JPH0526841B2 - - Google Patents
Info
- Publication number
- JPH0526841B2 JPH0526841B2 JP60094369A JP9436985A JPH0526841B2 JP H0526841 B2 JPH0526841 B2 JP H0526841B2 JP 60094369 A JP60094369 A JP 60094369A JP 9436985 A JP9436985 A JP 9436985A JP H0526841 B2 JPH0526841 B2 JP H0526841B2
- Authority
- JP
- Japan
- Prior art keywords
- chromium
- blowing
- hot metal
- chromium ore
- slag
- 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 - Lifetime
Links
- 239000011651 chromium Substances 0.000 claims description 105
- 229910052804 chromium Inorganic materials 0.000 claims description 83
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 73
- 238000007664 blowing Methods 0.000 claims description 56
- 239000002893 slag Substances 0.000 claims description 41
- 229910052751 metal Inorganic materials 0.000 claims description 35
- 239000002184 metal Substances 0.000 claims description 35
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 28
- 238000000034 method Methods 0.000 claims description 28
- 239000001301 oxygen Substances 0.000 claims description 28
- 229910052760 oxygen Inorganic materials 0.000 claims description 28
- 238000007670 refining Methods 0.000 claims description 23
- 238000005261 decarburization Methods 0.000 claims description 20
- 238000002844 melting Methods 0.000 claims description 15
- 230000008018 melting Effects 0.000 claims description 15
- 230000009467 reduction Effects 0.000 claims description 15
- 238000003756 stirring Methods 0.000 claims description 14
- 239000000571 coke Substances 0.000 claims description 13
- 238000003723 Smelting Methods 0.000 claims description 11
- 230000004907 flux Effects 0.000 claims description 11
- 239000002131 composite material Substances 0.000 claims description 8
- 238000010309 melting process Methods 0.000 claims description 5
- 239000000155 melt Substances 0.000 claims description 3
- 230000008569 process Effects 0.000 description 18
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 13
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 12
- 230000002829 reductive effect Effects 0.000 description 11
- 229910052717 sulfur Inorganic materials 0.000 description 7
- 239000002253 acid Substances 0.000 description 6
- 239000010935 stainless steel Substances 0.000 description 6
- 229910001220 stainless steel Inorganic materials 0.000 description 6
- 229910000831 Steel Inorganic materials 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 5
- 239000007789 gas Substances 0.000 description 5
- 238000007254 oxidation reaction Methods 0.000 description 5
- 238000011946 reduction process Methods 0.000 description 5
- 239000000377 silicon dioxide Substances 0.000 description 5
- 239000010959 steel Substances 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- 229910017082 Fe-Si Inorganic materials 0.000 description 4
- 229910017133 Fe—Si Inorganic materials 0.000 description 4
- 230000003247 decreasing effect Effects 0.000 description 4
- 239000011261 inert gas Substances 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 3
- 238000006477 desulfuration reaction Methods 0.000 description 3
- 230000023556 desulfurization Effects 0.000 description 3
- 239000004576 sand Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 2
- 239000003638 chemical reducing agent Substances 0.000 description 2
- 239000003245 coal Substances 0.000 description 2
- 229910052681 coesite Inorganic materials 0.000 description 2
- 229910052906 cristobalite Inorganic materials 0.000 description 2
