The present invention relates to a wedge setup/control method for rolling of a metal or other plate material.
In the rolling of a metal or other material, particularly in the rolling of a plate material, it was conventionally demanded that the wedge (thickness variation in the direction of the plate width) be eliminated. More specifically, it was demanded that the plate thickness on the work side be equal to the plate thickness on the drive side. Formerly, while there was no plate material after mill roll replacement, the roll gap was reduced by a force, for instance, of 1000 or 1500 tons to ensure that the same rolling force is applied to the work side and drive side.
In general, however, the rolled plate varied in plate thickness. More specifically, the plate thickness on the work side differed from the plate thickness on the drive side. This plate thickness difference was caused, for instance, by the difference of a mill elastic constant in a mill housing between the work side and load side, the mill hysteresis difference between the work side and load side, or the slab plate thickness between the work side and drive side.
A conventional technology disclosed, for instance, by Patent Document 1 uses a wedge measuring instrument, which is installed at the outlet side or inlet side of a rolled material, to measure the amount of wedge. When the wedge is measured on the outlet side, this technology exercises feedback control in accordance with the measured amount of wedge. When the wedge is measured on the inlet side, this technology exercises feed forward control while using the load differential between the right- and left-hand sides of a roll and the load applied to a side guide. In this manner, this technology simultaneously suppresses the camber and wedge (refer to Patent Document 1, for example).
[Patent Document 1]
Japanese Patent Laid-Open No. 210513/2002
It seems that there was few positive setup/control method for providing the work side and drive side with the same plate thickness in plate material rolling. If the wedge is great particularly in plate material rolling, it is difficult to continue with rolling, and the dimensional error of a rolled plate or other problem may arise.
The present invention, which is used in reversible rolling of a plate material with a rough mill for hot rolling, said method comprising the steps of:
preparing a wedge meter on the outlet side of the rough mill to measure the plate thickness in the direction of the plate width;
performing calculations on the wedge measured by the wedge meter by using the influence coefficient of a wedge for roll gap leveling of the rough mill;
determining the amount of roll gap leveling control; and
exercising feedback control to apply the amount of roll gap leveling control to the roll gap leveling of the rough mill.
The present invention, which is outlined above, can roll a plate in such a manner that the plate thickness on the work side is equal to the plate thickness on the drive side. A rolling operation can be normally performed because no plate camber or plate skew is encountered during rolling. Further, a take-up operation can be normally performed by a take-up device on the finishing mill outlet side. In addition, subsequent processes such as a cold rolling process can be smoothly performed because the plate thickness in the direction of the plate width is uniform. Furthermore, the accuracy of a product made of a plate material produced by the use of the present invention is increased because a uniform plate thickness is provided in the direction of the plate width.
The method and apparatus for wedge setup/control in plate rolling will now be described. As an example, a hot strip mill for slab hot rolling will be described below.
ΔW=hWS−hDS Equation (1)
where ΔW is the wedge, hWS is the plate thickness on the work side, and hDS is the plate thickness on the drive side.
The wedge meters 4, 14 measure the plate thickness with X-rays or gamma rays. In some cases, a sensor is moved in the direction of the plate width for measurement purposes. In some other cases, many sensors and detectors are used for measurement purposes.
In general, the plate thickness distribution in the direction of the plate width is measured. The plate thicknesses (hWS and hDS) on the work side and drive side are then measured by subjecting the measured plate thickness distribution to approximation by using, for instance, a polynomial expression. Further, the plate thickness at the center of the plate width is measured.
A first wedge setup/control method according to the present invention relates to wedge feedback control in the rough mills 2, 3. In rolling in the direction from the attached edger 2 to the horizontal mill 3 (odd-numbered pass), the wedge is measured on the rolling outlet side to exercise roll gap leveling control over the horizontal mill 3.
The horizontal mill 3 and finishing mills 7 to 13, which are rolling mills, are generally configured as shown in
When the first wedge setup/control method is employed, the first controller 5, which is shown in
The following equation is then obtained from the above equation:
In accordance with the above equation, the first wedge meter 4 is used to measure the wedge on the rolling outlet side and adjust the roll gap leveling value ΔL of the horizontal mill 3. ΔW is the measured wedge that is derived from Equation (1).
is the wedge influence coefficient for the roll gap leveling value ΔL. It can be otherwise calculated with a rolling schedule given or can be actually measured.
Control according to Equation (3) is provided by exercising successive integral control over the wedge measured by the wedge meter 4 shown in
A second wedge setup/control method according to the present invention relates to wedge feed forward control in the rough mills 2, 3. In rolling in the direction from the attached edger 2, which is shown in
The following equation is then obtained from the above equation:
In accordance with the above equation, the roll gap leveling value ΔL(x) for the horizontal mill 3 is controlled.
is the influence coefficient of roll gap leveling in an even-numbered pass for the wedge.
An alternative is to measure the inlet side plate thickness H(x) and inlet side wedge ΔW(x) at the center of the plate thickness in an even-numbered pass by using the wedge meter on the inlet side, provide a delay until the horizontal mill 3 is encountered, and apply the values to Equations (4) and (5).
