WO2013137292A1 - 溶鋼の真空精錬方法 - Google Patents
溶鋼の真空精錬方法 Download PDFInfo
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- 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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- molten steel
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- burner
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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.
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Abstract
Description
0.4≦(G/F)/(G/F)st≦1.1
ここで、G :燃焼用ガス供給速度(Nm3/min)
F :燃料供給速度(Nm3/min)
(G/F) :酸素燃料比(=燃焼用ガス供給速度/燃料供給速度)
(G/F)st:燃料が完全燃焼する酸素燃料比の化学量論値
を満たすよう供給して火炎を形成することを特徴とする溶鋼の真空精錬方法である。
Mn鉱石は、MnO2やMn2O3、MnO等、酸化数の異なる種々のMn酸化物を主成分とするものである。このMn鉱石を、マンガン源としてまた脱炭促進のための酸素源として溶鋼に添加する場合、Mn鉱石中の酸化数の異なるMn酸化物は、溶鋼中のCによって、下記(1)~(3)式;
MnO2+2C → Mn+2CO ・・・(1)
Mn2O3+3C → 2Mn+3CO ・・・(2)
MnO+C → Mn+CO ・・・(3)
に従って還元されると考えられる。
具体的には、上記予備実験では、上吹きランスとして、軸芯部に設けた中心孔先端のノズルから粉体のMn鉱石をキャリアガス(Arガス)とともに噴出することができ、かつ、上記中心孔の周囲に配設した複数の周囲孔先端のバーナーから燃料と燃焼用ガスを噴出して火炎を形成することができる多重管ランスを用いてMn鉱石を加熱し、上吹き添加した。この際、上記燃料と燃焼用ガスの供給速度およびバーナーによる加熱の有無を表1のように変えて添加し、上吹き添加前後におけるMn鉱石の温度変化およびMn鉱石中の酸化数が異なるMn酸化物の構成比率の変化を調査した。なお、上記予備実験では、キャリアガスにArガスを、燃料はプロパンガスを、燃焼用ガスに純酸素を用いた。
本発明は、上記の新規な技術思想と知見に基いて開発したものである。
本発明の溶鋼の真空精錬に用いることができる真空脱ガス設備には、RH真空脱ガス装置やDH真空脱ガス装置、VOD炉等があるが、それらの中で最も代表的なものは、RH真空脱ガス装置である。そこで、RH真空脱ガス装置を例にとって説明する。
このRH真空脱ガス設備は、溶鋼1を収容する取鍋2と、溶鋼を真空脱ガス処理(以降、端に「脱ガス処理」ともいう)する脱ガス部3から構成されている。上記脱ガス部3は、溶鋼を内部に導入して脱ガス処理する真空槽4と、それに接続する図示されていない排気設備とからなる。真空槽4の上部側面には排気設備につながる排気口7、および、合金原料(成分調整剤)や媒溶剤等の副原料を添加する投入口(シュート)8が設けられている。
図2は、本発明に用いて好適な上吹きランスの一例を示したものであり、(a)は垂直断面図、(b)は下面図である。この上吹きランスは、溶鋼に吹き付ける酸素ガスを供給する酸素ガス通路と、酸化物粉体および酸化物粉体のキャリアガスを供給する酸化物粉体・キャリアガス通路とを兼ねた通路(以降、単に「酸素ガス通路」または「粉体・キャリアガス通路」ともいう)11と、その通路の先端、即ち、ランス先端に設けられたノズル12からなる「中心孔」を軸芯部に備えた内部水冷筒体13と、その内部水冷筒体13の周囲を取り囲む外部水冷筒体14と、さらに、上記内部水冷筒体13と外部水冷筒体14との間に燃料や燃焼用ガスを供給する通路15と、その通路の先端、即ち、ランス先端に設けられたバーナー16とからなる複数本の「周囲孔」から構成されている。上記周囲孔は、2重管構造となっており、内管側には燃料、外管側には燃焼用ガスを流すようになっているが、燃料の通路と燃焼用ガスの通路とを取り替えてもよい。
