JPS6324762B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling plate warpage that can effectively prevent plate warping that occurs on the exit side of a rolling mill during thick plate rolling.

During thick plate rolling, plate warping (upward warping, downward warping) often occurs on the side of the plate material, and as a result,
Damage to the rolling mill and the equipment before and after it may lead to the suspension of operation, or it may impede the biting ability in the next pass, requiring time to straighten the sheet warp, reducing productivity. Warpage remains in the plate material itself, leading to quality deterioration, and in extreme cases, it becomes necessary to cut off even the effective ends, resulting in a reduction in yield, resulting in very serious damage. However, the reality is that effective board warpage control technology has not yet been put into practical use.

The reason for this is that, at present, not all of the causes and mechanisms that cause board warping are understood, and the causes that are currently known are, at most, temperature differences between the top and bottom surfaces of the material, or Due to this, there is a difference in deformation resistance, a difference in the surface properties of the upper and lower surfaces of the material (for example, a difference in the state of scale adhesion),
Difference in lubrication between the material and the contact surfaces of the upper and lower work rolls,
Roughness difference, diameter difference and peripheral speed difference between upper and lower work rolls,
Impact drop amount and difference in the rotational speed of the upper and lower work rolls when biting the material, reduction amount, relationship between plate thickness and width and peripheral speed difference of the upper and lower work rolls, and other information, material weight, creep, lower work roll pick-up, etc., and in actual rolling, these factors act simultaneously and in a complex manner. Therefore, it is fair to say that there has not been much elucidation, let alone quantitative elucidation, of the influence of each individual factor on board warpage, or even qualitative elucidation. In addition, one of the reasons for this is that the sheet warping phenomenon itself has not been quantitatively understood online, and among these factors, it is difficult to understand online. It also depends on the fact that there are many possibilities.

Therefore, in reality, the circumferential speed difference between the upper and lower work rolls is controlled visually by the operator, and its effectiveness is unclear and may not be effective at all.

Based on the current situation, the inventors of the present invention have conducted extensive research into elucidating the occurrence of plate warpage and measures to prevent it. As a result, the inventors have found that the phenomenon of warping on the side of the plate during thick plate rolling is caused by the front and rear table rollers of the rolling machine. We found that this is due to the geometrical vertical asymmetry of the biting of the rolled material into the roll bit due to the level difference between the lower work roll and the lower work roll. Regarding the relationship between the difference between the top surface level of the table roller on the front and rear surfaces of the rolling mill) and plate warpage, in the process of raising and lowering the lower work roll during rolling (during metal-in) during thick plate rolling, when the lower work roll is raised, Assuming that the material is clearly warped downward, and conversely the bottom work roll pick-up is extremely lowered to 0 to negative, the material will be bent upward at three points by the bottom work roll and the table roller and will warp upward. The present invention was completed based on the knowledge that controlling the lower work roll pickup is effective in controlling sheet warpage, since it can be easily estimated that this will occur.

Of the above-mentioned factors, the present invention is relatively easy to control, can be handled logically and quantitatively, and moreover, the present invention actively controls lower work roll pick-up, which is considered to have a large influence on board warping. The purpose is to provide a new method for controlling sheet warpage, and its gist is to provide a rolling mill with a pair of upper and lower work rolls, each equipped with table rollers on the entry and exit sides. When rolling a thick plate by rolling, the difference X between the top surface level of the lower work roll and the top surface level of the front and rear table rollers of the rolling machine becomes the value of the following formula before the rolled material is bitten in each rolling pass. A method for controlling plate warpage in thick plate rolling, which is characterized in that rolling is performed by adjusting the height of a lower work roll.

X = 1/2 ΔHi + α However, X: (lower work roll top surface level) - (rolling machine front and rear table roller top surface level) ΔHi: Reduction amount of the relevant pass α: Additional adjustment amount (α = 0 at the initial pass, After that, depending on the board warpage in the previous pass, the value is positive if the board is warped upwards, and negative if it is warped downwards.)

Hereinafter, the present invention will be described in detail based on examples. The embodiment is an example in which the present invention is applied to a four-high rolling mill.

