JP4277741B2 - Method for melting nitrogen-containing steel - Google Patents
Method for melting nitrogen-containing steel Download PDFInfo
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- JP4277741B2 JP4277741B2 JP2004172206A JP2004172206A JP4277741B2 JP 4277741 B2 JP4277741 B2 JP 4277741B2 JP 2004172206 A JP2004172206 A JP 2004172206A JP 2004172206 A JP2004172206 A JP 2004172206A JP 4277741 B2 JP4277741 B2 JP 4277741B2
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- 229910000831 Steel Inorganic materials 0.000 title claims description 84
- 239000010959 steel Substances 0.000 title claims description 84
- 238000000034 method Methods 0.000 title claims description 71
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 title claims description 23
- 238000002844 melting Methods 0.000 title claims description 16
- 230000008018 melting Effects 0.000 title claims description 16
- 238000009849 vacuum degassing Methods 0.000 claims description 57
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 32
- 238000005261 decarburization Methods 0.000 claims description 27
- 239000007789 gas Substances 0.000 claims description 23
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 22
- 229910052717 sulfur Inorganic materials 0.000 claims description 22
- 239000011593 sulfur Substances 0.000 claims description 22
- 239000000956 alloy Substances 0.000 claims description 21
- 229910045601 alloy Inorganic materials 0.000 claims description 21
- 238000010992 reflux Methods 0.000 claims description 21
- 229910052757 nitrogen Inorganic materials 0.000 claims description 10
- 238000010521 absorption reaction Methods 0.000 claims description 5
- 238000003795 desorption Methods 0.000 claims description 3
- 229910001873 dinitrogen Inorganic materials 0.000 description 12
- 238000007664 blowing Methods 0.000 description 10
- 230000001174 ascending effect Effects 0.000 description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- 239000000571 coke Substances 0.000 description 6
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 4
- 239000001301 oxygen Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 229910052786 argon Inorganic materials 0.000 description 3
- 230000005484 gravity Effects 0.000 description 3
- 238000007670 refining Methods 0.000 description 3
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 2
- RRZKHZBOZDIQJG-UHFFFAOYSA-N azane;manganese Chemical compound N.[Mn] RRZKHZBOZDIQJG-UHFFFAOYSA-N 0.000 description 2
- MYFXBBAEXORJNB-UHFFFAOYSA-N calcium cyanamide Chemical compound [Ca+2].[N-]=C=[N-] MYFXBBAEXORJNB-UHFFFAOYSA-N 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 229910001882 dioxygen Inorganic materials 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 238000010309 melting process Methods 0.000 description 2
- 101150006573 PAN1 gene Proteins 0.000 description 1
- 238000009841 combustion method Methods 0.000 description 1
- 238000007872 degassing Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- -1 first Substances 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 230000003134 recirculating effect Effects 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
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- Treatment Of Steel In Its Molten State (AREA)
Description
本発明は、鋼材の機械的性質を向上するためにＮを添加した鋼（以下、含窒素鋼という）を溶製するにあたって、Ｓ含有量を所定の範囲に精度良く調整して、含窒素鋼を安定して溶製する方法に関するものである。 In the present invention, when melting steel added with N in order to improve the mechanical properties of steel (hereinafter referred to as nitrogen-containing steel), the S content is precisely adjusted within a predetermined range, and nitrogen-containing steel is obtained. It relates to a method for stably melting.
一般に鋼の溶製工程では、Ｎは、溶鋼に不可避的に混入する不純物として可能な限り除去するための処理が施される。 In general, in the steel melting process, N is subjected to a treatment for removing it as much as possible as an impurity inevitably mixed in the molten steel.
しかし、靭性等の機械的性質を向上して特定の用途に用いる鋼材は、溶製工程でＮを添加する処理が施される。このような含窒素鋼は、転炉で脱炭処理を行ないながら溶鋼に窒素を添加し、次いで真空脱ガス処理を行なうことによって溶製される。 However, the steel material used for a specific application with improved mechanical properties such as toughness is subjected to a process of adding N in the melting process. Such a nitrogen-containing steel is melted by adding nitrogen to the molten steel while performing a decarburization process in a converter and then performing a vacuum degassing process.
