004중량% 이하, Mn: 0.4~0.6중량%로 정련하여 청정성을 개선시킨 Mn첨가 극저탄소 블랙플레이트의 제조방법에 관한 것이다.The present invention relates to a manufacturing method of Mn-added ultra-low carbon black plate (hereinafter referred to as 'BP material'), which is mainly used as a material for battery cases, aerosol domes, and fancy articles. In particular, the present invention relates to a method for producing Mn-added ultra low carbon black plate, which is refined to C: 0.004% by weight or less and Mn: 0.4 to 0.6% by weight in the steelmaking process.
C: 0.004중량% 이하, Mn: 0.4~0.6중량%를 함유하는 BP재는, 주로 건전지 케이스, 에어로졸 돔(Dome), 팬시(Fancy) 용품 등의 소재로 널리 사용되는 것으로, 이들 소재에는 우수한 청정성이 요구되기 때문에, 강중 비금속 개재물(Non-metallic inclusion)의 량을 적게 해야 한다. 따라서, 망간첨가 극저탄소 BP재에서는 15ppm 이하의 전산소량(Total Oxygen, 이하 T.[O]라 함)이 요구되고 있다.BP materials containing C: 0.004% by weight or less and Mn: 0.4-0.6% by weight are mainly used in materials such as battery cases, aerosol domes and fancy articles, and these materials have excellent cleanliness. As required, the amount of non-metallic inclusions in the steel should be reduced. Therefore, the manganese-added ultra-low carbon BP material is required to have a total oxygen content of 15 ppm or less (Total Oxygen, hereinafter referred to as T. [O]).
한편, 종래 제강공정에서 Mn첨가 극저탄소강을 정련하는 방법은, 도1과 같다.Meanwhile, a method of refining Mn-added ultra low carbon steel in the conventional steelmaking process is as shown in FIG. 1.
먼저, 전로 또는 전기로에서 정련이 완료된 용강을 레이들로 옮기는데(이하, 출강이라 함), 이 때 Mn성분을 첨가할 목적으로 0.5~7.0중량%의 C를 함유하는 페로망간(Fe-Mn)을 4.5~7.0kg/용강-톤 첨가하고, 슬래그 성분을 제어하기 위하여 3.5~4.0kg/용강-톤의 생석회(CaO)를 첨가하고, 그리고 슬래그 중 산화철과(FeO)과 망간산화물(MnO)을 감소시키기 위하여 금속 알루미늄을 40~60중량% 함유하는 2~3kg/용강-톤의 슬래그 탈산제를 첨가한다.First, the molten steel refined in the converter or the electric furnace is transferred to the ladle (hereinafter referred to as tapping). At this time, ferromanganese (Fe-Mn) containing 0.5 to 7.0% by weight of C is added for the purpose of adding Mn component. Add 4.5 ~ 7.0kg / mol-ton, add 3.5 ~ 4.0kg / t-lime of quicklime (CaO) to control slag composition, and reduce iron oxide (FeO) and manganese oxide (MnO) in slag In order to add 2 to 3 kg / molten-tonne slag deoxidizer containing 40 to 60% by weight of metallic aluminum.
그 다음, 상기 레이들로 출강된 용강을 RH 진공탈가스 장치(이하, RH라 함)로 이송하고, 용강중 C농도가 0.004중량% 이하에 도달할 때까지 산소를 취입하여 탄소성분을 제거(이하, 탈탄반응이라 함)시킨다.Then, the molten steel tapped into the ladle is transferred to an RH vacuum degassing apparatus (hereinafter referred to as RH), and oxygen is blown to remove carbon components until the C concentration in the molten steel reaches 0.004% by weight or less. Decarburization).
상기 탈탄반응이 종료되면 용강탈산제로서 알루미늄(Al)을 첨가하여 용존산소(Free oxygen)를 수ppm 수준으로 낮추고(이하, 용강탈산이라 함), 이어서 용강을 일정시간 환류시켜 탈산생성물, 즉 알루미나를 슬래그 층으로 부상분리시킴으로써 정련을 종료한다.When the decarburization reaction is completed, aluminum (Al) is added as a molten deoxidizer to lower dissolved oxygen (Free oxygen) to several ppm level (hereinafter referred to as molten steel deoxidation), and then the molten steel is refluxed for a predetermined time, ie, alumina. Refining is terminated by flotation into slag layers.
그러나, 상기 종래기술에서는 용존산소가 600~1000ppm인 용강을 출강하면서 다량의 Fe-Mn을 첨가하므로 Mn 성분은 증가하는 반면에, Mn이 용존산소와 하기 반응식(1)과 같이 반응하여 Mn의 수율(Recovery)이 감소될 뿐 아니라, 용존산소를 불필요하게 감소시키는 문제가 있었다. 특히, 다량의 (MnO)가 생성되어 RH 용강탈산 이후 탈산제로 첨가된 알루미늄과 하기 반응식(2)의 반응(이하, '재산화반응'이라 함)을 일으켜, 강의 청정성를 크게 저하시키는 문제점을 지니고 있다.However, in the prior art, since a large amount of Fe-Mn is added while dissolving molten steel having a dissolved oxygen of 600 to 1000 ppm, Mn component increases, while Mn reacts with dissolved oxygen as shown in Reaction Formula (1) below to yield Mn. In addition to the reduction of recovery, there was a problem of unnecessarily reducing dissolved oxygen. In particular, a large amount of (MnO) is generated to cause a reaction of the aluminum added as a deoxidizer after RH molten iron deoxidation and the reaction (2) (hereinafter referred to as 'reoxidation reaction'), which greatly reduces the cleanliness of steel. .
