JP2004018915A - Process for refining molten metal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the refractory cost spent for a lance by increasing the number of cycles the lance can be used when refining a molten metal by top-blowing oxygen against the molten metal housed inside a vessel, dipping the refractory-coated immersion lance into the molten metal and blowing a stirring gas, a refining agent or a flux from this lance. <P>SOLUTION: When refining the molten metal by top-blowing oxygen against the molten metal 2 housed inside the vessel 5 and blowing at least one chosen from the stirring gas, the refining agent or the flux through the refractory-coated immersion lance 8 dipped into the molten metal, the lance is raised or lowered along with the progression of the refinery process. Moreover, between refinery cycles, the lance is rotated around its central axis to increase the number of cycles it can be used. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
According to the present invention, oxygen is blown upward to a molten metal contained in a molten metal holding container, and an immersion lance coated with a refractory is immersed in the molten metal. The present invention relates to a molten metal refining method for refining molten metal while blowing gas, a refining agent or a slag-making agent.
[0002]
[Prior art]
When refining molten metal by blowing oxygen upward on the molten metal contained in the molten metal holding vessel, as in the pre-phosphorus treatment in the hot metal pretreatment, the refractory It is a common practice to immerse a lance in a molten metal for immersion in a molten metal, to blow a stirring gas from the lance for immersion in a refractory coating, and to refine the molten metal while stirring the molten metal. In this case, a refining agent or a slag-making agent is also blown from a refractory-coated immersion lance.
[0003]
In the refining of such a molten metal, a slag in a molten state is formed in the molten metal holding container by adding a reaction product, a refining agent, and a slag-making agent. Since this slag acts as a strong erosion agent for refractories, the slag is used for such refining in order to prevent melting of the molten metal holding container and the refractory-coated lance in contact with the slag. In the molten metal holding container and the refractory-covered immersion lance to be used, a so-called slag line portion that is in contact with the slag in a molten state is generally provided with a refractory having excellent corrosion resistance to slag.
[0004]
As a result, the number of times the molten metal holding container and the refractory-coated immersion lance were used was dramatically improved, and the refractory cost was greatly improved.
[0005]
[Problems to be solved by the invention]
However, due to the recent demand for higher quality from consumers, etc., the ratio of pre-phosphorus treatment of hot metal in steel production has expanded, and at present, pre-phosphorus treatment is performed on almost all hot metal discharged from blast furnaces. It has been applied. As a result, the cost of the refractory spent in the preliminary dephosphorization treatment has increased, and under such circumstances, there has been a keen desire to further reduce the refractory cost in the preliminary dephosphorization treatment of the hot metal.
[0006]
The present invention has been made in view of the above circumstances, and an object thereof is to blow oxygen upward into a molten metal contained in a molten metal holding container, such as a preliminary dephosphorization treatment or a preliminary desiliconization treatment of hot metal. The refractory-coated immersion lance is immersed in the molten metal, and when refining the molten metal while blowing a stirring gas or a refining agent or a slag-making agent from the refractory-coated immersion lance, It is an object of the present invention to provide a molten metal refining method capable of reducing the cost of refractory spent on a refractory coating immersion lance by extending the number of times of use of the metal.
[0007]
[Means for Solving the Problems]
Means for Solving the Problems The present inventors have conducted intensive studies on the preliminary dephosphorization treatment and preliminary desiliconization treatment of hot metal in order to solve the above problems. The results of the study are described below.
[0008]
First, the wear condition of the refractory-covered immersion lance used in the preliminary dephosphorization treatment and the preliminary desiliconization treatment of the hot metal was investigated. As described above, a refractory having excellent corrosion resistance to slag is applied to the slag line portion of the refractory-coated immersion lance. From the results of the investigation of the wear situation, although the amount of erosion in the slag line of the lance for refractory coating immersion was large, the lance did not melt by the time the number of times of use of the lance for refractory coating immersion was restricted. It has been found that the reason for limiting the number of times of use is mainly wear at a portion above the slag line portion that is in contact with the atmosphere. Therefore, this cause was examined.