含窒素鋼を溶製するにあたって、まず転炉で溶鋼に酸素を供給して脱炭処理（いわゆる１次精錬）を行なう。使用する転炉は、酸素の供給方法に応じて下記の (a)〜(c) の３種類に大別される。
(a) 上吹き転炉：転炉内の溶鋼にランスを介して上方から酸素ガスを吹付ける。
(b) 底吹き転炉：転炉の底部に設けた底吹き羽口を介して下方から溶鋼に酸素ガスを供給する。
(c) 上底吹き転炉：転炉内の溶鋼にランスおよび底吹き羽口を介して上下両方から酸素を供給する。
In melting nitrogen-containing steel, first, oxygen is supplied to the molten steel in a converter and decarburization treatment (so-called primary refining) is performed. The converters to be used are roughly divided into the following three types (a) to (c) according to the oxygen supply method.
(a) Top-blown converter: Oxygen gas is blown from above through molten steel in the converter.
(b) Bottom-blown converter: Oxygen gas is supplied to the molten steel from below through a bottom-blown tuyere provided at the bottom of the converter.
(c) Top-bottom blowing converter: Oxygen is supplied to the molten steel in the converter from both the top and bottom via the lance and bottom blowing tuyere.
なお (a)上吹き転炉と (c)上底吹き転炉で使用するランスを、後述する真空脱ガス処理のランスと区別するために、以下では転炉ランスと記す。 In order to distinguish the lance used in the (a) top blowing converter and (c) the top bottom blowing converter from the vacuum degassing lance described later, it will be referred to as a converter lance.
脱炭処理は、溶鋼中のＣと転炉ランスや底吹き羽口を介して供給されたＯとを反応させてＣＯあるいはＣＯ2 として排出するものである。脱炭処理を行ないながら溶鋼に窒素を添加するために、転炉ランスや底吹き羽口を介してＯのみならずＮを溶鋼に供給する。 In the decarburization treatment, C in the molten steel reacts with O supplied through a converter lance or a bottom blowing tuyere and discharged as CO or CO 2 . In order to add nitrogen to the molten steel while decarburizing, not only O but also N is supplied to the molten steel through a converter lance and bottom blowing tuyere.
転炉で脱炭処理とＮ添加を終了した後、溶鋼の真空脱ガス処理を行なう。真空脱ガス処理は、溶鋼中のガス成分を除去する技術であり、溶鋼を真空槽内へ吸上，排出を繰り返すＤＨ法と溶鋼を取鍋と真空槽との間で連続的に循環して処理するＲＨ法に大別される。ただし含窒素鋼の溶製では、溶鋼にＮを容易に添加できるＲＨ法が広く採用されている。ここでは真空脱ガス処理の例としてＲＨ法について説明する。 After completing the decarburization process and N addition in the converter, vacuum degassing of the molten steel is performed. Vacuum degassing is a technology that removes gas components in molten steel, and continuously circulates the molten steel between the ladle and the vacuum tank by the DH method, which repeatedly sucks and discharges the molten steel into the vacuum tank. Roughly divided into RH methods to be processed. However, in the melting of nitrogen-containing steel, the RH method that can easily add N to the molten steel is widely adopted. Here, the RH method will be described as an example of the vacuum degassing process.
図１は、ＲＨ法で真空脱ガス処理を行なう際の溶鋼と真空槽の配置の例を模式的に示す断面図である。 FIG. 1 is a cross-sectional view schematically showing an example of arrangement of molten steel and a vacuum chamber when performing vacuum degassing treatment by the RH method.
ＲＨ法で使用する真空槽３の下部には、２本の浸漬管が配設されており、その上昇浸漬管5aと下降浸漬管5bを取鍋１内の溶鋼２に浸漬する。次いで、真空槽３の上部に設けられる排気ダクト４から真空槽３内のガスを吸引して、真空槽３内を減圧する。
Two dip tubes are provided at the lower part of the
真空槽３内が減圧されることによって、取鍋１内の溶鋼２が真空槽３内に吸い上げられる。上昇浸漬管5aには環流ガス６の吹込みノズルが設けられており、上昇浸漬管5a内の溶鋼２に環流ガス６が吹込まれる。環流ガス６は気泡となって溶鋼２内を浮上する。その結果、上昇浸漬管5a内の溶鋼２の比重が相対的に減少し、下降浸漬管5b内の溶鋼２の比重は上昇浸漬管5a側に比べて大きくなる。
By reducing the pressure in the
溶鋼２に比重差を付与することによって、取鍋１内の溶鋼２が上昇浸漬管5aを通って真空槽３内に上昇し、さらに真空槽３内の溶鋼２は下降浸漬管5bを通って取鍋１に下降する。このようにして溶鋼２が取鍋１から真空槽３を経て再び取鍋１へ環流する間に、真空槽３内で溶鋼２の真空脱ガス処理を行なう。
By giving a difference in specific gravity to the
ＲＨ法で溶鋼２の真空脱ガス処理を行なうとともに窒素を添加する場合は、環流ガス６に窒素を混合する。あるいは図１に示すように、ランス７を介して上方から窒素ガス８を吹付ける。真空脱ガス処理で使用するランスを、転炉ランスと区別するために、以下では真空槽ランスと記す。
When performing vacuum degassing of the
また、窒素を混合した環流ガス６と真空槽ランス７からの窒素ガス８とを併用することも可能である。
Moreover, it is also possible to use the
このようにして含窒素鋼を溶製することができる。しかし、この技術では、Ｓのような界面活性元素を添加する必要のある鋼については含窒素鋼中のＳ含有量を所定の範囲に調整した上で含窒素鋼を溶製するのは困難であった。 In this way, nitrogen-containing steel can be melted. However, with this technique, it is difficult to melt the nitrogen-containing steel after adjusting the S content in the nitrogen-containing steel to a predetermined range for the steel to which a surface active element such as S needs to be added. there were.
