JPH0346527B2 - - Google Patents
Info
- Publication number
- JPH0346527B2 JPH0346527B2 JP9014884A JP9014884A JPH0346527B2 JP H0346527 B2 JPH0346527 B2 JP H0346527B2 JP 9014884 A JP9014884 A JP 9014884A JP 9014884 A JP9014884 A JP 9014884A JP H0346527 B2 JPH0346527 B2 JP H0346527B2
- Authority
- JP
- Japan
- Prior art keywords
- stainless steel
- hot metal
- blowing
- steel
- ladle
- 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
Links
- IJGRMHOSHXDMSA-UHFFFAOYSA-N nitrogen Substances N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 34
- 238000007664 blowing Methods 0.000 claims description 22
- 229910000831 Steel Inorganic materials 0.000 claims description 21
- 239000010959 steel Substances 0.000 claims description 21
- 239000007789 gas Substances 0.000 claims description 20
- 229910052757 nitrogen Inorganic materials 0.000 claims description 20
- 229910001220 stainless steel Inorganic materials 0.000 claims description 20
- 238000005261 decarburization Methods 0.000 claims description 18
- 230000004907 flux Effects 0.000 claims description 18
- 229910052751 metal Inorganic materials 0.000 claims description 17
- 239000002184 metal Substances 0.000 claims description 17
- 239000010935 stainless steel Substances 0.000 claims description 17
- ZLNQQNXFFQJAID-UHFFFAOYSA-L magnesium carbonate Chemical compound [Mg+2].[O-]C([O-])=O ZLNQQNXFFQJAID-UHFFFAOYSA-L 0.000 claims description 12
- 239000001095 magnesium carbonate Substances 0.000 claims description 12
- 229910000021 magnesium carbonate Inorganic materials 0.000 claims description 12
- 238000004519 manufacturing process Methods 0.000 claims description 10
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 5
- 229910052799 carbon Inorganic materials 0.000 claims description 5
- 229910052760 oxygen Inorganic materials 0.000 claims description 5
- 229910004261 CaF 2 Inorganic materials 0.000 claims description 4
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 4
- 229910052804 chromium Inorganic materials 0.000 claims description 4
- 239000011651 chromium Substances 0.000 claims description 4
- 239000001301 oxygen Substances 0.000 claims description 4
- 238000003756 stirring Methods 0.000 claims description 4
- 239000000126 substance Substances 0.000 claims description 4
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 3
- 239000002075 main ingredient Substances 0.000 claims description 2
- 238000000034 method Methods 0.000 description 17
- 238000007670 refining Methods 0.000 description 12
- 238000010079 rubber tapping Methods 0.000 description 9
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 5
- 239000003795 chemical substances by application Substances 0.000 description 5
- 238000007796 conventional method Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 239000002893 slag Substances 0.000 description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 description 3
- 229910001634 calcium fluoride Inorganic materials 0.000 description 3
- 235000011089 carbon dioxide Nutrition 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000009628 steelmaking Methods 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 229910000019 calcium carbonate Inorganic materials 0.000 description 2
