JP5874372B2 - Cold rolling method for metal strip - Google Patents

Description

  The present invention relates to a chattering prevention technique in a tandem rolling mill.

  Conventionally, in a tandem rolling apparatus that continuously cold-rolls a metal strip with a plurality of rolling mills, self-excited vibration is generated in the rolling mill when the rolling speed is increased (hereinafter referred to as “chattering”). . This chattering measure is based on a rule of thumb because the mechanism is not theoretically clarified.

  Chattering occurs due to a neutral point during rolling (lubricated state), rolling tension, rolling speed, roll roughness, and the like, and mainly occurs during acceleration of rolling speed or high speed rolling. When chattering occurs, there are adverse effects such as a decrease in yield due to sheet thickness hunting and a decrease in productivity due to operation at a reduced rolling speed. In the worst case, damage to the equipment due to self-excited vibration can be considered.

  As a chattering prevention technique, an improvement for improving lubricity between a rolled material and a work roll has been proposed. Specifically, since the lubricity depends on the rolling oil film thickness between the rolled material and the work roll, rolling oil supply systems and oil components for maintaining and improving these have been proposed (for example, Patent Documents 1 to 3). ).

  On the other hand, Patent Documents 4 to 7 propose methods for controlling the rolling oil by predicting the lubrication state. Patent document 4 estimates the oil film thickness which is a direct factor of a lubrication state by mixing a tracer in rolling oil. Patent Documents 5 to 7 propose to control the rolling oil flow rate by calculating a lubrication state index and its target value using an equation according to an empirical rule from rolling data and a partial theoretical equation. Yes.

  In the above method, a unique index is used for controlling the rolling oil flow rate. However, as a general index representing the lubrication state, a control method for determining the rolling oil flow rate using a friction coefficient or an advanced rate is disclosed in Patent Documents 8 to 11. Proposed in These set the target values of the friction coefficient and the advanced rate at which chattering does not occur, and control the rolling oil flow rate so that the friction coefficient and the advanced rate are within the target range.

  A model for directly predicting vibration is proposed in Patent Document 12. Patent Document 12 predicts the occurrence of chattering from a self-excited vibration model that considers the interaction (tension) between the rolling mill and the adjacent rolling mill, and parameters for preventing chattering are derived from rolling theory. This formula is incorporated into the self-excited vibration model, and this parameter is adjusted to prevent chattering.

JP 2010-99668 A JP 2009-242478 A JP 2009-190081 JP 2004-117117 A JP 2002-282926 A JP 2002-66622 A JP 09-239430 A JP 2002-346614 A JP 2001-321809 A JP 2000-317510 A JP 2000-94024 A JP 2005-297025 A

  However, in the methods of Patent Documents 1 to 3, chattering may occur even if the lubricity is improved, and the effect of preventing the occurrence of chattering cannot be stably obtained.

  The methods of Patent Documents 4 to 7 may not prevent chattering from occurring, and the effect of preventing chattering is insufficient. In addition, the rolling information used for prediction of the lubrication state becomes enormous and complicated calculation is required.

  The control methods of Patent Documents 8 to 11 do not eliminate the vibration source itself that generates chattering, and the effect of preventing the occurrence of chattering is limited.

  In Patent Document 12, in addition to the fact that the self-excited vibration model used for predicting the occurrence of chattering is complicated and has a large calculation capacity, and the parameters to be corrected when a difference from an actual rolling mill occurs are also complicated, The effect of preventing the occurrence of chattering is also limited.

  In view of the problems of the prior art, an object of the present invention is to provide a rolling method capable of preventing chattering by a simple method when cold rolling a metal strip in a tandem rolling mill.

  Means of the present invention for solving the above-mentioned problems are as follows.

