KR102166614B1 - Method for injecting heat source member for enhancement of the end point control capability of converter - Google Patents

Abstract

The present invention relates to a method for feeding a heat source material for improving the end point control capability of a converter. According to an embodiment of the present invention, the method for feeding a heat source material for improving the end point control capability of a converter comprises: a step of measuring the temperature and silicon (Si) content of molten metal; a step of transporting the molten metal to KR equipment; a step of depositing and rotating an impeller in the molten metal transported to the KR equipment; a step of feeding a desulfurizing agent to the molten metal to desulfurize the molten metal; a step of feeding a heat source material to the molten metal before ending the rotation of the impeller; and a step of ending the rotation of the impeller. A feeding amount of the heat source material is determined in accordance with the measured temperature and silicon (Si) content of the molten metal, and the heat source material is fed to allow the silicon (Si) content in the molten metal to become 0.6 wt% or lower.

Description

Method of inputting heat source material to improve control ability of converter end point {METHOD FOR INJECTING HEAT SOURCE MEMBER FOR ENHANCEMENT OF THE END POINT CONTROL CAPABILITY OF CONVERTER}

The present invention relates to a method of inputting a heat source material for improving a converter control ability. More specifically, the present invention relates to a method of introducing a heat source material for improving the control function of the end of the converter, which can reduce the variation in temperature rise of the molten steel in the converter and improve the temperature of the molten steel and the oxygen hit rate at the end of the converter.

The steel making process in the iron making process proceeds in the order of a hot-metal pretreatment process, a converter refining process, a secondary refining process, and a continuous casting process. The converter refining process is a process of removing carbon and other components in the form of CO gas or slag by charging the molten iron into the converter and blowing high-purity oxygen gas through the lance. Through this process, impurities such as phosphorus (P) are removed. The removed molten iron is called molten steel.

The target end point molten steel temperature and oxygen amount during converter refining will vary depending on the required temperature of the post process and the components of the steel type. In addition, in order to increase the hit rate of the target end point temperature and the amount of oxygen, a heat source material and a coolant are introduced during the furnace blowing. The amount of the heat source and coolant is determined by HMR (Hot Metal Ratio), the temperature of the molten iron, and the content of the molten iron components (C and Si, etc.), and if the heat source is sufficient, the coolant is added, and if the heat source is insufficient, silicon ( Si)-based heat source material is added to control the target molten steel temperature using the heat of oxidation reaction.

Background art related to the present invention is disclosed in Japanese Laid-Open Patent Publication No. 1996-302413 (published on November 19, 1996, title of the invention: a method for controlling an end point of blowing in a converter).

According to an embodiment of the present invention, a target molten steel temperature and an oxygen hit rate at an end point of a converter are excellent, and a method of introducing a heat source material capable of improving molten steel quality is provided.

According to an embodiment of the present invention, it is to provide a method of introducing a heat source material having excellent economic efficiency by minimizing the amount of heat source material input.

According to an embodiment of the present invention, it is to provide a method of introducing a heat source material having excellent process stability.

One aspect of the present invention relates to a method of introducing a heat source material for improving the control function of the end point of the converter. In one embodiment, the method of introducing the heat source material includes measuring the temperature and silicon (Si) content of the molten iron; Transferring the chartered iron to a KR facility; Immersing and rotating an impeller in the molten iron transferred to the KR facility; Desulfurizing by adding a desulfurization agent to the molten iron; Before ending rotation of the impeller, introducing a heat source material into the molten iron; And terminating the rotation of the impeller; wherein the input amount of the heat source material is determined according to the measured temperature of the molten iron and the silicon (Si) content, and the silicon (Si) content in the molten iron is 0.6% by weight or less Is put to be.

In one embodiment, the heat source may be ferrosilicon (Fe-Si) in the form of ferroalloy.

In one embodiment, the input of the heat source material is determined on the basis of a converter operation with a chartering ratio (HMR) of 82.5% by weight among the total charge of 345 tons of chartered and scrap, and the above It can be added to the charter by reducing by 600kg from the determined heat source input amount.

In one embodiment, the heat source material may be added to the molten iron 2 minutes before the end of the rotation of the impeller.

In one embodiment, when the measured temperature of the molten iron exceeds 1440° C., or the silicon content of the molten iron exceeds 0.6% by weight, the heat source material may not be added.

