JP2017164795A - Shape control method in cold rolling - Google Patents

Abstract

PURPOSE: To prevent both of drawing in slow rolling speed part at rolling start time and end time, and plate breaking in high rolling speed part, between stands in a cold tandem mill.CONSTITUTION: A shape control method in cold rolling comprises: determining a drawing limit value of tension at an outlet side of a plate end part that causes a drawing in a rolling material. and a break limit value of tension at the outlet side of the plate end part that causes plate breaking in the rolling material, in advance; calculating a prediction value of the tension at the outlet side of the plate end part, using 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 to be equal to or greater than the predetermined drawing limit value in slow rolling speed part at rolling start time and rolling end time, as well as to be equal to or less than the predetermined break limit value in high rolling speed part during rolling, on the basis of the calculated prediction value of the tension at the outlet side of the plate end part; and performing control of the tension at the at outlet side of the plate end part using the calculated control quantity of the shape control means.SELECTED DRAWING: Figure 11

Description

  The present invention relates to a method for optimizing rolling conditions so that a rolled metal strip does not cause sheet breakage and narrowing.

  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 medium-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 rolled material). 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, there are many small cracks at the plate end in the width direction, so the plate end exit tension is excessive when the average exit tension is large or the shape of the rolled material between the stands is medium stretch. Thus, the plate may be broken.

  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 extended ear shape.

  However, in the method disclosed in Japanese Patent Laid-Open No. 4-200904, the plate end portion exit side tension becomes excessive when the average exit side tension is large and the degree of ear extension is light, 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, in the method of Patent Document 2, the plate end portion exit side tension may be too small, and the rolled material may be narrowed down. The rolling load varies depending on the rolling speed. Generally, the load decreases as the rolling speed increases, and increases as the rolling speed decreases. In the rolling process, when the material starts to be put (at the start of rolling), it gradually changes from the low speed state (low speed part) to the high speed state (high speed part), and when the material is pulled out (at the end of rolling), it again changes to the low speed state (low speed part). Become. If it does so, a load will change with the front-end | tip of a board, and the middle, and a difference will also arise in board thickness.

  Specifically, the rolling oil uptake amount and the friction coefficient increase at the low speed part of the rolling speed at the start and end of rolling compared to the high speed part, thereby increasing the rolling load, and the rolling material. The rolled shape changes to an extended ear shape. Here, the low speed portion at the start and end of rolling includes a low speed portion at the start and end of rolling of one coil in the case of continuous rolling by welding coils as shown in FIG. Therefore, in order to prevent the plate breakage at the high speed part, if the plate end part exit side tension is reduced, the plate end part exit side tension becomes too low due to the shape of the ear extension at the low speed part, and the rolled material is narrowed down. There is.

  The present invention has been devised to solve such a problem, and suitably controls the sheet end portion exit side tension to prevent both narrowing at the low speed portion of the rolling speed and plate breakage at the high speed portion. An object is to provide a shape control method.

  In order to achieve these objects, the invention according to claim 1 is characterized in that the narrowing limit value (tension lower limit value) of the plate end portion exit side tension at which narrowing occurs in the rolled material and the plate end portion exit at which plate breakage occurs in the rolled material. The fracture end value (tension upper limit value) of the side tension is obtained in advance, and the predicted value of the plate end portion exit side tension is calculated using a prediction formula representing the plate end portion exit side tension, and the calculated plate end portion Based on the predicted value of the exit side tension, the above-mentioned squeezing limit value is obtained in advance at the low speed portion of the rolling speed at the start and end of rolling, and the above-mentioned fracture is obtained in the high speed portion of the rolling speed during rolling. A shape in cold rolling, characterized in that a control amount of the shape control means is calculated so as to be equal to or less than a limit value, and the strip end side tension is controlled using the calculated control amount of the shape control means. It is a control method.

  Further, the invention according to claim 2 obtains in advance the squeezing limit value of the sheet end portion exit side tension at which the rolled material is squeezed and the rupture limit value of the plate end portion exit side tension at which the rolled material is ruptured. Predicting formulas representing the end tension at the end of the plate end using the side tension, rolling load, and the control amount of the shape control means as variables are created in advance, and the average exit side tension and the low speed part of the rolling speed at the start and end of rolling. Further, the predicted value of the rolling load at the high speed part of the rolling speed during rolling is substituted into the prediction formula, and at the low speed part of the rolling speed at the start of rolling and at the end of rolling, it is equal to or higher than the above-mentioned narrowing limit value and rolling. The control amount of the shape control means is calculated so as to be equal to or less than the fracture limit value at the high speed portion of the rolling speed, and the plate end portion exit side tension is controlled using the calculated control amount of the shape control means. Cold A shape control method in the rolling.

