WO2018135344A1 - Desulfurization treatment method for molten steel, and desulfurization agent - Google Patents

Desulfurization treatment method for molten steel, and desulfurization agent Download PDF

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Publication number
WO2018135344A1
WO2018135344A1 PCT/JP2018/000280 JP2018000280W WO2018135344A1 WO 2018135344 A1 WO2018135344 A1 WO 2018135344A1 JP 2018000280 W JP2018000280 W JP 2018000280W WO 2018135344 A1 WO2018135344 A1 WO 2018135344A1
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Prior art keywords
molten steel
desulfurization
ladle
range
slag
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PCT/JP2018/000280
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French (fr)
Japanese (ja)
Inventor
勇輔 藤井
中井　由枝
秀弥 正木
菊池　直樹
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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 JP2018563279A priority Critical patent/JP6743915B2/en
Priority to CN201880007085.2A priority patent/CN110177889B/en
Priority to BR112019013592-8A priority patent/BR112019013592B1/en
Priority to KR1020197023942A priority patent/KR102290861B1/en
Priority to EP18741544.3A priority patent/EP3572534B1/en
Publication of WO2018135344A1 publication Critical patent/WO2018135344A1/en

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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
    • C21C7/0075—Treating in a ladle furnace, e.g. up-/reheating of molten steel within the ladle
    • 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
    • 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
    • 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

Definitions

  • the present invention relates to a method for desulfurizing molten steel and a desulfurizing agent.
  • the desulfurization process in the hot metal stage is not sufficient, and in addition to the desulfurization process in the hot metal stage, further desulfurization process in the molten steel stage. Is required.
  • desulfurization treatment at the molten steel stage is performed by an ASEA-SKF method, a VAD method, an LF method, or the like that has a means for heating and stirring the molten steel, and a means for blowing powder such as flux or alloy powder into the molten steel.
  • ASEA-SKF method a desulfurizing agent is added to a ladle containing molten steel melted by decarburization refining in a converter, and the molten steel and desulfurizing agent are agitated and mixed or arc heated to desulfurize.
  • the slag is formed by hatching the desulfurizing agent, and a slag-metal reaction is caused between the slag and the molten steel to transfer the sulfur component in the molten steel into the slag.
  • the desulfurizing agent a desulfurizing agent mainly composed of CaO (quick lime) and added with Al 2 O 3 (alumina), CaF 2 (fluorite), etc. for the purpose of lowering the melting point of the desulfurizing agent is used.
  • the added desulfurization agent is rapidly hatched, and the slag formed by the hatching of the desulfurization agent by increasing the stirring strength. It is important to increase the contact area between the metal and the metal.
  • the desulfurizing agent is generally added on top of the molten steel in the ladle. Even if the desulfurizing agent is hatched by arc heating after the addition, the desulfurizing agent is also stirred and mixed with the molten steel after the addition. Even if hatching, it takes a long time to hatch.
  • Patent Document 1 discloses a flux that is a mixture of quicklime, alumina, and fluorite is added, and then a bubbling treatment is performed, and the slag composition after the desulfurization treatment is changed to CaO. / Al 2 O 3 ⁇ 1.5, a method of desulfurization is disclosed a molten steel as CaF 2 ⁇ 5% by weight.
  • Patent Document 2 discloses a premelt of CaO—Al 2 O 3 (premixed and uniformly dissolved) or CaO—Al 2 O 3 —CaF 2 in order to promote hatching of the desulfurizing agent. A method of using melt flux as a desulfurizing agent is disclosed.
  • Patent Documents 3, 4 and 5 disclose a method in which a flux is mixed and blown into the stirring gas as means for increasing the stirring strength without increasing the stirring gas flow rate. .
  • the present invention has been made in view of the above problems, and its object is to provide a desulfurization treatment method and a desulfurization agent for molten steel that can efficiently perform a desulfurization treatment without using CaF 2 or a premelt flux. Is to provide.
  • the method for desulfurizing a molten steel according to the present invention includes adding a desulfurization agent containing quick lime to a ladle containing the molten steel, and stirring the molten steel in the ladle to reduce the sulfur concentration in the molten steel.
  • a desulfurizing agent containing quick lime having a pore volume within a range of 0.5 to 10 ⁇ m or less and having a total volume of pores of 0.1 mL / g or more is used.
  • the method for desulfurizing a molten steel according to the present invention is characterized in that, in the above-mentioned invention, the quicklime contains 90% or more of particles having a particle size in the range of 1 to 30 mm or less.
  • the desulfurization agent according to the present invention includes quick lime having a pore diameter within a range of 0.5 to 10 ⁇ m or less and a sum of pore volumes of 0.1 mL / g or more, and the quick lime has a particle size of 1 It is characterized by containing 90% or more of particles in the range of ⁇ 30 mm or less.
  • the desulfurization treatment method for molten steel according to the present invention is characterized in that, in the above-described invention, the molten steel is agitated so that the condition of the agitation power density represented by the following formula (1) is satisfied.
  • “Nm 3 ” means a gas volume in a standard state of an atmospheric pressure of 101325 Pa and a temperature of 273.15 K.
  • the method for desulfurizing a molten steel according to the present invention is the above-described invention, wherein the amount of aluminum introduced into the molten steel within 10 minutes after the desulfurization is started after the molten steel is removed from the converter satisfies the following formula (2). It is characterized by doing.
  • the method for desulfurizing molten steel according to the present invention is characterized in that, in the above invention, Ar gas is blown into the ladle so that the oxygen concentration in the ladle is 15% or less.
  • the desulfurization treatment method and desulfurizing agent of the molten steel according to the present invention it is possible to perform efficiently desulfurized without using CaF 2 and premelt flux.
  • FIG. 1 is a schematic side view of an LF facility used in carrying out the present invention.
  • FIG. 2 is a diagram showing hatching rates of the present invention example and the comparative example.
  • the inventors of the present invention have made extensive studies by paying attention to the particle size and pore size of lime and molten steel components. More specifically, the inventors of the present invention use a low-sulfur steel with a sulfur concentration of 0.0030% by mass or less as a main component of a desulfurizing agent using a CaO-containing material as a desulfurization method using a ladle refining method. Even when CaF 2 is not used as a part of the desulfurizing agent in the melting process, even if the desulfurizing agent is not a pre-melt flux, the flux added as the desulfurizing agent is rapidly hatched and efficiently. Various tests and research were repeated for the purpose of desulfurization treatment.
  • the inventors of the present invention can determine the temperature of the molten steel when the flux is added, sol. It has been found that Al concentration, lime particle size, and lime pore size are important. However, the temperature of the molten steel is determined by the temperature of the molten steel at the time of steel output from the converter, and increasing the temperature of the molten steel at the time of steel output unnecessarily increases the melting loss of the converter refractory and reduces the processing cost. It's not a good idea to cause an increase.
  • the inventors of the present invention mainly use quick lime having a pore volume within a range of 0.5 to 10 ⁇ m and having a total volume of 0.1 mL / g or more among pores of lime.
  • a powdery desulfurizing agent as a component, it was found that desulfurization treatment can be performed with high efficiency, and the present invention has been conceived.
  • the pore diameter distribution of quicklime was measured by the method shown below.
  • quicklime was dried at 120 ° C. for 4 hours.
  • the pore distribution of the dried quicklime having a pore diameter in the range of about 0.0036 to 200 ⁇ m is obtained by mercury porosimetry, and a cumulative pore volume curve is calculated. did. Further, the sum of the volumes of pores having a pore diameter in the range of 0.5 to 10 ⁇ m was determined from the calculated cumulative pore volume curve.
  • the hot metal discharged from the blast furnace is received in a hot metal transfer container such as a hot metal ladle or a topped car, and transferred to a converter for decarburization and refining in the next process.
  • a hot metal transfer container such as a hot metal ladle or a topped car
  • hot metal pretreatment such as desulfurization treatment or dephosphorization treatment is performed on the hot metal during the conveyance, and the present invention implements desulfurization treatment because it is a technique for producing low-sulfur steel.
  • dephosphorization is performed to prevent dephosphorization from the converter slag in the desulfurization after the converter steel. To do.
  • decarburization refining is performed in a converter on the hot metal subjected to desulfurization treatment and dephosphorization treatment, and the obtained molten steel is taken out into a ladle.
  • a small amount of quicklime (CaO) and a small amount of dolomite (MgCO 3 —CaCO 3 ) or calcined dolomite (MgO—CaO) ) As a flux to form slag (hereinafter referred to as “converter slag”) in the furnace.
  • This converter slag plays the role of promoting the dephosphorization reaction of the hot metal, but since the hot metal has already been dephosphorized, the main roles are to prevent the occurrence of iron splash during blowing and the converter lining refractory. Is to suppress melting damage.
  • the slag outflow prevention measures that are usually implemented will be implemented. Even if slag outflow prevention measures are implemented, it is difficult to completely prevent converter slag from flowing out, and a certain amount of converter slag enters the ladle and flows out into the molten steel. After steeling out, the converter slag that flows into the molten steel may be removed from the ladle, but the SiO 2 component in the converter slag is used to hatch the CaO-containing material that is subsequently added as a desulfurizing agent. It does not have to be removed because it contributes.
  • CaO—MgO—Al 2 O 3 —SiO 2 -based desulfurization slag having a predetermined composition in the ladle
  • CaO-containing material, MgO-containing material, Al 2 O 3 -containing material, and SiO 2 -containing as flux Add material into pan.
  • MgO has a lower desulfurization ability than CaO
  • the MgO-containing material may not be added.
  • metal Al is added in a ladle for deoxidation of molten steel and reduction of slag (reduction of Fe oxide and Mn oxide in slag).
  • These substances may be added in a post-process facility for performing desulfurization treatment by any one of the ASEA-SKF method, the VAD method, and the LF method, but from the viewpoint of promoting the hatching of CaO. It is preferable to add to the ladle at the time of steel removal from the converter to the ladle or immediately after the steel removal.
  • the quick lime added immediately after the steel is extracted has a pore volume having a pore diameter in the range of 0.5 to 10 ⁇ m among the fine pores of the quick lime, and the sum of the volumes is 0.1 mL / g or more. It is preferable to contain 90% or more of particles having a diameter in the range of 1 to 30 mm.
  • the addition amount of CaO-containing material, MgO-containing material, metal Al, Al 2 O 3 -containing material, and SiO 2 -containing material takes into account the mass and composition of the converter slag that has flowed into the ladle.
  • each addition amount so that (mass% MgO) / (mass% CaO) of the slag to be generated is 0.10 or less. Then, these substances are added to the ladle in a predetermined amount.
  • Metal Al is not necessarily the total amount added is Al 2 O 3, remain dissolved in the molten steel. Therefore, the ratio between the dissolved Al content that dissolves in the molten steel and the amount that becomes Al 2 O 3 in the slag is determined in advance, and the amount of metal Al added is set based on the ratio. CaF 2 is not added.
