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
  • C21C5/28—Manufacture of steel in the converter
  • C21C5/30—Regulating or controlling the blowing
  • C21C5/35—Blowing from above and through the bath
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
  • C21C7/04—Removing impurities by adding a treating agent
  • C21C7/064—Dephosphorising; Desulfurising
  • C21C7/0645—Agents used for dephosphorising or desulfurising
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • 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
  • C21C1/00—Refining of pig-iron; Cast iron
  • C21C1/02—Dephosphorising or desulfurising
  • C21C1/025—Agents used for dephosphorising or desulfurising
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • 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
  • C21C5/32—Blowing from above
• • 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
  • C21C7/064—Dephosphorising; Desulfurising
• • C—CHEMISTRY; METALLURGY
  • C21—METALLURGY OF IRON
  • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
  • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
  • C21C7/04—Removing impurities by adding a treating agent
  • C21C7/072—Treatment with gases

Definitions

• the present invention relates to a method for efficiently producing low-phosphorus hot metal by a dephosphorization treatment performed as a hot metal pretreatment.
• Hot metal pretreatment methods that perform dephosphorization at the hot metal stage instead of the conventional converter method have become widely used. This is because the lower the refining temperature, the more the dephosphorization reaction proceeds thermodynamically, so that the dephosphorization treatment can be performed with a smaller amount of the refining agent.
• a solid oxygen source such as iron oxide is added to the hot metal to perform a desiliconization treatment.
• a refining agent is added to perform a dephosphorization treatment. Do.
• a Ca-based refining agent such as lime is used as a purifying agent for the dephosphorization treatment, and a solid oxygen source (eg, iron oxide) or gaseous oxygen is used as an oxygen source.
• a processing container a torpedo car, a ladle (a charging pan), a converter type container, and the like are used. Also, it is widely used to add CaF 2 (fluorite) to promote slagging of CaO-based refining agents.
• the dephosphorization treatment conditions of the prior art include, for example, JP-A-7-70626, slag basicity of 0.6 to 2.5, treatment end temperature of 1250 ° C to 1400 ° C, bottom blow stirring power 1.
• the conditions indicate 0 kg / hot metal ton or more and an acid supply rate of 2.5 Nm 3 / hot metal ton or more.
• the reason for setting the slag basicity to 2.5 or less is that if the basicity is higher, the slag fluidity is deteriorated, so that high-temperature treatment that is disadvantageous for dephosphorization is required. And Also, 2.5 or less If so, the higher the slag basicity, the more dephosphorization proceeds.
• Japanese Patent Application Laid-Open No. H08-311153 discloses that hot metal in a converter type vessel is supplied with 0.7 to 2.0 Nm 3 / min / hot iron through a top blow lance. A method is shown in which oxygen is blown and a stirring gas of 0.05 to 0.30 Nm 3 / min / hot metal ton is blown from the bottom or side wall of the converter vessel, and this method is used. For example, by optimizing the amount of oxygen supplied in the top and bottom blowers, the slag can be quickly formed (CaO slag) and the FeO concentration in the slag can be optimized, resulting in efficient It is said that dephosphorization can be performed.
• the phosphorus distribution L p of slag depends on the slag basicity, and the higher the slag basicity, the higher the phosphorus distribution L p.
• the phosphorus distribution Lp is low. Therefore, it is necessary to increase the amount of slag by adding a large amount of lime (and adding a Sio 2 source as necessary).
• the slag basicity required to secure a predetermined phosphorus distribution L p is set, and the slag amount required to reach the target P under the slag basicity is determined,
• a refining agent is added, the slag basicity cannot be increased so much due to the slag fluidity, so the normal degassing performed on hot metal with an Si content of about 0.2
• the operation is performed with a slag amount (slag amount after treatment) of about 40 to 50 kg / hot metal ton.
• the amount of CaO (refining agent) charged is determined according to the P content in the hot metal to be dephosphorized, and the P content before treatment is 0.1 O mass, which is the normal level. %, About 20 kg / Ca ton of hot metal ton is charged, but the slag present in the refining vessel during the dephosphorization refining is S i 0 2 minutes generated by the de-siliconization reaction of hot metal, P 2 0 5 minutes generated by the de-siliconization reaction, and slag content (F e 0, M n °, etc.) generated from the hot metal component slag component Re that, caused by melting of the furnace body 'slag fraction (a 1 2 0 3, M g O , etc.), slag fraction adhering to the original furnace, slag fraction being brought to adhere to the charged scrap, The amount of slag generated from the added ore, etc. is added, and the amount (slag after treatment) is generally twice as large as the input CaO amount. Because it is
• An object of the present invention a low phosphorus capable and less seminal ⁇ amount effective dephosphorization can be performed by, thereby also minimized slag generation rate without adding a large amount of C a F 2
• An object of the present invention is to provide a method for producing hot metal.
• a refining agent that is an oxygen source and a CaO source is added to the hot metal.
• the method of supplying the oxygen source is to effectively reduce the temperature drop and effectively generate FeO.
• the method of blowing gaseous oxygen from the top blowing lance to the hot metal bath surface is preferable in that it can be accelerated.
• the slag is pushed by the energy of gaseous oxygen in the refining vessel to expose the molten metal surface (hot metal bath surface), and the rest of the molten metal surface to the slag.
• the slag in the refining vessel is not uniform. Therefore, the present inventors have been able to stabilize the dephosphorization efficiency at a high level with a small amount of scouring agent without being overwhelmed by the conventional concept of keeping the slag in a uniform molten state in the refining vessel.
• the method for producing a low-phosphorus hot metal of the present invention is based on such knowledge, and is characterized by adding a refining agent that is an oxygen source and a CaO source into a container holding hot metal,
• a dephosphorization treatment is performed by blowing gaseous oxygen and at least a part of a refining agent onto a hot metal bath surface through an upper blowing lance,
• the purpose is to reduce the amount of slag after treatment to 30 kg / hot metal ton or less.
• the more preferable slag amount after the treatment is not more than 20 kg Z hot metal ton, particularly not more than 10 kg / hot metal ton.
• a large amount of phosphorus can be obtained by utilizing the mechanism of direct dephosphorization reaction in the hot metal bath surface area to which gaseous oxygen is blown and fixation of P by the solid phase-based slag in the outer area.
• efficient dephosphorization can line Ukoto in and less seminal ⁇ amount without addition of C a F 2 of.
• it is desirable to perform a dephosphorization treatment on the low Si hot metal That is, it is desirable to perform a dephosphorization treatment on hot metal having a Si content of 0.15 mass% or less, preferably 0.07 mass% or less, and particularly preferably 0.03 raass ° / o or less. This provides optimum conditions for stably causing the dephosphorization reaction by the above mechanism.
• At least a part of the refining agent supplied from the top blowing lance is supplied to the hot metal bath surface region to which gaseous oxygen is blown. More preferably, at least a part of the refining agent supplied from the top blowing lance is preferably blown to a hot spot generated on the hot metal bath surface by blowing gaseous oxygen.
• the hot metal having a P content of 0.10 mass% or more be dephosphorized and refined to the P content (specified component value of steel) required for the crude steel. It is desirable that the P content in the hot metal is 0.010 mass% or less.
• the supply rate B (kg / mi of hot metal ton) of the refining agent sprayed onto the hot metal bath surface and the supply of gaseous oxygen blown onto the hot metal bath surface are measured.
• the dephosphorization treatment is performed so that the feed rate A (Nm 3 / min / hot metal ton) satisfies the following expression (1), preferably the following expression (2).
• the balance between the amount of FeO generated by the supply of gaseous oxygen and the amount of CaO supplied is optimized, and higher dephosphorization efficiency can be obtained.
• a pot-shaped or torpedo-car-shaped container is used as a container for holding hot metal, and gas oxygen and at least a part of the refining agent are sprayed onto the surface of the hot metal bath through an upper blowing lance.
• Dephosphorization is performed by blowing gas containing powder into the hot metal through a nozzle.
• the powder blown into the hot metal through the immersion lance or Z and the blowing nozzle is preferably a part of the refining agent, and the gas oxygen blown onto the hot metal bath surface through the top blowing lance is preferable.
• the amount is preferably 0.7 NmVmin / hot metal ton or less.
• the topping lance is used when the substantially entire amount of the refining agent is added by spraying onto the hot metal bath surface through the top blowing lance and blowing into the hot metal through the immersion lance or Z and the blowing nozzle.
• the amount of the refining agent be 20 to 80 mass% of the total amount of the refining agent, whereby the effect of spraying the refining agent onto the hot metal bath surface and the effect of hot metal by blowing into the hot metal A good stirring effect can be obtained.
• the dephosphorization treatment is performed so that the supply rate of the refining agent and the supply rate of gaseous oxygen sprayed onto the surface of the hot metal bath satisfy the following equations (3) and (4). This Therefore, an unnecessary amount of the refining agent is not added in the latter stage of the dephosphorization treatment, and the treatment is performed with the minimum necessary amount of the refining agent. Therefore, a more efficient dephosphorization treatment can be performed with a small amount of the refining agent. Can be.
• the purifying agent supply rate and the gas oxygen supply rate in terms of CaO can be changed continuously or / and stepwise during the dephosphorization period.
• dephosphorization is performed on hot metal having a Si content of 0.15 mass% or less by blowing gaseous oxygen and at least a part of the refining agent onto the hot metal bath surface through an upper blowing lance.
• the amount of lime Wcao_P (kg Z hot metal ton) obtained by the following equation (5) and the amount of lime Wcao_Si (3 ⁇ 4: ⁇ / on) and add the amount of lime. This makes it possible to carry out an efficient dephosphorization treatment with a minimum necessary amount of a refining agent.
• Wcao_P (hot metal [P] —target [P]) X (10/62) ⁇ 56 ⁇ 3 / ⁇ cao... (5)
• hot metal [P] P concentration in hot metal before dephosphorization (mass%)
• a refining agent corresponding to the amount of lime Wcao-Si one or more kinds selected from lime powder, lump lime, lump limestone, and iron slag containing unreacted CaO can be used.
• the depth L of the recess formed on the hot metal bath surface by spraying gas oxygen or spraying a purifying agent using gaseous oxygen as a carrier gas is set to 200 to 5 Control to 0 mm. This optimizes the form of supply of gaseous oxygen to the reaction site, the fire point, and enables more efficient dephosphorization with a small amount of scouring agent added.
• F 02 Rate of supply of gaseous oxygen from top blowing lance (Nm 3 / hr) n: Number of nozzle holes in top blowing lance
• the Si content is 0.1. against 5Raass% or less of molten iron, C a amount of F 2 to the 1 k gZ molten iron ton or less, or C a F 2 in conditions that do not substantially added, through the top lance and gaseous oxygen at least a portion of the fine ⁇ Is sprayed onto the hot metal bath surface to perform the dephosphorization treatment, and the hot metal temperature at the end of the dephosphorization treatment is set to 1360 ° C to 1450 ° C.
• a substance that absorbs heat of hot metal by a chemical reaction and / or a thermal decomposition reaction is supplied to a hot metal bath surface area to which gaseous oxygen is supplied.
• a rise in the temperature of the hot metal bath surface area to which gaseous oxygen is supplied is suppressed without hindering the slagging of the refining agent, so that higher dephosphorization efficiency can be obtained.
• the substance that absorbs the heat of the hot metal by a chemical reaction and / or a thermal decomposition reaction is supplied to a hot spot generated on the hot metal bath surface by blowing gaseous oxygen.
