CN108350515B - Iron liquid pretreatment method - Google Patents
Iron liquid pretreatment method Download PDFInfo
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- CN108350515B CN108350515B CN201780003749.3A CN201780003749A CN108350515B CN 108350515 B CN108350515 B CN 108350515B CN 201780003749 A CN201780003749 A CN 201780003749A CN 108350515 B CN108350515 B CN 108350515B
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
- C21C5/28—Manufacture of steel in the converter
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C1/00—Refining of pig-iron; Cast iron
- C21C1/02—Dephosphorising or desulfurising
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
- C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Abstract
The present invention provides a method for pretreating molten iron, which is a method for pretreating molten iron by recycling converter slag as a refining agent for pretreating molten iron, comprising the steps of: a first step 1 of sizing the converter slag so that the particle size of the converter slag is in a range of 3mm or more and less than 25mm, and the ratio of the converter slag having a particle size of 20mm or more and less than 25mm in the converter slag is 10 mass% or more and less than 15 mass% with respect to the total amount of the converter slag; a step 2 of charging the converter slag after the size reduction into a molten iron pretreatment vessel; a 3 rd step of adding 1.0 mass% or more and less than 10.0 mass% of Al to 100 mass% of the converter slag after the 1 st step and before the 2 nd step or simultaneously with the 2 nd step2O3Putting into the molten iron pretreatment container; and a 4 th step of charging MnO of 0.3 mass% or more and less than 10.0 mass% based on 100 mass% of the converter slag into the molten iron pretreatment vessel.
Description
Technical Field
The invention relates to a pretreatment method of molten iron.
The present application claims priority based on 2016-.
Background
Conventionally, in the hot metal pretreatment step, hot metal pretreatment (dephosphorization, desulfurization) is performed using a refining agent (dephosphorization agent, desulfurization agent) containing CaO as an essential component,Removing S). Here, since the melting point of CaO is as high as 2625 ℃, the following method has been widely used: CaO is pulverized to promote reaction slagging in the molten steel; addition of CaF2、Al2O3Or MgO to lower the melting point to promote the reaction of molten slag (also referred to as slag) with the molten iron.
Further, as a technique for recycling slag generated in a steel-making process (a molten iron pretreatment process to a converter refining process to a 2-time refining process), the following technique is disclosed: a method for improving the slag formation rate by cooling, pulverizing and refining converter slag generated in a converter refining (decarburization) step following a hot metal pretreatment step, and using the slag as a refining agent in the hot metal pretreatment step (patent document 1); ladle slag generated in the 2-pass refining step is used as a refining agent (patent document 2).
Among the above-described conventional techniques, the invention of patent document 1 is an invention that focuses on the fact that converter slag generated in a converter refining (decarburization) process contains a large amount of CaO and has a high basicity, and is significant in reducing the amount of converter slag discharged by recycling. However, according to experimental investigation by the present inventors, since the slagging rate of converter slag alone is limited to about 50%, it is necessary to additionally use a large amount of quicklime (not CaO derived from converter slag) separately, and the invention of patent document 1 has a problem that an effect of reducing the cost of a refining agent cannot be expected.
The invention of patent document 2 focuses on the fact that ladle slag generated in 2 refining steps contains a large amount of Al together with CaO2O3The invention thus made. The invention of patent document 2 can enjoy the effect of Al that lowers the melting point of slag2O3The slag formation promoting effect is brought about, but the viscosity of the slag is increased at the same time. When the viscosity of the slag is high, the slag is likely to foam, and there is a problem that the slag overflows from a reaction vessel such as a converter or a torpedo car, and the risk of occurrence of splash that hinders the operation is increased.
Documents of the prior art
Patent document
Patent document 1: japanese laid-open patent publication No. 4-120209
Patent document 2: japanese laid-open patent publication No. 2006-274349
Disclosure of Invention
Problems to be solved by the invention
The present invention has been made in view of the above circumstances, and an object thereof is to provide a method for pretreating molten iron, which can reduce the amount of quicklime used as a refining agent while reducing the amount of slag discharged from the system and avoiding the occurrence of splashing.
