JPS6139374B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement in a blowing control method for a pure oxygen top-blowing converter, and in particular, to accurately adjust the composition and temperature of molten steel (steel bath) to target values at the end of blowing. It is about the method.

Conventionally, in the blowing control of a pure oxygen top-blowing converter,
In order to achieve stable operation and a high target accuracy of steel bath composition and temperature, computer control methods are generally adopted. In blowing control using this computer, in order to achieve stable operation and a high target accuracy, the composition and temperature of the steel bath, the amount of blown oxygen and coolant used over time, and the lance height over time, etc. We have created a control formula that links all the data necessary for blowing, and we perform blowing based on this control formula. In addition, in the blowing control using the computer, ○a) Before the start of blowing, the following information is required: hot metal composition and amount, scrap type and amount, auxiliary raw material type and amount, blowing pattern (oxygen supply pressure of its height above the hot water surface over time), and target values (the composition and temperature of the steel bath that is ultimately intended to be obtained through blowing).
All other data necessary for blowing (for example, the total amount of oxygen used until the scheduled end of blowing,
A control method (this is called static control) that calculates and determines the planned total amount of coolant used during blowing, and performs blowing based on the calculation results without changing the calculated data during the blowing process. ○B After the start of blowing, the components and temperature of the steel bath are actually measured directly or indirectly, and the components and temperature of the steel bath at the end of blowing are predicted and calculated from these actual measurements, and based on the results of this calculation. Then, the amount of oxygen used, the amount of coolant used, etc. after the actual measurement is determined, and the blowing is performed so that the composition and temperature of the steel bath at the end of blowing are within the target values (this is a control method that uses a dynamometer). Note that in this dynamic control, before the actual measurement, other controls, such as static control, are usually used). The composition and temperature of the steel bath at that time are estimated from the history of the change in temperature and actual blowing values such as the amount of oxygen used, the amount of flux used, and the amount of iron ore used. Predict (determine) future oxygen usage, coolant usage, etc. by comparing and examining data for blowing control in Itsuku control.
However, a control method is known in which blowing is performed so that the composition and temperature of the steel bath at the end of blowing are within target values (this control method is called dynamic control).

In addition, after the blowing is completed, the predicted composition and temperature of the steel bath over time from various control formulas of the computer, and the actual results (as described later, the composition of the steel after the blowing is completed using various control formulas, (which can be calculated backwards from the temperature) and the temperature, and change the coefficients (characteristics) of various control equations for the next charge. Also known as feedback control.

However, in the above-mentioned static control, the blowing control data is not changed during blowing, so if blowing is not performed as planned, the accuracy rate of the steel bath composition and temperature to the target values will be greatly reduced. . In addition, in the above-mentioned dynamic control, the common method is to actually measure the components and temperature of the steel bath during blowing using a sublance with a measuring probe attached to the tip. must be carried out near the firing point of the oxygen lance, where intense reactions are occurring and segregation is occurring in that area and temperature; therefore, the measurement results may deviate from the actual values. Therefore, if blowing control is performed based on these measurement results, the accuracy of the steel bath composition and temperature to the target values will drop significantly, and even if measurements are performed with a sublance, the effects of oxygen blowing will In this case, the measurement may fail and no measurement data can be obtained, and in this case, blowing control becomes impossible or the accuracy of the steel bath composition and temperature to the target values is significantly reduced. Furthermore, unlike the dynamic control, the semi-dynamic control does not perform control based on actual measured values of the composition and temperature of the steel bath during blowing. There is a problem that the accuracy of bath composition and temperature to target values is poor.

Therefore, the present inventors conducted the following study in order to solve the above-mentioned problems in blowing control using a computer. That is, dynamic control is mainly used at the final stage of blowing, and has a higher accuracy rate for achieving target values for steel bath composition and temperature than other controls.

The composition and temperature of the steel bath during and after blowing, the height of the oxygen lance and the amount of oxygen used,
Or the history of actual values such as coolant usage, etc.
Through investigation and examination of estimation results, etc., the following reaction formula common to the static control, dynamic control, and semi-dynamic control was found: ∫ ⁿ _n dc = ∫ ⁿ _n f ₁ ([C], B, F, E, O, I,
K) dQ …(1) ∫ ⁿ _n dT=∫ ⁿ _n f ₂ ([C], B, F, E, O, I,
K) dQ...(2) {However, C: Carbon (amount of carbon in the steel bath) [C]: Carbon concentration in the steel bath B: Blowing pattern (height of oxygen lance and amount of oxygen used) F: Flux Amount used E: Concentration of components other than carbon in the steel bath O: Amount of iron ore used I: Initial conditions K: Coefficient Q: Amount of oxygen m, n: Time} Since these formulas can be used in a calculator, By inputting and using the information, blowing control can be performed by appropriately switching and using each of the above-mentioned controls. For example, in both formulas, m: 0, n: scheduled blowing end time, [C], B, F, E, O,
By using the planned values for I and K, the carbon concentration and temperature of the steel bath at the end of blowing can be estimated (static control), and during blowing,
The carbon concentration and temperature at the end of blowing can be estimated by actually measuring the carbon concentration and temperature of the steel bath and using these actual measured values to calculate where m is the time of the actual measurement and n is the scheduled time of completion of blowing. (dynamic control), further, m: 0, n: when a predetermined time has elapsed from the start of blowing, and the actual values of B, F, O and E, I, K from the start of blowing until the elapse of the predetermined time. By using the scheduled values, the carbon concentration and temperature of the steel bath after the predetermined time has elapsed can be estimated.

