JP3473388B2 - Refining method of molten stainless steel - Google Patents
Refining method of molten stainless steelInfo
- Publication number
- JP3473388B2 JP3473388B2 JP08153298A JP8153298A JP3473388B2 JP 3473388 B2 JP3473388 B2 JP 3473388B2 JP 08153298 A JP08153298 A JP 08153298A JP 8153298 A JP8153298 A JP 8153298A JP 3473388 B2 JP3473388 B2 JP 3473388B2
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- JP
- Japan
- Prior art keywords
- steel
- slag
- molten steel
- molten
- refining
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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- Treatment Of Steel In Its Molten State (AREA)
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、ステンレス溶鋼の
精錬方法に関し、特に、ＶＯＤ方式の減圧精錬装置を用
い、溶鋼中のＡｌ2 Ｏ3 系介在物の生成を抑制し、鋳造
時におけるノズルの閉塞を防止すると共に、該ステンレ
ス溶鋼の清浄度を高める技術である。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for refining molten stainless steel, and in particular, it uses a VOD-type vacuum refining apparatus to suppress the formation of Al 2 O 3 -based inclusions in molten steel, and It is a technique that prevents clogging and enhances the cleanliness of the molten stainless steel.
【０００２】[0002]
【従来の技術】ステンレス溶鋼の溶製に際しては、鋼中
の有害成分である酸素を低減するため、あるいは最終製
品としての鋼材特性を得るため、溶鋼中にアルミニウム
（以下、Ａｌ）を添加することがある。そのため、該溶
鋼中にＡｌ2 Ｏ3 系の非金属介在物、特にそれが多数凝
集した所謂クラスター状介在物が生成し、それが該溶鋼
の連続鋳造時に、タンディッシュ・ノズルの開口部に付
着してノズルの閉塞を起こしたり、溶鋼の清浄度を著し
く悪化させる。そこで、従来より、溶鋼中の非金属介在
物（以下、介在物）を減らしたり、あるいは該介在物の
組成を調整してクラスタ化し難くするための研究開発が
多々行われている。2. Description of the Related Art In the production of molten stainless steel, aluminum (hereinafter referred to as "Al") is added to the molten steel in order to reduce oxygen which is a harmful component in the steel or to obtain characteristics of a steel product as a final product. There is. Therefore, Al 2 O 3 -based non-metallic inclusions, especially so-called cluster-like inclusions, which are agglomerated in large numbers, are generated in the molten steel and adhere to the openings of the tundish nozzle during continuous casting of the molten steel. As a result, the nozzle is clogged and the cleanliness of the molten steel is significantly deteriorated. Therefore, there have been many studies and developments to reduce nonmetallic inclusions (hereinafter referred to as inclusions) in molten steel or adjust the composition of the inclusions to make cluster formation difficult.
【０００３】特に、図５に示すようなＶＯＤ方式の減圧
精錬装置１は、減圧下で溶鋼２中クロム（以下、Ｃｒ）
の酸化を伴わずに、該溶鋼２（以下、溶湯２ということ
あり）の脱炭ができるのみならず、底吹きガス３による
強力な撹拌で取鍋４内のスラグ５と溶湯２間の反応促進
も期待できることから、以前より、介在物量調整技術の
実施に多用されてきた。Particularly, in the VOD type vacuum refining apparatus 1 as shown in FIG. 5, chromium (hereinafter, Cr) in the molten steel 2 is decompressed.
Not only the molten steel 2 (hereinafter sometimes referred to as molten metal 2) can be decarburized without being oxidized, but the reaction between the slag 5 in the ladle 4 and the molten metal 2 can be performed by strong stirring by the bottom-blown gas 3. Since it can be expected to be promoted, it has been widely used for the practice of the technique for adjusting the amount of inclusions.
【０００４】例えば、特開昭６３−２７７７０８号公報
は、ステンレス鋼の清浄度を高める目的で、「転炉で粗
脱炭した含Ｃｒ溶鋼をＶＯＤ処理（脱炭、脱ガス、Ａ
ｌ，Ｓｉ添加による脱酸還元）した後、次いでＡｌを含
有する溶鋼とＶＯＤ処理後の該溶鋼浴面上にあるスラグ
とを大気中で直接撹拌して、該溶鋼中のＡｌにより該ス
ラグ中のＳｉＯ2 を還元し、該スラグ中のＳｉＯ2 濃度
を調整すると共に、Ｓｉよりも酸素との親和力の小さい
金属元素からなる金属酸化物のスラグ中総量を３重量％
以下にする」技術を開示した。For example, Japanese Patent Laid-Open No. 63-277708 discloses, in order to improve the cleanliness of stainless steel, "VOD treatment of Cr-containing molten steel roughly decarburized in a converter (decarburization, degassing, A
1, deoxidation reduction by addition of Si), and then the molten steel containing Al and the slag on the molten steel bath surface after the VOD treatment are directly stirred in the atmosphere, and Al in the molten steel is used in the slag. Of SiO 2 is reduced to adjust the SiO 2 concentration in the slag, and the total amount of metal oxides made of metal elements having a smaller affinity for oxygen than Si in the slag is 3% by weight.