- 238000005255 carburizing Methods 0.000 description 2
- 239000000571 coke Substances 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 238000009489 vacuum treatment Methods 0.000 description 2
- 229910019440 Mg(OH) Inorganic materials 0.000 description 1
- 239000010953 base metal Substances 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000007865 diluting Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000010802 sludge Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/005—Manufacture of stainless steel
Landscapes
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Treatment Of Steel In Its Molten State (AREA)
Description
本発明は低窒素ステンレス鋼に関するもので、
転炉精錬過程において脱窒を図り、さらに出鋼時
において窒素吸収を極力抑制して低窒素ステンレ
ス鋼を製造する方法に関する。
ステンレス鋼中の窒素は材料の強度を向上させ
る等の効果がある一方、Ti添加鋼のように窒化
物形成元素が存在すると、溶鋼中で窒化物が生成
し、製品で表面欠陥となり、歩留低下を招くため
極力低値に押えることが要求される。
また、フエライト系ステンレス鋼は耐応力腐食
割れ性に優れていることから、特に高純度ステン
レス鋼の用途が拡大されてきたが、侵入型元素で
ある窒素は母材および溶接部の靭性や耐食性を低
下させるので、窒素濃度［Ｎ］（以下、溶銑中お
よび溶鋼中の成分濃度は化学記号に［ ］を付し
て示す）の低減化が望まれている。
ステンレス鋼の製造法としてはVOD法は低窒
素鋼をつくるのに有利であると言われているが、
それでも約0.0008％以下の低窒素鋼の製造におい
てはVODでの精錬負荷は過大になりがちであつ
た。つまり、VODでの脱窒を強化しようとすれ
ば、減圧下でCOボイリングを活発にしなければ
ならず、そのためVOD前の［Ｃ］を高くする必
要があつた。しかし、VODの脱炭能力は小さい
ために、VOD精錬時間の大幅な延長とならざる
を得なかつた。また、活発化したCOボイリング
により、溶鋼が取鍋よりオーバーフローするとい
う事故を起す危険性が大であつた。
以上説明したように、従来のVOD法による低
窒素鋼の製造法では、脱窒の大部分をVODに依
存するために、VODにおける生産性や操業安全
性の低下を招くという問題があつた。
本発明はVOD工程以前、つまりステンレス鋼
の溶銑の段階で脱窒し、その後は吸窒を防止しつ
つVOD炉に溶鋼を装入することにより、VODで
の精錬負荷を軽減し、能率的に低窒素ステンレス
鋼を製造する方法を提供すること目的とする。
即ち、本発明によれば、クロムを10％以上含有
するスレンレス鋼用溶銑を、底吹き羽口を有する
転炉で、溶銑中の炭素濃度が４％以上になるまで
加炭し、酸素吹錬して脱炭し、脱酸処理を施すこ
となく取鍋に出鋼し、その際に、取鍋内に炭酸マ
グネシウム物質を供給し、その後真空脱炭処理す
ることを特徴とする低窒素ステンレス鋼の製造法
が提供される。
また本発明によれば、前記の方法であつて、転
炉における加炭後にCaOとCaF2を主剤とするフ
ラツクスを装入してArガスで撹拌する操作を加
えた方法が提供される。
本発明の方法において、加炭は加炭剤を挿入し
ながら、あるいは挿入後に底吹き羽口よりArガ
スを吹き込み撹拌しながら行なう。加炭剤として
はコークス、電極屑などが利用できる。加炭の目
的は２つあつて、第１は、よく知られた反応であ
るが、酸素吹錬による脱炭によつて生じるCOガ
ス稀釈による脱窒の促進であつて、次の(1)、(2)式
によつて示される。Ｃ
＋１／2O2（気体）→CO（気体） (1)
２Ｎ→N2（COバブル中の気体） (2)
本発明者らは脱炭前の［Ｃ］を種々に変化させ
て、脱窒率（DN）に及ぼす影響を調査したが、
第１図に示すように、脱炭前の［Ｃ］を４％以上
にするとDNが45％以上になるという工業的に有
利な関係があることを見出だした。ただし、Ｄは
(3)式で定義される。
（脱炭前の［Ｎ］）−（脱炭後の［Ｎ］）／（脱炭前の
［Ｎ］）×100
……(3)
その理由は、［Ｃ］を高めることにより(1)式に
おけるCOガスの生成量が増加し、(2)の脱窒反応
を促進するためと考えられる。
従来のステンレス鋼の溶銑の脱炭前の［Ｃ］は
１〜3.5％であり、この濃度ではあまり大きなDN
は得られない。
加炭の第２の目的は、フラツクス処理による脱
窒の促進である。炭素飽和溶鉄を高塩基度のフラ
ツクスで処理すれば脱窒反応が起ることは公知で
ある。しかし、工業的には炭素飽和状態まで加炭
することは困難であり、また可能であつたとして
も経済的でない。そこで本発明者らは経済的でか
つ脱窒効果の大きい加炭目標値およびフラツクス
の塩基度を求めるべく検討した結果、塩基度
（（wt％CaO）／（wt％SiO））は２以上で充分で
あり、かつ［Ｃ］は第２図に示すように４％以上
であれば、工業的に有利な脱窒速度係数(k)を有す
ることがわかつた。なおフラツクス処理による脱
窒反応は(4)〜(7)式で、脱窒速度式は(8)式で示され
る。
２Ｎ＋３Ｃ＋３（O2-）
→２（N3-）＋3CO（気体） ……(4)
２Ｎ＋３Ｃ＋（O2-）
→２（CN1-）＋CO（気体） ……(5)
Ｃ＋（O2-）→CO（気体）＋2e ……(6)
２Ｎ→N2（気体、COバブル中） ……(7)
−ｄ［Ｎ］／dt＝ｋ［Ｎ］2 (8)
上記式中、アンダーラインは溶銑中成分
（ ）内はスラグ成分中
ｔは時間
ｋは脱窒速度係数
を意味する。
以上のような目的で４％以上に加炭された溶銑
に対し、まずフラツクス処理を行なう。このフラ
ツクスはCaOとCaF2を主剤とするものであり、
その投入量は、スラグ塩基度を２以上にするこ
と、および流動性保持の観点から(9)および(10)式を
満足することが望ましい。
WCaO：43［％Si］ ……(9)
WCaF2：0.15WCaO (10)
ただし、
WCaO：溶銑1tあたりのCaO投入量（Kg／ｔ）
WCaF2：溶銑1tあたりのCaF2投入量（Kg／ｔ）
［％Si］：フラツクス投入時の溶銑中のSi濃度
フラツクス投入後、底吹き羽口よりArを吹き