さらに、脱炭処理と真空脱ガス処理を組合わせた含窒素鋼の溶製技術は、上記した技術の他に種々検討されている。 Furthermore, various techniques for melting nitrogen-containing steel by combining decarburization and vacuum degassing have been studied in addition to the techniques described above.
たとえば特許文献１には、転炉で脱炭処理を施し、さらに窒素ガスを吹込んだ後、真空槽で真空脱ガス処理を行なう技術が開示されている。特許文献２には、転炉で脱炭処理を施した後、真空槽でＮ含有量を目標範囲の下限値以下まで低減し、さらに窒素含有合金を添加する技術が開示されている。特許文献3には、転炉で脱炭処理を施した後、真空槽で還流ガスとして窒素ガスを用いて真空脱ガス処理を行なう技術が開示されている。特許文献４には、転炉で脱炭処理を施した後、真空槽で真空脱ガス処理を行ないながら窒素ガスを吹込む技術が開示されている。
For example, Patent Document 1 discloses a technique in which decarburization processing is performed in a converter, nitrogen gas is blown, and then vacuum degassing processing is performed in a vacuum chamber.
これらの技術は、いずれも含窒素鋼中のＳ含有量を所定の範囲に調整した上で含窒素鋼を溶製するのは困難であった。
本発明は上記のような問題を解消し、含窒素鋼を溶製するにあたって、Ｎ含有量のみならずＳ含有量も所定の範囲に精度良く調整して、含窒素鋼を安定して溶製する方法を提供することを目的とする。 The present invention solves the above-mentioned problems, and when melting nitrogen-containing steel, not only the N content but also the S content is accurately adjusted within a predetermined range, and the nitrogen-containing steel is stably melted. It aims to provide a way to do.
本発明は、転炉で溶鋼の脱炭処理を行なうとともに窒素を添加し、次いで真空脱ガス処理を行なう含窒素鋼の溶製方法において、転炉から出鋼した溶鋼のＮ含有量［Ｎ］（質量％）を測定し、［Ｎ］が目標範囲の上限値［Ｎmax ］（質量％）を超える場合は、下記の (1)式および (2)式から脱［Ｎ］時間Ｔ1 （分）を算出して、真空脱ガス処理の開始からＴ1 の間はＮの除去を行ない、Ｔ 1 が経過した後に硫黄もしくは硫黄を含む合金を投入し、［Ｎ］が目標範囲内を満足する場合は、真空脱ガス処理の環流開始と同時に硫黄もしくは硫黄を含む合金を投入し、［Ｎ］が目標範囲の下限値［Ｎmin ］（質量％）未満の場合は、下記の (3)式および (4)式から吸［Ｎ］時間Ｔ2 （分）を算出して、真空脱ガス処理の開始からＴ2 の間はＮの添加を行ない、Ｔ 2 が経過した後に硫黄もしくは硫黄を含む合金を投入する含窒素鋼の溶製方法である。
The present invention relates to a nitrogen-containing steel melting method in which molten steel is decarburized in a converter and nitrogen is added, followed by vacuum degassing, and the N content [N] of the molten steel discharged from the converter (% By mass) is measured, and when [N] exceeds the upper limit [N max ] (% by mass) of the target range, the [N] time T 1 ( Min), N is removed during T 1 from the start of the vacuum degassing treatment, and after T 1 , sulfur or an alloy containing sulfur is introduced, and [N] satisfies the target range. When the reflux of the vacuum degassing process is started, sulfur or an alloy containing sulfur is added. When [N] is less than the lower limit [N min ] (mass%) of the target range, the following (3) calculates the intake [N] time T 2 (min) from the formula and (4), between T 2 from the start of the vacuum degassing process performs addition of N A melting method of a nitrogen Motoko to inject alloy containing sulfur or sulfur after T 2 has elapsed.