  • the composition of the ladle slag after the desulfurization treatment is adjusted to a composition containing no CaF 2 substantially
  • the fluorine compound such as CaF 2 as a slag formation accelerators CaO exist means to adjust the slag composition after the desulfurization treatment without, fluorine unavoidably Kitasa have mixed in the CaO-containing material, Al 2 O 3, or the containing material, and the like used by the slag after the desulfurization treatment Even so, it is defined as slag substantially free of CaF 2 .
  • CaO-containing substance to be added quick lime (CaO), limestone (CaCO 3 ), slaked lime (Ca (OH) 2 ), dolomite (MgCO 3 —CaCO 3 ), calcined dolomite (MgO—CaO), etc. are used.
  • As the contained material magnesia clinker (MgO), dolomite (MgCO 3 —CaCO 3 ), calcined dolomite (MgO—CaO), or the like is used.
  • the average particle size of lime is preferably in the range of 1 to 30 mm from the viewpoint of reaction efficiency and addition yield. From the viewpoint of reducing the amount sucked into the exhaust system, it is desirable that the amount of fine powder is small, and it is preferable that lime having an average particle size of 30 mm or more is small.
  • the measuring method of the average particle diameter is as follows. Take 1kg of desulfurization agent, and screen through 9 stages of 500 ⁇ m or less, 500 ⁇ m to 1mm, 1 to 5mm, 5 to 10mm, 10 to 15mm, 15 to 20mm, 20 to 25mm, 25 to 30mm, 30mm or more. The diameter was calculated based on the weight ratio, and the diameter was calculated by the following formula (4).
  • Al 2 O 3 containing materials examples include aluminum dross (containing 20 to 70% by mass of metallic Al, the main component of the balance being Al 2 O 3 ), bauxite (Al 2 O 3 .2H 2 O), calcined alumina (Al using the 2 O 3) or the like. Almidros can also replace Al metal.
  • the SiO 2 containing material silica sand (SiO 2), using the wollastonite (CaO-SiO 2) or the like. In this case, when the mass of the converter slag flowing out into the ladle is large, it may not be necessary to add the SiO 2 -containing material.
  • FIG. 1 is a schematic side view of an LF facility used in carrying out the present invention.
  • reference numeral 1 is an LF facility
  • reference numeral 2 is a ladle
  • reference numeral 3 is an elevating lid
  • reference numeral 4 is an electrode for arc heating
  • reference numerals 5 and 6 are immersion lances
  • reference numerals 7 and 8 are bottom blown porous bricks
  • Reference numeral 9 denotes molten steel
  • reference numeral 10 denotes slag
  • reference numeral 11 denotes a raw material charging chute
  • reference numeral 12 denotes an Ar gas introduction pipe.
  • a ladle 2 that accommodates molten steel 9 loaded on a traveling carriage (not shown) is disposed at a predetermined position directly below the lid 3, and the lid 3 is lowered to move the upper end of the ladle 2.
  • Ar gas is supplied from the Ar gas introduction pipe 12 and the space surrounded by the ladle 2 and the lid 3 is made an Ar gas atmosphere.
  • Ar gas is preferably blown from a pipe attached around the furnace lid so that the oxygen concentration in the ladle 2 is 15% or less.
  • the flow rate of Ar gas blown from the ladle 2 is preferably a value of ⁇ L 2 / 4Q is to range to become a flow rate of 50 ⁇ 150 (m / min) , more preferably, 70 ⁇ 100 (m / min )
  • the flow rate is within the range of.
  • L is the diameter (m) of the ladle
  • Q is the Ar gas flow rate (Nm 3 / min). If the flow rate of Ar gas is small, the oxygen concentration is not sufficiently reduced. Conversely, if the flow rate of Ar gas is too high, the molten steel temperature is lowered.
  • the CaO-containing material, MgO-containing material, metal Al, Al 2 O 3- containing material, and SiO 2 -containing material are not added in advance in the ladle 2, and when the amount of addition of these materials is insufficient In this state, flux of these substances and metal Al are introduced into the ladle 2 through the raw material charging chute 11.
  • the metal Al is preferably added so as to satisfy the following formula (5) within 10 minutes from the start. That is, it is preferable for increasing the Al concentration in the molten steel to promote the desulfurization treatment by adding metal Al according to the Al concentration after the converter steel.
  • the electrode 4 is energized to generate an arc, the molten steel 9 is heated, and the added flux is hatched. Then, the immersion lance 5 or the immersion lance 6 is immersed in the molten steel 9, and the immersion lance 5 Then, Ar gas as a stirring gas is blown into the molten steel 9 from at least one of the immersion lance 6 or the bottom blown porous bricks 7 and 8, and the molten steel 9 is stirred. By stirring the molten steel 9, the flux is mixed with the molten steel 9, and the hatching of the flux proceeds to generate the slag 10.
  • the produced slag 10 is agitated and mixed with the molten steel 9 by the agitation of the molten steel 9, and a slag-metal reaction occurs between the molten steel 9 and the slag 10, and the sulfur component in the molten steel 9 is transferred into the slag.
  • a reaction occurs.
  • any one or more of Ca alloy powder, metal Mg powder, and Mg alloy powder is used together with Ar gas from the immersion lances 5 and 6. It is preferable to blow into the molten steel 9 or to blow the stirring gas from the immersion lances 5 and 6 and the stirring gas from the bottom blown porous bricks 7 and 8 at least at one time of the desulfurization treatment. .
  • Ca alloy powder Ca—Si alloy powder, Ca—Al alloy powder or the like is used, and as the Mg alloy powder, Mg—Al—Zn alloy powder, Mg—Si—Fe alloy powder or the like is used.
  • Mg alloy powder Mg—Al—Zn alloy powder, Mg—Si—Fe alloy powder or the like is used.
  • the desulfurization of molten steel 9 by ladle refining method using a CaO-containing material as a principal constituent of the desulfurizing agent, the slag composition after the desulfurization treatment, the content of SiO 2 Therefore, SiO 2 functions as a CaO hatching accelerator to promote the hatching of CaO, and the slag composition after desulfurization treatment is changed to [( Since mass% CaO) + (mass% MgO)] / (mass% Al 2 O 3 ) is adjusted to be in the range of 1.5 to 3.0, the slag 10 has a high desulfurization capability, As a result, even if CaF 2 is not used as a part of the desulfurizing agent and the desulfurizing agent is not a premelt flux, it is possible to efficiently desulfurize the molten steel 9.
  • the present invention can also be applied to an ASEA-SKF
  • Example 1 The hot metal discharged from the blast furnace is subjected to desiliconization, desulfurization, and dephosphorization, and then the hot metal is charged into a converter to carry out decarburization and refining. Approximately 250 tons of molten steel having a sulfur concentration in the range of 0.0041 to 0.0043% by mass and a phosphorus concentration in the range of 0.004 to 0.010% by mass was obtained. . After steeling out, the ladle slag that had flowed into the ladle was not gradually reduced, and the ladle to which metal Al, quicklime, light-burned dolomite, and aluminum dross were added was conveyed to the LF facility shown in FIG.
  • Table 1 shows the sulfur concentration (chemical analysis value) and desulfurization rate in the molten steel before and after the desulfurization treatment in each desulfurization test. Further, in the remarks column of Table 1, tests within the scope of the present invention are indicated as “examples of the present invention”, and other cases are indicated as “comparative examples”. In addition, a desulfurization rate is the value which displayed the difference of the sulfur concentration in the molten steel before and behind a desulfurization process with a percentage with respect to the sulfur concentration in the molten steel before a desulfurization process.
  • the desulfurization evaluation “ ⁇ ” indicates that the sulfur concentration in the molten steel after the desulfurization treatment was 0.0024% or less, and the desulfurization evaluation “x” indicates that the sulfur concentration in the molten steel after the desulfurization treatment is low. It shows that it was over 0.0024%.
  • test levels and results are shown in Table 1.
  • the desulfurization rate is compared with the present invention examples (test numbers 4 to 15).
  • the average particle size of quicklime was in the range of 1 to 30 mm, hatching was promoted and the desulfurization rate of the molten steel was high.
  • Example 2 The hot metal discharged from the blast furnace is subjected to desiliconization, desulfurization, and dephosphorization, and then the hot metal is charged into a converter to carry out decarburization and refining.
  • About 250 t of molten steel was obtained in the range of 0.09% by mass, the sulfur concentration in the range of 0.0041 to 0.0043% by mass, and the phosphorus concentration in the range of 0.004 to 0.010% by mass.
  • the ladle slag that had flowed into the ladle was not gradually removed, and the ladle to which metal Al, quicklime, light-burned dolomite, and aluminum dross were added was conveyed to the LF facility shown in FIG.
  • Table 2 shows the sulfur concentration (chemical analysis value) and desulfurization rate in the molten steel before and after the desulfurization treatment in each desulfurization test.
  • desulfurization evaluation "(circle)" has shown that the sulfur concentration in the molten steel after a desulfurization process was 0.0024% or less.
  • FIG. 2 is a diagram showing hatching rates of the present invention example and the comparative example.
  • Quick lime having a pore diameter in the range of 0.5 to 10 ⁇ m with a total volume of pores of 0.2 mL / g and a particle size of 20 mm or less is an example of the present invention, and the pore diameter is 0.5 to 10 ⁇ m.
  • Quick lime having a pore volume sum in the range of 0.03 mL / g and a particle size of 20 mm or less was used as a comparative example. As shown in FIG. 2, it was confirmed that hatching was promoted in the inventive example even when the stirring power density (135 W / t) was the same as in the comparative example.
  • Example 4 The hot metal discharged from the blast furnace is subjected to desiliconization, desulfurization, and dephosphorization, and then the hot metal is charged into a converter to carry out decarburization and refining. About 250 t of molten steel having a sulfur concentration within the range of 0.09 mass%, a sulfur concentration within the range of 0.0041 to 0.0044 mass%, and a phosphorus concentration within the range of 0.004 to 0.010 mass% was obtained.
  • the ladle slag that had flowed into the ladle was not gradually removed, and the ladle to which metal Al, quicklime, light-burned dolomite, and aluminum dross were added was conveyed to the LF facility shown in FIG.
  • quick lime having a pore volume within a range of 0.5 to 10 ⁇ m with a pore volume sum of 0.2 mL / g and a particle size of 20 mm or less was used.
  • Table 3 shows the sulfur concentration in the molten steel (chemical analysis value) and the desulfurization rate before and after the desulfurization treatment in each desulfurization test.
  • [sol.Al] 1 is the upper limit value (mass%) of the Al concentration standard of the steel type to be melted
  • [sol.Al] 2 is the Al concentration (mass%) in the molten steel after the converter steel.
  • desulfurization evaluation "(circle)" has shown that the sulfur concentration in the molten steel after a desulfurization process was 0.0024% or less.
