JP2009068096A - Method for refining stainless steel - Google Patents
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本発明は、ステンレス鋼の精錬方法に関し、特に、ＡＯＤ法またはＶＯＤ法によるステンレス鋼の精錬方法に関する。 The present invention relates to a method for refining stainless steel, and particularly to a method for refining stainless steel by an AOD method or a VOD method.
図１は、ステンレス鋼を製造する概略工程を説明する図である。同図に示すように、ステンレス鋼は、電気炉または転炉で溶製したステンレス粗溶鋼をＡＯＤ法、ＶＯＤ法、またはこれらの組合せによって二次精錬を行い、その溶鋼を鋳造し、圧延して製造される。 FIG. 1 is a diagram illustrating a schematic process for producing stainless steel. As shown in the figure, stainless steel is obtained by performing secondary refining of stainless steel coarsely melted in an electric furnace or converter using the AOD method, VOD method, or a combination thereof, casting the molten steel, and rolling it. Manufactured.
その際、電気炉では、所望の成分組成となるように、主原料としてのステンレススクラップ、および各種成分の原料を溶解し、粗溶鋼を溶製する。転炉では、溶銑にＣｒ合金鉄等を添加して粗溶鋼を溶製する。 At that time, in the electric furnace, the stainless steel scrap as the main raw material and the raw materials of various components are melted so as to obtain a desired component composition, and the molten steel is melted. In the converter, Cr alloy iron or the like is added to the molten iron to produce crude molten steel.
ＶＯＤ法による二次精錬においては、粗溶鋼をＶＯＤ用取鍋に移送し、減圧雰囲気下で、アルゴンガスを粗溶鋼内に吹き込むことによって粗溶鋼を攪拌させながら、酸素ガスを粗溶鋼の浴面に吹き付けて脱炭精錬を行い、溶鋼中のＣ濃度を目標値に調整する。その後、脱炭精錬時に付随的に酸化されて溶鋼中からスラグ中に移行したＣｒを回収するために、脱酸剤を添加し還元精錬を行う。還元精錬時に、Ｓｉ、Ｍｎ等の成分調整を行う。また、ＡＯＤ法による二次精錬においては、粗溶鋼をＡＯＤ用炉に移送し、アルゴンガスと酸素ガスを粗溶鋼内に吹き込むことによって粗溶鋼を攪拌させながら脱炭精錬を行い、その後、脱酸剤の添加により溶鋼を還元精錬し、成分調整を行う。 In secondary refining by the VOD method, the crude molten steel is transferred to a ladle for VOD, and oxygen gas is supplied to the bath surface of the molten molten steel while stirring the molten molten steel by blowing argon gas into the molten molten steel under a reduced pressure atmosphere. And decarburizing and refining to adjust the C concentration in the molten steel to the target value. Thereafter, in order to recover Cr that has been incidentally oxidized during the decarburization refining and transferred from the molten steel to the slag, a deoxidizing agent is added and reductive refining is performed. During reductive refining, components such as Si and Mn are adjusted. In the secondary refining by the AOD method, the molten steel is transferred to an AOD furnace, and decarburization refining is performed while the molten molten steel is stirred by blowing argon gas and oxygen gas into the molten molten steel. Additives are added to reduce and refine the molten steel to adjust the ingredients.
そして、二次精錬後の溶鋼を連続鋳造機にて鋳造し、得られた鋳片を熱間圧延、冷間圧延することにより、ステンレス鋼としての所望の鋼材が製造される。 And the desired steel material as stainless steel is manufactured by casting the molten steel after secondary refining with a continuous casting machine, and carrying out hot rolling and cold rolling of the obtained slab.
ここで、電気炉または転炉にて溶製した粗溶鋼中には、原料または合金鉄に含まれるＳ（硫黄）成分に起因して、高濃度のＳが含有され、ＡＯＤ法またはＶＯＤ法による二次精錬における脱炭精錬の後にも残留する。このため、脱炭精錬後の還元精錬工程において、脱酸剤の他に、造滓剤としてＣａＯを主成分とする生石灰を添加し、溶鋼中のＳをスラグに移行させる脱硫も行われる。 Here, due to the S (sulfur) component contained in the raw material or the alloyed iron, the high-concentration S is contained in the crude molten steel melted in the electric furnace or converter, and the AOD method or the VOD method is used. It remains after decarburization in secondary refining. For this reason, in the reductive refining process after decarburization refining, desulfurization which adds quick lime which has CaO as a main ingredient as a slagging agent other than a deoxidizer, and shifts S in molten steel to slag is also performed.
従来から、還元精錬工程における脱酸剤として、ＳｉおよびＡｌのいずれか１種が用いられてきた。Ｓｉを脱酸剤として用いる場合、減圧雰囲気下において、アルゴンガスと酸素ガスによる脱炭精錬を行う前に昇熱用としてＡｌを添加するが、この場合のＡｌは、脱炭精錬中に完全に酸化されるため、還元精錬時の脱酸剤として機能するものではない。一方、Ａｌを脱酸剤として用いる場合には、還元精錬の後に成分調整用としてＳｉを添加する。従って、従来のステンレス鋼の二次精錬においては、還元精錬工程の直前または還元精錬工程中に、ＳｉとＡｌの２種の脱酸剤を同時に溶鋼に添加することはなかった。 Conventionally, any one of Si and Al has been used as a deoxidizer in the reductive refining process. When Si is used as a deoxidizing agent, Al is added for heating up before decarburizing and refining with argon gas and oxygen gas in a reduced-pressure atmosphere. In this case, Al is completely removed during decarburizing and refining. Since it is oxidized, it does not function as a deoxidizer during reductive refining. On the other hand, when Al is used as a deoxidizer, Si is added for component adjustment after reductive refining. Therefore, in the conventional secondary refining of stainless steel, two types of deoxidizers of Si and Al were not simultaneously added to the molten steel immediately before or during the refining refining process.
