JP2008127597A - Ladle refining method - Google Patents

Ladle refining method Download PDF

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JP2008127597A
JP2008127597A JP2006311463A JP2006311463A JP2008127597A JP 2008127597 A JP2008127597 A JP 2008127597A JP 2006311463 A JP2006311463 A JP 2006311463A JP 2006311463 A JP2006311463 A JP 2006311463A JP 2008127597 A JP2008127597 A JP 2008127597A
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molten steel
ladle
flux
mass
refining
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Atsushi Tomioka
篤 富岡
Yasuyuki Ideta
保之 出田
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Kobe Steel Ltd
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Kobe Steel Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a ladle refining method which can be easily operated without changing pretreatment and facilities, and decreases the amount of sulfur and hydrogen contained in molten steel. <P>SOLUTION: This ladle refining method includes subjecting the molten steel to secondary treatment comprising the steps of adding a first flux of 5 to 8 kg per ton of the molten steel, which contains MgO of 95% or more but no CaO, before or during heating the molten steel poured into the ladle 3, and adding a second flux containing quicklime and/or calcium fluoride (CaF<SB>2</SB>) after having added the first flux into the molten steel so that slag after the refining step can acquire the following composition as a result of having added the first flux and the second flux; 20 to 40 mass% CaO, 20 to 30 mass% SiO<SB>2</SB>, 10 to 20 mass% CaF<SB>2</SB>, 20 to 25 mass% MgO, T. Fe+MnO+Cr<SB>2</SB>O<SB>3</SB>≤2.0 mass%, and (CaO+MgO)/SiO<SB>2</SB>:1.5 to 3.0. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、取鍋精錬での脱硫および脱ガス処理における取鍋精錬方法に関する。   The present invention relates to a ladle refining method in desulfurization and degassing treatment in ladle refining.

取鍋精錬は、転炉、電気炉等によって脱炭された溶鋼から不純物を除去し溶鋼の種々の成分の濃度を調製して例えば高清浄度の溶鋼を得る目的で広く行われている。取鍋精錬は、炉外精錬とも呼ばれ、転炉、電気炉等から溶鋼を受け入れた取鍋を精錬設備の一部として活用して行われる。
取鍋精錬は、脱硫および酸素、窒素、水素等の脱ガスが主に行われ、脱硫については、現在、生石灰（ＣａＯ）を含有するフラックスを溶鋼に添加して行うのが一般的である。
一方で、生石灰は水を吸収し易いという性質があり、水を吸収した（消石灰（Ｃａ（ＯＨ）2））、炭酸カルシウム（ＣａＣＯ2）を含む）生石灰を取鍋精錬に使用すると、溶鋼中の水素濃度が増加するという問題もある。図７は取鍋精錬に使用した生石灰の量と精錬により得られた溶鋼中の水素濃度との相関を示す図である。このように、生石灰の使用量と溶鋼中の水素濃度とに正の相関が見られ、従来、溶鋼に添加する前の生石灰を高温で乾燥させ、精錬後の溶鋼の水素濃度を低下させることも試みられていた。 Ladle refining is widely performed for the purpose of obtaining high-cleanness molten steel, for example, by removing impurities from molten steel decarburized by a converter, electric furnace, etc., and adjusting the concentrations of various components of the molten steel. Ladle refining, also called out-of-furnace refining, is performed using a ladle that has received molten steel from a converter, electric furnace, etc. as part of the refining equipment.
Ladle refining mainly involves desulfurization and degassing of oxygen, nitrogen, hydrogen, etc., and desulfurization is generally performed by adding flux containing quick lime (CaO) to molten steel.
On the other hand, quick lime has the property of being easy to absorb water, and when it is used for ladle refining that has absorbed water (including slaked lime (Ca (OH) 2 )) and calcium carbonate (CaCO 2 ), There is also a problem that the hydrogen concentration of the water increases. FIG. 7 is a diagram showing the correlation between the amount of quicklime used for ladle refining and the hydrogen concentration in the molten steel obtained by refining. Thus, there is a positive correlation between the amount of quicklime used and the hydrogen concentration in the molten steel. Conventionally, quicklime before being added to the molten steel can be dried at a high temperature to reduce the hydrogen concentration in the molten steel after refining. It was being tried.

