KR20020048204A - Method for controlling off-gauge width of strip in hot mill process - Google Patents

Abstract

PURPOSE: A method is provided in which a roll gap is pressed as thick as an off-gauge thickness before a material to be rolled is entered into each stands, and the roll gap is returned to a normal control set value when the normal portion of the material to be rolled is entered into the stands so that normal rolling is carried out. CONSTITUTION: The method for controlling a thickness of the ultra front part of a material to be rolled in hot finishing rolling process comprises the steps of judging whether the concerned material is the object of controlling or not when rolling a concerned material after accumulating data per types of steel, thicknesses and widths on a data table which is divided into the types of steel, thicknesses and widths by determining whether or not to perform controlling per each stands considering threading property of the material to be rolled; continuously obtaining a temperature of the front part of the material to be rolled through a thermoscope at the entrance side of the finishing rolling mill when the concerned material is determined to be the object of controlling; calculating an estimated off-gauge amount and an estimated off-gauge length using a deviation between the measured temperature of the front part and a temperature of the normal part of the material to be rolled; calculating control amounts per each stands of the finishing rolling mill and control continuation times after entrance into each stands from the calculated estimated off-gauge amount and the estimated off-gauge length; judging whether the material to be rolled reaches control initiation positions per each stands by tracking the proceeding state of the material to be rolled in the finishing rolling section of the hot rolling process; and narrowing a roll gap of the concerned stand as much as the calculated control amount, and returning the roll gap to the initial set value after the control continuation times calculated after the material to be rolled is entered into the concerned stand are elapsed when the material to be rolled reaches the control initiation positions per each of the stands.

Description

Thickness Control Method of Rolled Material Extreme Tip in Hot Finish Rolling Process

The present invention relates to a method of controlling the thickness of the extreme end of the rolled material in the finishing rolling process of the hot rolling mill, and more specifically, the roll gap is pressed by the thickness of the off gate before the rolled material enters each stand. The present invention relates to a method for controlling the thickness of a rolled material extreme end part in a hot finishing rolling process in which a roll gap is returned to a normal control set value when a top part of a rolled material is inserted into a normal control setting value.

In the finishing rolling process, as in the rolling material shown in FIG. 1, a plurality of rolling mills 1 are arranged in a line along the rolling material advancing direction, the roll gap of each rolling mill 1 is gradually reduced to a target value, and passed through rough rolling. It is an apparatus which produces the rolling material formed from the rolling material of predetermined thickness to a target thickness. At this time, each rolling mill of the finishing mill is referred to as a stand, and is referred to as a first stand F1, a second stand F2, ... n th stand Fn in this order from the entry direction. Then, the thickness of the rolling stand passing through the final stand (Fn) is fed back through the plate thickness measuring instrument (4), and the feedback control is performed to adjust the roll gap of each rolling mill to obtain a target thickness compared to the target value. .

In the hot finishing rolling, the temperature distribution in the longitudinal direction of the rolled material and the extreme end of the rolled material are the best in each rolling mill because the cooling of the tip end occurs more rapidly during the cooling of the material through the cooling zone after the rough rolling. Due to the tooth development of the rolling roll at the time of entry, a thickness defect at the extreme end of the rolling material occurs.

In addition, as in the rolled material shown in FIG. 1, a distance difference (about 3 to 4 m) from the final stand Fn to the plate thickness gauge 4 is generated, so that the feedback thickness is formed at the extreme tip 3 to 4 m of the rolled material. No control is made.

Conventionally, in order to prevent the thickness defect of the extreme tip part by the temperature nonuniformity of each part of such a rolling material, the rolling material which heats a rolling material so as to maintain a uniform temperature in the width direction and the longitudinal direction of a rolling material at the entrance side of a finishing rolling process. A method of uniformizing the temperature distribution of the rolled material by using a bar heater device (not shown) is used. However, this requires a huge cost to install the device. There were problems such as narrow installation site due to various existing equipments such as an edge heater, crop shear, and scale breaker.

In addition, since the off-gauge generation amount and off-gauge generation length for each steel grade or size are different, it is difficult to know this in advance.

For this reason, in the prior art, the extreme tip portion, which is a poor thickness part, is cut to about 3 to 5 m and about 7 to 8 m in length and is sent to the demand price. As a result, the increase in the amount of correction of hot rolling and the demand delay in delivery, lower error rate, and uncut material The demand for this has led to dissatisfaction.

