WO2020110392A1 - 鋼の製造方法及びスラグの塩基度低減方法 - Google Patents
鋼の製造方法及びスラグの塩基度低減方法 Download PDFInfo
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- WO2020110392A1 WO2020110392A1 PCT/JP2019/033574 JP2019033574W WO2020110392A1 WO 2020110392 A1 WO2020110392 A1 WO 2020110392A1 JP 2019033574 W JP2019033574 W JP 2019033574W WO 2020110392 A1 WO2020110392 A1 WO 2020110392A1
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- Prior art keywords
- furnace body
- slag
- converter
- basicity
- silica
- Prior art date
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- 239000002893 slag Substances 0.000 title claims abstract description 105
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 82
- 239000010959 steel Substances 0.000 title claims abstract description 82
- 238000000034 method Methods 0.000 title claims abstract description 74
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 32
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims abstract description 140
- 238000007670 refining Methods 0.000 claims abstract description 103
- 239000000377 silicon dioxide Substances 0.000 claims abstract description 70
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims abstract description 38
- 229910001882 dioxygen Inorganic materials 0.000 claims abstract description 38
- 230000001590 oxidative effect Effects 0.000 claims abstract description 30
- 238000010079 rubber tapping Methods 0.000 claims abstract description 23
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 18
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 18
- 239000001301 oxygen Substances 0.000 claims abstract description 18
- 238000007664 blowing Methods 0.000 claims description 70
- 239000000126 substance Substances 0.000 claims description 61
- 229910004298 SiO 2 Inorganic materials 0.000 claims description 21
- 239000002184 metal Substances 0.000 claims description 19
- 229910052751 metal Inorganic materials 0.000 claims description 19
- 239000007789 gas Substances 0.000 claims description 16
- 229910000805 Pig iron Inorganic materials 0.000 claims description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 abstract description 73
- 229910052742 iron Inorganic materials 0.000 abstract description 36
- 239000000463 material Substances 0.000 abstract description 12
- 230000009467 reduction Effects 0.000 abstract description 2
- 229910052681 coesite Inorganic materials 0.000 abstract 1
- 229910052906 cristobalite Inorganic materials 0.000 abstract 1
- 229910052682 stishovite Inorganic materials 0.000 abstract 1
- 229910052905 tridymite Inorganic materials 0.000 abstract 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 16
- 238000007654 immersion Methods 0.000 description 15
- 230000000052 comparative effect Effects 0.000 description 13
- 230000000694 effects Effects 0.000 description 13
- 229910052698 phosphorus Inorganic materials 0.000 description 13
- 239000011574 phosphorus Substances 0.000 description 13
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 11
- 238000007254 oxidation reaction Methods 0.000 description 11
- 238000002844 melting Methods 0.000 description 10
- 230000008018 melting Effects 0.000 description 10
- 230000003647 oxidation Effects 0.000 description 10
- 230000007423 decrease Effects 0.000 description 9
- 238000006243 chemical reaction Methods 0.000 description 8
- 239000003795 chemical substances by application Substances 0.000 description 8
- 239000000203 mixture Substances 0.000 description 8
- 239000002245 particle Substances 0.000 description 7
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 6
- 239000004575 stone Substances 0.000 description 6
- 239000002994 raw material Substances 0.000 description 5
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 4
- 229910052799 carbon Inorganic materials 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- 239000011261 inert gas Substances 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 3
- 235000011941 Tilia x europaea Nutrition 0.000 description 3
- 238000005261 decarburization Methods 0.000 description 3
- 239000004571 lime Substances 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 238000011017 operating method Methods 0.000 description 3
- 239000002436 steel type Substances 0.000 description 3
- 238000009628 steelmaking Methods 0.000 description 3
- 239000004215 Carbon black (E152) Substances 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000007599 discharging Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000003607 modifier Substances 0.000 description 2
- 230000001737 promoting effect Effects 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 239000000538 analytical sample Substances 0.000 description 1
- 239000012159 carrier gas Substances 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000007885 magnetic separation Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 238000011084 recovery Methods 0.000 description 1
- 238000002407 reforming Methods 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 239000000523 sample Substances 0.000 description 1
- 239000007787 solid 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
- 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
- C21C5/5211—Manufacture of steel in electric furnaces in an alternating current [AC] electric arc furnace
- C21C5/5217—Manufacture of steel in electric furnaces in an alternating current [AC] electric arc furnace equipped with burners or devices for injecting gas, i.e. oxygen, or pulverulent materials into the furnace
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B5/00—Treatment of metallurgical slag ; Artificial stone from molten metallurgical slag
- C04B5/06—Ingredients, other than water, added to the molten slag or to the granulating medium or before remelting; Treatment with gases or gas generating compounds, e.g. to obtain porous slag
-
- 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
- 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
-
- 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
-
- 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
- Y02P40/00—Technologies relating to the processing of minerals
- Y02P40/40—Production or processing of lime, e.g. limestone regeneration of lime in pulp and sugar mills
Definitions
- the present invention relates to a steel manufacturing method and a slag basicity reducing method.