まず、高炉から出銑した溶銑は、溶銑鍋やトーピードカー等の保持容器や搬送容器に受銑した後、脱炭精錬を行う製鋼工程に搬送する。通常、この搬送の途中で、溶銑に対して脱硫や脱燐等の溶銑予備処理を施すことが多いが、本発明においては、成分規格上、溶銑予備処理が必要でない場合でも、溶銑予備処理を施すことが好ましい。というのは、転炉では、マンガン源として添加するMn鉱石を添加するが、溶銑予備処理、特に脱燐処理を行わない場合には、転炉での吹錬時に脱炭と同時に脱燐を行うことが必要となり、そのためにCaO系フラックスを多量に添加するため、転炉のスラグ量が増加し、スラグに分配されるマンガン量が増加してMn歩留りが低下してしまうからである。
0.4≦(G/F)/(G/F)st≦1.1
ここで、G :燃焼用ガス供給速度(Nm3/min)
F :燃料供給速度(Nm3/min)
(G/F) :酸素燃料比(=燃焼用ガス供給速度/燃料供給速度)
(G/F)st:燃料が完全燃焼する酸素燃料比の化学量論値
を満たすことが必要である。先述したように、(G/F)/(G/F)stが1.1を超えると、火炎の酸化性が強くなり、Mn鉱石は加熱されるものの、Mn鉱石中のMn酸化物の還元が進行しない。一方、(G/F)/(G/F)stが0.4を下回ると、火炎自体が形成されないため、Mn鉱石を加熱することもできないからである。好ましい(G/F)/(G/F)stは0.4以上1.0未満の範囲である。
RH真空脱ガス装置に搬送した未脱酸状態のままの溶鋼は、必要に応じて、上吹きランス9の酸素ガス通路11およびその先端のノズル12を介して、酸素ガスを溶鋼に吹き付けて脱炭を行うリムド処理を所定時間行い、溶鋼中のC濃度が成分規格値以下の所定の値に達したなら、原料投入口8からAl等の強脱酸剤を溶鋼1に添加して溶鋼中の溶存酸素濃度を低減(脱酸)し、リムド処理を終了する。
0.4≦(G/F)/(G/F)st≦1.1
ここで、G :燃焼用ガス供給速度(Nm3/min)
F :燃料供給速度(Nm3/min)
(G/F) :酸素燃料比(=燃焼用ガス供給速度/燃料供給速度)
(G/F)st:燃料が完全燃焼する酸素燃料比の化学量論値
を満たすことが必要である。(G/F)/(G/F)stが1.1を超えると、火炎の酸化性が強くなり、脱硫剤は加熱されるものの、還元反応である脱硫反応が進行しない。一方、(G/F)/(G/F)stが0.4を下回ると、火炎自体が形成されないため、脱硫剤を加熱することもできないからである。好ましい(G/F)/(G/F)stは0.4以上1.0未満の範囲である。
転炉吹錬した溶鋼は、未脱酸のまま取鍋に出鋼し、上吹きランスを備えたRH真空脱ガス装置に搬送し、未脱酸状態のままで真空脱炭処理するリムド処理を伴う脱ガス処理を施した。なお、RH真空脱ガス装置到着時の溶鋼中O濃度は、0.03~0.07mass%の範囲であった。
なお、添加するMn鉱石は、粒度が5~20mmで、マンガン含有量が約58mass%のものを用い、Mn鉱石の添加速度は100kg/min、添加時間は10min、総添加量は1000kgで一定とした。
また、リムド処理後の溶鋼の目標成分は、C:0.002~0.003mass%、Mn:0.5~1.2mass%とし、リムド処理終了後、Mn濃度が低すぎた場合には、金属マンガンを添加してMn濃度調整を行った。
また、リムド処理時に酸素が不足している場合には、上吹きランス先端のノズルから酸素ガスを溶鋼の浴表面に吹き付け(送酸)ながら脱炭を行った。
まず、No.16~18は、図2の上吹きランスを使用し、リムド処理時にランス先端に火炎を形成したが、Mn鉱石を添加しなかった比較例であり、溶鋼温度は上昇しているものの、脱炭速度は0.0033~0.0036mass%/minであった。これに対して、Mn鉱石を添加したNo.1~15における脱炭速度は0.0040~0.0052mass%/minであり、Mn鉱石の添加により、脱炭が促進されていることがわかる。これは、Mn鉱石中のMn酸化物が固体酸素として有効に機能し、溶鋼の脱炭反応を促進したためであると考えられる。なお、このNo.16~18の比較例では、脱炭に要する酸素が不足し、送酸を行わざるを得なかったため、Mnロスが生じている。
