JP3825543B2 - Hot rolling method with excellent plateability - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rolling method in a hot rolling mill having a plurality of rolling stands.
[0002]
[Prior art]
Conventionally, a hot slab is rolled by a plurality of rolling stands to obtain a steel plate having a target thickness.
[0003]
This rolling is generally performed by, for example, a hot finish rolling mill having seven rolling stands, which will be described with reference to FIG.
[0004]
The rolling setting calculation device 28 is based on the dimensions, temperature, material, product plate thickness, etc. of the material to be rolled S before the material to be rolled (hot slab) S bites into the first rolling stand of the finishing mill. The initial rolling force of each of the first to seventh rolling stands of the finish rolling mill is calculated using a preset calculation model, and the initial roll interval of each rolling stand is calculated from the calculated initial rolling force of each rolling stand. To decide. And the roll space | interval of each rolling stand is set so that it may become the initial roll space | interval determined by the roll space | interval automatic adjustment apparatus 23 provided in each 1st-7th rolling stand.
[0005]
After that, the material to be rolled S is started to be rolled and sequentially bitten from the first rolling stand to the seventh rolling stand. The rolling force detector 24 installed in the rolling stand to measure the rolling force P _i of rolling stands each. Based on the measured rolling force P _i , sheet thickness control by a gauge meter method is started for the material to be rolled S by the sheet thickness adjusting device 25 installed in each rolling stand. Further, when the material to be rolled S reaches the product plate thickness detecting device 27 provided on the exit side of the seventh rolling stand, the plate thickness control by the plate thickness control device 26 by the feedback method is started, and the product plate thickness is controlled by both controls. The roll interval automatic adjusting device 23 is controlled so as to maintain a predetermined target plate thickness.
[0006]
[Problems to be solved by the invention]
When rolling with the above hot finish rolling mill row, the temperature of the material to be rolled at the entry side of the rolling mill row drops due to heat radiation etc., but the closer to the tail end of the material to be rolled, the more the material enters the rolling mill. Since the residence time on the side becomes longer, the temperature drop amount becomes larger. On the other hand, on the exit side of the finishing mill, as a result of increasing the sheet passing speed for securing the rolling temperature or improving productivity, the temperature rise amount at the tail end portion is larger than the tip portion of the material to be rolled.
[0007]
FIG. 3 is an actual measurement example of the inlet side temperature and the outlet side temperature of the finishing rolling mill row. While the inlet side temperature is reduced by about 100 ° C. from the tip to the tail end, the outlet side temperature is increased by about 50 ° C. from the tip to the tail end. If there is such a temperature change in the material to be rolled, the fluctuation of the rolling force (rolling reaction force) increases from the leading edge to the trailing edge at the rolling stand upstream of the finishing rolling mill row, and downstream of the finishing rolling mill row. It decreases at the rolling stand.
[0008]
In addition, as described above, the gauge thickness control device based on the gauge meter system independently performs the operation of keeping the thickness of each rolling stand constant, so that when the material to be rolled has a temperature change, for example, a temperature drop, the above rolling This will further increase the power.
[0009]
As described above, in the conventional rolling method, the rolling force at each rolling stand changes within the plate as the rolling progresses, but the thickness of the exit side at each rolling stand is kept constant. . Here, considering the flatness of the material to be rolled between the rolling stands, the change in the rolling force changes the deflection of the roll, which changes the thickness distribution in the plate width direction. The flatness in the longitudinal direction of the steel sheet caused by the material to be rolled changes. When this flatness is deteriorated, the sheet passing property is impaired, and in the case of remarkable, the plate breaks between rolling stands.
[0010]
An object of the present invention is to obtain a predetermined product plate thickness while making the flatness of the material to be rolled at each rolling stand in the plate pass substantially constant and preventing the plate passability from being impaired.
