JPH01210111A - Plate thickness control method for hot finish rolling - Google Patents

Abstract

PURPOSE:To roll a strip into uniformized plate thickness even if the deformation resistance of the innermost diameter is changed stepwise by obtaining the plasticity constant of the sheet bar from plate thicknesses and rolling loads at the inlet and outlet sides, then by obtaining plate temps. CONSTITUTION:In the stage of finish rolling, the innermost diameter part 1a of the hot sheet bar coil 1, the position of this innermost diameter part 1a is grasped and the plasticity constant of the sheet bar 21 is obtained from the inlet and outlet sides plate thicknesses and the rolling loads, when the innermost diameter part 1a reaches the (i)th stand, then the plate temp. is obtained. Based on this plate temp., an estimated temp. drop pattern of each stand is corrected, the plasticity constant is corrected through these corrected values, and the position of the rolling reduction on and after (i+1)th stands are corrected by a gauge meter equation. Thereby, even if the deformation resistance at the innermost diameter part is changed stepwise, the strip having the uniformized plate thickness is enabled of rolling to contribute to improve the yield rate and quality of the product.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for controlling plate thickness in hot finish rolling,
In particular, when a roughly rolled hot sheet bar is wound up with a coiler and then unwound and finished rolled, it is useful to improve the thickness accuracy of the innermost diameter part of the hot sheet bar coil wound up with the coiler. The present invention relates to a suitable plate thickness control method.

<Prior art> - In a method of hot rolling a sheet bar made of steel or the like,
During the processing steps from rough rolling to finish rolling, the hot sheet bar dissipates some of its retained heat into the atmosphere. The amount of heat dissipated is from the tip (LH) and tail end (TE) of the seat bar.
), and for example, as shown in Figure 5, the tail end (TE) is colder than the tip end (Ll).If the temperature distribution of the hot sheet bar is uneven in this way, There is a problem that it is difficult to adjust the rolling reduction value R111J of the finishing rolling mill, and it is not possible to roll a sheet bar of good quality.

In order to improve such problems, as disclosed in Japanese Patent Publication No. 50-30028, Japanese Patent Publication No. 51-26317, Japanese Patent Publication No. 52-45304, Japanese Patent Publication No. 53-16380, etc. , a method has been proposed in which a coiler is provided between a rough rolling mill and a finishing mill.

To explain such a technique in detail, as shown in FIG. 6, the rolling equipment includes a method for winding and unwinding a hot sheet bar 21 between a rough rolling mill 20 and a rolling mill 24. A coiler 23 is provided. The hot sheet bar 21 transferred on the conveyance table roller 22 is transferred to the -tan coiler 2.
By winding the hot sheet bar 21 into a coil shape, the entire length of the hot sheet bar 21 is kept warm and heated by the heat possessed by the hot sheet bar 21 itself. The soaked hot sheet bar 21 is rewound and sent to a finishing mill 25 consisting of a plurality of stands with the tail end TE at the time of rough rolling as the head, where it is finish rolled into a strip. It is.

<Problems to be Solved by the Invention> However, in the above-mentioned conventional example, the temperature distribution of the hot sheet bar 21 can be generally improved and uniform heating can be achieved; While the bar 21 is being heat-retained and equalized, the innermost diameter portion of the coil of the hot sheet bar 21 (near the tip LH during rough rolling) is exposed to the atmosphere, and heat radiation progresses. Therefore, when we measured the temperature distribution of the hot sheet bar 21 on the 25-man side of the finishing mill, we found that most of the hot sheet bar 21 was at a uniform temperature, as shown in Figure 7, but the tip part It was found that the temperature of the first turn at the innermost diameter portion including LH showed a rapid decrease.

As a result, when finish rolling the hot sheet bar 21,
The deformation resistance of this portion where the temperature is decreasing increases in a stepwise manner compared to other portions. Therefore, in order to cope with this deformation resistance, the rolling position of the finishing rolling mill 25 is controlled by an automatic plate thickness control device f (hereinafter referred to as AGC).
However, since the AGC has a response delay, it is unable to follow the step-like change in deformation resistance, and the thickness of the strip corresponding to the innermost diameter part after finish rolling is different from that shown in FIG. It is about 100 μm thicker than the other parts, and there has been a problem that the plate thickness accuracy cannot be ensured.

By the way, as a means to solve such problems, the present applicant has already proposed in Japanese Patent Application No. 191730/1986 the amount of temperature drop at the innermost diameter part of a wound coil, and The present invention proposes a plate thickness control method that corrects the rolling position of the finishing rolling mill based on the steel type data and the predicted temperature drop amount when the innermost diameter portion reaches the finishing rolling mill. There is.