Ｔ1 ＝ΔＮ1 ／ＶEX ・・・ (1)
ΔＮ1 ＝［Ｎ］−［Ｎmax ］ ・・・ (2)
Ｔ2 ＝ΔＮ2 ／ＶIN ・・・ (3)
ΔＮ2 ＝［Ｎ］−［Ｎmin ］ ・・・ (4)
［Ｎ］ ：脱炭処理終了後のＮ含有量（質量％）
［Ｎmax ］：真空脱ガス処理終了後の目標範囲の上限値（質量％）
［Ｎmin ］：真空脱ガス処理終了後の目標範囲の下限値（質量％）
ＶEX ：真空脱ガス処理における脱［Ｎ］速度（質量％／分）
ＶIN ：真空脱ガス処理における吸［Ｎ］速度（質量％／分）
Ｔ1 ：［Ｎ］が過多である場合の脱［Ｎ］時間（分）
Ｔ2 ：［Ｎ］が過少である場合の吸［Ｎ］時間（分）
本発明の含窒素鋼の溶製方法では、真空脱ガス処理で環流ガスとしてArを使用することが好ましい。
T 1 = ΔN 1 / V EX (1)
ΔN 1 = [N] − [N max ] (2)
T 2 = ΔN 2 / V IN (3)
ΔN 2 = [N] − [N min ] (4)
[N]: N content (mass%) after completion of decarburization treatment
[N max ]: Upper limit value (mass%) of the target range after completion of the vacuum degassing process
[N min ]: Lower limit of target range (mass%) after completion of vacuum degassing process
V EX : Desorption [N] rate (% by mass / min) in vacuum degassing treatment
V IN : Suction [N] rate (% by mass / min) in vacuum degassing
T 1 : [N] time (minutes) when [N] is excessive
T 2 : Absorption [N] time (min) when [N] is too small
In the method for melting nitrogen-containing steel of the present invention, it is preferable to use Ar as a reflux gas in vacuum degassing treatment.
本発明によれば、Ｓ含有量に関わらずＮ含有量を所定の範囲に精度良く調整して、含窒素鋼を安定して溶製することができる。 According to the present invention, the nitrogen-containing steel can be stably melted by accurately adjusting the N content within a predetermined range regardless of the S content.
本発明を適用して含窒素鋼を溶製するにあたって、転炉で溶鋼に酸素を供給して脱炭処理を行なう。転炉は従来から (a)上吹き転炉， (b)底吹き転炉， (c)上底吹き転炉が知られており、いずれの型式の転炉も使用できる。脱炭処理は一般に１次精錬と呼ばれており、転炉の型式や溶鋼の成分等に応じて、従来から知られている技術を適宜選択して使用する。 When melting the nitrogen-containing steel by applying the present invention, oxygen is supplied to the molten steel in a converter to perform a decarburization process. Conventionally known converters are (a) top blow converter, (b) bottom blow converter, and (c) top bottom converter, and any type of converter can be used. The decarburization process is generally called primary refining, and a conventionally known technique is appropriately selected and used according to the converter type, molten steel components, and the like.
転炉で脱炭処理を行なうと同時に、溶鋼にＮを添加する。Ｎの供給は、転炉ランスや底吹き羽口から窒素ガスを供給する方法，あるいはコークスを投入する方法等で行なう。コークスは多孔質であるから、コークスの内部に空気が浸入しており、コークスを溶鋼に投入することによってＮを添加することが可能である。 N is added to the molten steel at the same time as decarburization treatment is performed in the converter. N is supplied by a method of supplying nitrogen gas from a converter lance or bottom blowing tuyere, or a method of charging coke. Since coke is porous, air has entered the coke, and N can be added by putting coke into molten steel.
脱炭処理とＮ添加を終了した後、溶鋼を取鍋に出鋼してＮ含有量を測定する。脱炭処理を行なった後の溶鋼のＮ含有量（質量％）（以下、［Ｎ］という）の測定は、従来から知られている測定技術（たとえば燃焼法等）を使用する。 After finishing the decarburization process and N addition, the molten steel is put into a ladle and the N content is measured. Measurement of the N content (mass%) (hereinafter referred to as [N]) of the molten steel after the decarburization treatment uses a conventionally known measurement technique (for example, a combustion method).