- 230000003009 desulfurizing effect Effects 0.000 description 2
- 229910001873 dinitrogen Inorganic materials 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 229910052682 stishovite Inorganic materials 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- 229910052905 tridymite Inorganic materials 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229910004261 CaF 2 Inorganic materials 0.000 description 1
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- 229910005347 FeSi Inorganic materials 0.000 description 1
- 229910000805 Pig iron Inorganic materials 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 238000003763 carbonization Methods 0.000 description 1
- 238000005255 carburizing Methods 0.000 description 1
- 239000003610 charcoal Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 229910000423 chromium oxide Inorganic materials 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 229910001882 dioxygen Inorganic materials 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000012840 feeding operation Methods 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 230000004044 response Effects 0.000 description 1
- 239000012258 stirred mixture Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000012549 training Methods 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
Description
本発明は、固定のクロム鉱石を上底吹き可能な
複合吹錬転炉に装入して溶融し、これを還元して
有利にステンレス溶鋼などを製造できるようにし
たクロム鉱石の溶融還元法に関する。
従来において、ステンレス溶鋼等を製造するた
めの含クロム溶銑並びに母合金は、主として電気
炉でクロム鉱石をコークスと共に溶解することに
よつて製造されていた。この処方は多大のエネル
ギーを消耗する。
この確立された処方に対し、近年、上底吹き可
能な複合吹錬転炉によるクロム鉱石の直接溶融還
元法が検討されつつある。複合吹錬転炉は、炉底
に羽口を有すると共に上吹きランスを備えた転炉
であり、炉底の羽口から不活性ガス、また場合に
よつては酸素ガスを導入することができる。した
がつて、炉内装入物に充分な撹拌を与えることが
でき、また雰囲気制御もできる点で有利な面をも
つている。この特性を活かして、クロム鉱石を直
接的に溶融還元しようとする研究が種々なされて
いるが、まだ、実操業技術としては確立されてい
ないのが実情である。
複合吹錬転炉によるクロム鉱石の溶融還元を実
現するには、炉体耐火物の溶損が生じない条件下
で溶融還元を促進する適正条件の把握が必要であ
るが、実操業例のデータが不足し、実際には、ど
のようにしたら最も効率よくクロム鉱石の溶融還
元を進行させることができるか不明な点が多い。
特にクロム鉱石に同伴する脈石分（MgO、Al2O3
等）の溶融滓化を迅速に行わねばならなくなるが
これはどのようにしたら効率よく実施できるか不
明である。
本発明はこのような問題を克服することを目的
としたものであり、複合吹錬転炉によるクロム鉱
石の溶融と還元を実操業的に有利に実現する方法
を提供しようとするものである。
本発明によるクロム鉱石の複合吹錬転炉による
溶融還元法は、
母溶銑とクロム鉱石を上底吹き可能な複合吹錬
転炉に装入し、さらにフラツクスを溶融物のスラ
グ塩基度が0.5〜1.3となるように添加したうえ、
底吹き撹拌を行いながら酸素上吹き吹錬してクロ
ム鉱石を溶融滓化するクロム鉱石の溶融工程と、
この溶融滓化された溶融物にコークスを添加
し、酸素吹錬を実施するかまたはせずして高Ｃ含
クロム溶銑を製造する加炭還元工程と、そして、
得られた高Ｃ含クロム溶銑を脱炭精錬する脱炭精
錬工程と、からなる。
以下に本発明の内容を詳述する。
本発明において使用する上底吹き可能な転炉
は、炉底に不活性ガス例えば窒素ガスやアルゴン
ガスその他のガスを吹き込むことができる羽口を
もち且つ酸素上吹きランスを備えた複合吹錬転炉
である。
クロム鉱石の溶融工程とこれに引き続く加炭還
元工程は、少なくともこの複合吹錬転炉で実施す
る。クロム鉱石の溶融工程、加炭還元工程および
脱炭精錬工程を１基の複合吹錬転炉で実施するこ
ともできるが、より好ましくは、複合吹錬転炉を
少なくとも２基準備し、一方の１基でクロム鉱石
の溶融工程と加炭還元工程を実施し、脱炭精錬工
程は他方の１基で実施するのがよい。各工程を順
をおつて以下に説明する。
〔クロム鉱石の溶融滓化工程〕
この工程では、母溶銑とクロム鉱石とフラツク
スを添加して溶融物を製造する。母溶銑としては
Crを含有しない普通銑でもよいが、20重量％以
下のCrを含有する含クロム溶銑を使用するのが
有利である。含クロム溶銑は、通常の方法に従つ
て電気炉で製造することができる。クロム鉱石は
この母溶銑の装入と時期を同じくして装入する。
すなわちクロム鉱石の複合吹錬転炉への装入は、
クロム鉱石の溶融滓化を促進する意味から、母溶
銑装入時つまり初期に行う（クロム鉱石の還元剤
の添加時期とはずらす）のが望ましい。そして、
本工程において、クロム酸化物、鉄酸化物および
その他の脈石系の固体酸化物からなくクロム鉱石
を迅速に溶融滓化するには、フラツクスの添加と
その適正な調整、底吹き撹拌および酸素吹錬が必
要となる。
フラツクスは生成するスラグの塩基度および脈
石を含めたスラグの融点を調整するために添加す
る。添加するフラツクスとしてはCaOやSiO2な
どを含むものを使用するが、この種類と量は、ス
ラグの塩基度（CaO／SiO2）が0.5〜1.3、好まし
くは0.6〜1.2となるように選定するのがよい。こ
れよりスラグ塩基度の高い高塩基性スラグの場合
には、その溶融温度が高くなつて限られた時間内
にクロム鉱石の溶融を終了せしめるのが困難とな
る。また、これよりスラグ塩基度が低い低塩基性
スラグの場合には、クロム鉱石の溶融滓化は促進
されるものの、炉体耐火物の溶損が助長されるの
で好ましくない。すなわち、フラツクスの添加に
よつて、スラグの塩基度が0.5〜1.3、好ましくは
0.6〜1.2の範囲となるようにスラグ組成をコント
ロールすることによつて、クロム鉱石の溶融滓化
が促進され且つ炉体耐火物の溶損も比較的小さく
抑えることができる。
そして、このようにフラツクスを添加してクロ
ム鉱石を完全に溶融滓化するには、底吹き撹拌お
よび酸素吹錬が必要となる。底吹きガスとしては
窒素ガスやアルゴンガスを使用することができ
る。この底吹き撹拌により母溶銑と固体物質であ