• the substance that absorbs the heat of the hot metal by a chemical reaction and / or a thermal decomposition reaction is at least one selected from carbon dioxide, steam, nitrogen oxides, metal carbonates, and metal hydroxides.
• metal carbonate to generate C0 2 or H 2 0 by thermal decomposition, by thermal decomposition Rei_0 2 or 11 2 0 at least one member selected from among hydroxides of metals originating ⁇ It is preferable that In particular Among them, C a C0 3, C a (OH) 2, C aMg (C0 3) is preferably at least one Bareru selected from among 2.
• C a C0 3, C a (OH) 2, C aMg (C0 3) may be supplied to one or more selected from among 2.
• the C a C_ ⁇ 3, C a (OH) 2 , C a Mg (C0 3) at least a portion selected one or more Ru among 2, the molten iron bath surface by blowing of gaseous oxygen It is preferred to supply to the resulting flash point.
• FIGURES Figure 1 is a graph showing the relationship between the amount of slag after the dephosphorization treatment and the P content in the hot metal.
• Figure 2 is a graph showing the relationship between the Si content in the hot metal before the dephosphorization treatment and the slag amount after the dephosphorization treatment.
• FIG. 3 is an explanatory diagram showing one embodiment of the method of the present invention using a converter type vessel.
• FIG. 4 is a graph showing the relationship between the ratio of the added amount of the refining agent through the top blowing lance to the total amount of the refining agent and the required amount of lime in the second embodiment of the present invention.
• FIG. 5 shows that in the second embodiment of the method of the present invention, the entire amount of the refining agent is added by spraying the hot metal bath surface through the top blowing lance and blowing into the hot metal through the immersion lance or / and the blowing nozzle.
• 4 is a graph showing the relationship between the ratio of the amount of refining agent added through the top blowing lance to the total amount of refining agent added and the dephosphorization rate.
• FIG. 6 is an explanatory diagram showing an example of an implementation state of the second embodiment of the present invention method.
• Fig. 7 shows the Ca unit consumption and dephosphorization required for the P content in hot metal after dephosphorization to become 0.012 mass% in the third embodiment of the present invention method and the conventional method. 6 is a graph showing a relationship with efficiency.
• FIG. 8 is a graph showing the relationship between the Si content in the hot metal and the required lime amount for the fourth embodiment of the present invention method and the conventional method.
• FIG. 9 is a graph showing the relationship between the amount of lime required for dephosphorization and the lime efficiency ⁇ cao and the P content in the hot metal after the dephosphorization treatment in the fourth embodiment of the present invention and the conventional method.
• FIG. 10 shows the ratio X / Wcao-P between the amount of lime X sprayed from the top blowing lance to the hot metal bath surface and the amount of lime for de-P in the fourth embodiment of the present invention, X / Wcao-P, and after dephosphorization.
• 4 is a graph showing the relationship between P and the P content in the hot metal.
• FIG. 11 shows the depth L of the dent formed on the hot metal bath surface by spraying gaseous oxygen or a refining agent using gaseous oxygen as a carrier gas, the rate of defamation, and defamation in the fifth embodiment of the method of the present invention. It is a graph which shows the relationship with the P content in the hot metal after a process. 1 2, in the sixth embodiment of the present invention method, C a F 2 definitive in dephosphorization of additive-free, after S i content and dephosphorization processes during hot metal hot metal temperature and the dephosphorization lime efficiency 6 is a graph showing the relationship of.
• FIG. 13 shows the amount of added Ca F 2 and dephosphorized lime in the dephosphorization treatment at a hot metal temperature of 130 to 150 ° C. after the dephosphorization treatment in the sixth embodiment of the present invention. It is a graph which shows the relationship with efficiency.
• FIG. 14 is an explanatory diagram showing an example of a supply form of a gaseous oxygen, a purifying agent, and an endothermic substance to a hot metal bath surface using an upper blowing lance in the seventh embodiment of the present invention.
• FIG. 15 is an explanatory diagram schematically showing the state of slug Z-metal at the start of tapping in the conventional method using a converter type container and the method of the present invention.
• FIG. 16 is an explanatory diagram schematically showing the state of slag / metal near the tap at the end of tapping in the conventional method using a converter type container and the method of the present invention.
• FIG. 17 shows the ratio A / B between the supply rate A of gaseous oxygen and the supply rate B of the CaO-based refining agent in the example of the first embodiment of the present invention, and the ratio of hot metal after dephosphorization treatment.
• 4 is a graph showing the relationship between the P content and. DETAILED DESCRIPTION OF THE INVENTION
• Dephosphorization mechanism of hot metal has been considered conventionally, by C a O added to the fine ⁇ unit is to melt by being reacted with S i 0 2, F e O produced by the supply of oxygen, C a O- S i O z - F e O slag of homogeneous and high dephosphorization capacity of generating, dephosphorization of the hot metal by reaction with the slag and molten iron in P are those that proceed.
• the slag basicity is determined in consideration of the slag fluidity and dephosphorization ability as described above, and the target P is reached under this slag basicity. The amount of slag required for this has been determined.
• the present inventors under the condition that the amount of slag after treatment is considerably reduced compared to the prior art, more preferably By adopting a treatment method in which gaseous oxygen and a purifying agent are blown onto the surface of the hot metal bath through an upper blowing lance under a condition in which the Si content in the hot metal before treatment is set to a predetermined level or less, a mechanism completely different from the conventional technology is adopted. It has been found that it is possible to perform a very efficient defamation by using this method.
• a low-phosphorus hot metal is manufactured by adding a refining agent that is an oxygen source and a CaO source to a vessel (a refining vessel) holding hot metal, and performing a dephosphorization process as a hot metal pretreatment.
• dephosphorization treatment is performed by blowing gaseous oxygen and at least a part of the refining agent through the top blowing lance onto the hot metal bath surface.
• gaseous oxygen is blown onto the hot metal bath surface through the top blowing lance, a large amount of FeO is generated by the gaseous oxygen that collides with the bath surface, which is a very advantageous condition for promoting slagging of the refining agent.
• the refining agent is applied using a carrier gas other than gaseous oxygen (eg, an inert gas such as N 2 or Ar).
• a carrier gas other than gaseous oxygen eg, an inert gas such as N 2 or Ar.
• the surface may be sprayed, but even in this case, it is preferable to spray some or all of the refining agent onto the hot metal bath surface area to which gaseous oxygen is supplied (sprayed). This is because the hot metal bath area to which gaseous oxygen is supplied is a place where FeO is generated by oxygen supply, and by adding CaO directly to such a bath area, CaO slag is generated. Is promoted effectively, and the contact efficiency between CaO and Fe ⁇ increases.
• the refining agent it is most preferable to supply the refining agent to the so-called "fire point" of the hot metal bath surface area to which gaseous oxygen has been supplied, in particular, caused by the upward blowing of gaseous oxygen.
• This hot spot is the hot metal bath surface area where the temperature becomes the highest due to the collision of the gaseous oxygen gas jet, but the oxidation reaction due to gaseous oxygen is concentrated and the gaseous oxygen gas jet is concentrated. Therefore, it can be said that this is the region where the effect of the supply of CaO is most remarkably obtained.
• gaseous oxygen as the carrier gas for spraying the refining agent onto the hot metal bath surface.
• the gaseous oxygen is sprayed onto the hot metal bath surface together with the refining agent, thereby providing the refining agent. Is supplied directly to the hot spot, which results in the highest contact efficiency between aO and FeO on the hot metal bath surface.
• the aim is to cause an efficient dephosphorization reaction by the following basic mechanism.
• the refining agent (C a O) is blown through the top blowing lance to the hot metal bath surface area (preferably the hot spot) where gaseous oxygen is supplied in an optimal state
• this Ca O is generated at the hot spot Reacts rapidly with F e O to form a slag.
• the generated CaO-FeO-based melt is heated by the kinetic energy of the gaseous oxygen from the hot metal bath surface area where the gaseous oxygen is supplied, centering on the flash point, to reduce the oxygen potential around it.
• the method of the present invention is more efficient by utilizing the mechanism of direct dephosphorization reaction in the hot metal bath area around the fire point and fixation of P by slag mainly composed of solid phase in the outer area.
• the aim is to perform a simple dephosphorization treatment, simply spraying gaseous oxygen and a refining agent onto the surface of the hot metal bath cannot stably realize the defatting reaction by the above mechanism. That is, in order to stably realize the dephosphorization reaction by the above mechanism, in addition to adopting the above-mentioned specific supply form of gaseous oxygen and the purifying agent, the treatment is performed with a sufficiently small amount of slag.
• the slag amount after treatment must be 30 kg / hot metal ton or less, preferably 20 kg / hot metal ton or less, more preferably 10 kg / Z hot metal ton or less.
• the hot metal to be subjected to the dephosphorization treatment is low Si hot metal, specifically, the Si content is 0.15 mass% or less, more preferably 0.7 mass%.
• the hot metal is not more than 0.03 mass%.
• the reason why the treatment is performed under a small amount of slag in the present invention is as follows.
• gaseous oxygen through the upper blowing lance needs to be supplied to the hot metal bath surface by so-called soft blowing (low dynamic pressure).
• the gas oxygen jet cannot penetrate the slag layer, Is not supplied properly, and the production of FeO on the hot metal bath surface becomes insufficient, and the amount of the CaO-FeO-based melt produced is also reduced.
• the thick slag layer If gaseous oxygen is supplied by a hard pro (high dynamic pressure) so that the jet can penetrate, the supply area will be in a strong stirring state, so even if FeO is generated, it will be reduced by C in the hot metal. However, also in this case, the required amount of FeO cannot be secured, so that the generation of the CaO-FeO-based melt is reduced.
• the amount of slag is large, it is not possible to stably secure the amount of FeO or CaO-FeO-based melt produced, regardless of whether gaseous oxygen is supplied by soft blow or hard blow. It is difficult to stably generate a dephosphorization reaction by the above mechanism. Therefore, in order to appropriately supply gaseous oxygen to the hot metal bath surface by soft blow and effectively cause the defamation reaction by the mechanism described above, the amount of slag must be regulated and the thickness of the slag layer must be sufficiently small. Is an essential condition. Therefore, in the present invention, the slag amount after the treatment is 30 kg Z hot metal ton or less. For the reasons described above, it is desirable that the amount of slag after the treatment is as small as possible, especially 20 kg / hot metal ton or less, more preferably 10 kg / hot metal ton or less.
• the reason why it is preferable to perform the dephosphorization treatment on the low Si hot metal in the present invention is as follows.
• aO reacts with FeO to form a CaO—FeFe-based melt
• the CaO—FeO-based melt reacts directly with P in the hot metal to remove phosphorus.
• Si content in the hot metal is high, the generated CaO-FeE system-based melt is consumed in the reaction with Si and sufficient for the direct dephosphorization reaction described above.
• the optimal conditions for stably causing the dephosphorization reaction by the above mechanism satisfy the above-mentioned conditions for the amount of slag after treatment, and the S i content in the hot metal to be dephosphorized is sufficiently low. That is. Also, since less the amount of S i O 2 The less S i content in molten iron, which is advantageous in reduction of the processed slag amount. Therefore, in the present invention, the Si content is 0.15 mass% or less, more preferably 0.07 mass%. Hereinafter, it is more preferable to perform the dephosphorization treatment on the hot metal of not more than 0.03 mass%.
• the post-treatment slag amount is the slag amount present in the refining vessel (hot metal holding vessel) at the end of the dephosphorization treatment.
• the amount of slag after this treatment is the amount of lime added and the Ca in the slag.
