JP2628916B2 - Flatness control method during reverse rolling - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[Industrial applications]

The present invention relates to a flatness control method at the time of reverse rolling which is used when a rolled material such as a thick plate is rolled by reverse rolling.

[Prior art]

In general, in thick plate rolling, flatness defects are likely to occur in the second half pass in which the plate thickness becomes thin.Therefore, the rolling process having a predetermined thickness or less is called a shape control pass, and a rolling schedule is set in advance so that flatness defects do not occur. Decide on rolling. However, between the rolling schedule calculated in advance and the actual rolling, the prediction error of the rolling load due to the prediction error of the rolled material temperature, or the prediction of the roll profile (heat crown, roll wear) due to the heat crown or roll wear. Errors, or various errors such as plate crown prediction model errors, the roll crown change of the rolled material is actually different from the prediction, and this may cause poor flatness in the rolling mill. There is. Conventionally, in order to prevent the occurrence of such flatness defects, a method of controlling a work roll bending force based on shape measurement information (for example, JP-A-59-159208,
JP-A-52-17355) is known.

[Problems to be solved by the invention]

However, the conventional control method as described above is advantageous to be applied to a steady rolling state such as a tandem mill. However, in a mill that performs reverse rolling such as plate rolling, a rolling schedule for each slab or pass is used. However, there is a problem that a sufficient effect cannot be obtained due to the change in In other words, regarding the effect of the roll profile on the flatness, the roll profile is predicted using a heat crown prediction model or a roll wear prediction model, and this is reflected in the rolling reduction schedule calculation. In addition to the sheet crown change due to the roll profile change during rolling of the same rolled material,
A change in the sheet crown caused by the change in the roll profile also occurs, and any of these causes a poor flatness. In particular, in the reverse rolling of a thick plate, as shown in FIG. 3, the roll profile (especially the heat crown) is irregularly changed because the material width changes in each of the rolling stages of forming, tentering and thicknessing. Change. In addition, since the rolled material size changes for each slab, the change in the roll profile between the slabs is large. As for the prediction model of the strip crown, a simple formula based on a computer simulation result or actual machine data is usually used in consideration of online application, and the actual situation is that the accuracy is not always good. On the other hand, in thick plate rolling, the deterioration of the surrounding atmosphere caused by descaling or the like adversely affects existing sensors, so that the number of passes where flatness measurement can be performed is also limited. It is necessary to control up to the final pass based on the measurement result, and there is also a problem that the flatness cannot be sufficiently controlled. The present invention has been made in order to solve the above-described problems, and an object of the present invention is to provide a control method that can effectively prevent occurrence of poor flatness when rolling a thick plate or the like by reverse rolling. I do.

[Means for Solving the Problems]

The present invention relates to a flatness control method for reverse rolling used when a rolled material such as a thick plate is rolled by reverse rolling, wherein at least one of the front and rear surfaces of the rolling mill, The procedure of measuring the flatness and the sheet crown at least once, and from these measurement data and the actual rolling data, the prediction error of the rolling load, the prediction error of the roll profile and the procedure of estimating the prediction model error of the sheet crown, A step of determining a work roll bending force for preventing a flatness defect in rolling after the next pass based on the estimated value, thereby achieving the above object.

[Action]

In the present invention, first, in the reverse rolling, in consideration of the fact that the deterioration of the surrounding atmosphere has an adverse effect on the existing sensor and the number of passes in which flatness measurement cannot be performed is limited, at least one pass in the rolling pass ( That is, the flatness and the sheet crown of the rolled material are detected. Then, based on the measurement results of the flatness and the sheet crown, a prediction error of the rolling load, a prediction error of the roll profile, and a prediction model error of the sheet crown are estimated, and the next pass for preventing the flatness from the estimation results. Subsequent work roll bending power is determined. This makes it possible to perform high-precision flatness control even in a situation where the rolling schedule changes for each slab and each pass, which is peculiar to reverse rolling.

