JP2002105523A - Method for refining molten iron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high dephosphorizing efficiency in dephosphorization- refining using a molten iron ladle or a converter type vessel, or the like, performed before decarburization-refining. SOLUTION: When dephosphorizing treatment is performed by adding a CaO source and an oxygen source into molten iron tapped from a blast furnace, desiliconizing treatment is applied, as necessary, to the molten iron tapped from the blast furnace, the dephosphorizing treatment is performed to the molten iron having <=0.7 wt.% of Si content. Or, desirably the molten iron temperature when the dephosphorizing treatment starts, is adjusted to >=1,280 deg.C and the molten iron temperature when the dephosphorizing treatment completes, is adjusted to 1,280-1,380 deg.C to perform the dephosphorizing treatment. In this way, a drastically higher dephosphorizing efficiency in comparison with the conventional method, is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for refining hot metal, and more particularly to a method for refining hot metal with high efficiency.

[0002]

2. Description of the Related Art Conventionally, in converter steelmaking, dephosphorization and decarburization of hot metal have been performed in the same converter. However, in recent years, while the demand for steel quality has increased, with the expansion of continuous casting, and the spread of secondary refining of molten steel such as vacuum degassing and ladle refining, the tapping temperature in the converter has increased, The dephosphorization capacity in the converter has been reduced. This is because the higher the hot metal temperature, the lower the dephosphorization efficiency.

[0003] Against this background, there has been developed a hot metal pretreatment method in which hot metal is smelted in advance and, in particular, a phosphorus component is removed to some extent and then charged into a converter. In this method, dephosphorization and refining of hot metal is performed using a hot metal pot or a converter type vessel, and the dephosphorized hot metal is usually transferred to another converter to perform decarburization refining. In Japanese Patent Publication No. 2-14404 and Japanese Patent Publication No. 3-77246, one of two converter-type containers having a double-blowing function is used as a dephosphorization furnace and the other as a decarburization furnace. A method for refining hot metal under the following conditions has been proposed.

[0004]

However, such dephosphorization and refining of hot metal requires a constant slag volume, and is a low-temperature operation compared to decarburization blowing. As a result, there was a problem that the original dephosphorization efficiency could not be exhibited, and as a result, the dephosphorization treatment time was prolonged and the refining cost had to be increased in some cases. Further, depending on the raw material components such as iron ore, the concentration of impurities such as P may increase during tapping of the blast furnace, and it is necessary to flexibly cope with such fluctuations in operating conditions on the iron making side.

Accordingly, an object of the present invention is to solve such problems of the prior art, and to perform dephosphorization refining using a hot metal pot or a converter type vessel performed before decarburization refining with high efficiency. It is to provide a hot metal refining method.

[0006]

Means for Solving the Problems The present inventors have studied the conditions for increasing the dephosphorization efficiency in the above-mentioned dephosphorization refining mainly from the aspects of hot metal components, hot metal temperature, and conditions for adding a medium solvent. As a result, the amount of Si in the hot metal before the dephosphorization treatment is sufficiently reduced, specifically, the amount of Si is reduced to a level of 0.07 wt% or less, and the dephosphorization of such hot metal is performed. It has been found that by performing the treatment, the dephosphorization efficiency can be dramatically increased as compared with the conventional method. In addition, in such a dephosphorization treatment, the hot metal temperature at the start of the dephosphorization treatment and the hot metal temperature at the end of the dephosphorization are appropriately controlled. It was found that the efficiency of dephosphorization was further improved by the supply. Further, it was also found that by performing the desiliconization treatment of the hot metal under a predetermined condition using a ladle, the Si reduction of the hot metal can be stably achieved.

Conventionally, it has been qualitatively known that a lower amount of Si in the hot metal is advantageous for enhancing the dephosphorization efficiency. For this reason, desiliconization has been performed as part of the hot metal pretreatment. I have. However, in the conventional hot metal desiliconization treatment, the Si level in the hot metal after the desiliconization treatment is usually about 0.2 wt%, and the Si content in the hot metal before such dephosphorization treatment is high. It has been considered that the effect of reducing the amount of phosphorus is such that the dephosphorization efficiency gradually increases. On the other hand, in the present invention, by setting the content of Si in the hot metal before the dephosphorization treatment to a level one digit lower than that of the conventional technology (0.07 wt% or less), a remarkably high dephosphorization efficiency can be obtained. That's what I found.

[0008] The present invention has been made based on such findings, and the features thereof are as follows. [1] A method for refining hot metal comprising adding a CaO source and an oxygen source to hot metal and performing a dephosphorization process on the hot metal having a Si content of 0.07 wt% or less. [2] The hot metal refining method according to [1], wherein the hot metal is desiliconized to reduce the amount of Si to 0.07 wt% or less, and then dephosphorized.

[3] The hot metal refining method according to the above [1] or [2], wherein the hot metal temperature at the start of the dephosphorization treatment is 1280 ° C. or higher. [4] In the hot metal refining method according to any one of the above [1] to [3],
A hot metal refining method, wherein the hot metal temperature at the end of the dephosphorization treatment is 1280 to 1360 ° C. [5] In the hot metal smelting method according to any one of the above [2] to [4],
As a desiliconization treatment of the hot metal, at least a desiliconization treatment in a ladle is performed. In the desiliconization treatment in the ladle, at least gaseous oxygen is supplied as a desiliconization material, and the supply of the gaseous oxygen to the hot metal is performed. A hot metal refining method characterized by performing spraying and / or blowing into hot metal.

[6] In the hot metal refining method according to any one of the above [2] to [4], at least desiliconization in a ladle is performed as desiliconization of the hot metal, and desiliconization in the ladle is performed. A hot metal refining method characterized by supplying a gaseous oxygen and / or solid oxygen source as a desiliconizing material in the treatment and adjusting the hot metal temperature by adjusting the supply amount of the gaseous oxygen and / or solid oxygen source. [7] In the hot metal refining method according to any one of the above [1] to [6],
A method for refining molten iron, comprising supplying a CaO source and an oxygen source to a bath surface or the same position in a bath in a dephosphorization treatment vessel in the dephosphorization treatment.

[8] In the refining method according to any one of the above [1] to [7], the dephosphorization treatment is performed under the following condition (a), and then the decarburization treatment is performed under the following condition (b). Characteristic refining method. (A) In a smelting vessel, hot metal is dephosphorized and refined to a P content (specified steel component value) required for crude steel. (B) The dephosphorized and refined hot metal is charged into a converter type vessel, which is another refining vessel, and decarburized and refined without substantially charging a slag-making material.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below together with the reasons for limiting the same. FIG. 1 shows that the amount of Si is 0.19 wt%.
Hot metal and 0.05 wt% of hot metal are dephosphorized in a converter type vessel (hot metal temperature at the start of dephosphorization process: 128
0 ° C or higher, hot metal temperature at the end of dephosphorization treatment: 1280 to 13
60 ° C., on top of quick lime) shows the results of investigating the progress of hot metal dephosphorization, and the amount of Si: 0.05 wt.
% Of the hot metal in the hot metal dephosphorization treatment, the P content in the hot metal reaches the minimum level in less than half the time as compared with the case where the hot metal with the Si content: 0.19 wt% is dephosphorized, and the level is the same as the Si content:
It turns out that it is lower than the case where 0.19 wt% of hot metal is dephosphorized.

