KR100925593B1 - Molten slag deoxydation method for clean steel - Google Patents

Abstract

Provided is a slag deoxidation method in molten steel for producing high clean steel.

The present invention comprises the steps of measuring the dissolved oxygen content in the molten steel and SiO ₂ content (BOF _{SiO 2%} ) in the slag after the converter refining the end point oxygen refinement, and predicting the FeO content [FeO%] in the molten steel slag from the measured dissolved oxygen value; Predicting the amount of iron oxide [FeO _ladle (kg)] in the slag flowing out of the converter steel from the above, and then calculating the amount of slag deoxidizer, and then injecting it into the converter molten steel; When the molten steel is added to the ladle, the amount of sub-material (Flux1) and ferroalloy content (Flux2) are respectively measured. Then, the molten steel is released into the RH facility and the SiO ₂ content of the molten steel slag ( Measuring RH _{SiO 2%} ); Calculating the slag outflow (Ws) during the tapping of the converter in consideration of the SiO ₂ content change in the molten steel slag, and calculating the total amount of FeO [FeO _RH (kg)] in the molten steel slag arriving from RH; And calculating a slag deoxidizer input amount in RH using the calculated total amount of FeO, and injecting slag deoxidizer into the RH molten steel by the calculated amount. The molten steel slag deoxidation method for manufacturing a high clean steel comprising the It is about.

Slag Deoxidizer, Slag Flow Rate, Dissolved Oxygen, High Clean Steel

Description

Molten slag deoxydation method for clean steel}

1 is a flow chart showing the deoxidation method of the present invention

Figure 2 is a perspective view schematically showing the slag deoxidation operation

3 is a perspective view illustrating slag deoxidation reaction in ladles;

4 is a perspective view of a slag thickness measurement method by the manual measurement of the operator

5 is a perspective view of a slag thickness measurement method by POSRAM

6 is a perspective view of a slag thickness measurement method by the depth wave

7 is a perspective view of the diameter change of the molten steel ladle

8 is a graph showing a change in RH arrival (FeO) component according to the present invention

9 is a graph showing the (FeO) component change after the RH slag deoxidation in the present invention

Fig. 10 is a graph showing the change in dose [P] between converter and performance according to the present invention.

The present invention relates to a slag deoxidation method for reducing and removing lower oxides such as iron oxides in slag for the production of high clean steel in the steelmaking process. The present invention relates to a method for accurately measuring the amount of lower oxide using the slag component change at a time point, and reducing and removing the lower oxide effectively to a target level by adding a slag deoxidizer according to the amount of the lower oxide.

A general process of slag deoxidation is shown in FIG. 2. As shown in FIG. 2, the molten steel having completed the converter refining process is pulled out to the ladle, and then subjected to the second refining process in RH.

In this converter refining process, slag containing lower oxide such as FeO is generated on the molten steel. After the molten steel having such slag is tapped on the ladle, the first slag acid is charged, and the slag acid is charged into RH again to perform the second slag acid. However, in order to adjust the molten steel composition in RH, aluminum is added, and this aluminum is produced in a molten steel by inhibiting the molten steel blueness as shown in the following Reaction Formula 1 by slag containing a lower oxide such as FeO.

(Scheme 1)

3FeO + 2Al => Al ₂ O ₃ + 3Fe

Therefore, in order to solve this problem, as shown in FIG. 3, a technique of improving molten steel cleanness by deoxidizing slag by adding aluminum as a deoxidizer into slag formed in the upper part of the molten steel in the converter step is used.

However, if the amount of the slag deoxidizer is added, the technique can generally keep the content of the lower oxide lower than the target level, but when the slag deoxidizer is added in an amount more than necessary to reduce the lower oxide, the deoxidizer added according to Scheme 2 below. P ₂ O _{5 is} also reduced by heavy Al, and phosphorus ([P]) is easily picked up from slag into molten steel, which leads to a problem that an appropriate amount of deoxidizer is required.

(Scheme 2)

3 / 5P ₂ O ₅ + 2Al => Al ₂ O ₃ + [P]

Therefore, in order to know the proper amount of deoxidizer, it is necessary to accurately calculate the content of the lower oxide in the slag.

In order to calculate the lower oxide content, the total amount of the lower oxide can be obtained by knowing the lower oxide content of the converter slag and the slag flowed out with the molten steel during the converter tapping, and thus the slag deoxidizer input can be determined. However, as described above, while measuring the lower oxide content in the converter slag, since the molten steel is already finished tapping and is being processed in a post process, it is very difficult to set the slag deoxidizer input amount by the lower oxide content measurement.

