WO2022054553A1 - 含クロム溶鉄の製造方法 - Google Patents
含クロム溶鉄の製造方法 Download PDFInfo
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- WO2022054553A1 WO2022054553A1 PCT/JP2021/030760 JP2021030760W WO2022054553A1 WO 2022054553 A1 WO2022054553 A1 WO 2022054553A1 JP 2021030760 W JP2021030760 W JP 2021030760W WO 2022054553 A1 WO2022054553 A1 WO 2022054553A1
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- slag
- chromium
- basicity
- molten iron
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title claims abstract description 78
- 239000011651 chromium Substances 0.000 title claims abstract description 60
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 title claims abstract description 58
- 229910052804 chromium Inorganic materials 0.000 title claims abstract description 56
- 229910052742 iron Inorganic materials 0.000 title claims abstract description 39
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 18
- 239000002893 slag Substances 0.000 claims abstract description 111
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 claims abstract description 51
- 229910000423 chromium oxide Inorganic materials 0.000 claims abstract description 51
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 42
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 42
- 239000001301 oxygen Substances 0.000 claims abstract description 42
- 238000005261 decarburization Methods 0.000 claims abstract description 24
- 229910052751 metal Inorganic materials 0.000 claims abstract description 23
- 239000002184 metal Substances 0.000 claims abstract description 23
- 238000007664 blowing Methods 0.000 claims abstract description 22
- 238000000034 method Methods 0.000 claims abstract description 17
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 15
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 15
- 238000009628 steelmaking Methods 0.000 claims abstract description 5
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 4
- 239000010959 steel Substances 0.000 claims abstract description 4
- 239000002994 raw material Substances 0.000 claims description 35
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 12
- 238000002347 injection Methods 0.000 claims description 11
- 239000007924 injection Substances 0.000 claims description 11
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 5
- 238000003723 Smelting Methods 0.000 claims description 5
- 239000000463 material Substances 0.000 abstract description 7
- 238000007670 refining Methods 0.000 abstract description 7
- 238000010438 heat treatment Methods 0.000 abstract description 5
- 238000002844 melting Methods 0.000 abstract description 3
- 230000008018 melting Effects 0.000 abstract description 3
- 239000002699 waste material Substances 0.000 abstract description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 abstract 2
- 229910052681 coesite Inorganic materials 0.000 abstract 1
- 229910052906 cristobalite Inorganic materials 0.000 abstract 1
- 239000000377 silicon dioxide Substances 0.000 abstract 1
- 239000007858 starting material Substances 0.000 abstract 1
- 229910052682 stishovite Inorganic materials 0.000 abstract 1
- 229910052905 tridymite Inorganic materials 0.000 abstract 1
- 239000007791 liquid phase Substances 0.000 description 19
- 238000006722 reduction reaction Methods 0.000 description 14
- 239000002253 acid Substances 0.000 description 13
- 238000011156 evaluation Methods 0.000 description 7
- 239000003575 carbonaceous material Substances 0.000 description 6
- 238000011084 recovery Methods 0.000 description 5
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 4
- 239000003638 chemical reducing agent Substances 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000012546 transfer Methods 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
- 230000007613 environmental effect Effects 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 229910000604 Ferrochrome Inorganic materials 0.000 description 2
- 229910000519 Ferrosilicon Inorganic materials 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 2
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 2
- 229910000019 calcium carbonate Inorganic materials 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- JOPOVCBBYLSVDA-UHFFFAOYSA-N chromium(6+) Chemical compound [Cr+6] JOPOVCBBYLSVDA-UHFFFAOYSA-N 0.000 description 2
- 229910052593 corundum Inorganic materials 0.000 description 2
- 238000004090 dissolution Methods 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 239000008188 pellet Substances 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 239000007790 solid phase Substances 0.000 description 2
- 229910001845 yogo sapphire Inorganic materials 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 1
- 208000031481 Pathologic Constriction Diseases 0.000 description 1
- 229910000676 Si alloy Inorganic materials 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 235000011941 Tilia x europaea Nutrition 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- QDOXWKRWXJOMAK-UHFFFAOYSA-N dichromium trioxide Chemical compound O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 239000004571 lime Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 230000036262 stenosis Effects 0.000 description 1
- 208000037804 stenosis Diseases 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
Images
Classifications
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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
- C21C7/0025—Adding carbon material
-
- 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
- C21C5/005—Manufacture of stainless steel
-
- 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
- C21C5/30—Regulating or controlling the blowing
-
- 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
- C21C5/28—Manufacture of steel in the converter
- C21C5/36—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
- 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
- C21C7/06—Deoxidising, e.g. killing
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/068—Decarburising
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
- C21C7/04—Removing impurities by adding a treating agent
- C21C7/072—Treatment with gases
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C2250/00—Specific additives; Means for adding material different from burners or lances
- C21C2250/02—Hot oxygen
-
- 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
- C21C7/0037—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 by injecting powdered material
-
- 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
- C21C7/0068—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00 by introducing material into a current of streaming metal
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Definitions
- the present invention relates to a method for producing chromium-containing molten iron using a steelmaking smelting furnace.
