KR100370572B1 - Manufacturing method of aluminum killed steel for mini mill continuous casting - Google Patents

Manufacturing method of aluminum killed steel for mini mill continuous casting Download PDF

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KR100370572B1
KR100370572B1 KR1019970011948A KR19970011948A KR100370572B1 KR 100370572 B1 KR100370572 B1 KR 100370572B1 KR 1019970011948 A KR1019970011948 A KR 1019970011948A KR 19970011948 A KR19970011948 A KR 19970011948A KR 100370572 B1 KR100370572 B1 KR 100370572B1
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slag
steel
molten steel
ladle
aluminum
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KR19980075703A (en
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정용남
김만래
이계영
김기성
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주식회사 포스코
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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
    • 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
    • C21C5/52—Manufacture of steel in electric furnaces
    • C21C5/54—Processes yielding slags of special composition
    • 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
    • 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
    • F27D3/00—Charging; Discharging; Manipulation of charge
    • F27D3/0025—Charging or loading melting furnaces with material in the solid state
    • F27D3/0026—Introducing additives into the melt

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Treatment Of Steel In Its Molten State (AREA)

Abstract

PURPOSE: Provided is a manufacturing method of aluminum killed steel for mini mill continuous casting in which concentration of Si is low and the amount of nonmetallic inclusions contained in continuous casting slab is small. CONSTITUTION: The method comprises the first process of tapping the controlled molten steel after controlling the molten steel so that content of T.Fe+MnO in slag becomes 15 wt.% or more when tapping molten steel manufactured by electric furnace into ladle, and removing the slag from the ladle so that the amount of slag in the ladle becomes 12 kg/ton of molten steel or less after completing tapping; and the second process of simultaneously controlling dissolved oxygen in molten steel at 0.5 to 5 ppm by aluminum deoxidizing the molten steel from which slag is removed by the first process, and controlling constituents of the slag so that calcium oxide, silicon oxide and aluminum oxide are contained in the slag in the weight percent range of 0.25 to 0.45 and the content of T.Fe+MnO becomes 5 wt.% or less.

Description

미니밀 연속주조용 알루미늄 탈산강의 제조방법Manufacturing method of aluminum deoxidized steel for mini mill continuous casting

본 발명은 전기로-로외 정련법에 의해 준비된 열연 및 냉연용 알루미늄 킬드강에 관한 것으로 특히,[Si] 농도가 낮고 연주주편 내 비금속 개재물의 양이 적은 미니밀 연속주조용 알루미늄 탈산강의 제조방법에 관한 것이다.The present invention relates to hot-rolled and cold-rolled aluminum-kilted steel prepared by an electric furnace-extraoral refining method, and more particularly, to a method for manufacturing aluminum deoxidized steel for mini-mill continuous casting having a low [Si] concentration and a low amount of non-metallic inclusions in cast steel. will be.

