JPH01262011A - Controlling method for sheet width in hot rolling - Google Patents

Abstract

PURPOSE:To control the sheet width of a rolled stock with high precision by correcting width strain caused by the tension distributed in a width direction acting on the rolled stock and controlling the tension corresponding to a corrected targeted sheet width. CONSTITUTION:When the rolled stock passes between stands i-1, i, it receives plastic deformation and is deformed in width near the inlet side of the rolling mill. A tension distribution generated at this time is estimated and operated, a quantity of width strain caused by it is calculated by an arithmetic processing unit 3 and its gradient is controlled by a tension-controlling louver 2 through a motor M. A quantity of local strain on the inlet side of a roll bite is modified and the tension corresponding to a targeted sheet width is corrected to set the targeted sheet width. In this way, the sheet width of the rolled stock can be controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for controlling strip width in tension rolling using a hot tandem rolling mill, a hot reversible rolling mill, or the like.

[Conventional technology]

Recently, the proportion of materials that tend to fluctuate in strip width during hot finish rolling, such as ultra-low carbon steel for processing, has been increasing, and customers' requirements for strip width precision for rolled materials (strips) have become more stringent. Steel manufacturers also need to improve yields, so there is an urgent need to realize more advanced strip width control.

It has been empirically found that the width of the rolled material can be changed by controlling the tension between the stands, so the width control of the rolled material that has been practiced or proposed in the past is as follows:
Either set the target strip width, set the tension corresponding to this target strip width, and feedforward control the tension between the stands so that the set tension is obtained, or use the actual value of the strip width at the exit side of the rolling machine and the target strip width. The basis of sheet width control by tension rolling is to feedback control the tension between the stands according to the deviation from the stand.

[Problem to be solved by the invention]

By the way, the width deformation behavior during hot tension rolling cannot be explained from the consideration that 11] shrinkage occurs depending on the stress conditions within the roll bite (Japanese Patent Application No. 143288/1988). Consideration that width deformation is greatly influenced by the passing time between stands (Patent Application 1986-1049)
There are various theories such as (No. 71 Publication), and there are still many unclear points. Therefore, in the conventional sheet width control described above, the target tension and control tension are based on the assumption that the tension distribution in the width direction of the rolled material is uniform. Since the above-mentioned width deformation behavior is essentially set by simply modeling it, there is a limit to the improvement in board width control accuracy.

The present invention was made to solve this problem.
It is an object of the present invention to provide a method for controlling a strip width in hot rolling, which can improve the control accuracy of the strip width and improve the yield of rolled material compared to the conventional method.

[Means to solve the problem]

In setting the target strip width on the exit side of a rolling mill, the present invention predicts and calculates the width direction tension distribution of the rolled material near the entry side of the rolling mill, and calculates the width direction tension distribution on the entry side of the rolled material based on the width direction tension distribution. According to a second aspect of the present invention, in this predictive calculation, the plate shape of the rolled material is taken into consideration, In claim 3, the width strain of the rolled material within the roll bite of the work roll of the rolling mill is calculated, and the target plate width is set in consideration of this width strain, furthermore, in claim 4, In this case, the configuration is such that the amount of local width reduction of the rolled material at the entrance of the roll bite is also taken into consideration.

[Effect]

The rolled material undergoes plastic deformation for a short time between the stands that it passes, and if a portion with high tension distributed in the width direction occurs, this will have a large effect on the width deformation of the rolled material near the entry side of the rolling mill, and the Even if the tension is the same, if the generated tension distribution differs, the amount of width shrinkage near the entry side of the work roll will change, and the amount of width deformation within the roll bite of the work roll will also change. In comparison with the case, in the present invention, the target plate width (therefore, the set tension) is the width reduction amount,
In addition, the local width shrinkage at the entrance of the roll bite is further corrected by an amount corresponding to the above width deformation.

〔Example〕

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows hv, i − in a hot tandem rolling mill.
1 stand and NOi stand, S is the rolled material, IU and ID are the upper and lower work rolls of the rolling mill, respectively, 2 is the louver for tension adjustment, and 3 is the control device that controls the rolling line ( The No. i stand tension calculation processing unit in the CPU) takes in multiple parameters, calculates the set tension according to the flow shown in Fig. 2, and supplies power to the motor M that adjusts the slope of the looper 2. A control command signal is sent to the motor control device 4 that controls the current.

