TWI637062B - Method for manufacturing molten steel - Google Patents

Method for manufacturing molten steel Download PDF

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TWI637062B
TWI637062B TW106123467A TW106123467A TWI637062B TW I637062 B TWI637062 B TW I637062B TW 106123467 A TW106123467 A TW 106123467A TW 106123467 A TW106123467 A TW 106123467A TW I637062 B TWI637062 B TW I637062B
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slag
decarburization
furnace
cold
flux
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TW201812025A (en
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鈴木哲平
田代亘
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新日鐵住金股份有限公司
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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
    • 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
    • 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
    • C21C7/076—Use of slags or fluxes as treating agents
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Carbon Steel Or Casting Steel Manufacturing (AREA)
  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)

Abstract

在將前次加料所產生之爐渣的一部份留在脫碳爐內的狀態下，於現行加料中，將已使以往脫碳吹煉所生成之爐渣固化的爐渣投入前述脫碳爐中，接著將磷濃度小於0.060質量%之熔鐵裝入前述脫碳爐中並進行脫碳吹煉。此外，當現行加料中脫碳吹煉所生成之爐渣中的P2 O5 濃度在預定值以下時，將一部分的爐渣留在前述脫碳爐中以作為下次加料所用之爐渣。In a state in which a part of the slag generated by the previous feeding is left in the decarburization furnace, the slag which has solidified the slag generated by the conventional decarburization blowing is put into the decarburization furnace in the current feeding. Next, molten iron having a phosphorus concentration of less than 0.060% by mass is charged into the above-described decarburization furnace and subjected to decarburization blowing. Further, when the concentration of P 2 O 5 in the slag generated by the decarburization blowing in the current charging is below a predetermined value, a part of the slag is left in the decarburization furnace as the slag for the next feeding.

Description

熔鋼的製造方法Method for manufacturing molten steel

發明領域 本發明是有關一種特別適合用於削減在脫碳吹煉時所添加助熔劑的量之熔鋼的製造方法。FIELD OF THE INVENTION The present invention relates to a method for producing a molten steel which is particularly suitable for use in reducing the amount of flux added during decarburization blowing.

發明背景 以往，為了減低至所要求之製品規格的磷濃度以下，於脫碳爐中吹煉熔鐵以製造熔鋼之際，會由設置於轉爐上之投入滑槽投入助熔劑。投入到熔鐵中的助熔劑會在高溫之熔鐵表面熔融，而形成以CaO及SiO2 為主體的爐渣。並且，在吹煉中經由主噴槍往熔鐵吹入純氧，熔鐵中的磷會成為磷氧化物，並與爐渣中的CaO形成固熔體，而被除去到爐渣中。藉此，熔鐵中的磷濃度會降低。所投入之助熔劑的量是依熔鐵預備處理後之熔鐵成分、製品規格的磷濃度及目標溫度而決定，但近年，鋼鐵製品之高性能化及使用者規格的嚴格化不斷進展，為了使磷濃度更加降低，助熔劑的量有增加的傾向。BACKGROUND OF THE INVENTION Conventionally, in order to reduce the phosphorus concentration below the required product specification, the molten iron is blown in a decarburization furnace to produce a molten steel, and a flux is introduced from an input chute provided in the converter. The flux introduced into the molten iron melts on the surface of the molten iron at a high temperature to form a slag mainly composed of CaO and SiO 2 . Further, during the blowing, pure oxygen is blown into the molten iron through the main lance, and the phosphorus in the molten iron becomes phosphorus oxide, and forms a solid solution with CaO in the slag, and is removed into the slag. Thereby, the concentration of phosphorus in the molten iron is lowered. The amount of the flux to be charged is determined by the molten iron component after the molten iron preparation, the phosphorus concentration of the product specification, and the target temperature. However, in recent years, the high performance of steel products and the strictness of user specifications have been progressing. The phosphorus concentration is further lowered, and the amount of the flux tends to increase.

於是，為了在製鋼步驟中減低成本，作為削減新投入助熔劑的量的方法，有一種爐渣回收法。爐渣回收法有冷回收及熱回收之2種方法。在以下說明中，助熔劑是指由爐渣回收系統外導入的爐渣材，且令其為不含已回收之爐渣者。Therefore, in order to reduce the cost in the steel making step, there is a slag recovery method as a method of reducing the amount of newly added flux. The slag recovery method has two methods of cold recovery and heat recovery. In the following description, the flux refers to a slag material introduced from outside the slag recovery system, and is made to be free of recovered slag.

冷回收自以往便是於SRP法等逆流精煉中所廣泛使用的技術，在專利文獻1及專利文獻2中揭示有冷回收的技術。一般來說，在冷回收中，由脫碳爐被排渣至渣桶的爐渣(以下稱為脫碳爐渣)，是在冷卻後經過磁選、粉碎、篩分等步驟後，被搬運至製鋼工廠。然後，將所搬運之脫碳爐渣作為冷爐渣回收到脫磷爐內。The cold recovery is a technique widely used in countercurrent refining such as the SRP method, and Patent Document 1 and Patent Document 2 disclose a technique for cold recovery. Generally, in the cold recovery, the slag discharged from the decarburization furnace to the slag bucket (hereinafter referred to as the decarburization slag) is transported to the steelmaking plant after being subjected to magnetic separation, pulverization, sieving, etc. after cooling. . Then, the removed decarburization slag is recovered as a cold slag into the dephosphorization furnace.

另一方面，熱回收主要是MURC法中所使用的技術，揭示於例如專利文獻3及4。熱回收中，利用在同一轉爐中交互實施脫磷吹煉與脫碳吹煉之特徵，於脫碳出鋼後使熱爐渣殘留於爐內，並在下次加料時投入廢料藉此使熱爐渣凝固至可注入鐵水的程度，以進行下次加料的注入鐵水及脫磷吹煉。如上述，便可省略步驟外之爐渣處理，並可將爐渣挪用到下次加料之脫磷吹煉。On the other hand, heat recovery is mainly a technique used in the MURC method, and is disclosed, for example, in Patent Documents 3 and 4. In heat recovery, the characteristics of dephosphorization blowing and decarburization blowing are alternately carried out in the same converter. After the decarburization and tapping, the hot furnace slag remains in the furnace, and the waste is put into the next feeding to solidify the hot slag. To the extent that molten iron can be injected, the molten iron and dephosphorization blown for the next feeding. As described above, the slag treatment outside the step can be omitted, and the slag can be transferred to the dephosphorization blow of the next feed.

如以上，不論哪個方法都是將高鹼度的脫碳爐渣回收到鹼度較脫碳爐低之脫磷爐的方法，但也可將爐渣回收到脫碳爐。藉此，可減少在脫磷爐或脫碳爐中新投入之助熔劑的量。As described above, in either method, the high alkalinity decarburization slag is recovered to a dephosphorization furnace having a lower alkalinity than the decarburization furnace, but the slag may be recovered in the decarburization furnace. Thereby, the amount of newly added flux in the dephosphorization furnace or the decarburization furnace can be reduced.

此外，專利文獻5中雖揭示有一種技術，其在脫碳爐中排渣時會依P2 O5 的濃度區分回收脫碳爐渣，並視鋼種將最適合之P2 O5 濃度的脫碳爐渣冷回收或熱回收，但並未揭示在使熱回收之爐渣凝固時，使用冷回收的方法。另外，如專利文獻5，僅依排渣時之P2 O5 濃度來將脫碳爐渣冷回收或熱回收時，如果將磷濃度高之熔鐵裝入脫碳爐，爐渣中的P2 O5 濃度常常會變得很高，因此也有完全無法實施熱回收的課題。Further, Patent Document 5 discloses a technique in which the decarburization slag is separately classified according to the concentration of P 2 O 5 when slag is discharged in the decarburization furnace, and the most suitable P 2 O 5 concentration decarburization is determined depending on the steel grade. The slag is cold recovered or heat recovered, but it is not disclosed that a cold recovery method is used when solidifying the heat recovered slag. Further, as in Patent Document 5, when the decarburization slag is cold-recovered or heat-recovered only in accordance with the P 2 O 5 concentration at the time of slag discharge, if the molten iron having a high phosphorus concentration is charged into the decarburization furnace, P 2 O in the slag 5 The concentration often becomes very high, so there is also the problem that heat recovery cannot be performed at all.

又，在實施冷回收時，由於冷爐渣之粉狀部分多而容易含有水分，因此投入轉爐時反應性大，而有對排氣管或集塵濾布等造成較多負擔之疑慮。故，以冷回收要於脫碳爐中大量回收是有困難的。In addition, when cold storage is carried out, since the powdery portion of the cold slag is likely to contain water, the reactivity is large when it is put into a converter, and there is a concern that the exhaust pipe or the dust collecting filter cloth has a large burden. Therefore, it is difficult to recover a large amount of cold recovery in a decarburization furnace.