현대 대량 생산 체제하에서의 강재의 제조는 일단 용융 상태의 용강을 제조한 다음 일정 형상으로 주조하여 응고시킨 뒤압연 등의 가공 공정을 거쳐 제조하고 있다. 용융 상태의 용강을 제조하는 방법으로는 크게 용광로-전로법과 전기로법으로 대별된다. 용광로-전로법은 1차로 용광로내에서 철광석을 원료로 하여 선철을 제조한 뒤 전로에서 2차 처리하여 용강을 제조하는 방법으로서 비교적 경제적이므로 오늘날 가장 보편적으로 이용되고 있다. 이에 반해 전기로법에서는 고철을 용해하여 용강을 제조하고 있으므로 제품의 가격과 고철 원료의 수급 등 시황에 민감하고 원가도 높아 적용에 제한을 받아 왔다. 전로와 전기로에서 제조된 용강은 레이들(Ladle)이라는 용강 보관 용기에 출탕되어 후속되는 주조공정에 적합하도록 처리되고 있다. 용강의 주조는 조괴법과 연속주조법이 이용되고 있는데 조괴법은 제품의 품질 특성은 좋으나, 생산성, 실수율 및 에너지의 경제성이 낮은 단점이 있기 때문에 일부 특수강 및 고급강에 한정적으로 적용되고 있다. 반면에 연속주조법은 조괴법의 단점을 해결하고 또한 제품의 품질이 균일하도록 제어할 수 있는 장점이 있어 오늘날 널리 이용되고 있다.The production of steel materials under the modern mass production system is carried out through a process such as rolling after melting molten steel once and then casting and solidifying it into a certain shape. As a method of manufacturing molten steel in a molten state, it is roughly classified into a furnace- converter method and an electric furnace method. The furnace-converting method is the most widely used today because it is relatively economical as a method of manufacturing pig iron by using iron ore as a raw material in a blast furnace and then secondarily treating it in a converter. On the other hand, in the electric furnace method, molten steel is manufactured to melt molten steel, so it has been limited in application because it is sensitive to the market conditions such as price of products and supply of raw materials for scrap metal and high cost. Molten steel produced in converters and electric furnaces is melted in molten steel storage containers called ladles and processed to suit subsequent casting processes. In the casting of molten steel, ingot and continuous casting methods are used, and the ingot has good quality characteristics of products, but it is limited to some special steels and high-grade steels because of the disadvantages of low productivity, low error rate, and low energy efficiency. On the other hand, continuous casting method is widely used today because it has the advantage of controlling the shortcomings of the ingot method and controlling the product quality to be uniform.

표면 성상과 품질이 양호한 냉연 강판 소재로는 림드강(Rimmed Steel), 캡트강(Capped Steel) 및 알루미늄 킬드강(Al-killed Steel)이 주로 사용되고 있다.Cold rolled sheet materials with good surface properties and quality are mainly used as rimmed steel, capped steel, and aluminum-killed steel.

림드강 및 캡트강은 주조시 핀홀(Pin hole)과 같은 결함을 일으키고 응고층의 성장이 불안정하여 연속주조법으로는 제조하기가 곤란하다. 따라서, 연속주조법에 의해 생산되는 열연 및 냉연 강판은 알루미늄 킬드강이어야 한다. 알루미늄 킬드강에서는 강중에 실리콘([Si])이 함유되어 있으면 가공성과 도금성이 매우 불량하게 되고 제품용도에서 큰 제한이 되므로 통상 [Si]는 0.03% 이하가 되도록 엄격하게 관리하고 있다. 강중에 혼입되는 [Si]은 전기로에서 용강을 제조할 때 생성되어 레이들에 유입되는 전기로 슬래그로부터 기인되므로 전기로에서 출강시 슬래그가 혼입되는 것을 감지하고 혼입되지 않도록 하는 각종 방법과 장치가 고안되고 실용화되고 있다. 레이들 내에 전기로 슬래그가 혼입되는 것은 자연 현상인 용강의 와류(Vortex)에 슬래그가 섞여 나오는 현상이므로 슬래그의 유입을 막으면 필연적으로 전기로에서 출강되는 용강의 실수율이 낮아지게 되는 문제가 있다.Limed steel and cap steel cause defects such as pin holes during casting and unstable growth of the solidified layer, making it difficult to manufacture by continuous casting. Therefore, the hot rolled and cold rolled steel sheets produced by the continuous casting method should be aluminum-kilted steel. In the case of aluminum-kilted steel, when silicon ([Si]) is contained in the steel, workability and plating property are very poor, and since it is a large limit in product use, [Si] is strictly controlled to be 0.03% or less. [Si] which is mixed in steel is generated from the furnace slag which is generated when manufacturing molten steel in the electric furnace and flows into the ladle. Therefore, various methods and devices have been devised to detect and prevent the mixing of slag when tapping in the electric furnace. It is put to practical use. Since the slag is mixed into the ladle in the ladle, the slag is mixed in the vortex of the molten steel, which is a natural phenomenon, and thus preventing the inflow of the slag inevitably lowers the error rate of the molten steel exiting the electric furnace.

