JP2013023696A - Converter blowing control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a converter blowing control method that can enhance the control accuracy of a phosphorus concentration in a molten steel when stopping converter blowing.SOLUTION: The converter blowing control method includes at least: a measuring step of periodically measuring the exhaust gas components and exhaust gas flow amount in converter blowing to gain measured values; a constant presuming step of presuming the dephosphorizing speed constant based on the measured values gained from the converter blowing operational conditions and the measuring step; a concentration presuming step of sequentially presuming the phosphorus concentration in the molten steel during converter blowing using the presumed dephosphorizing speed constant; a concentration decision step of deciding whether or not the presumed phosphorus concentration in the molten steel is equal to or lower than the phosphorus concentration in a target molten steel; and a changing step of changing the converter blowing operational conditions so that the phosphorus concentration in the molten steel presumed in the concentration presuming step becomes equal to or lower than the target phosphorus concentration in the molten steel when the presumed phosphorus concentration in the molten steel is decided exceeding the target phosphorus concentration in the molten steel in the concentration decision step.

Description

  The present invention relates to a converter blowing control method, and more particularly to a converter blowing control method for controlling phosphorus concentration in molten steel.

  In converter blowing, the control of molten steel components at the time of blowing, especially the control of phosphorus concentration in molten steel, is very important for quality control of steel. In order to control the phosphorus concentration in molten steel, the amount of oxygen blown in, the amount of auxiliary materials such as quick lime and scale, the timing of injection, the top blowing lance height, the top blowing oxygen flow rate, the bottom blowing gas flow rate, etc. It is used. These operation amounts are often determined by information obtained before the start of blowing, such as a target phosphorus concentration, hot metal information, and a standard created based on past operation results.

  However, even under similar operating conditions, the reproducibility of the dephosphorization behavior in actual blowing is low, and in the case of blowing with the operation amount determined based only on the information obtained before the start of blowing, There was a problem that the dispersion of phosphorus concentration in molten steel at the time became large.

  In order to cope with the above-mentioned problems, technologies that utilize measured values of exhaust gas components and exhaust gas flow rates obtained at regular intervals during blowing have been proposed. For example, Patent Document 1 discloses FeO generation in a converter based on the accumulated oxygen amount obtained by sequentially calculating the oxygen balance from the composition and flow rate of exhaust gas during blowing, the flow rate of oxygen gas, the amount of auxiliary material input, and the hot metal component. High carbon that reduces the phosphorus concentration after treatment by estimating the amount and adjusting at least one of the top blowing lance height, oxygen gas flow rate and bottom blowing gas flow rate according to the estimated FeO amount A method for melting ultra-low phosphorus steel is disclosed. Patent Document 2 discloses that the actual value of decarbonation efficiency calculated from the analysis value of exhaust gas and the flow rate of exhaust gas follows the target change curve set in advance for each treatment pattern, A hot metal dephosphorization method is disclosed in which any one or more of speed, bottom blowing gas type and amount is adjusted.

JP 2006-206930 A Japanese Patent Application Laid-Open No. 2010-13685

  In patent document 1, only the reference of the flow rate adjustment method is mentioned regarding top blowing oxygen, and there is no description regarding the amount of blowing oxygen required in order to obtain target phosphorus concentration. In order to obtain the target phosphorus concentration, it is necessary to appropriately adjust not only the upper blown oxygen flow rate but also the upper blown oxygen amount, so that the predetermined phosphorus concentration in molten steel is obtained by the technique disclosed in Patent Document 1. Is expected to be difficult. In addition, the technique disclosed in Patent Document 2 refers to a method for adjusting the flow rate of the top blown oxygen, similar to the technique disclosed in Patent Document 1, but is necessary to obtain the target phosphorus concentration. There is no description about the amount of oxygen blown. Therefore, it is expected that it is difficult to obtain a predetermined phosphorus concentration in molten steel by the technique disclosed in Patent Document 2.

  Further, in Patent Document 1 and Patent Document 2, the top blowing lance height, the oxygen gas flow rate, and the bottom blowing gas flow rate are taken up as the manipulated variables. The effects on carbon dioxide efficiency, heat receiving efficiency, slag hatching rate, etc.) are very large. Therefore, it is generally not recommended to change these values frequently except during abnormal conditions such as slapping. In other words, the techniques disclosed in Patent Document 1 and Patent Document 2 have a problem that consideration for stabilization of operation of the converter is insufficient.