No.13~15は、図2の上吹きランスを使用し、副原料投入口(図1の8)から真空槽内へMn鉱石を加熱することなく添加した比較例であり、Mn鉱石添加に伴う顕熱や分解熱(潜熱)による温度ロスによって、溶鋼温度が30℃以上低下しており、脱炭速度は0.004mass%/min台で、Mn歩留りも40~50%台でしかない。
また、No.10~12は、図2に示した上吹きランスを用いているが、バーナーの火炎でMn鉱石を加熱せずに上吹き添加した比較例であり、上記No.13~15と同様、Mn鉱石添加に伴う顕熱や潜熱により溶鋼温度が大きく低下し、Mn歩留りも上記No.13~15と同様、低位となっている。
これに対して、No.19は、図3に示した従来技術の上吹きランスを用いて、ランス先端に形成した火炎でMn鉱石を加熱し、添加した発明例である。この発明例では、溶鋼温度が10℃以上上昇している。これは、Mn鉱石を加熱して添加したことで、温度ロスが低減でき、着熱効率が向上したためと考えられる。また、Mn歩留りも80%近くまで向上している。これは、Mn鉱石を還元性の火炎で加熱したことによって、Mn鉱石が還元されて添加されたためと考えられる。
さらに、No.1~6は、図2に示した上吹きランスを用いて、Mn鉱石をバーナーの火炎で加熱しつつ上吹き添加した発明例であり、リムド処理後の溶鋼温度が9℃以上上昇し、脱炭速度がすべて0.048mass%/min以上と高く、Mn鉱石中のMn歩留りも80%以上が得られている。
ここで、No.4の発明例とNo.19の発明例は、バーナーの燃焼条件((G/F)/(G/F)st)は同じであるが、No.4の発明例の方が、溶鋼温度の上昇量、脱炭速度、Mn歩留りとも優れている。この違いは、No.19で用いた図3の上吹きランスは、ランス先端でMn鉱石と燃焼用ガスが混合して噴出するのに対して、No.4で用いた図2の上吹きランスは、ランス先端のノズルからMn鉱石を噴射し、その噴流をノズルの周囲に配設されたバーナーの火炎で包み込むようにしてMn鉱石を加熱するので、図2のランスの方が、Mn鉱石を効率よく加熱・還元することができるためであると考えられる。
一方、No.7は、バーナーの燃焼条件((G/F)/(G/F)st)が本発明の範囲より高いこと以外は、No.1~6の発明例と同じ比較例であり、火炎が還元性ではなく、Mn鉱石が還元されなかったため、溶鋼温度は上昇しているものの、Mnの歩留りはNo.13~15と同様、低位である。
逆に、No.8,9は、((G/F)/(G/F)st)が本発明の範囲より低いこと以外は、No.1~6の発明例と同じ比較例であり、供給される酸素の不足により火炎が形成されず、Mn鉱石が加熱されなかったため、Mn鉱石添加に伴う顕熱や潜熱による温度ロスによって溶鋼温度が低下し、Mn歩留りもNo.13~15と同様、低位である。
転炉吹錬した溶鋼は、未脱酸のまま取鍋に出鋼し、上吹きランスを備えたRH真空脱ガス装置に搬送し、未脱酸状態のままで真空脱炭処理するリムド処理を伴う脱ガス処理を施した。RH真空脱ガス装置到着時の溶鋼中O濃度は、0.03~0.07mass%の範囲であった。
また、上吹きランス先端のバーナーに火炎を形成する場合には、燃料としてのLNGを240Nm3/hr、燃焼用ガスとしての純酸素を120~600Nm3/hrの範囲で変えて供給することで、バーナーの燃焼条件((G/F)/(G/F)st)を変化させた。なお、この場合の(G/F)stは2(燃料の供給速度Fが1Nm3/minに対し、燃焼用ガスの供給速度Gが2Nm3/min)である。
No.9は、図2に示した上吹きランスを用いているが、バーナーの火炎で脱硫剤を加熱せずに上吹き添加した比較例であり、脱硫剤添加に伴う顕熱により溶鋼温度が大きく低下し、脱硫率も60%台と低位である。
これに対して、No.1~6は、図2に示した上吹きランスを用い、かつ、脱硫剤をバーナーの火炎で加熱して上吹き添加した発明例であり、脱硫剤添加による温度ロスがほとんどない。これは、脱硫剤を加熱して添加したことで、温度ロスが低減し、着熱効率が向上したためと考えられる。また、脱硫率も78%以上が得られている。これは、バーナーの火炎が還元性であるため、溶鋼の脱硫反応が促進されたためと考えられる。
