CN101921889B

CN101921889B - Manufacture method of low-phosphorus molten iron

Info

Publication number: CN101921889B
Application number: CN201010264984A
Authority: CN
Inventors: 松野英寿; 村井刚; 菊地良辉; 樱井荣司; 竹滨良平; 川畑凉; 小平悟史; 菊地一郎; 田野学; 清水宏
Original assignee: NKK Corp
Current assignee: JFE Engineering Corp
Priority date: 2002-08-27
Filing date: 2002-08-27
Publication date: 2012-10-10
Anticipated expiration: 2022-08-27
Also published as: CN101921889A

Abstract

The invention aims to effectively carry out dephophorization treatment by adding a small amount of refining agent instead of a great amount of CaF2. Under the condition that the invention decreases the quantity of treated slag to a certain extent in compassion with the prior art, extremely effective dephosphorizing and refining can be carried out by utilizing the uneven melting states of the slag through providing oxygen and the refining agent to the liquid surface of the molten iron in a special mode and the dephophorization treatment is carried out by blowing the oxygen and at least one part of refining agent to the liquid surface of the molten iron through a top blowing gun, and the amount of the treated slag is below 300 kg per ton of molten iron, hopeful below 20 kg per ton of molten iron and preferably below 10 kg per ton of molten iron. Dephophorization treatment is hopeful to be carried out to the molten iron with the Si content below 0.15 percent by mass, hopeful below 0.07 percent by mass and preferably below 0.03 percent by mass.

Description

The method of manufacture of low-phosphorous molten iron

The application is to be August 27, application number in 2002 the dividing an application for the application for a patent for invention of " method of manufacture of low-phosphorous molten iron " that be 02823559.2 (international application no is PCT/JP02/08604), denomination of invention the applying date.

Technical field

The present invention relates to utilize the dephosphorization treatment of carrying out hot metal pretreatment, make the method for low-phosphorous molten iron effectively.

Background technology

Replace converter process to be widely used in the ironmaking stage in the past and carried out the hot metal pretreatment method of dephosphorization treatment.This is because the refining temperature of dephosphorisation reaction is low more, carries out more easily on the thermodynamics, can carry out dephosphorization treatment with refining agent still less.

Generally in hot metal pretreatment, at first in molten iron, add solid oxygen source such as red stone and carry out desiliconization and handle, after the slag that in handling this desiliconization, produces is removed, add refining agent and carry out dephosphorization treatment.Generally using the CaO of lime etc. as the refining agent of dephosphorization treatment is refining agent, uses solid oxygen source (red stone etc.) and gas oxygen as oxygen source.As processing vessel, use mixer type iron ladle car, hot metal ladle (charge packet), converter type container etc. in addition.Be widely used in addition and promote that CaO is the CaF of refining agent scorification ₂(fluorite).

As the dephosphorization treatment condition of prior art, for example special open the flat basicity of having delivered slag for 7-70626 number 0.6 or more 2.5 below, the processing end temp more than 1250 ℃ below 1400 ℃, more than the bottom blowing stirring power 1.0kg/ ton molten iron, oxygen supply speed 2.5Nm ³The above condition of/ton molten iron.In this technology, fix on the reason below 2.5 about basicity of slag, be because basicity on this worsens the flowability of slag, so must handle under the high temperature of dephosphorization being unfavorable for.This is external below 2.5, the high more dephosphorization that carries out more easily of basicity of slag.

This external spy opens in flat 8-311523 number and has delivered through the top blast rifle molten iron blowing CaO powder and 0.7～2.0Nm in the converter type container ³The oxygen of/min/ ton molten iron is simultaneously from the furnace bottom of converter type container or sidewall winding-up 0.05～0.30Nm ³The stirring of/min/ ton molten iron is adopted this method with the method for gas, utilizes the oxygen-supplying amount of the suitable top blast bottom blowing of control, realizes that the concentration that makes slag generate FeO in (CaO scorification) and the control slag rapidly is suitable, can effectively carry out dephosphorization treatment.

With above-mentioned spy open flat 7-70626 number with special to open flat be for 8-311523 number that master's existing dephosphorization of molten iron refining techniques is with according to dephosphorization equilibrium equation analysis and judgement, the even fusion of the slag after the processing, slag-metal is preceding topic near balance.Therefore the dephosphorizing capacity of slag (phosphorus distributes Lp=quality % (P)/quality % [P], quality % (P): the P concentration in the slag, quality % [P]: the P concentration in the metal) and slag amount also determine laggard line operate by so preceding topic.

The phosphorus of slag distributes Lp relevant with the basicity of slag, and basicity of slag high phosphorus more distributes Lp high more.But consider that basicity of slag was high in the past, the flowability of slag worsens, and becomes the condition that is unfavorable for dephosphorization.Because the low words phosphorus of basicity of slag distributes the Lp step-down, must add lime more and (also add SiO as required on the other hand ₂The source), slag amount is increased.

Can find out from above-mentioned; Phosphorus in order to ensure regulation distributes Lp in the prior art; Set necessary basicity, the basicity that definite P content that will reach target needs under this basicity of slag, and add refining agent; But can not make basicity of slag carry so highly, so si content is operated by the slag amount about 40～50kg/ ton molten iron (slag amount after the processing) in general dephosphorization treatment at the molten iron about 0.2 quality % from seeing with the relation of slag fluidity.For example opening the Intake Quantity of putting down CaO (refining agent) in 8-311523 number above-mentioned spy confirms according to the P content in the molten iron that carries out dephosphorization treatment; P content is under the situation about average 0.10 quality % before handling; The CaO of 20kg/ ton molten iron substantially packs into; And the slag in refining vessel is the slag part that is generated by the above-mentioned CaO of packing in the dephosphorization refining, adds the SiO that the desiliconization of hot metal reaction generates ₂Partly, the P of dephosphorisation reaction generation ₂O ₅The slag part (FeO, MnO etc.) that partly, produces, the slag part of bringing from last operation, the slag part (Al that the body of heater loss in smelting produces from other hot metal composition ₂O ₃, MgO etc.), the slag part of bringing into attached to the part of the slag on the body of heater, the waste material of packing into originally, from adding the formations such as slag part that ore etc. produces; General its total amount (slag amount after the processing) is about 2～2.5 times of CaO amount of packing into; So under the situation of the above-mentioned CaO about 20kg/ ton molten iron that packs into, the slag amount after the processing must reach about 40～50kg/ ton molten iron.

Considering from viewpoints such as environment protection in recent years, is being in master's the refining procedure with the dephosphorization operation, requires to reduce the slag amount that generates as far as possible, is limited but reduce slag amount with above-mentioned prior art, therefore can not fully tackle the requirement that reduces the slag growing amount.

In addition for CaF for promoting that refining agent scorification is added ₂, consider the influence of F in recent years, even in the refining of steel, also require to reduce CaF as far as possible to environment ₂Usage quantity, therefore attempt with adding CaF ₂Improving dephosphorization efficient also is restricted.

Summary of the invention

The purpose of this invention is to provide not heavy addition CaF ₂, and just can effectively carry out dephosphorization treatment with a spot of refining agent addition, can reduce the method for manufacture of the low-phosphorous molten iron of slag growing amount thus as far as possible.

In the dephosphorization of molten iron refining, molten iron is added oxygen source and as the refining agent in CaO source, as the supply method of oxygen source, reduce and can effectively promote FeO generation aspect to see from suppressing temperature, be fit to use from the method for top blast rifle to molten iron liquid level winding-up oxygen.Adopt the method for such oxygen supply, in refining vessel, utilize the energy extruding slag of oxygen, be divided into and exposed liquid level (molten iron liquid level) part and the liquid level part that is in addition covered by slag, the slag existence in refining vessel is not uniform.Therefore the inventor is not according in refining vessel, making slag keep the existing method that considers a problem of even molten state; Dephosphorizing method under the state of a small amount of refining agent addition, being stabilized in high dephosphorization efficient is studied; Its result finds that slag amount after making processing is than under the much lower condition of prior art; And then make preferably that Si content offers the molten iron liquid level through making oxygen and refining agent in a particular manner in the molten iron before handling under the condition below the prescribed level, make the even fused of slag consideration method opposite with having now; Utilize the uneven fused state of slag, can carry out the dephosphorization refining very effectively.

The method of manufacture of low-phosphorous molten iron of the present invention; Understanding with such is the basis;, the container of molten iron adds oxygen source in being housed and as the refining agent in CaO source; Make in the method for low-phosphorous molten iron as the dephosphorization treatment of hot metal pretreatment through carrying out, it is characterized in that carrying out dephosphorization treatment to molten iron liquid level winding-up oxygen with at least a portion refining agent, make simultaneously and handle afterwards slag amount below 30kg/ ton molten iron through the top blast rifle.More hope in addition to make and handle the back slag amount below 20kg/ ton molten iron, be preferably in below the 10kg/ ton molten iron.Adopt the method for this invention, be utilized in winding-up oxygen molten iron liquid level zone direct dephosphorisation reaction and be the P fixed mechanism of main slag with the solid phase at its exterior lateral area fixing, do not add a large amount of CaF ₂And add a spot of refining agent, just can carry out dephosphorization treatment effectively.

Make effect of the present invention more effective, hope low-Si molten iron is carried out dephosphorization treatment.Just hope Si content below 0.15 quality %, hope below the 0.07 quality %, the molten iron that is preferably in below the 0.03 quality % carries out dephosphorization treatment, makes the stable only condition that produces dephosphorisation reaction of above-mentioned mechanism of utilizing like this.

As the mode of adding refining agent from the top blast rifle to the molten iron liquid level; Hope is at least a portion from the refining agent that the top blast rifle provides; Jet to the molten iron liquid level of winding-up oxygen; More hope at least a portion from the refining agent that the top blast rifle provides, jet to winding-up oxygen and on the fire point that the molten iron liquid level generates.In addition, preferably make at least a portion in the refining agent, jet oxygen to the molten iron liquid level as vector gas.Like this, owing to provide oxygen to make the effective scorification of refining agent, can effectively promote dephosphorisation reaction in the molten iron liquid level zone that generates lot of F eO.

Make CaF among the present invention ₂Addition below 2kg/ ton molten iron or do not add CaF in fact ₂Condition under, can carry out dephosphorization treatment effectively.

Hope among the present invention to be refined to P content below the P content (the ingredient standard value of steel) that crude steel requires at the dephosphorization of molten iron more than the 0.10 quality %, hope that more P content is below 0.01 quality % in the molten iron after the dephosphorization treatment.Like this, can proceed bessemerize in fact without slag making materials, in fact only carry out Decarburising and refining.

Under above pacing items, can adopt following various ideal embodiment in the present invention.

In the 1st embodiment, carry out dephosphorization treatment, make the feed speed B (kg/min/ ton molten iron) that converts to the CaO of the refining agent of molten iron liquid level winding-up and to the feed speed A (Nm of the oxygen of molten iron liquid level winding-up ³/ min/ ton molten iron) satisfy following (1) formula, hope is to satisfy following (2) formula.Like this, because the CaO amount of FeO growing amount that supply oxygen causes and supply obtains suitable balance, can obtain higher dephosphorization efficient.

0.3≤A/B≤7……(1)

1.2≤A/B≤2.5……(2)

In the 2nd embodiment; Use the container of hot metal ladle type or mixer type iron ladle car type as the container of the molten iron of packing into; Jet to the molten iron liquid level through top blast small of the stock oxygen and at least a portion refining agent, jet the gas that contains powder through immersion rifle and/or winding-up nozzle simultaneously and in molten iron, carry out dephosphorization treatment.Like this, in the dephosphorization treatment of the container that uses hot metal ladle type or mixer type iron ladle car type, molten iron can obtain suitable stirring, can obtain higher dephosphorization efficient.

In this 2nd embodiment, hope it is the part of refining agent through the powder that immerses rifle and/or the nozzle of jetting is jetted in molten iron, in addition, hope at 0.7Nm to the amount of oxygen of molten iron liquid level winding-up through the top blast rifle ³Below/min/ ton the molten iron.Being hopeful to make more than the 80 quality % of the refining dosage that in dephosphorization treatment, adds jets through the top blast rifle again effectively handles to the molten iron liquid level.In addition; In molten iron, jet under the situation of adding to the molten iron liquid level with through immersing rifle and/or winding-up nozzle jetting refining agent total amount in fact through the top blast rifle; Hope accounts for 20～80 quality % of refining agent total addition level through the refining agent addition of top blast rifle, can make like this to the effect of molten iron liquid level spray refining agent and the effect that causes molten iron to stir through winding-up in molten iron and obtain good balance.

In the 3rd embodiment, carry out dephosphorization treatment to the refining agent feed speed and the condition of speed following by satisfying (3) formula of supplying with oxygen and (4) formula of the winding-up of molten iron liquid level.Do not add the refining agent of unnecessary amount like this in the dephosphorization treatment later stage, can add the processing of the refining agent of minimum demand, so can carry out effective dephosphorization treatment with a spot of refining agent addition.

(C1/D1)＞(C2/D2)……(3)

C1＞C2……(4)

C1 wherein: the MV (kg/min/ ton molten iron) of the refining agent feed speed that the CaO in dephosphorization treatment early stage converts

C2: the MV (kg/min/ ton molten iron) of the refining agent feed speed that the CaO in dephosphorization treatment later stage converts

D1: the MV (Nm of dephosphorization treatment oxygen feed speed in earlier stage ³/ min/ ton molten iron)

D2: the MV (Nm of the oxygen feed speed in dephosphorization treatment later stage ³/ min/ ton molten iron)

In this 3rd embodiment, during dephosphorization treatment, refining agent feed speed and oxygen feed speed continuity and/or interim change that CaO is converted.

In the 4th embodiment; To the molten iron of Si content below 0.15 quality %; Carry out dephosphorization treatment through the top blast rifle to molten iron liquid level winding-up oxygen and at least a portion refining agent, the lime of the accumulation amount of amount of lime Wcao-P (kg/ ton molten iron) that in this dephosphorization treatment, obtains with following (5) formula simultaneously and the amount of lime Wcao-Si (kg/ ton molten iron) that obtains with following (6) formula as the refining agent interpolation.Can carry out effective dephosphorization treatment with the refining agent addition of subsistence level limit like this.

Wcao-P=(molten iron [P]-target [P]) * (10/62) * 56 * 3/ η cao ... (5)

Wherein, molten iron [P]: the P concentration (quality %) in the molten iron before the dephosphorization treatment

Target [P]: as the P concentration (quality %) in the molten iron after the dephosphorization treatment of target

η cao (lime efficient)=0.5～1

Wcao-Si=molten iron [Si] * (10/28) * 56 * 2 ... (6)

Wherein, molten iron [Si]: the Si concentration (quality %) in the molten iron before the dephosphorization treatment

In the 4th embodiment, hope that the above lime of 80 quality % of amount of lime Wcao-P (wherein, the Wcao-P that obtains with η cao=1) is jetted to the molten iron liquid level through the top blast rifle, effectively handle.In addition, as the refining agent that is equivalent to amount of lime Wcao-Si, can from the blast furnace slag that contains lime powder, lump lime, block Wingdale, unreacted CaO, select to use more than a kind.

In the 5th embodiment, with the refining agent of oxygen as vector gas, producing cup depth L at the molten iron liquid level is 200～500mm by the utilization winding-up oxygen of following (7) formula definition or winding-up in control.Make fire point provide the form of oxygen suitable like this, can add a small amount of refining agent and carry out more effective dephosphorization treatment to reaction zone.

L＝L ₀×exp{(-0.78×L _H)/L ₀}……(7)

L ₀＝63×{(F ₀₂/n)/d _t} ^2/3

L wherein _H: the height of the rifle of top blast rifle (mm)

F ₀₂: the speed (Nm that oxygen is provided through the top blast rifle ³/ hr)

N: the nozzle hole count of top blast rifle

d _t: the nozzle bore of top blast rifle (mm) (being the mean pore size of whole nozzle bores under the nozzle bore condition of different of a plurality of nozzle bores wherein)

In the 6th embodiment,, make CaF to the molten iron of Si content below 0.15 quality % ₂Addition below 1kg/ ton molten iron or do not add CaF in fact ₂Condition under, carry out dephosphorization treatment through the top blast rifle to molten iron liquid level winding-up oxygen and at least a portion refining agent, the molten iron temperature when making the dephosphorization treatment end simultaneously is 1360 ℃～1450 ℃.Like this, even in pyroprocessing, also can carry out dephosphorization treatment effectively, can fully guarantee the waste heat of back operation.

