JPS60170519A - Method for preventing tail-end squeezing in continuous rolling of steel sheet - Google Patents

Abstract

PURPOSE:To prevent effectively the tail-end squeezing of a rolling material by adjusting the rolling reduction at each side based on the tension difference between the operating and driving sides while an interstand tension is working and leveling the rolling reductions based on the rate of the difference of rolling load at each side at the time when the tail end of material runs out. CONSTITUTION:After the running condition of rolling material is stabilized after biting the front tip of material by an optional stand Sn in the 2nd and subsequent stands of a tandem mill; the tension difference of material between the driving and operating sides at the outlet side of stand Sn is fixed as a lock-on value, and a draft-leveling control is performed so as to make the deviation between the lock-on value and the tension difference of material at each side during running to be zero. Next, the rate of rolling-load difference between the driving and operating sides at the time just after the tail end runs out of a stand Sn-1, is used as a lock-on value; and the draft-leveling control is performed so as to make the deviation between the lock-on value till the tail end runs out of the stand Sn and the rate of rolling load difference during running, to be zero. In this way, the tail end squeezing is prevented.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is applicable to continuous hot finish rolling of steel plates, rolling in which the till portion of the rolled material has a large meandering band in either the left or right direction, and The present invention relates to a rolling method for preventing scratches.

(Prior art) During hot continuous finish rolling of steel plates, the rolled material meandered,
If the rolling material is shifted toward the drive side or the work side, meandering occurs, and when the degree of meandering is large, the material to be rolled comes into contact with the side guides, making rolling difficult. The till part of the material to be rolled is rolled in a tension-free state, and the till shape is generally asymmetrical, which tends to cause left-right asymmetry in the rolling reduction rate, resulting in large meandering.

These problems are likely to occur.

The reason why the rolled material meanderes during rolling is that the distribution of the rolling reduction in the strip width direction is not symmetrical with respect to the center of the strip width. Therefore, in the past, when front and rear tensions are applied to the material to be rolled, the operator visually observes the asymmetry of the left and right reduction as a phenomenon of one-sided extension between the stands and performs reduction leveling. In addition, when performing bottom removal where the tension is not high in the material to be rolled, visually observe the till shape (change in width from side to side) of the material to be rolled at the entrance side of the rolling mill and level the downstream stand by rolling. That is, by visual observation, an operator manually adjusts the opening degree of the left and right rolls and adjusts the rolling reduction ratio of the left and right sides of the material to be rolled, thereby eliminating meandering and preventing tailing. In this way, the prevention of bottom squeezing, in which the operator visually observes and manually adjusts the reduction based on experience and intuition, has a problem of poor workability and lack of accuracy.

It has been known for some time that the occurrence of tailing cracks can be considerably reduced by controlling the meandering of the rolled material (O), and for this reason, several methods have been proposed to automatically detect and correct the deviation or bending of the rolled material. has been done.

For example, Japanese Patent Application Laid-Open No. 57-85607 discloses that based on the detected value of the amount of bending of a board at the outlet side of a reference stand, the amount of horizontal reduction of the stand is adjusted to correct the amount of bending in the stand, and A method is disclosed for correcting meandering of a rolled material by feedback control that sequentially performs adjustment control for the stand on the entry side to adjust the left-right deviation of the tension on the entry side of the stand, which occurs due to adjustment errors. However, this prior art is based on the premise that the rolling reduction of each stand is adjusted while the tension between the stands is acting on the material to be rolled. It was not sufficiently effective against the buttocks that occur frequently after the tension is reduced.

(Objective of the Invention) An object of the present invention is to provide a rolling method that can effectively prevent tail wrinkling.

(Structure-Function) First, the relationship between the inter-stand tension difference and meandering of a material to be rolled, and the relationship between rolling reaction force difference ratio (or rolling load difference ratio) and meandering, which are the basic idea of the present invention, will be explained.