The present invention has been proposed in order to solve the above conventional problems, and its object is to obtain temperature data of the rolling material at the inlet of the finishing mill, and calculate the control amount by calculating the expected off gauge length and the expected off gauge length after rolling. The initial roll gap is set on the basis of the top part, and the roll gap is pressed as much as the control amount before the roll material enters each stand, and then the roll gap is returned to the normal value to affect the thickness of the top part. It is to provide an extreme tip thickness control method in the hot filament rolling process that can prevent the thickness of the extreme tip portion, which is an abnormal portion, to be thickened without giving.

1 is a process chart showing a conventional thickness control method in a finishing mill.

2 is a process chart for explaining a method for controlling the extreme tip thickness of a plate according to the present invention in a finishing mill.

Figure 3 is a graph showing the thickness of the plate passed through the conventional finishing mill for each length.

Figure 4 is a graph showing the thickness of the rolled plate after the control method of the present invention is applied.

5 is a timing diagram showing a control flow according to the present invention in a finishing mill.

FIG. 6 is a flow chart sequentially showing a method of controlling the extreme tip thickness in a finishing mill according to the present invention.

Explanation of symbols on the main parts of the drawings

10: temperature measuring instrument

20: Crop Sheer

30: hot finishing mill

40: plate thickness meter

50: finishing rolling controller

In order to achieve the above object, the present invention provides a pressure measuring apparatus in a hot finishing rolling process in which a temperature measuring instrument is installed at an inlet side of a finishing mill consisting of a plurality of stands, a plate thickness meter is installed at an outlet side, and a roll gap of each rolling mill is set to an initial value. In the material extreme tip thickness control method,

(A) In the data table divided by steel grade, thickness, width, etc., it is determined whether control is performed for each stand in consideration of the mailability of the rolled material, and accumulated by steel grade, thickness, and width. Doing;

(B) if the rolled material is determined to be controlled, continuously obtaining the temperature of the tip of the rolled material through a temperature measuring device at the entrance of the finishing mill;

(C) calculating an estimated off gauge amount and an estimated off gauge length using a deviation between the temperature of the tip portion and the top temperature measured in step (b);

(D) calculating the control amount for each stand of the finishing mill and the control duration after entering each stand from the frost off gauge amount and the estimated off gauge length calculated in the step (c);

(E) tracing the progress of the rolled material during the finishing pressure study of the hot rolling process to determine whether the rolled material has reached the control start position for each stand;

(F) When the rolled material reaches the control start position of each stand, the roll gap of the stand is narrowed by the control amount calculated in the above step (d), and the roll gap after the control duration calculated after the rolled material enters the stand. It characterized by comprising the step of returning to the initial set value.

Hereinafter, with reference to the accompanying drawings will be described in detail with respect to the extreme tip thickness control method in the finishing mill according to the present invention.

2 is a process schematic diagram of the finishing rolling process to which the control method according to the present invention is applied, wherein 10 is a temperature for continuously measuring the temperature of the rolled material which is installed at the entry side of the finishing mill 30 and proceeds to the finishing mill 30. It is a measuring machine, 20 is a cropping machine which is a cutting equipment provided between the temperature measuring device 10 and the finishing mill 30, 30 represents a finishing mill consisting of a plurality of stands (F1 ~ Fn) each provided with a rolling mill, 40 is a plate thickness meter installed on the rolled material exit side of the finishing mill 30 to continuously measure the thickness of the rolled material, and 50 is an off gauge amount from the temperature distribution measured from the temperature detector 10 according to the present invention. The finishing rolling controller which predicts length and performs roll gap adjustment control of the stands F1-Fn to which a rolling material will enter according to the operation time of the crop shear 20 and each stand F1-Fn is shown.

6 is a flowchart sequentially showing a method of controlling the extreme tip thickness of the rolled material in the finishing mill according to the present invention described above.

The control operation according to the present invention in the above-described finishing rolling facility will be described with reference to the flowchart of FIG.

In the first step (601), the control object is determined in consideration of the influence of the steel grade and size of the rolled material on the rolling sheetability.