  Then, this invention makes it a subject to provide the converter blowing control method which can raise the control precision of the phosphorus concentration in molten steel at the time of converter blowing.

  It is assumed that the time change of phosphorus concentration [P] [%] in molten steel during blowing is expressed by the primary reaction formula of the following formula (1).

Here, [P] _ini is the initial phosphorus concentration in molten steel (molten phosphorus concentration) [%], and k is the dephosphorization rate constant [s ⁻¹ ].

  If an accurate dephosphorization rate constant k is obtained, the phosphorus concentration in molten steel at the time of blowing can be estimated with high accuracy. However, in general, the dephosphorization rate constant in actual blowing is not constant and is considered to vary under the influence of various operating factors. Therefore, the present inventors utilize not only static information such as hot metal components and hot metal temperature but also dynamic information during blowing such as measured values of exhaust gas components and exhaust gas flow rate measured at regular intervals. Thus, we tried to improve the estimation accuracy of the dephosphorization rate constant. Below, the estimation method of the phosphorus concentration in molten steel and the estimation method of a dephosphorization rate constant are demonstrated.

First, a method for estimating the phosphorus concentration in molten steel will be described.
From the above formula (1), the phosphorus concentration in molten steel t seconds after the start of blowing is expressed by the following formula (2).

The dephosphorization rate constant for each charge can be obtained using past operation result data. A dephosphorization rate constant k _i of a certain charge i is expressed by the following formula (3).

Here, [P] _{end, i} is the phosphorus concentration in molten steel [%] at the time of blowing, and tend _{, i} is the elapsed time [s] until the point of blowing.

FIG. 1 shows the frequency distribution of the dephosphorization rate constant obtained from the above formula (3) using the past operation record data. FIG. 1 shows that the dephosphorization rate constant varies greatly. As a result of intensive studies, the present inventors have expressed the following formula (4) using the dephosphorization rate constant k calculated according to the above formula (3) as an objective variable and various operating factors (X _j ) as explanatory variables. In the actual blowing operation, the dephosphorization rate constant is estimated from the following equation (4) using the operating factors at that time, and this is applied to the above equation (2). It was found that the phosphorus concentration in molten steel can be estimated in response to changes in operating factors by adopting a configuration that estimates the phosphorus concentration. Table 1 shows examples of operating factors.

Here, α ₀ and α _j are regression coefficients, and X _j is an operation factor.

As a result of diligent research, the inventors of the present invention have found that the amount of oxygen accumulated in the furnace obtained by calculating the oxygen balance from the exhaust gas flow rate during exhaust blowing, the exhaust gas component, the top bottom blowing gas flow rate, the amount of auxiliary material input, and the hot metal component. It has been found that the unit O _s (calculation method will be described later) greatly affects the dephosphorization rate constant k. Specifically, when the in-furnace oxygen storage unit O _s is large, a tendency for the dephosphorization rate constant k to increase was observed.

In order to promote the dephosphorization reaction shown below, it is necessary to increase the CaO concentration in the slag and the FeO concentration in the slag, but the amount of oxygen stored in the furnace corresponds to approximately (FeO). The trend is considered reasonable.
3 (CaO) +5 (FeO) +2 [P] = (3CaO · P ₂ O ₅ ) +5 [Fe]
Here, () indicates the inside of the slag, and [] indicates the inside of the hot metal.

  The present invention will be described below. In order to facilitate understanding of the present invention, reference numerals in the accompanying drawings are appended in parentheses, but the present invention is not limited to the illustrated embodiments.

