JPH05154525A - Method for deciding pass schedule in cold-continuous type rolling mill - Google Patents

Abstract

PURPOSE:To provide a deciding method for pass schedule in a cold continuous type rolling mill which can set up the rolling load in the desired permissible range. CONSTITUTION:This deciding method for pass schedule is provided with a stage for obtaining the rolling load of each stand based on the pre-decided specification, a stage for discriminating whether the rolling load is in the permissible range of the rolling load in each kind or not, a stage for obtaining tension between the stands to be in the permissible range and again recalculating the rolling load in the case the rolling load is not in the permissible range and a stage for obtaining a gap and rolling speed based on the rolling load in the permissible range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pass schedule determination method for a cold continuous rolling mill, and more particularly to a rolling load determination method.

[0002]

2. Description of the Related Art The calculation of a pass schedule of a cold continuous rolling mill is carried out in order to produce a steel plate having a target product thickness.
It determines the appropriate roll gap and roll speed for each stand. In the conventional pass schedule determination method, assuming the material specifications (original plate thickness, product thickness, plate width, etc.), tension between stands, reduction ratio of some stands, reduction distribution ratio, etc., the exit speed of each stand is assumed. And calculate the outlet plate thickness,
Further, these are used to determine the roll gap and roll speed of each stand.

In obtaining the target roll gap and roll speed of each stand, (1) restrictions are imposed on the rolling power. (2) Add restrictions to rolling load. (3) Add restrictions to the shape. There are methods such as these, and they are used properly according to operational requirements.

The outline of these pass schedules is as follows. (1) Regulation of rolling power: This is a method of maximally using the capacity of the motor by giving the rolling power distribution ratio of each stand in advance, and the rolling speed can be maximized. (Efficiency priority schedule) (2) Regulation of rolling load: The rolling load distribution ratio of each stand is given in advance to improve the shape or crown of the product. (3) Shape regulation: By keeping the crown ratio constant,
It is intended to obtain a good shape. For example, Japanese Patent Publication 5
No. 9-38042 discloses a hot strip mill draft schedule determination method.

[0005]

In the conventional path schedule calculation method, the path schedule is determined under any one of the above constraints after first assuming the tension. However, in the following cases, for example, it is necessary to limit the absolute value of rolling load itself. (1) When the rolling load is high and, for example, the coefficient of friction of the roll is large immediately after reassembling, or when the material has an extremely large deformation resistance, the roll temperature rises when the efficiency is good, which is called heat streak. The image sticking phenomenon occurs. (2) When the rolling load is low, for example, when a certain length is rolled after recomposition and the roll surface is worn and the friction coefficient is extremely reduced, rolling becomes unstable and slip occurs.

In the conventional pass schedule determination method, the absolute value of the rolling load is determined as a result of the pass schedule determination, and cannot be positively increased or decreased in accordance with the demand. For this reason,
When the above cases occur, the operator has performed the work of changing the rolling reduction and the tension after the calculation of the pass schedule, executing the schedule calculation again, and changing the load. This increases the load on the operator and is a major problem left over in the conventional path schedule determination method.

The present invention has been made to solve the above problems, and a pass schedule of a cold continuous rolling mill capable of setting the absolute value of the rolling load of each stand within an allowable range. The purpose is to obtain a decision method.

[0008]

A method for determining a pass schedule of a cold continuous rolling mill according to the present invention comprises a step of obtaining a rolling load of each stand on the basis of a predetermined specification, and a rolling load for each product type. The process of determining whether the rolling load is within the allowable range, and when the rolling load is not within the allowable range, the process of re-calculating the rolling load by obtaining the inter-stand tension that should be within the allowable range, and within the allowable range And a step of obtaining a roll gap based on a certain rolling load.

[0009]

In the present invention, the rolling load is set within the allowable range by appropriately changing the tension between stands.
Such a rolling load satisfies various operational requirements, reduces the operator's load, and prevents quality abnormalities due to roll baking, slip, and the like.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a flow chart showing a path schedule determining method according to an embodiment of the present invention. In this embodiment, a mode in which rolling load is prioritized is newly added to the conventional pass schedule setting algorithm, and the calculation process in the broken line is a part newly added to the conventional pass schedule. This mode is selected when it is necessary for the absolute load value to be within the load range determined by the operator from past rolling bonds of the relevant material.

First, various specifications are input (S1), and a draft is calculated based on the specifications (S2). This draft is calculated based on the following mass flow equation and power equation. Mass flow formula: vi · hi = (1 + fi) Vi · hi = U (constant) Power equation: AAi · Gi · Vi = γ _Li · L0 · ηi vi: Roll outlet material speed hi: Material roll outlet plate thickness fi: Advance rate vi: Roll speed AAi: Power conversion coefficient Gi: Rolling torque γ _Li : Rolling power distribution ratio L0: Total power ηi: Motor efficiency i: 1 to n n: Number of stands

Next, the deformation resistance k and the friction coefficient μ are calculated by the following equations (S3). k = k (H, h) μ = μ (h, v, P) H: Material roll inlet plate thickness P: Rolling load

Further, the rolling load is calculated by the following formula (S
Four). P = b · k {1- (tb + tf) / 2k} R '(H-
h) Dp Dp = Dp (μ, r, h, R ′) r = (H−h) / H R ′ = R ′ (R, H, h) tb: rear tension tf: front tension R ′: flat roll Radius Dp: Thickness deviation in width direction r: Reduction ratio R: Roll radius