(1) Damping coefficient Cm (Ns / m) of rolling mill, rolling load B (N), frequency C (1 / s) of rolling load fluctuation, acceleration rate α (m / m) in the vertical direction with respect to the metal strip from the rolling mill A method of cold rolling a metal strip, comprising rolling the metal strip so that s ² ) satisfies Cm−B × C / α> 0.

(2) Rolling machine damping coefficient Cm (Ns / m), rolling conditions and rolling load B (N), rolling load fluctuation frequency C (1 / s), vertical acceleration with respect to the metal strip from the rolling mill The relationship between the rate α (m / s ² ) is obtained in advance, and when the metal strip is cold-rolled, the damping coefficient Cm (Ns / m) obtained in advance, and the rolling conditions and the rolling load B (N), Using the relationship between the rolling load fluctuation frequency C (1 / s) and the vertical acceleration rate α (m / s ² ) with respect to the metal strip from the rolling mill, the rolling load B (N) and the rolling load fluctuation frequency C are used. (1 / s), the rolling conditions were determined and determined so that the vertical acceleration rate α (m / s ² ) with respect to the metal strip from the rolling mill satisfies the relationship of Cm−B × C / α> 0. A method for cold rolling a metal strip, comprising rolling the metal strip under rolling conditions.

(3) During rolling, the rolling load B, the frequency C of the rolling load fluctuation, and the acceleration rate α in the vertical direction with respect to the metal strip from the rolling mill are measured to obtain the rolling load B (N), the rolling load fluctuation frequency C ( 1 / s), it is determined whether the vertical acceleration rate α (m / s ² ) with respect to the metal strip from the rolling mill satisfies Cm−B × C / α> 0, and Cm−B × C / When α> 0 is not satisfied, the damping coefficient Cm (Ns / m) obtained in advance, the rolling condition and rolling load B (N) obtained by measurement, and the frequency C (1 / s) of the rolling load fluctuation are obtained. The rolling conditions are corrected so as to satisfy Cm−B × C / α> 0 using the relationship of the acceleration rate α (m / s ² ) in the vertical direction with respect to the metal strip from the rolling mill. The cold rolling method of the metal strip as described in said (2).

According to the present invention, the damping coefficient Cm of the rolling mill, the rolling load B, the frequency C of the rolling load fluctuation, and the acceleration rate α (m / s ² ) in the vertical direction with respect to the metal strip from the rolling mill are Cm−B × C. Since the metal strip is cold-rolled so as to satisfy the relationship of / α> 0, vibrations of the rolling mill can be suppressed, and even if vibrations occur, vibration expansion can be suppressed. Chattering can be suppressed.

It is a schematic diagram explaining the change of rolling load when a rolling condition is changed, and plate | board thickness change. It is a schematic side view of a tandem rolling mill having two stands. It is a figure which shows the relationship between the rolling oil flow rate of # 2 stand, and the rolling load B of # 2 stand. It is a figure which shows the relationship between the rolling oil flow rate of # 2 stand, and the acceleration rate (alpha) of the perpendicular direction with respect to the metal strip from a # 2 stand rolling mill. It is a figure which shows the relationship between ratio C of # 1 stand load with respect to # 2 stand load (load ratio of # 1 / # 2), and the frequency C of the rolling load fluctuation | variation of # 2 stand.

  The essence of chattering is the diverging phenomenon of rolling mill vibrations. In order to prevent chattering, it is necessary to eradicate the vibration source and to suppress the vibration expansion immediately after the vibration is generated. The present invention prevents chattering by creating a model of a vibration attenuation term from the vibration equation of vibration of a rolling mill, adjusting the rolling conditions so that the vibration attenuation term is larger than zero, and rolling. .

  The present invention will be described in detail below.

