KR20200021247A - Method of operating converter - Google Patents

Abstract

The present invention relates to a method of operating a converter. The method of operating a converter comprises: a process of preparing a plurality of ferroalloys; a process of setting the content of impurities and the content of alloy elements requiring adjustment in accordance with a steel type of molten steel; a process of calculating the feeding amount of the plurality of ferroalloys in accordance with the set content of alloy elements; a process of selecting reserve feeding targets from the plurality of ferroalloys for the set content of impurities; and a process of selecting a ferroalloy with the lowest cost among the ferroalloys selected as the reserve feeding targets as a feeding target. The quality of molten steel can be improved and manufacturing costs of molten steel can be reduced by selecting a ferroalloy in consideration of costs required to feed ferroalloys and the content of impurities contained in molten steel after feeding ferroalloys when selecting ferroalloys fed in molten steel tapping of a converter.

Description

Converter operation method {Method of operating converter}

The present invention relates to a converter operation method, and more particularly to a converter operation method that can improve the quality of the molten steel and reduce the manufacturing cost.

In general, converter operation involves charging hot metal and scrap as main raw materials into the converter, injecting oxygen into the converter, and adding subsidiary materials to convert the impurities into carbon (C), silicon (Si), A series of operations for removing manganese (Mn), phosphorus (P), sulfur (S), titanium (Ti) and the like by oxidation refining are collectively referred to. Here, the drilling operation uses slag to remove impurities such as phosphorus, sulfur, carbon, and titanium from molten iron by blowing oxygen gas into the converter, and slag is required for stable removal of impurities. It is possible to obtain a molten steel that can produce the desired steel species by removing impurity elements by subsidiary materials introduced during the blowing.

When the molten steel is manufactured as described above, the tapping work is performed to transfer the molten steel in the converter to the ladle, and the alloy iron is added to the molten steel during the tapping work to match the alloying elements according to the steel type. In this case, the input amount of ferroalloy may be calculated in consideration of the amount of molten steel, the content of the alloying elements contained in the molten steel at the end of the converter, the target amount, the amount of alloying elements in the ferroalloy.

For example, when adjusting the target amount of manganese, homogeneous ferroalloys such as FeMn, SiMn, and Mn-metal may be used. These homogeneous ferroalloys differ in manganese content, impurity content and cost. However, the worker mainly selects the ferroalloy in consideration of the target amount of manganese, and there is a problem that the impurity content in the molten steel increases after the ferroalloy is added to calculate the input amount.

JP 1997-316516 A

The present invention provides a converter operation method capable of improving the quality of molten steel.

The present invention provides a converter operation method that can reduce the manufacturing cost of molten steel by selectively using the same type of alloy iron when calculating the input amount of ferroalloy.

A converter operation method according to an embodiment of the present invention includes the steps of providing a plurality of ferroalloys; Setting the content of alloying elements and the content of impurities according to the steel type of the molten steel; Calculating input amounts of the plurality of ferroalloys, respectively, according to the content of the set alloy element; Selecting a preliminary injection target from a plurality of ferroalloys with respect to the set impurity content; And selecting a ferroalloy having a low cost among the ferroalloys selected as the preliminary input targets.

In the process of preparing the plurality of ferroalloys, a plurality of homogeneous ferroalloys containing the same alloying elements are provided, and the content of impurities, the content of the alloying elements, and the cost information per kg are provided for each of the plurality of homogeneous alloys. process; And selecting a homogeneous ferroalloy containing an alloying element that requires adjustment among the plurality of homogeneous ferroalloys.

The process of setting the content of the alloying element and the content of the impurity may include: determining a target range of the alloying element content to be contained in the molten steel and a target range of the impurity; Obtaining a measured value of the alloying element and a measured value of the impurity by measuring the content of the alloying element and the remaining impurities in the molten steel after the blowing; And determining a set value of the alloying element by reflecting the measured value in the target range of the alloying element content, and determining a set value of the impurity by reflecting the measured value in the impurity target range.

The process of determining the set value of the alloying element is a process of determining an average value from the upper limit value and the lower limit value of the alloy element to be contained in the molten steel and setting the difference value obtained by subtracting the measured value of the alloy element from the average value as the set value and the alloy to be contained in the molten steel. At least one of a process of setting the difference value obtained by subtracting the measured value of the alloying element from the lower limit of the element as a set value.

The determining of the set value of the alloying element may include selecting the set value according to the number of alloying elements that need adjustment and the type of the same type of ferroalloy.

If the number of alloying elements to be adjusted is two or more and the same type of ferroalloy includes two or more alloying elements, a difference value obtained by subtracting the measured value of the alloying elements from the lower limit of the alloying elements to be contained in the molten steel can be selected as the set value.

The setting of the set value of the impurity may include obtaining an average value from an upper limit value and a lower limit value of a target range of impurities to be contained in molten steel, and setting a difference value obtained by subtracting the measured value of the impurity from the average value as the set value of the impurity. can do.

The step of setting the set value of the impurity may include setting the difference value obtained by subtracting the measured value of the impurity from the lower limit of the target range of the impurity to be contained in the molten steel as the set value of the impurity and the upper limit of the target range of the impurity to be contained in the molten steel. It may include at least one of the process of setting the difference value minus the measured value of the impurity as the set value of the impurity.