- an oxidative refining process (decarburization process) is performed in the converter to add molten oxygen to the hot metal to produce molten steel.
- slag is generated due to the oxidation reaction of the added auxiliary material and the impurity components in the hot metal. After being collected, this slag is reused as a raw material for various purposes.
- slag generated in a converter is roadbed materials.
- the water immersion expansion coefficient needs to meet the quality standard defined by JIS or the like, and for example, the JIS standard needs to be 1.5% or less.
- JIS the quality standard defined by JIS or the like
- the basicity of the slag the ratio of the SiO 2 content to the CaO content of the slag ((%CaO)/(% It is important to reduce SiO 2 )
- the oxidation refining treatment in the converter generally, only the amount according to the target slag composition determined according to the blowing components such as the target components and target temperature of the molten iron after the oxidation refining treatment, the efficiency of the refining reaction, At the beginning of the oxidative refining process, auxiliary materials such as silica stone and lime are added. However, it was difficult to reduce the basicity of the slag during the oxidative refining treatment from the viewpoint of promoting the dephosphorization reaction.
- Patent Document 1 a substance containing one or more kinds of SiO 2 , Al 2 O 3 , FeO, Fe 2 O 3 , and P 2 O 5 in a steelmaking slag (hereinafter, referred to as “improved” It also discloses a method of modifying the slag by adding a material to which slag is added) and then performing heat treatment for 10 minutes or less at a temperature equal to or higher than the melting temperature.
- the present invention has been made by paying attention to the above problems, it is possible to reduce the basicity of the slag, it is possible to suppress the decrease in production efficiency, steel manufacturing method and the basicity of the slag
- the purpose is to provide a reduction method.
- a method for producing a molten steel by subjecting the hot metal to an oxidative refining treatment wherein the hot metal contains at least oxygen gas containing oxygen gas.
- a refining treatment step in which the molten pig iron is converted to the molten steel by adding a source and performing an oxidative refining treatment, and after the refining treatment step, the molten steel contained in the furnace body of the converter contains at least SiO 2 .
- a method for producing steel comprising: an addition step of adding a silica-containing substance; and a tapping step of tilting the furnace body and discharging the molten steel from the furnace body after the addition step.
- the basicity of slag that is reduced when producing molten steel by subjecting molten pig iron to an oxidative refining treatment is reduced.
- an oxygen source containing at least oxygen gas is added to the molten pig iron, and a refining treatment step is performed by subjecting the molten pig iron to the molten steel by performing an oxidation refining treatment, and after the refining treatment step, a furnace for the converter.
- the method for reducing the basicity of slag is provided.
- a steel manufacturing method and a slag basicity reducing method capable of reducing the basicity of slag and suppressing a decrease in production efficiency.
- a steel manufacturing method and a slag basicity reducing method capable of reducing the basicity of slag and suppressing a decrease in production efficiency.
- the molten steel 6 is produced by subjecting the molten iron 6 to an oxidative refining process using the upper-bottom blown type converter 1.
- the converter 1 includes a furnace body 2, a plurality of bottom blowing tuyere 3, an upper blowing lance 4, and a chute 5.
- the furnace body 2 is a refining container in which a refractory material is applied.
- the furnace body 2 has an opening called a furnace port 21 in the upper portion in the state shown in FIG. Further, the furnace body 2 is configured to be tiltable about a pair of trunnion shafts 22 provided on the side surfaces.
- the plurality of bottom blowing tuyeres 3 are tuyeres of double tubes provided at the bottom of the furnace body 2.
- the plurality of bottom blowing tuyeres 3 are configured to blow at least oxygen gas from the inner tube and hydrocarbon gas from the outer tube into the furnace body 2, respectively.
- the upper blowing lance 4 is a lance that can be inserted into the furnace body 2 from above the furnace body 2 through the furnace port 21.
- the upper blowing lance 4 is configured to be able to inject at least oxygen gas from a lance hole formed at the lower tip.
- the chute 5 is a device provided above the furnace body 2.
- the tip of the chute 5 is arranged toward the furnace port 21.
- the chute 5 conveys auxiliary materials such as a refining agent and a slag forming agent cut out from a hopper (not shown) and inputs the auxiliary raw material into the furnace body 2.