상기 반응식(1),(2)에서, [O]는 용존산소, (MnO)는 슬래그 중 MnO, [Al]은 용강중 Al 성분, Al2O3(s)는 강에 잔존하는 알루미나 개재물을 각각 의미함.In Reaction Formulas (1) and (2), [O] is dissolved oxygen, (MnO) is MnO in slag, [Al] is an Al component in molten steel, and Al 2 O 3 (s) is an alumina inclusion remaining in the steel, respectively. Meaning.
또한, 용존산소의 감소로 말미암아 RH에서 용강중 0.004중량% 이하의 탄소함량을 얻기에는 산소가 크게 부족하므로, RH 탈탄반응이 진행되는 동안 기체산소를 다량 취입해야 하는 문제가 있다. 따라서, RH 정련시간이 증가되고, 또한 산소취입으로 인해 하기 반응식(3)에서 알 수 있는 바와 같이 철(Fe)이 산화되어 (FeO) 성분이 증가되는 문제점도 안고 있다.In addition, since oxygen is not enough to obtain a carbon content of 0.004% by weight or less in molten steel in RH due to a decrease in dissolved oxygen, there is a problem that a large amount of gaseous oxygen is blown during the RH decarburization reaction. Therefore, the RH refining time is increased, and also due to oxygen blowing, iron (Fe) is oxidized and the (FeO) component is increased as can be seen in the following Reaction Formula (3).
한편, RH에서 산소취입으로 증가된 (FeO)는 RH 용강 탈산 이후, 용강과 슬래그 계면에서 하기 반응식(4)의 반응(이하, '재산화 반응'이라 함)을 일으켜, 강의청정도를 크게 악화시키는 문제점이 상존한다.On the other hand, (FeO) increased by oxygen blowing in RH causes reaction of reaction formula (4) below (hereinafter referred to as 'reoxidation reaction') at the interface between molten steel and slag after deoxidation of RH molten steel, which greatly deteriorates the cleanliness of steel. The problem exists.
이에, 본 발명의 발명자들은 상기와 같은 요구에 대응하기 위하여 연구와 실험을 행하고, 그 결과에 근거하여 본 발명을 제안하게 된 것으로, 본 발명은 Mn첨가 극저탄소 BP재의 제조시 제강단계에서 용강의 재산화 반응을 억제하고 RH 정련시간을 감소시킴으로써, 강의 청정성을 크게 향상시킨 Mn첨가 극저탄소 BP재의 제조방법을 제공하는데, 그 목적이 있다Therefore, the inventors of the present invention conducts research and experiments in order to respond to the above demands, and based on the results, the present invention proposes the present invention. The present invention relates to the use of molten steel in the steelmaking step of manufacturing Mn-added ultra low carbon BP materials. It is an object of the present invention to provide a method for producing Mn-added ultra-low carbon BP material which greatly improves the cleanliness of steel by suppressing reoxidation reaction and reducing RH refining time.
도1은 Mn첨가 극저탄소 블랙플레이트(이하, 'BP재'라 함)의 제조공정을 나타내는 개략도Figure 1 is a schematic diagram showing the manufacturing process of Mn-added ultra-low carbon black plate (hereinafter referred to as 'BP material')
도2는 RH 산소취입량과 슬래그중 (FeO) 농도와의 관계를 나타내는 그래프2 is a graph showing the relationship between the RH oxygen blowing amount and the concentration of (FeO) in slag
상기한 목적을 달성하기 위한 본 발명은,The present invention for achieving the above object,
중량%로 C: 0.004중량% 이하, Mn: 0.4~0.6중량%인 극저탄소 블랙 플레이트의 제조방법에 있어서,In the manufacturing method of ultra-low carbon black plate which is C: 0.004% by weight or less, Mn: 0.4-0.6% by weight,
용강을 전로 또는 전기로에서 레이들로 출강시 2.0~2.5kg/용강-톤의 Fe-Mn, 1.7~3.3kg/용강-톤의 생석회(CaO), 및 Al이 40% 이상인 슬래그 탈산제를 0.3~0.6kg/용강-톤 첨가하는 단계;2.0 ~ 2.5kg / melt-ton Fe-Mn, 1.7 ~ 3.3kg / melt-ton quicklime (CaO), and slag deoxidizer 0.3 ~ 0.6 when Al is used as ladle in converter or electric furnace adding kg / mol-ton;
상기 레이들을 RH로 이송하여 진공도를 5torr이하로 낮추고, 용강을 환류시키면서 탄소농도가 40ppm 이하에 도달할 때까지 탈탄반응을 행하는 단계;Transferring the ladle to RH to lower the vacuum to below 5 torr, and decarburizing the molten steel until the carbon concentration reaches 40 ppm or less;
상기 RH내에서 탈탄반응이 종료되면 용존산소를 30ppm 이하로 낮추도록, 용강탈산제를 첨가하는 단계;Adding a molten deoxidizer to lower the dissolved oxygen to 30 ppm or less when the decarburization reaction is completed in the RH;
상기 용강탈산제를 첨가한 후 2.5~4.0kg/용강-톤의 금속Mn을 첨가하는 단계;Adding 2.5 to 4.0 kg / melt-ton of metal Mn after adding the molten deoxidizer;
상기 금속 Mn첨가후 진공도를 0.5~50torr로 유지하면서 5~8분간 용강을 환류시키고 RH 정련을 종료하는 단계; 및Refluxing the molten steel for 5 to 8 minutes while maintaining the vacuum degree at 0.5 to 50 torr after adding the metal Mn and terminating the RH refining; And
상기 RH정련 종료직후 용강에 슬래그 탈산제를 0.2~0.6kg/용강-톤 첨가하는 단계를 포함하여 이루어지는 Mn첨가 극저탄소 블랙 플레이트의 제조방법에 관한 것이다.It relates to a method for producing a Mn-added ultra-low carbon black plate comprising the step of adding 0.2 ~ 0.6kg / molten-ton of slag deoxidizer to the molten steel immediately after the end of the RH refining.