Means for solving the problems
(1) A molten iron pretreatment method according to one aspect of the present invention is a molten iron pretreatment method for recycling converter slag, which is obtained when molten iron having undergone a molten iron pretreatment step is converter-refined, as a refining agent for the molten iron pretreatment, the method including the steps of: a first step 1 of sizing the converter slag so that the particle size of the converter slag is in a range of 3mm or more and less than 25mm, and the ratio of the converter slag having a particle size of 20mm or more and less than 25mm in the converter slag is 10 mass% or more and less than 15 mass% with respect to the total amount of the converter slag; a step 2 of charging the converter slag after the size reduction into a molten iron pretreatment vessel; a 3 rd step of adding 1.0 mass% or more and less than 10.0 mass% of Al to 100 mass% of the converter slag after the 1 st step and before the 2 nd step or simultaneously with the 2 nd step2O3Putting into the molten iron pretreatment container; and a 4 th step of charging MnO of 0.3 mass% or more and less than 10.0 mass% based on 100 mass% of the converter slag into the molten iron pretreatment vessel.
According to the molten iron pretreatment method including the above configuration, the amount of quicklime used as a refining agent can be reduced while avoiding the occurrence of splashing by reducing the amount of the slag discharged from the system.
(2) In thatIn the molten iron pretreatment method according to the above (1), the Al is2O3Al contained in secondary refining slag obtained when molten steel after a converter refining step is subjected to secondary refining may be used2O3。
(3) The method for pretreating molten iron according to (1) or (2) above may further comprise a 5 th step of charging into the molten iron pretreatment vessel iron oxide in an amount of 1.0 mass% or more and less than 20.0 mass% in terms of FeO with respect to 100 mass% of the converter slag after the 1 st step and before the 2 nd step or simultaneously with the 2 nd step.
(4) The molten iron pretreatment method according to any one of the above (1) to (3), further comprising a 6 th step of charging, into the molten iron pretreatment vessel, K in an amount of 0.3 mass% or more and less than 5.0 mass% based on 100 mass% of the converter slag simultaneously with the 3 rd step2O、Li2O、Na2O、CaF2MgO, SrO, and the like.
Effects of the invention
According to the hot metal pretreatment method of the present invention, since slagging of converter slag can be promoted without increasing the viscosity of slag in the hot metal pretreatment vessel, the amount of discharged slag from the system can be reduced, occurrence of splashing can be avoided, and the amount of quicklime used as a refining agent can be reduced.
Drawings
Fig. 1 is a flowchart for explaining the hot metal pretreatment method according to the present embodiment.
FIG. 2 is a graph showing the influence of the ratio of converter slag having a particle size of 20mm or more and less than 25mm in converter slag on the slag formation rate of converter slag and the incidence of clogging of a charging hopper.
FIG. 3 shows Al with reference to the slag charging time of the converter (0 second)2O3A graph showing a relationship between the charging timing (charging time) and the slag formation rate of the converter slag.
Detailed Description
Preferred embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.
The converter slag obtained when the hot metal after the hot metal pretreatment step is decarburized and refined in a converter has a low P (phosphorus) content and contains a large amount of CaO, which is a main component of the basic slag required for production of de-P or de-S (nitrogen).
In the hot metal pretreatment method according to the present embodiment, as shown in fig. 1, hot metal pretreatment of blast furnace hot metal, converter refining, and secondary refining are performed in this order. In the hot metal pretreatment method according to the present embodiment, the converter slag obtained by converter refining is recycled as a refining agent in the hot metal pretreatment step, thereby reducing the amount of quicklime (CaO not derived from the converter slag) used as the refining agent in the hot metal pretreatment step and reducing the system discharge amount of the converter slag.
Here, the melting point of the converter slag is about 1400 ℃ and the lumps of the converter slag do not dissolve at the pretreatment temperature of the molten iron, i.e., about 1300 ℃ to 1350 ℃.
