JP3767832B2 - Thickness control method in hot rolling - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sheet thickness control method in hot rolling.
[0002]
[Prior art]
In recent years, the demand for thickness accuracy of rolled products has become increasingly severe. On the other hand, the thickness accuracy in the longitudinal direction of the strip has a high control effect due to the rapid development of automatic plate thickness control. As this automatic plate thickness control (AGC), for example, as disclosed in Japanese Patent Publication No. 61-29807, (1) a change in the plate thickness on the inlet side is detected as a change in rolling load, and this detected load A method (so-called gauge meter type AGC) of adjusting the amount of roll reduction corresponding to the change. (2) A change in the sheet thickness on the entry side is detected by a thickness meter attached to the entry side of the rolling mill, and the reduction control amount is obtained using the detected thickness change, and the rolling mill position is determined from the speed of the material to be rolled. A method of detecting the arrival and adjusting the rolling reduction of the rolling mill (feed forward). (3) There is a method (monitor AGC or feedback AGC) in which a change in sheet thickness on the delivery side is detected by a thickness meter attached to the delivery side of the rolling mill and the reduction amount is adjusted by proportional integral control based on the detected thickness change. is there.
[0003]
As an improvement to these methods, a rolling load detection means installed in the rolling mill is obtained by obtaining a control amount necessary for matching the detected sheet thickness on the entry side of the rolling mill to the target value or a rolling load corresponding to the control amount. Or the control amount corresponding to the output is calculated, the control amount output to the plate thickness adjusting means is calculated using these two rolling loads or control amounts, and the plate thickness adjusting means is controlled by this calculated value. It is disclosed.
[0004]
[Problems to be solved by the invention]
Japanese Patent Publication No. 61-29807 described above is one of the automatic sheet thickness control methods of a rolling mill that controls the sheet thickness on the delivery side of the rolling mill to a target value. However, this automatic sheet thickness control method has a control gain. There is no mention about. Moreover, even if it changes, it is a change by a material unit, and it is normal to roll by control by a fixed value for every each material unit. However, the rolled material has a different plastic coefficient depending on the temperature, and there is a problem that the controlled rolling for each material unit does not always have a high precision and an appropriate control amount.
[0005]
[Means for Solving the Problems]
The present invention eliminates the above-described problems, predicts the temperature of the Ar ₃ transformation point of the rolled material, and changes the thickness control gain considering the plastic coefficient of the material at the Ar ₃ transformation point as a boundary. The present invention provides a sheet thickness control method in hot rolling that performs thickness control.
The gist of the invention is that
(1) Predicting the temperature in the longitudinal direction of the material in the finishing mill, predicting and calculating the temperature of the Ar ₃ transformation point of the rolled material, and using the Ar ₃ transformation point as a boundary, the part higher and lower than the Ar ₃ transformation point When changing the plate thickness control gain, fix the roll gap of any one of the finishing mills, find the plastic coefficient of the material from the inlet side plate thickness fluctuation, mill rigidity and load fluctuation, and set the initial plastic coefficient. The present invention provides a sheet thickness control method in hot rolling, characterized in that a ratio is obtained, the ratio is multiplied by an initial plastic coefficient for each stand, and a sheet thickness control gain is changed to control the sheet thickness.
[0006]
Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic view of a continuous hot rolling mill group in which a rough rolling mill and a finish rolling mill are continuously arranged. As shown in FIG. 1, in order to feed the rolled material 1 and feed it into the finishing mill by the rough rolling mills 2 groups R _{1 to} R ₆ , the rolled material 1 is rolled into a rolled material having an appropriate thickness. Rolling is performed sequentially from the _first rolling mill (F ₁ stand) of the three groups of mills, so that a rolled product with a predetermined thickness can be obtained at the outlet side of the _seventh rolling mill (F ₇ stand). It has become. In such a group of continuous rolling mills, the thermometer 4 is arranged in the middle of the roughing mill exit side, the finishing mill entry side, and the finishing mill, and each thermometer 4 is taken into the temperature calculator 5. When using the thermometers on the finishing mill entry side and the roughing mill exit side, the temperature in the longitudinal direction during the rolling of the finish rolling mills F _{1 to} F ₇ is predicted using them.
[0007]
In the case of an intermediate rolling thermometer, the temperature in the longitudinal direction during rolling of the stand after the intermediate rolling thermometer is predicted. In this case, the temperature prediction generally needs to be designed in consideration of air cooling, roll contact, desking, roll cooling water, and processing heat generation. In particular, the characteristic here is that the temperature is predicted continuously in the length direction.