込み撹拌する。
この際、雰囲気は非窒素性の中性もしくは還元
性雰囲気が望ましい。転炉の形状は底が深いため
に電気炉や取鍋よりも大気の侵入を防ぎやすく、
本フラツクス処理に適する。撹拌後、除滓を行な
い、その後O2吹錬により脱炭に移行する。なお、
初期窒素濃度が比較的低い時や、転炉精錬全体に
おける脱窒率として特に大きな値が要求されない
時は、以上のフラツクス処理を行なわなくてよ
い。
脱炭は通常のO2吹錬法で行なう。フラツクス
処理によつては溶銑の［Ｃ］はほとんど低下して
いないので、高い炭素濃度からの脱炭となるが、
転炉の脱炭能力は大きいために、それほど大きな
吹錬時間延長にならない。
脱炭終了後、浴温を調節して未脱酸のまま取鍋
内へ出鋼する。その際大気からの吸窒を防ぐため
に、出鋼中に取鍋へCO2発生剤を投入し、出鋼流
速および滝壷部周辺の雰囲気中のN2の分圧を低
下させる。
本発明者らはCO2ガス発生剤として炭酸マグネ
シウム、ドライアイス、炭酸カルシウについて製
鋼温度におけるガス発生速度を調査した。結果は
第３図に示す。前２者はガス発生速度が大きい
が、炭酸カルシウムはガス発生速度が小さく、転
炉出鋼所要時間（２〜３分）から考えて適当でな
いことが判明した。ドライアイスは高価であり、
また保管管理が面倒で経済的でない。結局炭酸マ
グネシウムが適当であることが判明した。本明細
書において使用される炭酸マグネシウム物質とい
う語は炭酸マグネシウムを含有する工業材料の意
味であり、純粋な炭酸マグネシウムを必ずしも意
味しない。工業用炭酸マグネシウムとよばれる材
料はMgCO2・Mg（OH）2・4H2Oを主成分とする。
いわゆる工業用炭酸マグネシウムは結晶水を含
むため、溶鋼がＯ、Ｈを吸収する可能性がある
が、本発明方法においては未脱酸鋼の処理であ
り、かつ出鋼後に真空処理を受けるので安全に使
用することができる。その他の場合にはこの材料
の使用は制限されるであろう。
出鋼後、VOD等で真空処理、還元精錬、最終
成分調整が行なわれ、低窒素ステンレス鋼とな
る。本発明によれば、VOD前の［Ｎ］が充分に
低いため、VOD工程での精錬は通常の［Ｎ］レ
ベルの場合と変らない。
次に実施例にもとづき本発明を具体的に説明す
る。実施の条件と結果を第１表にまとめて示し
た。
30トン電気炉で溶製された溶銑は
Ｃ：2.0〜3.5wt％
Si：0.1〜0.5wt％
Mn：0.1〜0.5wt％
Cr：17.0〜19.0wt％
を含み、残部Feおよび不可避的不純物よりなる
ものであつた。
製鋼番号A1〜A7は本発明方法によつて製造さ
れたものである。まず、底吹き羽口を有する転炉
中でコークスを投入してArガス撹拌して加炭す
るとともに、製鋼番号A2、A5、A6、A7はスラグ
塩基度を2.0〜3.0に高めるためにフラツクスとし
てCaO（32Kg／ｔ）およびCaF2（４Kg／ｔ）を加
え、その後、底吹き羽口よりArガスを吹き込ん
で（5Nm2／t.hr）10分間撹拌した。製鋼番号A1、
A3、A4についてはフラツクス処理はおこなわな
かつた。
次に除滓することなく、底吹き羽口より少量の
Arガスを吹き込みながら、上吹吹錬により脱炭
とともに脱窒を進行させた。O2吹錬を所定の時
間実施した後、浴温を調整し取鍋に出鋼した。本
発明方法の転炉精錬時間の延長はフラツクス処理
法で15分であつた。出鋼の際に、CO2ガス発生剤
としてフレーク状工業用炭酸マグネシウム（1.7
Kg／ｔ）を出鋼中に取鍋内に分割投入した。製鋼
番号B1、B2は従来法によつて製造したもので、
基本的工程は本発明方法と同様であるが、溶銑に
対して加炭もフラツクス処理も行なわず、単に
O2吹錬したもので、転炉からの出鋼時にもCO2ガ
ス発生剤は使用しなかつた。出鋼後のVOD精錬
は本発明と同様に全く通常の精錬
The present invention relates to low nitrogen stainless steel,
This invention relates to a method for manufacturing low-nitrogen stainless steel by denitrifying in the converter refining process and suppressing nitrogen absorption as much as possible during tapping. While nitrogen in stainless steel has the effect of improving the strength of the material, the presence of nitride-forming elements, such as in Ti-added steel, causes nitrides to form in the molten steel, resulting in surface defects in the product and reducing yield. To avoid this, it is necessary to keep the value as low as possible. In addition, ferritic stainless steel has excellent stress corrosion cracking resistance, so its use has been expanded, especially as a high-purity stainless steel.However, nitrogen, an interstitial element, impairs the toughness and corrosion resistance of the base metal and weld. Therefore, it is desired to reduce the nitrogen concentration [N] (hereinafter, component concentrations in hot metal and molten steel are indicated by adding [ ] to the chemical symbol). As a manufacturing method for stainless steel, the VOD method is said to be advantageous in producing low nitrogen steel.
