WO2022154023A1 - 転炉精錬方法 - Google Patents
転炉精錬方法 Download PDFInfo
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- WO2022154023A1 WO2022154023A1 PCT/JP2022/000794 JP2022000794W WO2022154023A1 WO 2022154023 A1 WO2022154023 A1 WO 2022154023A1 JP 2022000794 W JP2022000794 W JP 2022000794W WO 2022154023 A1 WO2022154023 A1 WO 2022154023A1
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- WO
- WIPO (PCT)
- Prior art keywords
- converter
- slag
- flux
- cao
- amount
- Prior art date
Links
- 238000000034 method Methods 0.000 title claims abstract description 49
- 238000007670 refining Methods 0.000 title claims abstract description 33
- 239000002893 slag Substances 0.000 claims abstract description 129
- 230000004907 flux Effects 0.000 claims abstract description 85
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 77
- 239000010959 steel Substances 0.000 claims abstract description 77
- 238000007599 discharging Methods 0.000 claims abstract description 4
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 60
- 238000006243 chemical reaction Methods 0.000 claims description 40
- 239000002184 metal Substances 0.000 claims description 39
- 229910052751 metal Inorganic materials 0.000 claims description 39
- 238000005261 decarburization Methods 0.000 claims description 37
- 238000007664 blowing Methods 0.000 abstract description 16
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 abstract description 8
- 239000000377 silicon dioxide Substances 0.000 abstract description 4
- 230000003247 decreasing effect Effects 0.000 abstract description 2
- 238000005262 decarbonization Methods 0.000 abstract 3
- 229910000805 Pig iron Inorganic materials 0.000 abstract 2
- 229910052681 coesite Inorganic materials 0.000 abstract 2
- 229910052906 cristobalite Inorganic materials 0.000 abstract 2
- 235000012239 silicon dioxide Nutrition 0.000 abstract 2
- 229910052682 stishovite Inorganic materials 0.000 abstract 2
- 229910052905 tridymite Inorganic materials 0.000 abstract 2
- 230000002401 inhibitory effect Effects 0.000 abstract 1
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 152
- 239000000292 calcium oxide Substances 0.000 description 76
- 235000012255 calcium oxide Nutrition 0.000 description 76
- 230000000052 comparative effect Effects 0.000 description 11
- 239000000203 mixture Substances 0.000 description 10
- 238000005303 weighing Methods 0.000 description 10
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 8
- 238000003723 Smelting Methods 0.000 description 7
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 6
- 229910052742 iron Inorganic materials 0.000 description 4
- 230000000694 effects Effects 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 3
- 239000002699 waste material Substances 0.000 description 3
- 241000209094 Oryza Species 0.000 description 2
- 235000007164 Oryza sativa Nutrition 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 229910052760 oxygen Inorganic materials 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 235000009566 rice Nutrition 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 1
- 235000019738 Limestone Nutrition 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- 229910001882 dioxygen Inorganic materials 0.000 description 1
- 239000010459 dolomite Substances 0.000 description 1
- 229910000514 dolomite Inorganic materials 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000006028 limestone Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000010450 olivine Substances 0.000 description 1
- 229910052609 olivine Inorganic materials 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000004575 stone Substances 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
Images
Classifications
-
- 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
- C21C1/00—Refining of pig-iron; Cast iron
- C21C1/04—Removing impurities other than carbon, phosphorus or sulfur
-
- 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
- C21C1/00—Refining of pig-iron; Cast iron
- C21C1/02—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
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
-
- 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
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/52—Manufacture of steel in electric furnaces
- C21C5/54—Processes yielding slags of special composition
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Definitions
- This application discloses a converter refining method.
- Process (II) is being developed.
- Process (I) has a high refining capacity, but requires two converters, so the equipment cost is high, and the heat dissipation loss increases, and the melting capacity of iron ore and scrap decreases. do.
- the process (II) can shorten the entire blowing time, reduce the amount of flux required for dephosphorization, and reduce the heat loss during refining.
- Patent Document 1 discloses a converter refining method in which a flux containing 60 to 99% of SiO 2 is divided into 2 parts of SiO and 1.0 to 4.0 kg is added per ton of molten steel produced before decarburization in the process (II). Has been done.
- Patent Document 2 discloses a method of using desiliconized slag in the decarburization treatment after the dephosphorization treatment.
