KR101977825B1 - Method for refining molten steel - Google Patents

Abstract

It provides a steelmaking refining method. The steelmaking refining method calculates the sulfur content in the molten steel at the completion of the refining of the converter, measures the oxygen concentration at the completion of the refining of the converter, calculates the amount of burnt lime to be supplied during the lubrication according to the calculated sulfur content and the measured oxygen concentration .

Description

{METHOD FOR REFINING MOLTEN STEEL}

The present invention relates to a steelmaking refining method.

Generally, molten iron produced in a blast furnace contains a large amount of carbon (C) and contains impurities such as phosphorus (P) and sulfur (S). In order to produce molten iron as a steel, A steelmaking process is performed to remove the steel sheet.

The steelmaking process can be divided into electric furnace steelmaking and converting steelmaking. The transformer steelmaking process can be divided into pre-treatment, converter refining, Bubbling and Powder Injection (BAP) for secondary refining, Ladle Furnace (LF) Process, and Ruhrstahl-Heraues degassing (RH) process.

In the converter refining process during the steel making process, oxygen is blown into the converter by a lance to remove impurities in the molten iron by the oxidation reaction.

However, since it is difficult to remove impurities such as sulfur, impurities are removed in a pre-treatment step before the converter refining step or a desulfurization treatment step using a KR (Kanvara Reactor) facility, and then scrap iron and charcoal are charged into the converter, .

In general, the concentration of sulfur in the molten iron is controlled to a set content (for example, 30 ppm) or less in the pretreatment process or the desulfurization process.

The steel product produced at a set content of sulfur (for example, 30 ppm or less) in steelmaking is subjected to a refining process for a converter, a BAP process for a second refining, an LF process, and an RH process Finally, the slab is transported to the performance process.

As described above, when the content of sulfur is less than the set content (for example, 30 ppm) and the vacuum degassing process is performed, gas injection and vacuum degassing must be performed at the same time as the molten steel treatment characteristics.

However, if the furnace is operated in the order of the electrolytic refining process, the BAP process, the LF process, the vacuum degassing process, and the performance process, the processing cost is increased and the manufacturing cost of the molten steel is increased.

Therefore, it is required to omit the vacuum degassing process in the rice process.

However, in the rice process, the amount of burnt lime is constant during the rise of sulfur by scrap iron, the amount of burnt lime added during the transfer to the furnace, and the evaluation of the gas supply for measuring the desulfurizing ability in the rice process. .

The present invention is to provide a steelmaking refining method capable of reducing costs by simplifying a vacuum degassing process by eliminating the LF process by refining to a sulfur content (30 ppm) or less set in a BAP process.

The steelmaking refining method according to an embodiment of the present invention includes a sulfur content calculating step of calculating the sulfur content in the molten iron and the sulfur content in scrap iron during the refining of the converter and calculating the sulfur content in the molten steel at the time when the refining of the converter is completed.

Further, the steelmaking refining method may include an oxygen concentration measuring step of measuring the oxygen concentration in the converter when the refining of the converter is completed.

The steelmaking refining method may include a step of determining the amount of burnt lime to be supplied with the iron oxide in the molten steel along with the iron content in the molten steel according to the sulfur content calculated in the sulfur content calculating step and the oxygen concentration measured in the oxygen concentration measuring step have.

The steelmaking smelting method outputs an evaluation value based on the difference between the upstream pressure and the downstream pressure of the gas supplied into the ladle from the lower nozzle at the lower portion of the ladle while the molten steel is conveyed to the ladle, Based bubbling condition evaluation step.

The steelmaking smelting method may include a lower bubbling performing step of performing a lower bubbling during a lower bubbling time set according to an evaluation value during the transfer of ladle to a BAP process.

A rice process operation method determination step of determining the additional burdens and the upper bubbling time of the rice process using the calculated sulfur content, the measured oxygen concentration, and the evaluation value before the lambs arrive at the rice process .

In the step of determining the amount of burnt lime, the amount of burnt lime based on sulfur to be fed into the ladle may be calculated according to the calculated sulfur content.

In the step of determining the amount of burnt lime, the amount of burnt lime based on the oxygen concentration to be supplied to the ladle may be calculated in accordance with the measured oxygen concentration.

The step of determining the amount of quicklime may include the step of inputting the first quicklime to input the amount of fresh lime based on the sulfur content based on the oxygen concentration based on the amount of the quicklime as the upper limit.