るクロム鉱石およびフラツクスが混合され、ま
た、この撹拌状態にある混合物に酸素吹錬が実施
されると母溶銑中の主としてＣの酸化反応が充分
におこなわれ、これに基づく発熱が生じる結果、
クロム鉱石とフラツクスを完全に溶融滓化するこ
とができる。
〔加炭還元工程〕
本発明においては、このクロム鉱石の溶融滓化
が実質上完了してからコークスを添加する。この
加炭は、滓化したCr2O3の還元に供することを主
目的とするものである。しかしCr2O3以外の酸化
物例えばFeOなどの還元や、後の脱炭精錬工程で
の熱源としても供される。この加炭の時期をクロ
ム鉱石が実質上溶融滓化した後とすることによつ
て、スラグ中に存在するCr2O3やFeOなどの酸化
物の還元が有利に行い得ることがわかつた。
この加炭操作は、前工程から引続き不活性ガス
を底吹きを続行しながら炉頂からコークスを添加
すればよい。粉炭吹き込みができる羽口であれば
この撹拌用ガスに同伴して粉炭吹き込みを実施し
てもよい。底吹き撹拌だけでコークスを溶解させ
ることができ、またこの底吹きを伴う加炭操作に
よつてスラグ中のCr2O3やFeOを還元することが
できる。この場合、羽口から酸素を同時に供給し
てもよい。酸素を供給する場合には、溶銑中のク
ロムの過度の酸化を防止する意味から送酸速度を
小さくするのがよい。一方、上吹きランスから送
酸する場合においても、溶銑中のクロムの過度の
酸化を防止するために送酸速度を小さくするのが
よい。かような酸素供給を行わなくても、底吹き
撹拌下での加炭だけでCr2O3やFeOの還元を行う
ことも可能である。また、加炭を数回に分けて実
施し、送酸を必要に応じて実施することも有利で
ある。いずれにしても、送酸する場合には、クロ
ムの酸化が起こらないような充分なＣ濃度に加炭
がなされていることが必要である。すなわち加炭
操作によつてＣ濃度を充分に高めることがCr2O3
の還元を有利には実施するうえで重要な要件とな
る。
この工程において推奨される処方は、底吹き撹
拌しながらコークスを添加し、充分なＣ濃度にな
つたら送酸を開始し、この送酸によつてＣ濃度が
低下した時期を見計らつて再び加炭を実施し、軽
度の送酸を実施するかまたは送酸を停止して底吹
き撹拌だけを行うという処方である。加炭の回数
と送酸の回数は必要に応じて増減することができ
るが、最後の段階では高いＣ濃度に維持したまま
送酸を停止する必要があり、次なる撹拌によつて
Cr2O3濃度を大幅に低下させ溶解物からのクロム
の還元回収をほぼ終了させ得る。そして、このよ
うにCr2O3濃度が低下した状態からクロムを更に
還元回収するには、Fe−Si等の金属系還元材を
添加して強制還元すればよい。この処方によると
Cr2O3はほぼ100％クロムに還元することが可能
となる。
このようにして、本工程の特徴は、加炭操作、
撹拌操作、そして必要に応じての送酸操作によつ
て、前工程でクロム鉱石が充分に溶融滓化してス
ラグ中に存在しているCr2O3やFeOを還元するこ
とにある。この工程終了時におけるCr2O3の還元
率は90％以上とすることができる。したがつてこ
の工程終了時の複合吹錬転炉内には、当初に装入
されたクロム鉱石中のクロム源の実質上全てが還
元された高Ｃ含クロム溶銑とスラグとからなる融
解物が存在することになる。得られた高Ｃ含クロ
ム溶銑は、スラグと分離されたあと、次の脱炭精
錬工程に供される。
〔脱炭精錬工程〕
前工程で生成したスラグは、クロム鉱石中の脈
石分や投入されたフラツクス成分などからなり、
比較的多量に発生する。このスラグを分離した高
Ｃ含クロム溶銑を本工程では精錬対象とする。ス
ラグの分離は、前二工程を実施した複合吹錬転炉
から溶銑を取鍋に受銑することによつて行うのが
実操業上有利である。そして、受銑した溶銑を脱
炭精錬炉に装入して脱炭精錬を実施する。この脱
炭精錬炉としては、前二工程を実施した複合吹錬
転炉を使用することができるが、別の精錬炉を使
用することもできる。この別の精錬炉としては同
じく複合吹錬転炉、取鍋精錬炉例えばVOD炉な
どを使用することができる。いずれにしてもこれ
らの精錬炉はCrの酸化損失を抑え、目標とする
Ｃレベルすなわち低炭素域まで脱炭することがで
きるものであればよい。すなわち、代表的には大
気圧下で不活性ガスによつて溶銑を撹拌しながら
脱炭精錬するか、もしくは減圧下で脱炭精錬する
など、従来のステンレス溶鋼等の製造に用いられ
ている任意の脱炭精錬炉を使用することができ
る。
本発明法においては、前工程において多量のコ
ークスを添加している関係上、得られた高Ｃ含ク
ロム溶銑中のＳ濃度はこのコークス量に応じて高
くなつている。このため脱硫処理を必要とするこ
とになるが、これは前工程終了後の取鍋へ受銑さ
れた段階で脱硫剤を添加して取鍋脱硫するか、脱
炭精錬の後で通常の脱硫処理を実施すればよい。
脱炭反応を進行させるさいに不可避的に生成し
たCr2O3は脱炭精錬炉として複合吹錬転炉を使用
した場合にはこの炉でSiを添加することによつて
還元回収することができ、また転炉と取鍋精錬炉
を併用する場合には、転炉で得られた粗溶鋼とス
ラグの両者を取鍋精錬炉に移し、この精錬炉でSi
を添加してクロムの回収を行うことができる。
つぎに本発明法の代表的な実施例を挙げる。
実施例 １
電気炉で溶解されたＣ：4.0％、Cr：16.8％、
Ｓ：0.008％の溶銑45トンを複合吹錬転炉に装入
し、表１にその組成を示すクロム鉱石３トンおよ
び硅砂290Kgを添加し、底吹きN2：85Nm3／Hr×
１羽口、上吹き酸素：流量5200Nm3／Hr、ラン
ス高さ1400mmで酸素吹錬を開始し、酸素の供給量
を1000Nm3まで送酸してクロム鉱石の溶融を行つ
たところ、添加したクロム鉱石は完全に溶融滓化
した。この時のＣ濃度は2.1％、Crは16.7％、温
度は1565℃であり、スラグはその塩基度（CaO／
SiO2）が1.2でその溶融温度は1480℃のものであ
つた。なお本例において、硅砂290Kgを添加した
が、この硅砂に代えて当量のSiをFeSiで装入し
ても同じ結果が得られる（以下、クロム鉱石の溶
融滓化工程）。
The present invention relates to a method for melting and reducing chromium ore, in which fixed chromium ore is charged into a top-bottom blowing composite blowing converter, melted, and reduced to advantageously produce molten stainless steel. . BACKGROUND ART Conventionally, chromium-containing hot metal and master alloy for producing molten stainless steel and the like have been mainly produced by melting chromium ore together with coke in an electric furnace. This prescription consumes a lot of energy. In response to this established recipe, in recent years, a method of direct smelting reduction of chromium ore using a composite blowing converter capable of top-bottom blowing has been studied. A combined blowing converter is a converter that has a tuyere at the bottom of the furnace and is equipped with a top