• a method of calculating from the mass balance with the concentration (slag analysis value), a method of adding tracer such as yttrium oxide and strontium oxide to slag, and a method of analyzing the tracer concentration in the treated slag, and directly measuring the slag thickness It can be obtained by a method.
• Figure 1 shows the relationship between the amount of slag after dephosphorization and the P content in hot metal based on the results of tests conducted by the present inventors.
• the P content in hot metal after treatment is the average value. Indicates the width of the patch.
• Figure 1 shows 5 kg_ / hot metal t or! ⁇ 10 kg hot metal ton, 10 kg / hot metal ton over ⁇ 20 kg / hot metal ton, 20 kg / hot metal ton over 30 kg / hot metal ton, 30 kg / hot metal ton over 40 kg / hot metal Ton, 40 kg / hot metal more than ton ⁇ 50 kg / hot metal ton
• the P content in the hot metal after dephosphorization of 6 to 72 ch is tabulated.
• hot metal produced in a blast furnace was desiliconized in a hot bed and, if necessary, in a hot metal pot, and then desulfurized in a hot metal pot using mechanical stirring.
• the dephosphorization treatment was performed within ton).
• the hot metal components before defamation are: C: 4.5 to 4.7 mass%, Si: 0.1 to 0.28 mass%, Mn: 0.15 to 0.25 mass%, P: 0.10 to 0.1 lnmss%, S: 0.001 to 0.003 mass%.
• Lime powder having a particle size of 1 mm or less was used as a dephosphorizing refining agent, and this was sprayed through a lance onto the hot metal bath surface using gaseous oxygen as a carrier gas.
• the amount of slag after the treatment increases, the P content after the dephosphorization treatment also increases, and the variation on the upper limit side increases.
• the amount of slag after treatment is less than 30 kg / hot metal ton, the variation in the upper limit of the P content is greatly reduced, and the P content is 0.020 mass% at the maximum.
• the P content in the hot metal after de-treatment is 0.015 mass% at maximum when the slag content is 20 kgZ hot metal ton or less, and when the slag content is 10 kg / hot metal ton or less.
• the maximum is 0.010 mass%.
• the amount of slag after treatment is 30 kg / hot metal ton or less, preferably 20 kg Z hot metal ton or less, particularly preferably 10 kg / hot metal ton or less.
• Fig. 2 shows the relationship between the Si content in the hot metal before the dephosphorization treatment and the slag amount after the treatment when the test of Fig. 1 was performed.
• the Si content in the hot metal before treatment is high, the amount of added lime increases and the slag amount increases, so the slag amount and the Si content in the hot metal before treatment are There is good correlation.
• the Si content in the hot metal before the defatting treatment needs to be 0.15 mass% or less.
• the Si content in the hot metal before dephosphorization must be 0.07 mass% or less. It can be seen that in order to reduce the amount to 10 k or less of hot metal ton, the Si content in the hot metal before dephosphorization must be set to 0.03 ma SS % or less. For the above reasons, in the present invention, the Si content is 0.15 mass% or less, preferably 0.07 nmss% or less, more preferably 0.03 mass%. It is desirable to perform a dephosphorization treatment on the following hot metal.
• the Si content in the hot metal before the dephosphorization treatment can be adjusted as follows.
• Hot metal is supplied from hot metal manufacturing facilities such as blast furnaces.However, methods to reduce the Si content of the hot metal to be manufactured include reducing the total amount of silicic acid charged through pretreatment of raw materials for hot metal production. In order to suppress the silicate reduction reaction in a furnace such as a blast furnace, it is effective to use a method such as low-temperature operation and uneven charging of the core. Therefore, when the Si content of hot metal produced in a blast furnace or the like is 0.15 raass% or less, the hot metal can be dephosphorized without performing the following desiliconization processing. Good. ,
• desiliconization is performed in a blast furnace, a slab, a hot metal pot, etc. prior to the dephosphorization treatment.
• the dephosphorization treatment is performed after reducing the Si content in the hot metal before the phosphorous treatment to 0.15 mass% or less.
• the hot metal is desiliconized by adding a solid oxygen source or gaseous oxygen to the hot metal.
• a solid oxygen source such as sintering powder or mill scale is placed on the hot metal bath surface or placed in the bath.
• gaseous oxygen is added to the hot metal bath surface or by blowing it into the bath.
• the desiliconization treatment of the hot metal can be performed by adding an oxygen source to the flow of the hot metal from the blast furnace floor to the transfer vessel such as the hot metal pot, in addition to the blast furnace floor and the hot metal pot.
• an oxygen source to the flow of the hot metal from the blast furnace floor to the transfer vessel such as the hot metal pot, in addition to the blast furnace floor and the hot metal pot.
• a stirring gas is blown into the hot metal in the vessel, or a Ca 0 source such as calcined lime is added to adjust the basicity of the slag to reduce the iron oxide in the desiliconized slag. Can be reduced as much as possible to increase the reduction efficiency.
• the method of the present invention there is no particular limitation on the method of spraying gaseous oxygen and the refining agent onto the surface of the hot metal bath using a top-blown lance. It is also possible to supply a refining agent to the hot metal bath surface using only gaseous oxygen, or a gaseous oxygen or a gas other than gaseous oxygen (for example, an inert gas such as nitrogen or Ar) as a carrier gas through another lance hole. it can. This makes it possible to add a refining agent to the hot metal bath surface area to which gaseous oxygen is being supplied.
• a gaseous oxygen or a gas other than gaseous oxygen for example, an inert gas such as nitrogen or Ar
• a main lance hole is provided at the center of the tip of the lance, and an upper blowing lance having a plurality of sub lance holes is used around the main lance hole.
• a refining agent to the hot metal bath surface using a gas other than the gaseous oxygen thus obtained as a carrier gas.
• the blowing of gaseous oxygen and the spraying of a purifying agent using gaseous oxygen or a gas other than the gaseous oxygen described above as a carrier gas may be performed using different upper blowing lances.
• the carrier gas of the purifying agent is gaseous oxygen in order to make the purifying agent most efficient.
• the gaseous oxygen used in the present invention may be either pure oxygen gas or oxygen-containing gas.
• a solid oxygen source such as iron oxide (for example, sintered powder or mill scale) can be used in addition to gaseous oxygen. It can be added by an arbitrary method such as induction.
• 50% or more of the oxygen source added to the refining vessel is preferable.
• 70% or more (gas oxygen equivalent amount) is gaseous oxygen supplied to the hot metal bath surface through the top blowing lance.
• gaseous oxygen is produced by methods other than spraying onto the hot metal bath surface, for example, by immersion lances or by injection into the hot metal bath through blowing nozzles provided on the side walls and bottom of the hot metal holding vessel. It may be supplied in the bath.
• a CaO-based purifying agent such as lime (a purifying agent mainly composed of CaO) is usually used. Powder is used as the refining agent sprayed onto the hot metal bath surface through the top blowing lance.
• a part of the refining agent may be added not only by spraying onto the hot metal bath surface by the top blowing lance but also by overhead charging or by injecting into the bath. It is advisable that the amount of the refining agent to be added be 2 Oraass% or less of the entire refining agent. If the ratio of the refining agent added by a method other than spraying onto the hot metal bath surface by the top blowing lance exceeds 2 O mass% of the whole, the dephosphorization reaction is promoted by blowing the refining agent together with gaseous oxygen onto the hot metal bath surface. The effect tends to decrease. Further, in order to improve the dephosphorization efficiency, it is preferable to agitate the hot metal with gas.
• This gas agitation is performed, for example, by blowing an inert gas such as nitrogen or Ar into the hot metal through a dipping lance, a blowing nozzle provided on a side wall or a bottom of the hot metal holding vessel, or the like.
• the supply amount of such a stirring gas 0 to order to achieve a sufficient bath agitation resistance. 0 2 N m 3 / min / and molten iron ton or more,, F e O produced with agitation of the bath is too strong Since the rate of reduction of C in the hot metal becomes too high, the hot metal is preferably set to 0.3 NmVm in or less.
• a converter type vessel is most preferable because a free board can be sufficiently secured, but, for example, any vessel such as a hot metal pot or a speed car is preferable. Can be used.
• FIG. 3 shows one embodiment of the method of the present invention using a converter type vessel
• 1 is a converter type vessel
• 2 is an upper blowing lance
• 3 is a bottom blowing nozzle provided at the bottom of the furnace
• the refining agent is applied to the metal bath surface using gaseous oxygen as the carrier gas from the top blowing lance 2. While being blown, the stirring gas is blown into the hot metal from the bottom blow nozzle 3.
• the method of the present invention does not substantially add C a F 2 (ie, does not add C a F 2 except as an unavoidable impurity in a refining agent) or adds a small amount of C a F 2 .
• a high dephosphorization efficiency can be obtained by just rinsing.
• the addition amount be 2 kg Z hot metal ton or less, preferably 1 kg / hot metal ton or less.
• the present invention has an effect that the amount of slag loss after treatment can be significantly reduced as compared with the conventional method, but no or little amount of C a F 2 is added. By suppressing the slag flow rate, the slag fluidity can be further reduced, so that the above effect can be further enhanced.
• the P content of the hot metal before the dephosphorization treatment is 0.10 mass% or more, but in the present invention, the P content is required to be lower than the P content required for the crude steel, that is, less than the steel component standard value (normally 0.02%). (0 mass% or less), preferably 0.010 raass% or less.
• the decarburization refining is performed substantially without charging the slag-making material.
• Decarburization refining is extremely simplified and the refining time is reduced.
• 3) Decarburization and refining use virtually no slag-making material, so manganese ore is added as a manganese source. In this case, a very high yield of M n can be obtained.
• the supply rate B (k / min of hot metal ton) of the refining agent sprayed on the hot metal bath surface and the gas oxygen blown on the hot metal bath surface It is preferable to perform the dephosphorization treatment so that the feed rate A (Nm 3 Zm in / hot metal ton) satisfies the following equation (2).
• the method of spraying gaseous oxygen and a refining agent onto the surface of a hot metal bath shows that the dephosphorization reaction changes depending on the supply rate of gaseous oxygen and the supply rate of CaO (refining agent). Specifically, it was confirmed that FeO was generated in the hot metal bath surface area to which gaseous oxygen was supplied, but that there was a favorable supply rate of CaO commensurate with the generated amount.
• the dephosphorization of the hot metal by the above-described dephosphorization reaction mechanism is disadvantageous, and a high dephosphorization rate tends to not be obtained. Also, if the supply rate of gaseous oxygen is too high, the amount of reactive oxygen other than the oxygen required for dephosphorization will increase, and this will be consumed for decarburization, etc. Leading to a significant increase in costs Become.
• the supply amount of CaO is excessive with respect to the supply amount of gaseous oxygen, so the amount corresponding to the supply amount of CaO in the hot metal bath surface area where gaseous oxygen is supplied F e O is not generated.
• the slagging of the supplied CaO does not proceed sufficiently, and the CaO remains unslagged and acts effectively for defamation. Therefore, the dephosphorization rate tends to decrease.
• the amount of CaO required for dephosphorization will be insufficient for the supply of gaseous oxygen, and in this case, too, the CaOFeO-based melt will not be sufficiently generated, and the dephosphorization rate will decrease. Tend to. Further, by setting the A / B in the range of 1.2 to 2.5, the balance between the amount of FeO generated by the supply of gaseous oxygen and the amount of supply of CaO is further optimized. High dephosphorization efficiency can be obtained.
• the second embodiment of the present invention is a defatting treatment method performed using a pot-type or torpedo-car-type container.
• gas oxygen and gas oxygen are passed through an upper blowing lance.
