JPH08246016A - Method for controlling end point of blowing in converter - Google Patents

Abstract

PURPOSE: To provide a control method suiting the end point temp. in a converter, by which the dropping temp. of molten steel after the end point of blowing in the converter is predicted to obtain a prescribed molten steel temp. at the time of continuous casting operation. CONSTITUTION: (1) A required molten steel temp. at the time of continuous casting operation, the operation starting schedule time in each apparatus, the operational necessary schedule time, the transporting time and the heat history and temp. raising rate, dropping rate results of each apparatus since the preceding blowing in the converter in the past, are collected. (2) The molten steel temp. dropping rate (▵T) up to the casting time in a continuous caster after completing the blowing in the converter is predicted according to the variations in the steelmaking process and the transportation. (3) The target temp. of the molten steel up to the end point of the blowing in the converter is corrected based on the predicted molten steel temp. dropping rate (▵T). (4) The end point control of the blowing in the converter is executed based on the corrected target temp. of the end point of the blowing in the converter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a blowing end point of a converter in a steelmaking process comprising a series of processes using a converter, a secondary refining device and a continuous casting machine.

[0002]

2. Description of the Related Art In a conventional converter end point control method, as shown in a control block diagram of a typical embodiment shown in FIG. 2, the end point temperature and the end point carbon concentration are mainly set in advance according to the steel type. Instructions for blowing conditions (oxygen supply amount / coolant input amount) from the time of sublance measurement during blowing to the end point are given. Regarding the molten steel temperature fluctuation during each process and transportation after the end of the converter, the blower estimates from each process schedule, and the target value of the end temperature is corrected at the discretion of the blower. It is the actual situation.

Japanese Patent Laid-Open No. 02-190413 discloses that in a refining furnace, feedback control is performed based on a prediction calculation of a time series model formula in consideration of past operation factors and prediction errors and the operation factors to obtain a target value. A refining control method has been proposed to improve the accuracy of accuracy. However, this method is just a measure to improve the accuracy of medium-term accuracy against a fixed target value in a smelting furnace single process system, and the influence of factor changes during each process of the lower process (secondary smelting and casting) and during transportation is considered. Didn't.

In Japanese Patent Laid-Open No. 62-297411 and Japanese Patent Laid-Open No. 01-246313, attention is paid to the temperature of bricks on the inner wall of the ladle, and a method of determining the amount of temperature drop of each process from the temperature drop curve of the ladle, and A method has been proposed for determining an appropriate target tapping temperature by correcting the target tapping temperature determined by the liquidus temperature or the like based on the component with the temperature drop estimated by measuring the temperature of the ladle refractory.

[0005]

The end temperature of the converter is determined mainly by the required molten steel temperature at the time of casting in a continuous casting machine in consideration of the average temperature drop after the converter for each steel type. However, in reality, the molten steel temperature at the time of casting of the continuous casting machine is due to the influence of the facility history of each process and the variation of the processing pitch and the molten steel transportation time,
If it is left as it is, it will be out of the required molten steel temperature. To compensate for this, it is necessary to uselessly raise or cool the temperature in the secondary refining device or the like in the lower step, and increase the amount of Al for heating or the amount of coolant to be added, which causes deterioration of these basic units. Become.

However, in the prior art, as described above, the prediction of time such as the tapping time and the transportation time, which has a great influence on the prediction of the temperature drop of molten steel, is not taken into consideration, or their prediction accuracy is insufficient. Therefore, it was impossible to set the target temperature of the molten steel at the end of the converter in real time and with high accuracy during blowing. In the prior art, for example, the deterioration of the converter structure such that the cross-sectional area of the tapped steel hole in the converter increases as the number of times it is used is not considered. The prediction accuracy of the tapping time, which is strongly affected by the

Further, as a general operation at present, the converter end point temperature is set to a high value from the safety side, and as a result, more heat than necessary is applied, so that the converter refractory and O ₂ There was a problem that the basic unit was worsened.

