JPS5926367B2 - Plate camber control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling plate camber in steel plate rolling, particularly in thick plate rolling.

In the rolling of thick plates, there is a problem in that a phenomenon in which the thick plate curves in the width direction of rolling during rolling, that is, plate camber occurs.

Due to the occurrence of such plate camber, it is not possible to obtain a rectangular thick plate with the required width, or by rolling the plate with an allowance in advance so that the plate width is sufficiently large, and cutting off unnecessary parts, it is possible to obtain a rectangular thick plate with the required width. This often results in a significant decrease in yield due to the need to obtain plates.

The causes of the plate camber mentioned above are due to the rolled material, such as the entrance side plate thickness being different on the left and right sides, that is, on both sides in the width direction, and due to poor parallelism between the upper and lower rolls of the rolling mill. There are also those caused by the mutual relationship between the rolling mill and the rolled material, such as rolling with the center line of the body length of the roll of the rolling mill and the center line of the rolled material in the width direction misaligned. In any case, if asymmetrical rolling is performed, the elongation rate on the left and right sides of the rolled material will be uneven, resulting in plate camber.

The present invention proposes a novel board camber control method for suppressing the occurrence of board camber as described above.

The plate camber control method according to the present invention includes the following steps when rolling a steel plate:
Prior to the final rolling pass, the amount of camber of the rolled material is measured, and from this measurement value, the elongation rate difference in the rolling direction at both the left and right ends of the rolled material in the rolling direction is calculated, and this calculated value and the separately determined level correction contribution are calculated. The method is characterized in that the amount of rolling correction on each of the left and right sides of the rolling mill is determined from the ratio, and the rolling position on each of the left and right sides of the rolling mill is adjusted according to the amount of rolling correction, and then the final rolling pass is carried out.

The present invention will be described in detail below based on drawings showing embodiments thereof.

FIG. 1 schematically shows an apparatus used to carry out the method of the present invention, in which a rolled material 1 is rolled in multiple passes by a reversible rolling mill 2 whose rolling position can be adjusted independently on the left and right sides. It is then rolled into a thick plate of a predetermined size.

The amount of camber of the rolled material 1 that has passed through the pass immediately before the final pass is first measured by an appropriate camber measuring device 3 (for example, one that is a combination of a sheet width measuring device and an arithmetic device).

FIG. 2 is a schematic plan view of the rolled material 1 that has passed through the previous pass, and plate camber has occurred.

The length of the center line in the plate width direction of this rolled material 1 excluding the cropped parts 1a and la at both front and rear ends is L, the plate width is B, and the cropped parts are If the dimensions leading to the line segments (chords) connecting the left front and rear ends and the right front and rear ends of the rolled material 1 excluding 1a and 1a, that is, the plate bending amounts, are ΔC1 and ΔC2, then the camber amount Δ
C is determined by the following equation (1) as the arithmetic average of ΔC1 and ΔC2.

ΔC-(ΔC1+ΔC2)/2 ・・・・・・(
1) The amount of camber is not limited to the single value obtained by the above formula (1), but can be expressed by a formula similar to formula (1) for each block formed by dividing the rolled material 1 into a plurality of parts in the longitudinal direction of the plate. The control may be refined by obtaining a plurality of camber amounts.

The camber amounts ΔC and B are input to the elongation rate difference calculation device 4 in order to determine the elongation rate difference Δξ between the left and right sides of the rolled material.

FIG. 3 is a geometrical surface view of the rolled material 1 excluding the cropped portions 1a, 1a.

Assuming that the left side is the long side and the right side is the short side due to the occurrence of board camber, the length of the left side is LL, and the length of the right side is LR.

The left and right sides and the center line that defines them can be approximately regarded as circular arcs, and for convenience it is assumed that the centers of the circles coincide.

Let ρ be the centerline radius regarded as a circular arc, and θ be the opening angle between the radii including the front and rear edges of the rolled material 1, excluding the cropped portions ia and la.