  Further, the invention according to claim 3 preliminarily obtains the limit value of the strip end side tension at which the rolling material is narrowed and the limit value of the strip end side tension at which the plate material is ruptured. Predictive formulas representing the strip edge exit side tension are created in advance using the side tension, rolling load, material crown amount and control amount of the shape control means as variables, and the average exit side tension, measured material crown value, and rolling start time And the predicted value of the rolling load at the low-speed part of the rolling speed at the end of rolling and the high-speed part of the rolling speed during rolling are substituted into the prediction formula, and the sheet end portion exit side tension is determined at the start of rolling and the end of rolling. In the low speed part, the control amount of the shape control means is calculated so as to be equal to or higher than the previously obtained narrowing limit value, and in the high speed part of the rolling speed during rolling, to be equal to or less than the predetermined fracture limit value. Shape control means A shape control method in a cold rolling and controlling the plate end exit side tension using the control amount.

  As described above, in the present invention, between the cold tandem mill stands, both the narrowing at the low speed portion of the rolling speed at the start and end of rolling and the sheet breakage at the high speed portion of the rolling speed during rolling. It becomes possible to prevent.

It is a figure explaining the low speed part of the rolling speed at the time of the rolling start and completion | finish, and the high speed part of the rolling speed during rolling. It is a figure showing 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 showing the influence which the work 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 showing 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 showing the influence which the 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 showing the influence which the amount of material crowns has on the elongation difference of the board edge part to the average value of the board width direction. It is a figure which shows the detail of the conditions 1-condition 10 of FIG. It is a figure showing the relationship between a board edge part exit side tension | tensile_strength and the presence or absence of narrowing. It is a figure which shows the detail of the conditions 1-condition 10 of FIG. It is a figure showing 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 calculated the plate end portion exit side tension using a prediction formula representing the plate end portion exit side tension, and the plate end portion exit side tension at the low speed part of the rolling speed at the start and end of rolling. By controlling the control amount of the shape control means so that it is below the limit value and below the fracture limit value at the high speed part of the rolling speed during rolling, the strip end side tension is controlled, and the low speed part is narrowed and the high speed part is controlled. Various investigations were conducted on shape control methods that can prevent both plate breaks.

  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 by controlling the control amount of the shape control means using a prediction formula that represents the tension at the edge of the plate end using the control amount of the shape control means as a variable, It has been found that it is possible to make the value not less than the value and not more than the fracture limit value at the high speed part of the rolling speed during rolling, and to prevent both narrowing of the low speed part and plate breaking of the high speed part.

  Hereinafter, as a shape control means installed in No. 3 stand of a cold tandem mill consisting of 4 stands, the shape control method of the present invention is applied to a work roll bender, an intermediate roll bender and a 6-high rolling mill having an intermediate roll shift. However, it goes without saying that 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 represented by the sum of the average exit side tension Tav and the tension difference (difference between the plate end portion exit side tension and the average exit side tension) ΔT as shown in the equation (1).
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. Of these, regarding the rolled material dimensions, if the table is divided for each plate thickness and width, the influence of the change in the rolled material size in the section on the shape can be reduced. The material, lubrication state, and front / rear tension affect the shape of the rolled material, but most of the effect is caused by changes in roll deflection through 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 object controlled by the “shape control means” refers to a part or all of a roll bender, a roll shift, a rolling reduction / rolling load, a spot clarant, and the like.

  FIG. 2 shows the influence of the rolling load P (kN) on the elongation difference Δε at the plate edge with respect to the average value in the plate width direction. A change in rolling load appears as a change in roll deflection, which 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, the elongation difference Δε at the plate end with respect to the average value in the plate width direction is also linearly related to the rolling load P.

  FIG. 3 shows the influence of the work roll bender force Wb (kN) 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 in the same manner as the rolling load, and the difference in elongation at the plate end Δε with respect to the average value in the work roll bender force Wb and the plate width direction. Is also in a linear relationship.

  FIG. 4 shows the influence of the intermediate roll bender force Ib (kN) on the elongation difference Δε at the plate end with respect to the average value in the plate width direction. Since the intermediate roll bender also changes the rolling shape by changing the roll deflection in the same manner as the rolling load, the intermediate roll bender force Ib and the elongation difference Δε at the plate end relative to the average value in the plate width direction are also included. It is in a linear relationship.