The calculating of the input amounts of the ferroalloys may include: calculating an input amount of the same type of ferroalloy selected to satisfy the set values of the alloying elements; Using the impurity content information and the input amount of the same type of ferroalloy, calculating the impurity content after being injected into the molten steel to obtain a predicted value of the impurity; And calculating a cost of the same type of ferroalloys using unit price information and input amount per kg of the same type of ferroalloys.

The selecting of the preliminary injection target may include selecting the same kind of ferroalloy as a preliminary injection target if the predicted value of the impurity is less than or equal to at least one of a set value of the plurality of impurities.

The selecting of the preliminary injection target may include selecting the same kind of ferroalloy as a preliminary injection target when the sum of the predicted value of the impurity and the measured value of the impurity is equal to or less than the upper limit of the impurity.

In the process of selecting the input target, a homogeneous ferroalloy having a relatively low cost among the homogeneous alloys selected as the preliminary input target may be selected as an input target.

According to an embodiment of the present invention, the quality of the molten steel is selected by selecting the ferroalloy in consideration of the impurities content of the molten steel after the ferroalloy and the cost of the ferroalloy when the ferroalloy is introduced. It can improve the manufacturing cost of molten steel. That is, the target range of the impurity contained in molten steel and the target range of the alloying element may be set in advance, and it is possible to selectively use the same kind of relatively inexpensive ferroalloy while satisfying the target range of the impurities. Therefore, it is possible to improve process efficiency and productivity by improving the quality of the molten steel to reduce the load generated in the subsequent secondary refining process. In addition, the cost of manufacturing molten steel can be reduced.

1 is a view conceptually showing a converter operation facility according to an embodiment of the present invention.
2 is a flowchart sequentially showing a converter operation method according to an embodiment of the present invention.
3 is a flow chart showing a process of selecting a pre-injection target in the converter operation method according to an embodiment of the present invention.
4 is a table showing examples of types of alloying elements and ferroalloys requiring adjustment according to steel grades.
FIG. 5 is a block diagram conceptually showing an example of blending ferroalloy for steel A type described in FIG. 4. FIG.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention in more detail. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the embodiments are intended to complete the disclosure of the present invention, and to those skilled in the art to fully understand the scope of the invention. It is provided to inform you. In the description, like reference numerals refer to like elements, and the drawings may be partially exaggerated in size in order to accurately describe embodiments of the present invention, and like reference numerals refer to like elements in the drawings.

1 is a view conceptually showing a converter operation facility according to an embodiment of the present invention.

Referring to FIG. 1, a converter operating facility according to an exemplary embodiment of the present invention includes a converter 100, a main lance 200 for blowing oxygen-containing gas into the converter 100, and accommodated in the converter 100. The target value of the sub lance 300 for collecting molten steel to be used, the raw material supply unit 400 for supplying raw materials including ferroalloy, deoxidizer, and carburizing agent to the molten steel, and the components that need to be adjusted according to the steel type of the molten steel. It may include a control unit 500 for controlling the operation of the raw material supply unit 400 to set, and to calculate the input amount of the raw material in accordance with the target value to be injected into the molten steel.

Converter 100 is a container having an internal space, the upper side is open (furnace 102) for charging molten iron and scrap, etc., the side is provided with a tap hole 104 for discharging molten steel. This converter 100 is made of a shell and a refractory material. In more detail, the converter 100 forms the outermost wall or the outer shape, and includes a bar made of a metal material and a lead made of a refractory formed on an inner wall surface of the bar. Here, the edible may include a permanent long edible constructed on the inner wall surface of the steel bar and a fired edible constructed on the inner wall surface of the permanent long edible.

In addition, a lower nozzle 110 through which an inert gas for stirring the molten steel is blown is provided below the converter 100. The low odor nozzle 110 provided below the converter 100 blows inert gas such as Ar gas into the converter 100, thereby improving stirring and reactivity of the raw materials introduced into the converter 100 during the blown operation.

As described above, the molten iron and scrap produced in the blast furnace may be put together in the converter 100, the scrap may be dissolved by the heat of the molten iron and the reaction heat generated during oxygen injection. Hereinafter, a state in which scrap is dissolved in molten iron is referred to as molten iron.

The main lance 200 is a means for blowing oxygen into the converter 100, is provided to be able to move up and down on the converter 100, and may be inserted through the furnace port 102 of the converter 100.

When oxygen is blown into the converter 100 through the main lance 200, an oxidation reaction occurs between the blown oxygen and impurities in molten iron, and thus impurities in molten iron may be removed. That is, the oxygen blown into the converter 100 is oxidized with impurities such as carbon (C), phosphorus (P), sulfur (S) in molten iron, and the reaction product may be discharged as exhaust gas or removed by slag. The slag is then discharged after the blowing of oxygen, that is, the blowing operation is completed, and the molten iron in which the impurities are removed or the impurity content is controlled is called molten steel.

When the molten steel is manufactured in the converter 100, the molten steel may be pulled out in the ladle 600 provided in advance on one side of the converter 100 by tilting the converter 100.

The sub lance 300 may sample the molten steel in order to measure the temperature of the molten steel at the end point of the converter, that is, before tapping the molten steel in the converter 100, that is, in the converter 100. The sub lance 300 may be provided to be movable up and down on one side of the main lance 200. The sub lance 300 may include a probe (not shown) capable of collecting molten steel loaded in the converter 100 and measuring temperature, components, and the like of the molten steel.

