KR950012411B1 - Refining method of low carbon steel - Google Patents
Refining method of low carbon steel Download PDFInfo
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- KR950012411B1 KR950012411B1 KR1019930024508A KR930024508A KR950012411B1 KR 950012411 B1 KR950012411 B1 KR 950012411B1 KR 1019930024508 A KR1019930024508 A KR 1019930024508A KR 930024508 A KR930024508 A KR 930024508A KR 950012411 B1 KR950012411 B1 KR 950012411B1
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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
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
- C21C5/30—Regulating or controlling the blowing
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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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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F27—FURNACES; KILNS; OVENS; RETORTS
- F27D—DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS, OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE
- F27D27/00—Stirring devices for molten material
- F27D2027/002—Gas stirring
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Abstract
Description
제1도는 본 발명과 비교재와의 효과평가에 사용되는 극저탄소강의 화학성분표도.1 is a chemical composition table of ultra low carbon steel used in the effect evaluation of the present invention and the comparative material.
제2도는 본 발명과 비교재와의 효과를 나타낸 비교도.2 is a comparative view showing the effect of the present invention and the comparative material.
본 발명은 냉연연속소둔(Continus Annealing Ling)용 극저탄소강의 정련방법에 관한 것으로서, 더욱 상세하게는 냉연연속소둔을 이용한 식음료 포장용기인 연질캔용 소재인 극저탄소강의 제조시 제강공정에서의 알루미나 비금속개재물을 저감시킬 수 있도록 한 것이다.The present invention relates to a method for refining ultra-low carbon steel for continuous annealing (Ling), and more particularly, to alumina non-metallic inclusions in the steelmaking process during the production of ultra-low carbon steel, a soft can, a food and beverage packaging container using cold continuous annealing. This is to reduce the.
일반적으로 탄소량이 0.007%이하의 극저탄소강이 일반 저탄소강(탄소량 0.03∼0.08%)에 비해 청정성의 확보가 어렵고 불리한데, 그 이유는 일반 저탄소강은 전로에서 취련시 강중의 탄소와 산소의 평형을 고려할 때 전로 취련완료시 강중 프리산소(FREE OXYGEN)를 500∼600ppm정도 존재시켜도 탄소 성분의 제어가 가능하며(알루미늄 탈산강에서 강중의 프리산소는 전량 탈산 생성물인 Al2O3로 되어 강중에 존재하며 부상분리하여 슬래그로 제거되기 때문에 가능한 적을수록 청정강제조 측면에서 유리하다)전로 출강중 탈산을 실시함에 따라 용강중에 프리산소가 존재하지 않아 전로 출강중 플럭스(Flux)를 투입하여 래들 슬래그중의 FeO, MnO등과 같은 저급산화물을 쉽게 저감시켜 슬래그에 의한 용강 재산화를 방지하기에 유리할 뿐만 아니라, 탈산 생성물과 같은 개재물을 부상분리시킬 수 있는 충분한 시간을 확보할 수 있는 반면, 극저탄소강은 전로에서 탄소량 0.007%이하를 제어할 수 없어 진공탈가스공정에서 강중의 탄소와 산소를 이용하여 CO반응을 일으켜 탈탄을 해야하기 때문에 진공탈가스처리전 강중에 350-450ppm정도의 적정 프리산소가 존재해야 하므로 전로취련 완료시 강중 프리산소가 600-900ppm정도는 존재해야 한다.In general, ultra-low carbon steel with a carbon content of less than 0.007% is difficult and disadvantageous in securing cleanliness compared to general low carbon steel (carbon content of 0.03 to 0.08%). Considering the equilibrium, it is possible to control the carbon content even if the free oxygen is in the range of 500 to 600ppm when the converter is completed (in the aluminum deoxidized steel, the free oxygen in the steel is Al 2 O 3 , which is the total deoxidation product. Since it exists in the air and is separated from the slag and removed as slag, it is advantageous in terms of clean steel production.) As the deoxidation is performed during converter tapping, there is no free oxygen in the molten steel, so the flux is added during the tapping. Lower oxides such as FeO, MnO and so on are easily reduced to prevent molten steel reoxidation by slag, as well as deoxidation products. While it is possible to secure sufficient time to float the material, ultra-low carbon steel cannot control less than 0.007% of carbon in the converter, so in the vacuum degassing process, CO reaction using carbon and oxygen in the steel causes decarburization. Since the appropriate free oxygen of 350-450ppm should exist in the steel before vacuum degassing treatment, the free oxygen in the steel should be present at 600-900ppm.
