JPS597413A - Method for controlling width of plate in hot rolling - Google Patents

Abstract

PURPOSE:To obtain a prescribed width of a plate with high accuracy, by determining the thickness of the plate in the stage of ending cross rolling from the thickness, width and temp. in the stage of starting the cross rolling and the target width and temp. in the stage of ending the cross rolling and controlling the thickness with said thickness as a target thickness. CONSTITUTION:When an actual cross rolling pass is started, a value actually measured with a thermometer or a calculated value determined by using the actual value for an equation for predicting temp. can be used for a material temp. Ts. Either of the material temp. TE determined by correcting the equation for predicitng temp. by the temp. determined by a schedule calculation and the actually measured value and determining the same again by the calculation for the pass schedule or the temp. predicted and calculated from the actually measured temp. value just before the final pass for cross rolling is used for the material temp. TE in the final pass stage of the cross rolling. The thickness calculated by using a gauge meter equation from the actually measured roll gap and actually measured load of the pass just before the start of the cross rolling or the actually measured thickness is used for the thickness HS in the stage of starting the pass for cross rolling. The final thickness HL is determined from the equation I , and the pass schedule for cross rolling with higher accuracy is obtd. by performing the calculation for the pass schedule again.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a strip width control force method in hot rolling, which is suitable for performing tentering rolling in the width direction of a rolled material to obtain a predetermined strip width.

In plate rolling, etc., in order to obtain a specified product plate width,
Several passes of widthwise rolling are performed in the width direction of the rolled material.

In this tentering rolling, the strip width control method to obtain a predetermined strip width is to control the strip thickness using the final tentering strip thickness HL calculated by the following formula (1) as the target strip thickness, thereby achieving the target product strip. This makes it possible to gain width.

The above H8 is the sheet thickness at the start of the tentering pass, and W8 is the sheet width at the start of the tentering pass, that is, the slab width (if there is a longitudinal rolling pass before the tentering rolling, the amount of width expansion due to this is also included).
WL is the target product board width, α is a correction term that takes into account width expansion, etc., and the above Hs, W8, and WL are all given as thermal dimension values.

Here, assuming that the above correction term α=0.0, the above H8, Ws, and WL are respectively 200 mm and 20 mm.
00wn.

If it is 4500 va, the HL calculated by the above equation (1) will be 88.89 m. Therefore, in the conventional sheet width control method, sheet thickness control is performed using this 88.89 tm as the target sheet thickness in the final tentering pass.

However, in an actual tentering pass, there is a temperature drop of the rolled material during the tentering pass, so if this temperature drop is taken into consideration, the control results will be as follows. That is, - As an example, if the material temperature at the start of the tentering pass is 105
The temperature of the material at the end of the tentering pass is 1000°C. According to literature and the like, the thermal expansion coefficient β of hot steel changes depending on the temperature and material components. For example, the thermal expansion coefficient β of each material shown in Table 1 is as shown in FIG.

Table 1 So, for example, the thermal expansion coefficient β of 1050 U in material cK45 is 1.0143 when read from Figure 1, and the cold dimension values of H, Ws, and WL mentioned above are each 197.18.
mm, 1971.80 fins, 4436.56 m. Similarly, ioo.

The coefficient of thermal expansion β in °C is 1.0133, and the above H
The cold dimension value of 88.89 m, which is the calculation result of L, is 87.7
2 tts. These H,, W8. From each cold dimension value of HL, the board width of the control result is calculated according to the constant volume law, 4432.281fi+! :Become. That is, there is a difference of approximately 4+w between the board width 4432.28 wn as a result of control at the cold stage and the target board width 4436.56 m. As is clear from the above explanation, this error is due to the temperature drop during the tentering pass, and the amount of temperature drop,
Variations occur depending on the target plate width, etc., and the amount of temperature drop varies depending on the initial temperature of the material, tentering ratio, etc.

In other words, the conventional strip width control method does not take into account the temperature drop during the tentering pass, which limits the improvement of strip width control accuracy, especially for thick plates that are hot-rolled to wide strip widths. In rolling, significant control errors occur due to the temperature drop.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for controlling strip width in hot rolling that obtains a predetermined strip width with high precision.

In order to achieve the above object, the present invention provides a sheet width control method in hot rolling for obtaining a predetermined sheet width by tentering rolling in the width direction of a rolled material. Using the thickness, plate width, and temperature as well as the target plate width and temperature of the rolled material at the end of tentering rolling, find the thickness of the rolled material at the end of tentering rolling so that the law of constant volume holds at the same temperature condition. The target board width is obtained by controlling the board thickness using this board thickness as the target board filling.

The present invention will be described in more detail below. In the present invention, the final plate thickness after tentering is determined by taking into consideration the amount of temperature drop of the material during the tentering pass. When calculating the final plate thickness HL in the tentering pass, from the material temperature Ts at the start of the tentering pass and the material temperature TE at the final tentering pass, the thermal expansion coefficient β of the material corresponding to these temperatures is calculated.
8°βΣ is determined, and the above-mentioned HL is calculated so that the law of constant volume holds during cold dimension.

According to this idea, the above HL is determined by the following ( Calculated using the formula 2) (note that the coefficient of thermal expansion at cold temperature is assumed to be 1).