[0013] Since these test results were obtained,
Furthermore, the effect of the amount of Si in the hot metal subjected to the dephosphorization treatment on the dephosphorization efficiency was examined. In this test, desiliconization was performed before the dephosphorization treatment to adjust the amount of Si in the hot metal, and the hot metal temperature at the start of the dephosphorization treatment in the converter type vessel as in the test of FIG.
1280 ° C or higher, hot metal temperature at the end of dephosphorization treatment: 1280
A dephosphorization treatment was performed at ~ 1360 ° C under the condition of addition over quicklime.

FIG. 2 shows the results together with the addition amount of the CaO source. When the amount of Si in the hot metal supplied for the dephosphorization treatment becomes 0.07 wt% or less, the dephosphorization efficiency is increased by increasing the basicity of the slag. Distribution Lp (= (wt% P) /
[Wt% P], (wt% P): P concentration in slag, [w
t% P]: P concentration in the hot metal rapidly increased, and a remarkable improvement in the dephosphorization efficiency was observed. Further, the dephosphorization efficiency increases as the Si content in the hot metal decreases, and the highest dephosphorization efficiency is obtained when the Si content in the hot metal is approximately 0.03 wt% or less.

[0015] Based on the above results, in the method of the present invention, the hot metal having a Si content of 0.07 wt% or less is subjected to a dephosphorization treatment. Further, from the results of FIG. 2, the more preferable Si amount before the dephosphorization treatment is 0.05 wt% or less, further preferably 0.03 wt% or less. In carrying out the method of the present invention, the amount of Si in the hot metal before the dephosphorization treatment is set to the above upper limit (0.
If the amount exceeds 0.7 wt%, preferably 0.05 wt%, particularly preferably 0.03 wt%), desiliconization is performed to reduce the amount of Si in the hot metal to an upper limit or less, and then dephosphorization is performed. . Generally, molten iron from a blast furnace etc.
About 0.50 wt% of Si is contained, and in the case of such a hot metal having a normal Si level, it is essential to perform a desiliconization treatment.

The desiliconization treatment may be carried out in either a hot metal desiliconization step (for example, cast bed desiliconization) or in a vessel. In the desiliconization process in a container, a ladle such as a hot metal pot or a charging pan, a torpedo, etc. are used as containers, and an efficient desiliconization process is performed by adding a desiliconizing material to the container and stirring. It can be carried out. As the desiliconizing material, either solid acid (usually, iron oxide such as mill scale) or gaseous acid (gaseous oxygen or oxygen-containing gas) may be used, or both may be used in combination.

The desiliconization treatment performed in the ladle can sufficiently stir the hot metal due to the shape of the hot metal holding, so that the silicon is more desiliconized than other hot metal desiliconization processes (for example, a desiliconization process using a cast bed or a torpedo). Efficient. Therefore, when the amount of Si in the hot metal that has been tapped is relatively high, desiliconization in the ladle is performed, or desiliconization in the casting bed is performed before desiliconization in the ladle. Is preferred. Further, in the conventional desiliconization of a cast bed, there is a problem that not only the desiliconization efficiency is low, but also the hot metal temperature is lowered because only a solid acid (mill scale or the like) is used as a desiliconization material. On the other hand, in the desiliconization treatment performed in the ladle, gaseous oxygen can be supplied as a desiliconization material, so that the maintenance and stabilization of the hot metal temperature is easy, and the supply of a solid oxygen source can be used together. In addition, it is easy to adjust the hot metal temperature.

Examples of the ladle include a so-called blast furnace pot for directly receiving hot metal through a blast furnace cast bed, and a so-called charging pot for transferring hot metal from a blast furnace pot for charging hot metal to a converter or the like. included. In addition, any pot having a hot metal holding shape similar to the blast furnace pot or the charging pot can be used as a ladle. The desiliconization treatment using a ladle may be performed in at least one of these blast furnace pans, charging pans, and other ladles.

FIG. 3 shows the relationship between the amount of Si in the hot metal after the desiliconization treatment and the desiliconization oxygen efficiency when desiliconization in the ladle and desiliconization of the casting bed are performed. According to the figure, in the cast bed desiliconization, as the amount of Si in the hot metal after the treatment decreases, the desiliconization oxygen efficiency decreases significantly. For this reason, a long time treatment is required to desiliconize to the Si content: 0.07 wt% or less which is the condition of the present invention, and such desiliconization treatment lacks practicality in actual operation. On the other hand, in the ladle desiliconization, a higher desiliconization oxygen efficiency is obtained as compared with the cast bed desiliconization, and the Si content: 0.07 wt% or less (preferably, 0.
It can be seen that it is preferable to carry out desiliconization in the ladle in order to efficiently desiliconize to not more than 05 wt%, more preferably 0.03 wt%).

Further, as described above, since the desiliconization treatment in the ladle is usually performed by supplying gaseous acid, there is a possibility that the temperature of the hot metal may be lowered which affects the handling of the hot metal and the refining in the lower step. It is easy to secure the hot metal temperature and adjust the temperature, and if necessary, switch the gaseous acid supply to the solid acid supply or adjust the hot metal temperature by using the gaseous acid supply and the solid acid supply together. It is also easy to stabilize to a desired level.

In the desiliconization treatment of the hot metal, the desiliconization width (Δ% S
When i) becomes large, slag forming becomes remarkable,
The operation may not be practically possible. Therefore, when the total desiliconization width is relatively large, after performing cast floor desiliconization, desiliconization in the ladle is performed, and slag forming is performed by reducing the desiliconization width in one desiliconization process. Preferably, it is suppressed. In addition, it is advantageous to perform the desiliconization treatment in two steps and to reduce the desiliconization width in one step, in particular, since the time required for desiliconization after the desiliconization in the ladle can be shortened.

As mentioned above, the desiliconization treatment in the ladle is
There is a great feature that the supply of gaseous acid as a desiliconization material enhances the desiliconization efficiency and prevents a drop in the hot metal temperature. Therefore, in this desiliconization treatment, gas is used as part or all of the desiliconization material. Preferably, an acid is used. The gaseous oxygen (gas acid) used in the present invention may be either an oxygen gas or an oxygen-containing gas. The method of supplying this gaseous acid into the ladle is: (1) a method of spraying hot metal from above with an upper blowing lance, (2) a method of blowing hot metal through an injection lance, and (3) a method provided in the ladle body. A method of blowing into the hot metal through a blowing nozzle such as a bottom blowing nozzle can be adopted, and the supply of gaseous acid can be performed by any of these methods or a combination of two or more methods.