- molten steel tapped from the blast furnace is housed in the furnace body 2 and subjected to oxidative refining treatment to manufacture molten steel.
- molten pig iron and molten steel are collectively referred to as molten iron 6.
- the hot metal subjected to the oxidative refining treatment may be previously subjected to hot metal pretreatment such as desiliconization treatment, dephosphorization treatment, and desulfurization treatment in another refining facility.
- molten iron 6 which is hot metal is charged into the furnace body 2, and then oxygen gas and hydrocarbon gas are blown into the molten iron 6 from a plurality of bottom blowing tuyere 3 and oxygen gas is blown from the upper blowing lance 4.
- the oxidative refining treatment is a treatment in which an oxygen source is added to the hot metal to oxidize and remove impurities such as carbon and phosphorus in the hot metal.
- a decarburization reaction in which at least carbon in the molten iron 6 is removed and a phosphorus removal reaction in which phosphorus in the molten iron 6 is removed proceed by the oxidative refining process.
- oxygen gas oxygen source
- blowing addition of oxygen gas (oxygen source) to molten iron 6 by blowing oxygen gas from a plurality of bottom blowing tuyere 3 and injecting oxygen gas from top blowing lance 4 is also referred to as blowing.
- the carbon in the molten iron 6 is oxidized and removed by the progress of the decarburization reaction, and molten steel having a low carbon concentration is manufactured.
- auxiliary materials such as a slag forming agent are put into the furnace body 2 in order to accelerate the dephosphorization reaction.
- a plurality of types of slag forming agents having different component compositions are added in an amount corresponding to the target slag composition.
- Auxiliary materials such as smelting agents are determined in advance according to various blowing conditions such as the composition and temperature of the molten iron 6 before the oxidation refining treatment, the target composition and target temperature of the molten iron 6 after the oxidation refining treatment, and the efficiency of the refining reaction.
- the determined input amount is input in the initial stage of the oxidative refining process.
- the ratio of the CaO concentration (mass%) to the SiO 2 concentration (mass%) ((%CaO)/(%SiO 2 )) is called basicity.
- the estimated basicity of the slag after the oxidative refining treatment is also calculated as the basicity based on the mass balance of the auxiliary raw materials and the components of the molten iron 6 to be charged, the planned amount of the oxygen source to be charged and the like.
- the calculated basicity is usually 4.0 or more in the upper-bottom blowing converter 1.
- the auxiliary raw materials are introduced and the refining process is performed, and the components and temperature of the molten iron 6 are set to target values, whereby the oxidation refining process is completed.
- an addition step of adding a silica-containing substance containing at least SiO 2 to the molten iron 6 that is the molten steel housed in the furnace body 2 via the chute 5 is performed.
- the operating procedure of the addition step is not particularly specified, but the following operating procedure is desirable because it promotes melting of the silica-containing substance.
- the converter 1 When the converter 1 is a top-blown or top-bottom-blended converter having a top-blown lance, after the refining process, the top-blown lance is in a standby position while injecting oxygen gas to prevent nozzle clogging.
- the addition of the silica-containing substance to the molten steel may be started during the period of increasing the temperature to In this case, when the necessary refining operation is completed, the operator (operator) operates the operation panel to send a refining end command. Immediately after sending this command, the required amount of silica-containing substance is cut out from the bunker into the hopper, and the gate of the hopper is opened.
- the silica-containing substance is added to the molten steel bath surface in the furnace through the chute after the top blowing lance starts to move to the standby position.
- the upper blowing lance has a lower flow rate than during the oxidative refining process, but the oxygen injection is continued during the rising.
- the molten steel is stirred by the blown oxygen gas (stirring effect).
- the oxygen gas blown oxidizes the molten steel and produces FeO, which promotes slag slag formation (slag formation effect). Therefore, the melting effect of the silica-containing substance is promoted by the stirring effect and the slagging effect of the oxygen gas.
- the planned amount of silica-containing substance is cut out from the bunker at the end of the refining process and stored in the hopper in an addable state,
- the operation of opening the gate of the hopper may be performed immediately after sending the refining end command.
- the silica-containing substance may be added to the molten steel during the period from when the condition for tilting the furnace body is switched to when the tilting of the furnace body is started. In this case, immediately after the operator operates the operation panel to send the refining end command, the necessary amount of the silica-containing substance is cut out from the bunker into the hopper and the gate of the hopper is opened.
- a refining end command is sent, in the case of a bottom-blown or bottom-blown converter that allows bottom blowing of oxygen gas, inert gas, or a mixed gas of oxygen gas and inert gas, it is blown from the bottom blowing tuyere.