이에 따라 강중 프리산소가 높아 탈산생성물이 많이 생기고 전로에서 출강중 탈산을 할 수 없어 래들내강중 프리산소가 존재함에 따라 래들 슬래그중에 저급산화물이 많아 용강 재산화가 많이 일어나고, 진공탈가스처리중에 탈산을 실시하므로 탈산생성물이 부상분리할 수 있는 충분한 시간확보가 어렵기 때문이다.As a result, the free oxygen in the river produces a lot of deoxidation products, and the deoxidation cannot be performed during the tapping in the converter.Therefore, there is a lot of lower oxides in the ladle slag, resulting in a lot of lower oxides in the ladle slag. This is because it is difficult to secure enough time for the deoxidation product to float.
강(鋼)의 품질을 좌우하는 제강공정에서 슬래그의 역할은 대단히 중요한데, 슬래그의 조성 및 양에 따라 강의 품질은 개선될 수도 있고 오히려 열화될 수도 있기 때문이다.The role of slag in the steelmaking process that influences the quality of steel is very important, because the quality of steel may be improved or deteriorated depending on the composition and amount of slag.
특히 2차정련시 래들에서 적정 슬래그 조성을 만들어 주는 것이 품질 확보에 가장 중요한데, 2차정련시 슬래그는 1) 탈산생성물 2) 전로출강시 유출된 전로슬래그 3) 용해된 래들 내화물 4) 래들에 잔류된 상기 래들 슬래그등으로 형성되며, 주요성분은 FeO, CaO, Al2O3, SiO2, MnO, MgO, P2O5, TiO2등이다.In particular, it is most important to ensure the proper slag composition in the ladle during the secondary refining, and in the second refining, the slag is 1) deoxidation product 2) converter slag spilled out during the converter ramp 3) molten ladle refractory 4) remaining in the ladle The ladle slag is formed, the main components are FeO, CaO, Al 2 O 3 , SiO 2 , MnO, MgO, P 2 O 5 , TiO 2 and the like.
산화반응에 대한 표준생성 자유에너지 변화값(ΔG°)이 상대적으로 낮은 값을 갖을수록, 즉 ΔG°가 음으로 클수록 산화물이 되려는 경향이 강하므로 엘링감도로부터 온도가 1550℃이상일 때 4/3 Al2O3＞MgO＞TiO2＞SiO2＞MnO＞Cr2O3＞FeO＞P205순으로 산화물이 되려는 경향이 강함을 알 수 있음에 따라 래들 슬래그중의 FeO, SiO2, MnO, P2O5등은 용강중의 산소친화성이 큰 합금원소-특히 강중 용존 알루미늄에 대하여-들에 대해서 강한 산화제로 작용하여 Al2O3로 되어 강중개재물로 존재 강의 청정성을 저해시키므로 슬래그중에 FeO, SiO2, MnO, P2O5등과 같은 저급산화물이 걱을수록 용강의 재산화가 적게 발생하므로 강의 청정성 확보에 유리하다.4/3 Al when the temperature is above 1550 ℃ from the ell sensitivity because the standard generation free energy change (ΔG °) for the oxidation reaction has a relatively low value, that is, the larger the ΔG °, the stronger the tendency to become an oxide. 2 O 3 ＞ MgO> TiO 2 ＞ SiO 2 ＞ MnO> Cr 2 O 3 ＞ FeO> P 2 0 5 It can be seen that the tendency to become an oxide in order is FeO, SiO 2 , MnO, P 2 O 5, etc. acts as a strong oxidizing agent for alloy elements with high oxygen affinity in molten steel, especially for dissolved aluminum in steel, and becomes Al 2 O 3 , which impairs the cleanliness of the steel as an intermediate in steel. As the lower oxides such as SiO 2 , MnO, P 2 O 5, and the like, less reoxidation of molten steel occurs, which is advantageous for securing steel cleanliness.