The step of determining the amount of quicklime may include a step of inputting the amount of fresh lime added to the raw lime by the second step in the rice (BAP) process.

The first lime input step may include a first lime lime input step in which the amount of quick lime to be initially charged is set before the quick lime is input.

And a first measuring step of measuring the temperature of the molten steel and the degree of deoxidation of the molten steel by firstly using the measuring device when the ladle reaches the rice process and collecting a sample of the molten steel.

The first upper bubbling may be performed for a set time after the first measurement step is performed.

The deoxidation degree of the molten steel measured in the first measurement step may be determined, and the amount of the deoxidizer may be further added to the first deoxidizer additionally.

The first component analysis value confirmation step of firstly confirming the component analysis value of the sample collected in the first measurement step and the sulfur component content of the component analysis value of the sample identified in the first component analysis value confirmation step can be processed in the rice process And a step of checking whether or not the sulfur content is above a threshold value for confirming whether or not the sulfur content is above a threshold value.

In the analysis of the primary component analysis value, when the value of the component analysis value of the sample is within the limit value, the upper bubbling and the lower bubbling time are first adjusted in the BAP process using the analyzed sulfur value. And a bubbling time adjustment step.

And an ELF process transfer step of transferring the ladle to the LF process when the sulfur value of the component analysis value of the sample identified in the first component analysis value confirmation step is equal to or larger than the threshold value.

And a secondary measuring step of measuring the temperature of the molten steel and the degree of deoxidation of the molten steel in a second order using the measuring device when the first controlled upper bubbling execution time is completed and collecting a sample of the molten steel.

A ladle withdrawing step of withdrawing ladle from the rice processing after the second measuring step is performed, a vacuum degassing processing step of vacuum degassing the ladle after withdrawing the ladle, and a performance process transfer step of transferring ladle to the performance process can do.

According to the embodiment of the present invention, the sulfur content in the molten steel is calculated, and the performance of the lower bubbling during the lubrication is quantified to produce a steel having a sulfur content less than the sulfur content set in the rice process so as not to undergo the LF process, Can be saved.

1 is a schematic diagram of a steelmaking refining method according to an embodiment of the present invention.
FIG. 2 is a schematic configuration diagram of an apparatus used in a steelmaking refining method according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Wherever possible, the same or similar parts are denoted using the same reference numerals in the drawings.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms as used herein include plural forms as long as the phrases do not expressly express the opposite meaning thereto. Means that a particular feature, region, integer, step, operation, element and / or component is specified, and that other specific features, regions, integers, steps, operations, elements, components, and / And the like.

All terms including technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs. Predefined terms are further interpreted as having a meaning consistent with the relevant technical literature and the present disclosure, and are not to be construed as ideal or very formal meanings unless defined otherwise.

FIG. 1 is a schematic configuration diagram of a steelmaking refining method according to an embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of an apparatus used in a steelmaking refining method according to an embodiment of the present invention.

1 and 2, a steelmaking refining method according to an embodiment of the present invention calculates sulfur content in molten iron and sulfur content in scrap iron during refinement (1) and calculates sulfur content in molten steel And a sulfur content calculating step (S10).

The steelmaking refining method may include an oxygen concentration measuring step (S20) for measuring the oxygen concentration in the converter at the time when the refining of the converter (1) is completed.

At the time when the converter (1) refining is completed, the oxygen concentration in the converter is indicated by the end point oxygen in the following [Table 10].

The steelmaking refining method includes a burnt lime input amount determining step S30 (see FIG. 2) for determining the amount of burnt lime to be charged together with iron alloy during ironing of molten steel according to the sulfur content calculated in the sulfur content calculating step S10 and the oxygen concentration measured in the oxygen concentration measuring step ).

The quicklime injection amount determination step S30 may include a sulfur content-based quicklime injection amount calculation step of calculating the sulfur content-based quicklime injection amount to be fed into the ladle 22 according to the sulfur content calculated in the sulfur content calculation step S10.

The quicklime injection amount determination step S30 may include an oxygen concentration-based quicklime injection amount calculation step of calculating an oxygen concentration-based quicklime injection amount to be input to the ladle 22 in accordance with the oxygen concentration measured in the oxygen concentration measurement step for quicklime .

The quicklime input amount determination step (S30) may include a primary quicklime input step of firstly inputting the sulfur content-based quicklime input amount at an upper limit value of the quicklime input amount based on the oxygen concentration during the running of molten steel.

