JP2993414B2 - Plate Profile Control Method in Hot Rolling - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a sheet profile in hot rolling for controlling the sheet profile during hot rolling over the entire length.

[0002]

2. Description of the Related Art Hot-rolled products are obtained by heating a slab produced by continuous casting or slab rolling by a heating furnace or receiving a hot slab as it is, and hot-rolling the slab by a rough rolling mill and a finishing rolling mill. It is made into a strip having a thickness of 0.0 to 25.4 mm, wound on a coil by a winder, cooled, and then processed in various refining lines. The strip obtained by hot rolling has a non-uniform temperature of the rolled material during hot rolling, that is, a change in the thickness in the longitudinal direction due to a change in the rolling load due to a temperature difference between the leading end and the trailing end of the rolled material, and the number of times of rolling. The roll of the rolling mill expands due to heat conduction from a high-temperature rolled material due to the increase of the roll (referred to as a thermal crown), and the shape of the roll changes with time.

[0003] The sheet profile in hot rolling is a general term for the cross-sectional shape of a hot strip in the width direction, and is generally managed in four categories: crown, wedge, high spot, and edge drop. The crown is a difference in the thickness between the center and the edge of the width of the strip, and is an element of the thickness variation. If the hot strip is a cold rolled material,
It is desirable that there be a crown amount suitable for the rolling operation in cold rolling. The wedge indicates a difference in thickness between strips, that is, a difference in thickness between both edges. The high spot refers to a local thickness bulge in the plate width direction. The edge drop refers to a sharply reduced thickness portion of a plate edge portion, and is a problem in a material having a high rolling load per unit width, such as a high-tensile steel plate.

As a method of controlling the sheet profile in the hot rolling, a fitting surface sealing mechanism and a fixing mechanism between the sleeve and the arbor are provided at both ends of the fitting surface of the sleeve and the arbor, and a sleeve at the center of the fitting surface is provided. A stepped gap is provided around the inner peripheral surface or the arbor outer peripheral surface or the both surfaces, and a pressurized fluid passage is provided from the sealed cylindrical gap through the arbor through hole to one end surface of the roll shaft. A method using a sleeve type backup roll (Japanese Patent Publication No. 55-125) can be considered.

[0005] In a hot rolling facility provided with a rolling mill for axially moving a roll relative to the width direction of the rolled material, the crown of the rolled material is corrected by rolling the rolled material into the rolling mill. While controlling the roll bender,
During the inter-pass time until the rolled material is extracted from the rolling mill and the next rolling is started, the sheet crown is adjusted by adjusting the amount of movement of the roll of the rolling mill in the roll axis direction so as to correspond to the rolling characteristics of the next rolled material. (JP-A-53-108864) has been proposed.

Further, a pair of work rolls having a tapered crown on one side end of a cylinder forming a rolling operation surface are vertically overlapped with each other in an alternate arrangement of the one side ends, and are movable in the roll axis direction. When rolling using a four-high rolling mill incorporated in the mill housing together with the backup roll, the upper and lower work rolls are placed at both ends of the plate to be rolled, respectively, between the roll operating surface of the lower work roll and the tapered grinding surface. (Japanese Patent Laid-Open No. 55-55)
No. 77903) has been proposed.

Furthermore, the strip crown of the hot-rolled coil delivered from the stand of the hot tandem rolling mill is measured after the start of steady rolling, and the control amount of the strip crown correcting means arranged on the stand is determined according to the above measured value. In the method for controlling the crown of a hot tandem rolling mill, wherein the variation of the crown is calculated to be within a predetermined range according to the control amount, the crown of the hot tandem rolling mill is controlled before the measurement of the crown. An initial control amount is set in the crown correcting means, a thermal compensation amount of the sheet crown correcting means is calculated based on an elapsed time and a rolling speed from the start of the steady rolling, and the plate is corrected according to a change in the rolling load of the stand. A method of calculating a load correction amount of the crown correcting means and correcting the initial control amount by the thermal compensation amount and the load correction amount (JP-A-62-224) 12 No.) have been proposed.

[0008]

SUMMARY OF THE INVENTION The above Japanese Patent Publication No. Sho 55-12
The method using a sleeve type roll (hereinafter, referred to as a VC roll) having a variable roll crown amount disclosed in Japanese Patent No. 5 can control a sheet crown during rolling, but cannot prevent edge drop. Also, JP-A-53-10
The method disclosed in Japanese Patent No. 8864 controls the roll bending device during rolling, controls the axial movement of the roll between passes with the next material, and controls the sheet crown. No two kinds of control means are used for the plate profile control.