脱炭処理が終了した後で測定した［Ｎ］と、後述する真空脱ガス処理が終了した後のＮ含有量の目標範囲とを比較し、Ｎ含有量の目標範囲の上限値［Ｎmax ］（質量％），下限値［Ｎmin ］（質量％）と［Ｎ］との関係に応じて下記の (A)〜(C) の３種類に分類する。なお、真空脱ガス処理が終了した後のＮ含有量の［Ｎmax ］，［Ｎmin ］は、製品の規格で規定されるＮ含有量の許容範囲の上限値，下限値と同一の値を設定しても良いし、あるいは設備の特性や溶鋼の成分に応じて個別に設定しても良い。
(A) ［Ｎ］が［Ｎmax ］を超える場合 ：［Ｎmax ］＜［Ｎ］
(B) ［Ｎ］が目標範囲内を満足する場合：［Ｎmin ］≦［Ｎ］≦［Ｎmax ］
(C) ［Ｎ］が［Ｎmin ］未満の場合 ：［Ｎ］＜［Ｎmin ］
一方、取鍋に出鋼した溶鋼を真空脱ガス設備に搬送して、ＲＨ法で真空脱ガス処理を行なう。真空脱ガス処理は２次精錬と呼ばれており、溶鋼中のガス成分を除去する処理である。本発明では、ガス成分を除去するとともに、Ｎ含有量が所定の目標範囲内を満足するように調整する。溶鋼中のＮ含有量［Ｎ］が目標範囲の上限値［Ｎmax ］を超える場合はＮを除去し、目標範囲の下限値［Ｎmin ］に満たない場合はＮを添加する。Ｎの除去は、真空脱ガス処理と同様に行なう。Ｎの添加は、環流ガスとして窒素ガスを用いる方法や真空槽ランスから窒素ガスを吹付ける方法，石灰窒素や窒化マンガンを添加する方法等で行なう。
The [N] measured after the decarburization process is compared with the target range of the N content after the vacuum degassing process described later is completed, and the upper limit [N max ] of the target range of the N content (Mass%), the lower limit [ Nmin ] (mass%) and [N] are classified into the following three types (A) to (C) according to the relationship between [N] Note that the N content [N max ] and [N min ] after the vacuum degassing process are the same as the upper and lower limits of the allowable range of N content defined in the product specifications. You may set, or you may set separately according to the characteristic of an installation, and the component of molten steel.
(A) When [N] exceeds the [N max]: [N max ] <[N]
(B) When [N] satisfies the target range: [N min ] ≦ [N] ≦ [N max ]
(C) When [N] is less than [N min ]: [N] <[N min ]
On the other hand, the molten steel delivered to the ladle is transported to a vacuum degassing facility, and vacuum degassing is performed by the RH method. The vacuum degassing process is called secondary refining, and is a process for removing gas components in molten steel. In this invention, while removing a gas component, it adjusts so that N content may satisfy the predetermined target range. N is removed when the N content [N] in the molten steel exceeds the upper limit [N max ] of the target range, and N is added when the lower limit [N min ] of the target range is not reached. N is removed in the same manner as the vacuum degassing process. N is added by a method using nitrogen gas as a reflux gas, a method of blowing nitrogen gas from a vacuum lance, a method of adding lime nitrogen or manganese nitride, or the like.
ただし真空脱ガス処理が終了した後のＮ含有量を所定の目標範囲内に精度良く調整するためには、環流ガスとしてArを使用するのが好ましい。その場合は、真空槽ランスから窒素ガスを吹付ける方法あるいは石灰窒素や窒化マンガンを添加する方法で溶鋼にＮを添加する。 However, in order to accurately adjust the N content after the vacuum degassing process within a predetermined target range, it is preferable to use Ar as the reflux gas. In that case, N is added to the molten steel by a method of blowing nitrogen gas from a vacuum tank lance or a method of adding lime nitrogen or manganese nitride.
次いで、真空脱ガス処理を行ないながら、溶鋼に硫黄もしくは硫黄を含む合金（たとえばFeＳ合金）を合金添加口から投入する方法が簡便で効果的である。ただしＳを溶鋼に投入する時期は、上記した (A)〜(C) の分類に応じて異なる。
(A) ［Ｎ］が［Ｎmax ］を超える場合
［Ｎmax ］＜［Ｎ］の場合は、真空槽内を減圧（すなわち真空脱ガス処理を開始）して脱［Ｎ］時間Ｔ1 （分）が経過した後、硫黄もしくは硫黄含有合金を投入する。脱［Ｎ］時間Ｔ1 は下記の (1)式および (2)式から算出される値である。なお (1)式中のＶEX値は、予め実験を行なって設定しても良いし、あるいは操業データを解析して設定しても良い。
Next, a method in which sulfur or an alloy containing sulfur (for example, FeS alloy) is introduced into the molten steel from the alloy addition port while performing vacuum degassing treatment is simple and effective. However, the time when S is added to the molten steel varies depending on the classifications (A) to (C) described above.