- the prior art related to the process (II) has the following problems. That is, in the prior art, there is a risk that the slag in the converter becomes low in basicity during decarburization and slag overflows (sloping) from the converter in the initial stage of decarburization, making stable operation difficult. There is. Alternatively, the slag in the converter becomes highly basic during decarburization and slag, the flux input for decarburization is not sufficiently slag, and a sufficient amount of slag with high dephosphorization ability cannot be secured, resulting in decarburization. It may be difficult to stably reduce the P concentration in the molten steel after slag. Alternatively, the amount of slag in decarburization and smelting becomes large, and sloping may occur in the initial stage of decarburization and smelting.
- the present inventor measured the molten slag at the time of intermediate slag with a "weighing instrument". As a result, it was found that the intermediate slag rate varied greatly from 50 to 95%, which was higher than the conventional assumption. That is, in the prior art, since the intermediate slag rate suddenly increased or decreased, the calculated basicity and the actual basicity deviated from each other, which caused the slag in the converter to have a lower basicity or a higher basicity during decarburization. It turned out to be one of the causes. Therefore, the present inventor has invented a method in which the intermediate slag rate is accurately specified at least once by a "weighing device or the like", and the operation is performed based on the accurately specified intermediate slag rate. Specifically, it is as follows.
- the present application is one of the means for solving the above problems.
- the first process in which hot metal is charged inside the converter, After the first step, the hot metal in the converter is dephosphorized while using the first flux, the second step. After the second step, at least a part of the slag in the converter is discharged to the outside of the converter, the third step. After the third step, a second flux is added to the converter and then decarburization is performed. With The second flux contains a CaO source and a SiO 2 source. The following equations (1) and (2) are satisfied. Disclose the converter refining method.
- C2 CaO conversion amount (kg / ton-steel) in the first flux
- C4 CaO conversion amount (kg / ton-steel) in the second flux
- S2 SiO 2 conversion amount (kg / ton-steel) in the first flux
- S4 SiO 2 conversion amount (kg / ton-steel) in the second flux
- ⁇ 3 Intermediate slag rate (%) in the third step
- the converter refining method of the present disclosure is After the fourth step, steel is ejected while leaving the slag produced in the fourth step in the converter, the fifth step, and After the fifth step, the slag in the converter is based on at least one of the estimated P 2 O 5 component amount of the slag in the converter and the P component target value of the steel in the next heat.
- the converter refining method of the present disclosure it is easy to suppress sloping in the initial stage of decarburization and smelting. Further, according to the converter refining method of the present disclosure, P in molten steel after decarburization and blowing is likely to be stably reduced.
- the hot metal 10 is charged into the converter 100, the first step (FIG. 1 (A)), the first step.
- hot metal dephosphorization is performed on the hot metal 10 in the converter 100 while using the first flux 21.
- the second step (FIG. 1 (B)), after the second step, the converter 100
- a second flux 22 was added to the converter 100 after the third step (FIG. 1 (C)) in which at least a part of the slag 31 inside was discharged to the outside of the converter 100 and the third step.
- a fourth step (FIGS. 1 (D) and (E)), in which decarburization is performed, is provided.
- the second flux 22 includes a CaO source and a SiO 2 source. Further, in the converter refining method of the present disclosure, the following equations (1) and (2) are satisfied.
- the hot metal 10 is charged inside the converter 100.
- the conditions in the first step are not particularly limited.
- the converter 100 may be the same as the conventional one.
- the converter 100 may be any of a top blown converter, a bottom blown converter and an upper bottom blown converter.
- the top-blown converter since there is no stirring from the bottom, it is difficult to reduce the iron oxide produced by the top-blown oxygen oxidizing iron, and the amount of slag tends to increase excessively.
- slag containing a large amount of iron oxide tends to slag CaO.
- the iron oxide concentration does not become so high, and the slagging of CaO tends to be difficult to proceed as compared with the case of the top-blown converter.
- the converter 100 may be one of a bottom blown converter and an upper bottom blown converter, and is an upper bottom blown converter. May be good.
- FIGS. 1 (A) to 1 (F) show an upper bottom blown converter as an example of the converter 100.
- the top-bottom blown converter 100 may be provided with a plurality of flow paths 101 for supplying bottom-blown gas into the furnace at the bottom thereof.