In the molten iron pretreatment method of the present embodiment, Al is used as a substance that promotes the melting of converter slag at a low melting point2O3、MnO、FeO、K2O、Li2O、Na2O、CaF2The respective components of MgO and SrO are added together with the converter slag, and the particle size of the converter slag is reduced. This makes it possible to rapidly melt converter slag to improve the slagging rate and to improve the refining efficiency, i.e., to reduce the amount of raw lime additionally used as a refining agent and to improve the depp ratio.
In the molten iron pretreatment method according to the present embodiment, converter slag obtained in converter refining (decarburization) is discharged, cooled, and then the slag that has been refined into fine particles is screened and screened as follows: the ratio of the converter slag having a particle size of 20mm or more and less than 25mm in the converter slag is set to be in the range of 3mm or more and less than 25mm in terms of particle size (equivalent spherical diameter), and is set to 10 mass% or more and less than 15 mass% with respect to the total amount of the converter slag (step 1).
Then, the converter slag after the size reduction is charged into the hot metal pretreatment vessel in order to recycle it as the refining agent (step 2).
By setting the particle size of the converter slag in the range of 3mm or more and less than 25mm, the reaction interface area is increased and heat transfer is promoted, so that the converter slag can be melted quickly.
By setting the particle size of the converter slag to 3mm or more, it is possible to suppress a part or all of the converter slag charged by dust collection from escaping to the outside of the reaction vessel and sufficiently contribute to the reaction. Therefore, the amount of the lime used additionally can be suppressed. By setting the particle size of the converter slag to less than 25mm, the specific surface area of the converter slag can be greatly secured, and the slag formation rate increases because the melting time of the slag is shortened. This increases the refining efficiency, and therefore, the amount of raw lime to be additionally used can be suppressed.
In addition, the inventors of the present invention performed tests in an actual machine operation while variously changing the ratio of slag having a particle size of, in particular, 20mm or more and less than 25mm among the converter slag granulated in the range of 3mm or more and less than 25mm as described above, and obtained results as shown in fig. 2.
From the results shown in fig. 2, when the ratio of the converter slag having a particle size of 20mm or more (and less than 25mm) to the total amount of the converter slag is 10 mass% or more, the rate of occurrence of clogging of the charging hopper is low, and the operation is not significantly hindered. In addition, when the ratio of the converter slag having a particle size of 20mm or more (and less than 25mm) is less than 15% by mass relative to the total amount of the converter slag, the slag formation rate of the converter slag increases.
Therefore, the ratio of the converter slag having a grain size of 20mm or more (and less than 25mm) to the total amount of the converter slag satisfies the above-described condition of the grain size of the converter slag within the range indicated by the arrow in the graph, and thus the converter slag can be efficiently reused as a refining agent without hindering the operation.
In the molten iron pretreatment method of the present embodimentBefore or simultaneously with the charging of the converter slag, that is, after the 1 st step and before the 2 nd step or simultaneously with the 2 nd step, Al is charged into the hot metal pretreatment vessel in an amount of 1.0 mass% or more and less than 10.0 mass% relative to 100 mass% (total amount) of the converter slag2O3(step 3), and 0.3 mass% or more and less than 10.0 mass% of MnO is charged (step 4). This can promote slagging of the converter slag while avoiding an increase in the viscosity of the slag.
In Al2O3When the amount of (b) is 1.0 mass% or more, the effect of lowering the melting point of the slag is sufficiently obtained, and the melting point of the slag reaches 1250 ℃ or less, which is the molten iron temperature, and the slag formation rate is improved. As a result, the amount of lime to be additionally used can be suppressed.
In Al2O3When the amount of (b) is less than 10.0 mass%, the increase in slag viscosity is suppressed, and the foaming of the slag is suppressed, so that the probability of occurrence of splashing of the slag overflowing from the reaction vessel can be reduced.
When the amount of MnO added is 0.3 mass% or more, an effect of suppressing an increase in slag viscosity can be obtained. As a result, the probability of occurrence of splash can be reduced.