  • Example 5 After desiliconization, desulfurization, and dephosphorization are performed on the hot metal discharged from the blast furnace, the hot metal is charged into the converter and decarburized and refined, and the carbon concentration is 0.05-0. About 250 t of molten steel was obtained in the range of 0.09 mass%, the sulfur concentration in the range of 0.0041 to 0.0044 mass%, and the phosphorus concentration in the range of 0.004 to 0.010 mass%. After the steel was tapped, the ladle slag that had flowed into the ladle was not gradually removed, and the ladle to which metal Al, quicklime, light-burned dolomite, and aluminum dross were added was conveyed to the LF facility shown in FIG.
  • Table 4 shows the sulfur concentration (chemical analysis value) and desulfurization rate in the molten steel before and after the desulfurization treatment in each desulfurization test.
  • desulfurization evaluation "(circle)" has shown that the sulfur concentration in the molten steel after a desulfurization process was 0.0024% or less.

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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)
  • Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)

Abstract

The desulfurization treatment method for molten steel according to the present invention is for reducing the sulfur concentration of molten steel, by adding a desulfurization agent containing quicklime to a ladle containing molten steel, and stirring the molten steel in the ladle, and is characterized in that the desulfurization agent used is one which contains quicklime, and in that the sum of the volumes of pores having a pore diameter falling within the range of 0.5-10 μm or less is 0.1 mL/g or more. This allows the desulfurization treatment to be efficiently performed without use of CaF2 or pre-melt flux.

Description

溶鋼の脱硫処理方法及び脱硫剤Method for desulfurizing molten steel and desulfurizing agent
　本発明は、溶鋼の脱硫処理方法及び脱硫剤に関する。 The present invention relates to a method for desulfurizing molten steel and a desulfurizing agent.
　近年、鋼の高付加価値化や鉄鋼材料の使用用途拡大等に伴う材料特性向上のために、高純度鋼製造に対する要求が高まっており、特に鉄鋼材料の靭性を低下させる元素である硫黄の含有量が少ない極低硫鋼に対する要求が高くなっている。鉄鋼材料の溶製過程においては、溶銑段階での脱硫処理と溶鋼段階での脱硫処理とがあり、通常、鉄鋼材料は溶銑段階での脱硫処理のみで溶製されている。ところが、高級電磁鋼板やラインパイプ用鋼材等の極低硫鋼の溶製過程では、溶銑段階での脱硫処理のみでは十分でなく、溶銑段階での脱硫処理に加えてさらに溶鋼段階での脱硫処理が必要となる。 In recent years, there has been an increasing demand for high-purity steel production in order to improve material properties accompanying increased value added steel and expanded use of steel materials, and in particular, the inclusion of sulfur, an element that lowers the toughness of steel materials. There is an increasing demand for low-sulfurized steel with a small amount. In the melting process of steel materials, there are a desulfurization process at the hot metal stage and a desulfurization process at the molten steel stage, and the steel material is usually melted only by the desulfurization process at the hot metal stage. However, in the process of producing ultra-low sulfur steel such as high-grade electrical steel sheets and steel for line pipes, the desulfurization process in the hot metal stage is not sufficient, and in addition to the desulfurization process in the hot metal stage, further desulfurization process in the molten steel stage. Is required.
　一般に、溶鋼段階での脱硫処理は、溶鋼のアーク加熱手段や攪拌手段、さらには溶鋼へのフラックス又は合金粉等の粉体吹き込み手段を有する、ＡＳＥＡ－ＳＫＦ法、ＶＡＤ法、ＬＦ法等の取鍋精錬法によって行われている。取鍋精錬法は、転炉での脱炭精錬によって溶製された溶鋼を収容する取鍋内に脱硫剤を添加し、溶鋼と脱硫剤とを攪拌・混合する又はアーク加熱することによって脱硫剤を滓化させ、脱硫剤の滓化により形成されたスラグと溶鋼との間でスラグ－メタル間反応を起こさせて溶鋼中の硫黄成分をスラグ中に移行させるという流れで行われる。 In general, desulfurization treatment at the molten steel stage is performed by an ASEA-SKF method, a VAD method, an LF method, or the like that has a means for heating and stirring the molten steel, and a means for blowing powder such as flux or alloy powder into the molten steel. This is done by the pot refining method. In the ladle refining method, a desulfurizing agent is added to a ladle containing molten steel melted by decarburization refining in a converter, and the molten steel and desulfurizing agent are agitated and mixed or arc heated to desulfurize. The slag is formed by hatching the desulfurizing agent, and a slag-metal reaction is caused between the slag and the molten steel to transfer the sulfur component in the molten steel into the slag.
　ここで、脱硫剤としては、ＣａＯ（生石灰）を主成分とし、これに脱硫剤の融点降下を目的とするＡｌ2Ｏ3（アルミナ）、ＣａＦ2（蛍石）等を加えた脱硫剤が使用されている。取鍋精錬法による脱硫処理方法で効率的な脱硫反応を起こさせるためには、添加した脱硫剤を早急に滓化させること、及び、攪拌強度を高めて脱硫剤の滓化によって形成されるスラグとメタルとの接触面積を増大させることが重要となる。脱硫剤は取鍋内の溶鋼上に上置き添加されることが一般的であり、添加後にアーク加熱によって脱硫剤を滓化するにしても、また、添加後に溶鋼との攪拌・混合で脱硫剤を滓化するにしても、滓化に長時間を要する。 Here, as the desulfurizing agent, a desulfurizing agent mainly composed of CaO (quick lime) and added with Al 2 O 3 (alumina), CaF 2 (fluorite), etc. for the purpose of lowering the melting point of the desulfurizing agent is used. Has been. In order to cause an efficient desulfurization reaction in the desulfurization treatment method using the ladle refining method, the added desulfurization agent is rapidly hatched, and the slag formed by the hatching of the desulfurization agent by increasing the stirring strength. It is important to increase the contact area between the metal and the metal. The desulfurizing agent is generally added on top of the molten steel in the ladle. Even if the desulfurizing agent is hatched by arc heating after the addition, the desulfurizing agent is also stirred and mixed with the molten steel after the addition. Even if hatching, it takes a long time to hatch.
　そこで、脱硫剤の滓化促進のために、特許文献１には、生石灰、アルミナ、及び蛍石との混合品であるフラックスを添加し、その後バブリング処理を行い、脱硫処理後のスラグ組成をＣａＯ／Ａｌ2Ｏ3≧１．５、ＣａＦ2≧５質量％として溶鋼を脱硫する方法が開示されている。また、特許文献２には、脱硫剤の滓化促進のために、ＣａＯ－Ａｌ2Ｏ3のプリメルトフラックス（事前に混合、均一溶解したもの）又はＣａＯ－Ａｌ2Ｏ3－ＣａＦ2のプリメルトフラックスを脱硫剤として使用する方法が開示されている。一方、溶鋼攪拌の強化については、攪拌用ガス流量を高めることなく攪拌強度を高める手段として、特許文献３，４，５には、フラックスを攪拌用ガスに混入して吹き込む方法が開示されている。 Therefore, in order to promote the hatching of the desulfurizing agent, in Patent Document 1, a flux that is a mixture of quicklime, alumina, and fluorite is added, and then a bubbling treatment is performed, and the slag composition after the desulfurization treatment is changed to CaO. / Al 2 O 3 ≧ 1.5, a method of desulfurization is disclosed a molten steel as CaF 2 ≧ 5% by weight. Patent Document 2 discloses a premelt of CaO—Al 2 O 3 (premixed and uniformly dissolved) or CaO—Al 2 O 3 —CaF 2 in order to promote hatching of the desulfurizing agent. A method of using melt flux as a desulfurizing agent is disclosed. On the other hand, for strengthening the molten steel stirring, Patent Documents 3, 4 and 5 disclose a method in which a flux is mixed and blown into the stirring gas as means for increasing the stirring strength without increasing the stirring gas flow rate. .
特開平８－２６００２５号公報JP-A-8-260025 特開平９－２１７１１０号公報JP-A-9-217110 特開昭６１－９１３１８号公報JP 61-91318 A 特開昭６１－２８１８０９号公報JP 61-281809 A 特開２０００－２３４１１９号公報JP 2000-234119 A
　しかしながら、特許文献１記載の方法によれば、ＣａＦ2を含有する脱硫剤を使用した場合、生成されるスラグ中のＣａＦ2によって取鍋を形成する耐火物が激しく溶損され、取鍋の寿命が大幅に短くなるという問題がある。また、特許文献２記載の方法によれば、プリメルトフラックスが非常に高価であり、処理コストが上昇するという問題がある。また、ＣａＦ2を含有する脱硫剤では前述した問題が同様に発生する。 However, according to the method described in Patent Document 1, when a desulfurizing agent containing CaF 2 is used, the refractory forming the ladle is severely melted by CaF 2 in the slag to be produced, and the life of the ladle There is a problem that is significantly shortened. Further, according to the method described in Patent Document 2, there is a problem that the premelt flux is very expensive and the processing cost is increased. In addition, the above-described problems similarly occur in the desulfurization agent containing CaF 2 .
　一方、特許文献３，４，５記載の方法では、吹き込みガス流量に対してフラックス吹き込み量に限界があり（固気比は５～３０ｋｇ／ｋｇが限界）、増加可能な攪拌力には限界がある。また、攪拌用ガス流量を増加した場合には、取鍋内の溶鋼湯面の乱れ（揺動）が激しくなり、スプラッシュが発生して地金が蓋に付着する、又は、電極と溶鋼との間で短絡する等してアークが安定せず、アーク加熱が困難になるという問題等が発生する。 On the other hand, in the methods described in Patent Documents 3, 4, and 5, there is a limit to the amount of flux blown with respect to the blown gas flow rate (the solid-gas ratio is limited to 5 to 30 kg / kg), and the stirring force that can be increased is limited. is there. In addition, when the stirring gas flow rate is increased, the molten steel surface in the ladle becomes turbulent (swaying), and splash occurs and the metal sticks to the lid, or the electrode and molten steel For example, the arc may not be stable due to short-circuiting, and arc heating becomes difficult.
　本発明は、上記課題に鑑みてなされたものであって、その目的は、ＣａＦ2やプリメルトフラックスを使用しなくても効率良く脱硫処理を行うことが可能な溶鋼の脱硫処理方法及び脱硫剤を提供することにある。 The present invention has been made in view of the above problems, and its object is to provide a desulfurization treatment method and a desulfurization agent for molten steel that can efficiently perform a desulfurization treatment without using CaF 2 or a premelt flux. Is to provide.