  FIG. 5 shows the influence of the intermediate roll shift position Ls (mm) 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. Since the intermediate roll shift also changes the rolling shape by changing the roll pressure by changing the contact pressure distribution between the work roll and the intermediate roll, the sheet edge with respect to the intermediate roll shift position Ls and the average value in the sheet width direction. There is also a linear relationship with the elongation difference Δε of the part.

  FIG. 6 shows the influence of the material crown amount Cr (μm) 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 by the difference in plate thickness between the plate edge and the plate width center. As a result, it can be seen that there is also a linear relationship between 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.

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. 2); be: slope of a straight line representing the relationship between the amount of material crown and elongation difference (FIG. 6). See), ce: slope of a straight line representing the relationship between work roll bender force and elongation difference (see FIG. 3), de: slope of a straight line representing the relationship between intermediate roll bender force and elongation difference (see FIG. 4), ee : Slope of a straight line representing the relationship between the intermediate roll shift position and elongation difference (see FIG. 5), fe: constant term.

  In a typical 6-high rolling mill having a work roll diameter of about 400 mm, a general 20-high rolling mill having a work roll diameter of 100 mm or less, and the like, the work roll is likely to be greatly deformed. Therefore, although the influence of the rolling load on the shape of the rolled material is large, the influence 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 narrowing in the plate thickness of 0.3 mm to 0.5 mm and the plate width of 850 mm to 1050 mm on the tandem mill exit side was investigated. In FIG. 7, each parameter (rolling load, material crown amount, average delivery tension, work roll bender force, intermediate roll bender force, intermediate roll shift position) is set for each rolling condition (condition 1 to condition 10). Yes. Therefore, the predicted value of the plate end portion exit side tension was calculated according to the above formula (4) for each condition, and the presence or absence of narrowing was investigated.

  The result is shown in FIG. As shown in FIG. 8, no narrowing occurred under conditions 1 to 5, but narrowing occurred under conditions 6 to 10. That is, it has been found that a narrowing limit value exists in the plate end portion exit side tension, and that narrowing occurs when the plate end portion exit side tension is equal to or less than the narrowing limit value. In this manner, the predicted value of the plate end portion exit side tension can be obtained from each condition and Expression (4), and it can be predicted whether or not narrowing will occur from the obtained predicted value.

  In other words, by setting the control amount of the shape control means so that the plate end portion exit side tension of the low speed portion calculated by the equation (4) is equal to or greater than the narrowing limit value, the low speed at the start and end of rolling. It becomes possible to prevent narrowing of the part.

  Similarly to the case of FIG. 8, the relationship between the plate end portion exit side tension and the presence or absence of plate breakage in the plate thickness of 0.3 mm to 0.5 mm and the plate width of 850 mm to 1050 mm on the tandem mill exit side was investigated. In FIG. 9, each parameter (rolling load, material crown amount, average delivery tension, work roll bender force, intermediate roll bender force, intermediate roll shift position) is set for each rolling condition (condition 1 to condition 10). Yes. Therefore, the predicted value of the plate end portion exit side tension was calculated according to the above formula (4) for each condition, and the presence or absence of plate breakage was investigated.

  The result is shown in FIG. As shown in FIG. 10, plate breakage did not occur under conditions 1-5, but plate breakage occurred under conditions 6-10. 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.

  In other words, by setting the control amount of the shape control means so that the plate end portion exit side tension of the high speed portion of the rolling speed calculated by the equation (4) is not more than the fracture limit value, the plate breakage at the high speed portion Can be prevented.

  Therefore, the shape control means of the shape control means so that the plate end portion exit side tension of the low speed portion of the rolling speed calculated by the equation (4) is not less than the narrowing limit value and the plate end portion exit side tension of the high speed portion is not more than the fracture limit value. If the control amount is set, it is possible to prevent both narrowing of the low speed part and plate breakage of the high speed part.

  In setting the shape control means, the rolling load Pl in the low speed part and the rolling load Ph in the high speed part are predicted using a rolling load expression such as the Brand & Ford equation, the Hill equation, etc., and the average exit side tension Tav, the low speed portion, Substituting the predicted values Pl and Ph of the rolling load at each high speed part and the measured value Cr of the material crown into the prediction formula (4) representing the sheet end exit side tension Te, the sheet end end exit side tension at the low speed part of the rolling speed The work roll bender force Wb, the intermediate roll bender force Ib, and the intermediate roll shift position Ls are calculated and set so that Tel is equal to or greater than the narrowing limit value and the plate end portion exit side tension Teh of the high speed portion is equal to or less than the fracture limit value. .

