JP6322065B2 - Stainless steel manufacturing method - Google Patents
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- JP6322065B2 JP6322065B2 JP2014128645A JP2014128645A JP6322065B2 JP 6322065 B2 JP6322065 B2 JP 6322065B2 JP 2014128645 A JP2014128645 A JP 2014128645A JP 2014128645 A JP2014128645 A JP 2014128645A JP 6322065 B2 JP6322065 B2 JP 6322065B2
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- 238000004519 manufacturing process Methods 0.000 title claims description 21
- 239000010935 stainless steel Substances 0.000 title claims description 21
- 229910001220 stainless steel Inorganic materials 0.000 title claims description 21
- 239000002893 slag Substances 0.000 claims description 104
- 229910045601 alloy Inorganic materials 0.000 claims description 43
- 239000000956 alloy Substances 0.000 claims description 43
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 16
- 229910052710 silicon Inorganic materials 0.000 claims description 6
- 238000006243 chemical reaction Methods 0.000 description 16
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 14
- 229910000831 Steel Inorganic materials 0.000 description 14
- 239000010959 steel Substances 0.000 description 14
- 239000007789 gas Substances 0.000 description 13
- 238000000034 method Methods 0.000 description 11
- 229910052799 carbon Inorganic materials 0.000 description 8
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 7
- 239000000395 magnesium oxide Substances 0.000 description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 6
- 238000007254 oxidation reaction Methods 0.000 description 6
- 239000002994 raw material Substances 0.000 description 6
- 238000009835 boiling Methods 0.000 description 5
- 238000002844 melting Methods 0.000 description 5
- 230000008018 melting Effects 0.000 description 5
- 230000003647 oxidation Effects 0.000 description 5
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 4
- 229910017060 Fe Cr Inorganic materials 0.000 description 4
- 229910002544 Fe-Cr Inorganic materials 0.000 description 4
- 235000011941 Tilia x europaea Nutrition 0.000 description 4
- UPHIPHFJVNKLMR-UHFFFAOYSA-N chromium iron Chemical compound [Cr].[Fe] UPHIPHFJVNKLMR-UHFFFAOYSA-N 0.000 description 4
- 229910052742 iron Inorganic materials 0.000 description 4
- 239000004571 lime Substances 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 4
- 239000002184 metal Substances 0.000 description 4
- 229910052804 chromium Inorganic materials 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 239000010410 layer Substances 0.000 description 3
- 229910000604 Ferrochrome Inorganic materials 0.000 description 2
- 229910000863 Ferronickel Inorganic materials 0.000 description 2
- 235000019738 Limestone Nutrition 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000009749 continuous casting Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000010891 electric arc Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 239000006028 limestone Substances 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 229910000519 Ferrosilicon Inorganic materials 0.000 description 1
- 229910001030 Iron–nickel alloy Inorganic materials 0.000 description 1
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 1
- 239000013626 chemical specie Substances 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000005261 decarburization Methods 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 230000003009 desulfurizing effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000006260 foam Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000011572 manganese Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000010079 rubber tapping Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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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
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
Description
本発明は、ステンレス鋼の製造方法に係るものであり、電気炉にてスラグの塩基度および合金溶湯のＳｉ濃度を適正値に制御することで、溶製した合金溶湯を取鍋に注ぐ際に発生するスラグボイルを防止する技術に関する。 The present invention relates to a method for producing stainless steel, and when the molten alloy melt is poured into a ladle by controlling the basicity of the slag and the Si concentration of the alloy melt to appropriate values in an electric furnace. The present invention relates to a technology for preventing generated slag boil.
