JP2017164794A - Shape control method in cold rolling - Google Patents

Abstract

PURPOSE: To prevent plate breaking, between stands in a cold tandem mill where no shape detector is installed, without interfering with plate thickness control.CONSTITUTION: A shape control method in cold rolling comprises: determining a breaking limit value of tension at an outlet side of a plate end part that causes plate breaking in the cold rolling mill in advance; creating a prediction formula representing the tension at the outlet side of the plate end part; calculating a control quantity for shape control means that makes the tension at the outlet side of the plate end part calculated by the prediction formula to be equal to or less than the breaking limit value; and performing control by setting or correcting the tension at the outlet side of the plate end part, using the calculated control quantity for the shape control means.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a method for optimizing rolling conditions so that a rolled metal strip does not break a plate.

  When rolling a steel strip in a cold rolling mill, a rolling shape defect is caused depending on the thickness of the steel strip and rolling conditions, resulting in poor product quality. Specifically, the rolling shape defect is a middle-elongation shape (the central portion of the length distortion in the rolling direction is extended) or an ear extension shape (of the length distortion in the rolling direction, the rolling band). For example, both ends of the end of the substrate may extend).

  In order to suppress such shape defects, in cold tandem mills, the plate shape between stands can be set by setting the control amount of the shape control means such as work roll bender, intermediate roll bender, intermediate roll shift to an appropriate value. It is designed not to get worse. However, since there are many small cracks at the end of the plate, if the average exit tension is large or the rolled material between the stands has a medium elongation, the exit tension on the end of the plate becomes excessive and the plate breaks. May occur.

  Therefore, in Japanese Patent Application Laid-Open No. 4-200904, the plate breaks by controlling the shape so that the steepness of the end of the metal band between the stands of the cold tandem mill is not less than the limit value where the ear crack does not grow. A cold rolling method for preventing the above has been proposed. This is a method of preventing plate breakage by reducing the plate end portion exit side tension when the average exit side tension is small and the rolled shape between the stands becomes an ear-extending shape.

  However, in the method disclosed in Japanese Patent Laid-Open No. 4-200904, when the average exit tension is large and the degree of ear extension is light, the exit end tension on the plate end is excessive, and the plate may break.

  Therefore, in Japanese Patent Laid-Open No. 8-141620, the total tension is reduced when the plate end portion exit side tension calculated based on the output of the shape detector in the cold reverse rolling mill becomes larger than a predetermined value. Therefore, a shape control method in a rolling mill has been proposed in which shape control is performed with the sheet end portion exit side tension being equal to or less than a predetermined value.

Japanese Patent Laid-Open No. 4-200904 JP-A-8-141620

  In the method of Patent Document 2, the shape of the material to be rolled is detected by a shape detector, and at least one of the maximum value of the unit tension in the width direction and the position unit tension in the specific width direction is more than a predetermined value. By reducing the total tension when it becomes larger, the plate end portion exit side tension can be reduced, thereby preventing the plate from breaking.

  However, generally, a shape detector is not installed between the stands of the cold tandem mill, and it is difficult to grasp the rolling shape between the stands. Therefore, it is impossible to apply the method of Patent Document 2 on the assumption that the plate end portion exit side tension is calculated based on the shape detector output. Moreover, in the method of Patent Document 2, in order to reduce the average delivery tension, there is a case where the thickness changes due to interference with thickness control.

  The present invention has been devised to solve such problems, and prevents plate breakage without interfering with plate thickness control even between cold tandem mill stands where no shape detector is installed. An object is to provide a possible shape control method.

  In order to achieve this object, the invention described in claim 1 preliminarily calculates a rupture limit value of a plate end portion exit side tension at which a plate breakage occurs in a rolled material, and previously calculates a prediction formula representing the plate end portion exit side tension. Create and calculate the control amount of the shape control means so that the plate end portion exit side tension calculated by the prediction formula is equal to or less than the fracture limit value, and using the calculated control amount of the shape control means It is a shape control method in cold rolling characterized by controlling by setting or correcting a sheet end portion exit side tension.

  The invention according to claim 2 is a method of obtaining in advance a rupture limit value of a strip end side tension at which a strip breaks in a rolled material, and using the average strip side tension, rolling load, and control amount of shape control means as variables. Predicting formula representing the exit side tension is prepared in advance, and the predicted values of the average exit side tension and rolling load are substituted into the prediction formula, and the shape control means so that the sheet end portion exit side tension is less than or equal to the fracture limit value. The shape control method in the cold rolling is characterized in that the control amount is calculated, and the strip end side tension is controlled using the calculated control amount of the shape control means.