지금까지 스틸을 소재로 하는 식음료 포장용 캔의 제조는 탄소량 0.04∼0.06%의 저탄소강으로 냉연 상소둔(batch anmealing lime)조업으로 생산을 하였으나, 최근에는 소둔시간이 많이 소요되는 냉연 상소둔보다는 소둔시간이 단시간인 연속소둔을 채택함에 따라 냉연 연속소둔라인을 이용한 투피스캔용 스틸소재 개발에 많은 관심을 갖게 되었다.Up to now, the production of food and beverage packaging cans made of steel has been produced by batch anmealing lime operation with low carbon steel of 0.04-0.06% of carbon content, but recently, rather than cold-rolled annealing that takes much time for annealing. The adoption of short time continuous annealing has led to much interest in the development of steel materials for two-piece cans using cold rolling continuous annealing lines.
냉연속소둔시에는 소둔시간이 짧기 때문에 탄소량 0.04∼0.06%의 저탄소강으로는 탄소량이 많아 조질도 2.5이하의 연질확보가 어려워 탄소량 0.07%이하의 극저탄소강으로 BP(Black plate)재 개발에 관심을 모으고 있다.In the case of cold continuous annealing, the annealing time is short, so low carbon steel with 0.04-0.06% of carbon content has a high carbon content, so it is difficult to secure softness of 2.5 or less. Therefore, BP (Black plate) material is developed with ultra-low carbon steel of 0.07% or less carbon. Attracting attention.
극저탄소강 BP(Black Plate)재는 연속소둔공정을 거치기 때문에 기존 저탄재에 비하여 생산기간이 훨씬 짧고 균일한 품질을 얻을 수 있는 장점이 있는 반면 제강공정에서 용강중 산소가 높고 출강시 미탈산으로 RH 진공탈탄후 알미늄 탈산을 하고 특수원소를 첨가하기 때문에 알루미나계 개재물의 부상분리 조건이 저탄재에 비해 불비하므로 통상적으로 개재물이 저탄재에 비하여 훨씬 높은 수준을 보이고 있다.Ultra-low carbon steel BP (Black Plate) material has the advantage of having a much shorter production period and uniform quality compared to the existing low carbon material because of the continuous annealing process, while high oxygen in molten steel in steelmaking process and RH vacuum After decarburization, aluminum is deoxidized and special elements are added, so floating separation conditions of alumina-based inclusions are inferior to low carbonaceous materials. Thus, the inclusions are generally much higher than low carbonaceous materials.
따라서, 연속소둔에 의해 캔용 소재를 생산하기 위해서는 먼저 캔 제관시 프랜지 크랙 발생율이 20ppm(백만개당 20개) 이하가 되도록 개재물 크기가 100㎛이하, 전산소량이 15ppm이하 수준으로 고청정가를 제조할 수 있는 정련방법이 개발되어야 한다.Therefore, in order to produce the material for cans by continuous annealing, high clean price can be manufactured with the inclusion size of 100 μm or less and the total oxygen content of 15 ppm or less so that the flange crack incidence rate is 20 ppm or less (20 per million). Refining methods should be developed.