The raw material supply unit 400 may supply raw materials, such as a deoxidizer, a carbonaceous agent, and ferroalloy, to the molten steel output from the converter 100. That is, when the refining of the molten steel is completed in the converter 100, the molten steel may be tapped through the tapping hole 104 by tilting the converter 100. At this time, the ladle 600 for receiving molten steel is provided at one lower portion of the converter 100, the raw material supplied from the raw material supply unit 400 may be introduced into the ladle 600 through the injector 440.

The raw material supply unit 400 communicates with some of the plurality of storage hoppers 410 for storing raw materials such as deoxidizer, carbonaceous agent, ferroalloy, slag modifier, and a plurality of storage hoppers 410, and the storage hopper 410. Ladle a plurality of basis weight hopper 420 for weighing the raw material discharged from the), the input hopper 430 and the raw material stored in the input hopper 430 to collect and store the raw materials weighed in the plurality of basis weight hopper 420 It may include an injector 440 that can be injected into (600). At this time, the storage hopper 410 may be stored independently of the aluminum used as the deoxidizer, quicklime used as a slag modifier, ferroalloy, and the like. In addition, the ferroalloy may include various ferroalloys including manganese (Mn), silicon (Si), chromium (Cr), or the like alone or in combination. In this case, the ferroalloy may include a plurality of homogeneous ferroalloys containing the same alloying element, and the ferroalloy may be stored in different storage hoppers 410, respectively. For example, the same type of ferroalloy containing manganese (Mn) includes FeMn (HC), FeMn (MC), SiMn, Mn-Metal, and the like, which may be stored in different storage hoppers 410, respectively. Here, FeMn (HC) and FeMn (MC) are classified according to carbon content, FeMn (HC) may contain 6 wt% or more of carbon, and FeMn (MC) may contain 1 to 3 wt% of carbon. have.

In addition, the storage hopper 410, the basis weight hopper 420, and the input hopper 430 may include a valve (not shown) to selectively discharge the raw material as necessary. And the injector 440 may be connected to the lower portion of the inlet hopper 430. The raw material in the input hopper 430 may be introduced into the molten steel through the input unit 440. The configuration of the raw material supply unit 400 is a well-known technique, and a detailed description thereof will be omitted.

The controller 500 may calculate an expected tapping amount of the molten steel and set a target value of a component that needs to be adjusted according to the steel type. And the raw material supply unit 400 to calculate the input amount of ferroalloy using the result measured in the sub lance 300, the expected withdrawal amount and the set target value of the molten steel, and to input the ferroalloy into the molten steel in the calculated amount. ) Can be controlled. When calculating the input amount of ferroalloy, the control unit 500 may calculate the input amount of each of the same type of ferroalloy containing alloy elements that need adjustment. In this case, the control unit 500 may calculate the amount of the impurity to be contained in the molten steel and the cost of the same type of ferroalloy added to the molten steel when the same kind of ferroalloy is added to the molten steel when calculating the input amount of the same alloy. In addition, the controller 500 selects alloy steels, for example, homogeneous alloy iron, which can secure the cleanliness of molten steel using the calculated results and reduce the manufacturing cost of molten steel, and inject the selected homogeneous alloy iron into molten steel. The operation of the raw material supply unit 400 can be controlled to do so.

Hereinafter, a converter operation method according to an embodiment of the present invention will be described.

2 is a flowchart showing a converter operation method according to an embodiment of the present invention in sequence, Figure 3 is a flowchart showing a process of selecting a pre-injection target in the converter operation method according to an embodiment of the present invention, Figure 4 is a steel According to the present invention is a table showing examples of the types of alloying elements and ferroalloys that require adjustment, and FIG. 5 is a block diagram conceptually illustrating an example of blending ferroalloy with steel A described in FIG. 4.

Referring to Figure 2, the converter operation method according to an embodiment of the present invention, the process of preparing a plurality of ferroalloys (S100), and to set the content of the alloying element and the amount of impurities that need to be adjusted according to the steel type of molten steel Process (S300), the process of calculating the input amount of the plurality of ferroalloys respectively according to the content of the set alloy element (S400), and the process of selecting a pre-injection target from the plurality of ferroalloys for the content of the set impurities (S500) And it may include a step (S600) of selecting the low-cost alloy iron of the alloy iron selected as a pre-injection target. In addition, before the process of setting the content of the alloying element and the content of the impurity may include the step of preparing a molten steel (S200), the process of tapping the molten steel after the process of selecting the input target (S700), and the input target The process may include the step of inputting the selected ferroalloy into the molten steel in the calculated amount (S800) and the step of completing the tapping of the molten steel (S900).

The process of preparing a plurality of ferroalloys can be performed as follows.

First, referring to FIG. 4, there are alloying elements that need to be adjusted according to steel grades and steel alloys that are needed accordingly. For example, in the case of steel A, it is necessary to control the content of three alloying elements, namely silicon (Si), manganese (Mn) and chromium (Cr). In this case, an alloy iron containing Si, such as a first alloy iron, an alloy iron containing Mn, such as a second alloy iron, and an alloy iron containing Cr, such as a third alloy iron, may be added to molten steel during tapping. Can be. In the case of steel B, it is necessary to control the content of two alloying elements, namely, silicon (Si) and manganese (Mn). In this case, when the molten steel is pulled out, the first alloy iron and the second alloy iron may be injected into the molten steel. In addition, in the case of C steel, it is necessary to control the content of one alloying element of manganese (Mn), and the second alloy iron may be added to molten steel during tapping.