이하, 본 발명에 대하여 상세히 설명한다.EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.
전로 또는 전기로에서 정련이 완료된 용강중에는, 0.03~0.08중량%의 C , 0.01중량% 이하의 Mn, 600~1000ppm의 [O] 등이 함유되고, 슬래그 염기도 즉, (CaO/SiO2)비가 3.0~4.0, (FeO)+(MnO)가 20~30중량%, 그리고 인산화물(P2O5)이 1~3중량%에 달하게 되는데, 이것이 레이들로 출강될 때 전로 슬래그는 5~10kg/용강-톤 유출된다.The molten steel refined in the converter or the electric furnace contains 0.03 to 0.08% by weight of C, 0.01% by weight or less of Mn, 600 to 1000 ppm of [O], and the slag basicity, that is, the (CaO / SiO 2 ) ratio of 3.0 to 4.0, (FeO) + (MnO) is 20 to 30% by weight, and phosphate (P 2 O 5 ) to 1 to 3% by weight, when it is cast to ladle converter slag is 5 ~ 10kg / molten steel -Tons spilled.
출강직후 상기 슬래그 중 (P2O5)는, 하기 반응식(5)과 같이 분해되기 때문에, 용강중에는 인(P) 성분이 증가하게 된다.Since (P 2 O 5 ) in the slag immediately after tapping decomposes as in the following reaction formula (5), phosphorus (P) component increases in molten steel.
본 발명에서는 상기 반응식(5)의 반응을 억제하기 위하여, 주성분이 CaO인 생석회를 용강 1톤당 1.7~3.3kg 첨가하여, 상기 반응식(6)의 반응을 유도하였다.In the present invention, in order to suppress the reaction of the reaction formula (5), 1.7 to 3.3 kg of quicklime whose main component is CaO is added per ton of molten steel to induce the reaction of the reaction formula (6).
그러나, 제강온도 1550~1650℃에서 (4CaO·P2O5)는 (P2O5)보다 열역학적으로 안정하므로 상기 식(5)의 분해반응이 억제될 것으로 생각되나, 상기 생석회의 양이 1.7kg/용강-톤인 경우에는, 상기 반응식(5)에 의해 용강중에 증가되는 P성분의 함량이 0.003중량%에 달하여 곤란하였다. 또한, CaO 첨가량이 3.3kg을 초과하는 경우에는 상기 반응식(6)의 반응을 효과적으로 일으켜 용강중 P농도가 증가되는 것을 방지할 수는 있으나, 슬래그 염기도, 즉 CaO/SiO2비 및 CaO/Al2O3비율이 크게 증가하여 슬래그가 비금속 개재물을 흡수하는 능력을 감소시키게 되므로 강의 청정성을 떨어뜨리는 문제가 있었다.However, since the (4CaO · P 2 O 5 ) is thermodynamically more stable than the (P 2 O 5 ) at the steelmaking temperature of 1550 ~ 1650 ℃, the decomposition reaction of the formula (5) is thought to be suppressed, but the amount of quicklime is 1.7 In the case of kg / mol-ton, the content of P component increased in molten steel by the reaction formula (5) was difficult to reach 0.003% by weight. In addition, when the amount of CaO added is more than 3.3kg it can effectively prevent the reaction of the reaction formula (6) to increase the P concentration in the molten steel, but the slag basicity, that is, the CaO / SiO 2 ratio and CaO / Al 2 O the three ratios increased significantly since the slag reduces the ability to absorb non-metallic inclusions had problems dropping the river cleanliness.