- the mainstream method is to recover the valuable metal chromium content in the molten iron from the chromium oxide generated at the same time as the oxidation of carbon, and then discharge the hot water.
- Patent Document 1 discloses a method of recovering chromium in molten iron by removing or removing slag without reducing it after oxygen blowing and reducing the slag with carbon or silicon in an electric furnace. Has been done.
- Patent Document 2 after the chromium oxide-containing slag is generated, hot water is discharged without reduction, and the hot metal is charged into the smelting furnace to add carbonaceous material and blow acid to recover chromium in the molten iron.
- Patent Document 3 after the chromium oxide-containing slag is produced, calcium carbonate is added without reduction to solidify the slag, so that only molten iron is discharged and the chromium oxide-containing slag is separately discharged into an electric furnace.
- a method of recovering chromium in molten iron by charging and reducing treatment is disclosed.
- Patent Document 1 In the method described in Patent Document 1, it is necessary to recharge the slag containing chromium oxide into another refining container after slagging, which causes a problem that heat loss is large and electric power cost or heat heating cost of carbonaceous material is large. there were.
- Patent Document 2 has a problem that the slag adheres to the furnace wall, the furnace mouth, and the vicinity of the hot water hole when the slag containing chromium oxide remains and is discharged, resulting in deterioration of the operation.
- the present invention has been made in view of such circumstances, and an object of the present invention is to propose a method for producing chromium-containing molten iron which is inexpensive and produces less waste without affecting the operation.
- the inventors focused on the fact that the solid phase ratio and viscosity of the chromium oxide-containing slag after oxygen supply greatly change depending on its basicity, and chromium oxidation
- chrome-containing molten iron that is inexpensive and produces less waste without affecting the operation can be obtained. It was found that it can be manufactured.
- the present invention has been made based on the above findings, and the gist thereof is as follows.
- the method for producing chromium-containing molten iron of the present invention uses a steelmaking slag furnace to melt raw materials containing a chromium-containing raw material, raise the temperature, and perform crude decarburization by blowing oxygen.
- a method for producing chrome-containing steel in which the basicity of slag before rough decarburization by oxygen injection is adjusted within the range of 1.5 or more and 3.0 or less, and the slag after crude decarburization by oxygen injection is adjusted. After adjusting the basicity within the range of 2.0 or more and 3.5 or less, the hot water is discharged while leaving the chromium oxide-containing slag generated by oxygen injection in the same furnace.
- It has a second step of reducing the chromium oxide-containing slag remaining by a newly added carbon source or metal source and recovering the chromium in the molten iron, and the basicity of the slag is based on the mass in the slag.
- the CaO concentration is divided by the SiO 2 concentration.
- the method for producing chromium-containing molten iron according to the present invention is as follows.
- C In the first step, the chromium oxide concentration in the slag is in the range of 5 mass% or more and 50 mass% or less by using one or two kinds selected from the Si-containing raw material and the Al-containing raw material after oxygen injection. To be inside, Etc. may be a more preferable solution.
- chromium oxide-containing slag remains in the furnace without affecting the operation and is reduced by a carbon source or a metal source newly added in the same refining furnace, so that the slag is inexpensive and produced. It is possible to produce chromium-containing molten iron with less slag, which can contribute to the reduction of environmental load.
- the melting point of chromium oxide is as high as 2300 ° C.
- the chromium oxide-containing slag after supplying oxygen to the chromium-containing molten metal has a temperature of about 1700 ° C. and contains a large amount of chromium oxide, so that the liquid phase ratio is low and the viscosity is very high. Therefore, when only molten iron is discharged without reducing the chromium oxide-containing slag, a large amount of the slag remains as fixed slag near the furnace wall, the furnace mouth, or the hot water hole, which hinders the operation.
- the inventors pay attention to the fact that the relationship between the liquid phase ratio of chromium oxide-containing slag and the basicity of slag changes greatly depending on the concentration of chromium oxide (Cr 2 O 3 ), and influences the operation.