ステンレス鋼の製造は、電気炉にてスクラップ、Ｆｅ−Ｃｒ、Ｆｅ−Ｎｉなどの原料を溶解し、その後、ＡＯＤあるいはＶＯＤにて脱炭、Ｃｒ還元、脱硫することで製造することが一般的である。Ｆｅ−Ｃｒは炭素濃度が高いために、溶解後の溶鋼中Ｃ濃度は１〜４％となる。電気炉で溶解する際に、スラグ中にＣｒ酸化物が存在すると、溶鋼中のＣとスラグ中のＣｒ酸化物が反応してＣＯガスを発生させ沸騰（スラグボイル）現象を起こす。特に、溶鋼とスラグが混合された場合には、反応が起こる両者の界面が増大し、スラグボイルが激しくなり、取鍋からスラグがオーバーフローする問題があった。 Stainless steel is generally manufactured by melting raw materials such as scrap, Fe-Cr, Fe-Ni, etc. in an electric furnace, and then decarburizing, reducing Cr, and desulfurizing with AOD or VOD. is there. Since Fe-Cr has a high carbon concentration, the C concentration in the molten steel after melting is 1 to 4%. When Cr oxide is present in the slag during melting in the electric furnace, C in the molten steel reacts with Cr oxide in the slag to generate CO gas and cause a boiling (slag boil) phenomenon. In particular, when molten steel and slag are mixed, there is a problem that the interface between the two where the reaction occurs increases, the slag boil becomes intense, and the slag overflows from the ladle.
現在までに、ステンレス鋼の電気炉操業では、スラグ中のＣｒ酸化物濃度を低下させて、Ｃｒロスを極力抑えるといった改善はなされてきた（例えば、特許文献１参照）。 To date, in stainless steel electric furnace operations, improvements have been made such as reducing the Cr oxide concentration in the slag and minimizing Cr loss (see, for example, Patent Document 1).
また、電気炉スラグの塩基度（ｍａｓｓ％ＣａＯ／ｍａｓｓ％ＳｉＯ２比率）を適正にして脱硫能力を確保する技術開発はなされてきた（例えば、特許文献２参照）。 Further, technical development has been made to ensure the desulfurization capability by making the basicity (mass% CaO / mass% SiO 2 ratio) of the electric furnace slag appropriate (see, for example, Patent Document 2).
しかしながら、溶鋼中のＣとスラグ中のＣｒ酸化物が反応してＣＯガスを発生させるスラグボイル現象は解決したとは言い難かった。 However, it has been difficult to say that the slag boil phenomenon in which C in molten steel and Cr oxide in slag react to generate CO gas has been solved.
上述のステンレス鋼の製造方法を詳述すると、原料をまず電気炉で溶解する。ここに石灰を投入して、昇温時に生成した酸化物を滓化し、合金溶湯の保温性を高めると共に、大気酸化を防止する役目を持つスラグを形成させた後、合金溶湯を取鍋に注ぎ、後の精錬工程に運ぶ。このスラグを伴う合金溶湯を取鍋に注いでいる最中に鍋内でスラグが発泡して沸き上がるスラグボイルという現象が起きる。スラグが鍋の外に溢れ出すと周辺設備の故障や火災に繋がるため、大変危険である。従って、注湯中にスラグボイルが発生したら沈静化するまで注湯作業を停止するしかないため、大幅な操業遅延による製造コストの増加を招く。また、スラグを除去して注湯すると、取鍋で多量の造滓剤を投入することになり、多大なコストがかかるのと同時に、造滓剤の溶解に熱を大きく奪われるため、合金溶湯の温度が大幅に低下し表層部が凝固してしまう。 The above-described method for producing stainless steel will be described in detail. First, the raw material is melted in an electric furnace. Lime is added here to hatch the oxide generated at the time of temperature rise, improve the heat retention of the molten alloy, and form slag that has the role of preventing atmospheric oxidation, and then pour the molten alloy into the ladle. And carry it to the later refining process. During the pouring of the molten alloy with slag into the ladle, a phenomenon called slag voiling occurs in which the slag foams and boils in the ladle. If the slag overflows from the pan, it will lead to failure of surrounding equipment and fire, which is very dangerous. Therefore, if slag voiling occurs during pouring, the pouring operation must be stopped until it settles down, resulting in an increase in manufacturing cost due to a significant delay in operation. In addition, if the slag is removed and poured, a large amount of the slagging agent is introduced in the ladle, which is very expensive and at the same time, the melting of the slagging agent is greatly deprived of heat. The temperature of the layer will drop significantly and the surface layer will solidify.