- the conditions for blowing the bottom-blown gas are switched from the conditions in the refining process step to the conditions for tilting the furnace body in the tapping step to be described later. Specifically, under the blowing conditions when tilting the furnace body for tapping, the type of bottom blowing gas is switched to the inert gas, and the flow rate of bottom blowing gas causes blockage of the bottom blowing tuyere during tapping. The flow rate is set to a low level.
- the silica-containing substance is a molten steel bath in the furnace from the hopper via the chute 5 during a period from immediately after the bottom blowing gas is blown into the furnace body to when the furnace body is tilted until the tilting of the furnace body is started. Will be added on the surface.
- the furnace body is preferably in an upright state while the silica-containing substance is added. With such an operating procedure, melting of the silica-containing substance is promoted by the stirring effect of the molten steel by the bottom-blown gas.
- the amount of silica-containing substance to be added is cut out from the bunker at the end of the refining process and added to the hopper in a state where it can be added. It may be stored and only the operation of opening the gate of the hopper may be performed immediately after sending the refining end command.
- Silica-containing material but may be any those containing SiO 2, preferably the majority of the components are SiO 2, it is preferably SiO 2 content higher.
- silica-containing substance silica stone containing mainly SiO 2 can be used.
- silica-containing substance it is preferable to use, among the slag-forming agents used in the refining treatment step, those mainly containing SiO 2 from the viewpoint of the restriction of storage equipment such as a hopper. Since silica stone is generally used as a slag forming agent, it is preferable to use silica stone also from this viewpoint.
- the particle size of silica stone is set to 5 mm or more and 40 mm or less.
- the smaller the particle size of the silica-containing substance the easier the melting.
- the particle size of the silica-containing substance is too small, the input yield may be reduced due to scattering.
- a fine powdery silica-containing substance is used by air, it may not be possible to secure a sufficient amount for continuous treatment due to restrictions of storage facilities and transportation facilities.
- the particle size of the silica-containing substance is preferably 5 mm or more and 40 mm or less.
- the input amount of the silica-containing substance is determined according to the calculated basicity after the slag 7 refining treatment step and the target basicity set from the water immersion expansion coefficient of the slag. Specifically, the slag amount is estimated to calculate basicity after refining process slag 7, SiO 2 amount required for slag 7 becomes the target basicity is determined, the SiO 2 amount min The amount of the silica-containing substance is the input amount.
- the water immersion expansion coefficient of the slag is F. It is a value determined by the content of CaO (Free-CaO), and increases as the basicity of the slag increases.
- the JIS stipulates that the water immersion expansion coefficient is 1.5% or less, and in this embodiment, the slag water expansion expansion coefficient is set to 0.
- the target is 5% or less.
- the target basicity is less than 3.8 in the case of the top-bottom blowing converter as in the present embodiment, and the target basicity is 3.6 or less. Is more preferable.
- the target basicity is preferably 3.0 or more.
- the target basicity that is, the calculated basicity of the slag 7 after adding the silica-containing substance is less than 3.0, the phosphorus distribution ratio of the slag decreases, and the phosphorus in the slag returns to the molten steel, thereby Re-phosphorus, which increases the phosphorus concentration, may occur. For this reason, it may be a problem in steel types with a strict upper limit of phosphorus concentration.
- the addition step it is judged whether or not the calculated basicity of the slag 7 after the refining step is 3.8 or more, and the silica is calculated only when the calculated basicity of the slag 7 after the refining step is 3.8 or more.
- the contained substance may be added. In this case, if the calculated basicity of the slag 7 after the refining step is less than 3.8, the silica-containing substance is not added and the tapping step described below is performed.
- the silica-containing substance added in the adding step is added from the chute 5 into the high temperature furnace body 2 to be added to the slag 7 floating above the molten iron 6. Then, the charged silica-containing substance is melted by the hot molten iron 6 and the slag 7 and becomes a part of the melted slag 7.
- a steel tapping process of tilting the furnace body 2 and discharging the molten iron 6 from the furnace body 2 is performed.
- the furnace body 2 is tilted about the pair of trunnion shafts 22 and the molten iron 6 is discharged from a tap hole (not shown) provided in the side wall portion of the furnace body 2.
- the discharged molten iron 6 is stored in a ladle (not shown) arranged below the furnace body 2 and sent to the next step.
- the molten iron 6 and the slag 7 flow inside the furnace body 2 due to the tilting of the furnace body 2, thereby further promoting the melting of the silica-containing substance charged in the addition step.
- the slag 7 remains in the furnace body 2. Then, the slag 7 remaining in the furnace body 2 is discharged downward from the furnace port 21 when the furnace body 2 is tilted to the side opposite to the steel tapping process. The discharged slag 7 is collected in a slag pot arranged below the furnace body 2 and then reused after undergoing an appropriate treatment such as aging treatment and magnetic separation treatment.