The following is disclosed.
【０００５】また、特開平８−２４６０３５号公報は、
「ＶＯＤ真空装置等によりステンレス鋼を製造するに際
して、真空精錬後のスラグ塩基度と溶鋼中のＡｌ濃度と
がある関係を満足するように精錬する」技術を開示し、
これにより、溶鋼中の介在物組成を制御して、鋳造工程
におけるノズル閉塞を防止するようにしている。Further, Japanese Patent Laid-Open No. 8-246035 discloses
Disclosed is a technique of "when manufacturing stainless steel using a VOD vacuum device or the like, refining so as to satisfy a relationship between slag basicity after vacuum refining and Al concentration in molten steel".
This controls the composition of inclusions in the molten steel to prevent nozzle clogging in the casting process.
【０００６】[0006]
【発明が解決しようとする課題】しかしながら、前記特
開昭６３−２７７７０８号公報記載の技術は、撹拌力の
弱い大気中で、スラグ中の低級酸化物を溶鋼中Ａｌで還
元するので、１つには、Ａｌ歩留りが安定せず、十分に
スラグ中の低級酸化物を還元することが困難であった。
また、還元ができても、処理に長時間を要し、その間に
取鍋の内張り耐火物の溶損や、溶鋼の温度降下が大きい
という問題があった。However, the technique described in JP-A-63-277708 reduces the lower oxides in the slag with Al in the molten steel in the atmosphere with a weak stirring power. However, the Al yield was not stable, and it was difficult to sufficiently reduce the lower oxide in the slag.
Further, even if the reduction can be achieved, there is a problem that the treatment takes a long time, and during that time, the melting loss of the refractory lining refractory of the ladle and the temperature drop of the molten steel are large.
【０００７】さらに、特開平８−２４６０３５号公報記
載の技術では、溶鋼中にＡｌを０．０１５重量％以上残
留させることができれば、Ａｌ2 Ｏ3 によるノズル閉塞
が防止できると考えられる。しかしながら、このこと
は、裏返せば、溶鋼中のＡｌ濃度が０．０１５重量％未
満の鋼種を安定して製造できないことを示唆している。
本発明は、かかる事情に鑑み、連続鋳造が安定して行え
ると共に、清浄度を従来より格段に高めることの可能な
ステンレス溶鋼の精錬方法を提供することを目的として
いる。Further, in the technique described in JP-A-8-246035, it is considered that if 0.015 wt% or more of Al can remain in the molten steel, the nozzle clogging due to Al 2 O 3 can be prevented. However, this suggests that it is impossible to stably produce a steel type having an Al concentration in the molten steel of less than 0.015% by weight by turning it over.
In view of such circumstances, an object of the present invention is to provide a method for refining stainless molten steel capable of stably performing continuous casting and significantly improving cleanliness as compared with conventional methods.
【０００８】[0008]
【課題を解決するための手段】発明者は、前記目的を達
成するため、溶鋼中のＡｌ濃度が低くても、溶鋼中にＡ
ｌ2 Ｏ3 系介在物が生成し難くなる精錬条件の発見に鋭
意努力した。その結果、溶鋼の脱酸処理時に、該溶鋼と
スラグ間の反応を適切に行うことで解決できることを見
いだし、それを本発明として完成させた。[Means for Solving the Problems] In order to achieve the above object, the inventor has found that even if the Al concentration in molten steel is low,
We made an earnest effort to find refining conditions that make it difficult for l 2 O 3 -based inclusions to form. As a result, they found that the reaction between the molten steel and the slag can be solved by appropriately performing the deoxidation treatment of the molten steel, and completed the present invention.
【０００９】本発明は、減圧精錬装置内で、溶鋼の脱炭
及び脱酸還元処理を順次行い、ステンレス溶鋼を溶製す
るに際して、前記溶鋼の脱炭を終了させた後、引き続い
て、脱酸還元処理の終了時にスラグ中のＣａＯ、ＳｉＯ
2 及びＴｏｔａｌ．Ｃｒ（以下、Ｔ．Ｃｒ）の濃度（い
ずれも、重量％）が下記式を満足するよう、該溶鋼にア
ルミニウムを投入し、撹拌することを特徴とするステン
レス溶鋼の精錬方法である。According to the present invention, decarburization and deoxidation reduction treatment of molten steel are sequentially performed in a depressurization refining apparatus, and when demolition of stainless molten steel is completed, after decarburization of the molten steel is finished, deoxidation is continued. CaO and SiO in the slag at the end of the reduction process
2 and Total. A refining method for molten stainless steel, which comprises charging aluminum and stirring the molten steel so that the concentration of Cr (hereinafter, T. Cr) (all in% by weight) satisfies the following formula.