　本発明に係る溶鋼の脱硫処理方法は、溶鋼を収容する取鍋内に生石灰を含む脱硫剤を添加し、取鍋内で溶鋼を攪拌することによって、溶鋼中の硫黄濃度を低減する溶鋼の脱硫処理方法であって、前記脱硫剤として、細孔直径が０．５～１０μｍ以下の範囲内にある細孔の容積の和が０．１ｍＬ／ｇ以上である生石灰を含む脱硫剤を用いることを特徴とする。 The method for desulfurizing a molten steel according to the present invention includes adding a desulfurization agent containing quick lime to a ladle containing the molten steel, and stirring the molten steel in the ladle to reduce the sulfur concentration in the molten steel. In the treatment method, as the desulfurizing agent, a desulfurizing agent containing quick lime having a pore volume within a range of 0.5 to 10 μm or less and having a total volume of pores of 0.1 mL / g or more is used. Features.
　本発明に係る溶鋼の脱硫処理方法は、上記発明において、前記生石灰が、粒径が１～３０ｍｍ以下の範囲内にある粒子を９０％以上含むことを特徴とする。 The method for desulfurizing a molten steel according to the present invention is characterized in that, in the above-mentioned invention, the quicklime contains 90% or more of particles having a particle size in the range of 1 to 30 mm or less.
　本発明に係る脱硫剤は、細孔直径が０．５～１０μｍ以下の範囲内にある細孔の容積の和が０．１ｍＬ／ｇ以上である生石灰を含み、前記生石灰が、粒径が１～３０ｍｍ以下の範囲内にある粒子を９０％以上含むことを特徴とする。 The desulfurization agent according to the present invention includes quick lime having a pore diameter within a range of 0.5 to 10 μm or less and a sum of pore volumes of 0.1 mL / g or more, and the quick lime has a particle size of 1 It is characterized by containing 90% or more of particles in the range of ˜30 mm or less.
　本発明に係る溶鋼の脱硫処理方法は、上記発明において、下記数式（１）で示される撹拌動力密度の条件が満足されるように前記溶鋼を攪拌することを特徴とする。なお、本明細書中において、「Ｎｍ３」とは、気圧１０１３２５Ｐａ、温度２７３．１５Ｋの標準状態での気体の体積のことを意味する。 The desulfurization treatment method for molten steel according to the present invention is characterized in that, in the above-described invention, the molten steel is agitated so that the condition of the agitation power density represented by the following formula (1) is satisfied. In the present specification, “Nm 3 ” means a gas volume in a standard state of an atmospheric pressure of 101325 Pa and a temperature of 273.15 K.
Figure JPOXMLDOC01-appb-M000003
Figure JPOXMLDOC01-appb-M000003
　本発明に係る溶鋼の脱硫処理方法は、上記発明において、前記溶鋼が転炉から出鋼されてから脱硫処理開始後１０分以内に溶鋼に投入されるアルミニウムの量が下記数式（２）を満足することを特徴とする。 The method for desulfurizing a molten steel according to the present invention is the above-described invention, wherein the amount of aluminum introduced into the molten steel within 10 minutes after the desulfurization is started after the molten steel is removed from the converter satisfies the following formula (2). It is characterized by doing.
Figure JPOXMLDOC01-appb-M000004
Figure JPOXMLDOC01-appb-M000004
　本発明に係る溶鋼の脱硫処理方法は、上記発明において、前記取鍋内における酸素濃度が１５％以下となるように前記取鍋内にＡｒガスを吹き込むことを特徴とする。 The method for desulfurizing molten steel according to the present invention is characterized in that, in the above invention, Ar gas is blown into the ladle so that the oxygen concentration in the ladle is 15% or less.
　本発明に係る溶鋼の脱硫処理方法及び脱硫剤によれば、ＣａＦ2やプリメルトフラックスを使用しなくても効率良く脱硫処理を行うことができる。 According to the desulfurization treatment method and desulfurizing agent of the molten steel according to the present invention, it is possible to perform efficiently desulfurized without using CaF 2 and premelt flux.
図１は、本発明を実施する際に用いたＬＦ設備の側面概略図である。FIG. 1 is a schematic side view of an LF facility used in carrying out the present invention. 図２は、本発明例及び比較例の滓化率を示す図である。FIG. 2 is a diagram showing hatching rates of the present invention example and the comparative example.
　本発明の発明者らは、上記課題を解決するべく、石灰の粒度及び細孔径や溶鋼成分に着目して鋭意検討を重ねた。より具体的には、本発明の発明者らは、硫黄濃度が０．００３０質量％以下である低硫鋼を、ＣａＯ含有物質を脱硫剤の主たる構成物質として使用して取鍋精錬法による脱硫処理で溶製するにあたり、ＣａＦ2を脱硫剤の一部として使用しなくても、また、脱硫剤がプリメルトフラックスでなくても、脱硫剤として添加したフラックスを迅速に滓化させ、効率良く脱硫処理を行うことを目的とし、種々試験・研究を重ねた。 In order to solve the above-mentioned problems, the inventors of the present invention have made extensive studies by paying attention to the particle size and pore size of lime and molten steel components. More specifically, the inventors of the present invention use a low-sulfur steel with a sulfur concentration of 0.0030% by mass or less as a main component of a desulfurizing agent using a CaO-containing material as a desulfurization method using a ladle refining method. Even when CaF 2 is not used as a part of the desulfurizing agent in the melting process, even if the desulfurizing agent is not a pre-melt flux, the flux added as the desulfurizing agent is rapidly hatched and efficiently. Various tests and research were repeated for the purpose of desulfurization treatment.
　その結果、本発明の発明者らは、脱硫剤として添加したフラックスの滓化促進のためには、フラックスを添加するときの溶鋼の温度、ｓｏｌ．Ａｌ濃度、石灰の粒度、及び石灰の細孔径が重要であることを知見した。但し、溶鋼の温度は、転炉からの出鋼時の溶鋼の温度によって決まり、むやみに出鋼時の溶鋼の温度を高くすることは、転炉耐火物の溶損を増大させ、処理コストの増加を招き得策ではない。 As a result, in order to promote the hatching of the flux added as a desulfurizing agent, the inventors of the present invention can determine the temperature of the molten steel when the flux is added, sol. It has been found that Al concentration, lime particle size, and lime pore size are important. However, the temperature of the molten steel is determined by the temperature of the molten steel at the time of steel output from the converter, and increasing the temperature of the molten steel at the time of steel output unnecessarily increases the melting loss of the converter refractory and reduces the processing cost. It's not a good idea to cause an increase.
　そこで、本発明の発明者らは、石灰が有する細孔のうち、細孔直径が０．５～１０μｍの範囲内にある細孔の容積の和が０．１ｍＬ／ｇ以上である生石灰を主成分とする粉状脱硫剤を用いることにより、高効率で脱硫処理を行うことができることを見出し、本発明を想到するに至った。なお、生石灰の細孔径分布は、以下に示す方法で測定した。 Therefore, the inventors of the present invention mainly use quick lime having a pore volume within a range of 0.5 to 10 μm and having a total volume of 0.1 mL / g or more among pores of lime. By using a powdery desulfurizing agent as a component, it was found that desulfurization treatment can be performed with high efficiency, and the present invention has been conceived. In addition, the pore diameter distribution of quicklime was measured by the method shown below.
　まず、前処理として、生石灰を１２０℃で４時間、恒温乾燥した。次いで、Ｍｉｃｒｏｍｅｒｉｔｉｅｓ社製のオートポアＩＶ９５２０を用いて、水銀圧入法により、乾燥させた生石灰の細孔直径が約０．００３６～２００μｍの範囲内にある細孔分布を求め、累積細孔容積曲線を算出した。さらに、算出された累積細孔容積曲線から細孔直径が０．５～１０μｍの範囲内にある細孔の容積の和を求めた。 First, as a pretreatment, quicklime was dried at 120 ° C. for 4 hours. Next, using an Autopore IV9520 manufactured by Micromerites, the pore distribution of the dried quicklime having a pore diameter in the range of about 0.0036 to 200 μm is obtained by mercury porosimetry, and a cumulative pore volume curve is calculated. did. Further, the sum of the volumes of pores having a pore diameter in the range of 0.5 to 10 μm was determined from the calculated cumulative pore volume curve.
　細孔直径は、以下の数式（３）に示すＷａｓｈｂｕｒｎの式を用いて算出した。なお、数式（３）において、Ｐは圧力、Ｄは細孔直径、σは水銀の表面張力（＝４８０ｄｙｎｅｓ／ｃｍ）、θは水銀と試料との接触角（＝１４０ｄｅｇｒｅｅｓ）をそれぞれ示す。 The pore diameter was calculated using the Washburn equation shown in the following equation (3). In Equation (3), P is the pressure, D is the pore diameter, σ is the surface tension of mercury (= 480 dynes / cm), and θ is the contact angle (= 140 degrees) between mercury and the sample.
Figure JPOXMLDOC01-appb-M000005
Figure JPOXMLDOC01-appb-M000005
　高炉から出銑された溶銑は、溶銑鍋やトピードカー等の溶銑搬送用容器で受銑され、次工程の脱炭精錬を行う転炉に搬送される。通常、この搬送途中で溶銑に対して脱硫処理や脱燐処理等の溶銑予備処理が施されており、本発明は、低硫鋼を製造する技術であることから脱硫処理を実施する。また、低硫鋼の成分規格上からは脱燐処理が必要でない場合であっても、転炉出鋼後の脱硫処理における転炉スラグからの復燐を防止するために、脱燐処理を実施する。 The hot metal discharged from the blast furnace is received in a hot metal transfer container such as a hot metal ladle or a topped car, and transferred to a converter for decarburization and refining in the next process. Usually, hot metal pretreatment such as desulfurization treatment or dephosphorization treatment is performed on the hot metal during the conveyance, and the present invention implements desulfurization treatment because it is a technique for producing low-sulfur steel. Also, even if dephosphorization is not necessary due to the component specifications of low-sulfur steel, dephosphorization is performed to prevent dephosphorization from the converter slag in the desulfurization after the converter steel. To do.
　次に、脱硫処理及び脱燐処理の施された溶銑に対して転炉で脱炭精錬を実施し、得られた溶鋼を取鍋に出鋼する。転炉での脱炭精錬は、溶銑には既に脱硫処理及び脱燐処理が施されているので、少量の生石灰（ＣａＯ）及び少量のドロマイト（ＭｇＣＯ3－ＣａＣＯ3）又は焼成ドロマイト（ＭｇＯ－ＣａＯ）をフラックスとして使用し、炉内にスラグ（以下、「転炉スラグ」と呼ぶ）を形成させる。この転炉スラグは、溶銑の脱燐反応を促進させる役割を担うが、溶銑が既に脱燐処理されていることから、主たる役割は、吹錬中の鉄スプラッシュの発生防止及び転炉内張り耐火物の溶損抑制である。 Next, decarburization refining is performed in a converter on the hot metal subjected to desulfurization treatment and dephosphorization treatment, and the obtained molten steel is taken out into a ladle. In the decarburization refining in the converter, since desulfurization treatment and dephosphorization treatment have already been performed on the hot metal, a small amount of quicklime (CaO) and a small amount of dolomite (MgCO 3 —CaCO 3 ) or calcined dolomite (MgO—CaO) ) As a flux to form slag (hereinafter referred to as “converter slag”) in the furnace. This converter slag plays the role of promoting the dephosphorization reaction of the hot metal, but since the hot metal has already been dephosphorized, the main roles are to prevent the occurrence of iron splash during blowing and the converter lining refractory. Is to suppress melting damage.
