WO2013137292A1 - 溶鋼の真空精錬方法 - Google Patents

溶鋼の真空精錬方法 Download PDF

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Publication number
WO2013137292A1
WO2013137292A1 PCT/JP2013/056932 JP2013056932W WO2013137292A1 WO 2013137292 A1 WO2013137292 A1 WO 2013137292A1 JP 2013056932 W JP2013056932 W JP 2013056932W WO 2013137292 A1 WO2013137292 A1 WO 2013137292A1
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Prior art keywords
molten steel
fuel
ore
flame
burner
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PCT/JP2013/056932
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English (en)
French (fr)
Japanese (ja)
Inventor
中井　由枝
奥山　悟郎
勇輔 藤井
菊池　直樹
泰志 小笠原
三木　祐司
Original Assignee
Ｊｆｅスチール株式会社
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Application filed by Ｊｆｅスチール株式会社 filed Critical Ｊｆｅスチール株式会社
Priority to CN201380012488.3A priority Critical patent/CN104169442B/zh
Priority to KR1020147023669A priority patent/KR101529454B1/ko
Priority to JP2013530266A priority patent/JP5382275B1/ja
Publication of WO2013137292A1 publication Critical patent/WO2013137292A1/ja

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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
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/064—Dephosphorising; Desulfurising
    • C21C7/0645—Agents used for dephosphorising or desulfurising
    • 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
    • C21C7/10—Handling in a vacuum

Definitions

  • the present invention relates to a method for vacuum refining of molten steel, and specifically to a method for melting low carbon high manganese steel and low sulfur steel with a vacuum degassing facility.
  • low carbon high manganese steel (hereinafter referred to as “low C high Mn steel”) having both high strength and high workability for the purpose of increasing the strength, weight and cost of the structure. .)
  • low C high Mn steel means the steel whose C density
  • manganese ore As an inexpensive manganese source used for adjusting the Mn concentration in molten steel, there are manganese ore (hereinafter also referred to as “Mn ore”), high carbon ferromanganese, and the like.
  • Mn ore manganese ore
  • the Mn ore is introduced into the converter for reduction, or high carbon ferromanganese is added to the molten steel when the converter is discharged.
  • the Mn concentration in molten steel is increased to a predetermined concentration (see, for example, Patent Document 1).
  • Patent Document 2 discloses that high carbon ferromanganese is contained in molten steel at the initial stage of decarburization refining in a vacuum degassing facility.
  • Patent Document 3 high-carbon ferromanganese is added until 20% of the decarburization time elapses when melting ultra-low carbon steel in a vacuum degassing furnace.
  • a method of input has been proposed.
  • oxygen is added during the vacuum decarburization treatment of molten steel containing a large amount of Mn, oxygen reacts not only with C in the molten steel but also with Mn, so that not only Mn oxidation loss occurs and Mn yield decreases.
  • the oxygen source in the decarburization process using the vacuum degassing equipment and the decarburization promotion method for example, in Japanese Patent Publication No. 4, solid oxygen such as a mill scale is introduced into the vacuum chamber, thereby
  • Mn ore is added to the molten steel in which the amount of C and the temperature at the time of converter blowing are regulated by a vacuum degassing apparatus
  • Patent Document 6 and Patent Document 7 when decarburizing steel from a converter, the decarburization method is directed to the surface of the molten steel in the vacuum tank, together with carrier gas, MnO powder and Mn ore.
  • Patent Document 8 The method of decarburizing the powder by blowing it up is also disclosed in Patent Document 8 in the molten steel in the vacuum tank of the RH vacuum degassing apparatus and the Mn ore powder together with the carrier gas via the nozzle provided on the side wall of the vacuum tank.
  • decarburization of molten steel is performed using oxygen in the Mn ore.
  • the method of increasing the Mn concentration is proposed.
  • the molten steel temperature decreases.
  • a method for compensating for the decrease in the molten steel temperature there are a method in which the molten steel temperature is increased in the pre-process of vacuum degassing, a method in which metal Al is added to the molten steel, and the molten steel temperature is increased by the combustion heat.
  • the method of increasing the molten steel temperature in the previous process causes a large amount of refractory wear in the previous process, leading to an increase in cost.
  • the method of increasing the temperature by adding metallic Al has problems such as a decrease in the cleanliness of the molten steel and an increase in the cost of secondary raw materials due to the generated Al oxide.
  • Patent Documents 10 and 11 which are methods for projecting oxide powder, add Mn ore as a manganese source in a vacuum degassing facility. No consideration has been given to the optimum conditions for doing so.