Further, the method disclosed in Japanese Patent Application Laid-Open No. 55-77903 is a method of moving the taper roll in the axial direction to prevent edge drop. Control is performed between coils (until the next material), and the taper roll is not moved in the axial direction during rolling. Furthermore, Japanese Patent Application Laid-Open No. 62-2244
The method disclosed in Japanese Patent Application Laid-Open No. 12-123456 is intended only for crown correction, and does not control edge drop.

[0010] An object of the present invention is to solve the above-mentioned disadvantages of the prior art, and to change the heat crown of a roll during hot rolling.
It is an object of the present invention to provide a method of controlling a sheet profile in hot rolling, which can simultaneously control a change in a sheet profile in a coil due to a change in a rolling load, that is, both a crown and an edge drop.

[0011]

Means for Solving the Problems The present inventors have conducted various tests and studies to achieve the above object. As a result, the roll profile, which changes due to the temperature rise of the work roll during rolling due to heat transfer from the material, and the rolling load, which changes due to the temperature change (thermal rundown) in the longitudinal direction of the material, predict the fluctuation of the plate profile, When operating the control amount of the control means so as to obtain the crown target value and the edge drop target value, the use of at least two types of control means (combinations effective for the center part and the end part of the plate) enables the change of the plate profile. That is, the inventors have found that both the crown and the edge drop can be controlled simultaneously, and have reached the present invention.

That is, according to the first aspect of the present invention, in the hot rolling step, a roll profile immediately before the start of rolling is predicted by performing a heat crown calculation and a wear calculation based on a rolling history, and a sheet profile during rolling is predicted by a heat crown calculation. The rolling load change is predicted and obtained from the roll profile change and the material temperature drop calculation, and the control amounts of at least two types of profile control means having different control characteristics are changed so that the sheet crown and edge drop during rolling become target values. This is a method of controlling a plate profile.

Further, the invention according to claim 2 of the present application uses a thickness measured value of at least two points on one side near the edge of the sheet and a thickness measured value of the central portion of the sheet during hot rolling, and sets a crown target value during rolling. 2. The method according to claim 1, wherein the correction is made to the target value and the edge drop target value.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG.
A description will be given based on FIG. FIG. 1 is an overall configuration diagram of a typical finishing line of a hot rolling line to which the present invention is applied, FIG. 2 is a schematic flow chart of control of the present invention, and FIG. 3 shows an example of a crown change when only initial setting is performed. Things
(A) is a schematic diagram showing the relationship between the roll crown amount and the time from the start of rolling, (b) is a schematic diagram showing the relationship between the rolling load and the time from the start of rolling, and (c) is the crown prediction. FIG. 4D is a schematic diagram showing the relationship between the value and the number of rolls, and FIG. 4D is a schematic diagram showing the relationship between the amount of roll wear and the time from the start of rolling.

In FIG. 1, reference numeral 1 denotes a finishing mill consisting of seven stands. A bending device is installed on all stands, and a VC roll is installed as a backup roll for the latter three stands. 2 is a thickness gauge at the center of the steel strip provided on the output side of the finishing mill 1; 3 is a width-direction scanning profile meter also provided on the output side of the finishing mill 1; 4 is a winder; It is a steel strip. Reference numeral 6 denotes a line control unit which calculates a roll profile by predicting a heat crown and a roll wear amount using a rolling history from a roll change to a material to be rolled at the start of rolling, calculates a roll profile, and calculates a roll profile and a rolling load prediction calculation value. The profile is calculated, the control amount of the control means of the bending device of all stands is determined, the control amount 7 is instructed to the control means of the bending device, and the hydraulic pressure of the VC roll of the latter three stands is calculated, and the hydraulic pressure of the VC roll is calculated. A control amount 8 is instructed to the control means. If you only have this initial setting,
As shown in FIG. 3, when the effect of the increase in the rolling load is large, the crown increases.

Therefore, when the rolling is started, the line controller 6 controls the central portion of the steel strip thickness input from the steel strip central thickness gauge 2 and the width direction scanning type profile meter 3 as shown in FIG. The measured value and the measured thickness of the steel strip width direction edge,
Based on the rolling pass schedule, roll cooling water amount, material length, rolling speed, finishing stand entrance temperature, etc., which are input from a host computer, the heat crown fluctuation of each stand of the finishing mill 1 is calculated, and the rolling load fluctuation is calculated. The control amounts of the bending devices of all the stands and the VC rolls of the following three stands are calculated, and the control means of the bending devices of all the stands and the hydraulic control means of the VC rolls of the latter three stands are used to calculate the control amounts 7 and 8. Print the changes.