상기한 문제점을 해결하기 위하여, 본 발명은 연속주조에 의해 생산되는 냉연용 알루미늄 킬드강을 제조하는데 있어서 [Si]의 혼입을 막을 수 있음과 동시에 T.[O]의 함량이 낮은 고청정강을 제조가능하며, 핀홀 및 빌로우홀과 같은 응고결함이 최대한 억제된 미니밀 연속주조용 알루미늄 탈산 강의 제조방법을 제공하는데 그 목적이 있다.In order to solve the above problems, the present invention can prevent the incorporation of [Si] in the production of cold-rolled aluminum-kilted steel produced by continuous casting and at the same time high clean steel with low content of T. [O]. It is an object of the present invention to provide a method of manufacturing aluminum deoxidized steel for mini-mill continuous casting, which is manufacturable and the coagulation defects such as pinholes and hollow holes are suppressed to the maximum.

도 1은 강중 실리콘 농도와 레이들 슬래그양과의 관계를 나타낸그래프도; 1 is a graph showing the relationship between silicon concentration in steel and ladle slag amount ;

도 2는 강중 실리콘 농도와 레이들 슬래그중 T.Fe+MnO의 관계를 나타낸그래프도; 2 is a graph showing the relationship between silicon concentration in steel and T.Fe + MnO in ladle slag ;

도 3은 슬래그중 산화칼슘/산화규소/산화알루미늄의 중량%비와 강중 산소 농도와의 관계를 나타낸그래프도; 3 is a graph showing the relationship between the weight percent ratio of calcium oxide / silicon oxide / aluminum oxide in the slag and the oxygen concentration in the steel ;

도 4는 슬래그중 산화철과 산화망간의 합이 강중 산소 농도에 미치는 영향을 나타낸그래프이다. 4 is a graph showing the effect of the sum of iron oxide and manganese oxide in the slag on the oxygen concentration in the steel .

상기한 목적을 달성하기 위하여, 본 발명은전기로에 의해 제조된 용강을 레이들로 출강할 때 슬래그 중에 존재하는 T.Fe+MnO의 함량이 15중량% 이상이 되도록조절한 다음출강하며, 출강완료 후에는레이들 내의슬래그 양이 용강톤당 12kg 이하가 되도록레이들로부터슬래그를 제거하는 제1공정과, 상기 제1공정에 의해 슬래그가 제거된 용강을 알루미늄 탈산에 의해 용강 중의 용해산소가 0.5∼5ppm이 되게 조절함과 동시에, 슬래그중 산화칼슘/산화규소/산화알루미늄의 중량%값이 0.25∼0.45이고, T.Fe+MnO의 함량이 5중량% 이하가 되도록 슬래그 성분을 조절하는 제2공정으로 이루어진 것을 특징으로 하는 미니밀 연속주조용 알루미늄 탈산강의 제조방법을 제공한다. In order to achieve the above object, the present invention is to adjust the content of T.Fe + MnO present in the slag when the steel is produced by the ladle to the ladle, and then tapping to make more than 15% by weight, tapping completed, After that , the slag is removed from the ladle so that the amount of slag in the ladle is 12 kg or less per ton of molten steel, and 0.5 to 5 ppm of dissolved oxygen in the molten steel by aluminum deoxidation of the molten steel from which the slag is removed by the first process. The second step of controlling the slag components such that the weight percentage value of calcium oxide / silicon oxide / aluminum oxide in the slag is 0.25 to 0.45 and the content of T.Fe + MnO is 5% by weight or less . It provides a method for producing a mini-milled continuous casting aluminum deoxidized steel, characterized in that made.

이하, 본 발명의 구성에 대하여 상세하게 설명한다.EMBODIMENT OF THE INVENTION Hereinafter, the structure of this invention is demonstrated in detail.