　出鋼の末期、溶鋼に混入して転炉スラグが取鍋内に流出するので、これを防止するために、通常実施されるスラグ流出防止対策を実施する。スラグ流出防止対策を実施しても、転炉スラグの完全な流出防止は困難であり、取鍋にはある程度の量の転炉スラグが溶鋼に混入して流出する。出鋼後、溶鋼に混入して流入した転炉スラグを取鍋から除去してもよいが、転炉スラグ中のＳｉＯ2成分が、脱硫剤としてその後に添加されるＣａＯ含有物質の滓化に寄与することから除去しなくてもよい。 Since the converter slag flows out into the ladle at the end of the steel output, the slag outflow prevention measures that are usually implemented will be implemented. Even if slag outflow prevention measures are implemented, it is difficult to completely prevent converter slag from flowing out, and a certain amount of converter slag enters the ladle and flows out into the molten steel. After steeling out, the converter slag that flows into the molten steel may be removed from the ladle, but the SiO 2 component in the converter slag is used to hatch the CaO-containing material that is subsequently added as a desulfurizing agent. It does not have to be removed because it contributes.
　取鍋内に所定の組成のＣａＯ－ＭｇＯ－Ａｌ2Ｏ3－ＳｉＯ2系の脱硫用スラグを形成するべく、フラックスとしてＣａＯ含有物質、ＭｇＯ含有物質、Ａｌ2Ｏ3含有物質、及びＳｉＯ2含有物質を取鍋内に添加する。但し、前述したように、ＭｇＯはＣａＯに比較して脱硫能が低いので、ＭｇＯ含有物質は添加しなくても構わない。また、溶鋼の脱酸及びスラグの還元（スラグ中のＦｅ酸化物及びＭｎ酸化物の還元）のために、取鍋内に金属Ａｌを添加する。 In order to form a CaO—MgO—Al 2 O 3 —SiO 2 -based desulfurization slag having a predetermined composition in the ladle, CaO-containing material, MgO-containing material, Al 2 O 3 -containing material, and SiO 2 -containing as flux Add material into pan. However, as described above, since MgO has a lower desulfurization ability than CaO, the MgO-containing material may not be added. Moreover, metal Al is added in a ladle for deoxidation of molten steel and reduction of slag (reduction of Fe oxide and Mn oxide in slag).
　これらの物質は、ＡＳＥＡ－ＳＫＦ法、ＶＡＤ法、及びＬＦ法のうちのいずれかの方法により脱硫処理を実施する後工程の設備で添加してもよいが、ＣａＯの滓化を促進させる観点から、転炉から取鍋への出鋼時又は出鋼直後に取鍋内に添加することが好ましい。出鋼直後に添加する生石灰は、生石灰が有する細孔のうち、細孔直径が０．５～１０μｍの範囲内にある細孔の容積の和が０．１ｍＬ／ｇ以上であり、且つ、粒径が１～３０ｍｍの範囲内にある粒子を９０％以上含有することが好ましい。 These substances may be added in a post-process facility for performing desulfurization treatment by any one of the ASEA-SKF method, the VAD method, and the LF method, but from the viewpoint of promoting the hatching of CaO. It is preferable to add to the ladle at the time of steel removal from the converter to the ladle or immediately after the steel removal. The quick lime added immediately after the steel is extracted has a pore volume having a pore diameter in the range of 0.5 to 10 μm among the fine pores of the quick lime, and the sum of the volumes is 0.1 mL / g or more. It is preferable to contain 90% or more of particles having a diameter in the range of 1 to 30 mm.
　ＣａＯ含有物質、ＭｇＯ含有物質、金属Ａｌ、Ａｌ2Ｏ3含有物質、及びＳｉＯ2含有物質の添加量は、取鍋内に流出した転炉スラグの質量及び成分組成を加味し、この転炉スラグを含めて添加されるフラックスが滓化した後に取鍋内に生成されるスラグの組成が、ＳｉＯ2含有量＝５～１５質量％の範囲内で、且つ、［（質量％ＣａＯ）＋（質量％ＭｇＯ）］／（質量％Ａｌ2Ｏ3）＝１．５～３．０の範囲内となるように、好ましくは［（質量％ＣａＯ）＋（質量％ＭｇＯ）］／（質量％Ａｌ2Ｏ3）＝１．８～２．５の範囲内となるように、ＣａＯ含有物質、ＭｇＯ含有物質、金属Ａｌ、Ａｌ2Ｏ3含有物質、及びＳｉＯ2含有物質のそれぞれの添加量を定める。 The addition amount of CaO-containing material, MgO-containing material, metal Al, Al 2 O 3 -containing material, and SiO 2 -containing material takes into account the mass and composition of the converter slag that has flowed into the ladle. the composition of the slag is the flux to be added, including is generated in the ladle after slag formation, in the range of SiO 2 content = 5-15 wt%, and, [(mass% CaO) + (mass % MgO)] / (mass% Al 2 O 3 ) = 1.5 to 3.0, preferably [(mass% CaO) + (mass% MgO)] / (mass% Al 2 The addition amounts of the CaO-containing material, the MgO-containing material, the metal Al, the Al 2 O 3 -containing material, and the SiO 2 -containing material are determined so that O 3 ) = 1.8 to 2.5.
　この場合、生成されるスラグの（質量％ＭｇＯ）／（質量％ＣａＯ）が０．１０以下になるようにそれぞれの添加量を定めることがより好ましい。そして、これらの物質を、定めた添加量だけ取鍋内に添加する。金属Ａｌは添加した全量がＡｌ2Ｏ3になるわけではなく、溶鋼中にも溶解して残る。従って、予め試験によって溶鋼に溶解する溶解Ａｌ分とスラグ中のＡｌ2Ｏ3になる分との比率を求めておき、それに基づき金属Ａｌの添加量を設定する。ＣａＦ2は添加しない。 In this case, it is more preferable to determine each addition amount so that (mass% MgO) / (mass% CaO) of the slag to be generated is 0.10 or less. Then, these substances are added to the ladle in a predetermined amount. Metal Al is not necessarily the total amount added is Al 2 O 3, remain dissolved in the molten steel. Therefore, the ratio between the dissolved Al content that dissolves in the molten steel and the amount that becomes Al 2 O 3 in the slag is determined in advance, and the amount of metal Al added is set based on the ratio. CaF 2 is not added.
　なお、本発明において、「脱硫処理後の取鍋内スラグの組成を、ＣａＦ2を実質的に含有しない組成に調整する」とは、ＣａＦ2等のフッ素化合物をＣａＯの滓化促進剤として使用しないで脱硫処理後のスラグ組成を調整することを意味し、使用するＣａＯ含有物質やＡｌ2Ｏ3含有物質等に不可避的に混入して持ち来たされるフッ素が脱硫処理後のスラグに存在しても、ＣａＦ2を実質的に含有しないスラグと定義する。 Incidentally, used in the present invention, "the composition of the ladle slag after the desulfurization treatment is adjusted to a composition containing no CaF 2 substantially" and the fluorine compound such as CaF 2 as a slag formation accelerators CaO exist means to adjust the slag composition after the desulfurization treatment without, fluorine unavoidably Kitasa have mixed in the CaO-containing material, Al 2 O 3, or the containing material, and the like used by the slag after the desulfurization treatment Even so, it is defined as slag substantially free of CaF 2 .
　添加するＣａＯ含有物質としては、生石灰（ＣａＯ）、石灰石（ＣａＣＯ3）、消石灰（Ｃａ(ＯＨ)2）、ドロマイト（ＭｇＣＯ3－ＣａＣＯ3）、焼成ドロマイト（ＭｇＯ－ＣａＯ）等を使用し、ＭｇＯ含有物質としては、マグネシアクリンカー（ＭｇＯ）、ドロマイト（ＭｇＣＯ3－ＣａＣＯ3）、焼成ドロマイト（ＭｇＯ－ＣａＯ）等を使用する。 As the CaO-containing substance to be added, quick lime (CaO), limestone (CaCO 3 ), slaked lime (Ca (OH) 2 ), dolomite (MgCO 3 —CaCO 3 ), calcined dolomite (MgO—CaO), etc. are used. As the contained material, magnesia clinker (MgO), dolomite (MgCO 3 —CaCO 3 ), calcined dolomite (MgO—CaO), or the like is used.
　石灰の粒度は、反応効率及び添加歩留の観点から平均粒径が１～３０ｍｍの範囲内にあることが好ましい。排気系に吸引される量を少なくする観点からは微粉分は少ない方が望ましく、平均粒径３０ｍｍ以上の石灰は少ないことが好ましい。平均粒径の測定方法は以下の通りである。脱硫剤を１ｋｇ採取し、５００μｍ以下、５００μｍ～１ｍｍ、１～５ｍｍ、５～1０ｍｍ、１０～１５ｍｍ、１５～２０ｍｍ、２０～２５ｍｍ、２５～３０ｍｍ、３０ｍｍ以上の９段階に篩い分けし、平均粒径を重量比率で計算することとし、以下に示す数式（４）により求めた。 As for the particle size of lime, the average particle size is preferably in the range of 1 to 30 mm from the viewpoint of reaction efficiency and addition yield. From the viewpoint of reducing the amount sucked into the exhaust system, it is desirable that the amount of fine powder is small, and it is preferable that lime having an average particle size of 30 mm or more is small. The measuring method of the average particle diameter is as follows. Take 1kg of desulfurization agent, and screen through 9 stages of 500μm or less, 500μm to 1mm, 1 to 5mm, 5 to 10mm, 10 to 15mm, 15 to 20mm, 20 to 25mm, 25 to 30mm, 30mm or more. The diameter was calculated based on the weight ratio, and the diameter was calculated by the following formula (4).