In the 7th embodiment, the material that absorbs the molten iron heat because of chemical reaction and/or pyrolysis is provided to the molten iron liquid level zone that oxygen is provided.Like this, can not hinder the scorification of refining agent, can suppress to provide the regional temperature of molten iron liquid level of oxygen to raise, therefore can obtain higher dephosphorization efficient.

In this 7th embodiment, hope to offer the fiery point that on the molten iron liquid level, produces because of through the oxygen of jetting having a part at least because of chemical reaction and/or pyrolysis absorb the material of molten iron heat.As the material that absorbs the molten iron heat because of chemical reaction and/or pyrolysis, hope from carbonic acid gas, water vapour, oxynitride, metal carbonate, metal hydroxides, to select more than a kind, hope especially from producing CO because of thermolysis ₂Or H ₂The metal carbonate of O, produce CO because of thermolysis ₂Or H ₂Select more than a kind in the metal hydroxides of O.In addition, wherein especially preferably from CaCO ₃, Ca (OH) ₂, CaMg (CO ₃) ₂More than a kind of middle selection.

In addition, in this 7th embodiment, replace as the part of the refining agent in CaO source or all, can be from absorb the CaCO of molten iron heat material as the refining agent resultant and because of chemical reaction and/or pyrolysis ₃, Ca (OH) ₂, CaMg (CO ₃) ₂The middle selection more than a kind offers the molten iron liquid level zone that is provided oxygen.In this embodiment, hope from CaCO ₃, Ca (OH) ₂, CaMg (CO ₃) ₂Have at least a part to offer the fiery point that produces on the molten iron liquid level in the middle material of selecting more than a kind through winding-up oxygen.

The 1st of above-described the inventive method～the 7th embodiment can be distinguished independent enforcement, also can implement the condition arbitrary combination of 2 above embodiments, and the condition of combination is many more, and the effect of the inventive method is good more.

Description of drawings

Fig. 1 is the figure of P relation with contents in slag amount and the molten iron of expression after the dephosphorization treatment.

The figure that Fig. 2 concerns for the slag amount after Si content in the molten iron of expression before the dephosphorization treatment and the dephosphorization treatment.

Fig. 3 is the explanatory view of a performance of the inventive method of expression use converter type container.

Fig. 4 is illustrated in the 2nd embodiment of the inventive method, and the interpolation refining dosage through the top blast rifle is with respect to the figure of the ratio of adding the refining agent total amount with the amount of lime relation that needs.

Fig. 5 is illustrated in the 2nd embodiment of the inventive method; In molten iron, jet whole refining agents under the situation of adding the figure that the refining agent addition through the top blast rifle concerns with respect to the ratio and the dephosphorization rate of refining agent total addition level to the winding-up of molten iron liquid level with through immersing rifle and/or winding-up nozzle through the top blast rifle.

Fig. 6 is the explanatory view of an example of the performance of the 2nd embodiment of expression the inventive method.

Fig. 7 for expression for the 3rd embodiment and the existing method of the inventive method, P content is 0.012 quality % in the molten iron after the dephosphorization treatment in order to make, the CaO unit consumption that needs and the figure of dephosphorization relationship between efficiency.

Fig. 8 is 4th embodiment and the existing method of expression for the inventive method, Si content and the figure that needs the amount of lime relation in the molten iron.

Fig. 9 is 4th embodiment and the existing method of expression for the inventive method, the figure of P relation with contents in the molten iron after the amount of lime that dephosphorization usefulness needs and lime efficiency eta cao and the dephosphorization treatment.

Figure 10 is illustrated in the 4th embodiment of the inventive method, from top blast rifle figure of P relation with contents the molten iron after the ratio X/Wcao-P of the amount of lime Wcao-P that the amount of lime X and the dephosphorization of molten iron liquid level winding-up are used and dephosphorization treatment.

Figure 11 is illustrated in the 5th embodiment of the inventive method, utilizes winding-up oxygen or winding-up with oxygen figure of P relation with contents as the refining agent of vector gas and in cup depth L that the molten iron liquid level produces and the molten iron after dephosphorization efficient and the dephosphorization treatment.

Figure 12 is illustrated in the 6th embodiment of the inventive method the CaF that does not add ₂Dephosphorization treatment in molten iron in molten iron temperature and the figure of dephosphorization lime relationship between efficiency after Si content and the dephosphorization treatment.

Figure 13 is illustrated in the 6th embodiment of the inventive method, and the molten iron temperature after the dephosphorization treatment is the CaF of 1360～1450 ℃ dephosphorization treatment ₂The figure of addition and dephosphorization lime relationship between efficiency.

Figure 14 is illustrated in the 7th embodiment of the inventive method, with top blast small of the stock oxygen, refining agent and the heat absorption material explanatory view to the presentation mode example of molten iron liquid level.

Figure 15 schematically illustrates in existing method and the inventive method with the converter type container, the explanatory view of the slag/metallic state when tapping a blast furnace beginning.

Figure 16 schematically illustrates in existing method and the inventive method with the converter type container, near the explanatory view of the slag/metallic state the iron notch in the latter stage of tapping a blast furnace.

The figure of P relation with contents in the molten iron after the ratio A/B of the feed speed B that Figure 17 is refining agent for the oxygen feed speed A among the embodiment of the 1st embodiment of expression the inventive method and CaO and the dephosphorization treatment.

Embodiment

In the past understanding dephosphorization of molten iron mechanism be to be added on CaO and SiO in the refining vessel because of providing oxygen to generate ₂, become molten mass after the FeO reaction, generate CaO-SiO ₂-FeO is evenly and has the slag of high dephosphorizing capacity, carries out dephosphorization of molten iron through the reaction of P in this slag and the molten iron.As preceding topic, consider flowability and the basicity that dephosphorizing capacity is confirmed slag of the slag of above-mentioned that kind with such dephosphorization mechanism, confirm under this basicity of slag, will reach the needed slag amount of target P simultaneously.In contrast; The inventor finds, compared with prior art, slag amount after the processing had under the condition that certain degree reduces; And then hope to make in the molten iron before handling Si content under the condition below the prescribed level; Utilization makes oxygen and refining agent jet to the treatment process of molten iron liquid level through the top blast rifle, according to the diverse mechanism of prior art, can carry out very effective dephosphorization refining.

Below, to the detailed content of the present invention that is the basis with such understanding with preferred embodiment describe.

In the methods of the invention; Utilization is added oxygen source and as the refining agent in CaO source in the container (refining vessel) of the molten iron of packing into; Carry out dephosphorization treatment as hot metal pretreatment; When making low-phosphorous molten iron, to molten iron liquid level winding-up oxygen and at least a portion refining agent, carry out dephosphorization treatment through the top blast rifle.Through the top blast rifle behind molten iron liquid level winding-up oxygen; Owing to generate lot of F eO with the ballistic oxygen of liquid level; Become the condition that is very beneficial for promoting refining agent scorification, utilize the zone that directly is provided to refining agent a large amount of generation FeO through the top blast rifle, can effectively promote the scorification of refining agent (CaO).

In addition, to molten iron liquid level winding-up oxygen and refining agent, also can use vector gas beyond the oxygen (N for example with the top blast rifle ₂, rare gas element such as Ar) to molten iron liquid level spray refining agent, even also hope in this case the part of refining agent or all jet to be provided (winding-up) oxygen the molten iron liquid level regional.This is because being provided the molten iron liquid level zone of oxygen is the position that generates FeO owing to the oxygen of supplying with, and through directly adding CaO to such liquid level zone, can effectively promote the scorification of CaO, and the contact efficiency of CaO and FeO also uprises simultaneously.In addition, in the molten iron liquid level zone of oxygen is provided, preferably make refining agent be provided to the zone that is called " fiery point " that produces owing to top blast oxygen.The molten iron liquid level zone of the top temperature that forms is impacted in the gas jet that this fire point is an oxygen; Owing to be that the oxidizing reaction that causes of oxygen is concentrated and the gas jet of oxygen causes the zone of stirring, so can be described as the zone of the most pronounced effects that can obtain providing CaO.In addition; On this meaning, say, be used for hoping to use oxygen to the vector gas that refining agent is jetted to the molten iron liquid level, in this case; Through jetting oxygen and refining agent together to the molten iron liquid level; Make refining agent directly supply to fiery point, its result, the efficient that contacts with FeO at the CaO of molten iron liquid level increases substantially.

In the methods of the invention, in the such interpolation oxygen and the mode of refining agent, be that the ultimate principle below utilizing makes dephosphorisation reaction effectively carry out being target.

That is, for the molten iron liquid level zone (hope is fiery point) that provides oxygen with optimum regime, during through top blast rifle spray refining agent (CaO), this CaO reacts and fusion (scorification) rapidly and at the FeO of fiery dot generation, forms the molten mass of CaO-FeO system.The molten mass of the CaO-FeO system that forms; Because the kinetic energy of oxygen is from being that the supply at center has the molten iron liquid level zone of oxygen to be pressed to the low zone of oxygen potential energy around it with the fire point, at first with molten iron in the Si reaction, FeO is reduced; Corresponding to Si content in the molten iron before handling, form 2CaOSiO ₂Etc. stable solid phase.In addition because after above-mentioned reaction made the Si content decrease to some degree in the molten iron, the molten mass of CaO-FeO system began and phosphorus reaction, form and be called 3CaOP ₂O ₅Same stable solid phase.Its result is with the generating of dephosphorization treatment, from being that the molten iron liquid level zone that is supplied to oxygen at center is become 2CaOSiO by a great deal of (or most of) that order is pressed to the slag of its exterior lateral area with the fire point ₂, 3CaOP ₂O ₅Stable solid phase exist.Because the solid phase slag that generates like this is highly stable, even the low also not fusion again of basicity of slag.Utilizing the slag in the zone that with the fire point is the center, directly carry out dephosphorisation reaction like this and to be pressed to its outside is that master's state exists with the solid phase, adds a spot of refining agent and just can carry out effective dephosphorization.

So in the method for the invention; Being conceived to be utilized in the fire point is direct dephosphorisation reaction and be the P fixed mechanism of master's slag in order to solid phase in its exterior lateral area in the molten iron liquid level zone at center; Effectively carry out dephosphorisation reaction; Only use separately to molten iron liquid level winding-up oxygen and refining agent, can not stablize the dephosphorisation reaction of realizing utilizing above-mentioned mechanism.Just for the stable dephosphorisation reaction of realizing utilizing above-mentioned mechanism; Adopt on the basis of the specific supply mode of above-mentioned oxygen and refining agent; To under the situation of enough few slag amount, handle; To make slag amount after the processing specifically below 30kg/ ton molten iron, hope below 20kg/ ton molten iron, to be preferably in below the 10kg/ ton molten iron.Consider from identical viewpoint the molten iron of dephosphorization treatment object hopes it is low-Si molten iron in addition, hope it is the molten iron of Si content below 0.15 quality % specifically, more hope the molten iron below 0.07 quality %, preferably the molten iron below the 0.03 quality %.

The reason of under the situation of a small amount of slag, handling in the present invention is following.For the dephosphorisation reaction that makes above-mentioned specific mechanisms effectively takes place, the oxygen through the top blast rifle must provide to the molten iron liquid level with so-called soft blow refining (low dynamic pressure).Just use in the dephosphorisation reaction of above-mentioned mechanism; With the fire point is that the supply at center has the molten iron liquid level zone of oxygen to become the main generation position of FeO; To this zone the also CaO and the FeO reaction of scorification are provided; Generating CaO-FeO is molten mass, through this CaO-FeO be molten mass directly with molten iron in P react, formed 3CaOP ₂O ₅Stable solid phase.And generate as prior art that slag amount is many, under the state of slag bed thickness; Supposing provides under the situation of oxygen with the soft blow refining; Because the oxygen jet flow can not the straight-flow furnace slag blanket; Can not suitably offer the molten iron liquid level to oxygen, the FeO that on the molten iron liquid level, generates is not enough, so CaO-FeO is that the growing amount of molten mass tails off.With hard blowing (high dynamic pressure) oxygen is provided on the other hand; Make the oxygen jet flow can connect the thick slag layer of generation; Because this provides the zone to become the strong mixing state; Even generate FeO, can not guarantee the FeO amount that needs in this case, so CaO-FeO is that the growing amount of molten mass also tails off also by the reduction of the C in the molten iron.Slag amount is many like this, can not stably guarantee all that with soft blow refining or hard blowing FeO and CaO-FeO are the growing amount of molten mass, also is difficult to make the stable generation of the dephosphorisation reaction that utilizes above-mentioned mechanism.Therefore in order suitably to the molten iron liquid level oxygen to be provided with the soft blow refining, carry out the dephosphorisation reaction of above-mentioned mechanism effectively, the restriction slag amount makes the enough thin conditio sune qua non that becomes of slag layer thickness.So below 30kg/ ton molten iron, be condition to handle the back slag amount in the present invention.In addition for above-mentioned reasons, it is the least possible to hope to handle the back slag amount, hopes especially below 20kg/ ton molten iron, more to hope below 10kg/ ton molten iron.

The reason of hoping low-Si molten iron is carried out dephosphorization treatment in addition in the present invention is following.As stated; In above-mentioned specific dephosphorization mechanism, to the molten iron liquid level zone that is provided oxygen (the main zone that generates of=FeO) that with the fire point is the center the also CaO and the FeO reaction of scorification are provided, generating CaO-FeO is molten mass; Through this CaO-FeO be molten mass directly with molten iron in P react and carry out dephosphorization; But the Si content in the molten iron is high, the CaO-FeO of generation be molten mass with the reaction of Si in be consumed, can not help above-mentioned direct dephosphorisation reaction fully.Therefore will stablize the dephosphorisation reaction that carries out above-mentioned mechanism, only condition is to satisfy the condition of slag amount after the above-mentioned processing, and enough low by the Si content in the molten iron of dephosphorization treatment.Poor words of Si in the molten iron in addition are because SiO ₂Growing amount also few, help reducing and handle the back slag amount.Therefore hope in the present invention to Si content below the 0.15 quality %, more hope below the 0.07 quality %, the molten iron that is preferably in below the 0.03 quality % carries out dephosphorization treatment.

The so-called back slag amount of handling is meant the slag amount in refining vessel (container of the molten iron of packing into) when dephosphorization treatment finishes among the present invention.Have again this handle back slag amount can use the mass balance Calculation Method of the CaO concentration (slag assay value) from add amount of lime and slag, in slag the tracer of interpolation yttrium oxide and strontium oxide etc., the method for the tracer concentration in the slag after the analyzing and processing, the method for directly measuring slag thickness wait and obtain.

The test-results of Fig. 1 for carrying out according to the inventor, the slag amount after the expression dephosphorization treatment and the figure of the P relation with contents in the molten iron have represented to handle the MV of P content in the molten iron of back and the amplitude of deviation.Fig. 1 is at 5kg/ ton molten iron～10kg/ ton molten iron, surpass 10kg/ ton molten iron～20kg/ ton molten iron, surpass 20kg/ ton molten iron～30kg/ ton molten iron, surpass 30kg/ ton molten iron～40kg/ ton molten iron, surpass various the processing back slag amount scope of 40kg/ ton molten iron～50kg/ ton molten iron, accumulates the figure of P content in the molten iron after the dephosphorization treatment of 6～72ch.

In this test, at the molten iron of blast furnace casting at the casting house of blast furnace or in hot metal ladle, carry out desiliconization as required and handle, in hot metal ladle, carry out the desulfurization processing with mechanical stirring then, after this in converter type container (300 tons), carry out dephosphorization treatment.Hot metal composition before the dephosphorization treatment is C:4.5～4.7 quality %, Si:0.01～0.28 quality %, Mn:0.15～0.25 quality %, P:0.10～0.11 quality %, S:0.001～0.003 quality %.The refining agent that dephosphorization is used uses the lime powder below the particle diameter 1mm, is it that vector gas is jetted to the molten iron liquid level with oxygen through the oxygen rifle.In refining agent, do not add CaF ₂Duration of blast stuck-at-0 minute in order to stir molten iron, provides 0.05～0.15Nm from furnace bottom ³The nitrogen of/min/ ton molten iron.The unit consumption of lime and oxygen changes according to Si content in the molten iron, removes delime, oxygen desiliconization part (2 calcium-silicates: form 2CaOSiO together ₂The stoichiometric calculation part) value be decided to be fixed 3.5kg/ ton molten iron, 9Nm respectively ³/ ton molten iron.Molten iron temperature before and after the dephosphorization treatment is decided to be 1250～1350 ℃.Calculated processing back slag amount from the amount of lime of interpolation and the mass balance of the CaO concentration the slag (slag assay value).