In other words, a data table divided by steel grade, thickness, and width is prepared, and it is determined whether to perform control for each stand (F1 to Fn) in consideration of the rolling plateability during hot rolling, and then accumulate by steel grade, thickness, and width. It is determined whether the material to be controlled when rolling the rolled material.

When the rolled material is determined to be controlled, the temperature of the rolled material is measured at a predetermined period (for example, 0.01 second period) in the temperature measuring device 10 installed at the entrance of the finishing mill 30 in the second step 602. The longitudinal temperature data is obtained at the tip, and the estimated off gauge amount of the material, that is, the thickness defect size, is obtained therefrom.

The method of calculating the expected off gauge amount is as follows.

From the temperature data of the rolling material measured at the set period (0.01 second period), the estimated off-gauge amount in the coil state of the corresponding material is obtained by calculating the temperature of the top part and the temperature of the abnormal part in the water cooling section temperature drop formula shown in Equation 1 below. The temperature in the rolling section for the top and abnormal parts is obtained by.

The rolling load RF obtained for the top and abnormal portions is determined by the usual rolling load calculation formula for the temperature of the rolling section thus obtained.

From the rolling load difference (ΔRF) of the top part and the abnormal part obtained as described above, an expected off gauge amount (defect thickness) is obtained by the following equation (2).

In the above, M is the elastic deformation coefficient (Ton / mm).

Then, when the rolled material is determined to be controlled, the expected off gauge length of the material is calculated from the longitudinal temperature data at the tip of the rolled material measured at the 0.01 second period in the temperature measuring device 10.

The expected off gauge length calculation process calculates the time difference between the temperature of the top part and the temperature of the abnormal part from the temperature data of the rolling material measured at 0.01 second intervals, and substitutes it into the following Equation 3 to obtain the pressure before entering the finishing mill 30. The length of the off gauge in the serial state is obtained in mm.

In Equation 3, ΔT is the time difference (sec) between the temperature of the top portion and the temperature of the abnormal portion, and Vbar is a rolling material feed rate (290mpm).

The estimated off gauge length in the coil state is obtained by substituting the off gauge length in the rolled material state thus obtained into the following expression (4).

Then, the roll gap control amount to be controlled by each of the n stands F1 to Fn from the off gauge amount (defect thickness size) of the rolled material obtained in the next third step 603 is obtained by the following equation (5), From the calculated off gauge length, the control length at each stand F1 to Fn is obtained by the following Equation 6, and the time for continuing the extreme tip thickness control at each stand F1 to Fn is represented by the following equation. Obtained by Equation 7.

In Equation 5, S denotes a roll gap, n denotes the number of the corresponding stand, ΔSn denotes the roll gap control amount (μm) at the nth stand Fn, and Mn is the elasticity at the nth stand Fn. Strain coefficient (Ton / mm), Qn is the nth stand (Fn) plastic strain coefficient (Ton / mm), ΔH is the amount of off gauge to be controlled (μm), Gn is the nth stand (Fn) Gain applied.

In Equation 6, Ln is a controlled length (mm) at the nth stand Fn, ΔL is an off gauge length (mm), and Hn is an exit thickness (mm) of the nth stand Fn. .

In Equation 7, Tn is the control duration (ms) of the nth stand (Fn), Ln is the control length (mm) of the nth stand (Fn), Vn is rolling of the nth stand (Fn) Speed (mpm).

Then, the roll gap control amount ΔSn and the control duration ΔTn for each stand F1 to Fn obtained as described above are transmitted to the controller 50 which controls the thickness of the actual finishing mill 30. .

Then, in the fourth step 604, in the finishing rolling controller 50 in which the control value calculated as described above is inputted, the progress of the rolling material is traced between the finishing pressure studies to determine whether the rolling material has reached a predetermined control start position. To judge. At this time, the control start position is before the rolled material enters the stand, the first and second stands (F1, F2) is the point at which the front end of the rolled material is cut at the crop shear 20, the third stand (F3 ~ After Fn), it is time to enter the electric stand (Fn-2) of the stand.

In a fifth step 605, when the tip portion of the rolled material reaches the control start position for each stand F1 to Fn in the comparison, the calculated control amount at the corresponding stands F1 to Fn ( [Delta] Sn adjusts the roll gap as much as possible and maintains the state in the sixth step 606 by the set control duration [Delta] Tn. That is, it is maintained until the off-gauge part of the rolling material passes completely.