A third wedge setup/control method according to the present invention relates to feed forward control that is exercised between the rough mill outlet side and finishing mills. On the outlet side of the rough mill final pass (odd-numbered pass, rolling in the direction from the attached edger 2 to the horizontal mill 3), the plate thickness hTB(x) at the center of the plate width and the wedge ΔWTB(x) are measured in accordance with the distance x from the plate leading end and then stored. TB stands for a transfer bar. These stored values are stored in the second controller 6, which is shown in
The present invention is characterized by the fact that the following relationship prevails on the outlet side of the finishing mill i-th stand:
where ηi is a wedge inheritance coefficient. If a rolling schedule is given, this coefficient can be separately calculated. It can also be determined on an experimental basis. The first term on the right side of Equation (6) is an element to which the wedge of the upstream stand (that is, the inlet side) is inherited. The second term on the right side of Equation (6) is an element that is controlled according to the stand's roll gap leveling value. When Equation (6) is expressed by the distance x between the transfer bar and plate leading end, the following equation is obtained:
As shown in
A characteristic strategy of the present invention uses the following equation:
where hi(x) is a plate thickness at the center of the plate. In
The following equation is obtained from Equation (9):
The above equation is substituted into the left sides of Equations (8-1) to (8-7).
Since ΔWTB(x) in Equation (8-1) is known, ΔL1(x) is determined. When ΔW1(x) in Equation (8-1) is substituted into Equation (8-2), ΔL2(x) is determined. In the same manner, ΔL1(x) is determined from Equation (8-1). In
An alternative is to determine the average values of the plate thickness hTB(x) at the plate center on the rough mill outlet side and of the wedge ΔWTB(x) over the whole length, subject the obtained average values to calculations according to Equations (8-1), (8-2), and (10), and apply the calculation results to the roll gap leveling values of the first to seventh stands 7 to 13 before rolling of the finishing mills. Transfer bar tracking is not required, and control is exercised only once.
A fourth wedge setup/control method according to the present invention relates to wedge feedback control that is exercised between the finishing mill side second wedge meter 14 and the third controller 15. When the plate leading end reaches the second wedge meter 14, the second wedge meter 14 measures the wedge ΔW1MEAS. Further, the plate thickness hi (i=1 to 7) at the center of the plate width on the outlet side of each stand is input into the third controller 15 from the mill setting calculation (not shown). The second wedge meter 14 is the same as the first wedge meter 4.
The present invention is characterized by the fact that Equation (6) is used. In other words, the third controller 15 uses the following relationships for various stands 7 to 13:
The first term ΔW0 of the right side of Equation (11-1) is a transfer bar wedge. However, the value 0 (zero) is used for ΔW0.
Further, the present invention is also characterized by the fact that the following control strategy is used:
where αi is a gain.
ΔW7=ΔW7MEAS (Equation 13)
When the above equation is true, the following equation is obtained from Equation (12):
When the above equation is substituted into the left sides of Equations (11-1) to (11-7), the following equation is obtained from Equation (11-1):
The above equation determines the roll gap leveling control amount for the first stand 7. Further, when ΔW1 in Equation (11-1) is substituted into Equation (11-2), the following equation is obtained:
The above equation determines the roll gap leveling control amount for the second stand 8. In the same manner, the roll gap leveling control amount for each stand is calculated. For the seventh stand 13, the following equation is obtained:
The roll gap leveling control amounts ΔLi (i=1 to 7), which have been determined as described above for the finishing mill stands 7 to 13, are applied to the stands as described below. The present invention uses two application methods.
The first method provides single-point control. First of all, ΔL1 is applied to the first stand 7, which is shown in
The second method provides simultaneous control. As the first control, the roll gap leveling control amounts ΔLi (i=1 to 7), which are determined by Equations (15-1) to (15-7), are simultaneously applied to the first to seventh stands 7 to 13. Point B, which exists at the first stand 7 at the time of the first control, is tracked. When point B reaches the second wedge meter 14 on the finishing mill outlet side, the wedge is measured again. Calculations are performed in the same manner as for the first control. The roll gap leveling control amounts ΔLi (i=1 to 7) are then simultaneously applied to the finishing mill stands. In the same manner as mentioned above, control is repeatedly exercised until the plate entirely passes through the finishing mill.
A fifth wedge setup/control method according to the present invention uses the second wedge meter 14 on the finishing mill outlet side, which is shown in
Wedge measurements are made over the whole length with the second wedge meter 14 and then averaged. The obtained average value is referred to as ΔW7AVERAGE. The following equation is obtained in relation to ΔW7MEAS, which is used with the method according to the fourth embodiment:
ΔW7MEAS=ΔW7AVERAGE Equation (16)
The same calculations are then performed as described in conjunction with the method according to the fourth embodiment to determine the finishing mill roll gap leveling control amounts ΔLi (i=1 to 7) for the whole length. The values ΔLi (i=1 to 7) are set to the first to seventh stands 7 to 13 before rolling of the next plate. In other words, this provides bar-to-bar setup.
As described above, the wedge setup/control method according to the present invention, which is used for rolling of metal or the like, ensures that the rolled plate thickness on the work side is equal to the one on the drive side. Thus, rolling operations are normally performed because no plate camber or plate skew occurs during rolling. In addition, subsequent processes such as a cold rolling process can be smoothly performed because the plate thickness in the direction of the plate width is uniform. Further, the accuracy of a product made of a plate material produced by the use of the present invention is increased because a uniform plate thickness is provided in the direction of the plate width.
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/JP04/10311 | 7/20/2004 | WO | 2/21/2006 |