また、水を吸収した生石灰を使用しても脱水素反応を促進させて溶鋼中の水素濃度を低減させることができる脱硫、脱水素装置も提案されている（特許文献１）。
特開平９−１７６７２５号公報 In addition, a desulfurization and dehydrogenation apparatus has been proposed that can accelerate the dehydrogenation reaction and reduce the hydrogen concentration in the molten steel even when quick lime that has absorbed water is used (Patent Document 1).
JP-A-9-176725

しかし、溶鋼に添加する前の生石灰を高温で脱水して精錬後の水素濃度を低下させる方法は、生石を乾燥させる工程を要することから、設備の増加、コストの上昇等の問題がある。
また、特許文献１に開示された技術では、かかる技術を実施するために特殊な構造の浸漬管を使用することから、取鍋精錬設備を改造する必要がある。
本発明は、上述の問題に鑑みてなされたもので、前処理および設備の変更を伴わずに簡便に実施することができ、溶鋼中の硫黄および水素の含有量が少ない取鍋精錬方法を提供することを目的とする。 However, the method of dehydrating quick lime before being added to the molten steel to reduce the hydrogen concentration after refining requires a step of drying the raw stone, and thus has problems such as an increase in equipment and cost.
Moreover, in the technique disclosed in Patent Document 1, since a dip tube having a special structure is used to implement such a technique, it is necessary to modify the ladle refining equipment.
The present invention has been made in view of the above problems, and can provide a ladle refining method that can be easily carried out without pretreatment and change of equipment, and that has low sulfur and hydrogen contents in molten steel. The purpose is to do.

前記目的を達成するため、本発明においては以下の技術的手段を講じた。
すなわち、本発明に係る取鍋精錬方法は、脱炭処理後の溶鋼を取鍋で受け、該取鍋で溶鋼の２次処理を行う取鍋精錬方法であって、前記取鍋に受けた前記溶鋼を昇温する前または昇温途中に、ＭｇＯ≧９５％、ＣａＯ＝０％である第１のフラックスを溶鋼１トンあたり５〜８ｋｇ添加し、前記第１のフラックスの添加後に、生石灰およびフッ化カルシウム（ＣａＦ2）を有する第２のフラックスを添加し、前記第１のフラックスおよび前記第２のフラックスの添加の結果として、精錬後のスラグが下記成分となるように溶鋼の２次処理を行う。 In order to achieve the above object, the present invention takes the following technical means.
That is, the ladle refining method according to the present invention is a ladle refining method for receiving molten steel after decarburization treatment with a ladle and performing secondary treatment of molten steel with the ladle, the ladle refining method Before or during the temperature rise of the molten steel, 5 to 8 kg of a first flux with MgO ≧ 95% and CaO = 0% is added per ton of molten steel, and after the addition of the first flux, quick lime and fluorine are added. A second flux containing calcium fluoride (CaF 2 ) is added, and as a result of the addition of the first flux and the second flux, secondary treatment of the molten steel is performed so that the slag after refining becomes the following components Do.

ＣａＯ ：２０〜４０ｍａｓｓ％
ＳｉＯ2 ：２０〜３０ｍａｓｓ％
ＣａＦ2 ：１０〜２０ｍａｓｓ％
ＭｇＯ ：２０〜２５ｍａｓｓ％
Ｔ．Ｆｅ＋ＭｎＯ＋Ｃｒ2Ｏ3 ≦２．０ｍａｓｓ％
（ＣａＯ＋ＭｇＯ）／ＳｉＯ2 ：１．５〜３．０ CaO: 20 to 40 mass%
SiO 2: 20~30mass%
CaF2: 10 to 20 mass%
MgO: 20-25 mass%
T.A. Fe + MnO + Cr 2 O 3 ≦ 2.0 mass%
(CaO + MgO) / SiO 2 : 1.5 to 3.0

本発明によると、前処理および設備の変更を伴わずに簡便に実施することができ、溶鋼中の硫黄および水素の含有量が少ない取鍋精錬方法を提供することができる。   According to the present invention, it is possible to provide a ladle refining method that can be easily carried out without pretreatment and change of equipment, and that contains a small amount of sulfur and hydrogen in the molten steel.