blowing lance, through which inert gas and, in some cases, oxygen gas can be introduced. . Therefore, it is advantageous in that sufficient stirring can be given to the contents in the furnace and the atmosphere can also be controlled. Although various studies have been conducted to directly melt and reduce chromium ore by taking advantage of this property, the reality is that it has not yet been established as an actual operational technology. In order to achieve smelting reduction of chromium ore using a combined blowing converter, it is necessary to understand the appropriate conditions to promote smelting reduction under conditions that do not cause melting of the furnace refractories. However, there is a shortage of chromium ore, and in reality, there are many points that are unclear as to how to proceed with the most efficient melting reduction of chromium ore.
In particular, the gangue content accompanying chromium ore (MgO, Al 2 O 3
etc.), but it is unclear how this can be done efficiently. The present invention aims to overcome such problems and provides a method for realizing melting and reduction of chromium ore using a composite blowing converter in an advantageous manner in actual operation. The smelting reduction method using a composite blowing converter for chromium ore according to the present invention involves charging mother hot metal and chromium ore into a composite blowing converter capable of top-bottom blowing, and further adding flux to the furnace until the slag basicity of the molten metal is 0.5 to 0.5. It was added so that it was 1.3, and
A chromium ore melting process in which chromium ore is turned into molten slag by oxygen top blowing while bottom blowing stirring is performed, and coke is added to this molten slag and oxygen blowing is performed. A carburization reduction process for producing high C chromium-containing hot metal without any problem, and
It consists of a decarburization refining step of decarburizing and refining the obtained high-C chromium-containing hot metal. The content of the present invention will be explained in detail below. The top-bottom blowing converter used in the present invention is a compound blowing converter having a tuyere capable of blowing an inert gas such as nitrogen gas, argon gas, or other gas into the bottom of the furnace, and equipped with an oxygen top-blowing lance. It is a furnace. The melting process of the chromium ore and the subsequent carburization and reduction process are carried out at least in this combined blowing converter. The chromium ore melting process, carburization reduction process, and decarburization refining process can be carried out in one combined blowing converter, but more preferably, at least two combined blowing converters are prepared, and one It is preferable that one unit performs the chromium ore melting process and carburization reduction process, and the other unit performs the decarburization refining process. Each step will be explained below in order. [Chromium ore melt slag formation process] In this process, mother hot metal, chromium ore, and flux are added to produce a molten product. As mother hot metal
Although ordinary pig iron containing no Cr may be used, it is advantageous to use chromium-containing hot metal containing 20% by weight or less of Cr. Chromium-containing hot metal can be produced in an electric furnace according to a conventional method. The chromium ore is charged at the same time as the mother hot metal.