【００１０】
スラグの目標塩基度が３．５未満の場合、
（Ｔ．Ｃｒ）≦０．７ …（１）
スラグの目標塩基度が３．５以上１５以下の場合、
（Ｔ．Ｃｒ）≦１．９５−０．５６Ａ＋０．０７２Ａ2 −０．００４Ａ3
＋０．００００８１Ａ4 …（２）
但し、Ａは、スラグの塩基度（ＣａＯ）／（ＳｉＯ2 ）
である。When the target basicity of the slag is less than 3.5, (T.Cr) ≦ 0.7 (1) When the target basicity of the slag is 3.5 or more and 15 or less, (T.Cr) ≦ 1.95-0.56A + 0.072A 2 -0.004A 3 + 0.000081A 4 ... (2) where, a is the slag basicity (CaO) / (SiO 2)
Is.
【００１１】また、本発明は、前記撹拌を、下記式で定
義される撹拌動力密度（ε）を３００ワット／トン−ｓ
ｔｅｅｌ以上として行うことを特徴とするステンレス溶
鋼の精錬方法である。
ε＝０．０２８５・Ｑ・Ｔ／Ｗ・ｌｏｇ（１＋Ｚ／１４８×７６０／Ｐ）
…（３）
ε：撹拌動力密度（ワット／トン−ｓｔｅｅｌ）
Ｑ：底吹きガス流量（ノルマル・リットル／分）
Ｔ：鋼浴温度（Ｋ°）
Ｗ：鋼浴重量（トン）
Ｚ：浴深さ（ｃｍ）
Ｐ：真空度（ｔｏｒｒ）
さらに、本発明は、前記減圧精錬装置がＶＯＤ方式のも
のであることを特徴とするステンレス溶鋼の精錬方法で
もある。In the present invention, the stirring power density (ε) defined by the following formula is 300 watt / ton-s.
It is a refining method for molten stainless steel, characterized in that it is carried out at or above the steel. ε = 0.0285 · Q · T / W · log (1 + Z / 148 × 760 / P) (3) ε: stirring power density (watt / ton-steel) Q: bottom blowing gas flow rate (normal·liter / min) ) T: Steel bath temperature (K °) W: Steel bath weight (ton) Z: Bath depth (cm) P: Vacuum degree (torr) Further, in the present invention, the vacuum refining apparatus is of VOD type. It is also a method for refining molten stainless steel, which is characterized in that.
【００１２】本発明によれば、減圧精錬処理中に、スラ
グ−メタルの撹拌が促進されると共に、還元後のスラグ
組成（主としてＴ．Ｃｒ及び塩基度（ＣａＯ／ＳｉＯ
2 ））が適切な値に調整されるようになるので、処理後
に溶鋼中に残存するＡｌ2 Ｏ3系介在物が大幅に低減さ
れ、しかも、スラグ中の低級酸化物による鋼中Ａｌの再
酸化が抑制されるので、極めて清浄度の高いステンレス
溶鋼が溶製されるようになる。その結果、ステンレス溶
鋼を連続鋳造して得られるスラブ（鋳片）等の手入れが
不要になり、固定費の大幅削減、及び以降の工程省略な
どの副次的な効果もある。さらに、該溶鋼の連続鋳造時
に、タンディッシュ・ノズルの開口部に付着しないよう
になり、ノズル閉塞を起こさずに溶鋼の安定鋳造ができ
るようになる。According to the present invention, the agitation of the slag-metal is promoted during the vacuum refining process, and the slag composition (mainly T.Cr and basicity (CaO / SiO) after the reduction is reduced.
2 )) is adjusted to an appropriate value, the Al 2 O 3 -based inclusions remaining in the molten steel after the treatment are significantly reduced, and moreover, the Al in the steel is regenerated by the lower oxides in the slag. Since oxidation is suppressed, extremely clean stainless molten steel comes to be melted. As a result, there is no need to care for the slab (cast slab) obtained by continuous casting of molten stainless steel, and there are secondary effects such as a significant reduction in fixed costs and the subsequent omission of steps. Further, during continuous casting of the molten steel, the molten steel is prevented from adhering to the opening of the tundish nozzle, and stable casting of the molten steel can be performed without causing nozzle clogging.