The P content of handling after the slag amount many more dephosphorization treatment of back according to Fig. 1 is also high more, and the deviation of the upper limit one side is also big more.In contrast, handle the back slag amount under the situation below the 30kg/ ton molten iron, the upper limit one lateral deviation difference of P content reduces significantly, and P content is 0.020 quality % to the maximum.Handle the back slag amount under the situation below the 20kg/ ton molten iron, the P content after the dephosphorization treatment in the molten iron is 0.015 quality % to the maximum, handles the back slag amount under the situation below the 10kg/ ton molten iron, and the P content after the dephosphorization treatment in the molten iron is 0.010 quality % to the maximum.The present invention for reason given above hopes to handle the back slag amount below 30kg/ ton molten iron, more hopes below 20kg/ ton molten iron, to be preferably in below the 10kg/ ton molten iron.

Fig. 2 carries out Si content and the figure that handles back slag amount relation in the molten iron before the dephosphorization treatment of Fig. 1 when testing for expression.Under this figure Si content is high in the molten iron before processing situation, the lime quantitative change of interpolation is many, and slag amount also increases, so slag amount is with to handle in the preceding molten iron Si content closely related.Therefore to judge in order making and to handle the back slag amount below 30kg/ ton molten iron, must make in the molten iron before the dephosphorization treatment Si content below 0.15 quality %.Can to judge equally in order making and to handle the back slag amount below 20kg/ ton molten iron; Must make in the molten iron before the dephosphorization treatment Si content below 0.07 quality %; And then handle the back slag amount below 10kg/ ton molten iron in order to make, must make in the molten iron before the dephosphorization treatment Si content below 0.03 quality %.According to above reason; To carry out dephosphorization treatment to the molten iron of Si content below 0.15 quality % in the present invention; Hope is carried out dephosphorization treatment to the molten iron of Si content below 0.07 quality %, preferably the molten iron of Si content below 0.03 quality % is carried out dephosphorization treatment.

Said just like preceding again; The low words of Si content in the molten iron; The CaO-FeO that generates is that the ratio of molten mass and Si reaction consumes tails off, and can obtain promoting to be the effect of the dephosphorisation reaction of molten mass with CaO-FeO directly, can think that the result of Fig. 1 has reflected such effect.

Si content can carry out following adjustment in the molten iron before the dephosphorization treatment.

Molten iron is provided by the equipment of manufacturing molten iron such as blast furnace; As the method that reduces the molten iron Si content of making; Carry out pre-treatment and wait the total Intake Quantity that reduces the silicic acid part making raw material that molten iron uses, or the biasing of carrying out cold operation and coke in order to be suppressed at the silicic acid reduction reaction in the stove such as blast furnace method such as pack into.Therefore the molten iron Si content made from blast furnace etc. can not carry out desiliconization to such molten iron to handle, and carry out dephosphorization treatment under the situation below the 0.15 quality %.

Si content at the molten iron made from blast furnace etc. surpasses under the situation of 0.15 quality % on the other hand; Before dephosphorization treatment, want earlier in the casting house of blast furnace and hot metal ladle etc., to carry out the desiliconization processing, Si content reaches under the situation below the 0.15 quality % and carries out dephosphorization treatment in the molten iron before making dephosphorization treatment.

It is to carry out through adding solid oxygen source and oxygen in the molten iron to that the desiliconization of general molten iron is handled; For example adopt through being contained in solid oxygen sources such as agglomerated powder and rolling iron scale from above the molten iron liquid level and in molten iron, adding to jetting, or oxygen to winding-up of molten iron liquid level or winding-up is added in molten iron method.

Desiliconization of hot metal is handled except at the casting house of blast furnace with the hot metal ladle in addition, for example also can be from the casting house of blast furnace interpolation oxygen source and carrying out to the transport box mobile molten iron stream of hot metal ladle etc.Also can be blown into stirring gas in the molten iron in container in order to improve desiliconization efficient in addition, or the CaO source of adding unslaked lime etc. adjusts the basicity of slag, reduce the red stone in the desiliconization slag as far as possible, improve reduction efficiency.

Carry out under the situation of dephosphorization treatment after handling through desiliconization of hot metal, the slag to desiliconization slag etc. carries out deslagging in advance, hopes to suppress to sneak into the silicic acid part as far as possible, carries out dephosphorization treatment effectively.Therefore from molten iron, separate slag with mechanical slag discharging device or manual operations before the dephosphorization treatment, carry out dephosphorization treatment then.

In the methods of the invention; Jet with top blast small of the stock oxygen and refining agent and in the method for molten iron liquid level, to have no particular limits; For example also can be respectively in a plurality of rifles hole of top blast rifle; Only to the molten iron liquid level oxygen being provided from a part of rifle hole, is that vector gas provides refining agent to the molten iron liquid level from other rifle holes with the gas (the for example rare gas element of nitrogen and Ar etc.) beyond oxygen or the oxygen.Can add refining agent to the molten iron liquid level that oxygen is provided like this.Use rifle central authorities that main rifle hole is arranged in addition in this case; The top blast rifle that a plurality of sublances hole is arranged around it; Hoping to offer the molten iron liquid level to oxygen from the sublance hole respectively, is that vector gas provides refining agent to the molten iron liquid level from main rifle hole with the gas beyond oxygen or the oxygen.In addition also can to winding-up oxygen be that different top blast rifles is used in vector gas spray refining agent with the gas beyond oxygen or the oxygen.But the refining agent that all situations will make down above-mentioned that kind is scorification most effectively, and the vector gas of hoping refining agent especially is an oxygen.

The oxygen that uses in the present invention can be purity oxygen, also can be oxygen containing gas.As the oxygen source that in refining vessel, adds, except oxygen, can use the solid oxygen source of red stone (for example agglomerated powder, rolling iron scale) etc., can adopt and pack into from above and be injected into the medium any method of molten iron.But in order to utilize the dephosphorization of molten iron that (winding-up) oxygen is provided to the molten iron liquid level to above-mentioned that kind effectively; Hope that the oxygen source more than 50% that adds in the refining vessel is the oxygen that offers the molten iron liquid level through the top blast rifle, hope that more the oxygen source more than 70% that adds in the refining vessel is the oxygen that offers the molten iron liquid level through the top blast rifle.

Except part of oxygen is jetted to the method the molten iron liquid level, for example also can be to be injected into method in the molten iron etc. oxygen is provided in molten iron through the nozzle that is blown into that immerses rifle, is arranged on dress molten iron container side wall and bottom.

Be the CaO of lime etc. that refining agent (is main refining agent with CaO) uses as refining agent generally.Use powder through the top blast rifle to the refining agent of molten iron liquid level winding-up in addition.

Except utilizing the top blast rifle to molten iron liquid level spray refining agent; Also can utilizing packs a part of refining agent into and be injected in the molten iron adds from above, and the refining dosage of hoping in this case to add with these methods is below 20 quality % of refining agent total amount.Use the 20 quality % that surpass total amount except the ratio of utilizing the method for top blast rifle to molten iron liquid level spray refining agent to add refining agent, utilizing jets refining agent and oxygen together promotes the effect of dephosphorisation reaction that the tendency of reduction is arranged to the molten iron liquid level.

Improve dephosphorization efficient, hope molten iron is carried out gas stirring.This gas stirring for example can adopt through immersing rifle, being arranged on the nozzle that is blown into of adorning molten iron container side wall and bottom, and carries out the blowing inert gas of nitrogen or Ar etc. to the method in the molten iron.In order to obtain sufficient molten iron whipping performance, hope that such stirring gas delivery volume is at 0.02Nm ³More than/min/ ton the molten iron, in addition molten iron stirred strong because the C in the molten iron makes the FeO reductive speed of generation become excessive, so hope at 0.3Nm ³Below/min/ ton the molten iron.

The container (refining vessel) that is used for the dress molten iron of dephosphorization treatment sees that from can fully guaranteeing the viewpoint of freeboard the converter type container is best, for example can use any containers such as hot metal ladle and mixer type iron ladle car.

Fig. 3 representes a performance with the inventive method of converter type container; 1 is that converter type container, 2 is that top blast rifle, 3 is for being arranged on the bottom blowing nozzle of furnace bottom; In this example; As vector gas, jet oxygen to metal bath surface to refining agent, jet in molten iron from bottom blowing nozzle 3 simultaneously and stir gas from top blast rifle 2.

In existing dephosphorization treatment,, in fact must add CaF in order to promote the scorification of CaO ₂(fluorite), but consider the influence of F in recent years to environment, even in the refining of steel, also require control CaF ₂Usage quantity.In this, the inventive method is not added CaF in fact ₂(just, do not add CaF except in refining agent, containing as the inevitable inclusion ₂) or only add a spot of CaF ₂Situation under, obtain high dephosphorization efficient.Even therefore add CaF for the scorification that promotes CaO ₂Situation under, this addition is hoped below 1kg/ ton molten iron also below 2kg/ ton molten iron.Of the back in addition, to compare with existing method in the present invention, the effect that can obtain making the slag number of dropouts after the processing to reduce is not significantly added CaF owing to can utilize ₂Or control its addition considerably lessly, and can make the flowability of slag lower, can further improve above-mentioned effect.

The P content of molten iron is more than 0.10 quality % before the general dephosphorization treatment; And the P content of hoping to be refined to its dephosphorization the crude steel requirement in the present invention; Just dephosphorization is refined to the ingredient standard value following (generally below 0.020 quality %) of steel, more hopes below 0.010 quality %.Bessemerize what proceed like this, the slag making materials of not packing in fact in fact only carries out Decarburising and refining, can obtain Decarburising and refining is extremely simplified, and shortens refining time; 2. can reduce the slag growing amount of Decarburising and refining effectively; 3. in Decarburising and refining owing to do not use slag making materials in fact, so add under the situation of manganese ore, can obtain the very high Mn recovery as the manganese source.

Several ideal embodiments in the face of the inventive method describe down.Through the embodiment of the present invention method, dephosphorisation reaction efficient is further improved in the described below embodiment.

In the 1st embodiment of the present invention, be to carry out that refining agent to molten iron liquid level winding-up is converted into the feed speed B (kg/min/ ton molten iron) of CaO and to the feed speed A (Nm of the oxygen of molten iron liquid level winding-up ³/ min/ ton molten iron) to satisfy the dephosphorization treatment of following (1) formula.

0.3≤A/B≤7……(1)

In addition in order to obtain higher dephosphorisation reaction efficient, hope to carry out that refining agent to the winding-up of molten iron liquid level is converted into the feed speed B (kg/min/ ton molten iron) of CaO and to the feed speed A (Nm of molten iron liquid level winding-up oxygen ³/ min/ ton molten iron) to satisfy the dephosphorization treatment of following (2) formula.

1.2≤A/B≤2.5……(2)

Result according to inventor's research recognizes with jetting oxygen and refining agent in the method for molten iron liquid level; Dephosphorisation reaction will change according to the feed speed of oxygen and the feed speed of CaO (refining agent); Generate FeO in the molten iron liquid level zone that is supplied to oxygen specifically, and have the desirable feed speed of growing amount corresponding C aO therewith.Too small words of oxygen feed speed in the ratio of the feed speed of oxygen and CaO wherein; Because the molten iron liquid level zone supplying with oxygen can not generate and the corresponding FeO of CaO feed rate; Can not carry out the scorification (generating CaO-FeO is molten mass) of CaO; Do not have the state of scorification to exist with CaO, can not play the effect of effective dephosphorization.The oxygen feed speed is excessive on the other hand, and the CaO that needs with respect to the dephosphorization of oxygen supply amount is not enough, and can not generate enough CaO-FeO in this case is molten mass.Therefore under various situation, all become the unfavourable condition in the dephosphorization that utilizes above-mentioned dephosphorisation reaction mechanism, have the tendency that can not obtain high dephosphorization speed.The oxygen feed speed is excessive in addition, and the invalid oxygen quantitative change except the oxygen that dephosphorization needs is many, because it is by consumption such as decarburizations, so heat source insufficiency in the operation of back can cause the running cost in carbonization treatment significantly to increase.

Above-mentioned A/B less than 0.3 situation under because the feed rate of CaO is superfluous with respect to the oxygen feed rate, can not generate and the corresponding FeO of CaO feed rate in the molten iron liquid level zone of supplying with oxygen.Therefore the scorification of the CaO that supplies with (generating CaO-FeO is molten mass) can not fully be carried out, and does not have the state of scorification to exist with CaO, can not play the effect of effective dephosphorization, so dephosphorization speed has the tendency of reduction.A/B surpasses 7 on the other hand, and needed CaO is not enough with respect to the dephosphorization of oxygen feed rate, is molten mass owing to can not generate enough CaO-FeO in this case, so dephosphorization speed has the tendency of reduction.Through making above-mentioned A/B in 1.2～2.5 scopes, the balance of FeO growing amount that supply oxygen causes and the feed rate of CaO is preferably, can obtain extra high dephosphorisation reaction efficient in addition.

The 2nd embodiment of the present invention is the dephosphorization treatment method of carrying out with hot metal ladle type or mixer type iron ladle car type container; In the dephosphorization treatment of using hot metal ladle or mixer type iron ladle car type refining vessel to carry out; Jet to the molten iron liquid level through top blast small of the stock oxygen and at least a portion refining agent, jet the gas that contains powder in molten iron through immersing rifle and/or nozzle simultaneously.

The result that the inventor studies the dephosphorization method for molten iron of more effectively using hot metal ladle type or mixer type iron ladle car type refining vessel shows; Jetting to the molten iron liquid level through top blast small of the stock oxygen and refining agent, is very effective through immersing the method that gas that handles such as rifle contain powder jets in the molten iron simultaneously.

In this 2nd embodiment, hope from the top blast rifle to the amount of oxygen (sending the oxygen amount) of molten iron liquid level winding-up at 0.7Nm ³Below/min/ ton the molten iron.From the excess oxygen that the top blast rifle provides, possibly produce sometimes because slag foaming makes slag blow out from refining vessel.Through making the oxygen amount that provides from the top blast rifle at 0.7Nm ³Below/min/ ton the molten iron, can suppress slag foaming, can stably operate.

In this 2nd embodiment; Also be except jetting refining agent to the molten iron liquid level with the top blast rifle; Also can pack a part of refining agent from above into or in molten iron, inject and add, also hope in this case to account for more than the 80 quality % of refining agent total amount with the refining dosage that the top blast rifle is jetted to the molten iron liquid level.The refining agent ratio of utilizing the top blast rifle to add to the molten iron liquid level is lower than 80 quality % of total amount, and utilizing jets refining agent and oxygen together promotes the effect of dephosphorisation reaction that the tendency of reduction is arranged to the molten iron liquid level.

Fig. 4 is the basis with the test-results that the inventor carries out; The figure of the refining dosage of top blast rifle interpolation with respect to ratio with the amount of lime relation that needs of refining agent total addition level passed through in expression; In this test; To the P content in the hot metal ladle type container (150 tons) of packing into: 0.10～0.11 quality %, Si content: the molten iron below the 0.07 quality %, as with oxygen (4.5～5.0Nm ³/ ton molten iron) is lime powder refining agent, particle diameter 1mm (0～6kg/ ton molten iron) of vector gas, jets to the molten iron liquid level, be blown into powder through the immersion rifle simultaneously and carry out dephosphorization treatment (treatment time: 15 minutes) from the top blast rifle.Amount through immersing rifle winding-up powder is fixed on 90kg/min.The lime part of the remnants that the part of this powder or whole use need, not enough part is used dust (Fe content is 40 quality %) or coke powder.In this dephosphorization treatment, do not add CaF in the refining agent ₂, handling the back slag amount is below the 20kg/ ton molten iron.Jet to the lime feed speed B (kg/min/ ton molten iron) of molten iron liquid level with to the feed speed A (Nm of molten iron liquid level winding-up oxygen ³/ min/ ton molten iron) A/B ratio is 2.0.The lime addition after in the scope of Wcao-P (kg/ ton molten iron) and Wcao-Si (kg/ ton molten iron) total of (5) formula of stating and (6) formula regulation.Utilizing winding-up in addition is the refining agent of vector gas with oxygen, is controlled in the scope of 200～500mm at the cup depth L (stating the L value of (7) formula definition after using) that the molten iron liquid level produces.Making the molten iron temperature of dephosphorization treatment front and back is 1300～1320 ℃.Handling the back slag amount is calculated by the mass balance of adding CaO concentration (slag assay value) in amount of lime and the slag.Fig. 4 has represented to make the amount of lime of handling P content needs when 0.02 quality % is following in the molten iron of back.