(A) When [N] exceeds the [N max] [N max] < For [N], pressure of the vacuum vessel (or starting the vacuum degassing treatment) to de [N] Time T 1 ( Minutes), sulfur or a sulfur-containing alloy is charged. [N] time T 1 is a value calculated from the following equations (1) and (2). The V EX value in the equation (1) may be set by conducting an experiment in advance, or may be set by analyzing operation data.
Ｔ1 ＝ΔＮ1 ／ＶEX ・・・ (1)
ΔＮ1 ＝［Ｎ］−［Ｎmax ］ ・・・ (2)
［Ｎ］ ：脱炭処理終了後のＮ含有量（質量％）
［Ｎmax ］：真空脱ガス処理終了後の目標範囲の上限値（質量％）
ＶEX ：真空脱ガス処理における脱［Ｎ］速度（質量％／分）
Ｔ1 ：［Ｎ］が過多である場合の脱［Ｎ］時間（分）
(B) ［Ｎ］が目標範囲内を満足する場合
［Ｎmin ］≦［Ｎ］≦［Ｎmax ］の場合は、真空槽内を減圧し、さらに上昇浸漬管に環流ガスを吹込んで、環流を開始すると同時に硫黄もしくは硫黄含有合金を投入する。
(C) ［Ｎ］が［Ｎmin ］未満の場合
［Ｎ］＜［Ｎmin ］の場合は、真空槽内を減圧（すなわち真空脱ガス処理を開始）して吸［Ｎ］時間Ｔ2 （分）が経過した後、硫黄もしくは硫黄含有合金を投入する。吸［Ｎ］時間Ｔ2 は下記の (3)式および (4)式から算出される値である。なお (3)式中のＶIN値は、予め実験を行なって設定しても良いし、あるいは操業データを解析して設定しても良い。
T 1 = ΔN 1 / V EX (1)
ΔN 1 = [N] − [N max ] (2)
[N]: N content (mass%) after completion of decarburization treatment
[N max ]: Upper limit value (mass%) of the target range after completion of the vacuum degassing process
V EX : Desorption [N] rate (% by mass / min) in vacuum degassing treatment
T 1 : [N] time (minutes) when [N] is excessive
(B) When [N] satisfies the target range When [N min ] ≦ [N] ≦ [N max ], the inside of the vacuum chamber is depressurized, and the reflux gas is blown into the ascending dip tube, At the same time, sulfur or a sulfur-containing alloy is introduced.
(C) When [N] is less than [N min ] When [N] <[N min ], the inside of the vacuum chamber is depressurized (that is, the vacuum degassing process is started), and the suction [N] time T 2 ( Minutes), sulfur or a sulfur-containing alloy is charged. The absorption [N] time T 2 is a value calculated from the following equations (3) and (4). The V IN value in the expression (3) may be set by conducting an experiment in advance, or may be set by analyzing operation data.
Ｔ2 ＝ΔＮ2 ／ＶIN ・・・ (3)
ΔＮ2 ＝［Ｎ］−［Ｎmin ］ ・・・ (4)
［Ｎ］ ：脱炭処理終了後のＮ含有量（質量％）
［Ｎmin ］：真空脱ガス処理終了後の目標範囲の下限値（質量％）
ＶIN ：真空脱ガス処理における吸［Ｎ］速度（質量％／分）
Ｔ2 ：［Ｎ］が過少である場合の吸［Ｎ］時間（分）
硫黄もしくは硫黄含有合金の投入量は、 (A)〜(C) のいずれの場合も、真空脱ガス処理後のＳ含有量の目標値に応じて設定する。
T 2 = ΔN 2 / V IN (3)
ΔN 2 = [N] − [N min ] (4)
[N]: N content (mass%) after completion of decarburization treatment
[N min ]: Lower limit of target range (mass%) after completion of vacuum degassing process
V IN : Suction [N] rate (% by mass / min) in vacuum degassing
T 2 : Absorption [N] time (min) when [N] is too small
The input amount of sulfur or a sulfur-containing alloy is set according to the target value of the S content after the vacuum degassing process in any of the cases (A) to (C).