The present invention has been made in view of the above-mentioned problems of the prior art, and predicts the molten steel temperature drop amount after the end of the blowing of a converter, and determines the predetermined molten steel temperature at the time of casting in a continuous casting machine. In order to obtain the above, an object of the present invention is to provide a control method for optimizing the converter end point temperature.

[0009]

The method for controlling the blowing end point of the converter in the steelmaking process in the equipment having the converter, the secondary refining device and the continuous casting machine (CCM) according to the present invention is performed by the following procedure. Characterize.

Continuous casting required molten steel temperature at the time of casting,
Collect the scheduled operation start time of the above converter, secondary refining equipment and continuous casting machine, scheduled operation time, transportation time and past thermal history of each equipment other than converter and temperature rise / fall amount of molten steel temperature. .

According to the variations in the steelmaking process and transportation, the molten steel temperature drop (ΔT) from the end of converter blowing to the casting of the continuous casting machine is predicted by the following equation.

ΔT = ΔTCL + ΔTLR + ΔTRH + ΔTRC where ΔT is the amount of molten steel temperature drop that occurs between the end of converter blowing and the start of pouring in a continuous casting machine ΔTCL: The end of converter blowing and ladle Molten steel temperature drop that occurs until the end of steel reception (temperature drop during tapping) △ TLR: Molten steel temperature drop that occurs between the end of ladle steel reception and the start of processing in the secondary refining equipment (temperature drop during transportation) △ TRH: Fluctuation of molten steel temperature during secondary refining equipment treatment △ TRC: Amount of molten steel temperature drop occurring from the end of treatment in the secondary refining equipment to the start of casting in the continuous casting machine The predicted amount of molten steel temperature drop (△ T ), The target temperature of molten steel at the end of converter blowing is corrected.

The blowing end point control of the converter is performed based on the above-mentioned corrected converter blowing end point target temperature.

[0014]

The function of the method of the present invention is that the actual values of the processing pitch and the transportation time of each process are the temperature drop amount before the pre-charge, the steel type of the target charge, the casting target temperature, etc., and the temperature after the end point of the converter of the target charge. The amount of descent is predicted, the target end temperature of molten steel is corrected based on it, and blowing end point control is performed. It should be noted that the correction of the target end temperature of the molten steel in the converter is performed every time the process and the transportation state after the completion of the blowing of the converter are changed.

FIG. 3 shows an outline of the steelmaking process. Converter 1
After completion of the smelting in, the molten steel is tapped into the ladle 2 and transported to the secondary refining device 3, where it is subjected to secondary refining treatment by a secondary refining device such as RH, It is transported to the continuous casting machine 4 by a ladle and continuously cast. As shown in FIG. 4 schematically showing the relationship between the time after the end of the converter and the molten steel temperature, the temperature drop (ΔTx
x) occurs. The prediction of this temperature drop amount is formulated as shown below. As shown in the equations (1) to (6), the molten steel temperature drop amount (ΔT) generated in the predicted steelmaking process is added to the molten steel casting target temperature (Tcc) in the continuous casting machine (CCM) to blow the converter. Set the molten steel target temperature at the end of smelting and at the arrival of the secondary refining equipment. The molten steel casting target temperature refers to a temperature that is predetermined from the molten steel solidification temperature that differs depending on the type of manufacturing steel.