• At least a part of the refining agent is sprayed on the hot metal bath surface, and gas containing powder is blown into the hot metal through an immersion lance or / and a blowing nozzle.
• the present inventors have studied a method for more efficiently dephosphorizing hot metal using a pot-type or torpedo-car-type refining vessel, and as a result, while blowing gas oxygen and a refining agent onto the hot metal bath surface through an upper blowing lance, It has been confirmed that the method of blowing gas containing powder into the hot metal through a lance or the like is very effective '.
• the amount of gaseous oxygen (the amount of acid supply) blown from the top blowing lance to the hot metal bath surface be 0.7 Nm 3 minZ hot metal ton or less. If the amount of acid supplied from the upper blowing lance is excessive, slag forming may cause slag to be blown out of the refining container. Slag forming is suppressed by controlling the amount of acid sent from the upper blowing lance to 0.7 NmVm in / hot metal ton or less. As a result, stable operations are possible.
• the refining agent may be partially added to the molten iron bath surface by overhead charging or injecting into the bath in addition to spraying onto the hot metal bath surface by the upper blowing lance.
• the amount of the refining agent sprayed onto the hot metal bath surface by the top blowing lance should be 80 mass% or more of the entire refining agent.
• the ratio of the refining agent added by spraying onto the hot metal bath surface with the top blowing lance is less than 80 mass%, the effect of accelerating the dephosphorization reaction by spraying the refining agent together with gaseous oxygen on the hot metal bath surface decreases. Tend.
• FIG. 4 shows the relationship between the ratio of the amount of the refining agent added through the top blowing lance to the total amount of the refining agent and the required amount of lime based on the test results performed by the present inventors.
• the amount of powder blown through the immersion lance was kept constant at 90 kg / min.
• the remainder of the required lime was used for part or all of this powder, and dust (Fe content 40 mass%) or coke powder was used for the deficiency.
• the ratio A / B of the supply rate B (kg / min / hot metal ton) of the lime sprayed onto the hot metal bath surface and the supply rate A (NmVm in / hot metal ton) of the gas oxygen blown onto the hot metal bath surface is 2.0.
• the amount of lime added is within the range of the sum of the lime amount Wcao-P (k hot metal ton) and the lime amount Wcao-Si (kg g hot metal ton) specified in equations (5) and (6) described below. I did it.
• the depth L of the dent formed on the hot metal bath surface by spraying a purifying agent with gaseous oxygen as the carrier gas (described later) was controlled within the range of 200 to 500 mm.
• the hot metal temperature before and after the dephosphorization treatment was 1300 to 1320.
• the amount of slag after treatment was calculated from the mass balance between the amount of added lime and the CaO concentration in slag (analytical value of slag).
• Fig. 4 shows the amount of lime necessary for the P content in the hot metal after treatment to be 0.02 mass% or less.
• the amount of lime required decreases as the ratio of the purifier supplied through the top blowing lance to the total purifier decreases, and especially when the ratio is 80111333% or more, the required lime amount is reduced most. ing.
• powder blown into the hot metal there are no particular restrictions on the type of powder blown into the hot metal along with the gas.
• some refiners such as lime powder, dust generated in steelworks such as converter dust, and carbon such as coke powder.
• powder to the source mainly, iron oxide, such as sintered powder or mill scale, C & C_ ⁇ 3, C a (OH) 2 , C aMg (CO 3) 1 or more kinds of powder, such as 2 Can be used.
• the injected refining agent is heated while floating in the hot metal and melts into slag when it floats on the hot metal bath surface. Is promoted.
• Iron oxide powder also becomes part of the oxygen source in the bath.
• gaseous oxygen pure oxygen gas or oxygen-containing gas
• inert gas such as N 2 or Ar, etc.
• the type of gas to be used may be selected in consideration of the total cost including the life of the lance and the nozzle.
• an immersion lance As a means for blowing the scouring agent into the hot metal, an immersion lance, a blowing nozzle provided in a scouring vessel, or both of them can be used. Any type of blowing nozzle, such as a bottom blowing nozzle or a side blowing nozzle, can be used.
• substantially the entire amount of the refining agent was added by spraying the hot metal bath surface through the top blowing lance and blowing into the hot metal through the immersion lance or the blowing nozzle.
• the amount of the refining agent added through the top blowing lance is preferably 20 to 80 mass% of the total amount of the refining agent. If the ratio of the refining agent sprayed onto the hot metal bath surface through the top blowing lance exceeds 80 mass% of the total amount of the refining agent added, the effect of blowing the refining agent into the hot metal is small because the effect of the hot metal on stirring is small. It is difficult to obtain the stirring power required for the reaction.
• Fig. 5 shows the case where the entire amount of the refining agent is added by spraying onto the hot metal bath surface through the top blowing lance and by immersion lance or / and blowing into the hot metal through the blowing nozzle. Based on the results of the test performed, adding a purifying agent through the top blowing lance This shows the relationship between the ratio of the added amount to the total amount of the refining agent added and the dephosphorization efficiency.
• gaseous oxygen (. 4. 5 ⁇ 5 0Nm 3 / hot metal t 0 n) of the particle size 1 is a fine ⁇ as a carrier gas lime powder (0 to 6) ⁇ ⁇ mm or less is blown from the top blowing lance onto the hot metal bath surface, and the remaining lime (0 to 6 kg / hot metal ton) is blown through the immersion lance.
• Dephosphorization treatment treatment time: 15 minutes). The C a F 2 in fine ⁇ the dephosphorization is not added, processed slag weight 2 0 kg "hot metal ton or less and the.
• Feed rate of limestone to be blown into the molten iron bath surface B (kg / min / hot metal a ton), the ratio a / B is 2.0 and the. lime addition amount of the supply rate of gaseous oxygen blown into the molten iron bath surface a (NmVm in / / hot metal ton) will be described later (5) and ( The amount of lime Wcao-P (kg / hot metal ton) and the amount of lime Wcao-Si (kg / hot metal ton) defined by equation (6) are set to be within the total range, and gaseous oxygen is used as the carrier gas.
• the depth L (L value defined by Eq.
• the amount of slag after treatment was calculated from the mass balance between the amount of lime added and the Ca ⁇ concentration in the slag (analyzed slag). .
• FIG. 5 shows an example in which the present embodiment is applied when performing hot metal dephosphorization in a blast furnace pot type dephosphorization facility. Depending on the Si content in the hot metal spiked from the blast furnace, if necessary, desiliconization such as bed desiliconization is performed before dephosphorization.
• the dephosphorization treatment is performed so that the supply rate of the refining agent and the supply rate of gaseous oxygen sprayed onto the surface of the hot metal bath satisfy the following equations (3) and (4). Is Umono.
• C1 the average value of the purifying agent supply rate in terms of CaO in the first stage of the dephosphorization treatment
• the P content in the hot metal is high, so that the higher the supply rate of the refining agent, the higher the dephosphorization rate.
• the P content in the hot metal becomes lower, and the movement of [P] in the metal to the reaction site becomes rate-limiting, which contributes more effectively to the dephosphorization action compared to the first stage of the dephosphorization treatment.
• the proportion of refining agent decreases. Therefore, the supply rate ratio of the scouring agent and the gaseous oxygen supplied to the hot metal bath surface in the specific form as described above (purifying agent supply speed / gas oxygen supply speed) and the supply speed of the purifying agent are determined by the dephosphorization treatment period.
• an efficient dephosphorization treatment can be performed with a smaller amount of the refining agent.
• the feed rate C (kg / min hot metal ton) of the refining agent sprayed on the hot metal bath surface is kept constant throughout the treatment period, and the above-mentioned supply rate C of the refining agent and the supply rate of gaseous oxygen D ( Dephosphorization treatment was performed with the ratio C / D to Nra 3 / min / hot metal ton) kept constant throughout the treatment.
• W Ca0 C a O unit price ( kg / hot metal ton)
• Gaseous oxygen was mainly used as the oxygen source, and this was added by spraying it from the top blowing lance onto the hot metal bath surface, and for some, the addition of a solid acid source (iron ore) was also used.
• the refining agent supply rate was 4.6 to 9.0 kg / hot metal ton, and the gas oxygen supply rate was 8.6 to 13 ⁇ 6 Nm 3 Z hot metal ton.
• the dephosphorization of 1 was CZD and 0. 50 ⁇ 0. 6 9 k gZNm 3.
• C1 is 0.88 ⁇ ; 1.00 kg / in / hot metal 1; 011 and 02 is 0.30 ⁇ 0.39 kg / min / hot metal ton, Cl / Dl the 0.
• the amount of slag after treatment was set to 20 k or less of hot metal ton.
• the amount of lime added is the sum of the amount of lime Wcao—P (kg / hot metal ton) and the amount of lime Wcao—Si (1 ⁇ ⁇ / hot metal 1 on) specified in Equations (5) and (6) below. It was made to be within the range.
• the depth of the depression (L value defined by equation (7) described later) generated on the hot metal bath surface by spraying a purifying agent using gaseous oxygen as the carrier gas is controlled within the range of 200 to 500 mm. did.
• the hot metal temperature before and after the dephosphorization treatment was 1300 to 1320.
• the same The amount of slag after treatment was calculated from the mass balance between the amount of lime added and the Ca ⁇ concentration in the slag (analyzed slag).
• the dephosphorization treatment of (2) has a smaller unit of CaO than the case of (1) and the dephosphorization efficiency is higher. This is because, in the case of 2, sufficient dephosphorization was performed in the latter stage of refining without adding an extra scouring agent, and high dephosphorization efficiency was obtained.
• the scouring agent and the gaseous oxygen may be supplied in accordance with the above conditions during the dephosphorization treatment period (early and late stages of the dephosphorization treatment).
• the mode of changing the feed rate is arbitrary, and can be changed continuously, stepwise, or both.
• dephosphorization is performed by spraying gaseous oxygen and at least a part of the refining agent onto the hot metal bath surface through an upper blowing lance to the hot metal having a Si content of 0.15 mass% or less.
• the amount of lime Wcao_P (kg g hot metal ton) determined by the following equation (5) and the amount of lime Wcao—Si (k) determined by the following equation (6) are used as a refining agent.
• gZ hot metal ton is added to the lime.
• Hot metal [P] (hot metal [P] —target [P]) X (10/62) v cao... (5)
• the slag volume is determined according to the phosphorus distribution L p on the assumption that the slag is maintained in a uniform liquid phase state. Therefore, the amount of the refining agent required was higher than that required to actually fix P and Si.
• the present invention utilizes the mechanism of direct dephosphorization reaction in the hot metal bath area around the ignition point and fixation of P by slag mainly composed of solid phase in the outside area. For this reason, dephosphorization is performed using the minimum amount of purifying agent as described above. The reaction can occur efficiently.
• the amount of lime actually consumed to fix P and Si in the hot metal can be calculated by the following formula.
• Wcao—Po is the amount of lime consumed to fix P in the hot metal (kg / hot ton)
• Wcao—Sio is the lime consumed to fix Si in the hot metal. Volume (kgZ hot metal ton).
• Wcao_Po (hot metal [P] —target [P]) X (10/62) X56X3
• hot metal [P] P content in hot metal before dephosphorization treatment (ma SS %)
• Target [P] P content in hot metal after target phosphorus removal (mass%)
• ⁇ cao Wcao_Po / (Total CaO— Wcao-one Sio)
• the lime efficiency cao is specified to be 0.5 to 1.
• the lower limit of the Tj cao is defined from the viewpoint that unnecessary lime addition is not performed and the dephosphorization reaction aimed at by the present invention appropriately occurs.