[0009]
In preliminary dephosphorization and preliminary desiliconization of hot metal, refining is performed while blowing oxygen from the top blowing lance toward the hot metal surface. Hot metal contains carbon.In the pre-phosphorus removal treatment and pre-siliconization treatment, refining is performed at an oxygen supply rate that minimizes the reaction between the supplied oxygen and the carbon in the hot metal. Due to its high concentration, the reaction between oxygen and carbon occurs to some extent.
[0010]
The reaction between oxygen and carbon generates CO gas, and the generated CO gas reacts with oxygen in the atmosphere to generate CO ₂ gas. The phenomenon in which the generated CO gas reacts with oxygen to generate CO ₂ gas is called secondary combustion. That is, what was CO gas in the vicinity of the hot metal surface was sucked by the dust collector and came into contact with the atmosphere and the top-blown oxygen as it rose in the hot metal holding container, causing secondary combustion in the container. Do you get it.
[0011]
The secondary combustion generates heat, and the heat generated by the secondary combustion locally melts a portion of the refractory-coated lance above the slag line. The portion to be melted is located at a substantially constant position from the molten metal surface and is on the side facing the top blowing lance, and therefore is locally damaged and limits the number of times the refractory-coated lance can be used. It has been found.
[0012]
Therefore, as the refining progresses, the refractory coating dipping lance is raised or lowered or rotated with respect to the axis thereof to disperse the portion damaged by the secondary combustion, thereby using the refractory coating dipping lance. The knowledge that the number of times can be extended was obtained. In addition, it has been found that the same effect can be obtained by rotating the refractory coating immersion lance by a predetermined angle between the refining of the pre-heating and the refining of the post-heating.
[0013]
The present invention has been made based on the above findings, and the method for refining molten metal according to the first invention is to blow oxygen upward into the molten metal contained in the holding vessel and immerse the molten metal in the molten metal. When refining the molten metal while blowing at least one of a stirring gas, a refining agent, and a slag-making agent through the refractory-coated immersion lance, the refractory-coated immersion lance is moved along with the refining process. It is characterized by being raised or lowered.
[0014]
The method for refining molten metal according to the second invention is the method according to the first invention, further comprising rotating the refractory-coated immersion lance with respect to its axis during a period between refining and refining. Is what you do.
[0015]
In the method for refining a molten metal according to the third invention, the molten metal contained in the holding container is blown upward with oxygen, and the gas for agitation and refining is passed through a refractory-coated immersion lance immersed in the molten metal. Agent, when refining the molten metal while blowing at least one or more of the slag-making agents, during refining or during the period between refining and refining, rotate the refractory coating immersion lance with respect to its axis It is characterized by the following.
[0016]
The method for refining molten metal according to a fourth invention is the method for refining molten metal according to any one of the first to third inventions, wherein the molten metal is hot metal, and It is characterized by removing phosphorus or silicon.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic diagram of a hot metal dephosphorization treatment facility used when performing the preliminary dephosphorization treatment according to the present invention, FIG. 2 is an enlarged view of the refractory coating immersion lance shown in FIG. 1, and FIG. FIG. 3 is a schematic view showing an example of a position of a refractory coating immersion lance in a preliminary dephosphorization process according to the present invention, wherein (a) shows a position at the start of the preliminary dephosphorization process, and (b) is a position at the end of the preliminary dephosphorization process. FIG. 4 is a schematic view showing another example of the position of the refractory coating immersion lance in the preliminary dephosphorization treatment according to the present invention, wherein (a) shows the position at the start of the preliminary dephosphorization treatment, and (b) () Is a diagram showing the position at the time of completion of the preliminary dephosphorization treatment.
