JP2007224367A - Method for producing high-nitrogen steel - Google Patents
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本発明は、高窒素含有鋼の溶製方法に係わり、特に、転炉で窒素ガスを吹込み、高窒素含有量で出鋼した溶鋼を、真空脱ガス装置で所謂「二次精錬」する際に、該溶鋼の窒素含有量を目標値に精度良く調整し、窒素含有量が90質量ppm以上の高窒素含有鋼を安定して溶製する技術に関する。 The present invention relates to a method for melting high nitrogen-containing steel, and in particular, when so-called “secondary refining” is performed by using a vacuum degassing apparatus for blowing molten steel that has been blown with nitrogen gas in a converter and discharged at a high nitrogen content. Furthermore, the present invention relates to a technique for accurately adjusting the nitrogen content of the molten steel to a target value and stably melting a high nitrogen-containing steel having a nitrogen content of 90 mass ppm or more.
従来、転炉で含窒素鋼を溶製するには、炉内に保持した溶湯(溶銑又は溶鋼)を酸素ガスで脱炭する際に、ガス上吹き用ランス、底吹き羽口等を介して、目標窒素含有量に応じた窒素ガスを吹き込むことで行われていた。ところが、そのような方法では、種々の理由から窒素歩留りが低く、目標窒素含有量が90質量ppm以上の高窒素含有鋼を安定して溶製するのが困難であったばかりでなく、目標値達成に必要な窒素ガスの量が著しく多くなるという経済的な欠点があった。また、窒素ガスの吹き込み時間が長くなるので、必然的に溶製能率の低下や転炉耐火物の損耗が増大するという別の問題もあった。 Conventionally, in order to melt nitrogen-containing steel in a converter, when the molten metal (hot metal or molten steel) held in the furnace is decarburized with oxygen gas, via a gas top blowing lance, bottom blowing tuyere, etc. This was done by blowing nitrogen gas according to the target nitrogen content. However, in such a method, not only is the yield of nitrogen low for various reasons, it is difficult to stably smelt high nitrogen-containing steel having a target nitrogen content of 90 mass ppm or more, and the target value is achieved. There is an economical disadvantage that the amount of nitrogen gas required for the process is remarkably increased. In addition, since the nitrogen gas blowing time becomes longer, there is another problem that the melting efficiency is inevitably lowered and the converter refractory wear increases.
そこで、本出願人は、先に、これらの問題点を全て克服し、溶鋼中窒素含有量が90質量ppm以上で且つ酸素や硫黄の含有量が少ない溶鋼を製造する技術を開発した。それは、ガス底吹き機能を有する転炉に保持した溶銑を酸素ガスで脱炭すると共に、炭素含有量の低下した溶鋼に窒素ガスを吹き込み、含窒素溶鋼とするに際して、前記溶鋼中への窒素ガスの吹き込みを、溶鋼中の炭素含有量が0.25〜0,15質量%の領域で行うようにしたものであり、その際、引き続いて、転炉から出鋼した溶鋼を真空脱ガス装置にかけ、攪拌ガス又は還流ガスとしてアルゴン・ガスを使用して脱ガス処理(二次精錬)すると一層良いという技術である(例えば、引用文献1参照)。 Therefore, the present applicant has first developed a technique for overcoming all of these problems and producing a molten steel having a nitrogen content of 90 ppm by mass or more and a low content of oxygen and sulfur. When the molten steel held in the converter having a gas bottom blowing function is decarburized with oxygen gas, nitrogen gas is blown into the molten steel having a reduced carbon content to form nitrogen-containing molten steel. Is blown in the region where the carbon content in the molten steel is 0.25 to 0.15% by mass. At that time, the molten steel discharged from the converter is subsequently subjected to a vacuum degassing apparatus. It is a technique that it is better to perform degassing treatment (secondary refining) using argon gas as a stirring gas or a reflux gas (see, for example, cited document 1).
また、本出願人は、別途、溶鋼の窒素含有量を目標値に調整する方法として、上記二次精錬後の溶鋼を連続鋳造機で鋳造し、鋼鋳片とする際に、連続鋳造機のタンディッシュ(鋳型上に配置され取鍋から注入された溶鋼の組成を均一にする中間容器)から鋳型へ溶鋼を導くノズル内へ窒素ガス(アルゴン・ガスを混合する場合もあり)を吹き込み、ノズルの詰まり防止と溶鋼の窒素含有量の調整とを行わせる技術も開示している(特許文献2参照)。 In addition, as a method of separately adjusting the nitrogen content of the molten steel to the target value, the present applicant casts the molten steel after the secondary refining with a continuous casting machine to obtain a steel slab. Nitrogen gas (which may be mixed with argon gas) is blown into the nozzle that guides the molten steel from the tundish (an intermediate container placed on the mold and made uniform from the ladle and injected from the ladle) to the mold. A technique for preventing clogging of the steel and adjusting the nitrogen content of the molten steel is also disclosed (see Patent Document 2).