図１は取鍋精錬の過程を示す図である。
図１において、取鍋精錬は取鍋精錬装置１および真空脱ガス装置２により行われる。
取鍋精錬装置１は、取鍋３、炉蓋４、加熱装置５および載置台６等で形成される。
取鍋３は、転炉、電気炉等において精錬鋼された溶鋼を受けるための容器でもある。取鍋３の底部には、装入された溶鋼内にＡｒなどの攪拌ガスを吹き込むための吹き込み口（ポーラス）７が設けられている。
炉蓋４は取鍋３の上端開口部を覆うためのものである。炉蓋４には、取鍋精錬の原料である生石灰（ＣａＯ）およびマグネシア（ＭｇＯ）等を取鍋３内の溶鋼に添加するための投入路８が設けられている。 FIG. 1 is a diagram showing a ladle refining process.
In FIG. 1, ladle refining is performed by a ladle refining apparatus 1 and a vacuum degassing apparatus 2.
The ladle refining device 1 is formed of a ladle 3, a furnace lid 4, a heating device 5, a mounting table 6, and the like.
The ladle 3 is also a container for receiving molten steel refined in a converter, electric furnace or the like. The bottom of the ladle 3 is provided with a blowing port (porous) 7 for blowing a stirring gas such as Ar into the charged molten steel.
The furnace lid 4 is for covering the upper end opening of the ladle 3. The furnace lid 4 is provided with a charging path 8 for adding quick lime (CaO), magnesia (MgO), etc., which are raw materials for ladle refining, to the molten steel in the ladle 3.

加熱装置５はアーク放電を行う複数の電極９，９，９からなり、電極９，９，９は炉蓋４を貫通して先端が取鍋３の内部に達している。
炉蓋４および加熱装置５のいずれも取鍋３に着脱可能に構成されている。
載置台６は取鍋３を支持するためのものであり、軌道上を移動する図示しない台車の上に設けられている。載置台６には、取鍋３の吹き込み口７に連通するガス導入管１０が設けられている。ガス導入管１０は、図示しないアルゴン供給装置に連通している。
真空脱ガス装置２は、取鍋３、密閉炉蓋１１および載置台６等で形成される。 The heating device 5 includes a plurality of electrodes 9, 9, 9 that perform arc discharge. The electrodes 9, 9, 9 pass through the furnace lid 4 and the tip reaches the inside of the ladle 3.
Both the furnace lid 4 and the heating device 5 are configured to be detachable from the ladle 3.
The mounting table 6 is for supporting the ladle 3 and is provided on a cart (not shown) that moves on the track. The mounting table 6 is provided with a gas introduction pipe 10 that communicates with the inlet 7 of the ladle 3. The gas introduction pipe 10 communicates with an argon supply device (not shown).
The vacuum degassing apparatus 2 is formed by a ladle 3, a closed furnace lid 11, a mounting table 6, and the like.

取鍋３は取鍋精錬装置１の主要な構成である。取鍋３の底部には、溶鋼内にアルゴンガスを吹き込んで溶鋼を撹拌するため吹き込み口７が設けられている。
密閉炉蓋１１は、取鍋３の上端開口部をパッキン等を介在させて密閉状態に維持するためのものである。密閉炉蓋１１には、図示しない減圧装置に連通し密閉された取鍋３の内部を減圧にするための排気管１２が貫通している。
次に、本発明にかかる取鍋精錬方法について説明する。
図２は本発明にかかる取鍋精錬における各処理を示すフローチャートである。 The ladle 3 is a main component of the ladle refining apparatus 1. The bottom of the ladle 3 is provided with a blowing port 7 for blowing argon gas into the molten steel and stirring the molten steel.
The closed furnace lid 11 is for maintaining the upper end opening of the ladle 3 in a sealed state with a packing or the like interposed therebetween. An exhaust pipe 12 for reducing the pressure inside the ladle 3 communicated and sealed with a decompression device (not shown) passes through the sealed furnace lid 11.
Next, the ladle refining method according to the present invention will be described.
FIG. 2 is a flowchart showing each process in the ladle refining according to the present invention.