従来、還元精錬時には、脱酸剤（ＳｉまたはＡｌ）および生石灰とともに、ＣａＦ2を主成分とする蛍石が造滓剤として添加されてきた。蛍石の添加は、スラグの融点を低下させてスラグの流動性を向上させるため、スラグと溶鋼の反応を促進させるのに有効である。従って、溶鋼に、脱酸剤および生石灰とともに蛍石を添加すると、スラグによる還元精錬および脱硫を効率的に行うことができる。 Conventionally, during refining and refining, fluorite containing CaF 2 as a main component has been added as a fossilizing agent together with a deoxidizer (Si or Al) and quicklime. The addition of fluorite is effective in promoting the reaction between the slag and molten steel because the melting point of the slag is lowered to improve the fluidity of the slag. Therefore, when fluorite is added to molten steel together with a deoxidizer and quicklime, reductive refining and desulfurization with slag can be performed efficiently.
ところで、上述したステンレス鋼の精錬過程で生成したスラグは、路盤材等の土木・建設用資材として活用されているが、近年、環境保全の観点から、その活用が制限される状況になっている。これは、従来のスラグには、還元精錬時の蛍石の添加によって多量のフッ素が必然的に含まれるが、環境基準として土木・建材用製鋼スラグ中に含まれるフッ素の溶出量を規制する土壌汚染に関する環境基準が定められたことによる。 By the way, although the slag produced | generated in the refining process of the stainless steel mentioned above is utilized as civil engineering and construction materials, such as a roadbed material, in recent years, the utilization is restricted from a viewpoint of environmental conservation. . This is because conventional slag necessarily contains a large amount of fluorine due to the addition of fluorite during refining and refining, but as an environmental standard, soil that regulates the elution amount of fluorine contained in steelmaking slag for civil engineering and building materials. This is due to the establishment of environmental standards for pollution.
そのため、近年において、土壌汚染の規制に対応して、スラグ中のフッ素を低減したり、スラグからのフッ素の溶出を防止する技術が種々提案されている。 Therefore, in recent years, various techniques for reducing fluorine in slag and preventing elution of fluorine from slag have been proposed in response to the regulation of soil contamination.
例えば、特許文献１には、電気炉にて溶鋼を精錬する際に、フッ素源である蛍石を使用せず、生成されたスラグの総量に対するＣａＯ、ＳｉＯ2、およびＡｌ2Ｏ3の濃度を所定範囲内に規定する技術が提案されている。特許文献２および３には、電気炉にて溶鋼を精錬する際に、蛍石を使用せず、生成されたスラグの塩基度（ＣａＯ／ＳｉＯ2）を０．６〜１．１に規定する技術が提案されている。 For example, Patent Document 1 discloses the concentration of CaO, SiO 2 , and Al 2 O 3 with respect to the total amount of slag generated without using fluorite as a fluorine source when refining molten steel in an electric furnace. Techniques for defining within a predetermined range have been proposed. In Patent Documents 2 and 3, when refining molten steel in an electric furnace, fluorite is not used, and the basicity (CaO / SiO 2 ) of the generated slag is defined as 0.6 to 1.1. Technology has been proposed.
しかし、前記特許文献１〜３に提案された技術では、スラグの低融点化は期待できるものの、いずれも電気炉における精錬を対象としていることから、スラグ中のＣａＯ濃度が低く規定されており（前記特許文献１では３０〜５０質量％、前記特許文献２および３では２０〜４０質量％）、溶鋼中から除去できるＳの量に限界がある。一方、近年のＡＯＤ法またはＶＯＤ法による二次精錬には、ステンレス鋼の高品質化への要請から、溶鋼中のＳを０．００１５質量％以下の極めて低濃度まで脱硫することが要求される。そのため、前記特許文献１〜３に提案された技術は、ＡＯＤ法またはＶＯＤ法による二次精錬における脱硫能が不十分であり、スラグ中のフッ素を低減する手段として適用できない。すなわち、スラグ中のフッ素を低減する技術は、前記特許文献１〜３に提案されているものの、高度な脱硫能も具備しつつ、スラグ中のフッ素を低減する技術は、実用化されていないのが現状である。 However, although the techniques proposed in Patent Documents 1 to 3 can be expected to lower the melting point of slag, since both are targeted for refining in an electric furnace, the CaO concentration in the slag is specified to be low ( In Patent Document 1, 30 to 50% by mass, and in Patent Documents 2 and 3, 20 to 40% by mass), the amount of S that can be removed from the molten steel is limited. On the other hand, in recent secondary refining by the AOD method or VOD method, it is required to desulfurize S in molten steel to a very low concentration of 0.0015% by mass or less due to a demand for high quality stainless steel. . For this reason, the techniques proposed in Patent Documents 1 to 3 have insufficient desulfurization ability in secondary refining by the AOD method or VOD method, and cannot be applied as a means for reducing fluorine in slag. That is, although the technology for reducing fluorine in slag has been proposed in Patent Documents 1 to 3, the technology for reducing fluorine in slag has not been put into practical use while having high desulfurization capability. Is the current situation.