【００１３】[0013]
【発明の実施の形態】以下、発明をなすに至った経緯も
含め、本発明の実施形態を説明する。まず、発明者は、
図５に示したＶＯＤ方式の減圧精錬装置１を用い、溶鋼
２中へ添加するＡｌ量を種々変更した多くの実験を行
い、その実験結果に基づき、溶鋼２中のＡｌ濃度が０．
０１５重量％より低い場合でも、スラグ成分による溶鋼
２中の各種成分元素の再酸化が生じないようにするには
いかにすれば良いかを解析した。つまり、脱酸処理の時
間を種々変更して実験を行い、処理終了時間の溶鋼中Ａ
ｌ濃度によって整理した結果、溶鋼中Ａｌ濃度が同じよ
うに０．０１５重量％以下の場合でも、脱酸処理の時間
が長い方が溶鋼中のＡｌ2 Ｏ3 系介在物量が少なくなっ
ていることがわかった。BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below, including the background to the invention. First, the inventor
Using the VOD-type vacuum refining apparatus 1 shown in FIG. 5, many experiments were conducted in which the amount of Al added to the molten steel 2 was variously changed, and based on the experimental results, the Al concentration in the molten steel 2 was 0.
The analysis was conducted on how to prevent reoxidation of various constituent elements in the molten steel 2 due to the slag component even when the content is less than 015% by weight. That is, the experiment was performed by changing the deoxidation treatment time variously and
As a result of arranging according to the concentration of l, the amount of Al 2 O 3 -based inclusions in the molten steel decreases as the deoxidation treatment time increases even when the Al concentration in the molten steel is 0.015 wt% or less. I understood.
【００１４】したがって、これら実験で得た知見から、
溶鋼２中のＡｌ2 Ｏ3 系介在物の量を低減するには、溶
鋼２中のＡｌ濃度によらず、溶鋼浴面上に存在するスラ
グを調整することが重要であり、減圧処理終了から鋳造
までの間に、取鍋内において、溶鋼がその上に存在する
スラグ５で再酸化されるのを防止することが必須である
との考えに至った。Therefore, from the findings obtained in these experiments,
In order to reduce the amount of Al 2 O 3 -based inclusions in the molten steel 2, it is important to adjust the slag existing on the molten steel bath surface regardless of the Al concentration in the molten steel 2. It came to the idea that it is essential to prevent the molten steel from being reoxidized by the slag 5 existing thereon in the ladle before the casting.
【００１５】そこで、発明者は、ＶＯＤでの脱酸処理終
了時のスラグ組成と、鋳造後の鋼材に発生するアルミナ
介在物起因の欠陥量との関係を詳細に調査した。その結
果、図４に示すように、鋼材中に介在物起因の欠陥が著
しく少なくなるスラグ中のＴ．Ｃｒ濃度と塩基度（Ｃａ
Ｏ／ＳｉＯ2 ）との適正な組み合わせ領域があることが
知見された。そして、この適正領域と不適領域の境界を
重回帰分析し、本発明でスラグの組成を限定する下記式
を得たのである。Therefore, the inventor has investigated in detail the relationship between the slag composition at the end of deoxidation treatment with VOD and the amount of defects due to alumina inclusions generated in the steel material after casting. As a result, as shown in FIG. 4, T.S. in slag in which the defects due to inclusions in the steel material are significantly reduced. Cr concentration and basicity (Ca
It was found that there is a proper combination area with O / SiO 2 ). Then, the multiple regression analysis was performed on the boundary between the proper region and the unsuitable region, and the following formula for limiting the composition of the slag was obtained in the present invention.
【００１６】 スラグの目標塩基度が３．５未満の場合、 （Ｔ．Ｃｒ）≦０．７ …（１） スラグの目標塩基度が３．５以上１５以下の場合、 （Ｔ．Ｃｒ）≦１．９５−０．５６Ａ＋０．０７２Ａ2 −０．００４Ａ3 ＋０．００００８１Ａ4 …（２） 但し、Ａ＝塩基度（ＣａＯ）／（ＳｉＯ2 ）であるWhen the target basicity of the slag is less than 3.5, (T.Cr) ≦ 0.7 (1) When the target basicity of the slag is 3.5 or more and 15 or less, (T.Cr) ≦ 1.95-0.56A + 0.072A 2 -0.004A 3 + 0.000081A 4 ... (2) where is A = basicity (CaO) / (SiO 2)
【００１７】なお、脱酸処理終了次のスラグ組成を
（１）式あるいは（２）式を満足するものとするには、
Ａｌの添加によって溶鋼の脱酸のみならず、スラグの還
元を十分に生ぜしめる必要がある。さらに、Ａｌの添加
量は、処理する溶鋼やスラグの組成や量に基づいて、最
終スラグ組成が上記関係を満足することから、演算で事
前に決定することになる。In order to make the slag composition after the deoxidation treatment satisfy the formula (1) or the formula (2),
Not only deoxidation of molten steel but also reduction of slag must be sufficiently caused by the addition of Al. Furthermore, the amount of Al added is to be determined in advance by calculation, since the final slag composition satisfies the above relationship based on the composition and amount of molten steel or slag to be treated.