Therefore, most steel mills use a very simple slag deoxidizer input standard to inject slag deoxidizer during tapping by applying the low oxide content of the converter slag and the conventional slag outflow. After collecting and analyzing the components and checking the content of the lower oxides, the slag deoxidizer is added to the secondary in RH when the lower oxides are high.

In addition, some steel mills measure the amount of slag spilled during tapping after the completion of tapping in order to effectively control the content of low oxides in slag, and calculate the amount of lower oxide in slag during the second slag deoxidation operation in the RH process and input the necessary deoxidizer amount. have.

Currently applied slag outflow measurement method is a manual measurement method by the operator as shown in FIG. 4, a dip rod buoyancy measurement method (POSRAM method) using the specific gravity difference between the slag and molten steel as shown in FIG. There is a radio wave measuring method that measures the slag amount by scanning the microwave and reflecting the pulses and electric conduction of molten steel and slag.

First, a manual measurement method by an operator is a method of depositing a thin iron pipe from the top of the slag to molten steel, there is a limit that a large deviation occurs depending on the method of measuring the slag thickness attached to the pipe surface or the skill of the operator. In addition, since both the POSRAM method and the radio wave measuring method measure the slag thickness and measure the slag outflow amount by the following Equation 1 using the diameter and the slag specific gravity of the molten steel lays, the number of times of use of the molten steel lays as shown in FIG. 7. It is difficult to accurately measure slag outflow due to the fact that its diameter changes due to refractory erosion, the slag swells and sinks depending on the operating conditions, and the slag specific gravity varies from 2.2 to 2.7. In addition, there are also problems associated with a considerable investment.

(Equation 1)

Slag outflow = π * r ² * h * δ

Where π = circumference, r = ladle radius, h = measured slag thickness, δ = slag specific gravity (2.2 to 2.7)

That is, it is difficult to accurately calculate the slag deoxidizer amount by the conventional slag outflow measurement method described above, and thus, it is difficult to control the lower oxide in the RH below the appropriate level and to suppress the abdominal phenomenon.

Therefore, the present invention has been made to solve the problems of the prior art described above, by calculating the amount of deoxidant to be injected into the converter by predicting the amount of iron oxide in the converter slag according to the converter end point oxygen level, and also during the tapping The slag spilled into the ladle can be quantitatively calculated to calculate the amount of lower oxides present in the slag, and the slag deoxidizer is automatically added according to the amount of lower oxides to ensure the cleanliness of molten steel and to manage the [P] component stably. It is an object of the present invention to provide a molten steel slag deoxidation method for manufacturing high clean steel.

The present invention for achieving the above object,

Converter polishing endpoint oxygen takes ryeonhu molten steel and measuring the amount of dissolved oxygen and SiO ₂ content in the slag (BOF _SiO2%), predict that to the measured dissolved oxygen values are substituted in equation 1 FeO content in the molten steel slags [FeO%] ;

Substituting the FeO content predicted from the above into Equation 2 below to predict the amount of iron oxide [FeO _ladle (kg)] out of the slag flowing out of the converter steel, and after calculating the amount of slag deoxidizer using the following Equation 3, Injecting slag deoxidizer into the converter molten steel by a calculated amount;

When the molten steel is added to the ladle, the amount of sub-material (Flux1) and ferroalloy content (Flux2) are respectively measured. Then, the molten steel is released into the RH facility and the SiO ₂ content of the molten steel slag ( Measuring RH _{SiO 2%} );

Using the following equations 4 and 5, the slag outflow during the tapping of the converter was calculated in consideration of the SiO ₂ content change in the molten steel slag, and from this, the total amount of FeO [FeO _RH (kg)] in the molten steel slag arriving at Calculating using relation 6; And

Substituting the calculated total amount of FeO into the following equation 7 to calculate the slag deoxidizer input amount in RH, the slag deoxidizer is added to the RH molten steel by the calculated amount; molten steel slag for manufacturing a high clean steel comprising a It relates to a deoxidation method.

(Relationship 1)

FeO (%) = [5.32087 + 0.0214623 × measured dissolved oxygen content (ppm)] × 1.287

(Relationship 2)

FeO _ladle (kg) = FeO% / 100 × average slag outflow over a period of time (kg)

(Relationship 3)

Slag deoxidizer input to converter = [[FeO _ladle (kg)-(0.02 × average slag outflow over time (kg))] × 16 (55.8 + 16) × 54/48 × Al reaction efficiency (0.9) ÷ slag Aluminum grade in deoxidizer] × 0.7
(Relationship 4)
RH _SiO2% = (Ws × BOF _SiO2% + Flux 1 × Flux 1 _SiO2% + Flux 2 × Flux 2 _SiO2% + ..) / (Ws + Flux1 + Flux2 + ...)