また、特許文献４には、スラグからのフッ素の溶出を防止する技術が提案されている。提案の技術は、溶鋼上のフッ素を含むスラグに、ＣａＯとＡｌ2Ｏ3を加えてカルシウムアルミネート相を形成し、その後にＭｇＯを加えてスラグを調製するものであり、フッ素の溶出を防止することができ、安定した脱硫能を期待することができるとしている。しかし、提案の技術が対象とするスラグは、プリメルトスラグであることから、溶鋼の脱酸を促進させるために、ＳｉまたはＡｌを新たに添加しなければならず、これによりスラグ量が増大し、コストも悪化するという問題がある。 Patent Document 4 proposes a technique for preventing elution of fluorine from slag. Proposed technology is to add CaO and Al 2 O 3 to slag containing fluorine on molten steel to form calcium aluminate phase, and then add MgO to prepare slag to prevent elution of fluorine. It is said that stable desulfurization ability can be expected. However, since the slag targeted by the proposed technology is pre-melt slag, Si or Al must be newly added to promote deoxidation of molten steel, which increases the amount of slag. There is a problem that the cost also deteriorates.
本発明は、上記の問題に鑑みてなされたものであり、低コストで効率良く、高度な脱硫および還元精錬を行うことができ、しかも、土木・建設用資材として土壌汚染を生ずることなく、安全なスラグを生成することができるステンレス鋼の精錬方法を提供することを目的とする。 The present invention has been made in view of the above-mentioned problems, and can perform high-grade desulfurization and reductive refining efficiently at low cost, and without causing soil contamination as a civil engineering / construction material. It is an object of the present invention to provide a method for refining stainless steel that can produce slag.
本発明者は、上記目的を達成するために、ステンレス鋼の鋼材を製造する際のＡＯＤ法またはＶＯＤ法による二次精錬において、スラグ中のフッ素を低減することを前提として、還元精錬の能力に優れ、合わせて溶鋼中のＳを０．００１５質量％以下にまで脱硫することができる精錬方法について鋭意検討を重ね、本発明を完成させた。 In order to achieve the above object, the present inventor has achieved the ability of reductive refining on the premise of reducing fluorine in slag in secondary refining by AOD method or VOD method when producing stainless steel materials. The present invention has been completed by intensively studying a refining method that is excellent and can desulfurize S in molten steel to 0.0015% by mass or less.
本発明は、ＡＯＤ法またはＶＯＤ法により、溶鋼とその浴面上に浮遊するスラグを形成し、溶鋼内に吹き込んだアルゴンガスによる攪拌にて溶鋼とスラグを反応させて溶鋼を精錬するステンレス鋼の精錬方法において、ＣａＦ2を主成分とする造滓剤（蛍石など）を用いることなしに、脱炭精錬後の溶鋼に生石灰、フェロシリコン、およびＡｌの３種を同時に添加し、スラグと溶鋼との間のＳ分配比を３００以上に制御することを特徴とするものである。 The present invention is a stainless steel that forms molten steel and slag floating on the bath surface by AOD method or VOD method, and refines molten steel by reacting molten steel and slag by stirring with argon gas blown into the molten steel. In the refining method, three types of lime, ferrosilicon, and Al are simultaneously added to the molten steel after decarburization refining without using a slagging agent (such as fluorite) containing CaF 2 as a main component. The S distribution ratio between and is controlled to 300 or more.
ここで、前記スラグの組成を、質量％で表したとき、下記（１）〜（３）の条件を満足するように制御することが望ましい。 Here, when the composition of the slag is expressed by mass%, it is desirable to control so as to satisfy the following conditions (1) to (3).
１．６≦ＣａＯ／（Ａｌ2Ｏ3＋ＳｉＯ2）≦２．２ ・・・（１）
０．３５≦Ａｌ2Ｏ3／ＳｉＯ2≦４．１０ ・・・（２）
ＣａＦ2≦１．０ ・・・（３）
本発明において、「Ｓ分配比」とは、スラグ中のＳ濃度と溶鋼中のＳ濃度との比を意味する。
1.6 ≦ CaO / (Al 2 O 3 + SiO 2 ) ≦ 2.2 (1)
0.35 ≦ Al 2 O 3 / SiO 2 ≦ 4.10 (2)
CaF 2 ≦ 1.0 (3)
In the present invention, the “S distribution ratio” means the ratio of the S concentration in the slag to the S concentration in the molten steel.
本発明のステンレス鋼の精錬方法によれば、脱炭精錬後の溶鋼に生石灰、金属Ｓｉ、および金属Ａｌを同時に添加することにより低融点のスラグが形成されるので、ＣａＦ2を主成分とする造滓剤を添加することなく、流動性および脱硫能の優れたスラグを得ることができる。その結果、スラグと溶鋼との間のＳ分配比を３００以上に制御することができ、溶鋼の精錬に際し、効率良く高度な脱硫および還元精錬を行うことが可能になる。 According to the method for refining stainless steel of the present invention, slag having a low melting point is formed by simultaneously adding quick lime, metal Si, and metal Al to molten steel after decarburization refining, so CaF 2 is the main component. A slag excellent in fluidity and desulfurization ability can be obtained without adding a faux former. As a result, the S distribution ratio between the slag and the molten steel can be controlled to 300 or more, and it is possible to efficiently perform advanced desulfurization and reductive refining when refining the molten steel.
また、二次精錬の際に、ＣａＦ2を主成分とする造滓剤を用いないことから、生成されたスラグ中のフッ素を著しく低減することができる。従って、このスラグは、土木・建設用資材として土壌汚染を生ずることなく、安全に活用することができる。 In addition, since the slagging agent mainly composed of CaF 2 is not used in the secondary refining, fluorine in the generated slag can be significantly reduced. Therefore, this slag can be safely used as a civil engineering / construction material without causing soil contamination.
さらに、溶鋼の脱酸を促進させるために、ＳｉまたはＡｌを新たに添加することは不要であるため、スラグ量の抑制ができ、コストの低減も可能である。 Furthermore, since it is not necessary to newly add Si or Al in order to promote deoxidation of the molten steel, the amount of slag can be suppressed and the cost can be reduced.