- the upper bottom blown converter 100 may be provided with a steel ejection port 102 for ejecting molten steel 12 on its side portion.
- the hot metal 10 charged inside the converter 100 for example, any general blast furnace hot metal can be adopted.
- the hot metal 10 contains P and C as impurities and may also contain Si.
- the desiliconization reaction of Si in the hot metal 10 proceeds by oxidative refining with oxygen gas, and then the dephosphorization reaction proceeds.
- desiliconization of the hot metal may be performed after the first step and before the hot metal dephosphorization in the second step.
- the desiliconized slag in the converter 100 may be discharged, or dephosphorization may be performed while leaving the desiliconized slag in the converter 100. In the latter case, the desiliconized slag may be used as the first flux 21.
- the hot metal 10 may be a mixture of molten iron 10a (for example, blast furnace hot metal) and an additive material such as scrap 10b.
- the method of charging the hot metal 10 into the converter 100 is not particularly limited, and examples thereof include a method of pouring the hot metal 10 into the converter 100 using a known container such as a hot metal pot.
- Second Step As shown in FIG. 1 (B), in the second step, after the first step, hot metal dephosphorization is performed using the first flux 21.
- the conditions for dephosphorization in the second step are not particularly limited.
- the first flux 21 may be charged into the converter 100 before the dephosphorization in the second step, or is derived from hot metal such as desiliconized slag produced by the desiliconization reaction as described above.
- the components may be used, or the decarburized slag 32 after decarburization refining in the preheat may be left in the converter 100 and used as a flux.
- the composition and amount of the first flux 21 are not particularly limited as long as they can achieve the desired dephosphorization.
- the first flux 21 may contain a CaO source. Examples of the CaO source include quicklime, limestone, dolomite, preheated decarburized slag 32, and the like. Further, the first flux 21 may contain a SiO 2 source.
- Examples of the SiO 2 source include desiliconized slag, preheated decarburized slag 32, silica stone, and olivine.
- the basicity CaO / SiO 2 of the first flux 21 may be 0.9 or more, or 1.4 or less. Further, the amount of the first flux 21 may be 5 kg / ton-steel or more, or 25 kg / ton-steel or less in terms of CaO. Further, the amount of the first flux 21 may be 0 kg / ton-steel or more, or 5 kg / ton-steel or less in terms of SiO 2 . In the present application, "kg / ton-steel" is the mass per ton of molten steel finally obtained.
- the oxidative refining may proceed while stirring the hot metal 10. Then, the agitation of the hot metal 10 during refining may be enhanced by continuously or intermittently blowing the bottom blowing gas from the bottom of the converter 100.
- the dephosphorized hot metal 11 is obtained.
- the P concentration in the dephosphorized hot metal 11 is not particularly limited.
- the dephosphorized hot metal 11 may contain P in an amount of 0.02% by mass or more or 0.03% by mass or more, or may contain 0.08% by mass or less or 0.06% by mass or less.
- the third step at least a part of the slag 31 in the converter 100 is discharged to the outside of the converter 100 after the second step.
- the slag 31 may be discharged to the outside of the system by tilting the converter 100.
- the slag 31 may be formed by continuously blowing the bottom blowing gas from the bottom of the converter 100. This makes it easier to remove the slag 31.
- the slag 31 slag 31 slag rate (intermediate slag 31) in the third step is not particularly limited, and may be, for example, 40% or more and 70% or less.
- the composition and the amount of slag 31 produced can be arbitrarily changed depending on the dephosphorization conditions in the second step.
- a second flux 22 is added to the converter 100 and then decarburization is performed.
- the fourth step is characterized in that the second flux 22 contains a CaO source and a SiO 2 source, and that the above formulas (1) and (2) are satisfied.
- Other decarburization conditions are not particularly limited.
- the second flux 22 is charged into the converter 100 before decarburization in the fourth step.
- a part of the slag 31 remaining in the converter 100 without being discharged in the third step can also be used as the flux 22x.
- the composition and amount of the second flux 22 are not particularly limited as long as the above formulas (1) and (2) are satisfied.
- the second flux 22 contains a CaO source and a SiO 2 source.