Before explaining the operation of this embodiment, the basic principle of the present invention will be explained below with reference to FIGS. 8 to 17.

Figure 8 shows the results of a short-time plastic deformation test conducted using a hydraulic servo type hot fatigue tester. , Si
: 0.08, Mn: 0.36, AI: 0.004). As can be understood from this figure, the elongation strain is
The stress increases rapidly from the moment the stress is applied, and after about 1 second, it transitions to a steady deformation that shows a linear relationship when logarithmic time and logarithmic strain are plotted. Furthermore, the elongation strain varies greatly depending on the temperature and stress level.

Traditionally, it has been assumed that during a short period of time, such as the transit time between finishing stands, the creep phenomenon due to tension (a phenomenon in which the material gradually undergoes plastic deformation when a stress lower than the yield stress is applied for a long time) hardly occurs. However, the present inventors have discovered that plastic deformation (hereinafter referred to as short-time plastic deformation) occurs in an extremely short time even at a stress level as low as several kg f/mm2.

Figure 9 shows the changes in plate width derived from the results of tension rolling experiments conducted using plasticine, that is, the upstream stand (i-1 stand) of the Mi stand (referred to as the stand).
This figure shows the change in the width of the rolled material from (lift, i-1) to the exit of the stand i. , (No. 21, width reduction is rapidly accelerated in the area near the i-stand entrance.

The above (1) is due to the short-time plastic deformation under hot low stress mentioned above, and as shown in Fig. 10, the steel type, temperature,
Significantly depends on tension, etc. In the same figure, A', B, .
C, D and E indicate the steel type, and the respective alloying element contents are as shown in FIG.

In addition, the width shrinkage acceleration phenomenon in roll high 1-population of Section 2 (2) is caused by the tension distribution becoming uneven in the sheet width direction due to the influence of rolling in the i-stand. Based on the increase in size (see Figure 12), and also due to the plate shape, as shown in Figure 14,
This acceleration phenomenon occurs due to the non-uniform tension distribution.
As shown in FIG. 15, it is greatly influenced by the shape between the stands of rolling+A'S.

(3) Furthermore, a slight widening occurs within the roll bite.

The width change within this roll bite is usually a widening, but the inventors have found that the width change here also depends on the magnitude of tension, and width widening occurs when there is no tension. As shown in Figure 2, we found that as the tension increases, the width decreases and eventually shifts to width contraction.

From the above, rolled material undergoes plastic deformation for a short time between the stands it passes, and if a portion with high tension distributed in the width direction occurs, this will have a large effect on axial deformation, and even if the tension between stands is the same. Even if there is a difference in the tension distribution generated, the width shrinkage near the roll bite will change, and the axiality shape within the roll bite will also change, and this tension distribution will change depending on the rolled material S.
It is understood that this is affected by the shape of the plate.

Based on the above-mentioned insight based on the above-mentioned experimental results, the present inventors took into account the above-mentioned tension distribution and axial deformation within the roll bite when setting the tension to obtain the target exit plate width. The process will be explained below with reference to the flowchart shown in FIG.

The m and i stand tension calculation processing unit 3 in FIG.
Input the distance between the 1 stand and the Nni stand, the type of rolled material S (steel type), rolling temperature, rolling speed, input strip width, output target strip width, initial value of set tension, etc., and perform the calculations described below. Execute.

(1) Calculation of inter-stand transit time of rolled material The stand transit time t is calculated from the following equation (1), where I7 is the distance between the stands, and ■ is the rolling speed.

t = L / V・・・・・・・・・・・・・・・(
1) However, L: Distance between stands ■ = Rolling speed (2) Predicted shape of exit side plate from the nearest stand Whether the shape of the exit side plate is flat or medium elongated,
Or the ear wave shape can be determined by a known method [Publication "Plasticity and Processing" page 37.17-. 180° is determined using the method described in 1976).