  In the invention according to claim 3, the breaking limit value of the sheet end portion exit side tension that causes sheet breakage in the rolled material is obtained in advance, and the average exit side tension, rolling load, material crown amount, and control amount of the shape control means are variables. A prediction formula representing the sheet end portion exit side tension in advance, and substituting the average exit side tension, the predicted value of the rolling load and the material crown amount into the prediction formula representing the sheet end portion exit side tension, The control amount of the shape control means is calculated so that the plate end portion exit side tension is equal to or less than the breaking limit value, and the plate end portion exit side tension is controlled using the calculated control amount of the shape control means. It is the shape control method in the cold rolling characterized by doing.

  Further, the invention according to claim 4 is the shape control method in cold rolling according to claim 2, wherein the rolling load is continuously measured during rolling of the rolled material, and the average exit side tension and the Substituting the measured value of the rolling load into a prediction formula representing the plate end portion exit side tension, calculating the control amount of the shape control means so that the plate end portion exit side tension is equal to or less than the fracture limit value, The shape control method in cold rolling according to claim 2, wherein the strip end side tension is controlled by correcting the control amount of the shape control means to the calculated control amount.

  The invention according to claim 5 is the shape control method in cold rolling according to claim 3, and further measures the rolling load continuously during rolling of the rolled material, the average delivery tension, the rolling load And the amount of the material crown is substituted into a prediction formula representing the plate end portion exit side tension, and the control amount of the shape control means is calculated so that the plate end portion exit side tension is equal to or less than the fracture limit value. 4. The shape control method in cold rolling according to claim 3, wherein the strip end side tension is controlled by correcting the control amount of the shape control means to the calculated control amount. .

  In the present invention, it is possible to prevent the breakage of the plate without interfering with the plate thickness control even between the stands of the cold tandem mill where no shape detector is installed.

It is a figure which shows the influence which a rolling load has on the elongation difference of the board edge part with respect to the average value of a board width direction. It is a figure which shows the influence which the work roll bender force has on the elongation difference of the board edge part with respect to the average value of a board width direction. It is a figure which shows the influence which the intermediate roll bender force exerts on the elongation difference of the board edge part with respect to the average value of a board width direction. It is a figure which shows the influence which an intermediate | middle roll shift position has on the elongation difference of the board edge part with respect to the average value of a board width direction. It is a figure which shows the influence which the amount of material crowns has on the elongation difference of the board edge part with respect to the average value of a board width direction. It is a figure which shows the detail of the conditions 1-condition 10 of FIG. It is a figure which shows the relationship between board edge part exit side tension | tensile_strength and the presence or absence of board fracture. It is the schematic of the 6-high rolling mill and control system which were used in the Example.

  The inventors calculate the plate end portion exit side tension using a prediction formula representing the plate end portion exit side tension, and shape control means so that the calculated plate end portion exit side tension is equal to or less than the fracture limit value. Set or correct the control amount of the plate to control the tension at the end of the plate end, and prevent breakage without interfering with the plate thickness control even between cold tandem mill stands where no shape detector is installed. Various possible shape control methods were investigated.

  As a result, paying attention to the fact that the plate end exit tension is almost linearly related to the average exit tension, rolling load, material crown amount, and control amount of the shape control means, the average exit side tension, rolling load, material crown amount And controlling the control amount of the shape control means using a predictive equation representing the plate end portion exit side tension with the control amount of the shape control means as a variable, thereby making the plate end portion exit side tension below the fracture limit value. It was possible. As a result, it has been found that plate breakage is prevented without interfering with plate thickness control even between cold tandem mill stands where no shape detector is installed.

  Hereinafter, the shape control method of the present invention is intended for a 6-roll mill having a work roll bender, an intermediate roll bender and an intermediate roll shift as a shape control means installed in No. 3 stand of a cold tandem mill consisting of 4 stands. Of course, the present invention is similarly applied to a rolling mill other than a six-high rolling mill such as a rolling mill or a four-high rolling mill installed in another stand.

The plate end portion exit side tension Te is expressed by the sum of the average exit side tension Tav and the tension difference due to the rolling shape (difference between the plate end portion exit side tension and the average exit side tension) ΔT as shown in Equation (1). The
Te = Tav + ΔT (1)

Then, as is apparent from the principle of the shape detector that calculates the elongation difference in the plate width direction from the tension difference in the plate width direction, the Young's modulus is E, and the difference in elongation at the plate edge relative to the average value in the plate width direction. Is Δε, the tension difference ΔT due to the rolling shape is expressed by equation (2).
ΔT = E · Δε · (−1) (2)

  Factors affecting the shape of the rolled material include the rolled material size, material, lubrication state, front / rear tension, rolling load, control amount of the shape control means, material crown amount, pre-rolling shape, and the like. Among these, when the rolled material dimensions are divided into tables for each plate thickness and width, the influence of changes in the rolled material dimensions within the sections on the shape can be reduced. The shape of the rolled material is affected by the material, the lubrication state, and the front / rear tension, but most of the influence is caused by changes in roll deflection due to the rolling load.