종래의 저탄 캔용 BP재는 출강중 알미늄 탈산을 실시하고, 슬래그 조성을 개질하여 염기도가 6∼8, 슬래그(FeO+Mn0)중량이 3%이하가 되도록한 후 진공탈가스 처리를 하는 정련방법을 적용하고 있다.Conventional low-carbon cans for BP materials are deoxidized during tapping, and the slag composition is modified to have a basicity of 6 to 8 and slag (FeO + Mn0) of 3% or less, followed by vacuum degassing. have.
그러나, 극저탄소강은 진공탈가스 처리단계에서 C+O→CO에 의한 진공탈탄을 시켜야 하기 때문에 출강시 탈산을 전혀하지 않고 진공탈가스 장치에 의해 탈탄을 한후 잔여 산소량을 알미늄으로 탈산시키고 연속주조를 하게 됨에 따라 알미늄 투입량은 감소했지만, 2Al+3O→Al2O3반응에 의하여 생성된 알루미나 개재물의 부상분리 시간이 매우 짧고 슬래그(FeO+MnO)중량이 20%로 매우 높아 재산화에 기인하여 통상 전산소량은 24∼28ppm, 알루미나 개재물비율은 50∼70%를 차지하여 캔용으로는 사용할 수가 없는 등의 문제점이 있었다.However, the ultra low carbon steel has to be vacuum decarburized by C + O → CO in the vacuum degassing step, so no deoxidation at the time of tapping is performed by degassing by vacuum degassing apparatus, followed by deoxidation of residual oxygen to aluminum and continuous casting. As the amount of aluminum decreased, the flotation time of the alumina inclusions produced by the reaction of 2Al + 3O → Al 2 O 3 was very short and the slag (FeO + MnO) weight was 20%. Usually, the amount of oxygen occupies 24 to 28 ppm and the alumina inclusion ratio occupies 50 to 70%, and there is a problem that it cannot be used for cans.
본 발명은 상기한 제반문제점을 해결하기 위한 것으로서, 본 발명은 미탈산 출강단계에서 용강중 산소량과 슬래그 중량을 최소로 하고, 슬래그 개질 및 탈산제로써 합성브리퀘트(Dexydation ＆ Modification Briquettee)를 출강중에 첨가한 후 가스교반을 시키며, 진공탈가스처리 단계에서는 진공탈산전 산소를 최대한 낮게 유지하여 탈산에 필요한 알루미늄량을 최소화하여 알루미나 개재물생성량을 저감시키고, 진공조내에 합성 브리퀘트를 처리초기, 탈산직후에 2분할 투입하여 개재물의 흡수제거와 용강재산화를 억제시킴으로써 전산소량 15ppm이하를 얻을 수 있는 냉연연속 소둔용 극저탄소강의 정련방법을 제공하는데 그 목적이 있다.The present invention is to solve the above problems, the present invention is to minimize the amount of oxygen in the molten steel and slag weight in the step of de-oxidizing tapping, and added synthetic briquette (Dexydation & Modification Briquettee) during tapping as slag reforming and deoxidizer After gas stirring, in the vacuum degassing step, oxygen is kept as low as possible before vacuum deoxidation to minimize the amount of aluminum needed for deoxidation to reduce the amount of inclusions of alumina, and the synthetic briquettes in the vacuum chamber are treated at the beginning and after deoxidation. It is an object of the present invention to provide a refining method of ultra low carbon steel for cold continuous annealing which can obtain 15 ppm or less of oxygen by dividing and removing the inclusions and suppressing molten steel reoxidation.