(3) Time transition of the tension distribution in the width direction of the rolled material (al The tension distribution T in the width direction of the rolled material S due to the tension between stands To, maximum tension Tp, rolling + A' S plate width W is given as shown in Fig. 4. However, equation (2) applies when the plate shape is flat, and when the plate shape is medium elongated. Or if it is an ear wave shape,
The coefficient of x2 in the first term of equation (2) has the opposite sign.

tll) Next, the time course of this width direction tension distribution T iw), that is, the width direction tension distribution in the vicinity of one work roll person in the Nai stand is predicted.

In the vicinity of the stand, the tension acting on the rolled material S increases as it approaches the inlet of the work roll.If this is modeled as shown in Figure 5, (b-1) the rolled material S
When the shape of the plate between the stands is flat, the maximum tension Tp applied to the rolled material S up to the vicinity of the work roll entrance of the Nai stand is: -WO When O≦t〈□, TI)=T.

■However, near the work roll entrance, W
V ・ ・ ・ ・ ・ ・ ・ (3) It is given by.

(+) -2) When the plate shape is not flat, the maximum tension 'rp applied to the rolled material S up to the vicinity of the work roll entrance of the No. 1 stand is -W When ○≦t〈□, T p = To'' However, near the work roll entrance, x (t −-) ・・
(4) However, To''' is given by the maximum tension in the width direction when the plate shape is not flat.

(4) Prediction of width shrinkage of rolled material S due to tension between stands of 1゜ The width shrinkage Ew of the rolled material is generally given by the following formula (5), EW= A , TV , t2 ・ ・ ・
・ ・ ・ ・ ・ ・ ・ ・ (5) This width reduction amount E
Since W differs mainly depending on the steel type of the rolled material S (rolling temperature also influences), constants A, 31, and Z are determined for the steel type and rolling temperature, and the rolled material S is Divided into n directions, each divided element width Δχ,
No, i Calculate the width reduction amount ΔEW (++) at the stand work roll entrance.

ΔEw(Ll=A−T(fly−t2), where: Distributed tension acting on the i-th width direction dividing element width ΔX = W/n Therefore, the width shrinkage amount ΔW due to the inter-stand tension T.

Furthermore, Fig. 16 shows the measurement results of the time course of the width reduction. ○
The marks are predicted values according to this example.

(5) Prediction of the amount of width strain within the roll bite Next, the amount of width strain within the roll bite of the NOi stand work roll is predicted based on the following formula.

ΔW8-ΔB-eXp (C-T)...(8)
ΔB: Amount of width distortion when the tension is zero C: Constant (6) Prediction of exit side plate width If Wi is the input side plate width of the work roll of the stand, the predicted value of the output side plate width at inter-stand tension T is Wo”
is, Wo'=Wi+ΔW, +ΔWB ・・・・・・・・・(9)
becomes.

The tension value T is corrected and the above calculation is repeated until this value W o ' reaches the output side target plate width WO (actually, until it reaches within the allowable range), and when it matches the output side target plate width WO. The tension of is stored as the set tension Ts, and the set tension TS
The motor control device 4 of the looper 2 uses the value of as a tension command signal.
Send to.

In this way, this embodiment focuses on the fact that the width direction tension distribution, which has conventionally been treated as uniform, causes a width strain ΔWT that cannot be ignored, and furthermore, the width strain ΔWB within the roll bite is Since it is affected by tension, the target board width W
When setting o, ΔW and AWB are corrected, so the tension setting becomes more accurate than before, and the control accuracy of the plate width can be improved. This is particularly noticeable for steel types that are susceptible to damage.

FIG. 6 (al) shows the accuracy of hitting the average plate width at the tip of the rolled material S when the plate width control of the example is performed in comparison with the conventional method; In the case of (b
1 shows the case of this embodiment, and from a comparison between the two figures, it can be seen that the accuracy of hitting according to this embodiment is significantly improved.

In addition, Fig. 6(C) shows the accuracy of hitting the average plate width of the tip of the rolled material S in the above example without considering the plate shape of the rolled material. If (
Although it is slightly lower than in FIG. 6(b)), it is significantly improved compared to the conventional method.

The upstream stand of the NOi stand (i-
In the change in board width from the No. 1 stand to the exit of the No. 1 stand, a localized increase in width shrinkage occurs near the roll bite. This phenomenon is the result of three-dimensional deformation such as width expansion within the roll bite that affects the roll high 1-population, and as shown in Figure 17, the larger the width expansion within the roll bite, the larger the , and is influenced by the plate shape of the rolled material S. Therefore, if the target plate width Wo is set in consideration of this local width reduction amount WL, control accuracy can be further improved.