In addition, the quicklime input amount determination step (S30) may include a second quick lime input step in which the input amount of the quick lime based on the sulfur content is subtracted from the input amount of quick lime based on the sulfur content in the rice (BAP) process.

Here, the BAP (Bubbling and Powder Injection) process refers to a process of blowing bubbling and Ca-Si powder to perform desulfurization, component adjustment, and separation of non-metallic inclusion.

The first lime lime feeding step (S33) may include a first lime lime feeding step in which the amount of quicklime to be initially charged is set and inputted before lime is firstly introduced for lime raw material.

Here, the quicklime means to dissolve the quicklime.

The evaluation value is outputted based on the difference between the front end pressure and the rear end pressure of the gas supplied into the ladle from the lower nozzle 23 at the lower portion of the ladle while the molten steel for which the converter refining is transferred to the ladle 22, And a lower bubbling state evaluation step (S40) in which evaluation is performed based on the evaluation value.

Here, the shear pressure refers to the pressure of the gas measured at the portion where the gas is supplied from the lower nozzle 23, and the pressure at the rear end refers to the pressure of the gas measured at the portion where the gas is discharged from the lower nozzle 23.

Further, in the lower bubbling performing step (S50) in which the lower bubbling is performed during the lower bubbling time set according to the evaluation value evaluated in the lower bubbling evaluation step (S40) while the ladle 22 is being transferred to the rice (BAP) ).

A rice process operation method determination step S60 (step S60) of determining an additional load amount and an upper bubbling time of the rice process using the sulfur content calculated before the ladle 22 arrives at the rice process, the measured oxygen concentration, ).

And a first measuring step (S70) of measuring the temperature of the molten steel and the degree of deoxidation of the molten steel by using the measuring device (33) when the ladle (22) arrives at the rice process and collecting a sample of the molten steel .

The primary measurement step (S70) is for producing a steel grade having a target component by fine-tuning the composition of the molten steel primarily.

The first upper bubbling performing step may be performed after performing the first measuring step (S70) and then performing the upper bubbling for the set time period first.

And further adding a first deacidifying agent addition step of firstly adding a deoxidizing agent amount by grasping the degree of deoxidation of the molten steel measured in the first measuring step S70.

And a first component analysis value verification step of firstly checking component analysis values of the sample collected in the first measurement step (S70).

And checking whether the sulfur content of the analyzed component values of the sample confirmed in the first component analysis value confirmation step is equal to or higher than a threshold value (43 ppm) of the sulfur content that can be processed in the rice process .

Here, the limit refers to the limit of the sulfur content that can be processed to a sulfur content (30 ppm) or less set in the rice process.

In the analysis of the primary component analysis value, when the value of the component analysis value of the sample is within the limit value, the upper bubbling and the lower bubbling time are first adjusted in the BAP process using the analyzed sulfur value. And a bubbling time adjustment step.

In addition, it may include an ELF process transfer step of transferring the ladle 22 to the LF process when the sulfur value of the component analysis value of the sample identified in the first component analysis value confirmation step is equal to or larger than the threshold value.

Here, an LF (Ladle Furnace) step refers to a step of raising the temperature of the molten steel in the ladle 22, performing degassing, and arranging the components on the non-metallic inclusion separator and adjusting the components.

When the first controlled upper bubbling execution time is completed, the secondary measurement step S80 of measuring the temperature of the molten steel and the degree of deoxidization of the molten steel by using the measuring device 33 and taking a sample of the molten steel is performed .

The secondary measurement step (S80) is for producing a steel product having a target component by fine adjustment of molten steel in a secondary step after the first measurement step (S70).

Performing a secondary measurement step S80, and then performing an upper bubbling for a set time secondarily.

The second deoxidizing agent addition step of adding the deoxidizing agent amount to the second deoxidizing agent amount by determining the deoxidation degree of the molten steel measured in the second measuring step S80.

And a secondary analysis value confirmation step of secondarily confirming the component analysis value of the sample collected in the secondary measurement step S80.

And a ladle extracting step S90 for extracting the ladle 22 from the rice process for transferring the ladle 22 after performing the second analysis value confirming step.

And a vacuum degassing step S100 for transferring the ladle 22 to the vacuum degassing process after the ladle 22 is taken out and performing a vacuum degassing process.

And a performance process transfer step S110 for completing the vacuum degassing process and transferring the ladle 22 to the performance process for slab manufacturing.