In one embodiment, before transferring the chartered iron to the KR facility, the slag included in the chartered iron is first removed, and after the rotation of the impeller is terminated, the slag included in the chartered iron may be secondarily discharged.

When applying the heat source input method for improving the controllability of the end of the converter, the target molten steel temperature and the oxygen hit rate at the end of the converter are excellent, the quality of the molten steel can be improved, and the amount of heat source material input is minimized to provide excellent economical efficiency. , Sloping phenomenon can be prevented during the converter process, and process stability can be excellent.

1 shows a method of introducing a heat source material for improving the control function of a converter end point according to an embodiment of the present invention.
2 shows a target molten steel temperature and an oxygen content hit rate at an end point of a converter according to an increase in the amount of heat source material input during the converter process.
3 is a graph comparing changes in the molten steel temperature and the oxygen content hit rate at the end of the converter as the silicon content in the molten steel increases under conditions in which a heat source material is input and not introduced during a converter process.
Figure 4 shows a method of introducing a heat source material according to an embodiment of the present invention.
5 shows a method of introducing a heat source material of Comparative Example 1 for the present invention.
6 is a graph comparing the hit ratio of the target molten steel temperature and the amount of oxygen at the end of the converter of Example and Comparative Example 1. FIG.
FIG. 7(a) is a photograph showing the chartered iron 50 seconds after the heat material input of the Example, and FIG. 7 (b) is a photograph showing the hot metal iron 50 seconds after the heat material input of Comparative Example 2.

Hereinafter, the present invention will be described in detail. In this case, when it is determined that a detailed description of known technologies or configurations related to the present invention may unnecessarily obscure the subject matter of the present invention, a detailed description thereof will be omitted.

In addition, terms to be described later are terms defined in consideration of functions in the present invention and may vary according to the intentions or customs of users and operators, and thus their definitions should be made based on the contents throughout the present specification describing the present invention.

Converter end point Controllability For improvement Heat source material Input method

One aspect of the present invention relates to a method of introducing a heat source material for improving the control function of the end point of the converter. 1 shows a method of introducing a heat source material for improving the control function of a converter end point according to an embodiment of the present invention. Referring to FIG. 1, the method of introducing the heat source material includes: (S10) measuring a molten iron temperature and a silicon content; (S20) KR facility transfer step; (S30) impeller deposition and rotation step; (S40) Desulfurization agent input step; (S50) heat source input step; And (S60) impeller rotation end step; includes.

More specifically, the method of introducing the heat source material includes: (S10) measuring the temperature and the silicon (Si) content of the molten iron; (S20) transferring the chartered iron to the KR facility; (S30) immersing and rotating an impeller in the molten iron transferred to the KR facility; (S40) adding a desulfurization agent to the molten iron to desulfurize; (S50) before terminating the rotation of the impeller, introducing a heat source material into the molten iron; And (S60) terminating the rotation of the impeller.

Hereinafter, the method of introducing the heat source material will be described in detail step by step.

(S10) Melting temperature and silicon content measurement step

The step is a step of measuring the temperature and silicon (Si) content of the molten iron. For example, in a blast furnace, iron ore and coal can be used to generate and ship a molten iron, and the temperature and silicon content of the molten iron repaired with a ladle can be measured.

(S20) KR facility transfer step

The step is a step of transferring the molten iron to the KR (Kanvara Reactor) facility. In one embodiment, before being transferred to the KR facility, the slag contained in the charter may be first removed. For example, after transferring the ladle repaired by the chartered iron to the KR facility, the ladle may be tilted to remove the slag floating on the charter by using a skimmer or the like to perform primary exhaustion. When the slag is first excluded, desulfurization efficiency may increase.

(S30) Impeller Immersion and rotation stage

The step is a step of immersing and rotating an impeller in the molten iron transferred to the KR facility.

(S40) Desulfurization agent input step

The step is a step of desulfurizing by adding a desulfurization agent to the molten iron. In one embodiment, the desulfurization agent may include quicklime, but is not limited thereto. When the desulfurization agent is introduced, desulfurization can be achieved by easily dispersing and contacting the molten iron by the stirring force caused by the rotation of the impeller.