【Example】

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In general, a factor directly affecting the flatness defect of a rolled material is a difference in elongation rate in the rolling direction at each position in the width direction of the rolled material. Therefore, in order to keep the elongation rate constant, the following expression (2) is used. Rolling is performed so that the crown ratio becomes constant. Crown ratio = Cr i / Hi (1) Outgoing plate crown in the Cr i: i pass Hi: i Outer plate thickness in the i pass When the crown ratio is not constant, the following equation (2) is used.
An elongation difference Δγ is generated at each position in the width direction represented by the following expression, and due to the elongation difference, flatness defect (steepness λ) accompanied by undulation as shown in a perspective view in FIG. 4 is generated. Δγ = Cr i / Hi−Cr _i−1 / H _i−1 (2) Cr i, Hi: Outer side crown at i-th pass, plate thickness Cr _i−1 , H _i-1 : i−1 pass Outer side plate crown, plate thickness Causes that the crown ratio does not become constant include a rolling load prediction error, a roll profile prediction error, and a sheet crown prediction model error caused by a temperature prediction error and the like. In the present invention, these error factors are estimated from the flatness meter (detection) information after i-pass, the sheet crown measurement (detection) information, and the actual rolling load in i-pass and i-1 pass, and the next pass (i + 1 pass). Determine the subsequent bending power and i + 1
The flatness after the pass is controlled with high accuracy.
The figure shows an outline of the information processing flow of the present embodiment. Hereinafter, this embodiment will be specifically described with reference to FIG. First, the prediction error of the roll profile and the prediction model error of the sheet crown will be described. The true plate crown value Cr i in the i-pass can be expressed by the following equation (4). Cr i = f (Pi, Cw , C B, Fi, β) ... (4) Pi: rolling load (actual) Cw: work roll crown (true value) C _B:-back up-roll crown (true value) Fi: Work Roll bending force (actual) β: Model correction coefficient (unknown) On the other hand, in rolling, it is generally known that there is a critical thickness Hcs at which flatness affects the elongation difference at each position in the width direction. The plate crown at this time
Crcs is represented by the following equation (5). Here, cs is a subscript indicating the limit. Crcs = f (Pcs, Cw, C _B , Fcs, β) (5) Accordingly, the change in crown ratio Δ causing poor flatness
The γ, Δγ = Cr i / Hi -Crcs / Hcs = f (Pi, Cw, C B, Fi, β) / Hi -f (Pcs, Cw, C B, Fcs, β) / Hcs with ... (6) You can ask. Further, when the actual crown ratio change Δγi is obtained from the flatness defect result (steepness) λi in the i-pass, the following equation (7) is obtained. Δγi = (π / 2 · λi) ² (7) In the above formula (6), since the back-up roll does not directly contact the material to be rolled, the back-up roll crown C _B
Assuming the true value because the amount of change in one Roruchiyansu is small, the prediction error of the work roll crown (roll Prof Eel) DerutaCw, the predicted value and Cw _P, as in (6) the following equation (8) become. _{Δγ = f (Pi, Cw P} + ΔCw, C B, Fi, β) / Hi -f (Pcs, Cw P + ΔCw, C B, Fcs, β) / Hcs ... (8) ( unknown ΔCw, β) above (7 ) And (8), the following equation (9) is obtained by setting Δγi = Δγ. ^{(Π / 2 · λi) 2} = f (Pi, Cw P + ΔCw, C B, Fi, β) / Hi -f (Pcs, Cw P + ΔCw, C B, Fcs, β) / Hcs ... (9) i path Of the crown measurement at Crai and the above equation (4)
Yotsute the placing equal Cr i, Crai = f (Pi , Cw P + ΔCw, C B, Fi, β) ... (10) is obtained. By solving equations (9) and (10) simultaneously, the prediction error Δ of the work roll crown (roll profile) can be obtained.
Cw can be calculated, and the correction coefficient β of the plate crown prediction model, that is, the plate crown prediction model error can be calculated. Next, the prediction error of the rolling load will be described. Rolling load prediction error (FCF _{i + 1} has a large effect of temperature prediction error,
Since there is almost the same tendency in the same slab, it is possible to reflect the ratio of actual / prediction up to the pass before the i-th pass and to reflect the ratio after the (i + 1) -th pass. be able to. FCF _{i + 1} = (actual load / predicted load) i × α + FCFi (1-
α) ... (11) P ' _{Pi + 1} = FCF _{i + 1} * P _{Pi + 1} ... (12) α: Exponential smoothing coefficient P _{Pi + 1} : Predicted rolling load (before correction) P' _{Pi + 1} : Predicted rolling Load (after correction) Using ΔCw, β, and FCF _{i + 1} obtained as described above, the crown ratio Cr _{i + 1} / H _{i + 1} after the i + 1 pass is set to a predetermined crown ratio. The work roll bending force F _{i + 1} is obtained and controlled. Usually, Crcs / Hcs is used as the predetermined crown ratio. From the following equation (13) obtained as a result, the above-mentioned _{Fi + 1} can be specifically calculated. _{f (P 'Pi + 1,} Cw P + ΔCw, C B, F i + 1, β) / H i + 1 = f (Pcs, Cw P + ΔCw, C B, Fcs, β) / Hcs ... (13) or In the above description, an example in which the shape (flatness and plate crown) measurement is performed after the i-th pass is shown. However, the present invention is not limited to this. It is needless to say that the flatness control can be performed by the above. Next, an example of a rolling mill applicable to the method of the above embodiment will be described based on a schematic configuration diagram shown in FIG. In the figure, reference numerals 1 and 1 'denote upper and lower work rolls, which are bent by bending devices 2 and 2'. Reference numeral 3 denotes a control device for controlling the bending force (pressure). Reference numeral 7 denotes a CPU for calculating the bending force, the actual load from the load cell 4, the flatness information from the flatness meter (detection device) 6, and the sheet crown information from the sheet crown measurement (detection) device 8. , Bending force results, and rolling condition data from the process computer 5 are respectively input. From these data, the load prediction error, the work roll crown prediction error, and the sheet crown prediction model error are calculated. And determine the bending power for the next pass and thereafter. The determination signal is output to the control device 3, which controls the upper and lower work rolls 1,
Appropriate bending force is applied to 1 'to enable rolling with high precision flatness. Reference numerals 9 and 9 'in the figure denote upper and lower back-up rolls. There is no particular difference between the hardware configuration in the bending control and the conventional hardware configuration, and a detailed description thereof will be omitted. The flatness meter 6 and the sheet crown measuring device 8
May be installed in at least one of the front and rear of the rolling mill. According to the flatness control method of the rolling mill of the present embodiment described in detail above, it is possible to accurately predict flatness in rolling and control the flatness to a high level, to prevent the occurrence of narrowing in rolling, and to correct straightening load. This can be effective in reducing the load on the refining process caused by the reduction in flatness and the flatness defect. In addition, the roll change, which is restricted from the viewpoint of flatness, can be expanded, so that the material distribution can be simplified. As described above, the present invention has been specifically described based on the embodiments. However, the method of the present invention is not limited to those shown in the above-described embodiments, and it can be appropriately changed without departing from the gist. Needless to say, applicable rolling mills are not limited to those shown in FIG. Although not particularly specified in the above embodiment, the measurement of the flatness and the crown of the rolling mill may be performed at least once,
You may go more than once. By performing the measurement twice or more, the accuracy of the control can be improved.