Chattering of a rolling mill can be considered as one-degree-of-freedom vibration. Chattering, which is a vibration divergence phenomenon, is related to the force (rolling load) input from the outside to the rolling mill. When a one-degree-of-freedom forced vibration model is applied to a rolling mill, the equation of motion of the rolling mill vibration can be expressed by equation (1). The left side shows the vibration state of the rolling mill, and the right side shows the external force.
m × Y ″ + Cm × Y ′ + k × Y = ΔP (1)
here,
Y: Vertical displacement of the rolling mill [m]
Y ′: Vertical speed of rolling mill [m / s]
Y ″: vertical acceleration of the rolling mill [m / s ² ]
m: Roll mass [kg]
Cm: Damping coefficient of rolling mill [Ns / m]
k: Spring constant of the rolling mill [kg / s ² ]
ΔP can be expressed by equation (2).
ΔP = A × Y′−D × Y (2)
A and D are the coefficients of the term Y ′ (velocity) and the term Y (displacement), and A is a factor that affects the divergence of vibration.

Equation (3) is obtained from Equation (1) and Equation (2).
mY ″ + (Cm−A) × Y ′ + (k + D) × Y = 0 (3)
In the one-degree-of-freedom forced vibration, the vibration is attenuated when the vibration attenuation term is larger than zero, and the vibration diverges when smaller than zero. In the expression (3), the attenuation term is Cm-A, so that chattering can be suppressed if the expression (4) is satisfied.
Cm-A> 0 (4)

In the present invention, the unit of A in the Y ′ term in the equation (2) is [N / (m / s)], the rolling load (N) input from the outside to the rolling mill, and the frequency of the rolling load fluctuation. It was divided into (1 / s) and the acceleration rate (m / s ² ) in the vertical direction with respect to the metal strip from the rolling mill, and expressed by equation (5).
A = B × C / α (5)
here,
B: Rolling load [N] input to the rolling mill from the outside
C: Frequency of rolling load fluctuation input to the rolling mill from the outside [1 / s]
α: Acceleration rate in the vertical direction with respect to the metal strip from the rolling mill (m / s ² )
Equation (6) is obtained from Equation (4) and Equation (5). If the expression (6) is satisfied, chattering can be suppressed.
(Cm−B × C / α)> 0 (6)

  Next, how to obtain Cm, B, C, and α will be described.

Cm:
Cm is a parameter unique to the rolling mill. Cm can use the damping coefficient of the rolling mill used when designing and manufacturing a tandem rolling mill. Cm may be obtained by actual measurement with a rolling mill. When obtaining by actual measurement with a rolling mill, B, C, and α, which will be described later, are measured at the time of rolling, and Cm is calculated from B, C, and α, which are the limits at which chattering does not occur by changing rolling conditions.

B, C, α:
B, C, and α are parameters whose values vary depending on the rolling conditions. B, C, and α are obtained by actual measurement with a rolling mill. Factors affecting B, C, α include rolling oil flow rate, initial roll roughness, rolling amount, rolling speed, entry side tension, exit side tension, roll gap, and the like.

  In order to obtain B, C, α, the rolling oil flow rate, the initial roll roughness, the rolling amount, the rolling speed, the entry side tension, the exit side tension, and the roll are in the initial state in the state where the metal strip is being rolled by a rolling mill. B, C, and α can be obtained by setting a gap, and then changing any one of the factors and measuring the load and thickness in accordance with time. B is obtained from the load input to the rolling mill, C is obtained from the frequency of load fluctuation, α is obtained by measuring the difference in peak thickness change per unit time and further dividing by unit time (FIG. 1). (See (c)).

  Chattering of a rolling mill is also affected by rolling conditions of an upstream rolling mill adjacent to the rolling mill. Accordingly, in addition to the rolling conditions of the rolling mill, the rolling conditions of the upstream rolling mill adjacent to the rolling mill (the rolling load input to the rolling mill, the rolling oil flow rate, the initial roll roughness, the rolling amount, the rolling speed) It is also preferable to obtain the relationship between B, C and α of the rolling mill, reflecting the rolling conditions such as the entry side tension, the exit side tension, and the roll gap. The relationship between the rolling conditions of the upstream rolling mill adjacent to the rolling mill and the B, C, and α of the rolling mill is the rolling conditions of the upstream rolling mill adjacent to the rolling mill when rolling with the rolling mill. Is changed, B, C, and α may be obtained by measuring changes in load and plate thickness with respect to time of the rolling mill.