Even when the amount of MnO added exceeds 10.0 mass%, no significant change in the effect is observed. Therefore, in order to suppress the cost, the amount of MnO added is preferably set to 10.0 mass% or less. As the MnO source, for example, manganese ore pulverized to about 30mm can be used. The 4 th step of charging MnO may be the same as charging Al2O3At the same time as the 3 rd step (b), before the 3 rd step or after the 3 rd step.
In addition, as a result of experimental studies, the inventors of the present invention clarified the relationship of fig. 3. From the results of fig. 3, it can be seen that: al as a slagging promoter2O3Before or simultaneously with the charging of the converter slag, the slagging rate of the converter slag is high (the range indicated by the arrow in the graph). On the other hand, it is known that: al is added after the converter slag is added2O3In the case of (2), the effect of promoting slagging is low.
As Al2O3The source is preferably recycled from the secondary refining slag obtained in the secondary refining of the molten steel after the converter refining step. Generally, about 20.0 to 40.0 mass% of Al is contained in the secondary refining slag2O3. Therefore, if the chemical composition of the secondary refining slag is analyzed in advance to determine the amount of the secondary refining slag to be charged, the desired Al can be achieved only by charging the secondary refining slag2O3And (4) concentration.
Thus, the secondary refining slag is made into Al2O3Recycling of the source is equivalent to reduction of the amount of discharged slag generated in the steel-making process (molten iron pretreatment process, converter refining process, and secondary refining process), and can reduce the cost and environmental load associated with slag disposal. That is, since the amount of secondary refined slag used is equal to the amount of slag system outward discharge reduction, the cost and environmental load caused by slag discard can be reduced by reducing the amount of secondary refined slag used.
In addition, secondary refining slag is not used as Al2O3As the source, bauxite, gibbsite or the like containing Al can be used2O3Minerals, waste high alumina bricks, etc.
The FeO is used as a solid oxygen source in the pretreatment of molten iron. Preferably, the method comprises a step 5 of charging into the molten iron pretreatment vessel iron oxide in an amount of 1.0 mass% or more and less than 20.0 mass% in terms of FeO with respect to 100 mass% of the converter slag.
This can improve the refining efficiency. As the iron oxide source, in addition to iron ore, a lump obtained by sintering fine ore, a pellet obtained by molding scale powder or dust, or the like can be used.
The 5 th step is preferably performed after the 1 st step and before the 2 nd step or simultaneously with the 2 nd step.
K as defined above2O、Li2O、Na2O、CaF2MgO and SrO are used as slag promoters for lowering the melting point of slag. Preferably, the method comprises a 6 th step of charging 1 or 2 or more of these slag accelerators in an amount of 0.3 mass% or more and less than 5.0 mass% based on 100 mass% of the converter slag into the molten iron pretreatment vessel. This increases the slag formation rate of the converter slag to improve the refining efficiency.
When the amount of the above-mentioned slagging promoter to be added is 0.3% by mass or more, the refining efficiency is further improved. In addition, when the amount of the above-mentioned slagging promoter to be charged is less than 5.0 mass%, the refining efficiency can be improved and the production cost can be suppressed.
In addition, the components of these slagging promoters are mixed with Al2O3The slag formation promoting effect of the converter slag can be enjoyed by the same timing of the introduction. As the form of the addition of these components, in addition to the chemical substance obtained by purifying the above-mentioned compound as a main component, a compound containing the above-mentioned component, for example, K2CO3、Li2CO3、Na2CO3、MgCO3、SrCO3Carbonate, ore such as fluorite, feldspar, and dolomite, or mineral powder of about 20mm in size can be used.
The converter slag and Al2O3、MnO、FeO、K2O、Li2O、Na2O、CaF2The method of charging the slagging promoter such as MgO or SrO is not particularly limited, and it is sufficient to add the slagging promoter to the iron melt pretreatment vessel during the iron melt pretreatment.
The present invention can be applied to an operation mode in which the converter refining and the hot metal pretreatment are performed in different refining vessels, and an operation mode in which the converter refining and the hot metal pretreatment are performed by alternately using the same converter.