Another feature of the desiliconization treatment in the ladle is that sufficient stirring of the hot metal is obtained, and the stirring of the hot metal is carried out in the hot metal with gaseous acid or other stirring gas (for example, nitrogen gas). )
Can be realized by injecting As a specific method, a method of blowing a gas into the hot metal through the above-described injection lance, a method of blowing a gas into the hot metal through a blowing nozzle, and the like can be adopted, and any one of these methods or a combination of two or more methods can be employed. It is feasible.

Usually, during the desiliconization treatment in the ladle, the slag-making material and, if necessary, the solid acid are supplied. As a method for supplying these solid additives, (1) a method using overhead addition, 2) A method of spraying hot metal from above through an upper blowing lance, (3) A method of blowing hot metal through an injection lance, etc., and supplying the solid additive by any one of these methods or a combination of two or more methods Can be.
However, as for the supply of the solid additive, the method of (3) can increase the stirring power of the hot metal by using the kinetic energy of the solid additive rather than the methods of (1) and (2) above. Therefore, it is advantageous in increasing the desiliconization efficiency. Usually, a CaO source such as lime powder is supplied as the slag-making material, and a mill scale or sintered powder is supplied as the solid acid.

FIG. 4 shows an example of a desiliconization process using a ladle. In this example, gaseous acid (oxygen gas) is blown through an upper blowing lance, and slag forming material (lime powder or the like) is injected through an injection lance. Pneumatic gas: N ₂ ) is blown,
Further, if necessary, a solid acid such as a sintered powder or a mill scale can be placed on the ladle from above. As an example of the operating conditions of the desiliconization treatment with such a ladle,
When performing hot metal desiliconization processing mainly using gas acid supply in a 150-ton blast furnace pot, the gas acid supply amount by the top blowing lance: 250
Operating conditions are: 0 Nm ³ / hr, supply amount of lime powder (slag forming material) by injection lance: about 200 kg / min.

Further, in order to secure the hot metal temperature at the start of the dephosphorization process described later, it is preferable to adjust the temperature of the hot metal in the desiliconization process as needed. This temperature adjustment can be performed by appropriately selecting and adding solid acid and gaseous acid as a desiliconizing agent, but as described above, desiliconization in a ladle more advantageously adjusts the hot metal temperature. be able to.

The dephosphorization treatment is performed by adding a CaO source and an oxygen source to hot metal having a Si content of 0.07 wt% or less. Usually, this dephosphorization treatment is performed using a hot metal pot or a converter type vessel, but there is no special restriction on the vessel used.In some cases, desiliconization treatment and dephosphorization treatment are sequentially performed in the same vessel. You may. In this case, at least part of the residue is removed after the desiliconization treatment, and then the dephosphorization treatment is performed. Normally, quick lime is used as a CaO source as a medium solvent, but is not limited thereto. These medium-soluble materials and solid acids are added to the container by a method such as overhead addition or injection. Also,
The gaseous acid is generally added by a method such as blowing and / or blowing oxygen gas onto the hot metal using a lance or a bottom blow nozzle.

Although there are no particular restrictions on the method and conditions for performing the dephosphorization treatment, it is preferable to perform the dephosphorization treatment under the following conditions in order to perform the dephosphorization treatment with particularly high efficiency. (1) The hot metal temperature at the start of the dephosphorization treatment is 1280 ° C or higher (more preferably, 1320 ° C or higher). (2) The hot metal temperature at the end of the dephosphorization treatment is 1280 to 1360 ° C
(More preferably, 1300 to 1340 ° C.). (3) Supply the CaO source and the oxygen source to the bath surface or the same position in the bath in the dephosphorization vessel. (4) A FeO-CaO-based solvent is added as part or all of the solvent.

First, the condition (1) will be explained. In the method of dephosphorizing low Si hot metal as in the method of the present invention, the basicity of slag (= CaO / SiO ₂ ) increases, so And the initial slag formation of the solvent becomes insufficient, which tends to lower the dephosphorization efficiency. In order to prevent such a decrease in the dephosphorization efficiency, the initial slagging is promoted by setting the hot metal temperature at the start of the dephosphorization treatment to a reference value or more,
It is effective to generate molten FeO at an early stage. Therefore, the hot metal temperature at the start of the dephosphorization treatment is preferably set to 1280 ° C. or higher, more preferably 1320 ° C. or higher.

FIG. 5 shows the relationship between the hot metal temperature at the start of the dephosphorization process and the dephosphorization efficiency when the dephosphorization process was performed in the converter type vessel and in the hot metal pot (at the end of the dephosphorization process). Hot metal temperature: 1280-1360 ° C, Si in hot metal before dephosphorization
Converter: container: quick lime placed on top, hot metal ladle: quick lime placed on top + some injections), and the hot metal temperature at the start of the dephosphorization treatment is 12
It is found that by setting the temperature to 80 ° C. or higher, more preferably 1320 ° C. or higher, particularly excellent phosphorus removal efficiency (phosphorus distribution Lp) can be obtained. According to the figure, the dephosphorization treatment using a converter type vessel has a higher stirring efficiency than the dephosphorization treatment using a hot metal ladle, and the treatment time is limited.
It can be seen that higher phosphorus removal efficiency was obtained.

Further, it is preferable to set the dephosphorization treatment start temperature higher as described above, since iron loss (granular iron loss suspended in slag) can be reduced. FIG. 6 shows the effect of the hot metal temperature at the start of the dephosphorization treatment on the iron loss to the slag during the dephosphorization refining. The iron loss is remarkable when the hot metal temperature is 1280 ° C. or more, more preferably 1320 ° C. or more. It can be seen that it has been reduced to Therefore, from the above viewpoint, the hot metal temperature at the start of the dephosphorization treatment is desirably 1280 ° C or higher, and preferably 1320 ° C or higher.

Next, the condition (2) will be explained. The dephosphorization efficiency of the hot metal is better in terms of equilibrium when the hot metal temperature is relatively low, but when the hot metal temperature is too low, the formation of slag of the medium solvent becomes difficult. The dephosphorization efficiency is rather reduced due to the insufficient dephosphorization, so that the dephosphorization is performed within the operation upper limit time, so that the dephosphorization treatment temperature has an appropriate range in terms of the dephosphorization efficiency. The appropriate temperature range is 1280 at the hot metal temperature at the end of the dephosphorization treatment.
１３1360 ° C., more preferably 1300-1340 ° C. By ending the dephosphorization treatment at this hot metal temperature, good dephosphorization efficiency can be secured.