これらの技術によれば、窒素歩留りが確かに従来より高い状態で、窒素が90質量ppm以上、酸素(30質量ppm以下)及び硫黄(14質量ppm以下)の低い高清浄度の含窒素鋼がある程度溶製できるようになった。 According to these techniques, a nitrogen-containing steel having a high cleanliness with low nitrogen yield of 90 mass ppm or more, oxygen (30 mass ppm or less) and sulfur (14 mass ppm or less) is obtained. It became possible to melt to some extent.
しかしながら、引用文献1記載の技術では、鋼中の非金属介在物を減少させて高清浄度を得る為に、真空脱ガス精錬にて撹拌ガス又は環流ガスとしてアルゴン・ガスを用いる必要がある。つまり、窒素ガスは溶鋼に可溶性のガスであり、撹拌ガス又は環流ガスとして利用した場合、アルゴン・ガスに比べて攪拌力が弱く、非金属介在物の浮上分離効果が小さいからである。ところが、アルゴン・ガスを利用したのでは、処理中の窒素濃度の低下が大きく、前記窒素歩留り向上の観点では満足のいく技術でないという問題がある。また、引用文献2記載の技術は、真空脱ガス精錬後に溶鋼の窒素含有量を微調整するには適しているが、窒素含有量の大幅な制御には採用し難い。 However, in the technique described in the cited document 1, it is necessary to use argon gas as a stirring gas or a reflux gas in vacuum degassing refining in order to reduce non-metallic inclusions in steel and obtain high cleanliness. That is, nitrogen gas is a gas soluble in molten steel, and when used as a stirring gas or a recirculation gas, the stirring power is weaker than that of argon gas, and the floating separation effect of nonmetallic inclusions is small. However, when argon gas is used, there is a problem that the nitrogen concentration during processing is greatly reduced, and the technique is not satisfactory from the viewpoint of improving the nitrogen yield. Moreover, although the technique of the cited reference 2 is suitable for fine-tuning the nitrogen content of molten steel after vacuum degassing refining, it is difficult to adopt for the significant control of the nitrogen content.
また、高窒素含有鋼としては、自動車用足回り部品に使用されるハイテン系鋼材のような硫黄含有量の規制が厳しいものばかりとは限らず、硫黄に関しては、規制のゆるい鋼種もある。そのような鋼種については、窒素歩留りをもっと高くして溶製できれば、経済的に望ましいと考えられる。
本発明は、かかる事情に鑑み、真空脱ガス処理の撹拌ガス又は環流ガスにアルゴン・ガスを用いても、従来より窒素歩留りを高くして窒素含有量が90質量%以上の溶鋼を安定して製造可能な高窒素含有鋼の溶製方法を提供することを目的としている。 In view of such circumstances, the present invention can stabilize a molten steel having a nitrogen content of 90% by mass or higher by increasing the nitrogen yield even when argon gas is used as the stirring gas or the reflux gas in the vacuum degassing treatment. It aims at providing the melting method of the high nitrogen content steel which can be manufactured.
発明者は、上記目的を達成するため鋭意研究を重ね、その成果を本発明に具現化した。 The inventor has intensively studied to achieve the above object, and the results have been embodied in the present invention.
すなわち、本発明は、溶銑予備処理脱硫を経て精錬容器に保持した溶銑を酸素ガスで脱炭し、その時期に窒素ガスを吹き込み、一旦目標値より高窒素含有量の溶鋼として前記精錬容器から出鋼し、引き続き、該溶鋼を真空脱ガス装置で攪拌ガス又は還流ガスにアルゴン・ガスを使用して脱ガス処理するに際して、前記脱ガス処理中の溶鋼に、含硫黄物質を添加して該溶鋼の硫黄含有量及び窒素含有量を調整することを特徴とする高窒素含有鋼の溶製方法である。 That is, according to the present invention, the hot metal held in the refining vessel through the hot metal pretreatment desulfurization is decarburized with oxygen gas, and nitrogen gas is blown in at that time, and once the molten steel having a nitrogen content higher than the target value is discharged from the refining vessel. Steel, and subsequently, when the molten steel is degassed by using argon gas as a stirring gas or a reflux gas in a vacuum degassing apparatus, a sulfur-containing substance is added to the molten steel being degassed. This is a method for melting high nitrogen-containing steel, characterized by adjusting the sulfur content and nitrogen content of the steel.