통상 제조되고 있는 알루미늄 킬드강에는 용강의 탈산 특성과 강의 기계적 성질을 향상시킬 목적으로 제품중 알루미늄 농도가 0.01∼0.07중량%가 될 수 있는 양만큼의 알루미늄을 첨가한다. 용강에 알루미늄을 첨가하면 산화물이 생성되는데 생성된 산화물은 90∼95%가 슬래그층으로 분리 제거되지만 강중에 잔존하게 되는 산화물은 비금속 개재물로 되어 후속 공정이나 제품의 사용시 각종 결함을 유발하거나 강의 기계적 성질을 저하시키므로 잔류 산화물량을 극력 낮추도록 노력하고 있다. 따라서 산화물계 비금속 개재물의 흡수능력이 큰 슬래그로써 용강을 처리해야 한다.Aluminum alloys, which are usually manufactured, are added in an amount such that the aluminum concentration in the product can be 0.01 to 0.07% by weight for the purpose of improving the deoxidation properties of the molten steel and the mechanical properties of the steel. When aluminum is added to molten steel, an oxide is formed. 90-95% of the produced oxide is separated and removed by the slag layer, but the oxide remaining in the steel becomes a non-metallic inclusion, which causes various defects in the subsequent process or use of the product, or the mechanical properties of the steel. As a result, the amount of residual oxide is reduced as much as possible. Therefore, molten steel should be treated as slag with large absorption capacity of oxide-based nonmetallic inclusions.

산화물계 비금속 개재물의 흡수능력이 큰 슬래그에 대해서는 많은 보고와 특허 등이 발표되어 있는데, 어느 경우를 보더라도 환원성 분위기의 유지가 가능하도록 산화도가 낮아야 하는 것으로 알려져 있다. 그런데 슬래그의 산화도는 산화철(FeO, Fe2O3등), 산화망간(MnO 등)과 같은 저급 산화물의 양이 많을수록 높아지므로 산화물계 개재물의 저감을 위해서는 용강과 접촉하고 있는 슬래그 중에 포함되어 있는 이들 저급 산화물의 농도를 감소시켜야만 한다.Many reports and patents have been published for slag having a high absorption capacity of an oxide-based nonmetallic inclusion, and in any case, it is known that the oxidation degree should be low to maintain a reducing atmosphere. However, the degree of oxidation of slag increases as the amount of lower oxides such as iron oxide (FeO, Fe 2 O 3, etc.) and manganese oxide (MnO, etc.) increases, so that the slag in contact with molten steel is included to reduce oxide inclusions. The concentration of these lower oxides must be reduced.

전기로에서 용해 및 정련시에는 산화성 분위기가 유지되는 것이 일반적이기 때문에 전기로에서 만들어지는 슬래그 역시 강산화성으로 되어 FeO, MnO 저급 산화물의 양이 30∼60중량% 정도로 많고 따라서 강중 비금속 개재물의 흡수능을 저하시키므로 레이들내의 유입을 극력 억제하거나 별도의 처리를 통하여 유입된 슬래그의유해성을 저감시켜야 한다.Since it is common to maintain an oxidizing atmosphere during melting and refining in an electric furnace, slag made in an electric furnace is also strongly oxidized, so that the amount of FeO and MnO lower oxides is about 30 to 60% by weight, thus reducing the absorption of nonmetallic inclusions in the steel. The ingress of ladle should be suppressed as much as possible or the harmfulness of slag introduced through separate treatment should be reduced.

이와 같은 목적으로 가장 널리 사용되고 있는 방법은 알루미늄 등을 함유하고 있는 슬래그 탈산제를 투입하여 저급 산화물을 저감시키는 방법으로써 현재 수종의 특허가 출원 또는 등록되어 있다(예: 대한민국특허 등록번호 56122호, 60757호및 출원번호 1992년 제10826호).The most widely used method for this purpose is a method of reducing lower oxides by adding a slag deoxidizer containing aluminum and the like, and several patents are currently applied or registered (for example, Korean Patent Registration Nos. 56122 and 60757). And application number 199226).

상기 특허들을 보면 용강중 비금속 개재물을 줄이고 청정도를 향상시킬 목적으로 레이들슬래그중 T.Fe+MnO 농도가 1.5∼3중량% 이하가 되도록 조절하고 있다.According to the above patents, the concentration of T.Fe + MnO in the ladle slag is controlled to be 1.5 to 3% by weight or less for the purpose of reducing non-metallic inclusions in molten steel and improving cleanliness.