2, reference numeral 4 denotes a sub-raw material hearth hopper, reference numeral 5 denotes a sub-material basis hopper, reference numeral 30 denotes an upper rear end pressure gauge, and reference numeral 32 denotes an upper front end pressure gauge.

Hereinafter, a process of a steelmaking refining method according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG.

In order to control the sulfur in the molten steel to a set value, for example 30ppm, scrap is charged in order to favor the heat setting in the converter refining process.

In addition, a charcoal whose sulfur content in the charcoal is controlled to 30 ppm or less, for example, is charged into the converter 1. [

When the charging of the converter 1 is completed and the refinement is started in the HMI (Human Machine Interface) 10, the converter controller 9 lowers the lance 2 into the converter 1, 1) Supply oxygen to the inside.

In the converter refining process, the sulfur content in the sulfur and scrap iron in the molten iron is calculated, and the sulfur content in the converter end point is calculated (S10). The sulfur content in the molten iron is used in the pretreatment process or the KR (Kanvera Reaction) process.

Here, the KR process is a process for removing sulfur in molten iron by a reduction reaction (CaO + FeS = CaS + FeO). The equipment having an impeller is rotated in a molten iron to cause a spiral reaction, The sulfur is removed by the reaction.

The content of sulfur in scrap iron is estimated by the following Table 1.

[Table 1] Sulfur content in scrap iron

For example, if the content of sulfur in the charcoal is 30 ppm, 8,000 Kg of sharps, 7,500 Kg of low grade scrap, 2,000 Kg of prawns, 15,000 Kg of manufactured scrap, and 7,500 Kg of present scrap now, the sulfur content in the molten iron is calculated to be 55 ppm.

In the quicklime injection amount determination step (S30) for determining the amount of quicklime charged for desulfurization at the point where the refining of the converter is completed, the input amount of quicklime is calculated using the calculated sulfur content.

The following [Table 2] is derived from the experience of operation.

[Table 2] Amount of burnt lime by sulfur content in molten steel

Using the value of [Table 2] derived as described above, the alloy iron to be charged into the alloy steel is weighed during the refining operation of the converter. Here, the basis weight is also referred to as a weighing amount, and indicates a work of supplying or putting in a desired amount.

If the dissolved oxygen in the molten steel is low at the completion of the refining of the converter 1, the burnt lime charged during lubrication does not become a commodity (state in which the quicklime is dissolved) in the converter input device 10, For example, 800 Kg.

Here, 800Kg of quicklime is the result of earning the best value of goods with experience of operating up to now.

The basis weight of quicklime put into the alloy steel becomes as follows.

When the converter input unit 10 gives a signal to the converter controller 9 to weigh the alloy iron weighing hopper 6 from the alloy iron weighing hopper 7 and the alloy iron weigh hopper 6 and the alloy iron weighing hopper 7, And is made as weigh as the raw material and the amount presented in the converter input device 10.

When the alloy iron is weighed in the converter input device 10, the converter controller 9 measures the temperature and the oxygen concentration of the molten steel using the sub-lance 3 in the state where the refining of the converter is completed (S20).

Using the measured oxygen concentration, it becomes more weight in the alloy iron hearth hopper 6 as shown in [Table 3] below depending on the oxygen concentration (end point oxygen) at the point where the refining is completed as shown below.

[Table 3] Ferroalloy content according to oxygen at the end point

The amount of the iron oxide quicklime according to the end point oxygen varies depending on the calculated sulfur content.

For example, when the calculated sulfur content is 50 ppm or less and the end point oxygen concentration is 400 ppm or less, 800 Kg is weighed and 200 Kg is fed in the bamboo basket (S30).

For example, when the calculated sulfur content is 50 ppm or less and the end point oxygen concentration is 600 ppm or more, the amount of burnt lime according to the calculated sulfur content is 1000 kg.

Therefore, in the converter input device 10, 800 Kg of primary quicklime is charged first, and at the point of time when oxygen is released from the molten steel after the completion of the blasting, the alloy iron hearth hopper 6 is instructed to be weighed so as to have a basis weight of 200 Kg.

Therefore, there is no additional burnt lime in the rice process.

In the step of transferring molten steel refined in the converter 1 to the ladle 22, the gas is supplied from the lower nozzle 23 provided at the lower part of the ladle 22, and the front end pressure of the supplied lower nozzle 23 and the rear end pressure And the lower bubbling state is evaluated based on the evaluation value (S40).