Then, the difference in elongation rate Δξ between the left and right sides can be obtained by the following equation (2).

Δξ= (LL LH) / L...
(2) On the other hand, as is clear from FIG. 3, the following equations (3), (4), and (5) hold geometrically.

LL-LR=θ・B (3)
θ p(1-cos-)-ΔC--(4) θ-L/
ρ...(5) Since ρ is sufficiently large compared to L, θ/2<1, so θ2 1- cos -÷(θ/2)2/2...
・The approximation to (6) holds true.

Then, from equations (4) to (6), ΔC-ρ・θ2/8=
L・θ/8 (7) Therefore, the left and right elongation rate Δξ is from formulas (2), (3), and (7), Δξ=
θ・B/L = 8 B・ΔC/L2 ・・・・・・(
8), the elongation rate difference calculation device 4 calculates the elongation rate difference Δξ according to equation (8), and inputs this to the reduction correction amount calculation device 5.

Now, the cause of the difference in elongation between the left and right sides of the rolled material is that due to the left-right asymmetry in rolling, the deformation of the rolls of the rolling mill becomes unevenly sharp on the left and right sides, causing a deviation in the thickness of the sheet at the exit side.

The means for determining the relationship between this deviation value, that is, the so-called wedge amount change and the elongation rate difference Δξ will be explained below.

Now, it is assumed that a rolled material of unit length on the input side extends to lengths LL and LR9L at the left, right, and center portions, respectively, on the output side, and the influence of metal flow in the width direction during rolling is small. shall be taken as a thing.

It is known that this holds true when the plate thickness/work roll diameter ratio is sufficiently small, and this condition is satisfied near the normal thick plate finishing pass.

As shown in FIGS. 4A and 4B, which show the cross-sectional profiles of the inlet and outlet sides of the rolled material, the left and right plate thicknesses are HL on the inlet side, respectively.

In addition, the plate thickness at the center in the width direction is expressed as H6, and on the exit side, the plate thickness at the center in the width direction is hc, which is hL and hHt, respectively, on the left and right sides.

Then, from the constant condition of mass flow of people and output, the following (
Equations 9), (10), and (n) hold true for the right side, center, and left side of the rolled material, respectively.

IXHR=hR-LR...(9) IXHo
= h o-L ・--(10) I X
HL = J, -LL. ...(13)
) Δw=hRhL (14
), and HL÷Ho−ΔW/2 −−−−−−(15
)HR:HC+ΔW/2 ・−・−・(
16) hL-:hc-Δw/2 ==(17
)hR4hC+Δw/2...Song (18).

Therefore, hc2)3w''/4.

Substituting equation (19) into equation (12) yields Δξ−Δw/h
o-ΔW/Ho...(2D).

In the case of multi-pass rolling, the left and right elongation rate differences generated in each pass are superimposed, so the left and right elongation rate difference Δξf after the f-th rolling pass is expressed by the following equation (21).

However, hi is the plate thickness at the central part on the exit side of the i-th pass, Δwi
is the wedge amount on the output side of the i-th pass.

Therefore, the thickness of the central part on the exit side of the i-1st pass is hh-,
and its wedge amount .DELTA.Wi-1 respectively mean the plate thickness at the central part on the entrance side of the next pass, that is, the i-th pass, and its wedge amount.

Further, Δξi −1 is the difference in elongation between the left and right sides that exists after the i-1th rolling pass.

Now, the camber amount ΔCf after the f-1st pass.

Considering the case where
1 is from equation (8), Δξf−1= 8 B ΔCfl /LF 11
......(22) However, Lf is the plate length at the center after the i-1th pass, and can be easily determined from actual measurement or the length of the rolled material before rolling and the rolling ratio. .

Now, if we set i=f in the equation (21), then if this f-th pass is regarded as the final finishing pass, then by setting Δξf=Oh, the rolled material after the final finishing pass is Focus on reducing the amount of camber to zero.