Such a plurality of ferroalloys, that is, the first alloy, the second alloy and the third alloy iron contains silicon (Si), manganese (Mn), chromium (Cr) and the like necessary for the production of molten steel alone or an alloying element. It may contain in combination. Among them, in the case of the same type of ferroalloy containing multiple kinds of alloying elements such as SiMn and FeSiCr, it can be used to simultaneously adjust two alloying elements.

Table 1 below shows the types of ferroalloy, the impurity content, the alloying element content, and the unit cost per kg.

C (wt%) Mn (wt%) Si (wt%) P (wt%) Cr (wt%) Unit price (KRW) Content Real rate Content Real rate Content Real rate Content Real rate Content Real rate FeMn
(HC) 6.7 100 78 95 1.2 95 0.4 100 - - 8,569 FeMn
(MC) 2 100 78 95 1.2 95 0.4 100 - - 10,991 Mn-
Metal - - 99.9 95 - - - - - - 11,221 FeSi 0.2 100 - - 65 95 0.05 100 - - 3,401 SiMn 2.5 100 63 95 13.5 95 0.03 100 - - 6,039 FeSiCr 0.07 100 - - 44.1 95 - - 36.7 95 7,552 FeCr
(MC) 0.32 100 - - - - 0.04 100 66.2 95 26,852 FeCr
(HC) 8.3 100 - - - - 0.026 100 69.5 95 7,859

Referring to Table 1, the first alloy iron containing silicon (Si) may include FeSi, SiMn, FeSiCr and the like. In addition, the second alloy iron containing manganese (Mn) may include FeMn, SiMn, Mn-metal, etc., FeMn (HC, high-carbon manganese) containing 6% or more by weight of FeMn and 1 to 3 FeMn (MC, bicarbonate manganese) containing about 1% by weight of carbon, and FeMn (LC, low carbon manganese) containing less than 1% by weight of carbon can be divided. In addition, the third alloy containing chromium (Cr) may include FeCr, FeSiCr, FeCr is FeCr (HC, high carbon chromium) containing 8% by weight or more carbon, depending on the carbon content, and 1% by weight It can be divided into FeCr (MC, low carbon chromium) containing the following carbon. As described above, the ferroalloy containing the same alloying element is called the same kind of ferroalloy, and may be stored in different storage hoppers 410, respectively.

The same type alloy irons prepared as described above may be used as one of the first alloy iron, the second alloy iron, and the third alloy iron, respectively.

5 conceptually shows a method of selecting and blending ferroalloy during molten steel tapping in the present invention. In the present invention, when selecting a ferroalloy to be added, the same type of ferroalloy is added to select a preliminary target according to the impurity content contained in the molten steel, and then a low cost homogeneous ferroalloy is selected as the input target. It is possible to suppress the deterioration of molten steel due to the input and to reduce the cost of manufacturing molten steel. In other words, after injecting ferroalloy into molten steel, a preliminary target of homogeneous ferroalloys of the first alloy is selected according to the impurity content in the molten steel, and the cost is low among the homogeneous ferroalloys selected as preliminary inputs. It is possible to select homogeneous ferroalloys, which have the lowest cost to input homogeneous ferroalloys. In this case, at least one homogeneous ferroalloy to be preliminarily added may be at least one, and at least one homogeneous ferroalloy to be injected. This will be described later.

Next, the process of preparing the molten steel can be performed as follows. Hereinafter, a steel grade that requires the content control of three alloy elements of silicon (Si), manganese (Mn) and chromium (Cr) will be described as an example.

The molten iron and scrap produced in the melting furnace, such as blast furnace is charged with a converter (100). And molten steel can be manufactured by blowing the oxygen containing gas into molten iron using the main lance 200 provided in the converter 100, and removing impurities contained in molten iron.

The estimated tapping amount of the molten steel may be calculated using the total loading of the molten iron and the scrap charged into the converter 100. The expected tapping amount of the molten steel may be calculated through the total loading of the molten iron and the scrap loaded into the converter 100, and about 90% of the total loading of the molten iron and the scrap may be calculated as the expected tapping amount of the molten steel. For example, when the total charge of the molten iron and scrap charged into the converter 100 is 300 tons, the expected tapping amount of the molten steel may be about 270 tons. Hereinafter, the case where the expected tapping amount of the molten steel is 275 tons will be described.

In addition, the steel grade is determined before the converter refining, by inputting the ferroalloy when tapping according to the steel grade it is possible to set the target range of the alloying element content and the impurity content to contain molten steel. In this case, the target range of the alloy element content and the target range of the impurity content may be set to a range having an upper limit value and a lower limit value, respectively, and the average value of the upper limit value and the lower limit value of each component may be used as the target value. Table 2 below shows an example of target values of impurities contained in molten steel after tapping and target values of alloying elements. Here, the target value may be a numerical value capable of adjusting the components of the molten steel in an optimal state, and the lower limit value may mean a numerical value capable of minimizing the components of the molten steel.