When the refining of the converter is completed, the molten steel is transferred to the ladle 22. At this time, the ladle 22 is transferred to the lower portion of the converter 1 by using the taking-in carriage 21 and the molten steel is transferred to the ladle 22 through the lug of the converter 1. [

When the amount of molten steel is transferred to the ladle 22 by a predetermined amount, for example, about 20 tons, the converter input unit 10 transmits a signal to the converter controller 9 with reference to the time previously played.

Then, the converter controller 9 opens the lower automatic valve 26 and causes the lower flow control valve 24 to supply the set flow rate to the lower nozzle 23. [ At this time, the flow rate is preferably 80 m < ³ > or more per minute, for example.

The reason for setting the flow rate as described above is that the molten steel is rapidly melted while supplying molten iron through the molten iron feed line 8, and the contact between the molten steel and the quicklime charged with the alloy steel is actively activated, It is to promote.

At this time, the evaluation value of [Table 4] is used to evaluate the lower bubbling state (S40).

Table 4 Lower Bubbling Condition Evaluation Table

The evaluation as described above is a result of deriving the operation result. When the evaluation value is 1 and the rear end pressure is 7 bar, all the supply flow rate is supplied through the lower nozzle 23.

If the rear end pressure is equal to the front end pressure or the rear end pressure is within 5 bar, the lower nozzle 23 may be blocked or the line may be punctured.

For example, when the evaluation value is evaluated as 1 or 2, the lower bubbling time is set to 5 minutes in the rice process input device 38, and the lower bubbling time is set to 7 minutes when the evaluation value is evaluated as 3.

If the evaluation value is 4, the lower bubbling time is set to 10 minutes, and if the evaluation value is 5, the lower bubbling time must be set to 12 minutes.

Even if the ladle 22 is completed and the ladle 22 is transferred to the rice process, the lower bubbling is continued.

Then, when the ladle 22 arrives at the rice process, the ladle 22 is connected to the rice process controller 37 and continues to perform the lower bubbling.

The rice process input device 38 calculates the additional raw lime feed amount of the rice process and the upper bubbling amount of the rice process using the sulfur content calculated in the converter 1, the oxygen concentration measured at the completion of the refining of the furnace, The time is determined (S60).

For example, if the calculated sulfur content is 50 to 60 ppm, the measured oxygen concentration is 400 ppm or less, the quicklime charged during the lecturing is 800 Kg, and the evaluation value of the lower bubbling during lecture was 1, , And the lower bubbling time is set to 5 minutes.

Also, in the rice process input device 38, the amount of quicklime is set to 700 Kg and is set so as to be supplied from 30 seconds after the lower bubbling is performed.

When the ladle 22 arrives at the rice process, a signal is sent from the rice process input device 38 to the rice process controller 37 to measure the temperature and degree of deoxidation of the molten steel using the measuring device 33, (S70).

After performing the first measurement step S70, using the value set in the rice process input device 38, for example, if the lower bubbling evaluation value is 1 during the lubrication, the upper bubbling and the lower bubbling time are set to 5 minutes do.

The rice process input device 38 sends a signal to the rice process controller 37 to lower the upper lance 28 to the inside of the ladle 22 to open the upper automatic valve 31 and open the upper flow control valve 29, The flow rate is set at the set flow rate.

The upper bubbling flow rate is preferably 80 m < ³ > or higher per minute, and the gas supplied through the upper lance 28 is preferably argon gas.

When nitrogen gas is supplied as the feed gas, the molten steel reacts with nitrogen to increase the nitrogen concentration in the molten steel, thereby lowering the quality of the molten steel.

When the ladle 22 arrives at the rice bobbin, the lower bubbling time, which is also supplied during the transfer to the rice process at the time of completion of the turnover of the converter, measures the lower bubbling time again in the rice process controller 37, .

The lower bubbling flow rate is preferably 80 m < ³ > or more per minute.

A signal is sent from the rice process input device 38 to the rice process controller 37 from 30 seconds after the start of the upper bubbling to load the fresh lime setting amount into the basin hopper 35 in the hearth hopper 34, (36) to the ladle (22).

The degree of deoxidation of the molten steel measured in the first measuring step (S70) is determined, and the amount of deoxidizing agent is firstly added.

For example, when the temperature of the molten steel is measured at 1610 ° C and the oxygen electromotive force is measured at -100 mv, the aluminum content in the molten steel is as low as 0.020%, and the oxygen content in the ladle slag is high.