Next, a method for determining the material temperature Ts at the start of the tentering pass and the material temperature TE at the final tentering pass, which are important elements in implementing the present invention, will be explained.

Generally, in thick plate rolling, a pass schedule is calculated before rolling starts, and the reduction distribution, that is, the target plate thickness for each pass is determined. This path schedule subtraction is the second
As shown in the flowchart in the figure, the initial plate thickness Hs1 target plate thickness HL1 initial temperature T8 are given, and the reduction distribution, predicted load, predicted temperature, etc. for each pass are determined using models such as the well-known rolling load formula and temperature prediction formula. By determining this predicted temperature, T, , TE can be determined. Here, the input data for the above path schedule calculation is l-18.
゜HL t 'r8 is required, but only Hs, T8 and the target plate width W section given by the cold dimension value or the target plate width (WL) given by the hot dimension value are known (in this case, the thermal The dimension value WL is obtained simply by multiplying the cold dimension value Wζ by a constant), and the parameter T for calculating HL using the above equation (2) is unknown. therefore,
In implementing the present invention, first, the final plate thickness HL for tentering is run using the conventional method that does not take into account the temperature drop during the tentering pass, that is, the equation (1) above, and thereby the first pass schedule is created. conduct.

Next, using the rsl TE obtained in the first creation pass schedule above, calculate the final plate thickness HL (referred to as H'L) from the 11 prefectures from the formula (2) Cζ, and calculate this H'L
A second pass schedule is created based on the following.

Therefore, compare Ts, TE obtained from the second creation pass schedule and Ts, l1lF, obtained from the previous creation pass schedule, and repeat the above steps until the difference between them falls within a certain value. , T are determined. Normally, by repeating the above operation two or three times, it is possible to keep the difference in T, , TE between Nox schedules within 5°C.

By calculating the pass schedule according to the above-described work procedure, it is possible to obtain a rolling schedule that achieves the object of the present invention. Normally, by proceeding with rolling according to the rolling schedule determined as above, it is possible to perform tenter rolling with high accuracy, but the load, temperature, etc. determined in the above rolling schedule are only predictions. It is based on the formula. Therefore, as the actual rolling progresses, there is a possibility that the cart, temperature, etc. in each pass may differ from the scheduled values based on model errors and the like. Therefore, in order to achieve OJ performance in strip width control with higher precision by implementing the present invention, a method of implementing the present invention after actual rolling has started will be described below.

That is, in order to further improve the plate width control accuracy according to the present invention, it is safe to improve the accuracy of the HL calculated by the above equation (2). For that purpose, HBIlls, l1, which is the calculation parameter in equation (2) above,
It is necessary to use an actual measured value for lE instead of a predicted value when calculating the path schedule. That is, once the actual tentering pass is started, it is possible to use the actual measured value from the thermometer or the calculated value obtained by using actual values as parameters of the temperature prediction formula for Ts. Also, as TF, (1)
+1 determined by schedule calculation! The temperature prediction formula was corrected using s and the actual measured value of 1゛8, and the pass schedule calculation was performed again. T did
9 can be used. In addition, for H8, it is possible to use the gauge meter plate jq1 calculated using the gauge meter formula from the actual roll opening degree and the measured load in the pass immediately before the tentering start pass, that is, the final pass of forming, or the plate thickness actually measured with a thickness meter. It becomes possible. Based on the above HB t Ts + "E, HL is obtained from the above equation (2) and the pass schedule calculation is performed again, thereby making it possible to obtain a tentative pass schedule with even higher accuracy. For example, it is possible to improve the variation in tentering accuracy due to the drop in material temperature during the tentering pass, that is, the variation of about a few degrees.For example, as mentioned above, for a target board width of 4500 wm, it is possible to improve If it is improved, it will be possible to improve the yield by about 0.1%.

As described above, the strip width control method in hot rolling according to the present invention is based on the strip thickness, strip width, and temperature of the rolled material at the start of tentering rolling, the target strip width and temperature of the rolled material at the end of tentering rolling. By determining the plate thickness of the rolled material at the end of tentering rolling so that the constant volume law is established under the same temperature condition, and performing plate thickness control using this plate thickness as the target plate thickness, the target plate can be obtained. Since the width is obtained, there is an effect that a predetermined plate width can be obtained with high precision.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between hot steel temperature and thermal expansion coefficient, and FIG. 2 is a flowchart showing the flow of pass schedule calculation. Hs...Plate thickness at the start of the tentering pass, HL...Final plate thickness for tentering, Ts...Material temperature at the start of the tentering pass, TF,
Material temperature during final tentering pass. Agent Patent Attorney Osamu Shiokawa

Claims (1)

[Claims] (1) In the plate width control force method in hot rolling to obtain a predetermined plate width by tentering rolling in the width direction of the rolled material, the plate thickness, plate width and temperature of the rolled material at the start of tentering rolling, Based on the target width and temperature of the rolled material at the end of tentering rolling, determine the thickness of the rolled material at the end of tentering rolling so that the law of constant volume holds at the same temperature, and use this thickness as the target thickness. A strip width control method in hot rolling, characterized in that the target strip width is obtained by controlling the strip thickness as follows.