Ttap = Tcc + ΔT (1) ΔT = ΔTCL + ΔTLR + ΔTRH + ΔTRC (2) ΔTCL = A0 ・ time0 + ΣAi ・ time1 + Σai (3) ΔTLR = ΣBi・ Time2 + Σbi ・ ・ ・ (4) △ TRH = ΣCi ・ time3 + Σci ・ ・ ・ (5) △ TRC = ΣDi ・ time4 + Σdi ・ ・ ・ (6) Where, Ttap: Converter end-point molten steel temperature Tcc: Molten steel pouring temperature Ai: each Operation factors (factors of molten steel temperature drop related to the time from converter steel output to ladle steel reception) (for example, the amount of heat transfer to the converter and ladle, the amount of radiant heat dissipation) ai: Each operation factor (converter output) Molten steel temperature drop factor irrelevant to the time from steel to ladle receiving (for example, coolant, alloy input amount, etc.) Bi: Each operating factor (molten steel temperature related to the time from receiving steel to arriving at the secondary refining equipment) Factors of fall) bi: Factors of each operation (regardless of the time until the secondary refining equipment arrives after receiving steel) Of the molten steel temperature) Ci: each operation factor (fluctuation factor of molten steel temperature related to time during secondary refining process) ci: each operation factor (factor of molten steel temperature change independent of time during secondary refining process) Di: Factors of each operation (factors of molten steel temperature drop related to the time until casting after secondary refining treatment) di: Factors of operation (factors of molten steel temperature decrease independent of time from the secondary refining device to casting) time0: Steel tapping Wait time time1: tapping time time2: transportation time (from converter to secondary refining equipment) time3: secondary refining processing time time4: transportation time (from secondary refining equipment to continuous casting machine) FIG. It is a block diagram which shows the structure of the arithmetic unit 5 for implementing. Hereinafter, the method of the present invention will be described with reference to FIG. 1 based on a specific embodiment.

(1) RH control model section (S-30) Here, the CCM-RH transport time (time4) is calculated from the required CCM casting temperature and the scheduled time according to the following equation (7).
And predict the temperature drop (△ TRC) (S-2
0) Based on the result, the RH reaching target temperature, the RH treatment start time, and the molten steel temperature fluctuation amount (ΔTRH) generated during the treatment of the secondary refining device are calculated using a general RH decarburization model formula.

For example, a model obtained by dividing molten steel in the RH apparatus into three as shown in FIG. 5 is used. At that time, if the molten steel volume and the carbon concentration in each region are Vi and Ci (i = 1 to 3), the secondary refining treatment time to reach the target carbon concentration is calculated based on the equation (8), and the result is obtained. And the equation (9) are used to obtain the secondary refining (RH) reaching temperature (initial temperature) by back calculation.

ΔTRC = {p1. (TRHE-Tn) + p2. (TRHE-Tatm)} / Wst.time4 (7) where time4 = C (constant obtained from operation results) Wst: molten steel weight TRHE: Temperature after RH treatment Tn: Ladle inner wall brick temperature (° C) Tatm: Atmospheric temperature (° C) pj: Constant obtained from operation data Vi (dCi / dt) = Qst (Ci-1 -Ci) -kA ( Ci-Ce) (8) Qst: molten steel reflux amount k: mass transfer coefficient A: decarburization reaction interfacial area Wst.Cp. (dTi / dt) = Cp.Qst. (Ti-1 -Ti) +. SIGMA.Qr- Qcl-Qls (9) Ti: Molten steel temperature in the i region Cp: Specific heat of molten steel ΣQr: Total reaction heat change rate Qcl: Cooling material cooling heat change rate Qls: Heat release to atmosphere (2) Converter end point Target temperature calculation unit (S-40) Prediction of temperature drop in each process after the blowing of the converter furnace Based on the above equation (1), the converter end point target temperature is calculated so that the continuous casting machine (CC) casting temperature becomes the required temperature. At this time, A for temperature rise in the secondary refining furnace
It is desirable to determine so that the l input coolant input is 0.

The calculation steps for predicting the temperature drop amount are as follows.

Prediction calculation of tapping time (S-51) Tapping time (time1) that strongly affects the temperature drop during tapping
) Is due to the melting loss of the tap hole that is a part of the converter structure, that is, as the number of times the tap hole is used increases, the melting loss of the refractory bricks around the tap hole causes Using the mass balance of molten steel under the assumption that the diameter becomes large, the following equation (10) is used for prediction.