Therefore, in the rice process input device 38, a signal is sent to the rice process controller 37 to weigh the aluminum from the weighing hopper 35 and feed the alloy iron from the weigh hopper 35 through the feed line 36 to the upper part of the slag .

At this time, for example, the aluminum content in the molten steel is increased by 0.01% per 40 kg of aluminum and the target value of aluminum in the molten steel is set as the upper limit value.

Also, the amount of quicklime to be inputted from the hearth hopper 34 composed of a plurality of lines is received by the rice process input device 38, and the corrected aluminum content according to the input of quicklime is calculated and input.

For example, if 200 kg of burnt lime is put in the rice process and the upper limit of aluminum in the molten steel is 0.045%, aluminum is 0.02% of aluminum estimated at the measured oxygen value.

Therefore, 100 kg of aluminum should be added because the aluminum content should be increased by 0.025%, and the correction value of the aluminum quick lime is 5 kg per 100 kg of quicklime, so 110 kg of aluminum should be supplied.

In the first step of checking the analytical value of the sample collected in the first measuring step, the content of sulfur analyzed is checked, and the lower and upper bubbling times are firstly adjusted in the rice process input device 38 as shown in [Table 5] Reset.

[Table 5] Upper and lower bubbling times in the rice process according to the sulfur content

The time in [Table 5] is the value obtained through operational experience. If the analyzed sulfur content is above the limit value (43 ppm) that can be processed in the rice process, the sulfur content in the rice process can not be controlled below the set content (30 ppm) , And LF (LF) processes.

When the analyzed sulfur content is within the limit value (43 ppm), the upper bubbling and the lower bubbling time are controlled using the sulfur content, and the upper bubble The ring and lower bubbling time are reset to proceed bubbling.

When the upper bubbling reset time is completed, secondary measurement is performed (S80).

When the time set in the rice process input device 38 is reached, a signal is sent to the rice process controller 37 to raise the upper lance 28.

When the upper lance 28 reaches the set position, the upper automatic valve 31 is closed and the upper flow control valve 29 is closed.

In addition, the lower bubbling flow rate is adjusted to 20 m ^{3 /} min to supply molten steel through the lower nozzle 23 with a small flow rate to remove non-metallic inclusions without fluctuating molten steel.

The rice process controller 37 sends a signal to the measuring device 33 to measure the temperature of the molten steel, the degree of deoxidation of the molten steel, and samples a molten steel.

In addition, the analytical value of the sample collected in the second measurement step is checked secondarily to confirm the analyzed sulfur content.

In order to feed the ladle 22, ladles are taken out from the rice process (S90).

When the ladle 22 is out of the rice process, the rice process controller 37 closes the lower automatic valve 26 and moves the lower flow control valve 24 to zero point.

Then, the ladle 22 is transferred to a vacuum degassing process, and the ladle 22 is subjected to vacuum degassing to remove gases such as hydrogen and nitrogen, thereby finely adjusting the components (S100).

The vacuum degassing process is completed and the ladle 22 is transferred to the casting process to manufacture a slab (S110).

Thus, by calculating the sulfur content in the molten steel and quantifying the results of the lower bubbling during the lubrication process, a steel having a sulfur content (30 ppm) or less set in the rice process is produced so as not to undergo the LF process to reduce the manufacturing cost of the molten steel .

[Example]

Steel samples having the same composition range as the following [Table 6] are described as an example.

[Table 6] Ingredient range of steel grade

The converter controller 9 loads the lance 2 into the converter 1 when the converter 1 is charged with 50 tons of scrap iron and 250 tons of charcoal to the converter 1 in order to produce the steel product, And the operation of supplying the oxygen is started.

In the converter input unit 10, the sulfur content in the charcoal is 12 ppm, and 8 tons of the single light in the scrap metal, 7.5 tons of the low grade scrap, 2 tons of the scrap metal, 25 tons of the manufactured scrap metal and 7.5 tons of the original scrap are grasped and the sulfur content is 42.5 ppm Respectively.

And the converter input unit 10 transmits a signal to the alloy iron hearth hopper 6 through the set value of 800 kg of quicklime, 550 kg of aluminum, 4200 kg of manganese manganese, 350 kg of high manganese manganese and 400 kg of silymanganese, The iron weighing hopper 7 is weighed.

The temperature of the molten steel is measured at 1674 DEG C and the oxygen concentration is measured at 593 ppm at the time when the converter refining operation is completed and the refining of the converter is completed.