  In the present invention, at least an exhaust gas component and an exhaust gas flow rate at the time of converter blowing are periodically measured to obtain measurement values (S2), and converter blowing operation conditions (also referred to as operation factors). And the constant estimation step (S5) for estimating the dephosphorization rate constant based on the measurement value obtained in the measurement step, and the converter using the dephosphorization rate constant estimated in the constant estimation step. A concentration estimation step (S6) for sequentially estimating the phosphorus concentration in the molten steel during blowing and a concentration determination step for determining whether or not the phosphorus concentration in the molten steel estimated in the concentration estimation step is less than or equal to the target phosphorus concentration in the molten steel (S7) and when it is determined that the estimated phosphorus concentration in the molten steel exceeds the target phosphorus concentration in the molten steel in the concentration determining step, the phosphorus concentration in the molten steel estimated in the concentration estimating step is To reduce the phosphorous concentration below, A changing step of changing the work condition (S8), characterized by having a a converter blowing control method.

  Moreover, in the said invention, the molten steel temperature in converter blowing may be contained in the measured value.

  Moreover, in the said invention, the measured value may contain the molten steel temperature and carbon concentration in molten steel during converter blowing.

  Moreover, in the said invention, the measured value may contain the molten steel temperature in converter blowing, the carbon concentration in molten steel, and the oxygen concentration in slag.

  According to the present invention, it becomes possible to estimate the phosphorus concentration in molten steel at the time of converter blowing with high accuracy. Therefore, it is possible to increase the control accuracy of the phosphorus concentration in molten steel at the time of converter blowing. A blowing control method can be provided.

It is a figure which shows frequency distribution of a dephosphorization rate constant. It is a figure explaining the estimation result of a dephosphorization rate constant. It is a figure explaining the estimation result of the phosphorus concentration in molten steel at the time of a blowing stop. It is a flowchart explaining the converter blowing control method of this invention. It is a figure explaining the system which can implement the converter blowing control method of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, embodiment shown below is an illustration of this invention and this invention is not limited to embodiment shown below. In the following description, the flow rate is a flow rate in a reference state (0 ° C., 101325 Pa) unless otherwise specified.

The method of calculating the furnace accumulated oxygen per unit O _s, shown below. Furnace accumulated oxygen per unit O _s corresponds to the FeO in the produced slag.

CO flow rate in the exhaust gas ^{[m 3 / h], CO} 2 flow rate in the exhaust gas _{^{[m 3 / h], O}} 2 flow rate in the exhaust gas ^[m 3 / h], and, _{N 2} flow rate of the exhaust gas ^[m 3 / h] is represented by the following formulas (5), (6), (7), and (8), respectively. In the following equations, h _{CO 2} , h _{CO 2} , and h _{O 2} are exhaust gas components [%], Q _offgas is an exhaust gas flow rate [m ³ / h], and i_delay is an exhaust gas analysis delay [−].

The CO flow rate [m ³ / h] generated in the furnace and the CO ₂ flow rate [m ³ / h] generated in the furnace are represented by the following equations.

The in-furnace accumulated oxygen change amount dO _s [m ³ / s] is expressed by the following equation.

Here, the sum of the upper blown oxygen flow rate and the oxygen flow rate contained in the auxiliary raw material charged into the furnace corresponds to the input oxygen into the furnace. Further, the flow rate of oxygen that is combined with carbon and discharged to the outside of the furnace as CO or CO ₂ of exhaust gas corresponds to the output oxygen to the outside of the furnace.

Using the in-furnace oxygen storage variation dO _s represented by the above formula (11), the in-furnace oxygen storage unit O _s [m ³ / ton] is represented by the following formula.

Here, (% SiO ₂ ) consumed oxygen is the amount of oxygen consumed in forming SiO ₂ [m ³ ], and W _st is the molten steel weight [ton]. Research study results, when calculating the furnace accumulated oxygen per unit _{O s} is molten iron in Table 1 [Mn], molten iron [P], and not necessary to consider the molten iron [Ti], molten iron [Si It was found that it is sufficient to consider only]. The hot metal [Si] in Table 1 is used when calculating the (% SiO ₂ ) consumed oxygen in the equation (12).