  In the rolling mill, the thickness after rolling is detected, and the load input to the rolling mill is controlled so that the detected thickness becomes a predetermined thickness. When a load is input from the outside to the rolling mill, vibration is generated in the rolling mill. The vibration of the rolling mill is measured as a load fluctuation by a load meter (load cell). FIG. 1 is a conceptual diagram for explaining a change with respect to time of a load fluctuation generated in a rolling mill due to a rolling load B input to the rolling mill from the outside.

  FIG. 1A shows a case where the rolling conditions satisfy Cm−B × C / α> 0. The load fluctuation generated by the vibration of the rolling mill is quickly attenuated, and the peak value of the load fluctuation does not increase with time. There is no divergence of vibration and chattering is suppressed.

  FIG. 1B shows a case where the rolling conditions do not satisfy Cm−B × C / α> 0. The peak value of the load fluctuation generated by the vibration of the rolling mill increases with time. In such a state, vibration diverges and chattering cannot be suppressed.

  In the present invention, the metal strip is cold-rolled as follows.

  Cm is obtained in advance by the above-described method, and the relationship between rolling conditions and B, C, α is obtained in advance, or is obtained by actual measurement during rolling. And the chattering prevention measures at the time of cold rolling a metal strip use the relationship between B, C, α and the damping coefficient Cm obtained above, the rolling condition obtained in advance or obtained by actual measurement during rolling. Thus, the rolling conditions are determined so as to satisfy the relationship of Cm−B × C / α> 0, and the metal strip is rolled. When changing the rolling conditions, the rolling conditions are determined so as to satisfy the relationship of Cm−B × C / α using the rolling conditions obtained above and the relationship of B, C, α, and the metal strip is rolled. To do. The relationship between the rolling conditions used when changing the rolling conditions and B, C, α is stored in the computer as data measured in advance and used when changing the rolling conditions. By rolling in this way, chattering of the rolling mill can be suppressed.

  Also, during rolling, the load fluctuation due to vibration generated in the rolling mill due to the rolling load B input to the rolling mill, the plate thickness fluctuation are measured, the frequency C of the load fluctuation, the vertical direction relative to the metal strip from the rolling mill The acceleration rate α is obtained, and it is determined whether or not B, C, and α satisfy Cm−B × C / α> 0. When Cm−B × C / α> 0 is not satisfied, the acceleration rate α is obtained in advance. Using the relationship between the rolling conditions and B, C, and α, the metal strip can be rolled by correcting the rolling conditions so as to satisfy Cm−B × C / α> 0. By rolling in this way, the effect of suppressing chattering of the rolling mill can be further improved.

  The series of processes can be performed via a computer. That is, for example, in a computer that controls the rolling mill, the damping coefficient Cm of the rolling mill obtained in advance, the rolling conditions and the rolling load B, the frequency C of the rolling load fluctuation, the vertical direction with respect to the metal band from the rolling mill The relationship of the acceleration rate α is stored, the rolling load B input to the rolling mill, the rolling load measured by the rolling mill load meter, and the sheet thickness data are input. From the input data, the rolling load fluctuation The frequency C and the acceleration rate α in the vertical direction with respect to the metal strip from the rolling mill are obtained by calculation, and it is determined whether or not the obtained B, C, α satisfy Cm−B × C / α> 0, and Cm When it is determined that −B × C / α> 0 is not satisfied, the relationship between the stored rolling conditions, the rolling load B, the frequency C of the rolling load fluctuation, and the vertical acceleration rate α with respect to the metal strip from the rolling mill In order to satisfy Cm−B × C / α> 0, Adding a condition modifying unit for modifying the conditions, it may be controlled rolling mill to roll in modified rolling conditions.