この場合、前記溶鋼の硫黄含有量を、0.012質量%〜許容値上限としたり、あるいは前記含硫黄物質にFeSを使用するのが良い。また、前記窒素ガスの吹き込みを開始する時期の溶鋼中炭素含有量を0.25〜0,15質量%としたり、あるいは前記溶鋼の目標窒素含有量を90〜110質量ppm及び目標硫黄含有量を0.012超え〜0.020質量%とするのが好ましい。さらに、本発明では、前記精錬容器を上吹き転炉、底吹き転炉、上底吹き転炉及びAOD炉から、並びに前記真空脱ガス装置をRH方式,DH方式及びVOD方式から選ばれた1種とするのが好ましい。 In this case, the sulfur content of the molten steel is preferably 0.012% by mass to the upper limit of the allowable value, or FeS is preferably used as the sulfur-containing substance. Also, the carbon content in the molten steel at the start of the nitrogen gas blowing is set to 0.25 to 0.15 mass%, or the target nitrogen content of the molten steel is 90 to 110 mass ppm and the target sulfur content is It is preferable to be more than 0.012 to 0.020% by mass. Further, in the present invention, the refining vessel is selected from the top blowing converter, bottom blowing converter, top bottom blowing converter and AOD furnace, and the vacuum degassing apparatus is selected from the RH method, DH method and VOD method. A seed is preferred.
本発明によれば、真空脱ガス処理の撹拌ガス又は環流ガスとしてアルゴン・ガスを用いても、該処理中の脱窒量を従来より低減できるので、硫黄含有量はある程度多いが、鋼中に非金属介在物元素の少ない高清浄度な高窒素含有鋼(窒素濃度90質量ppm以上)が安定して溶製できるようになる。
According to the present invention, even when argon gas is used as a stirring gas or a reflux gas for vacuum degassing treatment, the denitrification amount during the treatment can be reduced as compared with the conventional case. High cleanliness high nitrogen content steel (
以下、発明をなすに至った経緯をまじえ、本発明の最良の実施形態を説明する。 Hereinafter, the best embodiment of the present invention will be described based on the background of the invention.
まず、発明者は、従来技術で、精錬容器で脱炭中に窒素ガスを溶鋼中に吹き込み、窒素含有量を目標値以上に高めても、真空脱ガス処理で脱窒が起き、窒素歩留りが思ったほど向上しないことに着眼した。そして、真空脱ガス処理中での脱窒をもっと抑制する手段がないか模索することにした。そのため、真空脱ガス装置として図3に示すようなRH真空脱ガス装置を用い、脱窒を抑制する手段の発見に鋭意努力を重ねた。その結果、脱ガス処理中の取鍋内溶鋼に硫黄含有物質を添加すると、図2に示すように、硫黄含有物質の添加量増加に伴い、脱窒速度(―dN/dtで表す)が減少することを見出した。なお、図1より、―dN/dtが最小でほぼ一定値に落ち着くのは、硫黄含有量が0.012質量%であった。これは、溶鋼の表面活性元素である硫黄の添加でその濃度が高まると、溶鋼表面がガスの抜け難い状態になるためと考えられる。 First, the inventor, in the prior art, blows nitrogen gas into molten steel during decarburization in a smelting vessel, and even if the nitrogen content is increased to a target value or higher, denitrification occurs in the vacuum degassing process, and the nitrogen yield is increased. Focused on not improving as expected. And we decided to search for a means to further suppress denitrification during vacuum degassing. Therefore, an RH vacuum degassing apparatus as shown in FIG. 3 was used as a vacuum degassing apparatus, and intensive efforts were made to discover means for suppressing denitrification. As a result, when a sulfur-containing material is added to the molten steel in the ladle being degassed, the denitrification rate (expressed as -dN / dt) decreases as the amount of sulfur-containing material added increases, as shown in FIG. I found out. From FIG. 1, it was found that the sulfur content was 0.012% by mass when -dN / dt was minimized and settled to a substantially constant value. This is considered to be because when the concentration is increased by the addition of sulfur, which is a surface active element of molten steel, the molten steel surface is in a state where it is difficult for gas to escape.