- the CaO source and the SiO 2 source may be added into the converter 100 at the same time, or may be added separately. Specific examples of the CaO source and the SiO 2 source are as described above. Further, the basicity CaO / SiO 2 of the second flux 22 may be 3.2 or more, or 4.2 or less.
- the amount of the second flux 22 may be 8 kg / ton-steel or more or 25 kg / ton-steel or less in terms of CaO. May be good. Further, the amount of the second flux 22 may be more than 0 kg / ton-steel or 8 kg / ton-steel or less in terms of SiO 2 .
- the charging CaO / SiO defined by [C2 ⁇ (100- ⁇ 3) / 100 + C4] / [S2 ⁇ (100- ⁇ 3) / 100 + S4] It is important that 2 is 3.0 or more and 4.5 or less.
- the charged CaO / SiO 2 may be 3.2 or more, 3.4 or more, 3.6 or more, 3.8 or more, 4.0 or more, 4.2 or more, or 4.4 or more. According to the findings of the present inventor, if the charged CaO / SiO 2 is too small, CaO is insufficient and dephosphorization is difficult to proceed, and it is difficult to reduce the P concentration in the finally obtained molten steel 12.
- the charged CaO defined by C2 ⁇ (100- ⁇ 3) / 100 + C4 is 30.0 kg / ton-steel or less as described in the above formula (2). ..
- the charged CaO may be 25.0 kg / ton-steel or less, 22.0 kg / ton-steel or less, 19.0 kg / ton-steel or less, or 16.0 kg / ton-steel or less.
- the lower limit of the charged CaO is not particularly limited, and naturally exceeds 0 kg / ton-steel due to the relationship of the above formula (1).
- the lower limit of the charged CaO may be, for example, 2 kg / ton-steel or more, 4 kg / ton-steel or more, 6 kg / ton-steel or more, 8 kg / ton-steel or more, or 10 kg / ton-steel or more. According to the knowledge of the present inventor, if the amount of slag in the decarburization smelting is too large, sloping may occur in the initial stage of the decarburization smelting.
- the charging SiO 2 defined by S2 ⁇ (100- ⁇ 3) / 100 + S4 is not particularly limited as long as the above formulas (1) and (2) are satisfied.
- the range that the charged SiO 2 can take is naturally specified from the above formulas (1) and (2).
- C2 is the CaO conversion amount (kg / ton-steel) in the first flux 21, and C4 is the CaO conversion amount (kg / ton-steel) in the second flux 22.
- S2 is the SiO 2 conversion amount (kg / ton-steel) in the first flux 21, and S4 is the SiO 2 conversion amount (kg / ton-steel) in the second flux 22. That is, Ca contained in each flux is converted into CaO, Si is converted into SiO 2 , and the amount thereof is specified.
- the CaO conversion amount and the SiO 2 conversion amount of each flux can be obtained from the composition of the flux before being charged into the converter and the amount of the charged flux.
- the CaO conversion amount or the SiO 2 conversion amount may be specified based on the components contained in the slag after slag. As described above, when desiliconized slag is used as the first flux 21, it is considered that 100% of the silicon contained in the hot metal before desiliconization is changed to SiO 2 , and SiO 2 in the first flux 21 is used. The conversion amount may be specified.
- ⁇ 3 is an intermediate slag rate (%) in the third step.
- the intermediate discharge rate is determined from the amount of flux added to the converter 100 or the amount of flux existing in the converter 100 and the amount of slag (excluding bare metal) discharged from the converter 100. Can be identified.
- the intermediate slag rate may be empirically estimated from past operations or the like, or may be obtained from online or offline measured values during operations. In particular, it is desirable to measure the intermediate slag rate at least once with a weighing device or the like. By actually measuring the intermediate slag rate at least once, even if the use of the weighing instrument is interrupted due to a failure or trouble of the weighing instrument, etc., the past measured values are used and the operating conditions, etc.
- the intermediate slag rate can be estimated empirically and accurately.
- a weighing method other than the method using a weighing device as disclosed in Japanese Patent Application Laid-Open No. 2018-119195, a method of obtaining a slag rate based on the volume of discharged slag and the like can be mentioned.
- the step of specifying the intermediate waste rate ⁇ 3 in the third step, the specified intermediate waste rate ⁇ 3, and the CaO conversion amount and the SiO 2 conversion amount in the first flux are used.