Figure JPOXMLDOC01-appb-M000006
Figure JPOXMLDOC01-appb-M000006
　Ａｌ2Ｏ3含有物質としては、アルミドロス（金属Ａｌを２０～７０質量％含有、残部の主成分はＡｌ2Ｏ3）、ボーキサイト（Ａｌ2Ｏ3・２Ｈ2Ｏ）、仮焼アルミナ（Ａｌ2Ｏ3）等を使用する。アルミドロスは金属Ａｌの代替にもなる。ＳｉＯ2含有物質としては、珪砂（ＳｉＯ2）、珪灰石（ＣａＯ－ＳｉＯ2）等を使用する。この場合、取鍋内に流出した転炉スラグの質量が多い場合には、ＳｉＯ2含有物質の添加を必要としないことも起こり得る。また、ＭｇＯ含有物質は、ＭｇＯ含有物質を添加しなくても、スラグ組成が［（質量％ＣａＯ）＋（質量％ＭｇＯ）］／（質量％Ａｌ2Ｏ3）＝１．５～３．０の範囲内、好ましくは１．８～２．５の範囲内となるならば添加しなくてもよい。 Examples of the Al 2 O 3 containing materials include aluminum dross (containing 20 to 70% by mass of metallic Al, the main component of the balance being Al 2 O 3 ), bauxite (Al 2 O 3 .2H 2 O), calcined alumina (Al using the 2 O 3) or the like. Almidros can also replace Al metal. The SiO 2 containing material, silica sand (SiO 2), using the wollastonite (CaO-SiO 2) or the like. In this case, when the mass of the converter slag flowing out into the ladle is large, it may not be necessary to add the SiO 2 -containing material. Further, the MgO-containing material has a slag composition of [(mass% CaO) + (mass% MgO)] / (mass% Al 2 O 3 ) = 1.5 to 3.0 without adding an MgO containing substance. If it is within the range of, preferably 1.8 to 2.5, it may not be added.
　次いで、溶鋼を収容した取鍋をＡＳＥＡ－ＳＫＦ法、ＶＡＤ法、及びＬＦ法のうちのいずれかの方法によって脱硫処理を実施する設備に搬送し、溶鋼の脱硫処理を実施する。本発明では、脱硫処理をＬＦ設備で実施する場合を例として説明する。図１は、本発明を実施する際に用いたＬＦ設備の側面概略図である。図１において、符号１はＬＦ設備、符号２は取鍋、符号３は昇降式の蓋、符号４はアーク加熱用の電極、符号５，６は浸漬ランス、符号７，８は底吹きポーラス煉瓦、符号９は溶鋼、符号１０はスラグ、符号１１は原材料投入シュート、符号１２はＡｒガス導入管を示す。 Next, the ladle containing the molten steel is transported to a facility for desulfurization treatment by any one of the ASEA-SKF method, the VAD method, and the LF method, and the desulfurization treatment of the molten steel is performed. In the present invention, a case where the desulfurization process is performed in an LF facility will be described as an example. FIG. 1 is a schematic side view of an LF facility used in carrying out the present invention. In FIG. 1, reference numeral 1 is an LF facility, reference numeral 2 is a ladle, reference numeral 3 is an elevating lid, reference numeral 4 is an electrode for arc heating, reference numerals 5 and 6 are immersion lances, reference numerals 7 and 8 are bottom blown porous bricks Reference numeral 9 denotes molten steel, reference numeral 10 denotes slag, reference numeral 11 denotes a raw material charging chute, and reference numeral 12 denotes an Ar gas introduction pipe.
　このＬＦ設備１では、走行台車（図示せず）に積載された、溶鋼９を収容する取鍋２を蓋３の直下の所定位置に配置し、蓋３を下降させて取鍋２の上端部に密着させ、その状態でＡｒガス導入管１２からＡｒガスを供給して取鍋２と蓋３とで囲まれる空間をＡｒガス雰囲気とする。取鍋２内の酸素濃度が１５％以下となるように炉蓋の周囲に取り付けた配管からＡｒガスを吹き込むことが好ましい。取鍋２内の酸素濃度を低減させることにより、ＬＦ処理中に空気中の酸素と反応してロスするＡｌ量を減らすことができる。取鍋２から吹き込むＡｒガスの流量は、πＬ2／４Ｑの値が５０～１５０（ｍ／ｍｉｎ）の範囲内となる流量とすることが好ましく、より好ましくは、７０～１００（ｍ／ｍｉｎ）の範囲内となる流量である。ここで、Ｌは取鍋の直径（ｍ）、ＱはＡｒガス流量(Ｎｍ3／ｍｉｎ)である。Ａｒガスの流量が少ないと十分に酸素濃度が低下せず、逆にＡｒガスの流量が多すぎると溶鋼温度が低下する原因となる。 In this LF facility 1, a ladle 2 that accommodates molten steel 9 loaded on a traveling carriage (not shown) is disposed at a predetermined position directly below the lid 3, and the lid 3 is lowered to move the upper end of the ladle 2. In this state, Ar gas is supplied from the Ar gas introduction pipe 12 and the space surrounded by the ladle 2 and the lid 3 is made an Ar gas atmosphere. Ar gas is preferably blown from a pipe attached around the furnace lid so that the oxygen concentration in the ladle 2 is 15% or less. By reducing the oxygen concentration in the ladle 2, it is possible to reduce the amount of Al that reacts with oxygen in the air and is lost during the LF treatment. The flow rate of Ar gas blown from the ladle 2 is preferably a value of πL 2 / 4Q is to range to become a flow rate of 50 ~ 150 (m / min) , more preferably, 70 ~ 100 (m / min ) The flow rate is within the range of. Here, L is the diameter (m) of the ladle, and Q is the Ar gas flow rate (Nm 3 / min). If the flow rate of Ar gas is small, the oxygen concentration is not sufficiently reduced. Conversely, if the flow rate of Ar gas is too high, the molten steel temperature is lowered.
　取鍋２内にＣａＯ含有物質、ＭｇＯ含有物質、金属Ａｌ、Ａｌ2Ｏ3含有物質、及びＳｉＯ2含有物質が予め添加されていない場合、及び、これらの物質の添加量が不足する場合には、この状態で原材料投入シュート１１を介して取鍋２内にこれらの物質のフラックス及び金属Ａｌを投入する。金属Ａｌは開始１０分以内に以下に示す数式（５）を満たすように添加することが好ましい。すなわち、転炉出鋼後のＡｌ濃度に応じて金属Ａｌを添加し、溶鋼中のＡｌ濃度を高めることが脱硫処理を促進させる上で好ましい。 In the case where the CaO-containing material, MgO-containing material, metal Al, Al 2 O 3- containing material, and SiO 2 -containing material are not added in advance in the ladle 2, and when the amount of addition of these materials is insufficient In this state, flux of these substances and metal Al are introduced into the ladle 2 through the raw material charging chute 11. The metal Al is preferably added so as to satisfy the following formula (5) within 10 minutes from the start. That is, it is preferable for increasing the Al concentration in the molten steel to promote the desulfurization treatment by adding metal Al according to the Al concentration after the converter steel.
Figure JPOXMLDOC01-appb-M000007
Figure JPOXMLDOC01-appb-M000007
　次いで、必要に応じて電極４に通電してアークを発生させ、溶鋼９を加熱すると共に添加したフラックスを滓化させた後、溶鋼９に浸漬ランス５又は浸漬ランス６を浸漬させ、浸漬ランス５、浸漬ランス６、又は、底吹きポーラス煉瓦７，８のうちの少なくとも一箇所から溶鋼９に攪拌用ガスとしてのＡｒガスを吹き込み、溶鋼９を攪拌する。溶鋼９を攪拌することによってフラックスが溶鋼９と混合され、フラックスの滓化が進行してスラグ１０が生成される。 Then, if necessary, the electrode 4 is energized to generate an arc, the molten steel 9 is heated, and the added flux is hatched. Then, the immersion lance 5 or the immersion lance 6 is immersed in the molten steel 9, and the immersion lance 5 Then, Ar gas as a stirring gas is blown into the molten steel 9 from at least one of the immersion lance 6 or the bottom blown porous bricks 7 and 8, and the molten steel 9 is stirred. By stirring the molten steel 9, the flux is mixed with the molten steel 9, and the hatching of the flux proceeds to generate the slag 10.
　生成したスラグ１０は、溶鋼９の攪拌によって溶鋼９と攪拌・混合され、溶鋼９とスラグ１０との間でスラグ－メタル間反応が発生し、溶鋼９中の硫黄成分がスラグ中に移行する脱硫反応が発生する。この場合、脱硫反応を促進させる観点から、前述したように、浸漬ランス５，６からＡｒガスと共に、Ｃａ合金粉、金属Ｍｇ粉、及びＭｇ合金粉のうちのいずれか１種又は２種以上を溶鋼９中に吹き込むこと、或いは、脱硫処理の少なくとも一時期において、浸漬ランス５，６からの攪拌用ガスの吹き込みと底吹きポーラス煉瓦７，８からの攪拌用ガスの吹き込みとを同時に行うことが好ましい。 The produced slag 10 is agitated and mixed with the molten steel 9 by the agitation of the molten steel 9, and a slag-metal reaction occurs between the molten steel 9 and the slag 10, and the sulfur component in the molten steel 9 is transferred into the slag. A reaction occurs. In this case, from the viewpoint of promoting the desulfurization reaction, as described above, any one or more of Ca alloy powder, metal Mg powder, and Mg alloy powder is used together with Ar gas from the immersion lances 5 and 6. It is preferable to blow into the molten steel 9 or to blow the stirring gas from the immersion lances 5 and 6 and the stirring gas from the bottom blown porous bricks 7 and 8 at least at one time of the desulfurization treatment. .
　Ｃａ合金粉としては、Ｃａ－Ｓｉ合金粉やＣａ－Ａｌ合金粉等を使用し、Ｍｇ合金粉としては、Ｍｇ－Ａｌ－Ｚｎ合金粉やＭｇ－Ｓｉ－Ｆｅ合金粉等を使用する。これら金属粉の粒径は、吹き込み添加が可能である限り特定する必要はないが、反応界面積を確保する観点から最大粒径を１ｍｍ以下とすることが好ましい。溶鋼９の硫黄濃度が０．００１０質量％以下になったなら、溶鋼９へのＡｒガスの吹き込みを停止して脱硫処理を終了する。脱硫処理が終了した時点で溶鋼９の温度が目標温度よりも低い場合、アーク加熱を実施し、また、溶鋼９の成分が目標範囲内にない場合には、原材料投入シュート１１を介して成分調整用の合金鉄や金属を投入する。脱硫処理終了後は、必要に応じてＲＨ真空脱ガス装置等で脱ガス精錬を実施した後、連続鋳造機でスラブ鋳片に鋳造する。 As the Ca alloy powder, Ca—Si alloy powder, Ca—Al alloy powder or the like is used, and as the Mg alloy powder, Mg—Al—Zn alloy powder, Mg—Si—Fe alloy powder or the like is used. Although it is not necessary to specify the particle size of these metal powders as long as blowing addition is possible, it is preferable to make a maximum particle size into 1 mm or less from a viewpoint of ensuring reaction interface area. When the sulfur concentration of the molten steel 9 becomes 0.0010% by mass or less, the blowing of Ar gas into the molten steel 9 is stopped and the desulfurization process is ended. When the temperature of the molten steel 9 is lower than the target temperature at the time when the desulfurization treatment is completed, arc heating is performed, and when the component of the molten steel 9 is not within the target range, the component adjustment is performed via the raw material charging chute 11. Alloy iron and metal for use. After the desulfurization treatment is completed, degassing and refining is performed with an RH vacuum degassing apparatus as necessary, and then cast into a slab slab with a continuous casting machine.