Figure 1
Figures (a) and (b) are a front view and a plan view, respectively, showing the situations in which meandering occurs during the rolling process with m and 2b.

Fig. 1 (7) shows a state in which the material to be rolled 1 is stably threaded in the threading direction a, and Fig. 1 (bl) shows a state in which the left and right rolling balance has been disrupted. In the figure (Yaku), the rolling reduction ratio on the drive side (DS) of the work roll becomes larger than the rolling reduction ratio on the working side (WS) of the work roll, and the backward movement ratio on the drive side increases accordingly. As shown in Fig. 1<cJ, a rotational moment (moment) M toward the work side acts on the entry side material, so the center C! of the rolled material shifts from the center C in the width direction of the roll (like a mountain). Meandering occurs. That is, before the meandering occurs, a phenomenon of partial elongation of the rolled material appears on the driving side as shown in Fig. 2. In Fig. 2, the arrow drawn on the rolled material indicates the tension, and the arrow written below the bearing of the work roll indicates the reaction force, and the length of each arrow represents the magnitude of the force.At this time, the tension between the stands of the material to be rolled is the second In the example shown, the working side is larger than the driving side.

Therefore, in this case, if the rolling reduction is increased on the work side, the left-right rolling balance will be restored to its original state, the piece elongation will disappear, and the meandering will be corrected.

In other words, while the tension between the stands is acting, the difference in tension between the working side and the driving side of the material to be rolled between the stands is known, and the rolling reduction amount on either the working side or the driving side is adjusted based on this. This can prevent meandering.

Next, the relationship between the rolling load difference ratio and meandering during bottom removal when the tension between the stands of the rolled material is released will be explained. Third
Figures (α) to (q) show the process in which the rolled material 1 sometimes meanders when it is removed. Figure 3 shows that the shape of the tail of the rolled material is symmetrical and the width gradually decreases, so when removing the bottom of the rolled material, the center of the tail sometimes coincides with the center of the rolling roll.
Maintain a symmetrical rolling state. Therefore, the rolling reaction force on the left and right sides, the elongation of the housing, the roll gap, and the elongation of the rolled material on the left and right sides are equally meandering and no deviation, and finishing is completed in a stable state. In Figure 3 +1+, the tail of the rolled material gradually shifts toward the drive side, and as the tail advances, the center of the rolled material shifts from the center of the rolling roll to the drive side, and therefore the rolling load becomes heavier on the drive side. . For this reason, the elongation of the housing is small on the working side, and the roll gap is also small on the working side, so the elongation rate on the working side of the rolled material is not greater than that on the driving side, and as the tail portion of the rolled material advances, As the trailing edge progresses, the tail section meanders toward the drive side, resulting in trailing. Figure 3 (C) is Figure 3 1Al
Contrary to 1, since the tail portion of the rolled material is biased towards the working side, the bottom removal curves and meanders towards the working side as it progresses.

As mentioned above, in order to control the meandering of the rolled material when tension is not applied to the material to be rolled between the stands, it is necessary to detect the difference in rolling load between the drive side and the work side, and detect the rolling load immediately after the material passes through the front stand. It is sufficient to use the difference rate as a lock-on value and perform leveling by lowering the control stand until the tailing is completed.

The present invention was obtained through repeated experiments based on the above-mentioned matters. In a rolling method that prevents the tail portion of the material to be rolled from falling through the stand Sn by leveling control between the drive side and the work side of the stand Sn, the top of the material to be rolled is attached to the stand Sn. After the threading condition has stabilized after loading, the difference in the tension of the rolled material between the drive side and the work side on the exit side of the stand Sn is determined as a lock-on value, and the lock-on value and the drive side and work side during threading are determined as the lock-on value. Rolling leveling control is performed so that the deviation from the tension difference of the material to be rolled becomes zero, and then the rolling load difference between the driving side and the working side of the stand Sn immediately after the tail part of the stand 5n-1 has come through. Bottom drawing in continuous rolling of steel plate characterized by performing rolling leveling control so that the deviation between the lock-on value and the rolling load difference rate during sheet threading becomes zero until the stand Sn bottom slips out with the lock-on rate set as a lock-on value. This is a rolling method to prevent scratches.