상기한 목적을 달성하기 위해 본 발명은 전로 종점 탄소 및 산소량이 일정량이 되어 슬래그탈산 및 개질용으로 합성브리퀘트를 투입하는 출강단계와, 출강후 일정량의 가스유량으로 교반시키는 가스 교반단계와, 진공탈가스초기 및 탈산직후에 진공조내에 일정량을 투입하여 알루미나 개재물을 저감시키는 진공탈가스처리단계로 된 냉연연속소둔용 극저탄소강의 정련방법이다.In order to achieve the above object, the present invention provides a tapping step for introducing a synthetic briquette for slag and acid reforming, and a gas stirring step for stirring at a predetermined amount of gas flow rate after tapping as a predetermined amount of converter end carbon and oxygen. It is a refining method of ultra-low carbon steel for cold continuous continuous annealing that has a vacuum degassing step of reducing alumina inclusions by putting a certain amount into a vacuum chamber immediately after degassing and deoxidation.
이하, 본 발명의 실시예를 첨부도면 제1도 및 제2도를 참조하여 상세히 설명하면 다음과 같다.Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2.
제1도는 본 발명과 비교재의 효과평가에 사용되는 극저탄소강의 화학성분표이고, 제2도는 본 발명과 비교재와의 효과를 나타낸 비교표이다.FIG. 1 is a chemical composition table of the ultra low carbon steel used for the effect evaluation of the present invention and the comparative material, and FIG. 2 is a comparative table showing the effect of the present invention and the comparative material.
본 발명은 냉연연속소둔을 이용한 조질도 2.5이하의 식음료 포장용기인 캔 용 BP소재인 탄소량 0.007%이하인 극저탄소강을 제조하기 위한 슬라그 탈산제 및 개질제 및 용강정련법으로 전로종점 탄소량을 0.04∼0.06%, 산소량을 550∼700ppm으로 하고, 출강단계에서 슬래그탈산 및 개질용으로 그 조성이 중량%로 메탈릭(Metallic) Al이 40∼70%, Al2O38∼20, CaF24∼7, CaO 15∼30, 점결제 3∼5이고 입도가 20∼35mm인 합성브리퀘트를 출강단계에서 4∼10kg/t-s투입하고, 출강후 가스교반단계에서 가스유량 7∼20nN/t-s로 교반시키며, 진공탈가스 처리단계에서 합성브리퀘트를 진공탈가스초기에 0.3∼0.8kg/t-s, 진공탈산직후에 0.45∼0.7kg/t-s를 진공조내에 투입하여 알루미나 개재물을 크게 저감시킨다.The present invention is a slag deoxidizer and modifier and molten steel refining method for the production of ultra low carbon steel having a carbon content of 0.007% or less of BP material for cans, food and beverage packaging containers having a qualities of 2.5 or less using cold continuous annealing. ˜0.06%, the amount of oxygen is 550-700ppm, and the composition is 40% by weight for the composition of slag and acid in the tapping step, 40-70% of metallic Al, Al 2 O 3 8-20, CaF 2 4∼ 7, CaO 15-30, caking agent 3-5, particle size 20-35mm synthetic briquette is added 4 ~ 10kg / ts in the tapping step, the gas flow step is stirred at 7 ~ 20nN / ts in the gas stirring step after tapping In the vacuum degassing step, the synthetic briquette is 0.3-0.8 kg / ts in the initial stage of vacuum degassing, and 0.45-0.7 kg / ts is introduced into the vacuum chamber immediately after vacuum degassing to greatly reduce the alumina inclusions.
즉, 극저탄소강은 진공탈가스 처리단계에서 C+O→CO반응에 의해 강중 산소량을 0.007%까지 낮추어야 되기 때문에 진공탈탄이전에 전혀 탈산을 시키지 않고 탈탄에 의해 탄소량이 0.007%이하가 확보된 후에 알미늄으로 탈산시킨다.In other words, the ultra low carbon steel is required to lower the oxygen content in the steel to 0.007% by the C + O → CO reaction in the vacuum degassing step, so the carbon content is less than 0.007% by decarburization without any deoxidation before vacuum decarburization. Deoxidize with aluminum.