출강시 상기 생석회와 함께 투입되는 Fe-Mn는, [O] 감소량을 최소로 제어할 수 있는 양만큼 첨가하는 것이 바람직하다. 즉, Fe-Mn의 함량이 2.5kg/용강-톤 이상으로 다량 투입되면, 상기 반응식(1)의 반응으로 용존산소 [O]가 350ppm 이상으로 크게 감소하여 RH 탈탄반응에 요구되는 용존산소를 확보하기 곤란하고, 슬래그중 (MnO)가 4~5중량%로 크게 증가하게 되어 청정강으로 제조할 수 없다. 반면에,2.0kg/용강-톤 미만인 경우에는, 출강전후 [O] 감소량이 150ppm 이하, (MnO) 증가량이 2중량% 미만에 달하였으나, Mn을 0.4~0.6중량%로 제어하기 위해서 RH에서 금속 Mn을 다량 첨가해야 하므로 용강온도가 크게 감소되는 문제가 있었다. 따라서, 상기 Fe-Mn은 2.0~2.5kg/용강-톤으로 첨가하는 것이 바람직하다.Fe-Mn added together with the quicklime at the time of tapping is preferably added in an amount that can be controlled to the minimum [O] reduction amount. That is, when the content of Fe-Mn is added in a large amount of 2.5kg / mol-ton or more, dissolved oxygen [O] is greatly reduced to 350 ppm or more by the reaction of the reaction formula (1) to secure the dissolved oxygen required for RH decarburization reaction. It is difficult to do so, and (MnO) in slag is greatly increased to 4 to 5% by weight, and cannot be manufactured as clean steel. On the other hand, in case of less than 2.0 kg / mol-ton, the amount of [O] decrease after tapping was 150 ppm or less, and the (MnO) increase amounted to less than 2% by weight, but in order to control Mn to 0.4 to 0.6% by weight, Since a large amount of Mn should be added, there was a problem in that the molten steel temperature was greatly reduced. Therefore, the Fe-Mn is preferably added at 2.0 ~ 2.5kg / mol-ton.
또한, 출강중에는 CaO와 Fe-Mn첨가 직후 슬래그 탈산제를 0.3~0.6kg/용강-톤 첨가한다. 슬래그 탈산제는, 전로로부터 유출되는 슬래그에 포함된 (FeO), (MnO) 및 출강시 첨가된 Fe-Mn으로 발생되는 (MnO) 등을 하기 반응식(7) 및 (8)을 통해 감소시키기 위해 첨가한다. 따라서, 슬래그 탈산제는 Fe-Mn 첨가가 완료되고, 전로 슬래그가 유출되는 시점인 출강 말기에 첨가하는 것이 바람직하다.In addition, 0.3-0.6kg / mol-ton of slag deoxidizer is added immediately after adding CaO and Fe-Mn during tapping. The slag deoxidizer is added to reduce (FeO), (MnO) and (MnO) generated by Fe-Mn added during tapping in slag flowing out from the converter through the following schemes (7) and (8). do. Therefore, it is preferable to add the slag deoxidizer at the end of the tapping time when Fe-Mn addition is completed and converter slag flows out.
상기 반응식(7),(8)에 나타난 바와 같이, 금속 Al은 슬래그중 (FeO),(MnO) 등 저급산화물을 감소시키는 역할을 하는데, 그 함량이 슬래그 탈산제중 40중량% 미만인 경우에는 슬래그 탈산제 첨가량이 상대적으로 많아 모든 정련이 종료된 이후 발생되는 슬래그 양, 즉 폐기물 발생량이 증가되므로, 상기 슬래그 탈산제중 상기 금속 Al의 함량은 40중량% 이상으로 하는 것이 바람직하다.As shown in the reaction formulas (7) and (8), the metal Al serves to reduce lower oxides such as (FeO), (MnO) in the slag, when the content is less than 40% by weight of the slag deoxidizer slag deoxidizer Since the amount of addition is relatively large, the amount of slag generated after completion of all refining, that is, the amount of waste generated is increased, so the content of the metal Al in the slag deoxidizer is preferably 40% by weight or more.
한편, 상기 슬래그 탈산제를 0.3kg/용강-톤 미만 첨가하는 경우에는 저급산화물의 감소효과를 얻기가 어렵고, 0.6kg/용강-톤 이상 첨가하는 경우에는 저급산화물을 효과적으로 감소시킬수는 있지만, 슬래그 탈산제가 용존산소와 반응하여 용존 산소를 크게 감소시켜 정련효율을 떨어뜨린다. 따라서, 상기 슬래그 탈산제의 함량은 0.3~0.6kg/용강-톤으로 설정하는 것이 바람직하다.On the other hand, if the slag deoxidizer is added less than 0.3kg / molten-ton, it is difficult to obtain a lower oxide reduction effect, when adding more than 0.6kg / molten-ton can effectively reduce the lower oxide, the slag deoxidizer is By reacting with dissolved oxygen, the dissolved oxygen is greatly reduced, reducing the refining efficiency. Therefore, the content of the slag deoxidizer is preferably set to 0.3 ~ 0.6kg / mol-ton.
상기한 바와 같이 출강이 완료되면, 용강이 담긴 레이들을 RH(진공탈가스장치)로 이송하고, 진공도를 5torr이하로 유지시킨 후, 용강을 환류시키면서 탄소농도가 40ppm 이하에 이를 때까지 탈탄반응을 행한다. 상기 탈탄반응은, 하기 반응식(9)과 같이 행해져서 용강중 C는 제거되는데, 진공도가 높을수록 탈탄반응이 촉진된다. 만약 진공도가 5torr 보다 낮다면, 하기 반응식(9)의 탈탄반응이 지연되어 탈탄반응 시간이 증가되므로 바람직하지 않다.When the tapping is completed as described above, the ladle containing the molten steel is transferred to a vacuum degassing apparatus (RH), the vacuum is maintained below 5 torr, and the carbonization is carried out until the carbon concentration reaches 40 ppm or less while refluxing the molten steel. Do it. The decarburization reaction is carried out as in the following reaction formula (9) to remove C in the molten steel, but the higher the degree of vacuum, the more the decarburization reaction is promoted. If the degree of vacuum is lower than 5 torr, the decarburization reaction of the following reaction formula (9) is delayed, which is not preferable because the decarburization reaction time is increased.