FIG. 7 shows the relationship between the hot metal temperature at the end of the dephosphorization process and the dephosphorization efficiency when the dephosphorization process is performed in a converter type vessel (hot metal temperature at the start of the dephosphorization process: 1280 ° C. or more, Si content in hot metal before phosphorus treatment: 0.07 wt% or less, addition to quicklime), and the hot metal temperature at the end of the dephosphorization process was 12
80-1360 ° C, more preferably 1300-1340
C., it is possible to obtain particularly excellent phosphorus removal efficiency (phosphorus distribution L
It can be seen that p) is obtained.

Further, regarding the above condition (3), Ca
Supplying the O source and the oxygen source to the bath surface or the same position in the bath in the dephosphorization treatment vessel, that is, F by the supplied oxygen source;
By simultaneously supplying the CaO source to the eO generation point, slag formation by the reaction of CaO + FeO is promoted, and as a result, the dephosphorization efficiency is enhanced.

FIG. 8 shows the results of the dephosphorization treatment using a converter type container (hot metal temperature at the end of the dephosphorization treatment: 1280 to 1360 ° C., the amount of Si in the hot metal before the dephosphorization treatment: 0.07 wt% or less) When the CaO source and the oxygen source are supplied to the bath surface in the container or at separate positions in the bath (quick lime: overhead addition, gas oxygen: top blowing), the CaO source and the oxygen source are supplied to the bath surface or bath in the container. When supplied to the same position inside (quicklime + gaseous oxygen:
For top blowing, the relationship between the hot metal temperature at the start of the dephosphorization treatment and the dephosphorization efficiency is shown. According to the figure, supplying the CaO source and the oxygen source to the same position in the bath surface or bath in the container supplies the CaO source and the oxygen source to different positions in the bath surface or bath in the container. It can be seen that a relatively excellent dephosphorization efficiency (phosphorus distribution Lp) can be obtained.

In the condition (4), FeO—C containing a CaO source and an oxygen source in a part or all of the solvent is used.
By using the aO-based solvent, the CaO source and the oxygen source are supplied to the bath surface in the container or to the same position in the bath (3).
The same operational effects as in the case of are obtained. This FeO-Ca
Calcium ferrite, a sintered product of a mixture of calcia and ferrite, or the like can be used as the O-based solvent.

FIG. 9 shows the results of the dephosphorization treatment using a converter type vessel (hot metal temperature at the end of dephosphorization treatment: 1280 to 1360 ° C., Si content in hot metal before dephosphorization treatment: 0.07 wt% or less) Using quick lime as a CaO source (medium solvent),
When the O source and the oxygen source are supplied to the bath surface in the vessel or at separate positions in the bath (quick lime: overhead addition, gas oxygen: top blowing), the FeO-CaO-based medium solvent (FeO
The graph shows the relationship between the hot metal temperature at the start of the dephosphorization treatment and the dephosphorization efficiency in the case of using (a mixed sintered material of + CaO) (medium solvent: overhead addition, gas oxygen: top blowing). According to the figure, the use of the FeO-CaO-based solvent as the solvent is relatively superior to the supply of the CaO source and the oxygen source to the bath surface in the container or to separate positions in the bath. It turns out that the dephosphorization efficiency (phosphorus distribution Lp) is obtained.

As shown in FIG. 5, the method of the present invention has a particularly large effect when the dephosphorization treatment is performed using a converter type vessel. This is because the converter-type container has a large free board compared to a ladle or torpedo, so that the stirring power can be increased, thereby causing rapid slagging and P mass transfer.

As described above, in the hot metal refining method of the present invention, a high dephosphorization efficiency can be obtained. Therefore, even if the P concentration in the blast furnace hot metal is increased by using a raw material such as iron ore having a high P concentration, Loads such as an increase in the processing time and the amount of the solvent in the medium can be reduced as compared with the related art, and therefore, it is possible to flexibly cope with a change in the hot metal component. In addition, since the high dephosphorization efficiency is obtained as described above, the amount of slag generated at the same dephosphorization amount can be reduced as compared with the conventional method, and this also allows for a more flexible response to fluctuations in the hot metal component compared to the conventional method. it can.

When the dephosphorization treatment is performed using a converter type container, the entire amount of scrap to be charged into the converter type container is charged before charging the hot metal into the converter type container. The scrap is easily melted, and the production of dephosphorized and refined hot metal can be increased. In the dephosphorizing refining in the refining method of the present invention, particularly in the dephosphorizing refining using a converter type vessel, the dephosphorizing refining time can be shortened as compared with the conventional method. It is possible in time to charge the entire amount of scrap to be charged. Further, since the hot metal to be dephosphorized and refined easily dissolves scrap because of its high carbon content, a relatively large amount of scrap can be charged. In addition, in the conventional slag blowing (decarburization) using hot metal dephosphorized iron, there was a problem that scrap was hardly melted due to insufficient heat capacity and production elasticity was poor. A normal level of scrap usage can be ensured in the processing steps.

In addition, when the scrap is charged into the converter-type container as described above, part or all of the scrap to be charged is replaced with the slag generated in the dephosphorization step and / or the decarburization step. Magnetic waste can be used, whereby slag generation is smooth even when the hot metal temperature is relatively low, and the P content at the end of dephosphorization refining is stably reduced. The magnetic separation waste is a portion (usually about Fe: about 50 wt%) containing a large amount of granular iron and the like obtained by separating the slag generated in the dephosphorization step and the decarburization step by a magnetic separator.

By the way, in a steelmaking method in which hot metal is dephosphorized and refined in a refining vessel such as a ladle or a converter type vessel, and the dephosphorized and refined hot metal is transferred to another converter type vessel and decarburized and refined. ,
Although the amount of generated slag can be reduced as compared with the related art, a recent trend is to further reduce the amount of steelmaking slag. In this respect, for example, the above-mentioned Tokuhei 2-1
Japanese Patent No. 4404 discloses a technique for reducing the amount of slag generated in the entire steelmaking process by using slag generated in decarburization refining in dephosphorization refining. It cannot meet the demand for reduction.

In the decarburization refining, manganese ore is charged to save the use of expensive manganese alloys.
Although the reduction of the Mn content in molten steel has been partially carried out, the reduction yield of Mn in manganese ore to molten steel is not always sufficient. For example, in the technique disclosed in Japanese Patent Publication No. 2-14404, MnO contained in slag generated in decarburization refining is discharged outside the system without being effectively used. As a result, MnO in the slag is diluted by adding a new slag material in the decarburization refining, and this is one of the factors that reduce the reduction yield of Mn in the charged manganese ore to molten steel. Has become one.