Time1 = (Wst) / {π / 4 · (D0 + αN) ² · ρvs} (10) time1: tapping time D0: unused tapping hole diameter N: tapping hole usage frequency α: Coefficient obtained from actual operation data ρ: Molten steel density vs: Molten steel flow velocity Ladle temperature prediction calculation (S-52) Required for the previous use of the relevant steel ladle 2 from the end of casting to the start of preheating in the preheating field The ladle temperature before receiving the steel is predicted by the following formula (11) in consideration of operating factors such as the heating time, the preheating time, and the presence or absence of the lid in the standby before the preheating.

Ttb = TCCE- (q1 + q2.tkara + Hcov) + q3.ty- (q4 + q5.Lk). (Tmo + tst) ... (11) Ttb: Ladle temperature immediately before receiving steel TCCE: Casting at the time of previous use Finished molten steel temperature tkara: Time required from the end of casting in the previous use to the start of preheating ty: Preheating time Lk: Ladle usage time tmo: Ladle moving time tst: Ladle standby time qj: Constant obtained from operation results data (J = 1 to 5) Hcov: Temperature drop correction coefficient without preheating front lid Prediction calculation of temperature drop during tapping (S-53) In determining the effect coefficient of temperature drop that occurs during tapping, the converter structure is used. Prediction is made according to equation (12) in consideration of factors such as deterioration of certain converter furnace wall structure, deterioration of ladle refractory, manufacturing steel grade, and amount of auxiliary raw material input.

ΔTCL = m1 ・ time0 + m2 ・ Wre + {m3 ・ (Ttap + 273) ⁴ / Wst + m4 ・ (Ttap-Tn) / Wst} ・ time1 + Σβi ・ Gi / Wst ・ ・ ・ ・ (12) time0: Waiting for tapping Time Wre: Amount of coolant (T) injected after the end of blowing Ttap: Molten steel temperature (° C) at the end of converter Wst: Molten steel weight (T) βi: Input factor during tapping Gi: Alloy input (T) ( i = 1 to 10) mj: constant obtained from operation performance data (j = 1 to 4) transportation time prediction calculation (S-54) The transportation time of the ladle is as follows from the relationship with the casting conditions in the continuous casting machine ( Predict according to equation 13).

Time2 = s1 · tr0 + s2 · tr1 + s3 ··· (13) tr0: total casting number of continuous casting machine tr1: continuous casting machine casting serial number s1, s2, s3: parameters obtained from previous operation performance data (steel type) Calculation of temperature drop during transportation (S-55) Regarding temperature drop occurring during transportation, factors such as the transportation time predicted by the transportation time prediction calculation (S-54) and deterioration of ladle refractory are taken into consideration. Then, the prediction is made by the following equation (14).

ΔTLR = {n1. (Tla-Tn) + n2. (Tla-Tatm)} / Wst.time2 .... (14) Tla: Molten steel temperature at tapping (° C) nj: Obtained from operation result data Constant (3) Converter control model part (S-10) The above-mentioned converter end point target temperature calculation value is input, and the amount of oxygen transfer until the end point is set with the sublance measurement value (C%, temperature) during blowing as the initial value. , Calculate the amount of coolant input. This calculation is dynamically corrected every time the converter end point target temperature is changed.

For example, the following statistical model formulas (15) and (16) (oxygen balance formula and temperature balance formula) are used as calculation formulas.

[0028] The converter furnace temperature balance equation △ T = a0 (CS -CE) + a1 · ln (CS / CE) + a2 [(-1 / CS) - (- 1 / CE)] + a3 [0.5 (-1 / CS 2 ) -0.5 (-1 / CE ² )] + f (WCL) + K (15) a0, a1, a2, a3: constants obtained from the actual data of the preceding converter operation K: conversion to be controlled Variable determined by furnace operating conditions f (WCL): Function of coolant amount WCL injected from the time of sublance measurement to the end of blowing. CS: Measured carbon content in steel by sublance measurement at the end of blowing (%). CE: Carbon content in steel at the end of blowing (%) WCL: Amount of coolant injected into molten steel during the period from the time of sublance measurement to the end of blowing (T) Converter oxygen balance formula ΔO ₂ / WST = a0 (CS-CE) + a1.ln (CS / CE) + a2 [(-1 / CS)-(-1 CE)] + a3 [0.5 ( -1 / CS 2) - 0.5 (-1 / CE 2)] + K ···· (16) O 2: oxygen (Nm ³⁾ WST: estimated from the main raw material charging amount Molten Steel Weight (T)