  • Patent Document 12 which is a method of adding a desulfurizing agent by heating with a flame of a burner, does not consider any optimum condition when adding the desulfurizing agent in a vacuum degassing facility. .
  • the present invention has been made in view of the above-described problems of the prior art, and its purpose is to suppress a decrease in molten steel temperature and Mn loss when adding Mn ore as a manganese source in a vacuum degassing facility.
  • the decrease in molten steel temperature is suppressed when desulfurization is performed by adding a desulfurizing agent in a vacuum degassing facility.
  • it is to propose a method for producing low-sulfur steel that can be efficiently desulfurized.
  • the inventors made extensive studies by paying attention to the reaction behavior of C and Mn and the change behavior of the molten steel when decarburizing with a vacuum degassing facility.
  • the combustion conditions of the burner provided at the tip of the top blowing lance are controlled within an appropriate range and Mn ore
  • Mn ore By heating and reducing the above and adding it to the molten steel in the vacuum chamber, it is possible to add Mn with a high yield without deteriorating the molten steel temperature, and also to enjoy the effect of promoting decarburization.
  • the desulfurization agent is also heated and melted with a flame of a burner provided at the tip of the upper blowing lance, and added to the molten steel in the vacuum tank, and the desulfurization treatment is performed without causing a decrease in the molten steel temperature. It has been found that it is preferable to use a lance having an appropriate structure for that purpose, and the present invention has been developed.
  • the present invention is a molten steel in which oxide powder is heated with a flame formed in a burner at the top of an upper blowing lance disposed in a vacuum degassing facility, and added to the molten steel bath surface in the degassing tank.
  • G Combustion gas supply speed (Nm 3 / min)
  • F Fuel supply speed (Nm 3 / min)
  • G / F) st A molten steel vacuum refining method characterized in that a flame is formed by supplying fuel so as to satisfy the stoichiometric value of the ratio of oxygen fuel for complete combustion.
  • the oxide powder is a Mn ore and / or a CaO-based desulfurization agent.
  • the molten steel vacuum refining method of the present invention is a method of injecting Mn ore or a CaO-based desulfurization agent together with a carrier gas from a nozzle at the tip of the center hole provided in the shaft core portion of the upper blowing lance, and arranging it around the nozzle.
  • a fuel and a combustion gas are supplied from a plurality of peripheral hole burners provided, ignited to form a flame, and the oxide powder is heated by the flame.
  • the method for vacuum refining molten steel according to the present invention is characterized in that any one or more of a hydrocarbon-based gas fuel, a hydrocarbon-based liquid fuel, and a carbon-based solid fuel is supplied as the fuel. To do.
  • addition of Mn ore to molten steel in a vacuum degassing facility can be performed at a high Mn yield while suppressing a decrease in molten steel temperature, and the decarburization rate can be increased. Therefore, it becomes possible to produce low carbon high manganese steel with high productivity and low cost.
  • the addition of the desulfurizing agent to the molten steel in the vacuum degassing equipment can be carried out while suppressing the decrease in the molten steel temperature, and the desulfurization efficiency can be increased. Can be efficiently melted.
  • the Mn ore is mainly composed of various Mn oxides having different oxidation numbers such as MnO 2 , Mn 2 O 3 , and MnO.
  • Mn oxides having different oxidation numbers in Mn ore are represented by the following (1) to (3) depending on C in the molten steel. )formula; MnO 2 +2 C ⁇ Mn +2 CO (1) Mn 2 O 3 +3 C ⁇ 2 Mn + 3CO (2) MnO + C ⁇ Mn + CO (3) It is considered to be reduced according to
  • the inventors when adding powdered Mn ore into molten steel from the upper blowing lance arranged in the vacuum degassing equipment, the fuel combustion conditions in the burner provided at the tip of the upper blowing lance (Hereinafter, also referred to as “burner combustion conditions”) was controlled, and Mn ore was heated, and at the same time, Mn oxide in Mn ore was reduced and added.
  • powdered Mn ore can be ejected together with a carrier gas (Ar gas) from a nozzle at the tip of the center hole provided in the shaft core portion, and the center
  • a carrier gas Ar gas
  • the Mn ore was heated using a multi-tube lance capable of jetting fuel and combustion gas from a plurality of peripheral hole tip burners arranged around the hole to form a flame, and top-blown.
  • the supply rate of the fuel and combustion gas and the presence / absence of heating by a burner are changed as shown in Table 1, and the Mn ore temperature change before and after the top blowing addition and the oxidation number in the Mn ore are different. Changes in the composition ratio of objects were investigated.
  • Ar gas was used as the carrier gas
  • propane gas was used as the fuel
  • pure oxygen was used as the combustion gas.