電気炉または転炉で脱炭された溶鋼を収容した取鍋３は、搬送用の台車に積載される（＃１１）。取鍋３内の溶鋼に底部の吹き込み口７からアルゴンガスを噴出させ（＃１２）、上昇するアルゴンガスによって溶鋼に上昇流れと下降流れとを生じさせて撹拌が行われる。撹拌開始後に、投入路８からマグネシアを９５％以上含み生石灰（ＣａＯ）を含まない（ＣａＯ＝０％）フラックス（ＭｇＯクリンカー）が所定量溶鋼内に添加される（＃１３）。ここでいうフラックスは、本発明における第１のフラックスである。
続いて取鍋３を積載した台車は加熱ステーションに移動される（＃１４）。加熱ステーションでは取鍋３に炉蓋４および加熱装置５が取り付けられ、加熱装置５に電流が供給されてアーク放電によって取鍋３内の溶鋼の昇温が開始される（＃１５）。 The ladle 3 containing the molten steel decarburized in the electric furnace or converter is loaded on a carriage for transportation (# 11). Argon gas is blown into the molten steel in the ladle 3 from the blowing port 7 at the bottom (# 12), and the ascending flow and the descending flow are generated in the molten steel by the rising argon gas, and stirring is performed. After the start of stirring, a predetermined amount of flux (MgO clinker) containing 95% or more magnesia and not containing quick lime (CaO) is added from the charging path 8 into the molten steel (# 13). The flux here is the first flux in the present invention.
Subsequently, the cart loaded with the ladle 3 is moved to the heating station (# 14). In the heating station, the furnace lid 4 and the heating device 5 are attached to the ladle 3, current is supplied to the heating device 5, and the temperature rise of the molten steel in the ladle 3 is started by arc discharge (# 15).

昇温開始後速やかに生石灰およびフッ化カルシウム（ＣａＦ2）のそれぞれ所定量が投入路８から溶鋼内に添加される（＃１６）。この生石灰およびフッ化カルシウムは、本発明における第２のフラックスである。
ところで、生石灰を添加する前に添加されたマグネシアはスラグの流動性を悪化させる働きがある。そこで、マグネシアを取鍋３に添加すると、溶鋼の上面のスラグ層の動きが遅くなる。この動きが遅く安定したスラグ層の上に水分を含む生石灰が添加されると、スラグ層の動きが遅いために生石灰がスラグ層の上にしばらく滞留し、その間に溶鋼からの高熱によって脱水される。つまり、生石灰は、溶鋼内に捲き込まれる前しばらくの間はマグネシア層の上で脱水されるために、溶鋼内に持ち込まれる水分量が激減することになる。その結果、溶鋼内の水素含有量が低下する。このように、マグネシアが溶鋼内に添加された後に生石灰を添加することが、取鍋精錬後の溶鋼内の水素含有量の低減に重要である。 A predetermined amount of quicklime and calcium fluoride (CaF 2 ) is added from the charging path 8 into the molten steel immediately after the start of temperature increase (# 16). This quicklime and calcium fluoride are the second flux in the present invention.
By the way, magnesia added before adding quicklime has the function of deteriorating the fluidity of slag. Therefore, when magnesia is added to the ladle 3, the movement of the slag layer on the upper surface of the molten steel becomes slow. When quick lime containing moisture is added on the slow and stable slag layer, the slag layer moves slowly, so the quick lime stays on the slag layer for a while and is dehydrated by the high heat from the molten steel. . That is, quick lime is dehydrated on the magnesia layer for a while before being poured into the molten steel, so that the amount of moisture brought into the molten steel is drastically reduced. As a result, the hydrogen content in the molten steel is reduced. Thus, it is important for the reduction | restoration of the hydrogen content in the molten steel after ladle refining to add quick lime after magnesia is added in the molten steel.