[0018]
In FIG. 1, a ladle-type hot metal holding container 5 containing hot metal 2 tapped from a blast furnace (not shown) is mounted on a bogie 6 and carried into the dephosphorization treatment equipment 1. The dephosphorization treatment equipment 1 is provided with an upper blowing lance 7 and a refractory coating immersion lance 8, and the upper blowing lance 7 and the refractory coating immersion lance 8 can move up and down in the hot metal holding vessel 5. The refractory-coated immersion lance 8 is configured to be rotatable about its axis as a rotation axis. From the upper blowing lance 7, a gaseous oxygen source such as industrial pure oxygen is blown to the hot metal 2 as a dephosphorizing agent.
[0019]
As shown in FIG. 2, a slag line section 16 made of a refractory material having excellent corrosion resistance to the slag 15 is provided at a portion of the refractory-coated lance 8 that comes into contact with the slag 15 in the hot metal holding container 5. At a length of L. The slag 15 is formed by mixing of the blast furnace slag at the time of tapping from the blast furnace, the reaction product, and the added refining agent and slag-making agent. In the present invention, the slag line portion 16 is not necessarily required, but is preferably provided to increase the number of times the refractory-coated lance 8 is used.
[0020]
The refractory coating immersion lance 8 is connected to the storage tank 9 and the storage tank 10, and converts the solid oxygen source 3 stored in the storage tank 9 and the quick lime 4 stored in the storage tank 10 into an unreacted lime such as nitrogen or Ar. The active gas can be added as a carrier gas by blowing into the hot metal 2. The solid oxygen source 3 is added as a dephosphorizing agent, and iron ore, mill scale, or the like may be used. The quicklime 4 is a flux for dephosphorization, and is used for fixing phosphorus in the slag 15 by reacting with the phosphorus oxide generated by the dephosphorization reaction, and for adjusting the basicity of the generated slag 15. In this case, another flux may be mixed with the quicklime 4, or another flux may be used instead of the quicklime 4. The solid oxygen source 3 in the storage tank 9 and the quick lime 4 in the storage tank 10 can be blown independently by controlling the amount and time of addition. The molten metal 2 can be stirred by blowing only inert gas such as nitrogen or Ar from 8.
[0021]
The dephosphorization treatment equipment 1 is further provided with a raw material supply equipment comprising hoppers 11 and 12, a raw material transport conveyor 13 and a chute 14, and the solid material in the hopper 11 is The oxygen source 3 and the quicklime 4 in the hopper 12 can be placed in the hot metal holding vessel 5 and added.
[0022]
Next, a method of preliminarily dephosphorizing the hot metal 2 according to the present invention using the dephosphorization treatment equipment 1 having such a configuration will be described.
[0023]
An inert gas such as nitrogen or Ar is blown from the refractory coating immersion lance 8 as a stirring gas, and quick lime 4 is placed on the hot metal 2 via the chute 14 as a dephosphorizing flux, or the refractory coating immersion lance is used. A gas oxygen source is continuously blown from the upper blowing lance 7 toward the hot metal 2 accommodated in the hot metal holding container 5 while blowing into the hot metal 2 through the hot metal 8. The amount of the quicklime 4 that is the dephosphorizing flux can be changed according to the silicon concentration, the sulfur concentration, and the phosphorus concentration in the hot metal 2.
[0024]
If the oxygen source is only a gaseous oxygen source, the hot metal temperature may be too high and the dephosphorization reaction may be hindered. Therefore, the solid oxygen source 3 is continuously or intermittently placed via the chute 14 if necessary. It is added or it is blown into the hot metal 2 continuously through the refractory coating immersion lance 8 and added. The hot metal temperature can be lowered by adding the solid oxygen source 3. The ratio between the gas oxygen source addition amount and the solid oxygen source addition amount is appropriately changed according to the silicon concentration, the phosphorus concentration, and the carbon concentration in the hot metal 2. Further, iron scrap may be added as a coolant.