Even so, in the production of low nitrogen steel of approximately 0.0008% or less, the refining load in VOD tends to be excessive. In other words, in order to enhance denitrification with VOD, it was necessary to activate CO boiling under reduced pressure, and therefore it was necessary to increase [C] before VOD. However, since the decarburization capacity of VOD is small, the VOD refining time has to be significantly extended. In addition, there was a high risk of an accident in which molten steel overflowed from the ladle due to activated CO boiling. As explained above, in the conventional method for producing low nitrogen steel using the VOD method, most of the denitrification depends on VOD, which has led to a problem in that productivity and operational safety in VOD are reduced. The present invention denitrifies stainless steel before the VOD process, that is, at the stage of stainless steel hot metal, and then charges the molten steel into the VOD furnace while preventing nitrification, thereby reducing the refining load in VOD and improving efficiency. The object of the present invention is to provide a method for manufacturing low nitrogen stainless steel. That is, according to the present invention, hot metal for stainless steel containing 10% or more chromium is carburized in a converter having a bottom blowing tuyere until the carbon concentration in the hot metal reaches 4% or more, and then oxygen blowing is carried out. A low-nitrogen stainless steel characterized in that the steel is decarburized and tapped into a ladle without being subjected to deoxidation treatment, and at that time, a magnesium carbonate substance is supplied into the ladle, and then vacuum decarburization treatment is performed. A manufacturing method is provided. Further, according to the present invention, there is provided the above-mentioned method, which includes the addition of an operation of charging a flux containing CaO and CaF 2 as main ingredients after carburization in a converter and stirring with Ar gas. In the method of the present invention, carburization is carried out while inserting the carburizing agent, or after insertion, while blowing Ar gas through the bottom blowing tuyeres and stirring. Coke, electrode scraps, etc. can be used as a carburizing agent. There are two purposes for carburization. The first is to promote denitrification by diluting the CO gas produced by decarburization by oxygen blowing, which is a well-known reaction. , is shown by equation (2). C + 1/2O 2 (gas) → CO (gas) (1) 2 N → N 2 (gas in CO bubble) (2) The present inventors variously changed [C] before decarburization, We investigated the effect on denitrification rate (D N ), but
As shown in Figure 1, we have found that there is an industrially advantageous relationship in that when [C] before decarburization is increased to 4% or more, D N becomes 45% or more. However, D is
It is defined by equation (3). ([N] before decarburization) - ([N] after decarburization) / ([N] before decarburization) × 100 ... (3) The reason is that by increasing [C] (1) This is thought to be because the amount of CO gas produced in the equation increases, promoting the denitrification reaction in (2). The [C] content of conventional stainless steel hot metal before decarburization is 1 to 3.5%, and at this concentration, the D N is too large.