However, in predicting temperature drop using this method, it is necessary to use the measured value of the rough rolling mill exit temperature or finish rolling mill entrance temperature of the hot sheet bar as the starting point for the prediction calculation, so the following method is used: There is a problem.

In other words, a radiation thermometer is generally used to measure the temperature of a hot sheet bar, but the reheating state of a hot sheet bar changes depending on its thickness and temperature measurement time, and the roll coolant water It is undeniable that measurement errors occur in radiation thermometers due to changes in measurement conditions such as the amount of water in the water and the occurrence of surface scale, and this error becomes an error in the reduction correction amount, so accurate corrections can always be made. is difficult to do.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a method for controlling plate thickness in hot finish rolling with good plate thickness accuracy.

Means for Solving the Problems> In order to achieve the above object, the present invention involves rolling up a roughly rolled hot sheet bar with a coiler to form a coil, and then unwinding and finishing rolling with a finishing rolling mill. In the actual plate thickness control method, the tip side position of the innermost diameter part of the coil is grasped, and when this tip side position reaches the L stand of the finishing rolling mill, the performance at the entry and exit sides of this L stand is determined. The plastic constant of the sheet bar is determined using the plate thickness and actual rolling load, then the plate temperature is determined from the relationship between the plastic constant and plate temperature given in advance, and the predicted temperature drop pattern for each stand is calculated based on this plate temperature. is corrected, and the plastic constant is further corrected from these corrected values, and the rolling position of the finishing mill after the (++1) stand is corrected based on the gauge meter formula.

The configuration of the present invention will be specifically described below with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the method of the present invention. In FIG. 1, the same members as in the conventional example are designated by the same reference numerals and their explanations will be omitted.

In the figure, 1 is a coil of the hot sheet bar 21 wound up by a coiler 23, and 2 is a length measuring device for measuring the diameter of the innermost diameter portion 1a of the coil 1.

3 is a hot piece detector (hereinafter simply referred to as HMD) for ascertaining the position on the tip side of the innermost diameter portion 1a of the coil 1;
It is provided between the coiler 23 and the black rolling mill 24 and at a distance of Ll from the finishing mill 25.

4 is a length measuring pinch roll for measuring the length of the hot sheet bar 21;
and at a distance of from the finishing mill 25. For example, this length measuring pinch roll 4 has a
A pulse generator 5 that outputs pulses is connected.

Here, the circumferential length of the innermost diameter portion 1a of the coil l can be expressed by the following equation, assuming that the diameter of the innermost diameter portion 1a is D.

L・tD・・・・・・・・・・・・・・・= 0)
Therefore, in order to detect that the tip side of the innermost diameter part 1a of the coil 1 has reached the entry side of the finishing mill 25 after detecting the tail end (TE) of the hot sheet bar 21, it is necessary to detect at least the innermost diameter part 1a of the coil 1. It is necessary that the pulse transmitter 5 be able to track the progress until the tip of the portion 1a reaches the finishing rolling mill 25.

Therefore, the distance #L8 between the length measuring pinch roll 4 and the finishing roll 8!25 is relative to the circumference of the innermost diameter portion 1a.
<L, and the HMD 3 is installed at the distance i! between the position and the finishing rolling mill 25! 1ILl is selected as >L for the circumferential length.

Reference numeral 6.7 denotes plate thickness gauges for measuring the thickness of the hot sheet bar 21, which are installed at the entrance and exit sides of the l stand (the first stand in the figure) of the finishing rolling mill 25, respectively. A side plate thickness signal h・ and an exit side plate thickness signal h+ are transmitted.

Reference numeral 9 denotes a tracking device, which inputs the detection signal of the HMD 3 and the pulse signal from the pulse transmitter 5, and grasps the position of the innermost diameter portion 1a of the coil 1.

This tracking device 9 has distances Ll and L8 in advance.
The number of pulses of the pulse transmitter 5 from when the tail end is detected by the HMD 3 until the tip side of the innermost diameter portion 2 reaches the finishing rolling mill 25 is input as the pulse setting value P, based on the Then, the pulse transmitter 5 starts counting pulses based on the detection signal of the HMD 4, and after the count value matches the pulse setting value, a measurement command is output to the plate thickness gauge 6.7.