本発明の精錬方法は、上述したように、ＡＯＤ法またはＶＯＤ法により、溶鋼とその浴面上に浮遊するスラグを形成し、溶鋼内に吹き込んだアルゴンガスによる攪拌にて溶鋼とスラグを反応させて溶鋼を精錬するステンレス鋼の精錬方法において、蛍石を用いることなしに、脱炭精錬後の溶鋼に生石灰、フェロシリコン、およびＡｌの３種を同時に添加し、スラグと溶鋼との間のＳ分配比を３００以上に制御することを特徴とする。 As described above, the refining method of the present invention forms molten steel and slag floating on the bath surface by the AOD method or VOD method, and reacts the molten steel and slag by stirring with argon gas blown into the molten steel. In the refining method of stainless steel, the slag between the slag and the molten steel is added to the molten steel after decarburizing and refining by adding three kinds of quick lime, ferrosilicon, and Al simultaneously without using fluorite. The distribution ratio is controlled to 300 or more.
本発明の精錬方法を前記の通り規定した理由を以下に説明する。 The reason why the refining method of the present invention is defined as described above will be described below.
図２は、二次精錬で生成されたスラグにおける「ＣａＯ／（Ａｌ2Ｏ3＋ＳｉＯ2）」と、そのスラグと溶鋼との間のＳ分配比（（Ｓ）／［Ｓ］）との関係を示す図である。ここでは、スラグ中の酸化物の組成をＣａＯ−Ａｌ2Ｏ3−ＳｉＯ2の３元系のスラグ組成に換算している。「ＣａＯ／（Ａｌ2Ｏ3＋ＳｉＯ2）」は、スラグ中に含有されるＣａＯ、Ａｌ2Ｏ3、およびＳｉＯ2のそれぞれの濃度から算出した質量濃度比である。Ｓ分配比は、スラグ中のＳの濃度（Ｓ）と溶鋼中のＳの濃度［Ｓ］との比「（Ｓ）／［Ｓ］」を表したものである。濃度の単位は、すべて質量％である。 FIG. 2 shows the relationship between “CaO / (Al 2 O 3 + SiO 2 )” in the slag produced by secondary refining and the S distribution ratio ((S) / [S]) between the slag and molten steel. FIG. Here, the composition of the oxide in the slag is converted to a ternary slag composition of CaO—Al 2 O 3 —SiO 2 . “CaO / (Al 2 O 3 + SiO 2 )” is a mass concentration ratio calculated from the respective concentrations of CaO, Al 2 O 3 and SiO 2 contained in the slag. The S distribution ratio represents the ratio “(S) / [S]” between the concentration of S in the slag (S) and the concentration of S in the molten steel [S]. The unit of concentration is all mass%.
図２で示す黒塗潰しの丸印は、本発明で規定する構成をすべて満足する状態で行った本発明例の試験結果を示し、同白抜きの丸印は、本発明で規定する構成を一部満足しない状態で行った比較例の試験結果を示す。 The solid black circles shown in FIG. 2 show the test results of the examples of the present invention conducted in a state satisfying all the configurations defined in the present invention, and the white circles indicate the configurations defined in the present invention. The test result of the comparative example performed in the state which is not satisfied partially is shown.
本発明例では、ＶＯＤ法による二次精錬において、脱炭精錬後、溶鋼上の酸化物に生石灰、フェロシリコン、およびＡｌの３種を同時に投入して還元精錬および脱硫を行い、スラグの主成分をＣａＯ−Ａｌ2Ｏ3−ＳｉＯ2系に調整した。一方、比較例では、二次精錬における脱炭精錬後、脱酸剤として、Ａｌを用いずに専らＳｉを用いるか、またはＳｉを用いずに専らＡｌを用いた。また、本発明例および比較例とも、粗溶鋼の溶製時も含め、二次精錬時に、フッ素源となる蛍石を一切使用せずに試験を行った。 In the present invention example, in the secondary refining by the VOD method, after decarburization refining, three kinds of quick lime, ferrosilicon, and Al are simultaneously added to the oxide on the molten steel to perform refining refining and desulfurization, and the main component of slag Was adjusted to CaO—Al 2 O 3 —SiO 2 system. On the other hand, in the comparative example, after decarburization refining in the secondary refining, Si was used exclusively without using Al as the deoxidizer, or Al was used exclusively without using Si. In addition, both the inventive examples and the comparative examples were tested without using any fluorite as a fluorine source during secondary refining, including during the melting of the crude molten steel.
本発明例では、脱炭精錬後に添加するフェロシリコンとして、普通Ｆｅ−Ｓｉを使用したが、その他に低Ｐ Ｆｅ−Ｓｉを使用することもできる。Ａｌとしては、金属Ａｌを使用したが、その他にＡｌ合金を使用することができる。 In the examples of the present invention, Fe-Si is usually used as ferrosilicon added after decarburization refining, but low P Fe-Si can also be used. As Al, metal Al was used, but Al alloy can also be used.
さらに、本発明例では、還元および脱硫後のスラグの組成について、「Ａｌ2Ｏ3／ＳｉＯ2」で表される質量濃度比が０．３５〜４．１０となるように調整した。実績値として、還元および脱硫後のスラグ中のＣａＯ濃度は５４〜６２質量％で、還元および脱硫後の溶鋼中の［Ｓ］は０．０００７〜０．００１４質量％であった。 Furthermore, in the present invention example, the composition of the slag after reduction and desulfurization was adjusted such that the mass concentration ratio represented by “Al 2 O 3 / SiO 2 ” was 0.35 to 4.10. As actual values, the CaO concentration in the slag after reduction and desulfurization was 54 to 62 mass%, and [S] in the molten steel after reduction and desulfurization was 0.0007 to 0.0014 mass%.