- Molten iron 6 stored in a ladle (not shown) after the tapping process is appropriately subjected to secondary refining according to the target composition of the steel type to be manufactured, and then cast in a casting facility such as a continuous casting machine. Then, it becomes a cast piece.
- the obtained slab is subjected to rolling and heat treatment so that the dimension, shape, and characteristics satisfy the specifications of the shipped product, and becomes the product steel.
- the converter 1 is a top-bottom blow type converter, but the present invention is not limited to such an example.
- the converter 1 may be a top-blowing converter that injects oxygen gas only from the top-blowing lance 4 or a bottom-blowing converter that injects oxygen gas only from the bottom-blowing tuyere 3.
- the converter 1 when the converter 1 is a top-bottom blowing converter, it is a converter capable of bottom-blowing oxygen gas as in the above embodiment, and a bottom-blown converter capable of blowing only inert gas. Good.
- a lance hole different from oxygen gas is provided in the upper blowing lance 4, and an auxiliary material such as lime can be injected (projected) to the molten iron 6 together with the carrier gas from the lance hole. Good.
- the target basicity is set to be less than 3.8, more preferably 3.6 or less, but the present invention is not limited to this example. Further, in the adding step, it may be judged whether or not the silica-containing substance is added in the adding step, based on the judgment result of whether or not the calculated basicity of the slag 7 after the refining step is 3.8 or more. However, the present invention is not limited to such an example.
- the above target basicity and threshold value are 0.5% or less in a top-blown or bottom-blown converter, which is a converter-type refining in which the oxygen gas is blown from at least a plurality of bottom-blown tuyeres. It is suitable for achieving the water immersion expansion coefficient.
- the target basicity and the threshold value can be changed according to the target water immersion expansion rate and the difference in the blowing mode of the converter.
- the oxidative refining process is performed by adding oxygen gas as the oxygen source, but the present invention is not limited to this example.
- the oxygen source a solid oxygen source such as iron oxide may be used in addition to the oxygen gas.
- a method for producing steel according to an aspect of the present invention is a method for producing molten steel by subjecting molten iron to an oxidative refining treatment in a converter 1, which comprises: An oxygen source containing at least oxygen gas, and subjecting it to oxidation refining treatment to a refining treatment step in which molten iron is used as molten steel, and after the refining treatment step, at least the furnace body 2 of the converter 1 containing molten steel is An addition step of adding a silica-containing substance containing SiO 2 from above and a tapping step of tilting the furnace body 2 to discharge molten steel from the furnace body 2 after the addition step are provided.
- the silica-containing substance is added while the high-temperature molten steel, which is the molten iron 6, is housed inside the furnace body 2, the silica-containing substance is easily melted. Further, in the tapping process, the molten iron 6 and the slag 7 flow inside the furnace body 2 due to the tilting of the furnace body 2, whereby the melting of the silica-containing substance is further promoted. Therefore, the added silica-containing substance can be sufficiently melted, and the basicity of the slag 7 can be accurately reduced. Further, in the configuration of (1) above, the silica-containing substance is easily dissolved, so that a silica-containing substance having a larger particle size can be used. Thereby, the production efficiency can be improved and the manufacturing cost can be reduced.
- the configuration of (1) above it is not necessary to lower the basicity of the slag 7 in the refining treatment process.
- the slag 7 may be formed.
- the slag 7 is ejected from the furnace body 2 due to forming, it causes a decrease in yield and a collapse of the ladle wire under the furnace, which makes stable operation impossible.
- the occurrence frequency of forming of the slag 7 is suppressed, and stable operation can be performed.
- the phosphorus distribution ratio of the slag 7 becomes low, so that dephosphorization cannot be performed sufficiently or the CaO-containing slag forming agent is added to increase the amount of slag 7.
- the input amount of may increase.
- the period during which the basicity of the slag 7 decreases is a short period from the addition process to the tapping process, and the amount of reconstitution phosphorus due to the decrease in the phosphorus distribution ratio is extremely small. It will be From this, it is possible to minimize the influence of the decrease in the phosphorus distribution ratio, and it is possible to further reduce the manufacturing cost.
- the effect of the molten iron 6 on the composition of components is so small that the amount of re-phosphorus is extremely small, the product characteristics and the like are the same as conventional steel.
- the converter 1 has a bottom blowing tuyere 3 provided at the bottom of the furnace body 2, and in the refining treatment step, at least the bottom is used as oxygen gas contained in the oxygen source. Oxidation refining treatment is performed by blowing oxygen gas into the hot metal from the blowing tuyere 3. According to the configuration of (2) above, even in a bottom-blown or top-bottomed converter in which it is difficult to reduce the basicity of the slag as compared to the top-blown converter due to the difference in the blowing mode, Since the basicity of the slag can be reduced, the reuse of the slag can be promoted.