cannot be obtained. The second purpose of carburization is to promote denitrification through flux treatment. It is known that a denitrification reaction occurs when carbon-saturated molten iron is treated with a highly basic flux. However, industrially, it is difficult to carburize to a carbon saturated state, and even if possible, it is not economical. Therefore, the present inventors investigated to determine the basicity of flux and the target carburization value that is economical and has a large denitrification effect, and found that the basicity ((wt%CaO)/(wt%SiO)) is 2 or more. It was found that if the denitrification rate coefficient (k) is sufficient and [C] is 4% or more as shown in FIG. 2, the denitrification rate coefficient (k) is industrially advantageous. The denitrification reaction by flux treatment is expressed by equations (4) to (7), and the denitrification rate equation is expressed by equation (8). 2 N + 3 C + 3 (O 2- ) → 2 (N 3- ) + 3 CO (gas) ……(4) 2 N + 3 C + (O 2- ) → 2 (CN 1- ) + CO (gas) ……( 5) C + (O 2- ) → CO (gas) + 2e ……(6) 2 N → N 2 (gas, in CO bubble) ……(7) −d[N]/dt=k[N] 2 (8) In the above formula, the underline indicates the component in the hot metal ( ) indicates the slag component, t is time, and k is the denitrification rate coefficient. For the above purpose, hot metal that has been carburized to 4% or more is first subjected to flux treatment. This flux is mainly composed of CaO and CaF2 ,
The amount to be added preferably satisfies equations (9) and (10) from the viewpoint of making the slag basicity 2 or more and maintaining fluidity. W CaO : 43 [%Si] ...(9) W CaF2 : 0.15W CaO (10) However, W CaO : CaO input amount per 1 t of hot metal (Kg/t) W CaF2 : CaF 2 input amount per 1 ton of hot metal (Kg/t) [%Si]: Si concentration in hot metal when flux is introduced After flux is introduced, Ar is blown through the bottom blowing tuyere and stirred. At this time, the atmosphere is preferably a non-nitrogen neutral or reducing atmosphere. Because the converter has a deep bottom, it is easier to prevent air from entering than an electric furnace or ladle.
