JPH0559421A - Steelmaking method for converter with less-slag blowing charging molten iron melting cold iron source - Google Patents

Abstract

PURPOSE:To execute the stable less-slag blowing even in the case of using cold iron source in the steelmaking method for converter with the less-slag blowing charging molten iron melting the cold iron source. CONSTITUTION:In the charging stage 9, into an empty molten iron ladle 3 after charging the molten iron into the converter 2, beforehand, the cold iron is charged in the cold iron source charging preparing stage 7 from a cold iron source stock yard 6, and the molten iron from a blast furnace 1 is received into this molten iron ladle 3 with the molten iron receiving stage 8, and by heat with high temp. of the molten iron and stirring force, the cold iron source is perfectly melted. By shifting the molten iron ladle 3, alkali metal compound of CaO, CaF2, etc., from a stock yard 5, is incorporated with the dephosphorizing stage 4 and the dephosphorization is executed with the constant blended ratio of gaseous oxygen of oxygen gas and solid oxygen of mill scale, etc., (this is called to the gaseous oxygen ratio). Therein, the molten iron having <=0.030% the aimed P and <=0.080% the aimed Si can easily be obtd. Successively, the dephosphorized molten iron is charged in the converter 2, and the oxygen steelmaking with the less-slag blowing is executed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a converter steelmaking method of less slag blowing in which hot metal in which a cold iron source is melted is charged.

[0002]

2. Description of the Related Art In ironworks, hot metal produced in a blast furnace is received in a hot metal ladle for transportation, and pretreatment such as desiliconization, desulfurization, and dephosphorization is performed on the hot metal, and the hot metal is passed through a converter charging pot. It is charged into a converter and a converter steelmaking method is carried out by blowing less slag.

In this case, a hot metal furnace, a torpedo car, or the like may be used during the transportation of the hot metal.

In the converter steelmaking method using less slag blowing,
It is necessary to perform dephosphorization as a pretreatment. As the dephosphorization treatment, the following methods are generally mentioned.

A method of injecting quicklime-based flux or soda ash into the hot metal in the torpedo car. A method of injecting or spraying quicklime-based flux to the hot metal in the hot metal ladle. A method of spraying quicklime-based flux onto the hot metal in the blast furnace casting floor gutter. A method in which both upper and lower blowing converters are used and blowing is performed using quicklime-based flux. A method in which both upper and lower blowing converters are used and a converter slag (generated in a decarburizing furnace) is used as the main component for blowing.

On the other hand, as a converter steelmaking method by less slag blowing, "melting steel refining method for adjusting blown manganese" as proposed in Japanese Patent Publication No. 59-37323 has been proposed.

Here, hot metal which has been dephosphorized and desulfurized in advance is used, and the refining function in the oxygen steelmaking furnace is to decarburize as much as possible so that slag is not allowed to exist or heat is dissipated from the hot metal surface. Suppressing and collecting oxides in the hot metal bath generated by oxidation, and further performing refining in the presence of as little slag as possible necessary to prevent melting damage of refractory materials, By adding the contained ore or manganese-containing substance to the bath, the molten steel Mn content is increased at the time of blowing stop.

[0008]

However, in the converter steelmaking method, the amount of tapped iron in the blast furnace and the amount of the main raw material in the converter may not be sometimes balanced in some cases. In that case, various measures are taken by each steelworks. Generally, a cold iron source is directly charged into the converter to balance the amount of tapping iron and the amount of main raw material in the converter.

In such a case, the above-mentioned Japanese Patent Publication No. 59-3
When the converter steelmaking method by less slag blowing as shown in Japanese Patent No. 7323 is performed, there are the following problems.

Since Si, P, S, etc. in the cold iron source are brought into the furnace, it is necessary to add a solvent medium such as CaO to remove them. Therefore, an increase in the amount of slag causes a decrease in Mn yield.

Further, the charging of the cold iron source lowers the heat margin of the converter, so that the charging amount of Mn ore and Mn-containing substance decreases.

The above causes a decrease in the blown Mn concentration, and in order to supplement them, it is necessary to add an expensive iron-manganese alloy at the time of tapping.

Further, in the converter steelmaking method by less slag blowing, since dephosphorized hot metal is charged into the converter, Si and the like are low, and the hot metal temperature is generally lower than in the case of non-dephosphorized hot metal. For example, it becomes about 1280 ° C., and the heat margin is low. Therefore, when a cold iron source is charged into the converter, the hot metal mixing ratio is high.

The present invention is intended to solve the above problems, and an object of the present invention is to provide a converter steelmaking method capable of performing stable less-slag blowing even when a cold iron source is used.

[0015]

In order to achieve the above object, the present invention is to put a cold iron source in an empty container after charging molten iron into a converter and to charge the molten iron into it. The cold iron source is characterized by melting the cold iron source, dephosphorizing the completely melted hot metal, charging it into a converter, and blowing it with oxygen in the presence of the smallest possible amount of slag. This is a converter steelmaking method by less slag blowing in which hot metal in which the source is melted is charged.

According to the present invention, it is necessary to load a cold iron source into an empty container in advance. This makes it possible to effectively utilize the temperature of the hot metal charged into the container thereafter and the stirring function in the hot metal to completely promote the melting of the cold iron source.

In the present invention, it is necessary to dephosphorize the hot metal in which the cold iron source is completely dissolved. As a result, it is possible to sufficiently perform the target dephosphorization treatment of P ≦ 0.030% and Si ≦ 0.080%.