With respect to such a problem, by performing a high-efficiency dephosphorization treatment on hot metal in which the amount of Si has been sufficiently reduced in accordance with the method of the present invention, the hot metal can be converted to the P content of a normal crude steel component ( So-called steel component standard value, usually 0.02 wt% or less)
Dephosphorization and refining, and in the subsequent decarburization treatment step, substantially no debris is charged (therefore, without constantly discharging slag), and substantially only decarburization refining is performed. As a result, it was found that the steelmaking slag generation amount can be further reduced and the refining efficiency can be improved.

The preferred embodiment of the method of the present invention when such a steelmaking method is applied will be described below. [1] A refining method in which dephosphorization is performed under the following condition (a), and then decarburization is performed under the following condition (b). (A) In accordance with the method of the present invention, hot metal is dephosphorized and refined in a first refining vessel to a P content (standard component value of steel) required for crude steel. (B) The dephosphorized and refined hot metal is charged into a converter-type container, which is a second refining container, and decarburized and refined without substantially charging a slag-making material.

[2] In the refining method of the above [1], in the decarburization treatment step, the molten steel after the decarburization refining is produced, and only the slag corresponding to the amount of slag increased during the decarburization refining is required. Discharge according to. [3] In the refining method of [1] or [2], manganese ore is charged into a converter-type vessel for decarburization refining, and the Mn content in molten steel at the end point of decarburization refining is required by crude steel. M
Increase within the upper limit of n standard value. [4] In the refining method of the above [3], depending on the amount of SiO ₂ contained in the manganese ore charged, a predetermined basicity (Ca
O / SiO ₂ ) is charged with a slag material containing CaO.

[5] In the refining method according to any one of the above [1] to [4], prior to charging the dephosphorized and refined hot metal into a converter type vessel for decarburization and refining, Charge the slag solidifying agent into the container. [6] In the refining method of the above [5], lightly burned dolomite and / or raw dolomite is used as a slag solidifying agent. [7] The charging by the refining method according to any one of the above [1] to [6] is performed at a rate of 80% or more in a series of refining operations.

Further, in the above embodiments [1] to [7], in particular, the dephosphorization treatment is performed in a converter type vessel, that is, dephosphorization refining and decarburization refining are sequentially performed in different converter type vessels. The most efficient, preferred embodiment in this case is as follows. [8] In the refining method according to any one of the above [1] to [7], a converter type vessel is used as a first refining vessel for performing a dephosphorization treatment, and hot metal is charged into the converter type vessel. First, the entire amount of scrap to be charged into the converter type container is charged.

[9] In the refining method of the above [8], magnetic separation of slag generated in the dephosphorization step and / or the decarburization step is used as part or all of the scrap to be charged. [10] In the refining method of the above [8] or [9], the decarburizing refining is performed within the dephosphorizing refining time. Hereinafter, the reason or the effect of implementing the refining method of [1] to [10] will be described.

Method [1]: The hot metal having a sufficiently reduced amount of Si in accordance with the method of the present invention is subjected to a high-efficiency dephosphorization treatment, so that the hot metal has a P content of the crude steel (a steel component standard). Value), it is not necessary to add a slag forming material such as calcined lime for refining P in the subsequent decarburization refining, and the amount of slag generated can be reduced accordingly. In addition, the decarburization refining can be extremely simplified, and the refining time can be shortened. Therefore, the steelmaking efficiency can be improved as a whole.

Method [2]: In the decarburization refining, the slag-making material is not substantially charged, but light-burning dolomite or the like may be charged before the hot metal charging to extend the life of the furnace. Therefore, the amount of slag may increase to some extent. In such a case, the increased amount of slag in the furnace is discharged as needed.

Method of the above [3]: The Mn content of the blast furnace hot metal is usually 0.2 to 0.3 wt%, and the Mn content of the dephosphorized and refined hot metal is usually 0.15 to 0.25 wt%. is there.
The same is true for decarburization refining. On the other hand, the Mn content (standard value) of the crude steel varies depending on the steel type, but is, for example, 0.40 to 0.60 wt% for low carbon steel and 1.0 to 1.2 wt% for high manganese steel. In the conventional refining method, substantial dephosphorization refining is performed also in the decarburization treatment step, so that it is necessary to increase the FeO concentration in the slag. Further, since the slag-making material is also added, the MnO concentration in the slag is diluted. Therefore, even if manganese ore is charged in the decarburization treatment step, a sufficient Mn yield cannot be obtained, and an expensive manganese alloy is added at the time of tapping after dephosphorization refining to obtain a standard value.

On the other hand, in the refining method of the present invention, it is not necessary to perform substantial dephosphorization refining in the decarburization treatment step, so that it is not necessary to increase the FeO concentration in the slag, Since no new slag material is added, the MnO concentration in the slag can be kept high. Therefore, even if manganese ore is charged, it is efficiently reduced and a high Mn yield can be obtained. Therefore, the Mn content in the molten steel is reduced by charging the manganese ore to the upper limit (Mn content) of the Mn content in the crude steel.
n standard value), and more economical smelting operation becomes possible.

Method of the above [4]: Usually, manganese ore is 1
Since it contains silica (SiO ₂ ) of 0 wt% or less,
When the charged amount of manganese ore is large, the basicity of the slag (CaO / SiO ₂ ) decreases. Therefore, by introducing a slag material containing CaO to prevent rephosphorization to the hot metal,
At the same time, the melting of the furnace body is suppressed. Method [5] above: Prior to charging the dephosphorized and refined hot metal into the converter-type vessel for decarburization refining, the slag solidifying agent is charged into the converter-type vessel to remove phosphorus. It has the effect of suppressing bumping of hot metal when hot metal is charged, and secures safe operation.

Method of the above [6]: As the slag solidifying agent,
Brick waste, calcined lime, lightly burned dolomite, raw dolomite and the like can be used, and among them, lightly burned dolomite and / or raw dolomite are most preferable from the viewpoint of solubility, economy, and extension of the life of the furnace body.

The method of the above [7]: The reduction yield of Mn in the hot metal and Mn in the manganese ore greatly changes depending on the number of charges of the refining method of the present invention with respect to the total charge per day. Assuming that the number of charges used in the refining method is 80% or more of the total number of charges, the Mn yield (the total amount of Mn charged in the converter (= the total of the amount of Mn in the slag and the amount of Mn in the manganese ore)) (The ratio (%) of the amount of Mn in the melted steel to the molten steel) is preferably about 60% or more. Other charges (charges less than 20% of the total number of charges) may be performed by a normal refining method (a refining operation in which dephosphorizing refining and decarburizing refining are performed in the same blowing).