According to Fig. 4, increase with the ratio of the refining agent of supplying with through the top blast rifle with respect to the refining agent total amount, the amount of lime that the amount of lime minimizing, particularly this ratio that needs needs when 80 quality % are above reduces to minimum.

Powder kind to jetting together in the molten iron with gas has no particular limits, and for example can use dust-like that such iron works such as a part, converter dust of the refining agent of a part of lime powder more than a kind or 2 kinds etc. produce, coke powder etc. is red stone, the CaCO of main powder, sintering breeze and rolling iron scale etc. with the carbon source ₃, Ca (OH) ₂, CaMg (CO ₃) ₂Deng powder.

Wherein use under the situation of refining agent of lime powder etc. as powder, the refining agent of winding-up is heated during in molten iron, float, the fusion of the slag of promotion on floating to the molten iron liquid level time.

The dust-like that uses iron work to produce in addition can effectively utilize refuse.Just,, needed to carry out processing such as pelletizingization from easy-to-use viewpoint in the past, in this embodiment, do not need such energy of pelletizingization and cost, can directly utilize again powder in order to utilize it more again because dust-like is a powdery.Be main powder carburetting in molten iron in addition with the carbon source, effective thermal source in the operation under becoming.In addition, CaCO ₃, Ca (OH) ₂, CaMg (CO ₃) ₂Deng powder in molten iron, carry out thermolysis, produce gas (CO ₂, H ₂O), this gas helps to strengthen molten iron and stirs, and the CaO that thermolysis simultaneously generates has the function of refining agent.Croci becomes the part of oxygen source in molten iron in addition.

Gas (vector gas) kind of in molten iron, jetting with powder also has no particular limits, and can use oxygen (purity oxygen or oxygen containing gas), N ₂Or rare gas element such as Ar etc.Wherein use under the situation of blowing oxygen refining agent, so-called transient response promotes reaction in the time of can expecting to be utilized in the molten iron come-up.Owing to supply with oxygen from immersing rifle or nozzle, can generate FeO at the front end of rifle and nozzle, the life-span of rifle or nozzle becomes problem.In contrast, using N ₂Or under the situation of rare gas element such as Ar, can not be desirably in the effect of reaction aspect, but the life-span of rifle and nozzle is longer than the situation of using oxygen.Therefore can consider to comprise the kind of the total cost selection using gas of rifle and nozzle life etc.

As the device of spray refining agent in molten iron, can use and immerse rifle or be arranged on the nozzle that is blown on the refining vessel, or use its two kinds.Be blown into nozzle and can use bottom blowing nozzle or the horizontal nozzle that blows any ways such as nozzle.

In this external this 2nd embodiment; Utilization is jetted in molten iron to the winding-up of molten iron liquid level with through immersion rifle and/or nozzle through the top blast rifle and is added under the situation of whole in fact refining agents, hopes 20～80 quality % for the refining agent total amount through the refining dosage that the top blast rifle adds.The words that surpass 80 quality % of refining agent total amount through the top blast rifle to the refining agent ratio of molten iron liquid level winding-up; Because the molten iron mixing effect that the spray refining agent causes in molten iron is little; So be difficult to obtain the stirring power of dephosphorisation reaction needs; Be less than on the other hand under the situation of 20 quality %, can not fully obtain above-mentioned effect because of the promotion scorification that causes to molten iron liquid level spray refining agent.

Fig. 5 is the basis with the test-results that the inventor carries out; In molten iron, jetting and adding under the situation of whole refining agents to molten iron liquid level winding-up with through immersing rifle and/or being blown into nozzle through the top blast rifle; Expression is added refining dosage through the top blast rifle and is accounted for the ratio of refining agent total amount and the figure of dephosphorization relationship between efficiency; In this test; To the P content in the hot metal ladle type container (150 tons) of packing into: 0.10～0.11 quality %, Si content: the molten iron below the 0.07 quality %, as with oxygen (4.5～5.0Nm ³/ ton molten iron) be lime powder refining agent, particle diameter 1mm (0～6kg/ ton molten iron) of vector gas; Jet to the molten iron liquid level from the top blast rifle, be blown into the residue lime part (0～6kg/ ton molten iron) that needs through the immersion rifle simultaneously and carry out dephosphorization treatment (treatment time: 15 minutes).In this dephosphorization treatment, do not add CaF in the refining agent ₂, handling the back slag amount is below the 20kg/ ton molten iron.Jet to the lime feed speed B (kg/min/ ton molten iron) of molten iron liquid level with to the feed speed A (Nm of molten iron liquid level winding-up oxygen ³/ min/ ton molten iron) ratio A/B is 2.0.The lime addition after in the scope of Wcao-P (kg/ ton molten iron) and Wcao-Si (kg/ ton molten iron) total of (5) formula of stating and (6) formula regulation.Utilizing winding-up in addition is the refining agent of vector gas with oxygen, is controlled in the scope of 200～500mm at the cup depth L (stating the L value of (7) formula definition after using) that the molten iron liquid level produces.Making the molten iron temperature of dephosphorization treatment front and back is 1300～1320 ℃.Handling the back slag amount is calculated by the mass balance of adding CaO concentration (slag assay value) in amount of lime and the slag.

Be lower than 20 quality %, reducing significantly through the refining agent ratio of top blast rifle according to Fig. 5 to the winding-up of molten iron liquid level above dephosphorization efficient in the zone of 80 quality %.

When Fig. 6 handles in blast-melted bag type dephosphorization equipment, carrying out dephosphorization of molten iron, be applicable to the example of this embodiment.According to Si content from the molten iron of blast furnace casting, the words that are necessary carry out handling in the desiliconization of the casting house desiliconization of blast furnace etc. before dephosphorization treatment.Dephosphorization treatment is to pack molten iron in the blast-melted bag 4 into, injects lime powders (refining agent) from immersing rifle 5, jets lime powder (refining agent) to the molten iron liquid level together from top blast rifle 2 and oxygen simultaneously.The feed speed of the lime powder that inject this moment can fully stir molten iron.

In the 3rd embodiment of the present invention, to satisfy under following (3) formula and (4) formula condition at feed speed and to carry out dephosphorization treatment to the refining agent feed speed of molten iron liquid level winding-up and oxygen.

(C1/D1)＞(C2/D2)……(3)

C1＞C2……(4)

Wherein, C1: at the MV (kg/min/ ton molten iron) of the dephosphorization treatment refining agent feed speed that is converted into CaO in earlier stage

C2: at the MV (kg/min/ ton molten iron) of the dephosphorization treatment refining agent feed speed that is converted into CaO in earlier stage

D1: at the MV (Nm of dephosphorization treatment oxygen feed speed in earlier stage ³/ min/ ton molten iron)

D2: at the MV (Nm of the oxygen feed speed in dephosphorization treatment later stage ³/ min/ ton molten iron)

Because the P content in dephosphorization treatment molten iron in early stage is high; The zone that becomes the mobile domination full responsiveness of (P) in the big slag of dephosphorization speed change that the refining agent feed speed is big; P content step-down in dephosphorization treatment later stage molten iron in contrast; [P] in the metal be to the mobile domination full responsiveness of conversion zone, so compare in earlier stage with dephosphorization treatment, the ratio of dephosphorizing effective refining agent reduced.Therefore under above-mentioned specific mode; The dephosphorization treatment later stage with respect to dephosphorization treatment early stage the feed speed through the refining agent that reduces to supply with and oxygen to the molten iron liquid level than the feed speed of (refining agent feed speed/oxygen feed speed) and refining agent, can under the refining agent situation of interpolation less amount, carry out dephosphorization treatment effectively.

In the methods of the invention, since above-mentioned, in order to improve the reactivity worth of refining agent effectively, can add necessary minimal refining agent in the dephosphorization treatment later stage, carry out dephosphorization treatment effectively.

Fig. 7 is in converter type dephosphorization refining furnace (300 tons), following 1., do not add CaF under 2. the condition ₂Carry out dephosphorization treatment, research will make the CaO unit consumption that needs when the P content in the molten iron is 0.012 quality % after the dephosphorization treatment and the figure of dephosphorization relationship between efficiency.

1. the feed speed C (kg/min/ ton molten iron) that makes the refining agent of jetting to the molten iron liquid level be converted into CaO fixes during entire treatment, and makes the above-mentioned feed speed C and the oxygen feed speed D (Nm of refining agent ³/ min/ ton molten iron) ratio C/D is fixing during entire treatment, carries out dephosphorization treatment.

2. at C1: MV (kg/min/ ton molten iron), the C2 of the dephosphorization treatment refining agent feed speed that is converted into CaO in earlier stage: the MV of the refining agent feed speed that is converted into CaO in dephosphorization treatment later stage (kg/min/ ton molten iron), D1: the MV (Nm of dephosphorization treatment oxygen feed speed in earlier stage ³/ min/ ton molten iron), D2: the MV (Nm of the oxygen feed speed in dephosphorization treatment later stage ³/ min/ ton molten iron) under the situation, under the condition of (C1/D1)＞(C2/D2), carries out dephosphorization treatment.

It is 2CaOSiO that the desiliconization of thinking composition is arranged again ₂, remove the desiliconization composition, the dephosphorization efficiency eta _CaODefine with following formula.

η _CaO＝[{([％P] _i-[％P] _f)/(31×2)}×56×3×10]/[W _CaO-{([％Si] _i-[％Si] _f)/28}×56×2×10]

Wherein, W _CaO: the unit consumption of CaO (kg/ ton molten iron)

[%P] _i: the P content (quality %) before the dephosphorization treatment in the molten iron

[%P] _f: the P content (quality %) after the dephosphorization treatment in the molten iron

[%Si] _i: the Si content (quality %) before the dephosphorization treatment in the molten iron

[%Si] _f: the Si content (quality %) after the dephosphorization treatment in the molten iron

In this test, in blast furnace discharge yard and hot metal ladle, make blast-melted desiliconization as required after, desulfurization in hot metal ladle is transferred to this molten iron and is carried out dephosphorization treatment in the converter type container.P content is that 0.10～0.11 quality %, Si content are below the 0.07 quality % in the molten iron before the dephosphorization treatment.As refining agent only with not containing CaF ₂Be main unslaked lime with CaO.Mainly use oxygen as oxygen source in addition, utilize and to add from the top blast rifle it to the winding-up of molten iron liquid level, for a part and with the interpolation of solid oxygen source (iron ore).The refiner feed rate is 4.6～9.0kg/ ton molten iron, and the oxygen feed rate is 8.6～13.6Nm ³/ ton molten iron.In addition, about dephosphorization treatment 1., making C/D is 0.50～0.69kg/Nm ³About dephosphorization treatment 2., to make C1 be 0.88～1.00kg/min/ ton molten iron, make C2 is 0.30～0.39kg/min/ ton molten iron, make C1/D1 is 0.60～0.83kg/Nm ³, to make C2/D2 be 0.38～0.48kg/Nm ³, make (C1/D1) * 56～72%=(C2/D2).Make slag amount after the processing below 20kg/ ton molten iron.The addition that makes lime is in the scope that adds up of amount of lime Wcao-P (kg/ ton molten iron) that stipulates with following (5) formula and (6) formula and amount of lime Wcao-Si (kg/ ton molten iron).In addition, utilization, is controlled in the scope of 200～500mm at the cup depth L (stating the L value of (7) formula definition after using) that the molten iron liquid level produces as vector gas spray refining agent with oxygen.Making the molten iron temperature of dephosphorization treatment front and back is 1300～1320 ℃.Handle the back slag amount, calculate by the mass balance of adding CaO concentration (slag assay value) in amount of lime and the slag.

According to Fig. 7, judge in dephosphorization treatment 2., to compare the CaO unit consumption few with situation 1., and dephosphorization efficient is high.This is owing under situation 2., can not add unnecessary refining agent in the refining later stage and carry out sufficient dephosphorization, so obtain high dephosphorization efficient.

In this 3rd embodiment; It is (C1/D1)＞(C2/D2), C1＞C2 that utilization makes refining agent feed speed and oxygen feed speed; Can obtain desirable effect, special hope makes its scope at (C1/D1) * 30～80%=(C2/D2), C1 * 30～80%=C2.Under the situation of (C1/D1) * 30%＞(C2/D2), C1 * 30%＞C2; Because the refining agent feed rate is not enough; Dephosphorization efficient has the tendency of reduction; Under the situation of (C1/D1) * 80%＜(C2/D2), C1 * 80%＜C2, the refining agent feed rate unnecessary owing to the dephosphorization treatment later stage increases, so dephosphorization efficient has the tendency of reduction on the other hand.

In this 3rd embodiment; During dephosphorization treatment (early stage of dephosphorization treatment and later stage); As long as it is just passable according to above-mentioned condition supply refining agent and oxygen; Therefore the mode that refining agent feed speed and oxygen feed speed is changed is arbitrarily, can change continuously or change stage by stage, or use this vary in two ways.

In the 4th embodiment of the present invention; To Si content is the molten iron below the 0.15 quality %; Through the top blast rifle to molten iron liquid level winding-up oxygen and at least a portion refining agent; Carry out dephosphorization treatment, in this dephosphorization treatment, will add simultaneously the lime of the accumulation amount of amount of lime Wcao-P (kg/ ton molten iron) that obtains with following (5) formula and the amount of lime Wcao-Si (kg/ ton molten iron) that obtains with following (6) formula as refining agent.

Wcao-P=(molten iron [P]-target [P]) * (10/62) * 56 * 3/ η cao ... (5)

Wherein, molten iron [P]: P content (quality %) in the molten iron before the dephosphorization treatment

Target [P]: as P concentration (quality %) in the molten iron after the dephosphorization treatment of target

η cao (lime efficient)=0.5～1

Wcao-Si=molten iron [Si] * (10/28) * 56 * 2 ... (6)

Wherein, molten iron [Si]: Si content (quality %) in the molten iron before the dephosphorization treatment

As stated, in existing dephosphorization treatment technology, be to be that even liquid phase is preceding topic to keep slag, distribute Lp to confirm slag amount in advance based on phosphorus, therefore in fact fixedly P, Si need the refining agent of the above amount of necessary refining amount.In contrast; Be to have utilized in the molten iron liquid level zone that is the center direct dephosphorisation reaction in the present invention with the fire point and be that master's slag carries out P fixed mechanism in order to solid phase in its exterior lateral area; Therefore with the MIN refining dosage of above-mentioned needs, dephosphorisation reaction is effectively carried out.

In fact the amount of lime that consumes for fixedly P and Si can be calculated with following formula.In following formula, the amount of lime (kg/ ton molten iron) that Wcao-Po consumes for fixing P, Wcao-Sio is the fixing amount of lime (kg/ ton molten iron) of Si consumption.

Wcao-Po=(molten iron [P]-target [P]) * (10/62) * 56 * 3

Target [P]: as P content (quality %) in the molten iron after the dephosphorization treatment of target

Wcao-Sio=molten iron [Si] * (10/28) * 56 * 2

If adding the lime total amount is Total CaO (kg/ ton molten iron), help the lime efficiency eta cao of dephosphorization can use computes.

η cao=Wcao-P/ (total CaO-Wcao-Sio)

In this embodiment, stipulate that at first this lime efficiency eta cao is 0.5～1.The lower limit of this η cao is never to add useless lime, and the viewpoint that the present invention has the dephosphorisation reaction of target in mind takes place aptly stipulates.Just η cao is less than 0.5 words; Added useless lime in fact; Not only lost the effect of the present invention of carrying out effective dephosphorization treatment with a small amount of refining agent that adds, and with respect to the FeO that under regulation oxygen unit consumption, generates, amount of lime is added superfluous; A large amount of existence can not scorification CaO, such CaO that can not scorification can hinder the carrying out of above-mentioned dephosphorisation reaction.

Therefore to add the lime of the accumulation amount of amount of lime Wcao-P (kg/ ton molten iron) that obtains with following (5) formula and the amount of lime Wcao-Si (kg/ ton molten iron) that obtains with following (6) formula down at this embodiment.

Wcao-P=(molten iron [P]-target [P]) * (10/62) * 56 * 3/ η cao ... (5)

η cao (lime efficient)=0.5～1

Wcao-Si=molten iron [Si] * (10/28) * 56 * 2 ... (6)

Above-mentioned Wcao-P makes η cao make P in the molten iron as 3CaOP under 0.5～1 the situation ₂O ₅Fixing needed amount of lime, in addition, above-mentioned Wcao-Si makes Si in the molten iron as 2CaOSiO ₂Fixing needed amount of lime.