Then, in the last step 607, the progress of the rolled material is continuously tracked to determine whether the predetermined control duration has elapsed, and if the rolled material enters the nth stand Fn and the off gauge part passes completely, the stand The roll gap of (Fn) is returned to an initial setting value (roll gap setting value at a normal position).

As described above, after the roll gap is returned to the initial setting state, the feedback value measured from the plate thickness meter 40 provided on the exit side of the finishing mill 30 is input according to the conventional rolling thickness control method and reaches the set target value. The roll gap is feedback controlled.

FIG. 5 is a timing diagram showing the operation timing of each device of the finishing rolling facility shown in FIG. 2 when the control method according to the present invention is applied. According to the present invention, steel grades of the material to be rolled provided before the starting of finishing rolling are shown. The roll gap setting values of the rolling stands F1 to Fn are calculated from the thickness, the width, and the target thickness values, and the roll gaps of all the stands F1 to Fn are initialized to the setting values. In this state, at the time of the metal in which the rolled material enters the n-2nd stand (t1), the roll gap is reduced by the thickness control amount (ΔSn) of the extreme tip portion calculated at the nth stand, so that the rolled material enters the nth stand. When the duration ΔTn calculated by the equation (7) has elapsed from the time point t2, the roll gap is returned to the initial setting value.

The above operation is repeated for each stand until the thickness meter (that is, the plate thickness meter 40) is operated, thereby controlling the extreme tip thickness of the rolled material.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example

The thickness of the rolled material inserted into the finishing mill is 2.3 mm, the off-gauge amount obtained from the temperature difference between the top part and the abnormal part like the rolled material described above is 200 µm, the off-gauge length is 4000 mm, and the elastic modulus per stand is 420 to 555 (Ton / mm). ), The plasticity coefficient of each stand is 193 to 484 (Ton / mm), the exit thickness of each stand is 15.4 to 2.3mm, the speed by stand is 93 to 642mpm, the gain by stand is 0.85 to 1.4, workability For example, consider the case where the stand to be applied is 1 to 4 stands.

According to Equation 5, the roll gap control amount for each stand is 396 μm for the first stand F1, 395 μm for the second stand F2, 400 μm for the third stand F3, and 400 μm for the fourth stand F4. 300 μm, and according to Equation 6, the control length for each stand is 594 mm for the first stand (F1), 1023 mm for the second stand (F2), 1583 mm for the third stand (F3), and the fourth stand (F4). ) Was calculated as 2440mm, the control duration for each stand according to the equation (7) stands 383ms 1st stand (F1), 376ms 2nd stand (F2), 372ms 3rd stand (F3), 4th stand ( F4) was calculated to be 379 ms.

Accordingly, the first and second stands (F1, F2) were 396㎛, 395㎛ narrower than the initial gap when the rolling material reaches the crop shear, respectively, 0.383 seconds after the rolling material is inserted into the stand After 0.376 seconds, the roll gap was returned to the initial setting gap, and when the rolled material reached the first stand F1, the roll No. 3 narrowed the roll gap 400 µm from the initial setting gap, and the rolled material entered the stand. After 0.372 seconds, it returns to the initial setting gap, and when the rolled material reaches the stand F2, the fourth stand (F4) narrows the roll gap by 300 µm from the initial set gap, and then the rolled material is inserted into the corresponding stand. After 0.379 seconds, it returns to the initial setting gap.

In this way, the actual thickness chart which showed the state which the pole tip part of the board was controlled, and the thickness chart at the time of not applying this invention are shown in FIG. 4 and FIG. 3, respectively.

Figure 3 is a graph showing the thickness of the rolled rolling material when the thickness control of the extreme tip portion according to the present invention is not applied, as shown in the rolled material, at about 0.1 second intervals (about 1 m interval) from the extreme tip It can be seen that the result of measuring the thickness has a large difference such as 411 μm, 233 μm, 141 μm, etc., when compared with the normal range (26 μm).

On the contrary, FIG. 4 is a graph showing the thickness of the far-end rolled rolled material extreme tip when the thickness control of the extreme tip according to the present invention is applied, and the thickness error of the extreme tip is 113 µm, 41 µm, -15 µm, or the like. It can be seen that it is reduced to almost normal range.