(S50) Heat source material Input stage

The step is a step of injecting a heat source material into the molten iron before ending the rotation of the impeller. The heat source material contains silicon (Si).

2 shows the target molten steel temperature and oxygen content hit rate at the end of the converter according to the increase in the amount of heat source material input during the converter process. Referring to FIG. 2, it can be seen that as the amount of heat source material input in the converter process increases, the target molten steel temperature and the oxygen content hit rate at the end of the converter decrease significantly.

In addition, the following Figure 3 is a graph comparing changes in the molten steel temperature and the oxygen content hit rate (simultaneous hitting rate) at the end of the converter as the silicon content in the molten steel increases under conditions in which a heat source material is input/not introduced during the converter process. Referring to FIG. 3, it can be seen that even when the silicon content in the molten steel is the same, the hit rate is significantly lowered when the heat source material is added compared to the case where the heat source material is not added during the converter process.

The conventional heat source material is input during the converter process, and the input amount of the heat source material is determined by measuring the HMR (Hot Metal Ratio), the temperature of the molten iron, and the content of the molten iron components (C and Si, etc.) of the molten iron repaired in the ladle. I did. Then, the heat source material was added as much as the determined amount, and the heat of the oxidation reaction was used to control the molten steel temperature of the target. At this time, the oxidation reaction of the heat source material introduced into the converter occurs with a reaction with gaseous oxygen according to Formula 1 below and with iron oxide (FeO) in molten steel slag according to Formula 2 below:

[Formula 1]

Si + O ₂ = SiO ₂ + Q ₁ (7,460 kcal/kg)

[Formula 2]

Si + 2FeO = SiO ₂ + 2Fe + Q ₂ (2,888 kcal/kg)

Referring to Formula 1 and Formula 2, the difference in the heat of oxidation (Q ₁ and Q ₂ ) occurs according to the oxygen source participating in the oxidation reaction of the heat source material, through which the same amount of the heat source material is introduced into the converter. Even if it is dissolved in the molten steel and reacts with oxygen gas, it can be seen that the difference in the heating of molten steel occurs depending on the rate of reacting with the iron oxide in the molten steel slag. Accordingly, as shown in the results of FIGS. 2 and 3, it can be seen that as the amount of the heat source material input from the converter increases, the temperature of the molten steel end point and the hit rate of the end point oxygen amount decrease due to the variation in heating temperature of the molten steel.

On the other hand, the present invention is to control so that only the oxidation reaction according to Formula 1 above occurs by inputting a silicon-containing heat source material from the KR facility to convert it into molten silicon (Si), and to increase the molten steel according to the amount of heat source input compared to the prior art. It minimizes the deviation of heat and can improve the hit rate of the molten steel end point temperature and the end point oxygen amount of the converter.

In one embodiment, the input amount of the heat source material is determined according to the measured temperature of the molten iron and the silicon (Si) content. In addition, the heat source material is added so that the silicon (Si) content of the molten iron is 0.6% by weight or less. When the silicon content in the molten iron exceeds 0.6% by weight after the heat source is added, a slope phenomenon overflowing with molten steel and slag out of the furnace furnace may occur in the converter process, thereby seriously deteriorating operational stability.

As described above, when an excessive amount of silicon heat source material is added in the KR desulfurization process, cost loss is caused due to unnecessary heat source input, and the silicon content of the molten iron is excessively increased after the heat source material is input, so that a slope phenomenon in the converter process. Will occur. Accordingly, in the present invention, in the KR process, the minimum amount of the heat source material to be commonly input to all the molten irons manufactured by steel type during the converter process is introduced.

In one embodiment, the input amount of the heat source material may be determined using the minimum input amount of the heat source material to be introduced into the converter. The minimum input amount of the heat source material to be introduced into the converter may be calculated based on the measured molten iron temperature and the amount of molten silicon (Si).

Table 1 below is data showing the minimum input amount of the heat source material to be injected when the converter is blown according to the temperature of the molten iron repaired in the ladle and the content of silicon (Si) for the furnace operating condition of 82.5% by weight of the charter rate. In one embodiment, the minimum input amount of the heat source material when blowing the converter as shown in Table 1 may be derived using operation data related to the input amount of the heat source material in the converter. For example, it can be derived by subtracting the standard deviation input amount from the average input amount of heat source material when blowing in a converter (minimum input amount of heat material = average value of input amount of heat material-standard deviation of input amount).