另一方面，於脫碳爐中是進行不使用廢料之操作。因此，於脫碳爐實施熱回收時，由於熱爐渣並未充分固化，因此必須另行使用助熔劑來當作冷卻劑，而有未使用冷卻劑時便無法進行充分量之熱回收的課題。On the other hand, in the decarburization furnace, the operation of not using waste is performed. Therefore, when the heat recovery is performed in the decarburization furnace, since the hot slag is not sufficiently solidified, it is necessary to use a flux as a coolant separately, and there is a problem that a sufficient amount of heat recovery cannot be performed when the coolant is not used.

更進一步地，爐渣回收內含因爐渣中P2 O5 濃化而造成脫磷不良之疑慮。冷回收中，由於可進行脫碳爐渣之成分分析，因此可使用專利文獻5所記載之方法，依P2 O5 之濃度區分回收並依鋼種來選擇爐渣。然而，由於熱回收中會連續回收脫碳爐渣，故無法進行脫碳爐渣之成分分析而P2 O5 之濃化程度不明確。因此，僅能留有餘裕而使P2 O5 濃化至可避免脫磷不良的程度，因此也會有無法進行充分量之熱回收的課題。Further, the slag recovery contains a concern that dephosphorization is caused by the concentration of P 2 O 5 in the slag. In the cold recovery, since the component analysis of the decarburization slag can be performed, the method described in Patent Document 5 can be used, and the slag can be selected depending on the concentration of P 2 O 5 and depending on the steel grade. However, since the decarburization slag is continuously recovered in the heat recovery, the component analysis of the decarburization slag cannot be performed, and the degree of concentration of P 2 O 5 is not clear. Therefore, only a sufficient margin can be left to concentrate P 2 O 5 to the extent that dephosphorization can be avoided, and therefore there is a problem that a sufficient amount of heat recovery cannot be performed.

先前技術文獻 專利文獻 專利文獻1：日本專利特開平4-120209號公報 專利文獻2：日本專利特開昭64-75618號公報 專利文獻3：日本專利特許第2607328號公報 專利文獻4：日本專利特許第5671801號公報 專利文獻5：日本專利特許第3829696號公報CITATION LIST Patent Literature Patent Literature 1: Japanese Patent Laid-Open No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. No. Hei. Patent No. 5,671,801 Patent Document 5: Japanese Patent No. 3829696

非專利文獻 非專利文獻1：材料與製程 Vol.8(1995)， p.183Non-Patent Literature Non-Patent Document 1: Materials and Processes Vol.8 (1995), p.183

發明概要 發明欲解決之課題 本發明有鑑於前述問題點，而以提供一種可充分減低在脫碳吹煉中新投入助熔劑的量之熔鋼的製造方法為其目的。Disclosure of the Invention Problems to be Solved by the Invention The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for producing a molten steel which can sufficiently reduce the amount of flux newly introduced in decarburization and blowing.

用以解決課題之手段 本發明如以下所述。 (1)一種熔鋼的製造方法，其特徵在於：在將前次加料所產生之爐渣的一部份留在脫碳爐內的狀態下，於現行加料中，將已使以往脫碳吹煉所生成之爐渣固化的爐渣投入前述脫碳爐中，接著將磷濃度小於0.060質量%之熔鐵裝入前述脫碳爐中並進行脫碳吹煉。 (2)如上述(1)之熔鋼的製造方法，其中當現行加料中脫碳吹煉所生成之爐渣中的P2 O5 濃度在預定值以下時，將一部分的爐渣留在前述脫碳爐中以作為下次加料所用之爐渣。 (3)如上述(1)或(2)之熔鋼的製造方法，其中現行加料中，是將前述已固化之爐渣投入前述脫碳爐並投入助熔劑，且 前述助熔劑的量是根據前次加料所產生之爐渣中的P2 O5 濃度決定。 (4)如上述(1)~(3)之任1項的熔鋼的製造方法，其中前述已固化之爐渣粒徑為50mm以下。Means for Solving the Problems The present invention is as follows. (1) A method for producing a molten steel, characterized in that in a state in which a part of the slag produced by the previous feeding is left in the decarburization furnace, the conventional decarburization is blown in the current feeding. The slag solidified by the generated slag is placed in the decarburization furnace, and then molten iron having a phosphorus concentration of less than 0.060% by mass is charged into the decarburization furnace to perform decarburization blowing. (2) The method for producing a molten steel according to the above (1), wherein a part of the slag is left in the decarburization when a concentration of P 2 O 5 in the slag generated by the decarburization blowing in the current charging is below a predetermined value The furnace is used as the slag used for the next feeding. (3) The method for producing a molten steel according to the above (1) or (2), wherein in the current charging, the solidified slag is introduced into the decarburization furnace and a flux is introduced, and the amount of the flux is based on the former The concentration of P 2 O 5 in the slag produced by the secondary feed is determined. (4) The method for producing a molten steel according to any one of the above (1) to (3) wherein the solidified slag has a particle diameter of 50 mm or less.

發明效果 根據本發明，可提供一種能夠充分減低脫碳吹煉中新投入之助熔劑的量之熔鋼的製造方法。Advantageous Effects of Invention According to the present invention, it is possible to provide a method for producing a molten steel which can sufficiently reduce the amount of a flux newly charged in decarburization blowing.

用以實施發明之形態 以下，詳細說明本發明之實施形態。以下，附加於元素符號之符號[]是表示該元素於熔鐵或熔鋼中的濃度，附加於元素符號或化合物之符號()則表示該元素或化合物於爐渣中的濃度。Embodiments for Carrying Out the Invention Hereinafter, embodiments of the present invention will be described in detail. Hereinafter, the symbol [] attached to the element symbol indicates the concentration of the element in the molten iron or molten steel, and the symbol () added to the element symbol or compound indicates the concentration of the element or compound in the slag.

本發明中，將在脫碳爐中脫碳吹煉熔鐵時所生成的爐渣併用於冷回收與熱回收中，使用冷回收所生成之冷爐渣及熱回收所生成之熱爐渣進行脫碳吹煉，以使熔鋼中之[P]降低；前述熔鐵是經在轉爐以外之熔鐵預備處理或脫磷爐之脫磷處理等而脫磷之熔鐵。In the present invention, the slag generated when the molten iron is decarburized in the decarburization furnace is used for cold recovery and heat recovery, and the cold slag generated by cold recovery and the hot slag generated by heat recovery are used for decarburization blowing. Refining to reduce [P] in the molten steel; the molten iron is a molten iron which is dephosphorized by a molten iron preparation treatment other than a converter or a dephosphorization treatment of a dephosphorization furnace.

冷回收中，由脫碳爐將熔鋼出鋼後會將脫碳爐渣往渣桶排渣，並在冷卻後將所排渣之脫碳爐渣粉碎，且過篩調整至預定粒徑為止而獲得冷爐渣。然後，在數日後之加料中，由設置於脫碳爐上之投入滑槽將冷爐渣投入脫碳爐內。本實施形態是生成使用於脫碳爐而非脫磷爐之冷爐渣。In the cold recovery, after the molten steel is tapped by the decarburization furnace, the decarburization furnace slag is discharged into the slag bucket, and after the cooling, the decarburization slag of the discharged slag is pulverized and sieved to a predetermined particle size to obtain Cold furnace slag. Then, in a few days after the addition, the cold slag is put into the decarburization furnace by the input chute provided on the decarburization furnace. In this embodiment, cold slag which is used in a decarburization furnace instead of a dephosphorization furnace is produced.

熱回收中，由脫碳爐將熔鋼出鋼後並不將爐渣排渣，而將高溫脫碳爐渣(熱爐渣)殘留於脫碳爐內，並投入冷卻效果高之助熔劑等以使其固化。然後，注入下次加料之熔鐵，並轉移至脫碳吹煉。In the heat recovery, after the molten steel is tapped by the decarburization furnace, the slag is not discharged, and the high-temperature decarburization slag (hot furnace slag) remains in the decarburization furnace, and a flux having a high cooling effect is introduced to make it Cured. Then, the molten iron for the next feeding is injected and transferred to the decarburization blowing.

本實施形態中，首先藉由冷回收事先生成冷爐渣。然後，將前次加料所生成之熱爐渣直接留在脫碳爐後，於現行加料中，在有熱爐渣存在的狀態下投入冷爐渣，且當爐渣量不足時更進一步投入助熔劑，之後裝入熔鐵進行脫碳吹煉。並且，宜事前預測現行加料時爐渣中的(P2 O5 )，並判定現行加料中產生之脫碳爐渣可否回收到下次加料。當判定為可回收時，會將脫碳爐渣的一部分留在脫碳爐中以作為下次加料之熱爐渣。以下，詳細說明操作程序。In the present embodiment, first, cold slag is generated in advance by cold recovery. Then, the hot slag generated by the previous feeding is directly left in the decarburization furnace, and in the current feeding, the cold slag is put in the presence of the hot slag, and when the slag amount is insufficient, the flux is further injected, and then loaded. Into the molten iron for decarburization and blowing. Moreover, it is advisable to predict (P 2 O 5 ) in the slag at the time of the current feeding, and determine whether the decarburization slag generated in the current feeding can be recycled to the next feeding. When it is judged that it is recyclable, a part of the decarburization slag is left in the decarburization furnace as the hot slag for the next feeding. The operation procedure will be described in detail below.