- the converter 1 has an upper blowing lance 4, and in the adding step, after the refining process step, while injecting oxygen gas to prevent nozzle clogging, During the period in which the upper blowing lance 4 is raised to the standby position, the addition of the silica-containing substance to the molten steel is started. According to the configuration of (3) above, the melting of the silica-containing substance is promoted by the stirring effect and the slagging effect of the blown oxygen gas.
- the converter 1 has a bottom blowing tuyere 3 provided at the bottom of the furnace body 2, and the addition step includes a refining treatment step. Thereafter, during the period from when the blowing condition of the bottom blowing gas blown from the bottom blowing tuyere 3 is switched to the condition when the furnace body 2 is tilted until when the tilting of the furnace body 2 is started, the molten steel contains silica. Add substance. With configuration (4) above, the molten steel is agitated by the bottom-blown gas blown from the bottom-blown gas even in the addition step, and the melting of the silica-containing substance is promoted.
- the slag 7 in the adding step when the calculated basicity of the slag 7 in the furnace body 2 after the refining treatment step is 3.8 or more, the slag The amount of the silica-containing substance added is determined so that the calculated basicity of 7 is 3.6 or less.
- the water immersion expansion coefficient of the slag 7 can be set to 0.5% or less.
- the amount of the silica-containing substance added is adjusted so that the calculated basicity of the slag 7 in the furnace body 2 becomes 3.0 or more. To decide. According to the above configuration (6), the amount of rephosphorization can be sufficiently suppressed, and the manufacturing cost can be further reduced.
- a method for reducing the basicity of slag according to one aspect of the present invention is to reduce the basicity of slag 7 generated when molten steel is produced by subjecting molten iron to oxidative refining treatment in a converter 1.
- an adding step of adding a silica-containing substance containing at least SiO 2 to the molten steel housed in the furnace body 2 of the converter 1, and after the adding step, the furnace body 2 is tilted to discharge the molten steel from the furnace body. And a tapping process.
- the same effect as that of (1) above can be obtained.
- the converter 1 has the upper blowing lance 4, and in the adding step, the upper blowing lance 4 is injected after the refining treatment step while injecting oxygen gas to prevent nozzle clogging. During the period in which the steel is raised to the standby position, the addition of the silica-containing substance to the molten steel is started. With the configuration (8), the same effect as that of the configuration (3) can be obtained.
- the converter 1 has a bottom blowing tuyere 3 provided at the bottom of the furnace body 2, and in the adding step, bottom blowing is performed after the refining treatment step.
- a silica-containing substance is added to molten steel during a period from when the bottom blowing gas blown from the tuyere 3 is switched to a condition for tilting the furnace body 2 until the tilting of the furnace body 2 is started. ..
- the configuration (9) With the configuration (9), the same effect as that of the configuration (4) can be obtained.
- the molten steel 6 was refined in the converter 1 to reduce the basicity of the slag by using the steel manufacturing method similar to the above-described embodiment. Specifically, in the example, molten steel was manufactured by subjecting the hot metal to an oxidative refining treatment in the top-bottom blowing converter 1 in the refining treatment step. In the refining process step, the oxidative refining process of the molten iron 6 was performed under the condition that the calculated basicity was 4 or more. Next, in the adding step, silica was added as a silica-containing substance with a target basicity of 3.6 (Example 1) or 3.2 (Example 2).
- the tapping process when the molten iron 6 is discharged from the furnace body 2, the slag 7 in the furnace body 2 is sampled, and the CaO concentration and the SiO 2 concentration are measured to determine the basicity (also referred to as “actual basicity”). It was measured.
- FIG. 2 shows the relationship between the calculated basicity and the actual basicity in Examples and Comparative Examples.
- the plot shows the average value of a plurality of data, and the bars extending vertically and horizontally show the standard deviation ( ⁇ ). As shown in FIG.
- the basicity of the conventional slags shown in Comparative Examples 1 to 4 was a correlation between the calculated basicity and the actual basicity.
- the calculated basicity is calculated from the mass balance under the preliminarily predicted blowing conditions such as the amount of hot metal components and various auxiliary raw materials input, the amount of oxygen source containing oxygen gas, in the oxidative refining process. It is a thing. Therefore, due to factors such as actual reaction efficiency, the actual basicity tends to be lower than the calculated basicity by a certain amount.
- the slag 7 treated in the same manner as in the above example 1 was discharged from the furnace body 2 and recovered, and then the basicity analysis and the water immersion expansion coefficient were measured.