• cao is less than 0.5, lime is added substantially uselessly, and not only the effect of the present invention of performing efficient dephosphorization treatment with a small amount of scouring agent is lost, but also Since the amount of lime added is excessive with respect to the amount of FeO generated under a predetermined oxygen source unit, a large amount of non-slagging C a ⁇ is present, and such non-slagging C a O However, this inhibits the progress of the above-mentioned dephosphorization reaction. '
• the amount of lime Wcao-P (kg g hot metal ton) obtained by the following equation (5) and the amount of lime Wcao-Si (kg / hot metal ton) obtained by the following equation (6) are calculated Of lime is added for dephosphorization.
• cao_P (hot metal [P] —target [P]) X (10/62) ⁇ 56 ⁇ 3 / ⁇ ] cao... (5)
• hot metal [P] P content in hot metal before dephosphorization treatment (ma SS %)
• FIG. 8 shows, as an example, the case where the hot metal having a P content of 0.1 lmass% is subjected to a dephosphorization treatment to a P content of 0.015 mass%.
• the amount of lime to be added is shown in comparison with the amount of lime added in the conventional dephosphorization treatment.
• Wcao_Si is the amount of lime required for fixing Si
• Wcao— and 7j cao 1
• W is the amount of lime added in the conventional method.
• the amount of lime required in the conventional method is determined by the distribution of Lp and the required amount of slag corresponding to this, so that the lime amount of W is independent of the Si concentration in the hot metal. while the amount is filed necessary, lime amount to be added in advance this embodiment will be suffice [Wcao-Si + Wcao-Pj ⁇ [Wcao- Si + Wcao- ⁇ 0. 5], the conventional method Compared with this, the amount of lime added can be significantly reduced.
• Fig. 9 shows the relationship between the amount of lime required for dehydration and the lime efficiency ⁇ cao in this embodiment and the conventional method in relation to the P content in the hot metal after the dephosphorization treatment.
• the required amount of lime for P refers to [W-Wcao-Si] in Fig. 8. According to FIG. 9, it can be seen that in the present embodiment, the phosphorus removal treatment is performed with high lime efficiency using very little lime for de-P in comparison with the conventional method.
• Figure 10 shows the ratio between the amount of lime X and the amount of lime Wcao-P sprayed from the top blowing lance onto the hot metal bath surface, based on the test results performed by the present inventors, XZWcao-P and the hot metal after dephosphorization. This test shows the relationship with the medium P content. In this test, the P content held in the converter type container (340 ton): 0.095-0.135 mass%, Si content amount:.
• gaseous oxygen (1 0 ⁇ : 1 5N m 3 / hot metal ton) particle size less than 1 mm of lime powder as Kiyariagasu (. 4 to 1 0 kg / Hot metal ton) is sprayed from the top blowing lance onto the hot metal bath surface to perform dephosphorization treatment (processing time: 10 to 14 minutes), and then the hot metal is charged into a decarburization converter and decarburized. ⁇ .
• C a F 2 amount was set to 1 kg / molten pig iron ton hereinafter, processed slag amount was less 3 0 k gZ hot metal ton.
• Ratio A between supply rate B (kg / min / hot metal ton) of lime sprayed on hot metal bath surface and supply rate A (Nm 3 / min / hot metal ton) of gaseous oxygen blown on hot metal bath surface / B was 1.7.
• the depth L (L value defined by equation (7) to be described later) of the pit formed on the hot metal bath surface by spraying the refining agent with gaseous oxygen as the carrier gas is within the range of 200 to 500 mm. Controlled.
• the hot metal temperature before and after the dephosphorization treatment was set to 1300 to 1320 ° C.
• the amount of slag after treatment was calculated from the masparance of the amount of added lime and the CaO concentration (slag analysis value) in the slag.
• the amount of lime fixing the generated S i 0 2 is calcined lime.
• the substance is not limited to this, and may be any substance containing unreacted lime (Free Lime). Therefore, as a refining agent corresponding to the amount of lime Wcao__Si, at least one selected from lime powder, lump lime, lump limestone, and iron slag containing unreacted Ca ⁇ can be used.
• converter slag basic of about 3 to 4
• ladle slag generated in the decarburization process can be used.
• the Si content of the hot metal to be dephosphorized is set to 0.0 for the above-mentioned reason, and in order to obtain high dephosphorization efficiency with a small amount of refining agent added. 15 mass% or less, preferably 0.07 mass% or less, more preferably 0.03 mass% or less. When the Si content of the hot metal exceeds 0.15 mass%, the effect of reducing the amount of the refining agent added by the present embodiment is diminished.
• the depth L of the pit formed on the hot metal bath surface by the blowing of gaseous oxygen or the purifying agent using gaseous oxygen as a carrier gas is set to 200. It is controlled to ⁇ 50 Omm.
• Nozzle hole diameter of the top blowing lance (mm) (However, if the nozzle diameter of a plurality of nozzle holes is different, the average hole diameter of all nozzle holes)
• mm Nozzle hole diameter of the top blowing lance
• spray gaseous oxygen or gaseous oxygen and a purifying agent it was found that it is preferable to control the depth of the pits formed on the hot metal bath surface (theoretical pit depth calculated from the gas oxygen supply rate, the composition of the top blowing lance, and the operating conditions) within the optimum range.
• the slag may be out of the ignition point. Forming occurs, and the formed slag impedes the flow of the gaseous oxygen jet, which reduces the supply of gaseous oxygen to the fire point, which is a disadvantageous condition for improving the efficiency of defamation. Further, because supply such instability of oxygen to the fire point, oxygen required for dephosphorization is not supplied stably, with variation in the dephosphorization efficiency is increased, 3 C a O ⁇ P 2 0 5 However, the phosphorescence occurs.
• the depth L of the pit formed on the hot metal bath surface by blowing gas oxygen or by blowing a refining agent using gas oxygen as a carrier gas can be defined by the following equation (7).
• L H Lance height of upper blowing lance (mm)
• d t Nozzle hole diameter of the upper blowing lance (mm) (However, when the nozzle diameters of a plurality of nozzle holes are different, the average hole diameter of all nozzle holes)
• the depth of the dent on the hot metal bath surface Dephosphorization is performed by controlling L to 200 to 50 Omm.
• Fig. 11 shows the relationship between the pit depth L of the hot metal bath surface, the dephosphorization efficiency, and the P content in the hot metal after the dephosphorization treatment, based on the test results performed by the present inventors. In this test, the P content held in the converter type vessel (340 ton) was 0. . 0 9 5 ⁇ 0 1 3 5mass% , S i content:.
• Kiyariagasu Dephosphorization treatment treatment time: 10 to 14 minutes
• lime powder 4 to 1 O kg Z hot metal ton
• the hot metal was charged into a decarburization converter and decarburized. This de ⁇ sense, C a F 2 amount is less than 1 kg Bruno molten pig iron ton, processed slag amount was less 3 0 k gZ hot metal ton.
• the hot metal feed rate of limestone to be blown to the bath surface B (kg / mi nZ hot metal ton), the ratio A / B between the feed rate A of gaseous oxygen blown into the hot metal bath surface (Nm 3 / mi nZ hot metal ton) 1 .7.
• the amount of lime added should be within the range of the sum of the lime amount Wcao-P (1 ⁇ 8 hot metal 1 on) and the lime amount Wcao_Si (kg / hot metal ton) specified by the above formulas (5) and (6). I made it.
• the hot metal temperature before and after the dephosphorization treatment was set to 130 to 130 ° C.
• the amount of slag after treatment was calculated from the mass balance of the added lime and the CaO concentration of the slag analysis value.
• the dephosphorization treatment is performed by spraying on the hot metal bath surface, and the temperature of the hot metal at the end of the dephosphorization treatment is set to 1360 ° C to 1450 ° C.
• the dephosphorization reaction is an oxidation reaction of P
• the present inventors have found that the Si content in the hot metal to be dephosphorized in the method of the present invention is sufficiently low, and the deaeration is performed under the condition that the addition amount of CaF 2 is small or no addition.
• the refining agent is supplied to the hot metal bath surface region where a large amount of FeO is generated by gaseous oxygen.
• C a F 2 performs dephosphorization of hot metal under the condition of adding no, molten iron temperature (dephosphorization on dephosphorization efficiency (dephosphorization lime efficiency) in BOF type container (3 0 0 ton)
• dephosphorization lime efficiency dephosphorization lime efficiency
• FIG. 1 2 the fraction of total lime lime contributed to dephosphorization for (burnt lime) was added as a fine ⁇ , phosphorus oxides as 3 C a O 'P 2 0 5 It is derived from the stoichiometric ratio on the assumption that it is fixed.
• the hot metal was desiliconized in the hot metal bed and hot metal ladle as required, then desulfurized in the hot metal hot pot, and the hot metal was transferred to a converter-type vessel for de-sintering.
• the Si content of the hot metal to be treated and the hot metal temperature after the treatment were varied.
• the P content in the hot metal before the dephosphorization treatment is 0.10 to 0.1 l mass%, and the Si content is 0.15 mass% or less. 0 mass% or less.
• Gaseous oxygen was mainly used as the oxygen source, and was added by spraying it from the top blowing lance onto the hot metal bath surface, and for some parts, the addition of a solid acid source (iron ore) was also used.
• De ⁇ oxygen content was controlled in the range of between 1:10 I Nm 3 Bruno hot metal ton.
• the dephosphorization time was 10 to 11 minutes, and the hot metal temperature after dephosphorization was controlled by adjusting the hot metal temperature before dephosphorization and the amount of scrap added.
• the amount of slag after treatment was set at 30 kgZ hot metal ton or less.
• O is a test example (a :) in which lime is added by placing lime on top and the hot metal temperature at the end of the dephosphorization treatment is 1260 to 1350 ° C.
• This is a test example (b) in which the following lime powder was sprayed onto the hot metal bath surface using the above gaseous oxygen as a carrier gas, and the hot metal temperature at the end of the dephosphorization treatment was 1360 to 1450.
• the amount of lime added was varied in the range of 5 to 10 kg / tonne depending on the Si content in the hot metal.
• test example (b) the supply rate B of lime sprayed on the hot metal bath surface (kg / min / hot metal ton) and the supply rate of gaseous oxygen blown on the hot metal bath surface A (Nm 3 / min / hot metal ton)
• the ratio ⁇ , ⁇ is 1.7
• the amount of lime added is the amount of lime Wcao_P (kg g hot metal ton) and the amount of lime Wcao—Si (kg) defined by the above-mentioned equations (5) and (6). / Hot metal ton) within the total range.
• the depth L (L value defined by the above-mentioned equation (7)) of the dent formed on the hot metal bath surface by spraying a purifying agent using gaseous oxygen as the carrier gas is controlled within the range of 200 to 50 Omm. did.
• the amount of slag after treatment was calculated from the mass balance of the added lime and the CaO concentration of the slag analysis value.
• Figure 1 3 is a method of blowing fine ⁇ the molten iron bath surface with gaseous oxygen, in which examined the effect of the addition amount of C a F 2 on the dephosphorization efficiency (dephosphorization lime efficiency), the test of FIG. 1 2 Using the same converter type container as above, the addition type and the addition amount of the purifying agent and the oxygen source, the treatment time, and the like were also the same as those in Test Example (b) in FIG.
• the temperature of the hot metal at the end of the depilatory treatment was in the range of 1360 to 1450 ° C. Note that C a F 2 was added all at once in the initial stage of blowing by top-up charging.
• the amount of slag after treatment was set at 30 kg / hot metal ton or less.