【００１８】また、発明者の研究によれば、上記ＶＯＤ
真空処理の最終スラグ組成に到達するまでに、Ａｌ脱酸
によって生成したＡｌ2 Ｏ3 系介在物を、スラグ５中に
十分吸収せしめておくことが必要である。特に、溶鋼２
中のＡｌ濃度が０．０１５重量％以下を目標とする鋼種
では、Ａｌの添加直後であっても、溶鋼中の［Ａｌ］が
少ないので、溶鋼２の脱酸が完了した後も、スラグ５を
還元するには、十分なスラグ５と溶鋼２の接触が必要で
ある。そのため、本発明では、前記特開昭６３−２７７
７０８号公報記載の大気圧下での撹拌に代え、脱炭処理
に引き続いて溶鋼２中にＡｌを添加して脱酸還元する際
に、減圧下で撹拌動力密度３００ワット／トン−ｓｔｅ
ｅｌ以上の強撹拌を行うようにしたのである。この真空
下での撹拌は、取鍋４内の溶鋼２にガス３を吹き込んで
行う。すなわち、真空下でのガス吹き込み撹拌は、該ガ
スが、吹き込み圧力からＶＯＤ真空槽８内の圧力（真空
度）まで低下する間に膨張し、前記大気圧下でのガス吹
き込みに比べて、少ないガス流量で多大の撹拌効果を得
ることができる。なお、前記（３）式で示した撹拌動力
密度（ε）は、公知である。According to the research conducted by the inventor, the above VOD
It is necessary to sufficiently absorb the Al 2 O 3 -based inclusions generated by Al deoxidation in the slag 5 before reaching the final slag composition of the vacuum treatment. In particular, molten steel 2
In the steel type in which the Al concentration in the steel is targeted to be 0.015% by weight or less, the amount of [Al] in the molten steel is small even immediately after the addition of Al, so even after the deoxidation of the molten steel 2 is completed, the slag 5 In order to reduce the slag, it is necessary to bring the slag 5 into contact with the molten steel 2 sufficiently. Therefore, in the present invention, the above-mentioned JP-A-63-277 is used.
Instead of stirring under atmospheric pressure described in Japanese Patent No. 708, stirring power density 300 watt / ton-ste under reduced pressure when Al is added to molten steel 2 to perform deoxidation reduction following decarburization treatment.
It was designed to perform strong agitation above el. The stirring under vacuum is performed by blowing gas 3 into molten steel 2 in ladle 4. That is, the gas blowing agitation under vacuum expands while the gas decreases from the blowing pressure to the pressure (vacuum degree) in the VOD vacuum tank 8 and is less than the gas blowing under the atmospheric pressure. A large stirring effect can be obtained with the gas flow rate. The stirring power density (ε) shown in the equation (3) is publicly known.
【００１９】また、真空装置１内で撹拌するので、仮に
溶鋼２の表面が雰囲気に曝されたとしても、それによっ
て雰囲気から溶鋼が再酸化する恐れがない利点もある。Further, since the stirring is performed in the vacuum apparatus 1, even if the surface of the molten steel 2 is exposed to the atmosphere, there is an advantage that the molten steel is not reoxidized from the atmosphere.
【００２０】[0020]
【実施例】次に、本発明の実施例において、その効果を
明らかにする。まず、生産能力１６０トンの酸素上底吹
き転炉（図示せず）に、溶銑、スクラップ及びステンレ
ス鋼製造用母溶湯を装入し、酸素吹錬を行い粗脱炭し、
溶鋼２中炭素［Ｃ］が０．２０重量％、溶鋼中クロム濃
度［Ｃｒ］が１６重量％の溶鋼１６０トンを、取鍋４に
出鋼した。なお、出鋼に際しては、出鋼末期にスラグ・
ストッパーによってスラグのカットを行い極力取鍋への
スラグ流出量を低減した。Next, the effect of the present invention will be clarified. First, hot oxygen, scrap and a mother molten metal for producing stainless steel are charged into an oxygen top-bottom blowing converter (not shown) having a production capacity of 160 tons, and oxygen blowing is performed to perform rough decarburization.
160 tons of molten steel containing 0.20% by weight of carbon [C] in molten steel 2 and 16% by weight of chromium concentration [Cr] in molten steel was tapped into ladle 4. When tapping, slag /
The stopper was used to cut the slag to reduce the outflow of slag to the ladle as much as possible.