탈산후에는 알루미나 개재물과 용존알미늄이 공존하게 되고, 개재물은 슬래그층으로 부상하며, 용존알미늄은 슬래그층으로부터 공급되는 산소에 의해 재산화된다.After deoxidation, the alumina inclusions and the dissolved aluminum coexist, the inclusions rise to the slag layer, and the dissolved aluminum is reoxidized by oxygen supplied from the slag layer.
이와 같이 진공탈탄후 탈산하여 연속주조됨으로 개재물의 부상분리 조건이 극히 불리하게 하고, 슬래그(FeO+MnO)중량이 20∼26%가 되어 재산화가 매우 심하므로 알루미나 개재물이 증가하여 전산소량이 24∼28ppm에 이르고 있다.In this way, vacuum decarburization and deoxidation are carried out continuously so that the floating separation conditions of the inclusions are extremely unfavorable, and the slag (FeO + MnO) weight is 20-26%, so that the reoxidation is very severe. It is reaching 28 ppm.
따라서, 알루미나 개재물을 감소시키기 위해서는 1차적으로 전로종점 탄소량을 높여 산소량이 최소가 되도록 하고, 출강단계에서 슬래그 개질과 탈산이 동시에 될 수 있는 합성브리퀘트의 적정조성 투입량 및 투입시기등을 도출하여 재산화량 감소와 부상개재물의 흡수능을 증대시키며, RH처리단계에서 탈산전 산소를 최대한 낮게 유지하여 탈산 알루미나개재물의 절대 생산량을 저감시키는 동시에 개재물의 흡수능을 촉진해주는 것이 본 발명의 핵심기술이 된다.Therefore, in order to reduce alumina inclusions, first, increase the amount of carbon in the end point of the converter to minimize the amount of oxygen, and derive the appropriate composition input and input timing of the synthetic briquette which can be simultaneously reformed and deoxidized at the tapping stage. The core technology of the present invention is to reduce the reoxidation amount and increase the absorption capacity of the floating inclusions, and to maintain the oxygen before deoxidation as low as possible in the RH treatment step to reduce the absolute yield of the deoxidized alumina inclusions and to promote the absorption of the inclusions.
이하, 본 발명 작용효과를 상세히 설명하면 다음과 같다.Hereinafter, the effects of the present invention will be described in detail.
270톤 실조업에서 본 발명의 4패턴(A∼D)과 비교재 2패턴(E∼F)으로 시험했고, 효과를 파악하기 위한 분석용 시편은 슬라브의 중심부에서 60×100×230mm크기로 채취했으며, 슬라브의 개재물 집적대인 1/4두께지점에서 전산소 분석용 시료와 면분석에 의한 개재물 추출용 시편을 채취했다.In the 270 ton industry, the test was conducted with four patterns (A to D) of the present invention and two patterns (E to F) of the comparative material, and analytical specimens for grasping the effect were collected at 60 × 100 × 230 mm in the center of the slab. At the quarter-thickness point of the slab inclusion stack, specimens for oxygen analysis and specimens for inclusion extraction by surface analysis were taken.
전산소분석은 N2/O2동시분석기, 면분석은 lmage Analyzer를 사용하여 전산소량과 개재물갯수를 조사했고, 개재물의 크기를 조사하기 위해서는 Slime에 의하여 개재물을 추출했으며, 실조업에 사용된 극저탄소강의 화학성분은 제1도와 같고 본 발명과 비교재와의 효과비교는 제2도와 같다.Oxygen analysis was carried out using N 2 / O 2 simultaneous analyzer and surface analysis was performed using lmage analyzer to check the amount of oxygen and the number of inclusions.In order to investigate the size of inclusions, the inclusions were extracted by Slime, The chemical composition of the low carbon steel is shown in FIG. 1 and the effect comparison between the present invention and the comparative material is shown in FIG.