- the basicity was determined from the ratio of CaO concentration (mass%) and SiO 2 concentration (mass%) by performing fluorescent X-ray analysis on the analytical sample of slag 7.
- the water immersion expansion coefficient was measured according to Japanese Industrial Standard JISA5015 Annex B. As a result, it was confirmed that the basicity of the slag was 2.7 and the water immersion expansion coefficient was 0.5% or less.
- the slag treated by the same method as in the comparative example and having a calculated basicity of 4.0 or more was also analyzed for basicity and the water immersion expansion coefficient was measured after recovery.
- analysis and measurement were carried out in the same manner as in the above-mentioned examples. As a result, it was confirmed that the basicity of the slag was 3.5 and the water immersion expansion coefficient was 1.5% or more, and the target quality could not be satisfied.
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Abstract
Description
図1を参照して、本発明の一実施形態に係る鋼の製造方法について説明する。本実施形態では、上底吹き型の転炉1を用いて、溶鉄6を酸化精錬処理することで、溶銑から溶鋼を製造する。転炉1は、図1に示すように、炉体2と、複数の底吹き羽口3と、上吹きランス4と、シュート5とを備える。
炉体2は、内側に耐火物が施工された精錬容器である。炉体2は、図1に示す状態において上部に炉口21とよばれる開口部を有する。また、炉体2は、側面に設けられた一対のトラニオン軸22を中心として傾動可能に構成される。
上吹きランス4は、炉体2の上方から炉口21を通じて炉体2の内部に挿入可能に構成されるランスである。上吹きランス4は、下側の先端に形成されたランス孔から少なくとも酸素ガスを噴射可能に構成される。
シュート5は、炉体2の上方に設けられる装置である。シュート5は、先端が炉口21に向けて配される。シュート5は、不図示のホッパーから切り出された精錬剤や造滓剤等の副原料を搬送して、炉体2の内部に投入する。
添加工程の操業手順は特に規定しないが、以下の操業手順をとるとシリカ含有物質の融解が促進されるので望ましい。
添加工程にて添加されたシリカ含有物質は、シュート5から高温の炉体2の内部に投入されことで、溶鉄6の上方に浮上しているスラグ7へと添加される。そして、投入されたシリカ含有物質は、高温の溶鉄6やスラグ7によって融解し、溶融したスラグ7の一部となる。
出鋼工程を経て、取鍋(不図示)へ収容された溶鉄6は、製造すべき鋼種の目標成分組成に応じて適宜2次精錬を施された後、連続鋳造機などの鋳造設備で鋳造され、鋳片となる。得られた鋳片は、寸法形状や特性などが出荷製品の規格を満足するよう圧延や熱処理を施されて製品の鋼となる。
以上で、特定の実施形態を参照して本発明を説明したが、これら説明によって発明を限定することを意図するものではない。本発明の説明を参照することにより、当業者には、開示された実施形態とともに種々の変形例を含む本発明の別の実施形態も明らかである。従って、特許請求の範囲に記載された発明の実施形態には、本明細書に記載したこれらの変形例を単独または組み合わせて含む実施形態も網羅すると解すべきである。
さらに、上記実施形態では、酸素源として酸素ガスを添加することで酸化精錬処理を行うとしたが、本発明はかかる例に限定されない。例えば、酸素源として、酸素ガスの他に酸化鉄等の固体酸素源がさらに用いられてもよい。
(1)本発明の一態様に係る鋼の製造方法は、転炉1にて、溶銑に酸化精錬処理を施すことで溶鋼を製造する鋼の製造方法であって、転炉1にて、溶銑に少なくとも酸素ガスを含む酸素源を加え、酸化精錬処理を施すことで、溶銑を溶鋼とする精錬処理工程と、精錬処理工程の後、溶鋼が収容された転炉1の炉体2に、少なくともSiO2を含むシリカ含有物質を上方から添加する添加工程と、添加工程の後、炉体2を傾動させて炉体2から溶鋼を排出する出鋼工程と、を備える。