In other words, the charging of chromium ore into a complex blowing converter is as follows:
In order to promote the formation of chromium ore into molten slag, it is desirable to perform this at the time of charging the mother hot metal, that is, at the beginning (different from the time when the reducing agent is added to the chromium ore). and,
In this process, in order to rapidly convert chromium ore into molten slag without chromium oxide, iron oxide, and other gangue-based solid oxides, it is necessary to add flux and its proper adjustment, bottom-blowing stirring, and oxygen blowing. Training is required. Flux is added to adjust the basicity of the produced slag and the melting point of the slag including gangue. The flux to be added is one containing CaO, SiO2 , etc., and the type and amount are selected so that the basicity of the slag (CaO/ SiO2 ) is 0.5 to 1.3, preferably 0.6 to 1.2. It is better. In the case of a highly basic slag with a higher slag basicity, its melting temperature becomes higher and it becomes difficult to finish melting the chromium ore within a limited time. Furthermore, in the case of a low basicity slag having a lower slag basicity than this, although the formation of chromium ore into molten slag is promoted, the melting loss of the furnace refractory is promoted, which is not preferable. That is, by adding flux, the basicity of the slag is increased from 0.5 to 1.3, preferably
By controlling the slag composition to fall within the range of 0.6 to 1.2, the formation of chromium ore into molten slag can be promoted and the melting loss of the furnace refractory can be kept relatively small. In order to completely turn the chromium ore into molten slag by adding flux in this manner, bottom-blowing stirring and oxygen blowing are required. Nitrogen gas or argon gas can be used as the bottom blowing gas. This bottom-blown stirring mixes the mother hot metal with the solid substances chromium ore and flux, and when the stirred mixture is subjected to oxygen blowing, the oxidation reaction of mainly C in the mother hot metal takes place sufficiently. As a result of this, heat generation occurs,
It is possible to completely turn chrome ore and flux into molten slag. [Carburization and reduction step] In the present invention, coke is added after the molten slag formation of the chromium ore is substantially completed. The main purpose of this carbonization is to reduce the Cr 2 O 3 that has become a slag. However, it is also used as a heat source for reducing oxides other than Cr 2 O 3 , such as FeO, and for the subsequent decarburization and refining process. It has been found that by performing this carburization after the chromium ore has substantially turned into molten slag, oxides such as Cr 2 O 3 and FeO present in the slag can be effectively reduced. In this carburization operation, coke may be added from the top of the furnace while continuing to blow inert gas from the bottom from the previous step. As long as the tuyere is capable of blowing powdered coal, the blowing of powdered coal may be carried out along with this stirring gas. Coke can be dissolved only by bottom-blowing stirring, and Cr 2 O 3 and FeO in the slag can be reduced by the carburization operation accompanied by bottom-blowing. In this case, oxygen may be supplied from the tuyere at the same time. When supplying oxygen, it is preferable to reduce the oxygen supply rate in order to prevent excessive oxidation of chromium in the hot metal. On the other hand, even when oxygen is fed from a top-blowing lance, it is preferable to reduce the oxygen feeding rate in order to prevent excessive oxidation of chromium in the hot metal. Even without such oxygen supply, it is also possible to reduce Cr 2 O 3 and FeO simply by carburization under bottom-blowing stirring. It is also advantageous to carry out carburization in several parts and to carry out acid feeding as needed. In any case, when oxygen is supplied, it is necessary to carburize the carbon to a sufficient concentration so that oxidation of chromium does not occur. In other words, it is necessary to sufficiently increase the C concentration by carburizing Cr 2 O 3
This is an important requirement for the effective implementation of the reduction of The recommended recipe for this process is to add coke while stirring from the bottom, start to feed oxygen when a sufficient C concentration is reached, and wait until the C concentration has decreased due to this acid feeding to add coke again. The recipe is to carry out charcoal and carry out light acid feeding, or to stop acid feeding and perform only bottom-blowing stirring. The number of times of carburization and the number of times of acid feeding can be increased or decreased as necessary, but in the final stage, it is necessary to stop the acid feeding while maintaining a high C concentration, and the next stirring
The Cr 2 O 3 concentration can be significantly reduced and the reductive recovery of chromium from the melt can be almost completed. In order to further reduce and recover chromium from a state where the Cr 2 O 3 concentration has decreased in this manner, a metallic reducing agent such as Fe-Si may be added to perform forced reduction. According to this prescription
Cr 2 O 3 can be reduced to almost 100% chromium. In this way, the characteristics of this process are the carburization operation,
Through the stirring operation and, if necessary, the oxygen feeding operation, the chromium ore is sufficiently turned into molten slag in the previous step to reduce Cr 2 O 3 and FeO present in the slag. The reduction rate of Cr 2 O 3 at the end of this step can be 90% or more. Therefore, at the end of this process, the combined blowing converter contains a melt consisting of high C-containing hot metal and slag, in which substantially all of the chromium source in the initially charged chromium ore has been reduced. It will exist. The obtained high-C chromium-containing hot metal is separated from slag and then subjected to the next decarburization refining process. [Decarburization refining process] The slag produced in the previous process is composed of gangue components in chromium ore and flux components that have been input.