Suitable for this flux treatment. After stirring, the sludge is removed, and then decarburization begins with O 2 blowing. In addition,
When the initial nitrogen concentration is relatively low or when a particularly large denitrification rate is not required in the entire converter refining, the above flux treatment may not be performed. Decarburization is carried out using the usual O 2 blowing method. Depending on the flux treatment, [C] in the hot metal hardly decreases, so decarburization occurs from a high carbon concentration, but
Since the decarburization capacity of the converter is large, the blowing time will not be extended by that much. After decarburization, the bath temperature is adjusted and the steel is tapped into a ladle without being deoxidized. At this time, in order to prevent nitrogen absorption from the atmosphere, a CO 2 generating agent is introduced into the ladle during tapping to reduce the tapping flow rate and the partial pressure of N 2 in the atmosphere around the waterfall basin. The present inventors investigated the gas generation rate at steel-making temperatures using magnesium carbonate, dry ice, and calcium carbonate as CO 2 gas generating agents. The results are shown in Figure 3. The former two have a high gas generation rate, but calcium carbonate has a low gas generation rate, and was found to be unsuitable considering the time required for steel tapping in a converter (2 to 3 minutes). Dry ice is expensive;
Moreover, storage management is troublesome and uneconomical. In the end, it was found that magnesium carbonate was suitable. The term magnesium carbonate material as used herein refers to technical materials containing magnesium carbonate and does not necessarily mean pure magnesium carbonate. The main component of the material called industrial magnesium carbonate is MgCO 2 .Mg(OH) 2 .4H 2 O. So-called industrial magnesium carbonate contains crystallization water, so molten steel may absorb O and H. However, in the method of the present invention, undeoxidized steel is treated and vacuum treatment is performed after tapping, so it is safe. It can be used for. In other cases the use of this material will be limited. After tapping, it undergoes vacuum treatment using VOD, reduction refining, and final composition adjustment to become low-nitrogen stainless steel. According to the present invention, the [N] before VOD is sufficiently low, so that the refining in the VOD process is no different from that of the normal [N] level. Next, the present invention will be specifically explained based on Examples. The implementation conditions and results are summarized in Table 1. Hot metal melted in a 30-ton electric furnace contains C: 2.0 to 3.5 wt%, Si: 0.1 to 0.5 wt%, Mn: 0.1 to 0.5 wt%, Cr: 17.0 to 19.0 wt%, and the balance consists of Fe and inevitable impurities. It was hot. Steel production numbers A1 to A7 were produced by the method of the present invention. First, coke is charged into a converter with bottom-blowing tuyere, and the slag basicity is increased to 2.0 to 3.0 for steelmaking numbers A2 , A5 , A6 , and A7 . For this purpose, CaO (32 Kg/t) and CaF 2 (4 Kg/t) were added as fluxes, and then Ar gas was blown through the bottom blowing tuyere (5 Nm 2 /t.hr) and stirred for 10 minutes. Steelmaking number A 1 ,
No flux treatment was performed on A 3 and A 4 . Next, without removing slag, a small amount of air is poured from the bottom blowing tuyere.
Decarburization and denitrification were progressed by top blowing while blowing Ar gas. After performing O 2 blowing for a predetermined time, the bath temperature was adjusted and the steel was tapped into a ladle. The extension of the converter refining time in the method of the present invention was 15 minutes using the flux treatment method. Flake industrial magnesium carbonate (1.7
Kg/t) was charged in portions into the ladle during tapping. Steel production numbers B 1 and B 2 are manufactured using conventional methods.
The basic process is the same as the method of the present invention, but the hot metal is not subjected to carburization or flux treatment, and is simply
It was O 2 blown, and no CO 2 gas generating agent was used when tapping the steel from the converter. VOD refining after tapping is completely normal refining similar to the present invention.
【表】
法である。
第１表より明らかなように、従来法のVOD後
の［Ｎ］が0.010〜0.012％であるに対し、本発明
鋼では従来法とほとんど同じ精錬時間で0.0050〜
0.0085％［Ｎ］の低窒素ステンレス鋼が得られ
る。なお従来法においてVOD前の［Ｎ］を高め、
VODでの脱窒を強化した場合は、本発明法と同
様程度の低窒素鋼は得られるが、VOD精錬時間
の延長は著しいものとなる。
本発明の製造方法を利用すれば、フエライト系
ステンレス鋼以外のステンレス鋼でも低窒素鋼の
製造が可能であることは言うまでもない。[Table] It is a law. As is clear from Table 1, [N] after VOD in the conventional method is 0.010 to 0.012%, whereas in the steel of the present invention, the [N] after VOD is 0.005 to 0.005% in almost the same refining time as the conventional method.
A low nitrogen stainless steel of 0.0085% [N] is obtained. In addition, in the conventional method, [N] before VOD is increased,
If denitrification in VOD is strengthened, a low-nitrogen steel similar to the method of the present invention can be obtained, but the VOD refining time will be significantly extended. It goes without saying that by using the production method of the present invention, low nitrogen steel can be produced using stainless steels other than ferritic stainless steel.
第１図は脱炭前の［Ｃ］とO2吹錬による脱窒
率の関係を示す。第２図はフラツクス処理による
脱窒速度係数と［Ｃ］との関係を示す。第３図は
1570℃における工業用炭酸マグネシウム(a)と、ド
ライアイス(b)と、(c)CaCO3の分解（炭酸ガス発
生速度）を示す。
Figure 1 shows the relationship between [C] before decarburization and the denitrification rate by O 2 blowing. FIG. 2 shows the relationship between the denitrification rate coefficient and [C] by flux treatment. Figure 3 is
Decomposition (carbon dioxide gas generation rate) of industrial magnesium carbonate (a), dry ice (b), and (c) CaCO 3 at 1570°C.