なお、フッ化カルシウムはスラグの流動性を良好にする働きがあり、添加後徐々にスラグに混入して流動性を改善し、生石灰による脱硫反応の進行を促進させる。
続いて、予め採取した溶鋼サンプルの成分分析結果に基づいて、溶鋼の成分を調製するための合金添加が行われる（＃１７）。
合金添加後、スラグの流動性とスラグの色との観察およびスラグサンプルを採取し分析することのいずれかまたはいずれも行い、生石灰の量が不足する場合には必要量の生石灰を添加してスラグの成分の調製を行う（＃１８）。 Calcium fluoride has a function of improving the fluidity of the slag, and is gradually mixed into the slag after the addition to improve the fluidity and promote the progress of the desulfurization reaction with quick lime.
Subsequently, based on the component analysis result of the molten steel sample collected in advance, alloy addition for preparing the molten steel component is performed (# 17).
After adding the alloy, observe and / or observe slag fluidity and slag color and collect and analyze slag samples. If the amount of quicklime is insufficient, add the required amount of quicklime and add slag. Is prepared (# 18).

溶鋼が所定の温度にまで昇温したら（＃１９でＹＥＳ）加熱装置５および炉蓋４が取り外され、台車は真空ステーションまで移動される（＃２０）。
真空ステーションでは取鍋３に密閉炉蓋１１が取り付けられ、排気装置に接続された排気管１２から取鍋３内の排気が行われることにより溶鋼の真空脱ガス処理が行われる（＃２１）。なお、これまでの処理において断えることなく取鍋３の底部の吹き込み口７からアルゴンガスが溶鋼内に噴出され続ける。
所定時間真空脱ガス処理を行った後（＃２２でＹＥＳ）密閉炉蓋１１が取り外され、台車は再び加熱ステーションに移動される（＃２３）。溶鋼からサンプルが採取され、成分分析されて最終の成分調製のために合金添加が行われる。また、加熱ステーションでは取鍋３に炉蓋４および加熱装置５が取り付けられて、溶鋼温度の最終調整も行われる（＃２４）。 When the molten steel is heated to a predetermined temperature (YES in # 19), the heating device 5 and the furnace lid 4 are removed, and the carriage is moved to the vacuum station (# 20).
In the vacuum station, the closed furnace lid 11 is attached to the ladle 3 and the inside of the ladle 3 is evacuated from the exhaust pipe 12 connected to the exhaust device, whereby the molten steel is vacuum degassed (# 21). It should be noted that argon gas continues to be blown into the molten steel from the blowing port 7 at the bottom of the ladle 3 without any notice in the processing so far.
After performing vacuum degassing for a predetermined time (YES in # 22), the closed furnace lid 11 is removed, and the carriage is moved again to the heating station (# 23). A sample is taken from the molten steel, analyzed for ingredients, and alloyed for final component preparation. At the heating station, the furnace lid 4 and the heating device 5 are attached to the ladle 3 and the final adjustment of the molten steel temperature is also performed (# 24).

以上が取鍋精錬の工程である。溶鋼の成分調製および温度調整が終了するとアルゴンガスの噴出が停止される。溶鋼を収容する取鍋３は、炉蓋４および加熱装置５が取り外され吊り上げられて造塊工程に移動されて（＃２５）、取鍋精錬が終了する。
次に、本発明にかかる取鍋精錬方法におけるスラグ形成物の添加量について説明する。
取鍋精錬後の溶鋼における水素含有率２ｐｐｍ以下および硫黄含有率０．００５％以下を目標に、この目標に至らなかった取鍋精錬を比較例およびこの目標を達成した取鍋精錬を実施例として表１に示す。 The above is the ladle refining process. When the preparation of the molten steel and the temperature adjustment are completed, the ejection of argon gas is stopped. The ladle 3 containing the molten steel is removed by lifting the furnace lid 4 and the heating device 5 and moved to the ingot-making process (# 25), and the ladle refining is completed.
Next, the addition amount of the slag formation product in the ladle refining method according to the present invention will be described.
Taking the ladle smelting that did not reach this target as a comparative example and the ladle smelting that achieved this target as an example, aiming for a hydrogen content of 2 ppm or less and a sulfur content of 0.005% or less in molten steel after ladle refining Table 1 shows.

