JPH06200311A - Method for dephosphorizing molten iron - Google Patents

Abstract

PURPOSE:To efficiently and inexpensibly execute the dephosphorization of molten iron by using a converter or a refining furnace provided with a slag separating device. CONSTITUTION:In the converter or the refining vessel 1 having a slag separating device, the prescribed molten iron raw material and refining material are charged and slag of the wt. corresponding to >=1% molten iron treating wt. in the slag 5 generated after the dephosphorize-refining is remained in the converter, etc., and the remaining slag is discharged, and thereafter, the molten iron and the refining material are charged to repeatedly execute the dephosphorizing treatment. Further, when the slag generated at the preceding dephosphorize-refining has the dephosphorizing performance, after executing the dephosphorizing treatment two or more times while discharging the preceding slag to the outside of the refining furnace, the generated slag is partially remained to successively execute the dephosphorizing treatment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dephosphorizing hot metal using a converter or a refining furnace equipped with a slag separator (hereinafter referred to as a converter).

[0002]

2. Description of the Related Art Conventionally, in the dephosphorization treatment of hot metal, the lower the refining temperature is, the more thermodynamically advantageous the dephosphorization is. Therefore, it is desirable to make the refining temperature as low as possible unless the molten pig iron solidifies or there is an obstacle in the steel making step which is the next step. At this time, the problem is to promote the melting of the refined material at a low temperature and improve the reactivity.

As a method for accelerating the melting of the refined material, for example, as disclosed in Japanese Patent Laid-Open No. 047212/1990,
Idea to add a part or all of the refining material to the refining furnace as a powder, or a method of using a melting point lowering agent such as manganese oxide as a melting accelerator as seen in JP-A-2-250913, As described in JP-A-1-05531, a method of promoting melting by using a converter slag that has been once melted and then solidified, JP-A-2-2509
As described in Japanese Patent Publication No. 14, there is a method in which a refined material obtained by adding CO ₂ gas to quick lime is used and the refining by the dissociation of the CO ₂ gas is used.

[0004] These prior arts require crushing of the refined material, a powder transport supply device, etc. in order to make the refined material into powder. Also, the method of adding additives such as manganese oxide,
In addition to the high cost of manganese oxide, the slag generated by dephosphorization refining using the manganese oxide causes various problems when it is used as a roadbed material, for example. Further, in the method of utilizing the converter slag, a large amount of cost is required to recover it. Further, the method of adding carbon dioxide gas (CO ₂ ) to the above-mentioned quick lime and using it as a refining material has a problem that heat loss accompanying dissociation of lime carbonate is large.

[0005]

DISCLOSURE OF THE INVENTION The present invention is a method for promoting melting of a refining material which uses a converter or the like, does not require special equipment or expensive additives, and does not cause loss of heat quantity. The purpose of the present invention is to dephosphorize hot metal efficiently and inexpensively.

[0006]

[Means for Solving the Problems]

(1) A method for dephosphorizing hot metal, which comprises the following steps. (A) A converter or a refining furnace equipped with a slag separator (hereinafter referred to as a converter) is charged with a predetermined amount of hot metal raw material and a refining material to mainly perform dephosphorization refining, and (b) the dephosphorization. After refining, the dephosphorized hot metal is discharged from the molten metal outlet of the converter, etc., and 1% of the weight of the hot metal is contained in the slag generated subsequently.
The slag having a weight equivalent to the above is left in the converter etc., the rest is discharged, and (c) subsequently, a predetermined amount of hot metal raw material and refining material are charged into the converter etc. for dephosphorization refining. repeat.

(2) A method for dephosphorizing hot metal, which comprises the following steps: (A) A converter or a refining furnace equipped with a slag separator (hereinafter referred to as a converter) is charged with a predetermined amount of hot metal raw material and a refining material, and mainly dephosphorization refining is performed,
(B) After the dephosphorization refining, the dephosphorized hot metal is discharged from a molten metal outlet such as the converter, and the slag having a weight corresponding to 1% or more of the weight of the hot metal is continuously generated from the slag generated. It is left in the converter etc. and the rest is discharged. (C) Then,
The steps (a) to (b) are repeated once or more,
(D) After that, of the generated slag, 1 of the weight of the hot metal is used.
% Of slag remains in the converter or the like and the rest is discharged. (E) Further, a predetermined amount of hot metal raw material and refining material are charged into the converter or the like to dephosphorize the hot metal. Repeat refining.

[0008]

The following two conditions are required to efficiently dephosphorize the hot metal. It is essential to maintain the inside of a converter or the like at a high temperature and quickly dissolve the added refining material. On the other hand, in order to effectively perform dephosphorization, the equilibrium of dephosphorization is more advantageous as the temperature is lower as described above, and therefore it is necessary to make the temperature in the furnace as low as possible.