그러나, 이와 같이 레이들 슬래그중 T.Fe+MnO 농도를 낮게 유지하면 강중 [Si] 농도가 증가하게 되어 [Si] 농도를 알루미늄 킬드강에서 억제하는 농도 즉 0.03중량% 이하로 억제할 수 없다. 이것은 레이들 슬래그를 구성하는 한 항목인 전기로슬래그 중에는 산화규소가 상당량 포함되어 있는데 출강시에 레이들에 유입된 전기로 슬래그는 주편의 결함인 핀홀(Pin Hole)이나 블로우홀(Blow Hole) 또는 연속주조시 브레이크 아웃(Break-Out) 등 문제를 방지하기 위해 필수적으로 진행되는 탈산 작업시에 슬래그중 산화규소가 Si로 환원되어 용강 중으로 혼입되기 때문이다. [Si] 혼입을 막기 위해 그 근원이 되는 전기로 슬래그의 유입이 없도록 하는 것은 이론적으로 가능하지만 전술한 바와 같이 출강실수율이 저하되기 때문에 실제에 있어서는 상업성과 경제성을 감안하여 작업할 수밖에 없다.However, if the T.Fe + MnO concentration in the ladle slag is kept low, the concentration of [Si] in the steel is increased and the concentration of [Si] in the aluminum-kilted steel cannot be suppressed to 0.03 wt% or less. The furnace slag, which constitutes the ladle slag, contains a considerable amount of silicon oxide. The furnace slag that flows into the ladle at the time of tapping is a pin hole, blow hole, or continuous hole, which is a defect in the cast steel. This is because silicon oxide in slag is reduced to Si and mixed into molten steel during deoxidation, which is essential to prevent problems such as break-out during casting. In order to prevent the mixing of [Si], it is theoretically possible to prevent the inflow of slag from the source of electricity, but as mentioned above, since the attendance rate is lowered, it is necessary to work in consideration of commerciality and economic efficiency.

이하, 바람직한 실시예를 통하여 본 발명의 구성에 대한 수치한정 이유 및 본 발명의 작용을 설명한다.Hereinafter, the reason for numerical limitation and the operation of the present invention for the configuration of the present invention through a preferred embodiment.

도 1은 강중 실리콘 농도와 레이들 슬래그양과의 관계를 나타낸 그래프도이다.1 is a graph showing the relationship between the silicon concentration in steel and the amount of ladle slag.

전기로 슬래그의 레이들내 유입량은 작업 방법에 따라 달라지지만 통상 용강톤당 20∼90kg 정도이다. 전기로 슬래그의 유입량이 증가할수록 유입된 전기로 슬래그로부터 [Si]이 용강 중으로 혼입되는 정도가 증가된다. 도 1에는 전기로 슬래그의 유입량에 따른 강중 [Si]농도를 나타낸 것으로 이와 같은 사실을 잘 보여주고 있다.The inlet of the furnace slag in the ladle varies depending on the method of operation, but it is usually about 20 to 90 kg per tonne of steel. As the flow rate of the furnace slag increases, the degree of incorporation of [Si] into the molten steel from the introduced furnace slag increases. Figure 1 shows the fact that the river [Si] concentration according to the flow rate of the slag of the furnace well shows this fact.

특히, 도 1로부터 보면 슬래그의 유입량이 용강톤당 12kg을 초과하면, 강중 [Si]는 급격히 증가하며, 알루미늄 탈산강의 상한 허용값인 0.03%를 초과하게 된다. 한편, 강중 [Si] 농도는 전기로 슬래그의 유입량 뿐만 아니라 출강후 레이들 슬래그중의 T.Fe+MnO 농도에 따라 달라진다.In particular, when seen from Figure 1 when the inflow of slag exceeds 12kg per ton of steel, the steel [Si] increases rapidly, exceeding the upper limit of 0.03% of the aluminum deoxidized steel. Meanwhile, the [Si] concentration in the steel depends not only on the flow rate of slag in the electric furnace, but also on the T.Fe + MnO concentration in the ladle slag after the tapping.

도 2는 강중 실리콘 농도와 레이들 슬래그중 T.Fe+MnO의 관계를 나타낸 그래프도이다.2 is a graph showing the relationship between silicon concentration in steel and T.Fe + MnO in ladle slag.