そこで、発明者は、溶製する高窒素含有鋼がその硫黄含有量をある程度高めても良い鋼種(例えば、C:0.03〜0.05質量%、Si:0.03質量%以下、Mn:0.18〜0.35質量%、P:0.020質量%以下、S:0.021質量%以下、N:90〜140ppm、Al:0.023〜0.064質量%)であれば、真空脱ガス中での脱窒を抑制でき、効率良く高窒素含有鋼が溶製できると考え、本発明を完成させたのである。 Therefore, the inventor is a steel type that the high nitrogen content steel to be melted may increase its sulfur content to some extent (for example, C: 0.03 to 0.05 mass%, Si: 0.03 mass% or less, Mn : 0.18 to 0.35 mass%, P: 0.020 mass% or less, S: 0.021 mass% or less, N: 90 to 140 ppm, Al: 0.023 to 0.064 mass%) The present inventors have completed the present invention on the assumption that denitrification in vacuum degassing can be suppressed and high nitrogen-containing steel can be efficiently produced.
本発明では、従来通りに、真空脱ガス前に精錬容器で溶銑の脱炭を行って溶鋼とするが、そこで使用する溶銑は所謂「溶銑予備処理」のうちの「溶銑予備脱硫処理」を経たものであることが前提となる。現在の製鋼工程では、溶製する溶鋼の目標硫黄含有量を達成するため、事前に溶銑の「溶銑予備脱硫処理」を行い、その硫黄含有量を0.020質量%以下に低減してから脱炭精錬を行うのが一般的である。従って、「溶銑予備脱硫処理」を経たものであるという前提をいまさら宣言する必要がないように思われるが、本発明のように真空脱ガス処理で硫黄含有物質を添加するなら、脱炭工程で前記した予備脱硫処理を経ない溶銑の使用が考えられるからである。つまり、高炉から出銑された状態での溶銑は通常0.02〜0.04質量%の硫黄含有量であり、そのまま脱炭工程で使用すれば、真空脱ガス処理中に硫黄含有物質を添加する必要はない。 In the present invention, as before, the hot metal is decarburized in a refining vessel before vacuum degassing to obtain molten steel, but the hot metal used therein has undergone a "hot metal preliminary desulfurization process" of so-called "hot metal preliminary process". It is assumed that it is a thing. In the current steelmaking process, in order to achieve the target sulfur content of the molten steel to be smelted, the hot metal “preliminary desulfurization treatment” is performed in advance to reduce the sulfur content to 0.020% by mass or less. It is common to perform charcoal refining. Therefore, it seems that it is not necessary to declare the premise that it has undergone “hot metal preliminary desulfurization treatment”, but if a sulfur-containing substance is added by vacuum degassing treatment as in the present invention, the decarburization process This is because it is possible to use hot metal that does not undergo the above-described preliminary desulfurization treatment. That is, the hot metal in the state discharged from the blast furnace usually has a sulfur content of 0.02 to 0.04% by mass, and if used as it is in the decarburization process, the sulfur-containing material is added during the vacuum degassing process. do not have to.
しかしながら、現在実用される鋼材は、硫黄含有量が0.02〜0.040質量%という高いものはほとんどなく、どこかで脱硫が必須となる。ところが、脱硫は溶銑段階で行うのが最も効率が良く、脱炭以降で行うと経済的に不利になる。従って、事前に溶銑の「溶銑予備脱硫処理」を行い、その硫黄含有量をできるだけ低減してから脱炭精錬し、硫黄含有量の調整はその後に行うのが得策である。そのため、本発明では、真空脱ガス前に精錬容器で脱炭する前の溶銑として、「溶銑予備脱硫処理」を経たものであるという前提を特に設けたのである。溶銑予備脱硫の方式としては、特に限定するものではないが、取鍋に溶銑の機械攪拌手段を備え、生石灰を主体とした組成の脱硫剤を用いる方式の利用が良い。脱硫効率が高いからである。 However, there are almost no steel materials currently in practical use with a sulfur content as high as 0.02 to 0.040% by mass, and desulfurization is essential somewhere. However, desulfurization is most efficient when it is performed at the hot metal stage, and it is economically disadvantageous if it is performed after decarburization. Therefore, it is a good idea to perform “hot metal preliminary desulfurization treatment” of hot metal in advance, reduce the sulfur content as much as possible, decarburize and refine, and then adjust the sulfur content. For this reason, in the present invention, the premise that the hot metal before decarburization in the smelting vessel before vacuum degassing has undergone a “hot metal preliminary desulfurization process” is provided. The hot metal preliminary desulfurization method is not particularly limited, but it is preferable to use a method in which a ladle is provided with a hot metal mechanical stirring means and a desulfurizing agent mainly composed of quick lime is used. This is because the desulfurization efficiency is high.