• the amount of C a F 2 is improved and demi ⁇ ash efficiency becomes less than 1 kg / molten pig iron ton.
• C a F 2 has a function of accelerating the melting of C a ⁇ , and the addition of C a F 2 increases the liquid phase ratio of the slag.
• the treatment temperature hot metal temperature
• the rate of restoration from slag to metal increases and the equilibrium value increases. It is considered that the efficiency of dephosphorized lime deteriorates due to the easy access to ash. Therefore, in order to improve the dephosphorization efficiency by setting the treatment temperature (hot metal temperature) to 1360 ° C or more, it is necessary to minimize the amount of added Ca F 2 (less than or equal to lk gZ hot metal ton). There is.
• the hot metal temperature at the end of the dephosphorization treatment When the temperature of the hot metal at the end of the dephosphorization treatment exceeds 1450 °, the effect of increasing the P concentration in the hot metal in equilibrium with the slag is greater than the effect of melting the CaO by raising the temperature of the hot metal. Become. For this reason, the hot metal temperature at the end of the dephosphorization treatment must be 1450 ° or less.
• the Si content is 0.15 mass% or less, preferably 0.07 mass% Or less, particularly preferably 0.0 3 against mass% or less of molten iron, C a the amount of F 2 1 kg Z hot metal ton or less, or C a F dephosphorization treatment 2 at conditions that do not substantially added It can be seen that the dephosphorization treatment can be performed with a high dephosphorization efficiency even when the hot metal temperature at the end of the dephosphorization treatment is as high as 130 to 140 ° C.
• a high hot metal temperature can be secured at the end of the dephosphorization treatment, so that a sufficient heat margin in a subsequent process can be secured.
• T. Fe in the slag can be kept low, and the yield of dephosphorized iron is improved.
• the hot metal temperature before dephosphorization is about 125 ° C to 135 ° C, but the method of adjusting the hot metal temperature at the end of dephosphorization is usually a converter type in which scrap is melted.
• the method of adjusting the hot metal temperature at the end of dephosphorization is usually a converter type in which scrap is melted.
• there is a method of controlling the amount of scrap input In the case of dephosphorization using a de-smelting furnace, there is a method of controlling the amount of scrap input.
• a method of adjusting the input amount of a solid oxygen source such as a sintered powder may be used. Therefore, the hot metal temperature at the end of the treatment may be adjusted in the range of 1360 to 1450 ° C by such a method.
• the hot metal temperature during the dephosphorization treatment is calculated from the gas composition analysis value of the exhaust gas generated by the dephosphorization treatment and the exhaust gas temperature. It is the easiest to control based on this. That is, in this method, the exhaust gas and a gas composition analysis CO, with determining the C 0 2 concentration, to calculate the generation amount of the gas from the exhaust gas temperature. The calorific value in the furnace is calculated from these, and the hot metal temperature can be calculated based on the calorific value.
• a substance that absorbs heat of hot metal by a chemical reaction and / or a thermal decomposition reaction is supplied to a hot metal bath surface area to which gaseous oxygen is supplied.
• a hot metal bath surface area where gaseous oxygen is sprayed a large amount of iron oxide is generated by gaseous oxygen colliding with the bath surface, which is a very advantageous condition for accelerating slagging of refining agents.
• a high-temperature field is formed by an oxidation reaction in a bath surface area (particularly, a flash point) where gaseous oxygen collides, and the generation of such a high-temperature field is advantageous in terms of melting lime.
• this is disadvantageous in terms of dephosphorization equilibrium.
• the present inventor has studied a method for setting the hot metal bath surface area to which gaseous oxygen is supplied to a temperature condition advantageous for the dephosphorization reaction. As a result, the gaseous oxygen is reduced.
• gas oxygen is not hindered from promoting the slagging of the refining agent by gas oxygen. It has been found that the temperature rise in the hot metal bath surface area where iron is supplied is appropriately suppressed, and higher dephosphorization reaction efficiency can be obtained.
• the addition (supply) of a substance that absorbs the heat of hot metal by a chemical reaction or / and thermal decomposition reaction (hereinafter referred to as “endothermic substance”) to the hot metal bath surface depends on the heat generated by the gaseous oxygen supplied to the hot metal bath surface. Therefore, the endothermic substance must be supplied to the hot metal bath surface area to which gaseous oxygen has been supplied.
• the gas oxygen be supplied to a region called a "fire point" generated in the molten iron bath by the blowing of gaseous oxygen by the upper blowing lance in the region of the hot metal bath surface to which the gas oxygen is supplied.
• This hot spot is the hot metal bath surface area where the temperature becomes the highest due to the collision of the gaseous oxygen gas jet, where the oxidation reaction by gaseous oxygen (the reaction for generating Fe 0) is concentrated and is stirred by the gaseous oxygen gas jet. Therefore, it can be said that this is a region where the effect of the addition of the endothermic substance is most remarkably obtained.
• the endothermic substance there is no particular limitation on the endothermic substance as long as it is a substance that removes heat from the hot metal by a chemical reaction and / or a pyrolysis reaction when added to the hot metal, or both reactions. Therefore, this endothermic substance may be either gas or solid.
• Examples of the gas that can be used as the endothermic substance include carbon dioxide, water vapor, and nitrogen oxide (NO x), and one or more of these can be used.
• These gas endothermic substances mainly react with Fe when supplied to the hot metal bath surface. (E.g., C0 2 + F e ⁇ F e O + CO, H 2 0 + F e ⁇ F e O + H 2), absorbs the heat of the molten iron at that time.
• F e oxidation with gaseous oxygen F e + 1/20 2 ⁇ F e O
• the heat generation amount becomes endothermic total is significantly reduced.
• Examples of the solid that can be used as the endothermic substance include a metal carbonate, a metal hydroxide, and particularly preferably an alkali metal, an alkaline earth metal carbonate, and a hydroxide. , 'One or more of these can be used.
• These solid endothermic compound mainly cause thermal decomposition reaction, performs endothermic hot metal At that time, by pyrolysis generates C_ ⁇ 2 or H 2 0 by being supplied to the molten iron bath surface, the C0 2 Alternatively, since H 20 further functions as an endothermic substance as described above, a particularly high endothermic effect is obtained.
• Such genus carbonates C a C0 3, C aMg (C0 3) 2, Mg C0 3, Na C0 3, F e C0 3, Mn C0 3, N a HC 0 3
• bicarbonate Na Toriumu And metal hydroxides such as C a (OH) 2 , Mg (OH) 2 , B a (OH) 2, A 1 (OH) 3 Fe (OH) 2 , and Mn (OH ) n, N i (OH) n and the like, and one or more of these can be used.
• C a C ⁇ 3 , C a (OH) 2 , and C aMg (C ⁇ 3 ) 2 are not only easily available, but also generate C a O by the above thermal decomposition.
• this Ca is particularly preferable because it has a great advantage of functioning as a refining agent.
• these solid endothermic substances are added in the form of unfired or semi-fired limestone or dolomite.
• the solid endothermic substance is preferably in the form of powder having an average particle diameter of 5 mm or less, since thermal decomposition and the like do not proceed rapidly if the particle size is too large.
• gas endothermic substance and the solid endothermic substance described above may be used in combination, and the gas endothermic substance may be used as part or all of the carrier gas when the solid endothermic substance is supplied to the hot metal bath surface.
• Top-blowing lance spraying onto the hot metal bath surface by other lances, top-loading (using a heater for solid heat-absorbing substance, etc.)
• the endothermic substance can be reliably supplied to the hot metal bath surface area (particularly preferably, "fire point") to which gaseous oxygen has been supplied, and the effect described above can be obtained.
• the endothermic substance When the endothermic substance is supplied to the hot metal bath surface by the top blowing lance, (1) the endothermic substance is mixed with gaseous oxygen (for solid endothermic substance p, gaseous oxygen is used as carrier gas), and the hot metal bath surface is supplied through the same lance hole. (2) A method in which the endothermic substance and gaseous oxygen are supplied into the lance through separate gas supply lines and supplied to the hot metal bath surface from separate lance holes (for solid endothermic substances, supply of the endothermic substance In this case, a carrier gas other than gaseous oxygen is used).
• gaseous oxygen for solid endothermic substance p, gaseous oxygen is used as carrier gas
• Gaseous oxygen can be supplied to the hot metal bath surface area supplied through the lance hole.
• a gas heat absorbing substance is supplied from a central lance hole at the tip of the upper blowing lance, or a heat absorbing substance is supplied using a gas other than gaseous oxygen as a carrier gas, and gas is supplied from another lance hole around the central lance hole.
• a mode such as supplying oxygen is preferable.
• a carrier gas an inert gas such as N 2 or Ar is preferable, and a gas endothermic substance (for example, CO 2 ) is used as a carrier gas as described later. May be used.
• gaseous oxygen is supplied from some of the lance holes, and gaseous oxygen mixed with an endothermic substance (furthermore, a purifying agent is added) from other lance holes.
• gaseous oxygen mixed with an endothermic substance furthermore, a purifying agent is added
• it can also be supplied to the hot metal bath surface.
• a purifying agent is added to gas oxygen or a carrier gas or gas endothermic substance other than gas oxygen alone or mixed with an endothermic substance (gas or Z and solid) and supplied to the hot metal bath surface. You can also. .
• the oxygen supply line (header, piping, lance) of the upper blowing lance The endothermic substance may be supplied to a part or the whole of the gas oxygen flow path, etc., and mixed with the gas oxygen.
• the endothermic substance (gas or / and solid) or the endothermic substance and the refining agent may be supplied to the hot metal bath surface using a supply means other than the top-blowing lance (for example, another lance).
• a supply means other than the top-blowing lance for example, another lance.
• any lance can be used as long as it can supply the granular material to a predetermined position of the furnace ⁇ ⁇ in the same manner as the top-blown lance. It can be used if there is no problem with its cooling capacity.
• An overhead loading device such as a turret or pouring device may also be used if there is no problem with the durability at high temperatures and the accuracy of the loading position.
• the purifying agent is sprayed (projected) using gaseous oxygen or another carrier gas onto the hot metal bath surface region (particularly preferably, the above-mentioned “flash point” region) to which gaseous oxygen is supplied.
• gaseous oxygen or another carrier gas onto the hot metal bath surface region (particularly preferably, the above-mentioned “flash point” region) to which gaseous oxygen is supplied.
• gaseous oxygen or a gas other than gaseous oxygen for example, an inert gas such as nitrogen or Ar
• a purifying agent and an endothermic substance gas or / and solid
• gaseous oxygen or a gas other than the above-mentioned gaseous oxygen is used as a carrier gas.
• the spraying of gaseous oxygen and the spraying of the refining agent and the endothermic substance may be performed using different top blowing lances.
• the refining agent and the endothermic substance should be sprayed onto the hot metal bath surface together with gaseous oxygen. desirable.
• Figures 14 (a) to 14 (e) show some examples of the mode of supply of gaseous oxygen, scouring agent and endothermic material to the hot metal bath surface using a top blowing lance.
• Fig. 14 (a) shows the configuration in which gaseous oxygen, scouring agent, and endothermic substance (gas or Z and solid) are mixed and supplied from the lance hole (sprayed on the hot metal bath surface).
• gaseous oxygen, scouring agent, and endothermic substance gas or Z and solid
• FIG. 14 (c) 'is to supply carrier gas and purifying agent other than gaseous oxygen from some lance holes, and to supply gaseous oxygen and endothermic substances (gas or Z and solid) from other lance holes.