  Chattering is likely to occur at the final stand (final rolling mill) of the tandem rolling mill and its preceding stage, and is most likely to occur at the final stand. Therefore, the method of the present invention is preferably carried out by the final stand of the tandem rolling apparatus and the stand rolling of the preceding stage.

  Using a 2-stand tandem cold rolling mill, a steel plate having a thickness of 0.46 mm, a width of 840 mm, and a strength of 270 MPa was cold-rolled to a thickness of 0.20 mm at a rolling speed of 2000 mpm. At that time, the amount of sprayed rolling oil on the second stand was changed variously, B, C, and α were measured, and the presence or absence of chattering was investigated. When Cm−B × C / α> 0 was satisfied, chattering did not occur. When Cm−B × C / α> 0 was not satisfied, chattering occurred at the # 2 stand.

Using a tandem rolling apparatus having two stands (rolling mills), # 1 stand (# 1STD) and # 2 stand (# 2STD) shown in FIG. 2, the thickness is 0.46 mm, the width is 840 mm, and the strength is 270 MPa. The steel sheet was cold rolled to a thickness of 0.20 mm. In the rolling of the steel sheet, chattering does not occur at a rolling speed of 1500 mpm. However, when the rolling speed exceeds 1500 mpm, there is a problem of chattering. The damping coefficient Cm of the # 2 stand of this rolling mill is 1.15 × 10 ¹¹ (Ns / m).

  In this rolling mill, under the condition of a rolling speed of 2000 mpm (rolling speed of # 2 stand), the rolling oil flow rate supplied from the spray device 3 of # 2 stand is changed, the rolling load of # 2 stand is measured, and B is obtained. It was. The results are shown in Table 1 and FIG. When the rolling oil flow rate is increased, B becomes smaller. It is considered that when the rolling oil flow rate is increased, the rolling oil 3 enters between the metal strip 4 and the roll (rolling roll) 1 to form a thicker oil film. B is smaller when the roll roughness is smaller. Note that the change in C due to the rolling oil flow rate is considered to be small.

  Under the conditions of a rolling speed of 2000 mpm (rolling speed of # 2 stand), the flow rate of rolling oil supplied from the spray device of # 2 stand was changed, the rolling load of # 2 stand was measured, and α was obtained. The relationship between the rolling oil flow rate of the # 2 stand and α is shown in Table 2 and FIG. Increasing the rolling oil flow rate increases α. This is presumably because when the rolling oil flow rate is increased, the force (load) from the metal strip decreases, and the acceleration rate in the vertical direction with respect to the metal strip from the rolling mill, that is, the force for suppressing the metal strip increases.

  Also, under the conditions of rolling speeds of 1500 mpm and 2000 mpm (rolling speed of # 2 stand), the rolling load input to # 1 stand is changed, the rolling load of # 2 stand is measured, and C is obtained from the wave number of the load fluctuation. It was. The relationship between the ratio of the rolling load input to the # 1 stand to the rolling load input to the # 2 stand (load ratio of # 1 / # 2) and C of the # 2 stand was determined. The relationship between the load ratio of # 1 / # 2 and C of # 2 stand is shown in Table 3 and FIG. When the rolling speed is 1500 mpm, C does not change even if the load ratio of # 1 / # 2 is changed. When the rolling speed is 2000 mpm, C rapidly increases when the load ratio of # 1 / # 2 is 1.15 or more. When the load ratio is 1.15 or less, C can be stably reduced. Note that it is considered that changes in B and α due to the load ratio of # 1 / # 2 are small.