(Example) The present invention will be explained below based on drawings of embodiments.

FIG. 4 shows an example of the configuration of rolling equipment and a control device for carrying out the present invention. Fl, F2...F6 are hot continuous finishing rolling mills with six stands arranged in tandem;
A looper 3 for applying tension to the material to be rolled 1 is provided between each stand, and a load cell 4 for detecting the tension on the driving side and the working side is provided on the ruler 3. A load cell 5 detects the rolling reaction force of each stand, and the output of the load cell 5 is inputted to an arithmetic and control unit 6. The output signal of the tension detected by the load cell 4 is input to the arithmetic and control device 7a, and the signals from the arithmetic and control device 6 and the arithmetic and control device 7a are input to the leveling amount calculator 7b. The amount of leveling is calculated and outputted to the lowering device 9 of each stand via the leveling control device 8.

Although any stand after the second rolling stand F2 can be selected as the stand to be controlled in the present invention, the fourth rolling stand below can be selected as the stand to be controlled.
The control procedure will be explained based on the flowchart of FIG. 5, taking as an example the case where the high rolling stand F4 is the stand to be controlled an.

After the tip (top) of the material to be rolled is bitten by the stand Fs, the tension is measured by the looper 3a between the stands F4 and F25 until the rolling state is stabilized, and control is performed based on this. Specifically, the time from when the load cell 5 detects the jamming of the stand F6 until the threading state becomes stable is determined empirically, and whether control can be started is determined by setting a timer or the like.

When the sheet threading condition is stabilized, the control of the present invention is started, but first, it is confirmed that the tail part of the material to be rolled has not passed through the control stand F4, that is, the front stage stand F3 of Sn, that is, 5n-1, and the tension difference is Check whether the leveling lock-on flag is set. Initially, the flag is not set, so a lock-on value dTo of the tension difference is calculated.

The tension difference lock-on value dTo is the difference between the outputs from the tension detection load cells 4 on the drive side and the work side of the looper 3, and is calculated by equations 1, 9, and (11).

dTo = ToW - ToD ・++ e (11 However, ToW: Working side load cell output when locking on ToD: Driving side load cell output when locking on Next, after setting the leveling lock-on flag based on the tension difference, control using the rolling reaction force described later Reset the rolling reaction force difference rate lock-on flag that is set when performing .Next, the left and right tensions are measured with the load cell 4a installed in the looper 3a on the rear surface of the control stand F4, and the tension difference d is
Put on the T. Next, the tension difference dT and the tension difference lock-on value dT.

The leveling amount δ due to the tension difference is calculated using equation (2) using the deviation value ΔT.

However, G gain d; tension deviation! p; Distance between the centers of the left and right rolling devices E; Young's modulus W of the material to be rolled; Width of the material to be rolled. If the leveling amount δ is too large or too small, the balance of the control system will be lost. The range of the control amount for one run is determined in advance, and when the upper and lower limits are exceeded, a constant leveling amount δmax is used.

The polarity is reversed for half of the leveling amount δ determined by the above formula (2), and the leveling amounts of 1/2 δ and -1/2 δ are F
4. Carry out leveling for the left and right lowering devices of the 4th stand. As a result, the deviation between the tension difference dT between the drive side and the work side of the rolled material of the DF4/F55 stand and the tension difference lock-on value dTo becomes zero. The above control is performed until the till portion of the material to be rolled passes through the F8 stand.

Next, when the load cell 5 of the F3 stand detects that the till part has passed through the F3 stand, a rolling reaction force difference lock-on value t is calculated. The lock-on value r, is determined by equation (3).