そこで、本発明では、電気炉でのスラグの塩基度および合金溶湯のＳｉ濃度を適正値に制御することで、溶製した合金溶湯を取鍋に注ぐ際に発生するスラグボイルを防止するステンレス鋼の製造方法を提供することを目的としている。 Therefore, in the present invention, by controlling the basicity of the slag in the electric furnace and the Si concentration of the molten alloy to an appropriate value, the stainless steel that prevents slag boiling that occurs when the molten molten alloy is poured into the ladle The object is to provide a manufacturing method.
本発明は、上記状況に鑑みてなされたものであり、本発明のステンレス鋼の製造方法は、電気炉にて合金溶湯およびスラグを溶製し、電気炉から取鍋へ合金溶湯およびスラグを出鋼する際に、以下の説明において％は全てｍａｓｓ％にて、合金溶湯はＣ：１〜４％、Ｓｉ：０．１〜１％に調節され、スラグ成分は（ＣａＯ＋ＳｉＯ２）：６０〜８０％、塩基度（以下の説明において全て質量比にてＣａＯ／ＳｉＯ２）：０．５〜１．２、ＭｇＯ：１０〜３０％に調節されていることを特徴としている。 The present invention has been made in view of the above circumstances, and the method for producing stainless steel of the present invention melts molten alloy and slag in an electric furnace, and discharges the molten alloy and slag from the electric furnace to a ladle. when the steel, in all mass%% is in the following description, the molten alloy is C: 1 to 4% Si: adjusted to 0.1% to 1%, the slag component (CaO + SiO 2): 60~80 %, Basicity (CaO / SiO 2 in mass ratio in the following description ): 0.5 to 1.2, MgO: 10 to 30%.
本発明においては、１５００℃においてスラグの粘度が５Ｐ（０．５Ｐａ・ｓ）以下であることを好ましい態様としている。 In this invention, it is set as the preferable aspect that the viscosity of slag is 1500P or less at 1500 degreeC.
本発明においては、スラグ成分としてＦｅＯとＣｒ２Ｏ３濃度の合計を１０％以下とすることを好ましい態様としている。 In the present invention, it is a preferred embodiment that the sum of the FeO and Cr 2 O 3 concentration of 10% or less as a slag component.
本発明においては、スラグ塩基度ＣａＯ／ＳｉＯ２ ≧−０．１×ｌｎ（合金溶湯Ｓｉ％−０．１）＋０．６
を満たすようにスラグの塩基度および合金溶湯Ｓｉ濃度を制御することを好ましい態様としている。
In the present invention, slag basicity CaO / SiO 2 ≧ −0.1 × ln (molten alloy Si% −0.1) +0.6
It is a preferred embodiment to control the basicity of the slag and the molten alloy Si concentration so as to satisfy the above.
本発明によれば、成分が適正に調整されたスラグによって、ＣＯガスの発生が抑制され、また、僅かに発生するＣＯガスは速やかにスラグを通過して系外に排出されるので、スラグボイルの発生を防ぐことができるという効果を奏する。 According to the present invention, the generation of CO gas is suppressed by the slag whose components are appropriately adjusted, and the slightly generated CO gas quickly passes through the slag and is discharged out of the system. There exists an effect that generation | occurrence | production can be prevented.
本発明者らは、上記課題の解決に向けて、ボイルしたスラグを詳細に観察すると共に、スラグボイル発生に与える種々の影響因子について、実操業データの詳細解析を行い、発生機構および発生条件について鋭意検討を行った。その結果、下記（１）および（２）式にあるように、昇温時に原料中Ｃｒ、Ｆｅが酸化して不可避的に生成したＣｒ２Ｏ３、ＦｅＯが酸化源となり、合金溶湯中Ｃと反応してＣＯガスが発生することがスラグボイルの主原因であることが判明した。 In order to solve the above problems, the present inventors have observed the boiled slag in detail and conducted detailed analysis of actual operation data for various influencing factors on the generation of slag boil, and have earnestly studied the generation mechanism and conditions. Study was carried out. As a result, as shown in the following formulas (1) and (2), Cr 2 O 3 and FeO inevitably generated by oxidation of Cr and Fe in the raw material at the time of temperature rise become an oxidation source, and C in the molten alloy It has been found that the generation of CO gas upon reaction is the main cause of slag boil.