Letting the wedge amount on the exit side in this case be Δwf*, (23
) Formula, the rolling correction amount (level correction amount) ΔSf* on the left and right sides of the rolling mill 2 to realize this Δwf* is calculated by the rolling correction amount calculating device 5 as follows.

h The rolling correction amount is defined as the amount of change in the difference between the left and right rolling positions.

Now, FIG. 5 is a graph showing the correlation between the two, with the horizontal axis representing the reduction correction amount ΔS and the vertical axis representing the wedge amount ΔW on the exit side.

As understood from this graph, ΔW due to changes in ΔS
The change in ΔS is approximated by a straight line within a certain range of ΔS.

In other words, this straight line is Δw-A・ΔS+ΔW□ +++++-(zs
).

However, the slope of this straight line, that is, the level correction contribution rate A, is determined by the hardness of the rolled material plasticity curve (a known parameter that indicates the hardness of the rolled material), the mill dimensions, the left and right rigidity of the mill, the width dimension of the rolled material, etc. This value can be determined in advance by a rolling guide, roll deformation calculation, or experiment.

The cut ΔW (, is the amount of wedging on the exit side that occurs when the reduction correction amount is zero, and is due to the imbalance in the level of the left and right reduction positions of the mill,
It represents the plate thickness deviation caused by the deviation between the widthwise center of the rolled material and the center of the roll body length, or the deformation resistance distribution due to non-uniformity of burning within the width of the rolled material.

The level correction contribution rate A in the f-th pass is Af.

The wedge amount Δwo when the reduction correction amount is zero is Δwf.

Then, equation (25) becomes the following (25') as shown in Figure 5.
) is shown in equation 5.

3w4 ”= A4 'ΔS+Δwfo "・"
(255 Therefore, ΔSf* to obtain the above Δwf* is (
25) Formula % Formula % (26)

Substituting this equation (26) K into equation (24) yields the result.

Referring to equation (20), (C5) hf hl in equation (2'7) above.

It is clear that is the difference in the elongation rate between the left and right sides that occurs in the f-th pass when the rolling correction amount is zero in the f-th pass.

In the rolling of thick plates, which is the main object of the present invention, products are obtained from slabs through multiple passes by reversible rolling.In this case, when the reduction amount is not corrected during rolling, the Since the change in the left and right elongation rate of is considered to be extremely small, the term within 0 in equation (27) can be practically ignored, and in short, equation (27) can be transformed into the following equation (28).
Replaced with an approximation of the expression.

In the above equation (28), the elongation rate difference Δξf-7 in the f-1st pass, that is, the pass immediately before the final pass (fth pass), is expressed by the equation (22) (or (8)). This value is inputted from the elongation rate difference calculation device 4 to the reduction correction amount calculation device 5 as described above.

Also, the value of A in the f-th pass, that is, the final pass,
That is, the level correction contribution rate Af is determined in advance by, for example, performing roll deformation calculation by the level correction contribution rate calculation device 6, and is similarly input to the rolling correction amount calculation device 5.

Furthermore, hf is the plate thickness at the central part of the exit side of the f-th pass, that is, the final pass, in other words, the target plate thickness in a series of rolling, which is required for calculating the target plate thickness, rolling schedule, and other level correction contribution factors. It is stored in the setting device 7 along with data and the like, and is input to the reduction correction amount calculation device 5.

The reduction correction amount calculating device 5 is based on these input data! ! Calculate ΔSf* by calculating according to formula (28),
This is output to the reduction position control device 8.

The rolling position control device controls the rolling mill 2 to realize the input ΔSf* and performs rolling of the final finishing pass on the rolled material 1, thereby eliminating the plate camber of the rolled material that has passed through the final finishing pass. There are many things to be done.

The method for correcting the amount of reduction on the left and right sides is ±ΔS f*7 in order to avoid affecting the thickness of the central part of the plate on the exit side.
It is preferable to correct the left and right rolled positions by 2 in reverse directions, respectively.