• the gas endothermic substance and scouring agent are supplied from some lance holes, and the gas oxygen and endothermic substance (gas or Z and solid) are supplied from other lance holes.
• Fig. 14 (e) shows some lance holes Luo gaseous oxygen and seminal ⁇ , gaseous endothermic compound or gaseous endothermic material and a solid heat absorbing material from the other locking hole (blown onto the molten iron bath surface) for supplying respectively a form.
• the supply form of the gaseous oxygen, the purifying agent and the endothermic substance to the hot metal bath surface is not limited to these.
• C a C O 3 , C a (OH) 2 , and C a Mg (CO 3 ) 2 generate C a O by thermal decomposition, and this C a O functions as a refining agent Therefore, in the present embodiment, the solid endothermic substance is supplied in place of part or all of the CaO-based refining agent (mainly quicklime), and the CaO generated from this substance is substantially purified.
• Dephosphorization treatment can also be performed as an agent.
• the refining agent-forming substance and the chemical reaction and / or the thermal decomposition reaction are applied to the hot metal bath surface area to which gaseous oxygen is supplied.
• the heat of the hot metal as absorption heat material by, C a C0 3, C a (OH) 2, C aMg (C0 3) 2 of one or more of Bareru selected from among (hereinafter referred to as "fine ⁇ generation and endothermic compound") Is to supply.
• the refining agent generation and the endothermic substance supplied to the hot metal bath surface are thermally decomposed, whereby the hot metal is absorbed, and the thermal decomposition turns into CaO as a refining agent and an endothermic substance.
• the same effect as when both the aO-based refining agent and the endothermic substance are supplied is obtained, and as a result, a high dephosphorization reaction efficiency can be obtained.
• the above-mentioned refining agent-generating / endothermic substance is called "fire point" generated in the hot metal bath surface region to which gaseous oxygen is supplied, particularly by the acid supply by the top blowing lance.
• fire point generated in the hot metal bath surface region to which gaseous oxygen is supplied, particularly by the acid supply by the top blowing lance.
• gaseous oxygen is supplied to the area.
• the refining agent-forming / endothermic substance is usually added in the form of unfired or semi-fired limestone or dolomite. If the particle size of the refining agent-producing and endothermic substance is too large, thermal decomposition or the like does not proceed rapidly. Further, the scouring agent-producing and endothermic substance may be used in combination with the gas endothermic substance as described above, and a part or all of the carrier gas when supplying the refining agent-producing and endothermic substance to the hot metal bath surface. May be used as a gas endothermic substance.
• the method of the above (1) is more preferable from the viewpoint of reliably supplying the endothermic substance to the hot metal bath surface area to which the gaseous oxygen has been supplied, but the method of the above (2) is also preferable in the method of the above (2).
• Agent generation ⁇ Endothermic material can be supplied to the hot metal bath area supplied with gaseous oxygen through another lance hole.
• a gas other than gaseous oxygen is used as a carrier gas through a central lance hole at the tip of the upper blowing lance to generate a purifying agent, an endothermic substance is supplied, and gaseous oxygen is supplied from other lance holes around the central lance hole.
• a form such as supply is preferred.
• the carrier gas an inert gas such as N 2 or Ar is suitable, and a gas endothermic substance (for example, co 2 ) may be used as the carrier gas as described later.
• the oxygen supply line header, piping, A scouring agent generation / endothermic substance may be supplied to part or all of the gas oxygen flow path in the lance, etc., and mixed with gaseous oxygen.
• the refining agent producing / endothermic substance may be supplied to the hot metal bath surface using a supply means other than the top blowing lance (for example, another lance).
• a supply means other than the top blowing lance for example, another lance.
• any lance can be used as long as it can supply the granular material to a predetermined position in the furnace, similarly to the top-blown lance. It can be used if there is no problem with the cooling capacity inside.
• a top-loading device such as a scooter or a pouring device may be used if there is no problem with the durability at high temperatures and the accuracy of the charging position.
• Gaseous oxygen used for producing scouring agent and supplying endothermic substance may be either pure oxygen gas or oxygen-containing gas.
• first to seventh embodiments of the method of the present invention may be carried out independently, or the conditions of two or more embodiments (the second embodiment is a pot type as a refining container) Or only in the case of using a torpedo car type container).
• the effect of the method of the present invention can be further enhanced as the conditions for combination increase.
• an efficient dephosphorization treatment can be performed with a minimum amount of a refining agent, but as a further effect, the properties of the generated slag are mainly based on solid phase. Since it becomes a body, there is a great advantage that the slag can be appropriately prevented from flowing out of the hot water after the treatment.
• the phosphorus concentration in the slag will increase. Therefore, when tapping water after the dephosphorization treatment (particularly from a refining vessel with a tap hole such as a converter type vessel) It is important that the slag does not flow out with the metal at the time.
• methods for minimizing slag outflow to the next process after dephosphorization treatment using a converter type vessel include: (1) slag cutting technology during tapping from a converter type vessel, (2) There is a method of reducing the fluidity of the slag by controlling the slag composition after the treatment, and (3) a method of removing (slag removing) the slag from the ladle after tapping.
• the slag generated in the hot metal bath surface region centering on the fire point and sequentially extruded to the outside thereof is mainly composed of a stable solid phase, for this reason, the slag at the end of the dephosphorization treatment has a much lower fluidity than the slag generated by the conventional dephosphorization treatment, and as a result, when the tapping is completed after the dephosphorization treatment (particularly in a converter type vessel) Slag can be effectively prevented from flowing out of a refining vessel having a tap hole as described above. Also, as mentioned earlier, this effect is C a F 2 was the amount of added pressure either no or C a F 2 less 1 kg / molten pig iron ton, by suppressing the increase in the fluidity of the slag, more Can be enhanced.
• FIG. 15 shows the state of slag Z-metal at the start of tapping in a converter type vessel.
• the conventional method shown in FIG. 1 5 (a) is, for melting actively slag by adding or or C a F 2 low slag basicity in a large amount, the slag is then forming, The slag thickness is increasing. For this reason, if the furnace is tilted when tapping, As the slag passes through the tap, the slag will inevitably flow out.
• the slag is extremely thin because the slag exists mainly in the solid phase, and the slag outflow that occurs at the start of tapping can be ignored. Is.
• Figure 16 shows the state of slag / metal near the tap at the end of tapping.
• the metal vortex is generated due to the shallow metal depth, but in the conventional method shown in Fig. 16 (a), the molten slag on the metal is entrained in this vortex and flows out.
• the slag is mainly composed of the solid phase, so that the slag interferes and coalesces on the vortex of the metal. It is rarely caught in eddies.
• Hot metal from the blast furnace is desiliconized in the hot metal bed and, if necessary, in the hot metal pot, desulfurized in the hot metal pot using mechanical stirring, and then de-silvered in a converter type vessel (300 ton). Processing was performed.
• Hot metal composition C: 4.5 to 4.7 mass%, S i: 0.1 to 0.28 mass%, Mn: 0.15 to 0.25 mass%, P: 0.1 0 to 0.1 One recommendation s%, S: 0.001 to 0.003 mass%.
• Lime powder with a particle size of 1 mm or less was used as a dephosphorizing refining agent, and this was sprayed onto the hot metal bath surface as oxygen-carrying gas through a lance.
• the ratio AZB between (k / mi hot metal ton) and the supply rate A (Nm 3 / min / hot metal t 0 n) of gaseous oxygen blown to the hot metal bath surface was set to 1.7.
• the amount of lime added should be within the range of the sum of the amount of lime Wcao_P (kg / hot metal ton) and the amount of lime Wcao_Si (kg, hot metal ton) specified in Eqs. (5) and (6) described above. I made it.
• the depth L (L value defined by the above-mentioned equation (7)) of the depression formed on the hot metal bath surface by spraying a refining agent using gaseous oxygen as a carrier gas is in the range of 200 to 500 mm.
• the hot metal temperature before and after the dephosphorization treatment was set to 125 ° C to 135 ° C.
• the amount of slag after treatment was calculated from the mass balance between the amount of lime added and the CaO concentration in slag (analyzed slag).
• the results of each example are shown in Table 1 together with the dephosphorization conditions.
• the average values shown in Table 1 are 5 kg / hot metal ton to 10 kg / hot metal ton, 10 kg Z hot metal more than ton to 20 kg Z hot metal ton, 20 kg / hot metal more than ton to 30 kg Z hot metal Ton, 30 kg / hot metal over ton ⁇ 40 kg / hot metal ton, 40 kg Z hot metal over ton ⁇ 50 kg / hot metal ton It is the average of the values at.
• Hot metal from the blast furnace is desiliconized in the hot metal bed and, if necessary, in the hot metal ladle, then desulfurized in the hot metal pot using mechanical stirring, and then desulfurized in a converter type vessel (300 ton). It was treated with phosphorus.
• the P content in the hot metal before the dephosphorization treatment is 0.10 to 0.1 lraass, and the Si content is 0.15 mass. /. It was below.
• the hot metal temperature before and after this dephosphorization treatment was 1250 to 1350 ° C, and as a dephosphorizing agent, calcined lime mainly composed of Ca ⁇ which was sieved with a particle size of 200 mesh or less was used.
• the basic unit of CaO used was 5 to 15 kg Z hot metal ton depending on the Si content in the hot metal.
• a scouring agent and an oxygen source were supplied (blowing time: 10 minutes) by blowing gaseous oxygen as a carrier gas onto the bath surface as a carrier gas through a top blowing lance.
• the operation was carried out under various conditions with different ratios A / B between the supply rate A (Nm 3 / mi hot metal ton) of gaseous oxygen and the feed rate B (kg / min / hot metal ton) of the refining agent.
• Nitrogen gas as a stirring gas was blown into the hot metal at a flow rate of 0.05 to 0.15 Nni 3 / min / hot metal ton from the bottom blowing nozzle at the bottom of the furnace.
• processed slag amount was less 3 0 k pig iron ton.
• the amount of lime added is determined by the amount of lime Wcao-P defined by equations (5) and (6) described above.
• the depth L (L value defined by equation (7) described above) generated on the hot metal bath surface by blowing a refining agent using gaseous oxygen as the carrier gas is within the range of 200 to 500 mm.
• the amount of slag after treatment was calculated from the masparance of the amount of added lime and the CaO concentration (analytical value of slag) in the slag.
• Gaseous oxygen supply rate A (Nm 3 min / hot metal ton) and refining agent supply rate B
• Figure 17 shows the relationship between the ratio A / B to (kg / min / hot metal ton) and the P content in hot metal after dephosphorization.
• a / B in the example of the present invention is in the range of 0.3 to 7.
• the P content in the hot metal after the dephosphorization treatment is below the target [P] concentration of 0.015 ma SS % or less, and especially the Si content in the hot metal before the dephosphorization treatment is 0.1%.
• the low P standard [P] ⁇ 0.010 mass% is stably achieved.
• those having an A / B in the range of 1.2 to 2.5 have particularly low [P], indicating that the highest dephosphorization efficiency can be obtained in this region.
• the P content in the hot metal after the dephosphorization treatment falls below the target [P] concentration of 0.015 mass% or less for all AZB in the range of less than 0.3 and more than 7 Not reached. .
• hot metal from a blast furnace is desiliconized on a hot bed, it is received in a hot metal ladle, desiliconized in the hot metal ladle, and after discharging, the hot metal ladle is moved to a dephosphorization station. Then, a dephosphorization treatment was performed.
• lime powder refining agent
• gaseous oxygen as a carrier gas
• lime powder was blown into the hot metal through the immersion lance.