そして、電気炉を傾動し取鍋に注湯する際の攪拌によってメタル／スラグ界面の反応が促進され、反応過程で発生したＣＯガスがスラグから気相へ抜けずにスラグを泡立たせ、スラグ界面を上昇させることで、スラグボイルに至ることが明らかとなった。
Cr2O3(s) + 3C → 2Cr + 3CO(g) …（１）
FeO(s) + C → Fe(l) + CO(g) …（２）
Then, the reaction at the metal / slag interface is promoted by agitation when the electric furnace is tilted and poured into the ladle, and the CO gas generated in the reaction process is bubbled out without escaping from the slag to the gas phase. It became clear that the slag voile was reached by raising.
Cr 2 O 3 (s) + 3 C → 2 Cr + 3CO (g) (1)
FeO (s) + C → Fe (l) + CO (g) (2)
ここでの化学反応式にある下線は合金溶湯中に含まれることを示す。また、（ ）内は化学種の状態を示しており、ｓ：固相、ｌ：液相、ｇ：気相である。 The underline in the chemical reaction formula here indicates that it is contained in the molten alloy. Also, the inside of () indicates the state of the chemical species: s: solid phase, l: liquid phase, g: gas phase.
また、このＣＯ反応は溶鋼中にＳｉが充分含まれていれば、発生が抑制されることもわかった。つまり、Ｓｉが０．１％以上含まれれば、下記の反応が起こり、Ｃが酸化する前にＳｉが酸化する。
Si + 2O → SiO2(l) …（３）
It has also been found that this CO reaction is suppressed if Si is sufficiently contained in the molten steel. That is, if Si is contained in an amount of 0.1% or more, the following reaction occurs, and Si is oxidized before C is oxidized.
Si + 2 O → SiO 2 (l) (3)
また、スラグの塩基度も影響することも明らかとなった。本発明はこのようにして、操業データの解析およびスラグの測定結果を通して完成したものであり、具体的には以下の通りである。 It was also revealed that the basicity of slag has an effect. Thus, the present invention has been completed through the analysis of the operation data and the measurement result of the slag. Specifically, the present invention is as follows.
ステンレス鋼の製造にあたり、電気炉にて溶製した合金溶湯をＣ：１〜４％、Ｓｉ：０．１〜１％に調節して、スラグ成分を（ＣａＯ＋ＳｉＯ２）：６０〜８０％、塩基度（ＣａＯ／ＳｉＯ２）：０．５〜１．２、ＭｇＯ：１０〜３０％に調節し、電気炉から取鍋へ合金溶湯を注ぐ際に発生するスラグボイルを防止することを特徴とするステンレス鋼の製造方法である。 In the production of stainless steel, the molten alloy was melted in an electric furnace C: 1 to 4% Si: was adjusted to 0.1% to 1%, the slag component (CaO + SiO 2): 60~80 %, base (CaO / SiO 2 ): 0.5 to 1.2, MgO: 10 to 30%, stainless steel characterized by preventing slag boil generated when pouring molten alloy from an electric furnace to a ladle It is a manufacturing method of steel.
また、１５００℃においてスラグの粘度が５Ｐ（０．５Ｐａ・ｓ）以下であることが好ましく、スラグ成分としてＦｅＯとＣｒ２Ｏ３濃度の合計を１０％以下とすることが好ましく、さらに、下記の式を満足するようにスラグ塩基度とＳｉ濃度を制御することが最も好ましい。
スラグ塩基度ＣａＯ／ＳｉＯ２ ≧−０．１×ｌｎ（合金溶湯Ｓｉ％−０．１）＋０．６
It is preferable that the viscosity of the slag is not more than 5P (0.5Pa · s) at 1500 ° C., it is preferable that the sum of the FeO and Cr 2 O 3 concentration is 10% or less as the slag component, further, the following It is most preferable to control the slag basicity and the Si concentration so as to satisfy the equation.