Then, the converter input unit 10 sends a signal to the alloy iron hearth hopper 6, and weighs 200 kg of burnt lime further in the alloy iron weighing hopper 7 because the amount of burnt lime is 1000 Kg according to the calculated sulfur content.

When the refining of the converter is completed and the molten steel of the converter 1 is started to be introduced into the ladle 22, the converter input device 10, at the time when 20 tons of molten steel is filled in the ladle 22, The lower automatic valve 26 is opened to supply the gas to the nozzle 23.

Then, the lower flow control valve 24 is opened so that a flow rate of 80 m ³ or more per minute is supplied.

For example, if the expected travel amount is 280 tons and the previous lecture time is 5 minutes and 5 seconds, the time is 5 minutes, and after 22 seconds, the lower automatic valve 26 is opened to supply the gas to the lower nozzle 23.

Alloy iron is introduced through the alloy iron input line (8).

At this time, if the pressure of the lower front end pressure gauge 27 is set to 17.3 bar and the pressure of the lower rear end pressure gauge 25 is set and maintained at 7.5 bar, the converter input device 10 transmits the value to the rice process input device 38 .

The gas supplied from the lower portion of the ladle 22 is constantly supplied through the lower nozzle 23 even in the course of the ladle 22 being transferred to the rice process.

Before the ladle 22 reaches the rice process, the rice brewing and the lower bubbling time are set to 5 minutes in the rice process input device 38. [

When the ladle 22 arrives at the rice process, the rice process input device 38 sends a signal to the rice process controller 37 to lower the measuring device 33 down to perform a primary measurement operation.

The rice process input device 38 sends a signal to the rice process controller 37 to lower the upper lance 28 to the ladle 22 to open the upper automatic valve 31 and open the upper flow control valve 29, To be supplied with a flow rate of 80 m ³ or more per minute.

In the rice process input device 38, values for the temperature of the molten steel and the values of the oxygen electromotive force are set, and a formula is inputted so that aluminum in the molten steel can be estimated according to the values.

When the temperature of the molten steel is 1617 캜 and the oxygen electromotive force is measured at -120 mv in the rice process, the aluminum process value is estimated to be 0.02% in the rice process input device 38.

Then, a signal is sent to the rice process controller 37 by calculating the upper limit of 0.045% in Table 6, and the aluminum input amount is calculated to be 100 Kg. Then, a signal is sent to the hearth hopper 34 to weigh 100 Kg, Into the ladle 22 through the input line 36. [

During the above operation, the sample collected in the first measurement step is analyzed, and the analysis value is shown as [Table 7] below.

 [Table 7] 1st analysis value of sample

The analysis value of sulfur was confirmed to be 33 ppm. In the rice process, the upper bubbling and lower bubbling time were set as 5 minutes.

After the bubbling setting time of 5 minutes, the rice process input device 38 sends a signal to the rice process controller 37 to raise the upper lance 28, close the upper automatic valve 31 when the set height is reached, The opening degree of the valve 29 is adjusted to zero.

Further, a signal is sent to the lower flow control valve 24 to supply the flow rate at 20 m ³ per minute.

At the same time, the measurement device 33 is lowered to the ladle 22 to perform the secondary measurement step. When the secondary measurement step is completed, the ladle 22 is transferred to a vacuum degassing process.

When the ladle 22 leaves the rice process, the rice process input device 38 sends a signal to the rice process controller 37 to close the lower automatic valve 26 and zero the opening of the lower flow control valve 24 .

The analytical values of the samples taken in the second measurement step are shown in Fig.

The values in the following [Table 8] are the actual analytical values of the samples in the second measurement step after the rice processing is terminated.

[Table 8] Secondary analysis value of the sample

As shown in Table 8, the analysis value of sulfur was confirmed to be 28 ppm.

The molten steel transferred to the vacuum degassing process is subjected to the vacuum degassing operation and the fine adjustment of the components. The analytical values after the vacuum degassing process are shown in Table 9 below.

[Table 9] Analysis value after vacuum degassing process

As shown in [Table 9], it was possible to produce the steel grade as a component target by fine adjustment.

[Table 10] is a table summarized by comparing the embodiment and the conventional example.

[Table 10]

As shown in Table 10, molten steel having a sulfur content of 30 ppm or less in the rice process could be produced according to the example of the present invention.