表１における比較例４〜１６および実施例１〜４は、図２に示される方法で取鍋精錬されたものであり、比較例１〜３はマグネシアと生石灰の添加順序を図２と逆にしたほかは、また比較例１７はＭｇＯ源としてドロマイト（ＣａＯ：４０％，ＭｇＯ：６０％）を使用したほかは、図２に示される方法で取鍋精錬されたものである。
Comparative Examples 4 to 16 and Examples 1 to 4 in Table 1 were smelted in a ladle by the method shown in FIG. 2, and Comparative Examples 1 to 3 reversed the order of addition of magnesia and quicklime from FIG. 2. In addition, Comparative Example 17 was smelted in a ladle by the method shown in FIG. 2 except that dolomite (CaO: 40%, MgO: 60%) was used as the MgO source.

Figure 2008127597
図３は表１における溶鋼へのＭｇＯ添加量とスラグ中のＭｇＯ濃度との関係を示す図、図４は表１における溶鋼へのＣａＯ添加量とスラグ中のＣａＯ濃度との関係を示す図、図５は表１における溶鋼へのＣａＦ2添加量とスラグ中のＣａＦ2濃度との関係を示す図、図６は表１における溶鋼へのＭｇＯ添加量およびＭｇＯ添加量÷ＣａＯ添加量と精錬結果との関係を示す図である。なお、図３〜６におけるキー○は精錬結果が良好（目標：溶鋼中の水素が２ｐｐｍ以下かつ硫黄が０．００５％以下）な実施例１〜４を示し、キー■は得られた溶鋼中の水素または硫黄のいずれかの含有率が目標値以上であった比較例１〜１４（図６では比較例４〜１４）を示す。
Figure 2008127597
 FIG. 3 is a diagram showing the relationship between the amount of MgO added to the molten steel and the MgO concentration in the slag in Table 1, and FIG. 4 is a diagram showing the relationship between the amount of CaO added to the molten steel and the CaO concentration in the slag in Table 1. Figure 5 is CaF 2 amount and diagram showing the relationship between CaF 2 concentration in the slag, 6 refining result and MgO amount and MgO amount ÷ CaO addition amount of the molten steel in Table 1 to the molten steel in Table 1 It is a figure which shows the relationship. 3 to 6 show Examples 1 to 4 in which the refining results are good (target: hydrogen in molten steel is 2 ppm or less and sulfur is 0.005% or less), and key ■ is in the obtained molten steel. Comparative Examples 1 to 14 (Comparative Examples 4 to 14 in FIG. 6) in which the content of either hydrogen or sulfur was equal to or higher than the target value are shown.

表１に示されるように、取鍋精錬後の溶鋼の水素含有率および硫黄含有率のいずれも目標値を達成した実施例１〜４では、
（１） マグネシアを添加した後に生石灰を添加
（２） 溶鋼へのマグネシアの添加量が溶鋼１トンあたり約５〜８ｋｇ
（３） 精錬後のスラグ組成
ＣａＯ ：２０〜４０ｍａｓｓ％
ＳｉＯ2 ：２０〜３０ｍａｓｓ％
ＣａＦ2 ：１０〜２０ｍａｓｓ％
ＭｇＯ ：２０〜２５ｍａｓｓ％
（Ｔ．Ｆｅ＋ＭｎＯ＋Ｃｒ2Ｏ3） ≦１．９ｍａｓｓ％
（ＣａＯ＋ＭｇＯ）／ＳｉＯ2 ：１．５〜３．０
となっている。 As shown in Table 1, in Examples 1 to 4 in which both the hydrogen content and the sulfur content of the molten steel after ladle refining achieved the target values,
(1) Add quick lime after adding magnesia (2) Addition of magnesia to molten steel is about 5-8kg per ton of molten steel
(3) Slag composition after refining CaO: 20 to 40 mass%
SiO 2: 20~30mass%
CaF2: 10 to 20 mass%
MgO: 20-25 mass%
(T.Fe + MnO + Cr 2 O 3 ) ≦ 1.9 mass%
(CaO + MgO) / SiO 2 : 1.5 to 3.0
It has become.