Slag basicity CaO / SiO 2 ≧ −0.1 × ln (alloy molten metal Si% −0.1) +0.6
図１に示すように、本発明のステンレス鋼の製造方法では、まず電気炉１にて、カーボン電極からのアーク放電および酸素吹精によるＣ、Ｓｉ、Ａｌなどの酸化反応による熱を用いてスクラップやフェロニッケル、フェロクロムなどの原料を溶解して合金溶湯２を形成させる。ここに石灰を投入して、昇温時に生成した酸化物を滓化し、スラグ３を形成させた後、これら合金溶湯２およびスラグ３を図２に示す取鍋４に注ぎ、後の精錬工程５に運ぶ。ここで精錬された合金溶湯２は、再び取鍋４に注がれ、連続鋳造工程６に供されて製品である合金スラブが得られる。
As shown in FIG. 1, in the method for producing stainless steel according to the present invention, first, in an
上記工程のうち、電気炉１からスラグ３を伴う合金溶湯２を図２に示す取鍋４に注いでいる最中に、鍋内でスラグが発泡して沸き上がるスラグボイルという現象が起き、大幅な操業遅延による製造コストの増加を招く。この様子を示したのが図２および３である。図２に示すように、電気炉１からは、比重の小さいスラグ３がまず取鍋４内に注がれ、その後に合金溶湯２が取鍋４内に注がれる。この時、スラグ３と合金溶湯２は激しく攪拌された状態となる。
Of the above processes, while pouring the
図３（ａ）に示すように、出鋼前のスラグ３および合金溶湯２が静置され２層に分離している状態では、両者の界面は面積が最小の平面であるため、合金溶湯中Ｃとスラグ中ＦｅＯ／Ｃｒ２Ｏ３との反応は僅かである。この状態から、電気炉から出鋼され取鍋に注ぎ込まれると、図３（ｂ）〜（ｃ）に示すように、合金溶湯とスラグが攪拌されて、合金溶湯中Ｃとスラグ中ＦｅＯ／Ｃｒ２Ｏ３とが激しく反応してＣＯを発生させ、スラグボイルを生じさせることとなる。
As shown in FIG. 3 (a), in the state where the
これに対して、本発明においては、電気炉にてスラグの塩基度（ＣａＯ／ＳｉＯ２）および合金溶湯中Ｓｉ濃度からなる成分領域におけるスラグボイルの発生有無の境界線が、これら成分因子の関数で表され、適正な成分領域に制御すればスラグボイル発生を防止することが可能である。 In contrast, in the present invention, the boundary line of the presence or absence of slag boil in the component region consisting of the basicity of slag (CaO / SiO 2 ) and the Si concentration in the molten alloy in an electric furnace is a function of these component factors. It is possible to prevent the occurrence of slag boil if it is expressed and controlled to an appropriate component region.
以下に本発明に係るスラグボイル発生の防止方法について、原理および限定理由を詳細に説明する。上述したステンレス鋼の製造方法において、まず電気炉にて原料を溶解し、石灰を投入して、昇温時に生成した酸化物を滓化した後、スラグを伴う合金溶湯を取鍋に注ぐ。ここで、上述のように電気炉の傾動に伴う出湯流でメタル／スラグ間反応が促進され、上式（１）（２）の反応式にあるように、ＣＯガスが多量に発生することで起こる。 Hereinafter, the principle and reason for limitation of the method for preventing slag boil generation according to the present invention will be described in detail. In the stainless steel manufacturing method described above, first, raw materials are melted in an electric furnace, lime is added, and oxides generated at the time of heating are hatched, and then a molten alloy with slag is poured into a ladle. Here, as described above, the reaction between the metal and the slag is promoted by the tapping flow accompanying the tilting of the electric furnace, and a large amount of CO gas is generated as in the reaction formulas (1) and (2) above. Occur.
まず、溶鋼中の炭素濃度はＣ：１〜４％に調整するべきである。その理由として、Ｃは主として安価な高炭素Ｆｅ−Ｃｒに含有されている。１％未満であると高価な低炭素Ｆｅ−Ｃｒを配合せざるをなくなるので、コスト的に合わなくなる。一方、４％を超えて高いと、引き続き行う脱炭精錬の負荷が大きくなり、炉寿命の短縮などからコスト高となる。 First, the carbon concentration in the molten steel should be adjusted to C: 1-4%. For this reason, C is mainly contained in inexpensive high carbon Fe—Cr. If it is less than 1%, expensive low carbon Fe—Cr must be blended, so that it is not suitable in terms of cost. On the other hand, if it exceeds 4%, the load of subsequent decarburization refining becomes large, and the cost becomes high due to shortening of the furnace life.