  • G is the combustion gas supply rate (Nm 3 / min)
  • F is the fuel supply rate (Nm 3 / min)
  • G / F is the oxygen fuel ratio (fuel supply rate).
  • (G / F) st is the stoichiometric value of the oxyfuel ratio at which the fuel is completely combusted.
  • (G / F) st is 5, that is, the fuel supply rate F is 1 Nm 3 / min, whereas the combustion gas supply rate G is 5 Nm. 3 / min.
  • the vacuum degassing equipment used for the vacuum refining of the molten steel of this invention includes an RH vacuum degassing apparatus, a DH vacuum degassing apparatus, a VOD furnace, etc., but the most representative of them is RH It is a vacuum degassing device. Therefore, an explanation will be given taking the RH vacuum degassing apparatus as an example.
  • FIG. 1 is a vertical cross-sectional view of a typical RH vacuum degassing facility.
  • This RH vacuum degassing equipment includes a ladle 2 that accommodates molten steel 1 and a degassing unit 3 that vacuum-degasses the molten steel (hereinafter also referred to as “degassing process” at the end).
  • the said degassing part 3 consists of the vacuum tank 4 which introduce
  • an auxiliary material such as an alloy material (component regulator) or a medium solvent.
  • two dip tubes 5 and 6 are disposed in the lower part of the vacuum chamber 4, and one of the dip tubes (5 in FIG. 1) is a recirculation flow for causing the molten steel 1 to recirculate.
  • a pipe 10 for blowing gas into the dip pipe is connected.
  • the two dip tubes are immersed in the molten steel in the ladle, the vacuum tank 4 is evacuated by an unillustrated exhaust facility, and the molten steel 1 in the ladle 2 is evacuated to the vacuum tank.
  • a reflux gas ininert gas such as Ar gas
  • the molten steel in the dip tube 5 also rises together with the reflux gas and flows into the vacuum degassing tank, and after being degassed, descends through the other dip tube (6 in FIG. 1) and falls into the ladle.
  • the molten steel returns to the inside and the degassing process proceeds.
  • an upper blowing lance 9 is disposed on the upper part of the vacuum chamber 4 so as to be inserted into the vacuum chamber 4 from above.
  • the upper blow lance 9 is formed of oxygen gas, oxide powder such as Mn ore and CaO-based desulfurizing agent, and a carrier gas passage for transporting them, and jetting them to the tip of the passage to melt the molten steel bath surface.
  • a multi-tube lance in which a nozzle for spraying the fuel, a passage for fuel and a combustion gas for burning the fuel, and a burner for burning the fuel to form a flame are disposed at the end of the passage.
  • the top blowing lance 9 is connected to a hopper (not shown) that stores auxiliary materials, and oxide powder such as Mn ore and CaO-based desulfurizing agent is supplied together with a carrier gas.
  • the CaO-based desulfurization agent include quick lime (CaO), limestone (CaCO 3 ), slaked lime (Ca (OH) 2 ), dolomite (CaO—MgO), fluorite (CaF 2 ), and alumina (Al 2 O 3).
  • a mixture of about 5 to 30 mass% of a CaO hatching accelerator such as) is mainly used.
  • the carrier gas is usually an inert gas such as Ar gas or nitrogen gas.
  • the top blow lance 9 is connected to a fuel supply pipe and a combustion gas supply pipe (not shown).
  • the fuel include hydrocarbon gas fuels such as propane gas and natural gas, heavy oil and kerosene. At least one of hydrocarbon-based liquid fuels such as coke and coal, and oxygen-containing gases such as oxygen gas, oxygen-enriched air, and air as combustion gases. Supplied.
  • the upper blowing lance 9 is water-cooled, and is also connected to a cooling water supply / drain pipe (not shown) for supplying and discharging cooling water therefor.
  • FIG. 2 shows an example of an upper blowing lance suitable for use in the present invention, in which (a) is a vertical sectional view and (b) is a bottom view.
  • This upper blowing lance is a passage (hereinafter referred to as an oxygen gas passage for supplying oxygen gas blown to molten steel) and an oxide powder / carrier gas passage for supplying oxide powder and a carrier gas of oxide powder.
  • a water-cooled cylinder 13 an external water-cooled cylinder 14 surrounding the inner water-cooled cylinder 13, and a passage for supplying fuel and combustion gas between the internal water-cooled cylinder 13 and the external water-cooled cylinder 14 15 and a plurality of “peripheral holes” composed of a burner 16 provided at the tip of the passage, that is, the lance tip.
  • the peripheral hole has a double-pipe structure. Fuel is flown on the inner tube side and combustion gas is allowed to flow on the outer tube side, but the fuel passage and the combustion gas passage are replaced. May be.