(wt%) [C] (wt%) [Si] (wt%) [Mn] (wt%) [P] (wt%) [Cr] (wt%) Upper limit 0.095 0.4 1.55 0.013 0.5 Goal value 0.08 0.3 1.45 - 0.4 Lower limit 0.065 0.2 1.35 - 0.3

Thus, when molten steel is manufactured by converter refining, the temperature and components of molten steel can be measured using the sub lance 300. In this case, by using the sub lance 300, the molten steel is partially collected to measure the content of the alloying element and the impurity in the molten steel, thereby obtaining the measured value of the alloying element and the measured value of the impurity. Table 3 below shows an example of measuring the alloying element content and the impurity content of the molten steel at the end of the converter, that is, the content of the alloying element and impurities remaining in the molten steel after the blowing. This result can be used to calculate the dosage of ferroalloy.

Component at converter endpoint C (wt%) Si (wt%) Mn (wt%) P (wt%) Cr (wt%) 0.025 0.001 0.08 0.01 0

After measuring the composition of molten steel at the end of the converter, the estimated amount of molten steel, the measured alloy element of the molten steel measured at the end of the converter, and the input amount of ferroalloy to be input at the time of tapping using the target range or target value of the alloy element. Can be calculated. The dose of ferroalloy may be calculated by Equation 1 below.

The input amount of ferroalloy reflects the measured value in the target range of the alloying element, and sets the alloying element which is the content of the alloying element that molten steel can contain by injecting ferroalloy into the molten steel, and then satisfies the setting value of the alloying element. It can be calculated to That is, the target range of the alloying element includes the content of the alloying element remaining in the molten steel after blowing, that is, the measured value of the alloying element, and can be obtained as follows.

The set value of the alloying element may be a difference value obtained by subtracting the measured value of the alloying element from the target range of the alloying element, for example, the lower limit of the alloying element. Alternatively, the average value (target value) may be obtained from the upper limit value and the lower limit value of the alloy element, and the difference value obtained by subtracting the measured value of the alloy element from the average value may be determined as the set value of the alloy element. At this time, the set value of the alloying element can be selected according to the number of alloying elements which need to be adjusted, and accordingly the kind of the same type of ferroalloy which is injected into the molten steel. For example, if the number of alloy elements that need adjustment is two or three, and the same type of ferroalloy contains heterogeneous alloy elements, a difference value obtained by subtracting the measured value of the alloying elements from the lower limit of the alloying elements may be selected as a set value. have. Alternatively, when the number of alloying elements to be adjusted is one, the difference value obtained by subtracting the measured value of the alloying elements from the average value of the alloying elements may be selected as the set value. In this case, the number of alloying elements contained in the same type of ferroalloy may be excluded from consideration.

Thus, after setting the set value of the alloying element, the set value of the impurity can be determined. The set value of the impurity, that is, the content of the impurity that the molten steel can contain after the input of ferroalloy to the molten steel can be determined as follows.

After calculating the average value from the upper and lower limit values of the target range of the impurity to be contained in the molten steel, the difference value obtained by subtracting the measured value of the impurity from the average value may be set as the impurity set value.

Alternatively, the difference value obtained by subtracting the measured value of the impurity from the lower limit of the target range of impurities contained in the molten steel may be set as the set value of the impurity, or the difference value obtained by subtracting the measured value of the impurity from the upper limit of the target range of the impurity to be contained in the molten steel. May be set to the set value of the impurity.

As such, the reason for providing a plurality of set values of impurities may vary depending on the number of alloying elements that need to be adjusted, and thus the number of homogeneous ferroalloys added to the molten steel may vary. This is because the content of impurities in molten steel may increase. Therefore, if the number of alloying elements that need to be adjusted increases, and thus the number of homogeneous ferroalloys that are added to the molten steel increases, the difference between the lower limit of the impurities and the measured value of the impurities is subtracted from the lower limit of the impurities in order to appropriately control the content of impurities in the molten steel. It can be used as a set value of impurities. On the other hand, when the number of alloying elements to be adjusted is one, the difference value obtained by subtracting the measured value of the impurity from the target value or the upper limit of the impurity can be used as the setting value of the impurity.

When the set value of the ferroalloy is selected in this way, it is possible to calculate the input amount to the same type of alloy iron containing the same alloy element so as to satisfy the set value of the selected alloy element. When calculating the input amount of ferroalloy, when there are a plurality of alloying elements that need to be adjusted, the input amount of homogeneous ferroalloy is calculated for any one of the alloying elements, and the homogeneous for the remaining alloying elements is calculated based on the calculated amount of ferroalloy. The input amount of ferroalloy can be calculated. According to Table 2 it can be seen that the adjustment of the content of the alloying elements Si, Mn and Cr. In this case, after calculating the first alloying iron input for adjusting Si, the second alloying iron and the third alloying iron for adjusting the content of Mn and Cr can be calculated in this order. Here, although it demonstrates as calculating an iron-alloy input amount for adjusting the component of Si first, it is not limited to this. According to Table 1, since FeMn and SiMn contain Mn and Si in combination, there is a possibility that the target value may not be met due to the plural inputs. Therefore, the ferrous alloy input for adjusting the content of Si and Mn is the target value of the alloying element. It can calculate based on the lower limit of the alloying element which is not.