本発明で最も重要なのが、Ｓｉ濃度でありＳｉ：０．１〜１％に調節することである。０．１％未満だと、上記の（３）式に示すＳｉの酸化が優先されずに、（１）、（２）式のＣＯ反応が優先されてボイルを起こす。また、１％を超えて高くなると酸化するＳｉ量が多くなり、それに伴って石灰石の投入量も増えることとなり、スラグ量が多くなってしまう。そうなると、電気炉から出鋼できなくなる他にも、処理するスラグ量が増えてしまい処理費が高くなってしまう。 The most important thing in the present invention is to adjust the Si concentration to Si: 0.1 to 1%. If it is less than 0.1%, the oxidation of Si shown in the above formula (3) is not prioritized, and the CO reaction of the formulas (1) and (2) is prioritized to cause boiling. Moreover, when it exceeds 1% and the amount of Si which oxidizes will increase, the input amount of limestone will also increase in connection with it, and the amount of slag will increase. If it becomes so, in addition to not being able to produce steel from an electric furnace, the amount of slag to process will increase and processing cost will become high.
Ｓｉ濃度が０．１％以上と高い場合においても、僅かなＣＯ反応は進行する。つまり、電気炉の溶鋼表面は少なからず空気に触れるので酸化する。そのため、ごく表面はＳｉが消費してしまい、ＣＯ反応を起こす。そのとき発生した僅かなＣＯガスが、スラグの通過抵抗が大きいとやはりボイル現象が発生する。したがって、スラグ成分を（ＣａＯ＋ＳｉＯ２）：６０〜８０％、塩基度（ＣａＯ／ＳｉＯ２）：０．５〜１．２、ＭｇＯ：１０〜３０％に調節することは好ましい態様である。ここで、ＭｇＯは電気炉のライニングに使用するので、スラグに溶解して混入させる。ＭｇＯ：１０〜３０％に調節するには、スラグ塩基度を０．５〜１．２に調整すればよい。このようにスラグ成分を調整すると、スラグの粘度を適正な領域に制御できて、僅かなＣＯガスは抵抗なく大気層へと抜けるためボイルに至らない。 Even when the Si concentration is as high as 0.1% or more, a slight CO reaction proceeds. In other words, the surface of the molten steel in the electric furnace is oxidized because it touches air. Therefore, the very surface consumes Si and causes a CO reaction. If a small amount of CO gas generated at that time has a large passage resistance of the slag, a boil phenomenon occurs. Therefore, it is a preferable embodiment to adjust the slag component to (CaO + SiO 2 ): 60 to 80%, basicity (CaO / SiO 2 ): 0.5 to 1.2, and MgO: 10 to 30%. Here, since MgO is used for the lining of the electric furnace, it is dissolved and mixed in the slag. In order to adjust to MgO: 10 to 30%, the slag basicity may be adjusted to 0.5 to 1.2. When the slag component is adjusted in this way, the viscosity of the slag can be controlled in an appropriate region, and a slight amount of CO gas escapes to the atmosphere layer without resistance, and thus does not boil.
また、スラグ成分としてＦｅＯとＣｒ２Ｏ３濃度の合計を１０％以下とすることが好ましい。その理由は、ＦｅＯとＣｒ２Ｏ３濃度の合計が１０％を超えると、ＣＯ反応が活発になるからである。 Further, the sum of the FeO and Cr 2 O 3 concentration as slag component preferably 10% or less. The reason is that the CO reaction becomes active when the total concentration of FeO and Cr 2 O 3 exceeds 10%.