  In addition, when the rolling reduction is small as in skin pass rolling, the influence of the shape before rolling is large, but in normal cold rolling with a rolling reduction of 5% or more, the influence of the shape before rolling is small. Therefore, it can be said that the main factors affecting the shape change are the rolling load, the material crown amount, and the control amount of the shape control means.

  Therefore, the quantitative effects of the rolling load, the material crown amount, and the control amount of the shape control means on the rolling shape were examined. Here, the “shape control means” refers to a part or all of a roll bender, a roll shift, a rolling reduction / rolling load, a spot clant, and the like.

  FIG. 1 is a diagram showing the influence of the rolling load P on the elongation difference Δε at the plate end with respect to the average value in the plate width direction. The change in rolling load appears as a change in roll deflection and changes the shape of the rolled material. The relationship between the rolling load and the amount of roll deflection is almost linear since it is intended for deformation in the elastic region. Therefore, it can be seen that the elongation difference Δε at the plate edge relative to the average value in the plate width direction is also linearly related to the rolling load P (see FIG. 1).

  FIG. 2 is a diagram showing the influence of the work roll bender force Wb on the elongation difference Δε at the plate end with respect to the average value in the plate width direction. The work roll bender, which is a shape control means, also changes the rolling shape by changing the roll deflection similarly to the rolling load. Therefore, there is also a linear relationship between the work roll bender force Wb and the elongation difference Δε at the plate end with respect to the average value in the plate width direction (see FIG. 2).

  FIG. 3 is a diagram showing the influence of the intermediate roll bender force Ib on the elongation difference Δε at the plate end with respect to the average value in the plate width direction. The intermediate roll bender also changes the rolling shape by changing the roll deflection in the same manner as the rolling load. Therefore, there is also a linear relationship between the intermediate roll bender force Ib and the elongation difference Δε at the plate end with respect to the average value in the plate width direction (see FIG. 3).

  FIG. 4 is a diagram showing the influence of the intermediate roll shift position Ls on the elongation difference Δε at the plate end with respect to the average value in the plate width direction. The intermediate roll shift position is defined by the distance from the taper start point to the plate end. The case where the taper start point is inside the plate end is negative, and the case where the taper start point is outside is positive. The intermediate roll shift also changes the rolling shape by changing the roll deflection by changing the contact pressure distribution between the work roll and the intermediate roll. Therefore, there is also a linear relationship between the intermediate roll shift position Ls and the elongation difference Δε at the plate end with respect to the average value in the plate width direction (see FIG. 4).

  FIG. 5 is a diagram showing the influence of the material crown amount Cr on the elongation difference Δε at the plate end with respect to the average value in the plate width direction. The amount of material crown was defined as the difference in plate thickness between the plate edge and the plate width center. As shown in FIG. 5, it was found that the material crown amount Cr and the elongation difference Δε at the plate end with respect to the average value in the plate width direction are also in a linear relationship.

From the relationship between the above factors, the elongation difference Δε at the plate edge portion with respect to the average value in the plate width direction can be expressed by Equation (3) using ae, be, ce, de, ee, fe as influence coefficients. .
Δε = ae · P + be · Cr + ce · Wb + de · Ib + ee · Ls + fe (3)

  The influence coefficients ae, be, ce, de, ee, and fe are constants determined by the production type such as the plate width, plate thickness, and material, and are combined with the experiment or the elastic deformation analysis of the roll and the plastic deformation analysis of the material. It is obtained from the simulation by the analysis model. Each influence coefficient is set in a table for each section such as a plate width, a plate thickness, and a material, or expressed as a function as a function of the plate width, the plate thickness, the material, and the like.

  Specifically, each influence coefficient includes: ae: slope of a straight line representing the relationship between rolling load and elongation difference (see FIG. 1); be: slope of a straight line representing the relationship between the amount of material crown and elongation difference (FIG. 5). See), ce: slope of a straight line representing the relationship between work roll bender force and elongation difference (see FIG. 2), de: slope of a straight line representing the relationship between intermediate roll bender force and elongation difference (see FIG. 3), ee : Slope of a straight line representing the relationship between the intermediate roll shift position and elongation difference (see FIG. 4), fe: constant term.