First, the input amount of the first alloy iron containing Si can be calculated. In this case, the first alloy iron may include FeSi, SiMn, and FeSiCr as the same type of alloy iron. Thus, the input amounts of FeSi, SiMn and FeSiCr, which are the same type of alloy iron, can be calculated. Since the content and unit price of impurities contained in the same type of ferroalloy itself are known in advance, when the input of the same type of ferroalloy is calculated, the carbon (C) and phosphorus (P) that molten steel may have using the impurity content of the ferroalloy and the calculated dose The cost of the impurity content such as) and the input amount of ferroalloy can also be calculated. In this case, the calculated content of the impurity is referred to as the predicted value of the impurity, and the predicted value of the impurity means the content of the impurity that molten steel may have due to the addition of the same type of ferroalloy.

Table 4 below shows an example of calculating the input amount of the first alloy iron, that is, the same type of ferroalloy containing Si, the predicted value of impurities, and the cost of the alloying elements, respectively. The contents of each component described in Tables 4 to 8 were expressed as rounded values.

First alloy steel Input amount (㎏) C (wt%) Mn (wt%) Si (wt%) P (wt%) Cr (wt%) Cost (KRW) FeSi 870 0.001 0 0.199 0 0 1,923,595 SiMn 4189 0.039 0.929 0.199 0 0 19,356,081 FeSiCr 1282 0 0 0.199 0 0.166 7,826,099

In this way, when the input amount of the same type of iron alloy, the predicted value of impurities and the cost are calculated so as to satisfy the set value of the alloying element, a preliminary injection target can be selected from these. The pre-injection target may be selected according to the impurity content in the same type of ferroalloy as shown in FIG. That is, the target of preliminary injection may be selected by comparing the predicted value X of the impurity, the set value Y of the impurity, and the target range Z of the impurity (S510). At this time, when the predicted value X of the impurity is larger than the set value Y of the impurity or the target range Z of the impurity (X> Y, X> Z), the same ferroalloy is excluded from the preliminary injection target (S530). can do. On the other hand. If the predicted value of impurity (X) is equal to the impurity set value (Y) (X = Y) or smaller than the impurity set value (Y) (X <Y), the corresponding ferroalloy may be selected as a preliminary target. Can be. In addition, when the predicted value X of the impurity is included in the target range Z of the impurity (X = Z) or is smaller than the target range Z of the impurity (X <Z), the corresponding ferroalloy is used as a preliminary target. Can be selected. Here, the predicted value X of the impurity is smaller than the target range Z of the impurity, which includes all cases where the predicted value of the impurity is equal to or less than the upper limit of the impurity, is included between the upper and lower limits of the impurity, or smaller than the lower limit of the impurity. Can be.

Then, check whether there are more homogeneous ferroalloys to be selected as preliminary injection targets (S540), and if there are more homogeneous ferroalloys to be selected as preliminary injection targets, the predicted value (X) of impurities calculated at S400 and the set value (Y) of impurities and The pre-insertion target may be selected by repeating steps S510 to S530 using the target range Z of impurities. On the other hand, check whether there are more homogeneous ferroalloys to be selected as preliminary injection targets (S540), and if there are no homogeneous ferroalloys to be selected as preliminary injection targets, the next step may be performed.

Referring to Table 4, in order to adjust the content of Si, any one of the same type of FeSi, SiMn and FeSiCr containing Si can be added to the molten steel in the calculated amount. In this case, it is preferable to add FeSiCr containing no carbon and phosphorus. However, FeSiCr has a lower cost than SiMn, but costs about 4 times higher than FeSi.

On the other hand, FeSi has a significantly lower cost than SiMn and FeSiCr, and the FeSi is selected as a preliminary input for the first alloy because the carbon content is considerably lower than the lower limit of the set carbon even when considering the carbon content in the molten steel at the end of the converter. can do. Therefore, in order to adjust only the content of Si, it is preferable to add FeSi in the same type of alloy iron containing Si as the first alloy iron. However, since the result may vary depending on the impurity content or cost of ferroalloy for adjusting Mn and Cr, the target of preliminary input may be selected after calculating the ferroalloy input for adjusting Mn and Cr.

In this way, the input amount of the first alloy iron for adjusting the content of Si is calculated, and when the preliminary input target of the first alloy is selected using this, the input amount of the second alloy iron for adjusting the content of Mn based on this Can be calculated. The second alloy iron may also include a plurality of homogeneous alloy iron.

The input amount, the impurity content, the alloying element content and the cost of the second alloy iron in the same type of ferroalloy are shown in Table 5 below.