- the step of determining the additional amount of the second flux, the CaO conversion amount of the second flux and / or the SiO 2 conversion amount of the second flux so that the above formulas (1) and (2) are satisfied based on the above. It may be provided.
- a step of specifying the amount of slag 31 discharged in the third step, based on the specified amount of slag, of the above formulas (1) and (2) is satisfied based on the step of specifying the intermediate discharge rate ⁇ 3, the specified intermediate discharge rate ⁇ 3, and the CaO conversion amount and the SiO 2 conversion amount in the first flux.
- the amount of slag discharged and the intermediate slag rate can be accurately specified.
- the weight of the bullion contained in the slag may be empirically estimated from past operations or the like, or may be measured online or offline at the time of operation.
- the molten steel 12 in the converter 100 may be taken out of the converter 100 after the fourth step.
- the converter 100 may be tilted to allow the molten steel 12 to flow out from the steel outlet 102 on the side of the converter 100.
- the slag 32 produced in the fourth step is left in the converter 100 while the steel is discharged. It may be provided with a fifth step to be performed. Then, after the fifth step, the slag 32 in the converter 100 is based on at least one of the estimated P 2 O 5 component amount of the slag 32 in the converter 100 and the P component target value of the steel of the next heat. Either a treatment of leaving the entire amount of the slag in the converter 100 or a treatment of leaving a part of the slag 32 in the converter 100 in the converter 100 and discharging the others is selected and executed. A sixth step may be provided.
- the first step of the next heat may be performed with the slag 32 remaining in the converter 100.
- the slag 32 can be reused as the flux of the next heat by performing the first step of the next heat while leaving the slag 32 after decarburization remaining in the converter 100.
- Example 1 1.1 First step The molten iron and scrap were charged to 300 tons in a 300 ton top-bottom blown converter in which the decarburized slag of the previous heat remained.
- Table 1 shows the temperature and composition of the hot metal in the furnace in the first step.
- Table 2 shows the residual amount of decarburized slag in the preheat.
- the first flux used for dephosphorization is a combination of the flux containing CaO newly introduced into the furnace, the decarburized slag of the preheat, and the desiliconized slag generated by desiliconization. Equivalent to.
- Table 1 below shows the hot metal temperature, hot metal composition, and slag composition at the time when the second step is completed.
- Table 2 shows the amount of CaO newly added for the second step, the basicity of the first flux used in the second step, and the amount of slag generated in the second step.
- Table 3 shows the CaO conversion amount and the SiO 2 conversion amount in the first flux.
- the slag in the furnace was discharged intermediately by tilting the converter.
- the amount of intermediate slag was measured with a weighing device.
- the intermediate slag rate was specified from the measured intermediate slag amount. Specifically, the intermediate slag rate in the third step is obtained by dividing the weighing value measured by the weighing device corrected for the amount of the bullion by the amount of slag obtained in advance from the charge in the second step. Asked.
- Tables 1 and 3 below show the intermediate slag rate in the third step.
- the second flux was put into the furnace and decarburization was carried out.
- the input amounts of the CaO source and the silica source were adjusted according to the intermediate slag rate so that the charged CaO / SiO 2 shown in (1) below had a predetermined value.
- the amount of CaO source input was adjusted according to the intermediate slag rate so that the charged CaO shown in (2) below had a predetermined value.
- Table 1 below shows the molten steel temperature, molten steel composition and slag composition at the time when the fourth step is completed.
- Table 2 below shows the amount of CaO newly added for the fourth step, the amount of SiO 2 , and the amount of slag generated in the fourth step.
- Table 3 shows the CaO conversion amount and the SiO 2 conversion amount in the second flux, the value of the charged CaO / SiO 2 calculated from the following formula (I), and the charge calculated from the following formula (II) are shown. The value of the input CaO is shown.
- C2 CaO conversion amount in the first flux (kg / ton-steel)
- C4 CaO conversion amount in the second flux (kg / ton-steel)
- Table 4 shows the actual charging CaO / SiO 2 according to the formula (I), the charging CaO according to the formula (II), and the decarburized slag for each of Examples 1 to 6 and Comparative Examples 1 to 5.