한편, RH 탈탄반응이 진행되는 동안, 용강의 탈탄반응을 촉진시키기 위해서 용강에 기체산소를 취입할 수 있는데, 그 취입량이 지나치게 많으면 상기 반응식(3)의 반응에 의해 다량의 (FeO)가 생성되므로 일정 범위내로 제한하는 것이바람직한데, 본 발명에서는 0.35Nm3/용강-톤 이하로 설정하였다. 즉. 본 발명의 발명자들은 실험을 통해, RH에서 산소취입량이 0.35Nm3/용강-톤을 초과하면, 도 2에 나타난 바와 같이, 슬래그중 (FeO) 농도가 2중량%를 초과하게 되어 청정도 향상에 불리함을 알수 있었다.On the other hand, during the RH decarburization reaction, gaseous oxygen may be blown into the molten steel in order to promote the decarburization reaction of the molten steel, but if the amount is too large, a large amount of (FeO) is generated by the reaction of the reaction formula (3). It is preferable to limit it within a certain range, but in the present invention, it is set to 0.35 Nm 3 / molten steel-ton or less. In other words. The inventors of the present invention, when the oxygen injection amount in the RH exceeds 0.35Nm 3 / molten-ton through experiment, as shown in Figure 2, the concentration of (FeO) in the slag exceeds 2% by weight to improve the cleanliness I could see the disadvantages.
상기 RH에서 탈탄반응이 종료되는 시점에 용강탈산제로서 Al을 첨가하여 용강을 탈산하는데, 일례로 Al 탈산강을 연속주조하기 위해서는 용존산소를 30ppm 이하로 낮추는 것이 바람직하다. 그 이유는, 상기 용존산소가 30ppm을 초과하면, 연속주조동안 주편의 터짐(break-out)이 종종 발생하여 연속주조조업이 어렵게 되기 때문이다. 한편, 상기 탈탄반응의 종료시점은, 탈탄반응이 진행되는 동안 용강 시료는 채취하고 화학분석을 행하거나 또는 탈탄반응이 진행되는 동안 배출되는 가스 성분을 분석함으로써 판정이 가능하다.When the decarburization reaction is terminated at RH, Al is added as a molten steel deoxidizer to deoxidize molten steel. For example, in order to continuously cast Al deoxidized steel, the dissolved oxygen is preferably lowered to 30 ppm or less. The reason is that when the dissolved oxygen exceeds 30 ppm, break-out of the cast often occurs during continuous casting, making continuous casting operation difficult. On the other hand, the end point of the decarburization reaction can be determined by taking a molten steel sample during the decarburization reaction and performing a chemical analysis or analyzing the gas component discharged during the decarburization reaction.
다음, 상기 용강탈산제를 첨가한 후 2.5~4.0kg/용강-톤의 금속Mn을 첨가하는데, 그 첨가 시점은 용강탈산제 첨가후 3~5분으로 하는 것이 바람직하다. 즉, RH에서 용강탈산제 Al을 첨가하는 경우, 탈산평형에 도달되는 시간이 3분 정도 소요되므로, 3분 이후 즉, 탈산평형에 도달한 후 금속 Mn을 첨가해야 상기 반응식(1)의 반응에 의한 (MnO) 생성을 억제할 수 있게 된다. 그러나, 금속 Mn을 5분 이후에 첨가하면, 첨가된 금속 Mn이 용해되어 균질 농도에 도달하는데 요구되는 시간(약 5분)이 길어져 RH 정련시간이 지연되는 문제가 있다. 또한, 상기 금속Mn의 함량이 2.5kg/용강-톤 미만이면 Mn을 0.4중량%로 하기가 어렵고, 4.0kg/용강-톤을 초과하는 경우에는 Mn의 함량이 0.6중량%를 초과하기 때문에, 금속 망간은 2.5~4.0kg/용강-톤 첨가하는 것이 바람직하다.Next, after the molten deoxidizer is added, 2.5-4.0 kg / molten-ton metal Mn is added, and the addition time is preferably 3 to 5 minutes after the molten deoxidizer is added. That is, when the molten deoxidizer Al is added in RH, the deoxidation equilibrium takes about 3 minutes. Therefore, the metal Mn must be added after 3 minutes, that is, after the deoxidation equilibrium is reached. (MnO) formation can be suppressed. However, when the metal Mn is added after 5 minutes, the time required for dissolving the added metal Mn to reach a homogeneous concentration (about 5 minutes) becomes long, which causes a problem of delaying the RH refining time. In addition, when the content of the metal Mn is less than 2.5kg / molten-ton, it is difficult to make Mn 0.4% by weight, and when the content of Mn exceeds 4.0kg / molten-ton, the content of Mn exceeds 0.6% by weight. Manganese is preferably added 2.5 ~ 4.0kg / mol-ton.
