WO2022130473A1 - Procédé d'affinage d'acier en fusion contenant du chrome - Google Patents

Procédé d'affinage d'acier en fusion contenant du chrome Download PDF

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Publication number
WO2022130473A1
WO2022130473A1 PCT/JP2020/046619 JP2020046619W WO2022130473A1 WO 2022130473 A1 WO2022130473 A1 WO 2022130473A1 JP 2020046619 W JP2020046619 W JP 2020046619W WO 2022130473 A1 WO2022130473 A1 WO 2022130473A1
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WO
WIPO (PCT)
Prior art keywords
refining
molten steel
gas
pressure
torr
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PCT/JP2020/046619
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English (en)
Japanese (ja)
Inventor
辰 菊地
智昭 田中
隆二 中尾
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日鉄ステンレス株式会社
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Priority to PCT/JP2020/046619 priority Critical patent/WO2022130473A1/fr
Priority to JP2021517502A priority patent/JP6921365B1/ja
Publication of WO2022130473A1 publication Critical patent/WO2022130473A1/fr

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    • 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
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • 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
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/068—Decarburising
    • 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
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/072—Treatment with gases
    • 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
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/076—Use of slags or fluxes as treating agents
    • 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
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/10—Handling in a vacuum
    • 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

Definitions

  • the present invention relates to a method for refining chromium-containing molten steel, in which a gas containing oxygen gas is blown into the chromium-containing molten steel in a refining container to perform refining.
  • chrome-containing steel especially chrome-containing steel containing 11% or more of chromium, such as stainless steel
  • oxygen gas or a mixed gas of oxygen gas and inert gas is mixed in the molten steel contained in the smelting container.
  • a method of decarburizing and refining by the blowing AOD method is widely used.
  • the AOD method when the decarburization progresses and the concentration of [C] in the molten steel decreases, [Cr] is easily oxidized. Therefore, as the concentration of [C] decreases, Ar gas or the like in the blown gas A method has been adopted in which the ratio of the inert gas is increased to suppress the oxidation of [Cr].
  • Patent Document 1 oxygen gas or a mixed gas of oxygen gas and an inert gas is supplied as a blowing gas, and decarburization is performed under atmospheric pressure until the [C] concentration in the molten steel drops to 0.5% by mass.
  • a method of decarburizing the inside of the container by reducing the pressure to 200 torr or less after the treatment and the [C] concentration drops to this value or less. As a result, the treatment is performed under reduced pressure from a relatively high [C] concentration, and the decarburization treatment is performed with a mixed gas with oxygen gas under reduced pressure.
  • the decarburization rate can be improved, the Si basic unit for reduction and the expensive inert gas basic unit can be reduced, and the refining time can be shortened. It is said that the reason why the pressure inside the container in the reduced pressure treatment is 200 torr or less is that the decarboxylation efficiency decreases at a pressure higher than this.
  • Patent Document 2 describes, in a smelting method in which a gas containing oxygen gas is blown into a chromium-containing molten steel in a smelting container to perform smelting, a gas containing oxygen gas is blown into the container as a pressure in the range of 400 torr to atmospheric pressure. It is characterized by having a second step of depressurizing the inside of the container to 250 torr to 400 torr and blowing a gas containing oxygen gas, and a third step of depressurizing the inside of the container to 250 torr or less and blowing the gas.
  • a method for refining molten steel is disclosed.
  • the decarboxylation efficiency is high even at a pressure of 250 to 400 torr by performing strong stirring of the molten steel. Is obtained. Further, by setting the pressure of the reduced pressure operation to the range of 250 to 400 torr instead of the conventional pressure of 200 torr or less, the generation of dust can be suppressed. Further, by setting the pressure in the range of 250 to 400 torr, the amount of bottom-blown gas blown can be increased, and as a result, the refining time can be shortened.
  • the refining cost can be significantly reduced.
  • the present invention is a method for refining a chromium-containing molten steel in which a gas containing oxygen gas is blown into the chromium-containing molten steel by reducing the pressure in the refining container to achieve both reduction of refractory melting damage and reduction of the amount of reducing material used.
  • the purpose is to provide a refining method that can be used.