  In addition, in a 6-high rolling mill having a general work roll diameter of about 400 mm and a general 20-high rolling mill having a work roll diameter of 100 mm or less, a large bending deformation is likely to occur in the work roll. However, the effect of the material crown amount on the shape of the rolled material tends to be small. In this case, it is also possible to ignore the influence term of the material crown amount by setting the material crown amount Cr to zero in the equation (3).

From Equations (1) to (3), a prediction equation representing the plate end portion exit side tension with the average exit side tension, rolling load, material crown amount and control amount of the shape control means as variables is expressed by Equation (4). .
Te = Tav−E (ae · P + be · Cr + ce · Wb + de · Ib + ee · Ls + fe) (4)

  Next, the relationship between the plate end portion exit side tension and the presence or absence of plate breakage was investigated under the conditions of a plate thickness of 0.3 mm to 0.5 mm and a plate width of 850 mm to 1050 mm on the tandem mill exit side. In FIG. 6, parameters (rolling load, material crown amount, average delivery side tension, work roll bender force, intermediate roll bender force, intermediate roll shift position) are set for each rolling condition (condition 1 to condition 10). And the predicted value of the board edge part exit side tension was calculated by said Formula (4) for each condition, and the presence or absence of the board breakage was investigated.

  The result is shown in FIG. As shown in FIG. 7, plate breakage did not occur under conditions 1 to 5, but plate breakage occurred under conditions 6 to 10. In other words, it has been found that there is a break limit value in the plate end portion exit side tension, and that the plate end break occurs when the plate end portion exit side tension exceeds the break limit value. Thus, the predicted value of the plate end portion exit side tension can be obtained from each parameter and the equation (4), and it can be predicted from the obtained predicted value whether or not the plate breaks.

  That is, if the control amount of the shape control means is set or corrected so that the plate end portion exit side tension calculated by the equation (4) is equal to or less than the fracture limit value, the plate breakage can be prevented.

  For the initial setting of the shape control means, the rolling load P is predicted using a rolling load formula such as the Brand & Ford formula, the Hill formula, etc., and the average exit side tension Tav, the predicted value P of the rolling load, and the amount of material crown The measured value Cr is substituted into the prediction formula (4) representing the plate end portion exit side tension Te, and the work roll bender force Wb and the intermediate roll bender force Ib are set so that the plate end portion exit side tension Te is not more than the fracture limit value. The intermediate roll shift position Ls is calculated and set.

  In the shape control of the rolled material during rolling, the rolling load is continuously measured during rolling of the rolled material, and the average delivery side tension Tav, the measured value P of the rolling load, and the measured value Cr of the material crown are measured at the plate edge. The work roll bender force Wb, the intermediate roll bender force Ib, and the intermediate roll shift position Ls are substituted into the prediction formula (4) representing the partial exit side tension Te so that the plate end portion exit side tension Te is equal to or less than the fracture limit value. Calculate and correct.

  In the above description, it is assumed that the control amounts of the three shape control means of the work roll bender, the intermediate roll bender, and the intermediate roll shift are set or corrected. However, the combination of the shape control means to be used is the work roll bender, It is not limited to a combination of an intermediate roll bender and an intermediate roll shift. That is, even in a six-high rolling mill having a work roll bender, an intermediate roll bender, and an intermediate roll shift as shape control means, the work roll excluding the intermediate roll shift having poor responsiveness in shape control during rolling of the rolled material. The control amounts of the two shape control means of the bender and the intermediate roll bender may be corrected. In that case, it is preferable to fix the intermediate roll shift position Ls to the initial set value in the equation (4).

Further, when the shape control means is only a work roll bender as in the case of a four-high rolling mill, the formula (5) is used instead of the formula (4), and the plate end portion exit side tension Te is equal to or less than the fracture limit value. Thus, the work roll bender force Wb is calculated and set or corrected.
Te = Tav−E (ae · P + be · Cr + ce · Wb + fe) (5)

  When rolling a cold-rolled steel sheet 500 coil having a thickness of 0.3 mm to 0.5 mm on the tandem mill outlet side in a 6-high rolling mill installed in No. 3 stand of a cold tandem mill consisting of 4 stands, the present invention An example in which is applied will be described.

  As shown in FIG. 8, the six-high rolling mill 1 includes a work roll bender 2, an intermediate roll bender 3, and an intermediate roll shift 4 as shape control means. The host computer 5 has previously input rolling conditions (for example, work roll rotation speed, work roll diameter, friction coefficient, plate width, input / output side thickness, average input / output side tension, deformation resistance of the rolled material, etc.) The rolling load P is calculated according to the load equation.