이후, 금속Mn이 용해되어 균질Mn 농도에 도달하면, Al 첨가로 인해 생성된 Al2O3개재물의 부상분리를 도울 목적으로 용강을 적정시간 환류하는 것이 바람직한데, 이 때 진공도는 0.5~50torr, 환류시간은 5~8분으로 하는 것이 바람직하다. 그 이유는, 상기 진공도가 0.5torr 미만일 경우에는 진공을 형성하는데 소요되는 증기(steam) 사용량이 증가될 뿐 아니라 환류속도가 빨라져 RH 내화물 침식이 가중되는 문제가 있고, 50torr를 초과하는 경우에는 용강의 환류속도가 늦어져 RH 정련시간이 지연되기 때문이다. 또한, 상기 환류시간이 5분 미만일 경우에는 균질한 Mn 농도를 얻기가 곤란할 뿐 아니라 Al2O3개재물의 부상분리하는데 소요시간이 부족하여 강의 청정성이 나빠지고, 8분을 초과하는 경우에는 RH 처리시간이 지연됨에 따라 용강의 온도가 감소되어 RH 정련이 종료될 시점에 다시 용강을 승온해야 하는 문제점이 생기게 된다.Then, when the metal Mn is dissolved to reach a homogeneous Mn concentration, it is preferable to reflux the molten steel for an appropriate time in order to help floating separation of Al 2 O 3 inclusions generated by Al addition, wherein the vacuum degree is 0.5 to 50 torr, It is preferable to make reflux time into 5 to 8 minutes. The reason is that when the vacuum degree is less than 0.5torr, not only the amount of steam used to form the vacuum is increased but also the reflux rate is increased, which increases the RH refractory erosion. This is because the reflux rate is slowed and the RH refining time is delayed. In addition, when the reflux time is less than 5 minutes, it is difficult to obtain a homogeneous Mn concentration, and the cleanness of the steel is deteriorated due to insufficient time for floating separation of Al 2 O 3 inclusions, and RH treatment when exceeding 8 minutes. As the time is delayed, the temperature of the molten steel decreases, causing the molten steel to be heated again at the end of the RH refining.
이와 같은 RH 정련이 종료된 직후에는, 상기한 것과 동일한 슬래그탈산제를 0.2~0.6kg/용강-톤 첨가하는 것이 바람직하다. 그 이유는, RH정련 종료직후 슬래그탈산제를 첨가하면, 연속주조가 시작되기 이전에 상기 반응식(1) 및 (4)의 재산화반응이 일어나는 것을 효과적으로 방지할 수 있기 때문이다. 즉, 첨가된 슬래그 탈산제는 슬래그에 존재하는 저급산화물 (FeO), (MnO)와 상기 반응식(7),(8)의 화학반응을 일으켜, 슬래그중 (FeO),(MnO)을 감소시키고 알루미나 개재물의 생성을 억제하므로 강의 청정성을 향상시킬 수 있는 것이다. 이 때, 슬래그 탈산제의 첨가량이 0.2kg/용강-톤 미만이면 저급산화물을 감소시키기 어렵고, 0.6kg/용강-톤을 초과하는 경우에는 저급산화물 감소 효율이 크게 떨어지고, 슬래그 탈산제를 과잉으로 첨가하게 되므로 최종적으로 발생되는 슬래그 양이 증가되므로 불리한 문제가 있다.Immediately after such RH refining is completed, it is preferable to add 0.2-0.6 kg / molten-tonne of the same slag acid agent as mentioned above. The reason is that the addition of the slag oxidizing agent immediately after the end of the RH refining can effectively prevent the reoxidation reaction of the reaction formulas (1) and (4) from occurring before the continuous casting starts. That is, the added slag deoxidizer causes a chemical reaction of the lower oxides (FeO), (MnO) present in the slag and the reaction formulas (7) and (8), thereby reducing the (FeO), (MnO) in the slag and alumina inclusions. It is possible to improve the cleanliness of the steel by suppressing the formation of. At this time, if the added amount of the slag deoxidizer is less than 0.2kg / molten-ton, it is difficult to reduce the lower oxide, when it exceeds 0.6kg / molten-ton, the lower oxide reduction efficiency is greatly reduced, and the slag deoxidizer is added excessively There is a disadvantageous problem because the amount of slag generated finally increases.
상기한 방법에 의해 RH 정련이 종료되고, 슬래그 탈산제가 첨가된 용강은 연속주조공정으로 이송되어 연속주조가 실시됨으로써, 청정성이 우수한 망간첨가 극저탄소 BP재로 제조된다.RH refining is completed by the above-mentioned method, molten steel to which the slag deoxidizer is added is transferred to a continuous casting process, and continuous casting is performed, and it is manufactured from the manganese-added ultra low carbon BP material excellent in the cleanliness.
이하, 실시예를 통하여 본 발명을 보다 상세히 설명한다.Hereinafter, the present invention will be described in more detail with reference to Examples.
(실시예)(Example)
망간첨가 극저탄소 블랙플레이트를제조하기 위하여, 먼저 300톤 전로에서 정련을 종료한 용강을 분석한 결과 [C] 0.04중량%, [Mn] 0.09중량% [O] 690ppm임을 확인하였다. 이와 같은 용강을 레이들로 출강시, 하기 표 1과 같은 양의 생석회, Fe-Mn, 및 슬래그 탈산제를 첨가하였다. 여기서, 사용된 슬래그 탈산제는 금속 Al을 47.6중량% 함유하고, 상업적으로 판매되는 제품이다.In order to manufacture the manganese-added ultra-low carbon black plate, the molten steel which was first refined in the 300-ton converter was found to be [C] 0.04 wt% and [Mn] 0.09 wt% [O] 690 ppm. When the molten steel was pressed by ladle, the amount of quicklime, Fe-Mn, and slag deoxidizer as shown in Table 1 were added. The slag deoxidizer used here contains 47.6% by weight of metal Al and is a commercially available product.