Fig. 8 is for representing as an example; For P content is that the molten iron of 0.11 quality % carries out dephosphorization treatment; P content is reached under the situation of 0.015 quality %, in this embodiment, add with molten iron in the corresponding amount of lime of Si content, with the correlated figure of amount of lime that adds in the dephosphorization treatment of existing method; Wcao-Si is the amount of lime of fixing Si needs, Wcao-P ₁Be the fixing amount of lime that needs of P (dephosphorization) under the η cao=1 situation, Wcao-P _0.5Be the fixing amount of lime that needs of P under the η cao=0.5 situation, the amount of lime of W in existing method, adding.Shown in the figure like this, the amount of lime that in existing method, needs is distributed Lp and the corresponding therewith slag amount decision that needs by phosphorus; So it is irrelevant with Si concentration in the molten iron; The amount of lime of W is necessary, and in contrast, the amount of lime of in this embodiment, adding is with [Wcao-Si+Wcao-P ₁]～[Wcao-Si+Wcao-P _0.5] just enough, compare the addition that can cut down lime significantly with existing method.

Fig. 9 is illustrated in the figure that concerns between the P content in the molten iron after amount of lime that the dephosphorization in this embodiment and the existing method needs and lime efficiency eta cao and the dephosphorization treatment, the dephosphorization in the so-called existing method with need amount of lime be meant Fig. 8 [W-Wcao-Si].Can judge that based on Fig. 9 this embodiment and existing method are relatively used and considerably less taken off P and can carry out dephosphorization treatment with high lime efficient with lime.

In this this embodiment of the 4th, hope the above lime of 80 quality % of amount of lime Wcao-P (Wcao-P that tries to achieve with η cao=1, below identical), jet to the molten iron liquid level through the top blast rifle.Figure 10 is the basis with the test-results that the inventor carries out; The figure that expression concerns between the P content to the ratio X/Wcao-P of the amount of lime X of molten iron liquid level winding-up and amount of lime Wcao-P and the molten iron after the dephosphorization treatment from the top blast rifle; In this test; P content to the converter type container of packing into (340 tons): 0.095～0.135 quality %, Si content: the molten iron of 0.02～0.10 quality %, with oxygen (10～15Nm ³/ ton molten iron) for vector gas is that lime powder (4～10kg/ ton molten iron) below the 1mm is jetted to the molten iron liquid level through the top blast rifle, carries out dephosphorization treatment (treatment time: 10～14 minutes) to particle diameter, carry out the decarburization blowing to the molten iron decarburization of packing into after with converter then.In dephosphorization treatment, CaF ₂Addition is handled the back slag amount below 30kg/ ton molten iron below 1kg/ ton molten iron.Jet to the lime feed speed B (kg/min/ ton molten iron) of molten iron liquid level with to the feed speed A (Nm of molten iron liquid level winding-up oxygen ³/ min/ ton molten iron) ratio A/B is 1.7.Utilizing winding-up is the refining agent of vector gas with oxygen, is controlled in the scope of 200～500mm at the cup depth L (stating the L value of (7) formula definition after using) that the molten iron liquid level produces.Making the molten iron temperature of dephosphorization treatment front and back is 1300～1320 ℃.Handle the back slag amount, calculate by the mass balance of adding CaO concentration (slag assay value) in amount of lime and the slag.

According to Figure 10, the ratio that above-mentioned amount of lime X accounts among the amount of lime Wcao-P is less than 80 quality %, and dephosphorization efficient has the tendency of some reductions.This is because relative difficult obtains being utilized in fire point or near the oxygen supply area it of reaction zone the directly high reaction efficiency of the above-mentioned that kind of input refining agent.

Because Si compares easy burning with C with Fe, in molten iron, become SiO in the blowing ₂Can stable existence, therefore necessity does not make it at fire point and lime reaction.Therefore, be equivalent to the fixing SiO of generation ₂The lime source of amount of lime Wcao-Si, not limiting is unslaked lime, is that to contain the material of unreacted lime (Free Lime) just passable.Therefore the refining agent that is equivalent to amount of lime Wcao-Si can be from lime powder, lump lime, block Wingdale, contain the blast furnace slag of unreacted CaO and select to use more than a kind.For example also can use the converter slag (about basicity 3～4) that generates at decarbonization process and ladle slag etc. as blast furnace slag.

In this 4th embodiment; According to above-mentioned reason, in order under the situation of adding a small amount of refining agent, to obtain high dephosphorization efficient, the Si content that carries out the molten iron of dephosphorization treatment will be below 0.15 quality %; Hope is below 0.07 quality %, is preferably in below the 0.03 quality %.Molten iron Si content surpasses 0.15 quality %, utilizes the effect of the minimizing refining agent addition of this embodiment to reduce.

In the 5th embodiment of the present invention, with the refining agent of oxygen as vector gas, the cup depth L that produces at the molten iron liquid level is 200～500mm by the utilization winding-up oxygen of following (7) formula definition or winding-up in control.

L＝L ₀×exp{(-0.78×L _H)/L ₀}……(7)

L ₀＝63×{(F ₀₂/n)/d _t} ^2/3

Wherein, L _H: the rifle height (mm) of top blast rifle

N: the nozzle hole count of top blast rifle

Utilize the present invention to have the dephosphorisation reaction mechanism of target in mind; To under the situation of a small amount of refining agent addition, obtain high dephosphorization efficient; Especially preferably provide the method for oxygen suitable to fire point as reaction zone; Be through winding-up oxygen or winding-up oxygen and refining agent specifically, the cup depth (from the theoretic cup depth of oxygen feed speed and top blast rifle structure and working conditions calculating) that produces at the molten iron liquid level is controlled at optimum range.

At this moment; Utilize winding-up oxygen or winding-up oxygen and refining agent, too small at the cup depth that the molten iron liquid level produces, the words a little less than just oxygen or oxygen and refining agent were jetted; Bloating appears outside fire point; Because this blistered slag hinders flowing of oxygen jet flow, the supply that oxygen warms oneself in front of a fire a little descends, and becomes the condition that is unfavorable for improving dephosphorization efficient.In addition, because the oxygen that a little provides that warms oneself in front of a fire becomes unstable, the oxygen that can not stably provide dephosphorization to need, it is big that the deviation of dephosphorization efficient becomes, simultaneously 3CaOP ₂O ₅Decompose and phosphorus occurs returning.

On the other hand; Utilize winding-up oxygen or winding-up oxygen and refining agent, excessive at the cup depth that the molten iron liquid level produces, oxygen or oxygen and refining agent strong words of jetting just; Oxygen density in fire point is too high, and becoming fully to provide the P corresponding with the FeO that generates from metal.Its result because unnecessary FeO carries out decarburization, also can become improving the disadvantageous condition of dephosphorization efficient in this case.

Utilize winding-up oxygen or winding-up with the refining agent of oxygen,, can use the definition of following (7) formula at the cup depth L that the molten iron liquid level produces as vector gas.

L＝L ₀×exp{(-0.78×L _H)/L ₀}……(7)

L ₀＝63×{(F ₀₂/n)/d _t} ^2/3

Wherein, L _H: the rifle height (mm) of top blast rifle

N: the nozzle hole count of top blast rifle

d _t: be the nozzle bore (mm) (being the mean pore size of whole nozzle bores under the nozzle bore condition of different of a plurality of nozzle bores wherein) of top blast rifle

In this embodiment, the above-mentioned cup depth of control molten iron liquid level is 200～500mm, carries out dephosphorization treatment.Figure 11 is the basis for the test-results of carrying out with the inventor; The figure that concerns between the P content in the cup depth L of expression molten iron liquid level and the molten iron after dephosphorization efficient and the dephosphorization treatment; In this test, to the P content of the converter type container of packing into (340 tons): 0.095～0.135 quality %, Si content: the molten iron of 0.02～0.15 quality %, with oxygen (10～15Nm ³/ ton molten iron) for the particle diameter of vector gas is the lime powder (4～10kg/ ton molten iron) below the 1mm, jets to the molten iron liquid level, carry out dephosphorization treatment (treatment time: 10～14 minutes), carry out the molten iron decarburization of packing into decarburization after with converter and blow then through the top blast rifle.In dephosphorization treatment, CaF ₂Addition is handled the back slag amount below 30kg/ ton molten iron below 1kg/ ton molten iron.Jet to the lime feed speed B (kg/min/ ton molten iron) of molten iron liquid level with to the feed speed A (Nm of molten iron liquid level winding-up oxygen ³/ min/ ton molten iron) ratio A/B is 1.7.The lime addition is in the scope that the amount of lime Wcao-P (kg/ ton molten iron) and the amount of lime Wcao-Si (kg/ ton molten iron) of above-mentioned (5) formula and (6) formula regulation add up to.In addition, making the molten iron temperature of dephosphorization treatment front and back is 1300～1320 ℃.Handle the back slag amount, calculate by the mass balance of adding CaO concentration (slag assay value) in amount of lime and the slag.

According to Figure 11 (a) and (b), compare in the scope of 200～500mm with cup depth L, in less than 200mm, scope,, above-mentioned reason reduces owing to making dephosphorization efficient greater than 500mm, and P content has the tendency that increases in the molten iron after the processing.

In the 6th embodiment of the present invention, to Si content below the 0.15 quality %, hope below the 0.07 quality %, be preferably in the molten iron below the 0.03 quality %, make CaF ₂Addition is below 1kg/ ton molten iron or do not add CaF in fact ₂(just except the inclusion that in refining agent, unavoidably contains, no longer add CaF ₂) condition under, to molten iron liquid level winding-up oxygen and at least a portion refining agent, carry out dephosphorization treatment through the top blast rifle, the molten iron temperature when making the dephosphorization treatment end simultaneously reaches 1360 ℃～1450 ℃.

Dephosphorisation reaction is owing to be the oxidizing reaction of P, and molten iron temperature is favourable at low temperatures in the past is a general knowledge, in addition, has considered the problem that phosphorus takes place to return to metal from slag when handling with high molten iron temperature in the past.Therefore, thought in the past and carried out dephosphorization that it was difficult making in the molten iron P content drop to very low degree at the high-temperature area more than 1360 ℃.In contrast, the inventor confirms to make in the methods of the invention that Si content falls enough lowly in the molten iron of dephosphorization treatment, and is adding CaF ₂Amount seldom or not add CaF ₂Condition under carry out dephosphorization treatment, also produce from slag hardly and return phosphorus even carry out pyroprocessing to metal, can obtain high dephosphorisation reaction efficient.Even carrying out such pyroprocessing also can make and return the very little reason of phosphorus speed; Think supplying with refining agent because oxygen produces the molten iron liquid level zone of lot of F eO in the methods of the invention; Compare with the method for packing block lime into from above; CaO (refining agent) increases considerably with the FeO contact area, so the P of FeO oxidation ₂O ₅Also become greatly with the efficient and the speed of CaO reaction, the CaO-FeO molten mass fused time can shorten.Can think that just reason is the instantaneous completion of dephosphorisation reaction, because the slag fusion time after this is short, returning phosphorus speed possibly diminish.

Figure 12 is not for to add CaF in converter type container (300 tons) ₂Condition under carry out dephosphorization of molten iron and handle, the figure that Si content influences dephosphorization efficient (dephosphorization lime efficient) in the molten iron before the molten iron temperature of research (molten iron temperature when dephosphorization treatment finishes) and the dephosphorization treatment.So-called dephosphorization lime efficient shown in Figure 12 is meant whole lime (unslaked lime) lime ratio useful to dephosphorization of adding with respect to as refining agent, is that phosphorous oxides is with 3CaOP ₂O ₅Be fixed to preceding topic, derive from stoichiometric ratio.

In this test; After in blast furnace discharge yard and hot metal ladle, making blast-melted desiliconization as required,, transfer to this molten iron and carried out dephosphorization treatment in the converter type container at ladle desulfurisation; At this moment, make by the molten iron Si content of dephosphorization treatment with handle after molten iron temperature carry out all changes.P content is that 0.10～0.11 quality %, Si content are below the 0.15 quality % in the molten iron before the dephosphorization treatment, utilizes dephosphorization treatment to make that P content is below the 0.02 quality % in the molten iron.

Only use as refining agent and not contain CaF ₂Be main unslaked lime with CaO.In addition, mainly use oxygen as oxygen source, utilization is jetted it and is added to the molten iron liquid level from the top blast rifle, also uses the interpolation of solid oxygen source (iron ore) for a part.Oxygen amount except that desiliconization is controlled at 10～11Nm ³The scope of/ton molten iron.In addition, the time of dephosphorization treatment is decided to be 10～11 minutes, molten iron temperature and waste material addition before the adjustment dephosphorization treatment, the molten iron temperature after the control dephosphorization treatment.Slag amount after the processing is decided to be below the 30kg/ ton molten iron.

In Figure 12, zero for the lime of packing into from above adds, and the molten iron temperature that dephosphorization treatment is finished is 1260～1350 ℃ a Test Example (a); ▲ for being that vector gas is jetted lime (lime powder below the particle diameter 1mm) to the molten iron liquid level with above-mentioned oxygen, the molten iron temperature that dephosphorization treatment is finished is 1360～1450 ℃ a Test Example (b).Make the lime addition in 5～10kg/ ton molten iron range according to Si content in the molten iron.In Test Example (b), jet to the lime feed speed B (kg/min/ ton molten iron) of molten iron liquid level with to the feed speed A (Nm of molten iron liquid level winding-up oxygen ³/ min/ ton molten iron) ratio A/B is 1.7.The lime addition is in the scope that the amount of lime Wcao-P (kg/ ton molten iron) and the amount of lime Wcao-Si (kg/ ton molten iron) of above-mentioned (5) formula and (6) formula regulation add up to.In addition, utilizing winding-up is the refining agent of vector gas with oxygen, and the cup depth L (with the L value of aforementioned (7) formula definition) that produces at the molten iron liquid level is controlled in the scope of 200～500mm.Handling the back slag amount is calculated by the mass balance of adding CaO concentration in amount of lime and the slag.

According to Figure 12, no matter the supply method of the lime molten iron temperature during with the dephosphorization treatment end, Si content is low more in the molten iron, and CaO consumes at 2CaOSiO ₂On ratio few more; So dephosphorization lime efficient improves; But the molten iron temperature when dephosphorization treatment is finished is compared 1260～1350 ℃ situation (Test Example (a)); With jetting lime and oxygen together to the method for molten iron liquid level, the molten iron temperature when making the dephosphorization treatment end makes the raising of dephosphorization lime efficient 1360～1450 ℃ situation (Test Example (b)).In addition, Si content is low more in the molten iron, and such effect is remarkable more.Dephosphorisation reaction sees that from M.L. low temperature is favourable, thinks that its reason as a result of Figure 12 is in Test Example (b) because the meltbility of slag and the immobilization of dephosphorization resultant, makes to return phosphorus speed and diminish.

Figure 13 is jetting refining agent and oxygen in the method for molten iron liquid level together, research CaF ₂Addition uses the converter type container identical with the test of Figure 12 to the figure of dephosphorization efficient (dephosphorization lime efficient) influence, and also the Test Example (b) with Figure 12 is identical with addition, treatment time etc. for the addition manner of refining agent and oxygen source.Molten iron temperature when dephosphorization treatment is finished is 1360～1450 ℃ of scopes.Use the method for packing into to add whole CaF at the blowing initial stage from above ₂Handle the back slag amount and be decided to be 30kg/ ton molten iron.

According to Figure 13, CaF ₂Addition dephosphorization lime efficient when 1kg/ ton molten iron is following improves.CaF ₂Have the effect of the CaO of promotion fused, utilize and add CaF ₂The liquid phase ratio of slag is increased.Treatment temp (molten iron temperature) is added CaF under the situation more than 1360 ℃ ₂Slag liquid phase ratio is increased, think to make to become big, easily near equilibrium value, so dephosphorization lime degradation in efficiency to the phosphorus speed of returning of metal from slag.Therefore to make treatment temp (molten iron temperature) that dephosphorization efficient is improved, must be CaF ₂Addition is suppressed at minimum limit (below 1kg/ ton molten iron or do not add in fact).

In addition, the molten iron temperature when dephosphorization treatment finishes surpasses 1450 ℃, and the effect ratio that increases with P concentration value in the slag equilibrated molten iron makes molten iron make CaO fused effect also big at high temperature.Molten iron temperature when dephosphorization treatment is finished is below 1450 ℃.

Can find out from above result, Si content below 0.15 quality %, is hoped below 0.07 quality %, to be preferably in the molten iron below the 0.03 quality %, make CaF ₂Addition is carrying out dephosphorization treatment below the 1kg/ ton molten iron or under the condition of not adding in fact, even the molten iron temperature when dephosphorization treatment finishes also can carry out dephosphorization treatment with high dephosphorization efficient under 1360～1450 ℃ high temperature.