本発明例においては、「Ａｌ2Ｏ3／ＳｉＯ2」を０．３５以上に規定することにより、Ａｌ2Ｏ3源を確保し必要上の脱硫能を安定して得られる。但し、「Ａｌ2Ｏ3／ＳｉＯ2」を４．１以上とすると、Ａｌ2Ｏ3源が過剰となりスラグの流動性が得られず精錬スラグとして操業できなくなる。 In the example of the present invention, by defining “Al 2 O 3 / SiO 2 ” to be 0.35 or more, an Al 2 O 3 source can be secured and the necessary desulfurization ability can be stably obtained. However, if “Al 2 O 3 / SiO 2 ” is 4.1 or more, the Al 2 O 3 source becomes excessive, and the fluidity of the slag cannot be obtained, making it impossible to operate as a refined slag.
前記図２から明らかなように、本発明例においては、「ＣａＯ／（Ａｌ2Ｏ3＋ＳｉＯ2）」を１．６以上に規定することにより、Ｓ分配比を安定して３００以上に確保することができる。さらに、「ＣａＯ／（Ａｌ2Ｏ3＋ＳｉＯ2）」を１．９以上に規定すれば、Ｓ分配比を安定して４００以上に確保することも可能である。但し、「ＣａＯ／（Ａｌ2Ｏ3＋ＳｉＯ2）」が高くなり過ぎると、スラグの流動性が低下し、スラグと溶鋼との反応の促進が損なわれるため、「ＣａＯ／（Ａｌ2Ｏ3＋ＳｉＯ2）」の上限は２．２に規定する。スラグの流動性を一層重視する場合には、「ＣａＯ／（Ａｌ2Ｏ3＋ＳｉＯ2）」を２．０以下とするのが好適である。 As is apparent from FIG. 2, in the present invention example, by setting “CaO / (Al 2 O 3 + SiO 2 )” to 1.6 or more, the S distribution ratio is stably secured to 300 or more. be able to. Furthermore, if “CaO / (Al 2 O 3 + SiO 2 )” is specified to be 1.9 or more, the S distribution ratio can be stably secured to 400 or more. However, if too high "CaO / (Al 2 O 3 + SiO 2) ", decreases the fluidity of the slag, since the promotion of the reaction between the slag and the molten steel is impaired, "CaO / (Al 2 O 3 + SiO 2 ) ”is specified in 2.2. In the case where slag fluidity is more important, it is preferable to set “CaO / (Al 2 O 3 + SiO 2 )” to 2.0 or less.
一方、比較例においては、「ＣａＯ／（Ａｌ2Ｏ3＋ＳｉＯ2）」が１．６であるときのＳ分配比は高々２００であり、「ＣａＯ／（Ａｌ2Ｏ3＋ＳｉＯ2）」が２．２と高くてもＳ分配比が４００を超えることはない。 On the other hand, in the comparative example, when “CaO / (Al 2 O 3 + SiO 2 )” is 1.6, the S distribution ratio is 200 at most, and “CaO / (Al 2 O 3 + SiO 2 )” is 2 Even if it is as high as .2, the S distribution ratio does not exceed 400.
このような本発明例の試験結果から、蛍石を添加しなくても、脱炭精錬後に生石灰、金属Ｓｉ、および金属Ａｌを同時に添加し、Ｓ分配比を３００以上に制御することにより、高品質のステンレス鋼に精錬できる。 From the test results of the present invention example, by adding quick lime, metal Si, and metal Al at the same time after decarburization refining without adding fluorite, the S distribution ratio is controlled to 300 or higher. Can be refined to quality stainless steel.
特に、本発明の精錬方法では、脱炭精錬後に生石灰、金属Ｓｉ、および金属Ａｌを同時に添加することが重要である。先に金属Ｓｉを添加し、その後に生石灰と金属Ａｌを添加すると、生石灰を溶融させるための熱量が不足するか、または生石灰が溶解するまで時間が遅延する。この場合のスラグは、生石灰が完全に溶融しないことから、脱硫能が不安定で流動性が悪化したものとなる。そのため、そのスラグは、精錬スラグとして不適当であるばかりではなく、操業不能の事態をもたらす。これに対し、生石灰、金属Ｓｉ、および金属Ａｌを同時に投入することにより、金属Ｓｉおよび金属Ａｌの酸化還元反応熱が急激に発生するため、生石灰の溶融促進が可能となり、その結果、短時間で流動性の優れたスラグが得られ、しかも脱硫能の安定したスラグとなる。 In particular, in the refining method of the present invention, it is important to add quick lime, metal Si, and metal Al simultaneously after decarburization refining. If metal Si is added first, and quick lime and metal Al are added thereafter, the amount of heat for melting quick lime is insufficient, or the time is delayed until quick lime is dissolved. The slag in this case is one in which quick lime is not completely melted, so that the desulfurization ability is unstable and the fluidity is deteriorated. Therefore, the slag not only is not suitable as a refining slag, but also causes an inoperable situation. On the other hand, by simultaneously adding quick lime, metal Si, and metal Al, the oxidation-reduction heat of metal Si and metal Al is generated abruptly, so that quick lime melting can be accelerated. A slag having excellent fluidity is obtained, and the slag has a stable desulfurization ability.