  • the gist of the present invention is as follows. (1) In a refining method in which a gas containing oxygen gas is blown into a chromium-containing molten steel in a refining container to perform refining.
  • the inside of the container is the first step of blowing a gas containing oxygen gas as a pressure in the range of 400 torr super-atmospheric pressure or less, the second step of depressurizing the inside of the container to over 200 torr and 400 torr or less and blowing the gas containing oxygen gas, and the inside of the container. It has a third step of reducing the pressure to 200 torr or less and blowing gas.
  • the pressure in the furnace is divided into the first step to the third step and the pressure is sequentially reduced, and the amount of slag at the end of refining is 35 to 110 kg per ton of molten steel.
  • the present invention relates to a refining method in which a gas containing oxygen gas is blown into a chromium-containing molten steel in a refining container to perform refining.
  • the refining vessel 1 shown in FIG. 1A is used when performing vacuum refining
  • the refining vessel 1 shown in FIG. 1B is used, for example, when performing atmospheric pressure refining.
  • the molten steel 4 is housed in the refining container 1, a slag 6 is formed on the molten steel 4, and the bottom blowing gas 5 is blown into the chromium-containing molten steel in the refining container through the bottom blowing tuyere 2.
  • the smelting container 1 has a removable exhaust hood 3, and at the time of decompression smelting, the smelting container 1 is equipped with the exhaust hood 3 as shown in FIG. 1A, and gas suction is performed via the exhaust pipe 7. The pressure inside the smelting container is reduced. Since the exhaust hood 3 is not attached as shown in FIG. 1B during atmospheric pressure refining, it is possible to blow gas by using not only the bottom blowing tuyere 2 but also the top blowing lance 12.
  • the method for refining a chromium-containing molten steel of the present invention includes a first step of blowing a gas containing oxygen gas into the container as a pressure in the range of 400 torr or less, and depressurizing the inside of the container to over 200 torr to 400 torr or less and containing oxygen gas. It has a second step of blowing gas and a third step of reducing the pressure inside the container to 200 torr or less and blowing gas. Switching from the first step to the second step when the [C] concentration in the molten steel is 1.5 to 0.1% by mass%, and the second when the [C] concentration in the molten steel is 0.5 to 0.1%. Switch from step to third step.
  • the decarboxylation efficiency in this middle coal region can be maintained at a high value, and the generation of dust can be further suppressed.
  • the pressure in the range of more than 200 torr and 400 torr or less in the second step the amount of bottom blown gas blown can be increased, and as a result, the refining time can be shortened.
  • the bottom blowing gas blowing speed is preferably 0.4 Nm 3 / min or more per ton of molten steel.
  • the blowing speed of the bottom-blown gas can be reduced to molten steel. Even if it is 0.4 Nm 3 / min or more per ton, the amount of dust generated can be suppressed to a low level. More preferable results can be obtained when the bottom blowing gas blowing speed is more than 0.5 Nm 3 / min per ton of molten steel.
  • the time to shift from the first step where the pressure in the refining vessel is more than 400 torr to the second step where the pressure is more than 200 torr and less than 400 torr is when the [C] concentration in the molten steel is 1.5 to 0.1%.
  • the [C] region where the [C] concentration is higher than 1.5% even if decompression refining is performed, it is more efficient to set the pressure to a pressure higher than 400 torr and increase the oxygen gas blowing rate. This is because it is possible to secure a high oxygen gas blowing rate and efficiently perform refining by performing atmospheric pressure refining and also using top-blown oxygen gas blowing.
  • the time to shift from the second step where the pressure in the smelting vessel is more than 200 torr and 400 torr or less to the third step where the pressure is 200 torr or less is when the [C] concentration in the molten steel is 0.5 to 0.1%. do.
  • the method for refining chromium-containing molten steel of the present invention is characterized in that the amount of slag at the end of refining is 35 to 110 kg per ton of molten steel. This makes it possible to obtain a refining method for chromium-containing molten steel that achieves both reduction in refractory melting damage and reduction in the amount of reducing agent used.
  • the time when the smelting is completed means the time when the reduced pressure smelting and the subsequent reduction treatment are completed.
  • the slag generated in the pre-process of AOD is mainly brought into the molten steel and AOD.
  • an oxide containing any of CaO, MgO, SiO 2 , Al 2 O 3 and two or more kinds of CaF 2 are charged into the furnace, and these are the constituent elements of the slag at the end of refining. Will be.
  • Cr, Si, Al, and Mn in the molten steel are oxidized by oxygen refining, and the formed oxide becomes a component of slag at the end of refining.
  • the above conditions of the present invention were applied to the transition of the pressure in the furnace during refining.