The heat crown fluctuation in this case is:
It is calculated from the material temperature, the contact arc length between the roll and the material (determined from the rolling pass schedule and the load), the sheet width, the rolling speed, the material length, the roll material, and the roll cooling water amount by a difference method or the like.

[0018]

(Equation 1)

[0019]

(Equation 2)

[0020]

(Equation 3)

Where, θ: roll temperature, t: time, r: radial coordinate, z: body length coordinate, c
: Specific heat, ρ: density, λ: thermal conductivity, θo
: Ambient temperature, hw, ha: Heat transfer coefficient, q _s :
Heat flux from rolled material, δ (z): Delta function (1 in contact with rolled material, 0 in non-contact portion)

[0022]

(Equation 4)

Where ν: Poisson's ratio, α: coefficient of linear expansion, R: radius of roll

[0024]

(Equation 5)

Further, the calculation of the control amounts of the bending devices of all the stands and the VC rolls of the subsequent three stands is
The swelling of the C roll is considered to be a deformation of the cylindrical shell having a constant shell thickness, and the swelling amount Cv (z) is calculated by the following equation (6).
Ask for.

[0026]

(Equation 6)

[0027]

(Equation 7)

The control of the bending device and the VC roll is performed by calculating a sheet crown and an edge drop from a sheet thickness distribution in the width direction obtained by a roll deformation model shown below, changing a control amount so as to be a target value, and repeating the processing. Calculate and decide. That is, one half from the roll barrel center
And the distribution of the rolling load and the contact load between rolls in the roll axis direction is regarded as uniform in each divided section, and the unit width contact load between rolls in the i-th divided section from the center of the roll barrel is P (i), Assuming that the unit width rolling load applied to the work roll from the rolled material is q (i), the exit plate thickness is h (i), and the divided section width is ΔZ (i), the displacement conforming condition of the contact portion between the work roll and the backup roll is as follows. The displacement adaptation condition of the contact portion between the work roll and the rolled material can be obtained by the following equation (9).

[0029]

(Equation 8)

[0030]

(Equation 9)

Where J: bending force of the work roll, K _w : rigid displacement of the work roll, M _H : rigidity coefficient of the housing rolling system, S: rolling position, Rc
(I): roll profile (average value of upper and lower rolls),
a (i, j): Influence coefficient of roll axis displacement, _w , _B
: _Af (i, j) represents a work roll and a backup roll, respectively. Influence coefficient of flat displacement of the work roll surface, K: Spring constant between rolls.

According to the present invention, during rolling, the temperature of the work roll rises due to heat transfer from the material to be rolled, and the roll profile changes, and the rolling load changes due to the temperature change in the longitudinal direction of the material to be rolled. Therefore, at least two types of plate profile control means are used when the variation of the plate profile is predicted by calculation and the control amount of the plate profile control means is operated so as to attain the crown target value and the edge drop target value.

When operating the control amount of the plate profile control means, at least two types of plate profile control means are used.
If only the crown is used, one type of plate profile control means may be used, but two or more types of plate profile control means are required to simultaneously control the edge drop.
The plate profile control means includes a method called a cross roll in which a roll bending device, a VC roll, and a work roll are inclined with respect to a rolling direction, and a method in which the tapered roll is moved in an axial direction.

The above-mentioned plate profile control means do not have exactly the same control characteristics. Some have a relatively effective effect at the center of the plate and some have an effect at the end of the plate.
By combining these, crown and edge drop can be controlled. It should be noted that the method of moving the taper roll in the axial direction is actually difficult because a considerable driving force is required to move the taper roll during rolling, and it is a good idea to combine other means. For example, a combination of a VC roll that is relatively effective at the center and a roll bending device that is relatively effective at the plate edge, a cross-roll method that is relatively effective at the center, and an effect that is relatively effective at the plate end. A combination with a certain roll bending device or the like can be considered.

In claim 2 of the present invention, the thickness of at least two points on one side in the vicinity of the edge is determined in order to measure the crown. , B, the crown amount = C− (A +
B) / 2, the edge drop can be measured by measuring each of the two edges at two places, for example, 25 m from the plate edge.
This is because it is necessary to measure the plate thicknesses G and H of m and 15 mm and to obtain the edge drop amount = GH. Actually, in order to measure the plate thickness at each of the two end portions of each edge, it is general to measure several points in the vicinity and perform an averaging process, so that disturbance due to noise can be prevented.