[0011]
[Means for Solving the Problems]
The present invention has been made in order to solve the above-mentioned problems, and means 1 is a method for correcting a roll interval obtained by a gauge meter method and a feedback method in order to obtain a target product thickness in a rolling mill having a plurality of rolling stands. In the method of rolling while adjusting the roll interval of each rolling stand according to the amount, the rolling force amount P _{i of} each rolling stand measured by a rolling force detector provided in each rolling stand other than the final rolling stand of the rolling mill. And a predetermined difference P _i0 −P _i of the reference rolling force P _i0 of each rolling stand, and based on this value, the roll interval correction amount ∂S _i of each rolling stand other than the final rolling stand is expressed by the following formula (1) determined by), the obtained correction amount .differential.S _i and the gauge meter method, based on the roll gap correction amount determined by the feedback scheme, the rolling scan except the last rolling stand The roll distance at command is hot rolling method having excellent sheet passing of correcting the roll clearance adjusting device.
[0012]
[Formula 2]
[0013]
Here, i is a rolling stand number α _i : a coefficient determined for each stand (i = 1 to n−1).
n: Number of stands of rolling mill Further, the means 2 is the initial stage of each rolling stand in which the predetermined reference rolling force amount of each rolling stand is determined based on the size, temperature, material, and product thickness of the material S to be rolled. The amount of rolling force.
[0014]
In the present invention, the reference rolling force amount of means 1 may be a value within the range of the rolling capacity of the rolling mill, but was determined based on the dimensions, temperature, material, and product plate thickness of the material to be rolled. It is preferable to use the initial rolling force of each rolling stand.
[0015]
Hereinafter, the content of implementation of this invention is demonstrated in detail. The abnormality in the flatness of the material to be rolled during rolling is explained by the change in the crown ratio before and after rolling. In other words, the abnormality in the flatness of the material to be rolled is due to the uneven elongation rate in the width direction of the material to be rolled. The uneven elongation rate in the width direction causes internal stress in the material to be rolled. If a certain limit is exceeded, the material to be rolled will buckle, resulting in poor flatness. In order to improve the flatness, the elongation ratio from the center portion to the end portion of the material to be rolled may be made equal. For this purpose, the following equation (2) may be satisfied. Here, when considering the effect of the flatness of the material to be rolled on the sheet-passability, it is important to suppress changes in flatness between the rolling mills, but the flatness at the final rolling stand outlet side is important. Since it is sufficient to ensure the flatness required for the product, it is sufficient that the expression (2) is satisfied except at the final rolling stand.
[0016]
(Cr _{i -1} ) / (h _{i -1} ) = Cr _i / h _i (2)
here,
Cr _i / h _{i: i} rolling stands out crown ratio side plate cr _i: i roll stand delivery side of the strip crown h _i: i rolling stand out considering the thickness shorter side plate when the rolling force and the plate within that time The change in thickness is minute, and the change in the plate crown and thickness on the stand exit side is proportional to the change in rolling force. Therefore, Formula (2) can be expressed as the following Formula (3).
[0017]
(∂P _{i -1} ) / (P _{i -1} ) = ∂P _i / P _i (3)
here,
P _i: i rolling stand of the rolling force ∂P _i: rolling force variation type i rolling stand (3) means to maintain a constant ratio with the rolling force of the rolling mill. The certain ratio mentioned here may be calculated using, for example, the ratio of the reference rolling force amount P _i0 of each rolling stand . In this case, the rolling force change ∂P _i of each rolling stand is expressed by equation (4).
[0018]
[Formula 3]
[0019]
When operating all the rolling stands during rolling using the formula (4), naturally the outlet side plate thickness of each rolling stand including the final rolling stand is changed, so that the target product plate thickness is secured. I can't. Therefore, the control using the formula (4) must be performed in each rolling stand other than the final rolling stand. In order to secure the amount of change in rolling force shown in Formula (4) in each rolling stand other than the final rolling stand, the amount of roll interval correction in each rolling stand other than the final rolling stand is expressed by Formula (5). At the same time, at the final rolling stand, by controlling the plate thickness constant, the flatness of the plate between the rolling stands in the plate is kept constant, and it is possible to prevent the loss of plate passability while maintaining a predetermined product plate thickness. Can be obtained.