  • the oxide powder or the like ejected from the nozzle 12 at the tip of the powder / carrier gas passage 11 is heated by a flame formed on the burner 16 at the tip of the lance, heated / reduced, or heated. -It is melted and sprayed onto the molten steel bath surface in the vacuum chamber.
  • one of the eight peripheral holes is used as the pilot burner 17 for igniting the fuel to be ejected, so the number of burners is seven.
  • the fuel supplied from the fuel gas passage of the burner 16 and the combustion gas (oxidizing gas) supplied from the combustion gas passage are mixed instantaneously because their injection holes are close (overlapping).
  • the pilot burner is usually unnecessary, but may be provided.
  • the positional relationship between the center hole and the peripheral hole at the tip of the upper blowing lance that is, the positional relationship between the nozzle 12 and the burner 16 may be reversed, but around the jet including the oxide powder, Since it is possible to heat the oxide powder more efficiently by wrapping it with the flame of the burner, as shown in FIG. 2, a nozzle is disposed at the axial core portion of the lance, and a burner is disposed around the nozzle. Is preferred.
  • the shape of the nozzle 12 provided at the front end of the center hole of the upper blowing lance in FIG. 2 is a Laval nozzle composed of two cones, a portion whose cross section is reduced and a portion where the cross section is enlarged. It may be a nozzle.
  • the position where the narrowest cross section where the two cones of the reduced portion and the enlarged portion of the Laval nozzle are connected is usually called a throat.
  • the upper blowing lance 9 used in the present invention is not limited to the above-described range.
  • a plurality of burners are provided around the upper blowing lance, and the upper blowing lance is used by using the burner. You may make it heat the Mn ore blown from. Furthermore, you may install the top blowing lance and burner for Mn ore addition separately.
  • the hot metal discharged from the blast furnace is received in a holding container such as a hot metal ladle or a torpedo car or a transfer container, and then transferred to a steel making process for decarburization refining.
  • a holding container such as a hot metal ladle or a torpedo car or a transfer container
  • hot metal pretreatment such as desulfurization and dephosphorization is often performed on the hot metal, but in the present invention, the hot metal pretreatment is performed even if the hot metal pretreatment is not required due to the component specifications. It is preferable to apply.
  • an inexpensive manganese source such as Mn ore or high carbon ferromanganese is used, so the carbon concentration in the molten steel is inevitably high, but even in that case,
  • the C concentration is preferably suppressed to 0.2 mass% or less. If the C concentration exceeds 0.2 mass%, the decarburization processing time in the vacuum degassing facility in the next process becomes longer, which not only lowers the productivity, but also compensates for the decrease in molten steel temperature due to the extension of the decarburization processing time. Therefore, it is necessary to increase the steel output temperature, which causes a decrease in iron yield and an increase in refractory cost due to an increase in refractory wear.
  • the steel discharged from the converter is transported to a vacuum degassing facility such as an RH vacuum degassing apparatus, a DH vacuum degassing apparatus, or a VOD furnace, and subjected to degassing processing such as decarburization processing.
  • a vacuum degassing facility such as an RH vacuum degassing apparatus, a DH vacuum degassing apparatus, or a VOD furnace
  • degassing processing such as decarburization processing.
  • the undeoxidized molten steel 1 is vacuum decarburized (hereinafter, this process is also referred to as “rimd process”), and at the same time, Add Mn ore from lance 9 by top blowing.
  • the Mn ore needs to be added by being heated and reduced by a burner flame formed at the tip of the top blowing lance 9 and sprayed onto the molten steel bath surface.
  • the fuel is supplied through the fuel passage of the peripheral hole provided in the upper blowing lance 9 and the combustion gas is supplied to the burner 16 at the tip of the lance through the combustion gas passage to be ejected and ignited. By forming a flame on the burner.
  • Mn ore is ejected from the nozzle 12 at the tip of the lance through the powder / carrier gas passage 11 in the center hole, and the ejected Mn ore is heated and reduced by the burner flame and added by top blowing.
  • the flame formed in the burner at the tip of the lance in order to heat and reduce the Mn ore, the fuel and the combustion gas have the following formula: 0.4 ⁇ (G / F) / (G / F) st ⁇ 1.1
  • G Combustion gas supply speed (Nm 3 / min)
  • F Fuel supply speed (Nm 3 / min)
  • (G / F) / (G / F) st exceeds 1.1, the oxidation of the flame becomes strong and the Mn ore is heated, but the reduction of the Mn oxide in the Mn ore. Does not progress.