Further, in the method of the present invention, since the reduction amount is corrected within a short time between rolling passes, it is appropriate to use a hydraulic reduction control device with excellent control responsiveness.

Furthermore, in the above explanation, the elongation rate difference calculation device 4, the reduction correction amount calculation device 5, the level correction contribution rate calculation device 6, and the setting device 7 are described as separate units, but in reality, these are data processing devices such as a microcomputer. What can be configured with a single device is 5.
Not even 4.

Next, the results of implementing the method of the present invention will be described.

Thickness 215 mal, width 1500 mm, length 1.56 m
The slab is 13.3 mm thick, 2000 mm wide, and 1 mm long.
When finishing a product with a length of 8.9 m, the amount of camber of the rolled material after the pass immediately before the final finishing pass ΔCf-, C+2
There were 5 friends.

At this time, the length Lf-7 of the rolled material was 14.4 m, so the difference in elongation rate Δξf-1 between the left and right sides was obtained as 8 X2000 Ta.

On the other hand, the level correction contribution rate Af in the final pass was experimentally determined in advance to be 0.208.

Also, since hf is <13.3 mm as mentioned above, the reduction correction amount ΔSf* in the final finishing pass is 13.3 mm from equation (28).
3 Δsf*-X 0.00193=0.122mm0.
208, and the reduction correction amount ±ΔSf*/2 distributed to the left and right was ±ΔSf*/2=10.061 mm.

As a result of adjusting the rolling position in the final finishing pass based on this, the camber amount ΔCf was +5 mm, which was reduced to a reasonable value for most problems, whereas when the final pass rolling was performed without using the method of the present invention, The camber amount of the comparison material is +45m
It was 7n.

As described above, in the method of the present invention, the level correction contribution rate, which is a value determined by plate camber influencing factors such as the slope of the plasticity curve of the rolled material, the mill dimensions, the lateral rigidity of the mill, and the width dimension of the rolled material, is taken into consideration. Since the reduction correction amount is determined, the above-mentioned plate camber influence factors can be eliminated, and control accuracy and control accuracy can be improved.
The present invention has excellent effects, such as improving product quality and expecting a significant improvement in yield.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of an apparatus for carrying out the method of the present invention, Fig. 2 is a schematic plan view of a rolled material in which plate camber has occurred, and Fig. 3
The figure is a plan view of the rolled material expressed geometrically for deriving the calculation formula, Figure 4 A and B are cross-sectional dimensions of the rolled material at the entrance and exit sides of the rolling mill, and Figure 5 is the amount of rolling correction. FIG. DESCRIPTION OF SYMBOLS 1... Rolled material, 2... Rolling machine, 3... Camber measuring device, 4... Elongation rate difference calculation device, 5... Rolling correction amount calculation device, 6... Level correction contribution rate Arithmetic device, 7.
... Setting device, 8... Press down position control device.

Claims (1)

[Scope of Claims] 1. When rolling a steel plate, the amount of camber of the rolled material is measured prior to the final rolling pass, and from this measured value, the elongation rate difference in the rolling direction at both the left and right ends of the rolled material in the rolling direction is calculated. The calculated value and the level correction contribution rate A defined by the following formula: 3w = A・ΔS+Δw. However, ΔW: Amount of wedge on the exit side of the rolling mill ΔS: Amount of rolling reduction correction Δwo: A reduction correction of the final rolling pass on each of the left and right sides of the rolling mill according to the following formula based on the amount of wedge on the exit side that occurs when the reduction correction amount is zero. Find the amount ΔSf, where ΔSf:
Reduction correction amount hf of the final rolling pass: Output plate thickness Af of the final rolling pass: Level correction contribution rate Δξf- of the final rolling pass: Difference in elongation rate in the pass immediately before the final rolling pass, on both sides of the rolling mill according to the reduction correction amount A board camber control method characterized in that a final rolling pass is performed after adjusting the rolling position of the board.