- slag with a high chromium oxide concentration has a high liquid phase ratio at high basicity
- slag with a low chromium oxide concentration has a high liquid phase ratio at low basicity.
- the concentration of chromium oxide in the slag is not high in the peak decarburization period. Therefore, if the basicity of the slag is lowered, the liquid phase ratio is increased and the adhesion of the slag to the furnace wall is reduced.
- the temperature may be raised by adding a carbonaceous material and sending acid.
- it can be regarded as a temperature raising step until the temperature T (K) during acid feeding becomes higher than the temperature represented by the equilibrium equation (2) shown below.
- a Cr represents the activity of Cr in the molten metal
- a C represents the activity of C in the molten metal
- PCO represents the CO partial pressure (atm) of the atmosphere.
- FIG. 1 is a basic configuration flow chart of a method for producing chromium-containing molten iron according to an embodiment of the present invention.
- a raw material containing a chromium-containing raw material is melted (S0) using a steelmaking smelting furnace.
- heat is increased (S1) by using electric energy or adding a heat source.
- S2 rough decarburization
- the hot water (S3) is discharged while leaving the chromium oxide-containing slag produced by blowing oxygen in the furnace.
- the basicity of the slag is the CaO concentration divided by the SiO 2 concentration based on the mass in the slag.
- the heat rise is carried out by, for example, energization heating, addition of a carbonaceous material or a silicon-containing substance, and acid transfer.
- the chromium oxide-containing slag remaining in the furnace is reduced by a carbon source or a metal source newly added in the same furnace, and chromium is recovered in the molten iron (S4). ) Therefore, chromium-containing molten iron can be effectively produced.
- the CaO-containing raw material is additionally dissolved during the oxygen blowing. You may. Further, the CaO-containing raw material is additionally dissolved, and the basicity (C / S) pre of the slag before the rough decarburization by oxygen blowing and the basicity (C / S) of the slag after the rough decarburization by the oxygen blowing.
- Post preferably satisfies the following equation (1).
- the CaO-containing raw material may be newly added during oxygen blowing, or may be added from the beginning so that the massive CaO-containing raw material is dissolved during oxygen blowing.
- the dissolution rate of the raw material varies depending on the properties of the raw material, the shape of the furnace and the stirring condition, and various estimation formulas have been reported, but it may be empirically estimated from the actual change in basicity.
- a weak reduction (S5) is performed in which one or two selected from Si-containing raw materials and Al-containing raw materials are used to adjust the chromium oxide concentration in the slag within the range of 5 mass% or more and 50 mass% or less.
- FIG. 2 graphically shows the effect of the chromium oxide concentration on the relationship between the basicity of the slag and the liquid phase ratio produced at 1700 ° C. calculated using the thermodynamic calculation software Factsage.
- the MgO concentration and the Al2O3 concentration in the slag were set to 10 mass% and 10 mass%, respectively.
- the MgO concentration and the Al2O3 concentration are the compositions of slag in a general smelting furnace, and the magnitude of these concentrations does not significantly affect the calculation result.
- the chromium concentration in the slag shown in FIG. 2 is 5 mass%
- the basicity is relatively low, and the basicity of the slag is in the range of 1.0 to 3.0.
- High liquid phase ratio can be maintained.
- the basicity increases, the liquid phase ratio decreases.
- the liquid phase ratio increases as the basicity increases in the range where the basicity of the slag is 2.0 or more. I found out to do.
- a liquid phase generated in the range of basicity less than 2.0 becomes a liquid phase having a very high viscosity of about 1.2 basicity, which may cause adhesion to the furnace wall.
- the basicity in the liquid phase is the CaO concentration divided by the SiO 2 concentration based on the mass in the liquid phase. Since the liquid phase ratio is relatively high in the low chromium concentration region, there is no operational problem even if the liquid phase has a high viscosity.
- the basicity of the slag should be 3.5 or less. Therefore, the basicity of the slag at the end of acid feeding is preferably in the range of 2.0 or more and 3.5 or less.
- the basicity that maximizes the liquid phase ratio changes during oxygen blowing due to the change in the chromium oxide concentration during oxygen blowing. Therefore, the CaO-containing raw material is intentionally additionally dissolved during oxygen blowing, and the basicity (C / S) pre of the slag before rough decarburization by oxygen blowing and after rough decarburization by oxygen blowing. It is preferable that the basicity (C / S) post of the slag of No. 1 satisfies the following equation (1).