さらに、下記の式を満足するようにスラグ塩基度とＳｉ濃度を制御することが最も好ましい。
（スラグ塩基度ＣａＯ／ＳｉＯ２）≧−０．１×ｌｎ（合金用湯Ｓｉ％−０．１）＋０．６
この領域であれば、僅かに起こるＣＯ反応も抑制できるからである。つまり、ボイルは全く発生しなくなる領域である。なお、上記式は、Ｓｉ濃度％が０．１％の場合、ｌｎ（０）が無限大となってしまうが、これは、上記式が数学的な近似式であるためで、現実にはＳｉ濃度％が０．１％の場合にスラグボイルは発生せず問題は生じないので、本発明のＳｉ濃度範囲は０．１％以上１％以下とした。
Furthermore, it is most preferable to control the slag basicity and the Si concentration so as to satisfy the following formula.
(Slag basicity CaO / SiO 2 ) ≧ −0.1 × ln (hot water for alloying Si% −0.1) +0.6
This is because a slight CO reaction can be suppressed in this region. That is, it is an area where no boil occurs. In the above formula, when the Si concentration% is 0.1%, ln (0) becomes infinite. This is because the above formula is a mathematical approximation formula. When the concentration% is 0.1%, no slag boil occurs and no problem occurs. Therefore, the Si concentration range of the present invention is set to 0.1% to 1%.
本発明ステンレス鋼の製造方法は、合金溶湯中のＣおよびＳｉ成分と、スラグ中のＣａＯ、ＳｉＯ２、ＭｇＯ、ＦｅＯ、Ｃｒ２Ｏ３成分との相互作用によるスラグボイルを抑制するものであるから、合金溶湯およびスラグ中にこれら成分を含んでいればよい。即ち、ステンレス鋼としてＦｅおよびＣｒを含んでさえいれば、対象となるステンレス鋼は限定されず、あらゆる鋼種に適用可能である。 Since the manufacturing method of the present invention stainless steel suppresses slag boil due to the interaction between the C and Si components in the molten alloy and the CaO, SiO 2 , MgO, FeO, and Cr 2 O 3 components in the slag, What is necessary is just to contain these components in a molten alloy and slag. That is, as long as stainless steel contains Fe and Cr, the target stainless steel is not limited and can be applied to all types of steel.
以下、実施例および比較例により本発明を具体的に説明する。
６０トン電気炉にて、カーボン電極からのアーク放電によって、ステンレス鋼スクラップ、鉄屑、フェロニッケル、フェロクロム、フェロシリコン、マンガンなどの原料を溶解した。ここに石灰を投入して、昇温時にＳｉが酸化して生成したシリカを主体とする酸化物を滓化し、スラグを形成させた。なお、電気炉のライニングはマグネシアとした。その後、電気炉を傾動して取鍋に出鋼した。この際に、ボイルの程度を目視で以下の通り評価した。
◎：ボイルは全く発生せず。
○：ボイルは見られたが、スラグ表面が盛り上がらず。
△：ボイルし、スラグが盛り上がったが、取鍋からオーバーフローせず。
×：ボイルにより、取鍋からオーバーフロー発生。
Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.
In a 60-ton electric furnace, raw materials such as stainless steel scrap, iron scrap, ferronickel, ferrochrome, ferrosilicon, and manganese were melted by arc discharge from a carbon electrode. Lime was added here, and an oxide mainly composed of silica formed by oxidation of Si at the time of heating was hatched to form slag. The electric furnace lining was magnesia. After that, the electric furnace was tilted and steel was taken out in the ladle. At this time, the degree of boil was visually evaluated as follows.
A: No boil was generated.
○: Although boil was seen, the slag surface did not rise.
Δ: Boiled and slag swelled, but did not overflow from the ladle.
×: Overflow occurred from ladle due to boiling.
また、スラグ成分および合金溶湯成分のうち、Ｓｉ、Ｃｒ、Ｎｉは、蛍光Ｘ線分析装置で分析した。合金溶湯中のＣ濃度は燃焼重量法により分析した。スラグの粘度測定は、実機でサンプリングしたスラグ２００ｇを鉄坩堝中に入れて、炉を１５００℃にセットし回転円筒法により測定した。 Of the slag component and the molten alloy component, Si, Cr, and Ni were analyzed with a fluorescent X-ray analyzer. The C concentration in the molten alloy was analyzed by the combustion weight method. The slag viscosity was measured by putting 200 g of slag sampled with an actual machine into an iron crucible, setting the furnace at 1500 ° C., and rotating cylinder method.