【The invention's effect】

According to the flatness control method for a rolling mill of the present invention, the occurrence of poor flatness can be effectively prevented during reverse rolling of a thick plate or the like, so that a rolled material having a high flatness can be manufactured.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a flow of information processing in an embodiment of the present invention, FIG. 2 is a schematic configuration diagram showing reverse rolling applicable to the above embodiment, and FIG. FIGS. 4 (A) and 4 (B) are partial perspective views showing examples of a rolled material having poor flatness. 1, 1 '... work roll, 2, 2' ... bending device, 3 ... bending force control device, 4 ... load cell, 5 ... process computer, 6 ... flatness meter, 7 ... CPU, 8 ...... Sheet crown measuring device, 9, 9 '... Back-up roll.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Tsutomu Yoshizato 1-chome, Mizushima-Kawasaki-dori, Kurashiki-shi, Okayama Pref. )

Claims (1)

(57) [Claims] 1. A flatness control method for reverse rolling used when a rolled material such as a thick plate is rolled by reverse rolling, wherein at least one of a front surface and a rear surface of a rolling mill is rolled in a rolling pass. A procedure for measuring the flatness of the mill and the strip crown at least once, and a procedure for estimating a rolling load prediction error, a roll profile prediction error and a strip crown prediction model error from these measurement data and the actual rolling data. A means for determining a work roll bending force for preventing flatness failure in rolling after the next pass based on the estimated value, a flatness control method for reverse rolling.