FIG. 1 shows a material rolled by a four-high plate rolling mill having a pair of upper and lower work rolls 4, 5 and back-up rolls 1, 2, and table rollers 7, 8 on the entry and exit sides, respectively. 6 is schematically shown in the state in which it is being rolled. In addition, in the figure, 3 is the axle box of the lower back-up roll (upper back-up roll 1
9 is the top surface of the table rollers 7 and 8, 10 is a hydraulic cylinder as an actuator for controlling the lower work roll pickup (amount) X during rolling, and 11 is a hydraulic cylinder. The plunger 12 is oil in the cylinder and indicates that rolling is being carried out in the rolling direction indicated by the arrow.

In this rolling state, there are cases in which the rolled material 6 exhibits a tendency to warp downward (FIG. 2) and cases in which it exhibits a tendency to warp upward (FIG. 3) on the exit side of the rolling mill. The downward warping tendency shown in FIG. 2 occurs when the pick-up X is in the relationship X>1/2ΔH (where ΔH is the amount of rolling reduction), if disturbances caused by factors other than the lower work roll pick-up are ignored. Conversely, when there is a relationship of X<1/2 ΔH, an upward warping tendency as shown in FIG. 3 occurs.

The mechanism by which sheet warping occurs depending on the lower working roll pickup X will be explained with reference to FIG. 4, with reference to the case of downward warping shown in FIG. In the figure, A and B indicate the start points of the biting side contact of the rolled material 6 with the upper and lower work rolls 4 and 5, respectively, and C and D indicate the points at which the rolled material 6 is bitten out from the upper and lower work rolls 4 and 5, respectively. . (The same applies to A and B in FIG. 2.) The areas surrounded by A, B, C, and D are the areas that are being rolled by the upper and lower work rolls 4 and 5, and as shown in the figure, Compressive stress σ _U is applied to the upper work roll side and the lower work roll side of the rolled material 6, respectively.
σ _L occurs, and as a result, a bending moment is generated from the upper work roll 4 to the lower work roll 5 due to a compressive stress difference of σ _L −σ _U =Δσ.

Also, if the positions of A and B in the rolling direction are l,
The relationship between α, that is, X-1/2ΔH=α, is as shown in FIG.

Now, as shown in FIG. 3, assuming that the weight of the entry side rolled material 6 is P, the state of internal stress distribution in the rolled material 6 can be assumed as shown in the schematic diagram of FIG. 6. In addition, in the figure, H indicates the plate thickness, and W indicates the plate width. Here, assuming that the internal stress distribution is y=ax,
When balanced with the bending moment M, the following formula M=Pl......(1) Therefore, a=12Pl/H ³ , and since Δσ・W=a・H, the internal stress difference Δσ per unit width is Δσ=
a・H/W=12Pl/H ² W. Therefore, Δσ=0
Control l so that That is, by controlling X from the relationship between l and α shown in FIG. 5, it is possible to control the warp of the board without causing the warp phenomenon.

In accordance with what has been described above, an example will be described in which, in the case where an upward warping tendency or a downward warping tendency is actually exhibited due to some other disturbance factors, the board warping is controlled in the next pass.

First, as shown in Fig. 7, when a thick plate is rolled in a normal rolling state where no plate warpage occurs due to the relationship X = 1/2ΔH, due to several other disturbance factors, When an upward warpage occurs as shown in FIG. 8A, or a downward warpage occurs as shown in FIG.
(For example, an optical sensor, etc.) detects the board warping phenomenon, and as a result, in the next pass, for upward warping (Fig. 8 A), X = 1/2 ΔH + α (α > 0) The height of the lower work roll 5 is controlled to
The height of the lower work roll 5 is controlled so as to be 1/2ΔH+α (α<0), and rolling without warping of the sheet is performed in the next pass.

Next, an example of a control device used to implement the method of the present invention for controlling sheet warpage by controlling the pick-up of the lower work roll will be described.