[0029]

EXAMPLE In the steelmaking process which is actually in operation, the method of the present invention is controlled by the control block configuration shown in FIG.
At the end of blowing, the steel is transferred to the ladle, steel is transferred to the ladle, and then the secondary refining equipment (RH) and continuous casting machine (CC) are used.
It was applied to the steelmaking process up to M). Low carbon steel 5
When the conventional method of FIG. 2 and the method of the present invention were compared and verified with respect to 0 charge, the temperature accuracy within ± 10 ° C. was 54% in the conventional method. The predictive value of the method was 85%.

Further, the casting target temperature in the continuous casting machine is set to 1
A histogram of the actual values of the converter end point temperature of the low carbon steel 50 charge operated at 570 ° C. is as shown in FIG. 6, and it was confirmed that the average converter end point temperature of 12 ° C. was reduced by the method of the present invention.

As a substantial effect obtained by the above-mentioned improvement of the temperature appropriateness ratio and reduction of the converter end point temperature, the converter and the secondary refining unit refractory basic unit 6%, the secondary refining input cooling material 10
%, Al unit for temperature raising 12%, and oxygen unit for temperature raising 12%.

[0032]

As described above, according to the method of the present invention, by accurately predicting the temperature drop amount after the end of the converter, it is possible to properly set the end temperature of the blowing of the converter and the arrival temperature of the secondary refining device. Therefore, it becomes possible to reduce the extra operation in the converter or the secondary refining device, and the efficiency can be achieved in the steelmaking cost and the steelmaking time.

Further, the optimization of the converter end point temperature (reduction of the end point temperature) is achieved, and a great effect of improving the converter refractory, the O ₂ unit and the coolant unit is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an arithmetic unit according to an embodiment of a method of the present invention.

FIG. 2 is a control block diagram of a typical embodiment of a conventional converter end point control method.

FIG. 3 is a schematic view of a steelmaking process.

FIG. 4 is a schematic diagram showing the relationship between the time after the end of the converter and the molten steel temperature.

FIG. 5 is an explanatory diagram of an RH control model.

FIG. 6 is a histogram of converter end-point temperature actual values for 50 charges of low-carbon steel.

[Explanation of symbols]

 1 Converter 2 Ladle 3 Secondary Refining Device (RH) 4 Continuous Casting Machine (CCM) 5 Computing Device

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] March 16, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

FIG. 3 shows an outline of the steelmaking process. Converter 1
After completion of the smelting in, the molten steel is tapped into the ladle 2 and transported to the secondary refining device 3, where it is subjected to secondary refining treatment by a secondary refining device such as RH, It is transported to the continuous casting machine 4 by a ladle and continuously cast. As shown in FIG. 4 schematically showing the relationship between the time after the end of the converter and the molten steel temperature, the temperature drop (ΔTx
x) occurs. The prediction of this temperature drop amount is formulated as shown below. As shown in the equations (1) to (6), the molten steel temperature drop amount (ΔT) generated in the predicted steelmaking process is added to the molten steel casting target temperature (Tcc) in the continuous casting machine (CCM) to blow the converter. setting the Netsui Ryoji and secondary refining equipment arrival of the molten steel target temperature. The molten steel casting target temperature refers to a temperature that is predetermined from the molten steel solidification temperature that differs depending on the type of manufacturing steel.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

