JPS5921682B2 - Shape and plate crown control method in finishing rolling mill - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the shape and plate crown of a rolled material in a reverse mill or tamp mill.

Requirements for plate thickness accuracy of rolled products are becoming stricter year by year.

Regarding plate thickness accuracy, we are at a stage where we can be fully satisfied with the longitudinal direction due to advances in automatic plate thickness control, hydraulic lowering devices, and measurement technology, but there is no effective control means for the width direction. At present, the main reason is that it cannot be controlled at will.

In view of these circumstances, a rolling mill that can significantly change the roll curve by combining roll axial movement and roll bending (details of this rolling mill can be found in the Japanese Patent Publication No. 50
19510 and Japanese Unexamined Patent Publication No. 49-29263) has been developed and has exerted great power in controlling the shape of rolled material and plate crown.

On the other hand, as well-known methods for controlling the shape of rolled material and plate crown in conventional rolling mills, there are the following methods.

(a) Calculate the reduction schedule so that the reduction amount of each lotus (each stand in Kundem mill) and the ratio plate crown (the ratio of the thickness deviation in the width direction to the thickness at the center of the width) are constant. At the same time, the thickness distribution in the width direction of the plate at the final bath was actually measured, the roll deflection formula was revised based on the calculated value and the measured value, and the rolling schedule for the next rolled material was changed to obtain the desired cross-sectional shape. (Please refer to Japanese Patent Publication No. 49-20868).

(b) Shape control method for determining the target ratio plate crown of each bus so that the shape of the next rolled material can be rolled flat using the shape correction amount obtained by comparing the measured shape after rolling with the calculated shape ( Please refer to Japanese Patent Publication No. 49-48394.

) All of these methods are aimed at shape control.

The former assumes that the rolled material does not flow in the width direction of the plate,
Since the ratio plate crown is constant throughout each bus,
The target ratio plate crown in the final bath becomes the ratio plate crown of the base metal, and there is a disadvantage that the target value of the ratio plate crown in the final bath cannot be changed at will. Since the purpose is shape control,
Like the former, it has the disadvantage that the final pass target ratio plate crown cannot be controlled over a wide range.

An object of the present invention is to provide a shape and plate crown control method in a finishing rolling mill that can independently control the plate crown to a desired value without being influenced by the shape.

A feature of the present invention is that in a finishing rolling mill that subjects a rolled material to a plurality of rolling baths and controls the shape and plate crown of the rolled material, the shape of the proportion of the plate crown relative to the amount of change in the plate crown among all the rolling baths is At least one ratio plate crown correction bus is set in the rolling bath in the area where the cross flow coefficient, which is the ratio of the amount of change, is zero, to control the ratio plate crown of the rolled material, and then among all the rolling buses, the cross flow coefficient At least one shape control bus is set in a rolling bus in a region where the coefficient is greater than zero, and the shape and shape of a finishing rolling mill is controlled such that the shape of a rolled material subjected to ratio plate crown control is controlled to be flat. In the plate crown control method.

Figure 1 is the gist of the present invention, and shows the ratio C of the shape change amount Δλ to the inlet plate thickness h1 of the rolled material and the ratio plate crown change amount ΔC, which is referred to as the cross flow coefficient) η (=1Δλ/Δ
These are actual measurement results obtained by performing multi-bus rolling to determine the relationship between C1) and C1).

In FIG. 1, the entry side plate thickness (indicated by . in FIG. 1) where η starts to increase rapidly from 0 to 0 is defined as the boundary plate thickness.

ΔC=C2-C1 (1) Δλ-λ2-λ1 This is the value obtained from (2).

Ratio plate crown C (5uffix
1: entry side, 5uffix 2 (represents 2 exit side) is the board thickness at the center of the board width.

and the plate crown hb (-ri) expressed by the difference in plate thickness h8 at the plate width end position.

-ho) is defined by the following formula.

However, ho: thickness at the center of the plate, he: thickness at the edge of the plate width.

Also, the shape λ(5uff ix l
: Input side, 5uffix 2, exit side) is the length measured along the rolled material at the center of the plate width when the rolled material is cut to a certain predetermined length.

, the length measured along the rolled material at the edge of the plate width is l.

It is defined by the following formula. Here, the physical meaning of the cross flow coefficient η will be described.

The cross flow coefficient η is 0 from the ratio plate crown C1 (inlet side)
2 (output side), the change ΔC (=C2-0
This shows the extent to which 1) appears in the shape.

This is an indispensable basic quantity for plate crown control.

(1) When η = 0 In this case, the ratio crown plate (or plate crown)
No matter how you change it, the shape will remain flat.

In other words, since the shape is not affected, the plate crown can be modified to suit the control ability of the rolling mill.

This is the case in which plate crown control is easiest to perform because it is not influenced by the shape.

(ii) Case of η=1 In this case, the rolled material is in a so-called two-dimensional deformation state in which no deformation occurs in the plate width direction, and the ratio plate crown change and shape change correspond to l to l.

The shape can therefore be placed and handled on the plate crown.

That is, when the ratio plate crown (or plate crown) is modified, all the corrections appear in the shape, and it is no longer possible to control the plate crown with a flat shape.

In this state, priority is given to shape control with high product value.

(iii) When 0<η×l Plate crown control is possible unless η=1, but in this case, changing the ratio plate crown will deteriorate the shape, so this must be taken into consideration.

The smaller η is, the smaller the degree of deterioration in the shape due to ratio plate crown (or plate crown) correction, so the amount of correction can be increased.

Therefore, it is more effective to perform plate crown control in a region where η is small.

The present applicant et al. investigated the relationship curve between η and η shown in FIG. 1 under various conditions and found that η is expressed by the following function.