  The process computer 6 captures the influence coefficient (ae, be, ce, de, ee, fe) and the measured value of the material crown Cr that are calculated in advance for each of the plate width, plate thickness, and material classification, and the plate edge exit side The work roll bender force Wb, the intermediate roll bender force Ib, and the intermediate roll shift position Ls are calculated and initialized so that the plate end portion exit side tension Te is equal to or less than the fracture limit value by the prediction formula (4) representing the tension Te. . In addition, about the fracture | rupture limit value, the value calculated | required in FIG. 7 was employ | adopted.

  In addition, after the start of rolling, the rolling load P is continuously measured with the load meter 7 so that the plate end exit side tension Te is equal to or less than the fracture limit value according to the prediction formula (4) representing the plate end exit side tension Te. The work roll bender force Wb and the intermediate roll bender force Ib were calculated and corrected. The intermediate roll shift position Ls was fixed at an initial set value.

  As a result, the plate breakage was conventionally caused by 3 coils per 500 coils, but none of the 500 coils caused the plate breakage by applying the method of the present invention. In addition, since the control amount of the shape control means was set or corrected instead of the average delivery side tension, the thickness did not fluctuate due to interference with the thickness control.

  As described above, the plate end portion exit side tension is calculated using the prediction formula representing the plate end portion exit side tension of the present invention, and the shape control is performed so that the calculated plate end portion exit side tension is equal to or less than the fracture limit value. By controlling the tension at the plate end by setting or correcting the control amount of the means, the plate thickness can be controlled without interfering with the plate thickness control even between cold tandem mill stands where no shape detector is installed. It became possible to prevent breakage.

1: Six-high rolling mill 2: Work roll bender 3: Intermediate roll bender 4: Intermediate roll shift 5: Upper computer 6: Process computer 7: Load meter 8: Rolled material 9: Work roll 10: Intermediate roll 11: Backup roll

Claims (5)

Obtain in advance the rupture limit value of the exit end tension of the plate edge where the rupture occurs in the rolled material,
Preliminarily creating a prediction formula representing the plate end portion exit side tension, calculating the control amount of the shape control means so that the plate end portion exit side tension calculated by the prediction formula is equal to or less than the fracture limit value,
A shape control method in cold rolling, wherein the control is performed by setting or correcting the sheet end portion exit side tension using the calculated control amount of the shape control means. Obtain in advance the rupture limit value of the exit end tension of the plate edge where the rupture occurs in the rolled material,
Preliminarily creating a prediction formula representing the sheet end portion exit side tension with the average exit side tension, rolling load and control amount of the shape control means as variables,
Substituting the predicted value of the average exit side tension and rolling load into the prediction formula, and calculating the control amount of the shape control means so that the sheet end portion exit side tension is less than or equal to the fracture limit value,
The shape control method in cold rolling, wherein the sheet end portion exit side tension is controlled using the calculated control amount of the shape control means. Determine in advance the rupture limit value of the plate end portion exit tension that causes plate rupture in the rolled material,
A prediction formula representing the sheet end portion exit side tension is created in advance with the average exit side tension, rolling load, material crown amount and control amount of the shape control means as variables, and the average exit side tension, predicted value of the rolling load and Substituting the material crown amount into a prediction formula representing the exit end tension of the plate end,
Calculate the control amount of the shape control means so that the plate end portion exit side tension is less than or equal to the fracture limit value,
The shape control method in cold rolling, wherein the sheet end portion exit side tension is controlled using the calculated control amount of the shape control means. Furthermore, the rolling load is continuously measured during rolling of the rolled material,
Substituting the measured value of the average exit side tension and the rolling load into a prediction formula representing the end side exit side tension of the plate,
Calculate the control amount of the shape control means so that the plate end portion exit side tension is less than or equal to the fracture limit value,
The shape control method in cold rolling according to claim 2, wherein the strip end side tension is controlled by correcting the control amount of the shape control means to the calculated control amount. Furthermore, the rolling load is continuously measured during rolling of the rolled material,
Substituting the average exit side tension, the measured value of the rolling load, and the material crown amount into the prediction formula representing the exit end tension of the plate end,
Calculate the control amount of the shape control means so that the plate end portion exit side tension is less than or equal to the fracture limit value,
The shape control method in cold rolling according to claim 3, wherein the sheet end portion exit side tension is controlled by correcting the control amount of the shape control means to the calculated control amount.