JPS63238210A - Method for pretreating molten iron - Google Patents

Abstract

PURPOSE:To shorten treating time, to facilitate slag-off operation and to reduce unit consumption of dephosphorizing agent by providing desiliconizing stage, which dephosphorizing quantity is enlarged at the same time under specifying the condition, and dephosphorizing stage after receiving molten iron, at the time of treating by blowing powdery material by gas into the molten iron in a molten iron trough. CONSTITUTION:At a first stage, desiliconizing agent is blown into the molten iron by the carrier gas through a lance nozzle set above the molten iron on the casting bed of a blast furnace or submerged into the molten iron. Then, the siliconizing agent is blended so that slag basicity after treatment becomes to the range of >=0.5 and <1.2 and blowing rate is to be 5-25kg/ton/one lance and desiliconizing treatment is executed so that [Si] after treatment becomes to <=0.1% and the generated slag is naturally removed in the casting bed trough. Next, at a second stage, after receiving the molten iron into torpedo car, etc., the dephosphorizing agent is blown from submerged lance nozzle by the carrier gas, to execute the dephosphorization.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for performing preliminary treatments such as de-Si, de-P, and de-sulfur on hot metal for converter refining.

Conventional technology Conventionally, hot metal pretreatment methods include, for example, Japanese Patent Application Laid-Open No. 57-3.
5804. JP-A-58-1302011 topedo car.

Various methods have been adopted, such as processing in a hot metal transfer container such as a hot metal ladle, processing in a cast bed trough, or a combination thereof, and although each method has its own problems, overall In other words, there are major problems such as decreased productivity and decreased hot metal temperature due to process division.

In order to solve this problem, it is important to shorten the treatment time as much as possible, and among the above methods, the method of direct continuous treatment in the cast bed trough and simultaneous slag removal treatment is effective, but it is difficult to remove the slag easily. However, in some cases, there are problems such as the need for a considerable scale of slag drainage and conveying equipment, the high equipment cost of the equipment for adding powder to the cast bed trough, and the large loss of iron content in the slag. However, it has not yet reached the point where it is economically viable compared to other methods.

Problems to be Solved by the Invention The present invention solves the above-mentioned problems, and in order to reduce the drop in hot metal temperature, a processing method is adopted in which part of the processing in the cast bed trough is adopted and the slag can be easily discharged. Furthermore, the present invention aims to provide a hot metal pretreatment method that is economically viable as a whole process.

Namely, the present inventors are actively promoting tests to remove Si by blowing powder from a lance nozzle installed above the hot metal in a cast bed trough or by blowing powder through a lance nozzle installed in the hot metal. We also clarified the conditions that increase the simultaneous dephosphorization that conventionally occurs during Si removal, and the conditions that make the slag after Si removal have good fluidity and can be easily removed.

By increasing the simultaneous amount of P during Si removal, it becomes easier to remove P in the next step, shortening the processing time and reducing the unit consumption of the desulfurization agent, which can be an economically very advantageous method. Furthermore, since the Si-free slag can be easily removed, the process becomes sufficiently stable in terms of operation.

Means for Solving the Problems The gist of the present invention is as follows: (1) In the hot metal trough of the blast furnace casthouse, one or more pieces installed above the hot metal or immersed in the hot metal. Blend so that the basicity of the slag after processing the powder with a carrier gas through a lance nozzle is 0.5 or more and less than 1.2,
The amount of 5 to 25 kg/Ton per lance nozzle is blown into the hot metal, and after treatment, the resulting slab is subjected to a desilicon treatment to reduce the Sil content to 0.1% or less, and the resulting slab is naturally slaged in the cast bed gutter. After the first step, the powder is immersed in a torpedo car or hot metal ladle through a lance nozzle that is immersed in it to remove P by blowing it with a carrier gas.
, a hot metal pretreatment method consisting of a second step of removing S, and (2
) Between the first and second steps above, the powder is added from above in front of the tilting runner of the hot metal runner, and the powder is removed by stirring as it falls from the molten metal runner into the tilting runner and the torpedo car or hot metal pot. 2. The hot metal pretreatment method according to item 1 above.

action The present invention will be explained in detail below.

When performing Si removal treatment and removal treatment of Si removal slag in the cast bed gutter, in order to increase the reaction efficiency and lower the unit consumption of the Si removal agent, it is better to drop the Si removal agent onto the hot metal rather than letting it fall naturally from above. It is effective to blow powder from a nine-lance nozzle installed or to blow powder from a lance nozzle placed in hot metal.

The present inventors have demonstrated that during Si removal treatment by powder spraying over hot metal or powder injection into hot metal, the amount of P removed from the slag is influenced by the basicity of the slag, the post-treatment [Sil], and the iron oxide basic unit. ,Q, In order to obtain a large amount of P removal of 025% or more, the slag basicity after treatment must be 0.5 or more,
It was confirmed that l was required to be 0.10% or less.

Also, after processing [In order to lower the S eye, use lance nozzle 1]
It is necessary to set the unit consumption of the desiliconizing agent to 5 to 25 kg/l. In other words, if the flux unit per lance nozzle is too large, it will promote reactions such as C removal, which will reduce the Si removal reaction efficiency, and conversely, if the flux unit per lance nozzle is too small, the penetration depth of flux into the hot metal will decrease. This decreases the Si removal reaction efficiency.

In addition, the fluidity of slag is influenced by the hot metal temperature and basicity after treatment, and if the temperature after treatment is 1400°C or higher, the basicity is less than 1.2, preferably 1.0 or less, and the fluidity is good. It turned out to be.