On the other hand, a plate thickness meter 6 is provided in the finishing mill, and during rolling, the plate thickness control device 7 calculates the deviation between the detected value of the plate thickness meter 6 and the reference plate thickness as the inlet side plate thickness deviation, and on the output side. A necessary reduction control amount for ensuring the target plate thickness is output to the reduction device 8 via the control arithmetic device 9.
[0008]
Thus, the temperature in the longitudinal direction of the material in the finishing mill is predicted, but the material plasticity coefficient changes extremely at the Ar ₃ transformation point temperature of the rolled material. That is, the Ar ₃ transformation point of the rolled material varies depending on the steel type, and particularly affects carbon. In the case of extremely low carbon steel, the transformation point rises and there is an Ar ₃ transformation point at the finish rolling exit temperature, for example, 900 ° C. Below this temperature, transformation occurs and the material plasticity coefficient becomes extremely small. In particular, if carbon is low, the transformation point temperature rises and occurs during finish rolling. Therefore, extreme plasticity coefficient is divided into a varying Ar ₃ lower and higher than the Ar ₃ transformation point to transformation point as a boundary portion partially modeling the transformation behavior, the predetermined transformation on the basis of the model during hot finish rolling It is necessary to change the plate thickness control gain along the rate pattern.
[0009]
FIG. 2 is a block diagram showing a gain changing method according to the present invention. As shown in this figure, when the gauge meter thickness deviation is obtained and the gain is changed by PI control, the initial setting mill rigidity Ms, the initial setting material plasticity coefficient Qs, the mill rigidity M with respect to the rolling load that sequentially changes, and the actual rolling obtains the ratio {Ms / (Ms + Qs) } / {M / (M + Q)} between the plastic coefficient Q in, the Q one which changes when you turn off the Ar ₃ transformation point, change during rolling The mill rigidity is calculated for each load, and the roll gap amount is output as an operation. In this case, as shown in FIG. 3, the gain is changed according to the temperature, and further , an operation for changing the gain extremely near the Ar ₃ transformation point is performed. That is, FIG. 3 is a diagram showing a relationship between rolling mill passage predicted temperature and gain.
[0010]
FIG. 4 is a block diagram showing a gain changing method according to another embodiment of the present invention. A method of measuring the plastic coefficient Q during actual rolling by fixing the roll gap of any one stand of a finishing mill will be described . The load change ΔF can be expressed by the following equation.
ΔF = MQ / (M + Q) × ΔH−MQ / (M + Q) × ΔS
However, ΔH: Change in entry side plate thickness ΔS: If the roll gap change AGC is stopped, the term ΔS can be set to 0 to reduce the error.
Therefore, ΔF = MQ / (M + Q) × ΔH is established. In this case △ H is measured by installing or estimated calculated by the gauge meter thickness, or the thickness detector a. When this equation is transformed into the equation of Q,
Q = ΔF × M / (M × ΔH−ΔF).
[0011]
In this way, the plastic coefficient Q is obtained by continuously calculating during rolling. Note that QL in FIG. 4 means Q at the time of lock-on, and is multiplied by a constant k to obtain an operation output. Of course, the configuration of FIG. 2 may be used. In this manner, the ratio with the plastic coefficient QL that is preset in advance is obtained , and the ratio is multiplied by the plastic coefficient that is initially set for each subsequent stand to change the sheet thickness control gain to control the sheet thickness. .
[0012]
【The invention's effect】
Above As I mentioned, according to the present invention, to predict the temperature of the Ar ₃ transformation point of the rolled material, the gauge control for changing the gauge control gain considering the plasticity coefficient of rolling material as a boundary the Ar ₃ transformation point By doing so, it was possible to realize automatic plate thickness control with a plate thickness system with extremely small plate thickness deviation compared to the conventional one.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a group of continuous hot rolling mills in which a rough rolling mill and a finishing rolling mill are continuously arranged.
FIG. 2 is a block diagram showing a gain changing method according to the present invention;
FIG. 3 is a diagram showing the relationship between rolling mill passage predicted temperature and gain;
FIG. 4 is a block diagram showing a gain changing method according to another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Rolled material 2 Coarse rolling mill 3 Finish rolling mill 4 Thermometer 5 Temperature calculator 6 Plate thickness meter 7 Plate thickness control device 8 Reduction device 9 Control calculation device

Claims (1)

Predicts the temperature in the longitudinal direction of the material in the finish rolling mill, predicts and calculates the temperature of the Ar ₃ transformation point of the rolled material, and controls the thickness of the part higher and lower than the Ar ₃ transformation point with the Ar ₃ transformation point as a boundary. When changing the gain, fix the roll gap of any one of the finishing mills, calculate the plastic coefficient of the material from the inlet side thickness fluctuation, mill rigidity and load fluctuation, and obtain the ratio with the initially set plastic coefficient. A sheet thickness control method in hot rolling, wherein the sheet thickness control gain is changed by multiplying the ratio by an initial plastic coefficient for each subsequent stand to control the sheet thickness.

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