本発明の精錬方法によれば、ＡＯＤ法またはＶＯＤ法による二次精錬の際に、ＣａＦ2を主成分とする造滓剤である蛍石を用いないことから、生成されたスラグ中のフッ素を著しく低減することができる。この場合、生成されたスラグ中のフッ素に関連するＣａＦ２濃度は、多くても１．０質量％程度に過ぎず、このスラグは、土木・建設用資材として土壌汚染を生ずることなく、安全に活用することができる。 According to the refining method of the present invention, in the secondary refining by the AOD method or the VOD method, fluorite, which is a fossilizing agent mainly composed of CaF 2 , is not used. It can be significantly reduced. In this case, the CaF2 concentration related to fluorine in the generated slag is only about 1.0% by mass at most, and this slag can be safely used without causing soil contamination as a civil engineering / construction material. can do.
また、本発明の精錬方法によれば、脱炭精錬後の溶鋼に生石灰、金属Ｓｉ、および金属Ａｌの３種を同時に添加することにより低融点のスラグが形成されるので、蛍石の添加がなくても、流動性および脱硫能の優れたスラグを得ることができ、その結果、スラグと溶鋼との間のＳ分配比を３００以上に制御することができる。従って、溶鋼に効率良く高度な脱硫および還元精錬を行うことが可能になる。 Further, according to the refining method of the present invention, low melting point slag is formed by simultaneously adding three kinds of quick lime, metal Si, and metal Al to the molten steel after decarburization refining. Even if not, slag excellent in fluidity and desulfurization ability can be obtained, and as a result, the S distribution ratio between the slag and the molten steel can be controlled to 300 or more. Therefore, it is possible to efficiently perform advanced desulfurization and refining on the molten steel.
さらに、本発明の精錬方法は、前記特許文献４に提案された技術のような、溶鋼の脱酸を促進させるためのＳｉまたはＡｌの添加は不要であるため、スラグ量の抑制が可能であり、コストの低減が図れる。例えば、本発明の精錬方法によれば、前記特許文献４に提案された技術と比較して、溶鋼１ｔ当たり８．０ｋｇのスラグ量の減少効果が期待できる。 Furthermore, since the refining method of the present invention does not require the addition of Si or Al for promoting deoxidation of molten steel as in the technique proposed in Patent Document 4, the amount of slag can be suppressed. Cost can be reduced. For example, according to the refining method of the present invention, an effect of reducing the amount of slag of 8.0 kg per ton of molten steel can be expected as compared with the technique proposed in Patent Document 4.
本発明のステンレス鋼の精錬方法による効果を確認するため、脱硫および還元精錬の試験を行い、その結果を評価した。本実施例の試験では、電気炉でステンレススクラップを溶解し、または転炉で溶銑にＣｒを添加し、ステンレス粗溶鋼を７５ｔ／ｃｈ（チャージ）溶製した。各粗溶鋼を、先ずＡＯＤ法によって粗脱炭精錬および昇熱を実施し、さらに、スラグの還元精錬および溶鋼成分の粗調整を実施した。続いて、ＶＯＤ法によって脱炭精錬を実施し、その後に還元精錬および脱硫を実施した。 In order to confirm the effect of the method for refining stainless steel of the present invention, desulfurization and reduction refining tests were conducted and the results were evaluated. In the test of this example, stainless steel scrap was melted in an electric furnace, or Cr was added to the hot metal in a converter to melt stainless steel coarse molten steel at 75 t / ch (charge). Each of the crude molten steels was first subjected to rough decarburization refining and heating by the AOD method, and further slag reduction refining and coarse adjustment of the molten steel components. Subsequently, decarburization refining was performed by the VOD method, and then reduction refining and desulfurization were performed.
その際、ＶＯＤ法による二次精錬の脱炭精錬工程の後に、生石灰、金属Ｓｉ、および金属Ａｌを同時に添加し、スラグ組成を調整した。このとき、脱炭精錬後、すなわち脱硫精錬前における粗溶鋼中に含有されるＳの濃度は、０．０１５〜０．０２０質量％の範囲内に調整し、生石灰の投入量は、粗溶鋼１ｔ当たり２０〜４０ｋｇの範囲内とした。 At that time, after the decarburization refining process of secondary refining by the VOD method, quick lime, metal Si, and metal Al were simultaneously added to adjust the slag composition. At this time, the concentration of S contained in the crude molten steel after decarburization refining, that is, before desulfurization refining is adjusted within a range of 0.015 to 0.020 mass%, and the input amount of quick lime is 1 t of crude molten steel. The range was 20 to 40 kg per hit.
表１に、ＶＯＤ法による還元・脱硫後のスラグをＣａＯ−Ａｌ2Ｏ3−ＳｉＯ2の３元系に換算した組成と、各組成での評価をまとめた試験結果を示す。評価は、脱硫後の溶鋼中のＳ濃度［Ｓ］、Ｓ分配比、脱硫率、およびスラグの流動性により行った。 Table 1 shows a composition in which the slag after reduction and desulfurization by the VOD method is converted to a ternary system of CaO—Al 2 O 3 —SiO 2 and the test results summarizing the evaluation of each composition. The evaluation was performed based on the S concentration [S] in the molten steel after desulfurization, the S distribution ratio, the desulfurization rate, and the slag fluidity.
試験番号１〜８は、本発明で規定する条件の少なくとも一部を満足しない比較例を示し、試験番号９〜１５は、本発明で規定する条件をすべて満足する本発明例を示した。 Test numbers 1 to 8 show comparative examples that do not satisfy at least a part of the conditions specified in the present invention, and test numbers 9 to 15 show examples of the present invention that satisfy all the conditions specified in the present invention.