  In the method for estimating the phosphorus concentration in molten steel described above, the measured value by the sublance during blowing is not essential information. That is, after the start of blowing, the in-furnace accumulated oxygen amount basic unit is calculated by the above method using the hot metal conditions, the auxiliary material input information, and the measured exhaust gas information. By substituting information of operating factors such as the blowing lance height, the top blowing oxygen flow rate, and the bottom blowing gas flow rate into the above equation (4), the dephosphorization rate constant is estimated. Then, the estimated dephosphorization rate constant is substituted into the above equation (2), and the phosphorus concentration in the molten steel can be sequentially estimated using the actual value of the elapsed time from the start of blowing at an arbitrary time point to be estimated. . The calculation cycle of the successive estimation may be the same as the sampling cycle (for example, about 1 to 10 seconds) of the exhaust gas information (exhaust gas flow meter, exhaust gas analyzer).

As an explanatory variable of the above formula (4), dynamics during blowing such as the in-furnace oxygen storage unit obtained by utilizing the exhaust gas information, the top blowing lance height, the top blowing oxygen flow rate, and the bottom blowing gas flow rate FIG. 2 shows the result of the dephosphorization rate constant k estimated using various information. Moreover, the estimation result of the phosphorus concentration in molten steel calculated by substituting the estimated dephosphorization rate constant k into the above equation (2) is shown in FIG. As shown in FIG. 2, the determinant R ² = 0.61, and the dephosphorization rate constant k estimated using the above equation (4) was strongly correlated with the actual value of the dephosphorization rate constant k. . That is, the dephosphorization rate constant could be estimated with high accuracy by using the above equation (4). Further, as shown in FIG. 3, the phosphorus concentration in the molten steel could be estimated with high accuracy by substituting the estimated dephosphorization rate constant into the above equation (2).

  Next, a method for calculating the operation amount necessary to obtain the target phosphorus concentration in molten steel will be described.

Assuming that the elapsed time from the start of blowing to the present time is t ₁ and the estimated value of the dephosphorization rate constant obtained from the current operating conditions is k ₁ , the estimated value [P] ₁ of the phosphorus concentration in the molten steel at this time is Is obtained from the following equation (13).

Assuming that the scheduled time for finishing blowing is t ₂ , the predicted value [P] ₂ of the phosphorus concentration in the molten steel at the time of blowing is obtained from the following formula (14). However, in the following formula (14), it is assumed that the current dephosphorization rate constant k ₁ does not change from the current time to the end of blowing.

If [P] ₂ obtained from the above formula (14) is smaller than the target molten steel phosphorus concentration [P] _aim, no action (changing the operation amount) for promoting dephosphorization is required. However, when [P] ₂ obtained from the above formula (14) is larger than the target phosphorus concentration [P] _{aim in the} molten steel, it is necessary to change the operation amount for promoting dephosphorization. In the present invention, the required change amount of the operation amount is determined according to the priority shown in Table 2 below. Among operating quantities, lance height, top blowing oxygen flow rate, and bottom blowing gas flow rate have a significant effect on blowing characteristics other than dephosphorization (decarbonation efficiency, heat receiving efficiency, slag hatching rate, etc.) Therefore, the lowest priority is set. Moreover, since the increase in the amount of blown oxygen is an easy dephosphorization promoting method, the priority of the amount of blown oxygen is set higher than the amount of scale and the amount of quicklime.

<Operation amount of priority 1>
When [P] ₂ obtained from the above formula (14) is larger than the target molten steel phosphorus concentration [P] _aim , first, the blowing time t required to satisfy the target molten steel phosphorus concentration [P] _{aim 3} is obtained by the following equation (15).

Then, if the excess time Δt (= t ₃ −t ₂ ) from the scheduled blow end time t ₂ is within an allowable range, the blown oxygen amount is selected as the manipulated variable, and the excess time Δt (= t ₃ − Considering the amount of oxygen blown during t ₂ ), the planned blown oxygen amount is corrected as shown in the following formula (16), and blowing is performed according to this. The allowable range of the excess time Δt (= t ₃ −t ₂ ) can be determined, for example, by considering the lower limit value of [C] after processing.

_Here, ΔO _{2, aim} is scheduled blown oxygen amount ^{[m 3],} the first term on the right side is scheduled blown oxygen amount before correction _{^{[m 3], O 2,}} p is set oxygen flow rate ^[m 3 / s] (top blowing oxygen flow rate [m ³ / s]). It is assumed that the scheduled blowing end time t ₂ and the scheduled blown oxygen amount ΔO _{2, aim} are already calculated by a general blowing control system including an oxygen balance equation and a temperature balance equation.