首先，事先將因前次加料之脫碳吹煉而生成之脫碳爐渣的一部分留在脫碳爐中。該脫碳爐渣是藉由回收之判定而被判定為可回收之爐渣。關於回收之判定的詳細內容將於後說明。接著，在現行加料中，將熔鐵、冷爐渣及助熔劑投入脫碳爐，並進行脫碳吹煉。First, a part of the decarburization slag which is produced by the decarburization blowing of the previous feed is left in the decarburization furnace in advance. The decarburization slag is determined to be recyclable slag by the determination of the recovery. The details of the determination of the recycling will be described later. Next, in the current feeding, the molten iron, the cold slag, and the flux are put into a decarburization furnace, and decarburization blowing is performed.

投入脫碳爐之熔鐵的[P]是設為小於0.060質量%。將熔鐵中之[P]設為小於0.060質量%的理由是若熔鐵中之[P]在0.060質量%以上，會需要將脫磷量增大，且爐渣中之(P2 O5 )會變高，而變得不適合作為回收至脫碳爐之爐渣。且，投入脫碳爐之熔鐵的[P]宜為0.035質量%以下。由高爐出鐵之熔鐵中的[P]一般是超過0.100質量%左右，但針對令熔鐵中之[P]小於0.060質量%的方法並無特別限定。例如，可藉由利用脫磷爐之脫磷處理來令熔鐵中之[P]小於0.060質量%，又，亦可藉由應用周知的熔鐵預備處理技術，輕易地令熔鐵中之[P]小於0.060質量%。The [P] of the molten iron charged in the decarburization furnace was set to be less than 0.060% by mass. The reason why [P] in the molten iron is less than 0.060% by mass is that if [P] in the molten iron is 0.060% by mass or more, it is necessary to increase the amount of dephosphorization and (P 2 O 5 ) in the slag. It will become high and become unsuitable as a slag that is recycled to the decarburization furnace. Further, the [P] of the molten iron charged in the decarburization furnace is preferably 0.035 mass% or less. The [P] in the molten iron of the blast furnace is generally more than about 0.100% by mass, but the method of making the [P] in the molten iron less than 0.060% by mass is not particularly limited. For example, the [P] in the molten iron can be made less than 0.060% by mass by dephosphorization treatment using a dephosphorization furnace, and can also be easily obtained in the molten iron by applying a well-known molten iron preparation processing technique [ P] is less than 0.060% by mass.

在脫碳吹煉中，會視目標熔鋼的[P]及脫磷處理後之[P]來決定必需磷分配比，並藉此算出必需爐渣量。又，脫碳吹煉中是將鹼度設為3.6~3.8，且由保護熔解爐內之耐火物的觀點來看，是將爐渣中之(MgO)設為6~9質量%。根據該些條件即可決定助熔劑之投入量。In the decarburization blowing, the required phosphorus distribution ratio is determined depending on the [P] of the target molten steel and [P] after the dephosphorization treatment, and the necessary slag amount is calculated. Further, in the decarburization blowing, the alkalinity is 3.6 to 3.8, and from the viewpoint of protecting the refractory in the melting furnace, (MgO) in the slag is 6 to 9% by mass. Based on these conditions, the amount of flux input can be determined.

在此，磷分配比是將爐渣中之磷濃度除以熔鋼中之磷濃度的值((P)/[P])，必需磷分配比是在30~60左右的範圍，且當目標熔鋼的[P]小時，必需磷分配率會被設定為較大的值。由於出鋼之熔鋼量是可事先預測的，因此只要能夠設定磷分配比就可算出必需爐渣量。Here, the phosphorus distribution ratio is a value obtained by dividing the phosphorus concentration in the slag by the phosphorus concentration in the molten steel ((P)/[P]), and the required phosphorus distribution ratio is in the range of about 30 to 60, and when the target is melted For [P] hours of steel, the necessary phosphorus partition rate is set to a larger value. Since the amount of molten steel of tapping can be predicted in advance, the amount of necessary slag can be calculated as long as the phosphorus partition ratio can be set.

另一方面，已有報告指出磷分配比是與脫碳爐中各種爐渣成分、及終點溫度相關(參照例如非專利文獻1)。因此，會決定多數種助熔劑的組合，以滿足必需爐渣量、鹼度、爐渣中之(MgO)及上述相關式。而，助熔劑之組合的決定方法並非唯一，而是考量各爐中之操作經驗或助熔劑調度的容易性、以及成本等本地條件而決定。助熔劑的種類可舉出：生石灰、白雲石、矽石、橄欖岩、輕燒白雲石(Light burnt dolomite)等。如果是生石灰，粒徑宜為3~10mm，如果是輕燒白雲石，粒徑宜為5~30mm。On the other hand, it has been reported that the phosphorus partition ratio is related to various slag components and end temperature in the decarburization furnace (see, for example, Non-Patent Document 1). Therefore, a combination of a plurality of fluxes is determined to satisfy the necessary slag amount, alkalinity, (MgO) in the slag, and the above correlation. However, the method of determining the combination of the flux is not unique, but is determined by considering the operating experience in each furnace or the easiness of flux scheduling, and local conditions such as cost. Examples of the fluxing agent include quicklime, dolomite, vermiculite, peridotite, and light burnt dolomite. If it is quicklime, the particle size should be 3~10mm. If it is light burnt dolomite, the particle size should be 5~30mm.

並且，在由前次加料出鋼到現行加料中開始投入熔鐵為止的期間，事先將冷爐渣投入脫碳爐內。會在此期間投入冷爐渣的理由是為了要使前次加料中生成之熱爐渣固化，並且也是為了防止投入冷爐渣而導致的爆沸反應。且若在此期間投入冷爐渣，便可利用熱爐渣除去冷爐渣中的水分。於此，在生成冷爐渣之際，宜先過篩將粒徑調整為50mm以下。令冷爐渣之粒徑在50mm以下的理由在於容易儲存於熔解爐上之漏斗，而且容易由漏斗朝脫碳爐投入冷爐渣，並能在脫碳爐內順利渣化。另一方面，如果冷爐渣之粒徑超過50mm，則會有搬運、切出到漏斗等處理所伴隨的問題產生，且有在脫碳爐內需要較多時間傳熱及渣化的可能性。此外，也可將鏽皮作為溫度調整用的冷材而與冷爐渣、助熔劑一併投入。In addition, the cold slag is previously charged into the decarburization furnace during the period from the previous feeding and the current feeding to the start of the molten iron. The reason why the cold slag is put in during this period is to solidify the hot slag generated in the previous feeding, and also to prevent the boiling reaction caused by the input of the cold slag. Further, if cold slag is introduced during this period, the hot slag can be used to remove moisture from the cold slag. Here, when the cold slag is generated, it is preferable to sieve the particle size to 50 mm or less. The reason why the particle size of the cold slag is 50 mm or less is that the funnel is easily stored in the melting furnace, and it is easy to put the cold slag into the decarburizing furnace from the funnel, and it can be smoothly slag in the decarburizing furnace. On the other hand, if the particle size of the cold slag exceeds 50 mm, there are problems associated with handling such as handling and cutting out to the funnel, and there is a possibility that heat transfer and slag formation are required in the decarburization furnace for a long time. Further, the scale may be used together with the cold slag or the flux as a cold material for temperature adjustment.

如以上將熔鐵、冷爐渣及助熔劑投入脫碳爐中，並由主噴槍吹入氧氣開始脫碳吹煉。然後，當到達預定之[C]時，由脫碳爐將熔鋼出鋼至盛桶。而脫碳爐渣則是直接留在脫碳爐中作為熱爐渣。此時，也可以藉由脫碳爐渣中之(P2 O5 )來判定是否進行熱回收。As described above, the molten iron, the cold slag and the flux are put into the decarburization furnace, and the main lance is blown with oxygen to start decarburization and blowing. Then, when the predetermined [C] is reached, the molten steel is tapped to the barrel by the decarburization furnace. The decarburization slag is directly left in the decarburization furnace as the hot slag. At this time, it is also possible to determine whether or not heat recovery is performed by (P 2 O 5 ) in the decarburization slag.