[0020]
[Formula 4]
[0021]
here,
∂S _i : Roll interval correction amount of each rolling stand (i = 1 to n−1)
P _i0 : Reference rolling force of each rolling stand (i = 1 to n−1)
∂P _i : Rolling force change amount of each rolling stand (i = 1 to n−1)
α _i : Coefficient determined for each rolling stand (i = 1 to n−1)
n: Substituting ∂P _i of equation (4) into equation (5) above the number of rolling stands of the rolling mill, equation (5) can be modified as follows.
[0022]
[Formula 5]
[0023]
That is, the hot rolling of the present invention can be performed by correcting the roll interval of each rolling stand using the above formula (1).
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a system configuration diagram in the case of a hot rolling mill of first to seventh rolling stands.
[0025]
In the figure, 11 is a work roll of each rolling stand of the hot finish rolling mill, 12 is the backup roll, 13 is an automatic adjusting device for the roll interval, and 15 is based on the rolling force of the roll measured by the rolling force detector 14. A gauge meter plate thickness control device 16 for controlling a plate thickness by a gauge meter method, 16 is a feedback method based on a product plate thickness measured by a product plate thickness detector 17 provided on the exit side of the seventh rolling stand of the finishing mill. A feedback plate thickness adjusting device for performing plate thickness control, 18 is an arithmetic unit, 19 is a rolling mill setting calculation device, and S is a material to be rolled.
[0026]
The rolling mill setting calculation device 19 is set in advance based on the dimensions, temperature, material, and product thickness of the material to be rolled S before the material to be rolled bites into the first rolling stand of the finishing mill. The initial rolling force of each rolling stand of the finishing mill is calculated using the calculation model, and the initial roll interval of each rolling stand is determined from the calculated initial rolling force. The determined initial roll interval is given to each roll interval automatic adjusting device 13 provided in the first to seventh rolling stands via the arithmetic unit 18. In addition, the stand coefficient αi of each rolling stand necessary for the calculation of Expression (5) Is calculated from a model formula or the like preset in the rolling mill setting calculation device 19 and given to the calculation device 18.
[0027]
The roll interval automatic adjusting device 13 of the first to seventh rolling stands is determined by the rolling mill setting calculation device 19 input via the arithmetic device 18 before the material to be rolled S is engaged with the first rolling stand. The roll interval of the first to seventh rolling stands is adjusted based on the initial roll interval value of the stand. Further, after the material to be rolled S is caught in each rolling stand, the roll interval is determined by the roll interval correction amount given from the gauge meter plate thickness control device 15, the feedback plate thickness control device 16 and the calculation device 18 for each rolling stand. Make corrections.
[0028]
That is, the gauge meter plate thickness control device 15 performs gauge meter type plate thickness control after the material to be rolled S is caught in each rolling stand of the finish rolling mill row. The thickness control by this gauge meter method calculates and compensates for the elastic deformation of the rolling mill based on the rolling force measured by the rolling force detector 14 installed in each rolling stand and the rolling mill elastic constant of each rolling stand. Similarly, the roll interval correction amount ∂Sg is calculated, and the calculated roll interval correction amount ∂Sg is given to the roll interval automatic adjusting device 13 of the first to seventh rolling stands.
[0029]
Further, the feedback plate thickness adjusting device 16 performs plate thickness control after the material to be rolled S reaches the product plate thickness detecting device 17. In the thickness adjustment by this feedback method, the roll interval correction amount ∂Sf is calculated so as to compensate for the difference between the target product plate thickness and the detection plate thickness by the product plate thickness detection device 17, and this roll interval correction amount ∂Sf is calculated as the first value. To the respective roll interval automatic adjusting device 13 of the seventh rolling stand.
[0030]
The calculation device 18 stores the rolling coefficient S _i of each rolling stand given by the rolling mill setting calculation device 19 and the initial rolling force P _i0 before the material S to be rolled into the finishing mill. Further, it is detected that the material to be rolled S is caught in the first to seventh rolling stands of the finishing rolling mill row (detected by a change in rolling force measured by the rolling force detector 14 installed in each rolling stand). Then, input of the measured rolling force P _i is started. First, a difference P _i0 −P _i between the stored rolling force amount P _i of each rolling stand and a predetermined reference rolling force amount P _i0 of each rolling stand is obtained, and based on this value, the equation (1) is used. performs successive calculating a roll gap correction amount .differential.S _i for each rolling stands except the last rolling stand. The calculated roll interval correction amount S _{i is given} to the roll interval automatic adjusting device 13 of the first to sixth rolling stands.