<Operation amount of priority 2>
Even in the case of the priority 1 action, if the phosphorus concentration in the molten steel is expected not to be equal to or less than the target phosphorus concentration [P] _aim (for example, the allowable time in which the excess time Δt (= t ₃ −t ₂ ) exists) In the case of exceeding, the dephosphorization ability is improved by adding the scale and quick lime and increasing the dephosphorization rate constant itself. That is, the dephosphorization rate constant k ₂ at which the phosphorus concentration in the molten steel becomes the target phosphorus concentration in the molten steel [P] _aim at the blowing time t ₃ is expressed by the following equation (17), and the current dephosphorization rate constant k ₁ is The additional scale input amount ΔW _scale necessary to make k ₂ is expressed by the following equation (18). If the obtained additional scale input amount is within a certain allowable range, the obtained scale amount is additionally input. On the other hand, when the obtained additional scale input amount is outside a certain allowable range, and k ₂ cannot be obtained only by adding the scale, the additional quick lime input amount is calculated by the following equation (19). ΔW _CaO is obtained, and an additional amount of quick lime obtained in addition to the scale is added. The upper limit value of the additional scale input amount can be determined by, for example, the input capacity of the scale input facility, and the upper limit value of the additional quick lime input amount can be determined by, for example, the input capacity of the quick lime input facility. The reason why the addition of scale is prioritized over the addition of quicklime is that the scale has a higher immediate effect of promoting dephosphorization than quicklime.

Here, α _scale is the regression coefficient of the _scale in the above equation (4), and α _CaO is the regression coefficient of quick lime in the above equation (4).

<Operation amount of priority 3>
If it is expected that the phosphorus concentration in the molten steel will not be lower than the target phosphorus concentration in the molten steel even if additional scale and quicklime are added (for example, if both the ΔW _scale and the ΔW _CaO exceed the allowable range) In order to increase the dephosphorization rate constant itself, the lance height (main lance height), the top blowing oxygen flow rate, and the bottom blowing gas flow rate are appropriately operated. The lance height change amount Δlance [mm] is obtained from the following equation (20). If the obtained lance height change amount is within a certain allowable range, the lance height is changed. In contrast, in order to be out of tolerance with the lance height changing amount obtained, when the lance by only changing the height is not the k ₂ is obtained, blown on with changing the lance height Manipulate the oxygen flow rate. The change amount ΔFO ₂ [m ³ / s] of the top blowing oxygen flow rate is obtained from the following formula (21). If the amount of change in the obtained upper blown oxygen flow rate is within a certain allowable range, the lance height is changed and the upper blown oxygen flow rate is changed. In contrast, in order to be out of tolerance there is a change amount of oxygen blown onto the obtained flow, when the lance by only changing the height and the top-blown oxygen flow rate is not the k ₂ is obtained, the lance height The top blown oxygen flow rate is changed and the bottom blown gas flow rate is manipulated. The change amount ΔF _bottom [m ³ / s] of the bottom blowing gas flow rate is obtained from the following equation (22).

Here, alpha _lance is the regression coefficient of the lance height in the formula (4), alpha _FO2 is the regression coefficient of the top-blown oxygen flow rate in the above formula (4), α _Fbottom bottom in the formula (4) It is a regression coefficient of the blowing gas flow rate.

  Next, the estimation method of the phosphorus concentration in molten steel when the measured value by sublance is obtained during blowing will be described. However, it is assumed that the phosphorus concentration in the molten steel from the start of blowing to the sublance measurement time can be estimated successively by the above method.

  When the molten steel temperature is measured by the sublance measurement, a regression equation (formula (4)) including the sublance measured molten steel temperature as an operation factor is prepared in advance, and the molten steel temperature is obtained by the sublance measurement. Thereafter, the obtained molten steel temperature is substituted into the above formula (4) to estimate the dephosphorization rate constant, and the above formula (13) is used to estimate the phosphorus concentration in the molten steel.