表１から明らかなように、試験番号１〜８の比較例では、スラグの流動性、脱硫率の少なくとも一方を満足できなかった。すなわち、試験番号１および３では、スラグの流動性は確保できたが、「ＣａＯ／（Ａｌ2Ｏ3＋ＳｉＯ2）」、「Ａｌ2Ｏ3／ＳｉＯ2」およびＳ分配比が低いのに起因して、脱硫後の溶鋼中のＳ濃度が高くなり、精錬を中断した。試験番号２では、スラグの流動性は確保できたが、「Ａｌ2Ｏ3／ＳｉＯ2」が高く、Ｓ分配比が低いのに起因して、脱硫後の溶鋼中のＳ濃度を０．００１５質量％以下にまで低減できなかった。 As is clear from Table 1, in the comparative examples of test numbers 1 to 8, at least one of the slag fluidity and the desulfurization rate could not be satisfied. That is, in the test numbers 1 and 3, although the fluidity of the slag could be secured, “CaO / (Al 2 O 3 + SiO 2 )”, “Al 2 O 3 / SiO 2 ” and the S distribution ratio were low. As a result, the S concentration in the molten steel after desulfurization increased, and the refining was interrupted. In Test No. 2, the fluidity of the slag was secured, but due to the high “Al 2 O 3 / SiO 2 ” and the low S distribution ratio, the S concentration in the molten steel after desulfurization was 0.0015. It could not be reduced to less than mass%.
試験番号４では、脱硫後の溶鋼中のＳ濃度を０．００１５質量％以下にまで低減できたが、「Ａｌ2Ｏ3／ＳｉＯ2」が低いのに起因して、スラグの流動性が不十分となり、蛍石を添加し精錬を続行した。試験番号５では、「ＣａＯ／（Ａｌ2Ｏ3＋ＳｉＯ2）」が高く、「Ａｌ2Ｏ3／ＳｉＯ2」が低いのに起因して、Ｓ分配比が低く、脱硫後の溶鋼中のＳ濃度が高い上、スラグの流動性も悪化し、精錬を中断した。 In Test No. 4, the S concentration in the molten steel after desulfurization was reduced to 0.0015% by mass or less, but due to the low “Al 2 O 3 / SiO 2 ”, the fluidity of the slag was poor. After enough, fluorite was added and refining continued. In test number 5, “CaO / (Al 2 O 3 + SiO 2 )” is high and “Al 2 O 3 / SiO 2 ” is low, so the S distribution ratio is low, and S in the molten steel after desulfurization is low. The concentration was high and the fluidity of the slag deteriorated, so the refining was stopped.
試験番号６では、「ＣａＯ／（Ａｌ2Ｏ3＋ＳｉＯ2）」およびＳ分配比が低く、試験番号７では、「ＣａＯ／（Ａｌ2Ｏ3＋ＳｉＯ2）」が高く、Ｓ分配比が低く、試験番号８では、「Ａｌ2Ｏ3／ＳｉＯ2」が高く、Ｓ分配比が低いのに起因して、脱硫後の溶鋼中のＳ濃度を０．００１５質量％以下にまで低減できず、またスラグの流動性も不十分となり、精錬を中断した。 In test number 6, “CaO / (Al 2 O 3 + SiO 2 )” and the S distribution ratio are low, and in test number 7, “CaO / (Al 2 O 3 + SiO 2 )” is high and the S distribution ratio is low. In test number 8, “Al 2 O 3 / SiO 2 ” is high and the S distribution ratio is low, so the S concentration in the molten steel after desulfurization cannot be reduced to 0.0015% by mass or less. The fluidity of the slag became insufficient and refining was interrupted.
これらに対して、本発明例である試験番号９〜１５では、いずれも、Ｓ分配比が３００以上と高く、脱硫後の溶鋼中のＳ濃度は０．００１５質量％以下まで低減でき、良好な脱硫率が得られた。さらに、スラグの流動性も確保できた。 On the other hand, in test numbers 9 to 15 which are examples of the present invention, the S distribution ratio is as high as 300 or more, and the S concentration in the molten steel after desulfurization can be reduced to 0.0015% by mass or less. Desulfurization rate was obtained. In addition, the slag fluidity was secured.
本発明の精錬方法によれば、ＡＯＤ法またはＶＯＤ法による二次精錬において、ＣａＦ2を主成分とする造滓剤の添加がなくても、溶鋼に効率良く高度な脱硫および還元精錬を行うことができる。また、土木・建設用資材として土壌環境に安全に活用することが可能なスラグを得ることができる。さらに、スラグ量の抑制が可能であり、コストの低減も可能である。 According to the refining method of the present invention, in the secondary refining by the AOD method or the VOD method, efficient desulfurization and reductive refining can be efficiently performed on molten steel without the addition of a fossilizing agent mainly composed of CaF 2. Can do. Moreover, the slag which can be safely utilized for soil environment as a civil engineering / construction material can be obtained. Further, the amount of slag can be suppressed, and the cost can be reduced.
Claims (2)
蛍石を用いることなしに、脱炭精錬後の溶鋼に生石灰、フェロシリコン、およびＡｌの３種を同時に添加し、スラグと溶鋼との間のＳ分配比を３００以上に制御することを特徴とするステンレス鋼の精錬方法。 In the refining method of stainless steel, a slag floating on the molten steel and its bath surface is formed by the AOD method or the VOD method, and the molten steel and slag are reacted by stirring with argon gas blown into the molten steel to refine the molten steel.
3 types of quick lime, ferrosilicon, and Al are simultaneously added to the molten steel after decarburizing and refining without using fluorite, and the S distribution ratio between the slag and molten steel is controlled to 300 or more. To refine stainless steel.
１．６≦ＣａＯ／（Ａｌ2Ｏ3＋ＳｉＯ2）≦２．２ ・・・（１）
０．３５≦Ａｌ2Ｏ3／ＳｉＯ2≦４．１０ ・・・（２）
ＣａＦ2≦１．０ ・・・（３） 2. The method for refining stainless steel according to claim 1, wherein the slag composition is controlled so as to satisfy the following conditions (1) to (3) when expressed in mass%.