η=f (bl, b, k)...
(5) Here, hl: entry side plate thickness, b: width of the second plate, k: material.

The specific form of η can be expressed by formulating FIG.

Next, a formula for determining the exit side shape λi and ratio plate crown Ci in each pass when the hl-4 curve shown in FIG. 1 is used for a given rolling schedule will be explained.

Now, the following equation is obtained by rewriting equation (1) in the form of a path representation as the outgoing ratio plate crown Ci in the i-pass.

C・−C・+ΔC・・・・・・・(6)1
1-1 1 Ci in equation (6), C・−=C・−+ΔC・・・・(7)11121
Using the relationship of −1 and repeating this operation, Ci is expressed by the following formula % Formula % Similarly, the shape of the output side of the i path λi is expressed by the following formula.

However, L is the first passer in the pass area to be controlled.

The difference between ΔC・ in equation (8) and Δλi in equation (9) is Δλi−ηiΔCi (1
0) holds true, and the shape λ・ and the ratio plate crown Ci are (1
0) are related by the equation.

In equation (-10), ηi can be calculated from the hl-4 curve shown in Figure 1, or by calculating the value for the inlet thickness of each pass based on the given reduction schedule, or by formulating this curve into a formula ( (5) (concrete form of the function in equation (5)).

In the above equations (8) to (10), CL-i can be obtained by measuring the plate thickness between the center of the plate width and the edge of the plate width using a thickness gauge, and the plate crown calculation method for the rolling mill described above. (For example, the 25th Plastic Processing Union Lecture Proceedings,
P2O2-203, 1972-October) can be obtained from the regression equation of the calculation results.

λLl can be set to λL-1"" since the control start path has a plate thickness with almost no change in shape, but to improve accuracy, the shape actually measured by a shape detector is used.

Also, CN and λ of the final pass are CN-CD (target value)
, λ, = 0 is the intention of the present invention, and therefore, it is given as a target value.

Therefore, the number of unknowns in equations (8) to (10) is (4n
For 2), the number of equations is 3n, (n-2)
This increases the number of unknowns, but under appropriate control conditions, i.e., the range of shapes allowed for rolling operations at each stand: 1λ: 14λ8
, the shape of each pass and the ratio plate crown can be found.

The reinforcing roll shift amount δ and work roll pending force to obtain the target ratio plate crown of each stand determined in this manner are determined as follows.

The work roll bending force F compensates for variations in plate crown due to changes in rolling load within the coil, etc. Once F is determined,
The reinforcing roll shift amount δ is determined by calculating backward from equation (11) using the previously determined target plate crown C.

Another method is to take the ratio plate crown C1 on the horizontal axis as shown in FIG. 2, and the shape λ on the vertical axis, and then
It is also possible to calculate the value of η for the inlet plate thickness of each pass from the −η relationship and create a vector diagram.

Figures 3a to 3c show typical control examples of the present invention, with a base plate thickness of 25 mm.
A mild steel material with a plate width of 450 mm and a plate width of 450 mm is rolled to a finished plate thickness of 2 to 3 mm by axial movement of the reinforcing rolls 3 and 3 shown in Fig. 4 and by roll bending using the bending device 4 provided on the work rolls 2 and 2'. This is a case in which 6 passes of hot rolling were performed using a rolling mill that was used in combination with a rolling mill to control the shape and plate crown.

The pass area for controlling the shape and plate crown is 3 to 6 passes, and the 5th and 3rd to 4th passes of this control pass area are used to correct the target ratio plate crown after the final pass, i.e. the pass with η = 0 (ratio The 5th and 6th buses are used as a path for controlling the shape to be flat, that is, a path with η>0 (shape control path).

As shown in the control example, the present invention provides a ratio plate crown correction pass with a pass (η = 0) in the area where the boundary plate thickness hB is larger on the entry side plate thickness, and a pass (η = 0) in the area where the plate thickness on the entry side is smaller than hB (
A shape control path is provided at η=〉0), and the target ratio plate crown is controlled in the plate thickness region where the degree of deterioration of the shape is small, and the shape is controlled so as not to hinder the rolling operation. .

In addition, in Fig. 3, the target ratio plate crown CN after the final pass
' = 0.5, -〇, 5 coefficients are taken as an example, but it is of course possible to control CN = 0 as well.

According to the present invention, in the shape and plate cracking control of the finishing mill, it is possible to control the plate crown independently and to a desired value without being influenced by the shape, so the shape is always constant. The effect is that a desired plate crown can be obtained in good condition.

[Brief explanation of the drawing]

Figure 1 shows the relationship between the entrance plate thickness and the ratio of the shape change to the ratio plate crown change in each pass.
The figure is a vector diagram for determining the shape and ratio plate crown in each pass, Figure 3 is a diagram showing an example of control according to the present invention, and Figure 4 is a diagram showing a control example using the axial movement of the reinforcing roll and work roll bending. This is a rolling mill that controls the shape and plate crown. Explanation of symbols, 1...Rolled material, 2, 2'...Work a
-Role, 3.3'... Reinforcement roll, 4... Roll bending.

Claims (1)

[Claims] 1. In a finishing mill that applies multiple rolling pulses to a rolled material to control the shape and plate crown of the rolled material,
Among all the rolling buses, at least one ratio plate crown correction bus is set in the rolling bus in the area where the cross flow coefficient, which is the ratio of the shape change to the ratio plate crown change, is zero, and the ratio plate crumb of the rolled material is adjusted. Then, out of all the rolling buses, at least one shape control bus is set in a rolling bus in a region where the cross flow coefficient is greater than zero to control the shape of the rolled material subjected to ratio plate crown control. A method for controlling the shape and crown of a plate in a finishing rolling mill, characterized by controlling flatness.