(Relationship 5)

Ws = [(Flux1 × Flux1 _SiO2% + Flux2 × Flux2 _SiO2% + ..)-RH _SiO2% × (Flux1 + Flux 2+ ..)] ÷ (RH _SiO2% -BOF _SiO2% )

(Relationship 6)

FeO _RH (kg) = T.Fe _RH % × Ws × 1.128

(Relationship 7)

Slag deoxidizer input at RH = [(FeO _RH (kg)-0.02 × Ws (kg)) × 16 / (55.8 + 16) × 54/48 × Al reaction efficiency (0.9)] ÷ Al grade in slag deoxidizer

However, in relation (5), Flux1 _SiO2% and Flux2 _SiO2% refer to the SiO ₂ grade (%) contained in the sub-raw material and ferroalloy, respectively, inputted to the ladle during the converter tapping.

Hereinafter, the present invention will be described in detail.

The present invention is characterized in that the molten steel slag deoxidizer input amount is determined in consideration of the dissolved oxygen content in the molten steel after the oxygen freezing of the converter refining process, and the slag oxidizer input amount is determined in consideration of the SiO ₂ content change in the molten steel slag in the RH operation.

First, the present invention measures the dissolved oxygen content in molten steel and the SiO ₂ content (BOF _SiO2% ) in slag after the converter refining the end point oxygen refinement, and predicts the FeO content [FeO%] in the molten steel slag by using the measured dissolved oxygen value. .

That is, in the present invention, when the refining operation is completed in the converter, the dissolved oxygen ([O]) dissolved in the temperature and molten steel is measured by the automatic measuring equipment. Since the iron oxide content in slag increases with increasing dissolved oxygen concentration, the iron oxide content according to the dissolved oxygen level can be predicted. Ideally, it is ideal to directly analyze the iron oxide content in the molten steel slag and to determine the slag deoxidant dosage accordingly, but this analysis is not preferable because it takes a long time of about 10 minutes and greatly reduces the steelmaking productivity.

In the present invention, the molten steel slag is also collected and measured to measure the SiO ₂ content (BOF _{SiO 2%} ) in the slag, and this measurement data is used to determine the correct slag deoxidizer input amount in the RH operation described later.

It was confirmed that the relationship between the dissolved oxygen content in the molten steel and the iron oxide content in the slag in the converter process has a relationship of the following Equation 1.

(Relationship 1)                     

FeO (%) = [5.32087 + 0.0214623 × measured dissolved oxygen content (ppm)] × 1.287

Therefore, the FeO content in the molten steel slag can be predicted by substituting the measured dissolved oxygen value in the equation (1). In addition, the correlation between the dissolved oxygen value measured after the converter refining and the FeO content in the end slag collected during the converter tapping is accumulated and stored in the system operating device (not shown) every time the component analysis is performed. Updates make it possible to predict the most accurate iron oxide values for changes in operating conditions.

Subsequently, the FeO content (FeO _ladle (kg)) in the slag flowing out of the converter steel was predicted by substituting the predicted FeO content into the following Equation 2, and then the slag deoxidizer amount was calculated using the following Equation 3. Thereafter, slag deoxidizer is added to the converter molten steel by the calculated amount.

First, since the amount of slag flowing out of the converter is still unknown, the total amount of iron oxide in the slag leaked by reflecting the iron oxide content (FeO%) of the slag in the average value of the slag flow rate during a certain period of operation [FeO _ladle ( kg)] can be predicted as in Equation 2 below.

 (Relationship 2)

FeO _ladle (kg) = FeO% / 100 × average slag outflow over a period of time (kg)

When the total amount of iron oxide [FeO _ladle (kg)] of the outflowed slag is calculated, the slag deoxidizer input required to reduce the iron oxide can be estimated using the following Equation 3.

In general, it is very difficult to control the iron oxide content in the molten steel slag to "0", and the cost increases due to the addition of the deoxidizer. Therefore, the amount of deoxidizer aluminum required to lower the iron oxide content of the slag, which is known to have no problem in molten steel, was calculated. At this time, however, the slag flowing out during tapping applied an average value for a certain period of time, so that only 70% of the calculated slag deoxidizer was applied to the converter.