1.6 ≦ CaO / (Al 2 O 3 + SiO 2 ) ≦ 2.2 (1)
0.35 ≦ Al 2 O 3 / SiO 2 ≦ 4.10 (2)
CaF 2 ≦ 1.0 (3)
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103397131A (en) * | 2013-08-11 | 2013-11-20 | 山西太钢不锈钢股份有限公司 | Pure iron smelting method |
| CN109136470A (en) * | 2018-11-05 | 2019-01-04 | 北京首钢自动化信息技术有限公司 | A kind of VOD technique smelting autocontrol method |
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| KR20200044045A (en) * | 2017-08-25 | 2020-04-28 | 바오샨 아이론 앤 스틸 유한공사 | Smelting method of ultra-low carbon 13Cr stainless steel |
| CN112063801A (en) * | 2020-09-17 | 2020-12-11 | 浦项(张家港)不锈钢股份有限公司 | Stainless steel and preparation method thereof |
| JP2021059759A (en) * | 2019-10-08 | 2021-04-15 | Ｊｆｅスチール株式会社 | Production method of ultra-low sulfur stainless steel |
| CN115125366A (en) * | 2021-03-25 | 2022-09-30 | 上海梅山钢铁股份有限公司 | Intelligent production control method for argon blowing station |
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| CN104313309A (en) * | 2014-11-17 | 2015-01-28 | 中冶南方工程技术有限公司 | Technology and system for producing stainless steel by submerged arc furnace and AOD furnace duplex process |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS589914A (en) * | 1981-06-30 | 1983-01-20 | Sumitomo Metal Ind Ltd | Refining method for steel |
| JPH09263824A (en) * | 1996-03-29 | 1997-10-07 | Kawasaki Steel Corp | Vacuum refining method for chromium-containing molten steel |
| JP2002339014A (en) * | 2001-03-16 | 2002-11-27 | Kawasaki Steel Corp | Method for producing extra low sulfur steel |
| JP2006104531A (en) * | 2004-10-06 | 2006-04-20 | Sumitomo Metal Ind Ltd | Ti-CONTAINING STAINLESS STEEL MANUFACTURING METHOD |
| JP2007119837A (en) * | 2005-10-27 | 2007-05-17 | Nippon Steel Corp | Method for producing molten steel containing chromium and extremely little sulfur |
-
2007
- 2007-09-18 JP JP2007240610A patent/JP5338056B2/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS589914A (en) * | 1981-06-30 | 1983-01-20 | Sumitomo Metal Ind Ltd | Refining method for steel |
| JPH09263824A (en) * | 1996-03-29 | 1997-10-07 | Kawasaki Steel Corp | Vacuum refining method for chromium-containing molten steel |
| JP2002339014A (en) * | 2001-03-16 | 2002-11-27 | Kawasaki Steel Corp | Method for producing extra low sulfur steel |
| JP2006104531A (en) * | 2004-10-06 | 2006-04-20 | Sumitomo Metal Ind Ltd | Ti-CONTAINING STAINLESS STEEL MANUFACTURING METHOD |
| JP2007119837A (en) * | 2005-10-27 | 2007-05-17 | Nippon Steel Corp | Method for producing molten steel containing chromium and extremely little sulfur |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103397131A (en) * | 2013-08-11 | 2013-11-20 | 山西太钢不锈钢股份有限公司 | Pure iron smelting method |
| CN103397131B (en) * | 2013-08-11 | 2015-02-25 | 山西太钢不锈钢股份有限公司 | Pure iron smelting method |
| KR102294309B1 (en) * | 2017-08-25 | 2021-08-27 | 바오샨 아이론 앤 스틸 유한공사 | Smelting method of ultra-low carbon 13Cr stainless steel |
| KR20200044045A (en) * | 2017-08-25 | 2020-04-28 | 바오샨 아이론 앤 스틸 유한공사 | Smelting method of ultra-low carbon 13Cr stainless steel |
| JP2020531691A (en) * | 2017-08-25 | 2020-11-05 | 宝山鋼鉄股▲分▼有限公司 | Refining method of ultra-low carbon 13Cr stainless steel |
| CN109252013A (en) * | 2018-09-28 | 2019-01-22 | 中天钢铁集团有限公司 | A kind of bearing steel slagging process control method of full plastic occluded foreignsubstance |
| CN109136470A (en) * | 2018-11-05 | 2019-01-04 | 北京首钢自动化信息技术有限公司 | A kind of VOD technique smelting autocontrol method |
| CN109897938A (en) * | 2019-04-03 | 2019-06-18 | 西宁特殊钢股份有限公司 | Produce Cr13The electric furnace and refining furnace smelting control method of series stainless steel |
| JP2021059759A (en) * | 2019-10-08 | 2021-04-15 | Ｊｆｅスチール株式会社 | Production method of ultra-low sulfur stainless steel |
| JP7126096B2 (en) | 2019-10-08 | 2022-08-26 | Ｊｆｅスチール株式会社 | Manufacturing method of ultra-low sulfur stainless steel |
| CN112063801A (en) * | 2020-09-17 | 2020-12-11 | 浦项(张家港)不锈钢股份有限公司 | Stainless steel and preparation method thereof |
| CN115125366A (en) * | 2021-03-25 | 2022-09-30 | 上海梅山钢铁股份有限公司 | Intelligent production control method for argon blowing station |
| CN115125366B (en) * | 2021-03-25 | 2024-05-10 | 上海梅山钢铁股份有限公司 | Intelligent production control method for argon blowing station |
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