なお、本発明では、前記精錬容器としては、上吹き転炉、底吹き転炉、上底吹き転炉及びAOD炉から、並びに前記真空脱ガス装置としては、RH方式,DH方式及びVOD方式から選ばれた1種とするのが好ましい。これらのうちのいずれを用いても、本発明の円滑な実施が可能だからである。ただし、真空脱ガス装置の攪拌ガス又は還流ガスとしては、アルゴン・ガスの使用に限定する。前記したように、窒素ガスより溶鋼の攪拌効率が大きいからである。 In the present invention, the refining vessel is an upper blowing converter, a bottom blowing converter, an upper bottom blowing converter, and an AOD furnace, and the vacuum degassing apparatus is an RH method, a DH method, or a VOD method. The selected one is preferable. This is because any of these can be used to smoothly implement the present invention. However, the stirring gas or reflux gas of the vacuum degassing apparatus is limited to the use of argon gas. This is because, as described above, the stirring efficiency of molten steel is greater than that of nitrogen gas.
また、本発明では、硫黄含有物質の添加時期は特に限定しないが、該硫黄含有物質の溶解の見地より、脱ガス処理の開始当初にするのが良い。硫黄含有物質としては、硫黄を含む無機物質であれば良いが、他の不純元素による溶鋼の汚染を配慮してFeSの利用が好ましい。硫黄含有物質の添加量としては、溶鋼中の硫黄含有量が0.012質量%〜許容上限の範囲とする。該硫黄含有量が0.012質量%で―dN/dtが最小になり、それ以上で一定値になるからである。上限にはついては、当然のことながら溶製する高窒素含有鋼が許容する上限とする。 In the present invention, the timing of adding the sulfur-containing substance is not particularly limited, but it is preferable to start the degassing process from the viewpoint of dissolution of the sulfur-containing substance. The sulfur-containing substance may be an inorganic substance containing sulfur, but it is preferable to use FeS in consideration of contamination of the molten steel by other impure elements. As the addition amount of the sulfur-containing material, the sulfur content in the molten steel is in the range of 0.012 mass% to the allowable upper limit. This is because when the sulfur content is 0.012% by mass, −dN / dt is minimized, and when the sulfur content is higher than that, the value is constant. As a matter of course, the upper limit is allowed by the high nitrogen-containing steel to be melted.
さらに、前記精錬容器での脱炭工程における窒素ガスの吹き込みを開始する時期については、従来技術の通りに、溶鋼中炭素濃度が0.25〜0,15質量%の時にするのが好ましい。窒素歩留りの向上に有効だからである。 Furthermore, it is preferable to start the nitrogen gas blowing in the decarburization process in the refining vessel when the carbon concentration in the molten steel is 0.25 to 0.15% by mass, as in the prior art. This is because it is effective in improving the nitrogen yield.
以上述べたように、本発明に係る上記態様を実施することで、始めて目標硫黄含有量が0.012超え〜0.10質量%と特許文献1記載の溶鋼より高いが、目標窒素含有量が90〜120質量ppmの高窒素含有鋼が、高い窒素歩留りで確実に溶製できるようになるのである。 As described above, by implementing the above aspect of the present invention, the target sulfur content is over 0.012 to 0.10% by mass for the first time and higher than the molten steel described in Patent Document 1, but the target nitrogen content is high. 90 to 120 mass ppm of high nitrogen content steel can be melted reliably with a high nitrogen yield.