ΔTRC = {p1. (TRHE-Tn) + p2. (TRHE-Tatm)} / Wst.time4 (7) where time4 = C (constant obtained from operation results) Wst: molten steel weight TRHE: Temperature after RH treatment Tn: Ladle inner wall brick temperature (° C) Tatm: Atmospheric temperature (° C) pj: Constant obtained from operation data Vi (dCi / dt) = Qst (Ci-1 -Ci) -kA ( Ci-Ce) (8) Qst: molten steel reflux amount k: mass transfer coefficient A: decarburization reaction interfacial area Wst.Cp. (dTi / dt) = Cp.Qst. (Ti-1 -Ti) +. SIGMA.Qr- Qcl-Qls (9) Ti: Molten steel temperature in the i region Cp: Specific heat of molten steel ΣQr: Total reaction heat change rate Qcl: Cooling material cooling heat change rate Qls: Heat release to atmosphere (2) Converter end point Starring target temperature calculation unit (S-40) the amount of temperature drop prediction in rolling Ro吹 wrought after each process in the following steps Based on the above equation (1), the converter end point target temperature is calculated so that the continuous casting machine (CC) casting temperature becomes the required temperature. At this time, Al for heating in the secondary refining furnace
It is desirable to determine so that the input of the supplied coolant is zero.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction content]

The converter temperature balance equation △ T = u0 (CS -CE) + u1 · ln (CS / CE) + u2 [(-1 / CS) - (- 1 / CE)] + u3 [0.5 (-1 / CS 2 ) -0.5 (-1 / CE ² )] + f (WCL) + K (15) u0, u1, u2, u3 : Constant obtained from the actual data of the preceding converter operation K: Transfer to be controlled Variable determined by furnace operating conditions f (WCL): Function of coolant amount WCL injected from the time of sublance measurement to the end of blowing. CS: Measured carbon content in steel by sublance measurement at the end of blowing (%). CE: Carbon content in steel at the end of blowing (%) WCL: Amount of coolant injected into molten steel during the period from the time of sublance measurement to the end of blowing (T) Converter oxygen balance formula ΔO ₂ / WST = v0 (CS -CE) + v1 · ln (CS / CE) + v2 [(-1 / CS) - (- 1 CE)] + v3 [0.5 ( -1 / CS 2) - 0.5 (-1 / CE 2)] + K ···· (16) O 2: oxygen (Nm ³⁾ WST: estimated from the main raw material charging amount Molten Steel Weight (T) v0, v1, v2, v3: Based on actual data of preceding converter operation
Obtained constant

Claims (1)

[Claims] 1. A method for controlling a blowing end point of a converter in a steelmaking process in a facility having a converter, a secondary refining device and a continuous casting machine, wherein a required molten steel temperature at the time of continuous casting and casting, the converter, the secondary refining. Scheduled start time of operation of equipment and continuous casting machine, expected operation time, transportation time and past thermal history of each equipment other than converter According to the fluctuation, the molten steel temperature drop amount (ΔT) after the end of the converter blowing up to the casting time of the continuous casting machine is predicted by the following formula, and based on the predicted molten steel temperature drop amount (ΔT), the converter blowing is performed. A method for controlling the blowing end point of a converter, wherein the molten steel target temperature at the end point of the smelting is corrected, and the blowing end point control of the converter is performed based on the corrected target temperature of the blowing end point of the converter. ΔT = ΔTCL + ΔTLR + ΔTRH + ΔTRC where ΔT: amount of molten steel temperature drop that occurs from the end of converter blowing to the start of casting in a continuous casting machine ΔTCL: end of converter blowing and ladle receiving ΔTLR: Temperature drop of molten steel that occurs from the end of ladle steel reception to the start of processing in the secondary refining equipment △ TRH: Fluctuation of molten steel temperature that occurs during secondary refining equipment processing △ TRC: Two The amount of molten steel temperature drop that occurs from the end of processing at the next refining equipment to the start of casting at the continuous casting machine