[0025]
In this preliminary dephosphorization treatment, the refractory coating immersion lance 8 is raised or lowered as the refining progresses, or the lance 8 is rotated around its axis as a rotation axis. Further, the refractory coating immersion lance 8 may be raised or lowered while rotating. Here, when rotating the refractory coating immersion lance 8 during the preliminary dephosphorization treatment, if the refractory coating immersion lance 8 rotates at least half a rotation during the preliminary dephosphorization treatment, the rotation speed is particularly limited. No need.
[0026]
FIG. 3 is an example in which the refractory coating immersion lance 8 is raised, while FIG. 4 is an example in which the refractory coating immersion lance 8 is lowered. In this case, the amount of the slag 15 formed during the preliminary dephosphorization process is grasped in advance by the added reaction products such as the quicklime 4 and SiO ₂ , and the slag line section 16 starts from the start of the preliminary dephosphorization process. It is preferable that the slag 15 is always contacted until the end.
[0027]
For this purpose, the required length L of the slag line portion 16 is determined in advance, and the refractory-coated immersion lance 8 having the slag line portion 16 having the required length L is used. As shown in FIG. 3 (a), the preliminary dephosphorization process is started with the upper end side of the slag line portion 16 as the molten metal surface position of the hot metal 2, and the molten metal surface of the slag 15 rises with the progress of the preliminary dephosphorization process. The refractory-coated lance 8 is raised at a speed higher than the speed. On the other hand, when lowering the refractory coating immersion lance 8, as shown in FIG. 4 (a), the lower end side of the slag line section 16 is set to the molten metal surface of the hot metal 2 to start the preliminary dephosphorization treatment. As shown in b), the preliminary dephosphorization process is terminated at a position where the upper end position of the slab line portion 16 is higher than the molten metal surface position of the slag 15. By doing so, the slag line portion 16 is always brought into contact with the slag 15, and it is possible to suppress the erosion of the lance 8 by the slag 15. Needless to say, when the slag line section 16 is not installed in the refractory coating immersion lance 8, such a work is unnecessary, and it is possible to secure a state in which the stirring gas is blown into the hot metal 2. As long as possible, the lance 8 can be raised or lowered at an arbitrary speed with an arbitrary position of the refractory-coated lance 8 as a starting point.
[0028]
Further, during the period from the end of the previous preliminary dephosphorization to the start of the next preliminary dephosphorization, the refractory coating immersion lance 8 may be rotated at a predetermined angle, for example, by about 150 degrees. By rotating the refractory coating immersion lance 8 during the pause of the pre-phosphorus removal treatment and raising or lowering it during the pre-phosphorus removal treatment, the wear point of the refractory coating immersion lance 8 due to the secondary combustion is further uniformized. Thus, the number of times the refractory-coated lance 8 is used can be lengthened.
[0029]
By preliminarily dephosphorizing the hot metal 2 in this manner, the portions damaged by the secondary combustion of the refractory coating immersion lance 8 can be dispersed, and the number of times the refractory coating immersion lance 8 can be used can be extended. It becomes possible. As a result, it is possible to reduce the refractory cost spent on the refractory-coated immersion lance 8.
[0030]
Although the above description has been given of the example of the preliminary dephosphorization of the hot metal, the present invention is not limited to the preliminary dephosphorization of the hot metal. Refining the molten metal while blowing at least one of a stirring gas, a refining agent, and a slag-making agent through a refractory-coated immersion lance immersed in the molten metal while blowing oxygen upward on the molten metal. In this case, the present invention can be applied to refining of various molten metals. Further, the preliminary dephosphorization treatment is not limited to the above description, and the present invention can be applied to, for example, a preliminary dephosphorization treatment using a mixed iron wheel.
[0031]
【Example】
The present invention was applied to a case where 135 tons of hot metal discharged from a blast furnace was subjected to a preliminary dephosphorization treatment using the dephosphorization treatment equipment shown in FIG. The length of the refractory-coated immersion lance used was about 9 m, and the length L of the slag line portion was set in a range of 600 mm. The hot metal used had a carbon concentration of 4.5 mass%, a silicon concentration of 0.2 mass%, a phosphorus concentration of 0.09 to 0.11 mass%, and a hot metal temperature of 1330 to 1350 ° C.