- Basicity, amount of CaO not slag during decarburization (specified from the difference between charged CaO / SiO 2 and actual basicity of decarburized slag), presence or absence of sloping at the initial stage of decarburization, and finally The P concentration in the obtained molten steel, the total amount of slag discharged to the outside of the system through a series of steps (total amount of slag discharged outside the system), and the amount of new CaO (newly input in the second and fourth steps).
- the total amount of CaO obtained is shown.
- the “total amount of slag discharged outside the system” is the weight of the slag discharged to the outside of the furnace due to the intermediate slag in the third process and the amount of slag in the furnace after the completion of the fourth process so as to be the amount shown in Table 2 above. It was the integrated value with the weight of the slag discharged to the outside of the furnace when it was adjusted to.
- Example 1 From the conditions shown in Tables 1 to 3 and the results shown in Table 4, the following can be seen. (1) As is clear from the results of Example 1 and Comparative Example 1, even if the total amount of slag discharged from the system is about the same, Comparative Example 1 in which the charged CaO / SiO 2 is high and the amount of unstained CaO is large. Compared with the above, in Example 1 in which the charged CaO / SiO 2 was lowered and the SiO 2 source was appropriately added, the P concentration in the molten steel could be lowered.
- Example 2 As is clear from the results of Example 2 and Comparative Example 2, in Comparative Example 2 in which the charged CaO / SiO 2 was less than 3.0 due to the excessive addition of the SiO 2 source, P in the molten steel The concentration could not be reduced. On the other hand, in Example 2, although the addition of the SiO 2 source was larger than in Example 1, the charged CaO / SiO 2 was about 3.8, which was 3.0 or more, so that the P concentration in the molten steel could be lowered. did it. (3) As is clear from the results of Comparative Example 2, when the charged CaO / SiO 2 is less than 3.0, the slag during decarburization becomes excessively low in basicity, and a large amount of highly viscous and easily foaming slag occurs.