上吹き転炉を用いて溶鋼の脱炭処理を行ない、コークスを投入して溶鋼にＮを添加した。次いで、転炉から出鋼した溶鋼（脱炭処理終了後の溶鋼）のＮ含有量（質量％），Ｓ含有量（質量％）を測定した。次いで、図１に示す装置を用いてＲＨ法で真空脱ガス処理を行なった。このようにして含窒素鋼の溶製を８チャージ行なった。真空脱ガス処理では、環流ガス６として窒素ガス，アルゴンガス，窒素とアルゴンの混合ガスを使用し、環流時間はいずれも25分とした。各チャージの脱炭処理終了後のＮ含有量，Ｓ含有量および環流ガス６の種類は表１に示す通りである。表１中では、真空脱ガス処理を簡略化して脱ガスと記す。
The molten steel was decarburized using a top blow converter, coke was added, and N was added to the molten steel. Subsequently, N content (mass%) and S content (mass%) of the molten steel (melted steel after completion | finish of decarburization processing) which came out from the converter were measured. Next, vacuum degassing was performed by the RH method using the apparatus shown in FIG. In this way, the melting of the nitrogen-containing steel was performed 8 times. In the vacuum degassing treatment, nitrogen gas, argon gas, or a mixed gas of nitrogen and argon was used as the
また、真空脱ガス処理でＳを投入する時期も表１に示す。なお鋼中［Ｓ］の調整は、FeＳ合金を合金投入口から添加する方法で行なった。 Table 1 also shows the timing of introducing S in the vacuum degassing process. [S] in the steel was adjusted by a method of adding an FeS alloy from the alloy inlet.
Ｓを投入する時期は、表１に示すように、脱炭処理終了後のＮ含有量［Ｎ］とその真空脱ガス終了後の目標範囲との関係に応じて (A)〜(C) の３種類に分けて設定した。すなわち、
(A) ［Ｎmax ］＜［Ｎ］の場合は脱［Ｎ］時間Ｔ1 （分）を算出し、真空脱ガス処理の開始からＴ1 が経過した後、FeＳ合金を投入した。
(B) ［Ｎmin ］≦［Ｎ］≦［Ｎmax ］の場合は環流開始と同時にFeＳ合金を投入した。
(C) ［Ｎ］＜［Ｎmin ］の場合は吸［Ｎ］時間Ｔ2 （分）を算出し、真空脱ガス処理の開始からＴ2 が経過した後、FeＳ合金を投入した。
As shown in Table 1, the timing of introducing S depends on the relationship between the N content [N] after completion of the decarburization treatment and the target range after the completion of the vacuum degassing, as shown in (A) to (C). Three types were set. That is,
(A) In the case of [N max ] <[N], the de [N] time T 1 (minute) was calculated, and after T 1 elapsed from the start of the vacuum degassing treatment, the FeS alloy was charged.
(B) In the case of [N min ] ≦ [N] ≦ [N max ], the FeS alloy was charged simultaneously with the start of the reflux.
(C) When [N] <[N min ], the suction [N] time T 2 (minute) was calculated, and after T 2 had elapsed from the start of the vacuum degassing treatment, the FeS alloy was charged.
なお (A)における［Ｎmax ］および (C)における［Ｎmin ］は、製品の規格で機械される許容範囲の上限値および下限値とした。 Note that [N max ] in (A) and [N min ] in (C) are the upper limit value and lower limit value of the allowable range machined by the product standards.
また、Ｔ1 ，Ｔ2 の算出に必要なＶEX ,ＶINは，図２のデータを使用した。すなわち図２は、操業データを解析して求めた脱炭処理終了後のＳ含有量とＶEX,ＶINとの関係を示すグラフであり、Ｓ含有量の測定値からＶEX ,ＶINを読み取ることができる。このようにして (A)，(C) で算出したＴ1 ，Ｔ2 は表１に示す通りである。これを発明例とする。 The data shown in FIG. 2 was used for V EX and V IN necessary for calculating T 1 and T 2 . That is, FIG. 2, S content of decarburization after the end determined by analyzing the operational data and V EX, a graph showing the relationship between V IN, V EX from the measured values of S content, the V IN Can be read. Thus, T 1 and T 2 calculated in (A) and (C) are as shown in Table 1. This is an invention example.