Occurs in relatively large amounts. The high C chromium-containing hot metal from which this slag is separated is the object of refining in this process. In actual operation, it is advantageous to separate the slag by receiving hot metal into a ladle from the combined blowing converter in which the previous two steps were carried out. Then, the received hot metal is charged into a decarburization refining furnace to perform decarburization refining. As this decarburization refining furnace, the combined blowing converter in which the previous two steps were carried out can be used, but another refining furnace can also be used. As this other refining furnace, a combined blowing converter, a ladle refining furnace, for example a VOD furnace, etc. can be used. In any case, these smelting furnaces may be of any type as long as they can suppress the oxidation loss of Cr and decarburize to the target C level, that is, the low carbon range. That is, typically, any method used in the production of conventional molten stainless steel, such as decarburization refining while stirring hot metal with an inert gas under atmospheric pressure, or decarburization refining under reduced pressure, etc. decarburization smelting furnaces can be used. In the method of the present invention, since a large amount of coke is added in the previous step, the S concentration in the obtained high-C chromium-containing hot metal increases in proportion to the amount of coke. For this reason, desulfurization treatment is required, but this can be done either by adding a desulfurizing agent and desulfurizing the iron in the ladle after the previous process is finished, or by performing normal desulfurization after decarburization and refining. Just carry out the processing. When a combined blowing converter is used as a decarburization refining furnace, Cr 2 O 3 that is inevitably generated during the decarburization reaction can be reduced and recovered by adding Si in this furnace. In addition, when a converter and a ladle smelting furnace are used together, both crude molten steel and slag obtained in the converter are transferred to a ladle smelting furnace, and this smelting furnace is used to process Si.
can be added to recover chromium. Next, typical examples of the method of the present invention will be described. Example 1 C: 4.0%, Cr: 16.8%, melted in electric furnace
S: 45 tons of 0.008% hot metal was charged into a composite blowing converter, 3 tons of chromium ore and 290 kg of silica sand, whose composition is shown in Table 1, were added, and bottom blowing N 2 : 85 Nm 3 /Hr×
1 tuyere, top-blown oxygen: flow rate 5200Nm 3 /Hr, lance height 1400mm. Oxygen blowing was started, and the oxygen supply amount was increased to 1000Nm 3 to melt the chromium ore. The ore has completely turned into molten slag. At this time, the C concentration was 2.1%, Cr was 16.7%, the temperature was 1565℃, and the slag had a basicity (CaO/
SiO 2 ) was 1.2 and its melting temperature was 1480°C. In this example, 290 kg of silica sand was added, but the same result can be obtained even if an equivalent amount of Si is charged with FeSi instead of this silica sand (hereinafter referred to as chromium ore melt slag process).
【表】
ついで、コークスを2.5トン投入し、酸素をさ
らに1500Nm3供給した結果、Ｃ：2.0％、Cr：
17.8％、Ｓ：0.033％となり、クロム鉱石の約50
％が還元された。さらにコークスを1.5トン追加
投入し、酸素供給なしに30分保持した。その結果
溶銑の組成は、Ｃ：3.2％、Cr：18.7％、Ｓ：
0.043％となり、クロム鉱石中のCr2O3の約95％が
還元された。
その後、Fe−Siを投入して一部残存する未還
元CrのSiによる還元を実施した（加炭還元工
程）。
得られた高Ｃ含クロム溶銑を取鍋に受銑して、
これを別の複合吹錬転炉に移し、底吹きN2：
85Nm3／Hr×１羽口、酸素流量：6700Nm3／Hr
で15分間の脱炭精錬を行つた。その結果、Ｃ：
0.07％、Cr：18.2％、Ｓ：0.037％のステンレス溶
鋼が得られ、さらにFe−Si450Kg投入により吹錬
中に生成したCr2O3の還元を行い、また、
CaO500KgおよびCaF2150Kgの投入により脱硫処
理を行つた。その結果、Ｃ：0.05％、Cr：18.6
％、Ｓ：0.010％のステンレス溶鋼が得られた
（脱炭精錬工程）。
実施例 ２
母溶銑としてＣ：3.9％、Cr：8.5％、Ｓ：0.007