First
Ferroalloy Second alloy 2nd alloy input
(Kg) C (wt%) Mn (wt%) Si (wt%) P (wt%) Cr (wt%) Cost (KRW) FeSi FeMn (HC) 4628 0.115 1.270 0.020 0.002 0 39,652,358 FeMn (MC) 4628 0.034 1.270 0.020 0.003 0 50,859,347 Mn-metal 3613 0 1.270 0 0 0 40,543,062 SiMn FeMn (HC) 1244 0.031 0.341 0.005 0.001 0 10,657,222 FeMn (MC) 1244 0.009 0.341 0.005 0.001 0 13,669,284 Mn-metal 971 0 0.341 0 0 0 10,896,614 FeSiCr FeMn (HC) 4628 0.115 1.270 0.020 0.002 0 39,652,358 FeMn (MC) 4628 0.034 1.270 0.020 0.003 0 50,859,347 Mn-metal 3613 0 1.270 0 0 0 40,543,062

Table 5 shows the results of calculating the amount of the same type of ferroalloy of the second alloy, the amount of impurities (predicted impurities), the content of the alloying element and the cost of the same amount of ferroalloy of the first alloy. Referring to Table 5, when FeSi is added to the first alloy, it is shown that it is good to add Mn-metal in the amount of impurities to be contained in the molten steel, that is, in the predicted value or cost of impurities. In the case of adding SiMn and FeSiCr as the first alloy, it is shown that the addition of Mn-metal is good. When SiMn is introduced into the first alloy, FeMn (HC) is introduced into the second alloy, and the carbon content in the molten steel is equal to 0.95, which is the upper limit of carbon. Therefore, it is preferable to add Mn-metal rather than FeMn (HC) because the addition of a third ferroalloy for adjusting Cr may cause the carbon content of molten steel to be higher than the upper limit of carbon. Therefore, Mn-metal may be selected as a preliminary input target for the second alloy steel.

On the other hand, although depending on the steel type, if the content of phosphorus in the impurities contained in the ferroalloy is higher than the preset range may be excluded from the pre-injection target. For example, when FeSi or FeSiCr is used as the first alloy, FeMn (HC) and FeMn (MC) used to control Cr content are excluded from the preliminary input because they contain 0.002wt% or more of phosphorus (P). can do.

When the input amounts of the first alloy and the second alloy iron are calculated, the input amount of the third alloy iron for adjusting the Cr content can be calculated. The third alloy iron may include a plurality of homogeneous alloy iron containing Cr, and may calculate the input amount of each of the homogeneous alloy iron. The input amount, ferrous content, alloying element content and cost of the same ferroalloy of the third alloy iron are calculated and shown in Table 6 below.

First alloy steel 3rd alloy 3rd alloy input
(Kg) C (wt%) Mn (wt%) Si (wt%) P (wt%) Cr (wt%) Cost (KRW) FeSi
/ SiMn FeCr (MC) 1742 0.003 0 0 0 0.4 46,776,184 FeCr (HC) 1666 0.049 0 0 0 0.4 13,093,373 FeSiCr FeCrMC) 1005 0.001 0 0 0 0.234 26,976,209 FeCr (HC) 957 0.029 0 0 0 0.234 7,520,254

Table 6 shows the results of calculating the same input amount, the predicted value of impurities, the content of alloying elements and the cost of the same type of ferroalloy of the first alloy. In this case, since Cr is not likely to be additionally added even if Cr is added to adjust the Si and Mn, the input amount was calculated based on the target value of Cr. In this case, when FeSiCr is added to the first alloy, since Cr is contained in FeSiCr, the amount of Cr-containing allofer alloy (FeCr) can be reduced compared to when FeSi or SiMn is added to the first alloy.

Referring to Table 6, when FeSi is introduced into the first alloy, Mn-metal is added into the second alloy, and FeCr (MC) is used as the third alloy, the carbon concentration in the molten steel is smaller than the lower limit. . However, FeCr (MC) has a disadvantage in that its cost is high.However, combining the preliminary input of the first alloy with the preliminary input of the second alloy may affect the overall cost. can do.

 And FeCr (HC) with the third alloy has the advantage of low cost, but when added to the molten steel carbon concentration in the molten steel exceeds the upper limit can be excluded from the pre-injection target.

In the case of adding SiMn to the first alloy, Mn-metal to the second alloy, and FeCr (MC) to the third alloy, FeCr (HC) has a low carbon content, but FeCr (HC It is very expensive compared to). However, when FeCr (HC) is used as the third alloy, the carbon content is higher than when FeCr (MC) is used, but is lower than the lower limit of carbon. In addition, FeCr (HC) has the advantage that the cost can be reduced because the cost is much lower than FeCr (MC).

In this way, preliminary targets are selected from the same type of ferroalloy of the first alloy, the same type of ferroalloy of the second alloy, and the same type of ferroalloy of the third alloy. You can select the input target.

In this way, the input amount of ferroalloy is calculated for the alloy element that needs to be adjusted, the preliminary injection targets are selected in consideration of the impurity value, which is the impurity content of the ferroalloy, and the combinations of these preliminary injection targets are combined. Shown in

First alloy steel Second alloy 3rd alloy C (wt%) Mn (wt%) Si (wt%) P (wt%) Cr (wt%) Cost (KRW) FeSi Mn-metal FeCr (MC) 0.028 1.35 0.2 0.01 0.4 87,319,246 SiMn Mn-metal FeCr (MC) 0.077 1.35 0.205 0.01 0.4 77,028,879 FeSiCr Mn-metal FeCr (HC) 0.054 1.35 0.2 0.011 0.4 55,889,415

Referring to Table 8 above, when FeSi is used as the first alloy to adjust the target impurity and the alloy element target value, the second alloy is Mn-metal and the third alloy is FeCr (MC). It can be seen that it can be used. In addition, when SiMn is used as the first alloy, Mn-metal may be used as the second alloy, and FeCr (MC) may be used as the third alloy. When FeSiCr is used as the first alloy, the second alloy may be Mn-metal and tertiary alloy iron may use FeCr (HC).