Based on the actual measured values of the carbon concentration and temperature of the steel immediately after blowing, the carbon concentration of the steel bath and the temperature at the time of sublance measurement for dynamic control were calculated using the above formulas. However, since the sublance measurement time is at the end of blowing (usually after 80% of the total blowing time), the carbon concentration and temperature of the actual steel bath at the time of sublance measurement almost match. Based on this assumption, we conducted many operational tests and conducted the following investigation. That is,
In order to obtain steel with the same composition and temperature using the same converter, multiple blowing operations are carried out using semi-dynamic control throughout the entire blowing period. Only actual measurements of the carbon concentration and temperature of the bath were performed. Then, from the actual measured values of the carbon concentration and temperature of the steel immediately after blowing, the carbon concentration and temperature of the steel bath at the time of sublance measurement were calculated backward using the above formulas (hereinafter referred to as the back-calculated concentration and the back-calculated temperature). Based on the back-calculated concentration and back-calculated temperature, the carbon concentration and temperature of the steel bath measured by the sublance (hereinafter referred to as the sublance concentration and sublance temperature), and the above calculated in the semi-dynamic control. The difference between the carbon concentration and temperature of the steel bath at the time of sublance measurement (hereinafter referred to as calculated concentration and calculated temperature) was investigated for each blowing process. The resulting distribution of the difference between the back-calculated concentration and the sublance temperature is shown in FIG. 1, and the distribution of the difference between the back-calculated temperature and the calculated temperature is shown in FIG. As is clear from these figures, the sublance temperature has a small difference from the back-calculated temperature, that is, the one with good data accuracy, is more accurate than the calculated temperature. In other words, abnormal data is included, and when this abnormal data is incorporated, the accuracy rate for achieving the target values for the carbon concentration and temperature of the steel bath is lower than when other abnormal data are not included. I understand. Also, the calculated temperature is
Although there are fewer highly accurate data than those for sublance temperature, it was found that almost no abnormal data was included. Note that this was also true between the back-calculated concentration, the sublance concentration, and the calculated concentration.

The inventors of the present invention have conducted research focusing on the above-mentioned results, and have found that in order to improve the accuracy rate of the carbon concentration and temperature of the steel bath to the target values, it is necessary to It is clear that it is only necessary to adopt a control system, and in dynamic control, the control accuracy can be improved to reduce the carbon concentration in the steel bath.
In order to improve the accuracy of the target values for sublance and temperature, it is possible to eliminate abnormal data for sublance concentration and temperature and not use them, but instead, some data must be incorporated. Moreover, the data must be closer to the actual value than the abnormal data, and for this purpose, it is necessary to determine whether or not the sublance concentration and temperature are abnormal data during blowing. If it is determined that, it is sufficient to obtain alternative data that is closer to the actual value than the abnormal data, and since the calculated concentration and temperature have almost no abnormal data, the dynamic When performing moisture control, if the calculated concentration and temperature are also calculated by semi-dynamic control and compared with the above-mentioned sublance concentration and temperature during blowing, the above-mentioned sublance concentration and temperature can be compared. If the calculated concentration and temperature become abnormal data, it can be immediately known, and therefore, the abnormal data can be eliminated.If the calculated concentration and temperature are used instead, the calculated concentration and temperature will be more accurate than the abnormal data. Since it is clear that the value is close to the value of , we have obtained the knowledge that the accuracy of achieving the target value of the carbon concentration and temperature of the steel bath in dynamic control is improved.

This invention was made based on the above knowledge, and after a predetermined period of time has elapsed from the start of blowing, the carbon concentration and temperature of the steel bath are actually measured, and the steel bath at the time of the actual measurement is calculated based on the actual blowing results up to the time of the actual measurement. Estimate the carbon concentration and temperature of the steel bath, compare the actual measured values and estimated values of the carbon concentration and temperature of the steel bath, and if the difference between the two is within a predetermined range, the actual measured value is replaced with a value outside the same predetermined range. In this case, the carbon concentration and temperature of the steel bath at the end of blowing are predicted by incorporating the estimated value into a control equation for determining the carbon concentration and temperature of the steel bath calculated in advance, The blowing control method for a pure oxygen top-blowing converter is characterized by controlling the blowing based on this prediction result and adjusting the carbon concentration and temperature of the steel bath to the target values at the end of the blowing. have

Next, examples will be explained.