　以上説明したように、本発明によれば、ＣａＯ含有物質を脱硫剤の主たる構成物質として用いた取鍋精錬法による溶鋼９の脱硫処理において、脱硫処理後のスラグ組成を、ＳｉＯ2の含有量が５～１５質量％の範囲内になるように調整するので、ＳｉＯ2がＣａＯの滓化促進剤として機能してＣａＯの滓化が促進され、また、脱硫処理後のスラグ組成を、［（質量％ＣａＯ）＋（質量％ＭｇＯ）］／（質量％Ａｌ2Ｏ3）が１．５～３．０の範囲内になるように調整するので、スラグ１０には高い脱硫能力が確保され、その結果、ＣａＦ2を脱硫剤の一部として使用しなくても、また、脱硫剤がプリメルトフラックスでなくても、効率的に溶鋼９の脱硫処理を行うことが実現される。なお、上記説明はＬＦ設備で本発明を実施した例であるが、ＡＳＥＡ－ＳＫＦ設備及びＶＡＤ設備においても、上記に準じて本発明を適用することができる。 As described above, according to the present invention, the desulfurization of molten steel 9 by ladle refining method using a CaO-containing material as a principal constituent of the desulfurizing agent, the slag composition after the desulfurization treatment, the content of SiO 2 Therefore, SiO 2 functions as a CaO hatching accelerator to promote the hatching of CaO, and the slag composition after desulfurization treatment is changed to [( Since mass% CaO) + (mass% MgO)] / (mass% Al 2 O 3 ) is adjusted to be in the range of 1.5 to 3.0, the slag 10 has a high desulfurization capability, As a result, even if CaF 2 is not used as a part of the desulfurizing agent and the desulfurizing agent is not a premelt flux, it is possible to efficiently desulfurize the molten steel 9. Although the above description is an example in which the present invention is implemented with an LF facility, the present invention can also be applied to an ASEA-SKF facility and a VAD facility according to the above.
［実施例１］
　高炉から出銑された溶銑に対して脱珪処理、脱硫処理、及び脱燐処理を行った後、この溶銑を転炉に装入して脱炭精錬を実施し、炭素濃度が０．０５～０．０９質量％の範囲内、硫黄濃度が０．００４１～０．００４３質量％の範囲内、燐濃度が０．００４～０．０１０質量％の範囲内にある約２５０トンの溶鋼を得た。出鋼後、取鍋へ流出した転炉スラグを徐滓せず、金属Ａｌ、生石灰、軽焼ドロマイト、及びアルミドロスが添加された取鍋を図１に示すＬＦ設備に搬送した。電極をスラグに浸漬させてアーク加熱を行いながら、浸漬ランスから２０００ＮＬ／ｍｉｎのＡｒガスを溶鋼中に吹き込んで溶鋼を攪拌し、約３０分間脱硫処理を行い、硫黄濃度を０．００２４％以下とすることを目標に脱硫処理を実施した。 [Example 1]
The hot metal discharged from the blast furnace is subjected to desiliconization, desulfurization, and dephosphorization, and then the hot metal is charged into a converter to carry out decarburization and refining. Approximately 250 tons of molten steel having a sulfur concentration in the range of 0.0041 to 0.0043% by mass and a phosphorus concentration in the range of 0.004 to 0.010% by mass was obtained. . After steeling out, the ladle slag that had flowed into the ladle was not gradually reduced, and the ladle to which metal Al, quicklime, light-burned dolomite, and aluminum dross were added was conveyed to the LF facility shown in FIG. While the electrode is immersed in the slag and performing arc heating, Ar gas of 2000 NL / min is blown into the molten steel from the immersion lance, the molten steel is stirred, desulfurized for about 30 minutes, and the sulfur concentration is 0.0024% or less. The desulfurization treatment was carried out with the goal of doing so.
　以下に示す表１に各脱硫試験における脱硫処理前後の溶鋼中硫黄濃度（化学分析値）及び脱硫率を示す。また、表１の備考欄には、本発明の範囲内の試験は「本発明例」、それ以外は「比較例」として表示した。なお、脱硫率は、脱硫処理前後の溶鋼中硫黄濃度の差分を脱硫処理前の溶鋼中硫黄濃度に対して百分率で表示した値である。また、脱硫評価が「○」とは、脱硫処理後の溶鋼中硫黄濃度が０．００２４％以下であったことを示し、脱硫評価が「×」とは、脱硫処理後の溶鋼中硫黄濃度が０．００２４％超であったことを示している。 Table 1 below shows the sulfur concentration (chemical analysis value) and desulfurization rate in the molten steel before and after the desulfurization treatment in each desulfurization test. Further, in the remarks column of Table 1, tests within the scope of the present invention are indicated as “examples of the present invention”, and other cases are indicated as “comparative examples”. In addition, a desulfurization rate is the value which displayed the difference of the sulfur concentration in the molten steel before and behind a desulfurization process with a percentage with respect to the sulfur concentration in the molten steel before a desulfurization process. The desulfurization evaluation “◯” indicates that the sulfur concentration in the molten steel after the desulfurization treatment was 0.0024% or less, and the desulfurization evaluation “x” indicates that the sulfur concentration in the molten steel after the desulfurization treatment is low. It shows that it was over 0.0024%.
Figure JPOXMLDOC01-appb-T000008
Figure JPOXMLDOC01-appb-T000008
　試験水準と結果を合わせて表１に示す。細孔直径が０．５～１０μｍの範囲内にある細孔の容積の和が適正でない比較例（試験番号１～３）では、本発明例（試験番号４～１５）と比較して脱硫率が低位であった。また、本発明例において、生石灰の平均粒径が１～３０ｍｍの範囲内にある水準では、滓化が促進され溶鋼の脱硫率も高位であった。 The test levels and results are shown in Table 1. In the comparative examples (test numbers 1 to 3) in which the sum of the volumes of the pores having a pore diameter in the range of 0.5 to 10 μm is not appropriate, the desulfurization rate is compared with the present invention examples (test numbers 4 to 15). Was low. In the examples of the present invention, when the average particle size of quicklime was in the range of 1 to 30 mm, hatching was promoted and the desulfurization rate of the molten steel was high.
［実施例２］
　高炉から出銑された溶銑に対して脱珪処理、脱硫処理、及び脱燐処理を行った後、この溶銑を転炉に装入して脱炭精錬を実施し、炭素濃度が０．０５～０．０９質量％の範囲内、硫黄濃度が０．００４１～０．００４３質量％の範囲内、燐濃度が０．００４～０．０１０質量％の範囲内にある約２５０ｔの溶鋼を得た。出鋼後、取鍋へ流出した転炉スラグを徐滓せず、金属Ａｌ、生石灰、軽焼ドロマイト、及びアルミドロスの添加された取鍋を図１に示すＬＦ設備に搬送した。電極をスラグに浸漬させてアーク加熱を行いながら、浸漬ランスから５００～２０００ＮＬ／ｍｉｎのＡｒガスを溶鋼中に吹き込んで溶鋼を攪拌し、約３０分間脱硫処理を行い、硫黄濃度を０．００２４％以下とすることを目標に脱硫処理を実施した。 [Example 2]
The hot metal discharged from the blast furnace is subjected to desiliconization, desulfurization, and dephosphorization, and then the hot metal is charged into a converter to carry out decarburization and refining. About 250 t of molten steel was obtained in the range of 0.09% by mass, the sulfur concentration in the range of 0.0041 to 0.0043% by mass, and the phosphorus concentration in the range of 0.004 to 0.010% by mass. After the steel was tapped, the ladle slag that had flowed into the ladle was not gradually removed, and the ladle to which metal Al, quicklime, light-burned dolomite, and aluminum dross were added was conveyed to the LF facility shown in FIG. While the electrode is immersed in the slag and arc heating is performed, 500 to 2000 NL / min Ar gas is blown into the molten steel from the immersion lance and the molten steel is stirred, and the desulfurization treatment is performed for about 30 minutes, so that the sulfur concentration is 0.0024%. The desulfurization treatment was carried out with the goal of:
　以下に示す表２に各脱硫試験における脱硫処理前後の溶鋼中硫黄濃度（化学分析値）及び脱硫率を示す。なお、脱硫評価が「○」とは、脱硫処理後の溶鋼中硫黄濃度が０．００２４％以下であったことを示している。 Table 2 below shows the sulfur concentration (chemical analysis value) and desulfurization rate in the molten steel before and after the desulfurization treatment in each desulfurization test. In addition, desulfurization evaluation "(circle)" has shown that the sulfur concentration in the molten steel after a desulfurization process was 0.0024% or less.
Figure JPOXMLDOC01-appb-T000009
Figure JPOXMLDOC01-appb-T000009
　試験水準と結果を合わせて表２に示す。撹拌動力の増加に伴いＬＦ処理開始５分後の滓化率及び脱硫率が向上することが確認された。また、攪拌動力密度が以下に示す数式（６）を満足することにより、高い滓化率及び脱硫率が得られることが確認された。 The test levels and results are shown in Table 2. It was confirmed that the hatching rate and desulfurization rate improved 5 minutes after the start of the LF treatment as the stirring power increased. Moreover, it was confirmed that a high hatching rate and a desulfurization rate can be obtained when the stirring power density satisfies the following formula (6).
Figure JPOXMLDOC01-appb-M000010
Figure JPOXMLDOC01-appb-M000010
［実施例３］
　図２は、本発明例及び比較例の滓化率を示す図である。細孔直径が０．５～１０μｍの範囲内にある細孔の容積の和が０．２ｍＬ／ｇ、粒径が２０ｍｍ以下である生石灰を本発明例、細孔直径が０．５～１０μｍの範囲内にある細孔の容積の和が０．０３ｍＬ／ｇ、粒径が２０ｍｍ以下である生石灰を比較例とした。図２に示すように、本発明例では比較例に比べて同一の撹拌動力密度（１３５Ｗ／ｔ）であっても滓化が促進されることが確認された。 [Example 3]
FIG. 2 is a diagram showing hatching rates of the present invention example and the comparative example. Quick lime having a pore diameter in the range of 0.5 to 10 μm with a total volume of pores of 0.2 mL / g and a particle size of 20 mm or less is an example of the present invention, and the pore diameter is 0.5 to 10 μm. Quick lime having a pore volume sum in the range of 0.03 mL / g and a particle size of 20 mm or less was used as a comparative example. As shown in FIG. 2, it was confirmed that hatching was promoted in the inventive example even when the stirring power density (135 W / t) was the same as in the comparative example.