  On the other hand, when the carbon concentration in molten steel and the molten steel temperature are measured by the sublance measurement, a regression equation (formula (4)) in a form including the operational factors of the carbon concentration in the molten steel and the molten steel temperature in the sublance is previously calculated. Prepare. And after the timing when the carbon concentration and the molten steel temperature in the molten steel were obtained by the sublance measurement, the dephosphorization rate constant was estimated by substituting the obtained molten steel carbon concentration and the molten steel temperature into the above formula (4), The phosphorus concentration in molten steel is estimated using equation (13).

  On the other hand, when the carbon concentration in molten steel, the molten steel temperature, and the oxygen concentration in slag are measured by the sublance measurement, the carbon concentration in the sublance measured molten steel, the molten steel temperature in the sublance measurement, and the oxygen concentration in the sublance measured slag are operated. A regression equation (formula (4)) of the form included in the factor is prepared in advance, and the oxygen concentration in the furnace is corrected from the following formula (23) using the oxygen concentration in the slag obtained by the sublance measurement. Ask for. After the timing at which the carbon concentration in molten steel, the molten steel temperature, and the oxygen concentration in slag were obtained by the sublance measurement, the obtained carbon concentration in the molten steel and the molten steel temperature measured in the sublance, and the corrected oxygen storage basic unit Is substituted into the above equation (4) to estimate the dephosphorization rate constant, and the phosphorus concentration in the molten steel is estimated using the above equation (13).

Here, O _s ′ is the corrected in-furnace oxygen storage unit [m ³ / ton], O _s is the in-furnace oxygen storage unit [m ³ / ton], and O _slag is oxygen in the slag. Concentration [%], and η ₀ and η ₁ are regression coefficients.

  The calculation calculation of the manipulated variable required to obtain the target phosphorus concentration in the molten steel can be carried out in the same procedure as when the measured value by the sublance during blowing is not used.

  From the above, it is possible to estimate the phosphorus concentration in molten steel with high accuracy by applying an appropriate regression formula (estimation formula) according to various forms of sublance measurement, including when no sublance measurement is performed. In addition, it is possible to appropriately calculate the operation amount necessary to obtain the target phosphorus concentration in molten steel. Therefore, if the estimated phosphorus concentration in the molten steel exceeds the target phosphorus concentration in the molten steel, it is possible to control the phosphorus concentration in the molten steel below the target phosphorus concentration with high accuracy by changing the manipulated variable. become.

  FIG. 4 is a flowchart for explaining the converter blowing control method of the present invention. As shown in FIG. 4, the converter blowing control method of the present invention includes an input step (S1), a measurement step (S2), an in-furnace oxygen storage unit calculation step (S3), and an operation factor identification. A step (S4), a constant estimation step (S5), a concentration estimation step (S6), a concentration determination step (S7), a change step (S8), and a blowing determination step (S9). Yes.

  The input process (hereinafter referred to as “S1”) includes hot metal weight for each charge, hot metal components (C, Si, Mn, P, etc.), hot metal temperature, hot metal condition data such as hot metal ratio, and start of blowing. In the process of inputting the required time from the end of blowing to the end of blowing, the flow rate of top blown oxygen, the flow rate of bottom blown gas, the amount of auxiliary materials (for example, scale and quicklime), and the target phosphorus concentration in molten steel to the system described later is there.

  The measurement step (hereinafter referred to as “S2”) is a step of measuring the exhaust gas flow rate using an exhaust gas flow meter and measuring the exhaust gas component using an exhaust gas component analyzer.

  The in-furnace oxygen storage unit calculation step (hereinafter referred to as “S3”) is performed based on the data input in S1, the measurement result in S2, and the equations (5) to (12). This is a step of calculating the accumulated oxygen amount basic unit.

  The operation factor specifying step (hereinafter referred to as “S4”) is a step of specifying the operation factor used in the above equation (4). When estimating the dephosphorization rate constant using the measurement result by the sublance, the operation factor specified in S4 includes the molten steel temperature, the molten steel carbon concentration and the molten steel temperature, the molten steel carbon concentration, the molten steel temperature, And the oxygen concentration in the slag. On the other hand, when the dephosphorization rate constant is estimated without using the measurement result by the sublance, the operation factor specified in S4 does not include the carbon concentration in the molten steel, the molten steel temperature, and the oxygen concentration in the slag.