【００２１】次いで、該取鍋４を図５に示したと同様な
ＶＯＤ方式の真空精錬装置１に移行し、真空下で上吹き
ランス７を介して酸素８を吹錬し、脱炭、脱ガス処理を
行った。その後、引き続き、該溶鋼２に、Ａｌを６５０
ｋｇ、Ｆｅ−Ｓｉを７４５ｋｇ及び造滓剤としての生石
灰を２０００ｋｇ投入し、本発明に係る真空下での脱酸
還元処理を１５分間行った。その際、撹拌のためのガス
３は、アルゴン・ガスとし、流量１０００ノルマル・リ
ットル／分で底吹きし、撹拌動力密度（ε）を４５０ワ
ット／トン−ｓｔｅｅｌにした。なお、上記Ａｌ，Ｆｅ
−Ｓｉ，生石灰の投入量は、前記転炉出鋼時のスラグ成
分と量、及び本発明に係る処理終了時のスラグ組成を予
測した演算により決定している。Then, the ladle 4 is transferred to a VOD type vacuum refining apparatus 1 similar to that shown in FIG. 5, and oxygen 8 is blown through a top blowing lance 7 under vacuum to decarburize and degas. Processed. Then, subsequently, 650 Al is added to the molten steel 2.
kg, 745 kg of Fe-Si, and 2000 kg of quick lime as a slag forming agent were added, and the deoxidation reduction treatment under vacuum according to the present invention was performed for 15 minutes. At that time, the gas 3 for stirring was argon gas, and was blown at the bottom with a flow rate of 1000 normal liters / minute, and the stirring power density (ε) was set to 450 watts / ton-steel. The above Al and Fe
The amounts of —Si and quick lime added are determined by a calculation that predicts the slag composition and amount at the time of tapping the converter, and the slag composition at the end of the treatment according to the present invention.
【００２２】この真空処理の結果、成分が、［Ｃ］＝
０．０４５重量％、［Ｓｉ］＝０．０４１重量％、［Ｃ
ｒ］＝１６．３１重量％、［Ａｌ］＝０．０１２重量％
のステンレス溶鋼を得た。また、この処理によって、ス
ラグの組成は、ＣａＯ＝４６．１重量％、ＳｉＯ2 ＝１
０．２重量％、Ａｌ2 Ｏ3 ＝３８．２重量％、Ｔｏｔａ
ｌ．Ｃｒ＝０．５０重量％となり、（Ｔ．Ｃｒ）値及び
塩基度（ＣａＯ／ＳｉＯ 2 ）は、前記本発明に係るスラ
グ組成の限定式を満たしていた。As a result of this vacuum treatment, the component is [C] =
0.045% by weight, [Si] = 0.041% by weight, [C
r] = 16.31% by weight, [Al] = 0.012% by weight
Obtained stainless molten steel. In addition, this process
The composition of the rug is CaO = 46.1% by weight, SiO2 = 1
0.2% by weight, Al2 O3 = 38.2% by weight, Tota
l. Cr = 0.50% by weight, and the (T.Cr) value and
Basicity (CaO / SiO 2 ) Is the slurry according to the present invention.
It satisfied the limited formula of the composition.
【００２３】この処理結果を、従来の大気圧下でＡｌ脱
酸する精錬方法で得た結果と比較し、図１に示す。図１
より、本発明に係るＶＯＤ真空処理後に得た溶鋼を連続
鋳造して得た鋼材からの試料は、Ａｌ2 Ｏ3 系介在物が
殆ど含有されていないことが明らかである。これは、本
発明に係るステンレス溶鋼の精錬方法を採用すると、真
空精錬中にスラグの還元が十分促進されるばかりでな
く、減圧精錬終了後に連続鋳造される間も、鋼中Ａｌの
再酸化が抑制されているためである。なお、図１の横軸
は、連続鋳造における鋳造時間率を表わしている。ま
た、図２及び図３に示すように、本発明に係る精錬方法
によれば、連続鋳造時のタンディッシュ・ノズル詰りが
低減されると共に、製品鋼材の表面疵も大幅に減少して
いる。The result of this treatment is compared with the result obtained by the conventional refining method of deoxidizing Al under atmospheric pressure and shown in FIG. Figure 1
From the above, it is clear that the sample from the steel material obtained by continuously casting the molten steel obtained after the VOD vacuum treatment according to the present invention contains almost no Al 2 O 3 -based inclusions. This is because, when the method for refining molten stainless steel according to the present invention is adopted, not only the reduction of slag is sufficiently promoted during vacuum refining, but also the reoxidation of Al in steel is caused during continuous casting after completion of reduced pressure refining. This is because it is suppressed. The horizontal axis of FIG. 1 represents the casting time rate in continuous casting. Further, as shown in FIGS. 2 and 3, according to the refining method of the present invention, clogging of the tundish and nozzle during continuous casting is reduced, and surface defects of the product steel material are also significantly reduced.