Method of the above [8]: Prior to charging the hot metal into the converter-type vessel for dephosphorizing and refining, the entire amount of scrap to be charged into the converter-type vessel is easily discharged. The production of molten and dephosphorized and refined hot metal can be increased. In the dephosphorizing refining in the refining method of the present invention, particularly in the dephosphorizing refining using a converter type vessel, the dephosphorizing refining time can be shortened as compared with the conventional method. It is possible in time to charge the entire amount of scrap to be charged. In addition, since the hot metal to be dephosphorized and refined easily dissolves scrap due to its high carbon content,
A relatively large amount of scrap can be charged. In conventional slag blowing (decarburization) using hot metal dephosphorized iron,
Although there was a problem that the scrap was hardly melted due to the lack of heat capacity and the production elasticity was poor, according to the method of the present invention, a usual level of scrap consumption can be secured in the dephosphorization step.

Method [9]: As a part or all of the scrap to be charged in the dephosphorization refining, magnetic separation chips obtained by magnetically separating slag produced by dephosphorization refining and / or decarburization refining are used. Thereby, even when the hot metal temperature is relatively low, slag generation is smooth, and the P content at the end of the dephosphorization refining is stably reduced. Method of the above [10]: By performing the decarburization refining within the dephosphorization refining time, the dephosphorized and refined hot metal can be decarburized and refined without waiting time, and the steelmaking efficiency can be improved.

Hereinafter, the details of the refining methods [1] to [10] will be described based on preferred embodiments. In the following, a case where dephosphorization refining is performed using a converter type vessel will be described as an example. However, dephosphorization refining may be performed in a ladle, a topeed or a specially designed refining vessel. Usually, in dephosphorization refining performed in a converter type vessel, after charging hot metal, oxygen is blown from a lance or the like, and a predetermined amount of calcined lime or the like is charged as a slag-making material to prepare CaO, SiO ₂ , FeO. A slag composed mainly of, for example, is generated to remove P from the hot metal. Then, after the dephosphorization and refining of the hot metal, the furnace is fallen down and tapping is performed on the ladle through the tapping hole.

FIG. 10 shows an outline (an example) of a conventional hot metal dephosphorization refining. In this example, following charging of the scrap into the converter type container, for example, after charging 340 ton of hot metal,
Further, oxygen blowing is performed for about 13 minutes while charging calcined lime (6 ton / ch), fluorite (0.6 ton / ch) as a slag forming material, and raw dolomite as necessary. Thereafter, rinsing is performed for about 3 minutes in order to separate hot metal and slag. After that, wait about 4 minutes to calm down the slag forming, and then tap out. In the example shown in the figure, the dephosphorization refining time is about 36 minutes.

FIG. 11 shows an outline (an example) of the dephosphorization refining performed by using the 340-ton converter type vessel according to the above-described refining method of the present invention. Table 1 shows the composition of the hot metal before and after the dephosphorization refining and before and after the decarburization refining, and Table 2 shows the distribution of the refining time for the refining according to the present invention and the conventional example. As shown in Table 1, in the conventional example, the S
While the i content is about 0.3 to 0.5 wt%, in the refining according to the present invention, the Si content of the hot metal before the dephosphorization treatment is 0.07 wt% or less.

[0062]

[Table 1]

[0063]

[Table 2]

In the refining according to the present invention, the Si content is set at 0.1.
As shown in Table 1, the amount of slag is smaller than the conventional example (40 to 50 kg / ton) and 10 kg / ton or less, as shown in Table 1, in order to perform dephosphorization refining of hot metal of 07 wt% or less. Further, in the refining according to the present invention, although the dephosphorization refining is performed with a higher basicity and a smaller amount of slag than the conventional example,
P is a component standard value normally required for crude steel: 0.02w
Refined to less than t%. Therefore, in the subsequent decarburization refining, substantial dephosphorization refining does not need to be performed.

As shown in Table 2, in the refining according to the present invention, slag forming during dephosphorization refining is also small due to a small amount of slag, so that a sedation time (4 minutes in the conventional example) is not required. Further, the waste time after tapping was reduced from 3.1 minutes in the past to 1.0 minute. For this reason, the dephosphorization refining time can be reduced from the conventional 36 minutes to 29 minutes, which is almost the same as the decarburization refining time (29 minutes). On the other hand, the dephosphorization refining time of the conventional example is 36 minutes, and assuming that the decarburization refining time is the same as the above 29 minutes, the converter type vessel for performing the decarburization refining has a non-operating time of about 7 minutes. Will occur.

In the ordinary dephosphorization refining, P in the hot metal reacts with FeO in the slag to be absorbed by the slag, and P in the hot metal is removed. Therefore, it is necessary to increase the FeO concentration in the slag in order to promote such a dephosphorization reaction. For this reason, as shown in FIG. Is preferred. In addition, as shown in FIG. 11, an appropriate amount (for example, 0.5 ton / c)
h) of coke is charged. In the dephosphorization treatment, the slag basicity is preferably set to about 1.5 to 5 in order to increase the efficiency of the dephosphorization refining and shorten the refining time.

The dephosphorized and refined hot metal is transferred to another converter type vessel and subsequently decarburized and refined. FIG. 12 shows an outline (an example) of dephosphorization refining performed using a 300-ton converter type vessel in the refining method according to the present invention. In the above-mentioned refining method of the present invention, since the decarburization process is basically performed only for decarburization refining, it is preferable to increase the amount of oxygen to be blown.
The P content of the hot metal has already reached the standard value (0.02 wt%).
Because of the following, slag-making materials such as calcined lime, which are conventionally frequently used, are not charged in principle except for the first charge in a series of operations.

Therefore, in the above-mentioned decarburization refining, the increase in slag is small. However, in this decarburization refining, lightly fired dolomite or the like may be charged before the hot metal charging to extend the life of the furnace, so that the amount of slag may increase to some extent. In such a case, the slag in the furnace is discharged as necessary. As a result, as shown in Table 1, the amount of slag generated in the furnace is about 10 to 30 kg / ton, which is considerably smaller than the conventional example (25 to 35 kg / ton). Moreover, since slag remains in the furnace even after tapping in principle, the amount of slag to be discharged is limited to that of the conventional example (20 to 30 k
g / ton).

In the decarburization refining in the above refining method of the present invention, it is preferable to charge manganese ore as much as possible. As described above, in the conventional refining method, substantial dephosphorization refining is performed also in the decarburization treatment step, so that it is necessary to increase the FeO concentration in the slag. Further, since the slag-making material is also added, the MnO concentration in the slag is diluted. Therefore, even if manganese ore is charged in the decarburization treatment step, a sufficient Mn yield cannot be obtained, and an expensive manganese alloy is added at the time of tapping after dephosphorization refining to obtain a standard value.