上記(2)の構成によれば、吹錬形態の違いから上吹き型の転炉に比べて、スラグの塩基度を低くすることが難しい底吹き型や上底吹き型の転炉においても、スラグの塩基度を低減することができることから、スラグの再利用を促進することができる。
上記(3)の構成によれば、吹き付けられる酸素ガスによる撹拌効果と滓化効果によって、シリカ含有物質の融解が促進される。
上記(4)の構成によれば、添加工程においても底吹きガスから吹き込まれる底吹きガスによって、溶鋼が攪拌され、シリカ含有物質の融解が促進される。
上記(5)の構成によれば、上記(2)の構成の転炉1において、スラグ7の水浸膨張率を0.5%以下にすることができる。
上記(6)の構成によれば、復燐の量を十分に抑えることができ、製造コストをより低減することができる。
上記(7)の構成によれば、上記(1)と同様な効果を得ることができる。
上記(8)の構成によれば、上記(3)の構成と同様な効果が得られる。
上記(9)の構成によれば、上記(4)の構成と同様な効果が得られる。
2 炉体
21 炉口
22 トラニオン軸
3 底吹き羽口
4 上吹きランス
5 シュート
6 溶鉄
7 スラグ
Claims (9)
- 転炉にて、溶銑に酸化精錬処理を施すことで溶鋼を製造する鋼の製造方法であって、
前記転炉にて、前記溶銑に少なくとも酸素ガスを含む酸素源を加え、酸化精錬処理を施すことで、前記溶銑を前記溶鋼とする精錬処理工程と、
前記精錬処理工程の後、前記転炉の炉体に収容された前記溶鋼に、少なくともSiO2を含むシリカ含有物質を添加する添加工程と、
前記添加工程の後、前記炉体を傾動させて前記炉体から前記溶鋼を排出する出鋼工程と、
を備える、鋼の製造方法。 - 前記転炉は、前記炉体の底部に設けられた底吹き羽口を有し、
前記精錬処理工程では、前記酸素源に含まれる前記酸素ガスとして、少なくとも前記底吹き羽口から酸素ガスを前記溶銑に吹き込むことで、前記酸化精錬処理を施す、請求項1に記載の鋼の製造方法。 - 前記転炉は、上吹きランスを有し、
前記添加工程では、前記精錬処理工程の後、ノズル詰まり防止のために前記酸素ガスを噴射させながら前記上吹きランスを待機位置まで上昇させる期間中に、前記溶鋼への前記シリカ含有物質の添加を開始する、請求項1または2に記載の鋼の製造方法。 - 前記転炉は、前記炉体の底部に設けられた底吹き羽口を有し、
前記添加工程では、前記精錬処理工程の後、前記底吹き羽口から吹き込まれる底吹きガスの吹き込み条件を、前記炉体を傾動させるときの条件に切り替えてから、前記炉体の傾動を開始するまでの期間中に、前記溶鋼に前記前記シリカ含有物質を添加する、請求項1~3のいずれか1項に記載の鋼の製造方法。 - 前記添加工程では、前記精錬処理工程後の前記炉体内のスラグの計算塩基度が3.8以上となる場合に、前記スラグの計算塩基度が3.6以下となるように、前記シリカ含有物質の投入量を決定する、請求項1~4のいずれか1項に記載の鋼の製造方法。
- 前記添加工程では、前記炉体内のスラグの計算塩基度が3.0以上となるように、前記シリカ含有物質の投入量を決定する、請求項1~5のいずれか1項に記載の鋼の製造方法。
- 転炉にて、溶銑に酸化精錬処理を施すことで溶鋼を製造する際に生じるスラグの塩基度を低減される、スラグの塩基度低減方法であって、
前記転炉にて、前記溶銑に少なくとも酸素ガスを含む酸素源を加え、酸化精錬処理を施すことで、前記溶銑を前記溶鋼とする精錬処理工程と、
前記精錬処理工程の後、前記転炉の炉体に収容された前記溶鋼に、少なくともSiO2を含むシリカ含有物質を添加する添加工程と、
前記添加工程の後、前記炉体を傾動させて前記炉体から前記溶鋼を排出する出鋼工程と、
を備える、スラグの塩基度低減方法。 - 前記転炉は、上吹きランスを有し、
前記添加工程では、前記精錬処理工程の後、ノズル詰まり防止のために前記酸素ガスを噴射させながら前記上吹きランスを待機位置まで上昇させる期間中に、前記溶鋼への前記シリカ含有物質の添加を開始する、請求項7に記載のスラグの塩基度低減方法。 - 前記転炉は、前記炉体の底部に設けられた底吹き羽口を有し、
前記添加工程では、前記精錬処理工程の後、前記底吹き羽口から吹き込まれる底吹きガスの吹き込み条件を、前記炉体を傾動させるときの条件に切り替えてから、前記炉体の傾動を開始するまでの期間中に、前記溶鋼に前記シリカ含有物質を添加する、請求項7または8に記載のスラグの塩基度低減方法。
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JPH0711322A (ja) * | 1993-06-28 | 1995-01-13 | Kawasaki Steel Corp | 有効利用が可能な転炉スラグの製造方法 |
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JPH0711322A (ja) * | 1993-06-28 | 1995-01-13 | Kawasaki Steel Corp | 有効利用が可能な転炉スラグの製造方法 |
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