當實施熱回收時，相較於利用新投入之助熔劑所生成之爐渣來脫磷的情況，爐渣中之(P2 O5 )較為濃化。如果(P2 O5 )過度濃化，爐渣之脫磷能力便會降低。因此，也可事前預測爐渣中之(P2 O5 )，並判定是否可將現行加料中產生的脫碳爐渣回收到下次加料。爐渣中之(P2 O5 )是藉由以下式(1)~式(3)所示的質量平衡算式來預測。 爐渣中(P2 O5 )(質量%)=爐渣中(P2 O5 )(kg/t)÷爐渣量(kg/t)×100　　　　　‧‧‧(1) 爐渣中(P2 O5 )(kg/t)=殘留爐渣中(P2 O5 )(kg/t)+冷爐渣中(P2 O5 )(kg/t)+現行加料爐渣中(P2 O5 )(kg/t)+前次加料熱爐渣中(P2 O5 )(kg/t)　　　‧‧‧(2) 爐渣量kg/t)=殘留爐渣量(kg/t)+冷爐渣量(kg/t)+現行加料爐渣量(kg/t)+前次加料熱爐渣量(kg/t)　　　‧‧‧(3)When heat recovery is performed, (P 2 O 5 ) in the slag is concentrated compared to the case where dephosphorization is performed by the slag generated by the newly-added flux. If (P 2 O 5 ) is excessively concentrated, the dephosphorization ability of the slag is lowered. Therefore, it is also possible to predict (P 2 O 5 ) in the slag in advance and determine whether the decarburization slag produced in the current charging can be recovered to the next feeding. (P 2 O 5 ) in the slag is predicted by a mass balance formula represented by the following formulas (1) to (3). In the slag (P 2 O 5 ) (% by mass) = slag (P 2 O 5 ) (kg / t) slag amount (kg / t) × 100 ‧ ‧ (1) slag (P 2 O 5 ) (kg/t) = residual slag (P 2 O 5 ) (kg/t) + cold slag (P 2 O 5 ) (kg/t) + current feed slag (P 2 O 5 ) (kg/t ) + previous feeding hot slag (P 2 O 5 ) (kg / t) ‧ ‧ (2) slag amount kg / t) = residual slag amount (kg / t) + cold slag amount (kg / t) + Current feeding slag amount (kg/t) + previous feeding hot slag amount (kg/t) ‧‧‧(3)

在此，所謂「殘留爐渣」指的是由前一步驟而來之熔鐵中所伴隨的爐渣，其量可藉由爐渣成分的質量平衡調查結果來掌握。而，所謂「現行加料爐渣」指的是來自於助熔劑的爐渣。Here, the "residual slag" refers to the slag accompanying the molten iron from the previous step, and the amount thereof can be grasped by the mass balance investigation result of the slag component. The term "current feed slag" refers to slag from a flux.

所謂「前次加料熱爐渣」是指不將現行加料之前在前次加料中生成的脫碳爐渣完全排渣，且藉由殘留於爐內而回收之熱爐渣，其量是藉由排渣時之轉爐最終傾動角度而決定，因此是可掌握的。前次加料熱爐渣中(P2 O5 )(kg/t)雖難以直接對樣品進行成分分析，但因在前次加料中已利用式(1)算出爐渣中(P2 O5 )(質量%)，故可掌握。The term "pre-feeding hot slag" refers to hot slag which is not completely discharged from the decarburization slag which is formed in the previous feeding before the current feeding, and which is recovered by remaining in the furnace. The converter is ultimately determined by tilting the angle and is therefore manageable. Although it is difficult to directly analyze the composition of the sample in the previous charging furnace slag (P 2 O 5 ) (kg/t), the slag (P 2 O 5 ) has been calculated by using the formula (1) in the previous feeding. %), so you can master.

如以上，當爐渣中(P2 O5 )(質量%)在預定值以下時，是將一部分的脫碳爐渣排渣而實施熱回收，並在下次加料中，算出爐渣中之(P)且算出磷分配率，以決定助熔劑的量。此時，也可利用所排渣之脫碳爐渣來實施冷回收。又，如果不實施熱回收，則會將所有的脫碳爐渣排渣，且在下次加料中僅使用冷爐渣及助熔劑來進行脫碳吹煉。又，也可在下次加料中僅使用助熔劑來進行脫碳吹煉。As described above, when (P 2 O 5 ) (% by mass) of the slag is less than or equal to a predetermined value, a part of the decarburization slag is drained and heat is recovered, and (P) in the slag is calculated in the next feeding. The phosphorus partition rate is calculated to determine the amount of flux. At this time, cold recovery can also be performed by using the decarburization slag of the discharged slag. Further, if heat recovery is not performed, all the decarburization slag is discharged, and only the cold slag and the flux are used for the decarburization blowing in the next feeding. Further, it is also possible to carry out decarburization blowing using only a flux in the next feeding.

而，為了生成冷爐渣，當爐渣中(P2 O5 )(質量%)在預定值以下時，也可令部分加料中不實施熱回收，而實施冷回收。Further, in order to generate the cold slag, when the slag (P 2 O 5 ) (% by mass) is less than or equal to a predetermined value, heat recovery may be performed without partial heat recovery.

根據以上，即可在脫碳爐擴大脫碳爐渣之回收量，而能大幅減低新投入之助熔劑量。According to the above, the amount of recovery of the decarburization slag can be expanded in the decarburization furnace, and the newly added flux amount can be greatly reduced.

實施例 以下，針對本發明實施例加以說明，惟，實施例中之條件僅為用以確認本發明之可實施性及效果所採用的一條件例，且本發明不受該一條件例限定。只要能在不脫離本發明之宗旨下達成本發明之目的，本發明可採用各種條件。EXAMPLES Hereinafter, the examples of the present invention will be described, but the conditions in the examples are merely examples of conditions used to confirm the applicability and effects of the present invention, and the present invention is not limited by the conditions. The present invention can adopt various conditions as long as the object of the present invention can be achieved without departing from the gist of the present invention.

為了確認本發明之效果，實施例1~4是進行將磷濃度小於0.060質量%的熔鐵在脫碳爐中脫碳吹煉之操作。所使用之熔鐵是280~290t之經熔鐵脫磷處理的脫磷鐵，熔鐵成分含有：[C]=3.3~3.8質量%、[Si]≦0.01質量%、[Mn]=0.10~0.30質量%、及[P]=0.010質量%以上且小於0.060質量%。In order to confirm the effects of the present invention, Examples 1 to 4 are operations for decarburizing and blowing molten iron having a phosphorus concentration of less than 0.060% by mass in a decarburization furnace. The molten iron used is decalcified iron which is dephosphorized by molten iron of 280 to 290 tons, and the molten iron component contains: [C]=3.3 to 3.8% by mass, [Si]≦0.01% by mass, [Mn]=0.10~ 0.30% by mass, and [P]=0.010% by mass or more and less than 0.060% by mass.

脫碳吹煉是以將[P]=0.018%設為製品規格上限的鋼種為對象而實施。而，考量到二次精煉以後由爐渣復磷等之參差，而將由脫碳爐出鋼之熔鋼中的[P]≦0.015%設定為更佳範圍。脫碳爐渣是以非專利文獻1所記載之水渡的算式而將磷分配比設為30~60的範圍，並使用：生石灰、白雲石、矽石、橄欖岩等助熔劑、冷爐渣及熱爐渣來進行脫碳吹煉。The decarburization blowing is carried out for a steel grade in which [P] = 0.018% is the upper limit of the product specification. On the other hand, it is considered that the [P] ≦ 0.015% in the molten steel tapped from the decarburization furnace is set to a better range after the secondary refining. The decarburization slag is in the range of 30 to 60 in the formula of the water to be described in Non-Patent Document 1, and uses a flux such as quicklime, dolomite, vermiculite, peridotite, cold slag, and heat. The slag is used for decarburization blowing.

首先，針對冷爐渣，會事先在另一加料中將脫碳爐爐渣排渣並冷卻後實施磁選，且在以粉碎機粉碎後以孔徑25mm的篩網過篩，而篩上粒會再度回到粉碎機進行粉碎後再度過篩。然後，篩下粒則作為冷爐渣搬運到製鋼工廠。在製鋼工廠所接收之冷爐渣平均粒徑為10mm。First, for the cold slag, the decarburization furnace slag is discharged and cooled in another feed, and then magnetic separation is carried out, and after being pulverized by a pulverizer, it is sieved by a sieve having a pore diameter of 25 mm, and the sieve granules are returned again. The pulverizer is pulverized and sieved again. Then, the sieved granules are transported as cold slag to the steelmaking plant. The average size of the cold slag received at the steelmaking plant is 10 mm.

在本次加料中，從轉爐之爐上漏斗經由投入滑槽，將預定量之依上述製造的冷爐渣投入脫碳爐內。本發明效果是利用助熔劑之削減量、以及由脫碳爐出鋼之熔鋼中的[P]之2個指標來進行評估。而，以下所說明之實施比率是指相對於所有加料，有實施回收之加料的比率。針對未實施回收之加料，除了經判定可否回收而判定為「否」的情況，還包含因其他之操作上要因而未實施的加料。In this feeding, a predetermined amount of the cold slag produced in accordance with the above is put into the decarburization furnace through the input chute from the furnace funnel of the converter. The effect of the present invention is evaluated by using two factors of the amount of reduction of the flux and [P] in the steel tapped from the decarburization furnace. However, the ratio of implementation described below refers to the ratio of the feed to be recycled relative to all feeds. In the case where the feed which has not been subjected to the recovery is judged as "NO" by the determination of whether or not the charge is recovered, the feed which has not been carried out due to other operations is also included.