Claims (1)
銑を、底吹き羽口を有する転炉で、溶銑中の炭素
濃度が４％以上になるまで加炭し、ついで酸素吹
錬して脱炭し、脱酸処理を施すことなく取鍋に出
鋼し、その際に、取鍋内に炭酸マグネシウム物質
を供給し、その後真空脱炭処理することを特徴と
する低窒素ステンレス鋼の製造法。 ２ クロムを10％以上含有するステンレス鋼用溶
銑を、底吹き羽口を有する転炉で、溶銑中の炭素
濃度が４％以上になるまで加炭し、CaOとCaF2
を主剤とするフラツクスを装入し、底吹き羽口よ
りArガスを吹き込み撹拌しながら、酸素吹錬に
より脱炭し、脱酸処理を施すことなく取鍋に出鋼
し、その際に、取鍋内に炭酸マグネシウム物質を
供給し、その後真空脱炭処理することを特徴とす
る低窒素ステンレス鋼の製造法。[Claims] 1. Hot metal for stainless steel containing 10% or more chromium is carburized in a converter with a bottom blowing tuyere until the carbon concentration in the hot metal reaches 4% or more, and then oxygen blowing is carried out. A low-nitrogen stainless steel characterized in that the steel is decarburized and tapped into a ladle without being subjected to deoxidation treatment, and at that time, a magnesium carbonate substance is supplied into the ladle, and then vacuum decarburization treatment is performed. manufacturing method. 2 Stainless steel hot metal containing 10% or more chromium is carburized in a converter with bottom blowing tuyeres until the carbon concentration in the hot metal reaches 4% or more, and CaO and CaF 2
The flux is charged as a main ingredient, decarburized by oxygen blowing while stirring and blowing Ar gas from the bottom blowing tuyere, and tapped into a ladle without deoxidizing treatment. A method for producing low-nitrogen stainless steel, which is characterized by supplying a magnesium carbonate substance into a pot and then performing vacuum decarburization treatment.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9014884A JPS60234916A (en) | 1984-05-08 | 1984-05-08 | Manufacture of stainless steel containing low nitrogen |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9014884A JPS60234916A (en) | 1984-05-08 | 1984-05-08 | Manufacture of stainless steel containing low nitrogen |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS60234916A JPS60234916A (en) | 1985-11-21 |
| JPH0346527B2 true JPH0346527B2 (en) | 1991-07-16 |
Family
ID=13990411
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP9014884A Granted JPS60234916A (en) | 1984-05-08 | 1984-05-08 | Manufacture of stainless steel containing low nitrogen |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS60234916A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2013204086A (en) * | 2012-03-28 | 2013-10-07 | Nisshin Steel Co Ltd | Method for producing stainless steel |
| JP2016166427A (en) * | 2016-06-14 | 2016-09-15 | 日新製鋼株式会社 | Method for producing stainless steel |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3726599B2 (en) * | 1999-11-24 | 2005-12-14 | Ｊｆｅスチール株式会社 | Method for refining molten steel using refractory scrap containing carbon |
| KR100523106B1 (en) * | 2001-12-17 | 2005-10-19 | 주식회사 포스코 | method for refining a stainless steel sheet with low nitrogen |
| CN104409521A (en) * | 2014-11-13 | 2015-03-11 | 无锡中洁能源技术有限公司 | Nano-film solar cell substrate material and preparation method thereof |
| CN107385139A (en) * | 2017-07-30 | 2017-11-24 | 湖南华菱湘潭钢铁有限公司 | A kind of smelting process of high-carbon steel |
-
1984
- 1984-05-08 JP JP9014884A patent/JPS60234916A/en active Granted
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2013204086A (en) * | 2012-03-28 | 2013-10-07 | Nisshin Steel Co Ltd | Method for producing stainless steel |
| JP2016166427A (en) * | 2016-06-14 | 2016-09-15 | 日新製鋼株式会社 | Method for producing stainless steel |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS60234916A (en) | 1985-11-21 |
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