【００２４】[0024]
【発明の効果】以上述べたごとく、本発明により、溶鋼
中のＡｌ2 Ｏ3 系介在物の残存を大幅に低減でき、しか
も、スラグ中の低級酸化物による鋼中Ａｌの再酸化を抑
制できる。その結果、極めて清浄度の高いステンレス溶
鋼が溶製できると共に、スラブ（鋳片）の手入れが不要
になり、固定費の大幅削減や以降工程の省略などの副次
効果も生じる。さらに、連続鋳造時のタンディッシュ・
ノズル詰りが解消され、安定した鋳造が行えるようにな
る。As described above, according to the present invention, the residual of Al 2 O 3 -based inclusions in molten steel can be significantly reduced, and the reoxidation of Al in steel due to the lower oxide in the slag can be suppressed. . As a result, molten stainless steel having an extremely high degree of cleanliness can be melted, and maintenance of the slab (cast slab) is not required, resulting in secondary effects such as a significant reduction in fixed cost and omission of subsequent steps. In addition, tundish during continuous casting
Nozzle clogging is eliminated and stable casting can be performed.
【図１】本発明法及び従来法の実施で溶鋼中に残存する
Ａｌ2 Ｏ3 系介在物の量を、指数化して比較した図であ
る。FIG. 1 is a diagram comparing the amounts of Al 2 O 3 -based inclusions remaining in molten steel after carrying out the method of the present invention and the conventional method by indexing them.
【図２】本発明法及び従来法の実施で得た溶鋼の連続鋳
造時に生じるタンディッシュ・ノズルの詰りを、指数化
して比較した図である。FIG. 2 is a diagram in which clogging of a tundish nozzle that occurs during continuous casting of molten steel obtained by carrying out the method of the present invention and a conventional method is indexed and compared.
【図３】本発明法及び従来法の実施で得た溶鋼の鋳片に
発生したヘゲ疵を、指数化して比較した図である。FIG. 3 is a diagram comparing the bald defects generated in the molten steel slabs obtained by carrying out the method of the present invention and the conventional method by indexing them.
【図４】ＶＯＤ装置での脱酸処理終了時のスラグ組成
と、鋳造後の鋼材に発生するアルミナ介在物起因の欠陥
量との関係を示す図である。FIG. 4 is a diagram showing the relationship between the slag composition at the end of deoxidation treatment in a VOD device and the amount of defects due to alumina inclusions generated in a cast steel material.
【図５】ＶＯＤ方式の減圧精錬装置を示す縦断面図であ
る。FIG. 5 is a vertical cross-sectional view showing a VOD type vacuum refining device.
１ 真空精錬装置 ２ 溶鋼（溶湯） ３ 底吹きガス（アルゴン・ガス） ４ 取鍋 ５ スラグ ６ 真空槽 ７ 上吹きランス ８ 酸素 1 Vacuum refining equipment 2 Molten steel (molten metal) 3 Bottom blown gas (argon gas) 4 ladle 5 slag 6 vacuum tank 7 Top blowing lance 8 oxygen
フロントページの続き (56)参考文献 特開 平９−41021（ＪＰ，Ａ) 特開 平６−306446（ＪＰ，Ａ) 特開 平８−165511（ＪＰ，Ａ) 特開 平６−330148（ＪＰ，Ａ) 特開 平10−195521（ＪＰ，Ａ) 第126・127回西山記念講座，日本，社 団法人日本鉄鋼協会，1988年11月14日, 167−194 ステンレス鋼便覧，日本，日刊工業新 聞，1973年11月30日，599−600 第126・127回西山記念講座，日本，社 団法人日本鉄鋼協会，1988年11月14日, １−30 鉄鋼便覧，日本，社団法人日本鉄鋼協 会（丸善），1980年 ９月20日，695− 699 (58)調査した分野(Int.Cl.7，ＤＢ名) C21C 7/10 C21C 7/00 Continuation of the front page (56) Reference JP-A-9-41021 (JP, A) JP-A-6-306446 (JP, A) JP-A-8-165511 (JP, A) JP-A-6-330148 (JP , A) JP 10-195521 (JP, A) 126th and 127th Nishiyama Memorial Lecture, Japan, The Iron and Steel Institute of Japan, November 14, 1988, 167-194 Stainless Steel Handbook, Japan, Nikkan Kogyo Shinshin, November 30, 1973, 599-600 126th & 127th Nishiyama Memorial Lecture, Japan, The Iron and Steel Institute of Japan, November 14, 1988, 1-30 Iron and Steel Handbook, Japan, Nippon Steel Corporation Association (Maruzen), September 20, 1980, 695-699 (58) Fields investigated (Int.Cl. 7 , DB name) C21C 7/10 C21C 7/00
Claims (3)
処理を順次行い、ステンレス溶鋼を溶製するに際して、 前記溶鋼の脱炭を終了させた後、引き続いて、脱酸処理
の終了時にスラグ中のＣａＯ、ＳｉＯ2 及びＴｏｔａ
ｌ．Ｃｒ（いずれも重量％）の濃度が下記式を満足する
よう、該溶鋼にアルミニウムを投入し、撹拌することを