(實施例1(發明例1)) 首先，不將前次加料之脫碳爐爐渣完全排渣，而事先使其在脫碳爐內殘留約15kg/t作為熱爐渣，並將如上述經粒度調整之脫碳爐爐渣作為冷爐渣，由設置於脫碳爐上的投入滑槽投入10kg/t。並且，與冷爐渣一併投入生石灰、白雲石、矽石及橄欖岩作為助熔劑，並投入7kg/t左右之鏽皮作為溫度調整用的冷材。投入冷爐渣及助熔劑後，將280~290t之上述脫磷鐵裝入脫碳爐內，實施脫碳吹煉。又，在熱爐渣及冷爐渣中，(CaO)=42質量%、且(SiO2 )=11質量%。在此階段，削減了相當於以下之助熔劑。 CaO：(熱爐渣+冷爐渣)(kg/t)×0.42 SiO2 ：(熱爐渣+冷爐渣)(kg/t)×0.11(Example 1 (Inventive Example 1)) First, the slag of the decarburization furnace slag which was previously fed is not completely discharged, and about 15 kg/t is left as a hot slag in the decarburization furnace in advance, and the granules are as described above. The adjusted decarburization furnace slag is used as the cold slag, and 10 kg/t is input from the input chute provided on the decarburization furnace. In addition, quicklime, dolomite, vermiculite, and peridotite are used as a flux together with the cold slag, and a scale of about 7 kg/t is put into the cold material for temperature adjustment. After the cold slag and the flux are introduced, the dephosphorized iron of 280 to 290 tons is placed in a decarburization furnace to perform decarburization blowing. Further, in the hot slag and the cold slag, (CaO) = 42% by mass and (SiO 2 ) = 11% by mass. At this stage, the flux equivalent to the following is reduced. CaO: (hot furnace slag + cold furnace slag) (kg / t) × 0.42 SiO 2 : (hot furnace slag + cold furnace slag) (kg / t) × 0.11

此外，在現行加料之脫碳吹煉前或脫碳吹煉中，利用上述式(1)~(3)計算現行加料之爐渣中(P2 O5 )濃度。然後，脫碳吹煉後，將熔鋼出鋼，經計算當爐渣中(P2 O5 )(質量%)在2.5質量%以上時，實施脫碳爐渣之完全排渣，當爐渣中(P2 O5 )(質量%)小於2.5質量%時，並不完全排渣而將脫碳爐渣少量排渣以使熱爐渣為15kg/t左右。而，當已完全排渣時，在下次加料中會使用冷爐渣及助熔劑，或僅使用助熔劑進行脫碳吹煉。Further, in the pre-decarburization blowing or the decarburization blowing of the current feed, the concentration of (P 2 O 5 ) in the slag of the current feed is calculated by the above formulas (1) to (3). Then, after the decarburization and blowing, the molten steel is tapped, and when the (P 2 O 5 ) (% by mass) of the slag is calculated to be 2.5% by mass or more, the complete slag removal of the decarburization slag is carried out, and when the slag is in the slag (P When 2 O 5 ) (% by mass) is less than 2.5% by mass, the slag is not completely discharged, and a small amount of slag is discharged from the decarburization slag so that the hot slag is about 15 kg/t. However, when the slag is completely discharged, the cold slag and the flux are used in the next feeding, or only the flux is used for the decarburization blowing.

然後，重複以上操作恰200次加料。其結果，熱回收實施比率(=熱回收實施加料次數÷總加料次數)為61%，冷回收實施比率(=冷回收實施加料次數÷總加料次數)為98%。Then, repeat the above operation exactly 200 times. As a result, the heat recovery implementation ratio (= heat recovery execution feed times ÷ total feed times) was 61%, and the cold recovery implementation ratio (= cold recovery implementation feed times ÷ total feed times) was 98%.

(實施例2(發明例2)) 首先，不將前次加料之脫碳爐爐渣完全排渣，而事先使其在脫碳爐內殘留約15kg/t作為熱爐渣，並將如上述經粒度調整之脫碳爐爐渣作為冷爐渣，由設置於脫碳爐上的投入滑槽投入10kg/t。並且，與冷爐渣一併投入生石灰、白雲石、矽石及橄欖岩作為助熔劑，並投入7kg/t左右之鏽皮作為溫度調整用的冷材。投入冷爐渣及助熔劑後，將280~290t之上述脫磷鐵裝入脫碳爐內，實施脫碳吹煉。又，在熱爐渣及冷爐渣中，(CaO)=42質量%、且(SiO2 )=11質量%。在此階段，削減了相當於以下之助熔劑。 CaO：(熱爐渣+冷爐渣)(kg/t)×0.42 SiO2 ：(熱爐渣+冷爐渣)(kg/t)×0.11(Example 2 (Inventive Example 2)) First, the slag of the decarburization furnace slag which was previously fed is not completely discharged, and about 15 kg/t is left as a hot slag in the decarburization furnace in advance, and the granules are granulated as described above. The adjusted decarburization furnace slag is used as the cold slag, and 10 kg/t is input from the input chute provided on the decarburization furnace. In addition, quicklime, dolomite, vermiculite, and peridotite are used as a flux together with the cold slag, and a scale of about 7 kg/t is put into the cold material for temperature adjustment. After the cold slag and the flux are introduced, the dephosphorized iron of 280 to 290 tons is placed in a decarburization furnace to perform decarburization blowing. Further, in the hot slag and the cold slag, (CaO) = 42% by mass and (SiO 2 ) = 11% by mass. At this stage, the flux equivalent to the following is reduced. CaO: (hot furnace slag + cold furnace slag) (kg / t) × 0.42 SiO 2 : (hot furnace slag + cold furnace slag) (kg / t) × 0.11

並且，脫碳吹煉後，將熔鋼出鋼，且不考量可否實施往下次加料之熱回收，而直接將脫碳爐渣少量排渣以使熱爐渣為15kg/t左右，並連續實施熱回收。然後，重複以上操作恰200次加料。其結果，熱回收實施比率為82%，冷回收實施比率為98%。Moreover, after the decarburization and blowing, the molten steel is tapped, and it is not considered whether the heat recovery to the next feeding can be carried out, and a small amount of the slag is directly discharged from the decarburization slag so that the hot slag is about 15 kg/t, and the heat is continuously applied. Recycling. Then, repeat the above operation exactly 200 times. As a result, the heat recovery implementation ratio was 82%, and the cold recovery implementation ratio was 98%.

(實施例3(習知例1)) 首先，不將前次加料之脫碳爐爐渣完全排渣，而事先使其在脫碳爐內殘留約15kg/t作為熱爐渣，並投入生石灰、白雲石、矽石及橄欖岩作為助熔劑，且投入7kg/t左右之鏽皮作為溫度調整用的冷材。又，並未投入冷爐渣。投入助熔劑後，將280~290t之上述脫磷鐵裝入脫碳爐內，實施脫碳吹煉。又，在熱爐渣中，(CaO)=42質量%、且(SiO2 )=11質量%。在此階段，削減了相當於以下之助熔劑。 CaO：熱爐渣(kg/t)×0.42 SiO2 ：熱爐渣(kg/t)×0.11(Example 3 (Conventional Example 1)) First, the slag of the decarburization furnace slag which was previously fed is not completely discharged, and about 15 kg/t is left as a hot slag in the decarburization furnace, and the quicklime and the white cloud are put in. Stone, vermiculite and peridotite are used as fluxing agents, and a scale of about 7 kg/t is used as a cold material for temperature adjustment. Also, no cold slag was introduced. After the flux is charged, the dephosphorized iron of 280 to 290 tons is placed in a decarburization furnace to perform decarburization blowing. Further, in the hot slag, (CaO) = 42% by mass and (SiO 2 ) = 11% by mass. At this stage, the flux equivalent to the following is reduced. CaO: hot furnace slag (kg/t) × 0.42 SiO 2 : hot furnace slag (kg/t) × 0.11

並且，脫碳吹煉後，將熔鋼出鋼，且不考量可否實施往下次加料之熱回收，而直接將脫碳爐渣少量排渣以使熱爐渣為15kg/t左右，並連續實施熱回收。然後，重複以上操作恰200次加料。其結果，熱回收實施比率為72%。雖熱回收實施比率較實施例2在更低位，但這是由於未實施冷回收而導致熱爐渣固化需要時間，若是在加料期間短等時間上沒有餘裕的狀況下，便會將脫碳爐渣完全排渣之故。Moreover, after the decarburization and blowing, the molten steel is tapped, and it is not considered whether the heat recovery to the next feeding can be carried out, and a small amount of the slag is directly discharged from the decarburization slag so that the hot slag is about 15 kg/t, and the heat is continuously applied. Recycling. Then, repeat the above operation exactly 200 times. As a result, the heat recovery implementation ratio was 72%. Although the heat recovery implementation ratio is lower than that of Example 2, this is because it takes time to cure the hot slag without performing cold recovery. If there is no margin in the short period of the feeding period, the decarburization slag will be completely Drainage.