However, FoW: Load on the F4 working side immediately after the tail of F3 is missed (load cell output) FoD; Load on the F4 drive side immediately after the tail of Fs is missed (load cell output) Fot; Sum of the load on the drive side and the work side immediately after the tail of Fs is missed ( (Load cell output) Until the tail portion passes through the stand F4 to be controlled, leveling control is performed using the following rolling reaction force difference. That is, after determining the rolling reaction force difference rate γ using equation (4), the difference (γor) from the lock-on value γ0 is defined as the deviation value Δγ.

1'', where Ft: sum load FW on the drive side and work side; load FD on the work side; load deviation value Δγ on the drive side is rounded, then the leveling amount f is calculated using equation (5).

However, 5ahiN; Gain W: Board width △h; Reduction amount of the stand. After checking the upper and lower limits using the leveling amount δ calculated from this deviation value Δr as the control amount, reverse the polarity of half of the leveling amount and set it as 1/2 δ. -1/2δ is output to the rolling down devices on the left and right sides of stand F4, and feedback control is performed to keep the rolling load difference rate constant until F4 ends.

Now, when the stand to be controlled is the F4 stand, the plate passing control from before the tail part passes through the front stand F3 until it passes through the F4 stand is as described above, but in the present invention, the stand to be controlled is For example, just before the till section passes through the F4 stand, the stand to be controlled is switched to the next stage F11 stand and the same control is performed, allowing continuous sheet threading control to be performed up to the last stand. Of course it can be done. In a general hot continuous finishing mill, the successive plate thickness becomes thinner as it approaches the later stands, and tailing wrinkles tend to occur, so it is desirable to perform the control continuously.

(Effects of the Invention) According to the method of the present invention, after passing through the front stage stand, the clover squeezing at the stand to be controlled is significantly reduced.

In other words, the right and left elongation ratios of the rolled material are equal until just before the material to be rolled leaves the front stand, and correct lock-on is performed based on the tension difference. This enables highly accurate control by locking on the rolling load difference rate at a constant rate, and reduces tailing.

[Brief explanation of the drawing]

Figure 1 (Φ ~ tdJ is an explanatory diagram showing the meandering generation process, Figure 2 is a diagram showing the state of tension between stands, Figure 3 is a diagram showing the meandering generation process,
) is an explanatory diagram showing the occurrence of time meandering, FIG. 4 is a schematic diagram showing a configuration example of an apparatus for carrying out the present invention, and FIG. 5 is a block diagram showing the procedure of the method of the present invention. 1... Rolled material, 2a, 2b... Work roll, 3
... Louver, 4... Load cell, 6... Arithmetic control device, 7a... Arithmetic control device, 7b... Leveling amount calculator, 8... Leveling control device, 9... Lowering device . Agent Patent attorney Masaaki Aki Sawa Mitsugai 2 people speaking 2 mouths speaking 3 Sekis (Q) 7? 3 figures <b> Piece 3M (C)

Claims (1)

[Claims] (1) By controlling the rolling leveling of the driving side and working side of any stand Sn after the second stage stand of a plurality of hot continuous finishing mills arranged in tandem, the tail portion of the material to be rolled is adjusted to the stand Sn. In the rolling method for preventing the bottom squeeze when the bottom slips off, after the top of the material to be rolled is bitten by the stand Sn and the state of the material to be rolled is stabilized, the stand S is
The difference in tension between the rolled material between the driving side and the working side on the exit side is defined as the lock-on value, and the deviation between the lock-on value and the tension difference between the rolling material between the driving side and the working side during sheet threading is Rolling leveling control is performed so that the roll becomes zero, and then the rolling load difference ratio between the driving side and the working side of stand Sn is set as a lock-on value immediately after the tail part of stand Sn 21 falls out until the tail part of stand 8n falls out. A rolling method for preventing tail reduction in continuous rolling of steel sheets, characterized by performing reduction leveling control so that the deviation between the lock-on value and the rolling load difference rate during sheet threading becomes zero.