S10: Sulfur content calculation step
S20: oxygen concentration measurement step
S30: Determination of input amount of quicklime
S40: Lower bubbling condition evaluation step
S50: lower bubbling execution step
S60: Determination of rice processing method
S70: primary measurement step
S80: Secondary measurement step
S90: ladle withdrawal step
S100: Vacuum degassing step
S110: performance process transfer step

Claims (14)

A sulfur content calculating step of calculating the sulfur content in the molten iron and the sulfur content in the scrap iron during the refining of the converter and calculating the sulfur content in the molten steel at the time when the refining of the converter is completed,
An oxygen concentration measuring step of measuring the oxygen concentration in the converter at the time when the converter refining is completed,
Determining an input amount of quicklime to be input with the ferric iron during lubrication of the molten steel according to the sulfur content calculated in the sulfur content calculating step and the oxygen concentration measured in the oxygen concentration measuring step,
An evaluation value is output based on a difference between a front end pressure and a rear end pressure of the gas supplied from the lower nozzle of the lower portion of the ladle into the ladle while the molten steel is being transferred to the ladle, and the lower bubbling state is evaluated based on the evaluation value A lower bubbling state evaluation step,
A lower bubbling performing step of performing lower bubbling for a predetermined time according to the evaluation value while the ladle is being conveyed to a BAP (Bubbling and Powder Injection) process, and
A rice process operation method determination step of determining an additional burnt amount and an upper bubbling time of the rice process using the calculated sulfur content, the measured oxygen concentration, and the evaluation value before the ladle reaches the rice process
. The method according to claim 1,
Wherein the sulfur content-based quicklime input amount to be input to the ladle is calculated according to the calculated sulfur content in the quick lime input amount determination step. 3. The method of claim 2,
Wherein the amount of fresh lime based on the oxygen concentration to be fed into the ladle is calculated in accordance with the measured oxygen concentration in the quicklime injection amount determining step. The method of claim 3,
Wherein the step of determining the amount of fresh lime includes the step of inputting the fresh lime by firstly introducing the amount of fresh lime based on the sulfur content into the upper limit of the amount of fresh lime based on the oxygen concentration during the discharge of molten steel. 5. The method of claim 4,
Wherein the step of determining the amount of quicklime includes the step of injecting a second quicklime into which the amount of input of fresh lime based on sulfur content is subtracted from the amount of quicklime based on the oxygen concentration as a second step in the BAP process. 5. The method of claim 4,
Wherein the first quick lime charging step includes a first quick lime charging step of setting and inputting the amount of quick lime to be initially charged before the quick lime is charged first. 7. The method according to any one of claims 1 to 6,
And a primary measuring step of measuring the temperature of the molten steel and the degree of deoxidation of the molten steel at a first time using the measuring device when the ladle reaches the rice processing and collecting a sample of the molten steel. 8. The method of claim 7,
Further comprising a first upper bubbling performing step of performing the first upper bubbling for the set time after performing the first measuring step. 9. The method of claim 8,
Further comprising a first deoxidizing agent addition step of additionally adding a deoxidizing agent amount by first determining the deoxidation degree of the molten steel measured in the first measuring step. 10. The method of claim 9,
A first component analysis value confirmation step of firstly confirming component analysis values of the sample collected in the first measurement step, and
Further comprising a step of confirming whether or not the sulfur content of the component analysis value of the sample identified in the first component analysis value confirmation step is equal to or larger than a threshold value of the sulfur content that can be processed in the rice process, Way. 11. The method of claim 10,
The upper bubbling and the lower bubbling time in the rice (BAP) process are firstly adjusted by using the analyzed sulfur value when the sulfur value of the sample analysis values of the sample confirmed in the first component analysis value checking step is within the above-mentioned threshold value And a primary bubbling time adjustment step of performing a primary bubbling time adjustment step. 11. The method of claim 10,
And an ELF process transfer step of transferring the ladle to an LF (Ladle Furnace) process when the sulfur value among the component analysis values of the sample identified in the first component analysis value confirmation step is not less than the threshold value. Refining method. 12. The method of claim 11,
And a secondary measuring step of measuring the temperature of the molten steel in the second molten state and the degree of deoxidation of the molten steel using the measuring device when the first controlled upper bubbling execution time is completed, Steelmaking method. 14. The method of claim 13,
A ladle extracting step of extracting ladle from the rice process after performing the second measuring step,
A vacuum degassing treatment step of vacuum degassing the ladle after withdrawing the ladle, and
And a performance process transfer step of completing the vacuum degassing process step and transferring the ladle to a performance process.

Images