In the operation mode in which the converter refining and the hot metal pretreatment are performed by alternately using the same converter, a part of the converter slag may be left after the converter refining treatmentSlag is discharged, and molten iron to be pretreated, fine particles of the converter slag, and Al are charged into the slag2O3And waiting for slagging promoters to carry out iron liquid pretreatment.
As described above, the hot metal pretreatment method according to the present embodiment is a hot metal pretreatment method in which the converter slag obtained when the hot metal after the hot metal pretreatment step is converter refined is recycled as a refining agent for hot metal pretreatment.
The method for pretreating molten iron according to the present embodiment includes a step 1 of sizing converter slag so that the particle size of the converter slag is in a range of 3mm or more and less than 25mm, and the ratio of the converter slag having a particle size of 20mm or more and less than 25mm in the converter slag is 10 mass% or more and less than 15 mass% with respect to the total amount of the converter slag.
The hot metal pretreatment method according to the present embodiment includes a 2 nd step of charging the converter slag after the size reduction into a hot metal pretreatment vessel.
The method for pretreating molten iron according to the present embodiment includes a 3 rd step of adding 1.0 mass% or more and less than 10.0 mass% of Al to 100 mass% of the converter slag before the 2 nd step or simultaneously with the 2 nd step after the 1 st step2O3And (4) putting the molten iron into the molten iron pretreatment container.
The hot metal pretreatment method according to the present embodiment includes a 4 th step of charging MnO in an amount of 0.3 mass% or more and less than 10.0 mass% based on 100 mass% of the converter slag into the hot metal pretreatment vessel.
This can promote slagging of converter slag without increasing the viscosity of slag in the hot metal pretreatment vessel, and therefore can reduce the amount of slag discharged from the system, avoid splashing, and reduce the amount of quicklime used as a refining agent.
[ examples ]
Hereinafter, the results of the experimental examples and the like will be described in order to confirm the effect of the molten iron pretreatment method of the present invention.
First, after the converter slag obtained when the molten iron after the molten iron pretreatment step was converter-refined was cooled, the slag that had been made into fine particles was sieved, and fine particles of the converter slag having particle sizes set to those shown in table 1 below were obtained.
Al is added in a proportion shown in the following Table 1 based on 100 mass% (total amount) of fine particles in the converter slag2O3MnO and other auxiliary raw materials are put into the molten iron pretreatment container. Then, the dep treatment was performed under the same conditions as the other refining conditions.
In table 1, the column entitled "secondary refining slag ratio (% by mass)" indicates the numerical value of Al to be charged in the experimental examples2O3Derived from Al contained in secondary refining slag2O3。
In Table 1, Al described in each experimental example is shown2O3The time of charging converter slag after charging and the rate of removal of P ([% P)]Initial stage―[％P]After finishing)/[％P]Initial stage) Adding a quick lime to the converter slag in an amount of 100 mass% based on the converter slag to be added in the pretreatment of the molten iron, and adding Al to the converter slag2O3The melting point of the converter slag in the case of MnO and other auxiliary materials, the presence or absence of splashing, and the amount of discharged slag from the slag system by secondary refining slag recirculation, reduce the unit consumption resources, the incidence of hopper clogging of the auxiliary materials, the slag formation rate of the converter slag, and the like. The presence or absence of the splash was judged by visually checking the occurrence of the splash during the iron liquid pretreatment.
The rate of removal of P must be 80% or more in order to satisfy the allowable P concentration in the product. The amount of the added quicklime in the decarburization furnace is adjusted so as to achieve a dephosphorization ratio of 80% or more. Since the added quicklime is 60 to 90% in the case where the present invention is not applied, if it is less than 60%, it is considered that the refining efficiency is improved.
The melting point of the converter slag is about 1400 ℃ without carrying out the present invention. When the melting point of the converter slag is lowered to 1350 ℃ or less, which is the molten iron temperature, the slagging rate is increased, and improvement of the refining efficiency can be expected.
The amount of discharged slag system is reduced to a value that recycles secondary refined slag that should be discharged outside the system, and therefore is equivalent to Al2O3The unit consumption resources of the secondary refining slag amount input by the source are consistent.