  • (G / F) / (G / F) st is less than 0.4, the flame itself is not formed, so that the Mn ore cannot be heated.
  • Preferable (G / F) / (G / F) st is in the range of 0.4 or more and less than 1.0.
  • the temperature drop (temperature loss) of the molten steel accompanying the addition of the Mn ore can be suppressed. Also, since the Mn ore heated by the flame that satisfies the above combustion conditions is reduced and added to the molten steel, the reduction reaction of the Mn ore is promoted and the Mn yield is improved, so the amount of Mn alloy added is reduced. can do. Furthermore, the addition of Mn ore can reduce the rimming time and increase productivity because oxygen in the Mn ore functions as solid oxygen and promotes decarburization reaction.
  • oxygen gas is ejected through the oxygen gas passage 11 and the nozzle 12 at the tip thereof, and sprayed on the molten steel, thereby promoting decarburization.
  • the molten steel may be heated.
  • an inert gas such as nitrogen gas or Ar gas is allowed to flow in the fuel passage or the combustion gas passage to prevent the burner from being blocked by splash or the like. Is preferred.
  • a strong deoxidizer such as Al is added to the molten steel 1 from the raw material inlet 8 to dissolve in the molten steel.
  • the oxygen concentration is reduced (deoxidation), and the rimming process is terminated.
  • finish of a rimming process is lower than the temperature requested
  • the temperature of the molten steel may be raised by blowing oxygen to the bath surface (acid feeding) and burning Al.
  • a component adjusting agent such as Ni, Cr, Cu, Nb, Ti or the like is introduced into the molten steel 1 from the raw material inlet 8 to adjust the molten steel component to a predetermined composition range, and then the vacuum chamber 4 is returned to atmospheric pressure. The degassing process ends.
  • a strong deoxidizer such as Al is added to the molten steel 1 from the raw material inlet 8 to the molten steel.
  • the dissolved oxygen concentration is reduced (deoxidized), and the rimmed process is terminated.
  • the molten steel temperature after completion of the rimming process that is, after deoxidation is lower than the temperature required from the next process such as a continuous casting process
  • Al is further added to the molten steel from the raw material inlet
  • the molten steel temperature may be increased by blowing oxygen to the surface of the molten steel from the top blow lance (acid feeding) and burning Al.
  • the Mn ore may be added from the blowing lance 9 by blasting simultaneously with the rim treatment of the undeoxidized molten steel 1.
  • a CaO-based desulfurizing agent is sprayed from the top blowing lance 9 onto the deoxidized molten steel, and at the same time, heated and melted with a flame formed in the burner 16, sprayed onto the molten steel bath surface, added, and desulfurized.
  • the fuel is supplied through the fuel passage of the peripheral hole provided in the upper blow lance 9 and the combustion gas is supplied to the burner 16 at the tip of the lance to be ejected and ignited.
  • a CaO-based desulfurizing agent is ejected from the nozzle 12 at the tip of the lance through the powder / carrier gas passage 11 in the central hole, and the ejected CaO-based desulfurizing agent is heated by the flame of the burner. -Melt and add top spray.
  • group desulfurization agent it is preferable to previously form a flame in a burner.
  • the flame formed on the burner at the tip of the lance has the following formula: fuel and combustion gas: 0.4 ⁇ (G / F) / (G / F) st ⁇ 1.1
  • G Combustion gas supply speed (Nm 3 / min)
  • F Fuel supply speed (Nm 3 / min)
  • G / F) st It is necessary to satisfy the stoichiometric value of the oxygen fuel ratio at which the fuel is completely burned.
  • the desulfurizing agent by heating, it is possible to suppress the temperature drop (temperature loss) of the molten steel accompanying the addition of the desulfurizing agent. Moreover, since the flame which satisfy
  • the molten steel 1 deoxidized by adding the above deoxidizer is then subjected to a killing process in which the molten steel is circulated and degassed with an RH vacuum degassing apparatus, and then, if necessary, Al, Si, Mn, A component adjusting agent (alloy component) such as Ni, Cr, Cu, Nb, Ti or the like is introduced into the molten steel 1 from the raw material inlet 8 to adjust the molten steel component to a predetermined composition range, and then the vacuum chamber 4 is returned to atmospheric pressure.
  • the degassing process ends.
  • the hot metal discharged from the blast furnace is subjected to hot metal pretreatment for dephosphorization and desulfurization, and then blown in a 350-ton converter, C: 0.03 to 0.09 mass%, Si: 0.05 mass% or less, Mn: Steel having a component composition of 0.1 to 0.85 mass%, P: 0.03 mass% or less, and S: 0.003 mass% or less was used.