Like the above-described rolled material, the present invention relates to a method for controlling the thickness of the rolled material extreme end portion in the finishing rolling process of a hot rolling mill, which is caused by non-uniform temperature distribution in the length direction of the rolled material during hot rolling. By preventing the thickness defect of the extreme tip, which is an abnormal part, the cutting process of the defective part can be omitted, which can reduce the amount of correction work of hot rolling, thereby contributing to shortening the delivery time of the demand and improving the error rate. The demand for uncut material in defective areas has an excellent effect of resolving the complaints caused by delivery.

Claims (4)

In the method of controlling the extreme thickness of the rolled material in the hot finishing rolling process in which a temperature measuring instrument is installed at the inlet side of the finishing mill consisting of a plurality of stands, a plate thickness meter is installed at the exit side, and the roll gap of each rolling mill is set to an initial value. (A) In the data table divided by steel grade, thickness, width, etc., it is determined whether control is performed for each stand in consideration of the mailability of the rolled material, and accumulated by steel grade, thickness, and width. Doing; (B) if the rolled material is determined to be controlled, continuously obtaining the temperature of the tip of the rolled material through a temperature measuring device at the entrance of the finishing mill; (C) calculating an estimated off gauge amount and an estimated off gauge length using a deviation between the temperature of the tip portion and the top temperature measured in step (b); (D) calculating the control amount for each stand of the finishing mill and the control duration after entering each stand from the frost off gauge amount and the estimated off gauge length calculated in the step (c); (E) tracing the progress of the rolled material during the finishing pressure study of the hot rolling process to determine whether the rolled material has reached the control start position for each stand; (F) When the rolled material reaches the control start position of each stand, the roll gap of the stand is narrowed by the control amount calculated in the above step (d), and the roll gap after the control duration calculated after the rolled material enters the stand. Method of controlling the thickness of the rolled material extreme end portion in the hot finishing rolling process comprising the step of returning to the initial set value. The method of claim 1, wherein step (b) Detecting the tip temperature of the rolled material at predetermined intervals, Step (c) Substituting the temperature measurement value of the tip portion measured in step (b) into the following equation, Calculating a temperature drop amount in the water cooling section in the water cooling section, Calculating the rolling load at the tip and the rolling load at the top from the temperature in the rolling section calculated by the temperature drop; The calculated rolling load of the tip and the rolling load difference (ΔRF) of the top (M: elastic deformation coefficient (Ton / mm)) Here, the step of calculating the expected Off-Gauge amount (ΔH) by substituting for, Through the temperature data measured in step (b) as follows: Where ΔT is the time difference between the temperature of the top part and the temperature of the abnormal part (sec), Vbar is the feed rate of the rolled material (290mpm), and the off gauge length in the rolled state is obtained. The method of controlling the thickness of the rolled material extreme end portion in the hot finishing rolling process, comprising the steps of: obtaining an expected off gauge length in a coil state. The method of claim 1, wherein step (d) From the off-gauge of the rolling material obtained in the step (c), (In the above, n: stand number, Mn: n stand elastic modulus (Ton / mm), Qn: n stand plastic deformation coefficient (Ton / mm), ΔH: off gauge amount to be controlled (μm), Gn: obtaining a roll gap control amount to be controlled for each stand by n stand gain; And From the off gauge length obtained in the above step (c), After the control length is determined by (Ln: n stand control length (mm), ΔL: Off-Gauge (mm thickness) length (mm), Hn: n stand exit thickness (mm)), the control length from, The control duration for each stand is calculated according to the above (ΔTn: n stand control duration (ms), Ln: n stand control length (mm), Vn: n stand rolling speed (mpm)). Rolling material pole tip thickness control method in the hot finishing rolling process, characterized in that it comprises a step. According to claim 1, wherein the control start position for each stand in the step (e) is Before the rolled material enters the stand, stand No. 1 (F1) and stand No. 2 (F2) are the point at which the tip of the rolled material is cut at the crop shear located between the rolling mill and the temperature measuring instrument. Fn) and the rolling material pole tip thickness control method in the hot finishing rolling process, it characterized in that it is the time to enter the electric stand (Fn-2) of the stand.