- Comparative Example 3 which greatly exceeds, the slag could not be sufficiently produced due to the large amount of CaO slag, and the P concentration in the molten steel could not be reduced. Further, in Comparative Example 4, although the SiO 2 source was added, the amount added was not sufficient and the charged CaO / SiO 2 still exceeded 4.5, so that the P concentration in the molten steel could not be sufficiently reduced. rice field. (6) As is clear from the results of Comparative Example 5, when the charged CaO exceeds 30.0 kg / t-steel, the P concentration in the molten steel does not decrease and sloping occurs at the initial stage of decarburization and blowing. Occurred.
- Example 5 in which the charged CaO was 30.0 kg / t-steel or less, dephosphorization could be satisfactorily carried out without sloping. (7) From the comparison between Examples 1 to 5 and Example 6, it can be seen that the same effect is obtained regardless of whether the decarburized slag of the preheat is used as the first flux or not.
- the converter refining methods according to Examples 1 to 6 can easily suppress sloping in the initial stage of decarburization and smelting, and can stably reduce P in molten steel after decarburization and smelting. Do you get it.
- Hot metal 11 Dephosphorized hot metal 12 Molten steel 21 1st flux 22 2nd flux 31 Slag 32 Slag 100 converter
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Abstract
Description
転炉の内部に溶銑を装入する、第1工程、
前記第1工程の後で、前記転炉内の前記溶銑に対して、第1フラックスを用いつつ溶銑脱りんを行う、第2工程、
前記第2工程の後で、前記転炉内のスラグの少なくとも一部を前記転炉外に排滓する、第3工程、
前記第3工程の後で、前記転炉内に第2フラックスを追加したうえで脱炭を行う、第4工程、
を備え、
前記第2フラックスがCaO源とSiO2源とを含み、
下記式(1)及び(2)が満たされる、
転炉精錬方法
を開示する。
C4:前記第2フラックスにおけるCaO換算量(kg/ton-steel)
S2:前記第1フラックスにおけるSiO2換算量(kg/ton-steel)
S4:前記第2フラックスにおけるSiO2換算量(kg/ton-steel)
α3:前記第3工程における中間排滓率(%)
前記第4工程の後で、前記第4工程で生成したスラグを前記転炉内に残したまま出鋼を行う、第5工程、及び、
前記第5工程の後で、前記転炉内の前記スラグの推定P2O5成分量と、次ヒートの鋼のP成分目標値との少なくとも一方に基づいて、前記転炉内の前記スラグの全量を前記転炉内に残留させる処置、又は、前記転炉内の前記スラグの一部を前記転炉内に残留させつつその他を排滓する処置、のいずれかを選択して実行する、第6工程、
を備えてもよく、
前記第6工程の後で、前記転炉内に前記スラグを残留させたまま、次ヒートの第1工程を行ってもよい。
C4:第2フラックス22におけるCaO換算量(kg/ton-steel)
S2:第1フラックス21におけるSiO2換算量(kg/ton-steel)
S4:第2フラックス22におけるSiO2換算量(kg/ton-steel)
α3:第3工程における中間排滓率(%)
図1(A)に示されるように、第1工程においては、転炉100の内部に溶銑10を装入する。第1工程における条件は特に限定されるものではない。
図1(B)に示されるように、第2工程においては、第1工程の後で、第1フラックス21を用いつつ溶銑脱りんを行う。第2工程における脱りんの条件は特に限定されるものではない。
図1(C)に示されるように、第3工程においては、第2工程の後で、転炉100内のスラグ31の少なくとも一部を転炉100外に排滓する。例えば、図1(C)に示されるように、転炉100を傾動させることでスラグ31を系外に流出させればよい。また、第3工程において、転炉100の底部から底吹きガスを継続的に吹き込むことで、スラグ31をフォーミングさせてもよい。これによりスラグ31の排滓がより容易となる。
図1(D)及び(E)に示されるように、第4工程においては、第3工程の後で、転炉100内に第2フラックス22を追加したうえで脱炭を行う。第4工程においては、第2フラックス22がCaO源及びSiO2源を含むこと、及び、上記式(1)及び(2)が満たされることに特徴がある。それ以外の脱炭条件については特に限定されるものではない。
本開示の転炉精錬方法においては、図1(F)に示されるように、第4工程の後で、転炉100内の溶鋼12を転炉100外に出鋼してもよい。例えば、転炉100を傾動させて、転炉100の側部の出鋼口102から溶鋼12を流出させてもよい。
1.1 第1工程
前ヒートの脱炭スラグが残留している300tの上底吹き転炉内に、溶鉄及びスクラップを300tになるよう装入した。