After the desilicon treatment by the above method, the hot metal that has been drained is transferred to a torpedo car or a hot metal ladle, and then the powder is blown in with a carrier gas from a lance nozzle in which the powder is immersed to remove P.
In the step of removing S, a considerable amount of P is removed from the value of cast iron tapped iron [P], so the [P] before deP treatment is low, the unit consumption of the desiliconizing agent is small, and the processing time can be shortened.

In addition, after the above-mentioned cast bed desiliconization step, a test was performed in which S removal treatment was performed by adding powder from above in front of the tilting gutter of the cast bed gutter and stirring as it fell from the tilting gutter to the torpedo car or hot metal ladle. As a result, the relationship between the unit consumption of the S removal agent and the S removal rate as shown in the drawing was obtained.

By performing the above-mentioned S removal process after the castbed desiliconization process, the S removal process in the torpedo car or hot metal ladle can be reduced or eliminated, reducing the processing time and allowing the slag after S removal to cover the hot metal surface. It is possible to reduce the heat dissipated from hot metal during transportation in a torpedo car or hot metal pot, and to reduce the amount of drop in hot metal temperature.

Example The present invention will be explained below based on examples.

Table 1 shows a comparative example of the conventional pretreatment method for hot metal, in which the slag is removed after desorption treatment in a torpedo car, and then the S removal treatment is followed by the P removal treatment. Because the slag removal time is required after the Si removal, and the treatment time for Si removal and P removal (S removal) is long, the temperature of the hot metal decreases significantly, and the temperature of the hot metal charged into the converter was as low as 1245°C.

Table 2 also shows a comparative example of the conventional hot metal pretreatment method, in which a desiliconizing agent is added by gravity from above the hot metal just before the tilting gutter of the cast bed gutter, and when the hot metal falls from the tilting gutter to the torpedo car. This is a comparative example in which a desilicon agent and hot metal are mixed together to perform a desilicon treatment, and the desiliconized slag is slaged, followed by a desulfurization treatment in a torpedo car, followed by a dephosphorization (deS) treatment. As in Example 1, the slag removal time after Si removal was required and the deP (S removal) treatment time was long, resulting in a large drop in hot metal temperature, and the temperature of hot metal charged into the converter was as low as 1260°C.

Example 1 shown in Table 3 is an example of the present invention, and after the first step of removing Si by powder blowing in the cast bed gutter and simultaneous natural slag, P (deS) treatment was performed by blowing powder in a torpedo car. This is the case when the second step is performed, but the first step of removing Si
In the treatment, the basicity of the Si-free slag was 0.8, and it had very good fluidity and flowed naturally. In addition, the change in [P] in the first step is from 0.100% to 0.0135%, and the amount of P removed is very large, so it is easy to remove P in the second step, and the amount of P removed is 5 kg/l.
We were able to reduce [P] to 0.020% per unit of dephosphorization agent, and at the same time, because the processing time of the second step is short and the consumption tax P agent consumption rate is small, there is little drop in hot metal temperature. , the converter charging temperature was 1335°C and Comparative Example 1.2.
The temperature of the hot metal charged into the converter rose significantly, from 5 to 90 degrees Celsius.

In Example 2 shown in Table 4, a de-S agent was added by gravity from above the hot metal in front of the tilting gutter of the casting bed gutter between the first and second steps of Example 1, and This is an example of a case where an intermediate step of de-S treatment is included by mixing the de-S agent and hot metal by stirring when falling into the iron, and the [P] after the de-P (de-S) treatment is 0.005%. [S] is 0.00
3% and at the same time, the temperature of the hot metal charged into the converter was 1340
The temperature has become extremely high.

In Comparative Example 3 shown in Table 5, the same first and second steps as in Example 1 were carried out, but the basicity of the Si-removed slag in the first step was as high as 1.8, and natural slag could not be removed. At the same time, the basic unit of desiliconizing agent per lance nozzle was 35 (kg/kg).
l), so the [Si] after treatment is as high as 0.13%,
The change in [P] was relatively small from 0.103% to 0.090%, and the second step required the same amount of dephosphorization agent as the conventional process, so the processing time was long and the temperature of hot metal charged in the converter was low. The temperature remained at 1300°C, which was about 40 to 50° higher than the conventional process.

(The following is a blank space) Effects of the Invention The present invention enables economical hot metal pretreatment in which the temperature of the molten iron charged into the converter is high and the unit consumption of the desiliconizing agent and the dephosphorizing agent is small.

[Brief explanation of the drawing]

The drawing shows the basic unit of desulfurization agent and desulfurization agent when the desulfurization agent is added onto the hot metal surface by gravity in front of the tilting runner of the hot metal runner, and the desulfurization treatment is performed by stirring as it falls into the tilting runner and torpedo car. The figure which shows the relationship with S rate.

Claims (2)

[Claims] (1) In the hot metal trough of a blast furnace casthouse, a carrier gas is used to apply a desiliconant to the treated slag base through one or more lance nozzles installed above the hot metal or immersed in the hot metal. Blend so that the Si content is 0.5 or more and less than 1.2, and blow into the hot metal at 5 to 25 kg/Ton per lance nozzle, so that [Si] after treatment is 0.1% or less. The first step is to remove Si and naturally discharge the generated slag in a cast bed gutter, and then to remove P after receiving the pig iron into a torpedo car or hot metal ladle.
A hot metal pretreatment method consisting of a second step of dephosphorizing the agent by blowing it with a carrier gas through a submerged lance nozzle. (2) Between the first and second steps above, a desulfurization agent is added from above in front of the tilting runner of the hot metal runner, and stirring is performed when the hot metal falls from the runner to the tilting runner and then into the torpedo car or ladle. 2. The hot metal pretreatment method according to claim 1, which comprises a step of removing S by using sulfur.