- the upper limit of the following equation (1) is 2.0. (C / S) post- (C / S) pre ⁇ -0.2 ... (1)
- the concentration of chromium oxide is about 60 mass%, the basicity of the liquid phase portion does not increase so much even if the basicity of the slag is increased, so that the concentration of chromium oxide in the slag is preferably 50 mass% or less. If the chromium oxide concentration in the slag is less than 5%, the disadvantage of increasing the volume of the slag may outweigh the advantages of chromium that can be recovered by a newly charged carbon or metal source. Yes, it is preferable to secure 5% or more.
- the concentration of chromium oxide can be adjusted within this range by adding an appropriate amount of the Si-containing raw material or the Al-containing raw material. In this case, the slag basicity after acid feeding and after weak reduction changes due to the addition of the Si-containing raw material, but both the slag basicity after acid feeding and after weak reduction are 2.0 or more and 3.5 or less. It is preferably within the range.
- the slag basicity before the start of crude decarburization by acid transfer, after the end of acid transfer, and after weak reduction can be controlled by designing the weight of auxiliary materials charged during blowing and the timing of addition, respectively.
- chromium oxide-containing slag When chromium oxide-containing slag remains in the furnace, chromium can be reduced and recovered by adding a carbon source or a metal source to the chromium oxide-containing slag.
- the carbon source include hot metal prepared separately, high carbon-containing ferrochrome, and carbonaceous material.
- the metal source include ferrosilicon, aluminum pellets, and aluminum dross. Since the reduction reaction of chromium oxide by carbon is an endothermic reaction, it may be heated by energization, or it may be heated by supplying oxygen to supply heat.
- the composition of the slag may be adjusted again and the hot water may be discharged while the chromium oxide-containing slag remains in the furnace, or the hot water may be discharged after adding a metal reducing agent and draining once. ..
- Example 1 The hot metal was charged into a 150-ton converter, ferrochrome was added, and then decarburization and blowing was performed to raise the temperature and decarburize. After that, hot water was discharged. After the hot water was discharged, the hot metal was charged into the furnace again to reduce the chromium oxide-containing slag to recover the chromium, and the heat was increased by acid transfer decarburization.
- Table 1 The experimental conditions are shown in Table 1.
- the condition of the furnace opening was confirmed and the operational impact was evaluated.
- the results are shown in Table 2.
- the operational stability evaluation as an evaluation of the degree of blockage of the hearth, the reduction rate of the hearth area was evaluated from the photograph of the hearth.
- the amount of decrease in the furnace opening area after treatment was 1% or more of the furnace opening area before treatment, it was evaluated as ⁇ , when it was less than 1%, it was evaluated as ⁇ , and when there was no decrease in the furnace opening area, it was evaluated as ⁇ . ..
- the amount of reducing material used As an evaluation of the amount of reducing material used, when the amount of metal reducing material used, that is, the amount of ferrosilicon and aluminum pellets used was the same as the conventional one, it was evaluated as x, and when it was reduced from the conventional one, it was evaluated as ⁇ . Furthermore, as the chromium recovery rate, the proportion of chromium recovered in the second step was evaluated. Here, the chromium recovery rate was calculated as (chromium concentration (%) of molten metal x hot water discharge amount (t) / 100-added chromium amount (t)) / residual chromium amount (t) in the furnace on a mass basis. ..
- chromium recovery rate less than 0.3 was evaluated as x, and 0.3 or more was evaluated as ⁇ .
- the condition in which any of the operation stability evaluation, the reducing agent usage evaluation, and the chromium recovery rate was evaluated as ⁇ was evaluated as ⁇ , and the operation stability evaluation was ⁇ among the conditions not including ⁇ .
- the evaluated conditions were evaluated as ⁇ , and the other conditions were evaluated as ⁇ .
- Processing condition No. which is an example of the invention.
- the reduction and recovery of chromium was possible under all conditions, and the amount of reducing agent used could be reduced.
- the treatment condition No. adjusted so that the chromium oxide concentration in the slag was 5 mass% or more and 50 mass% or less.
- the stenosis rate of the furnace opening was relatively suppressed.
- the chromium-containing molten iron produced by the present invention has a high oxygen concentration in the molten iron, so that it is difficult to absorb nitrogen. Therefore, it is also useful as a method for obtaining high-purity molten iron.
- the molten iron discharged by this method is discharged in a state where the sulfur concentration is relatively high because the oxygen concentration in the molten iron is high, but desulfurization can be performed without any problem by performing a reduction treatment in a subsequent process. ..