• lime powder was not sprayed by the top blowing lance, but lime powder was blown into the hot metal through the immersion lance. In each case, the processing time was 20 minutes.
• the amount of slag after treatment was set to 20 kg / hot metal t on or less.
• the lime addition amount is the sum of the lime amount Wcao_P (kg Z hot metal ton) and the lime amount Wcao_Si (kg / hot metal ton) defined by the above-described equations (5) and (6). It was set within the range.
• the depth L (L value defined by the above-mentioned equation (7)) of the depression formed on the hot metal bath surface by spraying the refining agent using gaseous oxygen as the carrier gas is 200 to 50
• Control was performed within the range of 0 mm.
• the hot metal temperature before and after the dephosphorization treatment was 1300 to 13
• the amount of slag after treatment was calculated from the amount of lime added and the CaO concentration in the slag (analyzed slag) and the masparance of the CaO concentration.
• Table 2 shows the results of each example together with the dephosphorization treatment conditions.
• Hot metal from the blast furnace is desiliconized in the hot metal bed and, if necessary, in the hot metal pot, desulfurized in the hot metal pot using mechanical stirring, and then dephosphorized in a converter type vessel (300 ton). Processing was performed.
• the hot metal temperature before and after the treatment is set to 1250 to 135, gas oxygen is blown to the hot metal bath surface through the top blowing lance, and llime powder (refining agent) of lmm or less is sprayed on the hot metal bath surface, and (2) lime (refining agent) with a particle size of 1 to 3 mm is placed on top and charged by either method.
• Nitrogen gas was blown from the furnace bottom of the converter type vessel at a supply rate of 0.05 to 0.15 NmVmin / hot metal ton, and dephosphorization was performed for 9 minutes while stirring the hot metal.
• the amount of slag after treatment was set to 30 kg / hot metal t on or less.
• the lime addition amount is determined by the lime amount Wcao-P (kg «/ hot metal ton) and the lime amount Wcao_Si (kg hot metal) defined by the aforementioned equations (5) and (6) ton) within the total range.
• the depth M (L value defined by equation (7) described above) generated on the hot metal bath surface by spraying a refining agent with gaseous oxygen as the carrier gas is 200 to 500 mm. Controlled within range.
• the amount of slag after treatment was calculated from the mass balance between the amount of added lime and the CaO concentration in slag (analyzed slag).
• Table 3 shows the results of each example together with the conditions for the dephosphorization treatment.
• hot metal from a blast furnace is desiliconized on a hot bed, it is received in a hot metal ladle, desiliconized in the hot metal ladle, discharged, and then converted into a converter vessel (300 t0 n ) Was charged with hot metal.
• lime powder (refining agent) was sprayed onto the hot metal bath surface using oxygen gas as a carrier gas using a top-blowing lance, and in some examples, massive lime was also placed on the top. .
• lime powder was not sprayed through the top blowing lance, and massive lime was added by overhead charging.
• nitrogen gas was blown in from the furnace bottom of the converter type vessel at a supply rate of 0.07 to 0.12 Nm 3 / minZ hot metal ton, and dephosphorization was performed for 8 to 14 minutes.
• the hot metal temperature before and after the treatment was 1250 to 1350 ° C, and the slag amount after the treatment was 30 kg / hot metal ton or less.
• the ratio of the supply rate B (kg / min / hot metal ton) of lime sprayed to the hot metal bath surface and the supply rate A (Nm 3 Zm in / hot metal ton) of gaseous oxygen blown to the hot metal bath surface AZB is 1.7.
• the hot metal temperature before and after the defatting treatment was 1250-1350 ° C.
• the amount of slag after treatment was calculated from the mass balance between the amount of lime added and the CaO concentration in the slag (analyzed slag).
• Spraying Spraying lime powder (refining agent) onto the hot metal bath surface by top blowing lance Top placing: Lump lime (m) placed above
• the hot metal from the blast furnace is desiliconized on the hot bed, it is received in a hot metal ladle, desiliconized in the hot metal ladle, and the slag is discharged into a converter vessel (300 ton).
• the hot metal was charged into the furnace and dephosphorized.
• gas oxygen is sprayed onto the hot metal bath surface through the top blowing lance, and (1) lime powder (purifying agent) having a particle size of 3 mm or less is blown onto the hot metal bath surface using the above gas oxygen as a carrier gas.
• the refining agent was added in any of the following methods.
• Nitrogen gas was blown in from the furnace bottom of the converter vessel at a supply rate of 0.1 Nm 3 / min / hot metal ton, and the hot metal was stirred and dephosphorized for 10 to 11 minutes.
• the hot metal temperature at the end of dephosphorization was controlled by adjusting the hot metal temperature before dephosphorization and the amount of scrap added.
• the amount of slag after the treatment was set at 30 kgZ hot metal ton or less.
• the amount of lime added was determined by the amount of lime Wcao-P (kg / hot metal ton) and the amount of lime Wcao-Si (kg / lime) defined by the above-mentioned equations (5) and (6).
• the hot metal ton) was within the total range.
• the depth of the dent (L value defined by the above-mentioned equation (7)) formed on the hot metal bath surface by spraying a refining agent using gaseous oxygen as a carrier gas is controlled within the range of 200 to 500 mm. I controlled.
• the amount of slag after treatment is calculated based on the mass balance of the added lime and the Ca Table 8
• hot metal from a blast furnace is desiliconized on a hot bed, it is received in a hot metal ladle, desiliconized in the hot metal ladle, discharged, and then converted into a converter type vessel for dephosphorization. (300 ton) was charged with hot metal and dephosphorized.
• lime powder having a particle size of 1 mm or less and an endothermic substance were sprayed onto the hot metal bath surface using gaseous oxygen as a carrier gas through an upper blowing lance.
• C a C O 3 or C a (OH) 2 both having a particle size of 1 mm or less was mixed in advance with lime powder at a predetermined ratio.
• Nitrogen gas was supplied from the bottom of the converter type container to 0.1. While the hot metal was stirred at the supply rate of in / hot metal ton, a defamation treatment was performed for 10 to 11 minutes. The hot metal temperature before dephosphorization and the amount of scrap added were adjusted to control the hot metal temperature at the end of dephosphorization. The amount of slag after treatment was set to 30 kg / hot metal ton or less.
• the lime addition amount is determined by the lime amount Wcao_P (kgZ hot metal ton) and the lime amount Wcao_Si (kg / hot metal ton) defined by the above-described equations (5) and (6). The total was within the range.
• the depth L of the pit formed on the hot metal bath surface by spraying the refining agent with gaseous oxygen as the carrier gas (L value defined by the above-mentioned equation (7)) is within the range of 200 to 500 ram.
• the amount of slag after treatment was calculated from the mass balance of the added lime and the CaO concentration of the slag analysis value.
• Table 9 shows the results of each example together with the conditions for the dephosphorization treatment.
• Hot metal from the blast furnace was desiliconized in a hot metal ladle, discharged, and then charged into a converter type vessel (300 ton) for dephosphorization.
• a converter type vessel 300 ton
• Hot metal to the furnace bottom portion of the converter-type vessel is blown about 0 .. 1 Nm 3 / min Bruno hot metal ton of stirring gas (nitrogen)
• the top-blown bath surface above using the lance Supplied gaseous oxygen, lime powder (Ca O-based refining agent) and gas endothermic material to the hot metal bath surface Incidentally, C a F 2 during spinning ⁇ was not added.
• the amount of slag after treatment was set at 30 kg / hot metal ton or less.
• the hot metal feed rate of limestone to be blown to the bath surface B (kg / min / hot metal ton), the ratio AZB the supply rate A of gaseous oxygen blown into the hot metal bath surface (Nm 3 / mi nZ molten iron ton) 1. 7 was set.
• the amount of lime added is within the range of the sum of the lime amount Wcao_P (kg / hot metal ton) and the lime amount Wcao—Si (kg / hot metal ton) defined by the above-mentioned equations (5) and (6). I did it.
• the depth L (L value defined by the above-mentioned equation (7)) of the depression formed on the hot metal bath surface by spraying the refining agent using gaseous oxygen as the carrier gas is within the range of 200 to 50 Omm. Controlled.
• the hot metal temperature before and after the defatting treatment was 1250-1350.
• the amount of slag after treatment was calculated from the mass balance between the amount of lime added and the CaO concentration in slag (analyzed slag).
• the top blowing acid lance used had one central hole and three peripheral holes as lance holes.
• Use lime powder with a particle size of 3 mm or less cut out gaseous oxygen as a carrier gas from the cutout device, transport it through the piping and supply it to the top blowing lance, and supply it to the hot metal bath surface with gaseous oxygen from the center hole. I was doing it. On the other hand, gas oxygen was supplied to the top blowing lance through another piping line so that it was supplied from the surrounding holes to the hot metal bath surface. The total amount of acid supply was 1.5 Nm 3 / minZ hot metal ton.
• a gas endothermic substance was added to each of the two gas oxygen lines so as to have a predetermined concentration.
• This gas endothermic substance uses carbon dioxide and water vapor,
• the mixing ratio to be used was 10 to 40% by volume (external number with respect to oxygen gas 100).
• gas oxygen was supplied to the hot metal bath from the top blowing lance and lump lime (CaO-based refining agent) was placed on top.
• the blast furnace hot metal was desiliconized in the ladle, discharged, and dephosphorized in the ladle.
• gaseous oxygen and lime powder C a O 2 were blown from above the bath surface using a top lance while agitating the hot metal by injecting 3 Nm 3 of nitrogen per minute into the hot metal from one dipping lance.
• an endothermic substance were supplied in any of the following forms (1) to (4).
• C a F 2 during spinning ⁇ was not added.
• the amount of slag after treatment was set at 30 kg / hot metal ton or less.
• the ratio A / B of the supply rate B (kg / minZ hot metal ton) of lime sprayed onto the hot metal bath surface and the supply rate A (NmVminZZ hot metal ton) of gaseous oxygen blown onto the hot metal bath surface is 1. 7 was set.
• the amount of lime added is within the range of the sum of the lime amount Wcao-P (kg / hot metal ton) and the lime amount Wcao-Si (k hot metal ton) defined by the above-mentioned equations (5) and (6). I made it.
• the depth L (L value defined by the above-mentioned equation (7)) of the dent formed on the hot metal bath surface by spraying the refining agent using gaseous oxygen as the carrier gas is within the range of 200 to 500 mm. Controlled.
• the hot metal temperature before and after the dephosphorization treatment was 1250-1350.
• the amount of slag after treatment was calculated from the masparance of the amount of lime added and the CaO concentration in slag (analyzed slag).
• Lime powder, C a C0 3 (limestone), together with the C a (OH) 2 is used as the particle diameter equal to or less than 1 mm, to send transportable through the pipe cut as Kiyariagasu gaseous oxygen from these clipping device, the top-blown At the lance inlet, it merged with gaseous oxygen supplied through other pipes, and was supplied to the bath surface along with the gaseous oxygen jet from the three lance holes at the tip of the top lance.
• the oxygen-flow amount of the total was hourly 6000 Nm 3.
• C0 2 was set to the mixture ratio for the gaseous oxygen 25 vol% (outer number against the gaseous oxygen 100). Further, lime powder, C a C0 3 (limestone), C a (OH) 2 is C It was added so as to be 70 to 80 kg per minute in terms of aO.
• gaseous oxygen was supplied to the hot metal bath surface through the top blowing lance, and lime powder was injected into the hot metal through the immersion lance.
• the present invention is used for producing hot metal having a low phosphorus content in an intermediate step of steel production.

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• 2002
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