  • Mn concentration was adjusted by adding Mn ore as a manganese source.
  • the molten steel blown in the converter is put into a ladle with no deoxidation, transported to an RH vacuum degassing device equipped with an upper blowing lance, and subjected to a rimming process in which it is vacuum decarburized in an undeoxidized state.
  • the accompanying degassing treatment was performed.
  • the O concentration in the molten steel was in the range of 0.03 to 0.07 mass%.
  • the flow rate of the circulating gas is 1500 NL / min
  • the ultimate vacuum of the vacuum chamber is 6.7 to 40 kPa (constant under each condition)
  • the type of top blowing lance used the addition of Mn ore
  • the presence / absence and addition method, the combustion conditions of the burner at the tip of the lance (((G / F) / (G / F) st )) and the presence / absence of acid delivery were changed as shown in Table 2.
  • the Mn ore to be added has a particle size of 5 to 20 mm and a manganese content of about 58 mass%.
  • the addition rate of Mn ore is 100 kg / min, the addition time is 10 min, and the total addition amount is constant at 1000 kg. did.
  • the target components of the molten steel after rim treatment are C: 0.002 to 0.003 mass%, Mn: 0.5 to 1.2 mass%, and when the Mn concentration is too low after rim treatment, Metal manganese was added to adjust the Mn concentration. Further, when oxygen was insufficient during the rimming process, decarburization was performed while blowing oxygen gas from the nozzle at the tip of the top blowing lance to the surface of the molten steel bath (feeding acid).
  • the lance of FIG. 3 is provided with a fuel gas supply hole 24 connected to a fuel gas passage 23 in a divergent portion 22 connected to a throat 21 connected to an oxygen gas passage 20 provided in an axial core portion of the lance. Mn ore is ejected from an ejection hole 26 at the tip of the powder / carrier gas passage 25.
  • the Mn ore is added to the molten steel together with the carrier gas (Ar gas) through the center hole, that is, the powder / carrier gas passage 11 and the nozzle 12. This was done by spraying over the bath surface.
  • the LNG at 240 nm 3 / hr as the fuel, also pure oxygen supplied is changed in the range of 120 ⁇ 600Nm 3 / hr as combustion gases,
  • the burner combustion conditions ((G / F) / (G / F) st ) were changed.
  • (G / F) st is 2 (fuel supply speed F is 1 Nm 3 / min, combustion gas supply speed G is 2 Nm 3 / min).
  • the flame formation time was 10 min (constant) in all conditions.
  • Table 2 shows the molten steel components (C, Mn) before degassing treatment (before rimdo treatment), Mn concentration after rimdo treatment (but before concentration adjustment by adding metal manganese), Mn in Mn ore added by rimdo treatment
  • the yield, the decarburization speed during the rim treatment, and the temperature difference of the molten steel before and after the rim treatment were also shown.
  • the decarburization speed described in Table 2 is an average decarburization speed obtained by dividing the decarburization amount from the time of arrival of RH to the end of the rimdo process by the rimdo process time.
  • the molten steel temperature difference indicates that the molten steel temperature has increased when it is positive, and that the molten steel temperature has decreased when it is negative.
  • Table 2 shows the following.
  • no. Nos. 16 to 18 are comparative examples in which a top blow lance in FIG. 2 was used and a flame was formed at the tip of the lance during the rim treatment, but no Mn ore was added. The speed was 0.0033 to 0.0036 mass% / min.
  • no. The decarburization rate at 1 to 15 is 0.0040 to 0.0052 mass% / min, and it can be seen that the decarburization is promoted by the addition of Mn ore. This is thought to be because the Mn oxide in the Mn ore functioned effectively as solid oxygen and promoted the decarburization reaction of the molten steel.
  • this No. In Comparative Examples 16 to 18, Mn loss occurred because oxygen required for decarburization was insufficient and acid feeding was unavoidable.
  • No. Nos. 13 to 15 are comparative examples in which Mn ore was added without heating from the auxiliary material inlet (8 in FIG. 1) into the vacuum chamber using the top blowing lance of FIG. Due to temperature loss due to heat and heat of decomposition (latent heat), the molten steel temperature is lowered by 30 ° C or more, the decarburization rate is in the range of 0.004 mass% / min, and the Mn yield is only in the range of 40-50%.
  • No. Nos. 10 to 12 are comparative examples in which the top blowing lance shown in FIG. 2 is used, but Mn ore is added by heating without heating with a burner flame. Similar to Nos.
  • no. Nos. 1 to 6 are invention examples in which Mn ore was added by top blowing while heating with a burner flame using the top blowing lance shown in FIG.