  • the slag generated in the previous process was separated from the molten steel using a slag dragger before the AOD was charged. If the Si, Mn, and Al in the molten steel before the AOD treatment are high, they are oxidized to form slag between the start of the AOD treatment and the start of vacuum refining, and the slag is discharged and discharged to the outside of the furnace. As a result, the amount of slag at the end of refining was reduced.
  • the amount of slag at the end of refining is 110 kg or less per ton of molten steel, it is possible to achieve both reduction of refractory melting damage and reduction of the amount of reducing agent used. It is more preferable that the weight is 70 kg or less per ton of molten steel. It is more preferable that the weight is 65 kg or less per ton of steel.
  • the lower limit of the amount of slag at the end of refining was set to 35 kg per ton of molten steel.
  • a preferred embodiment of vacuum refining will be described.
  • the first step either the case of refining the whole under atmospheric pressure, the case of refining the whole under reduced pressure, or the case of initially refining under atmospheric pressure and then under reduced pressure may be adopted. ..
  • both top blowing and bottom blowing can be used together as gas blowing.
  • only oxygen can be used as the gas to be blown.
  • the first step of refining can be carried out initially under atmospheric pressure and then under reduced pressure with a pressure of over 400 torr. Decompression refining may be carried out from the beginning of the first step.
  • the bottom-blown gas blown gas type in the second step may be a mixed gas of oxygen and an inert gas from the beginning of the second step. It may be a pattern for increasing the ratio.
  • the pressure in the smelting vessel in the second step can be maintained at a constant pressure within a range of more than 200 torr and 400 torr or less, but it may be a pattern in which the pressure is sequentially changed from a high pressure to a low pressure.
  • the inside of the container is depressurized to 200 torr or less and gas is blown into it.
  • concentration of [C] in the molten steel decreases, the optimum pressure inside the vessel for obtaining high decarboxylation efficiency decreases. Therefore, in the third step in which decarboxylation progresses, a lower pressure than in the second step is adopted. Is preferable.
  • the lower the concentration of [C] the greater the influence of molten steel stirring on the decarburization reaction.
  • the lower the pressure inside the container the larger the expansion allowance of the gas and the larger the stirring force of the molten steel. Therefore, it is preferable to set the pressure lower than that of the second step.
  • the third step it is preferable to gradually reduce the pressure in the container as the concentration of [C] in the molten steel decreases.
  • the concentration of [C] is sufficiently lowered, it may be possible to blow only the inert gas without using oxygen gas as the blowing gas.
  • the present invention was applied to melt SUS304 stainless steel (8% by mass Ni-18% by mass Cr) in an AOD furnace with a molten steel amount of 60 tons as shown in FIGS. 1A and 1B.
  • the bottom blowing was performed without performing the top blowing in the embodiment shown in FIG. 1B, and in the reduced pressure refining, the bottom blowing was performed after depressurizing the inside of the refining vessel in the embodiment shown in FIG. 1A.
  • the [C] concentration in the molten steel at the start of melting is about 1.7%, and decarburization refining is performed to [C] 0.03%, and then oxidation is performed during decarburization while returning the pressure inside the container to atmospheric pressure.
  • Fe—Si alloy iron was added as a reducing agent for reducing the resulting chromium, and the reduction treatment was performed by blowing only Ar gas, and the steel was discharged to a pan.
  • Refining was performed using the pattern shown in Table 1.
  • the first step was atmospheric pressure refining and bottom blowing was performed.
  • [C] The concentration of 0.5% to 0.2% was set as the second step, and the pressure inside the container was set as a two-step pressure of 400 torr and 200 torr in the second step.
  • the pressure inside the vessel was set to a two-step pressure of 50 torr and 40 torr, and decarburization refining was performed to a [C] concentration of 0.03%.
  • Oxygen gas and argon gas were used in combination as the bottom blowing gas up to the pressure of 50 torr in the first step, the second step, and the third step.
  • Ar gas was blown alone.
  • the amount of slag at the end of refining was evaluated using a weigh scale attached to an overhead crane after the vacuum refining and reduction treatment were completed and discharged from the furnace, separated from the molten steel.
  • the amount of Fe—Si alloy iron used as a reducing agent was evaluated, and Invention Example No. It was indexed based on the value of 8 and shown in Table 2.
  • the refractory melting status of the refining furnace was evaluated by inserting a measuring rod with a scale from the outside of the bottom blowing tuyere after refining and recording the remaining dimensions at any time.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Treatment Of Steel In Its Molten State (AREA)