％の溶銑を使用した以外は、実施例１と同様のク
ロム鉱石の溶融滓化工程および加炭還元工程を繰
り返した。その結果、Ｃ：3.1％、Cr：10.5％、
Ｓ：0.045％の高Ｃ含クロム溶銑が得られた。
得られた高Ｃ含クロム溶銑を取鍋に受銑して、
これを別の複合吹錬転炉に移し、底吹きN2：
35Nm3／Hr×４羽口、酸素流量：7700Nm3／Hr
で13分間の脱炭精錬を行つた。その結果、Ｃ：
0.09％、Cr：10.0％、Ｓ：0.040％のステンレス溶
鋼が得られ、さらにFe−Si500Kg投入により吹錬
中に生成したCr2O3の還元を行つた結果、Ｃ：
0.05％、Cr：10.5％、Ｓ：0.04％のステンレス溶
鋼が得られた。この溶鋼は、次に、仕上精錬炉で
あるVOD炉において脱硫処理され、Ｓは0.005％
まで低下した。
比較例
本例は加炭を初期に行つた例である。
電気炉で溶解されたＣ：3.7％、Cr：19.8％、
Ｓ：0.007％の溶銑43トンを複合吹錬転炉に装入
し、同時に表１にその組成を示すクロム鉱石2.9
トン、コークス2.4トンおよびCaO1.4トンを添加
し、底吹きN2：50Nm3／Hr×２羽口、上吹き酸
素：流量5200Nm3／Hr、ランス高さ1600mmで酸
素吹錬を開始し、酸素供給量を3530Nm3まで送酸
し、Ｃ：0.71％までの吹錬を行つた。そのときの
温度は1745℃、スラグは、その融点が1720℃付近
の塩基度が高いものであつた。そして、酸素吹錬
後のCrは19.7％止まりでクロム鉱石中のCr2O3の
還元は殆ど進行しなかつた。これはクロム鉱石の
溶融が十分ではない状態でＣ濃度が0.71％まで低
下したからであろう。[Table] Next, 2.5 tons of coke was added and oxygen was further supplied at 1500Nm3 . As a result, C: 2.0%, Cr:
17.8%, S: 0.033%, about 50% of chromium ore
% was returned. An additional 1.5 tons of coke was added and held for 30 minutes without oxygen supply. As a result, the composition of the hot metal was C: 3.2%, Cr: 18.7%, S:
It was 0.043%, and about 95% of Cr 2 O 3 in the chromium ore was reduced. Thereafter, Fe-Si was introduced to reduce some of the remaining unreduced Cr with Si (carburization reduction step). The obtained high C chromium-containing hot metal is poured into a ladle,
Transfer this to another combined blowing converter and bottom blow N2 :
85Nm 3 /Hr x 1 tuyere, oxygen flow rate: 6700Nm 3 /Hr
Decarburization was carried out for 15 minutes. As a result, C:
0.07%, Cr: 18.2%, S: 0.037% stainless steel molten steel was obtained, and Cr 2 O 3 generated during blowing was reduced by adding 450 kg of Fe-Si.
Desulfurization treatment was carried out by adding 500 kg of CaO and 150 kg of CaF 2 . As a result, C: 0.05%, Cr: 18.6
%, S: 0.010% stainless molten steel was obtained (decarburization refining process). Example 2 Mother hot metal: C: 3.9%, Cr: 8.5%, S: 0.007
The same chromium ore slag slag process and carburization reduction process as in Example 1 were repeated, except that % hot metal was used. As a result, C: 3.1%, Cr: 10.5%,
High chromium-containing hot metal containing S: 0.045% was obtained. The obtained high C chromium-containing hot metal is poured into a ladle,
Transfer this to another combined blowing converter and bottom blow N2 :
35Nm 3 /Hr x 4 tuyeres, oxygen flow rate: 7700Nm 3 /Hr
Decarburization and refining was carried out for 13 minutes. As a result, C:
0.09%, Cr: 10.0%, S: 0.040% stainless steel molten steel was obtained, and as a result of reducing Cr 2 O 3 generated during blowing by adding 500 kg of Fe-Si, C:
A molten stainless steel containing 0.05%, Cr: 10.5%, and S: 0.04% was obtained. This molten steel is then desulfurized in a VOD furnace, which is a finishing refining furnace, and the S content is 0.005%.
It dropped to . Comparative Example This example is an example in which recarburization was performed at an early stage. C: 3.7%, Cr: 19.8%, melted in electric furnace
S: 43 tons of 0.007% hot metal was charged into a composite blowing converter, and at the same time 2.9 tons of chromium ore, the composition of which is shown in Table 1, was charged.
2.4 tons of coke and 1.4 tons of CaO were added, bottom-blown N 2 : 50Nm 3 /Hr x 2 tuyeres, top-blown oxygen: flow rate of 5200Nm 3 /Hr, and oxygen blowing was started with a lance height of 1600mm. Oxygen supply amount was increased to 3530Nm 3 and blowing was performed to C: 0.71%. The temperature at that time was 1745°C, and the slag had a high basicity with a melting point around 1720°C. The Cr content after oxygen blowing was only 19.7%, and the reduction of Cr 2 O 3 in the chromium ore hardly progressed. This is probably because the C concentration decreased to 0.71% when the chromium ore was not sufficiently melted.