Since the operation is greatly hindered when the rate of occurrence of clogging of the subsidiary raw material charge hopper exceeds 10%, the rate of occurrence of clogging of the subsidiary raw material charge hopper must be less than 10%.
The slagging rate of the converter slag is defined as (CaO concentration in slag after completion of refining)/(CaO concentration when the converter slag is completely dissolved) × 100 (%), and if it exceeds 40 (%), the amount of quicklime used as a refining material can be reduced, and therefore it is judged that the refining efficiency can be improved.
[ Table 1]
[ Table 2]
As shown in examples 1 to 30, it was confirmed that: the converter slag is granulated so that the ratio of converter slag having a grain size of 3mm or more and less than 25mm and a grain size of 20mm or more and less than 25mm in the converter slag is 10 mass% or more and less than 15 mass% with respect to the total amount of the converter slag, and 1.0 mass% or more and less than 10.0 mass% of Al2O3When the catalyst is used together with MnO in an amount of 0.3 mass% or more and less than 10.0 mass%, the amount of quicklime (CaO which is not derived from the slag of the converter) used can be reduced and a high dephosphorization ratio can be maintained as compared with comparative examples 1 to 41. In addition, the secondary refining slag is used as Al2O3When the source is used for recycling, the amount of slag discharged from the system can be reduced.
No intentional addition of Al2O3In comparative example 1, the melting of the converter slag did not progress, and the P removal rate was decreased. In order to ensure that the rate of removal of P is 80%, the amount of added quicklime is increased, and as a result, the added quicklime proportion reaches 66 mass%.
The converter slag of comparative example 2, in which the maximum grain size of the converter slag was set to 51mm, was also difficult to melt, and the amount of quicklime (CaO not derived from the converter slag) used was required to be increased to 90 mass% in order to ensure a depp removal rate of 82%.
In comparative example 3 in which MnO was not added, Al was considered2O3The viscosity of the slag was greatly increased, and the slag was likely to foam, and therefore, the occurrence of splashing was confirmed.
In comparative example 4 in which the minimum particle size of the converter slag was set to 0.8mm, the converter slag was not sufficiently charged into the molten iron pretreatment furnace because the converter slag was sucked and lost by the dust collector, and a large amount of quick lime was used to maintain the depp ratio.
With respect to Al2O3In comparative example 5 in which the charged amount was 12.0 mass%, the viscosity of the slag increased significantly, and spattering occurred.
In comparative example 6 in which the amount of MnO added was 17.0 mass%, the amount of quicklime used and the depp ratio were both good, but the cost increased and a loss occurred due to the use of a large amount of manganese ore.
In comparative examples 30 and 31 in which the ratio of the particle size of 20mm or more and less than 25mm was as high as 17 mass% and 50 mass%, respectively, the slag formation rate of the converter slag was low, and a large amount of quick lime was required to maintain the depp ratio.
With respect to Al2O3In comparative example 32 in which the amount of (3) was as low as 0.2 mass%, the slag formation rate of the converter slag was low, and a large amount of quicklime was required to maintain the depp rate.
With respect to Al2O3In comparative example 33 in which the amount of (3) was as high as 20.0 mass%, the viscosity of the slag increased, and therefore, significant splashing occurred, and the operation was hindered.
In comparative example 34 in which MnO was not added, since there was no effect of lowering the slag viscosity by MnO, splash was generated and the operation was hindered.
In comparative example 35 in which MnO was added in an amount of as much as 17.0 mass%, the amount of quicklime used and the depp ratio were both good, but the cost increased and the loss occurred due to the use of a large amount of manganese ore.
Al serving as a slagging promoter is added 78-257 seconds after the converter slag is added2O3In comparative examples 36 to 41, the slag formation rate of the converter slag was as low as 11 to 25%, and in order to increase the rate of removal of P, additional quicklime was used in the decarburization step, which increased the cost.
In comparative examples 7 to 29 in which the ratio of converter slag having a particle size of 20mm or more and less than 25mm was low, the amount of quicklime used and the depp ratio were good, but the rate of occurrence of clogging of the sub-raw material hopper was high, and the operation was hindered.