Among these combinations, the lowest cost can be selected as the input target alloy ferroalloy for molten steel. That is, if SiMn is used as the first alloy, Mn-metal is used as the second alloy, and FeCr (MC) is used as the third alloy, impurities in the molten steel can be adjusted to a predetermined content, that is, a target range. In addition, it can be seen that manufacturing costs can be reduced.

The molten steel is tapped into the ladle 600 which is disposed at one lower side of the converter 100 through the tapping hole 104 by tilting the converter 100. Then, while the molten steel is pulled out, the ferroalloys selected as input targets in the ladle 600 may be input in a calculated amount. The ferroalloy may be added between 2/5 and 3/5 after the start of the tap during the entire tapping time. This is because the reaction of the peat agent input during tapping is completed between 2/5 and 3/5 of the tapping time, so if the ferroalloy is added before, the error rate of the ferroalloy is lowered. This is because the time required for melting the ferroalloy is insufficient.

Thereafter, when the tapping is completed, the converter may be restored and the molten steel accommodated in the ladle 600 may be moved to a subsequent process.

As described above, in the detailed description of the present invention, specific embodiments have been described. However, various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims below and equivalents thereof.

100: converter 200: main lance
300: sub lance 400: raw material supply unit
500: control unit 600: ladle

Claims (12)

Providing a plurality of ferroalloys;
Setting the content of alloying elements and the content of impurities according to the steel type of the molten steel;
Calculating the input amounts of the plurality of ferroalloys according to the content of the set alloy element;
Selecting a preliminary injection target from a plurality of ferroalloys with respect to the set impurity content; And
A method for operating a converter including a step of selecting a low-cost alloy iron alloy among the selected ferroalloy target. The method according to claim 1,
The process of providing the plurality of iron alloys,
Provide a plurality of homogeneous ferroalloys containing the same alloying element,
Providing a content of impurities, an alloying element, and cost information per kg for each of the plurality of homogeneous ferroalloys; And
Selecting a homogeneous ferroalloy containing an alloying element in need of adjustment among the plurality of homogeneous ferroalloys. The method according to claim 2,
The process of setting the content of the alloying element and the content of impurities,
Determining a target range of alloy element content to be contained in molten steel and a target range of impurities;
Obtaining a measured value of the alloying element and a measured value of the impurity by measuring the content of the alloying element and the remaining impurities in the molten steel after the blowing; And
And determining a set value of the alloying element by reflecting the measured value in the target range of the alloying element content, and setting a set value of the impurity by reflecting the measured value in the impurity target range. The method according to claim 3,
The process of determining the set value of the alloy element,
Obtaining an average value from the upper limit value and the lower limit value of the alloy element to be contained in the molten steel, and setting the difference value obtained by subtracting the measured value of the alloy element from the average value as a set value; and
A converter operation method comprising at least one of a process of setting a difference value obtained by subtracting a measured value of an alloying element from a lower limit of an alloying element to be contained in molten steel. The method according to claim 4,
The process of determining the set value of the alloy element,
A converter operation method comprising the step of selecting a set value according to the number of alloying elements to be adjusted and the type of ferroalloy. The method according to claim 5,
If the number of alloying elements to be adjusted is two or more, and the same type of ferroalloy includes two or more alloying elements, a converter operation is selected in which a difference value obtained by subtracting the measured value of the alloying elements from the lower limit of the alloying elements to be contained in the molten steel is set. Way. The method according to claim 3,
Determining the set value of the impurity,
The process of obtaining the average value from the upper and lower limits of the target range of impurities contained in the molten steel, and
And setting the difference value obtained by subtracting the measured value of the impurity from the average value as the set value of the impurity. The method according to claim 3,
Determining the set value of the impurity,
Setting the difference value obtained by subtracting the measured value of the impurity from the lower limit of the target range of the impurity to be contained in molten steel as the set value of the impurity; and
A converter operation method comprising at least one of the steps of setting the difference value obtained by subtracting the measured value of the impurity from the upper limit of the target range of the impurity to be contained in molten steel as the set value of the impurity. The method according to any one of claims 3 to 8,
The process of calculating the input amount of the plurality of ferroalloys, respectively,
Calculating an input amount of the same kind of ferroalloy selected to satisfy the set value of the alloying element;
Using the impurity content information and the input amount of the same type of ferroalloy, calculating the impurity content after being injected into the molten steel to obtain a predicted value of the impurity; And
A method of operating a converter comprising the step of calculating the cost of homogeneous ferroalloys, using unit price information and input per kg of homogeneous ferroalloys. The method according to claim 9,
The process of selecting the preliminary input target,
And if the predicted value of the impurity is less than or equal to at least one of the set values of the plurality of impurities, selecting the same type of ferroalloy as a preliminary injection target. The method according to claim 10,
The process of selecting the preliminary input target,
And selecting the same type of ferroalloy as a preliminary injection target when the sum of the predicted value of the impurity and the measured value of the impurity is equal to or less than the upper limit of the impurity. The method according to claim 11,
The process of selecting the input target,
A converter operation method for selecting a homogeneous ferroalloy having a relatively low cost among the homogeneous ferroalloys selected as the preliminary inputs.

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