  The constant estimation step (hereinafter referred to as “S5”) is performed by using the in-furnace oxygen storage unit calculated in S3 and the equation (4) in which the operation factor is specified in S4. This is a step of estimating a phosphorus rate constant. In order to estimate the dephosphorization rate constant using the measurement result of the oxygen concentration in the slag by the sub lance, when the operation factor specified in S4 includes the oxygen concentration in the slag, in S5, the regression coefficient, the above S3 Substituting the in-furnace oxygen storage unit calculated in step 1 and the result of the measured oxygen concentration in the slag into the above equation (23), the corrected in-furnace oxygen storage unit is obtained. Then, the calculated dephosphorization rate constant is estimated by substituting the corrected in-furnace oxygen storage basic unit into the above equation (4).

The concentration estimation step (hereinafter referred to as “S6”) includes the molten iron phosphorus concentration [P] _ini input in S1, the dephosphorization rate constant estimated in S5, and the elapsed time from the start of blowing. the t ₁ is substituted into the equation (13) is a step of estimating the phosphorus concentration in the molten steel.

  The concentration determination step (hereinafter referred to as “S7”) is a step of determining whether or not the phosphorus concentration in molten steel estimated in S6 is equal to or less than the target phosphorus concentration in molten steel input in S1. When an affirmative determination is made in S7, it is not necessary to change the operation amount of the operation factor because the phosphorus concentration in molten steel estimated in S6 is equal to or less than the target phosphorus concentration in molten steel. Therefore, when an affirmative determination is made in S7, the process proceeds to the blowing determination process without going through a changing process described later. On the other hand, if a negative determination is made in S7, the phosphorus concentration in the molten steel estimated in S6 above exceeds the target phosphorus concentration in the molten steel, and if blowing under the current operating conditions is continued, There is a possibility that the phosphorus concentration in molten steel exceeds the target phosphorus concentration in molten steel. Therefore, when a negative determination is made in S7, the changing process is continuously performed so that the phosphorus concentration in the molten steel at the end of blowing is equal to or less than the target phosphorus concentration in molten steel.

  The changing step (hereinafter referred to as “S8”) is a step of changing the operation amount when a negative determination is made in S7. The operation amount is changed in the order of priority described in Table 2. The change amount of the operation amount can be calculated by the above formulas (16) to (22). The operation amount changed in S8 is input to the system described later.

  The blowing determination step (hereinafter referred to as “S9”) is performed following S7 if an affirmative determination is made in S7, and subsequent to S8 if a negative determination is made in S7. It is a process and it is a process of judging whether it is during blowing. When an affirmative determination is made in S9, the process returns to S2 and the same processing is repeated. On the other hand, if a negative determination is made in S9, the blowing control method of the present invention is terminated.

  By following the above procedure, it is possible to accurately estimate the phosphorus concentration in the molten steel from the start of blowing to the end of blowing using the exhaust gas information. It is possible to accurately target the medium phosphorus concentration.

  FIG. 5 is a diagram for explaining a converter blowing control system 10 capable of implementing the converter blowing control method of the present invention. As shown in FIG. 5, the converter blowing control system 10 estimates the phosphorus concentration in molten steel using the molten metal data 1, target data 2, parameter 3, and data sent from the exhaust gas information data editing unit 4. The molten steel phosphorus concentration estimating unit 5, the manipulated variable calculating unit 6, and the input / output unit 7 are used. In the exhaust gas information data editing unit 4, the measurement results by the exhaust gas flow meter 8 and the exhaust gas component analyzer 9 are used. .

  More specifically, the hot metal data 1 is data of hot metal conditions such as the hot metal weight for each charge, the hot metal components (C, Si, Mn, P, etc.), the hot metal temperature, the hot metal ratio, and the target data 2 is the charge. It is data of every molten steel target component (C, Si, Mn, P, etc.) and molten steel target temperature. In parameter 3, the regression coefficient of the above equation (4), the regression coefficient of the above equation (23), and the like are set. In the exhaust gas information data editing unit 4, the in-furnace oxygen storage basic unit is calculated based on the hot metal data 1, the exhaust gas information (exhaust gas flow rate and exhaust gas component), the top blown oxygen flow rate, and the auxiliary material input amount.