一方、比較例として、上吹き転炉を用いて溶鋼の脱炭処理を行ない、コークスを投入して溶鋼にＮを添加した。次いで、転炉から出鋼した溶鋼（脱炭処理終了後の溶鋼）のＮ含有量（質量％），Ｓ含有量（質量％）を測定した。次いで、図１に示す装置を用いてＲＨ法で真空脱ガス処理を行なった。このようにして含窒素鋼の溶製を５チャージ行なった。真空脱ガス処理では、環流ガス６として窒素ガス，アルゴンガスを使用し、環流時間はいずれも25分とした。各チャージの脱炭処理終了後のＮ含有量，Ｓ含有量および環流ガス６の種類は表１に示す通りである。鋼中［Ｓ］の調整は、いずれも環流開始と同時にFeＳ合金の粉末を合金投入口から添加する方法で行なった。
On the other hand, as a comparative example, decarburization treatment of the molten steel was performed using an upper blow converter, and coke was added to add N to the molten steel. Subsequently, N content (mass%) and S content (mass%) of the molten steel (melted steel after completion | finish of decarburization processing) which came out from the converter were measured. Next, vacuum degassing was performed by the RH method using the apparatus shown in FIG. In this way, the melting of the nitrogen-containing steel was performed for 5 charges. In the vacuum degassing treatment, nitrogen gas and argon gas were used as the
真空脱ガス処理が終了した後、各チャージの溶鋼のＮ含有量を測定した。その結果は表１に示す通りである。発明例では、真空脱ガス処理終了後のＮ含有量が76〜96質量ppm であったが、比較例では71〜99質量ppm であった。つまり発明例の方が、真空脱ガス処理終了後のＮ含有量のばらつきが小さかった。 After the vacuum degassing treatment was completed, the N content of the molten steel for each charge was measured. The results are as shown in Table 1. In the inventive examples, the N content after the vacuum degassing treatment was 76 to 96 mass ppm, whereas in the comparative examples, it was 71 to 99 mass ppm. That is, the variation in N content after the vacuum degassing process was smaller in the inventive example.
１ 取鍋
２ 溶鋼
３ 真空槽
４ 排気ダクト
5a 上昇浸漬管
5b 下降浸漬管
６ 環流ガス
７ 真空槽ランス
８ 窒素ガス
1
5a Ascending dip tube
Claims (2)
Ｔ1 ＝ΔＮ1 ／ＶEX ・・・ (1)
ΔＮ1 ＝［Ｎ］−［Ｎmax ］ ・・・ (2)
Ｔ2 ＝ΔＮ2 ／ＶIN ・・・ (3)
ΔＮ2 ＝［Ｎ］−［Ｎmin ］ ・・・ (4)
［Ｎ］ ：脱炭処理終了後のＮ含有量（質量％）
［Ｎmax ］：真空脱ガス処理終了後の目標範囲の上限値（質量％）
［Ｎmin ］：真空脱ガス処理終了後の目標範囲の下限値（質量％）
ＶEX ：真空脱ガス処理における脱［Ｎ］速度（質量％／分）
ＶIN ：真空脱ガス処理における吸［Ｎ］速度（質量％／分）
Ｔ1 ：［Ｎ］が過多である場合の脱［Ｎ］時間（分）
Ｔ2 ：［Ｎ］が過少である場合の吸［Ｎ］時間（分） In a method for melting nitrogen-containing steel in which molten steel is decarburized in a converter and nitrogen is added, followed by vacuum degassing, the N content [N] (% by mass) of the molten steel discharged from the converter ) And [N] exceeds the upper limit [N max ] (mass%) of the target range, the [N] time T 1 (min) from the following formulas (1) and (2) When N is removed during the period T 1 from the start of the vacuum degassing process and sulfur or an alloy containing sulfur is introduced after T 1 has elapsed, and [N] satisfies the target range Is charged with sulfur or an alloy containing sulfur simultaneously with the start of the reflux of the vacuum degassing treatment, and when [N] is less than the lower limit [N min ] (mass%) of the target range, the following formula (3) and (4) to calculate the absorption [N] time T 2 (min) from the equation, the addition of between the start of the vacuum degassing treatment of T 2 are N No method melting nitrogen Motoko, which comprises introducing an alloy containing sulfur or sulfur after T 2 has elapsed.
T 1 = ΔN 1 / V EX (1)
ΔN 1 = [N] − [N max ] (2)
T 2 = ΔN 2 / V IN (3)
ΔN 2 = [N] − [N min ] (4)
[N]: N content (mass%) after completion of decarburization treatment
[N max ]: Upper limit value (mass%) of the target range after completion of the vacuum degassing process
[N min ]: Lower limit of target range (mass%) after completion of vacuum degassing process
V EX : Desorption [N] rate (% by mass / min) in vacuum degassing treatment
V IN : Suction [N] rate (% by mass / min) in vacuum degassing
T 1 : [N] time (minutes) when [N] is excessive
T 2 : Absorption [N] time (min) when [N] is too small
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