特徴とするステンレス溶鋼の精錬方法。 スラグの目標塩基度が３．５未満の場合、 （Ｔｏｔａｌ．Ｃｒ）≦０．７ …（１） スラグの目標塩基度が３．５以上１５以下の場合、 （Ｔｏｔａｌ．Ｃｒ）≦１．９５−０．５６Ａ＋０．０７２Ａ2 − ０．００４Ａ3 ＋０．００００８１Ａ4 …（２） 但し、Ａは、スラグの塩基度（ＣａＯ）／（ＳｉＯ2 ）
である。1. When decarburizing and deoxidizing molten steel in the depressurization refining apparatus in order to produce stainless molten steel, after decarburizing the molten steel, the deoxidizing treatment is subsequently terminated. Sometimes CaO, SiO 2 and Tota in slag
l. A refining method for molten stainless steel, which comprises adding aluminum to the molten steel and stirring the mixture so that the Cr (all in weight%) concentration satisfies the following formula. When the target basicity of the slag is less than 3.5, (Total.Cr) ≦ 0.7 (1) When the target basicity of the slag is 3.5 or more and 15 or less, (Total.Cr) ≦ 1.95 -0.56A + 0.072A 2 - 0.004A 3 + 0.000081A 4 ... (2) where, a is the slag basicity (CaO) / (SiO 2)
Is.
力密度（ε）を３００ワット／トン−ｓｔｅｅｌ以上と
して行うことを特徴とする請求項１記載のステンレス溶
鋼の精錬方法。 ε＝０．０２８５・Ｑ・Ｔ／Ｗ・ｌｏｇ（１＋Ｚ／１４８×７６０／Ｐ） …（３） ε：撹拌動力密度（ワット／トン−ｓｔｅｅｌ） Ｑ：底吹きガス流量（ノルマル・リットル／分） Ｔ：鋼浴温度（Ｋ°） Ｗ：鋼浴重量（トン） Ｚ：浴深さ（ｃｍ） Ｐ：真空度（ｔｏｒｒ）2. The method for refining molten stainless steel according to claim 1, wherein the stirring is performed at a stirring power density (ε) defined by the following formula of 300 watt / ton-steel or more. ε = 0.0285 · Q · T / W · log (1 + Z / 148 × 760 / P) (3) ε: Agitation power density (watt / ton-steel) Q: Bottom blowing gas flow rate (normal liter / min) ) T: Steel bath temperature (K °) W: Steel bath weight (ton) Z: Bath depth (cm) P: Vacuum degree (torr)
あることを特徴とする請求項１又は２記載のステンレス
溶鋼の精錬方法。3. The method for refining a molten stainless steel according to claim 1, wherein the reduced pressure refining apparatus is of a VOD type.
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|---|---|---|---|
| JP08153298A JP3473388B2 (en) | 1998-03-27 | 1998-03-27 | Refining method of molten stainless steel |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP08153298A JP3473388B2 (en) | 1998-03-27 | 1998-03-27 | Refining method of molten stainless steel |
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| Publication Number | Publication Date |
|---|---|
| JPH11279631A JPH11279631A (en) | 1999-10-12 |
| JP3473388B2 true JP3473388B2 (en) | 2003-12-02 |
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| JP3480353B2 (en) * | 1999-02-25 | 2003-12-15 | Ｊｆｅスチール株式会社 | Method for melting Ag-containing steel |
| KR100428570B1 (en) * | 1999-11-29 | 2004-04-28 | 주식회사 포스코 | Method for deoxidizing stainless steel containing Ti by Al |
| JP2008240126A (en) * | 2007-03-28 | 2008-10-09 | Jfe Steel Kk | Method for refining molten stainless steel |
| KR101258785B1 (en) | 2011-08-01 | 2013-04-29 | 주식회사 포스코 | Manufacturing method of duplex 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 |
| JP7480751B2 (en) * | 2021-06-11 | 2024-05-10 | Ｊｆｅスチール株式会社 | METHOD FOR DENITRATION OF MOLTEN STEEL AND METHOD FOR PRODUCING STEEL |
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1998
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Non-Patent Citations (4)
| Title |
|---|
| ステンレス鋼便覧，日本，日刊工業新聞，１９７３年１１月３０日，５９９−６００ |
| 第１２６・１２７回西山記念講座，日本，社団法人日本鉄鋼協会，１９８８年１１月１４日，１−３０ |
| 第１２６・１２７回西山記念講座，日本，社団法人日本鉄鋼協会，１９８８年１１月１４日，１６７−１９４ |
| 鉄鋼便覧，日本，社団法人日本鉄鋼協会（丸善），１９８０年 ９月２０日，６９５−６９９ |
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