Owing to can guarantee dephosphorization treatment high molten iron temperature when finishing, can fully guarantee the waste heat of step operation in the present embodiment in the back.In addition,, can be suppressed at the T.Fe in the slag low-levelly, also can improve the yield rate of dephosphorization iron because the molten iron temperature after handling is high.

Molten iron temperature before the general dephosphorization treatment is about 1250～1350 ℃; The method of the molten iron temperature when the adjustment dephosphorization treatment finishes; Generally dissolve under the situation of dephosphorization treatment of converter type dephosphorization refining furnace of waste material the method that control waste material input amount is arranged that can give an example etc. in use.In addition, under the situation of the dephosphorization treatment of using hot metal ladle type container such as hot metal ladle and mixer type iron ladle car type container, having of can giving an example adjusted the method etc. of the solid oxygen source input amount of agglomerated powder etc.Thereby the molten iron temperature in the time of can finishing processing with such method is adjusted to 1360～1450 ℃ of scopes.

The concrete grammar of molten iron temperature when finishing as the control dephosphorization treatment in addition, the gas composition analysis value of the emission gases that produces from dephosphorization treatment and calculate molten iron temperature the dephosphorization treatment from temperature of exhaust gas, the method for controlling based on this is the easiest.Just in this method, emission gases is carried out gas composition analysis, obtain CO, CO ₂Concentration calculates the growing amount of gas simultaneously from temperature of exhaust gas.Calculate the thermal value in coming out of the stove then thus, can calculate molten iron temperature based on this.

In the 7th embodiment of the present invention, the material that absorbs the molten iron heat because of chemical reaction and/or pyrolysis is provided to the molten iron liquid level zone of supplying with oxygen.

The molten iron liquid level zone of winding-up oxygen because the oxygen of impact liquid level produces a large amount of red stone, becomes the very favorable condition that promotes refining agent scorification.Form high-temperature area in the ballistic liquid level zone of oxygen (particularly fiery point) because of oxidizing reaction on the other hand, forming such high-temperature area is favourable for making lime, still sees from dephosphorization balance aspect and plays unfavorable effect.

For this problem; The inventor studies the method for the favourable temperature condition of dephosphorisation reaction the molten iron liquid level zone of supplying with oxygen can be become; Its result finds, utilizes to the molten iron liquid level zone of supplying with oxygen the material that absorbs the molten iron heat because of chemical reaction and/or pyrolysis is provided, and can not hinder the effect of the promotion refining agent scorification that oxygen causes; The temperature that all right appropriate inhibition is supplied with the molten iron liquid level zone of oxygen rises, and can obtain higher dephosphorisation reaction efficient.

Add (supply) absorb the molten iron heat because of chemical reaction and/or pyrolysis material (below be called " heat absorption material ") at the molten iron liquid level; Can suppress to supply with oxygen to the molten iron liquid level and cause heating and molten iron temperature is excessively raise, therefore being necessary provides the heat absorption material to the molten iron liquid level zone of supplying with oxygen.Hope in addition that in the molten iron liquid level zone of supplying with oxygen the zone that is called " fiery point " that particularly produces in molten iron with top blast rifle winding-up oxygen provides.This fire point is because the oxygen jet flow is impacted the molten iron liquid level zone that forms top temperature; Owing to be the zone of the oxidizing reaction of utilizing oxygen (generating the reaction of the FeO) stirring concentrating and cause through the oxygen jet flow, can be described as the zone that can obtain adding heat absorption material most pronounced effects.

Wherein as the heat absorption material so long as utilize chemical reaction or pyrolysis or utilize two kinds of reactions can capture the material of (heat absorption) molten iron heat simultaneously when adding in the molten iron, have no particular limits.Therefore this heat absorption material can be a gas, also can be solid.

Can be used as the gas that the heat absorption material uses, that can give an example has carbonic acid gas, water vapour, an oxynitride (NO _X) etc., can use in them more than a kind.These gases heat absorption materials supply to that the molten iron liquid level is main and react with Fe (CO for example ₂+ Fe → FeO+CO, H ₂O+Fe → FeO+H ₂), carry out the molten iron heat absorption this moment.Its result with make Fe oxidation (Fe+1/2O because of oxygen ₂→ the heating that FeO) causes is opposite, becomes heat absorption generally or thermal value and reduces significantly.In this external above-mentioned gas heat absorption material, a large amount of carbonic acid gas and water vapour that produce obtain easily in steel mill, because the effect of heat is also big, are particularly suitable for using.Even sneak into nitrogen in these gases in addition, more or less make purity drop, but because dephosphorization treatment is not the terminal stage in steel-making, so there is not what particular problems.CO and H that carbonic acid gas of supplying with in addition and aqueous vapour reducing generate ₂The part of the emission gases during as dephosphorization treatment reclaims, and also has the effect that improves the emission gases heat.

What can be used as that solid that the heat absorption material uses can give an example has metal carbonate, a metal hydroxides, hopes it is carbonate, the oxyhydroxide of basic metal, alkaline-earth metal especially, can use more than a kind from wherein selecting.These solid heat absorption materials are provided to the molten iron liquid level pyrolysis mainly take place, and carry out the heat absorption of molten iron this moment, simultaneously because thermolysis generates CO ₂Or H ₂O, this CO ₂Or H ₂O also has the function as above-mentioned heat absorption material, so can obtain extra high endothermic effect.The carbonate of this metal, that can give an example has a CaCO ₃, CaMg (CO ₃) ₂, MgCO ₃, Na ₂CO ₃, FeCO ₃, MnCO ₃, NaHCO ₃(sodium hydrogencarbonate) etc. has a Ca (OH) as what metal hydroxides can be given an example in addition ₂, Mg (OH) ₂, Ba (OH) ₂, Al (OH) ₃, Fe (OH) ₂, Mn (OH) _n, Ni (OH) _nDeng, can be from wherein selecting use more than a kind.

CaCO in these solids heat absorption materials in addition ₃, Ca (OH) ₂, CaMg (CO ₃) ₂Not only obtain easily, and above-mentioned thermolysis generation CaO, because this CaO has the advantage as the function of refining agent, so special hope is used.General these solid heat absorption materials add with the Wingdale of not firing or partly firing, the mode of rhombspar.

The excessive words thermolysis of granularity of solid heat absorption material can not be carried out rapidly in addition, so hope it is the powder saccharoid of median size below 5mm.

Also can use above-mentioned gas heat absorption material and solid heat absorption material simultaneously, also can be used as the part of the vector gas of solid heat absorption material when the molten iron liquid level provides or whole using gas heat absorption material.

The addition means of heat absorption material (gas and/or solid) has no particular limits; Can with top blast rifle or other rifles to the winding-up of molten iron liquid level, the methods such as (utilizing the dumper etc. of the situation of solid heat absorption material to pack into) of packing into from above adds; But in order to be provided to the molten iron liquid level zone (special hope is " fiery point ") of supplying with oxygen to the heat absorption material reliably; Obtain foregoing effect, hope to offer the molten iron liquid level with rifle, special hope offers the molten iron liquid level with the top blast rifle.

Offering the heat absorption material under the situation of molten iron liquid level with the top blast rifle; Adopt 1. that (solid absorbs heat under the situation of material heat absorption material and oxygen mix; With oxygen is vector gas), the method that provides to the molten iron liquid level from same rifle hole, 2. make heat absorption material and oxygen supply with route through different gas, be provided in the rifle; Can from the method (under the situation of solid heat absorption material, the supply of heat absorption material can be used the vector gas beyond the oxygen) of dividing other rifle hole to offer the molten iron liquid level.

From in order to be provided to the heat absorption material viewpoint in the molten iron liquid level zone of supplying with oxygen reliably; More hope to adopt above-mentioned method 1.; But also can be in above-mentioned method 2., the heat absorption material that the rifle hole through regulation is provided offers the molten iron liquid level zone of supplying with oxygen through other rifle holes.Gas heat absorption material for example is provided from rifle hole, top blast rifle front end center specifically or is that vector gas provides the heat absorption material with the gas beyond the oxygen, from then on other rifle holes around the center rifle hole provide the mode of oxygen etc.Be fit to use N as vector gas ₂Or the rare gas element of Ar etc., in addition as illustrated later, also can be the gas material (CO for example that absorbs heat ₂) use as vector gas.

Can in a plurality of rifles hole, be oxygen also in this external above-mentioned method 1. from a part of rifle hole, from other rifle holes and heat absorption material (according to circumstances can also add refining agent) blended oxygen offer the molten iron liquid level respectively.

And then, above-mentioned 1., in 2. any method, also can mix refining agent separately or be mixed together the back with heat absorption material (gas and/or solid) the vector gas beyond oxygen or the oxygen or in gas heat absorption material provides to the molten iron liquid level.

Will be heat absorption material (gas and/or solid) or providing to the molten iron liquid level through the top blast rifle under the state of heat absorption material and refining agent and oxygen mix; For example can or the heat absorption material be provided all, with oxygen mix to the part of the oxygen supply circuit (the oxygen path in collector, pipe arrangement, the rifle etc.) of top blast rifle.

Also can use other feedwaies (for example other rifle) beyond the top blast rifle heat absorption material (gas and/or solid) or heat absorption material and refining agent to be provided to the molten iron liquid level.As the rifle beyond the top blast rifle can be with the top blast rifle stove internal fixing position that coexists mutually the rifle of powder material to be provided, and the sampling gun of usefulness such as general sample circuit thermometric etc. can not use as long as the cooling power in the stove is not the words of problem yet.Dumper and inflow device etc. is not that the words of problem also can be used from the device durability at high temperature of top input and the precision that drops into the position etc. in addition.

Jetting (input) with oxygen or other vector gas in the molten iron liquid level zone (special hope is above-mentioned " fiery point " zone) that is utilized in above-mentioned supply oxygen, and directly supplies with the heat absorption material in this zone, can promote dephosphorisation reaction most effectively.In this case; Can adopt the method for jetting to the molten iron liquid level with oxygen, refining agent and heat absorption material (gas and/or solid) the blended state that comes out from the top blast rifle; In addition for example also can be respectively in a plurality of rifles of top blast rifle hole, only to the molten iron liquid level oxygen be provided from a part of rifle hole, be that vector gas provides refining agent and the material (gas and/or solid) that absorbs heat to the molten iron liquid level from other rifle holes with the gas (the for example rare gas element of nitrogen and Ar etc.) beyond oxygen or the oxygen as required.In addition in this case; Special hope use has main rifle hole at the center of rifle; The top blast rifle that a plurality of sublances hole is arranged around it; To the molten iron liquid level oxygen is provided from the sublance hole respectively, providing from main rifle hole is vector gas with the gas beyond oxygen or the above-mentioned oxygen as required, to the molten iron liquid level refining agent and heat absorption material (gas and/or solid) is provided.Also can make winding-up oxygen use different top blast rifles with the heat absorption material in addition with the spray refining agent.But under various situation, will make above-mentioned refining agent scorification most effectively, special hope is jetted refining agent and heat absorption material (gas and/or solid) to the molten iron liquid level with oxygen.

Figure 14 (a)～(e) is that expression uses the top blast rifle that several examples of oxygen, refining agent and heat absorption material mode are provided to the molten iron liquid level.Wherein Figure 14 (a) mixes the back provides (jetting to the molten iron liquid level) from the rifle hole mode to oxygen, refining agent and heat absorption material (gas and/or solid); Figure 14 (b) provides oxygen and refining agent from a part of rifle hole, provides oxygen and heat absorption material (gas and/or solid) that the mode of (jetting to the molten iron liquid level) is provided respectively from other rifle holes; Figure 14 (c) provides vector gas and refining agent except that oxygen from a part of rifle hole, provides oxygen and heat absorption material (gas and/or solid) that the mode of (jetting to the molten iron liquid level) is provided respectively from other rifle holes; Figure 14 (d) provides gas heat absorption material and refining agent from a part of rifle hole, provide oxygen and heat absorption material (gas and/or solid) that the mode of (jetting to the molten iron liquid level) is provided respectively from other rifle holes; Figure 14 (e) provides oxygen and refining agent from a part of rifle hole, provides gas heat absorption material or gas heat absorption material and solid heat absorption material that the mode of (jetting to the molten iron liquid level) is provided respectively from other rifle holes.But provide the mode of oxygen, refining agent and heat absorption material to be not limited to this to the molten iron liquid level.

CaCO in the above-mentioned solid heat absorption material ₃, Ca (OH) ₂, CaMg (CO ₃) ₂Because thermolysis generates CaO; This CaO has the function as refining agent; Therefore above-mentioned solid heat absorption material part or whole replaced C aO are provided in this embodiment is refining agent (is main with unslaked lime), also can carry out dephosphorization treatment to the CaO of material generation from then on as refining agent in fact.Just be that instead of part or whole CaO are refining agent in this case, generate material and as the heat absorption material that absorbs the molten iron heat because of chemical reaction and/or pyrolysis, from CaCO with refining agent ₃, Ca (OH) ₂, CaMg (CO ₃) ₂In select more than a kind (below be called " refining agent generates the heat absorption material "), offer the molten iron liquid level zone of supplying with oxygen.

Adopt this method to generate the thermolysis of heat absorption material and absorb the molten iron heat, become the CaO and the CO that becomes the heat absorption material of refining agent simultaneously through thermolysis through the above-mentioned refining agent that offers the molten iron liquid level ₂Or H ₂O, this CO ₂Or H ₂Much less can be absorbed after O and the Fe reaction advantage of molten iron heat, can obtain with CaO is provided to the molten iron liquid level zone of supplying with oxygen simultaneously simultaneously is the refining agent and the identical effect of material of absorbing heat, its result can obtain high dephosphorisation reaction efficient.

This situation is also because with noted earlier identical, above-mentioned refining agent generates the heat absorption material to be had in the molten iron liquid level zone of oxygen in supply, is desirable to provide the zone that is called " fiery point " that generates to the oxygen supply of top blast rifle especially.

Above-mentioned refining agent generates the heat absorption material generally to be added with the Wingdale of not firing or partly firing, the mode of rhombspar.The granularity of refining agent generation heat absorption material is excessive, and thermolysis etc. can not be carried out rapidly, so hope it is the powder saccharoid below the median size 5mm.

Above-mentioned refining agent generates the heat absorption material and also can use simultaneously with foregoing gas heat absorption material, the part of the vector gas when generating refining agent the heat absorption material and offer the molten iron liquid level in addition or all also can using gas heat absorption material.

The addition means that refining agent generates the heat absorption material has no particular limits; Can with top blast rifle and other rifles to the winding-up of molten iron liquid level, use from above and pack into (utilize dumper etc. pack into) etc. to add; After offering the molten iron liquid level zone (hoping it is " fiery point " especially) of supplying with oxygen, the heat absorption material obtains above-mentioned effect in order to generate refining agent; Hope provides to the molten iron liquid level with rifle, particularly provides to the molten iron liquid level with the top blast rifle.

Providing under the situation of refining agent generation heat absorption material to the molten iron liquid level with the top blast rifle; Use 1. and generate heat absorption material and oxygen mix (being vector gas) to refining agent with oxygen; Offer from identical rifle hole the method for molten iron liquid level, 2. make refining agent generate heat absorption material and oxygen respectively the gas supply lines through separately supply in the rifle, the method that provides to the molten iron liquid level from separately rifle hole (supply with refining agent generate the heat absorption material use the vector gas beyond the oxygen) can.

From generating the viewpoint consideration that the heat absorption material offers the molten iron liquid level zone of supplying with oxygen to refining agent really; Hope to adopt above-mentioned method 1.; But also can be in above-mentioned method 2.; Make the refining agent that provides through regulation rifle hole generate the heat absorption material, offer the molten iron liquid level zone of supplying with oxygen through other rifle holes.Specifically, for example hope it is that to provide from rifle hole, top blast rifle front end center with the gas except oxygen be that vector gas provides refining agent to generate the heat absorption material, from then on other rifle holes on every side, center rifle hole provide the mode of oxygen etc.Be fit to use N as vector gas ₂Or the rare gas element of Ar etc., in addition as illustrated later, also can be the gas material (CO for example that absorbs heat ₂) use as vector gas.

In this external above-mentioned method 1., also can in a plurality of rifles of top blast rifle hole, only oxygen be provided respectively, or the oxygen that is mixed with refining agent generation heat absorption material be provided from other rifle holes to the molten iron liquid level to the molten iron liquid level from a part of rifle hole.