一方、No.7は、バーナーの燃焼条件((G/F)/(G/F)st)が本発明の範囲より高いこと以外は、No.1~6の発明例と同じ比較例であり、溶鋼温度は上昇しているものの、脱硫率は60%台と低位である。これは、火炎が還元性ではないため、還元反応である溶鋼の脱硫反応が進行しなかったためと考えられる。
逆に、No.8は、バーナーの燃焼条件((G/F)/(G/F)st)が本発明の範囲より低いこと以外は、No.1~6の発明例と同じ比較例であり、供給される酸素が不足して火炎が形成されず、脱硫剤が加熱されなかったため、温度ロスによって溶鋼温度が大きく低下している。しかし、未燃焼の還元性ガスで脱硫剤が供給されたため、脱硫率は88.1%と高位である。
2:取鍋
3:脱ガス部
4:真空槽
5,6:浸漬管
7:排気口
8:副原料投入口(シュート)
9:上吹きランス
10:環流ガス供給配管
11:酸素ガス通路または粉体・キャリアガス通路
12:ノズル
13:内部水冷筒体
14:外部水冷筒体
15:燃料・燃焼用ガス通路
16:バーナー
17:パイロットバーナー
20:酸素ガス通路
21:スロート部
22:末広がり部
23:燃料ガス通路
24:燃料ガス供給孔
25:粉体・キャリアガス通路
26:粉体・キャリアガス噴出孔
Claims (4)
- 真空脱ガス設備に配設された上吹きランス先端のバーナーに形成した火炎で酸化物粉体を加熱し、脱ガス槽内の溶鋼の浴面上に上吹き添加する溶鋼の精錬方法において、
前記バーナーに、燃料と燃焼用ガスが下記式を満たすよう供給して火炎を形成することを特徴とする溶鋼の真空精錬方法。
記
0.4≦(G/F)/(G/F)st≦1.1
ここで、G :燃焼用ガス供給速度(Nm3/min)
F :燃料供給速度(Nm3/min)
(G/F) :酸素燃料比(=燃焼用ガス供給速度/燃料供給速度)
(G/F)st:燃料が完全燃焼する酸素燃料比の化学量論値 - 前記酸化物粉体は、Mn鉱石および/またはCaO系脱硫剤であることを特徴とする請求項1に記載の溶鋼の真空精錬方法。
- 前記上吹きランスの軸芯部に設けられた中心孔先端のノズルからMn鉱石および/またはCaO系脱硫剤をキャリアガスとともに噴出し、前記ノズルの周囲に配設した複数の周囲孔先端のバーナーから燃料と燃焼用ガスを供給し、点火して火炎を形成し、該火炎によって前記酸化物粉体を加熱することを特徴とする請求項1または2に記載の溶鋼の真空精錬方法。
- 前記燃料として、炭化水素系の気体燃料、炭化水素系の液体燃料および炭素系の固体燃料のうちのいずれか1種以上を供給することを特徴とする請求項1~3のいずれか1項に記載の溶鋼の真空精錬方法。
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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 |
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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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 |
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 |
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 |
US20230142051A1 (en) * | 2020-04-01 | 2023-05-11 | Jfe Steel Corporation | Decarburization refining method for molten steel under reduced pressure |
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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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