Using a 300Ton converter, the same control formula was used to obtain steel with the same composition and temperature at the end of blowing, and the blowing was first controlled by semi-dynamic control from the start of blowing. And at the end of blowing, that is, the total amount of oxygen used until the end of blowing.
2000Nm ³ (approximately 2 minutes before the end of blowing), use a sublance to actually measure the carbon concentration and temperature of the molten steel (sublance concentration and temperature), and then perform multiple blowings using dynamic control. Perform Ren control. At the same time, the estimated carbon concentration and temperature (calculated concentration and temperature) of the steel bath at the time of the sublance measurement were calculated using semi-dynamic control. Furthermore, the carbon concentration and temperature of the steel are actually measured immediately after the completion of blowing, and the actual steel bath carbon concentration and temperature (back-calculated concentration and temperature) at the time of the sublance measurement are calculated from the actual measurement values using the control equation. The dispersion (standard deviation) of the difference (absolute value) between this back-calculated concentration and temperature, the sublance concentration and temperature, and the calculated concentration and temperature was investigated. The results were: 0.050 (wt%) at sublance concentration, 0.070 (wt%) at calculated concentration, 8.0 (°C) at sublance temperature, and 12.0 (°C) at calculated temperature.

Next, the following formula, which incorporates the variation (standard deviation) of the difference between the back-calculated concentration and temperature and the calculated concentration and temperature, is expressed as Cs<C _D +A〓σ _c ...(i) Cs>C _D -A〓σ _c ...(ii) Ts＜T _D +B〓σ _T ...(iii) Ts＞T _D −B〓σ _T ...(iv) {However, Cs: Sublance concentration C _D : Calculated concentration A and B: Constant σ _c : Variation in the difference between the sublance concentration and the calculated concentration (standard deviation) Ts : Sublance temperature T _D : Calculated temperature σ _T : Variation in the difference between the sublance temperature and the calculated temperature (standard deviation) Based on A and B Using a value between 0.5 and 3.0, the sublance concentration that satisfies the above equations (i) and (ii) is left as is, but if it does not, it is excluded and the calculated concentration is used instead, and the sublance concentration is calculated using equation (iii). , (iv) were used as they were, and when they were not satisfied, they were removed and the calculated concentrations were incorporated into the dynamic control for blowing.
The results showed that when both A and B were 1.4, the accuracy of achieving the target values for the carbon concentration and temperature of the steel bath was highest. In addition, the results of comparison between the carbon concentration and temperature target values of the steel bath of the present invention when both A and B are 1.4 are compared with those of the conventional dynamic control described above. (within ±0.02% of concentration)
While the conventional method is 90.0%, the method of the present invention is 93.6%, and the temperature accuracy rate (within ±12°C of the target temperature) is 82.0%, whereas the conventional method is 93.6%. The rate for the method of the present invention was 86.0%.

Thus, it is clear that the method of the present invention has a higher accuracy rate than the conventional method in terms of both carbon concentration and temperature.

As explained above, in this invention, the accuracy of the actual measured values of the carbon concentration and temperature of the steel bath during blowing is determined, and the actual measured or Since the carbon concentration and temperature of the steel bath at the end of blowing are predicted based on the estimated carbon concentration and temperature, prediction results that are always accurate within a predetermined range can be obtained. Since the blowing control is carried out, it is possible to improve the accuracy of the carbon concentration and temperature of the steel bath to the target values at the end of the blowing.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the distribution of the difference between the back calculation temperature and the sublance temperature, and FIG. 2 is a diagram showing the distribution of the difference between the back calculation temperature and the calculation temperature.

Claims (1)

[Claims] 1. After a predetermined period of time has elapsed from the start of blowing, the carbon concentration and temperature of the steel bath are actually measured, and the carbon concentration and temperature of the steel bath at the time of the actual measurement are determined from the actual blowing results up to the time of the actual measurement. and compare the actual measured values and estimated values of the carbon concentration and temperature of the steel bath, and if the difference between the two is within a predetermined range, use the actual measured value, and if the difference is outside the predetermined range, use the estimated value. The carbon concentration and temperature of the steel bath at the end of blowing are predicted by incorporating the values into the control formula for determining the carbon concentration and temperature of the steel bath, which have been calculated in advance, and based on this prediction result. A blowing control method for a pure oxygen top-blowing converter, characterized by performing blowing control to adjust the carbon concentration and temperature of a steel bath to target values at the end of blowing.