Further, the pulse setting value P is calculated by subtracting the circumferential length from the distance Ll as shown in the following equation (2) to calculate the moving distance Lm of the hot sheet bar 21, and this is shown in the following equation (3). It can be calculated by dividing by the circumferential length of the length measuring pinch roller 5 as follows.

L,・L,・L・・・・・・・・・・・・(2)P
! = L 3 / LP ・・・・・・・・・
- (3) 1O is an AGC that automatically controls the thickness of the hot sheet bar 21 to the final strip thickness by controlling the rolling position of each stand of the finishing rolling mill 25, and is Based on various rolling command signals and tracking signals from the tracking device 29, the l stand is
i+1) Calculate the correction value ΔS of the reduction amount after the stand and perform correction control of the reduction position.

The host computer 11 controls the entire rolling line,
Thickness of the hot sheet bar on the exit side of the rough rolling mill, time from the start of winding of the hot sheet bar in the coiler to the end of unwinding, surface temperature of the hot seed bar on the exit side of the rough rolling mill, steel type of the sheet bar data.

Rolling load P of the innermost diameter portion 1a of the coil in the l stand,
It has a function of determining the plastic constant m of the hot sheet bar 21 by inputting the board thickness ha and h+ of the i-stand person and exit side, respectively, and outputting it to ACCIO.

That is, the host computer 11 stores a characteristic curve A between the plastic constant m and the plate temperature T as shown in FIG.
Using the plate temperature obtained here, for example, 1 as the calculation starting point, predict the temperature drop in each stand of the finishing rolling mill 25 as shown in pattern B in Figure 3, and calculate the plastic constant m corresponding to that temperature using the ACCIO It gives instructions.

<For production> The operation of the present invention will be explained below.

(1) The diameter of the innermost diameter portion 1a of the coil 1 wound by the coiler 23 is measured with a length measuring device, and the tracking device 9
In this step, the inner circumference length is determined using equation (1), and the tracking start point is determined.

(2) The coil 1 is unwound by the coiler 23, the tip of the hot sheet bar 21 is sheared by the crop shear 24, and the length is measured by the length-measuring vinyl roll 4 and sent to the finishing mill 25 to form a strip. is finished rolled.

(3) When the tail end of the hot seat bar 21 is detected by the HMD 3, the tracking device 9 starts tracking the tip side of the innermost diameter portion 1a. When the output pulse of the pulse transmitter 5 reaches a preset pulse setting value P, a command to measure the thickness of the hot sheet bar 21 is output to the thickness gauge 6.7, and the input of the i-stand is performed. The side plate thickness signal hi and the exit side plate thickness signal hi are input to the host computer 11.

Further, the rolling load signal P, at that time is also inputted from the load cell 8 at the same time.

(4) In the upper computer 11, first, the following (4)
According to the formula, the plastic constant m of the hot sheet bar 21 at that time,
Calculate.

m + ・P + / (ho ・h t )
・・・=・(4) Furthermore, from the obtained plastic constant m, find the true plate temperature TI according to the characteristic curve A in Fig. 2,
The temperature prediction for each stand is revised from pattern B to pattern C shown in FIG.

(5) Now, assuming that the predicted temperature in pattern B is 1 at stand (i+1), pattern C
If the predicted temperature obtained by is T2, this difference Δ
Only T (-T, -7) will be modified.

Therefore, again in FIG. 2, the plastic constant m! is determined based on the predicted temperature T, and is output to ACCIO.

(6) In ACCIO, the reduction position correction amount ΔS of the (i+1) stand is calculated using the gauge meter equation of equation (5) below.

ΔS Δh・(,M + m z) / M・・・・(
5) Here, Δh - (s@+P/M), IiM: Mill constant S,: Roll gap 52 Output side target plate thickness (7) The obtained reduction position correction amount ΔS is tracked by the tracking device 9. Signal i.e. hot sheet bar 2
The part corresponding to the tip side of the innermost diameter part 1a of 1 is (i+1)
When reaching the stand, (i+1) correct the lowered position of the stand.

(8) Regarding the (i + 2) stand and beyond,
Similarly, the reduction is corrected by steps (5) to (7) above.

In addition, the innermost diameter part 1 of the coil l after the (i+1) stand
The tracking method for a can be easily carried out as follows by using the constant mass flow law.

That is, it is assumed that the finishing rolling mill 25 is composed of six stands, the interval between each stand is L, the roll circumferential speed at the final sixth stand is vh, the advance rate is f, and each stand output is The side plate thickness is h5 (= S05
+ PIiM5, i: 1-6)
Ru.

Further, the plate thickness gauge 7 on the exit side of the first stand is placed at a distance of l from the second stand.