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. However, the combination of the shape control means to be used is the work roll bender, the intermediate roll bender. 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 rolling speed is not limited to the combination of the Le bender and the intermediate roll shift. The work roll bender force Wb is calculated and set so that the plate end exit side tension Tel of the low speed portion is not less than the narrowing limit value and the plate end exit side tension Teh of the high speed portion is not more than the fracture limit value.
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 outlet side of the tandem mill in a 6-high rolling mill installed in a No. 3 stand of a cold tandem mill consisting of 4 stands, the present invention is used. An applied example will be described.

  As shown in FIG. 11, 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 in advance rolling conditions (for example, work roll rotation speed, work roll diameter, low and high speed friction coefficients, plate width, input / output side thickness, average input / output side tension, deformation resistance of the rolled material, etc.). The rolling load Pl of the low speed part and the rolling load Ph of the high speed part are calculated according to the rolling 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 In the prediction formula (4) representing the tension Te, the plate end portion exit side tension Tel at the low speed portion of the rolling speed at the start and end of rolling is equal to or greater than the narrowing limit value, and the plate end portion exit side tension Teh at the high speed portion of the rolling speed. The work roll bender force Wb, the intermediate roll bender force Ib, and the intermediate roll shift position Ls were calculated and set so that would be equal to or less than the breaking limit value. Then, the values of the work roll bender force Wb, the intermediate roll bender force Ib, and the intermediate roll shift position Ls were fixed and rolled as they were. In addition, the value calculated | required in FIG. 7 was employ | adopted about the narrowing-down limit value, and the value calculated | required in FIG. 9 was employ | adopted about the fracture limit value.

  As a result, in the past, two coils per 500 coils were narrowed down, and three coils were ruptured. By applying the present invention, one coil was squeezed out of 500 coils, and the plate was broken. Did not occur.

  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 plate end portion exit side tension of the low speed portion of the calculated rolling speed is equal to or greater than the narrowing limit value. In addition, by controlling the plate end exit side tension by setting the control amount of the shape control means so that the plate end exit side tension of the high speed part is below the fracture limit value, between the cold tandem mill stands It is possible to prevent both the occurrence of narrowing at the low speed portion and the occurrence of plate breakage at the high speed portion at the start and end of rolling.

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

Claims (3)

Obtain in advance the limit value of the sheet end portion exit side tension that causes the rolling material to be squeezed and the rupture limit value of the sheet end portion exit side tension that causes the plate material to break.
Using the prediction formula representing the plate end portion exit side tension, the predicted value of the plate end portion exit side tension is calculated,
Based on the calculated predicted value of the sheet end portion exit side tension, at the rolling speed low speed portion at the start of rolling and at the end of rolling, the rolling speed at the rolling speed during rolling is higher than the above-described narrowing limit value. In the above, the control amount of the shape control means is calculated so as to be equal to or less than the predetermined fracture limit value,
The strip end portion exit side tension is controlled using the calculated control amount of the shape control means. A shape control method of a rolled material in cold rolling. Obtain in advance the limit value of the sheet end portion exit side tension that causes the rolling material to be squeezed and the rupture limit value of the sheet end portion exit side tension that causes the plate material to break.
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 average exit side tension and the rolling load predicted value at the low speed part of the rolling speed at the start and end of rolling and the high speed part of the rolling speed during rolling into the prediction formula,
The control amount of the shape control means so that it is not less than the above-mentioned limit value obtained in advance at the low speed part of the rolling speed at the start and end of rolling, and not more than the above breaking limit value in the high speed part of the rolling speed during rolling. To calculate
The shape control method in cold rolling characterized by controlling the sheet end portion exit side tension using the calculated control amount of the shape control means. Obtain in advance the limit value of the sheet end portion exit side tension that causes the rolling material to be squeezed and the rupture limit value of the sheet end portion exit side tension that causes the plate material to break.
Preliminarily creating a prediction formula 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,
Substituting the average exit side tension, the measured value of the material crown, and the rolling load predicted value at the low speed part of the rolling speed at the start and end of rolling and the high speed part of the rolling speed during rolling into the prediction formula,
The exit end tension of the plate end portion is not less than the previously obtained narrowing limit value at the low speed portion at the start of rolling and at the end of rolling, and not more than the previously determined fracture limit value at the high speed portion of the rolling speed during rolling. To calculate the control amount of the shape control means,
The shape control method in cold rolling characterized by controlling the sheet end portion exit side tension using the calculated control amount of the shape control means.