즉,도 2에 도시된 바와 같이,강중 [Si]는 레이들 슬래그중의 T.Fe+MnO 농도가 감소되도록 증가하는 경향이 있는데 레이들 슬래그중의 T.Fe+MnO 농도가 15중량% 이하가 되면 급격히 증가하고 그 농도 역시 알루미늄 탈산강의 상한 허용값인 0.03%를 초과하게 된다.That is, as shown in FIG. 2, the steel [Si] tends to increase so that the T.Fe + MnO concentration in the ladle slag is reduced, but the T.Fe + MnO concentration in the ladle slag is 15 wt% or less. It increases rapidly and its concentration also exceeds the upper limit of 0.03%, which is the upper limit of aluminum deoxidized steel.

따라서 본 발명의 제1공정에서는 도 1 및 도 2에 보인 결과로부터 얻어진 결과에 기초하여, 출강후 레이들 슬래그중 T.Fe+MnO 농도가 15중량% 이상이 되도록 조절하였고, 전기로 슬래그가 과량으로 유입되면 후속 처리전에 제거하여 그 양을 용강톤당 12kg 이하로 유지한 것이다.Therefore, in the first step of the present invention, based on the results obtained from the results shown in Figs. 1 and 2, the T.Fe + MnO concentration in the ladle slag after the tapping was adjusted to 15% by weight or more, and the electric furnace slag was excessively If it is introduced into, it is removed before further treatment and the amount is kept below 12 kg per ton of molten steel.

제1공정과 같이 처리된 용강은 LF(Ladle Furnace)라고 불리는 로외 정련로에서 처리하게 된다. 로외 정련로에서 처리하는 목적은 크게 두 가지로서 (1)용강의 가열 (2)정련을 통한 탈산, 탈황 및 비금속 개재물의 제거로 요약된다.The molten steel treated in the first step is treated in an external furnace refinery called LF (Ladle Furnace). There are two main purposes of treatment in an external furnace: (1) heating of molten steel (2) deoxidation, desulfurization and removal of nonmetallic inclusions through refining.

상기 두 가지 목적을 달성하는 데에는 레이들 슬래그의 조성을 적정한 범위로 제어하는 것이 무엇보다도 중요하다. 전기로를 이용한 용강의 제조시 레이들 슬래그는 산화칼슘, 산화규소, 산화알루미늄이 주성분이다. 이 슬래그 조성에서 용강의 정련에 효과적인 슬래그 조건을 알아보기 위해 전기로에서 회수된 슬래그와 고주파 유도로를 이용하여 1600℃에서 실험을 실시하였다.In order to achieve the above two objectives, it is important to control the composition of the ladle slag in an appropriate range. In the production of molten steel using an electric furnace, ladle slag is mainly composed of calcium oxide, silicon oxide, and aluminum oxide. In order to find out the effective slag conditions for refining molten steel in this slag composition, experiments were conducted at 1600 ° C using slag recovered from the electric furnace and high frequency induction furnace.

도 3은 슬래그중 산화칼슘/산화규소/산화알루미늄의 중량%비와 강중 산소 농도와의 관계를 나타낸 그래프도이다.3 is a graph showing the relationship between the weight percent ratio of calcium oxide / silicon oxide / aluminum oxide in the slag and the oxygen concentration in the steel.

도 3에 도시된 바와 같이,조제된 슬래그중 산화칼슘/산화규소/산화 알루미늄의 중량%의 비 즉 ((%CaO)/(%SiO2)/(%Al2O3))의 값이 변화됨에 따른 강중 전산소 농도(T.[O])의 변화를 보여주는 그림으로 이 값이 0.25 이하 또는 0.45 이상에서는 T.[O]값이 높은 것을 보여주고 있다. 강중에 존재 하는 산소는 존재 형태에 따라 원자 상태로 용해된 용존 산소와 산화물과 결합된 개재물상의 산소로 구분된다. 알루미늄 탈산강에서는 용존 산소는 수ppm 이하이며 작업조건에 따라 별로 변하지 않으므로 강중 전산소 농도가 높다는 것은 산화물상의 산소 즉 개재물의 양이 많아서, 강의 청정도가 낮고 결함 발생율이 높다는 것을 의미한다. As shown in FIG. 3, the ratio of the weight percentage of calcium oxide / silicon oxide / aluminum oxide, that is, ((% CaO) / (% SiO 2 ) / (% Al 2 O 3 )) in the prepared slag is changed. The figure shows the change in total oxygen concentration (T. [O]) in the river, which shows that the T. [O] value is high at 0.25 or below 0.45 . Oxygen present in the steel is divided into dissolved oxygen dissolved in the atomic state and oxygen on inclusions combined with oxide, depending on the type of existence. In aluminum deoxidized steel, dissolved oxygen is several ppm or less and does not change very much depending on the working conditions. Therefore, high oxygen concentration in steel means that the amount of oxygen in the oxide phase, or inclusions, is high, resulting in low cleanliness and high defect generation rate.