(實施例4(習知例2)) 不實施熱回收而在前次加料中將脫碳爐渣完全排渣後，將280~290t之上述脫磷鐵裝入脫碳爐內，實施脫碳吹煉。然後，為了促進熔解，在吹煉開始起5分鐘以內投入10kg/t之上述冷爐渣，並投入生石灰、白雲石、矽石及橄欖岩作為助熔劑，且投入7kg/t左右之鏽皮作為溫度調整用的冷材。又，在冷爐渣中，(CaO)=42質量%、且(SiO2 )=11質量%。在此階段，削減了相當於以下之助熔劑。 CaO：冷爐渣(kg/t)×0.42 SiO2 ：冷爐渣(kg/t)×0.11(Example 4 (Conventional Example 2)) After the heat removal is performed and the decarburization slag is completely discharged in the previous feeding, the dephosphorized iron of 280 to 290 tons is placed in a decarburization furnace to perform decarburization blowing. Refining. Then, in order to promote the melting, 10 kg/t of the above-mentioned cold slag is charged within 5 minutes from the start of the blowing, and quicklime, dolomite, vermiculite, and peridotite are introduced as a flux, and a scale of about 7 kg/t is put as a temperature. Adjust the cold material used. Further, in the cold slag, (CaO) = 42% by mass and (SiO 2 ) = 11% by mass. At this stage, the flux equivalent to the following is reduced. CaO: cold slag (kg/t) × 0.42 SiO 2 : cold slag (kg/t) × 0.11

然後，在脫碳吹煉後，將熔鋼出鋼，並實施脫碳爐渣之完全排渣。重複以上操作恰200次加料。其結果，冷回收實施比率為65%，且冷回收實施比率較實施例1及2在更低位。如果不實施熱回收而在注入鐵水前投入冷爐渣，於注入熔鐵時就會因附著於轉爐渣的粉末及水分而產生很大的爆沸反應。因此，在實施例4中是在吹煉開始5分鐘後將冷爐渣投入轉爐。雖然在此情況也會於投入冷爐渣時產生爆沸反應，但相較於在注入鐵水前投入的情況，其反應較小。然而，在雨天時搬運含有水分之冷爐渣等情況下，冷爐渣中會含有很多水分而使得反應顯著，故可知其難以穩定使用，且可知僅以冷回收是無法確保回收量的。Then, after decarburization and blowing, the molten steel is tapped, and the complete slag removal of the decarburization slag is carried out. Repeat the above operation for exactly 200 feedings. As a result, the cold recovery implementation ratio was 65%, and the cold recovery implementation ratio was lower than that of Examples 1 and 2. If the heat recovery is not carried out and the cold slag is introduced before the injection of the molten iron, a large bump reaction occurs due to the powder and moisture adhering to the converter slag when the molten iron is injected. Therefore, in Example 4, the cold slag was put into the converter 5 minutes after the start of the blowing. Although a bumping reaction occurs in the case of inputting cold slag in this case, the reaction is small compared to the case before the injection of molten iron. However, in the case of transporting cold slag containing water in a rainy day, the cold slag contains a lot of water and the reaction is remarkable, so that it is difficult to use it stably, and it is understood that the recovery amount cannot be ensured only by cold recovery.

(實施例5(發明例3)) 實施例5是進行將磷濃度在0.035質量%以下之熔鐵在脫碳爐中脫碳吹煉之操作。所使用之熔鐵是280~290t之經熔鐵脫磷處理的脫磷鐵，熔鐵成分含有：[C]=3.3~3.8質量%、[Si]≦0.01質量%、[Mn]=0.10~0.30質量%、及[P]=0.010~0.035質量%。(Example 5 (Inventive Example 3)) Example 5 is an operation of decarburizing and blowing molten iron having a phosphorus concentration of 0.035 mass% or less in a decarburization furnace. The molten iron used is decalcified iron which is dephosphorized by molten iron of 280 to 290 tons, and the molten iron component contains: [C]=3.3 to 3.8% by mass, [Si]≦0.01% by mass, [Mn]=0.10~ 0.30% by mass and [P]=0.010 to 0.035 mass%.

首先，不將前次加料之脫碳爐爐渣完全排渣，而事先使其在脫碳爐內殘留約22kg/t作為熱爐渣，並將如上述經粒度調整之脫碳爐爐渣作為冷爐渣，由設置於脫碳爐上的投入滑槽投入11kg/t。並且，不投入助熔劑而投入7kg/t左右之鏽皮作為溫度調整用的冷材。投入冷爐渣後，將280~290t之上述脫磷鐵裝入脫碳爐內，實施脫碳吹煉。又，在熱爐渣及冷爐渣中，(CaO)=42質量%、且(SiO2 )=11質量%。在此階段，削減了相當於以下之助熔劑。 CaO：(熱爐渣+冷爐渣)(kg/t)×0.42 SiO2 ：(熱爐渣+冷爐渣)(kg/t)×0.11First, the slag of the decarburization furnace slag that was previously fed is not completely discharged, and about 22 kg/t is left as a hot slag in the decarburization furnace, and the slag of the decarburization furnace granules adjusted by the above-mentioned particle size is used as the cold slag. 11 kg/t was charged from the input chute provided on the decarburization furnace. Further, stainless steel of about 7 kg/t was put into the cold material for temperature adjustment without introducing a flux. After the cold slag is charged, the dephosphorized iron of 280 to 290 tons is placed in a decarburization furnace to perform decarburization blowing. Further, in the hot slag and the cold slag, (CaO) = 42% by mass and (SiO 2 ) = 11% by mass. At this stage, the flux equivalent to the following is reduced. CaO: (hot furnace slag + cold furnace slag) (kg / t) × 0.42 SiO 2 : (hot furnace slag + cold furnace slag) (kg / t) × 0.11

此外，在現行加料之脫碳吹煉前或脫碳吹煉中，利用上述式(1)~(3)計算現行加料之爐渣中(P2 O5 )濃度。然後，脫碳吹煉後，將熔鋼出鋼，經計算當爐渣中(P2 O5 )(質量%)在2.5質量%以上時，實施脫碳爐渣之完全排渣，當爐渣中(P2 O5 )(質量%)小於2.5質量%時，並不完全排渣而將脫碳爐渣少量排渣以使熱爐渣為20kg/t左右。而，當已完全排渣時，在下次加料中會使用冷爐渣及助熔劑，或僅使用助熔劑進行脫碳吹煉。Further, in the pre-decarburization blowing or the decarburization blowing of the current feed, the concentration of (P 2 O 5 ) in the slag of the current feed is calculated by the above formulas (1) to (3). Then, after the decarburization and blowing, the molten steel is tapped, and when the (P 2 O 5 ) (% by mass) of the slag is calculated to be 2.5% by mass or more, the complete slag removal of the decarburization slag is carried out, and when the slag is in the slag (P When 2 O 5 ) (% by mass) is less than 2.5% by mass, the slag is not completely discharged, and a small amount of slag is discharged from the decarburization slag so that the hot slag is about 20 kg/t. However, when the slag is completely discharged, the cold slag and the flux are used in the next feeding, or only the flux is used for the decarburization blowing.

然後，重複以上操作恰50次加料。其結果，熱回收實施比率為100%，冷回收實施比率為97%。Then, repeat the above operation exactly 50 times. As a result, the heat recovery implementation ratio was 100%, and the cold recovery implementation ratio was 97%.

(實施例6(習知例3)) 實施例6是進行將磷濃度在0.100質量%以下之熔鐵在脫碳爐中脫碳吹煉之操作。所使用之熔鐵是280~290t之經熔鐵脫磷處理的脫磷鐵，熔鐵成分含有：[C]=3.3~3.8質量%、[Si]≦0.01質量%、[Mn]=0.10~0.30質量%、及[P]=0.060~0.100質量%。(Example 6 (Conventional Example 3)) Example 6 is an operation of decarburizing and blowing molten iron having a phosphorus concentration of 0.100% by mass or less in a decarburization furnace. The molten iron used is decalcified iron which is dephosphorized by molten iron of 280 to 290 tons, and the molten iron component contains: [C]=3.3 to 3.8% by mass, [Si]≦0.01% by mass, [Mn]=0.10~ 0.30% by mass, and [P]=0.060 to 0.100% by mass.