On the other hand, in the refining method of the present invention, it is not necessary to perform substantial dephosphorization refining in the decarburization treatment step, so that it is not necessary to increase the FeO concentration of the slag. Since no new slag material is added, the MnO concentration in the slag can be kept high. For this reason, manganese ore (for example, Mn: about 50 wt.
%, Fe: about 10 wt% or less, SiO ₂ : about 10 wt%
Even if the following is charged, it is efficiently reduced and a high Mn yield can be obtained. Therefore, the Mn content of the molten steel is changed by charging the manganese ore to the upper limit (Mn) of the Mn content of the crude steel.
Standard value), which enables more economical smelting operations.

In order to minimize the amount of expensive manganese alloy added, it is preferable that the manganese ore be charged in as large a quantity as possible. As described above, in the refining method of the present invention, the FeO concentration of the slag in the decarburization refining is low,
Moreover, since the MnO concentration of the slag is maintained high before blowing, most of the charged manganese ore is reduced, and a high Mn yield is obtained.

However, since manganese ore usually contains silica (SiO ₂ ) of 10 wt% or less, if the amount of manganese ore charged is large, the basicity of slag (CaO / Si) is increased.
O ₂ ) may decrease. In this case, a slagging material containing CaO, such as calcined lime, is charged to prevent rephosphorization of molten steel and to suppress melting of the furnace body. Is preferred.

Further, in the decarburization refining in the refining method of the present invention, prior to charging the dephosphorized and refined hot metal into the converter type vessel for performing the decarburization refining, the slag is solidified in the converter type vessel. Preferably, the agent is charged. The slag solidifying agent has an effect of suppressing bumping of hot metal when dephosphorized hot metal is charged, thereby ensuring the safety of operation. As the slag solidifying agent, one or more of brick waste, calcined lime, lightly burned dolomite, raw dolomite and the like can be used.

Among the above-mentioned slag solidifying agents, light-burned dolomite and raw dolomite are particularly preferred from the viewpoints of solubility, economy and extension of the life of the furnace body. That is, when lightly burned dolomite and / or raw dolomite are added as a slag solidifying agent, they are sufficiently dissolved in the slag during the decarburization refining, and have the effect of increasing the MgO concentration. In addition, since such slag itself contains MgO to the solubility limit, the slag has an effect of suppressing wear of a furnace brick made of magnesium (MgO) brick and extending the life of the furnace body.

Furthermore, in the decarburization refining, it is preferable to perform so-called slag coating in which the furnace body is tilted after tapping of molten steel, and slag remaining in the furnace adheres to the bricks lining the furnace. This slag coating greatly contributes to extending the life of the furnace, and as a result, the converter type vessel for decarburization and refining can maintain the same furnace life as the converter type vessel for dephosphorization and refining.

The maximum amount of slag discharged from the converter type vessel for decarburization and refining by this slag coating is about 10 kg / ton. As already mentioned, the amount of slag generated by dephosphorization refining is also 1
Since the amount of slag is 0 kg / ton or less and a part of the slag can be recycled, the amount of slag discharged to the outside per 1 ton of crude steel can be reduced to about 20 kg / ton or less. As described above, the smelting vessel for performing the dephosphorizing refining may be a ladle, a toppedo, or a specially designed smelting vessel, but the reaction rate is the fastest and the highly efficient dephosphorizing smelting is performed. The converter type container is most preferable in that the process can be carried out.

The charge by the refining method of the present invention is
It is particularly desirable to carry out at a rate of 80% or more in a series of smelting operations because the Mn yield is about 60% or more. That is, the reduction yield of Mn in the manganese ore varies greatly depending on the number of charges of the refining method of the present invention with respect to the total charge per day, and the number of charges of the refining method of the present invention is 80% of the total number of charges. The above ratio is preferable because a Mn yield of about 60% or more can be obtained.

FIG. 13 shows that the final steel component is C: 0.03-
When smelting low carbon steel of 0.06 wt% and Mn: 0.30 to 0.50 wt%, C: about 4 wt%, Mn:
In a series of operations in which decarburization refining was performed using 0.15 to 0.25 wt% of dephosphorized hot metal, the refining method of the present invention was applied to all charges (total charges per day: about 40 charges). The relationship between the ratio of the number of charges and the Mn yield is shown. In this decarburization refining, 2.6 to 4.9 kg / ton (hot metal) of manganese ore was charged. According to FIG. 13, M increases as the ratio of the number of charges applied in the refining method of the present invention to the total number of charges per day increases.
It is understood that the n-yield is improved, and particularly when the ratio is 80% or more, the Mn-yield becomes maximum (about 60 to 80%).

The refining method of the present invention may be charged in any manner with respect to the total number of charges. For example, the refining according to the present invention is carried out for 5 consecutive charges,
Next, a normal refining operation (a refining operation in which dephosphorizing refining and decarburizing refining are performed in the same converter type vessel, and a charge that does not charge manganese ore) is repeated four times a day. Can be adopted.

In the refining method of the present invention, since the refining time in the dephosphorization refining using the converter type vessel can be shortened as compared with the conventional method, the charging is performed before charging the hot metal into the converter type vessel for performing the dephosphorization refining. It is possible in time to charge the entire amount of scrap to be charged. Further, since the hot metal to be dephosphorized and refined easily dissolves scrap because of its high carbon content, a relatively large amount of scrap can be charged. However, it is preferable that the amount of scrap charged be within about 10 wt% of the amount of hot metal from the viewpoint of heat balance. The charging of scrap increases the production of dephosphorized hot metal.

Further, as a part or all of the scrap, magnetic separation of slag generated in the dephosphorization step and / or the decarburization step can be used. The magnetic separation waste is a portion (usually about Fe: about 50 wt%) containing a large amount of granular iron and the like obtained by separating the slag generated in the dephosphorization step and the decarburization step by a magnetic separator. Since the magnetic waste contains about 50 wt% of dissolved slag, slag generation is smooth even at a low hot metal temperature, and the P content at the end of dephosphorization refining can be stably reduced.

In the refining method of the present invention, the decarburizing refining can be performed within the dephosphorizing refining time.
The decarburized refining hot metal can perform decarburization refining without waiting time, and can improve steelmaking efficiency. The converter type container (converter type container for dephosphorization processing, converter type container for decarburization processing) used in the above-described method of the present invention includes a top-blowing type converter and a bottom-blowing type converter. , Top and bottom blown converters, etc.
In addition, a side-blowing converter can also be used.

[0083]

EXAMPLES Example 1 Dephosphorization of blast furnace hot metal was performed using a 300-t converter. In this dephosphorization treatment, after charging the hot metal into the converter, a predetermined amount of slag-making material was added, and oxygen blowing was performed from an upper blowing lance. Note that the dephosphorization treatment was performed in the same treatment time in both the present invention example and the comparative example. In the comparative example, dephosphorization treatment was performed on the hot metal (Si content: 0.19 wt%) without desiliconization, while in the present invention, the molten hot metal was desiliconized to remove Si. Was reduced to 0.07% by weight or less, and a dephosphorization treatment was performed. In the desiliconization treatment performed in the example of the present invention, iron oxide (mill scale) is added as a desiliconization material in the case of cast floor desiliconization, and in the case of pot desiliconization (hot metal pot), temperature adjustment before and after the treatment is performed. In consideration of the above, gaseous oxygen and solid oxygen (iron oxide) were used together as a desiliconizing material.