[0036]

【Example】

Example 1 In a hot rolling mill consisting of 7 stands, C: 0.5
5% high carbon steel sheet, product thickness 2.0mm, width 10
A 50 mm steel strip was rolled with a target crown value of 30 μm and a target edge drop value of 40 μm or less, and the plate profile was measured at the front end, the center rear end, and the longitudinal direction of the product coil. In the embodiment of the present invention, the control at the start of rolling is
Increment vendors of all stands and VC rolls of the three subsequent stands were used.
The stand's increment vendor and VC rolls were used. Table 1 shows the results. In addition, the control during rolling may be performed by using the benders of all the stands, but the control is complicated, so that three stands are used. In addition, if the control is performed for only the last one stand, the flat shape is likely to be deteriorated.

As a comparative example, Table 1 shows a case where the crown is controlled to be constant by changing only the pressure of the bending device. Table 1 shows the results of the embodiment according to claim 2 of the present invention in which the VC roll pressure was controlled in accordance with the value measured by the profile meter during rolling. The value of the crown used was a deviation from the center thickness at a position 25 mm from the edge. For edge drop, a difference in plate thickness between 25 mm and 15 mm from the edge was used. The measurement of the sheet profile consists of one X-ray thickness gauge installed on the exit side of the rolling mill that measures the center of the sheet and the X-ray thickness installed on the exit side of the rolling mill that moves in the width direction near the edge of the sheet. This was performed using a total of one unit.

[0038]

[Table 1]

As shown in Table 1, in the comparative example in which only the pressure of the bending device was changed, the crown was accurately controlled during rolling, but the edge drop was greatly affected by the increase in the rolling load, and the rear end of the steel strip was large. Department has increased. On the other hand, in the embodiment of the present invention, the increment vendor and the VC roll of the three rear stands are used at the start of rolling, and the VC roll of the three rear stands are used for the control during the rolling. During the rolling, the crown and the edge drop hardly changed. Further, in the embodiment of claim 2 of the present invention in which the VC roll pressure is controlled in accordance with the measured value of the profile meter during rolling, it is understood that the target profile can be obtained with higher accuracy by correcting the calculation prediction accuracy error. .

FIG. 4 is a schematic diagram of a control timing chart according to the present invention in comparison with the conventional method. As shown in FIG. 4, in the method of the present invention, during rolling, the rolling load gradually increases due to thermal rundown. At first, the bending pressure is reduced in consideration of the roll profile change due to the heat crown. However, since the edge drop is expected to increase at the rear end, an increase in the edge drop can be suppressed by increasing the bending pressure while decreasing the VC roll pressure. On the other hand, in the conventional method, the edge drop increases at the rear end by controlling the VC roll pressure to be constant.

[0041]

As described above, according to the method of the present invention, it is possible to simultaneously control the sheet crown and the edge drop, thereby improving the crown accuracy in the coil and stabilizing the shape. be able to.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a typical finishing line of a hot rolling line to which the method of the present invention is applied.

FIG. 2 is a schematic flowchart of control of the method of the present invention.

FIGS. 3A and 3B show examples of changes in crown when only initial settings are made. FIG. 3A is a schematic diagram showing the relationship between the roll crown amount and time from the start of rolling, and FIG. 3B is a diagram showing rolling load and rolling. FIG. 4C is a schematic diagram showing the relationship between the time from the start, and FIG. 4C is a schematic diagram showing the relationship between the predicted crown value and the number of rolls. FIG. 4D is the schematic diagram showing the relationship between the amount of roll wear and the time from the start of rolling. FIG.

FIG. 4 is a schematic diagram of a control timing chart according to the method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Finishing rolling mill 2 Steel strip thickness gauge 3 Scanning profile meter 4 Winding machine 5 Hot rolled steel strip 6 Line controller 7, 8 Control amount

Claims (2)

(57) [Claims] In a hot rolling step, a roll profile immediately before the start of rolling is predicted by performing a heat crown calculation and a wear calculation based on a rolling history, and a sheet profile during rolling is subjected to a roll profile change by a heat crown calculation and a material temperature. A plate profile characterized by changing a control amount of at least two types of profile control means having different control characteristics so as to predict and obtain a change in rolling load from a descent calculation so that a plate crown and an edge drop during rolling become target values. Control method. 2. A correction to a crown target value and an edge drop target value during rolling, using a thickness measurement value of at least two points on one side and a thickness measurement value of a center portion of a sheet near a sheet edge during hot rolling. Claims 1 to 3 are modified.
The sheet profile control method in the hot rolling described in the paragraph [6].