Claims (1)
錬転炉に装入し、さらにフラツクスを溶融物のス
ラグ塩基度が0.5〜1.3となるように添加したう
え、底吹き攪拌を行いながら酸素上吹き吹錬して
クロム鉱石を溶融滓化するクロム鉱石の溶融工程
と、 この溶融滓化された溶融物にコークスを添加
し、酸素吹錬を実施するかまたはせずして高Ｃ含
クロム溶銑を製造する加炭還元工程と、 得られた高Ｃ含クロム溶銑を脱炭精錬する脱炭
精錬工程と、 からなるクロム鉱石の溶融還元法。 ２ 母溶銑は20重量％以下のCrを含有する含ク
ロム溶銑である特許請求の範囲第１項記載のクロ
ム鉱石の溶融還元法。 ３ 脱炭精錬工程は、クロム鉱石の溶融工程およ
び加炭還元工程とは別の精錬炉で実施する特許請
求の範囲第１項または第２項記載のクロム鉱石の
溶融還元法。[Scope of Claims] 1. Mother hot metal and chromium ore are charged into a composite blowing converter capable of top and bottom blowing, and flux is added so that the slag basicity of the melt becomes 0.5 to 1.3. A chromium ore melting process in which chromium ore is turned into a molten slag by top-blowing with oxygen while blowing and stirring, and with or without adding coke to the molten slag and carrying out oxygen blowing. A method for smelting and reducing chromium ore, comprising: a carburization reduction step for producing high-C chromium-containing hot metal; and a decarburization refining step for decarburizing the obtained high-C chromium-containing hot metal. 2. The method for melting and reducing chromium ore according to claim 1, wherein the mother hot metal is chromium-containing hot metal containing 20% by weight or less of Cr. 3. The chromium ore melting and reduction method according to claim 1 or 2, wherein the decarburization refining step is carried out in a smelting furnace separate from the chromium ore melting step and carburization reduction step.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9436985A JPS61253311A (en) | 1985-05-01 | 1985-05-01 | Method for melting and reducing chrome ore |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9436985A JPS61253311A (en) | 1985-05-01 | 1985-05-01 | Method for melting and reducing chrome ore |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS61253311A JPS61253311A (en) | 1986-11-11 |
| JPH0526841B2 true JPH0526841B2 (en) | 1993-04-19 |
Family
ID=14108400
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP9436985A Granted JPS61253311A (en) | 1985-05-01 | 1985-05-01 | Method for melting and reducing chrome ore |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS61253311A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| AT412349B (en) * | 2003-06-25 | 2005-01-25 | Voest Alpine Ind Anlagen | METHOD FOR PRODUCING AN ALLOYED METAL MELT AND PRODUCTION PLANT THEREFOR |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61166910A (en) * | 1985-01-18 | 1986-07-28 | Nippon Steel Corp | Production of chromium-containing alloy |
-
1985
- 1985-05-01 JP JP9436985A patent/JPS61253311A/en active Granted
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS61166910A (en) * | 1985-01-18 | 1986-07-28 | Nippon Steel Corp | Production of chromium-containing alloy |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS61253311A (en) | 1986-11-11 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP2947063B2 (en) | Stainless steel manufacturing method | |
| JPH0526841B2 (en) | ||
| JP4192503B2 (en) | Manufacturing method of molten steel | |
| JP3063537B2 (en) | Stainless steel manufacturing method | |
| JP2964861B2 (en) | Stainless steel manufacturing method | |
| JP2607328B2 (en) | Hot metal dephosphorization method | |
| JPS6247417A (en) | Melt refining method for scrap | |
| JP2607329B2 (en) | Hot metal dephosphorization method | |
| JPH0967608A (en) | Production of stainless steel | |
| JPH08319506A (en) | Method for dephosphorizing molten iron | |
| JP3414811B2 (en) | Recovery method of residual alloy components in slag after refining when smelting low alloy steel | |
| JPS5856005B2 (en) | High chromium steel melting method | |
| JPH01215917A (en) | Method for melting stainless steel | |
| JPS6152208B2 (en) | ||
| JP3173325B2 (en) | How to make stainless steel | |
| JPH0510403B2 (en) | ||
| JPH0673427A (en) | Method for refining molten high carbon iron being restrained from rephosphorization | |
| JPS61139614A (en) | Manufacture of steel | |
| JPH0841519A (en) | Steelmaking method | |
| JPH07310109A (en) | Production of stainless steel | |
| JPS6244533A (en) | Melting-reducing refining method for metallic oxide | |
| JPH02182820A (en) | Refining method for increasing mn-content in molten steel in converter | |
| JPH0328345A (en) | Production of low-phosphorus chromium alloy | |
| JPH01246309A (en) | Method for melting high alloy steel | |
| JPH01215951A (en) | Method for refining chromium-containing steel |