As described above, according to the hot metal pretreatment method of the present invention, slagging of converter slag can be promoted without increasing the viscosity of slag in the hot metal pretreatment vessel. In addition, according to the method for pretreating molten iron of the present invention, an operation-hindering factor such as a blockage of the charging hopper can be avoided.
Industrial applicability
The molten iron pretreatment method of the present invention can reuse slag generated in a steel-making process as a refining agent to reduce the amount of slag discharged from the system, and can avoid the occurrence of splashing due to the use of the refining agent.
Claims (5)
1. A method for pretreating molten iron is characterized in that,
the method for pretreating molten iron comprises recycling converter slag, which is obtained when the molten iron having undergone the molten iron pretreatment step is converter-refined, as a refining agent for the molten iron pretreatment,
the method comprises the following steps:
a first step 1 of sizing the converter slag so that the particle size of the converter slag is in a range of 3mm or more and less than 25mm, and the ratio of the converter slag having a particle size of 20mm or more and less than 25mm in the converter slag is 10 mass% or more and less than 15 mass% with respect to the total amount of the converter slag;
a 2 nd step of charging the converter slag after the size reduction in the 1 st step into an iron melt pretreatment vessel;
a 3 rd step of adding 1.0 mass% or more and less than 10.0 mass% of Al to 100 mass% of the converter slag after the 1 st step and before the 2 nd step or simultaneously with the 2 nd step2O3Putting into the molten iron pretreatment container; and
and a 4 th step of charging MnO in an amount of 0.3 mass% or more and less than 10.0 mass% based on 100 mass% of the converter slag into the molten iron pretreatment vessel simultaneously with the 3 rd step or before or after the 3 rd step.
2. The method of pretreating molten iron according to claim 1,
the Al is2O3Al contained in secondary refining slag obtained when molten steel after a converter refining step is subjected to secondary refining2O3。
3. The method of pretreating molten iron according to claim 1,
further comprising a 5 th step of charging into the molten iron pretreatment vessel, after the 1 st step and before the 2 nd step or simultaneously with the 2 nd step, 1.0 mass% or more and less than 20.0 mass% of iron oxide in terms of FeO with respect to 100 mass% of the converter slag.
4. The method of pretreating molten iron according to claim 2,
further comprising a 5 th step of charging into the molten iron pretreatment vessel, after the 1 st step and before the 2 nd step or simultaneously with the 2 nd step, 1.0 mass% or more and less than 20.0 mass% of iron oxide in terms of FeO with respect to 100 mass% of the converter slag.
5. The molten iron pretreatment method according to any one of claims 1 to 4,
further comprising a 6 th step of charging K in an amount of 0.3 mass% or more and less than 5.0 mass% based on 100 mass% of the converter slag into the molten iron pretreatment vessel simultaneously with the 3 rd step2O、Li2O、Na2O、MgO、CaF2And 1 or 2 or more of SrO.
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| PCT/JP2017/010850 WO2017159840A1 (en) | 2016-03-17 | 2017-03-17 | Molten-iron pretreatment method |
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| DE3836549C1 (en) * | 1988-10-27 | 1990-01-18 | Krupp Stahl Ag, 4630 Bochum, De | Process for desulphurising molten crude iron |
| JPH04120209A (en) | 1990-09-10 | 1992-04-21 | Sumitomo Metal Ind Ltd | Slag forming agent reutilizing converter slag |
| JPH06287615A (en) * | 1993-04-01 | 1994-10-11 | Nippon Steel Corp | Method for utilizing slag in converter |
| JP3097474B2 (en) * | 1994-12-05 | 2000-10-10 | 住友金属工業株式会社 | Hot metal dephosphorization method |
| JP2006274349A (en) | 2005-03-29 | 2006-10-12 | Sumitomo Metal Ind Ltd | Method for refining steel |
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| CN103370426B (en) * | 2011-02-10 | 2014-10-15 | 新日铁住金株式会社 | Method for desiliconizing and dephosphorizing hot metal |
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