  • the charcoal speed is all as high as 0.048 mass% / min or higher, and the Mn yield in the Mn ore is also 80% or higher.
  • the burner combustion conditions ((G / F) / (G / F) st ) are the same.
  • the invention example 4 is superior in the amount of increase in molten steel temperature, the decarburization rate, and the Mn yield.
  • the difference is that The top blow lance of FIG. 3 used in No. 19 was mixed with Mn ore and combustion gas at the tip of the lance and ejected.
  • the top blowing lance of FIG. 2 used in No. 4 injects Mn ore from the nozzle at the tip of the lance and heats the Mn ore by wrapping the jet with a burner flame disposed around the nozzle. It is considered that the lance of No. 2 is because the Mn ore can be heated and reduced more efficiently.
  • no. No. 7 is No. 7 except that the burner combustion conditions ((G / F) / (G / F) st ) are higher than the range of the present invention.
  • FIG. Examples 1 to 6 and No. 1 The relationship between the C concentration before RH treatment and the decarburization rate in Comparative Examples 7 to 15 is shown in FIG. Examples 1 to 6 and No. 1 7 shows the relationship between C concentration before RH treatment and Mn yield in Comparative Examples 7 to 15; From these figures, it can be seen that when the C concentration before RH treatment is at the same level, the decarburization rate is higher in the inventive example than in the comparative example, and the Mn yield is improved. This is because, as described above, when Mn ore is heated and added by top blowing with a flame of optimum combustion conditions, the reduction of Mn oxide proceeds before Mn ore reaches the molten steel. The amount of C required for reduction is reduced.
  • FIG. 6 shows No. 1 in which Mn ore was heated and added with a burner flame.
  • Examples 1 to 6 and Nos. 7 shows the relationship between ((G / F) / (G / F) st ) and Mn yield in Comparative Examples 7 to 9. From this figure, when ((G / F) / (G / F) st is in the range of 0.4 to 1.1, an Mn yield of 80% or more is obtained. Among them, ((G / F) / (G / F) It can be seen that when st is in the range of 0.4 to less than 1.0, an extremely high value of 90% or more of Mn yield is obtained.
  • the hot metal discharged from the blast furnace is subjected to hot metal pretreatment for dephosphorization and desulfurization, and then blown in a 350-ton converter, C: 0.03 to 0.09 mass%, Si: 0.05 mass% or less, Mn: Steel having a component composition of 0.1 to 0.85 mass%, P: 0.03 mass% or less, and S: 0.0037 to 0.0042 mass% was used.
  • the molten steel blown in the converter is put into a ladle with no deoxidation, transported to an RH vacuum degassing device equipped with an upper blowing lance, and subjected to a rimming process in which it is vacuum decarburized in an undeoxidized state.
  • the accompanying degassing treatment was performed.
  • the O concentration in the molten steel upon arrival of the RH vacuum degassing apparatus was in the range of 0.03 to 0.07 mass%.
  • the flow rate of the circulating gas is 1500 NL / min
  • the ultimate vacuum of the vacuum chamber is 6.7 to 40 kPa (constant under each condition)
  • oxygen gas is supplied from the nozzle at the tip of the top blowing lance to the molten steel.
  • the rimd treatment was carried out while sending acid to the bath surface. After the C concentration in the molten steel reached a predetermined value below the component standard value, Al was added to the molten steel for deoxidation, and the rimd treatment was completed. Thereafter, a CaO-based desulfurizing agent was added to the molten steel and subjected to desulfurization treatment.
  • the desulfurization agent As the desulfurization agent, a CaO—Al 2 O 3 premelt flux having a particle size of 2 mm or less was used, the desulfurization agent addition rate was 100 kg / min, the addition time was 10 min, and the total addition amount was constant at 1000 kg.
  • the desulfurization agent addition conditions (whether or not burner heating) and burner combustion conditions (((G / F) / (G / F) st )) were changed as shown in Table 3.
  • the desulfurizing agent is the surface of the molten steel bath together with the carrier gas (Ar gas) through the center hole, that is, the powder / carrier gas passage 11 and the nozzle 12, using the top blowing lance shown in FIG. Added to the spray.
  • Table 3 also shows the S concentration in the molten steel before and after the degassing treatment, the desulfurization rate obtained from the value, and the molten steel temperature difference before and after the desulfurization agent projection.
  • the molten steel temperature difference is positive, the molten steel temperature has increased, and when it is negative, the molten steel temperature has decreased.
  • Table 3 shows the following.
  • No. 9 is a comparative example in which the top blowing lance shown in FIG. 2 is used, but the top of the desulfurizing agent is not heated by the burner flame, and the temperature of the molten steel is greatly reduced by the sensible heat accompanying the addition of the desulfurizing agent.