［実施例４］
　高炉から出銑された溶銑に対して脱珪処理、脱硫処理、及び脱燐処理を行った後、この溶銑を転炉に装入して脱炭精錬を実施し、炭素濃度が０．０５～０．０９質量％の範囲内、硫黄濃度が０．００４１～０．００４４質量％の範囲内、燐濃度が０．００４～０．０１０質量％の範囲内にある約２５０ｔの溶鋼を得た。出鋼後、取鍋へ流出した転炉スラグを徐滓せず、金属Ａｌ、生石灰、軽焼ドロマイト、及びアルミドロスの添加された取鍋を図１に示すＬＦ設備に搬送した。ＬＦ処理では、細孔直径が０．５～１０μｍの範囲内にある細孔の容積の和が０．２ｍＬ／ｇ、粒径が２０ｍｍ以下である生石灰を用いた。 [Example 4]
The hot metal discharged from the blast furnace is subjected to desiliconization, desulfurization, and dephosphorization, and then the hot metal is charged into a converter to carry out decarburization and refining. About 250 t of molten steel having a sulfur concentration within the range of 0.09 mass%, a sulfur concentration within the range of 0.0041 to 0.0044 mass%, and a phosphorus concentration within the range of 0.004 to 0.010 mass% was obtained. After the steel was tapped, the ladle slag that had flowed into the ladle was not gradually removed, and the ladle to which metal Al, quicklime, light-burned dolomite, and aluminum dross were added was conveyed to the LF facility shown in FIG. In the LF treatment, quick lime having a pore volume within a range of 0.5 to 10 μm with a pore volume sum of 0.2 mL / g and a particle size of 20 mm or less was used.
　以下に示す表３に各脱硫試験における脱硫処理前後の溶鋼中硫黄濃度（化学分析値）及び脱硫率を示す。ここで、[ｓｏｌ.Ａｌ]1が溶製対象鋼種のＡｌ濃度規格上限値（質量％）、[ｓｏｌ.Ａｌ]2が転炉出鋼後の溶鋼中Ａｌ濃度（質量％）である。なお、脱硫評価が「○」とは、脱硫処理後の溶鋼中硫黄濃度が０．００２４％以下であったことを示している。 Table 3 below shows the sulfur concentration in the molten steel (chemical analysis value) and the desulfurization rate before and after the desulfurization treatment in each desulfurization test. Here, [sol.Al] 1 is the upper limit value (mass%) of the Al concentration standard of the steel type to be melted, and [sol.Al] 2 is the Al concentration (mass%) in the molten steel after the converter steel. In addition, desulfurization evaluation "(circle)" has shown that the sulfur concentration in the molten steel after a desulfurization process was 0.0024% or less.
Figure JPOXMLDOC01-appb-T000011
Figure JPOXMLDOC01-appb-T000011
　表３に示すように、ＬＦ処理開始１０分以内に投入したＡｌ量が上記数式（５）の範囲内にある水準では、ＬＦ処理終了時点の[ｓｏｌ.Ａｌ]3値が規格の範囲内であり、脱硫率も高位であった。一方、ＬＦ処理開始１０分以内に投入したＡｌ量が上記数式（５）に示す範囲よりも多かった水準では、ＬＦ処理終了時点の[ｓｏｌ.Ａｌ]　3値が規格上限値を上回っており、次工程のＲＨでの脱Ａｌ処理の必要が生じてしまい、ＲＨの処理時間が延長した。 As shown in Table 3, when the amount of Al input within 10 minutes from the start of the LF treatment is within the range of the above formula (5), the [sol.Al] 3 value at the end of the LF treatment is within the standard range. There was also a high desulfurization rate. On the other hand, at a level where the amount of Al input within 10 minutes from the start of the LF treatment is larger than the range shown in the above formula (5), the [sol.Al] 3 value at the end of the LF treatment exceeds the upper limit of the standard. The need for de-Al treatment with RH in the next step has arisen, and the RH treatment time has been extended.
［実施例５］
　高炉から出銑された溶銑に対して脱珪処理、脱硫処理、及び脱燐処理を行った後、溶銑を転炉に装入して脱炭精錬を実施し、炭素濃度が０．０５～０．０９質量％の範囲内、硫黄濃度が０．００４１～０．００４４質量％の範囲内、燐濃度が０．００４～０．０１０質量％の範囲内の約２５０ｔの溶鋼を得た。出鋼後、取鍋へ流出した転炉スラグを徐滓せず、金属Ａｌ、生石灰、軽焼ドロマイト、及びアルミドロスの添加された取鍋を図１に示すＬＦ設備に搬送した。ＬＦ処理では、細孔直径が０．５～１０μｍの範囲内にある細孔の容積の和が０．２ｍＬ／ｇ、粒径が２０ｍｍ以下である生石灰を用い、ＬＦ処理開始から１０分以内に上記数式（５）を満たすように、金属Ａｌを添加した。 [Example 5]
After desiliconization, desulfurization, and dephosphorization are performed on the hot metal discharged from the blast furnace, the hot metal is charged into the converter and decarburized and refined, and the carbon concentration is 0.05-0. About 250 t of molten steel was obtained in the range of 0.09 mass%, the sulfur concentration in the range of 0.0041 to 0.0044 mass%, and the phosphorus concentration in the range of 0.004 to 0.010 mass%. After the steel was tapped, the ladle slag that had flowed into the ladle was not gradually removed, and the ladle to which metal Al, quicklime, light-burned dolomite, and aluminum dross were added was conveyed to the LF facility shown in FIG. In the LF treatment, quick lime with a pore diameter within a range of 0.5 to 10 μm having a pore volume sum of 0.2 mL / g and a particle size of 20 mm or less is used within 10 minutes from the start of the LF treatment. Metal Al was added so as to satisfy the above mathematical formula (5).
　以下に示す表４に各脱硫試験における脱硫処理前後の溶鋼中硫黄濃度（化学分析値）及び脱硫率を示す。なお、脱硫評価が「○」とは、脱硫処理後の溶鋼中硫黄濃度が０．００２４％以下であったことを示している。 Table 4 below shows the sulfur concentration (chemical analysis value) and desulfurization rate in the molten steel before and after the desulfurization treatment in each desulfurization test. In addition, desulfurization evaluation "(circle)" has shown that the sulfur concentration in the molten steel after a desulfurization process was 0.0024% or less.
Figure JPOXMLDOC01-appb-T000012
Figure JPOXMLDOC01-appb-T000012
　表４に示すように、取鍋内酸素濃度が１５％以下である水準（試験番号３７～３９）では処理中Ａｌロスが減少することが確認された。なお、処理中Ａｌロス（エア巻き込み）は以下に示す数式（７）を用いて求めた。 As shown in Table 4, it was confirmed that Al loss was reduced during treatment at a level (test numbers 37 to 39) where the oxygen concentration in the ladle was 15% or less. In addition, Al loss (air entrainment) during processing was calculated | required using numerical formula (7) shown below.
Figure JPOXMLDOC01-appb-M000013
Figure JPOXMLDOC01-appb-M000013
　本発明によれば、ＣａＦ2やプリメルトフラックスを使用しなくても効率良く脱硫処理を行うことが可能な溶鋼の脱硫処理方法及び脱硫剤を提供することができる。 According to the present invention, it is possible to provide a desulfurization process method and desulfurizing agent which can efficiently perform the desulfurization process without using CaF 2 and premelt flux of molten steel.
　１　ＬＦ設備
　２　取鍋
　３　蓋
　４　電極
　５，６　浸漬ランス
　７，８　底吹きポーラス煉瓦
　９　溶鋼
　１０　スラグ
　１１　原材料投入シュート
　１２　Ａｒガス導入管 DESCRIPTION OF SYMBOLS 1 LF equipment 2 Ladle 3 Lid 4 Electrode 5,6 Immersion lance 7,8 Bottom blown porous brick 9 Molten steel 10 Slag 11 Raw material input chute 12 Ar gas introduction pipe

Claims (6)

  1. 　溶鋼を収容する取鍋内に生石灰を含む脱硫剤を添加し、取鍋内で溶鋼を攪拌することによって、溶鋼中の硫黄濃度を低減する溶鋼の脱硫処理方法であって、
    　前記脱硫剤として、細孔直径が０．５～１０μｍ以下の範囲内にある細孔の容積の和が０．１ｍＬ／ｇ以上である生石灰を含む脱硫剤を用いることを特徴とする溶鋼の脱硫処理方法。     A desulfurization treatment method for molten steel that reduces a sulfur concentration in molten steel by adding a desulfurization agent containing quick lime in a ladle containing molten steel and stirring the molten steel in the ladle,
    Desulfurization of molten steel, characterized in that a desulfurization agent containing quick lime whose sum of pore volumes having a pore diameter in the range of 0.5 to 10 μm or less is 0.1 mL / g or more is used as the desulfurization agent. Processing method.
  2. 　前記生石灰が、粒径が１～３０ｍｍ以下の範囲内にある粒子を９０％以上含むことを特徴とする請求項１に記載の溶鋼の脱硫処理方法。 The method for desulfurizing molten steel according to claim 1, wherein the quicklime contains 90% or more of particles having a particle size in a range of 1 to 30 mm or less.
  3. 　細孔直径が０．５～１０μｍ以下の範囲内にある細孔の容積の和が０．１ｍＬ／ｇ以上である生石灰を含み、前記生石灰が、粒径が１～３０ｍｍ以下の範囲内にある粒子を９０％以上含むことを特徴とする脱硫剤。 Including quick lime having a pore diameter in the range of 0.5 to 10 μm or less and having a sum of pore volumes of 0.1 mL / g or more, wherein the quick lime has a particle size in the range of 1 to 30 mm or less. A desulfurizing agent comprising 90% or more of particles.
  4. 　下記数式（１）で示される撹拌動力密度の条件が満足されるように前記溶鋼を攪拌することを特徴とする請求項１又は２に記載の溶鋼の脱硫処理方法。
    Figure JPOXMLDOC01-appb-M000001
         The molten steel desulfurization treatment method according to claim 1 or 2, wherein the molten steel is stirred so that a condition of a stirring power density represented by the following formula (1) is satisfied.
    Figure JPOXMLDOC01-appb-M000001
  5. 　前記溶鋼が転炉から出鋼されてから脱硫処理開始後１０分以内に溶鋼に投入されるアルミニウムの量が下記数式（２）を満足することを特徴とする請求項１、２、４のうち、いずれか１項に記載の溶鋼の脱硫処理方法。
    Figure JPOXMLDOC01-appb-M000002
         The amount of aluminum put into the molten steel within 10 minutes after the desulfurization treatment is started after the molten steel is discharged from the converter satisfies the following formula (2): The desulfurization processing method of the molten steel of any one.
    Figure JPOXMLDOC01-appb-M000002
  6. 　前記取鍋内における酸素濃度が１５％以下となるように前記取鍋内にＡｒガスを吹き込むことを特徴とする請求項１、２、４、５のうち、いずれか１項に記載の溶鋼の脱硫処理方法。 The molten steel according to any one of claims 1, 2, 4, and 5, wherein Ar gas is blown into the ladle so that the oxygen concentration in the ladle is 15% or less. Desulfurization processing method.
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