第1工程の後で、CaOを含むフラックスを新たに炉内に投入し、脱りん吹錬を実施した。尚、脱りん吹錬に用いられる第1フラックスは、新たに炉内に投入されたCaOを含むフラックスと、前ヒートの脱炭スラグと、脱珪によって生じた脱珪スラグとを合わせたものに相当する。
第2工程の後で、転炉を傾動することで炉内のスラグの中間排滓を行った。このとき、中間排滓量を秤量器により測定した。測定した中間排滓量から中間排滓率を特定した。具体的には、地金分を補正した秤量器により計測した秤量値を、第2工程における装入物から事前に求めておいたスラグ量で除すことによって、第3工程における中間排滓率を求めた。
第3工程の後で、炉内に第2フラックスを投入して脱炭吹錬を実施した。ここで、下記(1)で示される装入CaO/SiO2が所定の値となるように、中間排滓率に応じてCaO源及びシリカ源の投入量を調整した。また、下記(2)で示される装入CaOが所定の値となるように、中間排滓率に応じてCaO源の投入量を調整した。
C4:第2フラックスにおけるCaO換算量(kg/ton-steel)
S2:第1フラックスにおけるSiO2換算量(kg/ton-steel)
S4:第2フラックスにおけるSiO2換算量(kg/ton-steel)
α3:第3工程における中間排滓率(%)
表1~3に示される条件にて第1工程~第4工程を行った。
下記表4に、実施例1~6、比較例1~5の各々について、式(I)に係る装入CaO/SiO2、式(II)に係る装入CaO、脱炭スラグの実際の塩基度、脱炭中に滓化しなかったCaOの量(装入CaO/SiO2と脱炭スラグの実際の塩基度との差分から特定)、脱炭初期のスロッピングの有無、最終的に得られる溶鋼中のP濃度、一連の工程を経ることで系外に排出された総スラグ量(系外排出総スラグ量)、及び、新規CaO量(第2工程及び第4工程において新規に投入したCaO量の合計)を各々示す。尚、「系外排出総スラグ量」は、第3工程での中間排滓により炉外へ排滓したスラグの重量と、第4工程終了後に炉内スラグ量を上記表2の量になるように調整した際に炉外へ排滓されたスラグの重量との積算値とした。
(1)実施例1及び比較例1の結果から明らかなように、系外排出総スラグ量が同程度であったとしても、装入CaO/SiO2が高く未滓化CaOが多い比較例1に比べて、装入CaO/SiO2を下げてSiO2源を適切に添加した実施例1の方が、溶鋼中のP濃度を低下させることができた。
(2)実施例2及び比較例2の結果から明らかなように、SiO2源が過剰に添加されて装入CaO/SiO2が3.0未満となった比較例2では、溶鋼中のP濃度を低下させることができなかった。一方、実施例2では実施例1に比べSiO2源の添加は多かったものの、装入CaO/SiO2が3.8程度と3.0以上であったため、溶鋼中のP濃度を下げることができた。
(3)比較例2の結果から明らかなように、装入CaO/SiO2が3.0未満となると、脱炭時のスラグが過剰に低塩基度化し、粘性が高く泡立ち易いスラグが多量に生成し、脱炭吹錬初期において転炉内からスラグが溢れるスロッピングが生じた。
(4)実施例3及び4の結果から明らかなように、装入CaO/SiO2が4.5近傍で脱炭吹錬を実施した場合、溶鋼中のP濃度を十分に低下させることができた。特に、スラグ量が多くなるようにCaO源及びSiO2源を添加した実施例4の方が、溶鋼中のP濃度を低下させることができ、極低りん鋼の溶製が可能であった。
(5)実施例3及び4並びに比較例3及び4の結果から明らかなように、実施例3及び4と同程度の中間排滓率であったものの装入CaO/SiO2が4.5を大きく超える比較例3では、CaOの未滓化分が多いこともあり、スラグが十分に生成できず、溶鋼中のP濃度を低下させることができなかった。また、比較例4は、SiO2源を添加したものの添加量が十分でなく装入CaO/SiO2が依然として4.5を超えているため、溶鋼中のP濃度を十分に下げることができなかった。
(6)比較例5の結果から明らかなように、装入CaOが30.0kg/t-steelを超えると、溶鋼中のP濃度が下がらないことに加え、脱炭吹錬初期にスロッピングが発生した。一方で、装入CaOが30.0kg/t-steel以下である実施例5では、スロッピングすることなく脱りんを良好に実施できた。
(7)実施例1~5と実施例6との比較から、第1フラックスとして前ヒートの脱炭スラグを用いた場合でも、用いない場合でも、同様の効果が奏されることが分かる。
11 脱りん溶銑
12 溶鋼
21 第1フラックス
22 第2フラックス
31 スラグ
32 スラグ
100 転炉
Claims (2)
- 転炉の内部に溶銑を装入する、第1工程、
前記第1工程の後で、前記転炉内の前記溶銑に対して、第1フラックスを用いつつ溶銑脱りんを行う、第2工程、
前記第2工程の後で、前記転炉内のスラグの少なくとも一部を前記転炉外に排滓する、第3工程、
前記第3工程の後で、前記転炉内に第2フラックスを追加したうえで脱炭を行う、第4工程、
を備え、
前記第2フラックスがCaO源とSiO2源とを含み、
下記式(1)及び(2)が満たされる、
転炉精錬方法。
C4:前記第2フラックスにおけるCaO換算量(kg/ton-steel)
S2:前記第1フラックスにおけるSiO2換算量(kg/ton-steel)
S4:前記第2フラックスにおけるSiO2換算量(kg/ton-steel)
α3:前記第3工程における中間排滓率(%) - 前記第4工程の後で、前記第4工程で生成したスラグを前記転炉内に残したまま出鋼を行う、第5工程、及び、
前記第5工程の後で、前記転炉内の前記スラグの推定P2O5成分量と、次ヒートの鋼のP成分目標値との少なくとも一方に基づいて、前記転炉内の前記スラグの全量を前記転炉内に残留させる処置、又は、前記転炉内の前記スラグの一部を前記転炉内に残留させつつその他を排滓する処置、のいずれかを選択して実行する、第6工程、
を備え、
前記第6工程の後で、前記転炉内に前記スラグを残留させたまま、次ヒートの第1工程を行う、
請求項1に記載の転炉精錬方法。
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