In the present invention, as described above, since the hot metal in which the cold iron source is melted is charged into the converter in the stage of the pretreatment, as a whole, the converter steel making method by slag blowing with the cold iron source is blended. Becomes

[0019]

Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing the steps of the present invention. In this case, a case where 100 kg / ton of cold pig iron is charged as a cold iron source will be described. After the molten iron is charged into the converter 2 in the charging step 9, the cold iron is put in advance from the cold iron source storage 6 to the step 7 in the empty hot metal ladle 3 and the blast furnace 1 from the blast furnace 1 to the molten iron pan 3 in the step 8. By receiving the hot metal, the cold iron source is completely melted by the heat due to the high temperature of the hot metal (1450 ° C. or higher) and the stirring force in the hot metal, the hot metal ladle 3 is moved, and in the dephosphorization step 4, CaO from storage 5
An alkali metal compound such as CaF ₂ is added, and dephosphorization is performed at a fixed compounding ratio (hereinafter referred to as a gas-acid ratio) of gas-based acid by oxygen and solid acid by mill scale or the like. Here, it is possible to easily obtain the target hot metal having P ≦ 0.030% and Si ≦ 0.080%. The gas-acid ratio = gasic acid / (gasic acid + solid acid) × 100.

In this case, the temperature of the hot metal in the dephosphorization step is set to 1340 ° C. or lower immediately before the completion of dephosphorization. 1 just before the end of dephosphorization
Dephosphorization treatment at a temperature below 340 ° C
The above target value can be stably achieved.

However, if the temperature of the dephosphorized molten pig iron is too low, it becomes difficult to charge it into the converter due to the addition of a pan, and the heat margin in the converter decreases.

In the present invention, dephosphorization can be carried out stably, the hot metal after dephosphorization can be easily charged into the converter, and the thermal margin in the converter can be secured by adjusting the gas-acid ratio. The temperature after the dephosphorization treatment is adjusted.

That is, the temperature of the hot metal before dephosphorization is 100
In the case of charging kg / ton of hot metal, the temperature is about 1260 ° C. Therefore, the temperature of hot metal after dephosphorization treatment is changed to 13 by changing the vapor acid ratio.
Dephosphorization treatment is performed by adjusting the temperature between 20 ° C and 1340 ° C.

FIG. 2 shows the relationship between the gas-acid ratio and the amount of temperature rise. As a conventional example, a case of hot metal that does not melt a cold iron source is shown. Here, the gas-acid ratio is 40 to 60%, whereas it is 60 to 80% in the present invention.

In the above example, the gas-acid ratio was adjusted in the dephosphorization step, but the present invention is not limited to this, and in the case where the dephosphorization treatment is performed after the desiliconization treatment is performed. By adjusting the gas / acid ratio by desiliconization, the gas / acid ratio in the dephosphorization process can be adjusted to 40%.
It can be set to the same range as in the past, which is up to 60%.

As an example of the dephosphorization treatment according to the present invention,
Table 1 shows the specifications.

[0028]

[Table 1]

As is clear from Table 1, when cold pig iron is melted, the temperature of the hot metal before the treatment is lowered, but the solid acid is reduced and the vapor-acid ratio is increased, whereby the same treatment as the conventional method is carried out. The temperature can be obtained. That is, dephosphorized hot metal having the same composition and temperature could be obtained by reducing the sensible heat due to the dissolution of the cold pig iron by reducing the solid acid having a high cooling ability.

Next, 25 parts of the hot metal dephosphorized as described above is used.
Table 2 shows the results of charging into a 0 ton converter and performing oxygen steelmaking by less slag blowing.

[0031]

[Table 2]

As is clear from Table 2, the less slag blowing brings the scrap blending ratio to 5% or 7% as shown in the conventional method. Also, the amount of Mn ore charged decreases, and the addition of iron-manganese alloy increases accordingly.

On the other hand, in the present invention, as described above,
Even with 100kg of cold pig iron / ton of hot metal, the same amount of iron ore and Mn ore as in the conventional method can be charged.
Accordingly, it is sufficient to add the iron-manganese alloy to the same degree as in the conventional method.

In the present invention, as described above, it takes only a short time of about 10 minutes to charge the cold iron source into a container such as a hot metal ladle in advance, and the lead time between the blast furnace and the converter is normally set. Almost the same as in the case of hot metal treatment.

[0035]

According to the present invention, the following effects can be mainly obtained in less slag blowing.

In the low hot metal composition, it is possible to eliminate the carry-in of P, Si, S, etc. from the cold pig iron source to the converter. It is possible to expand the amount of iron source compounded when low-hot metal is compounded. It is possible to recover the heat radiated from containers such as hot metal pots. Stable less slag blowing of converter is possible. Since damage to the refractory lining of the converter due to charging of a cold iron source such as scrap can be avoided, as a result, its life can be extended. The life of floor bricks for containers such as hot metal pots can be extended. Fe-manganese alloys can be reduced in less slag blowing.

[Brief description of drawings]

FIG. 1 is a diagram showing a process of one embodiment of the present invention.

FIG. 2 is a diagram showing an example of dephosphorization treatment concerning the relationship between the vapor acid ratio and the temperature rise amount in the present invention.

[Explanation of symbols]

 1 Blast furnace 2 Converter 3 Hot metal ladle 4 Dephosphorization process 7 Cold iron source placement process 8 Iron receiving process

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hideo Kajitani, Marunouchi 1-2-2, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Hironori Yamamoto 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Japan Steel Pipe Co., Ltd. (72) Inventor Toshiyuki Hirose 1-2-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd. (72) Hirohisa Nakajima 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Sun Inside the steel pipe company

Claims (1)

[Claims] 1. An empty container after charging the hot metal into the converter,
Put a cold iron source, put hot metal into it, melt the cold iron source, dephosphorize the completely melted hot metal, put it in a converter, and put as little slag as possible. A converter steelmaking method of less slag blowing, which comprises charging hot metal in which a cold iron source is melted, characterized by performing oxygen blowing below.