FIG. 10 shows the closed loop of the pick-up control in a four-high plate rolling mill.
First, a signal X = 1/2 ΔH + α (α = 0 in the initial pass) is output from the process computer 18 that calculates the reduction schedule etc. to the hydraulic cylinder position control calculation unit 17 which is a lower pick-up control device, and this hydraulic cylinder position control calculation Device 1
7 outputs a valve opening command to the servo valve 15 that directly operates the pick-up control actuator (hydraulic cylinder 10) based on the signal X;
A hydraulic cylinder position sensor 14 built into the actuator feeds back a hydraulic cylinder position signal to a hydraulic cylinder position control calculation device 17, forming a minor closed circuit. In addition,
Reference numeral 16 denotes a hydraulic pressure generation source that operates the hydraulic cylinder 10.

In the main control loop, a detection signal from a sheet warp detection device 13 provided on the outlet side of the rolling mill is fed back to a process computer 18 via a sheet warp detection signal processing and calculation device 19, forming a main closed loop.

Note that although a hydraulic cylinder is illustrated as an example of the actuator, other actuators such as an electric type may be used.

As is clear from the above explanation, according to the present invention, the various problems in the prior art described above can be solved at once, and thick plate rolling can be carried out with high efficiency without causing the plate warping phenomenon, resulting in high quality. It is expected that significant effects such as making it possible to manufacture thick plate products with high yields can be expected.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing the state of rolling by a four-high plate rolling mill, FIG. 2 is a schematic explanatory diagram showing a case where the rolled material exhibits a downward warping tendency in the rolling mill of FIG. 1, and FIG. On the contrary, in the rolling mill of Fig. 1,
A schematic explanatory diagram when a rolled material exhibits a tendency to warp upward,
FIG. 4 is an explanatory diagram of the plate warpage generation mechanism in the case of downward warpage shown in FIG. 2, and FIG. 5 is a diagram showing the relationship between the upper and lower work roll biting start position difference l and the lower work roll pick-up α. , FIG. 6 is a schematic diagram illustrating the state of internal stress distribution in a rolled material, and FIG. 7 is a schematic diagram showing a case where thick plate rolling is performed in a normal rolling state without plate warping. 8 are schematic explanatory diagrams showing an example of board warpage control according to the present invention, in which figure A shows a case where upward warpage has occurred, and figure B shows a case in which downward warpage is performed in the next pass. FIG. 9 is a schematic diagram showing another example of sheet warping control according to the present invention, and FIG. Figure B shows a state in which the pick-up control of the lower work roll is carried out in the next pass in that case, and Fig. 10 is an example of the board warpage control device used in the implementation of the present invention, and shows the state in which the pick-up control of the lower work roll is carried out. It is an explanatory diagram showing a closed loop. 1... Upper back up roll, 2... Lower back up roll, 3... Lower back up roll shaft box, 4... Upper work roll, 5... Lower work roll,
6...Rolled material, 7...Entry side table roller, 8
... Output table roller, 9 ... Table roller top surface, 10 ... Hydraulic cylinder, 11 ... Hydraulic cylinder plunger, 12 ... Oil in hydraulic cylinder, 13 ... Board warpage detection device, 14 ...
Hydraulic cylinder position sensor, 15... Servo valve, 16... Hydraulic source, 17... Hydraulic cylinder position control calculation device, 18... Process computer, 19... Board warpage detection signal processing calculation device.

Claims (1)

[Scope of Claims] 1. When rolling a thick plate using a rolling mill that has a pair of upper and lower work rolls and is provided with table rollers on the entry and exit sides, The height of the lower work roll is adjusted so that the difference X between the top surface level of the lower work roll and the top surface level of the front and rear table rollers of the rolling machine becomes the value of the following formula. Method for controlling plate warpage in thick plate rolling. X = 1/2 ΔHi + α However, X: (lower work roll top surface level) - (rolling machine front and rear table roller top surface level) ΔHi: Reduction amount of the relevant pass α: Additional adjustment amount (α = 0 at the initial pass, After that, depending on the board warpage from the previous pass, if the board is warped upward, the value will be positive, and if it is warped downward, it will be negative.)