- the amount of the alloy reducing material such as the Si-containing raw material and the Al-containing raw material used is significantly reduced. It is also useful to melt the molten iron having a predetermined component concentration by combining the molten iron discharged by this method and the molten iron melted in another refining container.
- the method for producing chromium-containing molten iron of the present invention is industrially useful because it is inexpensive, can suppress slag produced, and can reduce the environmental load.
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Abstract
Description
特許文献1に記載の方法では、クロム酸化物含有スラグを排滓後に別の精錬容器に再度装入する必要があり、熱ロスが大きく電力コストもしくは炭材などの昇熱コストが大きくなる課題があった。
(a)前記第一工程における前記酸素吹込み中にCaO含有原料を追加溶解させること、
(b)前記第一工程における前記酸素吹込みによる粗脱炭前のスラグの塩基度(C/S)preと、前記酸素吹込みによる粗脱炭後のスラグの塩基度(C/S)postとが下記(1)式を満足すること、
(c)前記第一工程において、酸素吹込み後にSi含有原料およびAl含有原料のうちから選ばれる1種または2種を用いて、スラグ中のクロム酸化物濃度を5mass%以上50mass%以下の範囲内とすること、
などがより好ましい解決手段になり得るものと考えられる。
(C/S)post-(C/S)pre≧-0.2・・・(1)
酸化クロムの融点は2300℃と非常に高い。含クロム溶湯に酸素を供給した後のクロム酸化物含有スラグは、1700℃程度であり、かつ、酸化クロムを多量に含むため、液相率が低く、粘度が非常に高い。そのため、クロム酸化物含有スラグを還元することなく溶鉄のみを出湯した場合、そのスラグが炉壁、炉口、または出湯孔付近に固着スラグとして大量に残留し、操業を阻害してしまう。
(C/S)post-(C/S)pre≧-0.2・・・(1)
発明者らは、発明に先立って、酸化クロム濃度が異なるスラグの平衡相について、熱力学的検討を行った。図2に、熱力学計算ソフトFactsageを用いて算出した1700℃における、スラグの塩基度と生成する液相率の関係に与える酸化クロム濃度の影響をグラフで示す。ここで、スラグ中のMgO濃度およびAl2O3濃度をそれぞれ10mass%および10mass%とおいた。このMgO濃度とAl2O3濃度は一般的な精錬炉におけるスラグの組成であり、この濃度の大小は、計算結果に大きな影響を与えない。
(C/S)post-(C/S)pre≧-0.2・・・(1)
150t転炉に溶銑を装入し、フェロクロムを添加したのちに脱炭吹錬を実施し、昇温および脱炭を施した。その後、出湯を実施した。出湯後に、再度溶銑を炉内に装入してクロム酸化物含有スラグを還元してクロムを回収するとともに送酸脱炭による昇熱を実施した。実験条件を表1に示す。
Claims (4)
- 製鋼用精錬炉を用いて、含クロム原料を含む原料の溶解と、昇温と、酸素吹込みによる粗脱炭とを行う含クロム鋼の製造方法であって、
酸素吹込みによる粗脱炭前のスラグの塩基度を1.5以上3.0以下の範囲内に調整し、
酸素吹込みによる粗脱炭後のスラグの塩基度を2.0以上3.5以下の範囲内に調整したうえで、酸素吹込みにより生成したクロム酸化物含有スラグを炉内に残したまま出湯する第一工程と、
同一の炉内に新たに添加する炭素源または金属源により残留した前記クロム酸化物含有スラグを還元し、クロムを溶鉄中に回収する第二工程と、を有し、
前記スラグの塩基度は、スラグ中の質量基準で、CaO濃度をSiO2濃度で除したものであることを特徴とする含クロム溶鉄の製造方法。 - 前記第一工程における前記酸素吹込み中にCaO含有原料を追加溶解させることを特徴とする請求項1に記載の含クロム溶鉄の製造方法。
- 前記第一工程における前記酸素吹込みによる粗脱炭前のスラグの塩基度(C/S)preと、前記酸素吹込みによる粗脱炭後のスラグの塩基度(C/S)postと、が下記(1)式を満足することを特徴とする請求項1または請求項2に記載の含クロム溶鉄の製造方法。
(C/S)post-(C/S)pre≧-0.2・・・(1) - 前記第一工程において、前記酸素吹込み後にSi含有原料およびAl含有原料のうちから選ばれる1種または2種を用いて、スラグ中のクロム酸化物濃度を5mass%以上50mass%以下の範囲内とすることを特徴とする請求項1ないし3のいずれか一項に記載の含クロム溶鉄の製造方法。
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