首先，不將前次加料之脫碳爐爐渣完全排渣，而事先使其在脫碳爐內殘留約15kg/t作為熱爐渣，並將如上述經粒度調整之脫碳爐爐渣作為冷爐渣，由設置於脫碳爐上的投入滑槽投入10kg/t。並且，與冷爐渣一併投入生石灰、白雲石、矽石及橄欖岩作為助熔劑，並投入7kg/t左右之鏽皮作為溫度調整用的冷材。投入冷爐渣及助熔劑後，將280~290t之上述脫磷鐵裝入脫碳爐內，實施脫碳吹煉。又，在熱爐渣及冷爐渣中，(CaO)=42質量%、且(SiO2 )=11質量%。在此階段，削減了相當於以下之助熔劑。 CaO：(熱爐渣+冷爐渣)(kg/t)×0.42 SiO2 ：(熱爐渣+冷爐渣)(kg/t)×0.11First, the slag of the decarburization furnace slag of the previous feed is not completely discharged, and about 15 kg/t is left as a hot slag in the decarburization furnace, and the slag of the decarburization furnace granule adjusted by the above-mentioned particle size is used as the cold slag. 10 kg/t was charged from the input chute provided on the decarburization furnace. In addition, quicklime, dolomite, vermiculite, and peridotite are used as a flux together with the cold slag, and a scale of about 7 kg/t is put into the cold material for temperature adjustment. After the cold slag and the flux are introduced, the dephosphorized iron of 280 to 290 tons is placed in a decarburization furnace to perform decarburization blowing. Further, in the hot slag and the cold slag, (CaO) = 42% by mass and (SiO 2 ) = 11% by mass. At this stage, the flux equivalent to the following is reduced. CaO: (hot furnace slag + cold furnace slag) (kg / t) × 0.42 SiO 2 : (hot furnace slag + cold furnace slag) (kg / t) × 0.11

此外，在現行加料之脫碳吹煉前或脫碳吹煉中，利用上述式(1)~(3)計算現行加料之爐渣中(P2 O5 )濃度。然後，脫碳吹煉後，將熔鋼出鋼，經計算當爐渣中(P2 O5 )(質量%)在2.5質量%以上時，實施脫碳爐渣之完全排渣，當爐渣中(P2 O5 )(質量%)小於2.5質量%時，並不完全排渣而將脫碳爐渣少量排渣以使熱爐渣為15kg/t左右。而，當已完全排渣時，在下次加料中會使用冷爐渣及助熔劑，或僅使用助熔劑進行脫碳吹煉。Further, in the pre-decarburization blowing or the decarburization blowing of the current feed, the concentration of (P 2 O 5 ) in the slag of the current feed is calculated by the above formulas (1) to (3). Then, after the decarburization and blowing, the molten steel is tapped, and when the (P 2 O 5 ) (% by mass) of the slag is calculated to be 2.5% by mass or more, the complete slag removal of the decarburization slag is carried out, and when the slag is in the slag (P When 2 O 5 ) (% by mass) is less than 2.5% by mass, the slag is not completely discharged, and a small amount of slag is discharged from the decarburization slag so that the hot slag is about 15 kg/t. However, when the slag is completely discharged, the cold slag and the flux are used in the next feeding, or only the flux is used for the decarburization blowing.

然後，重複以上操作恰50次加料。其結果，熱回收實施比率為20%，冷回收實施比率為40%。Then, repeat the above operation exactly 50 times. As a result, the heat recovery implementation ratio was 20%, and the cold recovery implementation ratio was 40%.

(比較例) 不實施熱回收而在前次加料中將脫碳爐渣完全排渣後，將280~290t之上述脫磷鐵裝入脫碳爐內，實施脫碳吹煉。然後，投入生石灰、白雲石、矽石及橄欖岩作為助熔劑，並投入7kg/t左右之鏽皮作為溫度調整用的冷材。在脫碳吹煉後，將熔鋼出鋼，並實施脫碳爐渣之完全排渣。重複以上操作恰200次加料。(Comparative Example) After decarburization slag was completely discharged in the previous feeding without heat recovery, 280 to 290 tons of the above-mentioned dephosphorized iron was placed in a decarburization furnace to carry out decarburization blowing. Then, lime, dolomite, vermiculite, and peridotite are used as a flux, and a scale of about 7 kg/t is put as a cold material for temperature adjustment. After decarburization and blowing, the molten steel is tapped and the complete slag removal of the decarburization slag is carried out. Repeat the above operation for exactly 200 feedings.

(實驗結果) 圖1是顯示實施例1~4及比較例中脫碳爐渣之構成細項的圖。並且，如圖1所示，脫碳爐渣是由熱爐渣、冷爐渣、助熔劑(現行加料爐渣)及殘留爐渣所構成。不論哪種情況，合計的量皆為38kg/t左右，且殘留爐渣皆為5.3kg/t。因此，可將所回收之爐渣(熱爐渣及冷爐渣)量評估為已削減之助熔劑量。(Experimental Results) Fig. 1 is a view showing the details of the composition of the decarburization slags in Examples 1 to 4 and Comparative Examples. Further, as shown in Fig. 1, the decarburization slag is composed of hot slag, cold slag, flux (current feed slag), and residual slag. In either case, the total amount is about 38 kg/t, and the residual slag is 5.3 kg/t. Therefore, the amount of recovered slag (hot slag and cold slag) can be evaluated as the reduced flux.

又，在圖1中，熱爐渣及冷爐渣的值為各實施例之投入量乘以實施比率而得之值。如上述併用有冷回收及熱回收之實施例1及2為本發明例，其等可更加削減新投入之助熔劑量。特別是在不論爐渣中(P2 O5 )(質量%)而實施熱回收之實施例2，其新的助熔劑量是最為低位。助熔劑之削減量結果呈現出最大為實施例2之22.1kg/t，其次為實施例1之19.0kg/t。且，習知例之實施例3及4則呈現出新助熔劑之削減量少的結果。Further, in Fig. 1, the values of the hot slag and the cold slag are values obtained by multiplying the input amount of each example by the implementation ratio. Examples 1 and 2 in which cold recovery and heat recovery are used in combination are examples of the present invention, and the newly added flux amount can be further reduced. In particular, in Example 2 in which heat recovery was carried out regardless of (P 2 O 5 ) (% by mass) in the slag, the new fluxing amount was the lowest. The amount of flux reduction showed a maximum of 22.1 kg/t of Example 2, followed by 19.0 kg/t of Example 1. Further, Examples 3 and 4 of the conventional examples showed a result that the amount of reduction of the new flux was small.

圖2是顯示實施例1~4及比較例中由脫碳爐出鋼之熔鋼中的[P]的圖。在實施例1~4及比較例中，不論何者皆為小於所有加料中製品規格上限即[P]=0.018質量%之值。Fig. 2 is a view showing [P] in the molten steel discharged from the decarburization furnace in Examples 1 to 4 and Comparative Examples. In Examples 1 to 4 and Comparative Examples, the value of [P] = 0.018 mass%, which is less than the upper limit of the product specifications in all the feeds, was used.

在比較例中，由於不進行爐渣的回收且全部皆使用助熔劑，因此熔鋼中的[P]是在低位。 實施例1與比較例1同等，熔鋼中的[P]是在低位。這是由於再次利用熔融過之爐渣會比新投入助熔劑更能提升渣化性，且更進一步設定成僅在爐渣中(P2 O5 )(質量%)小於2.5質量%時才使用熱爐渣，而確保了脫磷能力之故。In the comparative example, since the slag was not recovered and all of the flux was used, [P] in the molten steel was at a low level. Example 1 is equivalent to Comparative Example 1, and [P] in the molten steel is at a low position. This is because the reuse of the molten slag can increase the slagability more than the newly added flux, and is further set to use the hot slag only when the slag (P 2 O 5 ) (% by mass) is less than 2.5% by mass. And ensure the dephosphorization ability.

實施例2並未判定熱爐渣可否回收，因此雖然助熔劑之削減量大，但卻呈熔鋼中之[P]的參差大之結果。再者，在共200次加料中，雖有2.0%之比例超出較佳範圍即[P] ≦0.015質量%的範圍外，但由於仍是小於製品規格上限[P]=0.018質量%的值，故可確認在製品上並無問題。In the second embodiment, it is not determined whether or not the hot slag can be recovered. Therefore, although the amount of flux reduction is large, it is a result of a large difference in [P] in the molten steel. Further, in a total of 200 additions, although the ratio of 2.0% is outside the range of the preferred range, that is, [P] ≦ 0.015 mass%, since it is still less than the upper limit of the product specification [P] = 0.018 mass%, Therefore, it can be confirmed that there is no problem in the product.

實施例3並未判斷可否熱回收，因此呈熔鋼中之[P]的參差大之結果。再者，在共200次加料中，雖有1.0%的比例超出較佳範圍即[P]≦0.015質量%的範圍外，但仍是小於製品規格上限[P]=0.018%的值。 實施例4僅實施冷回收而確保了脫磷能力，因此助熔劑之削減量雖少，但相較於實施例2及3，其熔鋼中之[P]是在低位。In Example 3, it was not judged whether or not heat recovery was possible, and therefore, the result of [P] in the molten steel was large. Further, in a total of 200 additions, although the ratio of 1.0% exceeded the range of the preferred range, i.e., [P] ≦ 0.015 mass%, it was still less than the upper limit of the product specification [P] = 0.018%. In Example 4, only the cold recovery was carried out to ensure the dephosphorization ability, so that the amount of flux reduction was small, but [P] in the molten steel was lower than that of Examples 2 and 3.