(Relationship 3)

Slag deoxidizer input to converter = [[FeO _ladle (kg)-(0.02 × average slag outflow over time (kg))] × 16 (55.8 + 16) × 54/48 × Al reaction efficiency (0.9) ÷ slag Aluminum grade in deoxidizer] × 0.7

Here, 16 means O atomic weight, 55.8 means Fe atomic weight, 54 means 2Al molecular weight, and 48 means 3/2 O ₂ molecular weight.

In the present invention, the relational expressions 1 to 3 are built into the system operating apparatus, and the deoxidant input amount may be automatically calculated and added according to the measured dissolved oxygen using the embedded relational expression.

Next, in the present invention, when tapping the converter molten steel to the ladle, the content of the auxiliary raw material (Flux1) and the ferrous alloy (Flux2) respectively measured in the ladle, and then the molten steel is outgoing RH facility Upon arrival, molten steel slag is collected and the SiO ₂ content (RH _{SiO 2%} ) is measured. Each numerical value measured here is used as a factor which determines slag outflow amount Ws mentioned later and slag deoxidizer input amount in RH operation.

In the present invention, the slag outflow (Ws) during the converter tapping is calculated in consideration of the SiO ₂ content change in the molten steel slag, and from this, the total amount of FeO [FeO _RH (kg)] in the molten steel slag arriving is calculated.

As described above, the slag deoxidation in the converter was first deoxidized by determining the deoxidant dose based on the reduction of only 70% of the iron oxide content calculated as the average value of the slag outflow over a period of time. Therefore, in the secondary deoxidation treatment of molten steel slag in RH, it is desired to accurately calculate the iron oxide content in the slag by calculating the slag outflow amount more precisely, and to input the slag deoxidizer input amount based thereon. Therefore, in the present invention, the molten steel slag component in the converter and the molten steel slag component in the RH are used in determining the slag deoxidizer input amount during the RH operation. However, since the molten steel slag component in the RH is changed by the subsidiary materials input during the tapping in the converter, the SiO ₂ component which is least affected by the subsidiary materials input during the tapping is used. In general, the SiO ₂ content (RH _{SiO 2%} ) in the molten steel slag that reaches RH is known to satisfy the following equation (4).

(Relationship 4)

RH _SiO2% = (Ws × BOF _SiO2% + Flux 1 × Flux 1 _SiO2% + Flux 2 × Flux 2 _SiO2% + ..)

/ (Ws + Flux1 + Flux2 + ...)

Here, Ws is the actual slag outflow (Kg) during the tapping of the converter, Flux 1, Flux2 ..: the sub-raw material (Kg), each of the ferroalloys introduced into the ladle during the converter tapping, and Flux1 _SiO2% , Flux2 _SiO2% Refers to the SiO ₂ grade (%) contained in the sub-raw material and ferroalloy, respectively, which are introduced into the converter during ladle.

Therefore, it can be seen from the relation 4 that the actual slag outflow amount (Ws) during the tapping of the converter can be calculated through the following equation (5), and also the T.Fe component of the slag after the RH arrival From the equation 6, the total amount of FeO [FeO _RH (kg)] in the molten steel slag of _RH can be calculated.

(Relationship 5)

Ws = [(Flux1 × Flux1 _SiO2% + Flux2 × Flux2 _SiO2% + ..)-RH _SiO2% × (Flux1 + Flux 2+ ..)] ÷ (RH _SiO2% -BOF _SiO2% )

 (Relationship 6)

FeO _RH (kg) = T.Fe _RH % × Ws × 1.128

In the present invention, by calculating the slag deoxidizer input amount in RH by substituting the calculated amount of FeO in the following relation 7, and by introducing the slag deoxidizer into the RH molten steel by the calculated amount for high clean steel production excellent in molten steel cleanliness Molten steel can be refined.

(Relationship 7)

Slag deoxidizer input at RH = [(FeO _RH (kg)-0.02 × Ws (kg)) × 16 / (55.8 + 16) × 54/48 × Al reaction efficiency (0.9)] ÷ Al grade in slag deoxidizer

On the other hand, all the processes described above in the present invention is embedded in the operating system as a program, and thus automatically determine the input amount of the slag deoxidizer in the process without the operator's calculation, it can be injected into the molten steel to produce a high clean steel will be.

Hereinafter, the present invention will be described in detail through examples.

(Example 1)

In deoxidizing converter molten slag, the slag deoxidizer is considered in consideration of the iron oxide content of the molten steel slag in RH and the dissolved oxygen content after the converter end point oxygen treatment in a conventional process in which a predetermined amount of slag deoxidizer is introduced into the converter. Determination of the amount of iron oxide in the molten steel RH-laminated slag subjected to the process of the present invention in which the deoxidizer was added to determine the input amount, the results are shown in FIG. As shown in Figure 8, in the case of molten steel subjected to the process of the present invention, the iron oxide content in the slag was 4.38%, which is lower than the conventional operation 4.46%, and the standard deviation is 1.41%, compared to the conventional operation 1.95% I could confirm the low.