Table 2 below shows the input amount of the heat source material during the KR process, which is derived using the data of the minimum input amount of the heat source material when blowing the converter in Table 1. When added under the above conditions, the silicon content in the molten iron is 0.6% by weight or less, so that the occurrence of converter slope can be suppressed. In addition, referring to Table 2 below, when the measured temperature of the molten iron exceeds 1440°C or the silicon content of the molten iron exceeds 0.6% by weight, it means that the heat source is sufficient, and thus the heat source material may not be added.

In one embodiment, the input of the heat source material is determined on the basis of the operation of the converter with a charter ratio (HMR) of 82.5% by weight among the total charge of 345 tons of chartered and scrap, per 1.5% by weight increase in the charter rate at the time of operation of the converter. It can be added to the charter by reducing by 600kg from the determined heat source input amount. When introduced under the above conditions, the silicon content in the molten iron is controlled not to exceed 0.6% by weight, and the target molten steel temperature and the oxygen hit rate at the end of the converter may be excellent.

The heat source may be ferrosilicon (Fe-Si) in the form of ferroalloy. When the ferrosilicon in the form of ferroalloy is added, the contact and reaction rate with the molten iron are excellent, so that the dissolution rate may be excellent.

As heat sources, there are ferrosilicon ferroalloys (silicon content of about 75% by weight) and ferrosilicon briquettes (silicon content of about 65% by weight), and in the KR process of the present invention, ferrosilicon in the form of ferroalloy is used in the form of briquette. Compared to silicone, the reactivity with molten iron is excellent, the dissolution rate is excellent, and the heating effect may be excellent.

In one embodiment, the heat source material may be introduced into the molten iron 2 minutes before the end of the rotation of the impeller. When introduced under the above conditions, the heat source material may be sufficiently dissolved in molten steel until the impeller rotation is terminated. When the heat source material is introduced after the rotation of the impeller is finished, the heat source material is located on the upper part of the desulfurization agent floating on the top of the molten iron, so that it is difficult to dissolve during the molten iron. For example, the injection can be completed up to 1 minute before the end of the impeller rotation.

(S60) Impeller End stage of rotation

The step is a step of ending rotation of the impeller. In one embodiment, after the rotation of the impeller is terminated, slag floating on the molten iron may be secondarily excluded. When the slag is removed, the ability to control the end point of the converter may be further improved.

In one embodiment, after the impeller rotation is finished and the slag is secondarily removed, the components of the molten iron are measured, and when the sulfur (S) content is less than the target reference value, the molten iron is started as a subsequent process, and the sulfur content is the target reference value. If it is exceeded, re-desulfurization may be performed by additionally adding a desulfurization agent.

When applying the heat source input method for improving the controllability of the end of the converter, the target molten steel temperature and the oxygen hit rate at the end of the converter are excellent, the quality of the molten steel can be improved, and the amount of heat source material input is minimized to provide excellent economical efficiency. , Sloping phenomenon can be prevented during the converter process, and process stability can be excellent.

Hereinafter, the configuration and operation of the present invention will be described in more detail through preferred embodiments of the present invention. However, this is presented as a preferred example of the present invention and cannot be construed as limiting the present invention in any sense.

Example

The heat source material was added in the KR process in the same manner as in FIG. 4. Specifically, the molten iron was produced in a blast furnace, and the temperature and silicon (Si) content of the molten iron repaired with long-laid ladles were measured.

Then, for the furnace operating condition of 82.5% by weight of the charter rate (based on the total loading amount of 345 tons), depending on the temperature of the molten iron repaired in the ladle and the content of silicon (Si), the heat source to be input in the converter process as shown in Table 1. Data for the minimum amount of ash was prepared. At this time, the minimum input amount of the heat source material was derived by subtracting the standard deviation input amount from the average input amount of the heat source material in the converter (minimum input amount of heat source material = average value of the input amount of heat material-standard deviation of input amount). Using the data in Table 1, the amount of heat raw material input in the KR process as shown in Table 2 was calculated. In consideration of the measured temperature of the molten iron (1280 ~ 1299 ℃) and the silicon content (0.1 ~ 0.2% by weight), the heat source material input amount as shown in Table 2 was calculated (1600 kg).