  From FIG. 3 to FIG. 5, when cold rolling a metal strip under conditions where chattering is likely to occur, the rolling load input to the upstream rolling mill adjacent to the rolling mill increases the rolling oil flow rate of the rolling mill. The ratio of the rolling load input to the rolling mill may be reduced so that B, C, and α of the rolling mill satisfy the relationship of Cm−B × C / α> 0. Since B becomes small when the roll roughness is small, it is advantageous to reduce the initial roll roughness if possible.

  In this example, during rolling, the rolling speed was increased from 1500 mpm to 2000 mpm, and the presence or absence of chattering was investigated. At that time, the present invention example shows the relationship between the rolling oil flow rate of the # 2 stand in FIG. 3 and B, the relationship between the rolling oil flow rate of the # 2 stand in FIG. 4 and α, the load ratio of # 1 / # 2 in FIG. Referring to the relationship of C, the rolling oil flow rate and the load ratio of # 1 / # 2 were determined so that B, C, and α satisfy the relationship of Cm−B × C / α> 0.

  The results are shown in Table 4.

  In the example of the present invention, chattering does not occur because rolling was performed such that the rolling condition when the rolling speed was increased to 2000 mpm satisfied Cm−B × C / α> 0. On the other hand, chattering occurred in the comparative example because the rolling condition at a rolling speed of 2000 mpm did not satisfy Cm-B × C / α> 0.

  According to the present invention, the damping coefficient Cm of the rolling mill, the rolling load B, the frequency C of the rolling load fluctuation, and the vertical acceleration rate α with respect to the metal strip from the rolling mill are such that Cm−B × C / α> 0. By rolling the metal strip so as to satisfy the requirements, the vibration of the rolling mill can be suppressed, and even if vibration occurs, vibration expansion can be suppressed, so chattering of the rolling mill can be suppressed by a simple method. Can do. The present invention is suitable as a method for cold rolling a metal strip in a rolling speed region exceeding 1500 mpm where chattering is likely to occur.

1 roll (rolling roll)
2 Spray equipment 3 Rolling oil 4 Metal strip

Claims (3)

The rolling mill damping coefficient Cm (Ns / m), rolling load B (N), rolling load fluctuation frequency C (1 / s), vertical acceleration α (m / s ² ) with respect to the metal strip from the rolling mill , Cm−B × C / α> 0 is satisfied, and the metal strip is rolled to satisfy the condition: Cm−B × C / α> 0. Rolling machine damping coefficient Cm (Ns / m), rolling conditions and rolling load B (N), rolling load fluctuation frequency C (1 / s), vertical acceleration α (m / S ² ) in advance, and when cold rolling the metal strip, the damping coefficient Cm (Ns / m) obtained in advance, the rolling conditions and rolling load B (N), and the rolling load fluctuation Using the relationship between the frequency C (1 / s) and the vertical acceleration α (m / s ² ) with respect to the metal strip from the rolling mill, the rolling load B (N) and the rolling load fluctuation frequency C (1 / s) The rolling conditions are determined so that the vertical acceleration α (m / s ² ) with respect to the metal strip from the rolling mill satisfies the relationship of Cm−B × C / α> 0. A method for cold rolling a metal strip, comprising rolling. During rolling, the rolling load B, the frequency C of the rolling load fluctuation, and the vertical acceleration α with respect to the metal strip from the rolling mill are measured to obtain the rolling load B (N), the rolling load fluctuation frequency C (1 / s). , Whether vertical acceleration α (m / s ² ) with respect to the metal strip from the rolling mill satisfies Cm−B × C / α> 0 is satisfied, and Cm−B × C / α> 0 is satisfied When not, the damping coefficient Cm (Ns / m) obtained in advance, the rolling conditions and the rolling load B (N) obtained by measurement, the frequency C (1 / s) of the rolling load fluctuation, from the rolling mill using the relationship between the acceleration in the vertical direction with respect to the metal strip ^{α (m / s 2),} Cm-B × cold characteristics and to Rukin genus band modifying the rolling conditions so as to satisfy the C / alpha> 0 Hot rolling method.

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