따라서, 본 발명에서는 슬래그중(산화칼슘/산화규소/산화알루미늄)의 중량%비율을 0.25∼0.45 로 유지하여 고청정강을 제조할 수 있도록 하였다.Therefore, in the present invention, by maintaining the weight percent ratio of (calcium oxide / silicon oxide / aluminum oxide) in the slag to 0.25 to 0.45 to be able to produce a high clean steel.

또한 강중 전산소 농도는 위에서 설명한 레이들 슬래그중 산화칼슘/산화규소/산화알루미늄의 중량%비 외에도 슬래그중의 (T.Fe+MnO)함량에 따라 달라진다.In addition, the total oxygen concentration in the steel depends on the content of (T.Fe + MnO) in the slag in addition to the weight% ratio of calcium oxide / silicon oxide / aluminum oxide in the ladle slag described above.

도 4는 슬래그중 산화철과 산화망간의 합이 강중 산소 농도에 미치는 영향을 나타낸 그래프이다.4 is a graph showing the effect of the sum of iron oxide and manganese oxide in the slag on the oxygen concentration in the steel.

도 4는 슬래그중 (T.Fe+MnO)와 강중 산소 농도와의 관계를 보인 것으로 (T.Fe+MnO)값이 적어질 수 있도록 T.[O]가 감소되어 5중량% 이하가 되면 최저치를 보이게 된다.Figure 4 shows the relationship between (T.Fe + MnO) in the slag and the oxygen concentration in the steel, so that T. [O] is reduced so that the value of (T.Fe + MnO) decreases to 5% by weight or less. Will be shown.

강중 산소 농도가 높다는 것은 강의 청정도가 좋지 않다는 것 즉 비금속 개재물의 양이 많아서 강의 품질이 저하된다는 의미와 같다. 따라서 본 발명에서는 (T.Fe+MnO)를 5중량% 이하로 한정하였다.The high oxygen concentration in the steel means that the cleanliness of the steel is not good, that is, the quality of the steel is deteriorated due to the large amount of nonmetallic inclusions. Therefore, in the present invention, (T.Fe + MnO) was limited to 5% by weight or less.

이상에서 본 발명의 제2공정에서 슬래그를 산화칼슘/산화규소/산화알루미늄의 중량%의 비 즉 ((%CaO)/(%SiO2)/(%Al2O3))의 값이 0.25∼0.45 , (T.Fe+MnO)가 5중량% 이하로 한정한 이유를 설명하였다.In the second step of the present invention, the ratio of the weight percentage of calcium oxide / silicon oxide / aluminum oxide, that is, ((% CaO) / (% SiO 2 ) / (% Al 2 O 3 )) is 0.25 to The reason why 0.45 and (T.Fe + MnO) was limited to 5% by weight or less was explained.

한편, 전기로에서 제조되는 용강 중에는 산소 농도가 조건에 따라 500∼2000ppm 정도 함유되어 있다. 강중 용존 산소 농도가 약 10ppm이상인 용강이 응고되면 핀홀(Pin Hole)이나 블로우홀(Blow Hole) 등 결함을 일으키거나, 후속 공정인 연속주조시 브레이크 아웃(Break-Out) 등 문제를 야기한다. 뿐만 아니라, 강중 용존 산소 농도가 높으면 다음 공정에서 투입하는 칼슘의 실수율이 저하된다.On the other hand, the molten steel manufactured by an electric furnace contains about 500-2000 ppm of oxygen concentrations according to conditions. If molten steel with a dissolved oxygen concentration of about 10 ppm or more in the steel solidifies, it may cause defects such as pin holes or blow holes, or may cause problems such as break-out during subsequent casting. In addition, when the dissolved oxygen concentration in the steel is high, the error rate of calcium added in the next process is lowered.