實施例5之熔鋼中的[P]比實施例1在更低位。這是由於僅以磷濃度在0.035質量%以下之熔鐵來進行脫碳處理，由此使得熱爐渣中(P2 O5 )(質量%)被保持在較低位之故。 實施例6是將磷濃度在0.065質量%以上之熔鐵脫碳，由此為確保脫磷能力而使得新的助熔劑增加，因此熔鋼中之[P]是在低位。又，由於有判斷可否熱回收，因此參差並不大。[P] in the molten steel of Example 5 was lower than Example 1. This is because the decarburization treatment is performed only with the molten iron having a phosphorus concentration of 0.035 mass% or less, whereby (P 2 O 5 ) (% by mass) in the hot slag is kept at a lower position. In the embodiment 6, the molten iron having a phosphorus concentration of 0.065 mass% or more is decarburized, whereby a new flux is increased to ensure the dephosphorization ability, so [P] in the molten steel is at a low position. Moreover, since there is a judgment as to whether or not heat recovery is possible, the difference is not large.

圖3是顯示熱爐渣中(P2 O5 )與出鋼後之熔鋼中[P]之關係的圖。為了使關係明確，抽出了已排除吹煉條件(脫磷後之熔鐵中的[P]、爐渣量、實際鹼度及終點[C])之影響的數據。隨著熱爐渣中(P2 O5 )的增加，出鋼後之熔鋼中的[P]也有增加的傾向。由此認為實施例2及3中，出鋼後之熔鋼中[P]的參差是因熱爐渣中(P2 O5 )的濃化所導致。Fig. 3 is a graph showing the relationship between (P 2 O 5 ) in the hot slag and [P] in the molten steel after tapping. In order to clarify the relationship, data on the effects of the blowing conditions ([P], slag amount, actual alkalinity, and end point [C]) in the molten iron after dephosphorization were extracted. As the (P 2 O 5 ) in the hot slag increases, [P] in the molten steel after tapping also tends to increase. Therefore, in Examples 2 and 3, the stagger of [P] in the molten steel after tapping was caused by the concentration of (P 2 O 5 ) in the hot slag.

圖4是顯示實施例1、5、6中脫碳爐渣的構成細項的圖，其顯示磷濃度在0.035質量%以下、小於0.060質量%、及0.100質量%以下之熔鐵中脫碳爐渣之構成的影響。並且，如圖4所示，脫碳爐渣是由熱爐渣、冷爐渣、助熔劑(現行加料爐渣)及殘留爐渣所構成。不論哪種情況，合計的量為38kg/t左右。因此，可將所回收之爐渣(熱爐渣及冷爐渣)量評估為已削減之助熔劑量。4 is a view showing the details of the composition of the decarburization slag in Examples 1, 5, and 6, and shows a decarburization slag in a molten iron having a phosphorus concentration of 0.035 mass% or less, less than 0.060 mass%, and 0.100 mass% or less. The impact of the composition. Further, as shown in Fig. 4, the decarburization slag is composed of hot slag, cold slag, flux (current feed slag), and residual slag. In either case, the total amount is about 38 kg/t. Therefore, the amount of recovered slag (hot slag and cold slag) can be evaluated as the reduced flux.

在圖4中，熱爐渣及冷爐渣的值為各實施例之投入量乘以實施比率而得之值。如上述併用有冷回收及熱回收之實施例5為本發明例，其可令新投入之助熔劑量為零。 另一方面，在實施例6中，新投入之助熔劑量為最大，無法削減助熔劑的量。這是因為被預測為脫碳爐渣中之(P2 O5 )高的加料較多，而導致熱回收之實施比率大幅降低之故。In Fig. 4, the values of the hot slag and the cold slag are values obtained by multiplying the input amount of each embodiment by the implementation ratio. Example 5, which uses cold recovery and heat recovery as described above, is an example of the present invention, which allows the newly-injected flux dose to be zero. On the other hand, in Example 6, the newly-introduced flux amount was the largest, and the amount of the flux could not be reduced. This is because the amount of (P 2 O 5 ) which is predicted to be high in the decarburization slag is large, and the implementation ratio of heat recovery is drastically lowered.

根據以上結果，本發明例即實施例1、2及5中，藉由適當組合熱回收及冷回收，熱爐渣會因冷爐渣而固化，且冷爐渣中的水分會因熱爐渣而除去，因此可緩解雙方之課題。藉此，回收量會擴大，因此可減低新投入之助熔劑，且可在將脫碳爐渣回收時利用提升爐渣之渣化性的效果，穩定地使熔鋼低[P]化。According to the above results, in the examples of the present invention, that is, in the first, second, and fifth embodiments, the heat recovery and the cold recovery are appropriately combined, the hot slag is solidified by the cold slag, and the moisture in the cold slag is removed by the hot slag. It can alleviate the problems of both parties. As a result, the amount of recovery can be increased, so that the newly-added flux can be reduced, and the effect of improving the slagability of the slag can be utilized to stably reduce the molten steel [P].

產業上之可利用性 根據本發明，可提供一種能夠充分減低脫碳吹煉中新投入之助熔劑量之熔鋼的製造方法，且其產業價值非常高。Industrial Applicability According to the present invention, it is possible to provide a method for producing a molten steel which can sufficiently reduce the amount of flux newly added in decarburization and blowing, and which has a very high industrial value.

圖1是顯示實施例1~4及比較例中脫碳爐渣之構成細項的圖。 圖2是顯示實施例1~6及比較例中由脫碳爐出鋼之熔鋼中的[P]的圖。 圖3是顯示熱爐渣中(P2 O5 )與出鋼後之熔鋼中[P]之關係的圖。 圖4是顯示實施例1、5、6中脫碳爐渣的構成細項的圖。Fig. 1 is a view showing the details of the composition of the decarburization slags in Examples 1 to 4 and Comparative Examples. Fig. 2 is a view showing [P] in a molten steel obtained by a decarburization furnace in Examples 1 to 6 and a comparative example. Fig. 3 is a graph showing the relationship between (P 2 O 5 ) in the hot slag and [P] in the molten steel after tapping. Fig. 4 is a view showing the details of the composition of the decarburization slags in Examples 1, 5, and 6.

Claims (5)

一種熔鋼的製造方法，其特徵在於：在將前次加料所產生之脫碳爐渣的一部份作為熱爐渣而留在脫碳爐內的狀態下，於現行加料中，將已使以往脫碳吹煉所生成之脫碳爐渣固化的冷爐渣投入前述脫碳爐中，接著將磷濃度小於0.060質量%之熔鐵裝入前述脫碳爐中並進行脫碳吹煉。 A method for producing a molten steel, characterized in that in a state in which a part of the decarburization slag generated by the previous feeding is left as a hot slag in a decarburization furnace, in the current feeding, the conventional removal is performed The cold slag in which the decarburization slag generated by the carbon blowing is solidified is put into the decarburization furnace, and then molten iron having a phosphorus concentration of less than 0.060% by mass is charged into the decarburization furnace to perform decarburization blowing. 如請求項1之熔鋼的製造方法，其中當現行加料中脫碳吹煉所生成之脫碳爐渣中的P2O5濃度在預定值以下時，將一部分的脫碳爐渣留在前述脫碳爐中以作為下次加料所用之熱爐渣。 The method for producing a molten steel according to claim 1, wherein a part of the decarburization slag is left in the decarburization when a concentration of P 2 O 5 in the decarburization slag generated by the decarburization smelting in the current feed is below a predetermined value. The furnace is used as the hot slag for the next feeding. 如請求項1或2之熔鋼的製造方法，其中現行加料中，是將前述已固化之冷爐渣投入前述脫碳爐並投入助熔劑，且前述助熔劑的量是根據前次加料所產生之脫碳爐渣中的P2O5濃度決定。 The method for producing a molten steel according to claim 1 or 2, wherein in the current feeding, the solidified cold slag is put into the decarburizing furnace and a flux is introduced, and the amount of the flux is generated according to the previous feeding. The concentration of P 2 O 5 in the decarburization slag is determined. 如請求項1或2之熔鋼的製造方法，其中前述已固化之冷爐渣粒徑為50mm以下。 The method for producing a molten steel according to claim 1 or 2, wherein the solidified cold slag has a particle diameter of 50 mm or less. 如請求項3之熔鋼的製造方法，其中前述已固化之冷爐渣粒徑為50mm以下。 The method for producing a molten steel according to claim 3, wherein the solidified cold slag has a particle diameter of 50 mm or less.
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