[0031]
As a result, the roll interval automatic adjusting device 13 has the roll interval correction amount ∂Sg calculated by the gauge meter plate thickness control device 15, the roll interval correction amount ∂Sf calculated by the feedback plate thickness control device 16, and the roll interval calculated by the calculation device 18. When the correction amount ∂S _i is inputted at the same time, the correction amounts ∂Si are added together, and the roll interval is adjusted by the added roll interval correction amount ∂St. In addition, when each is input individually, the interval between the rolls is adjusted individually.
[0032]
【Example】
An embodiment using the present invention is shown in FIG. FIG. 4 shows the results of implementing the present invention on a rolled material having a temperature distribution as shown in FIG. In FIG. 4, (a) is the flatness on the outlet side of each stand immediately after the start of rolling. (B) shows the flatness on the outlet side of each stand immediately before the end of rolling, and (c) shows the flatness on the outlet side of each rolling stand immediately before the end of rolling in the conventional example.
[0033]
As can be seen from this figure, the change in flatness from immediately after the start of rolling to just before the end of rolling is about 0.2% at maximum. The change in flatness of the conventional example (C) is 1.1% at the maximum, and it can be seen that the flatness on the exit side of each rolling stand is improved in this embodiment.
[0034]
【The invention's effect】
According to the method of the present invention, it is possible to keep the ratio of the rolling force constant over the entire length of the material to be rolled, so that the flatness of the material to be rolled between each stand of the finish rolling mill row can be kept good. Thus, it is possible to perform rolling with temperature change, speed change, etc. without impairing the sheet passing property and without causing breakage of the rolled material, thereby improving the efficiency of the rolling operation.
[Brief description of the drawings]
FIG. 1 is a control block diagram showing an embodiment of the present invention.
FIG. 2 is a control block diagram according to a conventional method.
FIG. 3 is a diagram showing the relationship between the temperature of the rolled material and the passage of time on the rolling mill entry / exit side.
FIG. 4 is a diagram showing the flatness of the rolled material on the outlet side of each stand when the present invention is carried out.
[Explanation of symbols]
11, 21 Work rolls 12, 22 Backup rolls 13, 23 Roll interval automatic adjustment devices 14, 24 Rolling force detectors 15, 25 Gauge meter plate thickness control devices 16, 26 Feedback plate thickness control devices 17, 27 Product plate thickness detectors 18, 28 arithmetic unit 19 rolling mill setting calculation device S material to be rolled

Claims (2)

In the method of rolling while adjusting the roll interval of each rolling stand according to the roll interval correction amount obtained by a gauge meter method and a feedback method in order to obtain a target product thickness in a rolling mill having a plurality of rolling stands, A difference P _i0 −P _i between a rolling force amount P _i of each rolling stand measured by a rolling force detector provided in each rolling stand other than the final rolling stand of the rolling mill and a predetermined reference rolling force amount P _i0 of each rolling stand is determined. determined, based on this value, the roll gap correction amount .differential.S _i for each rolling stands except the last rolling stand determined by the following formula (1), the obtained correction amount .differential.S _i and the gauge meter system, the feedback scheme Based on the obtained roll interval correction amount, the roll interval in each rolling stand other than the final rolling stand is corrected by a roll interval adjusting device. Excellent hot rolling method in passing plate resistance to.
[Formula 1]
Here, i is a rolling stand number α _i : a coefficient determined for each stand (i = 1 to n−1).
n: Number of rolling mill stands The reference rolling force amount of each of the predetermined rolling stands is an initial rolling force of each rolling stand determined based on the size, temperature, material, and product thickness of the material to be rolled S. A hot rolling method having excellent sheet-passability as described.