Want so that the state after refining agent generation heat absorption material and the oxygen mix offers the molten iron liquid level through the top blast rifle; For example can or all provide refining agent to generate the heat absorption material, with oxygen mix to the part of the oxygen supply circuit (the oxygen path in collector, pipe arrangement, the rifle etc.) of top blast rifle.

Also can use other supply methods (for example other rifle) beyond the top blast rifle to provide refining agent to generate the heat absorption material in addition to the molten iron liquid level.Rifle beyond the top blast rifle can be with the top blast rifle stove internal fixing position that coexists mutually the rifle of powder material to be provided, and the sampling gun of usefulness such as general sample circuit thermometric etc. can not use as long as the cooling power in the stove is not the words of problem yet.Dumper and inflow device etc. is not that the words of problem also can be used from the device durability at high temperature of top input and the precision that drops into the position etc. in addition.

The oxygen of supplying with the use of refining agent generation heat absorption material can be pure oxygen or oxygen containing gas.

The 1st of the invention described above method～the 7th embodiment can be distinguished independent use; Also can implement the implementation condition more than 2 (but the 2nd embodiment is limited to the situation of using hot metal ladle type or mixer type iron ladle car type container as refining vessel) combination; Much less the condition of combination is many more, and the effect of the inventive method is good more.

As stated; Adopt the inventive method under the condition of the refining agent addition of minimum limit, to carry out dephosphorization treatment effectively; Much less as effect; Because the character that generates slag and state are to be main with solid phase, so have the advantage of slag loss in the time of can suitably preventing after processing, to tap a blast furnace.

To improve dephosphorisation reaction efficient after the dephosphorization treatment; Because the phosphorus concentration in the slag improves, when tapping a blast furnace after the dephosphorization treatment when refining vessel with the such iron notch of converter type container taps a blast furnace (particularly from) slag is flowed out with metal is very important.After just carrying out the dephosphorization treatment about phosphorus distribution Lp=200; P content is at 0.015 quality % (prescribed value: under the situation 0.020 quality %) in the molten iron after the processing; Flow out the words of the slag about 5kg/ ton molten iron; Also be brought to the decarburization blowing up to the phosphorus of 0.015 quality % and use converter, so in decarburization is blown with converter, also must be useful on the lime of dephosphorization.This does not just reach the original purpose of hot metal pretreatment.Therefore prevent that the slag outflow from taking the dephosphorization slag to following operation is important.

After carrying out dephosphorization treatment with the converter type container now; As be used for reducing as far as possible slag flow out get into below the method for operation, have (1) slag from the converter type container taps a blast furnace to block technology, (2) and handle the method etc. that method that the back slag composition reduces slag fluidity, (3) hot metal ladle after tap a blast furnace is removed slag (slagging-off) through control.

The chien shih molten iron temperature reduced, makes the problems such as yield reduction of iron with removing slag when these existing methods had the loss that can not stably prevent slag, the cost that uses running stores improves, is used to operate.

In contrast; The words of employing the inventive method as stated; Form the fire point and be the molten iron at center also face zone, the formation that is pressed to its exterior lateral area by order is main form with the solid phase, so the slag of dephosphorization treatment when finishing compared with the slag of existing dephosphorization treatment method generation; Flowability is very little, and when the refining vessel with the such iron notch of converter type container taps a blast furnace (particularly from) slag flowed out when its result can prevent to tap a blast furnace after dephosphorization treatment from finishing effectively.In addition as stated, do not adding CaF ₂Or make CaF ₂Addition below 1kg/ ton molten iron, suppress the increase of slag fluidity, more can improve its effect.

Compare through slag below, prevent that the effusive mechanism of slag from describing when the slag that adopts the inventive method to generate is tapped a blast furnace with existing method generation.Figure 15 is illustrated in the state of the slag/metal when tapping a blast furnace beginning in the converter type container.Under the situation of the existing method shown in Figure 15 (a), reduce basicity of slag or add a large amount of CaF owing to utilize ₂Make the abundant fusion of slag, bloating, slag thickness increases.After when therefore tapping a blast furnace stove being fascinated, slag slag unavoidably can occur and flow out through iron notch during beginning.In contrast, under the situation of the inventive method shown in Figure 15 (b), because slag is to be that main state exists with the solid phase, slag thickness is extremely thin, and it is negligible level that the slag that takes place when tapping a blast furnace beginning flows out.

Near Figure 16 slag/metallic state the iron notch in latter stage of representing to tap a blast furnace.Metal depth shoals before the end of a period of tapping a blast furnace, and metal produces eddy current, and in the existing method shown in Figure 16 (a), the molten slag on the metal is involved in this eddy current and flows out.In contrast, under the situation of the inventive method shown in Figure 16 (b), because slag is main with the solid phase, in the interference between the slag on the eddy current of metal with fuse, so slag is involved in the eddy current of metal hardly.

Embodiment

[embodiment 1]

At the molten iron of blast furnace casting at casting house or in hot metal ladle, carry out desiliconization as required and handle, in hot metal ladle, carry out the desulfurization processing with mechanical stirring then, after this in converter type container (300 tons), carry out dephosphorization treatment.Hot metal composition before the dephosphorization treatment is C:4.5～4.7 quality %, Si:0.01～0.28 quality %, Mn:0.15～0.25 quality %, P:0.10～0.11 quality %, S:0.001～0.003 quality %.The refining agent of using as dephosphorization uses the lime powder below the particle diameter 1mm, is it that vector gas is jetted to the molten iron liquid level with oxygen through rifle.In refining agent, do not add CaF ₂Duration of blast stuck-at-0 minute in order to stir molten iron, provides 0.05～0.15Nm from furnace bottom ³The nitrogen of/min/ ton molten iron.The unit consumption of lime and oxygen changes according to Si content in the molten iron, removes delime, oxygen desiliconization part (2 calcium-silicates: form 2CaOSiO together ₂The stoichiometry part) value, be decided to be fixed 3.5kg/ ton molten iron, 9Nm respectively ³/ ton molten iron.Jet to the lime feed speed B (kg/min/ ton molten iron) of molten iron liquid level with to the feed speed A (Nm of molten iron liquid level winding-up oxygen ³/ min/ ton molten iron) ratio A/B is 1.7.The lime addition is in the scope that the Wcao-P (kg/ ton molten iron) and the Wcao-Si (kg/ ton molten iron) of above-mentioned (5) formula and (6) formula regulation add up to.Utilizing winding-up in addition is the refining agent of vector gas with oxygen, and the cup depth L (with the L value of aforementioned (7) formula definition) that produces at the molten iron liquid level is controlled in the scope of 200～500mm.Molten iron temperature before and after the dephosphorization treatment is decided to be 1250～1350 ℃.Calculated processing back slag amount from the amount of lime of interpolation and the mass balance of the CaO concentration the slag (slag assay value).

Result and the dephosphorization treatment condition of each embodiment of expression in the table 1.Respectively carry out the value of the 6～72ch dephosphorization treatment value after average in the various scopes of handling the back slag amount that each MV shown in the table 1 is 5kg/ ton molten iron～10kg/ ton molten iron, surpass 10kg/ ton molten iron～20kg/ ton molten iron, surpass 20kg/ ton molten iron～30kg/ ton molten iron, surpass 30kg/ ton molten iron～40kg/ ton molten iron, surpass 40kg/ ton molten iron～50kg/ ton molten iron.

[embodiment 2]

At the molten iron of blast furnace casting at casting house or in hot metal ladle, carry out desiliconization as required and handle, in hot metal ladle, carry out the desulfurization processing with mechanical stirring then, after this in converter type container (300 tons), carry out dephosphorization treatment.P content before the dephosphorization treatment is that 0.10～0.11 quality %, Si content are below 0.15 quality %.Making the molten iron temperature of dephosphorization treatment front and back is 1250～1350 ℃, and using refining agent as dephosphorization is to be main unslaked lime with CaO, uses the powder to sieve below 200 orders, and the unit consumption of CaO is decided to be 5～15kg/ ton molten iron according to Si content in the molten iron.

In this dephosphorization treatment, be that vector gas passes through top blast small of the stock refining agent and jets to liquid level with oxygen, refining agent and oxygen source (duration of blast: 10 minutes) are provided, this moment is with the feed speed A (Nm of oxygen ³/ min/ ton molten iron) and under the variant condition of the ratio A/B of the feed speed B of refining agent (kg/min/ ton molten iron) operate.In order to stir molten iron, 0.05～0.15Nm is provided from the bottom blowing nozzle of furnace bottom ³The nitrogen of/min/ ton iron flow is jetted in molten iron.In refining agent, do not add CaF ₂, making and handling the back slag amount is below the 30kg/ ton molten iron.The lime addition is in the scope that the Wcao-P (kg/ ton molten iron) and the Wcao-Si (kg/ ton molten iron) of above-mentioned (5) formula and (6) formula regulation add up to.Utilizing winding-up in addition is the refining agent of vector gas with oxygen, and the cup depth L (with the L value of aforementioned (7) formula definition) that produces at the molten iron liquid level is controlled in the scope of 200～500mm.Calculated processing back slag amount from the amount of lime of interpolation and the mass balance of the CaO concentration the slag (slag assay value).

Figure 17 representes the feed speed A (Nm of oxygen ³/ min/ ton molten iron) P relation with contents and after the ratio A/B of the feed speed B of refining agent (kg/min/ ton molten iron) and the dephosphorization treatment.Can find out according to this figure; The A/B of the present invention example P content in the molten iron of example after dephosphorization treatment in 0.3～7 zone is below the 0.015 quality % as target [P] concentration; Particularly Si content can stably reach [the P]≤0.010 quality % of low P standard in the preceding molten iron of dephosphorization treatment under the situation below the 0.10 quality %.A/B can obtain low especially [P] in the example in 1.2～2.5 zones in addition, can obtain the highest dephosphorisation reaction efficient in this zone.

In contrast, A/B is less than 0.3 with surpass that P content does not all reach below the 0.015 quality % as target [P] concentration in the molten iron of example after dephosphorization treatment in 7 zones.

[embodiment 3]

Handle carrying out desiliconization at casting house, pack it into then and in this hot metal ladle, carry out desiliconization after the hot metal ladle and handle, move on to the dephosphorization place to this hot metal ladle behind the deslagging, carry out dephosphorization treatment at the molten iron of blast furnace casting.

In dephosphorization treatment, be that vector gas passes through top blast small of the stock lime powder (refining agent) and jets to the molten iron liquid level with oxygen, be blown in the molten iron through immersing small of the stock lime powder simultaneously.Without top blast rifle winding-up lime powder, be blown in the molten iron in this external comparative example through immersing small of the stock lime powder.Treatment time all is decided to be 20 minutes.Handling the back slag amount is decided to be below the 20kg/ ton molten iron.For the present invention's example, the lime addition is in the scope that the Wcao-P (kg/ ton molten iron) and the Wcao-Si (kg/ ton molten iron) of above-mentioned (5) formula and (6) formula regulation add up to.Utilizing winding-up in addition is the refining agent of vector gas with oxygen, and the cup depth L (with the L value of aforementioned (7) formula definition) that produces at the molten iron liquid level is controlled in the scope of 200～500mm.Molten iron temperature before and after the dephosphorization treatment is decided to be 1300～1320 ℃.Calculated processing back slag amount from the amount of lime of interpolation and the mass balance of the CaO concentration the slag (slag assay value).

Result and the dephosphorization treatment condition of each embodiment of table 2 expression.

[embodiment 4]

At the molten iron of blast furnace casting at casting house or in hot metal ladle, carry out desiliconization as required and handle, in hot metal ladle, carry out the desulfurization processing with mechanical stirring then, after this in converter type container (300 tons), carry out dephosphorization treatment.In this dephosphorization treatment, the molten iron temperature before and after handling is decided to be 1250～1350 ℃.Through the top blast rifle to the molten iron liquid level winding-up oxygen time, with 1. above-mentioned oxygen as the lime powder (refining agent) of vector gas below molten iron liquid level winding-up particle diameter 1mm, certain method interpolation refining agent of 2. packing the lime of particle diameter 1～3mm (refining agent) into from above.From the furnace bottom of the converter type container 0.05～0.15Nm that to molten iron, jets ³The nitrogen of/min/ ton molten iron stirs, and carries out 9 minutes dephosphorization treatment.Making and handling the back slag amount is below the 30kg/ ton molten iron.For example of the present invention, the lime addition is in the scope that the Wcao-P (kg/ ton molten iron) and the Wcao-Si (kg/ ton molten iron) of above-mentioned (5) formula and (6) formula regulation add up to.Utilizing winding-up in addition is the refining agent of vector gas with oxygen, and the cup depth L (with the L value of aforementioned (7) formula definition) that produces at the molten iron liquid level is controlled in the scope of 200～500mm.Calculated processing back slag amount from the amount of lime of interpolation and the mass balance of the CaO concentration the slag (slag assay value).

Result and the dephosphorization treatment condition of each embodiment of table 3 expression.

[embodiment 5]

Handle carrying out desiliconization at casting house, pack it into then and in this hot metal ladle, carry out desiliconization after the hot metal ladle and handle the converter type of packing into behind deslagging container (300 tons) at the molten iron of blast furnace casting.

In dephosphorization treatment, be that vector gas passes through top blast small of the stock lime powder (refining agent) and jets to the molten iron liquid level with oxygen, in the embodiment of a part, use simultaneously simultaneously and pack block lime into from above.In addition, in comparative example, do not carry out, pack block lime from above into and add through top blast rifle winding-up lime powder.Each embodiment is from the furnace bottom of converter type container winding-up 0.07～0.12Nm ³The nitrogen of/min/ ton molten iron carries out 8～14 minutes dephosphorization treatment.In this dephosphorization treatment, make the molten iron temperature before and after handling be decided to be 1250～1350 ℃, handle the back slag amount and be decided to be below the 30kg/ ton molten iron.In example of the present invention, jet to the lime feed speed B (kg/min/ ton molten iron) of molten iron liquid level with to the feed speed A (Nm of molten iron liquid level winding-up oxygen ³/ min/ ton molten iron) ratio A/B is 1.7.Make the molten iron temperature of dephosphorization treatment front and back be decided to be 1250～1350 ℃.Calculated processing back slag amount from the amount of lime of interpolation and the mass balance of the CaO concentration the slag (slag assay value).

Result and the dephosphorization treatment condition of table 4～each embodiment of table 7 expression.

Table 5

* 1W cao-P is the amount of lime of calculating with η cao=1

Table 7

[embodiment 6]

Handle carrying out desiliconization at the molten iron of blast furnace casting at casting house, pack it into then and in this hot metal ladle, carry out desiliconization after the hot metal ladle and handle, the converter type of packing into behind deslagging container (300 tons) carries out dephosphorization treatment.In this dephosphorization treatment; Through the top blast rifle to the molten iron liquid level winding-up oxygen time, with 1. above-mentioned oxygen as the lime powder (refining agent) of vector gas below molten iron liquid level winding-up particle diameter 3mm, certain method interpolation refining agent of 2. packing block lime (refining agent) into from above.From the furnace bottom of the converter type container 0.1Nm that to molten iron, jets ³The nitrogen of/min/ ton molten iron feed rate stirs, and carries out 10～11 minutes dephosphorization treatment simultaneously.The molten iron temperature before the adjustment dephosphorization treatment and the addition of waste material, the molten iron temperature when the control dephosphorization treatment finishes.Making and handling the back slag amount is below the 30kg/ ton molten iron.For example of the present invention, the lime addition is in the scope that the Wcao-P (kg/ ton molten iron) and the Wcao-Si (kg/ ton molten iron) of above-mentioned (5) formula and (6) formula regulation add up to.Utilizing winding-up in addition is the refining agent of vector gas with oxygen, and the cup depth L (with the L value of aforementioned (7) formula definition) that produces at the molten iron liquid level is controlled in the scope of 200～500mm.Calculated processing back slag amount from the amount of lime of interpolation and the mass balance of the CaO concentration the slag (slag assay value).

Result and the dephosphorization treatment condition of each embodiment of table 8 expression.