ここで「Ｔ．Ｆｅ」とは全鉄分をいう。
精錬後のスラグを上記（３）のような組成にするためには、図３〜５に示されるように、生石灰（ＣａＯ）をほとんど含まない純度９５％以上のマグネシアを溶鋼トンあたり５〜８ｋｇ、生石灰を溶鋼トンあたり３〜５ｋｇ、およびフッ化カルシウムを溶鋼トンあたり３．５〜９ｋｇ添加するのが好ましい。また、図６に示されるように、溶鋼に添加するマグネシアと生石灰との比率は１．２３〜１．７３にするのが好ましい。
上に説明したマグネシア、生石灰およびフッ化カルシウムの添加量ならびに添加するマグネシアと生石灰との比率を調整すれば、通常、添加される合金に含まれる珪素（Ｓｉ）、マンガン（Ｍｎ）およびクロム（Ｃｒ）から生ずる酸化珪素（ＳｉＯ2）、酸化マンガン（ＭｎＯ）および酸化クロム（Ｃｒ2Ｏ3）により、精錬後のスラグ組成は上述の（３）のようになる。 Here, “T.Fe” means the total iron content.
In order to make the slag after refining into the composition as in the above (3), as shown in FIGS. 3 to 5, magnesia having a purity of 95% or more and containing almost no quick lime (CaO) is 5 to 8 kg per ton of molten steel. It is preferable to add 3-5 kg of quicklime per ton of molten steel and 3.5-9 kg of calcium fluoride per ton of molten steel. Moreover, as FIG. 6 shows, it is preferable that the ratio of magnesia and quicklime added to molten steel shall be 1.23-1.73.
By adjusting the amount of magnesia, quicklime and calcium fluoride and the ratio of magnesia and quicklime to be added as described above, silicon (Si), manganese (Mn) and chromium (Cr ) The slag composition after refining is as described in (3) above, due to silicon oxide (SiO 2 ), manganese oxide (MnO) and chromium oxide (Cr 2 O 3 ) produced from the above.

しかし、前工程である脱炭処理における酸素吹き込み量、製錬工程で添加されるスクラップ等の影響により精錬後のスラグ組成を上述の（３）の範囲に収められないことが、精錬途中のスラグ分析等により予測できる場合には、生石灰をさらに添加して精錬後のスラグ組成が上記（３）になるように調製される（＃１８）。
このように、本発明によれば、取鍋精錬において溶鋼へのスラグの添加をマグネシア、生石灰の順で行い、かつこれらの添加量および添加量比ならびにフッ化カルシウムの添加量を所定の範囲内で決定することにより、溶鋼に特別な前処理を施すことなく良質な溶鋼が得られる取鍋精錬を行うことができる。したがって、本発明の取鍋精錬方法では、精錬設備の変更を伴わずに簡便に実施することができ、品質の向上に伴うコストアップを防止することができる。 However, the slag composition during refining cannot be within the range of the above (3) due to the influence of the amount of oxygen blown in the decarburization process, the scrap added in the refining process, etc. When it can be predicted by analysis or the like, quick lime is further added so that the slag composition after refining is adjusted to the above (3) (# 18).
Thus, according to the present invention, in the ladle refining, slag is added to molten steel in the order of magnesia and quick lime, and the addition amount and addition ratio and the addition amount of calcium fluoride are within a predetermined range. By deciding in (1), ladle refining can be performed in which high quality molten steel can be obtained without any special pretreatment of the molten steel. Therefore, in the ladle refining method of the present invention, it can be easily carried out without changing the refining equipment, and the cost increase accompanying the improvement in quality can be prevented.

上述の実施形態において、図２に示されたフローチャートにおける各処理、取鍋装置１、ならびに取鍋装置１および真空脱ガス装置２の各構成または全体の構造、形状、寸法、個数、材質などは、本発明の趣旨に沿って適宜変更することができる。   In the above-described embodiment, each process in the flowchart shown in FIG. 2, the ladle device 1, and each configuration or overall structure, shape, size, number, material, etc. of the ladle device 1 and the vacuum degassing device 2 are as follows: These can be appropriately changed in accordance with the spirit of the present invention.