출강이 종료된 용강을 RH로 이송하고, RH 도착시점의 용존산소 및 (FeO+MnO)의 함량을 측정하여 하기 표 1에 나타낸 후, 슬래그를 채취하고 필립스사의 XRF로 주요 성분을 분석하였다. 이어서, 진공도를 5torr 이하로 유지하면서 탈탄반응을 행하고, 탈탄반응이 진행되는 동안 하기 표1의 양으로 기체산소를 취입하였다. 탈탄반응이 종료된 이후에는, 하기 표1의 양으로 탈산제인 Al을 첨가하여 탈산하고, 용강탈산제의 첨가로부터 3분 시점에 금속Mn을 첨가하였는데, 그 함량은 하기 표1과 같이 하였다. 그 후, 진공도를 30torr로 유지하면서 6분간 용강을 환류시키고, RH정련을 종료하였다. 이어서, 상기와 동일한 슬래그 탈산제를 RH도착 슬래그의 (FeO+MnO) 함량과 RH에서 산소 취입량에 따라 산정하여, 하기 표1의 양으로 첨가하고, 슬래그 시료를 채취 분석하였다.After the tapping was completed, the molten steel was transferred to RH, and the dissolved oxygen and (FeO + MnO) content at the time of arrival of RH were measured and shown in Table 1 below. The slag was collected and the main components were analyzed by XRF. Subsequently, decarburization was carried out while maintaining the vacuum degree at 5 torr or less, and gaseous oxygen was blown in the amounts shown in Table 1 during the decarburization reaction. After the decarburization reaction was completed, the deoxidizer was added and deoxidized in the amount shown in Table 1 below, and metal Mn was added 3 minutes after the addition of the molten steel deoxidizer, and the content thereof was as shown in Table 1 below. Thereafter, the molten steel was refluxed for 6 minutes while maintaining the vacuum degree at 30 torr, and the RH refining was completed. Subsequently, the same slag deoxidizer was calculated according to the (FeO + MnO) content of the RH-added slag and the amount of oxygen blown at RH, and then added in the amount shown in Table 1 below, and the slag sample was collected and analyzed.
이후, 용강을 연속주조함으로써, 망간첨가 극저탄소 BP재강의 생산을 완료하고, 주편을 채취하여 LECO 산소/질소 동시분석기로 강의 T.[O]를 분석하고, 그 결과를 하기 표 1에 정리하였다Subsequently, by continuously casting molten steel, the production of manganese-added ultra low carbon BP steel is completed, and the slabs are collected to analyze the T. [O] of the steel with a LECO oxygen / nitrogen simultaneous analyzer, and the results are summarized in Table 1 below.
상기 표 1에 나타난 바와 같이, 출강시 다량의 생석회, Fe-Mn, 및 슬래그 탈산제가 첨가된 종래예의 경우, RH 도착산소가 320ppm으로 RH 탈탄반응에 요구되는 용존산소를 확보할 수 없을 뿐 아니라, RH 도착 (FeO+MnO)가 14.6중량%로 매우 높음을 알 수 있는데, 이것은 출강중 Fe-Mn의 다량 첨가에 의해 상기 반응식(1)이 일어나 산소성분이 낮아지고, (MnO)가 생성되었기 때문이다. 또한, 상기 표1의 비교예와 같이 슬래그탈산제를 크게 감소시킨 경우, RH 도착산소가 크게 증가된 것으로부터, 다량 첨가된 슬래그 탈산제 중 Al이 용존산소와 반응한 것도, 용존산소의 감소에 어느정도 기여한 것으로 판단된다. 한편, 종래예는, RH 탈탄반응에 요구되는 산소가 부족하게 되어 RH 정련중 기체산소를 1.05N㎥/용강-톤 취입해야 했다. 또한, RH 정련이 종료된 이후 슬래그 탈산제를 0.6kg/용강-톤 첨가하였음에도 불구하고 (FeO+MnO)가 15.3중량%로 RH 도착에 비해 오히려 증가되었음을 확인하였다. 통상적으로는 RH 정련중 (FeO+MnO)가 1~3중량% 감소되나, 상기 종래예의 경우 오히려 0.7중량% 증가되었는데, 이것은 탈탄반응중 다량의 기체산소 취입으로 상기 반응식(3)의 반응이 진행된 것을 입증하는 것이다.As shown in Table 1, in the case of the conventional example in which a large amount of quicklime, Fe-Mn, and slag deoxidizer is added during tapping, the RH arrival oxygen is 320 ppm, so that the dissolved oxygen required for the RH decarburization reaction cannot be secured. It can be seen that the RH arrival (FeO + MnO) was very high, at 14.6 wt%, because the reaction formula (1) occurred by adding a large amount of Fe-Mn during tapping, resulting in lower oxygen content and (MnO). to be. In addition, when the slag oxidizing agent was greatly reduced as in the comparative example of Table 1, since the RH arrival oxygen was greatly increased, the reaction of Al with the dissolved oxygen in the large amount of the added slag deoxidant also contributed to the reduction of the dissolved oxygen to some extent. It seems to be. On the other hand, in the conventional example, the oxygen required for the RH decarburization reaction was insufficient, and gaseous oxygen during RH refining had to be blown at 1.05 Nm 3 / molten-ton. In addition, despite the addition of the slag deoxidizer 0.6kg / mol-ton after the completion of the RH refining (FeO + MnO) was confirmed to increase to 15.3% by weight rather than the RH arrival. Typically (FeO + MnO) in the RH refining is reduced by 1 to 3% by weight, but in the case of the conventional example was increased by 0.7% by weight, which is a reaction of the reaction formula (3) by the large amount of gaseous oxygen blowing during the decarburization reaction To prove that.