[embodiment 7]

Handle carrying out desiliconization at the molten iron of blast furnace casting at casting house, pack it into then and in this hot metal ladle, carry out desiliconization after the hot metal ladle and handle, the converter type of packing into behind deslagging container (300 tons) carries out dephosphorization treatment.In this dephosphorization treatment, through the top blast rifle with oxygen as the lime powder (refining agent) of vector gas below molten iron liquid level winding-up particle diameter 1mm and the material that absorbs heat.The heat absorption material uses CaCO ₃Or Ca (OH) ₂(particle diameter is all below 1mm) mixes with lime powder in advance to scale.From the furnace bottom of the converter type container 0.1Nm that to molten iron, jets ³The nitrogen of/min/ ton molten iron feed rate stirs, and carries out 10～11 minutes dephosphorization treatment simultaneously.The molten iron temperature before the adjustment dephosphorization treatment and the addition of waste material, the molten iron temperature when the control dephosphorization treatment finishes.Making and handling the back slag amount is below the 30kg/ ton molten iron.For example of the present invention, the lime addition is in the scope that the Wcao-P (kg/ ton molten iron) and the Wcao-Si (kg/ ton molten iron) of above-mentioned (5) formula and (6) formula regulation add up to.Utilizing winding-up in addition is the refining agent of vector gas with oxygen, and the cup depth L (with the L value of aforementioned (7) formula definition) that produces at the molten iron liquid level is controlled in the scope of 200～500mm.Calculated processing back slag amount from the amount of lime of interpolation and the mass balance of the CaO concentration the slag (slag assay value).

Result and the dephosphorization treatment condition of each embodiment of table 9 expression.

[embodiment 8]

In hot metal ladle, carry out desiliconization to molten iron and handle, carry out dephosphorization treatment to the molten iron converter type container (300 tons) of packing into behind the deslagging at blast furnace casting.In this dephosphorization treatment, from the about 0.1Nm of furnace bottom winding-up of converter type container ³The stirring gas (nitrogen) of/min/ ton molten iron stirs molten iron, through top blast rifle direction molten iron liquid level from the liquid level oxygen, lime powder (CaO is a refining agent) and gas heat absorption material is provided simultaneously.Do not add CaF in the refining agent ₂Make and handle the back slag amount below 30kg/ ton molten iron.Jet to the lime feed speed B (kg/min/ ton molten iron) of molten iron liquid level with to the feed speed A (Nm of molten iron liquid level winding-up oxygen ³/ min/ ton molten iron) ratio A/B is 1.7.The lime addition is in the scope that the Wcao-P (kg/ ton molten iron) and the Wcao-Si (kg/ ton molten iron) of above-mentioned (5) formula and (6) formula regulation add up to.Utilizing winding-up in addition is the refining agent of vector gas with oxygen, and the cup depth L (with the L value of aforementioned (7) formula definition) that produces at the molten iron liquid level is controlled in the scope of 200～500mm.Making the molten iron temperature of dephosphorization treatment front and back is 1250～1350 ℃.Handling the back slag amount is calculated by the mass balance of adding CaO concentration (slag assay value) in amount of lime and the slag.

Top blow oxygen lance uses the rifle that has 1 centre hole and 3 periphery holes as the rifle hole.

Lime powder uses the lime powder below the particle diameter 3mm, is it that vector gas is seen off with oxygen from carrying device, in pipe arrangement, carries to offer the top blast rifle, offers the molten iron liquid level from centre hole with oxygen.Pipe arrangement bundle of lines oxygen through other offers the top blast rifle on the other hand, provides to the molten iron liquid level from periphery holes.Always sending the oxygen amount is 1.5Nm ³/ min/ ton molten iron.

Add the gas heat absorption material of normality respectively in above-mentioned two oxygen line.Use carbonic acid gas and water vapour as this heat absorption material, making the ratio of mixture with respect to oxygen is 10～40 volume % (with respect to the numbers that are 100) with oxygen

In comparative example, offer the molten iron liquid level, pack block lime (CaO is a refining agent) into from above simultaneously from top blast small of the stock oxygen.

Result and the dephosphorization treatment condition of each embodiment of table 10 expression.

Table 10

* 1 with respect to the number that with oxygen is 100%

[embodiment 9]

In hot metal ladle, carry out desiliconization to the molten iron at blast furnace casting and handle, the deslagging continued is carried out dephosphorization treatment in this hot metal ladle.In this dephosphorization treatment, from 1 immersion rifle PM 3Nm that to molten iron, jets ³Nitrogen molten iron is stirred, simultaneously with the top blast rifle from liquid level top with 1. following～4. certain mode oxygen, lime powder (CaO is a refining agent) are provided, material absorbs heat.Have again and in refining agent, do not add CaF ₂Make and handle the back slag amount below 30kg/ ton molten iron.Jet to the lime feed speed B (kg/min/ ton molten iron) of molten iron liquid level with to the feed speed A (Nm of molten iron liquid level winding-up oxygen ³/ min/ ton molten iron) ratio A/B is 1.7.The lime addition is in the scope that the Wcao-P (kg/ ton molten iron) and the Wcao-Si (kg/ ton molten iron) of above-mentioned (5) formula and (6) formula regulation add up to.Utilizing winding-up in addition is the refining agent of vector gas with oxygen, and the cup depth L (with the L value of aforementioned (7) formula definition) that produces at the molten iron liquid level is controlled in the scope of 200～500mm.Making the molten iron temperature of dephosphorization treatment front and back is 1250～1350 ℃.Handling the back slag amount is calculated by the mass balance of adding CaO concentration (slag assay value) in amount of lime and the slag.

1. the present invention is routine: with the top blast rifle oxygen, lime powder, CO are provided ₂

2. the present invention is routine: with the top blast rifle oxygen, lime powder, CaCO are provided ₃(Wingdale) or Ca (OH) ₂(white lime).

3. the present invention is routine: with the top blast rifle oxygen, lime powder, CO are provided ₂, CaCO ₃(Wingdale).

4. the present invention is routine: with the top blast rifle oxygen, CaCO are provided ₃(Wingdale) or Ca (OH) ₂(white lime).

Lime powder, CaCO ₃(Wingdale) or Ca (OH) ₂Use the powder below the particle diameter 1mm; Is them in pipe arrangement, to carry after vector gas is seen off with oxygen from carrying device; Simultaneously and at the oxygen interflow that top blast rifle inlet provides through other pipe arrangements, offer liquid level with the oxygen jet flow from 3 rifle holes of top blast rifle front end.Make and always send the oxygen amount to be 6000Nm per hour ³

About CO ₂, making the ratio of mixture with respect to oxygen is 25 volume % (with respect to the numbers that are 100) with oxygen.Lime powder, CaCO ₃(Wingdale) or Ca (OH) ₂The amount that is scaled CaO is that PM adds 70～80kg.

In comparative example, to the molten iron liquid level oxygen is provided, in molten iron, sprays into lime powder through immersing rifle simultaneously through the top blast rifle.

Result and the dephosphorization treatment condition of each embodiment of table 11 expression.

The possibility of utilizing on the industry

The present invention is used for the low molten iron of operation manufacturing phosphorus content in the middle of steel-making.

Claims

1. the method for manufacture of a low-phosphorous molten iron; In the container of molten iron of packing into, add the refining agent in oxygen source and CaO source; Utilize the dephosphorization treatment of hot metal pretreatment to make low-phosphorous molten iron; It is characterized in that, carry out dephosphorization treatment jetting on the molten iron liquid level below the 0.15 quality % to Si content, make from the refining agent that the top blast rifle is supplied with, to have at least a part to be jetted to the molten iron liquid level zone of the said oxygen of winding-up through top blast small of the stock oxygen and at least a portion refining agent; And make and handle the back slag amount below 30kg/ ton molten iron

Make the feed speed B (kg/min/ ton molten iron) that converts to the CaO of the refining agent of molten iron liquid level winding-up and to the feed speed A (Nm of the oxygen of molten iron liquid level winding-up ³/ min/ ton molten iron) satisfy following (2) formula,

1.2≤A/B≤2.5……(2)

And, as refining agent, add the lime of the accumulation amount of amount of lime Wcao-P (kg/ ton molten iron) that obtains with following (5) formula and the amount of lime Wcao-Si (kg/ ton molten iron) that obtains with following (6) formula,

Wcao-P=(molten iron [P]-target [P]) * (10/62) * 56 * 3/ η cao ... (5)

Wherein, molten iron [P]: the P concentration (quality %) in the molten iron before the dephosphorization treatment,

Target [P]: as the P concentration (quality %) in the molten iron after the dephosphorization treatment of target,

η cao (lime efficient)=0.5～1,

Wcao-Si=molten iron [Si] * (10/28) * 56 * 2 ... (6)

Wherein, molten iron [Si]: the Si concentration (quality %) in the molten iron before the dephosphorization treatment.

2. the method for manufacture of low-phosphorous molten iron as claimed in claim 1 is characterized in that, satisfies under the condition of following (3) formula and (4) formula with the speed of supplying with oxygen at the refining agent feed speed to the winding-up of molten iron liquid level, carries out dephosphorization treatment,

(C1/D1)＞(C2/D2)……(3)

C1＞C2……(4)

Wherein, C1: the MV (kg/min/ ton molten iron) of the refining agent feed speed that dephosphorization treatment CaO in earlier stage converts

D2: the MV (Nm of the oxygen feed speed in dephosphorization treatment later stage ³/ min/ ton molten iron).

3. the method for manufacture of low-phosphorous molten iron as claimed in claim 2 is characterized in that, during dephosphorization treatment, and refining agent feed speed and oxygen feed speed continuity and/or interim change that CaO is converted.

4. like the method for manufacture of claim 1,2 or 3 described low-phosphorous molten irons, it is characterized in that, the molten iron of Si content below 0.07 quality % carried out dephosphorization treatment.

5. like the method for manufacture of claim 1,2 or 3 described low-phosphorous molten irons, it is characterized in that, the molten iron of Si content below 0.03 quality % carried out dephosphorization treatment.

6. like the method for manufacture of claim 1,2 or 3 described low-phosphorous molten irons, it is characterized in that from the refining agent that the top blast rifle is supplied with, having at least a part to be jetted to utilizing winding-up oxygen on the fire point that the molten iron liquid level generates.

7. like the method for manufacture of claim 1,2 or 3 described low-phosphorous molten irons, it is characterized in that, is at least a portion in the refining agent that vector gas is jetted to the molten iron liquid level with oxygen.

8. like the method for manufacture of claim 1,2 or 3 described low-phosphorous molten irons, it is characterized in that, make and handle the back slag amount below 20kg/ ton molten iron.

9. like the method for manufacture of claim 1,2 or 3 described low-phosphorous molten irons, it is characterized in that, make and handle the back slag amount below 10kg/ ton molten iron.

10. like the method for manufacture of claim 1,2 or 3 described low-phosphorous molten irons; It is characterized in that; Use the container of hot metal ladle type or mixer type iron ladle car type as the container of the molten iron of packing into; Jet to the molten iron liquid level through top blast small of the stock oxygen and at least a portion refining agent, jet the gas that contains powder in molten iron through immersion rifle and/or winding-up nozzle simultaneously.

11. the method for manufacture of low-phosphorous molten iron as claimed in claim 10 is characterized in that, is the part of refining agent through the powder that immerses rifle and/or the nozzle of jetting is jetted in molten iron.

12. the method for manufacture of low-phosphorous molten iron as claimed in claim 10 is characterized in that, through the top blast rifle to the amount of oxygen of molten iron liquid level winding-up at 0.7Nm ³Below/min/ ton the molten iron.

13. the method for manufacture of low-phosphorous molten iron as claimed in claim 10 is characterized in that, jets to the molten iron liquid level through the top blast rifle more than making 80 quality % of the refining dosage that in dephosphorization treatment, adds.

14. the method for manufacture of low-phosphorous molten iron as claimed in claim 10; It is characterized in that; The refining agent total amount through the top blast rifle jet to the molten iron liquid level and through immerse rifle and/or winding-up nozzle in molten iron, jet add time, make 20～80 quality % that account for the refining agent total addition level through the refining agent addition of top blast rifle.

15. the method for manufacture like claim 1,2 or 3 described low-phosphorous molten irons is characterized in that, the above lime of the 80 quality % of the amount of lime Wcao-P that η cao=1 obtains is jetted to the molten iron liquid level through the top blast rifle.

16. method of manufacture like claim 1,2 or 3 described low-phosphorous molten irons; It is characterized in that; As the refining agent that is equivalent to amount of lime Wcao-Si, can from the blast furnace slag that contains lime powder, lump lime, block Wingdale, unreacted CaO, select to use more than a kind.

17. method of manufacture like claim 1,2 or 3 described low-phosphorous molten irons; It is characterized in that; With the refining agent of oxygen as vector gas, the cup depth L that produces at the molten iron liquid level is controlled at 200～500mm by the utilization winding-up oxygen of following (7) formula definition or winding-up

L＝L ₀×exp{(-0.78×L _H)/L ₀}……(7)

L ₀＝63×{(F ₀₂/n)/d _t} ^2/3

Wherein, L _H: the rifle height (mm) of top blast rifle

N: the nozzle hole count of top blast rifle

d _t: the nozzle bore of top blast rifle (mm) wherein, is the mean pore size of whole nozzle bores under the nozzle bore condition of different of a plurality of nozzle bores.

18. the method for manufacture like claim 1,2 or 3 described low-phosphorous molten irons is characterized in that, makes CaF ₂Addition under the following condition of 2kg/ ton molten iron, carry out dephosphorization treatment.

19. the method for manufacture like claim 1,2 or 3 described low-phosphorous molten irons is characterized in that, does not substantially add CaF ₂Condition under carry out dephosphorization treatment, the said CaF that do not add in fact ₂Be meant except in refining agent, containing, do not add CaF as the inevitable inclusion ₂

20. the method for manufacture like claim 1,2 or 3 described low-phosphorous molten irons is characterized in that, to the molten iron of Si content below 0.15 quality %, makes CaF ₂Addition under the condition below the 1kg/ ton molten iron, carry out dephosphorization treatment through the top blast rifle to molten iron liquid level winding-up oxygen and at least a portion refining agent, the molten iron temperature when making the dephosphorization treatment end simultaneously is 1360 ℃～1450 ℃.

21. the method for manufacture like claim 1,2 or 3 described low-phosphorous molten irons is characterized in that, to the molten iron of Si content below 0.15 quality %, is not adding CaF ₂Condition under, carry out dephosphorization treatment through the top blast rifle to molten iron liquid level winding-up oxygen and at least a portion refining agent, the molten iron temperature when making the dephosphorization treatment end simultaneously is 1360 ℃～1450 ℃, the said CaF that do not add in fact ₂Be meant except in refining agent, containing, do not add CaF as the inevitable inclusion ₂

22. the method for manufacture like claim 1,2 or 3 described low-phosphorous molten irons is characterized in that, to the molten iron liquid level zone that oxygen is provided the material that absorbs the molten iron heat through chemical reaction and/or pyrolysis is provided.

23. the method for manufacture of low-phosphorous molten iron as claimed in claim 22 is characterized in that, has at least a part to absorb the material of molten iron heat through chemical reaction and/or pyrolysis, offers because of through jetting oxygen on the fire point that produces on the molten iron liquid level.

24. the method for manufacture of low-phosphorous molten iron as claimed in claim 22; It is characterized in that; Absorb the material of molten iron heat through chemical reaction and/or pyrolysis, be from carbonic acid gas, water vapour, oxynitride, metal carbonate, metal hydroxides, select more than a kind.

25. the method for manufacture of low-phosphorous molten iron as claimed in claim 24 is characterized in that, absorbs the material of molten iron heat through chemical reaction and/or pyrolysis, is from generating CO through thermolysis ₂Or H ₂The metal carbonate of O, produce CO through thermolysis ₂Or H ₂Select in the metal hydroxides of O more than a kind.

26. the method for manufacture of low-phosphorous molten iron as claimed in claim 25 is characterized in that, absorbs the material of molten iron heat through chemical reaction and/or pyrolysis, is from CaCO ₃, Ca (OH) ₂, CaMg (CO ₃) ₂More than a kind of middle selection.

27. method of manufacture like claim 1,2 or 3 described low-phosphorous molten irons; It is characterized in that; Replacement as the part of the refining agent in CaO source or all absorbs the material of molten iron heat as the refining agent resultant and through chemical reaction and/or pyrolysis, from CaCO ₃, Ca (OH) ₂, CaMg (CO ₃) ₂The middle selection more than a kind offers the molten iron liquid level zone that is provided oxygen.

28. the method for manufacture of low-phosphorous molten iron as claimed in claim 27 is characterized in that, from CaCO ₃, Ca (OH) ₂, CaMg (CO ₃) ₂In select have a part at least more than a kind, offer the fiery point that produces on the molten iron liquid level through winding-up oxygen.

29. the method for manufacture like claim 1,2 or 3 described low-phosphorous molten irons is characterized in that, the molten iron of P content more than 0.10 quality %, dephosphorization is refined to below the P content as the ingredient standard value of steel of crude steel requirement.

30. the method for manufacture of low-phosphorous molten iron as claimed in claim 29 is characterized in that, the P content after the dephosphorization treatment in the molten iron is below 0.010 quality %.