表１および図４に実施例を示して本発明をより明確に説明する。発明例のうち、Ｎｏ．１，２，３，５，７，８は、全ての請求項に示す条件を満たしたため、◎評価であった。つまり、全くボイルしなかった。Ｎｏ．４，６，９は、Ｓｉ濃度は０．１％以上含有していたが、ＦｅＯ＋Ｃｒ２Ｏ３濃度が１０％を超えていたため、○評価であった。つまり、ボイルは見られたが、スラグ表面は盛り上がらなかった。Ｎｏ．１０〜１２は比較的スラグ塩基度が低く、スラグ塩基度と合金溶湯Ｓｉ％の関係式を満たさなかったために、ＣＯガスの抜けが悪く、△評価であった。つまり、ボイルが発生しスラグが盛り上がったが、取鍋からオーバーフローしなかった。 Table 1 and FIG. 4 show examples to explain the present invention more clearly. Of the inventive examples, No. Since 1, 2, 3, 5, 7, and 8 satisfied the conditions shown in all the claims, they were evaluated as ◎. In other words, it did not boil at all. No. Nos. 4, 6, and 9 contained 0.1% or more of the Si concentration, but the evaluation was good because the FeO + Cr 2 O 3 concentration exceeded 10%. In other words, although boil was seen, the slag surface did not rise. No. Nos. 10 to 12 were comparatively low in slag basicity and did not satisfy the relational expression between slag basicity and molten alloy Si%. In other words, boil was generated and slag was raised, but it did not overflow from the ladle.
次に、比較例を説明する。Ｎｏ．１３〜１７は、いずれも、Ｓｉ濃度が０．１％未満であったため、×評価となった。つまり、ボイルによって、取鍋からスラグオーバーフローが発生してしまった。また、Ｎｏ．１８、１９は、スラグ塩基度が適正範囲より大きいか小さいためＣＯガスの抜けが悪く、ボイルによってスラグオーバーフローが発生してしまった。さらに、Ｎｏ．２０は、スラグボイルやオーバーフローは生じなかったものの、Ｓｉ濃度が１％を超えていたため酸化するＳｉ量が多くなり、それに伴って石灰石の投入量も増え、スラグ量が多くなり、スラグの処理費が高くなってしまった。 Next, a comparative example will be described. No. Nos. 13 to 17 were evaluated as x because the Si concentration was less than 0.1%. In other words, the slag overflow occurred from the ladle due to the boil. No. In Nos. 18 and 19, the slag basicity was larger or smaller than the appropriate range, so that the CO gas was not easily discharged, and slag overflow occurred due to boiling. Furthermore, no. No. 20 did not cause slag boil or overflow, but the Si concentration exceeded 1%, so the amount of oxidized Si increased, and the amount of limestone input increased accordingly, the amount of slag increased, and the slag processing cost was increased It has become expensive.
設備の故障や火災に繋がる危険なスラグボイルを抑制することができる。スラグボイルによるオーバーフローが発生した場合の大幅な操業遅延による製造コストの増加を防止する。 Dangerous slag boil that can lead to equipment failure and fire can be suppressed. Prevents an increase in manufacturing costs due to a significant delay in operation when overflow occurs due to slag voile.
１：電気炉、
２：合金溶湯、
３：スラグ、
４：取鍋、
５：精錬工程（ＡＯＤ）、
６：連続鋳造工程。
1: Electric furnace,
2: molten alloy,
3: Slag,
4: Ladle
5: Refinement process (AOD),
6: Continuous casting process.
Claims (4)
を満たすように前記スラグの塩基度および前記合金溶湯Ｓｉ濃度を制御することを特徴とする請求項１〜３のいずれかに記載のステンレス鋼の製造方法。 Slag basicity ( CaO / SiO 2 in mass ratio ) ≧ −0.1 × ln (molten alloy Si mass % −0.1) +0.6
The method for producing stainless steel according to any one of claims 1 to 3, wherein the basicity of the slag and the Si concentration of the molten alloy are controlled so as to satisfy the conditions.
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