이와 같은 종래예를 연속주조한 후, 그 주편을 채취해 T.[O]를 분석한 결과, 16.5ppm으로 높은 것을 알 수 있는데, 그 이유는 RH 정련으로부터 연속주조 공정까지 슬래그에 의한 재산화 반응이 일어났기 때문이다. 즉, (FeO+MnO) 성분이 높을수록 재산화반응이 촉진되고, 발생된 알루미나 개재물이 주편에 그대로 존재하여, T.[O]를 증가시킨 것이다.After continuous casting of such a conventional example, the cast was sampled and analyzed by T. [O]. As a result, it was found to be as high as 16.5 ppm, because the reoxidation reaction by slag from RH refining to continuous casting process. Because this happened. That is, the higher the (FeO + MnO) component, the more the reoxidation reaction is promoted, and the generated alumina inclusions remain in the cast steel, thereby increasing T. [O].
비교예의 경우에는, 종래예보다 출강시 Fe-Mn 및 슬래그 탈산제를 크게 감소시켰음에도 불구하고 RH 도착산소가 420ppm 정도로 부족하여, 탈탄반응을 원활하게 진행시키기 위해서는 RH 정련중 기체산소를 0.45 N㎥/용강-톤 취입해야 했다. 또한, RH 도착(FeO+MnO)가 10.3중량%로 양호 했음에도 불구하고, RH 슬래그탈산제 첨가 후 11.7%로 증가되었고, 주편의 T.[O]도 14.5ppm으로 비교적 높았다. 이와 같은 현상이 발생한 이유는, RH에서 다량의 산소 취입으로 인해 상기 반응식(3)에서 (FeO)가 증가되었고, RH로부터 연속주조전에 슬래그에 의한 용강의 재산화가 발생하였기 때문인 것으로 생각된다In the case of the comparative example, although the Fe-Mn and slag deoxidizer were greatly reduced during the tapping than the conventional example, the RH arriving oxygen was insufficient at about 420 ppm, so that the gaseous oxygen during the RH refining process was 0.45 Nm3 / Molten-ton had to be blown. In addition, although the RH arrival (FeO + MnO) was good at 10.3% by weight, it increased to 11.7% after the addition of the RH slagtal acid agent, and the T. [O] of the cast steel was also relatively high at 14.5 ppm. This phenomenon is thought to be due to the increase of (FeO) in the reaction formula (3) due to the large amount of oxygen blown in RH and the reoxidation of molten steel by slag before continuous casting from RH.
한편, 본 발명예(1),(2)의 경우에는, 출강중 Fe-Mn 첨가량을 적정범위로 조절하여 용존산소가 감소되는 것을 방지하였을 뿐 아니라, 슬래그 탈산제 중 Al이 용존산소와 반응하는 것을 어느 정도 방지하였다. 또한, RH 도착산소가 탈탄반응을 진행하기에 적합한 수준이었으나 탈탄반응을 촉진시킬 목적으로 기체산소를 취입하였고, 용강 탈산 이후 금속 망간을 첨가하여 Mn 성분을 목표범위 0.4~0.6중량%로 조절할 수 있었다. 한편, RH정련이 종료된 이후 슬래그 탈산제를 적당량 첨가하여 (FeO+MnO)를 각각 10.1 및 10.4중량%로 제어할 수 있었다.On the other hand, in the examples (1) and (2) of the present invention, the amount of Fe-Mn added during tapping was adjusted to an appropriate range to prevent dissolved oxygen from decreasing, and that Al in the slag deoxidizer reacted with the dissolved oxygen. To some extent. In addition, RH arriving oxygen was a suitable level for decarburization reaction, but gaseous oxygen was blown for the purpose of promoting decarburization reaction, and after the molten steel deoxidation, metal manganese was added to adjust the Mn component to the target range of 0.4 to 0.6% by weight. . On the other hand, after the completion of the RH refining, an appropriate amount of slag deoxidizer was added to control (FeO + MnO) to 10.1 and 10.4% by weight, respectively.
결과적으로, 발명예(1),(2)를 연속주조한 시편을 채취하여 T.[O]를 분석한 결과, 10.6ppm, 11.0ppm으로 작은 값을 얻을 수 있었다.As a result, specimens obtained by continuously casting Inventive Examples (1) and (2) were sampled and analyzed by T. [O]. As a result, small values of 10.6 ppm and 11.0 ppm were obtained.
상기한 바와 같은 본 발명에 의하면, 망간첨가 극저탄소 BP재를 제조시, 출강시 생석회와 페로망간 및 슬래그 탈산제를 소기의 범위로 한정하고, RH에서 산소취입량을 일정량 이하로 제한하여 정련함으로써, 청정성이 우수한 극저탄소 BP재를 얻을 수 있는 효과가 있는 것이다.According to the present invention as described above, when manufacturing manganese-added ultra-low carbon BP material, by limiting the quicklime and ferro-manganese and slag deoxidizer during the tapping to the desired range, and by limiting the amount of oxygen uptake in RH to a certain amount or less, It is effective to obtain ultra-low carbon BP material with excellent cleanliness.
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