However, the above conditions are contrary to each other. Therefore, in the present invention, in order to accelerate the refining material, the entire amount of slag remaining in the refining furnace is not discharged, but 1% of the hot metal treatment weight is left in the furnace and the remainder is discharged, whereby the purpose of the present invention is to Can be reached. The reason for this is that when the slag weight left in the refining furnace is less than 1%,
This is because almost all of the residual slag adheres to the inner wall of the refining vessel and does not contribute to the promotion of dissolution of the refined material at the initial stage of dephosphorization refining.

A concrete implementation method will be described with reference to FIGS. In this case, as a premise, the hot metal is first dephosphorized, the hot metal that has been dephosphorized is tapped, and the hot metal that has been sufficiently dephosphorized is charged to the next converter and decarburized and refined. It is premised on the process of finally manufacturing steel. As a part of the steelmaking work, the following dephosphorization refining is performed.

In the dephosphorization treatment shown in FIG. 1, the hot metal raw material charged in the hot metal converter and a predetermined refining material are added, oxygen is added by a lance or the like to heat the inside of the furnace and melt the refining material. Dephosphorization refining is performed (Fig. 1, upper left). As the hot metal raw material,
Some scrap is added. In the dephosphorization process in FIG. 1, as shown in the drawing, nitrogen gas or argon gas is often blown from the bottom of the converter to accelerate the refining reaction.

Upon completion of the dephosphorization reaction refining, the dephosphorized hot metal is tapped into the ladle 4 through the tap hole 2, for example, the tap hole 2 (top right of FIG. 1). After tapping the hot metal that has been dephosphorized and smelted, the converter is erected and further rotated in reverse to partially discharge the slag remaining in the furnace (bottom right of Fig. 1). At this time, in the present invention, a part of the slag remaining in the furnace, that is, 1% or more of the total weight of the hot metal is left in the furnace.

The method of controlling the residual amount is based on the inclination (θ) of the tilt of the furnace.
Done by. The relationship between the remaining amount and the tilting angle of the converter is shown in FIG. FIG. 3 shows the relationship between the tilting angle of the converter and the volume (v) remaining in the converter, and the specific gravity of the slag (about 1.
5 kg / l), the tilt angle and the amount of slag remaining in the furnace, that is, its weight (ton number) are shown.
Based on this figure, a predetermined amount of slag is left in the furnace. Note that FIG. 3 is a diagram showing the relationship between the tilt angle and the residual slag amount in the 350 ton converter.

Returning to FIG. 1 again, with the predetermined amount of slag remaining in the furnace, the hot metal or a predetermined amount of scrap hot metal raw material is charged (lower left in FIG. 1), and the necessary refining material is added. , Perform dephosphorization refining again (Fig. 1, upper left). By repeating such a cycle, the dephosphorized hot metal can be manufactured.

FIG. 2 shows another method for carrying out the present invention. In this figure, the slag remaining in the furnace after the molten metal 3 after dephosphorization and refining is discharged is used as it is, and then the hot metal or the hot metal is used. Then, scrap is charged and the phosphorus removal process is performed again. That is, when the above-mentioned slag still has sufficient dephosphorization refining ability, such an implementation method becomes possible. In this case, it is possible to reduce or omit the discharge of the generated slag to a place other than the refining container, and it is possible to accelerate the melting of the refining material by directly using the once molten high-temperature slag for the next dephosphorization treatment. Becomes

At this time, since an expensive accelerator is not required for accelerating the melting of the refined material, it is possible to suppress an increase in manufacturing cost. Further, it is possible to avoid an increase in the concentration of manganese oxide content, which is an obstacle when the slag is reused as a roadbed material or the like. Further, since a material at room temperature or a material that consumes a large amount of reaction heat is not used, it is possible to avoid a loss of required heat quantity.

Further, as a secondary effect of the present invention, the time required for discharging the slag to the outside of the refining container is shortened, the production efficiency is improved thereby, and the amount of hot metal mixed in the slag and discharged to the outside of the refining container is reduced. The loss can be reduced and the refractory can be protected by the slag adhering to the refining vessel. In addition,
Here, the converter includes not only an upper blowing converter for steelmaking but also a converter type refining furnace. Further, the refining furnace including the slag separating device includes a conventional electric furnace and further a special tapping device, for example, an electric furnace equipped with a bottom tapping device.