(Example 2)

In the addition of slag deoxidizer to the molten steel of RH arriving in the conventional molten steel refining process, slag deoxidation was performed by a conventional method of additionally adding a slag deoxidizer when the iron oxide content in the molten steel slag is above a certain level. In contrast to the conventional method, the slag deoxidizer input amount is determined by the present invention method considering the difference between the SiO ₂ content in the converter molten steel slag and the SiO ₂ content in the RH-added slag, and the deoxidizer is added as much as the input amount. 9 is shown.

As shown in FIG. 9, the method of the present invention obtained 1.95% of the iron oxide content in the slag after the RH treatment, which was lower than that of the conventional method 2.36%, and the standard deviation of the iron oxide in the slag was reduced from 1.08% to 0.73%. Could.

On the other hand, the present invention, as shown in Figure 10, by accurately measuring the iron oxide content in the molten steel slag, based on this, by adding only the required amount of slag deoxidizer can be significantly reduced compared to the conventional method the double shape caused by the excess deoxidizer injection have.

As described above, the present invention predicts the iron oxide content by the dissolved oxygen value after the converter refining, predicts the deoxidizer input amount accordingly, and automatically sets / injects the deoxidant input amount by the change of the molten steel slag component between the converter and the RH, and then slag after the RH treatment. It has a useful effect to improve the molten steel cleanness by significantly lowering the heavy iron oxide content.

Claims (1)

Converter polishing endpoint oxygen takes ryeonhu molten steel and measuring the amount of dissolved oxygen and SiO ₂ content in the slag (BOF _SiO2%), predict that to the measured dissolved oxygen values are substituted in equation 1 FeO content in the molten steel slags [FeO%] ; Substituting the FeO content predicted from the above into Equation 2 below to predict the amount of iron oxide [FeO _ladle (kg)] out of the slag flowing out of the converter steel, and after calculating the amount of slag deoxidizer using the following Equation 3, Injecting slag deoxidizer into the converter molten steel by a calculated amount; When the molten steel is added to the ladle, the amount of sub-material (Flux1) and ferroalloy content (Flux2) are respectively measured. Then, the molten steel is released into the RH facility and the SiO ₂ content of the molten steel slag ( Measuring RH _{SiO 2%} ); Using the following equations 4 and 5, the slag outflow during the tapping of the converter was calculated in consideration of the SiO ₂ content change in the molten steel slag, and from this, the total amount of FeO [FeO _RH (kg)] in the molten steel slag arriving at Calculating using relation 6; And Substituting the calculated total amount of FeO into the following equation 7 to calculate the slag deoxidizer input amount in RH, the slag deoxidizer is added to the RH molten steel by the calculated amount; molten steel slag for manufacturing a high clean steel comprising a Deoxidation method. (Relationship 1) FeO (%) = [5.32087 + 0.0214623 × measured dissolved oxygen content (ppm)] × 1.287 (Relationship 2) FeO _ladle (kg) = FeO% / 100 × average slag outflow over a period of time (kg) (Relationship 3) Slag deoxidizer input to converter = [[FeO _ladle (kg)-(0.02 × average slag outflow over time (kg))] × 16 (55.8 + 16) × 54/48 × Al reaction efficiency (0.9) ÷ slag Aluminum grade in deoxidizer] × 0.7 (Relationship 4) RH _SiO2% = (Ws × BOF _SiO2% + Flux 1 × Flux 1 _SiO2% + Flux 2 × Flux 2 _SiO2% + ..) / (Ws + Flux1 + Flux2 + ...) (Relationship 5) Ws = [(Flux1 × Flux1 _SiO2% + Flux2 × Flux2 _SiO2% + ..)-RH _SiO2% × (Flux1 + Flux 2+ ..)] ÷ (RH _SiO2% -BOF _SiO2% ) (Relationship 6) FeO _RH (kg) = T.Fe _RH % × Ws × 1.128 (Relationship 7) Slag deoxidizer input at RH = [(FeO _RH (kg)-0.02 × Ws (kg)) × 16 / (55.8 + 16) × 54/48 × Al reaction efficiency (0.9)] ÷ Al grade in slag deoxidizer However, in relation (5), Flux1 _SiO2% and Flux2 _SiO2% refer to the SiO ₂ grade (%) contained in the sub-raw material and ferroalloy, respectively, inputted to the ladle during the converter tapping.

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