Abstract

L'invention concerne un procédé d'affinage d'acier en fusion contenant du chrome, le procédé impliquant l'affinage par réduction de pression de l'intérieur d'un récipient d'affinage et le soufflage d'un gaz contenant de l'oxygène gazeux dans l'acier en fusion contenant du chrome, ledit procédé permettant d'équilibrer une réduction de l'érosion réfractaire et une réduction de la quantité de matériau réducteur utilisée.　Le procédé d'affinage d'acier en fusion contenant du chrome comprend une première étape consistant à régler la pression du récipient dans une plage supérieure à 400 torr et inférieure ou égale à la pression atmosphérique, et à introduire par soufflage un gaz contenant de l'oxygène gazeux ; une deuxième étape consistant à réduire la pression du récipient à une valeur supérieure à 200 torr et inférieure ou égale à 400 torr, et à introduire par soufflage un gaz contenant de l'oxygène gazeux ; et une troisième étape consistant à réduire la pression du récipient à une valeur égale ou inférieure à 200 torr, et à introduire par soufflage un gaz ; ledit procédé étant caractérisé en ce que la quantité de scories, lorsque l'affinage est achevé, est comprise entre 35 et 110 kg pour 1 tonne d'acier en fusion. Par conséquent, il est possible d'équilibrer une réduction de l'érosion réfractaire et une réduction de la quantité de matériau réducteur utilisée.
PCT/JP2020/046619 2020-12-14 2020-12-14 Procédé d'affinage d'acier en fusion contenant du chrome WO2022130473A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
PCT/JP2020/046619 WO2022130473A1 (fr) 2020-12-14 2020-12-14 Procédé d'affinage d'acier en fusion contenant du chrome
JP2021517502A JP6921365B1 (ja) 2020-12-14 2020-12-14 含クロム溶鋼の精錬方法

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PCT/JP2020/046619 WO2022130473A1 (fr) 2020-12-14 2020-12-14 Procédé d'affinage d'acier en fusion contenant du chrome

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62243711A (ja) * 1986-04-15 1987-10-24 Nippon Steel Corp 含クロム溶鋼の精錬法
JPH0885815A (ja) * 1994-09-16 1996-04-02 Nippon Steel Corp 脱炭滓を用いた効率的な含クロム溶鋼の精錬方法
JPH1150133A (ja) * 1997-07-31 1999-02-23 Nippon Steel Corp ステンレス鋼の脱ガス精錬方法
WO2003027335A1 (fr) * 2001-09-20 2003-04-03 Nippon Steel Corporation Procede d'affinage de fer en fusion contenant du chrome

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62243711A (ja) * 1986-04-15 1987-10-24 Nippon Steel Corp 含クロム溶鋼の精錬法
JPH0885815A (ja) * 1994-09-16 1996-04-02 Nippon Steel Corp 脱炭滓を用いた効率的な含クロム溶鋼の精錬方法
JPH1150133A (ja) * 1997-07-31 1999-02-23 Nippon Steel Corp ステンレス鋼の脱ガス精錬方法
WO2003027335A1 (fr) * 2001-09-20 2003-04-03 Nippon Steel Corporation Procede d'affinage de fer en fusion contenant du chrome

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JP6921365B1 (ja) 2021-08-18
JPWO2022130473A1 (fr) 2022-06-23

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