本発明は、取鍋精錬における脱硫、脱水素方法に利用することができる。   The present invention can be used for desulfurization and dehydrogenation methods in ladle refining.

図１は取鍋精錬の過程を示す図である。FIG. 1 is a diagram showing a ladle refining process. 図２は本発明にかかる取鍋精錬における各処理を示すフローチャートである。FIG. 2 is a flowchart showing each process in the ladle refining according to the present invention. 図３は表１における溶鋼へのＭｇＯ添加量とスラグ中のＭｇＯ濃度との関係を示す図である。FIG. 3 is a diagram showing the relationship between the amount of MgO added to the molten steel in Table 1 and the MgO concentration in the slag. 図４は表１における溶鋼へのＣａＯ添加量とスラグ中のＣａＯ濃度との関係を示す図である。FIG. 4 is a diagram showing the relationship between the amount of CaO added to the molten steel in Table 1 and the concentration of CaO in the slag. 図５は表１における溶鋼へのＣａＦ2添加量とスラグ中のＣａＦ2濃度との関係を示す図である。FIG. 5 is a diagram showing the relationship between the amount of CaF 2 added to the molten steel and the CaF 2 concentration in the slag in Table 1. 図６は表１における溶鋼へのＭｇＯ添加量およびＭｇＯ添加量÷ＣａＯ添加量と精錬結果との関係を示す図である。FIG. 6 is a diagram showing the relationship between the amount of MgO added to molten steel and the amount of MgO added / the amount of CaO added to the molten steel in Table 1 and the refining results. 図７は取鍋精錬に使用した生石灰の量と精錬により得られた溶鋼中の水素濃度との相関を示す図である。FIG. 7 is a diagram showing the correlation between the amount of quicklime used for ladle refining and the hydrogen concentration in the molten steel obtained by refining.

符号の説明Explanation of symbols

３ 取鍋 3 Ladle

Claims (1)

脱炭処理後の溶鋼を取鍋で受け、該取鍋で溶鋼の２次処理を行う取鍋精錬方法であって、
前記取鍋に受けた前記溶鋼を昇温する前または昇温途中に、ＭｇＯ≧９５％、ＣａＯ＝０％である第１のフラックスを溶鋼１トンあたり５〜８ｋｇ添加し、
前記第１のフラックスの添加後に、生石灰およびフッ化カルシウム（ＣａＦ2）を有する第２のフラックスを添加し、
前記第１のフラックスおよび前記第２のフラックスの添加の結果として、精錬後のスラグが下記成分となるように溶鋼の２次処理を行う
ことを特徴とする取鍋精錬方法。
ＣａＯ ：２０〜４０ｍａｓｓ％
ＳｉＯ2 ：２０〜３０ｍａｓｓ％
ＣａＦ2 ：１０〜２０ｍａｓｓ％
ＭｇＯ ：２０〜２５ｍａｓｓ％
Ｔ．Ｆｅ＋ＭｎＯ＋Ｃｒ2Ｏ3 ≦２．０ｍａｓｓ％
（ＣａＯ＋ＭｇＯ）／ＳｉＯ2 ：１．５〜３．０ A ladle refining method for receiving molten steel after decarburization treatment with a ladle and performing secondary treatment of molten steel with the ladle,
Before or during the temperature increase of the molten steel received in the ladle, 5-8 kg of 1st flux of MgO ≧ 95% and CaO = 0% is added per ton of molten steel,
After the addition of the first flux, a second flux having quick lime and calcium fluoride (CaF 2 ) is added,
As a result of the addition of the first flux and the second flux, secondary treatment of molten steel is performed so that the slag after refining has the following components.
CaO: 20 to 40 mass%
SiO 2: 20~30mass%
CaF2: 10 to 20 mass%
MgO: 20-25 mass%
T.A. Fe + MnO + Cr 2 O 3 ≦ 2.0 mass%
(CaO + MgO) / SiO 2 : 1.5 to 3.0
JP2006311463A 2006-11-17 2006-11-17 Ladle refining method Pending JP2008127597A (en)

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