[0032]
Preliminary dephosphorization treatment was performed by injecting quicklime from a refractory-coated immersion lance using nitrogen as a carrier gas, supplying oxygen from a top-blown lance and adding iron ore from a chute as a solid oxygen source. The amount of slag generated by this preliminary dephosphorization treatment was about 400 mm in terms of slag thickness. That is, the slag thickness in the hot metal holding vessel increases by approximately 400 mm during the preliminary dephosphorization treatment.
[0033]
Therefore, as shown in FIG. 3 (a), at the start of the preliminary dephosphorization treatment, the upper end side of the slag line portion is set to the hot metal surface position, and the refractory coating immersion lance is raised with the progress of the preliminary dephosphorization treatment. By the end of the treatment, it was raised by 450 mm. At the start of the treatment, slag having a thickness of about 100 mm generated in the preliminary desiliconization treatment in the previous step remained.
[0034]
As a result of performing the preliminary dephosphorization treatment of the hot metal in this way, the number of times the refractory-coated lance was used was 66 times on average. Conventionally, the average number of times of use of the refractory-coated immersion lance when the lance of the same material was used without moving the lance was 54 times. . As a result, refractory costs have been significantly reduced.
[0035]
【The invention's effect】
As described above, according to the present invention, it is possible to disperse the portions damaged by the secondary combustion of the refractory coating immersion lance, and it is possible to extend the number of times the refractory coating immersion lance is used. Thus, the cost of the refractory spent on the refractory-coated immersion lance can be significantly reduced, and an industrially beneficial effect is brought about.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a hot metal dephosphorization treatment facility used when performing a preliminary dephosphorization treatment according to the present invention.
FIG. 2 is an enlarged view of the refractory coating immersion lance shown in FIG.
FIG. 3 is a schematic view showing an example of a lance position of a refractory coating immersion lance in a preliminary dephosphorization treatment according to the present invention, wherein (a) shows a position at the start of the preliminary dephosphorization treatment, and (b) shows a preliminary dephosphorization treatment. It is a figure showing a position at the time of end.
FIGS. 4A and 4B are schematic views showing another example of a lance position for refractory coating immersion in the preliminary dephosphorization treatment according to the present invention, wherein FIG. 4A shows a position at the start of the preliminary dephosphorization treatment, and FIG. It is a figure which shows the position at the time of completion | finish of a phosphorus process.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 Dephosphorization treatment equipment 2 Hot metal 3 Solid oxygen source 4 Quick lime 5 Hot metal holding container 6 Cart 7 Top blowing lance 8 Refractory coating immersion lance 9 Storage tank 10 Storage tank 11 Hopper 12 Hopper 13 Material conveyor 14 Chute 15 Slag 16 Slag Line section

Claims (4)

Along with blowing oxygen upward on the molten metal contained in the holding container, at least one or more of a stirring gas, a refining agent, and a slag-making agent are blown through a refractory-coated immersion lance immersed in the molten metal. A method for refining a molten metal, which comprises raising or lowering the refractory coating immersion lance as the refining progresses while refining the molten metal. The method for refining molten metal according to claim 1, wherein the refractory-coated immersion lance is rotated with respect to its axis during a period between refining. Along with blowing oxygen upward on the molten metal contained in the holding container, at least one or more of a stirring gas, a refining agent, and a slag-making agent are blown through a refractory-coated immersion lance immersed in the molten metal. A method for refining molten metal, comprising: rotating the refractory-coated immersion lance with respect to its axis during refining or during refining when refining the molten metal. The molten metal is hot metal, and phosphorus or silicon in the hot metal is removed while blowing a gas for stirring from the refractory-coated immersion lance, wherein the molten metal is hot metal. The method for refining molten metal according to the above.

Images