Next, it is judged whether or not the load priority mode is set (S5). For example, when the load priority mode is set, an appropriate flag is set, and if the flag is set, it is determined that the load priority mode is set. If the load priority mode is set, next,
It is determined whether the rolling load obtained in (S4) is within a preset allowable range (S6). This allowable range is defined for each stand by product type, and consists of upper and lower limits determined by classifying by plate thickness, steel type, etc., and the rolling load of all stands is the upper and lower limits. If it is in between, the process proceeds to the same process as the conventional one, that is, the process (S10) described later. If the rolling load of one stand is not within the allowable range and the rolling load is not within the allowable range for a predetermined number of times or less (S7), as described below, The inter-stand tension is determined so as to reach the determined target rolling load of each stand.

First, a value inside the permissible range by a constant value from the overloaded load allowable value is determined as the target rolling load (S8). That is, when the rolling load obtained in the above process (S4) exceeds the upper limit value, the target value is set to a value slightly smaller than the upper limit value. Next, the tension is calculated by the Newton-Raphson method based on the newly set target rolling load (S9).

FIG. 2 is a flow chart showing the calculation method for this tension calculation. Initialize the count value j with j = 1 (S21). Then, the initial tension is set as shown in the following equation (S22). t _{i, j} = t _{i, o} Note that t _{i, o} is input when the specification is input, and this value is set as an initial value for calculation. Next, the deviation between the already calculated rolling load and the above target rolling load is obtained, and this is defined as a load deviation function. Pi (ti _{, j} ) = Piset-Piref Pi (ti _{, j} ): Load deviation function Piset: Set load Piref: Target load

Next, the tension that makes the load deviation function "0" is calculated by the Newton-Raphson method using the tension as a variable. Here, the tension t _{i, j as} a variable uses the front tension (tension between 1 and 2 stands) for only one stand, and uses the rear tension for the other stands. 1 to 1 of the calculated tension
Between the two stands, the average value of the calculated values of each of the one stand and the two stands is used as a determined value, and the calculated value of the other stands is used as a determined value. The details will be described below.

First, the differential coefficient Pi '(ti _{, j} ) of the load deviation function Pi (ti _{, j} ) is obtained (S24). Then, the renewal tension is calculated by the following equation. t _{i, j + 1} = t _{i, j} + ΔP / Pi ′ (t _{i, j} ) ΔP is a preset value. The absolute value of the difference between t _{i, j + 1} and t _{i, j} thus obtained is obtained and it is determined whether or not it is smaller than a predetermined value α (S26). | T _{i, j + 1} −t _{i, j} | <α Since j = 1 here, the absolute value of the difference between t _{i, 2} and t _{i, 1} is determined.

When the above conditions are not satisfied,
Next, it is judged whether j is larger than a predetermined constant β.
(S27). That is, if this calculation loop is performed more than β times, there is no room for calculation and an error is output. Here, j is still “1”, so j = j +
Increment j by setting 1 (= 2) (S28). Then, the tension is updated (S29). That is, t _i, j = t
_{i, j−1} . Here, t _{i, 2} = t
_{i, 1} . Then, it returns to the above processing (S23) again,
When the condition is satisfied in the above process (S26), the tension at that time is adopted (S30). That is, here, t _i = t _{i, j} .

When the tension is obtained as described above, the process returns to the flowchart of FIG. 1 and the processes (S2) to (S4) after the draft calculation are performed again. Then, if the rolling load obtained there is within the allowable range (S6), then the bending force Pbi is calculated (S10). Pb = Pb (b, P, WRδ, RBR, RWR, RBC, RW
C, HC) WRδ: Work roll δ RBR: Backup roll radius RWR: Work roll radius RBC: Backup roll crown RWC: Work roll crown HC: Base metal crown When the bending force is required, the roll gap Sri
Is required (S11). Sri = Sri (hi, Pi, Pbi) In addition, the above-mentioned processing (S1), (S2), (S3), (S4), (S10), (S
Although a part of the description in 11) is omitted, it is the same as the conventional method.

FIG. 3 is a diagram showing the unit tension, rolling load and strip thickness obtained by the conventional pass schedule determination method and that by the pass schedule determination method according to the present embodiment. According to this example, it can be seen that the rolling load is appropriately suppressed.

[0022]

As described above, according to the present invention, the rolling load of each stand can be set within a desired range,
As a result, it is possible to prevent abnormalities in the quality of the steel sheet due to roll baking, slipping, and the like.

[Brief description of drawings]

FIG. 1 is a flowchart showing a calculation method according to an embodiment of the present invention.

FIG. 2 is a flowchart showing a calculation method for tension calculation in FIG.

FIG. 3 is a diagram showing a unit tension, a rolling load, and a plate thickness obtained by a conventional pass schedule determination method and those by a pass schedule determination method according to the present embodiment.

Claims (1)

[Claims] 1. A step of obtaining a rolling load of each stand based on a predetermined specification, a step of determining whether or not the rolling load is within a permissible range of the rolling load of each product type, and a permissible rolling load. When it is not within the range, it is characterized by including a step of re-calculating the rolling load by obtaining the inter-stand tension that should be within the allowable range, and a step of determining the roll gap based on the rolling load within the allowable range. Method for determining pass schedule of cold continuous rolling mill.