제2도에서와 같이, 청정도수준을 대표하는 전산소량과 개재물갯수는 본 발명재에서 각각 10∼14ppm, 114∼117개인 반면, 종전 비교재에서는 24∼28ppm, 267∼288개를 나타내었고, 투피스캔 제관시 제일 중요한 것은 개재물의 크기인데 본 발명재의 개재물 크기는 20∼100㎛정도이며, 비교재는 150∼250㎛크기로 종전 비교재의 청정도로써는 캔용으로 적합하지 못하나, 본 발명재는 캔용 소재로 적합함을 알 수 있다.As shown in FIG. 2, the amount of oxygen and the number of inclusions representing the cleanliness level were 10-14 ppm and 114-117, respectively, in the present invention, whereas in the previous comparative materials, 24-28 ppm and 267-288 were shown. The most important thing in scanning canning is the size of inclusions. The inclusion size of the present invention is about 20-100 μm, and the comparative material is 150-250 μm in size, which is not suitable for cans due to the cleanliness of previous comparative materials, but the present invention is suitable for can materials. It can be seen.
본 발명재의 고청정도 확보와 각 요소들의 작용과 효과를 상세히 설명하면 먼저 종점탄소량은When securing the high cleanliness of the present invention and the operation and effects of each element in detail,
[현장실시예]Field Examples
진공탈가스 처리단계에서 탈탄시 도달탄소량이 0.007%이하가 될 수 있는 최적 종점탄소량을 0.04∼0.06%로 하면 종점산소량은 상대적으로 낮아져 550∼750ppm범위에 속하게 된다.In the vacuum degassing step, when the optimum carbon amount that can be reached to 0.007% or less in the decarburization process is 0.04 to 0.06%, the end point oxygen content is relatively low, and thus falls in the range of 550 to 750 ppm.
종점산소량을 비교적 낮게 유지하는 이유는 용강-슬래그간의 산소분배 평형에 따른 슬래그(FeO+MnO)중량을 감소시켜 진공에서 탈산후 재산화를 억제하기 위한 것이다.The reason for keeping the end point oxygen amount relatively low is to reduce the slag (FeO + MnO) weight according to the oxygen distribution equilibrium between molten steel and slag to suppress reoxidation after deoxidation in vacuum.
종점탄소량이 0.06%를 초과할 경우 진공에서 탈탄을 하더라도 0.007%이하 확보가 어렵고, 0.04%이하에서는 산소량이 증가하여 슬래그(FeO+MnO)중량이 상승하게 되며, 종점산소 700ppm 이상에서도 슬래그(FeO + MnO)중량이 증가하고, 550ppm이하에서는 전공에서 탈탄시 강제로 산소를 공급하여 탈탄해야 하기 때문에 용강중에 산소량이 증가하게 된다.If the end carbon amount exceeds 0.06%, it is difficult to secure less than 0.007% even if decarburized in vacuum, and below 0.04%, the amount of oxygen increases to increase the weight of slag (FeO + MnO) and slag (FeO +) even at the end point oxygen of 700 ppm or more. MnO) weight is increased, and below 550ppm, the amount of oxygen in molten steel is increased because oxygen must be decarburized by forcibly supplying oxygen when decarburizing in a major.
출강단계에서 슬래그탈산과 개질을 위해서 실시예와 같은 조성의 합성브리퀘트를 투입하면, 슬래그(FeO+MnO)중량이 2Al+3Al2O3→Al2O3+3Fe, 2Al+3MnO→Al2O3+3Mn의 반응에 의해 그 양이 8%이하가 되는 것이다.When the synthetic briquette of the same composition as in Example is added to the slag phthalic acid and the reforming step, the slag (FeO + MnO) weight is 2Al + 3Al 2 O 3 → Al 2 O 3 + 3Fe, 2Al + 3MnO → Al 2 The amount is less than 8% by the reaction of O 3 + 3Mn.