[0018]

EXAMPLES Examples will be described based on Table 1. Table 1 is 3
The refining method of the present invention was charged 90 times in a 40 ton converter and the average value is shown. At this time, the amount of hot metal was 340 tons and the total amount was 350 tons by adding scrap within 3%.
n was used as the hot metal raw material. The refining materials used conventionally are as shown in the table, and the amount of slag generated at this time is 23.2k.
It was g / ton. In the present invention, since 1% of the total amount of slag hot metal generated in the previous refining was left in the furnace, the amount of quick lime added was 9.8 kg / ton in the present invention, compared with 10.2 kg / ton in the conventional method. It was

Further, particularly in the conventional method, since quick lime and iron oxide are newly added, it is necessary to accelerate the dissolution of slag, so that 0.5 kg / ton of fluorite was added.
This expensive fluorspar addition could be eliminated by leaving about 1% slag. Therefore, the undissolved lime (CaO) was 2% in the conventional method, but it could be set to 0 in the method of the present invention.

As a result, the amount of slag generated is 21.8.
kg / ton, and the iron yield increased by 0.3 kg / ton. The refining time was 12 minutes in each case, and there was no change in production efficiency. Next, the refining results are shown in Table 2. In both the conventional method and the method of the present invention, the phosphorus content before dephosphorization refining is 0.110 wt% but after dephosphorization refining is 0.012 wt%, and in decarburization refining using this hot metal, There was no need for dephosphorization refining.

As described above, from Tables 1 and 2, the dephosphorization refining method of the present invention does not lower the production efficiency as compared with the conventional method, and the iron yield increases by 0.3 kg / ton and the excellent refining effect is obtained. Was obtained. In the above example, the slag generated in the previous dephosphorization refining is left in an amount of 1% of the total amount of hot metal, but the refining material used in one refining in advance is 1.5 times as much as that shown in Table 1. Alternatively, when the double amount is added in advance, it is not necessary to discharge the slag for each dephosphorization refining, and the same slag can be used again for the dephosphorization refining in the next refining. Such a method for carrying out the present invention is shown in FIG. 2. In this case as well, the refining effect as shown in Table 2 was substantially obtained.

[0022]

[Table 1]

[0023]

[Table 2]

[0024]

INDUSTRIAL APPLICABILITY According to the present invention, a part of the slag used in the previous dephosphorization refining is left in the converter or the like, and the refining material used in the next dephosphorization refining is rapidly dissolved. Since it is a method of accelerating the melting of a refined material that does not require an expensive additive and does not cause a loss of heat quantity, it is possible to dephosphorize hot metal efficiently and at low cost. As a secondary effect of the present invention, shortening the time required to discharge the slag out of the refining container,
As a result, the production efficiency can be improved, the loss of hot metal mixed in the slag and discharged to the outside of the refining vessel can be reduced, and the refractory can be protected by the slag adhering to the refining vessel.

[Brief description of drawings]

FIG. 1 is a diagram showing a series of refining work steps for carrying out the present invention.

FIG. 2 is another diagram showing a series of refining steps according to the embodiment of the present invention.

FIG. 3 is a tilt angle (θ) of the converter with respect to the vertical direction.
It is a figure which shows the relationship between the slag weight (ton) which remains in a converter furnace.

[Explanation of symbols]

 1 Converter 2 Steel tap 3 Dephosphorized hot metal 4 Ladle 5 Slag 7 Hot metal 8 Scrap

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Kamisui 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Inventor Masanori Komaya 1-2-1, Marunouchi, Chiyoda-ku, Tokyo No. Nippon Steel Tube Co., Ltd.

Claims (2)

[Claims] 1. A method for dephosphorizing hot metal, comprising the following steps: (a) a converter, or a smelting furnace equipped with a slag separator (hereinafter referred to as "converter") with a predetermined amount of hot metal raw material. Charge the refining material,
Mainly performing dephosphorization refining, (b) after the dephosphorization refining, the dephosphorized hot metal is discharged from the molten metal outlet of the converter, etc., and 1% or more of the weight of the hot metal in the slag generated subsequently. Slag having a weight equivalent to the above is left in the converter etc., the rest is discharged, and (c) subsequently, a predetermined amount of hot metal raw material and refining material are charged into the converter etc. and dephosphorization refining is repeated. . 2. A method for dephosphorizing hot metal, which comprises the following steps: (a) a converter or a smelting furnace equipped with a slag separator (hereinafter referred to as a converter) and a predetermined amount of hot metal raw material; Charge the refining material,
Mainly performing dephosphorization refining, (b) after the dephosphorization refining, dephosphorized hot metal is discharged from a molten metal outlet such as the converter, and 1% or more of the weight of the hot metal in the slag generated subsequently. Slag having a weight equivalent to the above is left in the converter or the like, the rest is discharged, and (c) and then the steps from (a) to (b) are repeated once or more, and (d) after that, Among the slags, the slag having a weight corresponding to 1% or more of the weight of the hot metal is left in the converter or the like, and the rest is discharged, and (e) further,
A predetermined amount of hot metal raw material and a refining material are charged into the converter or the like, and dephosphorization refining of the hot metal is repeated.