  In the molten steel phosphorus concentration estimation unit 5, molten iron data 1, top blown oxygen flow rate, auxiliary material input amount, regression coefficient set in parameter 3, and in-furnace oxygen storage unit calculated in exhaust gas information data editing function 4, In addition, when the measurement result by the sublance 12 is used, the dephosphorization rate constant is estimated by substituting the sublance measurement value into the above equation (4). And the phosphorus concentration in molten steel is estimated based on said Formula (13) using the estimated dephosphorization rate constant.

  In the operation amount calculation unit 6, the change amount of each operation amount for satisfying the target phosphorus concentration in the molten steel of the target data 2 is specifically calculated. When the change amount is calculated in the operation amount calculation unit 6, when changing the amount of blown oxygen, the supply of oxygen is stopped to the site that controls the ON / OFF of the oxygen supplied to the main lance 11. Information on power time (time after change) is sent, and when changing the amount of scale and quick lime, information on the scale and quick lime to be input to the site where scale and quick lime are input to the converter (after change) Information about the quantity) is sent. In addition, when changing the lance height, information on the height of the main lance 11 after the change is sent to the site for controlling the height of the main lance 11, and when changing the upper blown oxygen flow rate, When the information on the changed oxygen flow rate is sent to the site for controlling the flow rate of oxygen supplied to the main lance 11 and the bottom blown gas flow rate is changed, the bottom blown gas supplied to the converter is changed. Information on the changed bottom blown gas flow rate is sent to the site for controlling the flow rate.

  The input / output unit 7 has an interface function such as correction input of the target data 2 and the parameter 3 in addition to the function of displaying the estimated phosphorus concentration in the molten steel and the calculated change amount of each operation amount.

  By implementing the converter blowing control method of the present invention using the system 10 configured in this way, it becomes possible to increase the control accuracy of the phosphorus concentration in the molten steel at the time of converter blowing.

  Although the present invention has been described in connection with embodiments that are presently practical and preferred, the present invention is not limited to the embodiments disclosed herein, but is claimed. It can be appropriately changed without departing from the scope of the invention and the gist or idea of the invention that can be read from the entire specification, and it is understood that a converter blowing control method involving such a change is also included in the technical scope of the present invention. It must be.

DESCRIPTION OF SYMBOLS 1 ... Hot metal data 2 ... Target data 3 ... Parameter 4 ... Exhaust gas information data edit part 5 ... Molten steel phosphorus concentration estimation part 6 ... Manipulation amount calculation part 7 ... Input / output part 8 ... Exhaust gas flow meter 9 ... Exhaust gas component analyzer 10 ... Converter Blowing Control System 11 ... Main Lance 12 ... Sub Lance

Claims (4)

At least a measurement process for periodically measuring exhaust gas components and exhaust gas flow rate during converter blowing and obtaining measurement values;
A constant estimation step for estimating a dephosphorization rate constant based on operating conditions of converter blowing and the measurement value obtained in the measurement step;
Using the dephosphorization rate constant estimated in the constant estimation step, a concentration estimation step for sequentially estimating the phosphorus concentration in the molten steel during the converter blowing,
A concentration determination step of determining whether or not the phosphorus concentration in the molten steel estimated in the concentration estimation step is equal to or less than a target phosphorus concentration in molten steel;
When it is determined in the concentration determination step that the estimated phosphorus concentration in the molten steel exceeds the target phosphorus concentration in the molten steel, the phosphorus concentration in the molten steel estimated in the concentration estimation step is determined in the target molten steel. A changing step of changing the operating conditions of the converter blowing so as to be equal to or less than the phosphorus concentration;
A converter blowing control method, comprising: 2. The converter blowing control method according to claim 1, wherein the measured value includes a molten steel temperature during the converter blowing. 3. 2. The converter blowing control method according to claim 1, wherein the measured value includes a molten steel temperature and a carbon concentration in the molten steel during the converter blowing. 3. 2. The converter blowing control method according to claim 1, wherein the measured value includes a molten steel temperature, a carbon concentration in the molten steel, and an oxygen concentration in the slag during the converter blowing. 3.