高炉から出銑した溶銑を既存、且つ周知の溶銑予備処理工程で脱珪、脱燐及び脱硫を順次行い、得られた溶銑を容量200トンの所謂「上底吹き転炉」を精錬容器として採用し、酸素ガスで脱炭精錬を行った。その脱炭に際して、窒素ガスを上吹きランスを介して窒素ガスを溶鋼中の窒素含有量が120ppm以上になるように吹き付け、高窒素含有の溶鋼を多数チャージ溶製した。取鍋に出鋼した溶鋼の窒素含有量及び硫黄含有量の一例は、表1に示す通りである。その後、これらの溶鋼のそれぞれは、RH真空脱ガス装置を用いて本発明に係る方法及び従来の方法(特許文献1記載の方法)のいずれかによる脱ガス処理が施された。その際、還流ガスとしてはアルゴン・ガスを用い、20〜25分間の脱ガスを行った。なお、本発明の実施に際しては、脱ガスの開始時に硫黄含有物質のFeSを、溶鋼中の硫黄含有量が0.012質量%〜許容上限の範囲になるように添加した。 The hot metal extracted from the blast furnace is subjected to desiliconization, dephosphorization and desulfurization sequentially in the existing and well-known hot metal pretreatment process, and the obtained hot metal is used as a refining vessel with a so-called “top bottom blowing converter” with a capacity of 200 tons. And decarburization refining with oxygen gas. During the decarburization, nitrogen gas was blown through an upper blowing lance so that the nitrogen content in the molten steel was 120 ppm or more, and a large number of high nitrogen content molten steel was charged and melted. An example of the nitrogen content and sulfur content of the molten steel delivered to the ladle is as shown in Table 1. After that, each of these molten steels was subjected to degassing treatment using either the method according to the present invention or the conventional method (the method described in Patent Document 1) using an RH vacuum degassing apparatus. At that time, argon gas was used as the reflux gas, and degassing was performed for 20 to 25 minutes. In carrying out the present invention, the sulfur-containing material FeS was added at the start of degassing so that the sulfur content in the molten steel was in the range of 0.012 mass% to the allowable upper limit.
操業結果の一例を表1に同時に示す。また、真空脱ガス終了後の全ての溶鋼の窒素(記号:N)含有量と前記転炉出鋼後の窒素含有量との関係を図1に一括して示す。図1より、従来の方法による場合に比べて、本発明によれば、窒素含有量が確実に高くなることが明らかである。つまり、従来法では、真空脱ガス中の脱窒量は70質量ppmであるのに対して、本発明での脱窒量は硫黄添加量が0.012質量%の場合で50質量ppmに低減している。
また、本発明の実施で脱ガス処理中の脱窒量が20質量ppm低減できたので、窒素含有量が90質量ppm以上の高窒素含有鋼が安定して溶製できることも明らかである。
An example of the operation result is shown simultaneously in Table 1. Moreover, the relationship between nitrogen (symbol: N) content of all the molten steel after completion | finish of vacuum degassing and the nitrogen content after the said converter steel is shown collectively in FIG. From FIG. 1, it is clear that according to the present invention, the nitrogen content is reliably increased as compared with the conventional method. That is, in the conventional method, the denitrification amount in the vacuum degassing is 70 mass ppm, whereas the denitrification amount in the present invention is reduced to 50 mass ppm when the sulfur addition amount is 0.012 mass%. is doing.
Moreover, since the denitrification amount during the degassing treatment can be reduced by 20 ppm by carrying out the present invention, it is clear that high nitrogen-containing steel having a nitrogen content of 90 ppm by mass or more can be stably melted.
1 取鍋
2 脱ガス槽
3 溶鋼の還流を促進させるガス(還流ガス)
4 上昇管
5 下降管
6 溶鋼
7 排気方向を示す矢印
8 溶鋼の還流方向を示す矢印
DESCRIPTION OF SYMBOLS 1 Ladle 2 Degassing tank 3 Gas which promotes the reflux of molten steel (reflux gas)
4 Ascending
Claims (6)
前記脱ガス処理中の溶鋼に、含硫黄物質を添加して該溶鋼の硫黄含有量及び窒素含有量を調整することを特徴とする高窒素含有鋼の溶製方法。 The hot metal held in the smelting vessel through the hot metal pretreatment desulfurization is decarburized with oxygen gas, and nitrogen gas is blown at that time, and the steel is once discharged from the smelting vessel as a molten steel having a nitrogen content higher than the target value. When degassing molten steel using argon gas as stirring gas or reflux gas with vacuum degassing device,
A method for melting high nitrogen-containing steel, characterized by adding a sulfur-containing substance to the molten steel being degassed to adjust the sulfur content and nitrogen content of the molten steel.
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JP2009102706A (en) * | 2007-10-24 | 2009-05-14 | Sumitomo Metal Ind Ltd | Method for smelting high nitrogen steel |
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