합성브리퀘트 조성중 금속알미늄량은 70%이상의 투입이 필요없고, 40%이하에서는 충분히 탈산이 되지 못하며, Al2O3량은 20%이상에서 슬라그 융점과 점도가 상승되고, 8%이하에서는 형석(CaF2) 첨가량이 증가하게 된다.The amount of metal aluminum in the synthetic briquette composition does not need to be added more than 70%, it is not sufficiently deoxidized at 40% or less, and the Al 2 O 3 content is 20% or more, the slag melting point and viscosity are increased, and the fluorite is less than 8%. The addition amount of (CaF 2 ) increases.
CaO량은 30%이상에서 융점과 점도가 상승되어 형석첨가량이 증가하고, 15%이하에서는 염기도가 낮아지게 되며, CaF2는 7%이상에서 내화되어 침식이 증가하고, 4%이하에서는 유동성 촉진효과가 적어지게 된다.The CaO content increases the melting point and viscosity at 30% or higher, increasing the fluorspar addition, and the basicity is lowered at 15% or lower, and CaF 2 is refractory at 7% or higher, increasing erosion, and at 4% or lower, promoting fluidity. Will be less.
점결제는 주로 SiO2로 구성되어 있어서 5%일 경우 염기도를 떨어뜨리고, 3%이하가 되면 점결력이 부족하여 파쇄되기 쉬워지며, 입도는 35mm이상이 되면 용해속도가 떨어져 미용해 염려가 있고 20mm이하의 경우는 분쇄되어 분진발생율이 높아 환경과 작업성을 저해한다.The caking agent is mainly composed of SiO 2 , so if the 5% is lowered the basicity, if it is less than 3% it lacks the caking power, it is easy to be broken, and if the particle size is more than 35mm, the dissolution rate is lowered, there is a fear of cosmetic beauty 20mm In the following cases, it is pulverized and the dust generation rate is high, which impairs the environment and workability.
이와 같은 합성브리퀘트는 출강단계에서 용강톤당 4∼10kg씩을 투입하고 다시 진공탈가스처리단계에서 0.75∼1.5kg를 추가로 투입하여 출강이후 오염된 알루미나 및 탈탄시 생성된 알루미나 개재물을 흡수제거한다.Such synthetic briquettes are added 4 to 10 kg per ton of molten steel in the tapping step, and 0.75 to 1.5 kg is additionally added in the vacuum degassing step to absorb and remove contaminated alumina and alumina inclusions during decarburization after tapping.
슬래그개질 및 탈산을 실시한 후 효과를 높이기 위해 가스교반은 유량을 용강톤당 7∼20Nl로 취입하는데, 20Nl이상에서는 슬래그층을 너무 심하게 교반하여 대기중 산소와 접촉이 많아져 오히려 재산화요인이 되고, 용강탈산을 일으켜 RH에서 탈탄을 어렵게 하며, 7Nl이하의 경우는 슬라그의 교반효과가 적어져 슬라그 탈산 및 개질의 효율이 떨어진다.In order to increase the effect after slag reforming and deoxidation, the gas agitation blows the flow rate at 7-20Nl per ton of molten steel.At 20Nl or more, the slag layer is agitated too much to be in contact with oxygen in the atmosphere, which is rather a refactoring factor. It makes molten deoxidation difficult to decarburize in RH, and below 7Nl, slag deoxidation and reforming efficiency decreases.
이상에서와 같이, 본 발명은 내연연속소둔을 이용한 식음료포장용기인 극저탄소가의 제조시 제강공정에서의 알루미나 비금속개재물을 크게 저감시켜 고청정강을 얻을 수 있을 뿐만 아니라, 제조기간을 단축시킬 수 있는 등의 많은 장점이 구비된 매우 유용한 발명이다.As described above, the present invention can significantly reduce alumina non-metallic inclusions in the steelmaking process when manufacturing ultra-low carbon value food and beverage packaging containers using continuous continuous annealing to obtain high clean steel, and shorten the manufacturing period. It is a very useful invention with many advantages.
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