따라서 용존 산소 농도를 5ppm 이하로 억제하는 것이 좋다. 그러나, 강중 용존 산소 농도가 너무 낮으면 소비되는 탈산제의 양이 증가되어 원가 상승 요인이 되므로 0.1ppm이하는 바람직하지 않다.Therefore, it is good to suppress the dissolved oxygen concentration to 5 ppm or less. However, if the dissolved oxygen concentration in the steel is too low, the amount of deoxidizer consumed increases, which causes a cost increase.

이상에서 설명한 제2공정과 같이 처리된 용강은 LF에서 승온 후 연속주조공정으로 보내어진다.The molten steel treated in the same manner as the second step described above is sent to the continuous casting process after the temperature is raised in the LF.

본 방법에 의하여 전기로 슬래그로부터 Si의 혼입을 방지할 수 있으므로 용강중 [Si]의 농도를 0.03중량% 이하로 억제하면서 강중 비금속 개재물을 줄이고 청정도가 향상된 알루미늄 탈산강의 제조가 가능하다.In this way, it is possible to prevent the incorporation of Si from the electric furnace slag, thereby suppressing the concentration of [Si] in the molten steel to 0.03% by weight or less while reducing the non-metallic inclusions in the steel and improving the cleanness of the aluminum deoxidized steel.

Claims (1)

전기로에 의해 제조된 용강을 레이들로 출강할 때 슬래그 중에 존재하는 T.Fe+MnO의 함량이 15중량% 이상이 되도록 조절한 다음 출강하며, 출강완료 후에는 레이들 내의 슬래그 양이 용강톤당 12kg 이하가 되도록 레이들로부터 슬래그를 제거하는 제1공정과;When tapping the molten steel produced by the electric furnace with the ladle, the content of T.Fe + MnO present in the slag is adjusted to 15% by weight or more, and then the tapping is performed.After the completion of tapping, the slag amount in the ladle is 12kg per ton of steel. A first step of removing slag from the ladle to be below; 상기 제1공정에 의해 슬래그가 제거된 용강을 알루미늄 탈산에 의해 용강 중의 용해산소가 0.5∼5ppm이 되게 조절함과 동시에, 슬래그중 산화칼슘/산화규소/산화알루미늄의 중량%값이 0.25∼0.45이고, T.Fe+MnO의 함량이 5중량% 이하가 되도록 슬래그 성분을 조절하는 제2공정으로 이루어진 것을 특징으로 하는 미니밀 연속주조용 알루미늄 탈산강의 제조방법.The molten steel from which slag was removed in the first step was adjusted to 0.5 to 5 ppm of dissolved oxygen in molten steel by aluminum deoxidation, and the weight% value of calcium oxide / silicon oxide / aluminum oxide in the slag was 0.25 to 0.45. , The second process for adjusting the slag component so that the content of T.Fe + MnO is 5% by weight or less.
KR1019970011948A 1997-03-31 1997-03-31 Manufacturing method of aluminum killed steel for mini mill continuous casting KR100370572B1 (en)

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KR100865452B1 (en) 2007-09-05 2008-10-28 주식회사 포스코 Deoxidation method of pouring molten metal by minimill electric furnace
KR100878581B1 (en) * 2007-09-07 2009-01-15 주식회사 포스코 Vacuum refineing method

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KR100919425B1 (en) * 2002-12-18 2009-09-29 주식회사 포스코 Aluminum wire for production of ULC steel and method for lowering oxidation of slag using it

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100865452B1 (en) 2007-09-05 2008-10-28 주식회사 포스코 Deoxidation method of pouring molten metal by minimill electric furnace
KR100878581B1 (en) * 2007-09-07 2009-01-15 주식회사 포스코 Vacuum refineing method

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