Table 3 shows the results.
It can be seen that the dephosphorization treatment of the present invention in which the i content was reduced to 0.07 wt% or less and the dephosphorization treatment was significantly improved as compared with the comparative example. In addition, in Example 2 of the present invention in which the amount of Si in the hot metal before the dephosphorization treatment was sufficiently reduced by performing the cast-bed desiliconization and the pot desiliconization, particularly excellent dephosphorization efficiency was obtained.

[0085]

[Table 3]

Example 2 Low carbon steel (C: 0.1 wt%)
), Medium-carbon steel (C: 0.1 to 0.2 wt%), and high-carbon steel (C: more than 0.2 wt%) were manufactured by 50 charges. Hot metal desiliconization or ladle desiliconization before dephosphorization
Ladle desiliconization was performed to desiliconize Si to 0.07 wt% or less. Tables 4 and 5 show the composition of the hot metal in the manufacturing process.
Shown in According to Tables 4 and 5, S of the hot metal before the dephosphorization treatment
By making the i content 0.07 wt% or less, the P content of the crude steel is 0.02 wt% at the end of the dephosphorization treatment.
It is refined below. Further, the Mn content of the crude steel could be increased in accordance with the charged amount of manganese ore.

[0087]

[Table 4]

[0088]

[Table 5]

[0089]

As described above, according to the method of the present invention, the efficiency of the dephosphorization refining performed before the decarburization refining can be drastically increased as compared with the conventional method. And refining costs can be reduced. Further, according to the method of the present invention described in claim 8, the amount of steelmaking slag generated can be further reduced as compared with the conventional method, and the refining process can be performed with higher efficiency. In addition, since manganese ore can be used as a manganese source in the refining process, extremely economical steelmaking can be realized.

[Brief description of the drawings]

FIG. 1 is a graph showing the transition of dephosphorization when hot metal with Si contents of 0.19 wt% and 0.05 wt% is dephosphorized, respectively.

FIG. 2 is a graph showing the effect of the amount of Si in hot metal before dephosphorization on the dephosphorization efficiency.

FIG. 3 is a graph showing the relationship between the amount of Si in hot metal after desiliconization and the desiliconization oxygen efficiency in ladle desiliconization and cast floor desiliconization.

FIG. 4 is an explanatory diagram showing an example of an implementation state of desiliconization in a ladle;

FIG. 5 is a graph showing the relationship between the hot metal temperature at the start of the dephosphorization treatment and the dephosphorization efficiency in the method of the present invention.

FIG. 6 is a graph showing the relationship between the hot metal temperature at the start of the dephosphorization treatment and the iron loss in the dephosphorization refining slag in the method of the present invention.

FIG. 7 is a graph showing the relationship between the hot metal temperature and the dephosphorization efficiency at the end of the dephosphorization treatment in the method of the present invention.

FIG. 8 In the method of the present invention, when the CaO source and the oxygen source are supplied to the same position as the case where the CaO source and the oxygen source are supplied to separate positions in the bath or in the bath, the hot metal temperature at the start of the dephosphorization treatment and Graph showing the relationship with phosphorus efficiency

FIG. 9 shows a case in which quicklime is used as a solvent in the method of the present invention and the CaO source and the oxygen source are supplied to the bath surface in the vessel or at separate positions in the bath; Graph showing the relationship between the hot metal temperature at the start of dephosphorization and the dephosphorization efficiency when a CaO-based solvent is used.

FIG. 10 is an explanatory view showing an example of a dephosphorization refining process in a conventional refining method.

FIG. 11 is an explanatory view showing an example of a dephosphorization refining step in the refining method of the present invention.

FIG. 12 is an explanatory diagram showing an example of a decarburization refining process in the refining method of the present invention.

FIG. 13 is a graph showing the relationship between the ratio of the number of charges implemented by the refining method of the present invention to the total number of charges in a series of operations and the Mn yield.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Ichitoshi Kawashima 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Kokan Co., Ltd. (72) Inventor Atsushi Watanabe 1-1-2, Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (72) Inventor Shigeru Inoue 1-2-1, Marunouchi, Chiyoda-ku, Tokyo F-term in Nihon Kokan Co., Ltd. (Reference) 4K014 AA01 AA03 AB03 AB12 AC12 AC14 AD23 4K070 AB02 AB03 AB06 AB14 AC03 AC06 BA13 DA07 EA07 EA27

Claims (8)

[Claims] 1. A hot metal refining method characterized in that when performing a dephosphorization treatment by adding a CaO source and an oxygen source to hot metal, the hot metal having a Si content of 0.07 wt% or less is subjected to a dephosphorization treatment. 2. The hot metal is desiliconized to reduce the Si content to 0.07 watts.
2. The hot metal refining method according to claim 1, wherein the dephosphorization treatment is performed after adjusting to t% or less. 3. The hot metal temperature at the start of the dephosphorization treatment is 1280 ° C.
The hot metal smelting method according to claim 1 or 2, wherein: 4. The hot metal temperature at the end of the dephosphorization treatment is from 1280 to
The hot metal refining method according to claim 1, 2 or 3, wherein the temperature is 1360 ° C. 5. As a desiliconization treatment for hot metal, at least a desiliconization treatment is performed in a ladle. In the desiliconization treatment in the ladle, at least gaseous oxygen is supplied as a desiliconization material, and the gaseous oxygen is removed. 5. The method according to claim 2, wherein the supply is performed by spraying on hot metal and / or by blowing into hot metal.
2. The hot metal refining method according to 1. 6. As a desiliconization treatment of the hot metal, a desiliconization treatment is performed at least in a ladle. In the desiliconization treatment in the ladle, a gaseous oxygen and / or solid oxygen source is supplied as a desiliconization material, The hot metal temperature is adjusted by adjusting the supply amount of the gaseous oxygen and / or solid oxygen source.
Or the hot metal refining method according to 4. 7. The dephosphorization treatment, wherein the CaO source and the oxygen source are supplied to a bath surface or the same position in the bath in the dephosphorization treatment vessel. 7. The hot metal refining method according to 6. 8. The method according to claim 1, wherein the dephosphorization treatment is performed under the following condition (a), and then the decarburization treatment is performed under the following condition (b). 7. The refining method according to 7. (A) In a smelting vessel, hot metal is dephosphorized and refined to a P content (specified steel component value) required for crude steel. (B) The dephosphorized and refined hot metal is charged into a converter type vessel, which is another refining vessel, and decarburized and refined without substantially charging slag-making material.