Then, after the slag contained in the charter was first removed, the charter was transferred to a KR facility, and an impeller was immersed in the chartered bar and rotated. Then, a predetermined desulfurization agent (CaO) is added to the molten iron, while desulfurization, 1 minute before the rotation of the impeller ends, a heat source material (ferrosilicon ferroalloy (silicon content about 75% by weight)) 1600 kg in the molten iron. Was added to react with molten iron. Then, the rotation of the impeller was terminated, the slag contained in the molten iron was secondarily removed, and then the components of the molten iron were measured. The silicon content of the molten iron was measured to be 0.6% by weight or less, and the content of sulfur in the molten iron was measured to be less than the target value, and the molten iron was put into a converter (condition of a charter ratio = 82.5% by weight) and refined. At this time, during the refining, there was no slope or the like and stable operation was possible.

Comparative example One

Operation was carried out in the same manner as in FIG. 5 below. Specifically, the input amount of the heat source material was calculated in the same manner as in the above embodiment, but the operation was carried out in the same manner as in the above embodiment, except that the heat source material was added to the molten iron transferred to the converter.

Comparative example 2

One minute before the end of the rotation of the impeller, the operation was carried out in the same manner as in the above example, except that 1600 kg of a ferrosilicon briquette-type heat source material was added to the molten iron.

For Examples and Comparative Example 1, the molten steel temperature and the amount of oxygen at the end point of the converter were measured, and the hit ratio was evaluated by comparing the target molten steel temperature and the amount of oxygen, and the hit ratio is shown in FIG. 6 below. 6, the embodiment according to the present invention was superior to that of Comparative Example 1 in the molten steel temperature and the oxygen content hit rate at the end point of the converter, and through this, the heat source material was introduced during the KR desulfurization process to form silicon components of the molten iron. It was found that the converter end point control ability was excellent.

Fig. 7(a) below shows the molten iron (1300°C temperature condition) 50 seconds after the heat source material input of the above embodiment, and Fig. 7(b) is the time point 50 seconds after the heat source material input of Comparative Example 2 This is a picture showing the charter of Referring to FIG. 7, in the example of applying ferrosilicon in the form of ferroalloy of the present invention, the heat source material was completely dissolved in the molten iron, but in the case of Comparative Example 2 in which the ferrosilicon in the form of briquette was applied as the heat source material, the surface of the heat source material It was found that it was not completely dissolved due to the oxide film formed in the.

Simple modifications or changes of the present invention can be easily implemented by those of ordinary skill in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

Claims (6)

Measuring the temperature and silicon (Si) content of the molten iron;
Transferring the chartered iron to a KR facility;
Immersing and rotating an impeller in the molten iron transferred to the KR facility;
Desulfurizing by adding a desulfurization agent to the molten iron;
Before ending rotation of the impeller, introducing a heat source material into the molten iron; And
Including; terminating the rotation of the impeller,
The input amount of the heat source material is determined according to the measured temperature of the molten iron and the silicon (Si) content, but is added so that the silicon (Si) content in the molten iron is 0.6% by weight or less,
Before transferring the chartered ship to the KR facility, the slag contained in the chartered ship is firstly removed,
After the rotation of the impeller is terminated, the method of introducing a heat source material for improving control performance of an end point of a converter, characterized in that the slag contained in the molten iron is secondarily removed.
The method of claim 1,
The heat source material input method for improving the end point control ability of a converter, characterized in that the ferrosilicon (Fe-Si) in the form of ferroalloy.
The method of claim 1,
The input amount of the heat source material is determined based on the operation of a converter with a charter rate (HMR) of 82.5% by weight among the total amount of 345 tons of chartering and scrap loading,
Heat source input method for improving the control ability of the end of the converter, characterized in that for each increase of 1.5% by weight of the charter operation during operation of the converter, 600kg is reduced from the determined input amount of the heat source to the charter.
The method of claim 1,
The heat source material input method for improving the control function of a converter end point, characterized in that the heat source material is introduced into the molten iron 2 minutes before the end of the rotation of the impeller.
The method of claim 1,
When the measured temperature of the molten iron exceeds 1440° C. or the silicon content of the molten iron exceeds 0.6% by weight, the heat source material is not added.
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