Now, if the board speed at the exit side of the 6th stand is ■,
It is expressed by the following formula.

V chick V,・f.

Therefore, the time 1. from when the hot sheet bar 21 is rolled on the first stand and its tip passes the plate thickness gage 7 until it reaches the second stand is 1. is determined by the following formula.

1,=2・(hl/h&)/V Similarly, the time to reach the 3rd to 6th stands, ~t, is
Each is calculated as follows.

ts=t! + L ・(hz/ hh)/
vt 4- t s+ L ・(hs/ha)/
Vt s= t a+ t, ・<ha/h h
＞/Vth-ti+L'<hslhh>/v<
Examples> Next, the results of rolling by the method of this invention will be described below.

The material used for rolling was 5OS304, and the coiling thickness of the hot sheet bar coil wound by the coiler was 30.
6111, the circumference of the innermost diameter part is approximately 2 m, and the thickness and width of the rolled finished product strip are each 4.0 ms.
, 950 am. As a result of measuring the variation in the thickness of the strip product in the longitudinal direction, the data shown in FIG. 4 was obtained.

As is clear from this figure, it was confirmed that the plate thickness variation at the position corresponding to the innermost diameter portion 1a of the hot sheet bar 21, which had been a problem in the past, was within about 25 pm.

Therefore, the conventional thickness variation of 100 μm as shown in Fig. 8 has been reduced to 25 μm thickness variation of X, significantly improving plate thickness accuracy compared to the conventional example. was completed.

<Effects of the Invention> As explained above, according to the present invention, when finishing rolling the innermost diameter part of a hot sheet bar coil, the position of the innermost diameter part is grasped, and the innermost diameter part is placed in the finish rolling mill. When the i-stand is reached, the plastic constant of the sheet bar is determined from the plate thickness and rolling load on the i-stand person/exit side, then the plate temperature is determined, and the predicted temperature drop pattern for each stand is corrected based on this plate temperature. However, since the plastic constant was corrected from these corrected values and the rolled position after the (i+1) stand was corrected using a gauge meter method, even if the deformation resistance at the innermost diameter part changes in a stepwise manner, It becomes possible to roll strips of uniform thickness, contributing to improved product yield and quality.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one embodiment of the method of the present invention, Fig. 2 is a characteristic diagram showing the relationship between plate temperature and plastic constant during finish rolling, and Fig. 3 is a diagram showing the relationship between plate temperature and plasticity constant during finish rolling. FIG. 4 is a characteristic diagram showing the temperature prediction pattern; FIG. 4 is a characteristic diagram showing the strip thickness variation distribution when the method of the present invention is carried out;
The figure is a characteristic diagram showing the temperature distribution of the hot sheet bar at the entrance side of the finishing rolling machine, Figure 6 is a configuration diagram schematically showing a conventional example, and Figure 7 is
FIG. 8 is a characteristic diagram showing the temperature distribution of the hot sheet bar at the entrance side of the finishing rolling machine in the conventional example, and FIG. 8 is a characteristic diagram showing the strip thickness variation distribution in the conventional example. 1...Coil, la...Innermost diameter part. 2... Length measuring device, 3... HMD (hot piece detector). 4...Pinch roller for length measurement. 5...Pulse transmitter, 6.7...Plate thickness gauge. 8...Load cell, 9...Tracking device. 10...AGC (automatic plate thickness control device). 11... Upper computer, 20... Rough rolling mill. 21...Hot sheet bar, 23...Coiler. 24... Crop shear, 25... Finishing rolling mill. Patent Applicant Kawasaki Steel Corporation Figure 1 Figure 2 Figure 3 Figure 4 Strip tip Stritz tail Figure 5 Hot seat bar Figure 6

Claims (1)

[Claims] In a sheet thickness control method when a roughly rolled hot sheet bar is wound up with a coiler to form a coil, then unwound and finished rolled with a finish rolling mill, the tip side position of the innermost diameter part of the coil is grasped. , when this tip side position reaches the i-stand of the finishing rolling mill, the plastic constant of the sheet bar is determined using the actual plate thickness and actual rolling load at the entry and exit sides of this i-stand, and then The plate temperature is determined from the relationship between the plastic constant and the plate temperature, and the temperature drop prediction pattern for each stand is corrected based on this plate temperature.The plastic constant is then corrected from these corrected values and calculated using the gauge meter formula. A method for controlling plate thickness in hot finishing rolling, characterized in that the rolling position of a finishing mill after the (i+1) stand is corrected based on the above.