Figure 3 shows a flowchart when considering this local width reduction amount wL. The predicted width value ΔW o ' is Wo'
-Wi+ΔWT→-ΔWB+Δw,...(1D).

In addition, in FIG. 1, when feedback control of the board width is performed by disposing a width gauge on the exit side of the NOi stand, when setting the control gain, the above-mentioned ΔWT, ΔW, and Δ
Control accuracy can be improved by correcting the control gain by an amount corresponding to W. Note that FIG. 7 shows the accuracy and stability when gain correction is performed in comparison with the conventional method.

The figure (al) shows the case according to the conventional method, and the figure (b) shows the case according to the present embodiment.

In addition, in the above embodiment, when setting the target board width, ΔW
7. Although ΔWB and ΔW are corrected, ΔWB and ΔWL may be corrected as necessary depending on the steel type.

Further, in the above embodiments, the case of a hot tandem rolling mill has been described, but the present invention can be implemented to control the strip width of other rolling systems such as a hot reversible rolling mill to obtain similar effects.

〔Effect of the invention〕

As explained above, the present invention has a structure in which the width distortion caused by the widthwise distributed tension acting on the rolled material during tension rolling is corrected, and tension rolling is performed with a tension corresponding to the corrected target sheet width. As a result, control accuracy can be greatly improved compared to the conventional method, and the strip width at the starting end of the rolled material can be brought closer to the target strip width much more easily than in the past, resulting in a significant increase in yield. can be improved.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a part of the rolling line for explaining the present invention in detail, Fig. 2 is a flowchart for explaining the calculation operation of the tension calculation processing section in the above embodiment, and Fig. 3 is a diagram showing the present invention. Figure 6 (al~(
C1 is a diagram showing the plate width accuracy error at the tip of the rolled material, respectively;
Figures 7(a) and (bl are comparison diagrams of control accuracy, Figure 8 is a diagram for explaining short-term plastic deformation, Figure 9 is a diagram for explaining changes in plate width between stands, and Figure 10 is a diagram for explaining the change in plate width between stands. Figure 11 is a diagram to explain the tension distribution acting on the rolled material, Figure 11 is a comparison diagram of short-term plastic deformation by steel type, Figure 12 is a diagram showing the measurement of the tension distribution on the roll entrance side, and Figure 13 is the change in the inner width of the roll bite. Figure 14 is a diagram showing the relationship between the shape of the rolled material and tension distribution, Figure 15 is a diagram showing the relationship between the shape of the rolled material and the axiality, and Figure 16 is a diagram showing the relationship between the shape of the rolled material and the axiality. Figure 17, which shows the transition of interaxial deformation, is a diagram showing the relationship between the amount of local width shrinkage and the shape of the rolled material. Patent applicant: Kobe Steel, Ltd.

Claims (4)

[Claims] (1) Setting the target strip width of the rolled material at the exit side of the rolling mill,
In a strip width control method in hot rolling, the strip width of the rolled strip is controlled by controlling the tension of the rolled strip running through the rolling mill and the upstream rolling mill or winding engine to a tension corresponding to the target strip width, The widthwise tension distribution of the rolled material near the entrance side of the rolling mill is predicted and calculated, and the amount of width strain on the entry side of the rolled material is calculated based on the widthwise tension distribution, and this amount of width strain is taken into consideration. A strip width control method in hot rolling, characterized by setting the target strip width. (2) The width direction tension distribution of the rolled material near the entrance side of the rolling mill is predictively calculated in accordance with the plate shape of the rolled material between the rolling mill and the immediately upstream machine. Strip width control method in hot rolling. (3) The hot rolling according to claim 1 or 2, characterized in that the amount of width strain of the rolled material in the roll bit of the rolling mill is calculated, and the target plate width is set in consideration of this amount of width strain. Strip width control method in rolling. (4) In the hot rolling according to claim 1, claim 2, or claim 3, the target sheet width is set in consideration of the amount of local width shrinkage of the rolled material at the roll bite entrance of the rolling mill. Plate width control method.