  • the desulfurization rate is as low as 60%.
  • no. Nos. 1 to 6 are invention examples in which the top blowing lance shown in FIG. 2 was used, and the desulfurization agent was heated and added by a burner flame, and there was almost no temperature loss due to the addition of the desulfurization agent. This is presumably because the temperature loss was reduced and the heat receiving efficiency was improved by adding the desulfurizing agent by heating.
  • the desulfurization rate is 78% or more. This is thought to be because the desulfurization reaction of molten steel was promoted because the flame of the burner was reducing.
  • no. No. 7 is No. 7 except that the burner combustion conditions ((G / F) / (G / F) st ) are higher than the range of the present invention. It is the same comparative example as the inventive examples 1 to 6, and although the molten steel temperature is rising, the desulfurization rate is as low as 60%. This is presumably because the desulfurization reaction of molten steel, which is a reduction reaction, did not proceed because the flame was not reducible. Conversely, no. No. 8 is No.
  • the burner combustion conditions ((G / F) / (G / F) st ) are lower than the range of the present invention. It is the same comparative example as the inventive examples 1 to 6, and the molten steel temperature is greatly lowered due to the temperature loss because the supplied oxygen is insufficient and no flame is formed and the desulfurizing agent is not heated. However, since the desulfurizing agent is supplied with the unburned reducing gas, the desulfurization rate is as high as 88.1%.
  • FIG. 7 shows the case where the desulfurization agent was heated and added with the flame of a burner. Examples 1 to 6 and Nos.
  • the relationship between ((G / F) / (G / F) st ) and the desulfurization rate in Comparative Examples 7 and 8 is shown. From this figure, ((G / F) / (G / F) st is 1.1 or less, and a desulfurization rate of 78% or more is obtained. Among them, ((G / F) / (G / F) st is 0.
  • the desulfurization rate is as high as about 90%, and (G / F) / (G / F) st is high even at 0.3. Although a desulfurization rate can be obtained, this condition is not preferable because a flame is not formed and the temperature of the molten steel is greatly reduced as described above.
PCT/JP2013/056932 2012-03-15 2013-03-13 溶鋼の真空精錬方法 WO2013137292A1 (ja)

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JP2015155567A (ja) * 2014-02-21 2015-08-27 Ｊｆｅスチール株式会社 マンガン含有低炭素鋼の溶製方法
JP2016065274A (ja) * 2014-09-24 2016-04-28 Ｊｆｅスチール株式会社 低炭素高マンガン鋼の溶製方法
JP2016188401A (ja) * 2015-03-30 2016-11-04 Ｊｆｅスチール株式会社 高マンガン鋼の溶製方法
JP2018127654A (ja) * 2017-02-07 2018-08-16 Ｊｆｅスチール株式会社 溶銑の脱硫方法
JP2020019984A (ja) * 2018-07-31 2020-02-06 Ｊｆｅスチール株式会社 減圧下での溶鋼の精錬方法
US10745771B2 (en) * 2016-02-24 2020-08-18 Jfe Steel Corporation Method for refining molten steel in vacuum degassing equipment

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CN108220532A (zh) * 2016-12-13 2018-06-29 鞍钢股份有限公司 一种提高钢水洁净度的二次精炼方法
CN108611465A (zh) * 2016-12-13 2018-10-02 鞍钢股份有限公司 一种提高rh脱碳速率的钢水精炼方法
TWI698532B (zh) * 2018-04-17 2020-07-11 日商日本製鐵股份有限公司 鋼液的製造方法
CN115335537A (zh) * 2020-04-01 2022-11-11 杰富意钢铁株式会社 减压下的钢液的脱碳精炼方法

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JP2015155567A (ja) * 2014-02-21 2015-08-27 Ｊｆｅスチール株式会社 マンガン含有低炭素鋼の溶製方法
JP2016065274A (ja) * 2014-09-24 2016-04-28 Ｊｆｅスチール株式会社 低炭素高マンガン鋼の溶製方法
JP2016188401A (ja) * 2015-03-30 2016-11-04 Ｊｆｅスチール株式会社 高マンガン鋼の溶製方法
US10745771B2 (en) * 2016-02-24 2020-08-18 Jfe Steel Corporation Method for refining molten steel in vacuum degassing equipment
JP2018127654A (ja) * 2017-02-07 2018-08-16 Ｊｆｅスチール株式会社 溶銑の脱硫方法
JP2020019984A (ja) * 2018-07-31 2020-02-06 Ｊｆｅスチール株式会社 減圧下での溶鋼の精錬方法

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